The two clinical trials were initiated simultaneously in different groups of TIMI III clinical centers. All patients enrolled in the study received standard coronary care unit care, including bed rest and oxygen. In TIMI IIIA, patients received baseline angiograms and were randomized in a double-blind manner to t-PA or placebo. All patients then received intravenous heparin. The primary endpoint was the number of patients with a successful result of therapy, defined as an improvement in TIMI perfusion by two grades (from 0 to 2 or 3, or from 1 to 3) or a ten percent reduction in the severity of stenosis. The reduction was based on a comparison between the baseline angiogram and the follow-up angiogram obtained 18 to 48 hours later. Patients in TIMI IIIA were enrolled over a nine month period. The total duration was 24 months, including 12 months of data analysis.