Electrogastrography: measurement, analysis and prospective applications

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

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

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Who says you are so sick? An investigation on individual susceptibility to cybersickness triggers using EEG, EGG and ECG

In this research paper, we conducted a study to investigate the connection between three objective measures: Electrocardio-gram(EGG), Electrogastrogram (EGG), and Electroencephalogram (EEG), and individuals' susceptibility to cybersickness. Our primary objective was to identify which of these factors plays a central role in causing discomfort when experiencing rotations along three different axes: Roll, Pitch, and Yaw. This study involved 35 participants who were tasked with destroying asteroids using their eye gaze while undergoing passive rotations in four separate sessions. The results, when combined with subjective measurements (specifically, Fast motion sickness questionnaire (FMS) and Simulator sickness questionnaire (SSQ) score), demonstrated that EGG measurements were superior in detecting symptoms associated with nausea. As for ECG measurements, our observations did reveal significant changes in Heart Rate Variability (HRV) parameters. However, we caution against relying solely on ECG as a dependable indicator for assessing the extent of cybersickness. Most notably, EEG signals emerged as a crucial resource for discerning individual differences related to these rotational axes. Our findings were significant not only in the context of periodic activities but also underscored the potential of aperiodic activities in detecting the severity of cybersickness and an individual's susceptibility to rotational triggers.

Pulsed-field ablation does not induce esophageal and periesophageal injury-A new esophageal safety paradigm in catheter ablation of atrial fibrillation

INTRODUCTION

Esophageal injury is one of the most serious complications of pulmonary vein isolation (PVI) with thermic energy sources. Better tissue selectivity of primarily non-thermic pulsed field ablation (PFA) may eliminate collateral injury, particularly the risk of atrio-esophageal fistula (AEF).

OBJECTIVE

To compare the incidence of any (peri)-esophageal injury following PVI using PFA to thermic energy sources.

METHODS

Using endoscopy, endoscopic ultrasound, and electrogastrography before and after PVI, esophageal and periesophageal injury (mucosal lesions, food retention, periesophageal edema, or vagal nerve injury) were assessed following PFA and radiofrequency (RF)- or cryoballoon (CB)-PVI.

RESULTS

Between December 2022 and February 2023, 20 patients (67 ± 10 years, 53% male) undergoing PFA (Farapulse, Boston Scientific) for atrial fibrillation (AF) were studied and compared with a previous cohort of 57 patients who underwent thermic PVI (CB: n = 33; RF: n = 24). Following PFA-PVI, none of the patients had mucosal lesions, food retention, or ablation-induced vagal nerve injury; four patients showed periesophageal edema. Following thermic ablation, 33/57 patients (58%) showed esophageal and/or periesophageal injury (CB: 21/33 [64%], RF: 12/24 [50%]), in detail 4/57 mucosal lesions, 18/57 food retention, 17/57 vagal nerve injury, and 20/52 edema. Midterm success rates were similar for all energy sources.

CONCLUSION

In contrast to thermic ablation tools, PFA is not associated with relevant esophageal and periesophageal injury, and might, therefore, reduce or eliminate the risk of potentially lethal AEF in interventional treatment of AF. The etiology of ablation-induced periesophageal edema is unknown but has not been shown to be related to lesion progression.

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

BACKGROUND AND PURPOSE

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

Revised spectral metrics for body surface measurements of gastric electrophysiology

BACKGROUND

Electrogastrography (EGG) non-invasively evaluates gastric function but has not achieved common clinical adoption due to several technical limitations. Body Surface Gastric Mapping (BSGM) has been introduced to overcome these limitations, but pitfalls in traditional metrics used to analyze spectral data remain unaddressed. This study critically evaluates five traditional EGG metrics and introduces improved BSGM spectral metrics, with validation in a large cohort.

METHODS

Pitfalls in five EGG metrics were assessed (dominant frequency, percentage time normogastria, amplitude, power ratio, and instability coefficient), leading to four revised BSGM spectral metrics. Traditional and revised metrics were compared to validate performance using a standardized 100-subject database of BSGM tests (30 min baseline; 4-h postprandial) recorded using Gastric Alimetry® (Alimetry).

KEY RESULTS

BMI and amplitude were highly correlated (r = -0.57, p < 0.001). We applied a conservative BMI correction to obtain a BMI-adjusted amplitude metric (r = -0.21, p = 0.037). Instability coefficient was highly correlated with both dominant frequency (r = -0.44, p < 0.001), and percent bradygastria (r = 0.85, p < 0.001), in part due to misclassification of low frequency transients as gastric activity. This was corrected by introducing distinct gastric frequency and stability metrics (Principal Gastric Frequency and Gastric Alimetry Rhythm Index (GA-RI)^TM ) that were uncorrelated (r = 0.14, p = 0.314). Only 28% of subjects showed a maximal averaged amplitude within the first postprandial hour. Calculating Fed:Fasted Amplitude Ratio over a 4-h postprandial window yielded a median increase of 0.31 (IQR 0-0.64) above the traditional ratio.

CONCLUSIONS & INFERENCES

The revised metrics resolve critical pitfalls impairing the performance of traditional EGG, and should be applied in future BSGM spectral analyses.

Pulmonary vein isolation-induced vagal nerve injury and gastric motility disorders detected by electrogastrography: The side effects of pulmonary vein isolation in atrial fibrillation (SEPIA) study

INTRODUCTION

Safety of pulmonary vein isolation (PVI) has been established in clinical studies. However, despite prevention efforts the incidence of damage to (peri)-esophageal tissue has not decreased, and the pathophysiology is incompletely understood. Damage to vagal nerve branches may be involved in lesion progression to atrio-esophageal fistula. Using electrogastrography, we assessed the incidence of periesophageal vagal nerve injury (VNI) following atrial fibrillation ablation and its association with procedural parameters and endoscopic results.

METHODS

Patients were studied using electrogastrography, endoscopy, and endoscopic ultrasound before and after cryoballoon (CB) or radiofrequency (RF) PVI. The incidence of ablation-induced neuropathic pattern (indicating VNI) in pre- and postprocedural electrogastrography was assessed and correlated with endoscopic results and ablation data.

RESULTS

Between February 2021 und January 2022, 85 patients (67 ± 10 years, 53% male) were included, 33 were treated with CB and 52 with RF (38 with moderate power moderate duration [25-30 W] and 14 with high power short duration [50 W]). Ablation-induced VNI was detected in 27/85 patients independent of the energy form. Patients with VNI more frequently had postprocedural endoscopically detected pathology (8% mucosal esophageal lesions, 36% periesophageal edema, 33% food retention) but there was incomplete overlap. Pre-existing esophagitis increased the likelihood of VNI. Ablation data and esophageal temperature data did not predict VNI.

CONCLUSION

PVI-induced VNI is quite common and independent of ablation energy source. VNI is part of (peri)-esophageal damage and only partially overlaps with endoscopic findings. VNI-associated acidic reflux may be involved in the complex pathophysiology of esophageal lesion progression to fistula.

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.

