WO1990006087A1

WO1990006087A1 - Single axis/angled beam laser catheter

Info

Publication number: WO1990006087A1
Application number: PCT/US1989/005416
Authority: WO
Inventors: Miles A. Finn; Steven L. Jensen
Original assignee: Medilase, Incorporated
Priority date: 1988-12-01
Filing date: 1989-11-30
Publication date: 1990-06-14
Also published as: AU4809590A; CA2004417A1

Abstract

A laser catheter (10) for angioplasty is disclosed which fires a laser beam at an angle across the face of the catheter (12) allowing extremely precise aiming of the laser energy at any point within the cross-section of a vessel in which the catheter (10) is located. The catheter (10) has a control handle (14), body (15), and laser coupler fitting (29).

Description

SINGLE AXIS/ANGLED BEAM LASER CATHETER Field of the Invention This invention relates to catheters and similar devices having a mechanism for aiming light transmitting fibers or other working means requiring remote control. Although particularly described with reference to laser angioplasty, the invention has broad applicability to any medical instrument which fires a laser at a target. Background of the Invention This invention relates to medical instruments and in particular to devices for performing laser surgery e.g., angioplasty, the treatment of atherosclerosis and the like. Atherosclerosis is a disease which causes thickening and hardening of artery walls. It is characterized by lesions of raised atherosclerotic plaque which form within arterial lumens and occlude them partially or wholly. Coronary atherosclerosis is a leading cause of death in the United States. Atherosclerosis tends to increase progressively with age. The treatment of atherosclerosis typically consists of drug therapy, surgery or percutaneous balloon angioplasty. In percutaneous balloon angioplasty, small balloon tipped catheters were first developed which could be passed percutaneously into various arteries and then inflated to dilate areas of partial obstruction. While this procedure has gained a measure of acceptance as a less invasive alternative to surgery, in most cases balloon angioplasty simply redistributes the atherosclerotic plaque. Frequency of recurrence or restenosis of the plaque occlusions has caused some concern about the efficacy of this technique. Laser therapy has been suggested as another approach to percutaneous angioplasty. One such technique utilizes laser technology to emit radiation onto a light receiving surface of a heat generating element. The light is converted by the element to heat. The element can then be contacted against material in a patient's body, such as a clot, atherosclerotic deposit or tissue, to alter the same by melting, removing or destroying it. In another laser technique, laser radiation is applied directly to the plaque deposit, clot or the like to vaporize or ablate it. It is this second technique to which the subject invention is most particularly directed. This particular technique of laser angioplasty provides the ability to remove the atherosclerotic plaque and reopen even totally occluded vessels without significant trauma to the vessel wall. It also offers the potential of reduced restenosis rate. However, the current technology for impinging laser radiation directly on a selected discrete treatment area has its own problems. Most critical has been the lack of ability to precisely aim laser radiation to selected areas to be treated without accidental arterial perforation. Various attempts have been made to overcome the problem of aiming the laser at the target, while avoiding damage to the vessel wall. U.S. Patent No. 4,587,972 issued May 13, 1986 for a "Device for Diagnostic and Therapeutic Intravascular Intervention" discloses a device which contains a bundle of optic fibers in the center of a catheter. The device is capable of firing one or more of these laser fibers. However, the laser beam fires axially, which limits the precision with which the physician may aim the laser energy at targets close to the vessel wall. U.S. Patent No. 4,627,436 issued Dec. 9, 1986 for a "Angioplasty Catheter and Method For Use Thereof discloses another device which fires a laser beam axially. An expansion balloon permits the distal end of the catheter to be tilted for more precise aiming. The problem with this design is that targets close to the vessel wall remain difficult to hit due to the axial firing of this design. U.S. Patent No. 4,648,892 issued Mar. 10, 1987 for a "Method For Making Optical Shield For A Laser Catheter" discloses a device which fires one or more laser beams axially. The device has a shield which allows the distal end of the catheter to be put into contact with the target, allowing viewing of the target without the interference of any liquid, such as blood. Various types of elements may be placed within the shield to reflect the laser light. A problem with this design is that the distal end of the catheter must be manipulated such that the distal end comes into contact with the plaque. If the plaque is in a difficult to reach spot it may be difficult to ablate it. Another approach was disclosed in U.S. Patent No. 4,672,961 issued June 16, 1987 for a "Retrolasing Catheter and Method". This patent discloses a device which fires a group of laser fiber bundles spaced around the perimeter of the catheter, reflecting the laser beams backward through a window portion in the catheter wall to aim at a target. The energy from each bundle of fibers is focused on a different point around the perimeter of the catheter. A problem with this design is that it is difficult to determine where each of the laser fibers is being aimed since no imaging technique is used. This device also cannot be used in vessels so severely occluded that the catheter cannot be advanced through the obstruction. Applicants' invention allows even totally occluded vessels to be unblocked by carving away the plaque with the laser beam. U.S. Patent No. 4,681,104 issued July 21, 1987 for an "Apparatus For Focusing An Intravascular Laser Catheter" discloses a device which fires an array of laser fibers spaced around the perimeter of the catheter, angling the beams such that they focus at a point on the longitudinal axis of the catheter. The problem with this device are that it is only useful for targets which almost totally clog the vessel, due to the location of the focal point of the laser beams. If the laser beams are allowed to fire through the focal point and spread in an attempt to reach a target off axis, the vessel wall opposite the target may be damaged. This is true even -4-

