Ear your heart: transcutaneous auricular vagus nerve stimulation on heart rate variability in healthy young participants

Author: Giuseppe Forte#1,2, Francesca Favieri#1,2, Erik Leemhuis1,2, Maria Luisa De Martino1,2, Anna Maria Giannini2, Luigi De Gennaro1,2, Maria Casagrande3, Mariella Pazzaglia1,2
1 Body and Action Lab, IRCCS Fondazione Santa Lucia, Rome, Italy.
2 Department of Psychology, University of Roma "La Sapienza", Rome, Italy.
3 Dipartimento di Psicologia Clinica, Dinamica e Salute, University of Roma "La Sapienza", Rome, Italy.
Conference/Journal: PeerJ
Date published: 2022 Nov 21
Other: Volume ID: 10 , Pages: e14447 , Special Notes: doi: 10.7717/peerj.14447. , Word Count: 306

Transcutaneous auricular vagus nerve stimulation (taVNS) stimulating the auricular branch of the vagus nerve along a well-defined neuroanatomical pathway, has promising therapeutic efficacy. Potentially, taVNS can modulate autonomic responses. Specifically, taVNS can induce more consistent parasympathetic activation and may lead to increased heart rate variability (HRV). However, the effects of taVNS on HRV remain inconclusive. Here, we investigated changes in HRV due to brief alteration periods of parasympathetic-vagal cardiac activity produced by taVNS on the cymba as opposed to control administration via the helix.

Materials and methods:
We compared the effect of 10 min of active stimulation (i.e., cymba conchae) to sham stimulation (i.e., helix) on peripheral cardiovascular response, in 28 healthy young adults. HRV was estimated in the time domain and frequency domain during the overall stimulation.

Although active-taVNS and sham-taVNS stimulation did not differ in subjective intensity ratings, the active stimulation of the cymba led to vagally mediated HRV increases in both the time and frequency domains. Differences were significant between active-taVNS and both sham-taVNS and resting conditions in the absence of stimulation for various HRV parameters, but not for the low-frequency index of HRV, where no differences were found between active-taVNS and sham-taVNS conditions.

This work supports the hypothesis that taVNS reliably induces a rapid increase in HRV parameters when auricular stimulation is used to recruit fibers in the cymba compared to stimulation at another site. The results suggest that HRV can be used as a physiological indicator of autonomic tone in taVNS for research and potential therapeutic applications, in line with the established effects of invasive VNS. Knowledge of the physiological effect of taVNS short sessions in modulating cardiovagal processing is essential for enhancing its clinical use.

Keywords: Cardiac activity; Cymba conchae; Heart rate variability; Transcutaneous auricular vagus nerve stimulation; Vagus nerve; taVNS; tvns.

PMID: 36438582 PMCID: PMC9686410 DOI: 10.7717/peerj.14447