COMPOSITE MATERIAL HAVING A LUBRICOUS SURFACE FOR CATHETER USE

Abstract: A low friction intravascular catheter (10) component formed of a polymer matrix having incorporated within the matrix a finely divided lubricous particulate. The polymer matrix preferably is a thermoplastic polymer and suitable lubricous particulate includes graphite, molybdenum disulfide, TiC, MoC, graphite difluoride, and fluoropolymers. Typical components made of this low-friction material include the inner (12) or outer tubular members (14) of fixed-wire and over-the-wire dilatation catheters (10). A polysiloxane fluid may be incorporated within the matrix along with the lubricous particulate matter.

Description: COMPOSITE MATERIAL HAVING A LUBRICOUS SURFACE FOR CATHETER USE BACKGROUND OF THE INVENTION This invention generally relates to intraluminal catheters, such as guiding catheters and balloon dilatation catheters used in percutaneous transluminal coronary angioplasty PTCA). In classic PTCA procedures, a guiding catheter having a preshaped distal tip is percutaneously introduced by a Seldinger technique into the cardiovascular system of a patient and advanced therein until the preshaped distal tip of the guiding catheter is disposed within the aorta adjacent the ostium of the desired coronary artery. The guiding catheter is twisted or torqued from the proximal end to turn the distal tip of the - 1 - guiding catheter so that it can be guided into the desired coronary ostium. In over-the-wire systems, a guidewire and a balloon dilatation catheter are introduced into and advanced through the guiding catheter to the distal tip thereof, with the guidewire slidably disposed within an inner lumen of the dilatation catheter. The guidewire is first advanced out the distal tip of the guiding catheter, which is seated in the ostium of the patient's coronary artery, until the distal end of the guidewire crosses the lesion to be dilated. The dilatation catheter is then advanced out of the distal tip of the guiding catheter, over the previously advanced guidewire, until the balloon on the distal extremity of the dilatation catheter is properly positioned across the lesion. Once properly positioned, the balloon is inflated to a predetermined size with radiopaque liquid at relatively high pressures (e.g., generally 4-12 atmospheres) to dilate the stenosed region of the diseased artery. One or more inflations may be necessary to effectively dilate the stenosis. Additional stenoses may be dilatated with the same catheter. When the dilatations are completed, the balloon is deflated so that the dilatation catheter can be removed from the dilated stenosis and blood flow will resume through the dilated artery. Further details of guiding catheters, dilatation catheters, guidewires, and other devices for angioplasty procedures can be found in U.S. Patent 4,323,071 (Simpson-Robert); U.S. Patent 4,439,185 (Lundquist); U.S. Patent 4,468,224 (Enzmann et al); U.S. Patent 4,516,972 (Samson); U.S. Patent 4,438,622 (Samson et al); U.S. Patent 4,554,929 (Samson et al); U.S. Patent 4,582,185 (Samson); U.S. Patent 4,616,652 (Simpson); U.S. Patent 4,638,805 (Powell); U.S. Patent 4,748,986 (Morrison et al); U.S. Patent 4,898,577 (Badger et al); and U.S.Patent 4,827,943 (Taylor et al.) which are incorporated herein in their entirety by reference thereto. Fixed-wire dilatation catheters for coronary angioplasty, which were first described in U. S. Patent 4,252,181 (Samson) now Reissue patent 33,166, are similarly used except there is no longitudinal movement between the guidewire and the catheter. The fixed-wire dilatation catheters generally have an outer tubular member with an inflatable balloon on the distal section thereof which is capable of dilating a stenosis, and a guiding member extending out through the distal end of the balloon which aids in advancing the catheter to a desired location within the patient's vasculature. They also usually have no inner tubular member and therefore have lower profiles, e.g. transverse dimensions, than over-the-wire dilatation catheters having the same inflated balloon size. Moreover, because the fixed-wire catheters have the guidewire or guiding member fixed or at least restricted as to longitudinal movement, these catheters generally have greater pushability than over-the-wire type catheters such as described and claimed in U.S. Patent 4,323,071 (Simpson-Robert). The lower profile and greater pushability of the fixed-wire dilatation catheters allows them to cross tighter lesions and to be advanced much deeper into a patient's coronary anatomy than the over-the-wire dilatation catheters of comparable sizes. Various improvements have been made to intravascular catheters used in angioplasty and other intravascular procedures. Of particular note is a rapid exchange type catheters described and claimed in U.S. Patent 5,040,548 (Yock), U.S. Patent 5,061,273 (Yock), and U.S. Patent 4,748,982 (Horzewski et al), which are incorporated herein in their entirety by reference. The rapid exchange type dilatation catheter has a short guidewire receiving sleeve or inner lumen extending through the flexible distal portion of the catheter which extends out of the guiding catheter into the patient's coronary artery during the angioplasty procedure. The sleeve extends proximally a distance of at least 10 cm and