October 20, 2022 | A medical technology startup based in Auckland, New Zealand, expects its pioneering Gastric Alimetry wearable device for diagnosing gut disorders will one day do for gastroenterology what ECG testing for heart abnormalities has done for cardiology. The “body surface gastric mapping” (BSGM) test involves placing a sticky patch of sensors and a recording device onto the skin overlying the stomach and measures the underlying gastric electrical activity.
The Gastric Alimetry system already received marketing approval from regulators in the United States, United Kingdom, and New Zealand, and over the summer the company (Alimetry) opened its second corporate office in Minneapolis, Minnesota. The platform is currently being used in clinical practice to differentiate between chronic nausea and vomiting syndromes (NVSs) that originate in the gut and those that arise through a centrally mediated pathway—a phenotype often tied to anxiety and depression, says Peng Du, Ph.D., associate director of research at the Auckland Bioengineering Institute at the University of Auckland and chair of Alimetry’s Scientific Advisory Board.
Until recently, NVS was typically viewed as a single disease that is sometimes diagnosed using a nonsurgical endoscopy procedure or gastric emptying test (a nuclear medicine study that correlates weakly with symptoms), but more often based solely on patient-reported symptoms, says Du.
In a paper newly published in Science Translational Medicine (DOI: 10.1126/scitranslmed.abq3544), the two distinct NVS patient subgroups were discovered when Gastric Alimetry mapped the bioelectrical activity in the gut of 43 patients with NVS and 43 matched controls. The phenotypes correlate with symptoms, which should inform how patients get managed and therapeutic trials are designed.
Gastric Alimetry is engineered to be a plug-and-play system that is “so easy to setup you can practically throw it at a person, and it would work,” jokes Stefan Calder, a recent Ph.D. graduate of the Auckland Bioengineering Institute who serves as the company’s chief scientific officer.
As described on the company’s website, the testing process begins by applying an adhesive array to the surface of the abdomen and taking a 30-minute fasted recording of electrical waves and contractions that coordinate gastric motility. Patients then eat a test meal, and the recording continues for up to four hours. Throughout the test patients record their symptoms (e.g., discomfort level from stomach burn and when they last belched) using the Gastric Alimetry app.
The test data is sent to the Alimetry Cloud and processed using advanced algorithms. Clinicians can access and download patient reports on demand with details on gastric function, including frequency, stability of gastric electrical rhythms, meal-response profiles, amplitude of gastric contractions, validated symptom graphs, and technical data on test quality.
“We are currently engaging a lot of key opinion leaders in the gastroenterology field, especially in the U.S., to [drive the] move away from symptom-based diagnosis to a more functional-based matrix of symptoms,” says Du. Meanwhile, multiple clinical trials are underway in the U.S., Canada, Europe, and the United Kingdom to generate the clinical evidence required to optimize reimbursement coverage to enable widespread adoption of Gastric Alimetry in clinical practice.
In terms of research exploring the diagnostic potential of gastric surface mapping, “there are many clinical trials underway, investigating exciting areas that aim to help both patients and clinicians manage these difficult and life-altering diseases” says Calder. The novel system—comprising disposable sticky patches and a multi-use recording device—is currently being used in the context of intervention trials to categorize diseased populations in conjunction with other tests, such as endoscopy and gastric emptying, to increase the diagnostic yield.
But the objective is to see the Gastric Alimetry device become a “first-in-line test” of abnormal gastric activity, adds Du, just as an ECG is the definitive diagnostic test for heart attack when patients present in the emergency room with chest pain. The device is influenced by the American market, he adds, in terms of the manufacturing of some of its component parts and the large number of key opinion leaders coauthoring published clinical studies.
But the push to make the gastric mapping device a gamechanger in clinical practice started with Greg O’Grady, M.D., Ph.D., a general surgeon and principal investigator at the University of Auckland with whom Du did his Ph.D. The company was founded on this mission in 2019 by O’Grady (chief executive officer), Du, Calder, and Armen Gharibans (chief technology officer), who was awarded the top PhD Prize for his technical work on non-invasive gut diagnostics at the University of California, San Diego.
Poor signal quality has historically been the major holdup in adoption of surface mapping to detect bioelectrical activity in the body ever since researchers began searching for those elusive electrical signatures a century ago—first in the heart that rhythmically contracts to pump blood and later the gut that squeezes and relaxes as part of the digestion process, says Du. In the 1980s, with the emergence of multi-electrode mapping of the abdomen, interest in surface mapping of the gut was renewed even as the signal-to-noise ratio remained problematic.
At the time, he says, testing techniques involved only three to seven electrodes. The Gastric Alimetry device employs a dense field of 64 electrodes to assess gastric activity more reliably at high spatial resolution. But when it was first being developed a decade ago, the electrodes all had to be manually and individually placed on patients, which could take hours and limited its utility in clinical practice settings.
Previous studies reported a definitive correlation of frequency between recordings taken directly from the stomach and the body surface, says Du. In a second newly published paper by University of Auckland researchers, appearing in the American Journal of Physiology-Gastrointestinal and Liver Physiology (DOI: 10.1152/ajpgi.00049.2022), the Gastric Alimetry mapping tool was used in pigs to validate the BSGM approach. It was shown to reliably record bioelectrical activity on the gut’s surface and accurately detect changes in frequency and rhythm as well as direction of gastric slow waves.
As shown in the contemporaneously published clinical study with NVS patients who share common symptom profiles, the unique new set of biomarkers is what gives the device utility in identifying patients as either having gastric neuromuscular disease or dysregulation of the brain-gut interaction, Du says. About two-thirds of the symptomatic patient group appeared to have issues arising through the centrally mediated pathway rather than the gut itself. “Currently, this is all just lumped together under this one general umbrella of disease when in fact the actual treatment in these two cases is quite different.”
Moving forward, Alimetry will be publishing other papers looking at how the BSGM technique can be applied to patient populations beyond those with chronic NVSs, says Calder. But it’s a good starting point, given that these are prevalent and debilitating disorders that have a lot of symptom overlap with other gastrointestinal conditions, including functional dyspepsia and gastroparesis.