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June 27, 2026EP EuropaceOpen Access

Intraprocedural LBBAP measurements reveal ~90% of HFrEF patients with LBBB maintain residual left-sided native conduction.

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Why the study?

Persistent conduction through a septal fascicle may still be present in many patients with LBBB and HFrEF, prompting assessment of residual conduction heterogeneity within the left bundle branch during CIED implantation.

Population

40 consecutive patients with sinus rhythm, typical LBBB, normal A-V conduction, and HFrEF undergoing LBBAP

Design

Observational study with prospectively collected data

Key result

Intraprocedural measurements during LBBAP revealed that approximately 90% of patients with HFrEF and LBBB maintain some degree of residual left-sided native conduction.

Authors

SPS C PajaAPA M PupazaABA M Bacaliaro

Discussion

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Overview

Supports individualized site selection for fusion CRT in LBBB; leaves open prospective validation of delay patterns on outcomes.

Key Points

  • This study aims to evaluate residual conduction within the left bundle branch in patients with heart failure and left bundle branch block.
  • Observational study of patients with sinus rhythm, normal A-V conduction, and HFrEF undergoing Left Bundle Branch Area Pacing.
  • Collected demographic, clinical, ECG, echocardiographic data, and intraprocedural measurements.
  • Analyzed QRS duration, PR interval, and vital electrical intervals using intracardiac electrograms.
  • 90% of patients showed true incomplete left bundle branch block on surface ECG, while complete LBBB was overestimated.
  • Mean activation delay was longest at RVA (86.48 ms), followed by RVS (58.98 ms) and LVS (12 ms).
  • 90% had longer delays at RVA compared to RVS, indicating residual conduction through the left bundle.

Study Design

Type

Observational (n=40)

Structured PICO

P
Population
40 patients (mean age 65.3 years, 43% female) with HFrEF, typical LBBB, and normal A-V conduction undergoing Left Bundle Branch Area Pacing.
E
Exposure
Intraprocedural measurement of residual conduction heterogeneity within the left bundle branch using unipolar intracardiac electrograms during CIED implantation.
O
Outcome
Residual conduction heterogeneity within the left bundle branch, measured as the interval from QRS onset to local ventricular activation at the right ventricular apex (RVA), RV mid-septum (RVS), or left ventricular septum (LVS).surrogate

Intraprocedural mapping reveals that approximately 90% of patients with HFrEF and typical LBBB maintain some residual left-sided native conduction, suggesting true complete LBBB is often overestimated by surface ECG.

Cite This Study

Paja et al. (2026) conducted an observational in Heart failure with reduced ejection fraction (HFrEF) and left bundle branch block (LBBB) (n=40). Left Bundle Branch Area Pacing (LBBAP) was evaluated on Interval from QRS onset to local ventricular activation at the right ventricular apex (RVA), RV mid-septum (RVS), or left ventricular septum (LVS). Intraprocedural measurements during LBBAP revealed that approximately 90% of patients with HFrEF and LBBB maintain some degree of residual left-sided native conduction.

synapsesocial.com/papers/6a3f97bb125782b61d86594ehttps://doi.org/10.1093/europace/euag105.821
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