Patent Publication Number: US-11045314-B2

Title: Stent features for collapsible prosthetic heart valves

Description:
The present application is a continuation of U.S. patent application Ser. No. 15/868,031, filed Jan. 11, 2018, which is a continuation of U.S. patent application Ser. No. 15/181,708, filed Jun. 14, 2016, now U.S. Pat. No. 9,901,447, which is a continuation of U.S. patent application Ser. No. 14/304,293, filed on Jun. 13, 2014, now U.S. Pat. No. 9,387,072, which is a continuation of U.S. patent application Ser. No. 13/203,627, filed on Dec. 7, 2011, now U.S. Pat. No. 8,808,366, which is a national phase entry under 35 U.S.C. § 371 of International Application No. PCT/US2010/000561, filed Feb. 25, 2010, published in English, which claims the benefit of the filing date of U.S. Provisional Patent Application No. 61/208,834, filed Feb. 27, 2009, the disclosures of which are hereby incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     The present disclosure relates to prosthetic heart valves and, more specifically, to prosthetic heart valves having a collapsible stent frame. 
     Current collapsible prosthetic heart valve designs are for use within high-risk patients who may need a cardiac valve replacement, but who are not appropriate candidates for conventional open-chest, open-heart surgery. To address this problem, collapsible and re-expandable prosthetic heart valves have been developed that can be implanted transapically or percutaneously through the arterial system. However, such collapsible valves may have important clinical issues because of the nature of the patient&#39;s native stenotic leaflets that may not be resected as with the standard surgical practice of today. Additionally, patients with uneven calcification, bicuspid disease, and/or aortic insufficiency may not be treated well with the current collapsible prosthetic valve designs. The limitation of relying on evenly calcified leaflets has several issues, such as: (1) perivalvular leakage (PV leak), (2) valve migration, (3) mitral valve impingement, (4) conduction system disruption, etc., all of which can have adverse clinical outcomes. To reduce these adverse events, the optimal valve would seal and anchor to the cardiac tissue adequately without the need for excessive radial force that could harm nearby anatomy and physiology. An optimal solution may be to employ a stent that exerts a radial outward force just large enough to hold open the native stenotic/insufficient leaflets, and to use additional anchoring features more reliant on another anchoring methodology while reducing leaflet/stent stresses. 
     After multiple clinical valve failures during the late 1960 &#39;s and early 1970 &#39;s, a series of investigations on leaflet failure (e.g., dehiscence at the commissures) and stent post flexibility began and continue to be explored today. (Reis, R. L., et al., “The Flexible Stent: A New Concept in the Fabrication of Tissue Heart Valve Prostheses”,  The Journal of Thoracic and Cardiovascular Surgery,  683-689, 1971.) In-vitro, animal, and clinical investigations showed that “a flexible stent greatly reduces stress on the valve,” which was as large as a 90% reduction of the closing stresses near the commissures when flexibility and coaptation area were maximized. 
     In more recent years, several groups have shown (e.g., via numerical computations) the importance of stent post flexibility during opening and closing phases to reduce leaflet stress and therefore tissue failure. (Christie, G. W., et al., “On Stress Reduction in Bioprosthetic Valve Leaflets by the Use of a Flexible Stent,”  Journal of Cardiac Surgery , Vol. 6, No. 4, 476-481, 1991; Krucinski, S., et al., “Numerical Simulation of Leaflet Flexure in Bioprosthetic Valves Mounted on Rigid and Expansile Stents,”  Journal of Biomechanics , Vol. 26, No. 8, 929-943, 1993.) In response to several rigid Ionescu-Shiley clinical valve failures in which the leaflets tore free at the commissures, Christie et al. (cited above) explored what would happen if a similar design was made with optimal flexibility. Stresses at the post tops were shown to be five times greater than at the belly of a leaflet. Thus, to optimize the design, the stent was made more flexible until the stresses in the leaflets were comparable to those in the leaflet belly. It was shown that a 0.2-0.3 mm deflection was all that was needed to make a significant reduction in stress, but that a deflection of approximately 1.1 mm would reduce the stress by up to 80%. Furthermore, it was explained that deflection beyond 1.1 mm was not only difficult to achieve with the available material and design, but did not result in additional stress reduction. 
     Krucinski et al. (also cited above) have shown that a 10% expansion (as may be the case during the opening phase of a Nitinol stent) may reduce sharp flexural stresses by up to 40% (e.g., “hooking”). This is likely due to the stent functioning in harmony with the patient&#39;s aortic root, or in other words, the commissures of the native valve moving outward during systole. 
     Although the above analyses and data may not be directly applicable to the collapsible valve designs detailed later in this specification, the basic understanding and theory about how pericardial tissue leaflets interact with a stent design as it functions are important to incorporate into any design where durability is paramount. It is possible that with good engineering design of the post and leaflet attachment, commissural dehiscence will not be a primary failure mechanism. 
     BRIEF SUMMARY OF THE INVENTION 
     The present disclosure relates to prosthetic heart valves. In one embodiment, a prosthetic heart valve includes a stent having a proximal end, a distal end, an expanded condition and a collapsed condition. The stent includes a plurality of distal cells at the distal end, a plurality of proximal cells at the proximal end, a plurality of support struts coupling the proximal cells to the distal cells, and at least one support post connected to a multiplicity of the proximal cells. The proximal cells are longitudinally spaced apart from the distal cells. A valve structure is connected to the at least one support post. 
     In another embodiment, a prosthetic heart valve includes a stent having a proximal end, a distal end, an expanded condition and a collapsed condition. The stent includes a plurality of distal cells at the distal end, a plurality of proximal cells at the proximal end, and at least one support post connected to a multiplicity of proximal cells. At least a portion of the proximal cells are directly connected to the distal cells. A valve structure is connected to the at least one support post. 
     In a further embodiment, a prosthetic heart valve includes a stent having a proximal end, a distal end, an expanded condition and a collapsed condition. The stent includes a plurality of cells at the proximal end, a plurality of support struts at the distal end, and at least one support post connected to a multiplicity of the cells. Each support strut has a first end connected to one of the cells and a free end. A valve structure is connected to the at least one support post. 
     In yet another embodiment, a prosthetic heart valve includes a stent having a proximal end, a distal end, an expanded condition and a collapsed condition. The stent includes a plurality of cells, at least one support post connected to a multiplicity of the cells, and a reinforcement secured to the at least one support post. A valve structure is connected to the at least one support post, the reinforcement being adapted to secure leaflets of the valve. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various embodiments of the present invention will now be discussed with reference to the appended drawings. It is appreciated that these drawings depict only some embodiments of the invention and are therefore not to be considered limiting of its scope. 
         FIG. 1  is a schematic longitudinal cross-section of an aortic root; 
         FIG. 2  is a developed view of a stent with a plurality of posts each connected to cells at two locations; 
         FIG. 3  is a developed view of a stent with a plurality of posts each connected to cells only at their proximal ends; 
         FIG. 4  is a developed view of a stent with a plurality of posts each connected to cells at their proximal ends and middle portions; 
         FIG. 5A  is a developed view of a stent in an unexpanded condition with a plurality of posts each connected to cells at three locations; 
         FIG. 5B  is a developed view of the stent of  FIG. 5A  in an expanded condition; 
         FIG. 6A  is a developed view of a stent in an unexpanded condition with a plurality of posts each connected to cells at three locations; 
         FIG. 6B  is a developed view of the stent of  FIG. 6A  in an expanded condition; 
         FIG. 7A  is a partial perspective view of a stent showing a post connected to cells at two locations; 
         FIG. 7B  is a partial front elevational view of a stent showing a post connected to cells at three locations; 
         FIG. 8A  is a developed view of a stent in an unexpanded condition and including a plurality of posts and a plurality of spacers interconnecting certain cells; 
         FIG. 8B  is a front elevational view of the stent of  FIG. 8A  in an expanded condition; 
         FIG. 9A  is a developed view of a stent in an unexpanded condition including support struts each having a curved middle portion; 
         FIG. 9B  is a front elevational view of the stent of  FIG. 9A  in an expanded condition; 
         FIG. 10A  is a partial developed view of a stent in an unexpanded condition and including a plurality of substantially rigid posts and an interlocking feature; 
         FIG. 10B  is a partial front elevational view of a stent in an expanded condition and including a plurality of substantially rigid posts and an interlocking feature; 
         FIG. 10C  is a partial front elevational view of a stent in an expanded condition and including a plurality of substantially rigid posts and an interlocking feature; 
         FIG. 10D  is front elevational view of a stent flared to anchor at a sinotubular junction; 
         FIG. 10E  is a front elevational view of a stent flared to anchor just above the sinotubular junction and at the base of the aorta; 
         FIG. 10F  is a front elevational view of a stent flared to anchor within the ascending aorta; 
         FIG. 11A  is a developed view of a stent in an unexpanded condition and including a plurality of posts each connected at one end only to support struts; 
         FIG. 11B  is a developed view of a stent in an unexpanded condition and including a plurality of posts and a plurality of support strut sets, each set being connected directly to a post and to cells adjacent the post; 
         FIG. 11C  is a developed view of a stent in an unexpanded condition and including a plurality of posts and a plurality of support strut sets, each support strut set being directly connected to a single post; 
         FIG. 11D  is a developed view of a stent in an unexpanded condition and including a plurality of posts and a plurality of support struts, each support strut being connected directly to a distal end of a single post; 
         FIG. 12A  is a partial developed view of a stent in an unexpanded condition and including at least one shortened post; 
         FIG. 12B  is an enlarged view of an alternate post for incorporation into the stent of  FIG. 12A ; 
         FIG. 12C  is an enlarged view of an alternate post for incorporation into the stent of  FIG. 12A ; 
         FIG. 13A  is a partial developed view of a stent in an unexpanded condition and including a post with a slidable portion; 
         FIG. 13B  is a partial developed view of the stent of  FIG. 13A  in an expanded condition; 
         FIG. 14A  is a partial developed view of a stent in an unexpanded condition with an elongated support post having a diamond-shaped collapsible post structure; 
         FIG. 14B  is a partial developed view of the stent of  FIG. 14A  in an expanded condition; 
         FIG. 15A  is a partial developed view of a stent in an unexpanded condition with an elongated support post having a collapsible post feature; 
         FIG. 15B  is a partial developed view of the stent of  FIG. 15A  in an expanded condition; 
         FIG. 16A  is a partial developed view of a stent in an unexpanded condition with an elongated support post having an hourglass-shaped collapsible post feature; 
         FIG. 16B  is a partial developed view of the stent of  FIG. 16A  in an expanded condition; 
         FIG. 17A  is a developed view of a stent in an unexpanded condition with support struts connected to a proximal cell spaced from the elongated support post; 
         FIG. 17B  is a developed view of a proximal portion of the stent of  FIG. 17A ; 
         FIG. 18A  is a developed view of a stent with a support strut connected to a proximal cell located halfway between two elongated support posts; 
         FIG. 18B  is a perspective view of the stent of  FIG. 18A  in an expanded condition; 
         FIG. 18C  is a perspective view of the stent of  FIG. 18A  in an unexpanded condition; 
         FIG. 19  is a perspective view of the stent of  FIG. 18A  in an expanded condition and subjected to a torsional force; 
         FIG. 20A  is a perspective view of the stent of  FIG. 18A  in an expanded condition and being twisted; 
         FIG. 20B  is a perspective view of the stent of  FIG. 18A  in an expanded condition and under longitudinal compression; 
         FIG. 21A  is a side elevational view of a support strut with a tapered proximal end; 
         FIG. 21B  is a side elevational view of a support strut with a uniform width; 
         FIG. 21C  is a side elevational view of a support strut with a tapered middle portion; 
         FIG. 21D  is a side elevational view of a support strut with an inverted C-shaped middle portion; 
         FIG. 21E  is a side elevational view of a support strut with a C-shaped middle portion; 
         FIG. 21F  is a side elevational view of a support strut with a rectangular middle portion; 
         FIG. 21G  is a side elevational view of a support strut with nested longitudinal cells; 
         FIG. 21H  is a side elevational view of a support strut with a nested coil of cells; 
         FIG. 21I  is a side elevational view of a support strut with a sinusoidal-shaped middle portion; 
         FIG. 21J  is a side elevational view of a pair of support struts with offset sinusoidal-shaped middle portions; 
         FIG. 22  is a developed view of a stent with support struts cantilevered from proximal cells; 
         FIG. 23A  is a partial perspective view of an embodiment of the stent of  FIG. 22  in an expanded condition with support struts having C-shaped distal portions; 
         FIG. 23B  is a partial perspective view of an embodiment of the stent of  FIG. 22  in an expanded condition with support struts having hook-shaped distal portions; 
         FIG. 24  is a highly schematic, partial longitudinal cross-section showing the stent of  FIG. 23A  positioned in an aortic annulus; 
         FIG. 25  is a highly schematic, partial longitudinal cross-section showing the stent of  FIG. 23B  positioned in an aortic annulus; 
         FIG. 26  is a top partial view of a stent reinforced with two secondary posts; 
         FIG. 27  is a partial developed view of a portion of a stent with a cuff and reinforced with two secondary posts; 
         FIG. 28A  is a side elevational view of a secondary post with a substantially circular cross-section; 
         FIG. 28B  is a perspective view of the secondary post of  FIG. 28A ; 
         FIG. 28C  is a side elevational view of a secondary post with a substantially rectangular cross-section; 
         FIG. 28D  is a perspective view of the secondary post of  FIG. 28C ; 
         FIG. 28E  is a side elevational view of a secondary post with a substantially triangular cross-section; 
         FIG. 28F  is a perspective view of the secondary post of  FIG. 28E ; 
         FIG. 29A  is a side elevational view of a secondary post with a hollow core; 
         FIG. 29B  is a side elevational view of a secondary post with a hollow core and two different kinds of eyelets; 
         FIG. 30  is a side elevational view of a reinforcement for a stent including two columns connected by an arch; 
         FIG. 31A  is a highly schematic, partial longitudinal cross-section showing a reinforcement for use with a stent and adapted to be folded onto itself; 
         FIG. 31B  is a highly schematic top view of the reinforcement of  FIG. 31A  outlining the entire free end of a leaflet; 
         FIG. 32A  is a perspective view of a prosthetic valve incorporating the reinforcement of  FIG. 31A ; 
         FIG. 32B  is a perspective view of a prosthetic valve incorporating the reinforcement of  FIG. 31A  while the valve is subject to compression; and 
         FIG. 32C  is a perspective view of a prosthetic valve incorporating the reinforcement of  FIG. 31A  while the valve is subject to compression. 
