Coronary artery patency after thrombolytic therapy has important prognostic implications for survival after acute myocardial infarction. The ability to noninvasively identify patients early after thrombolysis may therefore allow other strategies, such as adjunctive therapy or rescue angioplasty, to be used to restore patency of the infarct-related artery. This study examined the use of a rapid creatine kinase (CK)-MB assay in conjunction with selected clinical variables for noninvasive detection of reperfusion after thrombolysis. Patients were enrolled in a study evaluating accelerated plasminogen activator dose regimens with patency assessments by first angiographic injection during acute angiography at a median and interquartile range (25th and 75th percentiles) 142 (96,195) minutes after starting thrombolytic therapy. Serum CK-MB samples measured by a rapid dual monoclonal antibody assay were obtained in 207 patients before (baseline) and 30 minutes, 90 minutes, and 3 hours after starting thrombolytic therapy. In 109 patients a CK-MB sample was obtained within 10 minutes of acute angiography (angio sample). At acute angiography the infarct-related artery was patent (Thrombolysis in Myocardial Infarction trial grade 2 to 3 flow) in 71%. Baseline CK-MB values were similar in patients with and without later reperfusion at acute angiography: 3 (0,8) ng/ml and 0 (0,4) ng/ml, respectively. At acute angiography, patients with successful reperfusion had higher CK-MB values [46 (20,138) ng/ml] compared with patients with persistent occlusion of the infarct-related artery [8 (3,63) ng/ml; p = 0.002).(ABSTRACT TRUNCATED AT 250 WORDS)