Revised spectral metrics for body surface measurements of gastric electrophysiology

AbstractBackgroundElectrogastrography (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.MethodsPitfalls 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 100 BSGM subject database (30 min baseline; 4-hrs postprandial), recorded using Gastric Alimetry (Alimetry, New Zealand).Key ResultsBMI 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 conflation of low frequency transients with gastric activity. This was corrected by introducing distinct gastric frequency and stability metrics (Principal Gastric Frequency and Gastric Alimetry Rhythm Index (GA-RI)) 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-hr postprandial window yielded a median increase of 0.31 (IQR 0-0.64) above the traditional ratio.Conclusions & InferencesThe revised metrics resolve critical pitfalls impairing the performance of traditional EGG, and should be applied in future BSGM spectral analyses.