     
    
    
     DETAILED DESCRIPTION 
     As used herein, the term “proximal” refers to the end of a stent closest to the heart when placing the stent in a patient, whereas the term “distal” refers to the end of the stent farthest from the heart when placing the stent in a patient. 
       FIG. 1  illustrates the anatomy of an aortic root  10  to aid in the understanding of how the stent/valve interacts with the aortic root. ( FIG. 1  is from Reul, H., et al., “The geometry of the aortic root in health, at valve disease and after valve replacement,”  Journal of Biomechanics , Vol. 23, No. 2, 181-91, 1990). The aortic root is the part of the aorta attached to the heart. The aorta is the largest artery in the body, which extends from the left ventricle of the heart down to the abdomen, where it branches off into two smaller arteries. The aorta supplies oxygenated blood to all parts of the body. The aortic root contains the aortic valve and gives rise to the coronary arteries, which are the arteries that supply blood to the heart muscle. As shown in  FIG. 1 , the aortic root  10  has several features, namely: a left ventricular outflow tract (LVOT)  1 ; an annulus  2 ; a sinus  3 ; sinotubular junction (STJ)  4 ; and an ascending aorta  5 .  FIG. 1  further depicts several geometrical parameters of aortic root  10 , to wit: D O =orifice diameter; D A =aortic diameter distal to the sinus  3 ; D B =maximum projected sinus diameter; L A =length of the sinus  3 ; and L B =distance between D O  and D B .
     Flexibility of Stent Via Post Connections   

     In all the embodiments disclosed herein, the stents are part of a prosthetic heart valve. The stents have an expanded condition and a collapsed condition. In the expanded condition, at least a portion of the stent may have a substantially cylindrical shape.  FIG. 2  depicts a developed view of stent  100  in an unexpanded condition, i.e., in a flat, rolled out condition as seen when laser cut from a tube. Stent  100  generally includes one or more rows of distal cells  102 , at least one support strut  104 , one or more rows of proximal cells  106 , at least one elongated support post  108 , and at least one post connection  110  coupling a support post  108  to at least some of the proximal cells  106 . One or more support struts  104  connect distal cells  102  to proximal cells  106 . In some embodiments, three support struts  104  may interconnect proximal cells  106  and distal cells  102 . Stent  100  may nonetheless include more or fewer support struts  104 . Regardless of the specific number of support struts  104 , support struts  104  longitudinally separate proximal cells  106  from distal cells  102  and, therefore, proximal cells  106  are located proximally relative to distal cells  102 . 
     Stent  100  or any other embodiment disclosed herein may be wholly or partly formed of any biocompatible material, such as metals, synthetic polymers, or biopolymers capable of functioning as a stent. Suitable biopolymers include, but are not limited to, collagen, elastin, and mixtures or composites thereof. Suitable metals include, but are not limited to, cobalt, titanium, nickel, chromium, stainless steel, and alloys thereof, including nitinol. Suitable synthetic polymers for use as a stent include, but are not limited to, thermoplastics, such as polyolefins, polyesters, polyamides, polysulfones, acrylics, polyacrylonitriles, and polyaramides. For example, stent  100  may be made of polyetheretherketone (PEEK). 
     Distal cells  102  are adapted to be positioned distally relative to sinus  3  to anchor at or near the ascending aorta  5  and sinotubular junction  4 . In certain embodiments, distal cells  102  may be arranged in longitudinal rows. In the embodiment shown in  FIG. 2 , stent  100  includes a single row  114  of distal cells  102 . The row  114  of distal cells  102  may be oriented substantially perpendicular to support struts  104 . While  FIG. 1  shows a single row  114  of distal cells  102 , stent  100  may include multiple rows of distal cells  102 . 
     Each distal cell  102  has a distal end  102   a , a proximal end  102   b , and a middle portion  102   c  between the distal end  102   a  and the proximal end  102   b . A cell connection  118  couples two adjacent distal cells  102 . As seen in  FIG. 2 , each cell connection  118  is positioned at a middle portion  102   c  of a distal cell  102 . Aside from the two adjacent distal cells  102 , cell connection  118  is not coupled to any other distal cell  102 . 
     All distal cells  102  collectively have a first end portion  120  and a second end portion  122 . In the embodiment shown in  FIG. 2 , first end portion  120  is aligned with the proximal ends  102   b  of the distal cells  102 , while the second end portion  122  is aligned with the distal ends  102   a  of the distal cells  102 . Distal cells  102  are connected to support struts  104  at the first end portion  120 . In some embodiments, support struts  104  are coupled to the proximal ends  102   b  of some distal cells  102 . 
     Support struts  104  interconnect distal cells  102  and proximal cells  106 . As discussed above, stent  100  may include one or more support struts  104 . As depicted in  FIG. 2 , stent  100  may include one support strut  104  for every five proximal cells  106 . Stent  100  may also include one support strut  104  for every seven distal cells  102 . However, these ratios are not critical, and will depend on the size of proximal cells  106  and distal cells  102 , the desired stiffness of stent  100  and other considerations. 
     Each support strut  104  has a first end portion  104   a , a second end portion  104   b , and a middle portion  104   c  located between the first and second end portions. The first end portion  104   a  of each support strut  104  is connected to the proximal end  102   b  of a distal cell  102 . The second end portion  104   b  of each support strut  104  is connected to the distal end  106   a  of a proximal cell  106 . Thus, a single support strut  104  may couple a single distal cell  102  to a single proximal cell  106 . 
     As shown in  FIG. 2 , the first and second end portions  104   a ,  104   b  of each support strut  104  may have straight or linear configurations, while the middle portion  104   c  may have a non-linear configuration. In the embodiment depicted in  FIG. 2 , the middle portion  104   c  of each support strut  104  has a sinusoidal or wave shape, but middle portions  102   c  of one or more support struts  104  may have other non-linear configurations. First and second end portions  104   a ,  104   b  of support struts  104  may be oriented substantially parallel to each other, and may be either longitudinally aligned or not aligned with each other. For example, first and second end portions  104   a ,  104   b  of support struts  104  may be longitudinally aligned with each other, as seen in  FIG. 2 . Alternatively, portions  104   a  and  104   b  may be laterally offset from each other, for instance, with portion  104   b  connected to the distal end  106   a  of a next adjacent proximal cell  106  to the left or right of the connection depicted in  FIG. 2 . 
     As discussed above, at least one support strut  104  is connected to one proximal cell  106 . Each proximal cell  106  has a distal end  106   a , a proximal end  106   b  and a middle portion  106   c  between the distal end  106   a  and the proximal end  106   b . Together, proximal cells  106  are configured to impart radial force against the leaflets of a heart valve. Proximal cells  106  may be arranged in longitudinal rows. For example, stent  100  may include a first row  124  of proximal cells  106  positioned distally of a second row  128  of proximal cells  106 . At least one support strut  104  is connected to a proximal cell  106  located in the first row  124 . 
     A cell connection  130  couples two adjacent proximal cells  106  positioned in the same row. The proximal cells  106  in the first row  124  are joined to the proximal cells  106  in the second row  128  by sharing one or more common cell legs. 
     The cells in the first row  124  and the cells in the second row  128  may not form continuous chains of cells. That is, the chain of cells forming the first row  124  and the chain of cells forming the second row  128  may each be disrupted by one or more elongated support posts  108 . Support posts  108  are intended to support the commissures along which the valve leaflets are joined to one another. In this embodiment, as in all of the embodiments described herein, the stent typically has three such support posts  108 , one for supporting each of the commissures of the aortic valve. However, where the stent is intended for use in a prosthetic valve other than an aortic valve, the stent may include a greater or lesser number of support posts. 
     Stent  100  may include sets of proximal cells  106  between elongated support posts  108 . For example, as shown in  FIG. 2 , stent  100  may include an elongated support post  108  between two sets of five proximal cells  106  in first row  124 . However, the number of cells between support posts  108  will depend on the size of proximal cells  106 , the number of cell rows and other such considerations. Support posts  108  may extend longitudinally adjacent first cell row  124 , second cell row  128  or both cell rows. Similarly, support posts  108  may be connected to proximal cells in first cell row  124 , second cell row  128  or both cell rows. 
     Stent  100  may include one support strut  104  for every set of proximal cells  106  located between two elongated support posts  108 . For instance, stent  100  may have one support strut  104  for every set of five proximal cells  106  located between two elongated support posts  108 . In this embodiment, the second end portion  104   b  of each support strut  104  is connected to the proximal cell  106  located midway between two elongated support posts  108 . Support strut  104  is not connected to a proximal cell  106  located adjacent to an elongated support post  108 . 
     The support posts  108  may be connected to one or more proximal cells  106  via post connections  110 . Each elongated support post  108  has a proximal end  108   a , a distal end  108   b , and a middle  108   c . A plurality of eyelets or apertures  132  are formed in each support post  108  and used for suturing the valve leaflets to stent  100 . As seen in  FIG. 2 , apertures  132  may have different sizes, shapes and positions. 
     In the embodiment depicted in  FIG. 2 , post connections  110  are located at or near the middle  108   c  of elongated support post  108  to allow for post flexibility during valve cycling, thereby reducing dynamic loading and the resulting in-leaflet stress. Specifically, the middle portions  106   c  of two proximal cells  106  located in the first row  124  are attached to opposite sides of the middle portion  108   c  of each elongated support post  108 . Two proximal cells  106  arranged in the second row  128  are attached near their middle portions  106   c  to opposite sides of the proximal end  108   a  of each elongate support post  108 . Although FIG.  2  shows post connections  110  at very specific locations, stent  100  may include post connections  110  at other locations. 
     In operation, a user may place a stent  100  (or any other stent disclosed herein) using any conventional methods. For instance, the user may first place stent  100  in a crimped condition and then insert it into a delivery instrument or system. The delivery instrument may be advanced through the patient&#39;s vasculature or through a transapical procedure until stent  100  reaches the desired destination near the aortic valve. Subsequently, the user deploys and expands stent  100  at the target site. The structure of stent  100  described above provides very flexible support posts  108  which reduce the maximum amount of stress at the commissural interfaces on valve cycling. That is, since the distal ends of the support posts  108  are free from connections to the proximal cells  106 , these ends can move freely like a cantilever beam. 
       FIG. 3  shows another embodiment of a stent  200  with post connections  210  coupling proximal cells  206  to elongated support posts  208  at different locations than for stent  100 . Stent  200  is similar to stent  100  and generally includes distal cells  202 , proximal cells  206 , and support strut arrays  204  interconnecting the distal cells  202  and the proximal cells  206 . In some embodiments, stent  200  may include a first longitudinal row  214  of distal cells  202 , a second longitudinal row  216  of distal cells  202 , and a single longitudinal row  224  of proximal cells  206 . 
     Each distal cell  202  has a distal end  202   a , a proximal end  202   b , and a middle portion  202   c  between the distal end  202   a  and the proximal end  202   b . Cell connections  218  located at the middle portions  202   c  of the distal cells  202  in each row join two adjacent distal cells in that row together. The distal cells  202  in the first row  214  are joined to the distal cells  202  in the second row  216  by sharing one or more common cell legs. 
