Clinical and echocardiographic analysis of patients with heart failure and reduced ejection fraction treated with cardiac resynchronisation therapy versus left bundle branch area pacing

Introduction

Cardiac resynchronisation therapy (CRT) has demonstrated efficacy in heart failure with reduced ejection fraction (HFrEF) since the MIRACLE and MUSTIC studies. Recently, physiological pacing in the left bundle branch (LBB) area has been established as an effective alternative, with comparable outcomes in mortality and hospitalisations, as well as shorter procedure and fluoroscopy times. Based on the experience of our unit, a comparative analysis between CRT and LBB area pacing was conducted with the aim of reproducing the findings reported in the literature and generating local evidence.

Objective

To compare the clinical progression (NYHA) and echocardiographic (LVEF) in patients with heart failure and reduced LVEF treated with CRT versus LBB area pacing (RI), identifying clinical characteristics associated with better response in our population.

Methods

Single-centre, descriptive, observational, retrospective study conducted in a tertiary hospital (2017–August 2025). Patients with heart failure and reduced LVEF treated with CRT or right ventricular area pacing were included. Functional class (NYHA), LVEF, and QRS were analysed before and after the procedure, considering a significant improvement as an increase ≥10% in LVEF and/or improvement in NYHA class.

Results

Of 168 patients (72 LBB pacing, 96 CRT), 140 met criteria. Mean age 58 years; 65% male.

Functional class (NYHA): CRT: Before: NYHA II (54.6%), III (28.9%); After: NYHA I (31.6%), II (50.5%), with a reduction in class III to 14.7% (p < 0.001). LBB pacing: Before: NYHA I (39.7%), II (56.2%); After: NYHA I (54.8%), with no cases in class III (p < 0.001). Both groups showed significant improvement; CRT benefited more advanced dysfunctions, and LBB pacing moderate cases.

QRS: CRT: 169.7 ± 30.9 ms → 126.6 ± 25.8 ms. LBB pacing: 137.9 ± 40.8 ms → 114.6 ± 16.9 ms. Significant reduction in both groups, indicating effective resynchronisation.

LVEF: Baseline LVEF was the most important predictor of post-procedure LVEF (β = 0.824; p < 0.001). There was no significant effect of baseline QRS or NYHA. In multivariate analysis, no differences were found by age, baseline NYHA, or QRS, although a better response was observed in males (p = 0.010).

Procedure times: LBB: 136.6 ± 51.6 min, fluoroscopy 29.9 min, dose 594.8 mGy. TRC: 185.4 ± 60.3 min, fluoroscopy 31.3 min, dose 934.5 mGy. Physiological pacing significantly reduced time and radiation.

Conclusions

Both therapies showed comparable efficacy with significant improvement in functional class, reduction in QRS, and increase in LVEF. Pacing in the LBB area offered technical advantages (less time and radiation) with results no worse than conventional CRT. Although a larger sample size is required to confirm the long-term impact on LVEF, the findings support physiological pacing as an effective and potentially preferable alternative in selected cases, depending on the patient's clinical and etiological profile.Tables and graphs 1Tables and graphs 2