Rationale of Extracardiac Vagal Stimulation
The rationale for both ECVS and CNA is grounded in the distribution of the cardiac autonomic nervous system20,21,22. Any medical procedure necessitates a method of control. Consequently, if the procedure aims to achieve vagal denervation, it should monitor and regulate the extent of this innervation and the elimination or reduction of the vagal response19, Figure 2-C. Furthermore, cardioinhibition typically involves a substantial bilateral vagal response, and the control method must replicate it as closely as possible. In clinical practice, the reproduction of cardioinhibition is achieved through the HUTT, and in the laboratory, the sole method capable of replicating a similar controlled condition is ECVS10,19,23. Both in spontaneous events and during the HUTT, there is a massive vagal response simultaneously affecting all regions with vagal innervation, particularly the sinus node, AV node, and atrial walls. This condition can be readily reproduced with ECVS as many times as necessary, depending on the operator, as illustrated in Figure 2-A and B. In this method, the extensive vagal stimulation, accompanied by an overdrive of the vagal efferent fibers, enables a clear, objective, and gradual control of the degree of vagal denervation, ultimately leading to the complete elimination of responses in the sinus node, AV node, and even atrial walls19, Figure 2. Consequently, aside from facilitating the rational conclusion of CNA, ECVS helps prevent over-ablation. Therefore, the significance of ECVS, which is quite intuitive from a rational standpoint, is statistically validated in this study.