Abstract:
The embodiments presented herein relate to concepts designed to eliminate the gap between a catheter and guide wire that can otherwise contribute to a catheter getting stuck within the vasculature.

Description:
RELATED APPLICATIONS 
       [0001]    This application claims priority to U.S. Provisional Application Ser. No. 62/293,522 filed Feb. 10, 2016 entitled  Intravascular Treatment Site  Access, which is hereby incorporated herein by reference in its entirety. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    Guidewires are typically used in interventional procedures to access treatment areas. Guide catheters are typically slid over the guidewire to access the target area and act as a conduit for subsequently deployed microcatheters and/or therapeutic/treatment devices. 
         [0003]    The vasculature can be particularly winding or tortuous, especially in the neurovasculature where small, tortuous blood vessels abound, making accessing the target area and delivering treatment devices particularly difficult. In a phenomenon known as the ledge effect, there is a gap between the guidewire and the distal end of the guide catheter which can get caught along blood vessel bifurcations, preventing the catheter from effectively tracking through the vasculature. The ophthalmic artery is just one region where there is a bifurcation, as well as significant tortuosity of the blood vessel, and is just one of many regions where the catheter can get stuck. 
         [0004]    A system which would minimize or eliminate the gap between the guidewire and guide catheter is desirable to prevent the catheter from getting stuck in the vasculature. 
       SUMMARY OF THE INVENTION 
       [0005]    In one embodiment, a microcatheter with an enlarged distal section is described. The enlarged portion of the microcatheter is located close to the inner diameter of the guide catheter in order to reduce any open space between the microcatheter and the guide catheter, and the guidewire can be placed through the microcatheter and used to guide the system. The microcatheter can include one or more marker bands to aid in aligning the microcatheter correctly relative to the guide catheter. After the guide catheter and microcatheter are tracked to the appropriate treatment site, the microcatheter can then be used to deploy various medical devices to treat a patient. 
         [0006]    In one embodiment, a microcatheter with an enlarged distal section includes multiple marker bands to aid in visualization. The marker bands can be used to align the microcatheter appropriately relative to the guide catheter so that the microcatheter enlarged distal section coincides with the guide catheter distal tip. The guidewire is used to access a treatment site and the microcatheter and guide catheter can be tracked over the guidewire. 
         [0007]    In one embodiment, an obstruction removal system is described. The obstruction removal system includes a guide catheter, a microcatheter with an enlarged distal section delivered through the guide catheter, and an obstruction removal device delivered through the microcatheter. A guidewire is tracked through the microcatheter and the guidewire is used to help track the microcatheter and guide catheter near the treatment site. Once the treatment site is accessed, the microcatheter can be used to deliver an obstruction removal device, such as a clot retrieval device (e.g., a stentriever), in order to remove an obstruction (e.g., a clot). 
         [0008]    In one embodiment, a guidewire is described. The guidewire includes a projection to minimize or eliminate the gap between the guidewire and the guide catheter. In one embodiment, the projection is bulbous. The projection can further include a radiopaque marker to aid in imaging and placement of the guidewire. 
         [0009]    In one embodiment, the guidewire includes a shapeable or malleable distal tip and a torque device. The shapeable or malleable distal tip can be bent in a particular direction, and the torque device clamps down on the guidewire to keep it fixed. The guidewire can then be rotated in a particular direction so that the distal tip lines up with a particular blood vessel in order to aid in tracking the guidewire through the vasculature. 
         [0010]    In one embodiment, a method of using a guidewire is described. The guidewire includes a distal projection and a radiopaque marker. A guide catheter also includes a radiopaque marker. The guidewire is retracted or the guide catheter is pushed so that the guidewire projection contacts the guide catheter. The guidewire and guide catheter can then be advanced together by pushing the guide catheter. The guide catheter radiopaque marker and guidewire radiopaque marker either sit flush or next to each other, and the user can tell due to the augmented radiopacity when viewed by traditional imaging systems. The user can optionally use a torquer to lock and rotate the guidewire so that the distal tip is directed in a particular direction to aid in navigating the guidewire through the vasculature. 
         [0011]    In one embodiment, a rapid exchange system is described. The rapid exchange system minimizes the gap between the guidewire and the guide catheter in scenarios where the catheter can be caught at vessel bifurcations, the rapid exchange system would track over the guidewire and includes a distal enlarged section to bridge the gap between the guidewire and the guide catheter. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    These and other aspects, features and advantages of which embodiments of the invention are capable of will be apparent and elucidated from the following description of embodiments of the present invention, reference being made to the accompanying drawings, in which: 
           [0013]      FIG. 1  illustrates a traditional guide catheter getting stuck at a vessel bifurcation, a phenomenon known as the ledge effect. 
           [0014]      FIGS. 2-3  illustrate a microcatheter with an enlarged distal section according to one embodiment, where the microcatheter can be used to address the ledge effect issue. 
           [0015]      FIG. 4  illustrates a guidewire with a projection according to one embodiment. 
           [0016]      FIG. 5  illustrates a guidewire with a projection and a guide catheter according to one embodiment. 
