Early and rapid diagnosis of perioperative myocardial infarction in aortocoronary bypass surgery by immunoturbidimetric myoglobin measurements.

STUDY OBJECTIVES To evaluate measurements of myoglobin in the diagnosis of perioperative myocardial tissue damage in aortocoronary bypass surgery. A new immunoturbidimetric myoglobin assay, which yields quantitative concentrations of myoglobin within approximately 1 min, was used. DESIGN Prospective clinical study. PATIENTS Thirty-two patients scheduled for elective aortocoronary bypass surgery. MEASUREMENTS AND RESULTS Myoglobin concentrations in patients without perioperative myocardial infarction (n = 27) increased with aortic unclamping, peaked after 1 h, and decreased to almost baseline values within 4 h. By contrast, myoglobin concentrations in patients with perioperative myocardial infarction (n = 5) further increased after 1 h of aortic unclamping and were significantly higher (p < 0.05) than in patients without myocardial infarction as soon as 3 h after aortic unclamping. In all patients with myocardial infarction, myoglobin concentrations exceeded 400 micrograms/L over a minimum period of 4 h. Ten of 27 patients without perioperative myocardial infarction had episodes of minor perioperative myocardial ischemia (defined as ST-T segment changes in the ECG without a concomitant increase in the activity of creatine kinase isoenzyme MB). Myoglobin concentrations (but not creatine kinase isoenzyme MB activity) were significantly higher in these 10 patients when compared to the 17 completely uneventful cases. CONCLUSIONS Plasma concentrations of myoglobin are a sensitive marker of perioperative myocardial tissue damage in aortocoronary bypass surgery. Myoglobin measurements with the immunoturbidimetric assay have an important contribution to make to the early and rapid diagnosis of perioperative myocardial infarction.