Duration of anticoagulation for venous thromboembolic events.

A 68 year-old woman with a history of hypertension, hyperlipidemia, and diverticulitis presents to your office for follow-up care. Three months ago, she developed 3 days of pain and swelling in her right calf and thigh. Lower extremity venous ultrasonography demonstrated a deep vein thrombosis in the right femoral vein. No identifiable cause was noted. She was started on therapeutic enoxaparin as a bridge to warfarin anticoagulation for idiopathic venous thromboembolism. Since discharge, her international normalized ratio (INR) has been maintained between 2 and 3. She has no history of prior bleeding or thromboembolic events. She wants to know how long to continue anticoagulation, and what she can do to minimize her risk of recurrent venous thromboembolism.