Abstract:
A catheter configured to carry one or more stents and having an inflatable balloon for expanding a stent surrounding the balloon. The catheter is characterized in having a positioner for moving the one or more stents relative to the balloon from a first position in which the stent does not surround the balloon to a second position in which the stent surrounds the balloon. Also disclosed is a method for deploying a stent at a desired location in the vascular system.

Description:
FIELD OF THE INVENTION  
         [0001]    This invention relates to catheters and more specifically to such catheters that are used to implant a stent in an artery.  
         BACKGROUND OF THE INVENTION  
         [0002]    Blood vessels, and particularly arteries, may become stenotic or occluded due to various atherosclerotic processes. A stenotic artery may be treated by balloon angioplasty in which an inflatable balloon mounted on a catheter tip is inserted into the arterial system and navigated through the arterial system to the diseased artery. The balloon is then inflated by means of a pressurized fluid. This causes the balloon to press radially on the arterial wall so as to open the stenosis. A stent may be crimped onto the balloon before insertion so that when the balloon is inflated the stent becomes expanded, The balloon is deflated and withdrawn leaving the expanded stent in the artery. These and other similar methods are well known to the skilled man of the art.  
           [0003]    It is often necessary to treat several stenoses in a single angioplastic session. For example, it may be necessary to insert a large diameter stent at one location, a small diameter stent at a second location and to perform a balloon angioplasty without a stent at a third location. This could be accomplished by sequential insertion and withdrawal of a catheter, the catheter being loaded each time with the appropriate stent prior to insertion. This however would cause much discomfort to the patient, prolongs the duration of the procedure and increases the chances of damaging a blood vessel.  
           [0004]    U.S. Pat. No. 6,027,519 discloses a catheter for deploying one or more stents. The stent has one or more individually expandable segments along its length. A stent, in its unexpanded states is loaded onto each expandable segment of the catheter. The catheter is inserted into the vascular system and positioned with the first expandable segment in a stenosis. An axial force is then applied to the segment causing it to buckle outwards and expand the stent. The force is then removed caused the segment to unbuckle leaving the stent in its expanded state. The catheter is then navigated to another stenosis. This process is repeated until all of the stents have been deployed.  
         SUMMARY OF THE INVENTION  
         [0005]    The present invention provides a catheter for deploying one or more stents in a cardiovascular system. The catheter is configured to carry one or more stents. Preferably, the catheter carries a plurality of stents. The stents may be of different or the same widths. An inflatable balloon is used to expand a stent surrounding the balloon. The catheter comprises a positioner for moving a stent relative to the balloon from a position in which the stent does not surround the balloon to a position that it does surround the balloon in order to prime the stent for expansion by the balloon. The phrase “for moving a stent relative to the balloon” includes two possibilities, i.e. moving the positioner relative to the balloon and moving the balloon relative to the positioner.  
           [0006]    In one embodiment of the invention the positioner comprises an element configured to slide along the catheter and push the stents distally along the catheter so as to move a stent adjacent to the balloon into a position in which it surrounds the balloon. The sliding element is pushed along the catheter by means of a wire extending along the catheter from its proximal end to the sliding element. In this embodiment, the stents are deployed in the order in which they are carried by the catheter, starting with the stent closest to the balloon.  
           [0007]    In another embodiment, the positioner comprises a flexible carriage configured to carry the one or more stents. The carriage is capable of sliding along the catheter in order to bring one of the stents from a position in which the stent does not surround the balloon to a position in which the stent surrounds the balloon. The carriage is moved in either direction along the catheter by means of a wire extending along the catheter from its proximal end to the carriage. It is also possible to position the stent opposite a desired location in the vascular system and slide the balloon through the carriage to a position opposite the stent. In this embodiment the stents may be deployed in the vascular system in any order.  
           [0008]    It a third embodiment, the catheter comprises two positioners, one posterior positioner as described above in the first embodiment positioned posterior to the balloon, and a second anterior positioner positioned anterior to the balloon. In this embodiment, the anterior positioner may be distanced from the balloon so as to provide a storage space between the anterior positioner and the balloon. The balloon in this embodiment may be a conventional balloon used in balloon angioplasty. In this embodiment also, the stents may be deployed in the vascular system in any order, and may be of different lengths.  
