Patent Publication Number: US-2011077730-A1

Title: Bifurcated balloon stent

Description:
FIELD 
     The present invention relates to the field of implantable stents, more particularly, to the field of bifurcated stents and methods of using same. 
     BACKGROUND 
     Implanting a stent or performing PTCA on a bifurcated lumen poses challenges for physicians beyond normal stenting procedures to treat stenosis of a blood vessel lumen. Current bifurcated stent designs have the side branch stent separate from the main branch stent, resulting in more time and difficulty than desirable required to install. It would be desirable to have a bifurcated stent design, and method of installation, that would enable the physician to implant both the main branch stent and side branch stent in less time, greater ease and with improved efficiency. 
     SUMMARY 
     Generally described, the present disclosure provides a stent on a novel delivery balloon which allows one to maintain access to a branch vessel guide wire during the stenting process. In a first aspect disclosed is a bifurcated stent assembly comprising a main branch stent unit comprising a main branch tubular stent, a main branch expandable member at least partially disposed within the stent material and having an outer wall, an inner wall, a proximal end, a distal end, an expandable portion disposed between the proximal and the distal ends, and a sheath associated with the outer wall of the expandable portion and being sized to allow a guide wire to pass therethrough. The sheath comprises a wall having an inner surface and an outer surface, a proximal opening, a distal opening, a top portion associated with the outer wall of the expandable member, a bottom portion generally parallel to and proximate to the top portion and associated with the outer wall of the expandable member, a frangible portion disposed between the proximal and distal openings and between the top and bottom portions, the frangible portion having a closed first configuration having a generally tubular shape when the main branch expandable member is in an uninflated configuration and an open second configuration when the main branch expandable member is in an inflated configuration whereby the frangible portion is separated and the top and bottom portions are separated so as to define a sheath edge opening therethrough, allowing a guide wire which is disposed within the sheath to be removable from the sheath via the sheath edge opening. The stent assembly also comprises a side branch stent unit comprising a side branch tubular stent, a side branch expandable member at least partially disposed within the stent material and having a proximal end, a distal end, and, an expandable portion disposed between the proximal and the distal ends. 
     The sheath frangible portion may be configured in any of several possible configurations, including, but not limited to, a series of perforations, zipper-like interleaved tabs and recesses, overlapping top and bottom edges, and the like. When the main branch expandable member is inflated the frangible portion separates to create an opening so that portion of the side branch guide wire disposed within the sheath can be released from the sheath via the opening. 
     Another aspect of the present disclosure further provides a method for treating a bifurcated vessel having a main branch and a side branch using a bifurcated stent assembly as described herein, comprising inserting the branch stent in the branch vessel; inserting the main vessel balloon in the main vessel; inflating the main vessel balloon; pulling back on the branch vessel stent until resistance is felt; deploying the branch vessel stent; removing the branch vessel stent balloon; inflating the main vessel balloon; removing the branch vessel stent; inserting the stent assembly over both the main vessel guide wire and the branch vessel guide wire; inserting the stent assembly into the main vessel; advancing and deploying the stent assembly in the main vessel; advancing the branch vessel balloon over the branch vessel guide wire; and, inflating the main vessel balloon and the branch vessel balloon. 
     Other features of the present disclosure will become apparent upon reading the following detailed description of embodiments, when taken in conjunction with the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention is illustrated in the drawings in which like reference characters designate the same or similar parts throughout the figures of which: 
         FIG. 1A  is a side view in cutaway of a bifurcated blood vessel lumen and a bifurcated stent according to one exemplary embodiment of the present invention showing a main branch stent unit installed and the main stent balloon expanded. 
         FIG. 1B  is a schematic side view of one exemplary embodiment of a bifurcated stent assembly according to  FIG. 1A . 
         FIG. 2  is a schematic view of a detail of a first exemplary embodiment of a frangible sheath associated with a main branch balloon. 
         FIG. 3  is a schematic view of a detail of a second exemplary embodiment of a frangible sheath associated with a main branch balloon. 
         FIG. 4  is a schematic view of a detail of a third exemplary embodiment of a frangible sheath associated with a main branch balloon. 
         FIG. 5  is a schematic view of a detail of a fourth exemplary embodiment of a frangible sheath associated with a main branch balloon. 
         FIG. 6A  is a schematic view of a detail of a fifth exemplary embodiment of a frangible sheath associated with a main branch balloon. 
         FIG. 6B  is a side elevation schematic view of the embodiment of  FIG. 6A . 
