Abstract:
A multiple-sided medical device comprises a closed frame of a single piece of wire or other resilient material and having a series of bends and interconnecting sides. The device has both a flat configuration and a second, folded configuration that comprises a self-expanding stent. The stent is pushed from a delivery catheter into the lumen of a duct or vessel. One or more barbs are attached to the frame of the device for anchoring or to connect additional frames. A covering of fabric or other flexible material such as DACRON, PTFE, or collagen, is sutured or attached to the frame to form an occlusion device, a stent graft, or an artificial valve such as for correcting incompetent veins in the lower legs and feet. A partial, triangular-shaped covering over the lumen of the device allows the valve to open with normal blood flow and close to retrograde flow.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This is a Continuation application of U.S. patent application Ser. No. 09/324,382 filed Jun. 2, 1999, now U.S. Pat. No. 6,200,336 B1, which claimed priority from U.S. Provisional patent application Serial No. 60/087,661 filed Jun. 28, 1998. 
    
    
     TECHNICAL FIELD 
     This invention relates to medical devices, more particularly, to intraluminal devices. 
     BACKGROUND OF THE INVENTION 
     As minimally invasive techniques and instruments for placement of intraluminal devices have developed over recent years, the number and types of treatment devices have proliferated as well. Stents, stent grafts, occlusion devices, artificial valves, shunts, etc., have provided successful treatment for a number of conditions that heretofore required surgery or lacked an adequate solution altogether. Minimally invasive intravascular devices have especially become popular with the introduction of coronary stents to the U.S. market in the early 1990s. Coronary and peripheral stents have been proven to provide a superior means of maintaining vessel patency, however, they have subsequently been used in conjunction with grafts as a repair for abdominal aortic aneurysm, fibers or other materials as occlusion devices, and as an intraluminal support for artificial valves, among other uses. 
     Some of the chief goals in designing stents and related devices include providing sufficient radial strength to supply sufficient force to the vessel and prevent device migration. An additional concern in peripheral use, is having a stent that is resistant to external compression. Self-expanding stents are superior in this regard to balloon expandable stents which are more popular for coronary use. The challenge is designing a device that can be delivered to the target vessel in as small of a configuration as possible, while still being capable of adequate expansion. Self-expanding stents usually require larger struts than balloon expandable stents, thus increasing their profile. When used with fabric or other coverings that require being folded into a delivery catheter, the problem is compounded. 
     There exists a need to have a basic stent, including a fabric covering, that is capable of being delivered with a low profile, while still having a sufficient expansion ratio to permit implantation in larger vessels, if desired, while being stable, self-centering, and capable of conforming to the shape of the vessel. 
     SUMMARY OF THE INVENTION 
     The foregoing problems are solved and a technical advance is achieved in an illustrative multiple-sided intraluminal medical device comprised of a single piece of wire or other material having a plurality of sides and bends interconnecting adjacent sides. The bends can be coils, fillets, or other configurations to reduce stress and fatigue. The single piece of wire is preferably joined by an attachment mechanism, such as a piece of cannula and solder, to form a closed circumference frame. The device has a first configuration wherein the sides and bends generally lie within a single, flat plane. In an embodiment having four equal sides, the frame is folded into a second configuration where opposite bends are brought in closer proximity to one another toward one end of the device, while the other opposite ends are folded in closer proximity together toward the opposite end of the device. In the second configuration, the device becomes a self-expanding stent. In a third configuration, the device is compressed into a delivery device, such as a catheter, such that the sides are generally beside one another. While the preferred embodiment is four-sided, other polygonal shapes can be used as well. 
     In another aspect of the present invention, one or more barbs can be attached to the frame for anchoring the device in the lumen of a vessel. The barbs can be extensions of the single piece of wire or other material comprising the frame, or they can represent a second piece of material that is separately attached to the frame by a separate attachment mechanism. An elongated barb can be used to connect additional devices with the second and subsequent frames attached to the barb in a similar manner. 
