Patent Publication Number: US-2022218462-A1

Title: Bifurcating branch modular iliac branch device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation application of U.S. application Ser. No. 16/855,780 filed on Apr. 22, 2020, which claims the benefit of U.S. Provisional Application No. 62/855,163 filed on May 31, 2019, entitled “BIFURCATING BRANCH MODULAR ILIAC BRANCH DEVICE” of Keith Perkins et al., which are incorporated herein by reference in their entirety. 
    
    
     FIELD 
     The present technology is generally related to endovascular devices, for example, devices for treatment of a diseased aorta. 
     BACKGROUND 
     A conventional stent-graft typically includes a radially expandable reinforcement structure, e.g., formed from a plurality of annular stent rings, and a cylindrically shaped layer of graft material defining a lumen to which the stent rings are coupled. Endovascular aneurysmal exclusion is a method of using a stent-graft to exclude pressurized fluid flow from the interior of an aneurysm, thereby reducing the risk of rupture of the aneurysm and the associated invasive surgical intervention. Challenges may occur in patients with certain types of aneurisms, such as an iliac aneurysm. Often the short length of the common iliac artery may prevent patients from receiving endovascular aneurysmal exclusion therapy to treat the iliac aneurysm. 
     SUMMARY 
     The techniques of this disclosure generally relate to a stent-graft system including a bifurcated stent-graft, a first bifurcating branch device, and a first branch extension. The bifurcated stent-graft includes a body, a first branch limb, and a second branch limb. The first bifurcating branch device includes a body segment coupled to the first branch limb of the bifurcated stent-graft, a first branch limb, and a second branch limb. The first branch extension is within the first branch limb of the first bifurcating branch device and within an external iliac artery. The first bifurcating branch device has a wide patient applicability since the treatment can be extended proximal to the anatomical iliac bifurcation and is not limited by the common iliac artery length. The stent-graft system is suitable to treat a wide range of internal and external iliac artery diameters. 
     In one aspect, the present disclosure provides a method including deploying a bifurcated stent-graft within an aorta proximal to an aortic bifurcation, deploying a body segment of a first bifurcating branch device coupled to a first branch limb of the bifurcated stent-graft, and deploying a first branch extension within a first branch limb of the first bifurcating branch device and within a first vessel, e.g., the external iliac artery. 
     In another aspect, the present disclosure provides a bifurcating branch device including an upper segment and a lower segment. The upper segment includes a nonflared portion and a flared portion having a greater diameter than the nonflared portion. The lower segment includes a first branch limb and a second branch limb. The flared portion is located between the nonflared portion and the lower segment. 
     The details of one or more aspects of the disclosure are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the techniques described in this disclosure will be apparent from the description and drawings, and from the claims. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a front view of a bifurcating branch device, according to one embodiment. 
         FIG. 2  is a front view of a bifurcating branch device having an extended limb portion, according to one embodiment. 
         FIGS. 3A, 3B, 3C, 3D, 3E, 3F, 3G, 3H, 3I, 3J, 3K  are schematic examples of a branching limb deployment sequence, according to one embodiment. 
         FIGS. 4 and 5  are schematic examples demonstrating deployment methods in accordance with various embodiments. 
         FIGS. 6A and 6B  are front schematic views of two example bifurcating branch devices in accordance with various embodiments. 
         FIG. 7  is a schematic view of a stent-graft system in accordance with one embodiment. 
         FIG. 8  is a schematic view of a stent-graft system in accordance with one embodiment. 
         FIG. 9  is a schematic view of an asymmetric bifurcated branch device (ABBD) in accordance with another embodiment. 
         FIG. 10  is a schematic view of a stent-graft system including the ABBD of  FIG. 9  in accordance with one embodiment. 
         FIG. 11  is a schematic view of a stent-graft system including the ABBD of  FIG. 9  in accordance with one embodiment. 
         FIGS. 12A, 12B, 12C, 12D, 12E, 12F, 12G  are an example deployment sequence of a stent-graft system in accordance with one embodiment. 
