Thrombolysis in Pulmonary Embolism

Abstract

Thrombolysis for acute pulmonary embolism (PE) remains a debatable indication because inadequate data exist to provide definitive management guidelines.1 As cardiologists, we have relied on large-scale randomized clinical trials to determine that thrombolysis benefits patients with ST-segment elevation acute myocardial infarction (MI). Yet, no clinical investigations similar in scope have been undertaken for pulmonary thromboembolism, even though this illness afflicts ≥100 000 patients annually in the United States2 and has a high case fatality rate.3 Intuitively, thrombolysis makes sense, especially for massive PE with cardiogenic shock. Nevertheless, only one small randomized controlled trial of 8 patients has tested this strategy among these desperately ill PE patients.4 The thrombolytic regimen was streptokinase, given in the MI dose of 1 500 000 U administered over a period of 1 hour. All 4 patients receiving thrombolysis plus heparin survived, whereas none were treated successfully with anticoagulation alone. Although the investigators originally intended to enroll 40 patients, they halted their trial for ethical reasons after the first 8 patients yielded such disparate results between the 2 groups. Despite these dramatic differences between the 2 groups, we should not craft treatment policy on the basis of an 8-patient trial. Shockingly, there are only 9 randomized trials of PE thrombolysis versus heparin, with a total of 100 patients. The first trial, the Urokinase Pulmonary Embolism Trial, enrolled 160 patients who were randomized to thrombolysis plus heparin or heparin alone.5 This has been the largest trial to date. The thrombolytic agent was urokinase, a drug that is currently not available. The investigators tested a 24-hour continuous-infusion dosing regimen of urokinase that we now know predisposes to major hemorrhage. Urokinase dissolved pulmonary arterial clot more rapidly than heparin alone and, in some patients, …