Abstract:
A self-expanding stent is disclosed, the self-expanding stent having a collapsed configuration and an expanded configuration. The self-expanding stent has three stent subunits, each including one or more longitudinally-oriented diamonds and one or more axially-oriented diamonds. The subunits are coupled together at a pivot joint. The longitudinally-oriented diamonds are configured to substantially hold their shape in both the expanded configuration of the stent and the collapsed configuration of the stent. The axially-oriented diamonds are configured to expand from the collapsed configuration to the expanded configuration. Expansion of the axially-oriented diamonds creates angulation between the stent subunits at the pivot joint. Thus, the stent can be inserted into a target location through a tubular catheter, once the stent is no longer constrained by the catheter, it will expand to an angled configuration.

Description:
[0001]    This application claims the benefit of priority under 35 U.S.C. §119(e) to U.S. Provisional Application No. 61/778,040, filed Mar. 12, 2013. The disclosures set forth in the referenced application is incorporated herein by reference in its entirety. 
     
    
     BACKGROUND 
       [0002]    Stents can be placed within the mammalian vasculature using endovascular techniques for the treatment of diseased vessels. Applications of stents include treatment of stenotic and atherosclerotic lesions in the coronary, peripheral, and cerebral vasculature. Another common application of stents is the treatment of cerebral aneurysms. Stents are designed to oppose the subject&#39;s inner vascular walls and provide an unobstructed conduit for blood flow within the stent lumen. 
         [0003]    Stents are generally designed as straight homogenous tubes using biocompatible materials designed to treat the vessel pathology. Placing stents into vessel bifurcations requires deployment of multiple stents given the materials currently available. When more than one device is placed with overlap, the risk of complication exponentially increases—vessel wall apposition is decreased and stent material of an overlapped stent extends into the vessel lumen more than stent material of a single, non-overlapping stent would extend into the vessel. 
         [0004]    There are several stent designs to overcome the problems associated with a bifurcation, but no current design is completely satisfactory for all applications. Highly flexible stents have been designed to fit the curvature of a bifurcated vessel but are not capable of extending through multiple branched vessels. Flexible stents with expanding elements may extend through bifurcated vessels slightly more, yet still incompletely. Other bifurcation reconstruction devices offer a solution for bifurcations but do not allow customization. 
       SUMMARY 
       [0005]    In illustrative embodiments, a self-expanding stent is disclosed, the self-expanding stent having a collapsed configuration and an expanded configuration. The self-expanding stent includes three stent subunits, which each include one or more longitudinally-oriented diamonds and one or more axially-oriented diamonds, as more fully described below. In an illustrative embodiment, the three subunits are oriented in the same plane and their terminal longitudinal diamonds are coupled together by a connector at a pivot joint. The terminal axial diamonds of the first subunit are also connected to axial subunits of the second and third stent subunits. The longitudinally-oriented diamonds are configured to substantially hold their shape in both the expanded configuration of the stent and the collapsed configuration of the stent. The axially-oriented diamonds are configured to expand from the collapsed configuration to the expanded configuration. The design allows the angle between the first stent subunit and the second and third stent subunits to enlarge with stent crimping and lessen with stent expansion. Thus, the stent can be inserted into a target location through a tubular catheter, and after the stent is no longer constrained by the catheter, it will expand to an angled configuration. 
