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 (rect-angular, 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 con-ductivities, based on measured values, along with linear fibre rotation, were used throughout the myocardium. Is-chaemia was included by taking into account three of the main physiological cellular consequences, including hy-perkalaemia, 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 is-chaemic region. As the ischaemic thickness was increased beyond 40%, areas of elevation and depression were ap-parent on the epicardium for rectangular and cylindrical ischaemic geometries. Elevation was not noticed for the ellipsoidal ischaemic geometry until the ischaemic thick-ness 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. 1