Abstract:
A stent for use in a prosthetic heart valve has a plurality of expandable and collapsible closed cells, a portion of which form an annulus section adapted for placement within the annulus of the native heart valve. Anchor features of the stent residing within at least some closed cells are adapted to engage tissue of the heart, including native valve leaflets, the sinotubular junction, or another implanted device when the prosthetic valve is implanted in the heart. The anchor features may help to retain the prosthetic valve in position, without interfering with the opening and closing of the valve leaflets. Furthermore, the anchor features may be configured to allow the stent to be resheathed into a delivery device after the portion of the stent with the anchor feature has expanded out of the delivery device.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application claims the benefit of the filing date of U.S. Provisional Patent Application No. 61/766,783 filed Feb. 20, 2013, the disclosure of which is hereby incorporated by reference herein. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention is directed to prosthetic heart valves for replacement of native heart valves, to stents for use in such prosthetic heart valves, and to methods of treating patients with such prosthetic heart valves. 
       BACKGROUND OF THE INVENTION 
       [0003]    Certain prosthetic heart valves incorporate an expandable stent body and valve elements such as prosthetic valve leaflets mounted to the stent body. Valves of this type may be implanted in the heart by advancing the valve into the body of the patient with the stent body in a collapsed condition in which the stent body has a relatively small diameter. Once the valve is positioned at the desired implantation site, the stent body is brought to an expanded condition in which the stent body bears on the surrounding native tissue and holds the valve in place. The valve acts as a functional replacement for the diseased native valve. Thus, the valve elements inside the stent body permit blood flow in the antegrade direction but substantially block flow in the opposite, retrograde direction. For example, a prosthetic valve may be advanced to a site within a diseased native aortic valve percutaneously through the arterial system and into the aorta to the native aortic valve. In a transapical placement, a prosthetic valve may be advanced through an incision in the apex of the heart and through the left ventricle to the native aortic valve. Other approaches through other access sites can be used. Once the prosthetic valve is in place, it permits flow from the left ventricle into the aorta when the left ventricle contracts during systole, but substantially blocks retrograde flow from the aorta into the left ventricle during diastole. 
         [0004]    There are significant challenges in the design of an expandable stent body and valve. For example, the stent body desirably can be collapsed to a relatively small diameter to facilitate advancement into the body. However, the stent body must be capable of expanding to an operative, expanded condition in which the stent body securely engages the surrounding native tissues to hold the valve in place. The valve should form a good seal with the surrounding native tissues to prevent leakage around the outside of the prosthetic valve, commonly referred to as perivalvular leakage. The stent body, in its expanded, operative condition, desirably does not apply excessive forces to the annulus of the native valve. Excessive forces on the annulus of the native aortic valve can disrupt the electrical conduction system of the heart and also can impair the functioning of the mitral valve. These issues are complicated by the fact that the native valve leaflets ordinarily are left in place when an expandable prosthetic valve is implanted. The diseased native valve leaflets and other diseased tissues may present an implantation site which is irregular. For example, patients with calcified or stenotic aortic valves may not be treated well with the current collapsible valve designs, and may encounter problems such as (1) perivalvular leakage (PV leak), (2) valve migration, (3) mitral valve impingement, (4) conduction system disruption, etc., all of which can lead to adverse clinical outcomes. To reduce these adverse events, the optimal valve would seal and anchor adequately without the need for excessive radial force that could harm nearby anatomy and physiology. 
         [0005]    As the patient population becomes younger with less tissue calcification, the use range of prosthetic heart valves expands to larger sizes and thus greater forces. Additionally, younger patients may be more likely to require bicuspid valve replacements and may have larger, more diseased, and more elliptically shaped aortic valves. Stent designs without an aortic section, as well as stents that need to anchor in the aorta, will need to anchor and support post deflection of the valve as it pulls inward from pressure closing the valve. If a valve is not designed to function in these environments, it may result in several types of adverse events described above since distortion of the valve can result in the loss of valve coaptation, loss of valve apposition, and overall higher stresses. In these environments, anchoring will become even more important to ensure valve coaptation in most all configurations with a reduction of high stresses in the critical areas of the prosthesis while maintaining valve apposition with native anatomy. 
