Patterns of Abnormal Gastric Pacemaking After Sleeve Gastrectomy Defined by Laparoscopic High-Resolution Electrical Mapping

Sleeve gastrectomy reveals the plasticity of the human gastric epithelium

Gastrin is secreted following a rise in gastric pH, leading to gastric acid secretion. Sleeve gastrectomy (SG), a bariatric surgery where 80% of the gastric corpus is excised, presents a challenge for gastric pH homeostasis. Using histology, and single-cell RNA sequencing of the gastric epithelium in 12 women, we observed that SG is associated with an increase in a sub-population of acid-secreting parietal cells that overexpress respiratory enzymes and an increase in histamine-secreting enterochromaffin-like cells (ECLs). ECLs of SG-operated patients overexpressed genes coding for biosynthesis of neuropeptides and serotonin. Mathematical modeling showed that pH homeostasis by gastrin is analogous to non-linear proportional and integral control, that drives adaptation of the epithelium to acid-secretion demand. Quantitative model predictions were validated in patients. The results demonstrate human gastric epithelium remodeling following SG at the molecular and cellular levels, and more generally how trophic hormones enable robust adaptation of tissue function to meet physiological demand.

Implications of compressive loading of the stomach wall: Interplay between mechanical deformation and microstructure

During gastric surgery, the stomach wall is compressed with clamps and sutures or staple lines. These short- and long-term deformations can severely compromise the integrity of the tissue and make it difficult for the stomach wall to respond and remodel to the new loading conditions. Consequently, serious intra- and postoperative complications such as the formation of leaks during bariatric surgeries, can be associated with these immense tissue deformations. Hence, the study aimed to investigate the effects of compressive loading of the stomach wall in the radial direction. This was done by macroscopic mechanical loading of the stomach wall in each region of the stomach and evaluating the microstructural changes inflicted in the tissue. For this purpose, several imaging techniques were used, i.e., a histological analysis, second-harmonic generation microscopy, and X-ray micro-computed tomography. The combination of these three methods allowed us to investigate the gradual compression of the different stomach layers as well as the local reorientation and deformation of the main microstructural components, e.g., collagen fibers and muscle bundles. Importantly, this study found that the collagen bundles in the stomach wall straighten and reorient toward the circumferential-longitudinal plane and partially fan out with increased radial compressive deformation. The 3D scans of the stomach wall indicated a deterioration of the blood vessels and buckling of the mucosal glands due to compression. Statement of significance Unfortunately, little is known about the load transfer in the stomach wall during gastric surgery and the associated deformations on the macro- and microscale. The present study investigates the structural changes of the stomach wall, its layers and the inherent biological building blocks using histology, multi-photon microscopy, and micro-computed tomography. For the first time, the layer-specific response to stepwise radial compression of the stomach wall was studied, the related collagen fiber parameters were estimated, and a 3D sample structure was visualized. This clinically-oriented study links the structural changes within the wall to the postoperative remodel- ing process and the irreversibly altered gastric motility, thereby underscoring its relevance to the field of biomedical engineering, e.g., the development and improvement of surgical instruments.

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

INTRODUCTION

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

METHODS

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

RESULTS

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

CONCLUSION

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

[A New Paradigm in Diagnosing Functional Gastroduodenal Disorders: High-Resolution Electrogastrography]

High-resolution electrogastrography (HR-EGG) presents a new paradigm in diagnosing and treating functional gastroduodenal disorders. Unlike traditional electrogastrography, HR-EGG allows for a more precise analysis of the gastric electrical activity, offering improved diagnostic accuracy. Recent studies have revealed the clinical potential of HR-EGG, particularly in detecting abnormal electrical patterns in patients with functional dyspepsia and gastroparesis, supporting the development of novel therapeutic strategies. The non-invasive HR-EGG method has shown promise in identifying new biomarkers. Moreover, further integration of artificial intelligence, is expected to enhance diagnostic efficiency and develop more refined treatment models for functional gastrointestinal disorders.

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

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

Auricular Acupressure in Relieving PONV and Promoting Gastrointestinal Function Recovery in Females After Laparoscopic Sleeve Gastrectomy: A Prospective Randomized Controlled Trial

BACKGROUND

The role of current pharmacological treatment after laparoscopic sleeve gastrectomy (LSG) is limited. The incidence of postoperative nausea and vomiting (PONV) after LSG remains high. Auricular acupressure (AA) is believed to relieve PONV after laparoscopic surgeries, but its role in patients with obesity after LSG has yet to be confirmed.

