Residual vein thrombosis to establish duration of anticoagulation after a first episode of deep vein thrombosis: the Duration of Anticoagulation based on Compression UltraSonography (DACUS) study.

Residual vein thrombosis (RVT) indicates a prothrombotic state and is useful for evaluating the optimal duration of oral anticoagulant treatment (OAT). Patients with a first episode of deep vein thrombosis, treated with OAT for 3 months, were managed according to RVT findings. Those with RVT were randomized to either stop or continue anticoagulants for 9 additional months, whereas in those without RVT, OAT was stopped. Outcomes were recurrent venous thromboembolism and/or major bleeding. Residual thrombosis was detected in 180 (69.8%) of 258 patients; recurrent events occurred in 27.2% of those who discontinued (25/92; 15.2% person-years) and 19.3% of those who continued OAT (17/88; 10.1% person-years). The relative adjusted hazard ratio (HR) was 1.58 (95% confidence interval [CI], 0.85-2.93; P = .145). Of the 78 (30.2%) patients without RVT, only 1 (1.3%; 0.63% person-years) had a recurrence. The adjusted HR of patients with RVT versus those without was 24.9 (95% CI, 3.4-183.6; P = .002). One major bleeding event (1.1%; 0.53% person-years) occurred in patients who stopped and 2 occurred (2.3%; 1.1% person-years) in those who continued OAT. Absence of RVT identifies a group of patients at very low risk for recurrent thrombosis who can safely stop OAT. This trial was registered at http://www.ClinicalTrials.gov as no. NCT00438230.