Patent Publication Number: US-9427307-B2

Title: Circumferentially constraining sutures for a stent-graft

Description:
RELATED APPLICATIONS 
     This application is a Division of and claims the benefit of U.S. application Ser. No. 13/458,076 filed Apr. 27, 2012, now allowed, the disclosures of which are herein incorporated by reference in their entirety. 
    
    
     FIELD OF THE INVENTION 
     This invention relates generally to endoluminal medical devices and procedures, and more particularly to an endoluminal prosthesis or stent-graft having circumferentially constraining sutures to circumferentially constrain the stent-graft for a partial deployment of the stent-graft. 
     BACKGROUND 
     Aneurysms and/or dissections may occur in blood vessels, and most typically occur in the aorta and peripheral arteries. Depending on the region of the aorta involved, the aneurysm may extend into areas having vessel bifurcations or segments of the aorta from which smaller “branch” arteries extend. Various types of aortic aneurysms may be classified on the basis of the region of aneurysmal involvement. For example, thoracic aortic aneurysms include aneurysms present in the ascending thoracic aorta, the aortic arch, and branch arteries that emanate therefrom, such as subclavian arteries, and also include aneurysms present in the descending thoracic aorta and branch arteries that emanate therefrom, such as thoracic intercostal arteries and/or the suprarenal abdominal aorta and branch arteries that emanate therefrom, which could include renal, superior mesenteric, celiac and/or intercostal arteries. Lastly, abdominal aortic aneurysms include aneurysms present in the aorta below the diaphragm, e.g., pararenal aorta and the branch arteries that emanate therefrom, such as the renal arteries. 
     For patients with aneurysms of the aorta, surgery to replace the aorta may be performed where a portion of the aorta is replaced with a fabric substitute in an operation that uses a heart-lung machine. In such a case, the aneurysmal portion of the aorta is removed or opened and a substitute lumen is sewn across the aneurysmal portion to span it. Such surgery is highly invasive, requires an extended recovery period and, therefore, cannot be performed on individuals in fragile health or with other contraindicative factors. 
     When aneurysms are near branch vessels or extend into branch vessels, stent-grafts are used with fenestrations, external couplings, or other means for branch stent-grafts to be deployed into the branch vessels. The location of such fenestrations or external couplings may be critical so as not to block branch vessels. Further, when aneurysms are near branch vessels, the “landing zone” for the stent-graft may be limited such that accurate placement of the stent-graft is critical. Thus, it is desirable to be able to accurately position the stent-graft. However, stents of the stent-graft are normally designed to expand to a size larger than the target vessel to ensure apposition against the vessel wall. Thus, re-positioning the stent-graft after deployment is difficult. It is thus desirable to partially deploy the stent-graft to a diameter larger than the delivery catheter diameter, but smaller than the fully deployed diameter to enable re-positioning of the stent-graft. 
     Further, when aneurysms are located near branch vessels, it may be desirable to deploy the stent-graft to a diameter smaller than the fully deployed diameter in the main vessel in order to perform various actions to cannulate the branch vessels prior to completely deploying the stent-graft. Partially deploying the stent-graft allows for space outside of the stent-graft within the main vessel to perform such actions. 
     Devices to maintain stent-grafts in a partially deployed configuration after release from a catheter have been contemplated. However, with current devices, the stent-graft may jump out of position when the stent-graft is deployed. Accordingly, it would be desirable to minimize any movement of the stent-graft when fully deploying the stent graft by releasing the circumferentially constraining sutures. 
     SUMMARY OF THE INVENTION 
     Embodiments hereof relate to circumferentially constraining sutures for a stent-graft. The stent-graft includes a tubular body of a graft material and a plurality of stents coupled to the tubular body. The circumferentially constraining suture in a reduced diameter configuration includes a first end attached to one of the stent and extending circumferentially around a complete circumference of the tubular body, with a loop of the circumferentially constraining suture disposed opposite the first end being coupled to a trigger wire extending in a longitudinal direction along the tubular body. In a deployed configuration, the trigger wire is disengaged from the loop such that the stent radially expands and the circumferentially constraining suture extends only partially around the circumference of the tubular body. 
     Embodiments hereof also relate to circumferentially constraining sutures for stent-grafts. The stent-graft includes a tubular body of a graft material and a plurality of stents coupled to the tubular body. The circumferentially constraining suture includes a first thread coupled at a first end to the tubular body or one of the stents and having a first thread loop disposed opposite the first end, the first thread extending only partially around a circumference of the tubular body when the stent-graft is in a radially expanded configuration. The circumferentially constraining suture further includes a second thread having a second thread loop interlocked with the first thread loop, the second thread extending from the first thread loop around a remainder of the circumference of the tubular body. The circumferentially constraining suture is configured such that pulling the second thread causes the first thread to circumferentially constrain the tubular body such that the tubular body constricts to a reduced diameter configuration. 
