Rf ablation apparatus and method having electrode/tissue contact assessment scheme and electrocardiogram filtering

摘要

A method of assessing the adequacy of contact between an ablation electrode and biological tissue within a biological organ having biological fluid therein includes the steps of positioning the ablation electrode proximal the biological tissue; positioning a reference electrode a distance from the ablation electrode; measuring the impedance between the ablation electrode and the reference electrode at a first frequency and measuring the impedance between the ablation electrode and the reference electrode at a second frequency. The percentage difference between the first-frequency impedance and the second-frequency impedance provides an indication of the state of electrode/tissue contact. In general, a percentage difference of at least approximately 10% serves as an indication of substantially complete electrode/tissue contact. A percentage difference in the approximate range between 5% and 10% serves as an indication of partial electrode/tissue contact. A percentage difference less than approximately 5% serves as an indication of no electrode/tissue contact. Ratiometric measurements may also be used to assess the state of electrode/tissue contact.