Cardiac arrest (sudden cardiac death) occurs relatively frequently in asymptomatic patients who have had myocardial infarctions, have ejection fractions less than 40 percent, and non-sustained ventricular tachycardia. However, it is not possible to predict who will die suddenly or when cardiac arrest will occur. Current efforts to reduce sudden death in such long-term survivors of myocardial infarction or in patients with coronary disease have produced results that are not very encouraging.