Measurement of myocardial conductivities with an eight-electrode technique in the frequency domain

Bidomain conductivities are evaluated from extracellular measurements on canine myocardial tissue with a modified four-electrode technique. The probe consists of two orthogonal rows of four electrodes with a suitable spacing for sampling the intracellular and interstitial conductivities. A subthreshold sinusoidal current (10 Hz to 10 kHz) is applied to the outermost electrodes of one row. Potential difference is measured between the innermost electrodes. The longitudinal and transverse potential measurements are fitted with a numerical three dimensional bidomain model with no restriction on the longitudinal to transverse anisotropy ratio. The Nelder-Mead algorithm permits one to find the conductivity values that minimize the error between the model and the physiological data