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Lim AH, Varghese C, Sebaratnam GH, Schamberg G, Calder S, Gharibans AA, Andrews CN, Foong D, Ho V, Ishida S, Imai Y, Wise MR, O'Grady G. Effect of menstrual cycle and menopause on human gastric electrophysiology. Am J Physiol Gastrointest Liver Physiol 2024; 327:G47-G56. [PMID: 38713629 PMCID: PMC11211038 DOI: 10.1152/ajpgi.00216.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/27/2023] [Revised: 04/22/2024] [Accepted: 04/23/2024] [Indexed: 05/09/2024]
Abstract
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.
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Affiliation(s)
- Alexandria H Lim
- Department of Surgery, The University of Auckland, Auckland, New Zealand
| | - Chris Varghese
- Department of Surgery, The University of Auckland, Auckland, New Zealand
| | | | - Gabriel Schamberg
- Department of Surgery, The University of Auckland, Auckland, New Zealand
- Alimetry, Ltd., Auckland, New Zealand
| | - Stefan Calder
- Department of Surgery, The University of Auckland, Auckland, New Zealand
- Alimetry, Ltd., Auckland, New Zealand
| | - Armen A Gharibans
- Department of Surgery, The University of Auckland, Auckland, New Zealand
- Alimetry, Ltd., Auckland, New Zealand
| | | | - Daphne Foong
- School of Medicine, Western Sydney University, Sydney, New South Wales, Australia
| | - Vincent Ho
- School of Medicine, Western Sydney University, Sydney, New South Wales, Australia
| | - Shunichi Ishida
- Graduate School of Engineering, Kobe University, Kobe, Japan
| | - Yohsuke Imai
- Graduate School of Engineering, Kobe University, Kobe, Japan
| | - Michelle R Wise
- Department of Obstetrics and Gynaecology, The University of Auckland, Auckland, New Zealand
| | - Greg O'Grady
- Department of Surgery, The University of Auckland, Auckland, New Zealand
- Alimetry, Ltd., Auckland, New Zealand
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Law M, Schamberg G, Gharibans A, Sebaratnam G, Foong D, Varghese C, Fitt I, Daker C, Ho V, Du P, Andrews CN, O'Grady G, Calder S. Short- and long-term reproducibility of body surface gastric mapping using the Gastric Alimetry® system. Neurogastroenterol Motil 2024; 36:e14812. [PMID: 38689428 DOI: 10.1111/nmo.14812] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/23/2023] [Revised: 04/03/2024] [Accepted: 04/15/2024] [Indexed: 05/02/2024]
Abstract
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.
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Affiliation(s)
- Mikaela Law
- The Department of Surgery, The University of Auckland, Auckland, New Zealand
- Alimetry Ltd., Auckland, New Zealand
| | - Gabriel Schamberg
- The Department of Surgery, The University of Auckland, Auckland, New Zealand
- Alimetry Ltd., Auckland, New Zealand
| | - Armen Gharibans
- The Department of Surgery, The University of Auckland, Auckland, New Zealand
- Alimetry Ltd., Auckland, New Zealand
- Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | | | - Daphne Foong
- Alimetry Ltd., Auckland, New Zealand
- School of Medicine, Western Sydney University, Sydney, New South Wales, Australia
| | - Chris Varghese
- The Department of Surgery, The University of Auckland, Auckland, New Zealand
| | - India Fitt
- The Department of Surgery, The University of Auckland, Auckland, New Zealand
| | - Charlotte Daker
- Alimetry Ltd., Auckland, New Zealand
- Department of Gastroenterology, Te Whatu Ora-Waitematā, Auckland, New Zealand
| | - Vincent Ho
- School of Medicine, Western Sydney University, Sydney, New South Wales, Australia
- Department of Gastroenterology and Hepatology, Campbelltown Hospital, Campbelltown, New South Wales, Australia
| | - Peng Du
- Alimetry Ltd., Auckland, New Zealand
- Auckland Bioengineering Institute, The University of Auckland, Auckland, New Zealand
| | - Christopher N Andrews
- Alimetry Ltd., Auckland, New Zealand
- Division of Gastroenterology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Greg O'Grady
- The Department of Surgery, The University of Auckland, Auckland, New Zealand
- Alimetry Ltd., Auckland, New Zealand
| | - Stefan Calder
- The Department of Surgery, The University of Auckland, Auckland, New Zealand
- Alimetry Ltd., Auckland, New Zealand
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Prats-Boluda G, Martinez-de-Juan JL, Nieto-Del-Amor F, Termenon M, Varón C, Ye-Lin Y. Vectorgastrogram: dynamic trajectory and recurrence quantification analysis to assess slow wave vector movement in healthy subjects. Phys Eng Sci Med 2024; 47:663-677. [PMID: 38436885 PMCID: PMC11166836 DOI: 10.1007/s13246-024-01396-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2023] [Accepted: 01/21/2024] [Indexed: 03/05/2024]
Abstract
Functional gastric disorders entail chronic or recurrent symptoms, high prevalence and a significant financial burden. These disorders do not always involve structural abnormalities and since they cannot be diagnosed by routine procedures, electrogastrography (EGG) has been proposed as a diagnostic alternative. However, the method still has not been transferred to clinical practice due to the difficulty of identifying gastric activity because of the low-frequency interference caused by skin-electrode contact potential in obtaining spatiotemporal information by simple procedures. This work attempted to robustly identify the gastric slow wave (SW) main components by applying multivariate variational mode decomposition (MVMD) to the multichannel EGG. Another aim was to obtain the 2D SW vectorgastrogram VGGSW from 4 electrodes perpendicularly arranged in a T-shape and analyse its dynamic trajectory and recurrence quantification (RQA) to assess slow wave vector movement in healthy subjects. The results revealed that MVMD can reliably identify the gastric SW, with detection rates over 91% in fasting postprandial subjects and a frequency instability of less than 5.3%, statistically increasing its amplitude and frequency after ingestion. The VGGSW dynamic trajectory showed a statistically higher predominance of vertical displacement after ingestion. RQA metrics (recurrence ratio, average length, entropy, and trapping time) showed a postprandial statistical increase, suggesting that gastric SW became more intense and coordinated with a less complex VGGSW and higher periodicity. The results support the VGGSW as a simple technique that can provide relevant information on the "global" spatial pattern of gastric slow wave propagation that could help diagnose gastric pathologies.
