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Sample records for expandable nitinol stent

  1. In situ cooling with ice water for the easier removal of self-expanding nitinol stents

    PubMed Central

    Merkel, Daniel; Brinkmann, Eckhard; Wiens, Daniel; Derwahl, Karl-Michael

    2015-01-01

    Background: It is yet to be determined what effects temperature has on the properties of nitinol in order to simplify the process of removing nitinol self-expanding metal stents (SEMS). Materials and methods: We describe the procedure for removal of SEMS in a total of 11 cases with 9 patients. A study involving cooling of nitinol stents in situ with ice water just before their removal was attempted. Results: All stents were removed successfully. In partially covered and in fully covered stents, the stent rigidity was noticeably reduced following cooling. Stent removal was performed by inversion, which was achieved by pulling on the stent from its distal end. No adverse events were observed during this trial. Conclusion: The higher pliability of the stents after ice-water cooling facilitates stent removal. With this method, a mobilization of all stents by the invagination technique was achieved. The separation of the uncoated stent ends from the intestinal wall by the invagination technique, as well as the mucosal vasoconstriction resulting from the cooling, lead to an easier SEMS removal and may serve to prevent severe bleeding of the mucosal wall during this process. PMID:26134772

  2. Shape optimization of stress concentration-free lattice for self-expandable Nitinol stent-grafts.

    PubMed

    Masoumi Khalil Abad, Ehsan; Pasini, Damiano; Cecere, Renzo

    2012-04-01

    In a mechanical component, stress-concentration is one of the factors contributing to reduce fatigue life. This paper presents a design methodology based on shape optimization to improve the fatigue safety factor and increase the radial stiffness of Nitinol self-expandable stent-grafts. A planar lattice free of stress concentrators is proposed for the synthesis of a stent with smooth cell shapes. Design optimization is systematically applied to minimize the curvature and reduce the bending strain of the elements defining the lattice cells. A novel cell geometry with improved fatigue life and radial supportive force is introduced for Nitinol self-expandable stent-grafts used for treating abdominal aortic aneurism. A parametric study comparing the optimized stent-graft to recent stent designs demonstrates that the former exhibits a superior anchoring performance and a reduction of the risk of fatigue failure. PMID:22304844

  3. Polyurethane-Covered Self-expandable Nitinol Stent for Malignant Biliary Obstruction: Preliminary Results

    SciTech Connect

    Han, Young-Min; Hwang, Seung-Bae; Lee, Soo-Teik; Lee, Jeong-Min; Chung, Gyung-Ho

    2002-10-15

    Purpose: To evaluate the immediate and long-term results in ten patients with malignant biliary obstruction using a polyurethane-covered, self-expandable nitinol stent.Methods: A nitinol stent, fully covered with high-elasticity polyurethane, with an unconstrained diameter of 10 mm and a total length of 60-80 mm, was placed transhepatically under fluoroscopic guidance in ten patients. The length of the biliary obstruction varied between 30-50 mm. The follow-up examination included a clinical assessment, serum bilirubin measurement, and ultrasound examinations at one-month intervals in all patients. Results: Initial stent deployment was successful in eight patients. Two patients experienced proximal migration,which was solved by insertion of two, uncovered Wallstents. One patient had the stent removed after two weeks because of severe nausea and vomiting. One patient had delayed migration of the covered stent after 40 weeks. The follow-up duration was 3-40 weeks (Mean: 16.9 weeks). Seven patients died(3-26 weeks) and three patients survived (24-40 weeks). The bilirubin measurements in all patients had significantly decreased one week after stent insertion. The levels of amylase and lipase had did not increase after stent insertion. Conclusions: Apolyurethane-covered, self-expandable nitinol stent can be used effectively and safely in the treatment of malignant biliary obstruction. The preliminary results are favorable, but there is a need for further large studies to determine both long-term survival and patency.

  4. Primary Self-Expandable Nitinol Stent Placement in Focal Lesions of Infrarenal Abdominal Aorta: Long Term Results

    SciTech Connect

    Lastovickova, Jarmila Peregrin, Jan H.

    2008-01-15

    Purpose. To evaluate the technical and clinical success, safety and long term results of percutaneous transluminal angioplasty/self-expandable nitinol stent placement of infrarenal abdominal aorta focal lesions. Materials and Methods. Eighteen patients underwent PTA of focal atherosclerotic occlusive disease of distal abdominal aorta. Two symptomatic occlusions and 16 stenoses in 10 male and 8 female patients (mean age 68.2 years) were treated with primary self-expandable nitinol stent placement. Results. Primary self-expandable nitinol stent placement was technically successful in all 18 procedures; clinical success was achieved in 100% of patients. No complications associated with the procedure occurred. During the 49.4 months of mean follow up (range 3-96, 4 months) all treated aortic segments remained patent. Conclusions. Endovascular treatment (primary self-expandable nitinol stent placement) of focal atherosclerotic lesions of distal abdominal aorta is a safe method with excellent primary technical and clinical success rates and favourable Long term results.

  5. Treatment of Benign Tracheal Stenosis Utilizing Self-Expanding Nitinol Stents

    SciTech Connect

    Sesterhenn, Andreas M. Wagner, Hans-Joachim; Alfke, Heiko; Werner, Jochen A.; Lippert, Burkard M.

    2004-08-15

    We assessed the results of self-expanding metallic stent insertion into benign proximal tracheal stenosis in patients not appropriate or unfit for surgical repair. Proximal benign tracheal stenoses had occurred in 11 patients (7 men, 4 women, mean age 68.8 years) after long-time intubation (n = 6), tracheostomy (n = 4), or chondropathia (n = 1). Fourteen self-expanding nitinol stents were placed in the patients under general anesthesia with endoscopical and fluoroscopical guidance. Stent insertion was successful in all cases and led to immediate relief of the morphological and functional airway obstruction. No immediate complications were noted. During the mean follow-up period of 67.5 weeks we observed one recurrent dyspnea 3 months after implantation and granuloma formation at the stent insertion site in another patient. Both complications were successfully treated with additional stent insertion in one case and laser resection of granulomas in the other. Self-expanding nitinol stents should be considered for the treatment of benign proximal tracheal obstruction in selected patients for whom surgical repair is contraindicated.

  6. Insertion of Self-Expandable Nitinol Stents Without Previous Balloon Angioplasty Reduces Restenosis Compared with PTA Prior to Stenting

    SciTech Connect

    Harnek, Jan; Zoucas, Evita; Stenram, Unne; Cwikiel, Wojciech

    2002-10-15

    Purpose: To compare the development of intimal hyperplasia after deployment of a self-expanding nitinol stent with and without previous percutaneous transluminal balloon angioplasty (PTA), with the results after PTA alone. Methods: In nine healthy pigs, the iliac arteries were divided into three groups: group 1 (n = 6 arteries) was treated with PTA; group 2 n 6)with insertion of self-expanding stents after PTA; and group 3 (n = 6) with stent insertion without previous PTA. After 8 weeks the vessels were examined with intravascular ultrasonography,histologic examination and morphometric analysis. Results: Although the injury index in group 1 (0.17{+-} 0.57) was lower (p <0.05) than in group 2 (0.26 {+-} 0.06) and group 3 (0.26 {+-} 0.08), PTA-treated arteries showed significantly (p <0.05) reduced mean luminal gain (0.53 {+-} 2.84) compared with arteries treated with PTA prior to stenting (2.58 {+-} 1.38) and compared with stenting alone (4.65 {+-}5.34). Stenting after PTA resulted in a higher (p<0.05) restenosis index (2.63 {+-} 1.06) compared with stenting without PTA (1.35 {+-} 0.59). Group 2 also had a significantly thicker intimap <0.05) and 83% and 74% higher intima/mediaratio (p <0.05) compared with groups 1 and 3, respectively. Conclusion: Insertion of a self-expandable nitinol stent without previous PTA results in less intimalhyperplasia than if PTA is performed prior to stenting, suggesting that direct stenting can be used in angioplasty sessions with a favorable outcome.

  7. Feasibility study for the investigation of Nitinol self-expanding stents by neutron techniques

    NASA Astrophysics Data System (ADS)

    Rogante, M.; Pasquini, U.; Rosta, L.; Lebedev, V.

    2011-02-01

    In this paper, neutron techniques - in particular, small angle neutron scattering (SANS) and neutron diffraction (ND) - are considered for the non-destructive characterization of Nitinol artery stents. This roughly equiatomic (50Ni-50Ti at%) shape memory alloy (SMA) exhibits significant properties of superelasticity and biocompatibility that make it suitable to be typically used as smart material for medical implants and devices. Nitinol self-expanding artery stents, as permanent vascular support structures, supply an ideal option to bypass surgery, but they are submitted for the whole of patient's life to the dynamical stress of the artery pulsation and the aggression from the biological environment. These stents, consequently, can suffer from wear and fracture occurrence likely due to a variety of cyclic fatigue, overload conditions and residual stresses. Neutrons have recently become a progressively more important probe for various materials and components and they allow achieving information complementary to those obtained from the traditional microstructural analyses. The outputs from the preliminary works already carried out in this field consent to consider neutron techniques capable to contribute to the development of these crucial medical implants. The achievable results can yield trends adoptable in monitoring of the stent features.

  8. ALD mediated heparin grafting on nitinol for self-expanded carotid stents.

    PubMed

    Wang, Fei; Zhang, Yan; Chen, Xiumian; Leng, Bing; Guo, Xin; Zhang, Tao

    2016-07-01

    Carotid-artery atherosclerosis is a common cause of ischemic stroke. Carotid-artery stenting (CAS) is one of the most effective treatments. However, In-stent restenosis (ISR) and re-endothelialization delay are two major issues of intravascular stent which affect clinical safety and reduce effects. In this study, atomic layer deposition (ALD) technology was applied to deposit a layer (10nm) of Al2O3 on Nitinol surface as an intermediate functional layer. The alumina covered surface was then modified with a coupling agent 3-aminopropyltriethoxysilane (APS) and heparin sequentially in order to improve the hemocompatibility of Nitinol stents. The successful graft of APS and heparin onto Nitinol was proven by X-ray photoelectron spectroscopy. Furthermore, the predicted improvement in the biocompatibilities of modified Nitinol was confirmed by water contact angle measurement, protein adsorption, platelet adhesion, and plasma recalcification time determination. The results of hemolysis assay, cell proliferation and cytotoxicity tests revealed that the grafting of heparin on NiTi kept the original positive performance of nitinol material. The results indicate that ALD technology is of great potential for the manufacture of medical devices, especially for surface modifications and functionalization. ALD technology can help with modifications of inert metallic surfaces and therefore benefit implantable medical devices, especially intravascular stents.

  9. Bronchobiliary Fistula Treated by Self-expanding ePTFE-Covered Nitinol Stent-Graft

    SciTech Connect

    Gandini, Roberto; Konda, Daniel Tisone, Giuseppe; Pipitone, Vincenzo; Anselmo, Alessandro; Simonetti, Giovanni

    2005-12-15

    A 71-year-old man, who had undergone right hepatectomy extended to the caudate lobe with terminolateral Roux-en-Y left hepatojejunostomy for a Klatskin tumor, developed bilioptysis 3 weeks postoperatively due to bronchobiliary fistula. Percutaneous transhepatic cholangiography revealed a non-dilated biliary system with contrast medium extravasation to the right subphrenic space through a resected anomalous right posterior segmental duct. After initial unsuccessful internal-external biliary drainage, the fistula was sealed with a VIATORR covered self-expanding nitinol stent-graft placed with its distal uncovered region in the hepatojejunal anastomosis and the proximal ePTFE-lined region in the left hepatic duct. A 10-month follow-up revealed no recurrence of bilioptysis and confirmed the complete exclusion of the bronchobiliary fistula.

  10. Self-Expanding Nitinol Renal Artery Stents: Comparison of Safety and Efficacy of Bare Versus Polyzene-F Nanocoated Stents in a Porcine Model

    SciTech Connect

    Kurz, P.; Stampfl, U.; Christoph, P.; Henn, C.; Satzl, S.; Radeleff, B.; Berger, I.; Richter, G. M.

    2011-02-15

    Objective: To investigate the safety and efficacy of a Polyzene-F nanocoat on new low-profile self-expandable nitinol stents in minipig renal arteries. Materials and Methods: Ten bare nitinol stents (BNS) and 10 stents coated with a 50 nm-thin Polyzene-F coating were randomly implanted into renal arteries of 10 minipigs (4- and 12-week follow-up, 5 animals/group). Thrombogenicity, on-stent surface endothelialization, vessel wall injury, late in-stent stenosis, and peristrut vessel wall inflammation were determined by quantitative angiography and postmortem histomorphometry. Results: In 6 of 10 BNS, >50% stenosis was found, but no stenosis was found in stents with a nanothin Polyzene-F coating. Histomorphometry showed a statistically significant (p < 0.05) different average maximum luminal loss of 55.16% {+-} 8.43% at 12 weeks in BNS versus 39.77% {+-} 7.41% in stents with a nanothin Polyzene-F coating. Stents with a nanothin Polyzene-F coating had a significantly (p < 0.05) lower inflammation score after 12 weeks, 1.31 {+-} 1.17 versus 2.17 {+-} 0.85 in BNS. The results for vessel wall injury (0.6 {+-} 0.58 for Polyzene-F-coated stents; 0.72 {+-} 0.98 for BNS) and re-endothelialization, (1.16 {+-} 0.43 and 1.23 {+-} 0.54, respectively) were not statistically significant at 12-week follow-up. No thrombus deposition was observed on the stents at either follow-up time point. Conclusion: Nitinol stents with a nanothin Polyzene-F coating successfully decreased in-stent stenosis and vessel wall inflammation compared with BNS. Endothelialization and vessel wall injury were found to be equal. These studies warrant long-term pig studies ({>=}120 days) because 12 weeks may not be sufficient time for complete healing; thereafter, human studies may be warranted.

  11. Chemical etching of nitinol stents.

    PubMed

    Katona, Bálint; Bognár, Eszter; Berta, Balázs; Nagy, Péter; Hirschberg, Kristóf

    2013-01-01

    At present the main cause of death originates from cardiovascular diseases. Primarily the most frequent cause is vessel closing thus resulting in tissue damage. The stent can help to avoid this. It expands the narrowed vessel section and allows free blood flow. The good surface quality of stents is important. It also must have adequate mechanical characteristics or else it can be damaged which can easily lead to the fracture of the implant. Thus, we have to consider the importance of the surface treatment of these implants. In our experiments the appropriate design was cut from a 1.041 mm inner diameter and 0.100 mm wall thickness nitinol tube by using Nd:YAG laser device. Then, the stent was subjected to chemical etching. By doing so, the burr created during the laser cutting process can be removed and the surface quality refined. In our research, we changed the time of chemical etching and monitored the effects of this parameter. The differently etched stents were subjected to microscopic analysis, mass measurement and in vivo environment tests. The etching times that gave suitable surface and mechanical features were identified.

  12. Chronic vascular response after self-expanding nitinol stent implantation in superficial femoral arteries: a serial intravascular ultrasound analysis.

    PubMed

    Nishimura, Machiko; Fujii, Kenichi; Fukunaga, Masashi; Kawasaki, Daizo; Miki, Kojiro; Saita, Ten; Horimatsu, Tetsuo; Tamaru, Hiroto; Imanaka, Takahiro; Naito, Yoshiro; Masuyama, Tohru

    2016-10-01

    The mechanical properties of the self-expanding nitinol stents (SENS) and chronic biological stimulation on the wall from the SENS have not been fully investigated. This study evaluated the mechanical vascular response to SENS implantation in superficial femoral artery (SFA) lesions using serial volumetric intravascular ultrasound (IVUS). Twenty-five symptomatic patients due to de novo SFA lesions scheduled for SENS placement were prospectively enrolled. Serial IVUS studies were performed immediately after crossing with a guidewire, immediately after the procedure, and at a 8-month follow-up. Serial IVUS volumetric analysis was conducted after stent deployment and at follow-up. Mean stent, lumen and neointimal areas were calculated as the volume divided by the stent length, and the calcium arc was measured. At follow-up, SENS had increased 40.6 % in overall volume. The chronic stent expansion tended to be larger, and the mean neointimal area at the 8-month follow-up was significantly larger in less calcified lesions compared to heavily calcified lesions. As a result, the mean late lumen area loss was significantly larger in lesions with calcium arcs of 0° and in the first and second quadrants than in those with calcium arcs in the third and fourth quadrants (2.8 ± 7.2, 1.3 ± 5.6, 0.6 ± 5.9, 1.2 ± 5.4, -0.8 ± 5.2 mm(2), respectively; p < 0.001). SENSs continued to enlarge with intimal proliferation over 8 months in all lesions. Although arterial calcium affected the degree of chronic stent expansion during the follow-up period, neointimal proliferation was smaller in heavily calcified lesion compared to less calcified lesion following SENS implantation.

  13. The New Nitinol Conformable Self-Expandable Metal Stents for Malignant Colonic Obstruction: A Pilot Experience as Bridge to Surgery Treatment

    PubMed Central

    2014-01-01

    Introduction. Self-expandable metal stents (SEMS) are a nonsurgical option for treatment of malignant colorectal obstruction also as a bridge to surgery approach. The new nitinol conformable stent has improved clinical outcomes in these kinds of patients. We report a pilot experience with nitinol conformable SEMS placement as bridge to surgery treatment in patients with colorectal obstruction. Materials and Methods. Between April and August 2012, we collected data on colonic nitinol conformable SEMS placement in a cohort of consecutive symptomatic patients, with malignant colorectal obstruction, who were treated as a bridge to surgery. Technical success, clinical success, and adverse events were recorded. Results. Ten patients (7 male (70%)), with a mean age of 69.2 ± 10.1, were evaluated. The mean length of the stenosis was 3.6 ± 0.6 cm. Five patients (50%) were treated on an emergency basis. The median time from stent placement to surgery was 16 days (interquartile range 7–21). Technical and clinical success was achieved in all patients with a significant early improvement of symptoms. No adverse events due to the SEMS placement were observed. Conclusion. This pilot study confirmed the important role of nitinol conformable SEMS as a bridge to surgery option in the treatment of symptomatic malignant colorectal obstruction. PMID:24526914

  14. Successful Endovascular Repair of an Iatrogenic Perforation of the Superficial Femoral Artery Using Self-Expanding Nitinol Supera Stents in a Patient with Acute Thromboembolic Limb Ischemia

    PubMed Central

    Eisele, Tom; Muenz, Benedikt M.

    2016-01-01

    The treatment of acute thromboembolic limb ischemia includes well-established surgical thrombectomy procedures and, in recent times, also percutaneous rotational thrombectomy using Straub Rotarex® system. This modality not only enables efficient treatment of such thrombotic occlusion but also in rare cases may imply the risk of perforation of the occluded artery. Herein, we report the case of a perforation of the superficial femoral artery (SFA) in an elderly female patient with thromboembolic limb ischemia. The perforation was successfully treated by implantation of self-expanding nitinol Supera stents and without the need for implantation of a stent graft. PMID:27213074

  15. Nitinol Esophageal Stents: New Designs and Clinical Indications

    SciTech Connect

    Strecker, Ernst-Peter; Boos, Irene; Vetter, Sylvia; Strohm, Michael; Domschke, Sigurd

    1996-11-15

    Purpose: To evaluate the clinical use of covered and noncovered, knitted nitinol stents in patients presenting new stent indications. Methods: Self-expandable, knitted nitinol stents were implanted in four patients for treatment of dysphagia. In two patients who had malignant strictures and had esophago-respiratory fistulae and in one patient with an esophagocutaneous fistula, polytetrafluoroethylene (PTFE)-covered stents were implanted. One patient received a noncovered stent, but a retrograde approach through a percutaneous endoscopic gastrostomy (PEG) fistula had to be chosen for recanalization of an esophageal occlusion. Two patients received stents for treatment of benign strictures. Results: Recanalization of the stricture and stent implantation were performed under fluoroscopic control without any procedure-related morbidity or mortality. Dysphagia improved in all patients and the esophageal fistulae could be sealed off by covered stents. During a maximum follow-up of 18 months, there was no stent migration or esophageal perforation. Complications observed were stent stenosis due to food impaction (1/4) and benign stent stenosis (2/2). Most complications could be treated by the interventional radiologist. Conclusion: Self-expandable, covered Nitinol stents provide an option for the treatment of dysphagia combined with esophageal fistulae. In combination with interventional radiology techniques, even complex strictures are accessible. For benign strictures, the value of stent treatment has not yet been proven.

  16. On the role of SMA modeling in simulating NiTinol self-expanding stenting surgeries to assess the performance characteristics of mechanical and thermal activation schemes.

    PubMed

    Saleeb, A F; Dhakal, B; Owusu-Danquah, J S

    2015-09-01

    The work is focused on a detailed simulation of the key stages involved in the NiTinol self-expanding stenting surgical procedure; i.e., crimping, deployment, SMA activation, as well as post-surgery steady-state cyclic behavior mimicking the systolic-to-diastolic pressure oscillations. To this end, a general multi-mechanism SMA model was utilized, whose calibration was completed using the test data from simple isothermal uniaxial tension experiments. The emphasis in the study was placed on the comparison of two alternative SMA activation protocols, in terms of both the immediate and long-term (post-surgery) performance characteristics. The first is 'hard' mechanical activation utilizing superelasticity, and the second is 'soft' thermal activation relying upon the combined one-way shape memory effect and constrained-recovery characteristics of the NiTinol material. The important findings are (1) the thermal activation protocol is far superior compared to the mechanical counterpart, from the point of view of lower magnitudes of the induced outward chronic forces, lesser developed stresses in the host tissue, as well as higher compression ratio with lesser crimping force for the same geometry of initial stent memory configuration, (2) the thermal activation protocol completely bypassed the complications of maintaining the high restraining force during deployment of the stent, and (3) there is no indication of any detrimental functional fatigue/degradation in the cured stenotic artery during cyclic pressure oscillations.

  17. Measurement and Comparison of Mechanical Properties of Nitinol Stents

    NASA Astrophysics Data System (ADS)

    Hanus, Josef; Zahora, Jiri

    2005-01-01

    The self expandable Nitinol stents or stentgrafts are typically used for miniinvasive treatment of stenosis and aneurysms in the cardiovascular system. The minimal traumatisation of the patient, shorter time of hospitalization are typical advantages of these methods. More than ten years of experience has yielded also important information about the performance of stents in interaction with biological system and the possible problems related with it. The leakage or the shift of stent are some typical disadvantages, that can be related among other in the construction of the stent. The problem is that the mechanical properties, dimensions and the dynamical properties of the stent do not exactly correspond to the properties of the vessel or generally of tissue where this stent is introduced. The measurement, the description and the comparison of the relations between the mechanical properties of stents and tissues can be one of the possible ways to minimize these disadvantages. The developed original computer controlled measuring system allows the measurement of mechanical properties of stents, the measurement of strain-stress curves or simulation of interaction of the stent and vessel for exactly defined hemodynamic conditions. We measured and compared the mechanical parameters of different selfexpandable Nitinol stents, which differed in geometry (radius and length), in the type of construction (number of branches and rising of winding) and in the diameter of used wire. The results of measurements confirmed the theoretical assumptions that just the diameter of the Nitinol wire significantly influences the rigidity and the level of compressibility of the stent as well. A compromise must be found between the required rigidity of the stent and the minimal size of the delivery system. The exact description of the relation between the mechanical properties and geometry and construction of the stents enables to design the stent to fit the patient and it is expected that

  18. Nitinol Stent Fatigue in a Peripheral Human Artery Subjected to Pulsatile and Articulation Loading

    NASA Astrophysics Data System (ADS)

    Harvey, Sean Michael

    2011-07-01

    Nitinol self-expanding stents are used to treat peripheral occluded vessels such as the superficial femoral artery or the carotid. The complex vessel articulation requires a stent device that is flexible and kink resistant yet durable. The present study shows how the latest advances in commercially available engineering software tools permit engineering simulations of the many aspects of the Nitinol stent design and analysis. Two stent geometries are evaluated: a helical type stent design, and a more traditional straight strut, with multiple crowns design. The fatigue performance of the two stents is compared. The results show that advanced nonlinear finite element simulations and fatigue predictions of the Nitinol stent are possible today inside realistic simulated human arteries. The finite element analysis software used in this study is SimXpert, Marc, and Mentat (MSC Software, Santa Ana, CA).

  19. Late Stent Expansion and Neointimal Proliferation of Oversized Nitinol Stents in Peripheral Arteries

    SciTech Connect

    Zhao, Hugh Q. Nikanorov, Alexander; Virmani, Renu; Jones, Russell; Pacheco, Erica; Schwartz, Lewis B.

    2009-07-15

    For peripheral endovascular intervention, self-expanding (SE) stents are commonly oversized in relation to target arteries to assure optimal wall apposition and prevent migration. However, the consequences of oversizing have not been well studied. The purpose of this study was to examine the effects of SE stent oversizing (OS) with respect to the kinetics of late stent expansion and the long-term histological effects of OS. Pairs of overlapped 8 x 28-mm Nitinol SE stents were implanted into the iliofemoral arteries of 14 Yucatan swine. Due to variations in target artery size, the stent-to-artery ratio ranged from 1.2:1 to 1.9:1. Lumen and stent diameters were assessed by quantitative angiography at the time of implantation. Following angiographic assessment at 6 months, stented arteries were perfusion-fixed, sectioned, and stained for histological analysis. Immediately following implantation, the stents were found to be expanded to a range of 4.7-7.1 mm, largely conforming to the diameter of the recipient target artery. The stents continued to expand over time, however, and all stents had enlarged to nearly their 8-mm nominal diameter by 6 months. The histological effects of OS were profound, with marked increases in injury and luminal area stenosis, including a statistically significant linear correlation between stent-to-artery ratio and area stenosis. In this experimental model of peripheral endovascular intervention, oversized Nitinol SE stents are constrained by their target artery diameter upon implantation but expand to their nominal diameter within 6 months. Severe OS (stent-to-artery ratio >1.4:1) results in a profound long-term histological response including exuberant neointimal proliferation and luminal stenosis.

  20. Computational Study of Axial Fatigue for Peripheral Nitinol Stents

    NASA Astrophysics Data System (ADS)

    Meoli, Alessio; Dordoni, Elena; Petrini, Lorenza; Migliavacca, Francesco; Dubini, Gabriele; Pennati, Giancarlo

    2014-07-01

    Despite their success as primary treatment for vascular diseases, Nitinol peripheral stents are still affected by complications related to fatigue failure. Hip and knee movements during daily activities produce large and cyclic deformations of the superficial femoral artery, that concomitant to the effects of pulsatile blood pressure, may cause fatigue failure in the stent. Fatigue failure typically occurs in cases of very extended lesions, which often require the use of two or more overlapping stents. In this study, finite element models were used to study the fatigue behavior of Nitinol stents when subjected to cyclic axial compression in different conditions. A specific commercial Nitinol stent was chosen for the analysis and subjected to cyclic axial compression typical of the femoral vascular region. Three different configurations were investigated: stent alone, stent deployed in a tube, and two overlapping stents deployed in a tube. Results confirm that stent oversizing has an influence in determining both the mean and amplitude strains induced in the stent and plays an important role in determining the fatigue response of Nitinol stents. In case of overlapping stents, numerical results suggest higher amplitude strains concentrate in the region close to the overlapping portion where the abrupt change in stiffness causes higher cyclic compression. These findings help to explain the high incidence of stent fractures observed in various clinical trials located close to the overlapping portion.

  1. Comparison of diamond-like carbon-coated nitinol stents with or without polyethylene glycol grafting and uncoated nitinol stents in a canine iliac artery model

    PubMed Central

    Kim, J H; Shin, J H; Shin, D H; Moon, M-W; Park, K; Kim, T-H; Shin, K M; Won, Y H; Han, D K; Lee, K-R

    2011-01-01

    Objective Neointimal hyperplasia is a major complication of endovascular stent placement with consequent in-stent restenosis or occlusion. Improvements in the biocompatibility of stent designs could reduce stent-associated thrombosis and in-stent restenosis. We hypothesised that the use of a diamond-like carbon (DLC)-coated nitinol stent or a polyethylene glycol (PEG)-DLC-coated nitinol stent could reduce the formation of neointimal hyperplasia, thereby improving stent patency with improved biocompatibility. Methods A total of 24 stents were implanted, under general anaesthesia, into the iliac arteries of six dogs (four stents in each dog) using the carotid artery approach. The experimental study dogs were divided into three groups: the uncoated nitinol stent group (n = 8), the DLC-nitinol stent group (n = 8) and the PEG-DLC-nitinol stent group (n = 8). Results The mean percentage of neointimal hyperplasia was significantly less in the DLC-nitinol stent group (26.7±7.6%) than in the nitinol stent group (40.0±20.3%) (p = 0.021). However, the mean percentage of neointimal hyperplasia was significantly greater in the PEG-DLC-nitinol stent group (58.7±24.7%) than in the nitinol stent group (40.0±20.3%) (p = 0.01). Conclusion Our findings indicate that DLC-coated nitinol stents might induce less neointimal hyperplasia than conventional nitinol stents following implantation in a canine iliac artery model; however, the DLC-coated nitinol stent surface when reformed with PEG induces more neointimal hyperplasia than either a conventional or DLC-coated nitinol stent. PMID:21325363

  2. On the Mechanical Properties and Microstructure of Nitinol forBiomedical Stent Applications

    SciTech Connect

    Robertson, Scott W.

    2006-01-01

    This dissertation was motivated by the alarming number of biomedical device failures reported in the literature, coupled with the growing trend towards the use of Nitinol for endovascular stents. The research is aimed at addressing two of the primary failure modes in Nitinol endovascular stents: fatigue-crack growth and overload fracture. The small dimensions of stents, coupled with their complex geometries and variability among manufacturers, make it virtually impossible to determine generic material constants associated with specific devices. Instead, the research utilizes a hybrid of standard test techniques (fracture mechanics and x-ray micro-diffraction) and custom-designed testing apparatus for the determination of the fracture properties of specimens that are suitable representations of self-expanding Nitinol stents. Specifically, the role of texture (crystallographic alignment of atoms) and the austenite-to-martensite phase transformation on the propagation of cracks in Nitinol was evaluated under simulated body conditions and over a multitude of stresses and strains. The results determined through this research were then used to create conservative safe operating and inspection criteria to be used by the biomedical community for the determination of specific device vulnerability to failure by fracture and/or fatigue.

  3. Corrosion resistance of polyurethane-coated nitinol cardiovascular stents.

    PubMed

    Mazumder, M M; De, S; Trigwell, S; Ali, N; Mazumder, M K; Mehta, J L

    2003-01-01

    Corrosion of metal stents implanted inside an artery can have two adverse effects: (1) tissue reaction and possible toxic effects from the metal ions leaching out of the stent, and (2) loss of mechanical strength of the stent caused by corrosion. The corrosion resistance of Nitinol (Nickel-Titanium) stents and its modulation with different film thickness of polymer coating was studied against an artificial physiological solution using a Potentiostat/Galvanostat and an electrochemical corrosion cell. The corrosion rate decreased rapidly from 275 microm/year for an uncoated surface down to less than 13 microm/year for a 30 microm thick polyurethane coating. Stainless steel (316L) and Nitinol both contain potentially toxic elements, and both are subject to stress corrosion. Minimization of corrosion can significantly reduce both tissue reaction and structural degradation.

  4. Neointimal Hyperplasia in Low-Profile Nitinol Stents, Palmaz Stents, and Wallstents: A Comparative Experimental Study

    SciTech Connect

    Schuermann, Karl; Vorwerk, Dierk; Kulisch, Arthur; Stroehmer-Kulisch, Eva; Biesterfeld, Stefan; Stopinski, Tadeusz; Guenther, Rolf W.

    1996-04-15

    Purpose: To compare neointima formation following insertion of low-profile Nitinol stents, Palmaz stents, and Wallstents. Methods: Nitinol stents, Palmaz stents, and Wallstents similar in size were transfemorally inserted into the iliac arteries of 12 sheep. Four stents per sheep were deployed; the position of the stents was varied so that each type of stent was placed in each position (right or left, proximal or distal) with equal frequency. Stent patency was followed by angiography. Six sheep were euthanized after 1 month, and the remaining six after 6 months. Iliac arteries were removed en bloc and prepared for histological examination. Neointimal and medial thickness were measured by light microscopy, and measurements were analyzed statistically. Results: Mean neointimal thickness both over (NO) and between (NB) the stent struts was greater in Wallstents (NO = 0.341 mm, NB = 0.368 mm) than in the Nitinol (NO = 0.260 mm, NB = 0.220 mm) and Palmaz stents (NO = 0.199 mm, NB = 0.204 mm), but differences were not significant (p> 0.05). Medial atrophy in the area between the stent struts was greater in Wallstents compared with Nitinol and Palmaz stents (p < 0.007 and p < 0.02, respectively); in the area under the stent struts there was a significant difference only between Palmaz stents and Wallstents (p < 0.02). Conclusion: Under defined experimental conditions, none of the three types of stent appears to be preferable to the others regarding neointima formation in the short- to mid-term follow-up period.

  5. Percutaneous Palliation of Pancreatic Head Cancer: Randomized Comparison of ePTFE/FEP-Covered Versus Uncovered Nitinol Biliary Stents

    SciTech Connect

    Krokidis, Miltiadis; Fanelli, Fabrizio; Orgera, Gianluigi; Tsetis, Dimitrios; Mouzas, Ioannis; Bezzi, Mario; Kouroumalis, Elias; Pasariello, Roberto; Hatzidakis, Adam

    2011-04-15

    The purpose of this study was to compare the clinical effectiveness of expanded polytetrafluoroethylene/fluorinated-ethylene-propylene (ePTFE/FEP)-covered stents with that of uncovered nitinol stents for the palliation of malignant jaundice caused by inoperable pancreatic head cancer. Eighty patients were enrolled in a prospective randomized study. Bare nitinol stents were used in half of the patients, and ePTFE/FEP-covered stents were used in the remaining patients. Patency, survival, complications, and mean cost were calculated in both groups. Mean patency was 166.0 {+-} 13.11 days for the bare-stent group and 234.0 {+-} 20.87 days for the covered-stent group (p = 0.007). Primary patency rates at 3, 6, and 12 months were 77.5, 69.8, and 69.8% for the bare-stent group and 97.5, 92.2, and 87.6% for the covered-stent group, respectively. Mean secondary patency was 123.7 {+-} 22.5 days for the bare-stent group and 130.3 {+-} 21.4 days for the covered-stent group. Tumour ingrowth occurred exclusively in the bare-stent group in 27.5% of cases (p = 0.002). Median survival was 203.2 {+-} 11.8 days for the bare-stent group and 247.0 {+-} 20 days for the covered-stent group (p = 0.06). Complications and mean cost were similar in both groups. Regarding primary patency and ingrowth rate, ePTFE/FEP-covered stents have shown to be significantly superior to bare nitinol stents for the palliation of malignant jaundice caused by inoperable pancreatic head cancer and pose comparable cost and complications. Use of a covered stent does not significantly influence overall survival rate; nevertheless, the covered endoprosthesis seems to offer result in fewer reinterventions and better quality of patient life.

  6. Fatigue-crack growth properties of thin-walled superelastic austenitic Nitinol tube for endovascular stents.

    PubMed

    Stankiewicz, J M; Robertson, S W; Ritchie, R O

    2007-06-01

    Over the past 10 years, the supereleastic nickel-titanium alloy Nitinol has found widespread application in the manufacture of small-scale biomedical devices, such as self-expanding endovascular stents. Although conventional stress/strain-life (S/N) analyses are invariably used as the primary method for design against fatigue loading and for predicting safe lifetimes, fracture mechanics-based methodologies provide a vital means of assessing the quantitative effect of defects on such lifetimes. Unfortunately, fracture mechanics studies on fatigue in Nitinol are scarce, and most results do not pertain to the (thin-walled tube) product forms that are typically used in the manufacture of endovascular stents. In the current work, we document the basic fatigue-crack growth properties of flattened thin-walled ( approximately 400 microm thick) Nitinol tubing in a 37 degrees C air environment. Crack-growth behavior is characterized over a wide range of growth rates ( approximately 6 orders of magnitude) and load ratios, that is, as a function of the alternating and maximum stress intensities, at 50 Hz. Limited experiments at both 5 and 50 Hz were also performed in 37 degrees C air and simulated body fluid to determine whether the cyclic frequency affects the fatigue behavior. Fatigue-crack growth-rate properties in such thin-walled Nitinol tube are found to be quite distinct from limited published data on other (mainly bulk) product forms of Nitinol, for example, bar and strip, both in terms of the relative fatigue thresholds and the variation in steady-state growth rates.

  7. Treatment of a Ruptured Anastomotic Esophageal Stricture Following Bougienage with a Dacron-Covered Nitinol Stent

    SciTech Connect

    Heindel, Walter; Gossmann, Axel; Fischbach, Roman; Michel, Olaf; Lackner, Klaus

    1996-11-15

    A patient suffering from esophagorespiratory fistula after bougienage of a benign stricture at the site of the anastomosis between a jejunal interposition and the esophagus was referred for interventional treatment. A prototype nitinol stent centrally covered with Dacron was implanted under regional anesthesia and fluoroscopic guidance. The self-expanding prosthesis dilated the stenosis completely and closed the fistula, with consequent improvement in respiratory and nutritional status and thus the general quality of life. The patient was able to eat and drink normally until death 3 months later due to progression of his underlying malignant disease.

  8. Double-Layered PTFE-Covered Nitinol Stents: Experience in 32 Patients with Malignant Esophageal Strictures

    SciTech Connect

    Park, Jung Gu; Jung, Gyoo-Sik Oh, Kyung Seung; Park, Seon-Ja

    2010-08-15

    We evaluated the effectiveness of a double-layered polytetrafluoroethylene (PTFE)-covered nitinol stent in the palliative treatment of malignant esophageal strictures. A double-layered PTFE-covered nitinol stent was designed to reduce the propensity to migration of conventional covered stent. The stent consists of an inner PTFE-covered stent and an outer uncovered nitinol stent tube. With fluoroscopic guidance, the stent was placed in 32 consecutive patients with malignant esophageal strictures. During the follow-up period, the technical and clinical success rates, complications, and cumulative patient survival and stent patency were evaluated. Stent placement was technically successful in all patients, and no procedural complications occurred. After stent placement, the symptoms of 30 patients (94%) showed improvement. During the mean follow-up of 103 days (range, 9-348 days), 11 (34%) of 32 patients developed recurrent symptoms due to tumor overgrowth in five patients (16%), tumor ingrowth owing to detachment of the covering material (PTFE) apart from the stent wire in 3 (9%), mucosal hyperplasia in 2 (6%), and stent migration in 1 (3%). Ten of these 11 patients were treated by means of placing a second covered stent. Thirty patients died, 29 as a result of disease progression and 1 from aspiration pneumonia. The median survival period was 92 days. The median period of primary stent patency was 190 days. The double-layered PTFE-covered nitinol stent seems to be effective for the palliative treatment of malignant esophageal strictures. We believe that the double-layer configuration of this stent can contribute to decreasing the stent's migration rate.

  9. Nitinol Stent Oversizing in Patients Undergoing Popliteal Artery Revascularization: A Finite Element Study.

    PubMed

    Gökgöl, Can; Diehm, Nicolas; Nezami, Farhad Rikhtegar; Büchler, Philippe

    2015-12-01

    Nitinol stent oversizing is frequently performed in peripheral arteries to ensure a desirable lumen gain. However, the clinical effect of mis-sizing remains controversial. The goal of this study was to provide a better understanding of the structural and hemodynamic effects of Nitinol stent oversizing. Five patient-specific numerical models of non-calcified popliteal arteries were developed to simulate the deployment of Nitinol stents with oversizing ratios ranging from 1.1 to 1.8. In addition to arterial biomechanics, computational fluid dynamics methods were adopted to simulate the physiological blood flow inside the stented arteries. Results showed that stent oversizing led to a limited increase in the acute lumen gain, albeit at the cost of a significant increase in arterial wall stresses. Furthermore, localized areas affected by low Wall Shear Stress increased with higher oversizing ratios. Stents were also negatively impacted by the procedure as their fatigue safety factors gradually decreased with oversizing. These adverse effects to both the artery walls and stents may create circumstances for restenosis. Although the ideal oversizing ratio is stent-specific, this study showed that Nitinol stent oversizing has a very small impact on the immediate lumen gain, which contradicts the clinical motivations of the procedure.

  10. In vitro and in vivo testing of a novel, hyperelastic thin film nitinol flow diversion stent.

    PubMed

    Kealey, C P; Chun, Y J; Viñuela, F E; Mohanchandra, K P; Carman, G P; Viñuela, F; Levi, D S

    2012-04-01

    A flexible, low profile, flow diversion stent could replace endovascular coiling for the treatment of intracranial aneurysms. Micropatterned-thin film nitinol (TFN) is a novel biomaterial with high potential for use in next-generation endovascular devices. Recent advancements in micropatterning have allowed for fabrication of a hyperelastic thin film nitinol (HE-TFN). In this study, the authors describe in vitro and in vivo testing of novel HE-TFN based flow diverting stents. Two types of HE-TFN with expanded pores having long axes of 300 and 500 μm were used to fabricate devices. In vitro examination of the early thrombotic response in whole blood showed a possible mechanism for the device's function, whereby HE-TFN serves as a scaffold for blood product deposition. In vivo testing in swine demonstrated rapid occlusion of model wide-neck aneurysms. Average time to occlusion for the 300-μm device was 10.4 ± 5.5 min. (N = 5) and 68 ± 30 min for the 500-μm device (N = 5). All aneurysms treated with bare metal control stents remained patent after 240 min (N = 3). SEM of acutely harvested devices supported in vitro results, demonstrating that HE-TFN serves as a scaffold for blood product deposition, potentially enhancing its flow-diverting effect. Histopathology of devices after 42 days in vivo demonstrated a healthy neointima and endothelialization of the aneurysm neck region. HE-TFN flow-diverting stents warrant further investigation as a novel treatment for intracranial aneurysms.

  11. Crush implantation of a self-expanding interwoven stent over a subintimally recanalized standard stent in a TASC D lesion of the superficial femoral artery.

    PubMed

    Vogel, B; Strothmeyer, A; Cebola, R; Katus, H; Blessing, E

    2012-11-01

    We demonstrate feasibility of implantation of a self-expanding interwoven nitinol stent in a claudicant, where recanalization attempt of a heavily calcified, occluded superficial femoral artery (TASC D lesion) was complicated by a previously implanted, fractured standard stent. Wire passage through the occlusion and beyond the fractured stent could only be achieved through the subintimal space. A dedicated reentry device was used to allow distal wire entry into the true lumen at the level of the popliteal artery. Despite crushing of the fractured stent with a series of increasingly sized standard balloons, a significant recoil remainded in the area of the crushed stent. To secure patency of the femoro-popliteal artery we therefore decided to implant the novel self-expanding interwoven nitinol stent (Supera Veritas (TM), IDEV), whose unique feature is an exceptional high radial strength. Patient presented asymptomatic without any impairment of his walking capacity at three month follow up and duplex ultrasound confirmed patency of the stent. Subintimal recanalizations can be complicated by previously implanted stents, in particular in the presence of stent fracture, where intraluminal wire passage often can not be achieved. Considering the high radial strength and fracture resistance, interwoven nitinol stents represent a good treatment option in those challenging cases and they can be used to crush standard nitinol and ballonexpandable stents. PMID:23129042

  12. Endovascular Treatment of a Giant Superior Mesenteric Artery Pseudoaneurysm Using a Nitinol Stent-Graft

    SciTech Connect

    Gandini, Roberto; Pipitone, Vincenzo; Konda, Daniel Pendenza, Gianluca; Spinelli, Alessio; Stefanini, Matteo; Simonetti, Giovanni

    2005-01-15

    A 68-year-old woman presenting with gastrointestinal bleeding (hematocrit 19.3%) and in a critical clinical condition (American Society of Anesthesiologists grade 4) from a giant superior mesenteric artery pseudoaneurysm (196.0 x 131.4 mm) underwent emergency endovascular treatment. The arterial tear supplying the pseudoaneurysm was excluded using a 5.0 mm diameter and 31 mm long monorail expanded polytetrafluoroethylene (ePTFE)-covered self-expanding nitinol stent. Within 6 days of the procedure, a gradual increase in hemoglobin levels and a prompt improvement in the clinical condition were observed. Multislice CT angiograms performed immediately, 5 days, 30 days and 3 months after the procedure confirmed the complete exclusion of the pseudoaneurysm.

  13. Finite element modeling of a progressively expanding shape memory stent.

    PubMed

    Thériault, Philippe; Terriault, Patrick; Brailovski, Vladimir; Gallo, Richard

    2006-01-01

    Cardiovascular stents are small cylindrical devices introduced in stenosed arteries to reopen the lumen and restore blood flow. However, this treatment presents complications, including restenosis, which is the reclosing of the artery's diameter after the insertion of a stent. The structure of the prosthesis penetrates into and injures the walls of the patient's artery. There then follows a proliferation of cells and the formation of scar tissue around the injury, similar to the scarring of other organic tissues. This reaction to the trauma subjects the artery to close. The proposed solution is to develop a Nitinol stent with a progressive expansion device made of polyethylene, allowing smooth and gradual contact between the stent and the artery's wall by creep effect. The purpose of this paper is to describe the technology and methodology for the numerical study of this kind of stent through the finite element method. ANSYS 8.0 software is used to perform the analysis. The Nitinol is modeled with a superelastic law and the polyethylene with a yield hardening law. A first simulation determines the final geometry of the stent laser cut from a small tube. A second simulation examines the behavior of the prosthesis during surgery and over the 4 weeks following the operation. The results demonstrate that a compromise can be reached between a limited expansion prior the inflation of the expandable balloon and a significant expansion by creep of the polymer rings.

  14. Endoscopic management of unresectable malignant gastroduodenal obstruction with a nitinol uncovered metal stent: A prospective Japanese multicenter study

    PubMed Central

    Sasaki, Reina; Sakai, Yuji; Tsuyuguchi, Toshio; Nishikawa, Takao; Fujimoto, Tatsuya; Mikami, Shigeru; Sugiyama, Harutoshi; Yokosuka, Osamu

    2016-01-01

    AIM: To determine the safety and efficacy of endoscopic duodenal stent placement in patients with malignant gastric outlet obstruction. METHODS: This prospective, observational, multicenter study included 39 consecutive patients with malignant gastric outlet obstruction. All patients underwent endoscopic placement of a nitinol, uncovered, self-expandable metal stent. The primary outcome was clinical success at 2 wk after stent placement that was defined as improvement in the Gastric Outlet Obstruction Scoring System score relative to the baseline. RESULTS: Technical success was achieved in all duodenal stent procedures. Procedure-related complications occurred in 4 patients (10.3%) in the form of mild pneumonitis. No other morbidities or mortalities were observed. The clinical success rate was 92.3%. The mean survival period after stent placement was 103 d. The mean period of stent patency was 149 d and the patency remained acceptable for the survival period. Stent dysfunction occurred in 3 patients (7.7%) on account of tumor growth. CONCLUSION: Endoscopic management using duodenal stents for patients with incurable malignant gastric outlet obstruction is safe and improved patients’ quality of life. PMID:27076769

  15. Statistical characteristics of surface integrity by fiber laser cutting of Nitinol vascular stents

    NASA Astrophysics Data System (ADS)

    Fu, C. H.; Liu, J. F.; Guo, Andrew

    2015-10-01

    Nitinol alloys have been widely used in manufacturing of vascular stents due to the outstanding properties such as superelasticity, shape memory, and superior biocompatibility. Laser cutting is the dominant process for manufacturing Nitinol stents. Conventional laser cutting usually produces unsatisfactory surface integrity which has a significant detrimental impact on stent performance. Emerging as a competitive process, fiber laser with high beam quality is expected to produce much less thermal damage such as striation, dross, heat affected zone (HAZ), and recast layer. To understand the process capability of fiber laser cutting of Nitinol alloy, a design-of-experiment based laser cutting experiment was performed. The kerf geometry, roughness, topography, microstructure, and hardness were studied to better understand the nature of the HAZ and recast layer in fiber laser cutting. Moreover, effect size analysis was conducted to investigate the relationship between surface integrity and process parameters.

  16. Polyurethane-Covered Nitinol Strecker Stents as Primary Palliative Treatment of Malignant Biliary Obstruction

    SciTech Connect

    Kanasaki, Shuzo; Furukawa, Akira; Kane, Teruyuki; Murata, Kiyoshi

    2000-03-15

    Purpose: To evaluate the clinical efficacy of the polyurethane-covered Nitinol Strecker stent in the treatment of patients with malignant biliary obstruction.Methods: Twenty-three covered stents produced by us were placed in 18 patients with malignant biliary obstruction. Jaundice was caused by cholangiocarcinoma (n = 5), pancreatic cancer (n = 6), gallbladder cancer (n = 4), metastatic lymph nodes (n = 2), and tumor of the papilla (n 1).Results: The mean patency period of the stents was 37.5 weeks (5-106 weeks). Recurrent obstructive jaundice occurred in two patients (11%). Adequate biliary drainage over 50 weeks or until death was achieved in 17 of 18 patients (94.4%). Late cholangitis was observed in two patients whose stents bridged the ampulla of Vater. Other late severe complications were not encountered.Conclusion: Although more study is necessary, our results suggest the clinical efficacy of our covered Nitinol Strecker stent in the management of obstructive jaundice caused by malignant diseases.

  17. Biomedical engineering in design and application of nitinol stents with shape memory effect

    NASA Astrophysics Data System (ADS)

    Ryklina, E. P.; Khmelevskaya, I. Y.; Morozova, Tamara V.; Prokoshkin, S. D.

    1996-04-01

    Our studies in the field of endosurgery in collaboration with the physicians of the National Research Center of Surgery of the Academy of Medical Sciences are carried out beginning in 1983. These studies laid the foundation for the new direction of X-ray surgery--X-ray Nitinol stenting of vessels and tubular structures. X-ray nitinol stents are unique self-fixing shells based on the shape memory effect and superelasticity of nickel-titanium alloys self- reconstructed under human body temperature. Applied for stenting of arteries in cases of stenosis etc., bile ducts in cases of benign and malignant stenoses, digestive tract in cases of oesophageal cancer and cervical canal uterus in cases of postsurgical atresiss and strictures of uterine. The purpose of stenting is restoration of the shape of artery or tubular structure by a cylinder frame formation. The especially elaborated original method of stenting allows to avoid the traditional surgical operation, i.e. the stenting is performed without blood, narcosis and surgical knife. The stent to be implanted is transported into the affected zone through the puncture under the X-ray control. Clinical applications of X-ray endovascular stenting has been started in March 1984. During this period nearly 400 operations on stenting have been performed on femoral, iliac, brachio-cephalic, subclavian arteries, bile ducts, tracheas, digestive tract and cervical canal uterus.

  18. Carotid Artery Stenting Using a Novel Self-Expanding Braided Nickel-Titanium Stent: Feasibility and Safety Porcine Trial

    SciTech Connect

    Ahlhelm, Frank Kaufmann, Ralf; Ahlhelm, Dirk Ong, Mai Fang; Roth, Christian Reith, Wolfgang

    2009-09-15

    We studied the deliverability and safety of a braided, self-expanding, closed-cell nickel-titanium (NiTi) stent (E-volution, Jotec GmbH, Hechingen, Germany) especially designed for the endovascular treatment of carotid artery bifurcation stenosis with special regard to in-stent stenosis and thrombosis compared with a laser-cut reference nitinol stent in a porcine model of percutaneous vascular interventions. We aimed to assess histopathologic response in minipig carotid and subclavian arteries. Eight minipigs received a total of 42 stents: 14 reference stents and 28 E-volution stents. Eleven of the E-volution stents were additionally coated with heparin. Control angiography was obtained immediately before and after vascular intervention as well as 4 weeks after the procedure. Primary endpoints were 28 days of angiographic analyses as well as histomorphometric analysis, including injury score, inflammation score, luminal diameter, vessel diameter, maximal neointimal thickness, and area of in-stent stenosis. Secondary end points were procedural success, 28-day mortality, and stent thrombosis. All stents could be delivered successfully without procedural complications, morbidity, or mortality during our observation time. As confirmed by histology, no in-stent thrombosis was observed. Compared with common carotid arteries, subclavian arteries are significantly more vulnerable to developing in-stent stenosis caused by neointima proliferation (p < 0.05). Compared with the use of 1 single stent/artery, serial application of two stents leads to a more excessive but not significantly different neointimal proliferation (p > 0.05). The E-volution stent, especially when heparin coated, is in line with the comparison to the laser-cut reference stent displaying similar results of angiographic, histologic, and histomorphometric analyses (p > 0.05). Compared with the reference laser-cut stent, the self-expanding nitinol stent (E-volution) with its advanced braiding technology is

  19. A Novel Thin Film Nitinol Covered Neurovascular Stent Significantly Decreases Intra-Aneurysmal Flow In Vitro

    NASA Astrophysics Data System (ADS)

    Chun, Youngjae; Hur, Soojung; Shayan, Mahdis; Kealey, Colin; Levi, Daniel; Mohanchandra, Kp; di Carlo, Dino; Carman, Gregory

    2013-11-01

    A novel thin film nitinol (TFN) stent has been developed to promote aneurysm quiescence by diminishing flow across the aneurysm's neck. Laboratory aneurysm models were used to assess the flow changes produced by stents covered with different patterns of TFN. Flow diversion stents were constructed by covering Wingspan stents (Boston Scientific, DxL:4x20mm) with TFNs (i.e., 77 and 82 percent porosity). The flow changes that occur after deployment of two different porous TFN covered stent in intracranial aneurysm models were evaluated in vitro. The 82 percent porous TFN covered stent reduced the intra-aneurysmal mean flow velocity by 86.42 percent, while a 77 percent porous TFN covered stent reduced to intra-aneurysmal mean flow velocity to 93.44 percent compared to a nonstented model. Local wall shear rates were also significantly reduced in wide-neck aneurysm model (i.e., 97.52 - 98.92 percent) with TFN stent placement. The results showed that TFN covered stents significantly reduced intra-aneurysmal flow velocity magnitudes and local wall shear rates. This suggests that TFN covered stents with both 77 and 82 percent porosity have great potential to promote thrombosis in both wide-necked and fusiform aneurysm sacs.

  20. Polyorethaoe-covered nitinol strecker stents as primary palliative treatment of malignant biliary obstruction

    SciTech Connect

    Kanasaki, Shuzo; Furukawa, Akira; Kane, Teruyuki; Murata, Kiyoshi

    2000-03-15

    Purpose: To evaluate the clinical efficacy of the polyure-thane-covered Nitinol Strecker stent in the treatment of patients with malignant biliary obstruction.Methods: Twenty-three covered stents produced by us were placed in 18 patients with malignant biliary obstruction. Jaundice was caused by cholangiocarcinoma (n=5), pancreatic Cancer (n=6), gallbladder Cancer (n=4), metastatic lymph nodes (n=2), and tumor of the papilla (n=1).Resulrs: The mean patency period of the Stents was 37.5 weeks (5-106 weeks). Recurrent obstructive jaundice occurred in two patients (11%). Adequate biliary drainage over 50 weeks or until death was achieved in 17 of 18 patients (94.4%). Late cholangitis was observed in two patients whose stents bridged the ampulla of Vater. Other late severe complications were not encountered.Conclusion: Although more study is necessary, our results suggest the clinical efficacy of our covered Nitinol Strecker stent in the management of obstructive jaundice caused by malignant diseases.

  1. Effect of laser polishing on the surface roughness and corrosion resistance of Nitinol stents.

    PubMed

    Park, Chan-Hee; Tijing, Leonard D; Pant, Hem Raj; Kim, Cheol Sang

    2015-01-01

    In this paper, we investigated the effect of laser polishing at different treatment times on the surface roughness and corrosion resistance of a biliary nickel-titanium (NiTi or Nitinol) stent. A specific area of the stent wire surface was checked for changes in roughness by scanning electron microscopy (SEM) and a noncontact profilometer. The corrosion resistance was assessed by potentiodynamic polarization test and electrochemical impedance spectroscopy. The surface characterization revealed that laser polishing reduced the surface roughness of stent by 34-64% compared to that of the as-received stent surface condition depending on the treatment time (i.e., 700-1600 μm). Measurements using potentiodynamic polarization in simulated body fluid solution showed better anti-corrosion performance of laser-polished stent compared to magnetically-polished stent and has comparable corrosion resistance with the as-received stent condition. In this paper, we have shown a preliminary study on the potential of laser polishing for the improvement of surface roughness of stent without affecting much its corrosion resistance. PMID:25585981

  2. Effect of laser polishing on the surface roughness and corrosion resistance of Nitinol stents.

    PubMed

    Park, Chan-Hee; Tijing, Leonard D; Pant, Hem Raj; Kim, Cheol Sang

    2015-01-01

    In this paper, we investigated the effect of laser polishing at different treatment times on the surface roughness and corrosion resistance of a biliary nickel-titanium (NiTi or Nitinol) stent. A specific area of the stent wire surface was checked for changes in roughness by scanning electron microscopy (SEM) and a noncontact profilometer. The corrosion resistance was assessed by potentiodynamic polarization test and electrochemical impedance spectroscopy. The surface characterization revealed that laser polishing reduced the surface roughness of stent by 34-64% compared to that of the as-received stent surface condition depending on the treatment time (i.e., 700-1600 μm). Measurements using potentiodynamic polarization in simulated body fluid solution showed better anti-corrosion performance of laser-polished stent compared to magnetically-polished stent and has comparable corrosion resistance with the as-received stent condition. In this paper, we have shown a preliminary study on the potential of laser polishing for the improvement of surface roughness of stent without affecting much its corrosion resistance.

  3. Fatigue behaviour of Nitinol peripheral stents: the role of plaque shape studied with computational structural analyses.

    PubMed

    Dordoni, Elena; Meoli, Alessio; Wu, Wei; Dubini, Gabriele; Migliavacca, Francesco; Pennati, Giancarlo; Petrini, Lorenza

    2014-07-01

    Fatigue resistance of Nitinol stents implanted into femoro-popliteal arteries is a critical issue for the particular biomechanical environment of this district. Hip and knee joint movements due to the cyclic daily activity expose the superficial femoral artery (SFA), and therefore the implanted stents, to quite large and cyclic deformations influencing stent fatigue resistance. Objective of this work is to provide a tool based on finite element analysis able to evaluate the biomechanical effect of SFA on stent fatigue resistance. Computer simulations of the treatment of stenotic vessel by angioplasty and stenting and of the subsequent in vivo loading conditions (axial compression and bending) were carried out. Three different stenotic vessel models were defined, by keeping a constant stenosis rate and changing the plaque sharpness and number of stenoses. The fatigue behaviour was analysed comparing the amplitude and mean value distribution of the first principal strain in the whole stent for the different simulated conditions. Results showed that the maximum mean strain is similar in all the models, while the alternating strain is related to both plaque shape and loading conditions. In conclusion, this study confirms the requisite of replicating in vivo loading conditions. It also reveals the importance of taking into account the thickness variation of the vessel in the stenotic zone in the assessment of the stent fatigue resistance.

  4. Use of Nitinol Stents Following Recanalization of Central Venous Occlusions in Hemodialysis Patients

    SciTech Connect

    Rajan, Dheeraj K. Saluja, Jasdeep S.

    2007-07-15

    Purpose. To retrospectively review the patency of endovascular interventions with nitinol stent placement for symptomatic central venous occlusions in hemodialysis patients. Methods. A retrospective review of all patients who underwent endovascular interventions for dysfunctional hemodialysis grafts and fistulas was performed from April 2004 to August 2006. A total of 6 patients presented with arm and/or neck and facial swelling and left brachiocephalic vein occlusion. The study group consisted of 3 men and 3 women with a mean age of 79.5 years (SD 11.2 years). Of these 6 patients, 1 had a graft and 5 had fistulas in the left arm. The primary indication for nitinol stent placement was technical failure of angioplasty following successful traversal of occluded central venous segments. Patency was assessed from repeat fistulograms and central venograms performed when patients redeveloped symptoms or were referred for access dysfunction determined by the ultrasound dilution technique. No patients were lost to follow-up. Results. Nitinol stent placement to obtain technically successful recanalization of occluded venous segments was initially successful in 5 of 6 patients (83%). In 1 patient, incorrect stent positioning resulted in partial migration to the superior vena cava requiring restenting to prevent further migration. Clinical success was observed in all patients (100%). Over the follow-up period, 2 patients underwent repeat intervention with angioplasty alone. Primary patency was 83.3% (95% CI 0.5-1.2) at 3 months, and 66.7% at 6 and 12 months (0.2-1.1, 0.1-1.2). Secondary patency was 100% at 12 months with 3 patients censored over that time period. Mean primary patency was 10.4 months with a mean follow-up of 12.4 months. No complications related to recanalization of the occluded central venous segments were observed. Conclusion. Our initial experience has demonstrated that use of nitinol stents for central venous occlusion in hemodialysis patients is

  5. Oversizing and Restenosis with Self-Expanding Stents in Iliofemoral Arteries

    SciTech Connect

    Saguner, Ardan M. Traupe, Tobias; Raeber, Lorenz; Hess, Nina; Banz, Yara; Saguner, Arhan R.; Diehm, Nicolas; Hess, Otto M.

    2012-08-15

    Purpose: Uncoated self-expanding nitinol stents (NS) are commonly oversized in peripheral arteries. In current practice, 1-mm oversizing is recommended. Yet, oversizing of NS may be associated with increased restenosis. To provide further evidence, NS were implanted in porcine iliofemoral arteries with a stent-to-artery-ratio between 1.0 and 2.3. Besides conventional uncoated NS, a novel self-expanding NS with an antiproliferative titanium-nitride-oxide (TiNOX) coating was tested for safety and efficacy. Methods: Ten uncoated NS and six TiNOX-coated NS (5-6 mm) were implanted randomly in the iliofemoral artery of six mini-pigs. After implantation, quantitative angiography (QA) was performed for calculation of artery and minimal luminal diameter. Follow-up was performed by QA and histomorphometry after 5 months. Results: Stent migration, stent fracture, or thrombus formation were not observed. All stents were patent at follow-up. Based on the location of the stent (iliac/femoral) and the stent-to-artery-ratio, stent segments were divided into 'normal-sized' (stent-to-artery-ratio < 1.4, n = 12) and 'oversized' (stent-to-artery-ratio {>=} 1.4, n = 9). All stent segments expanded to their near nominal diameter during follow-up. Normal-sized stent segments increased their diameter by 6% and oversized segments by 29%. A significant correlation between oversizing and restenosis by both angiography and histomorphometry was observed. Restenosis rates were similar for uncoated NS and TiNOX-coated NS. Conclusions: TiNOX-coated NS are as safe and effective as uncoated NS in the porcine iliofemoral artery. All stents further expand to near their nominal diameter during follow-up. Oversizing is linearly and positively correlated with neointimal proliferation and restenosis, which may not be reduced by TiNOX-coating.

  6. Popliteal artery aneurysm treated with implantation of a covered stent graft (fluency(®)) reinforced with a nitinol stent (S.M.A.R.T. (®)).

    PubMed

    Nishi, Masahiro; Zen, Kan; Yamaguchi, Shinichiro; Asada, Satoshi; Kambayashi, Daisuke

    2016-10-01

    A 60-year-old man was admitted for right knee pain provoked by an enlarging popliteal artery aneurysm (PAA) after endovascular therapy for thromboembolism in the right popliteal artery. The PAA was treated with implantation of a covered stent graft (Fluency(®)); however, acute thromboembolism occurred 6 months after the intervention. Therefore, we implanted a nitinol stent (S.M.A.R.T.(®)) in the proximal part of the covered stent where the major hinge point existed in addition to a stent fracture. No vascular event occurred during 4.5 years of follow-up.

  7. Assessment of a Polyester-Covered Nitinol Stent in the Canine Aorta and Iliac Arteries

    SciTech Connect

    Castaneda, Flavio; Ball-Kell, Susan M.; Young, Kate; Li Ruizong

    2000-09-15

    Purpose: To evaluate the patency and healing characteristics of a woven polyester fabric-covered stent in the canine model.Methods: Twenty-four self-expanding covered stents were placed in the infrarenal aorta and bilateral common iliac arteries of eight dogs and evaluated at 1 (n = 2), 3 (n = 2), and 6 (n = 4) months. Stent assessment was done using angiography prior to euthanasia, and light and scanning electron microscopy.Results: Angiographically, just prior to euthanasia, 8 of 8 aortic and 14 of 16 iliac endovascular covered stents were patent. Histologically, the stented regions showed complete endothelialization 6 months after graft implantation. A neointima had formed inside the stented vessel regions resulting in complete encasement of the fabric-covered stent by 3 months after graft implantation. Medial compression with smooth muscle cell atrophy was present in all stented regions. Explanted stent wires, examined by scanning electron microscopy, showed pitting but no cracks or breakage.Conclusion: The covered stent demonstrated predictable healing and is effective in preventing stenosis in vessels 10.0 mm or greater in diameter but does not completely preclude stenosis in vessels 6.0 mm or less in diameter.

  8. Underwater femtosecond laser micromachining of thin nitinol tubes for medical coronary stent manufacture

    NASA Astrophysics Data System (ADS)

    Muhammad, Noorhafiza; Li, Lin

    2012-06-01

    Microprofiling of medical coronary stents has been dominated by the use of Nd:YAG lasers with pulse lengths in the range of a few milliseconds, and material removal is based on the melt ejection with a high-pressure gas. As a result, recast and heat-affected zones are produced, and various post-processing procedures are required to remove these defects. This paper reports a new approach of machining stents in submerged conditions using a 100-fs pulsed laser. A comparison is given of dry and underwater femtosecond laser micromachining techniques of nickel-titanium alloy (nitinol) typically used as the material for coronary stents. The characteristics of laser interactions with the material have been studied. A femtosecond Ti:sapphire laser system (wavelength of 800 nm, pulse duration of 100 fs, repetition rate of 1 kHz) was used to perform the cutting process. It is observed that machining under a thin water film resulted in no presence of heat-affected zone, debris, spatter or recast with fine-cut surface quality. At the optimum parameters, the results obtained with dry cutting showed nearly the same cut surface quality as with cutting under water. However, debris and recast formation still appeared on the dry cut, which is based on material vaporization. Physical processes involved during the cutting process in a thin water film, i.e. bubble formation and shock waves, are discussed.

  9. Nitinol stent implantation for femoropopliteal disease in patients on hemodialysis: results of the 3-year retrospective multicenter APOLLON study.

    PubMed

    Fujihara, Masahiko; Higashimori, Akihiro; Kato, Yoshihiro; Taniguchi, Hiromasa; Iwasaki, Yusuke; Amano, Tomonori; Sumiyoshi, Akinori; Nishiya, Daisuke; Yokoi, Yoshiaki

    2016-09-01

    The clinical outcomes of nitinol stents for femoropopliteal arterial (FP) disease in patients on hemodialysis were assessed. Endovascular therapy (EVT) is accepted for symptomatic FP disease. However, the clinical outcomes of patients on dialysis are not well known. A multicenter retrospective study was conducted with data between November 2010 and August 2013. A total of 484 consecutive patients who successfully underwent EVT for FP disease with nitinol stents were recruited and analyzed. Patients were categorized into the hemodialysis group (N = 161) and non-hemodialysis group (N = 323). The primary measure was primary patency verified by duplex ultrasound at a rest peak systolic velocity (PSVR) of >2.5, and secondary measures were freedom from target lesion revascularization (TLR) and major amputation-free survival (AFS). Average follow-up duration was 19.5 ± 13.5 months. The primary patency rate at 3 years was significantly lower in the hemodialysis group than the non-hemodialysis group (33.8 vs. 43.7 %; p = 0.036). Freedom from TLR at 3 years was 55.0 % in the hemodialysis group and 66.1 % in the non-hemodialysis group (p = 0.032). The hemodialysis group showed a significantly lower AFS rate at 3 years than the non-hemodialysis group (86.4 vs. 58.2 %; p < 0.001). In hemodialysis patients, nitinol stent use resulted in a lower patency rate, higher TLR rate, and lower AFS rate compared to non-hemodialysis patients. These data suggest that nitinol stent implantation for FP arteries in hemodialysis patient needs to be reconsidered. PMID:26337619

  10. [Trimming with argon plasma of self-expanding metal stents: report of 7 cases].

    PubMed

    Jury, Gastón; Amieva, Leandro; López, Fagalde Rafael; Jury, Rubén

    2014-06-01

    The use of self-expandable enteral stents for palliation of malignant stenosis may present the complication of concealing the ampulla of Vater behind the metallic mesh. Anchoring in the duodenal wall (distal or partial migration) may also be a complication of biliary metallic stents and therefore may cause difficulty in gaining access to the biliary tract. In these cases of difficult access, a fenestration on the prosthesis ( biliary or enteral) can be created to allow reaching the obstructed biliary tract by means of argon plasma (AP). Were retrospectively analysed 7 cases. Under endoscopic vision, AP was directed to filgurate and cut 6 biliary prosthesis and a duodenal stent. Fulguration and cut of biliary stent was performed in 5 cases of distal partial migration and cholangitis. In one case of obstruction caused by distal migration inside the duodenal stent light, cutting of the biliary stent was performed. A window was created in the enteral prosthesis in order to access the ampulla of Vater and place a biliary tract prosthesis. All cases were resolved successfully and without complications. We conclude that the use of AP to fulgurate and cut nitinol prosthesis was effective and presented no complications in this series.

  11. Structural Evaluation of Radially Expandable Cardiovascular Stents Encased in a Polyurethane Film

    NASA Technical Reports Server (NTRS)

    Trigwell, Steve; De, Samiran; Sharma, Rajesh; Mazumder, Malay K.; Mehta, Jawahar L.

    2004-01-01

    A method of encasing cardiovascular stents with an expandable polyurethane coating has been developed to provide a smooth homogeneous inner wall allowing for a confluent growth of endothelial cells. In this design, the metal wire stent structure is completely covered by the polyurethane film minimizing biocorrosion of the metal (stainless steel or nitinol), and providing a homogeneous surface for surface treatment and incorporation of various eluting drugs to prevent platelet aggregation while supporting endothelialization. The polyurethane surface was treated with a helium plasma for sterilization and promotes growth of cells. The paper details the performance of the coated film to expand with the metal stent up to 225 % during deployment. We present stress/strain behavior of polyurethane films, and subsequent plasma treatment of the surface and the adhesion of the coating to the stent structure upon expansion. A film of less than 25 tm was found to be sufficient for corrosion resistance and flexibility without producing any excess stress on the stent structure. Straining the film to 225 % and plasma modification did not affect the mechanical and surface properties while allowing for improved biocompatibility as determined by the critical surface tension, surface chemistry, and roughness.

  12. Biodegradable and Elastomeric Poly(glycerol sebacate) as a Coating Material for Nitinol Bare Stent

    PubMed Central

    Kim, Min Ji; Hwang, Moon Young; Kim, JiHeung; Chung, Dong June

    2014-01-01

    We synthesized and evaluated biodegradable and elastomeric polyesters (poly(glycerol sebacate) (PGS)) using polycondensation between glycerol and sebacic acid to form a cross-linked network structure without using exogenous catalysts. Synthesized materials possess good mechanical properties, elasticity, and surface erosion biodegradation behavior. The tensile strength of the PGS was as high as 0.28 ± 0.004 MPa, and Young's modulus was 0.122 ± 0.0003 MPa. Elongation was as high as 237.8 ± 0.64%, and repeated elongation behavior was also observed to at least three times the original length without rupture. The water-in-air contact angles of the PGS surfaces were about 60°. We also analyzed the properties of an electrospray coating of biodegradable PGS on a nitinol stent for the purpose of enhancing long-term patency for the therapeutic treatment of varicose veins disease. The surface morphology and thickness of coating layer could be controlled by adjusting the electrospraying conditions and solution parameters. PMID:24955369

  13. Biodegradable and elastomeric poly(glycerol sebacate) as a coating material for nitinol bare stent.

    PubMed

    Kim, Min Ji; Hwang, Moon Young; Kim, JiHeung; Chung, Dong June

    2014-01-01

    We synthesized and evaluated biodegradable and elastomeric polyesters (poly(glycerol sebacate) (PGS)) using polycondensation between glycerol and sebacic acid to form a cross-linked network structure without using exogenous catalysts. Synthesized materials possess good mechanical properties, elasticity, and surface erosion biodegradation behavior. The tensile strength of the PGS was as high as 0.28 ± 0.004 MPa, and Young's modulus was 0.122 ± 0.0003 MPa. Elongation was as high as 237.8 ± 0.64%, and repeated elongation behavior was also observed to at least three times the original length without rupture. The water-in-air contact angles of the PGS surfaces were about 60°. We also analyzed the properties of an electrospray coating of biodegradable PGS on a nitinol stent for the purpose of enhancing long-term patency for the therapeutic treatment of varicose veins disease. The surface morphology and thickness of coating layer could be controlled by adjusting the electrospraying conditions and solution parameters.

  14. Results of the self-expandable BA9 stent for treatment of large angle coronary bifurcation.

    PubMed

    Lucisano, L; Calcagno, S; Pennacchi, M; Stio, R E; Mancone, M; Sardella, G

    2014-02-01

    Since the advent of coronary angioplasty the treatment of bifurcation lesions has always proved a complex issue resulting in lower angiographic success rates, increased risk of restenosis, higher rates of dissection, myocardial infarction, and acute vessel closure. The advent of coronary stenting reduced the risks, but in-stent restenosis was noted to be frequent at the ostium of the side branch; for this reasons two-stent techniques were developed to try to combat this phenomenon. Novel dedicated stents have recently been developed to provide easier access to the SB and to scaffold more effectively its ostium, matching the stent configuration more closely to the anatomy of the bifurcation. Most of bifurcation lesions that require treatment and which have a wide angle involving the left main coronary artery (LMCA). The impact of the angle and the asymmetry of bifurcation on flow dynamic are very important and may influence clinical outcome. More recently, percutaneous coronary intervention (PCI) to treat wide angle disease has increased in frequency, and is associated with improvements in interventional techniques and adjunctive drug therapy. Several studies have shown that stenting in LMCA, especially using drug-eluting stents (DES), is a safe and effective treatment strategy both at mid- and long-term follow-up. The AXXESS System is a self-expanding, conically-shaped stent from nitinol (nickel-titanium alloy) with strut thickness, specifically designed to conform to the anatomy at the level of the bifurcation carina. A special version of the AXXESS System has been designed for left main bifurcation lesions, allowing for larger diameters (up to 4.75 mm) and distinct bifurcation angles (flare-end diameters of 8, 10 and 12 mm). The AXXENT trial is the first study to evaluate the vascular response of the self-expanding biolimus-eluting AXXESS stent for the treatment of LMCA bifurcation lesions. It was designed to evaluate the safety and efficacy of the AXXESS

  15. Study of the Behavior of a Bell-Shaped Colonic Self-Expandable NiTi Stent under Peristaltic Movements

    PubMed Central

    Puértolas, José A.; López, Enrique

    2013-01-01

    Managing bowel obstruction produced by colon cancer requires an emergency intervention to patients usually in poor conditions, and it requires creating an intestinal stoma in most cases. Regardless of that the tumor may be resectable, a two-stage surgery is mandatory. To avoid these disadvantages, endoscopic placement of self-expanding stents has been introduced more than 10 years ago, as an alternative to relieve colonic obstruction. It can be used as a bridge to elective single-stage surgery avoiding a stoma or as a definitive palliative solution in patients with irresectable tumor or poor estimated survival. Stents must be capable of exerting an adequate radial pressure on the stenosed wall, keeping in mind that stent must not move or be crushed, guaranteeing an adequate lumen when affected by peristaltic waves. A finite element simulation of bell-shaped nitinol stent functionality has been done. Catheter introduction, releasing at position, and the effect of peristaltic wave were simulated. To check the reliability of the simulation, a clinical experimentation with porcine specimens was carried out. The stent presented a good deployment and flexibility. Stent behavior was excellent, expanding from the very narrow lumen corresponding to the maximum peristaltic pressure to the complete recovery of operative lumen when the pressure disappears. PMID:23841067

  16. Use of a Nitinol Wire Stent for Management of Severe Tracheal Stenosis in an Eclectus Parrot (Eclectus roratus).

    PubMed

    Mejia-Fava, Johanna; Holmes, Shannon P; Radlinsky, MaryAnn; Johnson, Dan; Ellis, Angela E; Mayer, Jörg; Schnellbacher, Rodney; Divers, Stephen J

    2015-09-01

    A 25-year-old, female eclectus parrot (Eclectus roratus) presented for dyspnea 3 weeks after anesthesia and surgery for egg yolk coelomitis. Radiography, computed tomography, and tracheoscopy revealed multiple tracheal strictures spanning a length of 2.6 cm in the mid to distal trachea. Histopathologic examination revealed mild fibrosis, inflammation, and hyperplasia consistent with acquired tracheal strictures. Tracheal resection was not considered possible because of the length of the affected trachea. The strictures were resected endoscopically, and repeated balloon dilation under fluoroscopic guidance over the course of 10 months resulted in immediate but unsustained improvement. Computed tomography was used to measure the stenotic area. A 4 × 36-mm, custom-made, nitinol wire stent was inserted into the trachea under fluoroscopic guidance. After stent placement, intermittent episodes of mild to moderate dyspnea continued, and these responded to nebulization with a combination of saline, acetylcysteine, and dexamethasone. Multiple attempts to wean the patient off nebulization therapy and to switch to a corticosteroid-free combination were unsuccessful. The parrot eventually developed complications, was euthanatized, and necropsy was performed. Histologically, the tracheal mucosa had widespread erosion to ulceration, with accumulation of intraluminal exudate and bacteria, severe degeneration of skeletal muscle and tracheal rings, prominent fibrosis, and mild to moderate, submucosal inflammation. Clinicopathologic findings in this case suggested tracheomalacia, which has not been previously described in birds. Custom-made tracheal stents can be used for severe tracheal stenosis in birds when tracheal resection and anastomosis is not possible. Complications of tracheal stent placement in birds may include tracheitis and tracheomalacia. To our knowledge, this is the first report of tracheal stent placement in an avian species. PMID:26378671

  17. Use of a Nitinol Wire Stent for Management of Severe Tracheal Stenosis in an Eclectus Parrot (Eclectus roratus).

    PubMed

    Mejia-Fava, Johanna; Holmes, Shannon P; Radlinsky, MaryAnn; Johnson, Dan; Ellis, Angela E; Mayer, Jörg; Schnellbacher, Rodney; Divers, Stephen J

    2015-09-01

    A 25-year-old, female eclectus parrot (Eclectus roratus) presented for dyspnea 3 weeks after anesthesia and surgery for egg yolk coelomitis. Radiography, computed tomography, and tracheoscopy revealed multiple tracheal strictures spanning a length of 2.6 cm in the mid to distal trachea. Histopathologic examination revealed mild fibrosis, inflammation, and hyperplasia consistent with acquired tracheal strictures. Tracheal resection was not considered possible because of the length of the affected trachea. The strictures were resected endoscopically, and repeated balloon dilation under fluoroscopic guidance over the course of 10 months resulted in immediate but unsustained improvement. Computed tomography was used to measure the stenotic area. A 4 × 36-mm, custom-made, nitinol wire stent was inserted into the trachea under fluoroscopic guidance. After stent placement, intermittent episodes of mild to moderate dyspnea continued, and these responded to nebulization with a combination of saline, acetylcysteine, and dexamethasone. Multiple attempts to wean the patient off nebulization therapy and to switch to a corticosteroid-free combination were unsuccessful. The parrot eventually developed complications, was euthanatized, and necropsy was performed. Histologically, the tracheal mucosa had widespread erosion to ulceration, with accumulation of intraluminal exudate and bacteria, severe degeneration of skeletal muscle and tracheal rings, prominent fibrosis, and mild to moderate, submucosal inflammation. Clinicopathologic findings in this case suggested tracheomalacia, which has not been previously described in birds. Custom-made tracheal stents can be used for severe tracheal stenosis in birds when tracheal resection and anastomosis is not possible. Complications of tracheal stent placement in birds may include tracheitis and tracheomalacia. To our knowledge, this is the first report of tracheal stent placement in an avian species.

