Influence of the rt-PA dose (1 mg/kg versus 1.5 mg/kg) and duration of administration on the patency of infarct-related coronary arteries in 81 patients

This open study compared the efficacy and side effects of two dose regimens of intravenous rt-PA initiated before the fifth hour after the onset of myocardial infarction. The first 40 patients (group A) received 1 mg/kg of rt-PA infused over 90 minutes, including a 10-mg initial bolus. The following 41 patients (group B) received 1.5 mg/kg (20-mg initial bolus, 60% over 60 minutes and 40% over 120 minutes). Noninvasive clinical, electrocardiographic, and biochemical parameters of reperfusion were recorded systematically, along with serial measurements of fibrinogen and hemoglobin levels. Coronary arteriography and left ventriculography were performed at the 48th hour or earlier, on an emergency basis, in the absence of signs of reperfusion, or if there were clinical and ECG signs of rethrombosis. Patency of the infarct-related artery (TIMI grades 2 and 3) was achieved in 55% of the group A patients vs. 83% of the group B patients (p<.01). Twelve emergency coronary arteriographies were performed in each group. No significant difference was observed in the ejection fraction (48% in group A vs. 52% in group B). The peak CPK level was similar in both groups, but the peak occurred earlier in group B (p<.001). There was no statistically significant difference between the two dose regimens in terms of reduction in fibrinogen or plasminogen levels. Two deaths occurred in group A vs. one death in group B. No cerebrovascular accidents occurred in either group. Overall, a rt-PA dose of 1.5 mg/kg administered over 180 minutes proved superior in producing patency of the infarct-related artery at approximately the 48th hour to an rt-PA dose of 1 mg/kg administered over 90 minutes, without increasing the incidence of adverse effects.