4 DISCUSSION
The value of this meta-analysis on LBBAP is that it included almost all
types of patients with pacing indications, and self control study showed
that LBBAP had a good therapeutic effect. Our meta-analysis demonstrated
that: (1) LBBAP produces a favorable QRS
duration, not only stabilizing
patients with a normal QRS duration, but also significantly shortening
the prolonged QRS duration; (2)In patients receiving LBBAP, there are
the following changes in pacemaker parameters after a period of
follow-up: a. the stable capture threshold for a long time; b.a
positive trend in R-wave amplitude; c. a negative trend in pacing
impedance; (3) In the included
studies, the average success rate of LBBAP was high, the overall safety
of the procedure was reliable, and there were no specific complications
of pacemaker surgery.
It has been confirmed that RV apical
pacing was associated with high incidence of heart failure, AF, and
mortality due to its abnormal activation propagation and obvious LV
contraction delay23-24.Other pacing sites just like
the septum or outflow tract did not show obvious results in improving
clinical outcomes25-26.Up to now, His-bundle pacing
was considered as the physiological pacing method. However, challenges
with His bundle pacing including difficulty in identifying the location
of the His bundle, a relative high capture threshold with potential
long-term instability, especially in patients who already have cardiac
conduction disease such as LBBB, which withheld the widespread
application of this pacing6,27.
. Pacing the LBB that directly capture the left bundle
branch by deep septal pacing was first introduced by Huang in
20178, which is
likely to fill many of the deficits of HBP.The left bundle branch is
flat banded and fan-shaped in the subendocardium, with a wider
distribution than His bundle and fewer fiber
wrapping28,29. For the LBBAP procedure, the anatomic
characteristics of the LBB provide a relatively large area for the
selection of a pacing site. Lead fixation could be more easily achieved
by screwing the lead into the ventricular septum. Baseline bundle branch
block might be more likely corrected by LBBAP beyond the site of
block8,17.
The sequence of ventricular
excitation and ventricular systolic synchrony are two important factors
affecting postoperative cardiac function. The coherence and similarity
of the QRS morphology between intrinsic QRS and paced QRS can indirectly
reflect the difference of the sequence of downward transmission and
ventricular excitation. So the QRS duration is an important indicator of
the synchronization of the contractions of both ventricles, which
affects the risk of death and heart failure in patients after pacing
surgery30-32. LBBAP proved its effectiveness both in
maintaining a normal QRS duration and in generating narrower QRS
duration in our study. The rich myocardial tissue surrounding the
electrodes guarantee the characteristic of higher R-wave amplitude with
a lower threshold for LBBAP, which was also confirmed in our study.
These stable pacing parameters indicated that some sensing or threshold
issues that are common in HBP or RVP might be avoided in LBBAP.
In our included study, LBBAP was shown to be effective in the treatment
of slow arrhythmias such as AVB and SND. In particular, in patients with
HBP failure or CRT indications, LBBAP can maintain better electrical and
mechanical synchronization, and its efficacy and safety have been
further validated as an excellent alternative to HBP.So it could become
a mainstream pacing technology in the future.