Abstract:
A tubular medical catheter having an inner liner comprising ultra high molecular weigh high density polyethylene, and methods of making the same, are provided herein.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to catheters having an inner liner comprising an ultra high molecular weight high density polyethylene (UHMW-HD PE). More specifically, the invention relates to catheters having an inner liner comprising an ultra high molecular weight high density polyethylene, the surface of which has been modified by a laser to enhance bonding between the inner liner and a polymer outer shell, and methods for making the same.  
         BACKGROUND OF THE INVENTION  
         [0002]    A number of intravascular procedures are currently utilized to treat a stenosis within a body vessel of a human being. A common intravascular procedure is referred to as percutaneous transluminal coronary angioplasty (PTCA or hereinafter “angioplasty”). During a typical angioplasty procedure, a guidewire is initially positioned within the body vessel and a guiding catheter is positioned over the guidewire. Next, a balloon catheter having an inflatable balloon is advanced through the guiding catheter and vessel until the balloon is adjacent to the stenosis. Subsequently, inflation of the balloon compresses the stenosis and dilates the body vessel.  
           [0003]    During many diagnostic or interventional catheterization procedures, it is necessary to route the catheter from an entry point, such as the femoral artery, to a target location within the vasculature. When a guiding catheter is properly placed into position, the balloon catheter, for example, should be able to be turned, pulled, and pushed so that the distal end of the catheter can navigate the twists and turns of guiding catheter on its path to the final location. In this regard, a guiding catheter having an inner liner that is manufactured using a lubricious material is helpful. Traditionally, Teflon® materials such as perfluoro ethylene-propylene (FEP) or polytetrafluoroethylene (PTFE) have been used to manufacture inner liners.  
           [0004]    The lubricious nature of Teflon® materials, however, makes them more difficult to bond to, for example, an outer shell without additional treatment of the surface of the inner liner. Typically, such surface treatment is carried out by a chemical etch process where, for example, the Teflon® material is subjected to an etch bath for a period of time sufficient to modify the surface of the Teflon® and enhance bonding to, for example, the outer shell.  
           [0005]    Another drawback to using inner liners manufactured using Teflon® materials such as PTFE is that these materials are often not melt-extrudable. As a consequence, PTFE, for example, can only be purchased in relatively short lengths, termed “sticks,” and thus requires inefficient one-at-a-time catheter manufacturing processes. In contrast, reel-to-reel processes are more cost-efficient than assembling catheters one-at-a-time.  
           [0006]    Accordingly, there is a need for a medical catheter that comprises an inner liner manufactured from a lubricious material that can bond to additional polymer materials, and that is simple to manufacture. The present invention addresses these needs, as well as other problems associated with existing medical catheters. The present invention also offers further advantages over the prior art and solves other problems associated therewith.  
         SUMMARY OF THE INVENTION  
         [0007]    The present invention is directed to medical catheters adapted for use within a body vessel. The medical catheter comprises a tubular catheter shaft having a distal end that fits within the body vessel. The tubular catheter shaft comprises an inner liner and an outer shell. The medical catheter comprises an inner liner that comprises UHMW-HD PE.  
           [0008]    In some embodiments, at least one region of the surface of the inner liner has been modified with a laser. The laser modification of the surface of the inner liner etches the surface of the inner liner and enhances bonding of the inner liner to other polymers, such as those that comprise the outer shell.  
           [0009]    In some embodiments, an adhesive bonds the modified surface of the inner liner to the outer shell. An example of a suitable adhesive is an epoxy.  
           [0010]    The present invention is also directed to methods for making a medical catheter having an inner liner comprising UHMW-HD PE. A medical catheter comprising a melt-extrudable UHMW-HD PE is provided. The surface of the inner liner is modified in a manner so as to enhance the bonding of the inner liner to another polymer. In some embodiments, the inner liner is modified using a laser to etch the surface of the inner liner. Upon modification of the surface of the inner liner, an adhesive is applied to enhance bonding to another polymer. In some embodiments, the inner liner and outer shell are bonded with adhesive, such as an epoxy. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]    The novel features of this invention, as well as the invention itself, both as to its structure and its operation, will be best understood from the accompanying drawings, taken in conjunction with the accompanying description, in which similar reference characters refer to similar parts, and in which:  
         [0012]    [0012]FIG. 1 is a perspective view, in partial cutaway, of a medical catheter having features of the present invention;  
         [0013]    [0013]FIG. 2 is an enlarged cutaway view of a portion of the medical catheter of FIG. 1;  
         [0014]    [0014]FIG. 3 is a perspective illustration of the medical catheter positioned within a patient; and  
         [0015]    [0015]FIG. 4 is an enlarged side plan assembly view of a portion of the catheter shaft illustrating a groove. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0016]    The present invention is directed to a catheter that has an inner liner comprising UHMW-HD PE. Any multi-layered medical catheter can be modified to have an inner liner comprising UHMW-HD PE. The catheters described herein are merely exemplary and the invention should not be construed to be limited to only the catheters described herein.  
