Myocardial impedance measurements with a modified four electrode technique

Experimental measurements of the impedance of canine myocardial tissue with a modified four electrode technique are presented. The probe consisted of two orthogonal rows of four electrodes with a 158 μm interelectrode spacing. By increasing from 10 Hz to 10 KHz the frequency of the current which is injected trough the outermost electrodes, more current flows into the intracellular domain through the membrane capacitance and the potentials measured between the innermost electrodes decrease. These extracellular potential measurements thus reflect the impedance of the extracellular domain at low frequency, and of both the extra- and intracellular domains at high frequency