Introduction
Right ventricular (RV) apical pacing causes ventricular dyssynchrony
with an increased risk of heart failure
[1]. Despite attempts to reduce it by
changing the pacing location (RV septal vs. RV apex), no clinical
benefit has been observed. As was shown, the standard fluoroscopic
criteria for exact lead placement are insufficient, and many leads that
were considered to be in the septum based on fluoroscopy, were, in fact,
anchored in the anterior wall [2,
3]. Furthermore, septal positions might
represent a mix of more or less dyssynchronous pacing, which ultimately
brings no advantage over RV apical pacing.
In recent years, His bundle pacing (HBP) has shown promising results
[4], but its benefits are
counterbalanced by an increase in pacing lead reinterventions
[5]. These shortcomings could
potentially be moderated by placing the lead tip in the ventricular
septal para-hisian area, beyond the annulus of the tricuspid valve. This
would ensure pure myocardial capture during low output pacing and
concomitant myocardial and conductive tissue capture during higher
output pacing. In our study, we called the high-output para-hisian
capture as conductive system septal pacing (cSp) to differentiate it
from myocardial septal (mSp) or pure myocardial para-hisian pacing in
which conduction tissue is not captured directly.
UHF-ECG is an imaging method displaying the activation pattern and time
differences between the activation of specific ventricular segments.
Time-spatial resolution is possible thanks to an analysis of the
ultra-high frequency components of ventricular myocyte action potentials
in peri-myocardial tissue and the practical use of UHF-ECG was
documented in previous reports [6,
7].
The aim of the study was to describe in detail the activation patterns
seen during RV pacing with and without direct conduction system
engagement.