     
    
    
     DETAILED DESCRIPTION 
       FIGS. 1 through 12G  disclose examples of bifurcating branch devices, as well as stent-graft systems including the device(s) and example methods for deploying the devices and systems. The devices, systems, and methods may be used in the treatment of intra-vascular diseases, such as aneurisms. The devices, systems, and methods are described herein with respect to treating disease of the iliac arteries, however, one of ordinary skill in the art will understand that the devices, systems, and methods may be used in other areas of the vasculature and/or for other pathologies like aorto-iliac occlusive disease. 
       FIGS. 1 and 2  show examples of bifurcating branch device  100 ,  100 A, respectively. The bifurcating branch devices  100 ,  100 A may generally include a graft material  102  and one or more stents  104  attached to the graft material  102 . In the embodiments shown, the stents  104  may include a plurality of spaced apart individual stent rings which are generally sinusoidal. Alternatively, there may be a single, continuous stent (e.g., a helical stent) or a combination of stent rings and continuous stents. The stents  104  may be self-expanding structures, e.g., formed of nickel titanium alloy (nitinol), or other shaped memory material, or they may be balloon expandable stents. The graft material  102  may be any suitable graft material known to be utilized in vascular grafts. For example, the graft material  102  may be a non-permeable material, e.g., a polyester terephthalate (PET), expanded polyester terephthalate (ePET), or polytetrafluoroethylene (PTFE) based material, or other non-permeable graft material. 
     As shown in  FIGS. 1 and 2 , the bifurcating branch devices (BBDs)  100 / 100 A may include an upper segment  106  and a lower segment  108 . The upper segment  106  may be referred to as the body or the limb segment  106 . As described in greater detail below, the upper segment  106  may be configured to be deployed within a previously deployed stent-graft, for example, in a more proximal region of the aorta, e.g., an abdominal aortic aneurism (AAA) device. The lower segment  108  may be a bifurcated segment including two articulating limbs  110 ,  112 , which may be referred to as branch limbs  110 ,  112 . The limbs  110 ,  112  may articulate or move independent of each other along substantially their entire length, e.g., except at the point of bifurcation. 
     In at least one embodiment, the bifurcated limbs  110 ,  112  may extend in a direction parallel to the upper segment  106 , e.g., their longitudinal axes may be parallel. The relative directions of the limbs  110 ,  112  and the upper segment  106  may refer to the bifurcating branch devices  100 / 100 A being in an unconstrained position, for example, as it exists outside of the body or a delivery system, e.g., as shown in  FIG. 1 . The legs may not be perfectly parallel to the upper body, such as shown in  FIG. 2 , but may generally extend in the same direction, e.g., within 5 or 10 degrees of parallel. This description of the relative directions of bifurcated limbs  110 ,  112  relative to their upper non-bifurcated portions  106  may apply to any bifurcated device described herein. 
     The body segment  106  may define a body lumen  114  that is configured to receive blood flow from proximal to the bifurcating branch devices  100 / 100 A. The blood may then flow into branch lumens  116 ,  118  defined by the branch limbs  110 ,  112 , respectively. In one embodiment, all blood that enters the body lumen  114  exits the bifurcating branch devices  100 / 100 A through the branch lumens  116 ,  118 . 
     The bifurcating branch devices  100 / 100 A in  FIGS. 1 and 2  are shown with some example dimensions, however, it is to be understood that these dimensions are strictly examples and are not intended to be limiting. In one example, the diameter of the body segment  106  may be approximately 16 mm, such as 10 to 25 mm, or any sub-range therein, e.g., 12 to 20 mm, 12 to 18 mm, or 14 to 18 mm. In the example shown in  FIG. 1 , the body segment  106  may have a length of approximately 30 mm, such as 20 to 40 mm, or any sub-range therein, e.g., 25 to 35 mm. 
     In both  FIGS. 1 and 2 , the two branch limbs  110 ,  112  of each bifurcating branch devices  100 / 100 A are shown as having the same diameter. In one embodiment, both branch limbs  110 ,  112  may be approximately 8 mm, such as 6 to 14 mm, or any sub-range therein, e.g., 6 to 12 mm, 6 to 10 mm, 8 to 12 mm. In the example shown in  FIG. 2 , the body segment  106  may be substantially longer than the body segment  106  of  FIG. 1 . For example, the body segment  106  in  FIG. 2  may have a length of at least 50 mm or 60 mm, such as 50 to 100 mm, or any sub-range therein. 