         FIG. 7  is a schematic view of a detail of a sixth exemplary embodiment of a frangible sheath associated with a main branch balloon. 
         FIG. 8  is a schematic view of a detail of a seventh exemplary embodiment of a frangible sheath associated with a main branch balloon. 
         FIG. 9  is a schematic view of a detail of a portion of a stent showing a balloon in an uninflated configuration and the frangible portion of the sheath intact. 
         FIG. 10  is a schematic view of a detail of a portion of a stent showing a balloon in an inflated configuration and the frangible portion of the sheath separated. 
         FIG. 11  is a side cutaway view of the detail view shown in  FIG. 9 . 
         FIG. 12  is a side cutaway view of the detail view shown in  FIG. 10 . 
         FIG. 13A  is a schematic view of a bifurcated stent according to one exemplary embodiment implanted in both lumens of a bifurcated vessel. 
         FIG. 13B  is a detail of  FIG. 13A  showing a main vessel balloon (without the stent, to better show the construction) with a sheath, the dashed lines showing the main vessel guide wire passing through the main branch balloon area and the side branch guide wire passing through the sheath. 
         FIG. 14  is a schematic view of a bifurcated lumen with a main branch guide wire and a side branch guide wire inserted, illustrating part of one exemplary embodiment of a first method of implanting a bifurcated stent assembly of the present disclosure. 
         FIG. 15  is a schematic view according to the method being described for  FIG. 14  and showing a side branch stent unit in an initial undeployed or collapsed position. 
         FIG. 16  is a schematic view according to method being described for  FIG. 15  and showing insertion of a main branch balloon. 
         FIG. 17  is a schematic view according to method being described for  FIG. 16  and showing the side branch stent in position with the main branch balloon inflated. 
         FIG. 18  is a schematic view according to method being described for  FIG. 17  and showing the side branch balloon inflated and the stent deployed. 
         FIG. 19  is a schematic view according to method being described for  FIG. 18  and showing the side branch stent deployed and both balloons removed. 
         FIG. 20  is a schematic view according to method being described for  FIG. 19  and showing the side branch stent deployed and the main branch stent in position for deployment. 
         FIG. 21  is a schematic view according to method being described for  FIG. 20  and showing both stents deployed. 
         FIG. 22  is a schematic view according to method being described for  FIG. 21  and showing an additional balloon placed on the side branch wire through the main branch stent. 
         FIG. 23  is a schematic view according to method being described for  FIG. 22  and showing simultaneous inflation of both balloons. 
         FIG. 24  is a schematic view according to a second method of implanting a bifurcated stent of the present disclosure and showing a main branch stent in position and deployed. 
         FIG. 25  is a schematic view according to the method of Claim  24  and showing the main branch stent in position and the side branch balloon being placed into the side branch. 
         FIG. 26  is a schematic view according to the method of Claim  25  and showing the simultaneous inflation of the balloons. 
         FIG. 27  is a is a schematic view according to the method of Claim  26  and showing the side branch stent deployed through the main branch stent. 
         FIG. 28  is a schematic view according to the method of Claim  27  and showing both balloons inflated and stents deployed. 
     
    
    
     DETAILED DESCRIPTION 
       FIGS. 1A and 1B  shows a bifurcated vessel  2  having a main lumen  4  defined by an inner wall  6 , and a side branch lumen  8  defined by an inner wall  9 . In one exemplary embodiment, the present disclosure provides a stent assembly  20  having an expandable main branch stent unit  22  and a side branch stent unit  24 . The main branch stent unit  22  has an inflatable main branch balloon  26  or other expandable member which is associated with a main branch catheter  27 . The balloon  26  is at least partially disposed within a stent material  28 , which may be a mesh, coil, rings, lattice or other expandable material or structure known to those skilled in the art. Typically, the stent material will be generally tubular in configuration. For purposes of the present disclosure, a balloon will be discussed as an illustrative, nonlimiting example of an expandable member. It may be possible to use other expandable members, such as, but not limited to, a tamponading member, such as an umbrella shaped structure, or the like. The purpose of the balloon is to expand the stent from an initial collapsed configuration which enables inserting into the lumen to an expanded or deployed configuration at the intended site in which the stent is to reside. The present invention is also contemplated for use with self-expanding stents. The main branch stent unit  22  also includes a guide wire  29 . 
     The side branch stent unit  24  has an inflatable side branch balloon  30  (as described above) which is at least partially contained within a side branch stent  32  (which may be made of the same material and in the same structural configuration as the main vessel stent  28  or may be made of a different material or have a different structural configuration). The side branch stent unit  24  also includes a side branch vessel guide wire  34  and a side branch catheter  36 . 
