Abstract:
A coronary guidewire ( 10 ) includes a flexible elongated core ( 20 ) and a coil ( 40 ) comprising a plurality of helical coil turns wound around a distal end portion of the core. The coil ( 40 ) has a proximal end ( 50 ) and an opposite distal end ( 52 ). A weld joint ( 62 ) connects the distal end ( 52 ) of the coil to the core ( 20 ) and defines a distal tip ( 80 ) of the guidewire. The distal end ( 52 ) can have a flexible bend radius as small as 0.2 mm-0.6 mm.

Description:
RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application Ser. No. 61/751,029, filed on Jan. 10, 2013, the disclosure of which is hereby incorporated by reference in its entirety. 
     
    
     TECHNICAL FIELD 
       [0002]    The present invention relates generally to a guidewire and, more particularly, to a coronary guidewire with a distal end portion adapted to advance through occlusions in a vessel. 
       BACKGROUND OF THE INVENTION 
       [0003]    The present invention relates in general to the field of medical devices and, in particular, to devices for use in interventional and diagnostic access, manipulation within, and negotiation of, the vascular system. 
         [0004]    The vascular field of medicine relates to the diagnosis, management and treatment of diseases affecting the arteries and veins. Even when healthy, the anatomy of these vessels is complex, with numerous divisions leading into progressively smaller branches. Development of disease within these vessels often complicates matters by altering their caliber, flexibility, and direction. The interior, or lumen, of a blood vessel may develop constrictions, known as stenoses, and at times may even be obstructed, as a result of the development of atherosclerotic plaques or by the occurrence of tears or lacerations in the vessel wall, known as dissections. These obstructions may complicate the vascular anatomy by leading to the formation of new collateral pathways that establish new routes around the obstructions in order to provide blood flow down-stream from the blockage. 
         [0005]    In order to diagnose and treat vascular diseases, a physician may in many instances perform a diagnostic or interventional angiogram. An angiogram is a specialized form of X-ray imaging, requiring physical access into a vessel with some form of cover, needle or guide in order to allow a contrast dye to be injected into the vasculature while X-rays are transmitted through the tissue to obtain an image. The contrast dye illuminates the interior of the vessels and allows the physician to observe the anatomy, as well as any narrowings, abnormalities, or blockages within the vessels. At times, more selective angiograms are used to delineate a particular area of concern or disease with greater clarity. Access to these more selective areas often requires the insertion of guidewires and guide catheters into the vessels. 
         [0006]    Vascular guidewires and guide catheters can be visualized from outside the body, even as they are manipulated through the body&#39;s vascular system, through the use of continuous low-dose fluoroscopy. The negotiation of the complex vascular anatomy, even when healthy, can be difficult, time consuming and frustrating. When narrowed or obstructed by disease, the vessels are even more difficult—and sometimes impossible—to negotiate. 
         [0007]    Attempts to address and overcome the difficulty of negotiating vascular anatomy have led to various devices, primarily guidewires and guide catheters, for assisting physicians. The devices vary in shape, diameter and length. In order to negotiate the smaller blood vessels as well as to provide some standardization within the industry, for example, many catheterization systems are sized to cooperate with guidewire diameters of 0.035″ or less (0.018″ and 0.014″ being the next most common sizes). 
       SUMMARY OF THE INVENTION 
       [0008]    The invention relates to a coronary guidewire that includes a flexible elongated core and a coil comprising a plurality of helical coil turns wound around a distal end portion of the core. The coil has a proximal end and an opposite distal end. A weld joint connects the distal end of the coil to the core and defines a distal tip of the guidewire. The weld joint can be a tungsten inert gas welded joint. The guidewire may include a solder joint that connects the proximal end of the coil to the core. A second solder joint may connect the coil to the core at a location between the welded distal end of the coil and the soldered proximal end of the coil. 
