Abstract:
According to one aspect of the present disclosure, a method and technique for manufacturing a stent are disclosed. The stent is a non-metallic stent having a furled small-diameter state and an expanded large-diameter state where the stent, in the furled small-diameter state, includes a plurality of central lobes arranged at spaced-apart intervals and extending longitudinally defining a stent axis, the plurality of central lobes defining a cylindrical plane of the stent. The stent also includes at least one peripheral lobe formed on at least one of the plurality of central lobes, the peripheral lobe oriented along the cylindrical plane.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application is a continuation of, and claims the benefit of priority from, U.S. application Ser. No. 12/947,767, entitled “Stent and Method for Manufacturing Thereof” and filed on Nov. 16, 2010, which is incorporated herein by reference. This application also claims the benefit of priority from U.S. Provisional Application No. 61/261,486 entitled “Stent and Method for Fabrication Thereof” and filed on Nov. 16, 2009, which is incorporated herein by reference. 
     
    
     BACKGROUND 
       [0002]    Stents are used for the treatment of various types of vascular conditions. A stent can be implanted within a vessel in a small configuration using a delivery catheter and then expanded to a larger size against the walls of the vessel. 
       BRIEF SUMMARY 
       [0003]    According to one aspect of the present disclosure, a stent and method and technique for manufacturing a stent are disclosed. According to one embodiment, the stent comprises a non-metallic stent having a furled small-diameter state and an expanded large-diameter state. The stent, in the furled small-diameter state, includes a plurality of central lobes arranged at spaced-apart intervals and extending longitudinally defining a stent axis, where the plurality of central lobes define a cylindrical plane of the stent. The stent also includes at least one peripheral lobe formed on at least one of the plurality of central lobes where the peripheral lobe is oriented along the cylindrical plane of the stent. 
         [0004]    According to another embodiment, the stent includes a first plurality of central lobes arranged at spaced-apart intervals and extending longitudinally defining a stent axis, where the first plurality of central lobes is formed by an element extending in a coiled manner from a proximal end of the stent to a distal end of the stent. The stent also includes a second plurality of central lobes arranged at spaced-apart intervals and extending longitudinally in the direction of the stent axis, where the second plurality of lobes is formed by the element returning from the distal end to the proximal end in a coiled manner. The stent further includes at least one peripheral lobe formed on at least one of the first plurality of central lobes and on at least one of the second plurality of central lobes, each peripheral lobe extending radially inward toward an internal area of the stent. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0005]    For a more complete understanding of the present application, the objects and advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which: 
           [0006]      FIG. 1  is a diagram illustrating an embodiment of a stent according to the present disclosure; 
           [0007]      FIG. 2  is a diagram illustrating an end view of the stent illustrated in  FIG. 1 ; 
           [0008]      FIG. 3  is a diagram illustrating an end view of another embodiment of a stent according to the present disclosure; 
           [0009]      FIG. 4  is a diagram illustrating an end view of another embodiment of a stent according to the present disclosure; 
           [0010]      FIG. 5  is a diagram illustrating another embodiment of a stent according to the present disclosure; 
           [0011]      FIG. 6  is a diagram illustrating another embodiment of a stent according to the present disclosure; and 
           [0012]      FIG. 7  is a diagram illustrating an end view of the stent illustrated in  FIG. 6 . 
       
    
    
     DETAILED DESCRIPTION 
       [0013]      FIG. 1  is a diagram illustrating an embodiment of a stent  10  in accordance with the present disclosure.  FIG. 1  illustrates stent  10  in a furled small-diameter state; it should be understood that stent  10  is expandable to a large-diameter state (e.g., by balloon catheter insertion and inflation/pressurization). Embodiments of stent  10  according to the present disclosure include an element  20  disposed in a coiled manner and extending in a longitudinal direction to define a longitudinal axis  22  of stent  10 . Element  20  is coiled in the direction of axis  22  to form a number of central lobes  24  (e.g., each rotation of element  20  forming one lobe  24 ). In some embodiments, lobes  24  are equally spaced along the longitudinal direction of stent  10  or have a uniform coil pitch along stent  10  (i.e., a uniform distance between each coil). However, it should be understood that the coil pitch may vary along one or more portions of stent  10 . 
