Duration of therapy for acute venous thromboembolism.

Prospective studies are providing a better understanding of the relative risk for recurrent thrombosis and anticoagulant-related bleeding in subgroups of patients with VTE, particularly during the extended phase of therapy. These findings in conjunction with the results of randomized trials evaluating specific anticoagulant and nonanticoagulant therapies are resulting in improvements in the management of VTE (Box 1). It is anticipated that ongoing studies will continue to identify clinical and biochemical risk factors for recurrent thrombosis and bleeding. Such research will determine whether lower intensities of oral anticoagulation (e.g., INR < 2.0) are indicated for long-term secondary prophylaxis of VTE. The data obtained will clarify the role of extended-duration LMWH therapy in patients with and without cancer and may result in the development of novel antithrombotic agents that overcome the limitations of current therapies.