High-Resolution Electrogastrogram: A Novel, Noninvasive Method for Determining Gastric Slow-Wave Direction and Speed

Abstract

Despite its simplicity and noninvasiveness, the use of the electrogastrogram (EGG) remains limited in clinical practice for assessing gastric disorders. Recent studies have characterized the occurrence of spatial gastric myoelectric abnormalities that are ignored by typical approaches relying on time-frequency analysis of single channels. In this paper we present the highresolution (HR) EGG, which utilizes an array of electrodes to estimate the direction and speed of gastric slow-waves. The approach was verified on a forward electrophysiology model of the stomach, demonstrating that an accurate assessment of slow-wave propagation can be made. Furthermore, we tested the methodology on eight healthy adults and calculated propagation directions (181 ± 29 degrees) and speeds (3.7 ± 0.5 mm/s) that are consistent with serosal recordings of slow-waves described in the literature. By overcoming the limitations of current methods, HR-EGG is a fully automated tool that may unveil new classes of gastric abnormalities. This could lead to a better diagnosis of diseases and inspire novel drugs and therapies, ultimately improving clinical outcomes.

Figures

Fig. 1

Schematic used to illustrate the eight neighboring electrodes that are used to calculate the finite-difference surface Laplacian. The source activity is within a measurement area centered at electrode P0.

Fig. 2

The false positive rate of white Gaussian noise being classified with PGD greater than 0.5 as a function of minimum sustained wave duration. The different lines indicate independent simulations.

Fig. 3

(a) Plot of stomach anatomy and electrode configuration used for the forward model. The black circles represent electrodes (5 by 5 array). The blue line corresponds to the location of the 1D serosal solution that is expanded to a 2D mesh to match the stomach geometry. The pacemaker (P), corpus (C), and antrum (A) regions of the stomach are labeled. (b) Time snapshots over a 16 second period for the 1D serosal solution are shown. The pulses are generated in the pacemaker (P) region, have a decreased speed and amplitude in the corpus (C) followed by an increase of both in the antrum (A), and eventually terminate in the pylorus.

Fig. 4

Depiction of electrode configuration on the abdominal surface. Electrodes are disposable pre-gelled Ag-AgCl electrodes with 95 mm2 measurement area and 2 cm center-to-center spacing. The middle of the array is selected as the reference and the ground electrode is placed on the right hip bone.

Fig. 5

Results from a 60 second simulation of cutaneous potentials from the forward model on a 5 by 5 array. (a) The voltage from three channels with a dotted black line illustrating wave propagation. (b) Estimate of wave direction (mean: 187 degrees) and (c) speed (mean: 5.3 mm/s). (d) The PGD is above 0.9 throughout the simulation.

Fig. 6

Individual time snapshots of the voltages for a 20 second segment from Subject 1. Voltage is presented in white-blue color (blue representing positive voltage) and time (in seconds) is labeled above each plot. The snapshots are interpolated for visualization purposes. This particular wave took approximately 20 seconds to propagate across the array at about 180 degrees relative to the positive x-axis.

Fig. 7

(a) Voltages of three channels from a 120 second segment of from Subject 1 data. Wave propagation observed by the phase delay between the channels is depicted by the black diagonal dotted line. A plot is shown the (b) direction, (c) speed, and (d) PGD as computed by the wave estimation algorithm at every time point. A PGD threshold is used to detect sustained waves (above 0.5 for at least 2 seconds). Blue indicates a sustained wave while red is used for points that do not meet the criteria.

Fig. 8

PGD as a function of frequency for the band-pass filtered data (bandwidth 0.04 Hz) from Subject 1. The star indicates the maximum PGD, which is at 0.05 Hz

Fig. 9

(a) A histogram of the PGD values from every time point throughout the recording for Subject 1. (b) The mean phase map, computed using the instantaneous phase for time points meeting the sustained wave criteria. The white arrow indicates the propagation direction of the waves based on the direction of the negative phase gradient. (c) Polar histogram showing the estimated direction of propagation for sustained waves. (d) Histogram of the estimated speed for sustained waves.