Apixaban, Warfarin, and On-X Mechanical Aortic ValvesAlthough vitamin K antagonists are the only oral anticoagulants approved with mechanical heart valves, this trial examined whether apixaban could be safely used in patients with an On-X mechanical aortic valve. A total of 863 such patients were assigned apixaban 5 mg twice daily or warfarin (target international normalized ratio 2.0 to 3.0). A total of 20 thrombotic events occurred in the apixaban group (4.2%/patient-year) and 6 events in the warfarin group (1.3%/patient-year). Major bleeding rates were 3.6%/patient-year with apixaban and 4.5%/patient-year with warfarin.