Patent Application
20070239267
1. Field of the Invention
The present invention relates generally to stent grafts, and more particularly to improving healing associated with placement of an endoluminal stent graft in a vessel.
2. Description of the Related Art
Vascular aneurysms are the result of abnormal dilation of an artery, resulting from disease, infection, trauma, and/or genetic predisposition, which can weaken the arterial wall and allow it to expand locally. While aneurysms can occur anywhere within the high pressure (arterial) side of the circulation, most occur within the aorta, more specifically, the abdominal aorta usually originating near the ostia of the renal arteries and often extending distally into one or both of the iliac arteries.
Aortic aneurysms are often treated in open surgical procedures where the diseased vessel segment is bypassed and repaired with an artificial vascular graft. While considered an effective surgical technique, conventional vascular graft surgery however, is frequently not advisable for elderly patients or those patients weakened from cardiovascular and/or other diseases.
An alternative to the open surgical procedure is the placement of an endovascular prosthesis, such as an endoluminal stent graft, within the vessel in order to eliminate blood flow and pressure from the aneurysm sac. Generally, endoluminal stent grafts are delivered to a desired location within a vessel using a catheter-based delivery technique. Before the endoluminal stent graft can be delivered and implanted, both the inner diameter of the vessel, near the neck of the aneurysm, and the length of the aneurysm must be precisely measured. Once the endoluminal stent graft is properly sized, it is typically compressed and housed in a removable sheathing. The sheathed endoluminal stent graft is inserted into a vessel, typically from a more distal location, and maneuvered to the desired location via the catheter-based delivery technique. Once the desired location is achieved, the sheath is removed thus allowing the endoluminal stent graft to expand and make contact with the luminal wall.
Endoluminal stent grafts typically include a graft material supported by a stent structure. Generally, endoluminal stent grafts are formed in a tubular shape with proximal and distal neck openings to allow for blood flow. Conventionally, the proximal end of the endoluminal stent graft is referenced with respect to the end closest to the heart (via the length of blood traveled from the heart.) Some endoluminal stent grafts further include openings or bifurcations to accommodate lateral branches off the main vessel.
Implantation of endoluminal stent grafts in the prior art can be subject to a number of technical problems with subsequent morbidity and mortality. In some patients, the aneurysm neck is diseased and is not a smooth surface; the proximal neck of the prior art endoluminal stent grafts do not heal and affix properly to these non-smooth luminal walls. This failure of the endoluminal stent graft to incorporate itself at the aneurysm neck (i.e. lack of healing) could allow an endoluminal stent graft to dislodge and migrate distally causing blood flow and pressure leakage into the aneurysm sac increasing the likelihood of rupture associated with such a Type I leak. In patients having aneurysms with severe neck angularity and/or those with an aortic neck shorter than 10 mm, incomplete contact surface with the vessel wall can produce insufficient anchoring forces for the endoluminal stent graft.
An endoluminal stent graft includes a healing-promoting material located within a distal anchor region and a proximal anchor region of the endoluminal stent graft. When correctly positioned within a vessel, the healing-promoting material promotes cellular growth and allows the vessel wall to heal to the endoluminal sent graft; consequently, the possibility of distal migration leading to endoleaks at the distal and proximal necks causing restored blood flow and pressure to the aneurysm sac is reduced. Alternatively, the healing-promoting material can be located only at the proximal neck of the endoluminal stent graft. In still another alternative, a ring-like insert can be included in the endoluminal stent graft and optionally covered with a material that promotes healing.
Common reference numerals are used throughout the drawings and detailed description to indicate like elements.
In one example, graft material 106 is a material formed to limit the leakage of blood through graft material 106. Examples of graft material 106 include substantially non-porous fabrics, such as low profile system (LPS) material, or densely knitted fabrics. Any of the commonly used graft materials are suitable for use herein.