Biosensor-Assisted Method for Abdominal Syndrome Classification Using Machine Learning Algorithm

The digestive system is one of the essential systems in human physiology where the stomach has a significant part to play with its accessories like the esophagus, duodenum, small intestines, and large intestinal tract. Many individuals across the globe suffer from gastric dysrhythmia in combination with dyspepsia (improper digestion), unexplained nausea (feeling), vomiting, abdominal discomfort, ulcer of the stomach, and gastroesophageal reflux illnesses. Some of the techniques used to identify anomalies include clinical analysis, endoscopy, electrogastrogram, and imaging. Electrogastrogram is the registration of electrical impulses that pass through the stomach muscles and regulate the contraction of the muscle. The electrode senses the electrical impulses from the stomach muscles, and the electrogastrogram is recorded. A computer analyzes the captured electrogastrogram (EGG) signals. The usual electric rhythm produces an enhanced current in the typical stomach muscle after a meal. Postmeal electrical rhythm is abnormal in those with stomach muscles or nerve anomalies. This study considers EGG of ordinary individuals, bradycardia, dyspepsia, nausea, tachycardia, ulcer, and vomiting for analysis. Data are collected in collaboration with the doctor for preprandial and postprandial conditions for people with diseases and everyday individuals. In CWT with a genetic algorithm, db4 is utilized to obtain an EGG signal wave pattern in a 3D plot using MATLAB. The figure shows that the existence of the peak reflects the EGG signal cycle. The number of present peaks categorizes EGG. Adaptive Resonance Classifier Network (ARCN) is utilized to identify EGG signals as normal or abnormal subjects, depending on the parameter of alertness (μ). This study may be used as a medical tool to diagnose digestive system problems before proposing invasive treatments. Accuracy of the proposed work comes up with 95.45%, and sensitivity and specificity range is added as 92.45% and 87.12%.

New device for active gastric mechanical stimulation

BACKGROUND

Gastroparesis is a chronic stomach disorder and effective treatment is the aim of different strategies. Alternative therapies consist of an electrical stimulation of the stomach to evoke a response in the gastric activity. We present the development and in vivo application of an electromagnet system to induce a mechanical stimulus in the stomach aiming for gastric contractile responses.

METHODS

The electromagnet system consisted of an implantable magnet and an external drive coil. We implanted the magnet at the greater curvature of the gastric body in rats. We applied an alternating current to the drive coils, inducing mechanical stimulation of the gastric wall. We measured the gastric contraction activity and gastric electrical activity in response to the stimulus using AC biosusceptometry and electrogastrography. Moreover, we used the phenol red to evaluate the stimulus effects on gastrointestinal transit.

KEY RESULTS

The stimulus increased the spectral intensity and signal-to-noise ratio significantly of gastric contraction activity and gastric electrical activity. Furthermore, we found a lower phenol red retention in the stomach in rats without stimulus. No significant differences were found in frequency and root mean square amplitude.

CONCLUSIONS & INFERENCES

We developed a new simple electromagnet system that evoked a contraction and gastric electrical response using a mechanical stimulus and decreased gastric emptying time. The system is an accessible tool and may contribute to gastroparesis studies in animals.

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.

Electrogastrography in Autonomous Vehicles-An Objective Method for Assessment of Motion Sickness in Simulated Driving Environments

Autonomous vehicles are expected to take complete control of the driving process, enabling the former drivers to act as passengers only. This could lead to increased sickness as they can be engaged in tasks other than driving. Adopting different sickness mitigation techniques gives us unique types of motion sickness in autonomous vehicles to be studied. In this paper, we report on a study where we explored the possibilities of assessing motion sickness with electrogastrography (EGG), a non-invasive method used to measure the myoelectric activity of the stomach, and its potential usage in autonomous vehicles (AVs). The study was conducted in a high-fidelity driving simulator with a virtual reality (VR) headset. There separate EGG measurements were performed: before, during and after the driving AV simulation video in VR. During the driving, the participants encountered two driving environments: a straight and less dynamic highway road and a highly dynamic and curvy countryside road. The EGG signal was recorded with a proprietary 3-channel recording device and Ag/AgCl cutaneous electrodes. In addition, participants were asked to signalize whenever they felt uncomfortable and nauseated by pressing a special button. After the drive they completed also the Simulator Sickness Questionnaire (SSQ) and reported on their overall subjective perception of sickness symptoms. The EGG results showed a significant increase of the dominant frequency (DF) and the percentage of the high power spectrum density (FSD) as well as a significant decrease of the power spectrum density Crest factor (CF) during the AV simulation. The vast majority of participants reported nausea during more dynamic conditions, accompanied by an increase in the amplitude and the RMS value of EGG. Reported nausea occurred simultaneously with the increase in EGG amplitude. Based on the results, we conclude that EGG could be used for assessment of motion sickness in autonomous vehicles. DF, CF and FSD can be used as overall sickness indicators, while the relative increase in amplitude of EGG signal and duration of that increase can be used as short-term sickness indicators where the driving environment may affect the driver.

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.

Artifact Rejection Methodology Enables Continuous, Noninvasive Measurement of Gastric Myoelectric Activity in Ambulatory Subjects

The increasing prevalence of functional and motility gastrointestinal (GI) disorders is at odds with bottlenecks in their diagnosis, treatment, and follow-up. Lack of noninvasive approaches means that only specialized centers can perform objective assessment procedures. Abnormal GI muscular activity, which is coordinated by electrical slow-waves, may play a key role in symptoms. As such, the electrogastrogram (EGG), a noninvasive means to continuously monitor gastric electrical activity, can be used to inform diagnoses over broader populations. However, it is seldom used due to technical issues: inconsistent results from single-channel measurements and signal artifacts that make interpretation difficult and limit prolonged monitoring. Here, we overcome these limitations with a wearable multi-channel system and artifact removal signal processing methods. Our approach yields an increase of 0.56 in the mean correlation coefficient between EGG and the clinical "gold standard", gastric manometry, across 11 subjects (p < 0.001). We also demonstrate this system's usage for ambulatory monitoring, which reveals myoelectric dynamics in response to meals akin to gastric emptying patterns and circadian-related oscillations. Our approach is noninvasive, easy to administer, and has promise to widen the scope of populations with GI disorders for which clinicians can screen patients, diagnose disorders, and refine treatments objectively.

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.

The Use of Continuous Wavelet Transform Based on the Fast Fourier Transform in the Analysis of Multi-channel Electrogastrography Recordings

This paper presents the analysis of multi-channel electrogastrographic (EGG) signals using the continuous wavelet transform based on the fast Fourier transform (CWTFT). The EGG analysis was based on the determination of the several signal parameters such as dominant frequency (DF), dominant power (DP) and index of normogastria (NI). The use of continuous wavelet transform (CWT) allows for better visible localization of the frequency components in the analyzed signals, than commonly used short-time Fourier transform (STFT). Such an analysis is possible by means of a variable width window, which corresponds to the scale time of observation (analysis). Wavelet analysis allows using long time windows when we need more precise low-frequency information, and shorter when we need high frequency information. Since the classic CWT transform requires considerable computing power and time, especially while applying it to the analysis of long signals, the authors used the CWT analysis based on the fast Fourier transform (FFT). The CWT was obtained using properties of the circular convolution to improve the speed of calculation. This method allows to obtain results for relatively long records of EGG in a fairly short time, much faster than using the classical methods based on running spectrum analysis (RSA). In this study authors indicate the possibility of a parametric analysis of EGG signals using continuous wavelet transform which is the completely new solution. The results obtained with the described method are shown in the example of an analysis of four-channel EGG recordings, performed for a non-caloric meal.