         [0006]    Numerous prosthetic valve and stent body designs have been proposed. However, despite all of the attention devoted to such designs, still further improvements would be desirable. 
       BRIEF SUMMARY OF THE INVENTION 
       [0007]    A stent for use with a prosthetic heart valve for replacement of a native heart valve comprises an expandable stent body having a collapsed configuration and an expanded configuration. The stent body includes a plurality of closed cells and at least one anchor feature formed integrally with the stent. Each anchor feature resides within a closed cell of the stent and has an engagement portion adapted to engage a surface in a heart. 
         [0008]    The engagement portion can be configured to engage any combination of a leaflet of the native heart valve, a portion of the sinotubular junction in the heart, and a portion of another device already implanted in the heart. 
         [0009]    The stent is arranged in the collapsed configuration when received within a delivery sheath overlying the stent in a sheathed position, and the stent is arranged in the expanded configuration when the sheath is not overlying the stent in an unsheathed position. The anchor feature is oriented at an oblique angle to a longitudinal axis of the delivery sheath so that the stent may be resheathed when the sheath is in a position between the sheathed position and the unsheathed position. The anchor feature slopes radially outwardly from the stent when the stent is in the expanded configuration, and the anchor feature extends axially when the stent is in the collapsed configuration. 
         [0010]    The engagement portion of the anchor feature can include an anchor tip with a first end connected to the stent, a second end connected to the stent, and an intermediate portion between the first and second ends. The intermediate portion of the anchor tip can include a single piece that is acute or blunted. The intermediate portion of the anchor tip can alternately include multiple separate pieces. These separate pieces can include different configurations, such as blunted ends. 
         [0011]    The stent can include a first annular row of cells connected to a second annular row of cells by at least one connector. The anchor feature is connected to the connector. The connector can be a commissure attachment feature. The anchor features can be connected on one or both sides to the connectors or commissure attachment features. The anchor features can be connected to the stent at a connector, proximal of the connector, or distally of the connector. Two or more anchor features can be connected on each side to the same connector or commissure attachment features for a nested anchor feature configuration. 
         [0012]    The engagement portion of the anchor feature can flare distally from the stent or proximally from the stent. A stent can include two anchor features with engagement portions, with the engagement portion of one anchor feature flaring distally from the stent and the engagement portion of one anchor feature flaring proximally from the stent. 
         [0013]    The latch members can include a variety of materials. These include animal tissues, such as porcine, ovine and bovine pericardium or porcine sub-mucosa. These materials also include fabrics, such as knit or woven polyester and non-woven fabrics. These materials can further include collagen and water-absorbing polymers such as poly(acrylic acid). The materials can still further include biocompatible adhesives such as epoxy amines. Still further, these materials can include bio-absorbable materials such as polyglactin, copolymers of lactide and caprolactone, and polylactides. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIG. 1  is a schematic sectional view of the aortic root tissue in a typical human heart; 
           [0015]      FIG. 2  is a perspective view of a prior art stent in an expanded configuration; 
           [0016]      FIG. 3  is an enlarged elevational view of a portion of a stent with anchor features residing within closed cells of the stent; 
           [0017]      FIG. 4  is a schematic of a stent, according to an embodiment of the invention, deployed in a human heart. 
           [0018]      FIG. 5A  is a highly schematic fragmentary side view depicting a portion of a stent incorporating an anchor feature according to an embodiment of the invention; 
           [0019]      FIGS. 5B-5F  are highly schematic fragmentary side views depicting portions of stents incorporating an anchor feature engaged with a heart or with an implanted device within a heart according to embodiments of the invention; 
           [0020]      FIGS. 6A-6E  are highly schematic fragmentary views depicting portions of stents according to further embodiments of the invention; and 
           [0021]      FIG. 7  is a fragmentary elevational view of a portion of a stent according to an embodiment of the invention with a portion of an attached valve leaflet, and with certain features omitted for clarity of illustration. 
       
    
    
     DETAILED DESCRIPTION 
       [0022]    While the present invention will be described more fully hereinafter with reference to the accompanying drawings, in which particular embodiments of stents and methods of delivery are shown, it is to be understood at the outset that persons skilled in the art may modify the invention herein described while achieving the functions and results of this invention. Accordingly, the descriptions that follow are to be understood as illustrative and exemplary of specific structures, aspects and features within the broad scope of the present invention and not as limiting of such broad scope. Like numbers refer to similar features of like elements throughout. 
