Prevention of recurrent idiopathic venous thromboembolism.

Idiopathic venous thromboembolism (VTE), unassociated with surgery or trauma, is a chronic illness that warrants the implementation of strategies to prevent recurrence over a lifetime. Clinical trials show that the benefit associated with extended anticoagulation therapy < or =1 year in patients with idiopathic VTE is not maintained over the long term once treatment is discontinued. Controlled trials have established the efficacy of indefinite-duration anticoagulation, even if the therapy used is a novel agent that is not a coumarin derivative. The PREVENT, ELATE, and THRIVE III trials demonstrate that a strategy of long-term anticoagulation in patients with idiopathic VTE, including those with isolated calf deep vein thrombosis, is safe and effective. This successful strategy appears beneficial across all subgroups, regardless of the presence of an identified thrombophilic state. These include both young and old patients of both sexes, those with factor V Leiden or the prothrombin gene mutation, and those with first-time or recurrent VTE. Thus, the default strategy for idiopathic VTE should be universal anticoagulation unless contraindicated. Implementing this proven approach on a population basis would enable prevention of VTE recurrence with minimal individualization of treatment. Because lifelong therapy can exact a psychological and medical cost on the patient as well as the health care provider, future research should be directed to risk stratification of those most susceptible to recurrence. Avenues of investigation currently being evaluated include measurement of d-dimer levels, examination of residual venous thrombosis on ultrasound, and application of risk nomograms.