Early detection of myocardial reperfusion by assay of plasma MM-creatine kinase isoforms in dogs.

To determine whether myocardial reperfusion can be detected promptly by changes in profiles of isoforms of MM-creatine kinase (CK) in plasma, coronary occlusion was induced in 30 conscious dogs and reperfusion was initiated after 1, 2, 3, or 4 hr in 21. The myocardial isoform of MM-CK, MMA, was quantified in serial plasma samples by chromatofocusing. Before coronary occlusion, MMA comprised 13 +/- 7% (SD) of the total CK activity in plasma. The percentage of MMA (MMA%) was elevated before reperfusion, but increased markedly and consistently to a peak of 52 +/- 13% (n = 21) between 30 min and 1 hr after the time of onset of reperfusion. The rate of increase in MMA% was significantly faster with reperfusion at 1 hr (1.44 +/- 0.42% min-1), 2 hr (1.28 +/- 0.45% min-1), or 3 hr (1.02 +/- 0.27% min-1) (p less than .001), but not with reperfusion at 4 hr (0.48 +/- 0.34% min-1) compared with the rate in nonreperfused control dogs (0.29 +/- 0.09% min-1). Furthermore, the rate of increase in MMA% was neither influenced by peak total CK activity (r = -.1) nor dependent on infarct size measured histochemically 24 hr after coronary occlusion (r = -.003). The time from coronary occlusion to the peak of MMA% was reduced by reperfusion at 1 to 3 hr compared with control, but this index was not identified as rapidly as the rate of increase in MMA%. Accordingly, characterization of the rate of increase in MMA% in plasma when reperfusion occurs early after the onset of myocardial infarction permits prompt, reliable, and noninvasive detection of myocardial reperfusion.