Daytime-Dependent Cardioprotection in Cardiac Surgery: A Large Propensity-matched Cohort Study

Background A recent article provided compelling evidence for a cardioprotective effect of afternoon compared with morning operation in patients undergoing aortic valve replacement. The present study sought to investigate any daytime-dependent effect on perioperative myocardial injury or clinical outcomes in a large cohort of patients undergoing elective cardiac surgery. Methods The study identified all patients who underwent nonemergency aortic valve replacement and/or on-pump coronary artery bypass grafting at the Department of Cardiothoracic and Vascular Surgery of Aarhus University Hospital, Aarhus, Denmark between 1999 and 2018. Propensity-score matching was used to create adjusted cohorts for morning and afternoon operation. The primary end point was a composite of 30-day mortality and in-hospital acute myocardial infarction (major adverse cardiac events). Secondary end points were new-onset in-hospital atrial fibrillation, peak creatine kinase-MB levels, and up to 19 years of follow-up for all-cause mortality. Results The study identified 7148 patients who underwent either aortic valve replacement with or without coronary artery bypass grafting (n = 2806) or isolated coronary artery bypass grafting (n = 4342). Propensity-score matching resulted in comparable cohorts of morning and afternoon operation. The morning and afternoon operation cohorts had no differences in the rates of major adverse cardiac events after both procedures. Similarly, no daytime-dependent variation in the rate of new-onset in-hospital atrial fibrillation, long-term all-cause mortality, or peak creatine kinase-MB levels could be identified. Conclusions In this large cohort study of Danish patients, who underwent either aortic valve replacement and/or coronary artery bypass grafting, the study identified no clinically relevant biorhythm for myocardial ischemia-reperfusion tolerance.