When we wait for a
heart surgerywe think about the surgeon, the type of intervention, the anesthetic risk. Much less at the time of going to the OR. A large British study, however, suggests that the time of day could slightly affect the chances of survival.
Researchers from the University of Manchester analyzed more than 24,000 records of elective heart surgery in the NHS, published in the journal Anaesthesia. Their objective: to know whether to start the intervention early in the morning, late morning or the afternoon changes something to the risk of death after the operation.
Heart surgery: what the study reveals about the schedule
The team studied 24,068 patients operated on between 2009 and 2016 in England, Wales and Northern Ireland, while around 25,000 heart surgeries are carried out each year in 37 UK hospitals, for an overall hospital mortality of 2.7%. The interventions, lasting on average three to five hours, were grouped into four slots: 7 a.m.–9:59 a.m., 10 a.m.–11:59 a.m., 12 p.m.–1:59 p.m. and 2 p.m.–7:59 p.m., the most frequent being the very beginning of the morning (47% of cases).
After adjustment for the EuroSCORE 2 operative risk score and the duration of surgery, the authors found a higher risk of death from cardiovascular causes when the operation begins at the end of the morning: +18% compared to the 7 a.m.–9:59 a.m. window (adjusted hazard ratio 1.18; 95% CI 1.00–1.39). The average predictive risk reached 3.7% in late morning, compared to 3.2% in early morning, 2.8% in early afternoon and 3.1% in late afternoon.
However, no difference appears in rehospitalizations for heart attack or acute heart failure, length of stay or all-cause mortality. “Although the risk of mortality from late morning cardiac procedures is statistically significant, it remains relatively modest and patients can be reassured that most will certainly not be affected. It is nevertheless our duty as clinicians to ensure the best possible outcomes, and adjusting schedules is a potentially inexpensive method of achieving this.” said Gareth Kitchen, lead author of the study and clinical lecturer at the University of Manchester.
Circadian rhythm and cardiac surgery: a possible explanation
Researchers are interested in the biological clock, this system of 24-hour cycles present in almost all our cells, including cardiac cells. Circadian rhythm modulates inflammation, sepsis response and wound healing; it could also influence the tolerance of the cardiac muscle to ischemia-reperfusion caused by extracorporeal circulation. In the study, the difference in mortality between early and late morning appears mainly in the first months following the operation, which points towards mechanisms linked to the perioperative period.
However, literature remains shared. A trial led by Professor David Montaigne and his colleagues at the Faculty of Medicine of Lille on aortic valve replacement reported fewer complications after afternoon surgery, possibly via the clock protein REV-ERBα. Other retrospective analyzes and meta-analyses have not found a systematic morning/afternoon effect, while a more recent synthesis mainly places the increased risk for operations beginning in the evening or at night. The signal observed specifically between 10 a.m. and 11:59 a.m. therefore completes a still nuanced picture.
How to interpret these results before heart surgery
For a scheduled patient, these data do not mean that late morning should be avoided at all costs or that a specific schedule should be required. The excess risk remains low in absolute value, and other parameters weigh heavily: general condition, type of intervention, emergency, organization of the team. Above all, the authors point out that adjusting schedules could become a simple lever for improvement across a health system.
Gareth Kitchen also mentions the possibility of one day personalizing these schedules according to each person’s chronotype: “As some people have a more morning circadian rhythm and others more nocturnal ones, it is relevant to explore the possibility of adapting operating times through additional research.“. Prospective trials remain necessary before considering cardiac surgery truly synchronized with the internal clock of each patient.