Abstract:
A wire guide has first and second portions with first and second diameters, respectively. The second portion is located distal of the first portion. 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. An outer sleeve may be positioned around one or more parts of the wire guide. A radiopaque element may be secured to the outer sleeve.

Description:
FIELD OF THE INVENTION 
     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 
     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 body lumen. 
     During placement of a wire guide, an operator must navigate the wire guide through the body lumen. Often, the body lumen 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 body lumen. In addition, the presence of a tortuous path may make it difficult to determine the position of the wire guide within the body lumen. 
     There is an unmet need for a wire guide that can navigate a tortuous path having impediments in which the path and position of the wire guide can be reliably monitored during the navigation. 
     BRIEF SUMMARY OF THE INVENTION 
     In a first aspect, a wire guide capable of manipulation about at least one of a tortuous path and an impediment is provided. An elongate member having a first portion and a second portion is provided. The second portion is located distal of the first portion. A loop is provided having an interior space, wherein the loop is affixed to the second portion. An outer sleeve is disposed along at least a portion of the loop. 
     In a second aspect, a wire guide is capable of manipulation about at least one of a tortuous path and an impediment is provided. An elongate member having a first portion with a first diameter and a second portion with a second diameter smaller than the first diameter is provided. The second portion is located distal of the first portion. A loop having an interior space, wherein the loop is affixed to the second portion, is also provided. A neck portion has a third diameter at a widest point of the neck portion, the third diameter being greater than the second diameter and smaller than the first diameter. The neck portion is positioned between the first portion and the second portion. A first outer sleeve is disposed along a loop and a second outer sleeve is disposed along the neck portion. 
     In a third aspect, the loop of the wire guide comprises a radiopaque member disposed thereover. The radiopaque member provides the loop tipped wire guide with enhanced radiopacity and/or other properties. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side view of a wire guide according to a first embodiment of the invention in which an outer sleeve is wrapped around the loop portion of the wire guide; 
         FIG. 2  is a side view of the outer sleeve shown as unbent; 
         FIG. 3  is a side view of a wire guide according to a second embodiment of the invention in which two outer sleeves are disposed over the distal end of the wire guide; and 
         FIGS. 4-6  are variants of a loop tip wire guide which may incorporate a first and a second outer sleeve. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       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 portion  18  is located distal of the first portion  14 . 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 . 
     The elongate member  12  defines a loop  22  which is closed by closure member  29 . In the presently preferred embodiment, the loop  22  comprises a section of the elongate member  12  bent back upon itself. As illustrated in  FIG. 1 , the second portion  18  preferably defines the entire loop  22 . Alternatively, the second portion  18  may define only a portion of the loop  22 , and an intermediate portion  21  defines at least a portion of the loop  22 . The taper of the intermediate portion  21  provides additional flexibility to the wire guide  10 , facilitating navigation of the loop  22  through the torturous path. 
     Preferably, as illustrated in  FIG. 1 , the loop  22  comprises a curvilinear loop forming a generally ovoid shape. Also preferably, 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’ as used herein refers to the distance between the two outer most surfaces of the bent sleeve  80  (discussed below) disposed about the elongate member  12  at the widest portion of the loop  22 . 
     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 preferably tapers to a point. As illustrated in  FIG. 1 , 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 ). Other embodiments are contemplated in which the distal end  26  is positioned adjacent to the first portion  14  or the second portion  18  of the elongate member  12 . 
     Any method of forming the loop  22  is contemplated. In one preferred embodiment, the closure member comprises a coil  29 . More specifically, two sections of the elongate member  12  are wound about each other. Preferably, the distal end  26  is wound such that a low profile is achieved. 
       FIG. 1  shows an outer sleeve  80  slidably disposed along the loop  22 . The term “sleeve” as used herein refers to any discrete structure adapted to be disposed about the loop  22 , including but not limited to a coiled structure, a cylindrical structure, or a helical structure. The outer sleeve  80  may be sufficiently radiopaque so as to allow a physician or other operator to fluoroscopically observe the loop  22  as it is being navigated through a body lumen. The term “radiopaque” as used herein refers to any type of material or structure that blocks radiation from being transmitted therethrough, thereby making the material or structure visible under x-rays. 
       FIG. 2  shows the outer sleeve  80  in an unbent configuration and unattached to the loop  22  of the wire guide  10 . The outer sleeve  80  comprises a first end  81 , a second end  82 , and a body portion  83  extending between the first and second ends  81  and  82 . Preferably, the outer sleeve  80  is slidably disposed over the entire loop  22 , as shown in  FIG. 1 , so as to increase the radiopacity of the entire loop  22 . 
