Kristen Sparrow • April 23, 2022
This is the abstract for my contribution to the International Neuromodulation Society World Congress in Barcelona May 21 to May 26th 2022.
HEART RATE VARIABILITY AS BIOMARKER FOR EFFECTIVE CLINICAL TRANSCUTANEOUS AURICULAR VAGAL NERVE STIMULATION: DIFFERENTIATING VAGAL VERSUS SYMPATHETIC ACTIVITY
This case series is part of an effort to refine a bedside Heart Rate Variability (HRV) protocol to monitor autonomic balance during Acupuncture and Transcutaneous Auricular Vagal Nerve Stimulation (TAVNS). Autonomic data showing patients’ response to needling and adjunct therapies might be useful in guiding treatment since stimulation parameters can be determinative to results.
Recent research has helped to define best parameters for TAVNS treatment. Furthermore, a 2021 study in Nature[i] showed that in mice, low intensity electrostimulation of hindlimb neurons with certain markers produces a parasympathetic response whereas high intensity stimulation produces a sympathetic response. In addition individual patient variation can affect the efficacy TAVNS and Acupunture.. Acupuncture can also improve autonomic balance[ii], which may be responsible for Acupuncture’s results. In addition to the generalized response to needling, This not only shows specificity of acupuncture points, but the need for precision in stimulation intensity.
The immune system has feedback mechanisms to keep inflammation in check. This immune mechanism employs the vagal parasympathetic activity and Hypothalamic-Pituitary-Axis to dampen the inflammatory response. With ongoing inflammation this feedback can be inadequate. Acupuncture triggers this immune feedback system with the NEI or Neuroendocrine Immune response. The NEI is a response to the injury of needling where pain fibers signal the brainstem which then signals the vagus to dampen inflammation. TAVNS can be used in the clinic in conjunction with Acupuncture to further enhance vagal activity.
Materials and Methods:
HRV monitored in supine position for 3 minutes baseline and for entire treatment including TAVNS (when used), needling, and resting with needles retained 20 minutes. HRV analyzed in 1 minute segments for LF/HF, LF, HF. TAVNS clip electrode applied to cymba concha left ear, 1hz. Standard TCM Acupuncture body treatment according to condition used.
LF/HF, HF, LF charted and compared show that in some cases, TAVNS produces a pronounced decrease in sympathetic (LF) activity compared to acupuncture treatment alone. Addition of electroacupuncture at 36 Stomach, had inconsistent HRV results.
Discussion: HRV use is feasible in the clinic, and though plagued by “noise”, the data obtained can help to identify treatments that might be contraindicated i.e. that actually stimulate sympathetic activity instead of increasing parasympathetic activity. HRV may help with refinement not only of stimulation parameters, but of optimal time of stimulation and needle retention. There are some exploratory investigations using heart rate variability (HRV) as feedback for implanted vagal nerve stimulation[iii] and for TAVNS also.
[i] Liu, S., Wang, Z., Su, Y. et al. A neuroanatomical basis for electroacupuncture to drive the vagal–adrenal axis. Nature 598, 641–645 (2021).
[ii] Ulloa L, Quiroz-Gonzalez S, Torres-Rosas R. Nerve Stimulation: Immunomodulation and Control of Inflammation. Trends Mol Med. 2017;23(12):1103-1120. doi:10.1016/j.molmed.2017.10.006
[iii] Romero-Ugalde HM1,2, Le Rolle V1,2, Bonnet JL3, et al A novel controller based on state-transition models for closed-loop vagus nerve stimulation: Application to heart rate regulation. PLoS One. 2017 Oct 27;12(10):17.