This investigation was performed in order to evaluate the degree of myocardial protection in a group of 20 dogs. They were submitted to myocardial anoxia by cross-clamping of the ascending aorta for sixty minutes under extracorporeal circulation, followed by reperfusion for 120 minutes. Hemodynamic changes of the myocardium were studied, and the protection to anoxia offered by cardioplegic solutions and hypothermia was evaluated. The animals were divided in four groups with five dogs in each. In the first and second group, called control-group, myocardial anoxia was induced in normothermia and hypothermia (28ºC). In the third and fourth groups, besides the 28ºC systemic hypothermia, coronary infusions of cardioplegic solutions with and without blood were performed. In each group of dogs a significant lowering of cardiac output was observed at 30 minutes of myocardial reperfusion. Followed 120 minutes, group III and IV dogs showed cardiac output recovevy, and the lack of elevation in left ventricular end-diastolic pressure, indicating preservation of its mechanical function. This was not observed in other animals, in which cardioplegia was not used. Both cardioplegic solutions used protect efficiently the myocardial cells against anoxia in functional aspects. It was not possible, however, to demonstrate any superiority of the blood solution over an acellular solution.
myocardial protection