     The inner diameter  84  ( FIG. 2 ) of the outer sleeve  80  may be assembled onto the loop  22  as follows. The wire guide  10  is extended linearly out so as to create a single, tapered wire having a first diameter  16  at a first portion  14 , a second diameter  20  smaller than the first diameter  16  at a second portion  18 , and an intermediate portion  21  between the first diameter  16  and the second diameter  20 . The outer sleeve  80  may then be slid over the distal end of the wire guide  10  so as to position the outer sleeve  80  about the second portion  18 . With the outer sleeve  80  secured over the second portion  18 , the second portion  18  and the outer sleeve  80  are bent to create the loop  22  as shown in  FIG. 1 . The distal end  26  of the second portion  18  is then wound about the intermediate portion  21 . The distal tip  28  of the second portion  18  rests at the intermediate portion  21 . The inner diameter  84  of the outer sleeve  80  is less than the first diameter  16  of the first portion  14 . As a result, the outer sleeve  80  need not be further secured to the wire guide  10 . The first and second ends  81  and  82  of the outer sleeve  80  remain freely movable about the second portion  18 . Having the outer sleeve  80  slidably disposed about the second portion  18  maintains the flexibility of the loop  22  as the wire guide  10  encounters impediments along a tortuous body lumen. 
     Other means for securing the outer sleeve  80  onto the loop  22  are contemplated. For example, the sleeve  80  may be affixed onto the second portion  18  of the loop  22  by the use of adhesives, fusion bonding (i.e., annealing at elevated furnace temperatures as to create a solid bond), or soldering. Such securing means may alter the flexibility and resiliency of the loop  22  as needed. Other means for securing the sleeve  80  may be used as known to one of ordinary skill in the art. 
     The sleeve  80  may be made from any type of biocompatible material. In one embodiment, the material may be a suitable thermoplastic polymer such as high density polyethylene (HDPE), polytetrafluorethylene (PTFE), polyethylene ethyl ketone (PEEK), polymethylmethacrylate (PMMA), polyimide, Ethylene Tetrafluoroethylene (ETFE), and polyether block amides. For use with guide wires, the polymer layer has a thickness ranging from about 0.001 to about 0.01 inches, and more preferably about 0.002 to about 0.005 inches. Such a thickness allows the loop  22  to retain flexibility. 
     The outer sleeve  80  may comprise a radiopaque element  89  disposed along the body portion  83  ( FIG. 2 ). The sleeve  80  and radiopaque element  89  may be formed from any number of suitable materials and possess any number of suitable structures. In a preferred embodiment, the outer sleeve  80  is formed from a tungsten coiled structure, and elemental gold is secured onto the outer sleeve  80  by electroplating the elemental gold onto the tungsten coiled structure. The term “secured” as used herein is intended to encompass any means by which a radiopaque element may be bounded to a sleeve, including but not limited to embedding, anchoring, chemically bonding, physically bonding, heat bonding, soldering, welding, impregnating, plating, and dip coating a radiopaque element to a sleeve  80 . The electroplating process involves using electrical current to deposit onto the tungsten coil a relatively thin layer of elemental gold. The current density, which is determined by the ratio of the electroplating current and the surface area of the tungsten coil to be plated, may determine the deposition rate of the elemental gold, the electroplating adherence of the elemental gold, as well as the overall quality of the electroplating of the elemental gold. The plating of elemental gold onto the tungsten coil may provide enhanced fluoroscopic imaging. 
     In another plating process, the entire exterior of the tungsten coiled structure may be plated with the radiopaque material (e.g., elemental gold). Afterwards, the electroplated material is selectively removed from the sleeve  80  by laser ablation, chemical etching, mechanical abrasion or grinding. The thickness of the electroplating material may range from about 0.1 to about 30 microns. Alternatively, the above-described electroplating process may be performed so as to deposit bands of radiopaque material onto the tungsten coiled structure. Selected areas of the tungsten coiled structure are masked so as to prevent electroplating thereon. 
     Other radiopaque materials such as bismuth, platinum, tin, tantalum, iridium, barium and the like can be secured to the outer sleeve  80 . The radiopaque materials may be secured to any surface of the outer sleeve  80 . 
     Securing the radiopaque element  89  to the outer sleeve  80  may be achieved in other ways as well. For example, the radiopaque element  89  may be embedded into the sleeve  80 . A mandrel may be used to set the shape of the sleeve  80 . After establishing the shape of the sleeve  80 , the radiopaque element  89  is applied to the sleeve  80 . Alternatively, the radiopaque element  89  may lie over the sleeve  80  and suitable heat shrink material may be applied over the radiopaque element  89  and the sleeve  80 . 
