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 .