Abstract:
A bifurcated stent for insertion into a bifurcated vessel such as a blood vessel. In one embodiment, a first sheet is formed into a first leg, a second sheet is formed into a second leg, a third sheet is formed into a stem, and the two legs are attached to the stem. In a second embodiment, a first sheet is formed into a member having a first leg and half of a stem, a second sheet is formed into a second member having a second leg and half of a stem, and the two stem halves are combined to form the bifurcated stent. In a third embodiment, the stent comprises two sections that are serially inserted and assembled within the vessel at the site of the bifurcation to be treated.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to stents, and more particularly to bifurcated stents and methods of making bifurcated stents for insertion within a branching vessel.  
         BACKGROUND OF THE INVENTION  
         [0002]    Stents are well known in the art. They are typically formed of a cylindrical metal mesh which can expand when pressure is internally applied. Alternatively, they can be formed of wire wrapped into a cylindrical shape or sheets of material formed into a cylindrical shape.  
           [0003]    Stents are devices which are usually implanted within bodily conduits including the vascular system to reinforce collapsing, partially occluded, weakened, or abnormally dilated sections of the blood vessel. Stents also have been successfully implanted in other areas, e.g., the urinary tract or the bile duct to reinforce such bodily conduits.  
           [0004]    U.S. Pat. No. 4,994,071 (MacGregor) discloses an expandable, bifurcating stent having a main cylindrical lattice formed from interconnected, flexible wire. Two additional cylindrical lattices, having smaller diameters than the main lattice, are similarly constructed. The main lattice includes a flexible wire interconnecting the main lattice to one of the additional lattices. A second flexible wire interconnects the main lattice to the other additional lattice. The flexible wires form backbones that extend axially along the length of the main lattice and along each of the additional lattices. One disadvantage of this bifurcating stent is the complex nature of the interconnection of the flexible wires forming the backbones with the loop structure of each lattice.  
         SUMMARY OF THE INVENTION  
         [0005]    The present invention solves these and other disadvantages of the prior art by providing bifurcated stents and methods of fabricating and deploying bifurcated stents having a stem portion and two leg portions.  
           [0006]    In a first embodiment of the invention, a bifurcated stent is made by providing three sheets patterned to a desired pattern, wherein two sheets are substantially the same size and the third sheet is wider than either of the first two sheets. Each of the sheets is formed into tubes by turning up the longitudinal edges and forming a joint by welding. The larger sheet forms a tube that acts as the stem portion of the bifurcated stent and the other sheets form tubes which act as the leg portions of the bifurcated stent. The two leg portions are then joined to the stem portion to form the bifurcated stent.  
           [0007]    In a second embodiment of the invention, the bifurcated stent is formed by preparing two stent sheets. For each sheet, the longitudinal edges of a portion of the sheet are turned up and secured to each other to form one of the two leg portions of the bifurcated stent. The remaining free edges of each of the two sheets are then joined to form the stem portion of the stent.  
           [0008]    In a third embodiment, the bifurcated stent comprises first and second tubular portions. The first portion has a proximal end which forms the stem portion and a distal end which forms one of the leg portions of the bifurcated stent. A branch aperture is disposed between the proximal end and the distal end of the first portion. The second portion is introduced into the longitudinal bore of the stem portion of the first portion and is advanced through the branch aperture so that it protrudes beyond the branch aperture to form a second leg. When the second portion is expanded, the proximal end of the second portion engages the material defining the branch aperture so as to secure the second leg in the desired position.  
           [0009]    It is an object of this invention to provide a method of making a bifurcated stent, comprising the steps of: a) preparing a first sheet having a first edge, a second edge, a third edge, and a fourth edge; b) preparing a second sheet having a first edge, a second edge, a third edge, and a fourth edge; c) preparing a third sheet having a first edge, a second edge, a third edge, and a fourth edge; d) attaching the second edge to the third edge of the first sheet to form a tubular first leg portion having a proximal end and a distal end; e) attaching the second edge to the third edge of the second sheet to form a tubular second leg portion having a proximal end and a distal end; f) attaching the second edge to the third edge of the third sheet to form a tubular stem portion having a proximal end and a distal end; and g) attaching the proximal end of the first leg portion and the proximal end of the second leg portion to the distal end of the stem portion.  
