Patent Publication Number: US-2022226134-A1

Title: Universal adapter for graft attachment to delivery systems

Description:
FIELD 
     The present disclosure relates to medical devices. 
     BACKGROUND 
     The statements in this section merely provide background information related to the present disclosure and may not constitute prior art. 
     Development of new universal delivery device systems may present design challenges for retaining existing stent grafts on new delivery devices and may require changing the delivery device system attachment site or increasing sheath compatibility size for the stent graft. Some solutions, such as retention systems including circumferentially asymmetric stent struts, may cause a bias in the radial force, and may infold under certain conditions. Stents that extend slightly beyond the edge of a graft material may pose problems including graft material folding, while not reducing material bulk enough to prevent modifications to the delivery system. The extension of stent structures beyond the edge of the graft material may interfere with blood flow into ancillary/branch vessels, and may cause access issues if additional procedures are required to treat the anatomy at a later time, thereby narrowing down treatment options, especially if conversion to open procedures is not possible or advisable. 
     Thus, there remains a need for further contributions in this area of technology. 
     SUMMARY 
     In one form of the present disclosure, a stent graft retention system for retaining a stent graft on a delivery device is provided. The stent graft retention system includes a stent graft including a first end, a second end, a first edge at the first end, and a stent including first apices and second apices, the first apices disposed adjacent the first end and the second apices extending toward the second end. The stent graft retention system further includes a plurality of discrete retention wire forms each including a first strut, a second strut, and an apex between the first and second struts. The first and second struts are attached to the stent graft a distance from the first edge and the apex extends beyond the first edge. The each discrete retention wire form is nested with an apex of the first apices. At least one of the plurality of discrete retention wire forms is configured to engage a trigger wire. 
     In another example of the present disclosure, a stent graft retention system for retaining a stent graft on a delivery device is provided. The stent graft retention system includes a stent graft including a first end, a second end, a first edge at the first end, and a stent comprising first apices and second apices, the first apices disposed adjacent the first end and the second apices extending toward the second end. The stent graft retention system further includes a plurality of discrete retention wire forms each including a first strut, a second strut, and an apex between the first and second struts. The first and second struts are attached to the stent graft a distance from the first edge and the apex extends beyond the first edge. The each discrete retention wire form is nested with an apex of the first apices. At least one of the plurality of discrete retention wire forms is configured to engage a trigger wire. The first and second struts of the each discrete retention wire form pass through eyelets in the stent graft and are attached to the stent graft on a first surface of the stent graft and the apex of the each discrete retention wire form extends beyond the first edge of a second surface of the stent graft, the second surface opposite the first surface. 
     In yet another example of the present disclosure, a stent graft retention system for retaining a stent graft on a delivery device is provided. The stent graft retention system includes a stent graft including a first end, a second end, a first edge at the first end, and a stent including first apices and second apices, the first apices disposed adjacent the first end and the second apices extending toward the second end. The stent graft retention system further includes a plurality of discrete retention wire forms each including a first loop, a second lop, and a wire attaching the first loop and the second loop. The first loop of the each discrete retention wire form is attached to the stent graft a distance from the first edge and the second loop extends beyond the first edge. The first loop of the each discrete retention wire form is attached to the stent graft between an apex of the first apices and the first edge. At least one of the plurality of discrete retention wire forms is configured to engage a trigger wire. 
     Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
    
    
     
       DRAWINGS 
       In order that the present disclosure may be well understood, there will now be described various forms thereof, given by way of example, reference being made to the accompanying drawings. The components in the figures are not necessarily to scale. Moreover, in the figures, like-referenced numerals designate corresponding parts throughout the different views. 
         FIG. 1  illustrates a perspective view of an example of a stent graft retention system according to the principles of the present disclosure; 
         FIG. 2A  illustrates an exploded partial perspective view of an example of a stent graft retention system including a plurality of discrete retention wire forms disposed symmetrically about an inner surface of a first edge of a stent graft, the each discrete retention wire form including first and second struts including flat hooks; 
         FIG. 2B  illustrates an exploded partial perspective view of another example of a stent graft retention system including a plurality of discrete retention wire forms disposed symmetrically about an outer surface of a first edge of a stent graft; 
         FIG. 3  illustrates an exploded partial perspective view of yet another example of a stent graft retention system, in which trigger wires of an example of a delivery device have engaged the plurality of discrete retention wire forms resulting in closing of the first edge of the stent graft; 
         FIG. 4A  illustrates an exploded partial perspective view of yet another example of a stent graft retention system including a plurality of discrete retention wire forms disposed symmetrically about an inner surface of a first edge of a stent graft, the each discrete retention wire form including first and second struts including “bar-bells”; 
         FIG. 4B  illustrates an exploded partial perspective view of yet another example of a stent graft retention system including a plurality of discrete retention wire forms disposed symmetrically about an outer surface of a first edge of a stent graft, the each discrete retention wire form including first and second struts including “bar-bells”; 
         FIG. 5A  illustrates an exploded partial perspective view of yet another example of a stent graft retention system including a plurality of discrete retention wire forms including first and second struts, attached to an outer surface of the stent graft, and apices extending past the inner (i.e., opposite) surface of a first edge of the stent graft; 
         FIG. 5B  illustrates an exploded partial perspective view of yet another example of a stent graft retention system including a plurality of discrete retention wire forms including first and second struts, attached to an inner surface of the stent graft, and apices extending past the outer (i.e., opposite) surface of a first edge of the stent graft; 
         FIG. 6A  illustrates an exploded partial perspective view of yet another example of a stent graft retention system including a plurality of discrete retention wire forms including first and second loops connected by a wire, the plurality of discrete retention wire forms disposed symmetrically about an inner surface of the stent graft, and attached to the stent graft at the first loop between a first apex of the stent and a first edge of the stent graft; 
         FIG. 6B  illustrates an exploded partial perspective view of yet another example of a stent graft retention system including a plurality of discrete retention wire forms including first and second loops connected by a wire, the plurality of discrete retention wire forms disposed symmetrically about an outer surface of the stent graft, and attached to the stent graft at the first loop between a first apex of the stent and a first edge of the stent graft; 
         FIG. 7A  illustrates an exploded partial perspective view of yet another example of a stent graft retention system including a stent graft including eyelets through which the first and second struts of the plurality of discrete retention wire forms pass, the first and second struts attached to an inner surface of the stent graft, and apices extending past the outer (i.e., opposite) surface of a first edge of the stent graft; 
         FIG. 7B  illustrates an exploded partial perspective view of yet another example of a stent graft retention system including a stent graft including eyelets through which the first and second struts of the plurality of discrete retention wire forms pass, the first and second struts attached to an outer surface of the stent graft, and apices extending past the inner (i.e., opposite) surface of a first edge of the stent graft; 
         FIG. 8A  illustrates an exploded partial perspective view of yet another example of a stent graft retention system including a plurality of discrete retention wire forms disposed symmetrically about an inner surface of a first edge of a stent graft, the each discrete retention wire form including first and second struts including loops; 
         FIG. 8B  illustrates an exploded partial perspective view of yet another example of a stent graft retention system including a plurality of discrete retention wire forms disposed symmetrically about an outer surface of a first edge of a stent graft, the each discrete retention wire form including first and second struts including loops; 
