Patent Publication Number: US-2021169669-A1

Title: Releasable knots for medical device delivery

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a national phase application of PCT Application No. PCT/US2018/049053, internationally filed on Aug. 31, 2018, which is herein incorporated by reference in its entirety for all purposes. 
    
    
     FIELD 
     The present invention relates to medical devices and methods for treating an anatomical space (e.g., vessels) of the body. More specifically, the invention relates to methods, apparatuses, and systems that include an implantable medical device prosthesis that allows for accurate deployment in the anatomical space. 
     BACKGROUND 
     Disease of the vasculature is increasingly common. Treatment of the vasculature may be difficult because of the tortuous nature and complexity of the vasculature. Aortic dissections, for example, commonly begin at or near the aortic valve root and continue to the ascending aorta and the aortic arch, and may also affect the upper part of the descending aorta. Medical devices implanted at a diseased state may be used for treatment of aortic dissections, aneurysms, and other diseases of the vasculature. 
     It remains desirable to provide medical devices, systems and methods for repairing disease along the aorta (or other tortuous vessels) and also for repairing branches extending therefrom. 
     SUMMARY 
     According to one example (“Example 1”), a delivery system includes an implantable medical device; an actuation line configured to steer the implantable medical device during delivery thereof; a tether coupled to a portion of the implantable medical device arranged through the actuation line and configured to couple the actuation line to the implantable medical device; and a releasable knot including portions of the tether forming a first loop, a second loop, and a third loop with the third loop arranged through the second loop and the second loop arranged through the first loop and configured to couple the actuation line to the implantable medical device. 
     According to another example (“Example 2”), further to the delivery system of Example 1, the first loop is an eyelet formed by a first fold of the tether bonded at an overlapping portion of the first fold of the tether. 
     According to another example (“Example 3”), further to the delivery system of Example 2, the second loop is formed by a second fold of the tether and the third loop is formed by a third fold of the tether. 
     According to another example (“Example 4”), further to the delivery system of any one of Examples 1-3, the releasable knot is configured to release in response to tension applied to one end of the tether. 
     According to another example (“Example 5”), further to the delivery system of Example 1, the system also includes a fourth loop formed by a portion of the tether arranged through the third loop to form the releasable knot and the first loop is formed by a first fold of the tether, the second loop is formed by a second fold of the tether, the third loop is formed by a third fold of the tether, and the fourth loop is formed by a fourth fold of the tether. 
     According to another example (“Example 6”), further to the delivery system of Example 5, the releasable knot is configured to release in response to tension applied to both ends of the tether. 
     According to another example (“Example 7”), further to the delivery system of Example 5, a first end of the tether is arranged through the first loop, and a second end of the tether is arranged through the fourth loop, and the releasable knot is configured to release in response to tension applied to the second end of the tether. 
     According to another example (“Example 8”), further to the delivery system of any one of Examples 1-7, the releasable knot is configured to couple the actuation line to the implantable medical device without tension applied to the tether. 
     According to another example (“Example 9”), further to the delivery system of any one of Examples 1-8, the releasable knot is configured to resist separation between the actuation line and the implantable medical device in response to force applied to the actuation line. 
     According to one example (“Example 10”), a method of coupling an actuation line to an implantable medical device includes arranging the actuation line adjacent to the implantable medical device; routing a tether through an eyelet of the actuation line and coupling the tether to the implantable medical device; and forming a releasable knot that includes portions of the tether forming a first loop, a second loop, and a third loop with the third loop arranged through the second loop and the second loop arranged through the first loop and configured to couple the actuation line to the implantable medical device. 
     According to another example (“Example 11”), further to the method of Example 10, the method also includes visually inspecting the releasable knot to verify that the releasable knot couples the actuation line to the implantable medical device, and the releasable knot fails visual inspection by the releasable knot failing to maintain a knotted configuration and the releasable knot becoming at least partially unlooped. 
     According to another example (“Example 12”), further to the method of any one of Examples 10-11, forming the releasable knot includes forming the first loop by creating a first fold of the tether and bonding the tether at an overlapping portion of the first fold of the tether. 
     According to another example (“Example 13”), further to the method of any one of Examples 10-12, forming the releasable knot includes forming a fourth loop with a portion of the tether arranged through the third loop, wherein the first loop is formed by a first fold of the tether, the second loop is formed by a second fold of the tether, the third loop is formed by a third fold of the tether, and the fourth loop is formed by a fourth fold of the tether 
     According to another example (“Example 14”), further to the method of any one of Examples 10-11, the method also includes releasing the releasable knot by applying tension to one or both ends of the tether. 
