Patent Publication Number: US-2021169635-A1

Title: Pararenal and Thoracic Arch Stent Graft and Methods for Use

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. Non-Provisional application Ser. No. 15/080,556, filed on Mar. 24, 2016 that claims the benefit of U.S. Provisional Application No. 62/138,299, filed on Mar. 25, 2015 and of U.S. Provisional Application No. 62/197,304, filed on Jul. 27, 2015, which are each hereby incorporated by reference in their entirety. 
    
    
     BACKGROUND 
     Unless otherwise indicated herein, the materials described in this section are not prior art to the claims in this application and are not admitted to be prior art by inclusion in this section. 
     Pararenal and juxtarenal aneurysms are infrarenal aneurysms located within about 5 mm of the renal arteries that have very short necks (i.e., less than 5 mm) or that involve 2-3 visceral arteries (e.g., right and left renal arteries and occasionally the superior mesenteric artery (“SMA”)) and that extend to within about 5 mm of the SMA. Since a pararenal aneurysm typically includes only a portion of the visceral trunk of the aorta, obtaining a proximal seal between a main body stent graft and the vascular tissue is difficult since blood flow must be maintained to the renal arteries, the SMA and the celiac artery. One technique to treat a pararenal aneurysm may involve placing bridging stent grafts in each of the foregoing arteries via a branched or manifold stent graft, for example. While this technique may provide a sufficient proximal seal between the stent graft and the vasculature, the proximal seal may also create a new risk, namely that blood flow to the lumbar arteries may be blocked by the proximal seal. Specifically, the lumbar arteries perfuse the spinal cord with blood, and they tend to be concentrated in the area of the thoracic aorta above the celiac arteries in the “seal zone” for stent grafts placed and anchored in the aorta. As such, cutting off blood flow to the lumbar arteries may cause a patient to become hemodynamically unstable (i.e., blood pressure is too low to sufficiently perfuse tissues with blood) and may put a patient at risk for paraplegia. In addition, the Great vessels located in the aortic arch near the heart may similarly have blood flow cutoff by known treatment devices and methods for thoracic aneurysm and may lead to stroke. 
     SUMMARY 
     Example embodiments beneficially provide stent grafts for treating pararenal, supra-renal, ascending, transverse and descending thoracic aneurysms, for example, and methods for placing these stent grafts. The stent graft disclosed herein provides several advantages over known techniques. For example, the stent graft may permit a pararenal aneurysm to be repaired endovascularly with minimal coverage of the aorta above the celiac artery. This may be accomplished through an indentation or scallop-shaped-hole defined at the proximal end of the main body stent graft and arranged below the lumbar arteries upon deployment in vivo, while the remainder of the proximal end of the stent graft extends along the visceral trunk of the aorta. The proximal end of the main body stent graft may in turn be supported by a proximal sealing ring having a bi-level construction defining an upper portion arranged along the most proximal edge of the main body stent graft and a lower portion arranged along the indentation or scallop-shaped hole. 
     In addition, the stent graft may beneficially provide a diaphragm disposed within the main lumen that defines at least three openings. In one embodiment, these openings may include first, second, third and fourth openings. This arrangement may permit one or more bridging stents that may be coupled directly to these openings or to stent grafts coupled to these openings. This allows the exclusion of an aneurysm distal to the main body stent graft down through the iliac arteries, for example. 
     Further, in one embodiment, stent graft extensions may be coupled to the third and fourth openings of the diaphragm and may be arranged to cross-over one another with gentle swooping paths for stenting to the renal arteries. This configuration may advantageously permit unobstructed blood flow and may minimize both the potential for kinking of the stent grafts and for turbulent blood flow. Also, in a further embodiment, the third and fourth openings may be positioned on opposite sides of the diaphragm between the sidewall of the main body stent graft and the center of the lumen defined by the main body stent graft. This arrangement may provide for a gentle swooping path of the stent graft extensions coupled to the third and fourth openings, because free ends of the stent graft extensions may have more space to cross to the opposite side of the main body stent graft. In an alternative embodiment, the third and fourth openings may be positioned in the diaphragm closer to the center of the lumen defined by the main body stent graft. This arrangement may beneficially result in a higher blood flow rate. 
     In addition, in one embodiment, a permeable membrane may be provided covering at least one of a visceral vessel opening and two renal openings. This permeable membrane may advantageously increase contact area with the aortic wall upon deployment, while at the same time permitting blood flow across the membrane for a temporary period of time while the blood is inhibited from forming clots due to heparinization, for example. The permeable membrane may be perforable by a guidewire and/or a stent graft and any resistant force against the stent graft may be negligible. Once deployed in vivo, thrombosis may be formed on the permeable membrane thereby beneficially extending the seal zone of the stent graft with the aortic wall. 
     Also, in one embodiment, a visceral chamber may be defined by a visceral sidewall coupled to one of the diaphragm and the second opening and to one of the sidewall of the main body stent graft and the visceral-vessel opening defined in the sidewall of the main body stent graft. This visceral chamber may beneficially permit native blood flow to continue to the celiac and SMA arteries. In addition, in the event that an aneurysm advances proximally after placement of the stent graft, the aneurysm may be repaired by a standard thoracic stent graft that may be deployed and mate directly with the lumen of the main body stent graft. 
     With respect to thoracic aneurysm, the stent graft may provide blood flow to all three Great vessels thereby treating from the sinotubular junction and providing unimpeded flow during debranching of the aneurysm. The stent graft may also advantageously provide a surgeon with the flexibility to choose between placing the arch bypass graft or debranching the Great vessels first. For example, it may be desirable to debranch the Great vessels first and thereby provide stroke protection during subsequent placement of the larger arch bypass graft. Thus, the stent graft allows the surgeon to elect between risks based upon the presentation of each individual patient. 
     Thus, in one aspect, a stent graft is provided including the features of (a) a main body stent graft defining a lumen having a first end and a second end, (b) a diaphragm coupled to the main body stent graft, where the diaphragm defines at least three openings, and (c) at least three stent graft extensions each defining a lumen, where a first end of each of the at least three stent graft extensions is coupled to one of the at least three openings. 
     In a second aspect, the stent graft includes the features of (d) a visceral-vessel opening defined in a sidewall of the main body stent graft between the first end and the second end of the main body stent graft, where the diaphragm is disposed within the lumen of the main body stent graft, where the at least three openings of the diaphragm comprise a first opening, a second opening, a third opening and a fourth opening, and (e) a visceral chamber defined by a sidewall coupled to one of the second opening and the diaphragm and to one of the visceral-vessel opening and the sidewall of the main body stent graft. 
     In a third aspect, a stent graft includes the features of (a) a visceral-vessel opening defined in a sidewall of the main body stent graft between the first end and the second end of the main body stent graft, where the diaphragm is disposed within the lumen of the main body stent graft, and where the at least three openings of the diaphragm comprise a first opening, a second opening, a third opening and a fourth opening. 
     In a fourth aspect, a method for placement of the stent graft is provided including the steps of (a) introducing a guidewire into any appropriately sized arterial configuration via arterial access, (b) loading a delivery catheter containing the stent graft according to the first aspect onto the guidewire, (c) moving the delivery catheter along the guidewire and introducing the delivery catheter into the appropriately sized arterial configuration via arterial access, and (d) deploying the stent graft into the appropriately sized arterial configuration and/or a lumen of a previously-placed stent graft. 
