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    WARFASA Trial Visual Abstract: Aspirin for preventing VTE Recurrence



    Summarized by / Author: Usama bin Nasir, MD

    Contribution To Literature:

    WARFASA trial established role of aspirin for prevention of recurrent VTE in patients who have completed 6-18 months course of anticoagulation and were no longer on it.

    Guidelines Adaptation

    According to ACCP (CHEST) Antithrombotic Therapy for VTE Disease 2016 guidelines, in patients with an unprovoked proximal DVT or PE who are stopping anticoagulant therapy and do not have a contraindication to aspirin, aspirin over no aspirin to prevent recurrent VTE (Grade 2B) is recommended.

    Study Design

    It was a multicenter, randomized, double-blind, placebo-controlled that took place and involved enrollment from 2004 to 2010. 403 patients were enrolled and distributed among the study groups. Median follow up period was 2 years.

     

    Inclusion criteria:

    • Age ≥18 years
    • Completed therapy with 6-18 months of vitamin K antagonist for first, symptomatic, unprovoked, objectively confirmed proximal DVT, PE, or both

    Exclusion criteria:

    Important exclusion criteria included

    • Cancer or major thrombophilia
    • Indication for long-term anticoagulation
    • Atherosclerotic disease requiring antiplatelet therapy
    • Active bleeding

    Primary outcomes:

    • Recurrent VTE was significantly decreased in patients on aspirin compared to patients on placebo. (HR 0.58; 95% CI 0.36-0.93; P=0.02)

    Secondary outcomes:

    • Bleeding (4 events in each group) and death rates (HR 1.04; 95% CI 0.32-3.42; P=0.95) were similar in both groups.

    Interpretation:

    The WARFASA trial successfully established role of aspirin in prevention of VTE recurrence. Another trial that was done during same time period was the ASPIRE trial. The ASPIRE trial results were non-significant but the important difference between the trials was that in WARFASA all patients completed minimum of 6 months oral anticoagulation. Recurrent rates of VTE after 3-6 months of OAC for unprovoked VTE can reach up to 11% (2) once the anticoagulation is stopped therefore starting aspirin is important and carries grade 2B recommendation per CHEST 2016 guidelines.

    References:

    1. Becattini C, Agnelli G, Schenone A, et al. Aspirin for preventing the recurrence of venous thromboembolism. N Engl J Med. 2012;366(21):1959-67. Source
    2. Prandoni P, et al. "The risk of recurrent venous thromboembolism after discontinuing anticoagulation in patients with acute proximal deep vein thrombosis or pulmonary embolism. A prospective cohort study in 1,626 patients."Haematologica 2007. 92(2):199-205.
    3. Antithrombotic Therapy for VTE Disease: CHEST Guideline and Expert Panel Report. Chest 2016;149:315-352.

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