     With reference to  FIGS. 3A-3K , an example deployment sequence of a stent-graft system  300  is shown. Each of  FIGS. 3A-3K  in the sequence is referred to herein as a step, however, it is to be understood that some portions of the deployment may occur between each shown step. 
     In a first step as shown in  FIG. 3A , an initial stent-graft  302  may be deployed in the aorta proximal to the aortic bifurcation. In the example shown, the stent-graft  302  is deployed with its proximal end near the renal arteries RA. In one embodiment, the stent-graft  302  may be a AAA device  302  that includes a bifurcation, such as one of the Endurant devices from Medtronic, Inc. Similar to the BBD  100 , the bifurcated stent-graft  302  may include a body  304  and two branch limbs  306 ,  308 . 
     In  FIG. 3A , the stent-graft  302  is partially deployed, with one branch limb  306  fully deployed and the other branch limb  308  only partially deployed. In the embodiment shown, the branch limbs  306 ,  308  have different lengths, however, in other embodiments the limb lengths may be the same. 
     In step two as shown in  FIG. 3B , with one branch limb  308  still partially deployed, BBD  100 , i.e., body segment  106 , is deployed within the already deployed branch limb  306  of the AAA device  302 . In the following sequence, BBD  100  of  FIG. 1  is illustrated and discussed, however, the discussion is equally applicable to BBD  100 A of  FIG. 2  or any of the BBDs as disclosed herein. When the BBD  100  is deployed, the branch limbs  110 ,  112  may extend into the common iliac artery CIA, which may be aneurysmal. 
     In steps three and four as shown in  FIGS. 3C and 3D , a branch extension  310  may be delivered to the BBD  100  and deployed within one branch limb  110  of the BBD  100 . The branch extension  310  may extend from the branch limb  110  to a non-aneurysmal portion of the external iliac artery EIA. 
     In the embodiment shown, the first branch extension  310  may extend into the external iliac artery EIA, however, in another embodiment it may be in the internal iliac artery IIA. The branch extension  310  may be comprised of generally similar components to the BBD  100 , e.g., a graft material and one or more stents. However, the specific materials of the graft and stents may differ from that of the BBD  100 , depending on the application, patient anatomy, or other considerations. 
     In step five as shown in  FIG. 3E , the other branch limb  308  of the AAA device  302  may be fully deployed. In addition, a guidewire  312  may be introduced through the second branch limb  112  of the BBD  100  via supra-aortic access. In steps five and six as shown in  FIGS. 3E and 3F , a second branch extension  314  may be delivered to the BBD  100  and deployed within the second branch limb  112  of the BBD  100 . The second branch extension  314  may extend into whichever iliac artery was not occupied by the first branch extension  310 . In the embodiment shown, the second branch extension  314  extends into the internal iliac artery IIA. 
     If only one of the common ilia arteries CIA is aneurysmal, the deployment may cease after step six as shown in  FIG. 3F , with the exception of a possible extension from the second branch limb  308  of the AAA device  302  to the other contralateral common iliac artery CIA. 
     However, if both common ilia arteries CIA are aneurysmal, then a second BBD  100 - 1  may be deployed in a manner similar to steps one to six as shown in  FIGS. 3A-3F . In step seven as shown in  FIG. 3G , the second BBD  100 - 1  may be delivered to the second branch limb  308  of the AAA device  302 . In steps eight and nine as shown in  FIGS. 3H and 3I , a branch extension  310 - 1 , sometimes called a third branch extension  310 - 1 , may be deployed within one branch limb  110  or  112  (branch limb  112  in the embodiment shown) of the BBD  100 - 1  and the branch extension  310 - 1  may extend into the external iliac artery EIA. In steps ten and eleven as shown in  FIGS. 3J and 3K , a second branch extension  314 - 1  may be delivered to the second branch limb  110  of the BBD  100 - 1 , for example via supra-aortic access. The second branch extension  314 - 1  may extend from the second branch limb  110  into the other iliac artery, the internal iliac artery IIA in the example shown. Following step eleven as shown in  FIG. 3K , all guidewires and catheters may be removed and a complete stent-graft system  300  may be in place to cover blood flow from the abdominal aorta through either one or both sets of iliac arteries. Note branch extensions  310 - 1 ,  314 - 1  are sometimes called third and fourth branch extensions  310 - 1 ,  314 - 1 . 