           [0009]    In use, the catheter is loaded with one or more stents and inserted into a vascular system. The catheter is navigated through the vascular system until the balloon or stent is positioned at a first desired location, typically the site of a stenosis. The stent or balloon is then moved by the positioner so that the stent surrounds the balloon and the balloon is inflated so as to expand the stent. The balloon is then deflated, leaving the expanded stent at the fist desired location. This process may be repeated, each time deploying a different stent at a different location. After one or more of the stents have been deployed, the catheter may be removed from the vascular system.  
           [0010]    The invention also provides a method for deploying a stent in a desired location of a vascular system comprising the steps of:  
           [0011]    (a) inserting a catheter according to the invention carrying one or more stents into the vascular system,  
           [0012]    (b) navigating the catheter through the vascular system until the balloon is positioned in the desired location;  
           [0013]    (c) moving a stent from a first position in which it does not surround the balloon to a second position in which it surrounds the balloon;  
           [0014]    (d) inflating the balloon so as to expand the stent; and  
           [0015]    (e) deflating the balloon. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]    In order to understand the invention and to see how it may be carried out in practice, a preferred embodiment will now be described, by way of non-limiting examples only, with reference to the accompanying drawings, in which:  
         [0017]    [0017]FIG. 1 shows a catheter in accordance with one embodiment of the invention;  
         [0018]    [0018]FIG. 2 shows the catheter of FIG. 1 carrying stents;  
         [0019]    [0019]FIG. 3 shows the catheter at FIG. 1 inserted in a blood vessel;  
         [0020]    [0020]FIG. 4 shows the catheter of FIG. 1 with a stent surrounding a balloon on the catheter;  
         [0021]    [0021]FIG. 5 shows the catheter in FIG. 1 after inflation of the balloon;  
         [0022]    [0022]FIG. 6 shows a catheter in accordance with another embodiment of the invention;  
         [0023]    [0023]FIG. 7 shows the catheter of FIG. 6 carrying stents;  
         [0024]    [0024]FIG. 8 shows the catheter at FIG. 6 inserted in a blood vessel;  
         [0025]    [0025]FIG. 9 shows the catheter of FIG. 6 with a stent surrounding a balloon on the catheter;  
         [0026]    [0026]FIG. 10 shows the catheter in FIG. 6 after inflation of the balloon;  
         [0027]    [0027]FIG. 11 is a sectional side view of a catheter in accordance with another embodiment of the invention;  
         [0028]    [0028]FIG. 12 illustrates the operation of the embodiment illustrated in FIG. 11; and  
         [0029]    [0029]FIG. 13 illustrates another detail of the operation of the embodiment of FIG. 11.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
     Example I  
       [0030]    [0030]FIG. 1 shows a catheter  100  for deploying stents in accordance with one embodiment of the invention. The catheter  100  has a distal end  108  and a proximal end  120 . The catheter  100  comprises a flexible tube  102 , which is connected to an inflatable balloon  104  proximate to its distal end. The balloon  104  is shown in the Figure in its deflated state. A radio-opaque marker  118  is located on the balloon wall. The catheter  100  has at its distal end  108  a tapered tip  110  that may be inserted into a stenosis in order to open the stenosis. A syringe  130  may be used to introduce a fluid into the tube  102  in order to inflate the balloon  104  as described in detail below.  
         [0031]    A longitudinal shaft  124  in the wall of the tube  102  is configured to receive a guidewire  126  used in navigating the catheter in the vascular system. A neck region  122  of the tube  102  intervenes between the distal end of the balloon  104  and the tip  110 . The proximal end of the tip  110  is broadened to form a shoulder at the distal end of the neck region  122 . A sliding positioner element in the form of an annular sliding ring  114  is mounted on the tube  102  proximal to the balloon  104 . The ring  114  is slidable along the tube  102  by means of a wire  116  that extends along the length of the tube  102  from the proximal end  120  of the catheter to the ring  114 .  
         [0032]    The sliding ring  114  and the wire  116  form a positioner for moving a stent from a position which it does not surround the balloon  104  to a position in which it surrounds the balloon  104 .  
         [0033]    [0033]FIG. 2 shows the catheter  100  having a plurality of stents (three are shown in FIG. 2)  206   a ,  206   b  and  206   c , mounted on the tube  102  between the sliding ring  114  and the balloon  104 . The stents are separated from each other by separating rings  208   a  and  208   b . The sliding ring  114  has been positioned so that the separating rings  208   a  and  208   b  and the stent  206  are contiguous with the balloon  104 . Each stent  206  bears a radio-opaque markers  210   a ,  210   b  and  210   c.    
