Abstract:
An elongated intracorporeal device, more specifically, a balloon catheter having an elongate shaft with a distal section. The distal section of the shaft has a distal inner tubular member with an inflatable balloon disposed about the distal inner tubular member. A radiopaque marker formed at least in part of a polymer is disposed on the distal inner tubular member. The flexible radiopaque marker can be formed either by doping a desired portion of the distal inner tubular member with an appropriate radiopaque material, or preforming the radiopaque marker from a polymer doped with a radiopaque material and subsequently securing the radiopaque marker to the distal inner tubular member.

Description:
BACKGROUND 
     The present invention is directed to elongate intracorporeal devices, and particularly intraluminal devices for stent deployment, percutaneous transluminal coronary angioplasty (PTCA), and the similar procedures that are facilitated by an inflatable tubular member. PTCA is a widely used procedure for the treatment of coronary heart disease. In this procedure, a balloon dilatation catheter is advanced into the patient&#39;s coronary artery and the balloon on the catheter is inflated within the stenotic region of the patient&#39;s artery to open up the arterial passageway and increase the blood flow through the artery. To facilitate the advancement of the dilatation catheter into the patient&#39;s coronary artery, a guiding catheter having a preshaped distal tip is first percutaneously introduced into the cardiovascular system of a patient by the Seldinger technique through the brachial or femoral arteries. The catheter is advanced therein until the preshaped distal tip of the guiding catheter is disposed within the aorta adjacent the ostium of the desired coronary artery. A balloon dilatation catheter may then be advanced through the guiding catheter into the patient&#39;s coronary artery until the balloon on the catheter is disposed within the stenotic region of the patient&#39;s artery. 
     Once properly positioned across the stenosis, the balloon is inflated one or more times to a predetermined size with radiopaque liquid at relatively high pressures (e.g., generally 4-12 atmospheres) to dilate the stenosed region of a diseased artery. After the inflations, the balloon is finally deflated so that the dilatation catheter can be removed from the dilatated stenosis to resume blood flow. 
     Similarly, balloon catheters may be used to deploy endoprosthetic devices such as stents. Stents are generally cylindrical shaped intravascular devices that are placed within a damaged artery to hold it open. The device can be used to prevent restenosis and to maintain the patency of blood vessel immediately after intravascular treatments. Typically, a compressed or otherwise small diameter stent is disposed about an expandable member such as a balloon on the distal end of a catheter, and the catheter and stent thereon are advanced through the patient&#39;s vascular system. Inflation of the balloon expands the stent within the blood vessel. Subsequent deflation of the balloon allows the catheter to be withdrawn, leaving the expanded stent within the blood vessel. 
     Typically, the distal section of a balloon catheter or other percutaneous device will have a radiopaque marker in order for the operator of the device to see it under x-ray or flouroscopy imaging. Generally, a band or ring of solid radiopaque metal is secured about an inner or outer shaft of a balloon catheter to serve as a radiopaque marker. Such a configuration, however, adds stiffness and discontinuity to the catheter shaft as the solid metal bands are relatively inflexible compared to a polymer balloon catheter shaft. What has been needed is a radiopaque marker for intracorporeal devices that adds little or no longitudinal stiffness to the device. 
     SUMMARY 
     The invention is directed to a balloon catheter having an elongate shaft with a proximal section and a relatively short distal section. The distal section has a distal inner tubular member with a longitudinal axis, an outer surface and an inner surface. An inflatable balloon is disposed about the distal inner tubular member. A radiopaque marker made at least in part of a polymer has an outer surface which is substantially radially congruent with the outer surface of the distal inner tubular member from the longitudinal axis of the distal inner tubular member. An inside surface of the radiopaque marker can optionally be substantially radially congruent with the inside surface of the distal inner tubular member, or the inside surface of the radiopaque marker can be disposed between the inside surface of the distal inner tubular member and the outer surface of the radiopaque marker. 
