The risk of recurrent venous thromboembolism.

Venous thromboembolism (VTE) is a chronic rather than acute disease. After withdrawal of secondary thromboprophylaxis, many patients will experience a subsequent episode of thrombosis. Of these patients, approximately 5% will die from pulmonary embolism. The risk of recurrent VTE depends on the number of risk factors and their severity. High-risk patients, i.e. those with a natural coagulation inhibitor deficiency, recurrent thrombosis, active cancer, the lupus anticoagulant or compound clotting defects most probably benefit from indefinite oral anticoagulation. In these patients the risk of bleeding due to anticoagulant treatment seems to be outweighed by the risk of VTE. Patients with hyperhomocysteinemia or high factor (F) VIII plasma levels are also at an increased risk of recurrence. The optimal duration of secondary thromboprophylaxis in these patients is currently under investigation. Patients with the heterozygous F V Leiden mutation or the G20210A mutation in the F II gene do not require extended anticoagulation since their risk of recurrence is similar as in patients without the aforementioned mutations. Patients with VTE secondary to surgery or trauma have a relatively low risk of recurrence. In these patients short-term secondary thromboprophylaxis (6 to 12 weeks) is justified whereas patients with a first episode of spontaneous VTE should be treated with oral anticoagulants for a longer period of time (3 to 6 months).