Abstract:
A catheter suitable for the delivery of laser energy to an obstruction in a body lumen is provided, which has an expandable, elastic distal end portion containing optical fibers whose exposed distal end faces are arranged in two or more substantially concentric arrays that merge into a narrower band array of a larger diameter upon radial expansion of the elastic distal end portion. The distal end portion of the catheter is more elastomeric than the catheter body.

Description:
FIELD OF THE INVENTION 
     This invention pertains to catheters for delivery of radiant energy. More particularly, the invention pertains to catheters for delivering directable laser energy to an obstructed region of a corporal lumen such as a blood vessel to ameliorate or remove the obstruction. 
     BACKGROUND OF THE INVENTION 
     Lasers have been used to provide heat energy, directly or indirectly, for the purpose of removing plaque or other obstructing materials in a corporal lumen. One such system is disclosed in Ginsburg et al. U.S. Pat. No. 4,790,310 (the &#39;310 patent) entitled &#34;Laser Catheter Having Wide Angle Sweep.&#34; Another such system is disclosed in Muiller et al. U.S. Pat. No. 5,066,292 (the &#39;292 patent) entitled &#34;Catheter System For Vessel Recanalization In The Human Body.&#34; 
     In the catheter device of the &#39;310 patent, laser energy is output from a distal end via four directable optical fibers. The optical fibers are evenly spaced from one another about the lumen of the catheter. A segmented distal end portion of the catheter spreads apart to enlarge the optical fiber spacing. The expanded spacing of optical fibers redirects the path of the emitted laser energy. 
     In the catheter device of the &#39;292 patent, laser energy is also output from a distal end via directable optical fibers. The optical fibers are arranged in jointed groups. Upon expansion of the catheter a distal end portion of the ring of optical fibers is expanded only in selected regions between jointed groups. 
     Although the devices disclosed in the above patents provide directable laser energy, several disadvantages exist. As the distal end portion of each device expands, the laser energy per area (power density) necessarily decreases since each optical fiber or optical fiber group moves apart from adjacent optical fibers. This causes the power density to decrease at a rate inversely proportional to the expansion of the distal end portion. Decreased power density will increase the time and possibly reduce the effectiveness of the procedure to remove the corporal lumen obstruction. 
     There continues to be a need to provide a cost effective catheter for efficient delivery of directable radiant energy, such as laser, for ablation of obstructions in a corporal lumen. 
     SUMMARY OF THE INVENTION 
     A catheter device for controllable delivery of radiant energy to a selected region within a corporal lumen includes optical fibers for delivery of energy from an expandable elastomeric distal end. The expandable elastomeric distal end has a greater elasticity than the rest of the catheter. The optical fibers preferably are arranged at the distal end of the catheter into at least two generally adjacent, substantially concentric annular arrays or in a generally annular compartmental arrangement. The optical fibers can be situated along and substantially parallel thereto the axis of the catheter. Or, the optical fibers may form a helix about the longitudinal axis of the catheter as long as they conduct radiant energy to the distal end of the catheter. The individual optical fibers can be tapered to alter the cross-section toward the distal end to distribute the laser energy over a larger area, if desired. The optical fibers may also have varying diameters. 
     At their distal end portion, the optical fibers can be bundled together by an elastic casing or a conventional binder, such as an elastic potting material. The elastic potting material can fill the spaces between the optical fibers at the distal end portion. 
     Alternatively, the potting material can be used from about 4 cm to 20 cm from the distal end face to secure the optical fibers along the catheter. This arrangement is used when no potting material is used at the distal end portion of the catheter or when the potting material used at the distal end portion is too soft to allow polishing of the catheter without the inner potting of the optical fibers. 
     The catheter terminates in a distal end portion which is made of an elastomeric material that facilitates the expansion of the distal end together with the optical fibers. The distal end is expanded by an expansion device preferably from within the distal end portion of the catheter. This device is preferably of an inflatable nature, such as a balloon. Alternatively, the distal end can be expanded by applying a tapered device, such as a wedge, a camming surface of which can be urged into the distal end to achieve the desired expansion. 
