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Comment by tacon | Hacker News Reader

The Texas Medical Center is moving ahead on its Bivacor rotary pump artificial heart.[0] It does not appear that Bivacor is a bridge to a transplant, but rather an end point. They kept a cow alive for many months a few years ago. Since it is a continuous rotary pump, the patient will have no pulse with this device.

One of the inventors behind Bivacor is Dr. Billy Cohn, an elite heart surgeon with a strong bent toward innovation. He would have an idea, hit his garage to cut up some plastic mesh, seal it, sterilize it, and be trying it in a patient in a few days. He jokes about Home Depot being his best source of medical equipment. In fact, he tells a hilarious Home Depot story in the middle of his standard talk on medical innovation.[1]

[0] https://www.bizjournals.com/houston/news/2021/05/19/bivacor-...

[1] https://youtu.be/iHTVTU8PPGk?t=623

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The Bivacor pump does have a pulse-like output, so I suspect some of the issues with earlier rotary pumps might not be so prevalent. Because it's a rotary pump though I suspect there's still issues with cell damage as they pass parts of the rotating assembly. The video claims that wide clearances reduce the risks of clotting from cell damage, but it's a reduction - not outright removal. See around the 3:40 to 4 minute mark on the video at https://www.bivacor.com/

Indeed. Patients I these types of pumps, and rotary LVADS as well need to be on anticoagulants for the whole time they are on the pumps.

I wonder if a pulse is required for any bodily functions we're not aware of, body tends to regulate a few rhythms.

Your small vessels are not grown to tolerate a constant pressure. You get aneurysms, clotting is super dangerous because they generally form and sit rather than getting sucked/pushed into the heart to potentially get broken up. Most importantly, forget your potential organ failure you wont notice until there's a lot of damage, and all the numbness you'll get, it's the brain function affects that bother me. Sluggish, memory problems, et al that accompanies tiny thromboses.

A rotary pump is an endgame-solution. It keeps you alive, at a cost and you die the end anyway (obviously).

Exactly. This is the cause of the phenomenon known as "pump head" that anesthesiologists refer to when patients are on long periods of support on heart lung bypass machines. These machines are peristaltic pumps with a continuous flow. Check out Ventriflo, a new type of pump intended for use in this area that has a biomimetic flow and pressure profile. Www.ventriflo.com

There's also Scandinavian Real Heart (https://realheart.se) from Sweden. They are developing a "total artificial heart" with two chambers and two pumps for a natural blood flow (and pulse).

Longterm animal tests are expected to commence after this summer.

This competition is good. Will push prices down a little bit.

I remember reading, years ago, about someone who was temporarily fitted with a rotary pump. He said his hearing required some adjustment, apparently we sort of constantly hear blood rushing without being aware of it, but that somehow changes when your pulse is gone.

How do these pumps affect blood pressure? Does it become constant? That can't be good for the elasticity of arteries & veins?

The sensation when your heart stops is sudden and terrible. It feels very quiet and you know for sure that something very bad is imminent.

I’m not sure if it comes from the absence of sound or from something else, like the stillness in your chest. The actual stoppages didn’t last that long with me (obviously), but they were very memorable.

When I get a couple of ectopics in a row I already feel like I'm about to keel over, I imagine that even a few missed beats would be immediately obvious and dreadful. Blood pressure would start to drop super fast and I suspect your brain won't be too pleased with that. Well done on surviving that!

I would hope your blood is still rushing about even with the rotary pump.

It is, but probably at a more constant speed, as opposed to the squeeze-and-relax approach of a normal heart.

It wouldn’t be a heartbeat associated with it, though.

I guess if we find that a pulse is required it will be relatively easy to add a "pressure relieve" valve to the rotary design. Pressure builds up and gets released regularly, just like ye good 'ol pump.

Pulse is central to traditional Indian medicine (Ayurveda) [1]. Will be interesting to see what the science finds, although I wouldn’t personally volunteer to have a pumpless-heart. Sounds likely to have unintended consequences as you suggest.

[1] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4890095/

People aren’t “volunteering” for this in any meaningful way. Their next-best option is pretty terrible.

The Carmat artificial heart was also developed as an end point, but it was easier for them to get it approved as a bridge to a transplant. One person had it at least for more than 2 years (it was in 2020 current fate is unknown).

This is not entirely correct. The default mode is pulse-less, but the bivacor can be spun up and down to simulate pulses (based on some articles I found looking at this a while back). I'm most curious about the auto rate adjustment. I'm assuming a built in oximeter? Also future revisions plan on a charge through skin internal battery. That'll be a killer (for lack of a better word) feature.

> I'm most curious about the auto rate adjustment. I'm assuming a built in oximeter?

Current cardiac pacemakers use oximeters as well as acceleration or jerk sensors as a proxy for physical activity.

It would be nice if they could install a USB port on the chest somewhere so you can use a good old power bank. But I don't think our biology agrees :)

https://www.bivacor.com/ has a good explanation and video description of the system. It sounds really promising. The things I was most curious about are, it gets a charge from a battery you carry around on your person like a purse, and, it has a ten hour recharge time and comes with two batteries. I think I'd get a few more spares.

I would worry about something like the battery becoming disconnected when I sleep. Hopefully it has a very insistent alarm to alert the user. I'd also worry about getting mugged and having the mugger demand the battery from me.

One idea that seems cool is if you could manually control your blood flow rate. They say it does change but don't clarify if it's manual change or automatic. If it were manual, it would unlock some abilities. You could calm yourself by dialing down your heart rate or "warm up" by dialing it up.

I hope this technology works!

The thought of altering my heart rate with the press of a button is terrifying.

> Since it is a continuous rotary pump, the patient will have no pulse with this device.

The former US Vice President Dick Cheney had a device (Heartmate II) that also resulted in him not having a pulse.

I'll refrain from any political jokes on HN.

Patients on those types of pumps (continuous flow LVADs) do actually have a pulse of their pump speed settings are properly set. The medical guidance is to set the pump speeds at a setting that allows the natural aortic valve to open once every few heartbeats. That makes it so the aortic valve doesn't calcify and get stuck shut. If they set the pump speed at that level the patients do still have a pulse, it's just a weak one.

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