         [0009]    The coil may include a proximal portion including the proximal end of the coil and a distal portion including the distal end of the coil. The proximal portion of the coil can be constructed of stainless steel, and the distal portion of the coil can be constructed of a platinum alloy. The distal end portion of the core can include a bend adjacent the distal tip. The bend in the core can have a bend radius in the range of 0.2 mm-0.6 mm. The coil may follow the bend such that adjacent coil turns along the bend are spaced from each other and can be moved toward each other to permit the bend in the core to straighten. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    For a better understanding of the invention, reference may be made to the accompanying drawings, in which: 
           [0011]      FIG. 1  is a plan view illustrating a guidewire, according to the invention; 
           [0012]      FIG. 2  is a plan view illustrating a portion of the guidewire of  FIG. 1 ; 
           [0013]      FIG. 3  is a plan view illustrating the guidewire of  FIG. 1  in a different condition; 
           [0014]      FIG. 4  is a magnified view of a portion of the guidewire of  FIG. 3 ; and 
           [0015]      FIGS. 5A-5E  are schematic views illustrating the operation of the guidewire of  FIGS. 1-4 . 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0016]    The invention relates to an apparatus  10  in the form of a guidewire for navigating a vessel, such as the human vasculature. The guidewire  10  may be especially suited to traverse a partial or total occlusion of the vessel. The guidewire  10  is illustrated in  FIGS. 1-4 . The guidewire  10  includes a flexible elongated core  20  that has longitudinally spaced proximal and distal ends  12  and  14 , respectively. The guidewire  10  also includes a cover  30  that wraps the core  20  and extends along a substantial portion of its length. The guidewire  10  further includes a coil  40  mounted to the core  20  at the distal end  14  of the guidewire. 
         [0017]    In this description, the term “longitudinal” is used to refer to a direction defined by the length of the guidewire  10 , generally horizontal as viewed in  FIGS. 1-4  and extending along a central axis  16  of the guidewire  10 . The term “lateral” is used herein to refer to a direction which is transverse to the longitudinal direction, i.e., transverse to the guidewire axis  16 . The term “radial” is used herein to refer to a direction which is radial with respect to the longitudinal direction, i.e., radial with respect to the guidewire axis  16 . 
         [0018]    A central body portion  18  of the guidewire  10  extends between the proximal end  12  and distal end  14 . The core  20  extends longitudinally from the length of the guidewire  10  from the proximal end  12  to the distal end  14 . The core  20  is flexible and may, for example, be constructed of a stainless steel material, such as a grade  304  surgical stainless steel. The core  20  has a proximal end  22  and a distal end  24 . The cover  30  wraps the core  20  from the proximal end  12 , along the body portion  18 , to the distal portion  14 . The cover  30  is constructed of a biocompatible material, such as a polymer material. The cover  30  can, for example, be constructed of a PTFE (Polytetrafluoroethylene) resin material. As best shown in  FIG. 2 , the cover  30  can leave a portion of the distal end  14  of the guidewire  10  uncovered. 
         [0019]    The body portion  18  has a generally uniform diameter D 1  along its length, which accounts for the majority of the length of the guidewire  10 . The diameter D 1  can be up to a 0.035 inch diameter. For example, the diameter D 1  could be a 0.014 inch diameter. In the embodiment of  FIGS. 1-4 , break lines in the body portion  18 , identified generally at  26 , are used to indicate a portion of the body portion that is omitted from the figures for purposes of clarity and simplicity. The length of the guidewire  10  can vary depending on its intended application. For instance, the guidewire  10  can be up to 1700-2000 mm or longer. In one particular example, the guidewire  10  can have a length of 1800 mm. 
         [0020]    The guidewire  10  has a diameter that is dictated primarily by the diameter of the core  20 . In the embodiment of  FIGS. 1-4 , the guidewire  10  has a generally uniform diameter D 1  along its length from the proximal end  12 , along the body portion  18  to proximate the distal end  14 . For example, the proximal end  12  and body portion  18  may have a nominal diameter of about 0.35 mm. The diameter of the guidewire  10  van vary along its length. For example, the distal end  14  of the guidewire  10  may have one or more sections or segments having tapered configurations of varying diameters. The tapered diameters of these segments may, for example, be selected to provide a desired degree of guidewire flexibility. 