The extraction of the new components from electrogastrogram (EGG), using both adaptive filtering and electrocardiographic (ECG) derived respiration signal

Electrogastrographic examination (EGG) is a noninvasive method for an investigation of a stomach slow wave propagation. The typical range of frequency for EGG signal is from 0.015 to 0.15 Hz or (0.015–0.3 Hz) and the signal usually is captured with sampling frequency not exceeding 4 Hz. In this paper a new approach of method for recording the EGG signals with high sampling frequency (200 Hz) is proposed. High sampling frequency allows collection of signal, which includes not only EGG component but also signal from other organs of the digestive system such as the duodenum, colon as well as signal connected with respiratory movements and finally electrocardiographic signal (ECG). The presented method allows improve the quality of analysis of EGG signals by better suppress respiratory disturbance and extract new components from high sampling electrogastrographic signals (HSEGG) obtained from abdomen surface. The source of the required new signal components can be inner organs such as the duodenum and colon. One of the main problems that appear during analysis the EGG signals and extracting signal components from inner organs is how to suppress the respiratory components. In this work an adaptive filtering method that requires a reference signal is proposed. In the present research, the respiratory component is obtained from non standard ECG (NSECG) signal. For purposes of this paper non standard ECG (namely NSECG) is used, because ECG signal was recorded by other than the standard electrodes placement on the surface of the abdomen. The electrocardiographic derived respiration signal (EDR) is extracted using the phenomena of QRS complexes amplitude modulation by respiratory movements. The main idea of extracting the EDR signal from electrocardiographic signal is to obtain the modulating signal. Adaptive filtering is done in the discrete cosine transform domain. Next the resampled HSEGG signal with attenuated respiratory components is low pass filtered and as a result the extended electrogastrographic signals, included EGG signal and components from other inner organs of digestive system is obtained. One of additional features of the proposed method is a possibility to obtain simultaneously recorded signals, such as: non-standard derivation of ECG, heart rate variability signal, respiratory signal, and EGG signal that allow investigating mutual interferences among internal human systems.

Normal and abnormal electrical propagation in the small intestine

As in other muscular organs, small intestinal motility is determined to a large degree by the electrical activities that occur in the smooth muscle layers of the small intestine. In recent decades, the interstitial cells of Cajal, located in the myenteric plexus, have been shown to be responsible for the generation and propagation of the electrical impulse: the slow wave. It was also known that the slow waves as such do not cause contraction, but that the action potentials ('spikes') that are generated by the slow waves are responsible for the contractions. Recording from large number of extracellular electrodes simultaneously is one method to determine origin and pattern of propagation of these electrical signals. This review reports the characteristics of slow wave propagation through the intestinal tube, the occurrence of propagation blocks along its length, which explains the well-known decrease in frequency, and the specific propagation pattern of the spikes that follow the slow waves. But the value of high-resolution mapping is highest in discovering and analysing mechanisms of arrhythmias in the gut. Most recently, circus movements (also called 're-entries') have been described in the small intestine in several species. Moreover, several types of re-entries have now been described, some similar to what may occur in the heart, such as functional re-entries, but others more unique to the small intestine, such as circumferential re-entry. These findings seem to suggest the possibilities of hitherto unknown pathologies that may be present in the small intestine.

A new method for attenuation of respiration artifacts in electrogastrographic (EGG) signals

Electrogastrography (EGG) is a test method designed for noninvasive assessment of gastric slow waves propagation. The EGG signal is obtained from the electrodes respectively arranged on the surface of the patient's abdomen. A significant problem during recording of the EGG signal is the elimination of disturbances occurring during registration and unwanted components of other signals such as: components of electrocardiographic (ECG), baseline drift or respiratory disturbances. These components are generally present in the signals registered from the surface of the abdomen of the patient. Since EGG frequency components partly overlap with the frequency components of respiratory artifacts, conventional band-pass digital or analog filtering may cause distortion in electrogastrographic signal. In the paper a method for removing respiratory interference occurring during registration of EGG signal and the effect of filtration on selected parameters of EGG signal analysis is presented. Respiratory artifacts are removed through the use of adaptive filter working in the DCT domain. The applied adaptive filtering method involves the use of the signal including respiratory disturbances. This signal is recorded synchronously with the EGG signal using a thermistor placed near the nose of the patient.

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.

The detection of intestinal spike activity on surface electroenterograms

Myoelectrical recording could provide an alternative technique for assessing intestinal motility, which is a topic of great interest in gastroenterology since many gastrointestinal disorders are associated with intestinal dysmotility. The pacemaker activity (slow wave, SW) of the electroenterogram (EEnG) has been detected in abdominal surface recordings, although the activity related to bowel contractions (spike bursts, SB) has to date only been detected in experimental models with artificially favored electrical conductivity. The aim of the present work was to assess the possibility of detecting SB activity in abdominal surface recordings under physiological conditions. For this purpose, 11 recording sessions of simultaneous internal and external myolectrical signals were conducted on conscious dogs. Signal analysis was carried out in the spectral domain. The results show that in periods of intestinal contractile activity, high-frequency components of EEnG signals can be detected on the abdominal surface in addition to SW activity. The energy between 2 and 20 Hz of the surface myoelectrical recording presented good correlation with the internal intestinal motility index (0.64 +/- 0.10 for channel 1 and 0.57 +/- 0.11 for channel 2). This suggests that SB activity can also be detected in canine surface EEnG recording.

Ultrasonographic comparison of gastric motility between diabetic gastroparesis patients with and without metabolic syndrome

BACKGROUND AND AIMS

Diabetic patients with poor glycemic control or long standing disease often have impaired gastric motility. Recently, metabolic factors such as blood glucose have been reported as influencing gastric motility independently of autonomic neuropathy. Many diabetic patients have metabolic syndrome, which is strongly associated with coronary and other diseases. We investigated whether metabolic syndrome influences diabetic gastroparesis patients.

METHODS

We observed gastric motility ultrasonographically in diabetic gastroparesis patients including nine with and nine without metabolic syndrome. Both groups complained of upper abdominal symptoms when hospitalized to improve blood sugar control. All patients underwent upper gastrointestinal endoscopy to rule out gastric and duodenal lesions. All had autonomic neuropathy. Gastric motility was evaluated within 3 days after admission by transabdominal ultrasonography after a test meal.

RESULTS

Gastric emptying was 45.0 +/- 13.7% in patients with and 39.1 +/- 11.9% in patients without metabolic syndrome, which was not statistically significant. Frequency of gastric contractions was 8.33 +/- 2.78 per 3 min in patients with metabolic syndrome and 7.44 +/- 2.13 per 3 min in the others, which was not statistically significant. The motility index, which involves antral contractility, was 3.21 +/- 2.18 in patients with metabolic syndrome and 2.80 +/- 1.87 in the others, which was not statistically significant.

CONCLUSIONS

Metabolic syndrome did not appear to contribute to delayed gastric motility in diabetic gastroparesis.

