Extracardiac vagal stimulation in cardioneuroablation procedures - comparison of two devices

Background Extracardiac vagal stimulation (ECVS) is a valuable tool for guiding cardioneuroablation (CNA). ECVS requires a high-frequency, high-output stimulation protocol. It appeared that neurostimulation cannot be accurately reproduced with conventional electrophysiology laboratory stimulators. Purpose To compare the efficacy of ECVS using two devices with different stimulation protocols. Methods The study was conducted in 40 patients (age 40 ± 11 years, 50% male) undergoing cardioneuroablation. Before ablation, each patient underwent sequential bilateral ECVS with (1) a dedicated neurostimulator Pachon (Brazil) and (2) an electrophysiological stimulator (Micropace EPS-320, Australia). The stimulation protocol for Pachon was as follows: frequency of 50 Hz, amplitude of 70 V, and pulse width of 0.05 ms. The stimulation protocol for Micropace was as follows: frequency of 33 Hz, current of 25 mA, pulse width of 10 ms. Relatively low output with Micropace vs Pachon (25 mA vs 70 V) was compensated by a much larger pulse width (10 vs 0.05 ms). Energy output with Micropace vs Pachon was higher but still safe (0.12 vs 0.02 W). Stimulation trains were always 5 seconds long. The right and then the left vagus nerves were stimulated; vagal responses were assessed for the sinus node (the longest P-P interval) and for the AV node (the longest R-R interval during atrial pacing at 100 bpm). The order of use of both devices in individual patients was randomized in a 1:1 ratio. Results Using the electrophysiology stimulator Micropace, sinus and AV nodal vagal responses induced by sequential bilateral ECVS were systematically weaker than those achieved with the neurostimulator Pachon (Table). Their magnitude, however, was fully sufficient for practical use. There were no adverse events related to ECVS performed by both devices. Conclusions The commercially unavailable neurostimulator Pachon can be replaced with the widely available Micropace EPS-320 stimulator to guide the CNA. This may increase the use of ECVS worldwide and improve the efficacy and safety of better-tailored CNA procedures.