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PubMedDate not supplied

Electrode system for permanent implantable defibrillators: transvenous catheter and subcutaneous plate electrodes.

The permanently implanted automatic defibrillator offers an alternative treatment for heart patients with high risk of ventricular fibrillation, who cannot be safely treated by surgery or drugs. Because of size and energy requirements, permanently implanted automatic defibrillators are not presently practical for many of these patinets, and sudden death from ventricular fibrillation remains a majof health problem. This study, which determines the optimal electrode configuration of the transvenous catheter when used in conjunction with a subcutaneous plate or disk electrode for transvenous ventricular defibrillation, attempts one of many changes needed to improve the defibrillator's efficiency so that it will be a viable alternative treatment for delicate heart patients.

Animals↗
PubMed1981

Automatic defibrillation in man. The initial surgical experience.

The automatic implantable defibrillator is an electronic device designed to detect and promptly correct malignant ventricular arrhythmias. Nineteen patients, all survivors of multiple cardiac arrests because of ventricular arrhythmias unresponsive to therapy, have undergone implantation of the automatic defibrillator. In seven patients who had had a previous cardiac operation, implantation was performed through a left lateral thoracotomy. A median sternotomy was used in five patients without a previous operation. In six patients cardiac procedures were performed concomitantly with defibrillator implantation. There were no operative deaths. The average follow-up is 6 months, the longest being 14 months. Following implantation, 47 episodes of malignant ventricular arrhythmias were documented. Twenty-six occurred spontaneously (17 of them outside the hospital); all were corrected with a single 25 joule pulse. Seventeen of 21 arrhythmias induced postoperatively were terminated. Although further validation is required, this study demonstrates that the automatic defibrillator is capable of diagnosing and terminating potentially lethal ventricular arrhythmias. Finally, implantation can be safely accomplished in an exceedingly high risk population.

Adolescent↗
PubMedDate not supplied

Determining transthoracic impedance, delivered energy, and peak current during defibrillation episodes.

A simplified method has been developed to determine peak current, transthoracic impedance, and delivered energy during a damped sinusoidal defibrillation pulse. The discharge waveform information is generated from sampling the peak discharge current through a current transformer and measuring the voltage stored on the energy storage capacitor. For a given defibrillator circuit a unique relationship exists between the peak discharge current IM and the unknown external impedance Rext presented to the defibrillator by the patient; hence, measurement of IM allows calculation of Rext. A microprocessor-controlled algorithm provides delivered energy information using known internal resistance, capacitance, and inductance parameters. The benefit of this method of delivered energy calculation is that the current and voltage waveforms need not be digitized and then integrated to provide the desired information. This method also keeps defibrillation circuitry ground isolated and simplifies operation through the high electromagnetic fields generated during the discharge. The delivered energy information, along with time, date, and other patient parameters, is documented automatically with an annotation strip-chart recorder.

Adult↗
PubMedDate not supplied

Do we know enough to introduce semi-automatic defibrillation by ambulancemen in Belgium?

The application of semi-automatic external defibrillators by ambulancemen or emergency medical technicians is in the U.S.A. accepted as a substantial progress in the treatment of out-of-hospital sudden death. A retrospective estimation of the percentage of patients registered by the Belgian Cardio-Pulmonary-Cerebral-Resuscitation study group between 1983 and 1987 that could benefit from early defibrillation yielded a gain in good survival of 1% for the whole population. In 1991 a prehospital semi automatic external defibrillation program was started as a feasibility study in several two-tiered emergency physician staffed systems with an ongoing registry of cardiac arrest events. For Bruges and Ghent there was a non-significant increase in prolonged survival in the ventricular fibrillation subgroups with respectively 4.7% and 5.1% since the introduction of the semi-automatic external defibrillators. Apparent differences between our emergency medical systems and e.g. Seattle, such as the number of 1st tier units covering the population and a short delay between 1st and 2nd tier might account for a lack of a statistically significant improvement so far.

Belgium↗
PubMed1998

Intra-atrial defibrillation for atrial fibrillation: animal data.