METHODS

Ninety-five female patients who underwent LSG were randomized into two groups: AA combined with conventional anti-nausea medication (AA group, 47 patients) or conventional anti-nausea medication group (control group, 48 patients). Index of nausea and vomiting and retching (INVR) scores, postoperative anti-vomiting medication use, time of first anus exhausting, time of first fluid intake, and time of first to get out of bed were collected within 48 h after surgery.

RESULTS

Demographic data of patients in both groups were balanced and comparable. INVR score (F = 7.505, P = 0.007), vomiting score (F = 11.903, P = 0.001), and retching score (F = 12.098, P = 0.001) were significantly lower in the AA group than that in the control group within 48 h postoperatively. Use of metoclopramide was significantly less in the AA group than in the control group (4.7 [5.5]) vs. 8.8 [7.6], P = 0.004); time to first anus exhausting was significantly less in the AA group than in the control group (17.50 [6.00] vs. 20.42 [8.62], P = 0.020).

CONCLUSIONS

AA combined with conventional anti-vomiting agents can alleviate PONV in female patients after LSG, and AA can promote gastrointestinal exhaustion.

TRIAL REGISTRATION

The trial has been registered in the Chinese Clinical Trial Registry (ChiCTR) with the registration no. ChiCTR2100047381 on June 13, 2021.

Vectorgastrogram: dynamic trajectory and recurrence quantification analysis to assess slow wave vector movement in healthy subjects

Functional gastric disorders entail chronic or recurrent symptoms, high prevalence and a significant financial burden. These disorders do not always involve structural abnormalities and since they cannot be diagnosed by routine procedures, electrogastrography (EGG) has been proposed as a diagnostic alternative. However, the method still has not been transferred to clinical practice due to the difficulty of identifying gastric activity because of the low-frequency interference caused by skin-electrode contact potential in obtaining spatiotemporal information by simple procedures. This work attempted to robustly identify the gastric slow wave (SW) main components by applying multivariate variational mode decomposition (MVMD) to the multichannel EGG. Another aim was to obtain the 2D SW vectorgastrogram VGGSW from 4 electrodes perpendicularly arranged in a T-shape and analyse its dynamic trajectory and recurrence quantification (RQA) to assess slow wave vector movement in healthy subjects. The results revealed that MVMD can reliably identify the gastric SW, with detection rates over 91% in fasting postprandial subjects and a frequency instability of less than 5.3%, statistically increasing its amplitude and frequency after ingestion. The VGGSW dynamic trajectory showed a statistically higher predominance of vertical displacement after ingestion. RQA metrics (recurrence ratio, average length, entropy, and trapping time) showed a postprandial statistical increase, suggesting that gastric SW became more intense and coordinated with a less complex VGGSW and higher periodicity. The results support the VGGSW as a simple technique that can provide relevant information on the "global" spatial pattern of gastric slow wave propagation that could help diagnose gastric pathologies.

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

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

Gastroparesis: An Evidence-Based Review for the Bariatric and Foregut Surgeon

Gastroparesis is a gastric motility disorder characterized by delayed gastric emptying. It is a rare disease and difficult to treat effectively; management is a dilemma for gastroenterologists and surgeons alike. We conducted a systematic review of the literature to evaluate current diagnostic tools as well as treatment options. We describe key elements in the pathophysiology of the disease, in addition to current evidence on treatment alternatives, including nutritional considerations, medical and surgical options, and related outcomes.

A novel scalable electrode array and system for non-invasively assessing gastric function using flexible electronics

BACKGROUND

Disorders of gastric function are highly prevalent, but diagnosis often remains symptom-based and inconclusive. Body surface gastric mapping is an emerging diagnostic solution, but current approaches lack scalability and are cumbersome and clinically impractical. We present a novel scalable system for non-invasively mapping gastric electrophysiology in high-resolution (HR) at the body surface.

METHODS

The system comprises a custom-designed stretchable high-resolution "peel-and-stick" sensor array (8 × 8 pre-gelled Ag/AgCl electrodes at 2 cm spacing; area 225 cm² ), wearable data logger with custom electronics incorporating bioamplifier chips, accelerometer and Bluetooth synchronized in real-time to an App with cloud connectivity. Automated algorithms filter and extract HR biomarkers including propagation (phase) mapping. The system was tested in a cohort of 24 healthy subjects to define reliability and characterize features of normal gastric activity (30 m fasting, standardized meal, and 4 h postprandial).

