Laser balloon catheter - Patent Review 4878492

What is claimed is:

1. A laser balloon catheter comprising:

an elongated flexible tube having a distal end and a proximal end;

an inflated balloon secured to said flexible tube at or near the distal end thereof;

means for inflating and deflating said balloon;

central shaft means disposed in said balloon and coupled to said flexible tube;

an optical fiber for carrying laser radiation through said flexible tube into said balloon; and

tip assembly means coupled to said optical fiber for directing laser radiation outwardly through a major portion of the balloon surface, said tip assembly means being located within said balloon between said central shaft means and the balloon surface and including means for limiting shadowing thereof by said central shaft means.

2. A laser balloon catheter as defined in claim 1 wherein said tip assembly means includes a tip portion of said optical fiber and shaping means for retaining the tip portion of said optical fiber in a desired shape having at least one turn around said shaft means.

3. A laser balloon catheter as defined in claim 2 wherein said shaping means comprises a heat-formable tube containing the tip portion of said optical fiber.

4. A laser balloon catheter as defined in claim 3 wherein said shaping means further comprises a material located between said heat-formable tube and the tip of said optical fiber and selected to match the indices of refraction of said heat-formable tube and said tip portion.

5. A laser balloon catheter as defined in claim 2 wherein said shaping means comprises a PET tube heat formed to the desired shape and containing the tip portion of said optical fiber.

6. A laser balloon catheter as defined in claim 5 wherein said shaping means further includes epoxy between said PET tube and said tip portion.

7. A laser balloon catheter as defined in claim 5 wherein said PET tube is attached at its distal end to said catheter shaft means.

8. A laser balloon catheter as defined in claim 2 wherein said tip portion of said optical fiber is tapered to a smaller diameter at the distal end thereof.

9. A laser balloon catheter as defined in claim 8 wherein he tip portion of said optical fiber has a uniform taper.

10. A laser balloon catheter as defined in claim 8 wherein the tip portion of said optical fiber has a greater rate of taper near the distal end thereof.

11. A laser balloon catheter as defined in claim 8 wherein the tip portion of said optical fiber has a greater rate of taper near the proximal end thereof.

12. A laser balloon catheter as defined in claim 2 wherein the tip portion of said optical fiber has a spiral shape.

13. A laser balloon catheter as defined in claim 1 wherein said central shaft means includes a laser radiation reflecting outer surface.

14. A laser balloon catheter as defined in claim 2 wherein said tip portion of said optical fiber includes about one full turn per centimeter around said central shaft means.

15. A laser balloon catheter as defined in claim 1 wherein said inflatable balloon is made of PET.

16. A laser balloon catheter as defined in claim 1 wherein said central shaft means comprises an inner tube, a concentric outer tube and a spring coil between said inner and outer tubes.

17. A laser balloon catheter as defined in claim 1 further including a gold layer disposed on an outer surface of said central shaft means for reflecting laser radiation.

18. A laser balloon catheter as defined in claim 17 wherein said gold layer is disposed on the outer surface of said central shaft means in a pattern generally matching the shape of the tip portion of said optical fiber.

19. A laser balloon catheter as defined in claim 1 wherein said flexible tube includes a first lumen for inflating and deflating the inflatable balloon, a second lumen for carrying said optical fiber and for venting air bubbles, and a third lumen for carrying a guide wire.

20. A laser balloon catheter as defined in claim 1 wherein said means for inflating and deflating said balloon includes means for inflating said balloon with a liquid having an attenuation of said laser radiation in a wavelength range between 0.9 and 1.8 micrometers that is less than the attenuation of saline.

21. A laser balloon catheter as defined in claim 1 wherein said means for inflating and deflating said balloon includes means for inflating said balloon with deuterium oxide.

22. A laser balloon catheter as defined in claim 21 wherein said laser radiation is in a wavelength range between 0.9 and 1.8 micrometers.

23. A laser balloon catheter as defined in claim 1 wherein said means for inflating and deflating said balloon includes means for inflating said balloon with infusate containing a dye dissolved in a solvent, said dye being responsive to said laser radiation of a first predetermined wavelength for emitting radiation at a second predetermined wavelength.

