P-wave Morphology of Bachmann’s Bundle Pacing Based on Electroanatomical Mapping and Intracardiac Echocardiography

BACKGROUND: Optimal criteria for Bachmann bundle (BB) pacing have not been established with direct anatomical visualization of BB engagement. OBJECTIVE: This study aimed to further characterize the optimal site for BB pacing incorporating local electrogram (EGM) and P-wave morphology. METHODS: This study included 20 patients who underwent a catheter ablation for atrial fibrillation. First, the right atrial BB insertion (BBRA) was identified anatomically by electroanatomical mapping (EAM) and intracardiac echocardiography (ICE). Local EGMs at and surrounding the anatomically defined BB were analyzed using a multipolar planar mapping catheter. Second, pace mapping was performed at five areas around and within the BB, and their P-wave morphologies were analyzed. RESULTS: In all cases, the echocardiographically identified BB was consistent with the BB determined by EAM. Local EGMs at the BBRA vary morphologically. In the P-wave morphology of the BBRA pacing, (1) the 12-lead P-wave axes recapitulated normal sinus rhythm P waves, (2) Inferior P-wave amplitude increased with BB capture relative to the native sinus rhythm P wave, (3) the P-wave duration was >10 ms shorter than that of the SR, and (4) there was no isoelectric interval pacing centrally at the right atrial Bachmann bundle breakout area. If all these four criteria are met, the BB can be predicted with 95% sensitivity and 86% specificity. CONCLUSION: Using a combined definition of the BB using EAM and ICE, paced P wave parameters were identified that can be used to confirm BB capture with high sensitivity and specificity, which could be useful when targeting the BB for permanent atrial pacing.