Computer-simulation of impedance vector dynamic of intra-cardiac 4-electrode bio-impedance measurement

In this study the complex bahavior of intra-cardiac impedance signal is investigated with computer-simulation. Dynamic impedance signals are simulated over one cardiac cycle using computer-model of the dynamic heart in combination with specific impedance characteristics of tissues. 4-electrode intra-ventricular catheter impedance signals are calculated with Finite Difference Method at 7 frequencies from 1 kHz to 1 Mhz. The magnitude of the signal was observed to be around 25 Omega with the dynamic change of less than 1 % at all frequencies. The change in phase angle was up to 20 % in some lower frequency cases, where the phase angle itself was below -1 degrees. At higher frequencies the phase angle increased to around -10 degrees but the change in the phase over the cardiac cycle was around 2 %. At each frequency the impedance vector traced a complex arc on the real-imaginary plane during the cardiac cycle. The impedance arc is unique for each frequency and we believe it will allow characterization of tissue state for myocardium health condition monitoring.