Plaque stabilisation using cryoenergy

1. A method of supplying cryoenergy to a plaque within a blood vessel, comprising:

expanding an expandable membrane of a catheter apparatus with a pressure of less than 5 ATM (507 kPa), the catheter apparatus having been placed in thermal contact with the plaque within the blood vessel, and the expandable membrane being compliant with the blood vessel; and,

establishing a temperature of between +15° C. (288K) and −35° C. (238K) at an interface of the expandable membrane and the blood vessel.

2. A method according to claim 1 , wherein the catheter apparatus has a single expandable membrane.

3. A method according to claim 1 , wherein the expandable membrane has a substantially smooth exterior surface.

4. A method according to claim 1 , further comprising determining expandable membrane characteristics using a sensor provided with the catheter apparatus.

5. A method according to claim 1 , further comprising imaging the catheter apparatus, wherein the expandable membrane comprises a radio opaque substance.

6. A method according to claim 1 , wherein the expandable membrane is expanded with a pressure of less than 4 ATM (405 kPa).

7. A method according to claim 6 , wherein the expandable membrane is expanded with a pressure of less than 3 ATM (304 kPa).

8. A method according to claim 7 , wherein the expandable membrane is expanded with a pressure of less than 2 ATM (203 kPa).

9. A method according to claim 8 , wherein the expandable membrane is expanded with a pressure of less than or approximately equal to 1 ATM (101 kPa).

10. A method according to claim 1 , wherein the expandable membrane is configured to contain refrigerant and wherein the act of establishing a temperature comprises supplying refrigerant to the expandable membrane.

11. A method according to claim 10 , wherein refrigerant inside the expandable membrane is maintained in a liquid state.

12. A method according to claim 11 , wherein the refrigerant has a boiling point at atmospheric pressure above +37° C. (310K), a freezing point at atmospheric pressure below −85° C. (358K) and a dynamic viscosity at −85° C. (188K) of below 10 cSt (10×10 −6 m 2 /s).

13. A method according to claim 10 , wherein refrigerant inside the expandable membrane is maintained at a temperature of between −25° C. (248K) and −55° C. (218K).

14. A method according to claim 10 , wherein the refrigerant comprises a perfluorocarbon.

15. A method according to claim 10 , further comprising determining refrigerant characteristics using a sensor provided with the catheter apparatus.

16. A method according to claim 10 , further comprising imaging the refrigerant, wherein the refrigerant comprises a radio opaque substance.

17. A method according to claim 1 , wherein the act of establishing a temperature comprises activating an endothermic reaction.

18. A method according to claim 17 , wherein the endothermic reaction is activated by pressurising the expandable membrane.

19. A method according to claim 17 , wherein the endothermic reaction is activated by expanding the expandable membrane.

20. A method according to claim 17 , wherein the endothermic reaction is a reaction between one or more of the following pairs of compounds: water and ammonium nitrate; water and ammonium chloride; barium hydroxide octahydrate crystals and dry ammonium chloride; water and ammonium chloride; thionyl chloride and cobalt(II) sulphate heptahydrate; water and potassium chloride; water and ammonium thiocyanate; ethanoic acid and sodium carbonate; and combinations thereof.

21. A method according to claim 1 , wherein the temperature within the expandable membrane is maintained by a cooling element positioned proximate to the expandable membrane.

22. A method according to claim 21 , wherein the cooling element comprises a thermoelectric cooling element.

23. A method according to claim 22 , wherein the cooling element comprises a peltier component.

24. A method according to claim 1 , further comprising determining a state of occlusion of the blood vessel using a temperature sensor provided with the catheter apparatus.

25. A method according to claim 1 , wherein the expandable membrane is expanded using a liquid remaining in a liquid phase.

26. A system comprising:

a catheter apparatus, the catheter apparatus having an expandable membrane configured to contain fluid;

a fluid supply for supplying fluid to the expandable membrane;

a pressure control system configured to regulate pressure of the fluid supply and the expansion of the expandable membrane such that the expandable membrane is expanded with a pressure of less than 5 ATM (507 kPa);

a cooling element configured to establish a temperature of between +15° C. (288K) and −35° C. (238K) at an interface between the expandable membrane and a blood vessel when the catheter apparatus has been placed in the blood vessel; and

a vacuum pump position in a return line between the expandable membrane and a fluid reservoir.

27. A system according to claim 26 , wherein the cooling element is selected from the group consisting of: a refrigerant; endothermic reaction components; a thermoelectric cooler; and combinations thereof.

28. A system according to claim 26 , further comprising a temperature control system configured to monitor temperature and adjust the cooling element to maintain the interface temperature between +15° C. (288K) and −35° C. (238K).

29. A system according to claim 26 , further comprising a connection apparatus adapted to cool a refrigerant supply line by a separate refrigerant line from the fluid supply.

30. A system according to claim 26 , wherein the pressure control system configured to regulate the expansion of the expandable membrane using a liquid remaining in a liquid phase.

31. A system according to claim 26 , wherein the catheter apparatus has a single expandable membrane.

32. A method of modifying the structure of a plaque within a blood vessel, comprising:

positioning a catheter apparatus in proximity to the plaque within the blood vessel;

expanding an expandable membrane of a catheter apparatus with a pressure of less than 5 ATM (507 kPa) wherein the expandable membrane is compliant with the blood vessel; and,

establishing a temperature of between +15° C. (288K) and −35° C. (238K) at an interface between the expandable membrane and the blood vessel.

33. A method according to claim 32 , wherein the expandable membrane is expanded using a liquid remaining in a liquid phase.

34. A method of supplying cryoenergy to a plaque within a blood vessel, comprising:

expanding an expandable membrane of a catheter apparatus with a pressure of less than 5 ATM (507 kPa), the catheter apparatus having been placed in thermal contact with the plaque within the blood vessel, and the expandable membrane being semi-compliant with the blood vessel; and,

establishing a temperature of between +15° C. (288K) and −35° C. (238K) at an interface of the expandable membrane and the blood vessel.

35. A method according to claim 34 , wherein the expandable membrane is expanded using a liquid remaining in a liquid phase.

36. A method according to claim 34 , wherein the catheter apparatus has a single expandable membrane.

37. A method of supplying cryoenergy to a plaque within a blood vessel, comprising:

expanding an expandable membrane of a catheter apparatus with a pressure of less than 5 ATM (507 kPa), the catheter apparatus having been placed in thermal contact with the plaque within the blood vessel, and the expandable membrane being non-compliant with the blood vessel; and,

establishing a temperature of between +15° C. (288K) and − 35 ° C. (238K) at an interface of the expandable membrane and the blood vessel.

38. A method according to claim 37 , wherein the expandable membrane is expanded using a liquid remaining in a liquid phase.

39. A method according to claim 37 , wherein the catheter apparatus has a single expandable membrane.