Abstract:
A wire guide has first and second portions with first and second diameters, respectively. A resilient loop positions a distal end of the wire guide adjacent another section of the wire guide. A closure member maintains the distal end in a fixed position relative to the remainder of the wire guide. A covering may be positioned around one or more parts of the wire guide.

Description:
RELATED APPLICATIONS  
       [0001]    This application claims the benefit of the filing date under 35 U.S.C. § 119(e) of Provisional U.S. Patent Application Serial No. 60/430,466, filed Dec. 2, 2002, which is incorporated by reference in their entirety. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The present invention relates to wire guides used in the placement of medical devices. More specifically, the present invention relates to a wire guide having a loop tip.  
         BACKGROUND OF THE INVENTION  
         [0003]    Wire guides are elongate flexible members used to provide a path along which another medical device can be moved. The path provided by the wire guide can be used to navigate another medical device, such as a catheter, through a body vessel. The use of wire guides to define such a path is known in the art. Briefly, a wire guide is navigated through a body vessel toward a point of treatment. Once positioned within the vessel, a second medical device, frequently a cannula such as a catheter is placed over the wire guide and moved along its length toward the point of treatment. Thus, the wire guide provides an established path for placing other devices, eliminating the need for performing delicate navigation procedures for each device passed into the vessel.  
           [0004]    During placement of a wire guide, an operator must navigate the wire guide through the vessel(s). Often, the vessel defines a torturous path due to the presence of natural bends and/or curves, or unnatural impediments, such as tumors, build-ups, and/or strictures. The presence of a torturous path may make navigation of a wire guide difficult. For example, the presence of an impediment may block the wire guide from navigating further into the vessel.  
           [0005]    The prior art contains many examples of wire guides having straight flexible tips intended to aid in the navigation around such impediment. The presence of a straight flexible tip, however, may in fact make navigation more difficult. For example, upon encountering an impediment, the straight flexible tip may bend toward one of the vessel walls, which may result in unintended contact between the tip and vessel wall. This situation may lead to undesirable effects in the vessel wall. Further, the straight tip may bend and turn back upon itself upon encountering the impediment. This formation of an unstable turn in the wire guide makes further navigation difficult.  
         BRIEF SUMMARY OF THE INVENTION  
         [0006]    The present invention provides a wire guide having a loop in one end. In one embodiment, a wire guide according to the present invention comprises an elongate member having a first portion with a first diameter and a second portion with a second diameter. The second diameter is smaller than the first diameter. The elongate member defines a loop, and a closure member closes the loop.  
           [0007]    In one embodiment, the elongate member further comprises an intermediate region defining a taper from the first diameter to the second diameter. Preferably, the loop places a distal end of the wire guide adjacent this intermediate portion. Alternatively, the loop can place the distal end adjacent the second portion.  
           [0008]    The second portion can define a portion of the loop, or the entire loop. If present, the intermediate portion can define a portion of the loop.  
           [0009]    The loop is resilient and is preferably fixed in overall size. The closure member preferably fixes the distal end relative to another portion of the elongate member. Also preferable, the loop defines a loop width that is greater than the first diameter of the first portion of the elongate member.  
           [0010]    In one embodiment, a covering is positioned over at least the closure member. Particularly preferable, the covering is positioned over the closure member and at least the first portion of the elongate member. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]    [0011]FIG. 1 is a side view of a wire guide according to a first embodiment of the invention.  
         [0012]    [0012]FIG. 2 is a side view of a wire guide according to a second embodiment of the invention.  
         [0013]    [0013]FIG. 3 is a side view of a wire guide according to a third embodiment of the invention.  
         [0014]    [0014]FIG. 4 is an elongate cross-sectional view of a wire guide according to a fourth embodiment of the invention.  
         [0015]    [0015]FIG. 5 is a side view illustrating a wire guide according to the present invention encountering an impediment in a body vessel.  
         [0016]    [0016]FIG. 6 is a side view illustrating a wire guide according to the present invention encountering a torturous path within a body vessel.  
         [0017]    [0017]FIG. 7 is a side view of a wire guide according to a fifth embodiment of the invention.  
         [0018]    [0018]FIG. 8 is a side view of a wire guide according to sixth embodiment of the invention.  
         [0019]    [0019]FIG. 9 is a side view of a wire guide according to a seventh embodiment of the invention.  
         [0020]    [0020]FIG. 10 is a side view of a wire guide according to an eighth embodiment of the invention.  
         [0021]    [0021]FIG. 11 is a side view of a wire guide according to a ninth embodiment of the invention.  
         [0022]    [0022]FIG. 12 is a side view of a wire guide according to a tenth embodiment of the invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0023]    [0023]FIG. 1 illustrates a wire guide  10  according to a first embodiment of the present invention. The wire guide comprises an elongate member  12  having a first portion  14  with a first diameter  16  and a second portion  18  with a second diameter  20 . The second diameter  20  is smaller than the first diameter  16 . The elongate member  12  has an intermediate portion  21  that defines a taper from the first diameter  16  to the second diameter  20 .  
