ULTRASTRUCTURAL-CHANGES DURING CONTINUOUS RETROGRADE WARM AND MILD HYPOTHERMIC BLOOD CARDIOPLEGIA FOR CORONARY-BYPASS OPERATIONS

Ultrastructural changes in myocardial tissue were studied in 21 patien ts undergoing elective aorta-coronary bypass operation, The patients w ere randomized into two groups, with 10 of them receiving continuous r etrograde warm and 11 continuous retrograde mild hypothermic blood car dioplegia, Biopsy specimens for electron microscopy were taken from th e apical part of the left ventricle before and at the end of the aorti c crossclamp period and after reperfusion of the myocardium. The ultra structural changes were analyzed with use of a semiquantitative scorin g system and classified as mild, moderate, or severe, Slight ultrastru ctural changes were found in both groups even before the aortic crossc lamp period, At the end of the aortic crossclamp period the most promi nent ultrastructural changes were mitochondrial swelling, damage of ca pillary endothelium, and clearing of the nucleoplasm or margination of chromatin, but some enlargement in intercalated discs was also discer nible, Reperfusion of the myocardium for 15 minutes somewhat further i ncreased the overall score of the ultrastructural changes, Two patient s in the warm cardioplegia group had a perioperative myocardial infarc tion, and this may be one reason for the higher postoperative creatine kinase MB efflux in this patient group, Despite this finding, no majo r differences in the ultrastructural changes between the two cardiople gia groups could be observed. We conclude that only mild to moderate a nd principally reversible ultrastructural changes occur in myocardium during continuous retrograde warm and mild hypothermic blood cardiople gia for coronary bypass operation.