     Embodiments hereof also relate to a method for temporarily reducing the diameter of at least a portion of a self-expanding stent-graft. The stent-graft includes a tubular body of a biocompatible graft material and a plurality of self-expanding stents. A first thread having a first thread loop and a second thread having a second thread loop are interlocked. The first thread at a first end opposite the first thread loop is attached to one of the stents. The first thread is extended around a first portion of the circumference of the tubular body and the second thread around is extended from the first thread around a second portion of the circumference of the tubular body. The second thread is pulled to cause the first loop of the first thread to move along the second portion of the circumference to reduce the diameter of the tubular body. A trigger wire is inserted longitudinally along the tubular body and through the first loop to retain the tubular body in a reduced diameter configuration after the second thread is removed. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a perspective view of a main vessel stent-graft including circumferentially constraining sutures according to an embodiment hereof, wherein the main vessel stent-graft in radially expanded configuration. 
         FIG. 2  is a schematic illustration of a circumferentially constraining suture. 
         FIG. 2A  is a schematic illustration of a circumferentially constraining suture. 
         FIG. 3  is zoomed in view of a portion of the stent-graft prosthesis of  FIG. 1  where an end of a first thread of a circumferentially constraining suture is attached to a stent and an end of a second thread of the circumferentially constraining suture exits the stent. 
         FIGS. 3A-3C  are schematic illustrations of embodiments of the first end of a first thread attached to a strut of a stent. 
         FIG. 4  is zoomed in view of a portion of the stent-graft of  FIG. 1  where the first thread and the second thread are interlocked. 
         FIG. 5  is a schematic illustration of a circumferentially constraining suture of the stent-graft of  FIG. 1  with the second thread pulled to tighten the first thread around the stent-graft. 
         FIG. 6  is a schematic illustration of a trigger wire being inserted through a first thread loop of a circumferentially constraining suture. 
         FIG. 7  is a schematic illustration of the stent graft prosthesis of  FIG. 1  in a reduced diameter configuration with the trigger wire extending through the first thread loop of each circumferentially constraining suture. 
         FIGS. 8-14  schematically illustrate a method of delivering the main vessel stent-graft of  FIG. 1  to a target site in the abdominal aorta, partial deployment of the stent-graft, and full deployment of the stent-graft after release of the circumferentially constraining sutures. 
     
    
    
     DETAILED DESCRIPTION 
     Specific embodiments of the present invention are now described with reference to the figures, wherein like reference numbers indicate identical or functionally similar elements. Specific embodiments are now described with reference to the figures, wherein like reference numbers indicate identical or functionally similar elements. Unless otherwise indicated, for the delivery system the terms “distal” and “proximal” are used in the following description with respect to a position or direction relative to the treating clinician. “Distal” and “distally” are positions distant from or in a direction away from the clinician, and “proximal” and “proximally” are positions near or in a direction toward the clinician. For the stent-graft prosthesis proximal is the portion nearer the heart by way of blood flow path while distal is the portion of the stent-graft further from the heart by way of blood flow path. In addition, the term “self-expanding” is used in the following description with reference to one or more stent structures of the prostheses hereof and is intended to convey that the structures are shaped or formed from a material that can be provided with a mechanical memory to return the structure from a compressed or constricted delivery configuration to an expanded deployed configuration. Non-exhaustive exemplary self-expanding materials include stainless steel, a pseudo-elastic metal such as a nickel titanium alloy or nitinol, various polymers, or a so-called super alloy, which may have a base metal of nickel, cobalt, chromium, or other metal. Mechanical memory may be imparted to a wire or stent structure by thermal treatment to achieve a spring temper in stainless steel, for example, or to set a shape memory in a susceptible metal alloy, such as nitinol. Various polymers that can be made to have shape memory characteristics may also be suitable for use in embodiments hereof to include polymers such as polynorborene, trans-polyisoprene, styrene-butadiene, and polyurethane. As well poly L-D lactic copolymer, oligo caprylactone copolymer and poly cyclo-octine can be used separately or in conjunction with other shape memory polymers. 
     The following detailed description is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. Although the description of the invention is in the context of treatment of blood vessels such as aorta, the invention may also be used in any other blood vessels and body passageways where it is deemed useful. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding technical field, background, brief summary or the following detailed description. 
     With reference to  FIGS. 1-7 , a self-expanding main vessel endovascular prosthesis or stent-graft  100  is configured for placement in a vessel such as the abdominal aorta. In the particular embodiment shown, main vessel stent-graft  100  is a bifurcated stent-graft configured to treat short-neck infrarenal, juxtarenal, and/or suprarenal aneurysms in a wide range of patient anatomies. However, the invention is not so limited and may also be used for stent-grafts for use in other areas and without all of the features described below. 