     In still another aspect of the present invention, a covering, such as DACRON, PTFE, collagen, or other flexible material, can be attached to the device with sutures or other means to partially, completely, or selectively restrict fluid flow. When the covering extends over the entire aperture of the frame, the frame formed into the second configuration functions as an vascular occlusion device that once deployed, is capable of almost immediately occluding an artery. A artificial valve, such as that used in the lower legs and feet to correct incompetent veins, can be made by covering half of the frame aperture with a triangular piece of material. The artificial vein traps retrograde blood flow and seals the lumen, while normal blood flow is permitted to travel through the device. In related embodiments, the device can be used to form a stent graft for repairing damaged or diseased vessels. In a first stent graft embodiment, a pair of covered frames or stent adaptors are used to secure a tubular graft prosthesis at either end and seal the vessel. Each stent adaptor has an opening through which the graft prosthesis is placed and an elongated barb is attached to both another stent graft embodiment, one or more frames in the second configuration are used inside a sleeve to secure the device to a vessel wall. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     FIG. 1 depicts a top view of one exemplary embodiment of the present invention; 
     FIG. 2 depicts a pictorial view of the embodiment of FIG. 1; 
     FIGS. 3 to  3 B depict a top view and enlarged, partial cross-sectional views of a second exemplary embodiment of the present invention; 
     FIG. 4 depicts a side view of the embodiment of FIG. 3 deployed in a vessel; 
     FIG. 5 depicts a enlarged partial view of the embodiment of FIG. 1; 
     FIG. 6 depicts a partially-sectioned side view of the embodiment of FIG. 1 inside a delivery system; 
     FIG. 7 depicts a top view of a third embodiment of the present invention; 
     FIG. 8 depicts a side view of the embodiment of FIG. 7 deployed in a vessel; 
     FIGS. 9-11 depict enlarged partial views of other embodiments of the present invention; 
     FIG. 12 depicts a top view of a fourth embodiment of the present invention; 
     FIGS. 13-14 depicts side views of the embodiment of FIG. 12; 
     FIG. 15 depicts a top view of a fifth embodiment of the present invention; 
     FIG. 16 depicts a side view of the embodiment of FIG. 15; 
     FIG. 17 depicts a side view of a sixth embodiment of the present invention; 
     FIG. 18 depicts an enlarged pictorial view of a seventh embodiment of the present invention; and 
     FIG. 19 depicts a top view of an eighth embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION 
     The invention is further illustrated by the following (preceding) pictorial embodiments, which in no way should be construed as further limiting. The present invention specifically contemplates other embodiments not illustrated but intended to included in the appended claims. 
     FIG. 1 depicts a top view of one embodiment of the medical device  10  of the present invention comprising a frame  11  of resilient material, preferably metal wire made of stainless steel or a superelastic material (e.g., nitinol). While round wired is depicted in each of the embodiments shown herein, other types, e.g., flat, square, or triangular, may be used to form the frame. In the illustrative embodiment, the frame comprises a closed circumference  62  of a single piece  59  of material that is formed into a device  10  having a plurality of sides  13  interconnected by a series of bends  12 . The depicted embodiment includes four sides  13  of approximately equal length. Alternative embodiment include forming a frame into any polygonal shape, for example a pentagon, hexagon, octagon, etc. One alternative embodiment is shown in FIG. 19 that includes a four-sided frame  11  having the general shape of a kite with two adjacent longer sides  66  and two adjacent shorter sides  67 . In the embodiment of FIG. 1, the bends  12  interconnecting the sides  13  comprise a coil  14  of approximately one and a quarter turns. The coil bend produces superior bending fatigue characteristics than that of a simple bend  40 , as shown in FIG. 9, when the frame is formed from stainless steel and most other standard materials. The embodiment of FIG. 9 may be more appropriate, however, if the frame is formed from nitinol (NiTi) or other superelastic alloys, as forming certain type of bends, such as coil  14 , may actually decrease fatigue life of a device of superelastic materials. Therefore, the bend  12  should be of a structure that minimizes bending fatigue. Alternative bend  12  embodiments include a outward-projecting fillet  41  as shown in FIG. 10, and an inward-projecting fillet  42  comprising a series of curves  63 , as shown in FIG.  11 . Fillets are well known in the stent art as a means to reduce stresses in bends. By having the fillet extend inward as depicted in FIG. 11, there is less potential trauma to the vessel wall. 
     When using stainless steel wire, the size of the wire depends on the size of device and the application. An occlusion device, for example, preferably uses 0.010″ wire for a 10 mm square frame, while 0.014″ and 0.016″ wire would be used for 20 mm and 30 mm frames, respectively. Wire that is too stiff can damage the vessel, not conform well to the vessel wall, and increase the profile of the device. 