     The expansion device is manipulated via a channel which is situated generally central in the catheter. The channel may be centered axially in the catheter. The channel may also define a conduit for a guidewire. The channel may terminate at the distal end, or in, adjacent, or proximal to the distal end portion. 
     When the expansion device is actuated, the distal end portion expands radially. As the distal end portion expands, the substantially concentric annular arrays of optical fibers are urged closer to one another and merge at least in part into a single annular array. Optical fibers from one array are urged into the spaces between optical fibers of an adjacent array. In effect, this expanded arrangement provides radiant energy delivery substantially uniformly about the circumference of that array. Thus, a predetermined density can be substantially maintained as the distal end of the catheter is expanded. 
     Other embodiments of the present invention include optical fibers having different diameters or cross-sectional geometries to facilitate this expanded arrangement. Moreover, a catheter having an exterior cross-sectional geometry that facilitates the merger of optical fiber-arrays upon expansion can also be utilized. For example, the body of the catheter may be axially fluted. Such a structure facilitates the merger of the optical fibers present since the fluted regions of the distal end portion deform more than the nonfluted regions. 
     A radiopaque marker can be situated at or near the distal end portion of the present laser catheter device so that the position of this device in a corporal lumen can be ascertained radiographically. 
     A preferred procedure to ablate an obstruction in a body corporal lumen, such as a blood vessel, using a catheter embodying the present invention includes the use of a guidewire the distal end of which is extended into or beyond the obstruction. Next, the laser catheter is inserted into the corporal lumen over the guidewire and advanced up to the obstruction. An expansion device, such as a balloon, is then expanded to a desired dimension to increase the diameter of a distal end portion of the catheter. Thereafter, laser energy is emitted from the distal end portion of the catheter to ablate the obstruction while the distal end portion of the catheter is urged forwardly. The expansion device, such as a balloon, may be disposed within the catheter beneath the elastomeric potting material encasing the distal ends of the optical fibers, or it may be mounted on the guidewire. 
     This procedure may also entail, after the distal end of the laser catheter has first passed through the obstruction, expanding the distal end of the catheter by the expansion means to further increase its diameter, activating the laser and pulling the catheter back through the obstruction in a retrograde manner, or withdrawing the catheter from the obstruction, expanding the distal end portion by the expansion means to further increase its diameter, and then again emitting laser energy, creating a relatively larger channel through the obstruction. 
     Another procedure can be performed where the expansion device alternatively expands and contracts the distal end portion of the catheter while laser energy is being emitted, and the distal end portion is urged through the obstruction. 
     Once the obstruction is minimized or removed, the catheter can be repositioned in the corporal lumen to the site of another obstruction, and the above procedures can be repeated. 
     Numerous other advantages and features of the present invention will become readily apparent from the following detailed description of the invention and the embodiments thereof, from the claims and from the accompanying drawings in which details of the invention are fully and completely disclosed as a part of this specification. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawings, 
     FIG. 1 is an overall, partially fragmented view of a laser catheter embodying the present invention; 
     FIG. 2 is an enlarged sectional view of the catheter distal end portion of the catheter shown in FIG. 1; 
     FIG. 3 is an end view of the catheter shown in FIG. 2; 
     FIG. 4 is a sectional view similar to that of FIG. 3 but in an expanded condition; 
     FIG. 5 is a graphical illustration of the catheter diameter as a function of applied pressure; 
     FIG. 6 is a cross-sectional view of an alternate embodiment of the expanding means of the present invention; and 
     FIG. 7 is a cross-sectional view of an alternative embodiment of the expanding means of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     While this invention is susceptible of embodiment in many different forms, there are shown in the drawings and will be described herein in detail specific embodiments thereof with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not to be limited to the specific embodiments illustrated. 
     As shown in FIG. 1, one preferred embodiment of a laser catheter assembly 10 according to the present invention includes a catheter 12, preferably associated with a conventional hemostatic &#34;Y&#34; connector 14 and hemostatic &#34;Y&#34; optical fiber port 11, through which optical fibers (not shown) extend into laser connector 18, as known in the art. Hemostatic &#34;Y&#34; connector 14 is connected to a syringe or inflation apparatus 16, as known in the art, and communicates with an inflation duct and a balloon (not shown) in catheter 12. Catheter 12 has a body portion 13 that terminates in a distal elastomeric end portion 20. Hemostatic &#34;Y&#34; fluid port 15 communicates with a central channel (not shown) in catheter 12, which channel extends through catheter body 13 and distal elastomeric end portion 20 for infusion of radio-opaque and other fluids. Extending through said central channel of catheter 12 is a conventional guidewire 22. 