           [0017]      FIG. 6  illustrates a guidewire with a projection, a catheter, and a torquer used to manipulate the guidewire according to one embodiment. 
           [0018]      FIGS. 7 a -7 b    illustrates a catheter with a radially reduced distal section according to one embodiment. 
           [0019]      FIG. 8  illustrates a guidewire with a wedge-shaped projection according to one embodiment. 
           [0020]      FIG. 9  illustrates a rapid exchange system to place over a guidewire according to one embodiment. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0021]    Specific embodiments of the invention will now be described with reference to the accompanying drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. The terminology used in the detailed description of the embodiments illustrated in the accompanying drawings is not intended to be limiting of the invention. In the drawings, like numbers refer to like elements. 
         [0022]    Many interventional procedures utilize a guide catheter, also known as a distal-access catheter (DAC), to access the vicinity of a treatment site. A thin, flexible guidewire is tracked through the vasculature and the guide catheter/DAC is tracked over this guidewire to access the treatment site. Once the region is accessed, a microcatheter is placed through the guide catheter and the guidewire is withdrawn. The microcatheter is then used to deliver to help deliver a therapeutic or treatment agent, for example a stent, clot retrieval device, or coils used to fill an aneurysm. Guide catheters typically have a relatively large diameter since they must accommodate both a guidewire and a microcatheter. Tracking a guide catheter through the vasculature can be difficult due to the tortuous nature of the anatomy, especially in the brain or neurovasculature where the vessels can be small and tortuous and branch vessels abound making it difficult to track a catheter to the proper treatment site. 
         [0023]    Vessel bifurcations present a navigational obstacle due to a gap between the guidewire and the distal end of the guide catheter which can become stuck at the bifurcation. This phenomenon is known as the ledge effect, and is shown in  FIG. 1  in which a gap  6  between guidewire  4  and guide catheter  8  gets caught at a vessel bifurcation  5 . In one example, a typical guide catheter  8  can have an inner diameter of 0.07″ while a guidewire  4  can have a diameter ranging from 0.014″-0.035″. The gap size  6  (defined as the radius of the guide catheter  8  minus the radius of the guidewire  4 ) will typically be between 0.0175″-0.028″. This gap size  4  corresponds to between 25-40% of the overall guide catheter inner diameter, which represents a significant amount of open space. Problems with guide catheter tracking can delay treatment or even make treatment impossible increasing the risk to the patient. The following embodiments address this issue. 
         [0024]    US2016/0022964 entitled “System and methods for intracranial vessel access” to Goyal, discloses a guidewire based system to treat the ledge effect complication with a guidewire having an enlarged region designed to bridge the gap between the overlying guide catheter and the underlying guidewire. US2016/0022964 is hereby incorporated by reference in its entirety. 
         [0025]      FIGS. 2-3  and the following disclosure relate to an intermediate microcatheter  10  that has an enlarged region  14  that minimizes any gap between the guidewire  22  and the overlying outer guide catheter  38 . In other words, the intermediate microcatheter  10  slides over the guidewire  22  and its enlarged distal end  14  takes up the open space within the lumen of outer guide catheter  38 . When the enlarged region  14  is positioned at or somewhat beyond the distal end of the outer guide catheter  38 , the “ledge” created by outer guide catheter  38  is diminished or eliminated, thereby avoiding being caught up at vessel bifurcations and other vessel shapes. Additionally, several later embodiments in this specification (see  FIGS. 4-9 ) disclose improved guidewire-based systems in which the guidewire has an enlarged region that bridges the gap between the overlying guide catheter and the guidewire. 
         [0026]      FIG. 2  illustrates a microcatheter  10  with a bulbous or enlarged distal section  14 . The bulbous/enlarged distal section  14  can have a generally cylindrical shape with tapered ends, a longitudinally rounded shape, or any other common shapes. Though distal section  14  is enlarged, the inner diameter defining the inner lumen  12  of microcatheter  10  is preferably consistent throughout the length of microcatheter  10 . Preferably the bulbous or enlarged distal section  14  of microcatheter  10  exactly matches up with or is slightly smaller than the inner diameter of the overlying guide catheter  38 . As seen in  FIG. 3 , this close fit of the enlarged distal section  14  bridges or fills the gap between the intermediate microcatheter  10  and guide catheter  38 , creating a snug interface between the two catheters to prevent any open exposed surface which could otherwise get caught at a vessel bifurcation. For example, the inner diameter of the outer guide catheter  38  is about 0.070 inch, while the diameter of the enlarged distal section  14  is about 0.067 inch. This reduces the gap size  26  to about 0.0015 inch on all sides, as opposed to a gap size  6  between the guidewire  22  and the outer guide catheter  38  of about 0.0175-0.028 inch on all sides (with a 0.014-0.035 inch guidewire). A gap size of 0.0015″ represents only about 2% of the total inner diameter of the outer guide catheter  38 . In other examples, the enlarged distal section  14  has a diameter that is almost the same diameter as the inner diameter of the guide catheter  38 . In either of these two examples, the diameter of the enlarged distal section  14  is close to the inner diameter of the outer guide catheter  38  and the limited open space does not provide enough room for a vessel to get caught. Bulbed/enlarged section  14  may have a linear taper  20  as shown in  FIG. 2 , or the taper may be rounded or elliptical in shape. The distal tip  18  of the intermediate microcatheter  10  preferably maintains an inner diameter size that is generally uniform of the proximal portions of the intermediate catheter  10  (i.e., a relatively close fit with the guidewire  22 ) in order to minimize the gap between the inner diameter of microcatheter  10  and guidewire  22 . 
