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1

Trends in Cardiac Pacemaker Batteries  

PubMed Central

Batteries used in Implantable cardiac pacemakers-present unique challenges to their developers and manufacturers in terms of high levels of safety and reliability. In addition, the batteries must have longevity to avoid frequent replacements. Technological advances in leads/electrodes have reduced energy requirements by two orders of magnitude. Micro-electronics advances sharply reduce internal current drain concurrently decreasing size and increasing functionality, reliability, and longevity. It is reported that about 600,000 pacemakers are implanted each year worldwide and the total number of people with various types of implanted pacemaker has already crossed 3 million. A cardiac pacemaker uses half of its battery power for cardiac stimulation and the other half for housekeeping tasks such as monitoring and data logging. The first implanted cardiac pacemaker used nickel-cadmium rechargeable battery, later on zinc-mercury battery was developed and used which lasted for over 2 years. Lithium iodine battery invented and used by Wilson Greatbatch and his team in 1972 made the real impact to implantable cardiac pacemakers. This battery lasts for about 10 years and even today is the power source for many manufacturers of cardiac pacemakers. This paper briefly reviews various developments of battery technologies since the inception of cardiac pacemaker and presents the alternative to lithium iodine battery for the near future. PMID:16943934

Mallela, Venkateswara Sarma; Ilankumaran, V; Rao, N.Srinivasa

2004-01-01

2

Space Derived Health Aids (Cardiac Pacemaker)  

NASA Technical Reports Server (NTRS)

St. Jude Medical's Cardiac Rhythm Management Division's (formerly known as Pacesetter Systems, Inc.) pacer is a rechargeable cardiac pacemaker that eliminates the recurring need for surgery to implant a new battery. The Programalith is an advanced cardiac pacing system which permits a physician to reprogram a patient's implanted pacemaker without surgery. System consists of a pacemaker, together with a physician's console containing the programmer and a data printer. Signals are transmitted by wireless telemetry. Two-way communications, originating from spacecraft electrical power systems technology, allows physician to interrogate the pacemaker as to the status of the heart, then to fine tune the device to best suit the patient's needs.

1981-01-01

3

Myopotential interference inducing pacemaker tachycardia in a DVI programmed pacemaker.  

PubMed

A 67-year-old male, suffering from ventricular tachycardia unresponsive to drug therapy, received a universal AV sequential pacemaker (DDD,M). The pacemaker was programmed in the DVI mode, pacing rate 100 bpm, AV interval 250 ms. After implantation, the patient experiences two episodes of tachycardia that proved to be pacemaker tachycardia with a rate of 150 bpm. The first period was self-terminating, and the second had to be stopped by reprogramming the pulse generator. Pacemaker tachycardia could easily be provoked by instructing the patient to contract the pectoral muscle adjacent to the pulse generator. To our knowledge, this is the first report of pacemaker tachycardia provoked by myopotentials in a pulse generator programmed in the DVI mode. PMID:6209636

van Gelder, L M; El Gamal, M I

1984-11-01

4

Sexual dimorphism in the complexity of cardiac pacemaker activity  

NSDL National Science Digital Library

Journal article titled "Sexual Dimorphism in the Complexity of Cardiac Pacemaker Activity" from The American Journal of PhysiologyÃÂHeart and Circulatory Physiology, by Terry B. J. Kuo, and Cheryl C. H. Yang.

Terry B. Kuo (Tzu Chi Buddhist General Hospital Department of Neurology); Cheryl C.H. Yang (Tzu Chi University Department of Physiology)

2007-10-03

5

Testing of Common Electromagnetic Environments for Risk of Interference with Cardiac Pacemaker Function  

PubMed Central

Background Cardiac pacemakers are known to be susceptible to strong electromagnetic fields (EMFs). This in vivo study investigated occurrence of electromagnetic interference with pacemakers caused by common environmental sources of EMFs. Methods Eleven volunteers with a pacemaker were exposed to EMFs produced by two mobile phone base stations, an electrically powered commuter train, and an overhead high voltage transmission lines. All the pacemakers were programmed in normal clinically selected settings with bipolar sensing and pacing configurations. Results None of the pacemakers experienced interference in any of these exposure situations. However, often it is not clear whether or not strong EMFs exist in various work environments, and hence an individual risk assessment is needed. Conclusions Modern pacemakers are well shielded against external EMFs, and workers with a pacemaker can most often return to their previous work after having a pacemaker implanted. However, an appropriate risk assessment is still necessary after the implantation of a pacemaker, a change of its generator, or major modification of its programming settings. PMID:24106646

Tiikkaja, Maria; Aro, Aapo L.; Alanko, Tommi; Lindholm, Harri; Sistonen, Heli; Hartikainen, Juha E.K.; Toivonen, Lauri; Juutilainen, Jukka; Hietanen, Maila

2013-01-01

6

Proton Beam Therapy Interference With Implanted Cardiac Pacemakers  

SciTech Connect

Purpose: To investigate the effect of proton beam therapy (PBT) on implanted cardiac pacemaker function. Methods and Materials: After a phantom study confirmed the safety of PBT in patients with cardiac pacemakers, we treated 8 patients with implanted pacemakers using PBT to a total tumor dose of 33-77 gray equivalents (GyE) in dose fractions of 2.2-6.6 GyE. The combined total number of PBT sessions was 127. Although all pulse generators remained outside the treatment field, 4 patients had pacing leads in the radiation field. All patients were monitored by means of electrocardiogram during treatment, and pacemakers were routinely examined before and after PBT. Results: The phantom study showed no effect of neutron scatter on pacemaker generators. In the study, changes in heart rate occurred three times (2.4%) in 2 patients. However, these patients remained completely asymptomatic throughout the PBT course. Conclusions: PBT can result in pacemaker malfunctions that manifest as changes in pulse rate and pulse patterns. Therefore, patients with cardiac pacemakers should be monitored by means of electrocardiogram during PBT.

Oshiro, Yoshiko [Department of Radiation Oncology, University of Tsukuba, Ibaraki (Japan)], E-mail: ooyoshiko@pmrc.tsukuba.ac.jp; Sugahara, Shinji [Department of Radiation Oncology, University of Tsukuba, Ibaraki (Japan); Noma, Mio; Sato, Masato; Sakakibara, Yuzuru [Department of Cardiovascular Surgery, University of Tsukuba, Ibaraki (Japan); Sakae, Takeji [Proton Medical Research Center, University of Tsukuba, Ibaraki (Japan); Hayashi, Yasutaka [Department of Radiation Oncology, University of Tsukuba, Ibaraki (Japan); Nakayama, Hidetsugu; Tsuboi, Koji; Fukumitsu, Nobuyoshi [Department of Radiation Oncology, University of Tsukuba, Ibaraki (Japan); Proton Medical Research Center, University of Tsukuba, Ibaraki (Japan); Kanemoto, Ayae [Department of Radiation Oncology, University of Tsukuba, Ibaraki (Japan); Hashimoto, Takayuki [Division of Radiation Oncology, Shizuoka Cancer Center Hospital, Shizuoka (Japan); Tokuuye, Koichi [Department of Radiation Oncology, University of Tsukuba, Ibaraki (Japan); Proton Medical Research Center, University of Tsukuba, Ibaraki (Japan)

2008-11-01

7

Permanent cardiac pacemakers: issues relevant to the emergency physician, part I  

Microsoft Academic Search

Many people benefit from the implantation of cardiac pacemakers for management of certain cardiac dysrhythmias. These patients are seen regularly in the emergency department with a variety of pacemaker complications and malfunctions. The presence of a pacemaker may also affect management of unrelated medical problems. This two-part series reviews the medical issues related to patients with permanent pacemakers. Part I

Taylor Y Cardall; Theodore C Chan; William J Brady; James C Perry; Gary M Vilke; Peter Rosen

1999-01-01

8

Cardiac arrest caused by undersensing of a temporary epicardial pacemaker.  

PubMed

The R-on-T phenomenon is a well-known entity that predisposes to dangerous arrhythmias. Typically, a premature ventricular complex occurring at the critical time during the T wave of the preceding beat precipitates ventricular tachycardia and fibrillation. This phenomenon can occur not only in asynchronous ventricular pacemakers, but also in synchronous pacemakers, if loss of sensing of the intrinsic rhythm becomes evident. A patient who was fitted with a temporary epicardial wire, following cardiac surgery and experienced repeated episodes of polymorphic ventricular tachycardia caused by the R-on-T phenomenon, is described. PMID:20101359

Chemello, D; Subramanian, A; Kumaraswamy, N

2010-01-01

9

[Infections secondary to implantation of cardiac pacemakers].  

PubMed

Infectious complications of pacemaker implantation are not common but may be particularly severe. Localised wound infections at the site of implantation have been reported in 0.5% of cases in the most recent series with an average of about 2%. The incidence of septicaemia and infectious endocarditis is lower, about 0.5% of cases. The operator's experience, the duration of the procedure and repeat procedures are considered to be predisposing factors. The main cause of these infections is though to be local contamination during the implantation. The commonest causal organism is the staphylococcus (75 to 92%), the staphylococcus aureus being the cause of acute infections whereas the staphylococcus epidermis is associated with cases of secondary infection. The usual clinical presentation is infection at the site of the pacemaker but other forms such as abscess, endocarditis, rejection of the implanted material, septic emboli and septic phlebitis have been described. The diagnosis is confirmed by local and systemic biological investigations and by echocardiography (especially transoesophageal echocardiography) in cases of right heart endocarditis. There are two axes of treatment: bactericidal double antibiotherapy and surgical ablation of the infected material either percutaneously or by cardiotomy. Though controversial, and unsupported by scientific evidence, the role of systematic, preoperative, prophylactic antibiotic therapy in the prevention of these complications seems to be increasing. PMID:9749192

Da Costa, A; Kirkorian, G; Chevalier, P; Cerisier, A; Chalvidan, T; Obadia, J F; Etienne, J; Isaaz, K; Touboul, P

1998-06-01

10

Factors influencing survival of patients with permanent cardiac pacemakers.  

PubMed Central

With the advent of permanent cardiac pacing, technology has produced power sources that will last two, four, and even 20 years. The cost of these devices is proportional to their complexity and expected life. Therefore, the selection of an appropriate pulse generator should be based on the patient's prognosis. An actuarial analysis of 319 consecutive patients receiving permanent cardiac pacemakers was performed in order to determine whether prepacing factors influenced prognosis. The survival probability at 5 years was not influenced by sex, race, type of conduction defect, or antecedent disease. Survival rate decreased only slightly for each decade of life, but even in the ninth decade there was an acceptable prognosis. PMID:831631

Nolan, S P; Crampton, R S; McGuire, L B; McGann, R C; Holz, H C; Muller, W H

1977-01-01

11

Effectiveness evaluation of shielding material for reducing electromagnetic interference of cardiac pacemaker by portable information terminals  

Microsoft Academic Search

A shielding technique is an effective means to protect implanted cardiac pacemaker users from portable information terminals, whereas no evaluation methods for this aim have been established. In this paper, an FDTD model for predicting EMI levels in the pacemakers was introduced for numerical shielding effectiveness evaluation. In the model the pacemaker acted as a receiving antenna, which resulted in

Jianqing Wang; Takeshi Ohshima; Osamu Fujiwara

2001-01-01

12

Plethyzmography in assessment of hemodynamic results of pacemaker functions programming  

NASA Astrophysics Data System (ADS)

The paper presents potential role of plethyzmography in optimization of heart hemodynamic function during pacemaker programming. The assessment of optimal stroke volume in patients, with implanted dual chamber pacemaker (DDD), by plethyzmography was a goal of the study. The data were collected during pacing rhythm. 20 patients (8 female and 12 male, average 77.4+/-4.6 years) with dual chamber pacemaker (DDD) and with pacing rhythm during routine pacemaker control and study tests were incorporated in the study group. Hemodynamic parameters were assessed during modification of atrio-ventricular delay (AVD) for pacing rhythm of 70 bpm and 90 bpm. The time of atrioventricular was programmed with 20 ms steps within range 100-200 ms and data were recorded with two minutes delay between two consecutive measurements. Stroke volume (SV) and cardiac output (CO) were calculated from plethyzmographic signal by using Beatscope software (TNO Holand). Highest SV calculated for given pacing rhythm was named optimal stroke volume (OSV) and consequently highest cardiac output was named maximal cardiac output (MCO). The time of atrio-ventricular delay for OSV was named optimal atrioventricular delay (OAVD). The results have showed: mean values of OAVD for 70 bpm - 152+/-33 ms and for 90 bpm -149+/-35 ms, shortening of the mean OAVD time caused by increase of pacing rate from 70 bpm to 90 bpm what resulted in statistically significant decrease of OSV with not statistically significant increase of MCO. The analysis of consecutive patients revealed three types of response to increase of pacing rhythm: 1. typical-shortening of OAVD, 2. neutral-no change of OAVD and 3.atypical-lengthening of OAVD.

Wojciechowski, Dariusz; Sionek, Piotr; Peczalski, Kazimierz; Janusek, Dariusz

2011-01-01

13

Pacemakers  

MedlinePLUS Videos and Cool Tools

... www.X-Plain.com] ct150109 Last reviewed: 01/17/2013 1 This reference summary explains how pacemakers ... www.X-Plain.com] ct150109 Last reviewed: 01/17/2013 2 A pacemaker is an electronic device ...

14

Conceptual Design of GaN Betavoltaic Battery using in Cardiac Pacemaker  

Microsoft Academic Search

Pacemaker is an electronic biomedical device which stimulates and regulates or amplify the human heartbeat by delivering weak electrical pulses to the cardiac muscle at regular intervals when its natural regulating mechanisms break down. The purpose of the present work is to introduce a kind of low power Betavoltaic battery using in nuclear powered cardiac pacemakers which have higher efficiency

M. Mohamadian; S. A. H. Feghhi; H. Afarideh

15

Intermittent pacemaker syndrome: revision of VVI pacemaker to a new cardiac pacing mode for tachy-brady syndrome.  

PubMed

A patient with tachy-brady syndrome manifested by paroxysmal atrial fibrillation and symptomatic sinus bradycardia and treated by VVI pacing developed pacemaker syndrome during episodes of ventricular pacing. His cardiac pacemaker was revised to a dual chamber system utilizing the new AV sequential DDI pacing mode which eliminated pacemaker-related tachycardias and totally abolished the pacemaker syndrome symptoms. There have been no further episodes of atrial fibrillation, possibly due to elimination of temporal dispersion of refractory periods during bradycardia. The propensity for atrial fibrillation has also been minimized by excluding competitive atrial stimulation during DVI pacing. The DDI mode provides the clinician increased utility and flexibility in the use of AV sequential pacing therapy. PMID:2437541

McCormick, D J; Shuck, J W; Ansinelli, R A

1987-03-01

16

[A new program-controlled telemetry technology for pacemakers].  

PubMed

This thesis is about a new technology of program-controlled telemetry for pacemakers. The system utilizes digital logic circuit design, and the program-controlled part uses single chip to control for display and debug. PWM and reflectance telemetry may improve the preciseness and correctness of signal transmission, and reduce the power consumption of pacemakers and prolong the lifetime. PMID:16104257

Wang, Yu; Huang, Xin-ming; Fang, Zu-xinag

2002-09-01

17

Advanced Pacemaker  

NASA Technical Reports Server (NTRS)

Synchrony, developed by St. Jude Medical's Cardiac Rhythm Management Division (formerly known as Pacesetter Systems, Inc.) is an advanced state-of-the-art implantable pacemaker that closely matches the natural rhythm of the heart. The companion element of the Synchrony Pacemaker System is the Programmer Analyzer APS-II which allows a doctor to reprogram and fine tune the pacemaker to each user's special requirements without surgery. The two-way communications capability that allows the physician to instruct and query the pacemaker is accomplished by bidirectional telemetry. APS-II features 28 pacing functions and thousands of programming combinations to accommodate diverse lifestyles. Microprocessor unit also records and stores pertinent patient data up to a year.

1990-01-01

18

Programmable Pacemaker  

NASA Technical Reports Server (NTRS)

Released in 1995, the Trilogy cardiac pacemaker is the fourth generation of a unit developed in the 1970s by NASA, Johns Hopkins Applied Physics Laboratory and St. Jude Medical's Cardiac Rhythm Management Division (formerly known as Pacesetter Systems, Inc.). The new system incorporates the company's PDx diagnostic and programming software and a powerful microprocessor that allows more functions to be fully automatic and gives more detailed information on the patient's health and the performance of the pacing systems. The pacemaker incorporates bidirectional telemetry used for space communications for noninvasive communication with the implanted pacemaker, smaller implantable pulse generators from space microminiaturization, and longer-life batteries from technology for spacecraft electrical power systems.

1996-01-01

19

Experimental and theoretical investigation of implantable cardiac pacemaker exposed to low frequency magnetic field.  

PubMed

This paper presents in vitro investigation of an implantable cardiac pacemaker exposed to low frequency magnetic fields. The method used in this study is based on the interaction by inductive coupling through the loop formed by the pacemaker and its loads and the surrounding medium. This interaction results in an induced electromotive force between the terminals of the pacemaker, which can potentially disturb its operation. The studied frequencies are 50/60 Hz and 10/25 kHz. The experimental tests were carried out on several cardiac pacemakers, single chamber, and dual chamber. The results show a window effect of the detection circuits of cardiac pacemakers for the four studied frequencies. The modelling of the test bed requires studying the effects of the induced currents generated by the application of a magnetic field. Analytical calculations and Numerical simulations were carried out. We modelled the interactions of the magnetic field with a simplified representation of pacemaker embedded in the medium. The comparison of the results in the air and in vitro enabled us to make an equivalent electric model. The results obtained in experimental and theoretical studies allowed us to validate the test bed. The method applied is valid for other medical implants such as cardiac defibrillators, implant hearing aids system...etc. PMID:19125341

Babouri, A; Hedjeidj, A; Guendouz, L

2009-04-01

20

Genetic isolation of stem cell-derived pacemaker-nodal cardiac myocytes.  

PubMed

Dysfunction of the cardiac pacemaker tissues due to genetic defects, acquired diseases, or aging results in arrhythmias. When arrhythmias occur, artificial pacemaker implants are used for treatment. However, the numerous limitations of electronic implants have prompted studies of biological pacemakers that can integrate into the myocardium providing a permanent cure. Embryonic stem (ES) cells cultured as three-dimensional (3D) spheroid aggregates termed embryoid bodies possess the ability to generate all cardiac myocyte subtypes. Here, we report the use of a SHOX2 promoter and a Cx30.2 enhancer to genetically identify and isolate ES cell-derived sinoatrial node (SAN) and atrioventricular node (AVN) cells, respectively. The ES cell-derived Shox2 and Cx30.2 cardiac myocytes exhibit a spider cell morphology and high intracellular calcium loading characteristic of pacemaker-nodal myocytes. These cells express abundant levels of pacemaker genes such as endogenous HCN4, Cx45, Cx30.2, Tbx2, and Tbx3. These cells were passaged, frozen, and thawed multiple times while maintaining their pacemaker-nodal phenotype. When cultured as 3D aggregates in an attempt to create a critical mass that simulates in vivo architecture, these cell lines exhibited an increase in the expression level of key regulators of cardiovascular development, such as GATA4 and GATA6 transcription factors. In addition, the aggregate culture system resulted in an increase in the expression level of several ion channels that play a major role in the spontaneous diastolic depolarization characteristic of pacemaker cells. We have isolated pure populations of SAN and AVN cells that will be useful tools for generating biological pacemakers. PMID:23877224

Hashem, Sherin I; Claycomb, William C

2013-11-01

21

Experimental Evaluation of SAR around an Implanted Cardiac Pacemaker Caused by Mobile Radio Terminal  

NASA Astrophysics Data System (ADS)

Although the effect of electromagnetic interference on an implanted cardiac pacemaker due to a nearby mobile phone has been investigated, there have been few studies on the enhancement of the specific absorption rate (SAR) around an implanted cardiac pacemaker due to a nearby mobile phone. In this study, the SAR distribution around a pacemaker model embedded in a parallelepiped torso phantom when a mobile phone was nearby was numerically calculated and experimentally measured. The results of both investigations showed a characteristic SAR distribution. The system presented can be used to estimate the effects of electromagnetic interference on implanted electric circuits and thus could lead to the development of guidelines for the safe use of mobile radio terminals near people with medical implants.

Endo, Yuta; Saito, Kazuyuki; Watanabe, Soichi; Takahashi, Masaharu; Ito, Koichi

22

Electromagnetic interference with implantable cardiac pacemakers by video capsule  

Microsoft Academic Search

Methods: A total of 100 consecutive patients (70 men, 30 women) with an implanted pacemaker (95 on bipolar mode) were studied. The testing was performed with a functional testing device (Test Cap) for the Given Diagnostic System that reproduces the effect of the video capsule by transmitting at exactly the same frequency. During continuous electrocardiographic monitoring and recording, 100 tests

Sergio Dubner; Yael Dubner; Sebastian Gallino; Liliana Spallone; David Zagalsky; Horacio Rubio; Joseph Zimmerman; Eran Goldin

23

Method to Detect Cardiac Abnormalities Based on Electrocardiography and Sinoatrial Pacemaker Model  

E-print Network

in the developed countries. Early diagnosis and medical treatment of heart diseases can prevent the sudden death, and Irisawa) model to analyze the pole-zero characteristics of the phase error between abnormal cardiac devices for medical treatment of heart diseases such as pacemakers are susceptible

Wu, Mingshen

24

Endotoxemia is associated with partial uncoupling of cardiac pacemaker from cholinergic neural control in rats.  

PubMed

Cardiac cycle is regulated by a complex interplay between autonomic nervous system and cardiac pacemaker cells. Decreased heart rate variability (HRV) and increased cardiac rhythm regularity are associated with poor prognosis in patients with systemic inflammation (e.g., sepsis). However, the underlying mechanism of decreased HRV in systemic inflammation is not understood. It is known that greater regularity in a complex system could indicate uncoupling of the system's components. The present study aimed to test the hypothesis that impaired responsiveness of cardiac pacemaker to autonomic nervous system may lead to uncoupling of the cardiovascular regulatory mechanisms during systemic inflammation. Systemic inflammation was induced by intraperitoneal injection of endotoxin (lipopolysaccharide, 1 mg/kg) in rats. Cardiovascular signals were recorded in conscious animals using a telemetric system. Heart rate dynamics was analyzed using Poincaré plot, and cardiac cycle regularity was assessed by sample entropy analysis. Spontaneously beating atria were isolated, and chronotropic responsiveness to adrenergic and cholinergic stimulation was assessed using standard organ bath. Sample entropy decreased significantly 4 h after endotoxin injection in conscious rats. Vagal modulation of cardiac cycle (as assessed by Poincaré plot) also exhibited a significant reduction in endotoxemic rats. Acute endotoxin challenge was associated with a significant hyporesponsiveness of isolated spontaneously beating atria to cholinergic stimulation. The chronotropic responsiveness to adrenergic stimulation was identical in controls and endotoxin-treated rats. These data propose that systemic inflammation is linked to reduced cardiac responsiveness to cholinergic stimulation. This may lead to partial uncoupling of cardiac pacemaker cells from autonomic neural control and can explain decreased HRV during systemic inflammation. PMID:22249221

Gholami, Masoumeh; Mazaheri, Parisa; Mohamadi, Amin; Dehpour, Tara; Safari, Fatemeh; Hajizadeh, Sohrab; Moore, Kevin P; Mani, Ali R

2012-02-01

25

Mortality in Patients on Renal Replacement Therapy and Permanent Cardiac Pacemakers  

PubMed Central

End stage renal disease is a relatively frequent disease with high mortality due to cardiac causes. Permanent pacemaker (PM) implantation rates are also very common; thus combination of both conditions is not unusual. We hypothesized that patients with chronic kidney disease with a PM would have significantly higher mortality rates compared with end stage renal disease patients without PM. Our objectives were to analyze mortality of patients on renal replacement therapy with PM. 2778 patients were on renal replacement therapy (RRT) and 110 had a PM implanted during the study period. To reduce the confounding effects of covariates, a propensity-matched score was performed. 52 PM patients and 208 non-PM matched patients were compared. 41% of the PM were implanted before entering the RRT program and 59% while on RRT. Mortality was higher in the PM group. Cardiovascular disease and infections were the most frequent causes of death. Propensity analysis showed no differences in long-term mortality between groups. We concluded that in patients on RRT and PM mortality rates are higher. Survival curves did not differ from a RRT propensity-matched group. We concluded that the presence of a PM is not an independent mortality risk factor in RRT patients. PMID:24977040

Vanerio, Gabriel; Garcia, Cristina; Gonzalez, Carlota; Ferreiro, Alejandro

2014-01-01

26

Apparent pacemaker failure due to reversion circuitry within the programming device.  

PubMed

While being evaluated for a recurrent tachyarrhythmia, a patient with a permanent pacemaker underwent reprogramming of the unit from the DVI to the VVI mode for assessment of the underlying rhythm. Subsequent reprogramming of the pacemaker to the DVI or DDD mode was impossible despite multiple attempts and the use of multiple programmers. The problem was considered to be a malfunction of the pacemaker circuitry, and plans were made for the pacemaker to be explanted and a replacement unit implanted. Before the procedure, the pacemaker company was notified of the explantation. We subsequently learned that a special programming sequence had to be carried out because of reversion circuitry present in the pacemaker but not described in the available literature. This report emphasizes the need for familiarity with each of the individual pacemakers being implanted and the need for the manufacturer to be as specific as possible given the complexity of current units. PMID:6200849

Hayes, D L; Holmes, D R; Merideth, J; Osborn, M J; Bardsley, W T

1984-03-01

27

[The current status of permanent cardiac pacing in Spain. A report of the National Pacemaker Data Bank].  

PubMed

We report the activity concerning permanent cardiac pacing in Spain during year 1995, based on data submitted to the National Pacemaker Registry corresponding to the European Pacemaker Card. We describe population, etiology and electrocardiographic alterations that determined the need for stimulation and the global distribution of stimulation modes (AAI 1.7%; DDD 20.2%; VDD 11.3% and VVI 66.8%). We emphasize, among other aspects, stimulation in A-V block cases, in sick-sinus syndrome and tendencies compared to 1994's data and limited data corresponding to 1996. PMID:9424698

Coma Samartín, R

1997-11-01

28

Design of wavelet-based ECG detector for implantable cardiac pacemakers.  

PubMed

A wavelet Electrocardiogram (ECG) detector for low-power implantable cardiac pacemakers is presented in this paper. The proposed wavelet-based ECG detector consists of a wavelet decomposer with wavelet filter banks, a QRS complex detector of hypothesis testing with wavelet-demodulated ECG signals, and a noise detector with zero-crossing points. In order to achieve high detection accuracy with low power consumption, a multi-scaled product algorithm and soft-threshold algorithm are efficiently exploited in our ECG detector implementation. Our algorithmic and architectural level approaches have been implemented and fabricated in a standard 0.35 ?m CMOS technology. The testchip including a low-power analog-to-digital converter (ADC) shows a low detection error-rate of 0.196% and low power consumption of 19.02 ?W with a 3 V supply voltage. PMID:23893202

Min, Young-Jae; Kim, Hoon-Ki; Kang, Yu-Ri; Kim, Gil-Su; Park, Jongsun; Kim, Soo-Won

2013-08-01

29

The relevance of non-excitable cells for cardiac pacemaker function  

PubMed Central

Age-dependent changes in the architecture of the sinus node comprise an increasing ratio between fibroblasts and cardiomyocytes. This change is discussed as a potential mechanism for sinus node disease. The goal of this study was to determine the mechanism through which non-excitable cells influence the spontaneous activity of multicellular cardiomyocyte preparations. Cardiomyocyte monolayers (HL-1 cells) or embryonic stem cell-derived cardiomyocytes were used as two- and three-dimensional cardiac pacemaker models. Spontaneous activity and conduction velocity (?) were monitored by field potential measurements with microelectrode arrays (MEAs). The influence of fibroblasts (WT-fibs) was determined in heterocellular cultures of different cardiomyocyte and fibroblast ratios. The relevance of heterocellular gap junctional coupling was evaluated by the use of fibroblasts deficient for the expression of Cx43 (Cx43?/?-fibs). The beating frequency and ? of heterocellular cultures depended negatively on the fibroblast concentration. Interspersion of fibroblasts in cardiomyocyte monolayers increased the coefficient of the interbeat interval variability. Whereas Cx43?/?-fibs decreased ? significantly less than WT-fibs, their effect on the beating frequency and the beat-to-beat variability seemed largely independent of their ability to establish intercellular coupling. These results suggest that electrically integrated, non-excitable cells modulate the excitability of cardiac pacemaker preparations by two distinct mechanisms, one dependent and the other independent of the heterocellular coupling established. Whereas heterocellular coupling enables the fibroblast to depolarize the cardiomyocytes or to act as a current sink, the mere physical separation of the cardiomyocytes by fibroblasts induces bradycardia through a reduction in frequency entrainment. PMID:17932143

Fahrenbach, John P; Mejia-Alvarez, Rafael; Banach, Kathrin

2007-01-01

30

Exercise training starting at weaning age preserves cardiac pacemaker function in adulthood of diet-induced obese rats.  

PubMed

Peripheral sympathetic overdrive in young obese subjects contributes to further aggravation of insulin resistance, diabetes, and hypertension, thus inducing worsening clinical conditions in adulthood. Exercise training has been considered a strategy to repair obesity autonomic dysfunction, thereby reducing the cardiometabolic risk. Therefore, the aim of this study was to assess the effect of early exercise training, starting immediately after weaning, on cardiac autonomic control in diet-induced obese rats. Male Wistar rats (weaning) were divided into four groups: (i) a control group (n = 6); (ii) an exercise-trained control group (n = 6); (iii) a diet-induced obesity group (n = 6); and (iv) an exercise-trained diet-induced obesity group (n = 6). The development of obesity was induced by 9 weeks of palatable diet intake, and the training program was implemented in a motor-driven treadmill (5 times per week) during the same period. After this period, animals were submitted to vein and artery catheter implantation to assess cardiac autonomic balance by methylatropine (3 mg/kg) and propranolol (4 mg/kg) administration. Exercise training increased running performance in both groups (p < 0.05). Exercise training also prevented the increased resting heart rate in obese rats, which seemed to be related to cardiac pacemaker activity preservation (p < 0.05). Additionally, the training program preserved the pressure and bradycardia responses to autonomic blockade in obese rats (p < 0.05). An exercise program beginning at weaning age prevents cardiovascular dysfunction in obese rats, indicating that exercise training may be used as a nonpharmacological therapeutic strategy for the treatment of cardiometabolic diseases. PMID:24806307

Carvalho de Lima, Daniel; Guimarães, Juliana Bohnen; Rodovalho, Gisele Vieira; Silveira, Simonton Andrade; Haibara, Andrea Siqueira; Coimbra, Cândido Celso

2014-08-01

31

SK4 Ca2+ activated K+ channel is a critical player in cardiac pacemaker derived from human embryonic stem cells  

PubMed Central

Proper expression and function of the cardiac pacemaker is a critical feature of heart physiology. Two main mechanisms have been proposed: (i) the “voltage-clock,” where the hyperpolarization-activated funny current If causes diastolic depolarization that triggers action potential cycling; and (ii) the “Ca2+ clock,” where cyclical release of Ca2+ from Ca2+ stores depolarizes the membrane during diastole via activation of the Na+–Ca2+ exchanger. Nonetheless, these mechanisms remain controversial. Here, we used human embryonic stem cell-derived cardiomyocytes (hESC-CMs) to study their autonomous beating mechanisms. Combined current- and voltage-clamp recordings from the same cell showed the so-called “voltage and Ca2+ clock” pacemaker mechanisms to operate in a mutually exclusive fashion in different cell populations, but also to coexist in other cells. Blocking the “voltage or Ca2+ clock” produced a similar depolarization of the maximal diastolic potential (MDP) that culminated by cessation of action potentials, suggesting that they converge to a common pacemaker component. Using patch-clamp recording, real-time PCR, Western blotting, and immunocytochemistry, we identified a previously unrecognized Ca2+-activated intermediate K+ conductance (IKCa, KCa3.1, or SK4) in young and old stage-derived hESC-CMs. IKCa inhibition produced MDP depolarization and pacemaker suppression. By shaping the MDP driving force and exquisitely balancing inward currents during diastolic depolarization, IKCa appears to play a crucial role in human embryonic cardiac automaticity. PMID:23589888

Weisbrod, David; Peretz, Asher; Ziskind, Anna; Menaker, Nataly; Oz, Shimrit; Barad, Lili; Eliyahu, Sivan; Itskovitz-Eldor, Joseph; Dascal, Nathan; Khananshvili, Daniel; Binah, Ofer; Attali, Bernard

2013-01-01

32

Multicellular automaticity of cardiac cell monolayers: effects of density and spatial distribution of pacemaker cells  

NASA Astrophysics Data System (ADS)

Self-organization of pacemaker (PM) activity of interconnected elements is important to the general theory of reaction–diffusion systems as well as for applications such as PM activity in cardiac tissue to initiate beating of the heart. Monolayer cultures of neonatal rat ventricular myocytes (NRVMs) are often used as experimental models in studies on cardiac electrophysiology. These monolayers exhibit automaticity (spontaneous activation) of their electrical activity. At low plated density, cells usually show a heterogeneous population consisting of PM and quiescent excitable cells (QECs). It is therefore highly probable that monolayers of NRVMs consist of a heterogeneous network of the two cell types. However, the effects of density and spatial distribution of the PM cells on spontaneous activity of monolayers remain unknown. Thus, a simple stochastic pattern formation algorithm was implemented to distribute PM and QECs in a binary-like 2D network. A FitzHugh–Nagumo excitable medium was used to simulate electrical spontaneous and propagating activity. Simulations showed a clear nonlinear dependency of spontaneous activity (occurrence and amplitude of spontaneous period) on the spatial patterns of PM cells. In most simulations, the first initiation sites were found to be located near the substrate boundaries. Comparison with experimental data obtained from cardiomyocyte monolayers shows important similarities in the position of initiation site activity. However, limitations in the model that do not reflect the complex beat-to-beat variation found in experiments indicate the need for a more realistic cardiomyocyte representation.

Elber Duverger, James; Boudreau-Béland, Jonathan; Le, Minh Duc; Comtois, Philippe

2014-11-01

33

Mechano-sensitivity of cardiac pacemaker function: Pathophysiological relevance, experimental implications, and conceptual integration with other mechanisms of rhythmicity  

PubMed Central

Cardiac pacemaker cells exhibit spontaneous, rhythmic electrical excitation, termed automaticity. This automatic initiation of action potentials requires spontaneous diastolic depolarisation, whose rate determines normal rhythm generation in the heart. Pacemaker mechanisms have been split recently into: (i) cyclic changes in trans-sarcolemmal ion flows (termed the ‘membrane-clock’), and (ii) rhythmic intracellular calcium cycling (the ‘calcium-clock’). These two ‘clocks’ undoubtedly interact, as trans-sarcolemmal currents involved in pacemaking include calcium-carrying mechanisms, while intracellular calcium cycling requires trans-sarcolemmal ion flux as the mechanism by which it affects membrane potential. The split into separate ‘clocks’ is, therefore, somewhat arbitrary. Nonetheless, the ‘clock’ metaphor has been conceptually stimulating, in particular since there is evidence to support the view that either ‘clock’ could be sufficient in principle to set the rate of pacemaker activation. Of course, the same has also been shown for sub-sets of ‘membrane-clock’ ion currents, illustrating the redundancy of mechanisms involved in maintaining such basic functionality as the heartbeat, a theme that is common for vital physiological systems. Following the conceptual path of identifying individual groups of sub-mechanisms, it is important to remember that the heart is able to adapt pacemaker rate to changes in haemodynamic load, even after isolation or transplantation, and on a beat-by-beat basis. Neither the ‘membrane-’ nor the ‘calcium-clock’ do, as such, inherently account for this rapid adaptation to circulatory demand (cellular Ca2+ balance changes over multiple beats, while variation of sarcolemmal ion channel presence takes even longer). This suggests that a third set of mechanisms must be involved in setting the pace. These mechanisms are characterised by their sensitivity to the cyclically changing mechanical environment, and – in analogy to the above terminology – this might be considered a ‘mechanics-clock’. In this review, we discuss possible roles of mechano-sensitive mechanisms for the entrainment of membrane current dynamics and calcium-handling. This can occur directly via stretch-activation of mechano-sensitive ion channels in the sarcolemma and/or in intracellular membrane compartments, as well as by modulation of ‘standard’ components of the ‘membrane-’ or ‘calcium-clock’. Together, these mechanisms allow rapid adaptation to changes in haemodynamic load, on a beat-by-beat basis. Additional relevance arises from the fact that mechano-sensitivity of pacemaking may help to explain pacemaker dysfunction in mechanically over- or under-loaded tissue. As the combined contributions of the various underlying oscillatory mechanisms are integrated at the pacemaker cell level into a single output – a train of pacemaker action potentials – we will not adhere to a metaphor that implies separate time-keeping units (‘clocks’), and rather focus on cardiac pacemaking as the result of interactions of a set of coupled oscillators, whose individual contributions vary depending on the pathophysiological context. We conclude by considering the utility and limitations of viewing the pacemaker as a coupled system of voltage-, calcium-, and mechanics-modulated oscillators that, by integrating a multitude of inputs, offers the high level of functional redundancy that is vitally important for cardiac automaticity. PMID:23046620

Quinn, T. Alexander; Kohl, Peter

2012-01-01

34

[Cardiac resynchronizing therapy. Selection of patients and their management after implantation of biventricular heart pacemaker].  

PubMed

Chronic heart failure (CHF) - a widely spread manifestation of various forms of heart diseases - is characterized by high mortality. Prognosis is especially unfavorable in patients with wide QRS complex. Method of resynchronizing therapy was elaborated for the treatment of this group of patients in addition of medical therapy. Its efficacy for improvement of clinical course and prognosis of CHF was demonstrated in a number of randomized controlled trials. However according to some data in 30-45% of cases application of the method is associated with no clinical improvement or reversal of cardiac remodeling when standard criteria (left ventricular ejection fraction less or equal 35%, QRS 120-150 ms, functional class II-IV) are used for patients selection. In this review we consider possibilities of various methods of selection of patients providing maximal probability of efficacy. We also present analysis of techniques of detection of implantation site of left ventricular lead and various tactics of management of patients after implantation of biventricular pacemaker. PMID:23548431

Mareev, Iu V; Shitov, V N; Saidova, M A

2013-01-01

35

Adrenaline: Mechanism of Action on the Pacemaker Potential in Cardiac Purkinje Fibers  

Microsoft Academic Search

The pacemaker potential in Purkinje fibers is generated by a slow fall in potassium current which allows the inward background currents to depolarize the membrane. Adrenaline shifts the relation between activation of the potassium current and membrane potential in a depolarizing direction. Consequently, during the pacemaker potential, the potassium current falls more rapidly to lower values and the inward currents

O. Hauswirth; D. Noble; R. W. Tsien

1968-01-01

36

Quantitative Verification of Implantable Cardiac Pacemakers Taolue Chen Marco Diciolla Marta Kwiatkowska Alexandru Mereacre  

E-print Network

of safety and reliability. Unfortunately, according to the US Food and Drug Administration (FDA) [1], errors.lastname}@cs.ox.ac.uk Abstract--Implantable medical devices, such as cardiac pace- makers, must be designed and programmed to the highest levels of safety and reliability. Recently, errors in embedded software have led to a substantial

Oxford, University of

37

Induced voltage to an implantable cardiac pacemaker in a voxcel human model by a near-field intra-body communication device  

Microsoft Academic Search

The interference voltage at the terminals of a unipolar-type implantable cardiac pacemaker induced by a nearfield intra-body communication device was investigated by numerical calculations. Operating frequency was assumed 5 MHz. The dependency of induced voltage on the electrical constants of a realistic human model was examined. The results showed that the induced voltage was inversely proportional to the absolute value

Yuki Yoshino; Masao Taki; Akinori Furuya; Nobutaro Shibata; Mitsuru Shinagawa; Mitsuo Hattori

2011-01-01

38

Electromagnetic interference in a cardiac pacemaker during cauterization with the coagulating, not cutting mode.  

PubMed

Electromagnetic interference in pacemakers has almost always been reported in association with the cutting mode of monopolar electrocautery and rarely in association with the coagulation mode. We report a case of electrocautery-induced electromagnetic interference with a DDDR pacemaker (dual-chamber paced, dual-chamber sensed, dual response to sensing, and rate modulated) in the coagulating and not cutting mode during a spine procedure. We also discuss the factors affecting intraoperative electromagnetic interference. A 74-year-old man experienced intraoperative electromagnetic interference that resulted in asystole caused by surgical electrocautery in the coagulation mode while the electrodispersive pad was placed at different locations and distances from the operating site (This electromagnetic interference did not occur during the use of the cutting mode). However, because of careful management, the outcome was favorable. Clinicians should be aware that the coagulation mode of electrocautery can cause electromagnetic interference and hemodynamic instability. Heightened vigilance and preparedness can ensure a favorable outcome. PMID:22096289

Abdelmalak, Basem; Jagannathan, Narasimhan; Arain, Faisal D; Cymbor, Susan; McLain, Robert; Tetzlaff, John E

2011-10-01

39

Small bowel capsule endoscopy in patients with cardiac pacemakers and implantable cardioverter defibrillators: Outcome analysis using telemetry review  

PubMed Central

AIM: To determine if there were any interactions between cardiac devices and small bowel capsules secondary to electromagnetic interference (EMI) in patients who have undergone small bowel capsule endoscopy (SBCE). METHODS: Authors conducted a chart review of 20 patients with a cardiac pacemaker (CP) or implantable cardioverter defibrillator (ICD) who underwent continuous electrocardiographic monitoring during their SBCE from 2003-2008. authors searched for unexplained electrocardiogram (ECG) findings, changes in CP and ICD set parameters, any abnormality in transmitted capsule data, and adverse clinical events. RESULTS: There were no adverse events or hemodynamically significant arrhythmias reported. CP and ICD set parameters were preserved. The majority of ECG abnormalities were also found in pre- or post- SBCE ECG tracings and the CP behavior during arrhythmias appeared appropriate. Two patients seemed to have episodes of undersensing by the CP. However, similar findings were documented in ECGs taken outside the time frame of the SBCE. One patient was observed to have a low signal encountered from the capsule resulting in lack of localization, but no images were lost. CONCLUSION: Capsule-induced EMI remains a possibility but is unlikely to be clinically important. CP-induced interference of SBCE is also possible, but is infrequent and does not result in loss of images transmitted by the capsule. PMID:22442746

Cuschieri, Justin R; Osman, Mohammed N; Wong, Richard CK; Chak, Amitabh; Isenberg, Gerard A

2012-01-01

40

Dosimetric perturbations due to an implanted cardiac pacemaker in MammoSite{sup Registered-Sign} treatment  

SciTech Connect

Purpose: To investigate dose perturbations for pacemaker-implanted patients in partial breast irradiation using high dose rate (HDR) balloon brachytherapy. Methods: Monte Carlo (MC) simulations were performed to calculate dose distributions involving a pacemaker in Ir-192 HDR balloon brachytherapy. Dose perturbations by varying balloon-to-pacemaker distances (BPD = 50 or 100 mm) and concentrations of iodine contrast medium (2.5%, 5.0%, 7.5%, and 10.0% by volume) in the balloon were investigated for separate parts of the pacemaker (i.e., battery and substrate). Relative measurements using an ion-chamber were also performed to confirm MC results. Results: The MC and measured results in homogeneous media without a pacemaker agreed with published data within 2% from the balloon surface to 100 mm BPD. Further their dose distributions with a pacemaker were in a comparable agreement. The MC results showed that doses over the battery were increased by a factor of 3, compared to doses without a pacemaker. However, there was no significant dose perturbation in the middle of substrate but up to 70% dose increase in the substrate interface with the titanium capsule. The attenuation by iodine contrast medium lessened doses delivered to the pacemaker by up to 9%. Conclusions: Due to inhomogeneity of pacemaker and contrast medium as well as low-energy photons in Ir-192 HDR balloon brachytherapy, the actual dose received in a pacemaker is different from the homogeneous medium-based dose and the external beam-based dose. Therefore, the dose perturbations should be considered for pacemaker-implanted patients when evaluating a safe clinical distance between the balloon and pacemaker.

Sung, Wonmo; Kim, Siyong; Kim, Jung-in; Lee, Jae-gi; Shin, Young-Joo; Jung, Jae-Yong; Ye, Sung-Joon [Interdisciplinary Program in Radiation Applied Life Science, Seoul National University College of Medicine, Seoul 110-799, South Korea and Institute of Radiation Medicine, Seoul National University Medical Research Center, Seoul 110-744 (Korea, Republic of); Department of Radiation Oncology, Mayo Clinic, Jacksonville, Florida 32224 (United States); Interdisciplinary Program in Radiation Applied Life Science, Seoul National University College of Medicine, Seoul 110-799, South Korea and Department of Radiation Oncology, Kangbuk Samsung Medical Center, Seoul 110-746 (Korea, Republic of); Institute of Radiation Medicine, Seoul National University Medical Research Center, Seoul 110-744, South Korea and Department of Biomedical Radiation Sciences, Seoul National University, Seoul 151-742 (Korea, Republic of); Department of Radiation Oncology, Sanggye Paik Hospital, Inje University, Seoul 139-707 (Korea, Republic of); Interdisciplinary Program in Radiation Applied Life Science, Seoul National University College of Medicine, Seoul 110-799 (Korea, Republic of); Institute of Radiation Medicine, Seoul National University Medical Research Center, Seoul 110-744 (Korea, Republic of); Department of Biomedical Radiation Sciences, Seoul National University, Seoul 151-742 (Korea, Republic of); Department of Radiation Oncology, Seoul National University, Seoul 110-799 (Korea, Republic of) and Advanced Institutes of Convergence Technology, Seoul National University, Suwon 443-270 (Korea, Republic of)

2012-10-15

41

Relation between QT interval and heart rate. New design of physiologically adaptive cardiac pacemaker  

Microsoft Academic Search

The relation between QT interval and heart rate has been studied in a group of patients undergoing physiological exercise, in a group undergoing atrial pacing without exercise, and in a group with complete heart block undergoing exercise at a fixed ventricular rate controlled by cardiac pacing. The expected shortening in QT interval during physiological exercise is only in part the

A F Rickards; J Norman

1981-01-01

42

Effects of 4-aminopyridine on inward rectifying and pacemaker currents of cardiac purkinje fibres  

Microsoft Academic Search

1.4-Aminopyridine (4-AP), in a concentration of 1–5mM, prolongs the action potential duration, induces spontaneous activity and depolarizes sheep cardiac Purkinje strands. These effects are different from those obtained with 0.1mM and are reversible.2.Voltage clamp experiments demonstrate that the higher drug concentrations affect membrane currents measured in the potential range between-100 and-40mV, in addition to the reduction of the transient outward

P. P. Van Bogaert; D. J. Snyders

1982-01-01

43

77 FR 37570 - Effective Date of Requirement for Premarket Approval for a Pacemaker Programmer  

Federal Register 2010, 2011, 2012, 2013

...been no 510(k) submissions for pacemaker programmers since 1995 with the...implantable cardiac devices including pacemakers and defibrillators. Because these...product codes including adaptive rate pacemakers (LWP); implantable...

2012-06-22

44

Numerical models based on a minimal set of sarcolemmal electrogenic proteins and an intracellular Ca(2+) clock generate robust, flexible, and energy-efficient cardiac pacemaking.  

PubMed

Recent evidence supports the idea that robust and, importantly, FLEXIBLE automaticity of cardiac pacemaker cells is conferred by a coupled system of membrane ion currents (an "M-clock") and a sarcoplasmic reticulum (SR)-based Ca(2+) oscillator ("Ca(2+)clock") that generates spontaneous diastolic Ca(2+) releases. This study identified numerical models of a human biological pacemaker that features robust and flexible automaticity generated by a minimal set of electrogenic proteins and a Ca(2+)clock. Following the Occam's razor principle (principle of parsimony), M-clock components of unknown molecular origin were excluded from Maltsev-Lakatta pacemaker cell model and thirteen different model types of only 4 or 5 components were derived and explored by a parametric sensitivity analysis. The extended ranges of SR Ca(2+) pumping (i.e. Ca(2+)clock performance) and conductance of ion currents were sampled, yielding a large variety of parameter combination, i.e. specific model sets. We tested each set's ability to simulate autonomic modulation of human heart rate (minimum rate of 50 to 70bpm; maximum rate of 140 to 210bpm) in response to stimulation of cholinergic and ?-adrenergic receptors. We found that only those models that include a Ca(2+)clock (including the minimal 4-parameter model "ICaL+IKr+INCX+Ca(2+)clock") were able to reproduce the full range of autonomic modulation. Inclusion of If or ICaT decreased the flexibility, but increased the robustness of the models (a relatively larger number of sets did not fail during testing). The new models comprised of components with clear molecular identity (i.e. lacking IbNa & Ist) portray a more realistic pacemaking: A smaller Na(+) influx is expected to demand less energy for Na(+) extrusion. The new large database of the reduced coupled-clock numerical models may serve as a useful tool for the design of biological pacemakers. It will also provide a conceptual basis for a general theory of robust, flexible, and energy-efficient pacemaking based on realistic components. PMID:23507256

Maltsev, Victor A; Lakatta, Edward G

2013-06-01

45

Novel cardiac pacemaker-based human model of periodic breathing to develop real-time, pre-emptive technology for carbon dioxide stabilisation  

PubMed Central

Background Constant flow and concentration CO2 has previously been efficacious in attenuating ventilatory oscillations in periodic breathing (PB) where oscillations in CO2 drive ventilatory oscillations. However, it has the undesirable effect of increasing end-tidal CO2, and ventilation. We tested, in a model of PB, a dynamic CO2 therapy that aims to attenuate pacemaker-induced ventilatory oscillations while minimising CO2 dose. Methods First, pacemakers were manipulated in 12 pacemaker recipients, 6 with heart failure (ejection fraction (EF)=23.7±7.3%) and 6 without heart failure, to experimentally induce PB. Second, we applied a real-time algorithm of pre-emptive dynamic exogenous CO2 administration, and tested different timings. Results We found that cardiac output alternation using pacemakers successfully induced PB. Dynamic CO2 therapy, when delivered coincident with hyperventilation, attenuated 57% of the experimentally induced oscillations in end-tidal CO2: SD/mean 0.06±0.01 untreated versus 0.04±0.01 with treatment (p<0.0001) and 0.02±0.01 in baseline non-modified breathing. This translated to a 56% reduction in induced ventilatory oscillations: SD/mean 0.19±0.09 untreated versus 0.14±0.06 with treatment (p=0.001) and 0.10±0.03 at baseline. Of note, end-tidal CO2 did not significantly rise when dynamic CO2 was applied to the model (4.84±0.47 vs 4.91± 0.45?kPa, p=0.08). Furthermore, mean ventilation was also not significantly increased by dynamic CO2 compared with untreated (7.8±1.2 vs 8.4±1.2?L/min, p=0.17). Conclusions Cardiac pacemaker manipulation can be used to induce PB experimentally. In this induced PB, delivering CO2 coincident with hyperventilation, ventilatory oscillations can be substantially attenuated without a significant increase in end-tidal CO2 or ventilation. Dynamic CO2 administration might be developed into a clinical treatment for PB. Trial Registration number ISRCTN29344450.

Baruah, Resham; Giannoni, Alberto; Willson, Keith; Manisty, Charlotte H; Mebrate, Yoseph; Kyriacou, Andreas; Yadav, Hemang; Unsworth, Beth; Sutton, Richard; Mayet, Jamil; Hughes, Alun D; Francis, Darrel P

2014-01-01

46

Mapping Cardiac Pacemaker Circuits: Methodological Puzzles of the Sino-Atrial Node Optical Mapping  

PubMed Central

Historically, milestones in science are usually associated with methodological breakthroughs. Likewise, the advent of electrocardiography, microelectrode recordings and more recently optical mapping have ushered in new periods of significance of advancement in elucidating basic mechanisms in cardiac electrophysiology. As with any novel technique, however, data interpretation is challenging and should be approached with caution, as it cannot be simply extrapolated from previously used methodologies and with experience and time eventually becomes validated. A good example of this is the use of optical mapping in the sinoatrial node (SAN): when microelectrode and optical recordings are obtained from the same site in myocardium, significantly different results may be noted with respect to signal morphology and as a result have to be interpreted by a different set of principles. Given the rapid spread of the use of optical mapping, careful evaluation must be made in terms of methodology with respect to interpretation of data gathered by optical sensors from fluorescent potential-sensitive dyes. Different interpretations of experimental data may lead to different mechanistic conclusions. This review attempts to address the origin and interpretation of the “double component” morphology in the optical action potentials obtained from the SAN region. One view is that these two components represent distinctive signals from the sinoatrial node and atrial cells, and can be fully separated with signal processing. A second view is that the first component preceding the phase 0 activation represents the membrane currents and intracellular calcium transients induced diastolic depolarization from the SAN. While the consensus from both groups is that ionic mechanisms, namely the joint action of the membrane and calcium automaticity, are important in the SAN function, it is unresolved whether the double-component originates from the recording methodology or represents the underlying physiology. This overview aims to advance a common understanding of the basic principles of optical mapping in complex three-dimensional anatomical structures. PMID:20133911

Efimov, Igor R.; Fedorov, Vadim V.; Joung, Boyoung; Lin, Shien-Fong

2009-01-01

47

[Pacemaker, implanted cardiac defibrillator and irradiation: Management proposal in 2010 depending on the type of cardiac stimulator and prognosis and location of cancer].  

PubMed

Ionizing radiation may interfere with electric components of pacemakers or implantable cardioverter-defibrillators. The type, severity and extent of radiation damage to pacemakers, have previously been shown to depend on the total dose and dose rate. Over 300,000 new cancer cases are treated yearly in France, among which 60% are irradiated in the course of their disease. One among 400 of these patients has an implanted pacemaker or defibrillator. The incidence of pacemaker and implanted cardioverter defribillator increases in an ageing population. The oncologic prognosis must be weighted against the cardiologic prognosis in a multidisciplinary and transversal setting. Innovative irradiation techniques and technological sophistications of pacemakers and implantable cardioverter-defibrillators (with the introduction of more radiosensitive complementary metal-oxide-semiconductors since 1970) have potentially changed the tolerance profiles. This review of the literature studied the geometric, dosimetric and radiobiological characteristics of the radiation beams for high energy photons, stereotactic irradiation, protontherapy. Standardized protocols and radiotherapy optimization (particle, treatment fields, energy) are advisable in order to improve patient management during radiotherapy and prolonged monitoring is necessary following radiation therapy. The dose received at the pacemaker/heart should be calculated. The threshold for the cumulated dose to the pacemaker/implantable cardioverter-defibrillator (2 to 5 Gy depending on the brand), the necessity to remove/displace the device based on the dose-volume histogram on dosimetry, as well as the use of lead shielding and magnet are discussed. PMID:21435931

Lambert, P; Da Costa, A; Marcy, P-Y; Kreps, S; Angellier, G; Marcié, S; Bondiau, P-Y; Briand-Amoros, C; Thariat, J

2011-06-01

48

An Intelligent System for Pacemaker Reprogramming  

E-print Network

cardiac pacemakers and the excitatory and conductive system of the heart have a clear physical structure, model�based reasoning, abductive reasoning. 1 Introduction Cardiac disease in a patient may cause the excitatory and conductive system of the heart to fail, resulting in an abnormal cardiac rhythm, usually

Utrecht, Universiteit

49

Bioimpedance in the pacemaker clinic.  

PubMed

Thoracic electrical bioimpedance (TEB) provides a rapid, accurate, cost-effective method of optimizing the atrioventricular delay in dual-chamber pacemakers. In addition to measurements of cardiac output, TEB provides other hemodynamic indices such as systolic time interval, left cardiac work index, and end diastolic index. The availability of this additional data can assist the clinician in the objective determination of the optimal atrioventricular delay for individual patients. Thoracic electrical bioimpedance is completely noninvasive and takes only minutes to perform. PMID:10745711

Belott, P

1999-08-01

50

Voltage clamp of bull-frog cardiac pace-maker cells: a quantitative analysis of potassium currents.  