         [0014]    In the embodiment illustrated in  FIG. 1 , stent  10  also includes peripheral lobes  28  formed on one or more central lobes  24 . Lobes  28  are formed by additional coils of element  20  during a coil rotation of a particular lobe  24 . In the embodiment illustrated in  FIG. 1 , each central lobe  24  includes three peripheral lobes  28 . However, it should be understood that the quantity of peripheral lobes  28  formed along central lobes  24  may vary (e.g., a greater or fewer quantity). Further, in  FIG. 1 , each central lobe  24  includes peripheral lobes  28 . However, it should be understood that some central lobes  24  may be devoid of a peripheral lobe  28 , or some central lobes  24  may include a greater or fewer quantity of peripheral lobes  28  than other central lobes  24 . 
         [0015]    In some embodiments, stent  10  comprises longitudinal support rods  30  extending in the axial direction of stent  10 . For example, in the embodiment illustrated in  FIG. 1 , stent  10  comprises three support rods  30 ; however, it should be understood that stent  10  may include a greater or fewer quantity of support rods  30 . In some embodiments, rods  30  may be located at substantially equal distances from each other as measured about a circumference or cylindrical plane formed by lobes  24 . However, it should also be understood that rods  30  may be located at unequal distances relative to each other. 
         [0016]    In some embodiments, element  20  and/or rods  30  may comprise a nonmetallic material, such as a polymer fiber or multiple polymer fibers. For example, in some embodiments, element  20  and/or rods  30  may be formed from Poly-L-Lactic Acid (PLLA). However, it should be understood that other materials may be used to form element  20  and/or rods  30 . Rods  30  may be attached or otherwise secured to lobes  24  using a variety of different methods or materials. For example, in some embodiments, rods  30  may be attached to lobes  24  using a PLLA material (e.g., PLLA dissolved in chloroform) such that the PLLA mixture is used to glue or weld rods  30  to lobes  24 . In some embodiments, rods  30  may be ultrasonically welded to lobes  24 . Rods  30  may be attached or otherwise secured to each successive lobe  24  along the longitudinal length of stent  10  or may be intermittently attached to lobes  24  as rod  30  extends along stent  10  (e.g., every other lobe  24 , every third lobe  24 , or at other uniform or non-uniform spacing intervals). Further, in some embodiments, rods  30  may be attached and/or otherwise secured to external sides of lobes  24 ; however, it should be understood that rods  30  may be attached and/or otherwise secured to internal sides of lobes  24 . For example, in some embodiments, rods  30  may be woven or intermittently transition from an external location to an internal location of stent  10  relative to lobes  24  as rods  30  extend along the longitudinal length of stent  10 . For example, and not by way of limitation, rod  30  may be secured to stent  10  by attaching rod  30  to an exterior surface of a first and second lobe  24 , to an interior surface of the third lobe  24 , to the exterior surface of the fourth and fifth lobes, etc. Thus, rods  30  may weave inwardly and outwardly between interior and exterior areas of stent as rods  30  extend in the longitudinal direction according to a uniform or non-uniform pattern. 
         [0017]    In the embodiment illustrated in  FIG. 1 , stent  10  is formed as a dual opposing helical stent  10 . For example, in the embodiment illustrated in  FIG. 1 , stent  10  is formed by member  20  having an end located and/or initiating at proximal end  40  of stent  10  and forming successive coils (forming lobes  24  and lobes  28 ) as member  20  advances in the axial direction  41  toward a distal end  42  of stent  10 . At distal end  42  of stent, member  20  returns and/or is coiled in a direction  43  toward proximal end  40  forming successive coils (forming lobes  24  and lobes  28 ) as member  20  advances in the axial direction  43  toward proximal end  40 . In  FIG. 1 , member  20  is wound in the same rotational direction (i.e., clockwise or counterclockwise) for forming coils in the directions  41  and  43  (e.g., clockwise winding in the direction  41 , followed by clockwise winding in the direction  43 ). In the embodiment illustrated in  FIG. 1 , member  20  comprises a continuous element such that coils in both directions  41  and  43  are formed from a continuous member  20 . However, it should be understood that in some embodiments, the coils formed in direction  41  may be formed from one or members  20 , where the coils formed in direction  43  may be formed by one or more different members  20 . 
         [0018]      FIG. 2  is a diagram illustrating an end view of stent  10  illustrated in  FIG. 1 . In the embodiment illustrated in  FIG. 1 , stent  10  comprises three rods  30   1-3  located at an equal spacing relative to each other. In the embodiment illustrated in  FIG. 2 , rod  30   1  is attached to an interior surface of lobe  24 . Further, in the embodiment illustrated in  FIG. 2 , peripheral coils  28  extend radially inward and are located at equal circumferential spacing relative to each other. Further, in the embodiment illustrated in  FIG. 2 , peripheral lobes  28  formed as member  20  is coiled in opposing directions along stent  10  (e.g., extending from end  40  to end  42 , then from end  42  to end  40 ) are located at substantially the same positions. 