     In a fifth aspect, a stent graft includes the features of (a) a main body stent graft defining a lumen having a first end and a second end, (b) a diaphragm coupled to the main body stent graft, where the diaphragm defines a first opening, a second opening and a third opening, (c) a first stent graft extension having a first end and a second end, where the first stent graft extension has a single lumen, where the first end of the first stent graft extension is coupled to the diaphragm and arranged surrounding the first opening, (d) a second stent graft extension having a first end and a second end, where the second stent graft extension has a single lumen at the first end and has a bifurcation defining two lumens at the second end, where the first end of the second stent graft extension is coupled to the diaphragm and arranged surrounding the second opening and (e) a third stent graft extension having a first end and a second end, where the third stent graft extension has a single lumen at the first end and where the first end of the third stent graft extension is coupled to the diaphragm and arranged surrounding the third opening. 
     In a sixth aspect, a stent graft includes the features of (a) a main body stent graft that defines a lumen with first and second ends, (b) a diaphragm coupled to the main body stent graft within the lumen, where the diaphragm defines at least three openings, (c) at least three stent graft extensions each defining a lumen, where a first end of each of the at least three stent graft extensions is coupled to one of the at least three openings, (d) a visceral vessel opening defined in the sidewall of the main body stent graft, (e) two renal openings defined in the sidewall of the main body stent graft distal to the diaphragm and (f) permeable membrane material covering at least one of the visceral vessel opening and the two renal openings. 
     These as well as other aspects, advantages, and alternatives, will become apparent to those of ordinary skill in the art by reading the following detailed description, with reference where appropriate to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a front view of the stent graft according to one example embodiment. 
         FIG. 2  is a cross-sectional side view of Section A:A from  FIG. 1 . 
         FIG. 3  is a back view of the stent graft according to the example embodiment of  FIG. 1 . 
         FIG. 4  is a side view of the stent graft according to the example embodiment of  FIG. 1 . 
         FIG. 5  is a cross-sectional top view of Section B:B from  FIG. 4 . 
         FIG. 6  is a top view of the stent graft according to the example embodiment of  FIG. 1 . 
         FIG. 7A  is a front view of the stent graft according to a second example embodiment. 
         FIG. 7B  is a front view of the stent graft according to the second example embodiment having a fifth opening coupled to stent extension graft. 
         FIG. 8A  is a side view of the stent graft according to the example embodiment of  FIG. 7A . 
         FIG. 8B  is a side view of the stent graft according to the example embodiment of  FIG. 7B . 
         FIG. 9  is a top view of the stent graft according to a third example embodiment. 
         FIG. 10  is a side cross-sectional view of the stent graft according to the example embodiment of  FIG. 9 . 
         FIG. 11  is a top view of the stent graft according to a fourth example embodiment. 
         FIG. 12  is a front view of the stent graft according to the example embodiment of  FIG. 11 . 
         FIG. 13A  is a side view of the stent graft according to the example embodiment of  FIG. 11 . 
         FIG. 13B  is a side view of the stent graft according to the example embodiment of  FIG. 11  further including a visceral vessel opening having an inverted U-shape defined in the sidewall of the main body stent graft. 
         FIG. 14  is a top view of the stent graft according to a fifth example embodiment. 
         FIG. 15  is a front view of the stent graft according to the example embodiment of  FIG. 14 . 
         FIG. 16  is a top view of the stent graft according to a sixth example embodiment. 
         FIG. 17  is a cross-sectional front view of the abdominal aorta with a perspective view of the stent graft according to the example embodiment of  FIG. 1  in an expanded condition. 
         FIG. 18  is a cross-sectional front view of the abdominal aorta with a perspective view of the stent graft according to the example embodiment of  FIG. 11  in an expanded condition. 
         FIG. 19  is a cross-sectional front view of the aortic arch with a perspective view of the stent graft according to the example embodiment of  FIG. 11  in an expanded condition. 
         FIG. 20  is a cross-sectional front view of the abdominal aorta with a perspective view of the stent graft according to the example embodiment of  FIG. 14  in an expanded condition. 
         FIG. 21  is a cross-sectional front view of the abdominal aorta with a perspective view of the stent graft according to the example embodiment of  FIG. 7  in an expanded condition. 
         FIG. 22  is a cross-sectional front view of the abdominal aorta with a perspective view of the stent graft according to the example embodiment of  FIG. 16  in an expanded condition. 
         FIG. 23  is a cross-sectional front view of the abdominal aorta with a perspective view of the stent graft according to the example embodiment of  FIG. 13B  in an expanded condition. 
         FIG. 24  is a side view of the stent graft according to a seventh example embodiment. 
         FIG. 25A  is a perspective view of the stent graft according to an eighth embodiment. 
         FIG. 25B  is a top view of the stent graft according to the example embodiment of  FIG. 25A . 
         FIG. 26A  is a perspective view of the stent graft according to a ninth embodiment. 
         FIG. 26B  is a top view of the stent graft according to the example embodiment of  FIG. 26A . 
         FIG. 27A  is a perspective view of the stent graft according to a sixth aspect. 
         FIG. 27B  is a top view of the stent graft according to the example embodiment of  FIG. 27A . 
     
    
    
     DETAILED DESCRIPTION 
     Example stent grafts, as well as methods of placement of the stent grafts, are described herein. Any example embodiment or feature described herein is not necessarily to be construed as preferred or advantageous over other embodiments or features. The example embodiments described herein are not meant to be limiting. It will be readily understood that certain aspects of the disclosed methods can be arranged and combined in a wide variety of different configurations, all of which are contemplated herein. 
     Furthermore, the particular arrangements shown in the Figures should not be viewed as limiting. It should be understood that other embodiments may include more or less of each element shown in a given Figure. Further, some of the illustrated elements may be combined or omitted. Yet further, an example embodiment may include elements that are not illustrated in the Figures. 
     As used herein, “about” means+/−5%. 
     As used herein, diameter ranges pertain to an unconstrained, ex vivo state of the stent graft and stent graft extensions. When the stent graft and stent graft extensions are in a deployed, in vivo state the diameter ranges will be on the order of about 10-20% smaller in diameter than the ex vivo state. 
     As used herein, “pararenal” means a region adjacent to the kidney. 
     As used herein, “infrarenal” means situated or occurring below the kidneys. 
     As used herein, “visceral trunk” refers to the portion of the aorta attached to the renal arteries, superior mesenteric artery (“SMA”), and the celiac artery. 
     As used herein, “proximal end” refers to the end of the main body stent graft that will be positioned closer to a patient&#39;s heart than the “distal end” upon deployment. 
     As used herein, a “sealing ring” is a structure configured to apply an outward circumferential force to create a fluid tight seal. In some embodiments, this circumferential force may be applied laterally against the sidewall of the main body stent graft. In other embodiments, the circumferential force may be applied to maintain a hole or opening in a sidewall of the main body stent graft both in an open condition and in contact with vasculature. A sealing ring may be circular or oval, may be continuous or discontinuous, and/or may be contoured or have a bi-level shape to accommodate indentations or scallop-shaped holes in the sidewall of the main body stent graft, among other possibilities. The sealing rings may include elastic recoil material, such as nitinol, a standard stent structure or a straight reinforced wire, an injectable sealing agent that may form a sealing structure similar to a gasket or “0” ring among other possibilities. 
