System and Method for Adaptive RF Ablation

• US 20120136346A1
• Filed: 04/28/2011
• Published: 05/31/2012
• Est. Priority Date: 11/29/2010
• Status: Active Grant

• Current Assignee: Medtronic Ablation Frontiers LLC (Medtronic Plc)
• Original Assignee: Medtronic Ablation Frontiers LLC (Medtronic Plc)
• Inventors: Condie, Catherine R., Sherman, Marshall L., Kasischke, Kathryn E., Corvi, Timothy J., Strunk, Aaron R.
• Granted Patent: US 9,504,518 B2
• Time in Patent Office: Days
• US Class Current: 606/33
• CPC Class Codes: A61B 18/1206 Generators therefor
• CPC Class Codes: A61B 18/14 Probes or electrodes 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 2018/0016 Energy applicators arranged in a two- or three dimensional array
• CPC Class Codes: A61B 2018/00214 Expandable means emitting energy, e.g. by elements carried thereon
• CPC Class Codes: A61B 2018/00267 having a basket shaped structure
• CPC Class Codes: A61B 2018/00351 Heart
• CPC Class Codes: A61B 2018/00577 Ablation
• CPC Class Codes: A61B 2018/00642 with feedback, i.e. closed loop control
• CPC Class Codes: A61B 2018/00648 using more than one sensed parameter
• CPC Class Codes: A61B 2018/00678 upper
• CPC Class Codes: A61B 2018/00702 Power or energy
• CPC Class Codes: A61B 2018/00714 Temperature
• CPC Class Codes: A61B 2018/00726 Duty cycle
• CPC Class Codes: A61B 2018/00779 Power or energy
• CPC Class Codes: A61B 2018/00791 Temperature
• CPC Class Codes: A61B 2090/065 for measuring contact or contact pressure

Abstract

A medical method, device, and system are provided, including advancing an ablation element of a medical device into contact with tissue to be treated, selecting a power level of energy to ablate the tissue, delivering energy at the selected power level to the ablation element, determining whether the ablation element is in continuous contact with the tissue, and reducing the selected power level when the ablation element ceases to be in continuous contact with the tissue.

Claims

1. A medical system, comprising:

a medical device having an ablation electrode and a temperature sensor;

a source of RF energy in electrical communication with the ablation element, the source having a variable power output;

a control unit in communication with the temperature sensor to receive a temperature signal from the temperature sensor;

the control unit programmed to determine the state of contact between the ablation electrode and biological tissue based at least in part on the temperature signal; and

a feedback controller coupled to the temperature sensor and the source of RF energy, wherein the output of the feedback controller modifies the power output of the source of RF energy.

2. The medical system of claim 1, wherein the source of RF energy has a duty cycle of selectable duration.

3. The medical system of claim 2, wherein the source of RF energy has a duty cycle with a base frequency of at most 10 ms

4. The medical system of claim 1, wherein the feedback controller is a P-I-D or P-I controller, and the integration period of the feedback controller is at least the duration of a human heartbeat.

5. The medical system of claim 1, wherein the state of contact comprises continuous tissue contact, lost tissue contact, or regained tissue contact.

6. The medical system of claim 5, further comprising:

the control unit programmed to modify the power output of the source of RF energy based at least in part on the state of contact.

7. The medical system of claim 6 further comprising:

the control unit programmed to prevent the feedback controller from increasing the power output of the source of the RF energy based at least in part on the state of contact being lost tissue contact.

8. The medical system of claim 5 further comprising:

the control unit programmed to allow the feedback controller to increase the power output of the source of the RF energy based at least in part on the state of contact being regained tissue contact.

9. A medical system, comprising:

means for advancing an ablation element of a medical device into contact with tissue to be treated;

means for supplying power to the ablation element to ablate the tissue;

means for determining whether the ablation element is in continuous contact with the tissue; and

means for modifying the supplied power to the ablation element based at least in part on the determination.

10. The medical system of claim 9, wherein the tissue to be treated is cardiac tissue.

11. The medical system of claim 9, further comprising means for permitting the power to the ablation element to be increased when the ablation element regains continuous contact with the tissue.

12. The medical system of claim 9, further comprising:

means for selecting a delay interval; and

means for increasing the power to the ablation element after the ablation element has continuous contact with the tissue for at least the delay interval.

13. The medical system of claim 12, wherein the selected delay interval is substantially equal to 3 seconds.

14. The medical system of claim 9, further comprising:

means for selecting a desired temperature of the ablation element;

means for monitoring a temperature of the ablation element; and

means for reducing the power to the ablation element when the monitored temperature exceeds the desired temperature.

15. The medical system of claim 9, further comprising:

means for selecting a maximum delivered power threshold;

means for monitoring power delivered to the ablation element;

means for calculating the average power produced by the means for supplying power; and

means for limiting the average power to the maximum delivered power threshold.

16. The medical system of claim 9, further comprising:

means for setting a maximum duty cycle equal to the current duty cycle value when the power is at least equal to the desired maximum power; and

means for reducing the selected power level by thereafter limiting the duty cycle value to the maximum duty cycle.

17. A medical system controller, comprising:

a power source for supplying power to an ablation element;

a control unit programmed to characterize the contact between the ablation element and biological tissue, said contact characterization comprising the states of continuous tissue contact, loss of continuous tissue contact, or regained tissue contact;

the control unit programmed to limit the power supplied to the ablation element based at least in part upon the characterization of contact as loss of continuous contact.

18. The medical system controller of claim 17, wherein said control unit is programmed to permit the power supplied to the ablation element to be increased when the contact characterization is regained tissue contact.

19. The medical system controller of claim 18, further comprising:

the control unit having a delay interval; and

the control unit programmed to permit the power supplied to the ablation element to be increased when the contact characterization is regained tissue contact and said contact characterization has continued for a time at least equal to the delay interval.

20. The medical system controller of claim 19 wherein the delay interval is substantially equal to 3 seconds.

21. The medical system controller of claim 17, further comprising:

the control unit having a maximum limit for the power supplied to the ablation element; and

the control unit programmed to measure the supplied power to the ablation element;

the control unit programmed to calculate the average power supplied to the ablation element; and

the control unit programmed to limit the average power to the maximum limit.

22. The medical system controller of claim 17, further comprising:

setting a maximum duty cycle equal to the current duty cycle value when the supplied power is at least equal to the maximum limit, and thereafter limiting the duty cycle value to the maximum duty cycle.

23. The medical system controller of claim 17, further comprising:

the control unit programmed to monitor a temperature of the ablation element;

the control unit programmed to select a desired temperature and a threshold variation;

the control unit programmed to calculate an average temperature of the ablation element, to calculate a difference between the ablation element temperature and the average ablation element temperature, and to calculate a continuity value by subtracting the difference from the desired temperature; and

the control unit programmed to reducing the desired temperature when the continuity value exceeds the threshold variation.

24. The medical system controller of claim 23 further comprising:

the control unit programmed to increasing the desired temperature when the continuity value falls below the threshold variation.

25. The medical system controller of claim 24 wherein the threshold variation is substantially equal to 5 degrees.