Open heart surgery appears to be safer in the afternoon because of the body's internal clock, scientists have said.
New research, published in the Lancet, suggests the heart is stronger and better able to withstand surgery in the afternoon than the morning. Doctors need to stop the heart to perform operations including heart valve replacements. This puts the organ under stress as the flow of oxygen to the heart tissue is reduced.
The doctors and researchers looked for complications including heart attacks, heart failure or death after surgery. They found:
- 54 out of 298 morning patients had adverse events
- 28 out of 298 afternoon patients had adverse events
- Afternoon patients had around half the risk of complications
Heart health is already known to fluctuate over the course of a day. The risk of a heart attack or stroke is highest first thing in the morning, while the heart and lungs work at their peak in the afternoon.
Other possible explanations for the findings included surgeons being tired in the morning or their own body clock affecting their surgical skill, particularly if they are not "morning people".
However, the researchers have gone to great lengths to show that the difference in survival rates was not down to the surgeons. The researchers are also investigating whether circadian rhythms have an impact on survival in other types of surgery.
Our associate medical director, Dr Mike Knapton, said:
“Thousands of people now have open heart surgery in the UK. These procedures can take many hours and come with a number of risks. The time of day appears to be a significant factor in the outcome from surgery, with better outcomes if your surgery is in the afternoon.
“If this finding can be replicated in other hospitals this could be helpful to surgeons planning their operating list, for non-urgent heart surgery.
“The study also suggests that modifying the genes responsible for this phenomenon could lead to the development of new drugs to protect the heart from damage during open heart surgery.”
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