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Affiliation(s)
- Gema Prats-Boluda
- Centro de Investigación e Innovación en Bioingeniería (CI2B), Universitat Politècnica de València (UPV), Valencia, Spain.
| | - Jose L Martinez-de-Juan
- Centro de Investigación e Innovación en Bioingeniería (CI2B), Universitat Politècnica de València (UPV), Valencia, Spain
| | - Felix Nieto-Del-Amor
- Centro de Investigación e Innovación en Bioingeniería (CI2B), Universitat Politècnica de València (UPV), Valencia, Spain
| | - María Termenon
- Centro de Investigación e Innovación en Bioingeniería (CI2B), Universitat Politècnica de València (UPV), Valencia, Spain
| | - Cristina Varón
- Centro de Investigación e Innovación en Bioingeniería (CI2B), Universitat Politècnica de València (UPV), Valencia, Spain
| | - Yiyao Ye-Lin
- Centro de Investigación e Innovación en Bioingeniería (CI2B), Universitat Politècnica de València (UPV), Valencia, Spain
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Milan AM, Menting GGA, Barnett MPG, Liu Y, McNabb WC, Roy NC, Hutchings SC, Mungure T, Weeks M, Li S, Hort J, Calder S, O'Grady G, Mithen RF. 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. Food Funct 2024; 15:5613-5626. [PMID: 38722062 DOI: 10.1039/d3fo04474b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/21/2024]
Abstract
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.
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Affiliation(s)
- Amber M Milan
- The Liggins Institute, The University of Auckland, Auckland, New Zealand.
- AgResearch Limited, Palmerston North, New Zealand.
- The High-Value Nutrition National Science Challenge, Auckland, New Zealand
| | | | - Matthew P G Barnett
- AgResearch Limited, Palmerston North, New Zealand.
- The Riddet Institute, Palmerston North, New Zealand.
| | - Yutong Liu
- The Liggins Institute, The University of Auckland, Auckland, New Zealand.
| | - Warren C McNabb
- The High-Value Nutrition National Science Challenge, Auckland, New Zealand
- The Riddet Institute, Palmerston North, New Zealand.
| | - Nicole C Roy
- The High-Value Nutrition National Science Challenge, Auckland, New Zealand
- The Riddet Institute, Palmerston North, New Zealand.
- Department of Human Nutrition, The University of Otago, Otago, New Zealand.
| | | | - Tanyaradzwa Mungure
- AgResearch Limited, Palmerston North, New Zealand.
- The University of Melbourne, Melbourne, Australia.
| | - Mike Weeks
- AgResearch Limited, Palmerston North, New Zealand.
| | - Siqi Li
- The Riddet Institute, Palmerston North, New Zealand.
| | - Joanne Hort
- The Riddet Institute, Palmerston North, New Zealand.
- Food Experience and Sensory Testing Lab, Massey University, Palmerston North, New Zealand.
| | - Stefan Calder
- Department of Surgery, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand.
- Auckland Bioengineering Institute, The University of Auckland, Auckland, New Zealand
| | - Greg O'Grady
- Department of Surgery, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand.
- Auckland Bioengineering Institute, The University of Auckland, Auckland, New Zealand
| | - Richard F Mithen
- The Liggins Institute, The University of Auckland, Auckland, New Zealand.
- The High-Value Nutrition National Science Challenge, Auckland, New Zealand
- The Riddet Institute, Palmerston North, New Zealand.
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5
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Huang IH, Calder S, Gharibans AA, Schamberg G, Varghese C, Andrews CN, Tack J, O'Grady G. Meal effects on gastric bioelectrical activity utilizing body surface gastric mapping in healthy subjects. Neurogastroenterol Motil 2024:e14823. [PMID: 38764250 DOI: 10.1111/nmo.14823] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/31/2023] [Revised: 05/01/2024] [Accepted: 05/09/2024] [Indexed: 05/21/2024]
Abstract
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.
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Affiliation(s)
- I-Hsuan Huang
- Translational Research Center for Gastrointestinal Disorders, University of Leuven, Leuven, Belgium
- Department of Gastroenterology and Hepatology, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan
| | - Stefan Calder
- Alimetry Ltd, Auckland, New Zealand
- Department of Surgery, University of Auckland, Auckland, New Zealand
| | - Armen A Gharibans
- Alimetry Ltd, Auckland, New Zealand
- Department of Surgery, University of Auckland, Auckland, New Zealand
| | - Gabriel Schamberg
- Alimetry Ltd, Auckland, New Zealand
- Department of Surgery, University of Auckland, Auckland, New Zealand
| | - Chris Varghese
- Department of Surgery, University of Auckland, Auckland, New Zealand
| | - Christopher N Andrews
- Alimetry Ltd, Auckland, New Zealand
- Division of Gastroenterology, Cumming School of Medicine, University of Calgary, Calgary, Canada
| | - Jan Tack
- Translational Research Center for Gastrointestinal Disorders, University of Leuven, Leuven, Belgium
| | - Greg O'Grady
- Alimetry Ltd, Auckland, New Zealand
- Department of Surgery, University of Auckland, Auckland, New Zealand
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Huang IH, Schol J, Calder S, Gharibans AA, Van den Houte K, Verheyden A, Broeders B, Carbone F, O'Grady G, Tack J. Effects of corticotropin-releasing hormone on gastric electrical activity and sensorimotor function in healthy volunteers: a double-blinded crossover study. Am J Physiol Gastrointest Liver Physiol 2024; 326:G622-G630. [PMID: 38375576 DOI: 10.1152/ajpgi.00298.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/12/2023] [Revised: 02/06/2024] [Accepted: 02/15/2024] [Indexed: 02/21/2024]
Abstract
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.
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Affiliation(s)
- I-Hsuan Huang
- Translational Research Center for Gastrointestinal Disorders, University of Leuven, Leuven, Belgium
- Department of Gastroenterology and Hepatology, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan
| | - Jolien Schol
- Translational Research Center for Gastrointestinal Disorders, University of Leuven, Leuven, Belgium
| | | | | | - Karen Van den Houte
- Translational Research Center for Gastrointestinal Disorders, University of Leuven, Leuven, Belgium
| | - Annelies Verheyden
- Translational Research Center for Gastrointestinal Disorders, University of Leuven, Leuven, Belgium
| | - Bert Broeders
- Translational Research Center for Gastrointestinal Disorders, University of Leuven, Leuven, Belgium
| | - Florencia Carbone
- Translational Research Center for Gastrointestinal Disorders, University of Leuven, Leuven, Belgium
| | - Greg O'Grady
- Alimetry, Ltd., Auckland, New Zealand
- Surgical and Translational Research Centre, The University of Auckland, Auckland, New Zealand
| | - Jan Tack
- Translational Research Center for Gastrointestinal Disorders, University of Leuven, Leuven, Belgium
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7
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Xu W, Williams L, Sebaratnam G, Varghese C, Cedarwall C, Daker C, Keane C. Gastric Alimetry® Testing and Healthcare Economic Analysis in Nausea and Vomiting Syndromes. Dig Dis Sci 2024:10.1007/s10620-024-08455-0. [PMID: 38689198 DOI: 10.1007/s10620-024-08455-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/08/2023] [Accepted: 04/17/2024] [Indexed: 05/02/2024]
Abstract
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.
