Patent Publication Number: US-2021177589-A1

Title: Leaflet frame attachment for prosthetic valves

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation of U.S. application Ser. No. 16/129,651, filed Sep. 12, 2018, which claims the benefit of U.S. Provisional Application No. 62/557,586, filed Sep. 12, 2017, and U.S. Provisional Application No. 62/564,031, filed Sep. 27, 2017, both of which are incorporated herein by reference in their entireties for all purposes. 
    
    
     FIELD 
     The present disclosure relates to prosthetic valves, including prosthetic heart valves. 
     BACKGROUND 
     A number of fabrication techniques have been used to couple prosthetic valve leaflets to associated prosthetic valve frames, including sewing, injection molding, and dip coating polymeric leaflet material onto frames. In operation, prosthetic valve leaflets typically open after upstream fluid pressure exceeds downstream fluid pressure and close after downstream fluid pressure exceeds upstream fluid pressure. The terminal edges of the prosthetic valve leaflets will generally come into contact and coapt under the influence of downstream fluid pressure, closing the prosthetic valve to form a temporary seal that inhibits downstream blood from flowing retrograde through the prosthetic valve. The repeated opening and closing of leaflets can give rise to reliability issues, or even failure over time. 
     SUMMARY 
     Various embodiments are directed toward prosthetic valves having a frame and a leaflet construct, where the leaflet is at least partially coupled to a frame outer side by a looped structure. Some examples are directed to apparatuses, systems, and methods for valve replacement, such as cardiac valve replacement, although a variety of applications are contemplated. 
     According to one example, (“Example 1”), a prosthetic valve includes a frame having a central longitudinal axis, an inner side, and an outer side, the frame including a plurality of frame members and a plurality of commissure posts spaced circumferentially about the frame, the frame defining a plurality of leaflet attachment regions, the plurality of commissure posts including a first commissure post extending in a longitudinal direction and having a first slot formed through the first commissure post in a longitudinal direction, the first slot having a height and a width; a leaflet construct including a plurality of leaflets spaced circumferentially about the leaflet construct, the plurality of leaflets including a first leaflet and a second leaflet positioned circumferentially-adjacent to the first leaflet, the first leaflet including a first outer retaining element, a body portion having a first side and a second side, a first commissure tab extending from the first side, and a second commissure tab extending from the second side of the body portion, the first commissure tab having a first portion that extends through the first slot and a second portion that extends through the first slot to define a first outer loop portion on the outer side of the frame, the first outer loop portion encircling the first outer retaining element such that the first outer loop portion has a width that is greater than the width of the first slot to secure the first outer loop portion from being pulled through the first slot. 
     According to another example (“Example 2”) further to Example 1, the second leaflet includes a second outer retaining element, a body portion having a first side and a second side, a first commissure tab extending from the first side of the body portion, and a second commissure tab extending from the second side of the body portion, the second commissure tab of the second leaflet having a first portion that extends through the first slot and a second portion that extends through the first slot to define a second outer loop portion on the outer side of the frame, the second outer loop portion encircling the second outer retaining element such that the second outer loop portion has a width that is greater than the width of the first slot to secure the second outer loop portion from being pulled through the first slot. 
     According to another example (“Example 3”) further to Example 1, the first commissure post has a second slot formed through the first commissure post in a longitudinal direction, the second slot having a height and a width, and further wherein the second leaflet includes a second outer retaining element, a body portion having a first side and a second side, a first commissure tab extending from the first side of the body portion, and a second commissure tab extending from the second side of the body portion, the second commissure tab of the second leaflet having a first portion that extends through the second slot and a second portion that extends through the second slot to define a second outer loop portion on the outer side of the frame, the second outer loop portion encircling the second outer retaining element such that the second outer loop portion has a width that is greater than the width of the second slot to secure the second outer loop portion from being pulled through the second slot. 
     According to another example, (“Example 4”) further to Examples 2 or 3, the first and second outer retaining elements are continuous to define a continuous outer retaining element extending between the first and second leaflets. 
     According to another example, (“Example 5”) further to Example 4, the first commissure post further includes a hanging feature over which the outer continuous retaining element is hung to axially support the leaflet construct relative to the frame. 
     According to another example (“Example 6”) further to any of the preceding Examples 1 to 5, the first leaflet further includes a first inner retaining element and the first commissure tab of the first leaflet further defines a first inner loop portion on the inner side of the frame, the first inner loop portion encircling the first inner retaining element such that the first inner loop portion has a width that is greater than the width of the first slot to secure the first inner loop portion from being pulled through the first slot. 
     According to another example (“Example 7”), further to Example 6 at least one of the first inner retaining element and the first outer retaining element is formed of one or more of a suture, a thread, a monofilament, a multifilament, and a bead of material. 
     According to another example (“Example 8”), further to Example 6 the first inner retaining element and the first outer retaining element are continuous to define a continuous retaining element. 
     According to another example (“Example 9”), further to any of the preceding examples, the leaflet construct defines a bridge between the first and second leaflets. 
     According to another example (“Example 10”), further to any of the preceding examples, wherein the first outer retaining element of the first leaflet is coupled to the first commissure tab by being molded, adhered and/or bonded to the first commissure tab of the first leaflet or wherein the leaflet includes a polymeric membrane and the first outer retaining element is coupled to the polymeric membrane by being molded, adhered and/or bonded to the polymeric membrane. 
     According to another example (“Example 11”), a prosthetic valve comprises a leaflet construct including a first leaflet and a first retaining element coupled to the first leaflet; and a frame having a slot operable to receive a portion of the leaflet therethrough that defines a first outer loop portion on an outer side of the frame through which a portion of the first retaining element is received, the frame further including a projection over which the first retaining element is received to axially support the leaflet construct. 
     According to another example (“Example 12”) further to Example 11, the prosthetic valve further comprises a second leaflet, a portion of which is passed through the slot of the frame to define a second outer loop portion. 
     According to another example (“Example 13”) further to Example 11, where the slot of the frame is a first slot and the frame further defines a second slot adjacent the first slot and the leaflet construct further includes a second leaflet, a portion of which is passed through the second slot of the frame to define a second outer loop portion. 
     According to another example (“Example 14”) further to Example 11 the first leaflet defines a tab portion that extends through the slot at least two times, wherein the tab portion defines the outer loop portion. 
     According to another example (“Example 15”) further to Example 11, the first leaflet defines a tab portion that extends through the slot at least three times, wherein the tab portion defines the outer loop portion and an inner loop portion on an inner side of the frame. 
     According to another example (“Example 16”) further to Example 15, the leaflet construct further includes a second retaining element that extends through the inner loop portion. 
     According to another example (“Example 17”) further to any of preceding Examples 14 to 16, a terminal end of the tab portion is coupled to another part of the tab portion by being molded, adhered, and/or bonded to another part of the tab portion. 
     According to another example (“Example 18”) further to any of preceding Examples 14 to 16 a terminal end of the tab portion is coupled to another part of the first leaflet by being molded, adhered, and/or bonded to the other part of the first leaflet. 
     According to another example (“Example 19”) further to any one of preceding Examples 11 to 18, the first leaflet includes a first tab portion a second tab portion, and a body portion between the first tab portion and the second tab portion, each of the first and second tab portions having a terminal end and a leaflet end opposite the terminal end, the first tab portion forming the first outer loop portion. 
     According to another example (“Example 20”) further to Example 19, wherein the terminal end of the first tab portion is coupled to another part of the leaflet by being molded, adhered and/or bonded to the other part of the leaflet. 
     According to another example (“Example 21”) a prosthetic valve includes a leaflet construct including a first leaflet; a first retaining element coupled to the first leaflet; a second retaining element coupled to the first leaflet; and a frame having a central longitudinal axis and a slot operable to receive a portion of the first leaflet therethrough that defines a first outer loop portion on an outer side of the frame through which a portion of the first retaining element is received and a first inner loop portion on an inner side of the frame through which a portion of the second retaining element is received. 
     According to another example (“Example 22”) further to Example 21, the frame further includes a projection over which at least one of the first and second retaining elements is received to axially support the leaflet construct. 
     According to another example (“Example 23”) further to any of preceding Examples 21 to 22, the leaflet construct includes a second leaflet and a bridge interconnecting the first and the second leaflets, wherein the bridge hangs over the projection. 
     According to another example (“Example 24”) further to Example 21, the first leaflet includes a body portion, a first tab portion extending from a first side of the body portion to a terminal end, and a second tab portion extending from a second side of the body portion to a terminal end, the first tab portion forming the first inner loop portion and the first outer loop portion and the terminal end of the first tab portion be positioned adjacent the outer side of the frame. 
     According to another example (“Example 25”), further to any of preceding Examples 21 to 24 where the slot is a closed slot or where the slot extends from an open end to a closed end. 
     According to another example (“Example 26”), further to any of preceding Examples 21 to 25 where the first and second retaining elements are continuous. 
     According to another example (“Example 27”), further to any preceding Examples 21 to 26 where the slot is formed through the frame in a radial direction relative to a central longitudinal axis of the frame or the slot is formed at an angle to a radial direction relative to the central longitudinal axis of the frame. 
     According to another example (“Example 28”), further to any preceding claims  21  to  27  where tension on the first leaflet reduces a width of the slot. 
     According to another example (“Example 29”), further to any preceding Examples 21 to 28 where a cross-sectional area of the first retaining element and the outer loop portion is greater than a width of the slot. 
     According to another example (“Example 30”), further to any preceding Examples 21 to 29 where the first retaining element and the second retaining element define a continuous, closed loop portion. 
     According to another example (“Example 31”), a prosthetic valve comprises a leaflet construct including a first leaflet having a body portion, a first tab portion extending from the body portion, and a second tab portion extending from the body portion opposite to the first tab portion; a first retaining element coupled to the first leaflet; and a frame having a central longitudinal axis and a slot through which the first tab portion extends multiple times, including a first pass, a second pass, and a third pass through the slot. 
     According to another example (“Example 32”), further to Example 31 the first pass and the third pass are coupled and positioned adjacent to one other. 
     According to another example (“Example 33”), further to Example 31 the first pass is adjacent the second pass which is adjacent the third pass. 
     According to another example (“Example 34”), further to any preceding Examples 31 to 33 the first, second, and third passes are coupled to each other. 
     According to another example (“Example 35”), further to any preceding Examples 31 to 34 the first tab portion forms a first outer loop portion adjacent an outer side of the frame and that is restrained from pulling through the slot. 
     According to another example (“Example 36”), further to any preceding Examples 31 to 35 the first tab portion forms a first inner loop portion adjacent an inner side of the frame and that is restrained from pulling through the slot. 
     According to another example (“Example 37”), further to any preceding Examples 35 to 36 a first retaining element extends through the first outer loop portion. 
     According to another example (“Example 38”), further to Example 37 the first retaining element is coupled to the first outer loop portion. 
     According to another example (“Example 39”), further to any preceding Examples 35 to 38 a second retaining element extends through the first inner loop portion. 
     According to another example (“Example 40”), further to Example 39 the second retaining element is coupled to the first inner loop portion. 
     According to another example (“Example 41”), further to any preceding Examples 39 to 40 the first and second retaining elements are continuous. 
     According to another example (“Example 42”), further to Example 31, the first tab portion forms a first loop, and the leaflet construct further includes a second leaflet having a second tab portion defining a second loop, and further wherein the first retaining element extends into the first loop of the first leaflet and into the second loop of the second leaflet. 
     According to another example (“Example 43”), further to any preceding Examples at least one end of the first retaining element is enlarged relative to an adjacent portion of the first retaining element. 
     According to another example (“Example 44”), a prosthetic valve includes a frame having a central longitudinal axis; a leaflet construct including a first leaflet defining a first commissure tab, a second commissure tab, and a body portion therebetween, each tab portion having a terminal end and a leaflet end opposite the terminal end; a first retaining element; and a second retaining element, the frame having an inner side and an outer side and defining a slot through which the first tab portion is received, the first tab portion passing through the slot from the inner side to the outer side, passing from the outer side to the inner side, and passing again from the inner side to the outer side to define a first loop defining a first outer loop portion adjacent the outer side of the frame through which a first retaining element is received and a second loop between the inner side and outer side through which a second retaining element is received. 
     According to another example (“Example 45”), further to Example 44 the first leaflet defines a plurality of attachment tabs around a perimeter of the first leaflet that extend over the frame and coupled to the outer side of the frame. 
     According to another example (“Example 46”), further to Example 45 where each the attachment tabs is separated from an adjacent attachment tab by an opening for receiving a portion of the frame and optionally wherein the attachment tabs of the leaflets each include a plurality of apertures. 
     According to another example (“Example 47”), further to any one of Examples 44 to 46, in which the frame defines a plurality of commissure posts each including a first post leg and a second post leg that are spaced to define a slot. 
     According to another example (“Example 48”), further to Example 47 the leaflet construct includes a plurality of leaflets interconnected with one another by a plurality of bridges that pass through the slots of the commissure posts. 
     According to another example (“Example 49”), further to any one of Examples 44 to 48, the frame includes a plurality of frame elements that define a plurality of leaflet attachment regions each having a shape of an isosceles trapezoid having two leaflet attachment region sides diverging from a leaflet base. 
     According to another example (“Example 50”), further to Example 49 the leaflet base is perpendicular to the frame central longitudinal axis. 
     According to another example (“Example 51”), further to any one of Examples 44 to 49 the leaflet construct comprises at least one fluoropolymer membrane layer. 
     According to another example (“Example 52”), further to Example 52 a second material is contained within a porous structure of the expanded fluoropolymer membrane layer, coated on one or both sides of the expanded fluoropolymer membrane layer, or a combination of coated on and contained within the expanded fluoropolymer membrane layer. 
     According to another example (“Example 53”), further to any one of Examples 44 to 52 the leaflet construct comprises a composite having more than one fluoropolymer membrane layer. 
     According to another example (“Example 54”), further to any one of Examples 44 to 53 the frame comprises a metal, such as a shape memory metal, stainless steel, and/or a nickel-titanium alloy. 
     According to another example (“Example 55”), further to any one of Examples 44 to 54, wherein the leaflet construct comprises a fluoropolymer membrane layer including ePTFE. 
     According to another example (“Example 56”), further to any one of Examples 44 to 55 the leaflet construct defines a continuous annular ring. 
     According to another example (“Example 57”), a method of implanting a prosthetic valve in a body of a patient includes positioning a prosthetic valve according to any one of the preceding examples at a desired treatment location within the body and securing the prosthetic valve at the desired treatment location. 
     According to another example (“Example 58”), further to Example 57, the desired treatment location is a native aortic valve orifice and the method includes positioning the prosthetic valve at the native aortic valve orifice and securing the prosthetic valve at the native aortic valve orifice. 
     According to another example (“Example 59”), further to any one of Examples 57 or 58, the method includes positioning the prosthetic valve at the desired treatment location endoluminally with a transcatheter delivery system. 
     According to another example (“Example 60”), further to any one of Examples 57 to 59 the prosthetic valve is a self-expanding prosthetic valve. 
     According to another example (“Example 61”), further to any one of Examples 57 to 59 the prosthetic valve is a balloon expandable prosthetic valve. 
     According to another example (“Example 62”), further to any one of Examples 57 or 58, the method includes surgically positioning the prosthetic valve at the desired treatment location. 