     The main branch balloon  26  has a sheath  40  associated with the exterior of the balloon  26 . The sheath  40  is elongated, and has a proximal (entrance) end  42  and a distal (exit) end  44 . A portion  50  along the length of the sheath  40  is frangible. For the purposes of the present disclosure the term “frangible” means an area which separable, tearable, rupturable or otherwise able to separate generally along the axial line of the sheath to allow a guide wire passing through the sheath to separate from the sheath through the wall of the sheath, rather than withdrawing axially through the end of the sheath. The frangible portion may be constructed in any of several possible configurations, several exemplary embodiments being shown in  FIGS. 2-8 . The frangible portion may have a top edge  52  and bottom edge  54 .  FIG. 2  shows the frangible portion  50  as a series of perforations  56 .  FIG. 3  shows the frangible portion  50  comprising two rows of interlaced teeth  58 ,  60 , similar to a zipper.  FIG. 4  shows the sheath  50  as having an axial first flap portion  62  which overlaps a second flap portion  64 , whereby the two flap portions can separate from one another.  FIG. 5  shows the frangible portion  50  as two rows of teeth  66 ,  68  in an alternating configuration.  FIGS. 6A and 6B  show the frangible portion  50  as an area  70  of thinner wall thickness than the rest of the sheath  40 .  FIG. 7  shows a sheath  40  having at least one and preferably a number of loops  72  attached to a platform  74  which is attached to the balloon  26 , whereby the loops  72  can be separated.  FIG. 8  shows a sheath  40  having at least one and preferably a number of curved hooks or barbs  76 ,  77  which alternative directions, the hooks being attached to the balloon directly, or by way of a platform  78 . The hooks  76 ,  77  are somewhat flexible and the branch guide wire  32  can be separated when the hooks  76 ,  77  flex to release the guide wire  32 . It is important that the sheath frangible portion  50 , when separated, avoid or minimize the likelihood of stray material separating from the sheath  40  and passing into the bloodstream. 
     The proximal (entrance) and distal (exit) ends  42 ,  44  of the sheath  40  may be reinforced at reinforced areas  80 ,  82  (see  FIG. 2 ), respectively, so that the guide wire does not puncture the balloon  26  when inserted. The reinforced areas  80 ,  82  are still separable or frangible and separates at the appropriate time. In one exemplary embodiment, the reinforced area  80 ,  82  can be the same material as the rest of the sheath, and having an increased thickness. Alternatively, the reinforced area  80  or  82  can be made of a different material from the rest of the sheath. In one embodiment, the distal end  44  of the sheath  40  is reinforced. In an alternative embodiment, both the proximal end  80  and distal end  82  of the sheath are reinforced. 
     As shown in  FIGS. 9-12 , the sheath  40  has a top edge  52  and a bottom edge  54 , both edges being attached to the balloon  26 . When the balloon  26  is expanded the diameter of the balloon  26  expands from the unexpanded configuration ( FIGS. 9 ,  11 ) into the expanded configuration ( FIGS. 10 ,  12 ), the distance between the top edge  52  and bottom edge  53  increases, leading to stress being placed on the frangible portion  50  of the sheath  40 . Upon application of sufficient stress, the frangible portion  50  ruptures, tears, separates, parts, un-overlaps, or the like, depending on the embodiment, allowing the side branch guide wire  32  to separate from the balloon  26 . The stent  32  is disposed outside and around at least a portion of the sheath  40  and balloon  26 . 
     The sheath  40  of the present invention allows for both guide wires  26 ,  32  to be simultaneously inserted in the stent assembly  20  (the main vessel guide wire  26  being inserted into the stent proximal opening and the branch vessel guide wire  32  being inserted into sheath proximal end  42  opening). The stent assembly  20  with the main vessel balloon  26  is inserted into the main branch lumen  4 . 
