Patent Publication Number: US-2023138365-A1

Title: Endoluminal prosthesis systems and methods

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 15/737,223, filed Dec. 15, 2017, which is a U.S. National Stage Application under 35 U.S.C. § 371 of International Application No. PCT/US2016/039414, filed Jun. 24, 2016, which claims priority from U.S. Provisional Patent App. Ser. No. 62/183,735, filed Jun. 24, 2015, the entire contents of each of which are incorporated by reference herein. 
    
    
     FIELD 
     Various embodiments disclosed herein relate generally to medical apparatuses and methods for treatment of arterial disease. More particularly, various embodiments relate to expandable prostheses and methods for treating abdominal and other aneurysms. Various embodiments relate to devices and methods of treating an abdominal, paravisceral, juxtarenal, peripheral, or thoracic aneurysms. 
     BACKGROUND 
     Aneurysms are enlargements or bulges in blood vessels that are often prone to rupture and which therefore present a serious risk to a patient. Aneurysms may occur in any blood vessel but are of particular concern when they occur in the cerebral vasculature or the patient&#39;s aorta. 
     Some embodiments of the present disclosure are concerned with aneurysms occurring in the aorta, particularly those referred to as aortic aneurysms. Abdominal aortic aneurysms (AAA&#39;s) are classified based on their location within the aorta as well as their shape and complexity. Aneurysms that are found below the renal arteries are referred to as infrarenal abdominal aortic aneurysms. Suprarenal abdominal aortic aneurysms occur above the renal arteries, while thoracic aortic aneurysms (TAA&#39;s) occur in the ascending, transverse, or descending part of the upper aorta. 
     Infrarenal aneurysms are the most common, representing about seventy percent (70%) of all aortic aneurysms. Suprarenal aneurysms are less common, representing about twenty percent (20%) of the aortic aneurysms. Thoracic aortic aneurysms are the least common and often the most difficult to treat. Many endovascular systems are also too large (above 4 mm in diameter) for percutaneous introduction. 
     The most common form of aneurysm is fusiform, wherein the enlargement extends about the entire aortic circumference. Less commonly, the aneurysms may be characterized by a bulge on one side of the blood vessel attached at a narrow neck. Thoracic aortic aneurysms are often dissecting aneurysms caused by hemorrhagic separation in the aortic wall, usually within the medial layer. The most common treatment for each of these types and forms of aneurysm is open surgical repair. Open surgical repair is quite successful in patients who are otherwise reasonably healthy and free from significant co-morbidities. Such open surgical procedures are problematic, however, since access to the abdominal and thoracic aortas is difficult to obtain and because the aorta must be clamped off, placing significant strain on the patient&#39;s heart. 
     Endoluminal grafts can be used for the treatment of aortic aneurysm in patients who cannot undergo open surgical procedures. In general, endoluminal repairs access the aneurysm endoluminally through either or both iliac arteries in the groin. Subclavian access is also used to perform branched procedures. The grafts, which can have fabric or membrane tubes supported and attached by various stent structures, are then implanted, and can require several pieces or modules to be assembled in situ. Successful endoluminal procedures can have a much shorter recovery period than open surgical procedures. 
     Many designs of helical stents for treating aneurysms require a lot of manual work during the manufacturing process in order to align and adjust the struts of the stent to achieve uniform geometry pattern. Helical stents when expanded may lengthen or foreshorten causing unpredictability in placement of the stent relative to an anatomy. Many times the branches associated with an aneurysm may also need to be stented. Aneurysms in the aorta may require that various branches, such as but not limited to renal arties, iliac arteries, the superior mesenteric artery (SMA), and the celiac artery be partially stented. Branched stents for repairing such branches often face challenges with respect to lacking enough flexibility to withstand the physiological motion of the branch vessels. 
     SUMMARY OF THE DISCLOSURE 
     A stent includes a main body having a plurality of rings that form a helix. In various embodiments, each of the plurality of rings includes a plurality of skewed v-shaped elements that each have a first leg and a second leg that is longer than the first leg. In various embodiments, the stent further includes an end ring, and a ring of the plurality of rings of the main body is angled with respect to the end ring. In some embodiments, the end ring is shaped to have a plurality of peaks of the end ring, and the skewed v-shaped elements and the connections between the skewed v-shaped elements in the ring of the plurality of rings of the main body form a plurality of peaks of the ring. In various embodiments, the stent further comprises a transition region including one or more struts, and each of the one or more struts connects a corresponding peak of the plurality of peaks of the end ring to a corresponding peak of the plurality of peaks of the ring. 
     In some embodiments, the stent includes a transition region including a first strut for connecting the end ring to the ring and a second connecting strut for connecting the end ring to the ring, where a length of the second strut is longer than a length of the first strut. In some embodiments, the transition region further includes a third strut for connecting the end ring to the ring, and a length of the third strut is longer than the length of the second strut. In some embodiments, a distance between the second strut and the third strut is greater than a distance between the first strut and the second strut. 
     In various embodiments, the stent includes a plurality of connecting struts for connecting a ring of the plurality of rings of the main body with an adjacent ring of the plurality of rings of the main body. In some embodiments, each of the plurality of connecting struts extends from a corresponding peak of a plurality of peaks of the ring to a corresponding valley of a plurality of valleys of the adjacent ring. In some embodiments, a distance between each of the plurality of connecting struts is greater than a width of a skewed v-shaped element of the plurality of skewed v-shaped elements. In some embodiments, a distance between each of the plurality of connecting struts is greater than double a width of a skewed v-shaped element of the plurality of skewed v-shaped elements. 
