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PubMed2006

New indications for implantable defibrillator therapy.

Implantable cardioverter defibrillator (ICD) therapy has been extensively evaluated in patients at high risk of sudden cardiac death. Most recently, the Sudden Cardiac Death in Heart Failure Trial found that patients with moderate symptoms of congestive heart failure, whether due to an ischemic or a nonischemic cause, have reduced mortality compared with patients treated only with conventional medical therapy for heart failure. The results of this trial confirm those of earlier trials finding a benefit of ICD therapy in patients with coronary artery disease and reduced left ventricular systolic function, and extend the indications for ICD therapy to those without coronary artery disease.

Anti-Arrhythmia Agents↗
PubMed2005

One conversion of ventricular fibrillation is adequate for implantable cardioverter-defibrillator implant: an analysis from the Low Energy Safety Study (LESS).

OBJECTIVES: The purpose of this study was to analyze defibrillation conversion data from the Low Energy Safety Study (LESS) to determine how implant criteria that use fewer inductions of ventricular fibrillation (VF) correlate with outcome and, in particular, to assess the reliability of using a single VF induction and test shock at 14 J. BACKGROUND: A safety margin of 10 J has become standard for implantation of an implantable cardioverter-defibrillator (ICD), but the specifics and rigor of the implant test sequence are not standardized. METHODS: In LESS, 611 ICD recipients completed a rigorous VF induction test scheme that began at 14 J and continued until the energy that succeeded three times without a failure was determined (DFT++). The data were analyzed to determine how well the outcome of the first 14-J shock and various other combinations of first and/or second shocks predicted a rigorous gold standard of DFT++ < or =21 J (i.e., three successes at < or =21 J). RESULTS: The positive predictive accuracy for the 91% of patients in whom the first 14-J shock succeeded was virtually identical to the positive predictive accuracy for the commonly used criteria of two successes at < or =17 J (99.1% vs 99.0%, P = .69), and slightly higher than the positive predictive accuracy for two successes at < or =21 J (98.8%, P = .51). A single success at 17 J or 21 J had a somewhat lower positive predictive accuracy of 98.2% (P = .17). Eliminating VF induction testing would have resulted in a significantly lower positive predictive accuracy of 97.1% (P = .01). CONCLUSIONS: A single conversion success at 14 J on the first VF induction provides similar positive predictive accuracy as two successes at 17 J or 21 J. Using this criterion, 91% of patients meet implant criteria with a single induction of ventricular fibrillation.

Aged↗
PubMed1997

Implantable Cardioverter-Defibrillator Implantation in the Electrophysiology Laboratory by Electrophysiologists.

Recent developments in implantable cardioverter-defibrillator (ICD) technology have helped simplify the surgical implantation technique of these devices. There has been a marked reduction in the size of these devices making them easier to implant pectorally. In addition ICDs have enhanced longevity and a more facile transvenous lead system. Surgical implantation is almost identical to the procedure used for permanent pacemaker implantation in conjunction with the performance of a short electrophysiologic/arrhythmia induction protocol. In general, the average implant time is approximately one hour and in our series minimal morbidity and no mortality was identified. In conclusion, ICDs can be safely and effectively implanted in the electrophysiology laboratory by electrophysiologists in a timely and cost-effective manner. These implant procedures can help to shorten the length of stay and improve the operating room utilization for more critical procedures.

Journal Article↗
PubMed1987

Relationship of left ventricular mass to defibrillation threshold for the implantable defibrillator: a combined clinical and animal study.