         [0023]      FIG. 1  is a simplified view of the geometry or anatomy of the aortic root tissue in a typical human heart. The left ventricular outflow tract (LVOT)  1  communicates with the ascending aorta  5  through the annulus  2  of the native aortic valve and the Valsalva sinus  3 . The sinus joins the aorta at the sinotubular junction (STJ)  4 . The native aortic valve typically includes three native valve leaflets  6 , of which only two are visible in  FIG. 1 . As the left ventricle contracts during systole, blood is forced from the LVOT  1  through the native valve and sinus and into the aorta  5 , moving generally in the downstream or antegrade flow direction indicated by arrow D. In a healthy individual, the native valve leaflets  6  open away from one another and move to the position schematically shown in broken lines at  6 ′ to permit flow in this direction. During diastole, when the ventricle is not contracting, the native valve leaflets  6  move back to the position indicated in solid lines in  FIG. 1 , where they abut one another or “coapt” so as to substantially block flow in the upstream or retrograde direction, opposite to arrow D. The direction “distal” as used herein with reference to a feature of the native circulatory system refers to the direction of antegrade flow, i.e., the predominant direction of blood flow through such feature, as indicated by arrow D. The direction “proximal” as used herein with reference to a feature of the native circulatory system is the opposite direction. 
         [0024]    The parameters identified in  FIG. 1  are as follows: DO=orifice diameter, i.e., the interior diameter of native annulus  2 ; DA=the diameter of the aorta just distal to the sinus; DB=maximum projected sinus diameter (this sinus is sometimes known as the Valsalva sinus); LA=length of the sinus, i.e., the dimension in the distal direction from the annulus  2  to the sinotubular junction  4 ; and LB=distance in the distal direction between DO and DB. 
         [0025]    The leaflets  6  have distal edges  9  remote from the annulus  2 . Each native leaflet  6  has a surface  7 , referred to herein as the “interior” surface of the leaflet, facing generally towards the other leaflets. Each native leaflet  6  also has a surface  8 , referred to herein as the “exterior” surface of the leaflet, facing outwardly, away from the other leaflets and toward the wall of the sinus  3 . The cross-sectional shape of such a native valve varies somewhat from individual to individual, and this variation can be increased by various types of disease. For example, disease can reshape the cross-section of a patient&#39;s valve to a circular, triangular, or elliptical shape, depending on the disease state. 
         [0026]      FIG. 2  shows a prior art collapsible stent for use with a prosthetic heart valve. Examples of collapsible prosthetic heart valves are described in U.S. Application Publication No. 2012/0053681 and U.S. Design Pat. No. D660,967, the entire contents of which are hereby incorporated by reference herein. An expandable stent body  10  is formed as a unitary structure as, for example, by laser cutting or etching a tube of a superelastic metal alloy such as a nickel-titanium alloy of the type sold under the designation NITINOL. Such a unitary structure can also be referred to as a “non-woven” structure, in that it is not formed by weaving or winding one or more filaments. In its fully-expanded, unconstrained configuration, the illustrated embodiment of stent body  10  includes an annulus section  12 , an aorta section  20  and support struts  30  extending between the annulus section and the aorta section. The annulus section  12  in the expanded configuration is generally in the form of a cylindrical tube having a central axis  14 , whereas aorta section  20  is generally in the form of a hoop coaxial with the annulus section. The annulus section  12  can be in the form of other shapes, such as elliptical or triangular, depending on the patient&#39;s anatomy. Not all embodiments of stent body  10  include an aorta section  20 . For example, stents for aortic valves, as well as stents for bicuspid and/or mitral valves may not include an aorta section  20 . 