     In various embodiments, the stent further includes a first plurality of connecting struts for connecting a ring of the plurality of rings of the main body with a first adjacent ring of the plurality of rings of the main body, and a second plurality of connecting struts for connecting the ring with a second adjacent ring of the plurality of rings of the main body. In some embodiments, each of the first plurality of connecting struts extends from a corresponding peak of a plurality of peaks of the ring to a corresponding valley of a plurality of valleys of the first adjacent ring, and each of the second plurality of connecting struts extends from a corresponding valley of a plurality of valleys of the ring to a corresponding peak of a plurality of peaks of the second adjacent ring. 
     In various embodiments, a particular connecting strut of the second plurality of connecting struts is equidistant from a corresponding two connecting struts of the first plurality of connecting struts that are nearest to the particular connecting strut. In some embodiments, the first leg and the second leg of each of the plurality of skewed v-shaped elements of each of the plurality of rings have respective lengths such that there is a group of v-shaped elements that have corresponding apices aligned with each other in a direction that is parallel to a longitudinal axis of the stent. 
     In various embodiments, the main body further comprises a second plurality of rings that form a second helix. Also, in various embodiments, an end ring of the stent includes a plurality of tear drop shaped elements, and the stent further includes a transition region connecting a peak of a tear drop shaped element of the plurality of tear drop shaped elements of the end ring to the main body. 
     In some embodiments, the stent includes a first end ring and a second end ring positioned to an opposite side of the main body from the first end ring, and each of the plurality of rings of the main body is angled with respect to the first end ring and the second end ring. In some embodiments, a width direction of an end of the first end ring and a width direction of an end of the second end ring are perpendicular to a longitudinal axis of the stent. In some embodiments, the stent includes a first transitional region for connecting the first end ring to the main body, and a second transitional region for connecting the second end ring to the main body. In various embodiments, the stent further includes a plurality of connecting struts extending between rings of the plurality of rings, where each of the plurality of connecting struts is arranged parallel to a longitudinal axis of the stent. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a perspective view of an endoluminal prosthesis according to an embodiment. 
         FIG.  2    is a perspective view of an end ring of the endoluminal prosthesis of  FIG.  1   . 
         FIG.  3    is a right orthogonal view of the endoluminal prosthesis of  FIG.  1   . 
         FIG.  4    is a left orthogonal view of the endoluminal prosthesis of  FIG.  1   . 
         FIG.  5    is a front orthogonal view of the endoluminal prosthesis of  FIG.  1   . 
         FIG.  6    is a top orthogonal view of the endoluminal prosthesis of  FIG.  1   . 
         FIG.  7    is a rear orthogonal view of the endoluminal prosthesis of  FIG.  1   . 
         FIG.  8    is a bottom orthogonal view of the endoluminal prosthesis of  FIG.  1   . 
         FIG.  9    is a flat view of an endoluminal prosthesis, according to an exemplary embodiment. 
         FIG.  10    is a flat view of a portion of the endoluminal prosthesis of  FIG.  9   . 
         FIG.  11    is a flat view of an endoluminal prosthesis, according to another exemplary embodiment. 
         FIG.  12    is a front orthogonal view of the endoluminal prosthesis of  FIG.  11   . 
         FIG.  13    is a top orthogonal view of the endoluminal prosthesis of  FIG.  11   . 
         FIG.  14    is a rear orthogonal view of the endoluminal prosthesis of  FIG.  11   . 
         FIG.  15    is a bottom orthogonal view of the endoluminal prosthesis of  FIG.  11   . 
         FIG.  16    is a flat view of an endoluminal prosthesis, according to another exemplary embodiment. 
         FIG.  17    is a front orthogonal view of the endoluminal prosthesis of  FIG.  16   . 
         FIG.  18    is a top orthogonal view of the endoluminal prosthesis of  FIG.  16   . 
         FIG.  19    is a rear orthogonal view of the endoluminal prosthesis of  FIG.  16   . 
         FIG.  20    is a bottom orthogonal view of the endoluminal prosthesis of  FIG.  16     
         FIG.  21    is a flat view of an endoluminal prosthesis, according to another exemplary embodiment. 
         FIG.  22    is a front orthogonal view of the endoluminal prosthesis of  FIG.  21   . 
         FIG.  23    is a top orthogonal view of the endoluminal prosthesis of  FIG.  21   . 
         FIG.  24    is a rear orthogonal view of the endoluminal prosthesis of  FIG.  21   . 
         FIG.  25    is a bottom orthogonal view of the endoluminal prosthesis of  FIG.  21   . 
         FIG.  26    is a flat view of an endoluminal prosthesis, according to another exemplary embodiment. 
         FIG.  27    is a front orthogonal view of the endoluminal prosthesis of  FIG.  26   . 
         FIG.  28    is a top orthogonal view of the endoluminal prosthesis of  FIG.  26   . 
         FIG.  29    is a rear orthogonal view of the endoluminal prosthesis of  FIG.  26   . 
         FIG.  30    is a bottom orthogonal view of the endoluminal prosthesis of  FIG.  26   . 