     With reference to  FIGS. 4 and 5 , an example is shown of an alternative deployment method that avoids the use of supra-aortic access, if such access is not possible or desired. In this example, access is achieved from the contralateral side instead of through supra-aortic access. 
       FIG. 4  is an alternative to the deployment step  5  shown in  FIG. 3E . From  FIG. 3D , deployment proceeds to  FIG. 4  in accordance with this embodiment. Paying particular now attention to  FIG. 4 , the other branch limb  308  of the AAA device  302  may be fully deployed. A steerable catheter  402 , sometimes called a steerable/deflectable sheath or guide, is advanced through the contralateral side, e.g., through the contralateral common iliac artery CIA and into the distal end of branch limb  308  of AAA device  302 . 
     Upon reaching the bifurcation of body  304  and the branch limbs  306 ,  308 , the obturator (if present) may be removed and the distal tip of the steerable catheter  402  may be deflected into a curved configuration (may be called a shepherds crook configuration), to point over the bifurcation (also called the flow divider) in the AAA device  302  and distally into the branch limb  306  of the AAA device  302 . In particular, the distal tip of the steerable catheter  402  may be aimed or directed at the branch limb  112  of the BBD  100 . In the embodiment shown in  FIGS. 4 and 5 , the distal tip of the steerable catheter  402  is disposed between the proximal end of the AAA device  302  and its bifurcation/flow divider. However, in other embodiments, the distal tip may be disposed anywhere above the bifurcation/flow divider, for example, the distal tip may be located above the AAA device  302  but may be aimed/directed downward into the branch limb  306  of the AAA device  302 , such as directed at the branch limb  112  of the BBD  100 . 
     The steerable catheter  402  may be any catheter configured to bend or deflect its distal end more than 90 degrees such that it faces at least partially back towards its proximal end. In one embodiment, the distal tip may be deflected with a radius of curvature of less than or equal to 25 mm, such as less than or equal to 20 mm, 18 mm, or less. In one example the radius of curvature may be about 17 mm and generally between 16-26 mm. The steerable catheter  402  may include one or more wires attached at or near the distal tip, which may be manipulated to generate the deflection of the tip. 
     In one embodiment, referring now to  FIGS. 4 and 5  together, the steerable catheter  402  is engineered to specifically provide the support needed to deliver a branch extension delivery system  500 , as illustrated in  FIG. 5 . More particularly, a guidewire  508  is advanced through the steerable catheter  402  and into the internal iliac artery IIA. 
     With reference to  FIG. 5 , the branch extension delivery system  500  for delivering the second branch extension  314  is advanced through the steerable catheter  402  and over the guidewire  508  to be located within the branch limb  112  and the internal iliac artery IIA. The steerable catheter  402  is robust enough to maintain the imparted curvature while tracking the relatively stiff branch extension delivery system  500  therethrough. The second branch extension  314  is deployed to bridge the branch limb  112  and the internal iliac artery IIA as shown at step  6  in  FIG. 3F . 
     In another embodiment, referring again to  FIG. 4 , using a buddy catheter inside of the steerable catheter  402 , a guidewire  404 , sometimes called a sheath reinforcing through-and-through (TnT) wire, is run up and over the AAA bifurcation into a nested sheath on the contralateral side. The guidewire  404  is externalized by tracking into the external iliac artery EIA and externalized through a femoral access site as illustrated in  FIG. 4 . The guidewire  404  extends from the steerable catheter  402  into the external iliac artery EIA and is externalized. In one embodiment, the guidewire  404  is snared to externalize the guidewire  404  though the external iliac artery EIA. 
     Further, a soft guidewire  406  is introduced inside of the buddy guide catheter through the hemostatic valve of the steerable catheter  402  and advanced to the internal iliac artery IIA. Once the internal iliac artery IIA is cannulated, a wire exchange is performed to exchange the soft guidewire  406  for a moderately stiff guidewire  508  (illustrated in  FIG. 5 ). 