As illustrated, proximal anchor region 102 is located at a proximal neck of stent graft 100, and healing promoter 116A forms a right circular cylinder around stent graft 100 within proximal anchor region 102 on an exterior circumferential surface of graft material 106. In this example, proximal anchor region 102 extends longitudinally from a proximal circumferential edge 122 longitudinally toward the distal end of stent graft 100 a specified distance W_proximal along an outer circumferential surface of stent graft 100. W_proximal should be in contact with tissue (endothelium inner layer of the vessel). Therefore, W_proximal should be, ideally, a distance equals to the aneurysm neck (AAA). This distance is usually determined in the individual patient by echography (ultrasonography) or Computed Tomography imaging (CT scanning, CT Scan). In one example, specified distance W_proximal defines a length of what is commonly referred to as the proximal neck of stent graft 100. Thus, a group of stent grafts is provided having a range of specified distances W_Aproximal so that the range of specified distances corresponds to the range of aneurysm necks commonly encountered in patients. A physician chooses a particular stent graft in the group based on the characteristics of the aneurysm neck in a particular patient.
Distal anchor region 104 is located at a distal neck of leg 118 of stent graft 100, and healing promoter 116B is attached to leg 118 within a distal anchor region 104 on an exterior circumferential surface of graft material 106 of leg 118. In this example, distal anchor region 104 extends from a distal circumferential edge 124 of leg 118 a specified longitudinal distance W_distal towards the proximal end of stent graft 100 and along an outer circumferential surface of leg 118. In the distal part of the graft the presumption is that the graft is substantially in contact with the inner endothelium tissue of the iliac artery. If this is indeed the case, then W_distance is chosen to be in the range of 5-10 mm. In one example, specified distance W_distal defines a length of what is commonly referred to as the distal neck of leg 118 of stent graft 100.
In one embodiment, healing promoter 116A, 116B is a substance that supports cellular in growth that aids in fixation of an endoluminal stent graft, such as stent graft 100, within a vessel. Location of healing promoter 116A in proximal anchor region 102 and promoter 116B in distal anchor region 104 promotes healing in of the proximal and distal necks, respectively, of stent graft 100 in a vessel reducing the risk of dislodgement and migration, thus reducing the occurrence of endoleaks that could otherwise form at the proximal and distal proximal necks.
In one example, healing promoter 116 is a porous fabric, such as a Dacron fabric, or non-woven material. Healing promoter should be a material with a “non-smooth surface”. In the particular case of AAA-endovascular graft, mainly endothelial, fibroblast and smooth muscle cells are able to adhere and migrate on the added “healing promoter” exposed surface. Cellular adhesion potential is related to the degree of roughness and wettability/surface charge (i.e. hydrophobicity) of the material surface (e.g. polymeric materials with a smooth surface inducing low cellular adhesion, demonstrate significant increased adhesion strength associated with increased surface roughness). In this respect, “knitted Dacron” (PET: polyethylene terephthalate) material would be appropriate. Fibrous polyurethane material could also be used. Porosity usually concerns material with a 3-D structure. However, certain non-woven PET fabrics (2-D) present defined porosity surfaces (low and high-porosity matrix). Pore sizes of at least 5 μm would be appropriate to stimulate tissue in growth, with pore sizes of at least 50 μm being more appropriate, and pore sizes of at least 100 μm being most appropriate.
In one example, healing promoter 116A, 116B includes a coating on a material that further promotes healing-in, such as a collagen coating. Collagen or any other peptide, protein or free amine group containing healing-promoting biomolecule can be coated onto the stent graft through a two-step process. The first step comprises grafting of an acrylic acid/acryl amide copolymer onto the Dacron substrate, after which collagen is immobilized onto the available functional groups in the acrylic acid/acrylamide copolymer graft.
