Recurrent venous thromboembolism.

A previous venous thromboembolism is the most important risk factor for predicting recurrence of the condition. Several studies have shown that routine testing for inherited thrombophilias is not helpful in predicting the risk of recurrence or altering treatment decisions, and therefore is not cost-effective. Updated practice guidelines from the American College of Chest Physicians shift the focus away from laboratory testing and place stronger emphasis on identifying clinical factors when making treatment decisions. The major determinants for treatment duration are whether the deep venous thrombosis was located in a distal or proximal vein, whether the thrombotic episode was an initial or recurrent event, and whether transient risk factors were present. Persistent elevations on the D-dimer test or the presence of residual thrombosis may provide further information to predict recurrence risk and determine treatment duration. Screening for antiphospholipid syndrome and/or malignancy should be considered in patients presenting with arterial thrombosis, thrombosis at an unusual site, or recurrent pregnancy loss. Patients with venous thromboembolism and a known malignancy should be treated with low-molecular-weight heparin rather than oral anticoagulation as long as the cancer is active. All patients with recurrent, unprovoked venous thromboembolism should be considered for long-term treatment.