     Referring to FIG. 2, the exterior of catheter 12 is defined by outer tube 24 which abuts distal end portion 20. Elastomeric skirt 21 is unitary with distal elastomeric end portion 20 and is attached to outer tube 24 by adhesive layer 23. Optical fibers 26 are situated along the longitudinal axis of the catheter and substantially parallel thereto. The sizes of individual optical fibers can vary. Also, the catheter distal end portion can include optical fibers of different diameters, some or all of which may be tapered to produce a larger end face area at their distal ends. Presently preferred are optical fibers having a core diameter of about 50 μm, but can range from about 30 μm to 300 μm. Hollow inner tube 44 is generally centrally located in catheter 12, defines a central channel 50 therethrough and may terminate at the distal end of distal elastomeric end portion 20 or may extend about 2 to 15 mm distally therefrom. Guidewire 22 slidably extends through the central channel 50 of inner tube 44. Middle hollow tube 28 may optionally be included to hold optical fibers 34 in place, extending through the central body of catheter 12 and terminating proximal to the main body of distal elastomeric end portion 20. 
     Distal elastomeric end portion 20 is made of an elastomeric material, such as polyurethane, having a Shore Durometer hardness value of about 70A. The elastomeric material holds the fibers in place for polishing their end faces, and it prevents broken fibers from exiting the laser catheter and their having to be removed from an artery surgically. Preferably the length-to-diameter ratio for the distal elastomeric end portion 20 is about 0.8 to about 1.2 for coronary artery use and about 1.5 to 0.8 for peripheral artery use. The external diameter of the distal end portion is substantially the same as that of catheter 12, itself, and can range from about 1.0 mm to about 6.0 mm. 
     In a typical laser catheter embodying the present invention for coronary artery use, the external diameter of the elastomeric distal end portion 20 in a non-expanded state is about 1.3 to 2.2 mm and the length of distal elastomeric end portion 20 extending distally from the distal end of outer tube 24 is about 1.5 to 4.0 mm. 
     For peripheral artery use, the external diameter of distal elastomeric end portion 20 in an unexpanded state is about 2.5 mm to 6.0 mm and the length of same extending from the distal end of catheter 12 is about 2.0 mm to 8.0 mm. 
     The composition of optical fibers 26 is dependent upon the type of laser energy that is to be transmitted through the fibers. Contemplated laser wavelengths for the present purposes are those of an excimer laser (wavelengths of 0.308 microns or 0.349 microns), requiring high OH quartz optical fibers; pulsed or continuous Nd:YAG lasers (wavelengths of 0.355 microns, 0.532 microns, 1.064 microns or 1,432 microns), enabling conventional quartz or fused silica optical fibers to be used; pulsed holmium:YAG lasers (wavelength of 2.01 microns), requiring low OH quartz optical fibers; and the like. 
     Catheter body portion 13 is composed, itself, of two portions. The distal 13-22 cm thereof has a shore hardness value of 100A, providing greater flexibility to the distal portion of catheter body portion 13. The proximal 100-120 cm portion of catheter body 13 has a shore hardness value of 60-70 D, providing greater pushability for that portion of body portion 13. These two segments are fused or bound together by a thermal welding process or an adhesive, as known in the art. 
     The distal ends of optical fibers 26 preferably are embedded in distal elastomeric end portion 20 and terminate at exposed end faces 34 that are substantially even with catheter distal end face 32. 
     A radiopaque material 39, such as platinum or gold foil, preferably is positioned proximal to the main body of distal elastomeric end portion 20, and may be attached to elastomeric skirt 21 thereof or to middle hollow tube 28, to enable monitoring of the location of the catheter tip within a body lumen radiographically. 
