Left ventricular functional outcomes in His vs. left bundle branch area pacing: Is lead distance important in LBBAP implantation?

BACKGROUND: Right ventricular pacing (RVP) has been associated with adverse left ventricular (LV) remodeling due to electrical and mechanical dyssynchrony. Conduction system pacing (CSP), including His bundle pacing (HBP) and left bundle branch area pacing (LBBAP), has emerged as a more physiological alternative to preserve ventricular function. However, comparative data between these CSP modalities particularly regarding the influence of lead-to-tricuspid annulus distance (LTTAD) in LBBAP remain limited. OBJECTIVE: To compare LV functional outcomes between HBP and LBBAP, and to assess the impact of LTTAD on LVEF improvement among LBBAP patients. METHODS: This prospective observational study included 51 patients who underwent CSP (28 with HBP and 23 with LBBAP). Echocardiographic parameters, including LVEF and global longitudinal strain (GLS), were measured at baseline and 12 months post-implantation. Subgroup analysis in the LBBAP group evaluated the relationship between LTTAD and LVEF improvement, using a ≥ 5% increase in LVEF as the threshold. RESULTS: Both groups demonstrated significant improvement in LVEF over 12 months, with greater improvement in the LBBAP group (+ 7.69% vs. +3.00%, P = 0.043). GLS improvement was also more pronounced in the LBBAP group (P < 0.001). Subgroup analysis revealed that patients with LTTAD ≥ 21.5 mm experienced improvements in left ventricular (LV) function that were not inferior compared to those with shorter LTTAD. CONCLUSION: Both HBP and LBBAP improve LV function, with LBBAP demonstrating more favorable pacing parameters. Distal lead positioning in LBBAP (LTTAD ≥ 21.5 mm) is not associated with deterioration in ventricular synchrony, supporting its broader use in CSP strategies.