The duration of oral anticoagulation after deep vein thrombosis. A randomized study

Eighty patients with deep vein thrombosis (DVT) were randomized between our routine duration of oral anticoagulation and 50% reduction thereof, in order to evaluate whether shorter therapy could be given without increased risks. The study was stratified, so that 20 patients with the 1st episode of DVT caused by a temporary risk factor were treated for 1.5 or 3 months, 40 patients with the 1st episode of DVT caused by a permanent risk factor for 3 or 6 months, and 20 patients with the 2nd episode of DVT for 6 or 12 months. When warfarin therapy was discontinued, the patients were followed by means of venous occlusion plethysmography every 3 months for 1 year, and clinically for 15-27 months in the different subgroups. Thromboembolic complications were registered and verified by venography and perfusion lung scan. We could not detect any difference between the groups. The rate of rethrombosis and embolism during 12 and 24 months after cessation of anticoagulant therapy was 8 and 10%, respectively, among the patients with reduced duration of treatment and 8 and 14%, respectively, among those with regular duration. One fatal, warfarin-induced hemorrhage occurred. It is important to reduce unnecessary extension of oral anticoagulation after DVT in order to minimize the negative side-effects without increasing the recurrence rate. More extensive trials should be performed to confirm our results and define the optimal duration of treatment.