Abstract:
A system and method are provided that use a balloon/stent catheter for placing a stent at the ostium of a blood vessel. Included is a barrier member that is attached to the catheter at a location proximal the balloon. In use, the barrier member is reconfigured, prior to insertion of the balloon/stent portion of the catheter through the ostium. With this reconfiguration, a barrier (array) is established that limits advancement of the catheter into the blood vessel to ensure proper placement of the stent at the ostium.

Description:
[0001]    This application claims the benefit of U.S. Provisional Patent Application Ser. No. 61/259,871, filed Nov. 10, 2009. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention pertains generally to intravascular catheter systems. More particularly, the present invention pertains to balloon catheters that are used to place stents in the vasculature of a patient. The present invention is particularly, but not exclusively, useful as a stent delivery system for placing a stent at the ostium of a blood vessel, wherein the catheter incorporates a barrier (array) that limits insertion of the balloon/stent through the ostium of the blood vessel, to ensure a proper placement of the stent at the ostium. 
       BACKGROUND OF THE INVENTION 
       [0003]    After an angioplasty procedure, it is well known that there is always the possibility of a restenosis or, perhaps, a collapse of the weakened blood vessel at the site of the procedure. To help minimize either of these possibilities, and to hopefully avoid them altogether, it has become a standard practice to place stents at the angioplasty site after the procedure. The purpose here is to give added strength to the wall of the blood vessel that may otherwise be lacking as a result of the angioplasty procedure. Typically, the placement of a stent in the vasculature of a patient (i.e. in a blood vessel) is accomplished using a balloon catheter. More specifically, after a stent has been positioned (crimped) onto the balloon of a balloon catheter (i.e. to create a balloon/stent catheter) the stent is advanced into the vasculature and to the site where it is to be placed. The balloon is then inflated to expand the stent, for placement of the stent against the wall of the blood vessel. Once the stent has been placed, the balloon is then deflated and the balloon catheter is withdrawn from the vasculature, leaving the stent in place. 
         [0004]    Under conditions where the stent placement site is located along the length of a blood vessel, placement of the stent is relatively straightforward. It is, however, an entirely other matter when the intended stent placement site is at the ostium of a blood vessel. In this latter case, not only does the stent need to be properly inserted into the ostium, its insertion must be limited to ensure a proper placement of the stent. Importantly, the complete stent needs to be placed at the ostium. Stated differently, there should not be a partial insertion that leaves part of the stent hanging outside the blood vessel, in the aorta, nor should the stent be inserted beyond the ostium, deeper into the blood vessel. Heretofore, a proper placement of the stent has relied solely on visual information provided by well-known imaging techniques, such as fluoroscopy. 
         [0005]    With the above in mind, it is an object of the present invention to provide a system and method for placing a stent at the ostium of a blood vessel that gives a tactile sensation for the task, in addition to visual information, to ensure the proper placement of a stent at the ostium. Another object of the present invention is to provide a system and method for placing a stent at the ostium of a blood vessel that prevents either too much overhang in the aorta or a deep placement of the stent into the blood vessel that causes the stent to miss the ostium. Yet another object of the present invention is to provide a system and method for placing a stent at the ostium of a blood vessel that is relatively simple to manufacture, is easy to use, and is comparatively cost effective. 
       SUMMARY OF THE INVENTION 
       [0006]    A delivery system for placing a stent at the ostium of a blood vessel includes a catheter having an inflatable balloon. The balloon is mounted at the distal end of the catheter, and a stent is positioned (crimped) onto the balloon. Thus, a balloon/stent catheter is created. Additionally, a ring is affixed to the catheter shaft at a location proximal to the balloon, and a barrier member is attached to the ring. In overview, the barrier member can be manipulated to ensure a proper placement of the stent at the ostium of a blood vessel in the vasculature of a patient. 
         [0007]    Structurally, the barrier member includes a plurality of deflectable extension members that are biased to flare outwardly from the shaft in a radial direction to create a pattern (array). To do this, each of the extension members is moveable in concert with the other extension members between a first configuration, wherein all of the extension members are aligned substantially parallel to the axis of the catheter, and a second configuration wherein all of the extension members are biased to extend substantially perpendicular to the axis. It is in this second configuration, that the plurality of extension members project in a radial direction from respective locations at the proximal end of the stent. Thus, they establish a structural array that can be operationally used as a barrier, to limit advancement of the catheter into the vasculature. 
         [0008]    In greater detail, the barrier member includes a base portion having a proximal end that is attached to the ring. The plurality of deflectable extension members that are disclosed above, are integral with the distal end of this base portion. Further, as implied above, when the barrier member is in its second configuration, deflectable extension members are biased into an array. More specifically, this array assumes a predetermined pattern, such as a web-like pattern, a fan-like pattern, or a pattern of elongated extension arms. Also, the base portion of the barrier member may be constructed in a manner that will allow it to be deformable when the balloon is inflated. 
