PHYSIOLOGIC OBSERVATIONS OF HEART 6 MONTHS AFTER ISCHEMIC NORMOTHERMIC CARDIOPLEGIA

Abstract

The late effects of normothermic ischemic cardioplegia were studied in 4 experimental groups of dogs subjected to intervals of aortic cross-clamping during cardiopulmonary bypass. Groups which had 0, 20, 30 or 40 min of aortic cross-clamping, respectively, were studied 6 mo. later for cardiac performance and morphology. The immediate operative mortality rate of animals subjected to 40 min of ischemia was 65%, compared to 22% in controls. There were no late deaths in any group. Compliance, histology, biochemical determination of DNA:RNA and Vmax determinations after cross-clamping revealed no differences between the experimental groups. Open chest isovolumetric contraction curves showed decreased function in the 40 min ischemia group at the extreme levels of cardiac stress. Under the conditions of this study normothermic cardiac ischemia of greater than 30 min in duration apparently results in a high initial mortality rate (65%) and leads to compromise of cardiac function under stress in the late postoperative period.