  18. Comparison of Small Intestinal Submucosa-Covered and Noncovered Nitinol Stents with PTFE Endografts in Injured Ovine Femoral Arteries: A Pilot Study

    SciTech Connect

    Nakata, Manabu; Pavcnik, Dusan Uchida, Barry T.; Van Alstine, William; Timmermans, Hans A.; Toyota, Naoyuki; Terada, Masaki; Brountzos, Elias; Kaufman, John A.; Keller, Frederick S.; Rosch, Josef

    2003-09-15

    The purpose of this study was to compare performance of small intestinal submucosa (SIS)-covered endografts (SCEs) to polytetra-fluoroethylene (PTFE)-covered endografts (PCEs) and to bare nitinol stents (BSs) in injured sheep femoral artery (FA). Bare Zilver 6 mm x 40 mm nitinol stents (n = 6), Zilver stents covered with SIS (n = 6), and Palmaz stents 6 mm x 37 mm covered with PTFE (n = 6) were implanted in the balloon-injured FAs of nine female sheep. Follow-up arteriograms were obtained before animal sacrifice at 1, 3 and 6 months, with three animals at each time point. The FAs with the implanted device were explanted for histologic studies and morphologic measurements. Stent implantation was technically successful in all sheep. All BS and SCEs were patent at each time point. Five BSs and five SCEs exhibited formation of progressive eccentric intimal hyperplasia (IH) that was more advanced in SCE at 6 months. Cross-sectional area narrowing averaged 60% for BSs and 67% for SCEs. One BS, one SCE and two patent PCEs exhibited mild-to-moderate formation of concentric IH. Four PCS occluded one at 1 month, two at 3 months and one at 6 months. Performance of the devices placed into sheep FAs depended on their relation to the curving peri-articular portion of the FA during extremity flexion. BSs and SCEs placed in this portion exhibited progressive growth of eccentric IH while PCEs placed in this portion occluded.

  19. Clinical impact and risk stratification of balloon angioplasty for femoropopliteal disease in nitinol stenting era: Retrospective multicenter study using propensity score matching analysis

    PubMed Central

    Tsuchiya, Taketsugu; Takamura, Takaaki; Soga, Yoshimitsu; Iida, Osamu; Hirano, Keisuke; Suzuki, Kenji; Yamaoka, Terutoshi; Miyashita, Yusuke; Kitayama, Michihiko; Kajinami, Koji

    2016-01-01

    Objective: Nitinol stenting could bring the better outcome in endovascular therapy for femoropopliteal disease. However, it might be expected that recent marked advances in both device technology and operator technique had led to improved efficacy of balloon angioplasty even in this segment. The aims of this study were to evaluate the clinical impact of balloon angioplasty for femoropopliteal disease and make risk stratification clear by propensity score matching analysis. Methods: Based on the multicenter retrospective data, 2758 patients (balloon angioplasty: 729 patients and nitinol stenting: 2029 patients), those who underwent endovascular therapy for femoropopliteal disease, were analyzed. Results: The propensity score matching procedure extracted a total of 572 cases per group, and the primary patency rate of balloon angioplasty and nitinol stenting groups after matching was significantly the same (77.2% vs 82.7% at 1 year; 62.2% vs 64.3% at 3 years; 47.8% vs 54.3% at 5 years). In multivariate Cox hazard regression analysis, significant predictors for primary patency were diabetes mellitus, regular dialysis, cilostazol use, chronic total occlusion, and intra-vascular ultra-sonography use. The strategy of balloon angioplasty was not evaluated as a significant predictor for the primary patency. After risk stratification using five items (diabetes mellitus, regular dialysis, no use of intra-vascular ultra-sonography, chronic total occlusion, and no use of cilostazol: the DDICC score), the estimated primary patency rates of each group (low, DDICC score 0–2; moderate, DDICC score 3; high risk, DDICC score 4–5) were 88.6%, 78.3%, and 63.5% at 1 year; 75.2%, 60.7%, and 39.8% at 3 years; and 66.0%, 47.1%, and 26.3% at 5 years (p < 0.0001). The primary patency rate of balloon angioplasty and nitinol stenting groups was significantly the same in each risk stratification. Conclusion: This study suggests that balloon angioplasty does not have

  20. In Vitro Comparison of Self-Expanding Versus Balloon-Expandable Stents in a Human Ex Vivo Model

    SciTech Connect

    Grenacher, Lars Rohde, Stefan Gaenger, Ellen; Deutsch, Jochen; Kauffmann, Guenter W.; Richter, Goetz M.

    2006-04-15

    The objective was to compare the radial strength and expansile precision of self-expanding stents and balloon-expandable stents in a human cadaver bifurcation model. Seven different self-expanding (LUMINEXX, JOSTENT SelfX, JOSTENT SelfX hrf, Sinus-Repo, Sinus SuperFlex, Easy Wallstent, SMART) and four different balloon-expandable stent models (Palmaz, Sinus Stent, SAXX Medium, JOSTENT peripheral), each type 10 stents (total n = 110 stents) were implanted into the common iliac arteries of human cadaver corpses. The maximum stent diameter was 10 mm for all models. After stent implantation, the specimens were filled with silicone caoutchouc. After 24 h, the vascular walls including the stents were removed from the hardened casts. Diameters were taken and the weight of the cast cylinders was measured in air and in purified water to calculate the volume of the bodies (according to Archimedes Law) as a relative but precise degree for the radial strength of the implanted stents. The cylindrical casts of the self-expanding stents showed lower mean diameters (8.2 {+-} 1.0 mm) and mean volumes (0.60 {+-} 0.14 ml/cm) than in the balloon-expandable stent group (10.1 {+-} 0.3 mm and 0.71 {+-} 0.04 ml/cm, respectively; p < 0.01). The nominal maximum diameter of 10 mm was not achieved in any of the self-expanding stents, but this was achieved in more than 70% (29/40) of the balloon-expandable stent specimens (p < 0.05). The variation between achieved volumes was significantly larger in self-expanding (range: 0.23-0.78 ml/cm) than in balloon-expandable stents (range: 0.66-0.81 ml/cm; p < 0.05). Self-expanding stents presented considerably lower radial expansion force and lower degree of precision than balloon-expandable stents.

  1. Simulations of Self-Expanding Braided Stent Using Macroscopic Model of NiTi Shape Memory Alloys Covering R-Phase

    NASA Astrophysics Data System (ADS)

    Frost, M.; Sedlák, P.; Kruisová, A.; Landa, M.

    2014-07-01

    Self-expanding stents or stentgrafts made from Nitinol superelastic alloy are widely used for a less invasive treatment of disease-induced localized flow constriction in the cardiovascular system. The therapy is based on insertion of a stent into a blood vessel to maintain the inner diameter of the vessel; it provides highly effective results at minimal cost and with reduced hospital stays. However, since stent is an external mechanical healing tool implemented into human body for quite a long time, information on the mechanical performance of it is of fundamental importance with respect to patient's safety and comfort. Advantageously, computational structural analysis can provide valuable information on the response of the product in an environment where in vivo experimentation is extremely expensive or impossible. With this motivation, a numerical model of a particular braided self-expanding stent was developed. As a reasonable approximation substantially reducing computational demands, the stent was considered to be composed of a set of helical springs with specific constrains reflecting geometry of the structure. An advanced constitutive model for NiTi-based shape memory alloys including R-phase transition was employed in analysis. Comparison to measurements shows a very good match between the numerical solution and experimental results. Relation between diameter of the stent and uniform radial pressure on its surface is estimated. Information about internal phase and stress state of the material during compression loading provided by the model is used to estimate fatigue properties of the stent during cyclic loading.

  2. Stent Fracture and Reocclusion After Placement of a Single Self-Expanding Stent in the Common Iliac Artery and Endovascular Treatment

    SciTech Connect

    Higashiura, Wataru Sakaguchi, Shoji; Morimoto, Kengo; Kichikawa, Kimihiko

    2008-09-15

    We present a case of fracture of a single self-expanding stent placed in the common iliac artery (CIA). An 80-year-old woman underwent placement of a self-expanding stent for CIA occlusion. Stent fracture and reocclusion were detected after 18 months. Successful revascularization was achieved using a stent-in-stent maneuver. The possibility of stent fracture with reocclusion should be considered following treatment with a single self-expanding stent for CIA occlusion.

  3. Determining Micromechanical Strain in Nitinol

    SciTech Connect

    Strasberg, Matthew; /SLAC

    2006-09-27

    Nitinol is a superelastic alloy made of equal parts nickel and titanium. Due to its unique shape memory properties, nitinol is used to make medical stents, lifesaving devices used to allow blood flow in occluded arteries. Micromechanical models and even nitinol-specific finite element analysis (FEA) software are insufficient for unerringly predicting fatigue and resultant failure. Due to the sensitive nature of its application, a better understanding of nitinol on a granular scale is being pursued through X-ray diffraction techniques at the Stanford Synchrotron Radiation Laboratory (SSRL) at the Stanford Linear Accelerator Center (SLAC). Through analysis of powder diffraction patterns of nitinol under increasing tensile loads, localized strain can be calculated. We compare these results with micromechanical predictions in order to advance nitinol-relevant FEA tools. From this we hope to gain a greater understanding of how nitinol fatigues under multi-axial loads.

  4. SU-E-T-115: Dose Perturbation Study of Self-Expandable Metal and Polyester Esophageal Stents in Proton Therapy Beams

    SciTech Connect

    Lee, S; Li, Z; Jalaj, S; McGaw, C; B K, John; J S, Scolapio; J C, Munoz

    2014-06-01

    Purpose: This work investigates dose perturbations due to Self-expandable metal and polyester esophageal stents undergoing proton radiotherapy for esophageal cancer. Methods: Five commercially available esophageal stents made of nitinol (Evolution, Wallflex and Ultraflex), stainless steel (Z-Stent) and polyester (Polyflex) were tested. Radiochromic film (GafChromic EBT3 film, Ashland, Covington, KY) wrapped around a stent and a 12cc syringe was irradiated with 2CGE (Cobalt Gray Equivalent) of proton beam in a custom fabricated acrylic phantom. An air-hollow syringe simulates the esophagus. Results: The Z-stent created the largest dose perturbations ranges from -14.5% to 6.1% due to the steel composition. The WallFlex, Evolution and Ultraflex stents produced the dose perturbation ranges of (−9.2%∼8.6%), (−6.8%∼5.7%) and (−6.2%∼6.2%), respectively. The PolyFlex stent contains the radiopaque tungsten markers located top, middle and bottom portions. When the focal cold spots induced by the markers were excluded in the analysis, the dose perturbation range was changed from (−11.6%∼6.4%) to (−0.6%∼5.0%). Conclusion: The magnitude of dose perturbation is related to material of a metallic stent. The non-metallic stent such as PolyFlex shows relatively lower dose perturbation than metallic stents except a radiopaque marker region. Overall Evolution and Ultraflex stent appear to be less dose perturbations. The largest dose perturbations (cold spots) were located at both edges of stents in distal area for the single proton beam irradiation study. The analysis of more than two proton beam which is more typical clinical beam arrangement would be necessary to minimize the doe perturbation effect in proton ratiotherapy.

  5. Mechanical Characteristics of Composite Knitted Stents

    SciTech Connect

    Tokuda, Takanori Shomura, Yuzo; Tanigawa, Noboru; Kariya, Shuji; Komemushi, Atsushi; Kojima, Hiroyuki; Sawada, Satoshi

    2009-09-15

    We used metal wires and fibers to fabricate a composite knitted stent and then compare the mechanical characteristics of this stent with those of a pure metallic stent of the same construction in order to develop a stent that offers a comparable degree of expandability as metallic stents but can be used for highly curved lesions that cannot be treated using metallic stents. We fabricated two types of composite knitted stent (N-Z stents), using nitinol wire with a diameter of 0.12 mm and polypara-phenylene-benzobisoxazole (PBO) multifilament fiber (Zyron AS; Toyobo, Osaka, Japan). Stents were knitted into a cylindrical shape using the same textile pattern as a Strecker stent. Two loop lengths (L) of nitinol wire were used in the N-Z stents: L = 1.84 mm (N-Z stent L = 1.84) and L = 2.08 mm (N-Z stent L = 2.08). For the sake of comparison, we fabricated a metallic stent of nitinol using the same textile pattern (N-N stent L = 1.92). We applied a radial compression force diametrically to each stent and applied a bending force diametrically at the free end of a stent with one end fixed in order to evaluate the relationship between stent elasticity and load values. In addition, we macroscopically evaluated the generation of kinks when the stent was bent 180{sup o}. The radial compressive force when the stent diameter was reduced by 53% was 6.44 N in the case of N-Z stent L = 1.84, 6.14 N in the case of N-Z stent L = 2.08, and 4.96 N in the case of N-N stent L = 1.92 mm. The composite stent had a radial compressive force higher than that of a metallic stent. The restoring force to longitudinal direction at a 90{sup o} bending angle was 0.005 N for N-Z stent L = 1.84, 0.003 N for N-Z stent L = 2.08, and 0.034 N for N-N stent L = 1.92. The restoring force of the composite stent was significantly lower. Finally, the composite stent generated no definitive kinks at a bending angle of 180{sup o}, regardless of loop length. However, the N-N stent clearly produced kinks, causing

  6. Virtual optimization of self-expandable braided wire stents.

    PubMed

    De Beule, Matthieu; Van Cauter, Sofie; Mortier, Peter; Van Loo, Denis; Van Impe, Rudy; Verdonck, Pascal; Verhegghe, Benedict

    2009-05-01

    At present, the deployment of self-expandable braided stents has become a common and widely used minimally invasive treatment for stenotic lesions in the cardiovascular, gastrointestinal and respiratory system. To improve these revascularization procedures (e.g. increase the positioning accuracy) the optimal strategy lies in the further development of the stent design. In the context of optimizing braided stent designs, computational models can provide an excellent research tool complementary to analytical models. In this study, a finite element based modelling strategy is proposed to investigate and optimize the mechanics of braided stents. First a geometrical and finite element model of a braided Urolume endoprosthesis was built with the open source pyFormex design tool. The results of the reference simulation of the Urolume stent are in close agreement with both analytical and experimental data. Subsequently, a simplex-based design optimization algorithm automatically adjusts the reference Urolume geometry to facilitate precise positioning by reducing the foreshortening with 20% while maintaining the radial stiffness. Therefore, the proposed modelling strategy appears to be a promising optimization methodology in braided stent design.

  7. Expandable Metal Stents for the Palliation of Malignant Gastroduodenal Obstruction

    SciTech Connect

    Razzaq, Rubeena; Laasch, Hans-Ulrich; England, Ruth; Marriott, Angie; Martin, Derrick

    2001-09-15

    Purpose: Gastric outlet obstruction is a debilitating complication of upper gastrointestinal malignancy. We present our experience with insertion of self-expanding metal stents (SEMS).Methods: Twenty-eight patients were referred, stenting being attempted in 23. Two patients had esophageal Wallstents inserted through a gastrostomy; 21 had an endoscopic approach with enteral Wallstents.Results: One stent insertion failed, ten patients (45%) returned to a normal diet, ten patients (45%) managed semi-solid food and two patients (9%) had no significant improvement. No immediate complications were seen. One patient subsequently developed pancreatitis. Reintervention (4 stents, 1 jejunostomy, 1 gastro jejunostomy) was required in six of 22 patients (27%) for inadequate stent expansion (1), second stricture (2), stent migration (1), and tumor ingrowth (2). The mean survival was 95.4 days (SD 78.8 days, range 3-230 days). The mean follow-up time was 98.9 days (SD 86.7 days, range 3-309 days).Conclusions: SEMS are effective in palliating malignant gastric outlet obstruction. A combined endoscopic/fluoroscopic approach allows the most complete assessment of the stricture and removes the need for gastrostomy insertion. Careful assessment of the gastrointestinal tract distal to the lesion is important.

  8. Treatment of an iatrogenic vertebral artery laceration with the Symbiot self expandable covered stent.

    PubMed

    Katsaridis, Vasilios; Papagiannaki, Chrysanthi; Violaris, Constantinos

    2007-07-01

    Vertebral artery laceration is difficult to treat surgically. Endovascular treatment with balloon expandable covered stents often fails due to their rigidity and poor navigability. We present a case of iatrogenic vertebral artery laceration where endovascular treatment with a balloon expandable covered stent failed. Eventually a self expandable symbiot covered stent was deployed over the laceration, securing hemostasis and preserving the vessel patency. The newer self expandable covered stents seem promising in the treatment of vertebral artery injury.

  9. Use of the Viatorr Expanded Polytetrafluoroethylene-Covered Stent-Graft for Transjugular Intrahepatic Portosystemic Shunt Creation in Children: Initial Clinical Experience

    SciTech Connect

    Mermuys, Koen; Maleux, Geert Heye, Sam; Lombaerts, Rita; Nevens, Frederik

    2008-07-15

    Four children, three boys and one girl, with a median age of 9 years 8 months, underwent transjugular intrahepatic portosystemic shunt creation with an expanded polytetrafluoroethylene (e-PTFE)-covered nitinol stent. The stent-graft was successfully placed in all four patients without any complication. Clinical and biochemical improvement was noted in all four patients during follow-up. Radiological follow-up with use of duplex ultrasound showed a recurrent stenosis of the shunt 180 days after stent-graft implantation in one patient. This was treated with placement of an additional stent-graft, re-expanding completely the recurrent stenosis. In the other three patients, the stent-graft remained fully patent until the end of the study or until orthotopic liver transplantation. These preliminary results suggest that use of the Viatorr ePTFE-covered stent-graft in children is safe and feasible, with potentially the same high patency rate and improved clinical outcome as reported in adult patients.

  10. Comparison of the Fatigue Performance of Commercially Produced Nitinol Samples versus Sputter-Deposited Nitinol

    NASA Astrophysics Data System (ADS)

    Siekmeyer, Gerd; Schüßler, Andreas; de Miranda, Rodrigo Lima; Quandt, Eckhard

    2014-07-01

    Self-expanding vascular implants are typically manufactured from Nitinol tubing, using laser cutting, shape setting, and electropolishing processes. The mechanical and fatigue behavior of those devices are affected by the raw material and its processing such as the melting process and subsequent warm and cold forming processes. Current trends focus on the use of raw material with fewer inclusions to improve the fatigue performance. Further device miniaturization and higher fatigue life requirements will drive the need toward smaller inclusions and new manufacturing methods. As published previously, the high-cycle fatigue region of medical devices from standard processed Nitinol is usually about 0.4-0.5% half-alternating strain. However, these results highly depend on the ingot and semi-finished materials, the applied manufacturing processes, the final dimensions of test samples, and applied test methods. Fabrication by sputter deposition is favorable, because it allows the manufacturing of micro-patterned Nitinol thin-film devices without small burrs, heat-affected zones, microcracks, or any contamination with carbides, as well as the fabrication of complex components e.g., 3D geometries. Today, however, there is limited data available on the fatigue behavior for real stent devices based on such sputter-deposited Nitinol. A detailed study (e.g., using metallographic methods, corrosion, tensile, and fatigue testing) was conducted for the first time in order to characterize the micro-patterned Nitinol thin-film material.

  11. Evaluation of the Effects of Temporary Covered Nitinol Stent Placement in the Prostatic Urethra: Short-Term Study in the Canine Model

    SciTech Connect

    Crisostomo, Veronica; Uson-Gargallo, Jesus

    2007-07-15

    Purpose. To evaluate the effect of temporary stent placement on the canine prostatic urethra. Methods. Retrievable PTFE-covered nitinol stents were placed in the prostatic urethras of 8 beagle dogs under fluoroscopic guidance. Retrograde urethrography was obtained before and after stenting. Retrograde urethrography and endoscopy were performed 1 and 2 months after deployment. The endoscopic degree of hyperplasia was rated on a scale of 0 to 4 (0 absence, 4 = occlusion). On day 60, stents were removed and urethrography was performed immediately before euthanasia. Pathologic analysis was performed to determine the degree of glandular atrophy, periurethral fibrosis, and urethral dilation. Results. Stent deployment was technically successful in 7 animals, and failed in 1 dog due to a narrow urethral lumen. Complete migration was seen in 2 animals at 1 month, and an additional stent was deployed. On day 30, endoscopy showed slight hyperplasia (grade 1) in 3 animals. On day 60, moderate hyperplasia (grade 2) was evidenced in 4 cases. No impairment of urinary flow was seen during follow-up. Retrieval was technically easy to perform, and was successful in all dogs. The major histologic findings were chronic inflammatory cell infiltrates; prostate glandular atrophy, with a mean value of 1.86 (SD 0.90); periurethral fibrosis, with a mean ratio of 29.37 (SD 10.41); and dilatation of the prostatic urethra, with a mean ratio of 6.75 (SD 3.22). Conclusion. Temporary prostatic stent placement in dogs is safe and feasible, causing marked enlargement of the prostatic urethral lumen. Retrievable covered stents may therefore be an option for bladder outlet obstruction management in men.

  12. Endoscopic Ultrasound-guided Antegrade Stenting in an Occluded Biliary Self-expandable Metal Stent

    PubMed Central

    Almadi, Majid A.; Eltayeb, Mohanned; Thaniah, Salem

    2016-01-01

    Endoscopic ultrasound-guided biliary drainage (EUS-BD) is an attractive option for patients who cannot undergo conventional endoscopic retrograde cholangiopancreatography (ERCP) and do not want surgery or percutaneous drainage procedures. We present the use of EUS-antegrade (EUS-AG) insertion of a self-expandable metal stent (SEMS) in a patient with a common hepatic duct cholangiocarcinoma, as well as a huge gastric lipoma, after recurrent biliary obstruction of a prior SEMS inserted via ERCP in the same session as a duodenal stent insertion for gastric outlet obstruction. PMID:27488330

  13. Use of a New Hybrid Heparin-Bonded Nitinol Ring Stent in the Popliteal Artery: Procedural and Mid-term Clinical and Anatomical Outcomes

    SciTech Connect

    Parthipun, Aneeta; Diamantopoulos, Athanasios; Kitrou, Panagiotis; Padayachee, Soundrie; Karunanithy, Narayan; Ahmed, Irfan; Zayed, Hany; Katsanos, Konstantinos E-mail: katsanos@med.upatras.gr

    2015-08-15

    PurposeTo report the immediate and mid-term clinical and anatomical outcomes of a novel, hybrid, heparin-bonded, nitinol ring stent (TIGRIS; Gore Medical) when used for the treatment of lesions located in the popliteal artery.Materials and MethodsThis was a prospective single-centre registry. Patients eligible for inclusion were individuals suffering from symptomatic popliteal arterial occlusive disease (Rutherford–Becker stage 3–6; P1–P3 segments) and treated with placement of the TIGRIS stent(s). Patients were prospectively scheduled for clinical review and duplex ultrasound follow-up after 6 and 12 months. Outcome measures included immediate technical success, primary vessel patency, in-stent binary restenosis (evaluable by Duplex at 50 % threshold; PSVR > 2.0), freedom from target lesion revascularization (TLR) and amputation-free survival (AFS) estimated by Kaplan–Meier (K–M) survival analysis. Cox proportional-hazards regression analysis was also performed to adjust for confounders and search for independent predictors of outcomes.ResultsFrom August 2012 to March 2014, a total of 54 popliteal TIGRIS stents were implanted in 50 limbs of 48 patients (27 men and 21 women; mean age 76.0 ± 1.7 years). Median Rutherford–Becker stage was five at baseline and 37/50 (74.0 %) were chronic total occlusions. Technical success was achieved in all cases (100 %). Stented lesion length was 114.2 ± 36.9 mm (range 6–20 cm). Median follow-up was 11.8 ± 0.8 months. After 12 months, primary patency of the TIGRIS stent was 69.5 ± 10.2 % with an 86.1 ± 5.9 % freedom from TLR and 87 ± 5.0 % AFS (K–M estimates).ConclusionThe TIGRIS hybrid heparin-bonded nitinol ring stent is a safe and effective endovascular option for complex occlusive disease of the popliteal artery.

  14. Square Stent: A New Self-Expandable Endoluminal Device and Its Applications

    SciTech Connect

    Pavcnik, Dusan; Uchida, Barry; Timmermans, Hans; Keller, Frederick S.; Roesch, Josef

    2001-07-15

    The square stent is a new, simply constructed, self-expanding device that has recently been described. Compared with other stents, the square stent has a minimal amount of metal and thus requires a smaller-diameter catheter for introduction. Despite the small amount of metal present, the square stent has adequate expansile force. We have been evaluating the square stent for various interventional applications. In addition to the basic square stent, combinations of square stents and coverings for square stents were developed and evaluated to expand its uses and indications. One of the coverings tested is a new biomaterial: small intestinal submucosa (SIS). This paper will discuss the various applications of the square stent, which include a retrievable inferior vena cava filter, vascular occluder, graft adapter, and venous and aortic valves. In addition, we will review the important properties of SIS as a covering for the square stent.

  15. Pancreatitis-Associated Splenic Artery Pseudoaneurysm: Endovascular Treatment with Self-Expandable Stent-Grafts

    SciTech Connect

    Brountzos, Elias N.; Vagenas, Kostantinos; Apostolopoulou, Sotiria C.; Panagiotou, Irene; Lymberopoulou, Dimitra; Kelekis, Dimitrios A.

    2003-02-15

    We present a patient with a splenic arterypseudoaneurysm (SAPA) treated with placement of self-expandable stent-grafts. The procedure was complicated by stent-graft migration,but successful management resulted in lasting exclusion of the SAPA,while the patency of the splenic artery was preserved. This is the first report of self-expandable stent-graft treatment of SAPA.

  16. Polymeric photosensitizer-embedded self-expanding metal stent for repeatable endoscopic photodynamic therapy of cholangiocarcinoma.

    PubMed

    Bae, Byoung-chan; Yang, Su-Geun; Jeong, Seok; Lee, Don Haeng; Na, Kun; Kim, Joon Mee; Costamagna, Guido; Kozarek, Richard A; Isayama, Hiroyuki; Deviere, Jacques; Seo, Dong Wan; Nageshwar Reddy, D

    2014-10-01

    Photodynamic therapy (PDT) is a new therapeutic approach for the palliative treatment of malignant bile duct obstruction. In this study, we designed photosensitizer-embedded self-expanding nonvascular metal stent (PDT-stent) which allows repeatable photodynamic treatment of cholangiocarcinoma without systemic injection of photosensitizer. Polymeric photosensitizer (pullulan acetate-conjugated pheophorbide A; PPA) was incorporated in self-expanding nonvascular metal stent. Residence of PPA in the stent was estimated in buffer solution and subcutaneous implantation on mouse. Photodynamic activity of PDT-stent was evaluated through laserexposure on stent-layered tumor cell lines, HCT-116 tumor-xenograft mouse models and endoscopic intervention of PDT-stent on bile duct of mini pigs. Photo-fluorescence imaging of the PDT-stent demonstrated homogeneous embedding of polymeric Pheo-A (PPA) on stent membrane. PDT-stent sustained its photodynamic activities at least for 2 month. And which implies repeatable endoscopic PDT is possible after stent emplacement. The PDT-stent after light exposure successfully generated cytotoxic singlet oxygen in the surrounding tissues, inducing apoptotic degradation of tumor cells and regression of xenograft tumors on mouse models. Endoscopic biliary in-stent photodynamic treatments on minipigs also suggested the potential efficacy of PDT-stent on cholangiocarcinoma. In vivo and in vitro studies revealed our PDT-stent, allows repeatable endoscopic biliary PDT, has the potential for the combination therapy (stent plus PDT) of cholangiocarcinoma.

  17. Evaluation of anti-migration properties of biliary covered self-expandable metal stents

    PubMed Central

    Minaga, Kosuke; Kitano, Masayuki; Imai, Hajime; Harwani, Yogesh; Yamao, Kentaro; Kamata, Ken; Miyata, Takeshi; Omoto, Shunsuke; Kadosaka, Kumpei; Sakurai, Toshiharu; Nishida, Naoshi; Kudo, Masatoshi

    2016-01-01

    AIM: To assess anti-migration potential of six biliary covered self-expandable metal stents (C-SEMSs) by using a newly designed phantom model. METHODS: In the phantom model, the stent was placed in differently sized holes in a silicone wall and retracted with a retraction robot. Resistance force to migration (RFM) was measured by a force gauge on the stent end. Radial force (RF) was measured with a RF measurement machine. Measured flare structure variables were the outer diameter, height, and taper angle of the flare (ODF, HF, and TAF, respectively). Correlations between RFM and RF or flare variables were analyzed using a linear correlated model. RESULTS: Out of the six stents, five stents were braided, the other was laser-cut. The RF and RFM of each stent were expressed as the average of five replicate measurements. For all six stents, RFM and RF decreased as the hole diameter increased. For all six stents, RFM and RF correlated strongly when the stent had not fully expanded. This correlation was not observed in the five braided stents excluding the laser cut stent. For all six stents, there was a strong correlation between RFM and TAF when the stent fully expanded. For the five braided stents, RFM after full stent expansion correlated strongly with all three stent flare structure variables (ODF, HF, and TAF). The laser-cut C-SEMS had higher RFMs than the braided C-SEMSs regardless of expansion state. CONCLUSION: RF was an important anti-migration property when the C-SEMS did not fully expand. Once fully expanded, stent flare structure variables plays an important role in anti-migration. PMID:27570427

  18. Endoscopic palliation for pancreatic cancer with expandable metal stents.

    PubMed

    Spitz, J D; Arregui, M E

    2000-05-01

    Pancreatic cancer is generally not amenable to curative resection. Consequently, therapeutic efforts for these patients are most commonly directed at palliation of symptoms. Historically, surgery has been considered the most effective method of providing relief for biliary and/or enteric obstruction. However, less invasive methods have become available that can provide effective relief of jaundice and duodenal obstruction. Surgeons should still play an integral role in the management of these patients. We present a case report in which self-expanding metallic stents were used to relieve obstruction of the bile duct and duodenum in a patient with unresectable pancreatic cancer.

  19. Self-expanding metal stents for palliative treatment of malignant biliary and duodenal stenoses.

    PubMed

    Maetani, I; Ogawa, S; Hoshi, H; Sato, M; Yoshioka, H; Igarashi, Y; Sakai, Y

    1994-10-01

    Patients with malignant biliary stenosis due to pancreatic head cancer often have the associated problem of duodenal obstruction. We report here the case of a 78-year-old woman with this clinical situation, who was treated with self-expanding Gianturco metal stents placed in the distal common bile duct and, nine months later, placed in the descending duodenum. The patient's frequent vomiting resolved, and she was able to tolerate peroral solid food; jaundice also decreased (bilirubin pre-stenting: 7.8; post-stenting: 1.2). Self-expanding metal stents therefore appear to be effective for the palliative treatment of malignant duodenal stenosis as well as biliary stenosis.

  20. Effect of the Palmaz balloon-expandable metallic stent in the trachea of pigs.

    PubMed

    Ruegemer, J L; Perkins, J A; Azarow, K S; O'Bryant, L K; Nielsen, R E; Thomas, R W

    1999-07-01

    Endoscopically placed airway stents offer a viable option in primary or adjunctive treatment of severe pediatric tracheobronchial stenoses. Optimistic clinical reports substantiate the need for experimental studies to more effectively evaluate their clinical role. Development of an animal model comparable with the pediatric airway, amenable to endoscopic instrumentation, and capable of assessing effect on growth was the purpose of this pilot project. Nine 4-week-old piglets underwent endoscopic midtracheal placement of the balloon-expandable Palmaz metallic stent. Initial expansion and stent position were verified fluoroscopically and by direct videobronchoscopy. Serial endoscopic examination and stent reexpansion were performed 2 and 4 weeks after stent insertion. Animal weight, clinical tolerance, tracheal growth, and stent integrity were observed. Tracheal inflammation was evaluated grossly and by objective histopathologic criteria. Successful endotracheal stent placement and expansion were accomplished in all piglets. One pig died of anesthesia complications less than 24 hours after stent insertion. The remaining pigs exhibited excellent clinical tolerance through experiment completion. No detrimental effect on growth was noted, and effective dilatation of the stented tracheal region was observed. Stent incorporation was evident with significant mucosal ingrowth. Inflammation in the form of nonobstructing granulation tissue was present, and no evidence of necrosis or cartilage invasion was evident. The piglet trachea appears to be an excellent model for evaluation of expandable metallic airway stents in management of congenital and acquired tracheobronchial stenoses.

  1. Thoracic Discitis as a Complication of Self-Expanding Metallic Stents in Esophageal Carcinoma

    SciTech Connect

    McQueen, A. S.; Eljabu, W.; Latimer, J. Raju, P. P. J.

    2011-02-15

    The role of metallic stents in the palliation of esophageal cancer is well established. Self-expanding metal stents (SEMSs) are frequently used, as they provide an effective and safe method of relieving malignant dysphagia. A number of complications are associated with the use of SEMSs, including esophageal perforation. We report a case of thoracic discitis occurring in a patient with advanced esophageal malignancy, treated with SEMSs. We propose that the likely etiology in this patient was esophageal perforation by a metallic stent.

  2. Self-Expandable Metallic Stent Placement in Malignant Gastric Outlet Obstruction: A Comparison Between 2 Brands of Stents.

    PubMed

    Ye, Bing-Wei; Lee, Kuei-Chuan; Hsieh, Yun-Cheng; Li, Chung-Pin; Chao, Yee; Hou, Ming-Chih; Lin, Han-Chieh

    2015-07-01

    Malignant gastric outlet obstruction is a late complication of intraabdominal malignancy. Self-expandable metallic stent placement has been a safe palliative treatment to relieve obstructive symptoms. We aimed to assess the efficacy and safety of metallic stents in our patients and analyzed the clinical outcome of different brands. Seventy-one patients with inoperable gastric outlet obstruction receiving WallFlex enteral stents (WallFlex group) or Bonastents (Bonastent group) since April 2010 were analyzed retrospectively. The overall technical and clinical success rates of stent placement were 100% and 93%, respectively. The baseline characteristics and clinical outcomes including procedure-related complications, restenosis, and reintervention rates were comparable between the 2 groups. However, the Bonastent group had a higher rate of stent fracture than the WallFlex group (13.3% vs 0%, P = 0.03). The mean duration of overall stent patency was 132.7 days. The mean duration of survival was 181.9 days. Resumption of regular diet or low residual diet at day 7 after stent insertion predicted stent patency (hazard ratio [HR]: 0.28, P = 0.01). Cancer with gastric origin (HR: 0.25, P = 0.045) and poststent chemotherapy (HR: 0.38, P = 0.006) predicted lower mortality; however, peritoneal carcinomatosis (HR: 3.09, P = 0.04) correlated with higher mortality. Metallic stent placement is a safe and effective method for relieving gastric outlet obstruction. Except higher rate of stent fracture in the Bonastent group, there is no significant difference in clinical outcomes between the Bonastent group and the WallFlex group.

  3. Elastic Deformation Properties of Implanted Endobronchial Wire Stents in Benign and Malignant Bronchial Disease: A Radiographic In Vivo Evaluation

    SciTech Connect

    Hautmann, Hubert; Rieger, Johannes; Huber, Rudolf M.; Pfeifer, Klaus J.

    1999-03-15

    Purpose: To evaluate the long-term mechanical behavior in vivo of expandable endobronchial wire stents, we imaged three different prostheses in the treatment of tracheobronchial disease. Methods: Six patients with bronchial stenoses (three benign, three malignant) underwent insertion of metallic stents. Two self-expandable Wallstents, two balloon-expandable tantalum Strecker stents and two self-expandable nitinol Accuflex stents were used. Measurements of deformation properties were performed during voluntary cough by means of fluoroscopy, at 1 month and 7-10 months after implantation. The procedures were videotaped, their images digitized and the narrowing of stent diameters calculated at intervals of 20 msec. Results: After stent implantation all patients improved with respect to ventilatory function. Radial stent narrowing during cough reached 53% (Wallstent), 59% (tantalum Strecker stent), and 52% (nitinol Accuflex stent) of the relaxed post-implantation diameter. Stent compression was more marked in benign compared with malignant stenoses. In the long term permanent deformation occurred with the tantalum Strecker stents; the other stents were unchanged. Conclusion: Endobronchial wire stents can be helpful in the treatment of major airway collapse and obstructing bronchial lesions. However, evidence of material fatigue as a possible effect of exposure to recurrent mechanical stress on the flexible mesh tube may limit their long-term use. This seems to be predominantly important in benign bronchial collapse.

  4. Palliative therapy using polyurethane-covered self-expandable metallic stents for malignant esophageal strictures: experiences in six patients.

    PubMed

    Kato, M; Saji, S; Kanematsu, M; Hoshi, H; Ishiguchi, T; Kunieda, K; Takao, H; Sugiyama, Y

    1996-12-01

    To evaluate the utility and limitations of palliative stenting with polyurethane-covered self-expandable metallic stents, 6 patients (3 males and 3 females ranging in age from 58-85 [mean 72.1] years) with malignant esophageal strictures were treated with these stents between April 1993 and October 1995. Three had esophageal carcinoma, two had gastric carcinoma and one had lung carcinoma. Song-type self-expandable metallic stents were inserted by intubation under local laryngeal anesthesia. A retriever was attached in 4 stents and an anti-reflux mechanism was attached in 2 stents placed over the esophagocardiac strictures. The stents were placed successfully in all patients, and no major complication related to intubation was encountered. All the stents fully expanded within 3 days after insertion. The grade of dysphagia was improved in 5 (83%) of the 6 patients. One stent was extracted using a retriever in one patient with no improvement. No reflux symptoms were observed in 2 patients whom received stents with an anti-reflux mechanism. No blockage of the stent due to food impaction or secondary stricture occurred in any patient during the observation period. One stent migrated into the stomach in one patient 27 days after insertion. Esophageal stenting with polyurethane-covered self-expandable metallic stents is a relatively safe and effective palliation for malignant esophageal strictures. PMID:9001352

  5. Removal of Endobronchially Placed Vascular Self-Expandable Metallic Stent Using Flexible Bronchoscopy.

    PubMed

    Kremens, Karol

    2016-04-01

    Self-expanding metallic stents (SEMS) are commonly placed in malignant airway obstruction and sometimes in benign obstruction. Complications from SEMS placement are common, especially after 30 days from deployment. SEMS removal can be complicated and often involves significant resources. We report a case of a 78-year-old man with small cell carcinoma who underwent placement of a Luminexx endovascular stent in his right main stem bronchus, complicated by stent migration after initiation of chemotherapy. Stent removal was performed by flexible bronchoscopy, utilizing forceps inserted via a working channel, as well as a goose neck snare operated parallel to the bronchoscope. The patient was discharged the same day with no complications. PMID:27197344

  6. Fracture and Collapse of Balloon-Expandable Stents in the Bilateral Common Iliac Arteries Due to Shiatsu Massage

    SciTech Connect

    Ichihashi, Shigeo Higashiura, Wataru; Itoh, Hirofumi; Sakaguchi, Shoji; Kichikawa, Kimihiko

    2012-12-15

    We report a case of stent fracture and collapse of balloon-expandable stents caused by shiatsu massage. A 76-year-old man presented with complaints of intermittent claudication of the right lower extremity. Stenoses of the bilateral common iliac arteries (CIAs) were detected. Balloon-expandable stents were deployed in both CIAs, resulting in resolution of symptoms. Five months later, pelvis x-ray showed collapse of both stents. Despite the stent collapse, the patient was asymptomatic, and his ankle brachial index values were within the normal range. Further history showed that the patient underwent daily shiatsu therapy in the umbilical region, which may have triggered collapse of the stent. Physicians should advise patients to avoid compression of the abdominal wall after implantation of a stent in the iliac artery.

  7. Deployment of self-expandable stents in aneurysmatic cerebral vessels: comparison of different computational approaches for interventional planning.

    PubMed

    Bernardini, A; Larrabide, I; Petrini, L; Pennati, G; Flore, E; Kim, M; Frangi, A F

    2012-01-01

    In the last few years, there has been a growing focus on faster computational methods to support clinicians in planning stenting procedures. This study investigates the possibility of introducing computational approximations in modelling stent deployment in aneurysmatic cerebral vessels to achieve simulations compatible with the constraints of real clinical workflows. The release of a self-expandable stent in a simplified aneurysmatic vessel was modelled in four different initial positions. Six progressively simplified modelling approaches (based on Finite Element method and Fast Virtual Stenting--FVS) have been used. Comparing accuracy of the results, the final configuration of the stent is more affected by neglecting mechanical properties of materials (FVS) than by adopting 1D instead of 3D stent models. Nevertheless, the differences showed are acceptable compared to those achieved by considering different stent initial positions. Regarding computational costs, simulations involving 1D stent features are the only ones feasible in clinical context.

  8. Role of self-expanding metal stents in the management of variceal haemorrhage: Hype or hope?

    PubMed Central

    Hogan, Brian J; O’Beirne, James P

    2016-01-01

    Despite the advances of medical, endoscopic and radiological therapy over recent years the mortality rates of acute variceal haemorrhage are still 16%-20% and the medium term outcome has not improved in the last 25 years. Early transjugular intrahepatic portosystemic shunt has proved to be an effective therapy for selected groups of patients with a high risk of re-bleeding and moderate liver disease. However, there is an unmet need for a therapy that can be applied in patients with a high risk of re-bleeding and advanced liver disease either as definitive therapy or as a bridge to permanent therapy. Self-expanding metal stents can be placed without the need for endoscopic or fluoroscopic control and, once in place, will provide effective haemostasis and allow a route for oral fluids and nutrition. They can remain in place whilst liver function recovers and secondary prophylaxis is initiated. We review the results of 6 case series including a total of 83 patients and the first randomised controlled trial of self-expanding metal stents vs balloon tamponade (BT) in the management of refractory variceal haemorrhage. We report that self-expanding metal stents provide effective haemostasis and perform better than BT in refractory bleeding, where they are associated with fewer complications. Whilst the most effective place for self-expanding metal stents in the management algorithm needs to be determined by further randomised controlled trials, currently they provide an effective alternative to BT in selected patients. PMID:26788260

  9. Role of self-expanding metal stents in the management of variceal haemorrhage: Hype or hope?

    PubMed

    Hogan, Brian J; O'Beirne, James P

    2016-01-10

    Despite the advances of medical, endoscopic and radiological therapy over recent years the mortality rates of acute variceal haemorrhage are still 16%-20% and the medium term outcome has not improved in the last 25 years. Early transjugular intrahepatic portosystemic shunt has proved to be an effective therapy for selected groups of patients with a high risk of re-bleeding and moderate liver disease. However, there is an unmet need for a therapy that can be applied in patients with a high risk of re-bleeding and advanced liver disease either as definitive therapy or as a bridge to permanent therapy. Self-expanding metal stents can be placed without the need for endoscopic or fluoroscopic control and, once in place, will provide effective haemostasis and allow a route for oral fluids and nutrition. They can remain in place whilst liver function recovers and secondary prophylaxis is initiated. We review the results of 6 case series including a total of 83 patients and the first randomised controlled trial of self-expanding metal stents vs balloon tamponade (BT) in the management of refractory variceal haemorrhage. We report that self-expanding metal stents provide effective haemostasis and perform better than BT in refractory bleeding, where they are associated with fewer complications. Whilst the most effective place for self-expanding metal stents in the management algorithm needs to be determined by further randomised controlled trials, currently they provide an effective alternative to BT in selected patients.

  10. Cholecystoduodenal fistula: A complication of inserted self-expandable metallic bilitary stents

    SciTech Connect

    Nishida, Hirotoshi; Inoue, Hiroki; Ueno, Kazuto; Nagata, Yukitaka; Kato, Takeshi; Miyazono, Nobuaki; Nakajo, Masayuki

    1998-05-15

    We encountered a case of hepatic hilar cholangiocarcinoma resulting in cholecystoduodenal fistula after insertion of self-expandable metallic biliary stents (EMBSs). To our knowledge, there has been no report of cholecystoduodenal fistula after insertion of EMBSs. This case suggests that immediate gallbladder decompression may be necessary if acute cholecystitis occurs after insertion of EMBSs.

  11. Cholecystoduodenal Fistula: A Complication of Inserted Self-Expandable Metallic Biliary Stents

    SciTech Connect

    Nishida, Hirotoshi; Inoue, Hiroki; Ueno, Kazuto; Nagata, Yukitaka; Kato, Takeshi; Miyazono, Nobuaki; Nakajo, Masayuki

    1998-05-15

    We encountered a case of hepatic hilar cholangiocarcinoma resulting in cholecystoduodenal fistula after insertion of self-expandable metallic biliary stents (EMBSs). To our knowledge, there has been no report of cholecystoduodenal fistula after insertion of EMBSs. This case suggests that immediate gallbladder decompression may be necessary if acute cholecystitis occurs after insertion of EMBSs.

  12. Efficacy of Self-Expandable Metallic Stent Inserted for Refractory Hemorrhage of Duodenal Cancer.

    PubMed

    Orii, Takashi; Karasawa, Yukihiko; Kitahara, Hiroe; Yoshimura, Masaki; Okumura, Motohiro

    2016-01-01

    Because of advances in the technology of gastrointestinal endoscopy and improvements in the quality of stents, it has become routine to place a stent as palliative therapy for malignant gastrointestinal obstruction. On the other hand, stent placement for malignant gastrointestinal hemorrhage has scarcely been reported, although it may be performed for hemorrhage of the esophageal varicose vein. We recently experienced a patient with refractory hemorrhage from an unresectable duodenal cancer who underwent placement of a self-expandable metallic stent (SEMS) and thereafter had no recurrence of the hemorrhage. A 46-year-old man underwent laparotomy to radically resect a cancer in the third portion of the duodenum, which invaded widely to the superior mesenteric vein and its branches and was considered unresectable. After stomach-partitioning gastrojejunostomy was performed, chemotherapy was initiated according to the regimen of chemotherapy of far advanced gastric cancer. One year and 4 months after induction of chemotherapy, gastrointestinal hemorrhage occurred. Upper gastrointestinal endoscopy revealed the hemorrhage oozing from the duodenal cancer, and endoscopic hemostasis, such as injection of hypertonic saline epinephrine and argon plasma coagulation, was unsuccessful. Twenty days after emergence of the hemorrhage, an endoscopic covered SEMS was placed with confirmation by fluoroscopy. Immediately after placement of the stent, the tarry stool stopped and the anemia ceased to progress. The recurrence of the hemorrhage has not been confirmed without migration of the stent. SEMS is an effective hemostatic procedure for malignant refractory hemorrhage. PMID:27403118

  13. Efficacy of Self-Expandable Metallic Stent Inserted for Refractory Hemorrhage of Duodenal Cancer

    PubMed Central

    Orii, Takashi; Karasawa, Yukihiko; Kitahara, Hiroe; Yoshimura, Masaki; Okumura, Motohiro

    2016-01-01

    Because of advances in the technology of gastrointestinal endoscopy and improvements in the quality of stents, it has become routine to place a stent as palliative therapy for malignant gastrointestinal obstruction. On the other hand, stent placement for malignant gastrointestinal hemorrhage has scarcely been reported, although it may be performed for hemorrhage of the esophageal varicose vein. We recently experienced a patient with refractory hemorrhage from an unresectable duodenal cancer who underwent placement of a self-expandable metallic stent (SEMS) and thereafter had no recurrence of the hemorrhage. A 46-year-old man underwent laparotomy to radically resect a cancer in the third portion of the duodenum, which invaded widely to the superior mesenteric vein and its branches and was considered unresectable. After stomach-partitioning gastrojejunostomy was performed, chemotherapy was initiated according to the regimen of chemotherapy of far advanced gastric cancer. One year and 4 months after induction of chemotherapy, gastrointestinal hemorrhage occurred. Upper gastrointestinal endoscopy revealed the hemorrhage oozing from the duodenal cancer, and endoscopic hemostasis, such as injection of hypertonic saline epinephrine and argon plasma coagulation, was unsuccessful. Twenty days after emergence of the hemorrhage, an endoscopic covered SEMS was placed with confirmation by fluoroscopy. Immediately after placement of the stent, the tarry stool stopped and the anemia ceased to progress. The recurrence of the hemorrhage has not been confirmed without migration of the stent. SEMS is an effective hemostatic procedure for malignant refractory hemorrhage. PMID:27403118

  14. Self-expanding metal stenting for obstructing left colon cancer: A district hospital experience.

    PubMed

    Harilingam, Mohan Raj; Khushal, Amjad; Aikoye, Abdulmalik

    2016-07-01

    Stenting of malignant colonic obstructions using self-expanding metal stents (SEMS) is commonly used for palliation and can be used as an interim procedure prior to definitive surgery. We retrospectively reviewed prospectively collected data from all consecutive colonic stenting procedures undertaken between September 2007 and December 2014 at a district general hospital. Technical and clinical success rates, mortality, colonic perforation, and other complications were documented and analyzed. Sixty-four colonic stenting procedures were undertaken. Fifty-three (83 %) were for palliation and eleven (17 %) were performed as a bridge to definitive surgery. Technical (98.4 %) and clinical (89.9 %) success rates were excellent. The single documented failure was secondary to complete luminal obstruction. Three stent occlusions (4.6 %), one colonic perforation (1.5 %), and one migration were encountered. There were no procedure-related deaths. Colonic stenting for obstructing left-sided colon cancer is a safe and effective procedure, even in the district general hospital setting. The use of SEMS as a bridge to elective surgery balances surgical and oncological considerations and, therefore, is most appropriate for high surgical risk patients in this setting. PMID:27448435

  15. Comparison of Endoscopic Vacuum Therapy and Endoscopic Stent Implantation With Self-Expandable Metal Stent in Treating Postsurgical Gastroesophageal Leakage.

    PubMed

    Hwang, Jae J; Jeong, Yeon S; Park, Young S; Yoon, Hyuk; Shin, Cheol M; Kim, Nayoung; Lee, Dong H

    2016-04-01

    The aim of the present study was to evaluate the more effective therapy for the postsurgical gastroesophageal leakage by a head-to-head comparison of endoscopic vacuum therapy (EVT) and endoscopic stent implantation with self-expandable metal stent (E-SEMS). In this hospital-based, retrospective, observative study, the patients were classified into 2 groups. Those treated with EVT were assigned to the EVT group (n = 7), and those treated with E-SMS were assigned to the E-SEMS group (n = 11). We evaluated the clinical characteristics and treatment outcomes between the 2 groups. All 7 patients (100%) were treated with EVT, but only 7 of 11 patients (63.6%) in the stenting group were treated successfully. The median time to clinical success was 19.5 (5-21) days in the EVT group and 27.0 (3-84) days in the E-SEMS group. The median hospital stay was 37.1 (13-128) days in the EVT group and 87.3 (17-366) days in the E-SEMS group. The complicaion rate was lower in the EVT group (0/7, 0.0%) than that in the E-SEMS group (6/11, 54.5%) with statistically significant difference (P = 0.042). EVT is more effective and has fewer adverse effects than E-SMS therapy as a treatment for postsurgical gastroesophageal leakage.

  16. Comparison of Endoscopic Vacuum Therapy and Endoscopic Stent Implantation With Self-Expandable Metal Stent in Treating Postsurgical Gastroesophageal Leakage

    PubMed Central

    Hwang, Jae J.; Jeong, Yeon S.; Park, Young S.; Yoon, Hyuk; Shin, Cheol M.; Kim, Nayoung; Lee, Dong H.

    2016-01-01

    Abstract The aim of the present study was to evaluate the more effective therapy for the postsurgical gastroesophageal leakage by a head-to-head comparison of endoscopic vacuum therapy (EVT) and endoscopic stent implantation with self-expandable metal stent (E-SEMS). In this hospital-based, retrospective, observative study, the patients were classified into 2 groups. Those treated with EVT were assigned to the EVT group (n = 7), and those treated with E-SMS were assigned to the E-SEMS group (n = 11). We evaluated the clinical characteristics and treatment outcomes between the 2 groups. All 7 patients (100%) were treated with EVT, but only 7 of 11 patients (63.6%) in the stenting group were treated successfully. The median time to clinical success was 19.5 (5–21) days in the EVT group and 27.0 (3–84) days in the E-SEMS group. The median hospital stay was 37.1 (13–128) days in the EVT group and 87.3 (17–366) days in the E-SEMS group. The complicaion rate was lower in the EVT group (0/7, 0.0%) than that in the E-SEMS group (6/11, 54.5%) with statistically significant difference (P = 0.042). EVT is more effective and has fewer adverse effects than E-SMS therapy as a treatment for postsurgical gastroesophageal leakage. PMID:27100431

  17. Comparison of Endoscopic Vacuum Therapy and Endoscopic Stent Implantation With Self-Expandable Metal Stent in Treating Postsurgical Gastroesophageal Leakage.

    PubMed

    Hwang, Jae J; Jeong, Yeon S; Park, Young S; Yoon, Hyuk; Shin, Cheol M; Kim, Nayoung; Lee, Dong H

    2016-04-01

    The aim of the present study was to evaluate the more effective therapy for the postsurgical gastroesophageal leakage by a head-to-head comparison of endoscopic vacuum therapy (EVT) and endoscopic stent implantation with self-expandable metal stent (E-SEMS). In this hospital-based, retrospective, observative study, the patients were classified into 2 groups. Those treated with EVT were assigned to the EVT group (n = 7), and those treated with E-SMS were assigned to the E-SEMS group (n = 11). We evaluated the clinical characteristics and treatment outcomes between the 2 groups. All 7 patients (100%) were treated with EVT, but only 7 of 11 patients (63.6%) in the stenting group were treated successfully. The median time to clinical success was 19.5 (5-21) days in the EVT group and 27.0 (3-84) days in the E-SEMS group. The median hospital stay was 37.1 (13-128) days in the EVT group and 87.3 (17-366) days in the E-SEMS group. The complicaion rate was lower in the EVT group (0/7, 0.0%) than that in the E-SEMS group (6/11, 54.5%) with statistically significant difference (P = 0.042). EVT is more effective and has fewer adverse effects than E-SMS therapy as a treatment for postsurgical gastroesophageal leakage. PMID:27100431

  18. Transjugular intrahepatic portosystemic shunting (TIPS) with balloon-expandable and self-expanding stents: Technical and clinical aspects after 3 1/2 years' experience

    SciTech Connect

    Tesdal, I. Kaare; Jaschke, Werner; Buehler, Mathias; Adamus, Ralf; Filser, Thomas; Holm, Eggert; Georgi, Max

    1997-01-15

    Purpose. To evaluate prospectively our experience with transjugular intrahepatic portosystemic shunt (TIPS) using four different metallic stents. Methods. Between November 1991 and April 1995, 57 patients (41 men and 16 women; age 35-72 years, mean 54 years) underwent the TIPS procedure. Techniques for portal vein localization before and during TIPS were fluoroscopy, computed tomography (CT) studies, wedged hepatic venography, arterial portography, and ultrasound. After predilation we deployed balloon-expandable (n=48) and self-expanding (n=45) metallic stents. Fifteen patients underwent variceal embolization. Initial follow-up angiograms (mean 6.9 months, range 3-24 months) were obtained in 39 of these patients. Results. Fifty-three patients (93%) had successful TIPS placement. The mean decrease in portal pressure was 42.7%. Besides fluoroscopy, the most helpful techniques for portal vein localization were venography and CT. Residual stenosis (n=1) and late shortening (n=4) of Wallstents resulted in shunt dysfunction. The technical problems encountered with the Palmaz stent resulted from its lack of flexibility. We combined balloon-expandable and self-expanding stents in 12 patients. The 30-day and late follow-up (mean 11.9 months) percutaneous reintervention rates were 11.3% and 64.2%, respectively. There were no clinically significant complications related to the TIPS insertions. Conclusion. An ideal stent does not exist for TIPS, and the authors recommend combining a Palmaz stent with a flexible self-expanding stent.

  19. Small caliber covered self-expanding metal stents in the management of malignant dysphagia

    PubMed Central

    Kucera, Stephen; Barthel, James; Klapman, Jason; Shridhar, Ravi; Hoffe, Sarah; Harris, Cynthia; Almhanna, Khaldoun

    2016-01-01

    Background Use of large caliber [≥18 mm body diameter (BD)] self-expanding metal stents (SEMS) for management of malignant dysphasia is associated with substantial adverse event (AE) and mortality rates (MRs). We sought to determine dysphagia response, stent migration rates, and AE and MRs, for small caliber covered SEMS (sccSEMS) with BDs between 10–16 mm in malignant dysphagia. Methods Thirty-one patients underwent direct endoscopic placement of 50 sccSEMS between January 2008 and March 2011. Patients were monitored for change in dysphagia score (DS), stent migration, AEs, and death through May 2011. Results DS improved in 30 of 31 patients (97%). The median DS decreased from 3 to 2 (P<0.0001). The median effective duration of first sccSEMS placement was 116 (95% CI: 75–196) days. Major and minor AE rates were 6.5% and 19.4% respectively. No stent related deaths were encountered. The overall migration rate was 36% (18/50). The anticipated migration rate was 45.7% (16/35) and the unanticipated migration rate was 13.3% (2/15) (P=0.052). Positive effective clinical outcome occurred in 93.5% (29/31) of cases. Conclusions In malignant dysphagia, direct endoscopic sccSEMS placement provided acceptable dysphagia control and migration rates with substantial reductions in stent related AEs and MRs compared to those reported for large caliber SEMS. PMID:27284474

  20. Self-expanding metallic stent placement with an exaggerated 5-cm proximal tumor covering for palliation of esophageal cancer

    PubMed Central

    Tahiri, Mehdi; Ferraro, Pasquale; Duranceau, André; Berthiaume, Melanie; Thiffault, Vicky; Liberman, Moishe

    2015-01-01

    Background The study aimed to evaluate the short- and long-term outcomes with a technique of self-expanding metallic stent insertion in palliative esophageal cancer patients. We hypothesized that a systematic attempt at exaggerated (5 cm) proximal tumor covering could prevent both stent migration and tumor overgrowth/undergrowth. Methods We reviewed retrospectively all patients who underwent esophageal stenting for palliation of malignant dysphagia over a 24-month period. Consecutive patients were identified from a prospective thoracic surgery interventional endoscopy database. This technique consisted of endoscopic stent insertion with the aim of landing the proximal portion of the stent 5 cm cephalad to the proximal extent of the tumor. All patients were followed at one month post-procedure and every three months thereafter, until death. Short- and long-term complications associated with the procedure and mortality were evaluated. Results Forty seven patients underwent endoscopic insertion of an esophageal stent in the context of an inoperable esophageal cancer using this technique over a 24-month period. The mean age was 70.4±9.6 years. Four (8.5%) patients underwent re-stenting due to proximal tumor overgrowth. No stent migration, perforation, tumor ingrowth or stent occlusion was reported. The mean patient survival was 146±26.5 days. Conclusions Esophageal stent insertion under endoscopic guidance with proximal tumor covering of 5 cm is effective and safe. No cases of stent migration and a low incidence of tumor overgrowth/undergrowth were observed with this technique. PMID:26126578

  1. Iliocaval Confluence Stenting for Chronic Venous Obstructions

    SciTech Connect

    Graaf, Rick de; Wolf, Mark de; Sailer, Anna M.; Laanen, Jorinde van Wittens, Cees; Jalaie, Houman

    2015-10-15

    PurposeDifferent techniques have been described for stenting of venous obstructions. We report our experience with two different confluence stenting techniques to treat chronic bi-iliocaval obstructions.Materials and MethodsBetween 11/2009 and 08/2014 we treated 40 patients for chronic total bi-iliocaval obstructions. Pre-operative magnetic resonance venography showed bilateral extensive post-thrombotic scarring in common and external iliac veins as well as obstruction of the inferior vena cava (IVC). Stenting of the IVC was performed with large self-expandable stents down to the level of the iliocaval confluence. To bridge the confluence, either self-expandable stents were placed inside the IVC stent (24 patients, SECS group) or high radial force balloon-expandable stents were placed at the same level (16 patients, BECS group). In both cases, bilateral iliac extensions were performed using nitinol stents.ResultsRecanalization was achieved for all patients. In 15 (38 %) patients, a hybrid procedure with endophlebectomy and arteriovenous fistula creation needed to be performed because of significant involvement of inflow vessels below the inguinal ligament. Mean follow-up was 443 ± 438 days (range 7–1683 days). For all patients, primary, assisted-primary, and secondary patency rate at 36 months were 70, 73, and 78 %, respectively. Twelve-month patency rates in the SECS group were 85, 85, and 95 % for primary, assisted-primary, and secondary patency. In the BECS group, primary patency was 100 % during a mean follow-up period of 134 ± 118 (range 29–337) days.ConclusionStenting of chronic bi-iliocaval obstruction shows relatively high patency rates at medium follow-up. Short-term patency seems to favor confluence stenting with balloon-expandable stents.

  2. Long-Term Results after Placement of Aortic Bifurcation Self-Expanding Stents: 10 Year Mortality, Stent Restenosis, and Distal Disease Progression

    SciTech Connect

    Houston, J. Graeme Bhat, Raj; Ross, Rose; Stonebridge, Peter A.

    2007-02-15

    Purpose. To retrospectively evaluate the 10 year follow-up results in patients who had 'kissing' self-expanding stent aortic bifurcation reconstruction. Methods. Forty-three patients were treated with 'kissing' self-expanding stents for aortoiliac occlusive disease. Early follow-up with clinical and ankle brachial pressure indices (ABPI) was performed at 3, 6, 12, and 24 months and with intra-arterial digital subtraction angiography at 12-24 months; clinical and angiographic follow-up was performed for symptom recurrence up to 10 years after treatment. Retrospective record review was performed to assess mortality, clinical patency, angiographic patency, and secondary assisted patency of both stents and downstream peripheral vessels at 5 and 10 years follow-up. Results. The 2 year primary angiographic and secondary assisted stent patencies were 89% and 93%, respectively. At 10 years follow-up in 40 patients the mortality was 38% (due to myocardial infarction, stroke, chronic renal failure, malignancy, and liver failure). At 5 and 10 years follow-up the primary clinical stent patency was 82% and 68%, and the secondary assisted stent patency 93% and 86%, respectively. At 5 and 10 years, the distal vessel patency was 86% and 72%, and the secondary assisted distal vessel patency treated by surgical or endovascular techniques was 94% and 88%, respectively. At 10 years there was no limb loss. Conclusion. The long-term (10 year) results of aortic bifurcation arterial self-expanding stent placement in patients with arterial occlusive disease show a 10 year primary stent patency rate of 68% but a secondary assisted patency rate of 86%. In addition there is a high overall mortality due to other cardiovascular causes and the rate of distal disease progression and loss of patency is similar to the loss of stent patency rate.

  3. Efficacy of laser photoablative therapy and expandable metal stents for esophageal carcinoma

    NASA Astrophysics Data System (ADS)

    Balachandar, Gowra; Trowers, Eugene A.

    2000-05-01

    Malignant dysphagia is a serious condition in which 70% of patients die within one year, regardless of the treatment received. It provokes a rapid deterioration of a patient's physical condition and a significant worsening of quality of life. The surgical treatment of dysphagia is frequently complicated with technical difficulties, and often the tumors cannot be excised because of extensive invasion into adjacent structures. Furthermore, many patients are considered inoperable due to advanced age, associated diseases and malnutrition. Laser photoablative therapy coupled with expandable metal stents restores luminal patency in more than 80% of patients allowing them to eat liquids and soft foods. The efficacy of laser photoablative therapy and expandable metal stents for the palliation esophageal carcinoma will be critically reviewed.

  4. Successful technical and clinical outcome using a second generation balloon expandable coronary stent for transplant renal artery stenosis: Our experience

    PubMed Central

    Salsamendi, Jason; Pereira, Keith; Baker, Reginald; Bhatia, Shivank S; Narayanan, Govindarajan

    2015-01-01

    Transplant renal artery stenosis (TRAS) is a vascular complication frequently seen because of increase in the number of renal transplantations. Early diagnosis and management is essential to optimize a proper graft function. Currently, the endovascular treatment of TRAS using angioplasty and/or stenting is considered the treatment of choice with the advantage that it does not preclude subsequent surgical correction. Treatment of TRAS with the use of stents, particularly in tortuous transplant renal anatomy presents a unique challenge to an interventional radiologist. In this study, we present three cases from our practice highlighting the use of a balloon-expandable Multi-Link RX Ultra coronary stent system (Abbott Laboratories, Abbott Park, Illinois, USA) for treating high grade focal stenosis along very tortuous renal arterial segments. Cobalt–Chromium alloy stent scaffold provides excellent radial force, whereas the flexible stent design conforms to the vessel course allowing for optimal stent alignment. PMID:26629289

  5. Combined Placement of Covered Self-Expanding Metallic Stents and Nasojejunal Tube for Managing Large Lower Esophageal Perforations

    PubMed Central

    Rana, Surinder S; Gupta, Rajesh; Dahiya, Divya; Behera, Arunanshu; Bhasin, Deepak K

    2014-01-01

    Covered self-expanding metallic stents (cSEMSs) have emerged as effective treatment option for esophageal perforations. However, the large lower esophageal perforations where the cSEMS is placed across gastroesophageal junction have lower healing rates because refluxed gastric contents constantly irritate perforation and also there is increased risk of stent migration. Moreover, gastric mucosa tends to prolapse into lumen of lower end of stent causing its obstruction, leading to seepage of saliva and fluids from upper end of stent even in the patients who are on parenteral nutrition. We present our experience of a novel technique of combined cSEMS and nasojejunal tube (NJT) placement in four patients (two males) with benign large lower esophageal perforations. The NJT was placed through the stent into the jejunum through which patients were given enteral feeding. The stents were placed 5 - 21 days after esophageal perforation with the size of perforation ranging from 4 to 6 cm. As the NJT formed a loop in stomach, it prevented migration of stent. And also its presence in lumen of stent prevented its obstruction by prolapsing gastric mucosa, thereby preventing seepage of saliva and fluids from side of stent. Both stents and NJT were removed after 6 weeks and leak closed in all patients. Combined cSEMS and NJT placement seems to be safe and effective for treating large lower esophageal perforations. NJT placement seems to decrease risk of migration, prevents seepage of fluids and permits early enteral nutrition, thereby improving the healing rates.

  6. Mechanical Interaction of an Expanding Coiled Stent with a Plaque-Containing Arterial Wall: A Finite Element Analysis.

    PubMed

    Welch, Tré R; Eberhart, Robert C; Banerjee, Subhash; Chuong, Cheng-Jen

    2016-03-01

    Wall injury is observed during stent expansion within atherosclerotic arteries, related in part to stimulation of the inflammatory process. Wall stress and strain induced by stent expansion can be closely examined by finite element analysis (FEA), thus shedding light on procedure-induced sources of inflammation. The purpose of this work was to use FEA to examine the interaction of a coiled polymer stent with a plaque-containing arterial wall during stent expansion. An asymmetric fibrotic plaque-containing arterial wall model was created from intravascular ultrasound (IVUS) images of a diseased artery. A 3D model for a coil stent at unexpanded state was generated in SolidWorks. They were imported into ANSYS for FEA of combined stent expansion and fibrotic plaque-distortion. We simulated the stent expansion in the plaqued lumen by increasing balloon pressure from 0 to 12 atm in 1 atm step. At increasing pressure, we examined how the expanding stent exerts forces on the fibrotic plaque and vascular wall components, and how the latter collectively resist and balance the expansive forces from the stent. Results show the expanding coiled stent creates high stresses within the plaque and the surrounding fibrotic capsule. Lower stresses were observed in adjacent medial and adventitial layers. High principal strains were observed in plaque and fibrotic capsule. The results suggest fibrotic capsule rupture might occur at localized regions. The FEA/IVUS method can be adapted for routine examination of the effects of the expansion of selected furled stents against IVUS-reconstructed diseased vessels, to improve stent deployment practices.

  7. Use of Self-Expanding Stents for the Treatment of Vertebral Artery Ostial Stenosis: a Single Center Experience

    PubMed Central

    Chung, Sun Young; Choi, Jin Woo; Choi, Byung Se; In, Hyun Sin; Kim, Sun Mi; Choi, Choong Gon; Kim, Sang Joon; Suh, Dae Chul

    2010-01-01

    Objective To evaluate our early experience using self-expanding stents to treat atherosclerotic vertebral artery ostial stenosis (VAOS), with respect to technical feasibility and clinical and imaging follow-up results. Materials and Methods A total of 20 lesions in 20 patients underwent stenting of the VAOS using a self-expanding stent (Precise RX; Cordis Neurovascular, Miami Lakes, FL). Two patients were asymptomatic. We analyzed the technical success rate, causes of technical failure, occurrence of any vascular or neurological event, and the occurrence of any neurological abnormality or in-stent restenosis (ISR) seen on follow-up. The imaging follow-up was performed with Doppler ultrasound (DUS) as a primary screening modality. Results One instance of technical failure was caused by failure of the guidewire passage. The stent diameter was 5 mm, and post-stenting balloon dilatations were necessary in all cases. Stent misplacement requiring placement of an additional stent occurred in four cases. Following a 14.8 month average clinical follow-up time, two patients showed anterior circulation ischemia, which was not attributed to the VAOS we treated. Following a 13.7 month average DUS follow-up, five patients showed a mild degree of diffuse or focal intimal thickening in the stent lumen; however, none of the stenosis showed luminal loss of more than 50% and no stent fracture was noted. Conclusion The use of self-expanding stents for treating VAOS was technically feasible and helped to improve artery patency during our limited follow-up interval. PMID:20191062

  8. Clinical outcomes of self-expandable stent placement for benign esophageal diseases: A pooled analysis of the literature

    PubMed Central

    van Halsema, Emo E; van Hooft, Jeanin E

    2015-01-01

    AIM: To analyze the outcomes of self-expandable stent placement for benign esophageal strictures and benign esophageal leaks in the literature. METHODS: The PubMed, Embase and Cochrane databases were searched for relevant articles published between January 2000 and July 2014. Eight prospective studies were identified that analyzed the outcomes of stent placement for refractory benign esophageal strictures. The outcomes of stent placement for benign esophageal leaks, perforations and fistulae were extracted from 20 retrospective studies that were published after the inclusion period of a recent systematic review. Data were pooled and analyzed using descriptive statistics. RESULTS: Fully covered self-expandable metal stents (FC SEMS) (n = 85), biodegradable (BD) stents (n = 77) and self-expandable plastic stents (SEPS) (n = 70) were inserted in 232 patients with refractory benign esophageal strictures. The overall clinical success rate was 24.2% and according to stent type 14.1% for FC SEMS, 32.9% for BD stents and 27.1% for SEPS. Stent migration occurred in 24.6% of cases. The overall complication rate was 31.0%, including major (17.7%) and minor (13.4%) complications. A total of 643 patients were treated with self-expandable stents mainly for postsurgical leaks (64.5%), iatrogenic perforations (19.6%), Boerhaave’s syndrome (7.8%) and fistulae (3.7%). FC SEMS and partially covered SEMS were used in the majority of patients. Successful closure of the defect was achieved in 76.8% of patients and according to etiology in 81.4% for postsurgical leaks, 86.0% for perforations and 64.7% for fistulae. The pooled stent migration rate was 16.5%. Stent-related complications occurred in 13.4% of patients, including major (7.8%) and minor (5.5%) complications. CONCLUSION: The outcomes of stent placement for refractory benign esophageal strictures were poor. However, randomized trials are needed to put this into perspective. The evidence on successful stent placement for benign

  9. A finite element study of balloon expandable stent for plaque and arterial wall vulnerability assessment

    NASA Astrophysics Data System (ADS)

    Karimi, Alireza; Navidbakhsh, Mahdi; Razaghi, Reza

    2014-07-01

    The stresses induced within plaque tissues and arterial layers during stent expansion inside an atherosclerotic artery can be exceeded from the yield stresses of those tissues and, consequently, lead to plaque or arterial layer rupture. The distribution and magnitude of the stresses in each component involved in stenting might be clearly different for different plaque types and different arterial layers. In this study, a nonlinear finite element simulation was employed to investigate the effect of plaque composition (calcified, cellular, and hypocellular) on the stresses induced in the arterial layers (intima, media, and adventitia) during implantation of a balloon expandable coronary stent into a stenosed artery. The atherosclerotic artery was assumed to consist of a plaque and normal/healthy arterial tissues on its outer side. The results indicated a significant influence of plaque types on the maximum stresses induced within the plaque wall and arterial layers during stenting but not when computing maximum stress on the stent. The stress on the stiffest calcified plaque wall was in the fracture level (2.38 MPa), whereas cellular and hypocellular plaques remain stable owing to less stress on their walls. Regardless of plaque types, the highest von Mises stresses were observed on the stiffest intima layer, whereas the lowest stresses were seen to be located in less stiff media layer. The computed stresses on the intima layer were found to be high enough to initiate a rupture in this stiff layer. These findings suggest a higher risk of arterial vascular injury for the intima layer, while a lower risk of arterial injury for the media and adventitia layers.

  10. Finite Element Modeling of A Novel Self-Expanding Endovascular Stent Method in Treatment of Aortic Aneurysms

    NASA Astrophysics Data System (ADS)

    Arokiaraj, Mark C.; Palacios, Igor F.

    2014-01-01

    A novel large self-expanding endovascular stent was designed with strut thickness of 70 μm × 70 μm width. The method was developed and investigated to identify a novel simpler technique in aortic aneurysm therapy. Stage 1 analysis was performed after deploying it in a virtual aneurysm model of 6 cm wide × 6 cm long fusiform hyper-elastic anisotropic design. At cell width of 9 mm, there was no buckling or migration of the stent at 180 Hg. Radial force of the stents was estimated after parametric variations. In stage 2 analysis, a prototype 300 μm × 150 μm stent with a cell width of 9 mm was chosen, and it was evaluated similarly after embedding in the aortic wall, and also with a tissue overgrowth of 1 mm over the stent. The 300/150 μm stent reduced the peak wall stress by 70% in the aneurysm and 50% reduction in compliance after embedding. Stage 3 analysis was performed to study the efficacy of stents with struts (thickness/width) 70/70, 180/100 and 300/150 μm after embedding and tissue overgrowth. The adjacent wall stresses were very minimal in stents with 180/100 and 70/70 μm struts after embedding. There is potential for a novel stent method in aortic aneurysm therapy.