     In yet another embodiment, the radiopaque element  89  may be formed from a shape memory material that is embedded or impregnated into the sleeve  80 . For instance, the radiopaque element  89  may be formed from NITINOL, which is a radiopaque nickel-titanium alloy. In one embodiment, the NITINOL may be a cylindrical band that is embedded within the sleeve  80  by utilizing the thermally induced deformation or recovery of the shape memory alloy. Initially, the cylindrical band would have an outer diameter substantially equal to or less than the outer diameter  85  of the sleeve  80 . The cylindrical band may then be cooled (e.g., by any conventional cooling method such as liquefied nitrogen) to a sufficiently low temperature below the shape recovering transition temperature so as to cause the shape forming material to become capable of physical deformation to an expanded diameter. While the cylindrical band is at the low temperature, it may be deformed into a deformed, expanded configuration that has a larger diameter than the original configuration. The larger diameter deformed cylindrical band may be obtained by applying a radial outward force to the inner surface of the band by, for example, a shaping rod through the center bore of the band. Once the band has been formed from its original configuration into its deformed configuration as represented by the deformed cylindrical band, the deformed band is positioned concentrically around the outer surface of the sleeve  80 . 
     Prior to raising the temperature of the NITINOL cylindrical band, a supporting mandrel is inserted through the passageway  88  ( FIG. 2 ) of the sleeve  80  so as to extend longitudinally along the band beyond both ends  81  and  82  of the sleeve  80 . The temperature of the NITINOL band is then raised above its predetermined transition temperature using, for example, hot air. As the band is raised to a temperature above the shape transition temperature, the band begins to return to its smaller diameter original configuration by moving radially inward into contact with the outer radial surface of the tubular sleeve  80 . Continued movement by the band radially inwardly causes the inner surface of the band to press against outer radial surface of the sleeve  80 . Simultaneously, the temperature of the band is high enough to soften and melt the sleeve  80  material immediately adjacent the band, thereby causing the band to sink into the material of the sleeve  80  until it reaches its original configuration. During the thermally induced deformation or shape recovery process into the original configuration, the support rod supports the inner radial surface of the sleeve against the radially inward force of band thereby maintaining the inner diameter  84  of the sleeve  80 . The support rod is then removed resulting in the NITINOL marker securely embedded into the material of the sleeve  80 . 
     Embedding the NITINOL band into the sleeve  80  is advantageous in that the cylindrical NITINOL band melts its way into embedded engagement with the sleeve  80  when moving into a physical rigid configuration, thereby not requiring any adhesives or other less dependable securing means for holding the band in place. Additionally, by sizing the band so that the outer diameter of the original configuration is no greater than the outer diameter of the sleeve  80 , the NITINOL marker band can be effectively attached to the sleeve  80  without increasing the sleeve&#39;s dimensional changes or creating transitions such as ridges on the outer surface of the sleeve  80 . Accordingly, a smooth outer radial surface of the sleeve  80  is maintained, thereby allowing easier navigation of the wire guide  10  through the body lumen. 
     Other means for embedding or impregnating radiopaque material into sleeve  80  include utilizing radiopaque inks, or the use of radiopaque shrink wrap or tubing over the sleeve  80  (e.g., radiopaque urethane). Alternatively, the sleeve  80  may be dipped into a solution of radiopaque polymer or loaded with radiopaque powder such as tungsten. In another embodiment, the inner diameter of a radiopaque element  89  is affixed to the outer diameter  85  of the sleeve  80  by a heat bond. The region of the sleeve  80  where the radiopaque element  89  is to be bonded is heated and slightly stretched down to enable slidably mounting the band onto the stretched down area. 
     In addition to the above-described structures for radiopaque element  89 , the radiopaque element  89  may possess other types of structures. In one embodiment, the radiopaque element  89  may take the form of ribbons, discrete bands, beads, or strips of foils embedded in the sleeve  80  or affixed to a surface of the sleeve  80 . The cross sectional shape of the radiopaque element  89  could be a rectangle, square, ovoid, circle, or the like. Alternatively, the radiopaque element  89  may be a cylindrical sleeve or a helical coil, both of which may be used without the sleeve  80 . 
