John U. Egbuji

Origin and propagation of human gastric slow-wave activity defined by high-resolution mapping

Slow waves coordinate gastric motility, and abnormal slow-wave activity is thought to contribute to motility disorders. The current understanding of normal human gastric slow-wave activity is based on extrapolation from data derived from sparse electrode recordings and is therefore potentially incomplete. This study employed high-resolution (HR) mapping to reevaluate human gastric slow-wave activity. HR mapping was performed in 12 patients with normal stomachs undergoing upper abdominal surgery, using flexible printed circuit board (PCB) arrays (interelectrode distance 7.6 mm). Up to six PCBs (192 electrodes; 93 cm(2)) were used simultaneously. Slow-wave activity was characterized by spatiotemporal mapping, and regional frequencies, amplitudes, and velocities were defined and compared. Slow-wave activity in the pacemaker region (mid to upper corpus, greater curvature) was of greater amplitude (mean 0.57 mV) and higher velocity (8.0 mm/s) than the corpus (0.25 mV, 3.0 mm/s) (P < 0.001) and displayed isotropic propagation. A marked transition to higher amplitude and velocity activity occurred in the antrum (0.52 mV, 5.9 mm/s) (P < 0.001). Multiple (3-4) wavefronts were found to propagate simultaneously in the organoaxial direction. Frequencies were consistent between regions (2.83 +/- 0.35 cycles per min). HR mapping has provided a more complete understanding of normal human gastric slow-wave activity. The pacemaker region is associated with high-amplitude, high-velocity activity, and multiple wavefronts propagate simultaneously. These data provide a baseline for future HR mapping studies in disease states and will inform noninvasive diagnostic strategies.

High-resolution mapping of in vivo gastrointestinal slow wave activity using flexible printed circuit board electrodes: methodology and validation.

High-resolution, multi-electrode mapping is providing valuable new insights into the origin, propagation, and abnormalities of gastrointestinal (GI) slow wave activity. Construction of high-resolution mapping arrays has previously been a costly and time-consuming endeavor, and existing arrays are not well suited for human research as they cannot be reliably and repeatedly sterilized. The design and fabrication of a new flexible printed circuit board (PCB) multi-electrode array that is suitable for GI mapping is presented, together with its in vivo validation in a porcine model. A modified methodology for characterizing slow waves and forming spatiotemporal activation maps showing slow waves propagation is also demonstrated. The validation study found that flexible PCB electrode arrays are able to reliably record gastric slow wave activity with signal quality near that achieved by traditional epoxy resin-embedded silver electrode arrays. Flexible PCB electrode arrays provide a clinically viable alternative to previously published devices for the high-resolution mapping of GI slow wave activity. PCBs may be mass-produced at low cost, and are easily sterilized and potentially disposable, making them ideally suited to intra-operative human use.

Origin, propagation and regional characteristics of porcine gastric slow wave activity determined by high‐resolution mapping

Background  The pig is a popular model for gastric electrophysiology studies. However, its normal baseline gastric activity has not been well characterized. High‐resolution (HR) mapping has recently enabled an accurate description of human and canine gastric slow wave activity, and was employed here to define porcine gastric slow wave activity.

High‐resolution spatial analysis of slow wave initiation and conduction in porcine gastric dysrhythmia

Background  The significance of gastric dysrhythmias remains uncertain. Progress requires a better understanding of dysrhythmic behaviors, including the slow wave patterns that accompany or promote them. The aim of this study was to use high‐resolution spatiotemporal mapping to characterize and quantify the initiation and conduction of porcine gastric dysrhythmias.