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Affiliation(s)
- William Xu
- The University of Auckland, Auckland, New Zealand
- Te Tai Tokerau District, Te Whatu Ora, Whangarei, New Zealand
- Department of Surgery, University of Auckland, Auckland, New Zealand
| | | | | | - Chris Varghese
- The University of Auckland, Auckland, New Zealand
- Counties Manukau District, Te Whatu Ora, Whangarei, New Zealand
- Department of Surgery, University of Auckland, Auckland, New Zealand
| | - Chris Cedarwall
- Capital and Coast District, Te Whatu Ora, Whangarei, New Zealand
| | | | - Celia Keane
- Te Tai Tokerau District, Te Whatu Ora, Whangarei, New Zealand.
- Department of Surgery, University of Auckland, Auckland, New Zealand.
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8
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Xu W, Wang T, Foong D, Schamberg G, Evennett N, Beban G, Gharibans A, Calder S, Daker C, Ho V, O'Grady G. Characterization of gastric dysfunction after fundoplication using body surface gastric mapping. J Gastrointest Surg 2024; 28:236-245. [PMID: 38445915 DOI: 10.1016/j.gassur.2023.12.023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/23/2023] [Revised: 12/09/2023] [Accepted: 12/22/2023] [Indexed: 03/07/2024]
Abstract
BACKGROUND Adverse gastric symptoms persist in up to 20% of fundoplication operations completed for gastroesophageal reflux disease, causing significant morbidity and driving the need for revisional procedures. Noninvasive techniques to assess the mechanisms of persistent postoperative symptoms are lacking. This study aimed to investigate gastric myoelectrical abnormalities and symptoms in patients after fundoplication using a novel noninvasive body surface gastric mapping (BSGM) device. METHODS Patients with a previous fundoplication operation and ongoing significant gastroduodenal symptoms and matched controls were included. BSGM using Gastric Alimetry (Alimetry Ltd) was employed, consisting of a high-resolution 64-channel array, validated symptom-logging application, and wearable reader. RESULTS A total of 16 patients with significant chronic symptoms after fundoplication were recruited, with 16 matched controls. Overall, 6 of 16 patients (37.5%) showed significant spectral abnormalities defined by unstable gastric myoelectrical activity (n = 2), abnormally high gastric frequencies (n = 3), or high gastric amplitudes (n = 1). Patients with spectral abnormalities had higher Patient Assessment of Upper Gastrointestinal Disorders-Symptom Severity Index scores than those of patients without spectral abnormalities (3.2 [range, 2.8-3.6] vs 2.3 [range, 2.2-2.8], respectively; P = .024). Moreover, 7 of 16 patients (43.8%) had BSGM test results suggestive of gut-brain axis contributions and without myoelectrical dysfunction. Increasing Principal Gastric Frequency Deviation and decreasing Rhythm Index scores were associated with symptom severity (r > .40; P < .05). CONCLUSION A significant number of patients with persistent postfundoplication symptoms displayed abnormal gastric function on BSGM testing, which correlated with symptom severity. Our findings advance the pathophysiologic understanding of postfundoplication disorders, which may inform diagnosis and patient selection for medical therapy and revisional procedures.
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Affiliation(s)
- William Xu
- Department of Surgery, University of Auckland, Auckland, New Zealand
| | - Tim Wang
- Department of Surgery, University of Auckland, Auckland, New Zealand
| | - Daphne Foong
- Alimetry Ltd, Auckland, New Zealand; School of Medicine, Western Sydney University, Penrith, Australia
| | - Gabe Schamberg
- Department of Surgery, University of Auckland, Auckland, New Zealand; Alimetry Ltd, Auckland, New Zealand
| | - Nicholas Evennett
- Department of Surgery, University of Auckland, Auckland, New Zealand
| | - Grant Beban
- Department of Surgery, University of Auckland, Auckland, New Zealand
| | - Armen Gharibans
- Alimetry Ltd, Auckland, New Zealand; Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand; Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States
| | - Stefan Calder
- Alimetry Ltd, Auckland, New Zealand; Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
| | - Charlotte Daker
- Alimetry Ltd, Auckland, New Zealand; Department of Gastroenterology, North Shore Hospital, Auckland, New Zealand
| | - Vincent Ho
- School of Medicine, Western Sydney University, Penrith, Australia; Department of Gastroenterology and Hepatology, Campbelltown Hospital, Campbelltown, Australia
| | - Greg O'Grady
- Department of Surgery, University of Auckland, Auckland, New Zealand; Alimetry Ltd, Auckland, New Zealand; Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand.
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9
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Seo SHB, Wells CI, Dickson T, Rowbotham D, Gharibans A, Calder S, Bissett I, O'Grady G, Erickson JC. Validation of body surface colonic mapping (BSCM) against high resolution colonic manometry for evaluation of colonic motility. Sci Rep 2024; 14:4842. [PMID: 38418514 PMCID: PMC10902299 DOI: 10.1038/s41598-024-54429-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2023] [Accepted: 02/13/2024] [Indexed: 03/01/2024] Open
Abstract
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.
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Affiliation(s)
- Sean H B Seo
- Department of Surgery, The University of Auckland, Auckland, New Zealand
| | - Cameron I Wells
- Department of Surgery, The University of Auckland, Auckland, New Zealand
- Department of Surgery, Auckland District Health Board, Auckland, New Zealand
| | - Tully Dickson
- Department of Surgery, The University of Auckland, Auckland, New Zealand
| | - David Rowbotham
- Department of Gastroenterology, Auckland City Hospital, Te Whatu Ora Health New Zealand, Auckland, New Zealand
| | - Armen Gharibans
- Alimetry Ltd, Auckland, New Zealand
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
| | - Stefan Calder
- Alimetry Ltd, Auckland, New Zealand
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
| | - Ian Bissett
- Department of Surgery, The University of Auckland, Auckland, New Zealand
- Department of Surgery, Auckland District Health Board, Auckland, New Zealand
| | - Greg O'Grady
- Department of Surgery, The University of Auckland, Auckland, New Zealand
- Alimetry Ltd, Auckland, New Zealand
| | - Jonathan C Erickson
- Alimetry Ltd, Auckland, New Zealand.
