Coronary thrombolysis and infarct size reduction after intravenous infusion of recombinant tissue-type plasminogen activator in nonhuman primates.

Occlusive thrombus was produced by thrombin-induced coagulation in the left anterior descending coronary artery (LAD) of 16 open-chest baboons. In six control animals, occlusive thrombosis persisting over a period of 4 h as evidenced by coronary arteriography resulted in large transmural infarction (63.1 +/- 3.5% of the perfusion area). In 10 animals, tissue-type plasminogen activator obtained by recombinant DNA technology (rt-PA) was infused systemically at a rate of 1,000 IU (10 micrograms)/kg per min for 30 min after 30-80 min of coronary thrombosis. Reperfusion occurred within 30 min in nine animals. In one animal, intravenous infusion was followed by an intracoronary infusion at the same rate, which resulted in thrombolysis within 8 min. In the rt-PA group, mean duration of occlusion before reperfusion was 77 +/- 24 min. Reocclusion occurred in one animal. Recanalization resulted in an overall reduction of infarct size (37.8 +/- 5.9%, P less than 0.05 versus controls). Residual infarction was related to the duration of occlusion (r = 0.80, P less than 0.01). Reperfusion was associated with reduced reflow. Myocardial blood flow in the perfusion area of the LAD was only 70% of normal after 4 h despite perfect angiographic refilling. The infusion of rt-PA was not associated with systemic activation of the fibrinolytic system, fibrinogen breakdown, or clinically evident bleeding. It is concluded that intravenous infusion of rt-PA may recanalize thrombosed coronary vessels without inducing systemic lysis. The extent of residual infarction is closely related to the duration of coronary artery occlusion before thrombolysis.