         FIG. 9A  illustrates an exploded partial perspective view of yet another example of a stent graft retention system including a plurality of discrete retention wire forms including a strut including a hook, and a loop, the hook and the loop connected by a wire, the plurality of discrete retention wire forms attached to an outer surface of the stent graft by the hook between a first apex of the stent and a first edge of the stent graft, the loop extending past the inner (i.e., opposite) surface of the first edge of the stent graft; 
         FIG. 9B  illustrates an exploded partial perspective view of yet another example of a stent graft retention system including a plurality of discrete retention wire forms including a strut including a hook, and a loop, the hook and the loop connected by a wire, the plurality of discrete retention wire forms attached to an inner surface of the stent graft by the hook between a first apex of the stent and a first edge of the stent graft, the loop extending past the outer (i.e., opposite) surface of the first edge of the stent graft; 
         FIG. 9C  illustrates an exploded partial perspective view of yet another example of a stent graft retention system including a plurality of discrete retention wire forms including a strut including a hook, and a loop, the hook and the loop connected by a wire, the plurality of discrete retention wire forms attached to an inner surface of the stent graft by the hook between a first apex of the stent and a first edge of the stent graft, the loop extending past the inner surface of the first edge of the stent graft; 
         FIG. 9D  illustrates an exploded partial perspective view of yet another example of a stent graft retention system including a plurality of discrete retention wire forms including a strut including a hook, and a loop, the hook and the loop connected by a wire, the plurality of discrete retention wire forms attached to an outer surface of the stent graft by the hook between a first apex of the stent and a first edge of the stent graft, the loop extending past the outer surface of the first edge of the stent graft; 
         FIG. 10A  illustrates an exploded partial perspective view of yet another example of a stent graft retention system including a plurality of discrete retention wire forms including a strut including a “bar-bell,” and a loop, the bar-bell and the loop connected by a wire, the plurality of discrete retention wire forms attached to an outer surface of the stent graft by the bar-bell between a first apex of the stent and a first edge of the stent graft, the loop extending past the inner (i.e., opposite) surface of a first edge of the stent graft; 
         FIG. 10B  illustrates an exploded partial perspective view of yet another example of a stent graft retention system including a plurality of discrete retention wire forms including a strut including a “bar-bell,” and a loop, the bar-bell and the loop connected by a wire, the plurality of discrete retention wire forms attached to an inner surface of the stent graft by the bar-bell between a first apex of the stent and a first edge of the stent graft, the loop extending past the outer (i.e., opposite) surface of the first edge of the stent graft; 
         FIG. 11A  illustrates an exploded partial perspective view of yet another example of a stent graft retention system including a plurality of discrete retention wire forms disposed symmetrically about an inner surface of a first edge of a stent graft, each discrete retention wire form including first and second struts including hooks extending inward from the inner surface of the stent graft; 
         FIG. 11B  illustrates an exploded partial perspective view of yet another example of a stent graft retention system including a plurality of discrete retention wire forms disposed symmetrically about an outer surface of a first edge of a stent graft, each discrete retention wire form including first and second struts including hooks extending outward from the outer surface of the stent graft; 
         FIG. 11C  illustrates an exploded partial perspective view of yet another example of a stent graft retention system including a plurality of discrete retention wire forms disposed symmetrically about an outer surface of a first edge of a stent graft, each discrete retention wire form including first and second struts including hooks extending inward through the stent graft; 
         FIG. 11D  illustrates an exploded partial perspective view of yet another example of a stent graft retention system including a plurality of discrete retention wire forms disposed symmetrically about an inner surface of a first edge of a stent graft, each discrete retention wire form including first and second struts including hooks extending outward through the stent graft; 
         FIG. 12  illustrates an exploded partial perspective view of yet another example of a stent graft retention system, in which trigger wires of an example of a delivery device have engaged the plurality of discrete retention wire forms including first and second loops connected by a wire, the trigger wires engaging the second loop of the each discrete retention wire form, resulting in closing of the first edge of the stent graft; 
         FIG. 13A  illustrates a longitudinal end view of yet another example of a stent graft retention system, in which three discrete retention wire forms are disposed evenly about the circumference of the inner surface of the stent graft; 
         FIG. 13B  illustrates a longitudinal end view of yet another example of a stent graft retention system, in which three discrete retention wire forms are disposed unevenly about the circumference of the inner surface of the stent graft; 
         FIG. 13C  illustrates a longitudinal end view of yet another example of a stent graft retention system in which two discrete retention wire forms are disposed evenly about the circumference of the inner surface of the stent graft; 
         FIG. 13D  illustrates a longitudinal end view of yet another example of a stent graft retention system in which a discrete retention wire form is attached to the inner surface of the stent graft; 
         FIG. 14  illustrates an exploded partial perspective view of yet another example of a stent graft retention system including a plurality of discrete retention wire forms disposed symmetrically about an outer surface of a first edge of a stent graft, the each discrete retention wire form including first and second struts including loops, the first and second struts extending past the first edge of the stent graft; 
         FIG. 15A  illustrates an exploded partial perspective view of yet another example of a stent graft retention system including a plurality of discrete retention wire forms including first and second loops connected by a wire, the plurality of discrete retention wire forms disposed symmetrically about an inner surface of the stent graft, and attached to the stent graft at the first loop between two apices of first apices of the stent; 
         FIG. 15B  illustrates an exploded partial perspective view of yet another example of a stent graft retention system including a plurality of discrete retention wire forms including first and second loops connected by a wire, the plurality of discrete retention wire forms disposed symmetrically about an outer surface of the stent graft, and attached to the stent graft at the first loop between two apices of first apices of the stent; 
         FIG. 16A  illustrates an exploded partial perspective view of yet another example of a stent graft retention system including a plurality of discrete retention wire forms including a strut including a hook, and a loop, the hook and the loop connected by a wire, the plurality of discrete retention wire forms attached to an outer surface of the stent graft by the hook between two apices of first apices of the stent, the loop extending past the inner (i.e., opposite) surface of a first edge of the stent graft; 
         FIG. 16B  illustrates an exploded partial perspective view of yet another example of a stent graft retention system including a plurality of discrete retention wire forms including a strut including a hook, and a loop, the hook and the loop connected by a wire, the plurality of discrete retention wire forms attached to an inner surface of the stent graft by the hook between two apices of first apices of the stent, the loop extending past the outer (i.e., opposite) surface of a first edge of the stent graft; 
         FIG. 16C  illustrates an exploded partial perspective view of yet another example of a stent graft retention system including a plurality of discrete retention wire forms including a strut including a hook, and a loop, the hook and the loop connected by a wire, the plurality of discrete retention wire forms attached to an inner surface of the stent graft by the hook between two apices of first apices of the stent, the loop extending past the inner surface of a first edge of the stent graft; 
         FIG. 16D  illustrates an exploded partial perspective view of yet another example of a stent graft retention system including a plurality of discrete retention wire forms including a strut including a hook, and a loop, the hook and the loop connected by a wire, the plurality of discrete retention wire forms attached to an outer surface of the stent graft by the hook between two apices of first apices of the stent, the loop extending past the outer surface of a first edge of the stent graft; 
         FIG. 17A  illustrates an exploded partial perspective view of yet another example of a stent graft retention system including a plurality of discrete retention wire forms including a strut including a “bar-bell,” and a loop, the bar-bell and the loop connected by a wire, the plurality of discrete retention wire forms attached to an outer surface of the stent graft by the bar-bell between two apices of the first apices of the stent, the loop extending past the inner (i.e., opposite) surface of a first edge of the stent graft; and 
         FIG. 17B  illustrates an exploded partial perspective view of yet another example of a stent graft retention system including a plurality of discrete retention wire forms including a strut including a “bar-bell,” and a loop, the bar-bell and the loop connected by a wire, the plurality of discrete retention wire forms attached to an inner surface of the stent graft by the bar-bell between two apices of the first apices of the stent, the loop extending past the outer (i.e., opposite) surface of a first edge of the stent graft. 