         [0021]    As shown in  FIGS. 1-3 , the guidewire body  18  has a first tapered segment  32  that tapers down to a first segment  34  with diameter D 2 , and a second tapered segment  36  that tapers down to a second segment  38  with diameter D 3 . In the illustrated embodiment, the cover  30  terminates at the second segment  38 . The cover  30  could terminate at other positions along the length of the core  20 . Referring to  FIG. 2 , at the distal end  14 , the core  20  has a third tapered segment  42  followed by a third segment  44  with diameter D 4 , and a fourth tapered segment  46  followed by a fourth segment  48  with diameter D 5 . The fourth segment  48  terminates at the distal tip of the core  20 . 
         [0022]    Referring to  FIGS. 1 ,  3  and  4 , the guidewire  10  includes a coil  40  that surrounds the core  20  along the length of the distal end portion  14 . A hydrophilic coating may coat or otherwise cover the coil  40 . In the illustrated embodiment, the coil  40  surrounds core  20  beginning at the second segment  38  and continues over the third tapered segment  42 , third segment  44 , fourth tapered segment  46 , and fourth segment  48 . The extent or coverage of the coil could diverge from that illustrated in the figures. For example, the coil  40  could extend along segments in addition to segments  38 ,  42 ,  44 ,  46 , and  48 , or one or more of these segments could be left uncovered by the coil. 
         [0023]    Referring to  FIG. 4 , the coil  40  has a proximal end  50  and an opposite distal end  52 . The coil  40  is interconnected with the core  20  at three locations along the length of the coil. The proximal end  50  of the coil  40  is secured to the second segment  38  of the core  20  by a soldered joint  60  formed, for example, of a gold-tin or silver-tin solder material. The distal end  52  of the coil  40  is secured to the fourth segment  48  at the distal end  24  of the core  20  by a welded joint  62 . An interface portion  70  of the coil  40  positioned between the proximal end  50  and distal end  52  is also connected to the core  20  by a soldered joint  72  formed, for example, of a gold-tin or silver-tin solder material. The coil  40  could have a greater number of connections with the core  20  or fewer connections with the core. 
         [0024]    The coil has an outer diameter D 6  and an inner diameter D 7  (see  FIG. 4 ). As best shown in  FIG. 4 , the diameters D 6  and D 7  can be substantially constant along the length of the coil  40 . In the illustrated embodiment, the inner diameter D 7  is about equal to the outer diameter D 3  of the second segment  38 . The diameter of the coil  40  could, however, vary along the length of the coil. For example, the coil diameter could follow the taper of the core  40  at one or both of the tapered sections  42  and  46 . 
         [0025]    In the embodiment of  FIGS. 1-4 , the coil  40  has a two material construction, with a proximal first coil portion  54  constructed of a stainless steel material, such as a  304  surgical grade stainless steel, and a distal second coil portion  56  constructed of a platinum alloy, such as a platinum-tungsten alloy. The interface portion  70  includes the stainless steel-platinum alloy interface  76 , where the first and second coil portions  54  and  56  of the coil  40  meet. The solder joint  72  thus connects both the distal end of the stainless steel first coil portion  54  and the proximal end of the platinum alloy second coil portion  56  to the fourth segment  48  of the core  20 . Similarly, the solder joint  60  connects the proximal end of the stainless steel first coil portion  54  to the second segment  38  of the core  20 , and the welded joint  62  connects the distal end of the platinum alloy second coil portion  56  to the fourth segment  48  of the core. 
         [0026]    The welded joint  62  also defines a distal tip  80  of the guidewire  10 . The distal tip  80  has a generally rounded configuration with a diameter about equal to the outer diameter of the coil  40 . More specifically, the distal tip  80  has a diameter about equal to the outer diameter of the distal end of the second coil portion  56  of the core  20 . Thus, in a construction in which the coil  40  has a multi-diameter configuration, the distal tip  80  may have a diameter that is different than other portions of the coil. Due to its welded construction, the distal tip  80  has a solid, homogeneous material construction that surrounds or encapsulates a distal end portion of the platinum alloy second coil portion  56 . 
         [0027]    The welded joint  62  is formed by tungsten inert gas (TIG) welding, which can also be referred to as gas tungsten arc welding (GTAW). The welded joint  62  is formed via TIG welding using a filler material, such as a surgical grade  304  stainless steel that matches the material of the core  20 . The filler material fills the space between the core  20  and the coil  40 , encapsulating the coil to thereby form a permanent connection with the coil. Simultaneously, the distal portion  24  of the core  40  may itself become molten or partially molten and combine with the molten filler material to form a homogeneous mixture that encapsulates the coil  40  and thereby forms the permanent connection with the coil. 
