Pressure-sensitive conductive composite contact sensor and method for contact sensing

• US 20080161786A1
• Filed: 12/29/2006
• Published: 07/03/2008
• Est. Priority Date: 12/29/2006
• Status: Active Grant

• Current Assignee: St. Jude Medical, Atrial Fibrillation Division, Inc. (Abbott Laboratories)
• Original Assignee: St. Jude Medical, Atrial Fibrillation Division, Inc. (Abbott Laboratories)
• Inventors: Paul, Saurav, Belhe, Kedar Ravindra
• Granted Patent: US 9,579,483 B2
• Time in Patent Office: Days
• US Class Current: 606/32
• 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 2018/00083 low, i.e. electrically insulating
• CPC Class Codes: A61B 2018/00577 Ablation
• CPC Class Codes: A61B 2018/00875 Resistance or impedance
• CPC Class Codes: A61B 2018/00988 Means for storing information, e.g. calibration constants, or for preventing excessive use, e.g. usage, service life counter
• CPC Class Codes: A61B 2090/064 for measuring force, pressure or mechanical tension
• CPC Class Codes: A61B 2090/065 for measuring contact or contact pressure
• CPC Class Codes: A61B 5/6885 Monitoring or controlling sensor contact pressure
• CPC Class Codes: A61M 2025/0002 with a pressure sensor at the distal end
• CPC Class Codes: A61M 25/00 Catheters; Hollow probes dilators A61M29/00; peritoneal catheters A61M1/285; tracheal tubes A61M16/04; for drainage A61M27/00; for uterus, vagina or rectum A61M31/00 ; for measuring or testing A61B; materials for catheters A61L29/00
• CPC Class Codes: G01L 1/20 by measuring variations in ohmic resistance of solid materials or of electrically-conductive fluids of piezo-resistive materials G01L1/18; by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electrical potential is produced or varied upon the application of stress

Abstract

A catheter assembly for assessing contact between the catheter assembly and tissue is disclosed. The assembly includes a catheter shaft and a pressure sensitive conductive composite member whose electrical resistance varies with pressure applied to the catheter assembly. The assembly also includes at least one measurement terminal to permit the measurement of changes in the electrical characteristics of the pressure sensitive conductive composite member. The assembly may optionally include a measurement device to measure resistance, impedance and/or other electrical characteristics. The assembly may utilize a reference electrode secured to the patient'"'"'s tissue, which permits the measurement device to measure changes between the reference electrode and the at least one measurement terminal. Optionally, the assembly may include a conductive outer layer. Also disclosed are sensor assemblies, contact sensor, methods of contact sensing, and methods of manufacturing relating to the use of pressure sensitive conductive composites.

Claims

1. An catheter assembly for assessing contact between the catheter assembly and tissue, said assembly comprising:

a catheter shaft;

a pressure sensitive conductive composite member wherein the pressure sensitive conductive composite member is configured such that a pressure that is applied to the catheter assembly causes the pressure sensitive conductive composite member to vary its electrical resistance; and

at least one measurement terminal to permit the measurement of changes in resistance of the pressure sensitive conductive composite member.

2. The catheter assembly of claim 1 further comprising:

a measurement device coupled to the at least one measurement terminal to measure changes in resistance of the pressure sensitive conductive composite member.

3. The catheter assembly of claim 2 further comprising:

a reference electrode that may be secured to tissue that may be contacted by the catheter assembly, said reference electrode also being coupled to the measurement device such that the measurement device may measure changes in the resistance of the pressure sensitive conductive composite member based on changes in electrical characteristics between the reference electrode and the at least one measurement terminal.

4. The catheter assembly of claim 3 wherein the reference electrode is connected to an electrical ground.

5. The catheter assembly of claim 1 wherein the pressure sensitive conductive composite member comprises a quantum tunneling composite.