usually not more than about 50 cm from a first guidewire port in the distal end of the catheter to a second guidewire port in the catheter spaced proximally from the inflatable balloon of the catheter. A slit, as described in Horzewski et al, is preferably provided in the catheter wall which extends distally from the second guidewire port, preferably to a location proximal to the proximal end of the inflatable balloon to aid in the removal of the catheter from a guidewire. The structure of the catheter allows for the rapid exchange of the catheter without the need for the use of an exchange wire or adding a guidewire extension to the proximal end of the guidewire. The design of this catheter has been widely praised by the medical profession and has met with much commercial success in the market place because of its unique design. A substantial improvement in the rapid exchange type dilatation catheters, such as described above, has recently been made by Mclnnes et al. which is described in copending applications Serial No. 07/476,056, filed February 7, 1990 and Serial No. 07/541,264 filed June 19, 1990, both entitled READILY EXCHANGEABLE PERFUSION DILATATION CATHETER, and which are incorporated herein by reference. In these rapid exchange type dilatation catheters, perfusion ports are provided in the catheter shaft, proximal and distal to the balloon, which are in fluid communication with the guidewire receiving inner lumen to allow blood to perfuse distal to the catheter when the balloon is inflated. Lubricous coatings have been applied to the surfaces of guiding catheters, dilatation catheters and other intraluminal catheters in order to reduce the friction between the surfaces of these catheters and other components of the catheter systems in which the catheters are employed during the intravascular procedures. For example, fluoropolymer linings such as Teflon ® are very frequently employed as the inner linings of guiding catheters in order to reduce the friction between the inner lining of the guiding catheter and the guidewire and the catheters which might be advanced through the inner lumen of the guiding catheter. Lubricous silicone coatings have been applied to the surfaces of guidewires and of dilatation catheters to likewise reduce the frictional characteristics of these devices. However, the application of these lubricous coatings and linings are for the most part complicated manufacturing processes. Moreover, very frequently these coatings and linings are not very durable and lose substantial portions of their lubricity during the intraluminal or intravascular procedure. What has been needed and heretofore unavailable is a durable high strength plastic surface having long lasting lubricity which does not require complicated manufacturing procedures. The present invention satisfies this and other needs. SUMMARY OF THE INVENTION The present invention is directed to an improved composite plastic material having a very durable lubricous surface and particularly to tubular products for intraluminal catheter procedures within a human patient made from such composite materials. The material of the invention generally includes a biocompatible polymer matrix having finely divided lubricous particulate matter incorporated within the matrix. The polymer matrix can be formed of thermoplastic or thermosetting materials, or mixtures thereof. However, thermoplastic materials, particularly thermoplastic polymers having substantial crystallinity such as polyethylene, are preferred when the final product has a tubular shape because thermoplastic resins can be more easily extruded or otherwise formed in a conventional fashion. When the lubricous particulate is well dispersed within the polymer matrix the extrusion pressure or other forces needed to form the product are significantly lowered and there is much better dimensional control during the extrusion process than the same plastic materials without the lubricous particulate matter incorporated therein. Increased strengths in addition to decreased frictional characteristics are also obtained by the incorporation of the lubricous particulate. The coefficient of friction of this material ranges from about 0.03 to about 0.20. The tubular products of the invention can be formed into the shafts or inflatable members, e.g. balloons, of intraluminal catheters such as balloon dilatation catheters for angioplasty procedures in a conventional manner. Both the shafts and the balloons exhibit the same improvements in lubricity and strength with the materials of the invention. These and other advantages of the invention will become more apparent from the following detailed description of the invention when taken in conjunction with the accompanying exemplary drawings. