 This study is an ancillary study of OAT. It will characterize the effects of late PCI of occluded IRAs on the most important and clinically relevant noninvasive markers of vulnerability to malignant ventricular arrhythmias: heart rate variability, T wave variability, and signal-averaged electrocardiography. These analyses will be performed in 300 participants at baseline, 30 days, and 1 year following a heart attack in order to determine the effects of late PCI on the autonomic nervous system, ventricular repolarization, and ventricular conduction abnormalities. 