A Comparison of Low-Molecular-Weight Heparin with Unfractionated Heparin for Acute Pulmonary Embolism

Abstract

Background. Low-molecular-weight heparin appears to be at least as effective and safe as standard, unfractionated heparin for the treatment of deep-vein thrombosis, but only limited data are available on the use of low- molecular-weight heparin to treat acute symptomatic pulmonary embolism. Methods. We randomly assigned 612 patients with symptomatic pulmonary embolism who did not require thrombolytic therapy or embolectomy to either subcutaneous low-molecular-weight heparin (tinzaparin) given once daily in a fixed dose or adjusted-dose, intravenous unfractionated heparin. Oral anti- coagulant therapy was begun between the first and the third day add was given for at least three months. We compared the treatments at day 8 and day 90 with respect to a combined end point of recurrent thromboembolism, major bleeding, and death. Results. In the first eight days of treatment, 9 of 308 patients assigned to receive unfractionated heparin (2.9 percent) reached at least one of the end points, as compared with 9 of 304 patients assigned to low-molecular-weight heparin (3.0 percent; absolute difference, 0.1 percentage point; 95 percent confidence interval. -2.7 to 2.6). By day 90, 22 patients assigned to unfractionated heparin (7.1 percent) and 18 patients assigned to low-molecular-weight heparin (5.9 percent) had reached at least one end point (P= 0.54; absolute difference, 1.2 percentage points; 95 percent confidence interval, -2.7 to 5.1). The risk of major bleeding was similar in the two treatment groups throughout the study. Conclusions. Under the conditions of this study, initial subcutaneous therapy with the low- molecular-weight heparin tinzaparin appeared to be as effective and safe as intravenous unfractionated heparin in patients with acute pulmonary embolism.