Congestive heart failure in patients surviving aortic valve replacement has been associated with a high late mortality. To determine whether myocardial dysfunction in these patients occurred preoperatively, perioperatively, or during the early postoperative period, 19 consecutive patients undergoing aortic valve replacement using cardioplegia and hypothermia were studied by multiple-gated cardiac blood pool imaging. The resting ejection fractions for 8 patients with aortic stenosis did not show significant changes following operation. The 11 patients with aortic insufficiency has resting preoperative values of 58 +/- 15%, which fell to 38 +/- 18% immediately postoperatively (p less than 0.01), with the late values being 51 +/- 16%. Eight of 18 patients (44%) showed deterioration of regional wall motion immediately after operation, which persisted in 3 during the late evaluation. The occurrence of new perioperative regional wall motion abnormalities and persistent perioperative depression in left ventricular function in some patients suggest the need for further improvement in myocardial protection during cardiopulmonary bypass for aortic valve replacement.