     According to another example (“Example 15”), further to the method of any one of Examples 10-14, the releasable knot is configured to resist separation between the actuation line and the implantable medical device in response to force applied to the actuation line. 
     According to another example (“Example 16”), a delivery system includes an implantable medical device; a line having an eyelet; and a tether coupled to the implantable medical device and arranged through the eyelet of the line and configured to couple the line to the implantable medical device and including portions of the tether having a first loop, a second loop, and a third loop with the third loop arranged through the second loop and the second loop arranged through the first loop and configured to couple the line to the implantable medical device. 
     According to another example (“Example 17”), further to the delivery system of Example 16, the releasable knot is configured to resist separation between the line and the implantable medical device in response to force applied to the line. 
     According to another example (“Example 18”), further to the delivery system of Example 16, the releasable knot is configured to couple the line to the implantable medical device without tension applied to the tether. 
     According to another example (“Example 19”), further to the delivery system of Example 16, the tether is configured to release the loops by applying tension to one or both ends of the tether. 
     According to another example (“Example 20”), further to the delivery system of Example 16, the system also includes a fourth loop formed by a portion of the tether arranged through the third loop, wherein the first loop is formed by a first fold of the tether, the second loop is formed by a second fold of the tether, the third loop is formed by a third fold of the tether, and the fourth loop is formed by a fourth fold of the tether. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings are included to provide a further understanding of the disclosure and are incorporated in and constitute a part of this specification, illustrate embodiments, and together with the description serve to explain the principles of the disclosure. 
         FIG. 1  shows an implantable medical device and an actuation line in accordance with an embodiment. 
         FIGS. 2A-2D  show an example tether and steps in forming a releasable knot with portions of the tether in accordance with an embodiment. 
         FIGS. 3A-3E  show another example tether and steps in forming a releasable knot with portions of the tether in accordance with an embodiment. 
         FIGS. 4A-4F  show another example tether and steps in forming a releasable knot with portions of the tether in accordance with an embodiment. 
         FIGS. 5A-5E  show side view illustrations of expandable device angulation relative to a target location in accordance with various aspects of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Persons skilled in the art will readily appreciate that various aspects of the present disclosure can be realized by any number of methods and apparatuses configured to perform the intended functions. It should also be noted that the accompanying drawing figures referred to herein are not necessarily drawn to scale, but may be exaggerated to illustrate various aspects of the present disclosure, and in that regard, the drawing figures should not be construed as limiting. 
     Various aspects of the present disclosure are directed toward apparatuses, systems, and methods that include an implantable medical device that may be used in treatment of the vasculature. The implantable medical device is delivered to the vasculature using a delivery system. In addition, the implantable medical devices described herein may be substantially cylindrical, include a bifurcation, or have any of a variety of features. Further, the implantable medical devices may be configured to conform to the vasculature into which the implantable medical device is implanted, low-profile in order to facilitate delivery of the implantable medical device using a minimally invasive procedure (e.g., via transcatheter techniques), and able to withstand forces and other stresses that occur once implanted in the vasculature. 
     The delivery system may be configured to position and/or steer the implantable medical device for placement in the vasculature. To position and or steer the implantable medical device, the delivery system may include a line that changes position of the implantable medical device in response to a user applying force to the line. The line may be releasably coupled to the implantable medical device (e.g., to permit removal of the line to avoid trauma to the vasculature after the implantable medical device is delivered and positioned). As discussed in further detail below, a tether may be used to releasably couple the line to the implantable medical device. The tether may be formed into a releasable knot that is easily manufacturable and facilitates proper deployment. The releasable knots discussed herein avoid entangling with the line during release. In other instances, the tether may also be used to releasably couple other lines to the implantable medical device 
       FIG. 1  shows an implantable medical device  100  and a line  102  in accordance with various aspects of the present disclosure. The implantable medical device  100  is releasably coupled to a delivery system for delivery of the implantable medical device  100  to a target location within a patient&#39;s vasculature. The delivery system may include a catheter  104  that includes a leading end  106  and a trailing end (not shown in  FIG. 1 ). The implantable medical device  100  may be arranged near the leading end  106  of the catheter  104 . The catheter  104  may extend through a lumen of the implantable medical device  100  toward and past a proximal end  108  of the implantable medical device  100 . The catheter  104  may also include a tip (not shown) at the leading end  106 . As shown in  FIG. 1 , the implantable medical device  100  includes stent and graft components, although the implantable medical device can take a variety of forms including a stent, graft, bifurcated implantable medical device, heart valve, and the like. 
