[Specificity of CK-MB enzyme in the diagnosis of acute myocardial infarction in the postoperative period following non-cardiac surgery].

Objectives: 1) To determine plasma concentrations of creatinphosphokinase-MB (CK-MB) enzyme during non-cardiac surgery for detecting postoperative myocardial infarction or ischemia. 2) To assess the specificity of CK-MB levels for the diagnosis of acute myocardial infarction (AMI) in patients undergoing non-cardiac surgery.

Patients And Method: Three hundred twenty-eight patients were studied prospectively. Inclusion criteria were as follows: 1) presenting cardiac risk factors; 2) major surgery; and 3) presence of associated pathology, unrelated to cardiac pathology. All patients were given an electrocardiogram and CK-MB levels were determined every 8 hours over the first 24 hours and on the second and third days. Total CK was measured at 24 hours.

Results: AMI was detected by electrocardiogram in 3.3% of the patients. ST-segment/T-wave changes were detected in 5.7% and myocardial ischemia was found in 14.7%. Mean levels of CK-MB in patients with postoperative AMI were significantly higher than in patients without AMI. Total CK levels in patients with electrocardiographic changes were not significantly different from those of other patients. Thoracic surgery produced a significant increase in total CK but no increase in CK-MB. Patients undergoing esophageal surgery presented high initial levels of CK-MB that became normal.

Conclusions: 1) The CK-MB/total CK ratio is highly specific for detection AMI after surgery. 2) Type of surgery affects total CK levels. 3) Detection of high levels of MB fraction should lead to a suspicion of myocardial damage. 4) Total CK level is not a good marker of myocardial necrosis in the postoperative period.