SOURCE: Middeldorp S, Hutten BA. Long-term vs short-term therapy with vitamin K antagonists for symptomatic venous thromboembolism. JAMA 2015;314:72-73.

After a symptomatic episode of acute venous thromboembolism, duration of treatment must be individualized. For leg thromboses, the most recent guidelines on antithrombotic therapy by the American College of Chest Physicians (AT9) suggest the decision for duration of warfarin treatment depends on whether the thrombosis is proximal or distal, whether it is provoked (e.g., surgery, trauma) or unprovoked, and whether the level of bleeding risk is low-moderate or high.

Middeldorp and Hutten summarized the evidence by reviewing a meta-analysis of 10 randomized trials (n = 1771) that compared short-term anticoagulation (1-3 months) vs long-term anticoagulation (3-48 months) for the outcome of recurrent venous thrombosis (DVT). Although warfarin was the most commonly employed anticoagulant in this meta-analysis, some trials used acenocoumarol, fluindione, or dicoumarol. For rate of recurrent DVT, no clinical trial indicated superior outcomes for short-term treatment.

Overall, long-term anticoagulation was associated with about an 80% reduction in recurrent venous thromboembolic events compared to short-term anticoagulation (30 events/1771 persons vs 155 events/1765 persons, respectively).

Despite the confirmed risk reduction, clinicians must still take baseline bleeding risk into consideration, since the risk-benefit balance shifts as bleeding risk increases.