CPK-MB isoenzyme: use in diagnosis of acute myocardial infarction in the early postoperative period.

The diagnosis of acute myocardial infarction (AMI) in the early postoperative period may be quite difficult in certain patients. Electrocardiograms fail to be diagnostic of AMI in as many as one third of patients with myocardial injury found at autopsy. Enzyme patterns commonly used to diagnose AMI in patients admitted to coronary care units are obscured by muscle injury, medications, cardioversion, surgical manipulation, and blood transfusion. The MB isoenzyme of creatinine phosphokinase (CPK) has been described as a specific indicator of myocardial injury. Therefore the CPK-MB isoenzyme level was evaluated as a potential aid in the diagnosis of AMI in the early postoperative period. Thirty patients undergoing cardiac surgery and 7 patients undergoing thoracic surgery not involving the heart were studied. CPK-MB isoenzyme was present in the serum in 10 of 30 patients after cardiac surgery but in none of 7 patients after thoracic surgery. The presence of CPK-MB isoenzyme was found to be a valuable adjunctive indicator in the diagnosis of AMI in the early postoperative period.