         [0017]    Referring to FIGS. 1, 2, and  4 , a first embodiment of medical catheter  10  having features of the present invention includes tubular catheter shaft  12 , hub  14 , and tubular flexible tip  16 . Catheter shaft  12  can optionally include groove  18 , which is cut out of catheter shaft  12  near distal end  20  of catheter shaft  12 .  
         [0018]    Medical catheter  10  illustrated herein is utilized to guide an interventional catheter (not shown) and is commonly referred to as a guiding catheter. FIG. 3 illustrates a portion of medical catheter  10  and guidewire  22  positioned in body vessel  24  of patient  26  during a procedure. The location of entry into patient  26  and the location of distal end  20  in patient  26  are merely exemplary.  
         [0019]    Referring back to FIGS. 1 and 2, hub  14  is secured to proximal end  28  of catheter shaft  12  while flexible tip  16  is secured to distal end  20  of catheter shaft  12 . The physician manipulates hub  14  and proximal end  28  to position medical catheter  10  in body vessel  24 . Flexible tip  16  assists in guiding medical catheter  10  in body vessel  24  and minimizes the trauma to vessel  24  and coronary ostium (not shown).  
         [0020]    Flexible tip  16  is made of a relatively soft material when compared to the catheter shaft  12 . Suitable materials for flexible tip  16  may include polymers such as a polyether block amide (“PEBA”) having a hardness of about  40  Shore D. Depending upon the materials utilized, hub  14  and flexible tip  16  can be thermally bonded or attached with an adhesive (not shown) to catheter shaft  12 . Those skilled in the art will recognize alternate ways to attach hub  14  and flexible tip  16  and that alternate materials can be utilized for flexible tip  16 .  
         [0021]    In the embodiment illustrated in FIGS. 1 and 2, tubular catheter shaft  12  includes inner liner  30 , optional reinforcing section  32 , and outer shell  34 . Further, when the catheter comprises groove  18 , fill section  35  may be positioned in groove  18 . Inner liner  30  is tubular and defines lumen  36 , which is sized and shaped to receive, for example, guidewire  22  and subsequently an interventional catheter (not shown).  
         [0022]    Typically, inner liner  30  is manufactured by extruding UHMW-HD PE, which provides good flexibility and movement over guidewire  22 . The composition of the inner liner, however, is not limited to only this polymer and any suitable polymer having lubricious properties and which is melt-extrudable can be used so that the catheter has the desired properties. A suitable inner liner  30  has an inner diameter of between about 0.08 and 0.09 inches and an inner liner thickness of about 1.5 mils. An additional lubricious coating (not shown) may be added to lumen  36  of inner liner  30  to facilitate even more movement of inner liner  30  over guidewire  22  and the interventional catheter within lumen  36 .  
         [0023]    Outer shell  34  provides support to catheter shaft  12  and covers reinforcing section  32  to protect body vessel  24  from reinforcing section  32 . Further, outer shell  34  prevents reinforcing section  32  from unwrapping. Outer shell  34  is tubular and coaxial with inner liner  30  and optional reinforcing section  32 . A suitable outer shell  34  has an inner diameter of about 0.1 inches and wall thickness  40  of about 2.5 mils.  
         [0024]    Typically, outer shell  34  is manufactured by extruding a polymer over the reinforcing section  32 . A suitable shell material for outer shell  34  is a nylon sold under the trademark “TROGAMID” by Creanova (Somerset, N.J.). The shell material may have a hardness of approximately  81  Shore D. Additionally, a lubricious coating (not shown) may be added to outer shell  34  to facilitate movement of catheter shaft  12  within vessel  24 .  
