Imaging for sudden cardiac death risk stratification: Current perspective and future directions.

Sudden cardiac death (SCD) accounts for one fifth of global deaths, and occurs when a trigger (e.g. myocardial ischemia, premature ventricular contraction) interacts with an arrhythmic substrate (e.g. myocardial scar, dilated cardiomyopathy). Multimodality imaging (echocardiographic, cardiac magnetic resonance and nuclear techniques) can potentially visualize many predisposing substrates and triggers. Implantable cardioverter-defibrillator (ICD) is the most effective approach to primary prevention of SCD, and current guidelines regarding ICD implantation are based on a left ventricular ejection fraction (LVEF) ≤35%. This practice is limited by a low sensitivity and specificity, and has limited value when applied to different etiologies. In this review, the role of multimodality imaging in SCD risk-stratification and the limitations of an LVEF-based approach, are discussed. Additional randomized, prospective data are eagerly awaited to inform on the role of imaging in SCD risk-stratification, and ongoing/ planned trials are subsequently discussed.