     
    
    
     The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. 
     DETAILED DESCRIPTION 
     The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features. 
     In adding reference denotations to elements of each drawing, although the same elements are displayed on a different drawing, it should be noted that the same elements have the same denotations. In addition, in describing one aspect of the present disclosure, if it is determined that a detailed description of related well-known configurations or functions blurs the gist of one aspect of the present disclosure, it will be omitted. 
     In the following discussion, the terms “first” and “second” will be used to describe the opposing axial ends of the stent grafts of the present disclosure, toward which the first and second apices of a stent extend, as well as the axial ends of various component features. The term “longitudinal” will be used to refer to an axis that aligns with the first-second axis of the device (or component). The terms “radially” and “radial” will be used to refer to elements, surfaces, or assemblies relative to one another that may extend perpendicularly from a longitudinal axis. The terms “circumference,” “circumferentially,” and “circumferential” will be used to refer to elements, surfaces, or assemblies relative to one another encircling a longitudinal axis at a radius. 
     The uses of the terms “a” and “an” and “the” and similar referents in the context of describing the present disclosure (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The use of the term “plurality of” is defined by the Applicant in the broadest sense, superseding any other implied definitions or limitations hereinbefore or hereinafter unless expressly asserted by the Applicant to the contrary, to mean a quantity of more than one. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. 
     As used herein the terms “comprise(s),” “include(s),” “having,” “has,” “can,” “contain(s),” and variants thereof, are intended to be open-ended transitional phrases, terms, or words that do not preclude the possibility of additional acts or structures. The present description also contemplates other embodiments “comprising,” “consisting of,” and “consisting essentially of,” the examples or elements presented herein, whether explicitly set forth or not. 
     In describing elements of the present disclosure, the terms 1 st , 2 nd , first, second, A, B, (a), (b), and the like, may be used herein. These terms are only used to distinguish one element from another element, but do not limit the corresponding elements irrespective of the nature or order of the corresponding elements. 
     Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meanings as those generally understood by those skilled in the art to which the present disclosure pertains. Such terms as those defined in a generally used dictionary are to be interpreted as having meanings equal to the contextual meanings in the relevant field of art. 
     Referring to  FIG. 1 , an example of a stent graft retention system  100  is illustrated. Stent graft retention system  100  includes stent graft  102  and retains stent graft  102  on a delivery device, such as a trigger wire. Stent graft  102  includes first end  104 , second end  106 , first edge  108  at first end  104 , and a stent  110  including first apices  112  and second apices  114 . First apices  112  may be disposed adjacent first end  104  and second apices  114  may extend toward second end  106 . Stent graft retention system  100  further includes a plurality of discrete retention wire forms  120 . Each discrete retention wire form  120  includes first strut  122 , second strut  124 , and apex  126 . First and second struts  122 ,  124  of the each discrete retention wire form  120  are attached to stent graft  102  a distance from first edge  108  such that apex  126  extends beyond first edge  108 . As shown in  FIG. 1 , apex  126  of the each discrete retention wire form  120  and apex  112  of the first apices  112  may be coaxial and first and second struts  122 ,  124  are attached to stent graft  102  on opposite sides, circumferentially, of an apex  112  of the first apices  112 . Alternatively, though not shown in  FIG. 1 , apex  126  of the each discrete retention wire form  120  may be positioned circumferentially between two apices  112  of the first apices  112 . The each discrete retention wire form  120  may be “v-shaped,” with the “bottom” of the “v-shape” corresponding to apex  126  and the “top” of the “v-shape” corresponding to first and second struts  122 ,  124 . Apex  126  may not necessarily be in the form of a sharp tip. Rather, first and second struts  122 ,  124  may extend away from apex  126  in a non-parallel fashion. The plurality of discrete retention wire forms  120  is attached to stent graft  102  such that the plurality of discrete retention wire forms  120  are evenly and symmetrically distributed about a circumference of stent graft  102 . In some examples not shown, the plurality of discrete retention wire forms  120  are unevenly and asymmetrically distributed about a circumference of stent graft  102 . 
     The stent  110  may be made from numerous metals and alloys. In one example, stent  110  includes a shape-memory material such as a nickel-titanium alloy (“nitinol”). Stent  110  may include materials such as stainless steel, MP35N, gold, tantalum, platinum or platinum iridium, platinum chromium, platinum iron, niobium, tungsten, inconel, ceramic, nickel, titanium, stainless steel/titanium composite, cobalt, chromium, cobalt/chromium alloys, magnesium, aluminum, or other biocompatible or bioresorbable metallic materials and/or composites or alloys. Examples of other materials that may be used to form stent  110  include carbon or carbon fiber; cellulose acetate, cellulose nitrate, silicone, polyethylene terephthalate, polyurethane, polyamide, polyester, polyorthoester, polyanhydride, polyether sulfone, polycarbonate, polypropylene, ultra-high molecular weight polyethylene, polytetrafluoroethylene, or another biocompatible polymeric material, or mixtures or copolymers of these; polylactic acid, polyglycolic acid, or copolymers thereof: a polyanhydride, polycaprolactone, polyhydroxybutyrate valerate, or another biodegradable polymer, or mixtures or copolymers of these; a protein, an extracellular matrix component, collagen, fibrin, or another biologic agent; or a suitable mixture thereof. 
     Moreover, the structure of stent  110  may be formed in a variety of ways to provide a suitable intraluminal support structure. The at least one stent  110  may be configured in the form of one or more “Z-stents” or Gianturco stents, each of which may comprise a series of substantially straight segments interconnected by a series of bent segments. The bent segments may include acute bends or apices, such as first apices  112  and second apices  114 . The Gianturco stents are arranged in a zigzag configuration in which the straight segments are set at angles relative to each other and are connected by first apices  112  and second apices  114 . The at least one stent  110  may be configured as a spiralized Z-stent. 
     Stent graft  102  may comprise a polymeric sheet having any suitable porosity. The porosity may be substantially porous or substantially non-porous and may be selected depending on the application. In one example, a porous polymeric sheet may comprise the polyurethane Thoralon®. In addition to, or in lieu of, a porous polyurethane, stent graft  102  may include any biocompatible polymeric material including non-porous polyurethanes, PTFE, expanded PTFE (ePTFE), polyethylene tetraphthalate (“PET”), aliphatic polyoxaesters, polylactides, polycaprolactones, and hydrogels. 