     The implantable medical device  100  includes a proximal end  108 , a distal end  110 , and a flow lumen extending therebetween. The proximal end  108  of the implantable medical device  100  may be considered the end of the implantable medical device  100  that is closest to the target location within the patient&#39;s vasculature. The line  102  may be coupled to the implantable medical device  100  at one or more locations. As shown in  FIG. 1 , the line  102  is attached adjacent to or near the proximal end  108  of the implantable medical device  100  and accessible to a user of the delivery system. 
     As shown, the line  102  is coupled to the implantable medical device  100  via at least one tether  112 . The tether  112  may be arranged through a portion of the implantable medical device  100  and through the line  102  to couple the line  102  to the implantable medical device  100 . In certain instances, and as shown in  FIG. 1 , the at least one tether  112  is arranged through the implantable medical device  100  near or adjacent to the proximal end  108  of the implantable medical device  100 . The at least one tether  112  may be a single tether, as shown in  FIG. 1 . 
     In some instances, the implantable medical device  100  may include a patch  114  attached or coupled to a surface (e.g., an exterior surface) of the implantable medical device  100 . The patch  114  may include a layer of graft material that forms a lumen between the surface of the implantable medical device  100  and the graft material. The tether  112  may be arranged through the patch  114  to couple the line  102  to the implantable medical device  100 . 
     In certain instances, the line  102  is an actuation line  102  configured to steer the implantable medical device  100  during delivery thereof. The actuation line  102  may include a column strength such that a user operating the delivery system may apply force to the actuation line  102  and bidirectionally steer (e.g., proximally and distally relative to the target location within the patient&#39;s vasculature) the implantable medical device  100 . For example, the actuation line  102  may have a stiffness that is greater than a stiffness of the tether  112 . The stiffness of the actuation line  102  and/or the location to which the actuation line  102  is coupled to the implantable medical device  100  may facilitate deploying and arranging the implantable medical device  100  relative to the target location within the patient&#39;s vasculature. For example, the implantable medical device  100  may be configured to deploy at a tortuous vessel having a curvature with at least one inflection point. In certain instances, the actuation line  102  is configured to maintain the proximal end  108  of the implantable medical device  100  approximately perpendicular to the inflection point in the curvature of the tortuous vessel during delivery of the implantable medical device  100 . 
     The actuation line  102  may be uncoupled or released from the implantable medical device  100  subsequent to the implantable medical device  100  being positioned and deployed at the target location within the patient&#39;s vasculature and removed from the patient. In certain instances, the tether  112  is configured to remain coupled or threaded through the implantable medical device  100  after the actuation line  102  is released or uncoupled from the implantable medical device  100 . The actuation line  102  can include an eyelet or opening in a distal end through which the tether  112  is arranged. In addition, the tether  112  may be formed from a bio-absorbable material that dissolves to release or uncouple the actuation line  102  from the implantable medical device  100 . In other instances, the tether  112  is configured to be removed or unthreaded to uncouple the actuation line  102  from the implantable medical device  100 . 
       FIGS. 2A-D  show an example tether  112  and steps in forming a releasable knot  200  with portions of the tether  112  in accordance with an embodiment. As explained in detail above with reference to  FIG. 1 , the tether  112  is coupled to a portion of an implantable medical device and arranged through a line (e.g., an actuation line) to couple the line to the implantable medical device. As shown in progressing through the steps shown in  FIGS. 2A-D , the tether  112  forms a releasable knot, which is shown in a completed form in  FIG. 2D . The tether  112  includes multiple loops in forming the releasable knot  200 . 
     In certain instances, and as shown in  FIG. 2A , the tether  112  includes first loop  202 . The first loop  202  can be an eyelet that is formed by a first fold of the tether  112  that is bonded at an overlapping portion  204  of the first fold of the tether  112 . The tether  112  may be bonded together by applying heat to bond the tether  112  to itself to form the first loop  202 . The tether  112  is routed or arranged through a line and an implantable medical device to couple the line to the implantable medical device. For ease of illustration, element  206  is representative of one of the line and an implantable medical device and element  208  is representative of the other of the line and an implantable medical device. In certain instances, the element  206  may be the patch (shown in  FIG. 1 ) or a hole in the implantable medical device and the element  208  may be an eyelet in the line. 
     As shown in  FIG. 2B , the tether  112  is arranged about the element  206  and the element  208 . In certain instances, the tether  112  is arranged through element  206  (the patch as shown in  FIG. 1 ) and through an eyelet of the line. After being arranged through or about the element  206  and the element  208 , the tether  112  may be folded to form a second loop  210  as shown in  FIG. 2C . The second loop  210  of the tether  112  is then arranged through the first loop  202  of the tether  112 . 