     
    
    
     DETAILED DESCRIPTION 
     In the following detailed description, reference is made to the accompanying drawings, which form a part hereof. In the drawings, similar symbols typically identify similar components, unless context dictates otherwise. The illustrative embodiments described in the detailed description, drawings, and claims are not meant to be limiting. Other embodiments may be utilized, and other changes may be made, without departing from the spirit or scope of the subject matter presented here. It will be readily understood that the aspects of the present disclosure, as generally described herein, and illustrated in the figures, can be arranged, substituted, combined, and designed in a wide variety of different configurations, all of which are explicitly contemplated and make part of this disclosure. 
     Referring to  FIGS.  1 ,  2 ,  3 ,  4 ,  5 ,  6 ,  7 , and  8   , a stent  100  is shown in accordance with an embodiment. In various views, the stent  100  is shown surrounding an exemplary mandrel  101  for ease of illustration. The stent  100  includes a first end ring  102 , a first transition region  104 , a main body  106 , a second transition region  108 , and a second end ring  110 . The stent  100  defines a longitudinal axis  103 . The stent  100  may be deployed in any blood vessel, including unbranched and branched blood vessels. In some embodiments, the various features of the stent  100  enhance the performance of the stent  100  for branched vessel applications. In various embodiments, the stent  100  is formed from a suitable biocompatible material, such as a biocompatible alloy, a biocompatible metal, or a biocompatible polymer that may be a thermoplastic material. In some embodiments, the stent  100  is formed from a steel, cobalt chromium, nitinol, and/or shape memory alloy. The stent  100  may be configured with an expandable geometry. For example, in some embodiments, the stent  100  is a self-expanding stent. In some embodiments, the stent  100  is a balloon-expandable stent. 
     Referring to  FIGS.  2  and  3   , the first end ring  102  is shown in more detail, and referring to  FIG.  4   , the second end ring  110  is shown in more detail. With reference to  FIGS.  1 ,  2 ,  3 , and  4   , the first and second end rings  102  and  110  are shown to be similar in construction. According to an exemplary embodiment, the first and second end rings  102  and  110  may be formed from elements  112  having a tear drop shape spaced about the circumference of the stent  100 . Each of the tear drop shaped elements  112  is coupled to others of the tear drop shaped elements  112  on either side via a joint  114  at the widest portion of the tear drop shaped elements  112  to form a complete ring, as shown in  FIG.  2   . In some embodiments, the tear drop shaped elements  112 , when coupled together at the joints  114 , form v-shaped elements  115   a  and  115   b . Each of the v-shaped elements  115   a  and  115   b  have an end or apex  116 . As shown in  FIG.  2   , the tear drop shaped elements  112  each include a first, outwardly pointed v-shaped element  115   a  and a second, inwardly-pointed v-shaped element  115   b , with the v-shaped elements  115   a  and  115   b  joined together at the joints  114 . There is a space  118  between the apex  116  of each of the v-shaped elements  115   a . In an exemplary embodiment, the v-shaped elements  115   a  and  115   b  are formed such that the arms of the v-shaped elements  115   a  and  115   b  are roughly sinusoidal in shape due to the construction of the stent  100  with a laser-cutting and expansion process. In other embodiments, the v-shaped elements  115   a  and  115   b  are formed such that the arms of the v-shaped elements  115   a  and  115   b  are otherwise shaped, such as straight, convex, concave, or the like. 
     In various embodiments, the two types of v-shaped elements  115   a  and  115   b  may be of different sizes. For example, the outwardly-pointing v-shaped elements  115   a  may have legs that are longer than legs of the inwardly-pointed v-shaped elements  115   b , thus resulting in the tear drop shaped elements  112 . In other embodiments, each of the end portions  102  and  110  include a plurality of diamond-shaped elements that each include two relatively similarly sized v-shaped elements spaced about the circumference of the stent  100  with each of the diamond-shaped elements being coupled to diamond-shaped elements on either side via a joint at the widest portion of the diamond-shaped elements. In some embodiments, the end portions  102  and  110  may include elements comprising only inwardly-pointed v-shaped elements  115   b . In some embodiments, one or both of the end portions  102  and  110  may be otherwise shaped. 
     Referring to  FIGS.  1  and  2   , the first transition region  104  and the second transition region  108  transition from the end rings  102  and  110 , respectively, to the helical shaped main body  106 . The first transition region  104  couples the first end ring  102  to the main body  106  and, on the other end of the stent  100 , the second transition region  108  connects the second end ring  110  to the main body  106 . The transition regions  104  and  108  may include one or more bridges or struts  105  that connect a corresponding apex  116  from the first end ring  102  or the second end ring  110  to a peak of an adjacent helical ring of the main body  106 . Because a helical ring of the main body  106  is angled relative to the end rings  102  and  110 , the distance between the main body  106  and the end rings  102  and  110  that is spanned by the struts  105  varies about the circumference of the stent  100 . Accordingly, the lengths of the struts  105  that connect the end rings  102  and  110  to the main body  106  may vary from one another. In some embodiments, the helically shaped main body  106  may be coupled directly to one of the apices  116  of the end rings  102  and  110 . 
     In some embodiments, the transition regions  104  and  108  may include three bridges or struts  105  that are variably spaced apart from each other. For example, the distance between bridges or struts  105  may increase by a distance equal to the width of one of the elements  112  of the end rings  102  and  110 . The transition regions  104  and  108  between the main body  106  and the end rings  102  and  110  may include a peak-to-peak connection, such as with the struts  105  extending between an apex  116  of the end ring  102  or  110  to an apex of the main body  106  to provide more stability to the end rings  102  and  110  and enable uniform expansion and contraction of the stent  100 . It is to be understood that the transition region  108  may be similar in construction to the transition region  104  or may vary in construction compared to the transition region  104 . For example, the transition region  108  may include more or fewer struts  105  compared to the transition region  104 . 
