T-wave alternans is an electrocardiographic finding that has been shown to predict the occurrence of future cardiac arrhythmias in patients who have had a heart attack. What is unknown about T-wave alternans testing is when is the best time to perform the test. In most studies, T-wave alternans testing is conducted 4 weeks or more after a heart attack. It is unknown if T-wave alternans testing performed prior to hospital discharge in heart attack patients is reliable. The objective of this project is to determine the diagnostic accuracy of T-wave alternans testing performed prior to hospital discharge and again at 30 days after hospital discharge in patients who have suffered a heart attack.

Inclusion Criteria:

• Acute Myocardial Infarction (MI) confirmed by electrocardiographic and or/ enzymatic criteria
• Patients with a left ventricular ejection fraction of 45% or less

Exclusion Criteria:

• Patients with (1) atrial fibrillation, (2) pacemaker rhythm, (3) left bundle branch block, (4) class III-IV heart failure, (5) inability to achieve a target heart rate with exercise or handgrip stress or (6) spontaneous sustained ventricular tachycardia/ventricular fibrillation will be excluded
• Patients with recurrent angina pectoris, MI, coronary revascularization, or any other adverse cardiovascular event in the 30 days following their initial MI will also be excluded

Hospitalized patients