Apparatus and method for cryogenic inhibition of hyperplasia
Post-angioplasty hyperplasia in blood vessels is treated using a cryosurgical balloon catheter. The balloon catheter is positioned at a target region within the blood vessel, and the balloon inflated by expanding a cryogenic fluid, such as liquid nitrogen, across an expansion orifice into a balloon. The balloon will be constructed so that cooling is achieved primarily in the central regions of the balloon, with the proximal and distal regions being less cold and acting to insulate adjacent regions of the blood vessel from excessive cooling.
1. A method for treating a blood vessel having a vessel wall, the method comprising:
introducing a catheter into the blood vessel;
expanding a balloon of the catheter near a target site within the vessel wall, the balloon having a balloon wall;
cooling the vessel wall with the balloon by coating at least a portion of an inner surface of the balloon wall with a liquid so that the liquid coating vaporizes, the coating engaging the balloon wall within the balloon.
2. The method of claim 1 , further comprising;
expanding the liquid at a first location within the balloon; and
expanding the liquid at a second location within the balloon to cryogenically evenly cool the engaged vessel wall, the second location being circumferentially separated from the first location.
3. The method of claim 2 , further comprising moving a diffuser head between the first location and the second location.
4. The method of claim 3 , wherein a housing separates the balloon and the vessel wall when the orifice head is at the first location, wherein fluid expansion is initiated at the first location, and wherein the moving step moves ports of the diffuser head from within the housing after a reduction in thermal of the gas expansion.
5. The method of claim 2 , wherein fluid expansion occurs simultaneously at the first and second locations, the balloon being axially elongate, the first and second locations being separated axially.
6. The method of claim 2 , wherein the fluid expansion occurs simultaneously at the first and second locations so that the fluid flows radially toward the vessel wall.
7. The method of claim 2 , wherein the first and second expansion steps comprise vaporization of at least a portion of the fluid from a liquid to a gas so that the enthalpy of vaporization cools the at least a portion of the engaged vessel wall.
8. A method for treating a blood vessel having a vessel wall, the method comprising:
introducing a catheter into the blood vessel;
expanding a balloon of the catheter near a target site within the vessel wall, the balloon having a balloon wall;
cooling the vessel wall with the balloon by coating at least a portion of an inner surface of the balloon wall with a liquid, the liquid vaporizing within the balloon.
9. The method of claim 8 , wherein the at least a portion of the inner surface of the balloon wall is coated by introducing a cryogenic cooling fluid through a port into balloon so that at least a portion of the cryogenic cooling fluid exits the port as the liquid.
10. The method of claim 9 , wherein the liquid coats the at least a portion of the inner surface of the balloon wall so as to enhance even cooling over at least a portion of the vessel wall engaged by the balloon.
11. The method of claim 10 , wherein the liquid coating the balloon wall vaporizes while the coating engaged the balloon wall within the balloon.