     With reference to  FIG. 5 , the branch extension delivery system  500  for delivering the second branch extension  314  is advanced through the steerable catheter  402  and over the stiff guidewire  508  to be located within the branch limb  112  and the internal iliac artery IIA. While the branch extension delivery system  500  is being delivered, constant tension is maintained on the guidewire  404  to keep the steerable catheter  402  from straightening out. The second branch extension  314  is deployed to bridge the branch limb  112  and the internal iliac artery IIA as shown at step  6  in  FIG. 3F . The branch extension delivery system  500 , the steerable catheter  402 , and the guidewires  404 ,  508  are then removed. 
     Although the guidewire  404  is illustrated in  FIGS. 4-5  and discussed, in the embodiment where the steerable catheter  402  is robust enough to maintain the imparted curvature while tracking the relatively stiff branch extension delivery system  500  therethrough, the guidewire  404  is not used and thus would not appear in the figures. Suitably, if use of the guidewire  404  is avoided, the procedure is simplified. 
     A suitable example of the branch extension delivery system  500  is the iCAST delivery system from Atrium. 
     The branch extensions, e.g.,  310 ,  314 , in any of the embodiments described herein may be formed of any suitable material, such as a PET based material or a PTFE based material. In one example, the branch extensions  310 ,  314  may be a covered stent wherein the stent is disposed/laminated between sheets of graft material, such as PTFE. One example of such a suitable branch extension is the iCAST balloon-expandable covered stent from Atrium. It has been found that for smaller diameter grafts, a PTFE based material may result in less occlusion of the stent-graft over time. Accordingly, a PTFE based material may be used in the branch extensions, particularly those having smaller diameters (e.g., less than 10 mm). 
     In one embodiment, the second branch extension  314 - 1  as shown in  FIG. 3K  is also deployed from the contralateral side using a method similar to the contralateral access method of  FIGS. 4 and 5  as those of skill in the art will understand in light of this disclosure. 
     With reference to  FIGS. 6A and 6B , examples are shown of bifurcating branch devices  600  and  600 A that are similar to those described above, but with a flare  605 , sometimes called the flared portion  605 . More particularly, a body segment  606  includes a nonflared proximal portion  607  and the flared portion  605 . The flared portion  605  is a flare, or increase, in the diameter between the proximal portion  607  of the body segment  606  and a bifurcated or lower segment  608 . The flare  605  may cause an increase in the diameter of the BBD  600 / 600 A such that a total diameter of the branch limbs  610 ,  612  may be greater than the diameter of the proximal portion  607  of the body segment  606 . 
     The diameter of the proximal portion  607  of the body segment  606  and the length of the bifurcated segment  608  may be similar to those described above with reference to  FIGS. 1 and 2 . In one embodiment, the flared portion  605  may have a diameter of approximately 20 mm, such as 18 to 26 mm, or any sub-range therein, e.g., 18 to 24 mm, 18 to 22 mm, or 20 to 24 mm. In the embodiments shown in  FIGS. 6A and 6B , the total length of the BBD  600 / 600 A may be longer than the embodiment shown in  FIG. 1  but shorter than the embodiment shown in  FIG. 2 . In one example, the BBD  600 / 600 A may have a total length of approximately 70 mm or 80 mm, such as 60 to 90 mm, or any sub-range therein, e.g., 60 to 80 mm, 65 to 85 mm, 65 to 80 mm, or 65 to 75 mm. 
     In the examples shown, the proximal portion  607  of the body segment  606 , e.g., the non-flared portion, may have a length of approximately 30 mm or 40 mm, such as 20 to 50 mm, or any sub-range therein, e.g., 25 to 50 mm, 25 to 45 mm, 30 to 50 mm, 30 to 45 mm, or 30 to 40 mm. The length of the non-flared portion  607  may depend on the number of stent rings to be included in said portion. For example, if there are three stent rings, the length may be approximately 30 mm, but if a fourth stent ring is added, then the length may be approximately 40 mm. The flared portion  605  of the BBD  600 / 600 A may have a diameter that is at least 2 mm larger than the proximal diameter, such as 2 to 10 mm larger, or any sub-range therein, e.g., 2 to 8 mm, 2 to 6 mm, or 2 to 4 mm. In one embodiment, the flared portion  605  may have a length of approximately 10 mm, such as 5 to 20 mm, or any sub-range therein, e.g., 5 to 15 mm, 6 to 14 mm, 8 to 14 mm, 8 to 12 mm, or 10 to 12 mm. 