  11. Gastrotracheal fistula: Treatment with a covered elf-expanding Y-shaped metallic stent

    PubMed Central

    Wang, Fei; Yu, Hong; Zhu, Ming-Hui; Li, Quan-Peng; Ge, Xian-Xiu; Nie, Jun-Jie; Miao, Lin

    2015-01-01

    A 67-year-old man had a sev-ere cough and pulmonary infection for 1 wk before seeking evaluation at our hospital. He had undergone esophagectomy with gastric pull-up and radiotherapy for esophageal cancer 3 years previously. After admission to our hospital, gastroscopy and bronchoscopy revealed a fistulous communication between the posterior tracheal wall near the carina and the upper residual stomach. We measured the diameter of the trachea and bronchus and determined the site and size of the fistula using multislice computed tomography and gastroscopy. A covered self-expanding Y-shaped metallic stent was implanted into the trachea and bronchus. Subsequently, the fistula was closed completely. The patient tolerated the stent well and had good palliation of his symptoms. PMID:25624743

  12. Self-expandable metallic stents for palliation of patients with malignant gastric outlet obstruction caused by stomach cancer

    PubMed Central

    Kim, Tae Oh; Kang, Dae Hwan; Kim, Gwang Ha; Heo, Jeong; Song, Geun Am; Cho, Mong; Kim, Dong Heon; Sim, Mun Sup

    2007-01-01

    AIM: To ascertain clinical outcome and complications of self-expandable metal stents for endoscopic palliation of patients with malignant obstruction of the gastrointestinal (GI) tract. METHODS: A retrospective review was performed throughout August 2000 to June 2005 of 53 patients with gastric outlet obstruction caused by stomach cancer. All patients had symptomatic obstruction including nausea, vomiting, and decreased oral intake. All received self-expandable metallic stents. RESULTS: Stent implantation was successful in all 53 (100%) patients. Relief of obstructive symptoms was achieved in 43 (81.1%) patients. No immediate stent-related complications were noted. Seventeen patients had recurrent obstruction (tumor ingrowth in 14 patients, tumor overgrowth in 1 patient, and partial distal stent migration in 2 patients). The mean survival was 145 d. Median stent patency time was 187 d. CONCLUSION: Endoscopic placement of self-expandable metallic stents is a safe and effective treatment for the palliation of patients with inoperable malignant gastric outlet obstruction caused by stomach cancer. PMID:17352023

  13. An overview of thin film nitinol endovascular devices.

    PubMed

    Shayan, Mahdis; Chun, Youngjae

    2015-07-01

    Thin film nitinol has unique mechanical properties (e.g., superelasticity), excellent biocompatibility, and ultra-smooth surface, as well as shape memory behavior. All these features along with its low-profile physical dimension (i.e., a few micrometers thick) make this material an ideal candidate in developing low-profile medical devices (e.g., endovascular devices). Thin film nitinol-based devices can be collapsed and inserted in remarkably smaller diameter catheters for a wide range of catheter-based procedures; therefore, it can be easily delivered through highly tortuous or narrow vascular system. A high-quality thin film nitinol can be fabricated by vacuum sputter deposition technique. Micromachining techniques were used to create micro patterns on the thin film nitinol to provide fenestrations for nutrition and oxygen transport and to increase the device's flexibility for the devices used as thin film nitinol covered stent. In addition, a new surface treatment method has been developed for improving the hemocompatibility of thin film nitinol when it is used as a graft material in endovascular devices. Both in vitro and in vivo test data demonstrated a superior hemocompatibility of the thin film nitinol when compared with commercially available endovascular graft materials such as ePTFE or Dacron polyester. Promising features like these have motivated the development of thin film nitinol as a novel biomaterial for creating endovascular devices such as stent grafts, neurovascular flow diverters, and heart valves. This review focuses on thin film nitinol fabrication processes, mechanical and biological properties of the material, as well as current and potential thin film nitinol medical applications.

  14. Implantation of self-expanding metal stent in the treatment of severe bleeding from esophageal ulcer after endoscopic band ligation.

    PubMed

    Mishin, I; Ghidirim, G; Dolghii, A; Bunic, G; Zastavnitsky, G

    2010-09-01

    Endoscopic variceal ligation is superior to sclerotherapy because of its lower rebleeding and complication rates. However, ligation may be associated with life-threatening bleeding from postbanding esophageal ulcer. We report a case of a 49-year-old male with massive hemorrhage from esophageal ulcer on 8th day after successful band ligation of bleeding esophageal varices caused by postviral liver cirrhosis (Child-Pugh class C). A removable polyurethane membrane-covered self-expanding metal stent (SX-ELLA stent Danis, 135 mm × 25 mm, ELLA-CS, Hradec-Kralove, Czech Republic) was inserted in ICU for preventing fatal hemorrhage. Complete hemostasis was achieved and stent was removed after 8 days without rebleeding or any complications. To the best of our knowledge, this is the first report in English literature regarding life-threatening hemorrhage from postbanding esophageal ulcer successfully treated by self-expanding metal stent in a patient with portal hypertension.

  15. Endoscopic Ultrasound-Guided Self-Expandable Metal Stent Placement for the Treatment of Infected Pancreatic Pseudocysts

    PubMed Central

    Masrour, Farbod; Mallat, Damien

    2014-01-01

    The standard endoscopic ultrasound (EUS) approach of cystogastrostomy involves the use of series of plastic pigtail stents that are placed through the wall of the cyst. The use of a single stent has also been described in the literature. Here we describe five cases of EUS-guided cystogastrostomy with irrigation of infected pancreatic pseudocysts using a single self-expandable metal stent (SEMS). To our knowledge this has not been described in the literature in the United States. This novice approach will have significant implications in the management of infected pseudocysts with a lower morbidity, mortality and overall cost compared to conventional management such as surgery or percutaneous drainage.

  16. Prevention of Intracranial In-stent Restenoses: Predilatation with a Drug Eluting Balloon, Followed by the Deployment of a Self-Expanding Stent

    SciTech Connect

    Vajda, Zsolt Guethe, Thomas Perez, Marta Aguilar Kurre, Wiebke; Schmid, Elisabeth Baezner, Hansjoerg; Henkes, Hans

    2013-04-15

    Stenting in intracranial atherosclerotic disease (ICAD) is increasingly debated, due to issues of procedural safety, technical efficacy, and in-stent recurrent stenoses (ISR). In the present study, feasibility, safety, and efficacy of angioplasty using a drug-eluting balloon (DEB) followed by the implantation of a self-expanding stent (Enterprise) were evaluated for the treatment of ICAD lesions. Fifty-two patients (median age: 71 years; range: 54-86 years; male/female ratio 37:15) underwent stenting of high-grade ICAD lesions between February 2010 and November 2011 in a single center. Angioplasty using a paclitaxel coated SeQuent Please (B. Braun, Germany) or DIOR (Eurocor, Germany) coronary PTCA balloon, followed by the implantation of a self-expanding stent (Enterprise, Codman, USA) was performed in 54 lesions. Angiographic and clinical follow-up was performed at 6 and 12 weeks, 6 and 12 months, and yearly thereafter. Technical success rate, periprocedural complications, occurrence of recurrent ischemic symptoms, and the development of an ISR were analyzed. Angioplasty using a DEB followed by stent implantation was successfully performed in 44 (81 %) cases. DEB insertion failed in 19 % of the cases and angioplasty was finally performed using a conventional PTCA balloon. The combined procedure related permanent neurologic morbidity and mortality rate (stroke, ICH, and subarachnoid hemorrhage) at 30 days and beyond was 5 %. Angiographic and clinical follow-up were obtained in 33 (61 %) lesions in 32 patients. Recurrent stenosis was seen in one (3 %) lesion. Angioplasty and stenting using a DEB is safe and yields encouragingly low ISR rates. Further technical developments to improve lesion accessibility are, nevertheless, mandatory.

  17. Fully Covered Self-Expandable Metal Stents for Treatment of Malignant Biliary Strictures due to Pancreatic Carcinoma

    PubMed Central

    Samie, Ahmed Abdel; Stumpf, Michael; Theilmann, Lorenz

    2012-01-01

    Background Transpapillary stents are used to treat malignant biliary strictures. However, there are different stent types and data are controversial in respect to success and complications. Recently, completely covered self-expandable metal stents (CSEMS) have become available. The aim of this study is to present a consecutive series of CSEMS placed to decompress the bile duct in malignant stenosis due to pancreatic carcinoma and to evaluate the effectiveness, complication rate and extractability of these devices. Methods We retrospectively reviewed the courses of 27 consecutive patients who received CSEMS due to malignant biliary strictures because of pancreatic carcinoma regardless of presumed resectability between January 2010 and May 2012 in our endoscopic unit. Results A total of 27 patients (12 male and 15 female) were included in the study. The mean age of the patients was 75 years. Endoscopic retrograde cholangiopancreatography (ERCP), endoscopic sphincterotomy (ES) and stent placement were successful at first attempt in all cases. The mean length of the stenosis was 20 mm. In 24 patients (89%) a stent length of 4 cm was sufficient to bridge the stenosis. In three cases a stent length of 6 cm was necessary. Drainage was achieved as monitored by a significant decrease or normalization of bilirubin in all cases (mean bilirubin 8.5 mg/dL and 1.5 mg/dL before and after stent placement respectively), 15 patients underwent surgery with pylorus preserving duodenopancreatectomy. In all patients who underwent surgery stents could be removed during the operation without difficulties. Leakage of the biliodigestive anastomosis occurred in one patient (6.6%). Four (15%) of the 27 patients developed complications related to the endoscopic procedure and/or stent placement respectively (cholecystitis in two patients, stent occlusion in one patient, and post-sphincterotomy bleeding in one patient). Conclusion The prolonged patency, extractability, and low complication rate

  18. Self-expandable metal stents for achalasia: Thinking out of the box!

    PubMed Central

    Sioulas, Athanasios D; Malli, Chrysoula; Dimitriadis, George D; Triantafyllou, Konstantinos

    2015-01-01

    Achalasia is a primary motor disorder of the esophagus diagnosed manometrically in the clinical setting of dysphagia to both solids and liquids. Currently established treatment options include pneumatic dilation, laparoscopic Heller myotomy, botulinum toxin injection performed endoscopically, oral agents that relax the lower esophageal sphincter and esophagectomy for refractory, end-stage disease. Despite their effectiveness, a significant proportion of patients eventually relapses and needs retreatment. In this setting, several new techniques are under investigation promising future enrichment of our therapeutic armamentarium for achalasic patients. Among them, peroral endoscopic myotomy and self-expandable metal stents placed across the gastro-esophageal junction represent the most encouraging modalities, as initial studies assessing their efficacy and safety indicate. This review highlights the role of self-expandable metal stents in the management of patients with achalasia. Their possible position in the therapeutic algorithm of achalasia along with established and novel techniques is also assessed. Finally, the need for large prospective randomized trials is underlined in order to elucidate the numerous relevant issues. PMID:25610533

  19. Quantification of biomechanical interaction of transcatheter aortic valve stent deployed in porcine and ovine hearts.

    PubMed

    Mummert, Joseph; Sirois, Eric; Sun, Wei

    2013-03-01

    Success of the deployment and function in transcatheter aortic valve replacement is heavily reliant on the tissue-stent interaction. The present study quantified important tissue-stent contact variables of self-expanding transcatheter aortic valve stents when deployed into ovine and porcine aortic roots, such as the stent radial expansion force, stent pullout force, the annulus deformation response and the coefficient of friction on the tissue-stent contact interface. Braided Nitinol stents were developed, tested to determine stent crimped diameter vs. stent radial force from a stent crimp experiment, and deployed in vitro to quantify stent pullout, aortic annulus deformation, and the coefficient of friction between the stent and the aortic tissue from an aortic root-stent interaction experiment. The results indicated that when crimped at body temperature from 26 mm to 19, 21 and 23 mm stent radial forces were approximately 30-40% higher than those crimped at room temperature. Coefficients of friction leveled to approximately 0.10 ± 0.01 as stent wire diameter increased and annulus size decreased from 23 to 19 mm. Regardless of aortic annulus size and species tested, it appeared that a minimum of about 2.5 mm in annular dilatation, caused by about 60 N of radial force from stent expansion, was needed to anchor the stent against a pullout into the left ventricle. The study of the contact biomechanics in animal aortic tissues may help us better understand characteristics of tissue-stent interactions and quantify the baseline responses of non-calcified aortic tissues.

  20. Drug-Eluting Nitinol Stent Treatment of the Superficial Femoral Artery and Above-the-Knee Popliteal Artery (The Zilver PTX Single-Arm Clinical Study): A Comparison Between Diabetic and Nondiabetic Patients

    SciTech Connect

    Fanelli, Fabrizio; Primo, Massimiliano Di; Boatta, Emanuele; Johnston, Krystal; Sapoval, Marc

    2013-10-15

    Purpose: To describe the 1-year results of drug-eluting nitinol stent placement in the femoropopliteal artery of diabetic and nondiabetic patients. Materials and Methods: All patients enrolled in this prospective, multicenter study underwent paclitaxel-eluting stent placement for de novo or restenotic lesions of the superficial femoral and/or popliteal artery. Baseline and follow-up walking impairment questionnaire (WIQ) scores, Rutherford classifications, and ankle-brachial index (ABI) measurements were obtained. Follow-up was completed at 1, 6, and 12 months. Results: There were 285 diabetic patients and 502 nondiabetic patients treated. There were no significant differences in mean lesion length or lesion calcification between patient groups. Procedural success in both treatment groups was >97 %. There were no significant differences between diabetic and nondiabetic groups in Kaplan-Meier estimates of patency, event-free survival (EFS), or freedom from target lesion revascularization (TLR) at 6 and 12 months. Both groups experienced a significant increase in ABI and WIQ values after treatment, and these improvements were sustained to 12-month follow-up; however, nondiabetic patients had significantly greater 6- and 12-month WIQ scores compared with diabetic patients. Based on covariate analysis, the only factors shown to be significant and to negatively influence patency were longer lesion length (p = 0.009), higher Rutherford classification (p = 0.02), and lack of hypertension (p = 0.02); diabetic status was not found to be a significant factor. Conclusion: Diabetic and nondiabetic patients had similar estimates of primary patency, EFS, and freedom from TLR; however, diabetic patients showed less improvement in WIQ scores compared with nondiabetic patients.

  1. Lubrication of Nitinol 60

    NASA Technical Reports Server (NTRS)

    Pepper, Stephen V.; DellaCorte, Christopher; Glennon, Glenn

    2010-01-01

    The mechanical properties of Nitinol 60, 60 wt% Ni, 40 wt% Ti (55 at.% Ni, 45 at.% Ti) are sufficiently attractive to warrant its consideration as a lubricated triboelement. Triboelements are always run lubricated. The ability to lubricate Nitinol 60 by the oils usually used on spacecraft mechanisms--Pennzane 2001A, Krytox 143AC and Castrol 815Z--was experimentally determined. These oils were run in the boundary lubrication regime for Nitinol 60 balls running against Nitinol 60 counterfaces in the vacuum spiral orbit tribometer. Test results consisting of the coefficient of friction versus time (friction traces) and relative degradation rates of the oils are presented. Contrary to the inability to successfully lubricate other metal alloys with high titanium content, it was found that Nitinol 60 is able to be lubricated by these oils. Overall, the results presented here indicate that Nitinol 60 is a credible candidate material for bearing applications.

  2. Fully Covered Self-Expandable Metal Stents for Treatment of Post-Sphincterotomy Bleeding

    PubMed Central

    Samie, Ahmed Abdel; Theilmann, Lorenz

    2012-01-01

    Endoscopic biliary sphincterotomy (ES) is the cornerstone of therapeutic endoscopic retrograde cholangiopancreatography (ERCP); however, serious complications are not uncommon. Post-sphincterotomy bleeding is one of the most frequent complications following ES and may occur in up to 10% of the patients. The spectrum of presentation may range from self-limited to severe live threatening hemorrhage. Different endoscopic treatment options are available. Angiographic embolisation and surgery are preserved for refractory cases not controlled by endoscopic means. Recently, completely covered self-expandable metal stents (CSEMS) have been applied to achieve hemostasis in severe post-sphincterotomy bleeding not controlled by other measures. We present our experience with this method to control delayed bleeding after ES in two patients requiring continuous therapeutic anticoagulation due to high cardiovascular embolic risk.

  3. Temporary placement of fully covered self-expandable metal stents for the treatment of benign biliary strictures

    PubMed Central

    Chaput, Ulriikka; Vienne, Ariane; Audureau, Etienne; Bauret, Paul; Bichard, Philippe; Coumaros, Dimitri; Napoléon, Bertrand; Ponchon, Thierry; Duchmann, Jean-Christophe; Laugier, René; Lamouliatte, Hervé; Védrenne, Bruno; Gaudric, Marianne; Chaussade, Stanislas; Robin, Françoise; Leblanc, Sarah

    2015-01-01

    Background Endoscopic treatment of benign biliary strictures (BBS) can be challenging. Objective To evaluate the efficacy of fully covered self-expandable metal stents (FCSEMS) in BBS. Methods Ninety-two consecutive patients with BBS (chronic pancreatitis (n = 42), anastomotic after liver transplantation (n = 36), and post biliary surgical procedure (n = 14)) were included. FCSEMS were placed across strictures for 6 months before endoscopic extraction. Early success rate was defined as the absence of biliary stricture or as a minimal residual anomaly on post-stent removal endoscopic retrograde cholangiopancreatography (ERCP). Secondary outcomes were the final success and stricture recurrence rates as well as procedure-related morbidity. Results Stenting was successful in all patients. Stenting associated complications were minor and occurred in 22 (23.9%) patients. Migration occurred in 23 (25%) patients. Stent extraction was successful in all but two patients with proximal stent migration. ERCP after the 6 months stenting showed an early success in 84.9% patients (chronic pancreatitis patients: 94.7%, liver transplant: 87.9%, post-surgical: 61.5%) (p = 0.01). Final success was observed in 57/73 (78.1%) patients with a median follow-up of 12 ± 3.56 months. Recurrence of biliary stricture occurred in 16/73 (21.9%) patients. Conclusions FCSEMS placement is efficient for patients with BBS, in particular for chronic pancreatitis patients. Stent extraction after 6 months indwelling, although generally feasible, may fail in a few cases. PMID:27403307

  4. Endovascular covered stent repair of an iatrogenic subclavian artery-to-pulmonary artery fistula and pseudoaneurysm.

    PubMed

    Wheeler, Shane C; Zinn, Kenneth M; Hughes, Terence W

    2007-06-01

    An iatrogenic fistula and consequent pseudoaneurysm developed between the right subclavian artery and right pulmonary artery as a result of misplacement of a hemodialysis access catheter. The patient, who was considered to be at high risk for surgical repair, successfully underwent endovascular treatment that involved insertion of two nitinol stents covered with expanded polytetrafluoroethylene (stent-grafts), one into the right subclavian artery and the other into a right upper lobe pulmonary artery. Multi-detector row computed tomographic angiography played an integral role in the evaluation of the patient's vascular injury and treatment planning. PMID:17538141

  5. Stent-Assisted Clip Placement for Complex Internal Carotid Artery Intracranial Aneurysms

    PubMed Central

    Qureshi, Adnan I.; Chughtai, Morad; Khan, Asif A.; Suri, M. Fareed K.; Sherr, Gregory T.

    2016-01-01

    BACKGROUND We report two procedures using a stent-assisted microsurgical clip placement to treat complex intracranial aneurysms originating from supraclinoid segment of the internal carotid artery. CASE DESCRIPTIONS In both procedures, primary clip placement was considered technically difficult due to either complex morphology or inferior protrusion of aneurysm fundus within the interclinoid space. A nitinol self-expanding stent was placed across the neck of the aneurysm either preoperatively or intraoperatively. Obliteration of aneurysm and patency of the artery was confirmed by angiography after clip placement. CONCLUSION Description of an integrated open microsurgical and endovascular approach and review of literature pertaining to considerations for treatment approach are discussed. PMID:26958150

  6. In Vitro Hemocompatibility of Thin Film Nitinol In Stenotic Flow Conditions

    PubMed Central

    Kealey, C.P.; Whelan, S.A.; Chun, Y.J.; Soojung, C.H.; Tulloch, A.W.; Mohanchandra, K.P.; DiCarlo, D; Levi, D.S.; Carman, G.P.; Rigberg, D.A.

    2010-01-01

    Because of its low profile and biologically inert behavior, thin film nitinol (TFN) is ideally suited for use in construction of endovascular devices. We have developed a surface treatment for TFN designed to minimize platelet adhesion by creating a super-hydrophilic surface. The hemocompatibility of expanded polytetrafluorethylene (ePTFE), untreated thin film nitinol (UTFN), and a surface treated superhydrophilic thin film nitinol (STFN) was compared using an in vitro circulation model with whole blood under flow conditions simulating a moderate arterial stenosis. Scanning electron microscopy analysis showed increased thrombus on ePTFE as compared to UTFN or STFN. Total blood product deposition was 6.3 ± 0.8 mg/cm2 for ePTFE, 4.5 ± 2.3 mg/cm2 for UTFN, and 2.9 ± 0.4 mg/cm2 for STFN (n = 12, p < 0.01). ELISA assay for fibrin showed 326 ± 42 µg/cm2 for ePTFE, 45.6 ± 7.4 µg/cm2 for UTFN, and 194 ± 25 µg/cm2 for STFN (n = 12, p < 0.01). Platelet deposition measured by fluorescent intensity was 79,000 ± 20000 AU/mm2 for ePTFE, 810 ± 190 AU/mm2 for UTFN, and 1600 ± 25 AU/mm2 for STFN (n = 10, p < 0.01). Mass spectrometry demonstrated a larger number of proteins on ePTFE as compared to either thin film. UTFN and STFN appear to attract significantly less thrombus than ePTFE. Given TFN's low profile and our previously demonstrated ability to place TFN covered stents in vivo, it is an excellent candidate for use in next-generation endovascular stents grafts. PMID:20810163

  7. Indications for stenting during thrombolysis.

    PubMed

    Bækgaard, N; Broholm, R; Just, S

    2013-03-01

    The most important vein segment to thrombolyse after deep venous thrombosis (DVT) is the outflow tract meaning the iliofemoral vein. Iliofemoral DVT is defined as DVT in the iliac vein and the common femoral vein. Spontaneous recanalization is less than 50%, particularly on the left side. The compression from adjacent structures, predominantly on the left side is known as the iliac vein compression syndrome. Therefore, it is essential that supplementary endovenous procedures have to be performed in case of persistent obstructive lesions following catheter-directed thrombolysis. Insertion of a stent in this position is the treatment of choice facilitating the venous flow into an unobstructed outflow tract either from the femoral vein or the deep femoral vein or both. The stent, made of stainless steel or nitinol, has to be self-expandable and flexible with radial force to overcome the challenges in this low-pressure system. The characteristics of the anatomy with external compression and often a curved vein segment with diameter difference make stent placement necessary. Ballooning alone has no place in this area. The proportion of inserted stents varies in the published materials with catheter-directed thrombolysis of iliofemoral deep venous thrombosis. PMID:23482545

  8. MR Angiography of Peripheral Arterial Stents: In Vitro Evaluation of 22 Different Stent Types.

    PubMed

    Burg, Matthias C; Bunck, Alexander C; Seifarth, Harald; Buerke, Boris; Kugel, Harald; Hesselmann, Volker; Köhler, Michael; Heindel, Walter; Maintz, David

    2011-01-01

    Purpose. To evaluate stent lumen visibility of a large sample of different peripheral arterial (iliac, renal, carotid) stents using magnetic resonance angiography in vitro. Materials and Methods. 21 different stents and one stentgraft (10 nitinol, 7 316L, 2 tantalum, 1 cobalt superalloy, 1 PET + cobalt superalloy, and 1 platinum alloy) were examined in a vessel phantom (vessel diameters ranging from 5 to 13 mm) filled with a solution of Gd-DTPA. Stents were imaged at 1.5 Tesla using a T1-weighted 3D spoiled gradient-echo sequence. Image analysis was performed measuring three categories: Signal intensity in the stent lumen, lumen visibility of the stented lumen, and homogeneity of the stented lumen. The results were classified using a 3-point scale (good, intermediate, and poor results). Results. 7 stents showed good MR lumen visibility (4x nitinol, 2x tantalum, and 1x cobalt superalloy). 9 stents showed intermediate results (5x nitinol, 2x 316L, 1x PET + cobalt superalloy, and 1x platinum alloy) and 6 stents showed poor results (1x nitinol, and 5x 316L). Conclusion. Stent lumen visibility varies depending on the stent material and type. Some products show good lumen visibility which may allow the detection of stenoses inside the lumen, while other products cause artifacts which prevent reliable evaluation of the stent lumen with this technique. PMID:22091380

  9. MR Angiography of Peripheral Arterial Stents: In Vitro Evaluation of 22 Different Stent Types

    PubMed Central

    Burg, Matthias C.; Bunck, Alexander C.; Seifarth, Harald; Buerke, Boris; Kugel, Harald; Hesselmann, Volker; Köhler, Michael; Heindel, Walter; Maintz, David

    2011-01-01

    Purpose. To evaluate stent lumen visibility of a large sample of different peripheral arterial (iliac, renal, carotid) stents using magnetic resonance angiography in vitro. Materials and Methods. 21 different stents and one stentgraft (10 nitinol, 7 316L, 2 tantalum, 1 cobalt superalloy, 1 PET + cobalt superalloy, and 1 platinum alloy) were examined in a vessel phantom (vessel diameters ranging from 5 to 13 mm) filled with a solution of Gd-DTPA. Stents were imaged at 1.5 Tesla using a T1-weighted 3D spoiled gradient-echo sequence. Image analysis was performed measuring three categories: Signal intensity in the stent lumen, lumen visibility of the stented lumen, and homogeneity of the stented lumen. The results were classified using a 3-point scale (good, intermediate, and poor results). Results. 7 stents showed good MR lumen visibility (4x nitinol, 2x tantalum, and 1x cobalt superalloy). 9 stents showed intermediate results (5x nitinol, 2x 316L, 1x PET + cobalt superalloy, and 1x platinum alloy) and 6 stents showed poor results (1x nitinol, and 5x 316L). Conclusion. Stent lumen visibility varies depending on the stent material and type. Some products show good lumen visibility which may allow the detection of stenoses inside the lumen, while other products cause artifacts which prevent reliable evaluation of the stent lumen with this technique. PMID:22091380

  10. Are Carotid Stent Fractures Clinically Significant?

    SciTech Connect

    Garcia-Toca, Manuel; Rodriguez, Heron E.; Naughton, Peter A.; Keeling, Aiofee; Phade, Sachin V.; Morasch, Mark D.; Kibbe, Melina R.; Eskandari, Mark K.

    2012-04-15

    Purpose: Late stent fatigue is a known complication after carotid artery stenting (CAS) for cervical carotid occlusive disease. The purpose of this study was to determine the prevalence and clinical significance of carotid stent fractures. Materials and Methods: A single-center retrospective review of 253 carotid bifurcation lesions treated with CAS and mechanical embolic protection from April 2001 to December 2009 was performed. Stent integrity was analyzed by two independent observers using multiplanar cervical plain radiographs with fractures classified into the following types: type I = single strut fracture; type II = multiple strut fractures; type III = transverse fracture; and type IV = transverse fracture with dislocation. Mean follow-up was 32 months. Results: Follow-up imaging was completed on 106 self-expanding nitinol stents (26 closed-cell and 80 open-cell stents). Eight fractures (7.5%) were detected (type I n = 1, type II n = 6, and type III n = 1). Seven fractures were found in open-cell stents (Precise n = 3, ViVEXX n = 2, and Acculink n = 2), and 1 fracture was found in a closed-cell stent (Xact n = 1) (p = 0.67). Only a previous history of external beam neck irradiation was associated with fractures (p = 0.048). No associated clinical sequelae were observed among the patients with fractures, and only 1 patient had an associated significant restenosis ({>=}80%) requiring reintervention. Conclusions: Late stent fatigue after CAS is an uncommon event and rarely clinically relevant. Although cell design does not appear to influence the occurrence of fractures, lesion characteristics may be associated risk factors.

  11. Biliary self-expandable metallic stent for unresectable malignant distal biliary obstruction: which is better: covered or uncovered?

    PubMed

    Isayama, Hiroyuki; Nakai, Yousuke; Kogure, Hirofumi; Yamamoto, Natsuyo; Koike, Kazuhiko

    2013-05-01

    Self-expandable metallic stents (SEMS) are a widely accepted biliary endoprosthesis for patients with unresectable malignant distal biliary obstruction. There are two types of SEMS: covered and uncovered. Uncovered SEMS (UCSEMS) embed into the biliary wall due to their mesh structure and self-expandability, and are resistant to migration. However, the disadvantage of UCSEMS is occlusion due to tumor ingrowth (TI) via the stent mesh, and TI is the main cause of UCSEMS occlusion. To overcome this, covered SEMS (CSEMS) were developed and showed longer patency than UCSEMS. However, migration due to the non-embedded stent body is the main cause of CSEMS dysfunction. There are some randomized studies comparing CSEMS and UCSEMS; however, the results are different according to each study. From one meta-analysis, CSEMS showed longer patency than UCSEMS. A literature review revealed that covered SEMS showed longer patency than UCSEMS. Some studies cannot clearly demonstrate the superiority of CSEMS, as the CSEMS used did not prevent TI or migration. Mechanical properties of SEMS may influence the occurrence of complications. A recent clinical study comparing the Covered Wallstent and the Covered WallFlex revealed superiority of the WallFlex for the prevention of migration. Reducing the axial force and increasing the radial force may lead to good results. Migration of CSEMS should be prevented by taking into consideration the mechanical properties of stents and development of anti-migration systems.

  12. Stent-Assisted Coil Embolization of a Mycotic Renal Artery Aneurysm by Use of a Self-Expanding Neurointerventional Stent

    SciTech Connect

    Rabellino, Martin; Garcia-Nielsen, Luis; Zander, Tobias Baldi, Sebastian; Llorens, Rafael; Maynar, Manuel

    2011-02-15

    Mycotic aneurysms are uncommon, especially those located in visceral arteries. We present a case of a patient with two visceral mycotic aneurysms due to bacterial endocarditis, one located in right upper pole renal artery and the second in the splenic artery. Both aneurysms were treated as endovascular embolization using microcoils. In the aneurysm located at the renal artery, the technique of stent-assisted coils embolization was preferred to avoid coils migration due to its wide neck. The stent used was the Solitaire AB, which was designed for the treatment of intracranial aneurysms and was used recently in acute stroke as a mechanical thrombectomy device. Complete embolization of the aneurysm was achieved, preserving all the arterial branches without nephrogram defects in the final angiogram.

  13. Carotid stenting using tapered and nontapered stents: associated neurological complications and restenosis rates.

    PubMed

    Brown, Katherine E; Usman, Asad; Kibbe, Melina R; Morasch, Mark D; Matsumura, Jon S; Pearce, William H; Amaranto, Daniel J; Eskandari, Mark K

    2009-01-01

    Self-expanding stent design systems for carotid artery stenting (CAS) have morphed from nontapered (NTS) to tapered (TS); however, the impact of this change is unknown. We reviewed the outcomes of CAS with these two broad categories of stents in a single-center retrospective review of 308 CAS procedures from May 2001 to July 2007. Nitinol self-expanding TS or NTS coupled with cerebral embolic protection devices were used to treat extracranial carotid occlusive disease. Data analysis included demographics, procedural records, duplex exams, and conventional arteriography. Mean follow-up was 18 months (range 1-69). Restenosis was defined as >or=80% in-stent carotid artery stenosis by angiography. The mean age of the entire cohort was 71.3 years (75% men, 25% women). Of the 308 cases, 233 were de novo lesions and 75 had a prior ipsilateral carotid endarterectomy (n = 44) or external beam radiation exposure (n = 31). Preprocedure neurological symptoms were present in 30% of patients. TS were used in 156 procedures and NTS in 152 procedures. The 30-day ipsilateral stroke and death rates were 1.3% and 0.3%, respectively. An additional three (1.0%) posterior circulation strokes occurred. There was no statistically significant difference in the 30-day total stroke rates between TS (3.2%, n = 5) and NTS (1.3%, n = 2) (p = 0.5). At midterm follow-up, restenosis or asymptomatic occlusion was detected in eight cases (2.6%). All occurred in arteries treated with NTS, and this was statistically different when compared to arteries treated with TS (p = 0.03). Furthermore, a post-hoc subgroup analysis revealed significant correlation (chi(2) = 0.02) for restenosis in "hostile necks" when separated by TS vs. NTS. Early CAS outcomes between TS and NTS are comparable. In contrast, self-expanding nitinol TS may have a lower incidence of significant restenosis or asymptomatic occlusion when compared to NTS.

  14. Carotid stenting using tapered and nontapered stents: associated neurological complications and restenosis rates.

    PubMed

    Brown, Katherine E; Usman, Asad; Kibbe, Melina R; Morasch, Mark D; Matsumura, Jon S; Pearce, William H; Amaranto, Daniel J; Eskandari, Mark K

    2009-01-01

    Self-expanding stent design systems for carotid artery stenting (CAS) have morphed from nontapered (NTS) to tapered (TS); however, the impact of this change is unknown. We reviewed the outcomes of CAS with these two broad categories of stents in a single-center retrospective review of 308 CAS procedures from May 2001 to July 2007. Nitinol self-expanding TS or NTS coupled with cerebral embolic protection devices were used to treat extracranial carotid occlusive disease. Data analysis included demographics, procedural records, duplex exams, and conventional arteriography. Mean follow-up was 18 months (range 1-69). Restenosis was defined as >or=80% in-stent carotid artery stenosis by angiography. The mean age of the entire cohort was 71.3 years (75% men, 25% women). Of the 308 cases, 233 were de novo lesions and 75 had a prior ipsilateral carotid endarterectomy (n = 44) or external beam radiation exposure (n = 31). Preprocedure neurological symptoms were present in 30% of patients. TS were used in 156 procedures and NTS in 152 procedures. The 30-day ipsilateral stroke and death rates were 1.3% and 0.3%, respectively. An additional three (1.0%) posterior circulation strokes occurred. There was no statistically significant difference in the 30-day total stroke rates between TS (3.2%, n = 5) and NTS (1.3%, n = 2) (p = 0.5). At midterm follow-up, restenosis or asymptomatic occlusion was detected in eight cases (2.6%). All occurred in arteries treated with NTS, and this was statistically different when compared to arteries treated with TS (p = 0.03). Furthermore, a post-hoc subgroup analysis revealed significant correlation (chi(2) = 0.02) for restenosis in "hostile necks" when separated by TS vs. NTS. Early CAS outcomes between TS and NTS are comparable. In contrast, self-expanding nitinol TS may have a lower incidence of significant restenosis or asymptomatic occlusion when compared to NTS. PMID:19128933

  15. Midterm Outcome of Femoral Artery Stenting and Factors Affecting Patency

    PubMed Central

    Yu, Jae Seoung; Park, Keun-Myoung; Jeon, Yong Sun; Cho, Soon Gu; Hong, Kee Chun; Shin, Woo Young; Choe, Yun-Mee; Shin, Seok-Hwan; Kim, Kyung Rae

    2015-01-01

    Purpose: The purpose of this study was to evaluate the early and midterm results of superficial femoral artery (SFA) stenting with self-expanding nitinol stents and to identify the factors affecting patency. Materials and Methods: SFA stenting was performed in 165 limbs of 117 patients from January 2009 to December 2013. Patients were followed-up for the first occurrence of occlusion or stenosis based on computed tomography and duplex scan results and a decrease in ankle brachial index of >15%. Results: During the follow-up period (mean, 15.3±3.2 months), no early thrombotic reocclusions occurred within 30 days, but in-stent restenosis developed in 78 limbs. The primary patency rates at 6, 12, 18, and 24 months were 78%, 66%, 42%, and 22%, respectively, and the secondary patency rates were 85%, 72%, 58%, and 58%, respectively. TASC II C or D lesions, stent length >8 cm, number of patent tibial arteries and diabetes were significantly associated with reintervention. Conclusion: The midterm results of stenting for SFA occlusive disease were disappointing because the primary and secondary patency rates at two years were 22% and 58%, respectively. Reintervention after SFA stenting remains a major problem, particularly in patients with diabetes mellitus or long TASC II C or D lesions. PMID:26719837

  16. Self expandable stent application to prevent limb occlusion in external iliac artery during endovascular aneurysm repair

    PubMed Central

    Lee, Jae Hoon

    2016-01-01

    Purpose Iliac extension of stent-graft during endovascular aneurysm repair (EVAR) increases the incidence of limb occlusion (LO). Hypothetically, adjunctive iliac stent (AIS) could offer some additional protection to overcome this anatomic hostility. But still there is no consensus in terms of effective stent characteristics or configuration. We retrospectively reviewed our center's experience to offer a possible answer to this question. Methods Our study included 30 patients (38 limbs) with AIS placed in the external iliac artery (EIA) from January 2010 to December 2013. We classified iliac tortuosity based on anatomic characteristics. AIS's were deployed in EIA with a minimum 5-mm stick-out configuration from the distal edge of the stent-graft. Results According to the iliac artery tortuosity index, grade 0, grade 1, and grade 2 were 5 (13.2%), 30 (78.9%), and 3 (7.9%), respectively. The diameter of all AIS was 12 mm, which was as large as or larger than the diameter of the stent-graft distal limb. SMART stents were preferred in 34 limbs (89.5%) and stents with 60-mm length were usually used (89.5%). During a mean follow-up of 9.13 ± 10.78 months, ischemic limb pain, which could be the sign of LO, was not noticed in any patients. There was no fracture, kinking, migration, in-stent restenosis, or occlusion of AIS. Conclusion The installation of AIS after extension of stent-graft to EIA reduced the risk of LO without any complications. AIS should be considered as a preventive procedure of LO if stent-graft needs to be extended to EIA during EVAR.

  17. Self expandable stent application to prevent limb occlusion in external iliac artery during endovascular aneurysm repair

    PubMed Central

    Lee, Jae Hoon

    2016-01-01

    Purpose Iliac extension of stent-graft during endovascular aneurysm repair (EVAR) increases the incidence of limb occlusion (LO). Hypothetically, adjunctive iliac stent (AIS) could offer some additional protection to overcome this anatomic hostility. But still there is no consensus in terms of effective stent characteristics or configuration. We retrospectively reviewed our center's experience to offer a possible answer to this question. Methods Our study included 30 patients (38 limbs) with AIS placed in the external iliac artery (EIA) from January 2010 to December 2013. We classified iliac tortuosity based on anatomic characteristics. AIS's were deployed in EIA with a minimum 5-mm stick-out configuration from the distal edge of the stent-graft. Results According to the iliac artery tortuosity index, grade 0, grade 1, and grade 2 were 5 (13.2%), 30 (78.9%), and 3 (7.9%), respectively. The diameter of all AIS was 12 mm, which was as large as or larger than the diameter of the stent-graft distal limb. SMART stents were preferred in 34 limbs (89.5%) and stents with 60-mm length were usually used (89.5%). During a mean follow-up of 9.13 ± 10.78 months, ischemic limb pain, which could be the sign of LO, was not noticed in any patients. There was no fracture, kinking, migration, in-stent restenosis, or occlusion of AIS. Conclusion The installation of AIS after extension of stent-graft to EIA reduced the risk of LO without any complications. AIS should be considered as a preventive procedure of LO if stent-graft needs to be extended to EIA during EVAR. PMID:27617255

  18. Corrosion Behavior of Platinum-Enhanced Radiopaque Stainless Steel (PERSS®) for Dilation-Baloon Expandable Coronary Stents

    SciTech Connect

    Covino, Jr., Bernard S.; Craig, Charles H.; Cramer, Stephen D.; Bullard, Sophie J.; Ziomek-Moroz, Margaret; Jablonski, Paul D.; Turner, Paul C.; Radisch, Jr., Herbert R.; Gokcen, Nev A.; Friend, Clifford M.; Edwards, Michael R.

    2002-05-01

    Dilation-balloon expandable coronary stents are commonly made of implant grade stainless steels conforming to ASTM F138/F139, e.g., Biodur? 316LS (UNS S31673). Typical of such stents is the Boston Scientific/Interventional Technologies? (BS/IVT) LP-StentTM. In 2000, BS/IVT determined that the addition of 5 to 6 wt % platinum to Biodur 316LS produced a stainless steel with enhanced radiopacity to make their stents more visible radiographically and thus more effective clinically. A goal of the program was to ensure platinum additions would not adversely affect the corrosion resistance of Biodur 316LS. The corrosion resistance of 5-6 wt % PERSS? alloys and Biodur 316LS was determined using electrochemical tests for general, pitting, crevice and intergranular corrosion. Experimental methods included ASTM A262E, F746, F2129, and potentiodynamic polarization. The 6 wt % PERSS? alloy (IVT 78) had a resistance to pitting, crevice and intergranular corrosion that was similar to the Biodur 316LS base material. IVT 78 was a single-phase austenitic alloy with no evidence of inclusions or precipitates. It was more resistant to pitting corrosion than 5 wt % PERSS? alloys. Performance of the PERSS? alloys was not a function of alloy oxygen content in the range 0.01 to 0.03 wt %.

  19. Self-expanding metal mesh stents and laser therapy: a complementary approach for the palliation of malignant dysphagia

    NASA Astrophysics Data System (ADS)

    Madhotra, Ravi; Raouf, A.; Sturgess, R.; Krasner, Neville

    1997-12-01

    Re-establishment of the oesophageal lumen is the main focus of care in patients with inoperable oesophageal carcinomas. The self-expanding metal mesh stents (MMS) are increasingly being used. 51 patients aged 44 - 89 with inoperable oesophago-gastric carcinomas were intubated with MMS. 18 of these patients had endoscopic laser therapy (ELT) as primary palliation. 25 patients required follow-up endoscopy at variable intervals after stent insertion. 17 patients were found to have significant tumor growth (9), overgrowth (4) and both (4). All these patients were treated with Nd:YAG or diode laser for maintenance of satisfactory swallowing. 4 patients being treated with Nd:YAG laser developed deformity of MMS. This complication was not encountered with diode laser. The reblockage of MMS due to ingrowth or overgrowth of tumor is a not uncommon complication. The timing of the stent insertion should be carefully chosen since the longer the stent is in situ, the greater is the likelihood of tumor ingrowth or overgrowth. ELT can effectively deal with tumor ingrowth and overgrowth. Nd:YAG laser can cause melting of MMS. Overall the combination of ELT and MMS may offer the best palliation, particularly when patient survival of several months is anticipated.

  20. Self-expandable metal stents for obstructing colonic and extracolonic cancer: European Society of Gastrointestinal Endoscopy (ESGE) Clinical Guideline.

    PubMed

    van Hooft, Jeanin E; van Halsema, Emo E; Vanbiervliet, Geoffroy; Beets-Tan, Regina G H; DeWitt, John M; Donnellan, Fergal; Dumonceau, Jean-Marc; Glynne-Jones, Robert G T; Hassan, Cesare; Jiménez-Perez, Javier; Meisner, Søren; Muthusamy, V Raman; Parker, Michael C; Regimbeau, Jean-Marc; Sabbagh, Charles; Sagar, Jayesh; Tanis, Pieter J; Vandervoort, Jo; Webster, George J; Manes, Gianpiero; Barthet, Marc A; Repici, Alessandro

    2014-11-01

    This Guideline is an official statement of the European Society of Gastrointestinal Endoscopy (ESGE). This Guideline was also reviewed and endorsed by the Governing Board of the American Society for Gastrointestinal Endoscopy (ASGE). The Grading of Recommendations Assessment, Development, and Evaluation (GRADE) system was adopted to define the strength of recommendations and the quality of evidence. Main recommendations The following recommendations should only be applied after a thorough diagnostic evaluation including a contrast-enhanced computed tomography (CT) scan. 1 Prophylactic colonic stent placement is not recommended. Colonic stenting should be reserved for patients with clinical symptoms and imaging evidence of malignant large-bowel obstruction, without signs of perforation (strong recommendation, low quality evidence). 2 Colonic self-expandable metal stent (SEMS) placement as a bridge to elective surgery is not recommended as a standard treatment of symptomatic left-sided malignant colonic obstruction (strong recommendation, high quality evidence). 3 For patients with potentially curable but obstructing left-sided colonic cancer, stent placement may be considered as an alternative to emergency surgery in those who have an increased risk of postoperative mortality, I. e. American Society of Anesthesiologists (ASA) Physical Status ≥ III and/or age > 70 years (weak recommendation, low quality evidence). 4 SEMS placement is recommended as the preferred treatment for palliation of malignant colonic obstruction (strong recommendation, high quality evidence), except in patients treated or considered for treatment with antiangiogenic drugs (e. g. bevacizumab) (strong recommendation, low quality evidence).

  1. Self-Expanding Metallic Stents for Palliation and as a Bridge to Minimally Invasive Surgery in Colorectal Obstruction

    PubMed Central

    Barbosa, Guilherme; Zeichen, Marianna S.; Mata, Wilmer N.; Maciel, Victor; Plasencia, Gustavo; Hartmann, Rene F.; Viamonte, Manuel; Fogel, Roberto

    2013-01-01

    Background and Objectives: Acute colorectal obstruction is a potentially life-threatening emergency that requires immediate surgical treatment. Emergency procedures had an associated mortality rate of 10% to 30%. This encouraged development of other options, most notably self-expanding metallic stents. The primary endpoint of this study to is to report our group's experience. Methods: We performed a retrospective review of 37 patients who underwent self-expanding metallic stent placement for colorectal obstruction between July 2000 and May 2012. Data collected were age, comorbidities, diagnosis, intent of intervention (palliative vs bridge to surgery), complications, and follow-up. Results: The study comprised 21 men (56.76%) and 16 women (43.24%), with a mean age of 67 years. The intent of the procedure was definitive treatment in 22 patients (59.46%) and bridge to surgery in 15 (40.54%). The highest technical success rate was at the rectosigmoid junction (100%). The causes of technical failure were inability of the guidewire to traverse the stricture and bowel perforation related to stenting. The mean follow-up period was 9.67 months. Pain and constipation were the most common postprocedure complications. Discussion: The use of a self-expanding metallic stent has been shown to be effective for palliation of malignant obstruction. It is associated with a lower incidence of intensive care unit admission, shorter hospital stay, lower stoma rate, and earlier chemotherapy administration. Laparoscopic or robotic surgery can then be performed in an elective setting on a prepared bowel. Therefore the patient benefits from advantages of the combination of 2 minimally invasive procedures in a nonemergent situation. Further large-scale prospective studies are necessary. PMID:23925013

  2. Y-Shaped Bilateral Self-Expandable Metallic Stent Placement for Malignant Hilar Biliary Obstruction: Data from a Referral Center for Palliative Care

    PubMed Central

    Di Mitri, R.; Mocciaro, F.

    2014-01-01

    Background and Aim. Malignant hilar strictures are a clinical challenge because of the current therapeutic approach and the poor prognosis. In recent years, self-expandable metallic stents have proven more effective than plastic stents for palliation of malignant hilar strictures, with the bilateral stent-in-stent technique registering a high success rate. We report our experience with Y-shaped endoscopic self-expandable metallic stents placement for treatment of advanced malignant hilar strictures. Methods. From April 2009 to August 2012, we prospectively collected data on patients treated with Y-shaped SEMS placement for advanced malignant hilar carcinoma. Data on technical success, clinical success, and complications were collected. Results. Twenty patients (9 males) were treated (mean age 64.2 ± 15.3 years). The grade of malignant hilar strictures according to the Bismuth classification was II in 5 patients (25%), IIIa in 1 (5%), and IV in 14 (70%). The mean bilirubin level was 14.7 ± 4.9 mg/dL. Technical success was achieved in all patients, with a significant reduction in bilirubin levels (2.9 ± 1.7 mg/dL). One patient experienced cholangitis as early complication, while in 2 patients stent ingrowth was observed. No stents migration was recorded. There was no procedure-related mortality. At the end of the follow-up (7.1 ± 3.1 months), 13 of the 20 patients (65%) had died. Conclusions. Our experience confirms endoscopic bilateral self-expandable metallic stents placement with stent-in-stent technique (Y-shaped configuration) as a feasible, effective, and safe procedure for palliation of unresectable malignant hilar strictures. PMID:24790548

  3. Treatment of esophageal anastomotic leakage with self-expanding metal stents: analysis of risk factors for treatment failure

    PubMed Central

    Persson, Saga; Rouvelas, Ioannis; Kumagai, Koshi; Song, Huan; Lindblad, Mats; Lundell, Lars; Nilsson, Magnus; Tsai, Jon A.

    2016-01-01

    Background and study aim: The endoscopic placement of self-expandable metallic esophageal stents (SEMS) has become the preferred primary treatment for esophageal anastomotic leakage in many institutions. The aim of this study was to investigate possible risk factors for failure of SEMS-based therapy in patients with esophageal anastomotic leakage. Patients and methods: Beginning in 2003, all patients with an esophageal leak were initially approached and assessed for temporary closure with a SEMS. Until 2014, all patients at the Karolinska University Hospital with a leak from an esophagogastric or esophagojejunal anastomosis were identified. Data regarding the characteristics of the patients and leaks and the treatment outcomes were compiled. Failure of the SEMS treatment strategy was defined as death due to the leak or a major change in management strategy. The risk factors for treatment failure were analyzed with simple and multivariable logistic regression statistics. Results: A total of 447 patients with an esophagogastric or esophagojejunal anastomosis were identified. Of these patients, 80 (18 %) had an anastomotic leak, of whom 46 (58 %) received a stent as first-line treatment. In 29 of these 46 patients, the leak healed without any major change in treatment strategy. Continuous leakage after the application of a stent, decreased physical performance preoperatively, and concomitant esophagotracheal fistula were identified as independent risk factors for failure with multivariable logistic regression analysis. Conclusion: Stent treatment for esophageal anastomotic leakage is successful in the majority of cases. Continuous leakage after initial stent insertion, decreased physical performance preoperatively, and the development of an esophagotracheal fistula decrease the probability of successful treatment. PMID:27092321

  4. Modeling smooth muscle cell proliferation of coronary artery expanded with a drug eluting stent

    NASA Astrophysics Data System (ADS)

    Lyu, Suping

    2010-03-01

    The drug eluting coronary stent is for the treatment of narrowed coronary artery. A high strength balloon is used to open the narrowed vessel and leave behind a tiny metal mesh, or stent, to mechanically prevent the vessel from re-narrowing and biologically slow down proliferation of the smooth muscle cells. However, the drug eluting stents that had better performance also more seriously prevented the healing processes of the vessels, which could cause serious thrombotic reactions. In this study, we assume the healing process is controlled by proper proliferation of smooth cells. We also assume that the inflammation reactions and mechanical traction drive the smooth muscle cells to proliferate while the drug loaded in the stents drives the processes at the opposite direction. Numerical calculation was applied to the system. The drug distribution and elution durations, inflammation reactions and mechanical traction were discussed.

  5. An Efficient Finite Element Framework to Assess Flexibility Performances of SMA Self-Expandable Carotid Artery Stents

    PubMed Central

    Ferraro, Mauro; Auricchio, Ferdinando; Boatti, Elisa; Scalet, Giulia; Conti, Michele; Morganti, Simone; Reali, Alessandro

    2015-01-01

    Computer-based simulations are nowadays widely exploited for the prediction of the mechanical behavior of different biomedical devices. In this aspect, structural finite element analyses (FEA) are currently the preferred computational tool to evaluate the stent response under bending. This work aims at developing a computational framework based on linear and higher order FEA to evaluate the flexibility of self-expandable carotid artery stents. In particular, numerical simulations involving large deformations and inelastic shape memory alloy constitutive modeling are performed, and the results suggest that the employment of higher order FEA allows accurately representing the computational domain and getting a better approximation of the solution with a widely-reduced number of degrees of freedom with respect to linear FEA. Moreover, when buckling phenomena occur, higher order FEA presents a superior capability of reproducing the nonlinear local effects related to buckling phenomena. PMID:26184329

  6. Treatment of malignant gastric outlet obstruction with endoscopically placed self-expandable metal stents.

    PubMed

    Gaidos, Jill K J; Draganov, Peter V

    2009-09-21

    Malignant gastroduodenal obstruction can occur in up to 20% of patients with primary pancreatic, gastric or duodenal carcinomas. Presenting symptoms include nausea, vomiting, abdominal distention, pain and decreased oral intake which can lead to dehydration, malnutrition, and poor quality of life. Endoscopic stent placement has become the primary therapeutic modality because it is safe, minimally invasive, and a cost-effective option for palliation. Stents can be successfully deployed in the majority of patients. Stent placement appears to lead to a shorter time to symptomatic improvement, shorter time to resumption of an oral diet, and shorter hospital stays as compared with surgical options. Recurrence of the obstructive symptoms resulting from stent occlusion, due to tumor ingrowth or overgrowth, can be successfully treated with repeat endoscopic stent placement in the majority of the cases. Both endoscopic stenting and surgical bypass are considered palliative treatments and, to date, no improvement in survival with either modality has been demonstrated. A tailored therapeutic approach, taking into consideration patient preferences and involving a multidisciplinary team including the therapeutic endoscopist, surgeon, medical oncologist, radiation therapist, and interventional radiologist, should be considered in all cases. PMID:19764086

  7. Self-Expandable Metal Stents for Persisting Esophageal Variceal Bleeding after Band Ligation or Injection-Therapy: A Retrospective Study

    PubMed Central

    Müller, Martin; Seufferlein, Thomas; Perkhofer, Lukas; Wagner, Martin; Kleger, Alexander

    2015-01-01

    Background and Study Aims Despite a pronounced reduction of lethality rates due to upper gastrointestinal bleeding, esophageal variceal bleeding remains a challenge for the endoscopist and still accounts for a mortality rate of up to 40% within the first 6 weeks. A relevant proportion of patients with esophageal variceal bleeding remains refractory to standard therapy, thus making a call for additional tools to achieve hemostasis. Self-expandable metal stents (SEMS) incorporate such a tool. Methods We evaluated a total number of 582 patients admitted to our endoscopy unit with the diagnosis “gastrointestinal bleeding” according to our documentation software between 2011 and 2014. 82 patients suffered from esophageal variceal bleeding, out of which 11 cases were refractory to standard therapy leading to SEMS application. Patients with esophageal malignancy, fistula, or stricture and a non-esophageal variceal bleeding source were excluded from the analysis. A retrospective analysis reporting a series of clinically relevant parameters in combination with bleeding control rates and adverse events was performed. Results The initial bleeding control rate after SEMS application was 100%. Despite this success, we observed a 27% mortality rate within the first 42 days. All of these patients died due to non-directly hemorrhage-associated reasons. The majority of patients exhibited an extensive demand of medical care with prolonged hospital stay. Common complications were hepatic decompensation, pulmonary infection and decline of renal function. Interestingly, we found in 7 out of 11 patients (63.6%) stent dislocation at time of control endoscopy 24 h after hemostasis or at time of stent removal. The presence of hiatal hernia did not affect obviously stent dislocation rates. Refractory patients had significantly longer hospitalization times compared to non-refractory patients. Conclusions Self-expandable metal stents for esophageal variceal bleeding seem to be safe and

  8. Endoscopic transluminal pancreatic necrosectomy using a self-expanding metal stent and high-flow water-jet system

    PubMed Central

    Hritz, István; Fejes, Roland; Székely, András; Székely, Iván; Horváth, László; Sárkány, Ágnes; Altorjay, Áron; Madácsy, László

    2013-01-01

    Walled-off pancreatic necrosis and a pancreatic abscess are the most severe complications of acute pancreatitis. Surgery in such critically ill patients is often associated with significant morbidity and mortality within the first few weeks after the onset of symptoms. Minimal invasive approaches with high success and low mortality rates are therefore of considerable interest. Endoscopic therapy has the potential to offer safe and effective alternative treatment. We report here on 3 consecutive patients with infected walled-off pancreatic necrosis and 1 patient with a pancreatic abscess who underwent direct endoscopic necrosectomy 19-21 d after the onset of acute pancreatitis. The infected pancreatic necrosis or abscess was punctured transluminally with a cystostome and, after balloon dilatation, a non-covered self-expanding biliary metal stent was placed into the necrotic cavity. Following stent deployment, a nasobiliary pigtail catheter was placed into the cavity to ensure continuous irrigation. After 5-7 d, the metal stent was removed endoscopically and the necrotic cavity was entered with a therapeutic gastroscope. Endoscopic debridement was performed via the simultaneous application of a high-flow water-jet system; using a flush knife, a Dormia basket, and hot biopsy forceps. The transluminal endotherapy was repeated 2-5 times daily during the next 10 d. Supportive care included parenteral antibiotics and jejunal feeding. All patients improved dramatically and with resolution of their septic conditions; 3 patients were completely cured without any further complications or the need for surgery. One patient died from a complication of prolonged ventilation severe bilateral pneumonia, not related to the endoscopic procedure. No procedure related complications were observed. Transluminal endoscopic necrosectomy with temporary application of a self-expanding metal stent and a high-flow water-jet system shows promise for enhancing the potential of this endoscopic

  9. Long term impact of balloon post-dilatation on neointimal formation: an experimental comparative study between second-generation self-expanding versus balloon-expandable stent technologies.

    PubMed

    Aboodi, Michael S; Milewski, Krzysztof; Tellez, Armando; Cheng, Yanping; Yi, Geng-Hua; Kaluza, Greg L; Granada, Juan F

    2014-02-15

    Background: Self-expanding stents (SES) are reemerging as therapeutic alternatives to treat coronary artery disease. It has been proposed that SES can improve clinical outcomes by inducing less injury at implantation and achieving better vessel wall apposition.To date, little data exists comparing the vascular response to both methods of deployment in a controlled experimental setting. Objective: To quantify differences in vascular injury and healing between second-generation SES and balloon-expandable stents (BES) and the effects of balloon post-dilatation in a porcine coronary model. Methods: Seventy-five bare SES (AXXESS or vProtect) and 42 BES (Vision) were implanted in porcine coronaries. A subset of these received balloon post-dilatation(SES 1 D 5 22, BES 1 D 5 20). Follow-up was scheduled at 30 (BES 5 10, BES 1 D 56, SES 5 19, SES 1 D 5 8), 90 (BES 5 6, BES 1 D 5 8, SES 5 19, SES 1 D 5 8), and 180 days (BES 5 6, BES 1 D 5 6, SES 5 15, SES 1 D 5 6). Results: In vivo imaging and histological analysis showed that neointimal formation peaks early (30 days) in BES. Conversely, for SES, the peak occurred later (90 days). However, the neointimal formation achieved in either group equalized at 180 days. For SES, post-dilatation shortened the peak of neointimal formation to 30 days. Conversely, for BES, post-dilatation delayed the peak of neointimal formation to 90 days. At 30 days, histology showed that SES had significantly less injury. However, at 90 days, injury scores tended to be higher for SES. By 180 days, injury scores were comparable between both groups. Conclusions: The mechanism of stent expansion influences the degree of vascular injury and healing. The synergistic use of balloon post dilatation changes the dynamics of healing and may impact the potential beneficial effects inherent to SES technologies.

  10. Intraluminal tracheal stent fracture in a Yorkshire terrier.

    PubMed

    Woo, Heung-Myong; Kim, Mi-Jeong; Lee, Seung-Gon; Nam, Hyun-Sook; Kwak, Ho-Hyun; Lee, Joon-Seok; Park, In-Chul; Hyun, Changbaig

    2007-10-01

    An 8-year-old Yorkshire terrier was presented with tracheal collapse. Two intraluminal nitinol stents were implanted. The implanted stents were found to be fractured 4 weeks after implantation. The fractured stents were removed. To restore the collapsed trachea, ring prostheses were applied. However, the dog was euthanized because of a bad outcome following surgery.

  11. In-Graft Endovascular Stenting Repair for Supravalvular Stenosis From Aortic Rupture After Balloon-Expanding Transcatheter Aortic Valve Implantation.

    PubMed

    Furukawa, Nobuyuki; Scholtz, Werner; Haas, Nikolaus; Ensminger, Stephan; Gummert, Jan; Börgermann, Jochen

    2015-01-01

    An 81-year-old man with high-grade aortic valve stenosis and status post-coronary artery bypass grafting and supracoronary replacement of the ascending aorta was referred for transcatheter aortic valve implantation. He was in New York Heart Association class III and had dyspnea. After appropriate screening, we implanted a 29-mm SAPIEN XT valve (Edwards Lifesciences, Irvine, CA USA) through a transapical approach because of severe peripheral arterial occlusive disease. Postinterventional aortography revealed correct positioning and function of the valve and free coronary ostia but contrast extravasation in the vicinity of the interposed vascular prosthesis, resulting in severe luminal narrowing. We chose to manage the stenosis with an endovascular stent. After stenting, extravascular compression was markedly reduced, and the pressure gradient disappeared. The patient was discharged home on the 20th postoperative day. Three months later, computed tomography depicted correct positioning of both grafts. The patient's general health is good, and he is now in New York Heart Association class II. This case illustrates a complication of transcatheter aortic valve implantation specific for patients with an ascending aortic graft. Although stenting may be a good solution, as depicted by this case, self-expanding transcatheter aortic valves should be preferred in patients with ascending aortic grafts to avoid the described complication.

  12. Balloon-Expandable Stent Placement in Patients with Immediate Reocclusion after Initial Successful Thrombolysis of Acute middle Cerebral Arterial Obstruction

    PubMed Central

    Lee, H.K.; Kwak, H.S.; Chung, G.H.; Hwang, S.B.

    2012-01-01

    Summary We present the results of our approach for treating 12 consecutive cases of acute middle cerebral artery (MCA) stroke by performing balloon-expandable stent (BES) placement after immediate reocclusion due to the underlying stenosis after intra-arterial thrombolysis (IAT). We retrospectively reviewed the clinical outcomes of 12 patients with acute MCA stroke who underwent recanalization by BES placement in an underlying stenosis after IAT. The time to treatment, urokinase dose, duration of the procedure, recanalization rates and symptomatic hemorrhage were analyzed. Clinical outcome measures were assessed on admission and at discharge (the National Institutes of Health stroke scores [NIHSS]) as well as three months after treatment (modified Rankin scales [mRS]). The median NIHSS score on admission was 8.6. Four patients received IV rtPA. The median time from symptom onset to IAT was 236 minutes and the median duration of IAT was 62 minutes. The median dose of urokinase was 140,000 units. Initial recanalization after stent deployment (thrombolysis in cerebral ischemia attack grade of II or III) was achieved in all patients. Two patients died in the hospital due to aspiration pneumonia during medical management. In two patients, in-stent reocclusion occurred within 48 hours after stent deployment. At discharge, the median NIHSS score in ten patients (including the patients with reobstruction) was 2.4. The three-month outcome was excellent (mRS, 0-1) in eight patients. In this study, BES deployment was safe and effective in patients with an immediately reoccluded MCA after successful IAT. PMID:22440605

  13. Targeting In-Stent-Stenosis with RGD- and CXCL1-Coated Mini-Stents in Mice

    PubMed Central

    Weinandy, Stefan; Schreiber, Fabian; Megens, Remco T. A.; Theelen, Wendy; Smeets, Ralf; Jockenhövel, Stefan; Gries, Thomas; Möller, Martin; Klee, Doris; Weber, Christian; Zernecke, Alma

    2016-01-01

    Atherosclerotic lesions that critically narrow the artery can necessitate an angioplasty and stent implantation. Long-term therapeutic effects, however, are limited by excessive arterial remodeling. We here employed a miniaturized nitinol-stent coated with star-shaped polyethylenglycole (star-PEG), and evaluated its bio-functionalization with RGD and CXCL1 for improving in-stent stenosis after implantation into carotid arteries of mice. Nitinol foils or stents (bare metal) were coated with star-PEG, and bio-functionalized with RGD, or RGD/CXCL1. Cell adhesion to star-PEG-coated nitinol foils was unaltered or reduced, whereas bio-functionalization with RGD but foremost RGD/CXCL1 increased adhesion of early angiogenic outgrowth cells (EOCs) and endothelial cells but not smooth muscle cells when compared with bare metal foils. Stimulation of cells with RGD/CXCL1 furthermore increased the proliferation of EOCs. In vivo, bio-functionalization with RGD/CXCL1 significantly reduced neointima formation and thrombus formation, and increased re-endothelialization in apoE-/- carotid arteries compared with bare-metal nitinol stents, star-PEG-coated stents, and stents bio-functionalized with RGD only. Bio-functionalization of star-PEG-coated nitinol-stents with RGD/CXCL1 reduced in-stent neointima formation. By supporting the adhesion and proliferation of endothelial progenitor cells, RGD/CXCL1 coating of stents may help to accelerate endothelial repair after stent implantation, and thus may harbor the potential to limit the complication of in-stent restenosis in clinical approaches. PMID:27192172

  14. Targeting In-Stent-Stenosis with RGD- and CXCL1-Coated Mini-Stents in Mice.

    PubMed

    Simsekyilmaz, Sakine; Liehn, Elisa A; Weinandy, Stefan; Schreiber, Fabian; Megens, Remco T A; Theelen, Wendy; Smeets, Ralf; Jockenhövel, Stefan; Gries, Thomas; Möller, Martin; Klee, Doris; Weber, Christian; Zernecke, Alma

    2016-01-01

    Atherosclerotic lesions that critically narrow the artery can necessitate an angioplasty and stent implantation. Long-term therapeutic effects, however, are limited by excessive arterial remodeling. We here employed a miniaturized nitinol-stent coated with star-shaped polyethylenglycole (star-PEG), and evaluated its bio-functionalization with RGD and CXCL1 for improving in-stent stenosis after implantation into carotid arteries of mice. Nitinol foils or stents (bare metal) were coated with star-PEG, and bio-functionalized with RGD, or RGD/CXCL1. Cell adhesion to star-PEG-coated nitinol foils was unaltered or reduced, whereas bio-functionalization with RGD but foremost RGD/CXCL1 increased adhesion of early angiogenic outgrowth cells (EOCs) and endothelial cells but not smooth muscle cells when compared with bare metal foils. Stimulation of cells with RGD/CXCL1 furthermore increased the proliferation of EOCs. In vivo, bio-functionalization with RGD/CXCL1 significantly reduced neointima formation and thrombus formation, and increased re-endothelialization in apoE-/- carotid arteries compared with bare-metal nitinol stents, star-PEG-coated stents, and stents bio-functionalized with RGD only. Bio-functionalization of star-PEG-coated nitinol-stents with RGD/CXCL1 reduced in-stent neointima formation. By supporting the adhesion and proliferation of endothelial progenitor cells, RGD/CXCL1 coating of stents may help to accelerate endothelial repair after stent implantation, and thus may harbor the potential to limit the complication of in-stent restenosis in clinical approaches.

  15. Comparative retrospective study on the use of plastic prostheses and self-expanding metal stents in the palliative treatment of malignant strictures of the esophagus and cardia.

    PubMed

    Mosca, F; Consoli, A; Stracqualursi, A; Persi, A; Portale, T R

    2003-01-01

    Palliative treatment of malignant strictures of the esophagus and cardia is usually carried out by the endoscopic placement of a prosthesis. The aim of this retrospective study was to evaluate short- and long-term outcomes of the use of expandable stents, compared with conventional plastic prostheses. One hundred and thirteen endoscopic intubations were carried out in 120 patients affected by malignant stenosis of the esophagus and cardia using plastic prosthesis and self-expanding metal stents. Dysphagia was scored according to Atkinson and Ferguson's classification and the preoperative median score (3.6) was comparable in both groups. The technical success rate was 94.4% with plastic prosthesis and 93.7% with self-expanding metal stent while the functional success rate was, respectively, 85.2% and 88.8%. Three deaths occurred with plastic prostheses (4.4%), while no deaths were observed with metal stents. A comparative analysis of the results of this study suggests that the endoscopic placement of self-expanding metal stents is effective and safe and has to be preferred to the conventional plastic prosthesis for easier implantation and lower morbidity. PMID:12823210

  16. Antireflux versus conventional self-expanding metallic Stents (SEMS) for distal esophageal cancer: results of a multicenter randomized trial

    PubMed Central

    Coron, E.; David, G.; Lecleire, S.; Jacques, J.; Le Sidaner, A.; Barrioz, T.; Coumaros, D.; Volteau, C.; Vedrenne, B.; Bichard, P.; Boustière, C.; Touchefeu, Y.; Brégeon, J.; Prat, F.; Le Rhun, M.

    2016-01-01

    Introduction: Self-expanding metal stents (SEMS) are commonly used in the palliation of dysphagia in patients with inoperable esophageal carcinoma. However, they predispose to gastroesophageal reflux when deployed across the gastroesophageal junction. The aims of this study were to: 1) assess the influence of the antireflux valve on trans-prosthetic reflux (primary outcome); and 2) compare the results of SEMS with and without antireflux valve in terms of reflux symptoms, quality of life (QOL), improvement of dysphagia and adverse events (secondary outcomes). Patients and methods: Thirty-eight patients were enrolled in nine centers. Carcinomas were locally advanced (47 %) or metastatic. After randomization, patients received either a covered SEMS with antireflux valve (n = 20) or a similar type of SEMS with no antireflux device but assigned to standard proton pump inhibitor therapy and postural advice (n = 18). Trans-prosthetic reflux was assessed at day 2 using a radiological score based on barium esophagography performed after Trendelenburg maneuver and graded from 0 (no reflux) to 12 (maximum). Monthly telephone interviews were conducted for Organisation Mondiale de la Santé (OMS) scoring from 0 (excellent) to 5 (poor), QOL assessment (based on the Reflux-Qual Simplifié scoring system) from 0 (poor) to 100 (excellent), dysphagia scoring from 0 (no dysphagia) to 5 (complete dysphagia) and regurgitation scoring from 0 (no regurgitation) to 16 (maximum). Results: No difference was noted in terms of age, sex, size of lesion, prosthesis length or need for dilation prior to SEMS placement. No difficulty in placing SEMS nor complications were noted. Radiological scores of reflux were found to be significantly lower in patients with an antireflux stent compared to the conventional stent and associated measures. The regurgitation scores were significantly decreased in patients with antireflux stents during the first 2 months after stent placement and

  17. Self-expandable metallic stents in the treatment of post-esophagogastrostomy/post-esophagoenterostomy fistula.

    PubMed

    Nowakowski, P; Ziaja, K; Ludyga, T; Kuczmik, W; Biolik, G; Cwik, P; Ziaja, D

    2007-01-01

    Esophageus or gaster resection in patients with malignant disease is still a treatment of choice. It is obvious that each surgical procedure in these patients carries some possibility of complications. Esophageo-gastric or esophageo-jejuno anastomosis has a 4-27% frequency of fistula occurrence. All these result in 65% mortality in cases of poorer prognosis. The aim of this paper is not to present all types of complications but to objectively analyse the usefulness of the covered stent placement in the treatment of anastomotic fistulas. We present six patients who were treated for postoperative fistula of esophageo-gastric anastomosis (1 case) or esophageo-jejuno anastomosis (5 cases). All patients were treated with stapler suture for digestive tract reconstruction after malignancy removal during the primary surgical procedure. Signs and symptoms of suture leak between 5-8 days post-surgery were observed. Conservative therapy was not effective. Thus a new method of treatment was employed - covered stent placement. The procedure was performed under X-ray control. In all treated patients there was change for the better and quick reduction of secretion from the fistulas was observed. All patients were discharged from the department after several days and all had survived at 30 days follow-up. Covered esophageal stent placement seems to be a safe and promising method of treatment for patients with anastomotic fistula which significantly reduces mortality and improves quality of live. Our experiences confirms that of other investigators.

  18. Nitinol-based nanotubular coatings for the modulation of human vascular cell function.

    PubMed

    Lee, Phin P; Cerchiari, Alec; Desai, Tejal A

    2014-09-10

    In this study, we describe the synthesis of an upright nanotubular coating with discrete, exposed nanotubes on top of superelastic Nitinol via anodization and characterization of the surface elemental composition and nickel release rates. We demonstrate, for the first time, that this coating could improve re-endothelialization by increasing the cell spreading and migration of primary human aortic endothelial cells on Nitinol. We also show the potential for reducing neointimal hyperplasia by decreasing the proliferation and expression of collagen I and MMP-2 in primary human aortic smooth muscle cells (HASMC). Furthermore, we did not observe the nanotubular surface to induce inflammation through ICAM-1 expression in HASMC as compared to the flat control. This coating could be used to improve Nitinol stents by reducing restenosis rates and, given the extensive use of Nitinol in other implantable devices, act as a generalized coating strategy for other medical devices.

  19. Fully covered self-expandable metal stent in the treatment of postsurgical colorectal diseases: outcome in 29 patients

    PubMed Central

    Cereatti, Fabrizio; Fiocca, Fausto; Dumont, Jean-Loup; Ceci, Vincenzo; Vergeau, Bertrand-Marie; Tuszynski, Thierry; Meduri, Bruno; Donatelli, Gianfranco

    2016-01-01

    Background: Self-expandable metal stent (SEMS) placement is a minimally invasive treatment for palliation of malignant colorectal strictures and as a bridge to surgery. However, the use of SEMS for benign colorectal diseases is controversial. The purpose of this retrospective study is to evaluate the efficacy and safety of fully covered SEMS (FCSEMS) placement in postsurgical colorectal diseases. Methods: From 2008 to 2014, 29 patients with 32 FCSEMS deployment procedures were evaluated. The indications for stent placement were: 17 anastomotic strictures (3/17 presented complete closure of the anastomosis); four anastomotic leaks; seven strictures associated with anastomotic leak; and one rectum-vagina fistula. Results: Clinical success was achieved in 18 out of 29 patients (62.1%) being symptom-free at an average of 19 months. In the remaining 11 patients (37.9%), a different treatment was needed: four patients required multiple endoscopic dilations, 4 patients colostomy confection, one patient definitive ileostomy and three patients revisional surgery. The FCSEMS were kept in place for a mean period of 34 (range: 6–65) days. Major complications occurred in 12 out of 29 patients (41.4%) and consisted of stent migration. Minor complications included two cases of transient fever, eight cases of abdominal or rectal pain, and one case of tenesmus. Conclusion: FCSEMS are considered a possible therapeutic option for treatment of postsurgical strictures and leaks. However, their efficacy in guaranteeing long-term anastomotic patency and leak closure is moderate. A major complication is migration. The use of FCSEMS for colonic postsurgical pathologies should be carefully evaluated for each patient. PMID:26929780

  20. The ovation abdominal stent graft for the treatment of abdominal aortic aneurysms: current evidence and future perspectives.

    PubMed

    Georgakarakos, Efstratios; Ioannou, Christos V; Georgiadis, George S; Storck, Martin; Trellopoulos, George; Koutsias, Stylianos; Lazarides, Miltos K

    2016-01-01

    The Ovation Abdominal Stent Graft System is a trimodular endoprosthesis recently introduced for the endovascular repair of abdominal aortic aneurysm (AAA). It uncouples the stages of stent-graft fixation and sealing with the suprarenal fixation achieved with a long, rigid anchored stent while the sealing onto the neck is accomplished via a pair of polymer-filled inflatable rings that accommodate to each patient's individual anatomy. Moreover, the lack of Nitinol support enables lower profiles of the endograft's delivery system, thus facilitating the navigation through angulated and stenosed iliac vessels. Ovation's novel design expands further the AAA eligibility to endovascular repair. This article discusses the clinical and hemodynamic consequences of the Ovation design and contributes to better understanding of current and future implications. PMID:26822951

  1. The expanding indications for virtual histology intravascular ultrasound for plaque analysis prior to carotid stenting.

    PubMed

    Schiro, B J; Wholey, M H

    2008-12-01

    Complications of carotid artery stenting (CAS), including stroke, remain relatively high when compared with carotid endarterectomy (CEA). Current selection criteria for patients undergoing CAS are based predominately on surgical risk related to other comorbidities. Little attention is given to the morphology of the atherosclerotic plaque, although studies have shown that extensive variability exists which confers certain risks for plaque vulnerability. Virtual Histology intravascular ultrasound (VH IVUS) offers a unique method of assessing plaque morphology prior to CAS. Herein, the authors review the concepts of atherosclerotic plaque morphology and discuss the background of VH IVUS and illustrate its use in the carotid system. With selection of the appropriate patient and the appropriate plaque, more favorable outcomes of CAS may be achieved which will solidify its place as a frontline treatment of carotid vascular disease.

