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PubMed2004

Clinical trials update from the American Heart Association meeting: Omega-3 fatty acids and arrhythmia risk in patients with an implantable defibrillator, ACTIV in CHF, VALIANT, the Hanover autologous bone marrow transplantation study, SPORTIF V, ORBIT and PAD and DEFINITE.

The American Heart Association meeting reported the results of several clinical trials of particular interest to those who care for patients with heart failure. Omega-3 fatty acids were associated with a trend to increased recurrence of ventricular arrhythmias but not mortality in patients with an implantable debrillator. The ACTIV in CHF study provides more evidence of a therapeutic role for arginine vasopressin antagonists in the treatment of heart failure. The VALIANT study provides further evidence to suggest that a combination of angiotensin receptor antagonist and ACE inhibitor does not reduce mortality but may reduce morbidity in post-MI patients with heart failure or major LV systolic dysfunction. A study of autologous bone marrow cell transplantation into myocardial scar give gave encouraging results. SPORTIF V showed ximelagation to be as effective as warfarin but with improved safety. ORBIT and PAD showed public access defibrillators saved lives but questioned their cost effectiveness. DEFINITE supported a role for ICDs in patients with non-ischemic cardiomyopathy, although cost-effectiveness remains in doubt.

Antidiuretic Hormone Receptor Antagonists↗
PubMed2005

Ejection fraction and QRS width as predictors of event rates in patients with implantable cardioverter defibrillators.

OBJECTIVES: The Multicenter Automatic Defibrillator Implantation Trial II in 2002 recommended implantable cardioverter defibrillators (ICDs) prophylactically for all patients with a prior myocardial infarction and ejection fraction (EF) of 30% or less. In June of 2003, the Centers for Medicare and Medicaid Services approved reimbursement for ICD placement in patients with an EF of 30% or less who have a QRS interval greater than 120 ms. The purpose of this study was therefore to determine the value of QRS duration in predicting the occurrence of ventricular arrhythmias within the first year after ICD implantation. These ICDs were placed over the past 5 years for various indications. METHODS: EF cut points of 30% or less and 31% or greater and QRS duration of 120 ms or less and 121 ms or greater were used to assess the risk of events. RESULTS: There was a significant increase in events in subjects with EF of 30% or less, compared with patients with EF of 31% or greater (P < 0.05), and there was a trend toward increased likelihood of arrhythmias in patients with widened QRS width. CONCLUSIONS: This study confirms the conclusion of the Multicenter Automatic Defibrillator Implantation Trial II and implies that the Centers for Medicare and Medicaid Services criteria for reimbursement may not be scientifically valid.

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PubMed1998

Advances in the treatment of arrhythmias: implantable cardioverter-defibrillators.

Implantable cardioverter-defibrillators are commonly used in patients who have life-threatening ventricular arrhythmias. With these implanted electronic devices, bradyarrhythmias and tachyarrhythmias can be recognized promptly and treated with electrical pacing, cardioversion or defibrillation. Implantable cardioverter-defibrillators have been shown to substantially reduce the incidence of sudden cardiac death in patients with known life-threatening ventricular arrhythmias. Their role in the primary prevention of sudden cardiac death in patients at high risk for ventricular arrhythmias is being evaluated. Technologic advances have allowed transvenous implantation of cardiac leads, obviating the need for open heart surgery and thereby lowering the risk of perioperative morbidity and mortality. Most electrical therapies are triggered appropriately to treat ventricular tachycardia/fibrillation. Inappropriate discharges may occur secondary to supraventricular causes of tachycardia, environmental interference from electromagnetic devices or malfunction of the cardioverter-defibrillator. All episodes of discharge merit investigation. With recurrent or frequent discharges, prompt evaluation and hospitalization are often necessary.

Arrhythmias, Cardiac↗
PubMed1992

Holter documented sudden death in a patient with an implanted defibrillator.