if a portion of the array of laser beams is in fact correctly aimed at the target. In addition, the multiple fiber configuration requires a larger diameter catheter than applicants' single fiber catheter. The invention disclosed herein overcomes these problems by providing a catheter device which may be aimed at any point within the cross-section of a vessel. The present invention fires a laser at an angle across the vessel, typically at a target on the opposite side of the vessel from the origin of the laser beam. Rotation of the catheter causes the laser beam to describe or inscribe a cone whose projection on the surface of the plaque is a circle or ellipse with radius increasing as the distance from the distal end of the catheter increases. Movement of the catheter axially along the vessel, combined with the rotation of the catheter allows the physician to aim the laser at any point within the cross-section of the vessel. Placement of the laser fiber off-center within the distal end portion of the catheter, with respect to the longitudinal axis of the catheter, allows for the ablation of plaque which is on the axis. It also allows the imaging means (typically an optical fiber bundle) to be placed at the center axis of the catheter, which may facilitate the aiming of the catheter. Another advantage of the present single fiber invention over the multiple fiber devices described above is that it allows for a smaller diameter device. Various types of lasers may be utilized in the context of the present invention. The pulsed dye laser is one that is often preferred for cardiovascular use due to its superior ability in avoiding damage to healthy tissue. This is due in part because the plaque tends to absorb the particular wavelength of light used by pulsed dye lasers more readily than the healthy tissue. Plaque is ablated by using pulsed energy as brief as about .5 to 50 microseconds, although the pulse time can vary. The pulsed dye laser is also preferred because more energy can be delivered through the relatively fragile fibers because of the relatively long pulse time. Excimer lasers as well as other types of lasers could also be used in the present invention. Optical fibers and fiber bundles have also been used in a variety of medical applications. An optical fiber is a relatively flexible clad plastic or glass core wherein the cladding is of a lower index of refraction than the core. When a plurality of such fibers are combined, a fiber optic bundle is produced. Optical fibers are flexible and are therefore capable of guiding light in a curved path defined by the placement of the fiber. Summary of the Invention The aiming arrangement of the invention is specifically described herein with reference to catheters for laser angioplasty but has broad applicability to any medical instrument which fires a laser at a target. The instrument may be used in both coronary and peripheral percutaneous angioplasty, but may also be used in intraoperative procedures, such as when the chest cavity or femoral artery are exposed incident to another procedure or as a primary procedure. In its most preferred form a device of the invention will comprise a fiber optic catheter suitable for performing medical procedures in a vascular lumen or other cavity within a patient. The catheter will have a distal end to be inserted into a patient and a proximal end including a control handle or the like held by a physician for directing the contemplated procedure. Such devices are typically constructed for disposal after a single use. More specifically, the catheter includes an elongated external tube containing a laser light transmitting means, such as an optical fiber. The catheter may also contain one or more fiber optic viewing bundles, one or more fiber optic illumination fibers and may also be provided with one or more fluid passageways through which gases or liquids may be evacuated or transmitted. The catheter may also