Abstract:
Methods and devices relating to guidewires. In one embodiment, a distal tip portion of a guidewire comprises a first tip member and a second tip member. The first tip member has a first end, and a second end. The second tip member has a distal portion and a proximal portion. The first and second tip members are coupled together, preferably in an arrangement that can effect the flexibility of the guidewire at certain points along its length.

Description:
FIELD OF THE INVENTION  
         [0001]    The invention is directed to guidewires. More particularly, the invention relates to guidewires having a relatively longitudinally stiff proximal portion, and a relatively laterally flexible distal portion.  
         BACKGROUND OF THE INVENTION  
         [0002]    It is often desirable to combine a number of performance features in a guidewire. For example, it is often desirable that a guidewire be relatively laterally flexible at certain points along its length, for example, near its distal end.  
         SUMMARY OF THE INVENTION  
         [0003]    The invention is directed to guidewires. One embodiment includes a guidewire including a first tip member and a second tip member. The first tip member has a first end, and a second end. The second tip member has a distal portion and a proximal portion. The two tip members are coupled together, preferably in an arrangement that can effect the flexibility of the guidewire at certain points along its length. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0004]    [0004]FIG. 1 is a plan view of a guidewire in accordance with an exemplary embodiment of the invention;  
         [0005]    [0005]FIG. 2 is a partial cross-sectional view of a distal tip portion of the guidewire of FIG. 1;  
         [0006]    [0006]FIG. 3 is a partial cross-sectional view of a distal tip portion of a guidewire in accordance with an additional exemplary embodiment of the invention;  
         [0007]    [0007]FIG. 4 is an additional partial cross-sectional view of a distal tip portion of the guidewire of FIG. 3;  
         [0008]    [0008]FIG. 5 is an additional partial cross-sectional view of a distal tip portion of the guidewire of FIG. 3;  
         [0009]    [0009]FIG. 6 is a perspective view of a distal tip portion of the guidewire of FIG. 3;  
         [0010]    [0010]FIG. 7 is an additional perspective view of a distal tip portion of the guidewire of FIG. 3;  
         [0011]    [0011]FIG. 8 is a partial cross-sectional view of a distal tip portion of a guidewire in accordance with an additional exemplary embodiment of the invention; and  
         [0012]    [0012]FIG. 9 is a partial cross-sectional view of a distal tip portion of a guidewire in accordance with an additional exemplary embodiment of the invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0013]    The following detailed description should be read with reference to the drawings, in which like elements in different drawings are numbered in like fashion. The drawings, which are not necessarily to scale, depict selected embodiments and are not intended to limit the scope of the invention. In some cases, the drawings may be highly diagrammatic in nature. Examples of constructions, materials, dimensions, and manufacturing processes are provided for various elements. Those skilled in the art will recognize that many of the examples provided have suitable alternatives which may be utilized.  
         [0014]    [0014]FIG. 1 is a plan view of a guidewire  100  in accordance with the invention. Guidewire  100  includes an elongate proximal portion  102  terminating at a proximal end  110  and distal tip portion  104  terminating at a distal end  112 . Elongate proximal portion  102  comprises an elongate body member  106 . Distal tip portion  104  includes an atraumatic tip  108  and a sheath  120 . In a preferred embodiment, the distal end of sheath  120  is fixed to atraumatic tip  108  and the proximal end of sheath  120  is fixed to elongate body member  106 .  
         [0015]    The sheath  120  comprises a wire  122  forming a plurality of turns  124 . In a preferred embodiment, adjacent turns  124  are disposed in close proximity to one another. In a particularly preferred embodiment, adjacent turns  124  contact each other across substantially their entire length. In this particularly preferred embodiment, sheath  120  has a high level of longitudinal pushability and a high level of lateral flexibility.  
