Interatrial Synchronized Pacing at the Posterosuperior Bundle: Feasibility, Mechanism, and Mid-Term Outcomes

BACKGROUND: Conventional atrial pacing at the right atrial appendage may impair interatrial synchrony. Posterosuperior bundle (PSB) pacing has been observed to offer anatomic accessibility by targeting the interatrial muscular connection within the superior vena cava. The study aimed to further validate the feasibility of PSB pacing and to observe mid-term outcomes through a retrospective cohort analysis. METHODS: This cohort enrolled 33 consecutive patients with pacing indications. PSB pacing was performed using a pacing lead delivered via a catheter to the medial wall of the superior vena cava, ≈1.5 cm superior to the junction of superior vena cava and right atrium. Electrophysiological and echocardiographic parameters were assessed before the procedure (baseline), acute phase, and at least 3 months after implantation. RESULTS: The mean follow-up period was 7.6±3.6 months, and PSB pacing was successful in all patients (100%), with stable lead fixation and no procedural complications, such as increased atrial capture threshold, atrial lead perforation, or atrial lead dislodgement. P-wave duration significantly shortened from baseline (120±15 ms) to follow-up (104±18 ms; P <0.05), particularly in patients with interatrial conduction delay (indicated by intrinsic P-wave duration ≥120 ms; baseline: 130±10 ms, follow-up: 111±17 ms; P <0.05). Atrial capture threshold (1.0±0.4 V) and sensing amplitudes (2.0±1.4 mV) remained stable. Structural and functional echocardiography showed maintained parameters in this study. Clinical events were minimal (1 heart failure hospitalization, 1 atrial fibrillation recurrence hospitalization, 1 syncope unrelated to pacing). CONCLUSIONS: PSB pacing is a feasible, safe, and effective strategy for atrial pacing. It maintains interatrial electrical synchrony, offers stable pacing parameters, and may provide potential functional benefits, especially in interatrial conduction delay, offering a new option for atrial physiological pacing. Further research is necessary to validate long-term outcomes. REGISTRATION: URL: https://www.clinicaltrials.gov ; Unique identifier: NCT06995027.