     As used herein, “passive fixation” refers to friction, interaction between the cloth of the grafts, radial strength of the stent structure and blood pressure that holds the component stent grafts together at the site of overlap. 
     As used herein, “active fixation” refers to features coupled to a stent, graft, or stent graft that may actively engage vasculature or another stent graft, including hooks, bi-directional hooks, stent structure elements, anchors, staples, bio-activated adhesive, or a combination thereof, among other possibilities. 
     As used herein, “string” refers to a low friction material such as GORE-TEX® Suture, for example. 
     As used herein, with respect to measurements, “about” means+/−5%. 
     As used herein, a “stent graft” is a tubular, radially-expandable device comprising a fluid-tight (i.e., blood-tight) fabric supported by a stent and may be used to bridge diseased arteries. Such stent grafts and methods for their deployment and use are known to those of skill in the art. For example, vascular sheaths can be introduced into the patient&#39;s arteries, through which items, including but not limited to, guidewires, catheters and, eventually, the stent graft, are passed. 
     As used herein, “stent” is typically a cylindrical frame and means any device or structure that adds rigidity, expansion force, or support to a prosthesis or native vasculature, while “stent graft” refers to a prosthesis comprising a stent and a graft material associated therewith that forms a fluid-tight lumen through at least a portion of its length. As used herein, “fluid tight” means a barrier that is configured to prevent or, upon deployment in vivo, becomes able to prevent blood or blood products (i.e. serum and its contents) from passing through, thus preventing an endoleak. For example, the stent structure may comprise coiled, mesh, zig-zag or woven wires or a laser cut tube. A “graft” is a substantially cylindrical liner or a non-linear graft in a tapered configuration that may be disposed on the stent&#39;s interior, exterior or both. In some embodiments, grafts may be woven as unitary structures with multiple lumens. For example, the main body stent graft, the diaphragm, the two renal lumens, the infrarenal lumen and the visceral chamber may all be woven together as a unitary structure or otherwise joined together to form a unitary structure. Further, when used in combination with a graft, the stent structure may further comprise a series of spaced apart stent rings disposed along the graft. A wide variety of attachment mechanisms are available to join the stent and graft together, including but not limited to, sutures, adhesive bonding, heat welding, and ultrasonic welding. 
     The stent can be made of any suitable material, including but not limited to biocompatible metals, implantable quality stainless steel wires, nickel and titanium alloys, and biocompatible plastics attached to a graft. Any suitable fluid tight (i.e., blood-tight) graft material can be used. In a preferred embodiment, the graft material is a biocompatible fabric, including but not limited to woven or knitted polyester, such as poly(ethylene terephthalate), polylactide, polyglycolide and copolymers thereof; fluorinated polymers, such as PTFE, expanded or electrospun PTFE and poly(vinylidene fluoride); polysiloxanes, including polydimethyl siloxane; and polyurethanes, including polyetherurethanes, polyurethane ureas, polyetherurethane ureas, polyurethanes containing carbonate linkages, woven nickel-titanium and polyurethanes containing siloxane segments. Materials that are not inherently biocompatible may be subjected to surface modifications in order to render the materials biocompatible. Examples of surface modifications include graft polymerization of biocompatible polymers from the material surface, coating of the surface with a crosslinked biocompatible polymer, chemical modification with biocompatible functional groups, and immobilization of a compatibilizing agent such as heparin or other substances. The graft material may also include extracellular matrix materials. 
     The covered stent grafts can be made of any suitable material, including but not limited topolytetrafluoroethylene (ePTFE) lined nickel-titanium alloy stent. The stent grafts are preferably covered and flexible. The stent grafts may contain any other suitable components, such as surface modifications including but not limited to covalent attachment of heparin. 
     In a first aspect, shown in  FIGS. 9-16 , the invention provides a stent graft, comprising: 
     a main body stent graft defining a lumen having a first end and a second end; 
     a diaphragm coupled to the main body stent graft, wherein the diaphragm defines at least three openings; and 
     at least three stent graft extensions each defining a lumen, wherein a first end of each of the at least three stent graft extensions is coupled to one of the at least three openings. 
     Referring now to  FIGS. 9-16 , a stent graft  200  is shown including a main body stent graft  205  defining a lumen that has a first end  207  and a second end  209 . In one embodiment, the first end  207  of the main body stent graft  205  may be the proximal end of the stent graft  200  configured to be positioned closer to a patient&#39;s heart than the second end  209  or distal end of the main body stent graft  205  upon deployment. The diaphragm  210  may be coupled to the main body stent graft  205  at a location within the lumen or at the first end  207  or the second end  209 . In one embodiment, the diaphragm  210  may be coupled to the main body stent graft  205  at a location ranging from the second or distal end  209  of the main body stent graft  205  up to a midsection of the main body stent graft  205 . This arrangement may beneficially permit pressure from blood flow to act upon the proximal sidewall of the main body stent graft above the diaphragm, which may aid in sealing and fixation of the stent graft to the lumen in which it is deployed. 
     The diaphragm  210  defines at least three openings. For example, in one embodiment, the diaphragm  210  may define a first opening  230  coupled to a first stent graft extension  231 , a second opening  235  coupled to a second stent graft extension  236 , a third opening  220  coupled to a third stent graft extension  221  and a fourth opening  225  coupled to a fourth stent graft extension  226 . In various embodiments, the first opening  230  may be used to receive a bridging stent for placement in the infrarenal segment of the aorta or other native vessel, the second opening  235  may be used to receive a bridging stent for placement in the celiac and SMA or other native vessel, the third and fourth openings  220 ,  225  may be used to receive a bridging stent for placement in the renal arteries or other native vessel. Alternatively, the first opening  230  may be used to receive a bridging stent for placement in the aortic arch, the second opening  235  may be used to receive a bridging stent for placement in the innominate (right common carotid artery and the right subclavian artery) or other native vessel, the third and fourth openings  220 ,  225  may be used to receive a bridging stent for placement in the left common carotid artery and the left subclavian artery or other native vessel. 
     In one embodiment, shown in  FIG. 11 , the first opening  230  may have a diameter larger than a diameter of the second opening  235 . In another embodiment, shown in  FIG. 11 , the diameter of the second opening  235  may be larger than a diameter of the third opening  220  and a diameter of the fourth opening  225 . In an alternative embodiment, shown in  FIGS. 9 and 14 , the second opening  235 , the third opening  220  and the fourth opening  225  may each have the same size diameter. In yet another embodiment shown in  FIG. 11 , the first opening  230  and the second opening  235  may be defined on opposite sides of the diaphragm  210 . In a still further embodiment, the first opening  230 , the second opening  235 , the third opening  220  and the fourth opening  225  may each be defined in different quadrants  211 - 214  of the diaphragm  210 , as shown in  FIG. 11 . 
