Abstract:
The present invention relates generally to intravascular catheters for performing medical procedures. An intravascular catheter is disclosed comprising a multi-layered shaft having a shapable distal end. The shaft may comprise an inner liner; a second layer disposed over the inner liner, the second layer having a proximal segment and a distal segment corresponding to the shapable portion of the shaft; a third layer disposed over the second layer; and a fourth layer disposed over the third layer.

Description:
CROSS REFERENCE TO CO-PENDING APPLICATIONS  
       [0001]    This application is a continuation-in-part of co-pending U.S. patent application Ser. No. 09/839,065, filed Apr. 20, 2001, entitled “Microcatheter with Improved Distal Tip and Transitions”, the entire disclosure of which is hereby incorporated by reference. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The present invention relates generally to intravascular catheters for performing medical procedures. More particularly, the present invention relates to intravascular catheters with improved shaft and distal tip designs.  
         BACKGROUND OF THE INVENTION  
         [0003]    Intravascular catheters are used in a wide variety of relatively non-invasive medical procedures. Such intravascular catheters may be used for diagnostic or therapeutic purposes. Generally, an intravascular catheter allows a physician to remotely perform a medical procedure by inserting the catheter into the vascular system of the patient at a location that is easily accessible and thereafter navigating the catheter to the desired target site. By this method, virtually any target site in the patient&#39;s vascular system may be remotely accessed, including the coronary, cerebral, and peripheral vasculature.  
           [0004]    Typically, the catheter 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 catheter 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 catheter. Frequently the path taken by a catheter through the vascular system is tortuous, requiring the catheter to change direction frequently. In some cases, it may even be necessary for the catheter to bend ninety degrees or more. In order for the catheter to navigate a patient&#39;s tortuous vascular system, it is desirable that intravascular catheters be very flexible, particularly near the distal end.  
           [0005]    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 2 cm, and the inside diameter of the vasculature at the target site is often less than 0.5 cm. Accordingly, intravascular catheters must be relatively long and thin. Furthermore, in order to navigate through the patient&#39;s tortuous vascular system, intravascular catheters must be very flexible. It is also desirable that intravascular catheters be relatively soft in order to minimize the probability of damaging vascular tissue.  
           [0006]    Intravascular catheters typically have a radiopaque portion and are guided through the patient&#39;s vascular system with the assistance of x-ray fluoroscopy. In this manner, a physician may manipulate the proximal end of the catheter and fluoroscopically monitor the corresponding movement of the distal end of the catheter. As such, it is desirable that intravascular catheters be sufficiently radiopaque along their length and particularly at their distal end such that the physician is able to clearly monitor the progress of the catheter as it is being advanced from the vascular access site to the vascular target site.  
           [0007]    After the intravascular catheter has been navigated through the patient&#39;s vascular system with the distal end thereof adjacent the target site, the catheter may be used for various diagnostic and/or therapeutic purposes. Frequently, diagnostic and therapeutic techniques require the infusion of fluids through the catheter. For example, it may be desirable to inject radiopaque contrast media through the catheter to provide enhanced fluoroscopic visualization for diagnostic purposes, or to inject pharmaceutical solutions (i.e., drugs) to the target site for therapeutic purposes.  
           [0008]    The blood vessels in the brain frequently have an inside diameter of less than 3 mm. Accordingly, it is desirable that intravascular catheters intended for use in these blood vessels have an outside diameter which allows the catheter to be easily accommodated by the blood vessel. The path of the vasculature inside the brain is highly tortuous, and the blood vessels are relatively fragile. Accordingly, it is desirable that the distal portion of a catheter be sized appropriately and be atraumatic for the neurological vasculature.  
         SUMMARY OF THE INVENTION  
         [0009]    The present invention comprises a unique intravascular catheter that incorporates a number of refinements to the shaft and distal tip. According to a preferred embodiment of the invention, a catheter comprises a shaft having a proximal end, a distal end, and a lumen. A hub is typically disposed at the proximal end and a distal tip is disposed at the distal end. The shaft may comprise multiple layers, including an inner liner, a second layer, a third layer, and a fourth layer.  
           [0010]    The second layer may be disposed over the inner liner extending from the proximal end of the shaft to a distal terminus. The distal terminus may be about 4 millimeters from the distal end. The absence of the second layer between the distal terminus and the distal end of the shaft improves the physical properties of the catheter. For example, the shaft may be more flexible or generally softer near the distal end, and may be more readily thermoformed.  
