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

The Impact of Alpha-Neurofeedback Training on Gastric Slow Wave Activity and Heart Rate Variability in Humans

INTRODUCTION

Neuromodulation of cortical brain regions associated with the gut-brain axis may have the potential to modulate gastric function. Previous studies have shown phase-amplitude coupling between the electroencephalogram (EEG) alpha band frequency of the insula (Ins) and gastric slow wave (GSW) activity. This study investigated the first evidence of alpha band EEG-neurofeedback (EEG-NF) training to explore its effects on GSW activity and heart rate variability (HRV).

METHODS

A randomized crossover design was employed with 20 healthy participants attending two separate sessions [active-training: uptraining left posterior Insula (LPIns) and active-control: uptraining primary visual cortex (PVC Brodmann area 17)] following the baseline recording period. A 5-min water loading test (5WLT) was conducted following the EEG-NF sessions. Finally, a post EEG-NF/5WL period was also recorded. Participants were blinded to the training program, and the sessions were randomized and conducted at least 48 h apart. Electrocardiogram (ECG), EEG, and electrogastrogram (EGG) data were recorded throughout theexperiment. In addition, the duration of successful NF training was also extracted. Correlation analysis was performed to assess the relationships between outcome variables.

RESULTS

Pearson correlation coefficient analysis revealed a significant relationship between the duration of successful NF training and HRV metrics (RMSSD: r = 0.59; p = 0.005, SI: r = -0.59; p = 0.006) in the LPIns training group and EGG-gastric rhythm index (r = -0.40; p = 0.028) in the PVC training group. Moreover, the duration of successful LPIns NF correlated with EEG activity of the infraslow band over the left anterior Ins (r = 0.45; p = 0.043), slow band over the right posterior Ins (r = -0.5; p = 0.022), and beta band over the left (r = 0.44; p = 0.04) and right anterior Ins (r = 0.45; p = 0.04). Significant correlations were also observed between LPIns NF duration and connectivity in the beta and gamma bands between cortical regions of interest.

CONCLUSION

The alpha band EEG-NF training of LPIns demonstrated significant association with HRV, and EEG (activity and functional connectivity)measures and did not show a negative correlation with Gastric Alimetry Rhythm Index (GA-RI) following the 5WLT as in the PVC training group. These findings underscore the importance of considering the duration of successful NF as an important variable when evaluating NF training efficacy in future studies.

Body Surface Gastric Mapping Delineates Specific Patient Phenotypes in Adolescents With Functional Dyspepsia and Gastroparesis

BACKGROUND

Diagnosing pediatric patients with chronic gastroduodenal symptoms is clinically challenging, with the role of gastric emptying testing being controversial. Body Surface Gastric Mapping (BSGM) is a new diagnostic test that can identify specific patient phenotypes in adults with gastric dysfunction. This study evaluates whether BSGM can delineate specific phenotypes in adolescents and provide clinically meaningful distinctions between gastroparesis and functional dyspepsia diagnoses.

METHODS

A prospective cross-sectional study recruited adolescents aged 12 to 21 between 2022 and 2024. Controls were recruited from New Zealand and patients from the Children's Hospital of Philadelphia, USA. BSGM followed a standardized protocol, including simultaneous symptom reporting and completion of validated symptom, psychometric, and physical health questionnaires.

KEY RESULTS

Fifty-six subjects were recruited (31 controls, 25 patients); median age 16; 96% of patients were female. Control data showed that adult reference intervals provided an acceptable interpretation framework. Patients with FD (n = 10) and gastroparesis (n = 15) had common symptoms, mental health, quality of life, and functional disability (all p > 0.05). Three distinct BSGM phenotypes were identified: BSGM Normal (n = 10), BSGM Delay (n = 8), and Low Stability/Low Amplitude (n = 7), having spectral differences in BMI-Adjusted Amplitude 34.6 versus 39.1 versus 19.9 (p = 0.01) and Gastric Alimetry Rhythm Index: 0.45 versus 0.45 versus 0.19 (p = 0.003). BSGM phenotypes demonstrated differences in symptoms (nausea p = 0.04), physical health (p = 0.04), and psychometrics (anxiety p = 0.03).

CONCLUSION AND INFERENCES

Adolescents with FD and gastroparesis have overlapping clinical profiles, making treatment challenging. Conversely, employing BSGM to categorize patients into distinct phenotypes reveals clinically relevant differences, offering avenues for individualized therapeutic pathways.

Relationship between intragastric meal distribution, gastric emptying and gastric neuromuscular dysfunction in chronic gastroduodenal disorders

Background

Chronic gastroduodenal symptoms arise from heterogenous gastric motor dysfunctions. This study applied multimodal physiological testing using gastric emptying scintigraphy (GES) with intragastric meal distribution (IMD) and Gastric Alimetry® body surface gastric mapping (BSGM) to define motility and symptom associations.

Methods

Patients with chronic gastroduodenal symptoms underwent simultaneous supine GES and BSGM with 30 m baseline, 99mTC-labelled egg meal, and 4 h postprandial recording. IMD (ratio of counts in the proximal half of the stomach to the total gastric counts) was calculated immediately after the meal (IMD0), with <0.568 defining impaired accommodation. BSGM phenotyping followed a consensus approach, based on normative spectral reference intervals.

Results

Among 67 patients (84% female, median age 40, median BMI 24), median IMD0 was 0.76 (IQR 0.69-0.86) with 5 (7.5%) meeting impaired accommodation criteria. Delayed gastric emptying (n=18) was associated with higher IMD0 (median 0.9 vs 0.7, p=0.004). On BSGM, 15 patients had abnormal spectrograms (5 [7.5%] high frequency and 10 (14.9%) low rhythm stability and/or amplitude); and in these patients, higher IMD0 (proximal retention) strongly correlated to delayed BSGM meal responses (R=-0.71, p=0.003). Lower IMD, indicating antral distribution, correlated with higher gastric frequencies (R=-0.27, p=0.03). BSGM abnormalities paired with impaired accommodation were associated with worse dyspeptic symptoms.