     The each discrete retention wire form may be in a “nested” relationship with an apex of the first apices of a stent. One or more of the apices of the first apices of a stent may be disposed coincident with or proximally beyond the distal ends (within the valley) of a v-shaped discrete retention wire form. In the case of a straight discrete retention wire form, the distal end of the straight discrete retention wire form may be disposed between two apices of the first apices of a stent such that the distal end is disposed coincident with or extends distally beyond the two apices of the first apices of the stent. In other words, the distal end of the straight discrete retention wire form extends to or into a valley between two apices of the first apices of the stent. 
     The term “biocompatible,” as used here, unless stated otherwise, alone or in combination with other terms, refers to a material that is substantially non-toxic in the in vivo environment of its intended use, and that is not substantially rejected by the patient&#39;s physiological system. A biocompatible structure or material, when introduced into a majority of patients, will not cause an undesirably adverse, long-lived, or escalating biological reaction or response. Such a response is distinguished from a mild, transient inflammation that typically accompanies surgery or implantation of foreign objects into a living organism. 
     Referring to  FIG. 2A , an exploded partial perspective view of an example of a stent graft retention system  200  is illustrated. Stent graft retention system  200  includes a plurality of discrete retention wire forms  120  attached to an inner surface of stent graft  102  by sutures  202  at first and second struts  122 ,  124 . As shown in  FIG. 2A , first and second struts  122 ,  124  of the each discrete retention wire form  120  include flat hooks. First and second struts  122 ,  124  of the discrete retention wire form  120  nested with apex  112  are positioned closer to first edge  224  of stent graft  102  than first and second struts  122 ,  124  of the discrete retention wire form  120  nested with apex  222 . First and second struts  122 ,  124  of the each discrete retention wire form  120  may be independently positioned between stent  110  and first edge  224  of stent graft  102  relative to each of the other the each discrete retention wire form  120 , or the plurality of discrete retention wire forms  120  may be positioned identically between stent  110  and first edge  224  of stent graft  102 . 
     Referring to  FIG. 2B , an exploded partial perspective view of another example of a stent graft retention system  210  is illustrated. Stent graft retention system  210  includes a plurality of discrete retention wire forms  212  attached to an outer surface of stent graft  102  by sutures  220  at first and second struts  216 ,  218 . 
     Referring to  FIG. 3 , an exploded partial perspective view of yet another example of a stent graft retention system  300  is illustrated. Stent graft retention system  300  includes stent graft  102 . As shown in  FIG. 3 , at least one of the plurality of discrete retention wire forms  120  engages trigger wires  302  of delivery device  306 . Trigger wires  302  confront apex  126  of each discrete retention wire form  120  on the side of each discrete retention wire form  120  toward second end  106 . Trigger wires  302  each run out of one hole in nose cone  304  of delivery device  306  and into another hole. Nose cone  304  is connected to body  308  of delivery device  306 . Trigger wires  302  continue into cannula  310  that passes through the center of stent  110  and stent graft  102  parallel to a center longitudinal axis  312  of stent graft  102 . When trigger wires  302  of delivery device  306  engage the plurality of discrete retention wire forms  120  at apex  126 , first edge  108  of stent graft  102  may close toward the center longitudinal axis  312 . 
     Referring to  FIG. 4A , an exploded partial perspective view of yet another example of a stent graft retention system  400  is illustrated. Stent graft retention system  400  includes a plurality of discrete retention wire forms  402  attached to an inner surface  412  of stent graft  410  by sutures  408  at first and second struts  404 ,  406 . As shown in  FIG. 4A , first and second struts  404 ,  406  of the each discrete retention wire form  402  include “bar-bell” shapes. Sutures  408  are configured to attach first and second struts  404 ,  406  to stent graft  410  around a “bar” of each “bar-bell” shape. 
     Referring to  FIG. 4B , an exploded partial perspective view of yet another example of a stent graft retention system  450  is illustrated. Stent graft retention system  450  includes a plurality of discrete retention wire forms  452  attached to an outer surface  462  of stent graft  460  by sutures  458  at first and second struts  454 ,  456 . As shown in  FIG. 4B , first and second struts  454 ,  456  of the each discrete retention wire form  452  include “bar-bell” shapes. Sutures  458  are configured to attach first and second struts  454 ,  456  to stent graft  460  around a “bar” of each “bar-bell” shape. 
     Referring to  FIG. 5A , an exploded partial perspective view of yet another example of a stent graft retention system  500  is illustrated. Stent graft retention system  500  includes a plurality of discrete retention wire forms  502  including first and second struts  504 ,  506  attached to an outer surface  508  of stent graft  514  by sutures  510 . First and second struts  504 ,  506  pass through stent graft  514 , such that apex  518  of the each discrete retention wire form  502  extends beyond a first edge  512  of inner surface  516  of stent graft  514 . Though not shown in  FIG. 5A , the plurality of discrete retention wire forms  502  may include first and second struts  504 ,  506  passing through stent graft  514  and attached to inner surface  516  of stent graft  514  by sutures  510 , such that apex  518  of the each discrete retention wire form  502  extends beyond a first edge  512  of outer surface  508  of stent graft  514 . 
     Referring to  FIG. 5B , an exploded partial perspective view of yet another example of a stent graft retention system  550  is illustrated. Stent graft retention system  550  includes a plurality of discrete retention wire forms  552  including first and second struts  554 ,  556  attached to an inner surface  566  of stent graft  564  by sutures  560 . First and second struts  554 ,  556  pass through stent graft  564 , such that apex  568  of the each discrete retention wire form  552  extends beyond a first edge  562  of outer surface  558  of stent graft  564 . 
     Referring to  FIG. 6A , an exploded partial perspective view of yet another example of a stent graft retention system  600  is illustrated. Stent graft retention system  600  includes stent graft  610  and retains stent graft  610  on a delivery device, such as a trigger wire. Stent graft retention system  600  further includes a plurality of discrete retention wire forms  620 . Each discrete retention wire form  620  includes first loop  602 , second loop  604 , and wire  606  attaching first loop  602  and second loop  604 . First loop  602  of the each discrete retention wire form  620  is attached to stent graft  610  a distance from first edge  608  by a suture  612  and second loop  604  extends beyond first edge  608 . First loop  602  of the each discrete retention wire form  620  is attached to inner surface  614  of stent graft  610  between an apex  622  of first apices  622  of stent  618  and first edge  608 . At least one of the plurality of discrete retention wire forms  620  is configured to engage a trigger wire at second loop  604 . Though not shown in  FIG. 6A , first loop  602  may be attached to one surface of stent graft  610 , and second loop  604  may extend beyond first edge  608  of an opposite surface of stent graft  610  such that wire  606  passes through stent graft  610 . 
