Feasibility and six-month stability of novel posterosuperior bundle pacing for interatrial synchrony using a stylet-driven fixed-helix pacing lead

Background The posterosuperior bundle (PSB) is a conduction pathway located posterior and superior to Bachmann’s bundle (BB), coursing along the interatrial groove near the sinus node region and extending along the superior vena cava (SVC) toward the right atrial wall. A recent case report [1] demonstrated the initial feasibility of targeting the SVC musculature for physiological interatrial pacing using a lumenless Model 3830 lead. This study aimed to further evaluate the acute and six-month feasibility, efficacy, and stability of PSB pacing using a stylet-driven fixed-helix lead. Methods Consecutive patients with standard pacing indications were enrolled. From a left axillary venous approach, a stylet-driven lead (Fineline II EZ 4471) was advanced through a fixed-curve delivery sheath (SSPC 2) to the posteromedial wall of the SVC, approximately 15 mm above the SVC/RA junction. Counterclockwise torque was applied to orient the tip toward the SVC wall. The combined use of the sheath and the stylet provided stable torque control, allowing direct lead tip fixation. PSB capture was confirmed by a narrow P-wave duration (PWD) comparable to the baseline intrinsic rhythm, with adequate sensing amplitude. Final location was verified by ECG, intracardiac electrogram, and post-fixation contrast injections. Atrial sensing amplitude, pacing capture threshold, pacing impedance, and paced PWD were assessed intraprocedurally and at 6-month follow-up. Results Nineteen patients (age 81 ± 8 years, 42% female) were enrolled. PSB pacing was successfully achieved in all patients (100%) without procedural complications. PWD, the key electrophysiological marker, was significantly narrower during PSB pacing (93 ± 13 ms) compared with baseline intrinsic rhythm (106 ± 9 ms, P < 0.001) and remained stable at follow-up (92 ± 10 ms, mean 6.2 ± 0.7 months, P = NS). At follow-up, sensing amplitude improved from 2.1 ± 1.1 mV to 4.4 ± 1.4 mV (P < 0.001), threshold decreased from 0.9 ± 0.5 V to 0.7 ± 0.1 V (P = 0.048), and impedance remained stable (466 ± 115 Ω vs. 453 ± 48 Ω, P = NS), indicating effective lead maturation. No lead dislodgement, perforation, or other pacing-related complications occurred. Conclusion PSB pacing using a stylet-driven fixed-helix lead is a feasible and reliable technique, with high implant success and stable mid-term performance. It produces a narrow, physiological P-wave, suggesting it a viable alternative atrial pacing modality for preserving interatrial synchrony.