     In one non-limiting example, the diameter of the BBD  600 / 600 A may flare from approximately 16 mm at the proximal portion  607  of the body segment  606  to approximately 20 mm at the transition (flare  605 ) from the body segment  606  to the bifurcated segment  608 . This may allow for branch limbs  610 ,  612  having diameters that add up to greater than the approximately 16 mm body diameter—approximately 10 mm and 8 mm in  FIG. 6A  and approximately 10 mm and 10 mm in  FIG. 6B . 
     The BBDs  600 / 600 A of  FIGS. 6A and 6B  having flared portions  605  may allow for the treatment of external iliac arteries EIAs or internal iliac arteries IIAs having larger diameters than that of  FIGS. 1 and 2 , e.g., about 8 mm. One or both of the branch limbs  610 ,  612  may have a larger diameter, such as approximately 10 mm or larger, e.g., 9 to 14 mm, 9 to 12 mm, or 10 to 12 mm. In one non-limiting example of  FIG. 6A , the left branch limb  610  is larger and is configured for an external iliac artery EIA of 10 mm or larger. The right branch limb  612  is smaller, approx. 8 mm, and is configured for an internal iliac artery IIA of less than 10 mm. In one non-limiting example of  FIG. 6B , both branch limbs  610 ,  612  are larger and are configured for an external iliac artery EIA and an internal iliac artery IIA of 10 mm or larger. 
     The devices, stent-graft systems, and methods described herein may address one or more therapy gaps in the commercially available endovascular treatment space. For example, up to an estimated 30% of AAAs involve the iliac arteries. Common iliac artery (CIA) diameters of &gt;20 mm have been shown to be independent predictors of late sac enlargement. Inadequate iliac fixation may cause stent graft migration and aneurysm sac pressurization leading to increased rupture risk and driving the need for costly and invasive secondary interventions. Current treatment options for iliac disease include intentional coverage of a single internal iliac artery. This can result in neurological injury, buttock claudication, impotency, spinal cord ischemia, and bowel infarcts. A few commercial off the shelf iliac branch stent grafts are available to allow for continued perfusion of the internal iliac artery, but they are severely limited in terms of patient anatomies they can treat. Estimates are that only 35% of repairs can be done “on label” with the current devices approved for sale in the US. 
     The BBDs disclosed herein have wide patient applicability since the treatment can be extended proximal to the anatomical iliac bifurcation and is not limited by the common iliac artery length. The device design is suitable to treat a wide range of internal and external iliac artery diameters. Supra-aortic access allows for direct cannulation access of internal and external iliac arteries without the procedural complexities required of crossover techniques. Easily adaptable to bilateral hypogastric perfusion. Articulating nature of the limb gates eases cannulation and allows for more natural and sweeping branch stent configurations. 
     One advantage of the BBD may be the flow divider in the bifurcation segment, which mimics natural anatomy. There is a transition from Aortic body to limb segments, and the smooth transition prevents flow disturbances that could lead to thrombosis of the device and attached limb stents. The design allows limb segments to achieve high angulation, up to 180 degrees and/or prolapse, without kinking or compromise of intralumenal flow areas. The unique transition at the flow divider promotes flexibility and enables the limb segments to achieve high angulation without kinking or compromise of intralumenal flow area. 
     Other advantages include: (1) additional patient applicability—can treat the diseased common iliac artery without seating below the aortic bifurcation; (2) flexible transition—designed to treat a variety of anatomical states; (3) additional flexibility of articulating limb segments facilitates cannulation; and (4) lining the limbs with a balloon expandable (BE) stent reduces graft material in-folding which further limits flow disturbances in the limbs that can lead to thrombosis. 