         [0025]    Those skilled in the art will recognize alternate ways to manufacture inner liner  30 , reinforcing section  32 , and outer shell  34  and that alternate materials can be utilized for inner liner  30 , reinforcing section  32 , and outer shell  34 . Those skilled in the art will also recognize alternate ways to apply reinforcing section  32  on inner liner  30 .  
         [0026]    The surface of inner liner  30  is modified so as to enhance bonding with outer shell  34 . UHMW-HD PE, however, is chemically resistant and, thus, cannot be chemically etched so as to create a surface that can bond to outer shell  34 . A solution to this problem, however, is to utilize a laser to modify the surface of the UHMW-HD PE inner liner  30  to enhance bonding between UHMW-HD PE and outer shell  34 . After the inner liner surface has been prepared, an adhesive, such as an epoxy, can be used to bond inner liner  30  to outer shell  34 .  
         [0027]    Outer shell  34  is extruded or molded over inner layer  30 . Next, the composite catheter tubing can be severed at desired cut points, forming multiple sub-assemblies of intended catheter length. Finally, catheters  10  are finished by securing the remaining components.  
         [0028]    In some embodiments, inner liner  30  and/or outer shell  34  comprise unfilled or low-loaded thermoplastic polymers. For example, inner liner  30  and outer shell  34  each, independently, may include a radiopaque material and/or filler and/or colorant, such that the total content of the radiopaque material and/or filler and/or colorant in inner liner  30  and/or outer shell  34  is between about 0.1% and about 10%, or between about 0.1% and about 5%, or between about 0.1% and about 2% of the total weight making up inner liner  30  and/or outer shell  34 . In some embodiments, inner liner  30  and outer shell  34  each, independently, may exclude a radiopaque material and/or filler and/or colorant, thus having 0% by weight of the total weight making up inner liner  30  and/or outer shell  34 . An unfilled inner liner  30  and/or outer shell  34  have the advantages of retaining mechanical integrity and modulus of elasticity.  
         [0029]    In some embodiments, an optional reinforcing section  32  enhances the torsional strength and prevents or reduces kinking of catheter shaft  12  during movement of medical catheter  10  in body vessel  24 . Reinforcing section  32  can be embedded between inner liner  30  and outer shell  34  and is substantially coaxial with inner liner  30  and outer shell  34 . Reinforcing section  32  may be formed by braiding wire mesh around inner liner  30 . Subsequently, outer shell  34  is formed around reinforcing section  32  by applying materials making up the outer shell. In any of the above embodiments of the invention, the optional reinforcing section  32  can be created around etched inner liner  30  before outer shell  34  is formed.  
         [0030]    There are many benefits of a catheter having an inner liner comprising UHMW-HD PE. For example, such a catheter possesses a lubricious inner liner, which provides enhanced guidance properties. Such a catheter also can be made in a reel-to-reel fashion, which provides an increased ease of manufacture compared to catheters having PTFE inner liners.  
         [0031]    As illustrated in FIG. 4, catheter shaft  12  can optionally include groove  18 , which is cut out of catheter shaft  12  near distal end  20  of catheter shaft  12 , as described in U.S. Pat. No. 6,059,769, which is incorporated herein by reference in its entirety. Groove  18  provides flexibility at distal end  20  of catheter shaft  12  without compromising the durability and torsional strength of catheter shaft  12 . Further, groove  18  functions as transitional region  21  between relatively stiff catheter shaft  12  and flexible tip  16 . This prevents or reduces kinking and/or collapsing of medical catheter  10 . As a result thereof, medical catheter  10  has improved tracking and movement in the vessel. Fill section  35  may be positioned in groove  18 . An embodiment of the invention may combine filled groove  18  with one or more regions of selectively varied lamination  55  to achieve a desirable combination of mechanical properties.  
         [0032]    While the particular medical catheter  10  as herein shown and disclosed in detail is fully capable of obtaining the objects and providing the advantages herein before stated, it is to be understood that it is merely illustrative of the presently preferred embodiments of the invention and that no limitations are intended to the details of construction or design herein shown other than as described in the appended claims.  
         [0033]    Various modifications of the invention, in addition to those described herein, will be apparent to those skilled in the art from the foregoing description. Such modifications are also intended to fall within the scope of the appended claims. Each reference cited in the present application is incorporated herein by reference in its entirety.