     One exemplary embodiment of a method of deploying a stent assembly  20  of the present disclosure for stenting of both a side branch lumen  8  and main vessel lumen  4  of a bifurcated lumen  2  ( FIGS. 13A and 13B  show the stent assembly  20  already in position) is described as follows. In this exemplary method the side branch stent unit  24  is deployed before the main branch stent unit  22 . A bifurcated stent assembly  20  is provided according to any of the embodiments as described hereinabove.  FIG. 14  shows a main branch lumen  4  and a side branch lumen  8  with main branch and side branch guide wires  29  and  34  in place in the lumens. The side branch stent unit  24  is inserted in the side branch lumen  8  ( FIG. 15 ). The main branch balloon  26  is inserted in the main lumen  4  and the balloon  26  is then expanded ( FIGS. 16-17 ). The operator pulls back on the side branch vessel guide wire  34  until resistance is felt. The side branch balloon  30  is then expanded so that the side branch stent  32  is expanded against the side branch lumen inner wall  9  ( FIGS. 17-18 ). The main branch balloon  26  is then deflated. The side branch stent balloon  30  is removed and then the main branch balloon  26  is removed ( FIG. 19 ). The main branch stent unit  22  is then inserted over both the main branch guide wire  29  and the side branch guide wire  34  into the main lumen  4  ( FIG. 20 ) and advanced and the main branch stent unit  22  is deployed in the main lumen  4  ( FIG. 21 ). While the main branch balloon  26  and main branch stent  28  remain in position the side branch balloon  30  is inserted over the side branch guide wire  34  outside of the body so that the side branch balloon  30  can be easily positioned inside both the side branch stent  32  and straddle into the main branch stent  28 . The side branch balloon  30  is advanced over the side branch guide wire  34  ( FIG. 22 ) in the body and the main branch balloon  26  and side branch balloon  30  are inflated ( FIG. 23 ). 
     A second exemplary embodiment of a method of deploying a stent assembly  20  according to the present disclosure for provisional stenting of a bifurcated lumen  2  comprises the following. A bifurcated stent assembly  20  is provided in any of the apparatus embodiments as described hereinabove. The main branch stent unit  22  is inserted over both the main branch guide wire  29  and the side branch guide wire  34  and the side branch guide wire  34  is inserted into the sheath  40 . This assembly  22  is then inserted into the main branch lumen  4  ( FIG. 24 ) and is advanced to the desired implantation site. The main branch balloon  26  is expanded and the main branch stent  28  is expanded against the main branch lumen inner wall  6 . 
     If no stenting of the side branch lumen  8  is required then the side branch balloon  30  is advanced over the side branch guide wire  34  ( FIG. 25 ) and the main branch balloon  26  and the side branch balloon  30  are inflated ( FIG. 26 ). 
     If stenting of the side branch lumen  8  is required, then the side branch stent unit  24  is advanced over the side branch guide wire  34  and positioned in the side branch lumen  8 . The main branch balloon  26  is then inflated. The user pulls back on the side branch guide wire  34  until resistance is felt. The side branch stent  28  is then deployed ( FIG. 27 ). The main branch balloon  26  is then deflated and the side branch balloon  30  is retracted slightly. The main branch balloon  26  and the side branch balloon  30  are inflated ( FIG. 28 ). 
     Expansion of the main branch balloon  26  causes expansion of the sides of the sheath  40 , thereby causing separation, parting, rupture, or the like of the frangible portion of the sheath ( FIGS. 11-12 ). The distance between the top edge  52  and bottom edge  54  of the uninflated main branch balloon  26  is shown as distance D 1  in  FIG. 11 . When the balloon inflates, the distance between the top edge  52  and bottom edge  54  increases to distance D 2  ( FIG. 12 ). In the alternative embodiment of the sheath  40  having the spaced alternating hooks  76  shown in  FIG. 8 , the separation upon expansion of the main branch balloon  26  causes the hooks  76  facing one way to separate or angle away from the hooks  77  facing the opposite way, thus releasing the guide wire from the hooks. 
     Upon insertion and expansion of both the main vessel stent and the branch vessel stent, the configuration may be as shown in  FIG. 13 . 
     A feature of the stent assembly  20  of the present disclosure is that both the main branch balloon  26  and the side branch balloon  30  can be inflated simultaneously, thereby avoiding the problem of crushing one stent while expanding the other. 
     The present invention also provides a kit comprising a stent assembly  20  (including a main branch stent unit  22  and a side branch stent unit  24  as described hereinabove) plus guide wires  29  and  34 . The kit may also include at least one catheter, a syringe, and one or more shafts over which the balloons may pass. The stent is mounted on the balloon and the balloon is slide over the shaft. The shaft is hollow and the guide wire passes through the shaft lumen, as is known to those skilled in the art. 
     Although only a few exemplary embodiments of this invention have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the exemplary embodiments without materially departing from the novel teachings and advantages of this invention. Accordingly, all such modifications are intended to be included within the scope of this invention as defined in the following claims. 
     It should further be noted that any patents, applications and publications referred to herein are incorporated by reference in their entirety.