Methods of assessing contact between an electrode and tissue using complex impedance measurements

Abstract

A system and method measures impedance across a plurality of electrodes and assesses proximity or contact between electrodes of a medical device and patient tissue. Contact is assessed between individual electrodes and cardiac tissue using bipolar electrode complex impedance measurements. Initially, baseline impedance values are established for each of the individual electrodes based on the responses of the electrodes to the applied drive signals. After establishing the baseline impedance values a series of subsequent impedance values are measured for each electrode. For each electrode, each subsequent impedance value may be compared to a previous baseline impedance value for that electrode. If a subsequent impedance value is less than the baseline impedance value for a given electrode, the baseline impedance value may be reset to the subsequent impedance value. Such systems and method are particularly applicable to medical devices having numerous electrodes.