Measurement of Bipolar Impedance for Monitoring Ablation of Cardiac TissueTechnology #ua99-014
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Background: Cardiac ablation is used to correct heart rhythm problems (arrhythmias). Unfortunately, give RF energy delivery can be difficult to control there may be collateral damage to neighboring tissue as the arrhythmia causing tissue is being destroyed. The exact amount energy delivered to ablate the arrhythmia causing tissue while conserving neighboring tissue needs to be optimally determined.
Invention: Inventors developed a detection means that can determine when a complete cardiac lesion has been formed. During application of radiofrequency or other forms of energy such as ultrasound, the bipolar impedance can be measured between the electrodes used to deliver the energy and an adjacent electrode. As the tissue temperature (measured 1-3 mm beneath the electrode) rise during energy application, the impedance falls. This inverse correlation is very consistent. Additionally, there is a bio-battery signal and temperature correlation where once an intra-tissue temperature has been reached; the bio-battery signal starts to drop off. This association along with the bio-impedance measurement suggests irreversible tissue damage or lesion formation.
Application: Bipolar bio-impedance has the potential to be used as a control parameter to regulate energy application for various ablation procedures. In addition, it will have the capability to monitor and quantitate lesion formation ablation of cardiac tissue as well as during other treatment regimens such as hyperthermia.
· The technology can determine the presence of a lesion based on strong and consistent correlation between non-obvious measurements simultaneously as RF energy is being administered to the tissue.
· Amongst those measurements are temperature and bio- impedance. The bipolar bio-impedance may be used as a control parameter to regulate energy application for various ablation procedures.
· This technology could also limit further damage to healthy neighboring cardiac tissue when monitoring and quantitatively assessing lesion formation ablation of cardiac tissue.
· Although unipolar tissue impedance (i.e., between electrode and backplate) indicates lesion formation, a bipolar design (this technology) may better correlate with intra-myocardial tissue temperature.
· This device would eliminate the use of thermistors and thermocouples imbedded in the electrode therefore limiting catheter costs and expanding catheter design.
Stage of Development: Test data obtained from in vitro studies verifies the correlation between decrease in impedance and increase in tissue temperature. U.S. Patent 6,423,057 issued 7/23/2002. UA OTT is seeking commercial partners to license the technology and integrate this technology into their ablation catheters.
Lead Inventor: Dr. Frank Marcus
Licensing Manager: Lisa Lin, PhD
UA ID: UA99-014