Electrical activity in the stomach underlies functional physiology and pathophysiology. Our preliminary data show that the magnetic fields associated with the gastric slow wave contain critical parameters that help to characterize rhythms and may be important indicators of gastropathy. While both the electrogastrogram (EGG) and the magnetogastrogram (MGG) contain frequencies that correlate well with myoelectric potentials in the gastric musculature, additional spatiotemporal information in the MGG allows assessment of gastric propagation. We have shown that MGG propagation characteristics differ when comparing normal subjects with gastroparesis patients. We have also been able to compute the propagation gradient of the gastric syncytium from noninvasive MGG measurements and have shown its correlation with serosal electrode data. To continue our research on the magnetic fields of the stomach, we are proposing: (1) to use a realistic abdominal volume-conductor model to study how abdominal thickness affects EGG and MGG data and how normal and uncoupled gastric musculature affects EGG and MGG patterns. Data from our studies contradicted our original hypothesis that body mass index (BMI) significantly affects these signals, which was based on theoretical studies that predict such influences from abdominal layers. We will utilize the model developed under this aim in the analysis of our experimental data from the other specific aims. (2) We propose to determine how gastrectomy affects EGG and MGG. The normal intact stomach produces slow wave propagation patterns observable with MGG. We hypothesize that although non-gastric signals may appear near the gastric slow wave frequency range, these signals will not exhibit the same gastric propagation. (3) We will determine how gastric uncoupling changes MGG propagation patterns by inducing uncoupling surgically or pharmacologically to measure the changes in propagation and coupling assessed by EGG and MGG. (4) We will correlate the degree of gastroparesis with abnormal patterns of MGG propagation. We showed that a variety of abnormal propagation patterns characterize gastroparesis and we will determine whether these pattern differences differentiate the severity of the disease. (5) Finally, we will determine whether similar differences exist between diabetic and idiopathic gastroparetics, and we will determine how much variation exists between patients. The ability to consistently evaluate the electrical activity of the stomach in terms of both frequency dynamics and propagation characteristics will help us to better understand underlying pathologies that will in turn inform and direct better and more effective treatment options for gastroparesis patients, and ultimately for patients suffering a variety of gastric disorders.

Public Health Relevance

The magnetogastrogram (MGG) measures both the frequency content and spatiotemporal dynamics of underlying gastric slow wave electrical activity in health and disease. Pathological conditions like gastroparesis may not affect frequency content commonly measured by EGG, but do alter propagation patterns detected by MGG. The ability to noninvasively characterize gastric slow wave abnormalities will ultimately lead to a deeper understanding of gastric pathology and will inform treatment protocols.

National Institute of Health (NIH)
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
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Special Emphasis Panel (ZRG1-SBIB-U (56))
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Hamilton, Frank A
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Vanderbilt University Medical Center
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Bradshaw, L Alan; Kim, Juliana H; Somarajan, Suseela et al. (2016) Characterization of Electrophysiological Propagation by Multichannel Sensors. IEEE Trans Biomed Eng 63:1751-9
Bradshaw, L A; Cheng, L K; Chung, E et al. (2016) Diabetic gastroparesis alters the biomagnetic signature of the gastric slow wave. Neurogastroenterol Motil 28:837-48
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Somarajan, Suseela; Cassilly, Summer; Obioha, Chibuike et al. (2013) Noninvasive biomagnetic detection of isolated ischemic bowel segments. IEEE Trans Biomed Eng 60:1677-84
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Kim, J H K; Bradshaw, L A; Pullan, A J et al. (2010) Characterization of gastric electrical activity using magnetic field measurements: a simulation study. Ann Biomed Eng 38:177-86
Erickson, Jonathan C; O'Grady, Gregory; Du, Peng et al. (2010) Falling-edge, variable threshold (FEVT) method for the automated detection of gastric slow wave events in high-resolution serosal electrode recordings. Ann Biomed Eng 38:1511-29

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