Conclusion

Proximal retention of food as assessed by intragastric meal distribution correlated with delayed emptying, and in the presence of neuromuscular spectral abnormalities (abnormal frequencies or rhythms), delayed motility responses on BSGM. Patients with multiple motor abnormalities experience worse dyspeptic symptoms.

Predicting symptomatic response to prokinetic treatment using Gastric Alimetry

Background

Chronic neurogastroduodenal disorders are challenging to manage, with therapy often initiated on a trial and error basis. Prokinetics play a significant role in management, but responses are variable and have been associated with adverse events, impacting widespread use. We investigated whether body surface gastric mapping (BSGM) biomarkers (using Gastric Alimetry ® ) could inform patient selection for prokinetic therapy.

Methods

Patients with chronic gastroduodenal symptoms taking oral prokinetic, regardless of gastric emptying status, were prospectively recruited and underwent BSGM (30 m baseline, 482 kcal standardised meal, 4 h postprandial recording) whilst off prokinetic. Patients were followed up with daily symptom diaries. A subset was compared to matched patients not taking prokinetics. Prokinetic responders were defined based on symptom improvement greater than a minimum clinically important difference methodology.

Key Results

42 patients (88% female; median age 36; median BMI 26) taking prokinetics were analysed. Prokinetic prescribing, compared to matched patients, was independent of BSGM metrics (p>0.15). In patients on existing prokinetics (withheld for BSGM), lower amplitudes predicted reduced symptom burden, whereas low rhythm stability predicted a worse symptom burden (p<0.05). In prokinetic-naive patients (i.e. started on a prokinetic during the study), a lower postprandial amplitude predicted responders (mean 37.5±10.6 uV in responders [n=5] vs mean 54.8±6.6 uV among non-responders [n=3], p=0.047).

Conclusions

Gastric Alimetry biomarkers may help in the prediction of prokinetic response in patients with chronic gastroduodenal symptoms. Lower post-prandial amplitudes, indicating a reduced meal response, appear to predict benefit, whilst impaired rhythm stability predicted poorer therapeutic response.

Assessing gastrointestinal system dysfunction in intensive care

PURPOSE OF REVIEW

To summarize the current knowledge on the assessment of gastrointestinal dysfunction.

RECENT FINDINGS

Clinical assessment is becoming more structured but remains largely subjective. Some instrumental tools to assess gastrointestinal motility have been developed but not yet widely applied in clinical practice. Imaging techniques offer a good method for static (i.e. nonfunctional) diagnostics but a standardized dynamic assessment at the bedside is currently unavailable. Recent studies on biomarkers have not provided convincing results for accurate evaluation of gastrointestinal function.

SUMMARY

Clinical assessment remains the main tool for assessing gastrointestinal dysfunction. A single sign or symptom does not reflect gastrointestinal dysfunction adequately, and a set of variables might be needed. Studies on tools reflecting gastrointestinal motility and biomarkers for response to enteral nutrients, including absorption, are warranted.

Assessment of Gastric Remnant Activity, Symptoms, and Quality of Life Following Gastric Bypass

INTRODUCTION

While most gastric bypass patients recover well, some experience long-term complications, including nausea, abdominal pain, food intolerance, and dumping. This study aimed to evaluate symptoms and quality of life (QoL) in association with the residual activity of the remnant stomach.

METHODS

Patients undergoing gastric bypass and conversion-to-bypass were recruited. The Gastric Alimetry® System (Auckland, NZ) was employed, comprising a high-resolution electrode array, wearable reader, and validated symptom logging app. The protocol comprised 30-min fasting baseline, a 218-kCal meal stimulus, and 4-h of post-prandial recordings. Symptoms and QoL were evaluated using validated questionnaires. Remnant gastric electrophysiology evaluation included frequency, BMI-adjusted amplitude, and Gastric Alimetry Rhythm Index (GA-RI, reflecting pacemaker stability), with comparison to validated reference intervals and matched controls.

RESULTS

Thirty-eight participants were recruited with mean time from bypass 46.8 ± 28.6 months. One-third of patients showed moderate to severe post-prandial symptoms, with patients' median PAGI-SYM 28 ± 19 vs controls 9 ± 17 (p < 0.01); PAGI-QOL 37 ± 31 vs 135 ± 22 (p < 0.0001). Remnant gastric function was markedly degraded shown by undetectable frequencies in 84% (vs 0% in controls) and low GA-RI (0.18 ± 0.08 vs 0.51 ± 0.22 in controls; p < 0.0001; reference range > 0.25). Impaired GA-RI and amplitude were correlated with worse PAGI-SYM and PAGI-QOL scores.

CONCLUSION

One-third of post-bypass patients suffered significant upper GI symptoms with reduced QoL. The bypassed remnant stomach shows highly deranged electrophysiology in-situ, reflecting disuse degeneration. These derangements correlated with QoL; however, causality is not implied by the present study.

Disorders of gastric motility

Gastroparesis is a disorder of delayed gastric emptying with associated symptoms of postprandial fullness, early satiety, nausea, vomiting, bloating, and abdominal pain. Functional dyspepsia is an upper gastrointestinal disorder of gut-brain interaction that presents with similar symptoms but is defined according to symptom patterns rather than gastric motor dysfunction. Although delayed gastric emptying is a defining feature of gastroparesis, other aspects of gastric neuromuscular dysfunction, such as gastric accommodation and visceral hypersensitivity might contribute to symptoms. Similarly, although functional dyspepsia is not defined by impaired gastric emptying, disordered gastric motility might underlie pathogenesis in some patients with functional dyspepsia. In the last decade, it has been increasingly recognised that these two disorders might represent varying presentations along a common continuum of neuromuscular dysfunction, although with differentiating features with respect to outcomes, diagnosis, and treatments. In this Review, an overview of gastroparesis and functional dyspepsia from the perspective of gastric motility is provided, discussing what is distinct and what is shared between these disorders.

