4.2 LBBAP as a resynchronization strategy for HFmrEF
In this meta-analysis, during the average follow-up of 9.1 ± 3.8 months, the mean decrease in QRS duration after LBBAP in patients with HFmrEF was -34.51 ms (95% CI: -60.00– -9.02; P<0.01). The mean LVEF increase was 10.9% (95% CI: 6.56–15.23, P<0.01), and the NYHA functional status improvement was -0.8 (only one article, P<0.01). This suggests that LBBAP is clinically beneficial for resynchronization therapy in the treatment of HFmrEF.
Interestingly, both HFrEF and HFmrEF exhibited significant improvements in LVEF after LBBAP. The LVEF attainment was 45.6% ± 7.9% for HFrEF and 50.5% ± 3.9% for HFmrEF, suggesting that intervention with more advanced cardiac remodeling before the LVEF reaches <35% may be more beneficial.
Current findings reveal that about 30% of patients for whom CRT is indicated are nonresponders.3,39,40 Moreover, among several studies that evaluated the effect of CRT in midrange HF with an LVEF >35%, CRT did not significantly increase the LVEF or clinical composite score.34,41 Among these studies, it is encouraging that the resynchronization strategy applied with conduction system pacing—especially LBBAP, which overcomes some of the limitations of HBP—showed significant improvement in LVEF in patients with HFmrEF.