Pacing lead/myocardium interface: modelling and characterization of the impedance

The electrical pattern of the pacing lead/myocardium interface can be simplified as a resistor R with, in parallel, a capacitor C and a resistor r. Our work is to evaluate these three impedance components of the interface. We fed a voltage across a serial resistor in the pacing lead circuit and we measured, sampled, digitized and recorded it. Then we calculated the electrical current through the pacing lead circuitry. The applied pacing waveform signal is a square wave at constant voltage and the current can be modeled as follows: I(t)=V(amiddote
^bt
+c). Using a digital analysis method, we assessed a, b and c whence we inferred the components of the interface impedance (R, r and C). The latter characterize the interface polarization and allow the calculation of the polarization voltage whatever the pacing waveform. Moreover, with this method, the characteristics of any pacing lead can easily be determined during pace-maker implantations