The primary endpoint of the study , the 1-year patency rate of the SV composite grafts , was 97.1 % ( 238 of 245 ) and was noninferior to that of the RITA composite grafts ( 97.1 % [ 198 of 204 ] ) with a 95 % lower confidence limit of -2.6 % ( P < .001 for noninferiority ) .