Five hundred fifty-nine patients undergoing aortocoronary operation were analyzed retrospectively according to the type of myocardial protection implemented during the period of ischemia. In Group 1 (253 patients), a rapid method of hypothermic cardioplegia alone was utilized. In Group 2 (306 patients), slower infusion of the same solution with topical hypothermia was implemented. Cardiac isoenzymes (CPK-MB, LDH1, LDH2, serum glutamic oxaloacetic transaminase [SGOT]) and myocardial infarct index (MII) were measured postoperatively for 48 hours. Immediately after operation, a significant difference was found between Groups 1 and 2 in the CPK-MB isoenzyme mean value levels—12.1 versus 18.6 IU, p < 0.01—and MII mean values—5.2 versus 8.1, p < 0.01. CPK-MB variances between subgroups receiving two, three, and four grafts were significantly different in favor of Group 1. Differences were also found in LDH1, LDH2, total lactic dehydrogenase (LDH), and SGOT: Group 2 levels were significantly higher than in Group 1. There were ten intraoperative infarctions in Group 2 and none in Group 1. In 45% of the patients in Group 2, inotropic agents were necessary in the postoperative period versus none in Group 1. Spontaneous cardiac rhythm following ischemia occurred in 89.7% of the patients in Group 1 versus 29% in Group 2. A method of pressurized high-flow rapid cardioplegia with intermittent reperfusions alone, seems to provide adequate protection of the myocardium during ischemia over a slower low-flow method of infusion combined with topical hypothermia.