     The proximal ends  202   b  of every distal cell  202  located in the second row  216  may be connected to a support strut ( 205  or  207 ) of the support strut arrays  204 . In the embodiment depicted in  FIG. 3 , stent  200  includes three support strut arrays  204  each connected to eight distal cells  202  and six proximal cells  206 . Each support strut array  204  may alternatively be connected to more or fewer distal cells  202  and proximal cells  206 . Regardless, each support strut array  204  includes one or more support struts ( 205  or  207 ) coupled to the proximal cells  206  adjacent to an elongated support post  208  to halt any significant distribution of the strains from post deflection to the remaining stent frame. 
     Each support strut array  204  may include two kinds of support struts, namely support struts  205  and support struts  207 . In some embodiments, each support strut array  204  may include four support struts  205  and two support struts  207 . Two support struts  207  may be positioned between two sets of two support struts  205 . It is envisioned, however, that support strut arrays  204  may each include more or fewer support struts  205  and  207 . 
     Each support strut  205  has a first end portion  205   a , a second end portion  205   b , and a middle portion  205   c  between the first and second end portions. First end portion  205   a  may be connected to a proximal end  202   b  of a distal cell  202  in the second row  216 . Second end portion  205   b  may be connected to a distal end  206   a  of a proximal cell  206 . Middle portion  205   c  has a straight or linear configuration and interconnects first and second end portions  205   a ,  205   b . The first end portion  205   a  of each support strut  205  defines an oblique angle relative to middle portion  205   c . This oblique angle may vary from one support strut  205  to another. The second end portion  205   b  of each support strut  205  may also define an oblique angle relative to middle portion  205   c . This oblique angle may also vary from one support strut  205  to another. 
     Support struts  207  each have a first end portion  207   a , a second end portion  207   b , and a middle portion  207   c  between the first and second end portions. Each support strut  207  includes a bifurcated section  207   d  extending from the middle portion  207   c  to the first end portion  207   a . Bifurcated section  207   d  of each support strut  207  includes two branches  207   e ,  207   f . Branches  207   e ,  207   f  are oriented substantially parallel to each other, except in a transition or angled portion  207   g  of the bifurcated section  207   d  in which the branches define an oblique angle with respect to each other and to first and second portions  207   h  and  207   i . Each branch  207   e ,  207   f  includes a first portion  207   h , a second portion  207   i , and the transition or angled portion  207   g  positioned between the first and second portions. In the first portion  207   h  of the bifurcated section  207   d , branches  207   e ,  207   f  are positioned farther apart from each other than in the second portion  207   i.    
     Each branch  207   e ,  207   f  is connected to the proximal end  202   b  of a distal cell  202  in the second row  216 . Branches  207   e ,  207   f  of each bifurcated section  207   d  converge into a single support member  207   k  at converging point  207   m . Each single support member  207   k  of support struts  207  may be connected to the distal end  206   a  of a single proximal cell  206  adjacent a support post  208 . 
     As discussed above, each support strut array  204  is connected to the distal ends  206   a  of a plurality of proximal cells  206 . Specifically, support struts  207  are connected to proximal cells  206  positioned adjacent a support post  208 , while support struts  205  are connected to the proximal cells  206  which are not adjacent a support post  208 . 
     Each proximal cell  206  has a distal end  206   a , proximal end  206   b  and a middle portion  206   c  between the distal end  206   a  and the proximal end  206   b . The proximal cells  206  collectively define a first end  238  closer to support strut arrays  204  and a second end  240  farther from support strut arrays  204 . Proximal cells  206  are arranged in a single longitudinal row. Cell connections  230  located at middle portions  206   c  join adjacent proximal cells  206  together. 
     Some of the proximal cells  206  are connected to an elongated support post  208 . As seen in  FIG. 3 , one or more elongated support posts  208  may extend beyond the first end  238  collectively defined by all the proximal cells  206  but may not extend past the second end  240 . Stent  200  may have, for example, one elongated post  208  for every six proximal cells  206 . 
     Each elongated support post  208  has a distal end  208   a , a proximal end  208   b  and a plurality of eyelets or apertures  232  for suturing the valve leaflets to the stent  200 . As shown in  FIG. 3 , apertures  232  may extend from distal end  208   a  to proximal end  208   b  and may have different shapes and sizes. In certain embodiments, apertures  232  may have substantially elliptical shapes. 
     Elongated support posts  208  are connected to proximal cells  206  by post connections  210 . In the embodiment shown in  FIG. 3 , post connections  210  are located only at or near the proximal end  208   b  of elongated support post  208  for allowing the elongated support post to deflect inwardly in the direction indicated by arrow G under diastolic back-pressure. Although  FIG. 3  shows post connections  210  at precise positions near proximal ends  208   b , post connections  210  may be positioned closer or farther from proximal ends  208   b  to allow for more or less post flexibility. Each elongated support post  208  may be connected to proximal cells  206  through two post connections  210  located on opposite sides of the elongated support post. 
       FIG. 4  shows a stent  300  including distal cells  302 , proximal cells  306 , support strut arrays  304 , elongated support posts  308  and post connections  310  at two locations along each elongated support post  308 . The positions of post connections  310  reduce post flexibility and the strains experienced in post connections  310  as compared to the post connections  210  in stent  200 . 
     In the embodiment depicted in  FIG. 4 , stent  300  includes a single row  314  of distal cells  302 . Each distal cell  302  has a distal end  302   a , a proximal end  302   b  and a middle portion  302   c  between the proximal end  302   b  and the distal end  302   a . Cell connections  318  join adjacent distal cells  302  at their middle portions  302   c.    
     Stent  300  may include one support strut array  304  for every eight distal cells  302 . Each support strut array  304  may include four support struts  305  joined to four distal cells  302 . Each support strut array  304  may nonetheless include more or fewer support struts  305 . In either event, support strut arrays  304  interconnect distal cells  302  and proximal cells  306 . 
     Each support strut  305  has a first end portion  305   a , a second end portion  305   b , and a middle portion  305   c  located between the first and second end portions. The first end portion  305   a  of each support strut  305  is connected to the proximal end  302   b  of at least one distal cell  302 , whereas the second end portion  305   b  of each support strut  305  is connected to the distal end  306   a  of at least one proximal cell  306 . 
     The middle portion  305   c  of each support strut  305  has a transition section  305   d  connected to the first end portion  305   a . Transition section  305   d  is oriented at an oblique angle relative to the middle portion  305   c . The middle portions  305   c  of support struts  305  are oriented substantially parallel to each other except at the transition sections  305   d . The first end portions  305   a  of support struts  305  are also oriented substantially parallel to each other. 
     The second end portion  305   b  of each support strut  305  is connected to the distal end  306   a  of at least one proximal cell  306 . Each second end portion  305   b  has a substantially curved configuration or profile. In some embodiments, each support strut array  304  may include four support struts  305  connected to the two proximal cells  306  adjacent to an elongated support post  308  and to the two next adjacent proximal cells. That is, two support struts  305  may be connected to a proximal cell  306  adjacent to one side of elongated support post  308  and to the next adjacent proximal cell, respectively, while another two support struts  305  may be connected to a proximal cell  306  adjacent to the opposite side of the same elongated support post  308  and to the next adjacent proximal cell, respectively. 
     Proximal cells  306  each have a distal end  306   a , a proximal end  306   b  and a middle portion  306   c  between the distal end  306   a  and the proximal end  306   b . Stent  300  may include a first row  324  of proximal cells  306  and a second row  328  of proximal cells  306 . First row  324  and second row  326  of proximal cells  306  are oriented substantially parallel to each other. First row  324  is located distally relative to second row  328 . All of the proximal cells  306  collectively define a first end  338  closer to the support strut arrays  304  and a second end  340  farther from support strut arrays  304 . The first end  338  of all the proximal cells  306  is defined by the distal ends  306   a  of the proximal cells located in first row  324 , whereas the second end  340  is defined by the proximal ends  306   b  of the proximal cells  306  located in the second row  328 . 
     A cell connection  330  joins the middle portions  306   c  of adjacent proximal cells  306  in the first row  324 . Other cell connections  330  join the middle portions  306   c  of adjacent proximal cells  306  in the second row  328 . The proximal cells  306  in the first row  324  are joined to the proximal cells in the second row  328  by sharing one or more common cell legs. 
     Elongated support posts  308  are connected to some proximal cells  306  by post connections  310 . In the embodiment depicted in  FIG. 4 , each elongated support post  308  traverses the longitudinal length of the proximal cells  306  in the first row  324  and at least a portion of the length of the proximal cells  306  in the second row  328 . Each elongated support post  308  has a distal end  308   a , a proximal end  308   b , and a middle  308   c . In addition, each elongated support post  308  includes a plurality of eyelets or apertures  332  for suturing stent  300  to valve leaflets. Apertures  332  may have different shapes and sizes. At least one elongated support post  308  may extend slightly beyond the first end  338  collectively defined by all the proximal cells  306 , as seen in  FIG. 4 . 
     Post connections  310  may be positioned at two locations along each elongated support post  308 . As noted above, such positioning reduces post flexibility and the strains experienced in post connections  310 . Two post connections  310  may be positioned on opposite sides of the proximal end  308   b  of an elongated support post  308  and join the elongated support post  308  to the proximal ends  306   b  of certain proximal cells  306  in the second row  328 . Another two post connections  310  may be located on opposite sides at or near the middle  308   c  of an elongated support post  308  and join the middle of the support post to the middle portions  306   c  of certain proximal cells  306  in the first row  324 . 
     With reference to  FIGS. 5A and 5B , a stent  400  includes a plurality of cells  402 , a plurality of support struts  404 , one or more elongated support posts  408  and post connections  410  coupling the elongated posts  408  to cells  402 .  FIG. 5A  shows stent  400  in a flat, rolled out, unexpanded condition, whereas  FIG. 5B  depicts stent  400  in a flat, rolled out, fully-expanded condition. Post connections  410  are positioned at three locations along each elongated support post  408 . Stent  400  further includes at least one runner or bar  450  extending longitudinally along cells  402 . Bars  450  enable the length of stent  400  to change substantially uniformly between the unexpanded and expanded conditions. The height and width of bars  450  may vary to accommodate various strength needs. 
     As discussed above, stent  400  includes a plurality of cells  402 . Several cell connections  430  join cells  402  to one another. Cells  402  may have a distal end  402   a , a proximal end  402   b , or both a distal end and a proximal end. All the cells  402  collectively define a first end  438  and a second end  440  and may be arranged in one or more longitudinal rows. For instance, stent  400  may include a first row  424 , a second row  426  and a third row  429  of cells  402  oriented substantially parallel to one another. The first row  424 , second row  426  and third row  429  of cells  402  are not continuous and may be disrupted by one or more elongated support posts  408  interposed in the rows. 
     Each elongated support post  408  includes a distal end  408   a , a proximal end  408   b , a middle  408   c , and a plurality of eyelets or apertures  432  for suturing stent  400  to the valve leaflets. The height H p  of each elongated support post  408  defines the distance between distal end  408   a  and proximal end  408   b . In the embodiment shown in  FIG. 5A , all elongated support posts  408  are positioned between the first end  438  and the second end  440  collectively defined by cells  402 . The distal ends  402   a  of the cells  402  in the first row  424  extend distally beyond the distal ends  408   a  of each elongated support post  408  in the unexpanded condition. The proximal ends of the cells  402  in the third row  429  extend proximally beyond the proximal ends  408   b  of each elongated support post  408  in the unexpanded condition. As a result, cells  402  in rows  424  and  429  can be bent outwardly into a C-shape in the directions indicated by arrows C so that stent  400  holds onto the stenotic native valve leaflets when the stent is positioned in the valve annulus  2 . 
     Post connections  410  join elongated support posts  408  to cells  402 . As shown in  FIG. 5B , stent  400  includes post connections  410  at three locations along each elongated support post  408 . First post connections  410  are located on opposite sides of (or near) the proximal end  408   b  of elongated posts  408 . Second post connections  410  are also positioned on opposite sides of (or near) the middle  408   c  of elongated support posts  408 . Third post connections  410  are located on opposite sides of elongated support posts  408  near distal ends  408   a . The post connections  410  near distal ends  408   a  may, for example, be positioned at about three-quarters of height H p . 
     As discussed above, stent  400  may further include one or more bars  450  for facilitating uniform expansion of the stent. Bars  450  join cells  402  from first row  424  through the third row  429 . As seen in  FIG. 5B , each bar  450  passes through cell connections  430  but does not extend past the first end  438  or the second end  440  collectively defined by cells  402 . Bars  450  pass through the valleys formed between cells  402 . 
     Stent  400  also includes one or more support struts  404  connected to a portion of the valleys formed between the distal ends  402   a  of cells  402  in the first row  424 . Alternatively, support struts  404  may be connected directly to the distal ends  402   a  of cells  402 . In some embodiments, support struts  404  may connect cells  402  to another group of cells (not shown). 
