Serum myoglobin/carbonic anhydrase III ratio as a marker of reperfusion after myocardial infarction.

BACKGROUND: Coronary patency is important for short- and long-term outcome after myocardial infarction. Serum myoglobin concentration is a sensitive marker of myocardial damage and its specificity can be improved by simultaneous measurement of carbonic anhydrase III, a skeletal muscle marker. In the present study we evaluated the role of myoglobin/carbonic anhydrase III ratio as a non-invasive marker of reperfusion. METHODS: We measured myoglobin, carbonic anhydrase III and creatine kinase MB-fraction release serially in 29 patients with acute myocardial infarction treated with thrombolysis and in 28 patients treated with primary coronary angioplasty. RESULTS: Thrombolytic therapy was followed by a 9.1+/-2.2-fold increase in myoglobin and 10.8+/-3.3-fold increase in creatine kinase MB-fraction during the first hour of treatment, while carbonic anhydrase III remained unchanged. The peak value of myoglobin/carbonic anhydrase III ratio was found at 2 h and that of creatine kinase MB-fraction at 8 h after thrombolysis. Knowledge of the reperfusion time point during primary angioplasty and follow-up of cardiac markers revealed that cut-off points of 3 and 10 h for the peak values of myoglobin/carbonic anhydrase III ratio and creatine kinase MB-fraction can be used as indicators for reperfusion, respectively. Myoglobin/carbonic anhydrase III ratio measured before treatment and at 2 and 4 h after the onset of treatment screened 23 of those 25 patients with probable reperfusion after thrombolysis. CONCLUSIONS: We conclude that measuring myoglobin/carbonic anhydrase III ratio during the first hours after initiation of thrombolysis may be useful in evaluating the success of reperfusion after acute myocardial infarction.

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.