Bachmann Bundle Pacing and Acute Changes in Left Atrial Mechanical Function in Patients With Interatrial Block: A Within‐Subject Echocardiography Analysis

BACKGROUND: Interatrial block (IAB) is associated with atrial electromechanical dysfunction and adverse cardiovascular outcomes. Bachmann bundle pacing (BBP) has emerged as a physiological atrial pacing strategy capable of restoring interatrial conduction synchrony. However, its impact on left atrial (LA) mechanical function and hemodynamics remains unclear. OBJECTIVE: To evaluate the acute effects of BBP on atrial mechanical parameters in patients with IAB. METHODS: In this prospective single-center study, 31 patients with IAB who underwent successful BBP implantation were enrolled. A standardized postoperative evaluation protocol was performed under intrinsic sinus rhythm (SR), right atrial septal pacing (RASP) at atrial lead threshold +0.5 V/0.4 ms, and BBP at 5 V/0.4 ms using a within-subject repeated-measures design. Electrocardiographic and echocardiographic parameters were analyzed using linear mixed-effects models, with additional adjustment for heart rate. RESULTS: BBP produced significantly greater P wave duration (PWD) shortening than RASP (p < 0.001). Compared with SR, BBP was associated with lower LA volume indices and higher LA emptying fraction and LA expansion index (all p < 0.001), with consistent superiority over RASP at acute postoperative phase. These associations remained significant after heart rate adjustment. The observed acute changes were consistent across partial and advanced IAB subgroups without significant interaction effects. CONCLUSIONS: In patients with IAB, electrical resynchronization during BBP was accompanied by acute changes in LA mechanical parameters compared with SR and RASP. These findings suggest that BBP may represent a promising physiological pacing strategy for patients with atrial conduction disease.