       FIG. 6A  shows a stent  500  in a flat, rolled out, unexpanded state, while  FIG. 6B  illustrates stent  500  in a flat, rolled out, expanded state. Stent  500  includes a plurality of cells  502 , one or more elongated support posts  508 , and one or more bars  550  for enabling the length of stent  500  to change substantially uniformly between the unexpanded and expanded states. The structure and operation of stent  500  are similar to the structure and operation of stent  400 , but stent  500  includes post connections  510  specifically located on opposite sides of the distal ends  508   a  of each elongated support post  508 , rather than inward of the distal ends as with stent  400 . Stent  500  may further include one or more support struts  504  joining the distal ends  502   a  of some cells  502  to another set of cells (not shown). 
     Cells  502  of stent  500  are arranged in rows, namely first row  524  and second row  528 . First row  524  and second row  528  of cells  502  are oriented substantially parallel to each other, as seen in  FIG. 6A . Several cell connections  530  join cells  502  to one another. Each cell connection  530  usually forms a valley or a peak between two cells  502 . Bars  550  interconnect adjacent cells  502  positioned in different rows. In some embodiments, bars  550  may be connected to three cell connections  530 . Cells  502  collectively define a first end  538  and a second end  540 . 
     Elongated support posts  508  are interposed between sets of cells  502  and traverse both rows of cells. Each support post  508  has a distal end  508   a , a proximal end  508   b , a middle  508   c , and a plurality of eyelets or apertures  532  for suturing stent  500  to the valve leaflets. The proximal end  508   b  of each elongated post  508  does not extend beyond the second end  540  collectively defined by all cells  502 . The distal end  508   a  extends slightly beyond the first end  538  collectively defined by all cells  502 . 
     As seen in  FIGS. 6A and 6B , stent  500  includes post connections  510  joining each elongated support post  508  to adjacent cells  502  at three particular locations along the length of the support post. First post connections  510  join opposite sides near the proximal end  508   b  of an elongated support post  508  to the adjacent cells  502  located in the second row  528 . Second post connections  510  join opposite sides of the middle  508   c  of each elongated support post  508  to the segments common to the adjacent cells  502  in the first row  524  and the second row  528 . Third post connections  510  join opposite sides of the distal end  508   a  of an elongated support post  508  to the adjacent cells  502  located in the first row  524 . These last post connections  510  may be located at the very end of the support post  508 . 
       FIGS. 7A and 7B  show similar stents  600 A and  600 B with different numbers of post connections  610 . With reference to  FIG. 7A , stent  600 A includes distal cells  602 , proximal cells  606  and support struts  604 ,  605  interconnecting the distal cells and proximal cells. Distal cells  602  and proximal cells  606  are continuously connected around the entire circumference of stent  600 A, thereby allowing symmetric expansion and increased radial force. 
     Distal cells  602  may be arranged in one or more longitudinal rows. For example, stent  600 A may include only one row  614  of distal cells  602 . Each distal cell  602  has a distal end  602   a  and a proximal end  602   b , and may have a diamond shape upon expansion. Distal cells  602  are connected to one another along row  614  via cell connections  618 . Each cell connection  618  is positioned at a valley formed between two adjacent distal cells  602 . The proximal ends  602   b  of distal cells  602  may be coupled in an alternating pattern to two different kinds of support struts  604  and  605 . 
     Support strut  605  has a distal end  605   a , a proximal end  605   b , and a middle portion  605   c  between the distal end and the proximal end. The distal end  605   a  of each support strut  605  is connected to the proximal end  602   b  of a distal cell  602 , whereas the proximal end  605   b  of each support strut  605  is connected to the distal end  606   a  of a proximal cell  606 . 
     Support strut  604  has a distal end  604   a , a proximal end  604   b , and a middle portion  604   c  between the distal end and the proximal end. The distal end  604   a  of each support strut  604  is connected to the proximal end  602   b  of a distal cell  602 . The proximal end  604   b  of each support strut  604  is coupled to the distal end  606   a  of a proximal cell  606 . The middle portion  604   c  of each support strut  604  includes a section  604   d  featuring a non-linear shape. For example, non-linear section  604   d  may have a sinusoidal or wave shape. 
     Proximal cells  606  are arranged in one or more longitudinal rows. For instance, stent  600 A may include a first row  624  and a second row  626  of proximal cells  606 . First row  624  and second row  626  of proximal cells  606  are oriented substantially parallel to each other. 
     Each proximal cell  606  may have an arrow shape in the expanded condition defined by a pair of peaks  606   a  on opposite sides of a valley  606   b  in one stent section, another pair of peaks  606   a  on opposite sides of a valley  606   b  in another stent section, and a pair of bars  650  connecting the stent sections together. 
     Cell connections  630  interconnect proximal cells  606  positioned in the same row. Each cell connection  630  may be positioned at a peak  606   a  shared by two adjacent proximal cells  606  located in the same row. 
     Bars  650  not only define proximal cells  606 , but also interconnect proximal cells  606  located in adjacent rows, thereby allowing uniform expansion of proximal cells  606 . Each bar  650  may be connected to one or more cell connections  630 . 
     Stent  600 A further includes one or more elongated support posts  608 . Each elongated support post  608  has a distal end  608   a , a proximal end  608   b , and a middle  608   c , and includes one or more eyelets or apertures  632  for suturing stent  600 A to the valve leaflets. 
     Stent  600  may further include an interlocking feature  680  protruding proximally from the proximal end  608   b  of elongated support post  608 . Interlocking feature  680  may have a substantially triangular shape and is configured to be attached to a delivery instrument or another cell. In one embodiment, interlocking feature  680  has a circular portion  682  having an aperture  684 . 
     Post connections  610  join each elongated support post  608  to proximal cells  606  located adjacent to the support post. In the embodiment shown in  FIG. 7A , stent  600 A includes two post connections  610  on opposite sides of the middle  608   c  of each elongated support post  608  and another two post connections  610  on opposite sides near the proximal end  608   b  of each elongated support post  608 . As a result, the distal ends  608   a  of elongated support posts  608  are free and disconnected from any proximal cell  606 . This configuration provides stent  600 A with a high degree of flexibility and reduces the likelihood of distortion in the distal portion of elongated support post  608  contorting the commissure region and thus the valve function. 
     The proximal cells  606  adjacent to the distal end  608   a  of elongated support post  608  may be joined to each other by a particular kind of cell connection  631 . Cell connection  631  does not form a peak but rather a straight line in the annular direction of stent  600 A. As seen in  FIG. 7A , cell connection  631  is not connected to elongated support post  608 , thereby enabling the distal end  608   a  of the stent post to flex. 
     Referring to  FIG. 7B , stent  600 B is substantially similar to stent  600 A. However, stent  600 B may include post connections  610  at three locations along elongated support post  608 . For example, stent  600 B may include post connections  610  on opposite sides of the distal end  608   a  of each elongated support post  608 , other post connections  610  on opposite sides of the middle  608   c  of each elongated support post  608 , and other post connections  610  on opposite sides near the proximal end  608   b  of each elongated support post  608 . As discussed above, post connections  610  join elongated support post  608  to proximal cells  606  adjacent to elongated support post  608 . 
     In the embodiment shown in  FIG. 7B , stent  600 B only includes struts  605  interconnecting the distal cells  602  and the proximal cells  606  and does not contain any struts  604  with a non-linear section  604   d . It is envisioned, however, that stent  600 B may include both struts  604  and struts  605 . 
     Stent  600 B may include additional cell structural members  660  located distally of each elongated support post  608 . Each cell structural member  660  includes a first support member  662  and a second support member  664  joined at a peak or distal end  666 . First support member  662  and second support member  664  together form a triangular structure connected to proximal cells  606  located on opposite sides of the distal end  608   a  of elongated support post  608 . Each first support member  662  may be connected to a distal end peak  606   a  of a proximal cell  606  via a cell connection  630 . Each second support member  664  may be connected to a straight connection  631 . In the embodiment shown in  FIG. 7B , connection  631  is not connected to proximal cells  606  or to an elongated support post  608 , and is only coupled to the second support members  664  of each cell structural member  660 . As shown in  FIG. 7B , the connection  631  and the connected portions of support members  664  and struts  605  may be fitted over an existing surgical or collapsible bioprosthetic valve V to lock the new valve in place. In lieu of elongated support post  608 , stent  600 A or stent  600 B may include continuous proximal cells  606  disjointed in the area where the leaflet commissures would be attached. 
       FIG. 8A  shows a stent  700  in a flat, rolled out, unexpanded condition and  FIG. 8B  shows stent  700  in an expanded condition. Stent  700  generally includes distal cells  702 , proximal cells  706 , and a plurality of support struts  704  interconnecting distal cells  702  and proximal cells  706 . 
     Distal cells  702  are arranged in one or more longitudinal rows. In the embodiment shown in  FIGS. 8A and 8B , stent  700  includes one longitudinal row  714  of distal cells  702 . Cell connections  718  join adjacent distal cells  702  arranged in the same row. Some adjacent distal cells  702 , however, are connected by spacers  770 . Spacers  770  allow symmetric expansion of distal cells  714  and additional spacing for the coronary arteries. Each spacer  770  may further include an interlocking feature, eyelets, radiopaque material, a landing-zone/latch-site for implanting another similar expandable valve, or a combination thereof. 
     Although both spacers  770  and cell connections  718  connect adjacent distal cells  702 , spacers  770  separate adjacent distal cells  702  farther from each other than cell connections  718 . In some embodiments, three cell connections  718  may continuously couple four adjacent distal cells  702  before a spacer  770  joins the next adjacent distal cell. Spacers  770  may be arranged between cells  702  so as to be positioned in axial alignment with support posts  708 . 
     Each distal cell  702  has a distal end  702   a  and a proximal end  702   b . Upon expansion of stent  700 , each distal cell  702  may have a diamond shape, as shown in  FIG. 8B . 
     The proximal ends  702   b  of each distal cell  702  may be connected to a support strut  704 . Each support strut  704  has a distal end  704   a  and proximal end  704   b . The distal end  704   a  of each support strut  704  is coupled to a distal cell  702 . The proximal end  704   b  of each support strut  704  is connected to a proximal cell  706 . Specifically, the proximal end  704   b  of each support strut  704  is coupled to a cell connection  730  located at a valley formed between two adjacent proximal cells  706 . 
     As seen in  FIG. 8B , the proximal end  704   b  of each support strut  704  is positioned proximally of the distal ends  708   a  of elongated support posts  708 . As a consequence, the outward flaring of stent  700  in an expanded condition can start proximally to the distal end of the cylindrical region (i.e., proximal cells  706 ). 
     Proximal cells  706  may be arranged in one or more longitudinal rows. In some embodiments, stent  700  may include a first row  724  and a second row  726  oriented substantially parallel to each other. Each proximal cell  706  may feature an arrow shape in the expanded condition defined by a distal end or peak  706   a  between two valleys  706   b  and  706   c  in one stent section, another peak  706   a  between two valleys  706   b  and  706   c  in another stent section, and a pair of bars  750  connecting the stent sections together. 
     Cell connections  730  couple adjacent proximal cells  706  arranged in the same row. Each cell connection  730  may be located at a valley  706   b ,  706   c  shared by two adjacent proximal cells  706  in the same row. 
     Bars  750  not only define proximal cells  706 , but also connect proximal cells  706  located in adjacent rows. Each bar  750  may interconnect several cell connections  730  and permit uniform expansion of proximal cells  706 . In some embodiments, each bar  750  passes through at least three cell connections  730  and is oriented substantially parallel to the elongated support posts  708 . 
     Each elongated support post  708  of stent  700  has a distal end  708   a , a proximal end  708   b , and a middle  708   c . Proximal cells  706  may be connected to an elongated support post  708  at three locations via connecting members  710 . A first pair of connecting members  710  may couple opposite sides of the distal end  708   a  of an elongated support post  708  to two cell connections  730  attached to support struts  704 . A second pair of connecting members  710  may couple opposite sides of the middle  708   c  of the elongated support post  708  to two cell connections  730  located at the proximal ends  706   b ,  706   c  of two different proximal cells  706 . A third pair of connecting members  710  may couple opposite sides near the proximal end  708   b  of the elongated support post  708  to two cell connections  730  located at the proximal ends  706   b ,  706   c  of two other proximal cells  706  located in the second row  726 . 
     Stent  700  further includes an interlocking feature  780  protruding proximally from the proximal end  708   b  of one or more elongated support posts  708 . Interlocking feature  780  is configured to be attached to a delivery system and/or another valve. For instance, a delivery system may hold onto stent  700  through interlocking feature  780 . In addition, another valve may be integrated with or attached to stent  700  via interlocking feature  780 . Interlocking feature  780  may have any suitable shape. In the illustrated embodiment, interlocking feature  780  has a triangular shape and a circular end portion  782  defining an aperture  784 . The stent  700  of a new valve may be fitted over an existing surgical or collapsible bioprosthetic valve V to lock the new valve in place. 
