Benefit of right inferior pacing on conduction across Bachmanns Bundle
Authors: Van Schie M S , Ramdat Misier N L , Taverne Y J H J , Heida A , Bogers A J J C , De Groot N M S 
Published: October 2022

Abstract

Background
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). Especially in patients with inter- and intra-atrial conduction disorders, the conventional site for placement of right atrial (RA) pacing lead in the RA appendage (RAA) has been questioned as it results in a higher incidence of AF. However, it remains unknown how pacing from various sites affects conduction at BB.

Purpose
To examine the impact of programmed stimulation from the left and right atrium on activation and electrophysiological features of BB.

Methods
Intra-operative high-resolution epicardial mapping of BB was performed during sinus rhythm (SR) and programmed stimulation in 32 patients (29 male, 65±10 years). Programmed stimulation 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 (RAinf) 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).

Results
The average cycle length during SR was 962 [869–1085] ms. Pacing from RAA resulted in comparable activation patterns as during SR. As expected, pacing from LAA resulted in left-to-right conduction across BB. However, during pacing from RAinf in most patients activation started in the centre of BB. Compared to SR, the least amount of differences in electrophysiological features was found during pacing from the RAA, followed by pacing from RAinf and LAA. Unipolar voltages, conduction velocity and potential type distribution were similar. However, during pacing from RAinf, total activation time decreased compared to SR (44 [38–62] ms vs 60 [51–67] ms, P=0.012), while total activation time increased by pacing from LAA (66 [60–72] ms, P=0.020). The total activation time during pacing from RAinf was lower compared to LAA (P&lt;0.001) and RAA pacing (P=0.001). During pacing from LAA, the amount of CDCB increased compared to SR (6.6 [4.1–9.9] % vs 8.7 [5.6–12.8] %, P=0.009), while there were no differences in CDCB between SR and pacing from both RAA and RAinf. Reduction of CDCB was most often achieved during pacing from RAinf (12 patients), especially in patients who already had a higher amount of CDCB during SR (8.0 [7.3–11.2] % vs 4.3 [3.0–5.9] %, P&lt;0.001). Reduction of both CDCB and total activation time was achieved in 10 patients by pacing from RAinf, while only 6 patients benefitted from RAA pacing. These patients had similar amount of conduction disorders.

Conclusions
Pacing from the inferior RA results in a remarkable decrease of total activation time and conduction disorders compared to pacing from the LAA or RAA. As specific patients may benefit more from inferior RA pacing, locations for pacing lead placement should be individualized.

Funding Acknowledgement
Type of funding sources: None.