Electrogastroenterographic examination of 22 patients before and after cholecystectomy

Reconstruction of normal and abnormal gastric electrical sources using a potential based inverse method

The use of cutaneous recordings to non-invasively characterize gastric slow waves has had limited clinical acceptance, primarily due to the uncertainty in relating the recorded signal to the underlying gastric slow waves. In this study we aim to distinguish and quantitatively reconstruct different slow wave patterns using an inverse algorithm. Slow wave patterns corresponding to normal, retrograde and uncoupled activity at different frequencies were imposed on a stomach surface model. Gaussian noise (10% peak-to-peak) was added to cutaneous potentials and the Greensite-Tikhonov inverse method was used to reconstruct the potentials on the stomach. The effectiveness of the number or location of electrodes on the accuracy of the inverse solutions was investigated using four different electrode configurations. Results showed the reconstructed solutions were able to reliably distinguish the different slow wave patterns and waves with lower frequency were better correlated to the known solution than those with higher. The use of up to 228 electrodes improved the accuracy of the inverse solutions. However, the use of 120 electrodes concentrated around the stomach was able to achieve similar results. The most efficient electrode configuration for our model involved 120 electrodes with an inter-electrode distance of 32 mm.

Reconstruction of multiple gastric electrical wave fronts using potential-based inverse methods

One approach for non-invasively characterizing gastric electrical activity, commonly used in the field of electrocardiography, involves solving an inverse problem whereby electrical potentials on the stomach surface are directly reconstructed from dense potential measurements on the skin surface. To investigate this problem, an anatomically realistic torso model and an electrical stomach model were used to simulate potentials on stomach and skin surfaces arising from normal gastric electrical activity. The effectiveness of the Greensite-Tikhonov or the Tikhonov inverse methods were compared under the presence of 10% Gaussian noise with either 84 or 204 body surface electrodes. The stability and accuracy of the Greensite-Tikhonov method were further investigated by introducing varying levels of Gaussian signal noise or by increasing or decreasing the size of the stomach by 10%. Results showed that the reconstructed solutions were able to represent the presence of propagating multiple wave fronts and the Greensite-Tikhonov method with 204 electrodes performed best (correlation coefficients of activation time: 90%; pacemaker localization error: 3 cm). The Greensite-Tikhonov method was stable with Gaussian noise levels up to 20% and 10% change in stomach size. The use of 204 rather than 84 body surface electrodes improved the performance; however, for all investigated cases, the Greensite-Tikhonov method outperformed the Tikhonov method.

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.

Fasting and postprandial small intestinal slow waves non-invasively measured in subjects with total gastrectomy

BACKGROUND AND AIM

Slow wave is essential to initiate gastrointestinal tract motility. Subjects with total gastrectomy (TG) provide an opportunity to study small intestinal slow wave in the absence of stomach interference. The aims of this study were to determine the origin of 3 cycles per min (cpm) slow wave recorded via electrogastrogram (EGG) and the characteristics of putative small intestinal slow waves in TG subjects.

METHODS

Thirty-three subjects with TG (25 male, age: 44-83 years) were consecutively enrolled. In each subject, the myoelectricity-like signals of the gastrointestinal tract were recorded using 3-channel EGG. Fourier transform-based spectral analysis was performed to derive the EGG parameters including dominant frequency/power, % normal rhythm (2-4 cpm), and power ratio.

RESULTS

Neither visual nor spectral analysis of the EGG revealed any waves at a frequency of about 3 cpm. The most frequently observed peaks in the power spectra of all subjects were those at approximately 1, approximately 6 and approximately 11 cpm with occurrences of 97%, 6.1% and 90.9%, respectively. Based on visual analysis of all recorded signals, the approximately 11 cpm signal was exactly rhythmically recorded rather than the approximately 1 cpm. The recorded approximately 11 cpm wave had a frequency of 10.9 +/- 1.0 cpm in the fasting state and 10.9 +/- 1.3 cpm in the fed state (NS), and a power of 31.5 +/- 3.2 dB in the fasting state and 35.2 +/- 3.8 dB in the fed state (P < 0.0001). None of other factors, including sex, age, and body mass index, had any impact on this approximately 11 cpm wave.

CONCLUSIONS

Small intestinal slow wave can be recorded non-invasively using EGG via cutaneous electrodes in TG subjects. Sex, age and body mass index have no effect on the intestinal slow waves. The power rather than frequency of intestinal slow wave is increased after a solid meal.

Gastric electrical activity in patients with cholelithiasis undergoing laparoscopic cholecystectomy: a prospective controlled study

BACKGROUND

The aim of the present study was to evaluate the effect of gallstone disease (GD) and laparoscopic cholecystectomy on gastric electrical activity of slow waves, which was recorded via transcutaneous electrogastrography (EGG).

METHODS

Twenty-one consecutive patients (M/F: 12/9, 52.7 +/- 15 years old) with GD and no previous history of abdominal operations or known disease affecting gastrointestinal motility were studied. The EGG was performed for 30 min prior to and 90 min after a standard meal, during a 4-6 month period prior to and after laparoscopic cholecystectomy. The percentile proportion of the three spectra of gastric slow waves frequency was studied, defined as follows: bradygastria, 1-2.1 cycles per min (c.p.m.); normogastria, 2.2-3.9 c.p.m.; and tachygastria, 4-9 c.p.m. The findings were compared to those of nine healthy subjects (M/F: 5/4, 49.5 +/- 14.8 years old).

RESULTS

No statistically significant difference was found in percentile distribution of bradygastria, normogastria and tachygastria, pre- or post-prandially, neither before or after laparoscopic cholecystectomy, nor between patients and controls.

CONCLUSIONS

Patients with GD do not exhibit differences in gastric electrical activity of slow waves in comparison to normal subjects and laparoscopic cholecystectomy does not alter gastric electrical activity. These findings suggest that cholelithiasis does not seem to cause dyspeptic symptoms due to gastric dysrythmias.

The effect of cholecystectomy on duodenojejunal motility in humans

We hypothesized that certain gastrointestinal symptoms following cholecystectomy could be explained by motor disturbances. To test this hypothesis, we compared pre- and post-operative motor patterns between symptomatic and asymptomatic patients after surgery to evaluate whether some motor changes could be induced by gallbladder removal and associated with symptoms. Twenty-three patients were prospectively evaluated before and 3 months after cholecystectomy. After surgery, 17 patients were asymptomatic and six were symptomatic. Duodenojejunal manometric recordings were performed for 3 h during fasting, then 3 h after a 750-kcal meal. Patient motor results were compared to those obtained in the duodenojejunum of 20 healthy controls. After surgery, only a few modifications in duodenojejunal motility were observed compared to the preoperative period. Motor changes related to cholecystectomy were increase in phase III amplitude and the absence of progressive decrease of the duodenojejunal motor response after the meal. After surgery, symptomatic patients had a lower postprandial duodenal motility index after the meal than asymptomatic patients (P < 0.03) and more frequent propagated clusters of contractions (PCCs) (P < 0.02). Preoperative motor patterns associated with postoperative symptoms were postprandial only and included a low duodenal motility index (P < 0.03), and a higher number of PCCs (P < 0.02). Removal of the gallbladder has a limited effect on duodenojejunal motility. Few motor differences existed between symptomatic and asymptomatic patients after surgery. However, a low duodenal motor response to a meal and PCCs were often associated with symptoms.