Effects of a low-molecular-weight heparin on thrombus regression and recurrent thromboembolism in patients with deep-vein thrombosis.

Background: Low-molecular-weight heparins are frequently used to treat veno us thromboembolism, but optimal dosing regimens and clinical outcomes need further definition. Methods: In this multicenter, open-label study with blinded adjudication of end points, we randomly assigned patients with acute deep-vein thrombosis to one of three treatment regimens: intravenous administration of unfractio nated heparin; subcutaneous administration of a low-molecular-weight hepari n, reviparin, twice a day for one week; or subcutaneous administration of r eviparin once a day for four weeks. The primary end point was evidence of r egression of the thrombus on venography on day 21; secondary end points wer e recurrent venous thromboembolism, major bleeding within 90 days after enr ollment, and death. Results: Of the patients receiving unfractionated heparin, 40.2 percent (12 9 of 321) had thrombus regression, as compared with 53.4 percent (175 of 32 8) of the patients receiving reviparin twice daily and 53.5 percent (167 of 312) of the patients receiving reviparin once daily. With regard to thromb us regression, reviparin administered twice daily was significantly more ef fective than unfractionated heparin (relative likelihood of thrombus regres sion, 1.28; 97.5 percent confidence interval, 1.08 to 1.52), as was revipar in administered once daily (relative likelihood, 1.29; 97.5 percent confide nce interval, 1.08 to 1.53). Mortality and the frequency of episodes of maj or bleeding were similar in the three groups. Conclusions: In acute deep-vein thrombosis, reviparin regimens are more eff ective than unfractionated heparin in reducing the size of the thrombus. Re viparin is also more effective than unfractionated heparin for the preventi on of recurrent thromboembolism and equally safe. (N Engl J Med 2001;344:62 6-31.) Copyright (C) 2001 Massachusetts Medical Society.