Effects of pulsed field ablation on the parasympathetic nervous system: a mechanistic approach

Abstract Background Pulsed field ablation (PFA) is an emerging technique in atrial fibrillation treatment. During electroporation, asystole episodes of varying lengths have been observed, yet the exact mechanisms remain unknown. Objective This study proposes that asystole occurring during PFA is related to the stimulation of parasympathetic ganglia (GP) located on the left atrial surface. Methods A total of 24 patients with paroxysmal atrial fibrillation were included (67% male, mean age 62.8 ± 11.0 years, BMI: 25.3 ± 5.6). PFA was performed, and the duration of cardiac pauses post-electroporation was measured for each application. To assess the effect on the parasympathetic nervous system, transjugular vagal stimulation (TJVS) was conducted through the right internal jugular before and after the isolation of each pulmonary vein. Results The Right Superior Pulmonary Vein (RSPV) exhibited the most significant reduction in TJVS-induced sinus pauses (RSPV: before 8.41 ± 4.53 sec vs. after 3.27 ± 3.53 sec, p<0.001; RIPV: before 6.76 ± 4.54 sec vs. 6.89 ± 5.07 sec, p=0.90; LSPV: before 6.76 ± 5.25 sec vs. after 6.93 ± 4.29 sec, p=0.61; LIPV: before 7.80 ± 4.06 sec vs. after 7.88 ± 3.84 sec, p=0.91). Post-PFA pauses were longest following LSPV ablation and shortest after RIPV ablation (LSPV: 3.57 ± 2.31 sec; RIPV: 1.62 ± 0.65 sec). Starting with the RSPV led to significantly shorter post-PFA pauses during the ablation of subsequent veins compared to starting with the LSPV (RSPV-first: 1.12 ± 0.24 sec; LSPV-first: 1.86 ± 1.74 sec, p<0.01). Conclusion PFA applications during PVI produce acute damage to the cardiac GPs, as evidenced by the decrease in TJVS-induced sinus and atrioventricular block. PFA-induced pauses are longest during applications on the LSPV, and shorter when prior isolation of the RSPV has been performed, suggesting a vagally-mediated mechanism involving the right superior GP.