     In one embodiment, the radiopaque marker can be a portion of the material of the distal inner tubular member which has been doped with a radiopaque material such as tungsten, bismuth, tantalum, barium, barium sulfate, compounds thereof or the like. In another embodiment, the radiopaque marker can be a separate discrete polymer member that is made of a radiopaque polymer or a radiolucent polymer doped with one or more radiopaque materials. The polymer of the radiopaque marker can be linear low density polyethylene, polyether block amide, alpha olefin copolymers, or the like, and can have a shore hardness or durometer selected so that the radiopaque marker and elongate inner tubular member which is axially coextensive with the radiopaque marker has a desired combined longitudinal stiffness. The combined longitudinal stiffness of the distal inner tubular member axially coextensive with the radiopaque marker and radiopaque marker can be selected such that it is substantially equal to or less than the nominal longitudinal stiffness of the distal inner tubular member axially adjacent the radiopaque marker. 
     Finally, two or more radiopaque markers as discussed above can be disposed along the distal inner tubular member. The radiopaque markers can be axially disposed at a proximal end of the inflatable balloon, a distal end of the inflatable balloon, at predetermined spacing to provide for a measuring function, or any other desired location or locations along the distal inner tubular member. These and other advantages of the invention will become more apparent from the following detailed description of the invention when taken in conjunction with the accompanying exemplary drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows an elevational view in partial section of a balloon catheter having features of the invention. 
     FIG. 2 is a longitudinal cross sectional view of the balloon catheter of FIG. 1 taken along lines  2 — 2  in FIG.  1 . 
     FIG. 3 is a transverse cross sectional view of the balloon catheter of FIGS. 1 and 2 taken along lines  3 — 3  in FIG.  2 . 
     FIG. 4 is a longitudinal cross sectional view of a portion of a balloon catheter having features of the invention. 
     FIG. 5 is a transverse cross sectional view of the balloon catheter of FIG. 4 taken along lines  5 — 5  of FIG.  4 . 
     FIG. 6 is a longitudinal cross sectional view of a portion of a balloon catheter having features of the invention. 
     FIG. 7 is transverse cross sectional view of the balloon catheter of FIG. 6 taken along lines  7 — 7  in FIG.  6 . 
    
    
     DETAILED DESCRIPTION 
     FIGS. 1-3 illustrate a balloon catheter  7  having features of the invention. The balloon catheter  7  has an elongate shaft with a proximal section  9  and a relatively short distal section  10 . The elongate shaft  8  has an elongate outer tubular member  11  with a proximal end  12  and a distal end  13  and is secured to a proximal Y-adaptor  14  at the proximal end  12 . The elongate shaft  8  also has an elongate inner tubular member  15  disposed within the elongate outer tubular member  11 . The elongate inner tubular member  15  has a distal end  16  and a distal section  17 . The distal section  17  of the elongate inner tubular member forms a distal inner tubular member  20  having an inner surface  18  and an outer surface  19 . An inflatable balloon  21  having a proximal end  22  and a distal end  23  is disposed about the distal inner tubular member  20 . The proximal end  22  of the inflatable balloon  21  is sealingly secured to the distal end  13  of the elongate outer tubular member  11 . The distal end of the inflatable balloon  23  is sealingly secured to the distal end  16  of the elongate inner tubular member  15 . 
     A radiopaque marker  24  having a proximal end  25 , a distal end  26 , an inner surface  27  and an outer surface  28  is disposed along the distal inner tubular member  20  between the proximal end  22  of the inflatable balloon  21  and the distal end  23  of the inflatable balloon  21 . The outer surface  28  of the radiopaque marker  24  is substantially radially congruent with the outer surface  19  of the distal inner tubular member  20 . In the embodiment of the balloon catheter  7  shown in FIGS. 1-3 a smooth longitudinal transition  31  between the outer surface  28  of the radiopaque marker  24  and the outer surface  19  of the distal inner tubular member  20  is formed. In addition, in the embodiment of the invention shown in FIGS. 1-3, the inside surface  27  of the radiopaque marker  24  is substantially radially congruent with the inner surface  18  of the distal inner tubular member  20 . A smooth longitudinal transition  32  between the inner surface  27  of the radiopaque marker  24  and the inner surface  18  of the distal inner tubular member  20  is also shown in FIGS. 1-3. 