     In addition, and as shown in  FIG. 2D , a third fold of the tether  112  may form a third loop  212 . Subsequently, the third loop  212  is arranged through the second loop  210 . Thus, the third loop  212  is arranged through the second loop  210 , and the second loop  210  is arranged through the first loop  202  to form the releasable knot  200  as shown in  FIG. 2D . In this configuration, the releasable knot  200  is configured to couple the actuation line to the implantable medical device. 
     After the multiple loops of the tether  112  are formed and arranged as discussed, tension may be applied to ends  214 ,  216  of the tether  112  to tighten the releasable knot  200 . To release or untie the releasable knot  200 , tension may be applied to one of the ends  214 ,  216 . 
     Forming the releasable knot  200  in the manner discussed above may be manufacturable. In certain instances, the releasable knot  200  is formed or tied by hand. The steps to create the releasable knot  200  are relatively simple (e.g., not numerous, minimal crossover or loop formation in the tether  112 ). In addition, and in manufacturing or forming the releasable knot  200 , it should be determined whether the releasable knot  200  is properly formed. The releasable knot  200  is properly formed when the releasable knot  200  couples the line to the implantable medical device. Forming the releasable knot  200  in the manner discussed above may also facilitate manufacturability by indicating whether the releasable knot  200  is properly formed. In this manner, the releasable knot  200  cannot be ineffectively formed. For example, if the steps in forming the releasable knot  200  are not followed, the releasable knot  200  will not maintain a knotted configuration (e.g., as shown in  FIG. 2D ) and the tether  112  will at least partially unloop. As a result, visually inspecting the releasable knot  200  to verify that the releasable knot  200  effectively couples the actuation line to the implantable medical device includes determining whether the releasable knot  200  maintains the knotted configuration or fails to do so. 
     In addition, the releasable knot  200  is configured to couple the actuation line to the implantable medical device without tension applied to the tether  112 . After the releasable knot  200  is formed, tension does not need to be applied to hold the releasable knot  200  in the knotted configuration (e.g., as shown in  FIG. 2D ). An end  216  of the tether  112  may be coupled to a deployment handle (not shown) or a proximal portion of a catheter (e.g., as described above with reference to  FIG. 1 ) such that a use may apply tension to the end  216  of the tether  112  or actuate a portion of the deployment handle that is coupled to the end  216  of the tether  112 . 
     As noted above with reference to  FIG. 1 , the line (an actuation line) may steer the implantable medical device in response to a force applied to the actuation line. In certain instances, the force may be applied to the actuation line to bidirectionally steer (e.g., proximally and distally relative to the target location within the patient&#39;s vasculature) the implantable medical device. The releasable knot  200  is configured to maintain the knotted configuration to maintain the line coupled to the implantable medical device during steering. In certain instances, the releasable knot  200  is configured to resist separation between the (actuation) line and the implantable medical device in response to force applied to the actuation line. After the implantable medical device is aligned in a patient&#39;s vasculature (as noted above with reference to  FIG. 1 ), the tether  112  is configured to release the second and third loops  210 ,  212  from the first loop  202  by applying tension to the end  216  of the tether  112 . 
       FIGS. 3A-E  show another example tether  112  and steps in forming a releasable knot  300  with portions of the tether  112  in accordance with an embodiment. As explained in detail above with reference to  FIG. 1 , the tether  112  is coupled to a portion of an implantable medical device and arranged through a line (e.g., an actuation line) to couple the line to the implantable medical device. As shown in progressing through the steps shown in  FIGS. 3A-E , the tether  112  forms a releasable knot  300 , which is shown in a completed form in  FIG. 3E . The tether  112  includes multiple loops in forming the releasable knot  300 . 
     In certain instances, and as shown in  FIG. 3A , the tether  112  includes first loop  202 . The first loop  202  may be formed by a first fold of the tether  112 . The tether  112  is routed or arranged through a line and an implantable medical device to couple the line to the implantable medical device. Similar to the illustration in  FIGS. 2A-D , element  206  is representative of one of the line and an implantable medical device and element  208  is representative of the other of the line and an implantable medical device. In certain instances, the element  206  may be the patch (shown in  FIG. 1 ) or a hole in the implantable medical device and the element  208  may be an eyelet in the line. The tether  112  is arranged about the element  206  and the element  208 . In certain instances, the tether  112  is arranged through element  206  (the patch as shown in  FIG. 1 ) and through an eyelet of the line. After being arranged through or about the element  206  and the element  208 , the tether  112  may be folded to form a second loop  210  as shown in  FIG. 3B . The second loop  210  of the tether  112  is then arranged through the first loop  202  of the tether  112 . 
