3.1 Studies selection and evaluation
In total, 694 articles were retrieved after excluding duplicates. The title and abstract of the articles were screened, and 566 were excluded due to being editorials/review articles, case reports/letters, having no relevant outcome, and not being in English. The remaining 128 articles underwent full-text review, and 120 were excluded for not meeting the inclusion criteria; finally, eight studies25-32 were retrieved (Figure 1 and Table 1).
The eight articles included five single-arm studies, and three comparative studies, published between 2020 and 2022. After pooled analysis, the total population included 211 patients with HF and an LVEF of 35–50%, who underwent LBBAP at one of 16 centers in seven countries. The average age was 65.1 years (n=211; 95% CI: 58.4–71.8), and 52.4% (n= 211; 95% CI: 24.2–80.6) of patients were male. The average baseline QRS duration and LVEF were 153 ms (n=2; 95% CI: 133–172) and 40% (n=207; 95% CI: 38–41), respectively. The average follow-up period was 9.1 ± 3.8 months. Regarding quality assessment, the Newcastle-Ottawa scale criteria was used to evaluate the quality of observational studies (presented in Table 2).