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Comment by xpl | Hacker News Reader

How does the device regulate the heartbeat speed? I mean, how does it know that it needs to pump blood faster or slower?

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Blood oxygen sensors seem relatively cheap and low power.

I wonder if they could use that as the feedback mechanism.

Ideally if the sensors are small, low power, and cheap enough CO2 and lactic acid levels would also be good to check on to increase bloodflow.

That’s a good question! As a layman I would assume there’s no way to read/detect the hormones that would demand acceleration of the heartbeat? So one has to take it easy for the rest of their life? Or maybe there’s a way to manipulate it manually?

If the heart is no longer the weak link, can you permanently increase level of blood flow to something akin to moderate exertion? Presumably you are now limited by what the veins can handle, but maybe they have more flexible performance characteristics?

Layman, but I imagine if your blood is flowing to fast doesn't help much the lungs have certain diffusion rates, the waste products wouldn't be increased because your not doing as much work. There is probably an optimal point where anymore just doesn't really matter.

I beat there is some psychological factors to thought you don't have a beat or pulse that is probably unsettling

IIRC this problem affects heart transplants as the nerve that controls the speed of the heart is severed during the operation.

Can't implants read from that nerve? Or the issue is that the "protocol" is hard to reverse?

My friend had this pump pack attached to him (the same thing Dick Cheney had) and it was constant flow. His heart technically worked but it was so weak you could barely detect it. The pump was just constant circulation, no pumping.

Hmm, do body processes depend on the fact that blood flows in pulses, and an optimal heart must be pulsed?

It used to be assumed to be the case because the heartbeat is so closely associated with life. This is why the first artificial hearts replicated pulses, despite requiring much more complexity. It turns out that your body can function more or less fine with continuous blood flow.

Yes, with this device, there is no pulse.

Do they do something unrelated to the function of pumping blood, just to make the patient feel a heartbeat for comfort?

I dont know for sure but the doctors were on TV in Houston a few months ago and IIRC they said no pulse.

They did mention that one has been running continuously for two years in vitro, and the idea is for it to be reliable enough to eventually implant permanently in some situations.

As a correction I saw some updated info where they say a pulse is definitely created by this device, so I must not have heard the brief TV mention accurately.

I think what impresses me a lot is a smoother-running machine :)

Not just for physical activity but for emotions as well, the palpitations before a skydive or the increased heart rate when you are kissing your crush/GF/wife

Not to mention the erection thing.

These things seems trival and of relative importance when compared with life or death but they are still important to go back to live a normal life.

It doesn't, neither do lvads

I would assume the kind of people who need a replacement heart are already on beta-blocker drugs, which clamp the peak heart-rate down significantly, so their body would already be used to a very limited heart-rate range.

Transplanted hearts don’t regulate as well as the original one. They seem to default to a higher resting rate, with less heart rate variability.

So maybe, for a temporary device, it isn’t necessary?

Accelerometers to measure physical activity?

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