         [0027]    In an alternative embodiment, the inner diameter of the lumen of the microcatheter  10  is larger within the enlarged region  14 . However, in this embodiment it would be desirable that the distal tip  18  of microcatheter  10  has a comparatively reduced inner diameter to eliminate any large gap between guidewire  22  and the intermediate microcatheter  10  in order to prevent any open, catching surfaces between the blood vessel and microcatheter  10 . 
         [0028]    Distal marker band  16   a  and proximal marker band  16   b  are located on the microcatheter body  11  at the distal and proximal ends of the enlarged distal section  14 , respectively, to aid in visualizing the position of intermediate microcatheter  10  and, in particular, the distal section of microcatheter  10 . In one embodiment, a third marker band (not shown) could be placed at the distal tip  18  of the intermediate microcatheter  10 , beyond the enlarged distal section  14 , such that the distal tip  18  of the device is viewable within a patient. 
         [0029]    In one illustrative example of a bulbed intermediate microcatheter  10  of the present invention, the outer guide catheter  30  has an inner diameter of about 0.07″, the enlarged distal section  14  of the intermediate microcatheter  10  has an outer diameter of about 0.067″, the area of the microcatheter body  11  proximal of the enlarged section  14  has an outer diameter of about 0.033″, while the distal tip  18  has an outer diameter of about 0.031″. A smaller outer diameter of the distal tip  18  will promote increased flexibility and trackability, while a larger outer diameter of the proximal section of the microcatheter body  11  will promote greater push strength. The inner diameter of intermediate microcatheter  10  is constant at about 0.021″. These dimensions can also vary based on which guidewire or guide catheter is used. For example, the outer diameter of the intermediate microcatheter  10  can range from about 0.013″ to about 0.073″, the length of the enlarged section  14  length is about 0.5 cm to about 3 cm, and the distal tip  18  has a length between about about 0.5 cm to about 6 cm. The inner diameter of the intermediate microcatheter  10  is consistent throughout its length at about 0.01 inches to about 0.045 inches. The working length of the intermediate microcatheter  10  is about 148-168 cm. A lubricious coating can optionally be used over the enlarged section  14  of the intermediate microcatheter  10 . 
         [0030]    The intermediate microcatheter  10  can be manufactured in a variety of ways. In one example, the inner liner of intermediate microcatheter  10  is comprised of PTFE, LDPE, LLDPE, or HDPE. A stainless steel coil is placed over the inner liner and is either a coiled wire or flat wound wire of about 0.00075 inches to about 0.0015 inches. A stainless steel flat wire or braid is placed over the coil. An outer shaft layer can be placed over the reinforcement, this outer layer can comprise different durometers and different types and amounts of material, for example ranging in shore hardness from  10 A to  72 D. Generally, it is desirable to have more stiffness at the proximal end and more flexibility at the distal end, so the outer layer proximal section would generally comprise stiffer material than the outer layer distal section. One or two platinum/iridium (90%/10%) marker bands are placed under the bulb for visualization, with an additional marker band placed at the distal tip  18  of intermediate microcatheter  10 . The enlarged outer diameter region  14  comprising the bulb is comprised of a relatively soft polymeric material such as polyblend  18 A,  30 A, a balloon, or any Shore Hardness A durometer material, this softness will aid flexibility as well as navigation through a guide catheter  38  in scenarios where the inner diameter of outer guide catheter  38  matches closely with the bulbed section  14  outer diameter, or scenarios where bulbed section  14  contacts a portion of the vessel and the soft material helps prevent vessel trauma (e.g., at a blood vessel bifurcation). 
         [0031]    Microcatheter  10  can utilize a lubricious coating along its entire length, or selectively along particular portions to augment tracking ability of the microcatheter. A lubricious coating would be particularly useful in the bulbed region  14  of microcatheter  10  since this is the largest cross-sectional portion of the microcatheter  10 , and is also the part of the microcatheter which is most likely to contact overlying guide catheter  38 . In one example, the lubricious coating is hydrophilic and can utilize multiple layers—for instance, a well-adhering basecoat layer formed from a crosslinker and a highly lubricious topcoat layer chemically adhered to the basecoat layer. 
         [0032]    Guide catheters  38  typically utilize a marker band  40  located approximately 3 cm from its distal tip so the user can visualize the distal tip within a patient (illustrated in  FIG. 3 ). The user would track microcatheter  10  through guide catheter  38  so that the bulbed/enlarged region  14  of intermediate microcatheter  10  is located flush with the distal tip of the outer guide catheter  38 , as shown in  FIG. 3 . This will ensure that there is no gap or a minimized gap between guide catheter  38  and microcatheter  10 . This minimized gap is shown as element  26  whereas the proximal gap  36  reflects the gap between guide catheter  38  and the reduced proximal portion of microcatheter  10 . Proximal gap  36  can be thought of as the normal gap between a microcatheter and guide catheter in scenarios where a typical microcatheter rather than a bulbed microcatheter was used. Gap  6 , as discussed earlier, represents the typical gap that is present between a guidewire  22  and a guide catheter  38  in the typical procedure where the guide catheter is directly tracked over the guidewire. 
