Abstract:
An endovascular grafting device having a main body component and limb components. The device is contemplated to be assembled in-situ for the purpose of treating vascular defects or conditions.

Description:
The present disclosure claims the benefit of U.S. provisional application 60/360,323 filed on Feb. 26, 2002, which is incorporated by reference in its entirety herein. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates to an endovascular graft assembly for treating vasculature of a patient and more specifically to graft system and the attachment of structures thereof. 
     It is well established that various fluid conducting body or corporeal lumens, such as veins and arteries, may deteriorate or suffer trauma so that repair is necessary. For example, various types of aneurysms or other deteriorative diseases may effect the ability of the lumen to conduct fluids and, in turn, may be life threatening. In some cases, the damage to the lumen is repairable only with the use of prosthesis such as an artificial vessel or graft. 
     For repair of vital lumens such as the aorta, surgical repair is significantly life threatening or subject to significant morbidity. Surgical techniques known in the art involve major surgery in which a graft resembling the natural vessel is spliced into the diseased or obstructed section of the natural vessel. Known procedures include surgically removing the damaged or diseased portion of the vessel and inserting an artificial or donor graft portion inserted and stitched to the ends of the vessel which were created by the removal of the diseased portion. More recently, devices have been developed for treating diseased vasculature through intraluminal repair. Rather than removing the diseased portion of the vasculature, the art has taught bypassing the diseased portion with a prosthesis and implanting the prosthesis within the vasculature. An intra arterial prosthesis of this type has two components: a flexible conduit, the graft, and the expandable framework, the stent (or stents). Such a prosthesis is called an endovascular graft. 
     It has been found that many abdominal aortic aneurysms extend to the aortic bifurcation. Accordingly, a majority of cases of endovascular aneurysm repair employ a graft having a bifurcated shape with a trunk portion and two limbs, each limb extending into separate branches of vasculature. Currently available bifurcated endovascular grafts fall into two categories. One category of grafts are those in which a preformed graft is inserted whole into the arterial system and manipulated into position about the area to be treated. This is a unibody graft. The other category of endovascular grafts are those in which a graft is assembled in-situ from two or more endovascular graft components. This latter endovascular graft is referred to as a modular endovascular graft. Because a modular endovascular graft facilitates greater versatility of the matching of individual components to the dimensions of the patient&#39;s anatomy, the art has taught the use of modular endovascular grafts in order to minimize difficulties encountered with insertion of the devices into vasculature and sizing to the patient&#39;s vasculature. 
     Although the use of modular endovascular grafts minimize some of the difficulties, there are still drawbacks associated with the current methods. Drawbacks with current methods can be categorized in three ways; drawbacks associated with delivery and deployment of the individual endovascular graft components, drawbacks associated with the main body portion, and drawbacks associated with securing the limb portions to the main body portion. 
     Moreover, a lack of healthy tissue near the aneurysm being treated provides difficulty with adequately anchoring the main body portion of a modular endovascular graft. If the aneurysm is too close to the renal arteries there may be a lack of healthy tissue to adequately anchor the superior end of the main graft portion without interfering with blood flow in the renal arteries. Anchoring the limb support branches of the main body component in the iliac arteries requires a larger main body component and additional effort and delivery hardware. Allowing the limb support branches of the main body component to float freely in the aneurysm presents additional difficulty with deploying the limb components of the modular endovascular graft within the main body component. 
     With regard to the main body component of modular endovascular graft, there therefore exists a need for a main body component that facilitates a minimized delivery profile, easier catheterization of the limb support portions and accurate deployment of the limb components, and anchoring of the neck portion near the renal arteries without disrupting cross-blood flow. 
     The devices of the present invention address these and other needs. 
     SUMMARY OF THE INVENTION 
     Briefly and in general terms, the present invention is embodied in an endovascular graft system composed of various components and the attachment of the components to a graft device. 
     In one aspect, the invention is a main body component of a modular endovascular graft with an attachment frame, for example, a self-expanding attachment structure or stent at its proximal end that is secured to a neck portion of the main body graft. Axial separation of the attachment structure from the main body graft of a modular endovascular graft is contemplated where anchoring the attachment stent above the renal arteries without disturbing cross-blood flow is a concern. If there is sufficient healthy tissue, additional self-expanding structures can be located at the proximal end of the neck portion and a distal end of a limb support portion. Moreover, catheterization of the limb portions of a bifurcated main body component and accurate deployment and attachment of modular limb components can be facilitated by incorporating additional self-expanding attachment or support structures into the main body component. Furthermore, the limb portions may be sutured together from the crotch to the distal end of the shortest limb portion to resist twisting and provide column strength to the main body component during implantation. 