     Referring to  FIG. 6B , an exploded partial perspective view of yet another example of a stent graft retention system  650  is illustrated. Stent graft retention system  650  includes stent graft  660  and retains stent graft  660  on a delivery device, such as a trigger wire. Stent graft retention system  650  further includes a plurality of discrete retention wire forms  670 . Each discrete retention wire form  670  includes first loop  652 , second loop  654 , and wire  656  attaching first loop  652  and second loop  654 . First loop  652  of the each discrete retention wire form  670  is attached to stent graft  660  a distance from first edge  658  by a suture  662  and second loop  654  extends beyond first edge  658 . First loop  652  of the each discrete retention wire form  670  is attached to outer surface  666  of stent graft  660 . At least one of the plurality of discrete retention wire forms  670  is configured to engage a trigger wire at second loop  654 . 
     Referring to  FIG. 7A , an exploded partial perspective view of yet another example of a stent graft retention system  700  is illustrated. Stent graft retention system  700  includes stent graft  702  with eyelets  704 . As shown in  FIG. 7A , first and second struts  708 ,  712  of the plurality of discrete retention wire forms  720  pass through eyelets  704  such that first and second struts  708 ,  712  are attached to inner surface  718  of stent graft  702  by sutures  710  and apex  706  of the each discrete retention wire form  720  extends beyond first edge  714  of outer surface  716 . Though not shown in  FIG. 7A , first and second struts  708 ,  712  may pass through eyelets  704  such that first and second struts  708 ,  710  are attached to outer surface  716  of stent graft  702  and apex  706  of the each discrete retention wire form  720  extends beyond first edge  714  of inner surface  718 . 
     Referring to  FIG. 7B , an exploded partial perspective view of yet another example of a stent graft retention system  750  is illustrated. Stent graft retention system  750  includes stent graft  752  with eyelets  754 . As shown in  FIG. 7B , first and second struts  758 ,  762  of the plurality of discrete retention wire forms  770  pass through eyelets  754  such that first and second struts  758 ,  762  are attached to outer surface  766  of stent graft  752  by sutures  760  and apex  756  of the each discrete retention wire form  770  extends beyond first edge  764  of inner surface  768 . First and second struts  758 ,  762  pass through eyelets  754  such that first and second struts  758 ,  762  are attached to outer surface  766  of stent graft  752  and apex  756  of the each discrete retention wire form  770  extends beyond first edge  764  of inner surface  768 . 
     Referring to  FIG. 8A , an exploded partial perspective view of an example of a stent graft retention system  800  is illustrated. Stent graft retention system  800  includes a plurality of discrete retention wire forms  812  attached to inner surface  818  of stent graft  802  at first and second struts  804 ,  806 . As shown in  FIG. 8A , first and second struts  804 ,  806  of the each discrete retention wire form  812  include loops. First and second struts  804 ,  806  of the each discrete retention wire form  812  are attached to stent graft  802  a distance from first edge  814  by sutures  810  such that apex  808  extends beyond first edge  814 . As shown in  FIG. 8A , apex  808  of the each discrete retention wire form  812  is “nested with” an apex  822  of the first apices  822  of stent  820 , such that apex  808  and apex  822  may be coaxial and first and second struts  804 ,  806  are attached to stent graft  802  on opposite sides, circumferentially, of an apex  822  of the first apices  822  of stent  820 . 
     Referring to  FIG. 8B , an exploded partial perspective view of an example of a stent graft retention system  850  is illustrated. Stent graft retention system  850  includes a plurality of discrete retention wire forms  862  attached to outer surface  866  of stent graft  852  at first and second struts  854 ,  856 . As shown in  FIG. 8B , first and second struts  854 ,  856  of the each discrete retention wire form  862  include loops. First and second struts  854 ,  856  of the each discrete retention wire form  862  are attached to stent graft  852  a distance from first edge  864  by sutures  860  such that apex  858  extends beyond first edge  864 . 
     Referring to  FIG. 9A , an exploded partial perspective view of an example of a stent graft retention system  900  is illustrated. Stent graft retention system  900  includes stent graft  902  and retains stent graft  902  on a delivery device, such as a trigger wire. Stent graft retention system  900  further includes a plurality of discrete retention wire forms  918 . Each discrete retention wire form  918  includes loop  906 , hook  904 , and wire  908  attaching loop  906  and hook  904 . Hook  904  of the each discrete retention wire form  918  is attached to outer surface  916  of stent graft  902  a distance from first edge  912  by suture  910  and loop  906  extends beyond first edge  912 . Hook  904  of the each discrete retention wire form  918  is attached to outer surface  916  of stent graft  902  between an apex  920  of first apices  920  of stent  922  and first edge  912 . At least one of the plurality of discrete retention wire forms  918  is configured to engage a trigger wire at loop  906 . Loop  906  extends beyond first edge  912  of inner surface  914  of stent graft  902  such that wire  908  passes through stent graft  902 . 
     Referring to  FIG. 9B , an exploded partial perspective view of an example of a stent graft retention system  926  is illustrated. Stent graft retention system  926  includes stent graft  928  and retains stent graft  928  on a delivery device, such as a trigger wire. Stent graft retention system  926  further includes a plurality of discrete retention wire forms  944 . Each discrete retention wire form  944  includes loop  932 , hook  930 , and wire  934  attaching loop  932  and hook  930 . Hook  930  of the each discrete retention wire form  944  is attached to inner surface  940  of stent graft  928  a distance from first edge  938  by suture  936  and loop  932  extends beyond first edge  938 . Hook  930  of the each discrete retention wire form  944  is attached to inner surface  940  of stent graft  928  between an apex  946  of first apices  946  of stent  948  and first edge  938 . At least one of the plurality of discrete retention wire forms  944  is configured to engage a trigger wire at loop  932 . Loop  932  extends beyond first edge  938  of outer surface  942  of stent graft  928  such that wire  934  passes through stent graft  928 . 
     Referring to  FIG. 9C , an exploded partial perspective view of an example of a stent graft retention system  950  is illustrated. Stent graft retention system  950  includes stent graft  952  and retains stent graft  952  on a delivery device, such as a trigger wire. Stent graft retention system  950  further includes a plurality of discrete retention wire forms  968 . Each discrete retention wire form  968  includes loop  956 , hook  954 , and wire  958  attaching loop  956  and hook  954 . Hook  954  of the each discrete retention wire form  968  extends through stent graft  952  from inner surface  964  a distance from first edge  962  by suture  960 , between an apex  970  of first apices  970  of stent  972  and first edge  962 , and loop  956  extends beyond first edge  962  of inner surface  964 . At least one of the plurality of discrete retention wire forms  968  is configured to engage a trigger wire at loop  956 . 
     Referring to  FIG. 9D , an exploded partial perspective view of an example of a stent graft retention system  976  is illustrated. Stent graft retention system  976  includes stent graft  978  and retains stent graft  978  on a delivery device, such as a trigger wire. Stent graft retention system  976  further includes a plurality of discrete retention wire forms  994 . Each discrete retention wire form  994  includes loop  982 , hook  980 , and wire  984  attaching loop  982  and hook  980 . Hook  980  of the each discrete retention wire form  994  extends through stent graft  978  from outer surface  992  a distance from first edge  988  by suture  986 , between an apex  996  of first apices  996  of stent  998  and first edge  988 , and loop  982  extends beyond first edge  988  of outer surface  992 . At least one of the plurality of discrete retention wire forms  994  is configured to engage a trigger wire at loop  982 . 
