RESULTS	After 1588 patient-years of follow-up ( mean 2.31.1 years ) , the primary efficacy event rates were 3.0 % and 4.3 % ( percent per 100 patient-years ) in the Watchman and warfarin groups , respectively ( relative risk , 0.71 ; 95 % confidence interval , 0.44 % -1.30 % per year ) , which met the criteria for noninferiority ( probability of noninferiority > 0.999 ) .\