     According to another example (“Example 63”), further to any one of Examples 57, 58, or 62, the prosthetic valve is a fixed frame, non-expandable prosthetic valve. 
     According to another example (“Example 64”), further to any preceding example, each of the plurality of leaflets defines two termini at an intersection of a leaflet free edge and a leaflet attachment region, the leaflet attachment region of each leaflet being coupled to the frame at a commissure attachment region of the frame such that the leaflet attachment regions adjacent the termini of two adjacent leaflets diverge relative to each other. 
     According to another example (“Example 65”), further to any preceding Example, the frame defines a pair of commissure attachment regions that diverge relative to each other toward a commissure post tip, and each leaflet is coupled to one of the commissure attachment regions such that adjacent leaflets define diverging free edges adjacent the commissure attachment regions. 
     According to another example (“Example 66”), further to any preceding Example, the frame defines a pair of adjacent commissure attachment regions that diverge relative to each other from a location away from a commissure post tip in an outflow direction towards the commissure post tip and a pair of adjacent leaflets of the plurality of leaflets is coupled to a respective one of the pair of adjacent commissure attachment regions such that the respective leaflet free edges of the pair of adjacent leaflets diverge from another at the adjacent commissure attachment regions when the pair of adjacent leaflets are in a closed, coapted configuration. 
     According to another example (“Example 67”), further to any preceding Example, each leaflet is attached to the frame such that adjacent leaflet free edges at the frame diverge relative to each other. 
     According to another example (“Example 68”), further to any preceding Example, each leaflet is attached to the frame at a diverging region of the frame such that adjacent leaflet free edges at the frame diverge relative to each other, wherein stress within each leaflet along the diverging region is reduced more than 40% relative to a non-diverging attachment when exposed to peak closing pressures of about 135 mmHg in the leaflet adjacent the free edges at the frame. 
     According to another example (“Example 69”), further to any one of Examples 1 to 10 or 64 to 68, a method of making the prosthetic valve includes coupling the first retaining element of a first leaflet to the first commissure tab of the first leaflet; and coupling the leaflet construct to the frame by extending the first portion and the second portion of the first commissure tab through the first slot of the frame to define the first outer loop portion on the outer side of the frame such that the first outer loop portion encircles the first outer retaining element and the first outer loop portion has a width that is greater than the width of the first slot to secure the first outer loop portion from being pulled through the first slot. 
     According to another example, (“Example 70”), further to any one of Examples 11 to 56 or 64 to 68, a method of making the prosthetic valve includes coupling the first retaining element to a first leaflet; and coupling the first leaflet of the leaflet construct to the frame by, receiving a portion of the leaflet through the slot that defines the first outer loop portion on the outer side of the frame with the first retaining element received through the first outer loop portion on the outer side of the frame, and receiving the first retaining element over the hanging feature of the frame to axially support the leaflet construct. 
     While multiple examples are disclosed, still other embodiments will become apparent to those skilled in the art from the following detailed description, which shows and describes illustrative examples. Accordingly, the drawings and detailed description are to be regarded as illustrative in nature and not restrictive. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings are included to provide a further understanding of the present disclosure and are incorporated in and constitute a part of this specification, illustrate embodiments described herein, and together with the description serve to explain the principles discussed in this disclosure. 
         FIG. 1  is an isometric view of a prosthetic valve, according to some embodiments. 
         FIG. 2  is an isometric view of a frame of the prosthetic valve of  FIG. 1 , according to some embodiments. 
         FIG. 3  is an enlarged view of a portion of the frame of  FIG. 2 , according to some embodiments. 
         FIG. 4  is an enlarged, schematic view of a portion of the frame of  FIG. 3  corresponding to a first leaflet attachment region, according to some embodiments. 
         FIG. 5  is flat view of a leaflet construct prior to assembly to a frame, according to some embodiments. 
         FIG. 6  is a flat view of the leaflet construct of  FIG. 5 , shown with retaining elements, according to some embodiments. 
         FIG. 6A  is an enlarged flat view of the leaflet construct of  FIG. 6 , shown with retaining elements, according to some embodiments. 
         FIG. 7  is an enlarged, schematic view of a portion of the frame of  FIG. 3  corresponding to a first leaflet attachment region, according to some embodiments. 
         FIG. 8  is a schematic, flat view showing a portion of the frame of  FIG. 3  corresponding to a first leaflet attachment region superimposed on a portion of the leaflet construct of  FIG. 6  corresponding to a first leaflet, according to some embodiments. 
         FIG. 9  is a sectional view showing a loop configuration of the prosthetic valve of  FIG. 1 , according to some embodiments. 
         FIG. 10  is an enlarged view of a portion of the prosthetic valve of  FIG. 1  during assembly, according to some embodiments. 
         FIG. 11  is a plan view of another prosthetic valve, according to some embodiments. 
         FIG. 11A  is an isometric view of the prosthetic valve of  FIG. 11 , according to some embodiments. 
         FIG. 12  is a front view of a frame of the prosthetic valve of  FIG. 11 , according to some embodiments. 
         FIG. 13  is an enlarged view of a commissure post of the frame of  FIG. 12 , according to some embodiments. 
         FIG. 14  is a flat, schematic view of a portion of the frame of  FIG. 12 , according to some embodiments. 
         FIG. 15  is a view of a leaflet pattern of the prosthetic valve of  FIG. 11 , according to some embodiments. 
         FIG. 16  is a flat, schematic view of a portion of the frame and an attachment element of the prosthetic valve of  FIG. 11 , according to some embodiments. 
         FIG. 17  is an overlay view for understanding assembly of the prosthetic valve of  FIG. 11 , according to some embodiments. 
         FIG. 18  is a transverse cross-section of the prosthetic valve of  FIG. 11  at a commissure post of the prosthetic valve taken along line W-W on  FIG. 12 , with portions of the prosthetic valve removed for ease of illustration, according to some embodiments. 
         FIGS. 19 and 20  are isometric views of a commissure post of the prosthetic valve, with portions of the prosthetic valve removed for ease of illustration, according to some embodiments. 
         FIG. 21  shows another attachment arrangement between leaflets and a commissure post of a prosthetic valve, according to some embodiments. 
         FIGS. 22 and 23  show features of another attachment arrangement between leaflets and a commissure post of a prosthetic valve, according to some embodiments. 
         FIGS. 24-28  show various retaining element arrangements usable for leaflets in attachment arrangements between leaflets and commissure posts, according to some embodiments. 
         FIGS. 29 to 31  show a potential modification for commissure attachment regions of the prosthetic valve of  FIG. 11 , according to some embodiments. 
         FIGS. 32 and 33  show methods of implanting a prosthetic valve, according to some embodiments. 
     
    
    
     Persons skilled in the art will readily appreciate that various aspects of the present disclosure can be realized by any number of methods and apparatus configured to perform the intended functions. Stated differently, other methods and apparatuses can be incorporated herein to perform the intended functions. It should also be noted that the accompanying drawing figures referred to herein are not necessarily drawn to scale, but may be exaggerated or represented schematically to illustrate various aspects of the present disclosure, and in that regard, the drawing figures should not be construed as limiting. 
     DETAILED DESCRIPTION 
     The present disclosure relates to prosthetic valves used for cardiac valve replacement or other applications associated with native valve or other valve orifices, and related systems, methods, and apparatuses. In various examples, the prosthetic valve is operable as a one-way prosthetic valve that defines a valve orifice into which leaflets open to permit flow and close so as to block or occlude the valve orifice and partially or entirely prevent flow in response to differential fluid pressure. 
     In the instant disclosure, the examples are primarily described in association with surgical or transcatheter cardiac valve applications, although it should be readily appreciated embodiments within the scope of this disclosure can be applied toward any prosthetic valve or mechanism of similar structure and/or function. For example, the prosthetic valve  100  of  FIG. 1  can be applied in non-cardiac applications, such as respiratory or gastrointestinal tract applications. Implantable valve orifices include anatomical structures into which a prosthetic valve can be placed. Such anatomical structures include, but are not limited to, a location wherein a cardiac valve may or may not have been surgically removed. Other anatomical structures that can receive a prosthetic valve include, but are not limited to, veins, arteries, ducts and shunts. A valve orifice or implant site may also refer to a location in a synthetic or biological conduit that may receive a prosthetic valve. 
     The term “leaflet” as used in the context of prosthetic valves is generally a flexible component operable to move between an open and closed position under the influence of pressure differentials. In an open position, the leaflet allows blood to flow through the prosthetic valve. In a closed position, the leaflet substantially blocks retrograde flow through the prosthetic valve. This retrograde flow is at least partially blocked, and typically fully blocked by the leaflet. In embodiments comprising multiple leaflets, each leaflet cooperates with at least one neighboring leaflet to block the retrograde flow of blood. Various embodiments relate to attachment mechanisms for coupling leaflets to an associated frame such that the leaflets resist inward forces, outward forces, and/or axial forces on the leaflets relative to the associated frame. The leaflet frame attachment mechanisms for prosthetic valves include the leaflet construct being at least partially coupled to a frame outer side by a looped structure. Such looped structures can help provide reduced stress concentrations, greater reliability of attachment, and ease of manufacture. 
     The pressure differential in the blood actuating the leaflets is caused, for example, by the contraction of a ventricle or atrium of the heart, such pressure differential typically resulting from a fluid pressure building up on one side of the leaflets when closed. As the pressure on an inflow side of the prosthetic valve rises above the pressure on the outflow side of the prosthetic valve, the leaflets open and blood flows therethrough. As blood flows through the prosthetic valve into a neighboring chamber or blood vessel, the pressure on the inflow side equalizes with the pressure on the outflow side. As the pressure on the outflow side of the prosthetic valve raises above the blood pressure on the inflow side of the prosthetic valve, the leaflet returns to the closed position to partially or fully block retrograde flow of blood through the prosthetic valve. 
       FIG. 1  is an isometric view of a prosthetic valve  100 , according to some embodiments. As shown, the prosthetic valve  100  includes a frame  102 , also described as a frame assembly or leaflet frame, a leaflet construct  104 , also described as a leaflet assembly or leaflet module, and an attachment element  106 , which can also be described as an attachment substrate or an attachment treatment. The prosthetic valve  100  can include any of a variety of additional features, such as one more sealing cuffs, for example. The leaflet construct  104  has a plurality of leaflets  180  ( FIG. 5 ) that come together where free edges  206  ( FIG. 5 ) flatten together (e.g., in a Y-shaped pattern in the case of three leaflets when viewed from the top), which can also be described as a coaptation region  107 . As the free edges  206  come together the prosthetic valve  100  closes. The prosthetic valve  100  closes in this fashion when the pressure of the blood on the outflow side O s  is greater than the pressure of the blood on the inflow side I s  of the prosthetic valve  100 . The leaflet free edges of leaflet construct  104  move apart to open the prosthetic valve  100  and to let blood flow through the prosthetic valve  100  from the inflow side I s  when the pressure of the blood on the inflow side I s  of the prosthetic valve  100  is greater than the pressure on the outflow side O s  of the prosthetic valve  100 . As shown, the prosthetic valve  100  defines a central longitudinal axis Xv, as well as an inner side  108  corresponding to a central lumen and an outer side  109  corresponding to the exterior of the prosthetic valve  100 . 
       FIG. 2  is a perspective view of the frame  102  of the prosthetic valve  100 , according to some embodiments. In various examples, the frame  102  serves to operatively support the leaflet construct  104  in a desired location within a patient (not shown). The frame  102  is optionally collapsible to a reduced profile, delivery configuration and then expandable (e.g., self-expanding or expanded by the application of an external force, such as by balloon expansion) in situ. As shown in  FIG. 2 , the frame  102  is optionally annular, defining a cylinder (e.g., a right circular cylinder) or cylindrical shape, and has a central longitudinal axis Xf. 
     Although the frame  102  generally defines a circular transverse cross-section, it should be understood that any variety of cross-sections (e.g., oval- or rectangular-shaped) cross-sections are also contemplated. The frame  102  has an inner side  110  and an outer side  112  opposite the inner side  110 . The inner side  110  faces toward the central longitudinal axis Xf, and the outer side  112  faces outwardly, or away from the central longitudinal axis Xf. As shown, the frame  102  includes a plurality of commissure posts  120  ( FIG. 3 ) and a plurality of frame elements  122 . 
     The frame  102  can be etched, cut, laser cut, stamped, three-dimensional printed or wire wound, among other suitable processes. The frame  102  can comprise, such as, but not limited to, any metallic or polymeric material, such as an elastically (e.g., nitinol) or plastically (e.g., stainless steel) deformable metallic or polymeric material that is generally biocompatible. Other materials suitable for the frame  102  include, but are not limited to, other titanium alloys, stainless steel, cobalt-nickel alloy, polypropylene, acetyl homopolymer, acetyl copolymer, a drawn filled tube (e.g., nitinol wire with a platinum core), other alloys or polymers, or any other material that is generally biocompatible having adequate physical and mechanical properties to function as a frame  102  as described herein. 
     In some embodiments, the plurality of commissure posts  120  are spaced from one another, and arranged at desired locations (e.g., equally spaced locations) around a circumference of the frame  102 . As shown, the plurality of commissure posts  120  extend parallel to the central longitudinal axis Xf, although angled configurations (e.g., commissure posts angled inwardly toward the central longitudinal axis Xf or outwardly away from the central longitudinal axis Xf) are also contemplated. Although three, equally circumferentially-spaced commissure posts  120  are shown, any number and spacing of commissure posts are contemplated. The plurality of commissure posts  120  define circumferentially-adjacent ones, or simply adjacent ones of the plurality of commissure posts  120  moving about the perimeter of the frame  102 . As shown in  FIG. 2 , other than location and orientation, each of the commissure posts  120  has a similar design, although examples where the commissure posts differ from one another in various respects are also contemplated. For ease of understanding, the features of each of the commissure posts  120  will be described in association with a first commissure post  120   a,  an enlarged view of which is shown in  FIG. 3 . 
     The features of the first commissure post  120   a  will generally be referenced with a numeral followed by an “a.” Similar features of a second commissure post may be subsequently referenced with the same numeral as the first commissure post  120   a,  but followed by a “b.” Similar features of a third commissure post may be subsequently referenced with the same numeral as the first commissure post  120   a,  but followed by a “c.” Similarly, when features of each of the commissure posts  120  are referenced collectively, those features are referenced with the same numeral as identified for the first commissure post  120   a,  but not followed by a letter. 
     As shown in  FIG. 3 , the first commissure post  120   a,  includes a first leg  130   a,  a second leg  132   a,  a slot  134   a  between the first leg  130   a  and the second leg  132   a,  which can also be described as a post slot, and a hanging feature  136   a,  which can also be described as a protuberance, hook, or projection. The first commissure post  120   a  has an outer side corresponding to the frame outer side  112  ( FIG. 2 ) and a post inner side corresponding to the frame inner side  110 ( FIG. 2 ). 
     As shown, the first and second legs  130   a,    132   a  extend longitudinally, or in a longitudinal direction. In some examples, the first and second legs  130   a,    132   a  extend in a longitudinal direction that is parallel to the central longitudinal axis Xf ( FIG. 2 ) of the frame  102 . In other examples, the first and second legs  130   a,    132   a  extend longitudinally, but at some offset relative to the central longitudinal axis Xf (e.g., angularly offset inwardly, toward the central longitudinal axis Xf, angularly offset transversely relative to the central longitudinal axis Xf, or a combination thereof). 
