Abstract:
An elongate intracorporeal guiding device for providing access to desired sites within a patients body. The device, which may be configured as a guidewire, is constructed so as to be compatible with sensitive imaging methods such as MRI and the like and not create imaging artifacts or interference with such imaging methods. The guiding device may be constructed so as to have a distal working section that has minimal metallic content or minimal content of materials that can cause imaging artifacts or interference with MRI imaging, other sensitive imaging methods or the like. The device may also have a dock exchange system to allow attachment and detachment of an extension guidewire.

Description:
RELATED APPLICATION  
       [0001]    This application is a continuation-in-part of U.S. Ser. No. 09/468,976 filed on Dec. 21, 1999, which is incorporated herein in its entirety by reference. 
     
    
     
       BACKGROUND  
         [0002]    This invention relates to the field of guidewires for advancing intraluminal devices such as stent delivery catheters, balloon dilatation catheters, atherectomy catheters and the like within a patient&#39;s body, specifically, within a patient&#39;s vasculature.  
           [0003]    In a typical percutaneous procedure in a patient&#39;s coronary system, a guiding catheter having a preformed distal tip is percutaneously introduced into a patient&#39;s peripheral artery, e.g., femoral, radial or brachial artery, by means of a conventional Seldinger technique and advanced therein until the distal tip of the guiding catheter is seated in the ostium of a desired coronary artery. There are two basic techniques for advancing a guidewire into the desired location within the patient&#39;s coronary anatomy, the first is a preload technique which is used primarily for over-the-wire (OTW) devices and the bare wire technique which is used primarily for rail type systems. With the preload technique, a guidewire is positioned within an inner lumen of an OTW device such as a dilatation catheter or stent delivery catheter with the distal tip of the guidewire just proximal to the distal tip of the catheter and then both are advanced through the guiding catheter to the distal end thereof. The guidewire is first advanced out of the distal end of the guiding catheter into the patient&#39;s coronary vasculature until the distal end of the guidewire crosses the arterial location where the interventional procedure is to be performed, e.g., a lesion to be dilated or a dilated region where a stent is to be deployed.  
           [0004]    The catheter, which is slidably mounted onto the guidewire, is advanced out of the guiding catheter into the patient&#39;s coronary anatomy over the previously introduced guidewire until the operative portion of the intravascular device, e.g. the balloon of a dilatation or a stent delivery catheter, is properly positioned across the arterial location. Once the catheter is in position with the operative means located within the desired arterial location, the interventional procedure is performed. The catheter can then be removed from the patient over the guidewire. Usually, the guidewire is left in place for a period of time after the procedure is completed to ensure reaccess to the arterial location if it is necessary. For example, in the event of arterial blockage due to dissected lining collapse, a rapid exchange type perfusion balloon catheter such as described and claimed in U.S. Pat. No. 5,516,336 (McInnes et al), can be advanced over the in-place guidewire so that the balloon can be inflated to open up the arterial passageway and allow blood to perfuse through the distal section of the catheter to a distal location until the dissection is reattached to the arterial wall by natural healing.  
           [0005]    With the bare wire technique, the guidewire is first advanced by itself through the guiding catheter until the distal tip of the guidewire extends beyond the arterial location where the procedure is to be performed. Then a rail type catheter, such as described in U.S. Pat. No. 5,061,273 (Yock) and the previously discussed McInnes et al. which are incorporated herein by reference, is mounted onto the proximal portion of the guidewire which extends out of the proximal end of the guiding catheter which is outside of the patient. The catheter is advanced over the guidewire, while the position of the guidewire is fixed, until the operative means on the rail type catheter is disposed within the arterial location where the procedure is to be performed. After the procedure the intravascular device may be withdrawn from the patient over the guidewire or the guidewire advanced further within the coronary anatomy for an additional procedure.  
