History of PVI

What is the history of PVI? My impression is that in the early days, the ablation was done inside PV. The downside was that it could cause stenosis, restricting blood flow. The lesion site was moved proximal, which reduced stenosis. Now the lesion is essentially on the atrial wall. Is that correct? Any details or correct terminology?

Misplaced PVI can also lead to pulmonary hypertension. Are there no historical treatments in any papers dealing with PVI? I'd have to go look myself.

Quote
Kwilk
What is the history of PVI? My impression is that in the early days, the ablation was done inside PV. The downside was that it could cause stenosis, restricting blood flow. The lesion site was moved proximal, which reduced stenosis. Now the lesion is essentially on the atrial wall. Is that correct? Any details or correct terminology?

That is correct.

Quote
Carey
That is correct.

Thank you. Any details you can add? Any other changes being worked on? I understand that not only does the antrum afford isolation, but that there are cardiac ANS clusters in the antrum as well, and that part of the effectiveness of the isolation the PV at the antrum is the inescapable/fortuitous killing off of those autonomic clusters.

The left posterior wall is another important source of afib and is often included in a standard ablation procedure by more experienced EPs. It's more dangerous territory because the posterior wall lies directly against the esophagus, so less experienced EPs are often reluctant to ablate it or proceed so timidly that they don't make durable lesions (that's the cause of my multiple ablations). That's because overheating the esophagus can lead to an atrioesophageal fistula, which is about the worst complication possible from an ablation (usually fatal). Several solutions to prevent this have been used, including temperature probes in the esophagus, devices to move the esophagus out of the way, and simply limiting time and power levels when operating in that area, all of which have limitations. Temperature monitors seem to be the dominant solution today, but PFA will probably be the real solution to this since it doesn't heat tissue.

For an historical view, see this 2015 article on this subject. (Sorry, Natale is lead author. )

Quote
Kwilk
there are cardiac ANS clusters in the antrum as well, and that part of the effectiveness of the isolation the PV at the antrum is the inescapable/fortuitous killing off of those autonomic clusters.

One of my questions before ablation has been the effect on the autonomic nervous system of ablating the autonomic ganglia. "Killing off" is not really what happens though, rather it is possible that some functions of the autonomic nervous system will be modified. Since I have Dysautonomia, this is an important question for me.

Quote
Daisy
Dysautonomia

Thanks. Do you have an idea of the cause and mechanism of yours?

Not sure if the following makes a difference @Daisy, and you certainly know more than me given our AF histories. I'm sure you already know what I meant, but in case not ... The clusters I tried to refer to are part of the local intracardiac nervous system. The cell bodies (and axons and dendrites) of the ICNS are embedded in cardiac tissue. This is in contrast to the vagal and paraspinal ganglion projections of axons into cardiac tissue. Well, that is my feeble understanding of the situation.

Quote
kwilk
killing off

I was under the impression that thermal ablation does not discriminate, all cell types within the thermal zone die. And there appear to be clusters of ICNS somata in the PV antrum, a frequent ablation zone for isolating PVs

Quote
web

source

Caption: <big snip> 487,106 cells and nuclei delineate 11 cardiac cell types and marker genes. <big snip>

Edited 1 time(s). Last edit at 10/09/2022 03:08PM by Kwilk.

Quote
Kwilk
Do you have an idea of the cause and mechanism of yours?

Dysautonomia is arising all too often in long Covid patients. Likewise, mine seems to have arisen after another very severe and prolonged viral illness. The mechanism, in me, (as per extensive autonomic testing) is sort of like the parasympathetic and the sympathetic branches of the autonomic nervous system compete for control during activities where one is supposed to be dominant. For me, the parasympathetic is usually the winner. The most evident manifestation of this is that I start to faint any time I am standing more than a couple of minutes.

Quote
Kwilk
I was under the impression that thermal ablation does not discriminate, all cell types within the thermal zone die. And there appear to be clusters of ICNS neurons in the PV antrum, a frequent ablation zone for isolating PVs

True, thermal ablation doesn't discriminate but a line is drawn rather than a thermal cluster bomb, so to speak. At least that is my understanding. So, while autonomic function may change (the higher HR after ablation seems to be one manifestation), it seems to be a modification rather than zapping the complete autonomic ganglia. At least this is my understanding.

Quote
Daisy
while autonomic function may change <snip> it seems to be a modification rather than zapping the complete autonomic ganglia.

Isn't that conflating the effect/message (ICNS modulation) with mechanism/messenger (ablation). The literature estimates 800+ cardiac ganglia each with between 2 and 1500 somata. After killing off 50, I'd imagine the ICNS function to be modulated.

Quote
Daisy
a line is drawn

What is the width of a typical ablation line?

In swine, which have similar atrial wall thickness, pulsed field achieved transmurality of with ablations line widths of 20 mm, typically.

In humans, I don't know what the width is, but my estimate is a width of at least several mm. PV antral wall thickness is greater than 2mm, meaning the width (at a minimum) of a transmural ablation line is typically 3mm (4 mm at the point of contact and 0 mm on the far wall).

On the other hand, cardiac ganglia dimensions are sub 1 mm.

Considering even the minimum ablation line width is quite a bit bigger than a ganglion, an entire ganglion would get killed off it if it was under the path.

Generally, neurons are much more fragile than other cell types. If the ablation caused an interruption (minutes+) of blood supply to ganglions outside the ablation zone, those would suffer (or completely zapped) as well.

Anyway, I'm no expert.


Sources:

2022 Pulsed Field Ablation to Treat Atrial Fibrillation

0.3 mm = (20um x cuberoot of 1500).

2016 Characterization of the intrinsic cardiac nervous system



Edited 1 time(s). Last edit at 10/09/2022 10:50PM by Kwilk.