     The slot  134   a  is optionally formed between the first and second legs  130   a,    132   a  and extends through a thickness of the first commissure post  120   a,  from the inner side  110  ( FIG. 2 ) of the frame  102  to the outer side  112  ( FIG. 2 ) of the frame  102 . The slot  134   a  is formed through the frame  102  in a radial direction relative to a central longitudinal axis Xf of the frame  102  or the slot  134   a  is formed at an angle to a radial direction relative to the central longitudinal axis Xf of the frame  102 . As shown, the slot  134   a  extends in a longitudinal direction that is parallel to the central longitudinal axis Xf ( FIG. 2 ) of the frame  102 . In other examples, the slot  134   a  extends longitudinally, but at some offset relative to the central longitudinal axis Xf (e.g., angularly offset inwardly, toward the central longitudinal axis Xf, angularly offset transversely relative to the central longitudinal axis Xf, or a combination thereof). As shown, the slot  134   a  is elongate in shape, with a length, or height, greater than its width (e.g., more than 2×, 5×, 10×, 20×, or 30×, although a variety of dimensions are suitable), and extends from a first end  140   a  to a second end  142   a.  As shown, the first end  140   a  of the slot  134   a  is open and the second end  142   a  of the slot  134   a  is closed. For example, the first end  140   a  is “open” in the sense that it opens to a much wider area in the frame  102  (e.g., more than 5×, 10×, or 20×), whereas the second end  142   a  is “closed” in the sense that it terminates at a distance from the first end  140   a  of the slot  134   a.  The width of the slot  134   a  is generally selected to allow a desired number of passes or loops of leaflet material through the slot  134   a  as described below. 
     In some embodiments, the hanging feature  136   a,  which can also be described as a hanger, a protuberance, a projection a shoulder, a pin, or a hook, for example, includes a body portion  150   a  and a head portion  152   a,  where the body portion  150   a  is secured through a hole  154   a,  or aperture, in the frame  102  (the receiving hole is hidden in  FIG. 3 , but can be seen in  FIG. 2  without the hanging feature  136   a  for ease of understanding). The head portion  152   a  generally defines a shoulder, and forms a channel  156   a  between the head portion  152   a  and the frame  102 . The depth and width of the channel  156   a  is generally selected to receive and retain a filament or other desired portion of the leaflet construct  104  for axially supporting the leaflet construct  104 . As shown, the hanging feature  136   a  is located longitudinally-adjacent the second end  142   a  of the slot  134   a,  and generally in alignment with the slot  134   a.  In other examples, the hanging feature  136   a  is offset from the slot  134   a  (e.g., laterally/circumferentially). 
       FIG. 4  is an enlarged, flattened view of a first leaflet attachment region  160   a  of the frame  102  between two adjacent commissure posts  120 , the first commissure post  120   a  and second commissure post  120   b,  according to some embodiments. The first leaflet attachment region  160   a  defines a first side  162   a,  a second side  164   a,  and a base  166   a.  Similar leaflet attachment regions  160  are defined between each of the adjacent commissure posts  120 , according to some embodiments. In  FIG. 4 , the first leaflet attachment region  160   a  of the frame  102  is represented in a flattened form for ease of illustration, although it should be understood that the frame  102  is three-dimensional and generally annular. As shown in  FIG. 4 , the first commissure post  120   a  is located at a first side of the first leaflet attachment region  160   a  of the frame  102  and a second commissure post  120   b  of the plurality of commissure posts  120  is located at a second side of the first leaflet attachment region  160   a  of the frame  102  shown in  FIG. 4 . In particular, the frame  102  defines the first leaflet attachment region  160   a  between the first and second commissure posts  120   a,    120   b,  as well as leaflet attachment regions between the remaining commissure posts of the plurality of commissure posts  120 . 
     In some embodiments, the frame elements  122  of the frame  102  include a plurality of leaflet attachment frame elements  170 , or simply leaflet attachment elements, that define leaflet attachment regions similar to the first leaflet attachment region  160   a  shown in  FIG. 4 . The leaflet attachment frame elements  170  are arranged to support the leaflet construct  104  and to help define a shape of leaflets  180  ( FIG. 5 ) of the leaflet construct  104 , where that leaflet  180  will project from the corresponding leaflet attachment region, such as the first leaflet attachment region  160   a.  In the example shown in  FIG. 2 , the frame  102  defines three sets of the leaflet attachment frame elements  170  corresponding to three leaflet attachment regions  160  that each generally follows the shape of an outline of a leaflet of the leaflet construct  104 . In different terms, the leaflet attachment frame elements  170  optionally support leaflets around at least a portion of each of the leaflets  180  except at the free edges  206  ( FIG. 5 ). 
       FIG. 5  shows the leaflet construct  104  as a flattened, plan view prior to assembly with the frame  102 . This flattened plan view can also be described as a cut pattern, or simply a leaflet pattern. From  FIG. 1 , for example, it should be understood that the leaflet construct  104  is folded and formed into a cylindrical shape when assembled to the frame  102 . As shown in  FIG. 5 , the leaflet construct  104  includes a plurality of leaflets  180  and a plurality of bridges  182 , or bridge regions, interconnecting the circumferentially-adjacent leaflets  180 . In some embodiments, the plurality of leaflets  180  are spaced from one another, and arranged at desired locations around a circumference of the leaflet construct  104  corresponding to the respective leaflet attachment regions  160  and commissure posts  120 . As shown in  FIGS. 5 and 6 , the leaflet pattern defines a connected and continuous (e.g., monolithic, contiguous or seamless) annular ring formed as a single piece and including the plurality of leaflets  180  and bridges  182  between each of the plurality of leaflets  180 . 
     Although three leaflets  180  are shown, any number of leaflets is contemplated. The plurality of leaflets  180  define circumferentially-adjacent ones, or simply adjacent ones of the plurality of leaflets  180  moving about the circumference of the leaflet construct  104 . The leaflet construct  104  can be formed in a variety of manners, including cutting a cylinder of material into a desired shape, cutting a sheet of material into a desired shape, and/or molding (e.g., compression or injection molding) the leaflet construct  104  with a desired shape. 
     As shown in  FIG. 6 , the leaflet construct  104  also includes a plurality of first retaining elements  184 , and a plurality of second retaining elements  186  (the retaining elements are not shown in  FIG. 5  for ease of visualization of the bridges  182 ). As used herein, a retaining element includes one or more of a strand, filament, monofilament, multifilament (whether braided, woven, twisted or an otherwise associated group of filaments), a bead of material, a thread, a suture, a rolled film, a multilayer lay-up of material, a wire, an embossed or other feature providing the functionality described herein. 
     The first and second retaining elements  184 ,  186  are optionally molded, adhered, and/or heat bonded, or otherwise coupled to the leaflet construct  104  as desired. As used herein, couple means to join, connect, attach, adhere, affix, or bond, whether directly or indirectly, and whether permanently or temporarily. 
     In some examples, the first retaining elements  184  are not present. For example, the retaining elements  184   a,    184   b  may be unnecessary in instances where there is a desired amount of support/retention provided by the second retaining elements  186 . 
     As shown in  FIGS. 5 and 6 , other than location and orientation, each of the plurality of leaflets  180  has a similar design, although examples where the leaflets differ from one another in various respects are also contemplated. Regardless, for ease of understanding, the features of each of the leaflets  180  will be described in association with a first leaflet  180   a.  The features of the first leaflet  180   a  will generally be referenced with a numeral followed by an “a.” Similar features of a second leaflet may be subsequently referenced with the same numeral as the first leaflet, but followed by a “b.” Similar features of a third leaflet may be subsequently referenced with the same numeral as the first leaflet  180   a,  but followed by a “c.” Similarly, when features of each of the leaflets  180  are referenced collectively, those features are referenced with the same numeral as identified for the first leaflet  180   a,  but not followed by a letter. 
     As indicated on  FIG. 5 , the first leaflet  180   a  optionally includes a body portion  190   a,  a plurality of attachment tabs  192   a  extending from the body portion  190   a,  a first commissure tab  194   a  extending from the body portion  190   a,  and a second commissure tab  196   a  extending from the body portion  190   a  (e.g., at opposite ends of free edge  206   a ). As previously discussed, the second and leaflets  180   b,    180   c  optionally include similar features. For example, as shown in  FIG. 5 , the second leaflet  180   b  includes a first commissure tab  194   b  and a second commissure tab  196   b.  As shown, the first commissure tab  194   a  is positioned adjacent the second commissure tab  196   b  and the second commissure tab  196   a  is positioned adjacent a first commissure tab  194   c  of the third leaflet  180   c.    
     The body portion  190   a,  also described as a leaflet belly, or belly portion, is bounded in broken lines for understanding purposes. The body portion  190   a  of the first leaflet  180   a  is the moving portion of the first leaflet  180   a  in the prosthetic valve  100 . It should be appreciated that when assembled to the frame  102 , the boundaries of the body portion  190   a  are defined and the body portion  190   a  takes on a three dimensional shape, rather than the flat shape shown in  FIG. 5 . As such, the broken lines are provided for general visualization purposes of the body portion  190   a.  In various examples, the shape of the body portion  190   a  is generally dictated by the lines, or areas of attachment to the frame  102 . The edges of the body portion  190   a  generally correspond to fold lines where the attachment tabs  192   a  and the first commissure tab  194   a  and the second commissure tab  196   a  are secured to the frame  102  ( FIG. 2 ). As will be described below, the leaflet construct  104  may be attached to the frame  102  using attachment element  106  ( FIG. 1 ), which in turn, may contribute to shape defined by the leaflet attachment regions  160  and the ultimate shape of the body portion  190   a.    
     As shown, the body portion  190   a  of the first leaflet  180   a  has the general shape of an isosceles trapezoid. Regardless of the exact shape, the body portion  190   a  generally has a first side  200   a,  a second side  202   a,  a base  204   a,  and a free edge  206   a  opposite the leaflet base  204   a  for coaptating with respective free edges  206  of respective other leaflets  180 . In general terms, the shape of the body portion  190   a  corresponds to the first side  162   a,  the second side  164   a,  and the base  166   a  of the first leaflet attachment region  160   a  ( FIG. 4 ). As shown, the two sides  200   a,    202   a  diverge from the leaflet base  204   a,  and the leaflet base  204   a  will be substantially straight in a transverse plane relative to the central longitudinal Xf of the frame  102 . In different terms, leaflet base  204   a  is perpendicular to the central longitudinal axis Xf of the frame  102  following assembly. 
     Although the body portion  190   a  is shown to take on the general shape of an isosceles trapezoid, any number of shapes is contemplated, and the body portion  190   a  need not be trapezoidal in overall appearance. For example, the body portion  190   a  may include a central region that defines a shape substantially that of an isosceles trapezoid, with side regions on each side that have a shape substantially that of a triangle. In still other embodiments, the body portion  190   a  may outline a shape that can be described as U-shaped, parabolic shaped, or a V-shaped, depending on the geometric outline defined by the first leaflet attachment region  160   a.    
     The first leaflet  180   a  generally defines a fold over portion  198   a,  also described as a fold over region, outside of the body portion  190   a,  as demarcated by the broken line in  FIG. 5 . The fold over portion  198   a  of the first leaflet  180   a  is the portion that is used to secure the first leaflet  180   a  to the frame  102 , where the remaining leaflets  180  optionally include similar features for securing to the frame  102 . The leaflet attachment frame elements  170  ( FIG. 4 ) fit into a fold that is formed between the body portion  190   a  and the fold over portion  198   a.  In general terms, the leaflets  180  extend radially inward from the frame  102  when coupled to the frame  102 . The body portion of each leaflet  180  includes enough material between the commissure posts  120  of the frame  102  so that the leaflet free edges  206  of the three leaflets  180  can come together or coapt in the interior of the prosthetic valve  100  to close the prosthetic valve  100  as shown in  FIG. 1 . 
     As shown, the plurality of attachment tabs  192   a  located in the fold over portion  198   a  are positioned about a perimeter of the body portion  190   a  and are separated from one another by openings  208   a  for receiving frame elements  122  (e.g., leaflet attachment frame elements  170 ) of the frame  102 . One or more of the plurality of attachment tabs  192   a  optionally includes a plurality of apertures (not shown) through the thickness of the attachment tabs  192   a.  The apertures may assist with coupling or otherwise securing the attachment tabs  192   a  to the frame  102  (e.g., directly or via the attachment element  106 ) using adhesives or bonding (e.g., to provide additional surface area for adhesion/bonding), fastening elements (e.g., holes for sutures), or combinations thereof. 
     In various examples, the first commissure tab  194   a  and the second commissure tab  196   a  assist with securing the first leaflet  180   a  to the first commissure post  120   a  and second commissure post  120   b  ( FIGS. 2, 4 ). As shown in  FIG. 5 , the first commissure tab  194   a  extends from the first side  200   a  of the body portion  190   a  and the second commissure tab  196   a  extends from a second side  202   a  of the body portion  190   a.  The first commissure tab  194   a  extends from a first end  210   a,  also described as a leaflet end, to a terminal end  212   a  ( FIG. 6 ). Similarly, the second commissure tab  196   a  extends from a first end  214   a  to a terminal end  216   a  ( FIG. 6 ). The first commissure tab  194   a  and second commissure tab  196   a  are shown with an optional taper toward the terminal ends  212   a,    216   a.    
     As shown, the plurality of bridges  182  extend between and interconnect the plurality of leaflets  180 .  FIG. 6A  is an enlarged view of a portion of  FIG. 6 , and illustrates a bridge  182   a  of the plurality of bridges  182 . Each of the bridges  182  is optionally substantially similar, and as such can be described cumulatively with reference to the bridge  182   a  (although varying bridge designs from bridge-to-bridge are also contemplated). As shown in  FIG. 6A , the bridge  182   a  interconnects, or otherwise extends between a first end  220   a  adjacent to the first leaflet  180   a  and a second end  222   a  adjacent the second leaflet  180   b.  When the leaflet construct  104  is folded into a cylindrical shape and the leaflet construct  104  is folded onto frame  102 , the bridge  182   a  (and each of the bridges  182 ) defines a loop between the first end  220   a  and the second end  222   a.  The loops defined by the bridges  182 , as well as the remaining portions of the leaflets  180  that are secured to the commissure posts  120  can also be described as coaptation necks. In some embodiments, These coaptation necks are operable to pass through the slots of the commissure posts  120 , such as the slot  134   a  of the first commissure post  120   a,  so that the loop formed by folding the bridge  182   a  is adjacent to the outer side  112  of the frame  102 , which also corresponds to the outer side of the first commissure post  120   a  ( FIG. 2 ). 