       FIG. 3C  shows a pathway for the tether  112  in forming the second loop  210 . As shown in  FIG. 2C , both portions of folded over tether  112  are used to form the second loop  210 . In addition, and as shown in  FIGS. 3A-E , each of the loops formed by the tether  112  include both portions of a folded over tether  112 . For example, and as shown in  FIG. 3D , a third fold of the tether  112  may form a third loop  212 . The third loop  212  is then arranged through the second loop  210 . Subsequently, the third loop  212  is arranged through the second loop  210 . As shown in  FIG. 3E , a fourth fold of the tether  112  may form a fourth loop  316 . The fourth loop  316  is then arranged through the third loop  212 . 
     After the fourth loop  316  is arranged through the third loop  212 , tension may be applied to ends  214 ,  216  of the tether  112  to tighten and complete the releasable knot  300 . To release or untie the releasable knot  300 , tension may be applied to both of the ends  214 ,  216 . After the releasable knot  300  is formed, tension does not need to be applied to hold the releasable knot  300  in the knotted configuration (e.g., as shown in  FIG. 3E ). One or both of the ends  214 ,  216  may be coupled to a deployment handle (not shown) or a proximal portion of a catheter (e.g., as described above with reference to  FIG. 1 ) such that a use may apply tension to one of the ends  214 ,  216  of the tether  112  or actuate a portion of the deployment handle that is coupled to one of the ends  214 ,  216  of the tether  112 . 
     Forming the releasable knot  300  in the manner discussed above may be manufactureable. The steps to create the releasable knot  300  are relatively simple (e.g., not numerous, minimal crossover or loop formation in the tether  112 ). In addition and in manufacturing or forming the releasable knot  300 , it should be determined whether the releasable knot  300  is properly formed. The releasable knot  300  is properly formed when the releasable knot  300  is able to couple the line to the implantable medical device. As a result, visually inspecting the releasable knot  200  to verify that the releasable knot  300  effectively couples the actuation line to the implantable medical device includes determining whether the releasable knot  200  maintains the knotted configuration or fails to do so. 
     As noted above with reference to  FIG. 1 , the line (an actuation line) may steer the implantable medical device in response to a force applied to the actuation line. In certain instances, the force may be applied to the actuation line to bidirectionally steer (e.g., proximally and distally relative to the target location within the patient&#39;s vasculature) the implantable medical device. The releasable knot  300  is configured to maintain the knotted configuration to maintain the line coupled to the implantable medical device during steering. In certain instances, the releasable knot  300  is configured to resist separation between the (actuation) line and the implantable medical device in response to force applied to the actuation line. After the implantable medical device is aligned in a patient&#39;s vasculature (as noted above with reference to  FIG. 1 ), the tether  112  is configured to release the second and third loops  210 ,  212  from the first loop  202  by applying tension to the ends  214 ,  216  of the tether  112 . 
       FIGS. 4A-F  show another example tether and steps in forming a releasable knot with portions of the tether in accordance with an embodiment. As explained in detail above with reference to  FIG. 1 , the tether  112  is coupled to a portion of an implantable medical device and arranged through a line (e.g., an actuation line) to couple the line to the implantable medical device. As shown in progressing through the steps shown in  FIGS. 4A-F , the tether  112  forms a releasable knot  400 , which is shown in a completed form in  FIG. 4F . As discussed in further detail below, the tether  112  forms a releasable knot  400  by way of multiple loops  202 ,  210 ,  212 ,  316 . 
     In certain instances, and as shown in  FIG. 4A , the tether  112  includes a first loop  202 . The first loop  202  may be formed by a first fold of the tether  112 . The tether  112  is routed or arranged through a line and an implantable medical device to couple the line to the implantable medical device. Similar to the illustration in  FIGS. 2A-D  and  FIGS. 3A-E , element  206  is representative of one of the line and an implantable medical device and element  208  is representative of the other of the line and an implantable medical device. In certain instances, the element  206  may be the patch (shown in  FIG. 1 ) or a hole in the implantable medical device and the element  208  may be an eyelet in the line. The tether  112  is arranged about the element  206  and the element  208 . In certain instances, the tether  112  is arranged through element  206  (the patch as shown in  FIG. 1 ) and through an eyelet of the line. 