include a balloon at the distal end to halt the flow of blood for the duration of the procedure. This balloon may not be needed for intraoperative procedures since the blood may have been removed from the vessel in question, or may not be flowing. A guide wire may also be inserted through one of these conduits or otherwise included in the catheter. The distal end of the catheter is advanced through a lumen to the area of the vessel where the procedure is to be performed. The fiber optic viewing bundles along with various other techniques such as fluoroscopy allow the physician to see what the laser is aimed at. The laser beam is situated such that it fires from near the edge of the catheter, at an angle across the distal end face of the catheter and through the longitudinal axis of the catheter. Rotation of the catheter causes the laser beam to inscribe a conic section, where the conic section is the projection of a circle or ellipse onto the surface of the plaque. By a combination of rotation of the catheter and axial movement of the catheter any point within the entire cross-section of the vessel can be precisely aimed at by the laser. Brief Description of the Drawings Fig. 1 is an elevational view of a preferred embodiment of the medical device of the invention; Fig. 2 is an enlarged detail view of the distal end of the device shown in Fig. 1; Fig. 3 is an end elevational view of Fig. 2; Fig. 4 is a simplified schematic showing of an alternative embodiment of the invention; Fig. 5 is a simplified schematic showing of another alternative embodiment of the invention; Fig. 6 is an elevational view of an alternative embodiment of the invention, and Fig. 7 is an end elevational view of Fig. 6. Description of the Preferred Embodiments While this invention can be embodied in many different forms, there are shown in the drawings and described in detail herein specific preferred embodiments of the invention. The present disclosure is an exemplification of the principles of the invention and is not intended to limit the invention to the particular embodiments illustrated. The present invention in preferred form comprises a medical device for delivering and applying laser radiation to a site in a vessel lumen of a patient. The radiation may be used to vaporize atherosclerotic plaque. Such instruments oftentimes take the form of microcatheters of extremely small diameter. Such instruments are usually readily available in various diameter sizes to suit the particular work site in the particular lumen in which they are to be located and used. Thus a physician will have a number of various sized catheters at his disposal during any given procedure. In some such devices, an elongated guide wire (not shown) may be selectively positioned within the lumen of the patient in association with the catheter. To this end, the catheter may include an elongated channel such as a slot, bore or conduit through which an external guide wire may slide longitudinally. The catheter can then be slid along the guide wire until a selected position in close proximity to a lesion which partially or totally occludes a vessel is reached. The aiming mechanism can be manipulated as desired and the laser radiation can then be selectively impinged on any area selected for treatment within the cross-section of the vessel . Some versions of such catheters are desirably constructed with at least a tip portion thereof including radio-opaque material (not shown). The radio-opaque material can then be used to locate the catheter under fluoroscopy which in combination with the image bundle aids in determining the location of the catheter tip relative to the plaque and aids in verifying the aiming. Referring now particularly to Figure 1 of the drawings, a catheter device of the present invention in one embodiment comprises an elongated catheter, generally designated 10, having a working distal end generally designated 12. The device is adapted -8-

