3.3 Changes in QRS duration and left ventricular systolic function
Five studies presented both the baseline and follow-up QRS durations, with means and standard deviations. Pooled analysis with a random effects model showed that LBBAP was related with a significantly reduced QRS duration (MD: -34.51 ms, 95% CI: -60.00– -9.02; P<0.01,I2 =92%; Figure 2A); the duration decreased from 152.6 ± 21.8 ms (n=42, 95% CI: 133.48–171.62 ms) at baseline, to 119.3 ± 10.9 ms (n=42, 95% CI: 109.75–128.85 ms) after LBBAP.
Seven studies presented both preimplant and postimplant LVEF values, with means and standard deviations (Table 3). The average LVEF among the seven studies was 39.8% ± 1.8% at baseline (n=207), and 50.5% ± 3.9% at follow-up (n=132). During the average follow-up of 9.1 ± 3.8 months, LVEF significantly improved (MD: 10.90%, 95% CI: 6.56–15.23; P<0.01, I2 =87%; Figure 2B). Five studies included patients with HF with reduced ejection fraction (HFrEF). When HFrEF and HFmrEF were compared, the estimated increase was 59.3% for HFrEF ([average LVEF] baseline, 28.1 ± 1.1%; follow-up, 45.6 ± 7.9%) and 27.6% for HFmrEF ([average LVEF] baseline, 39.8 ± 1.8%; follow-up, 50.5% ± 3.9%; Figure 3). Only one study compared LVEF changes in HFmrEF and HF with preserved ejection fraction; the estimated increase was 19.4% for HFmrEF (40.3 ± 5.2 to 48.1 ± 9.5; P=0.002) and 3.9% for HF with preserved ejection fraction (59.1 ± 4.2 to 61.4 ± 4.3; P=0.009).