           [0006]    Conventional guidewires for angioplasty, stent delivery, atherectomy and other vascular procedures usually comprise metallic elongated core member with one or more tapered sections near the distal end thereof and a flexible body such as a metallic helical coil or a tubular body of polymeric material disposed about the distal portion of the core member. A shapable member, which may be the distal extremity of the core member or a separate shaping ribbon which is secured to the distal extremity of the core member, extends through the flexible body and is secured to the distal end of the flexible body by soldering, brazing or welding which forms a rounded distal tip. Torquing means are provided on the proximal end of the core member to rotate, and thereby steer, the guidewire while it is being advanced through a patient&#39;s vascular system.  
           [0007]    Further details of guidewires, and devices associated therewith for various interventional procedures can be found in U.S. Pat. No. 4,748,986 (Morrison et al.); U.S. Pat. No. 4,538,622 (Samson et al.): U.S. Pat. No. 5,135,503 (Abrams); U.S. Pat. No. 5,341,818 (Abrams et al.); U.S. Pat. No. 5,345,945 (Hodgson, et al.) and U.S. Pat. No. 5,636,641 (Fariabi) which are hereby incorporated herein in their entirety by reference thereto.  
           [0008]    Conventional metallic guidewires using tapered distal core sections as, discussed above can be difficult to use with sensitive imaging systems such as Magnetic Resonance Imaging (MRI) and the like because the metal content of the guidewire can create imaging artifacts that obscure the image produced, and can be heated or moved around by the strong MRI magnetic field. MRI compatible alloys or metals have lower magnetic susceptibilities. Such alloys include certain grades of stainless steel, Elgiloy and Nitinol. What has been needed is a guidewire that is compatible for use with sensitive imaging systems and methods such as MRI and the like.  
         SUMMARY  
         [0009]    The invention is directed to an intracorporeal guiding device which can be in the form of a guidewire. The device includes an elongate member having a proximal section and a distal section. The distal section is made at least partially of a fiber composite matrix and has at least one segment with increasing flexibility in a distal direction. The fiber composite matrix can be configured to have little or no metal content so as to avoid creating imaging artifacts with sensitive imaging systems such as MRI and the like. In one embodiment, a flexible body is disposed about the distal section of the elongate member. Tihe flexible body can have a variety of configurations, including a helical coil and a polymer layer. In a particular embodiment, the flexible body which consists of a polymer layer can be doped with a radiopaque material in order to improve visualization of the device under fluoroscopic imaging and the like.  
           [0010]    In another embodiment, the elongate intracorporeal guiding device can have an elongate core disposed within a core lumen of the elongate member. The elongate core can be fixed or secured within the core lumen, or it may be moveable in an axial direction. Movement of the elongate core within the core lumen of the device may be used to adjust the flexibility of the distal section.  
           [0011]    In another embodiment, a shapeable segment can be secured to the distal end of the elongate member with the flexible body disposed at least partially about the shapeable segment. In some embodiments, the shapeable segment is comprised of metal which can be flattened to provide improved shapeability in a specified orientation.  
           [0012]    The invention is also directed to a method of making an elongate intracorporeal guiding device. The method includes disposing at least one layer of thin fiber about a mandrel. This can be done by winding, stranding, braiding or any other suitable method. A binding agent is then applied to the fiber material. If necessary, the binding agent can then be cured. Alternatively, a binding agent may be present on a thin fiber prior to disposing the thin fiber on the mandrel.  
           [0013]    Furthermore, the invention is directed to a method of advancing an elongate intracorporeal guiding device within a patient&#39;s body. The method includes providing an elongate intracorporeal guiding device having a distal section configured so as not to create imaging artifacts when used with MRI imaging. The elongate intracorporeal guiding device is then inserted into the patient&#39;s body and advanced within the patient&#39;s body under MRI imaging to a desired site. A distal section configured to not create imaging artifacts with MRI imaging, or other sensitive imaging methods, can be a distal section constructed essentially of non-metallic fiber composite matrix optionally including polymer materials having little or not metallic content.  
