Untersuchung der Morphologie von Vektorschleifen des oberflächennahen elektrischen Feldes während der Depolarisation des Herzens - ein Computermodell

Potential differences respectively the electric field measured with two orthogonal electrode pairs positioned on a plane near and parallel to the surface of cardiac tissue, describe a vector loop during the depolarization process. The large variety in loop morphology of such potential differences has been generally attributed to structural discontinuities. We examined, if the diversity of vector loops of the electric field found experimentally may also arise during continuous anisotrope conduction. For this purpose a monodomain computer model was developed, consisting of a two-dimensional sheet of excitable tissue surrounded with an unbounded volume conductor. Close to the tissue surface our computations predicted a narrow biphasic course of phi with peak-to-peak separation of less than 400 µm. The influence of parameters like activation sequence, inter-electrode spacing and probe orientation upon the reconstruction of the electric field was determined. It could be shown that for a precise measurement of the field inter-electrode spacings of less than 100 µm are necessary. These results can be seen as a basis for future measurements of the electric field and the local conduction velocity of the cardiac excitation with 4-electrode arrays.