# Phrenic nerve palsy and pulsed field ablation procedures for atrial fibrillation

Frederic Franceschi, Linda Koutbi, Baptiste Maille

► To cite this version:

Frederic Franceschi, Linda Koutbi, Baptiste Maille. Phrenic nerve palsy and pulsed field ablation procedures for atrial fibrillation. 2024, 10.1093/europace/euae202. hal-04973825

HAL Id: hal-04973825

https://amu.hal.science/hal-04973825v1

Submitted on 3 Mar 2025

HAL is a multi-disciplinary open access
archive for the deposit and dissemination of sci-
entific research documents, whether they are pub-
lished or not. The documents may come from
teaching and research institutions in France or
abroad, or from public or private research centers.

L'archive ouverte pluridisciplinaire HAL, est
destinée au dépôt et à la diffusion de documents
scientifiques de niveau recherche, publiés ou non,
émanant des établissements d'enseignement et de
recherche français ou étrangers, des laboratoires
publics ou privés.

<figure><img src="image_1.png" /></figure>

Distributed under a Creative Commons Attribution 4.0 International License
LETTER TO THE EDITOR

https://doi.org/10.1093/europace/euae202

Published online 9 August 2024

# Phrenic nerve palsy and pulsed field ablation procedures for atrial fibrillation

**Keywords** Pulsed field ablation • Phrenic nerve palsy • Compound motor action potential • Farapulse • Atrial fibrillation • Ablation • Complication

We read with great interest the study by Ollitrault et al.¹ Beyond the small sample size, it seems to present several limitations concerning the occurrence of phrenic nerve palsy (PNP).

Firstly, phrenic nerve (PN) stimulation is performed using a pentaspline pulsed field ablation (PFA) catheter. The method is not detailed (stimulation level, amplitude and pulse width, etc.). This is an unusual approach, as this therapeutic catheter is not designed for stimulation. The risk, as highlighted in our recently published case report,² is to stimulate the nerve below the level of conduction block and thus underestimate the incidence of PNP.

Secondly, no compound motor action potential (CMAP) values were reported in the study. The authors defined PN stunning as a drop in CMAP amplitude > 30% after application of PFA. This threshold is arbitrary. Incomplete CMAP recovery is probably not trivial, as CMAP amplitude reflects the number of diaphragmatic fibres that depolarize. For example, is the fact that 25% of fibres no longer depolarize after PFA a fact that should not be taken into account? What are the long-term consequences? To date, no one can answer these questions.

Thirdly, chest X-rays were performed in only 20 patients. This figure is far too low. We also know that chest X-rays can be falsely reassuring³ and that dynamic tests such as ultrasound or fluoroscopic sniff test should be preferred.

In addition, a case of delayed permanent PNP has already been reported with PFA.⁴ Several cases of delayed diaphragmatic paralysis have been reported in the literature, outside the field of atrial fibrillation (AF) ablation.⁵,⁶ The mechanism remains unclear, but as patients with PNP are asymptomatic in 90% of cases, delayed forms may be difficult to diagnose. Relying solely on what happens at the time of the procedure could be falsely reassuring.

Finally, pentaspline applications in the superior vena cava are parallel to the PN, unlike applications in the right pulmonary veins, which are perpendicular to the nerve. Assuming a traumatic mechanism, perpendicular applications should be more deleterious.

Under these conditions, no conclusion can be drawn from this study¹ as to the incidence of PNP in pulmonary veins isolation with PFA.

Nothing is known about the intimate phenomenon that leads to PNP during PFA procedures; nevertheless, several mechanisms could be involved. The first is probably purely electrical and could explain the transient phenomena. The second could be traumatic, with axonal degeneration below the level of trauma, and explain the persistent phenomena. Phrenic nerve palsy is a complication of AF ablation procedures,⁷ and it is undoubtedly also a complication of PFA. Its incidence was 1.3% in the ADVENT study,⁸,⁹ where 3 patients (1%) recovered only at the end of the follow-up at 1 year. This incidence has been reported in the absence of specific PN monitoring. On the other hand, in the MANIFEST 17K study,¹⁰ no persistent PNP was reported. However, the quality of data from this type of retrospective registry is probably much lower than that of a randomized trial such as ADVENT. Other studies have reported similar reassuring results regarding the incidence of diaphragmatic paralysis.¹¹⁻¹⁴ All these data have the same limitations: these are mainly retrospective observational studies where diaphragmatic monitoring is never performed. The true incidence

of PNP in PFA procedures is therefore unknown, as systematic diaphragm monitoring has never been performed in a large-scale cohort study.