           [0014]    Finally, the invention is also directed to a dock exchange system for composite guidewires. The incorporation of a dock exchange system into a composite guidewire must consider the filament nature of the composite guidewire and how it is manufactured. The docking mechanism of the present invention is a hypotube or a crimped or crimpable tube attached to the proximal end of the guidewire which receives the tip of an extension guidewire. The hypotube or crimped or crimpable tube and the extension tip are so designed that once the latter is inserted, it is held in place unless a certain amount of tensile force is applied. The mechanism involves, for example, crimping the extension tip or placing magnets inside the hollow section.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]    [0015]FIG. 1 is an elevational view in partial section of an intracorporeal guiding device having features of the invention.  
         [0016]    [0016]FIG. 2 is a transverse cross sectional view of the intracorporeal guiding device of FIG. 1 taken along lines  2 - 2  in FIG. 1.  
         [0017]    [0017]FIG. 3 is a transverse cross sectional view of the intracorporeal guiding device of FIG. 1 taken along lines  3 - 3  in FIG. 1.  
         [0018]    [0018]FIG. 4 is a transverse cross sectional view of the intracorporeal guiding device of FIG. 1 taken along lines  4 - 4  in FIG. 1.  
         [0019]    [0019]FIG. 5 is an elevational view in partial section of a part of a distal section of an intracorporeal guiding device having features of the invention.  
         [0020]    [0020]FIG. 6 is a transverse cross sectional view of the intracorporeal guiding device of FIG. 5 taken along lines  6 - 6  in FIG. 5.  
         [0021]    [0021]FIG. 7 is an elevational view in partial section of an intracorporeal guiding device having features of the invention.  
         [0022]    [0022]FIG. 8 is a transverse cross sectional view of the intracorporeal guiding device of FIG. 7 taken along lines  8 - 8  in FIG. 7.  
         [0023]    [0023]FIG. 9 is a schematic view of thin fibers being braided onto a mandrel  
         [0024]    [0024]FIG. 10 is a schematic view of a thin fiber being wound onto a mandrel.  
         [0025]    [0025]FIG. 11 is a schematic view of thin fibers being stranded onto a mandrel.  
         [0026]    [0026]FIG. 12 shows a dock exchange system in which the composite guidewire has a hollow proximal end for receiving the distal end of the extension wire.  
         [0027]    [0027]FIGS. 13 and 14 show alternative designs having a hypotube with an outer diameter identical to or smaller than the outer diameter of the proximal section of the composite guidewire.  
         [0028]    [0028]FIG. 15 shows a dock exchange system with a smaller inner diameter at the proximal end of the composite guidewire that constricts around the tip of the extension wire.  
         [0029]    FIGS.  16 - 18  show a dock exchange system in which the filler material is a solid cylinder cut in half along its length to create a larger surface area to hold onto the tip of the extension wire.  
         [0030]    [0030]FIG. 19 shows a dock exchange system in which the filler material has a texture that enhances the adhesion strength between the composite and extension guidewires.  
         [0031]    [0031]FIGS. 20 &amp; 21 show a dock exchange system in which the composite and extension guidewires are held together by magnetic force.  
         [0032]    [0032]FIG. 22 shows a dock exchange system in which the hollow proximal section of the composite guidewire has a constriction for preventing the tip of the extension wire from sliding out. 
