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 surgery in patients undergoing aortic valve replacement. The present study sought to investigate any daytime-dependent effect on perioperative myocardial injury and/or clinical outcomes in a large cohort of patients undergoing elective cardiac surgery Methods We identified all patients, who underwent non-emergent aortic valve replacement and/or on-pump coronary artery bypass grafting at our department between 1999 and 2018. Propensity-score matching was used to create adjusted cohorts for morning and afternoon surgery. The primary endpoint was a composite of 30-day mortality and in-hospital acute myocardial infarction (major adverse cardiac events). Secondary endpoints 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 We identified 7,148 patients who underwent either aortic valve replacement with or without coronary artery bypass grafting (n=2,806) or isolated coronary artery bypass grafting (n=4,342). Propensity-score matching resulted in comparable cohorts of morning and afternoon surgery. The morning and afternoon surgery cohorts had no differences in the rates of major adverse cardiac events following 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, we identified no clinically relevant biorhythm for myocardial ischemia-reperfusion tolerance.