     Regarding the articulating limbs, advantages include: (1) length of the pre-cannulated limb segment can be varied to provide a mechanism to stabilize the device during cannulation and branching of the internal iliac artery; (2) the internal luminal surfaces of the limb segments can be coated with an anti-thrombogenic agent, such as heparin, etc. to further mitigate the risk of thrombotic occlusion; (3) design allows for the placement of BE stents in the articulating limb segments which is advantageous in target vessels that are 10 mm or less; (4) for vessels larger than 10 mm, traditional self-expanding (SE) stents (e.g., PET covered) could be utilized; (5) associated diameters of the articulating limb segments can be up-sized to ensure compatibility for treatment in this situation (target vessels &gt;10 mm); (6) geometry enables simple cannulation of the articulating limb segments from above, via supra-aortic access, or from below via a contralateral cross-over technique; (7) external branch is pre-cannulated by the delivery system and thus does not require separate cannulation to perfuse the target branch; and (8) saves time, radiation exposure, and use of contrast during clinical procedure. 
       FIG. 7  is a schematic view of a stent-graft system  700  in accordance with one embodiment. Stent-graft system  700  of  FIG. 7  is similar to stent-graft system  300  as stage  11  as illustrated in  FIG. 3K  except includes a branch extension  702  instead of BBD  100 - 1  and branch extensions  310 - 1 ,  314 - 1 . More particularly, branch extension  702  extends from the inside of branch limb  308  of stent-graft  302  to the external iliac artery EIA and the internal iliac artery IIA is bypassed. Illustratively, a total length of BBD  100  is 60, 93, 124, 156, or 199 mm depending upon the particular application of BBD  100 . 
       FIG. 8  is a schematic view of a stent-graft system  800  in accordance with one embodiment. Stent-graft system  800  of  FIG. 8  is similar to stent-graft system  700  of  FIG. 7  except includes an additional branch extension  802  coupling BBD  100  and branch limb  306 . More particularly, branch extension  802  is deployed within the branch limb  308  of stent-graft  302 . BBD  100  is deployed within the branch extension  802 . 
       FIG. 9  is a schematic view of an asymmetric bifurcated branch device (ABBD)  900  in accordance with another embodiment. The ABBD  900  is similar to the BBD  600  of  FIG. 6  except a length of a branch limb  910  is greater than a length of the branch limb  612  and so the ABBD  900  is asymmetrical. Illustratively, the diameter and the length of the proximal portion  606  are 16 mm and 30 mm, respectively, the length of the flared portion  605  is 20 mm, the diameter and the length of the branch limb  612  is 8 mm and 30 mm, respectively, and the length of the branch limb  910  is greater than 30 mm. As further examples, the diameter at the distal end of the branch limb  910  is 10, 13, or 16 mm. All dimensions are approximate, e.g., within +/−2 mm. 
     In the embodiment shown, the distal end of the branch limb  910  may be flared such that is has a larger diameter than near the bifurcation. In other embodiments, the branch limb  910  may have a constant (or substantially constant) diameter, such as in  FIGS. 1 and 2 . While the ABBD  900  is shown with a flared portion  605 , it may also be configured without a flared portion, such as in  FIGS. 1 and 2 . 
       FIG. 10  is a schematic view of a stent-graft system  1000  including the ABBD  900  of  FIG. 9  in accordance with one embodiment. The stent-graft system  1000  of  FIG. 10  is similar to the stent-graft system  800  of  FIG. 8  and only the difference between the systems  1000 ,  800  are discussed below. The ABBD  900  is deployed within the branch extension  802  and the branch limb  910  extends directly into the external iliac artery EIA. 
     In one embodiment, the stent-graft  302  is initially deployed, the branch extension  802  is then deployed, and then the ABBD  900  is deployed. The branch limb  314  is then deployed through supra-aortic access or using the cross-over technique discussed above as desired. 
       FIG. 11  is a schematic view of a stent-graft system  1100  including the ABBD  900  of  FIG. 9  in accordance with one embodiment. The stent-graft system  1100  of  FIG. 11  is similar to the stent-graft system  1000  of  FIG. 10  and only the difference between the systems  1100 ,  1000  are discussed below. As illustrated in  FIG. 11 , in accordance with this embodiment, the branch extension  802  is deployed within the stent-graft  302  and the ABBD  900 . 
