In contrast , the @-day risk of stroke or death was significantly higher in patients treated by operators with low ( mean @ procedures/y ; risk @ % ; adjusted risk ratio = @ -LSB- @-@ @ -RSB- ) and intermediate annual in-trial volumes ( @-@ @ procedures/y ; @ % ; adjusted risk ratio = @ -LSB- @-@ @ -RSB- ) compared with patients treated by high annual in-trial volume operators ( > @ procedures/y ; @ % ) .