provide a solid foundation for the study of the structure-function relationship of myocardial
anisotropy, and provide approximations of the actual anatomical structure.
Recent studies used diffusion tensor magnetic resonance imaging (DT-MRI) to determine
the orientation of cardiac muscle fibers. 9,10,11 This technique yields an average diffusion tensor
for water in the tissue over an image voxel where the eigenvalues and eigenvectors determine the
magnitude and principal directions of diffusion rates, respectively. The principal direction
corresponds to the fiber orientation parallel to the long axis of the muscle fiber.4
Electrical conductivity is also a tensor, and it is predicted that electrical conductivity in
heart tissues is greatest along the cardiac muscle fiber direction.12 Cardiac fibers create a sheet-
like structure along the fiber direction. The next preferential direction for electrical conduction is
transverse to the fibers in the direction parallel with to the sheets. The least electrical conduction
occurs in the direction normal to the sheets.13
In this study, the underlying fiber direction information from the water diffusivity tensor
as measured by DT-MRI was used to predict intracellular electrical conductivity in cardiac
tissue. Based on this information an electrical finite element model of the heart was created.
Initially a two-dimensional model was created for validation purposes. Then, a steady-state
analysis in three dimensions was done and intracellular current paths were predicted in the left
ventricle. The current pathlines and voltage distribution was compared between models using
anisotropic and isotropic conductivity properties.
Such simulations are useful for predicting current propagation and current density
distribution patterns, as well as voltage distribution and sensitivity to electrical impulse location.
This may useful for establishing defibrillation threshold values and as well as optimizing
electrode placement. Ultimately, such models may be used to understand the consequences of