Abnormal gastric slow waves in patients with functional dyspepsia assessed by multichannel electrogastrography

Comparison of Gastric Alimetry® body surface gastric mapping versus electrogastrography spectral analysis

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.

Optical Mapping of Virtual Electrode Polarization Pattern and Its Relationship with Pacemaker Location during Gastric Pacing. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2023;2023:1-4. [PMID: 38082999 DOI: 10.1109/embc40787.2023.10340002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

Gastric rhythmic contractions are regulated by bioelectrical events known as slow waves (SW). Abnormal SW activity is associated with gastric motility disorders. Gastric pacing is a potential treatment method to restore rhythmic SW activity. However, to date, the efficacy of gastric pacing is inconsistent and the underlying mechanisms of gastric pacing are poorly understood. Optical mapping is widely used in cardiac electrophysiology studies. Its immunity to pacing artifacts offers a distinct advantage over conventional electrical mapping for studying pacing. In the present study, we first found that optical mapping can image pacing-induced virtual electrode polarization patterns in the stomach (adjacent regions of depolarized and hyperpolarized tissue). Second, we found that elicited SWs usually (15 of 16) originated from the depolarized areas of the stimulated region (virtual cathodes). To our knowledge, this is the first direct observation of virtual electrode polarization patterns in the stomach. Conclusions: Optical mapping can image virtual electrode polarization patterns during gastric pacing with high spatial resolution.Clinical Relevance- Gastric pacing is a potential therapeutic method for gastric motility disorders. This study provides direct observation of virtual electrode polarization pattern during gastric pacing and improves our understanding of the mechanisms underlying gastric pacing..

Review article: Functional dyspepsia-a gastric disorder, a duodenal disorder or a combination of both?

BACKGROUND

Functional dyspepsia (FD) is one of the most frequent conditions in gastroenterological outpatient health care. Most recent research in FD has shifted its focus to duodenal pathophysiological mechanisms, although current treatments still focus mainly the stomach.

AIM

The aim of the study was to provide a comprehensive overview of the pathophysiology of FD focusing on a paradigm shift from gastric towards duodenal mechanisms.

METHODS

We conducted a literature search in PubMed for studies describing mechanisms that could possibly cause FD.

RESULTS

The pathophysiology of FD remains incompletely understood. Recent studies show that duodenal factors such as acid, bile salt exposure and eosinophil and mast cell activation correlate with symptom pattern and burden and can be associated with gastric sensorimotor dysfunction. The evolving data identify the duodenum an interesting target for new therapeutic approaches. Furthermore, the current first-line treatment, that is proton pump inhibitors, reduces duodenal low-grade inflammation and FD symptoms.

CONCLUSION

Future research for the treatment of FD should focus on the inhibition of duodenal mast cell activation, eosinophilia and loss of mucosal integrity.

Effects of peristaltic amplitude and frequency on gastric emptying and mixing: a simulation study

The amplitude and frequency of peristaltic contractions are two major parameters for assessing gastric motility. However, it is not fully understood how these parameters affect the important functions of the stomach, such as gastric mixing and emptying. This study aimed to quantify the effects of peristaltic amplitude and frequency on gastric mixing and emptying using computational fluid dynamics simulation of gastric flow with an anatomically realistic model of the stomach. Our results suggest that both the increase and decrease in peristaltic amplitude have a significant impact on mixing strength and emptying rate. For example, when the peristaltic amplitude was 1.2 times higher than normal, the emptying rate was 2.7 times faster, whereas when the amplitude was half, the emptying rate was 4.2 times slower. Moreover, the emptying rate increased more than proportionally with the peristaltic frequency. The nearest contraction wave to the pylorus and the subsequent waves promoted gastric emptying. These results suggest the importance of maintaining parameters within normal ranges to achieve healthy gastric function.

Validation of noninvasive body-surface gastric mapping for detecting gastric slow-wave spatiotemporal features by simultaneous serosal mapping in porcine

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.

Engaging biological oscillators through second messenger pathways permits emergence of a robust gastric slow-wave during peristalsis

Peristalsis, the coordinated contraction—relaxation of the muscles of the stomach is important for normal gastric motility and is impaired in motility disorders. Coordinated electrical depolarizations that originate and propagate within a network of interconnected layers of interstitial cells of Cajal (ICC) and smooth muscle (SM) cells of the stomach wall as a slow-wave, underly peristalsis. Normally, the gastric slow-wave oscillates with a single period and uniform rostrocaudal lag, exhibiting network entrainment. Understanding of the integrative role of neurotransmission and intercellular coupling in the propagation of an entrained gastric slow-wave, important for understanding motility disorders, however, remains incomplete. Using a computational framework constituted of a novel gastric motility network (GMN) model we address the hypothesis that engaging biological oscillators (i.e., ICCs) by constitutive gap junction coupling mechanisms and enteric neural innervation activated signals can confer a robust entrained gastric slow-wave. We demonstrate that while a decreasing enteric neural innervation gradient that modulates the intracellular IP₃ concentration in the ICCs can guide the aboral slow-wave propagation essential for peristalsis, engaging ICCs by recruiting the exchange of second messengers (inositol trisphosphate (IP₃) and Ca²⁺) ensures a robust entrained longitudinal slow-wave, even in the presence of biological variability in electrical coupling strengths. Our GMN with the distinct intercellular coupling in conjunction with the intracellular feedback pathways and a rostrocaudal enteric neural innervation gradient allows gastric slow waves to oscillate with a moderate range of frequencies and to propagate with a broad range of velocities, thus preventing decoupling observed in motility disorders. Overall, the findings provide a mechanistic explanation for the emergence of decoupled slow waves associated with motility impairments of the stomach, offer directions for future experiments and theoretical work, and can potentially aid in the design of new interventional pharmacological and neuromodulation device treatments for addressing gastric motility disorders.

The coordinated contraction and relaxation of the muscles of the stomach, known as peristalsis is important for normal gastric motility and primarily governed by electrical depolarizations that originate and propagate within a network of interconnected layers of interstitial cells of Cajal (ICCs) and smooth muscle cells of the stomach wall as a slow-wave. Under normal conditions, a gastric slow-wave oscillates with a single period and uniform rostrocaudal lag, exhibiting network entrainment. However, the understanding of intrinsic and extrinsic mechanisms that ensure propagation of a robust entrained slow-wave remains incomplete. Here, using a computational framework, we show that in conjunction with an enteric neural innervation gradient along the rostrocaudal ICC chain, and intercellular electrical coupling, the intercellular exchange of inositol trisphosphate between ICCs prevents decoupling by extending the longitudinal entrainment range along the stomach wall, even when variability in intercellular coupling exists. The findings from our study indicate ways that ensure the rostrocaudal spread of a robust gastric slow-wave and provide a mechanistic explanation for the emergence of decoupled slow waves associated with motility impairments of the stomach.

Clinical associations of functional dyspepsia with gastric dysrhythmia on electrogastrography: A comprehensive systematic review and meta-analysis

BACKGROUND

Functional dyspepsia (FD) is a common gastroduodenal disorder, yet its pathophysiology remains poorly understood. Bioelectrical gastric slow-wave abnormalities are thought to contribute to its multifactorial pathophysiology. Electrogastrography (EGG) has been used to record gastric electrical activity; however, the clinical associations require further evaluation.

AIMS

This study aimed to systematically assess the clinical associations of EGG in FD.

METHODS

MEDLINE, EMBASE, and CENTRAL databases were systematically searched for articles using EGG in adults with FD. Primary outcomes were percentage normal versus abnormal rhythm (bradygastria, normogastria, and tachygastria). Secondary outcomes were dominant power, dominant frequency, percentage coupling, and the meal responses.

RESULTS

1751 FD patients and 555 controls from 47 studies were included. FD patients spent less time in normogastria while fasted (SMD -0.74; 95%CI -1.22 to -0.25) and postprandially (-0.86; 95%CI -1.35 to -0.37) compared with controls. FD patients also spent more fasted time in bradygastria (0.63; 95%CI 0.33-0.93) and tachygastria (0.45; 95%CI 0.12-0.78%). The power ratio (-0.17; 95%CI -0.83-0.48) and dominant frequency meal-response ratio (0.06; 95%CI -0.08-0.21) were not significantly different to controls. Correlations between EGG metrics and the presence and timing of FD symptoms were inconsistent. EGG methodologies were diverse and variably applied.

