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Comment by kerryfalk | Hacker News Reader

Admittedly I didn't read the whole story, the click-bait title got me.

I had a girlfriend with a similar device attached to her (an LVAD). At first it was a little unnerving seeing her unplug the batteries that were keeping her alive and charge them every night. It quickly became normal for me. Life with it seemed relatively normal except she had to have a purse with her at all times (it carried the batteries).

The interesting part was when she received a transplant and went cordless. After being attached to it for two years and not having a heartbeat the sound of her heat beating kept her up at night for a couple of weeks. I hadn't even considered the beating of a heart to be relevant to our daily lives until she had mentioned it once she heard hers beating again (an LVAD is just a constant velocity pump. The blood is always flowing).

Not sure how much it really adds to the conversation other than an interesting anecdote.

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Wow, I had no idea you have no pulse when you have an LVAD. That's really neat.

Do you have any idea if there have ever been studies on the effect of constant flow vs peristaltic flow on the circulatory system? I wonder if the constant flow creates or solves any issues.

That continuous flow is new(-ish). My father had an LVAD in 2002, and it was the older type that actually pumps rhythmically, so that was his pulse. At the time continuous-flow models were in research, and I do remember there were concerns with thrombosis (basically, the shifting force of the pulse helps break up clots).

I don't know the current state of the art, but there are definitely studies (the keyword is "pulsatile"). For example:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4250555/

For comparison, here's a picture of some LVADs. The one I've seen in person (after it had been taken back out!) is the one on the far left. Flow issues aside, I can imagine the smaller ones are easier on the patient in general, just from the perspective of surgery trauma.

http://reliantheart.com/wp-content/uploads/2013/04/VAD_Size_...

To elaborate a little bit more: the first generation of LVADs were had large mechanical pumps and were huge -- they could only be implanted in people with a large chest cavity, excluding a large number of patients (especially women) from eligibility for their device.

Current popular models are continuous flow rotors that are much smaller (enabling their use in almost anyone) and are non-pulsatile.

However, there's been a big push to move towards pulsatile devices. This is mostly driven by mechanobiolgy studies that show that there is a difference in the cellular programs of cells that are exposed to a continuous shear force versus a pulsatile shear force. Accordingly, to more closely replicate the natural physiology of the heart, there has been a big push towards using pulsatile devices.

There is a difference between pulse and heartbeat, the pulse is from the veins and you can feel it even with an LVAD.

The audible heartbeat is from the heart sliding in the pericardium sac when it beats, many people lose the audible heartbeat after having heart surgery when the pericardium sac has to be cut or removed completely e.g. if someone is having a bypass surgery.

Peripheral Veins are not pulsatile (near the heart, they have a complicated waveform). Peripheral pulse is arterial.

The audible heartbeat is from the valves closing.

Yeah! Maybe the OP has the heart sounds confused with a pericardial friction rub, which can happen in pathological states and is due to the heart sliding against the pericardium.

I didn't know there was a difference in terminology when I asked. This was a worthwhile question - I learned a lot.

Thanks for the great explanations!

How do you perform CPR on a person with an LVAD? Plug the device in.

I'm not being snarky. I saw several patients with LVADs on my cardiology rotation in medical school. As far as I know they are the only patients exempt from CPR if they have a cardiac arrest, although device failure should be the only reason for this.

There are two types of LVAD's- continuos flow and pulsed. LVAD's "piggyback" onto the existing heart and provide additional force to the left ventricle (which pumps blood to the body). The biggest issue with LVAD's is immune rejection and plaque buildup. As the body responds to a foreign object it will frequently form plaques on the LVAD's internal valves. It's very challenging to determine if this plaque buildup is occurring without literally opening up the patient's chest via surgery. If the plaque breaks loose, they frequently cause stroke or pulmonary embolisms.

I knew about the continuous flow, but hadn't considered that you wouldn't hear your own pulse as a result. My father in law has an LVAD, which has given him back a lot of freedom following a severe heart infection early last year which damaged his natural heart badly. He's now on the transplant list, so I'll point it out to him as a "hey, this could be weird" thing.

Do they mean that blood pressure is stable too, since you presumably wouldn't have a diastolic reading - no pressure reduction between beats, since there are no beats?

The diastolic reading isn't about pressure reduction in-between heartbeats but about the pressure created by the vascular walls.

When you usually measure blood pressure you increase the pressure to a value that's likely above the systolic value of the patient (say 180). Then you gradually release pressure. Once you hear a heartbeat that's the systolic value. Once you stop hearing the heartbeat that's the diastolic value, which is the vascular walls resisting the heartbeat

In this particular case instead of the usual heartbeat you'd likely hear something more like a constant flow but you'd still have systolic and diastolic values.

Just to expand:

With a blood pressure cuff, what you are doing is collapsing the arterial wall with outside pressure. You increase the pressure above systolic blood pressure and then gradually reduce it until you hear a sound. This sound isn't the heartbeat, but is instead the result of turbulent flow in the blood vessel. While you are between systolic and diastolic pressure, only spurts of blood can flow through the vessel creating noise. Eventually, you reduce the pressure enough and blood even during diastole (which is lower pressure) can expand the walls of the artery against the blood pressure cuff.

So, in both cases what you are hearing is due to blood pushing open the vascular walls.

"Clearest explanation" award for that second paragraph.

So that's how doctors do it with a manual pump and stethoscope. Never thought of asking one ...

Not an expert, but from reading what an LVAD is and reading the article, these are two very different things. He had a full heart replacement device strapped to his back. As in, the blood ran out one tube, into the pack, then back into his body. An LVAD is an internal pump for the left side of the heart and you just provide it power externally. Not to discount your girlfriends experience at all, but that seem quite different.

EDIT: Actually, watching a video, it looks like the tubes are for air maybe? Weird device in any case.

That's amazing. It's both awe-inspiring and unnervingly depressing to be reminded that we are ultimately just biological machines.

Reminds me of that procedure where a surgeon can freeze you, drain your blood, take out all your organs and then put them back in, stitch you up, pump blood back in and then warm you up and awaken you. It was like unplugging your PC, taking it apart and then putting it together and turning it back on.

I gotta say, this is a rare case where the link-bait title wasn't so much link-bait as a succinct description of what was in the article.

Click-baiting titles on sites these days are probably driving people to the comments section first rather than RTFA. Crowd-sourcing and displaying in-place article titles on sites would make for a great browser extension. Might be as bad for site owners' short-term business goals as ad-blockers are.

Artificial heart designers may thus consider doing something to simulate the noise and vibration of a heart beat, to prevent any awkwardness after the transplant.

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