COMBINED BODY SURFACE GASTRIC MAPPING AND GASTRIC EMPTYING TESTING REVEALS DISTINCT PATIENT SUBGROUPS IN GASTROPARESIS

Background: Gastric emptying testing is used to diagnose gastroparesis. However, gastroparesis is a heterogeneous disorder that may involve several distinct underlying pathophysiologies related to impaired gastric function. Body surface gastric mapping (BSGM) is an emerging noninvasive technique for measuring gastric myoelectrical activity that can identify distinct patient subgroups in nausea and vomiting syndromes with neuromuscular dysfunction (Gharibans et al, 2022). The aim of this study was to evaluate the clinical utility and meal response profiles provided when combining these two tests in gastric function.

Methods: A cohort of 151 consecutive patients with chronic gastroduodenal symptoms and negative gastroscopy (118 females, aged 18-80 years, BMI 24±4 kg/m²) underwent simultaneous BSGM and gastric emptying breath test (GEBT), conducted over 4.5 hours with 30 minutes fasting and 4 hours postprandial. Symptoms were captured every 15 minutes using the validated Gastric Alimetry App. Standardized metrics were analyzed for both tests, including Principal Gastric Frequency, BMI-adjusted amplitude, and Gastric Alimetry Rhythm Index (GA-RI) for BSGM, and t_1/2 emptying time for GEBT. In addition, a novel BSGM metric was introduced called ‘meal response ratio’ to assess meal response by comparing the amplitude in the first 2 hours postprandially to the last 2 hours. A normal ‘meal response ratio’ was empirically defined as >1.

Results: Complete data was available from 144 subjects, among which 45 showed abnormal spectral BSGM findings. Of remaining patients with a normal BSGM spectral analysis, 24/99 (24%) exhibited a delayed meal response ratio ≤1. This subgroup showed significantly longer GEBT T_1/2 times compared to those with normal meal response (126±69 vs. 85±39 min; p=.012; Figure 1), with a higher rate of delayed gastric emptying t1/2<100min (54% vs 23%; p=0.005). Among patients with normal BSGM meal response, the 23% with delayed emptying (17/75) showed a higher total symptom burden (p=.013), and increased severity in nausea (p=.007), upper abdominal pain (p=.040), excessive fullness (p=.018), and early satiation (p=.010) compared to those normal on both tests.

Conclusion: Combined BSGM and gastric emptying testing yields refined subgrouping of patients with chronic gastroduodenal symptoms. In addition to revealing neuromuscular abnormalities, BSGM is shown here to reveal a novel distinct subgroup of gastroparesis patients with a ‘delayed meal response’ phenotype. Improved patient phenotyping using these mechanistic biomarkers may enable better targeted therapy.