Comparison and analysis of inter-subject variability of simulated magnetic activity generated from gastric electrical activity

Electrogastrograms (EGGs) produced from gastric electrical activity (GEA) are used as a non-invasive method to aid in the assessment of a subject's gastric condition. It has been documented that recordings of the magnetic activity generated from GEA are more reliable. Typically, with magnetic measurements of GEA, only activity perpendicular to the body is recorded. Also, external anatomical landmarks are used to position the magnetic recording devices, SQUIDs, (Superconducting Quantum Interference Devices) over the stomach with no allowance made for body habitus. In the work presented here, GEA and its corresponding magnetic activity are simulated. Using these data, we investigate the effects of using a standard SQUID location as well as a customized SQUID position and the contribution the magnetic component perpendicular to the body makes to the magnetic field. We also explore the effects of the stomach wall thickness on the resultant magnetic fields. The simulated results show that the thicker the wall, the larger the magnitude of the magnetic field holding the same signal patterns. We conclude that most of the magnetic activity arising from GEA occurs in a plane parallel to the anterior body. We also conclude that using a standard SQUID position can be suboptimal.

Effect of ghrelin on gastric myoelectric activity and gastric emptying in rats

Ghrelin is a recently discovered peptide in the endocrine cells of the stomach, which may stimulate gastric motility via the vagal nerve pathway. However, the mechanism of ghrelin-induced changes in gastrointestinal motility has not been clearly defined. The purpose of this study was to investigate the pharmacological effects of ghrelin on gastric myoelectrical activity and gastric emptying in rats, and to investigate whether cholinergic activity is involved in the effects of ghrelin. The study was performed on Sprague-Dawley rats implanted with serosal electrodes for electrogastrographic recording. Gastric slow waves were recorded from fasting rats at baseline and after injection of saline, ghrelin, atropine, or atropine+ghrelin. Gastric emptying of non-caloric liquid was measured by the spectrophotometric method in conscious rats. Intravenous administration of rat ghrelin (20 microg/kg) increased not only dominant frequency, dominant power and regularity of the gastric slow wave but also the gastric emptying rate when compared with the control rats (P<0.01, P<0.05, P<0.05, P<0.001 respectively). These stimulatory actions of ghrelin on both gastric myoelectrical activity and gastric emptying were not fully eliminated by pretreatment with atropine sulphate. These results taken together suggest that ghrelin may play a physiological role in the enteric neurotransmission controlling gastric contractions in rats.

Clinical utility of electrogastrography and the water load test in patients with upper gastrointestinal symptoms

We assessed gastric myoelectric functioning in patients with various gastrointestinal symptoms and to determine the utility of electrogastrography in differentiating specific disease entities. Electrogastrography with a water load was performed in 101 patients with reflux disease, 55 patients with active gastric ulcer, 59 patients with functional dyspepsia, and 30 controls. Upper gastrointestinal symptoms were assessed in each patient. Electrogastrography was abnormal in 41 (40.6%) patients with reflux disease, 31 (56.4%) patients with active gastric ulcer, and 26 (44.1%) patients with functional dyspepsia (P=NS). Water load tolerance was greater in controls than any patient group (all P<0.05). Symptoms predicted abnormal electrogastrography in reflux patents with satiety (OR=2.9; P<0.05) and in dyspeptic patients with nausea (OR=3.1; P<0.05). Although electrogastrography is helpful in differentiating subgroups of patients with nausea or satiety, it cannot directly differentiate disease states such as reflux disease, gastric ulcer, and functional dyspepsia.

Cutaneous Electrical Stimulation of Mid-frequency on Acupiont Affects the Electrogastrogram

Acupuncture, including the manual acupuncture, electroacupuncture and cutaneous electrical stimulation on acupiont, is known to enhance the gastric motility. The aim of this paper is to study the changes in electrogastrogram (EGG) when the acupiont Zusanli is stimulated cutaneously by electrical signal of mid-frequency. The result shows that the regularity of EGG is enhanced after the stimulation, and the improvement is more obvious in the EGG recorded near the antrum.

Trans-cutaneous electrogastrographic study of gastric myoelectric activity in transposed intrathoracic stomach after esophagectomy

We examined the feasibility of trans-cutaneous electrogastrography (EGG) in recording myoelectric activity of the transposed thoracic stomach after esophagectomy. Nineteen patients who had Ivor-Lewis esophagectomy were studied. The EGG signal was recorded using cutaneous electrodes placed over the lower sternum. Eleven patients who underwent total gastrectomy served as controls. Normal rhythm pattern (2.4-3.6 cpm > or = 70%) and power ratio (PR > or = 2) was observed in five and 12 patients, respectively, after esophagectomy. The observation of normal gastric rhythm was more frequent in the postprandial period in the esophagectomy group (median 42.6%vs. 7.4%, P = 0.01), and the PR was significantly higher (median 2.27 vs. 1.38, P = 0.013) than the gastrectomy group. Feeding further increased the prevalence of normal gastric slow wave in the esophagectomy group (median 14.8% to 42.6%, P = 0.002) and improved the stability of dominant frequency (median 78% to 67%, P = 0.015). We conclude that gastric myoelectric activities of thoracic transposed stomach can be detected from cutaneous sternal electrodes. This represented a preservation of gastric motility even when the stomach is pulled up to the thorax as a substitute for the esophagus.

Electrogastrography in children and adolescents with type 1 diabetes: weak correlation with metabolic control parameters

AIM

To evaluate gastric myoelectrical activity with respect to duration and metabolic control of type 1 diabetes mellitus (T1DM).

METHODS

172 children and adolescents with T1DM (mean 14.4+/-3.7 y), divided into subgroups depending on diabetes duration (< 5 and > 5 y), and 35 healthy controls (mean 13.93+/-3.59 y) were examined. All subjects underwent electrogastrography (EGG) performed after overnight fasting. In subjects with T1DM, haemoglobin A1c (HbA1c) and blood glucose levels during EGG records were measured.

RESULTS

15.69% of T1DM patients and 91.42% of the controls fulfilled normal EGG criteria (p < 0.001). T1DM subjects had a lower percentage of fasting normogastria (34.56+/-27.35% vs 69.84+/-18.16%, p = 0.0001) and higher bradygastria (51.97+/-30.24% vs 19.11+/-15.01%, p = 0.0001) compared to controls. In diabetic patients, an increase in postprandial normogastria (60.37+/-23.96% vs 76.68+/-12.38, p < 0.05) and a decrease in bradygastria percentage (25.67+/-21.01% vs 9.58+/-7.13%, p < 0.05) was observed. In children with disease < 5 y, diabetes duration correlated with power ratio (r = - 0.27, p = 0.01), postprandial normogastria (r = - 0.24, p = 0.03) and tachygastria (r = 0.25, p = 0.02). Weak correlations between EGG parameters and glucose (preprandial dominant frequency r = - 0.19, p < 0.05; postprandial normogastria r = 0.23, p < 0.01) and HbA1c levels (preprandial bradygastria r = 0.19, postprandial dominant power r = 0.23; p < 0.05) were observed.

CONCLUSION

Gastric myoelectrical rhythm derangement is present in a large proportion of young diabetic patients. Bradygastria is the most prominent EGG abnormality. Weak correlation was found between EGG parameters and diabetes metabolic control.

Prevalence of EGG derangement in newly diagnosed type 1 diabetes in childhood

OBJECTIVE

To evaluate gastric myoelectrical activity in children with newly diagnosed type 1 diabetes melliltus (T1DM) in relation to blood glucose control and visceral neuropathy.