         [0006]    In another illustrative embodiment, the three subunits and connectors are replaced by a single component incorporating the shape and function described above. This can be accomplished by three-dimensional printing of a shape-memory material. This method allows for full customization of the stent, with respect to 1) stent angulation with expansion, 2) regional porosity, 3) regional stent radial force, 4) length of each subunit, 5) regional drug-elution, and 6) additional unforeseen customization requirements. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1A  is a top elevation view of an unrolled and expanded subunit of a stent in accordance with the present disclosure; 
           [0008]      FIG. 1B  is a top elevation view of the stent of  FIG. 1A  in a rolled and collapsed state; 
           [0009]      FIG. 2A  is a top elevation view of a first stent component of a stent in accordance with the present disclosure, the first stent component in an unrolled and expanded state; 
           [0010]      FIG. 2B  is a side view of the first stent component of  FIG. 2A  in a rolled and expanded state; 
           [0011]      FIG. 2C  is a front view of the first stent component of  FIG. 2A  in a rolled and expanded state; 
           [0012]      FIG. 3A  is a top elevation view of a second stent component of a stent in accordance with the present disclosure, the second stent component in an unrolled and expanded state; 
           [0013]      FIG. 3B  is a bottom view of the second stent component of  FIG. 3A  in a rolled and expanded state; 
           [0014]      FIG. 3C  is a side view of the second stent component of  FIG. 3A  in a rolled and expanded state; 
           [0015]      FIG. 4A  is a top elevation view of a branched wire of the present disclosure; 
           [0016]      FIG. 4B  is a top elevation view of a stent of the present disclosure in a rolled and collapsed stated; 
           [0017]      FIG. 4C  is a top elevation view of the branched wire of  FIG. 4A  inside the rolled and collapsed stent of  FIG. 4B ; 
           [0018]      FIG. 5  is a side perspective view of a stent of the present disclosure in a rolled and partially expanded state; 
           [0019]      FIG. 6  is a side perspective view of the stent of  FIG. 5  in a rolled and fully expanded state; 
           [0020]      FIG. 7A  is an isometric view of a stent of the present disclosure in a rolled and collapsed state; 
           [0021]      FIG. 7B  is an enlarged isometric view of a portion of  FIG. 7A , wherein the enlarged view depicts a junction in which arms of a second stent component are attached to a first stent component; and 
           [0022]      FIG. 8  is a top isometric view of the stent of  FIGS. 7A and 7B  in a rolled and fully expanded state. 
       
    
    
     DETAILED DESCRIPTION 
       [0023]    An illustrated stent  10  in which the principles of the present disclosure may be implemented includes a first stent component  14 , a second stent component  12  that is bifurcated or branched, and one or more junction points  16  configured to join the first second component  14  to the second stent component  12  at a junctional region  38 . The first stent component  14  and second stent component  12  are configured to include one or more longitudinally-oriented diamonds  30  and one or more axially-oriented diamonds  32  that, in part, form the structure of the stent  10 . As illustrated in  FIGS. 1A and 1B , the longitudinally-oriented diamonds  30  are configured to change shape less than the axially-oriented diamonds  32 . The axially-oriented diamonds  32  are configured to be movable from a first shape similar to the longitudinally-oriented diamonds  30  in a collapsed state to a second shape that is wider in the expanded state. The designs of the diamonds  30  and  32  allow the angle between the first stent component  14  and the second stent component  12  to enlarge with stent crimping and lessen with stent expansion. 
         [0024]    To form the stent  10 , the first stent component  14  is coupled to the second stent component  12  at apices  42  of the longitudinally-oriented diamonds  30 . When the stent  10  is in a collapsed state, the stent  10  may be inserted into a patient&#39;s blood vessel, for instance by a catheter (not shown), during angioplasty or other types of medical procedures and positioned to expand in the vessel at a point where the vessel branches or bifurcates into two or more vessels. The use of such catheter or insertion techniques may be as described in pending application number WO 2013/009976, the contents of which are incorporated herein by reference. 
         [0025]    The first stent component  14  and the second stent component  12  of the stent  10  are self-expanding elements. The first stent component  14  is configured to be placed in the proximal lumen of a vessel prior to a bifurcation; the second stent component  12  is configured to be placed in the lumens of both distal vessels of a bifurcation (after the bifurcation occurs). The second stent component  12  can be produced as two joined subunits  24  or as a single piece. The two stent components  14 ,  12  will be connected at the junction point  16  at apices  42 ,  44  of the longitudinally-oriented and axially-oriented diamonds  30 ,  32 , respectively, so that the junctional region  38  is aligned with a bifurcating point of the blood vessels (not shown) after the stent  10  is deployed in an expanded state. In an illustrative embodiment, the first stent component  14  and the second stent component  12  are laser-cut from Nitinol tubing, but other materials and methods are envisioned. 