6. A sensor assembly for assessing contact between the sensor assembly and tissue, said assembly comprising:

a catheter shaft;

a catheter tip;

a quantum tunneling composite member having a first end and a second end, and being located between the catheter shaft and the catheter tip; and

a measurement device coupled to each of the first end and the second end of the quantum tunneling composite member, such that said measurement device measures an electrical characteristic of the quantum tunneling composite member;

said catheter assembly being assembled such that a pressure applied to the catheter tip is transferred to the quantum tunneling composite member and changes the electrical characteristic of said quantum tunneling composite member, wherein said measurement device measures the change in electrical characteristics of the quantum tunneling composite member.

7. A sensor assembly for assessing contact between the sensor assembly and tissue, said assembly comprising:

a catheter shaft;

a conductive core having a first measurement terminal

a layer of a pressure sensitive conductive composite in electrical contact with said conductive core, said layer including a tissue contact surface that may be placed in contact with tissue; and

a measurement device coupled to the first measurement terminal such that said measurement device measures an electrical characteristic of the pressure sensitive conductive composite;

wherein when the tissue contact surface applies pressure to the tissue, the measurement device will measure a change in electrical characteristics of the pressure sensitive conductive composite and provide a user with information regarding a degree of contact between the sensor assembly and the tissue being contacted.

8. The catheter assembly of claim 7 further comprising:

a memory coupled to the measurement device for storing a plurality of electrical characteristic measurements; and

a processor coupled to the measurement device for assessing a degree of contact using a plurality of measurements stored in the memory.

9. The catheter assembly of claim 7 further comprising:

a conductive outer layer having a second measurement terminal, said conductive outer layer covering at least a portion of the layer of pressure sensitive conductive composite, and wherein the measurement device measures electrical characteristics of the layer of pressure sensitive conductive composite using the first measurement terminal and the second measurement terminal.

10. The catheter assembly of claim 9 further comprising:

a non-conductive outer layer covering at least a portion of the conductive outer layer.

11. The catheter assembly of claim 7 further comprising:

a reference electrode for electrically coupling to tissue, said reference electrode having a second measurement terminal;

wherein the measurement device measures electrical characteristics of the layer of pressure sensitive conductive composite using the first measurement terminal and the second measurement terminal.

12. A method of sensing contact between a catheter and tissue, said method comprising:

providing a catheter comprising;

a catheter shaft and at least one quantum tunneling composite material;

placing the catheter in contact with a tissue such that pressure is asserted on the quantum tunneling composite material; and

sensing a signal that is indicative of a degree of contact that exists between the catheter and the tissue.

13. The method of claim 12, wherein the step of sensing a signal that is indicative of a degree of contact comprises:

measuring resistance along a path of the quantum tunneling composite material;

generating a signal that is indicative of the measured resistance having dropped below a set threshold, thereby indicating a desired level of contact between the catheter and the tissue.

14. The method of claim 12, wherein the step of sensing a signal that is indicative of a degree of contact comprises:

applying a reference electrode to tissue that will be placed in contact with the catheter;

measuring impedance of a path including at least the reference electrode and at least a portion the quantum tunneling composite material;

generating a signal that is indicative of a degree of contact between the quantum tunneling composite material and the tissue.

15. The method of claim 12, wherein the step of sensing a signal that is indicative of a degree of contact comprises:

setting a pressure threshold that is representative of a desired level of contact between the quantum tunneling composite material and the tissue;

measuring impedance along a path of the quantum tunneling composite material;

generating a signal that is a degree of contact between the quantum tunneling composite material and the tissue has exceeded the pressure threshold.

16. A contact sensor assembly for assessing contact between the contact sensor assembly and tissue, said assembly comprising:

An elongate catheter body having a proximal end and a distal end;

A conductive core having a first measurement terminal, said conductive core extending at least a portion of the distal end;

A pressure sensitive conductive composite member electrically coupled to at least a portion of the conductive core located in the distal end of the catheter body;

a conductive layer having a second measurement terminal, said conductive layer covering at least a portion of the pressure sensitive conductive composite member, and said conductive layer extending at least a portion of the distal end of the catheter body;

wherein electrical characteristics of the pressure sensitive conductive composite member may be measured using the first measurement terminal and the second measurement terminal.

