Electronic Theses and Dissertations

Identifier

1289

Date

2014

Document Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Biomedical Engineering

Committee Chair

Amy L De Jongh Curry

Committee Member

John L Williams

Committee Member

Lin H Hsiang

Committee Member

David J Russomanno

Abstract

Atrial fibrillation (AF) is believed to be a result of uncontrolled and sustained spiral wave reentries. Few recent studies have discussed the effects of the heterogeneous nature of atrial tissue at cellular and microscopic levels, on the electrical activity of the heart and defibrillation of AF; however, the effect of macroscopic patches of heterogeneity in the size ranges 3-8 mm has not been studied. The purpose of this study is to examine the effects of macroscopic patches of heterogeneity on cardiac propagation and termination of reentry in a computationally inexpensive, 2D bidomain model of a sheet of cardiac tissue. Tissue heterogeneity was modeled as a circular area with lower tissue conductivities than the rest of the sheet of cardiac tissue. Cross-field stimulation was used to initiate sustained single wave reentry. Termination stimulus, which consisted of a single pulse of varied, amplitude, duration and timing, was applied via electrodes along two opposite walls of the tissue. On the introduction of patches with low conductivities, ectopic activity was observed. Consistent with previous studies, the results show that heterogeneities favor termination of reentries by splitting the circular reentry into flat wavefronts that are pushed to the walls of the sheet of tissue and hence annihilated. The minimum amplitude of the termination stimulus for successful termination of reentry increased with the size of the patch. Duration and timing of the termination stimulus were important parameters for successful termination. Patch location played a role in determining whether or not termination of the spiral wave was achievable. The minimum amplitude for successful termination also depended on the size of the stimulation electrodes. The study suggests that simplified and computationally inexpensive models can be insightful tools to better understand the mechanisms that cause AF and hence, more effective treatment methods.

Comments

Data is provided by the student.

Library Comment

Dissertation or thesis originally submitted to the local University of Memphis Electronic Theses & dissertation (ETD) Repository.

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