Experimental Procedure:
Graft procedure;
Two different types of stent graft materials, high density, e.g., as has been provided with the AneuRx® stent graft products, are grafted with acrylic acid/acryl amide. For grafting, an aqueous solution containing 25 wt % acrylic acid and 5 wt % acryl amide monomer is used. Grafting is performed for 30 minutes followed by overnight rinsing to stop the grafting process. Small pieces of each material are stained with Toluidine Blue (TB), whereby blue staining denotes successful copolymer grafting. When compared to also stained reference materials, the acrylic acid/acryl amide graft appeared clearly present on both the high density and RPM stent graft materials through the observed uptake of the dye. The intensity of the blue stain was the same on either substrate.
Next, both stent graft materials were immobilized with collagen;
Collagen immobilization;
One part of each type of material was immersed in a MES buffer containing hydroxysuccinimide and N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride (EDC). The reaction was allowed to continue for 30 minutes only at rT. After a quick rinse in deionized water the samples were immersed in a 0.5 wt % collagen solution in MES buffer for 16-18 hours at rT. Subsequently the samples were rinsed and dried at ambient conditions.
Staining with Coomassie Blue (protein dye) after collagen immobilization confirmed the presence of immobilized collagen on both stent graft materials. Collagen presence was also confirmed with FT-IR spectroscopy and X-Ray photonelectron spectroscopy.
In another example, healing promoter 116A, 116B includes at least one growth factor promoting agent, such as a ReGeneraTing Agent (RGTA). RGTA is chemically substituted dextran. RGTA is encapsulated in a material forming healing promoter 116A, 116B, or alternatively is applied directly to the material forming healing promoter 116A, 116B, for example, as a coating.
RGTA can be coated onto the stent graft as per the following procedure. First, RGTA will undergo controlled periodate oxidation as per the procedure previously described in U.S. Pat. No. 5,679,659 assigned to Medtronic, Inc. The periodate oxidized RGTA can then be immobilized onto the Dacron stent graft as follows: The Dacron stent graft material is provided with an acrylic acid/acrylamide copolymer graft as previously described [see previous paragraph 0026]. In a multi-step process that is similar to the procedure previously described in U.S. Pat. No. 5,607,475 assigned to Medtronic, Inc., then the periodate oxidized RGTA is immobilized and coated onto the stent graft material.
One could also use different approaches, using direct coating of collagen such as described by van der Bas et al. J Vasc Surg 2002. Instead of van der Bas' proposed impregnation of the collagen coating with growth factors, we could have the collagen also impregnated with RGTA, or any other desirable bioactive molecule.
Also, the Dacron substrate can be coated with a polymer overcoat, into which ‘releaseable’ bioactive substances, such as RGTA, can be imbibed. (Basically, the drug eluting stent approach). Many polymers could be used as a potential coating, e.g., synthetic, natural, biodegradable.
Synthetic polymers include alkyl cellulose, cellulose esters, cellulose ethers, hydroxyalkyl celluloses, nitrocelluloses, polyalkylene glycols, polyalkylene oxides, polyalkylene terephthalates, polyalkylenes, polyamides, polyanhydrides, polycarbonates, polyesters, polyglycolides, polymers of acrylic and methacrylic esters, polyacrylamides, polyorthoesters, polyphosphazenes, polysiloxanes, polyurethanes, polyvinyl alcohols, polyvinyl esters, polyvinyl ethers, polyvinyl halides, polyvinylpyrrolidone, poly(ether ether ketone)s, silicone-based polymers and blends and copolymers of the above. Specific examples of these broad classes of polymers include poly(methyl methacrylate), poly(ethyl methacrylate), poly(butyl methacrylate), poly(isobutyl methacrylate), poly(hexyl methacrylate), poly(isodecyl methacrylate), poly(lauryl methacrylate), poly(phenyl methacrylate), poly(methyl acrylate), poly(isopropyl acrylate), poly(isobutyl acrylate), poly(octadecyl acrylate), polyethylene, polypropylene, poly(ethylene glycol), poly(ethylene oxide), poly(ethylene terephthalate), poly(vinyl alcohols), poly(vinyl acetate), poly(vinyl chloride), polystyrene, polyurethane, poly(lactic acid), poly(butyric acid), poly(valeric acid), poly[lactide-co-glycolide], poly(fumaric acid), poly(maleic acid), copolymers of poly (caprolactone) or poly (lactic acid) with polyethylene glycol and blends thereof.