     Referring now to  FIGS.  1 ,  5 ,  6 ,  7 , and  8   , the main body  106  of the stent  100  includes helical rings  130  formed from v-shaped elements  120 . The v-shaped elements  120  are sized such that the elements  120  of each loop or ring  130  of the helix are aligned with the elements  120  of an adjacent ring  130 . Each ring  130  is angled relative to an axis perpendicular to the longitudinal axis of the stent  100 . The angle of each ring  130  may vary based on the design of the stent  100 . 
     Each of the v-shaped elements  120  is coupled to v-shaped elements  120  on either side via a joint, forming an apex  122 . The v-shape of each of the v-shaped elements  120  also forms an apex  122  at the middle portion of the v-shape. A first side of each apex  122  defines a peak  124  and a second, opposite side of the apex  122  defines a valley  126 . Each of the v-shaped elements  120  is skewed such that a first leg  123   a  of the v-shaped element  120  is shorter than a second leg  123   b  of the v-shaped element  120 . Because each of the v-shaped elements  120  are skewed with the shorter first leg  123   a  and the longer second leg  123   b , each of the groups  132  of v-shaped elements  120  on neighboring rings  130  that are aligned along a direction parallel to the longitudinal axis  103  of the stent  100  are aligned as a group parallel to the longitudinal axis  103  of the stent  100 . 
     In some embodiments, v-shaped elements  120  of neighboring loops  130  of the main body  106  are connected to each other with connecting struts  128 , where each connecting strut  128  extends from the peak  124  of a corresponding apex  122  on one ring  130  of the helix to the valley  126  of another corresponding apex  122  of another ring  130  of the helix for the stent  100 . The connecting struts  128  maintain the shape of the main body  106  of the stent  100  with the apices  122  of one ring  130  aligned with the corresponding apices  122  of the neighboring ring  130  in a direction parallel to the longitudinal axis  103  of the stent  100 , ensuring that peaks are nested in the center of the neighboring valleys, in some embodiments. Clearance is therefore provided for the v-shaped elements  120  to bend and flex, granting a great amount of flexibility to the main body  106  of the stent  100 . The connecting struts  128  maintain this alignment even when the main body  106  of the stent  100  is bent at a relatively large angle. 
     Each apex  122  of the v-shaped elements  120  forming the main body  106  may initiate and receive connecting struts  128  that connect to corresponding apices  122  of the v-shaped elements  120  of the adjacent ring. In various embodiments, the frequency of connecting struts  128  and the ratio apices  122  joined by connecting struts  128  versus free apices may vary. In some embodiments, the connecting struts  128  are spaced such that four v-shaped elements  120  are provided between each connecting strut  128 . In various embodiments, it is possible to have 1, 2, 3, 4, 5, 6, 7, or any other suitable number of v-shaped elements  120  between each connecting strut  128 . In some embodiments, every third v-shaped element  120  in a ring  130  has a connecting strut  128  to an adjacent ring  130 . Increasing the number of connections between rings  130  with the connecting struts  128  may decrease the flexibility of the endoluminal prosthesis, and conversely decreasing the number of connections between rings  130  with the connecting struts  128  may increase the flexibility of the endoluminal prosthesis. 
     The peak-to-valley arrangement of the connecting struts  128  allows the stent  100  to radially expand and contract in a uniform manner. Uniform radial expansion and contraction may lead to easier manufacturing, more uniform deployed shape, and better wall apposition. The peak-to-valley arrangement of the connecting struts  128  arranges the apices  122  of the v-shaped elements  120  to be aligned with each other in the direction parallel to the longitudinal axis  103  of the stent  100  during radial expansion/contraction of the stent  100 . 
     In various embodiments the helical configuration of the main body  106  provides additional flexibility for the bending of the stent  100  when a portion of the stent  100  is placed within a branch vessel originating in a larger vessel and the other portion is placed at an angle greater than or equal to ninety degrees in the larger vessel, such as but not limited to the aorta. Accordingly, the helical pattern of the main body  106  disclosed herein may allow the stent  100  to achieve more flexibility than other designs while retaining patency or blood flow to the organs through the larger vessel and the branch vessel. 
     Referring to  FIG.  9   , a flat view of a stent  200  is shown in accordance with an embodiment. The stent  200  may be similar in shape to the stent  100  discussed above with reference to  FIGS.  1 - 8   . The stent  200  includes a first end ring  202 , a first transition region  204 , a main body  206 , a second transition region  208  and a second end ring  210 . While the stent  200  is generally manufactured to be a generally cylindrical body, the flat view illustrated in  FIG.  9    is provided for clarity. End points on one side of the stent  200 , as shown by point A are understood to be continuous with corresponding end points on the opposite side of the stent  200 , as shown by point B. 
     The end rings  202  and  210  are formed from tear drop shaped elements  212 . Each of the tear drop shaped elements  212  is coupled to corresponding tear drop shaped elements  212  on either side via a joint  214  at the widest portion of the tear drop shaped elements  212  to form a complete ring. In some embodiments, each of the tear drop shaped elements  212  are formed by v-shaped elements  215   a  and  215   b  that each have an apex  216 . As shown in  FIG.  9   , the tear drop shaped elements  212  each include a first, outwardly-pointed v-shaped element  215   a  and a second, inwardly-pointed v-shaped element  215   b , with the v-shaped elements  215   a  and  215   b  joined together at the joints  214 . In an exemplary embodiment, the v-shaped elements  215   a  and  215   b  are formed such that the arms of the v-shaped elements  215   a  and  215   b  are roughly sinusoidal in shape due to the construction of the stent  200  with a laser-cutting and expansion process. In other embodiments, the v-shaped elements  215   a  and  215   b  are formed such that the arms of the v-shaped elements  215   a  and  215   b  are otherwise shaped, such as straight, convex, concave, or the like. 
