Influence of time to treatment on early infarct-related artery patency after different thrombolytic regimens....

In an in vitro model, recombinant tissue-type plasminogen activator was significantly more effective than streptokinase in dissolving 24-hour-old human blood clots. Therefore there might be a difference in the effect of time to treatment on the efficacy of these fibrinolytics with different fibrin specificity in patients with acute myocardial infarction.

The effect of the interval between symptom onset and initiation of therapy on the efficacy of 6 different thrombolytic regimens was studied in a retrospective analysis of 6 angiographic trials with similar design. The patency of the infarct-related artery was assessed by angiography 90 minutes after initiation of thrombolysis in patients who were seen within 6 hours after symptom onset. Patency rates of patients with an interval of 3 hours between symptom onset and start of therapy were compared. There was no difference for Thrombolysis in Myocardial Infarction (TIMI) grade 3 perfusion after front-loaded alteplase (72.5% vs 76. 3%) and reteplase (63.6% vs 63.2% ) between the 2 groups. In contrast, in patients treated with streptokinase (36.8% vs 27.6%, P =.09), anisoylated plasminogen streptokinase activator complex (59. 5% vs 34.8%, P =.004), and urokinase (62.3% vs 41.7%, P =.03), TIMI 3 patency decreased with the increasing interval between symptom onset and initiation of therapy.

We conclude from our data that the thrombolytic efficacy of recombinant tissue-type plasminogen activator and reteplase does not decrease with the increasing interval between symptom onset and initiation of therapy. In contrast, after anisoylated plasminogen streptokinase activator complex, streptokinase, and urokinase treatment, a decrease in patency, especially TIMI-3 patency in patients treated after >3 hours after symptom onset, was observed. These results may influence the choice of the thrombolytic agent in patients who are seen >3 hours after symptom onset.