Hierarchical Physiologic Pacing to Enhance Clinical Outcomes in Conduction System Pacing.

Background: Left bundle branch area pacing (LBBAP) includes left bundle branch pacing (truncal or fascicular) and left ventricular septal pacing (LVSP). Studies show that LBBP provides better outcomes than LVSP in heart failure.

Objective: We classified the lead placement with computed tomographic angiography (CTA) based method (CARA-Metis; CARA Medical Ltd.) into LBBP or LVSP and assessed the effect of pacing-lead location relative to the conduction tree hierarchy and the LV endocardium on clinical outcomes in patients with successful LBBAP.

Methods: Two-center, non-randomized, observational study that included LBBAP patients undergoing CTA. The CTA parameters analyzed: 1) Distance between lead-tip and the anterior position of the floor of the membranous septum (LH) and 2) distance between lead-tip and LV endocardium (LE).

Results: Among 264 patients analyzed, 172 (65%) with interpretable CTAs were included. Pacing lead-tip was categorized as LBBP in 153 (89%) and LVSP in 19 (11%) patients [Median (IQR) values were 27.7 [9.21] mm for LH and 0.80 [2.59] mm for LE]. Shorter LH was associated with greater improvement in left ventricular ejection fraction (LVEF) [each 1 mm shorter LH increased LVEF by 0.25% when adjusted for baseline LVEF (p=0.00637)]. Closer to the LV endocardium (Larger LE), increased LVEF response by 0.63% for each additional 1 mm (p=0.0133) in the entire cohort. Patients with depressed LVEF accrued significantly larger improvement in LVEF (p<0.0001 for both).

Conclusions: Hierarchical physiologic pacing with improved LVEF response is achieved with a closer position of the pacing lead to the His bundle and the LV-endocardium.