24. A laser balloon catheter as defined in claim 1 wherein said tip assembly means comprises a tip portion of said optical fiber and waveguide means surrounding said shaft means and said tip portion of said optical fiber for directing laser radiation circumferentially around said shaft means.

25. A laser balloon catheter as defined in claim 1 further including an inwardly-facing reflector on a portion of said balloon.

26. A laser balloon catheter as defined in claim 1 wherein said central shaft means includes a spring coil having multiple, relatively-rigid turns and wherein said tip assembly means comprises at least one optical fiber and means for pressing said optical fiber against the turns of said spring coil so that laser radiation is emitted from regions of contact between said spring coil and said optical fiber.

27. A laser balloon catheter as defined in claim 1 wherein said means for inflating and deflating said balloon includes means for inflating said balloon with a fluid containing a contrast media.

28. A laser balloon catheter as defined in claim 1 wherein said means for inflating and deflating said balloon includes means for inflating said balloon with a fluid containing a material with thermally-sensitive optical properties for temperature monitoring.

29. A laser balloon catheter as defined in claim 1 further including a second balloon surrounding said first-mentioned balloon and means for inflating said second balloon with gas.

30. A laser balloon catheter comprising:

an elongated flexible tube having a distal end and a proximal end;

an inflatable balloon secured to said flexible tube at or near the distal end thereof;

an optical fiber for carrying laser radiation through said flexible tube into said balloon; and

means for inflating said balloon with deuterium oxide.

31. A laser balloon catheter as defined in claim 30 wherein said optical fiber includes a tip portion for emitting laser radiation outwardly therefrom along its length and through said deuterium oxide.

32. A laser balloon catheter as defined in claim 31 wherein said inflatable balloon is made of PET.

33. A laser balloon catheter as defined in claim 30 further including means coupled to said optical fiber and disposed within said balloon for directing laser radiation carried by said optical fiber outwardly through said deuterium oxide and said balloon.

34. A laser balloon catheter as defined in claim 30 wherein said laser radiation is in a wavelength range between 0.9 and 1.8 micrometers.

35. A laser balloon catheter as defined in claim 31 wherein the tip portion of said optical fiber is tapered from a larger diameter at its proximal end to a smaller diameter at its distal end.

36. A laser balloon catheter as defined in claim 30 wherein said means for inflating and deflating said balloon includes means for inflating said balloon with a fluid containing a laser dye responsive to said laser radiation of a first predetermined wavelength for emitting radiation at a second predetermined wavelength.

37. A method of operating a laser balloon catheter comprising the steps of:

advancing a catheter having an inflatable balloon secured at or near its distal end and having an optical fiber terminating within the balloon through a body passage to a desired treatment location;

inflating the balloon with deuterium oxide; and

directing laser radiation through said optical fiber into said balloon such that the radiation passes through said deuterium oxide and said balloon for treatment.

38. A method of operating a laser balloon catheter as defined in claim 37 wherein the step of directing laser radiation includes directing laser radiation in a wavelength range between 0.9 and 1.8 micrometers so that the radiation passes through the deuterium oxide and the balloon without substantial absorption for heating of the surrounding tissue.

39. A method of operating a laser balloon catheter as defined in claim 38 wherein the step of directing laser radiation includes directing the laser radiation so as to produce substantially uniform heating of the body passage in a region surrounding the balloon.

40. A method of operating a laser balloon catheter as defined in claim 37 wherein the step of inflating the balloon includes inflating the balloon with solvent containing a laser dye responsive to said laser radiation of a first predetermined wavelength for emitting radiation at a second predetermined wavelength.

41. A method for operating a laser balloon catheter as defined in claim 37 wherein the step of inflating the balloon includes inflating the balloon with deuterium oxide containing a contrast agent.

42. A method of operating a laser balloon catheter as defined in claim 37 wherein the step of inflating the balloon includes the step of inflating the balloon with deuterium oxide containing a material with thermally-sensitive optical properties for temperature monitoring.

43. A laser balloon catheter comprising:

an elongated flexible tube having a distal end and a proximal end;

an inflatable transparent balloon secured to said flexible tube at or near the distal end thereof;

means for inflating and deflating said balloon;

a relatively incompressible central tube located in said balloon and coupled to said flexible tube for carrying a guide wire; and

an optical fiber for carrying laser radiation through said flexible tube into said balloon, said optical fiber including a tip portion in said balloon for emitting laser radiation outwardly therefrom through a major portion of the balloon, said tip portion extending around said central tube in a spiral configuration having at least one complete turn.

