AbstractAt the Toronto Hospital, 2,510 patients received isolated coronary bypass grafts (CABG). Overall mortality was 2.3%, the incidence of low output syndrome (as defined by need for inotropic agents or intraaortic balloon pump) was 9.2%, and mortality among low output syndrome patients was 16%. We have attempted to identify factors that minimize cardiac injury. We have previously shown that free radical injury occurs during CABG: coronary blood contains increased levels of conjugated dienes after cross‐clamp release; and, there is a reduction in the antioxidant, α‐tocopherol. In vitro studies revealed that ascorbic acid and α‐tocopherol protect cardiac myocytes, while endothelial cells are protected from free radical injury by superoxide dismutase and catalase. To test the former two antioxidants in vivo, we used left anterior descending artery (LAD) occlusion in the dog followed by 2 to 4 hours of reperfusion. When administered in deoxygenated saline at 30 seconds prior to reperfusion and 4 minutes after release of LAD occlusion, both agents significantly reduced the infarction area compared to simple reperfusion or deoxygenated saline alone. Antioxidants therefore have the potential to reduce the ischemic injury and myocardial stunning that accompa