           [0010]    It is another object of this invention to provide a method of making a bifurcated stent, comprising the steps of a) preparing a first sheet having a proximal end and a distal end; b) deforming the distal end of the first sheet to form a first leg and deforming the proximal end of the first sheet to form a first stem half; c) preparing a second sheet having a proximal end and a distal end; d) deforming the distal end of the second sheet to form a second leg and deforming the proximal end of the second sheet to form a second stem half; and e) joining the first stem half to the second stem half to form a stem.  
           [0011]    It is yet another object of this invention to provide a method of making a bifurcated stent comprising the steps of a) preparing a first expandable tubular member having a proximal end and a distal end and a longitudinal bore therethrough, the first tubular member provided with a branch aperture disposed between said proximal end and the distal end, the branch aperture communicating with said longitudinal bore and the aperture sized and adapted to receive and secure a second expandable tubular member; b) delivering the first expandable tubular member to a bifurcated vessel having a first lumen and a second lumen so that the first expandable member is disposed within the first lumen and the branch aperture communicates with the second lumen; c) expanding the first expandable member in an amount sufficient to secure the first expandable member in the first lumen; d) preparing a second expandable tubular member having a proximal end and a distal end and having longitudinal bore therethrough; e) widening the branch aperture; f) delivering the second expandable tubular member into the branch aperture so that the distal end of the second expandable tubular member is disposed within the second lumen and the proximal end of the second expandable tubular member is disposed within the longitudinal bore of the first longitudinal member; and g) expanding the second expandable tubular member in an amount sufficient to secure the second expandable tubular member within the second lumen and within said branch aperture. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]    [0012]FIG. 1 shows a bifurcated stent manufactured in accordance with the present invention;  
         [0013]    [0013]FIG. 2 shows sheets used to form the legs and stem of the stent shown in FIG. 1;  
         [0014]    [0014]FIG. 3 shows the sheets shown in FIG. 2 after they have been rolled into a tubular shape;  
         [0015]    [0015]FIG. 4 is a perspective view of the tubes shown in FIG. 3 prior to assembly;  
         [0016]    [0016]FIG. 5 is an end view of the tubes shown in FIGS. 3 and 4 after they have been assembled to form a stent;  
         [0017]    [0017]FIG. 6 is a top view of the assembled apparatus shown in FIG. 5;  
         [0018]    [0018]FIG. 7 shows sheets used to form another embodiment of a bifurcated stent manufactured in accordance with the invention;  
         [0019]    [0019]FIG. 7B shows sheets used to form another embodiment of a bifurcated stent manufactured in accordance with the invention;  
         [0020]    [0020]FIG. 8 shows the sheets of FIG. 7 with demarcation points;  
         [0021]    [0021]FIG. 9 shows the sheets of FIG. 8 after they have been rolled into a tubular shape;  
         [0022]    [0022]FIG. 9B shows the sheets of FIG. 7B after they have been rolled into a tubular shape;  
         [0023]    [0023]FIG. 10 shows the tubes of FIG. 9 just prior to assembly;  
         [0024]    [0024]FIG. 10B shows the tubes of FIG. 9B just prior to assembly;  
         [0025]    [0025]FIG. 11 is a side view of the tubes shown in FIGS. 9 and 10 after assembly;  
         [0026]    [0026]FIG. 11B is a side view of the tubes shown in FIGS. 9B and 10B after assembly;  
         [0027]    [0027]FIG. 12 is an end view of the assembled apparatus shown in FIG. 11;  
         [0028]    [0028]FIG. 12B is an end view of the assembled apparatus shown in FIG. 11B;  
         [0029]    [0029]FIG. 12C shows an alternative embodiment of a pattern that may be used in place of the patterns shown in FIGS. 7 and 7B;  
         [0030]    [0030]FIG. 13 shows a stem and first leg portion and a second leg portion used to form another embodiment of a bifurcated stent manufactured in accordance with this invention;  
         [0031]    [0031]FIG. 14 shows guide wires disposed in the trunk lumen and branch lumen to be treated;  
         [0032]    [0032]FIG. 15 shows the stem and first leg portion shown in FIG. 13 disposed on catheters and guide wires prior to introduction into the lumen to be treated;  
         [0033]    [0033]FIG. 16 shows the stem and first leg portion shown in FIG. 13 after it has been delivered to the bifurcation to be treated and prior to its expansion;  
         [0034]    [0034]FIG. 17 shows the second leg portion shown in FIG. 16 after it has been expanded;  
         [0035]    [0035]FIG. 18 shows expansion of the branch aperture;  
         [0036]    [0036]FIG. 19 shows the unexpanded second leg portion disposed in the branch aperture;  
         [0037]    [0037]FIG. 20 shows the expansion of the second leg portion shown in FIG. 19; and  
         [0038]    [0038]FIG. 21 shows the assembled bifurcated stent disposed in the bifurcated lumen to be treated. 
