Patients who have survived a myocardial infarction (MI) are at increased risk for sudden cardiac death (SCD) caused by ventricular tachycardia and ventricular fibrillation. A severely reduced left ventricular ejection fraction (LVEF) as a rough overall measure of impaired heart function after MI was shown to indicate a higher risk for SCD. Based on this observation, two landmark randomised trials, MADIT II and SCD-HeFT, were conducted between end of the 1990s and early 2000s. These trials compared the survival of patients with severely reduced LVEF who received an implantable cardioverter-defibrillator with the survival of patients being on medical therapy alone. They reported a significantly better survival of patients in the defibrillator arm and led to international guideline recommendations for routine implantation of defibrillators in survivors of MI with severely impaired LVEF as a means for primary prevention of SCD. Since then, the management of these patients has changed dramatically with the advent of a series of novel drug classes that reduce not only mortality but specifically SCD leading to a substantial decrease of the sudden death rates as well as of the rates of appropriate defibrillator therapies implanted for primary prevention of SCD. At the same time, the complication rates associated with the defibrilllator therapy remain significant without obvious decrease. Thus, the risk-benefit of routine defibrillator implantation for primary prevention of SCD in patients with severely reduced LVEF has substantially changed since the conduction of the landmark trials that established this therapy. Due to the inherent risks and considerable costs of the defibrillator, a novel randomised adequately powered assessment of the potential benefit or harm of the defibrillator in survivors of MI with reduced LVEF under contemporary optimal medical treatment (OMT) appears imperative. OBJECTIVE: To demonstrate that in post-MI patients with symptomatic heart failure who receive OMT for this condition, and with reduced LVEF ≤ 35%, OMT without ICD implantation (index group) is not inferior to OMT with ICD implantation (control group) with respect to all-cause mortality.