Noninvasive detection of reperfusion in acute myocardial infarction based on plasma activity of creatine kinase MB subforms

AbstractSuccessful thrombolytic therapy is associated with an accelerated release of creatine kinase (CK) MB from necrotic myocardium. With use of a previously validated assay, the plasma kinetics of the myocardial subform (MB2) and the plasma-modified subform (MB1) were determined in blood samples obtained from 56 patients with acute Q wave myocardial infarction: 33 patients who received thrombolytic therapy (group A) and 23 patients managed conservatively (group B).Plasma MB2activity increased more rapidly in the group A patients, but there was substantial overlap with group B. Plasma MB1activity did not differ significantly between the two groups. The MB2/MB1 ratio was significantly higher in group A patients than in group B patients between 2 and 10 h after the onset of infarction. Among group A patients, the ratio increased from 2.4 ± 1.6 to 4.6 ± 2.0 in the 1st h after therapy (p < 0.001). The peak ratio was 6.3 ± 2.5 in group A patients and 3.1 ± 1.2 in group B patients. Twenty-seven of the 33 group A patients had a peak ratio >3.8 versus 5 of the 23 group B patients (p < 0.001). In seven group A patients, the ratio was >3.8 before plasma CK MB activity was out of the normal range.Angiography was performed at 5.0 ± 3.5 days in 39 patients. Eighteen (90%) of 20 patients with a patent infarct-related artery had a peak ratio >3.8; 17 (89.5%) of 19 patients with an occluded infarct-related artery had a ratio <3.8 (p < 0.001).The MB2/MB1 plasma subform activity ratio reflects coronary artery patency within 1 to 2 h of intravenous thrombolytic therapy. This technique shows promise as a tool for rapidly identifying patients with an occluded infarct-related artery who might benefit from “salvage” angioplasty and avoiding catheterization in the majority of patients with a patent vessel. It might also be useful as an end point in trials comparing alterative thrombolytic regimens