KEY RESULTS

Gastric mapping was successfully achieved non-invasively in all cases (16 male; 8 female; aged 20-73 years; BMI 24.2 ± 3.5). In all subjects, gastric electrophysiology and meal responses were successfully captured and quantified non-invasively (mean frequency 2.9 ± 0.3 cycles per minute; peak amplitude at mean 60 m postprandially with return to baseline in <4 h). Spatiotemporal mapping showed regular and consistent wave activity of mean direction 182.7° ± 73 (74.7% antegrade, 7.8% retrograde, 17.5% indeterminate).

CONCLUSIONS AND INFERENCES

BSGM is a new diagnostic tool for assessing gastric function that is scalable and ready for clinical applications, offering several biomarkers that are improved or new to gastroenterology practice.

Clinical application and research progress of extracellular slow wave recording in the gastrointestinal tract

The physiological function of the gastrointestinal (GI) tract is based on the slow wave generated and transmitted by the interstitial cells of Cajal. Extracellular myoelectric recording techniques are often used to record the characteristics and propagation of slow wave and analyze the models of slow wave transmission under physiological and pathological conditions to further explore the mechanism of GI dysfunction. This article reviews the application and research progress of electromyography, bioelectromagnetic technology, and high-resolution mapping in animal and clinical experiments, summarizes the clinical application of GI electrical stimulation therapy, and reviews the electrophysiological research in the biliary system.

Changes in interstitial cells and gastric excitability in a mouse model of sleeve gastrectomy

Obesity is a critical risk factor of several life-threatening diseases and the prevalence in adults has dramatically increased over the past ten years. In the USA the age-adjusted prevalence of obesity in adults was 42.4%, i.e., with a body mass index (BMI, weight (kg)/height (m)2) that exceeds 30 kg/m2. Obese individuals are at the higher risk of obesity-related diseases, co-morbid conditions, lower quality of life, and increased mortality more than those in the normal BMI range i.e., 18.5-24.9 kg/m2. Surgical treatment continues to be the most efficient and scientifically successful treatment for obese patients. Sleeve gastrectomy or vertical sleeve gastrectomy (VSG) is a relatively new gastric procedure to reduce body weight but is now the most popular bariatric operation. To date there have been few studies examining the changes in the cellular components and pacemaker activity that occur in the gastric wall following VSG and whether normal gastric activity recovers following VSG. In the present study we used a murine model to investigate the chronological changes of gastric excitability including electrophysiological, molecular and morphological changes in the gastric musculature following VSG. There is a significant disruption in specialized interstitial cells of Cajal in the gastric antrum following sleeve gastrectomy. This is associated with a loss of gastric pacemaker activity and post-junctional neuroeffector responses. Over a 4-month recovery period there was a gradual return in interstitial cells of Cajal networks, pacemaker activity and neural responses. These data describe for the first time the changes in gastric interstitial cells of Cajal networks, pacemaker activity and neuroeffector responses and the time-dependent recovery of ICC networks and normalization of motor activity and neural responses following VSG.

Gastroesophageal Reflux Disease, Esophagitis, and Barrett's Esophagus 3 to 4 Years Post Sleeve Gastrectomy

BACKGROUND

Sleeve gastrectomy (SG) has become the most popular bariatric procedure worldwide. However, SG is associated with de novo gastroesophageal reflux (GERD) and esophagitis, with concerns for progression into Barrett's esophagus (BE). The purpose of this study is to assess the clinical and endoscopic progression of GERD, esophagitis, and BE 3 to 4 years after SG.

METHODS

Fifty-eight patients (pts) were assessed with endoscopy preoperative and at 3 to 4 years post SG, representing 44.9% follow-up. Endoscopy was offered to all SG pts regardless of symptoms. Outcomes including percent total weight loss (%TWL), PPI use, esophagitis progression, de novo reflux, and BE formation.

RESULTS

At post-op follow-up, the %TWL was 23%. The average BMI dropped from 49.07 to 37.5. De novo reflux developed in 13 pts (30.9%). Of the 16 pts with GERD pre-op, 37.5% improved, 25% had stable disease, and 37.5% had worsening symptoms. The rate of esophagitis nearly doubled from 37.9% pre-op to 70.6% post-op. A majority of post-op pts had mild esophagitis (87.8%), with 12.1% with LA classes C and D. Asymptomatic esophagitis was found in 68.2% of post-op pts. The incidence of BE was 12.7% post-op, with de novo BE developing in 4 pts, representing 7.2%.

CONCLUSION

SG is associated with increased rates of asymptomatic esophagitis and de novo reflux at 3 to 4 years post-op. De novo BE was detected as well, highlighting the importance of post-op screening. The majority of pts with GERD pre-op have stable disease or improve.

