Low power tissue ablation system

• US 8,834,461 B2
• Filed: 07/11/2006
• Issued: 09/16/2014
• Est. Priority Date: 07/11/2005
• Status: Active Grant

• Current Assignee: Medtronic Ablation Frontiers LLC (Medtronic Plc)
• Original Assignee: Medtronic Ablation Frontiers LLC (Medtronic Plc)
• Inventors: Werneth, Randell L., Kunis, Christopher G., Flaherty, J. Christopher, Sherman, Marshall L.
• Primary Examiner(s): Dvorak, Linda
• Assistant Examiner(s): SCOTT, AMANDA L
• Application Number:
  US11/484,878
• Publication Number:
  US 20070083195A1
• Time in Patent Office: 2,989 Days
• Field of Search: 606/34, 606/39, 606/41, 606/42, 606/45, 606/46
• US Class Current: 606/41
• 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 2017/00243 cardiac
• CPC Class Codes: A61B 2018/00214 Expandable means emitting energy, e.g. by elements carried thereon
• CPC Class Codes: A61B 2018/00351 Heart
• CPC Class Codes: A61B 2018/00666 using a threshold value
• CPC Class Codes: A61B 2018/00898 Alarms or notifications created in response to an abnormal condition
• CPC Class Codes: A61B 2018/1467 using more than two electrodes on a single probe
• CPC Class Codes: A61B 2018/1475 Electrodes retractable in or deployable from a housing

Abstract

Devices, systems and methods are disclosed for the ablation of tissue. Embodiments include an ablation catheter that has an array of ablation elements attached to a deployable carrier assembly. The carrier assembly can be constrained within the lumen of a catheter, and deployed to take on an expanded condition. The carrier assembly includes multiple electrodes that are configured to ablate tissue at low power. Additional embodiments include a system that includes an interface unit for delivering one or more forms of energy to the ablation catheter.

Claims

1. An ablation system for an operator to treat a patient, said system comprising:

an ablation catheter including a first carrier arm having ablation elements and a second carrier arm having ablation elements for delivering thermal ablative energy to tissue, said catheter comprising a flexible shaft with a proximal end and a distal end, each ablation element having an electrical, tissue contact portion configured to deliver thermal ablative energy to tissue, a thermal dissipation portion that is electrically isolated from the electrical portion and configured to dissipate heat from the electrical portion into circulating blood, and a fin projecting from the thermal dissipation portion;

an interface unit providing energy to the ablation catheter; and

the interface unit monitoring at least one parameter of the system and preventing energy delivered from exceeding a cumulative energy threshold value, the cumulative energy being calculated as a sum of energy delivered over time.

2. The system of claim 1 wherein the ablation catheter is configured to monitor the temperature of each ablation element.

3. The system of claim 2 wherein the higher of a first ablation element temperature on the first carrier arm and a second ablation element temperature on the first carrier arm is said at least one parameter monitored to prevent the energy delivered from exceeding said threshold value.

4. The system of claim 1 wherein the at least one monitored parameter is selected from the group consisting of:

temperature such as temperature from a temperature sensor;

a value of measured current;

a value of measured voltage;

a flow measurement value;

a force measurement value such as a measurement of strain;

a pressure measurement value; and

combinations thereof.

5. The system of claim 1 wherein the threshold is 4 Watts.

6. The system of claim 1 wherein said threshold value changes over time.

7. The system of claim 1 wherein said system is configured to deliver a first energy level followed by a second energy level, said first energy level of lesser magnitude than said second energy level.

8. The system of claim 7 wherein said threshold is modified after said first energy level is delivered.

9. The system of claim 1 wherein the ablation catheter further comprises a deployable carrier assembly fixedly attached to a control shaft, said carrier assembly including the first and second carrier arms.

10. The system of claim 9 wherein the carrier assembly is flexible.

11. The system of claim 10 wherein the carrier assembly is configured to conform with an endocardial surface of the heart.

12. The system of claim 9 wherein the ablation catheter further comprises a handle on its proximal end, said handle including means of deploying the catheter assembly.

13. The system of claim 1 wherein the ablation catheter further comprises an integral functional element is selected from the group consisting of:

a sensor;

a transmitter;

an imaging element; and

combinations thereof.

