MORPHOMETRIC EVALUATION ON MYOCARDIAL PROTECTION OF COLD CRYSTALLOID VERSUS WARM BLOOD CARDIOPLEGIA

Twenty patients undergoing open-heart valve replacement were divided r andomly into two groups in this study; intermittent perfusion of cold crystalloid (St. Thomas Hospital solution) with hypothermic cardiopulm onary bypass (CPB) (hypothermic group) and continuous administration o f warm blood cardioplegia with normothermic CPB (normothermic group) r espectively. Tissue samples were taken from the right atrium before we aning from CPB and from the right appendage 30 minutes after removal o f the cross-clamp. The results of pathological study in these two grou ps were as follows: the structural alterations were most severe during the ischemic period in the hypothermic group. Damages of the myocardi al mitochondria examined with transmission electron microscope were fo und more severe in the hypothermic group than in the normothermic grou p, and in the reperfusion period than in the ischemic period. Loss of integrity of the mitochondrial membrane could be noted during reperfus ion in the hypothermic group. The surface to volume ratios of mitochon dria of each period of the two groups were calculated by computerizing the microphotographs of the myocardium. It was shown that the average of the surface to volume ratios was smallest in the reperfusion perio d in the normothermic group. It seemed that the volumes of the mitocho ndria were larger in the warm group than in the cold one. Probably the results were due to more severe damages of the mitochondrial membrane s in the hypothermic group, which led to the release of the contents o ut of the mitochondria while in the normothermic group, the sodium-pum p was disordered and it made the mitochondria swell. Pathologically, b lood cardioplegic perfusion with the use of normothermic CPB is a feas ible method for myocardial protection in open-heart surgery.