     
    
     DETAILED DESCRIPTION  
       [0033]    [0033]FIG. 1 shows an intracorporeal guiding device  10  having features of the invention. An elongate member  11  made entirely of fiber composite matrix  12  has a proximal section  13 , a proximal end  14 , a distal section  15  and a distal end  16 . Optionally, the elongate member  11  can be made partially out of fiber composite matrix  12 . An optional core member  17  is disposed within a core lumen  18  of the elongate member  11  and is axially moveable within the core lumen  18  as indicated by arrow  21 . The core member  17  has a proximal end  22  and a distal end  23  and may also be secured within the core lumen  18  either by frictional force, an epoxy or other adhesive, or by any other suitable means. An optional shapeable segment  24  having a proximal end  25  and a distal end  26  has an end cap  27  disposed at the proximal end  25  of the shapeable segment  24 . The end cap  27  is disposed over and secured to the distal end  16  of the elongate member  11 . The end cap  27  may be secured to the distal end  16  of the elongate member  11  by a friction fit, adhesive such as an epoxy, or any other suitable method. A flexible body in the form of a helical coil  30  having a proximal end  31  and a distal end  32  is disposed about the shapeable segment  24 . The distal end  32  of the helical coil  30  is secured to the distal end  26  of the shapeable segment  24  with a body of solder  33  or the like. The proximal end  31  of the helical ccil  30  can be similarly secured to the proximal end  25  of the shapeable segment  24 .  
         [0034]    The fiber composite matrix  12  of the elongate member  11  may be formed in a variety of configurations and from a variety of materials. In the embodiment the intracorporeal guiding device  10  of FIG. 1, the fiber composite matrix  12  can be formed from a plurality of non-metallic thin fibers  34  made of carbon fiber braided over a mandrel (not shown) in one or more layers. A cured or hardened binding agent  35  such as an epoxy resin, polyester resin or other suitable material is disposed about the thin fibers  34  to form the fiber composite matrix  12 . The binding agent  35  can optionally be doped with a radiopaque material in order to provide radiopacity to the elongate member  11 . Materials such as gold, platinum, platinum-iridium, tungsten, barium compounds or bismuth compounds may be used for doping the binding agent  35 . In addition, one or more radiopaque thin fibers  34  can be made of the same or similar radiopaque materials discussed above with regard to radiopaque dopants for the binding agent and may be used when forming the fiber composite matrix  12  in order to provide radiopacity to the device  10 . In addition, a conductor, insulated or uninsulated, or other type of conduit capable of carrying an electric, light, or other type of signal can be substituted or molded into the thin fibers  34 . This can be done in order to carry a signal conveying information such as temperature of pressure from the distal end  16  to the proximal end  14  of the elongate member  11 . If a fiber optic is used, light or a light signal can be transmitted from the distal end  16  to the proximal end  14  of the elongate member  11 , or from the proximal end  14  to the distal end  16 . During formation of the elongate member  11 , the aforementioned mandrel is removed after the binding agent is cured.  
         [0035]    During the formation process for the elongate member  11 , the core member  17  could serve as a forming mandrel such as that discussed above, or a separate mandrel could be used for forming the fiber composite matrix  12  arid then be removed. A core member  17  could then be inserted into the core lumen  18  once the forming mandrel is removed. The thin fiber  34  could also be wound or stranded about the forming mandrel prior to curing of the binding agent. Any appropriate number of layers of thin fiber  34  may be braided, stranded or wound about a forming mandrel in order to achieve a desired thickness of the fiber composite matrix  12 . For an intracorporeal guiding member  10  having a elongate member  11  with a proximal section  13  having an outer diameter of about 0.008 to about 0.040 inches (about 0.020 to 0.102 cm), approximately 1 to about  10  layers of thin fiber  34  may be used, specifically, about 2 to about 6 layers of thin fiber. The thin fibers  34  can have a transverse dimension of about 0.0005 to about 0.002 inch (about 0.0013 to 0.0051 cm), specifically about 0.001 to about 0.0015 inch (about 0.0025 to 0.0038 cm) and can be made of carbon fiber. Other materials that can be used for the thin fibers  34  are polymeric substances such as Nylon (polyamides), Kevlar (polyarylamides), fiberglass and the like.  