14. The system of claim 13 wherein the functional element is a sensor selected from the group consisting of:

an electrical signal sensor such as a cardiac electrode;

a temperature sensor such as a thermocouple;

an imaging transducer such as an array of ultrasound crystals;

a pressure sensor;

a pH sensor;

a physiologic sensor such as a blood sensor;

a respiratory sensor;

an EEG sensor;

a pulse oximetry sensor;

a blood glucose sensor;

an impedance sensor;

a contact sensor;

a strain gauge;

an acoustic sensor; and

combinations thereof.

15. The system of claim 1 wherein at least one ablation element is an electrode.

16. The system of claim 1 wherein at least one ablation element has a surface area less than 2.5 mm².

17. The system of claim 16 wherein at least one ablation element is configured to ablate tissue when energized with less than 10 watts of energy.

18. The system of claim 1 wherein at least one ablation element has a mass of less than 0.05 grams.

19. The system of claim 18 wherein at least one ablation element is configured to ablate tissue when energized with less than 10 watts of energy.

20. The system of claim 1 wherein at least one ablation element has a volume of less than 3.0 mm³.

21. The system of claim 20 wherein at least one ablation element is configured to ablate tissue when energized with less than 10 watts of energy.

22. The system of claim 1 wherein at least one ablation element includes a temperature sensor.

23. The system of claim 22 wherein the temperature sensor is a thermocouple.

24. The system of claim 1 wherein the ablation catheter is configured to deliver multiple forms of energy.

25. The system of claim 1 wherein the delivered energy is selected from the group consisting of heat and cryogenic energies.

26. The system of claim 25 wherein radiofrequency energy is delivered.

27. The system of claim 26 wherein monopolar and bipolar radiofrequency energy are delivered.

28. The system of claim 27 wherein monopolar and bipolar energy are delivered sequentially.

29. The system of claim 27 wherein the power delivered to the at least one ablation element is less than ten watts.

30. The system of claim 25 wherein multiple forms of energy are delivered.

31. The system of claim 1 wherein the tissue is cardiac tissue.

32. The system of claim 1 wherein the tissue is selected from the group consisting of:

prostate;

brain;

gall bladder;

uterus;

tumor; and

combinations thereof.

33. The system of claim 1 wherein the interface unit is configured to provide information relating to the temperature of at least one ablation element.

34. The system of claim 33 wherein the information is rate of cooling information.

35. The system of claim 1 wherein the interface unit is configured to compare the temperature of at least one ablation element to a threshold.

36. The system of claim 35 wherein the threshold is adjustable by the operator.

37. The system of claim 35 wherein an ablation parameter is modified when said threshold is reached.

38. The system of claim 37 wherein modifying the ablation parameter results in a modification to the energy delivered to at least one ablation element.

39. The system of claim 37 wherein modifying the ablation parameter results in the activation of an alarm.

40. An ablation system, comprising:

an ablation catheter including ablation elements for delivering thermal ablative energy to tissue, said catheter comprising a flexible shaft with a proximal end and a distal end, each ablation element having an electrical, tissue contact portion configured to deliver thermal ablative energy to tissue, a thermal dissipation portion that is electrically isolated from the electrical portion and configured to dissipate heat from the electrical portion into circulating blood, and a fin projecting from the thermal dissipation portion; and

an interface unit providing energy to the ablation catheter; and

the interface unit monitoring at least one parameter of the system and preventing energy delivered from exceeding a cumulative energy threshold value, the cumulative energy being calculated as a sum of energy delivered over time.

41. The system of claim 40 wherein the threshold is 500 Watt-seconds.

42. The system of claim 40 wherein the threshold is 300 Watt-seconds.

43. An ablation system comprising:

an ablation catheter including a plurality of ablation elements for delivering thermal ablative energy to tissue, each ablation element having an electrical, tissue contact portion configured to deliver thermal ablative energy to tissue, a thermal dissipation portion that is electrically isolated from the electrical portion and configured to dissipate heat from the electrical portion into circulating blood, and a fin projecting from the thermal dissipation portion;

an interface unit providing energy to the ablation catheter;

a threshold comparator; and

the interface unit monitoring at least one parameter of the system and the threshold comparator comparing the at least one parameter to a cumulative energy threshold value and preventing energy delivered from exceeding the threshold value, the cumulative energy being calculated as a sum of energy delivered over time.

44. The system of claim 43 wherein the at least one parameter can be reset.

45. The system of claim 44 wherein the at least one parameter is reset each time energy delivered to the at least one ablation element is switched from off to on states.

46. The system of claim 44 wherein the at least one parameter is reset each time at least one of the carrier arms is repositioned by the operator.

47. The system of claim 43 wherein the threshold comparator is further configured to compare a second parameter to a second threshold.