         [0016]    [0016]FIG. 2 is a partial cross-sectional view of distal tip portion  104  of guidewire  100  of FIG. 1. In FIG. 2, it may be appreciated that atraumatic tip  108  of guidewire  100  is fixed to a distal end  134  of a first tip member  126  that extends distally from a body taper  130  of elongate body member  106 . An intermediate portion  132  of first tip member  126  extends between distal end  134  of first tip member  126  and a proximal end  136  of first tip member  126 . Intermediate portion  132  of first tip member  126  comprises a proximal segment  138 , a distal segment  140 , and a tapered portion  142  extending between proximal segment  138  and distal segment  140 .  
         [0017]    Distal tip portion  104  of guidewire  100  also includes a second tip member  128 . In a preferred embodiment, a proximal portion  144  of second tip member  128  is coupled to end  136  of first tip member  126 . Proximal portion  144  of second tip member  128  is fixed to body taper  130  of elongate body member  106  such that second tip member  128  is coupled to first tip member  126  via body taper  130 . Second tip member  128  may be fixed to body taper  130  of elongate body member  106  in various ways. Some examples of suitable methods of fixing second tip member  128  to elongate body member  106  include soldering, brazing, adhesive bonding, welding and the like. It is to be appreciated that various welding processes may be utilized without deviating from the spirit and scope of the present invention. Examples of welding processes that may be suitable in some applications include LASER welding, resistance welding, TIG welding, and microplasma welding. LASER welding equipment that may be suitable in some applications is commercially available from Unitek Miyachi of Monrovia, Calif. and Rofin-Sinar Incorporated of Plymouth, Mich. Resistance welding equipment that may be suitable in some applications is commercially available from Palomar Products Incorporated of Carlsbad, Calif. and Polaris Electronics of Olathe, Kans. TIG welding equipment that may be suitable in some applications is commercially available from Weldlogic Incorporated of Newbury Park, Calif. Microplasma welding equipment that may be suitable in some applications is commercially available from Process Welding Systems Incorporated of Smyrna, Tenn.  
         [0018]    The distal portion of slope  150  and/or tong  148  can be attached to the first tip member  126  using adhesives, for example polyurethane, silicone, cyanoacrylates, epoxies, and the like.  
         [0019]    A distal portion  146  of second tip member  128  is disposed about intermediate portion  132  of first tip member  126 . Preferably, distal portion  146  of second tip member  128  includes a slope  150  and a tong  148  that extends distally from second tip member  128 . It should be noted that embodiments of second tip member  128  are possible in which distal portion  146  does not include tong  148 . In a preferred embodiment, second tip member  128  comprises a tubular wall defining a lumen.  
         [0020]    Preferably, the shape of the distal portion  146  is arranged and configured such that the distance that the first tip member  126  deflects in a first direction before engaging the distal portion  146  of the second tip member  228  is different than the distance that the first tip member  126  deflects in a second direction before intermediate portion  132  of the first tip member  126  engages second tip member  128 . Preferably, the lateral stiffness of the distal portion  146  of the guidewire  100  changes when the first tip member  126  engages the second tip member  128 .  
         [0021]    In a preferred embodiment, second tip member  128  comprises a shape memory material. Examples of shape memory materials which may be suitable in some applications include shape memory polymers and shape memory alloys. Examples of shape memory alloys which may be suitable in some applications include nitinol. The word nitinol was coined by a group of researchers at the United States Naval Ordinance Laboratory (NOL) who were the first to observe the shape memory behavior of this material. The word nitinol is an acronym including the chemical symbol for nickel (Ni), the chemical symbol for titanium (Ti), and an acronym identifying the Naval Ordinance Laboratory (NOL). Nitinol is commercially available from Memry Technologies (Brookfield, Conn.), TiNi Alloy Company (San Leandro, Calif.), and Shape Memory Applications (Sunnyvale, Calif.). In an especially preferred embodiment, second tip member  128  comprises superelastic nitinol.  
