Revised spectral metrics for body surface measurements of gastric electrophysiology

Abstract

Background Electrogastrography (EGG) non‐invasively evaluates gastric function but has not achieved common clinical adoption due to several technical limitations. Body Surface Gastric Mapping (BSGM) has been introduced to overcome these limitations, but pitfalls in traditional metrics used to analyze spectral data remain unaddressed. This study critically evaluates five traditional EGG metrics and introduces improved BSGM spectral metrics, with validation in a large cohort. Methods Pitfalls in five EGG metrics were assessed (dominant frequency, percentage time normogastria, amplitude, power ratio, and instability coefficient), leading to four revised BSGM spectral metrics. Traditional and revised metrics were compared to validate performance using a standardized 100‐subject database of BSGM tests (30 min baseline; 4‐h postprandial) recorded using Gastric Alimetry® (Alimetry). Key Results BMI and amplitude were highly correlated (r = −0.57, p < 0.001). We applied a conservative BMI correction to obtain a BMI‐adjusted amplitude metric (r = −0.21, p = 0.037). Instability coefficient was highly correlated with both dominant frequency (r = −0.44, p < 0.001), and percent bradygastria (r = 0.85, p < 0.001), in part due to misclassification of low frequency transients as gastric activity. This was corrected by introducing distinct gastric frequency and stability metrics (Principal Gastric Frequency and Gastric Alimetry Rhythm Index (GA‐RI)TM) that were uncorrelated (r = 0.14, p = 0.314). Only 28% of subjects showed a maximal averaged amplitude within the first postprandial hour. Calculating Fed:Fasted Amplitude Ratio over a 4‐h postprandial window yielded a median increase of 0.31 (IQR 0–0.64) above the traditional ratio. Conclusions & Inferences The revised metrics resolve critical pitfalls impairing the performance of traditional EGG, and should be applied in future BSGM spectral analyses.

Non-invasive thoracoabdominal mapping of post-oesophagectomy conduit function

“…Previously, Gastric Alimetry has been exclusively performed in patients with normal gastric anatomies, in whom reference ranges were developed (12, 13, 17). Some adjustments to interpretations will therefore be required as the test is applied to post-operative patients.…”

“…After a 30 minute baseline recording, patients consumed a 218kCal meal (100mL nutrient drink and half an oatmeal energy bar), followed by a 4-hour postprandial recording with concurrent symptom logging. Spectral analysis was performed, encompassing four established metrics (12): Principal Gastric Frequency, BMI-Adjusted Amplitude, Gastric Alimetry Rhythm Index (GA-RI;…”

“…After a 30 minute baseline recording, patients consumed a 218kCal meal (100mL nutrient drink and half an oatmeal energy bar), followed by a 4-hour postprandial recording with concurrent symptom logging. Spectral analysis was performed, encompassing four established metrics (12): Principal Gastric Frequency, BMI-Adjusted Amplitude, Gastric Alimetry Rhythm Index (GA-RI; reflecting pacemaker stability), fed:fasted Amplitude Ratio (ff-AR; indicating meal response with contractions), with comparison to reference intervals (13). Frequency was not reported if there was no rhythm (as measured by GA-RI) (10).…”

“…Spectral analysis was performed, encompassing four established metrics (12): Principal Gastric Frequency, BMI-Adjusted Amplitude, Gastric Alimetry Rhythm Index (GA-RI; reflecting pacemaker stability), fed:fasted Amplitude Ratio (ff-AR; indicating meal response with contractions), with comparison to reference intervals (13). Frequency was not reported if there was no rhythm (as measured by GA-RI) (10).…”

Principles and clinical methods of body surface gastric mapping: Technical review

“…Electrogastrography (EGG) is now in its centennial year and has accrued a vast base of clinical studies, but has not achieved widespread use, primarily owing to persisting questions regarding test reliability, sensitivity to noise, and clinical utility 6–8 . However, a new generation of EGG devices have recently emerged, underpinned by high‐resolution (HR) electrode arrays, modern bioelectronics, automated artifact rejection, and novel analytical strategies 8–13 . This approach has been called HR‐EGG, 14,15 although the alternative term ‘Body Surface Gastric Mapping’ (BSGM) is now preferred as it encompasses a broader array of outputs including spatial wave profiling that move this test beyond the classical scope of EGG 9 …”