Does Heart Surgery in the Afternoon Improve Survival Rates?

Patients undergoing major heart surgery have a better chance of survival if their procedure takes place in the afternoon rather than the morning, suggests a new study.

Why are the afternoon hours safer for surgery? It appears the body’s internal clock, or its circadian rhythm, is in a balanced state that fosters a stronger heart and can allow the body to withstand the trauma of heart surgery, according to researchers from the Institut Pasteur de Lille in France who reported their findings in The Lancet.

During open heart surgery, doctors must stop the heart to perform delicate operations, such as replacing a heart valve. Stopping the heart causes loads of stress on the organ because blood flow is significantly reduced.

When the researchers compared statistics among those who underwent surgery in the morning versus those in the afternoon, they discovered some startling trends: 54 out of 298 patients, or 18 percent of patients, who had surgery in the morning had a major complication, such as heart attack, heart failure or death.

On the other hand, 28 out of 298 patients who had surgery in the afternoon suffered a serious complication. That’s about 9 percent of patients – or roughly half of the morning subset. All told, the researchers say their findings show that shifting surgical times to the afternoon would avoid one major complication for every 11 patients who undergo a heart procedure.

“We don’t want to frighten people from having surgery – it’s life saving,” study author Bart Staels of the Institut Pasteur de Lille told BBC News. “If we can identify patients at highest risk, they will definitely benefit from being pushed into the afternoon, and that would be reasonable,” Staels added.

Minding the Body’s Clock

Your circadian rhythm is like an internal clock that runs 24 hours of the day and cycles through various physical signals, including the body’s sleep/wake system. But the circadian rhythm does more than simply set your sleeping cycles – it also influences “hormone release, eating habits and digestion, body temperature, and other important bodily functions,” according to the National Institute of Health (NIH).

What happens when your internal rhythm gets interrupted? “Irregular rhythms have been linked to various chronic health conditions, such as sleep disorders, obesity, diabetes, depression, bipolar disorder, and seasonal affective disorder,” reports the NIH.

“Scientifically, it is not hugely surprising, because just like every other cell in the body, heart cells have circadian rhythms that orchestrate their activity,” Dr. John O’Neill, from the UK Medical Research Council’s Laboratory of Molecular Biology, told BBC News.

Related: Change in Weather Tied to Heart Events, Morbidity

When it comes to your heart’s rhythm, peak activity occurs in the afternoon hours, which makes the new study findings in line with previous circadian knowledge, say the researchers.

“Our cardiovascular system has the greatest output around mid/late-afternoon, which explains why professional athletes usually record their best performances around this time,” said O’Neill.

Ultimately, the new report may lead to practical changes in how hospitals arrange surgery times, especially for patients who show signs of risk factors.

“We believe we have identified a potential way to circumvent the disturbing observation that operations in the morning lead to more complications,” Staels told BBC News.