Abstract:
A method of making a non-porous tubular graft is disclosed. The method includes the step of securing a plurality of fastening elements extending through an outer layer of knitted, woven, or braided material along a length of the outer layer, wherein the fastening elements extend outwardly from the outer layer. The method further includes the steps of placing an inner layer of non-porous material within the outer layer such that an underside of each fastening element is positioned between the inner layer and the outer layer and laminating the outer layer to the inner layer to form the non-porous tubular graft.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application is a Divisional Application of U.S. patent application Ser. No. 10/748,610, filed Dec. 30, 2003. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention relates to a graft for use with a stent in body lumens. More specifically, the present invention relates to a graft adapted to be secured to a stent surrounding the graft.  
       BACKGROUND OF THE INVENTION  
       [0003]     A graft is typically used in conjunction with a stent to provide a prosthetic intraluminal wall, e.g., in the case of a stenosis or aneurysm, to provide an unobstructed conduit for blood in the area of the stenosis or aneurysm. A stent-graft may be endoluminally deployed in a body lumen, a blood vessel for example, at the site of a stenosis or aneurysm by so-called “minimally invasive techniques” in which the stent-graft is compressed radially inwards and is delivered by a catheter to the site where it is required, through the patient&#39;s skin, or by a “cut down” technique at a location where the blood vessel concerned is accessible. When the stent-graft is positioned at the correct location, the stent-graft is caused or allowed to re-expand to a predetermined diameter in the vessel.  
         [0004]     Some early stent-grafts were manufactured by bonding the graft material to the stent frame with an adhesive, e.g., Corethane®. However, such an adhesive alone may not be sufficient to secure the graft to the stent during loading, as the graft material may peel away (i.e., separate) from the stent. Suture ties may also be utilized to fix the graft to the stent. However, suture attachment of the graft to the stent may create holes throughout the graft resulting in porosity which may be undesirable. For these and other reasons, improvements in securing a graft to a stent may have significant utility as compared to prior stent-graft combinations.  
       SUMMARY OF THE INVENTION  
       [0005]     According to one aspect of this invention, a graft is adapted to be secured to a stent surrounding the graft in a novel way. The graft, typically tubular, includes an inner layer of a non-porous material, and an outer layer typically of knitted, woven, or braided material laminated to the inner layer. The graft further includes a plurality of fastening elements adapted to be secured to a stent surrounding the graft. An underside of each fastening element is fixed between the inner layer and the outer layer of the graft.  
         [0006]     According to another aspect of this invention, a method of making a non-porous graft, and a stent-graft using that graft, is provided. A plurality of fastening elements are secured to an outer layer typically of knitted, woven, or braided material along a length of the outer layer, wherein the fastening elements extend outwardly from the outer layer. An inner layer of non-porous material is placed within the outer layer such that an underside of each fastening element is positioned between the inner layer and the outer layer. The outer layer is laminated to the inner layer to form the non-porous graft, which is then placed within a surrounding graft. The fastening elements are then secured to the stent.  
         [0007]     The fastening elements may comprise loops which extend through openings in the stent and are adapted to secure the graft to the stent by a mating element, such as a linear element (or suture) which passes through each of these loops and secures them, optionally with a knot, to a structural part of the stent.  
         [0008]     The resultant stent-graft may be used to provide a fluid passage through a body lumen. It may also be adapted for endoluminal placement. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]      FIG. 1  is a plan view of a tubular graft including a plurality of fastening elements in accordance with the present invention;  
         [0010]      FIG. 2A  is a plan view of a non-porous tubular stent-graft including a plurality of fastening elements secured to a stent by a plurality of looped locking elements in accordance with the present invention;  
         [0011]      FIG. 2B  is a detail view of a fastening element secured to an element of the stent by a looped locking element illustrated in  FIG. 2A ;  
         [0012]      FIG. 3  is a plan view of a non-porous tubular stent-graft including a plurality of fastening elements secured to a stent by a linear locking element in accordance with the present invention; and  
         [0013]      FIG. 4  is a cross-sectional view of the non-porous tubular graft of  FIG. 1 , illustrating an outer layer laminated to an inner layer and a fastening element fixed between the layers. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0014]     Although the invention is illustrated and described herein with reference to specific embodiments, the invention is not intended to be limited to the details shown. Rather, various modifications may be made in the details within the scope and range of equivalents of the claims without departing from the invention.  
         [0015]     Referring specifically to  FIGS. 1-4 , there is shown a tubular graft  10  (best seen in  FIG. 1 ) adapted to be secured to a stent  12  surrounding graft  10  in different ways (as illustrated in  FIGS. 2A and 3 ). Stent  12  includes a plurality of structural members, four of which are identified in  FIG. 2B  as  12 A, B, C, and D.  FIG. 4  is a cross-sectional expanded view of graft  10  illustrating an inner layer  14  of a non-porous material, and an outer layer  16  of knitted, woven, or braided material laminated to inner layer  14 . Graft  10  further includes a plurality of fastening elements  18  (only one of which is seen in  FIG. 4 ) adapted to be secured on an outer surface  20  of stent  12  surrounding graft  10 . An underside  22  of each fastening element  18  is fixed between inner layer  14  and outer layer  16 . A plurality of fastening elements  18  may be distributed lengthwise along the length of graft  10 , as shown in  FIGS. 1, 2A , and  3 , and/or circumferentially about graft  10  (not shown).  
