Sudden Cardiac Death in Ischemic Heart Disease: From Imaging Arrhythmogenic Substrate to Guiding Therapies

Despite substantial medical advances over the past decades, sudden cardiac death (SCD) remains a leading cause of cardiovascular deaths in patients with ischemic heart disease. The presence of structural heart disease with left ventricular ejection fraction <35% is the current criteria for implantable cardioverter-defibrillator therapy as a primary prevention to SCD. However, more than 80% of patients who suffer SCD have a left ventricular ejection fraction >35%, whereas few patients who received an implantable cardioverter-defibrillator required appropriate defibrillation. Cardiac magnetic resonance enables the visualization of the arrhythmogenic myocardial substrate including the presence and pattern of scar and fibrosis. The most promising of these features, besides left ventricular function, strain analysis, and morphology, include tissue characterization using late-gadolinium enhancement, T1 mapping, and extracellular volume fraction calculation. We review the current evidence of SCD relating to ischemic heart disease, provide insights into imaging of the arrhythmogenic substrate that produces lethal ventricular arrhythmia, and discuss how imaging may guide therapies toward SCD prevention.