Non‐invasive Targeted Gastric Vagal Complex Stimulation: Preliminary in Human Cutaneous Measures of Gastric Slow Wave Function

Abstract

Gastric slow wave abnormalities have been associated with upper gastrointestinal motility disorders. Invasive studies in humans have described normal and abnormal propagation of the gastric slow wave, and recent non‐invasive studies have shown that multi‐electrode cutaneous measures of gastric slow wave function correlate with symptom severity in patients with gastroparesis and functional dyspepsia (Gharibans et al, Clinical Gastroenterology and Hepatology, 2019). Invasive Neurostimulation of gastric Vagal complexes are thought to result in satiety (Abiliti, Transcend), anti‐nausea (Entera) and general weight loss (vBLOC), but effects of invasive neuromodulation on gastric motility are not clear. Our group developed: 1) a wearable non‐invasive electrogastrography (EGG) device that reliably records gastric slow wave function and 2) a new non‐invasive targeted gastric Vagus nerve stimulation (ntG‐VNS) system. The challenge is to further develop a combined ntG‐VNS/EGG system that may be used as a tool to probe Gastric disease states, and eventually diagnose and or treat gastric motility disorders.MethodsA 10 lead ambulatory high resolution electrogastrogram (AHR‐EGG) system for ambulatory use (Gharibans et al, Scientific Reports, 2018) was used to record gastric myolectric activity cutaneously (Fig 1A). The gastric proximal fundus was visualized at a depth of 2cm using a Butterfly high frequency transducer at 1–5MHz (Fig 1b) and guided stimulator electrode placement. After fundus localization ntG‐VNS was applied inferior to the lower sternum with 2 (0.5 inch) disk electrodes 0.5 inch apart in rostral caudal orientation (Fig 1A) utilizing short pulsed intermittent stimulation for 14 minutes during simultaneous EGG. Cutaneous recordings were sampled at 250Hz, filtered below 0.15Hz and down‐sampled to 1Hz. Artifact rejection methods as described in (Gharibans et al, Scientific Reports, 2018) were next applied, followed by median filtering of the 0.05Hz power derived from spectrograms across all electrodes to derive EGG power. Baseline activity was derived from percentiles of power across the recording, and was subtracted to derive normalized EGG power to be used for subsequent analysis.ResultsEGG power prior to nTG‐VNS showed a center frequency of .0493 Hz (Fig 2A). Post nTG‐VNS EGG showed highly significant reduction of slow wave power (Fig 2B), below the baseline pre‐stimulation levels.ConclusionntG‐VNS immediately abolishes gastric slow wave propagation as measured by non‐invasive AHR‐EGG over a 14 min time period. Taken together, targeted non‐invasive gastric vagus nerve stimulation technology may prove to be a valuable human research tool, focused on improving our fundamental understanding of gastric motility vagal reflexes.Support or Funding InformationThis work was in part supported by the U.S. Department of Health and Human Services, Biological Advanced Research and Development Authority, BARDA: (75A50119C00038)Figure 1Figure 2