INTRODUCTION: Uncertainty remains regarding whether the time of day that cardiac surgery is performed affects postoperative outcomes or if the observed variation can be explained by patient or surgical factors.
METHODS: A secondary analysis of prospectively collected data was conducted to examine the association between time of cardiac surgery and clinical outcomes. Data were derived from four linked UK datasets: the National Adult Cardiac Surgery Audit; the Case Mix Programme; Hospital Episode Statistics; and Office for National Statistics mortality records. The primary outcomes were hazard of death due to cardiovascular disease and time to hospital readmission for myocardial infarction or acute heart failure. Secondary outcomes included duration of postoperative hospital stay; occurrence of major cardiovascular events; and all-cause mortality.
RESULTS: Linked data for 24,068 patients were identified. Surgeries performed in late morning (10:00 to 11:59) had the highest mean (SD) predicted risk of death (3.7% (4.6)), compared with 3.2% (3.7) for early morning (07:00 to 09:59), 2.8% (3.4) for early afternoon (12:00 to 13:59) and 3.1% (3.6) for late afternoon (14:00 to 19:59) surgeries, respectively. The primary outcome measures showed an increased hazard of death from cardiovascular disease in the late morning (adjusted hazard ratio 1.18, 95%CI 1.00-1.39), with no difference in hazard of readmission for myocardial infarction or acute heart failure (adjusted hazard ratio 0.97, 95%CI 0.85-1.11). There were no differences in the secondary outcome measures.
DISCUSSION: Time-of-day variation in postoperative death due to cardiovascular disease following cardiac surgery was observed, with the highest risk seen in late morning procedures. These findings suggest that intra-operative or organisational factors specific to this period may influence outcomes. Future research should explore whether individual circadian phenotypes or chronotypes contribute to this variation, supporting a move towards precision and personalised scheduling of cardiac surgery to optimise patient outcomes.