     
    
     DETAILED DESCRIPTION  
       [0039]    In the embodiment illustrated in FIG. 1, the bifurcation stent  5  comprises a first leg  10 , a second leg  15 , and a stem  20 . FIG. 2 shows a first sheet  25  which is used to form first leg  10 , a second sheet  30  which is used to form second leg  15 , and a third sheet  35  which is used to form stem  20 . The first sheet  25  and second sheet  30  are substantially flat and are sized to a predetermined length and width. For many applications, the first sheet  25  and second sheet  30  will have substantially the same dimensions so as to produce legs  10  and  15  that are substantially the same size, however, the legs  10  and  15 , and the sheets  25  and  30  used to produce them, may be of varying sizes as specific applications dictate. The stents of this invention may be sized so that when assembled they are their final size, however, in a preferred embodiment the stents are expandable and sized and adapted to assume their final dimensions upon expansion. The stent sheets  70  and  75  may be patterned or etched with perforations forming a variety of patterns as specific applications dictate to achieve the expandable features required as previously discussed. The third sheet  35  is sized so that when it is rolled into a tube its internal cross-section can be made to accommodate the cross-sectional external diameters of first leg  10  and second leg  15 . First sheet  25  has a first edge  26 , a second edge  27 , a third edge  28 , and a fourth edge  29 . Second sheet  30  has a first edge  31 , a second edge  32 , a third edge  33 , and a fourth edge  34 . Third sheet  35  has a first edge  36 , a second edge  37 , a third edge  38 , and a fourth edge  39 . After the sheet metal has been cut to form sheets  25 ,  30 , and  35 , it is deformed and rolled so as to cause two opposite edges to meet and create a cylinder. In the example shown in FIGS. 2 and 3, edge  27  is joined to edge  29  via weld run  14  to form first leg  10 . Edge  32  is joined to edge  34  via weld run  19  to form second leg  15 . Edge  37  is joined to edge  39  via weld run  29  to form stem  20 . The edges may be joined in a wide variety of ways well known to those skilled in the art as suitable for this purpose, e.g., screwing, crimping, soldering, however, in a preferred embodiment welding is utilized. In an especially preferred embodiment, spot welding is utilized. As shown in FIG. 3, first leg  10  has a proximal end  11 , a distal end  12 , and defines a longitudinal bore  13 . Second leg  15  has a proximal end  16 , a distal end  17 , and defines a longitudinal bore  18 . The stem  20  has a proximal end  26 , a distal end  27 , and defines a longitudinal bore  28 . FIG. 4 shows the first leg  10 , second leg  15 , and stem  20  just prior to assembly. To form the bifurcated stent  5 , the proximal end  11  of first leg  10  and the proximal end  16  of second leg  15  are joined to the distal end  27  of the stem portion  20  so that the longitudinal bores  13 ,  18 , and  28  are in communication with each other. FIG. 5 is an end view and FIG. 6 is a side view of the assembled apparatus.  