PubMed Central

Spontaneously active single cells have been obtained from the sinus venosus region of the bull-frog, Rana catesbeiana, using an enzymic dispersion procedure involving serial applications of trypsin, collagenase and elastase in nominally 0 Ca2+ Ringer solution. These cells have normal action potentials and fire spontaneously at a rate very similar to the intact sinus venosus. A single suction micro-electrode technique (Hamill, Marty, Neher, Sakmann & Sigworth, 1981; Hume & Giles, 1983) has been used to record the spontaneous diastolic depolarizations or pace-maker activity as well as the regenerative action potentials in these cells. This electrophysiological activity is completely insensitive to tetrodotoxin (TTX; 3 X 10(-6) M) and is very similar to that recorded from an in vitro sinus venosus preparation. The present experiments were aimed at identifying the transmembrane potassium currents, and analysing their role(s) in the development of the pace-maker potential and the repolarization of the action potential. Depolarizing voltage-clamp steps from the normal maximum diastolic potential (-75 mV) elicit a time- and voltage-dependent activation of an outward current. The reversal potential of this current in normal Ringer solution [( K+]0 2.5 mM) is near -95 mV; and it shifts by 51 mV per tenfold increase in [K+]0, which strongly suggests that this current is carried by K+. We therefore labelled it IK. The reversal potential of IK did not shift in the positive direction following very long (20 s) depolarizing clamp steps to +20 mV, indicating that 'extracellular' accumulation of [K+]0 does not produce any significant artifacts. The fully activated instantaneous current-voltage (I-V) relationship for IK is approximately linear over the range of potentials -130 to -30 mV. Thus, the ion transfer mechanism of IK may be described as a simple ohmic conductance in this range of potentials. Positive relative to -30 mV, however, the I-V exhibits significant inward rectification. A Hodgkin-Huxley analysis of the kinetics of IK, including a demonstration that the envelope of tails quantitatively matches the time course of the onset of IK during a prolonged depolarizing clamp step has been completed. The steady-state activation variable (n infinity) of IK spans the voltage range approximately -40 to +10 mV. It is well-fitted by a Boltzmann distribution function with half-activation at -20 mV. The time course of decay of IK is a single exponential. However, the activation or onset of IK shows clear sigmoidicity in the range of potentials from the activation threshold (-40 mV) to 0 mV.(ABSTRACT TRUNCATED AT 400 WORDS) Images PLATE 1 PLATE 2 PMID:2416914

Giles, W R; Shibata, E F

1985-01-01

51

Tertiapin-Q removes a large and rapidly acting component of vagal slowing of the guinea-pig cardiac pacemaker.  

PubMed

The participation of acetylcholine-activated potassium current (I(K,ACh)) and hyperpolarization-activated pacemaker current (I(f)) in vagal bradycardia were examined using vagally-innervated preparations of guinea-pig atria. Preparations were maintained in Krebs-Henseleit solution (36 degrees C). Before treatment, trains of vagal stimuli (10 s at 2, 5 and 10 Hz) produced graded bradycardias displaying rapid onset and offset. Tertiapin-Q (300 nM), which blocks I(K,ACh), had no effect on baseline atrial rate. In tertiapin-Q, vagal bradycardia displayed a gradual onset and offset, with a peak response ~50% of that recorded in control conditions. Cumulative addition of 1 mM ZD7288 (blocker of I(f)) caused atrial rate to fall by ~60%, but had no further effect on the amplitude of the vagal bradycardia, while response onset and offset became slightly faster. From these observations, we argue that (i) vagal bradycardia was attributable primarily to activation of I(K,ACh), (ii) vagal modulation of I(f) had a minor influence on the rate of onset and offset of bradycardia, and (iii) removal of the influence of I(K,ACh) unmasked a slow response, of undetermined origin, to vagal stimulation. In a separate set of experiments we compared the effects of 1 mM Ba(2+) and 300 nM tertiapin-Q on vagal bradycardia. Ba(2+) reduced baseline atrial rate and the response to vagal stimulation. Subsequent cumulative addition of tertiapin-Q had no additional effect on baseline atrial rate, but caused further reduction in the amplitude of vagal bradycardia, suggesting that 1 mM Ba(2+) did not achieve a complete block of I(K,ACh) in this preparation. PMID:19481505

Bolter, Chris P; Turner, Michael J

2009-10-01

52

42 CFR 410.49 - Cardiac rehabilitation program and intensive cardiac rehabilitation program: Conditions of coverage.  

Code of Federal Regulations, 2010 CFR

... (iii) Body mass index. (iv) Systolic blood pressure. (v) Diastolic blood pressure. (vi) The need for cholesterol, blood pressure, and diabetes medications. (3) A list of approved intensive cardiac rehabilitation programs,...

2010-10-01

53

42 CFR 410.49 - Cardiac rehabilitation program and intensive cardiac rehabilitation program: Conditions of coverage.  

Code of Federal Regulations, 2012 CFR

... (iii) Body mass index. (iv) Systolic blood pressure. (v) Diastolic blood pressure. (vi) The need for cholesterol, blood pressure, and diabetes medications. (3) A list of approved intensive cardiac rehabilitation programs,...

2012-10-01

54

Cardiac lipofibromatosis.  

PubMed

We present a case of cardiac lipofibromatosis associated with atrial fibrillation and complete heart block requiring permanent pacemaker implantation. Multimodality cardiac imaging including transthoracic echocardiography and cardiac magnetic resonance were useful for tissue characterization of this rare cardiac diagnosis. PMID:23146562

Shen, Seeger; Rizkallah, Jacques; Kirkpatrick, Iain D C; Khadem, Ali; Jassal, Davinder S

2013-04-01

55

A Programmable Implantable Microstimulator SoC With Wireless Telemetry: Application in Closed-Loop Endocardial Stimulation for Cardiac Pacemaker.  

PubMed

A low-power, wireless, and implantable microstimulator system on chip with smart powering management, immediate neural signal acquisition, and wireless rechargeable system is proposed. A system controller with parity checking handles the adjustable stimulus parameters for the stimulated objective. In the current paper, the rat's intra-cardiac electrogram is employed as the stimulated model in the animal study, and it is sensed by a low-voltage and low-power monitoring analog front end. The power management unit, which includes a rectifier, battery charging and detection, and a regulator, is used for the power control of the internal circuits. The stimulation data and required clock are extracted by a phase-locked-loop-based phase shift keying demodulator from an inductive AC signal. The full chip, which consumes 48 ?W only, is fabricated in a TSMC 0.35 ?m 2P4M standard CMOS process to perform the monitoring and pacing functions with inductively powered communication in the in vivo study. PMID:23852549

Shuenn-Yuh Lee; Su, M Y; Ming-Chun Liang; You-Yin Chen; Cheng-Han Hsieh; Chung-Min Yang; Hsin-Yi Lai; Jou-Wei Lin; Qiang Fang

2011-12-01

56

Interference between pacemakers/implantable cardioverter defibrillators and video capsule endoscopy  

PubMed Central

Our Letter to the Editor, related to the article “Small bowel capsule endoscopy in patients with cardiac pacemakers and implantable cardioverter defibrillators: Outcome analysis using telemetry” by Cuschieri et al, comments on some small errors, that slipped into the authors discussions. The given informations concerning the pacemaker- and implantable cardioverter defibrillators modes were inaccurate and differ between the text and the table. Moreover, as 8 of 20 patient’s pacemakers were programmed to VOO or DOO (“interference mode”) and one patient was not monitored by telemetry during capsule endoscopy, 9 of 20 patients (45%) lack the informations of possible interference between capsule endoscopy their implanted device. Another objection refers to the interpretation of an electrocardiogram (figure 1, trace B) presented: in contrast to the author’s opinion the marked spike should be interpreted as an artefact and not as ”undersensing of a fibrillatory wave”. Finally, three comments to cited reviews were not complete respectively not quoted correctly. PMID:23596547

Bandorski, Dirk; Gehron, Johannes; Holtgen, Reinhard

2013-01-01

57

Gene therapy: Biological pacemaker created by gene transfer  

NASA Astrophysics Data System (ADS)

The pacemaker cells of the heart initiate the heartbeat, sustain the circulation, and dictate the rate and rhythm of cardiac contraction. Circulatory collapse ensues when these specialized cells are damaged by disease, a situation that currently necessitates the implantation of an electronic pacemaker. Here we report the use of viral gene transfer to convert quiescent heart-muscle cells into pacemaker cells, and the successful generation of spontaneous, rhythmic electrical activity in the ventricle in vivo. Our results indicate that genetically engineered pacemakers could be developed as a possible alternative to implantable electronic devices.

Miake, Junichiro; Marbán, Eduardo; Nuss, H. Bradley

2002-09-01

58

21 CFR 870.3600 - External pacemaker pulse generator.  

...permanent pacemaker can be implanted, or to control irregular heartbeats in patients following cardiac surgery or a myocardial infarction. The device may have adjustments for impulse strength, duration, R-wave sensitivity, and other pacing variables....

2014-04-01

59

21 CFR 870.3600 - External pacemaker pulse generator.  

Code of Federal Regulations, 2013 CFR

...permanent pacemaker can be implanted, or to control irregular heartbeats in patients following cardiac surgery or a myocardial infarction. The device may have adjustments for impulse strength, duration, R-wave sensitivity, and other pacing variables....

2013-04-01

60

21 CFR 870.3600 - External pacemaker pulse generator.  

Code of Federal Regulations, 2011 CFR

...permanent pacemaker can be implanted, or to control irregular heartbeats in patients following cardiac surgery or a myocardial infarction. The device may have adjustments for impulse strength, duration, R-wave sensitivity, and other pacing variables....

2011-04-01

61

21 CFR 870.3600 - External pacemaker pulse generator.  

Code of Federal Regulations, 2012 CFR

...permanent pacemaker can be implanted, or to control irregular heartbeats in patients following cardiac surgery or a myocardial infarction. The device may have adjustments for impulse strength, duration, R-wave sensitivity, and other pacing variables....

2012-04-01

62

Pacemakers and implantable cardioverter defibrillators--general and anesthetic considerations.  

PubMed

A pacemaking system consists of an impulse generator and lead or leads to carry the electrical impulse to the patient's heart. Pacemaker and implantable cardioverter defibrillator codes were made to describe the type of pacemaker or implantable cardioverter defibrillator implanted. Indications for pacing and implantable cardioverter defibrillator implantation were given by the American College of Cardiologists. Certain pacemakers have magnet-operated reed switches incorporated; however, magnet application can have serious adverse effects; hence, devices should be considered programmable unless known otherwise. When a device patient undergoes any procedure (with or without anesthesia), special precautions have to be observed including a focused history/physical examination, interrogation of pacemaker before and after the procedure, emergency drugs/temporary pacing and defibrillation, reprogramming of pacemaker and disabling certain pacemaker functions if required, monitoring of electrolyte and metabolic disturbance and avoiding certain drugs and equipments that can interfere with pacemaker function. If unanticipated device interactions are found, consider discontinuation of the procedure until the source of interference can be eliminated or managed and all corrective measures should be taken to ensure proper pacemaker function should be done. Post procedure, the cardiac rate and rhythm should be monitored continuously and emergency drugs and equipments should be kept ready and consultation with a cardiologist or a pacemaker-implantable cardioverter defibrillator service may be necessary. PMID:24907883

Rapsang, Amy G; Bhattacharyya, Prithwis

2014-01-01

63

Recent Advances in Pacemaker Lead Technology  

Microsoft Academic Search

The cardiac pacemaker lead is a relatively fragile cable of insulated conductor wire implanted into the hostile environment of the human body. In comparison with the marked advances in pulse generator and sensor technology, concomitant advances in pacing leads have occurred slowly. This chapter will address recent engineering advances and clinical application of modern lead design.

Harry G. Mond

1999-01-01

64

The basis for activity controlled rate variable cardiac pacemakers: an analysis of mechanical forces on the human body induced by exercise and environment.  

PubMed

We conducted tests on six healthy volunteers and six pacemaker patients. With the aid of three straight line frequency acceleration pickups attached to the body, the mechanical signals were recorded on the three axes during different activities. Along with standardized exercise on bicycle and treadmill ergometers, we tested the influence of household activities and interference influences. The results were analyzed in terms of the amplitude and frequency content of the signals. For walking activities, we found a signal amplitude increasing in a largely linear fashion with the walking speed, the signal amplitudes being approximately twice as high on the vertical axis as on the other two axes. Exercise on the bicycle ergometer produced mechanical signals of clearly lower amplitude than comparable walking activities. The Fast-Fourier analysis showed amplitude peaks in the low frequency range of 1 to 4 Hz for all forms of physiological exercise, while interference influences showed amplitude peaks mainly in the range above 8 Hz. The use of a straight line-frequency acceleration pickup and a corresponding low pass filter might be a way of reducing the effect of unphysiological interference influences on an activity controlled pacemaker system. A sensor measuring on the horizontal axis appears to be the most favorable compromise for the various types of exercise. However, due to the considerable difference in signal amplitude for different types of exercise of the same intensity, an activity controlled pacemaker system cannot entirely meet metabolic conditions and requirements. PMID:2477823

Alt, E; Matula, M; Theres, H; Heinz, M; Baker, R

1989-10-01

65

Predictors of women's attendance at cardiac rehabilitation programs.  

PubMed

This descriptive study was conducted to identify the factors that influence womens attendance at cardiac rehabilitation programs and womens adherence to risk factor modification following a cardiac event. Women (N=196) admitted to hospital for a cardiac event were followed-up at 12 weeks postdischarge. Despite eligibility, only 64% (n=112) had been referred to cardiac rehabilitation programs. By 12 weeks postdischarge only 32% of the total sample (n=57) attended programs and 12% of the total sample (n=21) had dropped out before completion. The odds of a woman attending cardiac rehabilitation were decreased by myocardial infarction diagnosis, lack of employment, <55 years or >70 years, and experiencing a personal stressful event during follow-up. Women were likely to adhere to smoking, medication, and stress modification guidelines but unlikely to adhere to modification guidelines for diet and exercise. PMID:12893973

Gallagher, Robyn; McKinley, Sharon; Dracup, Kathleen

2003-01-01

66

Low frequency magnetic emissions and resulting induced voltages in a pacemaker by iPod portable music players  

PubMed Central

Background Recently, malfunctioning of a cardiac pacemaker electromagnetic, caused by electromagnetic interference (EMI) by fields emitted by personal portable music players was highly publicized around the world. A clinical study of one patient was performed and two types of interference were observed when the clinicians placed a pacemaker programming head and an iPod were placed adjacent to the patient's implanted pacemaker. The authors concluded that "Warning labels may be needed to avoid close contact between pacemakers and iPods". We performed an in-vitro study to evaluate these claims of EMI and present our findings of no-effects" in this paper. Methods We performed in-vitro evaluations of the low frequency magnetic field emissions from various models of the Apple Inc. iPod music player. We measured magnetic field emissions with a 3-coil sensor (diameter of 3.5 cm) placed within 1 cm of the surface of the player. Highly localized fields were observed (only existing in a one square cm area). We also measured the voltages induced inside an 'instrumented-can' pacemaker with two standard unipolar leads. Each iPod was placed in the air, 2.7 cm above the pacemaker case. The pacemaker case and leads were placed in a saline filled torso simulator per pacemaker electromagnetic compatibility standard ANSI/AAMI PC69:2000. Voltages inside the can were measured. Results Emissions were strongest (? 0.2 ?T pp) near a few localized points on the cases of the two iPods with hard drives. Emissions consisted of 100 kHz sinusoidal signal with lower frequency (20 msec wide) pulsed amplitude modulation. Voltages induced in the iPods were below the noise level of our instruments (0.5 mV pp in the 0 – 1 kHz band or 2 mV pp in the 0 – 5 MHz bandwidth. Conclusion Our measurements of the magnitude and the spatial distribution of low frequency magnetic flux density emissions by 4 different models of iPod portable music players. Levels of less than 0.2 ?T exist very close (1 cm) from the case. The measured voltages induced inside an 'instrumented-can' pacemaker were below the noise level of our instruments. Based on the observations of our in-vitro study we conclude that no interference effects can occur in pacemakers exposed to the iPod devices we tested. PMID:18241327

Bassen, Howard

2008-01-01

67

MRI-conditional pacemakers: current perspectives  

PubMed Central

Use of both magnetic resonance imaging (MRI) and pacing devices has undergone remarkable growth in recent years, and it is estimated that the majority of patients with pacemakers will need an MRI during their lifetime. These investigations will generally be denied due to the potentially dangerous interactions between cardiac devices and the magnetic fields and radio frequency energy used in MRI. Despite the increasing reports of uneventful scanning in selected patients with conventional pacemakers under close surveillance, MRI is still contraindicated in those circumstances and cannot be considered a routine procedure. These limitations prompted a series of modifications in generator and lead engineering, designed to minimize interactions that could compromise device function and patient safety. The resulting MRI-conditional pacemakers were first introduced in 2008 and the clinical experience gathered so far supports their safety in the MRI environment if certain conditions are fulfilled. With this technology, new questions and controversies arise regarding patient selection, clinical impact, and cost-effectiveness. In this review, we discuss the potential risks of MRI in patients with electronic cardiac devices and present updated information regarding the features of MRI-conditional pacemakers and the clinical experience with currently available models. Finally, we provide some guidance on how to scan patients who have these devices and discuss future directions in the field. PMID:24851058

Ferreira, Antonio M; Costa, Francisco; Tralhao, Antonio; Marques, Hugo; Cardim, Nuno; Adragao, Pedro

2014-01-01

68

Inappropriate ventricular blanking in a DDI pacemaker.  

PubMed

The DDI mode is a new pacing mode with potential advantages over DVI pacing. We describe anomalous post R wave ventricular pacing due to the presence of inappropriate ventricular blanking periods in a pacemaker programmed to the DDI mode. Although no adverse consequences were seen in our patients, potentially dangerous R-on-T pacing could occur, particularly if long atrioventricular delays are programmed. A method for eliminating this pacing anomaly is described. Patients programmed to the DDI mode with the pacemaker model described should be evaluated for post R wave ventricular pacing and corrective measures should be taken. PMID:2426670

Erlebacher, J A; Stelzer, P

1986-07-01

69

SCN5A and sinoatrial node pacemaker function  

Microsoft Academic Search

The SCN5A gene encodes specific voltage-dependent Na+ channels abundant in cardiac muscle that open and close at specific stages of cardiac activity in response to voltage change, thereby controlling the magnitude and timecourse of voltage-dependent Na+ currents (iNa )i n cardiac muscle cells. Although iNa has been recorded from sinoatrial (SA) node pacemaker cells, its precise role in SA node

Ming Lei; Henggui Zhang; Andrew A. Grace; H. Huang

2007-01-01

70

Clinical assessment of pacemaker power sources  

SciTech Connect

The development of power sources for cardiac pacemakers has progressed from a 15-year usage of mercury-zinc batteries to widely used and accepted lithium cells. At present, there are about 6 different types of lithium cells incorporated into commercially distributed pacemakers. The authors reviewed experience over a 5-year period with 1711 mercury-zinc, 130 nuclear (P238) and 1912 lithium powered pacemakers. The lithium units have included 698 lithium-iodide, 270 lithium-silver chromate, 135 lithium-thionyl chloride, 31 lithium-lead and 353 lithium-cupric sulfide batteries. 57 of the lithium units have failed (91.2% component failure and 5.3% battery failure). 459 mercury-zinc units failed (25% component failure and 68% battery depletion). The data show that lithium powered pacemaker failures are primarily component, while mercury-zinc failures are primarily battery related. It is concluded that mercury-zinc powered pulse generators are obsolete and that lithium and nuclear (P238) power sources are highly reliable over the 5 years for which data are available. 3 refs.

Bilitch, M.; Parsonnet, V.; Furman, S.

1980-01-01

71

Magnetic Resonance Imaging Conditional Pacemakers: Rationale, Development and Future Directions  

PubMed Central

Pacemakers and other cardiac implantable electronic devices (CIEDs) have long been considered an absolute contraindication to magnetic resonance imaging (MRI), a crucial and growing imaging modality. In the last 20 years, protocols have been developed to allow MR scanning of CIED patients with a low complication rate. However, this practice has remained limited to a relatively small number of centers, and many pacemaker patients continue to be denied access to clinically indicated imaging. The introduction of MRI conditional pacemakers has provided a widely applicable and satisfactory solution to this problem. Here, the interactions of pacemakers with the MR environment, the results of MR scanning in patients with conventional CIEDs, the development and clinical experience with MRI conditional devices, and future directions are reviewed. PMID:23071382

Cronin, Edmond M; Wilkoff, Bruce L

2012-01-01

72

Noninvasive evaluation of retrograde conduction times to avoid pacemaker-mediated tachycardia.  

PubMed

Pacemaker-mediated tachycardia is a potential complication of atrioventricular (AV) universal DDD pacemakers when retrograde ventriculoatrial (VA) conduction is slower than the postventricular-atrial refractory period of the pulse generator. The propensity for pacemaker-mediated tachycardia was noninvasively assessed in 17 patients with a unipolar DDD pacemaker using chest wall stimulation. Low amplitude stimuli were delivered to chest wall electrodes through a programmed stimulator. Using this method, 13 of the 17 patients were found to have absent VA conduction or VA conduction time less than the postventricular-atrial refractory period. In the four patients with noninvasively measured VA conduction time greater than the postventricular-atrial refractory period, sustained pacemaker-mediated tachycardia was induced. Reprogramming of pacemaker parameters prevented repeat induction of pacemaker-mediated tachycardia in only one of four patients. The three remaining patients had clinical pacemaker-mediated tachycardia and underwent pacemaker programming to the DVI mode. A total of 13 patients continue to use DDD mode after a mean follow-up period of 9.5 +/- 5.4 months. Invasive measurement of VA conduction was performed in 13 of the 17 patients. The noninvasive method accurately predicted the invasive measurement in each case. Noninvasive evaluation of VA conduction accurately predicts the propensity for pacemaker-mediated tachycardia under a variety of clinical conditions. Serial testing can be performed after pacemaker reprogramming or drug intervention. Noninvasive evaluation of retrograde VA conduction should predict most clinical episodes of pacemaker-mediated tachycardia. PMID:3998322

Greenspon, A J; Greenberg, R M

1985-06-01

73

Pacemaker patient-triggered event recording: accuracy, utility, and cost for the pacemaker follow-up clinic.  

PubMed

Many pacemaker patients have vague symptoms following implantation. It is often difficult for the physician to ascertain if they are cardiac in origin. A new pacemaker feature has been introduced, Patient-Triggered Event Records (PTER), to help the physician with this diagnosis. The PTER is a continuously running event record which stores the cardiac rhythm and rate. Brief application of a magnet will transfer the record into the device's memory. The data recorded will be the 97 events prior to the magnet application and the 30 events following magnet removal. The exact state of pacing (atrial and ventricular sensing/pacing, or premature ventricular events) and the rate of the ventricular events will be graphically displayed by the programmer for all 127 events. Thus, the exact pacer and cardiac rhythm can be determined during the period of the symptomatic episode. A total of three PTER's can be stored within the device. If a fourth is recorded, it will replace the oldest record. Three pacemakers with the PTER feature were tested in vitro with five different simulated cardiac rhythms. A beat-by-beat comparison between the PTER and the 15 simulated test rhythms revealed a 100% accurate documentation by PTER. Sixteen pacemaker patients which have the PTER feature were monitored using a King of Hearts for a total of 43 symptomatic events. The PTER records produced clinically relevant information 98% of the time while the King of Hearts produced clinically relevant information 81% of the time. A comparison of costs of the two different methods of monitoring these patients, was $2,432 versus $4,480 for the PTER and loop event monitor respectively. The PTER is an accurate, lower cost method for monitoring and diagnosing symptomatic pacemaker patients. The PTER can be used as the first diagnostic tool in troubleshooting patients with paroxysmal symptoms in the pacemaker clinic population. PMID:8945047

Machado, C; Johnson, D; Thacker, J R; Duncan, J L

1996-11-01

74

Echocardiography-guided biventricular pacemaker optimization: role of echo Doppler in hemodynamic assessment and improvement.  

PubMed

In spite of improvements in heart failure management and increasing utilization of cardiac resynchronization therapy (CRT), approximately 30-40% of CRT patients remain nonresponders and 50% or more are echocardiographic nonresponders (defined as less than 15% reduction in left ventricular end systolic volume post-CRT). Optimization guided by echocardiography has been studied as one of the methods to improve the nonresponder rate to CRT. Echo-guided biventricular (Biv) pacemaker optimization has been associated with improvement in acute cardiac hemodynamics and improvement in functional class. In this review, the authors discuss various methods to optimize Biv pacemaker by echocardiography, recent advances in pacemaker optimization and the limitations of echocardiography. The authors also demonstrate complex hemodynamic derangements in heart failure via multiple case examples highlighting the role of comprehensive echo Doppler in elucidating cardiac hemodynamics encountered in CRT nonresponders, as well as tailoring of Biv pacemaker optimization to the underlying physiologic derangement. PMID:22908920

Rafie, Reza; Naqvi, Tasneem Z

2012-07-01

75

Usability assessment of pacemaker programmers.  

PubMed

There is a perception among clinicians of usability differences in the user interface of pacemaker programmers, but there is an absence of literature in this area. The purpose of this study was to describe usability differences in pacemaker programmers. Forty-two programmer users completed self-administered questionnaires and two usability experts independently performed heuristic evaluation to identify features that violated general usability principles. Programmers from seven manufacturers (coded A-G) were evaluated. There was a balanced representation of users: nurses (58%) versus technologists (40%) who are employed in community (50%) versus academic (45%) hospitals, novice versus expert users based on the median users' programming experience of 60 months (range 1-300 months). Significant differences between programmers were found in overall user satisfaction and ease of programmer use (P < 0.0001) in the display, controls, operation, and physical dimension of the programmers (P < 0.05). Heuristic evaluations showed frequent violations of usability principles in all programmers. Problematic areas include reliance on user recall, inconsistency in operation of critical controls, poor readability, and not anticipating user wants or action. Programmer interface designs do not consistently meet user needs or general usability principles. This impacts on the safe and effective use of programmers. Guidelines in programmer design should be established, particularly with respect to labeling, location, and operation of critical controls. PMID:15511248

Chiu, Christine C; Vicente, Kim J; Buffo-Sequeira, Ilan; Hamilton, Robert M; McCrindle, Brian W

2004-10-01

76

Ventriculoatrial conduction: a cause of atrial malpacing in AV universal pacemakers. A report of two cases.  

PubMed

Retrograde atrial activation during ventricular pacing has often been a cause of intermittent or persistent arrhythmias (pacemaker-mediated tachycardia) in AV universal pacemakers. We recently encountered two cases in which VA conduction was responsible for atrial malpacing in patients with an implanted AV universal pacemaker, one programmed in DDD and one in DVI mode. Atrial malpacing was induced by the atrial refractoriness due to retrograde activation. In the first patient, it was observed when the pacemaker was programmed to a rate of 110 ppm (lower rate) and an AV interval of 200 ms in order to check crosstalk. In the second patient, it was observed after ventricular premature contractions. PMID:2578641

van Gelder, L M; El Gamal, M I

1985-01-01

77

In vitro investigation of eddy current effect on pacemaker operation generated by low frequency magnetic field.  

PubMed

This paper presents in vitro investigation of the eddy current induction effects to the cardiac pacemaker exposed to low frequency magnetic fields. The method used in this study is based to the interaction by inductive coupling through the loop formed by the pacemaker and its leads and the surrounding medium. This interaction results in an induced electromotive force between the terminals of the pacemaker which can potentially disturb the operation of this last. In this article we present experimental results, analytical calculations and numerical simulations using the finite element method. PMID:18003302

Babouri, A; Hedjeidj, A

2007-01-01

78

[Pacemaker implantation in a patient with cor triatriatum sinister - preoperative evaluation].  

PubMed

A case of 72 year old-male with cor triatriatum sinister, permanent atrial fibrillation and symptomatic bradycardia is presented. Patient was scheduled for pacemaker implantation. A preoperative evaluation with transesophageal echocardiography revealed a nonrestrictive membrane in left atrium, normal right superior vena cava and absence of persistent left superior vena cava and other cardiac anomalies. A right ventricular pacemaker lead was implanted through left subclavian approach. Preoperative evaluation shortened a radiation exposure and procedure time. PMID:19253197

Maziarz, Andrzej; Zabek, Andrzej; Ma?ecka, Barbara; Lelakowski, Jacek

2009-01-01

79

A gradient model of cardiac pacemaker myocytes  

Microsoft Academic Search

We have formulated a spatial-gradient model of action potential heterogeneity within the rabbit sinoatrial node (SAN), based on cell-specific ionic models of electrical activity from its central and peripheral regions. The ionic models are derived from a generic cell model, incorporating five background and exchange currents, and seven time-dependent currents based on three- or four-state Markov schemes. State transition rates

Nigel H. Lovell; Shaun L. Cloherty; Branko G. Celler; Socrates Dokos

2004-01-01

80

A randomized controlled clinical trial of pacemaker follow-up in clinic and by telemedical interpretation of the pacemakers' magnet mode.  

PubMed

We assessed a two-stage follow-up procedure for cardiac pacemakers, where in-clinic follow-ups were partly replaced by telemedical follow-ups. This was compared with the standard follow-up regime (in-clinic follow-up only). The new procedure required an electronic patient record, a telemedical follow-up unit for recording ECGs while the pacemaker was temporarily set to magnet mode, an ECG processing unit, and a reviewing and reporting unit. A total of 177 (86 female) patients were randomized to the control group and 182 (98 female) patients to the telemedicine group. In the telemedicine group, 234 telemedical follow-ups were performed. Out of these, 68 required an additional in-clinic follow-up, while 166 were sufficient for assessing the pacemakers' working status. During the study, there were 19 deaths in the telemedicine group and 20 in the control group. There was no significant difference between the two groups(P?=?0.40). The probability that an individual patient's pacemaker would not to be replaced over time was analysed in a similar way to the Kaplan-Meier survival function. Fewer pacemakers were replaced in the telemedicine group (14) than in the control group (18), but the difference was not significant (P?=?0.26). We conclude that alternating telemedical and in-clinic follow-ups brings no additional risks for patients. The follow-up procedure is feasible and interpretation of the pacemakers' magnet effect provides an easy-to-use, manufacturer-independent method of assessing the pacemakers' working status. This should reduce the patient load on pacemaker centres and decrease the overall costs of pacemaker therapy. PMID:24197403

Hayn, Dieter; Kollmann, Alexander; Perl, Sabine; Kos, Cornelia; Rotman, Brigitte; Lercher, Peter; Tscheliessnigg, Karl-Heinz; Schreier, Günter

2013-12-01

81

VideoLab: Optogenetic Pacemaker  

NSDL National Science Digital Library

In mammals, the heart's primary pacemaker lies in a specialized group of cells -- but do non-mammalian vertebrates have a similar control system? To find out, Arrenberg et al. genetically engineered zebrafish to express light-sensitive proteins, and then used light beams generated with a digital micromirror device to locate and manipulate the function of the pacemaker cells in the hearts of zebrafish embryos -- capturing the action on high-speed video.

Aristides B. Arrenberg (University of California; University of Freiburg;Department of Physiology; Institute of Biology); Didier Y. R. Stainier (University of California;Department of Biochemistry and Biophysics and Cardiovascular Research Institute); Herwig Baier (University of California;Department of Physiology); Jan Huisken (University of California; Max Planck Institute of Molecular Cell Biology and Genetics;Department of Biochemistry and Biophysics and Cardiovascular Research Institute)

2010-11-12

82

Runaway atrioventricular sequential pacemaker after radiation therapy.  

PubMed

Pacemaker malfunction manifested as a runaway circuitry occurred in two patients after they received radiation therapy for treatment of carcinoma. Both pacemakers were programmable atrioventricular sequential units (DVI) with complementary metal oxide semiconductor circuitry. One pacemaker was directly in the radiation field, whereas the other was not directly within the radiation port. Thus, direct irradiation of an implanted pacemaker should be avoided. It is advisable that a pacemaker be shielded even when the pacemaker is not in the direct field of radiation. PMID:3776991

Lee, R W; Huang, S K; Mechling, E; Bazgan, I

1986-11-01

83

Hydrogen-induced microelectronic capacitor failure in pacemakers.  

PubMed

Ceramic chip capacitors used in hybrid microelectronics for cardiac pacemakers are usually highly reliable. However, under certain conditions of capacitor construction, capacitor materials, mounting techniques, and environmental conditions, high failure rates may occur. A specific example is presented in which a ceramic capacitor used in an implanted pacemaker delaminated and failed approximately 30 days after being implanted. The failed capacitor caused a pulse rate rise, but due to circuit design techniques, the rate increase was limited to an acceptable value. The capacitor that failed was from an isolated lot of capacitors that was manufactured using pure palladium plates. The circuit containing this capacitor was hermetically sealed within a titanium case by welding. During the welding, a small amount of hydrogen was released from the titanium which, over a period of 2 to 4 weeks, was absorbed by the palladium plates in the capacitor. By absorbing the hydrogen, the palladium plates exhibit a volumetric expansion of sufficient magnitude to crack and delaminate the capacitor to the point of failure. Subsequently, the recurrence of this failure mode has been avoided by using capacitors containing special palladium alloys that cannot absorb hydrogen. This phenomenon is of interest to pacemaker designers since mercury batteries used in conventional pacemakers generate large amounts of hydrogen and potentially may be responsible for complications when used in conjunction with capacitors containing palladium. PMID:958043

Rainer, W G; Kolenik, S A; Whittaker, R E; Sadler, T R; Lapin, E S

1976-01-01

84

Cardiac Resynchronization Therapy and phase resetting of the sinoatrial node: A conjecture  

NASA Astrophysics Data System (ADS)

Congestive heart failure is a severe chronic disease often associated with disorders that alter the mechanisms of excitation-contraction coupling that may result in an asynchronous left ventricular motion which may further impair the ability of the failing heart to eject blood. In recent years a therapeutic approach to resynchronize the ventricles (cardiac resynchronization therapy, CRT) has been performed through the use of a pacemaker device able to provide atrial-based biventricular stimulation. Atrial lead senses the spontaneous occurrence of cells depolarization and sends the information to the generator which, in turn, after a settled delay [atrioventricular (AV) delay], sends electrical impulses to both ventricles to stimulate their synchronous contraction. Recent studies performed on heart rate behavior of chronically implanted patients at different epochs after implantation have shown that CRT can lead to sustained overall improvement of heart function with a reduction in morbidity and mortality. At this moment, however, there are no studies about CRT effects on spontaneous heart activity of chronically implanted patients. We performed an experimental study in which the electrocardiographic signal of five subjects under chronic CRT was recorded during the activity of the pacemaker programmed at different AV delays and under spontaneous cardiac activity after pacemaker deactivation. The different behavior of heart rate variability during pacemaker activity and after pacemaker deactivation suggested the hypothesis of a phase resetting mechanism induced by the pacemaker stimulus on the sinoatrial (SA) node, a phenomenon already known in literature for aggregate of cardiac cells, but still unexplored in vivo. The constraints imposed by the nature of our study (in vivo tests) made it impossible to plan an experiment to prove our hypothesis directly. We therefore considered the best attainable result would be to prove the accordance of our data to the conjecture through the use of models and physical considerations. We first used the data of literature on far-field effects of cardiac defibrillators to prove that the pacemaker impulses delivered to the two ventricles were able to induce modifications in membrane voltage at the level of the SA node. To simulate a phase resetting mechanism of the SA node, we used a Van der Pol modified model to allow the possibility of changing the refractory period and the firing frequency of the cells separately. With appropriate parameters of the model we reproduced phase response curves that can account for our experimental data. Furthermore, the simulated curves closely resemble the functional form proposed in literature for perturbed aggregate of cardiac cells. Despite the small sample of subjects investigated and the limited number of ECG recordings at different AV delays, we think we have proved the plausibility of the proposed conjecture.

Cantini, Federico; Varanini, Maurizio; Macerata, Alberto; Piacenti, Marcello; Morales, Maria-Aurora; Balocchi, Rita

2007-03-01

85

Cost-analysis of gym-based versus home-based cardiac rehabilitation programs  

Microsoft Academic Search

A cost-analysis of an existing gym-based program was compared with a proposed home-based program for delivering cardiac rehabilitation services in West Moreton, Queensland. Cost and baseline data were collected on 95 cardiac rehabilitation patients living in Ipswich and West Moreton. Cost data included costs to the program funders and patients. The average cost per patient rehabilitated was $1,933 in the

Louisa Collins; Paul Scuffham; Sue Gargett

2001-01-01

86

Current facts on pacemaker electromagnetic interference and their application to clinical care  

SciTech Connect

The development of the sensing demand cardiac pacemaker brought with it the problem of interference as a result of extraneous electric current and electromagnetic fields. This problem still deserves consideration, not only because harmful disruption of pacemaker function, while infrequent, can occur but also because myths and misunderstandings have flourished on the subject. Misinformation has often led to needless patient anxiety and unnecessary restrictions in activities of daily living. Similarly, when health care practitioners are misinformed about pacemaker interference, potentially hazardous situations can occur in the clinical environment. This article is a review of current information on the sources and effects of electromagnetic interference (EMI) on pacemakers and includes a discussion of their application to patient care.

Sager, D.P.

1987-03-01

87

Experience with a partnership program for cardiac surgery at a regional military medical center.  

PubMed

A Partnership Program between USAF Medical Center, Wright-Patterson (WPAFB) and Miami Valley Hospital (MVH), Dayton, Ohio, was created through CHAMPUS to provide cardiac surgical services for eligible patients. During the first year of this program, 82 patients underwent 89 percutaneous transluminal coronary angioplasty (PTCA) procedures. Sixty-one patients underwent cardiac surgery at WPAFB, 50 were referred to MVH due to ineligibility or other reasons, and five were referred to other military or civilian hospitals. The program has been successful with low morbidity and mortality (3%). Cost savings for PTCAs was $241,853 and for cardiac surgery was $462,046. PMID:1470351

Head, H D; Collins, G J; Oberheu, K H; Broderick, G T; Brown, G R; Scheidt, R A

1992-11-01

88

Effects of a brief intervention on retention of patients in a cardiac rehabilitation program.  

PubMed

This intervention assessed the effects of a brief intervention on dropout rate in a cardiac rehabilitation program. One hundred thirty five patients were recruited from a cardiac rehabilitation program and randomized to either a control or intervention group. The intervention group participated in four sessions of motivational interviewing and stress management-relaxation in addition to standard cardiac rehabilitation. The control group underwent cardiac rehabilitation alone. Patients who completed the intervention completed an average of 30 sessions while those who dropped out of the intervention completed about six (p < 0.001). Anxiety and depression measured at baseline were the primary predictors of dropout. Patients in both the intervention and controls groups who completed cardiac rehabilitation improved the distance walked, quality of life and decreased anxiety. PMID:25150038

McGrady, Angele; Burkes, Robert; Badenhop, Dalynn; McGinnis, Ron

2014-12-01

89

Design and Testing of a Percutaneously Implantable Fetal Pacemaker  

PubMed Central

We are developing a cardiac pacemaker with a small, cylindrical shape that permits percutaneous implantation into a fetus to treat complete heart block and consequent hydrops fetalis, which can otherwise be fatal. The device uses off-the-shelf components including a rechargeable lithium cell and a highly efficient relaxation oscillator encapsulated in epoxy and glass. A corkscrew electrode made from activated iridium can be screwed into the myocardium, followed by release of the pacemaker and a short, flexible lead entirely within the chest of the fetus to avoid dislodgement from fetal movement. Acute tests in adult rabbits demonstrated the range of electrical parameters required for successful pacing and the feasibility of successfully implanting the device percutaneously under ultrasonic imaging guidance. The lithium cell can be recharged inductively as needed, as indicated by a small decline in the pulsing rate. PMID:22855119

Loeb, Gerald E.; Zhou, Li; Zheng, Kaihui; Nicholson, Adriana; Peck, Raymond A.; Krishnan, Anjana; Silka, Michael; Pruetz, Jay; Chmait, Ramen; Bar-Cohen, Yaniv

2012-01-01

90

The role of the funny current in pacemaker activity.  

PubMed

Abstract: Pacemaking is a basic physiological process, and the cellular mechanisms involved in this function have always attracted the keen attention of investigators. The "funny" (I(f)) current, originally described in sinoatrial node myocytes as an inward current activated on hyperpolarization to the diastolic range of voltages, has properties suitable for generating repetitive activity and for modulating spontaneous rate. The degree of activation of the funny current determines, at the end of an action potential, the steepness of phase 4 depolarization; hence, the frequency of action potential firing. Because I(f) is controlled by intracellular cAMP and is thus activated and inhibited by beta-adrenergic and muscarinic M2 receptor stimulation, respectively, it represents a basic physiological mechanism mediating autonomic regulation of heart rate. Given the complexity of the cellular processes involved in rhythmic activity, an exact quantification of the extent to which I(f) and other mechanisms contribute to pacemaking is still a debated issue; nonetheless, a wealth of information collected since the current was first described more than 30 years ago clearly agrees to identify I(f) as a major player in both generation of spontaneous activity and rate control. I(f)- dependent pacemaking has recently advanced from a basic, physiologically relevant concept, as originally described, to a practical concept that has several potentially useful clinical applications and can be valuable in therapeutically relevant conditions. Typically, given their exclusive role in pacemaking, f-channels are ideal targets of drugs aiming to pharmacological control of cardiac rate. Molecules able to bind specifically to and block f-channels can thus be used as pharmacological tools for heart rate reduction with little or no adverse cardiovascular side effects. Indeed a selective f-channel inhibitor, ivabradine, is today commercially available as a tool in the treatment of stable chronic angina. Also, several loss-of-function mutations of HCN4 (hyperpolarization-activated, cyclic-nucleotide gated 4), the major constitutive subunit of f-channels in pacemaker cells, are known today to cause rhythm disturbances, such as for example inherited sinus bradycardia. Finally, gene- or cell-based methods for in situ delivery of f-channels to silent or defective cardiac muscle represent novel approaches for the development of biological pacemakers eventually able to replace electronic devices. PMID:20167941

DiFrancesco, Dario

2010-02-19

91

Tricuspid valve and pacemaker endocarditis due to Pseudallescheria boydii (Scedosporium apiospermum).  

PubMed

We report a case of native valve and pacemaker endocarditis in a 78-year-old male with diabetes mellitus who died after cardiac surgery. At autopsy, tricuspid valve vegetations and lung abscesses containing thick, hyaline, septate, and branching hyphae were present. The culture identified Scedosporium apiospermum, an infrequent cause of opportunistic infections in immunocompromised hosts. PMID:19373137

Laurini, Javier A; Carter, J Elliot; Kahn, Andrea G

2009-05-01

92

Interference of Cellular Phones and Metal Detectors With Pacemakers and ICDs: Still a Problem?  

Microsoft Academic Search

Electromagnetic interference (EMI) may affect the behaviour of some medical electrical equipment, including cardiac pacemakers and implanted cardioverter-defibrillators (ICDs) [1]. EMI occurs when an electronic device is subjected to any electromagnetic field with an amplitude higher than the interference threshold. The effects on the device depend on the energy of the electromagnetic signal interfering with the normal function of the

E. Occhetta; L. Plebani; M. Bortnik; P. Marino

93

Electrical interference in non-competitive pacemakers  

PubMed Central

Patients with 41 implanted non-competitive pacemakers were investigated. A variety of domestic electrical equipment, a motor-car, and a physiotherapy diathermy apparatus were each operated in turn at various ranges from the patient. Interference effects on pacemaker function were assessed on the electrocardiograph. Medtronic demand 5841 pacemakers were stopped by diathermy while Cordis Ectocor pacemakers developed a fast discharge rate. Cordis triggered pacemakers (both Atricor and Ectocor) were sensitive to interference from many items of domestic equipment and the motor car. The Elema EM153 ran at an increased rate when an electric razor was running close to the pacemaker. The Devices demand 2980 and the Medtronic demand 5841 were not affected by the domestic equipment tested. The significance of interference effects is discussed in relation to pacemaker design. Images PMID:5470044

Sowton, E.; Gray, K.; Preston, T.

1970-01-01

94

[Wide QRS tachycardia preceded by pacemaker spikes].  

PubMed

The differential diagnosis and therapeutic management of wide QRS tachycardia preceded by pacemaker spike is presented. The pacemaker-mediated tachycardia, tachycardia fibrillo-flutter in patients with pacemakers, and runaway pacemakers, have a similar surface electrocardiogram, but respond to different therapeutic measures. The tachycardia response to the application of a magnet over the pacemaker could help in the differential diagnosis, and in some cases will be therapeutic, as in the case of a tachycardia-mediated pacemaker. Although these conditions are diagnosed and treated in hospitals with catheterization laboratories using the application programmer over the pacemaker, patients presenting in primary care clinic and emergency forced us to make a diagnosis and treat the haemodynamically unstable patient prior to referral. PMID:23768570

Romero, M; Aranda, A; Gómez, F J; Jurado, A

2014-04-01

95

Safety Of Mris In Patients With Pacemakers And Defibrillators  

PubMed Central

With a burgeoning population, increases in life expectancy, and expanding indications, the number of patients with cardiac devices such as pacemakers and implantable cardioverter defibrillators continues to increase each year. A majority of these patients will develop an indication for magnetic resonance imaging (MRI) in their lifetime. MRIs have established themselves as one of the most powerful imaging tools for a variety of conditions. However, given the historic safety concerns, many physicians are reluctant to use MRIs in this patient population. In this paper, we discuss the potential adverse effects of MRIs in patients with cardiac devices, review key studies that have addressed strategies to limit adverse effects, and provide our cardiovascular MRI laboratory’s protocol for imaging patients with implanted cardiac devices. PMID:24066196

Baher, Alex; Shah, Dipan

2013-01-01

96

Preparation for pacemaker or implantable cardiac defibrillator implants in patients with high risk of thrombo-embolic events: oral anticoagulation or bridging with intravenous heparin? A prospective randomized trial  

PubMed Central

Aims Current guidelines recommend stopping oral anticoagulation (OAC) and starting heparin infusion before implanting/replacing a pacemaker/implantable cardioverter-defibrillator (ICD) in patients with high risk for thrombo-embolic events. The aim of this study was to demonstrate that the maintenance of OAC during device implantation/replacement is as safe as bridging to intravenous heparin and shortens in-hospital stay. Methods and results A cohort of 101 consecutive patients with high risk for embolic events and indication for implant/replacement of a pacemaker/ICD were randomized to two anticoagulant strategies: bridging from OAC to heparin infusion (n = 51) vs. maintenance of OAC to reach an INR = 2 ± 0.3 at the day of the procedure (n = 50). Haemorrhagic and thrombo-embolic complications were evaluated at discharge, 15 and 45 days after the procedure. A total of 4/51 patients (7.8%) from heparin group and 4/50 (8.0%) from the OAC group developed pocket haematoma following the implant (P = 1.00). One haematoma in each group required evacuation (1.9 vs. 2%, P = 1.00). No other haemorrhagic events or embolic complications developed during the follow-up. Duration of the hospital stay was longer in the heparin group [median of 5 (4–7) vs. 2 (1–4) days; P < 0.001]. Conclusion Implant of devices maintaining OAC is as safe as bridging to heparin infusion and allows a significant reduction of in-hospital stay. PMID:19487235

Tolosana, Jose M.; Berne, Paola; Mont, Lluis; Heras, Magda; Berruezo, Antonio; Monteagudo, Joan; Tamborero, David; Benito, Begona; Brugada, Josep

2009-01-01

97

Case study thoracic radiotherapy in an elderly patient with pacemaker: The issue of pacing leads  

SciTech Connect

To assess clinical outcome of patients with pacemaker treated with thoracic radiation therapy for T8-T9 paravertebral chloroma. A 92-year-old male patient with chloroma presenting as paravertebral painful and compressive (T8-T9) mass was referred for radiotherapy in the Department of Radiation Oncology, Institut Curie. The patient presented with cardiac dysfunction and a permanent pacemaker that had been implanted prior. The decision of Multidisciplinary Meeting was to deliver 30 Gy in 10 fractions for reducing the symptoms and controlling the tumor growth. The patient received a total dose of 30 Gy in 10 fractions using 4-field conformal radiotherapy with 20-MV photons. The dose to pacemaker was 0.1 Gy but a part of the pacing leads was in the irradiation fields. The patient was treated the first time in the presence of his radiation oncologist and an intensive care unit doctor. Moreover, the function of his pacemaker was monitored during the entire radiotherapy course. No change in pacemaker function was observed during any of the radiotherapy fractions. The radiotherapy was very well tolerated without any side effects. The function of the pacemaker was checked before and after the radiotherapy treatment by the cardiologist and no pacemaker dysfunction was observed. Although updated guidelines are needed with acceptable dose criteria for implantable cardiac devices, it is possible to treat patients with these devices and parts encroaching on the radiation field. This case report shows we were able to safely treat our patient through a multidisciplinary approach, monitoring the patient during each step of the treatment.

Kirova, Youlia M., E-mail: youlia.kirova@curie.net [Department of Radiation Oncology, Institut Curie, Paris (France); Menard, Jean; Chargari, Cyrus; Mazal, Alejandro [Department of Radiation Oncology, Institut Curie, Paris (France); Kirov, Krassen [Department of Anesthesiology and Reanimation, Institut Curie, Paris (France)

2012-07-01

98

Cardiac Rehabilitation Patient and Organizational Factors: What Keeps Patients in Programs?  

PubMed Central

Background Despite documented benefits of cardiac rehabilitation, adherence to programs is suboptimal with an average dropout rate of between 24% and 50%. The goal of this study was to identify organizational and patient factors associated with cardiac rehabilitation adherence. Methods and Results Facilities of the Wisconsin Cardiac Rehabilitation Outcomes Registry Project (N=38) were surveyed and records of 4412 enrolled patients were analyzed. Generalized estimating equations were used to account for clustering of patients within facilities. The results show that organizational factors associated with significantly increased adherence were relaxation training and diet classes (group and individual formats) and group?based psychological counseling, medication counseling, and lifestyle modification, the medical director's presence in the cardiac rehabilitation activity area for ?15 min/week, assessment of patient satisfaction, adequate space, and adequate equipment. Patient factors associated with significantly increased adherence were aged ?65 years, the American Association of Cardiovascular and Pulmonary Rehabilitation (AACVPR) high?risk category, having received coronary artery bypass grafting, and diabetes disease. Non?white race was negatively associated with adherence. There was no significant gender difference in adherence. None of the baseline patient clinical profiles were associated with adherence including body mass index, total cholesterol, low?density lipoprotein, high?density lipoprotein, triglycerides, and blood pressure. Conclusions Factors associated with adherence to cardiac rehabilitation included both organizational and patient factors. Modifiable organizational factors may help directors of cardiac rehabilitation programs improve patient adherence to this beneficial program. PMID:24145743

Turk-Adawi, Karam I.; Oldridge, Neil B.; Tarima, Sergey S.; Stason, William B.; Shepard, Donald S.

2013-01-01

99

Automatic extraction of comprehensive cardiac CT angiography parameters: a novel program with high accuracy and efficiency.  

PubMed

We tested the accuracy and efficiency of a novel automated program capable of extracting 15 cardiac computed tomography angiography (CTA) parameters from clinical CTA reports. Five hundred cardiac CTA reports were retrospectively collected and processed. All reports were pre-populated with a structured template per guideline. The program extracted 15 parameters with high accuracy (97.3 %) and efficiency (84 s). This program may be used at other institutions with similar accuracy if its report format follows the Society of Cardiovascular Computed Tomography (SCCT) guideline recommendation. PMID:24526519

Lee, Ashley M; Ghoshhajra, Brian B

2014-08-01

100

21 CFR 870.3620 - Pacemaker lead adaptor.  

...2014-04-01 2014-04-01 false Pacemaker lead adaptor. 870.3620 Section 870.3620...Prosthetic Devices § 870.3620 Pacemaker lead adaptor. (a) Identification. A pacemaker lead adaptor is a device used to adapt a...

2014-04-01

101

21 CFR 870.3620 - Pacemaker lead adaptor.  

Code of Federal Regulations, 2011 CFR

...2011-04-01 2011-04-01 false Pacemaker lead adaptor. 870.3620 Section 870.3620...Prosthetic Devices § 870.3620 Pacemaker lead adaptor. (a) Identification. A pacemaker lead adaptor is a device used to adapt a...

2011-04-01

102

21 CFR 870.3620 - Pacemaker lead adaptor.  

Code of Federal Regulations, 2012 CFR

...2012-04-01 2012-04-01 false Pacemaker lead adaptor. 870.3620 Section 870.3620...Prosthetic Devices § 870.3620 Pacemaker lead adaptor. (a) Identification. A pacemaker lead adaptor is a device used to adapt a...

2012-04-01

103

21 CFR 870.3620 - Pacemaker lead adaptor.  

Code of Federal Regulations, 2010 CFR

...2010-04-01 2010-04-01 false Pacemaker lead adaptor. 870.3620 Section 870.3620...Prosthetic Devices § 870.3620 Pacemaker lead adaptor. (a) Identification. A pacemaker lead adaptor is a device used to adapt a...

2010-04-01

104

21 CFR 870.3620 - Pacemaker lead adaptor.  

Code of Federal Regulations, 2013 CFR

...2013-04-01 2013-04-01 false Pacemaker lead adaptor. 870.3620 Section 870.3620...Prosthetic Devices § 870.3620 Pacemaker lead adaptor. (a) Identification. A pacemaker lead adaptor is a device used to adapt a...

2013-04-01

105

The challenge of staphylococcal pacemaker endocarditis in a patient with transposition of the great arteries endocarditis in congenital heart disease  

SciTech Connect

Staphylococcus aureus is a leading cause of septicaemia and infective endocarditis. The overall incidence of staphylococcal bacteraemia is increasing, contributing to 16% of all hospital-acquired bacteraemias. The use of cardiac pacemakers has revolutionized the management of rhythm disturbances, yet this has also resulted in a group of patients at risk of pacemaker lead endocarditis and seeding in the range of 1% to 7%. We describe a 26-year-old man with transposition of the great arteries who had a pacemaker implanted and presented with S. aureus septicaemia 2 years postpacemaker implantation and went on to develop pacemaker lead endocarditis. This report illustrates the risk of endocarditis in the population with congenital heart disease and an intracardiac device.

Ch'ng, Julie; Chan, William; Lee, Paul; Joshi, Subodh; Grigg, Leanne E.; Ajani, Andrew E

2003-06-01

106

SCAI expert consensus statement for advanced training programs in pediatric and congenital interventional cardiac catheterization.  

PubMed

Pediatric and Congenital Interventional Cardiology is the practice of catheter-based techniques that improve cardiac physiology and circulation through the treatment of heart disease in children and adults with congenital or acquired heart defects. Over the last decade, and since last published training guidelines for pediatric cardiac catheterization and interventional cardiology were published in 2005 [1] the field of Pediatric and Congenital Cardiac Catheterization has evolved into a predominantly interventional discipline. As there is no sub-specialty certification for interventional cardiac catheterization in pediatrics, the Congenital Heart Disease Committee of the Society of Cardiovascular Angiography and Interventions has put together this consensus statement for advanced training in pediatric and congenital interventional cardiac catheterization. The statement puts forth recommendations for program infrastructure in terms of teaching, personnel, equipment, facilities, conferences, patient volume and trainee assessment. This is meant to set a standard for training programs as well as giving applicants a basis on which to judge and compare programs. © 2014 Wiley Periodicals, Inc. PMID:24890705

Armsby, Laurie; Beekman, Robert H; Benson, Lee; Fagan, Thomas; Hagler, Donald J; Hijazi, Ziyad M; Holzer, Ralf; Ing, Frank; Kreutzer, Jacqueline; Lang, Peter; Levi, Daniel S; Latson, Larry; Moore, Phillip; Mullins, Charles; Ruiz, Carlos; Vincent, Robert

2014-11-01

107

Tricuspid valve malfunction and ventricular pacemaker lead: case report and review of the literature.  

PubMed

Pacemaker implantation can be associated with several complications, including myocardial perforation with or without pericardial effusion, venous thrombosis, vegetations of the tricuspid valve (TV) or pacing lead, and tricuspid regurgitation (TR). The TR is thought to be derived from deformity or perforation of the TV by the pacing lead or secondary to atrioventricular discordance with asynchronous ventricular pacing. Severe TR can be deleterious to the patient because it raises the central venous pressure by increasing the right sided preload. Chronically, the increase in right sided blood volume can result in an increase in the right atrial pressure leading to a decrease in venous return and low cardiac output. Severe TR from leaflet adhesion to the pacemaker lead has not been reported before. With the aging of the population and the expanding use of pacemakers and implantable cardioverter defibrillators (ICD) in clinical practice, this complication may be seen more frequently. We present a patient diagnosed with severe TR, years after his pacemaker implantation. His TR was thought to be caused by adhesion of the tricuspid valve to his pacemaker lead. PMID:16970722

Iskandar, Said B; Ann Jackson, S; Fahrig, Stephen; Mechleb, Bassam K; Garcia, Israel D

2006-09-01

108

Calcium Transient and Sodium-Calcium Exchange Current in Human versus Rabbit Sinoatrial Node Pacemaker Cells  

PubMed Central

There is an ongoing debate on the mechanism underlying the pacemaker activity of sinoatrial node (SAN) cells, focusing on the relative importance of the “membrane clock” and the “Ca2+ clock” in the generation of the small net membrane current that depolarizes the cell towards the action potential threshold. Specifically, the debate centers around the question whether the membrane clock-driven hyperpolarization-activated current, I f, which is also known as the “funny current” or “pacemaker current,” or the Ca2+ clock-driven sodium-calcium exchange current, I NaCa, is the main contributor to diastolic depolarization. In our contribution to this journal's “Special Issue on Cardiac Electrophysiology,” we present a numerical reconstruction of I f and I NaCa in isolated rabbit and human SAN pacemaker cells based on experimental data on action potentials, I f, and intracellular calcium concentration ([Ca2+]i) that we have acquired from these cells. The human SAN pacemaker cells have a smaller I f, a weaker [Ca2+]i transient, and a smaller I NaCa than the rabbit cells. However, when compared to the diastolic net membrane current, I NaCa is of similar size in human and rabbit SAN pacemaker cells, whereas I f is smaller in human than in rabbit cells. PMID:23606816

Verkerk, Arie O.

