AEROBIC BLOOD CARDIOPLEGIA FOR REVASCULARIZATION OF ACUTE INFARCT - EFFECTS OF DELIVERY TEMPERATURE

The effects of different cardioplegia temperatures on myocardial protection with continuous aerobic blood cardioplegia were studied in a canine model of acute regional injury after left anterior descending coronary artery occlusion and subsequent revascularization. Twenty-five animals underwent 90 minutes of occlusion followed by revascularization during 60 minutes of electromechanical arrest with continuous retrograde blood cardioplegia delivered at one of three temperatures: 18 degrees C (n = 8), 28 degrees C (n = 8), and 37 degrees C (n = 9). Left ventricular protection was assessed in a right heart bypass model in terms of the left ventricular pressure-volume relationships, myocardial oxygen consumption, regional myocardial blood flow, adenosine triphosphate concentration, and water content. The preload recruitable stroke work relationship at 90 minutes after reperfusion was better in the 18 degrees C and 28 degrees C groups than that in the 37 degrees C group (18 degrees C, 85 +/- 14 erg x 10(3)/mL; 28 degrees C, 77 a 17 erg x 10(3)/mL; 37 degrees C, 58 +/- 13 erg x 10(3)/mL; p < 0.05). The maximum elastance and stress-strain relationships showed there were no significant differences between the groups at 90 minutes. The myocardial oxygen consumption was greatest in the 37 degrees C group during the first hour after reperfusion (18 degrees C, 5.4 +/- 1.4 mL O-2 . min(-1) . 100 g(-1); 28 degrees C, 4.7 +/- 1.1 mL O-2 . min(-1) . 100 g(-1); 37 degrees C, 6.3 +/- 1.6 mL O-2 . min(-1) . 100 g(-1); p < 0.05). The regional myocardial blood now, adenosine triphosphate concentration, and myocardial water content were similar in the three groups. After 18 degrees C cardioplegic arrest, there was a trend toward a need for an increased number of countershocks to reestablish organized cardiac activity (18 degrees C, 1.8 +/- 1.2; 28 degrees C, 0.6 +/- 0.5; 37 degrees C, 0.8 +/- 1.2; p = 0.07). Continuous hypothermic aerobic retrograde blood cardioplegia brings about an improvement in ventricular functional protection compared with normothermic delivery and promotes efficient postarrest oxygen utilization.