The effect of ischaemia induced conductivity changes in models of cardiac tissue.
by
Peter Johnston
School of Biomolecular and Physical Sciences, Griffith University, Nathan, QLD.

The bidomain model for predicting electric potentials in cardiac tissue can be derived from homogenisation theory applied to a periodic cellular structure in three dimensions. Cardiac cells are assumed to form fibres, which, in turn, form sheets which are layered to form the final three dimensional structure. As input to this model, transverse and longitudinal conductivities are required in both the intra- and extracellular spaces (four values in all).

During ischaemia (a result of oxygen deprivation in the tissue) these conductivity values change. Initial changes are small but they become large as time increases. Using a perturbation analysis, we look at the changes in the electric field induced by small changes in the conductivity values. Further, experimental evidence suggests that changes in extracellular conductivity occur prior to changes in intracellular conductivity and we consider the consequences of this as a second simple example.

Date received: December 13, 2009