     After being arranged through or about the element  206  and the element  208 , the tether  112  may be folded to form a second loop  210  as shown in  FIG. 4B . The second loop  210  of the tether  112  is then arranged through the first loop  202  of the tether  112 .  FIG. 4C  shows a pathway for the tether  112  in forming the second loop  210 . As shown in  FIG. 4C , both portions of folded over tether  112  are used to form the second loop  210 . Each of the first loop  202  and the second loop  210  formed by the tether  112  include both portions of a folded over tether  112 . As shown in  FIG. 4D , a third fold of the tether  112  that may form a third loop  212  includes one of the portions of the tether  112 . As shown in  FIG. 4D , end  214  of the tether  112  is arranged back through the first loop  202  while end  216  of the tether  112  is folded to form the third loop  212 , which is arranged through the second loop  210 . 
     Similar to the third loop  212  formed in the releasable knot  400 , a fourth fold of the tether  112  may form a fourth loop  316  that includes the end  216  of the tether  112 . The fourth loop  316  is then arranged through the third loop  212  as shown in  FIGS. 4E-F . After the fourth loop  316  is arranged through the third loop  212 , tension may be applied to ends  214 ,  216  of the tether  112  to tighten and complete the releasable knot  400 . 
     To release or untie the releasable knot  400 , tension may be applied to the end  216 . In certain instances, the end  214  may be trimmed after the releasable knot  400  is formed. Further, the end  216  may be coupled to a deployment handle (not shown) or a proximal portion of a catheter (e.g., as described above with reference to  FIG. 1 ) such that a user may apply tension to the end  216  of the tether  112  or actuate a portion of the deployment handle that is coupled to the end  216  of the tether  112 . In addition, tension does not need to be applied to hold the releasable knot  400  in the knotted configuration (e.g., as shown in  FIG. 4F ). 
     Forming the releasable knot  400  in the manner discussed above may be manufactureable. The steps to create the releasable knot  400  are relatively simple (e.g., not numerous, minimal crossover or loop formation in the tether  112 ). In addition, and in manufacturing or forming the releasable knot  400 , it should be determined whether the releasable knot  400  is properly formed. The releasable knot  400  is properly formed when the releasable knot  400  is able to couple the line to the implantable medical device. As a result, visually inspecting the releasable knot  200  to verify that the releasable knot  400  effectively couples the actuation line to the implantable medical device includes determining whether the releasable knot  200  maintains the knotted configuration or fails to do so. 
     As noted above with reference to  FIG. 1 , the line (an actuation line) may steer the implantable medical device in response to a force applied to the actuation line. The releasable knot  400  is configured to maintain the knotted configuration to maintain the line coupled to the implantable medical device during steering. In certain instances, the releasable knot  400  is configured to resist separation between the (actuation) line and the implantable medical device in response to force applied to the actuation line. After the implantable medical device is aligned in a patient&#39;s vasculature (as noted above with reference to  FIG. 1 ), the tether  112  is configured to release the second and third loops  210 ,  212  from the first loop  202  by applying tension to one of the ends  214 ,  216  of the tether  112 . 
       FIGS. 5A-E  shows side view illustrations of expandable device angulation relative to a target location  500   a - e  in accordance with various aspects of the present disclosure. Each of  FIGS. 5A-E  show a side profile of a leading (or proximal) end  500   a - e  of an expandable device, consistent with various aspects of the present disclosure. In certain instances, the target location  500   a - e  may be at a tortuous vessel of a patient. The target location  500   a - e  into which the expandable device is implanted may have angulation (e.g., a curvature with at least one inflection point  504   a - e ). The target location  500   a - e  may be an angulated abdominal aortic aneurism (AAA), healthy tissue below the renal arteries, or other tortuous vessels. The releasable knots discussed herein enable actuation of the actuation wire at a location near a midpoint of the implantable device of distal to the midpoint (e.g., closer to the operator of the delivery system) on the implantable medical device. 
     In certain instances, one of the ends  502   a - e  of the expandable device may be deployed perpendicular to the inflection point (e.g., of a heathy vessel tissue) in the curvature of the tortuous vessel during delivery of the expandable device. Non-perpendicularity may negatively affect the ability of the expandable device to seal against the target location  500   a - e .  FIG. 5A  shows the leading (or proximal) end  502   a  deployed perpendicular to the inflection point  504   a . In certain instances, perpendicularity of the expandable device may be a function of device flatness, angulation, and rotational alignment.  FIG. 5B  shows the leading (or proximal) end  502   b  of an expandable device angled relative to the inflection point  504   b  of the target location  500   b .  FIG. 5C  shows the leading (or proximal) end  502   c  of an expandable device rotated relative to the inflection point  504   c  of the target location  500   c .  FIG. 5D  shows the leading (or proximal) end  502   d  of an expandable device deformed relative to the inflection point  504   b  of the target location  500   d .  FIG. 5E  shows the leading (or proximal) end  502   e  of an expandable device deformed or flat, rotated, and angled relative to the inflection point  504   e  of the target location  500   e.    
