Fibrinolytic effects of urokinase and heparin in acute pulmonary embolism: a randomized clinical trial.

Dissolution of pulmonary emboli with heparin and urokinase is ascribed, respectively, to anticoagulation and fibrinolysis. Since truly independent assessment of these effects in man is lacking, we administered each drug alone. Fibrinogen and plasminogen plasma levels and the resolution of pulmonary emboli were measured in three randomized groups of 10 patients each: groups A and C infused with small repeated doses of urokinase and a large single dose of urokinase, respectively, and group B who received heparin. After 6 h of treatment, fibrinogen fell in all the groups, while, after 12 h, remained equally reduced in groups A and B and declined further in group C. Plasminogen behaved similarly. Up to 60 h, statistical analysis showed that these effects were related to timing and amounts of urokinase and heparin infusion. These observations suggest that heparin may induce a lytic state. As to signs of pulmonary emboli resolution, no differences between groups were found in lung perfusion and gas exchange recovery at any time (from 1 day to 1 year) and in pulmonary artery pressure reduction at 1 week. The greater angiographic and scintigraphic recovery observed with urokinase, versus heparin alone, after 1 day of treatment in the Urokinase Pulmonary Embolism Trial may be ascribed to a synergistic effect with urokinase of heparin administered during the diagnostic work-out. The indications of heparin and urokinase should be evaluated in the light of these results.