To review the literature investigating the duration of oral anticoagulant therapy following a first event of idiopathic venous thromboembolism (VTE).
Data Source
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.
Study Selection and Data Extraction
The results of all trials and meta-analyses that were obtained are reviewed and critiqued.
Data Synthesis
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.
Conclusions
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.
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