Animal research in the area of atrial defibrillation has helped to bring about a greater understanding of the mechanisms and influencing factors of atrial defibrillation. Increased clinical interest in atrial tachyarrhythmias during the 1980s led to more intensive animal research in this area, in which concepts of intra-atrial cardioversion was only first described in 1974. Initially, the concept of one intracardiac catheter in conjunction with a subcutaneous electrode was evaluated. Further studies involved alternative waveforms, shock durations, electrode materials, and lead configurations to improve the percentage of successful cardioversions while reducing energy requirements. The results from ventricular defibrillation, in which the need for a homogenous field through the majority of fibrillating mass had been established, were applied to research for atrial defibrillation as well. An intracardiac vector with electrodes inside the heart was determined to be most efficient. Results concerning the feasibility, efficacy, and safety have been confirmed by clinical data. Further animal studies will help to evaluate new concepts for reducing energy requirements, such as new electrode materials and advanced shock timing. The clinical benefits of basic research in internal cardioversion of atrial fibrillation justifies additional animal research studies.

Atrial Fibrillation↗
PubMed2006

Cigarette smoking and the risk of supraventricular and ventricular tachyarrhythmias in high-risk cardiac patients with implantable cardioverter defibrillators.

INTRODUCTION: Nicotine elevates serum catecholamine concentration and is therefore potentially arrhythmogenic. However, the effect of cigarette smoking on arrhythmic risk in coronary heart disease patients is not well established. METHODS AND RESULTS: The risk of appropriate and inappropriate defibrillator therapy by smoking status was analyzed in 717 patients who received an implantable cardioverter defibrillator (ICD) in the Multicenter Automatic Defibrillator Implantation Trial-II. Compared with patients who had quit smoking before study entry (past smokers) and patients who had never smoked (never smokers), patients who continued smoking (current smokers) were significantly younger and generally had more favorable baseline clinical characteristics. Despite this, the adjusted hazard ratio (HR) for appropriate ICD therapy for fast ventricular tachycardia (at heart rates >or=180 b.p.m) or ventricular fibrillation was highest among current smokers (HR = 2.11 [95% CI 1.11-3.99]) and intermediate among past smokers (HR = 1.57 [95% CI 0.95-2.58]), as compared with never smokers (P for trend = 0.02). Current smokers also exhibited a higher risk of inappropriate ICD shocks (HR = 2.93 [95% CI 1.30-6.63]) than past (HR = 1.91 [95% CI 0.97-3.77]) and never smokers (P for trend = 0.008). CONCLUSIONS: In patients with ischemic left ventricular dysfunction, continued cigarette smoking is associated with a significant increase in the risk of life-threatening ventricular tachyarrhythmias and inappropriate ICD shocks induced by rapid supraventricular arrhythmias. Our findings stress the importance of complete smoking cessation in this high-risk population.

Aged↗
PubMed2006

Successful parental use of an automated external defibrillator for an infant with long-QT syndrome.

Congenital long-QT syndrome with 2:1 atrioventricular block presenting in the perinatal period is rare, has a poor prognosis, and leads to high risk for lethal ventricular arrhythmic events. An implantable cardioverter-defibrillator seems to be the most effective treatment in the prevention of arrhythmic sudden cardiac death in patients with long-QT syndrome. Technical limitations and risks associated with implantable cardioverter-defibrillators in asymptomatic infants is considered too great to justify use for primary prophylaxis against sudden cardiac death. In this case report we describe the first successful parental use of an automated external defibrillator prescribed for primary prophylaxis against sudden cardiac death in an infant with long-QT syndrome.

Anti-Arrhythmia Agents↗
PubMed2004

Implantable defibrillators for the prevention of mortality in patients with nonischemic cardiomyopathy: a meta-analysis of randomized controlled trials.

