Weekend effect on operative mortality following coronary artery bypass grafting

Objective It remains controversial whether patients undergoing coronary artery bypass grafting (CABG) late in the workweek or on weekends experience excess mortality. Methods Medicare beneficiaries undergoing isolated CABG from 2008-2019 were stratified by day of surgery (DOS; Monday-Sunday). A flexible parametric model adjusting for demographics, comorbidities, surgeon/hospital volume, and procedural details was used to evaluate whether CABG-DOS was associated with 30-day mortality. Regression standardization was applied to estimate standardized survival probabilities (SSP). SSPs for CABG performed on Friday, Saturday, and Sunday were compared to Monday-Thursday in the overall cohort and within cohorts defined by admission urgency (proxy for surgical urgency). Results Among 735,603 beneficiaries undergoing CABG, surgery was performed on Friday in 144,220 (19.6%), Saturday in 18,568 (2.5%), and Sunday in 11,502 (1.6%). From Monday-Friday, approximately 50% of CABG were elective; elective CABG comprised 30% of Saturday cases and 22% of Sunday cases. Risk-adjusted 30-day standardized survival probabilities were similar among CABG performed Monday-Thursday (97.0% [96.9-97.1%]) and Friday (97.1% [97.0-97.2%]) but lower on Saturday (96.2% [95.9-96.4%]) and Sunday (95.4% [95.0-95.7%]). A weekend effect on mortality was persistent across all admission urgency levels. Conclusions Compared with weekday operations, weekend CABG was associated with 1-2 excess mortalities per 100 procedures. These findings suggest that environmental factors specific to DOS, unique to weekends, and present regardless of case urgency, may adversely impact early post-CABG survival.