Principles and clinical methods of body surface gastric mapping: Technical review

Abstract

Background and PurposeChronic gastric symptoms are common, however differentiating specific contributing mechanisms in individual patients remains challenging. Abnormal gastric motility is present in a significant subgroup, but reliable methods for assessing gastric motor function in clinical practice are lacking. Body surface gastric mapping (BSGM) is a new diagnostic aid, employs multi‐electrode arrays to measure and map gastric myoelectrical activity non‐invasively in high resolution. Clinical adoption of BSGM is currently expanding following studies demonstrating the ability to achieve specific patient subgrouping, and subsequent regulatory clearances. An international working group was formed in order to standardize clinical BSGM methods, encompassing a technical group developing BSGM methods and a clinical advisory group. The working group performed a technical literature review and synthesis focusing on the rationale, principles, methods, and clinical applications of BSGM, with secondary review by the clinical group. The principles and validation of BSGM were evaluated, including key advances achieved over legacy electrogastrography (EGG). Methods for BSGM were reviewed, including device design considerations, patient preparation, test conduct, and data processing steps. Recent advances in BSGM test metrics and reference intervals are discussed, including four novel metrics, being the ‘principal gastric frequency’, BMI‐adjusted amplitude, Gastric Alimetry Rhythm Index™, and fed: fasted amplitude ratio. An additional essential element of BSGM has been the introduction of validated digital tools for standardized symptom profiling, performed simultaneously during testing. Specific phenotypes identifiable by BSGM and the associated symptom profiles were codified with reference to pathophysiology. Finally, knowledge gaps and priority areas for future BSGM research were also identified by the working group.

Effect of Menstrual Cycle and Menopause on Human Gastric Electrophysiology

“…Participants were scheduled to wear the Gastric Alimetry device (a non-invasive gastric mapping device comprising a 64-electrode array and a wearable reader) for a total of 4.5 hours after an overnight fast. A standardised test protocol was performed (15), consisting of a 30-minute pre-prandial recording followed by a test meal (Ensure (230 kcal, 230 mL; Abbott Nutrition, Chicago, IL) and an oatmeal energy bar (Clif Bar Nutrition Bar Chocolate Chip; 250 kcal, 5 g fat, 45 g carbohydrate, 10 g protein, 7 g fibre; Clif Bar & Company, Emeryville, CA), or a similar dietary equivalent, consumed over ten minutes, followed by a 4-hour post-prandial recording. During the test, participants were asked to rate any upper gastrointestinal symptoms of upper gut pain, nausea, bloating, heartburn, stomach burn, and excessive fullness every 15 minutes on visual analogue scales from 0 to 10 (0 indicating no symptoms; 10 indicating the worst imaginable extent of symptoms) using the validated Gastric Alimetry App (19).…”

Characterisation of post-fundoplication gastric dysfunction using Gastric Alimetry

“…Routine Gastric Alimetry test exclusions were also applied (BMI>35, fragile or damaged epigastric skin, unable to sit in a still position, or major allergy to adhesives). 12 Gastric Alimetry procedure All patients underwent a standard Gastric Alimetry test for evaluation of gut function, as described in detail elsewhere. 15,16 In brief, patients withheld GI motility affecting medications such as prokinetics and fasted for 8 hours prior, before undergoing a 30-minute baseline recording, followed by a standardised meal consisting of Ensure (232 kcal, 250 mL; Abbott Nutrition, IL, USA) and an oatmeal energy bar (250 kcal, 5 g fat, 45 g carbohydrate, 10 g protein, 7 g fibre; Clif Bar & Company, CA, USA), and a 4-hr postprandial recording.…”

“…Details of these metrics and the establishment of normative intervals are described in detail elsewhere. 17 Based on the above Gastric Alimetry metrics, patients were subsequently evaluated and classified to the following established phenotypes: 12 i) Gastric neuromuscular dysfunction: Gastric rhythm disorder or low amplitude, indicated by Gastric Alimetry Rhythm Index (GA-RI) <0.25, and/or BMI-adjusted amplitude <22 μV. 18 ii) High sustained BMI-adjusted amplitude: >70 μV suggesting possible gastric outlet resistance.…”

“…using Gastric Alimetry Ⓡ (Alimetry, New Zealand) is a novel diagnostic technique employing a dense array of electrodes at the epigastrium, which has been extensively validated for evaluation of gastric electrophysiological function. [12][13][14] We hypothesised these methods would provide novel insight into the pathophysiology of post-fundoplication symptoms, offering an improved mechanistic basis for treatment. The aim of this study was therefore to characterise gastric myoelectrical abnormalities in patients with persistent symptoms after fundoplication surgery using the Gastric Alimetry system.…”

Translation of an existing implantable cardiac monitoring device for measurement of gastric electrical slow‐wave activity

“…3 The recent development of body surface mapping approaches provides a noninvasive method for correlating symptoms with GI electrical activity. [7][8][9] However, it is limited to a recording duration of a few hours, where subjects must remain sedentary.…”