     The main body  206  of the stent  200  includes helical rings formed from v-shaped elements  220 , shown in more detail in  FIG.  10   . With reference to  FIGS.  9  and  10   , the v-shaped elements  220  are sized such that the v-shaped elements  220  of each ring  240  of the helix are aligned with corresponding v-shaped elements  220  in adjacent rings  240  in a direction parallel to a longitudinal axis of the stent  200 . Each of the v-shaped elements  220  is coupled to v-shaped elements  220  on either side via a joint, forming an apex  222 . The v-shape of each of the v-shaped elements  220  also forms an apex  222  at the middle portion of the v-shape. A first, exterior side of each apex  222  defines a peak  224  and a second, interior side of the apex  222  defines a valley  226 . Each of the v-shaped elements  220  includes a first leg  230  and a second leg  232  joined at a corresponding apex  222 . The length of the second leg  232  is greater than the length of the first leg  230 , forming a skewed v-shape and defining a lead angle  234  of the helical ring forming the main body  206 . The lead angle  234  is shown as the angle from horizontal formed by a lead line  235  passing through the bases of the legs  230  and  232 . Because the legs  230  and  232  of the v-shaped element  220  are of unequal lengths, the v-shaped element  220  is not oriented perpendicular to the lead line  235 . That is, a midline  236  of the v-shaped element  220  is not perpendicular to the lead line  235 . The midline  236  is defined as a line passing through the apex  222  at which the first leg  230  and second leg  232  meet and, according to an exemplary embodiment, the midline  236  of the v-shaped element  220  is oriented parallel to the longitudinal axis of the stent  200 . In this way, v-shaped elements  220  that line up with each other on neighboring rings  240  form a corresponding group  242  that is parallel to the longitudinal axis of the stent  200 . The skewed configuration of the v-shaped elements  220  forming the main body  206  that allow for groups  242  being oriented parallel to the longitudinal axis of the stent  200  allows the stent  200  to expand uniformly without rotating. Rotation of the rings  240  relative to each other can cause undesirable migration of the stent  200 . The ring  240  is shown to be inclined at an angle equal to the lead angle  234 . The lead angle  234  of the ring  240  is determined based on the desired application. In various embodiments, the lead angle  234  of each ring  240  may be increased or decreased. In some embodiments, the lead angle  234  of each ring  240  is set such that the main body  206  forms a single helix. As described in more detail below, in some embodiments, the lead angle  234  is set such that a sufficient clearance is provided between rings  240  of the helix to receive one or more additional helices, such as for a main body that may comprise a double helix, triple helix, or the like. 
     The v-shaped elements  220  of neighboring loops or rings  240  of the main body  206  are connected to each other with connecting struts  244  that extend from a corresponding peak  224  of one ring  240  of the helix to a corresponding valley  226  of another ring  240  of the helix. The connecting struts  244  maintain the shape of the main boy  206  of the stent  200  with the peaks  224  of one ring  240  aligned with the valleys  226  of the neighboring ring  240 , and vice-versa, thereby increasing the flexibility of the main body  206  and reducing the likelihood that a ring will impede an adjacent ring. Each ring  240  may be connected via connecting struts  244  extending from valleys  226  to peaks  224  of one adjacent ring  240  and may be connected via connecting struts  244  extending from peaks  224  to valleys  226  of another adjacent ring  240 . Accordingly, one side of the ring  240  has valleys  226  that are coupled to connecting struts  244  and another side of the ring  240  has peaks  224  that are coupled to connecting struts  244 . 
     Each apex  222  of the v-shaped elements  220  forming the main body  206  may initiate and receive connecting struts  244  that connect to corresponding apices  222  of the v-shaped elements  220  of the adjacent ring  240 . The connecting struts  244  may be coupled to any apex  222  of the main body  206 , such as a corresponding apex  222  formed between the legs  230  and  232  of a v-shaped element  220  or the apex  222  formed between adjacent v-shaped elements  220 . In various embodiments, the frequency of connecting struts  244  and the ratio of apices  222  joined by connecting struts  244  versus free apices  222  may vary. In some embodiments, a distance between each of the connecting struts  244  is greater than a width of one of the v-shaped elements  220 . In some embodiments, a distance between each of the connecting struts  244  is greater than double a width of one of the v-shaped elements  220 . In some embodiments, as shown in  FIG.  9   , the connecting struts  244  are spaced from each other such that four v-shaped elements  220  in each ring  240  are provided between each connecting strut  244  that is on one side of the ring  240 . 
     The main body  206  may be subdivided into a series of sub-rings  246  including four v-shaped elements  220 , each of which are coupled to an adjacent sub-ring  246  on one side with a connecting strut  244  from a corresponding valley  226  to a corresponding peak  224  and coupled to an adjacent sub-ring  246  on the opposite side with a connecting strut  244  from a corresponding peak  224  to a corresponding valley  226 . In some embodiments, the number of connecting struts  244  between adjacent rings  240  may vary. For example, some rings  240  may be coupled together with three connecting struts  244 , while other rings  240  may be connected together with two connecting struts  244 . Increasing the number of connecting struts  244  between rings  240  may decrease the flexibility of the stent  200  and conversely decreasing the number of connecting struts  244  between rings  240  may increase the flexibility of the stent  200 . In various embodiments, a particular connecting strut of the connecting struts  244  that is on one side of a particular ring of the rings  240  is equidistant from a corresponding two connecting struts of the connecting struts  244  that are nearest to the particular connecting strut. 