         [0009]    The system may also include a guiding catheter that cooperates with the balloon/stent catheter to perform at least two functions. One, is to advance the balloon/stent catheter through the vasculature. The other is to manipulate the barrier member of the balloon/stent catheter. Structurally, the guiding catheter is coaxial with the balloon/stent catheter, and is positioned over the balloon/stent catheter for axial movement relative to the catheter. Within this structure, the guiding catheter can alternately confine the array inside the guiding catheter with the array in its first configuration (i.e. advancement through the vasculature), or release the array into its second configuration for placement of the balloon/stent catheter at an ostium of a blood vessel. 
         [0010]    Additional features of the system include an extracorporeal inflation pump that is connected to the proximal end of the catheter, and is in fluid communication with the balloon for selectively inflating the balloon to deploy the stent. Also, a guide wire can be pre-positioned in the vasculature of a patient with the guide wire extending into the ostium of the blood vessel. The guide wire can then be engaged with the balloon/stent catheter for advancing the catheter through the vasculature to the ostium. As envisioned for the present invention, the barrier member is preferably made of cobalt, chromium, platinum, nitinol or stainless steel. 
         [0011]    For an operation of the present invention, a guide wire is pre-positioned in the vasculature of a patient, with the guide wire extending into the ostium of the blood vessel. The balloon/stent catheter is then advanced over the guide wire, inside the guiding catheter. This continues until the distal end of the balloon/stent catheter is near the ostium. At that point, either the balloon/stent catheter is advanced through the guiding catheter in a distal direction, or the guiding catheter is withdrawn in a proximal direction to reconfigure the barrier member from its first configuration, and into its second configuration. The balloon/stent catheter is then further advanced, with the array in the second configuration, for use of the barrier to prevent an advancement of the catheter into the ostium, after the stent has been properly positioned in the ostium. The balloon is then inflated to deploy and place the stent in the ostium. Next, the balloon is deflated, and the catheter, less the stent, is withdrawn into the guiding catheter. This withdrawal also returns the barrier member to its first configuration. The system is then withdrawn from the vasculature. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    The novel features of this invention, as well as the invention itself, both as to its structure and its operation, will be best understood from the accompanying drawings, taken in conjunction with the accompanying description, in which similar reference characters refer to similar parts, and in which: 
           [0013]      FIG. 1  is a presentation of the system of the present invention shown in its intended operational environment; 
           [0014]      FIG. 2  is a perspective view of the system with portions broken away for clarity; 
           [0015]      FIG. 3A  is a cross-section view of the distal portion of the balloon/stent catheter of the present invention as seen along the line  3 - 3  in  FIG. 2 , with the guiding catheter positioned over the balloon/stent catheter to confine the barrier member of the catheter in its first configuration; 
           [0016]      FIG. 3B  is a cross-section view of the distal portion of the balloon/stent catheter as in  FIG. 3A , with the guiding catheter withdrawn to bias the barrier member into its second configuration; 
           [0017]      FIG. 3C  is a cross-section view of the distal portion of the balloon/stent catheter as in  FIG. 3B , with the stent inserted into a blood vessel and the balloon inflated to place the stent in the ostium of the blood vessel; 
           [0018]      FIG. 4A  is a side view of the barrier member of the present invention with its base portion configured for deformation; 
           [0019]      FIG. 4B  is a side view of the barrier member of the present invention with its base portion alternately configured for deformation; 
           [0020]      FIG. 4C  is a side view of the barrier member of the present invention with its base portion further alternately configured for deformation; 
           [0021]      FIG. 5A  is an alternate embodiment of the array of the barrier member as seen from along the axis of the catheter; and 
           [0022]      FIG. 5B  is another alternate embodiment of the array of the barrier member as seen from along the axis of the catheter. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0023]    Referring initially to  FIG. 1  a system for delivering a stent to the ostium of a blood vessel in accordance with the present invention is shown and is generally designated  10 . As shown, the system  10  includes a balloon/stent catheter  12  that is being advanced into the vasculature of a patient  14 . Once the catheter  12  has been properly placed in the vasculature, an inflator  16  is activated to inflate a balloon  18 . With this inflation of the balloon  18 , a stent  20 , that is positioned (crimped) onto the balloon  18 , will expand. The stent  20  will then be left at the ostium of a blood vessel after the catheter  12  is withdrawn from the vasculature. Structural details of the balloon/stent catheter  12  will be best appreciated with reference to  FIG. 2 . 