- Department of Physics and Engineering, Washington and Lee University, Lexington, USA.
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Zhang P, Zhu B, Du P, Travas-Sejdic J. Electrochemical and Electrical Biosensors for Wearable and Implantable Electronics Based on Conducting Polymers and Carbon-Based Materials. Chem Rev 2024; 124:722-767. [PMID: 38157565 DOI: 10.1021/acs.chemrev.3c00392] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2024]
Abstract
Bioelectronic devices are designed to translate biological information into electrical signals and vice versa, thereby bridging the gap between the living biological world and electronic systems. Among different types of bioelectronics devices, wearable and implantable biosensors are particularly important as they offer access to the physiological and biochemical activities of tissues and organs, which is significant in diagnosing and researching various medical conditions. Organic conducting and semiconducting materials, including conducting polymers (CPs) and graphene and carbon nanotubes (CNTs), are some of the most promising candidates for wearable and implantable biosensors. Their unique electrical, electrochemical, and mechanical properties bring new possibilities to bioelectronics that could not be realized by utilizing metals- or silicon-based analogues. The use of organic- and carbon-based conductors in the development of wearable and implantable biosensors has emerged as a rapidly growing research field, with remarkable progress being made in recent years. The use of such materials addresses the issue of mismatched properties between biological tissues and electronic devices, as well as the improvement in the accuracy and fidelity of the transferred information. In this review, we highlight the most recent advances in this field and provide insights into organic and carbon-based (semi)conducting materials' properties and relate these to their applications in wearable/implantable biosensors. We also provide a perspective on the promising potential and exciting future developments of wearable/implantable biosensors.
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Affiliation(s)
- Peikai Zhang
- Centre for Innovative Materials for Health, School of Chemical Sciences, The University of Auckland, Auckland 1010, New Zealand
- MacDiarmid Institute for Advanced Materials and Nanotechnology, Victoria University of Wellington, Wellington 6012, New Zealand
- Auckland Bioengineering Institute, The University of Auckland, Auckland 1010, New Zealand
| | - Bicheng Zhu
- Centre for Innovative Materials for Health, School of Chemical Sciences, The University of Auckland, Auckland 1010, New Zealand
- MacDiarmid Institute for Advanced Materials and Nanotechnology, Victoria University of Wellington, Wellington 6012, New Zealand
| | - Peng Du
- Auckland Bioengineering Institute, The University of Auckland, Auckland 1010, New Zealand
| | - Jadranka Travas-Sejdic
- Centre for Innovative Materials for Health, School of Chemical Sciences, The University of Auckland, Auckland 1010, New Zealand
- MacDiarmid Institute for Advanced Materials and Nanotechnology, Victoria University of Wellington, Wellington 6012, New Zealand
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Du P, Maharjan A, Calder S, Schultz M, Schamberg G, Gharibans A, O'Grady G, Cakmak YO. Transcutaneous Auricular Vagus Nerve Stimulation Normalizes Induced Gastric Myoelectrical Dysrhythmias in Controls Assessed by Body-Surface Gastric Mapping. Neuromodulation 2024; 27:333-342. [PMID: 36997454 DOI: 10.1016/j.neurom.2023.02.078] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2022] [Revised: 01/24/2023] [Accepted: 02/13/2023] [Indexed: 03/31/2023]
Abstract
OBJECTIVES Transcutaneous auricular vagus nerve stimulation (TaVNS) is a supplementary treatment for gastric symptoms resulting from dysrhythmias. The main objective of this study was to quantify the effects of 10, 40, and 80 Hz TaVNS and sham in healthy individuals in response to a 5-minute water-load (WL5) test. MATERIALS AND METHODS Eighteen healthy volunteers aged between 21 and 55 years (body mass index: 27.1 ± 3.2) were recruited. Each subject fasted for up to eight hours and participated in four 95-minute sessions, which consisted of 30 fasted baseline, 30 minutes TaVNS, WL5, and 30 minutes post-WL5. Heart rate variability was assessed using sternal electrocardiogram. Body-surface gastric mapping and bloating (/10) were recorded. One-way ANOVA with post hoc Tukey test was performed to test the difference between TaVNS protocols in terms of frequency, amplitude, bloating scores, root mean square of the successive differences (RMSSD), and stress index (SI). RESULTS On average, the subjects consumed 526 ± 160 mL of water, with volume ingested correlated to bloating (mean score 4.1 ± 1.8; r = 0.36, p = 0.029). In general, the reduction in frequency and rhythm stability during the post-WL5 period in sham was normalized by all three TaVNS protocols. Both 40- and 80-Hz protocols also caused increases in amplitude during the stim-only and/or post-WL5 periods. RMSSD increased during the 40-Hz protocol. SI increased during the 10-Hz protocol but decreased during the 40- and 80-Hz protocols. CONCLUSION TaVNS proved effective in normalizing gastric dysrhythmias by WL5 in healthy subjects by altering both parasympathetic and sympathetic pathways.
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Affiliation(s)
- Peng Du
- Auckland Bioengineering Institute, The University of Auckland, Auckland, New Zealand
| | - Ashim Maharjan
- Department of Anatomy, University of Otago, Dunedin, New Zealand
| | - Stefan Calder
- Department of Surgery, The University of Auckland, Auckland, New Zealand; Alimetry Ltd, Auckland, New Zealand
| | - Michael Schultz
- Department of Medicine, University of Otago, Dunedin, New Zealand
| | | | - Armen Gharibans
- Department of Surgery, The University of Auckland, Auckland, New Zealand; Alimetry Ltd, Auckland, New Zealand
| | - Gregory O'Grady
- Department of Surgery, The University of Auckland, Auckland, New Zealand; Alimetry Ltd, Auckland, New Zealand
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12
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Wang WJ, Foong D, Calder S, Schamberg G, Varghese C, Tack J, Xu W, Daker C, Carson D, Waite S, Hayes T, Du P, Abell TL, Parkman HP, Huang IH, Fernandes V, Andrews CN, Gharibans AA, Ho V, O’Grady G. Gastric Alimetry Expands Patient Phenotyping in Gastroduodenal Disorders Compared with Gastric Emptying Scintigraphy. Am J Gastroenterol 2024; 119:331-341. [PMID: 37782524 PMCID: PMC10872929 DOI: 10.14309/ajg.0000000000002528] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/05/2023] [Accepted: 08/04/2023] [Indexed: 10/03/2023]
Abstract
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.
