Abstract:
A stent assembly comprises a stent sheath that includes distally and proximally removable portions separable from one another by manipulation of first and second guidewires, a contracted stent having a side aperture disposed in the stent sheath and a third guidewire extending between the removable portions and through the side aperture of the stent.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to stents, and particularly to bifurcated stents. 
     BACKGROUND OF THE INVENTION 
     A stent is a well known device used to support an intraluminal wall, used in procedures, such as but not limited to, percutaneous transluminal coronary angioplasty (PTCA). Various types of stent architectures are known in the art, including braided stents (filaments or wires, wound or braided into a particular configuration), or mesh stents (metal mesh bent or formed into a particular shape), among others. 
     Typically, a stent may be restrained in a radially compressed configuration by a sheath or catheter, and delivered by a deployment system or “introducer” to the site where it is required. The introducer may enter the body through the patient&#39;s skin, or through a blood vessel exposed by minor surgical means. When the introducer has been threaded into the body lumen to the stent deployment location, the introducer is manipulated to cause the stent to be released. The stent expands to a predetermined diameter at the deployment location, and the introducer is withdrawn. Stent expansion may be effected by spring elasticity, balloon expansion, or by the self-expansion of a thermally or stress-induced return of a shape memory alloy (such as a nickel-titanium alloy, e.g., NITINOL) to a pre-conditioned expanded configuration. 
     There are bifurcated lumens, such as but not limited to, the carotid artery, which may need support with a bifurcated stent. A bifurcated lumen (also called bifurcation) is an area of the vasculature where a first vessel is bifurcated into two or more branch vessels. Stenotic lesions may form in or around such bifurcations, that is, in or around one or more of the vessels. 
     However, delivering and deploying a stent to support a bifurcated lumen is a difficult challenge. Some of the problems include the difficulty of properly orienting the stent with respect to the bifurcation and the difficulty of providing a stent that supports the main trunk and branches of the bifurcation without blocking the passageways or causing turbulence or other flow disruptions. 
     SUMMARY OF THE INVENTION 
     The present invention seeks to provide a bifurcated stent assembly that may be disposed in a bifurcated lumen and which may overcome the abovementioned problems of the prior art. 
     There is thus provided in accordance with an embodiment of the present invention a stent assembly comprising a stent sheath that includes two individually removable portions. A stent may be disposed in the sheath in a contracted orientation. 
     In accordance with an embodiment of the present invention the removable portions comprise a distally removable portion and a proximally removable portion. 
     Further in accordance with an embodiment of the present invention the removable portions may be joined by a rupturable element. 
     Still further in accordance with an embodiment of the present invention the distally removable portion comprises a distal cap configured to facilitate movement of the stent assembly in a vasculature. 
     In accordance with an embodiment of the present invention at least one guidewire is attached to a portion of the stent assembly for manipulation thereof. 
     Further in accordance with an embodiment of the present invention one of the removable portions of the sheath is removable by distally sliding off the stent. 
     In accordance with an embodiment of the present invention the stent comprises a distal portion and a proximal portion connected by a flexible portion. The flexible portion may have axial flexibility and/or torsional flexibility. 
     Further in accordance with an embodiment of the present invention the stent is formed with a side aperture and a flange-forming structure at least partially surrounding the aperture. 
     Still further in accordance with an embodiment of the present invention the flange-forming structure is expandable to form a flange. 
     Additionally in accordance with an embodiment of the present invention the flange is connectable to a branch stent. An end face of the branch stent may be oblique to a side wall of the branch stent, or the flange may have an oblique shape. 
     There is also provided in accordance with an embodiment of the present invention a stent assembly comprising a stent formed with a side aperture and a flange-forming structure at least partially surrounding the aperture, wherein the flange-forming structure is expandable to form a flange. 
     There is also provided in accordance with an embodiment of the present invention a method comprising providing a stent in a stent sheath, the sheath being maneuverable by a proximally extending guidewire, and removing the sheath distally off the stent. 