2013-01-01

109

Core Components of Cardiac Rehabilitation\\/Secondary Prevention Programs: 2007 Update  

Microsoft Academic Search

The American Heart Association and the American Association of Cardiovascular and Pulmonary Rehabilitation recognize that all cardiac rehabilitation\\/secondary prevention programs should contain specific core components that aim to optimize cardiovascular risk reduction, foster healthy behaviors and compliance to these behaviors, reduce disability, and promote an active lifestyle for patients with cardiovascular disease. This update to the previous statement presents current

Gary J. Balady; Mark A. Williams; Philip A. Ades; Vera Bittner; Patricia Comoss; M. Foody; Barry Franklin; Bonnie K. Sanderson; Rn Douglas Southard

2007-01-01

110

Cardiac Arrhythmias in the Elderly  

Microsoft Academic Search

Cardiac arrhythmias are frequent in the elderly population, perhaps secondary to an increased prevalence of hypertension (HT) and coronary artery disease (CAD) as well as aging related changes resulting in loss of pacemaker cells and degenerative change of the conduction system. Management is especially challenging in view of significant associated morbidity and mortality, an increased risk of side effects with

Anoop K. Gupta; Alok Maheshwari; Donald D. Tresch; Ranjan K. Thakur

2002-01-01

111

Utility of the NavX(R) Electroanatomic Mapping System for Permanent Pacemaker Implantation in a Pregnant Patient with Chagas Disease  

PubMed Central

Chagas disease is a highly prevalent zoonosis in Mexico, Central, and South America. Early cardiac involvement is one of the most serious complications of this disease, and conduction disturbances may occur at an early age. We describe a young pregnant woman with Chagas disease and a high degree atrioventricular block, who required implantation of a permanent dual chamber pacemaker. Using an electroanatomic navigation EnSite NavX® system the pacemaker was successfully implanted with minimal fluoroscopic exposure. This case demonstrates the safety and feasibility of using an electroanatomic navigation system to guide permanent pacemaker implantation minimizing x-ray exposure in pregnant patients. PMID:23329872

Velasco, Alejandro; Velasco, Victor Manuel; Rosas, Fernando; Cevik, Cihan; Morillo, Carlos A

2013-01-01

112

Alterations of field potentials in isotropic cardiomyocyte cell layers induced by multiple endogenous pacemakers under normal and hypothermal conditions.  

PubMed

The use of autonomous contracting randomly grown cardiomyocyte monolayers cultivated on microelectrode arrays (MEAs) represents an accepted experimental setting for preclinical experimental research in the field of cardiac electrophysiology. A dominant pacemaker forces a monolayer to adhere to a regular and synchronized contraction. Randomly distributed multiple pacemakers interfere with this dominant center, resulting in more or less frequent changes of propagation direction. This study aims to characterize the impact of changing propagation directions at single electrodes of the MEA on the four intrinsic parameters of registered field potentials (FPs) FPrise, FPMIN, FPpre, and FPdur and conduction velocity (CV) under normal and hypothermal conditions. Primary cultures of chicken cardiomyocytes (n = 18) were plated directly onto MEAs and FPs were recorded in a temperature range between 37 and 29°C. The number and spatiotemporal distribution of biological and artificial pacemakers of each cell layer inside and outside of the MEA registration area were evaluated using an algorithm developed in-house. In almost every second myocardial cell layer, interfering autonomous pacemakers were detected at stable temperatures, showing random spatial distributions with similar beating rates. Additionally, a temperature-dependent change of the dominant pacemaker center was observed in n = 16 experiments. A significant spread-direction-dependent variation of CV, FPrise, FPMIN, and FPpre up to 14% could be measured between different endogenous pacemakers. In conclusion, based on our results, disregarding the spatial origin of excitation may lead to misinterpretations and erroneous conclusions of FP parameters in the verification of research hypotheses in cellular electrocardiology. PMID:25085965

Kienast, R; Stöger, M; Handler, M; Hanser, F; Baumgartner, C

2014-10-01

113

[Ambulatory control and follow-up of patients carrying a unicameral pacemaker].  

PubMed

The follow-up schedule after pacemaker implantation should be arranged to allow close monitoring during the immediate post-implant period, and frequent observations during the life of the system. Such follow-up has as major goals the evaluation of the electrical functions of the pacing system to detect malfunctions or imminent power source depletion and the evaluation of the patient cardiac status so that reprogramming can be accomplished. PMID:2236796

de Juan Montiel, J; Bardají, A; Vaño, J; Toda, R; Beret, T; Ridao, C

1990-01-01

114

Pacemaker twiddler's syndrome (rotation of the pacemaker around the electrode cable, a rare complication of pacemaker therapy).  

PubMed

Rotation of the pacemaker generator around the electrode cable (i.e. twiddler's syndrome) was observed by the authors in six cases during the implantation of 4250 pacemakers. Twiddler's syndrome developed in three cases following implantation and in three cases after the replacement of the pacemaker. As a result of the rotation of the device, displacement of the electrode occurred in all cases. The factors predisposing to rotation of the device were as follows: (i) a loose, dilated pocket in 5 cases; (ii) seroma formation around the device in 2 cases; (iii) manipulation with the pacemaker in one case. For treating twiddler's syndrome, reimplantation was performed, fashioning a small and tight pocket for the device and fixing it by transfixing sutures. After reimplantation, the patients became complaint free, no recurrences occurred. PMID:2596244

Solti, F; Moravcsik, E; Rényi-Vámos, F; Szabó, Z

1989-01-01

115

How Will a Pacemaker Affect My Lifestyle?  

MedlinePLUS

... check for changes in your heart's electrical activity. Battery Replacement Pacemaker batteries last between 5 and 15 years (average 6 ... doctor will replace the generator along with the battery before the battery starts to run down. Replacing ...

116

Improved treatment of coronary heart disease by implementation of a Cardiac Hospitalization Atherosclerosis Management Program (CHAMP)  

Microsoft Academic Search

Despite scientific evidence that secondary prevention medical therapies reduce mortality in patients with established coronary artery disease, these therapies continue to be underutilized in patients receiving conventional care. To address this issue, a Cardiac Hospital Atherosclerosis Management Program (CHAMP) focused on initiation of aspirin, cholesterol-lowering medication (hydroxymethylglutaryl coenzyme A [HMG CoA] reductase inhibitor titrated to achieve low-density lipoprotein [LDL] cholesterol

Gregg C Fonarow; Anna Gawlinski; Samira Moughrabi; Jan H Tillisch

2001-01-01

117

Deactivation of Pacemakers and Implantable Cardioverter-Defibrillators  

PubMed Central

Cardiac implantable electrical devices (CIEDs), including pacemakers (PMs) and implantable cardioverter-defibrillators (ICDs), are the most effective treatment for life-threatening arrhythmias. Patients or their surrogates may request device deactivation to avoid prolongation of the dying process or in other settings, such as after device-related complications or with changes in their health care goals. Despite published guidelines outlining theoretical and practical aspects of this common clinical scenario, significant uncertainty remains for both patients and health care providers regarding the ethical and legal status of CIED deactivation. This review outlines the ethical and legal principles supporting CIED deactivation at patients’ request, centered upon patient autonomy and authority over their own medical treatment. The empirical literature describing stakeholder views and experiences surrounding CIED deactivation is described, along with lessons for future research and practice guidance surrounding the care of patients with CIEDs. PMID:23217433

Kramer, Daniel B.; Mitchell, Susan L.; Brock, Dan W.

2013-01-01

118

The G-protein-gated K+ channel, IKACh, is required for regulation of pacemaker activity and recovery of resting heart rate after sympathetic stimulation  

PubMed Central

Parasympathetic regulation of sinoatrial node (SAN) pacemaker activity modulates multiple ion channels to temper heart rate. The functional role of the G-protein–activated K+ current (IKACh) in the control of SAN pacemaking and heart rate is not completely understood. We have investigated the functional consequences of loss of IKACh in cholinergic regulation of pacemaker activity of SAN cells and in heart rate control under physiological situations mimicking the fight or flight response. We used knockout mice with loss of function of the Girk4 (Kir3.4) gene (Girk4?/? mice), which codes for an integral subunit of the cardiac IKACh channel. SAN pacemaker cells from Girk4?/? mice completely lacked IKACh. Loss of IKACh strongly reduced cholinergic regulation of pacemaker activity of SAN cells and isolated intact hearts. Telemetric recordings of electrocardiograms of freely moving mice showed that heart rate measured over a 24-h recording period was moderately increased (10%) in Girk4?/? animals. Although the relative extent of heart rate regulation of Girk4?/? mice was similar to that of wild-type animals, recovery of resting heart rate after stress, physical exercise, or pharmacological ?-adrenergic stimulation of SAN pacemaking was significantly delayed in Girk4?/? animals. We conclude that IKACh plays a critical role in the kinetics of heart rate recovery to resting levels after sympathetic stimulation or after direct ?-adrenergic stimulation of pacemaker activity. Our study thus uncovers a novel role for IKACh in SAN physiology and heart rate regulation. PMID:23858001

Mesirca, Pietro; Marger, Laurine; Toyoda, Futoshi; Rizzetto, Riccardo; Audoubert, Matthieu; Dubel, Stefan; Torrente, Angelo G.; DiFrancesco, Mattia L.; Muller, Jana Christina; Leoni, Anne-Laure; Couette, Brigitte; Nargeot, Joel; Clapham, David E.; Wickman, Kevin

2013-01-01

119

The G-protein-gated K+ channel, IKACh, is required for regulation of pacemaker activity and recovery of resting heart rate after sympathetic stimulation.  

PubMed

Parasympathetic regulation of sinoatrial node (SAN) pacemaker activity modulates multiple ion channels to temper heart rate. The functional role of the G-protein-activated K(+) current (IKACh) in the control of SAN pacemaking and heart rate is not completely understood. We have investigated the functional consequences of loss of IKACh in cholinergic regulation of pacemaker activity of SAN cells and in heart rate control under physiological situations mimicking the fight or flight response. We used knockout mice with loss of function of the Girk4 (Kir3.4) gene (Girk4(-/-) mice), which codes for an integral subunit of the cardiac IKACh channel. SAN pacemaker cells from Girk4(-/-) mice completely lacked IKACh. Loss of IKACh strongly reduced cholinergic regulation of pacemaker activity of SAN cells and isolated intact hearts. Telemetric recordings of electrocardiograms of freely moving mice showed that heart rate measured over a 24-h recording period was moderately increased (10%) in Girk4(-/-) animals. Although the relative extent of heart rate regulation of Girk4(-/-) mice was similar to that of wild-type animals, recovery of resting heart rate after stress, physical exercise, or pharmacological ?-adrenergic stimulation of SAN pacemaking was significantly delayed in Girk4(-/-) animals. We conclude that IKACh plays a critical role in the kinetics of heart rate recovery to resting levels after sympathetic stimulation or after direct ?-adrenergic stimulation of pacemaker activity. Our study thus uncovers a novel role for IKACh in SAN physiology and heart rate regulation. PMID:23858001

Mesirca, Pietro; Marger, Laurine; Toyoda, Futoshi; Rizzetto, Riccardo; Audoubert, Matthieu; Dubel, Stefan; Torrente, Angelo G; Difrancesco, Mattia L; Muller, Jana Christina; Leoni, Anne-Laure; Couette, Brigitte; Nargeot, Joël; Clapham, David E; Wickman, Kevin; Mangoni, Matteo E

2013-08-01

120

[Selection of protection regimen of dual-chamber cardiac pacing against paroxysmal supraventricular tachycardia].  

PubMed

Criteria of selection of a type of protection against paroxysmal supraventricular tachycardia were studied in 38 patients with permanent dual-chamber cardiac pacing. Three types of protection were distinguished. Criteria for their selection were presence of "pacemaker syndrome", state of chronotropic function of the heart, frequency of attacks of supraventricular tachycardia, results of modeling of pathological atrial activity. During follow-up after programming of optimal type of protection of dual-chamber pacing (mean duration 5.1 years) chronic supraventricular tachycardia developed in 13.5% of patients, survival was 89.2%. PMID:12891250

Cherkasov, V A; Protopopov, V V; Molodykh, S V

2003-01-01

121

Pacemaker leads: performance and progress.  

PubMed

Pacing leads remain the "weaker link" of the permanent pacing system. Lead failure has been an issue since the beginning of implantable pacemaker therapy. Modern electronics have brought about considerable progress in pacing technology, but lead design has been slower to evolve and problems persist. IS-1 standardization must be considered a significant advance, but some issues regarding IS-1 standardization persist and have been the cause of some compatibility problems. With respect to lead insulation, silicone has proved to offer total reliability for > 30 years. In the search for better handling characteristics, polyurethane 80A was employed for bipolar leads, but it failed to demonstrate satisfactory insulating properties. New insulation materials, such as ethylene-fluoro-ethylene (ETFE), and coated wire technology look promising, having shown 99.32% survival at 5-year follow-up. Reliability is the main objective in lead design, but leads should provide low battery consumption as well. Low coil resistance, with high electrode impedance in steroid-eluting leads, is the standard at present. Low polarization is a desirable property for 2 main reasons: (1) in conjunction with low-threshold leads, it decreases battery consumption; and (2) it allows capture detection and, therefore, safer pacing at low battery consumption. Lead tip design as well as pacing pulse configuration can influence polarization. PMID:10089864

de Voogt, W G

1999-03-11

122

Involvement of Autophagy in Cardiac Remodeling in Transgenic Mice with Cardiac Specific Over-Expression of Human Programmed Cell Death 5  

PubMed Central

Programmed cell death 5 (PDCD5) is a cytosolic protein suppressing growth of multiple types of cancer cells through activating p53. We hypothesized that PDCD5 plays an essential role in cardiac remodeling and function. PDCD5 was significantly up-regulated in the hearts from mice subjected to angiotensin II treatment or transverse aortic constriction. Thus, we generated transgenic mice over-expressing human PDCD5 under the control of alpha myosin heavy chain promoter to examine the role of PDCD5 in cardiac remodeling. Transgenic founder died spontaneously displayed enlarged heart. The high PDCD5 over-expressing line (10-fold) showed reduced survival rate, increase in heart weight normalized to body weight. Real-Time RT-PCR analysis revealed fetal gene program was up-regulated. Echocardiography and histopathological examination showed characteristics of dilated cardiomyopathy and heart failure in transgenic mice. Western blot and immunohistochemistry analysis showed autophagy was dramatically increased in transgenic mice as compared to WT littermates control mice, while apoptosis remained unchanged. The enhanced autophagy in high over-expressing line was associated with significant increase in p53 activity and its downstream target damage-regulated autophagy modulator expression. The low over-expressing line (3.5-fold) appeared normal, but was more susceptible to angiotensin II-induced cardiac hypertrophy. This study is the first providing evidence that PDCD5 plays an important role in cardiac remodeling. PMID:22253891

An, Lin; Zhao, Xiwen; Wu, Jian; Jia, Jianguo; Zou, Yunzeng; Guo, Xizhi; He, Lin; Zhu, Hongxin

2012-01-01

123

Surgical approaches to epicardial pacemaker placement: does pocket location affect lead survival?  

PubMed

Permanent cardiac pacing in pediatric patients presents challenges related to small patient size, complex anatomy, electrophysiologic abnormalities, and limited access to cardiac chambers. Epicardial pacing currently remains the conventional technique for infants and patients with complex congenital heart disease. Pacemaker lead failure is the major source of failure for such epicardial systems. The authors hypothesized that a retrocostal surgical approach would reduce the rate of lead failure due to fracture compared with the more traditional subrectus and subxiphoid approaches. To evaluate this hypothesis, a retrospective chart review analyzed patients with epicardial pacemaker systems implanted or followed at Rady Children's Hospital San Diego between January 1980 and May 2007. The study cohort consisted of 219 patients and a total of 620 leads with epicardial pacemakers. Among these patients, 84% had structural congenital heart disease, and 45% were younger than 3 years at time of the first implantation. The estimated lead survival was 93% at 2 years and 83% at 5 years. The majority of leads failed due to pacing problems (54%), followed by lead fracture (31%) and sensing problems (14%). When lead failure was adjusted for length of follow-up period, no significant differences in the rates of failure by pocket location were found. PMID:20690018

Lichtenstein, Brian J; Bichell, David P; Connolly, Dana M; Lamberti, John J; Shepard, Suzanne M; Seslar, Stephen P

2010-10-01

124

[Infective endocarditis in patients with permanent pacemaker].  

PubMed

Five patients who had permanent pacemaker and infective endocarditis were analyzed. Diagnose was confirmed by a positive blood cultures in all patients and 2 of them had identifiable vegetation in the echocardiogram too. The etiologic agent was Staphylococcus aureus in 3, Staphylococcus epidermidis in 1 and Staphylococcus viridans in 1. Three patients were treated with antibiotics alone: one had no clinical conditions to be operated, one died before surgery and one had good response to antimicrobial therapy alone. Two patients were submitted to antibiotic therapy and surgical removal of the pacemaker system, without complications. It was concluded that the surgical removal of the pacemaker system, as soon as possible, is the choice's therapy. PMID:7998851

Jorge, S do C; Kormann, D D; Medeiros, P; Mateos, J C; Zamorano, M M; Silva, L M; Zambonini, M N; Arnoni, A S; Assef, J E; Magalhães, H M

1994-04-01

125

High-intensity track and field training in a cardiac rehabilitation program.  

PubMed

A 65-year-old male athlete with coronary artery disease enrolled in our cardiac rehabilitation (CR) program after successful coronary artery bypass graft surgery following an acute myocardial infarction. Unlike the typical sedentary cardiac patient in his age group, he loved to participate in hurdle events at masters division track meets (competitions for athletes aged 30 years and older). He expressed a strong desire to return to his sport, so we designed a sport-specific, symptom-limited exercise program that enabled him to train safely but at a higher intensity than is typically allowed in conventional CR programs. Although his measured peak heart rates during the sport-specific sessions were significantly higher than the calculated maximum heart rate limits usually imposed on patients during conventional CR exercise training, the patient had no adverse events and safely reached his fitness goal. When developing a CR plan, health care professionals should consider the patient's goals, not just his or her age. PMID:22275782

Kennedy, Kathleen; Adams, Jenny; Cheng, Dunlei; Berbarie, Rafic F

2012-01-01

126

Implementation of Ultraportable Echocardiography in an Adolescent Sudden Cardiac Arrest Screening Program  

PubMed Central

BACKGROUND Over a 12-month period, adolescent heart-screening programs were performed for identifying at-risk adolescents for sudden cardiac death (SCD) in our community. Novel to our study, all adolescents received an abbreviated, ultraportable echocardiography (UPE). In this report, we describe the use of UPE in this screening program. METHODS AND RESULTS Four hundred thirty-two adolescents underwent cardiac screening with medical history questionnaire, physical examination, 12-lead electrocardiogram (ECG), and an abbreviated transthoracic echocardiographic examination. There were 11 abnormalities identified with uncertain/varying clinical risk significance. In this population, 75 adolescents had a murmur or high ECG voltage, of which only three had subsequent structural abnormalities on echocardiography that may pose risk. Conversely, UPE discovered four adolescents who had a cardiovascular structural abnormality that was not signaled by the 12-lead ECG, medical history questionnaire, and/or physical examination. CONCLUSIONS The utilization of ultraportable, handheld echocardiography is feasible in large-scale adolescent cardiovascular screening programs. UPE appears to be useful for finding additional structural abnormalities and for risk-stratifying abnormalities of uncertain potential of adolescents’ sudden death.

Vanhecke, Thomas E; Weber, James E; Ebinger, Matthew; Bonzheim, Kimberly; Tilli, Frank; Rao, Sunilkumar; Osman, Abdulfatah; Silver, Marc; Fliegner, Karsten; Almany, Steve; Haines, David

2014-01-01

127

Involvement of Autophagy in Cardiac Remodeling in Transgenic Mice with Cardiac Specific Over-Expression of Human Programmed Cell Death 5  

Microsoft Academic Search

Programmed cell death 5 (PDCD5) is a cytosolic protein suppressing growth of multiple types of cancer cells through activating p53. We hypothesized that PDCD5 plays an essential role in cardiac remodeling and function. PDCD5 was significantly up-regulated in the hearts from mice subjected to angiotensin II treatment or transverse aortic constriction. Thus, we generated transgenic mice over-expressing human PDCD5 under

Lin An; Xiwen Zhao; Jian Wu; Jianguo Jia; Yunzeng Zou; Xizhi Guo; Lin He; Hongxin Zhu

2012-01-01

128

Update on arrhythmias and cardiac pacing 2013.  

PubMed

This report discusses a selection of the most relevant articles on cardiac arrhythmias and pacing published in 2013. The first section discusses arrhythmias, classified as regular paroxysmal supraventricular tachyarrhythmias, atrial fibrillation, and ventricular arrhythmias, together with their treatment by means of an implantable cardioverter defibrillator. The next section reviews cardiac pacing, subdivided into resynchronization therapy, remote monitoring of implantable devices, and pacemakers. The final section discusses syncope. PMID:24774592

Almendral, Jesús; Pombo, Marta; Martínez-Alday, Jesús; González-Rebollo, José M; Rodríguez-Font, Enrique; Martínez-Ferrer, José; Castellanos, Eduardo; García-Fernández, F Javier; Ruiz-Mateas, Francisco

2014-04-01

129

Predictive factors for pacemaker requirement after transcatheter aortic valve implantation  

PubMed Central

Background Transcatheter aortic valve implantation (TAVI) has been established as a treatment option for inoperable patients with symptomatic aortic valve stenosis. However, patients suffer frequently from conduction disturbances after TAVI. Methods Baseline, procedural as well as surface and intracardiac ECG parameters were evaluated for patients treated with TAVI and a comparison between patients requiring pacemaker with those not suffering from relevant conduction disorders were done. Results TAVI was successfully in all patients (n=45). Baseline surface and intracardiac ECG recording revealed longer PQ (197.1±51.2 msec versus 154.1±32.1 msec; p<0.001), longer AH (153.6±43.4 msec versus 116.1±31.2 msec; p<0.001) and HV interval (81.7±17.8 msec versus 56.8±8.5 msec; p<0.001) in patients with need for a pacemaker (n=23) versus control group (n=22); furthermore, 7-day follow-up analysis showed a higher prevalence of new left bundle branch block (LBBB) (87.0% versus 31.9%; p<0.001). Multivariate analysis revealed that only new LBBB, QRS duration >120 msec and a PQ interval >200 msec immediately (within 60 minutes) after implantation of the aortic valve were predictors for high-grade (type II second-degree and third-degree) AV block. Other clinical parameters as well as baseline electrocardiographic parameters had no impact on critical conduction delay. Conclusion Cardiac conduction disturbances are common after TAVI. The need for pacing after TAVI is predictable by surface ECG evaluation immediately (within 60 minutes) after the procedure. PMID:23035864

2012-01-01

130

Uptake of a technology-assisted home-care cardiac rehabilitation program.  

PubMed

The prevalence of cardiovascular disease, a major cause of disease burden in Australia and other developed countries, is increasing due to a rapidly ageing population and environmental, biomedical and modifiable lifestyle factors. Although cardiac rehabilitation (CR) programs have been shown to be beneficial and effective, rates of referral, uptake and utilisation of traditional hospital or community centre programs are poor. Home-based CR programs have been shown to be as effective as centre-based programs, and recent advances in information and communication technologies (ICT) can be used to enhance the delivery of such programs. The Care Assessment Platform (CAP) is an integrated home-based CR model incorporating ICT (including a mobile phone and the internet) and providing all the core components of traditional CR (education, physical activity, exercise training, behaviour modification strategies and psychological counselling). The mobile phone given to patients has an integrated accelerometer and diary application for recording exercise and health information. A central database, with access to these data, allows mentors to assess patients' progress, assist in setting goals, revise targets and give weekly personal feedback. Mentors find the mobile-phone modalities practical and easy to use, and preliminary results show high usage rates and acceptance of ICT by participants. The provision of ICT-supported home-based CR programs may enable more patients in both metropolitan and remote settings to benefit from CR. PMID:21401482

Varnfield, Marlien; Karunanithi, Mohanraj K; Särelä, Antti; Garcia, Elsa; Fairfull, Anita; Oldenburg, Brian F; Walters, Darren L

2011-02-21

131

Health-related quality of life of patients with implantable cardioverter defibrillators compared with that of pacemaker recipients  

Microsoft Academic Search

Aims Studies indicate a poorer quality of life (QoL) for implantable cardioverter defibrillator (ICD) patients than for the general population. However, studies comparing the QoL of ICD patients with that of patients with other implantable cardiac devices are scarce. We hypothesized that ICD patients had a poorer QoL than pacemaker patients. Methods and results All ICD patients living in Iceland

Margret Leosdottir; Engilbert Sigurdsson; Gudrun Reimarsdottir; Gizur Gottskalksson; Bjarni Torfason; Margret Vigfusdottir; Sveinn Eggertsson; David O. Arnar

132

CALCIUM-DRIVEN TRANSCRIPTION OF CARDIAC SPECIFYING GENE PROGRAM IN LIVER STEM CELLS  

EPA Science Inventory

We have previously shown that a cloned liver stem cell line (WB F344) acquires a cardiac phenotype when seeded in a cardiac microenvironment in vivo and ex vivo. Here we investigated the mechanisms of this transdifferentiation in early (...

133

Complete Atrial-Specific Knockout of Sodium-Calcium Exchange Eliminates Sinoatrial Node Pacemaker Activity  

PubMed Central

The origin of sinoatrial node (SAN) pacemaker activity in the heart is controversial. The leading candidates are diastolic depolarization by “funny” current (If) through HCN4 channels (the “Membrane Clock“ hypothesis), depolarization by cardiac Na-Ca exchange (NCX1) in response to intracellular Ca cycling (the "Calcium Clock" hypothesis), and a combination of the two (“Coupled Clock”). To address this controversy, we used Cre/loxP technology to generate atrial-specific NCX1 KO mice. NCX1 protein was undetectable in KO atrial tissue, including the SAN. Surface ECG and intracardiac electrograms showed no atrial depolarization and a slow junctional escape rhythm in KO that responded appropriately to ?-adrenergic and muscarinic stimulation. Although KO atria were quiescent they could be stimulated by external pacing suggesting that electrical coupling between cells remained intact. Despite normal electrophysiological properties of If in isolated patch clamped KO SAN cells, pacemaker activity was absent. Recurring Ca sparks were present in all KO SAN cells, suggesting that Ca cycling persists but is uncoupled from the sarcolemma. We conclude that NCX1 is required for normal pacemaker activity in murine SAN. PMID:24278453

Groenke, Sabine; Larson, Eric D.; Alber, Sarah; Zhang, Rui; Lamp, Scott T.; Ren, Xiaoyan; Nakano, Haruko; Jordan, Maria C.; Karagueuzian, Hrayr S.; Roos, Kenneth P.; Nakano, Atsushi; Proenza, Catherine; Philipson, Kenneth D.; Goldhaber, Joshua I.

2013-01-01

134

Cardiac rehabilitation outcomes following a 6-week program of PCI and CABG Patients  

PubMed Central

Coronary artery events requiring intervention are associated with depressed cardiac autonomic function. Whether a 6-week cardiac rehabilitation (CR) differs in effectiveness in improving exercise capacity (6MWT), cardiorespiratory function (peakVO2), and autonomic function (HRV) following either cardiac bypass surgery (CABG) or percutaneous coronary revascularization (PCI) is unknown. The current study therefore compared the change in 6MWT and peak VO2 to HRV variables following a 6-week CR program and with patients having either PCI or CABG. Thirty-eight patients, (PCI, n = 22 and CABG, n = 16) participated in the CR program and results for pre and post 6 min walk test (6MWT), peakVO2, and heart rate variability (HRV) were obtained. Our study has shown that a 6 weeks program following either PCI or CABG improves function. However, the effect on post-CABG differs to that of post-PCI patients. The change in distance walked (6MWT, metres) was higher in the CABG (?6MWT: 61, p < 0.001) compared to the PCI group (?6MWT: 41, p < 0.001). Maximum exercise capacity (peak VO2, ml/kg.min) also changed significantly with a greater change in the CABG group (?PCI: 0.7, p < 0.001; ?CABG: 1.0, p < 0.001) but did not reach normal population values. Although an improvement in HRV parameters was noted for the PCI group, a statistically significant improvement in HRV was observed only in the CABG group for the following; SDNN (ms) (baseline vs. post-rehabilitation (median ± IQR): 31.2 ± 25.6 vs. 51.8 ± 23.1, p < 0.01), RMSSD (19.32 ± 19.9 vs. 42.1 ± 34.2, p < 0.01); LF (ms2) (191 ± 216 vs. 631 ± 693, p < 0.01) and HF (107 ± 201 vs. 449 ± 795.0, p < 0.05). A significant interaction in the PCI group but not in the CABG group was observed using correlation analysis between the 6MWT and peak VO2 with HRV parameters indicating that being healthier that is, a better 6MWT and peak VO2 led to better HRV results but no significant effect of CR in the PCI group. When the results were investigated for baseline 6MWT and peak VO2 effect using a covariate analysis, a significant influence of CR on HRV parameters was retained in the CABG group (p = 0.0072). Our study indicates that a 6-weeks CR program benefits both patient groups in terms of exercise capacity, cardiorespiratory function and autonomic nervous system modulation of heart rate, with CABG patients showing the most improvement. HRV can be a useful additional variable to gauge cardiac function following CR. PMID:24198786

Jelinek, Herbert F.; Huang, Zhaoqi Q.; Khandoker, Ahsan H.; Chang, Dennis; Kiat, Hosen

2013-01-01

135

[Delayed atrial excitation following bifocal pacemaker stimulation].  

PubMed

A patient with drug-resistant ventricular tachycardia due to ischemic heart disease with severe left ventricular failure was successfully treated by the implantation of a DDD pacemaker system pacing at a rate of 90 beats/min (overdrive suppression). Additional therapy with high doses of beta-blockers was necessary. The ECG demonstrated a delay of 100 ms between atrial spike and p-wave. The hemodynamic effects of this ineffective atrial contraction were assessed by jugular venous puls tracing, phonocardiography, echocardiography, and radionuclide-ventriculography. The desired positive effects of physiological pacing could only be achieved by further prolongation of the A-V interval by these 100 ms. This observation shows that, with DDD pacemakers, AV intervals of varying length may be necessary with VAT or VDD and DVI modes in individual cases. PMID:6868743

Alt, E; Wirtzfeld, A; Seidl, K; Haller, F; von Bibra, H; Sauer, E

1983-04-01

136

76 FR 47085 - Effective Date of Requirement for Premarket Approval for a Pacemaker Programmer  

Federal Register 2010, 2011, 2012, 2013

...information submitted in response to the 515(i...This Proposal--Pacemaker Programmers (21...at an improper rate. 3. Misdiagnosis...ability to sense pacemaker function can lead...including adaptive rate pacemakers (LWP);...

2011-08-04

137

Transvenous Pacemaker Lead Removal in Pacemaker Lead Endocarditis with Large Vegetations: A Report of Two Cases  

PubMed Central

Pacemaker lead endocarditis is treated with total removal of the infected device and proper antibiotics. The outcomes of patients undergoing percutaneous lead extraction for large vegetations (>2 cm) have not yet been shown. In this case report, we present two patients with pacemaker lead endocarditis with large vegetations of maximum diameter 2.4 cm and 3.2 cm. The first patient had multiple vegetations attached to the tricuspid and mitral valves and developed septic emboli to the brain, lung, and liver. The second patient had a large, persistent vegetation on the tricuspid valve, even two weeks after complete removal of the leads. Both patients were successfully treated with transvenous pacemaker lead removal and antibiotics. PMID:24653742

Cho, Hyunsoo; Kim, Mihyun; Uhm, Jae-Sun; Pak, Hui-Nam; Lee, Moon-Hyoung

2014-01-01

138

Transvenous pacemaker lead removal in pacemaker lead endocarditis with large vegetations: a report of two cases.  

PubMed

Pacemaker lead endocarditis is treated with total removal of the infected device and proper antibiotics. The outcomes of patients undergoing percutaneous lead extraction for large vegetations (>2 cm) have not yet been shown. In this case report, we present two patients with pacemaker lead endocarditis with large vegetations of maximum diameter 2.4 cm and 3.2 cm. The first patient had multiple vegetations attached to the tricuspid and mitral valves and developed septic emboli to the brain, lung, and liver. The second patient had a large, persistent vegetation on the tricuspid valve, even two weeks after complete removal of the leads. Both patients were successfully treated with transvenous pacemaker lead removal and antibiotics. PMID:24653742

Cho, Hyunsoo; Kim, Mihyun; Uhm, Jae-Sun; Pak, Hui-Nam; Lee, Moon-Hyoung; Joung, Boyoung

2014-03-01

139

Myopotential inhibition of unipolar AV sequential (DVI) pacemaker.  

PubMed

Whereas myopotential inhibition of QRS-inhibited (VVI) pacemakers is well known, its occurrence in patients with AV sequential (DVI) pacemakers has not been reported. The present communication deals with spontaneous and induced myopotential inhibition of a multiprogrammable Intermedics unipolar AV sequential (DVI) pacemaker. The bedside maneuvers that were performed in the patient exposed the problem, therefore serving to establish the diagnosis. Although external adjustment of the sensitivity was the simple, non-invasive solution in this case, more studies are required to determine the success rate of this approach as well as the incidence and clinical significance of myopotential inhibition of unipolar DVI pacemakers. PMID:6181468

Echeverria, H J; Luceri, R M; Thurer, R J; Castellanos, A

1982-01-01

140

Comparison of Cardiac Rehabilitation Programs Combined with Relaxation and Meditation Techniques on Reduction of Depression and Anxiety of Cardiovascular Patients  

PubMed Central

Cardiovascular disease (CVD) is a major cause of death in developed countries. Most cardiac rehabilitation programs include psychological interventions. The aim of this study was to determine the effectiveness of rehabilitation techniques in cardiac patients including psychological-physical interventions such as Meditation and Relaxation. We enrolled 45 patients with CVD and depression. The patients were allocated to 3 groups (Relaxation, Meditation and Control). There was a significant reduction on depression, systolic blood pressure and heart rate in the Meditation group compared with the control group. Our findings suggest that meditation techniques have better outcomes in cardiac patients for improving depression, reduction of systolic and diastolic blood pressure, and heart rate than relaxation techniques. PMID:24179555

Delui, Mahdy Hassanzadeh; Yari, Maliheh; khouyinezhad, Gholamreza; Amini, Maral; Bayazi, Mohammad Hosein

2013-01-01

141

"False inhibition" of demand pacemaker due to leakage of fluid into the pacemaker lead socket.  

PubMed

"False inhibition" of a demand pacemaker usually occurs with a microfracture of the lead system resulting in a galvanic potential at the site of the fracture or with sensing of myopotential with exercise. An increase in the slope of the leading half edge of the pulse contour is generally considered diagnostic of lead fracture. We report the case of a patient in whom "false inhibition" at rest and an increase in the slope of the leading half edge of the pulse contour were caused by leakage of fluid into the pacemaker lead socket. PMID:642574

Chandra, M S; Patel, M R; Laughlin, D E; Rossi, N P

1978-05-01

142

The Mef2A Transcription Factor Coordinately Regulates a Costamere Gene Program in Cardiac Muscle*  

PubMed Central

The Mef2 family of transcription factors regulates muscle differentiation, but the specific gene programs controlled by each member remain unknown. Characterization of Mef2A knock-out mice has revealed severe myofibrillar defects in cardiac muscle indicating a requirement for Mef2A in cytoarchitectural integrity. Through comprehensive expression analysis of Mef2A-deficient hearts, we identified a cohort of dysregulated genes whose products localize to the peripheral Z-disc/costamere region. Many of these genes are essential for costamere integrity and function. Here we demonstrate that these genes are directly regulated by Mef2A, establishing a mechanism by which Mef2A controls the costamere. In an independent model system, acute knockdown of Mef2A in primary neonatal cardiomyocytes resulted in profound malformations of myofibrils and focal adhesions accompanied by adhesion-dependent programmed cell death. These findings indicate a role for Mef2A in cardiomyocyte survival through regulation of costamere integrity. Finally, bioinformatics analysis identified over-represented transcription factor-binding sites in this network of costamere promoters that may provide insight into the mechanism by which costamere genes are regulated by Mef2A. The global control of costamere gene expression adds another dimension by which this essential macromolecular complex may be regulated in health and disease. PMID:21724844

Ewen, Elizabeth P.; Snyder, Christine M.; Wilson, Megan; Desjardins, Danielle; Naya, Francisco J.

2011-01-01

143

A semi-infinite programming approach to preoperative planning of robotic cardiac surgery under geometric uncertainty.  

PubMed

In this paper, a computational framework for patient-specific preoperative planning of Robotics-Assisted Minimally Invasive Cardiac Surgery (RAMICS) is presented. It is expected that preoperative planning of RAMICS will improve the success rate by considering robot kinematics, patient-specific thoracic anatomy, and procedure-specific intraoperative conditions. Given the significant anatomical features localized in the preoperative computed tomography images of a patients thorax, port locations and robot orientations (with respect to the patients body coordinate frame) are determined to optimize qualities such as dexterity, reachability, tool approach angles and maneuverability. To address intraoperative geometric uncertainty, the problem is formulated as a Generalized Semi-Infinite Program (GSIP) with a convex lower-level problem to seek a plan that is less sensitive to geometric uncertainty in the neighborhood of surgical targets. It is demonstrated that with a proper formulation of the problem, the GSIP can be replaced by a tractable constrained nonlinear program that uses a multi-criteria objective function to balance between the nominal task performance and robustness to collisions and joint limit violations. Finally, performance of the proposed formulation is demonstrated by a comparison between the plans generated by the algorithm and those recommended by an experienced surgeon for several case studies. PMID:23033329

Azimian, H; Patel, R V; Naish, M D; Kiaii, B

2013-01-01

144

Quantification of fiber orientation in the canine atrial pacemaker complex using optical coherence tomography  

NASA Astrophysics Data System (ADS)

The atrial pacemaker complex is responsible for the initiation and early propagation of cardiac impulses. Optical coherence tomography (OCT), a nondestructive imaging modality with spatial resolutions of ˜1 to 15 ?m, can be used to identify unique fiber orientation patterns in this region of the heart. Functionally characterized canine sinoatrial nodes (SAN) (n=7) were imaged using OCT up to ˜1 mm below the endocardial tissue surface. OCT images were directly compared to their corresponding histological sections. Fiber orientation patterns unique to the crista terminalis (CT), SAN, and surrounding atrial myocardium were identified with dominant average fiber angles of 89±12 deg, 110±16 deg, and 95±35 deg, respectively. Both the CT and surrounding atrial myocardium displayed predominantly unidirectionally based fiber orientation patterns within each specimen, whereas the SAN displayed an increased amount of fiber disarray manifested quantitatively as a significantly greater standard deviation in fiber angle distribution within specimens [33±7 deg versus 23±5 deg, atrium (p=0.02); 18±3 deg, CT (p=0.0003)]. We also identified unique, local patterns of fiber orientation specific to the functionally characterized block zone. We demonstrate the ability of OCT in detecting components of the atrial pacemaker complex which are intimately involved in both normal and abnormal cardiac conduction.

Ambrosi, Christina M.; Fedorov, Vadim V.; Schuessler, Richard B.; Rollins, Andrew M.; Efimov, Igor R.

2012-07-01

145

The effect of an educational intervention on coronary artery bypass graft surgery patients' participation rate in cardiac rehabilitation programs: a controlled health care trial  

PubMed Central

Background Cardiac rehabilitation has a beneficial effect on the prognosis and quality of life of cardiac patients, and has been found to be cost-effective. This report describes a comprehensive and low cost educational intervention designed to increase the attendance at cardiac rehabilitation programs of patients who have undergone coronary artery bypass graft surgery. Methods/Design A controlled prospective intervention trial. The control arm comprised 520 patients who underwent coronary artery bypass graft surgery between January 2004 and May 2005 in five medical centers across Israel. This group received no additional treatment beyond usual care. The intervention arm comprised 504 patients recruited from the same cardiothoracic departments between June 2005 and November 2006. This group received oral and written explanations about the advantages of participating in cardiac rehabilitation programs and a telephone call two weeks after hospital discharge intended to further encourage their enrollment. The medical staff attended a one-hour seminar on cardiac rehabilitation. In addition, it was recommended that referral to cardiac rehabilitation be added to the letter of discharge from the hospital. Both study groups were interviewed before surgery and one-year post surgery. A one-year post-operative interview assessed factors affecting patient attendance at cardiac rehabilitation programs, as well as the structure and content of the cardiac rehabilitation programs attended. Anthropometric parameters were measured at pre- and post-operative interviews;- and medical information was obtained from patient medical records. The effect of cardiac rehabilitation on one- and three-year mortality was assessed. Discussion We report a low cost yet comprehensive intervention designed to increase cardiac rehabilitation participation by raising both patient and medical staff awareness to the potential benefits of cardiac rehabilitation. Trial registration ClinicalTrials.gov: NCT00356863 PMID:21982052

2011-01-01

146

Utility of isoproterenol in unmasking latent escape rhythm in pacemaker dependent patients undergoing pacemaker replacement.  

PubMed

Pacemaker generator replacement in dependent patients may be managed with a bridging temporary pacing lead or by replacing the generator very expediently. The 2 options involve a small risk, and temporary pacing introduces additional cost. This study was conducted to explore the utility of a graduated rate-decrease protocol with isoproterenol support in unmasking an intrinsic rhythm that would obviate the 2 strategies. The protocol was used in 100 consecutive pacemaker-dependent patients (mean age 74.4 +/- 13.7 years, 56% men) who underwent permanent pacemaker replacement. Device lower rates were decremented in 1-minute intervals to 60, 50, 40, and 30 beats/min. If no intrinsic rhythm of > or =30 beats/min was observed after 1 minute, isoproterenol was infused at 1 microg/min for 2 minutes, followed by 2 microg/min for 2 minutes. Of the 100 patients, 59 demonstrated intrinsic rhythm during pacing step-down alone. Of the remaining 41 patients, 28 (68.3%) demonstrated intrinsic rhythm during isoproterenol infusion. The escape rhythm was junctional in 29%, idioventricular in 23%, conducted atrial fibrillation in 16%, and sinus in 15%. Only 13 of 100 patients (13%) failed to demonstrate adequate intrinsic rhythm after the protocol. In conclusion, this suggests that a standardized protocol to elicit an underlying rhythm in patients previously assessed as pacemaker dependent effectively minimizes the need for temporary pacing during device replacement. PMID:18308011

Chihrin, Stephen M; Mohamed, Uwais; Yee, Raymond; Gula, Lorne J; Klein, George J; Skanes, Allan C; Krahn, Andrew D

2008-03-01

147

Autonomic control and innervation of the atrioventricular junctional pacemaker  

E-print Network

the junctional rate, and parasympathetic and sympathetic com- ponents can be separated with atropine system; Junctional rhythm; Junctional pacemaker (Heart Rhythm 2007;4:1326­1335) © 2007 Heart Rhythm junction may be- come the pacemaker of the heart. Unlike the well-characterized sinoatrial node (SAN

148

Electrocution induced symptomatic bradycardia necessitating pacemaker implantation.  

PubMed

Electrical or electrocution injury is a common accidental occurrence and mostly workplace related. Fatal arrhythmias, skin injury and sudden death may ensue. However, it is rare for electrocution to result in permanent low rate sinus bradycardia, incompatible with an active lifestyle. The probable mechanisms for this pathological sinus bradycardia are sinus node dysfunction and autonomic dysfunction with vagal predominance. We describe a young patient who suffered a non fatal electrocution with resultant low rate sinus bradycardia and its successful treatment with a dual chamber rate responsive pacemaker. PMID:25104983

Yew, Kuan Leong

2014-04-01

149

Electrocution Induced Symptomatic Bradycardia Necessitating Pacemaker Implantation  

PubMed Central

Electrical or electrocution injury is a common accidental occurrence and mostly workplace related. Fatal arrhythmias, skin injury and sudden death may ensue. However, it is rare for electrocution to result in permanent low rate sinus bradycardia, incompatible with an active lifestyle. The probable mechanisms for this pathological sinus bradycardia are sinus node dysfunction and autonomic dysfunction with vagal predominance. We describe a young patient who suffered a non fatal electrocution with resultant low rate sinus bradycardia and its successful treatment with a dual chamber rate responsive pacemaker. PMID:25104983

Yew, Kuan Leong

2014-01-01

150

Asynchronous response of coupled pacemaker neurons  

E-print Network

We study a network model of two conductance-based pacemaker neurons of differing natural frequency, coupled with either mutual excitation or inhibition, and receiving shared random inhibitory synaptic input. The networks may phase-lock spike-to-spike for strong mutual coupling. But the shared input can desynchronize the locked spike-pairs by selectively eliminating the lagging spike or modulating its timing with respect to the leading spike depending on their separation time window. Such loss of synchrony is also found in a large network of sparsely coupled heterogeneous spiking neurons receiving shared input.

Ramana Dodla; Charles J. Wilson

2009-02-03

151

Pre-ejection period by radial artery tonometry supplements echo doppler findings during biventricular pacemaker optimization  

PubMed Central

Background Biventricular (Biv) pacemaker echo optimization has been shown to improve cardiac output however is not routinely used due to its complexity. We investigated the role of a simple method involving computerized pre-ejection time (PEP) assessment by radial artery tonometry in guiding Biv pacemaker optimization. Methods Blinded echo and radial artery tonometry were performed simultaneously in 37 patients, age 69.1 ± 12.8 years, left ventricular (LV) ejection fraction (EF) 33 ± 10%, during Biv pacemaker optimization. Effect of optimization on echo derived velocity time integral (VTI), ejection time (ET), myocardial performance index (MPI), radial artery tonometry derived PEP and echo-radial artery tonometry derived PEP/VTI and PEP/ET indices was evaluated. Results Significant improvement post optimization was achieved in LV ET (286.9 ± 37.3 to 299 ± 34.6 ms, p < 0.001), LV VTI (15.9 ± 4.8 cm to 18.4 ± 5.1 cm, p < 0.001) and MPI (0.57 ± 0.2 to 0.45 ± 0.13, p < 0.001) and in PEP (246.7 ± 36.1 ms to 234.7 ± 35.5 ms, p = 0.003), PEP/ET (0.88 ± 0.21 to 0.79 ± 0.17, p < 0.001), and PEP/VTI (17.3 ± 7 to 13.78 ± 4.7, p < 0.001). The correlation between comprehensive echo Doppler and radial artery tonometry-PEP guided optimal atrioventricular delay (AVD) and optimal interventricular delay (VVD) was 0.75 (p < 0.001) and 0.69 (p < 0.001) respectively. In 29 patients with follow up assessment, New York Heart Association (NYHA) class reduced from 2.5 ± 0.8 to 2.0 ± 0.9 (p = 0.004) at 1.8 ± 1.4 months. Conclusion An acute shortening of PEP by radial artery tonometry occurs post Biv pacemaker optimization and correlates with improvement in hemodynamics by echo Doppler and may provide a cost-efficient approach to assist with Biv pacemaker echo optimization. PMID:21794181

2011-01-01

152

[A new dual-chamber pacemaker with an automatic antitachycardia system in the treatment of the bradycardia-tachycardia syndrome].  

PubMed

A new dual-chamber pacemaker with automatic tachycardia terminating system was used in three patients with bradycardia-tachycardia syndrome. This pacemaker (Medtronic Symbios 7008) is a multiprogrammable, bipolar device with bidirectional telemetry and six permanent pacing modes (DDD-DVI-VVI-DOO-VOO-AOO). The antitachycardia system can be programmed in two different modes: underdrive dual demand and overdrive atrial burts (1 to 16 stimuli with selectable coupling interval from 135 to 360 msec). The pacing modes are automatically activated when five consecutive R-R cycles shorter than the tachycardia detection interval are sensed. The pacemaker may sense the ventricle (when set on VVI or DVI mode) or sense both the atrium and the ventricle (in DDD mode). The pacemaker was programmed on DVI mode in all three patients, and the overdrive atrial burst program was used for tachycardia termination, with promptly and costantly effective results. The underdrive dual demand program was tested after the implantation, but it did not show constant results because inefficacy or late termination of tachycardias. PMID:4043644

Adornato, E; Polimeni, R M; Monea, P; Tassone, F; Pennisi, V

1985-04-01

153

Cardiac Rehabilitation  

MedlinePLUS

Cardiac rehabilitation (rehab) is a medically supervised program to help people who have A heart attack Angioplasty or coronary artery bypass grafting for coronary heart disease A heart valve repair or replacement A heart transplant or a lung transplant Angina Heart failure The ...

154

Cardiac arrhythmias in athletes: Clinical picture, diagnosis, rehabilitation, and prevention  

Microsoft Academic Search

When athletes present any kind of cardiac arrhythmia, it is essential to specify the underlying mechanisms and to identify the arrhythmia with the help of transesophageal computer?aided electrostimulation. This technique also allows earlier identification of previously undetected arrhythmias, specification of the underlying electro?physiologic cause and determination of the functional condition of both the conduction and pacemaking systems of the heart.

V. F. Antyufiev; M. V. Kazakov; N. A. Lepikhina; G. Y. Tayurov; N. P. Khromova

1993-01-01

155

Cardiac sarcoidosis responding to monotherapy with infliximab  

Microsoft Academic Search

Cardiac involvement is a rare and potentially life-threatening complication of sarcoidosis. We report the case of a young\\u000a previously healthy woman who presented with complete atrioventricular heart block. Further evaluation revealed non-caseating\\u000a granulomas in the hilar and mediastinal regions. A pacemaker was inserted, and she was treated with four doses of infliximab\\u000a after she refused treatment with steroids. Rapid resolution

Imad Uthman; Zahi Touma; Maurice Khoury

2007-01-01

156

High School Automated External Defibrillator Programs as Markers of Emergency Preparedness for Sudden Cardiac Arrest  

PubMed Central

Context: School-based automated external defibrillator (AED) programs have demonstrated a high survival rate for individuals suffering sudden cardiac arrest (SCA) in US high schools. Objective: To examine the relationship between high schools having an AED on campus and other measures of emergency preparedness for SCA. Design: Cross-sectional study. Setting: United States high schools, December 2006 to September 2009. Patients or Other Participants: Principals, athletic directors, school nurses, and certified athletic trainers represented 3371 high schools. Main Outcome Measure(s): Comprehensive surveys on emergency planning for SCA submitted by high school representatives to the National Registry for AED Use in Sports from December 2006 to September 2009. Schools with and without AEDs were compared to assess other elements of emergency preparedness for SCA. Results: A total of 2784 schools (82.6%) reported having 1 or more AEDs on campus, with an average of 2.8 AEDs per school; 587 schools (17.4%) had no AEDs. Schools with an enrollment of more than 500 students were more likely to have an AED (relative risk [RR] = 1.12, 95% confidence interval [CI] = 1.08, 1.16, P < .01). Suburban schools were more likely to have an AED than were rural (RR = 1.08, 95% CI = 1.04, 1.11, P < .01), urban (RR = 1.13, 95% CI = 1.04, 1.16, P < .01), or inner-city schools (RR = 1.10, 95% CI = 1.04, 1.23, P < .01). Schools with 1 or more AEDs were more likely to ensure access to early defibrillation (RR = 3.45, 95% CI = 2.97, 3.99, P < .01), establish an emergency action plan for SCA (RR = 1.83, 95% CI = 1.67, 2.00, P < .01), review the emergency action plan at least annually (RR = 1.99, 95% CI = 1.58, 2.50, P < .01), consult emergency medical services to develop the emergency action plan (RR = 1.18, 95% CI = 1.05, 1.32, P < .01), and establish a communication system to activate emergency responders (RR = 1.06, 95% CI = 1.01, 1.08, P < .01). Conclusions: High schools with AED programs were more likely to establish a comprehensive emergency response plan for SCA. Implementing school-based AED programs is a key step associated with emergency planning for young athletes with SCA. PMID:23672389

Toresdahl, Brett G.; Harmon, Kimberly G.; Drezner, Jonathan A.

2013-01-01

157

Recurrent pulmonary embolization following implantation of transvenous pacemaker.  

PubMed

A 44-year-old man developed recurrent pulmonary embolization after implantation of a permanent transvenous DVI pacemaker connected to polyurethane leads. Thrombus was found in the left innominate and subclavian veins around the pacemaker leads, but not in the right atrium or in the venous system of the pelvis and the lower extremities. The recurrence of pulmonary embolization followed discontinuation of treatment with Coumadin. This case demonstrates that lifelong anticoagulation is indicated in patients who have had pulmonary embolization and/or venous thrombosis around the pacemaker leads. PMID:6207489

Pasquariello, J L; Hariman, R J; Yudelman, I M; Feit, A; Gomes, J A; El-Sherif, N

1984-09-01

158

Peak Oxygen Uptake after Cardiac Rehabilitation: A Randomized Controlled Trial of a 12-Month Maintenance Program versus Usual Care  

PubMed Central

Background Exercise capacity is a strong predictor of survival in patients with coronary artery disease (CAD). Exercise capacity improves after cardiac rehabilitation exercise training, but previous studies have demonstrated a decline in peak oxygen uptake after ending a formal rehabilitation program. There is a lack of knowledge on how long-term exercise adherence can be achieved in CAD patients. We therefore assessed if a 12-month maintenance program following cardiac rehabilitation would lead to increased adherence to exercise and increased exercise capacity compared to usual care. Materials and Methods Two-centre, open, parallel randomized controlled trial with 12 months follow-up comparing usual care to a maintenance program. The maintenance program consisted of one monthly supervised high intensity interval training session, a written exercise program and exercise diary, and a maximum exercise test every third month during follow-up. Forty-nine patients (15 women) on optimal medical treatment were included following discharge from cardiac rehabilitation. The primary endpoint was change in peak oxygen uptake at follow-up; secondary endpoints were physical activity level, quality of life and blood markers of cardiovascular risk. Results There was no change in peak oxygen uptake from baseline to follow-up in either group (intervention group 27.9 (±4.7) to 28.8 (±5.6) mL·kg (-1) min (?1), control group 32.0 (±6.2) to 32.8 (±5.8) mL·kg (?1) min (?1), with no between-group difference, p?=?0.22). Quality of life and blood biomarkers remained essentially unchanged, and both self-reported and measured physical activity levels were similar between groups after 12 months. Conclusions A maintenance exercise program for 12 months did not improve adherence to exercise or peak oxygen uptake in CAD patients after discharge from cardiac rehabilitation compared to usual care. This suggests that infrequent supervised high intensity interval training sessions are inadequate to improve peak oxygen uptake in this patient group. Trial Registration ClinicalTrials.gov NCT01246570 PMID:25247991

Madssen, Erik; Arbo, Ingerid; Gran?ien, Ingrid; Walderhaug, Liv; Moholdt, Trine

2014-01-01

159

Incidence of new onset atrial fibrillation in patients with permanent pacemakers and the relation to the pacing mode  

PubMed Central

Background Atrial fibrillation is a relatively common arrhythmia often seen in patients with permanent pacemakers. In this study we aimed to assess the incidence of atrial fibrillation in patients whose pacemakers were programmed to pace in the right ventricle (VVI) and compared it with patients whose pacemakers were programmed in non-VVI mode(i.e. AAI or DDD). Material/Methods Records of the patients with permanent pacemaker or implantable-cardioverter-defibrillator were evaluated and analyzed. These patients had regular periodic follow-up evaluation over the last 10 years. (January 1, 2002 to December 31, 2012). Patient demographic, pacemaker data, pacing mode, review and analysis of arrhythmia log for occurrence of new atrial fibrillation and echocardiographic findings for left atrial size, mitral regurgitation, were analyzed and recorded. Left atrial size was classified as mild, moderate or severe enlargement, depending on the left atrial dimension. Results Average age was 68 years. There was no gender predominance (51% male). Mean follow-up duration was 6 years and 3 months. Hispanic population represented the majority of the patients (65.4%). Majority of the devices (80.0%) were programmed as DDD pacing mode. Fifty-five patients (52.8%) did not develop atrial fibrillation. 85.7% of the patients paced in VVI-mode had atrial fibrillation while atrial fibrillation occurred in 37.4% among patients paced in non-VVI-mode. This difference was statistically significant (P<0.0001). Conclusions Right ventricular pacing in a VVI mode was associated with higher incidence of atrial fibrillation, mitral regurgitation and left atrial enlargement. Non-VVI based pacing demonstrated lower incidence of new onset atrial fibrillation. PMID:24535068

Said, Sarmad; Alkhateeb, Haider; Cooper, Chad J.; Gosavi, Sucheta; Dwivedi, Alok; Paez, David; Abedin, Zainul

2014-01-01

160

21 CFR 870.3600 - External pacemaker pulse generator.  

Code of Federal Regulations, 2010 CFR

...electronic circuits that produce a periodic electrical pulse to stimulate the heart. This device, which is used outside the body, is used as a temporary substitute for the heart's intrinsic pacing sytem until a permanent pacemaker can be...