to be inserted into a patient and a remote control handle 14 is attached at a proximal end 13 for manipulation and control by a physician. The catheter is flexible and generally comprises an extruded sol d plastic body 15. Body 15 may consist of a single, soft, solid, extruded plastic material or it may consist of a plastic composite reinforced with plastic or metal braided filaments, such as Dacron^® polyester fiber or stainless steel. Plastics such as polytetrafluoroethylene, polyester, polyethylene and silicone may be used. When using the catheter in a vessel which contains an opaque fluid such as blood, it is often necessary to remove the opaque fluid and flush the area with a clear fluid such as saline solution to provide a viewable work area. To accomplish this, catheter body 15 may include conduits 18 and 19 (shown in Fig. 3), which open at distal end 12 and which are respectively connected to tubes 20 and 21 at the proximal end. Conduits 18 and 19 may be formed during extrusion of body 15. Tubes 20 and 21 include appropriate connector fittings 22 and 23, which will be familiar to those of ordinary skill in the art. Conduits 18 and 19 may thus function as suction tubes, fluid flushing tubes, supply tubes or for receiving a guide wire, in the already known manner. Referring now to Figures 1 and 2 together, provision is made for delivering laser radiation to the distal end 12 of catheter 10 by providing a laser light source, (not shown). The laser may be coupled as is known in the art to control handle 14 through an optical coupling fitting 29. This arrangement in turn directs laser radiation through control handle 14 and through a laser radiation transmitting fiber 30, which may be located within an internal conduit 31 in body 15. Preferably, a single glass or fused silica fiber 30 or other optical fiber with a core diameter of about 50 to about 600 microns is utilized for the laser radiation transmitting fiber 30. These are typical sizes presently available and are not critical; the smaller the fiber the better, as long as enough energy can be transmitted through the fiber without damage to the fiber. Such fibers are known in the art. However, other fiber arrangements may be used as they become available. Additionally, a bundle of ^~mry flexible and very small diameter optical fibers or imaging bundle 32 including a lens as well as illumination fibers 33 (shown in Fig. 3) may be included and will also extend through catheter 15. In the preferred embodiment bundle 32 runs down the center of catheter 15. The proximal end thereof is appropriately connected to a fitting 33 to provide imaging or viewing in the known manner. Imaging bundle 32 is coherently packed, such that light at the proximal end is in the same relationship to the fibers in the bundle as when the light enters the imaging bundle 32 at the distal end. The illumination fibers 33 are not arranged in a coherent bundle like the imaging bundle. This is because the illumination fibers need only transmit white light to allow the physician to see inside the vessel, and not receive and transmit an image in a coherent manner for viewing. Placing the imaging bundle 32 in the center of the catheter aids in the viewing of the vessel and in aiming the laser energy. However, it is to be understood that the viewing bundle 32 could be placed anywhere within catheter 15. Referring now specifically to Figures 2 and 3 together, it can be seen that laser transmitting fiber 30 running through conduit 31 terminates near chamber 50 at the distal end of the catheter. Chamber 50 contains a mirror 46 positioned to receive on a face 48 laser radiation as it leaves the distal end of fiber 30. The angled face 48 of mirror 46 includes a bevel angle calculated to reflect the laser energy such that it is directed out through opening 54 in distal end 12 of the catheter. The reflected laser energy emerges from opening 54 at a predetermined angle α shown at 56, and will intersect the longitudinal axis of the catheter at a point 58 which lies at a^* predetermined working distance D₀ from the end face of the