CONCLUSION

Abnormal gastric slow-wave rhythms are a consistent abnormality present in FD, as defined by EGG and, therefore, likely play a role in pathophysiology. The aberrant electrophysiology identified in FD warrants further investigation, including into underlying mechanisms, associated spatial patterns, and symptom correlations.

Interstitial Cells of Cajal: Potential Targets for Functional Dyspepsia Treatment Using Medicinal Natural Products

Introduction

The pathophysiology of functional dyspepsia (FD) remains uncertain, but the interstitial cells of Cajal (ICCs), pacemakers that regulate gastrointestinal motility, are garnering attention as key modulators and therapeutic targets in FD. This review comprehensively discusses the involvement of ICCs in the pharmacologic actions of FD and as therapeutic targets for herbal products for FD.

Methods

A search of the literature was performed using PubMed by pairing “interstitial cells of Cajal” with “medicinal plant, herbal medicine, phytotherapy, flavonoids, or traditional Chinese medicine (TCM).”

Results

From the 55 articles screened in the initial survey, 34 articles met our study criteria. The search results showed that herbal products can directly depolarize ICCs to generate pacemaker potentials and increase the expression of c-kit and stem cell factors, helping to repair ICCs. Under certain pathological conditions, medicinal plants also protect ICCs from oxidative stress and/or inflammation-induced impairment. Two representative herbal decoctions (Banhasasim-tang, 半夏泻心汤, and Yukgunja-tang, 六君子汤) have been shown to modulate ICC functions by both clinical and preclinical data.

Conclusion

This review strongly indicates the potential of herbal products to target ICCs and suggests that further ICC-based studies would be promising for the development of FD treatment agents.

The effect of chronic nausea on gastric slow wave spatiotemporal dynamics in children

BACKGROUND

Chronic nausea in adolescents with functional gastrointestinal disorders is an increasingly reported but poorly understood symptom that negatively affects quality of life. Functional gastrointestinal disorders are known to correlate closely with slow wave rhythm disturbances. The ability to characterize gastric electrophysiologic perturbations in functional nausea patients could provide potential diagnostic and therapeutic tools for nausea patients.

METHODS

We used high-resolution electrogastrograms (HR-EGG) to measure gastric slow wave parameters in pediatric chronic nausea patients and healthy subjects both pre- and postprandial. We computed the dominant frequency, percentage power distribution, gastric slow wave propagation direction, and speed from HR-EGG.

KEY RESULTS

We observed significant differences in the dominant frequency and power distributed in normal and bradyarrhythmia frequency ranges when comparing patients and healthy subjects. Propagation patterns in healthy subjects were predominantly anterograde, while patients exhibited a variety of abnormalities including retrograde, anterograde, and disrupted patterns. There was a significant difference in the preprandial mean slow wave direction between healthy subjects (222° ± 22°) and patients (103° ± 66°; p ˂ 0.01), although the postprandial mean direction between healthy subjects and patients was similar (p = 0.73). No significant difference in slow wave propagation speed was found between patients and healthy subjects in either pre- (p = 0.21) or postprandial periods (p = 0.75).

CONCLUSIONS AND INFERENCES

The spatiotemporal characterization of gastric slow wave activity using HR-EGG distinguishes symptomatic chronic nausea patients from healthy subjects. This characterization may in turn inform and direct clinical decision-making and lead to further insight into its pathophysiology.

Gastric ablation as a novel technique for modulating electrical conduction in the in vivo stomach

Gastric motility is coordinated by underlying bioelectrical "slow wave" activity. Slow wave dysrhythmias are associated with motility disorders, including gastroparesis, offering an underexplored potential therapeutic target. Although ablation is widely used to treat cardiac arrhythmias, this approach has not yet been trialed for gastric electrical abnormalities. We hypothesized that ablation can create localized conduction blocks and modulate slow wave activation. Radiofrequency ablation was performed on the porcine serosa in vivo, encompassing a range of parameters (55-85°C, adjacent points forming a line, 5-10 s/point). High-resolution electrical mapping (16 × 16 electrodes; 6 × 6 cm) was applied to define baseline and acute postablation activation patterns. Tissue damage was evaluated by hematoxylin and eosin and c-Kit stains. Results demonstrated that RF ablation successfully induced complete conduction block and a full thickness lesion in the muscle layer at energy doses of 65-75°C for 5-10 s/point. Gastric ablation may hold therapeutic potential for gastric electrical abnormalities in the future.NEW & NOTEWORTHY This study presents gastric ablation as a new method for modulating slow wave activation and propagation in vivo, by creating localized electrical conduction blocks in the stomach, validated by high-resolution electrical mapping and histological tissue analysis. The results define the effective energy dose range for creating conduction blocks, while maintaining the mucosal and submucosal integrity, and demonstrate the electrophysiological effects of ablation. In future, gastric ablation can now be translated toward disrupting dysrhythmic slow wave activation.

Gastric slow wave rhythm identification using new approach based on noise-assisted multivariate empirical mode decomposition and Hilbert-Huang transform

BACKGROUND

Electrogastrography (EGG) is the method of cutaneous recording of the myoelectrical activity of the stomach. A multi-channel signal is recorded non-invasively by means of electrodes placed outside the epigastric area. The normal electrical rhythm of the stomach (slow wave) may become significantly disturbed due to disorders of gastrointestinal tract. Abnormally fast electrical rhythms are termed tachygastria, while abnormally slow rhythms are known as bradygastria. Because some features of biological signals may go undetected using the classical methods of signal spectral analysis, we propose a new method for EGG rhythm identification.

METHODS

In this study, the calculation of the basic rhythms of multi-channel EGG signals is performed by means of the noise-assisted multivariate empirical mode decomposition (NA-MEMD) and Hilbert-Huang transform (HHT), using EGG data from eight healthy subjects. The results were compared with those obtained using classical spectral analysis.

KEY RESULTS

The mean values of the normogastric index for preprandial and two postprandial stages were found to be 64.78 ± 11.37%, 61.29 ± 15.86%, and 63.80 ± 13.24%, respectively. The obtained values of normogastric index are consistent with the normal human physiological value, which is approximately 70% for healthy subjects.

CONCLUSIONS

This method is able to capture features of the signal which are mostly undetectable by standard EGG processing methods. The EGG dominant rhythm identification using the instantaneous normogastric, bradygastric, and tachygastric indices provides new insights into biological EGG patterns.

Body surface mapping of the stomach: New directions for clinically evaluating gastric electrical activity

BACKGROUND

Gastric motility disorders, which include both functional and organic etiologies, are highly prevalent. However, there remains a critical lack of objective biomarkers to guide efficient diagnostics and personalized therapies. Bioelectrical activity plays a fundamental role in coordinating gastric function and has been investigated as a contributing mechanism to gastric dysmotility and sensory dysfunction for a century. However, conventional electrogastrography (EGG) has not achieved common clinical adoption due to its perceived limited diagnostic capability and inability to impact clinical care. The last decade has seen the emergence of novel high-resolution methods for invasively mapping human gastric electrical activity in health and disease, providing important new insights into gastric physiology. The limitations of EGG have also now become clearer, including the finding that slow-wave frequency alone is not a reliable discriminator of gastric dysrhythmia, shifting focus instead toward altered spatial patterns. Recently, advances in bioinstrumentation, signal processing, and computational modeling have aligned to allow non-invasive body surface mapping of the stomach to detect spatiotemporal gastric dysrhythmias. The clinical relevance of this emerging strategy to improve diagnostics now awaits determination.

PURPOSE

This review evaluates these recent advances in clinical gastric electrophysiology, together with promising emerging data suggesting that novel gastric electrical signatures recorded at the body surface (termed "body surface mapping") may correlate with symptoms. Further technological progress and validation data are now awaited to determine whether these advances will deliver on the promise of clinical gastric electrophysiology diagnostics.

TRANSCUTANEOUS MULTICHANNEL ELECTROGASTROGRAPHY: NORMAL PARAMETERS IN A BRAZILIAN POPULATION

BACKGROUND

Electrogastrography (EGG) is a noninvasive technique for the assessment of gastric myoelectrical activity using electrodes placed on the abdominal surface. Changes in gastric myoelectrical activity may be associated with diseases such as gastroparesis, functional dyspepsia, nausea, and recurrent vomiting. In Brazil, no studies to date have assessed gastric myoelectrical activity using multichannel EGG in healthy individuals.

