Electrocardiogram sources in a 2-dimensional anisotropic activation model

This paper develops a model of 2-dimensional anisotropic cardiac tissue which permits the examination of the electrical sources arising from excitation at a point. The specific results depend on the anisotropy parameters and two cases are considered in detail. For assumed equal anisotropicity ratios in the interstitial and intracellular space the isochrones are (asymptotically) confocal ellipses and the total double layer source is (asymptotically) uniform. Surface fields are calculated and plotted for this condition. (For nonequal anisotropy ratios the total double layer source is necessarily nonuniform). When the preparation is very thin so that all fibres are essentially in contact with the extracellular medium the isochrones are (asymptotically) confocal ellipses but the total double-layer sources are now nonuniform. The sources for this case are determined and the fields at the surface of the cardiac tissue evaluated and plotted. The aforementioned 'thin' and 'thick' tissue preparations are contrasted with each other and the effects of anisotropicity in cardiac tissue discussed.