  2. Study of Stent Deployment Mechanics Using a High-Resolution X-ray Imaging Detector

    PubMed Central

    Wang, Weiyuan; Ionita, Ciprian N; Bednarek, Daniel R; Rudin, Stephen

    2011-01-01

    To treat or prevent some of the 795,000 annual strokes in the U.S., self-expanding endo-vascular stents deployed under fluoroscopic image guidance are often used. Neuro-interventionalists need to know the deployment behavior of each stent in order to place them in the correct position. Using the Micro-Angiographic Fluoroscope (MAF) which has about 3 times higher resolution than commercially available flat panel detectors (FPD) we studied the deployment mechanics of two of the most important commercially available nitinol stents: the Pipeline embolization device (EV3), and the Enterprise stent (Codman). The Pipeline stent's length extends to about 3 times that of its deployed length when it is contained inside a catheter. From the high-resolution images with the MAF we found that upon the sudden release of the distal end of the Pipeline from a helical wire cap, the stent expands radially but retracts to about 30% (larger than for patient deployments) of its length. When released from the catheter proximally, it retracts additionally about 50% contributing to large uncertainty in the final deployed location. In contrast, the MAF images clearly show that the Enterprise stent self expands with minimal length retraction during deployment from its catheter and can be retrieved and repositioned until the proximal markers are released from clasping structures on its guide-wire thus enabling more accurate placement at the center of an aneurysm or stenosis. The high-resolution imaging demonstrated in this study should help neurointerventionalists understand and control endovascular stent deployment mechanisms and hence perform more precise treatments. PMID:21804747

  3. [Extraordinary role of self-expanding metal stent (SEMS) in the malignant colorectal obstruction: different care in two cases].

    PubMed

    Siquini, Walter; Macarri, Giampiero; Freddara, Umberto; Stortoni, Pierpaolo; Ridolfo, Raffaella; Petrolati, Paolo; Fianchini, Aroldo; Landi, Edoardo

    2007-01-01

    The colorectal cancer presents with bowel obstruction in 10%-30% of patients. Established treatment of this evolutive condition, until 15 years ago, was emergency surgery. Primary resection with or without ileostomy, staged resection, Hartmann's procedure, or definitive colostomy are the therapeutical options. There is ongoing controversy on the best procedure to apply, because the choice depends on the patient's condition, age, electrolyte imbalances, nutritional status, obstructional grade, comorbidity and surgeon's attitude. However, the obstruction and the emergency operation add risk of complications and mortality instead of elective surgery. The efficacy of self-expanding metal stent to solve the obstruction had recently changed the management of malignant luminal obstruction: it is safe, effective, with very low mortality, low morbidity and also cheap. In the inoperable cases it represents the first line therapy avoiding the colostomy. In the operable patients, instead of two-step surgery, the SEMS had to be preferred because is a one-time and election surgery and avoid colostomy too, even if temporary. SEMS versus emergency primary surgery, without randomized and controlled study, allows a safer single-staged surgery. Finally it improves the quality of life avoiding colostomy, and reducing operative risk. We present two different use of SEMS: the palliation in inoperable patient and the "bridge to surgery" in critical obstructed patient.

  4. Uncovered Self-Expanding Metal Stent (SEMS) Four Years After Placement for Long-Term Treatment of a Benign Colonic Obstruction

    PubMed Central

    Lewis, Ayanna; Buscaglia, Jonathan M.

    2014-01-01

    Self-expanding metal stents (SEMS) have emerged as an alternative to surgery in the treatment of malignant colorectal obstructions. There is limited data about their use for benign colonic obstructions, especially in regards to safety and long-term patency. We present a case in which long-term SEMS placement proved to be a durable option for over 4 years in a patient with a benign colonic stricture. PMID:26157878

  5. Self-Expandable Stent Placement in Infrapopliteal Arteries After Unsuccessful Angioplasty Failure: One-Year Follow-up

    SciTech Connect

    Peregrin, J. H. Smirova, S.; Koznar, B.; Novotny, J.; Kovac, J.; Lastovickova, J.; Skibova, J.

    2008-09-15

    The purpose of this prospective study was to evaluate whether stent placement in infrapopliteal arteries is helpful in failed percutaneous transluminal angioplasty (PTA). Infrapopliteal PTA was performed in 70 arteries of 66 patients with chronic critical lower limb ischemia. The group comprised 55 males and 11 females, with an average age of 63.4 (range, 42-82) years. Diabetes mellitus was present in 92.4% of patients. Only the palpable anterior tibial and posterior tibial arteries were evaluated. Stents (Xpert stent; Abbot Vascular, Redwood City, CA, USA) were placed in 16 arteries where PTA was not successful (the failure was defined as residual stenosis >30% after PTA). In 54 arteries simple PTA was performed and was technically successful. Twenty-four nondilated arteries with no significant stenosis served as a comparison group. The 12-month patency rate was evaluated according to a combination of palpation and Doppler ultrasound. In all cases stent placement restored the flow in the artery immediately after unsuccessful PTA. Twelve-month follow-up showed a patency rate of 82% in the PTA group, 78% in the stent group, and 69% in the comparison group. We conclude that stent placement in the case of unsuccessful infrapopliteal PTA changed technical failure to success and restored flow in the dilated artery. At 12-month follow-up the patency rate of infrapopliteal arteries stented for PTA failure did not differ significantly either from nonstented arteries with an optimal PTA result or from a comparison group of nonintervened arteries.

  6. Endoscopic ultrasound (EUS)-guided transhepatic anterograde self-expandable metal stent (SEMS) placement across malignant biliary obstruction.

    PubMed

    Nguyen-Tang, T; Binmoeller, K F; Sanchez-Yague, A; Shah, J N

    2010-03-01

    Endoscopic retrograde cholangiopancreatography (ERCP) with placement of self-expandable metal stents (SEMS) for palliation of malignant obstruction may not be possible in patients with an inaccessible biliary orifice. Endoscopic ultrasound (EUS)-guided drainage methods may be useful in this setting. This study aimed to determine the outcomes of EUS-guided anterograde SEMS placement across malignant strictures in patients with an inaccessible biliary orifice. Over a 2-year period, procedural and outcomes data on all patients undergoing EUS-guided anterograde SEMS drainage after failed ERCP were prospectively entered into a database and reviewed. Five patients underwent EUS-guided anterograde SEMS. Indications included: advanced pancreatic cancer (n = 3), metastatic cancer (n = 1), and anastomotic stricture (n = 1). The biliary orifice could not be reached endoscopically due to duodenal stricture (n = 4) or inaccessible hepaticojejunostomy (n = 1). EUS-guided punctures were performed transgastrically into left intrahepatic ducts (n = 4) or transbulbar into the common bile duct (n = 1). Guide wires were passed and SEMS were successfully deployed across strictures in an anterograde fashion in all patients. Jaundice resolved and serum bilirubin levels decreased in all cases. No procedure-related complications were noted during a mean follow-up of 9.2 months. EUS-guided anterograde SEMS placement appears to be a safe and efficient technique for palliation of biliary obstruction in patients with an endoscopically inaccessible biliary orifice. The procedure can be performed at the time of failed standard ERCP, and provides an alternative drainage option to percutaneous or surgical decompression and to EUS-guided creation of bilioenteric fistulae.

  7. FEM optimization with Nitinol.

    PubMed

    Reese; Christ

    2004-08-01

    The present contribution focuses on the structural modelling of Nitinol devices. Apart from a powerful material modelling which should consider the well-known phenomena pseudo-elasticity, pseudo-plasticity and the shape memory effect a computationally efficient finite element implementation is needed. The cost of the numerical simulation depends crucially on the implementation of the material model at the Gauss point level (local level) and on the finite element technology used. Concerning the first point it is meanwhile state of the art to work with a so-called consistent linearization. This is also pursued in the present paper. On the other hand, the question of finite element technology is hardly discussed in the literature on shape memory alloy (SMA) modelling, although it is one of the crucial points. We discuss here a new one Gauss point concept which avoids the well-known "locking" (artificial stiffening) of standard displacement-based formulations and which is even more efficient than many formulations available in commercial codes.

  8. Multidetector-Row Computed Tomography in the Evaluation of Transjugular Intrahepatic Portosystemic Shunt Performed with Expanded-Polytetrafluoroethylene-Covered Stent-Graft

    SciTech Connect

    Fanelli, Fabrizio Bezzi, Mario; Bruni, Antonio; Corona, Mario; Boatta, Emanuele; Lucatelli, Pierleone; Passariello, Roberto

    2011-02-15

    We assessed, in a prospective study, the efficacy of multidetector spiral computed tomography (MDCT) in the evaluation of transjugular intrahepatic portosystemic shunt (TIPS) patency in patients treated with the Viatorr (Gore, Flagstaff, AZ) expanded-polytetrafluoroethylene (e-PTFE)-covered stent-graft. Eighty patients who underwent TIPS procedure using the Viatorr self-expanding e-PTFE stent-graft were evaluated at follow-up of 1, 3, 6, and 12 months with clinical and laboratory tests as well as ultrasound-color Doppler (USCD) imaging. In case of varices, upper gastrointestinal endoscopy was also performed. In addition, the shunt was evaluated using MDCT at 6 and 12 months. In all cases of abnormal findings and discrepancy between MDCT and USCD, invasive control venography was performed. MDCT images were acquired before and after injection of intravenous contrast media on the axial plane and after three-dimensional reconstruction using different algorithms. MDCT was successfully performed in all patients. No artefacts correlated to the Viatorr stent-graft were observed. A missing correlation between UCSD and MDCT was noticed in 20 of 80 (25%) patients. Invasive control venography confirmed shunt patency in 16 (80%) cases and shunt malfunction in 4 (20%) cases. According to these data, MDCT sensitivity was 95.2%; specificity was 96.6%; and positive (PPV) and negative predictive values (NPV) were 90.9 and 98.2%, respectively. USCD sensitivity was 90%; specificity was 75%; and PPV and NPV were 54.5 and 95.7%, respectively. A high correlation (K value = 0.85) between MDCT and invasive control venography was observed. On the basis of these results, MDCT shows superior sensitivity and specificity compared with USCD in those patients in whom TIPS was performed with the Viatorr stent-graft. MDCT can be considered a valid tool in the follow-up of these patients.

  9. Coronary artery stent (image)

    MedlinePlus

    ... with a balloon catheter and expands when the balloon is inflated. The stent is then left there to help keep the artery open. ... with a balloon catheter and expands when the balloon is inflated. The stent is then left there to help keep the artery open.

  10. Transtracheal single-point stent fixation in posttracheotomy tracheomalacia under cone-beam computer tomography guidance by transmural suturing with the Berci needle – a perspective on a new tool to avoid stent migration of Dumon stents

    PubMed Central

    Hohenforst-Schmidt, Wolfgang; Linsmeier, Bernd; Zarogoulidis, Paul; Freitag, Lutz; Darwiche, Kaid; Browning, Robert; Turner, J Francis; Huang, Haidong; Li, Qiang; Vogl, Thomas; Zarogoulidis, Konstantinos; Brachmann, Johannes; Rittger, Harald

    2015-01-01

    Tracheomalacia or tracheobronchomalacia (TM or TBM) is a common problem especially for elderly patients often unfit for surgical techniques. Several surgical or minimally invasive techniques have already been described. Stenting is one option but in general long-time stenting is accompanied by a high complication rate. Stent removal is more difficult in case of self-expandable nitinol stents or metallic stents in general in comparison to silicone stents. The main disadvantage of silicone stents in comparison to uncovered metallic stents is migration and plugging. We compared the operation time and in particular the duration of a sufficient Dumon stent fixation with different techniques in a patient with severe posttracheotomy TM and strongly reduced mobility of the vocal cords due to Parkinson’s disease. The combined approach with simultaneous Dumon stenting and endoluminal transtracheal externalized suture under cone-beam computer tomography guidance with the Berci needle was by far the fastest approach compared to a (not performed) surgical intervention, or even purely endoluminal suturing through the rigid bronchoscope. The duration of the endoluminal transtracheal externalized suture was between 5 minutes and 9 minutes with the Berci needle; the pure endoluminal approach needed 51 minutes. The alternative of tracheobronchoplasty was refused by the patient. In general, 180 minutes for this surgical approach is calculated. The costs of the different approaches are supposed to vary widely due to the fact that in Germany 1 minute in an operation room costs on average approximately 50–60€ inclusive of taxes. In our own hospital (tertiary level), it is nearly 30€ per minute in an operation room for a surgical approach. Calculating an additional 15 minutes for patient preparation and transfer to wake-up room, therefore a total duration inside the investigation room of 30 minutes, the cost per flexible bronchoscopy is per minute on average less than 6

  11. Endoscopic treatment of large pancreatic fluid collections (PFC) using self-expanding metallic stents (SEMS) – a two-center experience

    PubMed Central

    Chaves, Dalton Marques; Mönkemüller, Klaus; Carneiro, Fred; Medrado, Bruno; dos Santos, Marcos; Wodak, Stephanie; Reimão, Sílvia; Sakai, Paulo; de Moura, Eduardo

    2014-01-01

    Background/study aim: During the last several years, endoscopic ultrasound (EUS)-guided pancreatic fluid collections’ (PFC) drainage has evolved into the preferred drainage technique. Recently, self-expanding metallic stents (SEMS) have been used as an alternative to double pigtail stents, with the advantage of providing a larger diameter fistula, thereby decreasing the risk of early obstruction and also allowing for direct endoscopic exploration of the cavity. The aim of this study was to evaluate the technical and clinical success, safety, and outcome of patients undergoing EUS-guided drainage of complex PFC using SEMS. Patients/materials and methods: The study was conducted at two tertiary hospitals from January 2010 to January 2013. All patients with PFC referred for endoscopic drainage were enrolled in a prospective database. The inclusion criteria were: (1) patients with pseudocysts or walled-off necrosis based on the revised Atlanta classification; (2) symptomatic patients with thick PFC; (3) PFC that persisted more than 6 weeks; and (4) large PFC diameter (≥ 9 cm). The exclusion criteria consisted of coagulation disorders, PFC bleeding or infection, and failure-to-inform written consent. Results: A total of 16 patients (9 females, 7 males; mean age 52.6, range 20 – 82) underwent EUS drainage with SEMS. There were 14 cases of pseudocysts and 2 cases of walled-off necrosis. The etiologies of the PFC were mainly gallstones (8 of 16 patients, 50 %) and alcohol (5 of 16 patients, 31 %). Technical success was achieved in 100 % of the cases. All patients had a complete resolution of the PFC. Conclusion: Transmural EUS-guided drainage of complex PFC using SEMS is feasible, appears safe, and is efficacious. However, the exchange of the UC (uncovered)-SEMS for plastic stents is mandatory within 1 week. Future prospective studies, preferably multicenter studies, comparing SEMS versus traditional plastic stents for the drainage of PFC are

  12. Anatomy-shaped design of a fully-covered, biliary, self-expandable metal stent for treatment of benign distal biliary strictures

    PubMed Central

    Weigt, Jochen; Kandulski, Arne; Malfertheiner, Peter

    2016-01-01

    Background and study aims: The treatment success of benign biliary strictures with fully covered metal stents (CSEMS) is altered by high stent dislocation rates. We aimed to evaluate a new stent design to prevent dislocation. Patients and methods: Patients with benign biliary strictures were treated with a newly designed double-coned stent (dcSEMS). Mechanical analysis of the new stent was performed and it was compared with a cylindrical stent. Results: A total of 13 dcCSEMS were implanted in 11 patients (2 female, 9 male, median age 47, range 33 – 71). All patients had distal biliary strictures due to chronic pancreatitis. No stent migration occurred. In all but one patient the stents were removed. One patient refused stent extraction and was lost to follow up. Stent occlusion occurred twice leading to cholangitis in both cases. The duration of stent treatment was 170 days (range 61 – 254). After extraction only one patient had early recurrent stricture and received the same stent again. Three stents showed minimal tissue granulation at the papilla. One stent presented ingrowth at the proximal end and was removed after implantation of a second fully covered stent. Mechanical examination revealed significantly lower radial expansion force of the new stent as compared to the cylindrical stent. Conclusions: The new stent design has a low rate of migration. Biomechanical properties may explain this effect. PMID:26793789

  13. Three cases of endoscopic resection for synchronous early colon cancers after self-expandable metallic stent placement for obstructive colon cancer

    PubMed Central

    Moroi, Rintaro; Endo, Katsuya; Ichikawa, Ryo; Takahashi, So; Shiroki, Takeharu; Shinkai, Hirohiko; Ishiyama, Fumitake; Kayaba, Shoichi

    2016-01-01

    Background and study aims: The feasibility of endoscopic resection for synchronous early colon cancer after placement of self-expandable metallic stents (SEMS) for malignant colorectal obstruction is unknown. Herein we evaluated 3 cases of endoscopic resection for synchronous early colorectal cancers after SEMS placement. Patient 1 was an 82-year-old man with obstructive sigmoid colon cancer. We curatively treated the synchronous descending colon cancer with endoscopic submucosal dissection (ESD) and the rectal cancer with endoscopic mucosal resection (EMR) after SEMS placement. This is the first reported case of a successful ESD for synchronous early colon cancer via the use of a colonic stent. Patient 2 was an 81-year-old man with obstructive ascending colon cancer. We resected the synchronous transverse colon cancer via ESD. Histologic findings indicated that the carcinoma cells had invaded the submucosal layer. Therefore, we immediately performed expanded right-hemicolectomy. Patient 3 was an 81-year-old man with obstructive sigmoid colon cancer. We curatively treated the synchronous transverse colon cancer with EMR after SEMS placement. There were no complications associated with the endoscopic treatments in any of the cases. Our results indicate that preoperative endoscopic resection combined with the ESD technique for synchronous colorectal cancer after SEMS placement could be effective as a surgical strategy for patients with malignant colorectal obstruction. PMID:27652303

  14. Three cases of endoscopic resection for synchronous early colon cancers after self-expandable metallic stent placement for obstructive colon cancer

    PubMed Central

    Moroi, Rintaro; Endo, Katsuya; Ichikawa, Ryo; Takahashi, So; Shiroki, Takeharu; Shinkai, Hirohiko; Ishiyama, Fumitake; Kayaba, Shoichi

    2016-01-01

    Background and study aims: The feasibility of endoscopic resection for synchronous early colon cancer after placement of self-expandable metallic stents (SEMS) for malignant colorectal obstruction is unknown. Herein we evaluated 3 cases of endoscopic resection for synchronous early colorectal cancers after SEMS placement. Patient 1 was an 82-year-old man with obstructive sigmoid colon cancer. We curatively treated the synchronous descending colon cancer with endoscopic submucosal dissection (ESD) and the rectal cancer with endoscopic mucosal resection (EMR) after SEMS placement. This is the first reported case of a successful ESD for synchronous early colon cancer via the use of a colonic stent. Patient 2 was an 81-year-old man with obstructive ascending colon cancer. We resected the synchronous transverse colon cancer via ESD. Histologic findings indicated that the carcinoma cells had invaded the submucosal layer. Therefore, we immediately performed expanded right-hemicolectomy. Patient 3 was an 81-year-old man with obstructive sigmoid colon cancer. We curatively treated the synchronous transverse colon cancer with EMR after SEMS placement. There were no complications associated with the endoscopic treatments in any of the cases. Our results indicate that preoperative endoscopic resection combined with the ESD technique for synchronous colorectal cancer after SEMS placement could be effective as a surgical strategy for patients with malignant colorectal obstruction.

  15. Enhanced Biocompatibility of Porous Nitinol

    NASA Astrophysics Data System (ADS)

    Munroe, Norman; Pulletikurthi, Chandan; Haider, Waseem

    2009-08-01

    Porous Nitinol (PNT) has found vast applications in the medical industry as interbody fusion devices, synthetic bone grafts, etc. However, the tendency of the PNT to corrode is anticipated to be greater as compared to solid nitinol since there is a larger surface area in contact with body fluids. In such cases, surface preparation is known to play a major role in a material’s biocompatibility. In an effort to check the effect of surface treatments on the in vitro corrosion properties of PNT, in this investigation, they were subjected to different surface treatments such as boiling in water, dry heating, and passivation. The localized corrosion resistance of alloys before and after each treatment was evaluated in phosphate buffer saline solution (PBS) using cyclic polarization tests in accordance with ASTM F 2129-08.

  16. Enhanced Biocompatibility of Porous Nitinol

    PubMed Central

    Munroe, Norman; Pulletikurthi, Chandan; Haider, Waseem

    2009-01-01

    Porous Nitinol (PNT) has found vast applications in the medical industry as interbody fusion devices, synthetic bone grafts, etc. However, the tendency of the PNT to corrode is anticipated to be greater as compared to solid nitinol since there is a larger surface area in contact with body fluids. In such cases, surface preparation is known to play a major role in a material’s biocompatibility. In an effort to check the effect of surface treatments on the in vitro corrosion properties of PNT, in this investigation, they were subjected to different surface treatments such as boiling in water, dry heating, and passivation. The localized corrosion resistance of alloys before and after each treatment was evaluated in phosphate buffer saline solution (PBS) using cyclic polarization tests in accordance with ASTM F 2129-08. PMID:19956797

  17. Process for making electroformed stents

    DOEpatents

    Hines, Richard A.

    2000-02-01

    This invention is directed to an expandable stent useful for implantation into an artery or the like. The stents are made using electroforming techniques in which an electrically-conductive mandrel is coated with a suitable resist material, after which the resist is exposed to an appropriate light pattern and frequency so as to form a stent pattern in the resist. The mandrel is then electroplated with a suitable stent material. The mandrel is etched away once a sufficient layer of stent material is deposited, leaving a completed stent.

  18. Electro and Magneto-Electropolished Surface Micro-Patterning on Binary and Ternary Nitinol

    PubMed Central

    Munroe, Norman; McGoron, Anthony

    2012-01-01

    In this study, an Atomic Force Microscopy (AFM) roughness analysis was performed on non-commercial Nitinol alloys with Electropolished (EP) and Magneto-Electropolished (MEP) surface treatments and commercially available stents by measuring Root-Mean-Square (RMS), Average Roughness (Ra), and Surface Area (SA) values at various dimensional areas on the alloy surfaces, ranging from (800 × 800 nm) to (115 × 115μm), and (800 × 800 nm) to (40 × 40 μm) on the commercial stents. Results showed that NiTi-Ta 10 wt% with an EP surface treatment yielded the highest overall roughness, while the NiTi-Cu 10 wt% alloy had the lowest roughness when analyzed over (115 × 115 μm). Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS) analysis revealed unique surface morphologies for surface treated alloys, as well as an aggregation of ternary elements Cr and Cu at grain boundaries in MEP and EP surface treated alloys, and non-surface treated alloys. Such surface micro-patterning on ternary Nitinol alloys could increase cellular adhesion and accelerate surface endothelialization of endovascular stents, thus reducing the likelihood of in-stent restenosis and provide insight into hemodynamic flow regimes and the corrosion behavior of an implantable device influenced from such surface micro-patterns. PMID:22754200

  19. A Case of Aorto-Bronchial Fistula After Insertion of Left Main Bronchial Self-Expanding Metallic Stent in a Patient with Recurrent Esophageal Cancer

    SciTech Connect

    Onishi, Hiroshi Kuriyama, Kengo; Komiyama, Takafumi; Tanaka, Shiho; Marino, Kan; Tsukamoto, Tatsuaki; Araki, Tsutomu

    2004-09-15

    We report a case of aorto-bronchial fistula (ABF) caused by a self-expanding metallic stent (EMS) 51 days after insertion into the left main bronchus. The patient presented with left main bronchial stenosis caused by post-operative local recurrence of esophageal cancer. Post-operative radio therapy totaling 40 Gy and post-recurrence radiotherapy totaling 34 Gy were administered, with daily fractions of 2 Gy. Stenosis of the left main bronchus improved slightly, and was followed with insertion of EMS to prevent re-stenosis. The patient experienced massive hemoptysis for 3 days before sudden death. Autopsy revealed the EMS edge perforating the descending aortic lumen. Tumor infiltration and bacterial infection were observed on the wall of the left bronchus, and atherosclerosis was present on the aortic wall around the fistula. It should be noted that the left main bronchus was at considerable risk of ABF after insertion of EMS for malignant stenosis, and prophylactic stent insertion into the bronchus without imperative need must be avoided.

  20. A Case of Late Femoral Pseudoaneurysm Caused by Stent Disconnection

    SciTech Connect

    Rivolta, Nicola; Fontana, Federico; Piffaretti, Gabriele Tozzi, Matteo; Carrafiello, Gianpaolo

    2010-10-15

    We present the case of a late superficial femoral artery stent disconnection causing an asymptomatic pseudoaneurysm successfully treated with a stent-graft. A 67-year-old female was referred to our department for evaluation of claudication of the left lower limb and was diagnosed to have a total occlusion of the superficial femoral artery. Three nitinol stents were used to revascularize this artery. At 48 months, duplex-ultrasonography control revealed the presence of a 45-mm saccular femoral dilatation; X-rays and CT angiography showed fractures of the proximal stents and the presence of a pseudoaneurysm at the site of the distal stents disconnection. The pseudoaneurysm was excluded using two stent-grafts. We conclude that patients and surgeons should be aware of structural complications with all stents. Rigorous follow-up controls should be mandatory. Endovascular repair proved to be feasible and durable to manage a previous endovascular procedure.

  1. The development of an in vitro test method for predicting the abrasion resistance of textile and metal components of endovascular stent grafts.

    PubMed

    Yao, Tong; Choules, Brian D; Rust, Jon P; King, Martin W

    2014-04-01

    Implantable endovascular stent grafts have become a frequent option for the treatment of abdominal and thoracic aneurysms. Given that such devices are permanent implants, the question of long-term biostability needs to be addressed. This article describes the development of an in vitro stent graft abrasion test method between the graft fabric and metal stent of an endovascular device. Three endpoints were established to determine the abrasion resistance between the fabric and stent surfaces after a predetermined number of abrasion cycles. During initial testing, two types of graft fabric materials, multifilament woven polyester fabric and monofilament woven polyester fabric, and two types of stent materials, laser cut nitinol stents and regular nitinol stent wire, were evaluated under dry and wet conditions. The results have shown that this test method is viable for testing the relative abrasion resistance of the components of endovascular stent grafts. The abrasion resistance of both fabrics was lower in a wet environment compared to being tested dry. Additionally, the multifilament polyester fabric had better abrasion resistance than the monofilament polyester fabric. The laser cut nitinol stent was more aggressive in creating holes and breaking yarns, while the regular nitinol stent wire caused a greater loss in fabric strength.

  2. The development of an in vitro test method for predicting the abrasion resistance of textile and metal components of endovascular stent grafts.

    PubMed

    Yao, Tong; Choules, Brian D; Rust, Jon P; King, Martin W

    2014-04-01

    Implantable endovascular stent grafts have become a frequent option for the treatment of abdominal and thoracic aneurysms. Given that such devices are permanent implants, the question of long-term biostability needs to be addressed. This article describes the development of an in vitro stent graft abrasion test method between the graft fabric and metal stent of an endovascular device. Three endpoints were established to determine the abrasion resistance between the fabric and stent surfaces after a predetermined number of abrasion cycles. During initial testing, two types of graft fabric materials, multifilament woven polyester fabric and monofilament woven polyester fabric, and two types of stent materials, laser cut nitinol stents and regular nitinol stent wire, were evaluated under dry and wet conditions. The results have shown that this test method is viable for testing the relative abrasion resistance of the components of endovascular stent grafts. The abrasion resistance of both fabrics was lower in a wet environment compared to being tested dry. Additionally, the multifilament polyester fabric had better abrasion resistance than the monofilament polyester fabric. The laser cut nitinol stent was more aggressive in creating holes and breaking yarns, while the regular nitinol stent wire caused a greater loss in fabric strength. PMID:24115449

  3. Mechanisms of Biliary Plastic Stent Occlusion and Efforts at Prevention

    PubMed Central

    Kwon, Chang-Il; Lehman, Glen A.

    2016-01-01

    Biliary stenting via endoscopic retrograde cholangiopancreatography has greatly improved the quality of patient care over the last 30 years. Plastic stent occlusion limits the life span of such stents. Attempts to improve plastic stent patency duration have mostly failed. Metal stents (self-expandable metal stents [SEMSs]) have therefore replaced plastic stents, especially for malignant biliary strictures. SEMS are at least 10 times more expensive than plastic stents. In this focused review, we will discuss basic mechanisms of plastic stent occlusion, along with a systematic summary of previous efforts and related studies to improve stent patency and potential new techniques to overcome existing limitations. PMID:27000422

  4. Creation of individual ideally shaped stents using multi-slice CT: in vitro results from the semi-automatic virtual stent (SAVS) designer.

    PubMed

    Hyodoh, Hideki; Katagiri, Yoshimi; Sakai, Toyohiko; Hyodoh, Kazusa; Akiba, Hidenari; Hareyama, Masato

    2005-08-01

    To plan stent-grafting for thoracic aortic aneurysm with complicated morphology, we created a virtual stent-grafting program [Semi Automatic Virtual Stent (SAVS) designer] using three-dimensional CT data. The usefulness of the SAVS designer was evaluated by measurement of transformed anatomical and straight stents. Curved model images (source, multi-planer reconstruction and volume rendering) were created, and a hollow virtual stent was produced by the SAVS designer. A straight Nitinol stent was transformed to match the curved configuration of the virtual stent. The accuracy of the anatomical stent was evaluated by experimental strain phantom studies in comparison with the straight stent. Mean separation length was 0 mm in the anatomical stent [22 mm outer diameter (OD)] and 5 mm in the straight stent (22 mm OD). The straight stent strain voltage was four times that of the anatomical stent at the stent end. The anatomical stent is useful because it fits the curved structure of the aorta and reduces the strain force compared to the straight stent. The SAVS designer can help to design and produce the anatomical stent.

  5. Comparative study of the corrosion behavior of peripheral stents in an accelerated corrosion model: experimental in vitro study of 28 metallic vascular endoprostheses

    PubMed Central

    Paprottka, Karolin J.; Paprottka, Philipp M.; Reiser, Maximilian F.; Waggershauser, Tobias

    2015-01-01

    PURPOSE Clinical cases of stent-fractures show that corrosion behavior might play a role in these fractures. Implanted in vivo, especially in combination with other implanted foreign materials, these metallic products are exposed to special conditions, which can cause a process of corrosion. Here, we aimed to test the corrosion potential of stents made of different materials in an in vitro setting. METHODS A total of 28 peripheral stents of different materials (nitinol, cobalt-chromium-nickel, tantalum, V4A) and surface treatments (electropolish, mechanical polish, no polish) were tested in vitro. Corrosion was accelerated by applying a constant voltage of 3.5 V and amperage of 1.16 mA in 0.9% NaCl. RESULTS Nitinol stents showed the lowest susceptibility to corrosion and the longest period without damage. The Memotherm II® (BARD Angiomed®) was the only stent that showed neither macroscopic nor microscopic damages. The worst performing material was cobalt-chromium-nickel, which showed corrosion damages about ten times earlier compared to nitinol. Considering the reasons for termination of the test, nitinol stents primarily showed length deficits, while V4A and tantalum stents showed fractures. Cobalt-chromium-nickel stents had multiple fractures or a complete lysis in equal proportions. When placed in direct contact, nitinol stents showed best corrosion resistance, regardless of what material they were combined with. In terms of polishing treatments, electropolished stents performed the best, mechanical-polished stents and those without polishing treatment followed. CONCLUSION The analysis of corrosion behavior may be useful to select the right stent fulfilling the individual needs of the patient within a large number of different stents. PMID:26268301

  6. Stent-grafts for the treatment of TIPS dysfunction: Fluency stent vs Wallgraft stent

    PubMed Central

    Luo, Xue-Feng; Nie, Ling; Wang, Zhu; Tsauo, Jiaywei; Liu, Ling-Jun; Yu, Yang; Zhou, Biao; Tang, Cheng-Wei; Li, Xiao

    2013-01-01

    AIM: To evaluate the clinical efficacy of an expanded polytetrafluoro-ethylene-covered Fluency stent compared with that of a polyethylene terephthalate-covered Wallgraft stent for the management of transjugular intrahepatic portosystemic shunt (TIPS) dysfunction. METHODS: A retrospective review of patients who underwent TIPS revision with stent-grafts between May 2007 and June 2011 was conducted. The patients were divided into two groups according to the stent-grafts implanted: the Fluency stent (Bard Incorporated, Karlsruhe, Germany) and the Wallgraft stent (Boston Scientific, Galway, Ireland). The primary patency rates were calculated and compared using the Kaplan-Meier method. RESULTS: A total of 73 patients were evaluated in this study: 33 with Fluency stents and 40 with Wallgraft stents. The primary patency rates at 12 and 24 mo were 91% and 85%, respectively, in the Fluency stent group and 78% and 63%, respectively, in the Wallgraft stent group. The primary shunt patency rates after TIPS revision were significantly better with the Fluency stent than with the Wallgraft stent (P = 0.033). CONCLUSION: TIPS revision with the Fluency stent has higher medium-term patency rates than that with the Wallgraft stent. PMID:23946607

  7. Drug-eluting stents to prevent stent thrombosis and restenosis.

    PubMed

    Im, Eui; Hong, Myeong-Ki

    2016-01-01

    Although first-generation drug-eluting stents (DES) have significantly reduced the risk of in-stent restenosis, they have also increased the long-term risk of stent thrombosis. This safety concern directly triggered the development of new generation DES, with innovations in stent platforms, polymers, and anti-proliferative drugs. Stent platform materials have evolved from stainless steel to cobalt or platinum-chromium alloys with an improved strut design. Drug-carrying polymers have become biocompatible or biodegradable and even polymer-free DES were introduced. New limus-family drugs (such as everolimus, zotarolimus or biolimus) were adopted to enhance stent performances. As a result, these new DES demonstrated superior vascular healing responses on intracoronary imaging studies and lower stent thrombotic events in actual patients. Recently, fully-bioresorbable stents (scaffolds) have been introduced, and expanding their applications. In this article, the important concepts and clinical results of new generation DES and bioresorbable scaffolds are described. PMID:26567863

  8. Drug-eluting stents to prevent stent thrombosis and restenosis.

    PubMed

    Im, Eui; Hong, Myeong-Ki

    2016-01-01

    Although first-generation drug-eluting stents (DES) have significantly reduced the risk of in-stent restenosis, they have also increased the long-term risk of stent thrombosis. This safety concern directly triggered the development of new generation DES, with innovations in stent platforms, polymers, and anti-proliferative drugs. Stent platform materials have evolved from stainless steel to cobalt or platinum-chromium alloys with an improved strut design. Drug-carrying polymers have become biocompatible or biodegradable and even polymer-free DES were introduced. New limus-family drugs (such as everolimus, zotarolimus or biolimus) were adopted to enhance stent performances. As a result, these new DES demonstrated superior vascular healing responses on intracoronary imaging studies and lower stent thrombotic events in actual patients. Recently, fully-bioresorbable stents (scaffolds) have been introduced, and expanding their applications. In this article, the important concepts and clinical results of new generation DES and bioresorbable scaffolds are described.

  9. Surface modification of Ni-Ti alloys for stent application after magnetoelectropolishing.

    PubMed

    Gill, Puneet; Musaramthota, Vishal; Munroe, Norman; Datye, Amit; Dua, Rupak; Haider, Waseem; McGoron, Anthony; Rokicki, Ryszard

    2015-05-01

    The constant demand for new implant materials and the multidisciplinary design approaches for stent applications have expanded vastly over the past decade. The biocompatibility of these implant materials is a function of their surface characteristics such as morphology, surface chemistry, roughness, surface charge and wettability. These surface characteristics can directly influence the material's corrosion resistance and biological processes such as endothelialization. Surface morphology affects the thermodynamic stability of passivating oxides, which renders corrosion resistance to passivating alloys. Magnetoelectropolishing (MEP) is known to alter the morphology and composition of surface films, which assist in improving corrosion resistance of Nitinol alloys. This work aims at analyzing the surface characteristics of MEP Nitinol alloys by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The wettability of the alloys was determined by contact angle measurements and the mechanical properties were assessed by Nanoindentation. Improved mechanical properties were observed with the addition of alloying elements. Cyclic potentiodynamic polarization tests were performed to determine the corrosion susceptibility. Further, the alloys were tested for their cytotoxicity and cellular growth with endothelial cells. Improved corrosion resistance and cellular viability were observed with MEP surface treated alloys. PMID:25746243

  10. Surface modification of Ni–Ti alloys for stent application after magnetoelectropolishing

    PubMed Central

    Musaramthota, Vishal; Munroe, Norman; Datye, Amit; Dua, Rupak; Haider, Waseem; McGoron, Anthony; Rokicki, Ryszard

    2015-01-01

    The constant demand for new implant materials and the multidisciplinary design approaches for stent applications have expanded vastly over the past decade. The biocompatibility of these implant materials is a function of their surface characteristics such as morphology, surface chemistry, roughness, surface charge and wettability. These surface characteristics can directly influence the material's corrosion resistance and biological processes such as endothelialization. Surface morphology affects the thermodynamic stability of passivating oxides, which renders corrosion resistance to passivating alloys. Magnetoelectropolishing (MEP) is known to alter the morphology and composition of surface films, which assist in improving corrosion resistance of Nitinol alloys. This work aims at analyzing the surface characteristics of MEP Nitinol alloys by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The wettability of the alloys was determined by contact angle measurements and the mechanical properties were assessed by Nanoindentation. Improved mechanical properties were observed with the addition of alloying elements. Cyclic potentiodynamic polarization tests were performed to determine the corrosion susceptibility. Further, the alloys were tested for their cytotoxicity and cellular growth with endothelial cells. Improved corrosion resistance and cellular viability were observed with MEP surface treated alloys. PMID:25746243

  11. Surface modification of Ni-Ti alloys for stent application after magnetoelectropolishing.

    PubMed

    Gill, Puneet; Musaramthota, Vishal; Munroe, Norman; Datye, Amit; Dua, Rupak; Haider, Waseem; McGoron, Anthony; Rokicki, Ryszard

    2015-05-01

    The constant demand for new implant materials and the multidisciplinary design approaches for stent applications have expanded vastly over the past decade. The biocompatibility of these implant materials is a function of their surface characteristics such as morphology, surface chemistry, roughness, surface charge and wettability. These surface characteristics can directly influence the material's corrosion resistance and biological processes such as endothelialization. Surface morphology affects the thermodynamic stability of passivating oxides, which renders corrosion resistance to passivating alloys. Magnetoelectropolishing (MEP) is known to alter the morphology and composition of surface films, which assist in improving corrosion resistance of Nitinol alloys. This work aims at analyzing the surface characteristics of MEP Nitinol alloys by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The wettability of the alloys was determined by contact angle measurements and the mechanical properties were assessed by Nanoindentation. Improved mechanical properties were observed with the addition of alloying elements. Cyclic potentiodynamic polarization tests were performed to determine the corrosion susceptibility. Further, the alloys were tested for their cytotoxicity and cellular growth with endothelial cells. Improved corrosion resistance and cellular viability were observed with MEP surface treated alloys.

  12. [Our experience with the use of a plastic prosthesis and self-expanding stents in the palliative treatment of malignant neoplastic stenoses of the esophagus and cardia. Comparative analysis of results].

    PubMed

    Mosca, Francesco; Consoli, Antonino; Stracqualursi, Antonio; Persi, Achille; Lipari, Giuseppe; Portale, Teresa Rosanna

    2002-01-01

    Rapid palliation of malignant dysphagia is usually possible by means of the endoscopic implantation of a plastic prosthesis, but this device has a high morbidity rate. Recently, expandable metal stents have become available and may reduce the morbidity and mortality rates. The aim of this retrospective study was to evaluate self-expanding metal stents compared with conventional plastic prosthesis in malignant strictures of the oesophagus and cardia. One hundred and thirteen endoscopic tube implantations were carried out in 120 patients with malignant stenosis of the oesophagus and cardia using a plastic prosthesis over the period 1980-1993 (72 cases) and self-expanding metal stents over the period 1993-2001 (48 cases). The underlying causes of strictures were oesophageal or cardial cancer in 108 cases and oesophageal invasion by lung cancer in 12. The indications for endoscopic intubation were advanced tumour stage and/or risk factors which made resection inadvisable. The stents used in the conventional group were the Celestin pulsion tube in 18, the Atkinson prosthesis in 23 and the Wilson-Cook tube in 27, while the Ultraflex stent was always employed in the other group. Dysphagia was scored according to the Atkinson and Ferguson classification and the preoperative median score (3.6) was comparable in the two groups. The technical success rate was 94.4% with the plastic prosthesis (68/72) and 93.7% with the self-expanding metal stents (45/48) because in 4 and 3 patients, respectively, it proved impossible to implant the stent. After intubation the dysphagia score was improved in both groups (median score = 0.9) and the functional success rates were 85.2% (58/68) and 88.8% (40/45), respectively, while 10 and 5 patients showed no improvement of symptoms. The early complication rate was 5.9% (4/68) in the conventional stent group (1 perforation, 2 severe bleedings and 1 stent proximal migration) and nil in the other group. Late complications occurred in 14 (20.6%) (7

  13. [Our experience with the use of a plastic prosthesis and self-expanding stents in the palliative treatment of malignant neoplastic stenoses of the esophagus and cardia. Comparative analysis of results].

    PubMed

    Mosca, Francesco; Consoli, Antonino; Stracqualursi, Antonio; Persi, Achille; Lipari, Giuseppe; Portale, Teresa Rosanna

    2002-01-01

    Rapid palliation of malignant dysphagia is usually possible by means of the endoscopic implantation of a plastic prosthesis, but this device has a high morbidity rate. Recently, expandable metal stents have become available and may reduce the morbidity and mortality rates. The aim of this retrospective study was to evaluate self-expanding metal stents compared with conventional plastic prosthesis in malignant strictures of the oesophagus and cardia. One hundred and thirteen endoscopic tube implantations were carried out in 120 patients with malignant stenosis of the oesophagus and cardia using a plastic prosthesis over the period 1980-1993 (72 cases) and self-expanding metal stents over the period 1993-2001 (48 cases). The underlying causes of strictures were oesophageal or cardial cancer in 108 cases and oesophageal invasion by lung cancer in 12. The indications for endoscopic intubation were advanced tumour stage and/or risk factors which made resection inadvisable. The stents used in the conventional group were the Celestin pulsion tube in 18, the Atkinson prosthesis in 23 and the Wilson-Cook tube in 27, while the Ultraflex stent was always employed in the other group. Dysphagia was scored according to the Atkinson and Ferguson classification and the preoperative median score (3.6) was comparable in the two groups. The technical success rate was 94.4% with the plastic prosthesis (68/72) and 93.7% with the self-expanding metal stents (45/48) because in 4 and 3 patients, respectively, it proved impossible to implant the stent. After intubation the dysphagia score was improved in both groups (median score = 0.9) and the functional success rates were 85.2% (58/68) and 88.8% (40/45), respectively, while 10 and 5 patients showed no improvement of symptoms. The early complication rate was 5.9% (4/68) in the conventional stent group (1 perforation, 2 severe bleedings and 1 stent proximal migration) and nil in the other group. Late complications occurred in 14 (20.6%) (7

  14. Comparison of in vitro human endothelial cell response to self-expanding stent deployment in a straight and curved peripheral artery simulator

    PubMed Central

    Ghriallais, Ríona Ní; McNamara, Laoise; Bruzzi, Mark

    2013-01-01

    Haemodynamic forces have a synergistic effect on endothelial cell (EC) morphology, proliferation, differentiation and biochemical expression profiles. Alterations to haemodynamic force levels have been observed at curved regions and bifurcations of arteries but also around struts of stented arteries, and are also known to be associated with various vascular pathologies. Therefore, curvature in combination with stenting might create a pro-atherosclerotic environment compared with stenting in a straight vessel, but this has never been investigated. The goal of this study was to compare EC morphology, proliferation and differentiation within in vitro models of curved stented peripheral vessel models with those of straight and unstented vessels. These models were generated using both static conditions and also subjected to 24 h of stimulation in a peripheral artery bioreactor. Medical-grade silicone tubes were seeded with human umbilical vein endothelial cells to produce pseudovessels that were then stented and subjected to 24 h of physiological levels of pulsatile pressure, radial distention and shear stress. Changes in cell number, orientation and nitric oxide (NO) production were assessed in straight, curved, non-stented and stented pseudovessels. We report that curved pseudovessels lead to higher EC numbers with random orientation and lower NO production per cell compared with straight pseudovessels after 24 h of biomechanical stimulation. Both stented curved and stented straight pseudovessels had lower NO production per cell than corresponding unstented pseudovessels. However, in contrast to straight stented pseudovessels, curved stented pseudovessels had fewer viable cells. The results of this study show, for the first time, that the response of the vascular endothelium is dependent on both curvature and stenting combined, and highlight the necessity for future investigations of the effects of curvature in combination with stenting to fully understand effects on

  15. Severe compression of a bailout self-expanding chimney stent for rescuing the miscoverage of left common carotid artery during TEVAR of a type B aortic dissection.

    PubMed

    Wang, Lixin; Guo, Daqiao; Jiang, Junhao; Shi, Zhenyu; Fu, Weiguo; Wang, Yuqi

    2014-04-01

    A 54-year-old man who suffered from paraplegia due to type B aortic dissection was treated with a Valiant stent-graft. However, attempts to gain secure proximal sealing resulted in an inadvertent coverage of the left common carotid artery by the endograft. The blood flow in the left common carotid artery was restored by a transcarotid Smart Control stent in a chimney fashion. At 6- and 18-month follow-up, computed tomography scan showed that the chimney stent was severely compressed by the stent graft, although the patient remained neurologically asymptomatic. PMID:24309751

  16. [An Analysis of Placement of a Self-Expanding Metallic Stent as Bridge to Surgery for Surgical Resection of StageⅣ Obstructive Colorectal Cancers].

    PubMed

    Kawahara, Yohei; Terada, Itsuro; Terai, Shiro; Watanabe, Toshifumi; Amaya, Koji; Yamamoto, Seiichi; Kaji, Masahide; Maeda, Kiichi; Shimizu, Koichi

    2015-11-01

    In our institution, placement of a self-expanding metallic stent (SEMS) for obstructive colorectal cancer to avoid emergency operations, namely as a bridge to surgery (BTS), was introduced in April 2012. Here, we assess the efficacy and safety of pre-operative SEMS placement for treatment of Stage Ⅳ obstructive colorectal cancer. We analyzed a total of 44 cases of Stage Ⅳ colorectal cancer, which consisted of 13 obstructive cases that were surgically resected following SEMS placement as BTS (BTS group), and 31 cases that were resected in elective operations without pre-operative SEMS placement (Ope group), from April 2012 to August 2014. None of the patients had any adverse events during the SEMS procedure or after SEMS placement, and all patients of BTS group could undergo the planned operations after sufficient decompression. In the postoperative period, 1 patient of BTS group (7.7%) had anastomosis bleeding, but no other complications, including anastomosis leakage, were observed in BTS group. However more progressive primary tumors were resected in BTS group (p=0.0115), there were no significant differences for post-operative course between the 2 groups; this indicated avoiding high-risk emergency operations contributed to adequate short-term outcomes in BTS group comparable to those in Ope group. SEMS placement as BTS could be performed safely for Stage Ⅳ obstructive colorectal cancer cases, and was 1 of the effective strategies for local treatment. PMID:26805087

  17. Use of self-expanding covered stent and negative pressure wound therapy to manage late rectal perforation after injury from an improvised explosive device: a case report.

    PubMed

    Ozer, M Tahir; Coskun, Ali K; Sinan, Huseyin; Saydam, Mehmet; Akay, Emin O; Peker, Subutay; Ogunc, Gokhan; Demirbas, Sezai; Peker, Yusuf

    2014-06-01

    Blast injuries, caused by explosions accompanied by high-pressure waves, produce tissue damage in the acute period, followed in the later period by circulatory disorders due to vascular endothelial damage and related tissue necrosis. Blunt rectal perforation is rare and difficult to diagnose. In the acute period following blast pelvic injuries, the main objectives are to stop bleeding, minimise contamination and preserve the patient's life. The patient in this report had major vascular injuries, severe pelvic injury and, in the later period, rectal perforation because of vascular endothelial damage caused by the blast effect. Our aim was to treat the patient conservatively because of his poor general condition. We placed a self-expanding covered stent (SECS) into the rectum and then applied negative pressure wound therapy (NPWT; V.A.C.® Therapy, KCI) to the pelvic region and perirectal area. At the end of the treatment, the rectal perforation was closed, and the patient was discharged with healing. In this article, we discuss the novel use of an SECS with NPWT and review related literature.

  18. Use of self-expanding covered stent and negative pressure wound therapy to manage late rectal perforation after injury from an improvised explosive device: a case report.

    PubMed

    Ozer, M Tahir; Coskun, Ali K; Sinan, Huseyin; Saydam, Mehmet; Akay, Emin O; Peker, Subutay; Ogunc, Gokhan; Demirbas, Sezai; Peker, Yusuf

    2014-06-01

    Blast injuries, caused by explosions accompanied by high-pressure waves, produce tissue damage in the acute period, followed in the later period by circulatory disorders due to vascular endothelial damage and related tissue necrosis. Blunt rectal perforation is rare and difficult to diagnose. In the acute period following blast pelvic injuries, the main objectives are to stop bleeding, minimise contamination and preserve the patient's life. The patient in this report had major vascular injuries, severe pelvic injury and, in the later period, rectal perforation because of vascular endothelial damage caused by the blast effect. Our aim was to treat the patient conservatively because of his poor general condition. We placed a self-expanding covered stent (SECS) into the rectum and then applied negative pressure wound therapy (NPWT; V.A.C.® Therapy, KCI) to the pelvic region and perirectal area. At the end of the treatment, the rectal perforation was closed, and the patient was discharged with healing. In this article, we discuss the novel use of an SECS with NPWT and review related literature. PMID:24851734

  19. Evaluation of electrospun PLLA/PEGDMA polymer coatings for vascular stent material.

    PubMed

    Boodagh, Parnaz; Guo, Dong-Jie; Nagiah, Naveen; Tan, Wei

    2016-08-01

    The field of percutaneous coronary intervention has seen a plethora of advances over the past few decades, which have allowed for its development into safe and effective treatments for patients suffering from cardiovascular diseases. However, stent thrombosis and in-stent restenosis remain clinically significant problems. Herein, we describe the synthesis and characterization of fibrous polymer coatings on stent material nitinol, in the hopes of developing a more suitable stent surface to enhance re-endothelialization. Electrospinning technique was used to fabricate polyethylene glycol dimethacrylate/poly l-lactide acid (PEGDMA/PLLA) blend fiber substrate with tunable elasticity and hydrophilicity for use as coatings. Attachment of platelets and arterial smooth muscle cells (SMC) onto the coatings as well as the secretory effect of mesenchymal stem cells cultured on the coatings on the proliferation and migration of arterial endothelial cells and SMCs were assessed. It was demonstrated that electrospun PEGDMA/PLLA coating with 1:1 ratio of the components on the nitinol stent-reduced platelet and SMC attachment and increased stem cell secretory factors that enhance endothelial proliferation. We therefore postulate that the fibrous coating surface would possess enhanced biological compatibility of nitinol stents and hold the potential in preventing stent failure through restenosis and thrombosis. PMID:27137629

  20. Biodegradable stents with elastic memory.

    PubMed

    Venkatraman, Subbu S; Tan, Lay Poh; Joso, Joe Ferry D; Boey, Yin Chiang Freddy; Wang, Xintong

    2006-03-01

    This work reports, for the first time, the development of a fully biodegradable polymeric stent that can self-expand at body temperatures (approximately 37 degrees C), using the concept of elastic memory. This self-expansion is necessary in fully polymeric stents, to overcome the problem of elastic recoil following balloon expansion in a body vessel. Bi-layered biodegradable stent prototypes were produced from poly-L-lactic acid (PLLA) and poly glycolic acid (PLGA) polymers. Elastic memory was imparted to the stents by temperature conditioning. The thickness and composition of each layer in the stents are critical parameters that affect the rate of self-expansion at 37 degrees C, as well as the collapse strengths of the stents. The rate of self-expansion of the stents, as measured at 37 degrees C, exhibits a maximum with layer thickness. The Tg of the outer layer is another significant parameter that affects the overall rate of expansion.

  1. A statistical approach to understand the role of inclusions on the fatigue resistance of superelastic Nitinol wire and tubing.

    PubMed

    Robertson, Scott W; Launey, Maximilien; Shelley, Oren; Ong, Ich; Vien, Lot; Senthilnathan, Karthike; Saffari, Payman; Schlegel, Scott; Pelton, Alan R

    2015-11-01

    Superelastic wires and diamond-shaped stent surrogates were manufactured from Nitinol rods and tubing, respectively, from five different mill product suppliers - Standard VAR, Standard VIM, Standard VIM+VAR, Process-Optimized VIM+VAR, and High-Purity VAR. High-cycle fatigue tests up to 10(7) cycles were conducted under tension-tension conditions for wires and bending conditions for diamonds. These materials were compared under both testing methods at 37°C with 6% prestrain and 3% mean strain (unloading plateau) with a range of alternating strains. The High-Purity VAR material outperformed all alloys tested with a measured 10(7)-fatigue alternating strain limit of 0.32% for wire and 1.75% for diamonds. Process-Optimized VIM+VAR material was only slightly inferior to the High Purity VAR with a diamond alternating bending strain limit of 1.5%. These two "second generation" Nitinol alloys demonstrated approximately a 2× increase in 10(7)-cycle fatigue strain limit compared to all of the Standard-grade Nitinol alloys (VAR, VIM, and VIM+VAR) that demonstrated virtually indistinguishable fatigue performance. This statistically-significant increase in fatigue resistance in the contemporary alloys is ascribed to smaller inclusions in the Process-Optimized VIM+VAR material, and both smaller and fewer inclusions in the High-Purity VAR Nitinol. PMID:26241890

  2. Image-based mechanical analysis of stent deformation: concept and exemplary implementation for aortic valve stents.

    PubMed

    Gessat, Michael; Hopf, Raoul; Pollok, Thomas; Russ, Christoph; Frauenfelder, Thomas; Sündermann, Simon Harald; Hirsch, Sven; Mazza, Edoardo; Székely, Gábor; Falk, Volkmar

    2014-01-01

    An approach for extracting the radial force load on an implanted stent from medical images is proposed. To exemplify the approach, a system is presented which computes a radial force estimation from computer tomography images acquired from patients who underwent transcatheter aortic valve implantation (TAVI). The deformed shape of the implanted valve prosthesis' Nitinol frame is extracted from the images. A set of displacement vectors is computed that parameterizes the observed deformation. An iterative relaxation algorithm is employed to adapt the information extracted from the images to a finite-element model of the stent, and the radial components of the interaction forces between the stent and the tissue are extracted. For the evaluation of the method, tests were run using the clinical data from 21 patients. Stent modeling and extraction of the radial forces were successful in 18 cases. Synthetic test cases were generated, in addition, for assessing the sensitivity to the measurement errors. In a sensitivity analysis, the geometric error of the stent reconstruction was below 0.3 mm, which is below the image resolution. The distribution of the radial forces was qualitatively and quantitatively reasonable. An uncertainty remains in the quantitative evaluation of the radial forces due to the uncertainty in defining a radial direction on the deformed stent. With our approach, the mechanical situation of TAVI stents after the implantation can be studied in vivo, which may help to understand the mechanisms that lead to the complications and improve stent design. PMID:24626769

  3. Hierarchical periodic micro/nano-structures on nitinol and their influence on oriented endothelialization and anti-thrombosis.

    PubMed

    Nozaki, Kosuke; Shinonaga, Togo; Ebe, Noriko; Horiuchi, Naohiro; Nakamura, Miho; Tsutsumi, Yusuke; Hanawa, Takao; Tsukamoto, Masahiro; Yamashita, Kimihiro; Nagai, Akiko

    2015-12-01

    The applications of hierarchical micro/nano-structures, which possess properties of two-scale roughness, have been studied in various fields. In this study, hierarchical periodic micro/nano-structures were fabricated on nitinol, an equiatomic Ni-Ti alloy, using a femtosecond laser for the surface modification of intravascular stents. By controlling the laser fluence, two types of surfaces were developed: periodic nano- and micro/nano-structures. Evaluation of water contact angles indicated that the nano-surface was hydrophilic and the micro/nano-surface was hydrophobic. Endothelial cells aligned along the nano-structures on both surfaces, whereas platelets failed to adhere to the micro/nano-surface. Decorrelation between the responses of the two cell types and the results of water contact angle analysis were a result of the pinning effect. This is the first study to show the applicability of hierarchical periodic micro/nano-structures for surface modification of nitinol.

  4. A two-center comparative study of plastic and lumen-apposing large diameter self-expandable metallic stents in endoscopic ultrasound-guided drainage of pancreatic fluid collections

    PubMed Central

    Ang, Tiing Leong; Kongkam, Pradermchai; Kwek, Andrew Boon Eu; Orkoonsawat, Piyachai; Rerknimitr, Rungsun; Fock, Kwong Ming

    2016-01-01

    Background and Objectives: Endoscopic ultrasound-guided drainage of walled-off pancreatic fluid collections (PFCs) (pseudocyst [PC]; walled-off necrosis [WON]) utilizes double pigtail plastic stents (PS) and the newer large diameter fully covered self-expandable stents (FCSEMS) customized for PFC drainage. This study examined the impact of type of stent on clinical outcomes and costs. Patients and Methods: Retrospective two-center study. Outcome variables were technical and clinical success, need for repeat procedures, need for direct endoscopic necrosectomy (DEN), and procedure-related costs. Results: A total of 49 (PC: 31, WON: 18) patients were analyzed. Initially, PS was used in 37 and FCSEMS in 12. Repeat transmural drainage was required in 14 (PS: 13 [9 treated with PS, 4 treated with FCSEMS]; FCSEMS: 1 [treated with PS]) due to stent migration (PS: 3; FCSEMS: 1) or inadequate drainage (PS: 10). Technical success was 100%. Initial clinical success was 64.9% (25/38) for PS versus 91.7% (11/12) for FCSEMS (P = 0.074). With repeat transmural stenting, final clinical success was achieved in 94.6% and 100%, respectively (P = 0.411). Compared to FCSEMS, PS was associated with greater need for repeat drainage (34.2% vs. 6.3%, P = 0.032). The need for and frequency of DEN was similar between both groups, but PS required more frequent balloon dilatation. PS was significantly cheaper for noninfected PC. Costs were similar for infected PC and WON. Conclusion: PS was associated with a higher need for a second drainage procedure to achieve clinical success. The use of FCSEMS did not increase procedural costs for infected PC and WON. PMID:27803905

  5. A Comprehensive Review of Esophageal Stents

    PubMed Central

    Hong, Jinwha; Lam-Tsai, Yvette; Gress, Frank

    2012-01-01

    Esophageal stents are important tools for palliative treatment of inoperable esophageal malignancies. With the development of multiple self-expandable stents, there are now several therapeutic options for managing benign and malignant esophageal diseases. This paper discusses the various types of esophageal stents currently available, indications for their placement, challenges and complications that gastroenterologists face when placing these stents, and some of the innovations that will become available in the near future. PMID:23293566

  6. A new flow diverter stent for direct treatment of intracranial aneurysm.

    PubMed

    Ma, Jiayao; You, Zhong; Peach, Thomas; Byrne, James; Rizkallah, Rafik R

    2015-12-16

    The use of a stand-alone flow diverter (FD) stent has demonstrated itself as an efficacious endovascular approach to intracranial aneurysm treatment. FD stents that are currently available adopt an interwoven braided design. The relatively low radial stiffness intrinsic to this design could cause difficulty in deployment and poor stent-wall apposition, leading to high complication rates. A new FD stent is proposed to overcome the problems of the interwoven FD stents. The new device is manufactured from a Nitinol tube through a laser-cutting technique, and its unique structure allows for both low porosity and high packaging efficiency. Computational simulation using Abaqus has been conducted to investigate the radial stiffness and longitudinal flexibility of the new device. The new device exhibits high radial stiffness when compared to interwoven FD stents and superior longitudinal flexibility. Results from on-going in-vivo experiments and CFD simulations have also demonstrated the efficacy of the new device as a FD stent.

  7. Single and Tandem Stents in Sheep Iliac Arteries: Is There a Difference in Patency?

    SciTech Connect

    Schuermann, Karl; Vorwerk, Dierk; Buecker, Arno; Grosskortenhaus, Stefanie; Guenther, Rolf W.

    1998-09-15

    Purpose: To compare patency and neointima formation of single and tandem arterial stents. Methods: In each of six sheep, two Memotherm nitinol stents (tandem stents) were inserted into the external iliac artery on one side and a single stent into the artery on the opposite side. The size of the iliac lumen was assessed in the proximal, middle, and distal segments of the stents by intravascular ultrasound (IVUS) before, immediately after, and 1 month after implantation when the sheep were killed. Neointimal thickness was determined in the proximal, middle, and distal segments of each stent by light microscopy. Results: All stents remained patent. There was no significant difference in lumen and neointimal thickness between single and tandem stents. Cranial tandem stents showed a significantly wider lumen and smaller neointimal thickness than caudal tandem stents. In the proximal and distal segments, the lumen of the stents was significantly smaller and the neointimal thickness greater than in the middle segment; differences in neointimal thickness were significant only between the proximal and the middle segment. Conclusion: In an experimental setting, tandem stents did not interfere with one another with regard to patency and neointima formation when compared with a single contralateral stent. Neointimal thickening after stent insertion seems to be inversely related to the original arterial diameter.

  8. Microstructured Thin Film Nitinol for a Neurovascular Flow-Diverter.

    PubMed

    Chen, Yanfei; Howe, Connor; Lee, Yongkuk; Cheon, Seongsik; Yeo, Woon-Hong; Chun, Youngjae

    2016-01-01

    A cerebral aneurysm occurs as a result of a weakened blood vessel, which allows blood to flow into a sac or a ballooned section. Recent advancement shows that a new device, 'flow-diverter', can divert blood flow away from the aneurysm sac. People found that a flow-diverter based on thin film nitinol (TFN), works very effectively, however there are no studies proving the mechanical safety in irregular, curved blood vessels. Here, we study the mechanical behaviors and structural safety of a novel microstructured TFN membrane through the computational and experimental studies, which establish the fundamental aspects of stretching and bending mechanics of the structure. The result shows a hyper-elastic behavior of the TFN with a negligible strain change up to 180° in bending and over 500% in radial stretching, which is ideal in the use in neurovascular curved arteries. The simulation determines the optimal joint locations between the TFN and stent frame. In vitro experimental test qualitatively demonstrates the mechanical flexibility of the flow-diverter with multi-modal bending. In vivo micro X-ray and histopathology study demonstrate that the TFN can be conformally deployed in the curved blood vessel of a swine model without any significant complications or abnormalities. PMID:27009500

  9. Microstructured Thin Film Nitinol for a Neurovascular Flow-Diverter

    PubMed Central

    Chen, Yanfei; Howe, Connor; Lee, Yongkuk; Cheon, Seongsik; Yeo, Woon-Hong; Chun, Youngjae

    2016-01-01

    A cerebral aneurysm occurs as a result of a weakened blood vessel, which allows blood to flow into a sac or a ballooned section. Recent advancement shows that a new device, ‘flow-diverter’, can divert blood flow away from the aneurysm sac. People found that a flow-diverter based on thin film nitinol (TFN), works very effectively, however there are no studies proving the mechanical safety in irregular, curved blood vessels. Here, we study the mechanical behaviors and structural safety of a novel microstructured TFN membrane through the computational and experimental studies, which establish the fundamental aspects of stretching and bending mechanics of the structure. The result shows a hyper-elastic behavior of the TFN with a negligible strain change up to 180° in bending and over 500% in radial stretching, which is ideal in the use in neurovascular curved arteries. The simulation determines the optimal joint locations between the TFN and stent frame. In vitro experimental test qualitatively demonstrates the mechanical flexibility of the flow-diverter with multi-modal bending. In vivo micro X-ray and histopathology study demonstrate that the TFN can be conformally deployed in the curved blood vessel of a swine model without any significant complications or abnormalities. PMID:27009500

  10. Microstructured Thin Film Nitinol for a Neurovascular Flow-Diverter.

    PubMed

    Chen, Yanfei; Howe, Connor; Lee, Yongkuk; Cheon, Seongsik; Yeo, Woon-Hong; Chun, Youngjae

    2016-03-24

    A cerebral aneurysm occurs as a result of a weakened blood vessel, which allows blood to flow into a sac or a ballooned section. Recent advancement shows that a new device, 'flow-diverter', can divert blood flow away from the aneurysm sac. People found that a flow-diverter based on thin film nitinol (TFN), works very effectively, however there are no studies proving the mechanical safety in irregular, curved blood vessels. Here, we study the mechanical behaviors and structural safety of a novel microstructured TFN membrane through the computational and experimental studies, which establish the fundamental aspects of stretching and bending mechanics of the structure. The result shows a hyper-elastic behavior of the TFN with a negligible strain change up to 180° in bending and over 500% in radial stretching, which is ideal in the use in neurovascular curved arteries. The simulation determines the optimal joint locations between the TFN and stent frame. In vitro experimental test qualitatively demonstrates the mechanical flexibility of the flow-diverter with multi-modal bending. In vivo micro X-ray and histopathology study demonstrate that the TFN can be conformally deployed in the curved blood vessel of a swine model without any significant complications or abnormalities.

  11. Microstructured Thin Film Nitinol for a Neurovascular Flow-Diverter

    NASA Astrophysics Data System (ADS)

    Chen, Yanfei; Howe, Connor; Lee, Yongkuk; Cheon, Seongsik; Yeo, Woon-Hong; Chun, Youngjae

    2016-03-01

    A cerebral aneurysm occurs as a result of a weakened blood vessel, which allows blood to flow into a sac or a ballooned section. Recent advancement shows that a new device, ‘flow-diverter’, can divert blood flow away from the aneurysm sac. People found that a flow-diverter based on thin film nitinol (TFN), works very effectively, however there are no studies proving the mechanical safety in irregular, curved blood vessels. Here, we study the mechanical behaviors and structural safety of a novel microstructured TFN membrane through the computational and experimental studies, which establish the fundamental aspects of stretching and bending mechanics of the structure. The result shows a hyper-elastic behavior of the TFN with a negligible strain change up to 180° in bending and over 500% in radial stretching, which is ideal in the use in neurovascular curved arteries. The simulation determines the optimal joint locations between the TFN and stent frame. In vitro experimental test qualitatively demonstrates the mechanical flexibility of the flow-diverter with multi-modal bending. In vivo micro X-ray and histopathology study demonstrate that the TFN can be conformally deployed in the curved blood vessel of a swine model without any significant complications or abnormalities.

  12. Characterization of Nitinol Laser-Weld Joints by Nondestructive Testing

    NASA Astrophysics Data System (ADS)

    Wohlschlögel, Markus; Gläßel, Gunter; Sanchez, Daniela; Schüßler, Andreas; Dillenz, Alexander; Saal, David; Mayr, Peter

    2015-12-01

    Joining technology is an integral part of today's Nitinol medical device manufacturing. Besides crimping and riveting, laser welding is often applied to join components made from Nitinol to Nitinol, as well as Nitinol components to dissimilar materials. Other Nitinol joining techniques include adhesive bonding, soldering, and brazing. Typically, the performance of joints is assessed by destructive mechanical testing, on a process validation base. In this study, a nondestructive testing method—photothermal radiometry—is applied to characterize small Nitinol laser-weld joints used to connect two wire ends via a sleeve. Two different wire diameters are investigated. Effective joint connection cross sections are visualized using metallography techniques. Results of the nondestructive testing are correlated to data from destructive torsion testing, where the maximum torque at fracture is evaluated for the same joints and criteria for the differentiation of good and poor laser-welding quality by nondestructive testing are established.

  13. Use of a novel covered self-expandable metal stent with an anti-migration system for endoscopic ultrasound-guided drainage of a pseudocyst.

    PubMed

    Téllez-Ávila, Félix Ignacio; Villalobos-Garita, Alvaro; Ramírez-Luna, Miguel Ángel

    2013-06-16

    The development of pseudocysts in patients with chronic pancreatitis has been reported in 23%-60% of cases and drainage is indicated when they become symptomatic. Endoscopic ultrasound-guided drainage with the placement of plastic or metallic stents to create a cystogastric anastomosis has been shown to be a reliable and efficacious maneuver. Metallic stent use appears to be a safe and effective alternative that shortens the length of time of the procedure and maintains a greater diameter in the cystogastric communication. However, important migration rates have been reported. The use of new metallic stents that are specially designed to prevent migration represents a promising development in the treatment of these group of patients that appears to be safe and effective for pseudocyst drainage and could importantly reduce migration rates, while at the same time having the advantage of a single step procedure and a larger fistula diameter in the endoscopic cystogastric anastomosis.

  14. Three-dimensional CT imaging and virtual endoscopy for the placement of self-expandable stents in oesophageal and tracheobronchial neoplastic stenoses.

    PubMed

    Di Simone, M P; Mattioli, S; D'Ovidio, F; Bassi, F

    2003-01-01

    We examined the value of multislice computed tomography (CT) with three-dimensional (3D) reconstruction of the images as a pre-treatment examination in order to plan endoluminal stenting in 14 patients with large tumours involving the oesophagus and/or the tracheobronchial tree. The measurement of the stenosis obtained during 3D reconstruction of the CT images corresponded to that obtained by endoscopy and to the prosthesis chosen in all cases, with the exception of one patient undergoing double stenting due to inadequate gaseous distension of the oesophageal lumen. 3D CT may add information with respect to axial imaging, and be helpful to better plan and perform stenting of the oesophagus and airways without burdening the preoperative work-up.

  15. Use of a novel covered self-expandable metal stent with an anti-migration system for endoscopic ultrasound-guided drainage of a pseudocyst

    PubMed Central

    Téllez-Ávila, Félix Ignacio; Villalobos-Garita, Álvaro; Ramírez-Luna, Miguel Ángel

    2013-01-01

    The development of pseudocysts in patients with chronic pancreatitis has been reported in 23%-60% of cases and drainage is indicated when they become symptomatic. Endoscopic ultrasound-guided drainage with the placement of plastic or metallic stents to create a cystogastric anastomosis has been shown to be a reliable and efficacious maneuver. Metallic stent use appears to be a safe and effective alternative that shortens the length of time of the procedure and maintains a greater diameter in the cystogastric communication. However, important migration rates have been reported. The use of new metallic stents that are specially designed to prevent migration represents a promising development in the treatment of these group of patients that appears to be safe and effective for pseudocyst drainage and could importantly reduce migration rates, while at the same time having the advantage of a single step procedure and a larger fistula diameter in the endoscopic cystogastric anastomosis. PMID:23772268

  16. Mechanical properties of different airway stents.

    PubMed

    Ratnovsky, Anat; Regev, Noa; Wald, Shaily; Kramer, Mordechai; Naftali, Sara

    2015-04-01

    Airway stents improve pulmonary function and quality of life in patients suffering from airway obstruction. The aim of this study was to compare main types of stents (silicone, balloon-dilated metal, self-expanding metal, and covered self-expanding metal) in terms of their mechanical properties and the radial forces they exert on the trachea. Mechanical measurements were carried out using a force gauge and specially designed adaptors fabricated in our lab. Numerical simulations were performed for eight different stent geometries, inserted into trachea models. The results show a clear correlation between stent diameter (oversizing) and the levels of stress it exerts on the trachea. Compared with uncovered metal stents, metal stents that are covered with less stiff material exert significantly less stress on the trachea while still maintaining strong contact with it. The use of such stents may reduce formation of mucosa necrosis and fistulas while still preventing stent migration. Silicone stents produce the lowest levels of stress, which may be due to weak contact between the stent and the trachea and can explain their propensity for migration. Unexpectedly, stents made of the same materials exerted different stresses due to differences in their structure. Stenosis significantly increases stress levels in all stents.

  17. Thermo-dynamic characteristics of NITINOL-reinforced composite beams

    NASA Astrophysics Data System (ADS)

    Baz, A.; Ro, J.

    The fundamental principles governing the operation of NITINOL-reinforced composite beams are investigated by determining the individual contributions of the composite matrix, the NITINOL fibers, and the shape memory effect to the overall dynamic performance of the beams. The effect of the temperature distribution inside the composite, which results from the activation of a small subset of the NITINOL fibers, on the overall performance of the entire beam was investigated theoretically and experimentally. Particular attention was given to the effects of intentional electrical heating of a selected subset of NITINOL fibers, and the associated thermal energy propagating through the composite, on the unintentional thermal activation of additional subsets of the fibers.

  18. Percutaneous Endoluminal Stent and Stent-Graft Placement for the Treatment of Femoropopliteal Aneurysms: Early Experience

    SciTech Connect

    Mueller-Huelsbeck, Stefan; Link, Johann; Schwarzenberg, Helmut; Walluscheck, Knut P.; Heller, Martin

    1999-03-15

    Purpose: To determine the efficacy of percutaneous endoluminal stents and stent-grafts for the treatment of isolated femoropopliteal aneurysms. Methods: Seven men (age 51-69 years) with femoropopliteal occlusions (n= 6) related to aneurysms and a patent femoropopliteal aneurysm (n= 1) were treated percutaneously. In two patients uncovered Wallstents and in five patients polyester-covered nitinol stents were implanted. Assessment was performed with Doppler ultrasound and duplex ultrasonography 24 hr, 1, 3, 6, 12, and 24 months after the intervention. Additionally, intraarterial angiography was performed at 6 months. Results: Stent placement succeeded in all cases. No immediate adjunctive surgical treatment was necessary. Ankle-brachial index (ABI) improved from 0.29 {+-} 0.29 (SD) before to 0.78 {+-} 0.23 (SD) 24 hr after the intervention. One patient was lost to follow-up. Stent-graft occlusion occurred in four patients: after 2 days (n1), 1 month (n= 2), and 3 months (n= 1). One of the patients, whose stent occluded at 1 month, underwent successful recanalization with local fibrinolysis therapy. Three of the seven, all with three-vessel run-off, demonstrated patency of the stent, which was assessed by duplex ultrasonography at 29, 31, and 34 months. Breaking of the stent struts or significant stent migration was not observed. Conclusions: These results in a small number of patients warrant further investigation to evaluate the role of percutaneous stents in femoropopliteal aneurysms. Until further data of clinical studies are available, this method cannot be recommended, and it cannot replace surgical treatment.

  19. Mechanical behavior of peripheral stents and stent-vessel interaction: A computational study

    NASA Astrophysics Data System (ADS)

    Dottori, Serena; Flamini, Vittoria; Vairo, Giuseppe

    2016-05-01

    In this paper stents employed to treat peripheral artery disease are analyzed through a three-dimensional finite-element approach, based on a large-strain and large-displacement formulation. Aiming to evaluate the influence of some stent design parameters on stent mechanics and on the biomechanical interaction between stent and arterial wall, quasi-static and dynamic numerical analyses are carried out by referring to computational models of commercially and noncommercially available versions of both braided self-expandable stents and balloon-expandable stents. Addressing isolated device models, opening mechanisms and flexibility of both opened and closed stent configurations are numerically experienced. Moreover, stent deployment into a stenotic peripheral artery and possible postdilatation angioplasty (the latter for the self-expandable device only) are simulated by considering different idealized vessel geometries and accounting for the presence of a stenotic plaque. Proposed results highlight important differences in the mechanical response of the two types of stents, as well as a significant influence of the vessel shape on the stress distributions arising upon the artery-plaque system. Finally, computational results are used to assess both the stent mechanical performance and the effectiveness of the stenting treatment, allowing also to identify possible critical conditions affecting the risk of stent fracture, tissue damage, and/or pathological tissue response.

  20. Percutaneous cholangioscopy in obstructed biliary metal stents

    SciTech Connect

    Hausegger, Klaus A.; Mischinger, Hans J.; Karaic, Radenko; Klein, Guenther E.; Kugler, Cristian; Kern, Robert; Uggowitzer, Martin; Szolar, Dieter

    1997-05-15

    Purpose. To reevaluate the reasons for the occlusion of self-expanding biliary metal stents, on the basis of cholangioscopic findings. Methods. Percutaneous transhepatic cholangioscopy (PTCS) was performed in 15 patients with obstructed biliary Wallstents. The reason for stent insertion was a malignant obstruction in 14 patients; 1 had a benign biliary stricture. Conventional noncovered stents had been inserted in 12 patients; in 3 cases a polyurethane-covered prototype Wallstent had been used. Stent occlusions occurred after 1-55 months. PTCS was performed with a 2.3-mm endoscope through an 11 Fr sheath. Biopsies were taken via the working channel of the endoscope. Results. In all patients with noncovered stents the inner surface of the stent was highly irregular with seaweed-like protrusions (biopsy-proven granulation tissue). Stent incorporation varied from absent (n=1) to subtotal (n=8), but was always incomplete, no matter how long the stent had been in place. Tumor ingrowth was histologically proven in 2 patients. One patient had a large occluding concrement at the proximal end of the stent. In patients with covered stents, the inner surface appeared more regular; however, viable granulation tissue was found inside two stents and tumor ingrowth in one of them. Conclusion. PTCS showed that incorporation of the stent is virtually always incomplete. The factors contributing most to stent occlusion are the buildup of granulation tissue, bile sludge, and tumor overgrowth. Stone formation and tumor ingrowth can also be important, although less common causes of occlusion. A polyurethane stent covering could not prevent tumor ingrowth in one patient and the buildup of viable granulation tissue inside the stent in two further patients; mean stent patency in the three patients with such a stent was 3 months.

