1. Electrostriction Effects During Defibrillation by Michelle Fritz Oakland University SMaRT Program July 28, 2006

2. During defibrillation a large electrical shock is applied to the heart to terminate chaotic mechanical and electrical effects caused by fibrillation. What are the mechanical effects on the heart from the applied electric field during defibrillation? This has not yet been investigated. Are these effects significant? Background

3. The heart is approximated as a cylinder with radius a in a uniform electric field. Fibers in the cardiac tissue are taken into consideration, which cause it to be anisotropic- conductivities differ parallel and perpendicular to the fibers. Approximation of the Heart

4. The electric field causes a charge distribution inside and on the outer surfaces of the heart tissue. This charge distribution causes mechanical forces to be exerted on the tissue in the form of stresses and strains As a result of the stresses and strains, there is a displacement of tissue. The goal of the following calculations is to determine how large this displacement is. Concepts

5. Electrical Model Solve for the potentials and using along with the boundary conditions at r = a, Calculations Mechanical Model In anisotropic tissue, Gauss’s law relates the charge density to the electric field. The body forces can be found this way. Equations for mechanical equilibrium (Navier’s equations) are used.

6. Results Pressure p and a stream function Ψ are found that satisfy Navier’s equations and boundary conditions. Once these are found, the components of the displacement are determined using and By using realistic values for the conductivities and Electric field, numerical values for the displacement at the surface of the tissue are obtained.