Advances in the prevention, diagnosis and treatment of deep venous thrombosis.

Deep venous thrombosis of the leg is associated with hospitalization in up to 600,000 Americans each year. Prevention is possible; the preventive strategy varies according to the degree of risk. Noninvasive techniques, especially impedance plethysmography, have revolutionized the diagnosis of deep venous thrombosis and should be the diagnostic methods of first choice. Patients with suspected calf vein thrombi but negative impedance plethysmography studies need not receive anticoagulation therapy as long as serial studies remain negative. Five days of intravenous heparin constitutes adequate treatment, and warfarin can be initiated on the first day of heparin therapy. Intravenous heparin will most likely be replaced by the subcutaneous, low-molecular-weight form once it becomes widely available. Bleeding is the principal side effect of anticoagulation therapy; careful attention to pharmacokinetics and pharmacodynamics can minimize this side effect. Use of the prothrombin time international normalized ratio allows safer, more reproducible anticoagulation with oral agents.