       FIG. 1  illustrates a perspective view of main vessel stent-graft  100  in a radially expanded configuration prior to placement within a delivery catheter. In this application, the terms “radially expanded configuration” and “deployed configuration” are used to describe the stent-graft when it is not in a delivery catheter and without circumferentially constraining sutures (described below) restricting the expansion of the stents of the stent-graft prosthesis. However, it would be recognized by those skilled in the art that the “radially expanded configuration” and the “deployed configuration” may not be exactly the same diameter because at least some of the stents of the stent-graft may be oversized to ensure a tight seal of the stent-graft to the vessel wall. Accordingly, the “deployed configuration” may be smaller than the “radially expanded configuration” in practice due to the vessel wall restricted expansion of the stents. However, for purposes of this application, the terms generally mean that there are no outside forces (other than the vessel wall) restricting expansion of the stent-graft prosthesis. Stent-graft  100  includes a generally tubular or cylindrical graft or body  102  that defines a lumen  107  and has a first edge or end  106  and a second edge or end  108 . Tubular graft  102  may be formed from any suitable graft material, for example and not limited to, a low-porosity woven or knit polyester, DACRON material, expanded polytetrafluoroethylene, polyurethane, silicone, ultra high molecular weight polyethylene, or other suitable materials. In another embodiment, the graft material could also be a natural material such as pericardium or another membranous tissue such as intestinal submucosa. A plurality of stents  104  are coupled to graft  102 . Stents  104  may be coupled to graft  102  by stitching  110  or by other means known to those skilled in the art. In the embodiment shown, stents  104  are coupled to an outside surface of graft  102 , but stents  104  may alternatively be coupled to an inside surface of graft  102 . 
     An anchor stent  112  is coupled to graft  102  adjacent first end  106  of graft  102 . Anchor stent  112  is a radially-compressible ring or scaffold that is operable to self-expand into apposition with an interior wall of a body vessel (not shown). Anchor stent  112  is constructed from a self-expanding or spring material, such as nitinol, and is a sinusoidal patterned ring including a plurality of crowns or bends  113 A,  113 B and a plurality of struts or straight segments  115  with each crown being formed between a pair of opposing struts. Anchor stent  112  is coupled to the graft material so as to have a first or proximal-most set of crowns  113 A that extend outside of or beyond first edge  106  of graft  102  in an open web or free-flow configuration and a second or opposing set of crowns  113 B that is coupled to first edge  106  of tubular graft  102 . Crowns  113 B are coupled to tubular graft  102  by stitches or other means known to those of skill in the art. In the embodiment shown, crowns  113 B are coupled to an outside surface of tubular graft  102 . However, crowns  113 B may alternatively be coupled to an inside surface of tubular graft  102 . Unattached or free crowns  113 A may include barbs  114  for embedding into and anchoring into vascular tissue when stent-graft prosthesis  100  is deployed in situ. In an embodiment, anchor stent  112  may be the Endurant II™ suprarenal stent, manufactured by Medtronic, Inc., of Minneapolis, Minn. 
     A scallop  117  cut out or removed from graft  102  at proximal or first end  106 . Scallop  117  is an open-topped fenestration. When deployed in situ, scallop  117  is positioned within the aorta distal of the superior mesenteric artery (SMA) and extends around and/or frames the ostium of the SMA. In short-neck infrarenal, juxtarenal, and/or suprarenal aneurysms, first edge  106  of tubular graft  102  is deployed within the abdominal aorta at or near the superior mesenteric artery (SMA). In order to avoid blockage of blood flow into the superior mesenteric artery (SMA), stent-graft  100  is positioned or oriented within the abdominal aorta such that scallop  117  is positioned around the ostium of the superior mesenteric artery (SMA) and the graft material of tubular graft  102  does not occlude the ostium of the SMA. The presence of scallop  117  for the SMA allows for main vessel stent-graft  100  to deploy and seal against a sufficient length, i.e., greater than 10 mm, of healthy or non-aneurysmal tissue distal to the SMA for patients suffering from short-neck infrarenal, juxtarenal, and/or suprarenal aneurysms. 