         [0024]    The elongate member  12  defines a loop  22 . In the presently preferred embodiment, the loop  22  comprises a section of the elongate member  12  bent back upon itself. As illustrated in FIGS. 1 and 2, the second portion  18  preferably defines the entire loop  22 . Alternatively, as illustrated in FIG. 3, the second portion  18  can defines only a portion of the loop  22 . In this embodiment, the intermediate portion  21  preferably defines at least a portion of the loop  22 .  
         [0025]    Preferably, as illustrated in the figures, the loop  22  comprises a curvilinear loop forming a generally ovoid shape. Also preferable, the loop  22  has a loop width  23  that is greater than the first diameter  16  of the first portion  14  of the elongate member  12 . The term ‘loop width’ refers to the distance between the two outer most surfaces of the elongate member  12  at the widest portion of the loop  22 .  
         [0026]    The elongate member  12  has a distal end  26  and a distal tip  28 . Preferably, the distal tip  28  tapers from the second diameter  20  to a smaller diameter, and particularly preferably tapers to a point. As illustrated in FIGS. 1 and 7, the loop  22  is preferably formed in a manner that positions the distal end  26  adjacent the intermediate portion  21 . Preferably, this placement also positions the distal tip  28  adjacent the intermediate portion  21 . Such placements provide a low profile over the portion of the elongate member  12  that has a double width (i.e., two sections of the elongate member  12 ). Alternatively, as illustrated in FIG. 2, the loop  22  can be formed such that the distal end  26  is positioned adjacent the second portion  18  of the elongate member  12 .  
         [0027]    Any method of forming loop  22  is contemplated. In one preferred embodiment, a closure member  24  closes the loop  22  such that no opening exists to the interior space of the loop  22 . As illustrated in FIGS. 1-7, the closure member  24  preferably positions the distal end  26  adjacent another portion of the elongate member  12 . Any suitable closure member can be used, including bonds, adhesives, and separate members. Examples of suitable closure members include sutures or other appropriate material tying the two sections together, adhesive bonds and other bonds (such as a solder bond, a welded bond, or a molded bond) and a connector (such as a rivet). As best illustrated in FIGS. 1-7, the closure member  24  preferably is a cannula defining an interior lumen. Two sections of the elongate member are positioned within the cannula to form the loop  22 . As shown in FIG. 7, the cannula preferably extends over and covers the distal end  26  and distal tip  28 . Preferably, the closure member  24  is tightened, such as by crimping, to fix the loop  22  in overall size.  
         [0028]    In the alternate preferred embodiment shown in FIG. 8, the closure member comprises a molded bond  25 . The loop  22  of wire guide  10  is formed by molding two sections of the elongate member together. In another alternate preferred embodiment shown in FIG. 9, the closure member comprises a solder or welded bond  27 . Two sections of the elongate member are welded or soldered together to form loop  22 . In the alternate preferred embodiments shown in FIGS. 10-12, the closure member comprises a coil  29 . The loop  22  of wire guide  10  is formed from a coiled wire. More specifically, two sections of the elongate member are wound about each other. Preferably, the distal end  26  is wound such that a low profile is achieved. As shown in FIG. 10, the coil  29  positions the distal end  26  adjacent the intermediate portion  21 . Alternatively, the coil  29  may extend along the length of elongate member as shown in FIG. 11. As shown in FIG. 12, the diameter of the first portion may be approximately the same as the diameter of the second portion. In yet another alternate preferred embodiment, the loop  22  and elongate member  12  of wire guide  10  may be formed using laser cutting techniques as are known to those skilled in the art.  
         [0029]    Any suitable material can be used for the elongate member  12 , and a variety of suitable materials are known to those skilled in the art. The material chosen need only be biocompatible and able to be formed into the structures described herein. Examples of suitable materials include stainless steel and nitinol. The elongate member  12  may comprise a wire, a tubular member or a sheet of material. Further, the elongate member  12  can be formed of a series of layers, or as a coated core structure. For example, in one embodiment, the elongate member  12  comprises a nitinol core with a polytetrafluoroethylene covering.  
         [0030]    The closure member  24  can be formed of any suitable material, and need only be biocompatible and capable of maintaining the loop  22  in a closed position. Preferably, the closure member  24  comprises a cannula formed of stainless steel or nitinol. Also preferable, the closure member  24  is able to maintain a tightened position on the elongate member  12  upon application of a suitable force, such as by applying a crimping workload to the closure member  24 .  
