Tissue heating and ablation systems and methods using time-variable set point temperature curves for monitoring and control

• US 5,755,715 A
• Filed: 06/03/1996
• Issued: 05/26/1998
• Est. Priority Date: 11/08/1991
• Status: Expired due to Term

• Current Assignee: EP Technology (Boston Scientific Corporation)
• Original Assignee: EP Technology (Boston Scientific Corporation)
• Inventors: Panescu, Dorin, Swanson, David K., Stern, Roger A.
• Primary Examiner(s): PEFFLEY, MICHAEL F
• Application Number:
  US08/656,756
• Time in Patent Office: 722 Days
• Field of Search: 606/27-34, 606/37-42, 606/45-52, 607/100-102
• US Class Current: 606/31
• CPC Class Codes: A61B 18/00 Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body eye surgery A61F9/007; ear surgery A61F11/00
• 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 2017/00017 Electrical control of surgical instruments
• CPC Class Codes: A61B 2017/00084 Temperature
• CPC Class Codes: A61B 2017/00101 using an array of thermosensors
• CPC Class Codes: A61B 2017/00292 mounted on or guided by flexible, e.g. catheter-like, means
• CPC Class Codes: A61B 2017/003 Steerable
• CPC Class Codes: A61B 2017/00482 with a code
• CPC Class Codes: A61B 2018/00083 low, i.e. electrically insulating
• CPC Class Codes: A61B 2018/00095 high, i.e. heat conducting
• CPC Class Codes: A61B 2018/00101 low, i.e. thermally insulating
• CPC Class Codes: A61B 2018/00178 Electrical connectors
• CPC Class Codes: A61B 2018/00351 Heart
• 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 2018/00684 using lookup tables
• CPC Class Codes: A61B 2018/0069 : using fuzzy logic
• CPC Class Codes: A61B 2018/00702 : Power or energy
• CPC Class Codes: A61B 2018/00779 : Power or energy
• CPC Class Codes: A61B 2018/00791 : Temperature
• CPC Class Codes: A61B 2018/00797 : measured by multiple temperature sensors
• CPC Class Codes: A61B 2018/00803 : with temperature prediction
• CPC Class Codes: A61B 2018/00815 : measured by a thermistor
• CPC Class Codes: A61B 2018/00827 : Current
• CPC Class Codes: A61B 2018/00869 : Phase
• CPC Class Codes: A61B 2018/00875 : Resistance or impedance
• CPC Class Codes: A61B 2018/00892 : Voltage
• CPC Class Codes: A61B 2018/00916 : with means for switching or controlling the main function of the instrument or device
• 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 2018/124 : switching the output to different electrodes, e.g. sequentially
• CPC Class Codes: A61B 2018/1253 : monopolar
• CPC Class Codes: A61B 2018/126 : bipolar
• CPC Class Codes: A61B 2018/1425 : Needle
• CPC Class Codes: A61B 2018/1435 : Spiral
• CPC Class Codes: A61B 2090/0803 : Counting the number of times an instrument is used
• CPC Class Codes: A61B 2562/08 : Sensors provided with means for identification, e.g. barcodes or memory chips
• CPC Class Codes: A61M 2205/273 : preventing reuse, e.g. of disposables
• CPC Class Codes: A61M 2205/6018 : providing set-up signals for the apparatus configuration
• CPC Class Codes: A61M 2205/6027 : Electric-conductive bridges closing detection circuits, with or without identifying elements, e.g. resistances, zener-diodes
• CPC Class Codes: A61M 2205/70 : with testing or calibration facilities
• CPC Class Codes: A61M 2230/50 : Temperature

Abstract

Systems and methods employ an energy emitting electrode to heat tissue. The systems and methods follow a prescribed temperature set curve, in which a setpoint temperature changes over time, to control the application of energy to the electrode.

Claims

1. An apparatus for ablating heart tissue with energy from an energy source, the apparatus comprising

an electrode for emitting energy from the energy source to ablate body tissue;

a sensing element for measuring temperature at the electrode; and

a controller coupled to the electrode and the sensing element, the controller including

memory means for storing a temperature set curve including a first region of temperature values established over a first time period of at least one second that are below tissue ablating temperatures and a second region of temperature values at tissue ablation temperatures established over a second time period of at least one second and after the first time period,

data acquisition means, coupled to the sensing element, for deriving temperature information at the energy emitting electrode during the first and second time periods based upon temperature measured by the sensing element, and

processing means, coupled to the memory element and the data acquisition means, for generating (i) a first output signal based upon comparing temperature information derived during the first time period to the first region of temperature values stored in the memory means and (ii) a second output signal based upon comparing temperature information derived during the second time period to the second region of temperature values stored in the memory means, and

output means, coupled to the processing means and to the energy source, for varying energy supplied by the energy source to the electrode in response to the first and second output signals to establish and maintain temperature at the electrode over time approximately along the temperature set curve.

