THE EFFECTS OF NONINVASIVE ULTRASOUND STIMULATION ON VAGUS NERVE ACTIVITY AND HEART RATE VARIABILITY

Abstract

Anxiety rates have skyrocketed in recent years with nearly one third of adolescents reporting that anxiety has negatively impacted their well-being. Additionally, nearly 50% of patients using standard treatment options are left with unwanted side effects or minimal symptom relief (Kessler et al., 2009). One alternative to current anxiety treatments is Vagus Nerve Ultrasound Stimulation (VNS), a fast-acting and less expensive approach to treat anxiety. Prior research has demonstrated that VNS effectively decreased inflammation markers and temporarily modulated heart rate in animal models (Coiado et al., 2016, Wasilczuk, 2019). In order to further investigate VNS as a potential treatment option, we analyzed fluctuations in heart rate variability (HRV). HRV is a measure of variation between individual heart beats and is an indicator of physiologic control via an interplay between the parasympathetic and sympathetic nervous systems. We investigated the effects of VNS on heart rate, HRV, and examined whether increased HRV predicts lower anxiety in healthy individuals. The results demonstrated a significant difference in baseline normalized RMSSD (a measure of heart rate variability) between sham and interval stimulation groups (F2,44 = 4.252, p= 0.020). There were significant differences in RMSSD and HR across timepoints within all groups, which may be indicative of effects due to pressure or temperature rather than the VNS itself. Changes in HRV did not predict differences in anxiety or mood scores. Future research is required to further examine the effects of ultrasound at different pulse parameters and carrier frequencies in enhancing or inhibiting cardiac vagal control.