         [0024]    In  FIG. 2  it will be seen that the balloon/stent catheter  12  includes a shaft  22  defining a longitudinal axis  24 . For the present invention, the balloon  18  is affixed to the shaft  22  at a location immediately proximal the distal end  26  of the shaft  22 . Further,  FIG. 2  shows that the catheter  12  includes a barrier member  28  which is affixed to the shaft  22  at a location immediately proximal the balloon  18 . As shown, the barrier member  28  includes a base portion  30  with a plurality of deflectable extension members  32  projecting therefrom. The extension members  32   a  and  32   b  shown in  FIG. 2  are only exemplary. 
         [0025]    Structurally, the base portion  30  of the barrier member  28  is mounted on a ring  34  that is affixed to the shaft  22  of the balloon/stent catheter  12 . Within this arrangement, it is an important aspect of the barrier member  28  that each extension member  32  is biased at a bending region  36  which is intermediate the base portion  30  and the extension members  32 . More specifically, in their relaxed state, the extension members  32  are biased to assume the configuration shown in  FIG. 2 . In this configuration, the extension members  32  extend outwardly, in a radial direction from the axis  24 . The bending regions  36   a  and  36   b  shown for respective deflection extension members  32   a  and  32   b  are exemplary. Preferably, the barrier member  28  is made of cobalt, chromium, platinum, nitinol or stainless steel. 
         [0026]    Still referring to  FIG. 2 , it will be seen that system  10  may also include a guiding catheter  38  and a guide wire  40 . For the system  10 , the purpose of this guiding catheter  38  is actually two-fold. For one, the guiding catheter  38  can be used to advance the balloon/stent catheter  12  through the vasculature of patient  14  to the ostium  42  of a blood vessel  44 . For this purpose, a configuration of the balloon/stent catheter  12  and its barrier member  28 , in combination with the guiding catheter  38 , is shown in  FIG. 3A . More specifically, in  FIG. 3A  it will be appreciated that all of the extension arms  32  are forced by the guiding catheter  38  to align substantially parallel to the axis  24 . As shown in  FIG. 3B , however, when either the stent/balloon  20 / 18  is advanced in a distal direction out of the guiding catheter  38 , or when the guiding catheter  38  is withdrawn in a proximal direction, the extension arms  32  of barrier member  28  are biased into a flared configuration. In this flared configuration, they extend outwardly in a radial direction substantially perpendicular to the axis  24  to establish an array  46 . 
         [0027]      FIG. 3C  indicates that once the guiding catheter  38  has been withdrawn from over the stent/balloon  20 / 18 , and the barrier member  28  consequently assumes its flared configuration to present the array  46 , the stent/balloon  20 / 18  can then be inserted into the ostium  42  of blood vessel  44 . Importantly, during this insertion, the array  46  that is established by the now-deflected extension members  32  of the barrier member  28  will act as a barrier to limit insertion of the catheter  12  into the blood vessel  44 . Moreover, because it is radiopaque, in addition to visual clues (i.e. fluoroscopy), the array  46  will give the user of the catheter  12  a tactile sensation of contact with the ostium  42 . 
         [0028]      FIG. 3C  also indicates that after the stent/balloon  20 / 18  has been inserted into the blood vessel  44 , the inflator  16  can be activated to inflate the balloon  18 , via an inflation tube  48  that connects the balloon  18  in fluid communication with the inflator  16 . When the balloon  18  has been inflated, the stent  20  is expanded and pressed against the wall  50  of the blood vessel  44 . Importantly, due to the constraint on advancement of the catheter  12 , as imposed by the array  46  of barrier member  28 , the stent  20  is properly positioned at the ostium  42  of the blood vessel  44 . The balloon  18  can then be deflated and retracted into the guiding catheter  38  (see  FIG. 3A ). The catheter  12 , less stent  20 , and the guiding catheter  38  can then be withdrawn from the vasculature. 
         [0029]    Referring now to  FIGS. 4A ,  4 B and  4 C, several structural variations for the base portion  30  of barrier member  28  are shown. Specifically, these different structures are intended to allow the base portion  30  to be at least somewhat deformed during an inflation of the balloon  18 . To do this,  FIG. 4A  shows the base portion  30  with a “Z” shaped slit  52 ;  FIG. 4B  shows it with an “angled” slit  54 ; and  FIG. 4C  shows an “S” shaped slit  56 . Further, in addition to the preferred configuration for array  46  shown in  FIG. 2 , wherein the extension members  32  flare radially outward from the axis  24 ,  FIG. 5A  shows a variation wherein the array  46 ′ is shown as a web-shaped pattern. As another alternative embodiment,  FIG. 5B  shows an array  46 ″ having a fan-shaped pattern. 
         [0030]    While the particular System and Method for Placing a Coronary Stent at the Ostium of a Blood Vessel as herein shown and disclosed in detail is fully capable of obtaining the objects and providing the advantages herein before stated, it is to be understood that it is merely illustrative of the presently preferred embodiments of the invention and that no limitations are intended to the details of construction or design herein shown other than as described in the appended claims.