Optimal duration of oral anticoagulant therapy following deep vein thrombosis of lower limbs

Deep vein thrombosis of the lower limbs is usually treated with an initial course of heparin or low-molecular-weight heparin associated with oral anticoagulants which are started simultaneously, thereby allowing heparin to be stopped after 4-7 days. Although consensus conferences have proposed a uniform duration of oral anticoagulant therapy of 3 months, great uncertainties remain as to the optimal treatment duration in an individual patient. Two large-scale studies have recently demonstrated that short treatment durations (4 weeks or 6 weeks, respectively) are associated with about two-fold higher rates of thromboembolic recurrences over follow-up periods of 1-2 years compared with longer treatment durations (3 months or 6 months, respectively). However, because treatment duration is also a major determinant of the hemorrhagic risk on oral anticoagulants, it is essential to balance the protective effect of these agents against their bleeding risk. This paper reviews the literature on the antithrombotic effects and hemorrhagic risks of different durations of oral anticoagulant therapy following lower limb deep vein thrombosis and suggests tentative recommendations which range from a short anticoagulant course of 4 weeks in a patient with a low risk of thromboembolic recurrence and a high hemorrhagic risk (e.g. postoperative distal vein thrombosis) to 6 months or more in a patient with a low hemorrhagic risk and a high risk of thromboembolic recurrence (e.g. idiopathic proximal vein thrombosis in a patient with inherited thrombophilia or malignancy).