I Might Have Been Wrong About Pulsed Field Ablation for Atrial Fibrillation

Emphasis on "might"

Hi everyone. I’ve been stunned about all the new subscribers. I am not sure what happened, but thank you for signing up.

I’ve had a busy late summer writing and podcasting—as well as practicing electrophysiology here in beautiful Louisville Kentucky.

Let’s start with a (possible) change of opinion.

I wrote in July of this year that my colleagues in heart rhythm medicine might be too easily impressed with new technology.

I took issue with our enthusiastic embrace of pulsed field ablation (PFA), which is a new way to destroy atrial myocardium for the ablation of AF.

PFA uses electric energy rather than thermal (heat or cold) energy. It’s fast and potentially safer because it does not damage non-cardiac cells, such as the esophagus.

In July, I wrote that the empirical data with PFA were hardly persuasive. Rates of AF suppression with PFA were no better than with standard thermal ablation. Complication rates were also similar. And procedure times, at least in the hands of US operators, were actually longer than standard thermal ablation.

The thing was that I hadn’t used PFA. I assessed PFA as a neutral Martian.

Now I have used PFA. And. It is somewhat amazing. It ablates cardiac tissue quickly and easily. Patients hardly feel chest pain after the procedure.

We make electrical maps after doing PFA and these show complete ablation of the electrical activity in the areas of the pulmonary veins. And. Since the procedure does not heat the esophagus I don’t have to worry about a patient dying from thermal esophageal damage 3-4 weeks after the ablation. (The risk of death from AF ablation due to esophageal damage is super super low, but it is not zero. Approximately half of experienced operators worldwide report having a catastrophic esophageal complication at their center.)

I don’t think my late embrace of PFA is due to susceptibility to marketing. (Though it might be.) I waited awhile and watched my partner use it. I now prefer PFA for AF ablation because it is easy and seemingly effective.

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You might wonder why the PFA studies failed to show superior efficacy and safety. I can easily explain the safety issue: At the catheter manipulation level, PFA-guided ablation is similar to thermal ablation. Typical procedural complications will, therefore, be similar to thermal ablation. In fact, the catheter and sheath used with PFA are stiffer, and cardiac perforation and tamponade may actually be slightly higher with PFA.

The safety aspect we love about PFA could never be shown in trials. That’s because the complication every EP doctor worries about is thermal esophageal injury. The incidence of this complication is in the 1 in 10,000 range. But when it occurs, the patient often dies. PFA does not heat the esophagus. So you reduce a complication that does not occur in 9,999 of 10,000 ablations. You can’t see that in trials of hundreds of patients. But it is a still a big deal.

The biggest unanswered question regards efficacy. Yes, after we deliver the electrical ablative energy, we obliterate atrial signals. The question is whether it’s durable. Preliminary studies have suggested that PFA is not more durable than thermal ablation. This is one reason why AF suppression rates are similar. The other reason of course is that we don’t understand AF and thus we often don’t ablate in the proper area.

PFA proponents argue that we are still early in the iterative process. Catheters will improve—as will the knowledge of the best dosage of energy delivery.

I am sympathetic to this argument because when we started biventricular pacing we had only clunky tools. Now, BiV pacing is much improved.

My main criticism of PFA remains: it is not a game-changer in AF treatment; it is merely another way to ablate atrial tissue. The main headwind of AF treatment is that we don’t understand the cause(s) of AF.

We don’t know why pulmonary vein isolation works; and we don’t know why it fails. Patients ask how I know where to ablate? This question always makes me smile. Because the true answer is that we do not know. We ablate the same area (PV isolation) in every patient. PFA does not answer any of these questions.

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Finally, I (and my colleagues) could be wrong about PFA. I put the probability of this quite low, but there is a non-zero chance that PFA will be less effective than thermal ablation. One reason for this is that PFA’s cardioselectivity render it less likely to modulate neurologic input to the heart. Thermal ablation often results in ablation of the ganglionic plexi—resulting in a slight increase in resting heart rate. GP ablation associates (weakly) with procedural success.

In sum: I might have been too skeptical of PFA. There is a high probability that it will make current modes of AF ablation easier, and avoidance of a catastrophic but rare complication is a positive.

Future generations of the technology will improve it further. But I still believe real advances in AF treatment will occur in basic science labs not ablation labs. JMM