         [0022]    In FIG. 2, it may be appreciated that wire  122  of sheath  120  of distal tip portion  104  has a generally circular cross-sectional shape. The term “wire”, as used in describing wire  122 , should not be mistaken as limiting wire  122  to elements having a circular cross section. The cross section of wire  122  may be any number of shapes. For example, the cross section of wire  122  could be rectangular, elliptical, and the like. Likewise, the term “wire”, as used in describing wire  122 , should not be mistaken as being limited to metallic materials. In fact, wire  122  may be comprised of many metallic and non-metallic materials. Examples of metallic materials that may be suitable in some applications include stainless steel, nitinol, tantalum, gold, and titanium. Examples of non-metallic materials that may be suitable in some applications may be found in the list immediately below which is not exhaustive: polycarbonate, poly(L-lactide) (PLLA), poly(D,L-lactide) (PLA), polyglycolide (PGA), poly(L-lactide-co-D,L-lactide) (PLLA/PLA), poly(L-lactide-co-glycolide) (PLLA/PGA), poly(D, L-lactide-co-glycolide) (PLA/PGA), poly(glycolide-co-trimethylene carbonate) (PGA/PTMC), polyethylene oxide (PEO), polydioxanone (PDS), polycaprolactone (PCL), polyhydroxylbutyrate (PHBT), poly(phosphazene), polyD,L-lactide-co-caprolactone) (PLA/PCL), poly(glycolide-co-caprolactone) (PGA/PCL), polyanhydrides (PAN), poly(ortho esters), poly(phoshate ester), poly(amino acid), poly(hydroxy butyrate), polyacrylate, polyacrylamid, poly(hydroxyethyl methacrylate), polyurethane, polysiloxane and their copolymers. Embodiments of the present invention have also been envisioned in which wire  122  has a tubular cross section.  
         [0023]    [0023]FIG. 3 is a partial cross-sectional view of a distal tip portion  204  of a guidewire  200  in accordance with an additional exemplary embodiment of the invention. In FIG.  3 , it may be appreciated that distal tip portion  204  of guidewire  200  includes a first tip member  226  having a first end  252 , a second end  254 , and an intermediate portion  232  extending therebetween. First end  252  of first tip member  226  is fixed to an atraumatic tip  208  of guidewire  200 . Second end  254  of first tip member is fixed to an elongate body member  206  of guidewire  200 .  
         [0024]    Distal tip portion  204  of guidewire  200  also includes a second tip member  228 . In a preferred embodiment, a proximal portion  244  of second tip member  228  is coupled to the second end  254  of first tip member  226 . Proximal portion  244  of second tip member  228  is fixed to body taper  230  of elongate body member  206  such that second tip member  228  is coupled to first tip member  226  via body taper  230 . Second tip member  228  may be fixed to body taper  230  of elongate body member  206  in various ways. Methods of fixing second tip member  228  to elongate body member  206  that may be suitable in some applications include soldering, brazing, adhesive bonding, welding, and the like.  
         [0025]    A distal portion  246  of second tip member  228  is disposed about intermediate portion  232  of first tip member  226 . In a preferred embodiment, first tip member  226  and second tip member  228  are configured such that intermediate portion  232  of first tip member  226  engages distal portion  246  of second tip member  228  after a pre-selected deflection of first tip member  226 . For example, intermediate portion  232  of first tip member  226  may seat against and/or couple with distal portion  246  of second tip member  228 . In a preferred embodiment, the lateral stiffness of distal tip portion  204  of guidewire  200  changes when intermediate portion  232  of first tip member  226  engages distal portion  246  of second tip member  228 .  
         [0026]    It is to be appreciated that embodiments of distal tip portion  204  are possible in which an adhesive joint is disposed between intermediate portion  232  of first tip member  226  and distal portion  246  of second tip member  228 . Embodiments of distal tip portion  204  are possible in which a soft polymer tube is disposed between first tip member  226  and second tip member  228 .  
