Abstract
Recent demonstrations of the efficacy of intravenous thrombolytic therapy in acute myocardial infarction have emphasized the need for a noninvasive index of successful reperfusion. The tissue form of MM creatine kinase (MM3) is known to undergo posttranslational conversion to modified forms MM2 and MM1 after release into the plasma following acute infarction. Since this conversion is rapid, sustained elevation of plasma MM3 may be a marker of the prolonged creatine kinase release characteristic of nonreperfused infarction. Therefore, we investigated the rate of decline of plasma MM3 in a consecutive series of patients undergoing thrombolytic therapy of acute myocardial infarction, all of whom underwent acute angiography to assess treatment success, as well as in 30 conventionally treated patients. Among 55 patients with angiographically documented successful reperfusion (group IA), the rate of decline of MM3 was 4.18 ± 1.25%/hr (mean ± SD); in contrast, the rate of decline was 2.37 ± 1.11%/hr in 39 patients with angiographically documented unsuccessful reperfusion (group IB) and 1.77 ± 1.46%/hr among the 30 patients receiving conventional treatment (group II) (p < .001 for groups IB and II vs group IA). A cutoff value of 3.1%/hr minimized the overlap between the groups; 48/55 (87%) patients with successful reperfusion had a rate of decline of MM3 of 3.1%/hr or more, while 29 of 39 (74%) patients in whom thrombolysis was unsuccessful and 27 of 30 (90%) patients receiving conventional treatment had a rate of decline less than 3.1%/hr (p < .001 for groups IB and II vs group IA). In contrast, the time from onset of symptoms to peak MB-creatine kinase, a commonly used marker of reperfusion, exhibited substantial overlap between groups. We conclude that creatine kinase isoform analysis may provide an early noninvasive index of successful reperfusion.