We believe it is imperative to remain vigilant and plan prospective trials targeted to appropriately detect persistent PNP, in order to assess its precise occurrence as a complication of PFA.

**Conflict of interest:** F.F. is a consultant for the company Circle-Safe. L.K. and B.M. have no conflict of interest.

## References

1. Ollitrault P, Chaumont C, Font J, Manninger M, Conti S, Patusik PT et al. Superior vena cava isolation using a pentaspline pulsed-field ablation catheter: feasibility and safety in patients undergoing atrial fibrillation catheter ablation. *Europace* 2024;26:euae160.

2. Franceschi F, Koutbi L, Maille B, Deharo JC. First electromyographic monitoring of a progressive phrenic nerve palsy in a pulsed field ablation procedure. *Heart Rhythm Case Rep* 2024;10:447–50.

3. Katsume Y, Miwa Y, Ueda A, Soejima K. Underdiagnosis of phrenic nerve palsy caused by cryoballoon ablation for atrial fibrillation with upright position chest radiography: usefulness of supine position dynamic chest radiography. *Europace* 2021;23:1567.

4. Turagam MK, Neuzil P, Schmidt B, Reichlin T, Neven K, Metzner A et al. Safety and effectiveness of pulsed field ablation to treat atrial fibrillation: one-year outcomes from the MANIFEST-PF registry. *Circulation* 2023;148:35–46.

5. Mir S, Serdaroglu E. An elevated hemidiaphragm 3 months after internal jugular vein hemodialysis catheter placement. *Semin Dial* 2003;16:281–3.

6. So Yeon K, Jong Sung P. Delayed onset transient diaphragmatic paralysis after pace-maker implantation. *Int J Arrhythm* 2016;17:108–11.

7. Heeger CH, Sohns C, Pott A, Metzner A, Inaba O, Straube F et al. Phrenic nerve injury during cryoballoon-based pulmonary vein isolation: results of the worldwide YETI registry. *Circ Arrhythm Electrophysiol* 2022;15:e010516.

8. Reddy VY, Gerstenfeld EP, Natale A, Whang W, Cuoco F, Patel C et al. Pulsed field or conventional thermal ablation for paroxysmal atrial fibrillation. *N Engl J Med* 2023;389:1660–71.

9. Franceschi F, Maille B. Pulsed field ablation for paroxysmal atrial fibrillation. *N Engl J Med* 2024;390:1054–5.

10. Ekanem E, Neuzil P, Reichlin T, Kautzner J, Van Der Voot P, Jais P. Safety of pulsed field ablation in more than 17,000 patients with atrial fibrillation in the MANIFEST-17 K study. *Nat Med* 2024;30:2020–9.

11. Zhang H, Zhang H, Lu H, Mao Y, Chen J. Meta-analysis of pulsed-field ablation versus cryoablation for atrial fibrillation. *Pacing Clin Electrophysiol* 2024;47:603–13.

12. Van De Kar MRD, Slingerland SR, van Steenbergen GJ, Brouwer T, Schulz DN, van Veghel D et al. Pulsed field versus cryoballoon ablation for atrial fibrillation: a real-world observational study on procedural outcomes and efficacy. *Neth Heart J* 2024;32:167–72.

13. Metzner A, Fiala M, Vijgen J, Ouss A, Gunawardene M, Hansen J et al. Long-term outcomes of the pentaspline pulsed-field ablation catheter for the treatment of paroxysmal atrial fibrillation: results of the prospective, multicentre FARA-Freedom Study. *Europace* 2024;26:euae053.

14. Badertscher P, Weidlich S, Knecht S, Stauffer N, Krisai P, Voellmin G et al. Efficacy and safety of pulmonary vein isolation with pulsed field ablation vs. novel cryoballoon ablation system for atrial fibrillation. *Europace* 2023;25:euad329.

Frederic Franceschi ID ¹,²,³*, Linda Koutbi ID ¹,², and Baptiste Maille ID ¹,²,³

¹Department of Cardiology, CHU Timone, 264 Rue Saint Pierre, 13005 Marseille, France; ²Department of Cardiology, Aix-Marseille University, 58 Boulevard Charles Livon, 13284 Marseille, France; and ³Center for CardioVascular and Nutrition Research (C2VN), INSERM, INRA, 27 Boulevard Jean Moulin, 13005 Marseille, France

*Corresponding author. Tel: +33675541346, E-mail address: frederic.franceschi@ap-hm.fr