OBJECTIVE

To establish normal values of transcutaneous multichannel EGG in healthy Brazilian individuals.

METHODS

This was a prospective study including 20 healthy individuals who underwent EGG. Recording was performed during two periods: a preprandial recording was performed for 30 minutes, and a postprandial recording was performed for 30 minutes after a soft-solid meal of 400 kcal (20 grams of proteins, 60 grams of carbohydrates, and 9 grams of fat).

RESULTS

We assessed dominant frequency (DF) parameters, %DF distribution, the instability coefficient, and the power ratio (PR). A total of 20 individuals (11 women and 9 men) with a mean age of 39.5±7.4 years were included. Mean DF (95%CI) ranged from 2.4 to 3.1 cpm in the resting phase and 2.6 to 3.2 cpm in the postprandial period. The %DF in normogastria range was >70% in all healthy individuals. We identified that only one individual did not present a positive response to the test meal, and the other 19 individuals showed a PR greater than 1. The instability coefficient did not change significantly with meal intake.

CONCLUSION

Multichannel EGG may be applied in future studies to evaluate gastric motility disorders in the Brazilian population.

Effects of magnetogastrography sensor configurations in tracking slow wave propagation

Magnetogastrography (MGG) is a non-invasive method of assessing gastric slow waves (SWs) by recording the resultant magnetic fields. MGG can capture both SW frequency and propagation, and identify SW dysrhythmias that are associated with motility disorders. However, the impact of the restricted spatial coverage and sensor density on SW propagation tracking performance is unknown. This study simulated MGG using multiple anatomically specific torso geometries and two realistic SW propagation patterns to determine the effect of different sensor configurations on tracking SW propagation. The surface current density mapping and center-of-gravity tracking methods were used to compare four magnetometer array configurations: a reference system currently used in GI research and three hypothetical higher density and coverage arrays. SW propagation patterns identified with two hypothetical arrays (with coverage over at least the anterior of the torso) correlated significantly higher with simulated realistic 3 cycle-per-minute SW activity than the reference array (p = 0.016, p = 0.005). Furthermore, results indicated that most of the magnetic fields that contribute to the performance of SW propagation tracking were located on the anterior of the torso as further increasing the coverage did not significantly increase performance. A 30% decrease in sensor spacing within the same spatial coverage of the reference array also significantly increased correlation values by approximately 0.50 when the signal-to-noise ratio was 5 dB. This study provides evidence that higher density and coverage sensor layouts will improve the utility of MGG. Further work is required to investigate optimum sensor configurations across larger anatomical variations and other SW propagation patterns.

Bioelectrical Signals for the Diagnosis and Therapy of Functional Gastrointestinal Disorders

Coordinated contractions and motility patterns unique to each gastrointestinal organ facilitate the digestive process. These motor activities are coordinated by bioelectrical events, sensory and motor nerves, and hormones. The motility problems in the gastrointestinal tract known as functional gastrointestinal disorders (FGIDs) are generally caused by impaired neuromuscular activity and are highly prevalent. Their diagnosis is challenging as symptoms are often vague and difficult to localize. Therefore, the underlying pathophysiological factors remain unknown. However, there is an increasing level of research and clinical evidence suggesting a link between FGIDs and altered bioelectrical activity. In addition, electroceuticals (bioelectrical therapies to treat diseases) have recently gained significant interest. This paper gives an overview of bioelectrical signatures of gastrointestinal organs with normal and/or impaired motility patterns and bioelectrical therapies that have been developed for treating FGIDs. The existing research evidence suggests that bioelectrical activities could potentially help to identify the diverse etiologies of FGIDs and overcome the drawbacks of the current clinically adapted methods. Moreover, electroceuticals could potentially be effective in the treatment of FGIDs and replace the limited existing conventional therapies which often attempt to treat the symptoms rather than the underlying condition.

Simulation-based Analysis of Magnetogastrography Sensor Configurations for Characterizing Gastric Slow Wave Dysrhythmias

The routine diagnosis of gastric motility disorders represents a significant problem to current clinical practice. Magnetogastrography (MGG) provides a non-invasive option for assessing gastric slow wave (SW) dysrhythmias that are associated with motility disorders. However, its ability to characterize SW propagation is impaired by the limited spatial coverage of existing superconducting quantum interference devices (SQUIDs). Recently developed optically-pumped magnetometers can potentially substitute SQUIDs and enable subject-specific MGG arrays with greater spatial coverage. This study developed simulations of gastric MGG to determine the distribution of the magnetic fields (MFs) generated by SWs above the torso, and investigated the impact of several realistic dysrhythmic patterns of propagation. The distribution of MFs was found to vary significantly for different patterns of SW propagation, with ectopic dysrhythmia displaying the greatest difference from normal. Notably, some important proportion of the MFs lay outside the coverage of an existing experimental SQUID array used in gastrointestinal research for some simulated SW propagation patterns, such as retrograde activity. Results suggest that MGG measurements should be made over the entire frontal face of the torso to capture all of the strongest MFs generated by SWs.Clinical relevance- This provides a guide for the placement of MGG sensors for the capture of both normal and dysrhythmic gastric slow wave propagation.

Effects and mechanisms of acupuncture and electroacupuncture for functional dyspepsia: A systematic review

BACKGROUND

Functional dyspepsia (FD) is a common digestive disease with limited therapeutic options. According to evidence-based clinical practice, acupuncture or electroacupuncture (EA) seems to be a promising therapy for patients with FD. However, there is still a lack of systematic reviews that have analyzed current clinical trials for a better understanding of mechanisms involved in the ameliorating effect of acupuncture and EA on FD.

AIM

To evaluate the results and qualities of existing clinical evidence for researching the underlying mechanisms of acupuncture/EA in treating FD.

METHODS

A systematic search of the literature was performed to identify randomized controlled trials in which research on the mechanism of acupuncture or EA was conducted in FD patients. Databases searched included PubMed, EMBASE, Cochrane Library, and Web of Science. Data extraction and quality assessment were completed by two investigators independently and the results of quality evaluation were exported through Review Manager V5.3.

RESULTS

Eight studies were included in this review with a total of 17 items for detecting techniques for mechanistic research. Positive effects of acupuncture and EA were observed in regulating gastric motility, gastric accommodation, mental status, gastrointestinal hormones, and central and autonomic functions while improving dyspeptic symptoms and quality of life.

CONCLUSION

The key findings of this systematic review support the potential of acupuncture and EA in altering the heterogeneous pathophysiology in patients with FD. However, high-quality studies with well-planned designs are necessary to provide more credible evidence.

Source localization for gastric electrical activity using simulated magnetogastrographic data

In this study, the use of magnetic dipole (MDP) approximation to localize the underlying source of magnetogastrographic (MGG) data was investigated. An anatomically realistic torso and a stomach model were used to simulate slow wave (SW) activities and magnetic fields (MFs). SW activity in the stomach was simulated using a grid-based finite element method. The SW activity at each time sample was represented by the dipoles generated for each element and MFs were computed from these dipoles including secondary sources in the torso. Gaussian noise was added to the MFs to represent experimental signal noise. MDP fitting was executed on the time samples of selected 2-second time frames, and goodness of fit (GOF) and the distance from the fitted MDP to the center of gravity (COG) of active dipoles were computed. Then, for each time frame, the spatial changes of COG and MDP positions in x-, y-, and z-directions and correlation scores were computed. Our results showed that MDP fitting was capable of identifying propagation patterns with mean correlation scores of 0.63 ± 0.30, 0.71 ± 0.19, and 0.81 ± 0.24 in x-, y-, and z-directions, respectively. The mean distance from COGs to the identified MDPs was 49±4 mm. The results were similar under the noise conditions as well. Our results suggest that source localization using MDP approximation can be useful to identify the propagation characteristics of SWs using MGG data.

Banha-sasim-tang improves gastrointestinal function in loperamide-induced functional dyspepsia mouse model

ETHNOPHARMACOLOGICAL RELEVANCE

Banha-sasim-tang (BST; Hange-shashin-to in Kampo medicine; Banxia xiexin tang in traditional Chinese medicine) is a traditional Chinese harbal medicine that has been commonly used for gastrointestinal disorders.

