Concordance of electrocardiographic and scintigraphic criteria of myocardial injury after cardiac surgery.

The concordance of transmural electrocardiographic (ECG) changes and myocardial infarct imaging in detecting myocardial injury in the perioperative period was evaluated in 50 patients undergoing coronary artery bypass surgery and in 6 patients without coronary artery disease undergoing valve replacement. Scintigraphy with technetium-99m (Sn) labeled pyrophosphate was performed 3 to 7 days after surgery. Plasma creatine phosphokinase (CPK) levels were determined preoperatively and daily for 7 days postoperatively. Plasma MB-CPK was assayed fluorometrically in samples obtained at 12 hour intervals for 36 hours. Total CPK and MB-CPK concentrations were normal in all patients preoperatively but increased in every patient postoperatively. A total of 8 patients (16%) had evidence of perioperative infarction. Six of these patients (12%) with coronary artery disease exhibited abnormal images after bypass surgery, associated with transmural ECG changes in each case. The other 2 patients (4%) with coronary artery disease who had abnormal images were among 4 patients who developed bundle branch block after the operation. Abnormal images did not occur in any patient undergoing valve replacement despite total CPK and MB-CPK elevations. These results indicate that total CPK and MB-CPK elevations occur consistently after cardiac surgery and cannot be relied upon for detection of transmural infarction. Furthermore, new conduction defects may not necessarily be a sign of perioperative infarction, and infarct imaging may be a useful means of establishing myocardial infarction in this group of patients.