Conduction system versus biventricular pacing in heart failure with non-left bundle branch block.

INTRODUCTION: The benefits of cardiac resynchronization therapy (CRT) with biventricular pacing (BiV) is significantly lower when applied to heart failure (HF) patients with non-left bundle branch block (LBBB) conduction delay. We investigated clinical outcomes of conduction system pacing (CSP) for CRT in non-LBBB HF. METHODS: Consecutive HF patients with non-LBBB conduction delay undergoing CSP were propensity matched for age, sex, HF-etiology, and atrial fibrillation (AF) in a 1:1 ratio to BiV from a prospective registry of CRT recipients. Echocardiographic response was defined as an increase in left ventricular ejection fraction (LVEF) by ≥10%. The primary outcome was the composite of HF-hospitalizations or all-cause mortality. RESULTS: A total of 96 patients were recruited (mean age 70 ± 11years, 22% female, 68% ischemic HF and 49% AF). Significant reductions in QRS duration and LV dimensions were seen only after CSP, while LVEF improved significantly in both groups (p < 0.05). Echocardiographic response occurred more frequently in CSP than BiV (51% vs. 21%, p < 0.01), with CSP independently associated with four-fold increased odds (adjusted odds ratio 4.08, 95% confidence interval [CI] 1.34-12.41). The primary outcome occurred more frequently in BiV than CSP (69% vs. 27%, p < 0.001), with CSP independently associated with 58% risk reduction (adjusted hazard ratio [AHR] 0.42, 95% CI 0.21-0.84, p = 0.01), driven by reduced all-cause mortality (AHR 0.22, 95% CI 0.07-0.68, p < 0.01), and a trend toward reduced HF-hospitalization (AHR 0.51, 95% CI 0.21-1.21, p = 0.12). CONCLUSIONS: CSP provided greater electrical synchrony, reverse remodeling, improved cardiac function and survival compared to BiV in non-LBBB, and may be the preferred CRT strategy for non-LBBB HF.