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Comment by cushychicken | Hacker News Reader

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.

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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.

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