Abstract:
The present invention is a stent delivery system that uses a short section of a guide wire that is fixedly attached to a distal section of a balloon angioplasty catheter. By not having a guide wire that slides through the balloon of the balloon angioplasty catheter, the balloon on which the stent is mounted can have a reduced diameter. Therefore, the outside diameter of the undeployed stent mounted onto that balloon is also minimized. This provides a minimum profile, i.e., a minimum outside diameter, for the stent. A minimum profile at the distal section of the stent delivery system is highly advantageous for improving the percentage of cases that can be treated by means of direct stenting; i.e., without requiring pre-dilation of a stenosis.

Description:
This application is a continuation of Ser. No. 09/444,104, filed Nov. 22, 1999, now U.S. Pat. No. 6,375,660. 

   BACKGROUND OF THE INVENTION 
   Stents are well known devices for placement in vessels of the human body to obtain and maintain patency of that vessel. The greatest use for stents has been for placement within a stenosis in a coronary artery. When a stent is used for treating a coronary artery stenosis, it has always been necessary to first place a guide wire through the stenosis. The next step in the stenting procedure is typically to pre-dilate the stenosis with a balloon angioplasty catheter that is advanced over that guide wire. The balloon angioplasty catheter is then removed and a stent delivery system that includes the stent is advanced over the guide wire and the stent is then deployed at the site of the dilated stenosis. 
   Recent improvements in the design of stent delivery systems has made it possible to eliminate the step of pre-dilatation for the treatment of many classes of stenoses. The delivery of a stent to the site of a stenosis without pre-dilatation has been given the name “direct stenting”. However, even with direct stenting, a guide wire is still required as a precursor to advancing the stent delivery system over that guide wire to place the stent at the site of a stenosis. 
   SUMMARY OF THE INVENTION 
   The present invention is a stent delivery system that uses a short section of a guide wire that is fixedly attached to a distal section of a balloon angioplasty catheter. By not having a guide wire that slides through the balloon of the balloon angioplasty catheter, the balloon on which the stent is mounted can have a reduced diameter. Therefore, the outside diameter of the undeployed stent mounted onto that balloon is also minimized. This provides a minimum profile, i.e., a minimum outside diameter, for the stent. A minimum profile at the distal section of the stent delivery system is highly advantageous for improving the percentage of cases that can be treated by means of direct stenting; i.e., without requiring pre-dilation of a stenosis. Another advantage of the present invention is that a separate guide wire is eliminated thus saving the cost of such a guide wire. Additionally, the time to perform a stent delivery procedure is reduced because a guide wire does not have to be placed prior to using the stent delivery system to place the stent at the site of a stenosis. 
   Thus an object of the present invention is to provide a means for placing a stent within a vessel of the human body without requiring a separate guide wire thus saving the cost of the guide wire and also saving the time required to place a separate guide wire through an obstruction such as an arterial stenosis. 
   Another object of the present invention is to reduce the outside diameter (i.e., the profile) of the distal section of the stent delivery system so as to optimize the capability of the stent delivery system for direct stenting. 
   Still another object of the present invention is to have a guide wire fixed at the end of a balloon angioplasty catheter with a stent mounted onto the catheter&#39;s inflatable balloon and further that the length of the cylindrical portion of the inflated balloon that extends beyond each end of the stent (the “balloon overhang”) is less than 1.0 mm, preferably less than 0.5 mm and optimally 0 mm; the minimum balloon overhang being advantageous for reducing the probability of arterial wall dissection beyond the edges of the stent when the balloon is inflated. 
   These and other important objects and advantages of this invention will become apparent from the detailed description of the invention and the associated drawings provided herein. 

   
     BRIEF DESCRIPTION OF THE DRAWING 
       FIG. 1  is a side view of a stent delivery system having a balloon angioplasty catheter and having a fixed guide wire extending beyond the distal end of the balloon angioplasty catheter. 
       FIG. 2  is a longitudinal cross section of the distal section of the stent delivery system that is shown in  FIG. 1 . 
       FIG. 3  is a highly enlarged transverse cross section of the distal section of the stent delivery system at section  3 — 3  of  FIG. 2 . 
       FIG. 4  is a longitudinal cross section of another embodiment of the present invention that utilizes an elongated core wire. 
