Duration of anticoagulant therapy after initial idiopathic venous thromboembolism.
OBJECTIVE
To review the literature investigating the duration of oral anticoagulant therapy following a first event of idiopathic venous thromboembolism (VTE).


METHODS
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.


METHODS
The results of all trials and meta-analyses that were obtained are reviewed and critiqued.


RESULTS
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.
D000553:Ambulatory Care; D000925:Anticoagulants / Q000627:therapeutic use*; D006801:Humans; D015201:Meta-Analysis as Topic; D013923:Thromboembolism / Q000188:drug therapy*; D013997:Time Factors; D016896:Treatment Outcome; D020246:Venous Thrombosis / Q000188:drug therapy*
D000925:Anticoagulants