A Comparison of Six Weeks with Six Months of Oral Anticoagulant Therapy after a First Episode of Venous Thromboembolism

Deep-vein thrombosis has a reported annual incidence of about 1.6 per 1000 in urban populations. 1 The incidence of first episodes of pulmonary embolism in acute care hospitals in the United States has been estimated to be 0.23 per 1000. 2 For both these problems, secondary prophylaxis with oral anticoagulants is routinely given. This practice is based on a retrospective study by Coon et al. 3 and on subsequent randomized trials in which the incidence of recurrence was 26 to 29 percent over 12 weeks if the initial treatment with heparin was followed only by ineffective prophylaxis with heparin (as indicated by a . . .