A Standardized Classification Scheme for Gastroduodenal Disorder Evaluation Using the Gastric Alimetry System: Prospective Cohort Study

Background and Aims

Gastric Alimetry™ (Alimetry, New Zealand) is a new clinical test for gastroduodenal disorders involving simultaneous body surface gastric electrical mapping and validated symptom profiling. Studies have demonstrated a range of distinct pathophysiological profiles, and a classification scheme is now required. We used Gastric Alimetry spectral and symptom profiles to develop a mechanism-based test classification scheme, then assessed correlations with symptom severity, psychometrics, and quality of life.

Methods

We performed a multicenter prospective cohort study of patients meeting the Rome IV criteria for functional dyspepsia and chronic nausea and vomiting syndromes. Patients underwent Gastric Alimetry profiling, and a standardized digital classification framework was devised and applied to separate patients into those with a) abnormal spectral analyses (ie aberrant gastric frequencies, amplitudes, and rhythms); and normal spectral analyses with b) symptoms correlated to gastric amplitude (subgroups: sensorimotor, postgastric, and activity-relieved), and c) symptoms independent of gastric amplitude (subgroups: continuous, meal-relieved, meal-induced).

Results

Two hundred ten patients were included (80% female, median age 37), of whom 169 met the criteria for chronic nausea and vomiting syndromes and 206 met the criteria for functional dyspepsia (79% meeting both criteria). Overall, 83% were phenotyped using the novel scheme, with 79/210 (37.6%) classified as having a spectral abnormality. Of the remainder, the most common phenotypes were "continuous pattern" (37, 17.6%), "meal-induced pattern" (28, 13.3%), and "sensorimotor pattern" (15, 7.1%). Symptom patterns independent of gastric amplitude were more strongly correlated with depression and anxiety (Patient Health Questionnaire 2: exp(β) 2.38, P = .024, State-Trait Anxiety Inventory Short-Form score: exp(β) 1.21, P = .021).

Conclusion

A mechanistic classification scheme for assessing gastroduodenal disorders is presented. Classified phenotypes showed independent relationships with symptom severity, quality of life, and psychological measures. The scheme is now being applied clinically and in research studies.

Pulsed-field ablation: an alternative ablative method for gastric electrophysiological intervention

Pulsed-field ablation (PFA) is an emerging ablative technology that has been used successfully to eliminate cardiac arrhythmias. As a nonthermal technique, it has significant benefits over traditional radiofrequency ablation with improved target tissue specificity and reduced risk of adverse events during cardiac applications. We investigated whether PFA is safe for use in the stomach and whether it could modulate gastric slow waves. Female weaner pigs were fasted overnight before anesthesia was induced using tiletamine hydrochloride (50 mg·mL-1) and zolazepam hydrochloride (50 mg·mL-1) and maintained with propofol (Diprivan 2%, 0.2-0.4 mg·kg-1·min-1). Pulsed-field ablation was performed on their gastric serosa in vivo. Adjacent point lesions (n = 2-4) were used to create a linear injury using bipolar pulsed-field ablation consisting of 40 pulses (10 Hz frequency, 0.1 ms pulse width, 1,000 V amplitude). High-resolution electrical mapping defined baseline and postablation gastric slow-wave patterns. A validated five-point scale was used to evaluate tissue damage in hematoxylin and eosin-stained images. Results indicated that PFA successfully induced complete conduction blocks in all cases, with lesions through the entire thickness of the gastric muscle layers. Consistent postablation slow-wave patterns emerged immediately following ablation and persisted over the study period. Pulsed-field ablation induces rapid conduction blocks as a tool to modulate slow-wave patterns, indicating it may be suitable as an alternative to radiofrequency ablation.NEW & NOTEWORTHY Results show that pulsed-field ablation can serve as a gastric slow-wave intervention by preventing slow-wave propagation across the lesion site. Stable conduction blocks were established immediately following energy delivery, faster than previous examples of radiofrequency gastric ablation. Pulsed-field ablation may be an alternative for gastric slow-wave intervention, and further functional and posthealing studies are now warranted.

Meal effects on gastric bioelectrical activity utilizing body surface gastric mapping in healthy subjects

BACKGROUND

Gastric sensorimotor disorders are prevalent. While gastric emptying measurements are commonly used, they may not fully capture the underlying pathophysiology. Body surface gastric mapping (BSGM) recently emerged to assess gastric sensorimotor dysfunction. This study assessed varying meal size on BSGM responses to inform test use in a wider variety of contexts.

METHODS

Data from multiple healthy cohorts receiving BSGM were pooled, using four different test meals. A standard BSGM protocol was employed: 30-min fasting, 4-h post-prandial, using Gastric Alimetry® (Alimetry, New Zealand). Meals comprised: (i) nutrient drink + oatmeal bar (482 kcal; 'standard meal'); (ii) oatmeal bar alone; egg and toast meal, and pancake (all ~250 kcal). Gastric Alimetry metrics included BMI-adjusted Amplitude, Principal Gastric Frequency, Gastric Alimetry Rhythm Index (GA-RI) and Fed:Fasted Amplitude Ratio (ff-AR).