2. An apparatus as claimed in claim 1, wherein the first time period is between approximately one second and approximately seven seconds.

3. An apparatus as claimed in claim 1, wherein the second time period is at least two seconds.

4. An apparatus as claimed in claim 1, wherein the controller further comprises second processing means for determining a temperature beneath the surface of the tissue.

5. An apparatus as claimed in claim 1, wherein the controller further comprises second processing means for determining whether an overtemperature condition persists for more than a predetermined period and power shutdown means for instituting a power shutdown in response to a determination that an overtemperature condition has existed for more than the predetermined period.

6. An apparatus as claimed in claim 1, wherein the first region includes temperature values in the range of 45°

C. to 50°

C.

7. An apparatus as claimed in claim 1, wherein the second region includes temperature values in the range of 50°

C. to 90°

C.

8. An apparatus for ablating heart tissue with energy from an energy source, the apparatus comprising

an electrode for emitting energy from the energy source to ablate body tissue,

a sensing element for measuring temperature at the electrode,

a controller coupled to the electrode and the sensing element and operable to provide both a diagnostic function and a therapeutic function comprising

a memory element to store a temperature set curve including a first region of temperature values established over a first time period of at least one second that are below tissue ablating temperatures to allow diagnostic thermal mapping of heart tissue during the first time period and a second region of temperature values at tissue ablation temperatures established over a second time period of at least one second and after the first time period to allow therapeutic tissue ablation during the second time period,

a data acquisition element coupled to the sensing element to derive temperature information at the energy emitting electrode during the first and second time periods based upon temperature measured by the sensing element, and

a processing element coupled to the memory element and the data acquisition element receiving derived temperature information from the data acquisition element to generate (i) a first output signal based upon comparing temperature information derived during the first time period to the first region of temperature values stored in the memory element and (ii) a second output signal based upon comparing temperature information derived during the second time period to the second region of temperature values stored in the memory element, and

an output element coupled to the processing element and to the energy source to vary energy supplied by the energy source to the electrode in response to the first and second output signals to establish and maintain temperature at the electrode over time approximately along the temperature set curve.

9. An apparatus according to claim 8

wherein the first region includes temperature values in the range of 45°

C. to 50°

C.

10. An apparatus according to claim 8

wherein the second region includes temperature values in the range of 50°

C. to 90°

C.

11. An apparatus as claimed in claim 8, wherein the first time period is between approximately one second and approximately seven seconds.

12. An apparatus as claimed in claim 8, wherein the second time period is at least two seconds.

13. An apparatus as claimed in claim 8, wherein the controller further comprises a second processing element for determining a temperature beneath the surface of the tissue.

14. An apparatus as claimed in claim 8, wherein the controller further comprises a second processing element for determining whether an overtemperature condition persists for more than a predetermined period and a power shutdown element for instituting a power shutdown in response to a determination that an overtemperature condition has existed for more than the predetermined period.

15. A method for ablating heart tissue comprising the steps of

establishing a temperature set curve for ablating tissue including a first region of temperature values established over a first time period of at least one second that are below tissue ablating temperatures to allow thermal mapping and a second region of temperature values at tissue ablation temperatures established over a second time period of at lest one second and after the first time period,

supply ablating energy to an electrode,

deriving diagnostic temperature information by sensing temperature at the electrode during the first time period,

deriving therapeutic temperature information by sensing temperature at the electrode during the second time period, and

controlling the supply of ablating energy to the electrode based, at least in part, upon comparing the diagnostic and therapeutic temperature information derived during the first and second time periods to the respective first and second regions of temperature values to establish and maintain temperature at the electrode over time approximately along the temperature set curve.

16. A method according to claim 15

wherein the first region includes temperature values in the range of 45°

C. to 50°

C.

17. A method according to claim 15

wherein the second region includes temperature values in the range of 50°

C. to 90°

C.

18. A method as claimed in claim 15, wherein the first time period is between approximately one second and approximately seven seconds.

19. A method as claimed in claim 15, wherein the second time period is at least two seconds.

20. A method as claimed in claim 15, wherein the step of deriving therapeutic temperature information comprises determining a temperature beneath the surface of the tissue.

21. A method as claimed in claim 15, wherein the step of controlling the supply of ablation energy comprises determining whether an overtemperature condition persists for more than a predetermined period and instituting a power shutdown in response to a determination that an overtemperature condition has existed for more than the predetermined period.