BIOIMPEDANCE MEASUREMENT SYSTEM AND METHOD

• US 20080200829A1
• Filed: 04/25/2008
• Published: 08/21/2008
• Est. Priority Date: 11/18/2005
• Status: Active Grant

• Current Assignee: Medtronic CryoCath LP (Medtronic Plc)
• Original Assignee: CryoCath Technologies Incorporated (Medtronic Plc)
• Inventors: Al Asmar, Johnny, Abboud, Marwan, Harmouche, Chadi
• Granted Patent: US 7,914,525 B2
• Time in Patent Office: Days
• US Class Current: 600/547
• CPC Class Codes: A61B 18/02 by cooling, e.g. cryogenic techniques devices for cooling specific reflex points of the body within cell-life limits A61H39/06
• CPC Class Codes: A61B 2017/00026 Conductivity or impedance, e.g. of tissue
• CPC Class Codes: A61B 2018/0022 Balloons
• CPC Class Codes: A61B 2018/0212 using an instrument inserted into a body lumen, e.g. catheter
• CPC Class Codes: A61B 5/0537 Measuring body composition by impedance, e.g. tissue hydration or fat content

Abstract

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.

Claims

1. A method for assessing ice coverage of a catheter treatment tip 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;

measuring a second impedance voltage between the first and second electrodes;

calculating a difference between the first and second measured impedance values; and

assessing ice coverage of the catheter treatment tip based at least in part upon the calculated difference.

2. The method according to claim 1, further comprising repositioning the catheter when the calculated difference between the first and second measured impedance values is greater than a predetermined value.

3. The method according to claim 1, wherein the predetermined value is approximately 0.

4. The method according to claim 1, further comprising delivering coolant to the catheter treatment tip.

5. The method according to claim 4, further comprising defining a saturation time threshold for the calculated difference to reach a predetermined value.

6. The method according to claim 5, further comprising

determining whether the calculated difference has reached the predetermined value within the defined saturation time threshold;

and

terminating coolant delivery to the treatment tip based at least in part upon the determination.

7. The method according to claim 6, further comprising repositioning the catheter treatment tip.

8. The method according to claim 7, further comprising reinitiating coolant delivery to the treatment tip.

9. The method according to claim 1, further comprising measuring a temperature of the treatment tip, and removing the catheter from the treatment site when the measured temperature has reached a predetermined value.

10. A method for assessing ice coverage of a catheter treatment tip comprising:

positioning a catheter at a tissue treatment site, the catheter including a first electrode and a second electrode;

delivering coolant to the catheter treatment tip;

applying an electrical current between the first and second electrode;

monitoring impedance voltage between the first and second electrodes; and

assessing ice coverage of the catheter treatment tip based at least in part upon the monitored impedance voltage.

11. The method according to claim 10, further comprising

determining that the impedance voltage has reached a maximum value;

and

correlating the determination to a condition of substantially full ice coverage of the treatment tip.

12. The method according to claim 10, further comprising defining a saturation time threshold for the monitored impedance voltage to reach a maximum value.

13. The method according to claim 12, further comprising

determining whether the monitored impedance voltage has reached a maximum value within the defined saturation time threshold;

and

terminating coolant delivery to the treatment tip based at least in part upon the determination.

14. The method according to claim 13, further comprising repositioning the catheter treatment tip.

15. The method according to claim 14, further comprising reinitiating coolant delivery to the treatment tip.

16. The method according to claim 10, further comprising measuring a temperature of the treatment tip, and removing the catheter from the treatment site when the measured temperature has reached a predetermined value.