Electrocardiographic and serum enzyme changes of myocardial infarction after coronary artery bypass surgery

Serial preoperative and postoperative electrocardiograms were obtained in 50 patients undergoing coronary artery bypass surgery, 15 undergoing aortic valve replacement and 13 undergoing mitral valve surgery. Postoperative infarction was defined as the appearance of new Q waves on the postoperative electrocardiogram. Infarction occurred in 5 of 50 patients (10 percent) who underwent coronary artery bypass surgery. Age, preoperative hypertension or a pattern of left ventricular hypertrophy on the electrocardiogram did not correlate with infarction. Coronary disease was more severe in patients with than in those without infarction (mean of 3.2 vessels with 50 percent stenosis compared to 2.4 vessels). There was no correlation with bypass time or use of cross-clamping of the aorta during surgery. Postoperatively, 4 of 5 patients (80 percent) with infarction had serum values for glutamic oxaloacetic transaminase (SGOT) and creatine phosphokinase (CPK) of more than 200 and more than 2,000 international units, respectively, whereas 3 of 45 (7 percent) without infarction had this pattern (P < 0.001).Of patients undergoing aortic valve replacement, 3 of 15 (20 percent) had postoperative infarction. All 3 of these patients had a serum glutamic oxaloacetic transaminase value of more than 200 and a creatine phosphokinase value of more than 2,000 units, compared to 2 of 12 (17 percent) without infarction. None of the 12 patients who underwent mitral valve surgery had postoperative infarction, and none had a serum glutamic oxaloacetic transaminase value of more than 200 or a creatine phosphokinase value of more than 2,000 units.Myocardial infarction after coronary artery bypass surgery is more likely in patients with at least three-vessel disease but appears to be unrelated to pump time or aortic cross-clamping. Localized snaring or clamping of coronary arteries may be important. Postoperative serum glutamic oxaloacetic transaminase and creatine phosphokinase levels correlate with electrocardiographic evidence of infarction.