         [0028]    The second coil portion  56 , being constructed of a platinum alloy material, has a melting point that is significantly higher than that of the stainless steel used to form the core  20  and welded joint  62 . Thus, the second coil portion  56  resists melting when the TIG/GTAW welding occurs, which allows the welded joint  62  to encapsulate the second coil portion without deforming it. The second coil portion  56  can therefore maintain its helical coil spring configuration and its spring properties throughout and after the formation of the weld joint  62 . 
         [0029]    The rounded shape of the distal tip  80  can be formed in a variety of manners. For example, the distal tip  80  can be formed in a rough shape during the welding and post-processed, by means such as grinding, polishing, etc. to achieve the final form. Alternatively, the distal portions of the core  20  and coil  40  could be welded and formed simultaneously, such as by welding the distal tip  80  in a mold or other shape-forming confinement constructed of a high-melting point material, such as a ceramic material. The distal tip  80  could, for example, be constructed of a silver brazing alloy or a gold brazing alloy. 
         [0030]    The guidewire  10  may also include one or more markers constructed of a radiopaque material, such as gold, platinum, iridium or a combination thereof, such as a platinum-iridium alloy, which can be easily viewed on x-rays. The inclusion of markers facilitates monitoring the progression of the guidewire  10  in a patient&#39;s vasculature. The markers can, for example, comprise portions of the core  20  that are plated with these materials. Example locations for markers are illustrated generally at  74  in  FIG. 1 . Alternative locations could also serve as markers. For example, the tip  80  of the guidewire  10  could be formed or coated with a radiopaque material and thus serve as a marker. 
         [0031]    The guidewire  10  has a stiffness that varies along its length due at least in part to factors such as the material construction of the core  20  and the diameter of the core. The term “stiffness” is used herein to indicate the resistance of an elastic body to deflection or deformation by an applied force. With regard to the guidewire  10 , its stiffness can be determined, for example, by applying a force axially or longitudinally. The stiffness of the guidewire  10  is judged in terms of the magnitude of the axial/longitudinal force required to cause a predetermined degree of bending. 
         [0032]    As shown in  FIG. 1 , the guidewire  10  can have a substantially uniform construction along a majority of its length. Approaching the distal portion  14 , the guidewire, i.e., the core  20  and its accompanying cover  30 , are reduced in diameter through the taper portions  32 ,  36 , and  42 , and their respective reduced diameter portions  34 ,  38 , and  44 . While the term “diameter” is used herein for simplicity, there is no requirement that the guidewire  10  or core  20  have a circular cross-section. Instead, any portion of the guidewire  10  can have any desired cross-sectional shape. In such an instance, the term “diameter” (as used herein) would refer to a cross-sectional dimension commensurate with cross-sectional size or area, as understood by one having ordinary skill in the art. In view of this, it can be appreciated that the guidewire  10  of  FIGS. 1 and 2  has a stiffness that is reduced over its length as the core  20  tapers down along the distal end  14  toward the distal tip  80 . 
         [0033]    The coil  40  has properties, e.g., elastic or spring properties, that cause it to resume its helical configuration after being deflected. Additionally, the coil  40  also increases the stiffness of the guidewire  10  along the portions of the core  20  covered by the coil. In the illustrated embodiment, the stiffness of the distal end  14  of the guidewire  10  is essentially equal to the stiffness of the core  20  plus the stiffness of the coil  40 . Thus, the overall stiffness of the distal end  14  of the guidewire  10  can be configured to have a predetermined stiffness by selecting the appropriate combination of coil  40  characteristics (e.g., materials and configurations) and core  20  characteristics (e.g., materials and configurations, diameters, tapers, cross-sections, etc.). 