         [0034]    In use, the catheter  100  is introduced into the vascular system and navigated to a stenosis by methods well known in the art. FIG. 3 shows the catheter  100  after having been navigated through the vascular system and positioned inside a blood vessel  202 . The balloon is located opposite a stenotic region  204  of the blood vessel  202 . The wire  116  is used to slide the sliding ring  114  distally along the tube  102  so as to push the stents  206   a ,  206   b ,  206   c , distally. The sliding ring  114  is pushed distally along the tube  102  so that the stent  206   a  is pushed over and around the balloon  104 , which is thereby brought into the lumen of the stent  206   a , and the marker  118  on the balloon coincides with the marker  210   a  of the stent, as determined for example by x-ray angiography. FIG. 4 shows the stent  206   a  surrounding the balloon  104 .  
         [0035]    A fluid is then introduced into the tube  102 . The fluid passes through the tube  102  and inflates the balloon  104 . It will be understood that the balloon may be inflated by other conventional means, as are known in the art. Inflation of the balloon  104  expands the stent  206   a  onto the stenotic region of the blood vessel  202 , as shown in FIG. 5.  
         [0036]    The fluid is then withdrawn from the tube  102 . Withdrawal of the fluid from the tube  102  causes the balloon to deflate. After deflation of the balloon, the stent  206   a  remains in situ in its expanded state.  
         [0037]    The catheter may then be navigated through the arterial system until the catheter is positioned with the balloon  104  at another stenotic region of a blood vessel. The sliding ring is pushed distally by the wire  116  so that the succeeding stent  206   b  overlies the balloon  104  and the marker  118  coincides with the marker  210   b  on the stent  206   b.  The distal separating ring  208   a  is pushed along the tube  102 , beyond the balloon  104  to the neck region  122  of the tube, where the separating rings are stored. The shoulder of the tip  110  retains the separating rings on the neck region. This process may be repeated until some or all of the stents  206  have been deployed. The catheter is then removed from the body.  
       Example II  
       [0038]    [0038]FIG. 6 shows a catheter  600  for deploying stents in accordance with another embodiment of the invention. The embodiment of FIG. 6 has many components in common with the embodiment of FIG. 1, and similar components are identified by the same reference numeral in both embodiments.  
         [0039]    The embodiment of FIG. 6 has a cylindrical carriage  605  mounted on the tube  102 . The carriage has a plurality of annular depressions (three are shown in FIG. 6)  610   a ,  610   b  and  610   c  configured to receive a stent as described below. The depressions  610  all have the same length A as indicated in FIG. 6, which is essentially equal to the length of the balloon  104 . Between the depressions  610  are barriers  620   a  and  620   b . The carriage  605  is made from an elastic material such as rubber. The carriage  605  is slidable along the tube  102  by means of a wire  116  that extends along the length of the tube  102  from the proximal end  120  of the catheter to the carriage  605 . The carriage  605  and the wire  116  form a positioner for moving a stent from a position in which it does not surround the balloon  104  to a position in which it surrounds the balloon  104 .  
         [0040]    [0040]FIG. 7 shows the catheter  600  having a plurality of stents (three are shown in FIG. 7)  206   a ,  206   b  and  206   c  mounted on the annular depressions of the tube  102 . The stents are separated from each other by the barriers  620   a  and  620   b . In the present embodiment the stents are of different lengths. However, they may also be of the same length. Each stent  206  bears a radio-opaque annular marker  210   a ,  210   b  and  210   c.    
         [0041]    The catheter  600  is introduced into the vascular system and navigated to a stenosis by methods well known in the art. FIG. 8 shows the catheter  600  after having been navigated through the vascular system and positioned inside a blood vessel  202 . The balloon is located within a stenotic region  204  of the blood vessel  202 . The wire  116  is used to slide the cage  605  distally along the tube  102  so as to move the stents  206  distally. The carriage  605  is pushed distally along the tube  102  until the balloon  104  is brought into the lumen of the stent  206   a  and the marker  118  on the tube coincides with the marker  210   a , as determined for example by x-ray angiography. In a similar manner, the balloon may be slid within the carriage until it is positioned opposite the stent. FIG. 9 shows the stent  206   a  surrounding the balloon  104 .  
         [0042]    A fluid is then introduced into the tube  102 . The fluid passes through the tube  102  and inflates the balloon  104 . Inflation of the tube  104  expands the portion of the carriage  605  surrounding the balloon  104  which in turn expands the stent  206   a  onto the stenotic region of the blood vessel  202 , as shown in FIG. 10.  