  1. Stent hypersensitivity and infection in sinus cavities

    PubMed Central

    Soufras, George D.; Hahalis, George

    2013-01-01

    Persistent mucosal inflammation, granulation tissue formation, hypersensitivity, and multifactorial infection are newly described complications of retained drug-eluting stents from endoscopic sinus surgery for refractory rhinosinusitis. In an important report published in Allergy and Rhinology, a 45-year-old male patient suffering from recalcitrant chronic rhinosinusitis underwent functional endoscopic sinus surgery and was found, for the first time, to have steroid-eluting catheters that were inadvertently left in the ethmoid and frontal sinuses. The retained catheters had caused persistent mucosal inflammation and formation of granulation tissue denoting hypersensitivity reaction. These consequences had induced perpetuation of symptoms of chronic rhinosinusitis. Meticulous removal of the retained stents with the nitinol wings from inflamed tissues of the frontal, ethmoidal, and sphenoethmoidal recesses in which they were completely imbedded was successfully performed without polypoid regrowth. Cultures of specimens taken from both left and right stents showed heavy growth of Stenotrophomonas maltophilia and moderate growth of Klebsiella oxytoca, coagulase negative Staphylococcus, and beta-hemolytic Streptococcus anginosus. Fungal infection was not detected. The current knowledge and experience regarding stent hypersensitivity and infection in relation with the use of stents in sinus cavities is reviewed. PMID:24498522

  2. Coronary artery stents: evaluating new designs for contemporary percutaneous intervention.

    PubMed

    Kandzari, David E; Tcheng, James E; Zidar, James P

    2002-08-01

    Intracoronary stents have markedly improved the short- and long-term safety and efficacy of percutaneous coronary intervention by improving acute gains in luminal dimensions, decreasing abrupt vessel occlusion, and reducing restenosis. At present, nearly 90% of all coronary interventions involve stenting. A variety of advances in stent technology and design have expanded the clinical application of stenting to include complex coronary lesions, multivessel disease, and small-diameter vessels. In addition, the development of stents as drug delivery systems for antithrombotic or antiproliferative agents has the potential to expand the role of coronary stenting, and early clinical experience appears promising. The purpose of this review is to describe recent developments in stent design, examine the results of clinical trials of contemporary stents, and present future directions for investigation of new stent technologies. PMID:12124974

  3. Educational Pathways through Nanoscience: Nitinol as a Paradigmatic Smart Material

    ERIC Educational Resources Information Center

    Lisotti, Annamaria; De Renzi, Valentina; Rozzi, Carlo Andrea; Villa, Elena; Albertini, Franca; Goldoni, Guido

    2013-01-01

    We developed an educational path based on nitinol, a shape memory alloy which conveniently exemplifies the smart material concept, i.e., a material that performs a predetermined, reversible action in response to a change in the environment. Nitinol recovers a given shape, changes its resistivity drastically and modifies its elastic properties if…

  4. Laser Cut Nitinol Tubing Fatigue Coupon: Design, Testing, and Endurance Limit

    NASA Astrophysics Data System (ADS)

    Forcucci, Stephen J.

    2014-07-01

    Nitinol medical device implants made from a laser cut tubing process (i.e., stents, valve structures, etc.) frequently require a fatigue durability assessment, which necessitates determining the material fatigue properties. Towards the goal of determining the strain-based endurance limit of medical grade superelastic Nitinol tubing, a coupon was designed and evaluated via FEA using Abaqus software, produced via laser cutting, shape setting, and electro-polishing processes, and then fatigue tested to 10 million cycles. FEA was used to determine the strain versus alternating displacement amplitude for the coupon. Error due to dimensional tolerances was determined. The coupons were then fatigue tested in a 37 °C temperature deionized water bath at alternating strain levels ranging from 0.75 to 4.0% at zero mean strain. Sample replication was greater than 90%, and the median alternating strain fatigue limit was determined via two methods. Confidence and reliability with maximum likelihood statistics are used to present a strain-based endurance limit for the material. The results seem to differ from previous published values.

  5. Nitinol-based Nanotubular and Nanowell Coatings for the Modulation of Human Vascular Cell Functions

    NASA Astrophysics Data System (ADS)

    Lee, Phin Peng

    Current approaches to reducing restenosis do not balance the reduction of vascular smooth muscle cell proliferation with the increase in the healing of the endothelium. Here, I present my study on the synthesis and characterization of a nanotubular coating on Nitinol substrates. I found that the coating demonstrated 'pro-healing' properties by increasing primary human aortic endothelial cell spreading, migration and collagen and elastin production. Certain cellular functions such as collagen and elastin production were also found to be affected by changes in nanotube diameter. The coating also reduced the proliferation and mRNA expression of collagen I and MMP2 for primary human aortic smooth muscle cells. I will also demonstrate the synthesis of a nanowell coating on Nitinol stents as well as an additional poly(lactic-co-glycolic acid) coating on top of the nanowells that has the potential for controlling drug release. These findings demonstrate the potential for the coatings to aid in the prevention of restenosis and sets up future explorations of ex vivo and in vivo studies.

  6. Nitinol 60 as a Material For Spacecraft Triboelements

    NASA Technical Reports Server (NTRS)

    Pepper, Stephen V.; DellaCorte, Christopher; Noebe, Ronald D.; Hall, David R.; Glennon, Glenn

    2009-01-01

    The mechanical properties of Nitinol 60, 60 w/o Ni, 40 w/oTi (55 a/o Ni, 45 a/o Ti) are sufficiently attractive to warrant its consideration as a lubricated spacecraft triboelement. The ability to lubricate Nitinol 60 by the oils usually used on spacecraft mechanisms--Pennzane 2001A, Krytox 143AC and Castrol 815Z - was experimentally determined. These oils were run in the boundary lubrication regime for Nitinol 60 balls running against a 440C steel counterface in the vacuum spiral orbit tribometer. Test results consisting of the coefficient of friction versus time (friction traces) and relative degradation rates are presented. Contrary to the inability to successfully lubricate other metal alloys with high titanium content, it was found that Nitinol 60 is able to be lubricated by these oils. Overall, the results presented here indicate that Nitinol 60 is a credible candidate material for spacecraft bearing applications.

  7. Flexibility and trackability of laser cut coronary stent systems.

    PubMed

    Szabadíts, Péter; Puskás, Zsolt; Dobránszky, János

    2009-01-01

    Coronary stents are the most important supports in present day cardiology. Flexibility and trackability are two basic features of stents. In this paper, four different balloon-expandable coronary stent systems were investigated mechanically in order to compare their suitability. The coronary stent systems were assessed by measurements of stent flexibility as well as by comparison of forces during simulated stenting in a self-investigated coronary vessel model. The stents were cut by laser from a single tube of 316L stainless steel or L-605 (CoCr) cobalt chromium alloy. The one-and four-point bending tests were carried out to evaluate the stent flexibility E x I (Nmm(2)), under displacement control in crimped and expanded configurations. The flexibility of stents would be rather dependent on the design than on raw material. In general a more flexible stent needs lower tracking force during the implantation. The L-605 raw material stents need lower track force to pass through in the vessel model than the 316L raw material stents. The sort and long stents passed through the curved vessel model in different ways. The long stents nestled to the vessel wall at the outer arc and bent, while the short stents did not bend in the curve, only the delivery systems bent.

  8. Passivation of nitinol wire for vascular implants--a demonstration of the benefits.

    PubMed

    O'Brien, B; Carroll, W M; Kelly, M J

    2002-04-01

    This study investigated a passivation process for polished nitinol wires and vascular stent components, after being given a typical shape setting heat treatment. Heat treated samples were passivated in a nitric acid solution and a series of corrosion tests, surface analysis and chemical analysis was performed. Potentiodynamic polarization tests demonstrated a significant increase in breakdown potential for passivated samples, compared to heat treated surfaces. Surface analysis indicated that the passivation reduces Ni and NiO content in the oxide and increases TiO2 content. Chemical analysis of passivation solutions suggests that the improvement in corrosion resistance is proportional to the quantity of nickel removed. Long term immersion tests demonstrate that nickel release from the surface of the material decreases with time and the quantity of nickel released is lower for passivated samples. The improved corrosion resistance is maintained after extended periods of immersion in saline solution.

  9. A new removable airway stent

    PubMed Central

    Amundsen, Tore; Sørhaug, Sveinung; Leira, Håkon Olav; Tyvold, Stig Sverre; Langø, Thomas; Hammer, Tommy; Manstad-Hulaas, Frode; Mattsson, Erney

    2016-01-01

    Background Malignant airway obstruction is a feared complication and will most probably occur more frequently in the future because of increasing cancer incidence and increased life expectancy in cancer patients. Minimal invasive treatment using airway stents represents a meaningful and life-saving palliation. We present a new removable airway stent for improved individualised treatment. Methods To our knowledge, the new airway stent is the world's first knitted and uncovered self-expanding metal stent, which can unravel and be completely removed. In an in vivo model using two anaesthetised and spontaneously breathing pigs, we deployed and subsequently removed the stents by unravelling the device. The procedures were executed by flexible bronchoscopy in an acute and a chronic setting – a ‘proof-of-principle’ study. Results The new stent was easily and accurately deployed in the central airways, and it remained fixed in its original position. It was easy to unravel and completely remove from the airways without clinically significant complications. During the presence of the stent in the chronic study, granulation tissue was induced. This tissue disappeared spontaneously with the removal. Conclusions The new removable stent functioned according to its purpose and unravelled easily, and it was completely removed without significant technical or medical complications. Induced granulation tissue disappeared spontaneously. Further studies on animals and humans are needed to define its optimal indications and future use. PMID:27608269

  10. Post-biliary sphincterotomy bleeding despite covered metallic stent deployment

    PubMed Central

    Donatelli, Gianfranco; Cereatti, Fabrizio; Dumont, Jean-Loup; Dhumane, Parag; Tuszynski, Thierry; Vergeau, Bertrand Marie; Meduri, Bruno

    2016-01-01

    Objectives: Several endoscopic techniques have been proposed for the management of post-sphincterotomy bleeding. Lately, self-expandable metal stents deployment has gained popularity especially as a rescue therapy when other endoscopic techniques fail. Methods-results: We report the case report of a massive post-sphincterotomy bleeding in a patient with a self-expandable metal stent in the biliary tree. Despite the presence of a correctly positioned self-expandable metal stent, a new endoscopic session was required to control the bleeding. Conclusions: Self-expandable metal stent may be useful to manage post-endoscopic sphincterotomy bleeding. However, up to now there is no specifically designed self-expandable metal stent for such complication. Large new designed self-expandable metal stent may be a useful tool for biliary endoscopist. PMID:27489716

  11. Nitinol for Prosthetic and Orthotic Applications

    NASA Astrophysics Data System (ADS)

    Henderson, Emma; Buis, Arjan

    2011-07-01

    As global populations age, conditions such as stroke and diabetes require individuals to use rehabilitation technology for many years to come due to chronic musculoskeletal, sensory, and other physical impairments. One in four males currently aged 45 will experience a stroke within 40 years and will often require access to prolonged rehabilitation. In addition, worldwide, one individual loses a limb every 30 s due to the complications of diabetes. As a result, innovative ideas are required to devise more effective prosthetic and orthotic devices to enhance quality of life. While Nitinol has already found much favor within the biomedical industry, one area, which has not yet exploited its unique properties, is in the field of physical rehabilitation, ranging from prosthetic and orthotic devices to assistive technology such as wheelchairs. Improved intervention capabilities based on materials such as Nitinol have the potential to vastly improve patients' quality of life and in the case of orthoses, may even reduce the severity of the condition over time. It is hoped that this study will spark discussion and interest for the materials community in a field which has yet to be fully exploited.

  12. Surface modifications of Nitinol for biomedical applications.

    PubMed

    Sun, F; Sask, K N; Brash, J L; Zhitomirsky, I

    2008-11-15

    Cathodic electrophoretic deposition (EPD) has been utilized for the fabrication of composite films for the surface modification of NiTi shape memory alloys (Nitinol). In the proposed method, chitosan (CH) was used as a matrix for the incorporation of other functional materials, such as heparin, hydroxyapatite and bioglass. Chitosan-heparin films were deposited from solutions of non-stoichiometric chitosan-heparin complexes. It was found that the addition of anionic heparin to the solutions of cationic chitosan resulted in a significant increase in the cathodic deposition rate. The thickness of the films prepared by this method varied in the range of 0.1-3 microm. The ability of the chitosan-heparin films to bind antithrombin, as measured by binding of (125)I-radiolabeled antithrombin, was much greater than that of pure chitosan films. Composite chitosan-hydroxyapatite films, with thickness of 1-30 microm, were obtained as monolayers or laminates, containing chitosan-hydroxyapatite layers, separated by layers of pure chitosan. The hydroxyapatite nanoparticles showed preferred orientation in the chitosan matrix with the c-axis parallel to the substrate surface. The films showed corrosion protection of the Nitinol substrates in Ringer's physiological solutions. The feasibility of the fabrication of composite films containing hydroxyapatite and bioglass in the chitosan matrix has been demonstrated. The method offers the advantages of room temperature processing. The deposition mechanisms and possible applications of the films are discussed.

  13. Effect of Stent Radial Force on Stress Pattern After Deployment: A Finite Element Study

    NASA Astrophysics Data System (ADS)

    Borghi, Alessandro; Murphy, Olive; Bahmanyar, Reza; McLeod, Chris

    2014-07-01

    The present article presents a method for assessing the radial stiffness of nitinol stents. An idealized stent model was created, and its radial stiffness was calculated by means of finite element modeling. The calculations were validated against experimental measurements. The variation of radial stiffness with geometrical dimensions was calculated, and the effect of increasing radial stiffness on endovascular deployment was analyzed. Peak tensile and compressive stresses as well as stent penetration were calculated in the case of an idealized pulmonary artery model having realistic dimensions as well as stiffness. The results of stress calculations were compared with a second set of simulations, where an idealized behavior of the stent (uniform expansion to a theoretical contact diameter) was modeled. The results show how in reality nitinol stents behave in a non-ideal way, having a non-uniform expansion and exerting non-uniform pressure on the contact areas with the artery. Such non-ideality decreases though with the increase in radial stiffness. The radial force alone may be insufficient in describing the stent-artery interaction, and numerical modeling proves to be necessary for capturing such complexity.

  14. Impact of thermomechanical texture on the superelastic response of Nitinol implants.

    PubMed

    Barney, M M; Xu, D; Robertson, S W; Schroeder, V; Ritchie, R O; Pelton, A R; Mehta, A

    2011-10-01

    The phenomenon of superelasticity in near-equiatomic NiTi, which originates from a first-order martensitic phase transition, is exploited in an increasing number of biomedical devices, most importantly endovascular stents. These stents are often manufactured from microtubing, which is shown to be highly textured crystallographically. Synchrotron X-ray microdiffraction provided microstructural, phase, and strain analysis from Nitinol tube sections that were deformed in situ along longitudinal, circumferential, and transverse orientations. We show that the large variation in the superelastic response of NiTi in these three tube directions is strongly influenced by the path that the martensitic transformation follows through the microstructure. Specifically, in severely worked NiTi, bands of [100] grains occur whose orientation deviates markedly from the surrounding matrix; these bands have an unusually large impact on the initiation and the propagation of martensite, and hence on the mechanical response. Understanding the impact of these local microstructural effects on global mechanical response, as shown here, leads to a much fuller understanding of the causes of deviation of the mechanical response from predictions and unforeseen fracture in NiTi biomedical devices.

  15. Influence of Microstructure on the Performance of Nitinol: A Computational Analysis

    NASA Astrophysics Data System (ADS)

    Weafer, F. M.; Bruzzi, M. S.

    2014-07-01

    One material that has found particular favor for use in biomedical endovascular stents is the near equi-atomic NiTi alloy, Nitinol. One remarkable trait exhibited by this superelastic material is the improvement of its fatigue performance with increasing mean strain (Ref 1, 2). Clarification into this phenomenon still remains incomplete in the literature. This study proposes a microstructural explanation for this unique macroscopic behavior; it is hypothesized stress-induced martensite (SIM) will stabilize with increasing strain which, in turn, leads to the observed increase in fatigue life. Finite element analysis (FEA) is employed to investigate the behavior of a "v-strut" stent subcomponent under various strain levels. The volume fraction of SIM is analyzed to identify its potential influence on macroscopic response and, ultimately, fatigue behavior. In addition, a computational investigation is performed on the effect of crystallographic texture on macroscopic response. Granular transformational behavior is analyzed using FEA models with realistic and idealized grain structures, specifically evaluating the effect of individual grain orientations on the stress-induced martensite transformation.

  16. Bilateral Renal Artery Aneurysm: Percutaneous Treatment with Stent-Graft Placement

    SciTech Connect

    Gandini, R.; Spinelli, A.; Pampana, E.; Fabiano, S.; Pendenza, G. Simonetti, G.

    2006-10-15

    A 51-year-old man with an 8-year history of hypertension (170/115 mmHg with two drugs) and altered renal function (5.6 mg/dl serum creatinine, 101 mg/dl BUN) was referred to our Department to evaluate the renal arteries and rule out renovascular hypertension. Doppler ultrasound and magnetic resonance angiography revealed significant bilateral renal artery stenosis and the presence of bilateral renal artery aneurysms. A self-expandable polytetrafluoroethylene (PTFE)-covered nitinol stent-graft was deployed in each renal artery to treat the stenoses and to exclude the aneurysm. Postprocedural digital subtraction angiography confirmed the resolution of the renal artery stenoses and the complete exclusion of the aneurysms. At the 6 month follow-up, color Doppler confirmed normal patency of the renal arteries with complete exclusion of the aneurysms and significant reduction of the blood pressure (130/85 mmHg with one drug) and serum creatinine levels (2.1 mg/dl)

  17. Hot Isostatic Pressing of 60-Nitinol

    NASA Technical Reports Server (NTRS)

    Stanford, Malcolm K.

    2015-01-01

    The effects of varying the time, temperature and pressure during consolidation of 60-Nitinol (Nickel Titanium alloy) by hot isostatic pressing (HIP) were examined. Six HIP cycles with a cycle time of either 2 or 20 hours, temperature of 900 or 1000 degrees Centigrade, and a chamber pressure of either 100 or 200 millipascals were used. The cycle representing the shortest cycle time at the highest temperature and pressure (2 hours/1000 degrees Centigrade/200 millipascals) produced material with the highest hardness (720 Vickers Pyramid Number (HV)). A modest increase in average grain size and significant porosity reduction were observed in material subjected to the longest cycle time at the highest temperature, regardless of the pressure applied. The intent of this study is to facilitate the technology transfer involved in the processing of this material.

  18. Dual-Source CT Angiography of Peripheral Arterial Stents: In Vitro Evaluation of 22 Different Stent Types

    PubMed Central

    Köhler, Michael; Burg, Matthias C.; Bunck, Alexander C.; Heindel, Walter; Seifarth, Harald; Maintz, David

    2011-01-01

    Purpose. To test different peripheral arterial stents using four image reconstruction approaches with respect to lumen visualization, lumen attenuation and image noise in dual-source multidetector row CT (DSCT) in vitro. Methods and Materials. 22 stents (nitinol, steel, cobalt-alloy, tantalum, platinum alloy) were examined in a vessel phantom. All stents were imaged in axial orientation with standard parameters. Image reconstructions were obtained with four different convolution kernels. To evaluate visualization characteristics of the stent, the lumen diameter, intraluminal density and noise were measured. Results. The mean percentage of the visible stent lumen diameter from the nominal stent diameter was 74.5% ± 5.7 for the medium-sharp kernel, 72.8% ± 6.4 for the medium, 70.8% ± 6.4 for the medium-smooth and 67.6% ± 6.6 for the smooth kernel. Mean values of lumen attenuation were 299.7HU ± 127 (medium-sharp), 273.9HU ± 68 (medium), 270.7HU ± 53 (medium-smooth) and 265.8HU ± 43. Mean image noise was: 54.6 ± 6.3, 20.5 ± 1.7, 16.3 ± 1.7, 14.0 ± 2 respectively. Conclusion. Visible stent lumen diameter varies depending on stent type and scan parameters. Lumen diameter visibility increases with the sharpness of the reconstruction kernel. Smoother kernels provide more realistic density measurements inside the stent lumen and less image noise. PMID:22091369

  19. A case of difficult catheterization of the contralateral limb of the Ovation Abdominal Stent Graft System in challenging aortoiliac anatomy, facilitated through the brachial access: a word of caution.

    PubMed

    Georgakarakos, Efstratios; Ioannou, Chris V; Kontopodis, Nikolaos; Tsetis, Dimitrios

    2015-02-01

    The Ovation Stent Graft System is a new trimodular endoprosthesis for the treatment of abdominal aortic aneurysms. A long nitinol stent with anchors serves the suprarenal fixation, whereas inflatable rings in the main body achieve sealing. This dissociation precludes the presence of a nitinol skeleton in the endograft, thus, avoiding competing for the same space within the delivery system, enabling the latter to achieve ultra-low profiles. However, the lack of nitinol support may render the endograft's docking limb prone to collapse in cases of narrow aortoiliac anatomy. We present a case of challenging contralateral limb catheterization, facilitated effectively through the brachial access. Preparing for the brachial route remains a useful and time-sparing adjunctive measure that guarantees the device's safety and effectiveness in challenging anatomies. PMID:25433281

  20. Development of a polymer stent with shape memory effect as a drug delivery system.

    PubMed

    Wache, H M; Tartakowska, D J; Hentrich, A; Wagner, M H

    2003-02-01

    The article presents a new concept for vascular endoprothesis (stent). Almost all commercially available stents are made of metallic materials. A common after effect of stent implantation is restenosis. Several studies on metal stents coated with drug show, that the use of a drug delivery system may reduce restenosis. The purpose of this work is to develop a new stent for the drug delivery application. The shape memory properties of thermoplastic polyurethane allow to design a new fully polymeric self-expandable stent. The possibility to use the stent as a drug delivery system is described.

  1. Stenting of the Upper Gastrointestinal Tract: Current Status

    SciTech Connect

    Katsanos, Konstantinos; Sabharwal, Tarun Adam, Andreas

    2010-08-15

    Minimally invasive image-guided insertion of self-expanding metal stents in the upper gastrointestinal tract is the current treatment of choice for palliation of malignant esophageal or gastroduodenal outlet obstructions. A concise review is presented of contemporary stenting practice of the upper gastrointestinal tract, and the procedures in terms of appropriate patient evaluation, indications, and contraindications for treatment are analyzed, along with available stent designs, procedural steps, clinical outcomes, inadvertent complications, and future technology. Latest developments include biodegradable polymeric stents for benign disease and radioactive or drug-eluting stents for malignant obstructions.

  2. Evaluation of Angiographic and Technical Aspects of Carotid Stenting with Diffusion-Weighted Magnetic Resonance Imaging

    SciTech Connect

    Blasel, Stella Hattingen, Elke; Berkefeld, Joachim; Kurre, Wiebke; Morawe, Gerald; Zanella, Friedhelm; Rochemont, Richard Du Mesnil de

    2009-07-15

    The detection of clinically silent ischemic lesions on postprocedural diffusion-weighted magnetic resonance images has become a preferred method for the description of embolic risks. The purpose of this single-center study was to evaluate whether diffusion-weighted imaging (DWI) could determine material related or technical risk factors of filter-protected carotid stenting. Eighty-four patients with symptomatic severe ({>=}60%) carotid artery stenoses received filter-protected carotid stenting. Standard DWI (b = 1000) was performed within 48 h before and after carotid stenting. The occurrence and load of new postinterventional DWI lesions were assessed. Multivariate analysis was performed to determine risk factors associated with DWI lesions, with emphasis on technical factors such as use of different access devices (guiding catheter method vs. long carotid sheath method), type of stent (open-cell nitinol stent vs. closed-cell Wallstent), and protective device (filters with 80-{mu}m vs. 110-120-{mu}m pore size). Markers for generalized atherosclerosis and for degree and site of stenosis were assessed to allow comparison of adequate risk profiles. Access, protective device, and stent type were not significantly associated with new embolic DWI lesions when we compared patients with equivalent risk profiles (long carotid sheath method 48% [11 of 23] vs. guiding catheter method 44% [27 of 61], Wallstent 47% [15 of 32] vs. nitinol stent 44% [23 of 52], and small pore size filter 61% [11 of 18] vs. large pore size filter 41% [27 of 66]). Single-center DWI studies with a moderate number of cases are inadequate for proper assessment of the embolic risk of technical- or material-related risk factors in carotid stenting. Larger multicenter studies with more cases are needed.

  3. Galvanic corrosion of nitinol under deaerated and aerated conditions.

    PubMed

    Pound, Bruce G

    2016-10-01

    Various studies have examined the corrosion rate of nitinol generally under deaerated conditions. Likewise, galvanic corrosion studies have typically involved deaerated solutions. This work addressed the effect of galvanic coupling on the corrosion current of electropolished nitinol in phosphate buffered saline and 0.9% sodium chloride under dearated and aerated conditions for times up to 24 h. Tests were performed on nitinol alone and coupled with MP35N in both the mechanically polished and passivated conditions. Aeration and galvanic coupling were found to have relatively little effect, indicating that the corrosion current is controlled by the anodic reaction. The current can be attributed entirely to Ni(2+) dissolution, which appears to be governed by solid-state mass transport of Ni(2+) through the passive oxide film. Because corrosion of EP nitinol is controlled by the anodic reaction, contact between EP nitinol and MP35N or other biomedical Co-Cr alloys is unlikely to result in significant galvanic effects in vivo. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 104B: 1322-1327, 2016.

  4. Long-Term Histopathologic and IVUS Evaluations of a Novel Coiled Sheet Stent in Porcine Carotid Arteries

    SciTech Connect

    Kaneda, Hideaki; Ikeno, Fumiaki Lyons, Jennifer; Rezaee, Mehrdad; Yeung, Alan C.; Fitzgerald, Peter J.

    2006-06-15

    Carotid angioplasty with stent placement has been proposed as an alternative method for revascularization of carotid artery stenosis. A novel stent with a laser-cut, rolled sheet of Nitinol (EndoTex Interventional Systems, Inc., Cupertino, CA) has been developed to customize treatment of stenotic lesions in carotid arteries utilizing a single stent, designed to adapt to multiple diameters and to tapered or nontapered configurations. The purpose of this study is to evaluate the conformability and vascular response to a novel stent in a chronic porcine carotid model using serial three-dimensional intravascular ultrasound (IVUS) analysis as well as histological examination. Ten Yucatan pigs underwent stent implantation in both normal carotid arteries with adjunctive balloon angioplasty. Three-dimensional IVUS analysis was performed before stent implantation, after adjunctive balloon angioplasty, and at follow-up [1 month (n = 6), 3 months (n = 6), or 6 months (n = 8)]. Histological examination (injury score, percent plaque obstruction, and qualitative analysis) was also performed. All stents were successfully deployed and well apposed in different sized vessels (lumen area range: 19-30 mm{sup 2}). Volumetric IVUS analysis showed no significant difference between the lumen areas before stent implantation and after adjunctive balloon angioplasty and no stent area change at each follow-up point compared to immediately postprocedure. Histological examination revealed minimal injury and neointimal hyperplasia at each follow-up point. In the chronic porcine carotid model, the novel stent system demonstrated good conformability, resulting in minimal vessel injury and neointimal formation.

  5. Repeat Procedures Within 30 days in Patients Stented for Malignant Distal Biliary Strictures: Experience of 508 Patients at a Tertiary Referral Center

    PubMed Central

    Byrne, Michael F; Chan, Calvin HY; Branch, Malcolm S; Jowell, Paul S; Baillie, John

    2012-01-01

    Background Stent related occlusion and migration remains a problem despite attempts to improve stent design over this time period. Flanged polyethylene plastic stents (FPS) remains the stent of choice in most centers. Early failure of stents placed for malignant extrahepatic biliary strictures (MEBS) has not previously been studied in detail. We set out to determine the incidence and reasons for biliary stent change within 30 days of the index procedure in a large tertiary center population during a period where (FPS) was the sole plastic stent used. Methods Retrospective analysis of endoscopic retrograde cholangiography (ERCP) was undertaken in patients who were stented for presumed or known MEBS between 1993 and 2001. Patients who required repeat stenting within 30 days were identified. Results All 508 patients were stented for MEBS. 5.7% of patients had a total of 34 repeat stenting procedures within 30 days of the index procedure; 27of 29 index stents were plastic, 2 were self-expandable metal stents (SEMS), 20 (3.9%) patients had stent failure as the reason for a stent exchange (plastic stent occlusion n = 15, mean time to stent change 14 ± 8.3 days; metal stent occlusion n = 2, mean time to stent change 24.5 ± 7.8 days; plastic stent migration n = 3, mean time to stent change 25 ± 5.3 days). There was a statistically significant difference in the time to stent change between the occluded plastic stent and migrated plastic stent cases (P = 0.045, 95% CI -21.7 to -0.29). 6 patients spent at least 2 additional days in hospital as a result of stent failure. Conclusions Early stent failure is an uncommon problem, especially in patients with SEMS. Early plastic stent failure appears to occur sooner with stent occlusion than with stent migration. Early stent failure is associated with significant morbidity and bears an economic impact in additional procedures and hospital stay.

  6. Educational pathways through nanoscience: nitinol as a paradigmatic smart material

    NASA Astrophysics Data System (ADS)

    Lisotti, Annamaria; De Renzi, Valentina; Rozzi, Carlo Andrea; Villa, Elena; Albertini, Franca; Goldoni, Guido

    2013-05-01

    We developed an educational path based on nitinol, a shape memory alloy which conveniently exemplifies the smart material concept, i.e., a material that performs a predetermined, reversible action in response to a change in the environment. Nitinol recovers a given shape, changes its resistivity drastically and modifies its elastic properties if subjected to a temperature change in a convenient range. Here, the properties are verified with laboratory protocols appropriate to a high-school environment. Use of mobile electronic devices is also suggested. The collected electrical and mechanical properties are analysed within a didactic path which emphasizes their common physical origin, i.e., the martensitic transition. Moreover, the peculiarities of this solid-to-solid transformation are put in correspondence with the apparently unrelated but more familiar liquid-vapour transition. The relationship with possible applications is emphasized by measuring the efficiency of using a nitinol spring as an actuator.

  7. Surface Modification of Nitinol by Chemical and Electrochemical Etching

    NASA Astrophysics Data System (ADS)

    Yang, Zhendi; Wei, Xiaojin; Cao, Peng; Gao, Wei

    2013-07-01

    In this paper, Nitinol, an equiatomic binary alloy of nickel and titanium, was surface modified for its potential biomedical applications by chemical and electrochemical etching. The main objective of the surface modification is to reduce the nickel content on the surface of Nitinol and simultaneously to a rough surface microstructure. As a result, better biocompatibility and better cell attachment would be achieved. The effect of the etching parameters was investigated, using scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectrometry (EDX) and X-ray photoelectron spectrometry (XPS). The corrosion property of modified Nitinol surfaces was investigated by electrochemical work station. After etching, the Ni content in the surface layer has been reduced and the oxidation of Ti has been enhanced.

  8. Basic Knowledge about Metal Stent Development.

    PubMed

    Jeong, Seok

    2016-03-01

    Biliary self-expandable metal stents (SEMS), a group of non-vascular stents, have been used in the palliative management of biliary obstruction around the world. However, there are still unmet needs in the clinical application of biliary SEMS. Comprehensive understanding of the SEMS is required to resolve the drawbacks and difficulties of metal stent development. The basic structure of SEMS, including the materials and knitting methods of metal wires, covering materials, and radiopaque markers, are discussed in this review. What we know about the physical and mechanical properties of the SEMS is very important. With an understanding of the basic knowledge of metal stents, hurdles such as stent occlusion, migration, and kinking can be overcome to develop more ideal SEMS.

  9. Basic Knowledge about Metal Stent Development

    PubMed Central

    Jeong, Seok

    2016-01-01

    Biliary self-expandable metal stents (SEMS), a group of non-vascular stents, have been used in the palliative management of biliary obstruction around the world. However, there are still unmet needs in the clinical application of biliary SEMS. Comprehensive understanding of the SEMS is required to resolve the drawbacks and difficulties of metal stent development. The basic structure of SEMS, including the materials and knitting methods of metal wires, covering materials, and radiopaque markers, are discussed in this review. What we know about the physical and mechanical properties of the SEMS is very important. With an understanding of the basic knowledge of metal stents, hurdles such as stent occlusion, migration, and kinking can be overcome to develop more ideal SEMS. PMID:27000423

  10. Successful treatment of endoleak Type I with uncovered EX-L stent after thoracic endovascular aneurysm repair†

    PubMed Central

    Buz, Semih; Zipfel, Burkhart; D'Ancona, Guiseppe; Hetzer, Roland

    2013-01-01

    Treatment of endoleaks after thoracic endovascular repair remains challenging, particularly when the proximal landing zone is small and partly includes the origin of the neck vessels. We report a Type Ia endoleak, occurring after thoracic endovascular aneurysm repair, which was successfully treated with a novel uncovered nitinol stent. With this success, we were able to avoid a conventional surgery to treat the endoleak. PMID:23255527

  11. Longitudinal stent deformation during coronary bifurcation stenting.

    PubMed

    Vijayvergiya, Rajesh; Sharma, Prafull; Gupta, Ankush; Goyal, Praveg; Panda, Prashant

    2016-03-01

    A distortion of implanted coronary stent along its longitudinal axis during coronary intervention is known as longitudinal stent deformation (LSD). LSD is frequently seen with newer drug eluting stents (DES), specifically with PROMUS Element stent. It is usually caused by impact of guide catheter tip, or following passage of catheters like balloon catheter, IVUS catheter, guideliner, etc. We hereby report a case of LSD during coronary bifurcation lesion intervention, using two-stents technique. Patient had acute stent thrombosis as a complication of LSD, which was successfully managed. PMID:26811144

  12. Symptomatic stent cast.

    PubMed

    Keohane, John; Moore, Michael; O'Mahony, Seamus; Crosbie, Orla

    2008-02-01

    Biliary stent occlusion is a major complication of endoscopic stent insertion and results in repeat procedures. Various theories as to the etiology have been proposed, the most frequently studied is the attachment of gram negative bacteria within the stent. Several studies have shown prolongation of stent patency with antibiotic prophylaxis. We report the case of stent occlusion from a cast of a previously inserted straight biliary stent; a "stent cast" in an 86-year-old woman with obstructive jaundice. This was retrieved with the lithotrypter and she made an uneventful recovery. This is the first reported case of a biliary stent cast.

  13. Carotid artery stenting: current and emerging options

    PubMed Central

    Morr, Simon; Lin, Ning; Siddiqui, Adnan H

    2014-01-01

    Carotid artery stenting technologies are rapidly evolving. Options for endovascular surgeons and interventionists who treat occlusive carotid disease continue to expand. We here present an update and overview of carotid stenting devices. Evidence supporting carotid stenting includes randomized controlled trials that compare endovascular stenting to open surgical endarterectomy. Carotid technologies addressed include the carotid stents themselves as well as adjunct neuroprotective devices. Aspects of stent technology include bare-metal versus covered stents, stent tapering, and free-cell area. Drug-eluting and cutting balloon indications are described. Embolization protection options and new direct carotid access strategies are reviewed. Adjunct technologies, such as intravascular ultrasound imaging and risk stratification algorithms, are discussed. Bare-metal and covered stents provide unique advantages and disadvantages. Stent tapering may allow for a more fitted contour to the caliber decrement between the common carotid and internal carotid arteries but also introduces new technical challenges. Studies regarding free-cell area are conflicting with respect to benefits and associated risk; clinical relevance of associated adverse effects associated with either type is unclear. Embolization protection strategies include distal filter protection and flow reversal. Though flow reversal was initially met with some skepticism, it has gained wider acceptance and may provide the advantage of not crossing the carotid lesion before protection is established. New direct carotid access techniques address difficult anatomy and incorporate sophisticated flow-reversal embolization protection techniques. Carotid stenting is a new and exciting field with rapidly advancing technologies. Embolization protection, low-risk deployment, and lesion assessment and stratification are active areas of research. Ample room remains for further innovations and developments. PMID:25349483

  14. Role of stents and laser therapy in biliary strictures

    NASA Astrophysics Data System (ADS)

    Chennupati, Raja S.; Trowers, Eugene A.

    2001-05-01

    The most frequent primary cancers causing malignant obstructive jaundice were pancreatic cancer (57%), hilar biliary cancer (19% including metastatic disease), nonhilar biliary cancer (14%) and papillary cancer (10%). Endoscopic stenting has widely replaced palliative surgery for malignant biliary obstruction because of its lower risk and cost. Self-expandable metal stents are the preferred mode of palliation for hilar malignancies. Plastic stents have a major role in benign biliary strictures. Major complications and disadvantages associated with metallic stents include high cost, cholangitis. malposition, migration, unextractability, and breakage of the stents, pancreatitis and stent dysfunction. Dysfunction due to tumor ingrowth can be relieved by thermal methods (argon plasma coagulator therapy). We present a concise review of the efficacy of metallic stents for palliation of malignant strictures.

  15. Percutaneous coronary angioscopy and stents

    NASA Astrophysics Data System (ADS)

    Heuser, Richard R.

    1994-05-01

    With the expanding array of therapies available for coronary intervention, the invasive cardiologist has many choices for treating a specific lesion in an individual patient. Certain types of lesions might respond more effectively with stents, particularly the rigid Palmax- Schatz device. Thrombus and dissection immediately following stent placement are associated with early occlusion, and the interventionist must be able to assess their presence pre- and post-stenting. Angiography is deficient in quantifying minimal disease and in defining lesion architecture and composition, as well as the plaque rupture and thrombosis associated with unstable angina. It is also imprecise in detecting dissection and thrombus. Intravascular ultrasound (IVUS) provides high-resolution images that delineate irregularities and other structures inside the lumen and within the vessel wall and surrounding tissues. Like angiography, IVUS has limited specificity for thrombus differentiation. Angioscopy is superior to angiography and IVUS in detecting thrombus and dissection. Angioscopy allows the clinician to assess the appearance of stent struts after deployment and at follow-up. This may aid in reducing acute complications as well as restenosis. Follow-up angioscopy of stents to detect thrombus or exposed struts may guide therapy in a patient who has clinical symptoms of restenosis.

  16. Randomized trial of Legflow® paclitaxel eluting balloon and stenting versus standard percutaneous transluminal angioplasty and stenting for the treatment of intermediate and long lesions of the superficial femoral artery (RAPID trial): study protocol for a randomized controlled trial

    PubMed Central

    2013-01-01

    Background Restenosis after percutaneous transluminal angioplasty (PTA) of the superficial femoral artery (SFA) may occur in 45% of patients at 2 years follow-up. Paclitaxel-coated balloons have been found to reduce neointimal hyperplasia, and thus reduce restenosis. Recently, the Legflow® paclitaxel-coated balloon (Cardionovum Sp.z.o.o., Warsaw, Poland) (LPEB) has been introduced. This balloon is covered with shellac, a Food and Drug Administration (FDA) approved natural resin, to obtain an equally distributed tissue concentration of paclitaxel. The RAPID trial is designed to assess restenosis after PTA using the Legflow balloon combined with nitinol stenting versus uncoated balloons with nitinol stenting in SFA lesions >5 cm. Methods/Design A total of 176 adult patients with Rutherford class 2 to class 6 symptoms due to intermediate (5–15 cm) or long (>15 cm) atherosclerotic lesions in the SFA will be randomly allocated for treatment with LPEB with nitinol stenting or uncoated balloon angioplasty with stenting. Stenting will be performed using the Supera® stent in both groups (IDEV Technologies Inc., Webster, TX). The primary endpoint is the absence of binary restenosis of the treated SFA segment. Secondary outcomes are target lesion revascularization (TLR), clinical and hemodynamic outcome, amputation rate, mortality rate, adverse events, and device-specific adverse events. Follow up consists of four visits in which ankle-brachial indices (ABI), toe pressure measurements, and duplex ultrasound (DUS) will be performed. Furthermore, a peripheral artery questionnaire (PAQ) will be completed by the patients at each follow-up. In the event that DUS reveals a symptomatic >50% restenosis, or a >75% asymptomatic restenosis, additional digital subtraction angiography will be performed with any necessary re-intervention. Discussion The RAPID trial is a multicenter randomized controlled patient blind trial that will provide evidence concerning whether the use of the

  17. A novel biodegradable esophageal stent: results from mechanical and animal experiments.

    PubMed

    Liu, Jin; Shang, Liang; Liu, Jiyong; Qin, Chengyong

    2016-01-01

    Biodegradable esophageal stents eliminate stent retrieval, but usually induce hyperplasia. This study investigated the properties of a novel biodegradable stent in vitro and in vivo. The degradation of the novel stent was observed in phosphate buffered saline (PBS) for 8 weeks. The radial forces, pH values, morphology, and retention rate of the intrinsic viscosity (R[η]) of the new biodegradable stent were all evaluated. In vitro, the pH values remained constant for 4 weeks and declined from weeks 4 to 8. The biodegradable threads degraded and ruptured at 6 weeks. Consequently, the radial force of the stent decreased to zero at that time. The curve of R[η] decreased with time linearly in PBS. To study the stents in vivo, we used a stricture model in which the middle esophagus of rabbits was damaged by alkali burn. Stents were inserted 2 weeks after injury and observed for 8 weeks. We assessed complications related to stent insertion, degradation of the stent, and survival of the rabbits. Two stents migrated, and one rabbit died. In the other rabbits, two stents degraded and moved into the stomach during the sixth week, five during the seventh week and one during the eighth week, respectively. One stent remained in position until the end of the study. In conclusion, our newly designed stent retained the strong radial force of self-expandable metal stents (SEMSs) and maintained the biodegradable properties of biodegradable (BD) stents. PMID:27158397

  18. A novel biodegradable esophageal stent: results from mechanical and animal experiments.

    PubMed

    Liu, Jin; Shang, Liang; Liu, Jiyong; Qin, Chengyong

    2016-01-01

    Biodegradable esophageal stents eliminate stent retrieval, but usually induce hyperplasia. This study investigated the properties of a novel biodegradable stent in vitro and in vivo. The degradation of the novel stent was observed in phosphate buffered saline (PBS) for 8 weeks. The radial forces, pH values, morphology, and retention rate of the intrinsic viscosity (R[η]) of the new biodegradable stent were all evaluated. In vitro, the pH values remained constant for 4 weeks and declined from weeks 4 to 8. The biodegradable threads degraded and ruptured at 6 weeks. Consequently, the radial force of the stent decreased to zero at that time. The curve of R[η] decreased with time linearly in PBS. To study the stents in vivo, we used a stricture model in which the middle esophagus of rabbits was damaged by alkali burn. Stents were inserted 2 weeks after injury and observed for 8 weeks. We assessed complications related to stent insertion, degradation of the stent, and survival of the rabbits. Two stents migrated, and one rabbit died. In the other rabbits, two stents degraded and moved into the stomach during the sixth week, five during the seventh week and one during the eighth week, respectively. One stent remained in position until the end of the study. In conclusion, our newly designed stent retained the strong radial force of self-expandable metal stents (SEMSs) and maintained the biodegradable properties of biodegradable (BD) stents.

  19. Past, Present, and Future of Gastrointestinal Stents: New Endoscopic Ultrasonography-Guided Metal Stents and Future Developments

    PubMed Central

    Lee, Hee Seung; Chung, Moon Jae

    2016-01-01

    Innovations in stent technology and technological advances in endoscopic ultrasonography have led to rapid expansion of their use in the field of gastrointestinal diseases. In particular, endoscopic ultrasonography-guided metal stent insertion has been used for the management of pancreatic fluid collection, bile duct drainage, gallbladder decompression, and gastric bypass. Endoscopic ultrasonography-guided drainage of intra-abdominal fluid collections using a plastic or metal stent is well established. Because of the various limitations—such as stent migration, injury and bleeding in the lumen—recently developed, fully covered self-expanding metal stents or lumen-apposing metal stents have been introduced for those fluids management. This article reviews the recent literature on newly developed endoscopic ultrasonography-guided metal stents and the efficacy thereof. PMID:27000424

  20. Past, Present, and Future of Gastrointestinal Stents: New Endoscopic Ultrasonography-Guided Metal Stents and Future Developments.

    PubMed

    Lee, Hee Seung; Chung, Moon Jae

    2016-03-01

    Innovations in stent technology and technological advances in endoscopic ultrasonography have led to rapid expansion of their use in the field of gastrointestinal diseases. In particular, endoscopic ultrasonography-guided metal stent insertion has been used for the management of pancreatic fluid collection, bile duct drainage, gallbladder decompression, and gastric bypass. Endoscopic ultrasonography-guided drainage of intra-abdominal fluid collections using a plastic or metal stent is well established. Because of the various limitations-such as stent migration, injury and bleeding in the lumen-recently developed, fully covered self-expanding metal stents or lumen-apposing metal stents have been introduced for those fluids management. This article reviews the recent literature on newly developed endoscopic ultrasonography-guided metal stents and the efficacy thereof. PMID:27000424

  1. The Thermobile: A Nitinol-Based Scientific Toy.

    ERIC Educational Resources Information Center

    Kauffman, George B.; Mayo, Isaac

    1998-01-01

    Provides information on the use of a toy engine with no visible power source that is designed to demonstrate the conversion of low-temperature thermal energy to mechanical energy by means of a Nitinol loop wrapped around a system of two pulleys. (DDR)

  2. Texture evolution during nitinol martensite detwinning and phase transformation

    SciTech Connect

    Cai, S.; Schaffer, J. E.; Ren, Y.

    2013-12-09

    Nitinol has been widely used to make medical devices for years due to its unique shape memory and superelastic properties. However, the texture of the nitinol wires has been largely ignored due to inherent complexity. In this study, in situ synchrotron X-ray diffraction has been carried out during uniaxial tensile testing to investigate the texture evolution of the nitinol wires during martensite detwinning, variant reorientation, and phase transformation. It was found that the thermal martensitic nitinol wire comprised primarily an axial (1{sup ¯}20), (120), and (102)-fiber texture. Detwinning initially converted the (120) and (102) fibers to the (1{sup ¯}20) fiber and progressed to a (1{sup ¯}30)-fiber texture by rigid body rotation. At strains above 10%, the (1{sup ¯}30)-fiber was shifted to the (110) fiber by (21{sup ¯}0) deformation twinning. The austenitic wire exhibited an axial (334)-fiber, which transformed to the near-(1{sup ¯}30) martensite texture after the stress-induced phase transformation.

  3. CHARACTERIZING SURFACE LAYERS IN NITINOL USING X-RAY PHOTOELECTRON SPECTROSCOPY

    SciTech Connect

    Christopfel, R.; Mehta, A.

    2008-01-01

    Nitinol is a shape memory alloy whose properties allow for large reversible deformations and a return to its original geometry. This nickel-titanium (NiTi) alloy has become a material used widely in the biomedical fi eld as a stent to open up collapsed arteries. Both ambient and biological conditions cause surface oxidation in these devices which in turn change its biocompatibility. The thickness of oxidized layers can cause fractures in the material if too large and can allow for penetration if too thin. Depending on the type and abundance of the chemical species on or near the surface, highly toxic metal ions can leak into the body causing cell damage or even cell death. Thus, biocompatibility of such devices is crucial. By using highly surface sensitive x-ray photoelectron spectroscopy to probe the surface of these structures, it is possible to decipher both layer composition and layer thickness. Two samples, both of which were mechanically polished, were investigated. Of the two samples, one was then exposed to a phosphate buffered saline (PBS) solution to mimic the chemical properties of blood, while the other remained unexposed. Although both samples were found to have oxide layers of appropriate thickness (on the order of a few nm), it was found that the sample exposed to the saline solution had a slightly thicker oxide layer and more signifi cantly, a phosphate layer very near the surface suggesting toxic metal components are well contained within the sample. These are considerable indications of a biocompatible device.

  4. Recanalization Results After Intracranial Stenting of Atherosclerotic Stenoses

    SciTech Connect

    Blasel, Stella Yuekzek, Zeynep; Kurre, Wiebke; Berkefeld, Joachim; Neumann-Haefelin, Tobias; Hattingen, Elke; Mesnil de Rochemont, Richard du

    2010-10-15

    The purpose of this investigation was to provide a detailed description of the angiographic results after stenting of high-grade intracranial stenosis using balloon-expandable stents. Forty consecutive patients with symptomatic atherosclerotic intracranial stenosis >50% received endovascular treatment by placement of balloon-expandable stents using the concept of slight underdilation and strict avoidance of overdilation. Intra-arterial digital subtraction angiography images before and after stenting in the same projection were reviewed for pre- and post-therapeutic measurement of the degree of stenosis and evaluation of morphologic criteria like plaque coverage, stent apposition, patency of side branches, and signs of dissection or vasospasm. Stenting decreased the mean percentage stenosis from 76.2 (WASID criteria) to 20.8%. Residual stenosis ranged from 0 to 55% with residual stenosis >50% in two of 40 cases. Technical success rate was 95%. There were no major vessel complications, but minor abnormalities like incomplete stent apposition (8/40) or plaque coverage (7/40), incomplete filling of side branches (13/40), and minor dissections after stenting (2/40) were seen. One case with incomplete stent apposition and two cases with side branch compromise were associated with clinical symptoms. In conclusion, intracranial stenting with slight underdilation avoided major vessel complication and created reliable luminal gain. Suboptimal recanalization results were frequently detected and may be the source of neurological complications in individual cases.

  5. A new flow diverter stent for direct treatment of intracranial aneurysm.

    PubMed

    Ma, Jiayao; You, Zhong; Peach, Thomas; Byrne, James; Rizkallah, Rafik R

    2015-12-16

    The use of a stand-alone flow diverter (FD) stent has demonstrated itself as an efficacious endovascular approach to intracranial aneurysm treatment. FD stents that are currently available adopt an interwoven braided design. The relatively low radial stiffness intrinsic to this design could cause difficulty in deployment and poor stent-wall apposition, leading to high complication rates. A new FD stent is proposed to overcome the problems of the interwoven FD stents. The new device is manufactured from a Nitinol tube through a laser-cutting technique, and its unique structure allows for both low porosity and high packaging efficiency. Computational simulation using Abaqus has been conducted to investigate the radial stiffness and longitudinal flexibility of the new device. The new device exhibits high radial stiffness when compared to interwoven FD stents and superior longitudinal flexibility. Results from on-going in-vivo experiments and CFD simulations have also demonstrated the efficacy of the new device as a FD stent. PMID:26592434

  6. Design and mechanical properties of a novel cerebral flow diverter stent.

    PubMed

    Ma, Jiayao; You, Zhong; Byrne, James; Rizkallah, Rafik R

    2014-05-01

    Brain arterial aneurysms are localised dilatation in the wall of cerebral arteries that are common among adult population and associated with high incidence of morbidity and mortality. Using flow diverter stent alone to treat cerebral aneurysm is recognized as a safe and effective method. However, flow diverter stents currently available have limitations due to their braided structures. In this paper a novel flow diverter stent is proposed. It is made out of nitinol tubes that provide adequate radial stiffness and tailored surface coverage to overcome problems of currently available braided stents while retaining low porosity and excellent longitudinal flexibility. Finite element analysis using Abaqus has been conducted to investigate radial stiffness, longitudinal flexibility, and maximum strain during packaging of a series of novel stent designs with varied geometric parameters. Results show that porosity below 70% can be achieved and provides radial stiffness and longitudinal flexibility comparable to those of the Neuroform stent that is commonly used for stent assisted coiling. The novel flow diverter has showed great potential for direct treatment of cerebral aneurysms. PMID:24449051

  7. Transhepatic contemporary palliation of biliary and duodenal stenoses by means of metallic stents.

    PubMed

    Cozzi, G; Chiaraviglio, F; Bonfanti, G; Civelli, E M

    2004-01-01

    We describe the treatment of a stenosing lesion of the horizontal duodenum by means of a large-bore metallic stent inserted percutaneously in a patient with transhepatic biliary drainage. In the same session, we used an expandable metallic stent in the biliary tree to relieve jaundice. We recommend the transhepatic approach for duodenal metallic stent insertion in patients with percutaneous biliary drainage.

  8. Fast Virtual Stenting with Active Contour Models in Intracranical Aneurysm.

    PubMed

    Zhong, Jingru; Long, Yunling; Yan, Huagang; Meng, Qianqian; Zhao, Jing; Zhang, Ying; Yang, Xinjian; Li, Haiyun

    2016-02-15

    Intracranial stents are becoming increasingly a useful option in the treatment of intracranial aneurysms (IAs). Image simulation of the releasing stent configuration together with computational fluid dynamics (CFD) simulation prior to intervention will help surgeons optimize intervention scheme. This paper proposed a fast virtual stenting of IAs based on active contour model (ACM) which was able to virtually release stents within any patient-specific shaped vessel and aneurysm models built on real medical image data. In this method, an initial stent mesh was generated along the centerline of the parent artery without the need for registration between the stent contour and the vessel. Additionally, the diameter of the initial stent volumetric mesh was set to the maximum inscribed sphere diameter of the parent artery to improve the stenting accuracy and save computational cost. At last, a novel criterion for terminating virtual stent expanding that was based on the collision detection of the axis aligned bounding boxes was applied, making the stent expansion free of edge effect. The experiment results of the virtual stenting and the corresponding CFD simulations exhibited the efficacy and accuracy of the ACM based method, which are valuable to intervention scheme selection and therapy plan confirmation.

  9. Fast Virtual Stenting with Active Contour Models in Intracranical Aneurysm

    PubMed Central

    Zhong, Jingru; Long, Yunling; Yan, Huagang; Meng, Qianqian; Zhao, Jing; Zhang, Ying; Yang, Xinjian; Li, Haiyun

    2016-01-01

    Intracranial stents are becoming increasingly a useful option in the treatment of intracranial aneurysms (IAs). Image simulation of the releasing stent configuration together with computational fluid dynamics (CFD) simulation prior to intervention will help surgeons optimize intervention scheme. This paper proposed a fast virtual stenting of IAs based on active contour model (ACM) which was able to virtually release stents within any patient-specific shaped vessel and aneurysm models built on real medical image data. In this method, an initial stent mesh was generated along the centerline of the parent artery without the need for registration between the stent contour and the vessel. Additionally, the diameter of the initial stent volumetric mesh was set to the maximum inscribed sphere diameter of the parent artery to improve the stenting accuracy and save computational cost. At last, a novel criterion for terminating virtual stent expanding that was based on the collision detection of the axis aligned bounding boxes was applied, making the stent expansion free of edge effect. The experiment results of the virtual stenting and the corresponding CFD simulations exhibited the efficacy and accuracy of the ACM based method, which are valuable to intervention scheme selection and therapy plan confirmation. PMID:26876026

  10. Elastic recoil of coronary stents: a comparative analysis.

    PubMed

    Barragan, P; Rieu, R; Garitey, V; Roquebert, P O; Sainsous, J; Silvestri, M; Bayet, G

    2000-05-01

    Minimum elastic recoil (ER) has became an essential feature of new coronary stents when deployed in artheromatous lesions of various morphologies. The ER of coronary stent might be an important component of 6-month restenosis rate by minimizing the luminal loss. We evaluated the intrinsic ER of 23 coronary stents with a mechanical test bench. The amount of ER for one size of stent (3.0 mm) was quantified using a 3D optical contactless machine (Smartscope MVP, Rochester, NY). The stents were expanded on their own balloon for the precrimped stents; the uncrimped stents were expended using identical 3.0-mm balloons. Two types of measurements were done without exterior stress and with a 0.2-bar exterior stress, directly on the stent at the end of balloon expansion, immediately after balloon deflation, and then 30 min, 60 min, and 120 min after. ER ranged from 1.54%+/-0.81% (Bestent BES 15) to 16.51%+/-2.89% (Paragon stent) without stress (P<0.01) and from 2.35%+/-1.14% (Bestent BES 15) to 18.34%+/-2.41% (Cook GR2) under 0.2-bar pressure (P<0.0001). Furthermore, there was a significant reduction between the mean result of tubular stents (TS) and coil stents (CS). The results of in vitro mechanical tests may confirm strongly the interest of a minimum ER in the prevention of the 6-month restenosis. PMID:10816295

  11. Stent migration during transcatheter management of coarctation of aorta.

    PubMed

    Kannan, Bhava R J; Srinivasan, Muthusamy

    2012-02-15

    A 13-year-old girl underwent endovascular stent placement for coarctation of aorta. The fully expanded stent migrated to ascending aorta which could be stabilized, recrimped, and repositioned with a 20-mm goose neck snare. Postdilatation was performed from the left brachial route resulting in a good outcome.

  12. Myths and Truths of Nitinol Mechanics: Elasticity and Tension-Compression Asymmetry

    NASA Astrophysics Data System (ADS)

    Bucsek, Ashley N.; Paranjape, Harshad M.; Stebner, Aaron P.

    2016-08-01

    Two prevalent myths of Nitinol mechanics are examined: (1) Martensite is more compliant than austenite; (2) Texture-free Nitinol polycrystals do not exhibit tension-compression asymmetry. By reviewing existing literature, the following truths are revealed: (1) Martensite crystals may be more compliant, equally stiff, or stiffer than austenite crystals, depending on the orientation of the applied load. The Young's Modulus of polycrystalline Nitinol is not a fixed number—it changes with both processing and in operando deformations. Nitinol martensite prefers to behave stiffer under compressive loads and more compliant under tensile loads. (2) Inelastic Nitinol martensite deformation in and of itself is asymmetric, even for texture-free polycrystals. Texture-free Nitinol polycrystals also exhibit tension-compression transformation asymmetry.

  13. Double-layered covered stent for the treatment of malignant oesophageal obstructions: Systematic review and meta-analysis

    PubMed Central

    Hussain, Zeiad; Diamantopoulos, Athanasios; Krokidis, Miltiadis; Katsanos, Konstantinos

    2016-01-01

    AIM To investigate the efficacy of double-layered covered stent in the treatment of malignant oesophageal obstructions. METHODS A systematic review and meta-analysis was performed following the PRISMA process. PubMed (Medline), EMBASE (Excerpta Medical Database), AMED (Allied and Complementary medicine Database), Scopus and online content, were searched for studies reporting on the NiTi-S polyurethane-covered double oesophageal stent for the treatment of malignant dysphagia. Weighted pooled outcomes were synthesized with a random effects model to account for clinical heterogeneity. All studies reporting the outcome of palliative management of dysphagia due to histologically confirmed malignant oesophageal obstruction using double-layered covered nitinol stent were included. The level of statistical significance was set at α = 0.05. RESULTS Six clinical studies comprising 250 patients in total were identified. Pooled technical success of stent insertion was 97.2% (95%CI: 94.8%-98.9%; I2 = 5.8%). Pooled complication rate was 27.6% (95%CI: 20.7%-35.2%; I2 = 41.9%). Weighted improvement of dysphagia on a scale of 0-5 scoring system was -2.00 [95%CI: -2.29%-(-1.72%); I2 = 87%]. Distal stent migration was documented in 10 out of the 250 cases examined. Pooled stent migration rate was 4.7% (95%CI: 2.5%-7.7%; I2 = 0%). Finally, tumour overgrowth was reported in 34 out of the 250 cases with pooled rate of tumour overgrowth of 11.2% (95%CI: 3.7%-22.1%; I2 = 82.2%). No funnel plot asymmetry to suggest publication bias (bias = 0.39, P = 0.78). In the sensitivity analysis all results were largely similar between the fixed and random effects models. CONCLUSION The double-layered nitinol stent provides immediate relief of malignant dysphagia with low rates of stent migration and tumour overgrowth

  14. Double-layered covered stent for the treatment of malignant oesophageal obstructions: Systematic review and meta-analysis

    PubMed Central

    Hussain, Zeiad; Diamantopoulos, Athanasios; Krokidis, Miltiadis; Katsanos, Konstantinos

    2016-01-01

    AIM To investigate the efficacy of double-layered covered stent in the treatment of malignant oesophageal obstructions. METHODS A systematic review and meta-analysis was performed following the PRISMA process. PubMed (Medline), EMBASE (Excerpta Medical Database), AMED (Allied and Complementary medicine Database), Scopus and online content, were searched for studies reporting on the NiTi-S polyurethane-covered double oesophageal stent for the treatment of malignant dysphagia. Weighted pooled outcomes were synthesized with a random effects model to account for clinical heterogeneity. All studies reporting the outcome of palliative management of dysphagia due to histologically confirmed malignant oesophageal obstruction using double-layered covered nitinol stent were included. The level of statistical significance was set at α = 0.05. RESULTS Six clinical studies comprising 250 patients in total were identified. Pooled technical success of stent insertion was 97.2% (95%CI: 94.8%-98.9%; I2 = 5.8%). Pooled complication rate was 27.6% (95%CI: 20.7%-35.2%; I2 = 41.9%). Weighted improvement of dysphagia on a scale of 0-5 scoring system was -2.00 [95%CI: -2.29%-(-1.72%); I2 = 87%]. Distal stent migration was documented in 10 out of the 250 cases examined. Pooled stent migration rate was 4.7% (95%CI: 2.5%-7.7%; I2 = 0%). Finally, tumour overgrowth was reported in 34 out of the 250 cases with pooled rate of tumour overgrowth of 11.2% (95%CI: 3.7%-22.1%; I2 = 82.2%). No funnel plot asymmetry to suggest publication bias (bias = 0.39, P = 0.78). In the sensitivity analysis all results were largely similar between the fixed and random effects models. CONCLUSION The double-layered nitinol stent provides immediate relief of malignant dysphagia with low rates of stent migration and tumour overgrowth PMID:27678367

  15. Hardness and Microstructure of Binary and Ternary Nitinol Compounds

    NASA Technical Reports Server (NTRS)

    Stanford, Malcolm K.

    2016-01-01

    The hardness and microstructure of twenty-six binary and ternary Nitinol (nickel titanium, nickel titanium hafnium, nickel titanium zirconium and nickel titanium tantalum) compounds were studied. A small (50g) ingot of each compound was produced by vacuum arc remelting. Each ingot was homogenized in vacuum for 48 hr followed by furnace cooling. Specimens from the ingots were then heat treated at 800, 900, 1000 or 1100 degree C for 2 hr followed by water quenching. The hardness and microstructure of each specimen was compared to the baseline material (55-Nitinol, 55 at.% nickel - 45 at.% titanium, after heat treatment at 900 degC). The results show that eleven of the studied compounds had higher hardness values than the baseline material. Moreover, twelve of the studied compounds had measured hardness values greater 600HV at heat treatments from 800 to 900 degree C.

  16. Addressing Machining Issues for the Intermetallic Compound 60-NITINOL

    NASA Technical Reports Server (NTRS)

    Stanford, Malcolm K.; Wozniak, Walter A.; McCue, Terry R.

    2012-01-01

    60-NITINOL (60 wt.% Ni - 40 wt.% Ti) is being studied as a material for advanced aerospace components. Frequent wire breakage during electrical-discharge machining of this material was investigated. The studied material was fabricated from hot isostatically pressed 60-NITINOL powder obtained through a commercial source. Bulk chemical analysis of the material showed that the composition was nominal but had relatively high levels of certain impurities, including Al and O. It was later determined that Al2O3 particles had contaminated the material during the hot isostatic pressing procedure and that these particles were the most likely cause of the wire breakage. The results of this investigation highlight the importance of material cleanliness to its further implementation.

  17. A method for investigating the mechanical properties of intracoronary stents using finite element numerical simulation.

    PubMed

    Tan, L B; Webb, D C; Kormi, K; Al-Hassani, S T

    2001-03-01

    The proliferation of stent designs poses difficult problems to clinicians, who have to learn the relative merits of all stents to ensure optimal selection for each lesion, and also to regulatory authorities who have the dilemma of preventing the inappropriate marketing of substandard stents while not denying patients the benefits of advanced technology. Of the major factors influencing long-term results, those of patency and restenosis are being actively studied whereas the mechanical characteristics of devices influencing the technical results of stenting remain under-investigated. Each different stent design has its own particular features. A robust method for the independent objective comparison of the mechanical performance of each design is required. To do this by experimental measurement alone may be prohibitively expensive. A less costly option is to combine computer analysis, employing the standard numerical technique of the finite element method (FEM), with targeted experimental measurements of the specific mechanical behaviour of stents. In this paper the FEM technique is used to investigate the structural behaviour of two different stent geometries: Freedom stent geometry and Palmaz-Schatz (P-S) stent geometry. The effects of altering the stent geometry, the stent wire diameter and contact with (and material properties of) a hard eccentric intravascular lesion (simulating a calcified plaque) on stent mechanical performance were investigated. Increasing the wire diameter and the arterial elastic modulus by 150% results in the need to increase the balloon pressure to expand the stent by 10-fold. Increasing the number of circumferential convolutions increases the pressure required to initiate radial expansion of mounted stents. An incompressible plaque impinging on the mid portion of a stent causes a gross distortion of the Freedom stent and an hour-glass deformity in the P-S stent. These findings are of relevance for future comparative studies of the

  18. Intracranial Stenting in the Treatment of Wide-Necked Aneurysms

    PubMed Central

    Leonardi, M.; Dall'olio, M.; Cenni, P.; Raffi, L.; Simonetti, L.

    2007-01-01

    Summary We positioned the following self-expanding stents certified for intracranial application: 16 Neuro form (Boston Scientific), three INX (Medtronic), one Leo (Balt). 6F calibre femoral introducers and guiding catheters were used for stent placement changing to 5F calibre introducers and guiding catheters (Envoy, Cordis) for the Neuroform 2 and 3 stents. All procedures were carried out under general anaesthesia and heparinization. Our pharmacological protocol consisted of adjunctive treatment with anti-aggregants during the interventional procedure and for the following six months, without premedication. From November 2000 to August 2006 we treated 28 patients (27 F/1M) with giant wide-necked aneurysms and one dissecting basilar artery aneurysm requiring the placement of 29 stents. We successfully positioned 20 stents: 11 stents combined with coils (8 immediate; 3 late) with complete exclusion of the aneurysm from the circulation in seven cases and subtotal exclusion in four; nine stents not followed by embolization with complete exclusion of the aneurysm from the circulation in six cases and subtotal exclusion in three. Stenting was not possible in nine cases due to extreme vessel tortuosity and the poor flexibility of release systems for the first stents. No late stent occlusion or subarachnoid haemorrhage were encountered after treatment. PMID:20566126

  19. New approach to quantitative angiographic assessment after stent implantation.

    PubMed

    Reimers, B; Di Mario, C; Di Francesco, L; Moussa, I; Blengino, S; Martini, G; Reiber, J H; Colombo, A

    1997-04-01

    The new generation quantitative angiographic systems apply the interpolated technique to calculate the reference diameter at the site of the stenosis by integrating measurements of the segments proximal and distal to the stenosis. After stent implantation these measurements can be misleading as the treated segment, which is frequently larger than the adjacent not stented segments, is included in the measurements. The consequence is an overestimation of the reference diameter and the residual diameter stenosis. The present study was performed to compare this conventional technique of measurement with a new method which excludes the stented segment for the calculation of the reference diameter. Fifty-two lesions treated with poorly radiopaque stents (56% Palmaz-Schatz, 28% NIR, 10% Gianturco-Roubin, 6% Wallstent) expanded at high pressure (> = or 16 atm) were analyzed according to the conventional and stent excluded method. After stent implantation the reference diameter was 3.39 +/- 0.48 mm with conventional measurements and 3.02 +/- 0.45 mm with the stent excluded method (P < 0.05). The corresponding % diameter stenosis was 13 +/- 9 for the conventional technique and 1 +/- 13 for the stent excluded analysis (P < 0.05). The new approach to quantitative coronary analysis after stenting provides higher accuracy in reference diameter calculations and allows a more appropriate matching of stented segments with adjacent normal segments.

  20. Thermophysical Properties of 60-NITINOL for Mechanical Component Applications

    NASA Technical Reports Server (NTRS)

    Stanford, Malcolm K.

    2012-01-01

    The linear thermal expansion coefficient, specific heat capacity, electrical resistivity and thermal conductivity of 60- NITINOL were studied over a range of temperatures representing the operating environment of an oil-lubricated bearing. The behavior of this material appears to follow wellestablished theories applicable to either metal alloys, in general, or to intermetallic compounds, more specifically and the measured data were found to be comparable to those for conventional bearing alloys.

  1. A Nitinol-Based Solar Array Deployment Mechanism

    NASA Technical Reports Server (NTRS)

    Choi, Shin John; Lu, Chia-Ao; Feland, John

    1996-01-01

    This document describes a simple, light weight, and scalable mechanism capable of deploying flexible or rigid substrate solar arrays that have been configured in an accordion-like folding scheme. This mechanism is unique in that it incorporates a Shape Memory Alloy (SMA) actuator made of Nitinol. This paper documents the design of the mechanism in full detail while offering to designers a foundation of knowledge by which they can develop future applications with SMA's.

  2. Thermal processing and characterization of 316LVM cardiovascular stent.

    PubMed

    Verma, Arpana; Choubey, Animesh; Raval, Ankur; Kothwala, Devesh

    2006-01-01

    In the current investigation, annealing was employed as a means to improve the mechanical performance of 316LVM coronary stents. Two different temperatures (1000 degrees C and 1150 degrees C) were explored for the thermal processing of the device. Acid pickling was done as a pre-annealing step to remove the debris and slag material attached to the stent after laser cutting. Post annealing operation involved the electrochemical polishing of the device which was also a parameter for assessment of the feasibility of the annealing process. Microstructural characterization, balloon expandability and tensile testing of the stents were performed to characterize the properties after thermal treatment. A fine grained austenitic structure with marked improvement in the % elongation (>40%) could be achieved after annealing the stents at 1000 degrees C. Balloon expandability tests of the stents annealed at 1000 degrees C indicated that the device was implantable. PMID:17119277

  3. Compliant articulation structure using superelastic NiTiNOL

    NASA Astrophysics Data System (ADS)

    Liu, Jiening; Hall, Benjamin; Frecker, Mary; Reutzel, Edward W.

    2013-09-01

    A device that can provide articulation to surgical tool tips is needed in natural orifice transluminal endoscopy surgery (NOTES). In this paper, we propose a compliant articulation structure that uses superelastic NiTiNOL to achieve a large deflection angle and force in a compact size. Six geometric parameters are used to define this structure, and constraints based on the fabrication process are imposed. Using finite element analysis, a family of designs is evaluated in terms of the free deflection angle and blocked force. The same family of designs is evaluated for both NiTiNOL and stainless steel. It can be seen that significant benefits are observed when using NiTiNOL compared to 316 stainless steel; a maximum free deflection angle of 64.8° and maximum blocked force of 24.7 N are predicted. The structures are designed to avoid stress concentrations, and design guidelines are recommended. The meso-scale articulation structure is fabricated using both a Coherent Avia Q-switched, 355 nm laser and a Myachi Unitek 200 W single mode pulsed fiber laser with active water cooling. Select fabricated structures are then tested to validate the finite element models.

  4. Fracture of Polymer-Coated Nitinol During Gamma Sterilization

    NASA Astrophysics Data System (ADS)

    Norwich, Dennis W.

    2012-12-01

    After gamma sterilization of a packaged medical device, fractures were discovered in the superelastic nitinol wire used as part of the assembly. The nitinol wire was encased in fluorinated ethylene propylene (FEP) shrink tube. The only fractures occurred where the encased wire was held under strain during gamma sterilization. A study was conducted to determine the susceptibility of nitinol to this type of failure. The variables studied included wire diameter, wire surface finish, wire oxide layer, quantity of wires encased, type of tubing, and strain level during gamma sterilization. The greatest susceptibility to fracture occurred to single wire samples with a light oxide layer held under high strain in FEP shrink tube. Gamma sterilization experiments were conducted to isolate and confirm this failure mechanism. Scanning electron microscopy was used to analyze the fractured samples. Chemical analysis was performed in an attempt to detect trace elements to determine the root cause of the failures. Stress corrosion cracking caused by the liberation of fluorine due to the degradation of the polymer during gamma sterilization is suspected.

  5. Small Bowel Stent-in-Stent Placement for Malignant Small Bowel Obstruction Using a Balloon-Assisted Overtube Technique

    PubMed Central

    Popa, Daniel; Ramesh, Jayapal; Peter, Shajan; Wilcox, C. Mel

    2014-01-01

    Self-expanding metal stents are a useful therapy to palliate malignant and benign luminal gastrointestinal obstruction. Self-expanding metal stents has been widely reported for colonic, esophageal, and gastric obstruction. However, endoscopic delivery and placement to the small bowel is more challenging and difficult. This case illustrates the usefulness and technical advantages of the balloon-overtube and enteroscopy technique for the palliative treatment of neoplastic stenosis affecting the small intestine. PMID:24570892

  6. A Meta-analysis of Stent Placement vs. Angioplasty for Dialysis Vascular Access Stenosis.

    PubMed

    Fu, Ning; Joachim, Emily; Yevzlin, Alexander S; Shin, Jung-Im; Astor, Brad C; Chan, Micah R

    2015-01-01

    Dysfunction of arteriovenous fistulas (AVF) and arteriovenous grafts (AVG) contribute significantly to morbidity and hospitalization in the dialysis population. Despite advances in endovascular techniques, the incidence of vascular access stenosis remains problematic. Currently, the role of endovascular stent placement in the treatment of vascular access stenosis is poorly defined. This meta-analysis compares the primary patency rates of stenotic vascular access treated with stent placement vs. angioplasty. We searched Medline for English language publications from 1980 through December 2013, along with national conference proceedings and reference lists of all included publications. Inclusion criteria were a measure of primary patency, secondary patency, or access dysfunction. Studies were excluded if they were not in English or if they included pediatric patients. Ten studies with a total of 860 subjects met the inclusion criteria, including six experimental studies and four observational studies. There was significantly higher overall primary patency in those receiving stent placement than in those treated with angioplasty (pooled relative risk [RR] = 0.79; 95% confidence interval [CI]: 0.65-0.96). The estimate did not differ by study design. The effect of treatment differed significantly (p = 0.001) by the type of stents used, however. In studies including nitinol stents (six studies, 678 patients), 6-month patency was significantly better for stent placement than angioplasty (pooled RR = 0.67; 95% CI: 0.54-0.84), whereas there was no significant differences between stent placement and angioplasty in those studies using bare metal stents exclusively (four studies, 182 patients; pooled RR = 1.09; 95% CI: 0.91-1.32). There was significant heterogeneity between studies (I(2)  = 70.6%; p < 0.0001). Our results suggest that stent placement may confer an advantage over balloon angioplasty in primary patency of dialysis access stenoses.

  7. Bioresorbable Stents in PCI.

    PubMed

    Lindholm, Daniel; James, Stefan

    2016-08-01

    The evolution of percutaneous coronary intervention has been considerable. Coronary stents were introduced to avoid vessel recoil and reduce acute and late vessel complications. Later, drug-eluting stents were developed to decrease the neointimal hyperplasia associated with bare metal stents in order to reduce restenosis. However, very late stent thrombosis remains problematic, and the permanent presence of a metal stent could be associated with local inflammation and impaired vascular physiology. Thus, bioresorbable stents have been developed, to prevent recoil initially when this risk is the highest, with subsequent degradation over time, to avoid long-term complications of the presence of stents in the coronary vasculature. Here, we review the current status of bioresorbable stents in percutaneous coronary intervention (PCI), with focus on the platforms that have been studied the most: ABSORB, DESolve, and DREAMS. In terms of clinical outcomes, bioresorbable stents have not yet shown superiority compared with current generation drug-eluting stents, but rather a signal of increased stent thrombosis. Further development and longer-term studies are needed before the routine implementation of bioresorbable stents in clinical practice. PMID:27312934

  8. iStent trabecular micro-bypass stent for open-angle glaucoma

    PubMed Central

    Le, Kim; Saheb, Hady

    2014-01-01

    Trabecular micro-bypass stents, commonly known as iStents, are micro-invasive glaucoma surgery (MIGS) devices used to treat open-angle glaucoma. Like other MIGS procedures that enhance trabecular outflow, the iStent lowers intraocular pressure (IOP) by creating a direct channel between the anterior chamber and Schlemm’s canal. iStents are typically implanted at the time of phacoemulsification for patients with open-angle glaucoma and visually significant cataracts. This review summarizes the published data regarding the efficacy, safety, and cost considerations of trabecular micro-bypass stents. Most studies found statistically significant reductions in mean IOP and ocular medication use after combined phacoemulsification with single or double iStent implantation. The devices were found to be very safe, with a safety profile similar to that of cataract surgery. Complications were infrequent, with the most common complications being temporary stent obstruction or malposition, which resolved with observation or secondary procedures. Future studies are needed to evaluate long-term outcomes, patient satisfaction, cost effectiveness, and expanded indications. PMID:25284980

  9. iStent trabecular micro-bypass stent for open-angle glaucoma.

