Programmed stimulation and threshold transition maneuvers in LBBAP: associations with electrical resynchronization and left ventricular functional response

Background

Left bundle branch area pacing (LBBAP) is increasingly adopted as a physiologic pacing strategy. However, the clinical value of conduction system capture verification maneuvers—threshold transition (TT) and programmed stimulation (PST)—remains incompletely defined. Their impact on electrical resynchronization and systolic function has not been systematically evaluated.

Objective

To assess whether conduction system capture verification maneuvers influence electrical resynchronization and left ventricular systolic improvement in patients undergoing LBBAP.

Methods

We retrospectively analyzed patients who underwent LBBAP and classified them into four groups based on capture-verification maneuvers:

TT+/PST+ (TT and/or PST positive),

TT-/PST+,

TT-/PST-,

No maneuvers (neither performed).

If one maneuver was missing, the available result was used and the missing one treated as negative.

Electrical parameters included QRS pre, QRS post, V6RWPT, interpeak RV6–V1, and percentage QRS narrowing (ΔQRS% defined as (QRS pre-QRS post )/ QRS pre %). Systolic function was assessed by EF pre, EF post and ΔEF. Pairwise Wilcoxon tests were used for group comparisons. Median follow-up was 9.5 months.

Results

A total of 131 patients were included: 41 TT+/PST+, 9 TT-/PST+, 53 TT-/PST-, and 28 No maneuvers.

QRS post was significantly narrower in TT+/PST+ vs No maneuvers (p=0.004*) and TT-/PST- vs No maneuvers (p=0.009*).

ΔQRS% was greater in groups undergoing verification maneuvers, with a strong trend for TT+/PST+ vs No maneuvers(p=0.089).

Importantly, TT-/PST+ patients showed electrical resynchronization (QRS_post, ΔQRS%, RV6–V1) comparable to TT+/PST+, despite negative TT.

Interpeak RV6–V1 was significantly shorter in TT+/PST+ vs TT-/PST+ (p=0.045*).

ΔEF did not differ significantly between groups, although maneuver-tested patients showed a numerical trend toward higher improvement compared with No maneuvers.

Conclusions

Capture-verification maneuvers during LBBAP are associated with superior electrical resynchronization, with significantly narrower QRS complexes and more favorable activation patterns.Patients with TT-/PST+ exhibited electrical characteristics comparable to TT+/PST+, supporting PST as a reliable marker of effective conduction system capture even when TT is negative. However, these electrical advantages did not translate into significant short-term differences in systolic function. Further prospective investigation is warranted to determine whether enhanced electrical resynchronization leads to long-term functional benefit.