Thrombolytic therapy for venous thrombosis and pulmonary embolism.

Streptokinase, urokinase, tissue plasminogen activator and similar drugs can all cause lysis of venous thrombi and pulmonary emboli, but there is small evidence that accelerated lysis achieves a significantly better clinical outcome, on average, in the shorter or longer term, than heparin alone. Thrombolytic therapy for deep leg vein thrombosis aims to restore flow and to preserve venous valves, and so to prevent chronic post-phlebitic disability, but no trial has convincingly demonstrated that the last can be achieved in more than a few patients. Only a small minority of people with extensive proximal thrombosis develop disabling post-phlebitic venous insufficiency, and there are no good clinical predictors of this outcome. As a result, any widespread use of thrombolytics would bring an immediate risk of major bleeding to many people who will never be destined to develop a clinically important problem. Thrombolytic therapy after venous thrombosis should be avoided except, perhaps, in a few carefully selected patients with severe obstruction. The case for using thrombolytics after recent pulmonary embolism is strongest in the limited number of patients with ongoing hypoxia, respiratory distress, pulmonary hypertension and right heart failure, because thrombolytic therapy often achieves an impressive and almost immediate clinical benefit in this clinical setting. Whether early relief from pulmonary artery obstruction translates into longer-term advantage over heparin remains uncertain, however, because no comparative trial has ever shown these drugs to reduce mortality after pulmonary embolism. In all cases, both the physician and the patient must balance the certainty of an immediate bleeding risk against the uncertainty of a better than marginal real benefit.