Introduction
Gastric emptying is controlled by phasic gastric contractions which occur at a frequency of ~3 cycles per minute (cpm) in phase with gastric slow waves. Tests to measure slow waves cannot directly detect abnormal contractions. The Atmo Capsule possesses an accelerometer that measures changes in capsule orientation and can thus detect gastric contractions. We analyzed accelerometer data to define its capability to characterize gastric contraction frequency and amplitude in patients with suspected dysmotility, and to assess if frequency or amplitude vary in relation to transit delay.
Aims & Methods
Gut transit was measured by the Atmo Capsule in 209 subjects: 48 with predominant upper GI (UGI) symptoms alone (suspected gastroparesis), 21 with lower GI (LGI) symptoms (suspected slow colon transit) alone, and 140 with combined UGI+LGI symptoms. This analysis utilized data from subjects recording valid gastric emptying time (GET) measures and did not incur protocol deviations affecting gastric transit. Delays in GET were categorized as: normal, <5 h; delayed, 5-10 h; severely delayed, ≥10 h. Fast Fourier Transformation (FFT) of the accelerometer data allows for the identification and analysis of the dominant gastric frequency and amplitude using 10-minute windows and a cutoff frequency of 4.5 cpm. Variability of frequency and amplitude measures were estimated by calculating interquartile range (IQR) and range (max-min) values and were analyzed in relation to presenting symptoms and gastric emptying delays.
Results
Gastric data from 190 subjects were suitable for analysis: gastric contractions with dominant frequencies of 3.30 cpm (IQR 0.47, range 1.47) and amplitudes of 0.10 arbitrary units (au) (IQR 0.04, range 0.14) were detected in 185 (97%) of subjects. Mean contraction frequency tended to be higher in those with delayed GET compared with no delay (p=0.016) and severe delay (p=0.005) (Table 1). Frequency IQR (p=0.002) and range (p=0.002) were higher for GET delay vs. no delay, while range was higher in severe GET delay vs no delay (p<0.001). Mean amplitude was higher in subjects with severe GET delay compared with normal delay (p=0.008) and normal transit (p=0.001). Amplitude IQR and range were both higher in those with severe GET delay compared with normal delay (p=0.002; p=0.001) and no delay (p<0.001 for both). Frequency metrics were similar irrespective of predominant symptoms. Amplitude means (p=0.022), IQR (p=0.030) and range (p=0.0004) were higher for UGI vs. LGI symptoms.
Table 1. Dominant gastric frequencies and amplitudes in relation to gastric emptying delays. Data shown as median (interquartile range) and analyzed via Kruskal-Wallis test.
| Metric
| Normal GET, <5 h
| Delayed GET, 5-10 h
| Severe GET delay, ≥10 h
| P value
|
Frequency (cpm)
| Mean | 3.29 (3.13, 3.45)
| 3.47 (3.31, 3.66) | 3.24 (3.13, 3.38)
| 0.007
|
| Interquartile range | 0.30 (0.20, 0.59)
| 0.83 (0.36, 1.16)
| 0.40 (0.30, 0.55)
| 0.001
|
| Range | 1.50 (1.00, 1.68)
| 1.70 (1.60, 1.90)
| 1.90 (1.70, 2.00)
| <0.001
|
Amplitude (au)
| Mean | 0.10 (0.08, 0.11)
| 0.08 (0.08, 0.10)
| 0.11 (0.10, 0.12)
| <0.001
|
Interquartile range
| 0.04 (0.02, 0.05) | 0.03 (0.02, 0.04)
| 0.05 (0.04, 0.07)
| <0.001
|
| Range | 0.10 (0.07, 0.15)
| 0.14 (0.08, 0.16)
| 0.25 (0.19, 0.29)
| <0.001
|
Conclusion
The Atmo Capsule accelerometer reliably characterizes 3 cpm gastric contraction frequency and amplitude in subjects with proposed delays in gut transit. Increased variabilities in contraction frequency and amplitude were defined in those with severely delayed gastric emptying and increased amplitude variability was found for predominant upper GI symptoms. We propose these higher variations identified by accelerometry may reflect hypomotility or contractile dropout, suggesting additional clinical utility of the Atmo Capsule in suspected gastroparesis.
Disclosure
These authors disclose the following: Braden Kuo, Anthony J. Lembo, Eammon M.M. Quigley, Satish S.C. Rao, and William D. Chey serve on the Medical Advisory Board of Atmo Biosciences. Michael Cline and Baharak Moshiree served on the Medical Advisory Board of Atmo Biosciences. Braden Kuo has received funding from NIH, Vanda, Atmo Biosciences, and Takeda and has consulted for Evoke, Takeda, Ironwood, Novo Nordisk, Cindome, and Neurogastrx. Thomas Abell has received funding from Gastric Dysrhythmias, Neurogastrx, NIH GpCRC, and Vanda and has consulted for Enterra Medical, Novo Nordisk, Nuvaira, and Vanda. Anthony J. Lembo has received funding from Ardelyx, Biomerica, GSK, Ironwood, Takeda, and Vibrant and holds stock with Allurion, Bristol Myer Squibb, and J&J. Abigail Stocker has received funding from Cindome, Enterra Medical, and Vanda. William D. Chey has received funding from Atmo Biosciences, Commonwealth Diagnostics Intl, QOL Medical, and Salix; has consulted for AbbVie, Ardelyx, Biomerica, Comvita, Gemelli, Ironwood, Nestle, QOL Medical, Phathom, Redhill, Salix, Vibrant, and Takeda; has filed patents with My Nutrition Health, Digital Manometry, and Rectal Expulsion Device; and holds stock options with Coprata, Evinature, Food Marble, Kiwi Bioscience, and Modify Health. The remaining authors disclose no conflicts.