AIM OF THE STUDY

To investigate the pharmacological effects of BST, a standardized herbal drug, on main symptoms of functional dyspepsia including delayed gastric emptying, and underlying mechanisms of action in mouse model.

METHODS AND MATERIALS

Balb/C mice were pretreated with BST (25, 50, 100 mg/kg, po) or mosapride (3 mg/kg, po) for 3 days, and then treated with loperamide (10 mg/kg, ip) after 19 h fasting. A solution of 0.05% phenol red (500 μL) or 5% charcoal diet (200 μL) was orally administered, followed by scarifying and assessment of gastric emptying or gastro-intestinal motility. C-kit (immunofluorescence), nNOS (western blot) and gastric contraction-related gene expression were examined in stomach tissue.

RESULTS

The loperamide injection substantially delayed gastric emptying, while the BST pretreatment significantly attenuated this peristaltic dysfunction, as evidenced by the quantity of stomach-retained phenol red (p < 0.05 or 0.01) and stomach weight (p < 0.05 or 0.01). The BST pretreatment significantly tempered the loperamide-induced inactivation of c-kit and nNOS (p < 0.05 or 0.01) as well as the contraction-related gene expression, such as the 5HT₄ receptor (5HT₄R), anoctamin-1 (ANO1), ryanodine receptor 3 (RYR3) and smooth muscle myosin light chain kinase (smMLCK). The BST pretreatment also significantly attenuated the alterations in gastro-intestinal motility (p < 0.01).

CONCLUSION

Our results are the first evidence of the prokinetic agent effects of Banha-sasim-tang in a loperamide-induced FD animal model. The underlying mechanisms of action may involve the modulation of peristalsis via activation of the interstitial cells of Cajal and the smooth muscle cells in the stomach.

Bioelectronics for mapping gut activity

Gastric peristalsis is initiated and coordinated by an underlying bioelectrical activity, termed slow waves. High-resolution (HR) mapping of the slow waves has become a fundamental tool for accurately defining electrophysiological properties in gastroenterology, including dysrhythmias in gastric disorders such as gastroparesis and functional dyspepsia. Currently, HR mapping is achieved via acquisition of slow waves taken directly from the serosa of fasted subjects undergoing invasive abdominal surgery. Recently, a minimally invasive retractable catheter and electrode has been developed for HR mapping that can only be used in short-term studies in subjects undergoing laparoscopy. Noninvasive mapping has also emerged from multichannel cutaneous electrogastrography; however, it lacks sufficient resolution and is prone to artifacts. Bioelectronics that can map slow waves in conscious subjects, postprandially and long-term, are in high demand. Due to the low signal-to-noise ratio of cutaneous electrogastrography, electrodes for HR mapping of gut activity have to acquire slow waves directly from the gut; hence, development of novel device implantation methods has inevitably accompanied development of the devices themselves. Initial efforts that have paved the way toward achieving these goals have included development of miniature wireless systems with a limited number of acquisition channels using commercially available off-the-shelf electronic components, flexible HR electrodes, and endoscopic methods for minimally invasive device implantation. To further increase the spatial resolution of HR mapping, and to minimize the size and power consumption of the implant for long-term studies, application-specific integrated circuitry, wireless power transfer, and stretchable electronics technologies have had to be integrated into a single system.

High-resolution Mapping of Hyperglycemia-induced Gastric Slow Wave Dysrhythmias

Background/Aims

It is now recognised that gastric dysrhythmias are best characterised by their spatial propagation pattern. Hyperglycemia is an important cause of gastric slow wave dysrhythmia, however, the spatiotemporal patterns of dysrhythmias in this context have not been investigated. This study aims to investigate the relationship between hyperglycemia and the patterns of dysrhythmias by employing high-resolution (multi-electrode) mapping simultaneously at the anterior and posterior gastric serosa.

Methods

High-resolution mapping (8 × 16 electrodes per serosal) was performed in 4 anesthetized hounds. Baseline recordings (21 ± 8 minutes) were followed by intravenous injection of glucagon (0.5 mg per dose) and further recordings (59 ± 15 minutes). Blood glucose levels were monitored manually using a glucose sensing kit at regular 5-minute intervals. Slow wave activation maps, amplitudes, velocity, anisotropic ratio, and frequency were calculated. Differences were compared between baseline and post glucagon injection.

Results

Baseline slow waves propagated symmetrically and antegrade. The blood glucose levels were increased by an average of 112% compared to the baseline by the end of the recordings. All subjects demonstrated elevated incidence of slow wave dysrhythmias following injection compared to the baseline (48 ± 23% vs 6 ± 4%, P < 0.05). Dysrhythmias arose simultaneously or independently on anterior and posterior serosa. Spatial dysrhythmias occurred before and persisted after the onset and disappearance of temporal dysrhythmias.

Conclusions

Infusion of glucagon induced gastric slow wave dysrhythmias, which occurred across a heterogeneous range of patterns and frequencies. The spatial dysrhythmias of gastric slow waves were shown to be more prevalent and persisted over a longer period of time compared to the temporal dysrhythmias.

Multi-day, multi-sensor ambulatory monitoring of gastric electrical activity

OBJECTIVE

Bioelectrial signals known as slow waves play a key role in coordinating gastric motility. Slow wave dysrhythmias have been associated with a number of functional motility disorders. However, there have been limited human recordings obtained in the consious state or over an extended period of time. This study aimed to evaluate a robust ambulatory recording platform.

APPROACH

A commercially available multi-sensor recording system (Shimmer3, ShimmerSensing) was applied to acquire slow wave information from the stomach of six humans and four pigs. First, acute experiments were conducted in pigs to verify the accuracy of the recording module by comparing to a standard widely employed electrophysiological mapping system (ActiveTwo, BioSemi). Then, patients with medically refractory gastroparesis undergoing temporary gastric stimulator implantation were enrolled and gastric slow waves were recorded from mucosally-implanted electrodes for 5 d continuously. Accelerometer data was also collected to exclude data segments containing excessive patient motion artefact.

MAIN RESULTS

Slow wave signals and activation times from the Shimmer3 module were closely comparable to a standard electrophysiological mapping system. Slow waves were able to be recorded continuously for 5 d in human subjects. Over the 5 d, slow wave frequency was 2.8  ±  0.6 cpm and amplitude was 0.2  ±  0.3 mV.

SIGNIFICANCE

A commercial multi-sensor recording module was validated for recording electrophysiological slow waves for 5 d, including in ambulatory patients. Multiple modules could be used simultaneously in the future to track the spatio-temporal propagation of slow waves. This framework can now allow for patho-electrophysiological studies to be undertaken to allow symptom correlation with dysrhythmic slow wave events.

EGG DWPack: System for Multi-Channel Electrogastrographic Signals Recording and Analysis

Electrogastrography (EGG) is a non-invasive examination method for investigating the myolectrical activity of a stomach. Nowadays, abdominal surface electrogastrography is the one of methods of stomach examination that is used for diagnosing patients with chronic intractable nausea, vomiting and gastroparesis. The electrogastrographic signals are recorded by using cutaneous electrodes placed on the stomach surface. EGG DWPack system is a highly developed and easy to use software package for four channel electrogastrography recording and analysis. The part of the software for analysis is a MATLAB based software and requires the specific ASCII format of the EGG data. The analyzed EGG signals could be conditioned with the wide range of sampling frequency and various resolutions of analog to digital conversion. Additionally, if the EGG data fulfills certain conditions associated with sampling frequency, the software can be used to study the basic parameters of heart rate variability (HRV) simultaneously with the EGG parameters. The software includes different digital filters for the EGG signal extraction and tools for artifacts exclusion. The software computes the majority of EGG parameters which are commonly used in a clinical practice. The EGG analysis can be made for several adjustable analysis settings and various methods, and it can optimize the analysis methods for different preferences or requirements. The analysis result can be saved in a MAT-file, and exported to MS Excel and ASCII files. Validation of the software was performed using synthetic and real EGG signals. This paper contains, as an example of use, an analysis of four synthetic, and fourteen human 4-channel EGG data recording with water, yogurt and a solid meal stimulation. The mean values of the dominant frequency for fast, and postprandial stage were found to be 2.96±0.21 cpm (cycle per minute), and 3.05±0.33 cpm, respectively. The values established in the validation process are consistent with typical human physiological values. In addition, the results were compared to outcomes from commercial system. The results of validation have proved that EGG DWPack software produces reliable outcomes. The software is available for free of charge for Windows operating system for the all possible non commercial use.