     In accordance with an embodiment of the present invention the sheath comprises a distally removable portion and a proximally removable portion, and the method further comprises removing the distally removable portion distally off the stent and removing the proximally removable portion proximally off the stent. The distally removable portion and the proximally removable portion may be removed simultaneously or one after another off the stent. Alternatively, either one of the distally removable portion and the proximally removable portion may be removed off the stent and the other removable portion may be left. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The present invention will be further understood and appreciated from the following detailed description taken in conjunction with the drawing in which: 
         FIG. 1  is a simplified pictorial illustration of a stent, constructed and operative in accordance with an embodiment of the invention; 
         FIG. 2  is a simplified illustration of a stent assembly comprising the stent of  FIG. 1 , and also comprising a sheath with a distally removable portion and a proximally removable portion, constructed and operative in accordance with an embodiment of the invention; 
         FIG. 3  is a simplified illustration of the stent assembly of  FIG. 2  introduced into a body lumen that has a bifurcation, in accordance with an embodiment of the invention; 
         FIG. 4  is a simplified illustration of the stent assembly of  FIG. 2  positioned in the body lumen such that a guide wire protrudes from a side aperture formed in the stent into a branch of the bifurcation, in accordance with an embodiment of the invention; 
         FIG. 5  is a simplified illustration of removing the distally removable portion and the proximally removable portion of the sheath of the stent assembly of  FIG. 2 , in accordance with an embodiment of the invention; 
         FIG. 6  is a simplified illustration of the stent assembly of  FIG. 2 , wherein the stent has expanded and the side aperture forms a flange at the bifurcation, in accordance with an embodiment of the invention; 
         FIG. 7  is a simplified illustration of the stent assembly of  FIG. 2 , wherein a branch stent has been introduced through the side aperture to the bifurcation, in accordance with an embodiment of the invention; 
         FIG. 8  is a simplified illustration of the stent assembly of  FIG. 2 , wherein the branch stent is affixed to the stent of the stent assembly and is expanded in place in the bifurcation, in accordance with an embodiment of the invention; and 
         FIGS. 9A and 9B  are more detailed illustrations of two possible attachments of the branch stent to the stent of the stent assembly. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Reference is now made to  FIG. 1 , which illustrates a stent  10 , constructed and operative in accordance with an embodiment of the invention. Stent  10  is illustrated as a uniform wire mesh stent, but the invention is not limited to this construction. Stent  10  may comprise a distal portion  12  and a proximal portion  14  connected by a flexible portion  16  (of same or different diameters). Flexible portion  16  may provide axial flexibility in a longitudinal direction indicated by arrows  18  and/or torsional flexibility in a radial direction indicated by arrows  20 . Stent  10  may be balloon-expandable, constructed from a suitable material, such as but not limited to, stainless steel 316L, or self-expanding, constructed from a suitable material, such as but not limited to, a shape memory alloy (such as a nickel-titanium alloy, e.g., NITINOL). Stent  10  may be formed with a side aperture  22  in any of the abovementioned portions thereof, namely, in flexible portion  16  (aperture  22  being shown there in solid lines in FIG.  1 ), or in distal portion  12  or proximal portion  14  (aperture  22  being shown there in phantom lines in FIG.  1 ). Stent  10  may alternatively be any kind of bifurcated stent. 
     Stent  10  may further comprise a flange-forming structure  24  at least partially surrounding aperture  22 . The flange-forming structure  24  may be constructed of a wire mesh pattern, for example, which upon expansion may form a flange  62  (shown in phantom lines in FIG.  1 ). The expansion of flange-forming structure  24  may be accomplished by any suitable method, such as but not limited to, expansion with a balloon, flexure or self-expansion by the flexibility or shape-memory properties of the material or by being pushed out by some object (not shown) introduced to the area of aperture  22 . 
     Reference is now made to  FIG. 2 , which illustrates a stent assembly  25  comprising stent  10  of  FIG. 1 , constructed and operative in accordance with an embodiment of the invention. Stent assembly  25  may comprise a stent sheath  30  in which stent  10  is initially disposed in a contracted orientation prior to deployment. Sheath  30  may include two individually removable portions  32  and  34 , which may be separable from one another. In the illustrated embodiment, sheath  30  comprises a distally removable portion  32  and a proximally removable portion  34 . Distally removable portion  32  and proximally removable portion  34  may be completely separate from one another. Optionally, they may be initially joined by a rupturable element  36 , such as but not limited to, a thin strip, wherein the rupturable element  36  may be severed, cut, ruptured, broken or otherwise removed so that the two portions  32  and  34  may be individually removed, as described hereinbelow. Distally removable portion  32  may comprise a distal cap  38 , configured (e.g., preferably smooth and rounded) to facilitate movement of the stent assembly  25  in the vasculature. 
