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 treatment and 90-min patency rates in patients receiving intravenous streptokinase (SK) or accelerated tissue-type plasminogen activator (t-PA). Background. Early patency of the infarct-related artery is major determinant of survival after thrombolysis for acute myocardial infarction. Some dat 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 retrospective analysis of cohort of 481 patients receiving thrombolytic therapy for acute myocardial infarction <6 h after pain onset, all of whom underwent 90-min coronary angiography. Patency of the infarct-related artery was graded by two observers who had no knowledge of the treatment received or the time between pain and therapy. Results. There was no difference in baseline clinical or angiographic characteristics according to the timing or nature of treatment. Thrombolysis in Myocardial Infarction (TIMI) flow grade 2 or 3 patency rate after SK correlated negatively with the time between onset of pain and thrombolysis (r = 0.8, p = 0.05), whereas the 90-min patency rate after t-P appeared stable as function of time to treatment. When patients were categorized as having received treatment <3 or ≥3 h after pain onset, the patency rate was similar with t-PA, but significantly higher when 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 negative effect of time to treatment on the patency probability for SK (p = 0.0001) but not for t-PA. Conclusions. The efficacy of streptokinase but not t-P in restoring early coronary patency after intravenous thrombolysis is markedly lower when patients are treated later after onset of pain.