March 23, 2026
View Full PaperIn the Search of Noninvasive Methods Delineating Left Bundle Branch Block Amendable With Conduction System Pacing
Key Result
Equivalent dipole trajectories from 12-lead hrECGs differentiated proximal from distal LBBB, with the proximal group achieving greater relative QRS shortening at 6 months (26% vs 14%, p<0.02).
Key Points
- This study aims to evaluate noninvasive methods for identifying patients with left bundle branch block suitable for conduction system pacing.
- Retrospective analysis of 12 lead hrECGs, equivalent dipole trajectories, and echocardiograms.
- Included 18 heart failure patients meeting Strauss criteria for left bundle branch block.
- Patients were randomized to the conduction system pacing arm of the ongoing CSP-Sync study.
- Patients with proximal left bundle branch block showed greater QRS duration shortening (26% vs. 14%, p < 0.02).
- Proximal group had significant reductions in end left ventricle systolic volumes (41.3% vs. 15.8%, p = 0.004).
- Ejection fraction improved more significantly in the proximal group (17.1% vs. 5.5%, p = 0.02).
- ED trajectories from hrECGs were superior in distinguishing patients with proximal or distal LBBB.
Study Design
Type
Cohort (n=18)
Structured PICO
Does equivalent dipole trajectory analysis from 12-lead hrECGs better differentiate proximal from distal LBBB to predict response to conduction system pacing in heart failure patients?
P
Population
Heart failure patients fulfilling Strauss criteria for left bundle branch block (LBBB) and indication for cardiac resynchronization therapy (CRT)
I
Intervention
Equivalent dipole (ED) trajectory analysis from 12-lead high-resolution ECGs
C
Comparator
Standard 12-lead ECG alone
O
Outcome
Differentiation of proximal vs distal LBBB (defined by achievement of left bundle branch capture with shortening of left ventricular activation time)surrogate
Equivalent dipole trajectories from high-resolution ECGs can noninvasively differentiate proximal from distal LBBB, helping to identify heart failure patients most likely to benefit from conduction system pacing.
Main Result
Absolute Event Rate: 26% vs 14%
p-value: p=<0.02
Abstract
ABSTRACT Conduction system pacing (CSP) is an emerging new method of cardiac resynchronization therapy (CRT), however, one third of patients with left bundle branch block (LBBB) have distal conduction disease, which is not amenable to correction with CSP. There is an emerging need for tailored analysis of ventricular depolarization patterns for patient selection for CRT pacing modality. We retrospectively analyzed 12 lead hrECGs, equivalent dipole (ED) trajectories and standard transthoracic echocardiograms of 18 heart failure patients fulfilling Strauss criteria for LBBB and indication for CRT randomized to the CSP arm of the ongoing CSP‐Sync study (NCT05155865). Based on achievement of left bundle branch capture with shortening of left ventricular activation time, 12 patients had proximal LBBB (pLBBB group), and 6 had intact proximal LBBB conduction (dLBBB group) with similar average baseline QRS durations between the groups (179±14 ms in the pLBBB and 165±20 ms in the dLBBB group, p = 0.1). All patients fulfilled the Strauss criteria with no significant difference in the additional criterion (R wave > 0.1 mV in V1; p = 0.7). In the pLBBB group ED trajectory had an initial leftward direction (six vs. zero patients, p = 0.03) with a uniform (12 vs. one patient, p < 0.001) and slower (0.57 ± 0.12 m/s in the pLBBB vs. 0.75 ± 0.15 m/s in the dLBBB group, p = 0.01) velocity. After 6 months the pLBBB group achieved greater relative QRS duration shortening (26% ± 8% vs. 14% ± 9%; p < 0.02) and relative reductions in end left ventricle systolic volumes (41.3% ± 17.6% vs. 15.8% ± 6.1%; p = 0.004) with better improvement in ejection fraction (17.1% ± 11.0% vs. 5.5% ± 1.0%; p = 0.02). The ED trajectories from 12‐lead hrECGs could better differentiate patients with proximal or distal LBBB than standard 12‐lead ECG alone.