Myocardial changes during open heart surgery: a clinical, histopathological and ultra structural study

ABSTRACT

Crystalloid cardioplegia and induced fibrillation reduce myocardial injury and improve metabolic recovery during open heart surgery. However, there is little evidence of a benefit of either technique in clinical practice. Twenty patients ASA physical status II and III from Alexandra Main University Hospital scheduled for open heart surgery with congenital or acquired cardiac lesions using cardiopulmonary bypass were included in the study. They were divided into two groups, group I received cold crystalloid and group II in whom hypothermic fibrillatory arrest was applied using the fibrillator. The time of whole operation, total cardiopulmonary bypass time, aortic cross clamp time and time to resume heart beating in both groups were recorded. The level of CK-MP, createnin kinase and lactic dehydrogenase were determined at 1, 6, and 24 hours after cross clamp. In addition histological studies for assessment of myocardial injury were done. The results of this study revealed a significant shorter cardiopulmonary bypass time and the fibrillation time in group II, also the recovery time was shorter in group II. As regards the enzymatic studies, the CK-MB was statistically high in group II than group I at 1 and 6 hours. The light microscope shows signs of ischemic damage were detected in both groups with a greater intensity in group II as compared to group I patients however no irreversible changes [myofibril necrosis] were observed in either group. The Electron microscopic examination shows no irreversible changes in the form of necrosis in the studied cases. The mean scores of ischaemic injury in group I patients were significantly lower [p=0.045] and more consistent than those in group II which showed a higher wider range and higher. Normothermic fibrillation and hypothermic crystalloid cardioplegia provide equal protection of the myocardium during open heart surgery and provide an optimum condition for the surgical field