Microwave treatment for cardiac arrhythmias

• US 5,904,709 A
• Filed: 04/17/1996
• Issued: 05/18/1999
• Est. Priority Date: 04/17/1996
• Status: Expired due to Fees

• Current Assignee: Department of Health and Human Services (State of Victoria), The United States of America As Represented By The Secretary of Agriculture, US Government As Represented By The Director National Security Agency
• Original Assignee: United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration
• Inventors: Arndt, G. Dickey, Carl, James R., Raffoul, George W., Pacifico, Antonio
• Primary Examiner(s): Jastrzab, Jeffrey R.
• Assistant Examiner(s): CARTER, RYAN CHRISTOPHER
• Application Number:
  US08/641,045
• Time in Patent Office: 1,126 Days
• Field of Search: 607/154-156, 607/100-102, 607/115-116, 607/122-123, 606/33-35, 606/37-40, 606/41-42, 606/45-50, 604/22
• US Class Current: 607/101
• 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 18/18 by applying electromagnetic radiation, e.g. microwaves radiation therapy A61N5/00
• CPC Class Codes: A61B 18/1815 using microwaves
• CPC Class Codes: A61B 2018/00351 Heart
• CPC Class Codes: A61B 2018/00577 Ablation
• CPC Class Codes: A61B 2018/00732 Frequency
• CPC Class Codes: A61B 2018/00791 Temperature
• CPC Class Codes: A61B 2018/1861 with an instrument inserted into a body lumen or cavity, e.g. a catheter
• CPC Class Codes: A61B 2018/1892 Details of electrical isolations of the antenna
• CPC Class Codes: A61F 2/00 Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents as cosmetic articles, see the relevant subclasses, e.g. wigs, hair pieces, A41G3/00, A41G5/00; artificial nails A45D31/00; dental prostheses A61C13/00; materials for prostheses A61L27/00; artificial hearts A61M60/00; artificial kidneys A61M1/14
• CPC Class Codes: A61N 1/06 for high-frequency therapy

Abstract

Method and apparatus are provided for propagating microwave energy into heart tissues to produce a desired temperature profile therein at tissue depths sufficient for thermally ablating arrhythmogenic cardiac tissue to treat ventricular tachycardia and other arrhythmias while preventing excessive heating of surrounding tissues, organs, and blood. A wide bandwidth double-disk antenna (700) is effective for this purpose over a bandwidth of about six gigahertz. A computer simulation provides initial screening capabilities for an antenna such as antenna, frequency, power level, and power application duration. The simulation also allows optimization of techniques for specific patients or conditions. In operation, microwave energy between about 1 Gigahertz and 12 Gigahertz is applied to monopole microwave radiator (600) having a surface wave limiter (606). A test setup provides physical testing of microwave radiators (854) to determine the temperature profile created in actual heart tissue or ersatz heart tissue (841). Saline solution (872) pumped over the heart tissue (841) with a peristaltic pump (862) simulates blood flow. Optical temperature sensors (838) disposed at various tissue depths within the heart tissue (841) detect the temperature profile without creating any electromagnetic interference. The method may be used to produce a desired temperature profile in other body tissues reachable by catheter (510) such as tumors and the like.

Claims

1. A method for thermally ablating arrhythmogenic cardiac tissue to treat arrhythmias while controlling temperature rise of proximately located blood and heart tissues, comprising:

providing a catheter with a microwave radiator at one end thereof;

selecting a frequency of operation for said microwave radiator within a frequency range of from 1.0 Gigahertz to 12.0 Gigahertz;

selecting a microwave power level of operation such that heat rise in said proximally located blood and a surface of said heart tissues due to absorption of microwave energy at said frequency of operation is limited by a blood flow rate and a specific heat of said blood to within a selected temperature rise;

determining a heating time for said arrhythmogenic cardiac tissue such that a combination of absorption of microwave energy at said frequency of operation and thermal conductivity of said arrhythmogenic cardiac tissue results in a sufficient temperature rise for thermal ablation of said arrhythmogenic cardiac tissue, said selected temperature rise of said of said proximally located blood and said surface of said heart tissues being less than said sufficient temperature rise for thermal ablation of said arrhythmogenic cardiac tissue;

positioning said catheter such that said microwave radiator is adjacent said arrhythmogenic cardiac tissue and is within said blood flow; and

conducting a microwave signal through said catheter to said cardiac tissue.