METHODS

Percutaneous electrogastrograpy (EGG) was performed on 42 children (20 F; mean age 12.9 +/- 3.1 years) with T1DM of <1 year's duration and on 35 healthy controls (18 F; mean age 13.4 +/- 3.6 years). After overnight fasting, a 30-minute EGG recording was followed by test meal consumption and then a 60-minute postprandial EGG aquisition. Fasting and postprandial periods were analyzed for gastric dysrhythmias, dominant frequency (DF) and additional parameters. In T1DM patients, HbA1c and blood glucose levels were measured and tests for visceral neuropathy were performed.

RESULTS

In 41 T1DM patients (98%), cardiovascular neuropathy tests were negative. In 12 of those patients (29%) and in 32 healthy controls (91%), electrogastrograms were normal. The percentages of fasting and postprandial gastric dysrhythmias were significantly higher in T1DM patients compared to controls (P < 0,05). In T1DM children after feeding, some normalization of gastric myoelectrical rhythm was observed: normogastria increased nearly 2-fold to 72.6 +/- 22.9% and bradygastria decreased to 20.8 +/- 20.4% from 52.3 +/- 32.4% (P < 0.05). The percentages of fasting bradygastria and normogastria were correlated with glycemia level (r = -0.55 and r = 0.51, respectively; P < 0.05), as was postprandial DF (r = 0.41; P < 0.05). There was no correlation between HbA1c levels and EGG parameters.

CONCLUSIONS

Derangement of the gastric myoelectrical activity is present in 71% of children with early stage T1DM. Glucose levels influence gastric myoelectrical activity, whereas long-term glucose control (HbA1c level) does not correlate with EGG parameters.

[Clinical research techniques in functional digestive disorders]

Functional digestive disorders are characterized by symptoms related to the digestive tract for which no pathological causes can be found using routine diagnostic techniques. In the last few years, several methods have been developed to the study digestive function allow relation between in humans functional alterations, mainly motor and sensory and to be related to functional digestive symptoms. As a result of these advances, both motor and sensory alterations have been identified in subgroups of patients with functional digestive disorders. This knowledge should enable current symptom-based classifications of these disorders to be replaced with new classifications based on specific physiopathologic mechanisms. This would allow more effective therapies aimed at the specific mechanism causing the symptoms to be developed.

Myoelectrical activity of the stomach after surgical correction of esophageal atresia

AIM

The aim of this study was to investigate the motor activity in the stomach of infants with repaired esophageal atresia (EA).

METHOD

Gastric myoelectrical activity was investigated by cutaneous electrogastrography in 15 infants after the surgical correction of EA. Ten infants with no gastrointestinal upset served as controls. Studies were done before and after a milk feed. The pH of the lower esophagus was measured for 24 hours to assess the gastroesophageal reflux (GER) in the infants with repaired EA.

RESULTS

After feeding, a significant increase in bradygastria and decrease in tachygastria were observed as compared with the preprandial period. Compared with healthy infants, the electrogram showed pathological patterns in 73.3% (11/15) of EA patients. Twelve of 15 EA patients showed some clinical sign of GER, and 60% of the EA patients proved to be GER-positive on esophageal pH monitoring. There was no difference in the distribution of gastric myoelectrical waves between the GER-positive and GER-negative EA patients either before or after meal.

CONCLUSION

Cutaneous electrogastrography is a noninvasive, harmless method for obtaining indirect information about the motor function of the stomach. The abnormal changes in physiological gastric myoelectrical activity in EA patients can serve as markers of disturbed neuromuscular function and can play a role in the pathogenesis of feeding disturbances after operative correction of EA. Gastroesophageal reflux, which often occurs after surgical repair of EA, seems to be connected not only with disordered gastric myoelectric activity, but also probably with other factors such as artificially straightened esophagogastric angle or brachyesophagus.

Extraction of gastric slow waves from electrogastrograms: combining independent component analysis and adaptive signal enhancement

The electrogastrogram (EGG), a cutaneous measurement of gastric electrical activity, is a mixture of gastric slow waves and noise. To detect the propagation of gastric slow waves, it is desired to obtain gastric slow waves in each of multichannel EGGs. Recently, independent component analysis (ICA) has shown its efficiency in separating the gastric slow wave from noisy multichannel EGGs. However, this method is not able to recover gastric slow waves in each of the multichannel EGGs. In this paper, a two-stage combined method was proposed for extracting gastric slow waves. First, ICA was performed to separate the gastric slow wave component from noisy multichannel EGGs. Second, adaptive signal enhancement with a reference input derived by the ICA in the first stage was employed to extract gastric slow waves in each channel. Quantitative analysis showed that, with the proposed method, the maximum root-mean-square error between the estimated time lag and its theoretical value in the simulations was only 0.65. The results from real EGG data demonstrated that the combined method was able to extract gastric slow waves from individual channels of EGGs which are important to identify the slow wave propagation. Therefore, the proposed method can be used to detect propagation of gastric slow waves from multichannel EGGs.

Ultrasonographic assessment of gastric motility in diabetic gastroparesis before and after attaining glycemic control

BACKGROUND

Glycemic control is important for maintaining gastric motility in diabetic patients, but gastric motility has not yet been studied ultrasonographically in relation to glycemic control.

METHODS

We made such observations before and after establishing glycemic control in diabetic patients with gastroparesis. We studied 30 diabetic patients with upper abdominal digestive symptoms who were hospitalized for correction of poor blood sugar control and who underwent upper digestive tract endoscopy to rule out structural causes such as gastric/duodenal lesions. Gastric motility was evaluated by transabdominal ultrasonography, using a test meal, before and after attainment of glycemic control (within 3 days after admission and 3 days before discharge). Also, upper abdominal digestive symptoms present on admission and at discharge were compared.

RESULTS

After glycemic control was established, contractions of the antral region were more frequent than before the attainment of control (8.93 +/- 1.17/3 min vs 7.63 +/- 2.22/3 min, respectively; P < 0.001). Glycemic control also significantly improved gastric emptying (before glycemic control, 49.2 +/- 14.8%; after, 67.1 +/- 11.5%; P < 0.001). This was also true for the motility index, concerning antral gastric contractility (before control, 2.97 +/- 1.57; after, 3.75 +/- 1.09; P < 0.05). Upper abdominal symptom scores were also significantly lower after attainment of control than before (0.47 +/- 0.78 vs 3.17 +/- 2.00, respectively; P < 0.001).

CONCLUSIONS

These findings suggest that attaining glycemic control improves gastric motility and attainments upper abdominal symptoms in diabetic patients with gastroparesis.

Electrogastrography in patients with Parkinson's disease

BACKGROUND

Impaired gastrointestinal motility in Parkinson's disease may affect absorption of levodopa and contribute to the disabling response fluctuations (RF). In this study gastric myoelectric activity was recorded with electrogastrography in patients with PD and correlated with the duration, severity and the presence of RF.

METHOD

Electrogastrography (EGG) was performed in 36 patients with PD of which 22 were men. The mean age was 67 years (48-81), mean duration of disease was 7.07 years (1-20), and mean duration of treatment with levodopa was 5.07 years (1-20). Gastric dysrhythmia was diagnosed when either preprandial or postprandial dysrhythmia for more than 30% of the recording period was detected.

