ObjectiveInvestigate the association between the presence and grafting of chronic total occlusions (CTO) and coronary artery bypass grafting (CABG) outcomes. MethodsThis was a post hoc analysis of the REGROUP trial, which randomized veterans undergoing isolated on-pump CABG to endoscopic versus open vein harvest (2014-2017). Patients were stratified based on the presence of at least one CTO vessel (a 100% occluded coronary lesion for greater than or equal to 3 months), and according to whether all CTO vessels were bypassed. Rates of major cardiac adverse events (MACE) were compared. ResultsAt least 1 CTO was present in 453/1,149 patients (39.4%). Over a median follow up of 4.7 years (interquartile range 3.84-5.45), MACE rates were 23.4% vs. 22.2% for the CTO vs. no CTO group, respectively (adjusted hazard ratio [AHR] 0.92, 95% CI 0.70-1.20). MACE rates for patients with complete CTO grafting vs. not were 23.1% vs. 25.0%, respectively (AHR 0.95, 95% CI 0.57-1.57) . In patients with right coronary dominance undergoing LAD grafting, bypassing a RCA CTO was associated with significantly lower rates of all-cause mortality (AHR 0.38, 95% CI 0.17-0.83). ConclusionsIn this REGROUP trial subanalysis, neither CTO presence or complete grafting of CTO vessels were associated with significantly different rates of MACE. However, the finding of possible survival benefit among a subgroup of patients undergoing grafting of a dominant RCA CTO vessel alongside LAD grafting warrants additional study.