    PubMed

    Le, Kim; Saheb, Hady

    2014-01-01

    Trabecular micro-bypass stents, commonly known as iStents, are micro-invasive glaucoma surgery (MIGS) devices used to treat open-angle glaucoma. Like other MIGS procedures that enhance trabecular outflow, the iStent lowers intraocular pressure (IOP) by creating a direct channel between the anterior chamber and Schlemm's canal. iStents are typically implanted at the time of phacoemulsification for patients with open-angle glaucoma and visually significant cataracts. This review summarizes the published data regarding the efficacy, safety, and cost considerations of trabecular micro-bypass stents. Most studies found statistically significant reductions in mean IOP and ocular medication use after combined phacoemulsification with single or double iStent implantation. The devices were found to be very safe, with a safety profile similar to that of cataract surgery. Complications were infrequent, with the most common complications being temporary stent obstruction or malposition, which resolved with observation or secondary procedures. Future studies are needed to evaluate long-term outcomes, patient satisfaction, cost effectiveness, and expanded indications.

  10. Primary Patency of Wallstents in Malignant Bile Duct Obstruction: Single vs. Two or More Noncoaxial Stents

    SciTech Connect

    Maybody, Majid Brown, Karen T.; Brody, Lynn A.; Covey, Anne M.; Sofocleous, Constantinos T.; Thornton, Raymond H.; Getrajdman, George I.

    2009-07-15

    The purpose of this study was to determine the primary patency of two or more noncoaxial self-expanding metallic Wallstents (Boston Scientific, Natick, MA) and to compare this with the primary patency of a single stent in malignant bile duct obstruction. From August 2002 to August 2004, 127 patients had stents placed for malignant bile duct obstruction. Forty-five patients were treated with more than one noncoaxial self-expanding metallic stents and 82 patients had a single stent placed. Two patients in the multiple-stent group were lost to follow-up. The primary patency period was calculated from the date of stenting until the first poststenting intervention for stent occlusion, death, or the time of last documented follow-up. The patency of a single stent was significantly different from that of multiple stents (P = 0.0004). In the subset of patients with high bile duct obstruction, the patency of a single stent remained significantly different from that of multiple stents (P = 0.02). In the single-stent group, there was no difference in patency between patients with high vs. those with low bile duct obstruction (P = 0.43). The overall median patency for the multistent group and the single-stent group was 201 and 261 days, respectively. In conclusion, the patency of a single stent placed for malignant low or high bile duct obstruction is similar, and significantly longer than, that of multiple stents placed for malignant high bile duct obstruction. Given the median patency of 201 days, when indicated, percutaneous stenting of multiple bile ducts is an effective palliative measure for patients with malignant high bile duct obstruction.

  11. The impact of material characteristics on the mechanical properties of a poly(L-lactide) coronary stent.

    PubMed

    Grabow, N; Martin, H; Schmitz, K P

    2002-01-01

    Biodegradable polymer stents as an alternative to metallic vascular stents have long been under discussion. However, for various reasons no such stent concept has been made available for commercial use until today. One reason may be, that still little is known about the mechanical properties of polymer stents and their dependency on the material characteristics. In this study, finite element analysis is used to investigate the mechanical properties of a balloon expandable PLLA stent under various load conditions. It is shown, how material parameters, such as elastic modulus, yield level and material hardening, influence stent recoil and collapse behavior. PMID:12451906

  12. Role of metallic stents in benign esophageal stricture

    NASA Astrophysics Data System (ADS)

    Shim, Chan Sup

    2012-10-01

    Simple esophageal strictures, which are focal, straight, and large in diameter, usually require 1 - 3 dilation sessions to relieve symptoms. However, complex strictures, which are long, tortuous, or associated with a severely compromised luminal diameter, are usually more difficult to treat with conventional bougie or balloon dilation techniques, and often have high recurrence rates. Although the permanent placement of self-expandable metal stents (SEMS) has been used to manage refractory benign esophageal strictures, this procedure is associated with additional problems, such as stricture from tissue hyperplasia, stent migration, and fistula formation. Thus, several new types of stents have been developed, including temporary SEMS, self-expandable plastic stents (SEPS), and biodegradable stents. The use of these new products has produced varied results. Temporary SEMS that have been used to relieve benign esophageal conditions have caused granulation tissue at both ends of the stent because of contact between the mucosa and the exposed metal components of the stent, thus hindering stent removal. We examined the tissue response to two new types of SEMS, a flange-type and a straighttype, each coated with a silicone membrane on the outside of the metal mesh. These two SEMS were evaluated individually and compared with a conventional control stent in animal experiments. Although the newly designed stents resulted in reduced tissue hyperplasia, and were thus more easily separated from the esophageal tissue, some degree of tissue hyperplasia did occur. We suggest that newly designed DES (drug-eluting stents) may provide an alternative tool to manage refractory benign esophageal stricture.

  13. Aortic stenting.

    PubMed

    Droc, Ionel; Calinescu, Francisca Blanca; Droc, Gabriela; Blaj, Catalin; Dammrau, Rolf

    2015-01-01

    The approach to aortic pathology is nowadays more and more endovascular at both thoracic and abdominal levels. Thoracic stenting has gained worldwide acceptance as first intention to treat pathologies of the descending thoracic aorta. Indications have been extended to aortic arch aneurysms and also to diseases of the ascending aorta. The current devices in use for thoracic endovascular repair (TEVAR) are Medtronic Valiant, Gore TAG, Cook Tx2 and Jotec. The choice of the endograft depends on the thoracic aortic pathology and the anatomical suitability. The technological evolution of the abdominal aortic endografts was very rapid, arriving now at the fourth generation. We report the results of 55 elective cases of endovascular abdominal aortic repair (EVAR) performed in two vascular surgical centers in Romania and Germany. The prostheses used were 16 E-vita Abdominal XT, 12 Excluder, eight Talent, seven PowerLink, three Endurant and nine custom-made, fenestrated or branched from Jotec. The mean follow-up was 18 months with CT-scan, duplex ultrasound and contrast-enhanced ultrasound. The mortality was 2%. EVAR tends to become the gold standard for abdominal aortic aneurysm repair. Technological development of the devices with lowest profile introduction systems will permit to extend the anatomical indications to new frontiers. PMID:26200430

  14. Exclusion of Atherosclerotic Plaque from the Circulation Using Stent-Grafts: Alternative to Carotid Stenting with a Protection Device?

    SciTech Connect

    Peynircioglu, Bora Geyik, Serdar; Yavuz, Kivilcim; Cil, Barbaros E.; Saatci, Isil; Cekirge, Saruhan

    2007-09-15

    Purpose. To retrospectively assess the feasibility, safety, and clinical mid-term outcome of patients undergoing carotid artery stenting with stent-grafts. Methods. Over a 4 year period stent-grafts were used in the endovascular treatment of symptomatic internal carotid artery stenosis in 12 patients (2 women, 10 men, aged 47-83 (mean 64) years). Protection devices were not used. Possible microembolic complications were evaluated by magnetic resonance imaging (MRI) examinations of the brain before and the day after the procedure in all patients. Mean follow-up was 22 months (range 1-42 months), by Doppler ultrasonography and conventional angiography as well as clinical examination .Results. The technical success rate was 100%. A total of 13 coronary stent-grafts were used. The mean stenosis rate (in terms of diameter) was 85% and the mean length of stent-grafts used was 20.9 mm. The mean diameter to which the stent-grafts were dilated was 4.66 mm. In-hospital complications occurred in 1 patient who suffered a minor femoral access hematoma that did not require transfusion or surgical decompression. Post-stenting diffusion-weighted MRI revealed several ipsilateral silent microemboli in only 1 case, which was completely asymptomatic. Two patients had a major stroke after 2 years of follow-up. Restenosis was found in 2 patients who underwent successful balloon dilatation followed by placement of a self-expandable bare stent within the stent-grafts. Conclusions. Stent-grafts may prevent microembolic complications during stenting of atherosclerotic carotid lesions in selected cases, offering immediate exclusion of the atherosclerotic lesion from the circulation by pressing the plaque against the vessel wall. Comparative, randomized studies in larger series of patients are needed with carotid-dedicated stent-graft designs.

  15. Control of the natural frequencies of nitinol-reinforced composite beams

    NASA Astrophysics Data System (ADS)

    Baz, A.; Poh, S.; Ro, J.; Gilheany, J.

    1995-08-01

    The natural frequencies of flexible fiberglass composite beams are controlled by activating optimal sets of shape memory alloy (NITINOL) wires which are embedded along the neutral axes of these beams. The underlying phenomena influencing the behavior of this class of composite structural members are presented. The individual contributions of the fiberglass-resin matrix, the NITINOL wires and the shape memory effect to the overall performance of the composite beam are determined at different operating temperatures and initial preloads of the wires. The modes of vibration of the fiberglass beams are measured with and without the NITINOL reinforcement at various operating conditions. With properly designed NITINOL reinforcement, it is shown that the beams can become stiffer and less susceptible to buckling. The modes of vibrations of the activated NITINOL-reinforced composite beams can also be shifted to higher frequency bands relative to those of the unactivated or un-reinforced beams. Finite element model is developed to described the interaction between the NITINOL wires and the fiberglass-resin matrix. Close agreement is obtained between theoretical predictions and experimental results. With such tunable characteristics, the NITINOL-reinforced composite beams can be effective in attenuating the vibrations induced by various external disturbances.

  16. Duodenal stents for malignant duodenal strictures.

    PubMed Central

    Johnston, S. D.; McKelvey, S. T. D.; Moorehead, R. J.; Spence, R. A. J.; Tham, T. C. K.

    2002-01-01

    Duodenal obstruction may be caused by inoperable malignant disease. Symptoms of nausea and vomiting have been traditionally palliated by surgery. The aim of the study was to determine the efficacy of the endoscopic placement of metal self expanding duodenal stents for the palliation of malignant duodenal obstruction. Four patients with malignant gastric outlet obstruction are described. One patient had a history of oesophagectomy for oesophageal adenocarcinoma and presented with further dysphagia. At endoscopy the recurrent oesophageal tumour and an adenocarcinoma involving the pylorus were both stented. In the other three patients there was a previous history of colonic carcinoma, cholangiocarcinoma and oesophageal adenocarcinoma respectively. All four patients were successfully stented with good palliation of their symptoms. Duodenal Wallstents are a useful alternative to surgery in patients with inoperable malignant duodenal obstruction or those who are unfit for surgery. Images Fig 1 Fig 2 PMID:12137161

  17. Fabrication and In Vitro Deployment of a Laser-Activated Shape Memory Polymer Vascular Stent

    SciTech Connect

    Baer, G M; Small IV, W; Wilson, T S; Benett, W J; Matthews, D L; Hartman, J; Maitland, D J

    2007-04-25

    Vascular stents are small tubular scaffolds used in the treatment of arterial stenosis (narrowing of the vessel). Most vascular stents are metallic and are deployed either by balloon expansion or by self-expansion. A shape memory polymer (SMP) stent may enhance flexibility, compliance, and drug elution compared to its current metallic counterparts. The purpose of this study was to describe the fabrication of a laser-activated SMP stent and demonstrate photothermal expansion of the stent in an in vitro artery model. A novel SMP stent was fabricated from thermoplastic polyurethane. A solid SMP tube formed by dip coating a stainless steel pin was laser-etched to create the mesh pattern of the finished stent. The stent was crimped over a fiber-optic cylindrical light diffuser coupled to an infrared diode laser. Photothermal actuation of the stent was performed in a water-filled mock artery. At a physiological flow rate, the stent did not fully expand at the maximum laser power (8.6 W) due to convective cooling. However, under zero flow, simulating the technique of endovascular flow occlusion, complete laser actuation was achieved in the mock artery at a laser power of {approx}8 W. We have shown the design and fabrication of an SMP stent and a means of light delivery for photothermal actuation. Though further studies are required to optimize the device and assess thermal tissue damage, photothermal actuation of the SMP stent was demonstrated.

  18. Fabrication and in vitro deployment of a laser-activated shape memory polymer vascular stent

    PubMed Central

    Baer, Géraldine M; Small, Ward; Wilson, Thomas S; Benett, William J; Matthews, Dennis L; Hartman, Jonathan; Maitland, Duncan J

    2007-01-01

    Background Vascular stents are small tubular scaffolds used in the treatment of arterial stenosis (narrowing of the vessel). Most vascular stents are metallic and are deployed either by balloon expansion or by self-expansion. A shape memory polymer (SMP) stent may enhance flexibility, compliance, and drug elution compared to its current metallic counterparts. The purpose of this study was to describe the fabrication of a laser-activated SMP stent and demonstrate photothermal expansion of the stent in an in vitro artery model. Methods A novel SMP stent was fabricated from thermoplastic polyurethane. A solid SMP tube formed by dip coating a stainless steel pin was laser-etched to create the mesh pattern of the finished stent. The stent was crimped over a fiber-optic cylindrical light diffuser coupled to an infrared diode laser. Photothermal actuation of the stent was performed in a water-filled mock artery. Results At a physiological flow rate, the stent did not fully expand at the maximum laser power (8.6 W) due to convective cooling. However, under zero flow, simulating the technique of endovascular flow occlusion, complete laser actuation was achieved in the mock artery at a laser power of ~8 W. Conclusion We have shown the design and fabrication of an SMP stent and a means of light delivery for photothermal actuation. Though further studies are required to optimize the device and assess thermal tissue damage, photothermal actuation of the SMP stent was demonstrated. PMID:18042294

  19. Palliative stenting of the digestive tract: a case series of a single centre

    PubMed Central

    Dekkers, Pascale E.P.

    2013-01-01

    Background and aim Obstruction of the gastrointestinal tract due to cancer can be treated with stenting. The aim was to review the local experience with endoscopic stenting. All patients treated with stenting in a ten years period from 2001-2010 were studied. Results Fifty one patients received 57 stents because of oesophageal cancer. Mean survival after stent placement was 141 days. No case of perforation occurred. In nine cases (17%) clogging with food occurred. Tumour overgrowth was noted in four cases. Twenty four patients received 28 stents in their colon or rectum. The stents were placed in the rectum (n=6), the sigmoid (n=14), the descending colon (n=1), and the transverse colon (n=3). Mean survival was 276 days. Perforation did not occur. Tumour ingrowth was seen in two patients. One patient received a second stent. Dislocation occurred in two cases. There were two cases of clogging (8%) by stool. Fourteen patients received a total of 18 stents because of obstructing stomach cancer. Mean survival after placement was 121 days. There was no perforation, one case of clogging, and four cases of tumour ingrowth. Eight patients had stent placement in their duodenum. Mean survival after stent placement was 84 days. No perforation or clogging occurred. But three cases of tumour ingrowth were seen. Conclusions The present series shows that placement of expandable stents in the digestive tract in normal daily practice is feasible, safe, with a low number of complications, and provides good palliation for their remaining life. PMID:23450097

  20. Monitorizing nitinol alloy surface reactions for biofouling studies

    NASA Astrophysics Data System (ADS)

    Dinu, C. Z.; Dinca, V. C.; Soare, S.; Moldovan, A.; Smarandache, D.; Scarisoareanu, N.; Barbalat, A.; Birjega, R.; Dinescu, M.; DiStefano, V. Ferrari

    2007-07-01

    Growth and deposition of unwanted bacteria on implant metal alloys affect their use as biomedical samples. Monitoring any bacterial biofilm accumulation will provide early countermeasures. For a reliable antifouling strategy we prepared nitinol (NiTi) thin films on Ti-derived substrates by using a pulsed laser deposition (PLD) method. As the microstructure of Ti-alloy is dictated by the tensile strength, fatigue and the fracture toughness we tested the use of hydrogen as an alloying element. X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM) investigated the crystalline structure, chemical composition and respectively the surface morphology of the nitinol hydrogen and hydrogen-free samples. Moreover, the alloys were integrated and tested using a cellular metric and their responses were systematic evaluated and quantified. Our attractive approach is meant to select the suitable components for an effective and trustworthy anti-fouling strategy. A greater understanding of such processes should lead to novel and effective control methods that would improve in the future implant stability and capabilities.

  1. Gastric and Duodenal Stents: Follow-Up and Complications

    SciTech Connect

    Pinto Pabon, Isabel Teresa; Paul Diaz, Laura; Ruiz de Adana, Juan Carlos; Lopez Herrero, Julio

    2001-05-15

    Purpose: To assess the efficacy of self-expanding metallic stents in treating inoperable gastric and duodenal stenoses during follow-up and to evaluate the complications encountered.Methods: A total of 31 patients suffering from gastroduodenal obstruction (29 malignant, 2 benign) were treated with a self-expanding metallic stent (Wallstent). In 24 cases insertion was by the peroral route, in seven cases via gastrostomy.Results: All the strictures were successfully negotiated under fluoroscopic guidance without having to resort to endoscopy. A total of 27 patients (87%) were able to resume a regular diet, a soft diet, or a liquid diet orally. Complications included one case of stent malpositioning, one case of leakage of ascitic fluid through the gastrostomy orifice, one case of perforation and fistula to the biliary tree, and two cases of hematemesis. In two patients (6%) additional stents were implanted to improve patency. In all patients follow-up was maintained until death. Recurrence of symptoms immediately before death occurred in seven cases (23%). Mean survival time of patients was 13.3 weeks (SE {+-} 4.6).Conclusions: The deployment of gastroduodenal stents resulted in good palliation of inoperable gastric and duodenal stenoses. Certain technical aspects, e.g., adaptation of stents to bowel morphology, is critical to proper stent function and avoidance of complications.

  2. Palliative Airway Stenting Performed Under Radiological Guidance and Local Anesthesia

    SciTech Connect

    Profili, Stefano; Manca, Antonio; Feo, Claudio F. Padua, Guglielmo; Ortu, Riccardo; Canalis, Giulio C.; Meloni, Giovanni B.

    2007-02-15

    Purpose. To assess the effectiveness of airway stenting performed exclusively under radiological guidance for the palliation of malignant tracheobronchial strictures. Methods. We report our experience in 16 patients with malignant tracheobronchial stricture treated by insertion of 20 Ultraflex self-expandable metal stents performed under fluoroscopic guidance only. Three patients presented dysphagia grade IV due to esophageal malignant infiltration; they therefore underwent combined airway and esophageal stenting. All the procedures were performed under conscious sedation in the radiological room; average procedure time was around 10 min, but the airway impediment never lasted more than 40 sec. Results. We obtained an overall technical success in 16 cases (100%) and clinical success in 14 patients (88%). All prostheses were successfully placed without procedural complications. Rapid clinical improvement with symptom relief and normalization of respiratory function was obtained in 14 cases. Two patients died within 48 hr from causes unrelated to stent placement. Two cases (13%) of migration were observed; they were successfully treated with another stent. Tumor overgrowth developed in other 2 patients (13%); however, no further treatment was possible because of extensive laryngeal infiltration. Conclusions. Tracheobronchial recanalization with self-expandable metal stents is a safe and effective palliative treatment for malignant strictures. Airway stenting performed exclusively under fluoroscopic view was rapid and well tolerated.

  3. Thermomechanical Properties, Collapse Pressure, and Expansion of Shape Memory Polymer Neurovascular Stent Prototypes

    PubMed Central

    Baer, Géraldine M.; Wilson, Thomas S.; Small, Ward; Hartman, Jonathan; Benett, William J.; Matthews, Dennis L.; Maitland, Duncan J.

    2011-01-01

    Shape memory polymer stent prototypes were fabricated from thermoplastic polyurethane. Commercial stents are generally made of stainless steel or other alloys. These alloys are too stiff and prevent most stent designs from being able to navigate small and tortuous vessels to reach intracranial lesions. A solid tubular model and a high flexibility laser etched model are presented. The stents were tested for collapse in a pressure chamber. At 37°C, the full collapse pressure was comparable to that of commercially available stents, and higher than the estimated maximum pressure exerted by intracranial arteries. However, there is a potential for onset of collapse, which needs further study. The stents were crimped and expanded, the laser-etched stent showed full recovery with an expansion ratio of 2.7 and a 1% axial shortening. PMID:19107804

  4. Fluoroscopic management of complications after colorectal stent placement.

    PubMed

    Lopera, Jorge E; De Gregorio, Miguel Angel

    2010-09-01

    Colorectal self-expanding metal stents have been widely used as a bridge to surgery in patients with acute malignant colonic obstruction by allowing a single-stage operation, or as a definitive palliative procedure in patients with inoperable tumors. Colonic stents are placed under either fluoroscopic or combined endoscopic and fluoroscopic guidance, with similar technical-success and complication rates. Placement of colonic stents is a very safe procedure with a low procedure-related mortality rate, but serious complications can develop and reinterventions are not uncommon. Most of the complications can be treated by minimally invasive or conservative techniques, while surgical interventions are required for most patients with perforation.

  5. Rare and fatal complication of Gianturco tracheobronchial stent.

    PubMed

    Asopa, Sanjay; Moorjani, Narain; Saad, Rasheed A; Turner, Jonathan T; Amer, Khalid M

    2007-11-01

    Tracheobronchial stents are increasingly being used for the management of compromised large airways. Traditionally they have been used to palliate malignant conditions; however, they are now being used more frequently for nonmalignant conditions. The use of Gianturco self-expanding metal stent (William Cook, Bjaeverskov, Denmark) has been challenged for treatment of tracheobroncheomalacia, as fracture of the metal work could prove fatal. In this report we describe a case of fracture in the metal framework of a Gianturco stent resulting in recurrent pneumothoraces; heralding fatal haemoptysis as a result of perforation of the left subclavian artery.

  6. Finite element analysis of the biomechanical interaction between coronary sinus and proximal anchoring stent in coronary sinus annuloplasty

    PubMed Central

    Pham, Thuy; Deherrera, Milton; Sun, Wei

    2013-01-01

    Recent clinical studies of the percutaneous transvenous mitral annuloplasty (PTMA) devices have shown a short-term reduction of mitral regurgitation (MR) after implantation. However, adverse events associated with the devices such as compression and perforation of vessel branches, device migration and fracture were reported. In this study, a finite element analysis was performed to investigate the biomechanical interaction between the proximal anchor stent of a PTMA device and the coronary sinus (CS) vessel in three steps including i) the stent release and contact with the CS wall, ii) the axial pull at the stent connector and iii) the pressure inflation of the vessel wall. To investigate the impact of the material properties of tissues and stents on the interactive responses, the CS vessel was modeled with human and porcine material properties, and the proximal stent was modeled with two different Nitinol materials with one being stiffer than the other. The results indicated that the vessel wall stresses and contact forces imposed by the stents were much higher in human than porcine models. However, the mechanical differences induced by the two stent types were relatively small. The softer stent exhibited a better fatigue safety factor when deployed in the human model than in the porcine model. These results underscored the importance of the CS tissue mechanical properties. Higher vessel wall stress and stent radial force were obtained in human model than those in porcine model, which also brought up questions as to the validity of using porcine model to assess device mechanical function. The quantification of these biomechanical interactions can offer scientific insight into the development and optimization of PTMA device design. PMID:23405942

  7. Virtual stenting workflow with vessel-specific initialization and adaptive expansion for neurovascular stents and flow diverters.

    PubMed

    Paliwal, Nikhil; Yu, Hongyu; Xu, Jinhui; Xiang, Jianping; Siddiqui, Adnan H; Yang, Xinjian; Li, Haiyun; Meng, Hui

    2016-10-01

    Endovascular intervention using traditional neurovascular stents and densely braided flow diverters (FDs) have become the preferred treatment strategies for traditionally challenging intracranial aneurysms. Modeling stent and FD deployment in patient-specific aneurysms and its flow modification results prior to the actual intervention can potentially predict the patient outcome and treatment optimization. We present a clinically focused, streamlined virtual stenting workflow that efficiently simulates stent and FD treatment in patient-specific aneurysms based on expanding a simplex mesh structure. The simplex mesh is generated using an innovative vessel-specific initialization technique, which uses the patient's parent artery diameter to identify the initial position of the simplex mesh inside the artery. A novel adaptive expansion algorithm enables the acceleration of deployment process by adjusting the expansion forces based on the distance of the simplex mesh from the parent vessel. The virtual stenting workflow was tested by modeling the treatment of two patient-specific aneurysms using the Enterprise stent and the Pipeline Embolization Device (commercial FD). Both devices were deployed in the aneurysm models in a few seconds. Computational fluid dynamics analyses of pre- and post-treatment aneurysmal hemodynamics show flow reduction in the aneurysmal sac in treated aneurysms, with the FD diverting more flow than the Enterprise stent. The test results show that this workflow can rapidly simulate clinical deployment of stents and FDs, hence paving the way for its future clinical implementation.

  8. Virtual Stenting Workflow with Vessel-Specific Initialization and Adaptive Expansion for Neurovascular Stents and Flow Diverters

    PubMed Central

    Xu, Jinhui; Xiang, Jianping; Siddiqui, Adnan; Yang, Xinjian; Li, Haiyun; Meng, Hui

    2016-01-01

    Endovascular intervention using traditional neurovascular stents and densely braided flow diverters (FDs) have become the preferred treatment strategies for traditionally challenging intracranial aneurysms (IAs). Modeling stent and FD deployment in patient-specific aneurysms and its flow modification results prior to the actual intervention can potentially predict the patient outcome and treatment optimization. We present a clinically focused, streamlined virtual stenting workflow that efficiently simulates stent and FD treatment in patient-specific aneurysms based on expanding a simplex mesh structure. The simplex mesh is generated using an innovative vessel-specific initialization technique, which uses the patient’s parent artery diameter to identify the initial position of the simplex mesh inside the artery. A novel adaptive expansion algorithm enables the acceleration of deployment process by adjusting the expansion forces based on the distance of the simplex mesh from the parent vessel. The virtual stenting workflow was tested by modeling the treatment of two patient-specific aneurysms using the Enterprise stent and the Pipeline Embolization Device (commercial FD). Both devices were deployed in the aneurysm models in a few seconds. Computational fluid dynamics analyses of pre- and post-treatment aneurysmal hemodynamics show flow reduction in the aneurysmal sac in treated aneurysms, with the FD diverting more flow than the Enterprise stent. The test results show that this workflow can rapidly simulate clinical deployment of stents and FDs, hence paving the way for its future clinical implementation. PMID:26899135

  9. Comparative cell culture effects of shape memory metal (Nitinol), nickel and titanium: a biocompatibility estimation.

    PubMed

    Putters, J L; Kaulesar Sukul, D M; de Zeeuw, G R; Bijma, A; Besselink, P A

    1992-01-01

    Nitinol is an equiatomic alloy of nickel and titanium which has been attracting increasing interest in the field of biomedical engineering. To quantify toxicity as a preliminary evaluation of biocompatibility, inhibition of mitosis in human fibroblasts in tissue cultures exposed to test materials is an accepted screening method, although a dose-effect relationship had never been investigated. In this experiment, the effect of an increasing dose exposure to Nitinol, nickel or titanium on human fibroblasts in cell cultures was tested in subgroups in comparison with a control group. The results showed that nickel induces a significant (p < or = 0.05) inhibition of mitosis in human fibroblasts, whereas no significant effects of this kind were found for titanium or Nitinol. According to the results of these studies, Nitinol is to be considered in this respect biocompatible and comparable to titanium, which would seem to justify application as a surgical implant.

  10. Influence of microstructural purity on the bending fatigue behavior of VAR-melted superelastic Nitinol.

    PubMed

    Launey, Maximilien; Robertson, Scott W; Vien, Lot; Senthilnathan, Karthikeyan; Chintapalli, Prashanth; Pelton, Alan R

    2014-06-01

    The bending fatigue resistance of commercially-available Standard versus High Purity Nitinol was evaluated at 3% mean strain and a range of strain amplitudes with the simple wire Z-specimen geometry. The Standard grade Nitinol demonstrated a 10(7)-cycle fatigue strain limit of 0.50% alternating strain, comparable to results reported elsewhere in the literature. Conversely, the High Purity grade VAR Nitinol demonstrated a 5-fold improvement in fatigue resistance with an impressive 10(7)-cycle fatigue strain limit of 2.5% alternating strain. The High Purity Nitinol has an oxygen+nitrogen content of 60wppm, maximum wrought-material inclusion length of 17µm, and inclusion volume fraction of 0.28%, all substantially less than industry standards. With all processing variables held constant except for inclusion content, it is clear that this marked fatigue superiority is due exclusively to the reduction in both size and area fraction of inclusions. PMID:24603214

  11. Fatigue of Nitinol: The state-of-the-art and ongoing challenges.

    PubMed

    Mahtabi, M J; Shamsaei, Nima; Mitchell, M R

    2015-10-01

    Nitinol, a nearly equiatomic alloy of nickel and titanium, has been considered for a wide range of applications including medical and dental devices and implants as well as aerospace and automotive components and structures. The realistic loading condition in many of these applications is cyclic; therefore, fatigue is often the main failure mode for such components and structures. The fatigue behavior of Nitinol involves many more complexities compared with traditional metal alloys arising from its uniqueness in material properties such as superelasticity and shape memory effects. In this paper, a review of the present state-of-the-art on the fatigue behavior of superelastic Nitinol is presented. Various aspects of fatigue of Nitinol are discussed and microstructural effects are explained. Effects of material preparation and testing conditions are also reviewed. Finally, several conclusions are made and recommendations for future works are offered.

  12. Effects of Thermomechanical History on the Tensile Behavior of Nitinol Ribbon

    NASA Technical Reports Server (NTRS)

    Lach, Cynthia L.; Turner, Travis L.; Taminger, Karen M.; Shenoy, Ravi N.

    2002-01-01

    Shape memory alloys (SMAs) have enormous potential for a wide variety of applications. A large body of work exists on the characterization of the microstructure and stress-strain behavior of these alloys, Nitinol (NiTi) in particular. However, many attributes of these materials are yet to be fully understood. Previous work at NASA Langley Research Center (LaRC) has included fabrication of hybrid composite specimens with embedded Nitinol actuators and modeling of their thermomechanical behavior. An intensive characterization effort has been undertaken to facilitate fundamental understanding of this alloy and to promote implementation of Nitinol in aerospace applications. Previous work revealed attributes of the Nitinol ribbon that were not easily rationalized with existing data in the literature. In particular, tensile behavior at ambient temperature showed significant dependence on the thermomechanical history prior to testing. The present work is focused on characterizing differences in the microstructure of Nitinol ribbons exposed to four different thermomechanical histories and correlation of the microstructure with tensile properties. Differential scanning calorimetry (DSC) and x-ray diffraction (XRD) analysis were employed to rationalize the microstructures present after exposure to various thermomechanical histories. Three of the Nitinol ribbon conditions were reversible upon heating (in the DSC) through the reverse transformation temperature (A(sub f) to transform the microstructure to austenite. However, the prior thermomechanical conditioning for the Nitinol ribbon that reflected the entire fabrication procedure (4% thermal cycle condition) was found to have an irreversible effect on the microstructure, as it remained unchanged after repeated complete thermal cycles. Tensile tests were conducted to determine the effect of prior thermomechancal conditioning on both the tensile behavior of the Nitinol ribbons and the stress state of the microstructure. The

  13. Development of a static bioactive stent prototype and dynamic aneurysm-on-a-chip(TM) model for the treatment of aneurysms

    NASA Astrophysics Data System (ADS)

    Reece, Lisa M.

    Aneurysms are pockets of blood that collect outside blood vessel walls forming dilatations and leaving arterial walls very prone to rupture. Current treatments include: (1) clipping, and (2) coil embolization, including stent-assisted coiling. While these procedures can be effective, it would be advantageous to design a biologically active stent, modified with magnetic stent coatings, allowing cells to be manipulated to heal the arterial lining. Further, velocity, pressure, and wall shear stresses aid in the disease development of aneurysmal growth, but the shear force mechanisms effecting wound closure is elusive. Due to these factors, there is a definite need to cultivate a new stent device that will aid in healing an aneurysm in situ. To this end, a static bioactive stent device was synthesized. Additionally, to study aneurysm pathogenesis, a lab-on-a-chip device (a dynamic stent device) is the key to discovering the underlying mechanisms of these lesions. A first step to the reality of a true bioactive stent involves the study of cells that can be tested against the biomaterials that constitute the stent itself. The second step is to test particles/cells in a microfluidic environment. Therefore, biocompatability data was collected against PDMS, bacterial nanocellulose (BNC), and magnetic bacterial nanocellulose (MBNC). Preliminary static bioactive stents were synthesized whereby BNC was grown to cover standard nitinol stents. In an offshoot of the original research, a two-dimensional microfluidic model, the Aneurysm-on-a-ChipTM (AOC), was the logical answer to study particle flow within an aneurysm "sac" - this was the dynamic bioactive stent device. The AOC apparatus can track particles/cells when it is coupled to a particle image velocimetry software (PIV) package. The AOC fluid flow was visualized using standard microscopy techniques with commercial microparticles/cells. Movies were taken during fluid flow experiments and PIV was utilized to monitor.

  14. Histological analysis of cobalt-chromium stents with and without Camouflage® polymer coating: experimental porcine carotid artery model.

    PubMed

    Grudtner, Marco Aurélio; de Lara Elesbão, Joao Luiz; Gutierrez, Paulo Sérgio; Meyer, Fabíola Schons; Pereira, Adamastor Humberto

    2011-04-01

    This study evaluated the arterial response to cobalt-chromium stents with and without polymer coating (Camouflage®, Hemoteq AG, Wuerselen, Germany) implanted in pigs. Cobalt-chromium balloon-expandable stents (4 × 16 mm) were implanted in the common carotid arteries of nine pigs. Histological analysis of endothelialization, inflammation and injury was performed one month later. All stents were successfully deployed, and all but one animal survived the 30 study days. All arteries were patent. Endothelialization was nearly complete in most sections of all carotid stents in both groups. There were mild inflammatory infiltrate and mild-to-moderate injury, which were associated with the stent shafts and not significantly different between groups. Our findings suggest that, in porcine carotid arteries, the histological response to balloon-expandable cobalt-chromium stents coated with polymer (Camouflage®, Hemoteq AG) is similar to the response to non-coated cobalt-chromium stents.

  15. Stent thrombosis: incidence and related factors in the R.I.S.E. Registry(Registro Impianto Stent Endocoronarico)

    PubMed

    De Servi, S; Repetto, S; Klugmann, S; Bossi, I; Colombo, A; Piva, R; Giommi, L; Bartorelli, A; Fontanelli, A; Mariani, G; Klersy, C

    1999-01-01

    Although stent thrombosis has been greatly reduced by adequate stent expansion with high-pressure balloon inflations and by the use of antiplatelet drugs, this event is still frightening, as it may lead to acute myocardial ischemia resulting in acute myocardial infarction or sudden death. Therefore, the definition of factors associated with stent thrombosis may provide a better understanding of the mechanisms underlying this phenomenon and may permit us to define therapeutic strategies to further reduce its occurrence. The purpose of this study was to assess factors responsible for the occurrence of stent thrombosis after coronary stent implantation in 939 consecutive patients enrolled in the Registro Impianto Stent Endocoronarico (R.I.S.E. Study Group). Consecutive patients undergoing coronary stent implantation at 16 medical centers in Italy were prospectively enrolled in the registry. Clinical data, and qualitative and quantitative angiographic findings were obtained from data collected in case report forms at each investigator site. The study group consisted of 781 men and 158 women with a mean age of 59 yr: 1,392 stents were implanted in 1,006 lesions and expanded at a maximal inflation pressure of 14.7 +/- 3 atm. The great majority of patients (92%) received only antiplatelet drugs after coronary stenting. During hospitalization there were 45 major ischemic complications in 39 patients (4.2%): 13 events were related to acute or subacute thrombosis (1.4%). Another stent thrombotic event occurred in the first month of follow-up. On multivariate logistic regression analysis, stent thrombosis was related to the following factors: unplanned stenting (OR 3.46, 95% CI 1.65-7.23), unstable angina (OR 3.37, 95% CI 1.11-10.14) and maximal inflation pressure (OR 0.83, 95% CI 0.75-0.93). In conclusion, this registry shows that in an unselected population of patients undergoing coronary stenting, stent thrombosis occurs in less than 2% of patients and is significantly

  16. Comparison of Devices Used for Stent-Assisted Coiling of Intracranial Aneurysms

    PubMed Central

    Izar, Benjamin; Rai, Ansaar; Raghuram, Karthikram; Rotruck, Jill; Carpenter, Jeffrey

    2011-01-01

    Introduction Two self-expandable stents, the Neuroform and the Enterprise stent, are widely used for stent-assisted coiling (SAC) of complex shaped intracranial aneurysms. However, comparative knowledge about technical feasibility, peri- and post-procedural morbidity and mortality, packing densities as well as follow-up data is limited. Material and Methods We conducted a retrospective study to investigate differences in aneurysms stented with the Enterprise or Neuroform stents. Angiographic follow-up (mean 19.42 months) was available in 72.6% (61/84) of aneurysms treated with stent-assisted coiling. We further sought to compare stent-assisted coiling to a matched patient population with aneurysms treated by conventional coil embolization. Results The stenting success rate of the Enterprise was higher compared to the Neuroform stent (46/48 and 42/51, respectively). In 5 of 9 cases in which the Neuroform stent was not navigable to the landing zone, we successfully deployed an Enterprise stent instead. Eventually, 42 aneurysms were coiled after stenting in each group. We observed no significant differences in peri-procedural complication rate, post-procedural hospital stay, packing density, recurrence rate or number of in-stent stenosis. Strikingly, 36.1% of followed aneurysms in the SAC group showed progressive occlusion on angiographic follow-up imaging. The packing density was significantly higher in aneurysms treated by SAC as compared to conventionally coiled aneurysms, while recanalization rate was significantly lower in the SAC group. Conclusion The procedural success rate is higher using the Enterprise, but otherwise both stents exhibited similar characteristics. Lower recurrence frequency and complication rates comparable to conventional coil embolization emphasize the importance of stent-assisted coiling in the treatment of complex aneurysms. Progressive occlusion on angiographic follow-up was a distinct and frequent observation in the SAC group and may in

  17. Charpy Impact Energy and Microindentation Hardness of 60-NITINOL

    NASA Technical Reports Server (NTRS)

    Stanford, Malcolm K.

    2012-01-01

    60-NITINOL (60 wt.% Ni 40 wt.% Ti) is being studied as a material for advanced aerospace components. The Charpy impact energy and microindentation hardness has been studied for this material, fabricated by vacuum induction skull melting (casting) and by hot isostatic pressing. Test specimens were prepared in various hardened and annealed heat treatment conditions. The average impact energy ranged from 0.33 to 0.49J for the hardened specimens while the annealed specimens had impact energies ranging from 0.89 to 1.18J. The average hardness values of the hardened specimens ranged from 590 to 676 HV while that of the annealed specimens ranged from 298 to 366 HV, suggesting an inverse relationship between impact energy and hardness. These results are expected to provide guidance in the selection of heat treatment processes for the design of mechanical components.

  18. Effect of heat treatment temperature on nitinol wire

    SciTech Connect

    Cai, S.; Schaffer, J. E.; Daymond, M. R.; Yu, C.; Ren, Y.

    2014-08-18

    In-situ synchrotron X-ray diffraction has been used to study the influence of the heat treatment temperature on the subsequent micromechanical behavior of nitinol wire. It was found that increase in the heat treatment temperature rotated the austenite texture from the (332){sub B2} fiber towards the (111){sub B2} fiber, and the texture of the Stress-Induced Martensite phase changed from the (1{sup ¯}40){sub B19'} to the (1{sup ¯}20){sub B19'} fiber accordingly. Heat treatment at a low temperature reduces the internal residual strains in the austenite during super-elastic deformation and therefore improves the materials fatigue performance. The development of internal residual strains in austenite is controlled by transformation induced plasticity and the reversal martensite to austenite transformation.

  19. Corrosion behaviour of Nitinol alloy coated with alkylsilanes and polypyrrole.

    PubMed

    Flamini, D O; Saidman, S B

    2014-11-01

    Nitinol (equiatomic Ni and Ti alloy (NiTi)) substrate was modified using a coating system formed by a self-assembled film of alkylsilane compounds (propyltrichlorosilane (C3H7SiCl3) or octadecyltrichlorosilane (C18H37SiCl3)) and polypyrrole (PPy) doped with sodium bis(2-ethylhexyl) sulfosuccinate (Aerosol OT or AOT). The combination of alkylsilanes and the presence of a voluminous molecule like AOT entrapped into the PPy films improve the pitting corrosion resistance of the substrate in chloride solution. The best performance was achieved with the longest alkylsilane chains, where the PPy film remains adhered to the underlying coating after a pitting corrosion test. PMID:25280711

  20. Endovascular Gene Delivery from a Stent Platform: Gene- Eluting Stents

    PubMed Central

    Fishbein, Ilia; Chorny, Michael; Adamo, Richard F; Forbes, Scott P; Corrales, Ricardo A; Alferiev, Ivan S; Levy, Robert J

    2015-01-01

    A synergistic impact of research in the fields of post-angioplasty restenosis, drug-eluting stents and vascular gene therapy over the past 15 years has shaped the concept of gene-eluting stents. Gene-eluting stents hold promise of overcoming some biological and technical problems inherent to drug-eluting stent technology. As the field of gene-eluting stents matures it becomes evident that all three main design modules of a gene-eluting stent: a therapeutic transgene, a vector and a delivery system are equally important for accomplishing sustained inhibition of neointimal formation in arteries treated with gene delivery stents. This review summarizes prior work on stent-based gene delivery and discusses the main optimization strategies required to move the field of gene-eluting stents to clinical translation. PMID:26225356

  1. [Stent implantation in the treatment of pharynx anastomotic stenosis after cervical esophageal resection: a case report].

    PubMed

    Zang, Chuanshan; Sun, Jian; Sun, Yan

    2016-03-01

    We report the treatment of one patient with pharynx anastomotic stenosis after cervical esophagealresection by stent implantation. The patient suffered from serious pharynx anastomotic stenosis after gastric-pha-ryngeal anastomosis. After balloon-dilatation,a domestic self-expanding Z-stents was implanted in the stricture ofthe esophagus under the X-rays. After stent implantation, the patient has been leading a normal life for threeyears. Balloon dilatation and stent implantation is an effective and safe method in the treatment of patients withpharynx anastomotic stenosis.

  2. [Stent implantation in the treatment of pharynx anastomotic stenosis after cervical esophageal resection: a case report].

    PubMed

    Zang, Chuanshan; Sun, Jian; Sun, Yan

    2016-03-01

    We report the treatment of one patient with pharynx anastomotic stenosis after cervical esophagealresection by stent implantation. The patient suffered from serious pharynx anastomotic stenosis after gastric-pha-ryngeal anastomosis. After balloon-dilatation,a domestic self-expanding Z-stents was implanted in the stricture ofthe esophagus under the X-rays. After stent implantation, the patient has been leading a normal life for threeyears. Balloon dilatation and stent implantation is an effective and safe method in the treatment of patients withpharynx anastomotic stenosis. PMID:27382696

  3. Critical overview of Nitinol surfaces and their modifications for medical applications.

    PubMed

    Shabalovskaya, S; Anderegg, J; Van Humbeeck, J

    2008-05-01

    Nitinol, a group of nearly equiatomic shape memory and superelastic NiTi alloys, is being extensively explored for medical applications. Release of Ni in the human body, a potential problem with Nitinol implant devices, has stimulated a great deal of research on its surface modifications and coatings. In order to use any of the developed surfaces in implant designs, it is important to understand whether they really have advantages over bare Nitinol. This paper overviews the current situation, discusses the advantages and disadvantages of new surfaces as well as the limitations of the studies performed. It presents a comprehensive analysis of surface topography, chemistry, corrosion behavior, nickel release and biological responses to Nitinol surfaces modified mechanically or using such methods as etching in acids and alkaline solutions, electropolishing, heat and ion beam treatments, boiling in water and autoclaving, conventional and ion plasma implantations, laser melting and bioactive coating deposition. The analysis demonstrates that the presently developed surfaces vary in thickness from a few nanometers to micrometers, and that they can effectively prevent Ni release if the surface integrity is maintained under strain and if no Ni-enriched sub-layers are present. Whether it is appropriate to use various low temperature pre-treatment protocols (< or = 160 degrees C) developed originally for pure titanium for Nitinol surface modifications and coatings is also discussed. The importance of selection of original Nitinol surfaces with regard to the performance of coatings and comparative performance of controls in the studies is emphasized. Considering the obvious advantages of bare Nitinol surfaces for superelastic implants, details of their preparation are also outlined.

  4. Development of a dynamic in vitro model of a stented blood vessel to evaluate the effects of stent strut material selection and surface coating on smooth muscle cell response

    NASA Astrophysics Data System (ADS)

    Winn, Bradley Huegh

    formation of this new tissue, primarily consisting of VSMCs of the synthetic phenotype and their subsequent extracellular matrix, is the sole causation of in-stent restenosis since the stent serves to prevent elastic recoil and negative remodeling. This doctoral research program is focused on endovascular stent biomaterials science and engineering. Overall, this doctoral project is founded on the hypothesis that smooth muscle cell hyperplasia, as an important causative factor for vascular restenosis following endovascular stent deployment, is triggered by the various effects of stent strut contact on the vessel wall including contact forces and material biocompatibility. In this program, a dynamic in vitro model of a stented blood vessel aimed at evaluating the effect of stent strut material selection, and surface coating on smooth muscle cell response was developed. The in vitro stented artery model was validated through the proliferation of VSMC in contact with stent struts. Additionally, it was demonstrated that, with respect to known biocompatible materials such as Nitinol and 316L stainless steel, DNA synthesis and alpha-actin expression, as indicators of VSMC phenotype, are independent of stent material composition. Furthermore, hydroxyapatite was shown to be a biocompatible stent surface coating with acceptable post-strain integrity. This coating was shown in a feasibility study to be capable of serving as a favorable drug delivery platform able to reliably deliver locally therapeutic doses of bisphosphonates, such as alendronate, to control VSMC proliferation in an in vitro model of a stented blood vessel. This stent coating/drug combination may be effective for reducing restenosis as a result of VSMC hyperplasia in vivo.

  5. Stent Recanalization of Chronic Portal Vein Occlusion in a Child

    SciTech Connect

    Cwikiel, Wojciech; Solvig, Jan; Schroder, Henrik

    2000-07-15

    An 8-year-old boy with a 21/2 year history of portal hypertension and repeated bleedings from esophageal varices, was referred for treatment. The 3.5-cm-long occlusion of the portal vein was passed and the channel created was stabilized with a balloon-expandable stent; a portosystemic stent-shunt was also created. The portosystemic shunt closed spontaneously within 1 month, while the recanalized segment of the portal vein remained open. The pressure gradient between the intrahepatic and extrahepatic portal vein branches dropped from 17 mmHg to 0 mmHg. The pressure in the portal vein dropped from 30 mmHg to 17 mmHg and the bleedings stopped. The next dilation of the stent was performed 12 months later due to an increased pressure gradient; the gastroesophageal varices disappeared completely. Further dilation of the stent was planned after 2, 4, and 6 years.

  6. Malignant Gastroduodenal Obstruction: Treatment with Self-Expanding Uncovered Wallstent

    SciTech Connect

    Gutzeit, Andreas Binkert, Christoph A.; Schoch, Eric; Sautter, Thomas; Jost, Res; Zollikofer, Christoph L.

    2009-01-15

    Purpose: To retrospectively evaluate the clinical effectiveness of a self-expanding uncovered Wallstent in patients with malignant gastroduodenal obstruction. Materials and Methods: Under combined endoscopic and fluoroscopic guidance, 29 patients with a malignant gastroduodenal stenosis were treated with a self-expanding uncovered metallic Wallstent. A dysphagia score was assessed before and after the intervention to measure the success of this palliative therapy. The dysphagia score ranged between grade 0 to grade 4: grade 0 = able to tolerate solid food, grade 1 = able to tolerate soft food, grade 2 = able to tolerate thick liquids, grade 3 = able to tolerate water or clear fluids, and grade 4 = unable to tolerate anything perorally. Stent patency and patients survival rates were calculated. Results: The insertion of the gastroduodenal stent was technically successful in 28 patients (96.5%). After stenting, 25 patients (86.2%) showed clinical improvement by at least one score point. During follow-up, 22 (78.5%) of 28 patients showed no stent occlusion until death and did not have to undergo any further intervention. In six patients (20.6%), all of whom were treated with secondary stent insertions, occlusion with tumor ingrowth and/or overgrowth was observed after the intervention. The median period of primary stent patency in our study was 240 days. Conclusion: Placement of an uncovered Wallstent is clinically effective in patients with malignant gastroduodenal obstruction. Stent placement is associated with high technical success, good palliation effect, and high durability of stent function.

  7. Hepatocellular Carcinoma Complicated by Gastroduodenal Obstruction: Palliative Treatment with Metallic Stent Placement

    SciTech Connect

    Lee, Ye Jin; Kim, Jin Hyoung Song, Ho-Young; Park, Jung-Hoon; Na, Han Kyu; Kim, Pyeong Hwa; Fan, Yong

    2012-10-15

    Purpose: To evaluate the clinical effectiveness of self-expandable metallic stents in seven patients with malignant gastroduodenal obstruction caused by inoperable hepatocellular carcinoma (HCC). Methods: Seven patients with gastroduodenal obstruction caused by advanced HCC underwent metallic stent placement from 2003 to 2010. These patients had total dysphagia (n = 5) or were able to eat only liquids (n = 2) before stent placement. Patients had Eastern Cooperative Oncology Group performance scores of 2 or 3, and Child-Pugh classification B or C. Results: Stent placement was technically successful in all seven patients (100%) and clinically successful in six (86%). Five patients could eat a soft diet, and one patient tolerated regular diet after stent placement. Stent-related obstructive jaundice occurred in one patient. One patient had hematemesis 11 days after stent placement. Overall mean survival was 51 days (range, 10-119 days). Stent patency was preserved in six patients with clinical success until death. Conclusion: Placement of a covered self-expandable metallic stent may offer good palliation in patients with gastroduodenal obstruction due to advanced HCC.

  8. Novel oesophago-gastro-duodenal stenting for gastric leaks after laparoscopic sleeve gastrectomy.

    PubMed

    Liu, Shirley Yuk-Wah; Wong, Simon Kin-Hung; Ng, Enders Kwok-Wai

    2015-01-01

    The management of gastric leak after laparoscopic sleeve gastrectomy (LSG) can be complex and challenging. Whilst operative interventions are mostly complicated and reserved for unstable or refractory cases, endoscopic self-expandable metal stenting (SEMS) is increasingly preferred as a safer treatment option. Yet, SEMS carries the problems of frequent stent migration and inconsistent healing as ordinary SEMS is designed mainly for stenotic disease. We hereby present two cases of early and chronic post-LSG leakage that were respectively failed to be treated by surgery and ordinary SEMS but were successfully managed by a dedicated extra-long oesophago-gastro-duodenal stent. In oesophago-gastro-duodenal stenting, the characteristics of extra-long stent length allow total gastric exclusion between the mid-oesophagus and the first part of duodenum to prevent stent migration and to equalise high pressure gradient within the gastric sleeve to promote fistula healing.

  9. Endovascular Stenting for Unsuccessful Angioplasty of the Aorta in Aortoarteritis

    SciTech Connect

    Tyagi, Sanjay; Kaul, Upkar A.; Arora, Ramesh

    1999-11-15

    Purpose: The efficacy and safety of endovascular stent implantation to correct dissection or a suboptimal result after percutaneous transluminal angioplasty (PTA) was evaluated in patients suffering from aortic stenosis due to aortoarteritis. Methods: Twelve children and young adults [aged (mean {+-} SD) 18.2 {+-} 8.7 years] underwent stent implantation after PTA of the aorta, seven for obstructive dissection, four for ineffective balloon dilatation, and one for recurrent restenosis. Nine patients underwent implantation of self-expandable stents and three received balloon-expandable Palmaz stents. Results: Stent implantation could be successfully performed in all 12 patients. After stent implantation, the peak systolic pressure gradient decreased from 91 {+-} 33.5 mmHg to 12.4 {+-} 12.5 mmHg (p < 0.001). The diameter of the stenosed segment increased from 4.6 {+-} 0.8 mm to 11.1 {+-} 1.9 mm (p < 0.001). The dissection was completely covered in all seven patients with dissection. Except for epigastric pain with vomiting in one patient, there was no complication. On follow-up, over 12-57 months (mean 26.8 {+-} 10.8 months), 11 patients (91.6%) had marked improvement in their blood pressure. Patients with congestive heart failure and claudication also showed improvement. Repeat catheterization in five patients, between 6-30 months (mean 16.8 {+-} 9.1 months) after stent implantation, showed sustained improvement in four and a fusiform, long segment, intrastent restenosis after 30 months in one child. The stenosis was safely redilated. Conclusion: Endovascular aortic stent implantation is safe and provides good immediate relief in patients with unsatisfactory results after balloon angioplasty. Improvement is sustained in most patients on intermediate-term follow-up.

  10. Spectral Imaging for Intracranial Stents and Stent Lumen

    PubMed Central

    Chen, David Yen-Ting; Chen, Chi-Jen; Hsu, Hui-Ling

    2016-01-01

    Introduction Application of computed tomography for monitoring intracranial stents is limited because of stent-related artifacts. Our purpose was to evaluate the effect of gemstone spectral imaging on the intracranial stent and stent lumen. Materials and Methods In vitro, we scanned Enterprise stent phantom and a stent–cheese complex using the gemstone spectral imaging protocol. Follow-up gemstone spectral images of 15 consecutive patients with placement of Enterprise from January 2013 to September 2014 were also retrospectively reviewed. We used 70-keV, 140-keV, iodine (water), iodine (calcium), and iodine (hydroxyapatite) images to evaluate their effect on the intracranial stent and stent lumen. Two regions of interest were individually placed in stent lumen and adjacent brain tissue. Contrast-to-noise ratio was measured to determine image quality. The maximal diameter of stent markers was also measured to evaluate stent-related artifact. Two radiologists independently graded the visibility of the lumen at the maker location by using a 4-point scale. The mean of grading score, contrast/noise ratio and maximal diameter of stent markers were compared among all modes. All results were analyzed by SPSS version 20. Results In vitro, iodine (water) images decreased metallic artifact of stent makers to the greatest degree. The most areas of cheese were observed on iodine (water) images. In vivo, iodine (water) images had the smallest average diameter of stent markers (0.33 ± 0.17mm; P < .05) and showed the highest mean grading score (2.94 ± 0.94; P < .05) and contrast/noise ratio of in-stent lumen (160.03 ±37.79; P < .05) among all the modes. Conclusion Iodine (water) images can help reduce stent-related artifacts of Enterprise and enhance contrast of in-stent lumen. Spectral imaging may be considered a noninvasive modality for following-up patients with in-stent stenosis. PMID:26731534

  11. Adhesion, Vitality and Osteogenic Differentiation Capacity of Adipose Derived Stem Cells Seeded on Nitinol Nanoparticle Coatings

    PubMed Central

    Strauß, Sarah; Neumeister, Anne; Barcikowski, Stephan; Kracht, Dietmar; Kuhbier, Jörn W.; Radtke, Christine; Reimers, Kerstin; Vogt, Peter M.

    2013-01-01

    Autologous cells can be used for a bioactivation of osteoimplants to enhance osseointegration. In this regard, adipose derived stem cells (ASCs) offer interesting perspectives in implantology because they are fast and easy to isolate. However, not all materials licensed for bone implants are equally suited for cell adhesion. Surface modifications are under investigation to promote cytocompatibility and cell growth. The presented study focused on influences of a Nitinol-nanoparticle coating on ASCs. Possible toxic effects as well as influences on the osteogenic differentiation potential of ASCs were evaluated by viability assays, scanning electron microscopy, immunofluorescence and alizarin red staining. It was previously shown that Nitinol-nanoparticles exert no cell toxic effects to ASCs either in soluble form or as surface coating. Here we could demonstrate that a Nitinol-nanoparticle surface coating enhances cell adherence and growth on Nitinol-surfaces. No negative influence on the osteogenic differentiation was observed. Nitinol-nanoparticle coatings offer new possibilities in implantology research regarding bioactivation by autologous ASCs, respectively enhancement of surface attraction to cells. PMID:23308190

  12. A Review of Similar and Dissimilar Micro-joining of Nitinol

    NASA Astrophysics Data System (ADS)

    Deepan Bharathi Kannan, T.; Ramesh, T.; Sathiya, P.

    2016-04-01

    NiTinol belongs to a class of smart materials which has a wide range of applications in the field of automotive, aerospace, biomedical, robotics, etc., owing to the growing trend in miniaturization of components. Micro-joining is becoming one of the important and familiar processes in the fabrication of miniaturized components. Recently, effective micro-joining of thin sheets has been gaining a lot of interest among researchers. In this article, the research and progress in micro-joining of NiTinol to itself and other metals are reviewed at different aspects. To date, laser welding, tungsten inert gas welding, and resistance welding have been used to a large extent in investigating the weldability of NiTinol alloys. Some important welding parameters used in micro joining by various researchers and their effects on weld qualities are detailed in this review. Metallurgical aspects, mechanical properties and corrosion aspects of micro-joined NiTinol sheets/wires are discussed. The aim of this report is to review the recent progress in micro-joining of NiTinol and to provide a basis for follow-on research.

  13. Should transjugular intrahepatic portosystemic shunt stent grafts be underdilated?

    PubMed

    Gaba, Ron C; Parvinian, Ahmad; Minocha, Jeet; Casadaban, Leigh C; Knuttinen, M Grace; Ray, Charles E; Bui, James T

    2015-03-01

    Although underdilation of transjugular intrahepatic portosystemic shunt (TIPS) stent grafts is commonly performed to limit complications arising from excessive portosystemic shunting, it is uncertain whether underdilated stents retain their smaller diameter indefinitely or eventually expand to nominal caliber. In this investigation, postprocedure computed tomography (CT) was used to compare diameters of underdilated TIPSs and TIPSs expanded to a nominal diameter of 10 mm in 61 cases. The groups had comparable shunt diameters on post-TIPS imaging (9.8 mm vs 9.9 mm; P = .079), with similar incidences of hepatic encephalopathy (34% vs 20%; P = .372), indicating stent self-expansion over time, and bringing into question the advantages of underdilation for customization of shunt caliber.

  14. Electronic structure of nitinol surfaces oxidized by low-energy ion bombardment

    SciTech Connect

    Petravic, M. Varasanec, M.; Peter, R.; Kavre, I.; Metikos-Hukovic, M.; Yang, Y.-W.

    2014-06-28

    We have studied the electronic structure of nitinol exposed to low-energy oxygen-ion bombardment, using x-ray photoemission spectroscopy (XPS) and near-edge x-ray absorption fine structure (NEXAFS) spectroscopy. XPS spectra reveal a gradual transformation of nitinol surfaces into TiO{sub 2} with increased dose of implanted oxygen. No oxidation of Ni atoms has been detected. NEXAFS spectra around O K-edge and Ti L{sub 2,3}-edge, reflecting the element-specific partial density of empty electronic states, exhibit features, which can be attributed to the creation of molecular orbitals, crystal field splitting, and the absence of long-range order, characteristic of the amorphous TiO{sub 2}. Based on these results, we discuss the oxidation kinetics of nitinol under low-energy oxygen-ion bombardment.

  15. On the experimental testing of fine Nitinol wires for medical devices.

    PubMed

    Henderson, E; Nash, D H; Dempster, W M

    2011-04-01

    Nitinol, a nickel titanium alloy, is widely used as a biocompatible metal with applications in high strain medical devices. The alloy exhibits both superelasticity and thermal shape memory behaviour. Basic mechanical properties can be established and are provided by suppliers; however the true stress-strain response under repeated load is not fully understood. It is essential to know this behaviour in order to design devices where failure by fatigue may be possible. The present work develops an approach for characterising the time varying mechanical properties of fine Nitinol wire and investigates processing factors, asymmetric stress-strain behaviour, temperature dependency, strain rate dependency and the material response to thermal and repeated mechanical loading. Physically realistic and accurately determined mechanical properties are provided in a format suitable for use in finite element analysis for the design of medical devices. Guidance is also given as to the most appropriate experimental set up procedures for gripping and testing thin Nitinol wire.

  16. State of the Art: Which Stent for Which Lesion in Peripheral Interventions?

    PubMed Central

    Henry, Michel; Klonaris, Christos; Amor, Max; Henry, Isabelle; Tzvetanov, Kiril

    2000-01-01

    Applications of endovascular procedures have been expanded dramatically throughout the human body for both occlusive and aneurysmal disease; arteries at the aortoiliac and femoropopliteal levels are no exception. Currently, interventional procedures are the 1st treatment option for most patients who have peripheral artery disease. Although balloon angioplasty alone offers good immediate and long-term results, the addition of stents has been proposed to improve the procedural success of angioplasty and extend its application to more patients with vascular disease. Stenting, however, is controversial. Its use is considered acceptable in the aortoiliac vessels but is more in dispute for the femoro-popliteal vessels. Moreover, the rapid development of endovascular stents for peripheral applications has made stent selection a complicated task for clinical practitioners. Many factors influence the type of stent selected; therefore, knowledge of the stents available—including various designs and individual properties—is mandatory. Appropriate selection depends on adequate preprocedural evaluation of the lesion; the choice of approach; the choice of primary versus selective stent placement; the location and characteristics of the lesion; the availability of stents in the intervention suite; and the experience of the operator. Several stents are now available, but they are not equivalent; it is important to select the stent that is best suited to the lesion. On the basis of our experience using different types of stents, as well as our review of the world medical literature, we summarize the properties of various stents and specific indications for their application. This report is intended for use as a practical guide to stent selection. PMID:10928499

  17. The location of obstruction predicts stent occlusion in malignant gastric outlet obstruction

    PubMed Central

    Grunwald, Douglas; Cohen, Jonah; Bartley, Anthony; Sheridan, Jennifer; Chuttani, Ram; Sawhney, Mandeep S.; Pleskow, Douglas K.; Berzin, Tyler M.; Mizrahi, Meir

    2016-01-01

    Background: Gastric outlet obstruction (GOO) can occur with locally invasive or metastatic cancer involving the upper gastrointestinal tract at the pylorus or the duodenum. Endoscopic management with self-expanding metal stents (SEMSs) is often the preferred palliative approach. Stent occlusion is a common reason for failure and reintervention. We set out to determine whether the location of the malignant obstruction is associated with the angulation of the stent and can predict stent occlusion. Methods: We performed a retrospective review of consecutive patients who underwent successful duodenal stenting with SEMS for malignant GOO between 2006 and 2015 at a large advanced endoscopy referral center. We determined the location of obstruction, the stent angle, and the rate of technical and clinical success of stent placement. We then identified cases of subsequent stent occlusion confirmed by endoscopic evaluation. Results: A total of 100 consecutive patients were included in the study; 91 of these patients had enough data to evaluate SEMS occlusion. A total of 21 patients (23%) developed stent occlusion with a median time of 39 days. The risk of occlusion sequentially increased as the obstruction occurred more distally from the antrum to the third or fourth portion of the duodenum (p = 0.006). This relationship was maintained after controlling for stent angle (p = 0.05). Conclusions: A distal location of malignant GOO was strongly predictive of stent occlusion, independent of stent angle. This may be due to longer and more complex distal obstructions, along with foreshortening of the stent during placement and tumor infiltration. If replicated, these results will have implications for endoscopic practice and future device development. PMID:27803736

  18. Nanomaterial coatings applied on stent surfaces.

    PubMed

    Bagheri, Mahsa; Mohammadi, Marzieh; Steele, Terry Wj; Ramezani, Mohammad

    2016-05-01

    The advent of percutaneous coronary intervention and intravascular stents has revolutionized the field of interventional cardiology. Nonetheless, in-stent restenosis, inflammation and late-stent thrombosis are the major obstacles with currently available stents. In order to enhance the hemocompatibility of stents, advances in the field of nanotechnology allow novel designs of nanoparticles and biomaterials toward localized drug/gene carriers or stent scaffolds. The current review focuses on promising polymers used in the fabrication of newer generations of stents with a short synopsis on atherosclerosis and current commercialized stents, nanotechnology's impact on stent development and recent advancements in stent biomaterials is discussed in context.

  19. Passive base isolation with superelastic nitinol SMA helical springs

    NASA Astrophysics Data System (ADS)

    Huang, Bin; Zhang, Haiyang; Wang, Han; Song, Gangbing

    2014-06-01

    Seismic isolation of structures such as multi-story buildings, nuclear reactors, bridges, and liquid storage tanks should be designed to preserve structural integrity. By implementing seismic isolation technology, the deformation of superstructures can be dramatically reduced, consequently helping to protect their safety as well. In this paper, an innovative type of passive base isolation system, which is mainly composed of superelastic nitinol SMA helical springs, is developed. In order to verify the effectiveness of the proposed system, a two-story experimental steel frame model is constructed, and two superelastic SMA helical springs are thermo-mechanically built in the laboratory. To describe the nonlinear mechanical properties of the superelastic SMA helical springs under reciprocating load, a phenomenological model is presented in terms of a series of tensile tests. Afterwards, a numerical model of the two-story frame with the suggested isolation system is set up to simulate the response of the isolated frame subjected to an earthquake. Both the experimental and the numerical simulation results indicate that the proposed base isolation system can remarkably suppress structural vibrations and has improved isolation effects when compared with a steel spring isolation system. Due to the capabilities of energy dissipation as well as fully re-centering, it is very applicable to utilize the suggested isolation system in base isolated structures to resist earthquakes.

  20. Preliminary Investigation of Surface Treatments to Enhance the Wear Resistance of 60-Nitinol

    NASA Technical Reports Server (NTRS)

    Stanford, Malcolm K.

    2016-01-01

    The use of protective surface treatments on 60-Nitinol (60wt%Ni-40wt%Ti) was studied. Various nitriding techniques as well as a (Ti, Al)N coating were evaluated visually, microscopically, and by hardness and scratch testing. The chemical composition of the surface treatments was investigated by x-ray techniques. The results indicate that very hard (greater than 1,000 HK) and adherent surface layers can be produced on 60-Nitinol. Further work is needed to determine the tribological properties of these surface treatments in relevant operating environments.

  1. Oxide Ceramic Films Grown on 60 Nitinol for NASA and Department of Defense Applications

    NASA Technical Reports Server (NTRS)

    Miyoshi, Kazuhisa; Street, Kenneth W.; Lukco, Dorothy; Cytron, Sheldon J.

    2005-01-01

    Both the NASA Glenn Research Center and the U.S. Army Research Laboratory, Development and Engineering Center (ARDEC) have worked to develop oxide ceramic films grown on 60 nitinol (60-wt% nickel and 40-wt% titanium) to decrease friction and increase wear resistance under unlubricated conditions. In general, oxide and nonoxide ceramic films have unique capabilities as mechanical-, chemical-, and thermal-barrier materials in diverse applications, including high-temperature bearings and gas bearings requiring low friction, wear resistance, and chemical stability. All oxide ceramic films grown on 60 nitinol were furnished by ARDEC, and materials and surface characterization and tribological experiments were conducted at Glenn.

  2. Effect of Inclusion Size and Distribution on the Corrosion Behavior of Medical-Device Grade Nitinol Tubing

    NASA Astrophysics Data System (ADS)

    Wohlschlögel, Markus; Steegmüller, Rainer; Schüßler, Andreas

    2014-07-01

    Nonmetallic inclusions in Nitinol, such as carbides (TiC) and intermetallic oxides (Ti4Ni2O x ), are known to be triggers for fatigue failure of Nitinol medical devices. These mechanically brittle inclusions are introduced during the melting process. As a result of hot and cold working in the production of Nitinol tubing inclusions are fractionalized due to the mechanical deformation imposed. While the role of inclusions regarding Nitinol fatigue performance has been studied extensively in the past, their effect on Nitinol corrosion behavior was investigated in only a limited number of studies. The focus of the present work was to understand the effect of inclusion size and distribution on the corrosion behavior of medical-device grade Nitinol tubing made from three different ingot sources during different manufacturing stages: (i) for the initial stage (hollow: round bar with centric hole), (ii) after hot drawing, and (iii) after the final drawing step (final tubing dimensions: outer diameter 0.3 mm, wall thickness 0.1 mm). For one ingot source, two different material qualities were investigated. Potentiodynamic polarization tests were performed for electropolished samples of the above-mentioned stages. Results indicate that inclusion size rather than inclusion quantity affects the susceptibility of electropolished Nitinol to pitting corrosion.

  3. Investigation of crystal structures of one-way shape memory Nitinol wire actuators for active steerable needle

    NASA Astrophysics Data System (ADS)

    Honarvar, Mohammad; Konh, Bardia; Hutapea, Parsaoran

    2015-04-01

    Due to its outstanding properties of Nitinol, known as shape memory and superelasticity, Nitinol wires have been used as actuators in many medical devices. For the medical applications, it is critical to have a consistent strain response of Nitinol wires. This work focuses on studying the effect of parameters such as biased stress, maximum temperature, and wire diameters that influence the strain response of Nitinol wires. Specifically, Nitinol phase transformations were studied from microstructural point of view. The crystal structures of one-way shape memory Nitinol wires of various diameters under different thermomechanical loading conditions were studied using X-Ray Diffraction (XRD) method. The location and intensity of characteristic peaks were determined prior and after the thermomechanical loading cycles. It was observed that Nitinol wires of diameters less than 0.19 mm exhibit unrecovered strain while heated to the range of 70ºC to 80ºC in a thermal cycle, whereas no unrecovered strains were found in larger wires. The observation was supported by the XRD patterns where the formation of R-phase crystal structure was showed in wire diameters less than 0.19 mm at room temperature.

  4. Development of Biliary and Enteral Stents by the Korean Gastrointestinal Endoscopists

    PubMed Central

    Shim, Chan Sup; Kim, Jin Hong; Bok, Gene Hyun

    2016-01-01

    Stenting in the gastrointestinal tract is a common procedure used for palliation of obstruction in the enteral and biliary tract. Today, stenting of malignant and benign strictures is performed at almost every major tertiary hospital in Korea. Moreover, Korea has become a major global supplier of cutting edge technology in the field of self-expanding metal stents. However, the history of stenting in Korea is relatively short and was far behind that of other nations such as Japan and Germany. The authors are humbled and gratified to have been able to observe the development and application of these stents in Korea, first hand. In this article, the authors review the overall history of stenting with a specific focus on the development of stenting in Korea. The development of esophageal, gastroduodenal, biliary, and colonic stents in Korea are reviewed in this article from a chronological and historical point of view, and a personal account of some of the significant moments of stent development in Korea are described. PMID:26956192

  5. In-situ investigation of stress conditions during expansion of bare metal stents and PLLA-coated stents using the XRD sin(2)ψ-technique.

    PubMed

    Kowalski, Wolfgang; Dammer, Markus; Bakczewitz, Frank; Schmitz, Klaus-Peter; Grabow, Niels; Kessler, Olaf

    2015-09-01

    Drug eluting stents (DES) consist of platform, coating and drug. The platform often is a balloon-expandable bare metal stent made of the CoCr alloy L-605 or stainless steel 316 L. The function of the coating, typically a permanent polymer, is to hold and release the drug, which should improve therapeutic outcome. Before implantation, DES are compressed (crimped) to allow implantation in the human body. During implantation, DES are expanded by balloon inflation. Crimping, as well as expansion, causes high stresses and high strains locally in the DES struts, as well as in the polymer coating. These stresses and strains are important design criteria of DES. Usually, they are calculated numerically by finite element analysis (FEA), but experimental results for validation are hardly available. In this work, the X-ray diffraction (XRD) sin(2)ψ-technique is applied to in-situ determination of stress conditions of bare metal L-605 stents, and Poly-(L-lactide) (PLLA) coated stents. This provides a realistic characterization of the near-surface stress state and a validation option of the numerical FEA. XRD-results from terminal stent struts of the bare metal stent show an increasing compressive load stress in tangential direction with increasing stent expansion. These findings correlate with numerical FEA results. The PLLA-coating also bears increasing compressive load stress during expansion.

  6. Experimental Study of Poly-l-Lactic Acid Biodegradable Stents in Normal Canine Bile Ducts

    SciTech Connect

    Yamamoto, Kiyosei Yoshioka, Tetsuya; Furuichi, Kinya; Sakaguchi, Hiroshi; Anai, Hiroshi; Tanaka, Toshihiro; Morimoto, Kengo; Uchida, Hideo; Kichikawa, Kimihiko

    2011-06-15

    Purpose: This study was designed to clarify the advantages of biodegradable stents in terms of mucosal reaction and biodegradation after placement. We designed a biodegradable stent and assessed stent degradation and changes in the normal bile ducts of dogs. Methods: The biodegradable stent is a balloon-expandable Z stent consisting of poly-l-lactic acid (PLLA) with a diameter of 6 mm and a length of 15 mm. We assessed four groups of three beagle dogs each at 1, 3, 6, and 9 months of follow-up. After evaluating stent migration by radiography and stent and bile duct patency by cholangiography, the dogs were sacrificed to remove the bile duct together with the stent. The bile duct lumen was examined macroscopically and histologically, and the stent degradation was examined macroscopically and by scanning electron microscopy (SEM). Results: Bile duct obstruction was absent and none of the stents migrated. Macroscopic evaluation showed moderate endothelial proliferation in the bile ducts at the implant sites at 3 and 6 months and a slight change at 9 months. Slight mononuclear cell infiltration was histologically identified at all time points and epithelial hyperplasia that was moderate at 3 months was reduced to slight at 6 and 9 months. Stent degradation was macroscopically evident in all animals at 9 months and was proven by SEM in two dogs at 6 months and in all of them at 9 months. Conclusions: Our results suggest that PLLA bioabsorbable stents seems to be useful for implantation in the biliary system with further investigation.

  7. Preliminary report on a new concept stent prototype designed for venous implant.

    PubMed

    Lugli, M; Maleti, O

    2015-08-01

    Venous obstruction at iliocaval level in both forms, primary and secondary, is a significant cause of severe chronic venous insufficiency. A new therapeutic approach to this pathology emerged with the introduction of stenting procedures that proved effective, leading to good long-term results. However, at present, the majority of implanted stents have been designed for arterial implant and this can pose a limit in particular districts. The purpose of this preliminary acute study was to verify the deliverability and safety of a new stent specially designed for venous-vessel implant. We assess the safety and deliverability of two braided, self-expanding, nickel-titanium stents (Jotec GmbH, Hechingen, Germany) specially designed for endovascular implant in veins. The two stents, despite being based on the same concept, have a different design: stent A presents a proximal tapering shape specially designed to reduce migration, while stent B does not. Both of them are enlarged at their distal extremity and present variable radial force the length of the stent itself, the said force becoming very high in the intermediate segment. Stents were implanted in the internal jugular vein of a sheep, showing optimal deliverability. The completion venography showed the migration of stent B into the right atrium. Stent A maintained its location, confirmed by intravascular ultrasound examination. No scaffolding effect was detected and an adequate adherence and adaptability to the vein wall was obtained. In conclusions, the stent A design matches the characteristics required by vein implants. Stability is achieved even where difficult anatomical conditions apply, such as in the jugular vein. Deployment is easy and precise in a given landing zone. Radial resistive force is very high, as required in specific vein districts, but is also associated with good flexibility. Following this preliminary acute report, further studies are required. PMID:24920424

  8. Collagen Matrix Remodeling in Stented Pulmonary Arteries after Transapical Heart Valve Replacement.

    PubMed

    Ghazanfari, Samaneh; Driessen-Mol, Anita; Hoerstrup, Simon P; Baaijens, Frank P T; Bouten, Carlijn V C

    2016-01-01

    The use of valved stents for minimally invasive replacement of semilunar heart valves is expected to change the extracellular matrix and mechanical function of the native artery and may thus impair long-term functionality of the implant. Here we investigate the impact of the stent on matrix remodeling of the pulmonary artery in a sheep model, focusing on matrix composition and collagen (re)orientation of the host tissue. Ovine native pulmonary arteries were harvested 8 (n = 2), 16 (n = 4) and 24 (n = 2) weeks after transapical implantation of self-expandable stented heart valves. Second harmonic generation (SHG) microscopy was used to assess the collagen (re)orientation of fresh tissue samples. The collagen and elastin content was quantified using biochemical assays. SHG microscopy revealed regional differences in collagen organization in all explants. In the adventitial layer of the arterial wall far distal to the stent (considered as the control tissue), we observed wavy collagen fibers oriented in the circumferential direction. These circumferential fibers were more straightened in the adventitial layer located behind the stent. On the luminal side of the wall behind the stent, collagen fibers were aligned along the stent struts and randomly oriented between the struts. Immediately distal to the stent, however, fibers on both the luminal and the adventitial side of the wall were oriented in the axial direction, demonstrating the stent impact on the collagen structure of surrounding arterial tissues. Collagen orientation patterns did not change with implantation time, and biochemical analyses showed no changes in the trend of collagen and elastin content with implantation time or location of the vascular wall. We hypothesize that the collagen fibers on the adventitial side of the arterial wall and behind the stent straighten in response to the arterial stretch caused by oversizing of the stent. However, the collagen organization on the luminal side suggests that

  9. Comparison of Nitinol Stapes Pistons with Conventional Stapes Pistons: A Cadaver Study

    PubMed Central

    Spear, Samuel A.; Crawford, James V.