Defibrillation results when a critical mass of myocardium is depolarized. The relationship between echocardiographic determinations of left ventricular mass, volume, and cavity radius to wall thickness ratio and defibrillation threshold for the implantable defibrillator was examined. Ten patients with two large patch defibrillating lead systems were studied. Defibrillation threshold was determined intraoperatively as the lowest energy terminating ventricular fibrillation. Left ventricular mass, volume, and radius/posterior wall thickness ratio were calculated from two-dimensional echocardiograms. A significant correlation was found between left ventricular mass and defibrillation threshold (r = 0.78, p less than 0.01). The correlations between defibrillation threshold and left ventricular volume (r = 0.59) and radius/wall thickness ratio (r = 0.55) were not significant. Subsequently, 11 dogs undergoing defibrillation trials with a transvenous catheter and a chest wall patch were studied. Defibrillation threshold was defined as the lowest energy-terminating ventricular fibrillation (four separate attempts). Subsequently, the heart was dissected, and the left ventricle (including the septum) was weighed. The correlation between left ventricular weight and defibrillation threshold (r = 0.76) was significant (p less than 0.01). We conclude that noninvasive assessment of left ventricular mass and direct measurement of left ventricular weight are significantly correlated with defibrillation threshold and consistent with the critical mass hypothesis.

Animals↗
PubMed1998

Late complications in patients with pectoral defibrillator implants with transvenous defibrillator lead systems: high incidence of insulation breakdown.

As the majority of ICDs with transvenous leads are now implanted in the pectoral region, complications associated with the technique are being identified. To determine the incidence of lead complications in patients with transvenous defibrillator leads and ICDs implanted in the pectoral region, 132 unselected consecutive patients with transvenous defibrillator leads had ICDs implanted in the pectoral region. Three lead systems were used: (1) lead system 1 (45 patients) consisted of a transvenous pacing sensing lead and a superior vena cava coil with a submuscular patch used for defibrillation; (2) lead system 2 (36 patients) utilized a CPI Endotak lead system; and (3) lead system 3 (51 patients) utilized a Medtronic Transvene lead system. Patients were followed for 3-54 months (cumulative 2,269, mean 18 months). The average duration of follow-up with the three systems was 32, 12 and 11 months, respectively. At 30 months follow-up, all three lead systems had a low incidence of complications. However, there was a 13% overall incidence (45% actuarial incidence) of erosion of the insulation of the pacing sensing lead of system 1 at 50 months of follow-up. All lead complications were seen in patients with ICDs whose weights were > 195 g and volumes > 115 cc. The erosion was probably a consequence of the pressure by the large ICD against the lead in the pectoral pocket. Follow-up with lead systems 2 and 3 is relatively short (average 12 months) but no lead erosions were seen. Pectoral implantation of ICDs with long transvenous leads and large generators is associated with a moderate risk of late complications in the form of insulation breaks caused by pressure of the generator against the leads. The use of less redundant leads coupled with smaller ICDs will probably eliminate this complication.

Defibrillators, Implantable↗
PubMed1995

Clinical predictors of the defibrillation threshold with the unipolar implantable defibrillation system.

OBJECTIVES: The purpose of this study was to determine the relation between clinical variables and the defibrillation threshold by using a standardized testing protocol and a uniform implantable defibrillator system. BACKGROUND: Past studied have not revealed useful correlations between clinical variables and the energy required to terminate ventricular fibrillation. Most of these studies did not use a uniform implantable defibrillator system or a standardized protocol to measure the defibrillation threshold and, thus, did not control for the influence of these technical influences. We postulated that defibrillator and defibrillation threshold measurement-based sources of variability overshadowed important clinical predictors. METHODS: The defibrillation threshold was measured by using a standardized protocol in 101 consecutive patients. We used a transvenous unipolar pectoral defibrillation system that employed a single endocardial right ventricular defibrillation coil as the anode and the shell of an 80-cm3 pulse generator as the cathode to deliver a 65% tilt biphasic pulse. RESULTS: Several clinical variables were found to be significantly associated with the defibrillation threshold: patient gender, height, weight, body surface area, heart rate at rest, QRS and corrected QT (QTc) intervals, left ventricular mass and several measures of heart and chest size by chest roentgenogram. None of these variables had a correlation coefficient > 0.45 with the defibrillation threshold. On multivariate analysis, left ventricular mass and heart rate at rest were the only independent predictors of the defibrillation threshold and explained only 25% of the observed variability. CONCLUSIONS: Despite the use of a uniform transvenous defibrillation system and a standardized protocol to measure the defibrillation threshold, no clinically relevant correlation was found between clinical variables and the defibrillation threshold. The defibrillation threshold is probably a function of a complex interaction of anatomic, physiologic and cellular variables that are not adequately represented by easily obtainable clinical information. It is probably not possible to predict defibrillation outcome from standard clinical variables.