     Prior to securing the sleeve  80  with the radiopaque element  89 , an electrically insulative material  99  is preferably disposed over the outer surface of the sleeve  80  comprising the radiopaque element  89 . Any electrically insulative material  99  may be utilized as known in the art. In a preferred embodiment, the electrically insulative material  99  comprises ethylene tetrafluoroethylene (ETFE). Preferably, the ETFE is extruded. The ETFE extrudate  99  may be disposed over the sleeve  80  in which the sleeve  80  preferably is a gold plated tungsten coil. The ETFE extrudate  99  serves as an electrical insulator which allows the material to be used with electrosurgical devices. ETFE is a thermoplastic copolymer derived from the polymerization of ethylene and tetrafluroethylene monomers. The resin is abrasion resistant, possesses a relatively high dielectric strength compared to other plastics and has a relatively low coefficient of friction. Because of its high dielectric strength, the ETFE extrudate  99  is a suitable electrical insulator for use in wire guided applications in which an electrical medical device (e.g., cautery catheter) is advanced over the wire guide  10 . The ETFE extrudate  99  as an electrical insulator may prevent electrical current from jumping onto the wire guide  10 . The ETFE extrudate  99  is preferably extruded over the outer sleeve  80  (e.g., preferably a tungsten coil) having a radiopaque element  89  in the form of elemental plated gold. In preferred embodiments, the thickness of the ETFE extrudate is between approximately 0.001 and 0.010 inches. In particularly preferred embodiments, the thickness of the extrudate is between approximately 0.001 and 0.005 inches. In still more preferred embodiments, the thickness of the extrudate is between approximately 0.001 and 0.002 inches. [David, please confirm. These preferred thicknesses provide suitable ETFE extrudate thicknesses while not adding significantly to the overall thickness of the device. Other fluoropolymers, polyurethanes, and other suitable electrically insulative materials as are known and used in the medical device arts may be utilized. 
     In another preferred embodiment, the radiopacity may be further enhanced by adding an additional radiopaque structure to the wire guide of  FIG. 1 .  FIG. 3  shows that a second outer sleeve  90  has been added along the neck or intermediate portion  21 . The second outer sleeve  90  may comprise a radiopaque element  91 . Any radiopaque material may be used for the second outer sleeve  90 . Preferably, the second outer sleeve  90  is a platinum coil spring. The platinum coil spring is slidably disposed over the intermediate portion  21 . The platinum coil is positioned along the intermediate portion  21  so as to be adjacent to the first outer sleeve  80 , which preferably also possesses a radiopaque element  89 . The platinum coil has a first end  93  which is in close proximity to sleeve  80 . The platinum coil has a second end  92  which preferably extends proximally along the intermediate portion  21 . The platinum coil may cover the entire intermediate portion  21 , as shown in  FIG. 3 . Preferably, the platinum coil will have a length ranging from about 3 centimeters to about 5 centimeters. 
     The platinum coil has an inner diameter  95  which is larger than the outer diameter of the intermediate portion  21  at its widest point and smaller than the outer diameter (i.e., first diameter  16 ) of the first portion  14 . Such a sized platinum coil enables it to remain entrapped along the intermediate portion  21  yet remain slidably disposed along the intermediate portion without reducing the flexibility of the wire guide  10 . The platinum coil may be assembled onto the intermediate portion  21  by introducing it from the proximal end of the wire guide  10 . The second outer sleeve may be formed from other radiopaque materials known to one of ordinary skill in the art besides platinum. Additionally, the second outer sleeve  90  may comprise various other structures besides a coiled structure. 
     Although sleeves  80  and  90  have been described with reference to the loop tip wire guide of  FIG. 1 , the radiopaque sleeves  80  and/or  90  may be secured to other variations of a loop tip wire guide. For example,  FIGS. 4 and 5  represent other types of loop tip wire guides which may have sleeves  80  and  90  disposed therealong, in which the sleeves  80  and/or  90  may be radiopaque. For example,  FIG. 4  shows a loop tip wire guide in which two sections of the elongate member  12  are welded or soldered together to form a loop  22 . Additionally, sleeve  80  may be configured about the loop  22  of  FIG. 6 , which shows the closure member  24  as a cannula closing the loop  22  and fixing the loop  22  in overall size. Sleeves  80  and  90  are shown disposed about the loop tip wire guide of  FIG. 5 .  FIG. 5  shows a closure member having a molded bond  25  in which the loop  22  of the wire guide  10  is formed by molding two sections of the elongate member  12  together. 
     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 ETFE covering. 
     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 millimeters and approximately 5 millimeters, and a width of between approximately 2 millimeters and approximately 3 millimeters. 
     Also, the outermost surface of the wire guide  10 , 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. 
     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 associated with the outer sleeves  80  and/or  90  as described above, in which a radiopaque element  80  and  91  are secured to their respective outer sleeves  80 ,  90  for enhanced radiopacity. Additionally, suitable heat shrink material, such as TEFLON, may be applied over a portion of the loop  22  to create a streamlined low profile. 
     As can be seen, utilizing outer sleeves  80  and/or  90 , which have radiopaque elements, ensures reliable monitoring of the position of the wire guide  10  during navigation within a body lumen to ensure that the wire guide  10  is advanced along the intended path. 
     While preferred embodiments have been described, it should be understood that the preferred embodiments are intended to be limiting in any way, and modifications may be made without departing from the invention. The scope of the invention is defined by the appended claims, and all devices that come within the meaning of the claims, either literally or by equivalence, are intended to be embraced therein. Furthermore, the advantages described above are not necessarily the only advantages of the invention, and it is not necessarily expected that all of the described advantages will be achieved with every embodiment of the invention.