Po-02-184 mapping-guided atrial lead placement determines optimal conduction across bachmann’s bundle: a rationale for patient-tailored pacing therapy

Bachmann’s Bundle (BB) is the main preferential route for interatrial conduction and plays an important role in initiation and perpetuation of atrial tachyarrhythmia such as atrial fibrillation (AF). Conventional right atrial appendage (RAA) pacing is associated with increased atrial activation time resulting in higher incidences of AF. Optimal pacing sites ideally shorten inter-atrial conduction delay thereby decreasing atrial excitation time. However, it remains unknown how pacing from various sites affects conduction at BB. To examine the impact of programmed stimulation from the left- and right atrium on activation and electrophysiological features of BB. High-resolution epicardial mapping of BB was performed during sinus rhythm (SR) and PES in 34 patients undergoing cardiac surgery. PES included a fixed rate sequence of average SR cycle length minus 50 ms provided from the RAA, junction of the RA with inferior caval vein (LRA) and left atrial appendage (LAA). Electrophysiological features included unipolar voltage, conduction velocity, potential type (single, short/long double and fractionated) and conduction delay/block (CDCB). The average cycle length during SR was 967 [874–1,185] ms. Pacing from either RAA or LAA resulted in respectively right- and left-sided conduction across BB. However, during LRA pacing in most patients (n=15) activation started in the center of BB. Compared to SR, the least amount of differences in electrophysiological features was found during pacing from the RAA, followed by pacing from LRA and LAA. Total activation time of BB during RAA pacing (63 [55–78] ms) was similar to SR (61 [52–68] ms, P=0.464), while it decreased during LRA (45 [39–62] ms, P=0.003) and increased during LAA pacing (67 [61–75] ms, P=0.009). Reduction of both conduction disorders and total activation time was most often achieved during LRA pacing (N=13), especially in patients who already had a higher amount of conduction disorders during SR (9.8 [7.3–12.3] vs 4.5 [3.5–6.6]%, P<0.001). Pacing from LRA results in a remarkable decrease of total activation time compared to pacing from the LAA or RAA. As the most optimal pacing site varies between patients, individualized positioning of the atrial pacing lead guided by mapping of BB may be one of the new frontiers for atrial pacing.