     Referring to  FIG. 10A , an exploded partial perspective view of an example of a stent graft retention system  1000  is illustrated. Stent graft retention system  1000  includes stent graft  1002  and retains stent graft  1002  on a delivery device, such as a trigger wire. Stent graft retention system  1000  further includes a plurality of discrete retention wire forms  1018 . Each discrete retention wire form  1018  includes loop  1006 , strut  1004  including a “bar-bell” shape, and wire  1008  attaching loop  1006  and strut  1004 . Strut  1004  of the each discrete retention wire form  1018  is attached to outer surface  1016  of stent graft  1002  a distance from first edge  1012  by suture  1010 , and loop  1006  extends beyond first edge  1012 . Suture  1010  is configured to attach strut  1004  to stent graft  1002  around a “bar” of each “bar-bell” shape. Strut  1004  of the each discrete retention wire form  1018  is attached to outer surface  1016  of stent graft  1002  between an apex  1020  of first apices  1020  of stent  1022  and first edge  1012 . At least one of the plurality of discrete retention wire forms  1018  is configured to engage a trigger wire at loop  1006 . Loop  1006  extends beyond first edge  1012  of inner surface  1014  of stent graft  1002  such that wire  1008  passes through stent graft  1002 . 
     Referring to  FIG. 10B , an exploded partial perspective view of an example of a stent graft retention system  1050  is illustrated. Stent graft retention system  1050  includes stent graft  1052  and retains stent graft  1052  on a delivery device, such as a trigger wire. Stent graft retention system  1050  further includes a plurality of discrete retention wire forms  1068 . Each discrete retention wire form  1068  includes loop  1056 , strut  1054  including a “bar-bell” shape, and wire  1058  attaching loop  1056  and strut  1054 . Strut  1054  of the each discrete retention wire form  1068  is attached to inner surface  1064  of stent graft  1052  a distance from first edge  1062  by suture  1060 , and loop  1056  extends beyond first edge  1062 . Suture  1060  is configured to attach strut  1054  to stent graft  1052  around a “bar” of each “bar-bell” shape. Strut  1054  of the each discrete retention wire form  1068  is attached to inner surface  1064  between an apex  1070  of first apices  1070  of stent  1072  and first edge  1062 . At least one of the plurality of discrete retention wire forms  1068  is configured to engage a trigger wire at loop  1056 . Loop  1056  extends beyond first edge  1062  of outer surface  1066  of stent graft  1052  such that wire  1058  passes through stent graft  1052 . 
     Referring to  FIG. 11A , an exploded partial perspective view of an example of a stent graft retention system  1100  is illustrated. Stent graft retention system  1100  includes stent graft  1102  and a plurality of discrete retention wire forms  1112  including apex  1108  and first and second struts  1104 ,  1106 , the first and second struts  1104 ,  1106  are attached to inner surface  1118  of stent graft  1102  by sutures  1110  such that apex  1108  extends beyond first edge  1114 . First and second struts  1104 ,  1106  include hooks extending inward from inner surface  1118  of stent graft  1102 . As shown in  FIG. 11A , apex  1108  of the each discrete retention wire form  1112  is “nested with” an apex  1120  of first apices  1120  of stent  1122 , such that apex  1108  and apex  1120  may be coaxial and first and second struts  1104 ,  1106  are attached to stent graft  1102  on opposite sides, circumferentially, of an apex  1120  of the first apices  1120  of stent  1122 . 
     Referring to  FIG. 11B , an exploded partial perspective view of an example of a stent graft retention system  1126  is illustrated. Stent graft retention system  1126  includes stent graft  1128  and a plurality of discrete retention wire forms  1138  including apex  1134  and first and second struts  1130 ,  1132 , the first and second struts  1130 ,  1132  attached to outer surface  1142  of stent graft  1128  by sutures  1136  such that apex  1134  extends beyond first edge  1140 . First and second struts  1130 ,  1132  include hooks extending outward from outer surface  1142  of stent graft  1128 . 
     Referring to  FIG. 11C , an exploded partial perspective view of an example of a stent graft retention system  1150  is illustrated. Stent graft retention system  1150  includes stent graft  1152  and a plurality of discrete retention wire forms  1162  including apex  1158  and first and second struts  1154 ,  1156 , the first and second struts  1154 ,  1156  include hooks extending inward through stent graft  1152  from outer surface  1166 . Sutures  1160  attach the first and second struts  1154 ,  1156  to outer surface  1166  of stent graft  1152 . Apex  1158  of the each discrete retention wire form  1162  extends beyond first edge  1164  of outer surface  1166  of stent graft  1152 . As shown in  FIG. 11C , apex  1158  of the each discrete retention wire form  1162  is “nested with” an apex  1170  of first apices  1170  of stent  1172 , such that apex  1158  and apex  1170  may be coaxial and first and second struts  1154 ,  1156  are attached to stent graft  1152  on opposite sides, circumferentially, of an apex  1170  of the first apices  1170  of stent  1172 . 
     Referring to  FIG. 11D , an exploded partial perspective view of an example of a stent graft retention system  1176  is illustrated. Stent graft retention system  1176  includes stent graft  1178  and a plurality of discrete retention wire forms  1188  including apex  1184  and first and second struts  1180 ,  1182 , the first and second struts  1180 ,  1182  include hooks extending outward through stent graft  1178  from inner surface  1192 . Sutures  1186  attach the first and second struts  1180 ,  1182  to inner surface  1192  of stent graft  1178 . Apex  1184  of the each discrete retention wire form  1188  extends beyond first edge  1190  of inner surface  1192  of stent graft  1178 . 
     Referring to  FIG. 12 , an exploded partial perspective view of yet another example of a stent graft retention system  1200  is illustrated. Stent graft retention system  1200  includes stent graft  1202 . As shown in  FIG. 12 , at least one of the plurality of discrete retention wire forms  1206  engages trigger wires  302  of delivery device  306 . Trigger wires  302  confront loop  1208  of each discrete retention wire form  1206 . Trigger wires  302  each run out of one hole in nose cone  304  of delivery device  306  and into another hole. Nose cone  304  is connected to body  308  of delivery device  306 . Trigger wires  302  continue into cannula  310  that passes through the center of the stent and stent graft  1202  parallel to a center longitudinal axis  312  of stent graft  1202 . When trigger wires  302  of delivery device  306  engage the plurality of discrete retention wire forms  1206  at loop  1208 , first edge  1204  of stent graft  1202  may close toward the center longitudinal axis  312 . 
     Referring to  FIG. 13A , a longitudinal end view of yet another example of a stent graft retention system  1300  is illustrated. Stent graft retention system  1300  includes a stent graft with a first edge  1302 . Stent graft retention system  1300  includes three discrete retention wire forms  1304  disposed evenly around the circumference of an inner surface of the stent graft, at approximately 0°, 120°, and 240° relative to one another. 
     Referring to  FIG. 13B , a longitudinal end view of yet another example of a stent graft retention system  1310  is illustrated. Stent graft retention system  1310  includes a stent graft with a first edge  1312 . Stent graft retention system  1310  includes three discrete retention wire forms  1314  disposed unevenly around the circumference of an inner surface of the stent graft. 