CONTEXT: Implantable cardioverter defibrillator (ICD) therapy is effective in primary and secondary prevention of sudden cardiac death among patients with prior myocardial infarction and depressed ejection fraction. However, conclusive evidence of survival benefit in patients with nonischemic cardiomyopathy (NICM) is still lacking. OBJECTIVE: To determine whether ICD therapy reduces all-cause mortality in patients with NICM. DATA SOURCES: MEDLINE (1966-2004), EMBASE (1991-2004), the Cochrane Central Register of Controlled Trials (through first quarter, 2004), reports presented at scientific meetings (2003-2004), and bibliographic review of secondary sources. Search terms included defibrillator, randomized controlled trials, clinical trials, and sudden death. STUDY SELECTION: Eligible studies were prospective randomized controlled trials of ICD or combined cardiac resynchronization therapy and defibrillator (CRT-D) vs medical therapy enrolling at least some individuals with NICM and reporting all-cause mortality as an outcome. Of 675 potentially relevant articles screened initially, 8 reports of randomized trials enrolling a total of 2146 patients with NICM were included. DATA EXTRACTION: Included studies were reviewed to determine the number of patients randomized, mean duration of follow-up, primary end point, mortality of ICD cohort, and mortality of control cohort. DATA SYNTHESIS: Five primary prevention trials enrolling 1854 patients with NICM were identified; pooled analysis suggested a significant reduction in total mortality among patients randomized to ICD or CRT-D vs medical therapy (risk ratio [RR], 0.69; 95% confidence interval [CI], 0.55-0.87; P = .002). Mortality reduction remained significant even after elimination of CRT-D trials. Two of the 3 secondary prevention trials presented subgroup estimates for ICD efficacy in NICM. Pooled analysis of these secondary prevention trials (n = 256 patients with NICM) indicated an equivalent but nonsignificant mortality reduction with ICD therapy (RR, 0.69; 95% CI, 0.39-1.24; P = .22). Analysis of all 7 trials combined demonstrated a statistically significant 31% overall reduction in mortality with ICD therapy (RR, 0.69; 95% CI, 0.56-0.86; P = .002). CONCLUSION: ICD therapy appears to significantly reduce mortality in selected patients with NICM.

Cardiomyopathies↗
PubMed2006

Evaluation and management of patients after implantable cardioverter-defibrillator shock.

CONTEXT: There has been a tremendous increase in the use of implantable cardioverter-defibrillators (ICDs) after several large clinical trials demonstrated their ability to effectively reduce mortality in selected populations of patients with cardiac disease. Thus, the nonelectrophysiologist will often encounter patients who have received an ICD shock. OBJECTIVE: To assess options for the evaluation and management of patients who have received an ICD shock. EVIDENCE ACQUISITION: Literature search using the PubMed and MEDLINE databases to identify articles published from January 1990 to September 2006, using the Medical Subject Headings defibrillators, implantable; defibrillators, implantable/adverse effects; anti-arrhythmic agents; electric countershock; quality of life; tachycardia therapy; algorithm; ventricular tachycardia/diagnosis; and supraventricular tachycardia/diagnosis. Case reports were excluded and articles were limited to those published in English. Scientific statements and guidelines from the American College of Cardiology, the American Heart Association, and the Heart Rhythm Society were also reviewed, as were the reference lists of retrieved articles, to identify any additional articles for inclusion. EVIDENCE SYNTHESIS: There are multiple causes of both appropriate and inappropriate ICD shocks. Irrespective of appropriateness, receiving ICD shocks substantially impairs a patient's quality of life. A variety of techniques are available using ICD programming to reliably limit the occurrence of appropriate or inappropriate ICD shocks. Antiarrhythmic medications can also effectively reduce the occurrence of shocks. CONCLUSIONS: Through the use of effective ICD programming and antiarrhythmic medications, the occurrence of ICD shocks can be reduced while maintaining the lifesaving ability of the ICD. A basic understanding of the range of available options is fundamental for evaluation and management of the patient who has received an ICD shock.

Arrhythmias, Cardiac↗
PubMed1999

Association of mood disturbance and arrhythmia events in patients after cardioverter defibrillator implantation.