2010-04-01

161

Pacemaker activity in the insect (T. molitor) heart: role of the sarcoplasmic reticulum.  

PubMed

The electrophysiological properties of the myogenic cardiac cells of insects have been analyzed, but the mechanisms that regulate the pacemaker activity have not been elucidated yet. In mammalian pacemaker cells, different types of membrane ion channels seem to be sequentially activated, perhaps in a cooperative fashion with the current generated by Ca(2+) extrusion mediated by the electrogenic Na(+)/Ca(2+) exchanger, which is sustained by the diastolic sarcoplasmic reticulum (SR) Ca(2+) release. The objective of the present work was to investigate the role of the SR function on the basal beating rate (BR), and BR modulation by extracellular Ca(2+) concentration ([Ca(2+)](o)) and neurotransmitters in the in situ dorsal vessel (heart) of the mealworm beetle Tenebrio molitor. The main observations were as follows: 1) basal BR was reduced by 50% by inhibition of SR function, but not affected by perfusion with CsCl or ZD7288; 2) spontaneous activity was abolished by Cd(2+); 3) a robust positive chronotropic response could be elicited to serotonin (5-HT), but not to norepinephrine or carbamylcholine; 4) SR inhibition abolished the sustained chronotropic stimulation by [Ca(2+)](o) elevation and by 5-HT, while the latter was unaffected by CsCl. It is concluded that, in T. molitor heart, BR is markedly, but not exclusively, dependent on the SR function, and that BR control and modulation by both [Ca(2+)](o) and 5-HT requires a functional SR. PMID:21917905

Feliciano, Danielle F; Bassani, Rosana A; Oliveira, Pedro X; Bassani, José W M

2011-12-01

162

Intracardiac Origin of Heart Rate Variability, Pacemaker Funny Current and their Possible Association with Critical Illness  

PubMed Central

Heart rate variability (HRV) is an indirect estimator of autonomic modulation of heart rate and is considered a risk marker in critical illness, particularly in heart failure and severe sepsis. A reduced HRV has been found in critically ill patients and has been associated with neuro-autonomic uncoupling or decreased baroreflex sensitivity. However, results from human and animal experimental studies indicate that intracardiac mechanisms might also be responsible for interbeat fluctuations. These studies have demonstrated that different membrane channel proteins and especially the so-called ‘funny’ current (If), an hyperpolarization-activated, inward current that drives diastolic depolarization resulting in spontaneous activity in cardiac pacemaker cells, are altered during critical illness. Furthermore, membrane channels kinetics seem to have significant impact upon HRV, whose early decrease might reflect a cellular metabolic stress. In this review article we present research findings regarding intracardiac origin of HRV, at the cellular level and in both isolated sinoatrial node and whole ex vivo heart preparations. In addition, we will review results from various experimental studies that support the interrelation between If and HRV during endotoxemia. We suggest that reduced HRV during sepsis could also be associated with altered pacemaker cell membrane properties, due to ionic current remodeling. PMID:22920474

Papaioannou, Vasilios E; Verkerk, Arie O; Amin, Ahmed S; de Bakker, Jaques MT

2013-01-01

163

A functional analysis of circadian pacemakers in nocturnal rodents  

Microsoft Academic Search

Summary 1.The circadian pacemakers controlling activity rhythms in four species of rodents are compared, as freerunning systems in constant darkness. In analyzing their stability the distinction is made between (1) spontaneous day-to-day instability of frequency, and (2) a longer-term lability, some of which is traceable to identified causes.2.Serial correlation analysis indicates that the precision (day-to-day stability) of the pacemaker's period

Colin S. Pittendrigh; Serge Daan

1976-01-01

164

Atrial trigeminy induced by a normally functioning DVI pacemaker.  

PubMed

Atrial trigeminy was seen in a patient with a normally functioning DVI pacemaker (Byrel-5992). Atrial competition resulted from coincidence of sinus and atrial escape rates together with late ventricular sensing. This resulted in atrial output stimuli occurring within the QRS complex. Alternate impulses occurred late enough to conduct to the ventricle after recovery of the AV node. Reprogramming the pacemaker to either a faster DVI rate or to VVI abolished the arrhythmia. PMID:6200856

Millar, R N; Obel, I W

1984-03-01

165

Thallium cardiac stressing by esophageal pacing  

SciTech Connect

Forty-three patients were examined with the transesophageal pacing method of cardiac stressing and thallium imaging. Transesophageal cardiac pacing, using a pill electrode or a permanent pacemaker lead, is a safe alternative for patients who are physically unable to exercise. Prior studies suggest that transvenous right atrial pacing with thallium injection is equivalent to physical exercise thallium studies in the detection of coronary artery disease. The esophageal pacing bipolar electrode similarly increases heart rate without the necessity of transvenous pacing or fluoroscopy and without the adverse side effects often seen when using pharmacologic stressing agents (i.e., dipyridamole). The results compare well with cardiac catheterization, echocardiographic, and electrocardiographic results. Cardiac paced stress testing requires no sedation, is performed on an out-patient basis, and causes little if any discomfort for the patient.

Allen, M.L.; Vacek, J.L.; Preston, D.F.; Robinson, R.G.; Feldkamp, M.J. (Univ. of Kansas Medical Center, Kansas City (USA))

1989-09-01

166

A successful cardiac transplantation program using combined university and community resources.  

PubMed Central

From August 1984 to August 1986, 75 patients with end-stage heart disease and cardiac failure were evaluated. Twenty-five patients received orthotopic cardiac transplants from donors as far away as 1300 miles with an ischemic time of less than 4 hours. Seventeen of 25 patients are alive 3-24 months after transplantation. Evidence of rejection was seen in each patient. Twelve patients had mild, easily controlled rejection; 13 patients had severe rejection averaging 3.1 episodes per patient. The initial immunosuppressive regimen included cyclosporine and prednisone. To decrease complications related to high dose steroids, azathioprine has recently been added to our maintenance regimen to lessen steroid requirements. Acute rejection episodes were treated with 500-1000 mg of methylprednisolone for 3 days; antithymocyte globulin or the murine monoclonal antibody, OKT3, was added for severe or resistant rejection episodes. Three patients died of rejection, and two patients died of infection. Seventeen of 18 survivors are New York Heart Association (NYHA) Class I; 15 patients have returned to employment or full activity. Because of new developments in support of transplant candidates and treatment of complications, as well as the introduction of cyclosporine, orthotopic cardiac transplantation has become an effective treatment for end-stage heart disease. PMID:3296972

Gray, L A; Slater, A D; Klein, J B

1987-01-01

167

Signature Program/Landmark Research Programs  

E-print Network

owned animals with naturally occurring heart disease (e.g., Doberman pinschers with dilated interventional cardiac studies (e.g., coronary stents, pacemakers). The importance of using animals in the development and testing of new cardiovascular agents and TAMU is well positioned to become a world leader

168

Pacemaker Endocarditis Caused by Propionibacterium acnes in an Adult Patient with Ebstein's Anomaly: A Report of a Rare Case.  

PubMed

We report a rare case of a Brazilian adult woman with Ebstein's Anomaly who presented with pacemaker endocarditis caused by Propionibacterium acnes. Ebstein's Anomaly is a rare congenital malformation of the heart. Infective endocarditis is defined as an infection of heart valves, of the mural endocardium, of a septal defect, or of a cardiac electronic implantable device. Propionibacterium acnes is a skin commensal bacterium, that is usually considered as a contaminant, but can, on rare occasions, cause serious infections including endocarditis of prosthetic valves, native valves and cardiac electronic implantable devices. Diagnosis was made after nearly two years of investigation by identification of the organism by the MALDI-TOF technique and transoesophageal echocardiogram. The patient was successfully treated with daptomycin and device removal. She remains free of endocarditis after 32 months of follow-up. PMID:25047281

Santo, Karla R E; Franceschi, Vinicius; Campos, André C B; Monteiro, Thaíssa S; Barbosa, Giovanna I F; Dantas, Angela; Lamas, Cristiane C

2014-10-01

169

Scientists Use Gene Therapy to Create 'Biological Pacemaker' in Pig Hearts  

MedlinePLUS

... enable JavaScript. Scientists Use Gene Therapy to Create 'Biological Pacemaker' in Pig Hearts Technique might one day ... transform ordinary pig heart muscle cells into a "biological pacemaker," a feat that might one day lead ...

170

Severe Pain Attack Associated with Neurocardiogenic Syncope Induced by Glossopharyngeal Neuralgia: Successful Treatment with Carbamazepine and a Permanent Pacemaker  

E-print Network

Glossopharyneal neuralgia (GPN) is generally considered to be a pain disease. However, it can be also be a life-threatening cardiac cause of syncope. Neuralgia in the throat and neck can trigger severe bradycardia up to the point of asystole, which can progress to cardiac syncope with or without seizures. A 65 year-old male patient diagnosed with glossopharyngeal neuralgia complained of severe paroxysmal pain in his right chin and ear followed by bradycardia, aystole and syncope. We report a case successfully treated with a permanent pacemaker and carbamazepine in a patient with GPN who had syncopal attacks preceded by paroxysms of pain. (Korean J Pain 2010; 23: 215-218) Key Words: carbamazepine, glossopharyngeal neuralgia, permanent pacemaker, syncope. Glossopharyngeal neuralgia (GPN) is an uncommon neuropathic condition characterized by paroxysms of unilateral and severe stabbing pain felt in the ear, base of the tongue, tonsillar fossa or beneath the angle of the jaw. It is commonly incited by swallowing, talking or coughing, which usually lasts from seconds to minutes, and may remit

unknown authors

171

Biasing the pacemaker in the behavioral theory of timing  

PubMed Central

In the behavioral theory of timing, pacemaker rate is determined by overall rate of reinforcement. A two-alternative free-operant psychophysical procedure was employed to investigate whether pacemaker period was also sensitive to the differential rate of reinforcement. Responding on a left key during the first 25 s and on a right key during the second 25 s of a 50-s trial was reinforced at variable intervals, and variable-interval schedule values during the two halves of the trials were varied systematically. Responding on the right key during the first 25 s and on the left key during the second 25 s was not reinforced. Estimates of pacemaker period were derived from fits of a function predicted by the behavioral theory of timing to right-key response proportions in consecutive 5-s bins of the 50-s trial. Estimates of pacemaker period were shortest when the differential reinforcer rate most strongly favored right-key responses, and were longest when the differential reinforcer rate most strongly favored left-key responses. The results were consistent with the conclusion that pacemaker rate is influenced by relative reinforcer rate. PMID:16812769

Bizo, Lewis A.; White, K. Geoffrey

1995-01-01

172

A 9-year-old boy with severe diphtherial infection and cardiac complications.  

PubMed

The incidence of diphtheria has decreased since the introduction of an effective vaccine. However, in countries with low vaccination rates it has now become a re-emerging disease. Complications from diphtheria commonly include upper airway obstruction and cardiac complications. We present a 9-year-old boy who was diagnosed with diphtheria. He presented with fever, tonsilar plaques, respiratory failure and an incomplete vaccination history. He was endotracheal intubated and received diphtheria antitoxin and penicillin on the first day of hospitalisation. He developed progressive arrhythmias and fulminant myocarditis despite early identification and treatment with equine antitoxin and antibiotics. After a temporary transvenous pacemaker insertion due to third-degree atrioventricular block and hypotension for 1?week, he developed myocardial perforation from the pacemaker tip resulting in pericardial effusion. The treatment included emergency pericardiocentesis and pacemaker removal. His electrocardiogram showed a junctional rhythm with occasional premature ventricular complexes. He then developed ventricular tachycardia and cardiac arrest and finally died. PMID:25414216

Washington, Charles Henry; Issaranggoon Na Ayuthaya, Satja; Makonkawkeyoon, Krit; Oberdorfer, Peninnah

2014-01-01

173

Laparoscopic-assisted retrieval of migrated intra-abdominal pacemaker generator.  

PubMed

A 5-year-old boy born with a congenital heart defect had insertion of an epicardial pacemaker that was found on routine evaluation to have been displaced into the rectovesical pouch. He underwent transvenous insertion of another pacemaker, and the displaced pacemaker was successfully retrieved by laparoscopy without incident. PMID:21479910

Kravarusic, Dragan; Chirdan, Lohfa; Freud, Enrique

2011-12-01

174

Magnetic Resonance Imaging in patients with ICDs and Pacemakers  

PubMed Central

Magnetic resonance (MR) imaging has unparalleled soft-tissue imaging capabilities. The presence of devices such as pacemakers and implantable cardioverter/defibrillators (ICDs), however, is historically considered a contraindication to MR imaging. These devices are now smaller, with less magnetic material and improved electromagnetic interference protection. This review summarizes the potential hazards of the device-MR environment interaction, and presents updated information regarding in-vivo and in-vitro experiments. Recent reports on patients with implantable pacemakers and ICDs who underwent MR scan shows that under certain conditions patients with these implanted systems may benefit from this imaging modality. The data presented suggests that certain modern pacemaker and ICD systems may indeed be MR safe. This may have major clinical implications on current imaging practice. PMID:16943868

Nair, Prashant; Roguin, Ariel

2005-01-01

175

Angiosarcoma-like presentation of pacemaker-related vascular proliferation.  

PubMed

A 90-year-old man presented with a rapidly growing vascular lesion after a pacemaker generator change. The rapid growth suggested a possible angiosarcoma. A less dramatic presentation of vascular proliferation has been described as reticular telangiectatic erythema, which has been reporting following insertion of pacemakers, implantable cardioverter defibrillators, and drug-delivery devices. The onset of the disorder is described as weeks to years after implantation or generator change. It is a benign condition that generally remains static or regresses over time. The vascular proliferation noted in this case resolved almost completely over a period of 1 year. PMID:22106983

Ringrose, J S; Banerjee, T; Hull, P R

2012-03-01

176

Femoral approach: an exceptional alternative for permanent pacemaker implantation.  

PubMed

The classic transvenous implantation of a permanent pacemaker in a pectoral location may be precluded by obstruction of venous access through the superior vena cava or recent infection at the implant site. When these barriers to the procedure are bilateral and there are also contraindications or technical difficulties to performing a thoracotomy for an epicardial approach, the femoral vein, although rarely used, can be a viable alternative. We describe the case of a patient with occlusion of both subclavian veins and a high risk for mini-thoracotomy or videothoracoscopy, who underwent implantation of a permanent single-chamber pacemaker via the right femoral vein. PMID:24931177

Tereno Valente, Bruno; Conceição, José M; Nogueira da Silva, Manuel; M Oliveira, Mário; S Cunha, Pedro; Lousinha, Ana; Galrinho, Ana; C Ferreira, Rui

2014-05-01

177

[Body movement as pacemaker induction value: comparison of 2 activity-triggered pacemakers].  

PubMed

This article compares the rate behavior of the activity-triggered pacemakers, the Activitrax (A) and the Sensolog (S), during bench tests as well as in patients under defined ergometric conditions and during every day life with special reference to the susceptibility of both systems to external noise. In the bench tests both pacemakers were mounted on a swingbord and subjected to controlled vibrational force. In the first experiment the frequency, in the second experiment the energy was varied. In two groups, one with S, one with A implanted, each consisting of 10 patients, the discriminating power of workload changes was examined under defined treadmill exercise. Furthermore in 5 patients of each group the rate behavior of S and A under daily life conditions and during common environmental noise was registered using Holter-ECG. In the bench tests S and A displayed a frequency-selective mode of operation between 2 Hz and 70 Hz with the highest sensitivity (resonance frequency) at 10 Hz. In patients, S showed a significantly higher discriminating power to changes of workload under treadmill exercise. According to y = 0.27x + 85.8 (r = 0.92) the relationship between the pacing rate of S and the power was linear whereas with y = 0.04x + 89.8 (r = 0.2) the pacing rate of A was almost independent of the given power. The susceptibility to external noise occurring during riding a car, streetcar or train with rate increases between 7 ppm and 12 ppm did not significantly differ in both systems.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:3388936

Stangl, K; Wirtzfeld, A; Lochschmidt, O; Basler, B; Mittnacht, A

1988-04-01

178

[{sup 13}N] Ammonia Cardiac Program At West Virginia University Health Sciences  

SciTech Connect

Due to the shortage of the more traditional cardiac imagining isotopes, specifically, Technicium-99, the Cardiologists at WVU have had to look to alternative imagining techniques such as PET. This has led to a dramatic increase in the use of [{sup 13}N] Ammonia PET scans at the Health Sciences Center. The patient load has gone from one to two patients one day a week to typically two to three patients, two days a week, with occasional add-on in-house patients; each patient typically requiring two target irradiations. In this paper, we will discuss the process that is being used to meet this increased demand from the production of the isotope through the final result.

Armbruster, John M. [IBA Molecular, NA, 3601 Morgantown Industrial Park, Morgantown, WV 26501 (United States)

2011-06-01

179

[13N] Ammonia Cardiac Program At West Virginia University Health Sciences  

NASA Astrophysics Data System (ADS)

Due to the shortage of the more traditional cardiac imagining isotopes, specifically, Technicium-99, the Cardiologists at WVU have had to look to alternative imagining techniques such as PET. This has led to a dramatic increase in the use of [13N] Ammonia PET scans at the Health Sciences Center. The patient load has gone from one to two patients one day a week to typically two to three patients, two days a week, with occasional add-on in-house patients; each patient typically requiring two target irradiations. In this paper, we will discuss the process that is being used to meet this increased demand from the production of the isotope through the final result.

Armbruster, John M.

2011-06-01

180

[Cardiac resynchronization through a persistent left superior vena cava].  

PubMed

Cardiac resynchronization therapy is effective in the treatment of patients with severe heart failure and intraventricular dysynchrony. However, we are sometimes faced with the unexpected presence of a persistent left superior vena cava. We report the case of a patient with dilated cardiomyopathy and left ventricular dysynchrony in which we implanted a resynchronization pacemaker exclusively through a persistent left superior vena cava that did not communicate with the right vena cava. PMID:17194405

Moriña-Vázquez, P; Barba-Pichardo, R; Venegas Gamero, J; Herrera Carranza, M

2006-12-01

181

Arteriovenous fistula following pacemaker lead removal: CT diagnosis  

Microsoft Academic Search

  \\u000a Arteriovenous fistula formation is a very rare complication of pacemaker lead extraction. Rapid diagnosis is essential due\\u000a to the life-threatening nature of this complication. CT angiography provides a noninvasive and quick method for assessment.

Preet Kang; Diego B. Nunez Jr

2003-01-01

182

Differentially timed extracellular signals synchronize pacemaker neuron clocks.  

PubMed

Synchronized neuronal activity is vital for complex processes like behavior. Circadian pacemaker neurons offer an unusual opportunity to study synchrony as their molecular clocks oscillate in phase over an extended timeframe (24 h). To identify where, when, and how synchronizing signals are perceived, we first studied the minimal clock neural circuit in Drosophila larvae, manipulating either the four master pacemaker neurons (LNvs) or two dorsal clock neurons (DN1s). Unexpectedly, we found that the PDF Receptor (PdfR) is required in both LNvs and DN1s to maintain synchronized LNv clocks. We also found that glutamate is a second synchronizing signal that is released from DN1s and perceived in LNvs via the metabotropic glutamate receptor (mGluRA). Because simultaneously reducing Pdfr and mGluRA expression in LNvs severely dampened Timeless clock protein oscillations, we conclude that the master pacemaker LNvs require extracellular signals to function normally. These two synchronizing signals are released at opposite times of day and drive cAMP oscillations in LNvs. Finally we found that PdfR and mGluRA also help synchronize Timeless oscillations in adult s-LNvs. We propose that differentially timed signals that drive cAMP oscillations and synchronize pacemaker neurons in circadian neural circuits will be conserved across species. PMID:25268747

Collins, Ben; Kaplan, Harris S; Cavey, Matthieu; Lelito, Katherine R; Bahle, Andrew H; Zhu, Zhonghua; Macara, Ann Marie; Roman, Gregg; Shafer, Orie T; Blau, Justin

2014-09-01

183

Supplementary Materials to Pace-Makers Lost: Shifting Spatial  

E-print Network

Supplementary Materials to Pace-Makers Lost: Shifting Spatial Epidemiology of Reemerging Pertussis of time chara- caterizing the US pertussis notification case time series, we performed our analyses on two of pertussis incidence of each state (one state per line), where the states are ordered by longitude. To ease

Choisy, Marc

184

Differentially Timed Extracellular Signals Synchronize Pacemaker Neuron Clocks  

PubMed Central

Synchronized neuronal activity is vital for complex processes like behavior. Circadian pacemaker neurons offer an unusual opportunity to study synchrony as their molecular clocks oscillate in phase over an extended timeframe (24 h). To identify where, when, and how synchronizing signals are perceived, we first studied the minimal clock neural circuit in Drosophila larvae, manipulating either the four master pacemaker neurons (LNvs) or two dorsal clock neurons (DN1s). Unexpectedly, we found that the PDF Receptor (PdfR) is required in both LNvs and DN1s to maintain synchronized LNv clocks. We also found that glutamate is a second synchronizing signal that is released from DN1s and perceived in LNvs via the metabotropic glutamate receptor (mGluRA). Because simultaneously reducing Pdfr and mGluRA expression in LNvs severely dampened Timeless clock protein oscillations, we conclude that the master pacemaker LNvs require extracellular signals to function normally. These two synchronizing signals are released at opposite times of day and drive cAMP oscillations in LNvs. Finally we found that PdfR and mGluRA also help synchronize Timeless oscillations in adult s-LNvs. We propose that differentially timed signals that drive cAMP oscillations and synchronize pacemaker neurons in circadian neural circuits will be conserved across species. PMID:25268747

Collins, Ben; Kaplan, Harris S.; Cavey, Matthieu; Lelito, Katherine R.; Bahle, Andrew H.; Zhu, Zhonghua; Macara, Ann Marie; Roman, Gregg; Shafer, Orie T.; Blau, Justin

2014-01-01

185

Pacemaker Heterogeneity in the Suprachiasmatic Nucleus: Origins and Network Implications  

Microsoft Academic Search

In mammals, the suprachiasmatic nuclei (SCN) in the ventral hypothalamus function as a circadian pacemaker, controlling daily rhythms in behavior and physiology. Together the SCN contain approximately 20,000 neurons that maintain rhythms in firing rate and gene expression. Previous studies led to the assumption that single SCN neurons are capable of self-sustained circadian rhythms. Whether and which SCN neurons can

Alexis Webb

2010-01-01

186

Does significant weight reduction in men with coronary artery disease manage risk factors after cardiac rehabilitation program?  

PubMed Central

Background: Vast majority of cardiac patients who refer to cardiac rehabilitation program (CRP) are obese and obesity is associated with coronary heart disease (CHD). So, the aim of this study is to investigate the effects of CRP on obesity indexes, lipid profiles, and functional capacity (FC) in obese men with CHD and to explore whether significant weight reduction affected these risk factors and FC or not. Materials and Methods: In an observational study, we evaluated 536 patients, including 464 non-obese men and 72 obese men. All participants completed CRP for 2 months; then, obese patients were divided into two groups: patients with weight reduction ? 5% and patients who didn’t have significant weight reduction. Data were analyzed with SPSS software version 15. For comparing the mean of outcomes independent t-tests and paired t-tests were used. Results: Results showed following CRP, non-obese men had significant improvement in obesity indexes (P = 0.00), lipid profiles (P < 0.05), and FC (P = 0.00) and in obese men, favorable improvement were seen in obesity indexes (P = 0.00), FC (P = 0.00), and total cholesterol (P = 0.02). Comparing two groups revealed that there were significant differences in obesity indexes, high-density lipoprotein cholesterol, and low-density lipoprotein cholesterol/high-density lipoprotein cholesterol ratio. In addition, comparing subgroup of obese patients revealed that there were significant differences in FC (P = 0.00) and low-density lipoprotein cholesterol/ high-density lipoprotein cholesterol ratio (P = 0.04). Conclusion: CRP has more advantage in management of obesity, FC, and lipid profiles in both obese and non-obese patients. Also, weight reduction may cause greater improvement in FC and fitness levels in obese men with CHD. PMID:24523781

Sadeghi, Masoumeh; Ghashghaei, Fatemeh Esteki; Rabiei, Katayoun; Golabchi, Allahyar; Noori, Fatemeh; Baboli, Mozhgan Teimourzadeh; Sarrafzadegan, Nizal

2013-01-01

187

Diabetes mellitus activates fetal gene program and intensifies cardiac remodeling and oxidative stress in aged spontaneously hypertensive rats  

PubMed Central

Background The combination of systemic arterial hypertension and diabetes mellitus (DM) induces greater cardiac remodeling than either condition alone. However, this association has been poorly addressed in senescent rats. Therefore, this study aimed to analyze the influence of streptozotocin-induced DM on ventricular remodeling and oxidative stress in aged spontaneously hypertensive rats (SHR). Methods Fifty 18 month old male SHR were divided into two groups: control (SHR, n?=?25) and diabetic (SHR-DM, n?=?25). DM was induced by streptozotocin (40 mg/kg, i.p.). After nine weeks, the rats underwent echocardiography and myocardial functional study in left ventricular (LV) isolated papillary muscle preparations. LV samples were obtained to measure myocyte diameters, interstitial collagen fraction, and hydroxyproline concentration. Gene expression of atrial natriuretic peptide (ANP) and ?- and ?-myosin heavy chain (MyHC) isoforms was evaluated by RT-PCR. Serum oxidative stress was assessed by measuring lipid hydroperoxide concentration and superoxide dismutase and glutathione peroxidase activities. Statistics: Student’s t test or Mann-Whitney test, p?cardiac dilation and functional impairment, increases oxidative stress and activates fetal gene program in aged spontaneously hypertensive rats. PMID:24134628

2013-01-01

188

Conduction block and chaotic dynamics in an asymmetrical model of coupled cardiac cells.  

PubMed

The initiation and propagation of the cardiac impulse depends on intrinsic properties of cells, geometrical arrangements, and intercellular coupling resistances. To address the issue of the interplay between these factors in a simple way, we have used a system, based on the van Capelle and Dürrer model, including a pacemaker and a non-pacemaker cell linked by an ohmic coupling resistance. The influence of asymmetrical cell sizes and electronic load was investigated by using numerical simulations and continuation-bifurcation techniques. The loading of a small pacemaker cell by a large non-pacemaker one (pacemaker: non-pacemaker size ratio = 0.3) was expressed as a pronounced early repolarization in the pacemaker cell and a quite long latency for the impulse propagation. Using coupling resistance as the continuation parameter, three behavioral zones were detected from low to high coupling resistance values: a zone of total quiescence (0:0), a zone of effective entertainment (1:1), and a zone of total block (1:0 pattern). At the boundary between 1:1 and 1:0 patterns, for relatively high coupling resistance values, a cascade of period doubling bifurcations emerged, corresponding to discrete changes of propagation patterns leading into irregular dynamics. Another route to irregular dynamics was also observed in the parameter space. The high sensitivity of the detected irregular dynamics to initial conditions and the positive value of the maximum Lyapunov exponent allowed us to identify these dynamics as being chaotic. Since neither intermediate block patterns nor irregular dynamics were observed with larger size ratios, we suggest that the interplay between resting membrane conductance of the non-pacemaker cell and intercellular coupling may bring about these rhythmic disturbances. PMID:9176640

Landau, M; Lorente, P

1997-05-01

189

Socioeconomic Status and Improvements in Lifestyle, Coronary Risk Factors, and Quality of Life: The Multisite Cardiac Lifestyle Intervention Program  

PubMed Central

Objectives. We sought to clarify whether patients of low socioeconomic status (SES) can make lifestyle changes and show improved outcomes in coronary heart disease (CHD), similar to patients with higher SES. Methods. We examined lifestyle, risk factors, and quality of life over 3 months, by SES and gender, in 869 predominantly White, nonsmoking CHD patients (34% female) in the insurance-sponsored Multisite Cardiac Lifestyle Intervention Program. SES was defined primarily by education. Results. At baseline, less-educated participants were more likely to be disadvantaged (e.g., past smoking, sedentary lifestyle, high fat diet, overweight, depression) than were higher-SES participants. By 3 months, participants at all SES levels reported consuming 10% or less dietary fat, exercising 3.5 hours per week or more, and practicing stress management 5.5 hours per week or more. These self-reports were substantiated by improvements in risk factors (e.g., 5-kg weight loss, and improved blood pressure, low-density lipoprotein cholesterol, and exercise capacity; P < .001), and accompanied by improvements in well-being (e.g., depression, hostility, quality of life; P < .001). Conclusions. The observed benefits for CHD patients with low SES indicate that broadening accessibility of lifestyle programs through health insurance should be strongly encouraged. PMID:18923113

Govil, Sarah R.; Merritt-Worden, Terri; Ornish, Dean

2009-01-01

190

Biomechanics of Early Cardiac Development  

PubMed Central

Biomechanics affect early cardiac development, from looping to the development of chambers and valves. Hemodynamic forces are essential for proper cardiac development, and their disruption leads to congenital heart defects. A wealth of information already exists on early cardiac adaptations to hemodynamic loading, and new technologies, including high resolution imaging modalities and computational modeling, are enabling a more thorough understanding of relationships between hemodynamics and cardiac development. Imaging and modeling approaches, used in combination with biological data on cell behavior and adaptation, are paving the road for new discoveries on links between biomechanics and biology and their effect on cardiac development and fetal programming. PMID:22760547

Goenezen, Sevan; Rennie, Monique Y.

2012-01-01

191

Improved pattern of rate responsiveness with dynamic slope setting for the QT sensing pacemaker.  

PubMed

We have recently described the electrophysiological basis of a new algorithm for the QT (TX) sensing rate responsive pacemaker. By using the new software program running on the standard programmer it has been possible to simulate the new algorithm in ten patients with complete heart block (seven patients had implanted TX units and three were paced with an external TX pacemaker) during routine exercise testing. In this way a single-blind, intra-patient comparison of the pattern of pacing rate change using both the existing and new algorithms was possible. In nine out of the ten cases the time taken to increase the pacing rate from 70 to 80 bpm was reduced significantly when the new algorithm was used (P = 0.037). Additionally, the correlation between the atrial and ventricular rates in those patients with normal sinus node function (seven patients) was determined. In all cases we have observed a significantly improved correlation between the atrial and ventricular paced rates during exercise with the new algorithm (P less than 0.001). PMID:2468141

Baig, M W; Wilson, J; Boute, W; Begemann, M J; Cobbold, J P; Perrins, E J

1989-02-01

192

Functional roles of Ca(v)1.3, Ca(v)3.1 and HCN channels in automaticity of mouse atrioventricular cells: insights into the atrioventricular pacemaker mechanism.  

PubMed

The atrioventricular node controls cardiac impulse conduction and generates pacemaker activity in case of failure of the sino-atrial node. Understanding the mechanisms of atrioventricular automaticity is important for managing human pathologies of heart rate and conduction. However, the physiology of atrioventricular automaticity is still poorly understood. We have investigated the role of three key ion channel-mediated pacemaker mechanisms namely, Ca(v)1.3, Ca(v)3.1 and HCN channels in automaticity of atrioventricular node cells (AVNCs). We studied atrioventricular conduction and pacemaking of AVNCs in wild-type mice and mice lacking Ca(v)3.1 (Ca(v)3.1(-/-)), Ca(v)1.3 (Ca(v)1.3(-/-)), channels or both (Ca(v)1.3(-/-)/Ca(v)3.1(-/-)). The role of HCN channels in the modulation of atrioventricular cells pacemaking was studied by conditional expression of dominant-negative HCN4 channels lacking cAMP sensitivity. Inactivation of Ca(v)3.1 channels impaired AVNCs pacemaker activity by favoring sporadic block of automaticity leading to cellular arrhythmia. Furthermore, Ca(v)3.1 channels were critical for AVNCs to reach high pacemaking rates under isoproterenol. Unexpectedly, Ca(v)1.3 channels were required for spontaneous automaticity, because Ca(v)1.3(-/-) and Ca(v)1.3(-/-)/Ca(v)3.1(-/-) AVNCs were completely silent under physiological conditions. Abolition of the cAMP sensitivity of HCN channels reduced automaticity under basal conditions, but maximal rates of AVNCs could be restored to that of control mice by isoproterenol. In conclusion, while Ca(v)1.3 channels are required for automaticity, Ca(v)3.1 channels are important for maximal pacing rates of mouse AVNCs. HCN channels are important for basal AVNCs automaticity but do not appear to be determinant for ?-adrenergic regulation. PMID:21406960

Marger, Laurine; Mesirca, Pietro; Alig, Jacqueline; Torrente, Angelo; Dubel, Stefan; Engeland, Birgit; Kanani, Sandra; Fontanaud, Pierre; Striessnig, Jörg; Shin, Hee-Sup; Isbrandt, Dirk; Ehmke, Heimo; Nargeot, Joël; Mangoni, Matteo E

2011-01-01

193

Absent right and persistent left superior vena cava: troubleshooting during a challenging pacemaker implant: a case report  

PubMed Central

Background Venous anomalies of the thorax can occur in isolation or in association with complex congenital heart disease. The incidence of an absent right superior vena cava in the setting of a persistent left superior vena cava is very rare in the general population with only a dozen cases documented in the medical literature. Such venous anomalies can make for very challenging electronic cardiac device implantation. We report our challenging dual chamber pacemaker implant in a patient with such complex anatomy and focus on our implantation technique that helped achieve adequate lead positioning. Case presentation A 73-year-old Caucasian female with degenerative complete heart block presented for dual chamber permanent pacemaker implant. Lead implantation was very challenging due to abnormal and rare vena cava anatomy; a persistent left superior vena cava drained directly into the coronary sinus and the right brachiocephalic vein drained directly into the left persistent superior vena cava as the patient had an absent right superior vena cava . Adequate right ventricular lead positioning was achieved following numerous lead-stylet manipulations and careful looping in the atria to redirect its trajectory to the ventricular apex. Conclusion Abnormal superior vena cava development is uncommon and can lead to technical challenges when venous access is required during various interventional procedures. Pre-operative imaging can help identify such challenging anatomy allowing appropriate operative planning; careful patient selection is warranted for venography given the risk of contrast nephrotoxicity. PMID:25047923

2014-01-01

194

Flexibility and Strength Measures in Children Participating in a Cardiac Rehabilitation Exercise Program.  

ERIC Educational Resources Information Center

A 12-week structured rehabilitation program featuring warm-up exercises, increased aerobic exercise, cool down, and home-based continuation of exercise helped 12 children with surgically corrected congenital heart disease improve lower extremity strength and flexibility. (Author/CB)

Koch, Barbara M.; And Others

1988-01-01

195

Dynamic clamp: a powerful tool in cardiac electrophysiology  

PubMed Central

Dynamic clamp is a collection of closely related techniques that have been employed in cardiac electrophysiology to provide direct answers to numerous research questions regarding basic cellular mechanisms of action potential formation, action potential transfer and action potential synchronization in health and disease. Building on traditional current clamp, dynamic clamp was initially used to create virtual gap junctions between isolated myocytes. More recent applications include the embedding of a real pacemaking myocyte in a simulated network of atrial or ventricular cells and the insertion of virtual ion channels, either simulated in real time or simultaneously recorded from an expression system, into the membrane of an isolated myocyte. These applications have proven that dynamic clamp, which is characterized by the real-time evaluation and injection of simulated membrane current, is a powerful tool in cardiac electrophysiology. Here, each of the three different experimental configurations used in cardiac electrophysiology is reviewed. Also, directions are given for the implementation of dynamic clamp in the cardiac electrophysiology laboratory. With the growing interest in the application of dynamic clamp in cardiac electrophysiology, it is anticipated that dynamic clamp will also prove to be a powerful tool in basic research on biological pacemakers and in identification of specific ion channels as targets for drug development. PMID:16873403

Wilders, Ronald

2006-01-01

196

Transcatheter aortic valve replacement: establishing a comprehensive program model for hybrid cardiac catheterization laboratories in the Department of Veterans Affairs.  

PubMed

Aortic valve disease, especially aortic stenosis, becomes progressively debilitating and carries a high mortality risk if it is categorized as severe and symptomatic (J Thorac Cardiovas Surg. 2012;144(3):e29-e84). In the past, the only treatment for aortic stenosis was surgical aortic valve replacement. Surgical treatment may require several hours of cardioplegia, and if the patient has comorbidities, such as renal failure or chronic obstructive pulmonary disease, their operative mortality percentage increases.In 2011, the US Food and Drug Administration approved the use of a transcatheter aortic valve replacement (TAVR) procedure for patients who were deemed high risk or inoperative for the routine surgical aortic valve replacement surgery. More than 20,?000 TAVRs have been performed in patients worldwide since 2002 when Dr Alain Cribier performed the first-in-man TAVR (Arch Cardiovasc Dis. 2012;105(3):145-152). The Edwards Lifesciences SAPIEN XT valve and the Medtronic CoreValve are commercially available.The clinical findings and economic statistic have supported the expansion of the TAVR procedure. However, there has been considerable controversy over where the procedure is to occur and who is directly responsible for directing the TAVR care. This debate has identified barriers to the implementation of a TAVR program. The operating rooms and a cardiac catheterization laboratory are underprepared for the hybrid valve replacement therapy. Because of the barriers identified, the Department of Veterans Affairs determined a need for a systematic approach to review the programs that applied for this structural heart disease program. A centralized team was developed to ensure room readiness and staff competency. The use of the Health Failure Mode and Effects Analysis can define high-risk clinical processes and conduct a hazard analysis. Worksheets can show potential failure modes and their probabilities, along with actions and outcome measures, team collaboration, extensive screening, and selection process. The TAVR program begins implementation with data entry with each case into CART-CL (Cardiovascular Assessment, Reporting and Tracking System for Cath Labs, Veteran Administration database for interventional cardiology procedures). If an untoward event occurs, within 24 hours the CART-CL Quality Assessment Team is activated to begin the review process. This provides real-time review and feedback to the local facility in an expeditious manner. Cardiac catheterization laboratories have been inundated with rapidly changing technological advances in the past decade. The era for structural heart repair is rapidly mobilizing from a surgical/operating room setting to a transcatheter/hybrid catheterization laboratory suite. The use of the new hybrid catheterization laboratories will continue to expand as the approval of future transcatheter therapies evolve. Editor's note: Due to the volume of important information presented in each table, only the first table is included in the print version of the article, however, all tables may be viewed in their entirety free of charge on the online version of this article: http://journals.lww.com/dccnjournal/pages/default.aspx. PMID:25144213

Speiser, Bernadette; Dutra-Brice, Cynthia

2014-01-01

197

Pacemakers in a Reaction-Diffusion Mechanics System  

Microsoft Academic Search

Non-linear waves of excitation are found in various biological, physical and chemical systems and are often accompanied by\\u000a deformations of the medium. In this paper, we numerically study wave propagation in a deforming excitable medium using a two-variable\\u000a reaction-diffusion system coupled with equations of continuum mechanics. We study the appearance and dynamics of different\\u000a excitation patterns organized by pacemakers that

R. H. Keldermann; M. P. Nash; A. V. Panfilov

2007-01-01

198

A Functional analysis of circadian pacemakers in nocturnal rodents  

Microsoft Academic Search

Summary 1Phase response curves for 15' bright light pulses of four species of nocturnal rodents are described. All show delay phase shifts early in the subjective night, advance shifts in the late subjective night, and relative insensitivity during the subjective day.2The broad scatter in measured phase-shifts is largely due to error of measurement: the response of the pacemakers to light

Serge Daan; Colin S. Pittendrigh

1976-01-01

199

Management of tachyarrhythmias with dual-chamber pacemakers.  

PubMed

Multiprogrammable dual-demand AV sequential (DVI, MN) pacemakers were implanted in twenty-three patients (in one of them a DVI, MN unit was used as a VVI, MN with the aid of an atrial plug) with supraventricular tachycardias after electrophysiological studies revealed a great variety of AV reentry circuits. The latter included tachycardias involving accessory pathways of the Kent type, manifest or concealed Wolff-Parkinson-White syndromes, nodo-ventricular (Mahaim) tracts, "enhanced" AV node (or extra AV nodal) pathways and dual AV pathways. In addition, multiprogrammable "non-committed" AV sequential (DVI, MN and DDD, M) pacemakers were permanently implanted to treat different forms of ventricular tachyarrhythmias that included: torsade de pointes in the Romano-Ward syndrome and Chagas' cardiomyopathy, ventricular tachycardia which is bradycardia-dependent (in Chagas' cardiomyopathy) and reciprocal beats induced by, and producing severe hemodynamic derangements in a patient with a conventional VVI unit. With small-size multiprogrammable units, arrhythmias may be treated by changing parameters non-invasively. By temporary inhibition, one may analyze the underlying rhythm and pacemaker dependency. In patients without chronic atrial flutter/fibrillation who require pacing and possibly tachyarrhythmia control, our experience with multiprogrammable "non-committed" AV sequential pacing has been very satisfactory. The evolution toward newer pacing modes which provide atrial sensing and tracking (DDD), and thus preserve AV synchrony over a wider range of atrial rates, may contribute even further to successful patient management. This may be applicable to pediatric patients as well. PMID:6189076

Medina-Ravell, V; Castellanos, A; Portillo-Acosta, B; Maduro-Maytin, C; Rodriguez-Salas, L; Hernandez-Arenas, M; La Salle-Toro, R; Mendoza-Mujica, I; Ortega-Maldonado, M; Berkovits, B V

1983-03-01

200

Starting a transradial vascular access program in the cardiac catheterization laboratory.  

PubMed

Over the past 20 years, since the first reports, transradial vascular access for coronary angiography and intervention has flourished in many countries while still accounting for less than 2% of all cases performed in the United States due, in part, to difficulties in introducing change to established practice patterns. The benefits of transradial access include decreased bleeding risk, increased patient comfort, lessened post-procedure nursing workload, and decreased hospital costs. A learning curve to gain the specific set of skills for transradial access has been well described. Although published data suggest that 100-200 cases are necessary to become proficient, the learning curve is likely highly individual, and some operators may become proficient sooner. The equipment to start a transradial program is minimal and includes modified sheaths and catheters. Patients with morbid obesity, peripheral vascular disease, and anticoagulation clearly benefit from this approach. To establish a transradial program and offer the benefits of this approach to most patients, a dedicated interventionalist must incorporate peers and hospital staff to create a multidisciplinary team. PMID:19734569

Cohen, Mauricio G; Alfonso, Carlos

2009-08-01

201

Two mechanisms of arrhythmia induction by a DDD pacemaker: a case report.  

PubMed

A 68-year-old man with sick sinus syndrome and a history of intermittent atrial fibrillation was treated by implantation of a DDD pacemaker. He subsequently developed recurrent episodes of shortness of breath and tachycardia. Investigation revealed two different arrhythmias, both induced by the pacemaker: (1) a tachycardia in which the dual-chamber pacemaker system provided the antegrade limb and the AV node provided the retrograde limb and (2) a triggered, ventricularly paced tachycardia caused by the pacemaker sensing atrial fibrillation waves. Both rhythms were abolished by reprogramming to the DVI mode. PMID:6192422

Kerr, C R; Cooper, J A; Wallace, T; Tyers, G F

1983-07-01

202

Potential of gallium-based leads for cardiac rhythm management devices.  

PubMed

We propose the use of gallium (Ga), a metal that is liquid at physiological temperatures, or one of its alloys, for use as the conducting material in the leads of implantable pacemakers or cardioverter defibrillators. It is proposed that a liquid conductor will make these leads more pliable and thus less susceptible to fracture in situ. As an initial step towards utilizing liquid gallium in leads, the biocompatibility of Ga was investigated via cytotoxicity, hemocompatibility, and intracutaneous injection testing. Unipolar pacing Ga prototypes were fabricated by adapting existing pacemaker leads. The electrical impedance and pulse transmission ability of these leads were examined. Ga was well tolerated both in vitro and in vivo. Additionally, the Ga prototypes conductors behaved as low magnitude resistances that did not distort pulses as generated by conventional pacemakers. These results indicate that Ga is an appropriate material for implantable cardiac stimulators and will be a focus of our liquid metal prototypes. PMID:22254318

Kyle, Aaron M; Leahy-Glass, Nichole; Combs, William; March, Keith L

2011-01-01

203

Pacemaker implantation in a patient with brugada and sick sinus syndrome.  

PubMed

Brugada syndrome (BrS) is a rare and inherited primary arrhythmic syndrome characterized by ST-segment elevations in the right precordial leads (V1-V3) with an increased risk of sudden cardiac death (SCD). Arrhythmias in BrS are often nocturne, and brady-arrhythmias are often seen in patients with loss-of-function mutations in SCN5A. In this case-report we present a 75-year old woman referred to our outpatient clinic for inherited cardiac diseases for a familial clinical work-up. Since childhood she had suffered from dizziness, absence seizures, and countless Syncope's. In 2004 sick sinus syndrome was suspected and she was treated with implantation of a pacemaker (PM) at another institution. An inherited cardiac disease was one day suddenly suspected, as the patient had a 61-year old brother who was diagnosed with symptomatic BrS, and treated with an implantable cardioverter defibrillator (ICD) after aborted SCD. A mutation screening revealed a SCN5A [S231CfsX251 (c.692-693delCA)] loss-of-function mutation not previously reported, and as a part of the cascade screening in relatives she was therefore referred to our clinic. In the 7 year period after PM implantation she had experienced no cardiac symptoms, although her electrocardiogram changes now were consistent with a BrS type 1 pattern. A genetic test confirmed that she had the same mutation in SCN5A as her brother. In this case-report we present a loss-of function mutation in SCN5A not previously associated with BrS nor presented in healthy controls. Sinus node dysfunction has previously been documented in patients with symptomatic BrS, which suggests it is not a rare concomitant. The only accepted treatment of BrS is today implantation of an ICD. In the future studies should evaluate if PM in some cases of symptomatic BrS can be used instead of ICDs in patients with a loss-of-function SCN5A mutations. PMID:23538678

Risgaard, Bjarke; Bundgaard, Henning; Jabbari, Reza; Haunsø, Stig; Winkel, Bo Gregers; Tfelt-Hansen, Jacob

2013-03-26

204

Stimulating Cardiac Muscle by Light: Cardiac Optogenetics by Cell Delivery  

PubMed Central

Background After the recent cloning of light-sensitive ion channels and their expression in mammalian cells, a new field, optogenetics, emerged in neuroscience, allowing for precise perturbations of neural circuits by light. However, functionality of optogenetic tools has not been fully explored outside neuroscience; and a non-viral, non-embryogenesis based strategy for optogenetics has not been shown before. Methods and Results We demonstrate the utility of optogenetics to cardiac muscle by a tandem cell unit (TCU) strategy, where non-excitable cells carry exogenous light-sensitive ion channels, and when electrically coupled to cardiomyocytes, produce optically-excitable heart tissue. A stable channelrhodopsin2 (ChR2) expressing cell line was developed, characterized and used as a cell delivery system. The TCU strategy was validated in vitro in cell pairs with adult canine myocytes (for a wide range of coupling strengths) and in cardiac syncytium with neonatal rat cardiomyocytes. For the first time, we combined optical excitation and optical imaging to capture light-triggered muscle contractions and high-resolution propagation maps of light-triggered electrical waves, found to be quantitatively indistinguishable from electrically-triggered waves. Conclusions Our results demonstrate feasibility to control excitation and contraction in cardiac muscle by light using the TCU approach. Optical pacing in this case uses less energy, offers superior spatiotemporal control, remote access and can serve not only as an elegant tool in arrhythmia research, but may form the basis for a new generation of light-driven cardiac pacemakers and muscle actuators. The TCU strategy is extendable to (non-viral) stem cell therapy and is directly relevant to in vivo applications. PMID:21828312

Jia, Zhiheng; Valiunas, Virginijus; Lu, Zongju; Bien, Harold; Liu, Huilin; Wang, Hong-Zhang; Rosati, Barbara; Brink, Peter R.; Cohen, Ira S.; Entcheva, Emilia

2011-01-01

205

Mitigation of postischemic cardiac contractile dysfunction by CaMKII inhibition: effects on programmed necrotic and apoptotic cell death.  

PubMed

While Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) has been suggested to be an important protein regulating heart function upon ischemia/reperfusion (I/R), the mechanisms responsible are not fully known. Furthermore, it is not known whether CaMKII activation can modulate necroptosis, a recently described form of programmed cell death. In order to investigate these issues, Langendroff-perfused rat hearts were subjected to global ischemia and reperfusion, and CaMKII inhibition was achieved by adding the CaMKII inhibitor KN-93 (0.5 ?mol/dm(3)) to the perfusion solution before the induction of ischemia. Immunoblotting was used to detect changes in expression of proteins modulating both necroptotic and apoptotic cell death. CaMKII inhibition normalized I/R induced increases in expression of necroptotic RIP1 and caspase-8 along with proteins of the intrinsic apoptotic pathway, namely cytochrome c and caspase-9. In addition, it increased the Bcl-2/Bax ratio and reduced caspase-3 and cleaved PARP1 content suggesting reduction of cell death. These changes coexisted with improvement of postischemic contractile function. On the other hand, there was no correlation between levels of pT287-CaMKII? and LVDP recovery after I/R. These results demonstrate for the first time that CaMKII inhibition may mitigate cardiac contractile dysfunction, at least partially, by limiting the contents of not only apoptotic, but also necroptotic proteins. Phosphorylation of CaMKII seems unlikely to determine the degree of postischemic recovery of contractile function. PMID:24347176

Szobi, Adrian; Rajtik, Tomas; Carnicka, Slavka; Ravingerova, Tana; Adameova, Adriana

2014-03-01

206

Teaching cardiac electrophysiology modeling to undergraduate students: laboratory exercises and GPU programming for the study of arrhythmias and spiral wave dynamics  

NSDL National Science Digital Library

As part of a 3-wk intersession workshop funded by a National Science Foundation Expeditions in Computing award, 15 undergraduate students from the City University of New York collaborated on a study aimed at characterizing the voltage dynamics and arrhythmogenic behavior of cardiac cells for a broad range of physiologically relevant conditions using an in silico model. The primary goal of the workshop was to cultivate student interest in computational modeling and analysis of complex systems by introducing them through lectures and laboratory activities to current research in cardiac modeling and by engaging them in a hands-on research experience. Results from these simulations, as well as some of the background and methodology taught during the workshop, is presented in this article along with the programming code and the explanations of simulation results in an effort to allow other teachers and students to perform their own demonstrations, simulations, and studies.

Ezio Bartocci (Stony Brook University); Flavio Fenton (Cornell University)

2011-12-01

207

High thresholds may alter end-of-life behavior in a dual chamber pacemaker.  

PubMed

We noted a series of 12 consecutive patients with a DDD Genisis pacemaker that showed an unexpected and a relatively rapid fall in battery voltage and output as these devices approached end-of-life (EOL). Twenty-one of 24 leads were Vitatron Helifix leads and there was a relatively high mean threshold (atrial 2.5 +/- 0.94 V; ventricular 2.9 +/- 0.65 V). These devices were replaced after 65 +/- 12 months. During the 9.3 +/- 3.5 months before replacement, a striking fall in voltage from 2.7 +/- 0.04 V to 2.49 +/- 0.05 V was seen. Battery impedance rose from 3 +/- 1.2 K omega to 10.2 +/- 4.3 K omega during this same period. We unexpectedly observed a marked difference between programmed and telemetered output for both atrial (50%) and ventricular leads (30%). A discrepancy between measured and telemetered magnet rate was also seen. Despite this relatively rapid fall in battery voltage, several of these devices did not meet the manufacturer's recommended replacement time (RRT) criteria by magnet rate or according to the projected RRT determined by the relationship of battery impedance to current drain. These data have implications for the selection of RRT and EOL criteria for this device. Magnet rate measured by surface ECG was the safest indicator for RRT. Follow-up for this pulse generator should be increased to every 2 months when battery impedance is > 2 KOhms or if there is a difference between programmed and measured output amplitude of more than 15%. The data also highlight the effect of combining high threshold leads with modern pacemakers with relatively "small" batteries as well as certain problems with telemetered data. PMID:9227769

Kraus, M; Buckingham, T A; Candinas, R

1997-06-01

208

Psychometric Properties of an Established Heart Disease Specific Health-related Quality of Life Questionnaire for Pacemaker Patients  

Microsoft Academic Search

Little is known about the HRQL of pacemaker patients due to the limited availability of disease-specific instruments. The aim of the Pacemaker Patients Quality of Life (PAPQoL) study was to determine the psychometric properties for the MacNew Heart Disease Health-related Quality of Life Questionnaire (MacNew) in patients before and after pacemaker implantation. Patients with a given indication for pacemaker therapy

S. Höfer; M. Anelli-Monti; T. Berger; F. Hintringer; N. Oldridge; W. Benzer

2005-01-01

209

Acceleratory Synapses on Pacemaker Neurons in the Heart Ganglion of a Stomatopod, Squilla Oratoria.  

National Technical Information Service (NTIS)

The pacemaker neurons of the heart ganglion are innervated from the CNS through two pairs of acceleratory nerves. The effect of acceleratory nerve stimulation was examined with intracellular electrodes from the pace-maker cells. The major effects on the p...

A. Watanabe, S. Obara, T. Akiyama

1969-01-01

210

Time and memory: towards a pacemaker-free theory of interval timing  

Microsoft Academic Search

A popular view of interval timing in animals is that it is driven by a discrete pacemaker-accumulator mechanism that yields a linear scale for encoded time. But these mechanisms are fundamentally at odds with the Weber law property of interval timing, and experiments that support linear encoded time can be interpreted in other ways. We argue that the dominant pacemaker-accumulator

J. E. R. STADDON; J. J. HIGA

1999-01-01

211

Effect of 1. 5 tesla nuclear magnetic resonance imaging scanner on implanted permanent pacemakers  

Microsoft Academic Search

Patients with a permanent pacemaker are currently restricted from diagnostic nuclear magnetic resonance (NMR) imaging because of potential adverse effects on the pacemaker by the magnet. Previous work has shown that NMR imaging will result in asynchronous pacing of the pulse generator within a given distance of the magnet. The radiofrequency signal generated by the system may also result in

David L. Hayes; David R. Holmes Jr.; Joel E. Gray

1987-01-01

212

From syncitium to regulated pump: a cardiac muscle cellular update  

NSDL National Science Digital Library

The primary purpose of this article is to present a basic overview of some key teaching concepts that should be considered for inclusion in an six- to eight-lecture introductory block on the regulation of cardiac performance for graduate students. Within the context of cardiac excitation-contraction coupling, this review incorporates information on Ca2+ microdomains and local control theory, with particular emphasis on the role of Ca2+ sparks as a key regulatory component of ventricular myocyte contraction dynamics. Recent information pertaining to local Ca2+ cycling in sinoatrial nodal cells (SANCs) as a mechanism underlying cardiac automaticity is also presented as part of the recently described coupled-clock pacemaker system. The details of this regulation are emerging; however, the notion that the sequestration and release of Ca2+ from internal stores in SANCs (similar to that observed in ventricular myocytes) regulates the rhythmic excitation of the heart (i.e., membrane ion channels) is an important advancement in this area. The regulatory role of cardiac adrenergic receptors on cardiac rate and function is also included, and fundamental concepts related to intracellular signaling are discussed. An important point of emphasis is that whole organ cardiac dynamics can be traced back to cellular events regulating intracellular Ca2+ homeostasis and, as such, provides an important conceptual framework from which students can begin to think about whole organ physiology in health and disease. Greater synchrony of Ca2+-regulatory mechanisms between ventricular and pacemaker cells should enhance student comprehension of complex regulatory phenomenon in cardiac muscle.

