3. Conduction system pacing: An “Electrical Bypass”
Therefore, given that the pacing of the RV myocardium beyond the apex is
not always associated with favorable clinical endpoints, the effort to
find and pace the conduction system in order to avoid Pacing-Induced
Cardiomyopathy is deemed essential. CSP comprises His bundle pacing
(HBP) and Left Bundle Branch Area pacing (LBBAP). This technique is
based on a pathophysiologically correct theory and could be considered
an “Electrical Bypass”. (Figure 3 ) The role of the venous
graft used in revascularization therapy is represented in this setting
by the pacing lead. By bypassing a lesion of the native pacing system,
which usually occurs in the area of the AV node, with the pacemaker
lead and transmitting the stimulus downward through the remaining intact
part of the system, results in faster transmission of the electrical
impulse with the normal mode, but also simultaneous stimulation of both
ventricles, and therefore the avoidance of the unfavorable phenomenon of
dyssynchrony. As a result, CSP could be characterized as an “ideal”
form of pacing. Speaking of an ideal pacing method, this should be
easily applicable to all patients with AV system disorders, without
complications, and with long-term beneficial clinical endpoints, namely,
a form of pacing where the answer to the question “when and to whom
patients” is “always and to everyone”!
This idea is not new. More than half a century before, in 1970, Narula
et al. in a series of 30 patients with conduction disturbances in the AV
node, through the transvenous technique, found the His Bundle, mapped
it, measured the corresponding intervals, and successfully induced
pacing.7 Nevertheless, permanent HBP has applied 30
years afterward, in 2000, in a series of 18 patients, with impaired left
ventricular systolic function and atrial fibrillation before AV node
ablation.8 Successful pacing was achieved in 14
patients, with satisfactory results as far as the improvement of left
ventricular dimensions and LVEF from 20 to 31%. However, despite the
good outcomes, the HBP procedure did not proceed on a large scale,
recording a plateau in clinical application and literature research.
That is because of the following three considerations, schematically
illustrated in Table 2 .