     Other features and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view, depicting a bifurcated endovascular graft main body component of the present invention; 
         FIG. 2  is a perspective view, depicting a limb component configured for mating with the main body component shown in  FIG. 1 ; 
         FIG. 3  is a partial perspective and enlarged view, depicting the attachment of limb components in a main body component; and 
         FIG. 4  is a perspective view, depicting an alternative embodiment of a bifurcated stent-graft main body component of the present invention. 
         FIG. 5  is a perspective view, depicting an enlarged view of one embodiment of an attachment stent; 
         FIG. 6  is a partial perspective view, depicting basic structure for another embodiment of stent structure; 
         FIG. 7  is a perspective view, depicting basic structure for yet another embodiment of stent structures; 
         FIG. 8  depicts a stent structure with hooks positioned at apices; 
         FIG. 9  depicts a stent structure with hooks positioned along a medial portion of the stent; and 
         FIG. 10  is a schematic view depicting a modular graft device incorporating straight tubular sections. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention relates to an endovascular graft and structure and methods for attaching and securing the individual components thereof. 
     With reference to  FIG. 1 , there is shown a main body component  30  and attachment stent  40  of a bifurcated endovascular graft that is one aspect of the present invention. The main body component  30  consists of a superior end neck  31 , trunk  32  and two limb portions  33 ,  34 . The limb portions  33 ,  34  facilitate insertion, deployment, and attachment of limb components of the modular endovascular graft. In one aspect of the present invention, one limb portion  34  can be shorter than the other limb portion  33 , though the limb portions can have any length as dictated by a particular application. Radiopaque markers  45  placed along the contra-lateral side of the graft material identify the neck  31  , mid-point, bifurcation point, and distal end of the contra-lateral limb portion  34 , thereby facilitating placement within a patient&#39;s body. 
     The attachment stent  40  can be attached to an inside wall of the main body  30  and includes attachment hooks or barbs  46 . The attachment stent is made from wire wound in a generally sinusoidal shape and can have helices at the apices. It is to be borne in mind, however, that the attachment stent  40  can alternatively be placed on an exterior of the main body  30 . The attachment stent  40  attachment hooks or barbs  46  facilitate anchoring the stent  40  in a lumen wall and prevent migration of the attachment stent  40  and attached main body component  30 . In the embodiment shown in  FIG. 1 , the hooks  46  extend radially outwardly from a point just beyond a superior end  48  of the main body  30 . 
     The limb portions  33 ,  34  of the main body  30  can further include stent structures attached to the inside or outside of the limb portions  33 ,  34 . As shown in  FIG. 1 , the stent structures can have a half-cell configuration  50  or a full-cell configuration  52 . The stent structures  50 ,  52  can be self-expanding or balloon expandable and operate to provide an opening for receiving additional graft components. The stent structures  50 ,  52  can also be employed to engage vasculature when the device is deployed at a repair site in some patient&#39;s anatomy. 
     The anchoring stent  40  and limb stent structure  50 ,  52  are sutured to the main body  30  using conventional techniques. The limb portions  33 ,  34  can also be sewn together to thereby provide a suitable platform for receiving medical devices or additional graft components and create column strength in the main body component during wiring and catheterization of the contra-lateral limb portion for insertion and deployment of the limb component  70 . Tufts of yarn  60  are attached to the graft material to aid in securely implanting the main graft  30  within vasculature through the promotion of tissue in-growth. 
     The main body component  30  can be fully supported along its length or can include stents arranged in a non-overlapping manner. The openings  64 ,  66  can be equipped with structure configured for mating with separate graft components. The devices can also rely on frictional fits for accomplishing in-situ assembly. 
     As shown in  FIG. 2 , a limb component  70  can be equipped with a stent structure  72  positioned interior the limb component  70  at a superior end  74  thereof. The stent structure  72  can be self-expanding or can be balloon expandable and further includes hooks  76  projecting through the graft material of the limb component  70 . An inferior end  78  can likewise be equipped with a stent  80  adapted to engage the lumen of the vasculature into which it is placed. The limb component  70  can have a generally tubular, flared or tapered profile and further includes radiopaque markers  82  positioned along its length. Moreover, the limb component  70  can have any suitable length for a particular purpose. 