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is an elevational view, partially in section of a balloon dilatation catheter embodying features of the invention. Fig. 2 is a transverse cross-sectional view of the catheter shown in Fig. 1 taken along the lines 2-2. Fig. 3 is a transverse cross-sectional view of the catheter shown in Fig. 1 taken along the lines 3-3. DETAILED DESCRIPTION OF THE INVENTION Figs. 1-3 illustrate a balloon dilatation catheter which embodies features of the invention. The dilatation catheter generally includes an outer tubular member 10, a dilatation balloon 11 on the distal portion of the outer tubular member, an inner member 12 disposed within the outer tubular member and the balloon and a multi-arm adapter 13 mounted on the proximal ends of the inner and outer tubular members. The distal end of the balloon 11 is sealed about the distal end of the inner tubular member 12 so that injection of inflation fluid under significant pressure through annular lumen 14 to the interior of the balloon will result in the inflation thereof. A guidewire 15 is slidably disposed within the inner lumen 16 of the inner tubular member 12. The distal end of the catheter is provided with a self venting means such as described in U.S. Patent 4,638,805 (Powell). A radiopaque marker 17 is disposed about the inner tubular member 12 at the mid-point of the balloon 11 to facilitate the fluoroscopic observation thereof during an angioplasty procedure. The brachial marker 20 and femoral marker 21 are provided on the proximal end of the inner tubular member 12. In accordance with the invention, the inner tubular member 12 is formed of composite material which generally includes a polymer matrix, preferably a readily extrudable thermoplastic polymer and incorporated within the polymer matrix is a finely divided lubricous particulate matter which range on the average from about 0.1 to about 100 microns, preferably about 0.5 to about 20 microns, in maximum dimensions. The amount of particulate matter in the polymer matrix thereof may range from about 0.5 to about 50%, preferably about 2 to about 20%, of the precured mixture thereof. As used herein all percentages are weight percent unless noted otherwise. Up to about 1% of a dispersing agent, such as lecithin, silicone oil, vegetable oil, polyethylene wax or mixtures thereof, may be incorporated into the mixture to facilitate effective mixing of the particulate within the polymer resin. A commercially available cooking oil described at least in part in U.S. Patent 4,188,412 and sold under the trademark PAM £ by Boyle-Midway Products, Inc., New York, New York, has been found to be particularly suitable. Particularly suitable lubricous particulate materials include graphite, fluoropolymers such as Teflon ® , molybdenum disulfide, titanium carbide, molybdenum carbide, graphite difluoride or mixtures thereof. Presently preferred lubricous particulate include Micro 850 and Micro 250 graphite available from the Asbury Graphite Mills, located in Asbury County, New Jersey. This graphite has an average maximum particle size from about 3 to about 10 microns in maximum dimension. In addition, silicone oils such as dimethylsiloxane polymers with a viscosity between about 300 and 100,000 centipoise, preferably about 1000 to about 30,000 centipoise, can be incorporated along with the solid lubricous particulate in amounts of up to 10%, preferably about 0.5 to about 4%. Suitable polymer materials include thermoplastic and thermosetting polymers or mixtures thereof, although thermoplastic polymer resins are preferred because of their ease in manufacturing tubular and other products by extruding and other types of pressure forming. Polymer materials such as polyethylene, polypropylene, polyvinyl chloride, polyethylene terephthalate, polyesters (e.g. nylon) and ionomers (e.g. Surlyn ® such as 8020 sold by E.I. duPont, deNemours & Co.) are particularly suitable. Blends of such materials may also be used. Formation of the products of the invention typically involve intimately mixing the lubricous particulate into the uncured polymer resin which forms the matrix of the cured product. A dispersant may be first mixed with the lubricous particulate to facilitate a more uniform dispersement of the particulate throughout the uncured resin. The dispersant may be advantageously added to the lubricous particulate as a solution of isopropyl alcohol or other suitable solvent to facilitate the incorporation thereof. The finely divided lubricous particulate has a tendency to agglomerate and an intimate and uniform mixture of the particulate within the polymer matrix can be very difficult to obtain without a dispersant. The polymer-parti cul ate mixture is then preferably extruded in a conventional manner into a tubular product having the desired dimensions. After extruding, the tubular product is then cured. If the polymer matrix is a thermoplastic material such as polyethylene, the extruded product may be cross-linked or modified by a conventional radiation treatment with gamma radiation or peroxide or other inorganic catalysts. Radiation levels of about 2 to about 150 //rads has been found to be suitable. After curing the tubing may be cut to the desired length depending upon the ultimate end use thereof. If the tubular product is to be used to form an inflatable member (e.g. a balloon) for an angioplasty catheter such as element 12 shown in the drawings, the distal portion of the tubular product is disposed within the interior of a hollow mold, which has the desired shape of the inflatable member to be made, and then the interior of the distal portion of the tubular product is subjected to heat and pressurized fluid to expand the distal section within the mold to form the inflatable member of the desired size and shape. To illustrate a presently preferred embodiment, a 4000 gram mixture was prepared containing 3830 grams (95.75%) of