6.1. Pacing for bradycardia
Several small studies have demonstrated the superiority of HBP over RV
pacing in avoiding Pacing-Induced Cardiomyopathy. Even though upgrading
simple RV to biventricular pacing could be a highly effective solution
in patients with post-implant LVEF <35%, nevertheless, it is
significantly underutilized even in those with lower preimplant
LVEF.28 The echocardiographically estimated LVEF is
used as a study indicator of Pacing-Induced Cardiomyopathy, knowing, of
course, the limitations of this indicator in terms of the impact of
clinical endpoints and mortality in patients with heart
failure.29 The older studies by Zanon et al. (2008),
Barba-Pichardo et al. (2010), and Kronborg et al. (2014) recorded an
LVEF improvement in 12, 59, and 32 patients, respectively, mainly with
atrioventricular block, with relatively short follow-up of 3-12 months,
in single-center trials.30-32 Sharma et al. (2015) and
Vijayaraman et al. (2018) included 75 patients in each study, recording
less heart failure hospitalization and a trend in lower mortality in
patients with >40% ventricular pacing, as well as no
difference in patients with atrial fibrillation, in HBP
group.27, 33
The largest study is that of Abdelrahman et al. (2018), a two-center
study that included 304 consecutive patients with HBP and 433 patients
with RV pacing at a sister hospital. In a 2-year follow-up, the study
showed the superiority of HBP in terms of the combined endpoint of
all-cause mortality, heart failure hospitalization, or upgrade to
biventricular pacing. The HBP superiority was even great in patients
with ventricular pacing >20% (HR 0.71 and 0.65,
respectively).34 Additionally, two recently published
studies with a small number of patients with bradycardia have documented
the adequacy of HBP in maintaining LVEF after transcatheter aortic valve
implantation, as well as in comparison with LBBAP.35,
36 The commonality of all the above studies is that the data came from
observational, single, or two-center studies, with few patients, with
short follow-up periods. For that reason, most authors emphasize the
need to conduct large, prospective, randomized control trials (RCTs)
comparing HBP to RV pacing to prove beneficial clinical endpoints, such
as reduction in hospitalizations and mortality attributable to HBP in
patients with bradycardia.