KEY RESULTS

238 participants (59.2% female) were included. All meals significantly increased amplitude and frequency during the first postprandial hour (p < 0.05). There were no differences in postprandial frequency across meals (p > 0.05). The amplitude and GA-RI of the standard meal (n = 110) were significantly higher than the energy bar alone (n = 45) and egg meal (n = 65) (all p < 0.05). All BSGM metrics were comparable across the three smaller meals (p > 0.05). A higher symptom burden was found in the oatmeal bar group versus the standard meal and pancake meal (p = 0.01, 0.003, respectively).

CONCLUSIONS & INFERENCES

The consumption of lower calorie meals elicited different postprandial responses, when compared to the standard Gastric Alimetry meal. These data will guide interpretations of BSGM when applied with lower calorie meals.

One More Tool in the Tool Belt: A Qualitative Interview Study Investigating Patient and Clinician Opinions on the Integration of Psychometrics Into Routine Testing for Disorders of Gut-Brain Interaction

Introduction Disorders of gut-brain interaction (DGBIs) encompass a common group of disorders characterised by chronic gastrointestinal symptoms. Psychological comorbidities are common in patients with DGBIs and are linked with poorer patient outcomes. Consequently, assessing and managing mental wellbeing may lead to improvements in symptoms and quality of life. Methods This study aimed to explore patients' and clinicians' opinions on integrating psychometrics into routine DGBI testing. Semi-structured interviews were conducted with 16 patients with gastroduodenal DGBI and 19 clinicians who see and treat these patients. Interviews were analysed using inductive, reflexive thematic analysis. Results Three key clinician themes were developed: (1) psychology as part of holistic care, emphasising the importance of a multidisciplinary approach; (2) the value of psychometrics in clinical practice, highlighting their potential for screening and expanding management; and (3) navigating barriers to utilising psychometrics, addressing the need for standardisation to maintain the therapeutic relationship. Four key patient themes were developed: (1) the utility of psychometrics in clinical care, reflecting the perceived benefits; (2) openness to psychological management, indicating patients' willingness to explore psychological treatments; (3) concerns with psychological integration, addressing potential stigma and fear of labelling; and (4) the significance of clinician factors, emphasising the importance of clinician bedside manner, knowledge and collaboration. Conclusions These themes demonstrate that patients and clinicians see value in integrating psychometrics into routine DGBI testing. Despite potential barriers, psychometrics advance patient and clinician understanding and facilitate multidisciplinary management. Recommendations for navigating challenges were provided, and considering these, patients and clinicians supported the use of psychometrics as screening tools for patients with DGBIs.

Development and validation of the Alimetry Gut-Brain Wellbeing Survey: a novel patient-reported mental health scale for patients with chronic gastroduodenal symptoms

Objective

There is currently a lack of validated questionnaires designed specifically to assess mental health within patients with chronic gastroduodenal symptoms. This research describes the multi-phase process used to develop and validate a novel mental health scale for patients with chronic gastroduodenal symptoms, the Alimetry® Gut-Brain Wellbeing (AGBW) Survey.

Methods

A patient-centered multi-phase process was implemented. In Phase 1, the most relevant concepts for this patient population were selected from existing mental health scales, using data from 79 patients. In Phase 2, an interdisciplinary panel of experts generated scale items. In Phase 3, the scale underwent pre-testing with gastroenterologists (n = 9), health psychologists (n = 3), and patients (n = 12), with feedback incorporated over multiple rounds. Lastly, the psychometric properties of the scale were assessed in a sample of 311 patients via an online survey.

Results

The AGBW Survey comprises a patient preface, 10 close-ended questions, and an optional open-ended question. This multidimensional scale assesses general mental health, alongside specific subscales relating to depression, stress, and anxiety. The subscale and total scores demonstrated high internal consistency (α = 0.91 for the total scale; α = 0.72-0.86 for subscales) and good convergent, divergent, concurrent validity, and known groups validity, with large effect sizes.

Conclusion

The AGBW Survey is a brief, valid, and reliable scale for assessing mental health in patients with chronic gastroduodenal symptoms. It can be used as a tool to complement physiological tests and has the potential to guide psychological referrals, inform multidisciplinary management, and evaluate treatment outcomes.

Effect of menstrual cycle and menopause on human gastric electrophysiology

Chronic gastroduodenal symptoms disproportionately affect females of childbearing age; however, the effect of menstrual cycling on gastric electrophysiology is poorly defined. To establish the effect of the menstrual cycle on gastric electrophysiology, healthy subjects underwent noninvasive Body Surface Gastric Mapping (BSGM; 8x8 array) with the validated symptom logging App (Gastric Alimetry, New Zealand). Participants included were premenopausal females in follicular (n = 26) and luteal phases (n = 18) and postmenopausal females (n = 30) and males (n = 51) were controls. Principal gastric frequency (PGF), body mass index (BMI) adjusted amplitude, Gastric Alimetry Rhythm Index (GA-RI), Fed:Fasted Amplitude Ratio (ff-AR), meal response curves, and symptom burden were analyzed. Menstrual cycle-related electrophysiological changes were then transferred to an established anatomically accurate computational gastric fluid dynamics model (meal viscosity 0.1 Pas) to predict the impact on gastric mixing and emptying. PGF was significantly higher in the luteal versus follicular phase [mean 3.21 cpm, SD (0.17) vs. 2.94 cpm, SD (0.17), P < 0.001] and versus males [3.01 cpm, SD (0.2), P < 0.001]. In the computational model, this translated to 8.1% higher gastric mixing strength and 5.3% faster gastric emptying for luteal versus follicular phases. Postmenopausal females also exhibited higher PGF than females in the follicular phase [3.10 cpm, SD (0.24) vs. 2.94 cpm, SD (0.17), P = 0.01], and higher BMI-adjusted amplitude [40.7 µV (33.02-52.58) vs. 29.6 µV (26.15-39.65), P < 0.001], GA-RI [0.60 (0.48-0.73) vs. 0.43 (0.30-0.60), P = 0.005], and ff-AR [2.51 (1.79-3.47) vs. 1.48 (1.21-2.17), P = 0.001] than males. There were no differences in symptoms. These results define variations in gastric electrophysiology with regard to human menstrual cycling and menopause.NEW & NOTEWORTHY This study evaluates gastric electrophysiology in relation to the menstrual cycle using a novel noninvasive high-resolution methodology, revealing substantial variations in gastric activity with menstrual cycling and menopause. Gastric slow-wave frequency is significantly higher in the luteal versus follicular menstrual phase. Computational modeling predicts that this difference translates to higher rates of gastric mixing and liquid emptying in the luteal phase, which is consistent with previous experimental data evaluating menstrual cycling effects on gastric emptying.