A 68-year-old man with recurrent attacks of monomorphic ventricular tachycardia (VT) received a pacer cardioverter defibrillator featuring antitachycardia pacing and cardioversion/defibrillation. Over 300 episodes of VT were successfully terminated by antitachycardia pacing. During Holter monitoring the patient experienced supraventricular tachycardia with delivery of multiple antitachycardia pacing, cardioversion, and defibrillation therapies ending with the death of the patient. The following factors played a role in the unfortunate outcome of this patient: 1. triggering of VT therapy by an unexpected high sinus rate; 2. atrial fibrillation induced by cardioversion therapy; 3. a gradual and continuous increase in rate during atrial fibrillation possibly caused by repeated VT and ventricular fibrillation therapies and/or by a thrombus, found at autopsy, in a bypass graft; and 4. the limited ability of presently available defibrillators to distinguish between ventricular and supraventricular arrhythmias.

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PubMed2003

Analysis of implantable cardioverter defibrillator therapy in the Antiarrhythmics Versus Implantable Defibrillators (AVID) Trial.

INTRODUCTION: The implantable cardioverter defibrillator (ICD) is commonly used to treat patients with documented sustained ventricular tachycardia (VT) or ventricular fibrillation (VF). Arrhythmia recurrence rates in these patients are high, but which patients will receive a therapy and the forms of arrhythmia recurrence (VT or VF) are poorly understood. METHODS AND RESULTS: The therapy delivered by the ICD was examined in 449 patients randomized to ICD therapy in the Antiarrhythmics Versus Implantable Defibrillators (AVID) Trial. Events triggering ICD shocks or antitachycardia pacing (ATP) were reviewed for arrhythmia diagnosis, clinical symptoms, activity at the onset of the arrhythmia, and appropriateness and results of therapy. Both shock and ATP therapies were frequent by 2 years, with 68% of patients receiving some therapy or having an arrhythmic death. An appropriate shock was delivered in 53% of patients, and ATP was delivered in 68% of patients who had ATP activated. The first arrhythmia treated in follow-up was diagnosed as VT (63%), VF (13%), supraventricular tachycardia (18%), unknown arrhythmia (3%), or due to ICD malfunction or inappropriate sensing (3%). Acceleration of an arrhythmia by the ICD occurred in 8% of patients who received any therapy. No physical activity consistently preceded arrhythmias, nor did any single clinical factor predict the symptoms of the arrhythmia. CONCLUSION: Delivery of ICD therapy in AVID patients was common, primarily due to VT. Inappropriate ICD therapy occurred frequently. Use of ICD therapy as a surrogate endpoint for death in clinical trials should be avoided.

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PubMed1994

The development of implantable cardioversion defibrillation systems: the clinical chronicle of defibrillation leads.

Clinical experience suggests that there is a significant advantage from both the standpoint of survival and thoracotomy morbidity in the use of cardioverter defibrillator implantation strategies with transvenous and subcutaneous leads. Bioengineering achievements making the latter possible remains somewhat preliminary in comparison with the highly advanced analytic technology from which the leads for bradycardia pacing have issued. Accordingly, a good deal remains to be accomplished in the technology evolution of leads for implantable cardioverter defibrillators (ICDs). While second- and third-generation leads have proved to be clinically useful, their development remains far from complete. To date most lead studies have focused on endocardial shock pathways, waveforms, and the linkage thereof affecting defibrillation thresholds. Experience suggests that asymmetric biphasic waveforms that use dual pathways (versus monophasic unidirectional shocks) yield a greater margin of safety for effective control of arrhythmias with existing ICD systems. The critical mass and region of myocardium encompassed by energy pathways, the simultaneous versus sequential pulsing of ICD antiarrhythmic discharges, as well as electrode combinations, locations, and polarity, remain under study. Although final adjudication of the superiority of endocardial systems that exclude the need for thoracotomy over those that use epicardial electrodes remains to be determined by further observational and randomized trials, it is reasonable to conclude at this juncture that ICDs with endocardial leads are feasible and facile, providing a highly promising alternative to other antiarrhythmic strategies.

Animals↗