BACKGROUND: Life stresses and negative emotions, such as anxiety and depression, are associated with adverse cardiac events, including arrhythmia. Patients undergoing implantation of an automatic internal cardioverter defibrillator provide a unique opportunity to characterize these relationships since all tachyarrhythmia episodes are recorded by the device. OBJECTIVES: The purpose of this study was to examine the association of emotional status after internal cardioverter defibrillator (ICD) implantation and subsequent arrhythmia events. METHODS: An analysis of data obtained in a prospective longitudinal study of responses to the ICD measured mood disturbance (Profile of Mood States; POMS) before implant and at 1, 3, 6, and 9 months postoperatively. Subjects included 144 men and 32 women with a mean age of 60 +/- 13 years and a mean left ventricular ejection fraction (LVEF) of 33 +/- 12%. Arrhythmia events were measured by self-report of shocks and by ICD device interrogation to obtain the number and type (defibrillation, cardioversion, and antitachycardia pacing) of therapies delivered by the ICD. For each time point, POMS scores of subjects who had arrhythmia events were compared with those who did not. For subjects who had ICD shocks, pre-event and post-event POMS scores were also compared. Multiple logistic regression was used at each time point to determine if clinical, demographic and psychological data could predict arrhythmia events. RESULTS: Patients with arrhythmia events had higher POMS scores throughout the 9 months of follow-up. Higher level of mood disturbance (specifically anxiety, fatigue, and confusion) at 1 and 3 months were independent predictors of subsequent arrhythmia events at 3 and 6 months after controlling for LVEF, the presence of coronary artery disease, pre-implant arrhythmia history, and the use of amiodarone and beta-blocking agents. There were no differences in POMS scores before and after ICD shocks, reinforcing the notion that negative emotions were a cause, rather than a consequence, of arrhythmia events. CONCLUSIONS: Mood disturbances, such as anxiety, may increase the risk for arrhythmia events after ICD insertion.

Adult↗
PubMed2001

Animal study on surface-modified defibrillator systems: Indications for enhanced infection resistance.

One of the most important problems with ICD systems is infection. The aim of this study was an in vivo evaluation of the efficacy of defibrillator systems in terms of infection resistance. The polyurethane leads were coupled with heparin and loaded with the antibiotic gentamicin, while the PGs were modified to release gentamicin. Group I was comprised of 10 pigs implanted with either a standard or a modified system for 2 weeks; group II was implanted during 4 weeks. The lead was inserted into the heart wall via the jugular vein. The other end was subcutaneously tunneled to the armpit where the PG was positioned. A cocktail of Staphylococcus aureus and epidermidis was injected at the site of the PG. Evaluation was performed macroscopically, by taking bacterial swabs during explantation and by microscopic processing. The results showed that 3 out of 5 modified defibrillator-systems in group I and 1-2 out of 5 in group II were judged as noninfected, whereas all standard systems were infected. Infection rates of the remaining modified defibrillators showed variances, as found with the standards, from slight to moderate to high, to even high/severe in group II (1x standard and 1x modified). With the modified systems, this may be related to production of humoral factors by an intensified early tissue reaction, as indicated by a swelling at day 6 at the site of the PG. When infected, whether or not modified, usually only Staphylococcus aureus was present. Spreading of infection seemed to occur by inoculation via blood, for example, based on the observation that group II in general showed an increase in infected fibrotic overgrowth in the heart, while infectious problems were low in the jugular vein. It is concluded that the modification at short term shows enhanced infection resistance. An increased infection rate already at 4 weeks, however, indicates that the modification may not hold in the long run. Special attention is needed concerning the more intense early tissue reaction.

Animals↗
PubMed1993

Visualization of implantable defibrillator patches by two-dimensional echocardiography.

Implantable cardioverter defibrillators are being used with increasing frequency for the management of life-threatening ventricular arrhythmias. In order to determine whether the titanium mesh of the defibrillator patch causes ultrasonographic acoustical interference, 30 patients underwent prospective serial echocardiographic examination. In addition, studies were reviewed to determine whether the defibrillator patches could be visualized with standard two-dimensional echocardiography. In no patient did the anterior patch produce acoustical interference, and, unless specific measures were utilized (such as a standoff pad, a zoom feature, or a 5-MHz transducer), the patches were rarely visualized.