         [0036]    The flexibility of the elongate member  11  can be controlled to some degree by varying the manner in which the one or more thin fibers are configured within the fiber composite matrix with respect to axial position along the elongate member  11 . Specifically, the angle the thin fiber  34  makes with a line parallel to a longitudinal axis  36  of the elongate member  12  adjacent the thin fiber  34  can affect the longitudinal flexibility of the elongate member and hence the intracorporeal guiding device  10 . In addition, the distal section  15  of the elongate member  11  can be tapered to a reduced outer transverse dimension distally in one or more segments in order to increase the flexibility of such a segment. The tapering of a segment can be achieved by grinding a segment of substantially constant outer diameter after formation of the elongate member  11 . Alternatively, the tapering of a segment could be achieved by varying the number of layers or configuration of the thin fiber or fibers  34  in the formation process of the elongate member  11 . Also, the diameter of the core lumen  18  within the elongate member  11  could be increased distally in a segment of the distal section  15  of the elongate member  11  in order to increase the flexibility of the segment.  
         [0037]    The core member  17  can be made from a metal such as stainless steel, MP35N, L605 or other high strength materials. The core member  17  may also be configured to be radiopaque and can have materials such as gold, platinum, platinum-iridium, tungsten and the like contained therein. The core member  17  may also be made of a fiber composite material similar to that of the elongate member  11  with a binding agent for such a fiber composite material being doped with a non-metallic radiopaque material in order to provide radiopacity to the core member  17  and avoid introduction of metallic content which might interfere with sensitive imaging methods as discussed above. The core member  17  can have an outer transverse dimension of about 0.001 to about 0.015 inches (about 0.0025 to 0.038 cm), specifically about 0.002 to about 0.005 inches (about 0.0051 to 0.0127 cm). The core member  17  can also be ground to have one or more tapered segments, specifically, tapered segment tapering distally to a reduced transverse dimension in order to provide greater flexibility in the distal section  15  of the elongate member  11 .  
         [0038]    Generally, the shapeable segment  24  can have a configuration similar to shapeable segments of guiding devices known in the art. Regarding the embodiment of the guiding device  10  shown in FIG. 1, the shapeable segment  24  is formed of stainless steel which has optionally been flattened. Specifically, the shapeable segment  24  has been flattened to a progressively greater degree in a distal direction. Thus, a thickness of the flattened portion at the proximal end  25  of the shapeable segment  24  is thicker than the thickness of the flattened portion of the shapeable segment  24  at the distal end  26  of the shapeable segment  24 . The length of the flexible segment  24  can be from about 2 to about 30 cm, specifically, about 3 to about 10 cm. The thickness of the shapeable segment  24  at the flattened distal end can be from about 0.0005 to about 0.006 inch (about 0.0013 to 0.0152 cm), specifically, about 0.001 to about 0.002 inch (about 0.0025 to 0.0051 cm). Other materials suitable for the shapeable segment  24  include MP35N, L605 or other high strength materials.  
         [0039]    The helical coil  30  can be made from a variety of suitable materials including stainless steel, platinum, platinum iridium, gold or the like. The helical coil  30  could also be made from a fiber composite matrix or other non-metal material in order to enable the intracorporeal guiding device  10  to have a distal section or an overall composition with a zero or minimum amount of metallic composition. As mentioned above, for certain applications and uses, minimizing the metallic content of the intracorporeal guiding device  10  improves compatibility with sensitive imaging devices such as MRI. The material of the helical coil  30  can have a transverse dimension of about 0.001 to about 0.005 inch (about 0.0025 to 0.0127 cm), specifically, about 0.002 to about 0.003 inch (about 0.0051 to 0.0076 cm).  
         [0040]    The nominal outer transverse dimension of the proximal section  13  of the elongate member  11  can be from about 0.005 to about 0.035 inch (about 0.0127 to 0.0889 cm), specifically, about 0.01 to about 0.02 inch (about 0.0254 to 0.13508 cm), and more specifically about 0.012 to about 0.016 inch (about 0.0305 to 0.0407 cm). The overall length of the intracorporeal guiding device  10  can be from about 100 to about 300 cm, specifically about 150 to about 200 cm.  