         [0033]    Bulbed intermediate microcatheter  10  acts as an intermediary between guidewire  22  and guide catheter  38  as previously described. When intermediate microcatheter  10  is appropriately placed as shown in  FIG. 3 , the user will see a line of marker bands—the microcatheter distal marker band  16   a , the outer guide catheter 3 cm marker band  40 , and the proximal marker band  16   b . Each of these marker bands can be either a series of discrete segments (one for each marker band) with gaps in between, or one elongated and continuous segment. This line of marker bands ensures proper alignment so the user can tell that the enlarged distal section of microcatheter  10  is past the distal tip of guide catheter  38 , such that the enlarged section  14  of microcatheter  10  occupies the space within guide catheter  38 . Once the user can confirm this, the user can proceed to track the guidewire, the intermediate microcatheter over the guidewire, and the guide catheter over the intermediate microcatheter. 
         [0034]    Since the intermediate microcatheter  10  is used as a bridging device between guidewire  22  and guide catheter  38 , there will also be a minor gap  30  present between guidewire  22  and microcatheter  10 . It is desirable that this gap  30  is not eliminated entirely to avoid friction between the guidewire  22  and the intermediate microcatheter  10 . However, this gap  30  is relatively small and therefore a vessel bifurcation will likely not get caught. In one example, microcatheter  10  has a consistent inner diameter of about 0.021″ which would accommodate a guidewire  22  sized from 0.014″ to 0.018″. Applying the earlier formula which defined the gap size as the radius of the outer element (here, microcatheter  10 ) minus the radius of the inner element (here, guidewire  22 ), this results in a gap size between the microcatheter and guidewire of about 0.00205″ to about 0.0035″. If a microcatheter were not used at all, as discussed earlier, the gap size could range from about 0.0175″-0.028″—in other words, the gap size is reduced to about 7-20% of its initial value simply by using a microcatheter. Using a bulbous microcatheter, as discussed earlier, will further reduce the gap between the microcatheter and the overlying guide catheter. Thus, the advantage of using a bulbed microcatheter  10  as an intermediate element between the guidewire  22  and guide catheter  38  is two-fold: 1) it minimizes the gap that is normally present between the guidewire and the guide catheter and 2) the presence of the bulbed/enlarged section  14  of microcatheter  10  minimizes the gap between microcatheter  10  and guide catheter  38 . Reducing or minimizing the gap in turn minimizes the amount of open space available for a blood vessel bifurcation to be caught, which in turn substantially enhances trackability of the device through the tortuous anatomy. 
         [0035]    Alternative embodiments could utilize a bulbed intermediate microcatheter  10  with more or fewer marker bands. In one example, bulbed intermediate microcatheter  10  could use three marker bands where the third intermediate marker band would sit in between distal marker band  16   a  and proximal marker band  16   b . This intermediate marker band would align with the guide catheter 3 cm distal tip marker  40 . The presence of so many marker bands might make them individually difficult to see, and therefore such an embodiment would be best served for a larger microcatheter with an elongated enlarged region  14 . In another example, intermediate microcatheter  10  could use one marker band where the microcatheter marker band would align with the guide catheter distal tip marker band  40  to ensure proper positioning of the intermediate microcatheter. 
         [0036]    In one method of use, a guidewire  22  is tracked through a patient&#39;s vessel and the guide catheter  38  is tracked over the guidewire  22 . When the guidewire  22  is navigated through a vessel bifurcation region, the user tracks the bulbed intermediate microcatheter  10  over the guidewire  22  so that the microcatheter  10  is located at the distal region of the guide catheter  38  and extend out of the distal tip of the guide catheter  38 , such that the distal tip  18  of the intermediate microcatheter  10  is located distal of the outer guide catheter  38  and the enlarged region  14  of the intermediate microcatheter  10  bridges the gap between the guidewire  22  and the guide catheter  38 . To achieve the desired position, the intermediate microcatheter  10  has 2 marker bands,  16   a  and  16   b , as shown in  FIGS. 2-3 . The user manipulates the intermediate microcatheter  10  so that the two marker bands  16   a  and  16   b  are located on either side of guide catheter 3 cm distal tip marker band  40 . The user tracks intermediate microcatheter  10  and guide catheter  38  together as a unit over the guidewire  22  by pushing both simultaneously through the bifurcation region. 
         [0037]    In another embodiment, bulbed intermediate microcatheter  10  is used as part of an implant delivery system. Bulbed microcatheter  10  addresses the ledge effect issue, while also being used a conduit to deliver an implant, such a stent, clot retrieval device, or embolic coils. After the guidewire  22  is used to navigate intermediate microcatheter  10  to the treatment site, the guidewire  22  is withdrawn through intermediate microcatheter  10 . The intermediate microcatheter  10  is subsequently used to deliver an implant. 