Amiodarone↗
PubMed2005

[Evaluation and surveillance of patients with an implantable defibrillator].

The implantable cardioverter-defibrillator became in some years the reference treatment of ventricular arrhythmias in association with heart disease. Recently, this technique showed its efficiency in primary prevention for patients at high risk of sudden death. The follow-up of patients with automatic defibrillator requires a detailed knowledge of both electrophysiology and stimulation. This training is based on a practical and theoretical formation. In France, a specific diploma validation is necessary and centres organisation is required. The purpose of this general review is to supply a set of updated data necessary for the coverage and the follow-up of patients with an implantable cardioverter-defibrillator.

Atrial Fibrillation↗
PubMed2004

Is defibrillation testing required for defibrillator implantation?

The assessment of defibrillation (DFT) efficacy has long been the standard of care during defibrillator implantation. To ensure an acceptable DFT safety margin, early defibrillator systems frequently required that the shock polarity and the location, type, or number of electrodes had to be altered. Advances in defibrillator and lead technology have resulted in lower and more consistent DFT thresholds in the range of 10 J, with an infrequent requirement to modify the DFT system. Yet, one can make an argument for and against continuation of DFT testing at the time of defibrillator implantation. The goal of this paper is to address both the data that do support and the data that do not support continuation of DFT testing at the time of device implantation. Scientifically, DFT testing should be abandoned only when prospective evidence demonstrates that defibrillator implantation without testing is as safe and has the same mortality benefits as implantation with testing. The most attractive aspect of eliminating DFT efficacy testing is that more patients may have the opportunity to be treated with this life-saving therapy. Perhaps there are alternative strategies to improve accessibility to defibrillator therapy without possibly eroding its effectiveness. In the end, will lives be saved or lost if we discontinue DFT efficacy testing and lower the barriers to implantable defibrillator therapy?

Defibrillators, Implantable↗
PubMedDate not supplied

Nonpharmacological therapy for malignant ventricular arrhythmias: implantable defibrillator trials.

Implantable cardioverter-defibrillators (ICDs) are an important nonpharmacological option in the treatment of malignant ventricular arrhythmias. Technological advances in current devices permit nonthoracotomy implantation with transvenous lead systems using biphasic shocks. Decreasing device size has resulted in pectoral implantation. Battery longevity is still short in comparison with that of pacemakers. Lead failure rates as well as pacing thresholds are significantly higher than those for cardiac pacing lead systems. Other complications of ICD systems include infection, perforation, and thrombosis. The long-term performance of nonthoracotomy lead systems for ICD devices has now been extensively studied. Sudden death recurrence rates for these systems are less than 2% in 3 years and less than 5% at 5 years. Clinical trials with both monophasic and biphasic systems show a high degree of prevention of sudden death. Comparison of ICD outcome with that of drug therapy in three large retrospective studies and two small prospective randomized trials favors improved survival and sudden death prevention with device therapy. However, these studies need corroboration from large prospective trials. Two large prospective trials, CIDS and the AVID study, are now in progress to address this issue.

Amiodarone↗
PubMed1998

Influence of body position on defibrillation thresholds of nonthoracotomy implantable defibrillators: a prospective randomized evaluation.