         [0026]      FIGS. 1A and 1B  illustrate an unrolled geometry of a stent subunit  24  of the present disclosure. Specifically,  FIG. 1A  depicts an open or expanded configuration of an unrolled stent subunit  24 , and  FIG. 1B  depicts a closed or collapsed configuration of an unrolled stent subunit  24 . The stent subunit  24  is configured to be coupled together with one or more other stent subunits  24  in order to form the first stent component  14  or the second stent component  12 . A portion of the stent subunit  24  may also be used to achieve the same effect. As illustrated, the stent subunit  24  includes the longitudinally-oriented diamonds  30  and the axially-oriented diamonds  32 , each of which are formed by four struts  26  of a predetermined length X. The longitudinally-oriented diamonds  30  tend to hold their shape in both the expanded configuration and the collapsed configuration, as illustrated in  FIGS. 1A and 1B . Unlike the longitudinally-oriented diamonds  30 , the axially-oriented diamonds  32  are configured to be spread wide in the open/expanded configuration but assume the shape of the longitudinally-oriented diamonds  30  in the closed/collapsed configuration. The axially-oriented diamonds  32  from one stent subunit  24  are configured to be connected to matching axially-oriented diamonds  32  from another stent subunit  24 . In this way, the subunits  24  may be parallel in the closed/collapsed configuration. Due to longitudinal compression forces on the diamonds  30 ,  32  in the open/expanded configuration, however, a connection between multiple subunits  24  may force a bend between the subunits  24  in the open/expanded configuration. 
         [0027]      FIGS. 2A ,  2 B and  2 C show an illustrative embodiment of the first stent component  14  as formed by combining one or more subunits  24  from  FIGS. 1A and 1B . The first stent component  14  may be cut from a nitinol tube. Specifically,  FIG. 2A  illustrates an expanded configuration of an unrolled first stent component  14  and demonstrates the shape of circumferential laser-cutting that may be used to form the first stent component  14 .  FIG. 2B and 2C  illustrate the side and front views, respectively, of an expanded configuration of the first stent component  14  in a rolled state and demonstrate illustrative dimensions of the first stent component  14 . The longitudinally-oriented diamonds  30  and the axially-oriented diamonds  32 , and the struts  26  forming the same, are depicted similar to those in  FIG. 1A and 1B . As illustrated in  FIG. 2B , additional median struts  36  of the same length X may also be added to bisect the axially-oriented diamond  32 . These median struts  36  or other additional struts may collapse completely in the closed form while providing additional strength, radial force, and stability to the stent  10 . 
         [0028]      FIGS. 3A ,  3 B and  3 C shows an illustrative embodiment of the second stent component  12 , which may also be cut from a single nitinol tube and formed from combining multiple subunits  24 . Specifically,  FIG. 3A  illustrates an expanded configuration of an unrolled second stent component  12 , and  FIGS. 3B and 3C  illustrate the bottom and side views, respectively, of an expanded configuration of the second stent component  12  in a rolled state. The second stent component  12  includes two symmetric or asymmetric arms  20 ,  22  which connect at a pivot joint  34 . The longitudinally-oriented diamonds  30 , the axially-oriented diamonds  32 , the struts  26  forming the same and the median struts  36  are consistent with the function and geometry of those components in  FIGS. 1A-2C . While the illustrated embodiment of the stent  10  comprises a second stent component  12  that includes two symmetric or asymmetric arms  20 ,  22 , the design allows precision orientation even if one of the two arms  20 ,  22  are omitted. 
         [0029]    In illustrative embodiments, a longitudinally-oriented diamond  30   a  from a first subunit  24  is coupled to a longitudinally-oriented diamond  30   b  from a second subunit  24  at the apex or apices  42   a  and  42   b  of the longitudinally-oriented diamonds  30   a  and  30   b , respectively. Therefore, pivot joint  34  is formed by connecting the apices  42   a  and  42   b  and may be cut from the same nitinol tube as both arms  20 ,  22  or the longitudinally-oriented diamonds  30   a  and  30   b.  In alternative embodiments, the longitudinally-oriented diamonds  30   a  and  30   b  or their apices  42   a  and  42   b  may be altered to allow a separate nitinol, other metal (including platinum or other radiopaque metal), or other biocompatible joining mechanism to be used to form the pivot joint  34 . 