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Affiliation(s)
- William Jiaen Wang
- Gastrointestinal Motility Disorders Unit, Western Sydney University, Australia
- Department of Gastroenterology and Hepatology, Campbelltown Hospital, Australia
- Gastroenterology and Hepatology, Princess Alexandra Hospital, Australia
| | - Daphne Foong
- Gastrointestinal Motility Disorders Unit, Western Sydney University, Australia
| | - Stefan Calder
- Department of Surgery, Auckland City Hospital, New Zealand
- Auckland Bioengineering Institute, University of Auckland, New Zealand
- Alimetry Ltd, Auckland, New Zealand
| | - Gabriel Schamberg
- Department of Surgery, Auckland City Hospital, New Zealand
- Alimetry Ltd, Auckland, New Zealand
| | - Chris Varghese
- Department of Surgery, Auckland City Hospital, New Zealand
| | - Jan Tack
- Translational Research Center for Gastrointestinal Disorders (TARGID), University of Leuven, Belgium
| | - William Xu
- Department of Surgery, Auckland City Hospital, New Zealand
| | - Charlotte Daker
- Department of Gastroenterology, North Shore Hospital, Auckland, New Zealand
| | - Daniel Carson
- Department of Surgery, Auckland City Hospital, New Zealand
| | | | - Thomas Hayes
- Department of Surgery, Auckland City Hospital, New Zealand
| | - Peng Du
- Auckland Bioengineering Institute, University of Auckland, New Zealand
| | - Thomas L. Abell
- Division of Gastroenterology, University of Louisville, KY, USA
| | - Henry P. Parkman
- Gastroenterology Section, Department of Medicine, Lewis Katz School of Medicine, Temple University, USA
| | - I-Hsuan Huang
- Translational Research Center for Gastrointestinal Disorders (TARGID), University of Leuven, Belgium
| | | | | | - Armen A. Gharibans
- Department of Surgery, Auckland City Hospital, New Zealand
- Auckland Bioengineering Institute, University of Auckland, New Zealand
- Alimetry Ltd, Auckland, New Zealand
| | - Vincent Ho
- Gastrointestinal Motility Disorders Unit, Western Sydney University, Australia
- Department of Gastroenterology and Hepatology, Campbelltown Hospital, Australia
| | - Greg O’Grady
- Department of Surgery, Auckland City Hospital, New Zealand
- Auckland Bioengineering Institute, University of Auckland, New Zealand
- Alimetry Ltd, Auckland, New Zealand
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13
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Varghese C, Dachs N, Schamberg G, McCool K, Law M, Xu W, Calder S, Foong D, Ho V, Daker C, Andrews CN, Gharibans AA, O'Grady G. Longitudinal outcome monitoring in patients with chronic gastroduodenal symptoms investigated using the Gastric Alimetry system: study protocol. BMJ Open 2023; 13:e074462. [PMID: 38011983 PMCID: PMC10685974 DOI: 10.1136/bmjopen-2023-074462] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/10/2023] [Accepted: 11/07/2023] [Indexed: 11/29/2023] Open
Abstract
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.
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Affiliation(s)
- Chris Varghese
- Department of Surgery, University of Auckland, Auckland, New Zealand
| | | | - Gabriel Schamberg
- Department of Surgery, University of Auckland, Auckland, New Zealand
- Alimetry Ltd, Auckland, New Zealand
| | | | - Mikaela Law
- Department of Surgery, University of Auckland, Auckland, New Zealand
- Alimetry Ltd, Auckland, New Zealand
| | - William Xu
- Department of Surgery, University of Auckland, Auckland, New Zealand
| | | | - Daphne Foong
- Western Sydney University, Penrith South, New South Wales, Australia
| | - Vincent Ho
- Western Sydney University, Penrith South, New South Wales, Australia
| | - Charlotte Daker
- Department of Gastroenterology, North Shore Hospital, Auckland, New Zealand
| | | | - Armen A Gharibans
- Department of Surgery, University of Auckland, Auckland, New Zealand
- Alimetry Ltd, Auckland, New Zealand
| | - Gregory O'Grady
- Department of Surgery, University of Auckland, Auckland, New Zealand
- Alimetry Ltd, Auckland, New Zealand
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14
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Varghese C, Harvey X, Gharibans AA, Du P, Collinson R, Bissett IP, Stinear CM, O'Grady G, Paskaranandavadivel N. Clinical utility of trans-sacral magnetic stimulation-evoked sphincter potentials and high-density electromyography in pelvic floor assessment: Technical evaluation. Colorectal Dis 2023; 25:2257-2265. [PMID: 37800177 DOI: 10.1111/codi.16753] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/10/2023] [Revised: 08/31/2023] [Accepted: 09/05/2023] [Indexed: 10/07/2023]
Abstract
AIM Faecal incontinence is common and of multifactorial aetiologies, yet current diagnostic tools are unable to assess nerve and sphincter function objectively. We developed an anorectal high-density electromyography (HD-EMG) probe to evaluate motor-evoked potentials induced via trans-sacral magnetic stimulation (TSMS). METHOD Anorectal probes with an 8 × 8 array of electrodes spaced 1 cm apart were developed for recording HD-EMG of the external anal sphincter. These HD-EMG probes were used to map MEP amplitudes and latencies evoked via TSMS delivered through the Magstim Rapid2 (MagStim Company). Patients undergoing pelvic floor investigations were recruited for this IDEAL Stage 2a pilot study. RESULTS Eight participants (median age 49 years; five female) were recruited. Methodological viability, safety and diagnostic workflow were established. The test was well tolerated with median discomfort scores ≤2.5/10, median pain scores ≤1/10 and no adverse events. Higher Faecal Incontinence Severity Index scores correlated with longer MEP latencies (r = 0.58, p < 0.001) and lower MEP amplitudes (r = -0.32, p = 0.046), as did St. Mark's Incontinence Scores with both MEP latencies (r = 0.49, p = 0.001) and MEP amplitudes (r = -0.47, p = 0.002). CONCLUSION This HD-EMG probe in conjunction with TSMS presents a novel diagnostic tool for anorectal function assessment. Spatiotemporal assessment of magnetically stimulated MEPs correlated well with symptoms and offers a feasible, safe and patient-tolerable method of evaluating pudendal nerve and external anal sphincter function. Further clinical development and evaluation of these techniques is justified.