     A seal stent  119  is coupled to graft  102  at first end  106 . Seal stent  119  is configured to accommodate scallop  117 . Seal stent  119  is a radially-compressible ring or scaffold that is coupled to tubular graft  102  for supporting the graft material and is operable to self-expand into apposition with an interior wall of a blood vessel (not shown). Seal stent  119  is constructed from a self-expanding or spring material, such as nitinol, and is a sinusoidal patterned ring including a plurality of crowns or bends and a plurality of struts or straight segments with each crown being formed between a pair of opposing struts. Seal stent  119  is coupled to tubular graft  102 , immediately distal of first end  106  thereof and distal of anchor stent  112 . Seal stent  119  is coupled to tubular graft  102  by stitches or other means known to those of skill in the art. In the embodiment shown, seal stent  119  is coupled to an outside surface of tubular graft  102 , but seal stent  119  may alternatively be coupled to an inside surface of tubular graft  102 . Seal stent  119  includes at least two struts that are lengthened or elongated with respect to the remaining struts to accommodate scallop  117 . 
     In the embodiment shown, stent-graft  100  includes a first tubular leg or extension  116  and a second tubular leg or extension  118 , each extending from second end  108 . Legs  116 ,  118  define lumens that are in fluid communication with lumen  107  of tubular graft  102 . In an embodiment, legs  116 ,  118  are integrally formed with tubular graft  102  as a unitary graft component and thus are formed from the same material as tubular graft  102 . In another embodiment, legs  116 ,  118  may be formed separately from tubular graft  102  and coupled thereto. In the embodiment shown, legs  116 ,  118  are of equal length and are oriented anterior and posterior within the abdominal aorta when deployed in the abdominal aorta. 
     Stent-graft  100  also includes couplings  120 ,  122  for connecting stent-graft  100  to branch vessel prostheses (not shown) to accommodate the left and right renal arteries, respectively. Tubular graft  102  includes opposing fenestrations or openings formed through a sidewall of the graft material. Couplings  120 ,  122  are disposed on an outside surface of main vessel stent-graft  100  corresponding to openings in tubular graft  102 . Couplings  120 ,  122  may be generally cylindrically shaped or frustoconically shaped. Couplings  120 ,  122  include coupling graft material. The graft material of couplings  120 ,  122  may be the same type of graft material as the graft material of tubular graft  102  or it may be a different material. Also, in the embodiment shown, couplings  120 ,  122  are separate components that are attached to tubular graft  102 . However, it would be understood by those of ordinary skill in the art that couplings  120 ,  122  may be formed as a continuation of tubular graft  102 . Couplings  120 ,  122  include self-expanding support stents or sinusoidal rings  124 ,  126 , respectively, coupled to the coupling graft material. Support stents  124 ,  126  are constructed from a self-expanding or spring material, such as nitinol, and is a sinusoidal patterned ring including a plurality of crowns or bends and a plurality of struts or straight segments with each crown being formed between a pair of opposing struts. In an embodiment, support stents  124 ,  126  are four peak stents and thus include eight crowns, although it will be apparent to one of ordinary skill in the art that the support stent may include more or less crowns. Other embodiments of couplings  124 ,  126  may be used as would be understood by those skilled in the art. 
     Although stent-graft  100  has been described generally above, more details of stent-graft  100  may be found in U.S. patent application Ser. Nos. 13/458,209 and 13/458,242 to Coghlan et al., filed Apr. 27, 2012 (now published as U.S. Pub. Nos. 2013/0289701 A1 and 2013/0289702 A1), herein incorporated by reference in their entirety. Further, although stent-graft  100  has been described with the particular features described above, the circumferentially constraining sutures described below may be used with any stent-graft where it is desirable to have a staged deployment of the stent-graft prosthesis. 
     As described above,  FIG. 1  shows stent-graft  100  in a radially expanded configuration prior to placement within a delivery catheter for delivery to a treatment site. In the embodiment shown, five circumferentially constraining sutures  130  are disposed around stent-graft  100 . Circumferentially constraining sutures  130 , when utilized as described in more detail below, reduce the diameter of stent-graft prosthesis  100  by about 40 to 70 percent from the radially expanded configuration. However, stent-graft  100  in the reduced diameter configuration has a diameter about 40 to 50 percent larger than in a delivery configuration wherein stent-graft  100  is disposed within a sleeve of a delivery catheter. Those of ordinary skill in the art would recognize that by adjusting the length of the threads of the circumferentially constraining sutures, as described in more detail below, the reduction in the diameter of stent-graft prosthesis by the circumferentially constraining sutures may be varied outside of the ranges noted above. 
     In the embodiment shown, circumferentially constraining sutures  130  are disposed around the graft material of tubular graft  102  adjacent five of stents  104 . As explained in more detail below, anchor stent  112  is held by a tip capture mechanism during delivery and partial deployment of stent-graft  100 . The tip capture mechanism holds proximal-most crowns  113 A of anchor stent  112  in a reduced diameter configuration after retraction of the outer sheath or sleeve covering stent-graft  100 , as known to those skilled in the art. Thus, anchor stent  112  and seal stent  119  do not include circumferentially constraining sutures because they do not fully deploy due to the tip capture mechanism. However, as would be understood by those skilled in the art, more or less circumferentially constraining sutures  130  may be utilized depending on the number of stents  104  coupled to tubular graft  102 , the particular application and procedure, and the locations where it is desirable to have a reduced diameter. 