     Referring still to  FIG.  9   , the first transition region  204  and the second transition region  208  transition from the end rings  202  and  210 , respectively, to the helical main body  206 . In various embodiments, the rings  240  are angled with respect to the end rings  202  and  210 . In various embodiments, a width direction of an end of the first end ring  202  and a width direction of an end of the second end ring  210  are perpendicular to the longitudinal axis of the stent  200 . The first transition region  204  couples the first end ring  202  to the main body  206  and, on the other end of the stent  200 , the second transition region  208  connects the second ring  210  to the main body  206 . The transition regions  204  and  208  may include one or more bridges or struts  248   a ,  248   b , and  248   c  that connect one or more of the apices  216  of the end rings  202  and  210 , respectively, to the corresponding apices  222  of an adjacent helical ring  240  of the main body  206 . In various embodiments, the connecting struts  244  coupling together adjacent rings  240  of the main body  260  are configured to connect a corresponding peak  224  of one ring  240  to a corresponding valley  226  of another ring  240  to allow for flexibility of the main body  206 . In various embodiments, the struts  248   a ,  248   b , and  248   c  of the transition regions  204  and  208  that connect the end rings  202  and  210 , respectively, to the main body  206  form a peak-to-peak connection between the apices  216  and the apices  222  to increase the stiffness of the end portions  202  and  210 . 
     Because the rings  240  of the helical main body  206  are angled relative to the end rings  202  and  210  that have straight ends, the distance between the main body  206  and the end rings  202  and  210  that is spanned by the struts  248   a ,  248   b , and  248   c  varies about the circumference of the stent  200 . Accordingly, the lengths of the struts  248   a ,  248   b , and  248   c  that connect the end rings  202  and  210  vary from one another. In some embodiments, the helically shaped main body  206  may be coupled directly to one of the apices  216  of the end rings  202  and  210 . In some embodiments, the first transition region  204  includes a direct connection  218  between a corresponding apex  216  of the end ring  202  and the corresponding apex  222  of the main body  206 , such as a strut with minimal or zero length, and also includes the first strut  248   a , the second strut  248   b  with a length greater than the first strut  248   a , and the third strut  248   c  with a length greater than the length of the second strut  248   b . According to an exemplary embodiment, the third strut  248   c  has a length approximately equal to the height of a v-shaped element  220  of the main body  260 . It is to be understood that the second transition region  208  may be similar in construction to the first transition region  204  as in  FIG.  9   , or may vary in construction compared to the first transition region  204 . For example, in some embodiments, the second transition region  208  may include more or fewer struts as compared to the first transition region  204  for connecting to the main body  206 . 
     In some embodiments, the transition regions  204  and  208  may include bridges, such as the struts  248   a ,  248   b , and  248   c , that are variably spaced apart from each other. In some embodiments, the distance between direct connection  218  and the first strut  248   a  is equal to the width of two v-shaped elements  220 , the distance between the first strut  248   a  and the second strut  248   b  is equal to the width of three v-shaped elements  220 , and the distance between the second strut  248   b  and the third strut  248   c  is equal to the width of four v-shaped elements  220 . In other embodiments, the struts  248   a ,  248   b , and  248   c  may be otherwise spaced. 
     Referring to  FIGS.  11 ,  12 ,  13 ,  14 , and  15   , a stent  300  is shown according to another exemplary embodiment. The stent  300  may be similar in shape to the stents  100  (refer to  FIGS.  1   ) and  200  (refer to  FIG.  9   ), discussed above. The stent  300  includes a first end ring  302 , a first transition region  304 , a main body  306 , a second transition region  308 , and a second end ring  310 . While the stent  300  is generally manufactured to be a generally cylindrical body, the flat view illustrated in  FIG.  11    is provided for clarity. End points on one side of the stent  300 , as shown by point A are understood to be continuous with corresponding end points on the opposite side of the stent  300 , as shown by point B. 
     With reference to  FIGS.  11 ,  12 ,  13 ,  14 , and  15   , the end rings  302  and  310  are shown to be formed from v-shaped elements  315  that form apices  316 . In other embodiments, the end rings  302  and  310  may include otherwise shaped elements, such as the diamond shaped or tear drop shaped elements described above. 
     The transition regions  304  and  308  couple the main body  306  to the end rings  302  and  310 , respectively. The transition regions  304  and  308  include one or more bridges or struts  348   a ,  348   b , and  348   c , that connect one or more of the apices  316  of the end rings  302  or  310  to the corresponding apices  322  of an adjacent helical ring  340  of the main body  306  with a peak-to-peak connection. The first transition region  304  includes a direct connection  318  between a corresponding apex  316  of the end ring  302  and the corresponding apex  322  of the main body  306 , such as a strut with minimal or zero length. The first transition region  304  also includes the first strut  348   a  , the second strut  348   b  with a length greater than the length of the first strut  348   a , and a third strut  348   c  with a length greater than the length of the second strut  348   b . According to an exemplary embodiment, the third strut  348   c  has a length approximately equal to the height of a v-shaped element  320  of the main body  306 . It is to be understood that the second transition region  308  may be similar in construction to the first transition region  304  or may vary in construction compared to the first transition region  304 . For example, the transition region  308  may include more or fewer struts as compared to the first transition region  304 . 
