There were no significant differences between the colchicine and placebo groups for the secondary end points of postoperative AF ( colchicine , 61 patients [ 33.9 % ] ; placebo , 75 patients [ 41.7 % ] ; absolute difference , 7.8 % ; 95 % CI , -2.2 % to 17.6 % ) or postoperative pericardial/pleural effusion ( colchicine , 103 patients [ 57.2 % ] ; placebo , 106 patients [ 58.9 % ] ; absolute difference , 1.7 % ; 95 % CI , -8.5 % to 11.7 % ) , although there was a reduction in postoperative AF in the prespecified on-treatment analysis ( placebo , 61/148 patients [ 41.2 % ] ; colchicine , 38/141 patients [ 27.0 % ] ; absolute difference , 14.2 % ; 95 % CI , 3.3 % -24.7 % ) .