Daytime variation of perioperative myocardial injury in non-cardiac surgery and effect on outcome

Objective Recently, daytime variation in perioperative myocardial injury (PMI) has been observed in patients undergoing cardiac surgery. We aim at investigating whether daytime variation also occurs in patients undergoing non-cardiac surgery. Methods In a prospective diagnostic study, we evaluated the presence of daytime variation in PMI in patients at increased cardiovascular risk undergoing non-cardiac surgery, as well as its possible impact on the incidence of acute myocardial infarction (AMI), and death during 1-year follow-up in a propensity score-matched cohort. PMI was defined as an absolute increase in high-sensitivity cardiac troponin T (hs-cTnT) concentration of >= 14 ng/L from preoperative to postoperative measurements. Results Of 1641 patients, propensity score matching defined 630 with similar baseline characteristics, half undergoing non-cardiac surgery in the morning (starting from 8: 00 to 11: 00) and half in the afternoon (starting from 14: 00 to 17: 00). There was no difference in PMI incidence between both groups (morning: 50, 15.8% (95% CI 12.3 to 20.3); afternoon: 52, 16.4% (95% CI 12.7 to 20.9), p=0.94), nor if analysing hs-cTnT release as a quantitative variable (median morning group: 3 ng/L (95% CI 1 to 7 ng/L); median afternoon group: 2 ng/L (95% CI 0 to 7 ng/L; p=0.16). During 1-year follow-up, the incidence of AMI was 1.2% (95% CI 0.4% to 3.2%) among morning surgeries versus 4.1% (95% CI 2.3% to 6.9%) among the afternoon surgeries (corrected HR for afternoon surgery 3.44, bootstrapped 95% CI 1.33 to 10.49, p log-rank=0.03), whereas no difference in mortality emerged (p=0.70). Conclusions Although there is no daytime variation in PMI in patients undergoing non-cardiac surgery, the incidence of AMI during follow-up is increased in afternoon surgeries and requires further study.