         [0027]    Distal portion  246  of second tip member  228  includes a slope  250 . In a preferred embodiment, the shape of distal portion  246  may preferably be selected so that the distance that first tip member  226  deflects in a first direction before engaging second tip member  228  is different than the distance that first tip member  226  deflects in a second direction before intermediate portion  232  of first tip member  226  engages second tip member  228 .  
         [0028]    [0028]FIG. 4 is an additional partial cross-sectional view of distal tip portion  204  of guidewire  200  of FIG. 3. First tip member  226  has been deflected in a first direction  256  such that first end  252  has been displaced by a first distance  258 . In FIG. 4, it may be appreciated that intermediate portion  232  of first tip member  226  is seated against distal portion  246  of second tip member  228 . In a preferred embodiment, first tip member  226  and second tip member  228  are configured such that intermediate portion  232  of first tip member  226  engages distal portion of second tip member  228  after a pre-selected deflection in first direction  256 . Also in a preferred embodiment, the lateral stiffness of distal tip portion  204  of guidewire  200  changes when intermediate portion  232  of first tip member  226  engages distal portion  246  of second tip member  228 .  
         [0029]    [0029]FIG. 5 is an additional partial cross-sectional view of distal tip portion  204  of guidewire  200  of FIG. 3. First tip member  226  has been deflected in a second direction  260  such that first end  252  has been displaced by a second distance  262 . In FIG. 5, it may be appreciated that intermediate portion  232  of first tip member  226  is seated against distal portion  246  of second tip member  228 . In a preferred embodiment, first tip member  226  and second tip member  228  are configured such that intermediate portion  232  of first tip member  226  engages distal portion  246  of second tip member  228  after a pre-selected deflection in second direction  260 . Also in a preferred embodiment, the lateral stiffness of distal tip portion  204  of guidewire  200  changes when intermediate portion  232  of first tip member  226  engages distal portion  246  of second tip member  228 .  
         [0030]    [0030]FIG. 6 is a perspective view of first tip member  226  and second tip member  228  of guidewire  200  of FIG. 3. For purposes of simplicity and clarity, only first tip member  226  and second tip member  228  are shown in FIG. 6. In the embodiment of FIG. 6, first tip member  226  has been deflected in a third direction  264  such that first end  252  has been displaced by a third distance. In FIG. 6, it may be appreciated that intermediate portion  232  of first tip member  226  is seated against distal portion  246  of second tip member  228 . In a preferred embodiment, first tip member  226  and second tip member  228  are configured such that intermediate portion  232  of first tip member  226  engages distal portion of second tip member  228  after a pre-selected deflection in third direction  264 . Also in a preferred embodiment, the lateral stiffness of distal tip portion  204  of guidewire  200  changes when intermediate portion  232  of first tip member  226  engages distal portion  246  of second tip member  228 .  
         [0031]    [0031]FIG. 7 is a perspective view of first tip member  226  and second tip member  228  of guidewire  200  of FIG. 3. For purposes of simplicity and clarity, only first tip member  226  and second tip member  228  are shown in FIG. 7. First tip member  226  has been deflected in a fourth direction  266  such that first end  252  has been displaced by a fourth distance. In FIG. 7, it may be appreciated that intermediate portion  232  of first tip member  226  is seated against distal portion  246  of second tip member  228 . In a preferred embodiment, first tip member  226  and second tip member  228  are configured such that intermediate portion  232  of first tip member  226  engages distal portion  246  of second tip member  228  after a pre-selected deflection in fourth direction  266 . Also in a preferred embodiment, the lateral stiffness of distal tip portion  204  of guidewire  200  changes when intermediate portion  232  of first tip member  226  engages distal portion  246  of second tip member  228 . In the embodiment of FIG. 6 and FIG. 7, the third distance is preferably substantially equal to the fourth distance.  
