Risk Stratification for Arrhythmic Sudden Cardiac Death: Identifying the Roadblocks

Athough it is difficult to determine the precise number, the range for the number of sudden cardiac deaths (SCDs) per year in the United States alone has been reported from 184 000 to 462 000,1 with estimates that 50% to 70% are due to tachyarrhythmic mechanisms. Regardless of where within this range the true number lies, this represents a large epidemiological problem that warrants serious attention and attempts to identify solutions. There are many obstacles to achieving this laudable goal. First and foremost, although the vast majority of SCD victims have underlying structural heart disease (in particular, coronary artery disease), a significant percentage of SCD victims have previously unrecognized cardiac disease2; on autopsy, advanced coronary artery disease with or without evidence of unstable plaques and acute or healed myocardial infarctions (often clinically silent) are commonly detected.2,3 The American Heart Association estimates that 195 000 first silent myocardial infarctions occur per year.4 Strategies to reduce SCD among individuals without known cardiac disease must therefore focus on better screening and identification of risk factors for coronary disease, with either known risk factors or heretofore unknown or unidentified risk factors. In patients with known cardiac disease, there may be diverse pathogeneses for sudden death, including primary ventricular tachyarrhythmias and acute myocardial ischemia/infarction, among others. Although therapies exist for treatment of life-threatening ventricular tachyarrhythmias and prevention of myocardial infarction/coronary artery plaque rupture, significant challenges exist in identifying the individual patient within population subgroups who is at substantial personal risk of these events, and in whom the most intensive therapies could and should be applied. Although the incidence of out-of-hospital cardiac arrest due to ventricular tachycardia/fibrillation appears to be declining over time,4 this pathogenesis for SCD still occurs commonly. This article will therefore focus on the challenges and roadblocks …