         [0016]     Fastening elements  18  extend outwardly from outer layer  16 , as illustrated in  FIG. 4 . Non-porous inner layer  14  reduces or minimizes the porosity of graft  10 , thus compensating for any such porosity in outer layer  16 . Fastening elements  18  are retained between outer layer  16 , which is laminated to inner layer  14 , sealing underside  22  of each fastening element  18  between outer layer  16  and inner layer  14 . The finished assembly remains non-porous, resulting in a non-porous graft  10 .  
         [0017]     Referring to  FIG. 2A , the exemplary configuration illustrates graft  10  attached to an inside surface of stent  12  with fastening elements  18  projecting through stent  12  and a plurality of looped locking elements  24 , shown in greater detail in  FIG. 2B , securing fastening elements  18  to stent  12 , thereby securing graft  10  to stent  12 . In this embodiment, each locking element  24  is knotted around both a fastening element  18  and an element or structural component of stent  12  to attach graft  10  to stent  12 .  FIG. 2B  is a detail view of a fastening element  18  secured to an element  12 A of stent  12  by a looped locking element  24 . Alternatively, a particular fastening element  18  may be secured to any one or more of elements  12 B,  12 C, or  12 D of stent  12  by looped locking element  24 .  
         [0018]     As shown in  FIG. 2B , fastening elements  18  may comprise D-shaped loops, the flat side of which is trapped between inner layer  14  and outer layer  16 , with the remainder of the loop projecting outwardly through outer layer  16 .  
         [0019]     Similar to  FIG. 2A , the exemplary configuration represented in  FIG. 3  illustrates graft  10  attached to an inside surface of stent  12  with fastening elements  18  projecting through stent  12 . However, instead of utilizing looped locking elements  24  as a means for securing fastening elements  18  to stent  12 , a linear locking element  26  may be looped through each fastening element  18  and secured to the stent  12  independently of its connection to the fastening elements  18 . More specifically, a linear locking element  26  may be threaded and looped through each fastening element  18  while remaining along an outside surface of stent  12 . The end points of linear locking element  26  are secured to stent  12 , thereby attaching graft  10  to stent  12 .  
         [0020]     Alternatively, a linear locking element  26  may be threaded through (not looped through) fastening elements  18  and secured to stent  12  at at least two points along a length of stent  12  (not shown). In other words, a linear locking element  26  may be threaded through fastening elements  18  while remaining along an outside surface of stent  12 , with each end of linear locking element  26  knotted around an element  12 A,  12 B,  12 C, or  12 D of stent  12  to attach graft  10  to stent  12 .  
         [0021]     The shape of the fastening elements  18  is not limited to a D-shaped ring, as illustrated in  FIG. 4 . Alternatively, fastening elements  18  may be round, square, triangular, or any other shape suitable for engagement with locking elements by which the graft  10 , through its fastening elements  18 , is secured to a stent  12  which surrounds it.  
         [0022]     A further embodiment of the present invention includes a plurality of fastening elements, which are an integral part of outer layer  16 , extending outwardly from outer layer  16  disposed along the length and/or circumference of outer layer  16  of tubular graft  10 . In other words, each fastening element is not a distinct component from outer layer  16  as illustrated in  FIG. 4 . Instead, the fastening elements are part of the material of outer layer  16 , i.e., loosely knitted, woven, or braided strands of material that form loops to act as fastening elements. At least some of the fastening elements are adapted to be secured on outer surface  20  of stent  12  surrounding graft  10 . The configurations of this embodiment with respect to means for securing the fastening elements to stent  12  (i.e., looped locking elements  24  or a linear locking element  26 ) are essentially the same as those of the embodiment of graft  10  comprising fastening elements  18  described previously herein with reference to  FIGS. 1-3 .  
         [0023]     An exemplary material for forming inner layer  14  of graft  10  is expanded polytetrafluoroethylene. The present invention, however, is not limited to polytetrafluoroethylene, and may include any material that offers the desired non-porous property of inner layer  14 . The material of outer layer  16  may be a woven or knit polyester. The present invention, however, is not limited to polyester, and may include any knitted, woven, or braided material suitable for lamination to inner layer  14 . Furthermore, the material of outer layer  16  is not limited to one that is porous, and may include any non-porous material suitable for lamination to inner layer  14 .  
         [0024]     Fastening elements  18  and/or locking elements  26  may comprise conventional suture material. Other materials may be used as well, however, and may comprise, for example, wire or plastic. One or both of the fastening element material and the locking element material may comprise, in whole or in part, a radiographically differentiable material.  
         [0025]     While preferred embodiments of the invention have been shown and described herein, it will be understood that such embodiments are provided by way of example only. Numerous variations, changes and substitutions will occur to those skilled in the art without departing from the spirit of the invention. Accordingly, it is intended that the appended claims cover all such variations as fall within the spirit and scope of the invention.