Year of Publication

2003

Degree Name

Master of Science (MS)

Document Type

Thesis

College

Graduate School

Department

Biomedical Engineering

First Advisor

Dr. Abhijit Patwardhan

Abstract

Spatio-temporal variation in action intervals during ventricular fibrillation (VF) suggestthat the excitable gap may also be distributed spatio-temporally. The observation leadus to hypothesize that distributed pacing can be used to modify and entrain electricalactivation during VF. We tested this hypothesis using simulated VF and animal studies.

We simulated VF in a 400 by 400 cell matrix. Simulation results showed that activationpattern could be entrained using spatially distributed stimulation. Up to a certain limit,increasing stimulus strength and density led to improved entrainment. Best entrainmentwas obtained by pacing at a cycle length similar to the intrinsic cycle length.

In order to verify whether activation could be entrained experimentally, eight opticallyisolated biphasic TTL addressable stimulators were fabricated. Distributed stimulationwas tested during electrically induced VF in two canines and two swine. Resultsshowed that electrical activation could be entrained in both species. Similar to that insimulation, better entrainment was obtained with denser pacing distribution and atpacing cycle length similar to the intrinsic cycle length. As expected, entrainment wasaffected by tissue thickness. Our results show that spatio-temporally distributed pacingstrength stimuli can be used to modify activation patterns during VF.

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