         [0027]    The stent body  10  is adapted for installation in the body of a patient with the annulus section  12  adjacent the annulus  2  and with the aorta section  20  adjacent the sinotubular junction  4  and aorta  5 . Thus, when the valve incorporating the stent body  10  is placed in the patient, the aorta section  20  will be disposed distal to the annulus section  12  in the frame of reference of the patient&#39;s circulatory system. Accordingly, as used with reference to features of the stent body and valve, the direction D ( FIGS. 1 and 2 ) along axis  14  from the annulus section  12  towards the aorta section  20  is referred to as the distal direction, and the opposite direction is taken as the proximal direction. Stated another way, the distal direction along the stent body is the direction from the end of the stent which is intended for disposition at a proximal location in the frame of reference of the circulatory system to the end of the stent which is intended for disposition at a more distal location in the frame of reference of the circulatory system. Also, the outward direction as used with reference to the stent body is the direction away from the proximal-to-distal axis  14 . The directions toward and away from axis  14  are also referred to herein as the “radial” directions. As used with reference to features of the stent body, the “circumferential” directions are the directions around axis  14 . 
         [0028]    As best seen in  FIG. 2 , the annulus section  12  includes numerous cells defined by interconnecting struts  16  which join one another at intersection points. These cells are disposed in a proximal row  70  and distal row  60 , each such row extending circumferentially around the proximal-to-distal axis  14  so that the cells cooperatively form a generally cylindrical wall. In the expanded condition, the struts  16  of each cell form a generally diamond-shaped structure. In the unexpanded or collapsed configuration, the struts  16  of each cell extend substantially proximally and distally, so that each cell is collapsed in the circumferential direction. The intersection points  18  between the struts  16  on the distal side of distal row  60  define the distal edge of the annulus section  12 . These intersection points are referred to herein as the distal crests  18  of the annulus section  12 . 
         [0029]    The annulus section  12  also includes a set of commissure features  40  formed integrally with the remainder of the stent body. The commissure features  40  are found at three locations spaced equally around the circumference of the annulus section. Each commissure feature  40  may include one or more eyelets  120  therein. Three prosthetic valve leaflets (not shown) are sutured to the commissure features  40 , so that the leaflets are disposed within the annulus section  12  of the stent body. The sutures (not shown) may extend through eyelets  120 . A lining or “cuff” (not shown) may be provided on the interior surface, exterior surface or both of the annulus section  12 , over all or part of the axial extent of the annulus section  12 . The leaflets and cuff may be formed from conventional biocompatible materials such as synthetic polymers and animal tissues such as pericardial tissues. Stent body  10  can include more than three or fewer than three commissure features  40 , for example to accommodate more or fewer than three valve leaflets. 
         [0030]    Aorta section  20  is formed by a set of struts  16  which define a row of half-cells. The configuration of the struts  16  in aorta section  20  may be varied from that shown. For example, the aorta section  20  may include one or more rows of full cells such as those constituting the annulus section  12 . Also, the support struts  16  may have a branched configuration, so that the distal end of each support strut is connected to plural points in the aorta section  20 . More or fewer support struts  16  may be provided. 
         [0031]    In one embodiment of the invention, best seen in  FIG. 3 , the stent body  10  also includes anchor features in the nature of latch members  50 . The latch members  50  are equally spaced from one another in the circumferential direction and reside within adjacent closed cells  80 . More specifically, the latch members  50  reside within the space of the distal crests  18  and commissure features  40  of the annulus section  12  and above the level of the leaflet belly  90  of the valve leaflet. The locations of the latch members  50  allow the stent body  10  to maintain a similar or identical crimp profile as the stent body  10  would have in the absence of the latch members  50 . Alternatively, the locations of the latch members  50  can be higher than the free edge of the prosthetic leaflet (not shown) to avoid contact between the prosthetic leaflet and the latch members  50  during crimping or other use. Although the highly schematic embodiment illustrated in  FIG. 3  has three latch members  50  (two of which can be seen in the highly schematic view) equally distanced around the circumference of the stent body  10 , the number and location of latch members  50  is a matter of design choice. For example, alternate embodiments of a stent could include a single latch member  50  or two or more latch members. The latch members  50  could also be spaced unequally around the circumference of the stent body  10 . For example, for a stent to be used with a bicuspid valve, it may be preferable to include only two latch members  50  (i.e., one latch member per leaflet). Depending on the specific anatomy of the heart valve and native leaflets into which the stent will be implanted, spacing between latch members  50  other than equal spacing may be preferred. Further, the number of latch members  50  does not necessarily need to correspond to the number of leaflets in the valve into which the stent is being deployed. For example, it may only be desired to utilize two latch members  50  in a tricuspid valve. In this scenario, two valve leaflets would be engaged by latch members with the remaining leaflet unengaged by any latch member. Additionally, latch members  50  do not need to reside in adjacent cells  80 . Rather, one or more empty cells  80  (i.e. cells without latch members  50 ) could reside between cells with latch members. 