     In further embodiments shown in  FIGS. 9, 14 and 16 , a fifth opening  237  may also be defined in the diaphragm  210  and coupled to a fifth stent graft extension  238 . In one embodiment, the fifth opening  237  may be used to receive a bridging stent for placement in the celiac and SMA or other native vessel. In one embodiment, the first opening  230  may have a diameter larger than a diameter of the second opening  235  and a diameter of the fifth opening  237  (see  FIGS. 9, 14 and 16 ). In a further embodiment shown in  FIG. 16 , the diameter of the second opening  235  and the diameter of the fifth opening  237  may be larger than a diameter of the third opening  220  and a diameter of the fourth opening  225 . In alternative embodiments, as shown in  FIGS. 9 and 14 , the diameter of the second opening  235  and the diameter of the fifth opening  237  may have the same dimension as a diameter of the third opening  220  and a diameter of the fourth opening  225 . In one embodiment, the first opening  230 , the second opening  235  and the fifth opening  237  may be arranged linearly in the diaphragm  210 , and the third opening  220  and the fourth opening  225  may be arranged on opposite sides of each of the first, second and fifth openings  230 ,  235 ,  237 , as shown in  FIG. 16 . In addition, as shown in  FIG. 9 , the third opening  220  and the fourth opening  225  may be arranged adjacent to each other and may be arranged together on a side of the diaphragm  210  opposite to the first opening  230 . Still further, in one embodiment, the first opening  230  may be arranged in a first quadrant  211  of the diaphragm  210 , the third opening  220  may be arranged in a second quadrant  212  of the diaphragm, the second opening  235  and the fifth opening  237  may be arranged in a third quadrant  213  of the diaphragm and the fourth opening  225  may be arranged in a fourth quadrant  214  of the diaphragm  210 , as shown in  FIG. 14 . 
     In yet another embodiment, at least a portion of the diaphragm  210  may be angled relative to a sidewall  218  of the main body stent graft  205  toward the second end  209  of the main body stent graft  205 . In one embodiment, as shown in  FIGS. 9-10 , the openings  220 ,  225 ,  230  in the diaphragm  210  may be defined in the center of the diaphragm  210 , and the diaphragm  210  may be substantially funnel-shaped. In a further embodiment, an end of at least one of the stent graft extensions may be tapered adjacent to the diaphragm  210 , as shown and described with respect to the first aspect of the invention. This arrangement may aid with guidewire alignment and entry into the respective lumens of the stent graft extensions in order to place extension or bridging stents and may encourage laminar blood flow. 
     In addition, in one embodiment, the openings of the diaphragm  210  may be reinforced to mate with bridging stent grafts or extension stent grafts, for example. The reinforcement material may include nitinol, for example, or any nonextendible, collapsible material that is biocompatible. In a further embodiment, the diaphragm  210  may have an expandable frame that may be configured to apply an outward radial force to the main body stent graft  205 , as discussed with respect to the first aspect of the invention. This frame may aid with fixation and seal with a vessel lumen. 
     In one embodiment, the diameter of the main body stent graft  205  may range from about 20 mm to about 65 mm, and preferably in the visceral segment from about 23 mm to about 40 mm or from about 28 mm to about 36 mm and preferably in the thoracic aorta from about 30 mm to about 65 mm or from about 40 mm to about 55 mm. In addition, the length of the main body stent graft  205  may range from about 10 mm to about 150 mm and preferably from about 20 mm to about 60 mm. Further, each of the second stent graft extension  236  and the fifth stent graft extension  238  may have a length ranging from about 0.5 mm to about 40 mm, in on example. In yet another embodiment, each of a diameter of the second stent graft extension  236  and a diameter of the fifth stent graft extension  238  may range from about 6 mm to about 14 mm. 
     In one embodiment, the first stent graft extension  231  may have a length of at least 30 mm and may have a diameter ranging from about 8 mm to about 25 mm. In another embodiment, the first opening  230  may have a diameter ranging from about 8 mm to about 25 mm. In a further embodiment the third opening  220  and the fourth opening  225  may each have a diameter ranging from about 4 mm to about 25 mm. In another embodiment, the third stent graft extension  221  and the fourth stent graft extension  226  may each have a diameter ranging from about 4 mm to about 12 mm. 
     The stent graft  200  may also include a plurality of sealing rings coupled to the main body stent graft  205 , as discussed above with respect to the first aspect of the invention. For example, in one embodiment, the plurality of sealing rings may include a proximal sealing ring  245  coupled to the main body stent graft  205  at or directly adjacent to the first end  207 . In one embodiment, the proximal sealing ring  245  may have a bi-level construction defining an upper portion and a lower portion. In an alternative embodiment, the proximal sealing ring may be ring-shaped. 
     In one embodiment, shown in  FIGS. 13B and 23 , the stent graft may include a visceral vessel opening  175  having an inverted U-shape defined in the sidewall of the main body stent graft  205  and extending from the diaphragm  210  to the second end  209  of the main body stent graft  205 . The visceral opening may advantageously avoid blocking blood flow and permit access to the celiac and SMA arteries. In a further embodiment, the plurality of sealing rings may include a distal sealing ring  176  coupled to the main body stent graft  205  between the diaphragm  210  and the second end  209  of the main body stent graft  205 . The distal sealing ring  276  may have a radial portion  277  arranged about a portion of the circumference of the main body stent graft  205  and an arch portion  278  aligned with the visceral vessel opening  275 . In one embodiment, each end of the radial portion  277  of the distal sealing ring  276  may transition to the arch portion  278  via two curved segments  279  each having a radius of curvature ranging from about 20 mm to about 50 mm. In still another embodiment, the length of the main body stent graft  205  between the first end  207  and the diaphragm  210  may range from about 10 mm to about 150 mm. In a further embodiment, the length of the main body stent graft  205  from the diaphragm  210  to the second end  209  of the main body stent graft  205  may range from about 0.05 mm to about 40 mm. 
     In another embodiment, as discussed below with respect to the second aspect of the invention, a pair of opposing helical stent structures may be coupled to one or more of the first stent graft extension  231 , the second stent graft extension  236 , the third stent graft extension  221 , the fourth stent graft extension  226  and the fifth stent graft extension  238 . 
     In still another embodiment, the first end  207  of the main body stent graft  205  may be coupled to a fixation stent, as described below with respect to the second aspect of the invention. 
     In an alternative embodiment, shown in  FIG. 19 , the stent graft may include a stent valve  280  affixed to the first end  207  of the main body stent graft  205 . In this arrangement, a free end of the stent valve may be covered and a portion of the stent valve extending between the free end and the main body stent graft  205  may be uncovered. As used herein, a “stent valve” is a percutaneous self-expanding valve affixed to a proximal or first end  207  of the main body stent graft  205  with the uncovered portion overlaying the coronary arteries to maintain blood flow. An exemplary embodiment of the stent valve includes the Corevalve® manufactured by Medtronic. In one embodiment, the free end of the stent valve may be covered with an impervious natural or synthetic material. In one embodiment, the stent valve may be placed in the outflow tract of the aortic valve. The stent valve&#39;s anchoring mechanism is derived from, for example, a funnel shape with a larger diameter at the free end and smaller diameter at the point where the covered portion meets the uncovered portion. 