           [0011]    The third layer may be disposed over the second layer and preferably comprises a coil that is wound over the second layer. The coil may be arranged in a single coil region near the distal end of the shaft. The single coil region is understood to be a single layer of coil wound around the second layer along a longitudinal axis thereof. The coil may further include a multiple coil region near the proximal end of the shaft wherein the coil is wound multiple times around the second layer along the longitudinal axis thereof.  
           [0012]    The fourth layer may be disposed over the third layer and may include a taper. Preferably, the taper decreases the diameter of the shaft near the distal end thereof. The decrease in diameter may comprise a suitable reduction in size appropriate for multiple uses of the catheter. For example, a generally small diameter distal tip may be used for procedures involving treatment of relatively small blood vessels. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]    [0013]FIG. 1 is a plan view of an intravascular catheter with an improved shaft, distal tip, and transitions according to a preferred embodiment of the invention;  
         [0014]    [0014]FIG. 2 is an enlarged view of a shaft of the intravascular catheter shown in FIG. 1;  
         [0015]    [0015]FIG. 3 is an enlarged view of an alternative shaft of the intravascular catheter shown in FIG. 1;  
         [0016]    [0016]FIG. 4 is an enlarged view of another alternative shaft of the intravascular catheter shown in FIG. 1; and  
         [0017]    [0017]FIG. 5 is an enlarged view of yet another alternative shaft of the intravascular catheter shown in FIG. 1.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0018]    The following description should be read with reference to the drawings wherein like reference numerals indicate like elements throughout the several views. The detailed description and drawings depict select embodiments and are not intended to be limiting.  
         [0019]    [0019]FIG. 1 is a plan view of an intravascular catheter  10  with an improved shaft, distal tip, and improved transitions according to a preferred embodiment of the invention. The intravascular catheter  10  comprises a shaft  12  having a proximal end  14  and a distal end  16 . A hub  18  is typically disposed at proximal end  14  of shaft  12  and a distal tip  20  having a shapable length is disposed at distal end  16  of shaft  12 . Shaft  12  further comprises a lumen  22  as best seen in FIG. 2. Lumen  22  may be a guidewire lumen and/or an infusion lumen. Lumen  22  may have a diameter compatible with a guide wire having an outside diameter of about 0.010 to 0.014 inches.  
         [0020]    Shaft  12  comprises multiple layers including an inner liner  24 . Preferably, inner liner  24  comprises polytetrafluoroethylene (PTFE). Polytetrafluoroethylene is a preferred material because it creates a smooth, low-friction surface for the passage of other devices or fluids through catheter  10 . In an alternate embodiment, inner liner  24  may comprise materials including, but not limited to, thermoplastics, high performance engineering resins, fluorinated ethylene propylene (FEP), polymer, polyethylene (PE), polypropylene (PP), polyvinylchloride (PVC), polyurethane, polyether-ether ketone (PEEK), polyimide, polyamide, polyphenylene sulfide (PPS), polyphenylene oxide (PPO), polysufone, nylon, or perfluoro(propyl vinyl ether) (PFA).  
         [0021]    Inner liner  24  may be formed by extrusion over a mandrel. Extrusion may result in inner liner  24  having a thickness of about 0.0005 inches to 0.00125 inches and a diameter of about 0.0175 inches to 0.019 inches over a length of about 135 cm to 200 cm. In an alternate embodiment, inner liner  24  may be formed by lamination over a mandrel. The mandrel may, for example, comprise nitinol and have a diameter of about 0.0165 inches. A person of ordinary skill in the art would be familiar with processes and equipment suitable for forming inner liner  24  according to multiple embodiments of the present invention.  
         [0022]    A second layer  26  is disposed over inner liner  24 . Second layer  26  is comprised of polyether block amide (PEBA). Polyether block amide is commercially available from Atochem Polymers of Birdsboro, Pa., under the trade name PEBAX. Second layer  26  may comprise PEBAX 55 having a diameter of about 0.0185 inches to 0.022 inches and a length of about 132 cm to 200 cm.  
