Patients meeting the criteria were randomized to treatment with an ICD or treatment with antiarrhythmic drug therapy. Allocation was stratified by clinical site and index arrhythmia, either ventricular fibrillation or ventricular tachycardia. Patients assigned to the antiarrhythmic drug therapy and without contraindications to sotalol underwent subrandomization to either empiric amiodarone or sotalol, the latter treatment guided by either ambulatory monitoring or electrophysiologic testing. Patients who, after subrandomization, had low levels (less than 30 beats per hour) of ventricular ectopic beats and no inducible ventricular arrhythmias at electrophysiologic study were not treated with sotalol and instead received empiric amiodarone. The AVID protocol allowed usual clinical practice but restricted interventions to state-of-the art ICD devices and first-line antiarrhythmic agents to amiodarone and sotalol. Patients who could not take amiodarone were not included in the trial. The protocol encouraged the use of concurrent drugs such as angiotensin-converting enzyme inhibitors, aspirin, and beta-blockers when appropriate, administered before randomization and maintained throughout the study. The primary endpoint was total mortality. Secondary endpoints were cost of health care and quality of life. Nonlethal events such as ICD shock, sustained arrhythmia, or syncope were tabulated.