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General Critical Care

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Apixaban or Warfarin in Patients with an On-X Mechanical Aortic Valve

In patients with an On-X mechanical aortic valve implanted more than 3 months earlier, apixaban at a dose of 5 mg twice daily did not demonstrate noninferiority to warfarin for the prevention of valve thrombosis or thromboembolism. Apixaban resulted in more valve thrombosis or valve-related thromboembolic events than warfarin, leading to the early termination of the PROACT Xa trial. Rates of major bleeding were not significantly different between apixaban- and warfarin-treated patients.


The study's results underscore the continued importance of warfarin as the standard oral anticoagulant for patients with mechanical heart valves, including those with an On-X mechanical aortic valve. While direct thrombin and factor Xa inhibitors have shown promise in other clinical settings, their use in mechanical valve patients remains challenging due to the higher risk of thromboembolic events observed in this trial. Ultimately, until new, more effective anticoagulants are identified, warfarin remains the recommended choice for anticoagulation in patients with mechanical heart valves.

Tracy Y. Wang, M.D., M.H.S., Lars G. Svensson, M.D., Ph.D., Jun Wen, M.S., Andrew Vekstein, M.D., Marc Gerdisch, M.D., Vijay U. Rao, M.D., Ph.D., Michael Moront, M.D., +18, for PROACT Xa Investigators Published May 6, 2023 NEJM Evid 2023;2(7) DOI: 10.1056/EVIDoa2300067 VOL. 2 NO. 7

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