         [0038]    In one embodiment, bulbed intermediate microcatheter  10  is part of a clot retrieval system. Clots can lead to issues such as ischemic stroke due to decreased bloodflow to areas distal of the clot. Clot retrieval devices are mechanical structures designed to grab, retain, and remove a clot from the vasculature. U.S. Pat. No. 9,211,132 entitled “Obstruction Removal System” discloses a clot retrieval device and is hereby incorporated by reference in its entirety. Stentrievers are one type of clot retrieval device which take the form of a unitary tubular wire mesh or cylindrical laser cut sheet element that are designed to retain a clot. U.S. Pat. No. 8,679,142, U.S. Pat. No. 8,357,179, U.S. Pat. No. 6,402,771 further disclose stentriever devices and are hereby incorporated by reference in their entirety. 
         [0039]    In one embodiment bulbed intermediate microcatheter  10  is part of a clot retrieval system. In another embodiment, bulbed microcatheter  10  is used as part of a stentriever system. Bulbed intermediate microcatheter  10  addresses the ledge effect issue, where the system helps a clot retriever access a problematic region (e.g. a bifurcation region in the neurovasculature). The system includes a guide catheter  38 , intermediate microcatheter  10 , guidewire  22 , and clot retriever or stentriever (not pictured). Guide catheter  38  is more structurally rigid than microcatheter  10  and would track through a majority of the vasculature to the general region of the delivery procedure. Intermediate microcatheter  10  is smaller than guide catheter  38 , is delivered through the guide catheter, and accesses the actual treatment site thus providing a conduit to the treatment site. Guidewire  22  helps track microcatheter  10  and guide catheter  38  through the vasculature to access the treatment site. The delivery procedure is similar to the one described above where the microcatheter can be tracked over the guidewire and placed beyond the distal tip of the guide catheter to track the system through vascular bifurcation regions. When the system is appropriately placed, guidewire  22  is withdrawn through bulbed intermediate microcatheter  10  and microcatheter  10  is then used as a conduit for a clot retriever or a stentriever. 
         [0040]    In one embodiment, the clot retrieval device or stentriever is pre-delivered through bulbed intermediate microcatheter  10  to a distal section of the intermediate microcatheter  10 , such that the distal end of the clot retrieval device or stentriever is located either flush with the distal end of the intermediate microcatheter  10  or beyond the distal end of the intermediate microcatheter  10 . Intermediate microcatheter  10  is housed within a guide catheter  38 , similar to  FIG. 3 . The outward force provided by the clot retrieval device can be used to help navigate the catheters and stentriever through a vessel bifurcation region and through the tortuous anatomy; that is, the force provided against the microcatheter by the clot retrieval device can help direct the system in a particular direction at a vessel bifurcation, and can also held direct the system through the tortuous anatomy. 
         [0041]    In some embodiments, the bulbed intermediate microcatheter  10  is used without the guidewire  22 , being used for the tracking of the guide catheter  38  and then for the delivery device of subsequently delivered therapeutic materials. The distal section  14  of bulbed intermediate microcatheter  10  is preferably coated with a lubricious coating, and this coating would both decrease tracking friction through guide catheter  38  and also promote smooth tracking through the vasculature. Additionally, since the distal inner diameter of the bulbed intermediate microcatheter  10  is significantly smaller than the inner diameter of the outer guide catheter  38 , there is less open lumen surface available for a vessel bifurcation to be caught. 
         [0042]    In some embodiments, guidewire  22  is first deployed and bulbed microcatheter  10  is then tracked over the guidewire  22 , while guide catheter  38  is separately tracked over the bulbed microcatheter  10 . In some embodiments, guidewire  22  is first deployed, while bulbed microcatheter  19  and guide catheter  38  are deployed simultaneously, and together, over the guidewire. 
         [0043]    Other contemplated embodiments used to address the ledge effect problem utilize a guidewire with an enlarged region that bridges the gap between the guidewire and guide catheter. For example,  FIG. 4  shows a guidewire  110  having a radial projection  116  at its distal end to radially bridge a gap within a guide catheter  38 . In this regard, an intermediate microcatheter with an enlarged distal end, as discussed in the previous embodiments, is unnecessary. 
         [0044]    The radial projection  116  is located within the distal section  110   b  of the guidewire  110  and can have a number of shapes, including ellipsoid, oval, circular, bulbous, or diamond. Projection  116 , in one particular example, has a bulbous shape. Projection  116  is preferably comprised of a soft-polymer material to enhance tracking through the patient&#39;s vessels. A soft-polymer is less stiff than a hard-polymer, and will be more malleable and less likely to jump or suddenly move when the radial projection  116  contacts a vessel wall. It is also preferable for projection  116  to slide rather than jump against the vessel wall in order to prevent any big, unexpected movements. The smooth transition formed by taper  116   a  on the projection  116  further prevents the guidewire  110  from jumping around after contacting the vessel wall within the vasculature. 
