A comparison of methods for limiting myocardial infarct expansion during acute reperfusion--primary role of unloading.

Current use of angioplasty, thrombolysis, and surgical techniques for prompt reperfusion of an acute myocardial infarction raises questions concerning the optimum reperfusion technique for maximum myocardial salvage. Alterations in the conditions of reperfusion and/or the composition of the initial reperfusate can exert a significant effect on the extent of myocardial salvage. In an effort to define an optimum reperfusion technique, we used 40 dogs in a series of experiments in which the left anterior descending coronary artery (LAD) was snared for 2 hr followed by reperfusion by one of five methods for 4 hr. In addition, in a control group(group I, n = 6) the LAD was occluded for 6 hr without any reperfusion. In group 2 (n = 12), simulating medical reperfusion, reperfusion was achieved by simply releasing the snare for 4 hr. Group 3 dogs (n = 6) were placed on pulsatile left atrial-femoral bypass throughout 4 hr of reperfusion. Group 4 dogs (n = 9) were placed on percutaneous, synchronized pulsatile cardiopulmonary bypass during reperfusion. The procedure in group 5 (n = 7) dogs simulated coronary artery bypass grafting with cardiopulmonary bypass and cold blood, low-Ca++ cardioplegia during reperfusion. Group 6 (n = 6) was treated similarly except that during reperfusion amino acid-enriched cardioplegia was administered by warm induction techniques. At the end of 4 hr of reperfusion, the left ventricular area of infarction was determined by triphenyltetrazolium chloride staining and expressed as a percentage of the left ventricular area at risk for infarction (area of infarction [AI]/area at risk [AR]).(ABSTRACT TRUNCATED AT 250 WORDS)