Cryogenic ablation system and method
A device for treating esophageal target tissue comprises a catheter, a balloon and a refrigerant delivery device. The catheter has a distal portion and a refrigerant delivery lumen. The balloon is mounted to and the refrigerant delivery device is coupled to the distal portion. The refrigerant delivery device comprises a chamber with the refrigerant delivery lumen opening into the chamber, a refrigerant delivery opening fluidly coupled to the balloon interior, and a distribution passageway fluidly coupling the chamber and the refrigerant delivery opening. A refrigerant is deliverable through the refrigerant delivery lumen, into the chamber, through the distribution passageway, through the refrigerant delivery opening and into the balloon interior so to place the balloon into an expanded, cooled state so that the balloon can press against and cool esophageal target tissue. The medical device may include means for sensing a leak in the balloon.
1. A method for cryogenically treating esophageal target tissue at a target site, the method comprising:
positioning a cryogenically-coolable balloon at the target site for cryogenic treatment of the esophageal target tissue within a target tissue treatment temperature range, the cryogenically-coolable balloon having an inner surface, the cryogenically-coolable balloon being made of balloon material having a glass transition temperature above the target tissue treatment temperature range, the cryogenically-coolable balloon having elastic properties above the glass transition temperature range and being stretch-resistant below the glass transition temperature range;
inflating the cryogenically-coolable balloon to a desired size; followed by:
cooling the inner surface of the cryogenically-coolable balloon to a temperature within the target tissue treatment temperature range but below the glass transition temperature of the cryogenically-coolable balloon material thereby preventing further expansion of the cryogenically-coolable balloon while cryogenically treating target tissue at the target site.
2. The method according to claim 1 , wherein:
the cryogenically-coolable balloon has the following material properties:
stretchy at body temperatures of about 37° C.; and
stretch-resistant at a chosen target tissue treatment temperature, the chosen target tissue treatment temperature being within a target tissue treatment temperature range of −15° C. to −90° C.
3. The method according to claim 1 , wherein:
the cryogenically-coolable balloon has the following material properties:
stretchy at body temperatures of about 37° C.; and
stretch-resistant at a chosen target tissue treatment temperature, the chosen target tissue treatment temperature being within a target tissue treatment temperature range of −30° C. to −60° C.
4. The method according to claim 1 , including cooling the inner surface of the cryogenically-coolable balloon by delivering a refrigerant into the cryogenically-coolable balloon, wherein the refrigerant is a liquid refrigerant.
5. The method according to claim 1 , including cooling the inner surface of the cryogenically-coolable balloon by delivering a refrigerant into the cryogenically-coolable balloon interior utilizing a refrigerant delivery device, the refrigerant delivery device comprising:
a flow deflector tube inside the cryogenically-coolable balloon;
a circumferentially-extending refrigerant delivery opening formed in the flow deflector tube and fluidly coupled to the cryogenically-coolable balloon interior; and
an axially-positionable flow deflector sleeve at least partially surrounding the flow deflector tube; and positioning the flow deflector sleeve to cover part or none of the circumferentially-extending refrigerant delivery opening thereby changing how much of the circumferentially-extending refrigerant delivery opening is exposed to adjust a circumferential extent of the spray of a refrigerant through the circumferentially-extending refrigerant delivery opening.
6. The method according to claim 5 , wherein:
the refrigerant delivery opening extends along a path having changing rotary and axial positions.
7. The method according to claim 6 , including using a catheter having a catheter axis to position the cryogenically-coolable balloon at the target site, and wherein:
the refrigerant delivery opening is a full circumference opening extending at an angle to the catheter axis.
8. The method according to claim 7 , wherein the flow director sleeve is cylindrical.
9. The method according to claim 5 , wherein:
the refrigerant delivery opening extends along a path having a constant axial position.
10. The method according to claim 9 , including using a catheter having a catheter axis to position the cryogenically-coolable balloon at the target site, and wherein the flow director sleeve has first and second edges, the first edge arranged at an angle to the catheter axis.
11. The method according to claim 10 , wherein the first edge is arranged at an angle of 45° to the catheter axis.