Adult↗
PubMed1994

Design principles of a low voltage cardiac defibrillator based on the effect of feedback resonant drift.

We explore the possibility of exploiting the phenomenon of the resonant drift of autowave vortices in the design of low-voltage cardiac defibrillators. The problem of reflection of resonantly drifting vortices by inexcitable boundaries is overcome by using feedback. Numerical studies show that the voltage needed for defibrillation by this method may be substantially less (by an order of magnitude) than that used in conventional single-shock defibrillation.

Defibrillators, Implantable↗
PubMed2001

[Usefulness of a VDD defibrillation electrode in recording atrial electrograms during atrial flutter and atrial fibrillation].

BACKGROUND: Monitoring of atrial signals improves the accuracy in identifying supraventricular tachyarrhythmias to prevent inappropriate therapies in patients with implantable cardioverter-defibrillators (ICD). Since complications due to the additional atrial lead were found in dual chamber ICD systems with 2 leads, we designed a single-pass VDD-lead for use with dual chamber ICDs. PATIENTS AND METHODS: After promising animal experiments in a German multicenter study a prototype VDD lead (single-coil defibrillation electrode with 2 additional fractally coated rings for bipolar sensing in the atrium) was temporarily used in 20 patients. Atrial and ventricular signals were recorded during sinus rhythm, atrial flutter, atrial fibrillation and ventricular tachycardia or ventricular fibrillation. Terminations of ventricular arrhythmias were performed by internal DC shock. RESULTS: The implantation of the electrode was successful in 18 of 20 patients. Mean atrial pacing threshold was 2.45 +/- 0.9 V/0.5 ms, mean atrial impedance was 215 +/- 31 Ohm. Atrial amplitudes were greater during sinus rhythm (2.7 +/- 1.6 mV) than during atrial flutter (1.36 +/- 0.28 mV, p < 0.05) or atrial fibrillation (0.92 +/- 0.29 mV, p < 0.01). During ventricular fibrillation atrial "sinus"-signals had significantly (p < 0.01) lower amplitudes than during sinus rhythm. Mean ventricular sensing was 13.3 +/- 7.9 mV, mean ventricular impedance was 577 +/- 64 Ohm. Defibrillation was successful with 20 J shock. 99.6% of P waves could be detected in sinus rhythm and 85 +/- 9.9% of flutter waves during atrial flutter. During atrial fibrillation 55% of atrial signals could be detected without modification of the signal amplifier. CONCLUSIONS: A new designed VDD dual chamber electrode provides stable detection of atrial and ventricular signals during sinus rhythm and atrial flutter. For reliable detection of atrial fibrillation modifications of the signal amplifier are necessary.

Aged↗
PubMed2001

Excimer laser for pacemaker and defibrillator lead extraction: techniques and clinical results.

Pacing and defibrillation leads may need to be removed for several reasons including infection, interference with others leads, lack of vascular access or redundancy. However, the removal of chronically implanted leads is a major technical challenge because of the extensive adhesions that develop along the course of the leads over time. The techniques to remove chronic leads have been greatly facilitated by the development of an excimer laser sheath. We undertook an analysis of our experience with laser extraction in the first 50 leads attempted. An excimer laser sheath system, developed by the Spectranetics Corporation, was used to extract 50 chronically implanted leads in 34 patients. The mean patient age was 64+/-12 years, all were male and the average duration that the leads had been implanted was 5.0+/-3.9 years. Two-thirds of the leads were pacemaker and one-third were defibrillator leads. There was a 100% clinical success rate and 48 of the 50 leads were completely removed. There were no major complications. There was one minor complication of subclavian vein thrombosis and two haemodynamically non-significant episodes of air embolism. The main limitation observed was failure of the excimer laser sheath to advance in 18% of cases, probably due to the presence of calcified adherences on leads. Two strategies were found useful to deal with this problem: under the clavicle stainless-steel sheaths were used to break up calcified adherences and within the venous system the laser sheath was upsized in order to advance over the calcification on the lead. It was concluded that excimer laser has greatly facilitated the removal of chronically implanted pacemaker and defibrillator leads. There is a high success rate and low complication rate in our experience. The main limitation of laser is the presence of calcified adherences.