Gastric Alimetry® Testing and Healthcare Economic Analysis in Nausea and Vomiting Syndromes

BACKGROUND

Chronic nausea and vomiting syndromes (CNVS), gastroparesis and functional dyspepsia (FD) are complex disorders. Body Surface Gastric Mapping (BSGM), a new test of gastric function, using Gastric Alimetry® (Alimetry, New Zealand) may be useful for de-escalating healthcare utilisation. This study aimed to define healthcare costs and estimate health economic impacts of implementing this test in patients with chronic gastroduodenal symptoms.

METHODS

Consecutive patients at a tertiary referral centre evaluated with Gastric Alimetry were included. Frequency and cost data relating to medical investigations, hospital and outpatient presentations were evaluated. Costs of healthcare utilisation were calculated, and the potential cost savings of implementing Gastric Alimetry within a diagnostic decision-tree model were estimated.

RESULTS

Overall, 31 consecutive patients (mean age 36.1 years; 83.9% female; predominant symptoms: nausea [83.9%], pain [61.3%], vomiting [67.7%] and bloating [35.5%]) completed Gastric Alimetry testing. Repeat gastroscopy and abdominal CT rates were 29% (8/28) and 85% (11/13), respectively. Gastric Alimetry testing identified spectral abnormalities in 45.2% of patients, and symptom profiling classified a further 29.1% of patients. Median annualised cost difference after test introduction was NZ$-12,032. Estimated reductions in investigation-related costs when incorporating Gastric Alimetry into the diagnostic workflow model were approximately NZ$1,300 per patient.

CONCLUSIONS

Healthcare utilisation and confirmatory testing rates remain high in nausea and vomiting syndromes. This study presents real-world data, together with a decision-tree analysis, showing Gastric Alimetry can streamline clinical care pathways, resulting in reduced healthcare utilisation and cost.

Short- and long-term reproducibility of body surface gastric mapping using the Gastric Alimetry® system

BACKGROUND

Many diagnostic tests for gastroduodenal symptoms, such as gastric emptying scintigraphy (GES), gastric emptying breath tests (GEBT), and electrogastrography (EGG) show variable intra-individual reproducibility over time. This study investigated the short- and long-term reproducibility of body surface gastric mapping (BSGM), a non-invasive test for assessing gastric function, in controls and patients with chronic gastroduodenal disorders.

METHODS

Participants completed three standardized BSGM tests using Gastric Alimetry® (Alimetry, New Zealand). The test encompassed a fasting baseline (30 min), a 482 kCal standard meal, and a 4 h postprandial recording. The first two tests were >6 months apart and the last occurred ~1 week after the second test, to evaluate long and short-term reproducibility.

RESULTS

Fourteen patients with upper gastrointestinal symptoms and 14 healthy controls were recruited. There were no significant differences in any BSGM metrics between the tests at short and long term (all p > 0.180). Lin's concordance correlation coefficients (CCC) for the primary metrics were high, ranging from 0.58 to 0.96, with intra-individual coefficients of variance (CVintra) ranging from 0.2% to 1.9%. Reproducibility was higher, and intra-individual variation lower, than in previous studies of GES (CCC = 0.54-0.83, CVintra = 3%-77%), GEBT (CVintra = 8%-11%), and EGG (CVintra = 3%-78%).

CONCLUSIONS

BSGM spectral metrics demonstrate high reproducibility and low intra-individual variation at both short and long term, with superior results to comparable tests. The high reproducibility of Gastric Alimetry supports its role as a diagnostic aid for gastric dysfunction and a reliable tool for evaluating treatment outcomes and disease progression over time.

Electrogastrography measurement systems and analysis methods used in clinical practice and research: comprehensive review

Electrogastrography (EGG) is a non-invasive method with high diagnostic potential for the prevention of gastroenterological pathologies in clinical practice. In this study, a review of the measurement systems, procedures, and methods of analysis used in electrogastrography is presented. A critical review of historical and current literature is conducted, focusing on electrode placement, measurement apparatus, measurement procedures, and time-frequency domain methods of filtration and analysis of the non-invasively measured electrical activity of the stomach. As a result, 129 relevant articles with primary aim on experimental diet were reviewed in this study. Scopus, PubMed, and Web of Science databases were used to search for articles in English language, according to the specific query and using the PRISMA method. The research topic of electrogastrography has been continuously growing in popularity since the first measurement by professor Alvarez 100 years ago, and there are many researchers and companies interested in EGG nowadays. Measurement apparatus and procedures are still being developed in both commercial and research settings. There are plenty variable electrode layouts, ranging from minimal numbers of electrodes for ambulatory measurements to very high numbers of electrodes for spatial measurements. Most authors used in their research anatomically approximated layout with two++ active electrodes in bipolar connection and commercial electrogastrograph with sampling rate of 2 or 4 Hz. Test subjects were usually healthy adults and diet was controlled. However, evaluation methods are being developed at a slower pace, and usually the signals are classified only based on dominant frequency. The main review contributions include the overview of spectrum of measurement systems and procedures for electrogastrography developed by many authors, but a firm medical standard has not yet been defined. Therefore, it is not possible to use this method in clinical practice for objective diagnosis.