         [0032]    The latch members  50  are connected on each side to either a distal crest  18  or commissure feature  40 . Each latch member  50  includes a pair of connection struts  54 . Similar to the remainder of stent body  10 , the connection struts  54  are elongated solid members formed of a superelastic metal alloy such as a nickel-titanium alloy and can be of any cross sectional shape such as circular or oval. The connection struts  54  can be formed of other materials, or additional materials, such as polymers, bio-absorbable materials, drug eluting materials, or fabric coatings to enhance tissues in-growth. These and other materials are discussed more completely below. Each connection strut  54  connects to either a distal crest  18  or a commissure feature  40 . Each latch member  50  also includes a generally U- or V-shaped intermediate global portion  57  joined between connection struts  54 . The latch members  50 , including connection struts and intermediate global portion  57 , can be formed integrally with the remainder of stent body  10 . For example, a single tube of a superelastic metal alloy can be laser cut or etched, forming the entire stent body  10 , including the latch members  50 , from the original single tube. Alternately, the latch members  50  can be formed separately from the stent body  10  and can later be connected to the stent body, for example by welding, suturing, gluing or other methods. 
         [0033]    In the expanded configuration of the stent body  10 , U-shaped portion  57  slopes radially outwardly so as to be disposed radially outward of the distal end of annulus section  12 . The U-shaped portion  57  lies at the distal end of the annulus section  12 . 
         [0034]    The structure of the latch member  50  allows it to collapse in the radial direction. Thus, in the collapsed configuration of the stent body  10 , the connection struts  54  and U-shaped portion  57  extend substantially axially. 
         [0035]    In operation, the valve is brought to a collapsed condition and mounted on a delivery device (not shown) such as an elongated probe having a sheath adapted to retain the stent body in the collapsed condition, and having provisions for moving the sheath relative to the stent body to release the stent body from the sheath. The delivery device is advanced into the patient&#39;s body until the valve is aligned with the native aortic valve, with the annulus section  12  adjacent the annulus  2  of the aorta. The valve is released from the sheath and stent body  10  expands under its own resilience. The resilient expansion may occur solely as a result of release of mechanical constraint of the stent body, or may include expansion resulting from the effects of temperature change on the material of the stent body. Preferably, the entire expansion of the stent body from its collapsed condition to its expanded, operative condition is brought about by the stent body itself. Stated another way, the stent body desirably is fully self-expanding and does not require a balloon or mechanical movement device to bring about any part of the expansion. Referring to  FIGS. 1 and 4 , the annulus section  12  engages the annulus  2  of the native aortic valve, and also engages the interior surfaces  7  of the native valve leaflets  6 . Each latch member  50  engages one of the native valve leaflets  6  at or near the distal edge  9  of such native leaflet. The U-shaped portion  57  (not labeled in  FIG. 4 ) of each latch member  50  upon expansion bears on the exterior surface  8  of the leaflet  6  at or near the distal edge. In other words, the native valve leaflets  6  are clamped between the latch members  50  and the remainder of the stent body  10 . It should be appreciated that the leaflets  6  typically have irregular shapes. For example, the leaflets  6  may be nodular or rough. The aorta section  20  engages the native anatomy at or near the sinotubular junction  4 . 