Coatings may be non-biodegradable. Examples of preferred non-biodegradable polymers include ethylene vinyl acetate (EVA), poly(meth)acrylic acid, polyamides, silicone-based polymers and copolymers and mixtures thereof.
Coatings may be biodegradable. The rate of degradation of the biodegradable coating is determined by factors such as configurational structure, copolymer ratio, crystallinity, molecular weight, morphology, stresses, amount of residual monomer, porosity and site of implantation. Examples of biodegradable polymers include synthetic polymers such as polyesters, polyanhydrides, poly(ortho)esters, polyurethanes, siloxane-based polyurethanes, poly(butyric acid), tyrosine-based polycarbonates, and natural polymers and polymers derived therefrom such as albumin, alginate, casein, chitin, chitosan, collagen, dextran, elastin, proteoglycans, gelatin and other hydrophilic proteins, glutin, zein and other prolamines and hydrophobic proteins, starch and other polysaccharides including cellulose and derivatives thereof (e.g. methyl cellulose, ethyl cellulose, hydroxypropyl cellulose, hydroxy-propyl methyl cellulose, hydroxybutyl methyl cellulose, carboxymethyl cellulose, cellulose acetate, cellulose propionate, cellulose acetate butyrate, cellulose acetate phthalate, cellulose acetate succinate, hydroxypropylmethylcellulose phthalate, cellulose triacetate, cellulose sulphate), poly-1-lysine, polyethylenimine, poly(allyl amine), polyhyaluronic acids, and combinations, copolymers, mixtures and chemical derivatives thereof (substitutions, additions of chemical groups, for example, alkyl, alkylene, hydroxylations, oxidations, and other modifications routinely made by those skilled in the art). In general, these materials degrade either by enzymatic hydrolysis or exposure to water in vivo, by surface or bulk erosion. The foregoing materials may be used alone, as physical mixtures (blends), or as a co-polymer. Biodegradable polyesters are for instance poly(glycolic acid) (PGA), poly(lactic acid) (PLA), poly(glycolic-co-lactic acid) (PGLA), poly(dioxanone), poly(caprolactone) (PCL), poly(3-hydroxybutyrate) (PHB), poly(3-hydroxyvalerate) (PHV), poly(lactide-co-caprolactone) (PLCL), poly(valerolactone) (PVL), poly(tartronic acid), poly(b-malonic acid), poly(propylene fumarate) (PPF) (preferably photo cross-linkable), poly(ethylene glycol)/poly(lactic acid) (PELA) block copolymer, poly(L-lactic acid-e-caprolactone) copolymer, and poly(lactide)-poly(ethylene glycol) copolymers. Biodegradable polyanhydrides are for instance poly[1,6-bis(carboxyphenoxy)hexane], poly(fumaric-co-sebacic)acid or P(FA:SA), and such polyanhydrides may be used in the form of copolymers with polyimides or poly(anhydrides-co-imides) such as poly-[trimellitylimidoglycine-co-bis(carboxyphenoxy)hexane], poly[pyromellitylimidoalanine-co-1,6-bis(carboph-enoxy)-hexane], poly[sebacic acid-co-1,6-bis(p-carboxyphenoxy)hexane] or P(SA:CPH) and poly[sebacic acids co-1,3-bis(p-carboxyphenoxy)propane] or P(SA:CPP).
