At a mean ( SD ) follow-up of @ ( @ ) years ( @ patient-years ) , there were @ events among @ patients ( @ % ) in the device group for a primary event rate of @ events per @ patient-years , compared with @ events among @ patients ( @ % ) for a primary event rate of @ events per @ patient-years with warfarin ( rate ratio , @ ; @ % credible interval , @-@ @ ) , meeting prespecified criteria for both noninferiority ( posterior probability , > @ % ) and superiority ( posterior probability , @ % ) .