    2011-01-01

    Objective. To visually compare the Nitinol “smart” stapes prosthesis to conventional manual crimping stapes pistons in temporal bone cadaver specimens. Main Outcome Measures. 10 otolaryngologists were given a photograph of the randomly ordered stapes pistons and asked to use the pictures to answer questions about each stapes piston. The answers to the survey were then recorded for analysis. Results. 8 of 9 Nitinol pistons were described as circular, and 3 of 9 manual crimped pistons were described as circular (P < .05). 6 of 9 Nitinol pistons were considered to be in contact with >66% of the incus and 3 of 9 to be in contact with 34–66% of the incus. 3 of 9 manually crimped pistons were considered to be in contact with >66% of the incus, 3 with 34–66% contact and 3 with less than 34% contact. Conclusions. The Nitinol “smart” stapes pistons were considered to provide a more circular and circumferential crimping and to have greater contact with the long process of the incus than conventional stapes pistons. PMID:23724262

  10. Overlap stenting for in-stent restenosis after carotid artery stenting

    PubMed Central

    Nishihori, Masahiro; Ohshima, Tomotaka; Yamamoto, Taiki; Goto, Shunsaku; Nishizawa, Toshihisa; Shimato, Shinji; Izumi, Takashi; Kato, Kyozo

    2016-01-01

    ABSTRACT Our aim was to assess the clinical safety and efficacy of overlap stenting for in-stent restenosis after carotid artery stenting. The study was conducted between July 2008 and February 2015. A database of consecutive carotid artery stenting procedures was retrospectively assessed to identify the cases of in-stent restenosis that were treated with overlap stenting under proximal or distal protection. The clinical and radiological records of the patients were then reviewed. Of the 155 CAS procedures in 149 patients from the database, 6 patients met the inclusion criteria. All the 6 patients were initially treated with moderate dilatation because of the presence of an unstable plaque. The technical success rate of the overlap stenting was 100%, with no 30-day mortality or morbidity. In addition, there was no further in-stent restenosis during a follow-up period of over 12 months. These results indicated that overlap stenting for in-stent restenosis after carotid artery stenting was both safe and effective in our cohort. PMID:27303101

  11. Overlap stenting for in-stent restenosis after carotid artery stenting.

    PubMed

    Nishihori, Masahiro; Ohshima, Tomotaka; Yamamoto, Taiki; Goto, Shunsaku; Nishizawa, Toshihisa; Shimato, Shinji; Izumi, Takashi; Kato, Kyozo

    2016-05-01

    Our aim was to assess the clinical safety and efficacy of overlap stenting for in-stent restenosis after carotid artery stenting. The study was conducted between July 2008 and February 2015. A database of consecutive carotid artery stenting procedures was retrospectively assessed to identify the cases of in-stent restenosis that were treated with overlap stenting under proximal or distal protection. The clinical and radiological records of the patients were then reviewed. Of the 155 CAS procedures in 149 patients from the database, 6 patients met the inclusion criteria. All the 6 patients were initially treated with moderate dilatation because of the presence of an unstable plaque. The technical success rate of the overlap stenting was 100%, with no 30-day mortality or morbidity. In addition, there was no further in-stent restenosis during a follow-up period of over 12 months. These results indicated that overlap stenting for in-stent restenosis after carotid artery stenting was both safe and effective in our cohort. PMID:27303101

  12. Endovascular Management of Chronic Type B Dissecting Aortic Aneurysm Utilizing Aortic and Renal Stents

    SciTech Connect

    Taylor, J. D. Dunckley, M.; Thompson, M.; Morgan, R. A.

    2008-07-15

    Over the last 10 years endovascular stent-graft placement has been increasingly used to treat complicated acute Type B thoracic aortic dissections. While studies have demonstrated the use of additional aortic stent-grafts to treat continued false lumen perfusion and case reports have detailed the use of renal artery stents to treat renal ischemia related to aortic dissection, to our knowledge the adjuvant use of renal artery stents to reduce false lumen perfusion has not been reported. We present the case of a 72-year-old male who had previously undergone endovascular repair of a complicated Type B thoracic aortic dissection and presented with an expanding false lumen in the peridiaphragmatic aorta despite coverage of the entire thoracic aorta. This was treated by closure of a right renal fenestration using a renal stent.

  13. A predictive study of the mechanical behaviour of coronary stents by computer modelling.

    PubMed

    Migliavacca, Francesco; Petrini, Lorenza; Montanari, Valeria; Quagliana, Isabella; Auricchio, Ferdinando; Dubini, Gabriele

    2005-01-01

    Intravascular stents are small tube-like structures expanded into stenotic arteries to restore blood flow perfusion to the downstream tissues. The stent expansion is an important factor to define the effectiveness of the surgical procedure: it depends on the stent geometry and includes large displacements and deformations, geometric and material non-linearity. Numerical analyses seem appropriate to study such a complex behaviour after a free stent expansion. In this study the finite element method (FEM) was applied to a new generation coronary stent. Results from computations were compared with those from a laboratory experiment in terms of radial expansion and elastic recoil. By means of a scanning electronic microscopy the area of plastic deformation were also detected and compared with those obtained in the numerical simulation. Matching between the different measurements was quite satisfactory even if some discrepancies were present due to the absence of the balloon in the numerical model. PMID:15604000

  14. An Experimental and Computational Study on the Effect of Caval Valved Stent Oversizing.

    PubMed

    Ismail, Munirah; Kumar, Gideon Praveen; Kabinejadian, Foad; Nguyen, Yen Ngoc; Cui, Fangsen; Tay, Edgar Lik Wui; Leo, Hwa Liang

    2016-09-01

    Heterotopic implantation of transcatheter tricuspid valve is a new treatment option for tricuspid regurgitation. Transcatheter tricuspid valves are implanted onto the cavoatrial junction in order to avoid the challenging task of anchoring the valve onto the complex tricuspid valve annulus. However, little is known about optimum extent of oversizing of the valved stent in a vena cava. In this study, we implanted valves of the same diameter onto the larger sized inferior vena cava (IVC) and a smaller sized superior vena cava (SVC). The valve in the IVC was oversized by 10.7% while the valve in the SVC was oversized by 21.6%. Finite element analysis was performed (i) to assess the strain on the nitinol stent during manufacturing and deployment; (ii) the stents were deployed in a patient-specific vena cava model and the intramural stress of the vena cava was calculated computationally. These valves were fabricated and placed in a silicone model of a patient-specific right atrium which was part of a mock circulatory system that emulated the patho-physiological flow rate and pressure of a patient with tricuspid regurgitation. Flow measurements were conducted by particle image velocimetry (PIV). It was found that the maximum crimping strain on the nitinol stent was 6.85% which was lower than the critical threshold of 10%. The maximum stress on the vena cava was located at the spot where the hooks met the wall. The maximum stress on the IVC was 0.5098 MPa while the maximum stress on the SVC was 0.7 MPa. The maximum Reynolds shear stress (mRSS) in the vena cava was found to be higher in the IVC than SVC with the highest mRSS being 1741 dynes/cm(2) found in the region of high flow during the peak flow phase. The overtly oversized valve in the SVC did not cause flow disturbances and exhibited mostly laminar flows. The mRSS at the downstream of the vena cava valve and the middle of the atrium remained at low magnitudes. However, velocity fluctuations were high in the IVC in

  15. Arsenic contamination of coarse-grained and nanostructured nitinol surfaces induced by chemical treatment in hydrofluoric acid.

    PubMed

    Korotin, D M; Bartkowski, S; Kurmaev, E Z; Borchers, C; Müller, M; Neumann, M; Gunderov, D V; Valiev, R Z; Cholakh, S O

    2012-10-01

    XPS measurements of coarse-grained and nanostructured nitinol (Ni(50.2)Ti(49.8)) before and after chemical treatment in hydrofluoric acid (40% HF, 1 min) are presented. The nanostructured state, providing the excellent mechanical properties of nitinol, is achieved by severe plastic deformation. The near-surface layers of nitinol were studied by XPS depth profiling. According to the obtained results, a chemical treatment in hydrofluoric acid reduces the thickness of the protective TiO(2) oxide layer and induces a nickel release from the nitinol surface and an arsenic contamination, and can therefore not be recommended as conditioning to increase the roughness of NiTi-implants. A detailed evaluation of the resulting toxicological risks is given.

  16. Stent-Induced Esophageal Perforation: Treatment by Means of Placing a Second Stent After Removal of the Original Stent

    SciTech Connect

    Jung, Gyoo-Sik Park, Sung-Dal; Cho, Young Duk

    2008-05-15

    A case of esophageal perforation caused by a retrievable covered stent is presented. The distal end of the stent was protruding into the mediastinum, which made it impossible to negotiate a guidewire through the stent into the distal esophagus. The stent was successfully removed with use of a stent retrieval set, and esophageal perforation was treated with a second, covered stent with a good result. Fatality associated with this complication might be prevented by virtue of the retrievability of the stent we used. This result points to the effectiveness of a retrievable stent for the palliative treatment of malignant esophageal stricture.

  17. Endovascular Exclusion of Visceral Artery Aneurysms with Stent-Grafts: Technique and Long-Term Follow-up

    SciTech Connect

    Rossi, Michele; Rebonato, Alberto Greco, Laura; Citone, Michele; David, Vincenzo

    2008-01-15

    This paper describes four cases of visceral artery aneurysms (VAAs) successfully treated with endovascular stent-grafts and discusses the endovascular approach to VAAs and the long-term results. Four balloon expandable stent-grafts were used to treat three splenic artery aneurysms and one bleeding common hepatic artery pseudoaneurysm. The percutaneous access site and the materials were chosen on the basis of CT angiography findings. In all cases the aneurysms were successfully excluded. In one case a splenic infarction occurred, with nonrelevant clinical findings. At 16- to 24-month follow-up three patients had patent stents and complete exclusion and shrinkage of the aneurysms. One patient died due to pancreatitis and sepsis, 16 days after successful stenting and exclusion of a bleeding pseudoaneurysm. We conclude that endovascular treatment using covered stent-grafts is a valid therapeutic option for VAAs. Multislice CT preoperative study helps in planning stent-graft positioning.

  18. Development of a New Hanging-Type Esophageal Stent for Preventing Migration: A Preliminary Study in an Animal Model of Esophagotracheal Fistula

    SciTech Connect

    Endo, Masayuki Kaminou, Toshio Ohuchi, Yasufumi; Sugiura, Kimihiko; Yata, Shinsaku Adachi, Akira Kawai, Tsuyoshi Takasugi, Syohei Yamamoto, Shuichi Matsumoto, Kensuke; Hashimoto, Masayuki; Ihaya, Takashi; Ogawa, Toshihide

    2012-10-15

    Purpose: Covered, self-expandable metallic stents (SEMS) have been enthusiastically adopted for the treatment of esophagotracheal fistula, but problems with stent migration have yet to be resolved. To overcome this problem, we have developed a new hanging-type esophageal stent designed to prevent migration, and we conducted an animal study to assess the efficacy of our method. Methods: A total of six female pigs were used in this study. The main characteristic of our stent was the presence of a string tied to the proximal edge of the stent for fixation under the skin of the neck. The first experiment was performed to confirm technical feasibility in three pigs with esophagotracheal fistula. The second experiment was performed to evaluate stent migration and esophagotracheal fistula in three pigs. Results: Creation of the esophagotracheal fistula and stent placement were technically successful in all pigs. In the first experiment, esophagotracheal fistula was sealed by stent placement. In the second experiment, no stent migration was seen 11 or 12 days after stent placement. Gross findings showed no fistulas on the esophageal or tracheal wall. Conclusions: Our new hanging-type esophageal stent seems to offer a feasible method for preventing stent migration.

  19. Effect of biologically active coating on biocompatibility of Nitinol devices designed for the closure of intra-atrial communications.

    PubMed

    Kong, Xiangqing; Grabitz, R G; van Oeveren, W; Klee, D; van Kooten, T G; Freudenthal, F; Qing, Ma; von Bernuth, G; Seghaye, M C

    2002-04-01

    Anti-thrombogenicity and rapid endothelialisation are prerequisites for the use of closure devices of intra-atrial communications in order to reduce the risk of cerebral embolism. The purpose of this study was therefore to assess the effect of bioactive coatings on biocompatibility of Nitinol coils designed for the closure of intra-atrial communications. Nitinol coils (n = 10, each) and flat Nitinol bands (n = 3, each) were treated by basic coating with poly(amino-p-xylylene-co-p-xylylene) and then coated with either heparin, r-hirudin or fibronectin. Anti-thrombogenicity was studied in vitro in a dynamic model with whole blood by partial thromboplastin time (PTT), platelet binding and thrombin generation, respectively, and cytotoxicity by hemolysis. Endothelialisation was studied on Nitinol bands with human umbilical venous endothelial cells (HUVEC) by 3-(4,5-dimethylthiazole-2yl)-2,5-triphenyl tetrazolium (MTT) assay and immnuofluorescence analysis of Ki67, vinculin, fibronectin and von Willebrand Factor. Uncoated or coated devices did not influence hemolysis and PTT. r-Hirudin (but not heparin) and fibronectin coating showed lower platelet binding than uncoated Nitinol (p < 0.005, respectively). Heparin and r-hirudin coating reduced thrombin formation (p < 0.05 versus Nitinol, respectively). HUVEC adhesion, proliferation, and matrix formation decreased in the order: fibronectin coating > uncoated Nitinol > r-hirudin coating > heparin coating > basic coating. MTT assay corroborated these findings. In conclusion, r-hirudin and fibronectin coating, by causing no acute cytotoxicity, decreasing thrombogenicity and increasing endothelialisation improve in vitro biocompatibility of Nitinol devices designed for the closure of intra-atrial communications.

  20. Dose perturbation of a novel cobalt chromium coronary stent on {sup 32}P intravascular brachytherapy: A Monte Carlo study

    SciTech Connect

    Mourtada, Firas; Horton, John L.

    2005-01-01

    Intravascular brachytherapy has been adopted for the indication of in-stent restenosis on the basis of results of clinical trials using mainly stainless steel stents. Recently, a new stent made of cobalt-chromium L-605 alloy (CoCr, {rho}=9.22 g/cm{sup 3}) (MULTI-LINK VISION{sup TM}) was introduced as an alternative to the 316L stainless steel stent design (SS, {rho}=7.87 g/cm{sup 3}) (MULTI-LINK PENTA{sup TM}). In this work, we used the Monte Carlo code MCNPX to compare the dose distribution for the {sup 32}P GALILEO{sup TM} source in CoCr and SS 8 mm stent models. The dose perturbation factor (DPF), defined as the ratio of the dose in water with the presence of a stent to the dose without a stent, was used to compare results. Both stent designs were virtually expanded to diameters of 2.0, 3.0, and 4.0 mm using finite element models. The complicated strut shapes of both the CoCr and SS stents were simplified using circular rings with an effective width to yield a metal-to-tissue ratio identical to that of the actual stents. The mean DPF at a 1 mm tissue depth, over the entire stented length of 8 mm, was 0.935 for the CoCr stent and 0.911 for the SS stent. The mean DPF at the intima (0.05 mm radial distance from the strut outer surface), over the entire stented length of 8 mm, was 0.950 for CoCr, and 0.926 for SS. The maximum DPFs directly behind the CoCr and SS struts were 0.689 and 0.644, respectively. All DPF estimates have a standard deviation of {+-}0.6%(k=2), approximating the 95% confidence interval. Although the CoCr stent has a higher effective atomic number and greater density than the SS stent, the DPFs for the two stents are similar, probably because the metal-to-tissue ratio and strut thickness of the CoCr stent are lower than those of the SS stent.

  1. Delayed complications after flow-diverter stenting: reactive in-stent stenosis and creeping stents.

    PubMed

    Cohen, José E; Gomori, John Moshe; Moscovici, Samuel; Leker, Ronen R; Itshayek, Eyal

    2014-07-01

    We assessed the frequency and severity of changes in stent configuration and location after the treatment of intracranial aneurysms, and patterns of in-stent stenosis. We retrospectively reviewed data for consecutive aneurysm patients managed with endovascular implantation of flow-diverter stents (Silk Flow Diverter [Balt Extrusion, Montmorency, France] and Pipeline Embolization Device [ev3/Coviden, Minneapolis, MN, USA]) from October 2011 to July 2012. Routine 2, 6, 9-12, and 16-20 month follow-up angiograms were compared, with a focus on changes in stent configuration and location from immediately after deployment to angiographic follow-up, and the incidence and development of in-stent stenosis. Thirty-four patients with 42 aneurysms met inclusion criteria. The Silk device was implanted in 16 patients (47%, single device in 15), the Pipeline device in 18 (53%, single device in 16). On first follow-up angiography, in-stent stenosis was observed in 38% of Silk devices and 39% of Pipeline devices. In-stent stenosis was asymptomatic in 12 of 13 patients. One woman presented with transient ischemic attacks and required stent angioplasty due to end tapering and mild, diffuse in-stent stenosis. Configuration and location changes, including stent creeping and end tapering were seen in 2/16 patients (13%) with Silk devices, and 0/18 patients with Pipeline devices. We describe stent creeping and end tapering as unusual findings with the potential for delayed clinical complications. In-stent stenosis, with a unique behavior, is a frequent angiographic finding observed after flow-diverter stent implant. The stenosis is usually asymptomatic; however, close clinical and angiographic monitoring is mandatory for individualized management. PMID:24524952

  2. Delayed complications after flow-diverter stenting: reactive in-stent stenosis and creeping stents.

    PubMed

    Cohen, José E; Gomori, John Moshe; Moscovici, Samuel; Leker, Ronen R; Itshayek, Eyal

    2014-07-01

    We assessed the frequency and severity of changes in stent configuration and location after the treatment of intracranial aneurysms, and patterns of in-stent stenosis. We retrospectively reviewed data for consecutive aneurysm patients managed with endovascular implantation of flow-diverter stents (Silk Flow Diverter [Balt Extrusion, Montmorency, France] and Pipeline Embolization Device [ev3/Coviden, Minneapolis, MN, USA]) from October 2011 to July 2012. Routine 2, 6, 9-12, and 16-20 month follow-up angiograms were compared, with a focus on changes in stent configuration and location from immediately after deployment to angiographic follow-up, and the incidence and development of in-stent stenosis. Thirty-four patients with 42 aneurysms met inclusion criteria. The Silk device was implanted in 16 patients (47%, single device in 15), the Pipeline device in 18 (53%, single device in 16). On first follow-up angiography, in-stent stenosis was observed in 38% of Silk devices and 39% of Pipeline devices. In-stent stenosis was asymptomatic in 12 of 13 patients. One woman presented with transient ischemic attacks and required stent angioplasty due to end tapering and mild, diffuse in-stent stenosis. Configuration and location changes, including stent creeping and end tapering were seen in 2/16 patients (13%) with Silk devices, and 0/18 patients with Pipeline devices. We describe stent creeping and end tapering as unusual findings with the potential for delayed clinical complications. In-stent stenosis, with a unique behavior, is a frequent angiographic finding observed after flow-diverter stent implant. The stenosis is usually asymptomatic; however, close clinical and angiographic monitoring is mandatory for individualized management.

  3. Wave reflection at a stent.

    PubMed

    Crespo, Antonio; García, Javier; Manuel, Fernando

    2013-01-01

    A simple analytical expression has been derived to calculate the characteristics of a wave that reflects at a stent implanted in a uniform vessel. The stent is characterized by its length and the wave velocity in the stented region. The reflected wave is proportional to the time derivative of the incident wave. The reflection coefficient is a small quantity of the order of the length of the stent divided by the wavelength of the unstented vessel. The results obtained coincide with those obtained numerically by Charonko et al. The main simplifications used are small amplitude of the waves so that equations can be linearized and that the length of the stent is small enough so that the values of the wave functions are nearly uniform along the stent. Both assumptions hold in typical situations. PMID:23516957

  4. [Stent Grafting for Aortic Dissection].

    PubMed

    Uchida, Naomichi

    2016-07-01

    The purpose of stent graft for aortic dissection is to terminate antegrade blood flow into the false lumen through primary entry. Early intervention for primary entry makes excellent aortic remodeling and emergent stent grafting for complicated acute type B aortic dissection is supported as a class I. On the other hand stent grafting for chronic aortic dissection is controversial. Early stent grafting is considered with in 6 months after on-set if the diameter of the descending aorta is more than 40 mm. Additional interventions for residual false lumen on the downstream aorta are still required. Stent graft for re-entry, candy-plug technique, and double stenting, other effective re-interventions were reported. Best treatment on the basis of each anatomical and physical characteristics should be selected in each institution. Frozen elephant trunk is alternative procedure for aortic dissection without the need to take account of proximal anatomical limitation and effective for acute type A aortic dissection. PMID:27440026

  5. Wave reflection at a stent.

    PubMed

    Crespo, Antonio; García, Javier; Manuel, Fernando

    2013-01-01

    A simple analytical expression has been derived to calculate the characteristics of a wave that reflects at a stent implanted in a uniform vessel. The stent is characterized by its length and the wave velocity in the stented region. The reflected wave is proportional to the time derivative of the incident wave. The reflection coefficient is a small quantity of the order of the length of the stent divided by the wavelength of the unstented vessel. The results obtained coincide with those obtained numerically by Charonko et al. The main simplifications used are small amplitude of the waves so that equations can be linearized and that the length of the stent is small enough so that the values of the wave functions are nearly uniform along the stent. Both assumptions hold in typical situations.

  6. Stent graft exclusion of a pseudoaneurysm in a Blalock-Taussig shunt.

    PubMed

    Sanchez-Recalde, Angel; Garzón, Gonzalo; Oliver, José M

    2010-08-01

    This case is the first report of slow-growing pseudoaneurysm after vessel dissection secondary to two stents implantation into classic Blalock Taussig shunt in a patient with pulmonary atresia and ventricular septal defect. Pseudoaneurysm was successfully excluded by a percutaneous approach with self-expandable stent graft deployment from the aorta to the middle of the Blalock Taussig shunt. Nearly 3 years after the procedure, the classic BT is patent, and there were no restenosis or thrombosis in spite of the very long length of the stented segment.

  7. Limitations of Endovascular Treatment with Stent-Grafts for Active Mycotic Thoracic Aortic Aneurysm

    SciTech Connect

    Ishida, Masaki; Kato, Noriyuki; Hirano, Tadanori; Shimono, Takatsugu; Yasuda, Fuyuhiko; Tanaka, Kuniyoshi; Yada, Isao; Takeda, Kan

    2002-06-15

    An 81-year-old woman with ruptured mycotic thoracic aortic aneurysm was treated with endovascular placement of stent-grafts fabricated from expanded polytetrafluoroethylene and Z-stents. Although exclusion of the aneurysm was achieved at the end of the procedure, a type I endoleak developed on the following day.Despite emergent surgical resection of the aneurysm and extra-anatomical reconstruction, the patient died 2 days later. Stent-graft repair may not be a suitable method for the treatment of ruptured mycotic aneurysm in the presence of active infection.

  8. An analysis of the contact between the stent and the artery using tube hydroforming simulation.

    PubMed

    Araújo, Rogério; Guimarães, Tobias A; Oliveira, Sônia A G

    2013-11-01

    Stents for angioplasty have been extensively used to treat coronary diseases. The aim of this study is to analyze the expansion of the stent and the contact with the artery using tube hydroforming simulation. In the simulation, the contact stress and the final shape of the artery after stent expansion process using the Stampack (®;) software will be studied. A model of a commercial stent made of 316L stainless steel was modeled by using an elastic-plastic constitutive law with isotropic hardening. The artery was modeled as a cylinder and made of hyperelastic material. The stent model studied in this work presented a good performance according to the results obtained. After expansion, any region of the stent's structure with strong risk of wrinkling, thinning, or buckling was not observed. In the forming limit diagram, all points were far from the Keeler-Goodwin diagram. Furthermore, the expanded stent model has a good conformability. In conclusion, our data show that the proposed methodology is a useful tool to check if the stent model implanted in the artery may cause restenosis after angioplasty; thus, our tests provided a reliable tool to analyze this risk.

  9. Endoscopic ultrasound-guided placement of AXIOS stent for drainage of pancreatic fluid collections

    PubMed Central

    Patil, Rashmee; Ona, Mel A.; Papafragkakis, Charilaos; Anand, Sury; Duddempudi, Sushil

    2016-01-01

    Pancreatic fluid collections (PFCs) have conventionally been treated with surgery, percutaneous drainage, or with the more recently established endoscopic ultrasound (EUS)-guided drainage modality. Currently, endoscopic plastic or metallic stents are used for PFC drainage. Plastic stents present issues with stent migration and premature occlusion requiring frequent stent exchanges or placement of additional stents. Metallic stents are tubular and may migrate, resulting in inefficient drainage, content leakage, retrieval and replacement, and possible mucosal injury. The aim of this review was to summarize and evaluate the clinical and technical effectiveness of EUS-guided placement of the recently developed AXIOS stent, a lumen-apposing self-expandable metallic stent (LASEMS)for PFC drainage. A literature review was performed to identify the studies describing this technique. In this review article we have summarized case series or reports describing EUS-guided LASEMS placement. The indications, techniques, limitations and complications reported are discussed. A total of 298 patients were included across all studies described thus far in the literature. Overall, a 97% technical success rate and a 96% clinical success rate have been reported. Early and late complications related to the placement or removal of LASEMS have been reported, however few cases have presented life-threatening results. EUS-guided PFC drainage and LASEMS placement can be a safe and effective alternative approach in the management of selected patients. PMID:27065729

  10. An analysis of the contact between the stent and the artery using tube hydroforming simulation.

    PubMed

    Araújo, Rogério; Guimarães, Tobias A; Oliveira, Sônia A G

    2013-11-01

    Stents for angioplasty have been extensively used to treat coronary diseases. The aim of this study is to analyze the expansion of the stent and the contact with the artery using tube hydroforming simulation. In the simulation, the contact stress and the final shape of the artery after stent expansion process using the Stampack (®;) software will be studied. A model of a commercial stent made of 316L stainless steel was modeled by using an elastic-plastic constitutive law with isotropic hardening. The artery was modeled as a cylinder and made of hyperelastic material. The stent model studied in this work presented a good performance according to the results obtained. After expansion, any region of the stent's structure with strong risk of wrinkling, thinning, or buckling was not observed. In the forming limit diagram, all points were far from the Keeler-Goodwin diagram. Furthermore, the expanded stent model has a good conformability. In conclusion, our data show that the proposed methodology is a useful tool to check if the stent model implanted in the artery may cause restenosis after angioplasty; thus, our tests provided a reliable tool to analyze this risk. PMID:23813983

  11. Expanding Universe

    NASA Astrophysics Data System (ADS)

    Murdin, P.

    2000-11-01

    A universe that expands with time. Although the possibility had been raised earlier through theoretical work carried out by Willem de Sitter (1872-1934), Aleksandr Friedmann (1888-1925), and the Abbé Georges Lemaître (1894-1966), that our universe is expanding was first demonstrated observationally in 1929 by Edwin P Hubble (1889-1953), through his measurements of the redshifts in the spectra of ...

  12. Influence of sodium hypochlorite treatment of electropolished and magnetoelectropolished nitinol surfaces on adhesion and proliferation of MC3T3 pre-osteoblast cells.

    PubMed

    Rokicki, Ryszard; Haider, Waseem; Hryniewicz, Tadeusz

    2012-09-01

    The influence of 6 % sodium hypochlorite (NaClO) treatment on adhesion and proliferation of MC3T3 pre-osteoblast cells seeded on electropolished (EP) and magnetoelectropolished (MEP) nitinol surfaces were investigated. The chemistry, topography, roughness, surface energy, wettability of EP and MEP nitinol surfaces before and after NaClO treatment were studied with X-ray photoelectron spectroscopy (XPS), profilometry, and contact angle meter. In vitro interaction of osteoblast cell and NaClO treated EP and MEP nitinol surfaces were assessed after 3 days of incubation by scanning electron microscopy. The XPS analysis shows that NaClO treatment increases oxygen content especially in subsurface oxide layer of EP and MEP nitinol. The changes of both basic components of nitinol, namely nickel and titanium in oxide layer, were negligible. The NaClO treatment did not influence physico-morphological surface properties of EP and MEP nitinol to a big extent. The osteoblast cells show remarkable adherence and proliferation improvement on NaClO treated EP and MEP nitinol surfaces. After 3 days of incubation they show almost total confluence on both NaClO treated surfaces. The present study shows that NaClO treatment of EP and MEP nitinol surfaces alters oxide layer by enriching it in oxygen and by this improves bone cell-nitinol interaction.

  13. Accidental Stenting Out of Stent: A Lesson from No-Reflow after New Stent Deployment Outside the Prior Stent

    PubMed Central

    Lai, Chih-Hung; Sung, Shih-Hsien; Lee, Wen-Lieng; Juan, Yu-Hsiang; Chang, Szu-Ling; Lu, Tse-Min

    2016-01-01

    An operator can be unaware that the guide wire has accidentally advanced into space outside the previous stent, which can result in deformation of the previous stent when a new stent is deployed outside the prior stent. We herein have reported a case of accidental guide wire advancement into a previously dissected lumen of right coronary artery (RCA), resulting in a new stent deploying outside the prior stent, resulting in deformity of the prior stent. Thrombus and friable atheromatous plaques dislodged and migrated to occlude distal RCA when attempting to restore the proximal luminal diameter by balloon inflation, resulting in profound shock with asystole. IVUS was successful in identifying the cause, and the thrombus was removed successfully by manual aspiration. Due to the poor endothelization of a recent stenting, clinicians should be particularly careful of possible wire advancing outside the stent structure, which can result in prominent thrombus or atheromatous debris occluding the distal vessel, and IVUS may be useful in confirming the cause of no-reflow. PMID:27274180

  14. Treatment of Pelvic Venous Spur (May-Thurner Syndrome) with Self-Expanding Metallic Endoprostheses

    SciTech Connect

    Binkert, Christoph A.; Schoch, Eric; Stuckmann, Gerd; Largiader, Jon; Wigger, Pius; Schoepke, Wolfdietrich; Zollikofer, Christoph L.

    1998-01-15

    Purpose: The application of self-expanding metallic endoprostheses (stents) to treat symptomatic pelvic venous spurs as an alternative to surgery. Methods: Wallstents with a diameter from 14 to 16 mm and one Cragg stent were placed in the left common iliac vein of eight patients (seven women, one man; mean age 42 years) with a symptomatic pelvic venous spur (left deep venous thrombosis or post-thrombotic leg swelling). Four patients had surgical thrombectomy prior to stent placement. Results: Technical success with immediate reduction of left leg circumference was achieved in all eight patients. A primary patency rate of 100% was observed during an average follow-up of 3 years (range 10-121 months). There were no procedural or stent-related complications. Conclusion: The percutaneous transfemoral placement of self-expanding metallic stents is an effective minimally invasive alternative to surgery in the treatment of symptomatic pelvic venous spur.

  15. Design, Manufacturing, and In Vitro Testing of a Patient-Specific Shape-Memory Expander for Nose Reconstruction With Forehead Flap Technique.

    PubMed

    Borghi, Alessandro; Rodgers, Will; Schievano, Silvia; Ponniah, Allan; O'Hara, Justine; Jeelani, Owase; Dunaway, David

    2016-01-01

    Forehead skin is widely acknowledged as a good donor site for total nasal reconstruction, thanks to its matching color, texture, and abundant vascularity. The forehead flap technique uses an axial pattern flap forehead skin to replace missing nasal tissue. To increase the amount of available tissue and reduce the size of the tissue defect after flap mobilization, tissue expanders may be used. Although this is a relatively established technique, limitations include reduced moldability of the forehead skin (which is thicker than the nasal skin), and the need for multiple sessions of expansion to achieve a sufficient yield to close the forehead.Shape-memory metals, such as nitinol, can be programmed to "remember" complex shapes. In this work, the methodology for producing a prototype of nitinol tissue expander able to mold the skin in a predetermined patient-specific skin shape is described. A realistic nose mold was manufactured using metal rapid prototyping; nitinol sheet and mesh were molded into nose-shape constructs, having hyperelastic as well as shape-memory capability. Computed tomography scanning was performed to assess the ability of the structure to regain its shape after phase transformation upon cooling within 2% of initial dimensions. The prototypes were implanted in a pig forehead to test its ability to impose a nose shape to the forehead skin.The shape-memory properties of nitinol offer the possibility of producing bespoke tissue expanders able to deliver complex, precisely designed skin envelopes. The hyperelastic properties of nitinol allow constant preprogrammed expansion forces to be generated throughout the expansion process. PMID:26674894

  16. Nasal packing and stenting

    PubMed Central

    Weber, Rainer K.

    2011-01-01

    Nasal packs are indispensable in ENT practice. This study reviews current indications, effectiveness and risks of nasal packs and stents. In endoscopic surgery, nasal packs should always have smooth surfaces to minimize mucosal damage, improve wound healing and increase patient comfort. Functional endoscopic endonasal sinus surgery allows the use of modern nasal packs, since pressure is no longer required. So called hemostatic/resorbable materials are a first step in this direction. However, they may lead to adhesions and foreign body reactions in mucosal membranes. Simple occlusion is an effective method for creating a moist milieu for improved wound healing and avoiding dryness. Stenting of the frontal sinus is recommended if surgery fails to produce a wide, physiologically shaped drainage path that is sufficiently covered by intact tissue. PMID:22073095

  17. Carotid stenting and endarterectomy.

    PubMed

    Yip, Hon-Kan; Sung, Pei-Hsun; Wu, Chiung-Jen; Yu, Cheuk-Man

    2016-07-01

    Stroke, either ischemic or hemorrhagic, remains the second commonest cause of death worldwide in the last decade. Etiologies for ischemic stroke (IS) vary widely. Atherothrombotic occlusion is an essential cause to which carotid artery stenosis (CAS) is a major contributor. Administration of anti-platelet agent to patients with CAS has been shown to reduce incidence of long-term IS. In additional, in patients with symptomatic CAS, clinical trials have demonstrated that carotid endarterectomy (CEA) is superior to medical therapy for prevention of future CAS-related IS. However, CEA is not suitable for CAS post-radiotherapy or those located at higher level of the internal carotid artery; and major complications of this procedure including cranial nerve injuries have stimulated the interest of using percutaneous transfemoral carotid stenting as an alternative approach. Although transfemoral arterial approach of carotid stenting is not inferior to CEA in improving clinical outcomes, it has been reported to be associated with vascular complication and has its limitations in patients with athero-occlusive disease of abdominal aorta or bilateral iliac arteries, level II or III aortic arch, or bovine type carotid arterial anatomy. Therefore, transradial/transbrachial arterial approach has emerged as a novel method for carotid stenting. This article provides a critical review on interventional approaches for the treatment of CAS.

  18. Zotarolimus-eluting stent fracture at initial implantation diagnosed with StentBoost

    PubMed Central

    Arat Ozkan, Alev; Sinan, Umit Yasar; Gurmen, Aziz T

    2016-01-01

    Stent fracture is a rare complication of drug-eluting stent implantation with a reported rate of 0.84%–3.2% in various clinical studies with first-generation drug-eluting stents and 29% in autopsy studies. Sirolimus-eluting stents with their closed cell design were reported to be more prone to fracture compared to paclitaxel-eluting stents. Other risk factors for stent fracture are multiple stenting, longer stent length, chronic renal failure, right coronary artery intervention, and a higher maximal inflation pressure. The role of angiography in diagnosing stent fracture is limited, a fact also questioning the reliability of angiographic data. Image enhancement techniques like StentBoost are widely available in new-generation angiography systems and are used to assess stent expansion, overlap size, or to localize the postdilation balloon. Here, we report a case of zotarolimus-eluting stent fracture at initial implantation diagnosed with StentBoost. PMID:27489714

  19. Zotarolimus-eluting stent fracture at initial implantation diagnosed with StentBoost.

    PubMed

    Arat Ozkan, Alev; Sinan, Umit Yasar; Gurmen, Aziz T

    2016-01-01

    Stent fracture is a rare complication of drug-eluting stent implantation with a reported rate of 0.84%-3.2% in various clinical studies with first-generation drug-eluting stents and 29% in autopsy studies. Sirolimus-eluting stents with their closed cell design were reported to be more prone to fracture compared to paclitaxel-eluting stents. Other risk factors for stent fracture are multiple stenting, longer stent length, chronic renal failure, right coronary artery intervention, and a higher maximal inflation pressure. The role of angiography in diagnosing stent fracture is limited, a fact also questioning the reliability of angiographic data. Image enhancement techniques like StentBoost are widely available in new-generation angiography systems and are used to assess stent expansion, overlap size, or to localize the postdilation balloon. Here, we report a case of zotarolimus-eluting stent fracture at initial implantation diagnosed with StentBoost. PMID:27489714

  20. iStent® Trabecular Microbypass Stent: An Update.

    PubMed

    Resende, Arthur Fernandes; Patel, Neal Sanjay; Waisbourd, Michael; Katz, L Jay

    2016-01-01

    Due to the high rates of complications and failure experienced with current glaucoma procedures, there is a continuous search for a safer and more effective glaucoma surgery. A new class of procedures termed minimally invasive glaucoma surgeries (MIGS) aim to fill this void by offering an alternative method of IOP reduction associated with markedly reduced complication rates and shorter recovery times. The iStent, a trabecular microbypass stent, is a MIGS device that has quickly gained popularity. The device allows aqueous humor to directly drain from the anterior chamber into Schlemm's canal by bypassing an obstructed trabecular meshwork. This review examines publications about the iStent, focusing on the device's efficacy, safety, and cost when a single iStent or multiple iStents are implanted in combination with cataract surgery or as a solo procedure. Current data suggest that the iStent is a safe and effective tool in the management of mild-to-moderate glaucoma, notable for its limited complications and absence of serious adverse events following implantation. As valuable experience is gained performing ab interno MIGS, increasing familiarity with angle anatomy and iStent placement, and as newer stent designs are developed, there is promise of continual improvement in the surgical management of glaucoma.

  1. iStent® Trabecular Microbypass Stent: An Update

    PubMed Central

    Resende, Arthur Fernandes; Patel, Neal Sanjay; Waisbourd, Michael; Katz, L. Jay

    2016-01-01

    Due to the high rates of complications and failure experienced with current glaucoma procedures, there is a continuous search for a safer and more effective glaucoma surgery. A new class of procedures termed minimally invasive glaucoma surgeries (MIGS) aim to fill this void by offering an alternative method of IOP reduction associated with markedly reduced complication rates and shorter recovery times. The iStent, a trabecular microbypass stent, is a MIGS device that has quickly gained popularity. The device allows aqueous humor to directly drain from the anterior chamber into Schlemm's canal by bypassing an obstructed trabecular meshwork. This review examines publications about the iStent, focusing on the device's efficacy, safety, and cost when a single iStent or multiple iStents are implanted in combination with cataract surgery or as a solo procedure. Current data suggest that the iStent is a safe and effective tool in the management of mild-to-moderate glaucoma, notable for its limited complications and absence of serious adverse events following implantation. As valuable experience is gained performing ab interno MIGS, increasing familiarity with angle anatomy and iStent placement, and as newer stent designs are developed, there is promise of continual improvement in the surgical management of glaucoma. PMID:27413541

  2. Hemodynamics in Idealized Stented Coronary Arteries: Important Stent Design Considerations.

    PubMed

    Beier, Susann; Ormiston, John; Webster, Mark; Cater, John; Norris, Stuart; Medrano-Gracia, Pau; Young, Alistair; Cowan, Brett

    2016-02-01

    Stent induced hemodynamic changes in the coronary arteries are associated with higher risk of adverse clinical outcome. The purpose of this study was to evaluate the impact of stent design on wall shear stress (WSS), time average WSS, and WSS gradient (WSSG), in idealized stent geometries using computational fluid dynamics. Strut spacing, thickness, luminal protrusion, and malapposition were systematically investigated and a comparison made between two commercially available stents (Omega and Biomatrix). Narrower strut spacing led to larger areas of adverse low WSS and high WSSG but these effects were mitigated when strut size was reduced, particularly for WSSG. Local hemodynamics worsened with luminal protrusion of the stent and with stent malapposition, adverse high WSS and WSSG were identified around peak flow and throughout the cardiac cycle respectively. For the Biomatrix stent, the adverse effect of thicker struts was mitigated by greater strut spacing, radial cell offset and flow-aligned struts. In conclusion, adverse hemodynamic effects of specific design features (such as strut size and narrow spacing) can be mitigated when combined with other hemodynamically beneficial design features but increased luminal protrusion can worsen the stent's hemodynamic profile significantly.

  3. The alloy with a memory, 55-Nitinol: Its physical metallurgy, properties, and applications

    NASA Technical Reports Server (NTRS)

    Jackson, C. M.; Wagner, H. J.; Wasilewski, R. J.

    1972-01-01

    A series of nickel titanium alloys (55-Nitinol), which are unique in that they possess a shape memory, are described. Components made of these materials that are altered in their shapes by deformation under proper conditions return to predetermined shapes when they are heated to the proper temperature range. The shape memory, together with the force exerted and the ability of the material to do mechanical work as it returns to its predetermined shape, suggest a wide variety of industrial applications for the alloy. Also included are discussions of the physical metallurgy and the mechanical, physical, and chemical properties of 55-Nitinol; procedures for melting and processing the material into useful shapes; and a summary of applications.

  4. Histomorphometric analysis of the response of rat tibiae to shape memory alloy (nitinol).

    PubMed

    Takeshita, F; Takata, H; Ayukawa, Y; Suetsugu, T

    1997-01-01

    The bone reaction to nitinol (Ni-Ti), a metal with shape memory, and other materials inserted transcortically and extending into the medullary canal of rat tibiae was quantitatively assessed using an image processing system. The materials examined were implants, all of the same shape and size, composed of nitinol, pure titanium (Ti), anodic oxidized Ti (AO-Ti), a titanium alloy (Ti-6Al-4V) and pure nickel (Ni). While the other four implant materials were progressively encapsulated with bone tissues, Ni was encapsulated with connective tissues through the 168-day experimental period, and the Ni implants showed no bone contact at any time during the experimental period. Histometric analysis revealed no significant difference among the tissue reactions to Ti, AO-Ti and Ti-6Al-4V, but Ni-Ti implants showed significantly (P < 0.01) lower percentage bone contact and bone contact area than any of the other titanium or titanium alloy materials.

  5. Nephroureteral Stents: Principles and Techniques

    PubMed Central

    Makramalla, Abouelmagd; Zuckerman, Darryl A.

    2011-01-01

    Nephroureteral stents including antegrade, retrograde, or internal (double-J) stents are routinely placed by interventional radiologists. The purpose of this review is to provide a detailed and comprehensive description of indications, contraindications, technique, and various technical challenges of these procedures. Also pre- and postprocedure management of patients will be discussed including routine follow-up and dealing with potential complications. PMID:23204635

  6. Are Aortic Stent Grafts Safe in Pregnancy?

    PubMed Central

    Khandanpour, Nader; Mehta, Tapan A.; Adiseshiah, M.; Meyer, Felicity J.

    2015-01-01

    Aortic stent grafts are increasingly used to treat aortic aneurysms and also other aortic pathologies. The safety of aortic stent grafts in pregnancy has never been studied or reported. We report on two cases of aortic stent grafts in pregnant women and discuss the effect of pregnancy on these aortic stent grafts. PMID:26229702

  7. Corrosion resistance, chemistry, and mechanical aspects of Nitinol surfaces formed in hydrogen peroxide solutions

    SciTech Connect

    Shabalovskay, Svetlana A.; Anderegg, James W.; Undisz, Andreas; Rettenmayr, Markus; Rondelli, Gianni C.

    2012-06-12

    Ti oxides formed naturally on Nitinol surfaces are only a few nanometers thick. To increase their thickness, heat treatments are explored. The resulting surfaces exhibit poor resistance to pitting corrosion. As an alternative approach to accelerate surface oxidation and grow thicker oxides, the exposure of Nitinol to strong oxidizing H2O2 aqueous solutions (3 and 30%) for various periods of time was used. Using X-Ray Photoelectron Spectroscopy (XPS) and Auger spectroscopy, it was found that the surface layers with variable Ti (6–15 at %) and Ni (5–13 at %) contents and the thickness up to 100 nm without Ni-enriched interfaces could be formed. The response of the surface oxides to stress in superelastic regime of deformations depended on oxide thickness. In the corrosion studies performed in both strained and strain-free states using potentiodynamic and potentiostatic polarizations, the surfaces treated in H2O2 showed no pitting in corrosive solution that was assigned to higher chemical homogeneity of the surfaces free of secondary phases and inclusions that assist better biocompatibility of Nitinol medical devices. © 2012 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 100B: 1490–1499, 2012

  8. FE Analysis of Nitinol Leaf Springs Used in a Compression Anastomosis Device

    NASA Astrophysics Data System (ADS)

    Weizman, Amir; Monassevitch, Leonid; Greenberg, Kobby; Millis, Shahar; Harari, Boaz; Dar, Idan

    2011-07-01

    Reconstruction of the digestive system lumen patency (anastomosis creation) after its partial surgical removal is a common and crucial procedure. The conventional anastomosis methods use devices for mechanical suturing which are associated with high failure risk and can lead to major complications. The compression anastomosis as a sutureless method seems to be a promising alternative. However, attempts during the last two centuries have not been completely successful due to the complex character of the tissue-healing process. The specific mechanical behavior of Nitinol alloys was applied to the force element of the compression devices. These devices are becoming more widely adopted in surgery practice. The compression anastomosis device enables the anastomosis of colonic and intestinal tissue based on compression forces exerted by Nitinol leaf springs. By means of changing the strain distribution in the stressed leaves with varying moments of inertia, one can gain full control of the different stages in the force-deflection profile (i.e., linear elastic stage and the force plateau stage). The target of this study is the comparison of different Nitinol leaf geometries and evaluation of the finite elements analysis as a tool for preliminary design of such geometries. The results of this analysis allow us to establish regulation of the spring's mechanical behavior, thus controlling the anastomosis creation in the compression anastomosis device.

  9. Irradiation-Assisted Stress-Corrosion Cracking of Nitinol During eBeam Sterilization

    NASA Astrophysics Data System (ADS)

    Smith, Stuart A.; Gause, Brock; Plumley, David; Drexel, Masao J.

    2012-12-01

    Medical device fractures during gamma and electron beam (eBeam) sterilization have been reported. Two common factors in these device fractures were a constraining force and the presence of fluorinated ethylene propylene (FEP). This study investigated the effects of eBeam sterilization on constrained light-oxide nitinol wires in FEP. The goal was to recreate these fractures and determine their root cause. Superelastic nitinol wires were placed inside FEP tubes and constrained with nominal outer fiber strains of 10, 15, and 20%. These samples were then subjected to a range of eBeam sterilization doses up to 400 kGy and compared with unconstrained wires also subjected to sterilization. Fractures were observed at doses of >100 kGy. Analysis of the fracture surfaces indicated that the samples failed due to irradiation-assisted stress-corrosion cracking (IASCC). This same effect was also observed to occur with PTFE at 400 kGy. These results suggest that nitinol is susceptible to IASCC when in the presence of a constraining stress, fluorinated polymers, and irradiation.

  10. Utility of magneto-electropolished ternary nitinol alloys for blood contacting applications.

    PubMed

    Pulletikurthi, Chandan; Munroe, Norman; Stewart, Danique; Haider, Waseem; Amruthaluri, Sushma; Rokicki, Ryszard; Dugrot, Manuel; Ramaswamy, Sharan

    2015-10-01

    The thrombogenicity of a biomaterial is mainly dependent on its surface characteristics, which dictates its interactions with blood. Surface properties such as composition, roughness wettability, surface free energy, and morphology will affect an implant material's hemocompatibility. Additionally, in the realm of metallic biomaterials, the specific composition of the alloy and its surface treatment are important factors that will affect the surface properties. The utility of magneto-electropolished (MEP) ternary Nitinol alloys, NiTiTa, and NiTiCr as blood contacting materials was investigated. The hemcompatibility of these alloys were compared to mechanically polished (MP) metallic biomaterial counterparts. In vitro thrombogenicity tests revealed significantly less platelet adherence on ternary MEP Nitinol, especially MEP NiTi10Ta as compared to the MP metals (p < 0.05). The enhanced anti-platelet-adhesive property of MEP NiTi10Ta was in part, attributed to the Ta2 O5 component of the alloy. Furthermore, the formation of a dense and mixed hydrophobic oxide layer during MEP is believed to have inhibited the adhesion of negatively charged platelets. In conclusion, MEP ternary Nitinol alloys can potentially be utilized for blood-contacting devices where, complications resulting from thrombogenicity can be minimized.

  11. Use of the Memokath Urethral Stent in the management of ileal conduit stomal stenosis

    PubMed Central

    Pan, Tzong-Yang; Al-Sameraaii, Ahmad

    2015-01-01

    Intoduction Ileal conduit stomal stenosis is a difficult complication to manage. Definitive treatment usually requires refashioning or a reconstruction of the conduit. There remains a need for minimally invasive procedures that can restore function to the stoma while avoiding the risks associated with a significant surgical procedure. This case illustrates a novel approach to the management of this complication. Presentation of case An 84 year old female with muscle-invasive bladder cancer underwent cystectomy with formation of an ileal conduit urinary diversion system. Her recovery was complicated by stomal stenosis leading to recurrent urinary tract infections. The Memokath Stent 045 is a thermo-expandable nickel–titanium stent designed for treatment of urethral strictures. The stent was inserted into the stoma under direct vision without the need for general anaesthesia or intraoperative radiography. The conduit remains patent 12 months after insertion and the metal stent showed no evidence of migration, calcification, oxidation or degradation. Discussion The use of a thermo-expandable nickel–titanium stent is able to provide the patency required to treat ileal conduit stomal stenosis. In this case, insertion of the stent was a simple procedure and no adverse events or degradation of the stent was identified at 12 months after insertion. The need for a significant surgical procedure such as a refashioning or reconstruction was avoided and general anaesthesia was not required to perform the procedure. Conclusion This case report highlights the possibility of using the thermo-expandable Memokath Stent 045 as an alternative to the long-term management of ileal conduit stomal stenosis. PMID:26745318

  12. Coronary stent technology: a narrative review.

    PubMed

    Chen, Daniel; Jepson, Nigel

    2016-09-19

    Coronary angioplasty and coronary artery stents have revolutionised interventional cardiology. Contemporary coronary stent technology continues to seek to improve on the outcomes of the preceding generation of devices by refining their design, structure and component materials. These technologies include new generations of drug-eluting stents, non-polymeric stents, bioresorbable polymer-coated stents, and fully bioresorbable scaffolds. This review discusses the evolution of coronary stent technology, the efficacy and safety of currently available devices, and the rationale for new generation platforms as efforts continue to design the ideal coronary stent technology. PMID:27627940

  13. Colonic Stents for Colorectal Cancer Are Seldom Used and Mainly for Palliation of Obstruction: A Population-Based Study.

    PubMed

    Borowiec, Anna M; Wang, Charlie S K; Yong, Elaine; Law, Calvin; Coburn, Natalie; Sutradhar, Rinku; Baxter, Nancy; Paszat, Lawrence; Tinmouth, Jill

    2016-01-01

    Self-expandable stents for obstructing colorectal cancer (CRC) offer an alternative to operative management. The objective of the study was to determine stent utilization for CRC obstruction in the province of Ontario between April 1, 2000, and March 30, 2009. Colonic stent utilization characteristics, poststent insertion health outcomes, and health care encounters were recorded. 225 patients were identified over the study period. Median age was 69 years, 2/3 were male, and 2/3 had metastatic disease. Stent use for CRC increased over the study period and gastroenterologists inserted most stents. The median survival after stent insertion was 199 (IQR, 69-834) days. 37% of patients required an additional procedure. Patients with metastatic disease were less likely to go on to surgery (HR 0.14, 95% CI 0.06-0.32, p < 0.0001). There were 2.4/person-year emergency department visits (95% CI 2.2-2.7) and 2.3 hospital admissions/person-year (95% CI 2.1-2.5) following stent insertion. Most admissions were cancer or procedure related or for palliation. Factors associated with hospital admissions were presence of metastatic disease, lack of chemotherapy treatment, and stoma surgery. Overall the use of stents for CRC obstruction remains low. Stents are predominantly used for palliation with low rates of postinsertion health care encounters. PMID:27446826

  14. Colonic Stents for Colorectal Cancer Are Seldom Used and Mainly for Palliation of Obstruction: A Population-Based Study

    PubMed Central

    Borowiec, Anna M.; Wang, Charlie S. K.; Yong, Elaine; Law, Calvin; Coburn, Natalie; Sutradhar, Rinku; Baxter, Nancy; Paszat, Lawrence; Tinmouth, Jill

    2016-01-01

    Self-expandable stents for obstructing colorectal cancer (CRC) offer an alternative to operative management. The objective of the study was to determine stent utilization for CRC obstruction in the province of Ontario between April 1, 2000, and March 30, 2009. Colonic stent utilization characteristics, poststent insertion health outcomes, and health care encounters were recorded. 225 patients were identified over the study period. Median age was 69 years, 2/3 were male, and 2/3 had metastatic disease. Stent use for CRC increased over the study period and gastroenterologists inserted most stents. The median survival after stent insertion was 199 (IQR, 69–834) days. 37% of patients required an additional procedure. Patients with metastatic disease were less likely to go on to surgery (HR 0.14, 95% CI 0.06–0.32, p < 0.0001). There were 2.4/person-year emergency department visits (95% CI 2.2–2.7) and 2.3 hospital admissions/person-year (95% CI 2.1–2.5) following stent insertion. Most admissions were cancer or procedure related or for palliation. Factors associated with hospital admissions were presence of metastatic disease, lack of chemotherapy treatment, and stoma surgery. Overall the use of stents for CRC obstruction remains low. Stents are predominantly used for palliation with low rates of postinsertion health care encounters. PMID:27446826

  15. Ureteral stents: new ideas, new designs

    PubMed Central

    Al-Aown, Abdulrahman; Kyriazis, Iason; Kallidonis, Panagiotis; Kraniotis, Pantelis; Rigopoulos, Christos; Karnabatidis, Dimitrios; Petsas, Theodore; Liatsikos, Evangelos

    2010-01-01

    Ureteral stents represent a minimally invasive alternative to preserve urinary drainage whenever ureteral patency is deteriorated or is under a significant risk to be occluded due to extrinsic or intrinsic etiologies. The ideal stent that would combine perfect long-term efficacy with no stent-related morbidity is still lacking and stent usage is associated with several adverse effects that limit its value as a tool for long-term urinary drainage. Several new ideas on stent design, composition material and stent coating currently under evaluation, foreseen to eliminate the aforementioned drawbacks of ureteral stent usage. In this article we review the currently applied novel ideas and new designs of ureteral stents. Moreover, we evaluate potential future prospects of ureteral stent development adopted mostly by the pioneering cardiovascular stent industry, focusing, however, on the differences between ureteral and endothelial tissue. PMID:21789086

  16. External-to-Internal Iliac Stent-Graft: Medium-Term Patency Following Exclusion of a Retrogradely Perfused Common Iliac Aneurysm

    SciTech Connect

    Nicholls, Marcus John; McPherson, Simon

    2010-08-15

    Following complicated aortic aneurysm surgery a complete left iliac occlusion resulted in buttock claudication. A retrogradely perfused right common iliac aneurysm expanded. Exclusion was by external-to-internal iliac stent-graft. No deterioration in claudication occurred with medium-term stent-graft patency.

  17. Use of PTFE Stent Grafts for Hemodialysis-related Central Venous Occlusions: Intermediate-Term Results

    SciTech Connect

    Kundu, Sanjoy Modabber, Milad; You, John M.; Tam, Paul; Nagai, Gordon; Ting, Robert

    2011-10-15

    Purpose: To assess the safety and effectiveness of a polytetrafluoroethylene (PTFE) encapsulated nitinol stents (Bard Peripheral Vascular, Tempe, AZ) for treatment of hemodialysis-related central venous occlusions. Materials and Methods: Study design was a single-center nonrandomized retrospective cohort of patients from May 2004 to August 2009 for a total of 64 months. There were 14 patients (mean age 60 years, range 50-83 years; 13 male, 1 female). All patients had autogenous fistulas. All 14 patients had central venous occlusions and presented with clinical symptoms of the following: extremity swelling (14%, 2 of 14), extremity and face swelling (72%, 10 of 14), and face swelling/edema (14%, 2 of 14). There was evidence of access dysfunction with decreased access flow in 36% (5 of 14) patients. There were prior interventions or previous line placement at the site of the central venous lesion in all 14 patients. Results were assessed by recurrence of clinical symptoms and function of the access circuit (National Kidney Foundation recommended criteria). Results: Sixteen consecutive straight stent grafts were implanted in 14 patients. Average treated lesion length was 5.0 cm (range, 0.9-7 cm). All 14 patients had complete central venous occlusion (100% stenosis). The central venous occlusions were located as follows: right subclavian and brachiocephalic vein (21%, 3 of 14), right brachiocephalic vein (36%, 5 of 14), left brachiocephalic vein (36%, 5 of 14), and bilateral brachiocephalic vein (7%, 1 of 14). A total of 16 PTFE stent grafts were placed. Ten- or 12-mm-diameter PTFE stent grafts were placed. The average stent length was 6.1 cm (range, 4-8 cm). Technical (deployment), anatomic (<30% residual stenosis), clinical (resolution of symptoms), and hemodynamic (resolution of access dysfunction) success were 100%. At 3, 6, and 9 months, primary patency of the treated area and access circuit were 100% (14 of 14). Conclusions: This PTFE encapsulated stent graft

  18. Expanding Universe

    NASA Astrophysics Data System (ADS)

    Schrödinger, E.

    2011-02-01

    Preface; Part I. The de Sitter Universe: 1. Synthetic construction; 2. The reduced model: geodesics; 3. The elliptic interpretation; 4. The static frame; 5. The determination of parallaxes; 6. The Lemaître-Robertson frame; Part II. The Theory of Geodesics: 7. On null geodesics; i. Determination of the parameter for null lines in special cases; ii. Frequency shift; 8. Free particles and light rays in general expanding spaces, flat or hyperspherical; i. Flat spaces; ii. Spherical spaces; iii. The red shift for spherical spaces; Part III. Waves in General Riemannian Space-Time: 9. The nature of our approximation; 10. The Hamilton-Jacobi theory in a gravitational field; 11. Procuring approximate solutions of the Hamilton-Jacobi equation from wave theory; Part IV. Waves in an Expanding Universe: 12. General considerations; 13. Proper vibrations and wave parcels; Bibliography.

  19. Expanding Gravity

    NASA Astrophysics Data System (ADS)

    Aisenberg, Sol

    2005-04-01

    Newton's gravitational constant Gn and Laws of Gravity are based upon observations in our solar system. Mysteries appear when they are used far outside our solar system Apparently, Newton's gravitational constant can not be applied at large distances. Dark matter was needed to explain the observed flat rotational velocity curves of spiral galaxies (Rubin), and of groups of remote galaxies (Zwicky). Our expansion of Newton's gravitational constant Gn as a power series in distance r, is sufficient to explain these observations without using dark matter. This is different from the MOND theory of Milgrom involving acceleration. Also, our Expanded Gravitational Constant (EGC) can show the correct use of the red shift. In addition to the Doppler contribution, there are three other contributions and these depend only upon gravity. Thus, velocity observations only based on the red shift can not be used to support the concept of the expanding universe, the accelerating expansion, or dark energy. Our expanded gravity constant can predict and explain Olbers' paradox (dark sky), and the temperature of the CMB (cosmic microwave background). Thus, CMB may not support the big bang and inflation.

  20. Resistance Microwelding of Ti-55.8 wt pct Ni Nitinol Wires and the Effects of Pseudoelasticity

    NASA Astrophysics Data System (ADS)

    Tam, Billy; Pequegnat, Andrew; Khan, Mohammad Ibraheem; Zhou, Yunhong

    2012-08-01

    Nitinol has revolutionized many traditional engineering designs with its unique properties that include pseudoelasticity and the shape-memory effect (SME). However, the general lack of understanding on welding Nitinol limits its full potential in practical applications. The current study examined the microstructure and mechanical properties of resistance microwelded (RMW) Ni-rich Nitinol wires at different applied currents. The results revealed a solid-state bonding mechanism that consisted of six main stages, including (1) cold collapse, (2) dynamic recrystallization, (3) interfacial melting, (4) squeeze out, (5) excessive flash, and (6) surface melting. The joint strength and fracture mechanism were linked closely to the metallurgical properties of the welds. Through differential scanning calorimetry (DSC) testing, it was found that the weld metal underwent phase transformation at lower temperatures compared with the base material. Also, the pseudoelastic property of Nitinol was found to have a large effect on the contact resistance during the onset of welding current. Compression tests with varying temperatures confirmed distinct differences in displacement ( i.e., cold collapse) under the welding load of 5 kg-f caused by changes in the thermodynamic stability of the austenite phase. Both the dynamic resistance and displacement measurements were found to be significantly different during the RMW of Nitinol crossed wires compared with welding 316 low-vacuum melted (LVM) stainless steel (SS) crossed wires.

  1. Materials and Manufacturing Technologies Available for Production of a Pediatric Bioabsorbable Stent

    PubMed Central

    Alexy, Ryan D.; Levi, Daniel S.

    2013-01-01

    Transcatheter treatment of children with congenital heart disease such as coarctation of the aorta and pulmonary artery stenosis currently involves the use of metal stents. While these provide good short term results, there are long term complications with their use. Children outgrow metal stents, obligating them to future transcatheter dilations and eventual surgical removal. A bioabsorbable stent, or a stent that goes away with time, would solve this problem. Bioabsorbable stents are being developed for use in coronary arteries, however these are too small for use in pediatric congenital heart disease. A bioabsorbable stent for use in pediatric congenital heart disease needs to be low profile, expandable to a diameter 8 mm, provide sufficient radial strength, and absorb quickly enough to allow vessel growth. Development of absorbable coronary stents has led to a great understanding of the available production techniques and materials such as bioabsorbable polymers and biocorrodable metals. Children with congenital heart disease will hopefully soon benefit from the current generation of bioabsorbable and biocorrodable materials and devices. PMID:24089660

  2. Endoscopic ultrasonography-guided placement of a transhepatic portal vein stent in a live porcine model

    PubMed Central

    Park, Tae Young; Seo, Dong Wan; Kang, Hyeon-Ji; Cho, Min Keun; Song, Tae Jun; Park, Do Hyun; Lee, Sang Soo; Lee, Sung Koo; Kim, Myung-Hwan

    2016-01-01

    Background and Objectives: Percutaneous portal vein (PV) stent placement is used to manage PV occlusion or stenosis caused by malignancy. The use of endoscopic ultrasonography (EUS) has expanded to include vascular interventions. The aim of this study was to examine the technical feasibility and safety of EUS-guided transhepatic PV stent placement in a live porcine model. Materials and Methods: EUS-guided transhepatic PV stent placement was performed in six male miniature pigs under general anesthesia using forward-viewing echoendoscope. Under EUS guidance, the left intrahepatic PV was punctured with a 19-gauge fine-needle aspiration (FNA) needle and a 0.025 inch guidewire inserted through the needle and into the main PV. The FNA needle was then withdrawn and a needle-knife inserted to dilate the tract. Under EUS and fluoroscopic guidance, a noncovered metal stent was inserted over the guidewire and released into the main PV. Results: A PV stent was placed successfully in all six pigs with no technical problems or complications. The patency of the stent in the main PV was confirmed using color Doppler EUS and transhepatic portal venography. Necropsy of the first three animals revealed no evidence of bleeding and damage to intra-abdominal organs or vessels. No complications occurred in the remaining three animals during the 8 weeks observation period. Conclusions: EUS-guided transhepatic PV stent placement can be both technically feasible and safe in a live animal model. PMID:27803904

  3. Stenting for malignant ureteral obstruction: Tandem, metal or metal-mesh stents.

    PubMed

    Elsamra, Sammy E; Leavitt, David A; Motato, Hector A; Friedlander, Justin I; Siev, Michael; Keheila, Mohamed; Hoenig, David M; Smith, Arthur D; Okeke, Zeph

    2015-07-01

    Extrinsic malignant compression of the ureter is not uncommon, often refractory to decompression with conventional polymeric ureteral stents, and frequently associated with limited survival. Alternative options for decompression include tandem ureteral stents, metallic stents and metal-mesh stents, though the preferred method remains controversial. We reviewed and updated our outcomes with tandem ureteral stents for malignant ureteral obstruction, and carried out a PubMed search using the terms "malignant ureteral obstruction," "tandem ureteral stents," "ipsilateral ureteral stents," "metal ureteral stent," "resonance stent," "silhouette stent" and "metal mesh stent." A comprehensive review of the literature and summary of outcomes is provided. The majority of studies encountered were retrospective with small sample sizes. The evidence is most robust for metal stents, whereas only limited data exists for tandem or metal-mesh stents. Metal and metal-mesh stents are considerably more expensive than tandem stenting, but the potential for less frequent stent exchanges makes them possibly cost-effective over time. Urinary tract infections have been associated with all stent types. A wide range of failure rates has been published for all types of stents, limiting direct comparison. Metal and metal-mesh stents show a high incidence of stent colic, migration and encrustation, whereas tandem stents appear to produce symptoms equivalent to single stents. Comparison is difficult given the limited evidence and heterogeneity of patients with malignant ureteral obstruction. It is clear that prospective, randomized studies are necessary to effectively scrutinize conventional, tandem, metallic ureteral and metal-mesh stents for their use in malignant ureteral obstruction.

  4. Biodegradable stents in gastrointestinal endoscopy

    PubMed Central

    Lorenzo-Zúñiga, Vicente; Moreno-de-Vega, Vicente; Marín, Ingrid; Boix, Jaume

    2014-01-01

    Biodegradable stents (BDSs) are an attractive option to avoid ongoing dilation or surgery in patients with benign stenoses of the small and large intestines. The experience with the currently the only BDS for endoscopic placement, made of Poly-dioxanone, have shown promising results. However some aspects should be improved as are the fact that BDSs lose their radial force over time due to the degradable material, and that can cause stent-induced mucosal or parenchymal injury. This complication rate and modest clinical efficacy has to be carefully considered in individual patients prior to placement of BDSs. Otherwise, the price of these stents therefore it is nowadays an important limitation. PMID:24605020

  5. Early Experiences of Neuroform Stent-Assisted Coiling in Ruptured Intracranial Aneurysms

    PubMed Central

    Kim, Young-Joon

    2007-01-01

    Summary Endovascular treatment of ruptured intracranial aneurysms with detachable coils has proven a favorable alternative to surgical clipping. However, coiling has limitations in the treatment of complex or broad neck aneurysms because of possible coil prolapse or coil migration into the parent vessel and long-term angiographic recurrences. To achieve reconstruction of intracranial vessels with preservation of the parent artery, the use of stents has the greatest potential for assisted coil embolization. Three-dimensional coils and reconstructive techniques such as balloon-assisted remodeling may overcome these problems. But these methods had some drawbacks. The Neuroform stent is the most recently developed endovascular stent with self-expandable and micro-delivery properties that are specially designed for the treatment of unruptured intracranial broad neck aneurysms. Aim of the following working is to report a single center experience of stent-assisted coiling on ruptured intracranial aneurysms with assessment of its efficacy and safety, and follow-up findings. PMID:20566127

  6. Enteral metallic stenting by balloon enteroscopy for obstruction of surgically reconstructed intestine.

    PubMed

    Nakahara, Kazunari; Okuse, Chiaki; Matsumoto, Nobuyuki; Suetani, Keigo; Morita, Ryo; Michikawa, Yosuke; Ozawa, Shun-ichiro; Hosoya, Kosuke; Kobayashi, Shinjiro; Otsubo, Takehito; Itoh, Fumio

    2015-06-28

    We present three cases of self-expandable metallic stent (SEMS) placement using a balloon enteroscope (BE) and its overtube (OT) for malignant obstruction of surgically reconstructed intestine. A BE is effective for the insertion of an endoscope into the deep bowel. However, SEMS placement is impossible through the working channel, because the working channel of BE is too small and too long for the stent device. Therefore, we used a technique in which the BE is inserted as far as the stenotic area; thereafter, the BE is removed, leaving only the OT, and then the stent is placed by inserting the stent device through the OT. In the present three cases, a modification of this technique resulted in the successful placement of the SEMS for obstruction of surgically reconstructed intestine, and the procedures were performed without serious complications. We consider that the present procedure is extremely effective as a palliative treatment for distal bowel stenosis, such as in the surgically reconstructed intestine.

  7. Endoluminal stenting of obstructed colorectal tumours.

    PubMed Central

    Boorman, P.; Soonawalla, Z.; Sathananthan, N.; MacFarlane, P.; Parker, M. C.

    1999-01-01

    A series of patients were selected to evaluate the clinical efficacy of a new self expanding metallic endoprosthesis in the management of left-sided colonic obstruction. The aim was to reduce the morbidity and mortality associated with the surgical management of patients with distal colonic obstruction. Six patients with complete sigmoid colon obstruction were managed with the Wallstent Enteral Endoprosthesis [Schneider (USA) Inc.]. Four underwent subsequent elective colonic resection, while two were placed for palliation. Stent placement was successful in all cases with resulting bowel decompression and there were no procedural complications. All four patients with resectable tumours avoided emergency surgery. Stenting allowed time for medical improvement and staging investigations in this group. Two patients with advanced metastatic colonic carcinoma were successfully palliated. We found the Wallstent Enteral Endoprosthesis to be safe and effective in relieving obstruction in patients with resectable colonic tumours, permitting elective surgery and avoiding a temporary stoma. It can also be used to palliate those patients with advanced disease. Images Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 PMID:10615192

  8. Endovascular stent placement for nutcracker phenomenon.

    PubMed

    Li, Heping; Sun, Xiangzhou; Liu, Guihua; Zhang, Yuanyuan; Chu, Jianping; Deng, Chunhua; Zhou, Bo; Chen, Wei; Yang, Jianyong

    2013-01-01

    The nutcracker syndrome is a rare clinic condition associated with severe hematuria and left flank pain due to the entrapment of the left renal vein between the superior mesenteric artery and the aorta. Its diagnostic criteria are not well defined, often causing delayed or misdiagnosis. Although surgical repair has been the standard of care, more recently endovascular stenting of the renal vein has been proposed. We presented six patients (aged 7 to 31 years old; median age, 16.5 years old) with nutcracker syndrome who were endovascularly managed from June 2002 to July 2011. All patients underwent laboratory test and computed tomography (CT) or ultrasound examination before and after endovascular procedures. Self-expandable stents were successfully placed in all cases. The diameter of the left renal vein at aorto-superior mesenteric artery portion significantly increased from 1.88 ± 0.95 mm pre-procedure to 5.24 ± 0.61 mm post-procedure (p< 0.01). Left renal vein pressure significantly decreased from 11.00 ± 4.34 mmHg pre-procedure to 6.00 ± 2.55 mmHg post-procedure (p< 0.01). Severe gross hematuria completely subsided within 2 months to 6 months and left flank pain completely subsided within 7 days to 1 month after treatment. Endovascular therapy provides an alternative therapy with satisfactory long-term clinical and imaging results for symptomatic patients with nutcracker syndrome.

  9. Endovascular Stents and Stent-Grafts: Is Heparin Coating Desirable?

    SciTech Connect

    Nelson, Stephen R.; Souza, Nandita M. de; Allison, David J.

    2000-07-15

    Heparins are glycosaminoglycans that, in addition to their anticoagulant activity, have interactions with growth factors and other glycoproteins. These interactions may stimulate neointimal hyperplasia when heparin is delivered locally on stents and stent-grafts. Modifying the structure of heparin to retain anticoagulant activity while minimizing these stimulatory effects on the vascular endothelium is desirable and may be achieved by understanding the relationships between the structure and function of the various parts of the heparin molecule.

  10. Fabrication of a silver particle-integrated silicone polymer-covered metal stent against sludge and biofilm formation and stent-induced tissue inflammation

    PubMed Central

    Lee, Tae Hoon; Jang, Bong Seok; Jung, Min Kyo; Pack, Chan Gi; Choi, Jun-Ho; Park, Do Hyun

    2016-01-01

    To reduce tissue or tumor ingrowth, covered self-expandable metal stents (SEMSs) have been developed. The effectiveness of covered SEMSs may be attenuated by sludge or stone formation or by stent clogging due to the formation of biofilm on the covering membrane. In this study, we tested the hypothesis that a silicone membrane containing silver particles (Ag-P) would prevent sludge and biofilm formation on the covered SEMS. In vitro, the Ag-P-integrated silicone polymer-covered membrane exhibited sustained antibacterial activity, and there was no definite release of silver ions from the Ag-P-integrated silicone polymer membrane at any time point. Using a porcine stent model, in vivo analysis demonstrated that the Ag-P-integrated silicone polymer-covered SEMS reduced the thickness of the biofilm and the quantity of sludge formed, compared with a conventional silicone-covered SEMS. In vivo, the release of silver ions from an Ag-P-integrated silicone polymer-covered SEMS was not detected in porcine serum. The Ag-P-integrated silicone polymer-covered SEMS also resulted in significantly less stent-related bile duct and subepithelium tissue inflammation than a conventional silicone polymer-covered SEMS. Therefore, the Ag-P-integrated silicone polymer-covered SEMS reduced sludge and biofilm formation and stent-induced pathological changes in tissue. This novel SEMS may prolong the stent patency in clinical application. PMID:27739486

  11. Silane surface modification for improved bioadhesion of esophageal stents

    NASA Astrophysics Data System (ADS)

    Karakoy, Mert; Gultepe, Evin; Pandey, Shivendra; Khashab, Mouen A.; Gracias, David H.

    2014-08-01

    Stent migration occurs in 10-40% of patients who undergo placement of esophageal stents, with higher migration rates seen in those treated for benign esophageal disorders. This remains a major drawback of esophageal stent therapy. In this paper, we propose a new surface modification method to increase the adhesion between self-expandable metallic stents (SEMS) and tissue while preserving their removability. Taking advantage of the well-known affinity between epoxide and amine terminated silane coupling agents with amine and carboxyl groups that are abundant in proteins and related molecules in the human body; we modified the surfaces of silicone coated esophageal SEMS with these adhesive self-assembled monolayers (SAMs). We utilized vapor phase silanization to modify the surfaces of different substrates including PDMS strips and SEMS, and measured the force required to slide these substrates on a tissue piece. Our results suggest that surface modification of esophageal SEMS via covalent attachment of protein-binding coupling agents improves adhesion to tissue and could offer a solution to reduce SEMS migration while preserving their removability.

  12. Engineering Stent Based Delivery System for Esophageal Cancer Using Docetaxel.

    PubMed

    Shaikh, Mohsin; Choudhury, Namita Roy; Knott, Robert; Garg, Sanjay

    2015-07-01

    Esophageal cancer patients are often diagnosed as "advanced" cases. These patients are subjected to palliative stenting using self-expanding metallic stents (SEMS) to maintain oral alimentation. Unfortunately, SEMS get reoccluded due to tumor growth, in and over the stent struts. To investigate potential solutions to this problem, docetaxel (DTX) delivery films were prepared using PurSil AL 20 (PUS), which can be used as a covering material for the SEMS. Drug-polymer miscibility and interactions were studied. Bilayer films were prepared by adhering the blank film to the DTX loaded film in order to maintain the unidirectional delivery to the esophagus. In vitro release and the local DTX delivery were studied using in vitro permeation experiments. It was found that DTX and PUS were physically and chemically compatible. The bilayer films exhibited sustained release (>30 days) and minimal DTX permeation through esophageal tissues in vitro. The rate-determining step for the DTX delivery was calculated. It was found that >0.9 fraction of rate control lies with the esophageal tissues, suggesting that DTX delivery can be sustained for longer periods compared to the in vitro release observed. Thus, the bilayer films can be developed as a localized sustained delivery system in combination with the stent.

  13. Non-polymeric coatings to control drug release from metallic coronary stents

    NASA Astrophysics Data System (ADS)

    Gupta, Celia Edith Macias

    Percutaneous transluminal coronary angiography (PTCA) is a procedure used to re-open narrowed coronary arteries. During PTCA, a coronary stent is expanded inside a diseased vessel and serves as a scaffold to keep the artery open. The major drawback of stenting is restenosis---a re-narrowing of the vessel resulting from the hyperproliferation of smooth muscle cells. Drug eluting stents (DES) reduce the rate of restenosis compared to bare metal stents. Paclitaxel (PAT) is commonly used in DES for its ability to prevent restenosis. However, DES have been associated with thrombosis due to the polymer carrier that controls drug delivery. Therefore, there is a need to change the drug delivery mechanisms to eliminate the need of polymers. The goal of this dissertation is to develop a novel polymer-free drug eluting stent that controls drug release using nanoscale metal coatings. The coating was designed to release PAT as the metal slowly degrades in biological conditions. Once all the Paclitaxel has eluted from the surface, the coating will continue to degrade until the final result is a bare metal stent. The results of this study include a novel non-polymeric drug delivery system using nanoscale coatings that release Paclitaxel at a rate similar to commercial stents, as well as the biocompatibility and efficacy of these coatings. The non-polymeric drug delivery system described here achieved a Paclitaxel release profile equivalent to clinically available Paclitaxel-eluting stents and effectively inhibits smooth muscle cell proliferation, thereby completely eliminating the need for polymers to control drug release from coronary stents.