It has been shown that about 20 μg RGTA in decellularized tissue could induce good healing process. [“A synthetic glycosaminoglycan mimetic binds vascular endothelial growth factor and modulates angiogenesis” Vincent Rouet et al. J Biol Chem. 2005 Jul. 13]. Rather than sue RGTA alone as a coating, we would combine RGTA with another material, not just coat it as is. Either covalent immobilization as described in more detail above, or imbibement/impregnation with a natural or synthetic (biodegradable) polymer overcoat.
Obviously, we can make the coating ‘exotic’—a first overcoat capable of releasing RGTA, followed by a second overcoat consisting of collagen, though such a process might be considered to be not practical.
Alternatively, rather than using a material, healing promoter 116A, 116B is a coating directly on graft material 106. In one example, healing promoter 116A, 116B is a drug impregnated coating that promotes the formation of thrombosis and tissue incorporation between stent graft 100 and a vessel. In another example, healing promoter 116A, 116B is coated on graft material 106, portions of the stent structure, such as any of first base spring 110, second support spring 112, and anchor spring 114, among others, or both.
To follow the copolymer grafting procedure as further detailed above, for metal substrates we would need a silanization priming step, similar to the one described in U.S. Pat. No. 5,607,475 assigned to Medtronic, Inc. Alternatively, for metal substrates, when wanting to use polymer based drug eluting coatings, first primer layers might be needed such as those well known and used for drug eluting stents. In case the stent graft material is not Dacron, but ePTFE, another widely used graft material, then also the ePTFE may need to be pre-treated prior to either copolymer grafting or applying an overcoat. Suited pre-treatment methods can be found in the vacuum deposition or irradiation technologies [e.g., L. J. Matienzo, J. A. Zimmerman, and F. D. Egitto, Surface modification of fluoropolymers with vacuum ultraviolet irradiation, Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films, Volume 12, Issue 5, pp. 2662-2671, 1994; M. K. Shi, L. Martinu, E. Sacher, A. Selmani, M. R. Wertheimer, A. Yelon, Angle-resolved XPS study of plasma-treated teflon PFA surfaces, Surface and Interface Analysis, Volume 23, Issue 2, Pages 99-104, 1995]; moreover wet chemical modification of ePTFE (Teflon) has been described comprising reduction of the carbon-fluorine bonds with the purpose of modifying its adhesive and wetting surface properties, as well as allowing subsequent surface modification reactions to take place.
In one embodiment, the drug impregnated coating includes at least one growth factor promoting agent, such as ReGeneraTing Agent (RGTA.
In another example, healing promoter 116A, 116B includes a plurality of loop-like structures, a plurality of tail-like structures, or both to promote to promote tissue incorporation, the formation of thrombosis, and fixation of an endoluminal stent graft, such as endoluminal stent graft 100, in the vessel. Loop structures exist in special PET material (velour Dacron). This Dacron material presents a non-regular/enterogenous surface topography that would dramatically enhanced cell/tissue adhesion. Alternatively, these loops or tail like structures would be manually braided into the original stent graft material. A particular diameter specification is not important. The loops (or tails for that matter) should provide for a “porous coating-like” structure of at least 1 μm, more preferably at least 5 μm, most preferably at least 10 μm thickness.
In yet another example, loops 204, tails 206, or both are made of a biocompatible copolymer. For example, loops 204, tails 206, or both are made of polyester, such as Dacron or polytetrafluoroethylene (PTFE). Additional extensive list of polymers is provided earlier.
In one application, loops 204, tails 206, or both are attached by sewing or weaving. Loops 204, tails 206, or both are attached to graft material 106, the stent structure, such as any of first base spring 110, second support spring 112, and anchor spring 114, among others, or both to promote tissue incorporation and the fixation of a stent graft, such as stent graft 100, in a vessel. In one embodiment, loops 204, tails 206, or may both initiate swelling when in contact with blood for the first few seconds prior to deployment. For the most part these loops and tails will largely be in contact with the tissue wall and not with (flowing) blood. They might get in contact with interstitial fluid with time. Hydrophylic polymers will swell, such as collagen-derived loops or tails or hydrophilic polyurethanes.