RESULTS

The EGG was abnormal in 24 of 36 patients. Significant association was found between preprandial dysrhythmia and duration of disease (P=0.002); duration of levodopa treatment (P=0.003), severity of 86RF (P=0.001), but not with age (P=0.076). Out of 18 patients with RF, 17 had at least one pattern of dysrhythmia. In 11 out of the 18 patients without RF, the EGG was normal while the remaining seven had at least one pattern of dysrhythmia.

CONCLUSION

Abnormal EGG was quite common in this group of patients with PD, particularly in those with RF. The most common pattern of abnormality was preprandial dysrhythmia, which was positively associated with disease duration and length of levodopa treatment. Although frequently asymptomatic, preprandial dysrhythmia leading to impaired gastric emptying may contribute to irregular absorption of levodopa from the small intestine and contribute to disabling response fluctuations.

Electrogastrography: basic knowledge, recording, processing and its clinical applications

The slow wave (SW) of the gastrointestinal (GI) tract mainly functions to trigger the onset of spike to elicit smooth muscle contraction, which provides the essential power of motility. Smooth muscle myogenic control activity or SW is believed to originate in the interstitial cells of Cajal (ICC). The electrical coupling promotes interaction between muscle cells, and ICC additionally contribute to SW rhythmicity. Stomach SW originates in the proximal body showing the continuous rhythmic change in the membrane potential and propagates normally to the distal antrum with a regular rhythm of approximately 3 c.p.m. A technique using electrodes positioned on the abdominal skin to pick up stomach rhythmic SW refers to electrogastrography (EGG). The stomach SW amplitude is very weak, while many visceral organs also produce rhythmic electricities, for example heartbeat, respiration, other organs of the GI tract and even body movements. Thus noise other than SW should be filtered out during the recording, while motion artifacts are visually examined and deleted. Finally, the best signal among all recordings is selected to compute EGG parameters based on spectral analysis. The latter is done not only to tranform frequency domain to time domain but also to provide information of time variability in frequency. Obtained EGG parameters include dominant frequency/power, % normal rhythm, % bradygastria, % tachygastria, instability coefficient and power ratio. Clinical experience in EGG has been markedly accumulated since its rapid evolution. In contrast, lack of standardized methodology in terms of electrode positions, recording periods, test meals, analytic software and normal reference values makes the significance of EGG recording controversial. Unlike imaging or manometrical studies, stomach motility disorders are not diagnosed based only on abnormal EGG parameters. Limitations of EGG recording, processing, computation, acceptable normal parameters, technique and reading should be known to conduct subjective assessments when EGG is used to resolve stomach dysfunction. Understanding basic SW physiology, recording methodology and indications may open EGG as a new domain to approach the stomach motor dysfunction.

Evolution of gastric electrical features and gastric emptying in children with Duchenne and Becker muscular dystrophy

OBJECTIVES

Although muscular dystrophy (MD) affects primarily striated muscles, smooth muscle cells of the gastrointestinal tract may also be involved. We recorded gastric electrical activity and gastric emptying time (GET) in children with MD at initial presentation and at 3-yr follow-up in order to detect gastric motor abnormalities and study their evolution along the clinical course.

METHODS

Twenty children with MD (median age: 4.6 yr; range age: 3-7 yr) were investigated by means of ultrasonography, for measuring GET, and by electrogastrography (EGG); 70 children served as controls.

RESULTS

Ten patients had Duchenne muscular dystrophy (DMD) and 10 Becker muscular dystrophy (BMD). GET was significantly more delayed in MD patients (DMD, median: 195 min; range 150-260 min; BMD, median: 197 min; range: 150-250 min) than in controls (median: 150 min; 110-180 min; p < 0.05); it markedly worsened at the follow-up in DMD (median: 270 min; range 170-310 min; p < 0.001 vs controls) but not in BMD patients (median: 205 min; 155-275 min; p < 0.05 vs DMD). Baseline EGG showed a significantly lower prevalence of normal rhythm and significantly higher prevalence of dysrhythmias in both groups of patients as compared to controls (% of normal rhythm: DMD 66.7 +/- 8.2, BMB 67.2 +/- 11.5, controls 85.3 +/- 7.2, p < 0.001; % of tachygastria: DMD 28.4 +/- 8.0, BMB 29.8 +/- 12.3, controls 10.6 +/- 5.1, p < 0.001; % of dominant frequency instability coefficient: DMD 36.1 +/- 6.0, BMB 33.2 +/- 2.9, controls 17.9 +/- 7.1, p < 0.001); furthermore, no difference in fed-to-fasting ratio of the dominant EGG power was found between the two groups and controls (DMD 2.84 +/- 1.27, BMB 2.82 +/- 0.98, controls 3.04 +/- 0.85, ns). However, at the follow-up no significant change in the prevalence of normal rhythm and dysrhythmias occurred in both groups (ns vs baseline values), whereas only DMD patients showed a marked reduction in fed-to-fasting power ratio (0.78 +/- 0.59; p < 0.001 vs controls and BMD; p < 0.05 vs baseline), which correlated with the progressive neuromuscular weakness occurring in DMD subjects (r, 0.75; p < 0.001).

CONCLUSIONS

In children with MD, there is an early abnormality in gastric motility that is due to deranged regulatory mechanisms, whereas contractile activity of smooth muscle cells seems to be preserved. At the follow-up, DMD patients exhibited a progressive failure in neuromuscular function, which was accompanied by a gastric motility derangement with worsening in GET and in EGG features suggesting an altered function of gastric smooth muscle cells.

Gastric myoelectrical activity post-chemoradiotherapy and esophagectomy: a prospective study using subscapular surface recording

The aims of this study were to prospectively evaluate gastric function in esophageal cancer patients after chemoradiotherapy and following surgery, using cutaneous electrogastrography (EGG). Twenty-three patients with esophageal adenocarcinoma were recruited to the study. A subset of patients (n = 11) underwent neoadjuvant chemoradiotherapy and were also studied at 14 days after treatment. All patients underwent EGG studies prior to and following surgery, at 3 months postoperatively. Ten of these patients were also studied at medians of 6 months and 12 months after surgery. Twenty normal volunteers were used as controls. Post-operative EGG studies were monitored with a modified technique; the electrodes being placed in the subscapular region in the area of the transposed stomach. Following neoadjuvant treatment there was a significant increase in abnormal gastric myoelectrical activity involving changes in tachygastrias and decreased motility as measured by power ratio. Post-operatively there was a significant increase in bradygastria which persisted at 6 months but not at 12 months. There was a corresponding decrease in normogastria which persisted at 6 months and to a lesser extent at 12 months. Dominant frequency remained significantly depressed at 3, 6 and 12 months. Gastric myoelectrical activity is normal in untreated esophageal cancer. Neoadjuvant chemoradiotherapy causes a disruption to normal myoelectrical activity involving reduced motility and tachygastrias. Surgery causes a depression in dominant frequency with a reduced incidence of normogastria at 3 months and 6 months but with a tendency towards normality at 12 months.

Stomach myoelectrical response of patients with gastroesophageal reflux disease receiving omeprazole treatment

BACKGROUND AND AIM

Proton pump inhibitor treatment is effective for gastroesophageal reflux disease (GERD). It is unknown whether these agents effect any change in the stomach myoelectricity of GERD patients. Electrogastrographic (EGG) recording was used to study the probable effect of omeprazole on GERD patients.