44. A laser balloon catheter as defined in claim 43 further including shaping means for retaining said tip portion of said optical fiber in said spiral configuration.

45. A laser balloon catheter as defined in claim 44 wherein said tip portion of said optical fiber is tapered to a smaller diameter at the distal end thereof.

46. A laser balloon catheter as defined in claim 45 wherein said shaping means comprises a preformed transparent tube containing the tip portion of said optical fiber and a material between said transparent tube and said tip portion selected to match the indices of refraction of said transparent tube and said tip portion.

47. A laser balloon catheter as defined in claim 46 wherein the material between said transparent tube and said tip portion contains a laser dye responsive to laser radiation of a first predetermined wavelength for emitting radiation at a second predetermined wavelength.

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FIELD OF THE INVENTION

This invention relates to laser balloon catheters and to methods for the manufacture and use of laser balloon catheters and, more particularly, to laser balloon catheters intended for use with a guide wire and capable of providing a high level of laser output power through the balloon wall into surrounding tissue. The laser balloon catheter of present invention is intended primarily for coronary angioplasty, but is not limited to such use.

BACKGROUND OF THE INVENTION

Balloon angioplasty has been utilized for a number of years to treat coronary arteries narrowed by plaque deposits. A catheter having an inflatable balloon secured to its distal end is advanced through an artery to a narrowed region. The balloon is then inflated with a fluid from an external source, causing the narrowed region of the artery to be expanded. The balloon is then deflated and withdrawn. A serious problem associated with balloon angioplasty has been the occurrence in up to 30% of the cases of so-called restenosis, either immediately after the procedure or within about six months. Immediate restenosis, also known as abrupt reclosure, results from flaps or segments of plaque and plaque-ridden tissue which are formed during balloon angioplasty and which can block the artery. Such blockage of the artery requires emergency surgery and often results in death. Furthermore, a surgical team is required to stand by during the balloon angioplasty procedure. Restenosis at a later time results from causes that are not totally known. Thrombus formation is believed to play an important part. Often repeat balloon angioplasty or surgery is required, and another episode of restenosis may occur.

A technique which has shown great promise for overcoming the problem of restenosis is the simultaneous application of heat and pressure to a plaque-narrowed region of an artery. The technique is described by John F. Hiehle, Jr. et al in "Nd-YAG Laser Fusion of Human Atheromatous Plaque-Arterial Wall Separations in Vitro," American Journal of Cardiology, Vol. 56, Dec. 1, 1985, pp. 953-957. In accordance with this technique, a catheter having an inflatable balloon at its distal end is advanced to a narrowed region of an artery and the balloon is inflated, as in the case of balloon angioplasty. However, in distinction to balloon angioplasty, sufficient heat is applied through the wall of the balloon to fuse the surrounding tissue and thereby eliminate the flaps which can later block the artery. One advantageous means of heating the surrounding tissue is by directing laser radiation through an optical fiber carried by the catheter and terminating within the balloon. The laser radiation is then directed through the balloon wall to cause heating of the surrounding tissue.

Although the laser balloon catheter has been proposed in principle, there are numerous problems and difficulties in constructing a practical catheter suitable for human use. The balloon containing the device for diffusing laser radiation and the deflated catheter containing the optical fiber must be extremely flexible and small in diameter (on the order of 1.0 to 1.5 millimeters) in order to permit navigation of the catheter through an artery to the desired site. The laser balloon catheter is preferably compatible with a guide wire which is used to guide the catheter through the artery to the desired location. Where the guide wire passes through the balloon, shadowing of the laser radiation pattern by the guide wire must be avoided.

Another critical factor is the technique used for heating the surrounding tissue and the associated power level. It has been found desirable to apply radiation which penetrates the surrounding plaque and plaque-ridden tissue and the artery wall and heats that region by radiant heating, in distinction to conductive heating by the balloon. Furthermore, it has been found desirable to apply such radiation at a power level on the order of 30-40 watts for times of on the order of thirty seconds. With such high power levels, it is extremely critical to efficiently transfer the input laser radiation through the fluid which inflates the balloon and through the balloon wall with minimum heat dissipation within the balloon.