         [0045]    Projection  116  further includes a radiopaque marker  118  that, in one example, is a circular marker band located around the polymeric radial projection  116 . The marker band can comprise platinum, tantalum, palladium, gold, or any similar highly dense metallic elements, alloys, or compounds which would be visible via imaging techniques. 
         [0046]    The distal section  110   b  of the guidewire  110  also includes a tapered section  132 , a reduced diameter section  134 , and a coil  117  which is located over the reduced diameter section  134 . Coil  117  is comprised of two different coil elements; a first non-radiopaque coil portion  114  (in one example comprised of stainless steel), and a second radiopaque coil portion  122  useful for imaging and viewing the distal section of the catheter (in one example comprised of platinum). Coil  117  aids in flexibility and provides a soft contact surface to avoid vessel trauma if the guidewire tip hits a vessel wall. 
         [0047]    Guidewire  110  also includes a shapeable distal tip  120  which can be shaped to aid in navigating the guidewire through the vasculature. A shaping mandrel can be used to help shape distal tip  120  of the guidewire  110  so that the distal tip bends in a particular direction. Guidewire shaping mandrels are currently used to pre-shape the distal tip of the guidewire. These shaping mandrels are typically packaged along with the guidewire, and the user uses the mandrels to impart a bent shape onto the distal tip of the guidewire prior to placing the guidewire within the patient&#39;s vasculature. The bent shape is useful to orient the guidewire to navigate the vasculature. The user can rotate the guidewire so the bent tip aligns with the direction the user wants the guidewire to go, such as at a vessel bifurcation point, thus aiding navigation of the guidewire and the catheter tracked over the guidewire through the tortuous anatomy. 
         [0048]    Guidewire  110  is preferably tapered so that its proximal section  110   a  has a larger diameter than the distal section  110   b . This tapered shape will aid in torque response, so that the torque generated by torqueing the proximal end of the system will easily carry through the guidewire  110  and result in a sufficient torque response at the distal tip  120  of guidewire  110 . In one example, guidewire  110  has a proximal diameter  112  of about 0.013 inches to about 0.014 inches, and in a more specific example has a diameter of about 0.0135 inches. This diameter can be slightly tapered or can be substantially constant. Guidewire  110  has a distal section diameter  124  of about 0.012 inches. The distal section diameter  124  is directed only to the diameter of the distal coil  117  comprising coil elements  114  and  122 . 
         [0049]      FIGS. 4-6  show an optional docking element  130  which is located at the proximal part of the guidewire  110  and that serves as a proximal guidewire extension to provide a physician to better grip the guidewire  110  and therefore increase the ease of advancing, retracting, and torqueing the guidewire  110 . In one example, docking element  130  is a proximal wire and guidewire  110  is built over a distal section of docking element  130 , where docking element  130  ends within a proximal section of guidewire  110 . 
         [0050]    In one example, the proximal section  110   a  of guidewire  110  is comprised of a stainless steel core wire and the distal section  110   b  of guidewire  110  (including tapered section  132  and reduced diameter section  134 ) is comprised of a nitinol core wire. 
         [0051]    In one example, guidewire  110  is about 200 centimeters. The stainless steel core wire comprising proximal section  110   a  extends for about 140 centimeters and the stainless steel core wire comprising distal section  110   b  extends for about 60 centimeters. The stainless steel coil  114  extends for about 37 centimeters while the platinum coil  122  covers about 3 centimeters. The shapeable length section  120  extends for about 1.4 centimeters. The hydrophilic coating on the distal section of guidewire  110  extends for about 140 centimeters (covering the distal part of the guidewire and extending until the distal tip of the guidewire). 
         [0052]      FIGS. 5-6  show guidewire  110  from  FIG. 4  along within a guide catheter  38 . In  FIG. 5 , guidewire  110  illustrates projection  116  and radiopaque marker  118 , while the distal part of guidewire  110  is located beyond the distal end of guide catheter  38 . This configuration the guidewire is used to access the vicinity of a target treatment site, and guide catheter  38  is subsequently pushed or tracked over the guidewire  110 . 
         [0053]    In  FIG. 6 , guidewire  110  is either pulled back into guide catheter  38 , or guide catheter  38  is pushed over guidewire  110  so that the projection  116  contacts and fits into guide catheter  38  (e.g., the projection  116  is undersized compared to the lumen of the guide catheter  38  or even slightly oversized but composed of a malleable material that can be deformed and withdrawn into the catheter  38 ). Alternatively, a push/pull combination technique can be used. If projection  116  has a bulbous shape, as shown in  FIGS. 4-6 , then guide catheter  38  should contact the area of projection  116  that has the largest diameter. Guide catheter  38  includes a radiopaque marker  127 . The guidewire radiopaque marker  118  either is located flush with the guide catheter&#39;s radiopaque marker  127 , or the guidewire radiopaque marker  118  is located just distal of guide catheter radiopaque marker  127 . In any case, the presence of two radiopaque elements so close to each other will augment the imaging of the system when viewed by the user, so the user can tell that the two elements are aligned and that guidewire  110  is snug with guide catheter  38  and the system can be pushed through the vasculature. 