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Affiliation(s)
- Chris Varghese
- Department of Surgery, University of Auckland, Auckland, New Zealand
| | - Xavier Harvey
- Department of Surgery, Auckland City Hospital, Auckland, New Zealand
| | - Armen A Gharibans
- Department of Surgery, University of Auckland, Auckland, New Zealand
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
| | - Peng Du
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
| | - Rowan Collinson
- Department of Surgery, Auckland City Hospital, Auckland, New Zealand
| | - Ian P Bissett
- Department of Surgery, University of Auckland, Auckland, New Zealand
- Department of Surgery, Auckland City Hospital, Auckland, New Zealand
| | - Cathy M Stinear
- Department of Medicine, University of Auckland, Auckland, New Zealand
| | - Greg O'Grady
- Department of Surgery, University of Auckland, Auckland, New Zealand
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
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15
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Foong D, Calder S, Varghese C, Schamberg G, Xu W, Daker C, Ho V, Andrews CN, Gharibans AA, O’Grady G. Gastric Alimetry ® Test Interpretation in Gastroduodenal Disorders: Review and Recommendations. J Clin Med 2023; 12:6436. [PMID: 37892572 PMCID: PMC10607701 DOI: 10.3390/jcm12206436] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2023] [Revised: 10/04/2023] [Accepted: 10/08/2023] [Indexed: 10/29/2023] Open
Abstract
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.
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Affiliation(s)
- Daphne Foong
- School of Medicine, Western Sydney University, Campbelltown, NSW 2560, Australia
| | - Stefan Calder
- Department of Surgery, Auckland City Hospital, Auckland 1023, New Zealand
- Alimetry Ltd., Auckland 1010, New Zealand
- Auckland Bioengineering Institute, University of Auckland, Auckland 1010, New Zealand
| | - Chris Varghese
- Department of Surgery, Auckland City Hospital, Auckland 1023, New Zealand
| | - Gabriel Schamberg
- Alimetry Ltd., Auckland 1010, New Zealand
- Auckland Bioengineering Institute, University of Auckland, Auckland 1010, New Zealand
| | - William Xu
- Department of Surgery, Auckland City Hospital, Auckland 1023, New Zealand
| | - Charlotte Daker
- Department of Gastroenterology, North Shore Hospital, Auckland 0620, New Zealand
| | - Vincent Ho
- School of Medicine, Western Sydney University, Campbelltown, NSW 2560, Australia
- Department of Gastroenterology and Hepatology, Campbelltown Hospital, Sydney, NSW 2560, Australia
| | - Christopher N. Andrews
- Division of Gastroenterology, Cumming School of Medicine, University of Calgary, Calgary, AB T2N 1N4, Canada
| | - Armen A. Gharibans
- Department of Surgery, Auckland City Hospital, Auckland 1023, New Zealand
- Alimetry Ltd., Auckland 1010, New Zealand
- Auckland Bioengineering Institute, University of Auckland, Auckland 1010, New Zealand
| | - Greg O’Grady
- Department of Surgery, Auckland City Hospital, Auckland 1023, New Zealand
- Alimetry Ltd., Auckland 1010, New Zealand
- Auckland Bioengineering Institute, University of Auckland, Auckland 1010, New Zealand
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16
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Schamberg G, Calder S, Varghese C, Xu W, Wang WJ, Ho V, Daker C, Andrews CN, O'Grady G, Gharibans AA. Comparison of Gastric Alimetry ® body surface gastric mapping versus electrogastrography spectral analysis. Sci Rep 2023; 13:14987. [PMID: 37696955 PMCID: PMC10495352 DOI: 10.1038/s41598-023-41645-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2023] [Accepted: 08/29/2023] [Indexed: 09/13/2023] Open
Abstract
Electrogastrography (EGG) non-invasively evaluates gastric motility but is viewed as lacking clinical utility. Gastric Alimetry® is a new diagnostic test that combines high-resolution body surface gastric mapping (BSGM) with validated symptom profiling, with the goal of overcoming EGG's limitations. This study directly compared EGG and BSGM to define performance differences in spectral analysis. Comparisons between Gastric Alimetry BSGM and EGG were conducted by protocolized retrospective evaluation of 178 subjects [110 controls; 68 nausea and vomiting (NVS) and/or type 1 diabetes (T1D)]. Comparisons followed standard methodologies for each test (pre-processing, post-processing, analysis), with statistical evaluations for group-level differences, symptom correlations, and patient-level classifications. BSGM showed substantially tighter frequency ranges vs EGG in controls. Both tests detected rhythm instability in NVS, but EGG showed opposite frequency effects in T1D. BSGM showed an 8× increase in the number of significant correlations with symptoms. BSGM accuracy for patient-level classification was 0.78 for patients vs controls and 0.96 as compared to blinded consensus panel; EGG accuracy was 0.54 and 0.43. EGG detected group-level differences in patients, but lacked symptom correlations and showed poor accuracy for patient-level classification, explaining EGG's limited clinical utility. BSGM demonstrated substantial performance improvements across all domains.
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Affiliation(s)
- Gabriel Schamberg
- Department of Surgery, The University of Auckland, Auckland, New Zealand
- Alimetry Ltd, Auckland, New Zealand
| | - Stefan Calder
- Department of Surgery, The University of Auckland, Auckland, New Zealand
- Alimetry Ltd, Auckland, New Zealand
| | - Chris Varghese
- Department of Surgery, The University of Auckland, Auckland, New Zealand
| | - William Xu
- Department of Surgery, The University of Auckland, Auckland, New Zealand
| | - William Jiaen Wang
- School of Medicine, Western Sydney University, Sydney, Australia
- Department of Gastroenterology and Hepatology, Campbelltown Hospital, Sydney, Australia
- Department of Gastroenterology and Hepatology, Townsville University Hospital, Townsville, Australia
- Department of Gastroenterology and Hepatology, Princess Alexandra Hospital, Brisbane, Australia
| | - Vincent Ho
- School of Medicine, Western Sydney University, Sydney, Australia
- Department of Gastroenterology and Hepatology, Campbelltown Hospital, Sydney, Australia
| | - Charlotte Daker
- Department of Gastroenterology, North Shore Hospital, Auckland, New Zealand
| | | | - Greg O'Grady
- Department of Surgery, The University of Auckland, Auckland, New Zealand
- Alimetry Ltd, Auckland, New Zealand
- Auckland Bioengineering Institute, The University of Auckland, Auckland, New Zealand
| | - Armen A Gharibans
- Department of Surgery, The University of Auckland, Auckland, New Zealand.
- Alimetry Ltd, Auckland, New Zealand.
- Auckland Bioengineering Institute, The University of Auckland, Auckland, New Zealand.