  14. Analysis of the stent expansion in a stenosed artery using finite element method: application to stent versus stent study.

    PubMed

    Imani, S Misagh; Goudarzi, A M; Ghasemi, S E; Kalani, A; Mahdinejad, J

    2014-10-01

    In this article, finite element method is used to investigate the mechanical behavior of a stent and to determine the biomechanical interaction between the stent and the artery in a stenting procedure. The main objective of this study is to reach to a model close to a real condition of coronary stent placement. Unlike most of the models proposed in the literature, all the steps of the deployment of a stent in the stenotic vessel (i.e. pressure increasing, constant load pressure and pressure decreasing) are simulated in this article to show the behavior of the stent in different stages of implantation. The results indicate that the first step of deployment, that is, pressure increasing, plays a main role in the success of stent implantation. So that, in order to compare the behavior of different types of stents, it is sufficient to compare their behavior at the end of pressure increasing step. In order to show the application of the findings in stent versus stent studies, three commercially available stents (the Palmaz-Schatz, Multi-Link and NIR stents) are modeled and their behavior is compared at the end of pressure increasing step. The effect of stent design on the restenosis rate is investigated. According to the findings, the possibility of restenosis is lower for Multi-Link and NIR stents in comparison with Palmaz-Schatz stent which is in good agreement with clinical results. Therefore, the testing methodology outlined here is proposed as a simple and economical alternative for "stent versus stent" complicated clinical trials.

  15. A Double-Layered Covered Biliary Metal Stent for the Management of Unresectable Malignant Biliary Obstruction: A Multicenter Feasibility Study

    PubMed Central

    Park, Jin-Seok; Jeong, Seok; Lee, Don Haeng; Moon, Jong Ho; Lee, Kyu Taek; Dong, Seok Ho

    2016-01-01

    Background/Aims The covered self-expandable metal stent (CMS) was developed to prevent tumor ingrowth-induced stent occlusion during the treatment of malignant biliary obstruction. However, complications such as cholecystitis, pancreatitis, and stent migration can occur after the endoscopic insertion of CMSs. The aim of the present study was to assess the efficacy and safety of a double-layered CMS (DCMS) for the management of malignant bile duct obstruction. Methods DCMSs were endoscopically introduced into 59 patients with unresectable malignant extrahepatic biliary obstruction at four tertiary referral centers, and the patient medical records were retrospectively reviewed. Results Both the technical and functional success rates were 100%. Procedure-related complications including pancreatitis, cholangitis, stent migration, and liver abscess occurred in five patients (8.5%). The median follow-up period was 265 days (range, 31 to 752 days). Cumulative stent patency rates were 68.2% and 40.8% at 6 and 12 months, respectively. At the final follow-up, the rate of stent occlusion was 33.9% (20/59), and the median stent patency period was 276 days (range, 2 to 706 days). Conclusions The clinical outcomes of DCMSs were comparable to the outcomes previously reported for CMSs with respect to stent patency period and complication rates. PMID:27172927

  16. Effect of a novel load-bearing trabecular Nitinol scaffold on rabbit radius bone regeneration

    NASA Astrophysics Data System (ADS)

    Gotman, Irena; Zaretzky, Asaph; Psakhie, Sergey G.; Gutmanas, Elazar Y.

    2015-10-01

    The research aim was to evaluate the bone regeneration capability of novel load-bearing NiTi alloy (Nitinol) scaffolds in a critical-size defect (CSD) model. High strength "trabecular Nitinol" scaffolds were prepared by PIRAC (Powder Immersion Reaction Assisted Coating) annealing of the highly porous Ni foam in Ti powder at 900°C. This was followed by PIRAC nitriding to mitigate the release of potentially toxic Ni ions. Scaffolds phase composition and microstructure were characterized by X-ray diffraction and scanning electron microscopy (SEM/EDS), and their mechanical properties were tested in compression. New Zealand white rabbits received bone defect in right radius and were divided in four groups randomly. In the control group, nothing was placed in the defect. In other groups, NiTi scaffolds were implanted in the defect: (i) as produced, (ii) loaded with bone marrow aspirate (BMA), and (iii) biomimetically CaP-coated. The animals were sacrificed after 12 weeks. The forelimbs with scaffolds were resected, fixed, sectioned and examined in SEM. New bone formation inside the scaffold was studied by EDS analysis and by the processing of backscattered electron images. Bone ingrowth into the scaffold was observed in all implant groups, mostly next to the ulna. New bone formation was strongly enhanced by BMA loading and biomimeatic CaP coating, the bone penetrating as much as 1-1.5 mm into the scaffold. The results of this preliminary study demonstrate that the newly developed high strength trabecular Nitinol scaffolds can be successfully used for bone regeneration in critical size defects.

  17. The Effect of Various Quenchants on the Hardness and Microstructure of 60-NITINOL

    NASA Technical Reports Server (NTRS)

    Thomas, Fransua

    2015-01-01

    The effect of various quenching media on the hardness and microstructure of 60 NITINOL (60 NiTi) were evaluated. Specimens of 60 NiTi were heat treated in air at 1000 degC for 30 min or 2 hr, then quench cooled by one of seven different methods. The microstructure and hardness of this material was examined post heat treatment. The results indicated that the quench method had little effect on the resulting hardness and microstructure of 60 NiTi.

  18. On intrinsic time measure in the modeling of cyclic behavior of a Nitinol cubic block

    NASA Astrophysics Data System (ADS)

    Chiroiu, Veturia; Florinel Ionescu, Marius; Sireteanu, Tudor; Ioan, Rodica; Munteanu, Ligia

    2015-03-01

    In this paper, the cyclic behavior of a superelastic-plastic nitinol cubic block is described by using the Bouc-Wen model coupled to an intrinsic time measure other than clock time, which governs the behavior of the materials. As a consequence, the thermodynamic admissibility of the Bouc-Wen model is provided by the endochronic theory of plasticity. The role of the intrinsic time measure is described by capturing the stiffness and strength degradation and the opposite phenomena. Such behavior is due to the permanent-strain addition of residual martensite and alterations in the properties of the texture during phase transformation.

  19. Cytotoxicity of Metal Ions Released from Nitinol Alloys on Endothelial Cells

    PubMed Central

    Haider, W.; Munroe, N.; Tek, V.; Gill, P.K.S.; Tang, Y.; McGoron, A.J.

    2011-01-01

    Most implantable medical devices are expected to function in the body over an extended period of time. Therefore, immersion tests under simulated conditions can be useful for assessing the amount of metal ions released in situ. In this investigation, dissolved ions from as-received binary and ternary Nitinol alloys in cell culture media were periodically measured under static and dynamic conditions. Endothelial cells were grown in aliquots of culture media obtained and the effect of dissolved ions on cell proliferation and viability of endothelial cells (HUVEC) was studied by cytotoxicity assays. The concentration of metal ions in the media was measured by inductively coupled plasma mass spectrometry. PMID:21666855

  20. Cytotoxicity of Metal Ions Released from Nitinol Alloys on Endothelial Cells

    NASA Astrophysics Data System (ADS)

    Haider, W.; Munroe, N.; Tek, V.; Gill, P. K. S.; Tang, Y.; McGoron, A. J.

    2011-07-01

    Most implantable medical devices are expected to function in the body over an extended period of time. Therefore, immersion tests under simulated conditions can be useful for assessing the amount of metal ions released in situ. In this investigation, dissolved ions from as-received binary and ternary Nitinol alloys in cell culture media were periodically measured under static and dynamic conditions. Endothelial cells were grown in aliquots of culture media obtained and the effect of dissolved ions on cell proliferation and viability of endothelial cells (HUVEC) was studied by cytotoxicity assays. The concentration of metal ions in the media was measured by inductively coupled plasma mass spectrometry.

  1. Surface modification and fatigue behavior of nitinol for load bearing implants

    NASA Astrophysics Data System (ADS)

    Bernard, Sheldon A.

    Musculoskeletal disorders are recognized amongst the most significant human health problems that exist today. Even though considerable research and development has gone towards understanding musculoskeletal disorders, there is still lack of bone replacement materials that are appropriate for restoring lost structures and functions, particularly for load-bearing applications. Many materials on the market today, such as titanium and stainless steel, suffer from significantly higher modulus than natural bone and low bioactivity leading to stress shielding and implant loosening over longer time use. Nitinol (NiTi) is an equiatomic intermetallic compound of nickel and titanium whose unique biomechanical and biological properties contributed to its increasing use as a biomaterial. An innovative method for creating dense and porous net shape NiTi alloy parts has been developed to improve biological properties while maintaining comparable or better mechanical properties than commercial materials that are currently in use. Laser engineered net shaping (LENS(TM)) and surface electrochemistry modification was used to create dense/porous samples and micro textured surfaces on NiTi parts, respectively. Porous implants are known to promote cell adhesion and have a low elastic modulus, a combination that can significantly increase the life of an implant. However, porosity can significantly reduce the fatigue life of an implant, and very little work has been reported on the fatigue behavior of bulk porous metals, specifically on porous nitinol alloy. High-cycle rotating bending and compression-compression fatigue behavior of porous NiTi fabricated using LENS(TM) were studied. In cyclic compression loading, plastic strain increased with increasing porosity and it was evident that maximum strain was achieved during the first 50000 cycles and remained constant throughout the remaining loading. No failures were observed due to loading up to 150% of the yield strength. When subjected

  2. The Development of Carotid Stent Material

    PubMed Central

    He, Dongsheng; Liu, Wenhua; Zhang, Tao

    2015-01-01

    Endovascular angioplasty with stenting is a promising option for treating carotid artery stenosis. There exist a rapidly increasing number of different stent types with different materials. The bare-metal stent is the most commonly used stent with acceptable results, but it leaves us with the problems of thrombosis and restenosis. The drug-eluting stent is a breakthrough as it has the ability to reduce the restenosis rate, but the problem of late thrombosis still has to be addressed. The biodegradable stent disappears after having served its function. However, restenosis and degradation rates remain to be studied. In this article, we review every stent material with its characteristics, clinical results and complications and point out the standards of an ideal carotid stent. PMID:26019710

  3. Angioplasty and stent placement - carotid artery

    MedlinePlus

    Carotid angioplasty and stenting; CAS; Angioplasty - carotid artery; Carotid artery stenosis - angioplasty; ... Carotid angioplasty and stenting (CAS) is done using a small surgical cut. Your surgeon will make a surgical cut ...

  4. Metallic stent in the endoscopic treatment of pancreatic fluid collections

    PubMed Central

    Tozlu, M.; Kocaman, O.; Baysal, B.; Ince, A.; Danalioglu, A.; Kayar, Y.; Senturk, H.

    2014-01-01

    Background and Aims: The endoscopic treatment of pancreatic fluid collections (PFCs) has become the preferred first-line approach. Fully covered self-expandable metal stents (FCSEMS) were considered as an alternative to multiple double pigtail stents. The aim of this study was to evaluate the results of the endosonography guided drainage (EUS-GD) of PFCs with FCEMS. Materials and Methods: A total of 33 consecutive patients were included. Cystogastrostomy and cystoduodenostomy were created with a linear echoendoscope under endosonographic and fluoroscopic control. Procedures were performed in a standard way of, puncture with a 19 gauge needle, bougie dilation and insertion of FCSEMS. Results: A total of 33 patients (mean age 52 years, 21 men, range: 18-77 years), were included. PFCs were 22 non-infected symptomatic pseudocyst and 11 walled-off necrosis or abscess. EUS-GD was successful in 30 (90.9%) patients. Stent insertion failed in one patient. Two patients needed surgery. Complications were observed in 8 (25%) patients (stent dislocation in 3, perforation in 2, bleeding in 2 and pneumoperitoneum in 1 patient). Procedure related mortality was not seen. The mean cyst size was 11.3 cm (5-22). FCSEMS were successful in the treatment of pseudocysts (after 1 month mean cyst size is 6.2 cm, range: 0-15 cm, with 54.8% decrement rate). During a mean follow-up of 15 months complete resolution was 66.6% (20 patients) and recurrence due to stent malfunction was 10%. All these cases were submitted to a new session of endoscopic drainage. Conclusions: EUS-GD, FCSEMS insertion provides an effective, minimally invasive, and safe approach in the management of PFCs. PMID:26425505

  5. Expanded Yegua

    SciTech Connect

    Hart, R.E.; Grayson, S.; Benes, J.

    1988-01-01

    The upper Eocene Yegua Formation expands dramatically across a regional flexure generally 12-15 km wide. During each of several postulated Yegua sea level drops, this flexure became a focal point for deltaic deposition of good to excellent reservoir-quality sands. From the western edge of the Houston salt dome basin to the San Marcos arch, this trend has yielded, since 1982, at least seven noteworthy discoveries: Toro Grande and Lost Bridge fields in Jackson County, and Black Owl, Shanghai, Shanghai East, El Campo, and Phase Four fields in Wharton County, Texas. El Campo field in Wharton County, Texas, was discovered in December 1985 by Ladd Petroleum Corporation with the drilling of the Ladd Petroleum 1 Popp well. Mud logs acquired while drilling indicated that a very sandy reservoir, with encouraging quantities of natural gas and condensate had been encountered. Subsequent open-hold logging generated more questions than answers about the prospective sand section. Additional open hole logs (EPT/ML,SHDT) were run to identify what turned out to be an extremely laminated sand-shale sequence over 400 ft thick. Subsequent development drilling and the acquisition of a 120 ft whole core provided valuable data in analyzing this prolific, geopressured natural gas and condensate Yegua reservoir. Whole-core data, open-hole logs, and computer logs were integrated to develop petro-physical evaluation procedures and to determine the environment of deposition. El Campo field is believed to represent an extremely thick, delta front slope to distal delta front facies.

  6. Impact of Stent Design on In-Stent Stenosis in a Rabbit Iliac Artery Model

    SciTech Connect

    Sommer, C. M. Grenacher, L.; Stampfl, U.; Arnegger, F. U.; Rehnitz, C.; Thierjung, H.; Stampfl, S.; Berger, I.; Richter, G. M.; Kauczor, H. U.; Radeleff, B. A.

    2010-06-15

    The purpose of this study was to evaluate the impact of stent design on in-stent stenosis in rabbit iliac arteries. Four different types of stent were implanted in rabbit iliac arteries, being different in stent design (crown or wave) and strut thickness (50 or 100 {mu}m). Ten stents of each type were implanted. Each animal received one crown and one wave stent with the same strut thickness. Follow-up was either 12 weeks (n = 10 rabbits) or 24 weeks (n = 10 rabbits). Primary study end points were angiographic and microscopic in-stent stenosis. Secondary study end points were vessel injury, vascular inflammation, and stent endothelialization. Average stent diameter, relative stent overdilation, average and minimal luminal diameter, and relative average and maximum luminal loss were not significantly different. However, a trend to higher relative stent overdilation was recognized in crown stents compared to wave stents. A trend toward higher average and minimal luminal diameter and lower relative average and maximum luminal loss was recognized in crown stents compared to wave stents with a strut thickness of 100 {mu}m. Neointimal height, relative luminal area stenosis, injury score, inflammation score, and endothelialization score were not significantly different. However, a trend toward higher neointimal height was recognized in crown stents compared to wave stents with a strut thickness of 50 {mu}m and a follow-up of 24 weeks. In conclusion, in this study, crown stents seem to trigger neointima. However, the optimized radial force might equalize the theoretically higher tendency for restenosis in crown stents. In this context, also more favorable positive remodeling in crown stents could be important.

  7. New Scopes, New Accessories, New Stents for Interventional Endoscopic Ultrasound

    PubMed Central

    Chapman, Christopher G.; Siddiqui, Uzma D.

    2016-01-01

    Technological advances have rapidly expanded the therapeutic potential of endoscopic ultrasound (EUS). Innovations in stent technology; directed adjunctive therapy for pancreatic tumors, including radiofrequency ablation and fiducial marker placement; advanced imaging modalities, including needle-based confocal laser endomicroscopy; and new echoendoscopes, such as the forward-viewing linear echoendoscope, are emerging as safe and effective tools and devices for providing a broad range of treatments and therapies previously not thought possible. In this review, we summarize and discuss the new echoendoscopes, accessories, and stents for interventional EUS and highlight the recent literature on technical and therapeutic efficacy. The therapeutic role and indications for EUS are rapidly evolving well beyond its current limits as new EUS-specific designed tools are designed, and ultimately, should help achieve the goal of improving patient outcomes. PMID:26855923

  8. Transient Hemolytic Anemia after Transjugular Intrahepatic Portosystemic Stent Shunt

    PubMed Central

    Garcia-Rebollo, Sagrario; Santolaria-Fernández, Francisco; Diaz-Romero, Francisco; Rodriguez-Moreno, Fermin; Martinez-Riera, Antonio

    1996-01-01

    Management of variceal bleeding secondary to portal hypertension constitutes a challenging issue, particularly in child's C cirrhotic patients. Recently, transjugular placement of self-expanding metallic stents in the liver (TIPS), creating a shunt between the portal and hepatic branches has provided a safe and promising therapeutic approach in this clinical situation. We report here the case of a 66-year-old male cirrhotic patient who developed a moderately severe clinical picture of a Coombsnegative hemolytic anemia (serum hemoglobin, 93 g/l, serum bilirubin 160.74 umol/L (9.4 mg/dl), indirect 6.3 mg/dl (107.73 umol/L); serum LDH 1220 u/l, reticulocytes, 5.1%. serum ferritin, 1221 ug/1, schistocytes in peripheral blood smear) the week after undergoing a TIPS, suggesting the development ofa microangiopathic hemolytic anaemia secondary to red blood cell disruption by passing through the metallic network of the stent. PMID:8809588

  9. New Scopes, New Accessories, New Stents for Interventional Endoscopic Ultrasound.

    PubMed

    Chapman, Christopher G; Siddiqui, Uzma D

    2016-01-01

    Technological advances have rapidly expanded the therapeutic potential of endoscopic ultrasound (EUS). Innovations in stent technology; directed adjunctive therapy for pancreatic tumors, including radiofrequency ablation and fiducial marker placement; advanced imaging modalities, including needle-based confocal laser endomicroscopy; and new echoendoscopes, such as the forward-viewing linear echoendoscope, are emerging as safe and effective tools and devices for providing a broad range of treatments and therapies previously not thought possible. In this review, we summarize and discuss the new echoendoscopes, accessories, and stents for interventional EUS and highlight the recent literature on technical and therapeutic efficacy. The therapeutic role and indications for EUS are rapidly evolving well beyond its current limits as new EUS-specific designed tools are designed, and ultimately, should help achieve the goal of improving patient outcomes. PMID:26855923

  10. New Scopes, New Accessories, New Stents for Interventional Endoscopic Ultrasound.

    PubMed

    Chapman, Christopher G; Siddiqui, Uzma D

    2016-01-01

    Technological advances have rapidly expanded the therapeutic potential of endoscopic ultrasound (EUS). Innovations in stent technology; directed adjunctive therapy for pancreatic tumors, including radiofrequency ablation and fiducial marker placement; advanced imaging modalities, including needle-based confocal laser endomicroscopy; and new echoendoscopes, such as the forward-viewing linear echoendoscope, are emerging as safe and effective tools and devices for providing a broad range of treatments and therapies previously not thought possible. In this review, we summarize and discuss the new echoendoscopes, accessories, and stents for interventional EUS and highlight the recent literature on technical and therapeutic efficacy. The therapeutic role and indications for EUS are rapidly evolving well beyond its current limits as new EUS-specific designed tools are designed, and ultimately, should help achieve the goal of improving patient outcomes.

  11. Fluid mechanics in stented arterial model

    NASA Astrophysics Data System (ADS)

    Bernad, S. I.; Totorean, A.; Bosioc, A.; Crainic, N.; Hudrea, C.; Bernad, E. S.

    2015-12-01

    Local hemodynamic factors are known affect the natural history of the restenosis critically after coronary stenting of atherosclerosis. Stent-induced flows disturbance magnitude dependent directly on the strut design. Strut shape, strut thickness and the distance between consecutive struts have been associated clinically with the with post-intervention clinical outcomes. Hemodynamically favorable designs according to computational modeling can reduced in-stent restenosis after coronary stenting intervention.

  12. Repositioning of Covered Stents: The Grip Technique

    SciTech Connect

    Kirby, John Martin; Guo Xiaofeng; Midia, Mehran

    2011-06-15

    Introduction: Retrieval and repositioning of a stent deployed beyond its intended target region may be a difficult technical challenge. Materials and Methods: A balloon-mounted snare technique, a variant of the coaxial loop snare technique, is described. Results: The technique is described for the repositioning of a covered transjugular intrahepatic portosystemic shunt stent and a covered biliary stent. Conclusion: The balloon-mounted snare technique is a useful technique for retrieval of migrated stents.

  13. Carotid Artery Stenting versus Endarterectomy

    PubMed Central

    Gahremanpour, Amir; Perin, Emerson C.; Silva, Guilherme

    2012-01-01

    For about 2 decades, investigators have been comparing carotid endarterectomy with carotid artery stenting in regard to their effectiveness and safety in treating carotid artery stenosis. We conducted a systematic review to summarize and appraise the available evidence provided by randomized trials, meta-analyses, and registries comparing the clinical outcomes of the 2 procedures. We searched the MEDLINE, SciVerse Scopus, and Cochrane databases and the bibliographies of pertinent textbooks and articles to identify these studies. The results of clinical trials and, consequently, the meta-analyses of those trials produced conflicting results regarding the comparative effectiveness and safety of carotid endarterectomy and carotid stenting. These conflicting results arose because of differences in patient population, trial design, outcome measures, and variability among centers in the endovascular devices used and in operator skills. Careful appraisal of the trials and meta-analyses, particularly the most recent and largest National Institutes of Healthsponsored trial (the Carotid Revascularization Endarterectomy vs Stenting Trial [CREST]), showed that carotid stenting and endarterectomy were associated with similar rates of death and disabling stroke. Within the 30-day periprocedural period, carotid stenting was associated with higher risks of stroke, especially for patients aged >70 years, whereas carotid endarterectomy was associated with a higher risk of myocardial infarction. The slightly higher cost of stenting compared with endarterectomy was within an acceptable range by cost-effectiveness standards. We conclude that carotid artery stenting is an equivalent alternative to carotid endarterectomy when patient age and anatomy, surgical risk, and operator experience are considered in the choice of treatment approach. PMID:22949763

  14. Percutaneous Endovascular Stent-Graft for Iliac Pseudoaneurysm Following Lumbar Discectomy

    SciTech Connect

    Hong, Seong J.; Oh, Joo H.; Yoon, Yup

    2000-11-15

    In a 24-year-old woman, an iliac pseudoaneurysm following lumbar discectomy was successfully treated by percutaneous placement of a self-expanding stent-graft. A postprocedural angiogram demonstrated complete exclusion of the pseudoaneurysm without leakage of contrast agent.

  15. Knotted stents: Case report and outcome analysis

    PubMed Central

    Lee, Ha Na; Hwang, Hokyeong

    2015-01-01

    A knotted ureteral stent is an extremely rare condition, with fewer than 20 cases reported in the literature; however, it is difficult to treat. We report a case in which a folded Terumo guidewire was successfully used to remove a knotted stent percutaneously without anesthesia. We also review the current literature on predisposing factors and management strategies for knotted ureteral stents. PMID:25964843

  16. 21 CFR 884.3900 - Vaginal stent.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Vaginal stent. 884.3900 Section 884.3900 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES... stent. (a) Identification. A vaginal stent is a device used to enlarge the vagina by stretching, or...

  17. 21 CFR 884.3900 - Vaginal stent.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Vaginal stent. 884.3900 Section 884.3900 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES... stent. (a) Identification. A vaginal stent is a device used to enlarge the vagina by stretching, or...

  18. 21 CFR 884.3900 - Vaginal stent.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Vaginal stent. 884.3900 Section 884.3900 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES... stent. (a) Identification. A vaginal stent is a device used to enlarge the vagina by stretching, or...

  19. 21 CFR 884.3900 - Vaginal stent.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Vaginal stent. 884.3900 Section 884.3900 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES... stent. (a) Identification. A vaginal stent is a device used to enlarge the vagina by stretching, or...

  20. Rotational Atherectomy of Three Overlapping Stent Layers.

    PubMed

    Frisoli, Tiberio M; Friedman, Harold; O'Neill, William W

    2016-09-01

    A patient was referred to us for Canadian Cardiovascular Society class III refractory angina. He was found to have in-stent restenosis within three layers of underexpanded stents implanted in 2004, 2011, and 2014. Rotational atherectomy safely yielded stent strut ablation (reduced to one layer), lesion expansion, and very good angiographic and physiologic results. PMID:27591692

  1. 21 CFR 884.3900 - Vaginal stent.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Vaginal stent. 884.3900 Section 884.3900 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES... stent. (a) Identification. A vaginal stent is a device used to enlarge the vagina by stretching, or...

  2. Therapies targeting inflammation after stent implantation.

    PubMed

    Okura, Hiroyuki; Takagi, Tsutomu; Yoshida, Kiyoshi

    2013-07-01

    Since the introduction of coronary vessel scaffold by metallic stent, percutaneous coronary intervention has become widely performed all over the world. Although drug-eluting stent technology has further decrease the incidence of in-stent restenosis, there still remaining issues related to stent implantation. Vessel inflammation is one of the causes that may be related to stent restenosis as well as stent thrombosis. Therefore, systemic therapies targeting inflammation emerged as adjunctive pharmacological intervention to improve outcome. Statins, corticosteroids, antiplatelets, and immunosuppresive or anti-cancer drugs are reported to favorably impact outcome after bare-metal stent implantation. In type 2 diabetic patients, pioglitazone may be the most promising drug that can lower neointimal proliferation and, as a result, lower incidence of restenosis and target lesion revascularization. On the other hand, several new stent platforms that might decrease inflammatory response after drug-eluting stent implantation have been introduced. Because durable polymer used in the first generation drug-eluting stents are recognized to be responsible for unfavorable vessel response, biocompatible or bioabsorbable polymer has been introduce and already used clinically. Furthermore, polymer-free drug-eluting stent and bioresorbable scaffold are under investigation. Although vessel inflammation may be reduced by using these new drug-eluting stents or scaffold, long-term impact needs to be investigated further. PMID:23905635

  3. Hemodynamics in coronary arteries with overlapping stents.

    PubMed

    Rikhtegar, Farhad; Wyss, Christophe; Stok, Kathryn S; Poulikakos, Dimos; Müller, Ralph; Kurtcuoglu, Vartan

    2014-01-22

    Coronary artery stenosis is commonly treated by stent placement via percutaneous intervention, at times requiring multiple stents that may overlap. Stent overlap is associated with increased risk of adverse clinical outcome. While changes in local blood flow are suspected to play a role therein, hemodynamics in arteries with overlapping stents remain poorly understood. In this study we analyzed six cases of partially overlapping stents, placed ex vivo in porcine left coronary arteries and compared them to five cases with two non-overlapping stents. The stented vessel geometries were obtained by micro-computed tomography of corrosion casts. Flow and shear stress distribution were calculated using computational fluid dynamics. We observed a significant increase in the relative area exposed to low wall shear stress (WSS<0.5 Pa) in the overlapping stent segments compared both to areas without overlap in the same samples, as well as to non-overlapping stents. We further observed that the configuration of the overlapping stent struts relative to each other influenced the size of the low WSS area: positioning of the struts in the same axial location led to larger areas of low WSS compared to alternating struts. Our results indicate that the overlap geometry is by itself sufficient to cause unfavorable flow conditions that may worsen clinical outcome. While stent overlap cannot always be avoided, improved deployment strategies or stent designs could reduce the low WSS burden.

  4. Automated detection of a prostate Ni-Ti stent in electronic portal images

    SciTech Connect

    Carl, Jesper; Nielsen, Henning; Nielsen, Jane; Lund, Bente; Larsen, Erik Hoejkjaer

    2006-12-15

    Planning target volumes (PTV) in fractionated radiotherapy still have to be outlined with wide margins to the clinical target volume due to uncertainties arising from daily shift of the prostate position. A recently proposed new method of visualization of the prostate is based on insertion of a thermo-expandable Ni-Ti stent. The current study proposes a new detection algorithm for automated detection of the Ni-Ti stent in electronic portal images. The algorithm is based on the Ni-Ti stent having a cylindrical shape with a fixed diameter, which was used as the basis for an automated detection algorithm. The automated method uses enhancement of lines combined with a grayscale morphology operation that looks for enhanced pixels separated with a distance similar to the diameter of the stent. The images in this study are all from prostate cancer patients treated with radiotherapy in a previous study. Images of a stent inserted in a humanoid phantom demonstrated a localization accuracy of 0.4-0.7 mm which equals the pixel size in the image. The automated detection of the stent was compared to manual detection in 71 pairs of orthogonal images taken in nine patients. The algorithm was successful in 67 of 71 pairs of images. The method is fast, has a high success rate, good accuracy, and has a potential for unsupervised localization of the prostate before radiotherapy, which would enable automated repositioning before treatment and allow for the use of very tight PTV margins.

  5. Fully Covered Metallic Stents for the Treatment of Benign Airway Stenosis

    PubMed Central

    Ocak, Sebahat; Gourdin, Maximilien; d'Odémont, Jean-Paul

    2016-01-01

    Introduction. We herein report our experience with new fully covered self-expanding metallic stents in the setting of inoperable recurrent benign tracheobronchial stenosis. Methods. Between May 2010 and July 2014, 21 Micro-Tech® FC-SEMS (Nanjing Co., Republic of Korea) were placed in our hospital in 16 patients for inoperable, recurrent (after dilatation), and symptomatic benign airway stenosis. Their medical files were retrospectively reviewed in December 2014, with focus on stent's tolerance and durability data. Results. Twenty-one stents were inserted: 13 for posttransplant left main bronchus anastomotic stricture, seven for postintubation tracheal stenosis, and one for postlobectomy anastomotic stricture. Positioning was easy for all of them. Stents were in place for a mean duration of 282 days. The most common complications were granulation tissue development (35%), migration (30%), and sputum retention (15%). Fifty-five % of the stents (11/20) had to be removed because of various complications, without difficulty for all of them. None of the patients had life-threatening complications. Conclusion. Micro-Tech FC-SEMS were easy to position and to remove. While the rate of complications requiring stent removal was significant, no life-threatening complication occurred. Further studies are needed to better define their efficacy and safety in the treatment of benign airway disease. PMID:27777507

  6. Effect of Slip Time in Forming Neo-Esophageal Stenosis After Replacement of a Thoracic Esophagus With Nitinol Artificial Esophagus.

    PubMed

    Liang, Xian-Liang; Liang, Jian-Hui

    2015-07-01

    Attempts have been made to investigate the effect of slip time of nitinol artificial esophagus for forming neo-esophageal stenosis after replacement of a thoracic esophagus with nitinol artificial esophagus in 20 experimental pigs. The pigs whose slip time was less than 90 days postoperatively had severe dysphagia (Bown's III) immediately after they were fed, and the dysphagia aggravated gradually later on (Bown's III-IV). The pigs whose slip time was more than 90 days postoperatively had mild/moderate dysphagia (Bown's I-II) immediately after they were fed, and the dysphagia relieved gradually later on (Bown's II-I-0). The ratios between the diameter of neo-esophagus in different slip time and normal esophagus were 25% (at 2 months postoperatively), 58% (at 4 months postoperatively), and 93% (at 6 months postoperatively), respectively. The relationship between nitinol artificial esophagus slip time and neo-esophageal stenosis showed a positive correlation. After replacement of a thoracic esophagus with nitinol artificial esophagus, the artificial esophageal slip time not only affected the original diameter of the neo-esophagus immediately, but also affected the neo-esophageal scar stricture forming process later on. The narrowing of neo-esophagus is caused by overgrowth of scar tissue. But there is the positive correlation between artificial esophagus slip time and neo-esophageal stenosis, so this can be a way of overcoming neo-esophageal stenosis by delaying slip time of artificial esophagus.

  7. a Study of the Effect of Potting Voids on the Fragmentation of AN Explosively Driven Nitinol Shell

    NASA Astrophysics Data System (ADS)

    Mukerji, R. J.; Myers, S. A.; Whiteman, G.

    2007-12-01

    An experiment was assembled to observe the effect of potting voids on the fragmentation of a Nitinol shell. The Nitinol shell was subjected to shock loading using a high explosive (HE) drive such that it would experience a near biaxial expansion. In between the HE and Nitinol was positioned a 0.5 mm thick layer of potting (Sylgard 184), in which two circular voids were sectioned, (⌀ 11.1 mm and ⌀ 19.1 mm). It was observed that as the shock wave sweeps across the coupon from the centre to the edge, the potting voids cause premature fracture of the Nitinol on the outer most point from detonation. The coupon then proceeds to fracture around the void from this point. It is believed that this was due to the build up of detonation products on the outer edge of the void. In addition, a strong effect on the orientation of the fragments was also noticed. This is believed to be due to the directional rolling of the material prior to it being pressed into the coupon imposing an anisotropy on the micro-structure of the material.

  8. A study of the effect of potting voids on the fragmentation of an explosively driven Nitinol Shell.

    NASA Astrophysics Data System (ADS)

    Mukerji, Robin; Myers, Sam; Whiteman, Glenn

    2007-06-01

    An experimental geometry was designed to determine the effect of potting voids on the fragmentation of a Nitinol ( Ni 55% Ti 45%) Shell. The nitinol shell was subjected to a shock loading using a HE drive such that it would experience an near bi-axial expansion. The region between the HE and the nitinol was filed with a thin layer of potting (Sylgard 184 elastomer), in which two circular voids were positioned. Presented here and results from high speed framing camera and flash x-radiography that were recorded. It was observed that as the shock wave sweeps across the coupon from the centre to the edge, the potting voids cause premature fracture of the nitinol on the outer most point from detonation. The coupon then proceeded to fracture around the void from this point. It is believed that this was due to the build up of detonation products on the outer edge of the void. In addition, a strong effect of the orientation of the fragments was also noticed. This was believed to be due to the directional rolling of the material prior to it being pressed into the coupon.

  9. Wireless implantable chip with integrated nitinol-based pump for radio-controlled local drug delivery.

    PubMed

    Fong, Jeffrey; Xiao, Zhiming; Takahata, Kenichi

    2015-02-21

    We demonstrate an active, implantable drug delivery device embedded with a microfluidic pump that is driven by a radio-controlled actuator for temporal drug delivery. The polyimide-packaged 10 × 10 × 2 mm(3) chip contains a micromachined pump chamber and check valves of Parylene C to force the release of the drug from a 76 μL reservoir by wirelessly activating the actuator using external radio-frequency (RF) electromagnetic fields. The rectangular-shaped spiral-coil actuator based on nitinol, a biocompatible shape-memory alloy, is developed to perform cantilever-like actuation for pumping operation. The nitinol-coil actuator itself forms a passive 185 MHz resonant circuit that serves as a self-heat source activated via RF power transfer to enable frequency-selective actuation and pumping. Experimental wireless operation of fabricated prototypes shows successful release of test agents from the devices placed in liquid and excited by radiating tuned RF fields with an output power of 1.1 W. These tests reveal a single release volume of 219 nL, suggesting a device's capacity of ~350 individual ejections of drug from its reservoir. The thermal behavior of the activated device is also reported in detail. This proof-of-concept prototype validates the effectiveness of wireless RF pumping for fully controlled, long-lasting drug delivery, a key step towards enabling patient-tailored, targeted local drug delivery through highly miniaturized implants. PMID:25473933

  10. Wireless implantable chip with integrated nitinol-based pump for radio-controlled local drug delivery.

    PubMed

    Fong, Jeffrey; Xiao, Zhiming; Takahata, Kenichi

    2015-02-21

    We demonstrate an active, implantable drug delivery device embedded with a microfluidic pump that is driven by a radio-controlled actuator for temporal drug delivery. The polyimide-packaged 10 × 10 × 2 mm(3) chip contains a micromachined pump chamber and check valves of Parylene C to force the release of the drug from a 76 μL reservoir by wirelessly activating the actuator using external radio-frequency (RF) electromagnetic fields. The rectangular-shaped spiral-coil actuator based on nitinol, a biocompatible shape-memory alloy, is developed to perform cantilever-like actuation for pumping operation. The nitinol-coil actuator itself forms a passive 185 MHz resonant circuit that serves as a self-heat source activated via RF power transfer to enable frequency-selective actuation and pumping. Experimental wireless operation of fabricated prototypes shows successful release of test agents from the devices placed in liquid and excited by radiating tuned RF fields with an output power of 1.1 W. These tests reveal a single release volume of 219 nL, suggesting a device's capacity of ~350 individual ejections of drug from its reservoir. The thermal behavior of the activated device is also reported in detail. This proof-of-concept prototype validates the effectiveness of wireless RF pumping for fully controlled, long-lasting drug delivery, a key step towards enabling patient-tailored, targeted local drug delivery through highly miniaturized implants.

  11. Rotary-bending fatigue characteristics of medical-grade Nitinol wire.

    PubMed

    Pelton, A R; Fino-Decker, J; Vien, L; Bonsignore, C; Saffari, P; Launey, M; Mitchell, M R

    2013-11-01

    The rotary bending fatigue properties of medical-grade Nitinol wires were investigated under conditions of 0.5-10% strain amplitudes to a maximum of 10(7) cycles. The results from this study provide insight into the behavior of Nitinol under fully reversed (εmin/εmax=-1) fatigue conditions for three compositions, two surface conditions and three test temperatures. For pseudoelastic conditions there are four distinct regions of the strain-cycle curves that are related to phases (austenite, stress-induced martensite, and R-Phase) and their respective strain accommodation mechanisms. In contrast, there are only two regions for the strain-cycle curves for thermal martensite. It was further observed that the strain amplitude to achieve 10(7)-cycles increases with both decreasing test temperature and increasing transformation temperature. Fatigue behavior was not, however, strongly influenced by wire surface condition. SEM of the fracture surfaces showed that the fatigue fracture area increased with decreasing strain amplitude. Finite element analysis was used to illustrate strain distributions across the wire as well as to calculate the tension-compression contributions to the rotary bending curves. The results from this investigation are discussed with respect to mechanisms of strain accommodation under cyclic tensile and compressive conditions. PMID:23838356

  12. Rotary-bending fatigue characteristics of medical-grade Nitinol wire.

    PubMed

    Pelton, A R; Fino-Decker, J; Vien, L; Bonsignore, C; Saffari, P; Launey, M; Mitchell, M R

    2013-11-01

    The rotary bending fatigue properties of medical-grade Nitinol wires were investigated under conditions of 0.5-10% strain amplitudes to a maximum of 10(7) cycles. The results from this study provide insight into the behavior of Nitinol under fully reversed (εmin/εmax=-1) fatigue conditions for three compositions, two surface conditions and three test temperatures. For pseudoelastic conditions there are four distinct regions of the strain-cycle curves that are related to phases (austenite, stress-induced martensite, and R-Phase) and their respective strain accommodation mechanisms. In contrast, there are only two regions for the strain-cycle curves for thermal martensite. It was further observed that the strain amplitude to achieve 10(7)-cycles increases with both decreasing test temperature and increasing transformation temperature. Fatigue behavior was not, however, strongly influenced by wire surface condition. SEM of the fracture surfaces showed that the fatigue fracture area increased with decreasing strain amplitude. Finite element analysis was used to illustrate strain distributions across the wire as well as to calculate the tension-compression contributions to the rotary bending curves. The results from this investigation are discussed with respect to mechanisms of strain accommodation under cyclic tensile and compressive conditions.

  13. In Situ Neutron Diffraction Studies of Increasing Tension Strains of Superelastic Nitinol

    NASA Astrophysics Data System (ADS)

    Pelton, Alan R.; Clausen, Bjørn; Stebner, Aaron P.

    2015-09-01

    A micromechanical study of the effect of varying amounts of tensile strains on the microstructures and subsequent mechanical behaviors of superelastic Nitinol rods is presented. It is found that strains up to ~8-9 % develop microstructures that assist both forward and reverse transformation relative to un-strained material. This superelastic phenomenon is explained to be analogous to two-way shape memory effect in Nitinol actuation materials. These results provide understanding as to why such "pre-strains" may lead to improvements in subsequent superelastic fatigue life. Beyond 9 %, a drastic change is observed, as large amounts of martensite (75 % and more) are retained in unloaded samples. Thus, a competition between transformation, plasticity, and reorientation is found to give rise to microstructures that inhibit complete transformation. Furthermore, even though similar inelastic strain magnitudes are observed in loading and unloading plateaus, micromechanical mechanisms differ substantially from samples with less pre-strain. For example, in highly pre-strained samples at least half of the plateau strains are due to martensite reorientation, whereas, in low and moderately pre-strained samples nearly the entirety of the plateau strain is due to transformation. We also find that latent heat of plastic flow is larger than latent heat of transformation.

  14. Geometrical deployment for braided stent.

    PubMed

    Bouillot, Pierre; Brina, Olivier; Ouared, Rafik; Yilmaz, Hasan; Farhat, Mohamed; Erceg, Gorislav; Lovblad, Karl-Olof; Vargas, Maria Isabel; Kulcsar, Zsolt; Pereira, Vitor Mendes

    2016-05-01

    The prediction of flow diverter stent (FDS) implantation for the treatment of intracranial aneurysms (IAs) is being increasingly required for hemodynamic simulations and procedural planning. In this paper, a deployment model was developed based on geometrical properties of braided stents. The proposed mathematical description is first applied on idealized toroidal vessels demonstrating the stent shortening in curved vessels. It is subsequently generalized to patient specific vasculature predicting the position of the filaments along with the length and local porosity of the stent. In parallel, in-vitro and in-vivo FDS deployments were measured by contrast-enhanced cone beam CT (CBCT) in idealized and patient-specific geometries. These measurements showed a very good qualitative and quantitative agreement with the virtual deployments and provided experimental validations of the underlying geometrical assumptions. In particular, they highlighted the importance of the stent radius assessment in the accuracy of the deployment prediction. Thanks to its low computational cost, the proposed model is potentially implementable in clinical practice providing critical information for patient safety and treatment outcome assessment. PMID:26891065

  15. An Assessment of Radiologically Inserted Transoral and Transgastric Gastroduodenal Stents to Treat Malignant Gastric Outlet Obstruction

    SciTech Connect

    Miller, Bethany H. T.; Griffiths, Ewen A.; Pursnani, Kishore G. Ward, Jeremy B.; Stockwell, Robert C.

    2013-12-15

    IntroductionSelf-expanding metallic stents (SEMS) are used to palliate malignant gastric outlet obstruction (GOO) and are useful in patients with limited life expectancy or severe medical comorbidity, which would preclude surgery. Stenting can be performed transorally or by a percutaneous transgastric technique. Our goal was to review the outcome of patients who underwent radiological SEMS insertion performed by a single consultant interventional radiologist. Methods: Patients were identified from a prospectively collected database held by one consultant radiologist. Data were retrieved from radiological reports, multidisciplinary team meetings, and the patients' case notes. Univariate survival analysis was performed. Results: Between December 2000 and January 2011, 100 patients (63 males, 37 females) had 110 gastroduodenal stenting procedures. Median age was 73 (range 39-89) years. SEMS were inserted transorally (n = 66) or transgastrically (n = 44). Site of obstruction was the stomach (n = 37), duodenum (n = 50), gastric pull-up (n = 10), or gastroenterostomy (n = 13). Seven patients required biliary stents. Technical success was 86.4 %: 83.3 % for transoral insertion, 90.9 % for transgastric insertion. Eleven patients developed complications. Median GOO severity score: 1 pre-stenting, 2 post-stenting (p = 0.0001). Median survival was 54 (range 1-624) days. Post-stenting GOO severity score was predictive of survival (p = 0.0001). Conclusions: The technical success rate for insertion of palliative SEMS is high. Insertional technique can be tailored to the individual depending on the location of the tumor and whether it is possible to access the stomach percutaneously. Patients who have successful stenting and return to eating a soft/normal diet have a statistically significant increase in survival.

  16. "Virtual" in-vivo bench test for bifurcation stenting with "StentBoost".

    PubMed

    Agostoni, Pierfrancesco; Verheye, Stefan; Vermeersch, Paul; Cornelis, Kristoff; Van Langenhove, Glenn

    2009-04-01

    "StentBoost" is a new angiographic technique that allows improved angiographic visualization of stents deployed in coronary arteries, by enhancing the X-ray focus of the region where the stent is placed. Using this technique we were able to assess the deformation and the expansion of a stent deployed to treat a bifurcation lesion between the mid-left anterior descending (LAD) artery and a big second diagonal branch, during sequential inflations of: (1) the stent per se in the LAD, (2) the ostium of the diagonal branch through the stent struts, (3) the stent again with a non compliant balloon, and (4) both branches with the kissing balloon technique. "StentBoost" guided our clinical and angiographic decision-making process and allowed us to create a "virtual" bench test of the stent deployed at the level of the bifurcation treated.

  17. Advances in helical stent design and fabrication thermal treatment and structural interaction studies of the simulated plaque-laden artery

    NASA Astrophysics Data System (ADS)

    Welch, Tre Raymond

    Advancements in processing biomaterials have lead to the development of bioresorbable PLLA drug-loaded stents with different geometric configurations. To further advance the technology, systematic studies have been carried out. This dissertation consists of five specific aims: (1) To characterize the effects of thermal annealing on the mechanical characteristics of PLLA helical stent, (2) To characterize the mechanical characteristics of a PLLA double helix stent, (3) To characterize the physical and chemical properties of PLLA films impregnated with niacin and curcumin, (4) To characterize the mechanical interaction of expanded stent and vascular wall with both model simulation and experimental studies using PDMS phantom arteries, (5) To simulate the stent-plaque-artery interactions using computer models. Results and their significances in bioresorbable PLLA drug-loaded stents technology as well as clinical prospects will be presented. For Aim1, thermal annealing is shown to improve mechanical characteristics of the helical stent, including pressure-diameter response curves, incremental stiffness, and collapse pressure. Differential scanning calorimetric analysis of stent fiber reveals that thermal annealing contribute to increased percent crystallinity, thus enhanced mechanical characteristics of the stent. For Aim 2, the new double helix design was shown to leads to improved mechanical characteristics of stent, including pressure-diameter response curves, incremental stiffness, and collapse pressure. Further, it was found to lead to an increased percent crystallinity and reduced degradation rate. For Aim 3, the changes in mechanical properties, crystallinity in PLLA polymer loaded with curcumin, or niacin, or both from that of control are clearly delineated. Results from Aim 4 shed lights on the mechanical disturbance in the vicinity of deployed stent and vascular wall as well as the abnormal shear stresses on the vascular endothelium. Their implications in

  18. Percutaenous mitral valve: A non-stented coronary sinus device for the treatment of functional mitral regurgitation in heart failure patients.

    PubMed

    Sack, Stefan; Kahlert, Philipp; Erbel, Raimund

    2009-01-01

    Functional mitral regurgitation in heart failure limits survival in a severity-graded fashion. Even mild mitral regurgitation doubles mortality risk. We report the use of a non-stented coronary sinus device to reduce mitral annulus dimension in order to re-establish mitral valve competence. The device (PTMA, Viacor, Inc., Wilmington, MA, USA) consists of a multi-lumen PTFE (Teflon) PTMA catheter in which Nitinol (nickel-titanium alloy) treatment rods are advanced. For individual use up to three rods of different length and stiffness can be used. Therefore dimension reduction can be performed in an incremental fashion. Fluoroscopy and 3 D echocardiography are performed throughout the procedure to visiualize the positioning and confirm maximum treatment effect. The case describes the use and the effect of PTMA treatment. Safety and efficacy of the PTMA device will be investigated in the upcoming PTOLEMY 2 trial.

  19. Percutaenous mitral valve: A non-stented coronary sinus device for the treatment of functional mitral regurgitation in heart failure patients.

    PubMed

    Sack, Stefan; Kahlert, Philipp; Erbel, Raimund

    2009-01-01

    Functional mitral regurgitation in heart failure limits survival in a severity-graded fashion. Even mild mitral regurgitation doubles mortality risk. We report the use of a non-stented coronary sinus device to reduce mitral annulus dimension in order to re-establish mitral valve competence. The device (PTMA, Viacor, Inc., Wilmington, MA, USA) consists of a multi-lumen PTFE (Teflon) PTMA catheter in which Nitinol (nickel-titanium alloy) treatment rods are advanced. For individual use up to three rods of different length and stiffness can be used. Therefore dimension reduction can be performed in an incremental fashion. Fluoroscopy and 3 D echocardiography are performed throughout the procedure to visiualize the positioning and confirm maximum treatment effect. The case describes the use and the effect of PTMA treatment. Safety and efficacy of the PTMA device will be investigated in the upcoming PTOLEMY 2 trial. PMID:19431068

  20. Stenting in Malignant Biliary Obstruction.

    PubMed

    Almadi, Majid A; Barkun, Jeffrey S; Barkun, Alan N

    2015-10-01

    Decompression of the biliary system in patients with malignant biliary obstruction has been widely accepted and implemented as part of the care. Despite a wealth of literature, there remains a significant amount of uncertainty as to which approach would be most appropriate in different clinical settings. This review covers stenting of the biliary system in cases of resectable or palliative malignant biliary obstruction, potential candidates for biliary drainage, technical aspects of the procedure, as well as management of biliary stent dysfunction. Furthermore, periprocedural considerations including proper mapping of the location of obstruction and the use of antibiotics are addressed.

  1. Ureteral Stent Coatings: What's Here and What's Coming

    NASA Astrophysics Data System (ADS)

    Razvi, Hassan

    2008-09-01

    Ureteral stents have become an indispensable tool to the urologist in the management of various disorders afflicting the urinary tract. While the ideal stent remains elusive, novel technical advances in stent coating technology offer the potential of enhancing stent biocompatibility and clinical application. Currently available stent coatings as well as new and emerging devices will be reviewed.

  2. Drug eluting biliary stents to decrease stent failure rates: A review of the literature

    PubMed Central

    Shatzel, Joseph; Kim, Jisoo; Sampath, Kartik; Syed, Sharjeel; Saad, Jennifer; Hussain, Zilla H; Mody, Kabir; Pipas, J Marc; Gordon, Stuart; Gardner, Timothy; Rothstein, Richard I

    2016-01-01

    Biliary stenting is clinically effective in relieving both malignant and non-malignant obstructions. However, there are high failure rates associated with tumor ingrowth and epithelial overgrowth as well as internally from biofilm development and subsequent clogging. Within the last decade, the use of prophylactic drug eluting stents as a means to reduce stent failure has been investigated. In this review we provide an overview of the current research on drug eluting biliary stents. While there is limited human trial data regarding the clinical benefit of drug eluting biliary stents in preventing stent obstruction, recent research suggests promise regarding their safety and potential efficacy. PMID:26839648

  3. Renal Artery Stent Placement Complicated by Development of a Type B Aortic Dissection

    SciTech Connect

    Haesemeyer, Scott W.; Vedantham, Suresh Braverman, Alan

    2005-01-15

    Percutaneous renal artery angioplasty and stent placement have demonstrated safety and effectiveness in the treatment of selected patients with renovascular hypertension and ischemic nephropathy. Major complications have been predominantly confined to the affected renal artery and kidneys, including renal artery dissection and/or thrombosis, distal embolization, and contrast-related nephropathy. We report a case in which treatment of an ostial renal artery lesion with placement of a balloon-expandable stent was complicated by the development of an acute Type B aortic dissection.

  4. Percutaneous Endoluminal Stent-Graft Repair of an Old Traumatic Femoral Arteriovenous Fistula

    SciTech Connect

    Uflacker, Renan; Elliott, Bruce M.

    1996-03-15

    A stent-graft was custom made to close a high-flow traumatic arteriovenous fistula of the left superficial femoral artery, present for 30 years, in a 60-year-old man with congestive heart failure and ischemic ulceration in the left foot. A balloon expandable Palmaz stent (P394; 2.5 mm x 3.9 cm) was covered with a polytetrafluoroethylene (PTFE) graft and was inserted percutaneously through an 11 Fr vascular sheath. Follow-up Doppler ultrasound at 6 months demonstrated occlusion of the arteriovenous fistula, patency of the artery, and luminal integrity of the artery and vein.

  5. Comparison of a New Polytetrafluoroethylene-Covered Metallic Stent to a Noncovered Stent in Canine Ureters

    SciTech Connect

    Chung, Hwan-Hoon Lee, Seung Hwa; Cho, Sung Bum; Park, Hong Suk; Kim, Young Sik; Kang, Byung Chul; Frisoli, Joan K.; Razavi, Mahmood K.

    2008-05-15

    The aim of this study was to determine the feasibility of using a newly designed polytetrafluoroethylene (PTFE)-covered metallic stent in the ureter by comparing its effectiveness with that of the noncovered stent in a canine model. We placed 14 stents in the ureters of seven mongrel dogs that weighed 30-40 kg each. The covered and noncovered stents were deployed in the right and left ureters, respectively, of six dogs. In the seventh dog, a covered stent and a double-J catheter were inserted in the right ureter, and a covered stent only was inserted in the left ureter. The first six dogs were sacrificed at 5, 10, and 15 weeks after deployment of the stents (two for each follow-up period), and the seventh dog was sacrificed at 30 weeks. There was no migration or poor expansion of any of the stents observed on plain radiography. On intravenous pyelogram and retrograde pyelogram, all of the covered stents at each follow-up period had patent lumens at the stented segments without hydronephrosis, and the passage of contrast material through it was well preserved. The noncovered stents in the dogs sacrificed at 5 and 10 weeks and one of the two dogs sacrificed at 15 weeks showed near-complete occlusion of the stent lumen due to ingrowth of the soft tissue, and severe hydronephrosis was also noted. The noncovered stent in the other dog sacrificed at 15 weeks showed the passage of contrast material without hydronephrosis, but the lumen of the stent was still nearly occluded by the soft tissue. There was no evidence of hydronephrosis or passage disturbance of the contrast material in both ureters of the dog sacrificed at 30 weeks. We conclude that the newly designed PTFE-covered stent effectively prevented the luminal occlusion caused by urothelial hyperplasia compared to the near-total occlusion of the noncovered stents, and no migration of the covered stents was noted.

  6. Impact of bifurcation dual stenting on endothelial shear stress

    PubMed Central

    Chen, Henry Y.; Koo, Bon-Kwon

    2015-01-01

    Despite advances in percutaneous coronary interventions and the introduction of drug eluding stents, in-stent restenosis and stent thrombosis remain a clinically significant problem for bifurcations. The aim of this study is to determine the effect of dual bifurcation stenting on hemodynamic parameters known to influence restenosis and thrombosis. We hypothesized that double stenting, especially with a longer side branch (SB) stent, likely has a negative effect on wall shear stress (WSS), WSS gradient (WSSG), and oscillatory shear index (OSI). To test this hypothesis, we developed computational models of dual stents at bifurcations and non-Newtonian blood simulations. The models were then interfaced, meshed, and solved in a validated finite-element package. Longer and shorter stents at the SB and provisional stenting were compared. It was found that stents placed in the SB at a bifurcation lowered WSS, but elevated WSSG and OSI. Dual stenting with longer SB stent had the most adverse impact on SB endothelial WSS, WSSG, and OSI, with low WSS region up to 50% more than the case with shorter SB stent. The simulations also demonstrated flow disturbances resulting from SB stent struts protruding into the main flow field near the carina, which may have implications on stent thrombosis. The simulations predict a negative hemodynamic role for SB stenting, which is exaggerated with a longer stent, consistent with clinical trial findings that dual-stenting is comparable or inferior to provisional stenting. PMID:26183473

  7. Silver deposition on polypyrrole films electrosynthesised onto Nitinol alloy. Corrosion protection and antibacterial activity.

    PubMed

    Saugo, M; Flamini, D O; Brugnoni, L I; Saidman, S B

    2015-11-01

    The electrosynthesis of polypyrrole films onto Nitinol from sodium salicylate solutions of different concentrations is reported. The morphology and corrosion protection properties of the resulting coatings were examined and they both depend on the sodium salicylate concentration. The immobilisation of silver species in PPy films constituted by hollow rectangular microtubes was studied as a function of the polymer oxidation degree. The highest amount of silver was deposited when the coated electrode was prepolarised at -1.00V (SCE) before silver deposition, suggesting an increase in the amount of non-oxidised segments in the polymer. Finally, the antibacterial activity of the coating against the Gram positive Staphylococcus aureus and Staphylococcus epidermidis bacteria was evaluated. Both strains resulted sensitive to the modified coatings, obtaining a slightly better result against S. aureus.

  8. Processing Issues for Preliminary Melts of the Intermetallic Compound 60-NITINOL

    NASA Technical Reports Server (NTRS)

    Stanford, Malcolm K.; Thomas, Fransua; DellaCorte, Christopher

    2012-01-01

    The effect of various high temperature heat treatments and cooling rates on the hardness of cast 60-NITINOL (60wt%Ni- 40wt%Ti) was studied. The hardness ranged from approximately 33 HRC for annealed specimens to 63 HRC for water quenched specimens. Aging did not have a further effect on the hardness of the heat-treated and quenched material. The issue of material contamination and its possible effect on quench cracking during heat treatment above 1000 C was explored. The Charpy impact energy of the material was found to be relatively low (ranging from 0.4 to 1.0 J) and comparable to that of cast magnesium. Selection of service environments and applications for this material based on these findings should consider the processing route by which it was produced.

  9. Cytotoxicity of Ni from Surface-Treated Porous Nitinol (PNT) on Osteoblast Cells

    NASA Astrophysics Data System (ADS)

    Pulletikurthi, C.; Munroe, N.; Gill, P.; Pandya, S.; Persaud, D.; Haider, W.; Iyer, K.; McGoron, A.

    2011-07-01

    The leaching of nickel from the surface of porous Nitinol (PNT) is mainly dependent on its surface characteristics, which can be controlled by appropriate surface treatments. In this investigation, PNT was subjected to two surface treatments, namely, water-boiling and dry-heating passivations. Phosphate buffer saline (PBS) solutions obtained from cyclic potentiodynamic polarization tests on PNT were employed to assess the cytotoxicity of Ni contained therein on osteoblast cells by Sulforhodamine B (SRB) assay. In addition, similar concentrations of Ni were added exogenously to cell culture media to determine cytotoxic effects on osteoblast cells. The morphologies of the untreated and the surface-treated PNTs were examined using SEM and AFM. Furthermore, growth of human osteoblast cells was observed on the PNT surfaces.

  10. Silver deposition on polypyrrole films electrosynthesised onto Nitinol alloy. Corrosion protection and antibacterial activity.

    PubMed

    Saugo, M; Flamini, D O; Brugnoni, L I; Saidman, S B

    2015-11-01

    The electrosynthesis of polypyrrole films onto Nitinol from sodium salicylate solutions of different concentrations is reported. The morphology and corrosion protection properties of the resulting coatings were examined and they both depend on the sodium salicylate concentration. The immobilisation of silver species in PPy films constituted by hollow rectangular microtubes was studied as a function of the polymer oxidation degree. The highest amount of silver was deposited when the coated electrode was prepolarised at -1.00V (SCE) before silver deposition, suggesting an increase in the amount of non-oxidised segments in the polymer. Finally, the antibacterial activity of the coating against the Gram positive Staphylococcus aureus and Staphylococcus epidermidis bacteria was evaluated. Both strains resulted sensitive to the modified coatings, obtaining a slightly better result against S. aureus. PMID:26249570

  11. Effect of a novel load-bearing trabecular Nitinol scaffold on rabbit radius bone regeneration

    SciTech Connect

    Gotman, Irena Gutmanas, Elazar Y.; Zaretzky, Asaph; Psakhie, Sergey G.

    2015-10-27

    The research aim was to evaluate the bone regeneration capability of novel load-bearing NiTi alloy (Nitinol) scaffolds in a critical-size defect (CSD) model. High strength “trabecular Nitinol” scaffolds were prepared by PIRAC (Powder Immersion Reaction Assisted Coating) annealing of the highly porous Ni foam in Ti powder at 900°C. This was followed by PIRAC nitriding to mitigate the release of potentially toxic Ni ions. Scaffolds phase composition and microstructure were characterized by X-ray diffraction and scanning electron microscopy (SEM/EDS), and their mechanical properties were tested in compression. New Zealand white rabbits received bone defect in right radius and were divided in four groups randomly. In the control group, nothing was placed in the defect. In other groups, NiTi scaffolds were implanted in the defect: (i) as produced, (ii) loaded with bone marrow aspirate (BMA), and (iii) biomimetically CaP-coated. The animals were sacrificed after 12 weeks. The forelimbs with scaffolds were resected, fixed, sectioned and examined in SEM. New bone formation inside the scaffold was studied by EDS analysis and by the processing of backscattered electron images. Bone ingrowth into the scaffold was observed in all implant groups, mostly next to the ulna. New bone formation was strongly enhanced by BMA loading and biomimeatic CaP coating, the bone penetrating as much as 1–1.5 mm into the scaffold. The results of this preliminary study demonstrate that the newly developed high strength trabecular Nitinol scaffolds can be successfully used for bone regeneration in critical size defects.

  12. Stent-graft repair for acute traumatic thoracic aortic rupture.

    PubMed

    Neuhauser, B; Czermak, B; Jaschke, W; Waldenberger, P; Fraedrich, G; Perkmann, R

    2004-12-01

    Traumatic rupture of the thoracic aorta is potentially life-threatening and leads to death in 75 to 90 per cent of cases at the time of injury. In high-risk patients, as traumatic injuries of the aorta combine with multiple associated injuries, endoluminal repair is now reported as a promising therapeutic strategy with encouraging results. This study determined the outcome of patients with traumatic thoracic aortic injury treated endovascularly during the past 7 years at our institution. Thirteen patients, 11 males and 2 females (mean age, 39 years; range, 19-82), with traumatic rupture of the otherwise unremarkable descending aorta (10 acute, 3 chronic), out of a series of 64 endovascular thoracic stent-graft procedures, were treated by implantation of Talent (n = 8), Vanguard (n = 5), and Excluder (n = 2) self-expanding devices between January 1996 and August 2003. The immediate technical success rate was 92 per cent (12/13). One patient showed a proximal endoleak type I, which was treated successfully by an additional stent-graft procedure. Secondary success rate was 100 per cent. The mortality rate was 0 per cent. Two additional stent-graft procedures were performed due to type I endoleaks after 18 and 28 months. There was no other intervention-related morbidity or mortality during the mean follow-up time of 26.4 months' (range, 6-86). Endovascular stent-graft repair of traumatic thoracic aortic injuries is a safe, effective, and low-morbidity alternative to open thoracic surgery and has promising midterm results.

  13. Endovascular Treatment of a Mycotic Intracavernous Carotid Artery Aneurysm Using a Stent Graft

    PubMed Central

    Gupta, Vivek; Jain, Vikash; Mathuria, SN; Khandelwal, N

    2013-01-01

    Summary Intracavernous carotid artery mycotic aneurysms are rare and management is determined by clinical presentation. We describe the first documented proximal intracranial mycotic aneurysm treated by a balloon expandable Aneugraft PCS covered stent. An 11-year-old female child presented with acute onset fever, headache, chemosis followed by diplopia, right-sided ptosis with ophthalmoplegia. Magnetic resonance imaging revealed bilateral cavernous sinus thrombosis. Subsequent work-up included serial computed tomographic arteriography and digital subtraction angiography which revealed a progressively enlarging intracavernous carotid aneurysm. An Aneugraft PCS covered stent was successfully deployed endovascularly, and complete exclusion of the aneurysm was achieved while maintaining the patency of the parent artery. The use of covered stents in intracranial vasculature can be an effective and safe treatment modality for exclusion of the mycotic aneurysm in selected cases. PMID:24070080

  14. [Migration of a stent implanted in the pulmonary artery of a patient with tetralogy of Fallot].

    PubMed

    Palomero Rodríguez, M A; Gabaldón Rivilla, M; Cabestrero Alonso, D; Gonzalez Cibrián, C; Abelleira Pardeiro, C; Centella Hernánez, T; Collado Gutierrez, R; Asuero de Lis, M S; Gómez González, R

    2014-05-01

    Tetralogy of Fallot is a congenital heart disease that accounts for 11-13% of the congenital cardiomyopathies. Stenosis and hyperplasia of the pulmonary arteries occur in a high proportion of them as this disease causes a native stenosis of the pulmonary branch, which can be surgically repaired with a stent. The use of balloon expandable intravascular stents is an alternative technique to further surgery in patients with congenital heart diseases. However, despite the gradual increase in their use, the limited number of procedures, combined with the wide anatomical variability and different characteristics of these patients, even in expert hands, stent implants are associated with a not inconsiderable incidence of complications. These are not always obvious and often require performing surgery in patients who have already had multiple interventions, thus increasing the complexity and the risk.

  15. Esophageal stenting for benign and malignant disease: European Society of Gastrointestinal Endoscopy (ESGE) Clinical Guideline.

    PubMed

    Spaander, Manon C W; Baron, Todd H; Siersema, Peter D; Fuccio, Lorenzo; Schumacher, Brigitte; Escorsell, Àngels; Garcia-Pagán, Juan-Carlos; Dumonceau, Jean-Marc; Conio, Massimo; de Ceglie, Antonella; Skowronek, Janusz; Nordsmark, Marianne; Seufferlein, Thomas; Van Gossum, André; Hassan, Cesare; Repici, Alessandro; Bruno, Marco J

    2016-10-01

    This Guideline is an official statement of the European Society of Gastrointestinal Endoscopy (ESGE), endorsed by the European Society for Radiotherapy and Oncology (ESTRO), the European Society of Digestive Endoscopy (ESDO), and the European Society for Clinical Nutrition and Metabolism (ESPEN). The Grading of Recommendations Assessment, Development, and Evaluation (GRADE) system was adopted to define the strength of recommendations and the quality of evidence. Main recommendations for malignant disease 1 ESGE recommends placement of partially or fully covered self-expandable metal stents (SEMSs) for palliative treatment of malignant dysphagia over laser therapy, photodynamic therapy, and esophageal bypass (strong recommendation, high quality evidence). 2 For patients with longer life expectancy, ESGE recommends brachytherapy as a valid alternative or in addition to stenting in esophageal cancer patients with malignant dysphagia. Brachytherapy may provide a survival advantage and possibly a better quality of life compared to SEMS placement alone. (Strong recommendation, high quality evidence.) 3 ESGE recommends esophageal SEMS placement as the preferred treatment for sealing malignant tracheoesophageal or bronchoesophageal fistula (strong recommendation, low quality evidence). 4 ESGE does not recommend the use of concurrent external radiotherapy and esophageal stent treatment. SEMS placement is also not recommended as a bridge to surgery or prior to preoperative chemoradiotherapy. It is associated with a high incidence of adverse events and alternative satisfactory options such as placement of a feeding tube are available. (Strong recommendation, low quality evidence.) Main recommendations for benign disease 1 ESGE recommends against the use of self-expandable stents (SEMSs) as first-line therapy for the management of benign esophageal strictures because of the potential for adverse events, the availability of alternative therapies, and costs (strong

  16. Influence of strut cross-section of stents on local hemodynamics in stented arteries

    NASA Astrophysics Data System (ADS)

    Jiang, Yongfei; Zhang, Jun; Zhao, Wanhua

    2016-05-01

    Stenting is a very effective treatment for stenotic vascular diseases, but vascular geometries altered by stent implantation may lead to flow disturbances which play an important role in the initiation and progression of restenosis, especially in the near wall in stented arterial regions. So stent designs have become one of the indispensable factors needed to be considered for reducing the flow disturbances. In this paper, the structural designs of strut cross-section are considered as an aspect of stent designs to be studied in details. Six virtual stents with different strut cross-section are designed for deployments in the same ideal arterial model. Computational fluid dynamics (CFD) methods are performed to study how the shape and the aspect ratio (AR) of strut cross-section modified the local hemodynamics in the stented segments. The results indicate that stents with different strut cross-sections have different influence on the hemodynamics. Stents with streamlined cross-sectional struts for circular arc or elliptical arc can significantly enhance wall shear stress (WSS) in the stented segments, and reduce the flow disturbances around stent struts. The performances of stents with streamlined cross-sectional struts are better than that of stents with non-streamlined cross-sectional struts for rectangle. The results also show that stents with a larger AR cross-section are more conductive to improve the blood flow. The present study provides an understanding of the flow physics in the vicinity of stent struts and indicates that the shape and AR of strut cross-section ought to be considered as important factors to minimize flow disturbance in stent designs.

  17. Esophageal Stent for Refractory Variceal Bleeding: A Systemic Review and Meta-Analysis

    PubMed Central

    Guo, Xiao-Zhong

    2016-01-01

    Background. Preliminary studies suggest that covered self-expandable metal stents may be helpful in controlling esophageal variceal bleeding. Aims. To evaluate the effectiveness and safety of esophageal stent in refractory variceal bleeding in a systematic review and meta-analysis. Methods. A comprehensive literature search was conducted on PubMed, EMBASE, and Cochrane Library covering the period from January 1970 to December 2015. Data were selected and abstracted from eligible studies and were pooled using a random-effects model. Heterogeneity was assessed using I2 test. Results. Five studies involving 80 patients were included in the analysis. The age of patients ranged from 18 to 91 years. The mean duration of follow-up was 46.8 d (range, 30–60 d). The success rate of stent deployment was 96.7% (95% CI: 91.6%–99.5%) and complete response to esophageal stenting was in 93.9% (95% CI: 82.2%–99.6%). The incidence of rebleeding was 13.2% (95% CI: 1.8%–32.8%) and the overall mortality was 34.5% (95% CI: 24.8%–44.8%). Most of patients (87.4%) died from hepatic or multiple organ failure, and only 12.6% of patients died from uncontrolled bleeding. There was no stent-related complication reported and the incidence of stent migration was 21.6% (95% CI: 4.7%–46.1%). Conclusion. Esophageal stent may be considered in patients with variceal bleeding refractory to conventional therapy. PMID:27517043

  18. One Year Clinical Outcomes of Renal Artery Stenting: The Results of ODORI Registry

    SciTech Connect

    Sapoval, M.; Tamari, I.; Goffette, P.; Downes, M.; Senechal, Q.; Fanelli, F.; Reimer, P.; Negaiwi, Z.; Cassin, P. De; Heye, S.; Korobov, V.; Tsetis, D.; Abada, H.

    2010-06-15

    The safety, efficacy and long term clinical benefits of renal artery revascularization by stenting are still a matter of debate. The aim of our study was to define the safety and efficacy of renal artery stenting with the Tsunami peripheral stent (Terumo Corporation, Tokyo, Japan). The ODORI was a prospective, multicentre registry which enrolled 251 consecutive patients, (276 renal arteries) in 36 centres across Europe. The primary endpoint was acute procedural success defined as <30% residual stenosis after stent placement. Secondary endpoints included major adverse events, blood pressure control, serum creatinine level, and target lesion revascularization (TLR) at 6 and 12 months. Patients were 70 {+-} 10 years old, 59% were male, 33% had diabetes, and 96% hypertension. The main indications for renal stent implantation were hypertension in 83% and renal salvage in 39%. Direct stent implantation was performed in 76% of the cases. Acute success rate was 100% with residual stenosis of 2.5 {+-} 5.4%. Systolic/diastolic blood pressure decreased from a mean of 171/89 at baseline to 142/78 mmHg at 6 months (p < 0.0001 vs. baseline), and 141/80 mmHg at 12 months (p < 0.0001 vs. baseline). Mean serum creatinine concentration did not change significantly in the total population. However, there was significant improvement in the highest tercile (from 283 {mu}mol/l at baseline to 205 and 209 {mu}mol/l at 6 and 12 months respectively). At 12-months, rates of restenosis and TLR were 6.6 and 0.8% respectively. The 12 month cumulative rate of all major clinical adverse events was 6.4% while the rate of device or procedure related events was 2.4%. In hypertensive patients with atherosclerotic renal artery stenosis Tsunami peripheral balloon-expandable stent provides a safe revascularization strategy, with a potential beneficial impact on hypertension control and renal function in the highest risk patients.

  19. Biodegradable esophageal stents in benign and malignant strictures – a single center experience

    PubMed Central

    Sigounas, Dimitrios E.; Siddhi, Sandeep; Plevris, John N.

    2016-01-01

    Background and study aims: Biodegradable (BD) esophageal stents were recently developed mainly for refractory benign strictures, but experience and available literature are limited. Patients and methods: This was a retrospective observational study. All patients who had BD stents inserted due to refractory benign esophageal strictures or malignant strictures, or were awaiting radical radiotherapy/chemotherapy or neo-adjuvant therapy and esophagectomy between March 2011 and July 2015 were included. Results: Stent placement was successful in all patients. Ten patients with benign strictures (3 male, median age 80.5 years, IQR: 68.75 – 89.5) were followed-up for a median of 171.5 weeks (IQR: 24 – 177.25). The interval between dilatations prior to the first BD stent placement (median: 34.25 days, IQR: 23.06 – 48.29) was significantly shorter than the interval between the first BD stent placement and the first intervention required (median: 149.5 days, IQR: 94.25 – 209.5) and this difference was statistically significant (P = 0.012). Ten patients with esophageal cancer (8 male, median age: 69 years, IQR: 59.25 – 80.75) were included and they were followed up for a median of 36 weeks (IQR: 26 – 58). Only 1 completed radical radiotherapy successfully, but developed refractory post-radiotherapy stricture. No one proceeded to esophagectomy and 50 % required a self-expanding metal stent (SEMS) at a median of 134 days (IQR: 100 – 263) following stent placement. Conclusions: BD stents were successfully deployed in both benign and malignant strictures. They offered a prolonged dilatation-free interval in benign strictures, yet in the majority of patients, strictures recurred. In malignant strictures, stent patency was similar to that of benign strictures, which suggests a potential value in ensuring adequate oral intake during oncologic therapy. In our cohort, however, use of stents did not contribute to improved outcome. PMID

  20. Below-the-ankle Angioplasty and Stenting for Limb Salvage: Anatomical Considerations and Long-term Outcomes

    SciTech Connect

    Katsanos, Konstantinos Diamantopoulos, Athanasios; Spiliopoulos, Stavros; Karnabatidis, Dimitris; Siablis, Dimitris

    2013-08-01

    PurposeTo report the long-term angiographic and clinical results in a series of below-the-ankle (BTA) angioplasty procedures and to present some biomechanical issues related to the unique anatomical geometry of the ankle.MethodsWe performed a retrospective analysis of BTA angioplasty procedures. Clinical end points included technical success, patient mortality, salvage of the treated foot, and repeat target lesion revascularization. Imaging end points included primary patency, binary restenosis of the target lesion at the 50 % threshold, and stent integrity (stent fracture, deformation, or collapse). Univariate subgroup analysis was performed.ResultsIn total, 40 limbs in 37 patients (age 73.5 {+-} 8.2 years) with critical limb ischemia were included and 42 inframalleolar lesions (4.2 {+-} 1.4 cm) were analyzed. Technical success was achieved in 95.2 % (40 of 42). Provisional stent placement was performed in 45.2 % (19 of 42). Two patients died, and two major amputations occurred up to 3 years. At 1 year, overall primary vessel patency was 50.4 {+-} 9.1 %, lesion binary restenosis rate was 64.1 {+-} 8.3 %, and repeat intervention-free survival was 93.6 {+-} 4.3 % according to life table analysis of all treated lesions. Pairwise subgroup analysis showed that BTA self-expanding stents were associated with significantly higher restenosis and poorer primary patency compared to plain balloon angioplasty or sirolimus-eluting balloon-expandable stents. Significant deformation and/or fracture of balloon-expandable stents placed BTA were identified in five of 11. Dynamic imaging showed that the dorsalis pedis artery is kinked during foot dorsiflexion, whereas the distal posterior tibial artery is kinked during plantar flexion of the foot.ConclusionBTA angioplasty for critical limb ischemia treatment is safe and feasible with satisfactory long-term results. BTA stent placement must be reserved for bailout indications.

  1. Rapid virtual stenting for intracranial aneurysms

    NASA Astrophysics Data System (ADS)

    Zhao, Liang; Chen, Danyang; Chen, Zihe; Wang, Xiangyu; Paliwal, Nikhil; Xiang, Jianping; Meng, Hui; Corso, Jason J.; Xu, Jinhui

    2016-03-01

    The rupture of Intracranial Aneurysms is the most severe form of stroke with high rates of mortality and disability. One of its primary treatments is to use stent or Flow Diverter to divert the blood flow away from the IA in a minimal invasive manner. To optimize such treatments, it is desirable to provide an automatic tool for virtual stenting before its actual implantation. In this paper, we propose a novel method, called