       FIG. 9A  shows a stent  800  in a flat, rolled out, unexpanded condition and  FIG. 9B  depicts stent  800  in an expanded condition. Stent  800  is substantially similar to stent  700  described above and generally includes distal cells  802 , proximal cells  806  and support strut arrays  804  interconnecting distal cells  802  and proximal cells  806 . Each support strut array  804  includes two kinds of support struts, namely a support strut  805  and two support struts  807 . 
     Each distal cell  802  has a distal end  802   a  and a proximal end  802   b . All distal cells  802  are arranged in one or more longitudinal rows  814 . Cell connections  818  join adjacent distal cells  802  in the same row  814 . In the embodiment shown in  FIGS. 9A and 9B , stent  800  includes only one row  814 . 
     Some distal cells  802  are not connected to any support struts, while other distal cells  802  are attached to a support strut  805  or  807 . The distal cells  802   e  that are not attached to any support strut  805  or  807  allow further expansion of the longitudinal row  814  of distal cells. In some embodiments, stent  800  includes three distal cells  802  connected to support struts  805 ,  807  for every distal cell  802   e  that is not attached to any support strut  805  or  807 . Each distal cell  802   e  that is not connected to any support strut  805  or  807  may be positioned between a series of distal cells  802  which is not connected to the support strut  805  or  807 . For example, in one embodiment, a single distal cell  802   e  which is not connected to support struts  805  or  807  may be located between and adjacent two distal cells  802  attached to support struts  807 . In this embodiment, shown in  FIG. 9A , each distal cell  802  coupled to a support strut  807  is located adjacent to a distal cell  802  connected to a support strut  805 . 
     As discussed above, each support strut array  804  includes two kinds of support struts—a support strut  805  and a pair of support struts  807 . Each support strut  805  has a distal end  805   a  and a proximal end  805   b  and may be formed of a substantially flexible material. Support struts  805  may have a linear configuration along their entire length. The distal end  805   a  of each support strut  805  is connected to a distal cell  802 , while the proximal end  805   b  of each support strut  805  is connected to a proximal cell  806 . 
     In some embodiments, support struts  805  may not be connected to all distal cells  802 . For example, support struts  805  may be coupled to one of every four distal cells  802 . Each support strut  805  may be positioned between two support struts  807 . 
     Each support strut  807  has a distal end  807   a , a proximal end  807   b  and a middle portion  807   c  between the distal end and the proximal end. The distal end  807   a  and the proximal end  807   b  of each support strut  807  have substantially linear or straight configurations. At least part of middle portion  807   c  of each support strut  807  has a curved profile or configuration. In some embodiments, middle portions  807   c  have a C-shape or an inverted C-shape. 
     The distal end  807   a  of each support strut  807  may be connected to a single distal cell  802 . The proximal end  807   b  of each support strut  807  may be coupled to a proximal cell  806 . In certain embodiments, support struts  807  may be connected only to the proximal cells  806  adjacent to an elongated support post  808 . As shown in  FIGS. 9A and 9B , one support strut  807  with a C-shaped middle portion  807   c  may be connected to a proximal cell  806  located adjacent one side of an elongated support post  808 , while another support strut  807  with an inverted C-shaped middle portion  807   c  may be connected to a proximal cell  806  positioned adjacent the opposite side of that elongated support post  808 . 
     Each proximal cell  806  may have an inverted arrow shape upon expansion defined by a pair of peaks  806   a  on opposite sides of a valley  806   b  in one stent section, another pair of peaks  806   a  on opposite sides of a valley  806   b  in another stent section, and a pair of bars  850  connecting the stent sections together. Proximal cells  806  may be arranged in one or more longitudinal rows. In some embodiments, stent  800  includes proximal cells  806  in a first row  824  and in a second row  826 . Cell connections  830  interconnect adjacent proximal cells  806  positioned in the same row. Each cell connection  830  may be located at a peak  806   a  shared by two adjacent proximal cells  806  located in the same row. The valleys  806   b  at the proximal ends of the cells in the second row  824  may also form the valleys  806   b  at the distal ends of the adjacent cells in the first row  826 . 
     As seen in  FIGS. 9A and 9B , all support struts  805  and  807  may be connected to the peaks  806   a  of the proximal cells  806  in first row  824 . Alternatively, some or all support struts  805  and  807  may be attached to the valleys  806   b  of the proximal cells  806  in the first row  824 . 
     Bars  850  not only define proximal cells  806 , but also connect proximal cells  806  located in adjacent rows. Specifically, each bar  850  may connect several cell connections  830 . In some embodiments, a bar  850  may join at least three cell connections  830  located in different rows and therefore permit uniform expansion of stent  800 . 
     Some proximal cells  806  may be attached to an elongated support post  808 . Stent  800  may have one or more elongated support posts  808 . In the embodiment shown in  FIG. 8A , stent  800  has three such support posts  808 . Each support post  808  has a distal end  808   a , a proximal end  808   b , and a middle  808   c . Post connections  810  attach some proximal cells  806  to opposite sides of the distal end  808   a , the proximal end  808   b  and the middle  808   c  of the elongated support post  808 . 
     Stent  800  may further include an interlocking feature  880  protruding proximally from the proximal end  808   b  of each elongated support post  808 . Interlocking feature  880  may be substantially similar to the interlocking feature  780  of stent  700 . The stent  800  of a new valve may be fitted over an existing surgical or collapsible bioprosthetic valve V to lock the new valve in place or may be used to lock the stent  800  at the sinotubular junction  4 . 
       FIGS. 10A, 10B, and 10C  illustrate several embodiments of stents with substantially rigid posts or bars. These stents also have different interlocking features configured to be engaged to a delivery system and/or another valve. 
       FIG. 10A  depicts a portion of a stent  900  in a flat, rolled out, unexpanded condition. Stent  900  generally includes distal cells  902 , proximal cells  906 , and support struts  904  and  905  interconnecting distal cells  902  and proximal cells  906 . Some proximal cells  906  are attached to one or more elongated support posts  908  made wholly or partly of a substantially solid or rigid material. 
     Distal cells  902  are arranged in one or more longitudinal rows. Stent  900  may include one longitudinal row  914  of distal cells  902 . Each distal cell  902  has a distal end  902   a , a proximal end  902   b , and a middle portion  902   c  between the distal end and the proximal end. Cell connections  918  join adjacent distal cells  902  at their middle portions  902   c.    
     At least one compartment  903  is interposed between the series of distal cells  902  in row  914 . Preferably, stent  900  includes one compartment  903  for each elongated support post  908 . Each compartment  903  includes a distal end  903   a , a proximal end  903   b , and a middle portion  903   c  between the proximal end and the distal end. The distal end  903   a  and the proximal end  903   b  of each compartment  903  may have substantially linear or straight configurations oriented substantially parallel to each other at least in the unexpanded condition of stent  900 . Thus, in the unexpanded condition, compartment  903  has a generally rectangular shape. Cell connections  918  may join opposite sides of the middle portion  903   c  of the compartment  903  to neighboring distal cells  902 . 
     The distal end  903   a  of compartment  903  may include an interlocking feature  980  configured to be attached to a delivery system and/or another valve. Interlocking feature  980  protrudes proximally from the distal end  903   a  into the interior of compartment  903 . In the embodiment shown in  FIG. 10A , interlocking feature  980  includes rounded protrusion  982  having an aperture  984 . 
     As discussed above, stent  900  includes support struts  904  and support struts  905 . At least some of support struts  904  and support struts  905  may be made partially or entirely of a substantially rigid material to minimize a change in stent length, thereby reducing the risk of valve damage during crimping of the prosthetic valve and providing a more consistent valve function in various implant diameters. Support struts  904  interconnect the proximal end  902   b  of a distal cell  902  to the distal end  906   a  of a proximal cell  906 . In some embodiments, every distal cell  902  may be connected to a proximal cell  906  via a support strut  904 . 
     Support struts  905  couple the proximal end  903   b  of compartment  903  to the distal end  908   a  of the elongated support post  908 . In some embodiments, stent  900  may include two support struts  905  connecting a single elongated support post  908  to a single compartment  903 . Each of the support struts  905  may have a distal end  905   a  and a proximal end  905   b , and the struts may collectively form a triangular shape in the unexpanded condition of stent  900 . The proximal ends  905   b  of the two support struts  905  may be connected to spaced apart portions of the same elongated support post  908 . The distal ends  905   a  of the two support struts  905  may converge for attachment to the proximal end  903   b  of compartment  903  at a single point. In this arrangement, support struts  905  define an oblique angle relative to one another. 
     All proximal cells  906  are arranged in one or more longitudinal rows and some are attached to at least one elongated support post  908 . Cell connections  930  connect proximal cells  906  arranged on the same row, while bars or runners  950  join adjacent proximal cells  906  located in different rows. 
     As noted above, stent  900  includes one or more elongated support posts  908 . Each elongated support post  908  includes a distal end  908   a , a proximal end  908 , and a middle  908   c . Post connections  910  join some proximal cells  906  to an elongated support post  908  at three locations. First post connections  910  connect two proximal cells  906  to opposite sides of the distal end  908   a  of the elongated support post  908 . Second post connections  910  connect two proximal cells  906  to opposite sides of the middle  908   c  of the elongated support post  908 . Third post connections  910  coupled two proximal cells  906  to opposite sides near the proximal end  908   b  of the elongated support post  908 . 
       FIG. 10B  illustrates a stent  1000 A and  FIG. 10C  illustrates a stent  1000 B which are substantially similar to one another. Stents  1000 A and  1000 B have interlocking features  1080  at different locations and different kinds of elongated support posts. 
     As shown in  FIG. 10B , stent  1000 A includes at least one elongated support post  1008 , distal cells  1002  and proximal cells  1006  but does not include support struts. In other words, distal cells  1002  are connected directly to proximal cells  1006 . 
     Distal cells  1002  may be arranged in one or more longitudinal rows. In some embodiments, stent  1000 A may include a first row  1014 , a second row  1016  and a third row  1022  of distal cells  1002  oriented substantially parallel to each other. Each distal cell has a distal end or peak  1002   a , a proximal end or valley  1002   b , and middle portions  1002   c . The valley  1002   b  of a distal cell  1002  in one row may join the peak  1002   a  of a distal cell in another row which is not adjacent to the one row. Upon expansion, each distal cell  1002  may have a diamond shape. Distal cells  1002  may be formed of a substantially flexible material and therefore the cells can lengthen and expand to larger diameters. 
     Cell connections  1018  join adjacent distal cells  1002  in the same row. Distal cells  1002  in adjacent rows are joined by sharing common cell segments. Stent  1000 A further includes one or more cell spacers  1070  each interconnecting two adjacent distal cells  1002  of the first row  1014 . Preferably, stent  1000 A includes a cell spacer  1070  for each elongated support post  1008 . In the embodiment shown in  FIG. 10B , a cell spacer  1070  may form a distal portion or end of a distal cell  1002  which is located in the second row  1016  and connected to an elongated support post  1008 . Cell spacer  1070  permits further expansion of stent  1000 A, and may provide clearance between distal cells  1002  to accommodate the coronary arteries. 
     As noted above, the proximal ends  1002   b  of a distal cell  1002  in the second row  1016  are connected to the distal end  1008   a  of an elongated support post  1008 . In addition, two distal cells  1002  in the third row  1022  may be connected by their middle portions  1002   c  to opposite sides of the distal end  1008   a  of the elongated support post  1008 . Post connections  1010  thus join the distal end  1008   a  of elongated support post  1008  to both a distal cell  1002  in second row  1016  and to two distal cells  1002  in third row  1022  positioned on opposite sides of elongated support post  1008 . 
     The distal cells  1002  in third row  1022  are directly connected to the proximal cells  1006  in a first row  1024  by a runner or bar  1050 . Bar  1050  is connected at one end to a cell connection  1018  in the third row  1022  of distal cells  1002 , and at the other end to cell connection  1030  in the first row  1024  of proximal cells  1006 . 
     Proximal cells  1006  may have a substantially inverted arrow shape upon expansion defined by a pair of distal peaks  1006   a  on opposite sides of a valley  1006   b  in one stent section, another pair of distal peaks  1006   a  on opposite sides of a valley  1006   b  in another stent section, and a pair of bars  1050  connecting the stent sections together. As seen in  FIG. 10B , proximal cells  1006  may be arranged in longitudinal rows, such as first row  1024  and second row  1026 . Cell connections  1030  located at distal peaks  1006   a  interconnect adjacent proximal cells  1006  located in the same row. 