2. The method of claim 1, further comprising:

maintaining said frequency of operation of said microwave power in the range of from 2.0 Gigahertz to 6.0 Gigahertz.

3. The method of claim 1 further comprising:

determining said blood temperature rise along a surface of said microwave radiator.

4. The method of claim 1 further comprising:

providing said catheter with a co-axial cable structure.

5. The method of claim 1, wherein:

said selecting of a microwave power level of operation is made such that heat rise in said proximally located blood due to absorption of microwave energy at said frequency of operation is limited by a blood flow rate and a specific heat of said blood to within a selected temperature rise less than about 2°

C.

6. The method of claim 1, further comprising:

providing said catheter with a non-helical microwave radiator at one end thereof.

7. The method of claim 1, further comprising:

providing said catheter with a monopole disk-loaded cylindrical wire microwave radiator at one end thereof.

8. A method for thermally ablating arrhythmogenic cardiac tissue to treat arrhythmias while controlling temperature rise of proximately located blood and heart tissues, comprising:

providing a catheter with a microwave radiator at one end thereof;

selecting a frequency of operation for said microwave radiator within a frequency range of from 1.0 Gigahertz to 12.0 Gigahertz;

selecting a microwave power level of operation such that heat rise in said proximally located blood due to absorption of microwave energy at said frequency of operation is limited by a blood flow rate and a specific heat of said blood to within a selected temperature rise;

determining a heating time for said arrhythmogenic cardiac tissue such that a combination of absorption of microwave energy at said frequency of operation and thermal conductivity of said arrhythmogenic cardiac tissue results in sufficient temperature rise for thermal ablation of said arrhythmogenic cardiac tissue;

positioning said catheter such that said microwave radiator is adjacent said arrhythmogenic cardiac tissue and is within said blood flow;

conducting a microwave signal through said catheter to said cardiac tissue; and

attenuating surface microwaves along said catheter by about 20 decibels.

9. A method for thermally ablating arrhythmogenic cardiac tissue to treat arrhythmias while controlling temperature rise of proximately located blood and heart tissues, comprising:

providing a catheter with a microwave radiator at one end thereof;

selecting a frequency of operation for said microwave radiator within a frequency range of from 1.0 Gigahertz to 12.0 Gigahertz;

selecting a microwave power level of operation such that heat rise in said proximally located blood due to absorption of microwave energy at said frequency of operation is limited by a blood flow rate and a specific heat of said blood to within a selected temperature rise;

determining a heating time for said arrhythmogenic cardiac tissue such that a combination of absorption of microwave energy at said frequency of operation and thermal conductivity of said arrhythmogenic cardiac tissue results in sufficient temperature rise for thermal ablation of said arrhythmogenic cardiac tissue;

positioning said catheter such that said microwave radiator is adjacent said arrhythmogenic cardiac tissue and is within said blood flow;

conducting a microwave signal through said catheter to said cardiac tissue; and

providing a catheter surface wave antennuator adjacent said microwave radiator end.

10. A method for thermally ablating arrhythmogenic cardiac tissue to treat arrhythmias while controlling temperature rise of proximately located blood and heart tissues, comprising:

providing a catheter with a microwave radiator at one end thereof;

selecting a frequency of operation for said microwave radiator within a frequency range of from 1.0 Gigahertz to 12.0 Gigahertz, selecting said frequency of operation for controlling a desired lesion volume from frequencies within said frequency range of from 1.0 Gigahertz to 12.0 Gigahertz, said desired lesion volume being variable with respect to said frequency of operation within said frequency range of from 1.0 Gigahertz to 12.0 Gigahertz;

selecting a microwave power level of operation such that heat rise in said proximally located blood due to absorption of microwave energy at said frequency of operation is limited by a blood flow rate and a specific heat of said blood to within a selected temperature rise;

determining a heating time for said arrhythmogenic cardiac tissue such that a combination of absorption of microwave energy at said frequency of operation and thermal conductivity of said arrhythmogenic cardiac tissue results in sufficient temperature rise for thermal ablation of said arrhythmogenic cardiac tissue;

positioning said catheter such that said microwave radiator is adjacent said arrhythmogenic cardiac tissue and is within said blood flow; and

conducting a microwave signal through said catheter to said cardiac tissue.

