Last updated on Jun 23rd, 2021 at 09:48 am

Outcomes for open heart surgery could potentially be improved by moving surgery to the afternoon, rather than in the morning…

The study, published in The Lancet on 26 October 2017, identifies a link between a person’s circadian clock and their risk of heart damage and major cardiac events after heart surgery.

Circadian/internal body clock

The study also provides early insights into the mechanism behind this link, identifying nearly 300 genes linking the circadian clock – the internal body clock that controls when people sleep, eat and wake up – to heart damage.

Following open heart surgery, some patients may develop heart damage impacting on the heart’s ability to pump blood, resulting in poor outcomes, including onset of heart failure and a heightened risk of death.

Reasons unclear

Previous research has suggested that cardiovascular events such as myocardial infarction (heart attacks) that happen in the morning may be associated with a higher risk of the damage, compared to afternoon events, but reasons have remained unclear.

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Four-part study

The study published today consisted of four parts: an observational study looking at the association between time of day of surgery and outcomes; a randomised controlled trial to investigate whether there was a causal link between time of day of surgery and outcomes; a human tissue analysis to identify genes involved in the circadian effect on heart surgery; and a mouse model further investigating the biological mechanism and a potential therapeutic approach. 

“Our study found that post-surgery heart damage is more common among people who have heart surgery in the morning, compared to the afternoon. Our findings suggest this is because part of the biological mechanism behind the damage is affected by a person’s circadian clock and the underlying genes that control it.

“As a result, moving heart surgery to the afternoon may help to reduce a person’s risk of heart damage after surgery,” says author Professor David Montaigne, University of Lille, France.

Larger trials needed

The authors note that the study will need to be replicated in larger trials to fully understand the association between the circadian clock and damage after heart surgery, and to confirm their findings. They also note that the research needs to be replicated in high-risk patients with diabetes and kidney failure, as they are at higher risk of heart disease and poor outcomes, and were not included in this study.


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