     For example, the ABBD  900  is initially deployed. The branch extension  314  is then deployed, e.g., through supra-aortic access or using the cross-over technique discussed above as desired. The stent-graft  302  is then deployed, at least partially. The branch extension  802  is deployed within the stent-graft  302  and the ABBD  900 . Further, the branch extension  702  is deployed. In one embodiment, stent-graft system  1100  is deployed using a method similar to that discussed below in reference to  FIGS. 12A-12G . 
     With reference to  FIGS. 12A-12G , an example deployment sequence of a stent-graft system  1200  is shown. Each of  FIGS. 12A-12G  in the sequence is referred to herein as a step, however, it is to be understood that some portions of the deployment may occur between each shown step. In a first step as shown in  FIG. 12A , a delivery system  1202  including the ABBD  900  is advanced over a guidewire  1204  into the common iliac artery CIA. In a second step as shown in  FIG. 12B , the ABBD  900  is partially deployed, with the branch limb  612  fully deployed and the other branch limb  910  only partially deployed. 
     In a third step as shown in  FIG. 12C , a delivery system  1206  including branch extension  314  is advanced from the contralateral common iliac artery CIA and over the aortic bifurcation over a guidewire  1208 . The delivery system  1206  is advanced through the branch limb  612  into the internal iliac artery IIA. The branch extension  314  is then deployed from the delivery system  1206  and deployment of ABBD  900  is completed as illustrated in a fourth step in  FIG. 12D . The branch extension  314  is deployed using a cross-over technique using a steerable catheter such as the steerable catheter  402  and guidewire  402  as described in the embodiments of  FIGS. 4-5  and/or using the TnT wire  404 . In another embodiment, the branch extension  314  is deployed from supra-aortic access in a manner similar to that illustrated in  FIGS. 3E, 3F . 
     In the fourth step as shown in  FIG. 12D , the stent-graft  302  may be deployed in the aorta proximal to the aortic bifurcation. In the example shown, the stent-graft  302  is deployed with its proximal end near the renal arteries RA. In  FIG. 12D , the stent-graft  302  is partially deployed, with one branch limb  306  fully deployed and the other branch limb  1210  only partially deployed. In the embodiment shown, the branch limbs  306 ,  1210  have different length, however they may have the same or similar lengths. 
     In the fifth step as shown in  FIG. 12E , a delivery system  1212  including the branch extension  802  is advanced through the external iliac artery EIA, through ABBD  900 , and into branch limb  306 . In a sixth step as illustrated in  FIG. 12F , the branch extension  802  is deployed within the branch limb  306  of the stent-graft  302  and the body segment  606  of the ABBD  900 . Finally, in a seventh step as illustrated in  FIG. 12G , deployment of the stent-graft  302  is completed. In this embodiment, the branch limb  1210  of the stent-graft  302  extends directly into the external iliac artery EIA and the internal iliac artery IIA is excluded. If branch limb  1210  does not reach the EIA, a bridging stent graft (or grafts) may be deployed. The embodiments shown and described with reference to  FIGS. 12A-G  relate to a single or unilateral procedure in which one set of iliac arteries are treated. However, in other embodiments, the procedure may be bilateral, such that both sets of iliac arteries are treated (e.g., as shown in  FIGS. 3A-K ). One of ordinary skill in the art will understand, based on the present disclosure, that the steps taken on the treated side (left side, as shown) may be repeated on the other side to complete the treatment. 
     It should be understood that various aspects disclosed herein may be combined in different combinations than the combinations specifically presented in the description and accompanying drawings. It should also be understood that, depending on the example, certain acts or events of any of the processes or methods described herein may be performed in a different sequence, may be added, merged, or left out altogether (e.g., all described acts or events may not be necessary to carry out the techniques). In addition, while certain aspects of this disclosure are described as being performed by a single module or unit for purposes of clarity, it should be understood that the techniques of this disclosure may be performed by a combination of units or modules associated with, for example, a medical device.