     Each circumferentially constraining suture  130  comprises a first thread or string  132  interlocked with a second thread or string  134  at interlocking location  140 . First thread  132  is formed into a first thread loop  136  by having a first end  146  and a second end  147  of first thread  132  disposed tied to each other at knot  137 , as shown in  FIG. 2 . Essentially, first thread  132  is folded back at approximately a mid-point thereof to form a first thread loop  136 . First thread  132  has a first thread length FL that is less than the circumference of stent-graft  100 . In particular, first thread length FL may be between 30% and 60% of the circumference of stent-graft  100 . Similarly, second thread  134  is folded back at approximately a mid-point thereof to form a second thread loop  138 , as shown in  FIG. 2 . As explained above, first thread length FL may be shorter to make the reduced diameter smaller and first thread length FL may be longer to make the reduced diameter larger. First thread loop  136  and second thread loop  138  are interlocked with each other at  140  as shown in  FIG. 2 . As also shown in  FIG. 2 , ends  142  and  143  of second thread  134  disposed opposite second thread loop  138  are tied or otherwise attached to a pull tab  144 . Pull tab  144  as shown is a circular, donut shaped tab with ends  142 ,  143  of second thread  134  tied to pull tab  144 . However, those of ordinary skill in the art would recognize that other pull tabs may be used, or a large knot tied in ends  142 ,  143  may function as a pull tab. Further, those of ordinary skill in the art would recognize that other ways of forming first and second threads with interlocked first and second thread loops may be used. For example, and not by way of limitation,  FIG. 2A  shows first end  246  of first thread  232  that may be attached to strut  105  (see  FIG. 3C  described below), and second end  247  may form a first thread loop  232  by forming a loop and tying second end  247  to first thread  232  and  245 . Similarly, one end  242  of second thread  234  may be tied to pull tab  244  and the other end  243  of second thread  234  may form a loop  238  and be tied to second thread  234  at  245 . Other ways of forming first and second thread loops may be used, as known to those skilled in the art. First thread  132 ,  232  and second thread  134 ,  234  may be monofilament or braided and formed of polyester, ultra high molecular weight polyethelene (UHMWPE), polypropylene, or other alternate thread materials known to those skilled in the art. 
     In the embodiment shown, first and second ends  146 ,  147  of first thread  132  are tied to each other to form first thread loop  136 , and first thread loop  136  is tied to a strut  105  of a stent  104 , as shown in detail in  FIG. 3A . First thread  132  then extends between stent  104  and the graft material of body  102 , as shown in  FIGS. 3 and 4 . First thread  132  also extends between stitches  110  which attach stent  104  to the graft material of body  102 , thereby keeping first thread  132  from moving longitudinally along stent-graft prosthesis  100 . First thread  132  is interlocked with second thread  134 , which also extends circumferentially around graft material  102  between the graft material and stent  104 , as shown in  FIG. 4 . Other ways of forming first thread loop  136  and of attaching first thread loop  136  to stent  104  may be utilized, as would be recognized by those skilled in the art. For example, and not by way of limitation, ends  146 ,  147  of first thread  132  may be tied to each other around strut  105 , as shown in  FIG. 3B . Further, using the first thread loop  234  shown in  FIG. 2A , first end  246  of first thread may be tied around strut  105  at knot  248  and first thread loop  236  is disposed at the opposite end of knot  248  by having second end  247  form loop  236  and then tying second end  247  to first thread  232 , as shown in  FIG. 3C . 
     Circumferentially constraining sutures  130  function to circumferentially constrain stent-graft  100 , as will be described with reference to  FIGS. 5-7 . First, as shown in  FIG. 5 , second thread  134  is pulled by pulling on pull tab  144 . Because first thread  132  is attached to a body stent  104  at an end opposite first thread loop  136 , and second thread  134  is disposed between graft  102  and stents  104 , pulling second thread  134  causes first thread to continue around the circumference of stent-graft  100 , following the path of second thread  134  until the location where pull tab  144  was initially located. At that point, pulling second thread  134  causes first thread to continue following second thread  134 , but first thread loop  136  may extend radially away from stent-graft  100 , as shown in  FIG. 5 . Further, because first thread  132  is fixed to a stent  104  at  148 , pulling second thread  134  and first thread  132  along with it causes first thread  132  to circumferentially close or tighten or shrink stent-graft  100  in the area of circumferentially constraining suture  130 , as also shown in  FIG. 5 . 