     In a second aspect, the stent graft provides: 
     a main body stent graft defining a lumen having a first end and a second end; 
     a diaphragm coupled to the main body stent graft, wherein the diaphragm defines at least three openings; 
     at least three stent graft extensions each defining a lumen, wherein a first end of each of the at least three stent graft extensions is coupled to one of the at least three openings; 
     a visceral-vessel opening defined in a sidewall of the main body stent graft between the first end and the second end of the main body stent graft, wherein the diaphragm is disposed within the lumen of the main body stent graft, wherein the at least three openings of the diaphragm comprise a first opening, a second opening, a third opening and a fourth opening; and a visceral chamber defined by a sidewall coupled to one of the second opening and the diaphragm and to one of the visceral-vessel opening and the sidewall of the main body stent graft. 
     Referring now to  FIGS. 1-6 , a stent graft  100  is shown including a main body stent graft  105  defining a lumen having an inlet  106  defined at a first or proximal end  107  of the main body stent graft  105  and having an outlet  108  defined at a second or distal end  109  of the main body stent graft  105 . In one embodiment, a portion of the lumen of the main body stent graft  105  arranged between the diaphragm  110  and the proximal end  107  of the main body stent graft  105  may have a diameter ranging from about 20 mm to about 65 mm and preferably from about 20 mm to about 46 mm. In another embodiment, the main body stent graft  105  may have a length ranging from about 10 mm to about 150 mm extending between the first end  107  of the main body stent graft  105  and the first end  116  of the visceral-vessel opening  115 . In a further embodiment, the main body stent graft  105  may have a length ranging from 0 mm to about 40 mm extending between the second or distal end  117  of the visceral-vessel opening  115  and the second end  109  of the main body stent graft  105 . 
     The stent graft  100  includes a diaphragm  110  disposed within the lumen of the main body stent graft  105  and coupled to the main body stent graft  105 . The diaphragm  110  defines a first opening  130 , a second opening  135 , a third opening  120  and a fourth opening  125 . In one embodiment, the first opening  130  may be used to stent the infrarenal segment, the second opening  135  may be used stent the celiac and SMA arteries, the third opening  120  and the fourth opening  125  may be used to stent the renal arteries. The second opening  135  may be aligned in a quadrant of the diaphragm  110  that lies above the visceral-vessel opening  115 , discussed in more detail below, and the first opening  130  and the third and fourth openings  120 ,  125  may be arranged in various configurations in the same or other quadrants of the diaphragm  110 . For example, in one embodiment, as shown in  FIG. 6 , the first opening  130  and the second opening  135  may be arranged on opposite sides of the diaphragm  110  with the third opening  120  and the fourth opening  125  likewise arranged on opposite sides of the diaphragm  110  between the first opening  130  and the second opening  135 . Alternatively, the third and fourth openings  120 ,  125  may be arranged on the same side of the diaphragm  110  between the first opening  130  and the second opening  135 . In other embodiments, the first opening  130  and one of the third and fourth openings  120 ,  125  and may be arranged on opposite sides of the diaphragm  110  with the other opening arranged therebetween. In a further embodiment, the first opening  130  and the third and fourth openings  120 ,  125  may be arranged such that there is no other inlet directly opposite the second opening  135 . 
     In one embodiment, the diaphragm  110  may be sloped or tapered in the regions surrounding these various openings. In one embodiment, the second opening  135  may be defined as a V-shape, a half-circle having a radius ranging from about 5 mm to about 15 mm or a complete circular opening with a diameter ranging from about 6 mm to about 20 mm, among other possibilities. In further embodiments, the third opening  120 , fourth opening  125 , first opening  130  may have a substantially circular shape. In one embodiment, three stent graft extensions  121 ,  126  and  131  may be directly coupled to the third opening  120 , the fourth opening  125  and the first opening  130 , respectively, in fluid-tight (blood-tight) manner prior to deployment of the stent graft  100 . These stent graft extensions  121 ,  126 ,  131  each define a lumen and are configured to receive extension or bridging stent grafts that may be held in place via passive or active fixation. This arrangement may provide blood flow between the stent graft  100  and the renal arteries and or may provide blood flow to the infrarenal arteries including, for example, the aorta and the common iliac arteries. 
     In various embodiments, the stent graft extensions  121 ,  126 ,  131  may be straight or gradually sweeping and their distal free ends  123 ,  128 ,  133  may be freely movable to place bridging stent grafts. In one embodiment, the stent graft extension  131  coupled to the first opening  130  may have a length of at least 30 mm and, in another embodiment, may have a length that ranges from about 10 mm to 120 mm. And in another embodiment, the stent graft extension  131  may have a diameter ranging from about 8 mm to about 25 mm. In another embodiment, the first opening  130  may have a diameter ranging from about 8 mm to about 25 mm. In yet another embodiment, the diameter of the first opening  130  may be larger than the diameter of the stent graft extension  131  coupled thereto such that a first or proximal end of the stent graft extension  131  is tapered  132 . In other embodiments, the third and fourth openings  120 ,  125  may each have a diameter ranging from about 4 mm to about 25 mm. In one embodiment, the stent graft extensions  121 ,  126  coupled to the third and fourth openings may each have a diameter ranging from about 4 mm to about 18 mm. In a further embodiment, the diameter of each of the third and fourth openings  120 ,  125  may be larger than the diameter of each of the stent graft extensions  121 ,  126  coupled thereto such that a first or proximal end of each of the stent graft extensions  121 ,  126  is tapered  122 ,  127 . Tapering from the diaphragm openings to the various stent graft extensions may aid with guidewire alignment and entry into the respective lumens to place extension or bridging stents and may encourage laminar blood flow. In another embodiment, the stent graft extensions  121 ,  126  and  131  may be placed separately after deployment. In this embodiment, the stent graft extensions  121 ,  126 ,  131  may have flared proximal ends that are arranged proximal of the diaphragm upon deployment. 
     In one embodiment, a pair of opposing helical stent structures may be coupled to and extend along the length of one or more of the stent graft extensions  121 ,  126  and  131 . The helical stent structures may advantageously prevent elongation of the lumens. These helical stent structures may be made from biocompatible materials with elastic shape memory, such as nitinol, stainless steel, plastics, polymers or any combination of such materials, among other possibilities. 
     In a further embodiment, according to the first, second and third aspects of the present disclosure, the diaphragm  110  may have an expandable frame  111 . This expandable frame  111  may be configured to apply an outward radial force to the main body stent graft  105  in response to a downward force applied to the diaphragm  110 . The downward force may be due to blood flow, for example. In one embodiment, the diaphragm  110  may be positioned within the lumen of the main body stent graft  105  at or between a first end  116  of the visceral-vessel opening  115  and a second end  117  of the visceral-vessel opening  115 . 
     The stent graft  100  also includes a visceral-vessel opening  115  defined in a sidewall  118  of the main body stent graft  105  between the first end  107  and the second end  109  of the main body stent graft  105 . In one embodiment, the visceral-vessel opening  115  may have a height ranging from about 10 mm to about 60 mm and may have a width ranging from about 5 mm to about 30 mm. In one embodiment, the visceral-vessel opening may be wider at a first or proximal end than at a second or distal end, which may provide more graft surface area between the visceral-vessel opening  115  and two renal openings  170  to provide a more robust seal between the stent graft and vasculature. In another embodiment, the visceral-vessel opening  115  may be covered with a flow-diverting material, for example, a high pick density braided or woven self-expanding stent material. This flow-diverting material may allow patency to the visceral vessels, for example, while minimizing the degree of unstented aortic wall to aid in anchoring and seal between the pararenal stent graft within vasculature. This may provide a more robust seal between the stent graft and aorta. The flow-diverting material may also permit formation of thrombus and arterial development therethrough, which may aid in appropriate blood flow and blood pressure through this region of the main body stent graft  105 . 