Gastrointestinal system: Gastrointestinal system

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

Automated Gastric Slow Wave Cycle Partitioning and Visualization for High-resolution Activation Time Maps

High-resolution (HR) multi-electrode mapping has become an important technique for evaluating gastrointestinal (GI) slow wave (SW) behaviors. However, the application and uptake of HR mapping has been constrained by the complex and laborious task of analyzing the large volumes of retrieved data. Recently, a rapid and reliable method for automatically identifying activation times (ATs) of SWs was presented, offering substantial efficiency gains. To extend the automated data-processing pipeline, novel automated methods are needed for partitioning identified ATs into their propagation cycles, and for visualizing the HR spatiotemporal maps. A novel cycle partitioning algorithm (termed REGROUPS) is presented. REGROUPS employs an iterative REgion GROwing procedure and incorporates a Polynomial-surface-estimate Stabilization step, after initiation by an automated seed selection process. Automated activation map visualization was achieved via an isochronal contour mapping algorithm, augmented by a heuristic 2-step scheme. All automated methods were collectively validated in a series of experimental test cases of normal and abnormal SW propagation, including instances of patchy data quality. The automated pipeline performance was highly comparable to manual analysis, and outperformed a previously proposed partitioning approach. These methods will substantially improve the efficiency of GI HR mapping research.

Automated detection of gastric slow wave events and estimation of propagation velocity vector fields from serosal high-resolution mapping

High-resolution (HR; multi-electrode) recordings have led to detailed spatiotemporal descriptions of gastric slow wave activity. The large amount of data conveyed by the HR recordings demands an automated way of extracting the key measures such as activation times. In this study, a derivative-based method of identifying slow wave events was proposed. The raw signal was filtered using a second order Butterworth filter (low-pass; 10 Hz). The signal in each channel was differentiated and a threshold was taken as the 4.5x of the average of the negative first derivatives. An active event was defined where the first derivatives of the signal were more negative than the threshold. The accuracy of the method was validated against manually marked times, with a positive predictive value of 0.71. The detected activation times were interpolated using a second-order polynomial, the coefficients of which were evaluated using a previously developed least-square fitting method. The velocity fields were calculated, showing detailed spatiotemporal profile of slow wave propagation. The average of slow wave propagation velocity was 5.86 ± 0.07 mms-1.

Detailed measurements of gastric electrical activity and their implications on inverse solutions

Significant research effort has been expended on investigating methods to non-invasively characterize gastrointestinal electrical activity. Despite the clinical success of the 12-lead electrocardiograms (ECG) and the emerging success of inverse methods for characterizing electrical activity of the heart and brain, similar methods have not been successfully transferred to the gastrointestinal field. The normal human stomach generates rhythmic electrical impulses, known as slow waves, that propagate within the stomach at a frequency of 3 cycles per minute. Disturbances in this activity are known to result in disorders in the motility patterns of the stomach. However, there is still limited understanding regarding the basic characteristics of the electrical propagation in the stomach. Contrary to existing beliefs, recent results from high resolution recordings of gastric electrical activity have shown that multiple waves, complete with depolarization and repolarization fronts, can be simultaneously present at any given time in the human stomach. In addition, it has been shown that there are marked variations in the amplitude and velocities in different regions in the stomach. In human recordings, the antrum had slow waves with significantly higher amplitudes and velocities than the corpus. Due to the presence of multiple slow wave events, single and multiple dipole-type inverse methods are not appropriate and distributed source models must therefore be considered. Furthermore, gastric electrical waves move significantly slower than electrical waves in the heart, and it is currently difficult to obtain structural images of the stomach at the same time as surface electrical or magnetic gastric recordings are made. This further complicates the application of inverse procedures for gastric electrical imaging.

W1766 A Novel Laparoscopic Device for the Measurement of Gastrointestinal Slow Wave Activity

abundant GIT epithelial expression of mShisa during development. We also confirm its upregulation at all stages of GIT development using RT-PCR. In addition, we demonstrate that FGFr2b expression pattern is co-distributed with mShisa in the developing GIT. Conclusion: Our data shows the abundant epithelial expression of mShisa and its up-regulation at all stages of GIT development. Furthermore, mShisa is known to bind Fgf receptors in the endoplasmic reticulum and Golgi complex where Fgf receptors are known to undergo posttranscriptional modification. Our findings suggest a potential regulatory role of mShisa on the FGF10/Fgfr2b signaling pathway.