     As shown, the first leaflet  180   a  includes a first retaining element  184   a  that is located on the first commissure tab  194   a  and the second leaflet  180   b  includes a first retaining element  184   b  that is located on the second commissure tab  196   b  of the second leaflet  180   b  near the first end  214   b  of the second commissure tab  196   b.  The first retaining elements  184   a,    184   b  of the respective leaflets  180   a,    180   b  are separate and discontinuous from one another and they are not formed as a single or contiguous piece. In turn, the second retaining element  186   a  extends across, or overlays, the bridge  182   a  and onto each of the first leaflet  180   a  and the second leaflet  180   b  and is optionally a single, connected and continuous (e.g., contiguous) member or element. The second retaining element  186   a  defines a first portion  230   a  on the first leaflet  180   a  and a second portion  230   b  on the second leaflet  180   b.  Each of the portions is optionally individually referred to as elements as well. In different terms, the first leaflet  180   a  includes second retaining element  186   a,  the second leaflet  180   b  includes second retaining element  186   b,  and the second retaining elements  186   a,    186   b  are connected and continuous (e.g., contiguous) with one another as a single piece to define the second retaining element  186   a.  As shown, the first retaining elements  184   a,    184   b  are spaced apart from the second retaining element  186   a.  In some examples, the first retaining elements  184  (e.g.,  184   a,    184   b ) are spaced apart from their adjacent second retaining elements  186  (e.g.,  186   a ) a distance at least as wide as the thickness of a corresponding commissure post  120  (e.g.,  120   a ) as measured from the inner side  110  to the outer side  112  of the frame  102 . 
     As previously referenced, the various retaining elements can take a variety of forms. In some examples, the first retaining elements  184  are formed as beads of material on the commissure tabs of the leaflets  180 , whereas the second retaining elements  186  are fibers (e.g., coated fibers). The various retaining elements are optionally molded, adhered and/or bonded to the underlying material of the leaflets  180 , such as by thermal bonding. In some examples, the second retaining elements  186  help reinforce the bridges  182 , provide connections between the leaflets  180 , and/or are used to affect retention of the first and the second commissure tabs  194 ,  196  in the slots  134  of the commissure posts  120 . As will be described below, in some examples, the second retaining elements  186  are located adjacent the slots  134  at the outer side  112  and the first retaining elements  184  are located adjacent the slots  134  at the inner side  110  of the frame  102 . The second retaining elements  186  are optionally used to help prevent the first and the second commissure tabs  194 ,  196  and bridges  182  from pulling inwardly through the slots  134 , wherein the first retaining elements  184  are optionally used to help prevent the leaflets  180  from pulling outwardly through the slots  134  to the outer side  112  of the frame  102 . For example, cross-sectional areas of the retaining elements  184 ,  186  and portions of the commissure tabs  194 ,  196  looped over them are greater than the widths of the slots  134 . 
     The first retaining elements  184  and/or the second retaining elements  186  can be formed from polymeric or metallic materials, fluoropolymers, one or more of FEP, PEEK, ePTFE filament(s) (mono- or multi-), nitinol, stainless steel, multiple folds or layers of material (e.g., ePTFE film), combinations thereof, or any of a variety of features configured to resist movement relative to the slot(s) and/or hanging feature(s). 
       FIG. 7  is a schematic, flat view of a portion of the frame  102  and attachment element  106 . The gray area in  FIG. 7  represents locations where the attachment element  106  is not present. For example, the attachment element is optionally one or more layers of material applied to the frame material. If desired, the openings, or gray areas in the attachment element  106  are optionally formed via laser cutting (e.g., where the attachment element is applied to the frame  102  as part of a tape wrapping process. Several locations of the attachment element  106  are marked on  FIG. 7  for ease of understanding. As previously referenced, the prosthetic valve  100  optionally includes attachment element  106 , which can also be described as an attachment substrate or an attachment treatment. The attachment element  106  is optionally one or more layers of material attached to the frame  102 . In some examples, the outer side  112  of the frame  102  is covered with the attachment element  106 , which is in the form of one or more layers of film material. One or more portions of the leaflet construct  104  can then be attached to the attachment element  106 , thereby helping to define the shapes of the leaflets  180 . 
       FIG. 8  shows an overlay of the frame  102 , the leaflet construct  104 , and the attachment element  106  in an area of the first leaflet attachment region  160   a,  for understanding, where similar principles of which apply in assembling the remaining leaflets  180  to leaflet attachment regions of the frame  102 . As referenced above, the leaflet construct  104  is attached to the frame  102  and/or attachment element  106  using fold over portions, such as the fold over portion  198   a  of the first leaflet  180   a.  Attachment tabs, such as the attachment tabs  192   a  of the first leaflet  180   a  are received over portions of the frame  102  and/or attachment element  106  and attached thereto to attach the leaflet construct  104  to the frame at the body portions of the leaflets  180 , such as the body portion  190   a  ( FIG. 5 ). As should be understood, one or more of the attachment tabs  192   a  may be folded to the attachment element  106 , rather than the frame  102 . As shown in  FIG. 8 , the lowermost attachment tab  192   a  may be folded to a relatively flat area at the bottom of the attachment element  106 , to define a relatively flat base corresponding to that shown for the body portion  190   a  in  FIG. 5 . In different terms, the attachment tabs do not necessarily have to follow the geometry of the frame  102 , but can follow a geometry separate from the frame  102  as defined by the attachment element  106 , for example. 
       FIGS. 9 and 10  illustrate attachment of the leaflets  180  to the commissure posts  120  according to some examples.  FIG. 9  is a transverse cross-section through the commissure post  120   a  at the slot  134   a  and  FIG. 10  is an isometric view of the prosthetic valve  100  in the area of the first commissure post  120   a.  Although relatively sharp corners are shown in  FIG. 9  at the slot  134   a  of the first commissure post  120   a,  it should be understood that chamfers, rounds, reliefs coatings and other features may be provided to avoid stress concentrations or other wearing of the leaflets  180   a,    180   b  at those slot edges. And, although  FIGS. 9 and 10  provide a specific example with regard to the first commissure post  120   a,  first leaflet  180   a,  and second leaflet  180 , it should be readily understood that similar techniques are employable for attaching the commissure tabs of the remaining leaflets  180  to the remaining commissure posts  120  of the frame  102 . 
     As shown in  FIG. 9 , the first commissure tab  194   a  of the first leaflet  180   a  and the second commissure tab  196   b  of the second leaflet  180   b  each pass through the slot  134   a  of the first commissure post  120   a  several times, with the first retaining elements  184   a,    184   b  positioned on the inner side  110  of the frame  102 , and thus on the inner side of the first commissure post  120   a,  and the first portion  230   a  and the second portion  230   b  of the second retaining element  186   a  ( FIG. 10 ) on the outer side  112  of the frame  102 , and thus the outer side of the first commissure post  120   a.  As shown, the first retaining elements  184   a,    184   b  secure the first and the second commissure tabs  194   a,    196   b,  respectively, from being pulled outwardly relative to the frame  102 . In turn, the first and second portions  230   a,    230   b  of the second retaining element  186   a  secure the first and the second commissure tabs  194   a,    196   b,  respectively, from being pulled inwardly relative to the frame  102 . If desired, sutures, film layers, adhesives, thermal bonding or other features can be used to help secure or otherwise couple the first retaining elements  184   a,    184   b  and/or the second retaining elements  186   a,    186   b.    
     As shown, the first commissure tab  194   a  of the first leaflet  180   a  defines a first pass  250   a  through the slot  134   a  (inside-out relative to the first commissure post  120   a ) and a second pass  252   a  through the slot  134   a  (outside-in relative to the first commissure post  120   a ) to define a first loop  254   a  through the slot  134   a.  The first portion  230   a  of the second retaining element  186   a  is positioned within the first loop  254   a  to form a widened cross-section for the first loop  254   a  on the outer side  112  of the frame  102 . The width of the first loop  254   a  is selected to resist, or be restrained from, pulling through the slot  134   a.  The first commissure tab  194   a  of the first leaflet  180   a  defines a third pass  256   a  through the slot  134   a  (outside-in relative to the first commissure post  120   a ) to define a second loop  258   a  passing through the slot  134   a.  The first retaining element  184   a  is positioned within the second loop  258   a  such that the second loop  258   a  encircles the first retaining element  184   a  to form a widened cross-section for the second loop  258   a  on the outer side  112  of the frame  102 . The width of the second loop  258   a  is selected to resist, or be restrained from, pulling through the slot  134   a.  As shown, the first pass  250   a  is positioned adjacent the second pass  252   a,  which is positioned adjacent the third pass  256   a  within the slot  134   a.    
     As shown, the second commissure tab  196   b  of the second leaflet  180   b  defines a first pass  250   b  through the slot  134   a  (inside-out relative to the first commissure post  120   a ) and a second pass  252   b  through the slot  134   a  (outside-in relative to the first commissure post  120   a ) to define a first loop  254   b  through the slot  134   a.  The second portion  230   b  of the second retaining element  186   b  ( FIG. 10 ) is positioned within the first loop  254   b  such that the first loop  254   b  encircles the second retaining element  186   b  to form a widened cross-section for the first loop  254   b  on the outer side  112  of the frame  102 . The width of the first loop  254   b  is selected to resist, or be restrained from, pulling through the slot  134   a.  The second commissure tab  196   b  of the second leaflet  180   b  defines a third pass  256   b  through the slot  134   a  (outside-in relative to the first commissure post  120   a ) to define a second loop  258   b  passing through the slot  134   a.  The first retaining element  184   b  is positioned within the second loop  258   b  such that the first retaining element  184   b  is encircled by the second loop  258   b  to form a widened cross-section for the second loop  258   b  on the outer side  112  of the frame  102 . The width of the second loop  258   b  is selected to resist, or be restrained from, pulling through the slot  134   a.  As shown, the first pass  250   b  is positioned adjacent the second pass  252   b,  which is positioned adjacent the third pass  256   b  within the slot  134   a.    
     The first loops  254   a,b,  are optionally described as outer loops and the second loops  258   a,b  are optionally described as inner loops. In some examples, one or more of the passes  250   a,b,    252   a,b,    256   a,b  are coupled to one another (e.g., by molding, heat sealing/bonding, adhesives, sutures, or other coupling means). Whether coupled or uncoupled (e.g., bonded or unbonded), the various passes can be inserted into the slot  134   a  with the first retaining elements  184   a  on the inner side  110  of the frame  102  and the second retaining element  186   a  outer side of the frame  102  by sliding the first commissure tab  194   a  and the second commissure tab  196   b  into the slot  134   a  through the first end  140   a  ( FIG. 3 ) of the slot  134   a,  which is an open end. In some other examples, the first commissure tab  194   a  and the second commissure tab  196   b  are threaded through the slot  134   a  inside-out and outside in to form the first loops  254   a,b  and the second loops  258   a,b  (e.g., as opposed being slid upwardly into the first slots  1134   a  and the second slots  1136   a ). Although three passes are shown for each of the commissure tabs in  FIG. 9 , fewer passes (two, where a single loop is desired) or more (e.g., where additional loops are desired) are contemplated. 
       FIG. 10  shows the second retaining element  186   a  (which includes the bridge  182   a  ( FIG. 6A ) received over the hanging feature  136   a  (head portion  152   a  is shown), and in particular behind the head portion  152   a  within the channel  156   a  ( FIG. 3 ) formed between the head portion  152   a  and the frame  102 . The second retaining element  186   a  thus defines a hanging loop  280   a  for supporting the first leaflet  180   a  and the second leaflet  180   b  ( FIG. 9 ) to which the second retaining element  186   a  is attached. The remaining first and second commissure tabs  194 ,  196  of the leaflets  180  are secured to and supported from the remaining commissure posts  120 . The relatively smooth turns and reinforcement provided by the retaining elements  184 ,  186  reduce stress concentrations at the commissure posts  120  due to transverse loading of the leaflet construct  104 . And, in turn, the axial support provided the hanging loops, similar to hanging loop  280   a,  provide axial support the leaflet construct  104  and help to reduce axial stress concentrations at the attachment interfaces between the commissure posts  120  and the leaflets  180  ( FIG. 5 ). 
       FIG. 11  is a plan view of another prosthetic valve  1100  and  FIG. 11A  is an isometric view of the prosthetic valve  1100 , according to some embodiments. As shown, the prosthetic valve  1100  includes a frame  1102 , also described as a frame assembly or leaflet frame, a leaflet construct  1104  including a plurality of leaflets  1180 , also described as a leaflet assembly or leaflet module, and an attachment element  1106 , which can also be described as an attachment substrate or an attachment treatment. As shown (e.g.,  FIG. 15 ), the leaflet construct  1104  may be comprised of a plurality of leaflets  1180  that are formed as individual components and then subsequently assembled to the frame  1102  to form the leaflet construct  1104 . The prosthetic valve  1100  can include any of a variety of additional features, such as one or more sealing cuffs, for example. As shown, the prosthetic valve  1100  defines a central longitudinal axis Yv, as well as an inner side  1108  corresponding to a central lumen and an outer side  1109  corresponding to the exterior of the prosthetic valve  1100 . The leaflet construct  1104  has three leaflets that come together, and in particular free edges that come together at a coaptation region in a Y-shaped pattern (when viewed from above), to close the prosthetic valve  1100 . The prosthetic valve  1100  closes in this fashion when the pressure of the blood on the outflow side is greater than the pressure of the blood on the inflow side of the prosthetic valve  1100 . The leaflet free edges of leaflet construct  1104  move apart to open the prosthetic valve  1100  and to let blood flow through the prosthetic valve  1100  from the inflow side when the pressure of the blood on the inflow side of the prosthetic valve  1100  is greater than the pressure on the outflow side of the prosthetic valve  1100 . 
       FIG. 12  is a perspective view of the frame  1102  of the prosthetic valve  1100 , according to some embodiments. In various examples, the frame  1102  serves to operatively support the leaflet construct  1104  in a desired location within the body of a patient (not shown). The frame  1102  is optionally collapsible to a reduced profile, delivery configuration and then expandable (e.g., self-expanding or expanded by the application of an external force, such as a balloon expansion) in situ. As shown in  FIG. 12 , the frame  1102  is optionally annular, defining a cylinder or cylindrical shape, and has a central longitudinal axis Yf. 
     Although the frame  1102  generally defines a circular transverse cross-section, it should be understood that any variety of cross-sections (e.g., oval- or rectangular-shaped) cross-sections are also contemplated. The frame  1102  has an inner side  1110  and an outer side  1112  opposite the inner side  1110 . The inner side  1110  faces toward the central longitudinal axis Yf, and the outer side  1112  faces outwardly, or away from the central longitudinal axis Yf. As shown, the frame  1102  includes a plurality of commissure posts  1120  and a plurality of frame elements  1122 . 
     The frame  1102  can be etched, cut, laser cut, stamped, three-dimensional printed or wire wound, among other suitable processes. The frame  1102  can comprise, such as, but not limited to, any elastically deformable metallic or polymeric material that is generally biocompatible. The frame  1102  can comprise a shape-memory material, such as nitinol, a nickel-titanium alloy. Other materials suitable for the frame  1102  include, but are not limited to, other titanium alloys, stainless steel, cobalt-nickel alloy, polypropylene, acetyl homopolymer, acetyl copolymer, other alloys or polymers, or any other material that is generally biocompatible having adequate physical and mechanical properties to function as a frame  1102  as described herein. 
     In some embodiments, the plurality of commissure posts  1120  are spaced from one another, and arranged at desired locations around a circumference of the frame  1102 . As shown, the plurality of commissure posts  1120  extend parallel to the central longitudinal axis Yf, although angled configurations (e.g., commissure posts angled inwardly toward the central longitudinal axis Yf or outwardly away from the central longitudinal axis Yf) are also contemplated. Although three commissure posts  1120  are shown, any number of commissure posts are contemplated. The plurality of commissure posts  1120  define circumferentially-adjacent ones, or simply adjacent ones of the plurality of commissure posts  1120  moving about the perimeter of the frame  1102 . 