         [0036]    Although the stent reaches an expanded configuration, it typically does not reach its fully-expanded, unconstrained configuration. Thus, the resilience of the stent body normally causes the aortic section  20  to bear on the sinotubular junction  4  and also causes the annulus section  12  to bear on the annulus  2  and on the interior surfaces of the leaflets. The prosthetic valve leaflets open to allow distal or antegrade flow of blood during systole, and close to block proximal or retrograde flow during diastole. The engagement of the latch members  50  with the native valve leaflets  6  helps to maintain the stent body  10 , and hence the valve, in position. In particular, such engagement helps to prevent movement of the valve in the proximal or retrograde direction. Therefore, the resilient engagement of the annulus section  12  and aorta section  20  with the native anatomy need not provide all of the force necessary to resist such movement. Moreover, the engagement of the latch members  50  with the native valve leaflets  6  tends to bias the native leaflets  6  inwardly toward the annulus section  12  of the stent body  10 . This tends to improve sealing between the native leaflets  6  and the stent body  10  and helps to resist perivalvular leakage or retrograde flow around the outside of the stent body. The latch members  50  facilitate satisfactory valve action without the need for extremely high radial forces between the annulus section  12  of the stent body  10  and the native valve anatomy. This is advantageous, inasmuch as excessive radial forces on the native anatomy may disrupt the electrical conduction system of the heart and or distort the mitral valve, which is disposed near the annulus  2  of the aortic valve. 
         [0037]    The latch members  50  may be altered in a variety of ways to further reduce PV leakage, especially near points of contact between the native leaflets  6  and the latch members  50 . The latch members  50  can include materials such as animal tissues as, for example, porcine, ovine and bovine pericardium, porcine sub-mucosa, and synthetic fabrics such as knit or woven polyester, and non-woven fabrics. Collagen-impregnated fabrics may be used. Also, bio-absorbable materials such as polyglactin, copolymers of lactide and caprolactone, and polylactides can be used. 
         [0038]    Latch members  50  covered in fabrics, for example, can promote tissue in-growth. As tissue grows into the fabric of the latch members  50 , a better seal is created at the sites of the latch members  50 , reducing the likelihood of PV leakage. Other alternatives to fabric that produce tissue in-growth at the site of the latch members  50  can also reduce PV leakage. 
         [0039]    Latch members  50  alternatively can include a hygroscopic or sponge-like material that collapses easily and fills to a larger volume when the stent is expanded after implantation. This hygroscopic material, for example, can be a collagen foam or sponge similar to the material commercially available under the trademark Angioseal which is used to plug arteries, and to the similar material currently used for embolic protection. 
         [0040]    In a further embodiment, material on the latch members  50  can be impregnated with a water-absorbing polymer. When allowed to expand as a result of implantation in a patient and consequent absorption of water from the patient&#39;s tissue and/or blood, these materials can fill any gaps between the latch members  50  and the native tissue to reduce PV leakage. 
         [0041]    In still further embodiments, mechanical means, such as small coil or torsion springs, can be used as alternate or additional means to fill any gaps between the stent body  10  and the native tissue to reduce PV leakage. The mechanical means can be formed integrally with the stent body  10 . For example, springs formed integrally with the stent body can project outwardly from the stent body  10  in the expanded condition, biasing the cuff outwardly toward the native tissue. Other mechanical means include coil springs that have a spring axis extending generally in a radially outward direction from the stent body  10 . Such small coils and torsion springs are described more fully in U.S. Patent Application Publication No. 2011/0098802, the entire contents of which are hereby incorporated by reference herein. 
         [0042]    The latch members  50  of the stent body  10  can be made to be bonded to native tissues as, for example, to native leaflets  6  during or after implantation. For example, a porcine pericardial strip on the latch members  50  can be used to bond a tissues-to-tissue joint. The bonding can be achieved, for example, by lower power lasers that minimize tissue vaporization, yet bond tissue together. Biocompatible adhesives, such as epoxy amines, have been applied in certain medical applications. Such adhesives can be applied around the perimeter of the latch members  50  to bond to native leaflets during or after implantation. These and other variants, as applied to a cuff of a prosthetic valve rather than latch members of a stent body, are described more fully in U.S. Patent Application Publication No. 2011/0098802. 
         [0043]    The resilience of the latch members  50  allows them to attach to both calcified and non-calcified leaflets  6 . For example, if a leaflet  6  is thick, nodular or both, the U-shaped portion  57  of the latch member  50  can be bent outwardly by the leaflet  6 . In this condition, the latch member  50  tends to push the leaflet  6  inwardly against the annulus section  12  of the stent body  10 . The systolic blood pressure tends to force the native valve leaflets  6  into engagement with the annulus section  12  of the stent body. By retaining the native leaflets  6  in position, the latch members  50  facilitate this action. 