INTRODUCTION: Defibrillation thresholds (DFTs) usually are determined with the patient in the supine position. However, patients may be in the upright position when a shock is delivered during follow-up, which may explain some first shock failures observed clinically. This study investigated whether body posture affects defibrillation energy requirements of nonthoracotomy implantable cardioverter defibrillators with biphasic shocks. METHODS AND RESULTS: Using a step up-down protocol, DFTs were compared intraindividually in 52 patients ("active-can" sytems in 41 patients, two-lead systems in 11 patients) for the supine and upright positions as achieved by a tilt table. The mean DFT was 7.3 +/- 4.2 J in the supine versus 9.2 +/- 4.8 J in the upright position (P = 0.002). Repeated comparison in reversed order 3 months after implantation in 22 patients revealed thresholds of 6.2 +/- 2.5 J (supine) versus 8.4 +/- 3.7 J (upright; P < 0.03) 1 week and 4.4 +/- 2.4 J (supine) versus 6.2 +/- 4.1 J (upright; P < 0.04) 3 months after implantation. DFTs decreased significantly for both body positions from 1 week to 3 months after implantation (P < 0.04). CONCLUSION: (1) DFTs for biphasic shocks delivered by nonthoracotomy defibrillators are higher in the upright compared to the supine body position. (2) Differences remain significant 3 months after implantation. For both body positions, DFT decreases significantly from 1 week to 3 months after implantation. These findings have important implications for programming first shock energy to lower than maximal values or for development of devices with lower maximal stored energy.

Defibrillators, Implantable↗
PubMed2005

Can microvolt T-wave alternans testing reduce unnecessary defibrillator implantation?

The Multicenter Automatic Defibrillator Implantation Trial II (MADIT II) and the Sudden Cardiac Death in Heart Failure Trial (SCD-HeFT) have established that patients with a reduced ejection fraction gain an overall mortality benefit from prophylactic implantable cardioverter-defibrillator therapy. Only a small proportion of the patients in these studies, however, have received life-saving therapy from the defibrillator. Because defibrillator therapy is invasive and expensive, patients with a low ejection fraction would benefit from effective risk stratification so that defibrillator therapy was used only in those at significant risk. In this review, we analyze prospective clinical trials that have evaluated microvolt T-wave alternans (MTWA) testing as a predictor of ventricular tachyarrhythmic events in populations of patients similar to those studied in MADIT II or SCD-HeFT; that is, patients with a reduced ejection fraction who were not selected on the basis of a history of ventricular tachyarrhythmias. In these studies, the average annual rate of fatal and nonfatal ventricular tachyarrhythmic events among the patients who tested negative for MTWA was around 1%. This rate is so low that it is unlikely that such patients would benefit from implantable cardioverter-defibrillator therapy. The mortality, moreover, was lower among MTWA-negative patients who did not receive implantable defibrillators than that observed in the MADIT II and SCD-HeFT patients who received implantable cardioverter-defibrillators. In response, patients with a low ejection fraction who are being considered for implantable cardioverter-defibrillator therapy should undergo MTWA testing as part of their evaluation.

Clinical Trials as Topic↗
PubMed2004

Analysis of mortality events in the Multicenter Automatic Defibrillator Implantation Trial (MADIT-II).

OBJECTIVES: The purpose of this study was to determine the efficacy of implantable cardiac defibrillator (ICD) therapy in preventing sudden cardiac death (SCD) in post-infarction patients with advanced left ventricular (LV) dysfunction. BACKGROUND: The Multicenter Automatic Defibrillator Implantation Trial (MADIT-II) randomized 1,232 post-infarction patients with an ejection fraction of < or =30% to ICD or conventional therapy. In the ICD group, there was a 31% decrease in the risk of total mortality. However, a better understanding of the mode of death is desirable in order to refine therapeutic interventions in high-risk populations. METHODS: We evaluated the 202 deaths, using a variation of the Hinkle-Thaler classification system as well as a clinical classification system to determine the incidence of SCD and the incidence of cardiac death due to progressive LV failure. RESULTS: The SCD rates were 10.0% in the conventional group and 3.8% in the ICD group (p < 0.01). The hazard ratio for the risk of SCD in the ICD group compared with the conventional therapy group was 0.33 (95% confidence interval 0.20 to 0.53, p < 0.0001). The ICD had no meaningful effect on non-sudden death (p = 0.32). The effect of defibrillator therapy in reducing SCD was similar in subgroup analyses stratified according to relevant baseline characteristics. CONCLUSIONS: The decrease in mortality with ICD therapy in MADIT-II is entirely due to a reduction in SCD, with similar reductions in SCD in a spectrum of subgroups stratified according to relevant baseline characteristics.