     The radiopaque marker  24  can be formed by doping a portion of the distal inner tubular member which corresponds to the dimensions of the radiopaque marker  24  with a radiopaque material such as tungsten, bismuth, tantalum, barium, barium sulfate, and compounds or alloys thereof. The radiopaque material may be in powder or particulate form which is mixed with the polymer material of the distal inner tubular member  20 . Alternatively, the radiopaque marker  24  may be formed from a separate discrete member which is preformed and subsequently secured, to the distal section of the distal inner tubular member  20 . Such a radiopaque marker  24  may be formed from a radiopaque polymer or a radiolucent polymer doped with a radiopaque material such as those discussed above. 
     In embodiments of the invention where the radiopaque marker  24  is formed from a separate discrete member, the radiopaque marker  24  may be secured to the distal inner tubular member  20  by an adhesive bond, a solvent bond, heat fusing of the radiopaque marker  24  to the distal inner tubular member  20 , or by any other suitable method. In embodiments of the invention where the radiopaque marker  24  is formed from a separate discrete member formed from a radiolucent polymer doped with a radiopaque material, the radiolucent polymer can be any of a variety of suitable polymers, including, but not limited to polyethylene, linear low density polyethylene, polyether block amide, alpha olefin copolymers, polyester and polyamide. 
     In embodiments of the invention where the outer surface  19  of the digital inner tubular member  20  is substantially radially congruent with the outer surface  28  of the radiopaque marker  24  and the radiopaque marker  24  is made from a separate discrete member, it may be necessary to remove material from the outer surface  19  of the distal inner tubular member  20  at the site where the radiopaque marker  24  is to be secured. In this way, the radiopaque marker  24  takes the place of the removed material of the distal inner tubular member  20  and can also yield a smooth longitudinal transition  31 . 
     In one embodiment of the invention, a thickness of material approximately equal to a wall thickness of the radiopaque marker  24  is removed from the outer surface  19  of the elongate inner tubular member  15  prior to securing the radiopaque marker  24  to the distal inner tubular member  20 . In such an embodiment, the radiopaque marker  24  can be stretched circumferentially to pass over the distal end  16  of the distal inner tubular member  20  and be positioned at a site where material has been removed from the outer surface  19  of the distal inner tubular member  20 . Once the circumferentially stretched radiopaque marker  24  is properly positioned axially, the radiopaque marker  24  can be relaxed to conform to the distal inner tubular member  20 . 
     Any number of radiopaque markers  24  as described above can be secured to the distal inner tubular member  20  having the same or varied configurations. In embodiments of the invention where a plurality of radiopaque markers  24  are secured to the distal inner tubular member  20 , the markers  24  may be spaced at regular intervals in order to provide a measuring tool or mechanism that can be visualized under radioscopic imaging, or the radiopaque markers  24  may be axially coextensive with and mark features of interest of the balloon catheter  7  structure, such as the proximal and distal ends  22  and  23  of the inflatable balloon  21 , rapid exchange ports (not shown), a distal extremity of the catheter or the like. 
     The length of the elongate inner tubular member  15  and the elongate outer tubular member  11  can be up to about 300 cm, specifically, about 100 to about 200 cm. An outer diameter of the elongate outer tubular member  11  can up to about 0.2 inch, specifically about 0.01 to about 0.1 inch. In some embodiments of the invention, the elongate inner tubular member  15  has a transverse dimension or diameter sized to have an inner diameter or lumen diameter appropriate for a coronary guidewire. In such embodiments, the elongate inner tubular member  15  may have an inner diameter of about 0.012 to about 0.02 inch. However, the elongate inner tubular member  15  can have any transverse dimension that leaves a lumen between the outer surface  19  of the elongate inner tubular member  15  and an inner surface  35  of the elongate outer tubular member  11  which is suitable for injection of inflation medium into the inflatable balloon  21 . 