     As shown in  FIG. 12 , other than location and orientation, each of the commissure posts  1120  has a similar design, although examples where the commissure posts differ from one another in various respects are also contemplated. Regardless, for ease of understanding, the features of each of the commissure posts  1120  will be described in association with a first commissure post  1120   a,  an enlarged view of which is shown in  FIG. 13 . The features of the first commissure post  1120   a  will generally be referenced with a numeral followed by an “a.” Similar features of a second commissure post may be subsequently referenced with the same numeral as the first commissure post, but followed by a “b.” Similar features of a third commissure post may be subsequently referenced with the same numeral as the first commissure post  1120   a,  but followed by a “c.” Similarly, when features of each of the commissure posts  1120  are referenced collectively, those features are referenced with the same numeral as identified for the first commissure post  1120   a,  but not followed by a letter. 
     As shown in  FIG. 13 , the first commissure post  1120   a,  includes a first leg  1130   a,  a second leg  1132   a,  a first slot  1134   a,  which can also be described as a first post slot, and a second slot  1136   a,  which can also be described as a second post slot. The first slot  1134   a  and the second slot  1136   a  are each located between the first leg  1130   a  and the second leg  1132   a.  As shown, the first commissure post  1120   a  also includes an intermediate leg  1138   a  positioned between the first leg  1130   a  and the second leg  1132   a.  The first commissure post  1120   a  defines the first slot  1134   a  between the first leg  1130   a  and the intermediate leg  1138   a  and the second slot  1136   a  between the second leg  1132   a  and the intermediate leg  1138   a.  The first commissure post  1120   a  has an outer side corresponding to the frame outer side  1112  and a post inner side corresponding to the frame inner side  1110 . 
     As shown, the first leg  1130   a  and the second leg  1132   a  extend longitudinally, or in a longitudinal direction. In some examples, the first leg  1130   a  and the second leg  1132   a  extend in a longitudinal direction that is parallel to the central longitudinal axis Yf ( FIG. 12 ) of the frame  1102 . In other examples, the first leg  1130   a  and the second leg  1132   a  extend longitudinally, but at some offset relative to the central longitudinal axis Yf (e.g., angularly offset inwardly, toward the central longitudinal axis Yf, angularly offset transversely relative to the central longitudinal axis Yf, or a combination thereof). 
     As shown, each of the first slot  1134   a  and the second slot  1136   a  extends through a thickness of the first commissure post  1120   a,  from the inner side  1110  ( FIG. 12 ) of the frame  1102  to the outer side  1112  ( FIG. 12 ) of the frame  1102 . The slots  1134   a,    1136   a  are formed through the frame in a radial direction relative to a central longitudinal axis Yf of the frame  1102  or the slot is formed at an angle to a radial direction relative to the central longitudinal axis Yf of the frame  1102 . In various examples, one or both of the first slot  1134   a  and the second slot  1136   a  extend in a longitudinal direction that is parallel to the central longitudinal axis Yf ( FIG. 12 ) of the frame  1102 . In other examples, one or both of the first slot  1134   a  and the second slot  1136   a  extend longitudinally, but at some offset relative to the central longitudinal axis Yf (e.g., angularly offset inwardly, toward the central longitudinal axis Yf, angularly offset transversely relative to the central longitudinal axis Yf, or a combination thereof). As shown, one or both of the first slot  1134   a  and the second slot  1136   a  are elongate in shape, with lengths, or heights, much greater than their widths (e.g., more than 2×, 5×, 10×, 20×, or 30×, although a variety of dimensions are suitable). 
     In some examples, the first slot  1134   a  extends from a first end  1140   a  to a second end  1142   a  and the second slot  1136   a  extends from a first end  1144   a  to a second end  1146   a.  As shown, the first ends  1140   a,    1144   a  are open and the second ends  1142   a,    1146   a  are closed. For example, the first ends  1140   a,    1144   a  are “open” in the sense that it opens to a much wider area in the frame  1102  (e.g., more than 5×, 10×, or 20×), whereas the second ends  1142   a,    1146   a  are “closed” in the sense that it terminates at the width of the first slot  1134   a  and the second slot  1136   a.  The widths of the first slot  1134   a  and the second slot  1136   a  are generally selected to allow a desired number of passes or loops of leaflet material through the first slot  1134   a  and the second slot  1136   a.    
     In some embodiments, the first commissure post  1120   a  defines a first hanging feature  1150   a,  also described as a protuberance, hook, or projection, and a second hanging feature  1152   a,  also described as a protuberance, hook, or projection. Each of the first and second hanging features  1150   a,    1152   a  is optionally described as a hanger, shoulder, pin, or hook, for example. The first hanging feature  1150   a  optionally projects longitudinally from the first leg  1130   a  (e.g., parallel to the longitudinal axis Yf of the frame  1102 ). The second hanging feature  1152   a  optionally projects longitudinally from the second leg  1132   a  (e.g., parallel to the longitudinal axis Yf of the frame  1102 ). The first commissure post  1120   a  optionally defines a first channel  1154   a  between the first hanging feature  1150   a  and the intermediate leg  1138   a.  The first commissure post  1120   a  also optionally defines a second channel  1156   a  between the second hanging feature  1152   a  and the intermediate leg  1138   a.  The depths and widths of the channels  1154   a,    1156   a  are generally selected to receive and retain filaments or other desired portions of the leaflet construct  1104  for axially supporting the leaflet construct  1104 . As shown, the hanging features  1150   a,    1152   a  are each located longitudinally-adjacent the second ends  1142   a,    1146   a  of the slots  1134   a,    1136   a  and generally in alignment with the first slot  1134   a  and the second slot  1136   a.  In other examples, the hanging features  1150   a,    1152   a  are offset from the first slot  1134   a  and the second slot  1136   a  (e.g., laterally/circumferentially). 
       FIG. 14  is an enlarged, flattened view of a portion of the frame  1102  between two adjacent commissure posts  1120 , according to some embodiments. Similar portions of the frame  1102  are defined between each of the adjacent commissure posts  1120 , according to some embodiments. In  FIG. 14 , the portion of the frame  1102  is represented in a flattened form for ease of illustration, although it should be understood that the frame  1102  is three-dimensional and generally annular. As shown in  FIG. 14 , the first commissure post  1120   a  is located at a first side of the portion of the frame  1102  and a second commissure post  1120   b  of the plurality of commissure posts  1120  is located at a second side of the portion of the frame  1102  shown in  FIG. 4 . In particular, the frame  1102  defines a first leaflet attachment region  1160   a  between the first commissure post  1120   a  and the second commissure post  1120   b,  as well as leaflet attachment regions  1160  between the remaining commissure posts  1120 . The first leaflet attachment region  1160   a  defines a first side  1162   a,  a second side  1164   a,  and a base  1166   a.  Similar leaflet attachment regions  1160  are defined between each of the adjacent commissure posts  1120 , according to some embodiments. 
     In some embodiments, the frame elements  1122  of the frame  1102  include a plurality of leaflet attachment frame elements  1170 , or simply leaflet attachment elements, that define the leaflet attachment regions, including the first leaflet attachment region  1160   a  shown in  FIG. 14 . The leaflet attachment frame elements  1170  are arranged to support the leaflet construct  1104  and to help define a shape of a leaflet of the leaflet construct  1104 , where that leaflet will project from the first leaflet attachment region  1160   a.  In the example shown in  FIG. 12 , the frame  1102  defines three sets of the leaflet attachment frame elements  1170  that each generally follows the shape of an outline of a leaflet of the leaflet construct  1104 . In different terms, the leaflet attachment frame elements  1170  optionally support leaflets around the leaflet perimeters except at the free edges. 
     As shown in  FIG. 11 , the leaflet construct  1104  includes a plurality of leaflets  1180 .  FIG. 15  shows a first leaflet  1180   a  of a plurality of leaflets  1180  ( FIG. 11 ) from a flattened, plan view prior to assembly with the frame  1102 . This flattened plan view can also be described as a cut pattern, or simply a leaflet pattern. From  FIG. 11 , for example, it should be understood that the leaflet construct  1104  is folded and turned into a cylindrical shape when assembled to the frame  1102 , with each of the plurality of leaflets  1180  being attached circumferentially about the frame  1102 . As should be understood from  FIG. 15 , the plurality of leaflets  1180  are optionally formed as separate components, which are then separately assembled to the frame  1102 . It should also be understood, however, that similar to the leaflet construct  104 , the leaflet construct  1104  optionally includes a plurality of bridges, or bridge regions (e.g. such as bridges  182 ), interconnecting circumferentially-adjacent leaflets  1180 . In such embodiments, the leaflet pattern defines a connected and continuous (e.g., contiguous) annular ring including the plurality of leaflets and bridges between each of the plurality of leaflets. As shown, the plurality of leaflets  1180  are spaced from one another, and arranged, or otherwise distributed at desired locations around a circumference of the leaflet construct  1104 . 
     Although three leaflets  1180  are shown in  FIG. 11 , any number of leaflets is contemplated. The plurality of leaflets  1180  define circumferentially-adjacent ones, or simply adjacent ones of the plurality of leaflets  1180  moving about the circumference of the leaflet construct  1104 . The leaflet construct  1104  can be formed in a variety of manners, including cutting a cylinder of polymer material into a desired shape, cutting a sheet of polymer material into a desired shape, and/or molding (e.g., compression or injection molding) the leaflet construct  1104  with a desired shape. 
     According to various examples, other than location and orientation, each of the plurality of leaflets  1180  has a similar design, although examples where the leaflets differ from one another in various respects are also contemplated. Regardless, for ease of understanding, the features of each of the leaflets  1180  will be described in association with a first leaflet  1180   a.  The features of the first leaflet  1180   a  will generally be referenced with a numeral followed by an “a.” Similar features of a second leaflet may be subsequently referenced with the same numeral as the first leaflet, but followed by a “b.” Similar features of a third leaflet may be subsequently referenced with the same numeral as the first leaflet  1180   a,  but followed by a “c.” Similarly, when features of each of the leaflets are referenced collectively, those features are referenced with the same numeral, but not followed by a letter. Similarly, when features of each of the leaflets  1180  are referenced collectively, those features are referenced with the same numeral, but not followed by a letter. 
     As shown in  FIG. 15 , the first leaflet  1180   a  includes a plurality of first retaining elements  1184   a  and a plurality of second retaining elements  1186   a,  where each of the leaflets  1180  optionally includes a similar first retaining element  1184  and second retaining elements  1186 . The first plurality of retaining elements  1184   a  and the second plurality of retaining elements  1186   a  are optionally molded, adhered and/or heat bonded, or otherwise coupled to the leaflet construct  1104  ( FIG. 11 ) as desired. 
     As indicated on  FIG. 15 , the first leaflet  1180   a  optionally includes a body portion  1190   a,  a plurality of attachment tabs  1192   a  extending from the body portion  1190   a,  a first commissure tab  1194   a  extending from the body portion  1190   a,  and a second commissure tab  1196   a  extending from the body portion  1190   a.    
     The body portion  1190   a,  also described as a leaflet belly, or belly portion, is bounded in broken lines for understanding purposes. The body portion  1190   a  of the first leaflet  1180   a  is the moving portion of the first leaflet  1180   a  in the prosthetic valve  1100  ( FIG. 11 ). It should be appreciated that when assembled to the frame  1102 , the boundaries of the body portion  1190   a  are defined and the body portion  1190   a  takes on a three dimensional shape, rather than the flat shape shown in  FIG. 15 . 
     As such, the broken lines are provided for general visualization purposes of the body portion  1190   a.  In various examples, the shape of the body portion  1190   a  is generally dictated by the lines, or areas of attachment to the frame  1102 . The edges of the body portion  1190   a  generally correspond to fold lines where the attachment tabs  1192   a  and first commissure tab  1194   a  and the second commissure tab  1196   a  are secured to the frame  1102 . As will be described below, the leaflet construct  1104  may be attached to the frame  1102  using attachment element  1106  ( FIG. 11 ), which in turn, may contribute to shape defined by the leaflet attachment regions  1160  and the ultimate shape of the body portion  1190   a.    
     As shown in  FIG. 15 , the body portion  1190   a  of the first leaflet  1180   a  has the general shape of an isosceles trapezoid. Regardless of the exact shape, the body portion  1190   a  generally has a first side  1200   a,  a second side  1202   a,  a leaflet base  1204   a,  and a free edge  1206   a  opposite the leaflet base  1204   a  for coaptating with other leaflets  1180 . In general terms, the shape of the body portion  1190   a  corresponds to the sides and base of the first leaflet attachment region  1160   a  ( FIG. 14 ). As shown, the two sides  1200   a,    1202   a  diverge from the leaflet base  1204   a,  and the leaflet base  1204   a  will be substantially straight in a transverse plane relative to the central longitudinal axis Yf of the frame  1102 . In different terms, leaflet base  1204   a  is perpendicular to the central longitudinal axis Yf of the frame  1102  following assembly. 
     Although the body portion  1190   a  is shown to take on the general shape of an isosceles trapezoid, any number of shapes is contemplated, and the body portion  1190   a  need not be trapezoidal in overall appearance. For example, the body portion  1190   a  may include a central region that defines a shape substantially that of an isosceles trapezoid, with side regions on each side that have a shape substantially that of a triangle. In still other embodiments, the body portion  1190   a  may outline a shape that can be described as U-shaped or a V-shapes, depending on the geometric outline defined by the first leaflet attachment region  1160   a  ( FIG. 14 ). 
     The first leaflet  1180   a  generally defines a fold over portion  1198   a,  also described as a fold over region, outside of the body portion  1190   a,  as demarcated by the broken line in  FIG. 15 . The fold over portion  1198   a  of the first leaflet  1180   a  is the portion that is used to secure the first leaflet  1180   a  to the frame  1102 , where the remaining leaflets  1180  optionally include similar features for securing to the frame  1102 . The leaflet attachment frame elements  1170  ( FIG. 14 ) fit into a fold that is formed between the body portion  1190   a  and the fold over portion  1198   a.  In general terms, the leaflets  1180  extend radially inward from the frame  1102  when coupled to the frame  1102 . The body portion of each leaflet  1180  includes enough material between the commissure posts  1120  of the frame  1102  so that the leaflet free edges of the three leaflet body portions can come together or coapt in the interior of the prosthetic valve  1100  to close the prosthetic valve  1100  as shown in  FIG. 11 . 
     As shown, the plurality of attachment tabs  1192   a  located in the fold over portion  1198   a  are positioned about a perimeter of the body portion  1190   a  and are separated from one another by openings  1208   a  for receiving frame elements  1122  (e.g., leaflet attachment frame elements  1170 ) of the frame  1102 . As shown, one or more of the plurality of attachment tabs  1192   a  optionally includes apertures (not shown) through the thickness of the attachment tabs  1192   a.  The apertures may assist with securing the tabs  1192   a  to the frame  1102  (e.g., directly or via the attachment element  1106 ) using molding, adhesives and/or bonding (e.g., to provide additional surface area for adhesion/bonding), fastening elements (e.g., holes for sutures), or combinations thereof. 
