T-Wave Alternans in the Sudden Cardiac Death in Heart Failure Trial Population

Although the cardiovascular death rate has fallen in recent years, the proportion of cardiovascular deaths attributed to sudden cardiac death (SCD) is on the rise. SCD is usually caused by ventricular tachyarrhythmias resulting from complex electroanatomic changes that follow myocardial injury, most often associated with coronary artery disease. Ventricular tachyarrhythmia episodes and the factors responsible for triggering them are poorly understood, usually occur without warning or provocation, and result almost invariably in death. Therefore, efforts aimed at predicting and preventing SCD have emerged as the major paradigm for addressing this significant unresolved public health dilemma.Article p 2022 Two major randomized clinical trials demonstrated that implantable cardioverter defibrillators (ICDs) reduce mortality in patients selected for primary prevention of SCD on the basis of reduced left ventricular ejection fraction (LVEF) alone.1,2 However, recent studies have questioned whether LVEF used in isolation from other disease markers is sufficient to guide SCD prevention.3 Although ICDs are highly effective in aborting SCD from ventricular fibrillation, only ≈1 of 15 patients satisfying current guidelines for prophylactic ICDs on the basis of an LVEF 0.35). Also, we have yet to ascertain how to incorporate estimates of competitive risk from nonarrhythmic and noncardiac mortality into the decision to implant ICDs. Finally, current paradigms that focus on assessing risk at 1 time point do not account for dynamic time-varying modulation of SCD substrates that occur in response to intervening cardiac events.Because LVEF only measures contractile but not electrophysiological dysfunction, it does not provide any direct assessment of functional electrophysiological substrates responsible for triggering SCD episodes. Therefore, it should not be surprising that most patients with markedly impaired LVEF do not benefit from ICDs, while it …