     The elongate outer tubular member  11  and elongate inner tubular member  15  may be made of conventional balloon catheter shaft materials such as polyurethane, polyethylene, PEBAX, Nylon or any other suitable material. The polymer of the radiopaque marker  24  can have a shore hardness or durometer selected so that the radiopaque marker  24  and distal inner tubular member  20  which is axially coextensive with the radiopaque marker  24  has a desired combined longitudinal stiffness. The combined longitudinal stiffness of the distal inner tubular member  20  and radiopaque marker  24  can be selected such that no longitudinal stiffness is added to the elongate inner tubular member  24  at the position of the radiopaque marker  24  relative to the longitudinal stiffness of portions of the distal inner tubular member  20  adjacent the radiopaque marker  24 . 
     The radiopaque marker  24  can have an axial length of up to about 50 mm, specifically, about 1 to about 40 mm, and more specifically, about 5 to about 30 mm, and even more specifically, about 10 to about 20 mm. The radiopaque marker  24  can have an outer transverse dimension or diameter similar to an outer transverse dimension or diameter of the distal inner tubular member  20 , specifically, up to about 0.18 inch, more specifically, about 0.01 to about 0.04 inch, and more specifically, about 0.015 to about 0.025 inch. The radiopaque marker  24  may be sized and positioned so as to be axially coextensive with the inflatable balloon  21 . 
     FIGS. 4 and 5 show a portion of an embodiment of a balloon catheter  35  having features of the invention. The balloon catheter  35  has an elongate shaft  36  with a proximal section (not shown) and a relatively short distal section  37 . The elongate shaft  36  has an elongate outer tubular member  38  with a distal end  39  and a proximal end secured a proximal Y-adaptor (not shown) similar to the proximal end  12  secured to the Y-adaptor  14  in FIG.  1 . The elongate shaft  36  also has an elongate inner tubular member  41  is disposed within the elongate outer tubular member  38 . The elongate inner tubular member  41  has a distal end  42  and a distal section  43 . The distal section  43  of the elongate inner tubular member  41  forms a distal inner tubular member  44  having an inner surface  45  and an outer surface  46 . An inflatable balloon  51  having a proximal end  52  and a distal end  53  has the proximal end  52  sealingly secured to the distal end  39  of the elongate outer tubular member  38 . The distal end  53  of the balloon  51  is sealingly secured to the distal end  42  of the elongate inner tubular member  41 . 
     A radiopaque marker  54  having a proximal end  55 , a distal end  56 , an inner surface  57  and an outer surface  58  is disposed along the distal inner tubular member  44  between the proximal end  52  of the inflatable balloon  51  and the distal end  53  of the inflatable balloon  51 . The outer surface  58  of the radiopaque marker  54  is substantially radially congruent with the outer surface  46  of the distal inner tubular member  44 . 
     In the embodiment of the balloon catheter  35  shown in FIGS. 4 and 5 a smooth longitudinal transition  61  between the outer surface  58  of the radiopaque marker  54  and the outer surface  46  of the distal inner tubular member  44  is formed. In addition, in the embodiment of the invention shown in FIGS. 4 and 5, the inner surface  57  of the radiopaque marker  54  is disposed between the inner surface  45  of the distal inner tubular member  44  and the outside surface  58  of the radiopaque marker  54 . 
     The radiopaque marker  54  can be formed by doping a portion of the distal inner tubular member  44  which corresponds to the dimensions of the radiopaque marker  54  with a radiopaque material such as tungsten, bismuth, tantalum, barium, barium sulfate, compounds thereof or the like. The radiopaque material may be in powder or particulate form which is mixed with the polymer material of the distal inner tubular member  44 . Alternatively, the radiopaque marker  54  may be formed from a separate discrete member which is preformed and subsequently secured the distal inner tubular member  44 . Such a radiopaque marker  54  may be formed from a radiopaque polymer or a radiolucent polymer doped with a radiopaque material such as those discussed above. The materials, dimensions and configuration of the radiopaque marker  54 , distal inner tubular member  44 , elongate outer tubular member  38  and inflatable balloon  51  can be the same as the materials, dimensions and configuration of the corresponding components of the balloon catheter  10  shown in FIGS. 1-3. 
