The comparative effects of normothermic intermittent ischemic arrest (IIA) and cardioplegia (C) on left ventricular (LV) performance were assessed by gated cardiac blood pool imaging in 57 patients undergoing aortocoronary bypass surgery. In 34 patients, IIA was employed; 23 patients received C. Patients were studied preoperatively, sequentially in the immediate postoperative period at 30-minute intervals, and at 1 week after the operation, C and IIA groups did not differ in mean (+/- SEM) age, anginal class, number of diseased vessels, previous myocardial infarction, or preoperative ejection fraction (EF)(50 +/- 3% vs 50 +/- 2% [p = ns]). Aortic cross clamp time was greater with C than IIA (50 +/- 5 minutes vs 28 +/- 3 minutes [p = 0.001]). During the six sequential postoperative studies, transient LV dysfunction (greater than or equal to 7% decrease in absolute EF) was observed in 10 patients receiving C and in 16 patients receiving IIA. By time of discharge, 24 of 26 patients had returned to preoperative EF. Mean EF at discharge in the cardioplegia group did not differ compared to preoperative EF; in the IIA group, EF increased compared to preoperative EF (50 +/- 2% vs 55 +/- 2% [p < 0.01]). These data suggest that in patients with normal preoperative LV performance both C and IIA afford satisfactory myocardial preservation during aortocoronary bypass surgery.