       FIG. 5  is a highly enlarged transverse cross section of the stent delivery system at section  5 — 5  of  FIG. 4  showing the connection between elongated core wire and the proximal tube of the stent delivery system. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIGS. 1 and 2  illustrate a stent delivery system  10  having a fixed guide wire  11  that is fixedly attached to the distal end of a balloon angioplasty catheter that has a minimum profile for the distal section of the balloon angioplasty catheter. The distal section of the stent delivery system  10  includes a guide wire  11 , a proximal elastic band  18 , a stent-on-balloon section  30  and a distal elastic band  16 . The stent-on-balloon section  30  includes an inflatable balloon  34  onto which a balloon expandable stent  32  is co-axially mounted. A cylindrically shaped distal section of the balloon  34  is fixedly attached to a proximal section of the guide wire  11  that includes a plastic cylinder  14  that is fixedly attached to a central core wire  13  of the guide wire  11 . A helical wire coil  15  is wrapped around the core wire  13  for most of the length of the core wire  13 . The outside diameter of the guide wire  11  would typically be 0.014 inches. However, outside diameters between 0.008 and 0.035 inches could be used. The diameter of the core wire  13  would typically be between 0.002 and 0.014 inches. However, it should be understood that the core wire  13  could have a tapered section and could also have a flattened section situated within the wire coil  15 . The flattened section of the core wire  13  is ideally suited for retaining a bend that is created by the doctor just before placing the stent delivery system  10  into a vessel of a human subject. 
   The material of the guide wire  11  would typically be stainless steel, tantalum, Nitnol or a combination of such metals. A distal section of the guide wire  11  could be substantially straight or it could be substantially curved as generally indicated in  FIGS. 1 and 2 . The curve could be as supplied by the manufacturer or it could be made or adjusted by the person placing the stent delivery system  10  into the patient. The length of the guide wire that lies distal to the distal end of the balloon  34  should be approximately 1.0 to 2.0 cm and certainly less than 5 cm. Furthermore, a plastic layer with a lubricious outer surface could be substituted for the helical wire coil  15 . It is also envisioned that the coil  15  could be coated with Teflon or another lubricious material. 
   A proximal section of the balloon  34  is fixedly attached to a distal section of a central cylindrical tube  20 . The central cylindrical tube  20  would typically be formed from a plastic material such as polyurethane, polyethylene, Nylon, Teflon, or any similar plastic that is used for balloon angioplasty catheters. The outside diameter of the tube  20  would typically be between 0.5 and 2.0 mm. The length of the tube  20  would typically be between 10 and 40 cm. 
   The central tube  20  can be joined at its proximal end to the distal end of a proximal cylindrical tube  21 . It is envisioned that the proximal tube  21  would extend for most of the length of the stent delivery system  10 . A Luer fitting  22  located at the proximal end of the proximal tube  21  would be used for fluid connection by means of the attachment thread  23  to a stop-cock (not shown) to which a syringe can be attached that provides a source of inflation fluid for the balloon  34 . The syringe can be used to inflate the balloon  34  with contrast medium to deploy the stent  32  into a stenosis. The syringe would also be used to deflate the balloon  34  after the stent  32  has been deployed. 
     FIG. 2  shows three layers of the balloon  34 , which layers would typically be formed by rolling the balloon  34  in a spiral manner like a jelly-role as seen in  FIG. 3 . For the sake of clarity, only three layers are shown in  FIG. 2  on each side of the balloon  34 . To be technically correct, a total of six layers should be shown in  FIG. 2  on each side of the balloon  34 . Although  FIG. 3  shows a rolled balloon  34 , it should be understood that a conventional balloon made with a multiplicity of folded wings could also be used. 
   It should be understood that a conventional guide wire must be able to be torqued in order to place it into a specific artery that has the stenosis that is to treated. To be effective as a stent delivery system for direct stenting, the stent delivery system  10  must have the capability to apply torque to the guide wire  11  so that the guide wire&#39;s distal tip  12  can be selectively advanced at an arterial bifurcation into the branch artery that is to be stented. 