PhD Donna H. Korzick (Pennsylvania State University Dept. of Physiology and Kinesiology)

2011-03-01

213

Development of the Mouse Circadian Pacemaker: Independence from Environmental Cycles*  

PubMed Central

Summary The freerunning period (?) of the circadian pacemaker underlying the wheel-running activity rhythm of Mus musculus was found to be unaffected by the periods of environmental cycles (maternal and light/dark) under which the mice are raised. Mice born to mothers entrained to periods (T) of 28 or 20 h (ratio of light to dark of 14/10) and maintained on those cycle until beyond puberty showed only a temporary difference in freerunning period when placed into constant darkness. Such temporary ‘after-effects ‘ of entrainment were shown, as had been previously, to occur in animals exposed to non-24-h cycles as adults only.After-effects on the ratio of activity to rest (?/?) were not even temporarily different in animals raised on T = 28 or T = 20.Rearing on T = 28 or T = 20 did not affect the abilities of animals to entrain to these cycles later in life.Measurements from young and old animals as well as remeasurement of the young animals later in their lives revealed several effects of age on the pacemaker: a) After-effects on freerunning period after T = 28 or T = 20 are not greater but last longer in older animals; b) Freerunning period is shorter in younger animals; and c) The ratio of activity to rest changes over time in constant darkness and is greater in young animals. Together these suggest that pacemaker ‘plasticity’ reflected in changes in ? and ?/? over time in constant darkness decreases with age.The length of gestation measured in ‘real’ time was the same in mice entrained to T = 28 or T = 20, demonstrating that gestation is not measured in circadian cycles.

Davis, Fred C.; Menaker, Michael

2013-01-01

214

Linear and nonlinear energy harvesters for powering pacemakers from heart beat vibrations  

NASA Astrophysics Data System (ADS)

Linear and nonlinear piezoelectric devices are introduced to continuously recharge the batteries of the pacemakers by converting the vibrations from the heartbeats to electrical energy. The power requirement of the pacemakers is very low. At the same time, after about 10 years from the original implantation of the pacemakers, patients have to go through another surgical operation just to replace the batteries of their pacemakers. We investigate using vibration energy harvesters to significantly increase the battery life of the pace makers. The major source of vibrations in chest area is due to heartbeats. Linear low frequency and nonlinear mono-stable and bi-stable energy harvesters are designed according to especial signature of heart vibrations. The proposed energy harvesters are robust to variations of heart beat frequency and can meet the power requirement of the pacemakers.

Karami, M. Amin; Inman, Daniel J.

2011-03-01

215

[A case of stone former with pacemaker treated by extracorporeal shock wave lithotripsy].  

PubMed

A stone former, a 60-year-old male with a pacemaker, was treated by extracorporeal shock wave lithotripsy (ESWL). He had been on a DVI pacemaker due to sick sinus syndrome since the age of 52. During treatment for left ureteral stone by ESWL, the pacemaker was stopped, since there was a possibility of extra systoles caused by coupled triggering of the shock wave with the pacemaker spike wave in ECG. Pulse and blood pressure were maintained by continuous drip infusion of phenylephrine chloride and isoproterenol. As a result, ESWL was accomplished and pacemaking was reestablished without any problem. KUB revealed that the patient became stone free on the postoperative 17th day. PMID:3195409

Kanazawa, T; Kishimoto, T; Senju, M; Sugimoto, T; Tsujino, T; Iimori, H; Nariyama, M; Yamamoto, K; Maekawa, M

1988-08-01

216

Pacemaker discomfort induced by the wearing of seat belts.  

PubMed

A survey was made of 100 consecutive pacemaker recipients to examine problems they may have experienced with seat belts whilst travelling by car, either as drivers (29 patients) or front seat passengers (50 patients). Twenty-one per cent of the drivers and 30% of the front seat passengers had experienced symptoms, usually of a mild nature. Re-siting of the generator was only necessary in 1 patient and no example of electrode displacement was observed. Suggestions are made as to how this problem might be overcome. PMID:4022858

Wallis, M; Todd, I; Aber, C P

1985-04-01

217

Cardiac metastases  

Microsoft Academic Search

Tumours metastatic to the heart (cardiac metastases) are among the least known and highly debated issues in oncology, and few systematic studies are devoted to this topic. Although primary cardiac tumours are extremely uncommon (various postmortem studies report rates between 0.001% and 0.28%), secondary tumours are not, and at least in theory, the heart can be metastasised by any malignant

R Bussani; F De-Giorgio; A Abbate; F Silvestri

2007-01-01

218

Cardiac asthma.  

PubMed

Cardiac dyspnea, especially if present only with exercise, is often confused with asthma and exercise-induced bronchospasm. Cardiac dyspnea or asthma is the consequence of pulmonary edema due to pulmonary venous hypertension and not due to asthmatic bronchoconstriction. In overt, acute congestive heart failure, the diagnosis may be readily made by history and physical examination and pertinent laboratory and imaging data. PMID:23337063

Buckner, Kern

2013-02-01

219

Short-term effects of exercise and music on cognitive performance among participants in a cardiac rehabilitation program  

Microsoft Academic Search

ObjectiveExercise has been associated with improved cognitive performance among patients with coronary artery disease. Music listening has been associated with enhanced cognitive functioning among healthy adults. This study evaluated the combined influence of exercise and music listening on cognitive performance among patients in cardiac rehabilitation (CR).

Charles F Emery; Evana T Hsiao; Scott M Hill; David J Frid

2003-01-01

220

The behavioral theory of timing: Reinforcer rate determines pacemaker rate  

PubMed Central

In the behavioral theory of timing, pulses from a hypothetical Poisson pacemaker produce transitions between states that are correlated with adjunctive behavior. The adjunctive behavior serves as a discriminative stimulus for temporal discriminations. The present experiments tested the assumption that the average interpulse time of the pacemaker is proportional to interreinforcer interval. Responses on a left key were reinforced at variable intervals for the first 25 s since the beginning of a 50-s trial, and right-key responses were reinforced at variable intervals during the second 25 s. Psychometric functions relating proportion of right-key responses to time since trial onset, in 5-s intervals across the 50-s trial, were sigmoidal in form. Average interpulse times derived by fitting quantitative predictions from the behavioral theory of timing to obtained psychometric functions decreased when the interreinforcer interval was decreased and increased when the interreinforcer interval was increased, as predicted by the theory. In a second experiment, average interpulse times estimated from trials without reinforcement followed global changes in interreinforcer interval, as predicted by the theory. Changes in temporal discrimination as a function of interreinforcer interval were therefore not influenced by the discrimination of reinforcer occurrence. The present data support the assumption of the behavioral theory of timing that interpulse time is determined by interreinforcer interval. PMID:16812723

Bizo, Lewis A.; White, K. Geoffrey

1994-01-01

221

Computational model of electrically coupled, intrinsically distinct pacemaker neurons.  

PubMed

Electrical coupling between neurons with similar properties is often studied. Nonetheless, the role of electrical coupling between neurons with widely different intrinsic properties also occurs, but is less well understood. Inspired by the pacemaker group of the crustacean pyloric network, we developed a multicompartment, conductance-based model of a small network of intrinsically distinct, electrically coupled neurons. In the pyloric network, a small intrinsically bursting neuron, through gap junctions, drives 2 larger, tonically spiking neurons to reliably burst in-phase with it. Each model neuron has 2 compartments, one responsible for spike generation and the other for producing a slow, large-amplitude oscillation. We illustrate how these compartments interact and determine the dynamics of the model neurons. Our model captures the dynamic oscillation range measured from the isolated and coupled biological neurons. At the network level, we explore the range of coupling strengths for which synchronous bursting oscillations are possible. The spatial segregation of ionic currents significantly enhances the ability of the 2 neurons to burst synchronously, and the oscillation range of the model pacemaker network depends not only on the strength of the electrical synapse but also on the identity of the neuron receiving inputs. We also compare the activity of the electrically coupled, distinct neurons with that of a network of coupled identical bursting neurons. For small to moderate coupling strengths, the network of identical elements, when receiving asymmetrical inputs, can have a smaller dynamic range of oscillation than that of its constituent neurons in isolation. PMID:15728775

Soto-Treviño, Cristina; Rabbah, Pascale; Marder, Eve; Nadim, Farzan

2005-07-01

222

Cardiac rhabdomyosarcoma.  

PubMed

Cardiac sarcoma is a very rare neoplasm and is difficult to diagnose. The case of a 51-year-old man with a left atrial tumour, locally recurrent three months after its surgical removal, is presented. Computed tomography showed metastatic spread to the lung parenchyma. On revised histology, the mass extirpated was a sarcoma. Because of the metastatic spread, further therapy was symptomatic only; the patient died 15 months after the first manifestation of his problems. Immunohistochemical staining confirmed cardiac rhabdomyosarcoma with metastatic spread to the lungs. Difficulty in diagnosing and treating cardiac tumours is discussed. PMID:20428274

Chlumský, J; Holá, D; Hlavácek, K; Michal, M; Svec, A; Spatenka, J; Dusek, J

2001-01-01

223

Glocal Clinical Registries: Pacemaker Registry Design and Implementation for Global and Local Integration - Methodology and Case Study  

PubMed Central

Background The ability to apply standard and interoperable solutions for implementing and managing medical registries as well as aggregate, reproduce, and access data sets from legacy formats and platforms to advanced standard formats and operating systems are crucial for both clinical healthcare and biomedical research settings. Purpose Our study describes a reproducible, highly scalable, standard framework for a device registry implementation addressing both local data quality components and global linking problems. Methods and Results We developed a device registry framework involving the following steps: (1) Data standards definition and representation of the research workflow, (2) Development of electronic case report forms using REDCap (Research Electronic Data Capture), (3) Data collection according to the clinical research workflow and, (4) Data augmentation by enriching the registry database with local electronic health records, governmental database and linked open data collections, (5) Data quality control and (6) Data dissemination through the registry Web site. Our registry adopted all applicable standardized data elements proposed by American College Cardiology / American Heart Association Clinical Data Standards, as well as variables derived from cardiac devices randomized trials and Clinical Data Interchange Standards Consortium. Local interoperability was performed between REDCap and data derived from Electronic Health Record system. The original data set was also augmented by incorporating the reimbursed values paid by the Brazilian government during a hospitalization for pacemaker implantation. By linking our registry to the open data collection repository Linked Clinical Trials (LinkedCT) we found 130 clinical trials which are potentially correlated with our pacemaker registry. Conclusion This study demonstrates how standard and reproducible solutions can be applied in the implementation of medical registries to constitute a re-usable framework. Such approach has the potential to facilitate data integration between healthcare and research settings, also being a useful framework to be used in other biomedical registries. PMID:23936257

da Silva, Katia Regina; Costa, Roberto; Crevelari, Elizabeth Sartori; Lacerda, Marianna Sobral; de Moraes Albertini, Caio Marcos; Filho, Martino Martinelli; Santana, Jose Eduardo; Vissoci, Joao Ricardo Nickenig; Pietrobon, Ricardo; Barros, Jacson V.

2013-01-01

224

Management of radiation oncology patients with a pacemaker or ICD: A new comprehensive practical guideline in The Netherlands  

PubMed Central

Current clinical guidelines for the management of radiotherapy patients having either a pacemaker or implantable cardioverter defibrillator (both CIEDs: Cardiac Implantable Electronic Devices) do not cover modern radiotherapy techniques and do not take the patient’s perspective into account. Available data on the frequency and cause of CIED failure during radiation therapy are limited and do not converge. The Dutch Society of Radiotherapy and Oncology (NVRO) initiated a multidisciplinary task group consisting of clinical physicists, cardiologists, radiation oncologists, pacemaker and ICD technologists to develop evidence based consensus guidelines for the management of CIED patients. CIED patients receiving radiotherapy should be categorised based on the chance of device failure and the clinical consequences in case of failure. Although there is no clear cut-off point nor a clear linear relationship, in general, chances of device failure increase with increasing doses. Clinical consequences of device failures like loss of pacing, carry the most risks in pacing dependent patients. Cumulative dose and pacing dependency have been combined to categorise patients into low, medium and high risk groups. Patients receiving a dose of less than 2 Gy to their CIED are categorised as low risk, unless pacing dependent since then they are medium risk. Between 2 and 10 Gy, all patients are categorised as medium risk, while above 10 Gy every patient is categorised as high risk. Measures to secure patient safety are described for each category. This guideline for the management of CIED patients receiving radiotherapy takes into account modern radiotherapy techniques, CIED technology, the patients’ perspective and the practical aspects necessary for the safe management of these patients. The guideline is implemented in The Netherlands in 2012 and is expected to find clinical acceptance outside The Netherlands as well. PMID:23176563

2012-01-01

225

Mechanisms that match ATP supply to demand in cardiac pacemaker cells during high ATP demand  

PubMed Central

The spontaneous action potential (AP) firing rate of sinoatrial node cells (SANCs) involves high-throughput signaling via Ca2+-calmodulin activated adenylyl cyclases (AC), cAMP-mediated protein kinase A (PKA), and Ca2+/calmodulin-dependent protein kinase II (CaMKII)-dependent phosphorylation of SR Ca2+ cycling and surface membrane ion channel proteins. When the throughput of this signaling increases, e.g., in response to ?-adrenergic receptor activation, the resultant increase in spontaneous AP firing rate increases the demand for ATP. We hypothesized that an increase of ATP production to match the increased ATP demand is achieved via a direct effect of increased mitochondrial Ca2+ (Ca2+m) and an indirect effect via enhanced Ca2+-cAMP/PKA-CaMKII signaling to mitochondria. To increase ATP demand, single isolated rabbit SANCs were superfused by physiological saline at 35 ± 0.5°C with isoproterenol, or by phosphodiesterase or protein phosphatase inhibition. We measured cytosolic and mitochondrial Ca2+ and flavoprotein fluorescence in single SANC, and we measured cAMP, ATP, and O2 consumption in SANC suspensions. Although the increase in spontaneous AP firing rate was accompanied by an increase in O2 consumption, the ATP level and flavoprotein fluorescence remained constant, indicating that ATP production had increased. Both Ca2+m and cAMP increased concurrently with the increase in AP firing rate. When Ca2+m was reduced by Ru360, the increase in spontaneous AP firing rate in response to isoproterenol was reduced by 25%. Thus, both an increase in Ca2+m and an increase in Ca2+ activated cAMP-PKA-CaMKII signaling regulate the increase in ATP supply to meet ATP demand above the basal level. PMID:23604710

Yaniv, Yael; Spurgeon, Harold A.; Ziman, Bruce D.; Lyashkov, Alexey E.

2013-01-01

226

Mechanisms that match ATP supply to demand in cardiac pacemaker cells during high ATP demand.  

PubMed

The spontaneous action potential (AP) firing rate of sinoatrial node cells (SANCs) involves high-throughput signaling via Ca(2+)-calmodulin activated adenylyl cyclases (AC), cAMP-mediated protein kinase A (PKA), and Ca(2+)/calmodulin-dependent protein kinase II (CaMKII)-dependent phosphorylation of SR Ca(2+) cycling and surface membrane ion channel proteins. When the throughput of this signaling increases, e.g., in response to ?-adrenergic receptor activation, the resultant increase in spontaneous AP firing rate increases the demand for ATP. We hypothesized that an increase of ATP production to match the increased ATP demand is achieved via a direct effect of increased mitochondrial Ca(2+) (Ca(2+)m) and an indirect effect via enhanced Ca(2+)-cAMP/PKA-CaMKII signaling to mitochondria. To increase ATP demand, single isolated rabbit SANCs were superfused by physiological saline at 35 ± 0.5°C with isoproterenol, or by phosphodiesterase or protein phosphatase inhibition. We measured cytosolic and mitochondrial Ca(2+) and flavoprotein fluorescence in single SANC, and we measured cAMP, ATP, and O? consumption in SANC suspensions. Although the increase in spontaneous AP firing rate was accompanied by an increase in O? consumption, the ATP level and flavoprotein fluorescence remained constant, indicating that ATP production had increased. Both Ca(2+)m and cAMP increased concurrently with the increase in AP firing rate. When Ca(2+)m was reduced by Ru360, the increase in spontaneous AP firing rate in response to isoproterenol was reduced by 25%. Thus, both an increase in Ca(2+)m and an increase in Ca(2+) activated cAMP-PKA-CaMKII signaling regulate the increase in ATP supply to meet ATP demand above the basal level. PMID:23604710

Yaniv, Yael; Spurgeon, Harold A; Ziman, Bruce D; Lyashkov, Alexey E; Lakatta, Edward G

2013-06-01

227

Implantable cardiac pacemaker electromagnetic compatibility testing in a novel security system Simulator  

Microsoft Academic Search

This work describes a novel simulator to perform electromagnetic compatibility (EMC) tests for active implantable medical devices (AIMDs) with electromagnetic fields emitted by security systems. The security system simulator was developed in response to over 100 incident reports over 17 years related to the interference of AIMD's with security systems and the lack of a standardized test method. The simulator

Wolfgang Kainz; Jon P. Casamento; Paul S. Ruggera; Dulciana D. Chan; Donald M. Witters

2005-01-01

228

Apparent discontinuities in the phase-resetting response of cardiac pacemakers  

Microsoft Academic Search

Injection of a brief stimulus pulse resets the spontaneous periodic activity of a sinoatrial node cell: a stimulus delivered early in the cycle generally delays the time of occurrence of the next action potential, while the same stimulus delivered later causes an advance. We investigate resetting in two models, one with a slow upstroke velocity and the other with a

T. Krogh-Madsen; L. Glass; E. J. Doedel; M. R. Guevara

2004-01-01

229

A Simulink Hybrid Heart Model for Quantitative Verification of Cardiac Pacemakers  

E-print Network

be used to check safety properties by means of approximate proba- bilistic verification. Keywords Hybrid mode switching and nonlinear continuous flows, e.g., electrical sig- nal or glucose level, while, developing effective methodologies to provide safety assurance in this setting by means of quanti- tative

Oxford, University of

230

Rhabdomyosarcoma associated with the lead wire of a pacemaker generator implant.  

PubMed

An 11-year-old female spayed Labrador Retriever was presented for a draining, painful subcutaneous mass palpated over a previously implanted pacemaker generator. Infection was suspected and the mass was removed surgically. On cut surface, the mass was friable and mottled tan to brown with firm pale tan nodules, surrounding the pacemaker lead wire adjacent to the pacemaker generator. Cytologic interpretation of impression smears was consistent with a sarcoma, and suggestive of a rhabdomyosarcoma due to the presence of strap-like cells. On histopathologic examination, a highly invasive nodular mass surrounded the pacemaker lead, composed of pleomorphic round, spindle and strap cells, and multinucleated giant cells. The population exhibited microscopic invasion into the deep portion of the fibrous capsule surrounding the pacemaker generator. There were tumor emboli within small to medium subcutaneous veins adjacent to the mass. Immunohistochemically, the neoplastic cells stained positive for ?-sarcomeric actin and vimentin, and negative for ?-smooth muscle actin, consistent with a rhabdomyosarcoma arising at the site of the pacemaker generator. To our knowledge, this is the first report of a rhabdomyosarcoma associated with the lead wire of a pacemaker generator in a dog. PMID:24654997

Thieman Mankin, Kelley M; Dunbar, Mark D; Toplon, David; Ginn, Pamela; Maisenbacher, Herbert W; Risselada, Marije

2014-06-01

231

Regional Difference in Dynamical Property of Sinoatrial Node Pacemaking: Role of Na+ Channel Current  

PubMed Central

To elucidate the regional differences in sinoatrial node pacemaking mechanisms, we investigated 1), bifurcation structures during current blocks or hyperpolarization of the central and peripheral cells, 2), ionic bases of regional differences in bifurcation structures, and 3), the role of Na+ channel current (INa) in peripheral cell pacemaking. Bifurcation analyses were performed for mathematical models of the rabbit sinoatrial node central and peripheral cells; equilibrium points, periodic orbits, and their stability were determined as functions of parameters. Structural stability against applications of acetylcholine or electrotonic modulations of the atrium was also evaluated. Blocking L-type Ca2+ channel current (ICa,L) stabilized equilibrium points and abolished pacemaking in both the center and periphery. Critical acetylcholine concentration and gap junction conductance for pacemaker cessation were higher in the periphery than in the center, being dramatically reduced by blocking INa. Under hyperpolarized conditions, blocking INa, but not eliminating ICa,L, abolished peripheral cell pacemaking. These results suggest that 1), ICa,L is responsible for basal pacemaking in both the central and peripheral cells, 2), the peripheral cell is more robust in withstanding hyperpolarizing loads than the central cell, 3), INa improves the structural stability to hyperpolarizing loads, and 4), INa-dependent pacemaking is possible in hyperpolarized peripheral cells. PMID:18390617

Kurata, Yasutaka; Matsuda, Hiroyuki; Hisatome, Ichiro; Shibamoto, Toshishige

2008-01-01

232

Antidepressants and food restriction cycles: evidence for multiple pacemakers in rodents.  

PubMed

Studies involving the suprachiasmatic nuclei (SCN) provide insufficient evidence to support the SCN as master pacemaker(s) in the rodent circadian system. Restricted feeding (RF) cycles act as strong zeitgebers for activity and corticosterone rhythms and provide support for the existence of important secondary pacemakers. These proposed pacemakers show anticipatory behavior, a limited range of entertainment for RF cycles, and prolonged free runs under certain circumstances. Additional evidence supporting a multiple pacemaker model of rodent circadian organization comes from studies involving antidepressants. Lithium treatment lengthens the free-running tau of rat activity rhythms and shifts the range of entrainment towards longer zeitgeber cycles. Lithium also phase delays many rodent rhythms but does not appear to affect the SCN-pineal axis. These data are difficult to explain without involving more than one pacemaker. Models of the rodent system can be developed incorporating multiple pacemakers. To test these models, a multivariate approach will be required. Combining the labeled 2-deoxyglucose method for metabolic mapping and the procedures of fractional desynchronization with antidepressant psychopharmacology and RF cycles may prove to be an important multivariate approach. PMID:3306700

McEachron, D L

1987-01-01

233

Cardiac Purkinje fibers: Cesium as a tool to block inward rectifying potassium currents  

Microsoft Academic Search

Summary When a cardiac Purkinje fiber is exposed to 20 mM Cs the membrane potential falls to about -60 mV within 1 min. In voltage clamp experiments, exposure to Cs blocks both the pacemaker currentiK2 and the instantaneous outward currentiK2, while the delayed outward rectifying potassium currentix is not affected. In the presence of 20 mM Cs, the steady state

G. Isenberg

1976-01-01

234

Heart rate deceleration after exercise predicts patients most likely to respond to cardiac resynchronisation therapy  

Microsoft Academic Search

ObjectiveThis study examines the relationship between heart rate recovery following exercise and subsequent response to cardiac resynchronisation therapy (CRT).BackgroundBlunted heart rate recovery is an adverse prognostic marker in heart failure and has been shown to correlate with disease severity.Methods37 patients receiving biventricular pacemakers for conventional indications underwent functional assessments; cardiopulmonary exercise test, 6-min walk test and quality-of-life assessment, together with

D. E. Thomas; S. A. Exton; Z. R. Yousef

2010-01-01

235

Heart Rate Reduction by Ivabradine Reduces Diastolic Dysfunction and Cardiac Fibrosis  

Microsoft Academic Search

Objectives: To determine if heart rate (HR) reduction with ivabradine (IVA), a selective inhibitor of the pacemaker If current, prevents cardiac dysfunction associated with dyslipidemia. Methods: New Zealand White rabbits received either a standard diet, a 0.5% cholesterol-enriched diet only (CD), or a 0.5% CD with IVA (17 mg\\/kg\\/day) for 12 weeks. HR, left ventricular (LV) systolic function, diastolic function

David Busseuil; Yanfen Shi; Mélanie Mecteau; Geneviève Brand; Marc-Antoine Gillis; Eric Thorin; Caroline Asselin; Philippe Roméo; Tack Ki Leung; Jean-Gilles Latour; Christine Des Rosiers; Muriel Bouly; Eric Rhéaume; Jean-Claude Tardif

2010-01-01

236

Cardiac responses to exercise in the dog before and after destruction of the sinoatrial node  

Microsoft Academic Search

Summary  Chronotropic and dromotropic responses to treadmill exercise were compared in conscious dogs prior to and following excision\\u000a of the sinoatrial node (SAN). The initial junctional rhythm accompanying removal of the SAN region was replaced within hours\\u000a to days by subsidiary atrial pacemaker (SAP) foci located in the inferior right atrium along the sulcus terminalis. With SAN\\u000a intact, cardiac acceleration was

K. S. Kim; J. L. Ardell; W. C. Randall; G. Pomeroy; D. Calderwood

1986-01-01

237

[Cardiac angiosarcoma].  

PubMed

The paper outlines the authors'case of cardiac angiosarcoma. It provides the gross and microscopic characteristics of this tumor and procedures for its clinical and immunomorphological diagnosis. PMID:21695990

Kir'ianov, N A; Terekhov, M V; Sukhanov, S A; Lozhkin, E A; Nikolaeva, N B

2011-01-01

238

Cardiac Cephalalgia  

Microsoft Academic Search

We report a patient with cardiac cephalalgia and review reported cases from the English-language literature based on the new diagnostic criteria published in the International Classification of Headache Disorders, ed 2. Twenty-two patients, including ours, with headaches of cardiac origin were reviewed. The cases fit three of the four new criteria well: Criteria B (acute myocardial ischemia has occurred, 100%),

Shih-Pin Chen; Jong-Ling Fuh; Wen-Chung Yu; Shuu-Jiun Wang

2004-01-01

239

Left Ventricular Synchrony and Function in Pediatric Patients with Definitive Pacemakers  

PubMed Central

Background Chronic right ventricular pacing (RVP) induces a dyssynchronous contraction pattern, producing interventricular and intraventricular asynchrony. Many studies have shown the relationship of RVP with impaired left ventricular (LV) form and function. Objective The aim of this study was to evaluate LV synchrony and function in pediatric patients receiving RVP in comparison with those receiving LV pacing (LVP). Methods LV systolic and diastolic function and synchrony were evaluated in 80 pediatric patients with either nonsurgical or postsurgical complete atrioventricular block, with pacing from either the RV endocardium (n = 40) or the LV epicardium (n = 40). Echocardiographic data obtained before pacemaker implantation, immediately after it, and at the end of a mean follow-up of 6.8 years were analyzed. Results LV diastolic function did not change in any patient during follow-up. LV systolic function was preserved in patients with LVP. However, in children with RVP the shortening fraction and ejection fraction decreased from medians of 41% ± 2.6% and 70% ± 6.9% before implantation to 32% ± 4.2% and 64% ± 2.5% (p < 0.0001 and p < 0.0001), respectively, at final follow-up. Interventricular mechanical delay was significantly larger with RVP (66 ± 13 ms) than with LVP (20 ± 8 ms). Similarly, the following parameters were significantly different in the two groups: LV mechanical delay (RVP: 69 ± 6 ms, LVP: 30 ± 11 ms, p < 0.0001); septal to lateral wall motion delay (RVP: 75 ± 19 ms, LVP: 42 ± 10 ms, p < 0.0001); and, septal to posterior wall motion delay (RVP: 127 ± 33 ms, LVP: 58 ± 17 ms, p < 0.0001). Conclusion Compared with RV endocardium, LV epicardium is an optimal site for pacing to preserve cardiac synchrony and function. PMID:24061683

Ortega, Michel Cabrera; Morejon, Adel Eladio Gonzales; Ricardo, Giselle Serrano

2013-01-01

240

[The electrode-myocardium interface at the cellular level and prospects of the use of implantable pacemakers].  

PubMed

The interaction of the autonomic nervous system (ANS) and the heart is the subject-matter of new investigations of the interdisciplinary science neurocardiology which represents the newest strategy in cardiac pacing. In this connection the priorities are both the renewal of chronotropy with physiological cardiac pacing of the closed circuit and the prevention and treatment of malignant arrhythmias through ANS modulation. To achieve this requires adequate monitoring the balance of autonomic influences and stimulation and hence neuromodulation of cardiac afferents. Under these conditions, the electrode which is both deflecting and stimulating, and its interface with the body at the cellular level gain prime importance. The physical, electrochemical and physiological properties of the electrode-myocardium interface (boundary) are determined by the structure of the Helmholz bilayer. Translayer electron transport and electrochemical reactions which determine the biological compatibility of the interface may be optimized via the microstructure of the surface of a solid-state component by covering this surface with titanium or iridium nitride with so-called fractal geometry. Experimental and clinical findings have demonstrated that the fractal surface structure ensures extremely low polarization and improvement deflection, hence this deflection of an evoked myocardial cell response monitors a myocardial nervous response as a result of increased chronotropic excitement. The stimulating electrode also monitors the sympathetic activity determined from intracardiac impedance measurements, thus providing a new principle of rhythm adaptation when the pacemaker is an integral part of ANS, recovering normal chronotropy. These benefits of the electrode interface open new avenues for the treatment and prevention of tachyarrhythmias and for the long-term management of the grafted heart to prevent its rejecting processes. PMID:8618541

Shal'dakh, M

1995-01-01

241

Neurobiology of Stomotoca. II. Pacemakers and conduction pathways.  

PubMed

Evidence is presented for separate conduction pathways for swimming and for tentacle coordination in the marginal nerves of the jellyfish Stomotoca. The effector muscles are fired through junctions sensitive to excess Mg++, probably represented by the neuromuscular synapses observed by electron microscopy. The swimming effector (striated muscle) fires one-to-one with nerve input signals and myoid conduction occurs. Tentacle responses (smooth muscle contractions) involve facilitation, presumably at the neuro-effector junction; responses are graded and nonpropagating. Electrical correlates of two further conducting systems using the marginal nerves have been recorded. Their functions are unknown. One, the bridge system, extends up the four radii and encircles the peduncle; the other (ring system) is confined to the margin. A fifth conducting system is inferred in the case of the pointing response and its distribution is plotted. Signals have not been obtained from it. Pointing is accompanied by a burst of muscle potentials in the radial smooth muscles and is exhibited after a lengthy latency, indicating a local pacemaker. A sixth conducting pathway is the epithelial system, which mediates crumpling, a response involving the radial muscles without pacemaker intervention. Characteristic conduction velocities and wave forms are noted for the first four systems and for epithelial pulses. All systems, except perhaps the pointing conduction system, through-conduct under excess Mg++. Spontaneous activity patterns are described for the swimming, tentacle pulse, and ring systems. Abrupt increases in light intensity inhibit spontaneous activity, sudden decreases augmenting it. In the absence of specialized photoreceptors, light is presumed to act directly on central neurons. Epithelial pulses inhibit swimming, apparently by blocking the generation or conduction of the primary nervous events. This observation, taken in conjunction with evidence of feedback inhibition of the primary swimming system by the cells it fires, is discussed in relation to possible mechanisms whereby the output of nerve cells might be altered by activity in the excitable epithelial cells which envelop them. PMID:241778

Mackie, G O

1975-07-01

242

About Cardiac Arrest  

MedlinePLUS

... High Blood Pressure Tools & Resources Stroke More About Cardiac Arrest Updated:Sep 10,2014 What is cardiac arrest? ... to heart disease and stroke. Start exploring today ! Cardiac Arrest • Home • About Cardiac Arrest • Understand Your Risk for ...

243

Rate-adaptive pacemaker controlled by motion and respiratory rate using neuro-fuzzy algorithm.  

PubMed

Rate-adaptive pacemakers use information from sensors to change the rate of heart stimulation. Until now, fuzzy-pacemaker algorithms have been used to combine inputs from sensors to improve heart rate control, but they have been difficult to implement. In this paper, a pacemaker algorithm which controlled heart rate adaptively by motion and respiratory rate was studied. After chronotropic assessment exercise protocol (CAEP) tests were performed to collect activity and respiratory rate signals, the intrinsic heart rate was inferred from these two signals by a neuro-fuzzy method. For 10 subjects the heart rate inference, using the neuro-fuzzy algorithm, gave 52.4% improved accuracy in comparison with the normal fuzzy table look-up method. The neuro-fuzzy method was applied to a real pacemaker by reduced mapping of the neuro-fuzzy look-up table. PMID:11804178

Shin, J W; Yoon, J H; Yoon, Y R

2001-11-01

244

Computational Modeling of the Regulation of Pacemaker Frequency in Dopamine Neurons Marco Huertas and Carmen Canavier  

E-print Network

Computational Modeling of the Regulation of Pacemaker Frequency in Dopamine disorder and drug addiction. The firing pattern of dopamine neurons in behaving a real time interface between a computer and a living neuron. We show

Ullmer, Brygg

245

[Optimalization of rate adaptation using Holter functions in DDD/R pacemakers].  

PubMed

Introduction of the pacing rate adaptation according to the momentary metabolic needs added other programmable parametres which demand physician's attention during the initial postimplantation programmation and also in follow-up of pacemaker patients. The parametres setting is strictly individual with a need of feedback control. In some devices it is enabled by Holter functions as a part of pacemaker software. These methods were used to set the rate adaptive parametres in the group of 23 patients with implanted DDD/R pacemaker. The walking stress test was used. Model follow-up situations are presented in 3 case reports. Using Holter functions enables the physician to put patient's subjective complains in relation with actual heart rate--this is used to optimize the parametres of rate adaptation. The authors consider the Holter functions a necessary part of rate adaptive pacemaker software. PMID:9820057

Novotný, T; Dvorák, R; Kozák, M; Vlasínová, J

1998-06-01

246

21 CFR 870.3610 - Implantable pacemaker pulse generator.  

...power supply and electronic circuits that produce a periodic electrical pulse to stimulate the heart. This device is used as a substitute for the heart's intrinsic pacing system to correct both intermittent and continuous cardiac rhythm...

2014-04-01

247

Percutaneous extraction of a fractured permanent pacemaker lead with no free end.  

PubMed

From various points of view abandoned or displaced permanent pacemaker leads should be extracted in indicated cases using a broad spectrum of catheter-based techniques. We describe a relatively easy extraction procedure of almost the whole pacemaker lead, which broke near the pulse generator and migrated into right-heart chambers; so both ends were indwelling. The described procedure was undertaken using a simple homemade nitinol-based extractor. PMID:16176545

Sochman, Jan; Peregrin, Jan H; Bytesnik, Jan

2005-09-01

248

Cardiac Regeneration  

PubMed Central

The heart is a pump that is comprised of cardiac myocytes and other cell types and whose proper function is critical to quality of life. The ability to trigger regeneration of heart muscle following injury eludes adult mammals, a deficiency of great clinical impact. Major research efforts are attempting to change this through advances in cell therapy or activating endogenous regenerative mechanisms that exist only early in life. By contrast with mammals, lower vertebrates like zebrafish demonstrate an impressive natural capacity for cardiac regeneration throughout life. This review will cover recent progress in the field of heart regeneration with a focus on endogenous regenerative capacity and its potential manipulation. PMID:22449849

Choi, Wen-Yee; Poss, Kenneth D.

2012-01-01

249

Irregular excitation patterns in reaction-diffusion systems due to perturbation by secondary pacemakers.  

PubMed

Spatiotemporal excitation patterns in the FitzHugh-Nagumo model are studied, which result from the disturbance of a primary pacemaker by a secondary pacemaker. The primary and secondary pacemakers generate regular waves with frequencies f(pace) and f(pert), respectively. The pacemakers are spatially separated, but waves emanating from them encounter each other via a small bridge. This leads to three different types I-III of irregular excitation patterns in disjunct domains of the f(pace)-f(pert) plane. Types I and II are caused by detachments of waves coming from the two pacemakers at corners of the bridge. Type III irregularities are confined to a boundary region of the system and originate from a partial penetration of the primary waves into a space, where circular wave fronts from the secondary pacemaker prevail. For this type, local frequencies can significantly exceed f(pace) and f(pert). The degree of irregularity found for the three different types is quantified by the entropy of the local frequency distribution and an order parameter for phase coherence. PMID:23679486

Lenk, Claudia; Einax, Mario; Maass, Philipp

2013-04-01

250

Transcription factor-driven conversion of quiescent cardiomyocytes to pacemaker cells  

PubMed Central

The heartbeat originates within the sinoatrial node (SAN), a small highly-specialized structure containing <10,000 genuine pacemaker cells. The ~5 billion working cardiomyocytes downstream of the SAN remain quiescent when it fails, leading to circulatory collapse and fueling a $6B/year electronic pacemaker industry. To engineer faithful biological replicas of rare SAN cells as an alternative therapeutic strategy, we expressed a gene critical for early SAN specification in working cardiomyocytes in vitro, and in vivo in a model of bradycardia. Within days of transduction with Tbx18, ventricular cardiomyocytes in culture developed spontaneous electrical firing physiologically indistinguishable from that of SAN cells, along with morphological and epigenetic features characteristic of SAN cells. Focal Tbx18 gene transfer in the guinea-pig ventricle yielded ectopic pacemaker activity in vivo, correcting a bradycardic disease phenotype. Myocytes transduced in vivo acquired the cardinal tapering morphology and physiological automaticity of native SAN pacemaker cells, while controls remained rectangular and quiescent. The creation of induced SAN-like pacemaker (iSAN) cells by Tbx18 gene transfer opens new prospects for bioengineered pacemakers. PMID:23242162

Kapoor, Nidhi; Liang, Wenbin; Marban, Eduardo; Cho, Hee Cheol

2013-01-01

251

Tachycardia-termination algorithm: a valuable feature for interruption of pacemaker-mediated tachycardia.  

PubMed

A 45-year-old man who had been implanted with a VVI pacemaker for sinus arrest complained of syncope, dizziness and throbbing in the neck. His pacemaker function was normal, but during ventricular pacing, retrograde V-A conduction was observed. This pacer was replaced by a DVI unit which caused periodic abdominal muscular contractions. We replaced this unit with an Intermedics Cosmos DDD-M pacemaker. This type of pacemaker in a patient with V-A conduction may cause pacemaker-mediated tachycardia (PMT). However, the Cosmos has a tachycardia-termination algorithm which detects continued pacing at the ventricular tracking rate, allows it to proceed for 15 consecutive pace events, and inhibits the 16th ventricular output pulse, thus breaking the reentry loop. The Cosmos pacer has a number of features to prevent initiation of PMT, and is also able to terminate the tachycardia when it occurs because of the tachycardia-termination algorithm. This feature is valuable in DDD-M pacemakers implanted in patients with V-A conduction. Whether this algorithm will be effective in all cases remains to be determined. PMID:6200858

van Gelder, L M; el Gamal, M I; Baker, R; Sanders, R S

1984-03-01

252

Cardiac conduction through engineered tissue.  

PubMed

In children, interruption of cardiac atrioventricular (AV) electrical conduction can result from congenital defects, surgical interventions, and maternal autoimmune diseases during pregnancy. Complete AV conduction block is typically treated by implanting an electronic pacemaker device, although long-term pacing therapy in pediatric patients has significant complications. As a first step toward developing a substitute treatment, we implanted engineered tissue constructs in rat hearts to create an alternative AV conduction pathway. We found that skeletal muscle-derived cells in the constructs exhibited sustained electrical coupling through persistent expression and function of gap junction proteins. Using fluorescence in situ hybridization and polymerase chain reaction analyses, myogenic cells in the constructs were shown to survive in the AV groove of implanted hearts for the duration of the animal's natural life. Perfusion of hearts with fluorescently labeled lec-tin demonstrated that implanted tissues became vascularized and immunostaining verified the presence of proteins important in electromechanical integration of myogenic cells with surrounding re-cipient rat cardiomyocytes. Finally, using optical mapping and electrophysiological analyses, we provide evidence of permanent AV conduction through the implant in one-third of recipient animals. Our experiments provide a proof-of-principle that engineered tissue constructs can function as an electrical conduit and, ultimately, may offer a substitute treatment to conventional pacing therapy. PMID:16816362

Choi, Yeong-Hoon; Stamm, Christof; Hammer, Peter E; Kwaku, Kevin F; Marler, Jennifer J; Friehs, Ingeborg; Jones, Mara; Rader, Christine M; Roy, Nathalie; Eddy, Mau-Thek; Triedman, John K; Walsh, Edward P; McGowan, Francis X; del Nido, Pedro J; Cowan, Douglas B

2006-07-01

253

Circadian Pacemaking in Cells and Circuits of the Suprachiasmatic Nucleus  

PubMed Central

The suprachiasmatic nucleus (SCN) of the hypothalamus is the principal circadian pacemaker of the brain. It co-ordinates the daily rhythms of sleep and wakefulness, as well as physiology and behaviour, that set the tempo to our lives. Disturbance of this daily pattern, most acutely with jet-lag but more insidiously with rotational shift-work, can have severely deleterious effects for mental function and long-term health. The present review considers recent developments in our understanding of the properties of the SCN that make it a robust circadian time-keeper. It first focuses on the intracellular transcriptional/ translational feedback loops (TTFL) that constitute the cellular clockwork of the SCN neurone. Daily timing by these loops pivots around the negative regulation of the Period (Per) and Cryptochrome (Cry) genes by their protein products. The period of the circadian cycle is set by the relative stability of Per and Cry proteins, and this can be controlled by both genetic and pharmacological interventions. It then considers the function of these feedback loops in the context of cytosolic signalling by cAMP and intracellular calcium ([Ca2+]i), which are both outputs from, and inputs to, the TTFL, as well as the critical role of vasoactive intestinal peptide (VIP) signalling in synchronising cellular clocks across the SCN. Synchronisation by VIP in the SCN is paracrine, operating over an unconventionally long time frame (i.e. 24 h) and wide spatial domain, mediated via the cytosolic pathways upstream of the TTFL. Finally, we show how intersectional pharmacogenetics can be used to control G-protein-coupled signalling in individual SCN neurones, and how manipulation of Gq/[Ca2+]i-signalling in VIP neurones can re-programme the circuit-level encoding of circadian time. Circadian pacemaking in the SCN therefore provides an unrivalled context in which to understand how a complex, adaptive behaviour can be organised by the dynamic activity of a relatively few gene products, operating in a clearly defined neuronal circuit, with both cell-autonomous and emergent, circuit-level properties. PMID:24329967

Hastings, M H; Brancaccio, M; Maywood, E S

2014-01-01

254

A missense mutation in the exon 8 of lamin A\\/C gene in a Japanese case of autosomal dominant limb-girdle muscular dystrophy and cardiac conduction block  

Microsoft Academic Search

A case of autosomal dominant limb-girdle muscular dystrophy with atrioventricular conduction block (LGMD1B) has been documented. In this family, 13 members, nine males and four females, had cardiac arrhythmia requiring pacemakers. The proband, a 67-year-old male, had longstanding proximal muscle weakness later associated with cardiac arrhythmia but showed neither rigid spine nor joint contracture. His muscle enzymes were within normal

Tetsuo Kitaguchi; Shiro Matsubara; Masaru Sato; Kazuhito Miyamoto; Shunsaku Hirai; Ketty Schwartz; Gisèle Bonne

2001-01-01

255

Cardiac ion channel expression and regulation: the role of innervation.  

PubMed

The expression and function of numerous cardiac ion channels change with development and disease. Whereas multiple regulatory processes and molecular mechanisms are certainly involved, one factor, sympathetic innervation, contributes to many of the developmental changes and is suggested to play a role in pathology. The onset of cardiac sympathetic innervation of the mammalian ventricle during early post-natal life has been associated with functional alterations in several ionic currents, including Na(+), L-type Ca(2+), pacemaker, inward rectifier and transient outward K(+) currents. The neural signaling molecule is not the same in each case, with evidence pointing to contributions from sustained activation of myocardial neuropeptide Y receptors, alpha-adrenergic receptors and beta-adrenergic receptors, as well as additional, but as yet unidentified, targets. Knowledge of the mechanisms by which innervation regulates ion channel expression and function during normal development may aid efforts to reverse remodel the diseased heart and to target pharmacologic agents to remodeled channels. PMID:15276014

Qu, Jihong; Robinson, Richard B

2004-08-01

256

Caffeine increases light responsiveness of the mouse circadian pacemaker.  

PubMed

Caffeine is the most commonly used psychoactive stimulant worldwide. It reduces sleep and sleepiness by blocking access to the adenosine receptor. The level of adenosine increases during sleep deprivation, and is thought to induce sleepiness and initiate sleep. Light-induced phase shifts of the rest-activity circadian rhythms are mediated by light-responsive neurons of the suprachiasmatic nucleus (SCN) of the hypothalamus, where the circadian clock of mammals resides. Previous studies have shown that sleep deprivation reduces circadian clock phase-shifting capacity and decreases SCN neuronal activity. In addition, application of adenosine agonists and antagonists mimics and blocks, respectively, the effect of sleep deprivation on light-induced phase shifts in behaviour, suggesting a role for adenosine. In the present study, we examined the role of sleep deprivation in and the effect of caffeine on light responsiveness of the SCN. We performed in vivo electrical activity recordings of the SCN in freely moving mice, and showed that the sustained response to light of SCN neuronal activity was attenuated after 6 h of sleep deprivation prior to light exposure. Subsequent intraperitoneal application of caffeine was able to restore the response to light. Finally, we performed behavioural recordings in constant conditions, and found enhanced period lengthening during chronic treatment with caffeine in drinking water in constant light conditions. The data suggest that increased homeostatic sleep pressure changes circadian pacemaker functioning by reducing SCN neuronal responsiveness to light. The electrophysiological and behavioural data together provide evidence that caffeine enhances clock sensitivity to light. PMID:25196050

van Diepen, Hester C; Lucassen, Eliane A; Yasenkov, Roman; Groenen, Inske; Ijzerman, Adriaan P; Meijer, Johanna H; Deboer, Tom

2014-11-01

257

KAYAK-? modulates circadian transcriptional feedback loops in Drosophila pacemaker neurons  

PubMed Central

Circadian rhythms are generated by well-conserved interlocked transcriptional feedback loops in animals. In Drosophila, the dimeric transcription factor CLOCK/CYCLE (CLK/CYC) promotes period (per), timeless (tim), vrille (vri) and PAR-domain protein 1 (Pdp1) transcription. PER and TIM negatively feed back on CLK/CYC transcriptional activity, while VRI and PDP1 negatively and positively regulate Clk transcription, respectively. Here, we show that the ? isoform of the Drosophila FOS homolog KAY is required for normal circadian behavior. KAY-? downregulation in circadian pacemaker neurons increases period length by 1.5 hours. This behavioral phenotype is correlated with decreased expression of several circadian proteins. The strongest effects are on CLK and the neuropeptide PIGMENT DISPERSING FACTOR (PDF), which are both under VRI and PDP1 control. Consistently, KAY-? can bind to VRI and inhibit its interaction with the Clk promoter. Interestingly, KAY-? can also repress CLK activity. Hence, in flies with low KAY-? levels, CLK derepression would partially compensate for increased VRI repression, thus attenuating the consequences of KAY-? downregulation on CLK targets. We propose that KAY-?’s double role in the two transcriptional loops controlling Drosophila circadian behavior brings precision and stability to their oscillations. PMID:23175847

Ling, Jinli; Dubruille, Raphaelle; Emery, Patrick

2012-01-01

258

Cardiac optogenetics  

PubMed Central

Optogenetics is an emerging technology for optical interrogation and control of biological function with high specificity and high spatiotemporal resolution. Mammalian cells and tissues can be sensitized to respond to light by a relatively simple and well-tolerated genetic modification using microbial opsins (light-gated ion channels and pumps). These can achieve fast and specific excitatory or inhibitory response, offering distinct advantages over traditional pharmacological or electrical means of perturbation. Since the first demonstrations of utility in mammalian cells (neurons) in 2005, optogenetics has spurred immense research activity and has inspired numerous applications for dissection of neural circuitry and understanding of brain function in health and disease, applications ranging from in vitro to work in behaving animals. Only recently (since 2010), the field has extended to cardiac applications with less than a dozen publications to date. In consideration of the early phase of work on cardiac optogenetics and the impact of the technique in understanding another excitable tissue, the brain, this review is largely a perspective of possibilities in the heart. It covers the basic principles of operation of light-sensitive ion channels and pumps, the available tools and ongoing efforts in optimizing them, overview of neuroscience use, as well as cardiac-specific questions of implementation and ideas for best use of this emerging technology in the heart. PMID:23457014

2013-01-01

259

Cardiac Surgery  

PubMed Central

Well into the first decades of the 20th century, medical opinion held that any surgical attempts to treat heart disease were not only misguided, but unethical. Despite such reservations, innovative surgeons showed that heart wounds could be successfully repaired. Then, extracardiac procedures were performed to correct patent ductus arteriosus, coarctation of the aorta, and tetralogy of Fallot. Direct surgery on the heart was accomplished with closed commissurotomy for mitral stenosis. The introduction of the heart-lung machine and cardiopulmonary bypass enabled the surgical treatment of other congenital and acquired heart diseases. Advances in aortic surgery paralleled these successes. The development of coronary artery bypass grafting greatly aided the treatment of coronary heart disease. Cardiac transplantation, attempts to use the total artificial heart, and the application of ventricular assist devices have brought us to the present day. Although progress in the field of cardiovascular surgery appears to have slowed when compared with the halcyon times of the past, substantial challenges still face cardiac surgeons. It can only be hoped that sufficient resources and incentive can carry the triumphs of the 20th century into the 21st. This review covers past developments and future opportunities in cardiac surgery. PMID:22163121

Weisse, Allen B.

2011-01-01

260

Cardiac natriuretic peptides act via p38 MAPK to induce the brown fat thermogenic program in mouse and human adipocytes  

PubMed Central

The ability of mammals to resist body fat accumulation is linked to their ability to expand the number and activity of “brown adipocytes” within white fat depots. Activation of ?-adrenergic receptors (?-ARs) can induce a functional “brown-like” adipocyte phenotype. As cardiac natriuretic peptides (NPs) and ?-AR agonists are similarly potent at stimulating lipolysis in human adipocytes, we investigated whether NPs could induce human and mouse adipocytes to acquire brown adipocyte features, including a capacity for thermogenic energy expenditure mediated by uncoupling protein 1 (UCP1). In human adipocytes, atrial NP (ANP) and ventricular NP (BNP) activated PPAR? coactivator-1? (PGC-1?) and UCP1 expression, induced mitochondriogenesis, and increased uncoupled and total respiration. At low concentrations, ANP and ?-AR agonists additively enhanced expression of brown fat and mitochondrial markers in a p38 MAPK–dependent manner. Mice exposed to cold temperatures had increased levels of circulating NPs as well as higher expression of NP signaling receptor and lower expression of the NP clearance receptor (Nprc) in brown adipose tissue (BAT) and white adipose tissue (WAT). NPR-C–/– mice had markedly smaller WAT and BAT depots but higher expression of thermogenic genes such as Ucp1. Infusion of BNP into mice robustly increased Ucp1 and Pgc-1? expression in WAT and BAT, with corresponding elevation of respiration and energy expenditure. These results suggest that NPs promote “browning” of white adipocytes to increase energy expenditure, defining the heart as a central regulator of adipose tissue biology. PMID:22307324

Bordicchia, Marica; Liu, Dianxin; Amri, Ez-Zoubir; Ailhaud, Gerard; Dessi-Fulgheri, Paolo; Zhang, Chaoying; Takahashi, Nobuyuki; Sarzani, Riccardo; Collins, Sheila

2012-01-01

261

Reexposure to nicotine during withdrawal increases the pacemaking activity of cholinergic habenular neurons.  

PubMed

The discovery of genetic variants in the cholinergic receptor nicotinic CHRNA5-CHRNA3-CHRNB4 gene cluster associated with heavy smoking and higher relapse risk has led to the identification of the midbrain habenula-interpeduncular axis as a critical relay circuit in the control of nicotine dependence. Although clear roles for ?3, ?4, and ?5 receptors in nicotine aversion and withdrawal have been established, the cellular and molecular mechanisms that participate in signaling nicotine use and contribute to relapse have not been identified. Here, using translating ribosome affinity purification (TRAP) profiling, electrophysiology, and behavior, we demonstrate that cholinergic neurons, but not peptidergic neurons, of the medial habenula (MHb) display spontaneous tonic firing of 2-10 Hz generated by hyperpolarization-activated cyclic nucleotide-gated (HCN) pacemaker channels and that infusion of the HCN pacemaker antagonist ZD7288 in the habenula precipitates somatic and affective signs of withdrawal. Further, we show that a strong, ?3?4-dependent increase in firing frequency is observed in these pacemaker neurons upon acute exposure to nicotine. No change in the basal or nicotine-induced firing was observed in cholinergic MHb neurons from mice chronically treated with nicotine. We observe, however, that, during withdrawal, reexposure to nicotine doubles the frequency of pacemaking activity in these neurons. These findings demonstrate that the pacemaking mechanism of cholinergic MHb neurons controls withdrawal, suggesting that the heightened nicotine sensitivity of these neurons during withdrawal may contribute to smoking relapse. PMID:24082085

Görlich, Andreas; Antolin-Fontes, Beatriz; Ables, Jessica L; Frahm, Silke; Slimak, Marta A; Dougherty, Joseph D; Ibañez-Tallon, Inés

2013-10-15

262

Characterization of the pace-maker current kinetics in calf Purkinje fibres.  

PubMed Central

Kinetics of the cardiac pace-maker current (if) were studied using high K+, low Na+ solutions under conditions where the current time course could be dissected from other components. Activation of if during relatively large negative pulses is S-shaped, and is approximated by an exponential function of time to the third power. Less-pronounced S-shaped activation occurs at potentials close to the middle of the activation curve (near -70/-80 mV). Here, allowing for the presence of a very slow component, the power required to fit the current activation approaches 1. The comparison between current activation and deactivation at the same potentials shows that although deactivation can be approximated by a single exponential, the two processes have a quite different time dependence, and this difference depends on the membrane potential. This behaviour is not compatible with Hodgkin-Huxley kinetics. While near the half-activation range the current decays with an apparently single exponential time course, at more positive potentials the current deactivation becomes sigmoidal. At least the third power of an exponential is required to fit its time course at potentials positive to about -40 mV. These data imply that both open and closed states correspond to several distinct channel configurations. The 'delay' in the current onset during a hyperpolarization is decreased by applying large, short hyperpolarizations before activation. Suitable pre-pulse durations and/or amplitudes can reduce the subsequent current activation to a single exponential. Records with and without a pre-pulse do not always superimpose. After the activation 'delay' has been removed by a suitable hyperpolarization preceding an activating pulse, the time course of its recovery can be studied by applying depolarizations of given amplitude and variable duration. The time course of the delay recovery does not seem to be linked to the time course of current deactivation recorded at the same voltage. Reduction of the activation 'delay' by conditioning pre-hyperpolarizations does not affect current decay during a subsequent depolarizing pulse. The current decay appears to depend only on the current amplitude reached before a deactivating pulse is applied. This, and the evidence in the preceding paragraph, suggest that the delay recovery and the current deactivation are independent processes. A reaction scheme is proposed, which has been developed on the basis of the experimentally determined kinetic properties of if. The channel model is composed of five gating subunits of three different types, not all independent in their movements.(ABSTRACT TRUNCATED AT 400 WORDS) PMID:6325672

DiFrancesco, D

1984-01-01

263

Revisiting the reticulum: feedforward and feedback contributions to motor program parameters in the crab cardiac ganglion microcircuit  

PubMed Central

The neurogenic heartbeat of crustaceans is controlled by the cardiac ganglion (CG), a central pattern generator (CPG) microcircuit composed of nine neurons. In most decapods, five “large” motor neurons (MNs) project from the CG to the myocardium, where their excitatory synaptic signals generate the rhythmic heartbeat. The processes of four “small” premotor neurons (PMNs) are confined to the CG, where they provide excitatory drive to the MNs via impulse-mediated chemical signals and electrotonic coupling. This study explored feedforward and feedback interactions between the PMNs and the MNs in the CG of the blue crab (Callinectes sapidus). Three methods were used to compare the activity of the MNs and the PMNs in the integrated CG to their autonomous firing patterns: 1) ligatures were tightened on the ganglion trunk that connects the PMNs and MNs; 2) TTX was applied focally to suppress selectively PMN or MN activity; and 3) sucrose pools were devised to block reversibly PMN or MN impulse conduction. With all treatments, the PMNs and MNs continued to produce autonomous rhythmic bursting following disengagement. Removal of PMN influence resulted in a significantly reduced MN duty cycle that was mainly attributable to a lower autonomous burst frequency. Conversely, after removal of MN feedback, the PMN duty cycle was increased, primarily due to a prolonged burst duration. Application of sucrose to block impulse conduction without eliminating PMN oscillations disclosed significant contributions of spike-mediated PMN-to-MN signals to the initiation and prolongation of the MN burst. Together, these observations support a view of the Callinectes CG composed of two classes of spontaneously bursting neurons with distinct endogenous rhythms. Compartmentalized feedforward and feedback signaling endow this microcircuit with syncytial properties such that the intrinsic attributes of the PMNs and MNs both contribute to shaping all parameters of the motor patterns transmitted to the myocardium. PMID:21775716

Garcia-Crescioni, Keyla

2011-01-01

264

A case for interstitial cells of Cajal as pacemakers and mediators of neurotransmission in the gastrointestinal tract  

Microsoft Academic Search

Electrical rhythmicity in gastrointestinal muscles has been studied for a century, but the pacemakers driving this phenomenon have been elusive. Anatomic studies suggest that interstitial cells of Cajal (ICC) may be pacemakers and conductors of electrical activity. ICC may also mediate neurotransmission from enteric neurons. Functional evaluations of ICC include the following. (1) Electrophysiology experiments on dissected muscle strips show

KM Sanders

1996-01-01

265

Strategies to improve cardiac resynchronization therapy.  

