System and method for varying return pressure to control tip temperature of a cryoablation catheter

• US 20060004350A1
• Filed: 06/30/2004
• Published: 01/05/2006
• Est. Priority Date: 06/30/2004
• Status: Active Grant

• Current Assignee: CryoCor Incorporated (Boston Scientific Corporation)
• Original Assignee: CryoCor Incorporated (Boston Scientific Corporation)
• Inventors: Ryba, Eric
• Granted Patent: US 7,357,797 B2
• Time in Patent Office: Days
• US Class Current: 606/21
• CPC Class Codes: A61B 18/02 by cooling, e.g. cryogenic techniques devices for cooling specific reflex points of the body within cell-life limits A61H39/06
• CPC Class Codes: A61B 2018/0212 using an instrument inserted into a body lumen, e.g. catheter
• CPC Class Codes: A61B 2018/0262 using a circulating cryogenic fluid

Abstract

A cryoablation device having a temperature control system includes an elongated catheter tube that has a central lumen and is formed with a closed distal tip. The distal end of a refrigerant supply line is positioned in the central lumen and distanced from the catheter tube'"'"'s distal tip to establish an expansion chamber therebetween. A return line, which can be established between the supply line and the catheter tube, is provided to exhaust expanded refrigerant from the chamber. The temperature control system includes a valve that is positioned at a predetermined location along the return line. The valve is adjustable to vary a pressure within the return line to control the operational temperature at the distal tip of the catheter tube. Specifically, the valve can be used to reduce the pressure in the return line to thereby increase the tip temperature, and vice versa.

Claims

1. A cryoablation device having a temperature control system, said device comprising:

a refrigerant supply unit;

an elongated catheter tube having a central lumen and formed with a closed distal tip;

a supply line having a proximal end connected to said refrigerant supply unit and a distal end disposed in the central lumen of said catheter tube and distanced from the distal tip thereof to establish an expansion chamber therebetween, said supply line for delivering a refrigerant from said refrigerant supply unit to the expansion chamber for expansion therein;

a return line in fluid communication with the expansion chamber for exhausting refrigerant from the expansion chamber; and

a valve positioned along the return line, said valve being adjustable to vary a pressure in the return line to control a temperature at the distal tip of the catheter tube.

2. A device as recited in claim 1 further comprising a means for measuring a temperature at the distal tip of the catheter tube.

3. A device as recited in claim 2 wherein said measuring means comprises a sensor positioned in the expansion chamber.

4. A device as recited in claim 2 further comprising a control unit for adjusting said valve in response to a measured temperature at the distal tip to obtain a pre-selected temperature at the distal tip.

5. A device as recited in claim 4 wherein said control unit further comprises:

a means for comparing the measured temperature with a reference temperature to create an error signal; and

a means for adjusting said valve to make the error signal a nullity.

6. A device as recited in claim 5 wherein the reference temperature is equal to the pre-selected temperature.

7. A device as recited in claim 1 wherein said catheter tube has an inner surface, said supply line has an outer surface and the return line is established between the inner surface of said catheter tube and the outer surface of said supply line.

8. A device as recited in claim 1 wherein said supply line comprises a supply tube and a capillary tube, said supply tube is formed with a lumen having a lumen diameter, D, and said capillary tube is formed with a lumen having a lumen diameter, d, with D>

d.

9. A device as recited in claim 1 wherein said supply line and said catheter tube are arranged co-axially.

10. A system for controlling a temperature at a distal tip of a cryoablation catheter, said catheter having a supply line for delivering a refrigerant to an expansion chamber at the distal tip for expansion therein and a return line for exhausting expanded refrigerant therefrom, said system comprising:

an adjustable valve for varying a pressure at a pre-selected location in the return line;

a means for measuring a temperature at the distal tip of said cryoablation catheter; and

a control unit for comparing the measured temperature with a pre-selected temperature to create an error signal and for adjusting said valve to make the error signal a nullity to obtain the pre-selected temperature at the distal tip of said cryoablation catheter.

11. A system as recited in claim 10 wherein said measuring means comprises a sensor positioned in the expansion chamber.

12. A system as recited in claim 10 wherein the pre-selected location is positioned wherein said valve remains at an extracorporeal location during a cryoablation procedure.

13. A method for cryoablating tissue at a treatment site in the vasculature of a patient, said method comprising the steps of:

providing an elongated catheter tube having a central lumen and formed with a closed distal tip;

placing the distal end of a supply line in the central lumen of said catheter tube at a distance from the distal tip thereof to establish an expansion chamber therebetween and a return line;

positioning a valve along the return line;

advancing the distal tip of said catheter tube through the patient'"'"'s vasculature to the treatment site;

introducing a refrigerant into said supply line for outflow from the distal end thereof and expansion in the expansion chamber; and

adjusting said valve to vary a pressure in the return line to control a temperature at the distal tip of said catheter tube.

14. A method as recited in claim 13 further comprising the step of measuring a temperature at the distal tip of said catheter tube.

15. A method as recited in claim 14 wherein said measuring step is accomplished using a sensor positioned in the expansion chamber.

16. A method as recited in claim 14 further comprising the steps of:

comparing the measured temperature with a reference temperature to create an error signal; and

adjusting said valve to make the error signal a nullity.

17. A method as recited in claim 13 wherein said catheter tube has an inner surface, said supply line has an outer surface and the return line is established between the inner surface of said catheter tube and the outer surface of said supply line.

18. A method as recited in claim 13 wherein said supply line comprises a supply tube and a capillary tube, said supply tube is formed with a lumen having a lumen diameter, D, and said capillary tube is formed with a lumen having a lumen diameter, d, with D>

d.

19. A method as recited in claim 13 wherein said supply line and said catheter tube are arranged co-axially.

20. A method as recited in claim 13 wherein said valve adjusting step varies a pressure in the return line to control a temperature at the distal tip of said catheter tube in accordance with a predetermined schedule.