Systematic Review Registration

https://www.prisma-statement.org/.

The impact of heat-set milk protein gel textures modified by pH on circulating amino acid appearance and gastric function in healthy female adults: a randomised controlled trial

Modification of dairy proteins during processing impacts structural assemblies, influencing textural and nutritional properties of dairy products, and release and availability of amino acids during digestion. By modifying only pH, acid heat-set bovine dairy gels with divergent textural properties were developed to alter protein digestion. In vitro assay confirmed faster digestion of protein from a firm gel (pH 5.65) versus a soft gel (pH 6.55). We hypothesised that firm gel (FIRM-G; pH 5.6) would result in greater indispensable amino acid (IAA) appearance in circulation over 5 h and corresponding differences in gastric myoelectrical activity relative to soft gel (SOFT-G; pH 6.2). In a randomised, single-blind cross-over trial, healthy females (n = 20) consumed 150 g of each gel; plasma amino acid appearance was assessed over 5 hours. Iso-nitrogenous, iso-caloric gels were prepared from identical mixtures of bovine milk and whey protein concentrates; providing 17.7 g (FIRM-G) and 18.9 g (SOFT-G) of protein per serving. Secondary outcomes included gastric myoelectrical activity measured by body surface gastric mapping, glycaemic, triglyceridaemic, and subjective appetite and digestive responses. Overall plasma IAA (area under the curve) did not differ between gels. However, plasma IAA concentrations were higher, and increased more rapidly over time after SOFT-G compared with FIRM-G (1455 ± 53 versus 1350 ± 62 μmol L-1 at 30 min, p = 0.024). Similarly, total, branched-chain and dispensable amino acids were higher at 30 min with SOFT-G than FIRM-G (total: 3939 ± 97 versus 3702 ± 127 μmol L-1, p = 0.014; branched-chain: 677 ± 30 versus 619 ± 34 μmol L-1, p = 0.047; dispensable: 2334 ± 53 versus 2210 ± 76 μmol L-1, p = 0.032). All other measured parameters were similar between gels. Peak postprandial aminoacidaemia was higher and faster following ingestion of SOFT-G. Customised plasma amino acid appearance from dairy is achievable by altering gel coagulum structure using pH during processing and may have minimal influence on related postprandial responses, with implications for targeting food design for optimal health. The Clinical Trial Registry number is ACTRN12622001418763 (https://www.anzctr.org.au) registered November 7, 2022.

Effects of corticotropin-releasing hormone on gastric electrical activity and sensorimotor function in healthy volunteers: a double-blinded crossover study

Biopsychosocial factors are associated with disorders of gut-brain interaction (DGBI) and exacerbate gastrointestinal symptoms. The mechanisms underlying pathophysiological alterations of stress remain unclear. Corticotropin-releasing hormone (CRH) is a central regulator of the hormonal stress response and has diverse impact on different organ systems. The aim of the present study was to investigate the effects of peripheral CRH infusion on meal-related gastrointestinal symptoms, gastric electrical activity, and gastric sensorimotor function in healthy volunteers (HVs). In a randomized, double-blinded, placebo-controlled, crossover study, we evaluated the effects of CRH on gastric motility and sensitivity. HVs were randomized to receive either peripheral-administered CRH (100 µg bolus + 1 µg/kg/h) or placebo (saline), followed by at least a 7-day washout period and assignment to the opposite treatment. Tests encompassed saliva samples, gastric-emptying (GE) testing, body surface gastric mapping (BSGM, Gastric Alimetry; Alimetry) to assess gastric myoelectrical activity with real-time symptom profiling, and a gastric barostat study to assess gastric sensitivity to distention and accommodation. Twenty HVs [13 women, mean age 29.2 ± 5.3 yr, body mass index (BMI) 23.3 ± 3.8 kg/m2] completed GE tests, of which 18 also underwent BSGM measurements during the GE tests. The GE half-time decreased significantly after CRH exposure (65.2 ± 17.4 vs. 78.8 ± 24.5 min, P = 0.02) with significantly increased gastric amplitude [49.7 (34.7-55.6) vs. 31.7 (25.7-51.0) µV, P < 0.01], saliva cortisol levels, and postprandial symptom severity. Eleven HVs also underwent gastric barostat studies on a separate day. However, the thresholds for discomfort during isobaric distensions, gastric compliance, and accommodation did not differ between CRH and placebo.NEW & NOTEWORTHY In healthy volunteers, peripheral corticotropin-releasing hormone (CRH) infusion accelerates gastric-emptying rate and increases postprandial gastric response, accompanied by a rise in symptoms, but does not alter gastric sensitivity or meal-induced accommodation. These findings underscore a significant link between stress and dyspeptic symptoms, with CRH playing a pivotal role in mediating these effects.

Validation of body surface colonic mapping (BSCM) against high resolution colonic manometry for evaluation of colonic motility

Abnormal cyclic motor pattern (CMP) activity is implicated in colonic dysfunction, but the only tool to evaluate CMP activity, high-resolution colonic manometry (HRCM), remains expensive and not widely accessible. This study aimed to validate body surface colonic mapping (BSCM) through direct correlation with HRCM. Synchronous meal-test recordings were performed in asymptomatic participants with intact colons. A signal processing method for BSCM was developed to detect CMPs. Quantitative temporal analysis was performed comparing the meal responses and motility indices (MI). Spatial heat maps were also compared. Post-study questionnaires evaluated participants' preference and comfort/distress experienced from either test. 11 participants were recruited and 7 had successful synchronous recordings (5 females/2 males; median age: 50 years [range 38-63]). The best-correlating MI temporal analyses achieved a high degree of agreement (median Pearson correlation coefficient (Rp) value: 0.69; range 0.47-0.77). HRCM and BSCM meal response start and end times (Rp = 0.998 and 0.83; both p < 0.05) and durations (Rp = 0.85; p = 0.03) were similar. Heat maps demonstrated good spatial agreement. BSCM is the first non-invasive method to be validated by demonstrating a direct spatio-temporal correlation to manometry in evaluating colonic motility.

