Serum CK-MB isoenzyme after aortic and mitral valve replacements.

A release of the MB fraction of creatine kinase (CK) enzyme into the serum due to myocardial manipulation and trauma occurs in patients undergoing cardiac surgery. Thus, the appearance of CK-MB activity as such is not sufficient to indicate of perioperative myocardial infarction. The mean (+/- SD) serum CK-MB isoenzyme level was 95 +/- 103 U/l 18 hours after aortic or mitral valve replacement in 76 patients. Thirteen patients undergoing closure of an atrial septal defect served as controls. They had a significantly lower (p less than 0.01) isoenzyme level postoperatively: 45 +/- 39 U/l. Two patients had the ECG changes of definite myocardial infarction after valve replacement and they also showed high CK-MB values, while the other patients with high enzyme level had no ECG signs suggesting acute infarction. CK-MB values correlated with the aortic cross-clamping time (r = 0.39, p less than 0.001) and weakly with the precordial ECG voltage of SV1 + RV5 (r = 0.25, p less than 0.01). While these findings may reflect the sensitivity of a thick myocardial wall to ischaemia during surgery, the postoperative recovery was not related to the serum CK-MB level.