Spatial effects from bipolar current injection in 3D myocardium: implications for conductivity measurements

This study aims at predicting the spatial extent of the polarization in myocardium (surface and in-depth patterns) resulting from bipolar current injection. The three-dimensional effects resulting from transmural fiber rotation and unequal anisotropy ratio for the intra- and extracellular domain are modeled using a 3D finite element bidomain model. Circular current and voltage electrodes with different radii and distance between them are considered. The authors assess the accuracy of the idealized models, applied in combination with the four electrode technique for interpretation of conductivity measurements in myocardium, in the presence of transmural rotation. Based on the spatial sensitivity of the extracellular and transmembrane potential fields to the underlying conductivity tensors the authors recommend an alternative placement of the sensing electrodes for standard electrical or optical measurements.