     The main body  306  includes the helical rings  340  formed from skewed, v-shaped elements  320  that each have two legs with one leg longer than the other leg. The legs of the v-shaped elements  320  are sized such that the v-shaped elements  320  of each ring  340  of the helix are aligned with other corresponding v-shaped elements  320  in the adjacent rings  340  in a direction parallel to a longitudinal axis of the stent  300 . Each of the v-shaped elements  320  is coupled to v-shaped elements  320  on either side within a corresponding ring  340  via a joint, forming a corresponding apex  322 . The v-shaped elements  320  on neighboring rings  340  of the helical main body  306  form groups  342  that are parallel to the longitudinal axis of the stent  300 . In some embodiments, the v-shaped elements  320  of neighboring rings  340  of the main body  306  are connected to each other with connecting struts  344 . The main body  306  may be subdivided into a series of repeating sub-rings  346  that each include four v-shaped elements  320 , and each of which are coupled to an adjacent sub-ring  346  on one side with a connecting strut  344  extending from a corresponding peak and coupled to an adjacent sub-ring  346  on the opposite side with a connecting strut  344  extending from a corresponding valley. 
     Referring to  FIGS.  9  and  11   , the stent  200  is generally constructed similarly to the stent  300 , with the main body  306  of the stent  300  having additional rings  340  as compared to the number of rings  240  of the main body  206  of the stent  200 , thereby providing an increased length of the stent  300  as compared to the stent  200 . A longer stent can be more flexible than a shorter stent and may be advantageously deployed in a vessel having a larger aneurysm. In various embodiments, the stent  300  may be tapered from one end to another end in the longitudinal direction. 
     Referring to  FIGS.  16 ,  17 ,  18 ,  19 , and  20   , a stent  350  is shown according to another exemplary embodiment. The stent  350  includes the first end ring  302 , the main body  306 , and the second end ring  310  that are similar in construction to the stent  300  (refer to  FIG.  11   ). 
     The transition regions  354  and  358  of the stent  350  couple the main body  306  to the end rings  302  and  310 , respectively. In contrast to the stent  300  (refer to  FIG.  11   ), which includes struts  348   a ,  348   b , and  348   c  coupling only some of the apices  316  of the end rings  302  or  310  to the apices  322  of the main body  306 , the stent  350  include struts  360  of various lengths connecting each of the apices  316  of the end rings  302  or  310  to the corresponding apex  322  of an adjacent ring  340  of the main body  306  with a peak-to-peak connection. By providing struts  360  connecting each of the apices  316  of the end rings  302  or  310  to the apices  322  of the adjacent ring  340  of the main body  306 , the stent  350  provides an end portion that is substantially stiffer than the end portion of the stent  300  (refer to  FIG.  11   ). 
     Referring to  FIGS.  21 ,  22 ,  23 ,  24 , and  25   , a stent  400  is shown according to another exemplary embodiment. The stent  400  includes a first end ring  402 , a first transition region  404 , a main body  406 , a second transition region  408 , and a second end ring  410 . While the stent  400  is generally manufactured to be a generally cylindrical body, the flat view illustrated in  FIG.  21    is provided for clarity. End points on one side of the stent  400 , as shown by points A and C are understood to be continuous with corresponding end points on the opposite side of the stent  400 , as shown by points B and D, respectively. 
     The end rings  402  and  410  are shown to be formed from v-shaped elements  415  that form apices  416 . In other embodiments, the end rings  402  and  410  may include otherwise shaped elements, such as the diamond shaped or tear drop shaped elements described above. 
     In contrast to the stents  100 ,  200 ,  300 , and  350  described above (refer to  FIGS.  1 ,  9 ,  11 , and  16   ), the main body  406  includes alternating helical rings  440   a ,  440   b  formed from skewed, v-shaped elements  420 , where the alternating helical rings  440   a ,  440   b  are connected differently at ends than the rings in the stents  100 ,  200 ,  300 , and  350 . The main body  406  includes the helical rings  440   a ,  440   b  formed from skewed, v-shaped elements  420  that each have two legs with one leg longer than the other leg. The legs of the v-shaped elements  420  are sized such that the v-shaped elements  420  of each ring  440   a ,  440   b  of the helix are aligned with other corresponding v-shaped elements  420  in the adjacent rings  440   a ,  440   b  in a direction parallel to a longitudinal axis of the stent  400 . Each of the v-shaped elements  420  is coupled to v-shaped elements  420  on either side via a joint, forming an apex  422 . 
     According to an exemplary embodiment, the main body  406  includes the helical rings  440   a ,  440   b  forming a double helix. The helices are intertwined, with rings  440   a  of the first helix alternating with rings  440   b  of the second helix of the main body  406 . The v-shaped elements  420  on neighboring rings  440   a  and  440   b  form groups  442  in a direction that is parallel to the longitudinal axis of the stent  400 . In some embodiments, the v-shaped elements  420  of neighboring rings  440   a  and  440   b  of the main body  406  are connected to each other with connecting struts  444 . The main body  406  may be subdivided into a series of sub-rings  446  including four v-shaped elements  420 , each of which are coupled to an adjacent sub-ring  446  on one side with a connecting strut  444  extending from a peak and coupled to an adjacent sub-ring  446  on the opposite side with a connecting strut  444  extending from a valley. In various embodiments, each of the corresponding rings  440   a  and  440   b  may be coupled together with three connecting struts  444  between each ring  440   a  and  440   b . In various embodiments, an even distribution of connecting struts  444  between the rings  440   a  and  440   b  improves pressure distribution along the length of the main body  406 , such as for providing a pressure applied by the main body  406  to the walls of a blood vessel in which the stent  400  is disposed, and improves the long-term durability of the stent  400 . In various embodiments, the number and distribution of the connecting struts  444  may vary. Increasing the number of connections may decrease the flexibility of the endoluminal prosthesis, and conversely decreasing the number of connections may increase the flexibility of the endoluminal prosthesis. 
