Selection criteria
To qualify for analysis, studies must include randomized controlled trials, cross-sectional studies, case-control studies, or cohort studies evaluating the outcomes of LBBAP implantation in HFrEF patients. Case reports and case series were excluded from the study. The qualified studies must have statistical outcomes in the form of mean ± standard deviation (SD) or median (interquartile range Q1–Q3) with p-values to determine the level of significance in the statistical hypothesis test. The inclusion of studies was not limited by sample size or ethnicity of the population. Any disagreements concerning study choices were settled through a collaborative discussion between the two investigators. The Newcastle-Ottawa quality assessment scale and the modified Newcastle-Ottawa scale were used to assess the quality of study for case-control studies and the result of interest for cohort and cross-sectional studies (Tables 1–2) [22] . The evaluation was conducted in three domains: four items of study group selection (S), two items of group comparability (C), and three items of exposure and outcome (O). The bias assessment results were displayed as a number, with the S, C, and O domains receiving a maximum of 4, 2, and 3, respectively.