         [0034]    The distal end  14  of the guidewire  10  includes an end segment  100  that extends from the solder joint  72  up to and including the distal tip  80 . In the illustrated embodiment, the end segment  100  includes the fourth segment  48  of the core  20 , the welded joint  62  forming the distal tip  80 , and the platinum alloy second coil portion  56  of the coil  40 . The end segment  100  has a bent or curved configuration defined by a bend  102  in which the fourth core segment  48  is bent at an angle relative to the axis  16 . The bend angle is indicated generally at A in  FIG. 4 . The bend angle A can be any desired angle. For example, the bend angle A can be about 24-32 degrees. 
         [0035]    Additionally, the bend  102  of the end segment  100  can be configured to occur at any desired location along the length of the distal end  14  of the guidewire  10 . For example, the bend  102  can begin at a location that is 0.20 mm-1.00 mm from the distal tip  80 . Other bend locations are possible. To facilitate a desired bend location, the lengths and positions of the tapered segment  46  and core segment  48  can be configured accordingly. 
         [0036]    Advantageously, the welded construction of the distal tip  80  permits the bend  102  to be positioned in such close proximity (e.g., 0.20 mm-1.00 mm) to the tip. The weld joint  62 , formed from a stainless steel material that matches the material of the core  20 , results in a homogeneous construction in which the material properties do not differ substantially at the transition from core  20  to tip  80 . Thus, when the bend  102  is applied, the materials of the core and the tip respond similarly or identically and thereby resist any failure (e.g., rupture, cracking, etc.) that might otherwise occur where different materials are used. 
         [0037]    The bend  102  can be produced in the core segment  48  before or after the assembly of the coil  40  to the core  20 . Due at least in part to the fact that the bend  102  is defined between the solder joint  72  and the welded joint  62  in which the coil  40  is connected to the core  20 , the coil follows the bend. As a result, portions of the coils of the second coil portion  56  are moved close together along an inner bend radius R 1  of the bend  102 . The inner bend radius R 1  can, for example, be 0.10 mm-1.70 mm. Additionally, portions of the coils of the second coil portion  56  are moved away from each other along an outer radius R 2  of the bend  102 . The outer bend radius R 2  can, for example, be 0.40 mm-2.10 mm. 
         [0038]    This construction of the end segment  100  provides advantageous features. If, during use, a force applied to the end segment  100  causes it to deflect in a manner that unbends or straightens the bend  102 , the spaced coil portions along the outer radius R 2  can move towards each other to thereby allow the deflection to take place. Once the deflecting force is removed, the bend  102  in the end segment  100  is free to resume its configuration under the resilient properties of the core  20  and those of the coil  40 . 
         [0039]    During use, the bend  102  in the end portion  100  facilitates navigating the guidewire  10  in the vasculature to penetrate an occlusion in a lumen. This is illustrated in  FIGS. 5A-5E . Referring to  FIG. 5A , during use, the guidewire  10  approaches an occlusion  112  in a lumen  110  (i.e., a blood vessel). The tip  80  and the bend  102  in the end portion  100  in combination to allow the user/surgeon to navigate the guidewire  10  so that the tip engages the occlusion  112 . Navigation can be monitored via x-ray using the markers  74  (see  FIGS. 1-3 ). 
         [0040]    Referring to  FIG. 5B , the guidewire  10  is navigated and advanced so that the tip  80  enters the occlusion  112 . While the guidewire  10  continues advancing in the lumen  110 , the end portion  100  deflects, which causes the bend  102  to unbend or straighten. The straightening of the bend  102  allows the guidewire  10  to advance through the occlusion  112 , as shown in  FIG. 5C . At this point, the bend  102  can be almost completely straightened so that the end portion  100  extends essentially coaxially with the remainder of the guidewire  10 . 
         [0041]    Referring to  FIG. 5D , upon further advancement of the guidewire  10  through the occlusion  112 , the tip  80  eventually emerges. As shown in  FIG. 5E , after the tip  80  exits the occlusion  112 , the end portion  100  emerges and the bend  102  resumes its configuration under the resilience of the second spring portion  56  and the core  10 . The bend  102  is therefore available to perform its function in allowing the user/surgeon to navigate the lumen  110 , having traversed the occlusion  112 . 
         [0042]    From the above description of the invention, those skilled in the art will perceive improvements, changes and modifications. Such improvements, changes and modifications within the skill of the art are intended to be covered by the appended claims.