Myocardial protection during open-heart surgery: intermittent aortic crossclamping versus coronary perfusion

Twenty-seven patients undergoing open-heart surgery were divided into three groups, i.e., control, intermittent aortic crossclamping and coronary perfusion groups. Myocardial oxygen extraction, lactate extraction, arterial-coronary sinus hydrogen ion difference, potassium difference and glucose difference were determined during the operation, as well as, postoperative stroke and cardiac indices and comparisons were made. When the ascending aorta was not crossclamped, myocardial metabolism was well preserved during and after the perfusion at a flow rate of 2.0 L./min/m2. Intermittent aortic crossclamping for 15 minutes alternating with a period of perfusion for five minutes at 30 degrees C was sufficient to protect the myocardium from ischemia. Perfusion of the left coronary artery alone at a flow rate of six per cent of total body perfusion (150 to 200 ml per minute) at 30 degrees C was sufficient to protect the myocardium when the aorta was opened. Since intermittent perfusion of the left coronary artery may produce myocardial derangement, coronary perfusion should be continuous. Otherwise topical cardiac cooling or other means of myocardial protection should be used.