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Mechanisms of Action for the Enterra Medical Gastric Electrical Stimulator

Background: Gastric electrical stimulation applied by a surgically implanted device effectively alleviates upper gastrointestinal symptoms in the majority of individuals with medically refractory gastroparesis. Despite its efficacy, the mechanisms of action have been minimally explored in previous studies, and it is unknown why some individuals experience limited symptom-lowering effects. Aim: The investigators aim to investigate two of the potential mechanisms of action leading to symptom-reducing effects of gastric electrical stimulation: 1) possible central effects in the brainstem and brain by enhanced parasympathetic vagal activity, and 2) peripheral effects in the stomach by improved gastric accommodation. Methods: Up to thirty individuals with drug-refractory gastroparesis having an implanted gastric electrical stimulator will be enrolled in this cross-sectional and observational study. Of these, 15 will be responders (substantial symptomatic improvement) and 15 non-responders (minor symptomatic improvement). Electroencephalography (EEG) will evaluate the stimulation-induced activity in the brain and brainstem to assess whether the gastric stimulation generates evoked potentials. Electrocardiography (ECG) will investigate stimulation-induced changes in the autonomic regulation of the heart. Gastric ultrasound will investigate the effect of stimulation on stomach accommodation, contractions, and wall tension. These central and peripheral measures will be assessed during one study day before and after activating the gastric electrical stimulator, following an increase in stimulation intensity and post-meal consumption. Furthermore, results will be compared between responders and non-responders. Perspectives: Adjusting the parameters of gastric electrical stimulation based on objective markers in the brain, heart, or stomach, rather than relying on symptom fluctuations, may enhance the effectiveness of symptom improvement. In the future, these objective markers may aid in differentiating between responders and non-responders, which may lead to optimised selection criteria for surgery.