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

BACKGROUND

Despite evidence that slow-wave dysrhythmia in the stomach is associated with clinical conditions such as gastroparesis and functional dyspepsia, there is still no widely available device for long-term monitoring of gastric electrical signals. Actionable biomarkers of gastrointestinal health are critically needed, and an implantable slow-wave monitoring device could aid in the establishment of causal relationships between symptoms and gastric electrophysiology. Recent developments in the area of wireless implantable gastric monitors demonstrate potential, but additional work and validation are required before this potential can be realized.

METHODS

We hypothesized that translating an existing implantable cardiac monitoring device, the Reveal LINQ™ (Medtronic), would present a more immediate solution. Following ethical approval and laparotomy in anesthetized pigs (n = 7), a Reveal LINQ was placed on the serosal surface of the stomach, immediately adjacent to a validated flexible-printed-circuit (FPC) electrical mapping array. Data were recorded for periods of 7.5 min, and the resultant signal characteristics from the FPC array and Reveal LINQ were compared.

KEY RESULTS

The Reveal LINQ device recorded slow waves in 6/7 subjects with a comparable period (p = 0.69), signal-to-noise ratio (p = 0.58), and downstroke width (p = 0.98) to the FPC, but with reduced amplitude (p = 0.024). Qualitatively, the Reveal LINQ slow-wave signal lacked the prolonged repolarization phase present in the FPC signals.

CONCLUSIONS & INFERENCES

These findings suggest that existing cardiac monitors may offer an efficient solution for the long-term monitoring of slow waves. Translation toward implantation now awaits.

Gastric Alimetry Expands Patient Phenotyping in Gastroduodenal Disorders Compared with Gastric Emptying Scintigraphy

INTRODUCTION

Gastric emptying testing (GET) assesses gastric motility, however, is nonspecific and insensitive for neuromuscular disorders. Gastric Alimetry (GA) is a new medical device combining noninvasive gastric electrophysiological mapping and validated symptom profiling. This study assessed patient-specific phenotyping using GA compared with GET.

METHODS

Patients with chronic gastroduodenal symptoms underwent simultaneous GET and GA, comprising a 30-minute baseline, 99m TC-labelled egg meal, and 4-hour postprandial recording. Results were referenced to normative ranges. Symptoms were profiled in the validated GA App and phenotyped using rule-based criteria based on their relationships to the meal and gastric activity: (i) sensorimotor, (ii) continuous, and (iii) other.

RESULTS

Seventy-five patients were assessed, 77% female. Motility abnormality detection rates were as follows: GET 22.7% (14 delayed, 3 rapid), GA spectral analysis 33.3% (14 low rhythm stability/low amplitude, 5 high amplitude, and 6 abnormal frequency), and combined yield 42.7%. In patients with normal spectral analysis, GA symptom phenotypes included sensorimotor 17% (where symptoms strongly paired with gastric amplitude, median r = 0.61), continuous 30%, and other 53%. GA phenotypes showed superior correlations with Gastroparesis Cardinal Symptom Index, Patient Assessment of Upper Gastrointestinal Symptom Severity Index, and anxiety scales, whereas Rome IV Criteria did not correlate with psychometric scores ( P > 0.05). Delayed emptying was not predictive of specific GA phenotypes.

DISCUSSION

GA improves patient phenotyping in chronic gastroduodenal disorders in the presence and absence of motility abnormalities with increased correlation with symptoms and psychometrics compared with gastric emptying status and Rome IV criteria. These findings have implications for the diagnostic profiling and personalized management of gastroduodenal disorders.

Exploring the Gut-Brain Connection in Gastroparesis With Autonomic and Gastric Myoelectric Monitoring

OBJECTIVE

The goal of this study was to identify autonomic and gastric myoelectric biomarkers from throughout the day that differentiate patients with gastroparesis, diabetics without gastroparesis, and healthy controls, while providing insight into etiology.

METHODS

We collected 19 24-hour recordings of electrocardiogram (ECG) and electrogastrogram (EGG) data from healthy controls and patients with diabetic or idiopathic gastroparesis. We used physiologically and statistically rigorous models to extract autonomic and gastric myoelectric information from the ECG and EGG data, respectively. From these, we constructed quantitative indices which differentiated the distinct groups and demonstrated their application in automatic classification paradigms and as quantitative summary scores.

RESULTS

We identified several differentiators that separate healthy controls from gastroparetic patient groups, specifically around sleep and meals. We also demonstrated the downstream utility of these differentiators in automatic classification and quantitative scoring paradigms. Even with this small pilot dataset, automated classifiers achieved an accuracy of 79% separating autonomic phenotypes and 65% separating gastrointestinal phenotypes. We also achieved 89% accuracy separating controls from gastroparetic patients in general and 90% accuracy separating diabetics with and without gastroparesis. These differentiators also suggested varying etiologies for different phenotypes.

CONCLUSION

The differentiators we identified were able to successfully distinguish between several autonomic and gastrointestinal (GI) phenotypes using data collected while at-home with non-invasive sensors.

SIGNIFICANCE

Autonomic and gastric myoelectric differentiators, obtained using at-home recording of fully non-invasive signals, can be the first step towards dynamic quantitative markers to track severity, disease progression, and treatment response for combined autonomic and GI phenotypes.