     An expansion chamber 36 is defined by the interior surface 38 of distal elastomeric end portion 20 and an expansion device, balloon 40, surrounding inner hollow tube 44. Balloon 40 is inflated through inflation duct 46 of balloon 40. Inflation duct 46 is in fluid communication with hemostatic &#34;Y&#34; connector 14 (not shown). 
     Inner tube 44 defines a central channel 50 for slidably receiving guidewire 22 which, as shown in FIG. 2, extends through central channel 50 and beyond the distal end face 32 of catheter 12. Hemostatic fluid port 15 (not shown) is in fluid communication with central channel 50 for infusion of radiopaque fluids, saline or drugs. Balloon 40 may be contiguous with balloon tube 48, or balloon 40 may be joined to balloon tube 48 by thermal welding and an adhesive, as known in the art. Balloon 40 and balloon tube 48 can be made of polyurethane tubing, or balloon tube 48 can be made of a less elastic grade of polyurethane tubing, a heat shrinkable plastic tubing or the like. 
     A preferred arrangement of exposed end faces 34 of optical fibers 26 can best be seen by reference to FIG. 3. Shown are four rows of optical fibers with respective end faces 34 arranged as generally adjacent, substantially concentric annular arrays embedded in distal elastic end portion 20. 
     The operation of the present preferred embodiment may be illustrated by referring to FIG. 4 in conjunction with FIG. 2. Balloon 40 is pressurized via inflation duct 46 and expands in cavity 36 against inner surface 38 of distal elastomeric end portion 20. As the diameter of distal elastomeric end portion 20 increases, the separate annular arrays of optical fibers 26 merge into a substantially narrower array of a substantially increased diameter. Optical fibers 26 in an outer annular array are repositioned during expansion of balloon 40 farther from one another forming a space therebetween. The formed space is then taken up, at least in part, by some of the optical fibers in the next inner array. 
     As shown in FIG. 4, as the respective individual annular arrays commingle, a single, substantially continuous annular array is maintained. Thus, laser energy from optical fibers 26 does not undergo a substantial loss in its energy density over the expanded annular arrays. 
     FIG. 5 shows the relationship between the diameter of distal elastic end portion of a catheter embodying this invention and the pressure applied to its expansion balloon. As can be seen, the diameter of distal elastomeric end portion is a generally linear function of the pressure applied to the balloon. 
     Optionally, the optical fibers 26 may be disposed in two or more bundles at their proximal ends and arranged in a similar number of sections in an annular array at their distal ends, so that the laser energy may be transmitted serially thereinto, from one bundle to the other, and emitted therefrom from one section to the next, or in such other pattern as may be desired. 
     In a alternative embodiment, as seen in FIG. 6, balloon tube 48 extends over guidewire 22 and terminates at balloon 40, which is disposed about guidewire 22 near its distal end. Guidewire 22 slidably extends through central channel 50 of laser catheter 12. Radiopaque markers 39(A) and 39(B) are disposed about the proximal and distal ends of balloon 40 to enable its position relative to radiopaque marker 39 of laser catheter 12 to be ascertained radiographically. Balloon 40 is inflated by inflation channel 46, which is created by the space between balloon tube 46 and guidewire 22. 
     As seen in FIG. 7, in this embodiment, balloon tube 48 is disposed about independent flexible tube 49 and terminates at balloon 40, which is disposed about the distal end of independent flexible tube 49, creating inflation channel 46 therebetween. Radiopaque markers 39(A) and 39(B) enable the location of the balloon 40 to be ascertained radiographically. This assemblage is slidably moveable through central channel 50 of laser catheter 12 (not shown). Guidewire 22 (not shown) is slidably moveable through central channel 51 of independent flexible tube 49. 
     Components such as lasers, laser connectors, optical fibers, guidewires, &#34;Y&#34; connectors, syringes and inflation devices, all as known in the art, are not described in detail herein and form no part of the present invention. Numerous variations and modifications of the embodiments described above may be effected without departing from the spirit and scope of the novel features of the invention. It is to be understood that no limitations with respect to the specific device illustrated herein are intended or should be inferred. It is, of course, intended to cover by the appended claims all such modifications as fall within the scope of the claims.