Weekend effect on operative mortality following coronary artery bypass grafting

Whether patients undergoing coronary artery bypass grafting (CABG) late in the workweek or on weekends experience excess mortality remains controversial.

Medicare beneficiaries undergoing isolated CABG from 2008 to 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 (SSPs). SSPs for CABG performed on Friday, Saturday, and Sunday were compared to those for CABG performed on Monday to Thursday in the overall cohort and within cohorts defined by admission urgency (proxy for surgical urgency).

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 to Friday, approximately 50% of CABGs were elective; elective CABG composed 30% of Saturday cases and 22% of Sunday cases. Risk-adjusted 30-day SSPs were similar for CABGs performed on Monday to Thursday (97.0%; 95% confidence interval [CI], 96.9%-97.1%) and Friday (97.1%; 95% CI, 97.0%-97.2%) but were lower for CABGs performed on Saturday (96.2%; 95% CI, 95.9%-96.4%) and Sunday (95.4%; 95% CI, 95.0%-95.7%). A weekend effect on mortality was persistent across all admission urgency levels.

Compared with weekday operations, weekend CABG was associated with 1 to 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.