high density polyethylene, 160 grams (4%) of Micro 250 graphite and 10 grams (0.25%) of lecithin. The lecithin was first dissolved in 200 ml of isopropyl alcohol and then mixed with the graphite to form a homogeneous mass. The graphite with dispersant was then mixed with the polyethylene in a stainless steel tumbler for 16 hours and then extruded into pellets of about 5-6 mm. The pellets were extruded into a tubular product having nominal inner and outer diameters of about 0.019 and 0.0256 inch (0.48-0.65 mm), respectively, and the extruded tubular member was irradiated with gamma radiation at a level of about 10 μrads. The tubular member was then cut to length and used in the manufacture of a prototype dilatation catheter as shown in Figs. 1-3. The tubular member had a coefficient of friction of about 0.1. While the invention has been described herein primarily in terms of an inner tubular member for an over-the-wire type dilatation catheter of concentric design, the composite material of the invention can be utilized in a wide variety intraluminal catheter components. For example, the material can be used to form the outer tubular member in an over-the- wire dilatation catheter or a fixed-wire dilatation catheter. All or a portion of the outer tubular member may be formed of the polymer matrix-fmely divided lubricous particulate. The material can also be used to form the inflatable member or balloon of a dilatation catheter. Guidewire receiving inner tubular members such as described in the Yock and Horzewski et al. patents, which have been incorporated herein, may be made of the composite material formed of polymer and low friction particulate. Another use is the formation of guiding catheters in which the composite material is used to form at least the inner liner of the catheter to provide the lubricous inner lumen required in this type of intravascular catheter. Other uses include shafts and inflatable members of urethral dilatation catheters and Foley type catheters. While the invention is described herein in terms of certain presently preferred embodiments, those skilled in the art will recognize that various changes and improvements can be made to the present invention without departing from the scope thereof.

Claims: WHAT IS CLAIMED IS: 1. A dilatation catheter comprising: a) an elongated catheter shaft which is formed at least in part of a first tubular member having a lubricous surface comprising a thermoplastic polymer matrix and finely divided solid lubricous particulate material dispersed within the matrix which defines a guidewire receiving inner lumen extending within the first tubular member; and b) an inflatable member on a distal portion of the elongated catheter shaft having an interior in fluid communication with an inner inflation lumen extending within the catheter shaft. 2. The dilatation catheter of claim 1 wherein the catheter shaft has a second tubular member disposed about the first tubular member and defining with the first tubular member the inner inflation lumen. 3. The dilatation catheter of claim 2 wherein the second tubular member has an inflatable element formed in a distal extremity thereof which has an interior in fluid communication with the inner inflation lumen. 4. The dilatation catheter of claim 1 wherein the solid lubricous particulate material is selected from the group consisting of graphite, molybdenum disulfide, TiC, MoC, graphite difluoride, fluoropolymers and mixtures thereof. 5. The dilatation catheter of claim 1 wherein the lubricous particulate material has an average particle size of about 0.1 to about 100 microns in maximum dimension. 6. The dilatation catheter of claim 1 wherein the lubricous particulate has an average particle size of about 0.5 to about 20 microns in maximum dimension. 7. The dilatation catheter of claim 1 wherein the amount of lubricous particulate matter ranges from about 0.5 to about 50% of the composite material. 8. The dilatation catheter of claim 1 wherein the amount of lubricous particulate matter ranges from about 1 to about 25% of the lubricous surface. 9. The dilatation catheter of claim 1 wherein the lubricous surface is formed from a mixture of thermoplastic polymer, solid lubricous particulate matter and from about 0.01 to about 5% of a dispersing agent. 10. The dilatation catheter of claim 1 wherein the lubricous surface is formed from a mixture of polymer, lubricous particulate matter and from about 0.05 to about 1% of a dispersing agent. 11. The dilatation catheter of claim 10 wherein the dispersing agent is selected from the group consisting of lecithin, silicone oil, vegetable oil, polyethylene wax and mixtures thereof. 12. A dilatation catheter comprising: a) an elongated catheter shaft which has a surface which is formed at least in part of a composite material including a thermoplastic polymer matrix and finely divided, solid lubricous particulate material dispersed within the polymer matrix; and b) an inflatable member on a distal portion of the elongated catheter shaft having an interior in fluid communication with an inner lumen extending within the catheter shaft. 13. The dilatation catheter of claim 12 wherein the catheter shaft is a tubular element formed of the composite material and has a guiding element extending at least through a portion of the inflatable member. 