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.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK058697-11
Application #
8331558
Study Section
Special Emphasis Panel (ZRG1-SBIB-U (56))
Program Officer
Hamilton, Frank A
Project Start
2001-03-01
Project End
2013-08-31
Budget Start
2012-09-01
Budget End
2013-08-31
Support Year
11
Fiscal Year
2012
Total Cost
$296,258
Indirect Cost
$95,045
Name
Vanderbilt University Medical Center
Department
Surgery
Type
Schools of Medicine
DUNS #
004413456
City
Nashville
State
TN
Country
United States
Zip Code
37212
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
Somarajan, S; Muszynski, N D; Cheng, L K et al. (2015) Noninvasive biomagnetic detection of intestinal slow wave dysrhythmias in chronic mesenteric ischemia. Am J Physiol Gastrointest Liver Physiol 309:G52-8
Somarajan, S; Cassilly, S; Obioha, C et al. (2014) Effects of body mass index on gastric slow wave: a magnetogastrographic study. Physiol Meas 35:205-15
Somarajan, Suseela; Cassilly, Summer; Obioha, Chibuike et al. (2013) Noninvasive biomagnetic detection of isolated ischemic bowel segments. IEEE Trans Biomed Eng 60:1677-84
Obioha, Chibuike; Erickson, Jon; Suseela, Somarajan et al. (2013) Effect of Body Mass Index on the sensitivity of Magnetogastrogram and Electrogastrogram. J Gastroenterol Hepatol Res 2:513-519
Somarajan, S; Muszynski, N D; Obioha, C et al. (2012) Biomagnetic and bioelectric detection of gastric slow wave activity in normal human subjects--a correlation study. Physiol Meas 33:1171-9
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
Bradshaw, L A; Irimia, A; Sims, J A et al. (2009) Biomagnetic signatures of uncoupled gastric musculature. Neurogastroenterol Motil 21:778-e50

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