     Device deployment and performance can be enhanced by steering the device to an appropriate location while maintaining one of the ends of the expandable device perpendicular to the target location  500   a - e  (e.g., curvature of a vessel with at least one inflection point  504   a - e ) during and after deployment. The actuation lines and arrangements thereof discussed herein facilitate maintaining the expandable device perpendicular during and after deployment (as shown in  FIG. 5A ) and mitigate against non-perpendicular, angled, or flat deployment (as shown in  FIGS. 5B-E ). 
     The lines discussed herein may be formed from metallic, polymeric or natural materials such as stainless steels, cobalt-chromium alloys and nitinol. Further, the lines can also be formed from high strength polymer fibers such as ultra high molecular weight polyethylene fibers (e.g., Spectra™., Dyneema Purity™., etc.) or aramid fibers (e.g., Technora™, etc.). 
     The graft components of the implantable medical device and/or the patch may be made up of any material which is suitable for use as a graft in the chosen body lumen and being resistant to expansion as discussed herein. The graft components may be composed of the same or different materials. Furthermore, the graft components may include multiple layers of material that can be the same material or different material. In one embodiment, said materials can be used in combination and assembled together to comprise a graft. The graft materials used in a stent graft can be extruded, coated or formed from wrapped films, or a combination thereof. Polymers, biodegradable and natural materials can be used for specific applications. 
     Examples of synthetic polymers include, but are not limited to, nylon, polyacrylamide, polycarbonate, polyform aldehyde, polymethylmethacrylate, polytetrafluoroethylene, polytrifluorochlorethylene, polyvinylchloride, polyurethane, elastomeric organosilicon polymers, polyethylene, polypropylene, polyurethane, polyglycolic acid, polyesters, polyamides, their mixtures, blends and copolymers are suitable as a graft material. In one embodiment, said graft is made from a class of polyesters such as polyethylene terephthalate including DACRON®. and MYLAR and polyaramids such as KEVLAR®., polyfluorocarbons such as polytetrafluoroethylene (PTFE) with and without copolymerized hexafluoropropylene (TEFLON®. or GORE-TEX®), and porous or nonporous polyurethanes. In another embodiment, said graft comprises expanded fluorocarbon polymers (especially PTFE) materials described in British Pat. Nos. 1,355,373; 1,506,432; or 1,506,432 or in U.S. Pat. Nos. 3,953,566; 4,187,390; or 5,276,276, the entirety of which are incorporated by reference. Included in the class of preferred fluoropolymers are polytetrafluoroethylene (PTFE), fluorinated ethylene propylene (FEP), copolymers of tetrafluoroethylene (TFE) and perfluoro(propyl vinyl ether) (PFA), homopolymers of polychlorotrifluoroethylene (PCTFE), and its copolymers with TFE, ethylene-chlorotrifluoroethylene (ECTFE), copolymers of ethylene-tetrafluoroethylene (ETFE), polyvinylidene fluoride (PVDF), and polyvinyfluoride (PVF). Especially preferred, because of its widespread use in vascular prostheses, is ePTFE. In another embodiment, said graft comprises a combination of said materials listed above. In another embodiment, said graft is substantially impermeable to bodily fluids. Said substantially impermeable graft can be made from materials that are substantially impermeable to bodily fluids or can be constructed from permeable materials treated or manufactured to be substantially impermeable to bodily fluids (e.g. by layering different types of materials described above or known in the art). In another embodiment, said outermost tube comprises ePTFE. In another embodiment, said innermost tube comprises ePTFE. In another embodiment, said innermost and outermost tube comprises ePTFE film that has been wrapped into a tube. In another embodiment, said secondary stent is covered with any of the material disclosed herein or known in the art. In another embodiment, the secondary stent covering comprises ePTFE. 