The various embodiments of the invention described herein with reference to
In the present embodiment, graft material 306 is a material formed to limit the leakage of blood from lumen 308 through graft material 306. Examples of graft material 306 include substantially non-porous fabrics, such as low profile system (LPS) material, or densely knitted fabrics.
As illustrated, proximal anchor region 302 is located at a proximal neck of stent graft 300, and healing promoter 116C is within distal anchor region 302 on an exterior circumferential surface of graft material 306 and on an interior circumferential surface of graft material 306. Proximal anchor region 302 extends longitudinally from a proximal circumferential edge 322 longitudinally toward the distal end of stent graft 300 a specified distance W3_proximal. In one example, healing promoter 116C overlaps proximal circumferential edge 322 from the exterior side of graft material 306 to the interior side of graft material 306. In another example, healing promoter 116C is included on the interior circumferential surface of graft material 306 within distal anchor region 302, but has a length less than specified distance W3_proximal.
Distal anchor region 304 is located at the distal neck of leg 318 of stent graft 300, and healing promoter 116D is within distal anchor region 304 on the exterior circumferential surface of graft material 306 and on the interior circumferential side of graft material 306. In one example, distal anchor region 304 extends from a distal circumferential edge 324 longitudinally towards the proximal end of stent graft 300 a specified distance W3_distal. In one example, healing promoter 116D overlaps distal circumferential edge 324 from the exterior side of graft material 306 to the interior side of graft material 306. In another example, healing promoter 116D is included on an interior circumferential surface of graft material 306 within proximal anchor region 304, but has a length less than specified distance W3_proximal.
In some applications, it may be desirable to provide more intimate contact between an endoluminal stent graft and the interior vessel walls by including a ring-like insert within healing promoter 116E as further described herein with reference to
In the present embodiment, stent graft 400 is shaped to form a lumen 408 that bifurcates. Optionally, an extension 420 is included as part of stent graft 400.
Proximal anchor region 402 extends from a proximal circumferential edge 422 longitudinally toward the distal end of stent graft 400 a specified distance W4_proximal. Ring-like insert 426 is included within proximal anchor region 402. In one example, material 427 covers ring-like insert 426 and overlaps proximal circumferential edge 422 from the exterior side of graft material 406, i.e., the non-luminal side, to the interior side of graft material 406, i.e., the luminal side. In some applications, healing promoter 116E (See
The thickness of ring-like insert 426 is selected to provide better intimate contact between stent graft 400 and a vessel in which stent graft 400 is positioned. For example, a ring like a ring as used in annuloplasty devices for repair of cardiac valves: 2-3 mm in thickness. In one example, ring-like insert 426 is formed of silicon rubber. In another example, ring-like insert 426 is formed of one or more closed metal bands. In yet another example, ring-like insert 426 is formed of one or more open metal bands. Other polymers than silicone can be used, as long as they are as flexible
In one application, ring-like insert 426 is a reservoir of healing promoting agents and thus includes one or more healing promoting agent(s). The one or more healing promoting agent(s) are selected from a group consisting of growth factors, growth factor protecting agents, such as RGTA, alone or in combination with (heparin binding) growth factors. Examples of healing promoting growth factors are FGF, VEGF, PDGF, IGF, EGF). One could further think of pro- and anti-inflammatory cytokines as possible suitable healing promoting agents. Examples would be members of the interleukin family, TNFalpha, IFN, TGFbeta and others. Pseudo healing promoting agents that may be used include: hormone, antibiotics, immunosuppressant, and gene containing.
