On multivariate analysis , both the ZRS ( HR = 1.41 ; 95 % confidence interval [ CI ] = 1.27 to 1.56 ; P < 0.001 ) and log NT-proBNP ( HR = 2.09 ; 95 % CI = 1.59 to 2.74 ; P < 0.001 ) independently predicted death at 30 days .