     Additional examples of graft materials include, but are not limited to, vinylidinefluoride/hexafluoropropylene hexafluoropropylene (HFP), tetrafluoroethylene (TFE), vinylidenefluoride, 1-hydropentafluoropropylene, perfluoro(methyl vinyl ether), chlorotrifluoroethylene (CTFE), pentafluoropropene, trifluoroethylene, hexafluoroacetone, hexafluoroisobutylene, fluorinated poly(ethylene-co-propylene (FPEP), poly(hexafluoropropene) (PHFP), poly(chlorotrifluoroethylene) (PCTFE), poly(vinylidene fluoride (PVDF), poly(vinylidene fluoride-co-tetrafluoroethylene) (PVDF-TFE), poly(vinylidene fluoride-co-hexafluoropropene) (PVDF-HFP), poly(tetrafluoroethylene-co-hexafluoropropene) (PTFE-HFP), poly(tetrafluoroethylene-co-vinyl alcohol) (PTFE-VAL), poly(tetrafluoroethylene-co-vinyl acetate) (PTFE-VAC), poly(tetrafluoroethylene-co-propene) (PTFEP) poly(hexafluoropropene-co-vinyl alcohol) (PHFP-VAL), poly(ethylene-co-tetrafluoroethylene) (PETFE), poly(ethylene-co-hexafluoropropene) (PEHFP), poly(vinylidene fluoride-co-chlorotrifluoroe-thylene) (PVDF-CTFE), and combinations thereof, and additional polymers and copolymers described in U.S. Publication 2004/0063805, incorporated by reference herein in its entirety for all purposes. Additional polyfluorocopolymers include tetrafluoroethylene (TFE)/perfluoroalkylvinylether (PAVE). PAVE can be perfluoromethylvinylether (PMVE), perfluoroethylvinylether (PEVE), or perfluoropropylvinylether (PPVE), as described in U.S. Publication 2006/0198866 and U.S. Pat. No. 7,049,380, both of which are incorporated by reference herein for all purposes in their entireties. Other polymers and copolymers include, polylactide, polycaprolacton-glycolide, polyorthoesters, polyanhydrides; poly-am inoacids; polysaccharides; polyphosphazenes; poly(ether-ester) copolymers, e.g., PEO-PLLA, or blends thereof, polydimethyl-siolxane; poly(ethylene-vingylacetate); acrylate based polymers or copolymers, e.g., poly(hydroxyethyl methylmethacrylate, polyvinyl pyrrolidinone; fluorinated polymers such as polytetrafluoroethylene; cellulose esters and any polymer and copolymers described in U.S. Publication 2004/0063805, incorporated by reference herein in its entirety. 
     The graft components, as discussed herein, may be attached to the self-expanding stent elements by using a coupling member that is generally a flat ribbon or tape having at least one generally flat surface. In certain instances, the tape member is made from expanded PTFE (ePTFE) coated with an adhesive. The adhesive may be a thermoplastic adhesive. In certain instances, the thermoplastic adhesive may be fluorinated ethylene propylene (FEP). More specifically, an FEP-coated side of the ePTFE may face toward and contact an exterior surface of the self-expanding stent and graft component, thus attaching the self-expanding stent to the graft component. Materials and method of attaching a stent to the graft is discussed in U.S. Pat. No. 6,042,602 to Martin, incorporated by reference herein for all purposes in its entirety. 
     The stent component(s) discussed herein can be fabricated from a variety of biocompatible materials. These materials may include 316L stainless steel, cobalt-chromium-nickel-molybdenum-iron alloy (“cobalt-chromium”), other cobalt alloys such as L605, tantalum, Nitinol, or other biocompatible metals. In certain instances, as discussed in detail above, the stent (and graft) may be self-expanding. In other instances, the prosthesis may be balloon expandable. 
     The stent component(s) discussed herein may be constructed from a reasonably high strength material, i.e., one which is resistant to plastic deformation when stressed. In one embodiment, the stent component(s) comprise a line which is helically wound around a mandrel having pins arranged thereon so that the helical turns and undulations can be formed simultaneously. Other constructions may also be used. In certain instances, the stent component(s) are made from a super-elastic alloy. There are a variety of disclosures in which super-elastic alloys such as nitinol are used in stents. See for example, U.S. Pat. No. 4,503,569, to Dotter; U.S. Pat. No. 4,512,338, to Balko et al.; U.S. Pat. No. 4,990,155, to Wilkoff; U.S. Pat. No. 5,037,427, to Harada, et al.; U.S. Pat. No. 5,147,370, to MacNamara et al.; U.S. Pat. No. 5,211,658, to Clouse; and U.S. Pat. No. 5,221,261, to Term in et al. 
     A variety of materials variously metallic, super elastic alloys, such as Nitinol, are suitable for use in the stent component(s). Primary requirements of the materials are that they be suitably springy even when fashioned into very thin sheets or small diameter lines. Various stainless steels which have been physically, chemically, and otherwise treated to produce high springiness are suitable as are other metal alloys such as cobalt chrome alloys (e.g., ELGILOY®), platinum/tungsten alloys, and especially the nickel-titanium alloys generically known as “nitinol”. 
     The invention of this application has been described above both generically and with regard to specific embodiments. It will be apparent to those skilled in the art that various modifications and variations can be made in the embodiments without departing from the scope of the disclosure. Thus, it is intended that the embodiments cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.