         [0019]      FIG. 3  is a diagram illustrating an end view of another embodiment of stent  10 . In the embodiment illustrated in  FIG. 3 , stent  10  comprises rods  30   4-9  attached to exterior sides of lobes  24 . In  FIG. 4 , some of rods  30   4-9  are located at unequal distances relative to each other as measured along the cylindrical plane formed by lobes  24 . For example, in  FIG. 3 , a set of rods  30   4 ,  30   6  and  30   8  are located substantially equidistant from each other as measured along the cylindrical plane of stent  10 , and rods  30   5 ,  30   7  and  30   9  are located substantially equidistant from each other as measured along the cylindrical plane of stent  10 . However, each set of rods  30  are offset slightly from each other such that the distance between rods  30   4  and  30   5 , for example, is less than the distance between rods  30   4  and  30   9 . Thus, it should be understood that the spacing of rods  30  on stent may vary. 
         [0020]      FIG. 4  is a diagram illustrating an end view of another embodiment of stent  10 . In the embodiment illustrated in  FIG. 4 , peripheral lobes  28  formed while member  20  is coiled in direction  41  are positioned at different locations than lobes  28  formed as member  20  is coiled in the direction  43 . For example, referring to  FIGS. 1 and 4 , as member  20  is coiled in direction  41 , peripheral lobes  28  are formed at the positions indicated in  FIG. 4  by  281 - 283 . As member  20  is coiled in the direction  43  from end  42  toward end  40 , peripheral lobes  28  are formed at the positions indicated in  FIG. 4  by  284 - 286 . Thus, in some embodiments, lobes  28  formed as member  20  is coiled in direction  41  may be offset from the positions of lobes  28  formed as member  20  is coiled in direction  43 . In  FIG. 4 , lobes  28  are illustrated having an equal spacing there between (e.g., corresponding to each coil direction). However, it should be understood that the spacing between lobes  28  may vary (e.g., for each individual lobe  28  and/or between coil directions  41  or  43 ). 
         [0021]    In some embodiments, stent  10  is formed on a mandrel or other type of coil or winding tool to facilitate coiling of member  20  to form lobes  24  and  28  and/or to facilitate attachment of rods  30 . In some embodiments, while stent  10  is located on such tool or mandrel, stent  10  is annealed to enable shape retention of stent as well as to align and/or otherwise form polymer chain orientation characteristics. For example, in a PLLA application, stent  10  may be annealed at a temperature slightly above a glass transition temperature for a desired time period (e.g., 62° Celsius to 90° Celsius for approximately twenty-five minutes). Stent  10  may then be allowed to cool to room temperature for some period of time (e.g., eighteen hours). However, it should be understood that the annealing process may be varied, especially for different types of stent materials. 
         [0022]      FIG. 5  is a diagram illustrating another embodiment of stent  10 . In the embodiment illustrated in  FIG. 5 , stent  10  comprises lobes  24 , lobes  28  and rods  30 . In  FIG. 5 , stent  10  is formed as a counter coil helical stent  10 . For example, in the embodiment illustrated in  FIG. 5 , stent  10  is formed by member  20  having an end located and/or initiating at proximal end  40  of stent  10  and forming successive coils (forming lobes  24  and lobes  28 ) as member  20  advances in direction  41  toward distal end  42  of stent  10 . At distal end  42  of stent, member  20  returns and/or is coiled in direction  43  toward proximal end  40  forming successive coils (forming lobes  24  and lobes  28 ) as member  20  advances in the direction  43  toward proximal end  40 . In the embodiment illustrated in  FIG. 5 , member  20  is coiled or wound in one rotational direction for forming coils as member  20  is moved in direction  41  and is coiled or wound in an opposite rotational direction for forming coils as member  20  is moved in direction  43  toward end  40 . For example, in some embodiments, the coils formed as member  20  is moved in direction  41  result from winding member  20  in the direction indicated by  50  (i.e., clockwise). The coils formed as member  20  is moved in direction  43  result from winding member  20  in the direction indicated by  52  (i.e., counterclockwise). As described above in connection with  FIGS. 1-4 , the spacing, quantity and locations of lobes  28  and/or rods  30  may vary. In the embodiment illustrated in  FIG. 5 , member  20  comprises a continuous element such that coils in both directions  41  and  43  are formed from a continuous member  20 . However, it should be understood that in some embodiments, the coils formed in direction  41  may be formed from one or members  20 , where the coils formed in direction  43  may be formed by one or more different members  20 . 
