Six-week low-molecular-weight heparin versus 12-week warfarin for calf deep vein thrombosis: A randomized, prospective, open-label study.

Current guidelines suggest a 3-month anticoagulant treatment course for isolated distal deep vein thrombosis (IDDVT), but shorter durations of treatment are frequently prescribed in clinical practice. We investigated whether a 6-week treatment with low-molecular-weight heparin (LMWH) at intermediate dosage can be an effective and safe alternative to vitamin K antagonists (VKA) in patients with IDDVT (non-inferiority trial). In a multicenter, open-label, randomized trial, 260 outpatients with symptomatic IDDVT were randomly assigned to receive either LMWH followed by VKA for 12 weeks or LMWH 1 mg/kg subcutaneously twice a day for 2 weeks followed by 1 mg/kg subcutaneously once a day for 4 weeks. The follow-up was 6 months and the primary endpoint was the composite measure of recurrent venous thromboembolism (VTE) defined as: recurrence or extension of IDDVT, proximal DVT, and pulmonary embolism (PE). The study was stopped prematurely due to slow recruiting rates. The primary efficacy outcome occurred in 14 patients receiving LMWH (10.8%) and in five patients receiving VKA (3.8%); risk difference was 0.069 (95% CI: 0.006-0.132), hazard ratio 2.8 (95% CI: 1.04-7.55). There was one PE in the VKA group and one proximal DVT in the LMWH group. IDDVT recurrence was 10.0% in the LMWH group versus 3.1% in the VKA group (p = .024). Two patients had clinically relevant bleedings (1.6%) in the LMWH group versus one (0.8%) in VKA group (p = .56). In conclusion, VKA for 12 weeks seems superior to LMWH for 6 weeks in reducing the risk of VTE recurrences in our cohort of outpatients with IDDVT.