Abstract Body (Do not enter title and authors here): Background: Pulsed field ablation is a novel non-thermal energy source for pulmonary vein isolation that offers potential procedural and safety advantages over thermal modalities. However, its acute anatomical effects and compatibility with same-session left atrial appendage closure remain insufficiently characterized.

Objective: To evaluate the feasibility, safety, and anatomical response of combining PFA-based PVI with LAAC using the WATCHMAN FLX Pro device in a healthy canine model.

Methods: Nine canines underwent PVI with either PFA (n=6) or radiofrequency ablation (RFA; n=3), followed by LAAC with the WATCHMAN FLX Pro in a single session. Procedural success, tissue remodeling, device compression, and peri-device leaks were assessed using serial transesophageal echocardiography and computed tomography over a 45-day period, with terminal pathological analysis.

Results: All procedures were completed without complications, and LAAC met PASS criteria in all animals. TEE confirmed complete seal at implant and at 45 days in both groups. PFA was associated with greater post-ablation reduction in LAA diameters and significantly higher device compression (23±8% vs. 13±4% by TEE) despite smaller average device sizes. CT demonstrated greater early compression loss in the PFA group, with gradual recovery by Day 45. Two minor peri-device leaks (<5 mm) were identified on CT in the PFA group only. Ridge edema and anatomical remodeling were pronounced acutely in the PFA group but resolved by 45 days. No thrombus, embolic events, or device dislodgement occurred at any point during the study.

Conclusion: In this preclinical study, the combination of PFA and LAAC using the WATCHMAN FLX Pro device was feasible and acutely safe. PFA was associated with greater acute anatomical remodeling compared to RFA, including more pronounced tissue edema and device compression. These changes resolved over time without compromising device seal or position. Small peri-device leaks (<5 mm) were observed on follow-up CT but not TEE imaging in the pulsed field ablation group only. Further studies are warranted to assess the long-term implications of PFA–associated remodeling and its potential impact on device performance.