     Returning to FIG. 1, the single piece  59  of material comprising the frame  11  is formed into the closed circumference by securing the first and second ends  60 , 61  with an attachment mechanism  15  such as a piece of metal cannula. The ends  60 , 61  of the single piece  59  are then inserted into the cannula  15  and secured with solder  25 , a weld, adhesive, or crimping to form the closed frame  11 . The ends  60 , 61  of the single piece  59  can be joined directly without addition of a cannula  15 , such as by soldering, welding, or other methods to join ends  61  and  62 . Besides, joining the wire, the frame could be fabricated as a single piece of material  59 , by stamping or cutting the frame  11  from another sheet (e.g., with a laser), fabricating from a mold, or some similar method of producing a unitary frame. 
     The device  10  depicted in FIG. 1 is shown in its first configuration  35  whereby all four interconnections or bends  20 , 21 , 22 , 23  and each of the sides  13  generally lie within a single flat plane. To resiliently reshape the device  10  into a second configuration  36 , shown in FIG. 2, the frame  11  of FIG. 1 is folded twice, first along a diagonal axis  24  with opposite bends  20  and  21  being brought into closer proximity, followed by opposite bends  22  and  23  being folded together and brought into closer proximity in the opposite direction. The second configuration  36 , depicted in FIG. 2, has two opposite bends  20 , 21  oriented at the first end  68  of the device  10 , while the other opposite bends  22 , 23  are oriented at the second end  69  of the device  10  and rotated approximately 180° with respect to bends  20  and  21  when viewed in cross-section. The medical device in the second configuration  36  can be used as a stent  44  to maintain an open lumen  34  in a vessel  33 , such as a vein, artery, or duct. The bending stresses introduced to the frame  11  by the first and second folds required to form the device  10  into the second configuration  36 , apply radial force against the vessel wall  70  to hold the device  10  in place and prevent vessel closure. Absent any significant plastic deformation occurring during folding and deployment, the device in the second configuration  36  when removed from the vessel or other constraining means, will at least partially return to the first configuration  35 . It is possible to plastically form the device  10  into the second configuration  36 , such that it does not unfold when restraint is removed. This might be particularly desired if the device is made from nitinol or a superelastic alloy. 
     The standard method of deploying the medical device  10  in a vessel  33 , depicted in FIG. 6, involves resiliently forming the frame  11  into a third configuration  37  to load into a delivery device  26 , such as a catheter. In the third configuration  37  the adjacent sides  13  are generally beside each other in close proximity. To advance and deploy the device from the distal end  28  of the delivery catheter  26 , a pusher  27  is placed into the catheter lumen  29 , When the device  10  is fully deployed, it assumes the second configuration  36  within the vessel as depicted in FIG.  2 . The sides  13  of the frame, being made of resilient material, conform to the shape of the vessel wall  70  such that when viewed on end, the device  10  has a circular appearance when deployed in a round vessel. 
     A second embodiment of the present invention is depicted in FIG. 3 wherein one or more barbs  19  are included to anchor the device  10  following deployment. As understood, a barb can be a wire, hook, or any structure attached to the frame and so configured as to be able to anchor the device  10  within a lumen. The illustrative embodiment includes a first strut  17  with up to three other barbed struts  18 , 71 , 72 , indicated in dashed lines, representing alternative embodiments. As depicted in detail view FIG. 3A, in the combination  38  that comprises struts  17  and  18 , each strut is an extension of the single piece  59  of material of the frame  11  beyond the closed circumference  59 . The attachment cannula  15  secures and closes the single piece  59  of material into the frame  11  as previously described, while the first and second ends  60 , 61  thereof, extend from the cannula  15 , running generally parallel with the side  13  of the frame  11  from which they extend, each preferably terminating around or slightly beyond respective interconnections or bends  20 , 23 . To facilitate anchoring, the distal end of the strut  17  in the illustrative embodiment contains a bend or hook defining barb  19 . 
     Optionally, the tip of the distal end can be ground to a sharpened point for better tissue penetration. To add a third and fourth barb as shown, a double-barbed strut  39  comprising barbs  71  and  72  is attached to the opposite side  13  as defined by bends  21  and  22 . Unlike combination  38 , the double-barbed strut  39 , as shown in detail view FIG. 3B, comprises a piece of wire, usually the length of combination  38 , that is separate from the single piece  59  comprising the main frame  11 . It is secured to the frame by attachment mechanism  15  using the methods described for FIG.  1 . FIG. 4 depicts barb  19  of strut  17  engaging the vessel wall  70  while the device  10  is in the second, deployed configuration  36 . While this embodiment describes up to a four barb system, more than four can be used. 