         [0040]    [0040]FIG. 11 shows a second embodiment of a bifurcation stent manufactured in accordance with this invention. The stent  50  is provided with a first leg  55  and a second leg  60  attached to a stem portion  65 . The bifurcation stent  50  is formed from a first sheet  70  and a second sheet  75  as shown in FIG. 7. The stent sheets  70  and  75  may be patterned or etched with perforations forming a variety of patterns as specific applications dictate to achieve the expandable features required as previously discussed. The sheets  70  and  75  are substantially flat and have a predetermined length and width. First sheet  70  has a first edge  71 , a second edge  72 , a third edge  73  and a fourth edge  74 . The second sheet  75  has a first edge  76 , a second edge  77 , a third edge  78 , and a fourth edge  79 . To form the legs of the stent a portion of edge  72  is rolled towards a portion of edge  74  and a portion of edge  77  is rolled towards a portion of edge  79 . Demarcation points  80 ,  81 ,  82 , and  83  are selected on sheets  70  and  75  as shown in FIG. 8. These demarcation points  80 ,  81 ,  82 , and  83  are selected to meet the requirement of specific applications and may be adjusted depending upon the length required for legs  55  and  60  and the length required for stem  65 . Demarcation points  80  and  81  that are equidistant from edges  73  and  71  and demarcation points  82  and  83  that are equidistant from edges  76  and  78  will result in a stent in which the legs  55  and  60  have a length that is substantially equal to stem portion  65 . If the demarcation points are selected to be closer to edges  73  and  78  than to edges  71  and  76  the stem will have a length that is greater than the length of each of the legs. If the demarcation points are selected to be closer to edges  71  and  76  than to edges  73  and  78 , each of the legs  60  and  65  will have a length that is greater than the length of the stem  65 . In a preferred embodiment, however, the demarcation points  80 ,  81 ,  82 , and  83 , are selected so that proximal edges  72 ″,  74 ″,  77 ″, and  79 ″ are about ⅓ the length of edges  72 ,  74 ,  77 , and  79 . As shown in FIG. 8, demarcation point  80  divides edge  72  at approximately its midpoint into a distal edge  72 ′ and a proximal edge  72 ″. Demarcation point  81  divides edge  74  at approximately its midpoint into a distal edge  74 ′ and a proximal edge  74 ″. Demarcation point  82  divides edge  77  at approximately its midpoint into a distal edge  77 ′ and a proximal edge  77 ″ and demarcation point  83  divides edge  79  at approximately its midpoint into a distal edge  79 ′ and a proximal edge  79 ″.  
         [0041]    To form the stent, edge  72 ′ is connected to edge  74 ′ via weld run  90  to form first member  95  having a first leg portion  55  and a first stem half  65 ′ as shown in FIG. 9. Edge  77 ′ is connected to edge  79 ′ via weld run  91  to form second member  100  having a second leg portion  60  and a second stem half  65 ″. As previously discussed, the edges may be connected in a variety of ways well known to those skilled in the art. FIG. 10 shows the first member  95  and the second member  100  shown in FIG. 9 in alignment just prior to assembly. To produce the bifurcated stent  50  shown in FIGS. 11 and 12, edge  72 ″ is connected to edge  79 ″ via weld run  92  and edge  74 ″ is connected to edge  77 ″ via weld run  93  so that first stem half  65 ′ and second stem half  65 ″ form stem  65 . FIG. 12 is a cross-sectional end view of the stent shown in FIG. 11.  
         [0042]    In the embodiment shown in FIG. 7, sheets  70  and  75  are squares or rectangles. The sheets  70  and  75  are not limited to this configuration, however, as shown in FIG. 7B. FIG. 11B shows a bifurcation stent manufactured using the sheets  270  and  275  shown in FIG. 7B. The stent  250  is provided with a first leg  255  and a second leg  260  attached to a stem portion  265 . The bifurcation stent  250  is formed from a first sheet  270  and a second sheet  275  as shown in FIG. 7B. The stent sheets  270  and  275  may be sized and etched as previously discussed. As shown in FIG. 7B, first sheet  270  has a first edge  271 , a second edge  272 , a third edge  273 , a fourth edge  274 , a fifth edge  275 , and a sixth edge  276 , a seventh edge  146 , and an eighth edge  147 . The second sheet  275  has a first edge  277 , a second edge  278 , a third edge  279 , a fourth edge  280 , a fifth edge  281 , a sixth edge  282 , a seventh edge  148 , and an eighth edge  149 . As shown in FIG. 9B, edge  274  is connected to edge  276  via weld run  290  to form first member  295  having a first leg portion  255  and a first stem half  265 ′. Edge  280  is connected to edge  282  via weld run  291  to form second member  300  having a second leg portion  260  and a second stem half  265 ″. As previously discussed, the edges may be connected in a variety of ways well known to those skilled in the art. FIG. 10B shows the first member  295  and the second member  300  shown in FIG. 9B in alignment just prior to assembly. To produce the bifurcated stent  250  shown in FIGS. 11B and 12B, edge  272  is connected to edge  149  via weld run  292  and edge  278  is connected to edge  147  via weld run  293  so that first stem half  265 ′ and second stem half  265 ″ form stem  265 . FIG. 12B is a cross-sectional end view of the stent shown in FIG. 11B. FIG. 12C shows an alternative pattern that may be used in place of the patterns shown in FIGS. 7 and 7B.  
