Demonstration of Ischemia-Reperfusion Injury Separate From Postoperative Infarction in Coronary Artery Bypass Graft Patients

Background. In patients undergoing coronary artery bypass grafting there are two possible causes of myocardial injury: (1) global ischemic myocardial injury during aortic cross-clamping and subsequent reperfusion, and (2) postoperative myocardial infarction. We studied the use of cardiac marker proteins to specifically and separately detect such injury. Methods. Serum levels of enzymes (creatine kinase and creatine kinase-MB) and nonenzymatic proteins (fatty acid-binding protein and myoglobin) were measured in 8 low-risk patients undergoing coronary artery bypass grafting with cardiopulmonary bypass, 8 low-risk patients undergoing coronary artery bypass grafting without cardiopulmonary bypass, and 39 high-risk patients undergoing coronary artery bypass grafting with cardiopulmonary bypass, of whom 7 experienced a postoperative myocardial infarction. Results. At 0.5 hours after reperfusion significantly increased plasma levels of all markers were noted in patients having the operation with cardiopulmonary bypass, but not in patients having the operation without cardiopulmonary bypass. In patients who had a postoperative myocardial infarction, a second significant increase of each marker was found, but that of fatty acid-binding protein was recorded 4 hours earlier than that of creatine kinase, creatine kinase-MB, or myoglobin. Conclusions. Perioperative myocardial injury can be diagnosed from the release of cardiac marker proteins into plasma already at 0.5 hours after the start of reperfusion. For early assessment of postoperative myocardial infarction, fatty acid-binding protein is a more suitable plasma marker than are creatine kinase, creatine kinase-MB, or myoglobin.