catheter. The laser energy continues through point 58. In practice the distal end of the catheter may be closer to the target than D₀, but the predetermined distance D₀ establishes a useful reference point to aid in aiming the laser energy. Conic sections 70, 72, 74, and 76 are representations of a cross-section taken through the cone which the l ser energy inscribes as catheter 10 is rotated. The corresponding working distances are shown as D D₂, D₃, and D₄. These conic sections demonstrate how the catheter may be rotated and moved axially to reach any point within the cross-section of the vessel due to the angularly directed laser beam. By moving the catheter axially along the vessel the catheter may be placed the exact distance from the target such that the diameter of the cone at that point will include the target and the laser radiation will strike it. The conic sections also demonstrate that the diameter of the cone may exceed the diameter of the catheter if the vessel is large enough to allow the laser radiation to travel far enough. With axially firing prior art arrangements it was difficult to aim at a target which was outside the diameter of the catheter. Referring now to Figure 4, an alternative embodiment of the invention is shown which uses a prism 78 to refract the laser energy such that the laser beam still fires at an angle α. It is well known in the art to use various prism configurations to refract laser radiation at a predetermined angle. Referring now to Figure 5, yet another alternative embodiment of the invention is shown which uses a beveled catheter distal end 80 to refract the laser energy such that the laser beam fires at an angle α. It is well known in the art that laser energy moving from a material with an index of refraction N_t to a material with an index of refraction of N₂ will be refracted an an angle which can be controlled by choosing the various indices of refraction and the bevel angle of 80. It is to be understood that any other reflective or refractive means of delivering laser energy at an angle a are contemplated as being within the scope of the invention, as long as they are positioned off-center with respect to the longitudinal axis of the catheter and fire across the end face of the catheter. Referring now to Figure 6 another embodiment of the invention is shown. In this embodiment catheter body 15 is slidably received by a sheath 90. Sheath 90 may be self steering or may be guided to the target site with a guide wire as is well known in the art. Sheath 90 is provided with a conduit 92 for providing saline or other liquid for the inflation or deflation of balloon 94. Conduit 96 provides a slow continous flow of saline or other liquid which acts as a lubricant for catheter body 15. The saline or other liquid is introduced via connectors 98 and 100 which are familiar to those skilled in the art. Rubber seal 102 prevents the saline or liquid from escaping out the proximal end of the catheter sheath. Stiffening members 104 and 106 provide additional strength or strain relief at the proximal end of the catheter. The continous flow of a small volume of saline or other liquid between the catheter body 15 and the inside wall of the sheath 108 acts as a lubricant. This allows the catheter body to be moved axially within the vessel and rotated much easier. By positioning the occlusion balloon on the sheath rather than on the catheter, it is possible to rotate and move the catheter body axially without having to deflate and re-inflate the balloon. This will cut down wear and tear on the vessel wall. Referring now to Figure 7 an end view of figure 6 taken along line 7 - 7 is shown. The outer concentric circle is occlusion balloon 94. The middle concentric circle is the sheath body, with the conduit shown at 92. The catheter body is shown at 15. This completes the description of the preferred and alternate embodiments of the invention. Those skilled in the art will recognize other equivalents to the specific embodiments described herein which equivalents are intended to be encompassed by the claims attached hereto.

