4. Discussion
The clinical importance of cardiac resynchronization in patients with HF
has already been demonstrated.1-3 Indications for CRT
in patients with HFrEF with an LVEF <35% are well
established, whereas those for patients with HFmrEF and an LVEF of
35–50% are less certain.4,5,33 In the PROSPECT
prospective multicenter study, all echocardiograms were analyzed by a
core laboratory; among patients with a NYHA functional Class III–IV
status, and QRS>130 ms, those with a core
laboratory-measured LVEF >35% who underwent CRT
demonstrated significant clinical benefit. Additionally, they exhibited
both clinical and structural benefit from CRT.34,35Meanwhile, among patients with HF and an LVEF <50% who
required pacing due to atrioventricular block, the BLOCK-HF trial showed
that CRT was superior to right ventricular pacing regarding mortality
and HF hospitalization.11 Based on these study
results, guidelines state that HBP or biventricular pacing can be
considered when the ventricular pacing burden exceeds 40% in HFmrEF;
still, the resynchronization strategy for HFrEF has not been clearly
established.36 As the prevalence of HFmrEF increases,
its clinical importance is emerging.37 Although
researches have been reported to demonstrate the feasibility, efficacy,
and safety of LBBAP adaptation to cardiac resynchronization (LOT-CRT,
LBBAP-CRT),17,18 it is necessary to shed light on its
role in the treatment of HFmrEF.