Left bundle branch area pacing improves S-ICD ECG eligibility

Objectives

The subcutaneous implantable cardioverter-defibrillator (S-ICD) represents an effective extravascular alternative to transvenous defibrillators for the prevention of sudden cardiac death, particularly in young patients or those at increased risk of infection. Its efficacy relies on stringent ECG screening, which may be compromised by certain QRS morphologies, especially in the setting of ventricular pacing. Until now, a new pacing indication in S-ICD patients necessitates device explantation in favor of a conventional transvenous system.

We hypothesized that left bundle branch area pacing (LBBAP), by preserving ventricular activation and QRS morphology, could maintain S-ICD eligibility, thereby paving the way for a novel conservative management strategy.

Methods

We conducted a prospective single-center study involving 25 patients who underwent LBBAP implantation between November 2024 and March 2025. Automated S-ICD screening (AST 2.0) was performed before and after implantation. Data included electrophysiological measurements (QRS duration, V6 RWPT, V6–V1 RWPT), pacing parameters (capture threshold, impedance, sensed amplitude) and the number of validated S-ICD vectors. Paired comparisons were made using the Student's t-test for normally distributed data, the Wilcoxon signed-rank test for non-parametric variables, and McNemar’s test for categorical variables.

Results

Mean QRS duration decreased from 116±28.4 ms to 112±11.5 ms (p=0.041) post-LBBAP, and S-ICD eligibility increased from 76% to 100% (p=0.031). The median number of validated S-ICD vectors increased from 5 to 7 (p=0.037). All initially ineligible patients (n=6) became eligible after LBBAP, primarily due to improved R/T ratios and increased R-wave amplitudes.

Conclusion

LBBAP significantly improves ECG compatibility with the S-ICD. This approach might reflect a new conservative management strategy in patients with an S-ICD who subsequently develop a pacing indication, thereby avoiding device explantation. Larger-scale studies are warranted to confirm these findings.S-ICD eligibilityEvolution in S-ICD screening