         [0043]    A third embodiment of this invention comprises two portions which are deployed serially in two steps and assembled within the patient to form a bifurcated stent. FIG. 13 shows stem and first leg portion  110  provided with a longitudinal bore  131  and having a proximal end  115  defining a stem portion  125  and a distal end  120  defining a first leg portion  130 . Second leg portion  140  is provided with a longitudinal bore  132  and has a proximal end  145  and a distal end  150 . Stem and first leg portion  110  and second leg portion  140  may be sized and patterned or etched as previously discussed. A branch aperture  135  is disposed between the proximal end  115  and the distal end  120  of stem and first leg portion  110 . The branch aperture  135  is sized to receive second leg portion  140  and is adapted to engage and secure the second leg portion  140  when it has been expanded within the branch aperture  135 . Second leg portion  140  is sized and adapted to engage and be secured into branch aperture  135  upon expansion. FIGS.  14  to  21  show how the bifurcated stent is assembled within a bifurcated lumen. As shown in FIGS.  14  to  21 , the area to be treated is a bifurcated lumen having a first or trunk lumen  190  and a second or branch lumen  195 . As shown in FIG. 14, a first guide wire  155  is introduced into the trunk lumen  190  and a second guide wire  156  is introduced into the branch lumen  195 . As shown in FIG. 15, a balloon expandable stem and first leg portion  110  is disposed on the tip of a first balloon catheter  170  so that the balloon  175  is disposed within longitudinal bore  131 . A second balloon catheter  171  is then introduced into longitudinal bore  131  of stem and first leg portion  110  and is advanced so that the balloon  176  is disposed within aperture  135 . First catheter  170  is mounted on first guide wire  155  and second catheter  171  is mounted on second guide wire  156 . As shown in FIG. 16, the unexpanded stem and first leg portion  110  is guided to the area to be treated so that first leg portion  130  is disposed within trunk lumen  190  and branch aperture  135  communicates with branch lumen  195 . Guide wire  156  facilitates the orientation of the branch aperture  135  with the branch lumen  195 . The size of the conventional catheters and balloons is not to scale and details well known to those skilled in the art have been omitted for clarity. Balloon  175  is inflated which causes the stem and first leg portion  110  to expand, as shown in FIG. 17, to secure it in the desired position. After expansion, the external wall of stem and first leg portion  110  would contact the interior walls of trunk lumen  190 , however, a gap has been intentionally left for clarity. The balloon  175  on first catheter  170  is left inflated and the balloon  176  on second catheter  171  is then inflated to enlarge the branch aperture  135  as shown in FIG. 18. As the branch aperture  135  is enlarged a portion of the stent defining the branch aperture  135  is pushed outward to form a branch securing lip  180 .  
         [0044]    Balloons  175  and  176  are deflated, second catheter  171  is withdrawn, and second guide wire  156  is left in place in the branch lumen  195 . Second leg portion  140  is then applied to second catheter  171  so that balloon  176  is disposed in longitudinal bore  132  and second catheter  171  is then applied to second guide wire  156 . Second leg portion  140  is then guided to, and introduced into, the longitudinal bore  131  of the stem and first leg portion  110  and is advanced and passed through branch aperture  135  so that the distal end  150  of the second leg portion  140  protrudes into the branch lumen  195  and the proximal end  145  communicates with longitudinal bore  131 , as shown in FIG. 19. The balloon  176  on second catheter  171  is partially inflated and the balloon  175  on first catheter  170  is then partially inflated to a pressure substantially equal to the pressure in balloon  176 . Both balloons  175  and  176  are then simultaneously inflated to substantially equal pressures. As shown in FIG. 20, inflation of the balloon  176  on second catheter  171  causes second leg member  140  to expand so that its external walls engage and are secured to the area surrounding aperture  135 . Inflation of the balloon  175  on the first catheter  170  prevents stem and first leg portion  110  from collapsing when balloon  176  is inflated. After expansion, the external walls of second leg  140  would contact the inner wall of lumen  195 , however, a gap has been intentionally left for clarity. The balloons  175  and  176  are deflated, catheters  170  and  171  and guide wires  155  and  156  are withdrawn, and the assembled bifurcated stent  160  is left in place as shown in FIG. 21.