CORONARY-ARTERY ENDOTHELIAL DYSFUNCTION AFTER GLOBAL-ISCHEMIA, BLOOD CARDIOPLEGIA, AND REPERFUSION

This study tests the hypothesis that blood cardioplegia (BCP) attenuates endothelial dysfunction related to nitric oxide after global normothermic ischemia, cardioplegic arrest, and reperfusion in anesthetized open-chest dogs plated on cardiopulmonary bypass. The dogs were divided into five groups to identify the time when endothelial injury occurred: group 1 = control without ischemia; group 2 = 45 minutes of normothermic ischemia only; group 3 = 45 minutes of normothermic ischemia plus unmodified reperfusion; group 4 = 45 minutes of ischemia plus intermittent BCP without reperfusion; and group 5 = ischemia plus BCP and reperfusion. In vitro coronary vascular relaxation responses to the nitric oxide stimulator acetylcholine (endothelium-dependent, receptor-dependent), the calcium ionophore A23187 (endothelium-dependent, receptor-independent), and acidified NaNO2 (endothelium-independent) were measured at the end of the protocol. Maximum in vitro coronary vascular responses to acetylcholine were similar among groups 1, 2, and 4, indicating an absence of endothelial injury. In contrast, significantly impaired relaxations to acetylcholine were demonstrated in the two reperfused groups (groups 3 and 5). Relaxation responses to A23187 and NaNO2 were not altered markedly in any group. Electron microscopy showed intact endothelium in groups 1, 2, and 4. However, moderately severe endothelium damage was seen in groups 3 and 5. We conclude that morphologic and functional endothelial damage occurs after blood reperfusion with or without BCP, and 1-hour hypothermic BCP arrest after normothermic ischemia is not associated with extension of endothelial damage.