Pulsed Field Ablation: Stunning or Just Stunning?

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EP LAB DIGEST. 2023;23(9):6.

Dear Readers,

Pulsed field ablation (PFA) has emerged as a promising new energy source for cardiac ablation. Based on experimental and patient data so far, the hope is that PFA will be a nearly non-thermal energy source that is relatively selective for cardiac tissue allowing for highly efficient ablation, with minimal if any risk of collateral injury to the phrenic nerve or esophagus. Multiple companies are working on various platforms targeting pulmonary vein isolation (PVI) for patients with atrial fibrillation (AF). A few PFA systems are already commercially available in Europe. Several clinical trials have been completed in the United States that will likely lead to FDA approval in the next few months. It is my estimate that first to the US market will likely be the PulseSelect PFA System (Medtronic), then the Farapulse PFA System (Boston Scientific), followed by VariPulse (Biosense Webster, Inc, a Johnson & Johnson company). Medtronic already received CE Mark approval in March 2023 for the Affera Mapping and Ablation System.

Despite the continued enthusiasm for PFA and a positive experience reported thus far, some questions remain. These include the incidence of silent cerebral emboli, creation of coronary vasospasm, and the durability of lesions. Durability has been tested outside the United States in patients who have undergone mandatory remapping after PFA procedures regardless of recurrence. A study by Reddy et al suggested a very high durability with PFA using iterations of the Farapulse system; with successive waveform refinement, durability at 3 months improved from 18% to 100% of patients with all PVs isolated.¹ However, these findings do not apply to every PFA system, as each has its own delivery catheter, pulse recipe, waveform, and recommended number of applications.

The Farapulse system is commercially available in Europe and there are already centers with significant clinical experience. A recent paper² suggested that the durability of PFA is not as high as anticipated in real-world practice. However, the most important feature of this study to note is that remapping was only performed in patients who had clinical recurrences. This experience will inherently detect patients who have PV reconnection. The authors studied 341 patients who underwent PVI using the Farapulse PFA system following a protocol analogous to what is part of the clinical trial protocol in the United States. During the index procedure, PVI was successful in nearly all veins. Recurrence of any atrial arrhythmia after PVI was 17% at 9 months. Half (8.5%) of those patients underwent redo ablation 6 months on average after their first procedure. For comparison, in the STOP AF Post-Approval Trial,³ 20% of patients who underwent cryoballoon PVI for paroxysmal AF had a redo procedure within 3 years. Of all the patients undergoing a repeat procedure in the PFA study, just over half had the procedure for AF, with the remaining having the procedure for atrial flutter or atrial tachycardia. Durable PVI was present at the time of the redo procedure in only 60% to 70% of the veins depending on which PV, for an average rate of durable PVI of 63%. This translated into persistent isolation of all PVs in only 21% of patients.

Although this recently published redo PV mapping trial in patients who had undergone PVI revealed a fairly high recurrence of PV reconnection, it is important to emphasize that these findings are only from patients who had clinical recurrences. On the other hand, it is clear that PFA, at least in one of its iterations, does not result in completely permanent lesions in all patients. This may be somewhat disappointing to fans and developers of PFA, but compared to the very early experiences with radiofrequency ablation and cryoablation, these numbers are relatively impressive. While these PFA systems are being developed for effectiveness, it is also likely there is a rush to be the first to receive approval. Over time, future versions of PFA systems will push the envelope to develop more powerful systems that allow for even greater durability. In addition, with more experience, new techniques, and catheters that allow for better contact, as well as the development of ablation indices as surrogates for lesion creation, durability and patient outcomes will improve considerably. 

Disclosures: Dr Knight has served as a paid consultant to Medtronic and was an investigator in the PULSED AF trial. In addition, he has served as a consultant, speaker, investigator, and/or has received EP fellowship grant support from Abbott, AltaThera, AtriCure, Baylis Medical, Biosense Webster, Biotronik, Boston Scientific, CVRx, Philips, and Sanofi; he has no equity or ownership in any of these companies.

References

1. Reddy VY, Neuzil P, Koruth JS, et al. Pulsed field ablation for pulmonary vein isolation in atrial fibrillation. J Am Coll Cardiol. 2019;74(3):315-326. doi:10.1016/j.jacc.2019.04.021

2. Kueffer T, Stefanova A, Madaffari A. et al. Pulmonary vein isolation durability and lesion regression in patients with recurrent arrhythmia after pulsed-field ablation. J Interv Card Electrophysiol. 2023 July 31. doi:10.1007/s10840-023-01608-7

3. Knight BP, Novak PG, Sangrigoli R, et al; STOP AF PAS Investigators. Long-term outcomes after ablation for paroxysmal atrial fibrillation using the second-generation cryoballoon: final results from STOP AF post-approval study. JACC Clin Electrophysiol. 2019;5(3):306-314. doi:10.1016/j.jacep.2018.11.006