Resistivity calculations in arterially perfused rabbit ventricles using a 4-electrode method

Resistivities were calculated from extracellular measurements on the left ventricular epicardium of isolated, arterially perfused rabbit hearts. A 4-electrode technique was used. The electrode configuration used consisted of four silver point electrodes in a line spaced 0.9 mm apart. A subthreshold current pulse was applied through the outer electrodes and the potential difference was measured through the inner electrodes. The analytical solution for calculation of resistivities derived by Plonsey and Barr was used to calculate the resistivities in the longitudinal and transverse fiber directions. The resistivities calculated were within the range of those found in other investigations. The ratio of transverse to longitudinal resistivity was found to be approximately 2:1.