Background. Fibrin generation during and after therapy with alteplase may depend on the level of concomitant anticoagulation. The hypothesis that fibrinopeptide A (FPA) levels, as markers of ongoing in vivo fibrin formation, correlate with the angiographic and clinical outcome of thrombolysis is tested. Methods and Results. Serial plasma FPA levels were determined in 334 patients of the randomized European Cooperative Study Group trial comparing heparin versus placebo plus alteplase and aspirin in patients with acute myocardial infarction. Median FPA levels (with the 10th to 90th percentiles) were 21 ng/ml (2-390 ng/ml) before treatment in placebo-allocated patients (n = 166) and increased to 49 (15-580), 34 (4-320), 27 (2-240), 29 (2-430), and 30 (3-390) ng/ml after 0.75, 3, 12, 24, and 36 hours, respectively. In heparinallocated patients (n = 168), median baseline FPA values were 18 ng/ml (2-210 ng/ml) and decreased to 6 (1-110), 5 (1-75), 5 (1-60), 7 (1-100), and 10 (1-170) ng/ml at corresponding time points (p < 0.0001) for the difference at each time point). Adequate anticoagulation, defined as no activated partial thromboplastin time value below twice the pretreatment value at 3, 12, 24, and 36 hours after initiation of treatment, was obtained in 48 patients assigned to heparin. It was associated with normal median FPA levels (less-than-or-equal-to 4 ng/ml) at all time points compared with 12 (2-80), 16 (2-240), and 15 (2-240) ng/ml at 12, 24, and 36 hours, respectively, in heparin-assigned but inadequately anticoagulated patients (n = 102, p < 0.001 for each time point). In the heparin-treated group, median FPA values tended to be lower at all time points in patients with patent vessels than in patients with occluded arteries, but the difference was significant only at 24 hours (p = 0.04). FPA levels did not correlate with clinically apparent recurrent ischemia or with left ventricular thrombosis on two-dimensional echocardiography. Conclusions. During and after thrombolytic therapy with alteplase, the enhanced fibrin generation is suppressed by sustained concomitant anticoagulation with intravenous heparin. Adequate anticoagulation warrants individual titration of the heparin dose. High plasma FPA levels 24 hours after alteplase therapy are specific but insensitive markers of vessel occlusion in anticoagulated patients. They do not correlate with clinical outcome.
