Refining Patient Selection for Primary Prevention Implantable Cardioverter-Defibrillator Therapy

The Multicenter Automatic Defibrillator Implantation Trial (MADIT) II and Sudden Cardiac Death in Heart Failure Trial (SCD-HeFT) prospectively tested the hypothesis that implantable cardioverter-defibrillators (ICDs) could reduce mortality in patients at increased risk for sudden death from ventricular tachycardia (VT) or ventricular fibrillation (VF).1,2 These trials, which demonstrated 5% to 7% absolute mortality reductions over 2 to 4 years, established ICDs as a standard of care for primary prevention of sudden cardiac death. However, the significant risks and high cost of ICD therapy, combined with the high number needed to treat to save 1 life in these populations, have led some to ask whether we have cast the net of sudden death prevention too widely. In this issue, Levy et al3 provide cautionary evidence that ICD therapy is futile in an identifiable subgroup of SCD-HeFT patients because their heart failure is too advanced.Article see p 835 Most risk stratification efforts to identify candidates for primary prevention ICDs have been based on the hypothesis that patients are likely to benefit if their risk of sudden death is high enough. Various electric measures of arrhythmic risk, such as T-wave alternans, signal-averaged ECG, and electrophysiological study, have not demonstrated adequate or consistent discriminatory power.4,5 Paradoxically, the mortality reduction benefit of primary prevention ICDs was established only when risk stratification was based on measures of left ventricular dysfunction and functional class (left ventricular ejection fraction <30% after myocardial infarction in MADIT II or left ventricular ejection fraction <35% with New York Heart Association class II to III in SCD-HeFT) rather than direct measures of arrhythmic risk.Presently, the number needed to treat to save 1 life for primary prevention ICDs is 15 to 20.1,2 Analysis of SCD-HeFT demonstrated an incremental cost-effectiveness ratio <$100 000 only by extrapolating 3 years …