Biatrial activation patterns and hemodynamics during Bachmann's bundle pacing: Learnings from a porcine model.

BACKGROUND

Right atrial appendage (RAA) pacing impairs atrioventricular (AV) coupling and is associated with atrial fibrillation and adverse outcomes. Bachmann's bundle (BB) pacing restores interatrial conduction delay, but its acute hemodynamic impact remains unclear.

OBJECTIVE

To characterize atrial activation and the immediate hemodynamic effects of BB vs RAA pacing in a porcine model under AV-synchronized and non-synchronized conditions.

METHODS

Six Landrace pigs underwent high-density biatrial electroanatomical mapping and invasive pressure monitoring of the left atrium, left ventricle (LV), right ventricle, and femoral artery. A sequential activation- and pace-mapping workflow was used to identify the BB area. Total atrial activation times and P-wave characteristics were compared during BB and RAA pacing. Hemodynamic responses were assessed during non-AV-synchronized pacing in all pigs and during AV-sequential pacing with His bundle active-fixation lead capture in 3 pigs.

RESULTS

BB pacing reproduced sinus P-wave duration and morphology (72.6 ± 9.1 ms vs 73.0 ± 8.6 ms), whereas RAA pacing significantly prolonged P-wave duration (106.2 ± 17.5 ms; P = .001). Total atrial activation time was shorter with BB vs RAA pacing (142.8 ± 18.5 ms vs 167.2 ± 25.6 ms; P = .006), with the disappearance of slow-conduction zones seen during RAA pacing. Without AV synchronization, BB pacing increased mean LV, right ventricle, and femoral pressures and LV maximal rate of pressure change over time (max dP/dT) vs RAA pacing and baseline, without raising left atrium pressure. Under AV-sequential pacing, BB pacing modestly reduced intracardiac pressures relative to RAA pacing while preserving higher LV contractility vs baseline.

CONCLUSION

In this porcine model, BB pacing shortens atrial activation and confers immediate improved mechanical performance over conventional RAA pacing, supporting BB as a physiological atrial pacing target.