Electric field penetration depth of myocardial surface catheters and the measurement of myocardial resistivity.

The in vivo measurement of cardiac conductance in mice offers a method to generate an instantaneous left ventricular volume signal. In order to translate the measured conductance to volume, it is necessary to determine the resistivity of the myocardial tissue. This is done using tetrapolar surface conductance catheters, placed on the surface of the left ventricle. It is important to determine the depth of penetration of the electric field of this surface catheter to ensure that the electric field is confined within the myocardium and does not extend into the left ventricle blood volume. The depth of penetration is experimentally determined by a technique described by Foster et al. [2].