Aged↗
PubMed2004

Long-term clinical course of patients after termination of ventricular tachyarrhythmia by an implanted defibrillator.

BACKGROUND: The implanted cardioverter defibrillator (ICD) improves survival in high-risk cardiac patients. This analysis from the MADIT-II trial database examines the long-term clinical course and subsequent mortality risk of patients after termination of life-threatening ventricular tachyarrhythmias by an ICD. METHODS AND RESULTS: Life-table survival analysis was performed, and proportional hazards regression analysis was used to evaluate the contribution of baseline clinical factors and time-dependent defibrillator therapy to mortality during long-term follow-up. Of 720 patients with an ICD (average follow-up 21 months), 169 patients received 701 antiarrhythmic device therapies for ventricular tachyarrhythmias. Few baseline characteristics distinguished patients who received appropriate ICD therapy for their first ventricular tachyarrhythmic episode. The probability of survival for at least 1 year after first therapy for ventricular tachycardia (VT) or ventricular fibrillation (VF) was 80%. The hazard ratios for the risk of death due to any cause in those who survived appropriate therapy for termination of VT and VF were 3.4 (P<0.001) and 3.3 (P=0.01), respectively, compared with those who survived without receiving ICD therapy, with a high frequency of heart failure and late nonsudden cardiac death after first successful ICD therapy for VF. CONCLUSIONS: Successful appropriate therapy by an ICD for VT or VF is associated with 80% survival at 1 year after arrhythmia termination. These patients are at increased risk for heart failure and nonsudden cardiac death after device termination of VT or VF and should receive special attention for the prevention and management of progressive left ventricular dysfunction during long-term follow-up.

Cardiovascular Diseases↗
PubMed2006

Mortality following defibrillator implantation in patients with renal insufficiency.

INTRODUCTION: Patients with renal insufficiency have an increased risk of atherosclerotic coronary artery disease, cardiovascular events, and sudden cardiac death. Due to under-representation of patients with renal disease in large clinical trials, outcomes of implantable cardioverter defibrillator (ICD) implantation in this group remain unclear. METHODS AND RESULTS: Inpatient and ambulatory records were reviewed for 741 consecutive patients undergoing 947 defibrillator implants or replacements at Department of Defense Medical Facilities. Demographics, medical history, and mortality were reviewed. The mean age of the cohort was 64 +/- 14 years and 599 (80.8%) were male. There were 173 patients (23.3%) with chronic renal insufficiency, 22 (3.0%) undergoing hemodialysis, and 546 (73.7%) without reported renal disease. The mean number of annual hospital admissions for heart failure among patients with and without renal failure was 3.8 +/- 4.0 versus 1.2 +/- 1.9 (P < 0.0001), respectively. The 1-year survival for those without renal insufficiency was 96.6%, compared to 87.8% for those with chronic renal insufficiency, and 88.7% for those undergoing hemodialysis. Multivariate analysis demonstrated a significant association between mortality among ICD patients and renal insufficiency, independent of coexisting congestive heart failure, ischemic cardiomyopathy, and diabetes mellitus (P < 0.0001). CONCLUSIONS: Among ICD recipients, those with renal insufficiency have a significantly higher mortality rate than those without renal insufficiency. Among a cohort of patients with ICDs, those with known renal insufficiency have higher rates of health care resource utilization and more heart failure admissions. Development of a national registry for ICDs should include data with regard to renal function.

