Noninvasive imaging markers associated with sudden cardiac death.

Sudden cardiac death (SCD) accounts for approximately 15-20% of all deaths worldwide. While the majority of SCDs occur in adults, children, and adults <35 years (<1%) may also be affected. Currently the most effective strategy for both primary and secondary prevention of SCD is the implantable cardioverter-defibrillator (ICD). However, identification of patients who will benefit from ICD implantation remains challenging. Left ventricular ejection fraction (LVEF) is the most frequent imaging parameter used to select patients for ICD implantation for primary prevention. However, LVEF has shown to be suboptimal for prediction of benefit. Non-invasive cardiac imaging permits characterization of the arrhythmogenic substrate, including dispersion of electromechanical activation, presence of myocardial scar, and cardiac innervation status. The arrhythmogenic substrate may change across the different underlying diseases. While in ischemic cardiomyopathy, differentiation and characterization of infarct core and peri-infarct zone have been shown to refine the risk stratification of patients, in non-ischemic cardiomyopathies, the substrate may be more heterogeneous and tissue characterization assessing focal and diffuse fibrosis and inflammation processes may be more relevant. Furthermore, in channelopathies, assessment of mechanical dispersion between myocardial layers may identify the patients with increased risk of ventricular arrhythmias. Finally, potential triggers of ventricular arrhythmias such as myocardial ischemia can be evaluated. The role of noninvasive imaging in the risk stratification of SCD and the selection of candidates for ICD will be discussed in this article.