     Bars  1050  not only define proximal cells  1006 , but also interconnect proximal cells  1006  located in adjacent rows. In particular, each bar  1050  may connect several cell connections  1030  located in different rows. Bars  1050  may be formed of a substantially solid or rigid material, thereby minimizing or limiting the change in stent length during expansion of stent  1000 A. 
     As previously noted, each elongated support post  1008  has a distal end  1008   a . Additionally, each elongated stent post  1008  has a proximal end  1008   b  and a middle  1008   c , and may include a plurality of eyelets or apertures  1032 . Elongated support posts  1008  may be formed of a substantially solid or rigid material, thereby minimizing or limiting changes in the stent length during expansion of stent  1000 A. 
     In addition to the post connections  1010  described above, stent  1000 A may include post connections  1010  joining two proximal cells  1006  to opposite sides of the middle  1008   c  of the elongated support post  1008 . Other post connections  1010  may connect two proximal cells  1006  to opposite sides of the elongated support post  1008  near proximal end  1008   b.    
     Stent  1000 A further includes an interlocking feature  1080  protruding proximally from the proximal end  1008   b  of the elongated support post  1008 . As discussed below, interlocking feature  1080  may be positioned at other locations. Interlocking feature  1080  is configured to be attached to a delivery system or another valve. In the embodiment shown in  FIG. 10B , interlocking feature  1080  has a triangular shape and a circular portion  1082  having an aperture  1084 . 
     Referring to  FIG. 10C , stent  1000 B is substantially similar to stent  1000 A shown in  FIG. 10B . However, stent  1000 B includes an interlocking feature  1080  protruding distally from spacer  1070 . Moreover, stent  1000 B includes an elongated support post  1008  having a different configuration than the elongated support post of stent  1000 A. The elongated support post  1008  of stent  1000 B includes a post section  1008   d  which has a narrower width relative to the rest of elongated support post  1008 , thereby enhancing the flexibility of the elongated support post. In addition, the proximal end  1008   b  of the elongated support post  1008  shown in  FIG. 10C  does not include eyelets or apertures  1032 , as do the distal end  1008   a  and middle  1008   c.    
     The stent designs depicted in  FIGS. 10A, 10B, and 10C  may be configured to have shorter lengths than depicted in the figures to anchor at different locations of the aortic root anatomy. For example, in  FIG. 10D , stent  1000 C is substantially similar to stent  1000 A of  FIG. 10B  but has a suitable stent length L C  (with fewer rows of distal cells) and a flared configuration for anchoring at the sinotubular junction  4  of the aortic root  10  in the expanded condition. (See  FIG. 1 .) With reference to  FIG. 10E , stent  1000 D is substantially similar to stent  1000 A shown in  FIG. 10B . Stent  1000 D nonetheless features a suitable stent length L D  and a flared configuration anchoring just above the sinotubular junction  4  and at the base of the aortic root  10  in the expanded condition. Stent  1000 D includes an interlocking feature  1080  protruding proximally from each elongated support post  1008  and another interlocking feature protruding distally from each spacer  1070 . Referring to  FIG. 10F , stent  1000 E is substantially similar to stent  1000 D illustrated in  FIG. 10E , but includes an additional row of distal cells, such as illustrated previously in  FIG. 1000A . Stent  1000 E may thus have a suitable stent length L E  and a flared configuration for anchoring within the ascending aorta. 
       FIGS. 11A-11D  show several stent designs with different kinds of support post connections. These several types of support post connections reduce the amount of fatigue occurring at the joints connecting the support posts to the remainder of the stent, and provide a desired amount of post flexibility. 
     Referring specifically to  FIG. 11A , stent  1100  is similar to stent  200  of  FIG. 3 . Stent  1100 , however, includes support struts  1107  directly connected to the distal end  1108   a  of the elongated support post  1108 . Specifically, stent  1100  includes support strut arrays  1104  interconnecting distal cells  1102  and elongated support posts  1108 . Each support strut array  1104  may include two support struts  1107 . Although the drawings show each support strut array  1104  as having two support struts  1107 , support strut arrays  1104  may include more or fewer support struts  1107 . 
     Each support strut  1107  has a distal end portion  1107   a , a proximal end portion  1107   b , and a middle portion  1107   c  between the distal end portion and the proximal end portion. As seen in  FIG. 11A , each support strut  1107  includes a bifurcated section  1107   d  with a first branch  1107   e  and a second branch  1107   f . Each of the first branch  1107   e  and the second branch  1107   f  is connected to a single distal cell  1102 . Accordingly, each support strut  1107  is attached to two distal cells  1102 . First and second branches  1107   e  and  1107   f  are oriented substantially parallel to each other except at a transition or angled region  1107   g . At the transition region  1107   g , the first branch  1107   e  and second branch  1107   f  define an oblique angle relative to one another. In a portion of bifurcated section  1107   d  located distally to transition region  1107   g , the first branch  1107   e  and second branch  1107   f  are farther apart from each other than in the portion of bifurcated section  1107   d  located proximally of transition region  1107   g.    
     The first branch  1107   e  and second branch  1107   f  converge into a single support member  1107   k  at or near the proximal end portion  1107   b  of each support strut  1107 . Each single support member  1107   k  is coupled to the distal end  1108   a  of the elongated support post  1108 . Single support members  1107   k  each have a folded configuration, such as a tightly folded C-shape. Post connections  1110  join two single support members  1107   k  to the opposite sides of the distal end  1108   a  of the elongated support post  1108 . Other post connections  1110  couple two proximal cells  1106  to opposite sides of the elongated support post  1108  near proximal end  1108   b.    
     With reference to  FIG. 11B , stent  1200  is substantially similar to stent  1100 . Stent  1200  includes distal cells  1202 , proximal cells  1206 , at least one elongated support post  1208  attached between the proximal cells  1206 , and at least one support strut array  1204  coupling the distal cells  1202  to both the elongated support posts  1208  and the proximal cells  1206 . Preferably, there is a support strut array  1204  for each elongated support post  1208 . 
     Each support strut array  1204  is similar to support strut array  1104  of stent  1100 . For example, each support strut array  1204  includes one or more support struts  1207  with a bifurcated section  1207   g  and a single support member  1207   k . In this embodiment, single support member  1207   k  is not directly connected to an elongated support member  1208 . Rather, each single support member  1207   k  divides into two arms—a first arm  1207   p  and a second arm  1207   m . First arm  1207   p  extends proximally from single support member  1207   k  and is directly connected to a proximal cell  1206  adjacent to elongated support post  1208 . Second arm  1207   m  extends distally from single support member  1207   k  and may double back upon itself to form an inverted U-shape before directly connecting to the distal end  1208   a  of the elongated support post  1208 . 
     With reference to  FIG. 11C , stent  1300  is substantially similar to the stent  1100  shown in  FIG. 11A . Stent  1300  includes distal cells  1302 , proximal cells  1306 , at least one elongated support post  1308  attached between the proximal cells  1306 , and at least one support strut array  1304  connecting the distal cells  1302  to the elongated support post  1308 . Preferably, there is a support strut array  1304  for each elongated support post  1308 . Each support strut array  1304  includes one or more support struts  1307 . In the embodiment illustrated in  FIG. 11C , each support strut array  1304  includes two support struts  1307 . In any event, each support strut  1307  has a bifurcated section  1307   g  connected to distal cells  1302  and a single support member  1307   k  attached to the distal end  1308   a  of the elongated support post  1308 . Bifurcated section  1307   g  of each support strut  1307  has two branches, each of which connects to a single distal cell  1302 . Single support member  1307   k  connects directly to the distal end  1308   a  of the elongated support post  1308  and is substantially shorter in length than the bifurcated section  1307   g . The single support members  1307   k  of two support struts  1307  may be connected to opposite sides of the distal end  1308   a  of the elongated support post  1308 . 
       FIG. 11D  illustrates a stent  1400  substantially similar to stent  100  depicted in  FIG. 2 . Stent  1400 , however, includes at least one support strut  1404  with its proximal end  1404   b  connected to the distal end  1408   a  of an elongated support post  1408 . Preferably, stent  1400  includes a support strut  1404  for each elongated support post  1408 . Each support strut  1404  has a distal end  1404   a , a proximal end  1404   b  and a middle portion  1404   c  between the distal end and the proximal end. The distal end  1404   a  of each support strut  1404  is connected to a single distal cell  1402 . The middle portion  1404   c  of each support strut  1404  has a sinusoidal or wave shape. 
     With reference to  FIG. 12A , stent  1500  includes a support post  1508  with a shorter post length as compared to the support post lengths of the previously described stents. Shortened support post  1508  has a distal end  1508   a  and a proximal end  1508   b  and, during use, reduces the amount of space taken up by the stent and valve material when in the unexpanded condition. The design of stent  1500  allows for a strong structural anchoring of the valve leaflets V at the distal end  1508   a  of the shortened support post  1508 . As seen in  FIG. 12A , leaflets V gradually taper away from shortened support post  1508 . Since leaflet V is not connected all the way to the proximal end  1508   b  of the post  1508 , a reduced amount of leaflet material engages stent  1500 , permitting stent  1500  to be crimped down to a smaller diameter. 
     Two post connections  1510  couple two proximal cells  1506  to opposite sides of the distal end  1508   a  of the shortened support post  1508 . Another post connection  1510  joins a single central point of the proximal end  1508   b  of the shortened support post  1508  to two additional proximal cells  1506 . There is no stent material proximally of the post connection  1510  at the proximal end  1508   b  of shortened post  1508 . Indeed, stent  1500  has a gap  1590  defined between the proximal cells  1506  positioned proximally of the proximal end  1508   b  of the shortened support post  1508 . Accordingly, stent  1500  has a less stiff cantilevered post  1508  and can be flexible even though post  1508  is connected to proximal cells  1506  at both its distal end  1508   a  and its proximal end  1508   b.    
     Stent  1500  may alternatively incorporate a full-length or elongated support post  1509  as shown in  FIG. 12B . Elongated support post  1509  is longer and narrower than shortened support post  1508  and includes reduced width portion  1509   d . Reduced width portion  1509   d  is located near the proximal end  1509   b  of the elongated support post  1509  and allows stent  1500  to be more compactly crimped. The overall reduced width of elongated support post  1509  also allows a user to secure the knots connecting a valve to elongated support post  1509  away from the cells. In addition to the reduced width portion  1509   d , elongated support post  1509  includes eyelets or apertures  1532  and a base portion  1509   e . Eyelets  1532  extend from the distal end  1509   a  of elongated support post  1509  along the section located distally of the reduced width portion  1509   d . Reduced width portion  1509   d  and base portion  1509   e  do not have eyelets  1532 . Base portion  1509   e  is wider than reduced width portion  1509   d  and may have a rectangular or paddle shape. In use, base portion  1509   e  may function as an interlocking feature configured to be attached to a delivery system or another valve. 
     Referring to  FIG. 12C , stent  1500  may alternatively incorporate elongated support post  1511 , which is substantially similar to elongated support post  1509 . Elongated support post  1511  is narrower than both the shortened support post  1508  of  FIG. 12A  and the elongated support post  1509  of  FIG. 12B , thus enabling an even smaller overall diameter when crimped. In addition, elongated support post  1511  has a reduced width portion  1511   d , a base portion  1511   e  and a plurality of merged eyelets  1533 . Merged eyelets  1533  constitute two eyelets  1532  as shown in  FIG. 12B  merged together. Eyelets  1533  are larger than eyelets  1532  of  FIG. 12A , thus making elongated support post  1511  more flexible than elongated support post  1509 . Base portion  1511   e  can function as an interlocking feature configured to be attached to a delivery system or another valve. 
     With reference to  FIGS. 13A and 13B , a stent  1600  includes a plurality of cells  1602  and an elongated support post  1608 . Some of these cells  1602  are connected to the elongated support post  1608  via post connections  1610 . One group of post connections  1610  couple two cells  1602  to opposite sides of the distal end  1608   a  of the elongated support post  1608 . Another group of post connections  1610  join two other cells  1602  to opposite sides of the proximal end  1608   b  of the elongated support post  1608 . 
     Ordinarily, because of the fixed length of elongated support post  1608 , the cells  1602  immediately adjacent to the support post would not be able to expand away from the support post to create a space therebetween. To overcome this, however, and provide for the full expansion of stent  1600 , elongated support post  1608  may be provided with a sliding mechanism  1660  that enables the length of the elongated support post to shorten upon expansion of stent  1600 . Sliding mechanism  1660  includes a central longitudinal slot  1666  which extends distally from the proximal end  1608   b  of elongated support post  1608 , and a finger  1670  adapted for sliding engagement in slot  1666 .  FIG. 1670  is fixedly connected to a cross-member  1672  positioned proximally of the elongated support post  1608 . A pair of concave indentations  1668  on opposite sides of longitudinal slot  1666  can be used to secure a ring, suture, clip, or other structure that may be used as a guide. Upon expansion of stent  1600 , finger  1670  is able to slide into slot  1666 , thereby allowing elongated support post  1608  to shorten. As a consequence, the cells  1602  immediately adjacent to elongated support post  1608  are able to expand away from the support post. Sliding mechanism  1660  also allows different amounts of post deflection during use of stent  1600  in a prosthetic valve. As seen in  FIG. 13B , the leaflet attachments and contour V allow movement of elongated support post  1608  in an area that does not affect the leaflet. 