Aged↗
PubMed2002

Quality of life in the antiarrhythmics versus implantable defibrillators trial: impact of therapy and influence of adverse symptoms and defibrillator shocks.

BACKGROUND: Implantable cardioverter defibrillator (ICD) use reduces mortality in patients with serious ventricular arrhythmias compared with antiarrhythmic drug (AAD) use. However, the relative impact of these therapies on self-perceived quality of life (QoL) is unknown. METHODS AND RESULTS: Three self-administered instruments were used to measure generic and disease-specific QoL in Antiarrhythmics Versus Implantable Defibrillators trial participants. Generalized linear models were used to assess the relationships between self-perceived QoL and treatment (AAD versus ICD) and adverse symptoms and ICD shocks. To minimize the impact of missing data, only patients surviving 1 year were included in the primary analyses. Baseline characteristics among QoL participants (n=905) and nonparticipants (n=111) were similar, but participants who survived 1 year (n=800) were healthier at baseline than nonsurvivors (n=105). Of the 800 patients in the primary analysis, characteristics of those randomized to AAD (n=384) versus ICD (n=416) were similar. Overall, ICD and AAD use were associated with similar alterations in QoL. The development of sporadic shocks and adverse symptoms were each associated with reduced physical functioning and mental well-being and increased concerns among ICD recipients, whereas development of adverse symptoms was associated with reduced physical functioning and increased concerns among AAD recipients. CONCLUSIONS: ICD and AAD therapy are associated with similar alterations in self-perceived QoL over 1-year follow-up. Adverse symptoms were associated with reduced self-perceived QoL in both groups, and sporadic shocks were associated with reduced QoL in ICD recipients.

Aged↗
PubMed2002

MADIT II, the Multi-center Autonomic Defibrillator Implantation Trial II stopped early for mortality reduction, has ICD therapy earned its evidence-based credentials?

In a press conference on Nov. 20, 2001 it was announced that the Multi-center Autonomic Defibrillator Implantation Trial II (MADIT II) was stopped early because of a 30% reduction in mortality in patients randomised to receive an implantable defibrillator device. The 4 year multi-centre trial of 1200 patients was terminated early after an independent board observed that the post-MI patients with impaired left ventricular function receiving the implantable defibrillator had improved survival rates compared to those receiving conventional treatment. The MADIT II trial's aim was to test whether an AICD will reduce mortality in high-risk patients with coronary artery disease and left ventricular dysfunction with no arrhythmia entry criteria. The intention was to recruit 1200 patients aged 21-85 years with left ventricular ejection fraction (EF) <or=0.30. Exclusion criteria included myocardial infarction within 1 month, coronary artery bypass graft or percutaneous transluminal coronary angioplasty within 2 months, and any patient already satisfying criteria for receiving an AICD by satisfying the entry criteria for the first MADIT trial. The primary end-point was all-cause mortality. Pre-specified secondary outcomes included non-cardiovascular mortality, sudden death, non-fatal myocardial infarction, fatal myocardial infarction, non-fatal cardiac arrest, fatal cardiac arrest, quality of life, and an economic evaluation. A positive outcome for this trial would be a major step forward both in delineating the indication for AICD therapy but also in guiding routine therapy for patients with impaired left ventricular function as defined by a reduced LVEF. This is not the first positive trial for the AICD approach to preventing sudden deaths due to ventricular tachyarrhythmias. Previous trials (MADIT, MUSST and AVID) have demonstrated that implantable defibrillators improve survival in other patient populations. Under current U.S. Food and Drug Administration (FDA) guidelines restricting the use of AICD therapy to defined patient criteria, 300,000 patients each year in the United States are estimated to be eligible to receive an implantable defibrillator. Guidant was quoted as saying that once the complete study findings of MADIT II are published it plans to submit an application to the FDA that, if approved, could double the population of patients eligible for the implanted devices in the USA, clearly having a major impact on care and its costs for the heart failure and post-MI populations.

Adult↗