Background: Pulsed-field ablation (PFA) is a novel, non-thermal energy source for catheter ablation of atrial fibrillation (AF). Initial clinical data found high efficacy and safety of PFA-based pulmonary vein isolation (PVI). The exact extent of left atrial (LA) lesion formation and chronic scarring after PFA is unknown. Cardiac magnetic resonance imaging (cMRI) using late gadolinium enhancement (LGE) sequences is an established imaging modality for assessment of cardiac fibrosis and iatrogenic lesions created by catheter ablation. We sought to investigate chronic LA lesion formation using a specific cMRI protocol in patients who underwent PFA-based PVI.

Objective: To assess LA lesion formation 3 months after PFA-based PVI using cMRI.

Methods: Patients undergoing PVI by PFA and patients undergoing PVI by radiofrequency (RF)-based ablation, which served as a control group, were analyzed. No further ablation beyond PVI was conducted in all patients. PFA was conducted with a commercially available catheter system allowing for ablation with a pentaspline catheter. All PFA were guided by 3D mapping to assess acute lesion formation and complete PVI. All patients underwent cMRI 3 months after the ablation procedure using a LGE protocol and sequence processing with a specialized analysis software. Analysis of LA LGE burden (total and per pulmonary vein (PV) area) was conducted. Clinical follow-up was obtained via telephone calls and outpatient clinic visits. Statistical analysis contained comparison of mean values with a students t test and analysis of contingency tables with a Fisher exact test.

Results: Thirteen patients undergoing PFA-based PVI and 15 patients undergoing RF-based ablation were analysed. LV function was normal in all patients, 10 (PFA-based PVI) and 12 (RF PVI) patients suffered from paroxysmal AF. Mean procedure duration was 74.7±12.2 minutes for PFA and 68.7±18.9 minutes for RF ablation. Isolation of all PVs was achieved in 100% of patients. MRI at 3 months post ablation demonstrated a significantly different mean amount of the LA with LGE of 6.5±4.0% in PFA patients as compared to a mean of 9.3±1.9% in RF ablation patients (p=0.033). The amount of right and left PV area LGE was significantly smaller in PFA patients as compared to RF-based PVI patients (9.9±6.1% vs. 24.9±7.3% for amount of right PV area, p<0.001 and 20.1±12.2% vs. 32.5±6.7% for amount of left PV area, p=0.004). Arrhythmia recurrence occurred in 1/13 patients (7.8%) who underwent PFA-based PVI and in 1/15 patients (6.7%) who underwent RF-based  PVI after a mean follow-up of 202±74 days (p=1.0).

Conclusion: PFA-based PVI results in less amount of LA areas with LGE as compared to PVI by RF-based ablation, indicating less chronic scar tissue formation by PFA. The underlying causes of the less pronounced scar formation after PFA, its clinical impact and potential optimization in imaging techniques for improved visualization have to be clarified in further studies.