     In various examples, the first commissure tab  1194   a  and the second commissure tab  1196   a  assist with securing the first leaflet  1180   a  to the first commissure post  1120   a  and second commissure post  1120   b  ( FIG. 2 ). As shown in FIG. 15 , the first commissure tab  1194   a  extends from the first side  1200   a  of the body portion  1190   a  and the second commissure tab  1196   a  extends from a second side  1202   a  of the body portion  1190   a.  The first commissure tab  1194   a  extends from a first end  1210   a,  also described as a leaflet end, to a terminal end  1212   a.  Similarly, the second commissure tab  1196   a  extends from a first end  1214   a  to a terminal end  1216   a.  The first commissure tab  1194   a  and the second commissure tab  1196   a  are shown as generally rectangular in shape, with a constant width, although tapers (e.g., toward the terminal ends  1212   a,    1216   a ) are also contemplated. 
     Though not shown in  FIG. 15 , where included (e.g., as shown in  FIGS. 23 and 24 ) bridges extend between and interconnect the plurality of leaflets  1180 . For example, each of the bridges is optionally substantially similar and interconnects, or otherwise extends between adjacent leaflets  1180 . In such examples, it is also contemplated that, when the leaflet construct  1104  is folded into a cylindrical shape and the leaflet construct  1104  is folded onto frame  1102 , the bridges define loops for attachment to the commissure posts  1120 . 
     As shown, the first leaflet  1180   a  includes first retaining elements  1184   a  that are located on each of the first commissure tab  1194   a  and the second commissure tab  1196   a.  Similarly to those of the first leaflet  180   a  and the second leaflet  180   b  of the leaflet construct  104  ( FIG. 5 ), the first retaining elements  1184  of the respective leaflets  1180  are separate and discontinuous from one another (in different terms, they are not contiguous). As shown, the first leaflet  1180   a  also includes second retaining elements  1186   a  that are located on each of the first commissure tab  1194   a  and the second commissure tab  1196   a.  As shown, the first retaining elements  1184   a  and the second retaining elements  1186   a  of the first commissure tab  1194   a  are optionally connected and continuous with one another (e.g., contiguous) and are distinct and not connected to another one of the leaflets  1180 . Similarly, the first retaining elements  1184   a  and the second retaining elements  1186   a  of the second commissure tab  1196   a  are also optionally connected and continuous with one another (e.g., contiguous) and are distinct and not connected to another one of the leaflets  1180 . In other examples (e.g.,  FIGS. 23 and 26 ), connected and continuous (e.g., contiguous) retaining elements between adjacent leaflets  1180  are contemplated. 
     In some examples, the first retaining elements  1184   a  are spaced apart from their adjacent second retaining elements  1186   a  a distance at least as wide as the thickness of a corresponding commissure post  1120  (e.g.,  1120   a ) as measured from the inner side  1110  to the outer side  1112  of the frame  1102 . 
     As previously referenced, the various retaining elements can take a variety of forms. In some examples, one or both of the first retaining elements  1184 ,  1186  are formed as beads of material and/or fibers (e.g., coated fibers) on the commissure tabs of the leaflets  1180 . The various retaining elements are optionally molded, adhered and/or bonded to the underlying material of the leaflets  1180 , such as by thermal bonding. 
     As will be described below, in some examples, the second retaining elements  1186  ( FIG. 15 ) are located adjacent the slots  1134 ,  1136  ( FIG. 13 ) at the outer side  1112  ( FIG. 11 ) and the first retaining elements  1184  ( FIG. 15 ) are located adjacent the slots  1134 ,  1136  at the inner side  1110  of the frame  1102  ( FIG. 12 ). The second retaining elements  1186  are optionally used to help prevent the first and second commissure tabs  1194 ,  1196  ( FIG. 15 ) from pulling inwardly through the slots  1134 ,  1136 , wherein the first retaining elements  1184  are optionally used to help prevent the commissure tabs  1194 ,  1196  from pulling outwardly through the slots  1134 ,  1136  to the outer side  1112  of the frame  1102 . 
     The first retaining elements  1184  and the second retaining elements  1186  can be formed similarly to, and from any of the materials described in association with the first retaining elements  1184  and the second retaining elements  1186 . 
       FIG. 16  shows a portion of the frame  1102  and attachment element  1106 . As previously referenced, the prosthetic valve  1100  optionally includes attachment element  1106 , which can also be described as an attachment substrate or an attachment treatment. The shaded area in  FIG. 16  represents locations where the attachment element  1106  is not present. For example, the attachment element  1106  is optionally one or more layers of material applied to the frame material. If desired, the openings, or gray areas in the attachment element  1106  are optionally formed via laser cutting (e.g., where the attachment element is applied to the frame  1102  as part of a tape wrapping process. Several locations of the attachment element  1106  are marked on  FIG. 7  for ease of understanding. The attachment element  1106  is optionally one more layers of material attached to the frame  1102 . In some examples, the outer side  1112  of the frame  1102  is covered with the attachment element  1106 , which is in the form of one or more layers of film material. One or more portions of the leaflet construct  1104  can then be attached to the attachment element  1106 , thereby helping to define the shapes of the leaflets  1180 . 
       FIG. 17  shows an overlay of portions of the prosthetic valve  1100  illustrating parts of the frame  1102 , first leaflet  1180   a  and the second leaflet  1180   b  of the leaflet construct  1104 , and the attachment element  1106  in an area of the first commissure post  1120   a,  for understanding of assembly thereof, where similar concepts apply in assembling the remaining leaflets  1180  to the frame  1102 . As referenced above, the leaflet construct  1104  ( FIG. 11 ) is attached to the frame  1102  and/or attachment element  1106  using fold over portions, such as the fold over portion  1198   a  ( FIG. 15 ) of the first leaflet  1180   a.  Attachment tabs, such as the attachment tabs  1192   a,    1192   b  of the first leaflet  1180   a  and the second leaflet  1180   b  are received over portions of the frame  1102  and/or attachment element  1106  and attached thereto to attach the leaflet construct  1104  to the frame. As should be understood, one or more of the attachment tabs  1192   a,    1192   b  may be folded to the attachment element  1106 , rather than the frame  1102 . For example, the lowermost attachment tab  1192   a  may be folded to a relatively flat area at the bottom of the attachment element  1106  (not shown), to define a relatively flat base corresponding to that shown for the body portion  1190   a  in  FIG. 15 . In different terms, the attachment tabs do not necessarily have to follow the geometry of the frame  1102 , but can be folded or otherwise attached to follow a geometry separate from that of the frame  1102 , such as that defined by the attachment element  1106 , for example. 
     The fold over portions can be secured in place using adhesives, sutures, sintering, or by other methods as desired. In some examples, apertures, such as the apertures  1199   a  are used to assist with coupling (e.g., molding, adhering and/or bonding) and/or to assist with aligning the attachment tabs at their proper positions. 
       FIGS. 18 to 20  illustrate attachment of the leaflets  1180  to the commissure posts  1120  according to some examples.  FIG. 18  is a transverse cross-section through the first commissure post  1120   a  at the first slot  1134   a  and the second slot  1136   a.  Although relatively sharp corners are shown in  FIG. 18  at the first and second slots  1134   a,    1136   a  of the first commissure post  1120   a,  it should be understood that chamfers, rounds, reliefs coatings and other features may be provided to avoid stress concentrations or other wearing of the first and second leaflets  1180   a,    1180   b  at those slot edges.  FIGS. 19 and 20  are isometric view of the prosthetic valve  1100  in the area of the first commissure post  1120   a.  In this regard, a specific example with regard to the first commissure post  1120   a,  first leaflet  1180   a,  and second leaflet  1180   b  is provided, although and as previously mentioned, it should be readily understood that similar techniques are employable for attaching the remaining commissure tabs of the leaflets  1180  to the remaining commissure posts  1120  of the frame  1102 . 
     As shown in  FIG. 18 , the first commissure tab  1194   a  of the first leaflet  1180   a  extends through the first slot  1134   a  and the second commissure tab  1196   b  of the second leaflet  1180   b  extends through the second slot  1136   a  of the first commissure post  1120   a  several times, with the first retaining elements  1184   a,    1184   b  positioned on the inner side  1110  of the frame  1102 , and thus on the inner side of the first commissure post  1120   a.  The second retaining elements  1186   a,    1186   b  are shown on the outer side  1112  of the frame  1102 , and thus the outer side of the first commissure post  1120   a.  As shown, the first retaining elements  1184   a,    1184   b  secure the first and second commissure tabs  1194   a,    1196   b,  respectively, from being pulled outwardly relative to the frame  1102 . In turn, the second retaining elements  1186   a,    1186   b  secure the commissure tabs  1194   a,    1196   b,  respectively, from being pulled inwardly relative to the frame  1102 . For example, cross-sectional areas of the first and second retaining elements  1184 ,  1186  and portions of the commissure tabs  1194 ,  1196  looped over them are greater than the widths of the slots  1134 . 
     As shown, the first commissure tab  1194   a  of the first leaflet  1180   a  defines a first pass  1250   a  through the first slot  1134   a  (inside-out relative to the first commissure post  1120   a ) and a second pass  1252   a  through the first slot  1134   a  (outside-in relative to the first commissure post  120   a ) to define a first loop  1254   a  through the first slot  1134   a.  The second retaining element  1186   a  is positioned within the first loop  1254   a  such that the second retaining element  1186   a  is encircled to form a widened cross-section for the first loop  1254   a  on the outer side  1112  of the frame  1102 . The width of the first loop  1254   a  is selected to resist, or be restrained from, pulling through the first slot  1134   a.  The first commissure tab  1194   a  of the first leaflet  1180   a  defines a third pass  1256   a  through the first slot  1134   a  (inside-out relative to the first commissure post  1120   a ) to define a second loop  1258   a  passing through the first slot  1134   a.  The first retaining element  1184   a  is positioned within the second loop  1258   a  to encircle the first retaining element  1184   a  and form a widened cross-section for the second loop  1258   a  on the outer side  1112  of the frame  1102 . The width of the second loop  1258   a  is selected to resist, or be restrained from, pulling through the first slot  1134   a.  As shown, the first pass  1250   a  is positioned adjacent, and opposite the second pass  1252   a,  and adjacent the third pass  1256   a,  with the third pass  1256   a  between the first pass  1250   a  and the second pass  1252   a  within the first slot  1134   a.    
     As shown, the second commissure tab  1196   b  of the second leaflet  1180   b  defines a first pass  1250   b  through the second slot  1136   a  (inside-out relative to the first commissure post  1120   a ) and a second pass  1252   b  through the second slot  1136   a  (outside-in relative to the first commissure post  1120   a ) to define a first loop  1254   b  through the second slot  1136   a.  The second retaining element  1186   b  is positioned within the first loop  1254   b  to encircle the second retaining element  1186   b  and form a widened cross-section for the first loop  1254   b  on the outer side  1112  of the frame  1102 . The width of the first loop  1254   b  is selected to resist, or be restrained from, pulling through the second slot  1136   a.  The second commissure tab  1196   b  of the second leaflet  1180   b  defines a third pass  1256   b  through the first slot  1134   a  (inside-out relative to the first commissure post  1120   a ) to define a second loop  1258   b  passing through the first slot  1134   a.  The first retaining element  1184   b  is positioned within the second loop  1258   b  to encircle the first retaining element  1184   b  and form a widened cross-section for the second loop  1258   b  on the outer side  1112  of the frame  1102 . The width of the second loop  1258   b  is selected to resist, or be restrained from, pulling through the second slot  1136   a.  As shown, the first pass  1250   b  is positioned adjacent, and opposite the second pass  1252   b,  and adjacent the third pass  1256   b  with the third pass  1256   b  between the first pass  1250   b  and the second pass  1252   b  within the second slot  1136   a.    
     The first loops  1254   a,b,  are optionally described as outer loops and the second loops  1258   a,b  are optionally described as inner loops. In some examples, one or more of the passes  1250   a,b,    1252   a,b,    1256   a,b  are coupled to one another (e.g., by molding, heat sealing/bonding, adhesives, sutures, or other means). Whether coupled or uncoupled (e.g., bonded or unbonded), the various passes can be inserted into the respective slots  1134   a,    1136   a  with the first retaining elements  1184   a,    1184   b  on the inner side  1110  of the frame  1102  and the second retaining elements  1186   a,    1186   b  outer side of the frame  1102  by sliding the first commissure tab  1194   a  and the second commissure tab  1196   b  into the respective first slot  1134   a  and second slot  1136   a  through the first ends  1140   a,    1144   a  ( FIG. 13 ) of the first and second slots  1134   a,    1136   a,  respectively. As shown, each of the first ends  1140   a,    1144   a  are open ends. In some other examples, the first commissure tab  1194   a  and the second commissure tab  1194   b  are threaded through the slots  1134   a,    1136   a  inside-out and outside-in to form the loops  1254   a,b,    1258   a,b  (e.g., as opposed being slid upwardly into the slots  1134   a,    1136   a ). Additionally, although three passes are shown for each of the commissure tabs in  FIG. 18 , fewer passes (two, where a single loop is desired) or more (e.g., where additional loops are desired) are contemplated. 
     As shown, the first leaflet  1180   a  and the second leaflet  1180   b  are spaced from one another at the inner side  1110  of the frame  1102 , which can be described as the leaflets defining a commissure gap  1260  at the first commissure post  1120   a.  In some embodiments, the prosthetic valve  1100  defines a similar commissure gap  1260  between each of the circumferentially-adjacent leaflets  1180 . In some examples, the commissure gap  1260  helps permit flow (e.g., both forward and backward flow) through the gap  1260 , forming a small leak through the gap  1260 . This localized flow region (available when valve closed, and also when the valve is open) helps prevent thrombus propagation adjacent the frame  1102 , next to the commissure posts  1120 , where there might otherwise be low, or stagnant flow. 
       FIGS. 19 and 20  shows the first retaining element  1184   a  and the second retaining element  1186   a  of the first leaflet  1180   a  received over the first hanging feature  1150   a  and in within the first channel  1154   a  ( FIG. 13 ). The first retaining element  1184   a  and the second retaining element  1186   a  thus defines a hanging loop  1280   a  for supporting the first leaflet  1180   a,  and specifically the first commissure tab  1194   a  from the first commissure post  1120   a.  Also shown is the  FIGS. 19 and 20  the first retaining element  1184   b  and the second retaining element  1186   b  of the second leaflet  1180   b  similarly received over the second hanging feature  1152   a  and in within the second channel  1156   a  ( FIG. 13 ). The first retaining element  1184   b  and the second retaining element  1186   b  thus define a hanging loop  1280   b  for supporting the second leaflet  1180   b,  and specifically the second commissure tab  1196   b  from the first commissure post  1120   a.    
     The remaining commissure tabs of the leaflets  1180  are secured to and supported from the remaining commissure posts  1120 . Whereas the relatively smooth turns and reinforcement provided by the first and second retaining elements  1184 ,  1186  reduce stress concentrations at the commissure posts  1120  due to transverse loading of the leaflet construct  1104 , the axial support provided the hanging loops, similar to hanging loops  1280   a,    1280   b  provide axial support the leaflet construct  1104  and help to reduce axial stress concentrations at the attachment interfaces between the commissure posts  1120  and the leaflets  1180 . 
       FIG. 21  is illustrative of another leaflet attachment configuration between leaflets and commissure posts of a valve, such as the prosthetic valves  100 ,  1100 , for example.  FIG. 21  shows a first commissure post  2120   a  that includes the same features as the first commissure post  1120   a  unless otherwise indicated. As such, the description of the features and options of the first commissure post  1120   a  apply equally with respect to the first commissure post  2120   a  and operation and use of the first commissure post  2120   a  should be understood with reference to substitution or modification of the features of the prosthetic valve  100  or the prosthetic valve  1100 . 
