The hazard ratios ( HRs ) for ICD therapy compared to placebo were estimated within tertiles of baseline 6MW distance : HR : 0.42 ( 95 % confidence interval [ CI ] : 0.26 to 0.66 ) for 6MW distance > 386 m ( top tertile ) ; HR : 0.57 ( 95 % CI : 0.39 to 0.83 ) for 6MW distance 288 to 386 m ( middle tertile ) ; and HR : 1.02 ( 95 % CI : 0.75 to 1.39 ) for 6MW distance < 288 m ( bottom tertile ) .