Cardioneuroablation Acutely Affects the Amplitude and Efficiency of Respiratory Heart Rate Variability

<b>Background/Objectives</b>: Cardioneuroablation (CNA) is used to treat reflex syncope by parasympathetic denervation of the cardiac conduction system. Respiratory heart rate variability (RespHRV) constitutes an important physiological mechanism that optimizes lung perfusion. The impact of CNA on various components of RespHRV remains unclear. <b>Methods</b>: Eleven subjects (36.8 ± 14.1 years) undergoing CNA for the treatment of cardioinhibitory, vagally mediated syncope were enrolled. For the RespHRV assessment, we used continuous respiratory flow measurement and an electrocardiogram. RespHRV analysis included the following: (a) amplitude, reflecting the overall magnitude of changes in RR interval during the respiratory cycle (RespHRVpv, ms); and (b) efficiency, defined as the percentage of inspirations accompanied by RR shortening (short-RRi inspirations, %), and expirations accompanied by RR prolongation (long-RRi expirations, %). Baroreflex sensitivity (BRS, ms/mmHg) was assessed with a sequential method using a noninvasive hemodynamic monitor. Both RespHRV and BRS were captured 48 h apart, before and after CNA. <b>Results</b>: A significant reduction was observed in RespHRVpv (57 [30-131] vs. 13 [7-16] ms, <i>p</i> = 0.003), short-RRi inspirations (97.0 [77.8-100.0] vs. 36.0 [14.3-63.2] %, <i>p</i> = 0.003), and long-RRi expirations (88.0 [78.1-97.6] vs. 31.1 [21.4-65.8] %, <i>p</i> = 0.008). Moreover, we found a strong relationship between ΔBRS and ΔRespHRVpv (r = 0.77, <i>p</i> = 0.005) following CNA. <b>Conclusions</b>: Our results indicate a substantial role of the cardiac parasympathetic system in RespHRV development, including both its amplitude and efficiency. The marked decrease in key RespHRV measures after CNA highlights the need for further research into its long-term clinical effects.