Over 50 percent of deaths in patients who survive an acute myocardial infarction (MI) are due to fatal ventricular tachyarrhythmias. Patients who survive an episode of sustained ventricular arrhythmia are at highest risk of recurrent cardiac arrest. Electrophysiological studies have been found to be useful in guiding therapy and reducing mortality in these patients. However, evaluation and treatment of nonsustained ventricular tachycardia following MI remains controversial. Asymptomatic patients at high risk after MI include those who have significant left ventricular dysfunction, positive late potentials on signal-averaged electrocardiogram (SAECG), high grade ventricular ectopy and abnormal heart rate variability. These tests, however, have a low positive predictive accuracy and are not helpful to guide therapy with antiarrhythmic drugs which are usually ineffective and can frequently harm these patients. Beta-adrenoreceptor blocking agents, however, have been shown to reduce mortality after an acute myocardial infarction.