thromboembolism ( nine patients , 2.2 % per patient-year ) occurred more frequently after double ( 3.7 % per patient-year ) or mitral valve replacement ( 2.3 % per patient-year ) than after aortic valve replacement ( 1.3 % per patient-year ) and more frequently in 12 patients receiving aspirin and dipyridamole ( 6.5 % per patient-year ) than in 173 patients receiving warfarin ( 1.9 % per patient-year ) .
C0040038
thromboembolism
C0043031
warfarin