         [0023]    Second layer  26  extends from proximal end  14  of shaft  12  to a distal terminus  28 . Distal terminus  28  is set back from distal end  16  a distance that is equal to or greater than the shapable length of distal tip  20 . For example, distal terminus  28  may be 4 millimeters to 3 centimeters from distal end  16  depending on the flexibility and shapable length desired. The absence of second layer  26  between distal terminus  28  and distal end  16  of shaft  12  improves the physical properties of catheter  10 . For example, shaft  12  may be more flexible or generally softer near distal end  16 , and/or may be more shapable by thermoforming techniques.  
         [0024]    Second layer  26  may be formed by securing outer layer  26  near distal end  16  of shaft  12  and laminating to proximal end  14  thereof. Alternatively, second layer  26  may be disposed over inner liner  24  by extrusion.  
         [0025]    A third layer  30  is disposed over second layer  26 . Third layer  30  comprises a coil manufactured from materials including, but not limited to, stainless steel, metal, nickel alloy, nickel titanium alloy, polymer, round wire, flat wire, magnetic resonance imaging compatible metal, and combinations thereof. A magnetic resonance imaging compatible metal is understood to comprise non-magnetic or non-ferrous metals.  
         [0026]    Third layer  30  further comprises a single coil region  32  near distal end  16 . The coil may be wound around second layer  26  along a substantial portion of the length thereof. Single coil region  42  is understood to be a single layer of coil wound around second layer  26  along a longitudinal axis thereof, e.g., 0.0125 inch outside diameter stainless steel round wire. Third layer  30  further includes a multiple coil region  42  near proximal end  14  of shaft  12  wherein coil is wound multiple times around second layer  26  at a particular point along the longitudinal axis thereof.  
         [0027]    Single coil region  32  further comprises a first pitch region  34  and a second pitch region  36 . First pitch region  34  comprises a pitch between about 0.050 inches per turn and 0.004 inches per turn. Second pitch region  36  comprises a pitch between about 0.020 inches per turn and 0.002 inches per turn. Those skilled in the art will recognize that a number of values may be used to describe the pitch of first pitch region  34  and second pitch region  36  without deviating from the spirit and scope of the invention. For example, first pitch region  34  and second pitch region  36  may be substantially equal.  
         [0028]    A distal end  38  of third layer  30  may be secured to a radiopaque marker  40 . Preferably, radiopaque markers  40  produce a relatively bright image on a fluoroscopy screen during a medical procedure. This relatively bright image aids the user of catheter  10  in determining the location of distal end  16  of shaft  12 . Radiopaque markers  40  may comprise a number of radiopaque materials including, but not limited to, gold, platinum, and plastic material loaded with a radiopaque filler. Catheter  10  may further comprise additional radiopaque markers.  
         [0029]    A fourth layer  44  is disposed over third layer  30 . Fourth layer  44  comprises polyether block amide (PEBA). Alternately, fourth layer  44  may be comprised of materials similar to those disclosed above, including polymers and metals. Fourth layer  44  may have a length of about 135 cm to 200 cm.  
         [0030]    Fourth layer  44  further comprises a proximal end  46 , a distal end  48 , a first middle section  49 , and a second middle section  50 . Each individual section of fourth layer  44  may comprise polyether block amide. The durometer of each section may be different. At distal end  48 , the preferred material is a low durometer polymer (e.g., PEBAX 2533) to maintain a soft, atraumatic tip. At proximal end  46 , the preferred material is a high durometer polymer (e.g., PEBAX 7233) to provide pushability. First middle section  49  and second middle section  50  may provide a smooth transition between proximal end  46  and distal end  48 . For example, first middle section  49  may comprise PEBAX 5533 and second middle section  50  may comprise PEBAX 4033. Generally, the durometer decreases from proximal end  46  to distal end  48 . Alternatively, fourth layer  44  may be comprised of a single section having a differing durometer on opposite ends.  
         [0031]    Fourth layer  44  further comprises a taper  52 . Taper  52  decreases the diameter of shaft  12  near distal end  16 . Taper  52  may decrease the diameter of shaft  12  to varying degrees. The outside diameter of fourth layer  44  may be about 0.026 inches to 0.035 inches near proximal end  46  and about 0.021 inches to 0.026 inches at distal end  48 . Preferably, the outside diameter of shaft  12  from taper  52  to distal end  16  is sized appropriately for insertion into generally small blood vessels. For example, distal end  16  may be sized to facilitate entry of shaft  12  into the coronary, peripheral, and neurological vasculature.  