Methods for High-Resolution Electrical Mapping in the Gastrointestinal Tract

Over the last two decades, high-resolution (HR) mapping has emerged as a powerful technique to study normal and abnormal bioelectrical events in the gastrointestinal (GI) tract. This technique, adapted from cardiology, involves the use of dense arrays of electrodes to track bioelectrical sequences in fine spatiotemporal detail. HR mapping has now been applied in many significant GI experimental studies informing and clarifying both normal physiology and arrhythmic behaviors in disease states. This review provides a comprehensive and critical analysis of current methodologies for HR electrical mapping in the GI tract, including extracellular measurement principles, electrode design and mapping devices, signal processing and visualization techniques, and translational research strategies. The scope of the review encompasses the broad application of GI HR methods from in vitro tissue studies to in vivo experimental studies, including in humans. Controversies and future directions for GI mapping methodologies are addressed, including emerging opportunities to better inform diagnostics and care in patients with functional gut disorders of diverse etiologies.

Progress in Mathematical Modeling of Gastrointestinal Slow Wave Abnormalities

Gastrointestinal (GI) motility is regulated in part by electrophysiological events called slow waves, which are generated by the interstitial cells of Cajal (ICC). Slow waves propagate by a process of "entrainment," which occurs over a decreasing gradient of intrinsic frequencies in the antegrade direction across much of the GI tract. Abnormal initiation and conduction of slow waves have been demonstrated in, and linked to, a number of GI motility disorders. A range of mathematical models have been developed to study abnormal slow waves and applied to propose novel methods for non-invasive detection and therapy. This review provides a general outline of GI slow wave abnormalities and their recent classification using multi-electrode (high-resolution) mapping methods, with a particular emphasis on the spatial patterns of these abnormal activities. The recently-developed mathematical models are introduced in order of their biophysical scale from cellular to whole-organ levels. The modeling techniques, main findings from the simulations, and potential future directions arising from notable studies are discussed.

Assessment of slow wave propagation in multichannel electrogastrography by using noise-assisted multivariate empirical mode decomposition and cross-covariance analysis

Electrogastrography (EGG) is a noninvasive technique for recording the myoelectrical activity of the stomach. An electrogastrographic signal recorded by using a four-channel system with electrodes placed on the surface of the skin is a mixture of a low-frequency gastric pacesetter potential known as a slow wave, electrical activity from other organs, and random noise. The aim of this work was to investigate the possibility of detecting the propagation of the gastric slow wave from multichannel EGG data. Noise-assisted multivariate empirical mode decomposition (NA-MEMD) and cross-covariance analysis (CCA) are proposed as new detection tools. NA-MEMD was applied to attenuate the noise and extract the EGG signal from four channels, while CCA was performed to assess the time shift between the EGG signal channels. Validation of the method was performed using synthetic EGG signals and the methodology was tested on four young, healthy adults. After validation, the proposed method was applied for two kinds of human EGG data: 10-min (short) EGG data from the preprandial phase and 90-120-min (long) EGG data from the preprandial phase as well as the postprandial phase. The results obtained for both synthetic and human EGG data confirm that the proposed method could be a useful tool for assessing the propagation of slow waves. The time shift calculation from the preprandial phase of the EGG examination yielded more consistent results than the postprandial phase. The mean value of the slow wave time lag between neighbouring channels for synthetic data was found to be 4.99±0.47 s. In addition, it was confirmed that the proposed method, that is, NA-MEMD and CCA together, are robust to noise.

Circulating motilin, ghrelin, and GLP-1 and their correlations with gastric slow waves in patients with chronic kidney disease

Patients with chronic kidney disease (CKD) commonly complain upper gastrointestinal (GI) symptoms, especially anorexia. Hemodialysis (HD) has been noted to improve GI symptoms; however, the underlying mechanisms are unclear. This study was designed 1) to study effects of HD on GI symptoms and gastric slow waves; and 2) to investigate possible roles of ghrelin and glucagon-like peptide-1 (GLP-1): the study recruited 13 healthy controls, 20 CKD patients without HD (CKD group), and 18 CKD patients with HD (HD group). Dyspeptic symptoms, autonomic functions, gastric slow waves, and plasma level of ghrelin and GLP-1 were analyzed. First, the CKD patients with HD showed markedly lower scores of anorexia (0.6 ± 0.2 vs. 3.2 ± 0.4, P < 0.001) compared with patients without HD. Second, the CKD group but not HD group showed a significant reduction (25.6%) in the percentage of normal gastric slow waves, compared with controls. Third, the CKD group exhibited a significantly lower ghrelin level compared with the HD group (26.8 ± 0.9 vs. 34.1 ± 2.3 ng/l, P < 0.02) and a higher GLP-1 level (29.4 ± 2.8 vs. 20.0 ± 2.1 pmol/l, P < 0.05) compared with controls. Moreover, the percentage of normal slow waves was positively correlated with ghrelin (r = 0.385, P = 0.019) but negatively correlated with GLP-1 (r = -0.558, P < 0.001) in all CKD patients. Hemodialysis improves upper GI symptoms and gastric slow waves in CKD patients. An increase in ghrelin and a decrease in GLP-1 might be involved in the HD-induced improvement in gastric slow waves.

High-resolution electrical mapping of porcine gastric slow-wave propagation from the mucosal surface

BACKGROUND

Gastric motility is coordinated by bioelectrical slow waves, and gastric dysrhythmias are reported in motility disorders. High-resolution (HR) mapping has advanced the accurate assessment of gastric dysrhythmias, offering promise as a diagnostic technique. However, HR mapping has been restricted to invasive surgical serosal access. This study investigates the feasibility of HR mapping from the gastric mucosal surface.

METHODS

Experiments were conducted in vivo in 14 weaner pigs. Reference serosal recordings were performed with flexible-printed-circuit (FPC) arrays (128-192 electrodes). Mucosal recordings were performed by two methods: (i) FPC array aligned directly opposite the serosal array, and (ii) cardiac mapping catheter modified for gastric mucosal recordings. Slow-wave propagation and morphology characteristics were quantified and compared between simultaneous serosal and mucosal recordings.

KEY RESULTS

Slow-wave activity was consistently recorded from the mucosal surface from both electrode arrays. Mucosally recorded slow-wave propagation was consistent with reference serosal activation pattern, frequency (P≥.3), and velocity (P≥.4). However, mucosally recorded slow-wave morphology exhibited reduced amplitude (65-72% reduced, P<.001) and wider downstroke width (18-31% wider, P≤.02), compared to serosal data. Dysrhythmias were successfully mapped and classified from the mucosal surface, accorded with serosal data, and were consistent with known dysrhythmic mechanisms in the porcine model.

CONCLUSIONS & INFERENCES

High-resolution gastric electrical mapping was achieved from the mucosal surface, and demonstrated consistent propagation characteristics with serosal data. However, mucosal signal morphology was attenuated, demonstrating necessity for optimized electrode designs and analytical algorithms. This study demonstrates feasibility of endoscopic HR mapping, providing a foundation for advancement of minimally invasive spatiotemporal gastric mapping as a clinical and scientific tool.

Functional physiology of the human terminal antrum defined by high-resolution electrical mapping and computational modeling

High-resolution (HR) mapping has been used to study gastric slow-wave activation; however, the specific characteristics of antral electrophysiology remain poorly defined. This study applied HR mapping and computational modeling to define functional human antral physiology. HR mapping was performed in 10 subjects using flexible electrode arrays (128-192 electrodes; 16-24 cm²) arranged from the pylorus to mid-corpus. Anatomical registration was by photographs and anatomical landmarks. Slow-wave parameters were computed, and resultant data were incorporated into a computational fluid dynamics (CFD) model of gastric flow to calculate impact on gastric mixing. In all subjects, extracellular mapping demonstrated normal aboral slow-wave propagation and a region of increased amplitude and velocity in the prepyloric antrum. On average, the high-velocity region commenced 28 mm proximal to the pylorus, and activation ceased 6 mm from the pylorus. Within this region, velocity increased 0.2 mm/s per mm of tissue, from the mean 3.3 ± 0.1 mm/s to 7.5 ± 0.6 mm/s (P < 0.001), and extracellular amplitude increased from 1.5 ± 0.1 mV to 2.5 ± 0.1 mV (P < 0.001). CFD modeling using representative parameters quantified a marked increase in antral recirculation, resulting in an enhanced gastric mixing, due to the accelerating terminal antral contraction. The extent of gastric mixing increased almost linearly with the maximal velocity of the contraction. In conclusion, the human terminal antral contraction is controlled by a short region of rapid high-amplitude slow-wave activity. Distal antral wave acceleration plays a major role in antral flow and mixing, increasing particle strain and trituration.