     Referring to  FIG. 13C , a longitudinal end view of yet another example of a stent graft retention system  1320  is illustrated. Stent graft retention system  1320  includes a stent graft with a first edge  1322 . Stent graft retention system  1320  includes two discrete retention wire forms  1324  disposed evenly around the circumference of an inner surface of the stent graft, at approximately 180° relative to one another. 
     Referring to  FIG. 13D , a longitudinal end view of yet another example of a stent graft retention system  1330  is illustrated. Stent graft retention system  1330  includes a stent graft with a first edge  1332 . Stent graft retention system  1330  includes a discrete retention wire form  1334  disposed on the inner surface of the stent graft. 
     Referring to  FIG. 14 , an exploded partial perspective view of yet another example of a stent graft retention system  1400  is illustrated. Stent graft retention system  1400  includes stent graft  1402  and retains stent graft  1402  on a delivery device, such as a trigger wire. Stent graft  1402  includes first edge  1412  at a first end, and a stent  1418  including first apices  1422  and second apices  1424 . First apices  1422  may be disposed adjacent the first end and second apices  1424  may extend in the direction opposite first edge  1412 . Stent graft retention system  1400  further includes a plurality of discrete retention wire forms  1420 . Each discrete retention wire form  1420  includes first strut  1404 , second strut  1406 , and apex  1408 . First and second struts  1404 ,  1406  include loops. Apex  1408  of the each discrete retention wire form  1420  is attached to stent graft  1402  by sutures  1410  on outer surface  1414  of stent graft  1402  a distance from first edge  1412  such that first and second struts  1404 ,  1406  extend beyond first edge  1412 . As shown in  FIG. 14 , apex  1408  of the each discrete retention wire form  1420  is “nested with” an apex  1424  of the second apices  1424 , such that apex  1408  and apex  1424  may be coaxial. The each discrete retention wire form  1420  may be “A-shaped,” with the “top” of the “A-shape” corresponding to apex  1408  and the “bottom” of the “A-shape” corresponding to first and second struts  1404 ,  1406 . Apex  1408  may not necessarily be in the form of a sharp tip. Rather, first and second struts  1404 ,  1406  may extend away from apex  1408  in a non-parallel fashion. 
     Referring to  FIG. 15A , an exploded partial perspective view of an example of a stent graft retention system  1500  is illustrated. Stent graft retention system  1500  includes stent graft  1510  and retains stent graft  1510  on a delivery device, such as a trigger wire. Stent graft retention system  1500  further includes a plurality of discrete retention wire forms  1520 . Each discrete retention wire form  1520  includes first loop  1502 , second loop  1504 , and wire  1506  attaching first loop  1502  and second loop  1504 . First loop  1502  of the each discrete retention wire form  1520  is attached to stent graft  1510  a distance from first edge  1508  by a suture  1512  and second loop  1504  extends beyond first edge  1508 . First loop  1502  of the each discrete retention wire form  1520  is attached to inner surface  1514  of stent graft  1510  between two apices  1522  of first apices  1522  of stent  1518 . At least one of the plurality of discrete retention wire forms  1520  is configured to engage a trigger wire at second loop  1504 . Though not shown in  FIG. 15A , first loop  1502  may be attached to one surface of stent graft  1510 , and second loop  604  may extend beyond first edge  1508  of an opposite surface of stent graft  1510  such that wire  1506  passes through stent graft  1510 . 
     Referring to  FIG. 15B , an exploded partial perspective view of yet another example of a stent graft retention system  1550  is illustrated. Stent graft retention system  1550  includes stent graft  1560  and retains stent graft  1560  on a delivery device, such as a trigger wire. Stent graft retention system  1550  further includes a plurality of discrete retention wire forms  1570 . Each discrete retention wire form  1570  includes first loop  1552 , second loop  1554 , and wire  1556  attaching first loop  1552  and second loop  1554 . First loop  1552  of the each discrete retention wire form  1570  is attached to stent graft  1560  a distance from first edge  1558  by a suture  1562  and second loop  1554  extends beyond first edge  1558 . First loop  1552  of the each discrete retention wire form  1570  is attached to outer surface  1566  of stent graft  1560 . At least one of the plurality of discrete retention wire forms  1570  is configured to engage a trigger wire at second loop  1554 . 
     Referring to  FIG. 16A , an exploded partial perspective view of an example of a stent graft retention system  1600  is illustrated. Stent graft retention system  1600  includes stent graft  1602  and retains stent graft  1602  on a delivery device, such as a trigger wire. Stent graft retention system  1600  further includes a plurality of discrete retention wire forms  1618 . Each discrete retention wire form  1618  includes loop  1606 , hook  1604 , and wire  1608  attaching loop  1606  and hook  1604 . Hook  1604  of the each discrete retention wire form  1618  is attached to outer surface  1616  of stent graft  1602  a distance from first edge  1612  by suture  1610  and loop  1606  extends beyond first edge  1612 . Hook  1604  of the each discrete retention wire form  1618  is attached to outer surface  1616  of stent graft  1602  between two apices  1620  of first apices  1620  of stent  1622 . At least one of the plurality of discrete retention wire forms  1618  is configured to engage a trigger wire at loop  1606 . Loop  1606  extends beyond first edge  1612  of inner surface  1614  of stent graft  1602  such that wire  1608  passes through stent graft  1602 . 
     Referring to  FIG. 16B , an exploded partial perspective view of an example of a stent graft retention system  1626  is illustrated. Stent graft retention system  1626  includes stent graft  1628  and retains stent graft  1628  on a delivery device, such as a trigger wire. Stent graft retention system  1626  further includes a plurality of discrete retention wire forms  1644 . Each discrete retention wire form  1644  includes loop  1632 , hook  1630 , and wire  1634  attaching loop  1632  and hook  1630 . Hook  1630  of the each discrete retention wire form  1644  is attached to inner surface  1640  of stent graft  1628  a distance from first edge  1638  by suture  1636  and loop  1632  extends beyond first edge  1638 . Hook  1630  of the each discrete retention wire form  1644  is attached to inner surface  1640  of stent graft  1628  been two apices  1646  of first apices  1646  of stent  1648 . At least one of the plurality of discrete retention wire forms  1644  is configured to engage a trigger wire at loop  1632 . Loop  1632  extends beyond first edge  1638  of outer surface  1642  of stent graft  1628  such that wire  1634  passes through stent graft  1628 . 
     Referring to  FIG. 16C , an exploded partial perspective view of an example of a stent graft retention system  1650  is illustrated. Stent graft retention system  1650  includes stent graft  1652  and retains stent graft  1652  on a delivery device, such as a trigger wire. Stent graft retention system  1650  further includes a plurality of discrete retention wire forms  1668 . Each discrete retention wire form  1668  includes loop  1656 , hook  1654 , and wire  1658  attaching loop  1656  and hook  1654 . Hook  1654  of the each discrete retention wire form  1668  extends through stent graft  1652  from inner surface  1664  a distance from first edge  1662  by suture  1660 , between two apices  1670  of first apices  1670  of stent  162 , and loop  1656  extends beyond first edge  1662  of inner surface  1664 . At least one of the plurality of discrete retention wire forms  1668  is configured to engage a trigger wire at loop  1656 . 
