Pulsed Field Ablation for Left Posterior Wall in PVI Non-Responders: Initial Outcomes in Patients with Normal Left Atrial Voltage and Suspected Arrhythmogenic Posterior Wall

Background:
In patients with recurrent atrial fibrillation (AF) despite durable pulmonary vein isolation (PVI), the posterior wall (PW) of the left atrium (LA) is a potential ablation target. Durable posterior wall isolation (PWI) using radiofrequency ablation (RFA) poses challenges due to the adjacent esophagus and the potential for gaps in ablation lines. Pulsed field ablation (PFA) has shown promise as a safe and effective alternative. This study presents the first clinical experience using PFA for PW ablation in cryoballoon PVI non-responders with healthy LA and suspected arrhythmogenic PW.

 

Methods:
A prospective, single-center observational feasibility study was conducted in patients undergoing reablation following cryoballoon PVI. Ultra-high-density 3D electro-anatomical mapping (3D-UHD-EAM) was performed (Rhythmia Boston Scientific) and triggers were evaluated using standard stimulation protocols with isoprenaline. Patients were included in case of normal LA-Voltage, durable PVI of most PVs and suspected PW triggers. The PW was ablated using a pentaspline PFA catheter (FARAWAVE 31 mm, Boston Scientific) in its flower configuration, with 4 ablations in 5 or 6 positions, guided by fluoroscopy and ICE. It was allowed to reisolate and/or widen circumferential PV ablations with the same catheter. Repeat 3D-UHD-EAM and pacing confirmed complete PW ablation. The acute efficacy and safety were evaluated.

Results:
Between January and May 2024, 12 patients were included. The median age was 61 years. Eight patients (66.7%) had persistent AF, one patient had additional atrial tachycardia. Five patients (42%) were female. The median CHA2DS2-VASc score was 1, with 3 patients (25%) having arterial hypertension, the median EHRA score was 3. The median number of AF episodes was 9 per year, and the median number of previous ablation procedures was 1.5. One patient showed significant LA substrate, located at the PW after previous incomplete PWI. Eleven patients (92%), showed healthy LA voltage. Durable iPVI of all PVs was found in 8 patients (66.7%), encompassing 39 out of 47 PVs (83%). In 10 out of 12 patients, PFA of all PVs was performed either for reisolation or expanding antral PVI lesions. The mean number of PFA deliveries at the PW per patient was 24 (±4). Additional RFA was performed in 5 out of 12 patients (42%). In 4 of these, RFA was used for cavotricuspid isthmus ablation. In 1 patient, an incomplete anterior line was closed, and in another patient, a focal right atrial tachycardia was ablated. The median procedure time was 2.4 h (IQR 2), the mean fluoroscopy time was 32 min. (±14), the median radiation dose was 471 cGyxcm2 (IQR 1756). No complications occurred during or after the ablation in any of the patients. After a median follow-up of 1 month, 11 patients (92%) were free from recurrences. One patient reported AF recurrence during remote follow-up.

Conclusion:

In this feasibility study, the strategy of ablating the PW in patients with durably isolated PVs, normal LA Voltage and suspected arrhythmogenic PW demonstrated outstanding efficacy, safety and short-term outcomes using the pentaspline PFA catheter. While long-term outcomes and lesion durability remain to be seen, the concept of PFA for PWI presents a promising alternative by circumventing limitations of RFA. Future discussions should focus on the impact of such large-scale ablations on LA function and appropriate patient selection for this strategy.