         [0041]    [0041]FIG. 2 is a transverse cross sectional view of the intracorporeal guiding device  10  of FIG. 1 taken along lines  2 - 2  in FIG. 1. The fiber composite matrix  12  is substantially concentrically disposed about the core member  17  as discussed above. In FIG. 3, the end cap  27  is disposed about the fiber composite matrix  12  which is substantially concentrically disposed about the core lumen  18 . In FIG. 4, the helical coil  30  is disposed about the shapeable segment  24 .  
         [0042]    [0042]FIGS. 5 and 6 depict an alternative embodiment of a shapeable segment  40  wherein the end cap  27  of the shapeable segment  24  of FIG. 1 has been replaced with a handle portion  41  which is disposed within and secured to the distal end  42  of the elongate member  43 . A configuration such as that shown in FIG. 5 allows for a smooth continuous transition from an outer surface  44  of the elongate member  43  to an outer surface  45  of the helical coil  46 . A fiber composite matrix  47  is substantially concentrically disposed about the handle portion  41  of the shapeable segment  40 . Components of the embodiment of the intracorporeal guiding device  48  shown in FIGS. 5 and 6 could have similar relationships, dimensions and materials to similar components of the embodiment of the intracorporeal guiding device  10  shown in FIGS.  1 - 4 .  
         [0043]    [0043]FIGS. 7 and 8 show another embodiment of an intracorporeal guiding device  50  having features of the invention. An elongate member  51  has a proximal section  52 , a proximal end  53 , a distal section  54  and a distal end  55 . The distal section  54  has a tapered segment  56  which tapers distally to a reduced transverse dimension in order to increase the flexibility of the distal section  54 . The elongate member  51  is formed of a fiber composite matrix  57  such as that described above with regard to other embodiments of the invention. A core member  58  is optionally secured within a core lumen  61  of the elongate member  51 . The core member  58  can be made of a non-metallic fiber composite matrix or other essentially non-metallic material in order to avoid interference with sensitive imaging systems such as MRI and the like. The tapered segment  56  of the distal section  54  of the elongate member  51  tapers in a curved configuration which can provide a smooth transition in flexibility. A flexible body in the form of a polymer layer  62  is substantially concentrically disposed about the distal section  54  of the elongate member  51 . A rounded polymer cap  63  is secured to the distal end  55  of the elongate member  51  to facilitate securement of the polymer layer  62  to the elongate member  51  and to provide a rounded non-traumatic tip for the intracorporeal guiding device  50 . The rounded polymer cap  63  can be a separate element as shown in FIG. 7, or it may be a continuation and integral portion of polymer layer  62 . The polymer layer  62  has a proxial end  63  and distal end  64 .  
         [0044]    The polymer layer  62  can be made from a diverse range of materials, including polyurethane, polyethylene, Nylon, silicone, or any other suitable polymer. The polymer layer  62  can optionally be doped with a radiopaque material in order to facilitate imaging of the guiding device  50  under fluoroscopy. The polymer layer  62  can be applied by coextrusion, heat shrink, bonding with a suitable adhesive or any other appropriate method. The polymer layer  62  can be formed on the distal section  54  of the elongate member  51  or may be extruded independently and later secured to the distal section  54 . The length and outer dimensions of the polymer layer  62  can be similar to those of the helical coil  30  discussed above. FIG. 8 is a transverse cross sectional view of the intracorporeal guiding device  50  of FIG. 7 taken along lines  8 - 8  in FIG. 7. The polymer layer  62  is shown substantially concentrically disposed about the fiber composite matrix  57  which is substantially concentrically disposed about the core member  58 . Components of the embodiment of the intracorporeal guiding device  50  shown in FIGS. 7 and 8 could have similar relationships, dimensions and materials to similar components of the embodiment of the intracorporeal guiding device  10  shown in FIGS.  1 - 6 .  