         [0031]    A variety of shapes and sizes of elongate members and loops can be used, and these can both be optimized based on particular applications. The dimensions of the elongate member  12  and loop  22  will depend upon various factors, including the intended use of the wire guide and the vessels into which the wire guide will be positioned. For a wire guide intended to cannulate the common bile duct, suitable dimensions include a first diameter  16  of between approximately 0.016 inches and approximately 0.038 inches, and preferably comprises a diameter of approximately 0.035 inches. The second diameter  20  of the wire guide preferably has a diameter of between approximately 0.003 inches and approximately 0.010 inches, and preferably comprises a diameter of approximately 0.006 inches. The intermediate portion of this wire guide defines a taper between the first diameter  16  and the second diameter  20 . The taper may be smaller or approximately the same size as the second diameter  20 . Preferably, the intermediate portion defines a taper from approximately 0.006 inches to approximately 0.016 inches. For this wire guide, the loop is preferably ovoid in shape with a length of between approximately 4 and approximately 5 millimeters, and a width of between approximately 2 and approximately 3 millimeters.  
         [0032]    [0032]FIG. 4 illustrates a wire guide  10  according to a fourth embodiment of the present invention. In this embodiment, a covering  30  is positioned over the closure member  24 . The covering  30  can be polytetrafluoroethylene, or another suitable material. Examples of suitable coverings include fluoropolymers, polyurethanes, and other suitable coatings used in the medical device arts. Also, the covering  30  preferably is positioned over the closure member  24  and at least a section of the first portion  14 . Particularly preferable, the covering is positioned over the first  32  and second  34  transition areas between the closure member  24  and the elongate member  12 . This positioning of the covering  30  ensures a smooth surface at the transition areas  32 ,  34 .  
         [0033]    Alternatively, the covering  30  can comprise a coating on the elongate member  12 . The coating is preferably applied to the entire elongate member  12 , including the loop  22 . Alternatively, the coating can be applied to only a portion of the elongate member. The coating may be applied by dipping, molding, or spraying a suitable coating material, such as polytetrafluoroethylene, urethane, and/or other polymeric coatings, directly to the elongate member  12 .  
         [0034]    A thin PTFE heat shrinkable material is a preferred coating. The heat shrinkable nature of these materials facilitate manufacturing while providing a lubricious coating, which facilitates navigation. In preferred embodiments, the thickness of the coating is between approximately 0.001 and 0.010 inches. In particularly preferred embodiments, the thickness of the coating is between approximately 0.001 and 0.005 inches. In still more preferred embodiments, the thickness of the coating is between approximately 0.001 and 0.002 inches. These preferred thicknesses provide suitable coatings while not adding significantly to the overall thickness of the device.  
         [0035]    Also, the wire guide  10 , with or without the covering  30 , may be treated with a hydrophilic coating or hybrid polymer mixture, such as those based on polyvinyl puroladine and cellulose esters in organic solvent solutions. These solutions make the wire guide particularly lubricious when in contact with body fluids, which aids in navigation.  
         [0036]    Radiopaque materials such as bismuth or gold can be added in the covering  30 . Also, radiopaque markers known in the art can be placed on the elongate member  12 , the loop  22 , and/or the closure member  24 . Several examples of suitable radiopaque materials and markers are known in the art, and any suitable material and/or marker can be utilized in the present invention.  
         [0037]    As illustrated in the figures, the loop  22  is preferably formed by the elongate member  12 . As an alternative, a separate member defining the loop can be affixed to a substantially straight elongate member to form the wire guide of the present invention. This may be advantageous when it is desirable to form the loop and elongate member of different materials. For example, a nylon or silicon loop could be formed and attached, such as by a closure member, to an elongate member formed of nitinol. Such an assembly could be coated and or associated with a covering as described above.  
         [0038]    [0038]FIG. 5 illustrates a wire guide  10  according to the present invention encountering an impediment  42  within a body vessel  40 . As illustrated in the figure, the loop  22  deforms in response to its encounter with the impediment  42 . Due to the presence of the loop  22  and closure member  24 , the distal end  26  does not move relative to the remainder of the elongate member  12 . Also, the loop  22  deforms in response to the impediment, enabling the wire guide to continue navigating along the interior of the vessel  40 . The resiliency of the loop  22  creates a force opposing the impediment  42  and forces the loop  22  away from the impediment  42 , which defines a path for the remainder of the wire guide  10  to follow.  
         [0039]    [0039]FIG. 6 illustrates a wire guide  10  according to the present invention encountering a torturous path  44  within a body vessel  40 . As illustrated in the figure, the loop  22  deforms slightly in response to the torturous path  44 . Also, due to the presence of the loop  22  and closure member  24 , the distal end  26  does not move relative to the remainder of the elongate member  12 . This allows the wire guide  10  to continue navigating along the interior of the body vessel  40 . The taper of the intermediate region  21  provides additional flexibility to the wire guide  10 , facilitating navigation of the loop  22  through the torturous path  44 .  
         [0040]    The above Figures and disclosure are intended to be illustrative and not exhaustive. This description will suggest many variations and alternatives to one of ordinary skill in the art. All such variations and alternatives are intended to be encompassed within the scope of the attached claims. Those familiar with the art may recognize other equivalents to the specific embodiments described herein, which equivalents are also intended to be encompassed by the attached claims.