         [0023]      FIG. 6  is a diagram illustrating another embodiment of stent  10 . In the embodiment illustrated in  FIG. 6 , stent  10  comprises lobes  24 , lobes  28  and rods  30 . In  FIG. 6 , lobes  28  are formed to lie substantially in the cylindrical plane formed by lobes  24 . For example,  FIG. 7  is a diagram illustrating an end view of stent  10  illustrated in  FIG. 6 . As illustrated in  FIG. 7 , peripheral lobes  28  are formed to lie and/or reside substantially in the cylindrical plane formed by lobes  24 . In the embodiment illustrated in  FIGS. 6 and 7 , stent  10  includes three lobes  28  per turn or coil (e.g., per lobe  24 ). However, the quantity and/or spacing of lobes  28  within a particular lobe  24  may vary. Further, the quantity, spacing and/or place of attachment of rods  30  (e.g., interior surface or exterior surface of lobes  24 ) may vary. As described above, stent  10  may be annealed to secure and/or otherwise maintain the positioning of lobes  28  substantially within the cylindrical plane of stent  10 , thereby reducing the likelihood that lobes  28  would interfere and/or obstruct the insertion of a delivery catheter into the interior area of stent  10 . 
         [0024]    In the embodiment illustrated in  FIG. 6 , stent  10  also comprises a bifurcated area or portion  60 . For example, in some embodiments, stent  10  may be formed such that the axial pitch between successive coils in a medial portion of stent  10  is increased, thereby resulting in a location where another stent may be attached to and/or inserted through a wall of stent  10 . For example, in some embodiments, the bifurcated portion  60  is formed such that the axial pitch between successive coils is large enough to accommodate a branch stent attachment to stent  10  and/or insertion of another stent through portion  60  (e.g., into a branching vessel). The medial location of portion  60  along stent  10  may vary (e.g., closer to end  40 , closer to end  42 , or anywhere in between). It should also be understood that bifurcated portion  60  may be included in the embodiments of stent  10  illustrated and described in connection with  FIGS. 1 and 5 . 
         [0025]    In some embodiments, peripheral lobes  28  are formed having a generally circular form. However, it should be understood that the shape of lobes  28  may vary (e.g., elliptical, rhomboidal, or other non-circular shape). Further, the size of lobes  24  and/or lobes  28  may vary. 
         [0026]    In some embodiments, a radio-opaque material may be used in stent  10  to enable x-ray and/or fluoroscopic identification of stent  10  during delivery or deployment. For example, in some embodiments, barium sulfate, water-soluble iodine and/or other materials may be laced or loaded into the polymer material used to form member  10  and/or rods  30 . In some embodiments, a radio-opaque material may be used in combination with a PLLA material (e.g., PLLA dissolved in chloroform) such that the PLLA mixture having a radio-opaque material loaded therein is used to glue or weld rods  30  to lobes  24 , thereby providing fluoroscopic visibility of stent  10 . In some embodiments, a radio-opaque material may be attached to stent, such as securing a radio-opaque metal (e.g., platinum) to rod(s)  30  and/or member  10 . The radio-opaque material may be attached using a PLLA material or other type of attachment mechanism. Further, in some embodiments, a radio-opaque sheath may be used with stent  10 . For example, in some embodiments, a film comprised of a PLLA material loaded with a radio-opaque material is wrapped partially or entirely around stent  10  to enable x-ray and/or fluoroscopic identification of stent  10  during delivery or deployment. 
         [0027]    Thus, embodiments of the present disclosure provide a flexible, expandable stent that enables increased ease and flexibility of delivery and expansion. Further, embodiments of the present disclosure provide a stent with excellent mechanical properties while providing plastic deformation. 
         [0028]    The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. 
         [0029]    The corresponding structures, materials, acts, and equivalents of all means or step plus function elements in the claims below are intended to include any structure, material, or act for performing the function in combination with other claimed elements as specifically claimed. The description of the present disclosure has been presented for purposes of illustration and description, but is not intended to be exhaustive or limited to the disclosure in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the disclosure. The embodiment was chosen and described in order to best explain the principles of the disclosure and the practical application, and to enable others of ordinary skill in the art to understand the disclosure for various embodiments with various modifications as are suited to the particular use contemplated.