         [0030]    The bottom of the second stent component  12  may be open so that the lumen of the second stent component  12  can communicate or be joined with another component or subunit  24 , including but not limited to the first stent component  14 . This connection may be configured to be located at or near the pivot joint  34 . The top of the second stent component  12  may include a junctional region  38  that allows additional stent coverage with minimal loss of flexibility the pivot joint  34  of the stent  10 . In one embodiment, the junctional region  38  may include first and second scaffolding  40   a  and  40   b,  as illustrated in  FIG. 3A , that are fitted to the second stent component  12  for such a purpose. In another embodiment, a flexible and collapsible nitinol design may be extend in the junctional region  38  to provide flexibility of other variations of the first and second scaffolding  40   a  and  40   b.  In yet another embodiment, the scaffolding  40   a  and  40   b  may be connected by separate metal or biocompatible flexible and/or elastic joining material. The opposing scaffolding  40   a  and  40   b  of the junctional region  38  can be varied so that this portion of the stent  10  can be tailored to the desired anatomy/pathology. 
         [0031]      FIG. 4A  shows a branched wire  50  that may be used to assist with placement and expansion of the stent  10  inside a blood vessel. Specifically, the branched wire  50  includes a proximal end  54 , a distal end  52 , and a junction  56  that couples the proximal end  54  to the distal end  52 . The distal end  52  includes two arms  60  and  62  joined together at the junction  56 . In general, when the stent  10  is in a collapsed state, the proximal end  54  corresponds with the first stent component  14 , the distal end  52  corresponds with the second stent component  12 , and the arms  60  and  62  of the distal end  52  correspond with the arms  20  and  22  of the second stent component  12 , as illustrated in  FIGS. 4A-4C . As illustrated in  FIG. 4B  specifically, the rolled and collapsed second stent component  12  is bent in half at the junctional region  38  with its two arms  20  and  22  in parallel alignment with each other. The first stent component  14  is connected to the second stent component  12  at the pivot joint  34  at junction points  16 .  FIG. 4C  illustrates the rolled and collapsed stent  10  inside the branched wire  50  prior to deployment or expansion. 
         [0032]    In illustrative embodiments, the stent  10  may be inserted into the vessel through the use of a catheter (not shown), as more fully described in WO 2013/009976. For example, the catheter may constrain the stent  10  as it is inserted into the vessel, and then the catheter may be removed or modified such that it no longer constrains the stent  10 . When the stent  10  is no longer constrained, it naturally expands to an expanded configuration, as shown in  FIG. 5 . 
         [0033]      FIG. 5  and  FIG. 6  show the complete stent  10  in a rolled and expanded configuration as assembled by coupling the first and second stent components  14  and  12  at the junction points  16 . Specifically,  FIG. 5  illustrates the rolled stent  10  after partial expansion and  FIG. 6  illustrates the rolled stent  10  after full expansion. Four junction points,  16   a,    16   b,    16   c,  and  16   d,  connect the two stent components  14 ,  12  of the stent  10 . Two of these junction points  16   a  and  16   b  connect the arms  20  and  22  of the second stent component  12  with the first component  14  by connecting the apex  42   a  of a longitudinally-oriented diamond  30   a  of the arm  20 , the apex  42   b  of a longitudinally-oriented diamond  30   b  of the arm  22 , and an apex  42   c  of a longitudinally-oriented diamond  30   c  of the first stent component  14 . Because of the viewpoint, only junction point  16   a  is shown in  FIGS. 5 and 6 . 
         [0034]    Another junction point  16   c  connects the arm  20  of the second stent component  12  with the first component  14  by connecting an apex  44   a  of an axially-oriented diamond  32   a  of the arm  20  and an apex  44   c  of an axially-oriented diamond  32   c  of the first stent component  14 . The last junction point  16   d  connects the arm  22  of the second stent component  12  with the first component  14  by connecting an apex  44   b  of an axially-oriented diamond  32   b  of the arm  22  and an apex  44   c  of an axially-oriented diamond  32   c  of the first stent component  14 . Similar to the joining of stent components  20 , 22  at junction  34  in  FIG. 3 , the four junction points  16  of the stent  10 , can be connected by a variety of methods including, but not limited to, braided metal and/or plastics, a metal and/or plastic joining component, or other biocompatible joining mechanism. 