Other techniques involving the application of heat in a coronary artery include the so-called "hot tip" as disclosed in U.S. Pat. No. 4,646,737 issued Mar. 3, 1987 to Hussein et al and U.S. Pat. No. 4,662,368 issued May 5, 1987 to Hussein et al, wherein a thermally conductive tip located at the end of a catheter is heated by laser radiation and conducts heat to the surrounding region as it is pushed through a narrowed artery. The hot tip reaches temperatures on the order of several hundred degrees Celsius in order to produce the necessary conductive heating as it is pushed through the artery. The hot tip is unable to expand the artery beyond the conductive tip diameter, which must be limited for passage through the artery. Another heating technique wherein a microwave-radiating antenna is located within an inflatable balloon is disclosed in U.S. Pat. No. 4,643,186 issued Feb. 17, 1987 to Rosen et al. A coaxial transmission line is carried through a catheter and connects to the antenna.

An endoscopic device wherein low power, narrow beam laser radiation is directed through a balloon wall is disclosed in U.S. Pat. No. 4,470,407 issued Sept. 11, 1984 to Hussein. The problem of providing relatively uniform heating of tissue surrounding a balloon at high power levels and without shadowing is not addressed by the Hussein patent.

Prior art techniques have been disclosed for directing laser radiation outwardly from the tip of an optical fiber. A tapered optical fiber surrounded with a diffusing medium for laser radiation treatment of tumors is disclosed in U.K. Patent Application No. 2,154,761 published Sept. 11, 1985. An optical fiber surrounded with a scattering medium for producing a cylindrical pattern of light at the tip of an optical fiber is disclosed in U.S. Pat. No. 4,660,925 issued Apr. 28, 1987 to McCaughan, Jr. A technique for roughening the surface of an optical fiber tip to cause wide angle radiation of laser energy is disclosed by H. Fujii et al, "Light Scattering Properties of A Rough-ended Optical Fiber," Optics and Laser Technology, February 1984, pp. 40-44. None of the prior art techniques provide the combination of small diameter, flexibility, power handling capability and compatibility with a guide wire necessary for a laser balloon catheter.

It is a general object of the present invention to provide an improved laser balloon catheter.

It is a further object of the present invention to provide a laser balloon catheter suitable for use in coronary angioplasty.

It is another object of the present invention to provide a laser balloon catheter capable of delivering and surviving a high power output.

It is another object of the present invention to provide a laser balloon catheter which can be utilized with a guide wire for advancing the catheter through an artery.

It is another object of the present invention to provide a laser balloon catheter which produces substantially uniform heating of tissue surrounding the balloon.

It is still another object of the present invention to provide a method for manufacturing a laser balloon catheter.

It is yet another object of the present invention to provide a laser balloon catheter which is small in diameter and flexible so that it is easily advanced through an artery.

It is yet another object of the present invention to provide a laser balloon catheter wherein heat dissipation of laser radiation within the balloon is limited to allow heating deep into an artery wall without excessive total energy.

It is a further object of the present invention to provide a laser balloon catheter wherein a relatively high proportion of the input laser radiation is delivered through the balloon wall to the surrounding tissue.

SUMMARY OF THE INVENTION

According to the present invention, these and other objects and advantages are achieved in a laser balloon catheter comprising an elongated flexible tube having a distal end and a proximal en, an inflatable balloon secured to the flexible tube at or near the distal end thereof, means for inflating and deflating the balloon, a central shaft disposed within the balloon and coupled to the flexible tube, an optical fiber for carrying laser radiation through the flexible tube into the balloon, and tip assembly means in the balloon and coupled to the optical fiber for directing laser radiation outwardly through a major portion of the balloon area while limiting shadowing by the central shaft.

Preferably, the tip assembly means includes a tip portion of the optical fiber which is tapered to a smaller diameter at the distal end thereof and shaping means for retaining the tip portion of the optical fiber in a shape having at least one turn around the central shaft. The tip portion of the optical fiber preferably has a generally spiral shape. In a preferred embodiment, the shaping means includes a heat-formable tube containing the tip portion of the optical fiber and a material located between the heat-formable tube and the tip of the optical fiber selected to match the indices of refraction of the heat-formable tube and the tip portion. The spiral tip portion of the optical fiber is flexible and emits laser radiation outwardly over its length while limiting shadowing by the central shaft.