Simultaneous anterior and posterior serosal mapping of gastric slow-wave dysrhythmias induced by vasopressin

NEW FINDINGS

What is the central question of this study? This study aimed to provide the first comparison of simultaneous high-resolution mapping of anterior and posterior gastric serosa over sustained periods. What is the main finding and its importance? Episodes of spontaneous gastric slow-wave dysrhythmias increased significantly following intravenous infusion of vasopressin compared with the baseline state. A number of persistent dysrhythmias were defined, including ectopic activation, conduction block, rotor, retrograde and collision/merger of wavefronts. Slow-wave dysrhythmias could occur either simultaneously or independently on the anterior and posterior gastric serosa, and interacted depending on activation-repolarization and frequency dynamics. High-resolution mapping enables mechanistic insights into gastric slow-wave dysrhythmias and is now achieving clinical translation. However, previous studies have focused mainly on dysrhythmias occurring on the anterior gastric wall. The present study simultaneously mapped the anterior and posterior gastric serosa during episodes of dysrhythmias induced by vasopressin to aid understanding of dysrhythmia initiation, maintenance and termination. High-resolution mapping (8 × 16 electrodes on each serosa; 20-74 cm2 ) was performed in anaesthetized dogs. Baseline recordings (21 ± 8 min) were followed by intravenous infusion of vasopressin (0.1-0.5 IU ml-1 at 60-190 ml h-1 ) and further recordings (22 ± 13 min). Slow-wave activation maps, amplitudes, velocity, interval and frequency were calculated, and differences compared between baseline and postinfusion. All dogs demonstrated an increased prevalence of dysrhythmic events following infusion of vasopressin (17 versus 51%). Both amplitude and velocity demonstrated significant differences (baseline versus postinfusion: 3.6 versus 2.2 mV; 7.7 versus 6.5 mm s-1 ; P < 0.05 for both). Dysrhythmias occurred simultaneously or independently on the anterior and posterior serosa, and then interacted according to frequency dynamics. A number of persistent dysrhythmias were compared, including the following: ectopic activation (n = 2 animals), conduction block (n = 1), rotor (n = 2), retrograde (n = 3) and collision/merger of wavefronts (n = 2). We conclude that infusion of vasopressin induces gastric dysrhythmias, which occur across a heterogeneous range of frequencies and patterns. The results demonstrate that different classes of gastric dysrhythmias may arise simultaneously or independently in one or both surfaces of the serosa, then interact according to their relative frequencies. These results will help to inform interpretation of clinical dysrhythmia.

A novel retractable laparoscopic device for mapping gastrointestinal slow wave propagation patterns

BACKGROUND

Gastric slow waves regulate peristalsis, and gastric dysrhythmias have been implicated in functional motility disorders. To accurately define slow wave patterns, it is currently necessary to collect high-resolution serosal recordings during open surgery. We therefore developed a novel gastric slow wave mapping device for use during laparoscopic procedures.

METHODS

The device consists of a retractable catheter constructed of a flexible nitinol core coated with Pebax. Once deployed through a 5-mm laparoscopic port, the spiral head is revealed with 32 electrodes at 5 mm intervals. Recordings were validated against a reference electrode array in pigs and tested in a human patient.

RESULTS

Recordings from the device and a reference array in pigs were identical in frequency (2.6 cycles per minute; p = 0.91), and activation patterns and velocities were consistent (8.9 ± 0.2 vs 8.7 ± 0.1 mm s^-1; p = 0.2). Device and reference amplitudes were comparable (1.3 ± 0.1 vs 1.4 ± 0.1 mV; p = 0.4), though the device signal-to-noise ratio was higher (17.5 ± 0.6 vs 12.8 ± 0.6 dB; P < 0.0001). In the human patient, corpus slow waves were recorded and mapped (frequency 2.7 ± 0.03 cycles per minute, amplitude 0.8 ± 0.4 mV, velocity 2.3 ± 0.9 mm s^-1).

CONCLUSION

In conclusion, the novel laparoscopic device achieves high-quality serosal slow wave recordings. It can be used for laparoscopic diagnostic studies to document slow wave patterns in patients with gastric motility disorders.

Altered postprandial responses in gastric myoelectrical activity and cardiac autonomic functions in healthy obese subjects

BACKGROUND

It is unknown whether gastric myoelectrical activity (GMA) and autonomic functions are altered in obesity. The aims of this study were to investigate GMA and autonomic functions in obese subjects and to compare their responses to different meals with lean subjects.

METHODS

The study was performed in 12 lean and 12 obese subjects. GMA was measured using electrogastrography, and autonomic functions were assessed using spectral analysis of heart rate variability.

RESULTS

The study achieved the following key results: (1) Compared to lean subjects, obese subjects showed unaltered gastric slow waves at baseline but enhanced responses to both fatty and protein meals. The lean subjects showed a reduced percentage of normal gastric slow waves with a fatty meal, which was not seen in obese subjects; lean subjects showed no changes in the dominant frequency or power of the gastric slow waves with a protein meal, whereas both of these parameters were increased in obese subjects. (2) Autonomic functions were altered in obese subjects in both fasting and fed states. Obese subjects showed an increased sympathetic activity in the fasting state, but absence of a normal postprandial response in sympathovagal balance to both fatty and protein meals.

CONCLUSIONS

The findings on gastric slow waves demonstrate that obese subjects are more receptive to fatty meals and more responsive to protein meals. Obese subjects have impaired autonomic functions in both fasting and fed states. The alterations in gastric and autonomic functions may contribute to eating disorders in the obese.

Recent progress in gastric arrhythmia: pathophysiology, clinical significance and future horizons

Gastric arrhythmia continues to be of uncertain diagnostic and therapeutic significance. However, recent progress has been substantial, with technical advances, theoretical insights and experimental discoveries offering new translational opportunities. The discoveries that interstitial cells of Cajal (ICC) generate slow waves and that ICC defects are associated with dysmotility have reinvigorated gastric arrhythmia research. Increasing evidence now suggests that ICC depletion and damage, network disruption and channelopathies may lead to aberrant slow wave initiation and conduction. Histological and high-resolution (HR) electrical mapping studies have now redefined the human 'gastric conduction system', providing an improved baseline for arrhythmia research. The application of HR mapping to arrhythmia has also generated important new insights into the spatiotemporal dynamics of arrhythmia onset and maintenance, resulting in the emergence of new provisional classification schemes. Meanwhile, the strong associations between gastric functional disorders and electrogastrography (EGG) abnormalities (e.g. in gastroparesis, unexplained nausea and vomiting and functional dyspepsia) continue to motivate deeper inquiries into the nature and causes of gastrointestinal arrhythmias. In future, technical progress in EGG methods, new HR mapping devices and software, wireless slow wave acquisition systems and improved gastric pacing devices may achieve validated applications in clinical practice. Neurohormonal factors in arrhythmogenesis also continue to be elucidated and a deepening understanding of these mechanisms may open opportunities for drug design for treating arrhythmias. However, for all translational goals, it remains to be seen whether arrhythmia can be corrected in a way that meaningfully improves organ function and symptoms in patients.

Current status of multichannel electrogastrography and examples of its use

Electrogastrography (EGG) is a non-invasive diagnostic motility for recording gastric myoelectrical activity. Gastric myoelectrical activity was first recorded in 1922. Advances in recording equipment enabled widespread use of cutaneous EGG after 1985. Later, introduction of multichannel EGG (M-EGG) enabled measurement of electrical activity transmission. At present, M-EGG findings are used as objective indicators of gastric motility disorders caused by various diseases. EGG measures two categories of gastric electrical activity: electrical response activity, or spike potentials; and electrical control activity, or slow waves. The appearance of abnormal rhythmic electrical activity is indicative of abnormalities in gastric motility. The normal frequency range of gastric electrical activity (normogastria) is around 3 cycles per min. Multiple EGG parameters assist in the assessment of gastric myoelectrical activity, and significant correlations between EGG and other gastric motility tests have been demonstrated in many studies. In Japan, however, EGG remains in the exploratory stage, and its clinical use is limited. There are large variations in procedures and systems used in previous studies, thus there is a need for standardization of EGG procedures and technical terminology. Here, we outline the current status of EGG and report the M-EGG procedures used in our department in addition to our M-EGG findings.