PubMed

Cardiac resynchronization therapy (CRT) emerged 2 decades ago as a useful form of device therapy for heart failure associated with abnormal ventricular conduction, indicated by a wide QRS complex. In this Review, we present insights into how to achieve the greatest benefits with this pacemaker therapy. Outcomes from CRT can be improved by appropriate patient selection, careful positioning of right and left ventricular pacing electrodes, and optimal timing of electrode stimulation. Left bundle branch block (LBBB), which can be detected on an electrocardiogram, is the predominant substrate for CRT, and patients with this conduction abnormality yield the most benefit. However, other features, such as QRS morphology, mechanical dyssynchrony, myocardial scarring, and the aetiology of heart failure, might also determine the benefit of CRT. No single left ventricular pacing site suits all patients, but a late-activated site, during either the intrinsic LBBB rhythm or right ventricular pacing, should be selected. Positioning the lead inside a scarred region substantially impairs outcomes. Optimization of stimulation intervals improves cardiac pump function in the short term, but CRT procedures must become easier and more reliable, perhaps with the use of electrocardiographic measures, to improve long-term outcomes. PMID:24839977

Vernooy, Kevin; van Deursen, Caroline J M; Strik, Marc; Prinzen, Frits W

2014-08-01

266

In vivo powering of pacemaker by breathing-driven implanted triboelectric nanogenerator.  

PubMed

The first application of an implanted triboelectric nanogenerator (iTENG) that enables harvesting energy from in vivo mechanical movement in breathing to directly drive a pacemaker is reported. The energy harvested by iTENG from animal breathing is stored in a capacitor and successfully drives a pacemaker prototype to regulate the heart rate of a rat. This research shows a feasible approach to scavenge biomechanical energy, and presents a crucial step forward for lifetime-implantable self-powered medical devices. PMID:25043590

Zheng, Qiang; Shi, Bojing; Fan, Fengru; Wang, Xinxin; Yan, Ling; Yuan, Weiwei; Wang, Sihong; Liu, Hong; Li, Zhou; Wang, Zhong Lin

2014-09-01

267

Origins of Cardiac Fibroblasts  

PubMed Central

Cardiac fibroblasts play a critical role in maintenance of normal cardiac function. They are indispensable for damage control and tissue remodeling on myocardial injury and principal mediators of pathological cardiac remodeling and fibrosis. Despite their manyfold functions, cardiac fibroblasts remain poorly characterized in molecular terms. Evidence is evolving that cardiac fibroblasts are a heterogeneous population and likely derive from various distinct tissue niches in health and disease. Here, we review our emerging understanding of where cardiac fibroblasts come from, as well as how we can possibly use this knowledge to develop novel therapies for cardiac fibrosis. PMID:21106947

Zeisberg, Elisabeth M.; Kalluri, Raghu

2011-01-01

268

Extreme Events as Pacemaker of Adaptation to Climate Change1 William R. Travis  

E-print Network

1 Extreme Events as Pacemaker of Adaptation to Climate Change1 William R. Travis Department of Geography and Center for Science and Technology Policy Research Cooperative Institute for Research are thought of as propelling adaptation to climate change (Füssel, 2007; IPCC, 2012). In the simplest

Neff, Jason

269

Measuring contraction propagation and localizing pacemaker cells using high speed video microscopy  

NASA Astrophysics Data System (ADS)

Previous studies have shown the ability of many lymphatic vessels to contract phasically to pump lymph. Every lymphangion can act like a heart with pacemaker sites that initiate the phasic contractions. The contractile wave propagates along the vessel to synchronize the contraction. However, determining the location of the pacemaker sites within these vessels has proven to be very difficult. A high speed video microscopy system with an automated algorithm to detect pacemaker location and calculate the propagation velocity, speed, duration, and frequency of the contractions is presented in this paper. Previous methods for determining the contractile wave propagation velocity manually were time consuming and subject to errors and potential bias. The presented algorithm is semiautomated giving objective results based on predefined criteria with the option of user intervention. The system was first tested on simulation images and then on images acquired from isolated microlymphatic mesenteric vessels. We recorded contraction propagation velocities around 10 mm/s with a shortening speed of 20.4 to 27.1 ?m/s on average and a contraction frequency of 7.4 to 21.6 contractions/min. The simulation results showed that the algorithm has no systematic error when compared to manual tracking. The system was used to determine the pacemaker location with a precision of 28 ?m when using a frame rate of 300 frames per second.

Akl, Tony J.; Nepiyushchikh, Zhanna V.; Gashev, Anatoliy A.; Zawieja, David C.; Coté, Gerard L.

2011-02-01

270

Pacemakers in large arrays of oscillators with nonlocal coupling Gabriela Jaramillo and Arnd Scheel  

E-print Network

Pacemakers in large arrays of oscillators with nonlocal coupling Gabriela Jaramillo and Arnd Scheel dimensional array of oscillators with nonlocal coupling. We assume the oscillators obey simple phase dynamics in systems of coupled oscillators has attracted a tremendous amount of interest. Self

Scheel, Arnd

271

Neurotensin modulates pacemaker activity in interstitial cells of Cajal from the mouse small intestine.  

PubMed

Neurotensin, a tridecapeptide localized in the gut to discrete enteroendocrine cells of the small bowel mucosa, is a hormone that plays an important role in gastrointestinal secretion, growth, and motility. Neurotensin has inhibitory and excitatory effects on peristaltic activity and produces contractile and relaxant responses in intestinal smooth muscle. Our objective in this study is to investigate the effects of neurotensin in small intestinal interstitial cells of Cajal (ICC) and elucidate the mechanism. To determine the electrophysiological effects of neurotensin on ICC, whole-cell patch clamp recordings were performed in cultured ICC from the small intestine. Exposure to neurotensin depolarized the membrane of pacemaker cells and produced tonic inward pacemaker currents. Only neurotensin receptor1 was identified when RT-PCR and immunocytochemistry were performed with mRNA isolated from small intestinal ICC and c-Kit positive cells. Neurotensin-induced tonic inward pacemaker currents were blocked by external Na?-free solution and in the presence of flufenamic acid, an inhibitor of non-selective cation channels. Furthermore, neurotensin-induced action is blocked either by treatment with U73122, a phospholipase C inhibitor, or thapsigargin, a Ca²?-ATPase inhibitor in ICC. We found that neurotensin increased spontaneous intracellular Ca²? oscillations as seen with fluo4/AM recording. These results suggest that neurotensin modulates pacemaker currents via the activation of non-selective cation channels by intracellular Ca²?-release through neurotensin receptor1. PMID:22441675

Lee, Jun; Kim, Young Dae; Park, Chan Guk; Kim, Man Yoo; Chang, In Yeoub; Zuo, Dong Chuan; Shahi, Pawan Kumar; Choi, Seok; Yeum, Cheol Ho; Jun, Jae Yeoul

2012-05-01

272

Neurotensin Modulates Pacemaker Activity in Interstitial Cells of Cajal from the Mouse Small Intestine  

PubMed Central

Neurotensin, a tridecapeptide localized in the gut to discrete enteroendocrine cells of the small bowel mucosa, is a hormone that plays an important role in gastrointestinal secretion, growth, and motility. Neurotensin has inhibitory and excitatory effects on peristaltic activity and produces contractile and relaxant responses in intestinal smooth muscle. Our objective in this study is to investigate the effects of neurotensin in small intestinal interstitial cells of Cajal (ICC) and elucidate the mechanism. To determine the electrophysiological effects of neurotensin on ICC, whole-cell patch clamp recordings were performed in cultured ICC from the small intestine. Exposure to neurotensin depolarized the membrane of pacemaker cells and produced tonic inward pacemaker currents. Only neurotensin receptor1 was identified when RT-PCR and immunocytochemistry were performed with mRNA isolated from small intestinal ICC and c-Kit positive cells. Neurotensin-induced tonic inward pacemaker currents were blocked by external Na+- free solution and in the presence of flufenamic acid, an inhibitor of non-selective cation channels. Furthermore, neurotensin-induced action is blocked either by treatment with U73122, a phospholipase C inhibitor, or thapsigargin, a Ca2+-ATPase inhibitor in ICC. We found that neurotensin increased spontaneous intracellular Ca2+ oscillations as seen with fluo4/AM recording. These results suggest that neurotensin modulates pacemaker currents via the activation of non-selective cation channels by intracellular Ca2+-release through neurotensin receptor1. PMID:22441675

Lee, Jun; Kim, Young Dae; Park, Chan Guk; Kim, Man Yoo; Chang, In Yeoub; Zuo, Dong Chuan; Shahi, Pawan Kumar; Choi, Seok; Yeum, Cheol Ho; Jun, Jae Yeoul

2012-01-01

273

Circadian pacemaker interferes with sleep onset at specific times each day: role in insomnia  

E-print Network

Circadian pacemaker interferes with sleep onset at specific times each day: role in insomnia STEVEN at specific times each day: role in insomnia. Am. J. Physiol. 253(Regulatory Integrative Comp.Physiol. 22):R of the circadianpacemakermayunderliethe insomniaassociatedwith sleep-schedulingdisorders. insomnia; circadian rhythm; sleep

Schumaker, Mark

274

Light and Diurnal Cycle Affect Human Heart Rate: Possible Role for the Circadian Pacemaker  

Microsoft Academic Search

Humans and animals demonstrate diurnal rhythms in physiology and behavior, which are generated by the circadian pacemaker, located in the supra-chiasmatic nucleus (SCN). The endogenous diurnal rhythm of the SCN is synchronized to the diurnal cycle most effectively by light. However, light also influences the SCN and its output instantaneously, as is demonstrated for the immediate effects of light on

Frank A. J. L. Scheer; Lorenz J. P. van Doornen; Ruud M. Buijs

1999-01-01

275

[Venous thrombosis as a clinical problem after pacemaker implantation--case report].  

PubMed

Although transvenous pacing is a safe treatment modality for bradyarrhythmias, serious thrombotic and embolic complications are reported to occur in 0.6-3.5% of cases. We describe a case of pacemaker-associated thrombosis, with an axillary and subclavia veins thrombosis. The patient was treated with subcutaneous heparin which proved successful as the sole treatment. PMID:20712247

Lelakowski, Jacek; Majewski, Jacek; Zabek, Andrzej; Ma?ecka, Barbara; Kuniewicz, Margin; Kafara, Mariusz

2010-07-01

276

Iyengar Yoga Increases Cardiac Parasympathetic Nervous Modulation among Healthy Yoga Practitioners  

Microsoft Academic Search

Relaxation techniques are established in managing of cardiac patients during rehabilitation aiming to reduce future adverse cardiac events. It has been hypothesized that relaxation- training programs may significantly improve cardiac autonomic nervous tone. However, this has not been proven for all available relaxation techniques. We tested this assumption by investigating cardiac vagal modulation during yoga.We examined 11 healthy yoga practitioners

Kerstin Khattab; Ahmed A. Khattab; Jasmin Ortak; Gert Richardt; Hendrik Bonnemeier

2007-01-01

277

Out-of-body experience and auditory and visual hallucinations in a patient with cardiogenic syncope: Crucial role of cardiac event recorder in establishing the diagnosis  

Microsoft Academic Search

Out-of-body experience (OBE) and visual and auditory hallucinations can occur in a variety of medical conditions. We describe a 48-year-old male patient who experienced several paroxysmal events with different combinations of the aforementioned symptoms that could finally be attributed to cardiogenic syncope after subcutaneous implantation of an event recorder and that ceased after implantation of a cardiac pacemaker. Hallucinations and

Christian Brandt; Corinna Kramme; Hermann Storm; Bernd Pohlmann-Eden

2009-01-01

278

Basal cGMP regulates the resting pacemaker potential frequency of cultured mouse colonic interstitial cells of Cajal.  

PubMed

Cyclic guanosine 3',5'-monophosphate (cGMP) inhibited the generation of pacemaker activity in interstitial cells of Cajal (ICCs) from the small intestine. However, cGMP role on pacemaker activity in colonic ICCs has not been reported yet. Thus, we investigated the role of cGMP in pacemaker activity regulation by colonic ICCs. We performed a whole-cell patch-clamp and Ca(2+) imaging in cultured ICCs from mouse colon. 1H-[1,2,4]Oxadiazolo[4,3-a]quinoxalin-1-one (ODQ, an inhibitor of guanylate cyclase) increased the pacemaker potential frequency, whereas zaprinast (an inhibitor of phosphodiesterase) and cell-permeable 8-bromo-cGMP decreased the pacemaker potential frequency. KT-5823 (an inhibitor of protein kinase G [PKG]) did not affect the pacemaker potential. L-N(G)-nitroarginine methyl ester (L-NAME, an inhibitor of nitric oxide [NO] synthase) increased the pacemaker potential frequency, whereas (±)-S-nitroso-N-acetylpenicillamine (SNAP, a NO donor) decreased the pacemaker potential frequency. Glibenclamide (an ATP-sensitive K(+) channel blocker) did not block the effects of cell-permeable 8-bromo-cGMP and SNAP. Recordings of spontaneous intracellular Ca(2+) ([Ca(2+)]i) oscillations revealed that ODQ and L-NAME increased [Ca(2+)]i oscillations. In contrast, zaprinast, 8-bromo cGMP, and SNAP decreased the [Ca(2+)]i oscillations. Basal cGMP levels regulate the resting pacemaker potential frequency by the alteration on Ca(2+) release via a PKG-independent pathway. Additionally, the endogenous release of NO seems to be responsible maintaining basal cGMP levels in colonic ICCs. PMID:24676911

Shahi, Pawan Kumar; Choi, Seok; Jeong, Yu Jin; Park, Chan Guk; So, Insuk; Jun, Jae Yeoul

2014-07-01

279

Specific brainstem neurons switch each other into pacemaker mode to drive movement by activating NMDARs  

PubMed Central

Rhythmic activity is central to brain function. In the vertebrate central nervous system, the neuronal circuits for breathing and locomotion involve inhibition and also neurons acting as pacemakers, but identifying the neurons responsible has proven difficult. By studying simple hatchling Xenopus laevis tadpoles, we have already identified a population of electrically coupled hindbrain neurons (dINs) which drive swimming. During rhythm generation dINs release glutamate to excite each other and activate NMDA receptors (NMDARs). The resulting depolarization enables a network mechanism for swimming rhythm generation which depends on reciprocal inhibition between antagonistic right and left sides. Surprisingly, a surgically isolated hemi-CNS without inhibition can still generate swimming-like rhythms. We have now discovered that activation of NMDARs transforms dINs, which normally fire singly to current injection, into pacemakers firing within the normal swimming frequency range (10-25 Hz). When dIN firing is blocked pharmacologically, this NMDAR activation produces 10 Hz membrane potential oscillations which persist when electrical coupling is blocked but not when the voltage-dependent gating of NMDARs by Mg2+ is removed. The NMDA-induced oscillations and pacemaker firing at swimming frequency are unique to the dIN population and do not occur in other spinal neurons. We conclude that NMDAR-mediated self-resetting switches critical neurons which drive swimming into pacemaker mode only during locomotion where it provides an additional, parallel mechanism for rhythm generation. This allows rhythm generation in a half CNS and raises the possibility that such concealed pacemaker properties may be present underlying rhythm generation in other vertebrate brain networks. PMID:21148000

Li, W.-C.; Roberts, A.; Soffe, S. R.

2010-01-01

280

Are pacemaker properties required for respiratory rhythm generation in adult turtle brain stems in vitro?  

PubMed

The role of pacemaker properties in vertebrate respiratory rhythm generation is not well understood. To address this question from a comparative perspective, brain stems from adult turtles were isolated in vitro, and respiratory motor bursts were recorded on hypoglossal (XII) nerve rootlets. The goal was to test whether burst frequency could be altered by conditions known to alter respiratory pacemaker neuron activity in mammals (e.g., increased bath KCl or blockade of specific inward currents). While bathed in artificial cerebrospinal fluid (aCSF), respiratory burst frequency was not correlated with changes in bath KCl (0.5-10.0 mM). Riluzole (50 microM; persistent Na(+) channel blocker) increased burst frequency by 31 +/- 5% (P < 0.05) and decreased burst amplitude by 42 +/- 4% (P < 0.05). In contrast, flufenamic acid (FFA, 20-500 microM; Ca(2+)-activated cation channel blocker) reduced and abolished burst frequency in a dose- and time-dependent manner (P < 0.05). During synaptic inhibition blockade with bicuculline (50 microM; GABA(A) channel blocker) and strychnine (50 muM; glycine receptor blocker), rhythmic motor activity persisted, and burst frequency was directly correlated with extracellular KCl (0.5-10.0 mM; P = 0.005). During synaptic inhibition blockade, riluzole (50 microM) did not alter burst frequency, whereas FFA (100 microM) abolished burst frequency (P < 0.05). These data are most consistent with the hypothesis that turtle respiratory rhythm generation requires Ca(2+)-activated cation channels but not pacemaker neurons, which thereby favors the group-pacemaker model. During synaptic inhibition blockade, however, the rhythm generator appears to be transformed into a pacemaker-driven network that requires Ca(2+)-activated cation channels. PMID:17522127

Johnson, Stephen M; Wiegel, Liana M; Majewski, David J

2007-08-01

281

CARDIAC MUSCLE  

PubMed Central

With light and electron microscopy a comparison has been made of the morphology of ventricular (V) and Purkinje (P) fibers of the hearts of guinea pig, rabbit, cat, dog, goat, and sheep. The criteria, previously established for the rabbit heart, that V fibers are distinguished from P fibers by the respective presence and absence of transverse tubules is shown to be true for all animals studied. No evidence was found of a permanent connection between the sarcoplasmic reticulum and the extracellular space. The sarcoplasmic reticulum (SR) of V fibers formed couplings with the sarcolemma of a transverse tubule (interior coupling) and with the peripheral sarcolemma (peripheral coupling), whereas in P fibers the SR formed only peripheral couplings. The forms of the couplings were identical. The significance, with respect to excitation-contraction coupling, of the difference in the form of the couplings in cardiac versus skeletal muscle is discussed together with the electrophysiological implications of the differing geometries of bundles of P fibers from different animals. PMID:5645545

Sommer, Joachim R.; Johnson, Edward A.

1968-01-01

282

The Transcriptional Coactivator CAMTA2 Stimulates Cardiac Growth by Opposing  

E-print Network

HDAC5 or HDAC9 develop massively enlarged hearts in response to stress (Zhang et al., 2002; Chang et al by hypertrophic growth and activation of a fetal gene program. In an effort to discover regulators of cardiac, enhanced assembly of contractile units, and reactivation of a fetal cardiac gene program (Seidman

Gleeson, Joseph G.

283

Baf250a orchestrates an epigenetic pathway to repress the Nkx2.5-directed contractile cardiomyocyte program in the sinoatrial node.  

PubMed

The sinoatrial node (SAN) is essential for rhythmic beating of the heart; however, our understanding of what controls proper functioning of the SAN remains primitive. To explore molecular control of SAN function, we specifically deleted Baf250a, a key regulatory component of the ATP-dependent chromatin remodeling complex SWI/SNF, in the SAN. Deletion of Baf250a in the SAN led to sinus bradycardia. Time series analysis of dysregulated genes after deletion of Baf250a reveals a transcriptional hierarchy maintaining pacemaker cell identity, i.e., Baf250a activates the expression of Tbx3, and Baf250a, Tbx3 and histone deacetylase 3 coordinately repress the expression of Nkx2.5. Disruption of this repressive pathway switches on expression of Nkx2.5, which stimulates expression of Gata4 and Tbx5. These three cardiac transcription factors further turn on a contractile cardiomyocyte program in the SAN, which eventually leads to sick sinus disease (SSD). Our study suggests that disruption of key genetic pathways regulating cardiac lineage segregation may cause SSD and cardiac arrhythmias in general. PMID:25145359

Wu, Meng; Peng, Siwu; Yang, Jialiang; Tu, Zhidong; Cai, Xiaoqiang; Cai, Chen-Leng; Wang, Zhong; Zhao, Yong

2014-10-01

284

Baf250a orchestrates an epigenetic pathway to repress the Nkx2.5-directed contractile cardiomyocyte program in the sinoatrial node  

PubMed Central

The sinoatrial node (SAN) is essential for rhythmic beating of the heart; however, our understanding of what controls proper functioning of the SAN remains primitive. To explore molecular control of SAN function, we specifically deleted Baf250a, a key regulatory component of the ATP-dependent chromatin remodeling complex SWI/SNF, in the SAN. Deletion of Baf250a in the SAN led to sinus bradycardia. Time series analysis of dysregulated genes after deletion of Baf250a reveals a transcriptional hierarchy maintaining pacemaker cell identity, i.e., Baf250a activates the expression of Tbx3, and Baf250a, Tbx3 and histone deacetylase 3 coordinately repress the expression of Nkx2.5. Disruption of this repressive pathway switches on expression of Nkx2.5, which stimulates expression of Gata4 and Tbx5. These three cardiac transcription factors further turn on a contractile cardiomyocyte program in the SAN, which eventually leads to sick sinus disease (SSD). Our study suggests that disruption of key genetic pathways regulating cardiac lineage segregation may cause SSD and cardiac arrhythmias in general. PMID:25145359

Wu, Meng; Peng, Siwu; Yang, Jialiang; Tu, Zhidong; Cai, Xiaoqiang; Cai, Chen-Leng; Wang, Zhong; Zhao, Yong

2014-01-01

285

Cardiac Syndrome X  

MedlinePLUS

Related terms: angina, microvascular angina Cardiac syndrome X patients have the pain of angina , but they do not have coronary artery disease ( CAD ). So even though patients with cardiac syndrome X ...

286

5-Hydroxytryptamine Generates Tonic Inward Currents on Pacemaker Activity of Interstitial Cells of Cajal from Mouse Small Intestine  

PubMed Central

In this study we determined whether or not 5-hydroxytryptamine (5-HT) has an effect on the pacemaker activities of interstitial cells of Cajal (ICC) from the mouse small intestine. The actions of 5-HT on pacemaker activities were investigated using a whole-cell patch-clamp technique, intracellular Ca2+ ([Ca2+]i) analysis, and RT-PCR in ICC. Exogenously-treated 5-HT showed tonic inward currents on pacemaker currents in ICC under the voltage-clamp mode in a dose-dependent manner. Based on RT-PCR results, we found the existence of 5-HT2B, 3, 4, and 7 receptors in ICC. However, SDZ 205557 (a 5-HT4 receptor antagonist), SB 269970 (a 5-HT7 receptor antagonist), 3-tropanylindole - 3 - carboxylate methiodide (3-TCM; a 5-HT3 antagonist) blocked the 5-HT-induced action on pacemaker activity, but not SB 204741 (a 5-HT2B receptor antagonist). Based on [Ca2+]i analysis, we found that 5-HT increased the intensity of [Ca2+]i. The treatment of PD 98059 or JNK II inhibitor blocked the 5-HT-induced action on pacemaker activity of ICC, but not SB 203580. In summary, these results suggest that 5-HT can modulate pacemaker activity through 5-HT3, 4, and 7 receptors via [Ca2+]i mobilization and regulation of mitogen-activated protein kinases. PMID:21860590

Shahi, Pawan Kumar; Choi, Seok; Zuo, Dong Chuan; Yeum, Cheol Ho; Yoon, Pyung Jin; Lee, Jun; Kim, Young Dae; Park, Chan Guk; Kim, Man Yoo; Shin, Hye Rang; Oh, Hyun Jung

2011-01-01

287

Genetic Elimination of GABAergic Neurotransmission Reveals Two Distinct Pacemakers for Spontaneous Waves of Activity in the Developing Mouse Cortex  

PubMed Central

Many structures of the mammalian CNS generate propagating waves of electrical activity early in development. These waves are essential to CNS development, mediating a variety of developmental processes, such as axonal outgrowth and pathfinding, synaptogenesis, and the maturation of ion channel and receptor properties. In the mouse cerebral cortex, waves of activity occur between embryonic day 18 and postnatal day 8 and originate in pacemaker circuits in the septal nucleus and the piriform cortex. Here we show that genetic knock-out of the major synthetic enzyme for GABA, GAD67, selectively eliminates the picrotoxin-sensitive fraction of these waves. The waves that remain in the GAD67 knock-out have a much higher probability of propagating into the dorsal neocortex, as do the picrotoxin-resistant fraction of waves in controls. Field potential recordings at the point of wave initiation reveal different electrical signatures for GABAergic and glutamatergic waves. These data indicate that: (1) there are separate GABAergic and glutamatergic pacemaker circuits within the piriform cortex, each of which can initiate waves of activity; (2) the glutamatergic pacemaker initiates waves that preferentially propagate into the neocortex; and (3) the initial appearance of the glutamatergic pacemaker does not require preceding GABAergic waves. In the absence of GAD67, the electrical activity underlying glutamatergic waves shows greatly increased tendency to burst, indicating that GABAergic inputs inhibit the glutamatergic pacemaker, even at stages when GABAergic pacemaker circuitry can itself initiate waves. PMID:24623764

Easton, Curtis R.; Weir, Keiko; Scott, Adina; Moen, Samantha P.; Barger, Zeke; Folch, Albert; Hevner, Robert F.

2014-01-01

288

[Detection and therapy of respiratory dysfunction by implantable (cardiac) devices].  

PubMed

Sleep-disordered breathing (SDB) represents a common comorbidity in cardiac patients. The prevalence of obstructive sleep apnea (OSA) and central sleep apnea (CSA) is very high, particularly in patients with heart rhythm disorders and heart failure (HF). Patients with pacemakers (PM) and implantable defibrillators (ICD) including cardiac resynchronization therapy (CRT) show SDB prevalences up to 75%. However, some modern PM, ICD and CRT devices allow the detection of SDB via transthoracic impedance analysis with high sensitivity compared to polysomnographic (PSG) controls. Thus, this method could be of relevance in screening and monitoring SDB in patients with implantable cardiac devices. Preliminary studies demonstrated the possibility to treat OSA in selected patients by stimulation of the cranial nerves, especially the hypoglossal nerve. However, this requires extensive diagnostics and advanced surgical approaches including many medical disciplines and is not part of this review article. However, unilateral and transvenous stimulation of the phrenic nerve to treat central sleep apnea and Cheyne-Stokes respiration in HF patients in particular can be performed by cardiologists. This article summarizes preliminary data on the results of this promising therapy. PMID:24638158

Fox, H; Oldenburg, O; Nölker, G; Horstkotte, D; Gutleben, K-J

2014-02-01

289

Initial experience with excimer laser-assisted pacemaker and defibrillator lead extraction.  

PubMed

Explantation of chronically implanted pacemaker or defibrillator leads can be technically demanding. We present the results of the first 44 leads extracted with excimer laser sheaths in 25 patients with a median lead implantation time of 7 years (range: 2 to 20 years). Indications for extraction were lead fracture in 17 patients, pocket infection in 4, septicemia in 2, and lead endocarditis in 2 cases. Complete extraction was achieved in 43 leads (97.7%), while the lead tip (<4cm) was abandoned in 1 case. There was no in-hospital mortality. The excimer laser-assisted system is a safe and efficient alternative for pacemaker and defibrillator lead extraction. This technology has resulted in excellent outcomes in our series, allowing us to treat remarkably difficult cases. PMID:24775960

Mosquera, Víctor X; Pérez-Álvarez, Luisa; Ricoy-Martínez, Enrique; Mosquera-Pérez, Ignacio; Castro-Beiras, Alfonso; Cuenca-Castillo, José J

2011-09-01

290

[Initial experience with excimer laser-assisted pacemaker and defibrillator lead extraction].  

PubMed

Explantation of chronically implanted pacemaker or defibrillator leads can be technically demanding. We present the results of the first 44 leads extracted with excimer laser sheaths in 25 patients with a median lead implantation time of 7 years (range: 2 to 20 years). Indications for extraction were lead fracture in 17 patients, pocket infection in 4, septicemia in 2, and lead endocarditis in 2 cases. Complete extraction was achieved in 43 leads (97.7%), while the lead tip (< 4 cm) was abandoned in 1 case. There was no in-hospital mortality. The excimer laser-assisted system is a safe and efficient alternative for pacemaker and defibrillator lead extraction. This technology has resulted in excellent outcomes in our series, allowing us to treat remarkably difficult cases. PMID:21696878

Mosquera, Víctor X; Pérez-Álvarez, Luisa; Ricoy-Martínez, Enrique; Mosquera-Pérez, Ignacio; Castro-Beiras, Alfonso; Cuenca-Castillo, José J

2011-09-01

291

Lack of intestinal pacemaker (C-KIT-positive) cells in infantile hypertrophic pyloric stenosis  

Microsoft Academic Search

The pathogenesis of infantile hypertrophic pyloric stenosis (IHPS) is not well understood. Recent studies have shown that the protooncogene c-kit is essential for the development or maintenance of autonomic gut motility, and also show that the c-kit gene protein product (C-KIT) positive cells in the mammalian gut are responsible for intestinal pacemaker activity. This study examines cells in the pyloric

Atsuyuki Yamataka; Toshio Fujiwara; Yoshifumi Kato; Tadaharu Okazaki; Masakatsu Suhagawa; Takeshi Miyano

1996-01-01

292

Recent innovations in the development of magnetic resonance imaging conditional pacemakers and implantable cardioverter-defibrillators.  

PubMed

The first generation of magnetic resonance conditional pacemakers and implantable cardioverter-defibrillators has finally arrived in clinical practice after many years of development. These devices have been optimized to properly function within magnetic fields of 1.5 T and ensure safe operation in controlled environments. Further progress is needed to develop a new generation of magnetic resonance imaging (MRI) conditional devices that can operate in higher powered MRI machines (3 T) which produce clearer images. PMID:22298178

Lobodzinski, S Suave

2012-01-01

293

Atrial lead malposition in a dual chamber (DDD,M) pacemaker.  

PubMed

A model 7000 pacemaker in the DVI mode emitted two stimuli, the first stimulating the right ventricle and the second 110 ms later. The atrial lead was found in the right ventricular outflow tract. The QRS complex produced by the atrial lead fell after the blanking period, and "committed" the ventricular stimulus 110 ms after the "atrial." Intracardiac electrography during the original implant would have enabled proper atrial lead position. PMID:6641312

Barber, K; Amikam, S; Furman, S

1983-12-01

294

Teaching Cardiac Electrophysiology Modeling to Undergraduate Students: Laboratory Exercises and GPU Programming for the Study of Arrhythmias and Spiral Wave Dynamics  

ERIC Educational Resources Information Center

As part of a 3-wk intersession workshop funded by a National Science Foundation Expeditions in Computing award, 15 undergraduate students from the City University of New York collaborated on a study aimed at characterizing the voltage dynamics and arrhythmogenic behavior of cardiac cells for a broad range of physiologically relevant conditions…

Bartocci, Ezio; Singh, Rupinder; von Stein, Frederick B.; Amedome, Avessie; Caceres, Alan Joseph J.; Castillo, Juan; Closser, Evan; Deards, Gabriel; Goltsev, Andriy; Ines, Roumwelle Sta.; Isbilir, Cem; Marc, Joan K.; Moore, Diquan; Pardi, Dana; Sadhu, Sandeep; Sanchez, Samuel; Sharma, Pooja; Singh, Anoopa; Rogers, Joshua; Wolinetz, Aron; Grosso-Applewhite, Terri; Zhao, Kai; Filipski, Andrew B.; Gilmour, Robert F., Jr.; Grosu, Radu; Glimm, James; Smolka, Scott A.; Cherry, Elizabeth M.; Clarke, Edmund M.; Griffeth, Nancy; Fenton, Flavio H.

2011-01-01

295

Measurement of functional capacity requirements of police officers to aid in development of an occupation-specific cardiac rehabilitation training program  

Microsoft Academic Search

This study was designed to measure the functional capacity of healthy subjects during strenuous simulated police tasks, with the goal of de- veloping occupation-specific training for cardiac rehabilitation of police officers. A calibrated metabolic instrument and an oxygen consumption data collection mask were used to measure the oxygen consumption and heart rates of 30 Dallas Police Academy officers and cadets

Jenny Adams; Jonna Schneider; Matthew Hubbard; Dunlei Cheng; Kay Simms; Julie Hartman; Paul Hinton; Danielle Strauss

2010-01-01

296

Lmo Mutants Reveal a Novel Role for Circadian Pacemaker Neurons in Cocaine-Induced Behaviors  

PubMed Central

Drosophila has been developed recently as a model system to investigate the molecular and neural mechanisms underlying responses to drugs of abuse. Genetic screens for mutants with altered drug-induced behaviors thus provide an unbiased approach to define novel molecules involved in the process. We identified mutations in the Drosophila LIM-only (LMO) gene, encoding a regulator of LIM-homeodomain proteins, in a genetic screen for mutants with altered cocaine sensitivity. Reduced Lmo function increases behavioral responses to cocaine, while Lmo overexpression causes the opposite effect, reduced cocaine responsiveness. Expression of Lmo in the principal Drosophila circadian pacemaker cells, the PDF-expressing ventral lateral neurons (LNvs), is sufficient to confer normal cocaine sensitivity. Consistent with a role for Lmo in LNv function, Lmo mutants also show defects in circadian rhythms of behavior. However, the role for LNvs in modulating cocaine responses is separable from their role as pacemaker neurons: ablation or functional silencing of the LNvs reduces cocaine sensitivity, while loss of the principal circadian neurotransmitter PDF has no effect. Together, these results reveal a novel role for Lmo in modulating acute cocaine sensitivity and circadian locomotor rhythmicity, and add to growing evidence that these behaviors are regulated by shared molecular mechanisms. The finding that the degree of cocaine responsiveness is controlled by the Drosophila pacemaker neurons provides a neuroanatomical basis for this overlap. We propose that Lmo controls the responsiveness of LNvs to cocaine, which in turn regulate the flies' behavioral sensitivity to the drug. PMID:15550987

2004-01-01

297

[Malignant cardiac tumors].  

PubMed

Cardiac neoplasms are a rare occurrence in clinical practice. The various frequencies of primary and secondary malignant tumors vary from report to report, approximately 1% in most autopsy series and 4% in cancer patient's autopsies. Cardiac malignancies account for less 1% of cardiac surgery and about for 0.1% of cardiac echographic studies. The presence of metastatic tumor to the heart usually indicates widespread metastases. Lung carcinomas are the most commonly encountered tumor followed by breast and pancreas cancer and melanoma. Apart from primary pericardial mesothelioma, primary cardiac tumors are high-grade sarcomas with a high metastatic potency that often becomes evident early after surgery. Symptoms are non specific, occur late in the disease and affect few patients; especially secondary neoplasms of the heart take their course so fast that they cannot become symptomatic. The signs of cardiac neoplasms are divided into systemic symptoms (fever, arthralgias and myalgias), cardiac symptoms (congestive heart failure, arrhythmia, chest pain) and uncommon embolisms. Diagnosis is actually made easier with cardiac echography. Cardiac RMI is helpful to estimate vessels and pericardium involvement. Due to its poor prognosis, treatment of cardiac metastases is restricted to best supportive care. For primary cardiac neoplasms, surgery must be carefully discussed because operative intervention is often followed by rapid widespread metastases that adjuvant chemotherapy cannot avoid in most cases. PMID:15899620

Debourdeau, Philippe; Gligorov, Joseph; Teixeira, Luis; Aletti, Marc; Zammit, Christine

2004-11-01

298

Cardiac gated ventilation  

SciTech Connect

There are several theoretic advantages to synchronizing positive pressure breaths with the cardiac cycle, including the potential for improving distribution of pulmonary and myocardial blood flow and enhancing cardiac output. The authors evaluated the effects of synchronizing respiration to the cardiac cycle using a programmable ventilator and electron beam CT (EBCT) scanning. The hearts of anesthetized dogs were imaged during cardiac gated respiration with a 50 msec scan aperture. Multi slice, short axis, dynamic image data sets spanning the apex to base of the left ventricle were evaluated to determine the volume of the left ventricular chamber at end-diastole and end-systole during apnea, systolic and diastolic cardiac gating. The authors observed an increase in cardiac output of up to 30% with inspiration gated to the systolic phase of the cardiac cycle in a non-failing model of the heart.

Hanson, C.W. III [Hospital of the Univ. of Pennsylvania, Philadelphia, PA (United States). Dept. Anesthesia; Hoffman, E.A. [Univ. of Iowa College of Medicine, Iowa City, IA (United States). Div. of Physiologic Imaging

1995-12-31

299

Cardiac gated ventilation  

NASA Astrophysics Data System (ADS)

There are several theoretic advantages to synchronizing positive pressure breaths with the cardiac cycle, including the potential for improving distribution of pulmonary and myocardial blood flow and enhancing cardiac output. We evaluated the effects of synchronizing respiration to the cardiac cycle using a programmable ventilator and electron beam CT (EBCT) scanning. The hearts of anesthetized dogs were imaged during cardiac gated respiration with a 50msec scan aperture. Multislice, short axis, dynamic image data sets spanning the apex to base of the left ventricle were evaluated to determine the volume of the left ventricular chamber at end-diastole and end-systole during apnea, systolic and diastolic cardiac gating. We observed an increase in cardiac output of up to 30% with inspiration gated to the systolic phase of the cardiac cycle in a nonfailing model of the heart.

Hanson, C. William, III; Hoffman, Eric A.

1995-05-01

300

Precision of the pacemaker nucleus in a weakly electric fish: network versus cellular influences.  

PubMed

We investigated the relative influence of cellular and network properties on the extreme spike timing precision observed in the medullary pacemaker nucleus (Pn) of the weakly electric fish Apteronotus leptorhynchus. Of all known biological rhythms, the electric organ discharge of this and related species is the most temporally precise, with a coefficient of variation (CV = standard deviation/mean period) of 2 x 10(-4) and standard deviation (SD) of 0.12-1.0 micros. The timing of the electric organ discharge is commanded by neurons of the Pn, individual cells of which we show in an in vitro preparation to have only a slightly lesser degree of precision. Among the 100-150 Pn neurons, dye injection into a pacemaker cell resulted in dye coupling in one to five other pacemaker cells and one to three relay cells, consistent with previous results. Relay cell fills, however, showed profuse dendrites and contacts never seen before: relay cell dendrites dye-coupled to one to seven pacemaker and one to seven relay cells. Moderate (0.1-10 nA) intracellular current injection had no effect on a neuron's spiking period, and only slightly modulated its spike amplitude, but could reset the spike phase. In contrast, massive hyperpolarizing current injections (15-25 nA) could force the cell to skip spikes. The relative timing of subthreshold and full spikes suggested that at least some pacemaker cells are likely to be intrinsic oscillators. The relative amplitudes of the subthreshold and full spikes gave a lower bound to the gap junctional coupling coefficient of 0.01-0.08. Three drugs, called gap junction blockers for their mode of action in other preparations, caused immediate and substantial reduction in frequency, altered the phase lag between pairs of neurons, and later caused the spike amplitude to drop, without altering the spike timing precision. Thus we conclude that the high precision of the normal Pn rhythm does not require maximal gap junction conductances between neurons that have ordinary cellular precision. Rather, the spiking precision can be explained as an intrinsic cellular property while the gap junctions act to frequency- and phase-lock the network oscillations. PMID:10669509

Moortgat, K T; Bullock, T H; Sejnowski, T J

2000-02-01

301

Ca2+-regulated-cAMP/PKA signaling in cardiac pacemaker cells links ATP supply to demand  

PubMed Central

Rationale In sinoatrial node cells (SANC), Ca2+ activates adenylate cyclase (AC) to generate a high basal level of cAMP-mediated/protein kinase A (PKA)-dependent phosphorylation of Ca2+ cycling proteins. These result in spontaneous sarcoplasmic-reticulum (SR) generated rhythmic Ca2+ oscillations during diastolic depolarization, that not only trigger the surface membrane to generate rhythmic action potentials (APs), but, in a feed-forward manner, also activate AC/PKA signaling. ATP is consumed to pump Ca2+ to the SR, to produce cAMP, to support contraction and to maintain cell ionic homeostasis. Objective Since a negative feedback mechanism links ATP-demand to ATP production, we hypothesized that (1) both basal ATP supply and demand in SANC would be Ca2+-cAMP/PKA dependent; and (2) due to its feed–forward nature, a decrease in flux through the Ca2+-cAMP/PKA signaling axis will reduce the basal ATP production rate. Methods and Results O2 consumption in spontaneous beating SANC was comparable to ventricular myocytes (VM) stimulated at 3 Hz. Graded reduction of basal Ca2+-cAMP/PKA signaling to reduce ATP demand in rabbit SANC produced graded ATP depletion (r2=0.96), and reduced O2 consumption and flavoprotein fluorescence. Neither inhibition of glycolysis, selectively blocking contraction nor specific inhibition of mitochondrial Ca2+ flux reduced the ATP level. Conclusions Feed-forward basal Ca2+-cAMP/PKA signaling both consumes ATP to drive spontaneous APs in SANC and is tightly linked to mitochondrial ATP production. Interfering with Ca2+-cAMP/PKA signaling not only slows the firing rate and reduces ATP consumption, but also appears to reduce ATP production so that ATP levels fall. This distinctly differs from VM, which lack this feed-forward basal cAMP/PKA signaling, and in which ATP level remains constant when the demand changes. PMID:21835182

Yaniv, Yael; Juhaszova, Magdalena; Lyashkov, Alexey E.; Spurgeon, Harold A.; Sollott, Steven J.; Lakatta, Edward G.

2011-01-01

302

Review of radiation safety in the cardiac catheterization laboratory  

SciTech Connect

With the increasing use of coronary arteriography and interventional procedures, radiation exposure to patients and personnel working in cardiac catheterization laboratories has increased. Proper technique to minimize both patient and operator exposure is necessary. A practical approach to radiation safety in the cardiac catheterization laboratory is presented. This discussion should be useful to facilities with well-established radiation safety programs as well as facilities that require restructuring to cope with the radiation environment in a modern cardiac catheterization laboratory.

Johnson, L.W.; Moore, R.J.; Balter, S. (St. Joseph's Hospital Health Center, Syracuse, NY (United States))

1992-03-01

303

Cardiac rehabilitation in the elderly.  

PubMed

Coronary heart disease (CHD) is the leading cause of death worldwide. Advanced age is associated with a higher prevalence of CHD as well as increased morbidity and mortality. One key vulnerability relates to the fact that older individuals are generally among the least fit, least active cohort and at increased risk of complications after an acute cardiac event and/or major surgery. There is ample evidence to demonstrate the beneficial effects of exercised-based cardiac rehabilitation (CR) programs on improving functional capacity and other indices of cardiovascular (CV) health. Although the predominant number of studies is in middle-aged patients, there is an escalating amount of new information that establishes the cardioprotective role of CR and, in particular, structured exercise therapy (ET) among the elderly. The present review summarizes the current data available regarding CR and ET and its salutary impact on today's growing population of older adults with CHD. PMID:25216614

Menezes, Arthur R; Lavie, Carl J; Forman, Daniel E; Arena, Ross; Milani, Richard V; Franklin, Barry A

2014-01-01

304

Mauthner Cell-Initiated Electromotor Behavior Is Mediated via NMDA and Metabotropic Glutamatergic Receptors on Medullary Pacemaker Neurons in a Gymnotid Fish  

Microsoft Academic Search

Weakly electric fish generate meaningful electromotor behav- iors by specific modulations of the discharge of their medullary pacemaker nucleus from which the rhythmic command for each electric organ discharge (EOD) arises. Certain electromo- tor behaviors seem to involve the activation of specific neuro- transmitter receptors on particular target cells within the nu- cleus, i.e., on pacemaker or on relay cells.

Sebastian Curti; Atilio Falconi; Francisco R. Morales; Michel Borde

1999-01-01

305

Surgical management of superior vena cava syndrome following pacemaker lead infection: a case report and review of the literature.  

PubMed

Superior vena cava (SVC) syndrome is a known but rare complication of pacemaker lead implantation, accounting for approximately less than 0.5% of cases. Its pathophysiology is due to either infection or endothelial mechanical stress, causing inflammation and fibrosis leading to thrombosis, and therefore stenosis of the SVC. Due to the various risks including thrombo-embolic complications and the need to provide symptomatic relief, medical and surgical interventions are sought early. We present the case of a 48-year Caucasian male who presented with localised swelling and pain at the site of pacemaker implantation. Inflammatory markers were normal, but diagnostic imaging revealed three masses along the pacemaker lead passage. A surgical approach using cardiopulmonary bypass and circulatory arrest was used to remove the vegetations. Culture from the vegetations showed Staphylococcus epidermidis. The technique presented here allowed for safe and effective removal of both the thrombus and infected pacing leads, with excellent exposure and minimal post-procedure complications. PMID:24947452

Kokotsakis, John; Chaudhry, Umar A R; Tassopoulos, Dimitris; Harling, Leanne; Ashrafian, Hutan; Vernandos, Michail; Kanakis, Meletis; Athanasiou, Thanos

2014-01-01

306

Surgical management of superior vena cava syndrome following pacemaker lead infection: a case report and review of the literature  

PubMed Central

Superior vena cava (SVC) syndrome is a known but rare complication of pacemaker lead implantation, accounting for approximately less than 0.5% of cases. Its pathophysiology is due to either infection or endothelial mechanical stress, causing inflammation and fibrosis leading to thrombosis, and therefore stenosis of the SVC. Due to the various risks including thrombo-embolic complications and the need to provide symptomatic relief, medical and surgical interventions are sought early. We present the case of a 48-year Caucasian male who presented with localised swelling and pain at the site of pacemaker implantation. Inflammatory markers were normal, but diagnostic imaging revealed three masses along the pacemaker lead passage. A surgical approach using cardiopulmonary bypass and circulatory arrest was used to remove the vegetations. Culture from the vegetations showed Staphylococcus epidermidis. The technique presented here allowed for safe and effective removal of both the thrombus and infected pacing leads, with excellent exposure and minimal post-procedure complications. PMID:24947452

2014-01-01

307

VDD single pass lead pacing: sustained pacemaker mediated tachycardias unrelated to retrograde atrial activation.  

PubMed

Pacemaker mediated tachycardias (PMTs) are a well known complication of P synchronous pacing. Although the initiating mechanisms are several, all of them are associated with retrograde atrial activation, which is sensed by the atrial sensing channel, resulting in ventricular pacing. In 19 patients suffering from symptomatic AV conduction disturbances and normal sinus node function, a VDD pacing system connected to a single pass ventricular lead with dual chamber electrodes was implanted. The bipolar atrial electrode, floating in the right atrium, was used to detect endocardial atrial electrograms that were differentially processed within the pacemaker for optimal discrimination and filtering of undesirable signals. The widely programmable atrial sensitivity (amplitude and filtering) allowed stable P synchronized ventricular pacing in all patients, but in five of them, sustained PMTs not related to retrograde atrial activation was documented during the follow-up. The common mechanism for the onset and maintenance of these PMTs was traced to the abnormal sensing of the terminal forces of ventricular activation and/or of the T wave. The possibility of interferences between ventricular and atrial electrodes (crosstalk) was also considered. The reduction of atrial channel sensitivity represented in all cases the only effective procedure to prevent this type of PMT. In conclusion, the bet signal to noise ratio is an important endpoint to assure the proper function of a single lead VDD pacing system. Furthermore, using the differential amplifier built within the pacemaker, consideration should be given to the optimal mode of rejection of the terminal forces of the QRS and T wave. PMID:1279569

Sermasi, S; Marconi, M

1992-11-01

308

Sensitivity of the human circadian pacemaker to nocturnal light: melatonin phase resetting and suppression  

NASA Technical Reports Server (NTRS)

Ocular exposure to early morning room light can significantly advance the timing of the human circadian pacemaker. The resetting response to such light has a non-linear relationship to illuminance. The dose-response relationship of the human circadian pacemaker to late evening light of dim to moderate intensity has not been well established. Twenty-three healthy young male and female volunteers took part in a 9 day protocol in which a single experimental light exposure6.5 h in duration was given in the early biological night. The effects of the light exposure on the endogenous circadian phase of the melatonin rhythm and the acute effects of the light exposure on plasma melatonin concentration were calculated. We demonstrate that humans are highly responsive to the phase-delaying effects of light during the early biological night and that both the phase resetting response to light and the acute suppressive effects of light on plasma melatonin follow a logistic dose-response curve, as do many circadian responses to light in mammals. Contrary to expectations, we found that half of the maximal phase-delaying response achieved in response to a single episode of evening bright light ( approximately 9000 lux (lx)) can be obtained with just over 1 % of this light (dim room light of approximately 100 lx). The same held true for the acute suppressive effects of light on plasma melatonin concentrations. This indicates that even small changes in ordinary light exposure during the late evening hours can significantly affect both plasma melatonin concentrations and the entrained phase of the human circadian pacemaker.

Zeitzer, J. M.; Dijk, D. J.; Kronauer, R.; Brown, E.; Czeisler, C.

2000-01-01

309

The emergence of subcellular pacemaker sites for calcium waves and oscillations  

PubMed Central

Calcium (Ca2+) waves generating oscillatory Ca2+ signals are widely observed in biological cells. Experimental studies have shown that under certain conditions, initiation of Ca2+ waves is random in space and time, while under other conditions, waves occur repetitively from preferred locations (pacemaker sites) from which they entrain the whole cell. In this study, we use computer simulations to investigate the self-organization of Ca2+ sparks into pacemaker sites generating Ca2+ oscillations. In both ventricular myocyte experiments and computer simulations of a heterogeneous Ca2+ release unit (CRU) network model, we show that Ca2+ waves occur randomly in space and time when the Ca2+ level is low, but as the Ca2+ level increases, waves occur repetitively from the same sites. Our analysis indicates that this transition to entrainment can be attributed to the fact that random Ca2+ sparks self-organize into Ca2+ oscillations differently at low and high Ca2+ levels. At low Ca2+, the whole cell Ca2+ oscillation frequency of the coupled CRU system is much slower than that of an isolated single CRU. Compared to a single CRU, the distribution of interspike intervals (ISIs) of the coupled CRU network exhibits a greater variation, and its ISI distribution is asymmetric with respect to the peak, exhibiting a fat tail. At high Ca2+, however, the coupled CRU network has a faster frequency and lesser ISI variation compared to an individual CRU. The ISI distribution of the coupled network no longer exhibits a fat tail and is well-approximated by a Gaussian distribution. This same Ca2+ oscillation behaviour can also be achieved by varying the number of ryanodine receptors per CRU or the distance between CRUs. Using these results, we develop a theory for the entrainment of random oscillators which provides a unified explanation for the experimental observations underlying the emergence of pacemaker sites and Ca2+ oscillations. PMID:24042497

Nivala, Michael; Ko, Christopher Y; Nivala, Melissa; Weiss, James N; Qu, Zhilin

2013-01-01

310

The emergence of subcellular pacemaker sites for calcium waves and oscillations.  

PubMed

Calcium (Ca(2+)) waves generating oscillatory Ca(2+) signals are widely observed in biological cells. Experimental studies have shown that under certain conditions, initiation of Ca(2+) waves is random in space and time, while under other conditions, waves occur repetitively from preferred locations (pacemaker sites) from which they entrain the whole cell. In this study, we use computer simulations to investigate the self-organization of Ca(2+) sparks into pacemaker sites generating Ca(2+) oscillations. In both ventricular myocyte experiments and computer simulations of a heterogeneous Ca(2+) release unit (CRU) network model, we show that Ca(2+) waves occur randomly in space and time when the Ca(2+) level is low, but as the Ca(2+) level increases, waves occur repetitively from the same sites. Our analysis indicates that this transition to entrainment can be attributed to the fact that random Ca(2+) sparks self-organize into Ca(2+) oscillations differently at low and high Ca(2+) levels. At low Ca(2+), the whole cell Ca(2+) oscillation frequency of the coupled CRU system is much slower than that of an isolated single CRU. Compared to a single CRU, the distribution of interspike intervals (ISIs) of the coupled CRU network exhibits a greater variation, and its ISI distribution is asymmetric with respect to the peak, exhibiting a fat tail. At high Ca(2+), however, the coupled CRU network has a faster frequency and lesser ISI variation compared to an individual CRU. The ISI distribution of the coupled network no longer exhibits a fat tail and is well-approximated by a Gaussian distribution. This same Ca(2+) oscillation behaviour can also be achieved by varying the number of ryanodine receptors per CRU or the distance between CRUs. Using these results, we develop a theory for the entrainment of random oscillators which provides a unified explanation for the experimental observations underlying the emergence of pacemaker sites and Ca(2+) oscillations. PMID:24042497

Nivala, Michael; Ko, Christopher Y; Nivala, Melissa; Weiss, James N; Qu, Zhilin

2013-11-01

311

Beam Profile Disturbances from Implantable Pacemakers or Implantable Cardioverter-Defibrillator Interactions  

SciTech Connect

The medical community is advocating for progressive improvement in the design of implantable cardioverter-defibrillators and implantable pacemakers to accommodate elevations in dose limitation criteria. With advancement already made for magnetic resonance imaging compatibility in some, a greater need is present to inform the radiation oncologist and medical physicist regarding treatment planning beam profile changes when such devices are in the field of a therapeutic radiation beam. Treatment plan modeling was conducted to simulate effects induced by Medtronic, Inc.-manufactured devices on therapeutic radiation beams. As a continuation of grant-supported research, we show that radial and transverse open beam profiles of a medical accelerator were altered when compared with profiles resulting when implantable pacemakers and cardioverter-defibrillators are placed directly in the beam. Results are markedly different between the 2 devices in the axial plane and the sagittal planes. Vast differences are also presented for the therapeutic beams at 6-MV and 18-MV x-ray energies. Maximum changes in percentage depth dose are observed for the implantable cardioverter-defibrillator as 9.3% at 6 MV and 10.1% at 18 MV, with worst distance to agreement of isodose lines at 2.3 cm and 1.3 cm, respectively. For the implantable pacemaker, the maximum changes in percentage depth dose were observed as 10.7% at 6 MV and 6.9% at 18 MV, with worst distance to agreement of isodose lines at 2.5 cm and 1.9 cm, respectively. No differences were discernible for the defibrillation leads and the pacing lead.

Gossman, Michael S., E-mail: mgossman@tsrcc.com [Tri-State Regional Cancer Center, Medical Physics Section, Ashland, KY (United States); Comprehensive Heart and Vascular Associates, Heart and Vascular Center, Ashland, KY (United States); Medtronic, Inc., External Research Program, Mounds View, MN (United States); Nagra, Bipinpreet; Graves-Calhoun, Alison; Wilkinson, Jeffrey [Tri-State Regional Cancer Center, Medical Physics Section, Ashland, KY (United States); Comprehensive Heart and Vascular Associates, Heart and Vascular Center, Ashland, KY (United States); Medtronic, Inc., External Research Program, Mounds View, MN (United States)

2011-01-01

312

Entrainment of the human circadian pacemaker to longer-than-24-h days  

PubMed Central

Entrainment of the circadian pacemaker to the light:dark cycle is necessary for rhythmic physiological functions to be appropriately timed over the 24-h day. Nonentrainment results in sleep, endocrine, and neurobehavioral impairments. Exposures to intermittent bright light pulses have been reported to phase shift the circadian pacemaker with great efficacy. Therefore, we tested the hypothesis that a modulated light exposure (MLE) with bright light pulses in the evening would entrain subjects to a light:dark cycle 1 h longer than their own circadian period (?). Twelve subjects underwent a 65-day inpatient study. Individual subject's circadian period was determined in a forced desynchrony protocol. Subsequently, subjects were released into 30 longer-than-24-h days (daylength of ? + 1 h) in one of three light:dark conditions: (i) ?25 lux; (ii) ?100 lux; and (iii) MLE: ?25 lux followed by ?100 lux, plus two 45-min bright light pulses of ?9,500 lux near the end of scheduled wakefulness. We found that lighting levels of ?25 lux were insufficient to entrain all subjects tested. Exposure to ?100 lux was sufficient to entrain subjects, although at a significantly wider phase angle compared with baseline. Exposure to MLE was able to entrain the subjects to the imposed sleep–wake cycles but at a phase angle comparable to baseline. These results suggest that MLE can be used to entrain the circadian pacemaker to non-24-h days. The implications of these findings are important because they could be used to treat circadian misalignment associated with space flight and circadian rhythm sleep disorders such as shift-work disorder. PMID:17502598

Gronfier, Claude; Wright, Kenneth P.; Kronauer, Richard E.; Czeisler, Charles A.

2007-01-01

313

Hypoxia-activated Ca2+ currents in pacemaker neurones of rat rostral ventrolateral medulla in vitro.  

