Isoforms of creatine kinase MM and MB in acute myocardial infarction: a clinical evaluation

Abstract

Serum creatine kinase (CK, EC 2.7.3.2) isoenzymes MM and MB were resolved, respectively, into three (MM 1, MM 2, MM 3) and two (MB 1, MB 2) isoforms (sub-forms derived from the same isoenzyme) by electrophoresis and the isoform patterns were determined in multiple sequential serum samples, timed from the onset of chest pain, from 58 patients with acute myocardial infarction (AMI). During the first 3 h after the onset of chest pain, the serum isoform activity resembled the pattern seen in normal volunteers. Specimens obtained 6 h after AMI showed predominantly MM 3 and MB 2 (45% and 11% of the total CK activity, respectively). Between 10 and 72 h, there was a gradual shift in which MM 3, MM 2 and MB 2 decreased, while MM 1 and MB 1 increased. MB 2 and MB 1 disappeared from the pattern for samples collected after 24–48 h, while MM 1 was always the most prominent band at the end of the observation period (66%, range 41–77%, at 48 h). These data suggest that a single determination of CK isoform pattern, drawn between 6 and 48 h after AMI, may provide an effective means of predicting the time of onset of necrosis. There were no significant differences in the CK. isoform patterns according to infarct location and functional status of patients.