     In addition, the stent graft  100  includes a visceral chamber  140  defined by a sidewall  141  coupled to one of the diaphragm  110  and the second opening  135  and to one of the sidewall of the main bode stent graft and the visceral-vessel opening. The visceral chamber  140  may provide blood flow to the SMA and celiac arteries. In addition, a surgeon may utilize the visceral chamber  140  to place bridging stents in the SMA and/or celiac arteries 
     In one embodiment, the stent graft  100  may further include a plurality of sealing rings coupled to the main body stent graft  105 . In another embodiment, the plurality of sealing rings may include a proximal sealing ring  145  coupled to the main body stent graft  105  at or directly adjacent to the first end  107  of the main body stent graft  105 . In a further embodiment, the proximal sealing ring  145  may have a bi-level construction defining an upper portion  146  and a lower portion  147 . The lower portion  147  of the proximal sealing ring  145  may be aligned with and arranged proximal to the visceral-vessel opening  115 , and the lower portion  147  may be arranged distal to the upper portion  146  of the proximal sealing ring  145 . In one embodiment, the upper portion  146  of the proximal sealing ring  145  may be longitudinally spaced apart from the lower portion  147  along the main body stent graft  105  by a distance ranging from about 0 mm to about 40 mm. In the bi-level embodiment, a peripheral edge  104  of the first end  107  of the main body stent graft  105  may have the same bi-level contour as the proximal sealing ring  145 . In one embodiment, the main body stent graft  105  may have a length ranging from about 0 mm to about 20 mm extending between the lower portion  147  of the proximal sealing ring  145  of the main body stent graft  105  and the first end  116  of the visceral-vessel opening  115 . 
     The graft material of the main body stent graft  105  may have the same boundary as the proximal sealing ring  145  to avoid covering the lumbar arteries that deliver blood to the spine. In other embodiments, the graft material may have a uniform circumference along the upper boundary of the proximal sealing ring  145 . In still further embodiments, the graft material may extend beyond the upper proximal boundary of the proximal sealing ring  145  to the top or proximal edge of a fixation stent  150 . 
     In another embodiment, the plurality of sealing rings may include a visceral-vessel sealing ring  155  coupled to the main body stent graft  105  such that the visceral-vessel sealing ring  155  surrounds the visceral-vessel opening  115 . For example, the visceral-vessel sealing ring  155  may apply a circumferential force to keep the visceral-vessel opening  115  intact upon deployment providing a fluid tight seal about the SMA and celiac arteries. The plurality of sealing rings may also include at least one support sealing ring  160  coupled to the main body stent graft  105  such that a first end  161  of the at least one support sealing ring  160  is coupled to a first side of the visceral-vessel sealing ring  155  and a second end  162  of the at least one support sealing ring  155  is coupled to a second side of the visceral-vessel sealing ring  155 . The visceral-vessel sealing ring  155  may also work in combination with the support sealing ring  160  to provide a circumferential radial force relative to the main body stent graft  105  to provide a fluid tight (i.e., blood-tight) seal with the aorta, for example. In a further embodiment, the at least one support sealing ring  160  may include a proximal support sealing ring  163 , a distal support sealing ring  164  and a central support sealing ring  160 . In one embodiment, the central support sealing ring  160  may be coupled to the visceral vessel sealing ring  155 . The proximal support sealing ring  163  may be coupled to the main body stent graft  105  between the first end  107  of the main body stent graft  105  and the central support sealing ring  160 . And the distal support sealing ring  164  may be coupled to the main body stent graft  105  between the second end  109  of the main body stent graft  105  and the central support sealing ring  160 . 
     In still another embodiment, the plurality of sealing rings may include a distal sealing ring  165  coupled to the main body stent graft  105  at or directly adjacent to the second end  109  of the main body stent graft  105 . In one embodiment, two renal openings  170  may be defined in the sidewall  118  of the main body stent graft  105  distal to the diaphragm  110 . In one embodiment, the distal sealing ring  165  may have two radial portions  166  joined by two arch portions  167 . The two arch portions  167  may be arranged longitudinally along the sidewall  118  of the main body stent graft  105  and the two radial portions  166  are arranged about the circumference of the main body stent graft  105 . The two arch portions  167  are aligned with the two renal openings  170 . In one embodiment, an effective diameter extending between the two radial portions  166  of the distal sealing ring  165  may range from about 20 mm to about 50 mm. In one embodiment, the two arch portions  167  may have a width ranging from about 4 mm to about 30 mm. In an embodiment in which renal openings  170  are not provided in the sidewall  118  of the main body stent graft  105 , the length of the main body stent graft  105  may be shortened to permit the renal stent grafts to exit from the second end  109  such that they are able to have a gentle sweep or large radius of curvature from the renal inlet and the target vessel ostium when bridging stents are placed. In still another embodiment, shown in  FIGS. 7A-8B , the two renal openings  170  in the sidewall of the main body stent graft may be fenestrations sized and shaped to allow access to the native arteries. 
     In one embodiment, applicable to the first, second and third aspects of the present disclosure, a bridging stent graft may comprise spaced-apart stent rings coupled to two wires longitudinally disposed along the length of and on opposite sides of the bridging stent graft in a helical shape. This arrangement may beneficially prevent elongation of the bridging stent graft. An appropriate overlap with the stent graft extensions  121 ,  126  coupled to the third and fourth openings  120 ,  125  or stent graft extension  131  coupled to the first opening  130  may be adequate to achieve passive fixation with a bridging stent graft during stent graft debranching procedures. The length of this overlap region may be less if active fixation features are also employed with the stent grafts, for example. 
     In a third aspect, the stent graft provides: 
     a main body stent graft defining a lumen having a first end and a second end; 
     a diaphragm coupled to the main body stent graft, wherein the diaphragm defines at least three openings; and 
     at least three stent graft extensions each defining a lumen, wherein a first end of each of the at least three stent graft extensions is coupled to one of the at least three openings; and 
     a visceral-vessel opening defined in a sidewall of the main body stent graft between the first end and the second end of the main body stent graft, wherein the diaphragm is disposed within the lumen of the main body stent graft, and wherein the at least three openings of the diaphragm comprise a first opening, a second opening, a third opening and a fourth opening. 
     Referring now to  FIGS. 7A and 7B , a stent graft  100  is shown including a main body stent graft  105  defining a lumen having first end  107  and a second  109  that may correspond to a proximal end and a distal end, respectively, in one embodiment. A visceral-vessel opening  115  is defined in a sidewall of the main body stent graft  105  between the first end  107  and the second end  109  of the main body stent graft  105 . In addition, a diaphragm  110  is disposed within the lumen of the main body stent graft  105  and coupled to the main body stent graft  105 . The diaphragm defines a first opening, a second opening, a third opening and a fourth opening. In one embodiment, each of the openings may receive a bridging stent, for example, and couple the infrarenal segment to the first opening  130 , couple the celiac and SMA arteries to the second opening  135  and couple the couple the renal arteries to the third and fourth openings  120 ,  125 . 
