In vivo experimental validation of detection of gastric slow waves using a flexible multichannel electrogastrography sensor linear array

Transcutaneous Auricular Vagus Nerve Stimulation Normalizes Induced Gastric Myoelectrical Dysrhythmias in Controls Assessed by Body-Surface Gastric Mapping

OBJECTIVES

Transcutaneous auricular vagus nerve stimulation (TaVNS) is a supplementary treatment for gastric symptoms resulting from dysrhythmias. The main objective of this study was to quantify the effects of 10, 40, and 80 Hz TaVNS and sham in healthy individuals in response to a 5-minute water-load (WL5) test.

MATERIALS AND METHODS

Eighteen healthy volunteers aged between 21 and 55 years (body mass index: 27.1 ± 3.2) were recruited. Each subject fasted for up to eight hours and participated in four 95-minute sessions, which consisted of 30 fasted baseline, 30 minutes TaVNS, WL5, and 30 minutes post-WL5. Heart rate variability was assessed using sternal electrocardiogram. Body-surface gastric mapping and bloating (/10) were recorded. One-way ANOVA with post hoc Tukey test was performed to test the difference between TaVNS protocols in terms of frequency, amplitude, bloating scores, root mean square of the successive differences (RMSSD), and stress index (SI).

RESULTS

On average, the subjects consumed 526 ± 160 mL of water, with volume ingested correlated to bloating (mean score 4.1 ± 1.8; r = 0.36, p = 0.029). In general, the reduction in frequency and rhythm stability during the post-WL5 period in sham was normalized by all three TaVNS protocols. Both 40- and 80-Hz protocols also caused increases in amplitude during the stim-only and/or post-WL5 periods. RMSSD increased during the 40-Hz protocol. SI increased during the 10-Hz protocol but decreased during the 40- and 80-Hz protocols.

CONCLUSION

TaVNS proved effective in normalizing gastric dysrhythmias by WL5 in healthy subjects by altering both parasympathetic and sympathetic pathways.

The effect of single and repeated doses of rivastigmine on gastric myoelectric activity in experimental pigs

BACKGROUND

Rivastigmine is a pseudo-irreversible cholinesterase inhibitor used for therapy of Alzheimer's disease and non-Alzheimer dementia syndromes. In humans, rivastigmine can cause significant gastrointestinal side effects that can limit its clinical use. The aim of this study was to assess the impact of rivastigmine on gastric motor function by means of electrogastrography (EGG) in experimental pigs.

METHODS

Six experimental adult female pigs (Sus scrofa f. domestica, hybrids of Czech White and Landrace breeds; 3-month-old; mean weight 30.7 ± 1.2 kg) were enrolled into the study twice and created two experimental groups. In group A, a single intragastric dose of 6 mg rivastigmine hydrogen tartate was administered in the morning to fasting pigs before EGG recording. In group B, rivastigmine was administered to overnight fasting animals in a dietary bolus in the morning for 7 days (6 mg per day). On day 8, an intragastric dose of 12 mg rivastigmine was given in the morning to fasting pigs before EGG. EGG recording was accomplished by means of an EGG standalone system. Recordings from both groups were evaluated in dominant frequency and EGG power (areas of amplitudes).

RESULTS

In total, 1,980 one-minute EGG intervals were evaluated. In group A, basal EGG power (median 1290.5; interquartile range 736.5-2330 μV2) was significantly higher in comparison with the power of intervals T6 (882; 577-1375; p = 0.001) and T10 (992.5; 385-2859; p = 0.032). In group B, the dominant frequency increased significantly from basal values (1.97 ± 1.57 cycles per minute) to intervals T9 (3.26 ± 2.16; p < 0.001) and T10 (2.14 ± 1.16; p = 0.012), respectively. In group B, basal EGG power (median 1030.5; interquartile range 549-5093) was significantly higher in comparison with the power of intervals T7 (692.5; 434-1476; p = 0.002) and T8 (799; 435-1463 μV2; p = 0.004).

CONCLUSIONS

Both single as well as repeated intragastric administration of rivastigmine hydrogen tartrate caused a significant decrease of EGG power (areas of amplitudes) in experimental pigs. EGG power may serve as an indirect indicator of gastric motor competence. These findings might provide a possible explanation of rivastigmine-associated dyspepsia in humans.

Normative Values for Body Surface Gastric Mapping Evaluations of Gastric Motility Using Gastric Alimetry: Spectral Analysis

INTRODUCTION

Body surface gastric mapping (BSGM) is a new noninvasive test of gastric function. BSGM offers several novel and improved biomarkers of gastric function capable of differentiating patients with overlapping symptom profiles. The aim of this study was to define normative reference intervals for BSGM spectral metrics in a population of healthy controls.

METHODS

BSGM was performed in healthy controls using Gastric Alimetry (Alimetry, New Zealand) comprising a stretchable high-resolution array (8 × 8 electrodes; 196 cm 2 ), wearable Reader, and validated symptom-logging App. The evaluation encompassed a fasting baseline (30 minutes), 482 kCal meal, and 4-hour postprandial recording. Normative reference intervals were calculated for BSGM metrics including the Principal Gastric Frequency, Gastric Alimetry Rhythm Index (a measure of the concentration of power in the gastric frequency band over time), body mass index (BMI)-adjusted amplitude (μV), and fed:fasted amplitude ratio. Data were reported as median and reference interval (5th and/or 95th percentiles).

RESULTS

A total of 110 subjects (55% female, median age 32 years [interquartile range 24-50], median BMI 23.8 kg/m 2 [interquartile range 21.4-26.9]) were included. The median Principal Gastric Frequency was 3.04 cycles per minute; reference interval: 2.65-3.35 cycles per minute. The median Gastric Alimetry Rhythm Index was 0.50; reference interval: ≥0.25. The median BMI-adjusted amplitude was 37.6 μV; reference interval: 20-70 μV. The median fed:fasted amplitude ratio was 1.85; reference interval ≥1.08. A higher BMI was associated with a shorter meal-response duration ( P = 0.014).

DISCUSSION

This study provides normative reference intervals for BSGM spectral data to inform diagnostic interpretations of abnormal gastric function.