Diagnostic significance of serum CK-MB elevations following surgical damage to skeletal muscles.

Total creatine kinase (CK) and its isoenzyme MB (CK-MB) were studied in the serum of 14 patients following thoracotomy, mostly for pulmonary surgery, and in various thoracic muscles from another 9 patients subjected to the same procedure. CK-MB consistently appeared in the serum and was present in all muscle samples examined. CK-MB as a percentage of total CK (the CK-MB/CK ratio) was of similar order in serum and muscle, approximately 1.5%. Compared with previous findings after cardiopulmonary bypass surgery, maximum serum CK-MB activity occurred later, and the CK-MB levels as well as the CK-MB/CK ratio were considerably lower after non-cardiac thoracic surgery. It is suggested that the CK-MB/CK ratio 24 hours after operation may be used in the diagnosis of peri-operative myocardial infarction, particularly in non-cardiac surgery. After thoracotomy, this ratio was below 2.2%. In a series of patients with acute myocardial infarction, reported previously, the ratio was above 5.4%. Secondary rises of serum CK-MB following cardiac surgery should, apparently also be analysed in relation to the simultaneous total CK level.