TRANSMURAL ABLATION SYSTEMS AND METHODS

• US 20080015562A1
• Filed: 07/20/2007
• Published: 01/17/2008
• Est. Priority Date: 04/26/2001
• Status: Active Grant

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Francischelli, David, Stewart, Mark, Hong, Jinback
• Granted Patent: US 7,959,626 B2
• Time in Patent Office: Days
• US Class Current: 606/34
• CPC Class Codes: A61B 18/1206 Generators therefor
• CPC Class Codes: A61B 18/14 Probes or electrodes therefor
• CPC Class Codes: A61B 18/1442 Probes having pivoting end effectors, e.g. forceps
• CPC Class Codes: A61B 2017/00092 using thermocouples
• CPC Class Codes: A61B 2018/0016 Energy applicators arranged in a two- or three dimensional array
• CPC Class Codes: A61B 2018/00351 Heart
• CPC Class Codes: A61B 2018/00363 Epicardium
• CPC Class Codes: A61B 2018/00577 Ablation
• CPC Class Codes: A61B 2018/00666 using a threshold value
• CPC Class Codes: A61B 2018/00678 upper
• CPC Class Codes: A61B 2018/00702 Power or energy
• CPC Class Codes: A61B 2018/00708 switching the power on or off
• CPC Class Codes: A61B 2018/00761 Duration
• CPC Class Codes: A61B 2018/00791 Temperature
• CPC Class Codes: A61B 2018/00875 Resistance or impedance
• CPC Class Codes: A61B 2018/00886 Duration
• CPC Class Codes: A61B 2018/1467 using more than two electrodes on a single probe
• CPC Class Codes: A61B 2218/002 Irrigation
• CPC Class Codes: A61B 5/053 Measuring electrical impedance or conductance of a portion of the body
• CPC Class Codes: A61B 5/7203 for noise prevention, reduction or removal

Abstract

A method of applying ablation energy to achieve transmurality including applying ablation energy at a starting power to a tissue site and monitoring the impedance of the tissue site. The power applied to the tissue site can be increased in response to detection of a power plateau or application of a first power for a minimum time according to some embodiments. A power applied to the tissue site can be reduced in response to an increase in impedance according to some embodiments. Transmurality can be indicated in response to a transmurality plateau following a rise in impedance according to some embodiments.

Claims

1. A method of applying ablation energy to achieve transmurality at a tissue site, the method comprising:

applying ablation energy at a first power to the tissue site;

monitoring impedance of the tissue site; and

reducing the ablation energy applied to the tissue site to a second power in response to a rise in impedance.

2. The method of claim 1 further comprising applying ablation energy at a first power for a start-up blanking period.

3. The method of claim 2 wherein the start-up blanking period is a programmable setting.

4. The method of claim 1, further comprising increasing the ablation energy applied to the tissue site to a third power in response to a power plateau.

5. The method of claim 4, further comprising increasing the ablation energy applied to the tissue site to a third power only if a minimum time at the second power has been met.

6. The method of claim 1, further comprising reducing the ablation energy applied to the tissue site to a second power in response to a rise in impedance only if a rise blanking period has been met.

7. The method of claim 1, further comprising monitoring total ablation energy and terminating delivery of ablation energy if the total ablation energy exceeds a preset minimum following a rise in impedance.

8. The method of claim 1, further comprising determining a rate of increase in impedance and assigning the rate of increase in impedance to one of at least three levels.

9. The method of claim 8, wherein the second power is selected based on the assigned level.

10. The method of claim 1, further comprising indicating transmurality in response to a transmurality plateau following a rise in impedance.

11. The method of claim 10, further comprising terminating delivery of ablation energy to the tissue site in response to a transmurality plateau following a rise in impedance.

12. The method of claim 10, wherein transmurality is indicated only after ablation energy has been delivered to the tissue site for a minimum period, t_min, following a transmurality plateau.

13. The method of claim 1, further comprising indicating transmurality in response to the monitored impedance of the tissue site exceeding an impedance limit, Z_limit.

14. The method of claim 1, further comprising indicating transmurality in response to detecting a rise in the monitored impedance of the tissue site occurring after a minimum total energy, E_min, has been delivered.

15. The method of claim 1, further comprising indicating transmurality in response to detecting a rise in a temperature of the tissue site occurring after a minimum total energy, E_min, has been delivered.

16. A method of applying ablation energy to achieve transmurality at a tissue site, the method comprising:

applying ablation energy at a first power to the tissue site;

monitoring impedance of the tissue site;

increasing the ablation energy applied to the tissue site to a second power in response to a rise in impedance; and

increasing the ablation energy applied to the tissue site to a third power in response to a power plateau only if ablation energy has been applied to the tissue site at the second power for a minimum time.

17. A method of applying ablation energy to achieve transmurality at a tissue site, the method comprising:

applying ablation energy at a starting power level to the tissue site;

monitoring an impedance of the tissue site;

increasing the ablation energy applied to the tissue site to a second power level in response to at least one of detection of a power plateau and application of the ablation energy at the starting power level for a minimum time;

reducing the ablation energy applied to the tissue site to a third power level in response to an increase in the impedance of the tissue site; and

indicating transmurality in response to a transmurality plateau following a rise in impedance.

18. The method of claim 17, wherein the ablation energy applied to the tissue site is increased to the second power level only after ablation energy has been applied at the starting power level for the minimum time.

19. The method of claim 18, wherein the minimum time applies only if the starting power level has been previously decreased.

20. The method of claim 17, further comprising reducing the ablation energy applied to the tissue site to the third power level in response to the increase in impedance only if a rise blanking period has been met.

21. The method of claim 17, further comprising monitoring total ablation energy delivered, and indicating transmurality if the total ablation energy delivered exceeds a preset minimum following the rise in impedance.

22. The method of claim 17, wherein the reduction in power in response to the increase in impedance is a function of a rate of increase in impedance.

23. The method of claim 17, further comprising determining a rate of increase in impedance and assigning the rate of increase in impedance to one of at least three levels.

24. The method of claim 23, wherein the reduction in power is selected based on the assigned level.

25. A system for assessing transmurality of an ablation procedure being performed at a tissue site, the system comprising:

a sensor that determines impedance of the tissue site;

a controller adapted to communicate with the sensor to monitor the impedance of the tissue site;

the controller being adapted to increase ablation energy applied to the tissue site to a second power level in response to at least one of detection by the sensor of a power plateau and application of ablation energy at a first power level for a minimum time;

the controller being adapted to reduce ablation energy applied to the tissue site to a third power level in response to an increase in impedance of the tissue site;

the controller being further adapted to indicate transmurality in response to a transmurality plateau following a rise in impedance of the tissue site.

26. The system of claim 25, wherein the controller is a microprocessor.

27. The system of claim 25, wherein the system is implemented in an electrosurgical device.

28. The system of claim 25, wherein the controller indicates transmurality in response to a total ablation energy provided exceeding a preset minimum following a rise in impedance.