     Referring to  FIG. 16D , an exploded partial perspective view of an example of a stent graft retention system  1676  is illustrated. Stent graft retention system  1676  includes stent graft  1678  and retains stent graft  1678  on a delivery device, such as a trigger wire. Stent graft retention system  1676  further includes a plurality of discrete retention wire forms  1694 . Each discrete retention wire form  1694  includes loop  1682 , hook  1680 , and wire  1684  attaching loop  1682  and hook  1680 . Hook  1680  of the each discrete retention wire form  1694  extends through stent graft  1678  from outer surface  1692  a distance from first edge  1688  by suture  1686 , between two apices  1696  of first apices  1696  of stent  1698 , and loop  1682  extends beyond first edge  1688  of outer surface  1692 . At least one of the plurality of discrete retention wire forms  1694  is configured to engage a trigger wire at loop  1682 . 
     Referring to  FIG. 17A , an exploded partial perspective view of an example of a stent graft retention system  1700  is illustrated. Stent graft retention system  1700  includes stent graft  1702  and retains stent graft  1702  on a delivery device, such as a trigger wire. Stent graft retention system  1700  further includes a plurality of discrete retention wire forms  1718 . Each discrete retention wire form  1718  includes loop  1706 , strut  1704  including a “bar-bell” shape, and wire  1708  attaching loop  1706  and strut  1704 . Strut  1704  of the each discrete retention wire form  1718  is attached to outer surface  1716  of stent graft  1702  a distance from first edge  1712  by suture  1710 , and loop  1706  extends beyond first edge  1712 . Suture  1710  is configured to attach strut  1704  to stent graft  1702  around a “bar” of each “bar-bell” shape. Strut  1704  of the each discrete retention wire form  1718  is attached to outer surface  1716  of stent graft  1702  between two apices  1720  of first apices  1720  of stent  1722 . At least one of the plurality of discrete retention wire forms  1718  is configured to engage a trigger wire at loop  1706 . Loop  1706  extends beyond first edge  1712  of inner surface  1714  of stent graft  1702  such that wire  1708  passes through stent graft  1702 . 
     Referring to  FIG. 17B , an exploded partial perspective view of an example of a stent graft retention system  1750  is illustrated. Stent graft retention system  1750  includes stent graft  1752  and retains stent graft  1752  on a delivery device, such as a trigger wire. Stent graft retention system  1750  further includes a plurality of discrete retention wire forms  1768 . Each discrete retention wire form  1768  includes loop  1756 , strut  1754  including a “bar-bell” shape, and wire  1758  attaching loop  1756  and strut  1754 . Strut  1754  of the each discrete retention wire form  1768  is attached to inner surface  1764  of stent graft  1752  a distance from first edge  1762  by suture  1760 , and loop  1756  extends beyond first edge  1762 . Suture  1760  is configured to attach strut  1764  to stent graft  1752  around a “bar” of each “bar-bell” shape. Strut  1754  of the each discrete retention wire form  1768  is attached to inner surface  1764  between two apices  1770  of first apices  1770  of stent  1772 . At least one of the plurality of discrete retention wire forms  1768  is configured to engage a trigger wire at loop  1756 . Loop  1756  extends beyond first edge  1762  of outer surface  1766  of stent graft  1752  such that wire  1758  passes through stent graft  1752 . 
     Although the present disclosure has been described with reference to examples and the accompanying drawings, the present disclosure is not limited thereto, but may be variously modified and altered by those skilled in the art to which the present disclosure pertains without departing from the spirit and scope of the present disclosure. 
     The subject-matter of the present disclosure may also relate, among others, to the following aspects: 
     A first aspect relates to a stent graft retention system for retaining a stent graft on a delivery device, comprising: a stent graft comprising: a first end; a second end: a first edge at the first end; and a stent comprising first apices and second apices, the first apices disposed adjacent the first end and the second apices extending toward the second end; and a plurality of discrete retention wire forms each comprising a first strut, a second strut, and an apex between the first and second struts; wherein the first and second struts are attached to the stent graft a distance from the first edge and the apex extends beyond the first edge; wherein the each discrete retention wire form is nested with an apex of the first apices; and wherein at least one of the plurality of discrete retention wire forms is configured to engage a trigger wire. 
     A second aspect relates to the stent graft retention system of aspect  1 , further comprising sutures configured to attach the first and second struts of the each discrete retention wire form to the stent graft. 
     A third aspect relates to the stent graft retention system of any preceding aspect, wherein the each discrete retention wire form is v-shaped. 
     A fourth aspect relates to the stent graft retention system of any preceding aspect, wherein the first and second struts of the each discrete retention wire form comprise flat hooks. 
     A fifth aspect relates to the stent graft retention system of any of aspects  1  to  3 , wherein the first and second struts of the each discrete retention wire form comprise bar-bells. 
     A sixth aspect relates to the stent graft retention system of aspect  5 , further comprising sutures configured to attach the first and second struts of the each discrete retention wire form to the stent graft; wherein the sutures are configured to attach the first and second struts around a bar of each bar-bell. 
     A seventh aspect relates to the stent graft retention system of any preceding aspect, wherein the first and second struts of the each discrete retention wire form are attached to the stent graft on a first surface of the stent graft and the apex of the each discrete retention wire form extends beyond the first edge of a second surface of the stent graft, the second surface opposite the first surface. 
     An eighth aspect relates to the stent graft retention system of aspect  7 , wherein the first and second struts of the each discrete retention wire form pass through eyelets in the stent graft. 
     A ninth aspect relates to the stent graft retention system of any preceding aspect, wherein the plurality of discrete retention wire forms are disposed symmetrically about a circumference of the first edge. 
     A tenth aspect relates to a stent graft retention system for retaining a stent graft on a delivery device, comprising: a stent graft comprising: a first end; a second end; a first edge at the first end; and a stent comprising first apices and second apices, the first apices disposed adjacent the first end and the second apices extending toward the second end; and a plurality of discrete retention wire forms each comprising a first loop, a second loop, and a wire attaching the first loop and the second loop; wherein the first loop of the each discrete retention wire form is attached to the stent graft a distance from the first edge and the second loop extends beyond the first edge; wherein the first loop of the each discrete retention wire form is attached to the stent graft between an apex of the first apices and the first edge; and wherein at least one of the plurality of discrete retention wire forms is configured to engage a trigger wire. 
     An eleventh aspect relates to the stent graft retention system of aspect  10 , further comprising sutures configured to attach the first loop of the each discrete retention wire form to the stent graft. 
     A twelfth aspect relates to the stent graft retention system of aspects  10  or  11 , wherein the first loop of the each discrete retention wire form is attached to the stent graft on a first surface of the stent graft and the second loop of the each discrete retention wire form extends beyond the first edge of a second surface of the stent graft, the second surface opposite the first surface. 
     A thirteenth aspect relates to the stent graft retention system of aspect  12 , wherein the wire of the each discrete retention wire form passes through an eyelet in the stent graft. 
     In addition to the features mentioned in each of the independent aspects enumerated above, some examples may show, alone or in combination, the optional features mentioned in the dependent aspects and/or as disclosed in the description above and shown in the figures.