Conduction system pacing has emerged as a potential alternative to conventional biventricular pacing (BiVP) for delivering cardiac resynchronization therapy (CRT). The recent LEFT-BUNDLE-CRT trial aimed to determine if left-bundle branch area pacing (LBBAP) is non-inferior to BiVP in patients with guideline-based indications for CRT and left-bundle branch block (LBBB).¹

Methodology

The LEFT-BUNDLE-CRT trial was a multi-centre, randomized, investigator-initiated, non-inferiority study conducted in Spain.¹ A total of 176 patients with guideline-based CRT indications and LBBB per Strauss criteria were randomized to receive either LBBAP-CRT (n=92) or BiVP-CRT (n=84).

The primary endpoint was the proportion of patients achieving a positive CRT response at 6 months, defined as either an improved clinical composite score (CCS) or a reduction in left ventricular end-systolic volume (LVESV) of ≥15%. The non-inferiority margin was set at 10%. Secondary endpoints included echocardiographic, clinical, and quality-of-life outcomes over a 12-month follow-up period.

Results

At baseline, patient characteristics were similar between groups, although the LBBAP group had a wider intrinsic QRS duration (median 172 ms vs 165 ms; p=0.04). Crossovers occurred in 26 patients (14.9%).

In the intention-to-treat analysis, the trial did not meet its primary endpoint for non-inferiority. A positive CRT response was achieved in 89.7% of patients in the LBBAP-CRT group compared to 94.6% in the BiVP-CRT group (RR 0.95; 95% CI 0.88–1.02).¹

Regarding secondary outcomes, CCS improved in 68% of LBBAP-CRT patients and 77% of BiVP-CRT patients. A ≥15% reduction in LVESV was observed in 79% and 85% of patients in the LBBAP and BiVP groups, respectively. The rates of adverse events and hospitalisation for heart failure were similar between the two treatment arms.

In Practice

The findings from the LEFT-BUNDLE-CRT trial suggest that while LBBAP achieves a high response rate, it was not shown to be non-inferior to the current standard of BiVP for CRT in this patient population. The study authors concluded, “In CRT candidates with typical LBBB, LBBAP-CRT was not shown to be non-inferior to BiVP-CRT. Both strategies yielded high response rates and similar clinical outcomes.”¹ This indicates that while LBBAP is a viable technique, BiVP remains a robust and effective standard for these patients.

References

1. Cano Ó, Pérez-Roselló V, Di Marco A, et al. Left bundle branch area vs biventricular pacing for cardiac resynchronization therapy: the LEFT-BUNDLE-CRT trial. European Heart Journal. 2026;ehag225. https://doi.org/10.1093/eurheartj/ehag225

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