     In one embodiment, a visceral chamber  140  may be defined by the diaphragm  110 , the sidewall of the main body stent graft  105  and a visceral sidewall  141  extending between the diaphragm  110  and the sidewall of the main body stent graft  105 . In another embodiment, a fifth opening  137  is defined in the diaphragm between the visceral sidewall and the sidewall of the main body stent graft  105 . This fifth opening  137  may beneficially permit blood flow to the celiac and SMA arteries while the second opening  135  is being actively stented or otherwise blocked and vice versa. The fifth opening  137  may also allow for more than one of the celiac and SMA arteries to be bridged with stents grafts. 
     The second and fifth openings  135 ,  137  are defined in the diaphragm  110  between the visceral sidewall  141  and the sidewall of the main body stent graft  105 . The visceral sidewall  141  surrounds a portion of the visceral-vessel opening  115  defined between the second end  109  of the main body stent graft  105  and the diaphragm  110 . 
     In one embodiment, the second opening  135  and the fifth opening  137  may be arranged adjacent to each other. In another embodiment, the second opening  135  may be coupled to a stent graft extension  136  defining a lumen, and the fifth opening  137  may also be coupled to a stent graft extension  138  defining a lumen. In further embodiments, each of the stent graft extensions coupled to one of the second and fifth openings may have a diameter ranging from about 6 mm to about 14 mm and may have a length ranging from about 0.5 mm to about 40 mm. 
     In a further embodiment, one or more of the first  130 , second  135 , third  120 , fourth  125  and fifth  137  openings may be reinforced. 
     In one embodiment, shown in  FIG. 24  and applicable to all of the aspects of the present disclosure, the stent graft  300  includes a plurality of anchors  385  that each define an eyelet. The plurality of anchors  385  are arranged longitudinally at intervals along the main body stent graft  305 . In a further embodiment, the stent graft  300  includes a string  386  having a first end  387  and a second end  388 . The string  386  may be slidably disposed through the eyelets of the plurality of anchors  385  such that the main body stent graft  305  has a partially-expanded condition and a fully-expanded condition. In the partially-expanded condition, the string  386  may be under tension and the first end  387  of the string may be fixedly coupled to a first anchor  390  of the plurality anchors  385  and the second end  388  of the string  386  may be releasably coupled to a second anchor  391  of the plurality of anchors. In the fully-expanded condition (see  FIG. 24 ), the second end of the string  388  may be released from the second anchor  391  and the string  386  may be untensioned. 
     In one embodiment, the main body stent graft  305  may expand from 50% to 95% of the fully-expanded diameter in the partially-expanded condition. As such, the partially-expanded condition may enable the stent graft to be deployed into a lumen and then subsequently repositioned. For example, the smaller diameter of the partially-expanded stent graft may permit the stent graft to be moved proximally and distally to the desired location in the lumen and rotated for alignment with appropriate branch vasculature. Once in position, the releasable end  388  of the string  386  may be decoupled from an anchor  391 , as described below, and the stent graft  300  may transition into the fully-expanded condition due to shape memory of stents or balloon expansion, for example. 
     In another embodiment, the plurality of anchors may be arranged on a side of the main body stent graft opposite to a visceral-vessel opening. In a further embodiment, the plurality of anchors may be arranged as laterally opposed pairs (see  FIG. 24 ). In another embodiment, the plurality of anchors may be arranged in a zig-zag pattern. 
     In one embodiment, the eyelets of the plurality of anchors  385  and the string  386  may be made of a low-friction material to enable the stent graft  300  to transition from the partially-expanded condition to the fully-expanded condition. 
     The stent grafts of the present disclosure may contain any further suitable components, including but not limited to radiopaque markers to aid in visualization and to facilitate accurate placement of the stent graft. These radiopaque markers may take the form of gold bands at the distal end of each individual lumen of a given stent graft or a directional marker, for example in the shape of an “S” or any other suitable form for indicating direction and orientation of the stent graft. In one embodiment, the first or proximal end  107 ,  207  of the main body stent graft  105  may be coupled to a fixation stent  150 . In addition, bi-directional anchoring hooks may be formed as part of the fixation stent  150  may be utilized to gain solid purchase in the non-diseased portion of a vessel wall. This fixation stent  150  may provide for radial-force fixation within the vessel in conjunction with bidirectional hooks. In another embodiment, the fixation stent  150  may be biased away from the lumen of the main body stent graft  105  to maintain fixation with vasculature in a deployed condition even if an aneurysm advances proximally. 
     In a fourth aspect, the invention provides a method for placement of the stent graft  100  according to the first aspect of the invention. The method includes (a) introducing a guidewire into any appropriately sized arterial configuration via arterial access, (b) loading a delivery catheter containing the stent graft of any of the foregoing embodiments onto the guidewire, (c) moving the delivery catheter along the guidewire and introducing the delivery catheter into the appropriately sized arterial configuration via arterial access and (d) deploying the stent graft into the appropriately sized arterial configuration and/or a lumen of a previously-placed stent graft. 
     In one embodiment, the method may further include maintaining the stent graft in a partially-compressed condition via a tensioned string disposed through a plurality of anchors that each define an eyelet. In one embodiment, the tension on the string may be reduced by releasing one end of the wire from a first anchor of the plurality of anchors. Once tension on the string is reduced, the stent graft may then expand into the fully-expanded condition. 
     In one embodiment, the second aspect may further include (e) loading a second delivery catheter containing a bridging stent graft onto the guidewire, (f) moving the second delivery catheter along the guidewire and introducing the second delivery catheter into the proximal end  107  of main body lumen of the stent graft  105  via arterial access, (g) selecting from among the first renal inlet  120 , the second renal inlet  125 , the infrarenal inlet  130  or the visceral inlet  135  defined in the diaphragm  110 , (h) introducing the second delivery catheter into the selected inlet and into either a lumen  121 ,  126 ,  131  coupled to the selected inlet or an appropriately sized arterial lumen and (i) deploying all or a portion of the bridging stent graft into the selected inlet or the appropriately sized arterial lumen. 
     In a fifth aspect, a stent graft provides: 
     a main body stent graft defining a lumen having a first end and a second end; 
     a diaphragm coupled to the main body stent graft, wherein the diaphragm defines a first opening, a second opening and a third opening; 
     a first stent graft extension having a first end and a second end, wherein the first stent graft extension has a single lumen, wherein the first end of the first stent graft extension is coupled to the diaphragm and arranged surrounding the first opening; 
     a second stent graft extension having a first end and a second end, wherein the second stent graft extension has a single lumen at the first end and has a bifurcation defining two lumens at the second end, wherein the first end of the second stent graft extension is coupled to the diaphragm and arranged surrounding the second opening; and a third stent graft extension having a first end and a second end, wherein the third stent graft extension has a single lumen at the first end, wherein the first end of the third stent graft extension is coupled to the diaphragm and arranged surrounding the third opening. 