Preferably, the central shaft, which is typically used for carrying a guide wire, includes an inner tube, a concentric outer tube and a spring coil between the inner and outer tubes. The spring coil prevents the central shaft from collapsing when the balloon is inflated. The central shaft includes a laser radiation-reflecting outer surface such as white vinyl or a thin layer of gold disposed on the outer tube.

In another important aspect of the invention, a laser balloon catheter is inflated with a liquid which attenuates laser radiation at the wavelength of interest less than saline in order to limit heat dissipation within the balloon and to increase output power. Preferably, the liquid has an attenuation of less than about 0.16/cm at a preferred laser wavelength of 1.06 micrometer. In a preferred embodiment, the balloon is inflated with deuterium oxide for reduced absorption of laser radiation in comparison with conventional inflation fluids such as saline or water. The deuterium oxide absorbs a negligible amount of energy at the preferred laser wavelength of 1.06 micrometer. Deuterium oxide can be advantageously used in any laser balloon catheter to reduce energy absorption and is not limited to the laser balloon catheter described herein. The deuterium oxide is biologically safe and is preferably utilized in conjunction with a transparent PET balloon.

According to other features of the invention, a dye responsive to laser radiation of a predetermined first wavelength for emitting radiation at a predetermined second wavelength, and a dye solvent, can be mixed in the inflation fluid. The inflation fluid can contain a contrast agent to facilitate location of the balloon during use. A material with thermally sensitive optical properties can also be mixed in the inflation fluid for monitoring the temperature of the balloon along the optical fiber. An inwardly-facing reflector can be provided on a portion of the balloon to control the heating pattern produced by the laser radiation.

According to another aspect of the present invention, there is provided a method of operating a laser balloon catheter comprising the steps of advancing a catheter having an inflatable balloon secured at or near its distal end and having an optical fiber terminating within the balloon through a body passage to a desired treatment location, inflating the balloon with a low attenuation liquid such as deuterium oxide and directing laser radiation through the optical fiber into the balloon such that the radiation passes through the low attenuation liquid and the balloon for treatment.

According to still another aspect of the present invention, there is provided a method of making an optical fiber tip assembly for emitting laser radiation outwardly therefrom along its length comprising the steps of providing an optical fiber having a tapered tip portion, inserting the tapered tip portion into a transparent tube and filling the space between the transparent tube and the tapered tip portion with a material that is selected to match the indices of refraction of the transparent tube and the tip portion. Preferably, the transparent tube is heat-formable and the method further includes the step of preforming the transparent tube to a desired shape. The step of filling the space between the transparent tube and the tip portion preferably includes the steps of immersing a silicon tube in freon to cause expansion thereof, slipping the expanded silicon tube over the transparent tube, permitting the silicon tube to contract to its normal size and injecting the material from a syringe through the silicon tube into the transparent tube.

According to still another aspect of the invention, there is provided a method of making a laser balloon catheter comprising the steps of forming a spiral tip assembly at one end of an optical fiber, providing a flexible tube having a distal end and a proximal end and having at least two lumens therethrough, attaching a central shaft for carrying a guide wire to the distal end of the flexible tube so that a passage through the central shaft is aligned with one of the lumens, inserting the optical fiber through another of the lumens so that the spiral tip assembly is disposed at the distal end of the flexible tube around the central shaft, and sealing an inflatable balloon to the distal end of the flexible tube around the spiral tip assembly and the central shaft.

In another embodiment of the tip assembly, a transverse optical waveguide surrounds the optical fiber and the central shaft. The transverse waveguide directs a portion of the laser radiation around the central shaft and limits shadowing.

In yet another embodiment of the tip assembly, one or more optical fibers are stressed at multiple points by pressing them against a spring coil in the central shaft. The regions of stress emit laser radiation outwardly.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the present invention together with other and further objects, advantages and capabilities thereof, reference is made to the accompanying drawings which are incorporated herein by reference and in which:

FIG. 1 is a fragmented illustration of a laser balloon catheter in accordance with the present invention;

FIG. 2 is an enlarged cross-sectional view of the distal end of the laser balloon catheter taken alo