- Little data exist on the value of intravenous thrombolysis for acute myocardial infarction in patients with previous coronary bypass surgery. The Thrombolysis In Myocardial Infarction (TIMI) 4 trial was a randomized study comparing tissue plasminogen activator, anistreplase, or a combination in patients with evolving myocardial infarction; patients with previous coronary bypass surgery were not excluded. Coronary angiography was performed 90 minutes and 18–36 hours after randomization, a myocardial perfusion scan was performed at 18–36 hours and predischarge, and a radionuclide ventriculogram was obtained predischarge. Angiographic and clinical outcome variables were determined in patients with and without a history of coronary bypass surgery. A total of 416 patients were randomized and 13 of them had previous bypass surgery; of these, 6 had an occluded vein graft as the infarct-related vessel. The incidence of TIMI grade 3 flow at 90 minutes was lower in patients with previous coronary surgery as compared with controls (42% vs. 49%), and overall patency was significantly lower (50% vs. 77%, p = 0.04). This trend persisted at 18–36 hours after randomization. Furthermore, patients with previous coronary surgery had more thrombus in their infarct-related arteries, especially with occlusion of a vein graft (83% vs. 32%, p=0.04) and higher rates of recurrent ischemia (15% vs. 8%) and recurrent infarction (23% vs. 5%, p=0.03) than controls. Thus, in patients with previous coronary bypass surgery intravenous thrombolysis yields results that are inferior to those achieved in patients without such a history and alternative methods of reperfusion should be considered.