Heparin-induced prolongation of partial thromboplastin time after thrombolysis: Relation to coronary artery patency

Having previously shown in the Heparin Aspirin Reperfusion Trial that the empiric use of early intravenous heparin after recombinant tissue-type plasminogen activator (rt-PA) is an important component in the overall treatment strategy, we examine in this report the specific relation between the degree of prolongation of activated partial thromboplastin time and coronary artery patency. To evaluate the hypothesis that arterial patency after administration of rt-PA for acute myocardial infarction is sustained by effective anticoagulation, activated partial thromboplastin time of heparin recipients was determined 8 and 12 h after the start of thrombolysis. Mean activated partial thromboplastin time was higher among patients with an open infarct-related artery than in those with a closed artery (81 ± 4 vs. 54 ± 9 s, p < 0.02). Only 45% of patients with values <45 s at both 8 and 12 h had Thrombolysis in Myocardial Infarction (TIMI) flow grade 2 or 3 in the infarct-related artery at 18 h. In contrast, 88% of patients with activated partial thrombopiastin time >45 s and 95% of those with values >60 s had an open infarct-related artery at 18 h (p = 0.003 and 0.0006, respectively). Among patients with an initially patent infarct-related artery who underwent repeat angiography at 7 days, activated partial thromboplastin time was similar in those with a persistently patent artery and those with late reocclusion. Excessive anticoagulation did not appear to increase hemorrhagic risk except that access site-related hemorrhage was more common in patients with activated partial thromboplastin time >100 s at 8 h. These observations support the view that effective heparimzation maintains coronary artery patency after thrombolysis with rt-PA.