Optimal duration of anticoagulant therapy in patients with venous thromboembolism

Venous thromboembolism, a frequent and severe disease, has clinically important early and late complications and a strong tendency to recur. Anticoagulant therapy is the mainstay of treatment, performed by immediate administration of: i) parenteral anticoagulants followed by vitamin K antagonists, either dabigatran or edoxaban, two direct oral anticoagulants (DOACs); or ii) direct rivaroxaban or apixaban, two DOACs that can be used as single-drug approach. Treatment should last no less than 3 months in all patients though how long it should last thereafter is a more complex issue. The risk of recurrence results from several event- or patient-associated factors. Some patients have low risk and may be treated for 3 to 6 months only. Others (the majority) have a high risk of recurrence (approximately 50% in 10 years). Unfortunately, the protective effect of anticoagulation against recurrence is present only during treatment and is lost when therapy is stopped. For this reason, international guidelines recommend that there is no pre-definite period of anticoagulation (e.g. 1 or 2 years, and so on) in patients at high risk and suggest instead indefinite (extended) anticoagulation, provided there is no high risk of bleeding. When the decision is difficult, adjunctive criteria may be adopted, such as male sex and abnormal D-dimer assessed after anticoagulation is stopped, to identify patients at high risk who need indefinite therapy. The use of DOACs, especially at lower doses with a lower risk of bleeding, may make indefinite anticoagulation for patients easier.