         [0054]    When guidewire projection  116  contacts guide catheter  38 , there is substantially no gap between guidewire  110  and guide catheter  38 . This helps mitigate the ledge effect since there is substantially no gap or open surface for the vessel to snag onto. Normally, the presence of a gap creates a void where the guide catheter can get stuck. However, when the guidewire projection  116  is located snug with the guide catheter  38 , there is no such gap and the projection slides against the vessel so that the guide catheter does not get stuck at the vessel bifurcation. As discussed earlier, the projection preferably comprises a soft polymer to promote a sliding effect when the projection contacts the vessel. Additional hydrophilic coating, additional lubricious coatings, or lubricious polymers can be used to further enable the projection to slide against the vessel wall. 
         [0055]    The guidewire  110  of  FIGS. 4-6  can be advanced in a few different ways. In a first method, guidewire  110  is deployed distal of guide catheter  126  and guide catheter  38  is pushed over guidewire  110 . If guide catheter  38  gets stuck (for example, due to the ledge effect), guidewire  110  is retracted so that the guidewire projection  116  contacts guide catheter  38 . Guide catheter  38  is then pushed forward, which advances both guidewire  110  and guide catheter  38  as a unit. Guidewire  110  also advances as guide catheter  38  advances since the guide projection  116  contacts the guide catheter  38 . In a second method, the user places the guidewire projection  116  at the distal section of the guide catheter  38 , and guidewire  110  and guide catheter  38  are pushed together as a unit through the vasculature. Once guide catheter  38  is appropriately placed, a microcatheter can be tracked through the guide catheter and the guidewire  110  is withdrawn, and the microcatheter can be used to deliver a therapeutic agent (e.g. stents, coils, clot retrieval devices), or alternatively the guide catheter  38  itself can be used to deliver a therapeutic agent. 
         [0056]    As discussed earlier with regard to the bulbed microcatheter  10  embodiments, small gaps may be allowable as long as they are too small for the vessel bifurcation to get caught therein—therefore, some embodiments may utilize a small gap between guidewire projection  116  and guide catheter  38  such that the projection  116  does not necessarily contact the guide catheter  38 . 
         [0057]      FIG. 6  shows a torquer  128  used to lock and torque guidewire  110 . The torquer  128  includes a compressible collet that pushes down on and lock the guidewire  110 . The torquer  128  can be twisted or rotated to compress the collet to lock the guidewire  110 , or torquer  128  can contain a movable element linked to the collet to lock guidewire  110  via the collet. In  FIG. 6 , the torquer  128  is shown being applied to a proximal section of guidewire  110 . Torquer  128  is used to lock on to the guidewire  110  so the guidewire distal tip  120  is in a fixed position relative to the torquer  128 . The user would lock the guidewire  110  and then push the guidewire  110  through the vasculature. Since guidewire  110  is locked in a certain position via torquer  128 , the direction of the bent distal tip  120  will not change unless torquer  128  is rotated. Torquer  128  allows the guidewire orientation to be locked and prevents accidental rotation of guidewire  110  while the guidewire  110  is pushed to advance said guidewire through the vasculature. When the user is stuck at a bifurcation and wants to reorient guidewire  110 , the user can then rotate torquer  128  which rotates the guidewire  110  to change the orientation of the guidewire distal tip  120  so that its aligned in another direction. 
         [0058]    In other embodiments, the guidewire projection  116  can selectively lock to guide catheter  38 . In one example, the projection  116  can include threaded elements which thread into a corresponding groove in the guide catheter  38  so the two elements can be locked together similar to a screw. In another example, the projection  116  can include an enlarged ring which mates with a corresponding recess in guide catheter  38 . In another example, guidewire projection  116  includes a recess and the guide catheter  38  includes a projecting ring which mates with said recess. The mating can be done by force, where if the user applies enough force the elements will mate (to lock) and un-mate (to unlock) relative to each other. In one example, a torquer similar to the one described above can be used to lock the guidewire  110  to the guide catheter  38  when the two elements are in contact with each other or mated to each other. 
         [0059]    The earlier description discussed advantages of a soft polymer used for guidewire projection  116 , where one advantage is that the material properties of the soft polymer would promote a sliding contact interface between guidewire projection  116  and the blood vessel. One further advantage of a soft polymer used for the projection is malleability. When guidewire  116  is withdrawn, the user can retract guidewire  116  through the guide catheter  38 . The malleability of a soft polymer will enable the guidewire projection  116  to compress and be retracted through guide catheter  38  with ease. 
         [0060]    In one embodiment, guidewire projection  116  comprises a soft plastic polymer—specifically a unitary polymer piece with a hole through it which the guidewire is placed through. Alternatively, the polymer projection can be extruded over guidewire  110 . Alternatively, the projection can be manufactured separately and affixed over guidewire  110  via adhesive. The projection  116  can have a number of shapes, as contemplated earlier. In particular, the shape of the sides will affect how projection  116  reacts on contact with a vessel wall. Shape examples for projection  116  include a gradual, conical shape as shown in  FIG. 8  as element  116   a  or a concave or convex rounded shape. 