METHODS

Nineteen endoscopically confirmed GERD patients and 38 dyspepsia-free controls were invited to receive EGG recording. After daily omeprazole treatment for 4 weeks, the symptomatic response of GERD patients was scaled, healing of erosive esophagitis was endoscopically assessed, and EGG recording was repeated for comparison.

RESULTS

Before treatment, GERD patients and controls displayed similar dominant frequency, whereas the former had higher dominant power compared with controls, either in fasting (29.2 +/- 6.0 dB compared with 25.3 +/- 3.8 dB, P < 0.01) or postprandial (31.9 +/- 5.6 dB compared with 27.7 +/- 3.8 dB, P < 0.001) recording. They also had diminished percentile normal rhythm (2-4 c.p.m.), irrespective of fasting (40.2 +/- 14.5% compared with 65.8% +/- 23.5%, P < 0.001) or postprandial (47.5 +/- 23.3% compared with 77.9 +/- 16.8%, P < 0.001) recording. After omeprazole treatment, healing was achieved in 12 patients (63.2%). Among the abnormal EGG parameters, only the postprandial percentile normal rhythm was restored (47.5 +/- 23.3% compared with 65.2 +/- 20.8%, P < 0.01).

CONCLUSIONS

Gastroesophageal reflux disease patients may have obvious dysrhythmia and higher myoelectrical power. Effective omeprazole treatment only improves the postprandial myoelectrical regularity, whereas abnormal EGG parameters remain impaired.

Gastric myoelectrical activity in neonates of different gestational ages by means of electrogastrography

PURPOSE

to describe the patterns of the gastric myoelectrical activity, pre-and postprandially, in clinically stable neonates of different gestational ages, during their first two weeks of life by means of Electrogastrography.

PATIENTS AND METHODS

Electrogastrography was recorded in forty-five clinically stable neonates of different gestational ages (group I: 15 neonates of > 37 weeks, group II: 15 premature neonates of 32-37 weeks; Group III: 15 premature neonates of 28-31 weeks) receiving intermittent enteral feedings during their first two weeks of life. Electrogastrography recordings were performed for 1 hour pre-and postprandially. The Electrogastrography signal was recorded using the portable MicroDigitrapper Electrogastrography recording device and after motion artifacts were deleted, the remaining Electrogastrography data were submitted to quantitative analysis based on the "Running Spectrum Analysis".

RESULTS

The percentages of normogastria, pre-and postprandially were greater than the percentages of gastric dysrythmias in all three studied groups. Furthermore, all neonates had the mean values of the Electrogastrography dominant frequency predominantly within the normogastria range, in both periods analyzed. There were no significant differences in the relative change of the Electrogastrography dominant power among the groups.

CONCLUSION

This study demonstrates that the Electrogastrography patterns are similar between premature and full term neonates during the pre-and postprandial periods. The results of this study also indicate that the gastric myoelectrical activity in premature and full term neonates is immature, as compared to that described for older neonates, children and adults.

Gastric myoelectrical activity and gut hormone secretion in myotonic dystrophy

BACKGROUND

Myotonic dystrophy (MD) is a systemic disease affecting striated, cardiac and smooth muscles, as well as nerve structures and endocrine glands. Patients with MD may suffer from slow gastric emptying.

OBJECTIVE

To study electrogastrograms (EGG) and postprandial gut hormone profiles in MD in order to evaluate whether disturbances in these regulatory mechanisms could explain, or contribute to, the delayed gastric emptying.

SUBJECTS

Ten patients with MD complaining of symptoms consistent with slow gastric emptying, and ten healthy matched controls.

METHODS

After an overnight fast, the patients and the control subjects were examined with standard EGG using surface electrodes before and during intake of a standard meal. Blood tests were drawn at regular time intervals for hormone analyses.

RESULTS

The EGG in MD showed a reduced amount of normal three cycles per minute activity compared with controls (P < 0.04). The dominant frequency in MD was less stable than in controls (P < 0.03), and the power of the signal showed less increase after a meal. The postprandial increase in plasma motilin (P < 0.05) and glucagon-like peptide-1 (GLP-1) (P < 0.001) was significantly less pronounced in MD compared with controls, whereas the plasma concentrations of cholecystokinin (CCK), neurotensin (NT), peptide YY (PYY) and somatostatin (SOM) did not differ significantly.

CONCLUSION

Disturbed electrophysiological control of the stomach and impaired secretion of gastrointestinal peptide hormones could contribute to slow gastric emptying in MD. Combined impairment of gastric pacing and gastrointestinal hormone responses was found in patients with the most prominent retardation of gastric emptying.

Ambulatory electrogastrography in patients with sclerodermia, delayed gastric emptying, dyspepsia, and irritable bowel syndrome. Is there any clinical relevance?

Background: Changes in electrogastrographic parameters are described in patients with irritable bowel syndrome, sclerodermia, dyspepsia, and delayed gastric emptying in static measurements. However, no information is available about changes in ambulatory measurements. The objective of this study was to find parameters that discriminate between these diseases using cutaneous 24-h-electrogastrography. Methods: Cutaneous 24-h electrogastrography (EGG) measurements were taken from 20 patients with dyspepsia, 10 patients with systemic sclerosis (sclerodermia, SSc), 7 patients with irritable bowel syndrome (IBS), 7 patients with delayed gastric emptying, and 10 healthy volunteers. Measurements were made using a DIGITRAPPER EGG (Synectics Medical Inc., Stockholm, Sweden) and the accompanying computerized data analysis package (ElectroGastroGram Version 6.30, Gastrosoft Inc., Synectics Medical Inc., Stockholm, Sweden). Frequency and power were compared pre- and postprandially, as well as during the entire day of measurement. Results: The 24-h measurements in healthy volunteers revealed 45.00%+/-12.12% normal values (2.4-3.7 cpm), 30.10%+/-7.15% bradygastric values (<2.4 cpm), and 24.20%+/-7.76% tachygastric values (>3.7 cpm). There was no significant change in frequency between rest and motion, but there was a significant increase in power (P<0.05). There was significantly more bradygastria in patients with dyspepsia periprandially as well as after 24 h (P<0.01) than in healthy volunteers. The mean power of patients with dyspepsia was significantly higher than that of patients with IBS (P<0.05). Conclusion: Cutaneous 24-h-EGG may be used as an additional means of differentiating between dyspepsia and IBS.

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

The aim of this study was to utilize multichannel electrogastrography to investigate whether patients with functional dyspepsia had impaired propagation or coordination of gastric slow waves in the fasting state compared with healthy controls. The study was performed in 10 patients with functional dyspepsia and 11 healthy subjects. Gastric myoelectrical activity was measured by using surface electrogastrography with a specially designed four-channel device. The study was performed for 30 min or more in the fasting state. Special computer programs were developed for the computation of the propagation and coupling of the gastric slow wave. It was found that, compared with the healthy controls, the patients showed a significantly lower percentage of slow wave propagation (58.0 +/- 8.9 vs. 89.9 +/- 2.6%, P < 0.002) and a significantly lower percentage of slow wave coupling (46.9 +/- 4.4 vs. 61.5 +/- 6.9%, P < 0.04). In addition, the patients showed inconsistencies in the frequency and regularity of the gastric slow wave among the four-channel electrogastrograms (EGGs). It was concluded that patients with functional dyspepsia have impaired slow wave propagation and coupling. Multichannel EGG has more information than single-channel EGG for the detection of gastric myoelectrical abnormalities.

