Heart surgery beginning in the late morning is linked to a modest increase in cardiovascular mortality when compared to other times of the day, according to a study led by researchers at The University of Manchester.
The study, supported by the National Institute for Health and Care Research (NIHR) Manchester Biomedical Research Centre (BRC) is published in the journal Anaesthesia today
The findings, based on the analysis of four linked national datasets comprising over 24,000 patients in England, Wales and Northern Ireland, hold true even when accounting for the different complexities and durations of the surgery.
The data showed late-morning surgery was linked to an 18% higher risk of death - almost one fifth - from heart related causes compared with early-morning surgery.
And the most common surgical start time was 07:00-09:59- early morning - accounting for 47% of all surgeries.
Though complication rates and readmissions were unaffected by the time of day, the findings still pose questions about the best time to schedule heart surgery.
They also give an important insight into the potential influence of the body clock - a set of 24-hour biological cycles present in our cells and organs - on surgery as a whole.
Lead author is Dr Gareth Kitchen, Clinical Senior Lecturer at The University of Manchester. He is also part of the Respiratory Theme and Co-Lead for Industry and Commercialisation at the NIHR Manchester BRC.
He said: "Given that over 25,000 heart operations are performed across the UK every year with around a 2.7% mortality, even small improvements in timing-related outcomes could have significant benefits to patients.
"This research shows a slightly higher risk of heart related mortality is likely to occur when heart surgery starts in in late morning.
"However, though the risk is statistically significant, it is relatively modest and patients can be reassured that most people will almost certainly be unaffected.
"It is though, our duty as clinicians to ensure the best possible outcomes, and moderating timings is a potentially inexpensive method to achieve that."
The researchers compared four starting times for the 3 to 5 hour operations: early morning (07:00 to 09:59); late morning (10:00 to 11:59); early afternoon (12:00 to 13:59); and late afternoon (14:00 to 19:59).
The main outcomes they examined were hazard of death from cardiovascular disease and time to hospital readmission for heart attack or acute heart failure.
Secondary outcomes included duration of postoperative hospital stay, occurrence of major cardiovascular events and all-cause mortality.
The researchers accounted for potential bias by taking into account key mortality predictors such as age, sex, diabetes and urgency of surgery.
Dr Kitchen added: "Integrating body clock biology into the planning of heart surgery could support a more personalised, precision medicine approach.
"As some people's body clock makes them early birds and others makes them night owls, it is worth exploring tailored operative times through further research.
"With more understanding of how body clock biology varies between individuals, precision and personalised scheduling of cardiac surgery may one day allow us to achieve better patient outcomes."