         [0032]    Fourth layer  44  may be disposed over third layer  30  by heat fusing separate tube sections  46 ,  48 ,  49 , and  50  by extrusion. Alternatively, fourth layer  44  is disposed over third layer  30  by lamination.  
         [0033]    The combination of layers at distal end  16  of shaft  12  comprises a level of flexibility which makes it unlikely to damage the blood vessels of a patient. According to this embodiment, distal tip  20  is understood to comprise an atraumatic and shapable tip. Moreover, the shapable length of distal tip  20  can be heat set, for example by steam.  
         [0034]    [0034]FIG. 3 is an enlarged view of an alternate shaft  112  that is essentially similar to shaft  12  with a refinement to second layer  26 . Second layer  126  extends from proximal end  14  of shaft  112  to distal terminus  128 . Second layer  126  further comprises a second segment  56 . Preferably, first segment  54  extends from proximal end  14  of shaft  112  to distal terminus  128  and is substantially similar to second layer  26  as depicted in FIG. 2. Second segment  56  preferably extends from distal terminus  128  to distal end  16  of shaft  112 . Distal terminus  128  is set back from distal end  16  of shaft  112  a distance equal to or greater than the shapable length of distal tip  20 . The durometer of first segment  54  and second segment  56  are different. For example, first segment  54  comprises a generally harder durometer (e.g., PEBAX 5533D) than second segment  56  (e.g. PEBAX 2533D).  
         [0035]    Shaft  112  may be manufactured substantially similar to what is disclosed above for shaft  12 . A person of ordinary skill in the art would be familiar with alterations in the method of manufacture according to multiple embodiments of the invention.  
         [0036]    [0036]FIG. 4 is an enlarged view of an alternate shaft  212  that is essentially similar to shaft  112  with a refinement to second layer  126  and second segment  56 . The first segment  54  of the second layer  126  extends from proximal end  14  of the shaft  212  to distal terminus  228 . The second segment  56  of the second layer  126  extends from distal terminus  228  to the distal marker band  40  proximal of the distal end  16  of shaft  212 . The distal marker band  40  resides within the distal end  48  of the fourth layer  44 , which is tapered down to encase the distal marker band  40  and to be connected to the inner layer  24  at the distal end  16  of the shaft  212 . Distal terminus  228  is set back from distal end  16  of shaft  212  a distance equal to or greater than the shapable length of distal tip  20 . The first segment  54  may have a generally harder durometer (e.g., PEBAX 5533D) than the second segment  56  (e.g. PEBAX 2533D).  
         [0037]    Shaft  212  may be manufactured substantially similar to what is disclosed above for shaft  12 . A person of ordinary skill in the art would be familiar with alterations in the method of manufacture according to multiple embodiments of the invention.  
         [0038]    [0038]FIG. 5 is an enlarged view of an alternative shaft  312  that is essentially similar to shaft  12  with a refinement to fourth layer  44 . Fourth layer  144  is disposed over third layer  30 . Fourth layer  144  further comprises proximal end  146  and distal end  148 . Preferably, fourth layer  144  is comprised of a single layer of PEBA having a differing durometer on opposite ends. For example, the durometer of proximal end  146  may be greater than the durometer of distal end  148 . Fourth layer  144  can be disposed over third layer  30  by gradient extrusion. Gradient extrusion is described in U.S. patent application Ser. No. 09/430,327 to Centell et al., which is hereby incorporated by reference. In summary, gradient extrusion is understood to be an extrusion technique wherein polymers of differing durometer may be disposed onto an object so as to form a smooth transition in a physical property (e.g., durometer). For example, gradient diffusion of fourth layer  144  may result in a generally harder durometer (e.g., PEBAX 7233) near proximal end  146  and a generally softer durometer (e.g., PEBAX 2533) near distal end  148 . In addition, gradient diffusion of fourth layer  144  would result in a substantially gradual decrease in durometer from proximal end  146  to distal end  148 .  
         [0039]    In a preferred embodiment, shaft  312  may be manufactured substantially similar to what is disclosed above for shaft  12 . A person of ordinary skill in the art would be familiar with alterations in the method of manufacture according to multiple embodiments of the invention.  
         [0040]    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 steps without exceeding the scope of the invention. The invention&#39;s scope is, of course, defined in the language in which the appended claims are expressed.