Cardiac muscle death caused by coronary artery occlusion is a dynamic process that often takes hours or days. Emergency revascularization (saphenous vein bypass graft (SVBG) during acute myocardial infarction (MI) can interrupt myocardial necrosis, salvage ischemic myocardium and revascularize vessels with obstructive lesions not involved in the MI. In this report we describe a preliminary experimental study of 75 patients in which emergency SVBG was the therapy for acute MI. Group 1, 16 patients, required vasoactive medications and/or intraaortic balloon pumping to maintain their blood pressure preoperatively. There was one operative death and two late deaths. Group 2 consisted of 59 hemodynamically stable patients. There were no deaths. The average preop CPK in group 1 was 892 vs 504 in group 2 (p > 0.05). Surgical techniques were routine. The average time from the onset of chest pain that continued to surgery was 6.5 hours. Forty patients were restudied. Post- vs presurgical hemodynamics revealed ejection fraction increased by 34% (p > 0.05), left ventricular end-diastolic pressure reduced by 40% (p > 0.01). End-systolic and end-diastolic volume reduced by 30% (p > 0.05), and 15% (p > 0.01), and stroke volume improved 25% (p > 0.05). Operative mortality was 1.3% and late mortality 2.8%. These results suggest that cautious continued trial of emergency SVBG in patients with evolving MI is warranted.