The gastric conduction system in health and disease: a translational review

Gastric peristalsis is critically dependent on an underlying electrical conduction system. Recent years have witnessed substantial progress in clarifying the operations of this system, including its pacemaking units, its cellular architecture, and slow-wave propagation patterns. Advanced techniques have been developed for assessing its functions at high spatiotemporal resolutions. This review synthesizes and evaluates this progress, with a focus on human and translational physiology. A current conception of the initiation and conduction of slow-wave activity in the human stomach is provided first, followed by a detailed discussion of its organization at the cellular and tissue level. Particular emphasis is then given to how gastric electrical disorders may contribute to disease states. Gastric dysfunction continues to grow in their prevalence and impact, and while gastric dysrhythmia is established as a clear and pervasive feature in several major gastric disorders, its role in explaining pathophysiology and informing therapy is still emerging. New insights from high-resolution gastric mapping are evaluated, together with historical data from electrogastrography, and the physiological relevance of emerging biomarkers from body surface mapping such as retrograde propagating slow waves. Knowledge gaps requiring further physiological research are highlighted.

Intraoperative serosal extracellular mapping of the human distal colon: a feasibility study

BACKGROUND

Cyclic motor patterns (CMP) are the predominant motor pattern in the distal colon, and are important in both health and disease. Their origin, mechanism and relation to bioelectrical slow-waves remain incompletely understood. During abdominal surgery, an increase in the CMP occurs in the distal colon. This study aimed to evaluate the feasibility of detecting propagating slow waves and spike waves in the distal human colon through intraoperative, high-resolution (HR), serosal electrical mapping.

METHODS

HR electrical recordings were obtained from the distal colon using validated flexible PCB arrays (6 × 16 electrodes; 4 mm inter-electrode spacing; 2.4 cm2, 0.3 mm diameter) for up to 15 min. Passive unipolar signals were obtained and analysed.

RESULTS

Eleven patients (33-71 years; 6 females) undergoing colorectal surgery under general anaesthesia (4 with epidurals) were recruited. After artefact removal and comprehensive manual and automated analytics, events consistent with regular propagating activity between 2 and 6 cpm were not identified in any patient. Intermittent clusters of spike-like activities lasting 10-180 s with frequencies of each cluster ranging between 24 and 42 cpm, and an average amplitude of 0.54 ± 0.37 mV were recorded.

CONCLUSIONS

Intraoperative colonic serosal mapping in humans is feasible, but unlike in the stomach and small bowel, revealed no regular propagating electrical activity. Although sporadic, synchronous spike-wave events were identifiable. Alternative techniques are required to characterise the mechanisms underlying the hyperactive CMP observed in the intra- and post-operative period.

NEW FINDINGS

The aim of this study was to assess the feasibility of detecting propagating electrical activity that may correlate to the cyclic motor pattern in the distal human colon through intraoperative, high-resolution, serosal electrical mapping. High-resolution electrical mapping of the human colon revealed no regular propagating activity, but does reveal sporadic spike-wave events. These findings indicate that further research into appropriate techniques is required to identify the mechanism of hyperactive cyclic motor pattern observed in the intra- and post-operative period in humans.

Endoscopic Evaluation and Management of Late Complications After Bariatric Surgery: a Narrative Review

Despite ongoing evolution in technique and a low mortality rate, clinicians may care for patients who suffer late complications (> 90 days of surgery) after bariatric surgery. Endoscopic techniques are used to identify and manage many of the late complications of the two most commonly performed bariatric surgeries: sleeve gastrectomy and Roux-en-Y gastric bypass. Stenosis at the incisura angularis and gastroesophageal reflux disease may occur in patients who have undergone a sleeve gastrectomy. Patients who underwent a Roux-en-Y gastric bypass can suffer marginal ulceration, gastrojejunal anastomotic stricture, and gastro-gastric fistula. Clinicians may also encounter biliary pathologies such as choledocholithiasis, chronic abdominal pain, and weight regain. This narrative review provides an update on the endoscopic evaluation and management of patients with late complications after sleeve gastrectomy or Roux-en-Y gastric bypass.

Strategies to Refine Gastric Stimulation and Pacing Protocols: Experimental and Modeling Approaches

Gastric pacing and stimulation strategies were first proposed in the 1960s to treat motility disorders. However, there has been relatively limited clinical translation of these techniques. Experimental investigations have been critical in advancing our understanding of the control mechanisms that innervate gut function. In this review, we will discuss the use of pacing to modulate the rhythmic slow wave conduction patterns generated by interstitial cells of Cajal in the gastric musculature. In addition, the use of gastric high-frequency stimulation methods that target nerves in the stomach to either inhibit or enhance stomach function will be discussed. Pacing and stimulation protocols to modulate gastric activity, effective parameters and limitations in the existing studies are summarized. Mathematical models are useful to understand complex and dynamic systems. A review of existing mathematical models and techniques that aim to help refine pacing and stimulation protocols are provided. Finally, some future directions and challenges that should be investigated are discussed.

