A comparison of bidomain and monodomain models in calculating the cardiac extracellular potentials induced by an external field

The objective of this study is to compare the cardiac extracellular potentials due to an external field, as predicted by three different models. The three models are: (1) a monodomain isotropic model; (2) a monodomain anisotropic model; and (3) a bidomain anisotropic model. The myocardium is modeled as a spherical shell with the curved and rotating cardiac fibers characterized by conductivity tensors. The field-induced potentials are calculated using 3-D finite element methods. The cardiac potentials predicted by the monodomain and bidomain anisotropic models differ by less than 5% RMS. Those predicted by the monodomain isotropic model, however, can differ from the bidomain model by as much as 21% RMS. The results suggest that (1) including cardiac fiber anisotropy has a considerable effect on the accuracy of the model, and (2) little is gained by using the complex bidomain model when calculating the extracellular potentials.