   When the stent delivery system is percutaneously placed into a vessel of a human body, the Luer fitting  22  remains exterior to that body where it can be held and rotated by the physician in order to apply a torque to rotate the distal end  12  of the guide wire  11 . When a twist is applied to the Luer fitting  22 , the spiral-shaped balloon  34  would tend to form a tightened spiral or would loosen depending upon the direction of the twist that is applied. By having the proximal elastic band  18  and distal elastic band  16  shrunk onto the portions of the balloon  34  that have the shape of a frustum of a cone when the balloon  34  is inflated, loosening of the spiral shape of the folded balloon  34  is prevented even if the direction of twist applied to the Luer fitting  22  would otherwise have unwound that spiral. In this manner, the structure shown in  FIGS. 1 and 2  is capable of using the Luer fitting  22  to apply the torque that is required for positioning the guide wire into virtually any arterial stenosis that is selected for direct stenting. 
   It should be noted that the elastic bands  16  and  18  should be made from an elastomer such as silicone rubber. The portion of the band that lies over the balloon  34  can expand radially when the balloon  34  is inflated to deploy the stent  32 . The elastic bands  16  and  18  could be solvent swelled and then placed in position or heat shrinking could be used for their placement. In either case, after placement they would snugly fit onto the balloon  34  as shown in  FIGS. 1 and 2 . Furthermore, the band  16  could be adhesively bonded to the guide wire  11  and/or the balloon  34 . The band  18  can be adhesively bonded to the central tube  20 . 
   Another embodiment of the present invention is shown in  FIGS. 4 and 5 . This embodiment differs from the embodiment of  FIGS. 1 and 2  in that the core wire  13  of  FIG. 1 and 2  is considerably lengthened. Explicitly, the elongated core wire  43  of  FIGS. 4 and 5  extends through the balloon  34  and into and through the central tube  20 . Although the elongated core wire  43  could have its proximal end terminate within the central tube  20 , it would more advantageously extend into the proximal tube  21 . The core wire  43  could even extend to the Luer fitting  22 . The proximal end of the core wire  43  can be fixedly attached to a cylindrical, multi-lumen connector  44  that has lumens  46  through which fluid can be passed to inflate and deflate the balloon  34 . The arrows  45  indicate the direction of fluid flow for inflating the balloon  34 . The purpose of the elongated core wire  43  is to provide additional pushability and also to enhance the transmission of torque to the guide wire  11 . Another purpose of the core wire  43  is to prevent inadvertent separation of the guide wire  11  from the stent delivery system  10 . That is, it is desirable to have an additional level of safety to prevent the guide wire  11  from breaking off and embolizing downstream into the arterial circulation. 
   An important feature of the stent delivery system  10  would be to minimize the length of the cylindrical portion of the balloon  34  that extends beyond each end of the stent  32  when the balloon is inflated. This length is called “balloon overhang”. Because the guide wire  11  cannot remain in the treated stenosis after the stent delivery system  10  is taken out of the patient, it is urgently important that edge dissections of the arterial wall that occur more frequently with longer lengths of balloon overhang be avoided. To accomplish a reduced occurrence of stent edge dissections, balloon overhang of the balloon  34  at each end of the stent  32  should be less than 1.0 mm and preferably less than 0.5 mm. Ideally, the balloon overhang should be 0±0.5 mm. How to achieve reduced balloon overhang is explained in detail in the U.S. patent application. Ser. No. 09/373,552, entitled “Stent Delivery Catheter with Enhanced Balloon Shape” which is included herein by reference. 
   In  FIGS. 2 ,  3  and  4 , the balloon  34  is shown to bulge outward between the struts of the stent  32 . This method for holding the stent  32  more securely onto the balloon  34  is called “nesting”. It is understood that the stent  32  could either be mechanically crimped onto the balloon  34  or it could be nested as described in the U.S. patent application entitled “Stent Delivery System Having a Stent Nested Onto a Non-Adhering Lubriciously Coated Balloon” that is filed on even date herewith by the same co-inventors and is included herein by reference. 
   It should be understood that the proximal tube  21  could extend from the proximal end of the balloon  34  to the Luer fitting  22  that is situated at the proximal end of the stent delivery system  10 . That is, this invention will function satisfactorily without having a central tube  20 . Furthermore, wire reinforcing in the wall of either or both the tube  20  or the tube  21  is envisioned for improving the pushability of the stent delivery system  10 . 
   Various other modifications, adaptations, and alternative designs are of course possible in light of the above teachings. Therefore, it should be understood at this time that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described herein.