11. A method for thermally ablating arrhythmogenic cardiac tissue to treat arrhythmias while controlling temperature rise of proximately located blood and heart tissues, comprising:

providing a catheter with a microwave radiator at one end thereof;

selecting a frequency of operation for said microwave radiator within a frequency range of from 1.0 Gigahertz to 12.0 Gigahertz;

selecting a microwave power level of operation such that heat rise in said proximally located blood due to absorption of microwave energy at said frequency of operation is limited by a blood flow rate and a specific heat of said blood to within a selected temperature rise;

determining a heating time for said arrhythmogenic cardiac tissue such that a combination of absorption of microwave energy at said frequency of operation and thermal conductivity of said arrhythmogenic cardiac tissue results in sufficient temperature rise for thermal ablation of said arrhythmogenic cardiac tissue;

positioning said catheter such that said microwave radiator is adjacent said arrhythmogenic cardiac tissue and is within said blood flow;

conducting a microwave signal through said catheter to said cardiac tissue; and

maintaining a standing wave ratio on said catheter of less than three to one at an antenna input.

12. The method of claim 11 wherein said step of maintaining a standing wave further comprises:

maintaining said standing wave ratio of less than three to one from approximately 1.5 Gigahertz to more than 8.0 Gigahertz for effecting a broad bandwidth.

13. The method of claim 11 wherein said step of maintaining a standing wave further comprises maintaining a standing wave ratio of less than two to one from approximately 1.5 Gigahertz to more than 8.0 Gigahertz for effecting good impedance matching over a broad bandwidth.

14. A method for thermally ablating arrhythmogenic cardiac tissue to treat arrhythmias while controlling temperature rise of proximately located blood and heart tissues, comprising:

providing a catheter with a microwave radiator at one end thereof providing said catheter with a waveguide structure such that said microwave waveguide has an outer conductor defining a waveguide cavity, said waveguide cavity being filled with an inner insulative material of selected permittivity, said waveguide cavity having no inner conductor therein such that said microwave waveguide is not a coaxial cable;

selecting a frequency of operation for said microwave radiator within a frequency range of from 1.0 Gigahertz to 12.0 Gigahertz;

selecting a microwave power level of operation such that heat rise in said proximally located blood due to absorption of microwave energy at said frequency of operation is limited by a blood flow rate and a specific heat of said blood to within a selected temperature rise;

determining a heating time for said arrhythmogenic cardiac tissue such that a combination of absorption of microwave energy at said frequency of operation and thermal conductivity of said arrhythmogenic cardiac tissue results in sufficient temperature rise for thermal ablation of said arrhythmogenic cardiac tissue;

positioning said catheter such that said microwave radiator is adjacent said arrhythmogenic cardiac tissue and is within said blood flow; and

conducting a microwave signal through said catheter to said cardiac tissue.

15. A method for thermally ablating arrhythmogenic cardiac tissue to treat arrhythmias while controlling temperature rise of proximately located blood and heart tissues, comprising:

providing a catheter with at least three microwave radiators at one end thereof such that each of said at least three microwave radiators is formed from at least three physical discontinuities in a non-helical monopole antenna such that substantially all microwave radiation from said antenna is emitted from said at least three physical discontinuities;

selecting a frequency of operation for said microwave radiator within a frequency range of from 1.0 Gigahertz to 12.0 Gigahertz;

selecting a microwave power level of operation such that heat rise in said proximally located blood due to absorption of microwave energy at said frequency of operation is limited by a blood flow rate and a specific heat of said blood to within a selected temperature rise;

determining a heating time for said arrhythmogenic cardiac tissue such that a combination of absorption of microwave energy at said frequency of operation and thermal conductivity of said arrhythmogenic cardiac tissue results in sufficient temperature rise for thermal ablation of said arrhythmogenic cardiac tissue;

positioning said catheter such that said microwave radiator is adjacent said arrhythmogenic cardiac tissue and is within said blood flow; and

conducting a microwave signal through said catheter to said cardiac tissue.