         [0044]    The prosthetic valve allows antegrade flow into the aorta, and also allows flow into the Valsalva sinus and thus into the coronary arteries C which communicate with the sinus. Engagement of the native valve leaflets  6  by the latch members  50  may help to assure that the native valve leaflets  6  do not block the openings of the coronary arteries. 
         [0045]    Various embodiments of latch members  50  can be used in conjunction with a stent having a closed cell design.  FIG. 5A  shows a side view of an embodiment of a latch member  50  along with the portion of the stent body  10  on which the latch member  50  is located. For simplicity of illustration, only a portion of the stent body  10  is depicted. The latch member  50  generally flares radially outward from the stent body  10  and also extends proximally from the points of attachment of the stent body  10  between distal crest  18  and commissure feature  40  (not visible in  FIG. 5A ). The location of the latch member  50  within the space between the distal crests  18  allows for the latch member  50  to be compressed radially inward in the direction of the arrow R shown in  FIG. 5A . Additionally, the direction in which latch member  50  flares allows for the resheathability of the stent body  10 . In the event that the proximal end of stent body  10  emerges from a deployment device (not shown) before the distal end of the stent body, the proximal end of the stent body will expand first while the distal end of the stent body remains within the deployment device. If repositioning becomes necessary, the direction in which latch member  50  flares will not hinder stent body  10  from being resheathed into the deployment device. 
         [0046]      FIG. 5B  shows the stent body  10  illustrated in  FIG. 5A  after it has been implanted into a patient. In this embodiment, the flared portion of latch member  50  engages a native leaflet  6  of the native heart valve. Referring now to  FIGS. 5C-5F , there are shown side views of different embodiments of stent body  10  with latch members  50  implanted in the heart tissue of a patient.  FIG. 5C  shows an embodiment of stent body  10  with a latch member  50  that flares in substantially the opposite direction to that shown in  FIG. 5B . In this embodiment, the latch member  50  flares distally from the stent body  10 . This configuration allows the latch member  50  to primarily engage the tissue at the sinotubular junction  4 . Engagement of the sinotubular junction  4  aids the stent in resisting migration in the distal direction. Additionally, the direction in which the latch member  50  flares allows resheathing of the stent if the distal end of stent body  10  is deployed from the delivery device (not shown) before the proximal end. 
         [0047]      FIG. 5D  shows another embodiment of stent body  10  with a pair of latch members  50 ,  50 ′. The distally flaring latch member  50  engages the sinotubular junction  4 , while the proximally flaring latch member  50 ′ simultaneously engages a leaflet  6  of the native heart valve. This configuration allows for added anchoring capability from the use of multiple latch members. 
         [0048]      FIGS. 5E and 5F  each show embodiments of stent body  10  with latch members  50  that do not primarily engage native heart tissue. In the embodiments shown in  FIGS. 5E and 5F , the latch members  50  are similar to that shown in  FIG. 5B  in that the latch members flare outwardly in a proximal direction. However, in the embodiment shown in  FIG. 5E , the latch member engages a surgical valve  200  that has already been implanted in the patient rather than a native heart structure. In the embodiment shown in  FIG. 5F , the latch member  50  engages stent features of another transcatheter aortic valve implant  250 , such as between open cells  252  of the second implant. Latch members  50  can be designed to correspondingly mate to a device already implanted in the heart, such as surgical valve  200  or stent  250 , depending on the specific features of the device already implanted in the heart. For example, if the surgical valve  200  is thicker than an average native leaflet, the latch member  50  could be designed to extend initially more radially outward to ensure that the latch member sufficiently engages or “hooks” the surgical valve, as seen in  FIG. 5E . Similarly, for latch members  50  to engage cells of another stent  250 , such as that shown in  FIG. 5F , the latch members may extend farther or less far in the proximal or distal directions, may flare distally or proximally, or may extend at a more or less acute angle. The specific design of the latch members  50  will depend on the corresponding features of the already-implanted device. Also, as described above, the latch members  50  can be covered with any of a variety of materials. For latch members  50  that primarily engage other implanted devices, especially metal devices, it may be desirable to provide a fabric or other coating on the latch members to avoid metal-on-metal contact. In the absence of a coating on the latch members  50 , the metal-on-metal contact could cause, for example, fretting corrosion, abrasion, or other types of corrosion or wear. 
