AN INTEGRAL-EQUATION MODEL FOR INTRACARDIAC ELECTROGRAM SENSING

Electrogram sensed by an intracardiac electrode has long been characte rized based on two approaches: 1) presume that the electrode is very s mall and does not disturb the potential prior to applying the electrod e, and 2) take an average of the prior potential over the electrode su rface, In fact, any intracardiac sensing electrode has a finite surfac e area where electrical charges are induced and disturb the external p otential field, thus, the sensed potential is different from the poten tial prior to placing the electrode, In this paper, in integral equati on model is pro; posed based on the current continuity equation in hom ogeneous myocardial medium, The new model cah accurately characterize the electrogram sensed by an electrode with a nonnegligible surface ar ea and a load impedance, The dew model can be solved numerically via t he method of moments to obtain the potential induced on the electrode surface by ari arbitrary dipole volume source. As an application of th e proposed theory, several electrode configurations with different loa ds have been analyzed with an intent to show that a finite electrode s urface will significantly reduce the electrogram peak amplitude and sl ope, and a load impedance lower than 20 k Ohm will also degrade the el ectrogram sensitivity.