PubMed Central

We examined the effects of brief periods of hypoxia or application of cyanide on the discharge and membrane properties of medullary pacemaker neurones in slices of the rostral ventrolateral reticular nucleus (RVL) of the medulla oblongata of rats. Stable intracellular recordings were obtained from seventy-nine neurones within the RVL which exhibited spontaneous rhythmic discharge in the absence of excitatory postsynaptic potentials (EPSPs). The membrane potential cycles of these neurones could be reset with an evoked spike without eliciting EPSPs or inhibitory postsynaptic potentials and hence met criteria of RVL pacemaker neurones. Hypoxia, produced by reducing O2 from 95 to 20% for 40 s or exposure to cyanide (30-300 microM for 40 s), reversibly increased neuronal discharge 1.6-fold (20% O2) or 2.6-fold (300 microM cyanide), respectively, in association with membrane depolarization and a significant fall in membrane resistance. The membrane responses to hypoxia and cyanide were observed in the presence of tetrodotoxin (TTX) at a concentration (10 microM) which eliminated spontaneous spikes or spikes evoked by intracellular depolarization. When recorded at a holding potential of -70 mV by single-electrode voltage clamp, hypoxia or cyanide (300 microM) elicited inward currents of 0.44 +/- 0.06 and 0.58 +/- 0.08 nA, respectively, which are attenuated by reducing the concentration of extracellular Ca2+ ions, and abolished by 2 mM CoCl2 and 100 microM NiCl2, but not affected by 50 microM CdCl2, replacement of 83% extracellular Na+, or adenosine deaminase (2U ml-1). We conclude that hypoxia and cyanide directly excite RVL pacemaker neurones in vitro by a common mechanism: activation of Ca2+ channel conductance. Images Figure 5 PMID:8046626

Sun, M K; Reis, D J

1994-01-01

314

Ethnocultural diversity in cardiac rehabilitation.  

PubMed

Cardiovascular disease is the leading cause of death globally. Despite a greater burden of disease, ethnocultural minorities in both the United States and Canada are significantly less likely to access cardiac rehabilitation (CR). Without equitable access to CR, these patients may be more likely to experience recurrent cardiac events and unnecessarily premature death. In this article, the current state of ethnocultural diversity in CR patients and unique barriers that ethnocultural minority patients face are reviewed. Strategies for CR program delivery and diversity of CR program staff are considered. Guidance on ethnocultural considerations in American and Canadian associations of CR is also reviewed. Lower rates of access to CR are seen among ethnocultural minorities in both American and Canadian CR programs. Only 2 studies evaluating ethnoculturally tailored CR could be identified in the literature. American CR staff are predominantly white (?96%), whereas ethnocultural data are not collected from Canadian CR professionals. American guidelines emphasize the importance of ethnocultural competency. Meanwhile, Canadian guidelines underscore the low use of CR services among ethnocultural minorities, and support ethnoculturally informed CR delivery. The American and Canadian populations are rapidly diversifying, yet the CR workforce is not, and ethnocultural minorities continue to be underrepresented in our programs. Although recent CR guidelines have made some preliminary recommendations to overcome these discrepancies, more focused efforts are needed. Thirteen points of action are proposed for the CR community with the goal of promoting the development and delivery of more ethnoculturally sensitive CR services. PMID:25357126

Midence, Liz; Mola, Ana; Terzic, Carmen M; Thomas, Randal J; Grace, Sherry L

2014-01-01

315

Endovascular management of multiple arteriovenous fistulae following failed laser-assisted pacemaker lead extraction.  

PubMed

A woman presented for evaluation of new-onset left arm edema after failed laser-assisted pacemaker lead extraction. Initial workup demonstrated a left subclavian artery to vein arteriovenous fistula (AVF). She underwent repair of the AVF with placement of a covered stent in the subclavian artery, however, her symptoms did not completely resolve. Investigation revealed a left common carotid artery to left innominate vein AVF, which was repaired by deploying a covered stent retrograde into the left common carotid artery. Her symptoms subsequently resolved. Multiple iatrogenic AVF can be repaired endovascularly, however, a high degree of suspicion for multiple injuries should be maintained. PMID:20304582

O'Connor, David J; Gross, Jay; King, Brian; Suggs, William D; Gargiulo, Nicholas J; Lipsitz, Evan C

2010-06-01

316

Corrosion and degradation of a polyurethane/Co-Ni-Cr-Mo pacemaker lead.  

PubMed

An investigation to study changes in the metal surfaces and the polyurethane insulation of heart pacemaker leads under controlled in vitro conditions was conducted. A polyurethane (Pellethane 2363-80A)/Co-Ni-Cr-Mo (MP35N) wire lead was exposed in Hanks' physiological saline solution for 14 months and then analyzed using scanning electron microscopy, x-ray energy dispersive analysis, and small angle x-ray scattering. Results showed that some leakage of solution into the lead had occurred and changes were present on both the metal and the polyurethane surfaces. PMID:3429467

Sung, P; Fraker, A C

1987-12-01

317

Implantation strategy of the atrial dipole impacts atrial sensing performance of single lead VDD pacemakers.  

PubMed

Intermittent atrial undersensing is observed in a considerable percentage of patients with single lead VDD pacemakers. Analyzing the 2-year data of the Saphir Multicenter Follow-Up Study, the authors investigated predictors for the occurrence of undersensing. The study included 194 patients with high degree AV block who received a VDD pacemaker system with an identical sensing amplifier. Placement strategy of the atrial dipole was left to the discretion of the implanting physician. At the final position, atrial potential amplitudes were measured during deep and shallow respiration. Atrial dipole position was determined by intraoperativefluoroscopy subdividing the right atrium in a high, mid, and low portion. Undersensing was defined by evidence of at least one not sensed P wave during Holter monitoring or exercise testing and by the presence of 0.1-0.2 mV amplitudes in the P wave amplitude histogram of the pacemaker. Incidence of undersensing was 25.8%; 9.3% of patients showed frequent (> 5%) or symptomatic undersensing. Patients with undersensing were older (76.6 +/- 10.6 vs 64.2 +/- 14.8 years), showed a lower minimum of intraoperative atrial potential amplitude (P(min) 0.86 +/- 0.64 vs 1.43 +/- 0.77 mV), a wider range of potential amplitude (deltaP 1.71 +/- 1.44 vs 0.94 +/- 0.84 mV), and a higher incidence of dipole placement in the low right atrium (50.0% vs 11.1 %, P < 0.001 for all comparisons). In a multivariate regression analysis, patient age > 66 years, Pmin < 0.6 mV, > 1.3 mV and atrial dipol placement in the lowright atrium were independently predictive for undersensing. Minimal atrialpotential amplitude, range of potential amplitude, and atrial dipole position influence atrial sensing performance in single lead VDD pacing. Thus, implantation guidelines should reflect these rules to improve the outcome of VDD pacemaker recipients. PMID:11990661

Wiegand, Uwe K H; Nowak, Bernd; Reisp, Udo; Peiffer, Torsten; Bode, Frank; Potratz, Jürgen

2002-03-01

318

Bilateral central vein stenosis in a dialysis patient with a pacemaker.  

PubMed

Central vein stenosis is not uncommon in hemodialysis-dependent patients as a result of mechanical damage to the vessel walls from prior cannulation. It can cause ipsilateral upper limb swelling and pain, resulting in suboptimal hemodialysis. It is unfortunate for bilateral central vein stenosis to develop concomitantly, and rare in the setting of an in-situ pacemaker. This case illustrates the successful ligation of a nondependent left arteriovenous fistula and stenting of the right subclavian vein with functioning ipsilateral arteriovenous fistula, to overcome the problem of symptomatic bilateral upper limb swelling. PMID:24887840

Yew, Kuan Leong; Anderson, Steven; Farah, Razali; Lim, Siong Hee

2014-10-01

319

Arrhythmias, Sudden Cardiac Death and incapacitation of pilots  

PubMed Central

Inflight medical emergencies occur at a rate of 20 to 100 per million passengers, with a death rate of 0.1 to 1 per million. Cardiac, neurologic, and respiratory complaints comprise the more serious emergencies, as defined by aircraft diversion or use of ground-based medical assistance. In this paper, we review changes seen in the resting electrocardiogram in normal individuals exposed to high altitude, alongside important implications for patients with heart diseases in high altitude exposures and the possible effects of high altitude to permanent cardiac pacemakers. Arrhythmias in pilots and public safety are revisited together with the guidelines of the Joint Aviation Requirements (JAR) in Europe. The situation of Military flights is also discussed. Physicians ought to become knowledgeable about the specific medical job standards for their patients when asked to render opinions regarding fitness to fly. A database must be established to obtain prospective data that defines the risk of accidents in patients who are or were being treated for arrhythmias. Current guidelines could then be updated and revised as appropriate. PMID:19050752

Mantziari, L; Styliadis, C; Kourtidou-Papadeli, C; Styliadis, I

2008-01-01

320

Sudden cardiac death  

Microsoft Academic Search

The rate of cardiac deaths that are sudden is approximately 50%, and decreases with age. The causes of sudden cardiac death are diverse, and are a function of age. In children and adolescents, coronary anomalies, hypertrophic cardiomyopathy and myocarditis are frequent substrates for lethal arrhythmias; in adults, coronary atherosclerosis and acquired forms of cardiomyopathy are the most common findings at

Renu Virmani; Allen P Burke; Andrew Farb

2001-01-01

321

Hybrid Pediatric Cardiac Surgery  

Microsoft Academic Search

Minimally invasive strategies can be expanded by combining standard surgical and interventional techniques. We performed a longitudinal prospective study of all pediatric patients who have undergone hybrid cardiac surgery at the University of Chicago Children's Hospital. Hybrid cardiac surgery was defined as combined catheter-based and surgical interventions in either one setting or in a planned sequential fashion within 24 hours.

E. A. Bacha; Z. M. Hijazi; Q. L. Cao; R. Abdulla; J. P. Starr; J. Quinones; P. Koenig; B. Agarwala

2005-01-01

322

Functional cardiac tissue engineering  

PubMed Central

Heart attack remains the leading cause of death in both men and women worldwide. Stem cell-based therapies, including the use of engineered cardiac tissues, have the potential to treat the massive cell loss and pathological remodeling resulting from heart attack. Specifically, embryonic and induced pluripotent stem cells are a promising source for generation of therapeutically relevant numbers of functional cardiomyocytes and engineering of cardiac tissues in vitro. This review will describe methodologies for successful differentiation of pluripotent stem cells towards the cardiovascular cell lineages as they pertain to the field of cardiac tissue engineering. The emphasis will be placed on comparing the functional maturation in engineered cardiac tissues and developing heart and on methods to quantify cardiac electrical and mechanical function at different spatial scales. PMID:22397609

Liau, Brian; Zhang, Donghui; Bursac, Nenad

2013-01-01

323

Intrinsically Active and Pacemaker Neurons in Pluripotent Stem Cell-Derived Neuronal Populations  

PubMed Central

Summary Neurons generated from pluripotent stem cells (PSCs) self-organize into functional neuronal assemblies in vitro, generating synchronous network activities. Intriguingly, PSC-derived neuronal assemblies develop spontaneous activities that are independent of external stimulation, suggesting the presence of thus far undetected intrinsically active neurons (IANs). Here, by using mouse embryonic stem cells, we provide evidence for the existence of IANs in PSC-neuronal networks based on extracellular multielectrode array and intracellular patch-clamp recordings. IANs remain active after pharmacological inhibition of fast synaptic communication and possess intrinsic mechanisms required for autonomous neuronal activity. PSC-derived IANs are functionally integrated in PSC-neuronal populations, contribute to synchronous network bursting, and exhibit pacemaker properties. The intrinsic activity and pacemaker properties of the neuronal subpopulation identified herein may be particularly relevant for interventions involving transplantation of neural tissues. IANs may be a key element in the regulation of the functional activity of grafted as well as preexisting host neuronal networks. PMID:24672755

Illes, Sebastian; Jakab, Martin; Beyer, Felix; Gelfert, Renate; Couillard-Despres, Sebastien; Schnitzler, Alfons; Ritter, Markus; Aigner, Ludwig

2014-01-01

324

Drosophila ATF-2 regulates sleep and locomotor activity in pacemaker neurons.  

PubMed

Stress-activated protein kinases such as p38 regulate the activity of transcription factor ATF-2. However, the physiological role of ATF-2, especially in the brain, is unknown. Here, we found that Drosophila melanogaster ATF-2 (dATF-2) is expressed in large ventral lateral neurons (l-LN(v)s) and also, to a much lesser extent, in small ventral lateral neurons, the pacemaker neurons. Only l-LN(v)s were stained with the antibody that specifically recognizes phosphorylated dATF-2, suggesting that dATF-2 is activated specifically in l-LN(v)s. The knockdown of dATF-2 in pacemaker neurons using RNA interference decreased sleep time, whereas the ectopic expression of dATF-2 increased sleep time. dATF-2 knockdown decreased the length of sleep bouts but not the number of bouts. The ATF-2 level also affected the sleep rebound after sleep deprivation and the arousal threshold. dATF-2 negatively regulated locomotor activity, although it did not affect the circadian locomotor rhythm. The degree of dATF-2 phosphorylation was greater in the morning than at night and was enhanced by forced locomotion via the dp38 pathway. Thus, dATF-2 is activated by the locomotor while it increases sleep, suggesting a role for dATF-2 as a regulator to connect sleep with locomotion. PMID:18694958

Shimizu, Hideyuki; Shimoda, Masami; Yamaguchi, Terumi; Seong, Ki-Hyeon; Okamura, Tomoo; Ishii, Shunsuke

2008-10-01

325

Three-dimensional autonomous pacemaker in the photosensitive Belousov-Zhabotinsky medium  

NASA Astrophysics Data System (ADS)

In experiments with the photosensitive Belousov-Zhabotinsky reaction (PBZR) we found a stable three-dimensional organizing center that periodically emits trigger waves of chemical concentration. The experiments are performed in a parameter regime with negative line tension using an open gel reactor to maintain stationary non-equilibrium conditions. The observed periodic wave source is formed by a scroll ring stabilized due to its interaction with a no-flux boundary. Sufficiently far from the boundary, the scroll ring expands and undergoes the negative line tension instability before it finally develops into scroll wave turbulence. Our experimental results are reproduced by numerical integration of the modified Oregonator model for the PBZR. Stationary and breathing self-organized pacemakers have been found in these numerical simulations. In the latter case, both the radius of the scroll ring and the distance of its filament plane to the no-flux boundary after some transient undergo undamped stable limit cycle oscillations. So far, contrary to their stationary counterpart, the numerically predicted breathing autonomous pacemaker has not been observed in the chemical experiment.

Azhand, A.; Totz, J. F.; Engel, H.

2014-10-01

326

Responses of a bursting pacemaker to excitation reveal spatial segregation between bursting and spiking mechanisms  

PubMed Central

Central pattern generators (CPGs) frequently include bursting neurons that serve as pacemakers for rhythm generation. Phase resetting curves (PRCs) can provide insight into mechanisms underlying phase locking in such circuits. PRCs were constructed for a pacemaker bursting complex in the pyloric circuit in the stomatogastric ganglion of the lobster and crab. This complex is comprised of the Anterior Burster (AB) neuron and two Pyloric Dilator (PD) neurons that are all electrically coupled. Artificial excitatory synaptic conductance pulses of different strengths and durations were injected into one of the AB or PD somata using the Dynamic Clamp. Previously, we characterized the inhibitory PRCs by assuming a single slow process that enabled synaptic inputs to trigger switches between an up state in which spiking occurs and a down state in which it does not. Excitation produced five different PRC shapes, which could not be explained with such a simple model. A separate dendritic compartment was required to separate the mechanism that generates the up and down phases of the bursting envelope (1) from synaptic inputs applied at the soma, (2) from axonal spike generation and (3) from a slow process with a slower time scale than burst generation. This study reveals that due to the nonlinear properties and compartmentalization of ionic channels, the response to excitation is more complex than inhibition. PMID:21360137

Maran, Selva K; Sieling, Fred H; Demla, Kavita; Prinz, Astrid A; Canavier, Carmen C

2011-01-01

327

Time and memory: towards a pacemaker-free theory of interval timing.  

PubMed Central

A popular view of interval timing in animals is that it is driven by a discrete pacemaker-accumulator mechanism that yields a linear scale for encoded time. But these mechanisms are fundamentally at odds with the Weber law property of interval timing, and experiments that support linear encoded time can be interpreted in other ways. We argue that the dominant pacemaker-accumulator theory, scalar expectancy theory (SET), fails to explain some basic properties of operant behavior on interval-timing procedures and can only accommodate a number of discrepancies by modifications and elaborations that raise questions about the entire theory. We propose an alternative that is based on principles of memory dynamics derived from the multiple-time-scale (MTS) model of habituation. The MTS timing model can account for data from a wide variety of time-related experiments: proportional and Weber law temporal discrimination, transient as well as persistent effects of reinforcement omission and reinforcement magnitude, bisection, the discrimination of relative as well as absolute duration, and the choose-short effect and its analogue in number-discrimination experiments. Resemblances between timing and counting are an automatic consequence of the model. We also argue that the transient and persistent effects of drugs on time estimates can be interpreted as well within MTS theory as in SET. Recent real-time physiological data conform in surprising detail to the assumptions of the MTS habituation model. Comparisons between the two views suggest a number of novel experiments. PMID:10220931

Staddon, J E; Higa, J J

1999-01-01

328

Drosophila TRPA1 functions in temperature control of circadian rhythm in pacemaker neurons  

PubMed Central

Most animals from flies to humans count on circadian clocks to synchronize their physiology and behaviors. Daily light cycles are well-known environmental cues for setting circadian rhythms. Warmer and cooler temperatures that mimic day and night are also effective in entraining circadian activity in most animals. Even vertebrate organisms can be induced to show circadian responses through exposure to temperature cycles. In poikilothermic animals such as Drosophila, temperature differences of only 2–3°C are sufficient to synchronize locomotor rhythms. However, the molecular sensors that participate in temperature regulation of circadian activity in fruit flies or other animals are enigmatic. It is also unclear whether such detectors are limited to the periphery or may be in the central brain. Here, we showed that Drosophila TRPA1 (Transient Receptor Potential Cation Channel A1) was necessary for normal activity patterns during temperature cycles. The trpA1 gene was expressed in a subset of pacemaker neurons in the central brain. In response to temperature entrainment, loss of trpA1 impaired activity, and altered expression of the circadian clock protein Period (Per) in a subset of pacemaker neurons. These findings underscore a role for a thermoTRP in temperature regulation that extends beyond avoidance of noxious or suboptimal temperatures. PMID:23595730

Lee, Youngseok; Montell, Craig

2013-01-01

329

High resolution mechanical function in the intact porcine heart: mechanical effects of pacemaker location.  

PubMed

The necessity to quantify the mechanical function with high spatial resolution stemmed from the advancement of myocardial salvaging techniques. Since these therapies are localized interventions, a whole field technique with high spatial resolution was needed to differentiate the normal, diseased, and treated myocardium. We developed a phase correlation algorithm for measuring myocardial displacement at high spatial resolution and to determine the regional mechanical function in the intact heart. Porcine hearts were exposed and high contrast microparticles were placed on the myocardium. A pressure transducer, inserted into the left ventricle, synchronized the pressure (LVP) with image acquisition using a charge-coupled device camera. The deformation of the myocardium was measured with a resolution of 0.58+/-0.04 mm. Within the region of interest (ROI), regional stroke work (RSW), defined as the integral of LVP with respect to regional area, was determined on average at 21 locations with a resolution of 27.1+/-2.7 mm2. To alter regional mechanical function, the heart was paced at three different locations around the ROI. Independent of the pacemaker location, RSW decreased in the ROI. In addition, a gradient of increasing RSW in the outward direction radiating from the pacemaker was observed in all pacing protocols. These data demonstrated the ability to determine regional whole field mechanical function with high spatial resolution, and the significant alterations induced by electrical pacing. PMID:16439241

Azeloglu, Evren U; Yun, Yang H; Saltman, Adam E; Krukenkamp, Irvin B; Chiang, Fu-Pen; Chen, Weiliam; Gaudette, Glenn R

2006-01-01

330

The "automatic mode switch" function in successive generations of minute ventilation sensing dual chamber rate responsive pacemakers.  

PubMed

Automatic mode switch (AMS) from DDDR to VVIR pacing is a new algorithm, in response to paroxysmal atrial tachyarrhythmias. With the 5603 Programmer, the AMS in the Meta DDDR 1250 and 1250H (Telectronics Pacings Systems, Inc.) operates when VA is shorter than the adaptable PVARP. With the 9600 Programmer, an atrial protection interval can be defined after the PVARP. The latest generation, Meta DDDR 1254, initiates AMS when 5 or 11 heart cycles are > 150, 175, or 200 beats/min. From 1990 to 1993, 61 patients, mean age 61 years, received a Meta DDDR: in 24 a 1250, in 12 a 1250H and in the remaining 25 a 1254 model. Indication for pacing was heart block in 39, sick sinus syndrome in 15, the combination in 6, and hypertrophic obstructive cardiomyopathy in 1. Paroxysmal atrial tachyarrhythmias were present in 43. All patients had routine pacemaker surveillance, including 52 Holter recordings. In 32 patients, periods of atrial tachyarrhythmias were observed, with proper AMS to VVIR, except during short periods of 2:1 block for atrial flutter in 4. In two others, undersensing of the atrial arrhythmia disturbed correct AMS. With the 1250 and 1250H model, AMS was observed on several occasions during sinus rate accelerations in ten patients. This was never seen with the 1254 devices. Final programmation was VVIR in 2 (chronic atrial fibrillation), AAI in 1 (fracture of the ventricular lead), VDDR in 1 (atrial pacing during atrial fibrillation), DDD in 5, and DDDR in 53, 48 of whom had AMS programmed on.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:7845791

Provenier, F; Jordaens, L; Verstraeten, T; Clement, D L

1994-11-01

331

An Update: The Cardiac Wellness Training Project.  

ERIC Educational Resources Information Center

This article reports on the scope of activities and the effectiveness of a Colorado program that trained community park and recreation personnel to carry out local cardiac wellness services. Participants were trained to provide rehabilitation and fitness activities for those recovering from heart attacks or surgery and for other high-risk persons.…

Zinn, Lorraine; Long, Patrick

1983-01-01

332

MRI and cardiac implantable electronic devices; current status and required safety conditions.  

PubMed

Magnetic resonance imaging (MRI) has evolved into an essential diagnostic modality for the evaluation of all patient categories. This gain in popularity coincided with an increase in the number of implanted cardiac implantable electronic devices (CIEDs). Therefore, questions arose with regard to the MRI compatibility of these devices. Various investigators have reported the harmless performance of MRI in patients with conventional (non-MRI conditional) devices. The recently published European Society of Cardiology (ESC) guidelines on cardiac pacing and cardiac resynchronisation therapy (CRT) indicate that MRI can be safely performed in patients with an implanted pacemaker or ICD (MRI conditional or not), as long as strict safety conditions are met. This is a major modification of the former general opinion that patients with a pacemaker or ICD were not eligible to undergo MRI. This review paper attempts to elucidate the current situation for practising cardiologists by providing a clear overview of the potential life-threatening interactions and discuss safety measures to be taken prior to and during scanning. An overview of all available MRI conditional devices and their individual restrictions is given. In addition, an up-to-date safety protocol is provided that can be used to ensure patient safety before, during and after the scan. Key points • Historically, MRI examination of patients with a CIED has been considered hazardous. • Ongoing advances in technology and increasing usage of MRI in clinical practice have led to the introduction of MRI conditional CIEDs and to more lenient regulations on the examination of patients with non-conditional CIEDs. • MRI investigations can be performed safely in selected patients when adhering to a standardised up-to-date safety protocol. PMID:24733688

van der Graaf, A W M; Bhagirath, P; Götte, M J W

2014-06-01

333

Modeling inherited cardiac disorders.  

PubMed

Advances in the understanding and treatment of cardiac disorders have been thwarted by the inability to study beating human cardiac cells in vitro. Induced pluripotent stem cells (iPSCs) bypass this hurdle by enabling the creation of patient-specific iPSC-derived cardiomyocytes (iPSC-CMs). These cells provide a unique platform to study cardiac diseases in vitro, especially hereditary cardiac conditions. To date, iPSC-CMs have been used to successfully model arrhythmic disorders, showing excellent recapitulation of cardiac channel function and electrophysiologic features of long QT syndrome types 1, 2, 3, and 8, and catecholaminergic polymorphic ventricular tachycardia (CPVT). Similarly, iPSC-CM models of dilated cardiomyopathy (DCM) and hypertrophic cardiomyopathy (HCM) have shown robust correlation of predicted morphologic, contractile, and electrical phenotypes. In addition, iPSC-CMs have shown some features of the respective phenotypes for arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVD/C), LEOPARD syndrome, Pompe's disease, and Friedriech's ataxia. In this review, we examine the progress of utilizing iPSC-CMs as a model for cardiac conditions and analyze the potential for the platform in furthering the biology and treatment of cardiac disorders.?? PMID:24632794

Sallam, Karim; Kodo, Kazuki; Wu, Joseph C

2014-01-01

334

Cardiac involvement in leptospirosis.  

PubMed

Leptospirosis is a neglected global disease with significant morbidity and mortality. Cardiac complications such as chest pain, arrhythmias, pulmonary oedema and refractory shock have been reported in patients with severe disease. However, the frequency and extent of cardiac involvement in leptospirosis, are under-reported and poorly understood. Multiple factors may contribute to clinical manifestations that suggest cardiac involvement, causing diagnostic confusion. A variety of electrocardiographic changes occur in leptospirosis, with atrial fibrillation, atrioventricular conduction blocks and non-specific ventricular repolarization abnormalities being the most common. Electrolyte abnormalities are likely to contribute to electrocardiographic changes; direct effects on Na(+)-K(+)-Cl(-) transporters in the renal tubules have been postulated. Echocardiographic evidence of myocardial dysfunction has not been adequately demonstrated. The diagnostic value of cardiac biomarkers is unknown. Histopathological changes in the myocardium have been clearly shown, with myocardial inflammation and vasculitis present in postmortem studies. Nonetheless, the pathophysiology of cardiac involvement in leptospirosis is poorly understood. Cardiac involvement, demonstrated electrocardiographically or clinically, tends to predict poor outcome. No specific therapies are available to prevent or treat cardiac involvement in leptospirosis; current management is based on correction of deranged homeostasis and supportive therapy. Evidence suggests that direct myocardial damage occurs in patients with severe leptospirosis, and further studies are recommended to elucidate its pathophysiology, clinical features and contribution to overall prognosis, and to identify appropriate diagnostic investigations and specific therapies. PMID:22818758

Navinan, Mitrakrishnan Rayno; Rajapakse, Senaka

2012-09-01

335

Optic lobe circadian pacemaker sends its information to the contralateral optic lobe in the cricket Gryllus bimaculatus  

Microsoft Academic Search

The bilaterally paired optic lobe pacemakers of the cricket Gryllus bimaculatus are mutually coupled. In the present study we recorded the neural activity conveyed from the brain toward the optic lobe with a suction electrode to examine the coupling signals. The results demonstrated that the brain efferents to the optic lobe encode the circadian information: Both in constant light (LL)

K. Tomioka; M. Nakamichi; M. Yukizane

1994-01-01

336

Computational modeling of anoctamin 1 calcium-activated chloride channels as pacemaker channels in interstitial cells of Cajal.  

PubMed

Interstitial cells of Cajal (ICC) act as pacemaker cells in the gastrointestinal tract by generating electrical slow waves to regulate rhythmic smooth muscle contractions. Intrinsic Ca(2+) oscillations in ICC appear to produce the slow waves by activating pacemaker currents, currently thought to be carried by the Ca(2+)-activated Cl(-) channel anoctamin 1 (Ano1). In this article we present a novel model of small intestinal ICC pacemaker activity that incorporates store-operated Ca(2+) entry and a new model of Ano1 current. A series of simulations were carried out with the ICC model to investigate current controversies about the reversal potential of the Ano1 Cl(-) current in ICC and to predict the characteristics of the other ion channels that are necessary to generate slow waves. The model results show that Ano1 is a plausible pacemaker channel when coupled to a store-operated Ca(2+) channel but suggest that small cyclical depolarizations may still occur in ICC in Ano1 knockout mice. The results predict that voltage-dependent Ca(2+) current is likely to be negligible during the slow wave plateau phase. The model shows that the Cl(-) equilibrium potential is an important modulator of slow wave morphology, highlighting the need for a better understanding of Cl(-) dynamics in ICC. PMID:24481603

Lees-Green, Rachel; Gibbons, Simon J; Farrugia, Gianrico; Sneyd, James; Cheng, Leo K

2014-04-15

337

Ambulatory Holter monitoring in asymptomatic patients with DDD pacemakers - do we need ACC/AHA Guidelines revision?  

PubMed Central

Introduction We sought to determine the usefulness of ambulatory 24-hour Holter monitoring in detecting asymptomatic pacemaker (PM) malfunction episodes in patients with dual-chamber pacemakers whose pacing and sensing parameters were proper, as seen in routine post-implantation follow-ups. Material and methods Ambulatory 24-hour Holter recordings (HM) were performed in 100 patients with DDD pacemakers 1 day after the implantation. Only asymptomatic patients with proper pacing and sensing parameters (assessed on PM telemetry on the first day post-implantation) were enrolled in the study. The following parameters were assessed: failure to pace, failure to sense (both oversensing and undersensing episodes) as well as the percentage of all PM disturbances. Results Despite proper sensing and pacing parameters, HM revealed PM disturbances in 23 patients out of 100 (23%). Atrial undersensing episodes were found in 12 patients (p < 0.005) with totally 963 episodes and failure to capture in 1 patient (1%). T wave oversensing was the most common ventricular channel disorder (1316 episodes in 9 patients, p < 0.0005). Malfunction episodes occurred sporadically, leading to pauses of up to 1.6 s or temporary bradycardia, which were, nevertheless, not accompanied by clinical symptoms. No ventricular pacing disturbances were found. Conclusions Asymptomatic pacemaker dysfunction may be observed in nearly 25% of patients with proper DDD parameters after implantation. Thus, ambulatory HM during the early post-implantation period may be a useful tool to detect the need to reprogram PM parameters. PMID:24273562

Klimczak, Artur; Wranicz, Jerzy Krzysztof

2013-01-01

338

[Cross-stimulation in endocardiac AV sequential demand DVI pacemaker associated with great dilatation of the right atrial appendage].  

PubMed

We report on a case of ventricular stimulation by an atrial electrode in endocardiac DVI sequential pacemaker implanted in a patient with cardiomegaly and great atrial appendage. The appropriately placement of the electrode was confirmed by open-heart surgery in the valve replacement. This rare malfunction could be exceptionally studied anatomically. PMID:2146722

Candel Delgado, J M; Guerrero, J A; Marcote, F; Calleja Hernández, M

1990-01-01

339

Acute desensitization of acetylcholine and endothelin-1 activated inward rectifier K+ current in myocytes from the cardiac atrioventricular node.  

PubMed

The atrioventricular node (AVN) is a vital component of the pacemaker-conduction system of the heart, co-ordinating conduction of electrical excitation from cardiac atria to ventricles and acting as a secondary pacemaker. The electrical behaviour of the AVN is modulated by vagal activity via activation of muscarinic potassium current, IKACh. However, it is not yet known if this response exhibits 'fade' or desensitization in the AVN, as established for the heart's primary pacemaker--the sinoatrial node. In this study, acute activation of IKACh in rabbit single AVN cells was investigated using whole-cell patch clamp at 37 °C. 0.1-1 ?M acetylcholine (ACh) rapidly activated a robust IKACh in AVN myocytes during a descending voltage-ramp protocol. This response was inhibited by tertiapin-Q (TQ; 300 nM) and by the M2 muscarinic ACh receptor antagonist AFDX-116 (1 ?M). During sustained ACh exposure the elicited IKACh exhibited bi-exponential fade (?f of 2.0 s and ?s 76.9 s at -120 mV; 1 ?M ACh). 10 nM ET-1 elicited a current similar to IKACh, which faded with a mono-exponential time-course (? of 52.6 s at -120 mV). When ET-1 was applied following ACh, the ET-1 activated response was greatly attenuated, demonstrating that ACh could desensitize the response to ET-1. For neither ACh nor ET-1 was the rate of current fade dependent upon the initial response magnitude, which is inconsistent with K+ flux mediated changes in electrochemical driving force as the underlying mechanism. Collectively, these findings demonstrate that TQ sensitive inwardly rectifying K+ current in cardiac AVN cells, elicited by M2 muscarinic receptor or ET-1 receptor activation, exhibits fade due to rapid desensitization. PMID:22683635

Choisy, Stéphanie C M; James, Andrew F; Hancox, Jules C

2012-07-01

340

Taking cardiac surgery to the people.  

PubMed

Cardiovascular disease (CVD) is currently the leading cause of mortality in the world, and it is estimated that 80 % of the disease burden is encountered in low- and middle-income countries (LMICs). While numerous wake-up calls have been issued in the recent years to face this emerging epidemic, little has been achieved. One particularly deficient area is cardiac surgery. This article aims to address the challenges and barriers to establishing cardiac surgery programs in LMICs and some of the existing efforts to overcome them, focusing on a center in Aswan, Egypt, as an example. PMID:25361602

Yacoub, Magdi; ElGuindy, Ahmed; Afifi, Ahmed; Yacoub, Lisa; Wright, Gavin

2014-12-01

341

Cardiac muscle cells  

NSDL National Science Digital Library

Cardiac muscles are found only in the heart. They work together to bring deoxygenated blood in and push oxygenated blood out into the body. Essentially, they keep your heart pumping and your body alive.

Nathanael Reveal (None;)

2007-07-02

342

Cardiac ablation procedures  

MedlinePLUS

... 4(6):816-61. Miller JM, Zipes DP. Therapy for cardiac arrhythmias. In: Libby P, Bonow RO, Mann DL, Zipes DP, eds. Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine . 8th ed. Philadelphia, ...

343

Integrative Cardiac Health Project.  

National Technical Information Service (NTIS)

The Integrative Cardiac Health Project (ICHP) aims to lead the way in Cardiovascular Disease (CVD) Prevention by conducting novel research utilizing a Systems Biology / personalized medicine design to discover and develop practical, effective and preempti...

A. H. Nixon, M. N. Vernalis

2013-01-01

344

Integrative Cardiac Health Project.  

National Technical Information Service (NTIS)

The Integrative Cardiac Health Project (ICHP) aims to lead the way in Cardiovascular Disease (CVD) Prevention by conducting novel research utilizing a Systems Biology / personalized medicine design to discover and develop practical, effective and preempti...

A. H. NIxon, M. N. Vernalis

2011-01-01

345

Integrative Cardiac Health Project.  

National Technical Information Service (NTIS)

The Integrative Cardiac Health Project (ICHP) aims to lead the way in Cardiovascular Disease (CVD) Prevention by conducting novel research utilizing a Systems Biology / personalized medicine design to discover and develop practical, effective and preempti...

A. H. Nixon, M. N. Vernalis

2012-01-01

346

Cardiac thin filament regulation  

PubMed Central

Myocardial contraction is initiated upon the release of calcium into the cytosol from the sarcoplasmic reticulum following membrane depolarization. The fundamental physiological role of the heart is to pump an amount blood that is determined by the prevailing requirements of the body. The physiological control systems employed to accomplish this task include regulation of heart rate, the amount of calcium release, and the response of the cardiac myofilaments to activator calcium ions. Thin filament activation and relaxation dynamics has emerged as a pivotal regulatory system tuning myofilament function to the beat-to-beat regulation of cardiac output. Maladaptation of thin filament dynamics, in addition to dysfunctional calcium cycling, is now recognized as an important cellular mechanism causing reduced cardiac pump function in a variety of cardiac diseases. Here, we review current knowledge regarding protein–protein interactions involved in the dynamics of thin filament activation and relaxation and the regulation of these processes by protein kinase-mediated phosphorylation. PMID:18421471

Kobayashi, Tomoyoshi; Jin, Lei; de Tombe, Pieter P.

2010-01-01

347

Functional cardiac MR imaging  

NASA Astrophysics Data System (ADS)

Undersampled projection reconstruction acquisitions are investigated for use in functional cardiac MR imaging. 256×256 resolution is obtainable using only 64 projections, with acceptable artifact level. Reduced FOV techniques decrease artifact. Variable angular sampling using projection reconstruction is investigated.

Peters, Dana C.; Epstein, Frederick H.; McVeigh, Elliot R.

2000-10-01

348

Effects of sphingosine-1-phosphate on pacemaker activity of interstitial cells of Cajal from mouse small intestine.  

PubMed

Interstitial cells of Cajal (ICC) are the pacemaker cells that generate the rhythmic oscillation responsible for the production of slow waves in gastrointestinal smooth muscle. Spingolipids are known to present in digestive system and are responsible for multiple important physiological and pathological processes. In this study, we are interested in the action of sphingosine 1-phosphate (S1P) on ICC. S1P depolarized the membrane and increased tonic inward pacemaker currents. FTY720 phosphate (FTY720P, an S1P(1,3,4,5) agonist) and SEW 2871 (an S1P(1) agonist) had no effects on pacemaker activity. Suramin (an S1P(3) antagonist) did not block the S1P-induced action on pacemaker currents. However, JTE-013 (an S1P(2) antagonist) blocked the S1P-induced action. RT-PCR revealed the presence of the S1P(2) in ICC. Calphostin C (a protein kinase C inhibitor), NS-398 (a cyclooxygenase-2 inhibitor), PD 98059 (a p42/44 inhibitor), or SB 203580 (a p38 inhibitor) had no effects on S1P-induced action. However, c-jun NH(2)-terminal kinase (JNK) inhibitor II suppressed S1P-induced action. External Ca(2+)-free solution or thapsigargin (a Ca(2+)-ATPase inhibitor of endoplasmic reticulum) suppressed action of S1P on ICC. In recording of intracellular Ca(2+) ([Ca(2+)](i)) concentration using fluo-4/AM S1P increased intensity of spontaneous [Ca(2+)](i) oscillations in ICC. These results suggest that S1P can modulate pacemaker activity of ICC through S1P(2) via regulation of external and internal Ca(2+) and mitogenactivated protein kinase activation. PMID:23307289

Kim, Young Dae; Han, Kyoung Taek; Lee, Jun; Park, Chan Guk; Kim, Man Yoo; Shahi, Pawan Kumar; Zuo, Dong Chuan; Choi, Seok; Jun, Jae Yeoul

2013-01-01

349

Effects of Sphingosine-1-Phosphate on Pacemaker Activity of Interstitial Cells of Cajal from Mouse Small Intestine  

PubMed Central

Interstitial cells of Cajal (ICC) are the pacemaker cells that generate the rhythmic oscillation responsible for the production of slow waves in gastrointestinal smooth muscle. Spingolipids are known to present in digestive system and are responsible for multiple important physiological and pathological processes. In this study, we are interested in the action of sphingosine 1-phosphate (S1P) on ICC. S1P depolarized the membrane and increased tonic inward pacemaker currents. FTY720 phosphate (FTY720P, an S1P1,3,4,5 agonist) and SEW 2871 (an S1P1 agonist) had no effects on pacemaker activity. Suramin (an S1P3 antagonist) did not block the S1P-induced action on pacemaker currents. However, JTE-013 (an S1P2 antagonist) blocked the S1P-induced action. RT-PCR revealed the presence of the S1P2 in ICC. Calphostin C (a protein kinase C inhibitor), NS-398 (a cyclooxygenase-2 inhibitor), PD 98059 (a p42/44 inhibitor), or SB 203580 (a p38 inhibitor) had no effects on S1P-induced action. However, c-jun NH2-terminal kinase (JNK) inhibitor II suppressed S1P-induced action. External Ca2+-free solution or thapsigargin (a Ca2+-ATPase inhibitor of endoplasmic reticulum) suppressed action of S1P on ICC. In recording of intracellular Ca2+ ([Ca2+]i) concentration using fluo-4/AM S1P increased intensity of spontaneous [Ca2+]i oscillations in ICC. These results suggest that S1P can modulate pacemaker activity of ICC through S1P2 via regulation of external and internal Ca2+ and mitogen-activated protein kinase activation. PMID:23307289

Kim, Young Dae; Han, Kyoung Taek; Lee, Jun; Park, Chan Guk; Kim, Man Yoo; Shahi, Pawan Kumar; Zuo, Dong Chuan; Choi, Seok; Jun, Jae Yeoul

2013-01-01

350

Cardiac Rehabilitation: The Nutrition Counseling Component  

Microsoft Academic Search

\\u000a \\u000a \\u000a \\u000a \\u000a • \\u000a \\u000a \\u000a Cardiac rehabilitation following a cardiac event is a comprehensive, multidisciplinary program that includes lifestyle counseling\\u000a in nutrition, physical activity, stress management, and smoking cessation.\\u000a \\u000a \\u000a \\u000a \\u000a • \\u000a \\u000a \\u000a Special concerns that can affect implementation of cardiac rehabilitation in older patients include complicated co-morbidities;\\u000a functional limitations, alterations in taste, smell, and appetite; difficulties with medication use\\/effectiveness; and limited\\u000a financial, social, and\\/or caregiver resources.

William E. Kraus; Julie D. Pruitt

351

Cardiac arrest during pregnancy.  

PubMed

Cardiac arrest is a rare event during pregnancy. The pregnant population represents a unique subset of cardiac arrest victims. Not only are there unique causes of circulatory collapse during the pregnant state, but the physiological modifications to the maternal physiology during pregnancy require specific modifications to the standard management of the arrest. Lastly, the pregnant victim presents herself with the challenges of a second patient who needs to be considered in the decision-making process. PMID:25314090

Montufar-Rueda, Carlos; Gei, Alfredo

2014-12-01

352

Platelet aggregating activity in serum from patients with HLA-B27 associated rheumatic and cardiac disorders: a possible link to the proliferative vascular changes.  

PubMed Central

OBJECTIVE--To search for possible serum factors (immunochemical abnormalities) that reflect HLA-B27 associated inflammatory process with the proliferative endarteritis, which is an important cause of severe bradycardia and aortic valve regurgitation. PATIENTS AND METHODS--Seventy four men with pacemakers were studied: 24 were HLA-B27 positive and had associated rheumatic and cardiac disorders, 13 were B27 positive but had no clinical or radiographic signs of a related rheumatic condition, and 37 were B27 negative controls. Randomly obtained serum samples were examined for a series of serum factors. RESULTS--Thirteen (57%) of the 23 patients with HLA-B27 and associated rheumatic and cardiac conditions had platelet aggregating activity in their serum. No such activity was found in sera from patients in the other groups. None the less, immunochemical abnormalities were common among patients of all groups; 30 (41%) had antinuclear antibodies or rheumatoid factor or both. CONCLUSION--The platelet aggregating activity found in patients with HLA-B27 and associated rheumatic and cardiac conditions may reflect serum factors that increase the stickiness of platelets and increase their adhesion to the vessel wall. This suggests a link via release of platelet derived growth factor(s) with the characteristic histopathological feature of proliferative endarteritis. Immunochemical abnormalities were common in serum from all men with pacemakers. PMID:2029440

Bergfeldt, L; Edhag, O; Holm, G; Norberg, R

1991-01-01

353

Developmental determinants of cardiac sensitivity to hypoxia.  

PubMed

Cardiac sensitivity to oxygen deprivation changes significantly during ontogenetic development. However, the mechanisms for the higher tolerance of the immature heart, possibilities of protection, and the potential impact of perinatal hypoxia on cardiac tolerance to oxygen deprivation in adults have not yet been satisfactorily clarified. The hypoxic tolerance of an isolated rat heart showed a triphasic pattern: significant decrease from postnatal day 1 to 7, followed by increase to the weaning period, and final decline to adulthood. We have observed significant ontogenetic changes in mitochondrial oxidative phosphorylation and mitochondrial membrane potential, as well as in the role of the mitochondrial permeability transition pores in myocardial injury. These results support the hypothesis that cardiac mitochondria are deeply involved in the regulation of cardiac tolerance to oxygen deprivation during ontogenetic development. Ischemic preconditioning failed to increase tolerance to oxygen deprivation in the highly tolerant hearts of newborn rats. Chronic hypoxic exposure during early development may cause in-utero or neonatal programming of several genes that can change the susceptibility of the adult heart to ischemia-reperfusion injury; this effect is sex dependent. These results would have important clinical implications, since cardiac sensitivity in adult patients may be significantly affected by perinatal hypoxia in a sex-dependent manner. PMID:24873901

Ostadal, Bohuslav; Ostadalova, Ivana; Kolar, Frantisek; Sedmera, David

2014-07-01

354

Emerging roles of inositol 1,4,5-trisphosphate signaling in cardiac myocytes  

PubMed Central

Inositol 1,4,5-trisphosphate (IP3) is a ubiquitous intracellular messenger regulating diverse functions in almost all mammalian cell types. It is generated by membrane receptors that couple to phospholipase C (PLC), an enzyme which liberates IP3 from phosphatidylinositol 4,5-bisphosphate (PIP2). The major action of IP3, which is hydrophilic and thus translocates from the membrane into the cytoplasm, is to induce Ca2+ release from endogenous stores through IP3 receptors (IP3Rs). Cardiac excitation–contraction coupling relies largely on ryanodine receptor (RyR)-induced Ca2+ release from the sarcoplasmic reticulum. Myocytes express a significantly larger number of RyRs compared to IP3Rs (?100:1), and furthermore they experience substantial fluxes of Ca2+ with each heartbeat. Therefore, the role of IP3 and IP3-mediated Ca2+ signaling in cardiac myocytes has long been enigmatic. Recent evidence, however, indicates that despite their paucity cardiac IP3Rs may play crucial roles in regulating diverse cardiac functions. Strategic localization of IP3Rs in cytoplasmic compartments and the nucleus enables them to participate in subsarcolemmal, bulk cytoplasmic and nuclear Ca2+ signaling in embryonic stem cell-derived and neonatal cardiomyocytes, and in adult cardiac myocytes from the atria and ventricles. Intriguingly, expression of both IP3Rs and membrane receptors that couple to PLC/IP3 signaling is altered in cardiac disease such as atrial fibrillation or heart failure, suggesting the involvement of IP3 signaling in the pathology of these diseases. Thus, IP3 exerts important physiological and pathological functions in the heart, ranging from the regulation of pacemaking, excitation–contraction and excitation–transcription coupling to the initiation and/or progression of arrhythmias, hypertrophy and heart failure. PMID:18603259

Kockskamper, Jens; Zima, Aleksey V.; Roderick, H. Llewelyn; Pieske, Burkert; Blatter, Lothar A.; Bootman, Martin D.

2008-01-01

355

Simple, rapid /sup 125/I-labeled cyclosporine double antibody/polyethylene glycol radioimmunoassay used in a pediatric cardiac transplant program  

SciTech Connect

We modified the Sandoz cyclosporine radioimmunoassay because of our need for frequent clinical monitoring of cyclosporine drug levels in allo- and xenograft pediatric cardiac transplant patients. With application of a commercially available (/sup 125/I)cyclosporine label in place of (/sup 3/H)cyclosporine and a second antibody/polyethylene glycol (PEG) method of separation in place of charcoal separation, we simplified and enhanced the speed and precision of assay performance. Studies of 140 whole blood samples comparing this new method to the (/sup 3/H)cyclosporine radioimmunoassay (RIA) method of Berk and colleagues yielded a coefficient of correlation of 0.96 (p less than 0.00001) with means of 626 and 667 ng/ml for (/sup 3/H)RIA and (/sup 125/I)RIA, respectively, and a regression equation of y = 28 + 1.02x. The major advantages are that total assay time is reduced to approximately 1 h; (/sup 125/I)cyclosporine label is used, avoiding the problems associated with liquid scintillation counting; and precision is enhanced by separating bound and free fractions with second antibody/PEG. These modifications should provide for greater ease of assay performance and improved clinical utility of cyclosporine monitoring not only in the pediatric but also in the adult transplant patient.

Berk, L.S.; Webb, G.; Imperio, N.C.; Nehlsen-Cannarella, S.L.; Eby, W.C.

1986-01-01

356

Circadian rhythms in healthy aging--effects downstream from the pacemaker  

NASA Technical Reports Server (NTRS)

Using both previously published findings and entirely new data, we present evidence in support of the argument that the circadian dysfunction of advancing age in the healthy human is primarily one of failing to transduce the circadian signal from the circadian timing system (CTS) to rhythms "downstream" from the pacemaker rather than one of failing to generate the circadian signal itself. Two downstream rhythms are considered: subjective alertness and objective performance. For subjective alertness, we show that in both normal nychthemeral (24 h routine, sleeping at night) and unmasking (36 h of constant wakeful bed rest) conditions, advancing age, especially in men, leads to flattening of subjective alertness rhythms, even when circadian temperature rhythms are relatively robust. For objective performance, an unmasking experiment involving manual dexterity, visual search, and visual vigilance tasks was used to demonstrate that the relationship between temperature and performance is strong in the young, but not in older subjects (and especially not in older men).

Monk, T. H.; Kupfer, D. J.

2000-01-01

357

Thoracic epidural infusion with chloroprocaine for postoperative analgesia following epicardial pacemaker placement in an infant  

PubMed Central

In critically ill neonates and infants, major interventions, including thoracotomy, may result in significant postoperative respiratory insufficiency and pain leading to the need for postoperative mechanical ventilation. Although there are many potential options for providing postoperative analgesia, there continues to be expanding use of regional anesthesia in this population. One of the many reported advantages is the provision of postoperative analgesia while avoiding the deleterious effects on respiratory function that may be seen with systemic opioids. We report the use of thoracic epidural anesthesia using a continuous infusion of chloroprocaine to provide analgesia following thoracotomy and epicardial pacemaker placement in an infant. The perioperative plan was complicated by comorbid conditions including congenital complete heart block, recent rhinovirus infection with residual respiratory involvement, and prematurity. PMID:25364272

Kamata, Mineto; Corridore, Marco; Tobias, Joseph D

2014-01-01

358

Pacemaker phase control versus masking by light: setting the circadian chronotype in dual Octodon degus.  

PubMed

There are two main processes involved in the expression of circadian rhythmicity: entrainment and masking. Whereas the first operates via the central pacemaker to anticipate predictable environmental conditions, masking (mainly induced by light) functions as a direct modulator of the circadian output signal induced by nonpredictable events. The Chilean rodent Octodon degus presents both diurnal and nocturnal chronotypes when given free access to an exercise wheel. Two steady-entrainment phases and graded masking by light seem to generate the wide variability of chronotypes in this species. The aim of this study was to characterize the differential masking by light according to the individual chronotypes, their stability over time, and the influence of wheel running availability and ambient temperature upon the degus' nocturnality. To this end, diurnal and nocturnal degus were subjected to ultradian cycles (1:1-h light-dark [LD]), with and without wheel running availability, and under both normal and high diurnal ambient temperature cycles. The present results show that diurnal and nocturnal degus present a stable masking by light, each according to its respective chronotype. Thus, whereas diurnal animals increased their activity with light, in nocturnal degus light induced a sharp drop in wheel running activity. These two types of masking responses appeared not only when the animals were synchronized to the 12:12-h LD cycle, but also under ultradian cycles. Different masking effects persisted when wheel running was made unavailable and when the animals shifted their circadian activity patterns in response to ultradian cycles or to diurnal exposure to high temperatures. In conclusion, our results show that the positive and negative masking effects of light on diurnal and nocturnal degus, respectively, seem to occur independently of relative phase control by the central pacemaker or the negative masking induced by high environmental temperatures. PMID:20795881

Vivanco, Pablo; Rol, Maria Angeles; Madrid, Juan Antonio

2010-08-01

359

Persistent sodium current drives conditional pacemaking in CA1 pyramidal neurons under muscarinic stimulation.  

PubMed

Hippocampal CA1 pyramidal neurons are normally quiescent but can fire spontaneously when stimulated by muscarinic agonists. In brain slice recordings from mouse CA1 pyramidal neurons, we examined the ionic basis of this activity using interleaved current-clamp and voltage-clamp experiments. Both in control and after muscarinic stimulation, the steady-state current-voltage curve was dominated by inward TTX-sensitive persistent sodium current (I(NaP)) that activated near -75 mV and increased steeply with depolarization. In control, total membrane current was net outward (hyperpolarizing) near -70 mV so that cells had a stable resting potential. Muscarinic stimulation activated a small nonselective cation current so that total membrane current near -70 mV shifted to become barely net inward (depolarizing). The small depolarization triggers regenerative activation of I(NaP), which then depolarizes the cell from -70 mV to spike threshold. We quantified the relative contributions of I(NaP), hyperpolarization-activated cation current (I(h)), and calcium current to pacemaking by using the cell's own firing as a voltage command along with specific blockers. TTX-sensitive sodium current was substantial throughout the entire interspike interval, increasing as the membrane potential approached threshold, while both Ih and calcium current were minimal. Thus, spontaneous activity is driven primarily by activation of I(NaP) in a positive feedback loop starting near -70 mV and providing increasing inward current to threshold. These results show that the pacemaking "engine" from I(NaP) is an inherent property of CA1 pyramidal neurons that can be engaged or disengaged by small shifts in net membrane current near -70 mV, as by muscarinic stimulation. PMID:24048831

Yamada-Hanff, Jason; Bean, Bruce P

2013-09-18

360

Interplay between myogenic pacemakers and enteric neurons determine distinct motor patterns in the rat colon.  

PubMed

Waxing and waning of slow waves amplitude has been recently associated with a segmentation motor pattern in the murine small intestine. The 'wax and wane' phenomenon in this area of the gastrointestinal tract seems to be the result of modulation of slow waves by a second pacemaker of a lower frequency displayed by the interstitial cells of Cajal near the deep muscular plexus (ICC-DMP). In the rat colon, smooth muscle cyclic depolarizations causing low-frequency (LF) contractions (0.9 ± 0.1 cpm) occur together with slow wave activity associated to high-frequency (HF) contractions (14 ± 0.3 cpm; ripples). In the present manuscript, we demonstrate the presence of 'wax and wane' in rat colonic slow waves. Depolarization from the 'wax' to the 'wane' was 7.6 ± 1.2 mV, i.e., smooth muscle cells went from a resting membrane potential (RMP) of -50.0 mV to a RMP of -42.4 mV. The amplitude of the slow wave decreased from 14.0 ± 2.2 mV to 3.4 ± 0.7 mV. The wax and wane phenomenon occurred at 0.9 ± 0.1 cpm, coinciding with the frequency of cyclic depolarizations. Therefore, we hypothesized that the 'wax and wane' of slow waves in the rat colon could be the result of their interaction with the LF pacemaker. We describe three different myogenic motor patterns that depend on the level of smooth muscle and ICC excitation: (i) LF propulsive contractions, (ii) regular slow waves causing ripples, and (iii) a wax and wane pattern that may lead to segmentation. Different intra- and extra-luminal inputs probably determine the dominating motor pattern in each area through the enteric nervous system. PMID:25088991

Mañé, N; Jimenez, M

2014-10-01

361

Persistent Sodium Current Drives Conditional Pacemaking in CA1 Pyramidal Neurons under Muscarinic Stimulation  

PubMed Central

Hippocampal CA1 pyramidal neurons are normally quiescent but can fire spontaneously when stimulated by muscarinic agonists. In brain slice recordings from mouse CA1 pyramidal neurons, we examined the ionic basis of this activity using interleaved current-clamp and voltage-clamp experiments. Both in control and after muscarinic stimulation, the steady-state current–voltage curve was dominated by inward TTX-sensitive persistent sodium current (INaP) that activated near ?75 mV and increased steeply with depolarization. In control, total membrane current was net outward (hyperpolarizing) near ?70 mV so that cells had a stable resting potential. Muscarinic stimulation activated a small nonselective cation current so that total membrane current near ?70 mV shifted to become barely net inward (depolarizing). The small depolarization triggers regenerative activation of INaP, which then depolarizes the cell from ?70 mV to spike threshold. We quantified the relative contributions of INaP, hyperpolarization-activated cation current (Ih), and calcium current to pacemaking by using the cell's own firing as a voltage command along with specific blockers. TTX-sensitive sodium current was substantial throughout the entire interspike interval, increasing as the membrane potential approached threshold, while both Ih and calcium current were minimal. Thus, spontaneous activity is driven primarily by activation of INaP in a positive feedback loop starting near ?70 mV and providing increasing inward current to threshold. These results show that the pacemaking “engine” from INaP is an inherent property of CA1 pyramidal neurons that can be engaged or disengaged by small shifts in net membrane current near ?70 mV, as by muscarinic stimulation. PMID:24048831

Yamada-Hanff, Jason

2013-01-01

362

A model of cellular cardiac-neural coupling that captures the sympathetic control of sinoatrial node excitability in normotensive and hypertensive rats.  

