Serial determination of serum isoforms of creatine kinase MM（CK-MM） isoenzyme in the diagnosis of acute myocardial infarction（AMI）

Using electrophoretic method, the changes of three CK-MM isoiorms in the serum of 12AMI patients were monitored for 3 days. In post-AMI period, MM₃ reached a peak first （518.6u/l）, 14.0h after infarction, followed by MM₂（19.8h, 640.5u/l） and MM₁（28.7h, 641.3u/l）. The MM₃/MM₁ ratio raised beyond the upper limit found in healthy subiects, about 3.5 h after the onset of symptom and peaks 10.6h after AMI, even earier than the peaks of isoforms, CK and CK-MB. Thus the MM₃/MM₁ ratio is an earlier and more sensitive indicator of AMI.