Assessment of Electrode Coupling for Tissue Ablation

• US 20080300589A1
• Filed: 12/06/2006
• Published: 12/04/2008
• Est. Priority Date: 12/06/2005
• 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, Cao, Hong, Belhe, Kedar Ravindra
• Granted Patent: US 9,283,026 B2
• Time in Patent Office: Days
• US Class Current: 606/34
• CPC Class Codes: A61B 18/1206 Generators therefor
• 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 2018/00303 active, e.g. with a motor creating vibrations
• CPC Class Codes: A61B 2018/00357 Endocardium
• CPC Class Codes: A61B 2018/00577 Ablation
• CPC Class Codes: A61B 2018/00642 with feedback, i.e. closed loop control
• CPC Class Codes: A61B 2018/00666 using a threshold value
• CPC Class Codes: A61B 2018/00702 Power or energy
• CPC Class Codes: A61B 2018/0075 Phase
• CPC Class Codes: A61B 2018/00755 Resistance or impedance
• CPC Class Codes: A61B 2018/00869 Phase
• CPC Class Codes: A61B 2018/00875 Resistance or impedance
• 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 34/20 Surgical navigation systems; Devices for tracking or guiding surgical instruments, e.g. for frameless stereotaxis
• CPC Class Codes: A61B 5/053 Measuring electrical impedance or conductance of a portion of the body

Abstract

An electrode catheter (14) and a method for assessing electrode-tissue contact and coupling are disclosed. An exemplary electrode catheter (14) comprises an electrode (20) adapted to apply electrical energy. A measurement circuit (42) is adapted to measure impedance between the electrode (20) and ground as the electrode approaches a target tissue (24). A processor (50) determines a contact and coupling condition for the target tissue (24) based at least in part on reactance of the impedance measured by the measurement circuit (42). In another exemplary embodiment, the electrode catheter (14) determines the contact and coupling condition based at least in part on a phase angle of the impedance.

Claims

1. A coupling sensing system comprising:

a catheter;

an electrode located on the catheter and adapted to apply electrical energy;

a measurement circuit adapted to measure impedance between the electrode and ground as the electrode approaches a target tissue; and

a processor for determining a coupling condition at a particular moment in time for the target tissue based at least in part on the impedance measured by the measurement circuit relative to a baseline value determined in the blood.

2. The system of claim 1, wherein coupling between the electrode and target tissue is mechanical contact.

3. The system of claim 1, wherein coupling between the electrode and target tissue is electrical coupling.

4. The system of claim 3, wherein electrical coupling allows electrical energy to pass from the electrode to the target tissue.

5. The system of claim 3, wherein electrical energy passing from the electrode to the target tissue is sufficient to create lesion during ablation.

6. The system of claim 1, wherein the level of coupling directly corresponds to the reactance of the measured impedance.

7. The system of claim 6, wherein a reactance approaching zero (0) indicates little or no contact.

8. The system of claim 6, wherein increasingly negative reactance indicates increasing electrode-tissue coupling.

9. The system of claim 1, wherein the level of coupling directly corresponds to the phase angle of the measured impedance.

10. The system of claim 9, wherein a phase angle approaching zero (0) indicates little or no coupling.

11. The system of claim 9, wherein increasingly negative phase angles indicate increasing electrode-tissue coupling.

12. The system of claim 1, further comprising an output device for indicating the coupling condition to a user.

13. The system of claim 12, wherein the output device includes analog output corresponding to the coupling condition.

14. The system of claim 1, wherein the measurement circuit includes an RCL meter.

15. The system of claim 1, wherein the measurement circuit includes a phase detection circuit.

16. The system of claim 1, wherein the electrode is adapted to apply electrical energy for both coupling assessment and tissue ablation.

17. The system of claim 1, further comprising a constant current source to apply electrical energy for coupling assessment.

18. The system of claim 1, further comprising a variable current source to apply electrical energy for coupling assessment.

19. The system of claim 1, further comprising a constant voltage source to apply electrical energy for coupling assessment.

20. The system of claim 1, further comprising a variable voltage source to apply electrical energy for coupling assessment.

21. A method of assessing electrode-tissue coupling for tissue ablation, comprising

measuring impedance between an electrode and ground as the electrode approaches a target tissue;

separating a reactance component from the measured impedance; and

indicating a coupling condition for the target tissue based at least in part on the reactance component relative to a baseline value determined in the blood without determining an actual impedance value of the tissue.

22. The method of claim 21, wherein the coupling condition corresponds to a level of coupling with the target tissue, the reactance approaching zero (0) as the level of coupling decreases.

23. The method of claim 21, further comprising indicating for a user:

less electrode-tissue coupling as the reactance component approaches zero (0); and

more electrode-tissue contact as the reactance component becomes more negative.

24. The method of claim 21, further comprising computing a phase angle from the measured impedance.

25. The method of claim 24, wherein the coupling condition corresponds to a level of coupling with the target tissue, the phase angle approaching zero (0) as the level of coupling decreases.

26. The method of claim 24, further comprising indicating for a user:

less electrode-tissue coupling as the reactance component approaches zero (0); and

more electrode-tissue coupling as the reactance component becomes more negative.

27. A method for assessing lesion formation in tissue, the method comprising the following steps:

(a) providing an ablation device;

(b) confirming coupling between the ablation device and the tissue

(c) ablating the tissue; and

(d) monitoring physiological changes in the tissue

28. The method of claim 27, wherein the coupling is electrical coupling via a phase angle sensor.

29. The method of claim 27 wherein the coupling is mechanical coupling via an electromechanical sensor.

30. The method of claim 27 wherein the physiological change monitored comprises the tissue'"'"'s resistance.

31. The method of claim 27 wherein the physiological change monitored comprises the tissue'"'"'s reactance.

32. The method of claim 27 wherein the physiological change monitored comprises the tissue'"'"'s temperature.

33. A method for assessing characteristics of a lesion formed, the method comprising the following steps:

(a) providing an ablation device;

(b) confirming coupling between the ablation device and the tissue

(c) ablating the tissue; and

(d) monitoring physiological changes in the tissue

34. A tissue sensing system for assessing lesion formation and lesion characteristics, the system comprising a coupling confirmation device selected from the group consisting of an electrical coupling sensor and an electromechanical sensor.