     Next, as shown in  FIG. 6 , a release or trigger wire  150  extending generally longitudinally along stent-graft  100  is inserted through first thread loop  136 . The steps of  FIGS. 5 and 6  are repeated for each circumferentially constraining suture  130  of stent-graft  100 . Preferably, the same trigger wire  150  is used for all the circumferentially constraining sutures, but it is not necessary. Although  FIGS. 5 and 6  show the middle circumferentially constraining suture  130 , it would be understood that with a single trigger wire  150 , it is preferable to proceed from either the proximal-most or the distal-most circumferentially constraining suture  130  and proceed either distally or proximally, respectively, with trigger wire  150  advancing along either distally or proximally, respectively, to engage each first thread loop  136  of each first thread  132 . 
     When each first thread loop  136  of each first thread  132  is engaged by trigger wire  150 , each second thread  134  may be removed. This causes the stent  104  associated with the circumferentially constraining suture to try to expand to its radially expanded diameter. However, because trigger wire  150  holds first threaded loop  136  at the location where second thread  134  exited from between graft  102  and the stent  104 , and the first thread length FL of first thread  132  is fixed and is less than the circumference of stent-graft  100 , trigger wire  150  holds stent-graft  100  in a reduced diameter configuration. It is preferable that pull tab  144  is located adjacent knot  148 , as shown in  FIG. 3 . In other words, it is preferable that when trigger wire  150  holds circumferentially constraining suture  130  such that stent-graft  100  is in the reduced diameter configuration, first thread  132  extends completely around the circumference of stent-graft  100 . In such an embodiment, the first thread length FL of first thread  132  determines the amount that the circumferentially constraining suture  130  reduces the diameter of stent-graft  100 . Further, in such an embodiment, the circumferentially constraining suture  130  constrains stent-graft  100  around the entire circumference of stent-graft  100 , thereby applying equal restraining force around the circumference of the stent-graft to minimize movement of the stent-graft when releasing stent graft prosthesis  100  from the circumferentially constraining sutures  130  by removing the trigger wire  150 . 
     After the trigger wire  150  is disposed through first thread loop  136  of each circumferentially constraining suture  130 , second thread  134  can be removed such as by cutting second thread loop  138 . This leaves stent-graft  100  in the reduced diameter configuration with trigger wire  150  disposed through each first thread loop  136  of each first thread  132  of each circumferentially constraining suture  130 , as shown in  FIG. 7 . Trigger wire  150  extends within a delivery catheter to a handle of the delivery catheter such that a user may pull trigger wire  150  to release each circumferentially constraining suture  130  such that stent-graft prosthesis  100  may expand to its deployed configuration, as described in more detail below. Trigger wire  150  may be any suitable wire formed of any suitable material. For example, and not by way of limitation, trigger wire may be formed of nitinol, and may have a diameter in the range of 0.010 to 0.014 inch. However, it is understood that different materials and different sizes can be used provided that the trigger wire can perform the functions described herein of holding first thread  132  to maintain the stent-graft in a reduced diameter configuration and of releasing the circumferentially constraining suture by retraction of the trigger wire without excessive force by the user. 
     Stent-graft  100  can then be disposed within a delivery catheter as known to those skilled in the art. After delivery to a target site and partial deployment of stent-graft prosthesis  100  from a sheath or outer cover of the delivery system, trigger wire  150  may be retracting proximally (i.e., towards the clinician) to release circumferentially constraining sutures  130  and allow stent-graft prosthesis  100  to fully deploy to its radially expanded or deployed configuration, as described in more detail below. With second thread  134  removed from each circumferentially constraining suture  130 , only first thread  132  remains. The drawings and description regarding delivery and deployment of the stent-graft  100  may refer to first thread  132  and circumferentially constraining suture  130  interchangeably. 
