Risk stratification for sudden cardiac death in North America - current perspectives.

Sudden cardiac death (SCD) accounts for approximately 360,000 deaths annually in the United States, and is the cause of half of all cardiovascular deaths. In patients with severely depressed left ventricular ejection fraction (LVEF), implantable cardioverter-defibrillators (ICDs) have been shown to significantly reduce total mortality, but many factors beyond LVEF influence the relative benefit afforded by ICD implantation. In fact, among patients with prior myocardial infarction, approximately half of all SCDs occur in patients without severe LV dysfunction, and in analyses of large ICD trials, certain patient subgroups derive no benefit to ICD implantation despite having low LVEF, often due to competing non-arrhythmic mortality. Improved risk stratification tools to help select patients who are likely to derive the most benefit from ICD implantation are therefore needed. This manuscript will review studies evaluating use of ICDs in patients with mild LV systolic dysfunction and LVEF >35%, currently available ICD risk stratification models, and the rationale for designing a cohort study to prospectively validate use of an ICD risk stratification score.