         [0049]    As mentioned above and shown in the embodiment illustrated in  FIG. 3 , the central portion  57  of the latch member  50  may be generally “U” shaped. Other shapes are within the scope of the invention and may be selected depending on the specific anatomy of the patient. Different embodiments of the central portion are illustrated in  FIGS. 6A-6E . For example,  FIG. 6A  illustrates a central portion  510  with a very narrow or acute “V” shape. The central portion  520  of  FIG. 6B  is generally “U” shaped, but with a squared off or blunted tip.  FIG. 6C  shows a central portion that consists of two separate pieces  530 , as opposed to the continuous central portions shown in  FIGS. 6A-B . Other possible shapes of the central portion of latch member  50  include, but are not limited to, central portions with blunt piece  540  and a separate circular piece  545  as seen in  FIG. 6D , and a central portion having a generally acute “V” shaped portion  550  with a blunt extension piece  555  as shown in  FIG. 6E . 
         [0050]    The choice of a particular shape for the central portion of latch member  50  may be based on a number of factors, such as particular types of trauma existing in the patient&#39;s heart tissue, the need for resheathability of the stent, and the specific type of interface with which the latch member central portion will engage. For example, a latch member  50  having an acute “V”-shaped central portion  510  would apply relatively high force at the point of engagement. However, if a particular patient would be at a high risk of having his cardiac tissue pierced by such relatively high force, a blunted central portion  520  might be more appropriate as it would distribute the applied forces across a larger area. In patients with nodules of calcification on their native heart valves, for instance, the central portion with separate pieces  530  may provide the greatest flexibility for optimal engagement of the latch member to the site of engagement. Similarly, the latch member with separate blunt pieces  540  and  545  shown in  FIG. 6D  could provide greater flexibility for maintaining contact with irregular surfaces and still provide a relatively large area over which the contact forces may be distributed. When engaging a previously existing implant, such as another transcatheter aortic valve implant, the latch member central portion may be shaped to enhance engagement capabilities based on the specific shape of the previously existing implant. 
         [0051]    Although specific embodiments of latch members  50  have been described, other sizes and shapes are within the scope of the invention. For example, latch members  50  with larger or smaller cross sections may be used to provide different levels of resilience. Further, shapes not discussed above may been implemented, for example, to match the condition of the patient&#39;s native valve leaflets  6  as measured, for example, by imaging techniques before or during the procedure. A kit including different valves with stent bodies having different latch members may be provided to facilitate such selection. 
         [0052]      FIG. 7  shows a continuous run of stent cells  600  within a portion of stent body  10  to illustrate, but not limit, different attachment locations of the latch members  50 . For example, the latch members  50  may be attached at one end to a commissure attachment feature  40  to which a valve leaflet  90  may also be attached, or above or below such commissure feature, and at the other end to a distal crest  18  (this configuration not shown in  FIG. 7 ). The latch members  50  may also be attached at both ends to the distal crests  18 , or above or below such distal crests. Additionally, multiple connections per distal crest  18  or commissure attachment feature  40  are possible to create nested latch members  50  within a single cell, as illustrated in  FIG. 7 . Preferably, the connections are made far enough distally of the leaflet belly  90  and the free edge  92  of the leaflet to avoid contact between the latch members  50  and the leaflets as the leaflets open and close and as the stent body  10  is crimped or expanded. 
         [0053]    Numerous other variations and combinations of the features described above may be employed. For example, features described in one or more embodiments may be combined with the features described in other embodiments. The cellular structure of the stents described above may also be varied. For example, the features described above may be employed in woven stent bodies and in stent bodies which are not fully self-expanding as, for example, stent bodies which are forcibly expanded by a balloon or mechanical device during implantation. 
         [0054]    Although the foregoing most frequently refers to prosthetic aortic valves, it will be appreciated that prosthetic valves in accordance with this invention may be used for other cardiac valves. As just one example of this, elliptical prosthetic valves in accordance with the invention may be used as prosthetic mitral valves. 
         [0055]    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.