Apparatus and method for thermal ablation
First Claim
1. Apparatus for ablating tissue at an ablation site in the heart of a human being, said apparatus comprising in combination:
- (a) a source of RF energy for irradiating the tissue at the ablation site to cause a temperature rise of the tissue at the ablation site;
(b) a first electrode for contacting an area of tissue of the human being and for irradiating the tissue with RF energy to heat the tissue at the ablation site, said first electrode comprising a material having a first work function;
(c) transmission means for conveying RF energy from said source to said first electrode;
(d) a second electrode displaced from said first electrode and of a material having a second work function different from the first work function for electrically contacting another area of tissue of the human being;
(e) a galvanic cell formed by said first electrode, said second electrode and the tissue of the human being serving as an electrically interconnecting electrolyte for generating an electrical current corresponding with the temperature rise of the tissue at the ablation site; and
(f) a control circuit responsive to said electrical current generated by said galvanic cell for regulating the operation of said source of RF energy to control RF irradiation of the ablation site and thereby control the temperature of the tissue at the ablation site.
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Accused Products
Abstract
A catheter for use in an electrophysiological procedure to ablate a site includes a metallic tip having a first work function and energized by a source of RF energy. The RF energy return path is through a relatively large plate of a metallic material having a second work function and disposed at a location removed from the ablation site. The difference in work functions of the tip and the plate, operating in the presence of an electrolyte represented by the intermediate tissue, produces an exchange of electrical charges through chemical reaction to create a galvanic cell. By loading the galvanic cell with a shunt resistor, it becomes a current source providing a current linear with and highly dependent on the tissue temperature at the ablation site. This accurate representation of the tissue temperature at the ablation site is used to regulate the RF energy applied to maintain the tissue at the ablation site at a predetermined temperature during the ablation procedure.
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Citations
23 Claims
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1. Apparatus for ablating tissue at an ablation site in the heart of a human being, said apparatus comprising in combination:
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(a) a source of RF energy for irradiating the tissue at the ablation site to cause a temperature rise of the tissue at the ablation site; (b) a first electrode for contacting an area of tissue of the human being and for irradiating the tissue with RF energy to heat the tissue at the ablation site, said first electrode comprising a material having a first work function; (c) transmission means for conveying RF energy from said source to said first electrode; (d) a second electrode displaced from said first electrode and of a material having a second work function different from the first work function for electrically contacting another area of tissue of the human being; (e) a galvanic cell formed by said first electrode, said second electrode and the tissue of the human being serving as an electrically interconnecting electrolyte for generating an electrical current corresponding with the temperature rise of the tissue at the ablation site; and (f) a control circuit responsive to said electrical current generated by said galvanic cell for regulating the operation of said source of RF energy to control RF irradiation of the ablation site and thereby control the temperature of the tissue at the ablation site. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. Apparatus for ablating tissue at an ablation site, said apparatus comprising in combination:
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(a) a first electrode locatable in electrical contact with the tissue; (b) a second electrode locatable in electrical contact with tissue for creating a galvanic cell in combination with said first electrode and the tissue acting as an electrolyte to provide a current output signal corresponding with the temperature of the tissue; (c) an RF generator for applying RF energy to the tissue through said first and second electrodes to heat the tissue; and (d) a control circuit for regulating the RF energy generated by said RF generator as a function of the current output signal to regulate the temperature of the tissue. - View Dependent Claims (11, 12, 13, 14, 15)
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16. Apparatus for ablating tissue, said apparatus comprising in combination:
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(a) an RF generator for applying RF energy to the tissue to heat the tissue; (b) a first electrode adapted to be in contact with the tissue for irradiating the tissue with RF energy; (c) a transmission line for conveying RF energy from said RF generator to said first electrode; (d) a second electrode adapted to be in contact with the tissue at a location remote from said first electrode; (e) a temperature sensor for sensing the temperature of the tissue and for producing a signal reflective of the temperature sensed, said temperature sensor comprising said first electrode, said second electrode and an electrolyte in electrical contact with said first and second electrodes; and (f) a control circuit responsive to the signal produced by said temperature sensor for regulating the applied RF energy to establish the temperature at the tissue within a predetermined range. - View Dependent Claims (17, 18)
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19. A method for ablating tissue in the heart of a human being, said method comprising the steps of:
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(a) generating RF energy from a source of RF energy; (b) irradiating the tissue with RF energy through a first electrode in contact with the tissue to heat the tissue, the first electrode comprising a material having a first work function; (c) conveying RF energy from the source to the first electrode; (d) electrically contacting an area of tissue of the human being with a second electrode displaced from the first electrode and of a material having a second work function different from the first work function; (e) generating an electrical current corresponding with the temperature rise of the tissue by a galvanic cell formed by the first electrode, the second electrode and the tissue of the human being serving as an electrically interconnecting electrolyte; and (f) regulating the operation of the source of RF energy with a control circuit responsive to the electrical current generated by said generating step to control RF irradiation of the tissue and thereby control the temperature of the tissue.
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20. A method for ablating tissue at an ablation site, said method comprising the steps of:
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(a) generating RF energy with an RF generator; (b) conveying RF energy from the RF generator to a first electrode through a transmission line; (c) irradiating the tissue with RF energy through the first electrode proximate the ablation site; (d) sensing the temperature at the tissue with a temperature sensor and producing a signal reflective of the temperature sensed, the temperature sensor comprising the first electrode, a second electrode displaced from the first electrode and an electrolyte in electrical contact with the first and second electrodes; and (e) regulating the output of the RF generator with a control circuit responsive to the signal produced by said sensing step to establish the temperature at the tissue within a predetermined range.
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21. Apparatus for mapping tissue to locate a site to be ablated and for ablating the site located, said apparatus comprising in combination:
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(a) a probe having a plurality of electrodes disposed therealong for placement adjacent the tissue to be mapped, each electrode of said plurality of electrodes having a first work function and including a further electrode having a second work function different from the first work function, said further electrode being locatable in electrical contact with tissue for creating a galvanic cell in combination with said plurality of electrodes and the tissue acting as an electrolyte to provide a current output signal corresponding with a site to be located and ablated; (b) a data acquisition circuit for performing mapping functions in response to signals generated by the tissue proximate each electrode of said plurality of electrodes to identify and locate a tissue site to be ablated; (c) an RF generator for generating RF energy to ablate the located ablation site; (d) a switching circuit for selectively interconnecting said data acquisition circuit and said RF generator to each electrode of said plurality of electrodes; (e) a plurality of conductors interconnecting said switching circuit with said plurality of electrodes; and (f) a control circuit for regulating the RF energy generated by said RF generator as a function of said current output signal to regulate the temperature of the site being ablated. - View Dependent Claims (22, 23)
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Specification