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Implantable Defibrillators -- Who Should Get Them?

Data from two ICD trials help to answer this question.

Implantable cardioverter-defibrillators (ICDs) are used to prevent sudden death in high-risk patients with myocardial infarction or heart failure. Data from two randomized trials elucidate this therapy's risks and benefits.

In one trial, patients with recent MIs (within the previous 6-40 days), left-ventricular ejection fractions (LVEFs) 35%, and evidence of impaired cardiac autonomic function received ICD therapy (332 patients) or no ICD therapy (342 patients). During a mean follow-up of 30 months, the two groups had similar numbers of all-cause deaths (62 [ICD] and 58 [control]), but the ICD group had significantly fewer deaths from arrhythmia (12 vs. 29). Notably, the ICD group had significantly more nonarrhythmic cardiac deaths (34 vs. 20).

In the other trial, 2521 patients with NYHA class II-III heart failure and LVEFs 35% received placebo, amiodarone, or ICD therapy; all received standard heart-failure therapy. About half the cohort had nonischemic cardiomyopathy. Median follow-up was 46 months. Mortality was significantly lower in the ICD group than in the amiodarone or placebo groups (22% vs. 28% and 29%); amiodarone was no better than placebo.

Comment: In the first study, ICDs did not reduce all-cause mortality when implanted a few weeks after MI; a reduction in arrhythmic deaths was negated by deaths from other cardiac causes. This result contrasts with the all-cause mortality benefit of ICD therapy shown in the MADIT-II trial, in which nearly all patients received ICDs more than 6 months after MI (Journal Watch Apr 16 2002). The second study provides additional support for the benefits of ICDs in both ischemic and nonischemic cardiomyopathy. Its data helped to shape the recent decision to expand Medicare coverage for ICDs, provided that patients participate in a registry to help answer remaining questions about this novel, expensive therapy.

— Kirsten E. Fleischmann, MD, MPH

Published in Journal Watch General Medicine February 8, 2005

Citation(s):

Hohnloser SH et al. Prophylactic use of an implantable cardioverter-defibrillator after acute myocardial infarction. N Engl J Med 2004 Dec 9; 351:2481-8.

• Original article (Subscription may be required)
• Medline abstract (Free)

Bardy GH et al. Amiodarone or an implantable cardioverter-defibrillator for congestive heart failure. N Engl J Med 2005 Jan 20; 352:225-37.

• Original article (Subscription may be required)
• Medline abstract (Free)

McClellan MB and Tunis SR. Medicare coverage of ICDs. N Engl J Med 2005 Jan 20; 352:222-4.

• Original article (Subscription may be required)
• Medline abstract (Free)

Kadish A. Prophylactic defibrillator implantation -- Toward an evidence-based approach. N Engl J Med 2005 Jan 20; 352:285-7.

• Original article (Subscription may be required)
• Medline abstract (Free)