Simulation of Intra-Cardiac Catheter Complex Impedance Signals with Variable Stroke Volume

In this study computer models are used for simulating electrical impedance signals from intracardiac catheter inserted to the bottom of the left ventricle of the heart. Frequency dependent models are used for tissue impedance simulation that produce complex impedance signals. 3D dynamic heart is composed of dynamic spline surfaces. Five different stroke volumes of the heart have been studied. Impedance signals from the catheter electrodes are calculated with Finite Difference Method using complex tissue impedance values at frequencies 1 kHz and 1 MHz. We were able to see clear correlation between the volume change of the left ventricle and the simulated signal. The signal magnitude change was really small-less than 0.3 %. The phase angle of the simulated signal and its´ dynamic change was more pronounced at 1 kHz frequency and had a small change but was a lot higher overall at 1Mz frequency. The correlation of phase angle with left ventricle volume change was clearer than signal magnitude and appeared to be less influenced by electrode positioning. We therefore conclude that phase angle of the impedance signal can contain valuable information that can be used additionally to the signal magnitude when estimating cardiac stroke volume