BIOIMPEDANCE MEASUREMENT SYSTEM AND METHOD
Methods and systems for detecting fluid egress, assessing lesion quality, determining tissue composition or structure, determining ice coverage of catheter tip and providing tissue contact assessment, by providing a catheter having a shaft with a proximal end portion and a distal end portion, the proximal end portion and the distal end portion define at least one fluid pathway therebetween with the shaft having a plurality of electrodes, positioning the catheter at a tissue treatment site, applying an electrical current between at least two of the plurality of electrodes, measuring impedance voltage between the at least two of the plurality of electrodes and, processing the measured impedance voltage caused by the applied electrical current to determine if fluid egress is present, to assess lesion quality, to determine tissue composition, ice cover of catheter tip, and to provide contact assessment. The system may have a control unit, a microprocessor, an impedance measuring device or the like to perform processing of impedance data.
1 . A method for assessing tissue composition comprising:
positioning a catheter at a tissue treatment site, the catheter including a first electrode and a second electrode;
applying an electrical current between the first and second electrode;
measuring a first impedance voltage between the first and second electrodes;
identifying a tissue type based at least in part upon a comparison of the measured impedance voltage to a predefined impedance range for a predetermined tissue type.
2 . The method of claim 1 , further comprising re-positioning at least a portion of the catheter as a result of the identified tissue type.
3 . The method of claim 1 , further comprising ablating tissue at the tissue treatment site.
4 . The method of claim 3 , wherein ablating tissue includes circulating a cryogenic fluid through the catheter.
5 . The method of claim 3 , further comprising measuring a second impedance voltage between the first and second electrodes to assess a lesion quality resulting from the ablation.
6 . The method of claim 1 , wherein the catheter further includes a cooling chamber in fluid communication with the at least one fluid pathway; the first electrode located near the distal side of the cooling chamber and the second electrode located near the proximal side of the cooling chamber.
7 . The method of claim 6 , wherein the cooling chamber is an expandable device.
8 . A method for assessing tissue composition comprising:
establishing an impedance range for a tissue type;
positioning a catheter at a tissue treatment site, the catheter including a first electrode and a second electrode;
circulating a coolant through the catheter to cool the tissue treatment site;
applying an electrical current between the first and second electrode;
measuring a first impedance voltage between the first and second electrodes; and
determining whether the measured impedance voltage is within the established range.
9 . The method of claim 8 , identifying a tissue type based at least in part upon the determination of whether the measured impedance voltage is within the established range.
10 . The method of claim 8 , further comprising re-positioning at least a portion of the catheter as a result of the determination of whether the measured impedance voltage is within the established range.
11 . The method of claim 10 , further comprising monitoring a measured impedance voltage until the measured impedance voltage is within the established impedance range.
12 . The method of claim 8 , further comprising ablating tissue at the tissue treatment site.
13 . The method of claim 12 , wherein ablating tissue includes circulating a cryogenic fluid through the catheter.
14 . The method of claim 12 , further comprising measuring a second impedance voltage between the first and second electrodes to assess a lesion quality resulting from the ablation.
15 . The method of claim 8 , wherein the catheter further includes a cooling chamber in fluid communication with the at least one fluid pathway; the first electrode located near the distal side of the cooling chamber and the second electrode located near the proximal side of the cooling chamber.
16 . The method of claim 15 , wherein the cooling chamber is an expandable device.