A surface charge integral equation model for intracardiac electrogram sensing electrodes

Sensing of an intracardiac electrogram is critical to pacemaker design and operation. Characterization of an intracardiac electrogram sensing electrode has long been based on the assumption that the electrode is very small and has no effect on the field it senses. In fact, any intracardiac sensing electrode has a significantly large surface area where electrical charges are induced and disturb the sensed potential field. To account for the effect of electrode size and position on electrogram sensing, a surface charge integral equation is formulated, based an the current continuity equation in homogeneous myocardial medium. A numerical method, such as the method of moments, is then applied to obtain the solution of the integral equation, meanwhile the potential sensed by the electrode. As an application of the proposed technique, several electrode configurations have been analyzed and their relative electrogram sensitivities are compared