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.

Design and Validation of a Surface-Contact Electrode for Gastric Pacing and Concurrent Slow-Wave Mapping

OBJECTIVE

Gastric contractions are, in part, coordinated by slow-waves. Functional motility disorders are correlated with abnormal slow-wave patterns. Gastric pacing has been attempted in a limited number of studies to correct gastric dysmotility. Integrated electrode arrays capable of pacing and recording slow-wave responses are required.

METHODS

New flexible surface-contact pacing electrodes (SPE) that can be placed atraumatically to pace and simultaneously map the slow-wave activity in the surrounding area were developed. SPE were applied in pigs in-vivo for gastric pacing along with concurrent high-resolution slow wave mapping as validation. Histology was conducted to assess for tissue damage around the pacing site. SPE were compared against temporary cardiac pacing electrodes (CPE), and hook-shaped pacing electrodes (HPE), for entrainment rate, entrainment threshold, contact quality, and slow-wave propagation patterns.

RESULTS

Pacing with SPE (amplitude: 2 mA, pulse width: 100 ms) consistently achieved pacemaker initiation. Histological analysis illustrated no significant tissue damage. SPE resulted in a higher rate of entrainment (64%) than CPE (37%) and HPE (24%), with lower entrainment threshold (25% of CPE and 16% of HPE). High resolution mapping showed that there was no significant difference between the initiated slow-wave propagation speed for SPE and CPE (6.8 ± 0.1 vs 6.8 ± 0.2 mm/s, P>0.05). However, SPE had higher loss of tissue lead contact quality than CPE (42 ± 16 vs 13 ± 10% over 20 min).

CONCLUSION

Pacing with SPE induced a slow-wave pacemaker site without tissue damage.

SIGNIFICANCE

SPE offered an atraumatic pacing electrode with a significant reduction of power consumption and placement time compared to impaled electrodes.

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.

Robust Methods to Detect Abnormal Initiation in the Gastric Slow Wave from Cutaneous Recordings

Upper gastrointestinal (GI) disorders are highly prevalent, with gastroparesis (GP) and functional dyspepsia (FD) affecting 3% and 10% of the US population, respectively. Despite overlapping symptoms, differing etiologies of GP and FD have distinct optimal treatments, thus making their management a challenge. One such cause, that of gastric slow wave abnormalities, affects the electromechanical coordination of pacemaker cells and smooth muscle cells in propelling food through the GI tract. Abnormalities in gastric slow wave initiation location and propagation patterns can be treated with novel pacing technologies but are challenging to identify with traditional spectral analyses from cutaneous recordings due to their occurrence at the normal slow wave frequency. This work advances our previous work in developing a 3D convolutional neural network to process multi-electrode cutaneous recordings and successfully classify, in silico, normal versus abnormal slow wave location and propagation patterns. Here, we use transfer learning to build a method that is robust to heterogeneity in both the location of the abnormal initiation on the stomach surface as well as the recording start times with respect to slow wave cycles. We find that by starting with training lowest-complexity models and building complexity in training sets, transfer learning one model to the next, the final network exhibits, on average, 80% classification accuracy in all but the most challenging spatial abnormality location, and below 5% Type-I error probabilities across all locations.

Pyloric distensibility measurement after gastric surgery: Which surgeries are associated with pylorospasm?

BACKGROUND AND STUDY AIMS

History of gastric surgery is found in 10% of patients with gastroparesis, and vagal lesion is often suspected to be the cause of pylorospasm. Recently, pyloric distensibility measurement using the EndoFLIP^® system showed that pylorospasm was present in 30%-50% of gastroparetic patients. Our objective was to assess whether pylorospasm, diagnosed using EndoFLIP^® system was observed in three different types of gastric surgeries: antireflux surgery, sleeve gastrectomy, and esophagectomy.

PATIENTS AND METHODS

Pyloric distensibility and pressure were measured using the EndoFLIP^® system in 43 patients from two centers (18 antireflux surgery, 16 sleeve gastrectomy, and nine esophagectomy) with dyspeptic symptoms after gastric surgery, and in 21 healthy volunteers. Altered pyloric distensibility was defined as distensibility below 10 mm² /mm Hg as previously reported.

