Afternoon is the best time to undergo heart surgery, according to a new study published on Friday in British medical journal The Lancet.
According to the study led by professor David Montaigne of the University of Lille, France, afternoon heart surgery syncs with the body’s circadian clock and is linked to better outcomes for patients.
The circadian clock is a person’s internal body clock which controls when people sleep, eat and wake up.
The study found people who had surgery in the afternoon had a 50 per cent lower risk of a major cardiac event, compared to people who had surgery in the morning.
It was conducted between from January 2009 and December 2015 and involved researchers tracking the medical records of 596 people who had heart valve replacement surgery.
Half of the sample had surgery in the morning, half in the afternoon and monitoring continued for 500 days, looking for any major cardiac events such as a heart attack, heart failure or death.
Researchers said the results showed afternoon surgery “could equate to one major event being avoided for every 11 patients”.
Surgeons have long puzzled over why open heart surgery can be followed by cell damage and impacts on the heart’s ability to pump blood, with a heightened risk of heart failure and death.
Previous research has suggested heart attacks that happen in the morning may be associated with a higher risk of damage, compared to afternoon events, but reasons have remained unclear.
Outcomes for open heart surgery could now be improved by moving surgery to the afternoon, according to the study which identified nearly 300 genes linking the circadian clock.
“Currently, there are few other surgical options to reduce the risk of post-surgery heart damage, meaning new techniques to protect patients are needed,” said Professor Montaigne.
“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,” he said.
A genetic analysis of these samples also showed that 287 genes linked to the circadian clock were more active in the afternoon surgery samples, compared to the morning surgery samples. This suggests the heart is subject to the body’s circadian clock and surgical outcomes reflect the heart’s poorer ability to repair in the morning compared with the afternoon.
The authors note 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 the findings.
They also note the research needs to be replicated in high-risk patients with other condition such as diabetes and kidney failure, as they are at higher risk of heart disease and poor outcomes and were not included in this study.