     Referring now to  FIGS. 25A-26B , a stent graft  400  is shown having a main body stent graft  405  defining a lumen having a first end  406  and a second end  407 . Coupled to the main body stent graft  405  is a diaphragm  410  that defines a first opening  415 , a second opening  420  and a third opening  425 . A first stent graft extension  430  defines a single lumen and has a first end  431  and a second end  432 , and the first end  431  of the first stent graft extension  430  is coupled to the diaphragm  410  and arranged surrounding the first opening  415 . A second stent graft extension  435  has a single lumen at a first end  436  and has a bifurcation  437  defining two lumens at the second end  438 . The first end  436  of the second stent graft extension  435  is coupled to the diaphragm  410  and arranged surrounding the second opening  420 . And a third stent graft extension  440  has a first end  441  and a second end  442 . The third stent graft extension  440  has a single lumen at the first end  441 , and the first end  441  of the third stent graft extension  440  is coupled to the diaphragm  410  and arranged surrounding the third opening  425 . 
     In one embodiment, shown in  FIGS. 26A-B , the first opening  415  may be circular, the second opening  420  may be elliptical and the third opening  425  may be circular. In this embodiment, the stent graft  400  may further include a fourth opening  445  defined in the diaphragm  410  that is circular. And a fourth stent graft extension  450  having a first end  451  and a second end  452 , wherein the fourth stent graft extension  450  has a single lumen at the first end  451 , and the first end  451  of the fourth stent graft extension  450  is coupled to the diaphragm  410  and arranged surrounding the fourth opening  445 . In one embodiment, the third opening  425  and the fourth opening  445  may be arranged adjacent to each other. In alternative embodiments (not shown), the first opening may be circular, the second opening may be circular and the third opening may be elliptical. In a further embodiment, a fourth opening may be defined in the diaphragm that is circular and located adjacent to the second opening. 
     In another embodiment, the first opening  415  is circular, the second opening  420  is elliptical and the third opening  425  is elliptical. The third stent graft extension  440  may have a bifurcation  443  defining two lumens at the second end  442 . In one embodiment, the second opening  420  is arranged between the first opening  415  and the third opening  425 . In a further embodiment, a major axis of the second opening  420  may be arranged perpendicular to the major axis of the third opening  425 . In yet another embodiment, a minor axis of the second opening  420  is aligned with the major axis of the third opening  425 . 
     In one embodiment, the two lumens of the second stent graft extension  435  each have a diameter ranging from about 4 mm to about 12 mm. In another embodiment, a major axis of the second opening  420  may have a length ranging from about 4 mm to about 36 mm, and a minor axis of the second opening  420  may have a length ranging from about 4 mm to about 24 mm. 
     In another embodiment, the two lumens of the third stent graft extension  440  may each have a diameter ranging from about 6 mm to about 14 mm. In a further embodiment, a major axis of the third opening has a length ranging from about 6 mm to about 42 mm, and wherein a minor axis of the third opening has a length ranging from about 6 mm to about 28 mm. 
     In a still further embodiment, the bifurcation  437  of the second stent graft extension  435  may occur at a location ranging from about 0 mm to about 50 mm from the diaphragm  410  and the bifurcation  443  of the third stent graft extension  440  occurs at a location ranging from about 0 mm to about 50 mm from the diaphragm  410 . In some embodiments, recessing the bifurcation away from the diaphragm may create a cavity that permits selection of one of the two lumens of the second and third graft extensions via an articulable catheter tip. This may help reduce the time it takes to advance a bridging stent into place, thereby reducing the amount of fluorescence and radiation used to visualize device placement during surgery. In another embodiment, the first stent graft extension  430 , the second stent graft extension  435  and third stent graft extension  440  may each have a length ranging from about 5 mm to about 50 mm. 
     In one embodiment, the first end  438  of the second stent graft extension  435  is tapered, and the first end  441  of the third stent graft extension  440  is tapered. In a further embodiment, the first end  431  of the first stent graft extension  430  is tapered. 
     In a sixth aspect, a stent graft provides: 
     a main body stent graft defining a lumen having a first end and a second end; 
     a diaphragm coupled to the main body stent graft within the lumen, wherein the diaphragm defines at least three openings; 
     at least three stent graft extensions each defining a lumen, wherein a first end of each of the at least three stent graft extensions is coupled to one of the at least three openings; 
     a visceral vessel opening defined in the sidewall of the main body stent graft; 
     two renal openings defined in the sidewall of the main body stent graft distal to the diaphragm; and 
     permeable membrane material covering at least one of the visceral vessel opening and the two renal openings. 
     Referring now to  FIGS. 27A-B , a stent graft  500  is shown having a main body stent graft  505  that defines a lumen with a first end  506  and a second end  507 . A diaphragm  510  is coupled to the main body stent graft  505  within the lumen, and the diaphragm  510  defines at least three openings. In the embodiment shown, the diaphragm  510  has four openings, namely a first opening  530 , a second opening  535 , a third opening  520  and a fourth opening  525 . Stent graft  500  also includes stent graft extensions  521 ,  526 ,  531 ,  536  each having a first end coupled to one of the openings  520 ,  525 ,  530 ,  535 , respectively, and each defining a lumen. A visceral vessel opening  515  is defined in the sidewall  518  of the main body stent graft  505 . Two renal openings  570  are also defined in the sidewall  515  of the main body stent graft  505  distal to the diaphragm  510 . A permeable membrane material  571  covers at least one of the visceral vessel opening  518  and the two renal openings  570 . 
     In one embodiment, the permeable membrane material  571  may be perforable. For example, a catheter, a guidewire, a bridging stent graft or other implement may be used to perforate the permeable membrane material  571 . In operation, a bridging stent graft may be placed through the perforation in the permeable membrane material  571  such that there is seal between the bridging stent graft and the permeable membrane material  571 . In a further embodiment, the permeable membrane material  571  may be configured to be sealed via thrombosis in vivo. In another embodiment, the permeable membrane material  571  may include, but is not limited to, one or more of nitinol, polytetrafluoroethylene (“PTFE”), polyester, nonabsorbale polymer and combinations thereof. Still further, the permeable membrane material  571  may be woven, mesh, or electrospun, for example. 
     In another embodiment, the second end  507  of the main body stent graft  505  may be arranging distal with respect to bloodflow, such that bloodflow enters the first end  506  and exits the second end  507 . The diameter of the main body stent graft  505  at the second end  507  may be greater than the diameter of the main body stent graft  505  at the first end  506 . This arrangement may help anchor the stent graft  500  against the aortic wall and resist migration due to bloodflow. In a further embodiment, the second end  507  of the main body stent graft  505  is bell-shaped, as shown in  FIG. 27A  in an expanded ex vivo condition. 
     In one embodiment, the stent graft may include one or more sealing rings  555  coupled to the main body stent graft  505  surrounding one or more of the two renal openings  570  and the visceral vessel opening  518 . 
     In one embodiment, the two renal openings  570  may be fenestrations. In another embodiment, the two renal openings  570  may be two arch portions as described above with respect to the second aspect of the invention. 
     Various embodiments of the stent grafts according to the first, second, third, fifth and sixth aspects of the invention are shown in  FIGS. 17-23 and 25A-27B  in one of the visceral trunk or thoracic aorta after deployment in vivo according to the methods of the fourth aspect of the invention. 
     Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that any arrangement that is calculated to achieve the same purpose may be substituted for the specific embodiments shown. This application is intended to cover any adaptations or variations of embodiments of the present invention. It is to be understood that the above description is intended to be illustrative, and not restrictive, and that the phraseology or terminology employed herein is for the purpose of description and not of limitation. The above embodiments and other embodiments may be combined as is apparent to those of skill in the art upon studying the above description, unless noted otherwise.