RESULTS

Compared to healthy volunteers (distensibility: 25.2 ± 2.4 mm² /mm Hg; pressure: 9.7 ± 4.4 mm Hg), pyloric distensibility was decreased in 61.1% of patients in the antireflux surgery group (14.5 ± 3.4 mm² /mm Hg; P < .01) and 75.0% of patients in the esophagectomy group (10.8 ± 2.1 mm² /mm Hg; P < .05), while pyloric pressure was only increased in the antireflux surgery group (18.9 ± 2.2 mm Hg; P < .01). Pyloric distensibility and pressure were similar in healthy volunteers and in sleeve gastrectomy (distensibility: 20.3 ± 3.8 mm² /mm Hg; pressure: 15.8 ± 1.6 mm Hg) groups, with decreased pyloric distensibility affecting 18.7% of sleeve gastrectomy patients.

CONCLUSION

Antireflux surgery and esophagectomy were associated with pylorospasm although pylorospasm was not found in all patients. Sleeve gastrectomy was not associated with altered pyloric distensibility nor altered pyloric pressure.

A Higher Preoperative Glycemic Profile Is Associated with Rapid Gastric Emptying After Sleeve Gastrectomy for Obese Subjects

BACKGROUND

Recent reports have shown that sleeve gastrectomy (SG) accelerates gastric emptying (GE), but the etiology remains unclear. This study aimed to investigate the factors affecting GE before and after SG.

METHODS

We enrolled 35 normal weight healthy subjects and 23 obese patients receiving SG. The normal individuals and obese patients before and 3 months after SG received oatmeal-based scintigraphy to measure GE. Gastrointestinal symptoms and circulating levels of peptide YY (PYY) were also measured.

RESULTS

There were no differences in the GE parameters, including simple half-time at 3 h and percentage of gastric retention at 0.5, 1, 2, and 3 h between healthy controls and pre-SG obese subjects. SG led to accelerated GE, more gastrointestinal symptoms, and increased fasting PYY levels postoperatively. Based on our previously established normal GE values, 18 (78.3%) obese patients with rapid postoperative GE had higher levels of preoperative fasting glucose and glycated hemoglobin, and homeostasis model assessment of the insulin resistance index than those with normal postoperative GE. Twelve (52.2%) obese patients had preoperative diabetes mellitus (DM), and only four (17.4%) remained diabetic after SG. The post-SG gastric retention at 0.5 and 1 h was lower in patients with preoperative DM than in those without preoperative DM. Neither severity of gastrointestinal symptoms nor fasting PYY levels were associated with postoperative GE alterations.

CONCLUSION

Most of the obese patients had accelerated GE after SG. A higher preoperative glycemic profile was associated with rapid post-SG GE.

Slow-wave coupling across a gastroduodenal anastomosis as a mechanism for postsurgical gastric dysfunction: evidence for a "gastrointestinal aberrant pathway"

Postsurgical gastric dysfunction is common, but the mechanisms are varied and poorly understood. The pylorus normally acts as an electrical barrier isolating gastric and intestinal slow waves. In this report, we present an aberrant electrical conduction pathway arising between the stomach and small intestine, following pyloric excision and surgical anastomosis, as a novel disease mechanism. A patient was referred with postsurgical gastroparesis following antrectomy, gastroduodenostomy, and vagotomy for peptic ulceration. Scintigraphy confirmed markedly abnormal 4-h gastric retention. Symptoms included nausea, vomiting, postprandial distress, and reflux. Intraoperative, high-resolution electrical mapping was performed across the anastomosis immediately before revision gastrectomy, and the resected anastomosis underwent immunohistochemistry for interstitial cells of Cajal. Mapping revealed continuous, stable abnormal retrograde slow-wave propagation through the anastomosis, with slow conduction occurring at the scar (4.0 ± 0.1 cycles/min; 2.5 ± 0.6 mm/s; 0.26 ± 0.15 mV). Stable abnormal retrograde propagation continued into the gastric corpus with tachygastria (3.9 ± 0.2 cycles/min; 1.6 ± 0.5 mm/s; 0.19 ± 0.12 mV). Histology confirmed ingrowth of atypical ICC through the scar, defining an aberrant pathway enabling transanastomotic electrical conduction. In conclusion, a "gastrointestinal aberrant pathway" is presented as a novel proposed cause of postsurgical gastric dysfunction. The importance of aberrant anastomotic conduction in acute and long-term surgical recovery warrants further investigation.NEW & NOTEWORTHY High-resolution gastric electrical mapping was performed during revisional surgery in a patient with severe gastric dysfunction following antrectomy and gastroduodenostomy. The results revealed continuous propagation of slow waves from the duodenum to the stomach, through the old anastomotic scar, and resulting in retrograde-propagating tachygastria. Histology showed atypical interstitial cells of Cajal growth through the anastomotic scar. Based on these results, we propose a "gastrointestinal aberrant pathway" as a mechanism for postsurgical gastric dysfunction.