         [0032]    [0032]FIG. 8 is a partial cross-sectional view of a distal tip portion  304  of a guidewire  300  in accordance with an additional exemplary embodiment of the invention. In FIG. 8, it may be appreciated that distal tip portion  304  of guidewire  300  includes a first tip member  326  having a first end  352 , a second end  354 , and an intermediate portion  332  extending therebetween. First end  352  of first tip member  326  is fixed to an atraumatic tip  308  of guidewire  300 . Second end  354  of first tip member is fixed to an elongate body member  306  of guidewire  300 . Intermediate portion  332  of first tip member  326  comprises a proximal segment  338 , a distal segment  340 , and a tapered portion  342  extending between proximal segment  338  and distal segment  340 .  
         [0033]    Distal tip portion  304  of guidewire  300  also includes a second tip member  328  which is disposed about first tip member  326 . In a preferred embodiment, a proximal portion  344  of second tip member  328  is coupled to second end  354  of first tip member  326 . A proximal portion  344  of second tip member  328  is fixed to a body taper  330  of elongate body member  306  such that second tip member  328  is coupled to first tip member  326  via body taper  330 . Second tip member  328  may be fixed to body taper  330  of elongate body member  306  in various ways. Methods of fixing second tip member  328  to elongate body member  306  that may be suitable in some applications include soldering, brazing, adhesive bonding, welding, and the like.  
         [0034]    A distal portion  346  of second tip member  328  is disposed about intermediate portion  332  of first tip member  326 . Second tip member  328  comprises a tubular wall defining a lumen. Distal portion  346  includes a necked portion  368 . In a particularly preferred embodiment, second tip member  328  comprises nitinol. In an especially preferred embodiment, second tip member  328  comprises superelastic nitinol. When second tip member  328  comprises nitinol, necked portion  368  of second tip member  328  preferably provides a smooth transition in the lateral stiffness of distal tip portion  304  of guidewire  300 .  
         [0035]    [0035]FIG. 9 is a partial cross-sectional view of a distal tip portion  404  of a guidewire  400  in accordance with yet another exemplary embodiment of the invention. In FIG. 9, it may be appreciated that distal tip portion  404  of guidewire  400  includes a distal tip member  470  having a first end  452 , a second end  454 , and an intermediate portion  432  extending therebetween. First end  452  of distal tip member  470  is fixed to an atraumatic tip  408  of guidewire  400 .  
         [0036]    Second end  454  of distal tip member  470  is fixed to a distal portion  446  of a second tip member  472 . A proximal portion  444  of second tip member  472  is fixed to a body taper  430  of an elongate body member  406  of guidewire  400 . Methods of fixing second tip member  472  to elongate body member  406  that may be suitable in some applications include soldering, brazing, adhesive bonding, welding, and the like.  
         [0037]    In a preferred embodiment, second tip member  472  comprises a tubular wall defining a lumen. A distal portion  446  of second tip member  472  includes a slope  450  and a tong  448  that extends distally from intermediate tip member  472 . In a particularly preferred embodiment, second tip member  472  comprises nickel and titanium. In an especially preferred embodiment, second tip member  472  comprises nitinol.  
         [0038]    Guidewires embodying the invention can be utilized in a wide variety of medical procedures. For example, guidewires are often utilized to assist in advancing the intravascular catheter through the vasculature of a patient. A guidewire may be inserted into the vascular system of the patient at an easily accessible location and urged forward through the vasculature until the tip of the guidewire is proximate the target site. A proximal end of the guidewire may then be inserted into a guidewire lumen of a catheter. The tip of the catheter may be advanced along the length of the guidewire until it reaches the target site.  
         [0039]    Typically, the guidewire enters the patient&#39;s vasculature at a convenient location such as a blood vessel in the neck or near the groin. Once the distal portion of the guidewire has entered the patient&#39;s vascular system, the physician may urge the distal tip forward by applying longitudinal forces to the proximal portion of the guidewire. For the guidewire to effectively communicate these longitudinal forces, it is desirable that the guidewire have a high level of pushability and kink resistance, particularly near its proximal end.  