       FIG. 8  shows a main vessel delivery system  882 , with main vessel stent-graft  100  compressed therein, advanced over a main vessel guide wire  884  and to the target site in the abdominal aorta A. Guide wire  884  is typically inserted into the femoral artery and routed up through the left iliac artery LI to abdominal aorta, as is known in the art.  FIGS. 8-14  show a posterior view of the aorta A and the vessels that branch therefrom. Accordingly, the superior mesenteric artery (SMA), for example, is shown exiting the anterior side of the aorta opposite the posterior side shown in the drawings, and is therefore shown in phantom where blocked by the aorta.  FIGS. 8-14  show similar devices as those shown and described in co-pending U.S. patent application Ser. Nos. 13/457,535 and 13/457,544 to Maggard et al., filed Apr. 27, 2012 (now published as U.S. Pat. Pub. Nos. 2013/0289696 A1 and 2013/0289693 A1, respectively); U.S. patent application Ser. Nos. 13/457,537 and 13/457,541 to Argentine et al., filed Apr. 27, 2012 (now published as U.S. Pat. Pub Nos. 2013/0289691 A1 and 2013/0289692 1, respectively); and U.S. patent application Ser. Nos. 13/458,209 and 13/458,242 to Coghlan et al., filed Apr. 27, 2012 (now published as U.S. Pat. Pub. Nos. 2013/0289701 A1 and 2013/0289702 A1), herein incorporated by reference in their entirety. However, in the above-identified applications, the views of the delivery and deployment of the stent-graft prosthesis are anterior views of the aorta. Delivery system  882  is fully described in co-pending U.S. patent application Ser. Nos. 13/457,535 and 13/457,544 to Maggard et al., filed Apr. 27, 2012 (now published as U.S. Pat. Pub. Nos. 2013/0289696 A1 and 2013/0289693 A1, respectively); and U.S. patent application Ser. Nos. 13/457,537 and 13/457,541 to Argentine et al., filed Apr. 27, 2012 (now published as U.S. Pat. Pub. Nos. 2013/0289691 A1 and 2013/0289692 A1, respectively), herein incorporated by reference in their entirety. Main vessel stent-graft prosthesis  100  is mounted on a catheter shaft  988  (see  FIG. 9 ) of the delivery system and an outer delivery sheath  886  of the delivery system covers and restrains main vessel stent-graft prosthesis  100  in a radially compressed delivery configuration for delivery thereof. As will be understood by those of ordinary skill in the art, delivery system  882  may include a tip capture mechanism (not shown) which engages the proximal-most set of crowns of anchor stent  112  until retraction of the tip capture mechanism releases the proximal-most set of crowns for final deployment of main vessel stent-graft prosthesis  100 . 
       FIG. 9  illustrates a first or initial step to deploy main vessel stent-graft prosthesis  100  in which outer delivery sheath  886  of delivery system  882  is retracted to release or uncover a proximal end portion of main vessel stent-graft prosthesis  100 . When first released from the delivery system, the proximal end portion may be positioned such that scallop  117  (not shown in  FIG. 9 ) is below the target site of the superior mesenteric artery (SMA). The proximal-most set of crowns of anchor stent  112  is captured or restrained by the tip capture mechanism of delivery system  882 . Delivery sheath  886  is retracted to expose at least seal stent  119 . In the embodiment of  FIG. 9 , delivery sheath  886  is shown as retracted to expose a body stent  104 . 
     As described in co-pending U.S. patent application Ser. Nos. 13/457,535 and 13/457,544 to Maggard et al., filed Apr. 27, 2012 (now published as U.S. Pat. Pub. Nos. 2013/0289696 A1 and 2013/0289693 A1, respectively); U.S. patent application Ser. Nos. 13/457,537 and 13/457,541 to Argentine et al., filed Apr. 27, 2012 (now published as U.S. Pat. Pub. Nos. 2013/0289691 and 2013/0289692 A1, respectively); and U.S. patent application Ser. Nos. 13/458,209 and 13/458,242 to Coghlan et al., filed Apr. 27, 2012 (now published as U.S. Pat. Pub. Nos. 2013/0289701 A1 and 2013/0289702 A1), previously incorporated by reference in their entirety, the superior mesenteric artery (SMA) is cannulated and the main vessel stent-graft  100  is repositioned to align scallop  117  with the superior mesenteric artery (SMA). The terms “cannulation” and “cannulate” are used herein with reference to the navigation of a guidewire and guide catheter into a target vessel. 
     With the proximal end portion of main vessel stent-graft  100  now positioned as desired, delivery sheath  886  is shown retracted in  FIG. 10  to expose at least couplings  120 ,  122  of main vessel stent-graft prosthesis  100 . Anchor stent  112  is still captured or restrained by the tip capture mechanism of delivery system  882  such that the proximal end portion of stent-graft  100  does not fully deploy. Further, first threads  132  of circumferentially constraining sutures  130  prevent the stent-graft prosthesis  100  from fully deploying in the areas that have been released from sheath  886 . These areas radially expand from the delivery configuration to a reduced diameter configuration that is radially larger than the delivery configuration but 30 to 60% smaller in diameter than the deployed configuration, as explained above. 
