Recent work suggests that having aortic valve surgery in the morning increases risk for cardiac-related complications. This study therefore explored whether mortality and cardiac complications, specifically low cardiac output syndrome, differ for morning and afternoon cardiac surgeries.

The study included adults who had aortic and/or mitral valve repair/replacement and/or coronary artery bypass grafting from 2011 to 2018. The components of the in-hospital composite outcome were in-hospital mortality and low cardiac output syndrome, defined by requirement for at least two inotropic agents at 24 to 48 h postoperatively or need for mechanical circulatory support. Patients who had aortic cross-clamping between 8 and 11 am (morning surgery) versus between 2 and 5 pm (afternoon surgery) were compared on the incidence of the composite outcome.


Among 9,734 qualifying operations, 0.4% (29 of 6,859) died after morning, and 0.7% (20 of 2,875) died after afternoon surgery. The composite of in-hospital mortality and low cardiac output syndrome occurred in 2.8% (195 of 6,859) of morning patients and 3.4% (97 of 2,875) of afternoon patients: morning versus afternoon confounder-adjusted odds ratio, 0.96 (95% CI, 0.75 to 1.24; P = 0.770). There was no evidence of interaction between morning versus afternoon and surgery type (P = 0.965), and operation time was statistically nonsignificant for surgery subgroups.


Patients having aortic valve surgery, mitral valve surgery, and/or coronary artery bypass grafting with aortic cross-clamping in the morning and afternoon did not have significantly different outcomes. No evidence was found to suggest that morning or afternoon surgical timing alters postoperative risk.

Editor’s Perspective
What We Already Know about This Topic
  • Whether complications differ with morning and afternoon cardiac surgery remains unclear
What This Article Tells Us That Is New
  • A retrospective cohort study evaluated 9,734 patients who had aortic valve, mitral valve, and/or coronary artery bypass graft surgery over 7 yr at a single center
  • The confounder-adjusted incidence of the composite outcome of in-hospital low cardiac output syndrome or mortality was similar for morning and afternoon surgery
  • The results do not support selective morning or afternoon scheduling for cardiac surgery