     FIG. 7 depicts a top view of a third embodiment of the present invention in the first configuration  35  that includes a plurality of frames  11  attached in series. In the illustrative embodiment, a first frame  30  and second frame  31  are attached by a strut  16  that is secured to each frame by their respective attachment mechanisms  15 . The strut  16  can be a double-barbed strut  39  as shown in FIG. 3 (and detail view FIG. 3B) that is separate from the single pieces  59  comprising frames  30  and  31 , or the strut may represent a long extended end of the one of the single pieces  59  as shown in detail view FIG.  3 A. Further frames, such as third frame  32  shown in dashed lines, can be added by merely extending the length of the strut  16 . FIG. 8 depicts a side view of the embodiment of FIG. 7 in the second configuration  36  as deployed in a vessel  33 . 
     FIGS. 12-18 depict embodiments of the present invention in which a covering  45  comprising a sheet of fabric, collagen (such as small intestinal submucosa), or other flexible material is attached to the frame  11  by means of sutures  50 , adhesive, heat sealing, “weaving” together, crosslinking, or other known means. FIG. 12 depicts a top view of a fourth embodiment of the present invention while in the first configuration  35 , in which the covering  45  is a partial covering  58 , triangular in shape, that extends over approximately half of the aperture  56  of the frame  11 . When formed into the second configuration  36  as shown in FIGS. 13-14, the device  10  can act as an artificial valve  43  such as the type used to correct valvular incompetence. FIG. 13 depicts the valve  43  in the open configuration  48 . In this state, the partial covering  58  has been displaced toward the vessel wall  70  due to positive fluid pressure, e.g., normal venous blood flow  46 , thereby opening a passageway  65  through the frame  11  and the lumen  34  of the vessel  33 . As the muscles relax, producing retrograde blood flow  47 , as shown in FIG. 14, the partial covering  58  acts as a normal valve by catching the backward flowing blood and closing the lumen  34  of the vessel. In the case of the artificial valve  43 , the partial covering  58  is forced against the vessel wall to seal off the passageway  65 , unlike a normal venous valve which has two leaflets, which are forced together during retrograde flow. Both the artificial valve  43  of the illustrative embodiment and the normal venous valve, have a curved structure that facilitates the capture of the blood and subsequent closure. In addition to the triangular covering, other possible configurations of the partial covering  58  that result in the cupping or trapping fluid in one direction can be used. 
     Selecting the correct size of valve for the vessel ensures that the partial covering  58  properly seals against the vessel wall  70 . If the lumen  34  of the vessel is too large for the device  10 , there will be retrograde leakage around the partial covering  58 . 
     FIG. 15 depicts a top view of a fifth embodiment of the present invention in the first configuration  35 , whereby there is a full covering  57  that generally covers the entire aperture  56  of the frame  11 . When the device  10  is formed into the second configuration  36 , as depicted in FIG. 16, it becomes useful as an occlusion device  51  to occlude a duct or vessel, close a shunt, repair a defect, or other application where complete prevention of flow is desired. As an intravascular device, studies in swine have shown occlusion to occur almost immediately when deployed in an artery or the aorta with autopsy specimens showed thrombus and fibrin had filled the space around the device. The design of the present invention permits it to be used successfully in large vessels such as the aorta. Generally, the occlusion device should have side  13  lengths that are at least around 50% or larger than the vessel diameter in which they are to be implanted. 
     FIGS. 17-18 depict two embodiments of the present invention in which the device  10  functions as a stent graft  75  to repair a damaged or diseased vessel, such as due to formation of an aneurysm. FIG. 17 shown a stent graft  75  having a tubular graft prosthesis  54  that is held in place by a pair of frames  11  that function as stent adaptors  52 , 53 . Each stent adaptor  52 , 53  has a covering attached to each of the frame sides  13  which includes a central opening  55  through which the graft prosthesis  54  is placed and held in place from friction or attachment to prevent migration. One method of preventing migration is placement of a smaller device of the present invention at each end and suturing it to the covering. The stent adaptors  52 , 53  provide a means to seal blood flow while centering the graft prosthesis in the vessel. A long double-ended strut  39  connects of each stent adaptor  52 , 53  and includes barb assists to further anchor the stent graft  75 . In the embodiment depicted in FIG. 18, the covering  45  comprises an outer sleeve  64  that is held in place by first and second frames  30 , 31  that function as stents  44  to hold and seal the sleeve  64  against a vessel wall and maintain an open passageway  65 . In the illustrative embodiment, the stents  44  are secured to the graft sleeve  64  by sutures  50  that are optionally anchored to the coils  14  of the bends  12 . If the embodiment of FIG. 18 is used in smaller vessels, a single frame  11  can be used at each end of the stent graft  75 .