- Perelman School of Medicine, University of Pennsylvania, Pennsylvania, United States.
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Tsianou CC, Kvetina J, Radochova V, Kohoutova D, Rejchrt S, Valis M, Zdarova Karasova J, Tacheci I, Knoblochova V, Soukup O, Bures J. The effect of single and repeated doses of rivastigmine on gastric myoelectric activity in experimental pigs. PLoS One 2023; 18:e0286386. [PMID: 37262057 DOI: 10.1371/journal.pone.0286386] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2022] [Accepted: 05/16/2023] [Indexed: 06/03/2023] Open
Abstract
BACKGROUND Rivastigmine is a pseudo-irreversible cholinesterase inhibitor used for therapy of Alzheimer's disease and non-Alzheimer dementia syndromes. In humans, rivastigmine can cause significant gastrointestinal side effects that can limit its clinical use. The aim of this study was to assess the impact of rivastigmine on gastric motor function by means of electrogastrography (EGG) in experimental pigs. METHODS Six experimental adult female pigs (Sus scrofa f. domestica, hybrids of Czech White and Landrace breeds; 3-month-old; mean weight 30.7 ± 1.2 kg) were enrolled into the study twice and created two experimental groups. In group A, a single intragastric dose of 6 mg rivastigmine hydrogen tartate was administered in the morning to fasting pigs before EGG recording. In group B, rivastigmine was administered to overnight fasting animals in a dietary bolus in the morning for 7 days (6 mg per day). On day 8, an intragastric dose of 12 mg rivastigmine was given in the morning to fasting pigs before EGG. EGG recording was accomplished by means of an EGG standalone system. Recordings from both groups were evaluated in dominant frequency and EGG power (areas of amplitudes). RESULTS In total, 1,980 one-minute EGG intervals were evaluated. In group A, basal EGG power (median 1290.5; interquartile range 736.5-2330 μV2) was significantly higher in comparison with the power of intervals T6 (882; 577-1375; p = 0.001) and T10 (992.5; 385-2859; p = 0.032). In group B, the dominant frequency increased significantly from basal values (1.97 ± 1.57 cycles per minute) to intervals T9 (3.26 ± 2.16; p < 0.001) and T10 (2.14 ± 1.16; p = 0.012), respectively. In group B, basal EGG power (median 1030.5; interquartile range 549-5093) was significantly higher in comparison with the power of intervals T7 (692.5; 434-1476; p = 0.002) and T8 (799; 435-1463 μV2; p = 0.004). CONCLUSIONS Both single as well as repeated intragastric administration of rivastigmine hydrogen tartrate caused a significant decrease of EGG power (areas of amplitudes) in experimental pigs. EGG power may serve as an indirect indicator of gastric motor competence. These findings might provide a possible explanation of rivastigmine-associated dyspepsia in humans.
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Affiliation(s)
| | - Jaroslav Kvetina
- Biomedical Research Centre, University Hospital, Hradec Kralove, Czech Republic
| | - Vera Radochova
- Animal Laboratory, Faculty of Military Health Sciences, University of Defence, Hradec Kralove, Czech Republic
| | - Darina Kohoutova
- Biomedical Research Centre, University Hospital, Hradec Kralove, Czech Republic
- The Royal Marsden NHS Foundation Trust, London, United Kingdom
| | - Stanislav Rejchrt
- 2nd Department of Internal Medicine-Gastroenterology, Faculty of Medicine in Hradec Kralove and University Hospital Hradec Kralove, Charles University, Hradec Kralove, Czech Republic
| | - Martin Valis
- Department of Neurology, Faculty of Medicine in Hradec Kralove and University Hospital Hradec Kralove, Charles University, Hradec Kralove, Czech Republic
| | - Jana Zdarova Karasova
- Biomedical Research Centre, University Hospital, Hradec Kralove, Czech Republic
- Department of Toxicology and Military Pharmacy, Faculty of Military Health Sciences, University of Defence, Hradec Kralove, Czech Republic
| | - Ilja Tacheci
- 2nd Department of Internal Medicine-Gastroenterology, Faculty of Medicine in Hradec Kralove and University Hospital Hradec Kralove, Charles University, Hradec Kralove, Czech Republic
| | | | - Ondrej Soukup
- Biomedical Research Centre, University Hospital, Hradec Kralove, Czech Republic
| | - Jan Bures
- Biomedical Research Centre, University Hospital, Hradec Kralove, Czech Republic
- Institute of Gastrointestinal Oncology, Military University Hospital Praha, Praha, Czech Republic
- Department of Medicine, First Faculty of Medicine, Charles University, Nové Město, Czech Republic
- Military University Hospital Praha, Praha, Czech Republic
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18
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Wang Y, Chen JDZ, Nojkov B. Diagnostic Methods for Evaluation of Gastric Motility-A Mini Review. Diagnostics (Basel) 2023; 13:803. [PMID: 36832289 PMCID: PMC9955554 DOI: 10.3390/diagnostics13040803] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2022] [Revised: 02/11/2023] [Accepted: 02/18/2023] [Indexed: 02/23/2023] Open
Abstract
Gastric motility abnormalities are common in patients with disorders of gut-brain interaction, such as functional dyspepsia and gastroparesis. Accurate assessment of the gastric motility in these common disorders can help understand the underlying pathophysiology and guide effective treatment. A variety of clinically applicable diagnostic methods have been developed to objectively evaluate the presence of gastric dysmotility, including tests of gastric accommodation, antroduodenal motility, gastric emptying, and gastric myoelectrical activity. The aim of this mini review is to summarize the advances in clinically available diagnostic methods for evaluation of gastric motility and describe the advantages and disadvantages of each test.
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Affiliation(s)
| | | | - Borko Nojkov
- Division of Gastroenterology, University of Michigan, Ann Arbor, MI 48109, USA
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19
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Han X, Zhu H. Endoscopic mucosal electrodes: New directions for recording and regulating gastric myoelectric activity. Front Surg 2023; 9:1035723. [PMID: 36684308 PMCID: PMC9852521 DOI: 10.3389/fsurg.2022.1035723] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2022] [Accepted: 11/22/2022] [Indexed: 01/09/2023] Open
Abstract
With the gradual deepening of the study of gastric motility disorders, people increasingly realize that gastric myoelectric activity plays an important role in coordinating gastric function. This article introduces the advantages of endoscopic mucosal electrodes compared with traditional electrodes. Several different types of mucosal electrodes and how to fix the electrodes by endoscope are introduced. Endoscopic mucosal electrodes can record and regulate gastric myoelectric activity, which has great value in the study of gastric motility. Endoscopic mucosal electrode technique refers to the fixation of the electrode in the designated part of the gastric mucosa by endoscope. Through endoscopic mucosal electrodes, on the one hand, we can record gastric myoelectric activity, on the other hand, we can carry out gastric electrical stimulation to interfere with gastric rhythm. Endoscopic mucosal electrodes have higher accuracy than traditional cutaneous electrodes, less trauma and lower cost than serosal electrodes. Endoscopic mucosal electrodes have a good application prospect for diseases such as gastroparesis and obesity.