Claims

WHAT IS CLAIMED IS: 1. A catheter comprising: an elongate catheter body constructed and arranged for insertion and axial movement within a vessel whereby the catheter may be placed in selected positions therein, and further being constructed and arranged for rotation about its longitudinal axis when in the vessel, the body having proximal and distal end portions; laser beam delivery means carried interiorly of said body and off-axis with respect to the longitudinal axis of said body and terminating in the distal end portion of the catheter body, said delivery means being constructed and arranged to direct a laser beam at an angle from the distal end of the catheter body. 2. The catheter of claim 1 wherein the laser delivery means further comprises a reflective means positioned near the termination of the laser delivery means for directing the laser beam at said angle. 3. The catheter of claim 1 wherein the laser delivery means further comprises a refractive means positioned near the termination of the laser delivery means for directing the laser beam at said angle. 4. The catheter of claim 3 wherein the refractive means comprises an optical fiber terminating in a beveled end which is constructed and arranged such that the laser beam is delivered at said angle. 5. The catheter of claim 3 wherein the refractive means comprises a prism constructed and arranged such that the laser beam is delivered at said angle. 6. The catheter of claim 3 wherein the refractive means comprises a lens constructed and arranged such that the laser beam is delivered at said angle. 7. The catheter of claim 1 further including an elongate hollow sheath body constructed and arranged for insertion and axial movement within a vessel whereby the sheath body may be placed in selected positions therein, the sheath body having proximal and distal end portions, and an inner and outer surface; the catheter being carried interiorly of the inner surface of said sheath body, said catheter being rotatable around its longitudinal axis and axially movable within said sheath body; an occlusion balloon carried on the outside surface of the distal end of the sheath body; a balloon inflation lumen extending the length of said sheath body, between said inner and outer surfaces, said lumen carrying liquid for inflation and deflation of said occlusion balloon, and a continuous flow of liquid between said catheter and said inner surface of said sheath body, whereby the rotation and axial movement of said catheter within said sheath body is facilitated. 8. A catheter for laser angioplasty comprising: an elongate catheter body constructed and arranged for insertion and axial movement within a vessel whereby the catheter may be placed in selected positions therein, and further being constructed and arranged for rotation about its longitudinal axis when in the vessel, the body having proximal and distal end portions; laser beam delivery means carried interiorly of said body and off-axis with respect to the longitudinal axis of said body and terminating in the distal end portion of the catheter body, said delivery means being constructed and arranged to direct a laser beam from the distal end of the catheter body at an angle to the longitudinal axis thereof such that the beam intersects the longitudinal axis of the body at a point forward of the distal end of the catheter and wherein the beam inscribes a cone as the catheter is rotated about its longitudinal axis, whereby the beam may be directed anywhere within the entire cross-section of the vessel by the combination of rotation and axial movement of the catheter body. 9. The catheter of claim 8 wherein the laser delivery means further comprises a reflective means positioned near the termination of the laser delivery means for delivering the laser beam at said angle. 10. The catheter of claim 8 wherein the laser delivery means further comprises a refractive means positioned near the termination of the laser del very means for del vering the laser beam at said angle. 11. The catheter of claim 10 wherein the refractive means comprises an optical fiber terminating with a beveled end constructed and arranged such that the laser beam is delivered at said angle. 12. The catheter of claim 10 wherein the refractive means comprises a prism constructed and arranged such that the laser beam is delivered at said angle. 13. The catheter of claim 10 wherein the refractive means comprises a lens constructed and arranged such that the laser beam is delivered at said angle. 14. The catheter of claim 8 further including an elongate hollow sheath body constructed and arranged for insertion and axial movement within a vessel whereby the sheath body may be placed in selected positions therein, the sheath body having proximal and distal end portions, and an inner and outer surface; the catheter being carried interiorly of the inner surface of said sheath body, said catheter being rotatable around its longitudinal axis and axially movable within said sheath body; an occlusion balloon carried on the outside surface of the distal end of the sheath body; a balloon inflation lumen extending the length of said sheath body, between said inner and outer surfaces, said lumen carrying liquid for inflation and deflation of said occlusion balloon, and a continuous flow of liquid between said catheter and said inner surface of said sheath body, whereby the rotation and axial movement of said catheter within said sheath body is facilitated. 15. A sheath for use with a catheter comprising: an elongate hollow sheath body constructed and arranged for insertion and axial movement within a vessel whereby the sheath body may be placed in selected positions therein, the sheath body having proximal and distal end portions, and an inner and outer surface; a catheter carried interiorly of the inner surface of said sheath body, said catheter being rotatable around its longitudinal axis and axially movable within said sheath body; an occlusion balloon carried on the outside surface of the distal end of the sheath body; a balloon inflation lumen extending the length of said sheath body, between said inner and outer surfaces, said lumen carrying liquid for inflation and deflation of said occlusion balloon, and a continuous flow of liquid between said catheter and said inner surface of said sheath body, whereby the rotation and axial movement of said catheter within said sheath body is facilitated.