A Deep Convolutional Neural Network Approach to Classify Normal and Abnormal Gastric Slow Wave Initiation From the High Resolution Electrogastrogram

OBJECTIVE

Gastric slow wave abnormalities have been associated with gastric motility disorders. Invasive studies in humans have described normal and abnormal propagation of the slow wave. This study aims to disambiguate the abnormally functioning wave from one of normalcy using multi-electrode abdominal waveforms of the electrogastrogram (EGG).

METHODS

Human stomach and abdominal models are extracted from computed tomography scans. Normal and abnormal slow waves are simulated along stomach surfaces. Current dipoles at the stomachs surface are propagated to virtual electrodes on the abdomen with a forward model. We establish a deep convolutional neural network (CNN) framework to classify normal and abnormal slow waves from the multi-electrode waveforms. We investigate the effects of non-idealized measurements on performance, including shifted electrode array positioning, smaller array sizes, high body mass index (BMI), and low signal-to-noise ratio (SNR). We compare the performance of our deep CNN to a linear discriminant classifier using wave propagation spatial features.

RESULTS

A deep CNN framework demonstrated robust classification, with accuracy above 90% for all SNR above 0 dB, horizontal shifts within 3 cm, vertical shifts within 6 cm, and abdominal tissue depth within 6 cm. The linear discriminant classifier was much more vulnerable to SNR, electrode placement, and BMI.

CONCLUSION

This is the first study to attempt and, moreover, succeed in using a deep CNN to disambiguate normal and abnormal gastric slow wave patterns from high-resolution EGG data.

SIGNIFICANCE

These findings suggest that multi-electrode cutaneous abdominal recordings have the potential to serve as widely deployable clinical screening tools for gastrointestinal foregut disorders.

High-Amplitude Gastric Contractions following Laparoscopic Sleeve Gastrectomy

A proportion of laparoscopic sleeve gastrectomy patients experience symptoms of regurgitation and epigastric pain postoperation. The appearance of gastric sleeve contractions has been documented but its implications have not been adequately investigated. This case describes a 61-year-old female following laparoscopic sleeve gastrectomy. The patient underwent high-resolution impedance esophageal manometry that identified compartmentalized pressurization leading to propagating contractions throughout the gastric sleeve. Combined treatment with calcium channel blockers and gastric sleeve dilation relieved all symptoms. This case highlights the application of high-resolution impedance esophageal manometry to assess motor function and bolus transit in patients following laparoscopic sleeve gastrectomy.

Gastroparesis

Gastroparesis is a disorder characterized by delayed gastric emptying of solid food in the absence of a mechanical obstruction of the stomach, resulting in the cardinal symptoms of early satiety, postprandial fullness, nausea, vomiting, belching and bloating. Gastroparesis is now recognized as part of a broader spectrum of gastric neuromuscular dysfunction that includes impaired gastric accommodation. The overlap between upper gastrointestinal symptoms makes the distinction between gastroparesis and other disorders, such as functional dyspepsia, challenging. Thus, a confirmed diagnosis of gastroparesis requires measurement of delayed gastric emptying via an appropriate test, such as gastric scintigraphy or breath testing. Gastroparesis can have idiopathic, diabetic, iatrogenic, post-surgical or post-viral aetiologies. The management of gastroparesis involves: correcting fluid, electrolyte and nutritional deficiencies; identifying and treating the cause of delayed gastric emptying (for example, diabetes mellitus); and suppressing or eliminating symptoms with pharmacological agents as first-line therapies. Several novel pharmacologic agents and interventions are currently in the pipeline and show promise to help tailor individualized therapy for patients with gastroparesis.

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.

Intra-operative high-resolution mapping of slow wave propagation in the human jejunum: Feasibility and initial results

BACKGROUND

Bioelectrical slow waves are a coordinating mechanism of small intestine motility, but extracellular human studies have been restricted to a limited number of sparse electrode recordings. High-resolution (HR) mapping has offered substantial insights into spatiotemporal intestinal slow wave dynamics, but has been limited to animal studies to date. This study aimed to translate intra-operative HR mapping to define pacemaking and conduction profiles in the human small intestine.

