Left bundle brunch pacing versus conventional right ventricular pacing in patients with bradycardia and conduction system disorders: a systematic review and meta-analysis

Funding Acknowledgements Type of funding sources: None. Background Right Ventricular Pacing (RVP) is well established as the widely accepted pacing method. However, its effects in ventricular function can be detrimental, causing electrical and mechanical dysynchrony and potential LVEF impairment. Left Bundle Branch Pacing (LBBP) is a new pacing strategy that appears to have better results preserving left ventricular function, by directly engaging the intrinsic conduction pathway of the heart. Purpose The aim of this systematic review and meta-analysis is to compare the safety and efficacy of the two pacing methods (LBBP and RVP) in patients suffering from bradyarrhythmia and conduction system disorders. Methods Medline, Embase and Pubmed databases were searched for studies comparing LBBP with RVP. Outcomes were QRSd (QRS duration), ventricular mechanical synchrony, LVEF changes, and Heart Failure Hospitalizations (HFH) to assess the efficacy, lead properties and complications to assess the safety. Two independent reviewers identified studies, extracted data, and assessed the risk of bias using the Cochrane Risk of Bias 2 tool for randomized clinical trials and the Newcastle-Ottawa-Scale for observational studies. Pairwise meta-analysis was conducted using random and fixed effects models. Risk Ratios (RRs) and weighted and standard mean difference (WMD, SMD) with 95% confidence intervals (CIs) were used to report dichotomous and continuous variables respectively. Heterogeneity was assessed with the I² statistic. Results 1318 articles were identified, and finally 25 trials with 4250 patients (2127 LBBP and 2123 RVP) were included in the analysis. Pooled analyses verified that QRSd is shorter in LBBP group both at implantation (WMD:-32.32, CI 95%:-35.18 to -29.45; I²=88%; P<.001) and at Follow Up (WMD: -32.20, CI 95%: -40.70 to -23.71; I²=92%; P<.001) and LBBP succeeded better interventricular mechanical synchrony (SMD:-2.04, CI 95%:-2.32 to -1.76; I²=21%; P<.001) than RVP. Intraventricular mechanical synchrony was also significantly better in LBBP vs RVP independently of the way of measurement in each study (SMD:-1.77, CI 95%:-2.45 to -1.09; I²=90%; P<.001) and in the subgroup analysis of the studies that implemented the same way of measurement (P<.001; I²=26%). LVEF alteration was not significant in the LBBP compared to native (P=.68; I²=52%), while in the RVP group showed a significant reduction (P<.001; I²=51%). LBBP showed, significantly better results in HFH (P<.001; I²=0%) and achieved similar pacing thresholds (P=.86) and higher R wave amplitudes (P<.05) than RVP while lead related complications had no difference between the two groups (LBBP=1.90% vs RVP=1.72%; P=0.71). Conclusions To our knowledge this is the first meta-analysis that assess the safety and efficacy of LBBP in such an important number of patients. LBBP preserves ventricular electrical and mechanical synchrony, shows a reduction in HFH compared to RVP and has excellent pacing parameters, without compromising safety.