The WEARIT-III registry enrolls subjects with ischemic cardiomyopathy and heart failure (including NYHA II, III, IV and an ejection fraction ≤ 35%) who wear a medically prescribed ZOLL LifeVest Wearable Defibrillator. The primary objective of the WEARIT-III Registry is to prospectively document the clinical course of high-risk cardiac patients with heart failure and ischemic cardiomyopathy prescribed with Wearable Cardioverter Defibrillator (WCD), such as left ventricular function recovery, arrhythmia, Implantable Cardioverter Defibrillator (ICD), Cardiac Resynchronization Therapy (CRT), Left Ventricular Assist Device (LVAD), heart transplantation, and to assess the benefit of WCD in heart failure patients with ischemic cardiomyopathy.