EFFICACY OF STREPTOKINASE, BUT NOT TISSUE-TYPE PLASMINOGEN-ACTIVATOR,IN ACHIEVING 90-MINUTE PATENCY AFTER THROMBOLYSIS FOR ACUTE MYOCARDIAL-INFARCTION DECREASES WITH TIME TO TREATMENT

Objectives. We sought to examine the relation between time to treatmen t and 90-min patency rates in patients receiving intravenous streptoki nase (SK) or accelerated tissue type plasminogen activator (t-PA). Bac kground. Early patency of the infarct related artery is a major determ inant of survival after thrombolysis for acute myocardial infarction. Some data suggest that time to treatment may influence the efficacy of nonfibrin-specific thrombolytic agents in restoring early patency of the infarct-related vessel. Methods. We performed a retrospective anal ysis of a cohort of 481 patients receiving thrombolytic therapy for ac ute myocardial infarction <6 h after pain onset, all of whom underwent 90-min coronary angiography, Patency of the infarct related artery wa s graded by two observers who had no knowledge of the treatment receiv ed or the time between pain and therapy. Results. There was no differe nce in baseline clinical or angiographic characteristics according to the timing or nature of treatment, Thrombolysis in Myocardial Infarcti on (TIMI) flow grade 2 or 3 patency rate after SK correlated negativel y with the time between onset of pain and thrombolysis (r = 0.8, p = 0 .05), whereas the 90-min patency rate after t-PA appeared stable as a function of time to treatment. When patients were categorized as havin g received treatment <3 or greater than or equal to 3 h after pain ons et, the patency rate was similar with t-PA, but significantly higher w hen SK was administered early rather than late, regardless of whether TIMI flow grades 2 and 3 were pooled (86.9% vs, 59.4%, p = 0.0001) or TIMI flow grade 3 alone was considered to indicate patency (81.7% vs. 53.6%, p = 0.0001), Multivariate logistic regression analysis showed a negative effect of time to treatment on the patency probability for S K (p = 0.0001) but not for t-PA. Conclusions. The efficacy of streptok inase but not t-PA in restoring early coronary patency after intraveno us thrombolysis is markedly lower when patients are treated later afte r onset of pain. (C) 1998 by the American College of Cardiology.