     Guidewires are preferably attached to portions of stent assembly  25  for manipulation thereof. For example, a guidewire  40  may be attached to distally removable portion  32 ; a guidewire  42  may be attached to proximally removable portion  34 ; a guidewire  44  may be attached to stent  10 , such as at a distal end thereof; and a guidewire  46  may be provided for passing through side aperture  22 . The guidewires may be grasped and manipulated at the proximal end of a stent deployment catheter (not shown) as is well known in the art. 
     Reference is now made to  FIG. 3 , which illustrates stent assembly  25  introduced into a body lumen  50  that has a bifurcation comprising trunk  52  and branches  54  and  56 , in accordance with an embodiment of the invention. The stent deployment catheter (not shown) may be used to deliver stent assembly  25  into body lumen  50 . 
     Reference is now made to  FIG. 4 , which illustrates stent assembly  25  positioned in body lumen  50  such that side aperture  22  is aligned with branch  56  of the bifurcation. Guide wire  46  may be manipulated to protrude from side aperture  22  into branch  56 . 
     Reference is now made to  FIG. 5 , which illustrates one method of deploying stent  10  in the bifurcation. The distally removable portion  32  of sheath  30  may be removed by distally slipping (sliding) it off stent  10  by distally pushing with guidewire  40  (as indicated by an arrow  58 ). The proximally removable portion  34  of sheath  30  may be removed by proximally slipping (sliding) it off stent  10  by proximally pulling with guidewire  42  (as indicated by an arrow  60 ). Distally removable portion  32  and proximally removable portion  34  of sheath  30  may be removed simultaneously or one after the other or individually. (By individually it is meant that either one of the distally removable portion  32  and the proximally removable portion  34  is removed off stent  10  and the other removable portion is left on stent  10 .) After their removal, as seen in  FIG. 6 , sheath  10  expands and is affixed to the bifurcation, wherein aperture  22  is aligned with branch  56 . Upon expansion of stent  10 , the flange-forming structure  24  may also expand to form a flange  62  which may hug and overlap the juncture of branch  56  with the bifurcation. The distally removable portion  32  of sheath  30  may be removed from the vasculature by pulling it proximally through stent  10 , since the expanded stent  10  now has a larger diameter than the sheath  30 . The proximally removable portion  34  of sheath  30  may also be removed from the vasculature. 
     In accordance with another embodiment of the invention, sheath  30  may comprise distally removable portion  32  without proximally removable portion  34 . Sheath  30  may be removed from stent  10  by distally sliding distally removable portion  32  off stent  10 . Stent  10  then expands to a larger diameter than the sheath  30 , and distally removable portion  32  of sheath  30  may be removed from the vasculature by pulling it proximally through stent  10 , as mentioned before. 
     Reference is now made to  FIG. 7 , which illustrates introducing a branch stent  64  through side aperture  22  to the bifurcation. The branch stent  64  may also be a self-expanding wire mesh stent constructed from a shape memory alloy, but the invention is not limited to this construction. The branch stent  64  may be introduced with a conventional sheath and catheter (not shown) as well known in the art. 
     Reference is now made to  FIG. 8 , which illustrates branch stent  64  expanded in place in branch  56 . Branch stent  64  may be affixed to flange  62  of stent  10 . For example, branch stent  64  may snap-fit or press-fit together with flange  62 , or by any other joining means. 
     Reference is now made to  FIGS. 9A and 9B , which illustrate two possible attachments of branch stent  64  to flange  62 . In  FIG. 9A , branch stent  64  has an end face  66  which is more or less perpendicular to a side wall  68  of branch stent  64 . In such a case, flange  62  may be formed with a tilted configuration, that is, with an oblique shape, so as to better envelop and hold branch stent  64  around its periphery. In  FIG. 9B , branch stent  64  has an end face  70  which is oblique to a side wall  68  of branch stent  64 . In such a case, the obliqueness of branch stent  64  permits forming flange  62  with a uniform, non-oblique shape. 
     It will be appreciated that the invention is not limited to what has been described hereinabove merely by way of example. Rather, the invention is limited solely by the claims that follow.