Duration of anticoagulant therapy after initial idiopathic venous thromboembolism.

Abstract

To review the literature investigating the duration of oral anticoagulant therapy following a first event of idiopathic venous thromboembolism (VTE). MEDLINE (1967-April 2003) and bibliographic searches of the English-language literature pertaining to the duration of oral anticoagulant therapy following a first event of idiopathic VTE was conducted. Search terms included venous thromboembolism, anticoagulation, duration of treatment, warfarin, and idiopathic. The results of all trials and meta-analyses that were obtained are reviewed and critiqued. The risk of recurrent VTE following a first idiopathic event is similar to the risk in patients with a permanent risk factor. Conventional-intensity oral anticoagulant therapy reduces this risk by 80-90%, but at an annual risk of bleeding of approximately 2-3%. According to the PREVENT trial, low-intensity anticoagulation also affords protection against VTE recurrence, but at a lower risk of bleeding. Older trials indicated that longer therapy was superior to shorter therapy; however, data from recent trials have demonstrated that the benefit was maintained only while receiving therapy. Patients with a first episode of idiopathic proximal VTE should be considered for indefinite anticoagulant therapy. The appropriate intensity of anticoagulation is still controversial; however, it appears that low-intensity treatment would be appropriate in most patients. For patients who will not continue therapy indefinitely, there does not appear to be any long-term benefit to extending the duration of therapy from 3 to 6 months.