         [0043]    The fluid is then withdrawn from the tube  102  into the syringe  130 . Withdrawal of the fluid from the tube  102  causes the balloon to deflate. After deflation of the balloon, the stent  206   a  remains in its expanded state.  
         [0044]    The catheter is then navigated through the arterial system until the catheter is positioned with the balloon  104  in another stenotic region of a blood vessel. The catheter is then pushed distally by the wire  116  so that the stent  206   b  overlies the balloon  104  and the marker  118  coincides with the marker  210   b  on the stent  206   b.  In this embodiment, the stents may be deployed in any order. This process may be repeated until some or all of the stents  206  have been deployed. The catheter is then removed from the body.  
       Example III  
       [0045]    This example illustrates an embodiment which is an improvement over the embodiment described in Example I. With reference to FIG. 11, there is shown a catheter  700  having a distal end  108  and a proximal end  120 . As in FIG. 1, the catheter  700  comprises a flexible tube  102 , which is connected to an inflatable balloon  704  proximate to its distal end. A radio-opaque marker  118  is located on the balloon wall. The catheter  700  has at its distal end  108  a tapered tip  110 , but unlike in Example I, there is no neck region, and the tip is not enlarged. The balloon in this embodiment may be a conventional inflatable balloon used in balloon angioplasty.  
         [0046]    As in Example I, a guidewire  126  extends along the tube  102 , exiting at the distal end  108  of the catheter. An anterior positioner in the form of a perforated sphere  706  is fixed to the guidewire anterior to the balloon  704 , e.g. the guidewire passes through a bore channel extending through the sphere. The diameter of the sphere is slightly larger than the diameter of the retracted stents which are mounted on the catheter. The purpose of the sphere will be explained below.  
         [0047]    The catheter  700  has a sliding ring  114  (being the posterior positioner) and a plurality of stents (three are shown in FIG. 11)  206   a ,  206   b  and  206   c , mounted on the tube  102  between the sliding ring  114  and the balloon  704 . While the anterior stents are generally of the same length, the posterior stent may be longer or shorter. In the illustrated embodiment, the posterior stent  206   c  is shorter than the other stents. Each stent  206  bears at least one radio-opaque marker  210   a ,  210   b  and  210   c , respectively. The stents are separated by separating rings  708   a  and  708   b  which are of the same length as the anterior stents. An anterior ring  710  is positioned between the most anterior stent  206   a  and the balloon  704  and protects the distal edge of the anterior stent. This anterior ring may be shorter than the separating rings.  
         [0048]    The operation of this embodiment may be understood with reference to FIG. 12. As in Example I, the wire  116  is used to slide the sliding ring  114  distally along the tube  102  so as to push the stents  206   a ,  206   b ,  206   c , distally. The sphere  706  is distanced from the distal end  108  of the catheter by pushing the guidewire  126 , thus providing free guidewire  712  on which components of the catheter may be stored. In FIG. 12, it may be seen that the anterior ring  710  and the separating ring  708   a  have been pushed beyond the balloon  704  and onto the free guidewire  712 . The anterior stent  206   a  (not shown) has been expanded and deployed within the blood vessel wall, and the middle stent  206   b  is mounted on the balloon  704 , ready to be expanded. The radio-opaque marker  210   b  of the stent  206   b  is positioned opposite the radio-opaque marker  118  of the balloon  704 .  
         [0049]    Thus, this embodiment also differs from that of Example I in having more room to store the separating rings. In addition, all of the mounted stents and rings may be moved distally and proximally by pulling and pushing the anterior and posterior positioners, being the sphere  706  and sliding ring  114 , respectively, so that the stents may be deployed in any order. This differs from Example I where the stents were required to be deployed in the order in which they were placed on the catheter.  
         [0050]    [0050]FIG. 13 shows the catheter after the 2 anterior stents  206   a  and  206   b  (not shown) have been deployed, and the anterior  710  and separating  708   a  &amp;  708   b  rings are positioned on the free guidewire  712  between the sphere  706  and the balloon  704 . It may be seen that the separating rings have annular protrusions  714  protruding from their outer surface. The purpose of these protrusions is to protect the blood vessel inner wall from being injured by the stents as the catheter travels through the vessel. The posterior stent  206   c  is mounted on the distal half of the balloon  704 , while the anterior portion of the sliding ring  114  envelops the proximal end of the balloon. Thus, when the balloon is inflated, only the distal half expands (since the sliding ring resists the pressure of the balloon), expanding the stent  206   c  and deploying it in the blood vessel.