Longitudinal outcome monitoring in patients with chronic gastroduodenal symptoms investigated using the Gastric Alimetry system: study protocol

INTRODUCTION

The Gastric Alimetry platform offers a multimodal assessment of gastric function through body surface gastric mapping (BSGM) and concurrent symptom-tracking via a validated App. We aim to perform a longitudinal cohort study to examine the impact of Gastric Alimetry, and changes in clinical management on patient symptoms, quality of life and psychological health.

METHODS AND ANALYSIS

This is a prospective multicentre longitudinal observational cohort study of participants with chronic gastroduodenal symptoms. Consecutive participants undergoing Gastric Alimetry will be invited to participate. Quality of life will be assessed via EuroQol-5D and the Patient Assessment of Upper Gastrointestinal Disorders-Quality of Life score. Gastrointestinal symptoms will be assessed via the Patient Assessment of Upper Gastrointestinal Symptom Severity index, and the Gastroparesis Cardinal Symptom Index. Psychometrics will be assessed, including anxiety via the General Anxiety Disorder-7, perceived stress using the Perceived Stress Scale 4, and depression via the Patient Health Questionnaire 9. Clinical parameters including diagnoses, investigations and treatments (medication and procedures) will also be captured. Assessments will be made the week after the BSGM test, at 30 days, 90 days, 180 days and 360 days thereafter. The primary outcome is feasibility of longitudinal follow-up of a cohort that have undergone Gastric Alimetry testing; from which patients' continuum of care can be characterised. Secondary outcomes include changes in patient-reported symptoms, quality of life and psychometrics (anxiety, stress and depression). Inferential causal analyses will be performed at the within patient level to explore causal associations between treatment changes and clinical outcomes. The impact of Gastric Alimetry on clinical management will also be captured.

ETHICS AND DISSEMINATION

The protocol has been approved in Aotearoa New Zealand by the Auckland Health Research Ethics Committee. Results will be submitted for conference presentation and peer-reviewed publication.

Abnormal gastrointestinal motility is a major factor in explaining symptoms and a potential therapeutic target in patients with disorders of gut-brain interaction

The objective of this article is to review the evidence of abnormal gastrointestinal (GI) tract motor functions in the context of disorders of gut-brain interaction (DGBI). These include abnormalities of oesophageal motility, gastric emptying, gastric accommodation, colonic transit, colonic motility, colonic volume and rectal evacuation. For each section regarding GI motor dysfunction, the article describes the preferred methods and the documented motor dysfunctions in DGBI based on those methods. The predominantly non-invasive measurements of gut motility as well as therapeutic interventions directed to abnormalities of motility suggest that such measurements are to be considered in patients with DGBI not responding to first-line approaches to behavioural or empirical dietary or pharmacological treatment.

Gastric Alimetry in the Management of Chronic Gastroduodenal Disorders: Impact to Diagnosis and Health Care Utilization

INTRODUCTION

Chronic gastroduodenal symptoms are frequently overlapping within existing diagnostic paradigms, and current diagnostic tests are insensitive to underlying pathophysiologies. Gastric Alimetry has emerged as a new diagnostic test of gastric neuromuscular function with time-of-test symptom profiling. This study aimed to assess the impact to diagnosis and health care utilization after the introduction of Gastric Alimetry into clinical care.

METHODS

Consecutive data of patients from 2 tertiary centers with chronic gastroduodenal symptoms (Rome-IV defined or motility disorder) having integrated care and Gastric Alimetry testing were evaluated. Changes in diagnoses, interventions, and management were quantified. Pretest and posttest health care utilization was reported. A preliminary management framework was established through experiential learning.

RESULTS

Fifty participants (45 women; median age 30 years; 18 with gastroparesis, 24 with chronic nausea and vomiting syndrome, and 6 with functional dyspepsia) underwent Gastric Alimetry testing. One-third of patients had a spectral abnormality (18% dysrhythmic/low amplitude). Of the remaining patients, 9 had symptoms correlating to gastric amplitude, while 19 had symptoms unrelated to gastric activity. Gastric Alimetry aided management decisions in 84%, including changes in invasive nutritional support in 9/50 cases (18%; predominantly de-escalation). Health care utilization was significantly lower post-Gastric Alimetry testing when compared with the average utilization cost in the year before Gastric Alimetry testing (mean ± SD $39,724 ± 63,566 vs $19,937 ± 35,895, P = 0.037).

DISCUSSION

Gastric Alimetry aided diagnosis and management of patients with chronic gastroduodenal symptoms by enabling phenotype-informed care. The high majority of results aided management decisions, which was associated with reduced health care utilization.

Gastric Alimetry® Test Interpretation in Gastroduodenal Disorders: Review and Recommendations

Chronic gastroduodenal symptoms are prevalent worldwide, and there is a need for new diagnostic and treatment approaches. Several overlapping processes may contribute to these symptoms, including gastric dysmotility, hypersensitivity, gut-brain axis disorders, gastric outflow resistance, and duodenal inflammation. Gastric Alimetry® (Alimetry, New Zealand) is a non-invasive test for evaluating gastric function that combines body surface gastric mapping (high-resolution electrophysiology) with validated symptom profiling. Together, these complementary data streams enable important new clinical insights into gastric disorders and their symptom correlations, with emerging therapeutic implications. A comprehensive database has been established, currently comprising > 2000 Gastric Alimetry tests, including both controls and patients with various gastroduodenal disorders. From studies employing this database, this paper presents a systematic methodology for Gastric Alimetry test interpretation, together with an extensive supporting literature review. Reporting is grouped into four sections: Test Quality, Spectral Analysis, Symptoms, and Conclusions. This review compiles, assesses, and evaluates each of these aspects of test assessment, with discussion of relevant evidence, example cases, limitations, and areas for future work. The resultant interpretation methodology is recommended for use in clinical practice and research to assist clinicians in their use of Gastric Alimetry as a diagnostic aid and is expected to continue to evolve with further development.