US5904709A
Expired / Lapsed
US
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Microwave treatment for cardiac arrhythmias
Assignee: US GOVERNMENT NATIONAL AERONAUTICS AND SPACE ADMINSTRATION, Administrator of
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Filing: 1996-04-17
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Granted: 1999-05-18
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Expires: 2016-04-17
Abstract
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.
Inventors
- 👤 G. Dickey Arndt
- 👤 James R. Carl
- 👤 George W. Raffoul
- 👤 Antonio Pacifico
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 18:20
CPC Classifications
A; A61; A61F; A61F2/00; A61B; A61B18/00; A61B18/04; A61B18/12; A61B18/14; A61B18/1492; A61B18/18; A61B18/1815; A61N; A61N1/00; A61N1/02; A61N1/04; A61N1/06; A61B18/1206; A61B2018/00315; A61B2018/00345; A61B2018/00351; A61B2018/00571; A61B2018/00577; A61B2018/00636; A61B2018/00696; A61B2018/00732; A61B2018/00773; A61B2018/00791; A61B2018/1861; A61B2018/1892
Claims Analysis
Total Claims: 22
Claim 1
Independent Claim
218 words
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.
Claim 2
Independent Claim
218 words
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.
Claim 3
Dependent Claim
26 words
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.
Claim 4
Dependent Claim
19 words
The method of claim 1 further comprising: determining said blood temperature rise along a surface of said microwave radiator.
Claim 5
Dependent Claim
15 words
The method of claim 1 further comprising: providing said catheter with a co-axial cable structure.
Claim 6
Dependent Claim
62 words
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.
Claim 7
Dependent Claim
19 words
The method of claim 1, further comprising: providing said catheter with a non-helical microwave radiator at one end thereof.
Claim 8
Dependent Claim
22 words
The method of claim 1, further comprising: providing said catheter with a monopole disk-loaded cylindrical wire microwave radiator at one end thereof.
Claim 9
Independent Claim
187 words
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.
Claim 10
Independent Claim
187 words
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.
Claim 11
Independent Claim
188 words
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.
Claim 12
Independent Claim
188 words
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.
Claim 13
Independent Claim
225 words
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.
Claim 14
Independent Claim
225 words
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.
Claim 15
Independent Claim
195 words
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.
Claim 16
Independent Claim
195 words
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.
Claim 17
Dependent Claim
40 words
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.
Claim 18
Dependent Claim
44 words
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.
Claim 19
Independent Claim
228 words
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.
Claim 20
Independent Claim
228 words
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.
Claim 21
Independent Claim
220 words
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.
Claim 22
Independent Claim
220 words
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.
References Cited (Backward Citations)
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