       FIG. 14A  shows a stent  1700  in a flat, rolled out, unexpanded condition and  FIG. 14B  illustrates stent  1700  in a flat, rolled out, expanded condition. Stent  1700  is substantially similar to stent  1600  but does not include a sliding mechanism. Instead, stent  1700  includes an elongated support post  1708  having a collapsible feature  1760  which enables the length of the support post to shorten upon expansion of the stent. As with previous embodiments, elongated support post  1708  has a distal end  1708   a , a proximal end  1708   b , and a middle  1708   c . In addition, elongated support post  1708  includes eyelets or apertures  1732 . As shown in  FIG. 14B , since the leaflet attachments of valve V only need the eyelets  1732  positioned near the distal end  1708   a  of elongated support post  1708 , collapsible feature  1760  may be located between the middle  1708   c  and the proximal end  1708   b  of the elongated support post. Nevertheless, collapsible feature  1760  may be positioned at any suitable location along the length of elongated support post  1708 . Irrespective of its position, collapsible feature  1760  enables elongated support post  1708  to shorten axially during expansion of stent  1700 , as shown in  FIGS. 14A and 14B . 
     Collapsible feature  1760  may have a first end  1760   a  and a second end  1760   b . The first end  1760   a  of the collapsible feature  1760  may be connected to a portion of the elongated support post  1708  close to its middle  1708   c , while the second end  1760   b  of the collapsible feature may be connected to a portion of the elongated support post  1708  near its proximal end  1708   b . Collapsible feature  1760  may have a plurality of legs  1764  arranged substantially in a diamond shape between its first end  1760   a  and its second end  1760   b , with a central opening  1762  defined in the interior of legs  1764 . Legs  1764  may be formed from a flexible or bendable material that can readily deform upon the expansion or crimping of stent  1700 . The central opening  1762  allows collapsible feature  1760  to collapse when stent  1700  expands or to expand when stent  1700  is collapsed. Consequently, elongated support post  1708  may lengthen or shorten as stent  1700  expands or collapses. 
     Referring to  FIGS. 15A and 15B , stent  1800  is substantially similar to stent  1700  but includes a different kind of collapsible post structure. Stent  1800  includes cells  1802  and an elongated support post  1808  with a collapsible feature  1860 . Elongated support post  1808  has a distal end  1808   a , a proximal end  1808   b  and a middle  1808   c  between the distal end and the proximal end. Collapsible feature  1860  may be located between the middle  1808   c  and the proximal end  1808   b  of the elongated support post  1808  and may include a first collapsible member  1862  having a serpentine or sinusoidal shape and a second collapsible member  1864  having a similar serpentine or sinusoidal shape, with a central opening  1866  defined between them. As shown in  FIGS. 15A and 15B , collapsible members  1862  and  1864  are flexible and therefore can freely move between an expanded condition and a collapsed condition. Central opening  1866  facilitates the movement of collapsible members  1862  and  1864  between the expanded and the collapsed conditions. Collapsible members  1862  and  1864  allow elongated support post  1808  to shorten upon expansion of stent  1800 . In operation, collapsible feature  1860  axially extends when stent  1800  is collapsed to a smaller diameter, and axially shortens when stent  1800  is expanded to a larger diameter. 
     With reference to  FIGS. 16A and 16B , stent  1900  is substantially similar to stent  1800  shown in  FIGS. 15A and 15B , but includes a different kind of collapsible post structure. Stent  1900  includes cells  1902  and an elongated support post  1908  with a collapsible feature  1960 . Elongated support post  1908  has a distal end  1908   a , a proximal end  1908   b , and a middle  1908   c  between the distal end and the proximal end. The collapsible feature  1960  may be located between the middle  1908   c  and the proximal end  1908   b  of the elongated support post  1908 . Collapsible feature  1960  may include a first collapsible member  1962  and a second collapsible member  1964 , with a central opening  1966  defined between them. Collapsible members  1962  and  1964  are flexible and together may define an hourglass shape. Collapsible feature  1960  may move between a lengthened condition ( FIG. 16A ) with stent  1900  in an unexpanded state, and a shortened condition ( FIG. 16B ) with stent  1900  in an expanded state, allowing the elongated support post  1908  to change its length when a stent  1900  is expanded or crimped. 
     Flexibility of Stent Via Support Strut Connections 
     The support strut location and type is another primary design parameter that can change the amount of flexibility of the support post. As the support strut is connected farther from the support post, it allows the load from the commissural region during back-pressure to be distributed along the stent body gradually, instead of abruptly at the commissures and struts connected to the stent. This not only decreases the dynamic loading on the valve leaflets, but also reduces strain on the stent. The highest dynamic loads are experienced in the embodiments in which the support struts are connected directly to the support posts (e.g.,  FIGS. 11A-11D ). Embodiments with support strut connections adjacent to the support posts (e.g.,  FIGS. 3 and 4 ) experience slightly less dynamic loads, while embodiments with support strut connections located farther from the support posts (e.g.,  FIGS. 17A and 17B ) experience even less dynamic loads. Embodiments with support strut connections located halfway between two adjacent support posts (e.g.,  FIGS. 5A, 5B and 18A, 18B, and 18C ) experience the least dynamic loads. 
       FIG. 17A  shows a stent  2000  in a flat, rolled out, unexpanded condition and  FIG. 17B  shows a proximal portion of stent  2000  in a flat, rolled out, fully-expanded condition. Stent  2000  generally includes a distal sinusoidal or serpentine pattern of half-cells  2002 , proximal cells  2006 , support struts  2004  interconnecting distal half-cells  2002  and proximal cells  2006 , and elongated support posts  2008  attached to some proximal cells  2006 . Stent  2000  may include only half-cells  2002  (not complete cells) to reduce its overall length due to the possibility of aortic arch bend constraints. 
     Each support strut  2004  has a distal end  2004   a  connected to a distal half-cell  2002 , a proximal end  2004   b  attached to a proximal cell  2006 , and a middle portion  2004   c  between the distal end and the proximal end. The middle portion  2004   c  of each support strut  2004  may have a serpentine or sinusoidal shape, as shown in  FIG. 17A . 
     Proximal cells  2006  may be arranged in one or more rows. In the illustrated embodiment, stent  2000  includes a first row  2024  of proximal cells  2006  and a second row  2026  of proximal cells. Some proximal cells  2006  in the first row  2024  and the second row  2026  are attached to an elongated support post  2008 . The first row  2024  includes certain proximal cells  2006  which are joined to support struts  2004 . The proximal end  2004   b  of each support strut  2004  is connected to a proximal cell  2006   f  located one cell beyond the proximal cell  2006  adjacent to the elongated support post  2008 . 
     A plurality of cell connections  2030  may join adjacent proximal cells  2006  in the same row. Proximal cells  2006  in different rows may be joined by sharing common cell segments. Cell connections  2030  may be positioned at the distal end of a proximal cell  2006  in the second row  2026 , which is coextensive with a middle portion of an adjacent proximal cell located in the first row  2024 . Cell connections  2030  may also be positioned at the proximal end of a proximal cell  2006  in the first row  2024 , which is coextensive with the middle portion of an adjacent proximal cell  2006  in the second row  2026 . Some proximal cells  2006  in the second row  2026  may be discontinuous in their middle portions, such as through a disconnection or break  2090  at a cell connection  2030 , to allow cell expansion in a different way as compared to previous embodiments. 
     Synergistic Physiological Stent Behavior Via Post Connections 
     The configuration and connections of the support struts may have an effect on the annulus portion (i.e., proximal cells) of the stent and therefore the valve function. For instance, the annulus section can function virtually independently in the torsional degree-of-freedom when the heart twists relative to the aorta during beating if the support struts are designed and connected to the cells as shown in  FIGS. 18A, 18B and 18C . 
       FIGS. 18A, 18B, and 18C  show a stent  2100  which is substantially similar to stent  100  shown in  FIG. 2 . Stent  2100  includes support struts  2104  connected to proximal cells  2106  located midway between two elongated support posts  2108 .  FIG. 18A  illustrates stent  2100  in a flat, rolled out, unexpanded condition;  FIG. 18B  shows stent  2100  perspectively in a fully expanded and deployed condition; and  FIG. 18C  depicts stent  2100  perspectively in an unexpanded condition. Stent  2100  generally includes distal cells  2102 , proximal cells  2106 , support struts  2104  interconnecting distal cells  2102  and proximal cells  2106 , and elongated support posts  2108  attached to some proximal cells  2106 . 
     Each support strut  2104  has a distal end  2104   a , a proximal end  2104   b  and a middle portion  2104   c  between the distal end and the proximal end. The distal end  2104   a  of each support strut  2104  is connected to a distal cell  2102 . The proximal end  2104   b  of each support strut  2104  is connected to a proximal cell  2106 . Specifically, each support strut  2104  is connected to a proximal cell  2106   f  located midway between two elongated support posts  2108  in order to increase flexibility and minimize the dynamic loads exerted on the elongated support posts. Stent  2100  may include at least three support struts  2104  connected to three proximal cells  2106   f , as seen in  FIGS. 18A, 18B and 18C , for providing a stable connection of the aorta portion to the annulus portion while providing the greatest amount of stent frame flexibility. Preferably, stent  2100  has the same number of support struts  2104  as elongated support posts  2108 . 
       FIG. 18B  illustrates stent  2100  in a substantially straight configuration as if the heart is not twisting during beating relative to the aorta, and the aortic arch bend is not an issue.  FIG. 19  depicts the same stent  2100  with the valve section (i.e., proximal cells  2106 ) operating relatively free of adverse contortion from the twisting of the heart while still not allowing the stent to migrate. 
     Additional physiological concerns may arise due to translational (shortening or lengthening) motion and the bending and straightening of the ascending aorta. As seen in  FIGS. 20A and 20B , however, the type and locations of the support struts  2104  of stent  2100  also aid in maintaining proper physiological motion, reduce leaflet stress, improve relatively independent valve function, and reduce certain stent strains, all while maintaining the necessary valve anchoring.  FIG. 20A  illustrates the ability of stent  2100  to conform to an aortic arch bend with little effect on its valve-functioning part (i.e., proximal cells  2106 ).  FIG. 20B  shows stent  2100  with the valve section (i.e., proximal cells  2106 ) functioning relatively free of adverse contortion from shortening and lengthening motions of the relative anatomical structures. 
     Any of the presently disclosed embodiments of stent may include different kinds of support struts depending on the desired post flexibility and anatomical conformance. See e.g.,  FIGS. 21A-21J . Each of the support struts illustrated in  FIGS. 21A-21J  has its own directional advantage. The flexibility of the illustrated support struts aids in the ability to deliver the valve around tortuous vascular anatomy and the aortic arch when collapsed. 
       FIG. 21A  shows a support strut  2204 A with a tapered proximal portion  2204   t .  FIG. 21B  illustrates a support strut  2204 B featuring a uniform diameter or cross-section along its entire length.  FIG. 21C  depicts a support strut  2204 C with a tapered middle portion  2204   k . The support struts shown in  FIGS. 21A, 21B, and 21C  can bend and twist but cannot elongate. 
       FIG. 21D  shows a support strut  2204 D with a bent middle portion  2204   m . Middle portion  2204   m  has a generally rectangular inverted C-shape with three sides  2204   n  and two corners  2204   o . Two sides  2204   n  may be oriented substantially parallel to each other and substantially orthogonal to the remainder of strut  2204 D, while the third side interconnecting the first two sides may be substantially parallel to the remainder of strut  2204 D. Corners  2204   o  interconnect the different sides  2204   n  and may be rounded. FIG.  21 E illustrates a support strut  2204 E with a bent middle portion  2204   r . Middle portion  2204   r  has a generally rounded C-shaped profile. The support struts shown in  FIGS. 21D and 21E  can bend and twist more than the struts of  FIGS. 21A, 21B, and 21C , and can also shorten and elongate. 
       FIG. 21F  shows a support strut  2204 F with a rectangular middle portion  2204   s . Middle portion  2204   s  has a substantially rectangular shape and includes four sides  2204   u  connected to one another and collectively defining a central opening  2204   q . Support strut  2204 F can bend, twist, shorten and elongate. The middle portion  2204   s  provides redundant support to strut  2204 F. 
       FIG. 21G  shows a support strut  2204 G with nested longitudinal cells  2204   v  in its middle portion and extending toward the proximal end of the support strut. Support strut  2204 G can bend more easily than previous embodiments, but may have limited elongation capabilities.  FIG. 21H  shows a support strut  2204 H with a nested coil of cells  2204   x  in its middle portion. The nested coil of cells  2204   x  can bend, twist and elongate via a circular nested mechanism. 