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20
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O'Grady G, Carbone F, Tack J. Gastric sensorimotor function and its clinical measurement. Neurogastroenterol Motil 2022; 34:e14489. [PMID: 36371709 PMCID: PMC10078602 DOI: 10.1111/nmo.14489] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/30/2022] [Revised: 10/24/2022] [Accepted: 10/24/2022] [Indexed: 11/15/2022]
Abstract
BACKGROUND Gastroduodenal symptoms are highly prevalent, with underlying sensorimotor dysfunction contributing in many patients. Common symptoms include early satiation, postprandial fullness, epigastric bloating, pain or burning, nausea and vomiting, which collectively affect over 7% of adults. However, the clinical evaluation of these symptoms remains challenging, with current tests of gastric function remaining limited in their ability or availability to separate specific patient subgroups or guide-targeted care. PURPOSE In the current edition of Neurogastroenterology & Motility, Silver et al. present new data showing correlations between patterns of intragastric meal distribution and symptom profiles in a large series of patients undergoing gastric emptying scintigraphy. Studies of this type are important, as they motivate understanding beyond existing disease labels, and orient focus toward deeper mechanistic profiling. This brief review provides an overview of gastric sensorimotor function and profiles several current and emerging methods of clinical evaluation. Perspectives are provided on accommodation testing, gastric emptying, measuring gastric myoelectrical activity including new approaches, and antroduodenal manometry. Although gastric physiology is complex, recent progress has been encouraging, with the heterogenous pathophysiology of gastric symptoms continuing to be unraveled, and new techniques for evaluating gastric function and symptoms emerging. CONCLUSIONS AND INFERENCES Ongoing progress will now depend on continuing to accurately profile the underlying mechanisms of gastroduodenal disorders to identify specific disease phenotypes that inform care.
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Affiliation(s)
- Greg O'Grady
- Department of Surgery, The University of Auckland, Auckland, New Zealand.,Alimetry Ltd, Auckland, New Zealand.,Auckland Bioengineering Institute, The University of Auckland, Auckland, New Zealand
| | - Florencia Carbone
- Department of Gastroenterology, University Hospital Leuven (UZ Leuven), Leuven, Belgium
| | - Jan Tack
- Department of Gastroenterology, University Hospital Leuven (UZ Leuven), Leuven, Belgium.,Translational Research Center for Gastrointestinal Diseases (TARGID), department of Chronic Diseases and Metabolism (ChroMeta), University of Leuven, Leuven, Belgium.,Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden.,Rome Foundation, Raleigh, North Carolina, USA
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21
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Calder S, Cheng LK, Andrews CN, Paskaranandavadivel N, Waite S, Alighaleh S, Erickson JC, Gharibans A, O'Grady G, Du P. Validation of noninvasive body-surface gastric mapping for detecting gastric slow-wave spatiotemporal features by simultaneous serosal mapping in porcine. Am J Physiol Gastrointest Liver Physiol 2022; 323:G295-G305. [PMID: 35916432 DOI: 10.1152/ajpgi.00049.2022] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Gastric disorders are increasingly prevalent, but reliable noninvasive tools to objectively assess gastric function are lacking. Body-surface gastric mapping (BSGM) is a noninvasive method for the detection of gastric electrophysiological features, which are correlated with symptoms in patients with gastroparesis and functional dyspepsia. Previous studies have validated the relationship between serosal and cutaneous recordings from limited number of channels. This study aimed to comprehensively evaluate the basis of BSGM from 64 cutaneous channels and reliably identify spatial biomarkers associated with slow-wave dysrhythmias. High-resolution electrode arrays were placed to simultaneously capture slow waves from the gastric serosa (32 × 6 electrodes at 4 mm spacing) and epigastrium (8 × 8 electrodes at 20 mm spacing) in 14 porcine subjects. BSGM signals were processed based on a combination of wavelet and phase information analyses. A total of 1,185 individual cycles of slow waves were assessed, out of which 897 (76%) were classified as normal antegrade waves, occurring in 10 (71%) subjects studied. BSGM accurately detected the underlying slow wave in terms of frequency (r = 0.99, P = 0.43) as well as the direction of propagation (P = 0.41, F-measure: 0.92). In addition, the cycle-by-cycle match between BSGM and transitions of gastric slow wave dysrhythmias was demonstrated. These results validate BSGM as a suitable method for noninvasively and accurately detecting gastric slow-wave spatiotemporal profiles from the body surface.NEW & NOTEWORTHY Gastric dysfunctions are associated with abnormalities in the gastric bioelectrical slow waves. Noninvasive detection of gastric slow waves from the body surface can be achieved through multichannel, high-resolution, body-surface gastric mapping (BSGM). BSGM matched the spatiotemporal characteristics of gastric slow waves recorded directly and simultaneously from the serosal surface of the stomach. Abnormal gastric slow waves, such as retrograde propagation, ectopic pacemaker, and colliding wavefronts can be detected by changes in the phase of BSGM.
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Affiliation(s)
- Stefan Calder
- Auckland Bioengineering Institute, The University of Auckland, Auckland, New Zealand.,Alimetry Ltd., Auckland, New Zealand
| | - Leo K Cheng
- Auckland Bioengineering Institute, The University of Auckland, Auckland, New Zealand
| | - Christopher N Andrews
- Alimetry Ltd., Auckland, New Zealand.,Division of Gastroenterology and Hepatology, University of Calgary, Calgary, Alberta, Canada
| | | | | | | | - Jonathan C Erickson
- Department of Physics-Engineering, Washington and Lee University, Lexington, Virginia
| | - Armen Gharibans
- Auckland Bioengineering Institute, The University of Auckland, Auckland, New Zealand.,Alimetry Ltd., Auckland, New Zealand
| | - Gregory O'Grady
- Auckland Bioengineering Institute, The University of Auckland, Auckland, New Zealand.,Alimetry Ltd., Auckland, New Zealand
| | - Peng Du
- Auckland Bioengineering Institute, The University of Auckland, Auckland, New Zealand.,Alimetry Ltd., Auckland, New Zealand
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