The metal inserts could be dip-coated thus being provided with a polymer overcoat from which the agent can be released. The polymer insert can be provided with bioactive agents in several ways: pre-mixing polymer with agents then forming the ring insert (will depend on agent stability throughout processing); solvent swelling-induced imbibement with agents (again will depend on agent stability throughout processing). Alternatively, both metal and polymer inserts can be provided with surface pits or grooves into which the agents can be deposited for subsequent release. In some applications, the one or more healing promoting agents are slow releasing up to maximally 28 days is preferred
To provide efficient folding and unfolding of stent graft 400 using a catheter-based delivery technique, ring-like insert 426 is cut in at one point to allow folding of ring-like insert 426 by overlapping the cut free ends of ring-like insert 426 with subsequent unfolding when positioned in a vessel lumen.
Although the example illustrated and described with reference to
FIGS. 5 to 7 illustrate additional examples of an endoluminal stent graft in which a healing promoter is included in selected portions defined by the stent structure of the endoluminal stent graft.
In particular,
Graft material 506 is a material that limits the leakage of blood from lumen 508 through graft material 506. Examples of graft material 506 include substantially non-porous fabrics, such as low profile system (LPS) material, or densely knitted fabrics.
As illustrated, proximal anchor region 502 is located at a proximal neck of stent graft 500, and healing promoter 116F is included within distal anchor region 502 on the exterior circumferential surface of graft material 506. Proximal anchor region 502 extends longitudinally from a proximal circumferential edge 522 toward the distal end of stent graft 500 a specified distance W5_proximal. Substantially all of first (base) spring 510 and nearly one-half(½) of second (support) spring 512 are sewn to healing promoter 116F and healing promoter 116F is sewn to graft material 506.
Graft material 606 is a material that limits the leakage of blood from lumen 608 through graft material 606. Examples of graft material 606 include substantially non-porous fabrics, such as low profile system (LPS) material, or densely knitted fabrics.
As illustrated, proximal anchor region 602 is located at a proximal neck of stent graft 600, and healing promoter 116G is included within distal anchor region 602 on the exterior side of graft material 606. Proximal anchor region 602 extends longitudinally from a proximal circumferential edge 622 toward the distal end of stent graft 600 a specified distance W6_proximal. Substantially all of first (base) spring 610 and second (support) spring 612 are sewn to healing promoter 116G and healing promoter 116G is sewn to graft material 606.
Graft material 706 is a material that limits the leakage of blood from lumen 708 through graft material 706. Examples of graft material 706 include substantially non-porous fabrics, such as low profile system (LPS) material, or densely knitted fabrics.
As illustrated, proximal anchor region 702 is located at a proximal neck of stent graft 700, and healing promoter 116H is included within distal anchor region 702 on the exterior side of graft material 706, i.e., the non-luminal side. Proximal anchor region 702 extends longitudinally from a proximal circumferential edge 722 longitudinally toward the distal end of stent graft 700 a specified distance W7_proximal. Substantially all of first (base) spring 710 and second (support) spring 712, and a portion of a next spring adjacent second (support) spring 712, i.e., adjacent spring 726, are sewn to healing promoter 116H and healing promoter 116H is sewn to graft material 706.
Although the examples illustrated and described with reference to
This disclosure provides examples according to the present invention. In particular, examples having the healing promoter located in a proximal anchor region and in distal anchor regions can be varied to eliminate the healing promoter in the distal anchor regions. Further, examples having the healing promoter located in a proximal anchor region can be varied to further include the healing promoter in one or more distal anchor regions. Additionally, examples illustrated and described without ring-like insert 426, can be varied to further include ring-like insert 426. Also, the healing promoter can be of different materials, such as a fabric at a proximal anchor region and a coating in a distal anchor region. Numerous variations, whether explicitly provided for by the specification or implied by the specification or not, such as variations in structure, dimension, type of material and manufacturing process may be implemented by one of skill in the art in view of this disclosure.
Also, although the above examples illustrated and described herein used an endoluminal stent graft having a bifurcated structure, these examples are applicable to a wide variety of endoluminal stent graft designs, such as other bifurcated and non-bifurcated designs, as well as other stent structures, such as other spring structures, strut structures, and interlocking structures, among others.