METHODS

Immediately following laparotomy, flexible-printed-circuit arrays were applied around the serosa of the proximal jejunum (128-256 electrodes; 4-5.2 mm spacing; 28-59 cm² ). Slow wave propagation patterns were mapped, and frequencies, amplitudes, downstroke widths, and velocities were calculated. Pacemaking and propagation patterns were defined.

KEY RESULTS

Analysis comprised nine patients with mean recording duration of 7.6 ± 2.8 minutes. Slow waves occurred at a frequency of 9.8 ± 0.4 cpm, amplitude 0.3 ± 0.04 mV, downstroke width 0.5 ± 0.1 seconds, and with faster circumferential velocity than longitudinal (10.1 ± 0.8 vs 9.0 ± 0.7 mm/s; P = .001). Focal pacemakers were identified and mapped (n = 4; mean frequency 9.9 ± 0.2 cpm). Disordered slow wave propagation was observed, including wavefront collisions, conduction blocks, and breakout and entrainment of pacemakers.

CONCLUSIONS & INFERENCES

This study introduces HR mapping of human intestinal slow waves, and provides first descriptions of intestinal pacemaker sites and velocity anisotropy. Future translation to other intestinal regions, disease states, and postsurgical dysmotility holds potential for improving the basic and clinical understanding of small intestine pathophysiology.

Impact of Laparoscopic Sleeve Gastrectomy on Gastrointestinal Motility

Objective

Laparoscopic sleeve gastrectomy (LSG) was considered mainly as a restrictive procedure due to anatomic alterations in the upper gastrointestinal tract. Additionally, due to neurohormonal alterations, LSG modifies the gastrointestinal motility, which controls appetite and feeling of satiety.

Aim

The aim of the study was to review the impact of laparoscopic sleeve gastrectomy on gastrointestinal motility.

Material and Methods

A search of the medical literature was undertaken in Pubmed, Web of Science, and Cochrane library. Esophageal, gastric, bowel motility were assessed separately.

Results

Nine studies assessed esophageal motility. The data remain debatable attributing to the heterogeneity of follow-up timing, surgical technique, bougie size, and distance from pylorus. The stomach motility was assessed in eighteen studies. Functionally, the sleeve was divided into a passive sleeve and an accelerated antrum. All scintigraphic studies revealed accelerated gastric emptying after LSG except of one. Patients demonstrated a rapid gastroduodenal transit time. The resection of the gastric pacemaker had as a consequence aberrant distal ectopic pacemaking or bioelectrical quiescence after LSG. The bowel motility was the least studied. Small bowel transit time was reduced; opposite to that the initiation of cecal filling and the ileocecal valve transit was delayed.

Conclusion

Laparoscopic sleeve gastrectomy has impacts on gastrointestinal motility. The data remain debatable for esophageal motility. Stomach and small bowel motility were accelerated, while the initiation of cecal filling and the ileocecal valve transit was delayed. Further pathophysiological studies are needed to evaluate the correlation of motility data with clinical symptoms.

Improved Visualization of Gastrointestinal Slow Wave Propagation Using a Novel Wavefront-Orientation Interpolation Technique

OBJECTIVE

High-resolution mapping of gastrointestinal (GI) slow waves is a valuable technique for research and clinical applications. Interpretation of high-resolution GI mapping data relies on animations of slow wave propagation, but current methods remain as rudimentary, pixelated electrode activation animations. This study aimed to develop improved methods of visualizing high-resolution slow wave recordings that increases ease of interpretation.

METHODS

The novel method of "wavefront-orientation" interpolation was created to account for the planar movement of the slow wave wavefront, negate any need for distance calculations, remain robust in atypical wavefronts (i.e., dysrhythmias), and produce an appropriate interpolation boundary. The wavefront-orientation method determines the orthogonal wavefront direction and calculates interpolated values as the mean slow wave activation-time (AT) of the pair of linearly adjacent electrodes along that direction. Stairstep upsampling increased smoothness and clarity.

RESULTS

Animation accuracy of 17 human high-resolution slow wave recordings (64-256 electrodes) was verified by visual comparison to the prior method showing a clear improvement in wave smoothness that enabled more accurate interpretation of propagation, as confirmed by an assessment of clinical applicability performed by eight GI clinicians. Quantitatively, the new method produced accurate interpolation values compared to experimental data (mean difference 0.02 ± 0.05 s) and was accurate when applied solely to dysrhythmic data (0.02 ± 0.06 s), both within the error in manual AT marking (mean 0.2 s). Mean interpolation processing time was 6.0 s per wave.

CONCLUSION AND SIGNIFICANCE

These novel methods provide a validated visualization platform that will improve analysis of high-resolution GI mapping in research and clinical translation.

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.