The effect of ischaemic region shape on st potentials using a half-ellipsoid model of the left ventricle

Extracellular epicardial potential distributions (EPDs) were obtained using a half-ellipsoidal model of the left ventricle for three separate ischaemic geometries (rectangular, cylindrical and semi-ellipsoidal). The transient bidomain equations were numerically solved using a finite volume method for the spatial discretisation and a semi-implicit method for the time integration. Anisotropic conductivities, based on measured values, along with linear fibre rotation, were used throughout the myocardium. Ischaemia was included by taking into account three of the main physiological cellular consequences, including hyperkalaemia, acidosis and anoxia. Results showed that, at low thicknesses of ischaemia (<;40%), a single depression was found on the EPDs for all ischaemic geometries, located above the border of the ischaemic region. As the ischaemic thickness was increased beyond 40%, areas of elevation and depression were apparent on the epicardium for rectangular and cylindrical ischaemic geometries. Elevation was not noticed for the ellipsoidal ischaemic geometry until the ischaemic thickness reached 50%. As the ischaemia became transmural, the EPDs for all three ischaemic geometries were quite similar, with an area of elevation located directly over the ischaemic region, surrounded by depression.