     Turning now to  FIG. 3 , there is shown a main body component  30  having two limb components  70  attached thereto. Once the limb components  70  are placed within the limb portions  33 ,  34  of the main body component, the hooks or barbs  76  of the stent structure  72  project through the graft material defining the limb portion  33 ,  34 . Moreover, the stent structure themselves securely engage the limbs  33 ,  34 . In this way, the limb portions  70  are fixed to the main body component  30 . As shown in the drawings, the hooks  76  can be angled in such a manner to take advantage of blood flow. In  FIG. 3 , the assembly shown is contemplated to be employed when blood flows in a direction from the main body  30  to the limbs  33 ,  34 . 
     The endovascular device shown in  FIGS. 1-3  embodies a modular design that provides flexibility in sizing to the anatomy of the patient. Additional graft extenders can be employed at both the proximal and distal ends of the assembly. That is, additional limb components  70  can be joined to limb components  70  to further extend the assembly to repair vasculature. For example, in the event it is determined that healthy tissue does not exist at a bifurcation, it may be necessary to place additional limb components  70  within the branch vessel. Similar structure can be employed to extend the main body  30  within the main vessel. As stated, each of these components can be straight, flared or tapered tubular members of increasing or decreasing diameter. It is further contemplated that the grafting system includes various limb sizes, each of which connect to standard sized main body components  30 . By employing such a system, lower profile delivery systems can be utilized. For example, a 21.5 fr delivery system (not shown) can be used for a 26 mm implant. 
     In an alternative embodiment ( FIG. 4 ), the main body component  90  includes an attachment stent  92  particularly configured for transrenal or suprarenal placement. That is, where there is insufficient healthy tissue or where it is otherwise dictated by a patient&#39;s anatomy, the main body  30  can employ an attachment stent  92  having hooks or lumen engagement structure  94  which are longitudinally separated from a superior end  96  of the main body  30 . In this way, the hooks or barbs  94 , for example, can be affixed transrenally or suprarenally while the main body resides inferior the renal arteries. The same approach can be used anywhere in the body where blood through cross-branches in vasculature must be avoided. The attachment stent  92  is made from a tube (such as laser cut) and the hooks or barbs  94  are shape-set to project out from the cylindrical body when the stent is unconstrained by a delivery system. The main body component  90  can be tapered, flared or straight. 
     The main body component  90  also includes a plurality of supporting structures  98 ,  100 ,  102 ,  104  positioned along its length using conventional techniques. Such structure aids in holding the main body  70  open as well as in some patient&#39;s anatomy providing structure for engaging vasculature. As before, limb components can be attached to the main body component  90  as necessary. Also, the limbs  106 ,  108  can be sewn or otherwise affixed together for providing additional structural support to the device. It is contemplated that such a device can treat aortic necks up to 30 mm via a 20 fr delivery system. 
     Enlarged views of the basic structure of the various attachment stents and support structures shown in  FIGS. 1-4  are provided for convenience in  FIGS. 5-7 . In particular,  FIG. 5  depicts the basic structure for the attachment stent  40  shown in  FIG. 1  and clearly shows helical apices  150 .  FIGS. 6 and 7  depict basic underlying structure of the full-cell and half-cell stent structures  52 ,  50  shown in the previous figures. It is to be recognized that the basic underlying structure shown  200 ,  202  in  FIGS. 6 and 7  lack both hooks as well as the looped apices shown in  FIG. 1-4  but it is to be recognized that such structures can be added as desired and as previously described. For example, as shown in  FIGS. 8 and 9 , the stent structures  210 ,  212  can include hooks  216  configured along a midsection  220  of the stent structure (See also  FIG. 2 ) or at each apex  222  (See also  FIG. 4 ). 
     Shown in  FIG. 10  is a modular graft device  250  incorporating the previously described combination of flared, tapered and straight tubular sections. The assembly depicted in  FIG. 10  is merely exemplary in that the present application contemplates a graft with sections that can assume any of the stated configurations. That is, a leg portion can be tapered in one embodiment and flared or a straight tube in another. Likewise, the superior end  252  of the graft device can also embody each of these shapes. Moreover, any of the disclosed stent devices can be positioned along any portion of the inside or outside of the graft devices. Also, as previously described and shown in  FIG. 10 , a stent device  200  can be placed axially removed from the graft itself to thereby provide anchoring across branch vessels. Although also contemplated, an extender attached to a superior end of the graft device  250  is not shown. 
     Thus, it will be apparent from the foregoing that, while particular forms of the invention have been illustrated and described, various modifications can be made without the parting from the spirit and scope of the invention. For example, the main body and limb components can each be generally tubular, flared, bifurcated or trifurcated. Also, the stents and other supporting structures can be placed either interior or exterior a particular graft component. Accordingly, it is not intended that the invention be limited, except as by the appended claims.