The abstract of this manuscript was presented during an educational seminar titled "Current status of gastrointestinal motility tests and keys for immediate implementation" at the 54th Annual Meeting of the Japan Society of Smooth Muscle Research

A system and method for online high-resolution mapping of gastric slow-wave activity

High-resolution (HR) mapping employs multielectrode arrays to achieve spatially detailed analyses of propagating bioelectrical events. A major current limitation is that spatial analyses must currently be performed "off-line" (after experiments), compromising timely recording feedback and restricting experimental interventions. These problems motivated development of a system and method for "online" HR mapping. HR gastric recordings were acquired and streamed to a novel software client. Algorithms were devised to filter data, identify slow-wave events, eliminate corrupt channels, and cluster activation events. A graphical user interface animated data and plotted electrograms and maps. Results were compared against off-line methods. The online system analyzed 256-channel serosal recordings with no unexpected system terminations with a mean delay 18 s. Activation time marking sensitivity was 0.92; positive predictive value was 0.93. Abnormal slow-wave patterns including conduction blocks, ectopic pacemaking, and colliding wave fronts were reliably identified. Compared to traditional analysis methods, online mapping had comparable results with equivalent coverage of 90% of electrodes, average RMS errors of less than 1 s, and CC of activation maps of 0.99. Accurate slow-wave mapping was achieved in near real-time, enabling monitoring of recording quality and experimental interventions targeted to dysrhythmic onset. This work also advances the translation of HR mapping toward real-time clinical application.

Effects of body mass index on gastric slow wave: a magnetogastrographic study

We measured gastric slow wave activity simultaneously with magnetogastrogram (MGG), mucosal electromyogram (EMG) and electrogastrogram (EGG) in human subjects with varying body mass index (BMI) before and after a meal. In order to investigate the effect of BMI on gastric slow wave parameters, each subject's BMI was calculated and divided into two groups: subjects with BMI ≤ 27 and BMI > 27. Signals were processed with Fourier spectral analysis and second-order blind identification (SOBI) techniques. Our results showed that increased BMI does not affect signal characteristics such as frequency and amplitude of EMG and MGG. Comparison of the postprandial EGG power, on the other hand, showed a statistically significant reduction in subjects with BMI > 27 compared with BMI ≤ 27. In addition to the frequency and amplitude, the use of SOBI-computed propagation maps from MGG data allowed us to visualize the propagating slow wave and compute the propagation velocity in both BMI groups. No significant change in velocity with increasing BMI or meal was observed in our study. In conclusion, multichannel MGG provides an assessment of frequency, amplitude and propagation velocity of the slow wave in subjects with differing BMI categories and was observed to be independent of BMI.

Toward the virtual stomach: progress in multiscale modeling of gastric electrophysiology and motility

Experimental progress in investigating normal and disordered gastric motility is increasingly being complimented by sophisticated multiscale modeling studies. Mathematical modeling has become a valuable tool in this effort, as there is an ever-increasing need to gain an integrative and quantitative understanding of how physiological mechanisms achieve coordinated functions across multiple biophysical scales. These interdisciplinary efforts have been particularly notable in the area of gastric electrophysiology, where they are beginning to yield a comprehensive and integrated in silico organ modeling framework, or 'virtual stomach'. At the cellular level, a number of biophysically based mathematical cell models have been developed, and these are now being applied in areas including investigations of gastric electrical pacemaker mechanisms, smooth muscle electrophysiology, and electromechanical coupling. At the tissue level, micro-structural models are being creatively developed and employed to investigate clinically significant questions, such as the functional effects of ICC degradation on gastrointestinal (GI) electrical activation. At the organ level, high-resolution electrical mapping and modeling studies are combined to provide improved insights into normal and dysrhythmic gastric electrical activation. These efforts are also enabling detailed forward and inverse modeling studies at the 'whole body' level, with implications for diagnostic techniques for gastric dysrhythmias. These recent advances, together with several others highlighted in this review, collectively demonstrate a powerful trend toward applying mathematical models to effectively investigate structure-function relationships and overcome multiscale challenges in basic and clinical GI research.

Electrogastrography: methodology, validation and applications

Electrogastrography (EGG) is a non-invasive method for the measurement of gastric myoelectrical activity. It was first discovered in 1921 and popularized in 1990s. EGG is attractive because it is non-invasive. However, due to its non-invasive nature, there have also been controversies regarding validity and applications of EGG. The aim of this review is to discuss the methodologies, validation and applications of EGG. Pros and cons of EGG will also be discussed in detail. First, the gastric slow wave and its correlation with gastric motility are presented. The association between gastric dysrhythmia and impaired gastric motility is reviewed. Secondly the method for recording the electrogastrogram is presented in detail and pitfalls in the recording and analysis of EGG are discussed. Thirdly, findings reported in the literature demonstrating the accuracy of EGG in recording gastric slow waves and gastric dysrhythmia are reviewed and discussed. The correlation of the electrogastrogram with gastric contraction is carefully discussed. Finally, applications of EGG in a few major areas are reviewed.

Electrogastrography: methodology, validation and applications

Electrogastrography (EGG) is a non-invasive method for the measurement of gastric myoelectrical activity. It was first discovered in 1921 and popularized in 1990s. EGG is attractive because it is non-invasive. However, due to its non-invasive nature, there have also been controversies regarding validity and applications of EGG. The aim of this review is to discuss the methodologies, validation and applications of EGG. Pros and cons of EGG will also be discussed in detail. First, the gastric slow wave and its correlation with gastric motility are presented. The association between gastric dysrhythmia and impaired gastric motility is reviewed. Secondly the method for recording the electrogastrogram is presented in detail and pitfalls in the recording and analysis of EGG are discussed. Thirdly, findings reported in the literature demonstrating the accuracy of EGG in recording gastric slow waves and gastric dysrhythmia are reviewed and discussed. The correlation of the electrogastrogram with gastric contraction is carefully discussed. Finally, applications of EGG in a few major areas are reviewed.

The importance of interstitial cells of cajal in the gastrointestinal tract

Gastrointestinal (GI) motility function and its regulation is a complex process involving collaboration and communication of multiple cell types such as enteric neurons, interstitial cells of Cajal (ICC), and smooth muscle cells. Recent advances in GI research made a better understanding of ICC function and their role in the GI tract, and studies based on different types of techniques have shown that ICC, as an integral part of the GI neuromuscular apparatus, transduce inputs from enteric motor neurons, generate intrinsic electrical rhythmicity in phasic smooth muscles, and have a mechanical sensation ability. Absence or improper function of these cells has been linked to some GI tract disorders. This paper provides a general overview of ICC; their discovery, subtypes, function, locations in the GI tract, and some disorders associated with their loss or disease, and highlights some controversial issues with regard to the importance of ICC in the GI tract.

Evaluation of electrical activity after vagus nerve-preserving distal gastrectomy using multichannel electrogastrography

BACKGROUND

Multichannel electrogastrography (M-EGG) can be used to evaluate gastrointestinal motility. The myoelectric activity of the remnant stomach after surgery has not been measured by M-EGG. This study examined whether myoelectric activity varied with surgical technique and compared vagus nerve-preserving distal gastrectomy (VP-DG) with standard distal gastrectomy without vagus nerve preservation (DG). Furthermore, we examined the relationship between the M-EGG findings and patients' postoperative symptoms.

METHODS

Twenty-six patients who underwent VP-DG, 20 who underwent DG, and 12 healthy volunteers as controls were examined with M-EGG. The Gastrointestinal Symptom Rating Scale (GSRS) was used to assess postoperative symptoms.

RESULTS

Longer periods of normal gastric function (normogastria, 2.0-4.0 cycle min(-1)) were detected in channel 1 in the VP-DG group than in the DG group in either the fasted or fed state (P<0.05). The percentage of slow wave coupling (%SWC) in the fed state correlated negatively with GSRS scores (reflux, r=-0.59, P=0.02; abdominal pain, r=-0.51, P=0.04, indigestion, r=-0.59, P=0.02 and total score, r=-0.75, P=0.02).

