Strain-based evaluation of septal function after left bundle branch area pacing

Left bundle branch area pacing (LBBAP) requires deep lead implantation within the septum to engage the left-sided conduction system. Although LBBAP is effective, its impact on septal contractility remains uncertain.

The purpose of this study was to evaluate the effect of deep septal lead deployment on septal contraction and activation sequence during LBBAP.

A total of 84 adult patients who underwent successful LBBAP were prospectively analyzed using strain imaging preimplantation and, at latest follow-up, during intrinsic rhythm and VVI pacing. Global longitudinal strain, peak septal strain (PSS), and mid-septal strain curves were assessed.

After 37 ± 14 months of follow-up, patients with normal baseline septal function exhibited no significant change in intrinsic PSS after implantation (preimplantation: -17.8 ± 5.6; postimplantation: -19.2 ± 4.5; P > .05). In contrast, patients with reduced baseline PSS (<-16) demonstrated a significant improvement after implantation (from -12.7 ± 4.1 to -14.8 ± 4.6; P < .001). No significant differences were observed between septal segments with and without lead placement. During VVI pacing, 4 distinct septal contraction patterns were identified: pattern I (29%), pattern II (39%), pattern III (14%), and pattern IV (18%). Higher pattern scores correlated with progressively reduced ventricular function and more discoordinated septal activation sequence. Among clinical and electrical variables, only the absence of a terminal R' wave in lead V₁ significantly predicted discoordinated septal contraction patterns (P < .001).

Deep septal lead placement does not impair septal contractility at mid-term follow-up in the majority of patients. Most patients retain normal contraction patterns (patterns I and II) postimplantation. However, the absence of an R' wave in lead V₁ is linked to abnormal septal contraction and may influence LBBAP outcomes.