PubMed

Hypertension is associated with sympathetic hyperactivity. To represent this neural-myocyte coupling, and to elucidate the mechanisms underlying sympathetic control of the cardiac pacemaker, we developed a new (to our knowledge) cellular mathematical model that incorporates signaling information from cell-to-cell communications between the sympathetic varicosity and sinoatrial node (SAN) in both normotensive (WKY) and hypertensive (SHR) rats. Features of the model include 1), a description of pacemaker activity with specific ion-channel functions and Ca(2+) handling elements; 2), dynamic ?-adrenergic modulation of the excitation of the SAN; 3), representation of ionic activity of sympathetic varicosity with NE release dynamics; and 4), coupling of the varicosity model to the SAN model to simulate presynaptic transmitter release driving postsynaptic excitability. This framework captures neural-myocyte coupling and the modulation of pacemaking by nitric oxide and cyclic GMP. It also reproduces the chronotropic response to brief sympathetic stimulations. Finally, the SHR model quantitatively suggests that the impairment of cyclic GMP regulation at both sides of the sympathetic cleft is crucial for development of the autonomic phenotype observed in hypertension. PMID:21806927

Tao, T; Paterson, David J; Smith, Nicolas P

2011-08-01

363

76 FR 64223 - Cardiovascular Devices; Reclassification of External Pacemaker Pulse Generator Devices  

Federal Register 2010, 2011, 2012, 2013

...under the Federal Food, Drug, and Cosmetic Act (the FD&C Act), as amended...heartbeats in patients following cardiac surgery or a myocardial infarction. The...under the Federal Food, Drug, and Cosmetic Act and under authority...

2011-10-17

364

A Web-Based Nutrition Program Reduces Health Care Costs in Employees With Cardiac Risk Factors: Before and After Cost Analysis  

PubMed Central

Background Rising health insurance premiums represent a rapidly increasing burden on employer-sponsors of health insurance and their employees. Some employers have become proactive in managing health care costs by providing tools to encourage employees to directly manage their health and prevent disease. One example of such a tool is DASH for Health, an Internet-based nutrition and exercise behavior modification program. This program was offered as a free, opt-in benefit to US-based employees of the EMC Corporation. Objective The aim was to determine whether an employer-sponsored, Internet-based diet and exercise program has an effect on health care costs. Methods There were 15,237 total employees and spouses who were included in our analyses, of whom 1967 enrolled in the DASH for Health program (DASH participants). Using a retrospective, quasi-experimental design, study year health care costs among DASH participants and non-participants were compared, controlling for baseline year costs, risk, and demographic variables. The relationship between how often a subject visited the DASH website and health care costs also was examined. These relationships were examined among all study subjects and among a subgroup of 735 subjects with cardiovascular conditions (diabetes, hypertension, hyperlipidemia). Multiple linear regression analysis examined the relationship of program use to health care costs, comparing study year costs among DASH participants and non-participants and then examining the effects of increased website use on health care costs. Analyses were repeated among the cardiovascular condition subgroups. Results Overall, program use was not associated with changes in health care costs. However, among the cardiovascular risk study subjects, health care costs were US$827 lower, on average, during the study year (P = .05; t 729 = 1.95). Among 1028 program users, increased website use was significantly associated with lower health care costs among those who visited the website at least nine times during the study year (US$14 decrease per visit; P = .04; t 1022 = 2.05), with annual savings highest among 80 program users with targeted conditions (US$55 decrease per visit; P < .001; t 74 = 2.71). Conclusions An employer-sponsored, Internet-based diet and exercise program shows promise as a low-cost benefit that contributes to lower health care costs among persons at higher risk for above-average health care costs and utilization. PMID:19861297

Cabral, Howard; Kazis, Lewis E; Jarrett, Kelli M; Vetter, Delia; Richmond, Russell; Moore, Thomas J

2009-01-01

365

Bandura's Self-Efficacy TheoryA Guide for Cardiac Rehabilitation Nursing Practice  

Microsoft Academic Search

To help patients achieve the greatest benefit from cardiac rehabilitation programs, nurses must assist them to modify unhealthy behaviors. Many cardiac rehabilitation programs, however, lack a theoretical foundation; therefore, interventions are usually executed without accounting for the complexities of human behavior, and little consideration is given to the difficulties encountered in altering unhealthy behavior patterns. Bandura's self-efficacy theory is considered

Chii Jeng; Lynne T. Braun

1994-01-01

366

Pediatric sudden cardiac arrest.  

PubMed

Pediatric sudden cardiac arrest (SCA), which can cause sudden cardiac death if not treated within minutes, has a profound effect on everyone: children, parents, family members, communities, and health care providers. Preventing the tragedy of pediatric SCA, defined as the abrupt and unexpected loss of heart function, remains a concern to all. The goal of this statement is to increase the knowledge of pediatricians (including primary care providers and specialists) of the incidence of pediatric SCA, the spectrum of causes of pediatric SCA, disease-specific presentations, the role of patient and family screening, the rapidly evolving role of genetic testing, and finally, important aspects of secondary SCA prevention. This statement is not intended to address sudden infant death syndrome or sudden unexplained death syndrome, nor will specific treatment of individual cardiac conditions be discussed. This statement has been endorsed by the American College of Cardiology, the American Heart Association, and the Heart Rhythm Society. PMID:22451713

2012-04-01

367

Dynamic Control of Cardiac Alternans  

NASA Astrophysics Data System (ADS)

A dynamic control technique was used to suppress a cardiac arrhythmia called an alternans rhythm in a piece of dissected rabbit heart. Our control algorithm adapted to drifting system parameters, making it well suited for the control of physiological rhythms. Control of cardiac alternans rhythms may have important clinical implications since they often precede serious cardiac arrhythmias and are a harbinger of sudden cardiac death.

Hall, Kevin; Christini, David J.; Tremblay, Maurice; Collins, James J.; Glass, Leon; Billette, Jacques

1997-06-01

368

Attitudes of Implanting Physicians about Cardiac Rhythm Management Devices and Their Features.  

PubMed

Modern cardiac rhythm management systems have become increasingly complex. The decision on which specific system to implant in a given patient often rests with the implanting physician. We conducted a multiple-choice survey to assess the opinions and preferences of cardiologists and electrophysiologists who implant and follow cardiac rhythm management systems. Reliability and battery longevity were viewed as the most important characteristics in device selection. Patient characteristics which most affected device choice were pacing indication and life expectancy. Remote technology was used in 47% of pacemaker patients, 64% of ICD patients, and 65% of CRT-D patients, with wireless (radiofrequency) remote patient monitoring associated with higher patient compliance rates (74% versus 64%, resp.). Wireless remote patient management with alerts for atrial tachyarrhythmias was felt to be important by 76% of respondents. When choosing an MR-conditional device, physicians deemed patients with prior orthopedic problems, a history of cancer, or neurological disorders to be more likely to require a future MRI. Device longevity and reliability remain the most important factors which influence device selection. Wireless remote patient monitoring with alerts is considered increasingly important when choosing a specific cardiac rhythm management system to implant. PMID:24490084

Elmouchi, Darryl A; Chalfoun, Nagib; Gauri, Andre

2013-01-01

369

Cell and gene therapy for arrhythmias: Repair of cardiac conduction damage  

PubMed Central

Action potentials generated in the sinoatrial node (SAN) dominate the rhythm and rate of a healthy human heart. Subsequently, these action potentials propagate to the whole heart via its conduction system. Abnormalities of impulse generation and/or propagation in a heart can cause arrhythmias. For example, SAN dysfunction or conduction block of the atrioventricular node can lead to serious bradycardia which is currently treated with an implanted electronic pacemaker. On the other hand, conduction damage may cause reentrant tachyarrhythmias which are primarily treated pharmacologically or by medical device-based therapies, including defibrillation and tissue ablation. However, drug therapies sometimes may not be effective or are associated with serious side effects. Device-based therapies for cardiac arrhythmias, even with well developed technology, still face inadequacies, limitations, hardware complications, and other challenges. Therefore, scientists are actively seeking other alternatives for antiarrhythmic therapy. In particular, cells and genes used for repairing cardiac conduction damage/defect have been investigated in various studies both in vitro and in vivo. Despite the complexities of the excitation and conduction systems of the heart, cell and gene-based strategies provide novel alternatives for treatment or cure of cardiac arrhythmias. This review summarizes some highlights of recent research progress in this field. PMID:22783301

Xiao, Yong-Fu

2011-01-01

370

Usefulness of Hemodynamic Sensors for Physiologic Cardiac Pacing in Heart Failure Patients  

PubMed Central

The rate adaptive sensors applied to cardiac pacing should respond as promptly as the normal sinus node with an highly specific and sensitive detection of the need of increasing heart rate. Sensors operating alone may not provide optimal heart responsiveness: central venous pH sensing, variations in the oxygen content of mixed venous blood, QT interval, breathing rate and pulmonary minute ventilation monitored by thoracic impedance variations, activity sensors. Using sensors that have different attributes but that work in a complementary manners offers distinct advantages. However, complicated sensors interactions may occur. Hemodynamic sensors detect changes in the hemodynamic performances of the heart, which partially depends on the autonomic nervous system-induced inotropic regulation of myocardial fibers. Specific hemodynamic sensors have been designed to measure different expression of the cardiac contraction strength: Peak Endocardial Acceleration (PEA), Closed Loop Stimulation (CLS) and TransValvular Impedance (TVI), guided by intraventricular impedance variations. Rate-responsive pacing is just one of the potential applications of hemodynamic sensors in implantable pacemakers. Other issues discussed in the paper include: hemodynamic monitoring for the optimal programmation and follow up of patients with cardiac resynchronization therapy; hemodynamic deterioration impact of tachyarrhythmias; hemodynamic upper rate limit control; monitoring and prevention of vasovagal malignant syncopes. PMID:21461359

Occhetta, Eraldo; Bortnik, Miriam; Marino, Paolo

2011-01-01

371

Usefulness of hemodynamic sensors for physiologic cardiac pacing in heart failure patients.  

PubMed

The rate adaptive sensors applied to cardiac pacing should respond as promptly as the normal sinus node with an highly specific and sensitive detection of the need of increasing heart rate. Sensors operating alone may not provide optimal heart responsiveness: central venous pH sensing, variations in the oxygen content of mixed venous blood, QT interval, breathing rate and pulmonary minute ventilation monitored by thoracic impedance variations, activity sensors. Using sensors that have different attributes but that work in a complementary manners offers distinct advantages. However, complicated sensors interactions may occur. Hemodynamic sensors detect changes in the hemodynamic performances of the heart, which partially depends on the autonomic nervous system-induced inotropic regulation of myocardial fibers. Specific hemodynamic sensors have been designed to measure different expression of the cardiac contraction strength: Peak Endocardial Acceleration (PEA), Closed Loop Stimulation (CLS) and TransValvular Impedance (TVI), guided by intraventricular impedance variations. Rate-responsive pacing is just one of the potential applications of hemodynamic sensors in implantable pacemakers. Other issues discussed in the paper include: hemodynamic monitoring for the optimal programmation and follow up of patients with cardiac resynchronization therapy; hemodynamic deterioration impact of tachyarrhythmias; hemodynamic upper rate limit control; monitoring and prevention of vasovagal malignant syncopes. PMID:21461359

Occhetta, Eraldo; Bortnik, Miriam; Marino, Paolo

2011-01-01

372

Penetrating Cardiac Injury: A Review  

PubMed Central

Cardiac injury presents a great challenge to the emergency resident because these injuries require urgent intervention to prevent death. Sometimes serious cardiac injury may manifest only subtle or occult symptoms or signs. As there is an epidemic of cardiac injuries in Kashmir valley due to problems of law and order, we herein present a review on management of such injuries. PMID:24829887

Lateef Wani, Mohd; Ahangar, Ab Gani; Wani, Shadab Nabi; Irshad, Ifat; Ul-Hassan, Nayeem

2012-01-01

373

Cardiac Response and Personality Organization  

ERIC Educational Resources Information Center

This study examines the level and variability of cardiac response during complex problem-solving and interposed rest periods and their differing relationships to estimates of personality integration on the Rorschach. Findings suggest cardiac variability may be a more differentiated measure than level of cardiac response. (Author)

Blatt, Sidney J.; Feirstein, Alan

1977-01-01

374

Application of the root locus technique to the closed-loop SO\\/sub 2\\/ pacemaker-cardiovascular system  

Microsoft Academic Search

A previously developed nonlinear model of the pacemaker-cardiovascular system (G.F. Inbar et al. ibid., vol.35, p.679-90, 1988) is converted to a linear model using a Taylor's series expansion procedure. As the expansion is about a steady-state value, the linear model operates at specified exercise levels. Using the linear forward-loop transfer function a root locus plot of the closed-loop s-plane poles

G. K. Hung

1990-01-01

375

Cyclic AMP Signaling Control of Action Potential Firing Rate and Molecular Circadian Pacemaking in the Suprachiasmatic Nucleus  

Microsoft Academic Search

Circadian pacemaking in suprachiasmatic nucleus (SCN) neurons revolves around transcriptional\\/posttranslational feedback loops, driven by protein products of “clock” genes. These loops are synchronized and sustained by intercellular signaling, involving vasoactive intestinal peptide (VIP) via its VPAC2 receptor, which positively regulates cAMP synthesis. In turn, SCN cells communicate circadian time to the brain via a daily rhythm in electrophysiological activity. To

Susan E. Atkinson; Elizabeth S. Maywood; Johanna E. Chesham; Christian Wozny; Christopher S. Colwell; Michael H. Hastings; Stephen R. Williams

2011-01-01

376

Reduction of scale invariance of activity fluctuations with aging and Alzheimer's disease: Involvement of the circadian pacemaker  

Microsoft Academic Search

Human motor control systems orchestrate complex scale-invariant patterns of activity over a wide range of time scales (minutes to hours). The neural mechanisms underlying scale-invariance are unknown in humans. In rats, the master circadian pacemaker [suprachiasmatic nucleus (SCN)] is crucially involved in scale-invariant activity fluctuations over multiple time scales from minutes to 24 h. Aging and Alzheimer's disease (AD) are

Kun Hu; Eus J. W. van Someren; Steven A. Shea; Frank A. J. L. Scheer

2009-01-01

377

Temperature-dependent development of cardiac activity in unrestrained larvae of the minnow Phoxinus phoxinus.  

PubMed

The minnow (Phoxinus phoxinus) was raised up to the stage of swim bladder inflation at temperatures between 10 degrees C and 25 degrees C, and the time of development significantly decreased at higher temperatures. Accordingly, initiation of cardiac activity was observed at day 2 in 25 degrees C animals and at day 4 in 12.5 degrees C animals. Only a minor increase in body mass was observed during the incubation period, and, at the end of the incubation period, animals raised at 25 degrees C did not have a significantly lower body mass compared with animals raised at 15 degrees C. Metabolic activity, determined as the rate of oxygen consumption of a larva, increased from 3.3 to 19.5 nmol/h during development at 15 degrees C and from 5.6 to 47.6 nmol/h during development at 25 degrees C. Heart rate showed a clear correlation to developmental stage as well as to developmental temperature, but at the onset of cardiac activity, diastolic ventricular volume and also stroke volume were higher at the lower temperatures. Furthermore, stroke volume increased with development, except for the group incubated at 12.5 degrees C, in which stroke volume decreased with development. Initial cardiac output showed no correlation to incubation temperature. Although metabolic activity increased severalfold during development from egg to the stage of swim bladder inflation at 15 degrees C and at 25 degrees C, weight-specific cardiac output increased only by approximately 40% with proceeding development. At 12.5 degrees C, cardiac output remained almost constant until opening of the swim bladder. The data support the notion that oxygen transport is not the major function of the circulatory system at this stage of development. The changes in heart rate with temperature appear to be due to the intrinsic properties of the pacemaker; there was no indication for a regulated response. PMID:11049845

Schönweger, G; Schwerte, T; Pelster, B

2000-11-01

378

Multiple mechanisms of spiral wave breakup in a model of cardiac electrical activity  

NASA Astrophysics Data System (ADS)

It has become widely accepted that the most dangerous cardiac arrhythmias are due to reentrant waves, i.e., electrical wave(s) that recirculate repeatedly throughout the tissue at a higher frequency than the waves produced by the heart's natural pacemaker (sinoatrial node). However, the complicated structure of cardiac tissue, as well as the complex ionic currents in the cell, have made it extremely difficult to pinpoint the detailed dynamics of these life-threatening reentrant arrhythmias. A simplified ionic model of the cardiac action potential (AP), which can be fitted to a wide variety of experimentally and numerically obtained mesoscopic characteristics of cardiac tissue such as AP shape and restitution of AP duration and conduction velocity, is used to explain many different mechanisms of spiral wave breakup which in principle can occur in cardiac tissue. Some, but not all, of these mechanisms have been observed before using other models; therefore, the purpose of this paper is to demonstrate them using just one framework model and to explain the different parameter regimes or physiological properties necessary for each mechanism (such as high or low excitability, corresponding to normal or ischemic tissue, spiral tip trajectory types, and tissue structures such as rotational anisotropy and periodic boundary conditions). Each mechanism is compared with data from other ionic models or experiments to illustrate that they are not model-specific phenomena. Movies showing all the breakup mechanisms are available at http://arrhythmia.hofstra.edu/breakup and at ftp://ftp.aip.org/epaps/chaos/E-CHAOEH-12-039203/ INDEX.html. The fact that many different breakup mechanisms exist has important implications for antiarrhythmic drug design and for comparisons of fibrillation experiments using different species, electromechanical uncoupling drugs, and initiation protocols.

Fenton, Flavio H.; Cherry, Elizabeth M.; Hastings, Harold M.; Evans, Steven J.

2002-09-01

379

Erbb2 Is Required for Cardiac Atrial Electrical Activity during Development  

PubMed Central

The heart is the first organ required to function during embryonic development and is absolutely necessary for embryo survival. Cardiac activity is dependent on both the sinoatrial node (SAN), which is the pacemaker of heart's electrical activity, and the cardiac conduction system which transduces the electrical signal though the heart tissue, leading to heart muscle contractions. Defects in the development of cardiac electrical function may lead to severe heart disorders. The Erbb2 (Epidermal Growth Factor Receptor 2) gene encodes a member of the EGF receptor family of receptor tyrosine kinases. The Erbb2 receptor lacks ligand-binding activity but forms heterodimers with other EGF receptors, stabilising their ligand binding and enhancing kinase-mediated activation of downstream signalling pathways. Erbb2 is absolutely necessary in normal embryonic development and homozygous mouse knock-out Erbb2 embryos die at embryonic day (E)10.5 due to severe cardiac defects. We have isolated a mouse line, l11Jus8, from a random chemical mutagenesis screen, which carries a hypomorphic missense mutation in the Erbb2 gene. Homozygous mutant embryos exhibit embryonic lethality by E12.5-13. The l11Jus8 mutants display cardiac haemorrhage and a failure of atrial function due to defects in atrial electrical signal propagation, leading to an atrial-specific conduction block, which does not affect ventricular conduction. The l11Jus8 mutant phenotype is distinct from those reported for Erbb2 knockout mouse mutants. Thus, the l11Jus8 mouse reveals a novel function of Erbb2 during atrial conduction system development, which when disrupted causes death at mid-gestation. PMID:25269082

Tenin, Gennadiy; Clowes, Christopher; Wolton, Kathryn; Krejci, Eliska; Wright, Jayne A.; Lovell, Simon C.; Sedmera, David; Hentges, Kathryn E.

2014-01-01

380

The Physics of Cardiac Fibrillation: Strings that kill  

NASA Astrophysics Data System (ADS)

Fibrillation is a state of spatio-temporal chaos in a 3d-biological excitable medium, namely the heart muscle. The building blocks are wave-emitting three-dimensional topological singularities in the electric excitation field of the tissue. These string like singularities send out a rotating wave fields with very fast frequencies (up to 10 times normal heart rate) and thus dominate over the pacemaker. The incoherent electrical excitation of the spatio-temporal chaotic dynamics leads to an unsynchronized contraction of the cardiac muscle and to the loss of the pumping action, and if untreated to death. Due to the topological nature of the spatio-temporal chaotic state it is very difficult to control. Current defibrillation technologies use strong electric field pulses (1 kV, 30 A, 12 ms) to reset the whole muscle. Here we report that natural muscle heterogeneities act as wave emitting sites when a weak electric field pulse is applied across the tissue. We report theoretical predictions on the physics and support the findings by results from experiment. This work was conducted in collaboration with Stefan Luther (MPIDS), Falvio Fenton ( Cornell), Amgad Squires (Cornell), Robert Gilmour (Cornell), Valentin Krinsky (MPIDS), Alain Pumir (NIce).

Bodenschatz, Eberhard

2009-03-01

381

Slow progressing cardiac complications--a case report  

PubMed Central

Abstract Objective This case presentation describes an uncommon development of complete heart block. Within 48 hours after a motor vehicle accident with the deployment of the air bag against the patient's chest, the patient reported exertional bradycardia and shortness of breath. Clinical Features A 51-year-old man was in a motor vehicle accident. After the collision, he noticed a slow onset of chest discomfort with exertion and bradycardia. The patient experienced cardiac difficulty during a stress electrocardiogram. During the 4 months after the motor vehicle accident, symptoms progressed; and a diagnosis of vagal sympathetic reflex was suggested. Intervention and Outcome A pacemaker was finally required because of the ventricular pacing of 35 to 40 beats per minute, which was symptomatic of a complete atrioventricular block. Conclusion A gradual progression to complete atrioventricular block over a period longer than 3 weeks is unusual. This case demonstrates that a patient manifesting exertional bradycardia and shortness of breath shortly after chest trauma should be regularly monitored until all symptoms are resolved. PMID:19674717

Williams, Jonathan C.; Elkington, William C.

2008-01-01

382

Surgical management of cardiac implantable electronic device infections  

PubMed Central

Purpose The infection of cardiac implantable electronic devices (CIED) is a serious and potentially lethal complication. The population at risk is growing, as the device implantation is increasing especially in older patients with associated comorbid conditions. Our purpose was to present the management of this complicated surgical condition and to extract the relevant conclusions. Methods During a 3-year period 1,508 CIED were implanted in our hospital. We treated six cases of permanent pacemaker infection with localized pocket infection or endocarditis. In accordance to the recent AHA/ACC guidelines, complete device removal was decided in all cases. The devices were removed under general anaesthesia, with a midline sternotomy, under extracorporeal circulation on the beating heart. Epicardial permanent pacing electrodes were placed on the right atrium and ventricle before the end of the procedure. Results The postoperative course of all patients was uncomplicated and after a follow up period of five years no relapse of infection occurred. Conclusions Management protocols that include complete device removal are the only effective measure for the eradication of CIED infections. Although newer technologies have emerged and specialized techniques of percutaneous device removal have been developed, the surgical alternative to these methods can be a safe solution in cases of infected devices. PMID:24672692

Koutentakis, Michael; Siminelakis, Stavros; Korantzopoulos, Panagiotis; Petrou, Alexandra; Priavali, Eleftheria; Mpakas, Andreas; Gesouli, Eleftheria; Apostolakis, Eleftheria; Tsakiridis, Kosmas; Katsikogiannis, Nikolaos; Kougioumtzi, Ioanna; Machairiotis, Nikolaos; Tsiouda, Theodora; Zarogoulidis, Konstantinos

2014-01-01

383

Inhibition of pacemaker activity in interstitial cells of Cajal by LPS via NF-?B and MAP kinase  

PubMed Central

AIM: To investigate lipopolysaccharide (LPS) related signal transduction in interstitial cells of Cajal (ICCs) from mouse small intestine. METHODS: For this study, primary culture of ICCs was prepared from the small intestine of the mouse. LPS was treated to the cells prior to measurement of the membrane currents by using whole-cell patch clamp technique. Immunocytochemistry was used to examine the expression of the proteins in ICCs. RESULTS: LPS suppressed the pacemaker currents of ICCs and this could be blocked by AH6809, a prostaglandin E2-EP2 receptor antagonist or NG-Nitro-L-arginine Methyl Ester, an inhibitor of nitric oxide (NO) synthase. Toll-like receptor 4, inducible NO synthase or cyclooxygenase-2 immunoreactivity by specific antibodies was detected on ICCs. Catalase (antioxidant agent) had no action on LPS-induced action in ICCs. LPS actions were blocked by nuclear factor ?B (NF-?B) inhibitor, actinomycin D (a gene transcription inhibitor), PD 98059 (a p42/44 mitogen-activated protein kinases inhibitor) or SB 203580 [a p38 mitogen-activated protein kinases (MAPK) inhibitor]. SB 203580 also blocked the prostaglandin E2-induced action on pacemaker currents in ICCs but not NO. CONCLUSION: LPS inhibit the pacemaker currents in ICCs via prostaglandin E2- and NO-dependent mechanism through toll-like receptor 4 and suggest that MAPK and NF-?B are implicated in these actions. PMID:23482668

Zuo, Dong Chuan; Choi, Seok; Shahi, Pawan Kumar; Kim, Man Yoo; Park, Chan Guk; Kim, Young Dae; Lee, Jun; Chang, In Yeoup; So, Insuk; Jun, Jae Yeoul

2013-01-01

384

Pediatric Cardiac Surgery in Developing Countries  

Microsoft Academic Search

Pediatric cardiac surgery in developing countries is a major challenge. It is a challenge to employ evolving methods to cater\\u000a to the surgical needs of a very large number of children with congenital heart defects while dealing with severe budgetary\\u000a constraints, finding funding to maintain the program, and maintaining quality in the backdrop of constant turnover of trained\\u000a medical, nursing,

Suresh G. Rao

2007-01-01

385

Advanced Cardiac Life Support.  

ERIC Educational Resources Information Center

This document contains materials for an advanced college course in cardiac life support developed for the State of Iowa. The course syllabus lists the course title, hours, number, description, prerequisites, learning activities, instructional units, required text, six references, evaluation criteria, course objectives by units, course…

Kirkwood Community Coll., Cedar Rapids, IA.

386

Nonexercise cardiac stress testing  

SciTech Connect

Many patients who require evaluation for coronary artery disease are unable to undergo exercise stress testing because of physiologic or psychological limitations. Drs Vacek and Baldwin describe three alternative methods for assessment of cardiac function in these patients, all of which have high levels of diagnostic sensitivity and specificity. 23 references.

Vacek, J.L.; Baldwin, T. (Univ. of Kansas Medical Center, Kansas City (USA))

1989-09-15

387

Cardiac disease in pregnancy.  

PubMed

Cardiac disease complicates approximately 1% to 3% of pregnancies and is responsible for 10% to 15% of maternal mortality. The number of women of childbearing age with congenital disease is increasing as advances in diagnosis and treatment improve survival rates and overall health, allowing successful pregnancy. Pregnant women with severe cardiac disease or women who experience a cardiac event during pregnancy will require admission and stabilization in an adult critical care unit. This group of patients can prove challenging for the obstetrical staff and the critical care staff because they require blending of the knowledge and skills of 2 highly specialized areas of healthcare. The key component to a comprehensive and organized approach to management that ensures the best possible outcome for the woman is a multidisciplinary team that devises a plan on the basis of the most current information, communicates with each other and the patient effectively, and assumes responsibility for implementation of the plan. The purpose of this article is to review management of the woman with cardiac disease throughout pregnancy. PMID:16456361

Arafeh, Julie M R; Baird, Suzanne McMurtry

2006-01-01

388

Cardiac and Pulmonary Injury  

Microsoft Academic Search

Cardiac and pulmonary injuries present major chal- lenges in diagnosis and treatment. Distinct differences between penetrating and blunt trauma of these or- gans exist. Outcomes for severe injuries are still grave. Organized trauma systems can provide optimal care by minimizing prehospital time, allowing easy access to imaging modalities, and offering state-of-the-art treatment strategies. A multidisciplinary approach, including surgeons, intensivists, and

George C. Velmahos; Muhammad U. Butt

2008-01-01

389

The cardiac malpositions.  

PubMed

Dextrocardia was known in the 17th century and was 1 of the first congenital malformations of the heart to be recognized. Fifty years elapsed before Matthew Baillie published his account of complete transposition in a human of the thoracic and abdominal viscera to the opposite side from what is natural. In 1858, Thomas Peacock stated that "the heart may be congenitally misplaced in various ways, occupying either an unusual position within the thorax, or being situated external to that cavity." In 1915, Maude Abbott described ectopia cordis, and Richard Paltauf's remarkable illustrations distinguished the various types of dextrocardia. In 1928, the first useful classification of the cardiac malpositions was proposed, and in 1966, Elliott et al's radiologic classification set the stage for clinical recognition. The first section of this review deals with the 3 basic cardiac malpositions in the presence of bilateral asymmetry. The second section deals with cardiac malpositions in the presence of bilateral left-sidedness or right-sidedness. Previous publications on cardiac malpositions are replete with an arcane vocabulary that confounds rather than clarifies. Even if the terms themselves are understood, inherent complexity weighs against clarity. This review was designed as a guided tour of an unfamiliar subject. PMID:21861958

Perloff, Joseph K

2011-11-01

390

Ethical Issues in Cardiac Surgery  

PubMed Central

While ethical behavior has always been part of cardiac surgical practice, ethical deliberation has only recently become an important component of cardiac surgical practice. Issues such as informed consent, conflict of interest, and professional self-regulation, among many others, have increasingly attracted the attention of cardiac surgeons. This review covers several broad topics of interest to cardiac surgeons and cardiologists, and treats several other topics more briefly. There is much uncertainty about what the future holds for cardiac surgical practice, research, and culture, and we discuss the background of ethical issues to serve as a platform for envisioning what is to come. PMID:22642634

Kavarana, Minoo N.; Sade, Robert M.

2012-01-01

391

Cardiac surgery outcomes.  

PubMed

Accrediting organizations and payers are demanding valid and reliable data that demonstrate the value of services. Federal agencies, healthcare industry groups, and healthcare watchdog groups are increasing the demand for public access to outcomes data. A new and growing outcomes dynamic is the information requested by prospective patients in an increasingly consumer-oriented business. Patients demand outcomes, and resources are developing to meet these demands. Physicians are increasingly confronted with requests for information about their mortality and morbidity rates, malpractice suits, and disciplinary actions received. For example, in Virginia, prospective patients have access to data provided by the nonprofit group Virginia Health Information. After numerous resolutions by the Virginia Senate since 1999, the prospective Virginia medical consumer now has access to several annual publications: Virginia Hospitals: A Consumer's Guide, 1999 Annual Report and Strategic Plan Update, and the 1999 Industry Report: Virginia Hospitals and Nursing Facilities. Consumers have access to cardiac outcomes data stratified by hospital, gender, and cardiac service line (cardiac surgery, noninvasive cardiology, and invasive cardiology). This is particularly relevant to IHI because Virginia Health Information specifically targets cardiac care. IHI has a sizable investment in cardiovascular outcomes and has found outcomes measurement and research are key to providing quality care. IHI's goal is to move from an outcomes management model to a disease management model. The hope is to incorporate all aspects of the patient's continuum of care, from preoperative and diagnostic services through cardiac interventions to postoperative rehabilitation. Furthermore, every step along the way will be supported with functional status and quality of life assessments. Although these goals are ambitious and expensive, the return on investment is high. PMID:14618772

Halpin, Linda S; Barnett, Scott D; Beachy, Jim

2003-01-01

392

Cardiac surgery in Germany during 2013: a report on behalf of the German Society for Thoracic and Cardiovascular Surgery.  

PubMed

On the basis of a voluntary registry of the German Society for Thoracic and Cardiovascular Surgery (GSTCVS), data of all cardiac surgical procedures performed in 79 German cardiac surgical units during the year 2013 are presented. In 2013, a total of 99,128 cardiac surgical procedures (implantable cardioverter defibrillator [ICD] and pacemaker procedures excluded) were submitted to the registry. More than 13.8% of the patients were older than 80 years, which remains equal in comparison to the previous year. In-hospital mortality in 40,410 isolated coronary artery bypass grafting procedures (84.5% on-pump and 15.5% off-pump) was 2.9%. In 29,672 isolated valve procedures (including 7,722 catheter-based procedures), an in-hospital mortality of 4.7% was observed. This long-lasting registry of the GSTCVS will continue to be an important tool for quality control and voluntary public reporting by illustrating current facts and developments of cardiac surgery in Germany. PMID:24995534

Funkat, A; Beckmann, A; Lewandowski, J; Frie, M; Ernst, M; Schiller, W; Gummert, J F; Cremer, J

2014-08-01

393

Dynamic cardiac mapping on patient-specific cardiac models.  

PubMed

Minimally invasive techniques for electrophysiological cardiac data mapping and catheter ablation therapy have been driven through advancements in computer-aided technologies, including magnetic tracking systems, and virtual and augmented-reality environments. The objective of this work is to extend current cardiac mapping techniques to collect and display data in the temporal domain, while mapping on patient-specific cardiac models. This paper details novel approaches to collecting spatially tracked cardiac electrograms, registering the data with a patient-specific cardiac model, and interpreting the data directly on the model surface, with the goal of giving a more comprehensive cardiac mapping system in comparison to current systems. To validate the system, laboratory studies were conducted to assess the accuracy of navigating to both physical and virtual landmarks. Subsequent to the laboratory studies, an in-vivo porcine experiment was conducted to assess the systems overall ability to collect spatial tracked electrophysiological data, and map directly onto a cardiac model. The results from these experiments show the new dynamic cardiac mapping system was able to maintain high accuracy of locating physical and virtual landmarks, while creating a dynamic cardiac map displayed on a dynamic cardiac surface model. PMID:18979839

Wilson, Kevin; Guiraudon, Gerard; Jones, Doug; Linte, Cristian A; Wedlake, Chris; Moore, John; Peters, Terry M

2008-01-01

394

Experimental observation of transition from chaotic bursting to chaotic spiking in a neural pacemaker  

NASA Astrophysics Data System (ADS)

The transition from chaotic bursting to chaotic spiking has been simulated and analyzed in theoretical neuronal models. In the present study, we report experimental observations in a neural pacemaker of a transition from chaotic bursting to chaotic spiking within a bifurcation scenario from period-1 bursting to period-1 spiking. This was induced by adjusting extracellular calcium or potassium concentrations. The bifurcation scenario began from period-doubling bifurcations or period-adding sequences of bursting pattern. This chaotic bursting is characterized by alternations between multiple continuous spikes and a long duration of quiescence, whereas chaotic spiking is comprised of fast, continuous spikes without periods of quiescence. Chaotic bursting changed to chaotic spiking as long interspike intervals (ISIs) of quiescence disappeared within bursting patterns, drastically decreasing both ISIs and the magnitude of the chaotic attractors. Deterministic structures of the chaotic bursting and spiking patterns are also identified by a short-term prediction. The experimental observations, which agree with published findings in theoretical neuronal models, demonstrate the existence and reveal the dynamics of a neuronal transition from chaotic bursting to chaotic spiking in the nervous system.

Gu, Huaguang

2013-06-01

395

A lack of intestinal pacemaker (c-kit) in aganglionic bowel of patients with Hirschsprung's disease.  

PubMed

Recent experimental studies in mice have shown that the proto-oncogene c-kit plays a key role in the development of a component of the pacemaker system that is required for generation of autonomic gut motility. These studies further suggest that interaction of the c-kit receptor and its ligand (stem cell factor, SCF) is critical for the development of the enteric nervous system. The authors investigated the presence of c-kit-positive (c-kit+) cells as well as the expression of SCF in bowel from 12 patients with Hirschsprung's disease (HD), 4 patients with total colonic aganglionosis (TCA), 2 patients with extensive aganglionosis (EA) and 14 controls. Our methods involved the use of immunohistochemistry with antihuman c-kit sera and antihuman SCF sera. A few c-kit+ cells were found in the muscle layers of aganglionic bowels from HD, TCA and EA, in contrast to many c-kit+ cells in ganglionic bowel segments from control, HD, and TCA patients. Expression of SCF was identified in the muscle layers as well as in myenteric plexus of ganglionic bowel, in contrast to its absence in the muscle layers of aganglionic bowel specimens. A lack of c-kit and SCF might be of significance for autonomic gut dysmotility in aganglionic bowel segments of patients with HD and allied disorders such as chronic idiopathic intestinal pseudo-obstruction. PMID:7539078

Yamataka, A; Kato, Y; Tibboel, D; Murata, Y; Sueyoshi, N; Fujimoto, T; Nishiye, H; Miyano, T

1995-03-01

396

Flight test of carbon-phenolic on a spacecraft launched by the pacemaker vehicle system  

NASA Technical Reports Server (NTRS)

Carbon-phenolic material consisting of 50 percent carbon fibers and 50 percent phenolic resin was flight tested on a recoverable spacecraft launched by the Pacemaker vehicle system. The heat shield of the spacecraft was fabricated so that the carbon fibers in the ablator material had different orientations over several areas of the spacecraft. The environment in which the spacecraft was tested produced heating rates on the hemispherical nose up to 13.6 MW/sq m (1200 Btu/sq ft/sec) and stagnation-point pressures up to 1.27 MN/sq m (12.5 atm). The experimental results are presented. Due to high heating rates and possible spallation and mechanical char removal the greatest mass loss occurred in the nose region. Essentially uniform surface recession and char thickness were observed on the conical section of the spacecraft. A comparison of measured heating rates with computed turbulent and laminar heating rates, as well as measurements of sound-pressure fluctuations in the boundary layer obtained with acoustic sensors, indicated that the boundary layer underwent transition. The acoustic sensor provides an interesting new data form for the general study of boundary-layer transition for free-flight investigations.

Walton, T. E., Jr.; Witte, W. G.

1972-01-01

397

Aging Might Increase the Incidence of Infection from Permanent Pacemaker Implantation  

PubMed Central

Aim. The elderly are the major population receiving the implantation of a permanent pacemaker (PPM). Infection is a devastating complication. The present study is to verify the relationship between age and PPM implantation infection. Methods. All patients (162 adult and 292 elder patients) received the implantation of PPM. Subcutaneous tissue samples solution was collected in three time points, the first sample was got at skin incision, and the second sample was got when the PPM had been implanted. And the third sample was got after 0.9% NaCl quick rinse. And the tissue solutions were cultured. If culture results are positive, it is considered as evidence of the presence of bacteria in pocket in operation of PPM implantation. Results. The data demonstrated that compared with that in the adult patients, subcutaneous bacterial survival rate was higher significantly in the elderly. Staphylococcus epidermidis is the major bacterial strain. The rinse decreased subcutaneous bacterial survival rates in the adult group. Conclusion. With the age increasing, PPM implantation might be easier to result in infection. Simple rinse can prevent implantation infection significantly. However, age alleviated the protective effects of rinse. Therefore, we should pay more attention to post implantation infection in the elderly. PMID:24379903

Li, Zhi Zhong; Zhang, Jingmei; Zhang, Jinrong; Fan, Qian; Du, Jie

2013-01-01

398

ABC transporter functions as a pacemaker for sequestration of plant glucosides in leaf beetles  

PubMed Central

Plant-herbivore interactions dominate the planet’s terrestrial ecology. When it comes to host–plant specialization, insects are among the most versatile evolutionary innovators, able to disarm multiple chemical plant defenses. Sequestration is a widespread strategy to detoxify noxious metabolites, frequently for the insect’s own benefit against predation. In this study, we describe the broad-spectrum ATP-binding cassette transporter CpMRP of the poplar leaf beetle, Chrysomela populi as the first candidate involved in the sequestration of phytochemicals in insects. CpMRP acts in the defensive glands of the larvae as a pacemaker for the irreversible shuttling of pre-selected metabolites from the hemolymph into defensive secretions. Silencing CpMRP in vivo creates a defenseless phenotype, indicating its role in the secretion process is crucial. In the defensive glands of related leaf beetle species, we identified sequences similar to CpMRP and assume therefore that exocrine gland-based defensive strategies, evolved by these insects to repel their enemies, rely on ABC transporters as a key element. DOI: http://dx.doi.org/10.7554/eLife.01096.001 PMID:24302568

Strauss, Anja S; Peters, Sven; Boland, Wilhelm; Burse, Antje

2013-01-01

399

ABC transporter functions as a pacemaker for sequestration of plant glucosides in leaf beetles.  

PubMed

Plant-herbivore interactions dominate the planet's terrestrial ecology. When it comes to host-plant specialization, insects are among the most versatile evolutionary innovators, able to disarm multiple chemical plant defenses. Sequestration is a widespread strategy to detoxify noxious metabolites, frequently for the insect's own benefit against predation. In this study, we describe the broad-spectrum ATP-binding cassette transporter CpMRP of the poplar leaf beetle, Chrysomela populi as the first candidate involved in the sequestration of phytochemicals in insects. CpMRP acts in the defensive glands of the larvae as a pacemaker for the irreversible shuttling of pre-selected metabolites from the hemolymph into defensive secretions. Silencing CpMRP in vivo creates a defenseless phenotype, indicating its role in the secretion process is crucial. In the defensive glands of related leaf beetle species, we identified sequences similar to CpMRP and assume therefore that exocrine gland-based defensive strategies, evolved by these insects to repel their enemies, rely on ABC transporters as a key element. DOI: http://dx.doi.org/10.7554/eLife.01096.001. PMID:24302568

Strauss, Anja S; Peters, Sven; Boland, Wilhelm; Burse, Antje

2013-01-01

400

Simulation of LV pacemaker lead in marginal vein: potential risk factors for acute dislodgement.  

PubMed

Although left ventricular (LV) coronary sinus lead dislodgement remains a problem, the risk factors for dislodgement have not been clearly defined. In order to identify potential risk factors for acute lead dislodgement, we conducted dynamic finite element simulations of pacemaker lead dislodgement in marginal LV vein. We considered factors such as mismatch in lead and vein diameters, velocity of myocardial motion, branch angle between the insertion vein and the coronary sinus, degree of slack, and depth of insertion. The results show that large lead-to-vein diameter mismatch, rapid myocardial motion, and superficial insertion are potential risk factors for lead dislodgement. In addition, the degree of slack presents either a positive or negative effect on dislodgement risk depending on the branch angle. The prevention of acute lead dislodgment can be enforced by inducing as much static friction force as possible at the lead-vein interface, while reducing the external force. If the latter exceeds the former, dislodgement will occur. The present findings underscore the major risk factors for lead dislodgment, which may improve implantation criterion and future lead design. PMID:21303182

Zhao, Xuefeng; Burger, Mike; Liu, Yi; Das, Mithilesh K; Combs, William; Wenk, Jonathan F; Guccione, Julius M; Kassab, Ghassan S

2011-03-01

401

Retrograde Bone Morphogenetic Protein Signaling Shapes a Key Circadian Pacemaker Circuit  

PubMed Central

The neuropeptide pigment-dispersing factor (PDF) synchronizes molecular oscillations within circadian pacemakers in the Drosophila brain. It is expressed in the small ventral lateral neurons (sLNvs) and large ventral lateral neurons, the former being indispensable for maintaining behavioral rhythmicity under free-running conditions. How PDF circuits develop the specific connectivity traits that endow such global behavioral control remains unknown. Here, we show that mature sLNv circuits require PDF signaling during early development, acting through its cognate receptor PDFR at postsynaptic targets. Yet, axonal defects by PDF knockdown are presynaptic and become apparent only after metamorphosis, highlighting a delayed response to a signal released early on. Presynaptic expression of constitutively active bone morphogenetic protein (BMP) receptors prevents pdfr mutants misrouting phenotype, while sLNv-restricted downregulation of BMP signaling components phenocopied pdf01. Thus, we have uncovered a novel mechanism that provides an early “tagging” of synaptic targets that will guide circuit refinement later in development. PMID:23303947

Gorostiza, E. Axel; Ceriani, M. Fernanda

2013-01-01

402

Experimental observation of transition from chaotic bursting to chaotic spiking in a neural pacemaker.  

PubMed

The transition from chaotic bursting to chaotic spiking has been simulated and analyzed in theoretical neuronal models. In the present study, we report experimental observations in a neural pacemaker of a transition from chaotic bursting to chaotic spiking within a bifurcation scenario from period-1 bursting to period-1 spiking. This was induced by adjusting extracellular calcium or potassium concentrations. The bifurcation scenario began from period-doubling bifurcations or period-adding sequences of bursting pattern. This chaotic bursting is characterized by alternations between multiple continuous spikes and a long duration of quiescence, whereas chaotic spiking is comprised of fast, continuous spikes without periods of quiescence. Chaotic bursting changed to chaotic spiking as long interspike intervals (ISIs) of quiescence disappeared within bursting patterns, drastically decreasing both ISIs and the magnitude of the chaotic attractors. Deterministic structures of the chaotic bursting and spiking patterns are also identified by a short-term prediction. The experimental observations, which agree with published findings in theoretical neuronal models, demonstrate the existence and reveal the dynamics of a neuronal transition from chaotic bursting to chaotic spiking in the nervous system. PMID:23822491

Gu, Huaguang

2013-06-01

403

Alterations induced by chronic lead exposure on the cells of circadian pacemaker of developing rats  

PubMed Central

Lead (Pb) exposure alters the temporal organization of several physiological and behavioural processes in which the suprachiasmatic nucleus (SCN) of the hypothalamus plays a fundamental role. In this study, we evaluated the effects of chronic early Pb exposure (CePbe) on the morphology, cellular density and relative optical density (OD) in the cells of the SCN of male rats. Female Wistar rats were exposed during gestation and lactation to a Pb solution containing 320 ppm of Pb acetate through drinking water. After weaning, the pups were maintained with the same drinking water until sacrificed at 90 days of age. Pb levels in the blood, hypothalamus, hippocampus and prefrontal cortex were significantly increased in the experimental group. Chronic early Pb exposure induced a significant increase in the minor and major axes and somatic area of vasoactive intestinal polypeptide (VIP)- and vasopressin (VP)-immunoreactive neurons. The density of VIP-, VP- and glial fibrillary acidic protein (GFAP)-immunoreactive cells showed a significant decrease in the experimental group. OD analysis showed a significant increase in VIP neurons of the experimental group. The results showed that CePbe induced alterations in the cells of the SCN, as evidenced by modifications in soma morphology, cellular density and OD in circadian pacemaker cells. These findings provide a morphological and cellular basis for deficits in circadian rhythms documented in Pb-exposed animals. PMID:21324006

Rojas-Castaneda, Julio Cesar; Vigueras-Villasenor, Rosa Maria; Rojas, Patricia; Chavez-Saldana, Margarita; Perez, Oscar Gutierrez; Montes, Sergio; Rios, Camilo

2011-01-01

404

Millimeter waves thermally alter the firing rate of the Lymnaea pacemaker neuron  

SciTech Connect

The effects of millimeter waves (mm-waves, 75 GHz) and temperature elevation on the firing rate of the BP-4 pacemaker neuron of the pond snail Lymnaea stagnalis were studied by using microelectrode techniques. The open end of a rectangular waveguide covered with a thin Teflon film served as a radiator. Specific absorption rates (SARs), measured in physiological solution at the radiator outlet, ranged from 600 to 4,200 W/kg, causing temperature rises from 0.3 to 2.2 C, respectively. Irradiation at an SAR of 4,200 W/kg caused a biphasic change in the firing rate, i.e., a transient decrease in the firing rate followed by a gradual increase to a new level that was 68 {+-} 21% above control. The biphasic changes in the firing rate were reproduced by heating under the condition that the magnitude (2 C) and the rate of temperature rise were equal to those produced by the irradiation. The addition of 0.05 mM of ouabain caused the disappearance of transient responses of the neuron to the irradiation. It was shown that the rate of temperature rise played an important role in the development of a transient neuronal response. The threshold stimulus for a transient response of the BP-4 neutron found in warming experiments was a temperature rise of 0.0025 C/s.

Alekseev, S.I.; Kochetkova, N.V. [Russian Academy of Sciences, Puschino (Russian Federation). Inst. of Cell Biophysics] [Russian Academy of Sciences, Puschino (Russian Federation). Inst. of Cell Biophysics; Ziskin, M.C.; Bolshakov, M.A. [Temple Univ. Medical School, Philadelphia, PA (United States). Center for Biomedical Physics] [Temple Univ. Medical School, Philadelphia, PA (United States). Center for Biomedical Physics

1997-05-01

405

Epigenetic regulation of axonal growth of Drosophila pacemaker cells by histone acetyltransferase tip60 controls sleep.  

PubMed

Tip60 is a histone acetyltransferase (HAT) enzyme that epigenetically regulates genes enriched for neuronal functions through interaction with the amyloid precursor protein (APP) intracellular domain. However, whether Tip60-mediated epigenetic dysregulation affects specific neuronal processes in vivo and contributes to neurodegeneration remains unclear. Here, we show that Tip60 HAT activity mediates axonal growth of the Drosophila pacemaker cells, termed "small ventrolateral neurons" (sLNvs), and their production of the neuropeptide pigment-dispersing factor (PDF) that functions to stabilize Drosophila sleep-wake cycles. Using genetic approaches, we show that loss of Tip60 HAT activity in the presence of the Alzheimer's disease-associated APP affects PDF expression and causes retraction of the sLNv synaptic arbor required for presynaptic release of PDF. Functional consequence of these effects is evidenced by disruption of the sleep-wake cycle in these flies. Notably, overexpression of Tip60 in conjunction with APP rescues these sleep-wake disturbances by inducing overelaboration of the sLNv synaptic terminals and increasing PDF levels, supporting a neuroprotective role for dTip60 in sLNv growth and function under APP-induced neurodegenerative conditions. Our findings reveal a novel mechanism for Tip60 mediated sleep-wake regulation via control of axonal growth and PDF levels within the sLNv-encompassing neural network and provide insight into epigenetic-based regulation of sleep disturbances observed in neurodegenerative diseases like Alzheimer's disease. PMID:22982579

Pirooznia, Sheila K; Chiu, Kellie; Chan, May T; Zimmerman, John E; Elefant, Felice

2012-12-01

406

Clone mixtures and a pacemaker: new facets of Red-Queen theory and ecology.  

PubMed Central

Host-parasite antagonistic interaction has been proposed as a potential agent to promote genetic polymorphism and to favour sex against asex, despite its twofold cost in reproduction. However, the host-parasite gene-for-gene dynamics often produce unstable cycles that tend to destroy genetic diversity. Here, we examine such diversity destroying coevolutionary dynamics of host and parasite, which is coupled through local or global migration, or both, between demes in a metapopulation structure. We show that, with global migration in the island model, peculiar out-of-phase islands spontaneously arise in the cluster of islands converging to a global synchrony. Such asynchrony induced by the 'pacemaker islands' serves to restore genetic variation. With increasing fraction of local migration, spots of asynchrony are converted into loci or foci of spiral and target patterns, whose rotating arms then cover the majority of demes. A multi-locus analogue of the model reproduces the same tendency toward asynchrony, and the condition arises for an advantage of asexual clones over their sexual counterpart when enough genetic diversity is maintained through metapopulation storage-migration serves as a cheap alternative to sex. PMID:11958707

Sasaki, A; Hamilton, W D; Ubeda, F

2002-01-01

407

Electromagnetic immunity of implantable pacemakers exposed to wi-fi devices.  

PubMed

The purpose of this study is to evaluate the potential for electromagnetic interference (EMI) and to assess the immunity level of implantable pacemakers (PM) when exposed to the radiofrequency (RF) field generated by Wi-Fi devices. Ten PM from five manufacturers, representative of what today is implanted in patients, have been tested in vitro and exposed to the signal generated by a Wi-Fi transmitter. An exposure setup that reproduces the actual IEEE 802.11b/g protocol has been designed and used during the tests. The system is able to amplify the Wi-Fi signal and transmits at power levels higher than those allowed by current international regulation. Such approach allows one to obtain, in case of no EMI, a safety margin for PM exposed to Wi-Fi signals, which otherwise cannot be derived if using commercial Wi-Fi equipment. The results of this study mitigate concerns about using Wi-Fi devices close to PM: none of the PM tested exhibit any degradation of their performance, even when exposed to RF field levels five times higher than those allowed by current international regulation (20 W EIRP). In conclusion, Wi-Fi devices do not pose risks of EMI to implantable PM. The immunity level of modern PM is much higher than the transmitting power of RF devices operating at 2.4 GHz. PMID:25162422

Mattei, Eugenio; Censi, Federica; Triventi, Michele; Calcagnini, Giovanni

2014-10-01

408

Cardiac nuclear medicine  

SciTech Connect

The book begins with a review of the radionuclide methods available for evaluating cardiac perfusion and function. The authors discuss planar and tomographic thallium myocardial imaging, first-pass and equilibrium radionuclide angiography, and imaging with infarct-avid tracers. Several common but more specialized procedures are then reviewed: nonogemetric measurement of left ventricular volume, phase (Fourier) analysis, stroke volume ratio, right ventricular function, and diastolic function. A separate chapter is devoted to drug interventions and in particular the use of radionuclide ventriculography to monitor doxorubicin toxicity and therapy of congestive heart failure. The subsequent chapters provide a comprehensive guide to test selection, accuracy, and results in acute myocardial infarction, in postmyocardial infarction, in chronic coronary artery disease, before and after medical or surgical revascularization, in valvular heart disease, in cardiomyopathies, and in cardiac trauma.

Gerson, M.C.

1987-01-01

409

Cardiac assist device infections  

Microsoft Academic Search

Cardiac assist devices have emerged as an increasingly important option for circulatory support in patients with advanced\\u000a congestive heart failure. Infection has been the leading cause of death with use of ventricular assist devices for the past\\u000a 25 years, and continues to be a major cause of morbidity and mortality in this population. Infections may involve the internal\\u000a (blood-containing) components,

Shmuel Shoham; Leslie W. Miller

2009-01-01

410

Oxytocin in cardiac ontogeny  

PubMed Central

Previous studies demonstrated the presence of oxytocin (OT) and oxytocin receptors (OTRs) in the heart. The present work provides results supporting a potential role of OT in cardiomyogenesis. Here, we show a maximal OT and OTR protein level in the developing rat heart at day 21 of gestation and postnatal days 1-4, when cardiac myocytes are at a stage of intense hyperplasia. Between postnatal days 1 and 66, OT decreased linearly in all heart chambers (4.1- to 6.6-fold). Correspondingly, immunocytochemistry demonstrated that OTRs, which were eminent in postnatal cardiomyocytes, declined with age to low levels in adults. Interestingly, in coronary vasculature, OTRs developed in endothelial cells at postnatal days 12 and 22 and achieved a plateau in adult rats. These findings suggest that OT can be involved in developmental formation of the coronary vessels. In vivo, the OT/OTR system in the fetal heart was sensitive to the actions of retinoic acid (RA), recognized as a major cardiac morphogen. RA treatment produced a significant increase (2- to 3-fold) both in the OT concentration and in the OT mRNA levels. Ex vivo, an OT antagonist inhibited RA-mediated cardiomyocyte differentiation of P19 embryonic stem cells. The decline of cardiac OT expression from infancy to adulthood of the rat and changes in cell types expressing OTR indicate a dynamic regulation of the OT system in the heart rather than constitutive expression. The results support the hypothesis that RA induces cardiomyogenesis by activation of the cardiac OT system. PMID:15316117

Jankowski, Marek; Danalache, Bogdan; Wang, Donghao; Bhat, Pangala; Hajjar, Fadi; Marcinkiewicz, Mieczyslaw; Paquin, Joanne; McCann, Samuel M.; Gutkowska, Jolanta

2004-01-01

411

Oxytocin in cardiac ontogeny.  

PubMed

Previous studies demonstrated the presence of oxytocin (OT) and oxytocin receptors (OTRs) in the heart. The present work provides results supporting a potential role of OT in cardiomyogenesis. Here, we show a maximal OT and OTR protein level in the developing rat heart at day 21 of gestation and postnatal days 1-4, when cardiac myocytes are at a stage of intense hyperplasia. Between postnatal days 1 and 66, OT decreased linearly in all heart chambers (4.1- to 6.6-fold). Correspondingly, immunocytochemistry demonstrated that OTRs, which were eminent in postnatal cardiomyocytes, declined with age to low levels in adults. Interestingly, in coronary vasculature, OTRs developed in endothelial cells at postnatal days 12 and 22 and achieved a plateau in adult rats. These findings suggest that OT can be involved in developmental formation of the coronary vessels. In vivo, the OT/OTR system in the fetal heart was sensitive to the actions of retinoic acid (RA), recognized as a major cardiac morphogen. RA treatment produced a significant increase (2- to 3-fold) both in the OT concentration and in the OT mRNA levels. Ex vivo, an OT antagonist inhibited RA-mediated cardiomyocyte differentiation of P19 embryonic stem cells. The decline of cardiac OT expression from infancy to adulthood of the rat and changes in cell types expressing OTR indicate a dynamic regulation of the OT system in the heart rather than constitutive expression. The results support the hypothesis that RA induces cardiomyogenesis by activation of the cardiac OT system. PMID:15316117

Jankowski, Marek; Danalache, Bogdan; Wang, Donghao; Bhat, Pangala; Hajjar, Fadi; Marcinkiewicz, Mieczyslaw; Paquin, Joanne; McCann, Samuel M; Gutkowska, Jolanta

2004-08-31

412