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 bundle (BB) pacing restores the interatrial conduction delay, but its acute hemodynamic impact remains unclear. OBJECTIVE: To characterize atrial activation and immediate hemodynamic effects of BB versus 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 left atrium (LA), left ventricle (LV), right ventricle (RV), 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 three pigs. RESULTS: BB pacing reproduced sinus P-wave duration and morphology (72.6±9.1 vs 73.0±8.6ms), whereas RAA pacing significantly prolonged P-wave duration (106.2±17.5ms; P=0.001). Total atrial activation time was shorter with BB versus RAA pacing (142.8±18.5ms vs 167.2±25.6ms; P=0.006), with disappearance of slow conduction zones seen during RAA pacing. Without AV-synchronization, BB pacing increased mean LV, RV, femoral pressures and LV dP/dT versus RAA pacing and baseline, without raising LA pressure. Under AV-sequential pacing, BB pacing modestly reduced intracardiac pressures relative to RAA pacing while preserving higher LV contractility versus baseline. CONCLUSIONS: 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.