Electrogastrography: a non-invasive measurement of gastric function

BACKGROUND

Electrogastrography (EGG) is the non-invasive measurement of gastric electrical activity. With the development of modern technology, improved recording and automated analysis, it is a reliable and accurate technique for the measurement of gastric myoelectrical activity providing information about the frequency and regularity of the gastric slow wave.

AIM

The aim of this report is to evaluate its role in clinical practice.

METHODS

The literature is reviewed and its role investigated.

RESULTS

EGG has been successfully used in the investigation of gastroparesis, non-ulcer dyspepsia (NUD), gastric emptying (GE) disorders and diabetes mellitus (DM). EGG also provides an insight into the effect of medications on gastric function, e.g. edrophonium, cisapride, erythromycin and proton-pump inhibitors (PPI).

CONCLUSIONS

EGG has a developing role in the assessment of gastric dysfunction and on the effect of medical treatment. The effect of surgery and anaesthesia on gastric myoelectric activity is less clear.

Adaptive independent component analysis of multichannel electrogastrograms

The electrogastrogram (EGG), a cutaneous measurement of gastric electrical activity, can be severely contaminated by endogenous biological noise sources such as respiratory signal. Therefore it is important to establish effective artifact removal methods. In this paper, a novel blind signal separation method with a flexible non-linearity is introduced and applied to extract the gastric slow wave from multichannel EGGs. Simulation results show that our algorithm is able to separate a wide range of source signals, including mixtures of Gaussian sources. On real data, we demonstrate the successful applications of our procedure to extract the gastric slow wave from multichannel EGGs. As a result, the extracted clean gastric slow wave can be used to facilitate further analysis, e.g. as a reference signal for multichannel adaptive enhancement of the EGG.

Gastric involvement in systemic sclerosis: a prospective study

OBJECTIVES

This study aims to assess the prevalence of gastric electrical activity dysfunction with cutaneous electrogastrography (EGG), disturbances of gastric emptying function using radiopaque pellets, and gastric endoscopic abnormalities in patients with systemic sclerosis (SSc). We also investigate for an association between EGG and gastric-emptying data with clinical manifestations and esophageal motor disturbances.

METHODS

Fasting and postprandial gastric electrical activity was studied in 22 consecutive patients with SSc (17 with and 5 without clinical gastric manifestations) and 22 age- and sex-matched healthy subjects. Gastric emptying of radiopaque pellets and gastroscopy were also performed in SSc patients.

RESULTS

The prevalence of EGG disturbances was as high as 81.82% in SSc patients. SSc patients exhibited, compared with controls, higher median percentage of dominant frequency in bradygastria during the fasting period and lower median values for postprandial electrical power and postprandial to fasting ratio for electrical power. Gastric emptying of radiopaque pellets was delayed in 11 SSc patients, and gastroscopy demonstrated "watermelon stomach" in 3 SSc patients. No correlation was found between the severity of gastric impairment and clinical presentation, SSc duration and subsets, and esophageal manometric impairment.

CONCLUSIONS

Our study underlines the high frequency of gastric dysfunction in SSc patients. It suggests the usefulness of EGG in SSc in noninvasively detecting disorders of gastric electrical activity at an early stage and symptomatic patients with gastroparesis (because there was a correlation between values of postprandial to fasting ratio for electrical power of < 1 on EGG and delayed gastric emptying). Gastric-emptying evaluation of radiopaque pellets may further be a helpful method to depict symptomatic SSc patients with gastroparesis. Finally, our series confirms that watermelon stomach diagnosis should be excluded in SSc patients presenting with gastrointestinal hemorrhage or with anemia related to iron deficiency.

Effect of gastric myoelectric activity on carbohydrate absorption of fruit juice in children

Juices have a different rate of gastric emptying than other foods. This may alter the rate of delivery of carbohydrates to the small bowel for absorption. The aim of the study is to demonstrate that faster gastric emptying is associated with greater production of hydrogen through a randomized, crossover study of 39 healthy children. The electrogastrography (indicator of the gastric myoelectric activities) and breath hydrogen tests (indicator of carbohydrate malabsorption) were performed at baseline and after ingestion of 240 to 330 mL of grape or pear juice given in a random order. The cutaneous electrogastrogram was analyzed by running spectral analysis to compute pre- and postprandial period dominant power (PDP) and running spectrum total power (RSTP). Postprandial PDP and RSTP were higher (p < 0.02) in the pear juice group than in the grape juice group, suggesting higher antral myoelectric activities. Twenty three percent of the subjects had significant movement artifacts that suggested discomfort after drinking pear juice compared to 5% after grape juice (p < 0.03). Breath hydrogen test was more frequently positive (increase >20 part per million [ppm] above baseline) after pear juice (52.2%; mean, 36 +/- 33 ppm) than after grape juice (4.3%, 6 +/- 6 ppm). In a multiple regression analysis, the most predictive independent variable of hydrogen concentration was found to be either postprandial PDP (r2 = 0.24; p < 0.002), or RSTP (r2 = 0.37; p < 0.001). Juices affect gastric myoelectric activity. Grape juice induces lower antral myoelectric activities and is better absorbed. The malabsorption of carbohydrates of juices is in part related to their effect on the gastric physiology.

Effect of meal and intravenous erythromycin on manometric and electrogastrographic measurements of gastric motor and electrical activity

Electrogastrography (EGG) measures, on the skin surface, the myoelectrical activity attributable to gastric smooth muscle cells. The physiological significance of signal amplitude and variation has not been clearly established. The increased signal amplitude after eating a meal may be related to increased contractile activity or to gastric distension. This study investigates the effect of increased gastric motor activity, unaccompanied by gastric distension, on the EGG recording and compares it to the effect of a meal. Nine children (3 months to 15 years old), were assessed by antroduodenal manometry for chronic intestinal pseudoobstruction (N = 5), chronic vomiting (N = 2), and abdominal distension (N = 2). Synchronized EGG recording was performed simultaneously. During the study, four children were given a meal and five were given intravenous erythromycin 3 mg/kg over 1 hr. The ratio of the antral motor index (MI = number of waves x sum of amplitudes) determined 1 hr before a meal (or erythromycin) to that determined 1 hr after a meal (or during intravenous erythromycin) was calculated. The ratio of the running total spectrum power of the electrical signal at the same times was also calculated. Antral MI increased after a meal [MI ratio (mean +/- SE) 5.33 +/- 2.2] and after intravenous erythromycin (MI ratio: 9.36 +/- 2.6). The amplitude of the electrical activity also increased after the meal [power ratio (mean +/- SE) 3.01 +/- 0.65] and after intravenous erythromycin (power ratio: 1.23 +/- 0.39), but the increase was greater after the meal (P < 0.05 vs intravenous erythromycin). No correlation was found between antral MI ratio and running total spectrum power ratio. In conclusion, the increased amplitude of the gastric electrical activity recorded by the EGG after a meal seems to be only partly due to the increase in antral motor activity. The increase in power is also related to gastric distension.