     As shown in  FIG. 21 , the first commissure post  2120   a  includes a first leg  2130   a,  a second leg  2132   a,  a first slot  2134   a,  which can also be described as a first post slot, and a second slot  2136   a,  which can also be described as a second post slot. The first slot  2134   a  and the second slot  2136   a  are each located between the first leg  2130   a  and the second leg  2132   a.  As shown, the first commissure post  2120   a  also includes an intermediate leg  2138   a  positioned between the first leg  2130   a  and the second leg  2132   a.  The first commissure post  2120   a  defines the first slot  2134   a  between the first leg  2130   a  and the intermediate leg  2138   a  and the second slot  2136   a  between the second leg  2132   a  and the intermediate leg  2138   a.  The first commissure post  2120   a  has an outer side corresponding to a frame outer side  2112  and a post inner side corresponding to a frame inner side  2110 . The first commissure post  2120   a  further defines a first side  2148   a,  also described as a first lateral edge, and a second side  2149   a,  also described as a second lateral edge. 
       FIG. 21  shows a first leaflet  2180   a  that optionally includes the same features as the first leaflet  1180   a  unless otherwise indicated. As such, the description of the features and options of the first leaflet  1180   a  apply equally with respect to the first leaflet  2180   a.  As shown, the first leaflet  2180   a  includes a first commissure tab  2194   a,  a first retaining element  2184   a  and a second retaining element  2186   a.  The first retaining element  2184   a  and the second retaining element  2186   a  are optionally similar to the first retaining element  1184   a  and the second retaining element  1186   a,  with the first retaining element  2184   a  and the second retaining element  2186   a  being connected and continuous (e.g., contiguous) to define a loop (not shown) for hanging the first leaflet  2180   a  (e.g., from a hanging feature of the first commissure post  2120   a  similarly to the prosthetic valve  1100 ). Although the first retaining element  2184   a  and the second retaining element  2186   a  are optionally connected and define a loop for hanging, they are optionally separate as desired (e.g., similar to the first retaining element  1184   a  and the second retaining element  1186   a  of the first leaflet  1180   a ). 
       FIG. 21  shows a second leaflet  2180   b  that includes the same features as the second leaflet  1180   b  unless otherwise indicated. As such, the description of the features and options of the second leaflet  1180   b  apply equally with respect to the second leaflet  2180   b.  As shown, the second leaflet  2180   b  includes a second commissure tab  2196   b,  a first retaining element  2184   b  and a second retaining element  2186   b.  The first retaining element  2184   b  and the second retaining element  2186   b  are optionally similar to the first retaining element  1184   b  and the second retaining element  1186   b,  with the first retaining element  2184   b  and the second retaining element  2186   b  being connected and continuous (e.g., contiguous) to define a loop (not shown) for hanging the second leaflet  2180   b.  Although the first retaining element  2184   b  and the second retaining element  2186   b  are optionally connected and define a loop for hanging, they are optionally separate as desired (e.g., similar to the first retaining element  1184   b  and the second retaining element  1186   b  of the second leaflet  1180   b ). 
     As shown in  FIG. 21 , the first commissure tab  2194   a  of the first leaflet  2180   a  extends through the first slot  2134   a  a plurality of times (also described as a plurality of passes) and the second commissure tab  2196   b  of the second leaflet  2180   b  extends through the second slot  2136   a  of the first commissure post  2120   a  a plurality of times (also described as a plurality of passes), with the first retaining elements  2184   a,    2184   b  positioned on the outer side  2112  of the frame  2102 , and thus on the outer side of the first commissure post  2120   a.    
     The second retaining elements  2186   a,    2186   b  are also positioned on the outer side  2112  of the frame  2102 , and thus the outer side of the first commissure post  2120   a.  As shown, the first retaining elements  2184   a,    2184   b  secure the commissure tabs  2194   a,    2196   b,  respectively, from being pulled outwardly relative to the frame  2102 . In turn, the second retaining elements  2186   a,    2186   b  secure the commissure tabs  2194   a,    2196   b,  respectively, from being pulled inwardly relative to the frame  2102 . 
     As shown, the first commissure tab  2194   a  of the first leaflet  2180   a  defines a first pass  2250   a  through the first slot  2134   a  (inside-out relative to the first commissure post  2120   a ) and a second pass  2252   a  through the first slot  2134   a  (outside-in relative to the first commissure post  2120   a ) to define a first loop  2254   a  through the first slot  2134   a.  The second retaining element  2186   a  is positioned within the first loop  2254   a  to encircle the second retaining element  2186   a  and form a widened cross-section for the first loop  2254   a  on the outer side  2112  of the frame  2102 . The width of the first loop  2254   a  is selected to resist, or be restrained from, pulling through the first slot  2134   a.    
     The first commissure tab  2194   a  of the first leaflet  2180   a  defines a third pass  2256   a  around the outside of the first commissure post  2120   a,  from the inner side  2110  around the first side  2148   a  to the outer side  2112  and then back from the outer side  2112  to the first side  2148   a  to define a fourth pass  2259   a,  the third and fourth passes  2256   a,    2259   a  defining a second loop  2258   a  passing outside the commissure post  2120   a  on the first side  2148   a.  The first retaining element  2184   a  is positioned within the second loop  2258   a  to encircle the first retaining element  2184  and form a widened cross-section for the second loop  2258   a  on the outer side  2112  of the frame  2102 . The width of the second loop  2258   a  is selected as desired (e.g., to fit against the outer side  2112  between the first leaflet  2180   a  and the second leaflet  2180   b.  As shown, the first pass  2250   a  is positioned adjacent, and opposite the second pass  2252   a,  and the third pass  2256   a  and fourth pass  2259   a  are positioned adjacent each other. 
     The second commissure tab  2196   b  defines a similar set of features to those of the first commissure tab  2194   a,  which are labeled on  FIG. 21  for reference. As shown, the second commissure tab  2196   b  of the second leaflet  2180   b  defines a first pass  2250   b  through the second slot  2136   a  (inside-out relative to the first commissure post  2120   a ) and a second pass  2252   b  through the second slot  2136   a  (outside-in relative to the first commissure post  2120   a ) to define a first loop  2254   b  through the second slot  2136   a.  The second retaining element  2186   b  is positioned within the first loop  2254   b  to encircle the second retaining element  2186   b  and form a widened cross-section for the first loop  2254   b  on the outer side  2112  of the frame  2102 . The width of the first loop  2254   b  is selected to resist, or be restrained from, pulling through the second slot  2136   a.    
     The second commissure tab  2196   b  of the second leaflet  2180   b  defines a third pass  2256   b  around the outside of the first commissure post  2120   a,  from the inner side  2110  around the second side  2149   a  to the outer side  2112  and then back from the outer side  2112  to the second side  2149   a  to define a fourth pass  2259   b,  the third and fourth passes  2256   b,    2259   b  defining a second loop  2258   b  passing outside the commissure post  2120   a  on the second side  2149   a.  The first retaining element  2184   a  is positioned within the second loop  2258   a  to encircle the first retaining element  2184   a  and form a widened cross-section for the second loop  2258   b  on the outer side  2112  of the frame  2102 . The width of the second loop  2258   b  is selected as desired (e.g., to fit against the outer side  2112  between the first leaflet  2180   a  and the second leaflet  2180   b ). 
     As shown, the first retaining elements  2184   a,    2184   b,  and thus the second loops  2258   a,    2258   b  are secured together (e.g., with an adhesive or one or more fasteners, such as sutures or staples). In  FIG. 21 , a secondary coupler  2290  is shown in broken lines secured around the first retaining elements  2184   a,    2184   b.  As shown, the secondary coupler  2290  is a filament, such as a suture or staple, for securing the first retaining elements  2184   a,    2184   b  together. In other examples, the secondary coupler  2290  includes coating(s) or layer(s) of material over molded or otherwise disposed on the exterior and/or interior side of the frame  2102  to help couple the first loops  2254  and the second loops  2258  to one another and the frame  2102 . For example, one or more layers of tape may be overwrapped onto first loops  2254  and/or second loops  2258 , one or more jackets or covers of material may be placed over and secured to the first loops  2254  and/or second loops  2258 , or other techniques may be employed. Generally, such materials may be selected not only to secure the first loops  2254  and the second loops  2258  in place, but may also be employed to form a continuous surface without cracks or other defects, which may help avoid tissue ingrowth and/or thrombus formation where such avoidance is desirable. Similarly, any of the other loop and post arrangements provided in this disclosure may be coupled with one or more secondary couplers (e.g., by one or more sutures, filaments, layers, and/or coatings). With the arrangement shown the second loops  2258   a,    2258   b  can help prevent the first loops  2254   a,    2254   b  from pulling outwardly (radial outward) from the commissure post  2120   a.    
     The first loops  2254   a,b,  are optionally described as outer loops and the second loops  2258   a,b  are also optionally described as outer loops. In some examples, one or more of the passes  2250   a,b,    2252   a,b,    2256   a,b,    2259   a,b  are coupled to one another (e.g., by molding, heat sealing, adhesives, sutures, or other means). Whether coupled or uncoupled (e.g., bonded or unbonded), the passes can be inserted into the first slot  2134   a  and second slot  2136   a,  respectively, with the first retaining elements  2184   a,b  on the outer side  2112  of the frame  2102  and the second retaining elements  2186   a,b  outer side of the frame  2102  by sliding the first and second commissure tabs  2194   a,    2196   b  into the first slot  2134   a  and the second slot  2136   a  through open ends of the slots (not shown, but see the first commissure post  2120   a  for an example). 
     In some other examples, the first and second commissure tabs  1194   a,    1194   b  are threaded through the slots  2134   a,    2136   a  and around the sides  2148   a,    2149   a  (e.g., rather than being slid up into the slots  2134   a,    2136   a  and around the first and second legs  2130   a,    2132   a.  Although the described number of passes are shown for each of the commissure tabs in  FIG. 21 , fewer or greater passes are also contemplated. 
     With the arrangement shown in  FIG. 21 , none of the first retaining elements  2184 , second retaining elements  2186 , first loops  2254 , or second loops  2258  resides on the inner side  2110  of the frame  2102 . Thus, those features are outside of the flow field and do not interfere with blood flow through the prosthetic valve  1100 . Although relatively sharp corners are shown in  FIG. 21  at the first and second slots  2134   a,    2136   a  of the first commissure post  2120   a,  it should be understood that chamfers, rounds, reliefs coatings and other features may be provided to avoid stress concentrations or other wearing of the first and second leaflets  2180   a,    2180   b  at those slot edges. 
     As shown, the first leaflet  2180   a  and the second leaflet  2180   b  are spaced from one another at the inner side  2110  of the frame  2102 , which can be described as the leaflets defining a commissure gap  2260  at the commissure post  2120   a.  In some embodiments, the prosthetic valve (e.g., prosthetic valve  1100 ) defines similar commissure gaps between each, circumferentially-adjacent leaflets of the prosthetic valve. 
       FIG. 22  shows another, first commissure post  3120   a  for a prosthetic valve, such as the prosthetic valve  100  or prosthetic valve  1100 . As shown, the first commissure post  3120   a  is substantially similar to the first commissure post  1120   a,  although the first commissure post  3120   a  forms a single slot  3134   a  (as opposed to two slots as with the first commissure post  1120   a.    FIG. 23  shows an example of first leaflet  3180   a  and the second leaflets  3180   b  secured to the first commissure post  3120   a  similarly to the first commissure post  1120   a,  although the first commissure tab  3194   a  and the second commissure tab  3196   b  are secured in the single slot  3134   a,  rather than two slots as with the first commissure post  1120   a  of the prosthetic valve  1100 . That is, the design of the first commissure post  3120   a  and attachment arrangement are optionally employed for the prosthetic valve  1100  for one or more of the commissure posts  1120  as desired. Again, although relatively sharp corners are shown, it should be understood that chamfers, rounds, reliefs coatings and other features may be provided to avoid stress concentrations or other wearing of the leaflets  3180   a,    3180   b  at the slot edges. 
       FIGS. 24-28  show various alternative arrangements of first retaining elements  5184  and second retaining elements  5186  on first commissure tabs  5194  and second commissure tabs  5196  of leaflets  5180 . As previously mentioned, the suffix “a” generally denotes a first one of the leaflets  5180   a  and “b” a second one of the leaflets  5180   b.    FIG. 24  illustrates a similar arrangement as that of the prosthetic valve  100 .  FIG. 25  illustrates a similar arrangement as that of the prosthetic valve  100 , with the second retaining element  5186  being separate and a bridge  5182  extending between the leaflets  5180 .  FIG. 26  is similar to  FIG. 25 , but without a bridge.  FIG. 27  shows a similar arrangement as  FIG. 24 , but without a bridge. Finally,  FIG. 28  shows an arrangement without a bridge and with first retaining elements and second retaining elements that are looped, or interconnected on each of the respective commissure tabs  5194 ,  5196 . It should be understood that any of the foregoing arrangements are contemplated and can be employed as appropriate to achieve loop configurations for securing leaflets to commissure posts as described above. 
     Prosthetic valve leaflets detaching from a support structure, or frame, constitute a high risk to a patient into which it is placed. One factor contributing to leaflet detachment can be peak stress in the leaflet at the commissure region when the prosthetic valve is closed and under fluid backpressure.  FIGS. 29 and 30  show a commissure attachment region variation and associated leaflet closing profile at the outflow end that can be employed in any of the embodiments and examples previously described. Adjacent, diverging leaflet attachment regions, may provide beneficial overall stress profiles in the leaflet adjacent the commissure regions of the leaflets. 
     As shown in  FIG. 29 , the commissure attachment regions  6034 ,  6036  (which may correspond to a modified version of the slots  1134 ,  1136  of  FIG. 13  or the slots  2134 ,  2136  of  FIG. 21 ) of commissure post  6120  (which may correspond to commissure posts  1120  or  2120 ) are modified to provide means by which to preserve, if not shorten, prosthetic valve height while reducing the peak commissure stress in the leaflet at the commissure post without altering the leaflet material properties. 
       FIG. 30  shows a prosthetic valve  6100 , which may be substantially the same as the prosthetic valve  1100 , apart from the diverging commissure attachment region modification. As shown, the prosthetic valve  6100  includes a frame  6102  (designated generally in  FIG. 30 ) including a plurality of the commissure posts  6120  configured similarly to the example of  FIG. 29 . The prosthetic valve  6100  also includes a plurality of leaflets  6040  coupled to and supported by the frame  6102 . 
     As shown in  FIG. 29 , the upper most portion of adjacent commissure attachment regions  6134 ,  6136  (e.g., the slots  1134 ,  1136  or the slots  2134 ,  2136 ) on the frame (e.g., the frame  1102  or  2102 ) have been modified from being non-divergent (e.g., parallel as shown in  FIGS. 1, 11A, and 22 ) to being divergent. For example, the adjacent commissure attachment regions  6134 ,  6136  of each commissure post  6120  optionally terminate by extending away from a middle axis Yf positioned centrally between each of the adjacent commissure attachment regions  6134 ,  6136 , the pair diverging from a location below the commissure post tip in the outflow direction. The adjacent commissure attachment regions  6134 ,  6136  may diverge along their entire heights, or may have a base portion  6134   b,    6136   b  that is parallel or otherwise non-diverging and a terminal portion  6134   t,    6136   t  that is diverging as shown in  FIG. 29 . 
