Serum myoglobin/carbonic anhydrase III ratio in the diagnosis of perioperative myocardial infarction during coronary bypass surgery.

Objective: The purpose of the present study was to evaluate the usefulness of the myoglobin/carboanhydrase III (Myo/CAIII) ratio in the diagnosis of perioperative myocardial infarction during coronary artery bypass surgery.

Design: Thirty patients undergoing elective coronary artery bypass grafting (CABG) were included in the series. The patients were randomized in two groups: one received conventional normothermic retrograde blood cardioplegia, while the other was subjected to a 5-min period of ischemic preconditioning before cardioplegia. Biochemical markers for myocardial and skeletal muscle injury were measured in serial blood samples taken postoperatively from 4 h after aortic declamp.

Results: Three patients were diagnosed to have suffered from perioperative myocardial infarction on the basis of significant elevations of troponin T and creatine kinase MB-isoenzyme (CK-MB) concentrations. In these particular patients the Myo/CAIII ratio increased rapidly after aortic declamping. In uncomplicated patients, the median value of the Myo/CAIII ratio remained within normal limits. There was a positive correlation between the net output of lactate during the aortic cross-clamping period and postoperative Myo/CAIII ratio. The Myo/CAIII ratio proved to be a more specific indicator for myocardial damage than myoglobin alone. The Myo/CAIII ratio was higher in the preconditioning group than in the control group.

Conclusion: Myo/CAIII ratio is a sensitive and specific marker for perioperative myocardial infarction increasing rapidly after aortic declamping. This ratio could also be used when assessing the extent of ischemic myocardial injury and comparing different surgical and cardioprotective techniques.