       FIG. 21I  illustrates a support strut  2204 I with a single serpentine or sinusoidal link  2204   y  in its middle portion. Support strut  2204 I can bend and twist and can also elongate more easily than previous embodiments.  FIG. 21J  shows a pair of support struts  2204 J each having serpentine-shaped links  2204   z  in their middle portions. The serpentine-shaped link  2204   z  of one support strut  2204 J is offset to the left (or away from the other support strut  2204 J), while the serpentine-shaped link  2204   z  of the other support strut  2204 J is offset to the right (or away from the other support strut  2204 J). 
     Flexibility of Stent Post and Anatomical Conformance Via Independent Post Connections 
     Stents may not only have both an annular portion (i.e., proximal cells) and an aortic/sinotubular junction portion (i.e., distal cells), but may alternatively have independently contouring support struts to conform to the differences in anatomy/physiology around the circumference of the aortic root. This can help to anchor the valve with the least amount of unwanted load transfer to the support post area of the valve. 
     Referring to  FIG. 22 , stent  2300  generally includes proximal cells  2306 , elongated support posts  2308 , and a plurality of support struts  2304  each connected at a proximal end  2304   b  to a proximal cell  2306 , and extending distally therefrom in a cantilevered fashion to a free distal end  2304   a . Each elongated support post  2308  is attached at its distal end  2308   a , proximal end  2308   b  and middle  2308   c  to some of cells  2306 . Each support strut  2304  is free to move independently and to contour to the anatomy/physiology of the patient&#39;s aortic root. Since the support struts  2304  can be independently contoured to the anatomy, the distal end  2304   a  of each support strut  2304  can anchor in the aorta, above and/or below the sinotubular junction, around the free edge of the valve leaflets. Stent  2300  does not have distal cells. The absence of distal cells provides stent  2300  with greater post flexibility while still providing additional anchoring capabilities. Although  FIG. 22  shows support struts  2304  with a substantially straight configuration, this preferably is prior to final processing to provide the support struts with desired configurations. 
       FIGS. 23A and 23B  show some different configurations which cantilevered support struts  2304  may have. In the interest of simplicity,  FIGS. 23A and 23B  show the valve portion of the stent (e.g., proximal cells and elongated support posts) as a ring. This ring, however, does not really exist and merely illustrates that the support struts  2304  are held in place by other structures of the stent. In the embodiments shown in  FIGS. 23A and 23B , each support strut  2304  has a proximal end  2304   b  attached to proximal cell or an elongated support post (not shown) and a free distal end  2304   a . However, the distal ends  2304   a  of the support struts  2304  of these two embodiments have different configurations. 
     In the embodiment shown in  FIG. 23A , each support strut  2304  has a curved profile  2304   c  near its distal end  2304   a . The curved profiles  2304   c  initially bend outwardly or away from one another to anchor just distally of the sinotubular junction, but, closer to the distal ends  2304   a , the curved profiles  2304   c  bend inwardly or toward one another to reduce the possibility of aortic perforation or dissection by a support strut  2304 . 
     In  FIG. 23B , the stent includes support struts  2304  designed to seat around and/or just proximal to the sinotubular junction in the distal portion of the sinus. The support struts  2304  of the embodiment shown in  FIG. 23B  also have a curved profile  2304   d  near their distal ends  2304   a . This curved profile  2304   d  initially bends outwardly (or away from one another) and then proximally, thereby forming a hook, but, closer to the distal ends  2304   a , the curved profile  2304   d  bends distally. 
     A single stent  2300  may have the support struts shown in both  FIGS. 23A and 23B . Additionally, support struts  2304  may be used to latch onto features of previously implanted prosthetic valves, such as the spacer  770  shown in  FIGS. 8A and 8B . 
       FIG. 24  shows how the curved profile or anchoring feature  2304   c  of the support strut  2304  shown in  FIG. 23A  can be contoured to fasten above the stenotic leaflets or prosthetic valve  6  and below the sinotubular junction  4 . The curved profile  2304   c  of stent  2300  bluntly anchors to the aortic root to minimize migration. The remaining part of stent  2300  is anchored to a stenotic leaflet or prosthetic valve  6  and the annulus  2  of the aortic root. In addition, a fabric and/or tissue layer T may be attached to the interior of the stent  2300 , and a leaflet L may be attached to the tissue layer. The tissue layer T and leaflet L function as a valve to prevent backflow, as indicated by arrow F, when in the closed condition. 
       FIG. 25  shows how the curved profile  2304   d  of the support strut  2304  shown in  FIG. 23B  can be contoured to fasten above the stenotic leaflets or prosthetic valve  6  and below the sinotubular junction  4 . The curved profile or anchoring feature  2304   d  of stent  2300  anchors to the aortic root, thereby minimizing migration. As discussed above, a fabric or tissue layer T may be attached to the interior of stent  2300 , and a leaflet L may be attached to the tissue layer. The tissue layer T and the leaflet L act as a valve, preventing or least hindering backflow when in the closed condition, as indicated by arrow F. 
     Leaflet Reinforcement to Reduce Stress at Commissures 
     As the flexibility of the post and/or stent frame decreases (due to, for example, more connections along the support post), it may be necessary to distribute the greater stress at the commissures. The stress may be distributed to the commissures by, for example, reinforcements at the support posts. The reinforcements may also reduce the possibility of the leaflets hitting the stent frame. 
       FIG. 26  is a top view of a stent  2500  having a support post  2508  and secondary posts  2510  used for reinforcement. Secondary posts  2510  may be made from a material, such as stainless steel, which is more resistant to fatigue than Nitinol, from which stent  2500  may be made. Support post  2508  has at least two eyelets or apertures  2532 . Each secondary post  2512  has two eyelets  2512  oriented substantially perpendicular to each other in a crossing pattern. Secondary posts  2510  may be attached to support post  2508  using sutures S. One suture S passes through one eyelet  2532  of support post  2508  and through a corresponding eyelet  2512  of one secondary post  2510 , thereby attaching that secondary post to the support post. Another suture S passes through another eyelet  2532  of support post  2508  and through a corresponding eyelet  2512  of the other secondary post  2510 , thereby attaching that secondary post to the support post. Thus, both secondary posts  2510  are attached to support post  2508  with sutures S. 
     The secondary posts  2510  may also be attached to each other by passing a suture S through an eyelet  2512  of one secondary post  2510  and another eyelet  2512  of the other secondary post  2510 . In the embodiment shown in  FIG. 26 , the secondary posts  2510  sandwich the tissue of the two leaflets K. Leaflets K may be tissue, but this design lends itself to polymer dip coating onto secondary posts  2510  before attaching the resulting subassembly onto strut  2500  via large eyelets at the top and bottom of the support posts. 
     The foregoing reinforcement technique may also be used with stents which do not have support posts.  FIG. 27  shows one-third of the side of a stent  2600  that does not have support posts. Stent  2600  includes at least two rows of cells  2606 , and may include a first row  2622  and a second row  2624  of cells  2606 . Cell connections  2630  interconnect adjacent cells  2606  in the same row. Bars  2650  couple cells  2606  positioned in adjacent rows and may be formed of a substantially rigid material. A fabric or tissue cuff  2690  may be attached around the interior or exterior of stent  2600  and cover almost the entirety of the cells  2606 , leaving only open areas  2692  for the coronary arteries. Open areas  2692  expose only distal portions  2606   a  of some cells  2606 . Secondary posts  2610  may be sutured to the cuff  2690 , to bars  2650  and/or to the segments forming cells  2606 . 
       FIGS. 28A-28F  illustrate different reinforcements or secondary posts  2710 ,  2720 , and  2730 , which may be attached as rigid structures to any suitable stent as shown in  FIG. 26 . All secondary posts  2710 ,  2720 ,  2730  may have eyelets  2732  along their length for receiving sutures. Eyelets  2732  may also be positioned on multiple sides of each secondary post  2710 ,  2720 ,  2730  to allow for multidirectional suturing. The eyelet  2732  closest to the distal end  2702  of the secondary post  2710 ,  2720 , or  2730  may not be spaced apart from the adjacent eyelet  2732  as much as the other eyelets  2732  are spaced apart from each other. Further, the edges of the eyelets  2732  and the edges of the secondary posts  2710 ,  2720  and  2730  are preferably rounded to eliminate suture and leaflet abrasion. 
     Each secondary post  2710 ,  2720 ,  2730  may have a different shape or cross-section. For example, secondary post  2710  has a substantially circular cross-section, as seen in  FIGS. 28A and 28B . Secondary post  2720  may have a substantially rectangular shape or cross-section, as seen in  FIGS. 28C and 28D . Secondary post  2730  may have a triangular shape or cross-section, as seen in  FIGS. 28E and 28F . 
       FIGS. 29A and 29B  show reinforcements or secondary posts  2810  and  2820  adapted to be attached to a stent as shown in  FIG. 26 . Posts  2810  and  2820  have a hollow core and may feature a smoothly curved or cylindrical shape. Post  2810  has eyelets  2812  along its length. Eyelets  2812  may have an oblong or elliptical shape. Post  2820  may have two different kinds of eyelets  2822  and  2824 . Eyelets  2822  are in the form of alternating through-holes with a substantially oblong or elliptical shape. A partial eyelet  2824  located near the distal end  2820   a  of post  2820  has a substantially circular shape to hold a suture. 
       FIG. 30  shows a reinforcement  2900  that may be attached to the stent, as shown in  FIG. 26 , in lieu of the secondary posts. Reinforcement  2900  includes a first column  2910 , a second column  2912 , and an arch  2914  interconnecting the first and second columns. First column  2910  has a first end  2910   a  and a second end  2910   b . Second column  2912  has a first end  2912   a  and a second end  2912   b . Arch  2914  connects the first end  2910   a  of the first column  2910  to the first end  2912   a  of the second column  2912  and sets the width W between the first and second columns. The first column  2910  and the second column  2912  define a gap  2916  between them. Gap  2916  has a width W and is dimensioned to receive the valve leaflets K ( FIG. 26 ). With leaflets K sandwiched between the first column  2910  and the second column  2912 , arch  2914  absorbs the opening load of the leaflets instead of the sutures since columns  2910  and  2912  may want to pull apart. 
       FIG. 31A  shows a pliable reinforcement  3000  folded over a free edge of a leaflet and sutured to itself and to the stent frame or post. In some embodiments, reinforcement  3000  may be attached to a free edge of a leaflet at the commissure  9 , but away from the belly region  8  of the valve leaflet, as shown in  FIG. 31A . Alternatively, reinforcement  3000  may be attached to the entire sutured edge of the leaflet, which would result in the shape seen in  FIG. 31B . 
     Reinforcement  3000  includes a securing section  3004  and an optional flap  3002  for additional suturing and securement to a support post. As seen in  FIG. 31A , reinforcement  3000  is folded onto itself along a folding line F L . In particular, a folding area  3008  is folded over a securing section  3004  as indicated by arrow M to form a substantially V-shaped structure. At this point, reinforcement  3000  partially wraps a free edge of a valve leaflet. Sutures may be used to secure reinforcement  3000  in a folded condition. One or more sutures may pass over the free edge of the leaflet outside of reinforcement  3000  to secure the reinforcement  3000  in a folded condition. In such case, the suture should be more than  1   mm  from the free edge of the leaflet. For thicker leaflets, it may be necessary to enlarge the folding area  3008  to allow the reinforcement  3000  to wrap over the free edge of the leaflet. Folding area  3008  defines cutout  3010  which may be substantially V-shaped for straddling the leaflets. 
     Securing section  3004  has a base  3006  aligned with an eyelet at the proximal end of a support post, and an angled side  3014  oriented at an oblique angle relative to folding line F L  and base  3006 . Angled side  3014  of securing section  3004  biases the valve opening away from a support post. For instance, angled side  3014  may bias the valve opening about 3 mm away from a support post. 
     As discussed above, reinforcement  3000  may optionally include a flap  3002  which provides additional securement to the support post. For example, additional sutures may attach the flap  3002  to the support post. Flap  3002  may also protect moving leaflets from knots securing the reinforcement  3000  to the support post. The distance between the edge of flap  3002  and angled side  3014  along folding line F L  should be sufficient to keep the leaflets from opening against the stent. Reinforcement  3000  may be attached to a stent S T  as shown in  FIG. 33A . Regardless of the manner in which stent S T  is deformed, as shown in  FIGS. 33B and 33C , there is a low likelihood of the valve leaflet abrading against the stent. 
     Although the invention herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims. 
     It will be appreciated that the various dependent claims and the features set forth therein can be combined in different ways than presented in the initial claims. It will also be appreciated that the features described in connection with individual embodiments may be shared with others of the described embodiments.