Are we more likely to survive heart surgery in the afternoon?

Does our body clock really affect the safest time for us to not only conduct heart surgery, but to survive it as well? Well according to some new research, our circadian rhythms may have the power of dictating this.

Every cell in our system follows a daily rhythm, with the Suprachiasmatic nuclei (SCN) located in the brain taking the lead and acting as the master clock. Our SCN is controlled by light signals which receptors pick up in the eyes, allowing it to maintain a 24-hour pattern (eg. more melatonin is made during the night, making us sleepy). Dr John O’Neill said, “…just like every other cell in the body, heart cells have circadian rhythms that orchestrate their activity”.

According to recent studies, our heart has been found to induce maximum performance during the afternoon. Whereas in the morning (between 6-9am), there is an increased risk of a heart attack  due to thicker blood, stiffer blood vessels and a higher blood pressure; the patient’s heart can be the most vulnerable at this time. Consequently, with stronger cardiac muscle and increased bpm during the afternoon, this seems to be the safer option of the two as the heart is more likely to withstand the pressures of surgery. Statistics already support this new evidence, with around 54 out of 298 morning patients experiencing adverse reactions post-surgery. The figure is reduced to almost a half for afternoon surgery.

Dr O’Neill, supports this claim, saying:

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

Furthermore, the surgeon’s own body clock could affect their performance in the morning, leaving them feeling quite tired and more prone to mistakes. It is only later on in the day when the levels of our stress hormone, cortisol, start rising, boosting the surgeon’s alertness (apart from a dip straight after lunch).

Open heart surgery can be a very stressful experience for the heart, as the organ is stopped and oxygen supplied to it is reduced. Therefore, anything which can minimise this stress could be a potential finding for doctors, helping us to improve survival rates and reduce complications after surgery. Professor Bart Staels adds, “If we can identify patients at highest risk, they will definitely benefit from being pushed into the afternoon and that would be reasonable.”

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Isra Ahmed




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