17. The contact sensor assembly of claim 16, further comprising:

a measurement device that measures a signal using the first and second measurement terminals and that generates an output signal that is indicative of the pressure being applied to the tissue by the distal end.

18. A method of sensing contact between a catheter and tissue, said method comprising:

providing a catheter comprising a catheter shaft and a pressure sensitive conductive composite element;

placing the catheter in contact with a tissue; and

monitoring the electrical characteristics of the pressure sensitive conductive composite element for a change that is indicative of contact having been made between the catheter and tissue.

19. The method of claim 18,

wherein the catheter further comprises an electrode tip of a material that is not the same as the material comprising the pressure sensitive conductive composite element, said electrode tip being in contact with the pressure sensitive conductive composite element;

and

wherein said step of placing the catheter in contact with a tissue comprises;

placing the electrode tip in contact with a tissue such that pressure is exerted on the pressure sensitive conductive composite element.

20. The method of claim 19,

wherein the step of monitoring the electrical characteristics of the pressure sensitive conductive composite element comprises:

measuring impedance along a path of the pressure sensitive conductive composite element;

using the measured impedance to generating a signal that is indicative of pressure that exists between the electrode tip and the tissue.

21. The method of claim 18, wherein the step of monitoring the electrical characteristics of the pressure sensitive conductive composite element comprises:

measuring impedance along a path of the pressure sensitive conductive composite element;

correlating the measured impedance to a pressure level; and

generating a signal that is indicative of a threshold level of contact between the electrode tip and the tissue.

22. The method of claim 18, further comprising:

applying a first known amount of pressure to the catheter;

measuring a first electrical signal indicative of impedance along a path of the pressure sensitive conductive composite element; and

recording a first information data set regarding the first electrical signal indicative of the impedance along the path of the pressure sensitive conductive composite element; and

associating the first information data set with the first known amount of pressure that was applied to generate the first electrical signal.

23. The method of claim 22, further comprising:

applying a second known amount of pressure to the catheter;

measuring a second electrical signal indicative of impedance along a path of the pressure sensitive conductive composite element; and

recording a second information data set regarding the second electrical signal indicative of the impedance along the path of the pressure sensitive conductive composite element; and

associating the second information data set with the second known amount of pressure that was applied to generate the second electrical signal.

24. The method of claim 23, further comprising:

applying a pressure to the catheter to apply pressure to the tissue;

measuring a third electrical signal indicative of impedance along a path of the pressure sensitive conductive composite element; and

estimating the amount of pressure that is being applied to the tissue using at least;

a) the first information data set and its associated first known amount of pressure; and

b) the second information data set and its associated second known amount of pressure.

25. A method of manufacturing a contact sensor for sensing contact between an electrode and tissue, the method comprising:

forming a catheter shaft having a distal end and a proximal end;

forming a conductive core extending from the distal end of the catheter shaft, said conductive core having a first measurement terminal that is electrically coupled to the conductive core; and

forming a distal end of the contact sensor, said distal end comprising pressure sensitive conductive composite material covering at least a portion of the conductive core;

wherein the first measurement terminal may be connected to an analyzer for analyzing the electrical characteristics of the pressure sensitive conductive composite material.

26. The method of claim 25, wherein the step of forming a PSCC sensor comprises:

coating the conductive core with a layer of a quantum tunneling composite material.

27. The method of claim 25, wherein the step of forming a conductive core comprises:

forming an electrically non-conductive flexible shaft;

forming an electrically conductive element about the electrically non-conductive flexible shaft; and

electrically coupling a first measurement terminal to the conductive coil.

28. The method of claim 27, wherein the electrically conductive element is formed as a helical coil.

29. The method of claim 27, wherein the electrically conductive element is formed as a wire mesh.

30. The method of claim 25, further comprising:

forming a conductive layer over at least a portion of the pressure sensitive conductive composite material; and

electrically coupling a second measurement terminal to the conductive layer;

wherein the first measurement terminal and the second measurement terminal may be connected to an analyzer for analyzing electrical characteristics of the pressure sensitive conductive composite material.