Daytime and outcomes after cardiac surgery: Systematic review and metaanalysis, insights from a large UK database review and post-hoc trial analysis.

Background: Several studies have suggested a variation of myocardial tolerance to ischaemia depending on the daytime of surgery. To test this hypothesis, we conducted a three-level analysis: metaanalysis, national patient-level dataset analysis and a post-hoc trial analysis.

Methods: We first performed a systematic review and metaanalysis of available studies comparing clinical outcomes following cardiac surgery performed in the morning (am) versus afternoon (pm). Then, we interrogated the UK national adult cardiac surgery audit database (NACSA) and analysed the am or pm outcomes of patients undergoing non-emergency aortic valve replacement (AVR) or coronary artery bypass grafting (CABG). In a post-hoc analysis, we further investigated the effect of time of surgery on serum troponin release and ventricular myocardial biopsy adenine nucleotide metabolism.

Results: A total of 18377 patients undergoing uncomplicated isolated CABG or isolated AVR on the same day am or pm were included in the metaanalysis. Meta-analytic estimates showed no difference in the risk of MI between patients operated in pm vs am (OR 1.02, 95% CI:0.79-1.32) and in the risk of mortality (OR 1.1, 95% CI:0.85-1.42). Outcomes of 91248 patients from the NACSA dataset were analysed according to the daytime of the procedure. Patient-level analysis showed no significant effect of daytime for both isolated AVR (p=0.094) and isolated CABG (p=0.425). Finally, we performed a post-hoc trial database analysis in 124 patients undergoing isolated AVR or CABG of serial cardiac troponin and nucleotides metabolism on ventricular myocardial biopsies. We found no significant diurnal changes in the perioperative cardiac troponin release or nucleotide metabolism in the AVR (p=0.30) or the CABG cohort (p=0.97).

Conclusion: The present three-level analysis found no evidence that daytime influences clinical outcomes and myocardial injury in patients undergoing cardiac surgery.