14. The dilatation catheter of claim 12 wherein the inflatable member is formed of the composite material. 15. The dilatation catheter of claim 1 - 1' wherein the plastic matrix is formed of a biocompatible polymer material. 15. The dilatation catheter of claim 1 wherein the plastic matrix is formed of a biocompatible polymer material. 16. The dilatation catheter of claim 1 including a silicone oil incorporated within the matrix. 17. The composite material of claim 1 having a coefficient of friction from about 0.03 to about 0.2. 18. A method for making a component for an intravascular catheter having a durable lubricous coating thereon comprising: a) mixing a biocompatible polymer resin with lubricous particulate; b) forming the resin-particulate mixture into a desired shape for the component; and c) curing the resin-particulate in the desired shape to form the component. 19. The method of claim 18 wherein the resin-particulate mixture is formed into a desired shape by extruding the mixture. 20. The method of claim 18 wherein the formed resin-particulate mixture is cured by radiation. 21. The method of claim 18 wherein the desired shape is a hollow tube. 22. The method of claim 21 including the step of applying internal fluid pressure within the hollow tube with a portion of said tube disposed within the interior of a hollow mold at sufficient pressure and temperature to cause the portion of the tube within the mold to expand therein and take the shape of the interior thereof. 23. The method of claim 18 wherein the polymer resin is a thermoplastic resin. 24. The method of claim 18 wherein the lubricous particulate is selected from the group consisting of graphite, molybdenum disulfide, TiC, MoC, graphite difluoride, fluoropolymers and mixtures thereof. 25. The method of claim 24 wherein the lubricous particulate material has an average particle size of about 0.1 to about 100 microns in maximum dimension. 26. The method of claim 24 wherein the lubricous particulate material has a particle size of about 0.5 to about 20 microns in maximum dimension. 27. The method of claim 24 wherein the amount of lubricous particulate matter ranges from about 0.5 to about 50%. 28. The method of claim 24 wherein the amount of lubricous particulate matter ranges from about 1 to about 25%. 29. The method of claim 24 wherein from about 0.05 to about 1% of a dispersing agent is mixed with the polymer and lubricous particulate matter. 30. The method of claim 24 wherein the dispersing agent is selected from the group consisting of lecithin, silicone oil, vegetable oil, polyethylene wax and mixtures thereof. 31. An intravascular catheter comprising an elongated extruded tubular element having a lubricous surface formed of a thermoplastic polymer matrix and finely divided solid lubricous particulate material well dispersed within the matrix. 32. The intravascular catheter of claim 31 having a second tubular member with an inner lumen extending therein with the extruded tubular element having a lubricous surface is disposed within the inner lumen of the second tubular member. 33. The intravascular catheter of claim 31 wherein the extruded tubular element is an outer tubular member and has formed therein an inflatable element. 34. The intravascular catheter of claim 31 wherein the lubricous particulate material is selected from the group consisting of graphite, molybdenum disulfide, TiC, MoC, graphite difluoride, fluoropolymers and mixtures thereof. 35. The intravascular catheter of claim 31 wherein the lubricous particulate material has an average particle size of about 0.1 to about 100 microns in maximum dimension. 36. The intravascular catheter of claim 31 wherein the lubricous particulate has an average particle size of about 0.5 to about 20 microns in maximum dimension. 37. The intravascular catheter of claim 31 wherein the amount of lubricous particulate matter ranges from about 0.5 to about 50%. 38. The intravascular catheter of claim 31 wherein the amount of lubricous particulate matter ranges from about 1 to about 25%. 39. The intravascular catheter of claim 31 formed from a mixture of polymer, lubricous particulate matter and from about 0.01 to about 5% of a dispersing agent. 40. The intravascular catheter of claim 31 formed from a mixture of polymer, lubricous particulate matter and from about 0.05 to about 1% of a dispersing agent. 41. The intravascular catheter of claim 33 wherein the dispersing agent is selected from the group consisting of lecithin, silicone oil, vegetable oil, polyethylene wax and mixtures thereof. 42. The intravascular catheter of claim 31 wherein the tubular element having a lubricous surface defines a short guidewire receiving inner lumen of a readily exchangeable dilatation catheter. 43. The intravascular catheter of claim 31 wherein the tubular element having a lubricous surface is an outer tubular element of a fixed-wire dilatation catheter. 44. The intravascular catheter of claim 31 wherein the tubular element having a lubricous surface has an inflatable member formed therein.

Inventors: AINSWORTH ROBERT D, CHENG TAI CHUN, HARRINGTON DOUGLAS C, AINSWORTH, ROBERT, D., CHENG, TAI, CHUN, HARRINGTON, DOUGLAS, C.
Applicants: ADVANCED CARDIOVASCULAR SYSTEM, ADVANCED CARDIOVASCULAR SYSTEMS, INC.
Application year: 1993
Main classification: A61M29
IPC codes: A61L29, A61M25, A61M29