         [0040]    The path taken by a guidewire through the vascular system is often tortuous, requiring the guidewire to change direction frequently. In some cases, it may even be necessary for the guidewire to double back on itself. In order for the guidewire to conform to a patient&#39;s tortuous vascular system, it is desirable that guidewires be laterally flexible, particularly near the distal end.  
         [0041]    While advancing the guidewire through the tortuous path of the patient&#39;s vasculature, physicians often apply torsional forces to the proximal portion of the guidewire to aid in steering the guidewire. To facilitate the steering process, the distal portion of the guidewire may be bent by the physician. Torsional forces applied on the proximal end must translate to the distal end to aid in steering. It is therefore desirable that the proximal portion of a guidewire have a relatively high level of torqueability to facilitate steering.  
         [0042]    The distance between the access site and the target site is often in excess of 100 cm. The inside diameter of the vasculature at the access site is often less than 5 mm. In light of the geometry of the patient&#39;s body, it is desirable to combine the features of torqueability, pushability, and flexibility into a guidewire that is relatively long and has a relatively small diameter.  
         [0043]    Ideally, the distal end of a guidewire will be adapted to reduce the probability that the vascular tissue will be damaged as the guidewire progresses through the vascular system. This is sometimes accomplished by fixing a rounded tip member to the distal end of the guidewire.  
         [0044]    After the guidewire has been navigated through the patient&#39;s vascular system so that its distal end is adjacent the target site, an intravascular catheter may be advanced over the guidewire. The catheter may be used for various diagnostic and/or therapeutic purposes. One example of a diagnostic use for a catheter is the delivery of radiopaque contrast solution to enhance fluoroscopic visualization. In this application, the catheter provides a fluid path leading from a location outside the body to a desired location inside the body of a patient.  
         [0045]    Examples of therapeutic purposes for catheters include percutaneous transluminal angioplasty (PTA) and percutaneous transluminal coronary angioplasty (PTCA). These angioplasty techniques typically involve the use of a balloon catheter. During these procedures, the distal end of the guidewire is often positioned in the ostium of the coronary artery. The balloon catheter may then be advanced over the guidewire such that the balloon is positioned proximate the restriction in the diseased vessel. The balloon is then inflated and the restriction in the vessel is opened. In this application, it is desirable that the guidewire provide a low friction path for the balloon catheter.  
         [0046]    One additional example of a useful therapeutic application of catheters is the treatment of intracranial aneurysms in the brain. An aneurysm which is likely to rupture, or one which has already ruptured may be treated by delivering an embolic device to the interior of the aneurysm. The embolic device encourages the formation of a thrombus inside the aneurysm. The formation of a thrombus reduces the probability that an aneurysm will rupture. Or, in cases where an aneurysm has already ruptured, the formation of a thrombus will reduce the probability that the previously ruptured aneurysm will re-bleed. One commonly used embolic device comprises a tiny coil of wire.  
         [0047]    When treating an aneurysm with the aid of a catheter, the catheter tip is typically positioned proximate the aneurysm site. The embolic device is then urged through the lumen of the catheter and introduced into the aneurysm. Shortly after the thrombus agent is placed in the aneurysm, a thrombus forms in the aneurysm and is shortly thereafter complemented with a collagenous material that significantly lessens the potential for aneurysm rupture.  
         [0048]    Having thus described some embodiments of the present invention, those of skill in the art will readily appreciate that yet other embodiments may be made and used within the scope of the claims hereto attached. Numerous advantages of the invention covered by this document have been set forth in the foregoing description. It will be understood, however, that this disclosure is, in many respects, only illustrative. Changes may be made in details, particularly in matters of shape, size, and arrangement of parts without exceeding the scope of the invention. The invention&#39;s scope is defined in the language in which the appended claims are expressed.