Driving electrode configurations in cardiac conductance volumetry

Modifications to the intracavitary conductance catheter used to determine cardiac left ventricular volumes in animals and man are evaluated in a spherical geometry using solutions to Poisson's equation to determine sensitivity to wall motion as an estimate of efficiency in recording the volumetric signal. A monopole configuration yields the greatest sensitivity, a widely spaced dipole less sensitivity, and a closely spaced dipole very poor sensitivity. The nature of the solutions suggests additional significant advantages of a monopolar driving geometry for sensitivity to long-axis shortening because of the nondirectionality of the monopole field.<>