         [0045]    [0045]FIG. 9 illustrates four thin fibers  70  being braided onto a mandrel. FIG. 10 illustrates a single thin fiber  72  being wound onto a mandrel  73 . A double layer section  74  is shown where the thin fiber  72  been wound back onto itself in order to form two layers. FIG. 11 shows four thin fibers  75  being stranded onto a mandrel  76 . Also shown is the pitch angle  77  that a line  78  extending from one of the thin fibers  75  makes with a line  79  orthogonal to a longitudinal axis  80  of the mandrel  76 . The pitch angle  77  of stranded, braided or wound thin fiber  75  can vary significantly. The pitch angle  77  can be just over zero degrees for a single thin fiber  75  being wound close spaced so that adjacent windings are touching each other. The pitch angle  77  can be up to 90 degrees for multiple stranded thin fibers  75  which extend essentially parallel to the longitudinal axis  80  of the mandrel  76 . In one embodiment, the pitch angle  77  can be from about 20 to about 70 degrees, specifically, about 30 to about 60 degrees, and more specifically about 40 to about 50 degrees. Such variations in pitch angle  77  can be used to control the flexibility of the resulting elongate member for a fixed cross section of fiber composite material.  
         [0046]    FIGS.  12 - 22  illustrate dock exchange systems of the present invention for composite guidewires. FIG. 12 shows a dock exchange system in which the composite guidewire  80  has a hollow proximal end  81  for receiving the distal end  82  of the extension wire  83 . FIGS. 13 and 14 show alternative designs having a hypotube or a crimped or crimpable tube  84 . The outer diameter of the hypotube or the crimped or crimpable tube is either identical to (FIG. 13) or smaller than that of the proximal section of the composite guidewire (FIG. 14).  
         [0047]    The hypotube or crimped or crimpable tube may be made of a metal (such as steel), an alloy (such as Nitinol) or a polymer (such as a polyetheretherketone). The tube is from about 1 cm to about 3 cm in length. The wall of the tube is from about 0.0002 inches to about 0.003 inches in thickness.  
         [0048]    If the composite filaments are wound around a continuous spool of mandrel that is removed after winding and cutting to length, then the hollow section is naturally made at the proximal end. If a hypotube or crimped or crimpable tube is desired, these can be added after the mandrel is removed. They can be inserted into the hollow left by the mandrel, or can be attached to the end of the composite guidewire using glue, thermal bonding, mechanical bonding or the combination thereof.  
         [0049]    If the composite filaments are wound around a precut length of the mandrel that is removed after the winding process, then the hollow section is also naturally made at the proximal end. In this construction, if a hypotube or crimped or crimpable tube is desired, these can be temporarily attached to the end of the mandrel before the winding process and left in place when the mandrel is removed. Alternatively, they can also be inserted into the hollow left by the mandrel, or can be attached to the end of the composite guidewire using glue, thermal bonding, mechanical bonding or the combination thereof.  
         [0050]    If the composite filaments are wound around a continuous spool of mandrel that becomes a permanent part of the guidewire, then the hollow section is created by drilling into the proximal end of the mandrel after the composite wire has been cut to length. If a hypotube or crimped or crimpable tube is desiredi, these can be attached after winding and cutting to length to the end of the composite guidewire using glue, thermal bonding, mechanical bonding or the combination thereof.  
         [0051]    If the composite filaments are wound around a precut length of the mandrel that becomes a permanent part of the guidewire, then the hollow section is created by just winding past the end of the mandrel. If a hypotube or crimped or crimpable tube is desired, these can be attached either permanently to the proximal end of the mandrel before the winding process or afterwards in a similar fashion as stated above.  
         [0052]    The hollow proximal section of the composite guidewire or the hypotube may be partially or totally filled with a filler material to enhance the attachment strength between the composite guidewire and the extension guidewire. With a hollow proximal section, the filler material may be incorporated during the braiding or winding process to make the composite guidewire. In other words, the composite wires are wound around the filler material. With a hypotube or crimped or crimpable tube, the filler material may be added before or after the braiding or winding process to make the composite guidewire.  
