Background and Aims: Left bundle branch area pacing (LBBAP) promotes physiological synchronous activation of the left ventricle and may be particularly beneficial in patients with atrioventricular block (AVB), but its mortality benefit remains unclear. This study aims to compare long-term survival in AVB patients receiving either LBBAP or right ventricular pacing (RVP) and to analyse predictors of mortality during LBBAP. Methods: MELOS RELOADED, a multicentre European collaboration, was a registry-based study of pacemaker patients with AVB, left ventricular ejection fraction (LVEF) >40% and ventricular pacing >20%. The primary outcome was all-cause mortality based on national registries. A 1:1 propensity score matching was performed between the RVP and LBBAP groups. Kaplan–Meier curves and multivariable Cox proportional hazards models were used to estimate survival. Results: In total, 3382 patients receiving LBBAP or RVP were matched. At 4-year follow-up, the Kaplan–Meier curve showed an absolute difference in survival of 11.8% in favour of LBBAP (P < .001). LBBAP was a robust predictor of reduced mortality with a hazard ratio (HR) of 0.53 (95% confidence interval 0.42–0.65, P < .001). Within the LBBAP group, the following independent predictors of increased mortality were identified: lack of confirmed left bundle branch capture (HR 1.85, P < .001), lower percentage of ventricular pacing (HR 1.12), and age. Conclusions: This is the first large study demonstrating the long-term survival benefit of LBBAP. This strengthens the use of LBBAP in AVB patients with preserved/mildly reduced LVEF while awaiting the results of randomized trials. Confirmation of left bundle branch capture seems advisable to achieve optimal results with LBBAP.

Conduction system pacing (CSP) modalities, including His-bundle pacing (HBP) and left bundle branch pacing (LBBP), are increasingly used as alternatives to biventricular (BiV) pacing in heart failure (HF) patients scheduled for pace and ablate strategy. The aim of the study was to compare clinical outcomes of HF patients with refractory AF who received either BiV pacing or CSP in conjunction with atrio-ventricular node ablation (AVNA). Fifty consecutive patients (male 48%, age 70 years (IQR 9), left ventricular ejection fraction (LVEF) 39% (IQR 12)) were retrospectively analysed. Thirteen patients (26%) received BiV pacing, 27 patients (54%) HBP and 10 patients (20%) LBBP. All groups had similar baseline characteristics and acute success rate. While New York Heart. Association (NYHA) class improved in both HBP (p < 0.001) and LBBP (p = 0.008), it did not improve in BiV group (p = 0.096). At follow-up, LVEF increased in HBP (form 39% (IQR 15) to 49% (IQR 16), p < 0.001) and LBBP (from 28% (IQR 13) to 40% (IQR 13), p = 0.041), but did not change in BiV group (p = 0.916). Conduction system pacing modalities showed superior symptomatic and echocardiographic improvement compared to BiV pacing after AVNA. With more stable pacing parameters, LBBP could present a more feasible pacing option compared to HBP.

Background: There are limited prospective randomized studies comparing left bundle branch area pacing (LBBAP) and biventricular (BiV) pacing for cardiac resynchronization therapy (CRT). Aim: The study tested whether LBBAP is noninferior to BiV pacing in patients with Class I indication for CRT. Methods: The CSP-SYNC study is an investigator-initiated, randomized, single-center study. Sixty-two patients were randomized 1:1 to LBBAP or BiV. The primary study endpoint was change in left ventricular ejection fraction (LVEF) at 6 months. Secondary endpoints included changes in echo and clinical parameters after 6 months and 12 months. Results: Thirty-one patients were randomized to each arm. Most patients were males (71%), and 32 % had ischemic cardiomyopathy. At 6 months, similar improvement of LVEF was observed in the LBBAP group compared to the BiV group (14.0% (95% CI: 11.2-16.8) in LBBAP vs. 8.5% (95% CI: 5.6-11.2) in BiV) with mean intergroup difference of 5.6% (95% CI: 1.6-9.5; P<0.001 for noninferiority). Both groups showed comparable decrease in LVESV (-64 ml (95% CI: -78 to -50) vs -40 ml (95% CI: -54 to -25) respectively, mean difference -24 ml (CI 95%: -44 to -4); P<0.001 for noninferiority), changes in 6-minute walk test (P<0.001 for noninferiority) and NYHA class (P=0.011 for noninferiority). Temporal trends of LV remodelling and heart failure hospitalization rates were also comparable. Conclusions: In patients with a Class I indication for CRT, LBBAP was noninferior to BiV pacing in improving LVEF and provided similar structural and electrical remodelling.

Background: His bundle pacing (HBP) is a physiological alternative to biventricular (BiV) pacing. We compared short-term results of both pacing approaches in symptomatic atrial fibrillation (AF) patients with moderately reduced left ventricular (LV) ejection fraction (EF ≥35% and <50%) and narrow QRS (≤120 ms) who underwent atrioventricular node ablation (AVNA). Methods: Thirty consecutive AF patients who received BiV pacing or HBP in conjunction with AVNA between May 2015 and January 2020 were retrospectively assessed. Electrocardiographic, echocardiographic, and clinical data at baseline and 6 months after the procedure were assessed. Results: Twenty-four patients (age 68.8 ± 6.5 years, 50% female, EF 39.6 ± 4%, QRS 95 ± 10 ms) met the inclusion criteria, 12 received BiV pacing and 12 HBP. Both groups had similar acute procedure-related success and complication rates. HBP was superior to BiV pacing in terms of post-implant QRS duration, implantation fluoroscopy times, reduction of indexed LV volumes (EDVi 63.8 (49.6–81) mL/m² vs. 79.9 (66–100) mL/m², p = 0.055; ESVi 32.7 (25.6–42.6) mL/m² vs. 46.4 (42.9–68.1) mL/m², p = 0.009) and increase in LVEF (46 (41–55) % vs. 38 (35–42) %, p = 0.005). However, the improvement of the NYHA class was similar in both groups. Conclusions: In symptomatic AF patients with moderately reduced EF and narrow QRS undergoing AVNA, HBP could be a conceivable alternative to BiV pacing. Further prospective studies are warranted to address the outcomes between both ‘ablate and pace’ strategies.