Serum creatine kinase MB isoenzyme activity in long-term hemodialysis patients.

Serum creatine kinase MB isoenzyme (CK-MB) activity was determined in 46 male long-term hemodialysis patients without evidence of myocardial infarction. Thirteen (28.3%) showed mild elevations. The abnormality persisted in seven of eight patients on repeated measurement at three- to eight-month intervals. There was a significant correlation between serum CK-MB and CK-MN activity, and the activity of both enzymes rose after intramuscular injection. The reason for the abnormality is not known. It is possible that skeletal muscle is the source of elevated enzyme activity. Caution should be exercised in the interpretation of serum CK-MB activity in the diagnosis of acute myocardial infarction in this patient population.