     The renal arteries, right renal artery RR and left renal artery LR, are then cannulated, as described in co-pending U.S. patent application Ser. Nos. 13/457,535 and 13/457,544 to Maggard et al., filed Apr. 27, 2012 (now published as U.S. Pat. Pub. Nos. 2013/0289696 A1 and 2013/0289693 A1, respectively); U.S. patent application Ser. Nos. 13/457,537 and 13/457,541 to Argentine et al., filed Apr. 27, 2012 (now published as U.S. Pat. Pub. Nos. 2013/0289691 A1 and 2013/0289692 A1, respectively); and U.S. patent application Ser. Nos. 13/458,209 and 13/458,242 to Coghlan et al., filed Apr. 27, 2012 (now published as U.S. Pat. Pub. Nos. 2013/0289701 A1 and 2013/0289702 A1), previously incorporated by reference in their entirety. The renal arteries are cannulated while sheath  886  is partially retracted as shown in  FIG. 10 . After the renal arteries have been cannulated, the sheath  886  is fully retracted to release stent-graft  100  from sheath  886  and the branch vessel prosthesis delivery systems are advanced into the renal arteries. This leaves main vessel stent-graft  100  partially deployed in a reduced diameter configuration due to first threads of circumferentially constraining sutures  130 , as shown in  FIG. 11 . 
     Trigger wire  150  is then retracted proximally (i.e. towards the physician), as shown by the arrow in  FIG. 12 . As trigger wire  150  moves past stents  104 A and  104 B, first threads  132 A and  132 B of circumferentially constraining sutures are released, allowing that portion of stent-graft  100  to expand to the deployed configuration. First threads  132 A,  132 B remain attached at one end to stents  104 A,  104 B, respectively, as described above and shown at  148 A, and first threads  132 A,  130 B extend between graft  102  and stents  104 A,  104 B. Because first threads  132 A and  132 B are each shorter than the circumference of the deployed stent-graft prosthesis  100 , each first thread  132 A,  132 B extends only partially around the circumference of stent-graft prosthesis  100 . Further, since first thread loop  136  (not shown in  FIG. 12 ) of first threads  132 A,  132 B is not attached to trigger wire  150  or any portion of stent-graft prosthesis  100 , first and second threads  132 A,  132 B do not exert a radial force to constrain stent-graft  100  in a reduced diameter configuration. As trigger wire  150  continues to be retracted proximally, the remaining first threads  132 C,  132 D,  132 E of the respective circumferentially constraining sutures  130  are released, thereby allowing stent-graft  100  to fully deploy, as shown in  FIG. 13 . In addition, anchor stent  112  may be released from the tip capture mechanism of the delivery system  882 , as also shown in  FIG. 13 . When anchor stent  112  is released from delivery system  882 , seal stent  119  fully expands and conformingly engages and seals the edges of scallop  117  with the blood vessel inner wall. Trigger wire  150  for circumferentially constraining sutures  130  may also be used as a capture mechanism (not shown) as described in co-pending U.S. patent application Ser. Nos. 13/457,535 and 13/457,544 to Maggard et al., filed Apr. 27, 2012 (now published as U.S. Pat. Pub. Nos. 2013/0289696 A1 and 2013/0289693 A1, respectively); and U.S. patent application Ser. Nos. 13/457,537 and 13/457,541 to Argentine et al., filed Apr. 27, 2012 (now published as U.S. Pat. Pub. Nos. 2013/0289691 A1 and 2013/0289692 A1, respectively), previously incorporated by reference herein in their entirety. 
     The branch vessel stent-graft prostheses may then be deployed within right renal artery RR and left renal artery LR, respectively, by retracting outer sheaths of the branch vessel stent-graft delivery systems, as known to those skilled in the art and described in co-pending U.S. patent application Ser. Nos. 13/457,535 and 13/457,544 to Maggard et al., filed Apr. 27, 2012 (now published as U.S. Pat. Pub. Nos. 2013/0289696 A1 and 2013/0289693 A1, respectively); U.S. patent application Ser. Nos. 13/457,537 and 13/457,541 to Argentine et al., filed Apr. 27, 2012 (now published as U.S. Pat. Pub. Nos. 2013/0289691 A1 and 2013/0289692 A1, respectively); and U.S. patent application Ser. Nos. 13/458,209 and 13/458,242 to Coghlan et al., filed Apr. 27, 2012 (now published as U.S. Pat. Pub. Nos. 2013/0289701 A1 and 2013/0289702 A1), previously incorporated by reference in their entirety. Further, limb prostheses may be delivered and deployed within legs  116 ,  118  of main vessel stent-graft prosthesis  100 , extending into right iliac artery RI and left iliac artery LI, respectively, as shown in  FIG. 14 . All the delivery systems are removed, leaving the main vessel stent-graft  100 , the branch vessel prostheses, and the limb prostheses, as shown in  FIG. 14 . 
     While various embodiments according to the present invention have been described above, it should be understood that they have been presented by way of illustration and example only, and not limitation. It will be apparent to persons skilled in the relevant art that various changes in form and detail can be made therein without departing from the spirit and scope of the invention. It will also be understood that each feature of each embodiment discussed herein, and of each reference cited herein, can be used in combination with the features of any other embodiment. All patents and publications discussed herein are incorporated by reference herein in their entirety.