       FIG. 31  is a schematic view of one of the plurality of leaflets  6040  (e.g., which may correspond to one of the plurality of leaflets  1180  or one of the plurality of leaflets  2180 ) having a cusp  6050 , a free edge  6054 , and commissure regions  6052 . The free edge  6054  extends to two termini  6056 . The two termini  6056  are defined at an intersection of the leaflet free edge  6054  and the leaflet attachment region  6043 . The leaflet attachment regions  6043  of adjacent leaflets  6040  are configured to be coupled to the commissure posts  6120  at locations on the adjacent leaflets  6040  that are adjacent the termini  6056  of the adjacent leaflets  6040 . 
     As illustrated schematically in  FIG. 31 , a (dashed) fold line  6058  defines an outer margin  6042  of the cusp  6050  and commissure regions  6052  used to secure the leaflet  6040  to the frame  6102  (e.g., frame  1102  or frame  2102 ). A free edge region  6046  is that location of the leaflet  6040  including and adjacent to the leaflet free edge  6054 . The outer margin  6042  of each leaflet  6040  is coupled to the frame  6102 , and the free edge  6054  of the leaflet  6040  extends across a cylindrical region defined by the frame  6102 . In terms of the first leaflet  1180   a  ( FIG. 15 ) of the plurality of leaflets  1180 , the cusp  6050  of  FIG. 31  corresponds to the body portion  1190   a  and the outer margin  6042  corresponds to the fold over portion  1198   a,  with the free edge  6054  corresponding to the free edge  1206   a  ( FIG. 15 ). The same features of the leaflets  2180  similarly correspond to those of the leaflet  6040 . As previously described in association with the leaflets  1180 ,  2180 , the outer margin  6042  (the fold over portions) are used to secure the leaflet  6040  onto a frame, such as the frame  1102  or frame  2102 . 
     In various examples, the commissure regions  6052  of adjacent ones of the leaflets  6040  are operable to pass through the adjacent commissure attachment regions  6134 ,  6136  (e.g., slots) in a side-by-side relationship. The commissure regions  6052  of adjacent leaflets  6040  are coupled to the frame  6020  at the diverging commissure attachment regions  6134 ,  6136 . Because the commissure post  6120  defines diverging commissure attachment regions  6134 ,  6136  that diverge in the outflow direction towards the commissure post tip the commissure regions  6052  of adjacent, respective leaflets  6040  will also diverge from a location away from the commissure post tip in the outflow direction when adjacent leaflets are in a closed, coapted position. 
     Non-diverging commissure attachment regions (e.g., such as those shown in  FIGS. 11 and 22 ) may have a maximal stress at the region corresponding to the terminus  6056  when a leaflet is in the closed position. It turn, use of diverging commissure attachment regions (e.g., as shown in  FIGS. 29 and 30 ), may help translate the region of maximal stress away from the termini  6056  of adjacent leaflets  6040 , to be distributed over a larger area, and to also have a reduced magnitude. For example, stress force vectors within the leaflets  6040  along diverging regions proximate the termini  6056  may be reduced relative to the same basic frame and leaflet arrangement but with non-diverging commissure attachment regions by a reduction of 41% of peak stress in the leaflets  6040  in the free edges  6054  at the termini  6056  for a given frame length. The stress within the leaflets  6040  along the diverging region (e.g., in the free edges  6054  at the termini  6056 ) may be reduced more than 40% relative to a non-diverging attachment when exposed to peak closing pressures of about 135 mmHg for a given support structure length. It has been demonstrated that the location of maximum loaded stress can be moved to a predetermined and more favorable location and the magnitude and distribution of stress that a given region of the leaflet  6040  experiences can be changed by changing the geometry of the support attachment region (i.e., by using diverging attachment regions for adjacent leaflets), and similar results are expected by modifying the divergence and curvature of the slots  1134 ,  1136  and slots  2134 ,  2136  similar to that of the leaflet attachment regions  6134 ,  6136 , for example. 
     Although some examples have been provided, it should be understood that similar diverging attachment regions may be implemented with cut tube, wire frame, or any other type of frame (or frame material) as desired to achieve reduced, and more distributed stresses from the leaflet termini. The attachment configurations described above can be particularly advantageous when employed with polymeric (e.g., ePTFE-based) leaflets, although any of a variety of leaflet materials are contemplated. 
     Leaflet Materials 
     In various examples, any of the leaflet constructs described herein (e.g., leaflet construct  104  or  1104 ) may be formed of a biocompatible, synthetic material (e.g., including ePTFE and ePTFE composites, or other materials as desired). Other biocompatible polymers which can be suitable for use in synthetic leaflets include but are not limited to the groups of urethanes, silicones (organopolysiloxanes), copolymers of silicon-urethane, styrene/isobutylene copolymers, polyisobutylene, polyethylene-co-poly(vinyl acetate), polyester copolymers, nylon copolymers, fluorinated hydrocarbon polymers and copolymers or mixtures of each of the foregoing. 
     In other examples, such leaflet construct is formed of a natural material, such as repurposed tissue, including bovine tissue, porcine tissue, or the like. 
     As used herein, the term “elastomer” refers to a polymer or a mixture of polymers that has the ability to be stretched to at least 1.3 times its original length and to retract rapidly to approximately its original length when released. The term “elastomeric material” refers to a polymer or a mixture of polymers that displays stretch and recovery properties similar to an elastomer, although not necessarily to the same degree of stretch and/or recovery. The term “non-elastomeric material” refers to a polymer or a mixture of polymers that displays stretch and recovery properties not similar to either an elastomer or elastomeric material, that is, considered not an elastomer or elastomeric material. 
     In accordance with some embodiments herein, the leaflet construct comprises a composite material having at least one porous synthetic polymer membrane layer having a plurality of pores and/or spaces and an elastomer and/or an elastomeric material and/or a non-elastomeric material filling the pores and/or spaces of the at least one synthetic polymer membrane layer. In accordance with other examples, the leaflet construct further comprises a layer of an elastomer and/or an elastomeric material and/or a non-elastomeric material on the composite material. In accordance with some examples, the composite material comprises porous synthetic polymer membrane by weight in a range of about 10% to 90% 
     An example of a porous synthetic polymer membrane includes expanded fluoropolymer membrane having a node and fibril structure defining the pores and/or spaces. In some examples, the expanded fluoropolymer membrane is expanded polytetrafluoroethylene (ePTFE) membrane. Another example of porous synthetic polymer membrane includes microporous polyethylene membrane. 
     Examples of an elastomer and/or an elastomeric material and/or a non-elastomeric material include, but are not limited to, copolymers of tetrafluoroethylene and perfluoromethyl vinyl ether (TFE/PMVE copolymer), (per)fluoroalkylvinylethers (PAVE), urethanes, silicones (organopolysiloxanes), copolymers of silicon-urethane, styrene/isobutylene copolymers, polyisobutylene, polyethylene-co-poly(vinyl acetate), polyester copolymers, nylon copolymers, fluorinated hydrocarbon polymers and copolymers or mixtures of each of the foregoing. In some examples, the TFE/PMVE copolymer is an elastomer comprising essentially of between 60 and 20 weight percent tetrafluoroethylene and respectively between 40 and 80 weight percent perfluoromethyl vinyl ether. In some examples, the TFE/PMVE copolymer is an elastomeric material comprising essentially of between 67 and 61 weight percent tetrafluoroethylene and respectively between 33 and 39 weight percent perfluoromethyl vinyl ether. In some examples, the TFE/PMVE copolymer is a non-elastomeric material comprising essentially of between 73 and 68 weight percent tetrafluoroethylene and respectively between 27 and 32 weight percent perfluoromethyl vinyl ether. The TFE and PMVE components of the TFE-PMVE copolymer are presented in wt %. For reference, the wt % of PMVE of 40, 33-39, and 27-32 corresponds to a mol % of 29, 23-28, and 18-22, respectively. 
     In some examples, the TFE-PMVE copolymer exhibits elastomer, elastomeric, and/or non-elastomeric properties. 
     In some examples, the composite material further comprises a layer or coating of TFE-PMVE copolymer comprising from about 73 to about 68 weight percent tetrafluoroethylene and respectively from about 27 to about 32 weight percent perfluoromethyl vinyl ether. 
     In some examples, the leaflet construct is an expanded polytetrafluoroethylene (ePTFE) membrane having been imbibed with TFE-PMVE copolymer comprising from about 60 to about 20 weight percent tetrafluoroethylene and respectively from about 40 to about 80 weight percent perfluoromethyl vinyl ether, the leaflet construct further including a coating of TFE-PMVE copolymer comprising from about 73 to about 68 weight percent tetrafluoroethylene and respectively about 27 to about 32 weight percent perfluoromethyl vinyl ether on the blood-contacting surfaces. 
     As discussed above, the elastomer and/or an elastomeric material and/or a non-elastomeric material may be combined with the expanded fluoropolymer membrane such that the elastomer and/or the elastomeric material and/or the non-elastomeric material occupies substantially all of the void space or pores within the expanded fluoropolymer membrane. 
     In accordance with an embodiment, the composite material can include an expanded fluoropolymer material made from porous ePTFE membrane, for instance as generally described in U.S. Pat. No. 7,306,729 to Bacino. 
     The expanded fluoropolymer membrane, used to form some of the composites described, can comprise PTFE homopolymer. In alternative embodiments, blends of PTFE, expandable modified PTFE and/or expanded copolymers of PTFE can be used. Non-limiting examples of suitable fluoropolymer materials are described in, for example, U.S. Pat. No. 5,708,044, to Branca, U.S. Pat. No. 6,541,589, to Baillie, U.S. Pat. No. 7,531,611, to Sabol et al., U.S. patent application Ser. No. 11/906,877, to Ford, and U.S. patent application Ser. No. 12/410,050, to Xu et al. 
     Frame Materials 
     The various frames can be etched, cut, laser cut, stamped, three-dimensional printed or wire wound, among other suitable processes. The frames can be self-expanding or balloon expandable (e.g., when configured for transcatheter implantation) or non-expandable (e.g., when configured for surgical implantation). The various frames can comprise materials, such as, but not limited to, any metallic or polymeric material, such as an elastically (e.g., nitinol) or plastically (e.g., stainless steel) deformable metallic or polymeric material that is generally biocompatible. Other materials suitable for any of the frames described herein include, but are not limited to, other titanium alloys, stainless steel, cobalt-nickel alloy, polypropylene, acetyl homopolymer, acetyl copolymer, a drawn filled tube (e.g., nitinol wire with a platinum core), other alloys or polymers, or any other material that is generally biocompatible having adequate physical and mechanical properties to function as a frame as described herein. 
     Methods of Making 
     Various methods of making prosthetic valves are contemplated for the various prosthetic valves described herein. Generally, the methods include providing a frame and a leaflet construct according to any of the above-described embodiments and securing the leaflet construct to the frame. 
     In some methods, the leaflet construct is at least partially coupled to the frame by a looped structure. For example, in some methods part of the leaflet construct (e.g., the bridge and/or the retaining element) is secured over the hanging element of the frame to axially support the leaflet construct from the hanging element. Additionally or alternatively, the commissure tabs of the leaflet construct define one or more loops that are passed through slots in the commissure posts of the frames, such as the commissure posts according to any of the frame embodiments previously described. In some examples, inner retaining elements pass through one or more of the loops to help widen the loops and help prevent the loop(s), or passes of material, from pulling outwardly through the slots in the commissure posts. Outer retaining elements additionally or alternatively help prevent the loop(s), or passes of material, from pulling inwardly through the slots in the commissure posts. In various examples, the loop(s) of material are optionally coupled to one another and/or to the frame (e.g., bonded, over molded, coated, adhered by an outer wrap of film, sutured, and/or otherwise secured) to help secure the commissure tabs to the commissure posts. The body portions of the leaflets are optionally attached to the frame using attachment tabs secured through and folded over the outer side of the frame and/or attachment element. 
     Transcatheter Delivery System 
     In some embodiments, with reference to  FIG. 32 , a prosthetic valve delivery system  7000  comprises a prosthetic valve  7100  (such as any of the prosthetic valves previously described) configured as a transcatheter prosthetic valve having a collapsed configuration and an expanded configuration and an elongated flexible catheter  7200 , such as a balloon catheter, configured to deploy the prosthetic valve  7100  via catheter. The catheter  7200  can comprise a balloon to expand the prosthetic valve  7100  and/or if required, to touch up the prosthetic valve  7100  to ensure proper seating. The prosthetic valve  7100  can be mounted to the distal section of the catheter  7200  for delivery through the vasculature. In order to hold the prosthetic valve  7100  in a collapsed configuration on the catheter  6200 , the prosthetic valve delivery system  7000  may further comprise a removable sheath (not shown) to closely fit over the transcatheter prosthetic valve  7100 . 
     Some methods of delivery include the steps of radially compressing a prosthetic valve (such as any of the prosthetic valves previously described) into its collapsed configuration onto the distal end of an elongate flexible catheter having proximal and distal ends; delivering the prosthetic valve to a tissue orifice, such as a native aortic valve orifice  7400 , via a transfemoral or transapical route, and expanding the prosthetic valve into the tissue orifice  7400 . The prosthetic valve can be expanded by inflating a balloon or can be self-expanding, for example. 
     Some methods of delivery include the steps of radially compressing a prosthetic valve (such as any of the prosthetic valves previously described) into its collapsed configuration, onto the distal section of an elongated flexible catheter having proximal and distal ends. A restraint, which can be connected to a tether that passes through the orifice of prosthetic valve and the lumen of the catheter, is fitted around the posts of the prosthetic valve. The prosthetic valve is then delivered to a native valve orifice, such as a native aortic valve orifice, via a route of delivery and expanded into the native orifice. The route of delivery can comprise a transfemoral or transapical route, for example. The prosthetic valve can be expanded by inflating a balloon or can be self-expanding, for example. 
     Surgical Embodiments 
     It is appreciated that any of the prosthetic valves previously described may be surgically implanted rather than using transcatheter techniques. As shown in  FIG. 33 , a surgically implanted prosthetic valve  7100  (such as any of the prosthetic valves previously described) may be substantially the same as those described above, with the addition of a sewing cuff  7300  adjacent to the frame outer side. The sewing cuff  7300 , which is well known in the art, is operable to provide structure that receives suture for coupling the prosthetic valve  7100  to an implant site, such as the tissue orifice  7400 . The sewing cuff may comprise any suitable material, such as, but not limited to, double velour polyester. The sewing cuff may be located circumferentially around the frame of the prosthetic valve  7100  or perivalvular depending from the frame of the prosthetic valve  7100 . 
     Numerous characteristics and advantages have been set forth in the preceding description, including various alternatives together with details of the structure and function of the devices and/or methods. The disclosure is intended as illustrative only and as such is not intended to be exhaustive. It will be evident to those skilled in the art that various modifications can be made, especially in matters of structure, materials, elements, components, shape, size and arrangement of parts including combinations within the principles of the disclosure, to the full extent indicated by the broad, general meaning of the terms in which the appended claims are expressed. To the extent that these various modifications do not depart from the spirit and scope of the appended claims, they are intended to be encompassed therein.