High-Resolution Mapping Techniques for Slow Wave Recovery Analysis

Abstract

Gastrointestinal (GI) bio-electrical slow waves are, in part, responsible for coordinating motility. Abnormal slow wave propagation has been associated with functional disorders such as gastroparesis and chronic unexplained nausea and vomiting. Experimental slow wave recordings provide an improved understanding of the mechanisms that initiate and perpetuate these disorders. Two types of slow wave morphologies, biphasic and monophasic, are commonly recorded extracellularly. The activation phase of biphasic slow waves has been quantified through high-resolution (HR) mapping of normal and abnormal propagation patterns. Monophasic recordings, in comparison to biphasic recordings, enables more reliable capture of the recovery phase of slow waves which can aid in improving our understanding of normal and abnormal propagation patterns. For example, in the cardiac field, monophasic recordings have enabled investigations into restitution curve to improve our understanding of normal and abnormal rhythm. Current methods in the GI field have employed only a limited number of electrodes for monophasic slow wave recordings. The additional information that can be provided by monophasic slow waves deserves more attention. In addition, HR monophasic slow wave recording methods are required to provide information about the spatiotemporal characteristics of monophasic potentials. This thesis aimed to improve the understanding of the mechanisms that underpin GI dysrhythmia, by analysing monophasic slow waves recorded from pig stomachs using novel electrodes and computational analysis methods. Three types of electrodes were designed and fabricated to record monophasic slow waves: (i) bipolar contact electrode, (ii) dry suction electrode, (iii) wet suction electrode. These designs were validated against conventional HR flexible printed circuit (FPC) surface contact electrode arrays. The performance of the designs was compared in terms of the ability to record gastric monophasic slow waves. The results showed that from 86% pig studies, the wet suction electrode design recorded monophasic slow waves. This rate of success was higher than the other 2 designs (67% for bipolar contact electrode design and 60% for dry suction electrode design). The HR wet suction electrode array was therefore used for all the subsequent studies in this thesis.....