     FIGS. 6 and 7 show a portion of an embodiment of a balloon catheter  60  having features of the invention. The balloon catheter  60  has an elongate shaft  61  with a proximal section (not shown) and a relatively short distal section  62 . The elongate shaft  61  has an elongate outer tubular member  63  with a distal end  64  and a proximal end secured a proximal Y-adaptor (not shown) similar to the proximal end  12  secured to the Y-adaptor  14  in FIG.  1 . The elongate shaft  61  also has an elongate inner tubular member  66  is disposed within the elongate outer tubular member  63 . The elongate inner tubular member  66  has a distal end  67  and a distal section  68 . The distal section  68  of the elongate inner tubular member  66  forms a distal inner tubular member  73  having an inner surface  74  and an outer surface  75 . An inflatable balloon  76  having a proximal end  77  and a distal end  78  has the proximal end  77  sealingly secured to the distal end  64  of the elongate outer tubular member  63 . The distal end  78  of the balloon  76  is sealingly secured to the distal end  67  of the elongate inner tubular member  66 . 
     A first radiopaque marker  81  is disposed along the distal inner tubular member  73 . The first radiopaque marker  81  has a proximal end  82 , a distal end  83 , an inner surface  84  and an outer surface  85  is disposed along the distal inner tubular member  73  between the proximal end  77  of the inflatable balloon  76  and the distal end  78  of the inflatable balloon  76 . The outer surface  85  of the first radiopaque marker  81  is substantially radially congruent with the outer surface  75  of the distal inner tubular member  73 . 
     In the embodiment of the balloon catheter  60  shown in FIGS. 6 and 7 a smooth longitudinal transition  86  between the outer surface  85  of the first radiopaque marker  81  and the outer surface  75  of th e distal inner tubular member  73  is formed. In addition, in the embodiment of the invention shown in FIGS. 6 and 7, the inner surface  84  of the first radiopaque marker  81  is disposed between the inner surface  74  of the distal inner tubular member  73  and the outside surface  85  of the first radiopaque marker  81 . 
     The first radiopaque marker  81  can be formed by doping a portion of the distal inner tubular member  73  which corresponds to the dimensions of the first radiopaque marker  81  with a radiopaque material such as tungsten, bismuth, tantalum, barium, barium sulfate, compounds thereof or the like. The radiopaque material may be in powder or particulate form which is mixed with the polymer material of the distal inner tubular member  73 . Alternatively, the first radiopaque marker  81  may be formed from a separate discrete member which is preformed and subsequently secured the distal inner tubular member  73 . Such a first radiopaque marker  81  may be formed from a radiopaque polymer or a radiolucent polymer doped with a radiopaque material such as those discussed above. The materials, dimensions and configuration of the first radiopaque marker  81 , distal inner tubular member  73 , elongate outer tubular member  63  and inflatable balloon  76  can be the same as the materials, dimensions and configuration of the corresponding components of the balloon catheter  10  shown in FIGS. 1-3. 
     A second radiopaque marker  88  disposed distally of the first radiopaque marker  81  can be formed in a manner similar to that of the first radiopaque marker  81  and can have dimensions, materials and configurations similar to those of the first radiopaque marker  81 . Although FIGS. 6 and 7 show only a first and second radiopaque markers  81  and  88 , any number of markers may be used and disposed along the distal inner tubular member  73  or along any other portion of the elongate inner tubular member  66  generally. In addition, the first and second radiopaque markers  81  and  88  may have distal ends spaced axially at any desired predetermined distance, such as 1, 2, 5, or 10 mm, so as to allow the operator of the balloon catheter  60  to measure features within a patient&#39;s vasculature under flouroscopy, such as lesion length and the like. 
     While particular forms of the invention have been illustrated and described, it will be apparent that various modifications can be made without departing from the spirit and scope of the invention. Accordingly, it is not intended that the invention be limited, except as by the appended claims.