Adult↗
PubMed2004

Arrhythmia risk stratification with regard to prophylactic implantable defibrillator therapy in patients with dilated cardiomyopathy. Results of MACAS, DEFINITE, and SCD-HeFT.

To date, generally accepted indications for prophylactic defibrillator implantation in patients with dilated cardiomyopathy do not exist. Recently, the Marburg Cardiomyopathy Study (MACAS) revealed left ventricular ejection fraction to be the only significant arrhythmia risk predictor in a relatively large patient population with dilated cardiomyopathy. Meanwhile, the preliminary results of two prospective randomized trials evaluating prophylactic defibrillator therapy in dilated cardiomyopathy have been reported. The Defibrillators in Nonischemic Cardiomyopathy Treatment Evaluation study (DEFINITE) randomized 458 patients with a history of symptomatic heart failure, a left ventricular ejection fraction < or = 35% and arrhythmias on Holter to an ICD versus no ICD. As a result, ICD therapy was associated with a significant reduction of arrhythmic deaths, which failed to result in a significant decrease in total mortality due to an insufficient number of patients in DEFINITE. The Sudden Cardiac Death in Heart Failure Trial (SCD-HeFT) was a three-arm study comparing placebo to amiodarone to prophylactic ICD therapy in a total of 2,521 patients with ischemic cardiomyopathy (51%) or nonischemic dilated cardiomyopathy (49%). All patients in SCD-HeFT had a left ventricular ejection fraction inverted exclamation mark U 35% despite optimized medical heart failure therapy. SCD-HeFT showed a significant reduction of total mortality in the ICD group, whereas amiodarone did not improve survival.

Arrhythmias, Cardiac↗
PubMed2002

[The Wearable Cardioverter Defibrillator (WCD) for the prevention of sudden cardiac death -- a single center experience].

The Wearable Cardioverter Defibrillator (WCD) is an external defibrillator that automatically detects and treats ventricular tachyarrhythmias without the need for assistance from a bystander while at the same time allowing the patient to ambulate freely. The main components of the system are the defibrillator unit and a chest belt with electrodes for arrhythmia detection and therapy delivery. Between December 1998 and October 2001, 84 patients used the device at our institution. The majority of patients had a history of acute myocardial infarction or coronary artery bypass surgery with an increased risk for sudden cardiac death or were awaiting heart transplantation. During a mean follow-up of 116+/-90 days, 7 episodes of ventricular tachyarrhythmias were detected and terminated successfully by the WCD in 5 patients. In 9720 days, there was one inappropriate shock due to oversensing of electrical noise. Four patients died during follow-up; none of them had a cardiac arrest while wearing the device. Five patients were excluded because of irregularities in device use. An ICD was implanted in 24 patients at the end of the follow-up period. The WCD is effective in detecting and treating ventricular tachyarrhythmias in patients with an intermittently increased risk for sudden cardiac death. Further use of the system in larger patient populations is needed to confirm its safety and cost effectiveness.

Aged↗
PubMed2005

Implantation of an "extracardiac" internal cardioverter defibrillator in a 6-month-old infant.

In infants and small children, ICD implantation is a challenge due to technical limitations and a significant number of complications. This report describes ICD implantation in a 6-month-old infant (body weight 5.5 kg). A completely extracardiac defibrillation system was implanted using a transvenous lead subcutaneously in the back below the left scapula as the defibrillation electrode and an active-can device in the right upper abdomen. Defibrillation threshold of implantation was < or =10 J. During the follow-up of 3 months, 8 adequate ICD discharges were noted. The technique described seems feasible to facilitate ICD implantation in small infants.

Defibrillators, Implantable↗