         [0053]    The filler material may be certain grades of silicone, textured polymer, adhesive materials, magnets or a combination of two or more thereof.  
         [0054]    When the distal end of the extension guidewire is inserted into or in contact with the filler material it remains attached due to the interfacial adhesion or magnetic attraction force between the filler material and the tip of the extension guidewire.  
         [0055]    The filler material  85  may be tubular in form  86  with a small inner diameter  87  that constricts around the tip of the extension wire as shown in FIG. 15. In addition to being tubular, the filler polymer may have a constricted end, which prevents the tip of the extension guidewire from easily sliding out once it is inserted. The filler material may also be a solid cylinder cut in half along its length  88  which creates a larger surface area to hold onto the tip  82  of the extension guidewire  83  as shown in FIGS.  16 - 18 . The filler material may also be a piece of solid, which the tip of the extension guidewire may puncture into.  
         [0056]    [0056]FIG. 19 shows that when the filler material  85  is a textured polymer, such as can be imparted by a molding or extrusion process or the proper selection of polymer blends, the surface of the filler material that comes in contact with the tip  82  of the extension guidewire  83  may have a texture that enhances the adhesion strength between the composite and extension guidewires. When the filler material is an adhesive material, such as some classes of silicones or acrylates, the filler material may be an adhesive glue that is designed to strongly hold on the tip of the extension guidewire yet still allow repeated attachment and detachment of the tip.  
         [0057]    The proximal section of the composite guidewire may instead have one or several magnets that are incorporated before, during or after the winding process. In the design as shown in FIG. 20, the magnet(s)  89  are cylindrical and embedded at the bottom closed end of the hollow section. When the tip of the extension guidewire is inserted into the hollow section, hypotube, crimped or crimpable tube, it is held in place due to its attraction to the magnets. The tip of the extension guidewire may also be fitted with magnets  90  that are aligned to enhance the attractive force to the magnets. FIG. 21 shows that the magnet or magnets inside the composite guidewire may instead form a half cylinder  91  that sets inside the hollow section, hypotube, or crimped or crimpable tube. The tip of the extension guidewire may be shaped as a half-cylinder or have a correctly aligned half-cylinder magnet  92  as well. This tip can then slide into the proximal end of the composite guidewire and due to the attraction of the two magnets or the magnet to the metal, it stays in place.  
         [0058]    Alternatively, the hollow proximal section, hypotube, or the crimped or crimpable tube may have a constriction or constrictions  93  along its length that prevent the tip of the extension guidewire from readily sliding out once inserted, as shown in FIG. 22.  
         [0059]    In order to enhance dockability, the tip of the extension guidewire may have one or more of the following characteristics. The tip of extension guidewire may be made of a metal, an alloy or a polymer, as those described above for the hypotube and crimped or crimplable tube. The tip of the extension guidewire may be uncoated or coated with a tacky material such as certain grades of silicon, textured polymers or adhesives to enhance the adhesion strength. The extension guidewire may be round, flat or oblong along its length and it may be nontapered or tapered with one or more dimensions increasing or decreasing as one moves distally along its length. The tip of the extension guidewire may be formed with a ball, flared or expanded end. Furthermore, the tip of the extension guidewire may have a magnet or magnets as described above.  
         [0060]    In another embodiment, the end of the composite guidewire may be fitted with the tip as described above. In other words, the extension guidewire now has the docking station. In this case, the tip or tips are attached either before, during or after the winding process to make the composite guidewire. The tip may instead be a modification to the proximal end of the mandrel if the mandrel is to become a permanent part of the composite guidewire. The modification may be done before or after the winding process to make the composite guidewire.  
         [0061]    While particular forms of the invention have been illustrated and described, it will be apparent that various modifications can be made without departing from the spirit and scope of the invention. Accordingly, it is not intended that the invention be limited, except as by the appended claims.