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Optimal duration of anticoagulation after venous thromboembolism.

Case 1: A 79-year-old woman suffered idiopathic proximal right popliteal and calf deep vein thrombosis (DVT) 6 years previously. She had a normal hypercoagulability workup. Her warfarin has been managed successfully by a centralized pharmacist-run anticoagulation service, and she has easily achieved and maintained her target international normalized ratio range between 2.0 and 3.0. She has had no bleeding or thrombotic complications. She and her referring physicians want to know whether she should continue to take warfarin. Two years after her initial DVT, a repeat venous ultrasound examination showed recanalization of the right popliteal and calf veins.

Case 2: A 24-year-old woman presented with a painful, swollen right leg and persistent shortness of breath in Tanzania after climbing Mt Kilimanjaro. She was diagnosed with right iliofemoral vein thrombosis by venous ultrasound and with pulmonary embolism (PE) by chest computed tomographic scan. She had been taking oral contraceptives, and she had suffered dehydration and altitude sickness while mountain climbing. Her maternal grandmother had DVT after total hip replacement. She has been anticoagulated for 14 months, most recently with enoxaparin as monotherapy without warfarin because of difficulty achieving a therapeutic international normalized ratio with warfarin. Her mother and sister have protein C deficiency. We were consulted to advise whether the patient should continue anticoagulation.

Advising patients and referring physicians about the optimal duration of anticoagulation after acute venous thromboembolism (VTE) is our most common PE/DVT consultation in the outpatient setting. Evaluation is complex and requires balancing the risks of recurrent VTE in the absence of anticoagulation against the risks of bleeding complications with continued pharmacological therapy.1 Discussion with our patients must include their preferences, and the message that we communicate must be nuanced yet understandable.

Risk factors for VTE recurrence (Table 1) during anticoagulation include immobilization, cancer, and chronic obstructive pulmonary …