S3111 Characterization of Gastric Contractility Using the Atmo Capsule: Differences in Contractile Amplitude Based on Gastric Phase and Transit Delay

Introduction: Gastric contractions occur at a frequency of approximately 3 cycles per minute (cpm) in phase with gastric slow waves. These contractions occur at high amplitude in the fed state to aid digestion, and less frequently or at lower amplitudes in the fasted state, until progression toward phase III of the migrating motor complex. Weaker gastric contractions have been implicated in delayed gastric emptying. The Atmo Capsule possesses an onboard accelerometer that can detect contractions by measuring changes in capsule orientation. We analyzed the accelerometer data of the Atmo Capsule to interrogate its ability to measure gastric contractions in different gastric phases, and how they relate to delayed gastric transit. Methods: Gut transit was measured by the Atmo Capsule in 209 patients with suspected dysmotility. This analysis utilized data from patients with valid transit and accelerometer measures in the stomach. Gastric emptying times (GET) ≥5 hours were considered delayed. Fast Fourier Transformation of the accelerometer data using 5 min windows and a cutoff frequency of 4.5 cpm allowed the dominant gastric contraction frequency and amplitudes to be identified. The contraction frequency and amplitudes (as arbitrary units) were assessed across 60 min following meal ingestion and 60 min before gastric emptying of the capsule indicative of early and late gastric phases, and in relation to GET delay. Results: Delayed GET was observed in 57/187 (30%) patients. Contraction frequencies in early and late gastric phases were similar in patients with normal (3.1 cpm for both) and delayed GET (3.0 cpm for both) (P > 0.05 for both). Contraction amplitudes in the early gastric phase were similar between patients with normal (11.7 [9.1-14.4]) and delayed GET (12.5 [8.7-14.9]) (P > 0.05). In the late gastric phase, contraction amplitudes were higher in patients with normal (9.2 [7.5-12.2]) compared with delayed GET (6.4 [4.2-8.7]) (P < 0.01). Conclusion: The Atmo Capsule accelerometer provided a reproducible characterization of the frequency and amplitude of gastric contractions in patients with suspected dysmotility, showing that contraction amplitude was lower in the late compared with early phase of gastric residence. This difference was more pronounced in those with delayed GET, suggesting there may be differences in fasting antral activity in relation to gastric transit. These findings indicate that the device may offer additional clinical utility for evaluating gastric physiology beyond assessment of transit time.