Superiority of surgical versus medical reperfusion after regional ischemia

Abstract

This study tests the hypothesis that surgical revascularization (i.e., simulating coronary artery bypass grafting) with control of reperfusion conditions (total vented bypass) and of reperfusate composition (substrate-enriched blood cardioplegic solution) produces better recovery than is possible in the non-surgical setting (i.e., normal blood in beating, working hearts to simulate streptokinase and angioplasty). Eighteen dogs underwent 2 hours of left anterior descending coronary artery ligation (35% of the left ventricle at risk) followed by 2 hours of reperfusion. In five dogs the ligature was released to simulate streptokinase thrombolysis and angioplasty in working hearts (medical). In 13 dogs, surgical reperfusion was accomplished during total vented bypass, where six dogs received normal blood and seven others received substrate-enriched blood cardioplegic solution with 1 additional hour of aortic clamping (i.e., a total of 3 hours of ischemia). Segmental shortening with ultrasonic crystals, tissue water content, and vital staining (triphenyltetrazolium chloride) were assessed. Ischemia produced severe systolic bulging (-42% of control systolic shortening, p less than 0.05). Medical reperfusion resulted in failure to restore regional contractility (-27% systolic shortening, p less than 0.05), severe edema (82.4% H2O content, p less than 0.05), and extensive transmural nonstaining (44%, p less than 0.05). In contrast, surgical reperfusion with substrate-enriched blood cardioplegic solution during total vented bypass restored regional contraction to 46% of control values (p less than 0.05) and resulted in less edema (80.6% H2O content, p less than 0.05), and only mild nonstaining (21%, p less than 0.05) restricted to the subendocardial region. Surgical revascularization with controlled reperfusion conditions and reperfusate composition produces better myocardial salvage than is possible in the medical setting, despite a longer period of ischemia.