         [0035]      FIGS. 7A ,  7 B, and  8  show a further embodiment of a complete stent  10  as assembled by coupling the first and second stent components  14 ,  12  at the junction points  16   a - 16   d.  Specifically,  FIGS. 7A and 7B  illustrate the rolled and collapsed stent  10  before expansion and  FIG. 8  illustrates the rolled and expanded stent  10  after full expansion. Four junction points  16   a,    16   b,    16   c,    16   d  connect the two stent components  14 ,  12  of the stent. Two of these junction points  16   a,    16   c  connect the arms  20 ,  22  of the second stent component  12  with the first component  14  by connecting the apex  42   a  one of the opposing longitudinally-oriented diamonds  30   a  of the arm  20 , the apex  42   b  of one of the opposing longitudinally-oriented diamonds  30   b  of the arm  22 , and the apex  42   c  of one of the opposing longitudinally-oriented diamonds  30   c  of the first stent component  14 . 
         [0036]    Another junction point  16   b  connects the arm  20  of the second stent component  12  with the first component  14  by connecting an apex  44   a  of an axially-oriented diamond  32   a  of the arm  20  and an apex  44   c  of an axially-oriented diamond  32   c  of the first stent component  14 . The last junction point  16   d  connects the arm  22  of the second stent component  12  with the first component  14  by connecting the apex  44   b  of an axially-oriented diamond  32   b  of the arm  22  and an apex  44   c  of an axially-oriented diamond  32   b  of the first stent component  14 . Similar to the joining of the stent components  20 ,  22  at junction  34  in  FIG. 3 , the four junction points  16   a - 16   d  of the stent  10  can be connected by a variety of methods including, but not limited to, braided metal and/or plastics, a metal and/or plastic component  70 , as seen in  FIGS. 7A and 7B , or any other suitable biocompatible joining mechanism. 
         [0037]    Because a stent  10  once deployed/expanded will assume a precise and expected orientation within a blood vessel, the stent  10  can be modified to meet the needs of a particular patient&#39;s anatomy and pathology. The example stent  10  as described and shown in the FIGS. is merely a basic scaffold structure upon which an infinite number of additional stent features may be added or modified. Such features include, but are not limited to: variable porosity along the site of pathology or for protection of normal anatomy; matching of a bifurcation angle by changing the angle ratios of the longitudinally-oriented diamonds  30  or axially-oriented diamonds  32  of the stent  10 ; variation of size of the arms  20 ,  22  of the second stent component  12 ; and variation of diameter of the stent subunits  24 . 
         [0038]    In illustrative embodiments, in the open or expanded state, the stent  10  may be branched so that the distal arms  20  and  22  of the second stent component  12  form an angle with the first stent component  14 , typically between 90 and 180 degrees. Thus, an angle between the two distal arms  20  and  22  may be between 0 to 180 degrees. This angle may be maintained by the bend of the second stent component  12  at the junctional region  38 . 
         [0039]    In illustrative embodiments, in the closed or collapsed state, the stent  10  may be configured to pass through a single catheter lumen (not shown) before reaching the end of the deployment catheter (not shown). In this collapsed state, the angle between the first stent component  14  and the arms  20  and  22  of the second stent component  12  must approximate 180 degrees. Thus, the arms  20  and  22  of the second stent component  12  must be bent so that they are parallel to each other during delivery through the catheter. The branched wire  50  may assist with delivery or deployment of the stent  10  in the catheter and/or blood vessel. Thus, unique features of the stent design allow the stent  10  to be delivered as a single unit, where the collapsed state is ideal for delivery, and the expanded state is ideal for final stent position, particularly in a bifurcated vessel. 
         [0040]    Examples of use are provided herein for illustrative purposes, and are not intended to limit the scope of the disclosure. In one embodiment, the stent  10  may be used for the treatment of an intracranial aneurysm. The second stent component  12  may be deployed with or without the first stent component  14  to cover a neck of the intracranial aneurysm in order to aid in curative embolization. In another embodiment, the stent  10  may be used to treat stenosis of the vessels at a bifurcation. Bifurcations include, but are not limited to, those of the coronary arteries, carotid arteries, intracranial arteries, aortic bifurcation, and peripheral vessels.