         [0061]    In one example, the proximal  110   a  and distal  110   b  portion of guidewire  110  are manufactured separately. Projection  116  is placed over the distal portion  110   b  of the guidewire  110  utilizing any of the techniques described above. The distal portion  110   b  and proximal portion  110   a  of guidewire  110  are then mated together utilizing various techniques such as heat treatment, adhesive, soldering, welding, etc. In another example, guidewire  110  is manufactured as one piece and any of the techniques described above are used to place projection  116  over the distal portion of guidewire  110 . 
         [0062]    Guidewire  110  can be used with an aspiration or suction catheter, where a vacuum source is placed at the proximal end of the aspiration/suction catheter. Aspiration or suction is sometimes used to aid in clot retrieval, where said aspiration or suction is used to remove a clot lodged in the vasculature. Here, aspiration or suction could be used to seal guidewire  110  relative to the guide catheter  38 . In one example, suction is used to seal guidewire projection  16  to the guide catheter  38  to seal the gap between said guidewire  110  and said guide catheter  38 . The guide catheter  38  is then advanced through the vasculature while suction is applied at the proximal end of the guide catheter  38  to continue to seal the guidewire projection to the catheter. 
         [0063]    In one embodiment, the distal part of guide catheter  38  is radially smaller compared to the rest of the guide catheter. Guidewire  110  with projection  116  can be pushed through guide catheter  38 , while projection  116  will contact the radially reduced distal portion of guide catheter  126  to seal the gap between guide catheter  38  and guidewire  110 . A distal-tip segment  138  can be radially smaller as shown in  FIG. 7 a   , or alternatively the distal-tip  138  can be tapered inwards in order to contact the projection as shown in  FIG. 7 b   . In some embodiments, a marker band  129  as shown in  FIG. 7 a    could optionally be used directly next to the radially reduced region where the guidewire projection marker band  118  would align with the guide catheter  38  radially reduced section marker band  129  so the user could confirm proper placement of guidewire  110  relative to the guide catheter  38 . In another embodiment, guide catheter  38  has a relatively consistent diameter and guidewire projection  116  is malleable enough so that when the user pushes and pulls the guidewire  110 , guidewire projection  116  will contract and easily pass through guide catheter  38 . 
         [0064]    In one embodiment shown in  FIG. 8 , guidewire projection  116  takes on a wedge-shape and has tapered distal  116   a  and proximal  116   b  surfaces. The tapered proximal surface is about the size of the guide catheter  116  diameter or slightly oversized compared to the guide catheter diameter in order to eliminate any gap between guidewire  116  and the guide catheter  38 . If guidewire projection  116  is slightly oversized compared to the guide catheter  38 , the guidewire projection should be malleable to enable compression to allow guidewire  110  to be tracked (pushed/pulled) through guide catheter  38  without issue. 
         [0065]    Another embodiment, shown in  FIG. 9 , can utilize an intermediate rapid exchange system in which an easily deployable device bridges the gap between a guidewire and the guide catheter, and said device can be tracked over the guide wire to eliminate this gap. In operation, a traditional guidewire would be used and if there is a gap between the guidewire and the overlying guide catheter and this gap is caught on a vessel bifurcation, the user can track the rapid exchange device over the guidewire to eliminate the gap. Alternatively, if the user was operating the guidewire through a bifurcation region, he or she could preemptively track the rapid exchange system over the guidewire to bridge the gap between the guidewire and guide catheter and mitigate a potential problem with the ledge effect. 
         [0066]      FIG. 9  shows a rapid exchange intermediate catheter  151  utilizing a core wire  144  with a proximal handle  144   a  that the user uses to manipulate (e.g. push and pull) the catheter  151 . The distal portion of the core wire  144  connects to a tubular portion  148  that has a proximal opening  146  and a distal opening  154  to allow passage of the guidewire  22 . Tubular portion  148  can optionally use a radiopaque marker band  152 . Guide catheters typically include a marker band at a point 3 centimeters from the distal tip, so the tubular portion&#39;s marker band  152  can be used to ensure proper alignment with the distal tip of the guide catheter. The distal portion of tubular portion  148  includes a bulbous or enlarged region  150  that bridges the gap between the tubular portion  148  and the interior of the guide catheter  38 . Region  150  is navigated to the distal tip of the guide catheter  38  such that the gap between the guidewire  151  and the distal opening of the guide catheter  38  is eliminated. In practice, if the user wants to eliminate the guide catheter distal tip gap between a guidewire already deployed within a guide catheter and the guide catheter, the user would track tubular portion  148  of the rapid exchange system over the guidewire, pushing the system via core wire  144  until the system is appropriately placed such that enlarged region  150  fills the gap between the guide catheter and the guide wire. 
         [0067]    Please note figures offered are provided as illustrative visual examples helped in interpretation; sizes and measurements are only offered as illustrative examples and not meant to be specifically limited to what is literally cited. 
         [0068]    Although the invention has been described in terms of particular embodiments and applications, one of ordinary skill in the art, in light of this teaching, can generate additional embodiments and modifications without departing from the spirit of or exceeding the scope of the claimed invention. Accordingly, it is to be understood that the drawings and descriptions herein are proffered by way of example to facilitate comprehension of the invention and should not be construed to limit the scope thereof.