Main findings
A total of 1,604 publications were identified, and 1,225 were screened after excluding duplicates. Twenty full-text articles were assessed for eligibility after 1,205 were excluded with abstract and title screening. After the assessment of full-text articles, 10 publications were excluded for: no LBBP group data separately reported from HBP/CSP group, no human study, published study protocol without data, and no control group with BVP. Ten studies (9 observational studies and 1 randomized controlled trial) were included (Figure 1).
The included studies comprised 616 patients across 15 centers, enrolled from December 2012 to June 2021, with the median being 2019 (Table 1). Patient baseline characteristics were reported in all studies (Table 2).
Left ventricular ejection fraction (LVEF) improvement was reported in all 10 studies. Compared to BVP, LBBP was associated with greater improvement (MD 5.80, 95% CI 4.81-6.78, I2=0%, P<0.01, percentage) at the end of follow-up period. Left ventricular end-diastolic diameter (LVEDD) reduction was also higher in the LBBP group (MD 2.11, 95% CI 0.12-4.10, I2=18%, P=0.04, millimeter). There was a greater improvement in New York Heart Association function (NYHA) class with LBBP (MD 0.37, 95% CI 0.05-0.68, I2=61%, P=0.02). Figure 2.
A composite outcome of heart failure-related hospitalization (HFH) and all-cause mortality was also lower with LBBP compared to BVP CRT [Risk ratio (RR) 0.48, 95% CI 0.25-0.90, I2=0%, p=0.02] driven mainlyby heart failure hospitlizations (HFH) reduction (RR 0.39, 95% CI 0.19-0.82, I2=0%, p=0.01). However, all-cause mortality rates were low in both groups (1.52% vs. 1.13%) and similar (RR 0.98, 95%CI 0.21-4.68, I2=0%, p=0.87). Figure 3.