     The transition regions  404  and  408  couple the main body  406  to the end rings  402  and  410 , respectively. The transition regions  404  and  408  include one or more bridges or struts  448   a ,  448   b , and  448   c  that connect one or more of the apices  416  of the end rings  402  or  410  to the corresponding apices  422  of an adjacent helical ring of the main body  406  with a peak-to-peak connection. For each of the helical rings, such as the rings  440   a  or  440   b  that are proximate to the end ring  402 , the first transition region  404  includes a direct connection  418  between an apex  416  of the end ring  402  and a corresponding apex  422  of the main body  406 , such as a strut with minimal or zero length, and the first transition region  404  also includes first struts  448   a , second struts  448   b  with a length greater than the length of the first struts  448   a , and third struts  448   c  with a length greater than the length of the second struts  448   b . According to an exemplary embodiment, the third struts  448   c  each have a length approximately equal to the height of the v-shaped elements  420  of the main body  406 . It is to be understood that the second transition region  408  may be similar in construction to the first transition region  404  or may vary in construction compared to the first transition region  404 . For example, the second transition region  408  may include more or fewer struts as compared to the first transition region  404 . 
     Referring to  FIGS.  26 ,  27 ,  28 ,  29 , and  30   , a stent  450  is shown according to another exemplary embodiment. The stent  450  includes the first end ring  402 , the main body  406 , and the second end ring  410  that are similar in construction to the stent  400  (refer to  FIG.  21   ), and like numbered labels represent similar elements among the figures. 
     The transition regions  454  and  458  couple the main body  406  to the end rings  402  and  410 , respectively. In contrast to the stent  400  (refer to  FIG.  21   ), which includes struts  448   a ,  448   b , and  448   c  coupling only some of the apices  416  of the end rings  402  or  410  to the apices  422  of the main body  406 , the stent  450  include struts  460  of various lengths connecting each of the apices  416  of the end rings  402  or  410  to the corresponding apices  422  of adjacent helical rings of the main body  406  with peak-to-peak connections. By providing struts  460  connecting each of the apices  416  of the end rings  402  or  410  to the corresponding apices  422  of the adjacent helical rings of the main body  406 , the stent  450  provides an end portion that is substantially stiffer than the end portion of the stent  400  (refer to  FIG.  21   ). 
     With reference to  FIG.  1   , a method of manufacturing in accordance with an embodiment includes manufacturing the stent  100  having the structure depicted in  FIG.  1   . Also, a method of use of the stent  100  in accordance with an embodiment includes inserting the stent  100  into a blood vessel of a patient in an unexpanded state, and then expanding the stent  100  within the blood vessel. With reference to  FIG.  9   , a method of manufacturing in accordance with an embodiment includes manufacturing the stent  200  having the structure depicted in  FIG.  9   . Also, a method of use of the stent  200  in accordance with an embodiment includes inserting the stent  200  into a blood vessel of a patient in an unexpanded state, and then expanding the stent  200  within the blood vessel. With reference to  FIGS.  11  and  12   , a method of manufacturing in accordance with an embodiment includes manufacturing the stent  300  having the structure depicted in  FIGS.  11  and  12   . Also, a method of use of the stent  300  in accordance with an embodiment includes inserting the stent  300  into a blood vessel of a patient in an unexpanded state, and then expanding the stent  300  within the blood vessel. With reference to  FIGS.  16  and  17   , a method of manufacturing in accordance with an embodiment includes manufacturing the stent  350  having the structure depicted in  FIGS.  16  and  17   . Also, a method of use of the stent  350  in accordance with an embodiment includes inserting the stent  350  into a blood vessel of a patient in an unexpanded state, and then expanding the stent  350  within the blood vessel. 
     With reference to  FIGS.  21  and  22   , a method of manufacturing in accordance with an embodiment includes manufacturing the stent  400  having the structure depicted in  FIGS.  21  and  22   . Also, a method of use of the stent  400  in accordance with an embodiment includes inserting the stent  400  into a blood vessel of a patient in an unexpanded state, and then expanding the stent  400  within the blood vessel. With reference to  FIGS.  26  and  27   , a method of manufacturing in accordance with an embodiment includes manufacturing the stent  450  having the structure depicted in  FIGS.  26  and  27   . Also, a method of use of the stent  450  in accordance with an embodiment includes inserting the stent  450  into a blood vessel of a patient in an unexpanded state, and then expanding the stent  450  within the blood vessel. 
     Various embodiments described above may eliminate the need for manual working post laser cutting of a stent. The foregoing description of illustrative embodiments has been presented for purposes of illustration and of description. It is not intended to be exhaustive or limiting with respect to the precise form disclosed, and modifications and variations are possible in light of the above teachings or may be acquired from practice of the disclosed embodiments.