Hot tip catheter assembly

Abstract

A hot tip catheter assembly is disclosed which resolves atherosclerotic plaque buildup in vivo. The catheter has a heater, a cap, a thermocouple, power leads, thermocouple leads, and a central distal lumen to position the catheter within the artery. The catheter tip has a thin, non-adhesive coating of a hard, heat-conducting material. The thermocouple is used to continuously evaluate the temperature at the tip of the catheter, and the temperature is then regulated by a computer-controlled feedback system. The catheter can completely melt the buildup without damage to the artery by direct contact with the plaque, without use of balloon catheter angioplasty.

We claim: 
     
       1. A method of applying heat to the interior of a vessel in vivo, said method comprising the steps of: inserting an electrically heatable, voltage responsive, hot tip catheter assembly having a catheter tip into the vessel;   positioning said catheter tip in the vicinity of the vessel interior to be heated;   heating said catheter tip;   monitoring the temperature of said catheter tip;   comparing said temperature with a set point temperature representative of a predetermined temperature set point for said catheter tip;   determining the deviation between tip temperature and set point temperature;   determining the rate of change of said deviation; and applying a voltage to said catheter tip in accordance   with both said deviation and said rate of change of said deviation in order to control the temperature of said catheter tip at said set point temperature.   
     
     
       2. The method as set forth in claim 1, further including the step of applying said voltage to at least one avalanche diode as part of said catheter assembly for heating thereof. 
     
     
       3. The method as set forth in claim 2, further including the step of applying said voltage to three avalanche diodes connected in series. 
     
     
       4. The method as set forth in claim 1, further including the step of providing a thermocouple for monitoring said tip temperature. 
     
     
       5. The method as set forth in claim 1, further including the step of providing a microcomputer as means for performing said monitoring, comparing and determining steps. 
     
     
       6. An apparatus for applying heat to the interior of a vessel in vivo, said apparatus comprising: an electrically heatable, voltage responsive, hot tip catheter assembly having a catheter tip configured for insertion into the vessel and for positioning of said catheter tip in the vicinity of the vessel interior to be heated said assembly including means for heating said catheter tip; and   heat control means operably coupled with said catheter assembly for controlably heating said catheter tip, said control means including means for monitoring the temperature of said catheter tip;   means for comparing said temperature with a set point temperature representative of a predetermined temperature set point for said catheter tip;   means for determining the deviation between tip temperature and set point temperature and for determining the rate of change of said deviation; and   means for applying a voltage to said catheter tip in accordance with both said deviation and said rate of change of said deviation in order to control the temperature of said catheter tip at said set point temperature.   
     
     
       7. The apparatus as set forth in claim 6, said catheter tip including at least one avalanche diode responsive to the application of said voltage for producing heat. 
     
     
       8. The apparatus as set forth in claim 7, said catheter tip including three of said avalanche diodes connected in series. 
     
     
       9. The apparatus as set forth in claim 6, said temperature monitoring means including a thermocouple. 
     
     
       10. The apparatus as set forth in claim 6, said control means including a microcomputer. .Iadd.11. A method for applying energy to heat tissue comprising the steps of locating a catheter with an energy applying element next to tissue,   applying energy to the element while monitoring the temperature of the element,   comparing the monitored temperature of the element with a selected temperature,   determining the deviation between the monitored temperature of the element and the selected temperature,   determining the change of the deviation over time, and   applying energy to the element in response to both the deviation and the change of the deviation over time. .Iaddend..Iadd.12. A method according to claim 11   and further including the step of providing a thermocouple for monitoring the temperature of the element. .Iaddend..Iadd.13. A method according to claim 11   using a computer to perform the steps of determining the deviation and the change of the deviation over time. .Iaddend..Iadd.14. A system for applying energy to heat tissue comprising   a catheter with an energy applying element,   a source of energy for the element,   a temperature sensor associated with the element,   processing means operatively connected to the temperature sensor for deriving (i) the deviation between the temperature sensed by the temperature and a selected temperature and (ii) the change of the deviation over time, and   control means operatively connecting the energy source and the catheter element for applying energy from the source to the catheter element in response to both the deviation and the change of the deviation over time derived by the processing means. .Iaddend..Iadd.15. A system according to claim 14   wherein the temperature sensor comprises a thermocouple carried by the catheter. .Iaddend..Iadd.16. A system according to claim 15   wherein the energy applying element comprises a heat-transferring member. .Iaddend..Iadd.17. A system according to claim 16   wherein the heat-transferring member comprising at least one avalanche diode responsive to the application of voltage for producing heat. .Iaddend..Iadd.18. A system according to claim 17   wherein the temperature sensor comprises a thermocouple. .Iaddend..Iadd.19. A system according to claim 14   wherein the processing means includes a computer. .Iaddend..Iadd.20. A system according to claim 14   wherein the catheter includes a distal tip, and   wherein the energy applying element is carried adjacent the distal tip. .Iaddend..Iadd.21. A system according to claim 20   wherein the energy applying element comprises a heat-transferring memeber. .Iaddend..Iadd.22. A system according to claim 21   wherein the heat-transferring member comprises at least one avalanche diode responsive to the application of voltage for producing heat. .Iaddend..Iadd.23. A system according to claim 21   wherein the temperature sensor includes a thermocouple. .Iaddend..Iadd.24. An apparatus for use in association with a catheter having an energy applying element and a temperature sensor associated with the element, the apparatus being operable for applying energy to the energy applying element, comprising   a source of energy for the catheter element,   first means operative, when connected with the temperature sensor, for registering temperature sensed by the temperature sensor,   second means for storing a comparison temperature,   processing means for comparing the temperature registered by the first means with the comparison temperature for deriving both (i) a deviation between the temperature registered by the first means and the comparison temperature and (ii) the change in the deviation over time, and   control means connected to the energy source and the processing means and operative, when connected with the energy applying element, for applying energy from the energy source to the energy applying element in response to both the deviation and the change of the deviation over time derived by the processing means. .Iaddend..Iadd.25. An apparatus according to claim 24   wherein the processing means includes a computer. .Iaddend.