CONCLUSIONS

Slow waves can be recorded non-invasively using M-EGG in the remnant stomach following gastrectomy. The VP-DG group showed better preserved gastric myoelectric activity than the DG group, and the %SWC showed a significant negative correlation with scores of GSRS (reflux, abdominal pain, indigestion and total score) in the VP-DG group.

Electrogastrography associated with symptomatic changes after prokinetic drug treatment for functional dyspepsia

AIM: To evaluate the effect of prokinetic drugs on electrogastrography (EGG) parameters according to symptomatic changes in patients with functional dyspepsia (FD).

METHODS: Seventy-four patients with FD were prospectively enrolled in this study between December 2006 and December 2010. We surveyed the patients using a questionnaire on dyspeptic symptoms before and after an 8-wk course of prokinetic drug treatment. We also measured cutaneous pre-prandial and post-prandial EGG recordings including percentage of gastric waves (normogastria, bradygastria, tachygastria), dominant frequency (DF), dominant power (DP), dominant frequency instability coefficient (DFIC), dominant power instability coefficient (DPIC), and the ratio of post-prandial to fasting in DP before and after the 8-wk course of prokinetic drug treatment.

RESULTS: Fifty-two patients (70%) achieved symptomatic improvement after prokinetic drug treatment. Patients who had normal gastric slow waves showed symptom improvement group after treatment. Post-prandial DF showed a downward trend in the symptom improvement group, especially in the itopride group. Post-prandial DP was increased regardless of symptom improvement, especially in the itopride group and mosapride group. Post-prandial DFIC and DPIC in the symptom improvement group were significantly increased after the treatment. The EGG power ratio was increased after treatment in the symptom improvement group (0.50 ± 0.70 vs 0.93 ± 1.77, P = 0.002), especially in the itopride and levosulpiride groups.

CONCLUSION: Prokinetics could improve the symptoms of FD by regulating gastric myoelectrical activity, and EGG could be a useful tool in evaluating the effects of various prokinetics.

Analysis of pacemaker activity in the human stomach

Extracellular electrical recording and studies using animal models have helped establish important concepts of human gastric physiology. Accepted standards include electrical quiescence in the fundus, 3 cycles per minute (cpm) pacemaker activity in corpus and antrum, and a proximal-to-distal slow wave frequency gradient. We investigated slow wave pacemaker activity, contractions and distribution of interstitial cells of Cajal (ICC) in human gastric muscles. Muscles were obtained from patients undergoing gastric resection for cancer, and the anatomical locations of each specimen were mapped by the operating surgeon to 16 standardized regions of the stomach. Electrical slow waves were recorded with intracellular microelectrodes and contractions were recorded by isometric force techniques. Slow waves were routinely recorded from gastric fundus muscles. These events had similar waveforms as slow waves in more distal regions and were coupled to phasic contractions. Gastric slow wave frequency was significantly greater than 3 cpm in all regions of the stomach. Antral slow wave frequency often exceeded the highest frequency of pacemaker activity in the corpus. Chronotropic mechanisms such as muscarinic and prostaglandin receptor binding, stretch, extracelluar Ca(2+) and temperature were unable to explain the observed slow wave frequency that exceeded accepted normal levels. Muscles from all regions through the thickness of the muscularis demonstrated intrinsic pacemaker activity, and this corresponded with the widespread distribution in ICC we mapped throughout the tunica muscularis. Our findings suggest that extracellular electrical recording has underestimated human slow wave frequency and mechanisms of human gastric function may differ from standard laboratory animal models.

A multiscale model of the electrophysiological basis of the human electrogastrogram

The motility of the stomach is coordinated by an electrical activity termed "slow waves", and slow-wave dysrhythmias contribute to motility disorders. One major method for clinically evaluating gastric dysrhythmias has been electrogastrography (EGG); however, the clinical utility of EGG is limited partly due to the uncertainty regarding its electrophysiological basis. In this study, a multiscale model of gastric slow waves was generated from a biophysically based continuum description of cellular electrical events, coupled with a subject-specific human stomach model and high-resolution electrical mapping data. The model was then applied using a forward-modeling approach, within an anatomical torso model, to define how slow wave activity summates to generate the EGG potentials. The simulated EGG potentials were shown to be spatially varying in amplitude (0.27-0.33 mV) and duration (9.2-15.3 s), and the sources of this variance were quantified with respect to the activation timings of the underlying slow wave activity. This model constitutes an improved theory of the electrophysiological basis of the EGG, and offers a framework for optimizing the placement of EGG electrodes, and for interpreting the EGG changes occurring in disease states.

Gastrointestinal system

The functions of the gastrointestinal (GI) tract include digestion, absorption, excretion, and protection. In this review, we focus on the electrical activity of the stomach and small intestine, which underlies the motility of these organs, and where the most detailed systems descriptions and computational models have been based to date. Much of this discussion is also applicable to the rest of the GI tract. This review covers four major spatial scales: cell, tissue, organ, and torso, and discusses the methods of investigation and the challenges associated with each. We begin by describing the origin of the electrical activity in the interstitial cells of Cajal, and its spread to smooth muscle cells. The spread of electrical activity through the stomach and small intestine is then described, followed by the resultant electrical and magnetic activity that may be recorded on the body surface. A number of common and highly symptomatic GI conditions involve abnormal electrical and/or motor activity, which are often termed functional disorders. In the last section of this review we address approaches being used to characterize and diagnose abnormalities in the electrical activity and how these might be applied in the clinical setting. The understanding of electrophysiology and motility of the GI system remains a challenging field, and the review discusses how biophysically based mathematical models can help to bridge gaps in our current knowledge, through integration of otherwise separate concepts.

Effects of volume conductor and source configuration on simulated magnetogastrograms

Recordings of the magnetic fields (MFs) arising from gastric electrical activity (GEA) have been shown to be able to distinguish between normal and certain abnormal GEA. Mathematical models provide a powerful tool for revealing the relationship between the underlying GEA and the resultant magnetogastrograms (MGGs). However, it remains uncertain the relative contributions that different volume conductor and dipole source models have on the resultant MFs. In this study, four volume conductor models (free space, sphere, half space and an anatomically realistic torso) and two dipole source configurations (containing 320 moving dipole sources and a single equivalent moving dipole source) were used to simulate the external MFs. The effects of different volume conductor models and dipole source configurations on the MF simulations were examined. The half space model provided the best approximation of the MFs produced by the torso model in the direction normal to the coronal plane. This was despite the fact that the half space model does not produce secondary sources, which have been shown to contribute up to 50% of the total MFs when an anatomically realistic torso model was used. We conclude that a realistic representation of the volume conductor and a detailed dipole source model are likely to be necessary when using a model-based approach for interpreting MGGs.

Development of c-kit immunopositive interstitial cells of Cajal in the human stomach

Interstitial cells of Cajal (ICC) include several types of specialized cells within the musculature of the gastrointestinal tract (GIT). Some types of ICC act as pacemakers in the GIT musculature, whereas others are implicated in the modulation of enteric neurotransmission. Kit immunohistochemistry reliably identifies the location of these cells and provides information on changes in ICC distribution and density. Human stomach specimens were obtained from 7 embryos and 28 foetuses without gastrointestinal disorders. The specimens were 7-27 weeks of gestational age, and both sexes are represented in the sample. The specimens were exposed to anti-c-kit antibodies to investigate ICC differentiation. Enteric plexuses were immunohistochemically examined by using anti-neuron specific enolase and the differentiation of smooth muscle cells (SMC) was studied with anti-alpha smooth muscle actin and anti-desmin antibodies. By week 7, c-kit-immunopositive precursors formed a layer in the outer stomach wall around myenteric plexus elements. Between 9 and 11 weeks some of these precursors differentiated into ICC. ICC at the myenteric plexus level differentiated first, followed by those within the muscle layer: between SMC, at the circular and longitudinal layers, and within connective tissue septa enveloping muscle bundles. In the fourth month, all subtypes of c-kit-immunoreactivity ICC which are necessary for the generation of slow waves and their transfer to SMC have been developed. These results may help elucidate the origin of ICC and the aetiology and pathogenesis of stomach motility disorders in neonates and young children that are associated with absence or decreased number of these cells.