An aspirin a day to keep the clots away: can aspirin prevent recurrent thrombosis in extended treatment for venous thromboembolism?

Abstract

Patients presenting with deep vein thrombosis (DVT) in the absence of any identifiable risk factors are said to have an unprovoked or idiopathic DVT. Recurrent events are much more common in these patients (10% versus ≤ 3% at 1 year) compared with patients with a DVT provoked by a reversible risk factor, and such events represent a major healthcare problem.1 Three months of anticoagulation is sufficient to decrease the risk of recurrent thrombosis related to the initial DVT. However, once therapy is discontinued, the risk for recurrence rises dramatically. It has been suggested that 30% to 50% of patients experience a recurrence at 10 years.2,3 Factors associated with a higher likelihood of recurrence are male sex, elevated D dimer, incomplete resolution of DVT, body mass index ≥30, and post-thrombotic syndrome.4 In fact, a number of tools have been developed to determine the risk of recurrence after DVT. Article see p 1062 In the current management paradigm, patients with unprovoked DVT are evaluated for long-term anticoagulation after initial treatment with 3 to 6 months of anticoagulation. The risks of major bleeding during prolonged therapy are periodically weighed against the benefits of continuing anticoagulation in high-risk patients. Data supporting this approach come from 4 studies demonstrating a decrease in recurrent venous thromboembolism (VTE) by 90% with extended conventional dose vitamin K antagonists (VKA) therapy.5 Major bleeding occurs in 20 per 1000 patients, and as of yet no validated prediction tool exists to predict risk–benefit ratio of extended therapy.6 Factors associated with an increased risk of bleeding include advanced age >75 years, history of gastrointestinal bleeding, noncardioembolic stroke, renal or hepatic disease, concomitant antiplatelet usage, and poor control of anticoagulation.5 In the interest of diminishing the bleeding risk while conferring protection against recurrent venous thromboembolism …