CK-MB in serum and in heart and skeletal muscles in patients subjected to mitral valve replacement.

Serum catalytic concentrations of total creatine kinase (CK) and its more heart-specific isoenzyme CK-MB were studied in 25 consecutive patients subjected to isolated mitral valve replacement (Björk--Shiley prosthesis). Heart and skeletal muscle CK and CK-MB content was determined in 10 cases. The postoperative serum levels did not reflect differences in myocardial CK-MB content between patients. CK-MB as a percentage of total CK at peak serum CK-MB (16 +/- 1%) (mean +/- SEM) was of similar order as the percentage of CK-MB in the myocardium (papillary muscle 20.9 +/- 1.3%, right auricle 18.2 +/- 0.5%). A small proportion of CK-MB was present in all skeletal muscle samples examined (diaphragm 4.2 +/- 0.6%, rectus abdominis 0.4 +/- 0.1%), indicating that the total CK level should also be taken into account in attempts to determine the origin of a raised postoperative serum CK-MB activity. The degree of postoperative CK-MB elevation was related to the duration of operation and of aortic cross-clamping. Perioperative myocardial infarction occurred in one patient, and serum CK-MB kinetics in this patient, with a biphasic enzyme curve, differed from those in the other patients.