Vagal responses induced by endocardial left atrial autonomic ganglion stimulation before and after pulmonary vein antrum isolation for atrial fibrillation

BACKGROUND Elimination of vagal inputs into the left atrium (LA) may be necessary for successful catheter ablation of atrial fibrillation (AF). These vagal inputs are clustered in autonomic ganglia (AG) that are close to the pulmonary vein antrum (PVA) borders, but whether standard intracardiac echocardiography (ICE)guided PVA isolation (PVAI) affects these inputs is unknown. OBJECTIVE The purpose of this study was to assess whether standard ICE-guided PVAI affects vagal responses induced by endocardiat AG stimulation in the LA. METHODS Twenty consecutive patients undergoing first-time PVAI (group 1) and 20 consecutive patients undergoing repeat PVAI for AF recurrence (group 2) were enrolled in the study. Before ablation, electrical stimulation (20 Hz, pulse duration 10 ms, voltage range 12-20 V) was performed through an 8-mm-tip ablation catheter. Based on prior data, regions around ail. four PVA borders were carefully mapped and stimulated to localize AG inputs. A positive stimulated vagal response was defined as atrioventricutar (AV) block, asystole, or increase in mean RR interval by > 50%. Locations of positive vagal. responses were recorded wth biplane fluoroscopy and CARTO. All patients then underwent standard ICE-guided PVAI by an operator blinded to the locations of vagal. responses. Stimulation of the AG Locations was then repeated postablation. RESULTS Patients (age 54 +/- 11 years, 30% female, ejection fraction 54% +/- 7%) had a history of paroxysmal (75%) and persistent (25%) AF. In group 1, vagal responses were induced in all 20 patients around a mean of 3.8 +/- 0.4 PVAs per patient. The most common response was asystote (53%), mean RR stowing > 50% (28%), and AV block (20%). PostabLation, vagal responses could no longer be induced in at[ 20 patients. A diminished response was induced (RR stowing < 50%) in 2/20 patients around one PVA each. In group 2, vagal responses were not induced in any of the 20 repeat patients. Stimulation capture postablation was confirmed because transient, nonsustained (< 30 seconds) AF or atria[ flutter was induced in all 40 patients with stimulation, whether vagat responses were induced or not. CONCLUSIONS Standard ICE-guided PVAI eliminates vagal responses induced by AG stimutation. Responses are not seen in patients presenting for repeat PVAI, despite clinical recurrence of AF.