Duration of Anticoagulant Therapy for Unprovoked Venous Thrombosis

Researchers identify a subgroup of women who might not need indefinite anticoagulation.

Risk for recurrent venous thrombosis (VT) varies: Patients with single major reversible VT risk factors (e.g., recent surgery) have risk for recurrent VT of 3%, whereas those with unprovoked VT have 10% risk for recurrence. In this multinational prospective study in 600 patients with first episodes of unprovoked VT or pulmonary embolism, researchers attempted to identify factors that predicted low recurrence risk. All patients had received 5 to 7 months of anticoagulation before enrollment. During a mean follow-up of 18 months, the annualized rate of recurrent VT was higher among men than women (13.7% vs. 8.9%). Men with post-thrombotic symptoms (leg hyperpigmentation, edema, or redness) had 24.0% annual risk for recurrence; no subgroup of men could be identified in whom risk for recurrence was while they received warfarin; body-mass index, 30 kg/m2; or age 65. Women with two or more factors had annual risk of 14.1%.

Comment:

The American College of Chest Physicians guideline suggests that patients with first unprovoked venous thromboses be considered for indefinite anticoagulation; however, the guideline recommends a minimum of 6 to 12 months of anticoagulation. In this study, researchers attempted to define a subgroup of patients for whom about 6 months of anticoagulation therapy after unprovoked venous thrombosis would be sufficient. No such group could be identified for men; however, women with [Photo]1 standard risk factor had low risk for recurrence. If the results of this study are replicated, shorter anticoagulation courses should be considered for such women.

— Jamaluddin Moloo, MD, MPH