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I was thinking about artificial hearts, and how much of a problem it is to 'know' the right speed to beat at.

Which made me wonder: what happens if your heart beats at max speed, when you are at rest? Does anything go wrong? Is it just energy minimization that motivates variable heart rate?

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    – Chris Rogers
    Sep 21, 2021 at 14:37
  • Just to clarify, you're asking for effects on the rest of the body, not on the heart itself? As you mention an artificial heart this could presumably be constructed like a pump that can actually sustain the high rate, not like the real heart. So the question is if rest of the body suffers damage from sustained high pressure?
    – Stephan Matthiesen
    Sep 22, 2021 at 8:26

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I think it's a matter of energy minimization. It simply doesn't make sense for the heart to beat so fast when your body doesn't need the huge amount of oxygen and nutrients the heart cycles through the body with the advanced speed it operates.

The heart -- a muscle -- may actually suffer damage from sustaining contraction at max speed at all times.

As research on excessive endurance exercise and its effect on the heart shows,

Heavy and sustained ET [exercise training] generates large quantities of free radicals that likely outstrip the buffering capacity of the system, leaving these individuals susceptible to oxidative stress and transient cardiomyocyte dysfunction.

Potential Adverse Cardiovascular Effect From Excessive Endurance Exercise

Not to mention, the heart operating at max speed will not pump enough blood to the organs and extremities, actually reducing blood flow to throughout your body as compared to a heart with variable heartrate.

Supraventricular tachycardia, a heart condition that features episodes of an abnormally fast heart rate, is a short-term example of your 'max heart rate' hypothesis.

According to NHSinform.scot,

In SVT [Supraventricular tachycardia], the heart muscle is contracting so fast that it cannot relax between contractions. This reduces the amount of blood being pumped around the body, which can make you feel dizzy and short of breath.

And sustained tachycardia (>= 30 seconds) is especially dangerous for the human heart.

It [sustained tachycardia] may lead to more serious ventricular arrhythmias, such as ventricular fibrillation.

Ventricular fibrillation involves sudden, rapid, irregular, and chaotic heartbeats in the ventricle. These erratic electrical impulses, sometimes triggered by a heart attack, cause your heart’s ventricles to quiver.

Supraventricular tachycardia

[Ventricular Tachycardia][3]

[3]: https://www.hopkinsmedicine.org/health/conditions-and-diseases/ventricular-tachycardia#:~:text=But%20when%20sustained%2C%20ventricular%20tachycardia,threatening%20arrhythmia)

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  • Welcome to MedicalSciences.SE. The first paragraph is so-so but the last is questionable in my mind. We work differently to many SE sites, where we have a strict policy that all answers should be backed up with reliable references so that the answer can be independently verified, regardless of the reader's background. See this list of reliable sources. Unreferenced claims can be challenged and lead to deletion of your answer
    – Chris Rogers
    Sep 21, 2021 at 14:37
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    Thank you for pointing out the errors in my submission. I've edited the answer to include verifiable references.
    – Stardust
    Sep 21, 2021 at 15:31
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    To greatly improve this answer, find out what happens to hearts that remain in sustained tachycardia for prolonged periods (weeks, months). SVT is an example of what can cause that.
    – Carey Gregory ♦
    Sep 21, 2021 at 16:19
  • This does answer my question (thank you!). I'm still curious about what would happen if an artificial heart kept that speed without loss of flow rate though, since it doesn't look like SVT would necessarily arise with an artificial heart. My hypothesis is that an artificial heart could literally beat at 200bpm for a decade and you'd be just fine, maybe even function better than normal.
    – Matt
    Sep 22, 2021 at 2:45
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    @Matt Doubt you'd be just fine. It's not how the human body evolved.
    – Carey Gregory ♦
    Sep 22, 2021 at 5:47

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