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Comment by tombert | Hacker News Reader

Genuine question: why is an artificial heart such a hard thing to make? At least from a lay-person's perspective, it's just some pumps and valves, which we've gotten pretty good at making.

Obviously I'm wrong about that because there really isn't a permanent artificial heart yet, but it's something I have wondered for awhile.

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It has been done, as mentioned by other comments. My recollection is that aside from power & control, the hardest problem is clotting. The natural heart apparently causes the blood to flow in a way that there is no pooling or stagnation, whereas almost any fixed-shape chamber apparently has locations where the fluid will stagnate, and with blood, that will cause clots in a very short time. When those clots get loose, they can then go to the lungs and cause a pulmonary embolism, or to the brain and cause a stroke, both of which are very bad and often fatal. So, getting a mechanism that won't do that even once in years of continuous operation is ... nontrivial.

EDIT - this is what I recall reading, but I'm not a biomed, I'd like to see a more detailed description from someone in the field.

This was indeed the case for the early total artificial hearts implants (Jarvik-7), https://youtu.be/0Xn5u-LzsW8 is a nice short documentary about it

Indeed, but they've done it. Check out LVADs like the Heartmate 3 and Heartmate 2.

There are artificial hearts, and people survived for years on them. The record is 7 years, I think.

They aren't cheap, $100K to $300K for the first year, depending on the device. Then it's around $18K/year to maintain.

I don't know why they are that expensive.

And LVADs too, folks have lived over a decade on those. Tens of thousands have been implanted.

See "total artificial heart": https://en.wikipedia.org/wiki/Artificial_heart

Layperson speculation: hard to power 24/7 without an external power source, it must connect seamlessly to the blood stream (can't have it disconnect from the aorta after five weeks), and the surfaces exposed to the blood must not cause blood clots (so careful at the seams).

It does make me wonder how the transplanted pig heart or any transplanted heart connects so seamlessly.

The issue simply heals and grows together with the foreign tissue?

They use a common medical technique called anastomosis. Basically they just sew the two arteries/vessels together with suture and the blood and tissue seals it as any other cut or nick in the body. Sometimes they use "bioglue" but its not strictly needed, just a timesaver.

And the pig tissue then connects with the human tissue and eventually heals to form a connected vessel? or it never grows together but it is sealed with a blood cloth?

Exactly, the former.

So say I carve a wound onto my skin, and then put live skin with a sufficient tissue match onto it and connect the blood vessels so that the new live skin does not die; then the live skin graft and my own damaged skin will hen heal into each other and form a connected totality?

For skin & a "sufficient tissue match", yes. See e.g. tissue scaffolds.

It's not quite all that seamless - since we can't hook up the nerves, your new heart won't adjust its rate the way your original did.

I didn't know that. Do all heart transplants come with pacemakers then?

Edit: looks like it's just some nerves, not all.

> Your transplanted heart will respond to activity a little differently. Your heart rate will not increase like it used to. And you will have a higher resting heart rate. This is because some of the nerves that control your heart were cut during your surgery.

https://www.cham.org/HealthwiseArticle.aspx?id=hw30661

My understanding -- which should be taken with two grains of salt, I'm a programmer not a doctor -- is that the pacemaker cells which actually go "beat now beat now beat now" are part of the heart itself, and transplanted with it: https://en.wikipedia.org/wiki/Cardiac_pacemaker

The nerves from the rest of the body are needed to tell these cells "we need more oxygen, beat faster" or "sleepy time, beat slower".

Could a surgeon cut the nerves and pacemaker cells away from the diseased heart and implant them into the donor heart?

I assume if they could reconnect the nerves to the new heart they would. There's no need to replace the pacemaker cells in the new heart with the old ones though.

Friendly reminder that the heart produces electricity; ergo, it can be used to mine crypto.

I've seen the Matrix, I know how this ends.

Spoiler alert

In addition to soft flexible machinery being somewhat difficult to manufacture, you would also have to hook it up to the brain. Not exactly an easy feat.

Why would you need to hook it up to the brain? I am assuming to respond to signals, for example stressed -> beat faster? But what would happen if you didn't have this automatic response? Let's say the heartbeat could be controlled by an algorithm or an app - for example if you lie down, it slows down automatically or if you expect to do some exercise, you can turn it up.

I'm fairly certain you don't want your heart controlled by an app on your phone.

An open source app in and of itself would be a little scary, but I can't imagine the startup making your connected artificial heart posting an "incredible journey" blog.

Or having to learn from Hacker News that Google is dropping support for your organs.

Ransomware would be brutal

You don't need to hook it up the brain. Transplanted hearts are generally not innervated.

https://academic.oup.com/eurheartj/article/39/20/1799/290050...

As a result, they do not correctly respond to higher demand by beating faster, but this is a deficiency that is considered acceptable. Heart transplant recipients aren't routinely running marathons.

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