Electrode having non-joined thermocouple for providing multiple temperature-sensitive junctions

• US 6,440,129 B1
• Filed: 02/10/2000
• Issued: 08/27/2002
• Est. Priority Date: 05/05/1998
• Status: Expired due to Term

• Current Assignee: Heart Rhythm Technologies, Inc. (Boston Scientific Corporation)
• Original Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Inventors: Simpson, John A.
• Primary Examiner(s): PEFFLEY, MICHAEL F
• Application Number:
  US09/502,196
• Time in Patent Office: 929 Days
• Field of Search: 606/31-35, 606/41, 606/42, 606/45-50, 607/101, 607/102, 600/374, 600/549
• US Class Current: 606/42
• CPC Class Codes: A61B 18/1492 having a flexible, catheter-like structure, e.g. for heart ablation A61B18/1477 takes precedence
• CPC Class Codes: A61B 2017/00084 Temperature
• CPC Class Codes: A61B 2018/00702 Power or energy
• CPC Class Codes: A61B 2018/00726 Duty cycle
• CPC Class Codes: A61B 2018/00791 Temperature
• CPC Class Codes: A61B 2018/00797 measured by multiple temperature sensors
• CPC Class Codes: A61B 2018/00821 measured by a thermocouple
• CPC Class Codes: A61B 2018/00892 Voltage

Abstract

The non-joined thermocouple electrode configuration, for use in an RF ablation catheter for ablating biological tissue such as cardiac tissue, allows temperature to be monitored at two locations of a band electrode while only using a single pair of thermocouple wires. The thermocouple wires are connected to the electrode at separate locations. They preferably are formed of metallic materials having Seebeck coefficients that are substantially equal in magnitude but opposite in sign relative to the electrode material connecting the two. In the case of a band electrode, the two thermocouple wires are preferably spaced apart on the band electrode so that the first junction contacts the tissue having a first temperature and the second junction contacts circulating blood having a second temperature. The voltage across the thermocouple wires provides an indication of the average of the two junctions temperatures so that by monitoring the temperature of the blood, the temperature of the first junction can be determined from this average temperature.

Claims

1. An apparatus for providing a signal indicative of a temperature, said apparatus comprising:

an electrically conductive element formed of a first metallic material;

a first electrically conductive member formed of second metallic material, the first member connected to the electrically conductive element at a first junction;

a second electrically conductive member formed of a third metallic material, the second member connected to the electrically conductive element at a second junction; and

wherein the first, second and third metallic materials are chosen such that when the first and second junctions are at different temperatures a voltage output is produced across the electrode proportional to the temperature difference between the two junctions.

2. The apparatus of claim 1 wherein the first and second junctions are spaced apart on the electrically conductive element such that the voltage output is indicative of a temperature which is the average of the first and second junction temperatures.

3. The apparatus of claim 1 wherein the second and third metallic materials are metallic materials having Seebeck coefficients relative to the first metallic material that are substantially equal in magnitude but opposite in sign.

4. The apparatus of claim 1 further comprising:

a voltmeter for determining the voltage across the first electrically conductive member and the second electrically conductive member; and

a processor for converting each voltage to a temperature value.

5. An apparatus for collecting temperature data from biological tissue, said apparatus comprising:

a medical device having an electrically conductive element formed of a first metallic material disposed thereon, the medical device adapted to be positioned so that the electrically conductive element is located proximal the biological tissue;

a first electrically conductive member formed of second metallic material, the first member connected to the electrically conductive element at a first junction;

a second electrically conductive member formed of a third metallic material, the second member connected to the electrically conductive element at a second junction; and

wherein the first, second and third metallic materials are chosen such that when the first and second junctions are at different temperatures a voltage output is produced across the electrically conductive element proportional to the temperature difference between the two junctions.

6. The apparatus of claim 5 wherein the first and second junctions are spaced apart on the electrically conductive element such that the voltage output is indicative of a temperature which is the average of the first and second junction temperatures.

7. The apparatus of claim 5 wherein the first and second junctions are spaced apart on the electrically conductive element such that when the electrically conductive element is located proximal the biological tissue one of the junctions is adapted to be positioned near the electrically-conductive-element/tissue interface while the other junction is adapted to be positioned away from the electrically-conductive-element/tissue interface.

8. The apparatus of claim 5 wherein the electrically conductive element is a band electrode and the first and second junctions are located on the band electrode approximately 180 degrees apart around the band electrode circumference.

9. The apparatus of claim 5 wherein the second and third metallic materials are metallic materials having Seebeck coefficients relative to the first metallic material that are substantially equal in magnitude but opposite in sign.

10. An apparatus for collecting temperature data within a biological structure in which biological fluids flow past the tissue, said apparatus comprising:

a catheter having a plurality of band electrodes formed of a first metallic material, the band electrodes disposed at a distal end of the catheter, the distal end adapted to be positioned so that at least one of the band electrodes is located proximal the biological tissue;

a plurality of first electrically conductive members formed of second metallic material, for each of the plurality of band electrodes, one first member connected to the electrode at a first junction; and

a plurality of second electrically conductive members formed of a third metallic material, for each of the plurality of band electrodes, one second member connected to the electrode at a second junction, wherein the first, second and third metallic materials are chosen such that when the first and second junctions are at different temperatures a voltage output is produced across the electrode proportional to the temperature difference between the two junctions.

11. The apparatus of claim 10 wherein the first and second junctions are spaced apart on each band electrode such that the voltage output is indicative of a temperature which is the average of the first and second junction temperatures of that band electrode.

12. The apparatus of claim 10 wherein the first and second junctions are spaced apart on each band electrode such that when the band electrode is located proximal the biological tissue one of the junctions is adapted to be positioned near the electrode/tissue interface while the other junction is adapted to be positioned in the biological fluid.

13. The apparatus of claim 10 wherein the first and second junctions are located on the band electrode approximately 180°

apart around the band electrode circumference.

14. The apparatus of claim 10 wherein the second and third metallic materials are metallic materials having Seebeck coefficients relative to the first metallic material that are substantially equal in magnitude but opposite in sign.

15. A method for collecting temperature data from biological tissue, the biological tissue located in a biological structure in which fluids flow past the tissue, said method comprising the steps of:

positioning a medical device proximal the biological tissue, the medical device having an electrically conductive element formed of a first metallic material and first and second electrically conductive members connected to the electrically conductive element at a first junction and a second junction, respectively, the first and second electrically conductive members being formed of second and third metallic materials, respectively, such that when the two junctions are at different temperatures, a voltage output is produced across the electrically conductive element proportional to the temperature difference between the two junctions, the first and second electrically conductive members being spaced apart on the electrically conductive element;

positioning the electrically conductive element against the tissue so that a portion of the electrically conductive element is available for contact with the fluids in the biological structure; and

measuring the voltage output across the electrically conductive element as an indication of a temperature which is the average of the two junction temperatures.

16. The method of claim 15 further comprising the steps of:

placing the first junction in contact with the biological tissue and the second junction in contact with the biological fluid;

measuring the temperature of the biological fluid; and

determining the temperature of the first junction from the average temperature.

17. The method of claim 15 wherein the electrically conductive element is a band electrode and the method further comprises the steps of:

placing the first junction in contact with the biological tissue and the second junction approximately 180 degrees away from the first junction around the band electrode circumference;

measuring the temperature of the biological fluid; and

determining the temperature of the first junction from the average temperature.

18. The method of claim 15 wherein the second and third metallic materials are metallic materials having Seebeck coefficients relative to the first metallic material that are substantially equal in magnitude but opposite in sign.