Patent Publication Number: US-2023149159-A1

Title: Prosthetic heart valves with h-shaped commissure windows and methods for assembly thereof

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of PCT Application No. PCT/US2021/042161, filed Jul. 19, 2021, which claims the benefit of U.S. Provisional Application No. 63/054,394, filed Jul. 21, 2020, all of which are incorporated by reference herein. 
    
    
     FIELD 
     The present disclosure relates to prosthetic heart valves, and to methods and assemblies for forming and installing leaflet assemblies to frames of such prosthetic heart valves. 
     BACKGROUND 
     The human heart can suffer from various valvular diseases. These valvular diseases can result in significant malfunctioning of the heart and ultimately require repair of the native valve or replacement of the native valve with an artificial valve. There are a number of known repair devices (e.g., stents) and artificial valves, as well as a number of known methods of implanting these devices and valves in humans. Percutaneous and minimally-invasive surgical approaches are used in various procedures to deliver prosthetic medical devices to locations inside the body that are not readily accessible by surgery or where access without surgery is desirable. In one specific example, a prosthetic heart valve can be mounted in a crimped state on the distal end of a delivery device and advanced through the patient&#39;s vasculature (e.g., through a femoral artery and the aorta) until the prosthetic valve reaches the implantation site in the heart. The prosthetic valve is then expanded to its functional size, for example, by inflating a balloon on which the prosthetic valve is mounted, actuating a mechanical actuator that applies an expansion force to the prosthetic valve, or by deploying the prosthetic valve from a sheath of the delivery device so that the prosthetic valve can self-expand to its functional size. Prosthetic valves that rely on a mechanical actuator for expansion can be referred to as “mechanically expandable” prosthetic heart valves. The actuator typically takes the form of pull cables, sutures, wires and/or shafts that are configured to transmit expansion forces from a handle of the delivery apparatus to the prosthetic valve. 
     Expandable, transcatheter heart valves can comprise an annular metal frame or stent and prosthetic leaflets mounted inside the frame. The leaflets can be attached to a portion of the frame via commissure tab assemblies, for example, by passing through and/or wrapping around a commissure window. Each commissure tab assembly can be preassembled by connecting tabs of adjacent leaflets to each other and then attached by suture to commissure window. However, such commissure tab assemblies may be relatively complex and time-consuming to assemble. Moreover, certain configurations of the commissure window may suffer from reliability issues (e.g., due to undesirable changes in shape during expansion of the prosthetic heart valve) and/or commissure mounting problems. 
     Accordingly, a need exists for improved prosthetic heart valves and methods for securing leaflet assemblies to a frame of the prosthetic heart valve. 
     SUMMARY 
     Described herein are embodiments of prosthetic heart valves and methods for assembling prosthetic heart valves. A valvular structure, formed by a plurality of leaflets, is supported by an expandable annular frame of the prosthetic heart valve. Each leaflet can have a pair of tabs. In some embodiments, each tab can have upper and lower portions. Commissures formed by paired tabs of adjacent leaflets can be coupled to corresponding commissure windows to support the valvular structure within the frame. Each commissure window can have upper and lower openings or channels separated from each other by a crossbar. For example, each commissure window can be substantially H-shaped in respective side view, with the crossbar connecting between a pair of struts extending along an axial direction of the valve. A thickness of each axially-extending strut of the H-shaped commissure window and a location of the crossbar along the axial direction can be selected such that the H-shape does not deform, or experiences minimal deformation, as the frame transitions between fully-expanded and crimped states. 
     In some embodiments, the upper and lower tab portions can extend through the upper and lower openings, respectively, of the corresponding commissure window. In other embodiments, the paired tabs of a commissure extend through only one of the upper and lower openings of the corresponding commissure window. One or more wedge members can be coupled to the tab portions. The wedge member(s) can prevent the leaflet tab from passing back through the commissure window, thereby retaining the valvular structure to the annular frame. Embodiments of the disclosed subject matter may thus offer simple and cost-effective methods for reliably mounting the valvular structure to the frame of the prosthetic valve while avoiding stitching sutures (or at least reducing the impact thereof) through dynamic portions of the leaflets, thereby reducing the risk of leaflet tearing. 
     In one representative embodiment, an assembly method for a prosthetic heart valve is provided. The method can comprise providing first and second leaflets for a valvular structure of the prosthetic heart valve. Each leaflet can have a pair of tabs, and one of the tabs can be on an opposite side from the other of the tabs with respect to a centerline of the leaflet. Each tab can have an upper tab portion and a lower tab portion separated from the upper tab portion along a direction parallel to the centerline by a gap. The method can further comprise disposing the upper and lower tab portions of a second tab of the pair of tabs of the second leaflet adjacent to the upper and lower tab portions of a first tab of the pair of tabs of the first leaflet, respectively. The method can also comprise stitching together the upper tab portions of the first and second leaflet tabs, and stitching together the lower tab portions of the first and second leaflet tabs. The method can further comprise folding the upper and lower tab portions of the first leaflet tab. The method can also comprise conveying the first and second leaflet tabs through a commissure window of an expandable annular frame of the prosthetic heart valve. The commissure window can have upper and lower openings separated from each other along an axial direction of the annular frame by a crossbar. The conveying can be along a radial direction of the annular frame from a radially inner-side of the commissure window to a radially-outer side of the commissure window. The conveying can be such that the upper tab portions are inserted through the upper opening and the lower tab portions are inserted through the lower opening. The method can further comprise inserting one or more wedge members between facing surfaces of the folded upper tab portion of the first leaflet tab and between facing surfaces of the folded lower tab portion of the first leaflet tab. The method can also comprise folding the upper tab portion of the second leaflet tab around the folded upper tab portion of the first leaflet tab, and folding the lower tab portion of the second leaflet tab around the folded lower tab portion of the first leaflet tab. The method can further comprise stitching together the one or more wedge members and the upper tab portions of the first and second leaflet tabs, and stitching together the one or more wedge members and the lower tab portions of the first and second leaflet tabs. 
     In another representative embodiment, an assembly method for a prosthetic heart valve is provided. The method can comprise providing first and second leaflets for a valvular structure of the prosthetic heart valve. Each leaflet can have a pair of tabs, and one of the tabs can be on an opposite side from the other of the tabs with respect to a centerline of the leaflet. Each tab can have an upper tab portion and a lower tab portion separated from the upper tab portion along a direction parallel to the centerline by a gap. The method can further comprise disposing the upper tab portion of a first tab of the pair of tabs of the first leaflet to surround at least a portion of a circumference of a first wedge member, and disposing the lower tab portion of the first leaflet tab to surround at least a portion of a circumference of a second wedge member. The method can also comprise stitching together the first wedge member and at least the upper tab portion of the first leaflet tab, and stitching together the second wedge member and at least the lower tab portion of the first leaflet tab. The method can further comprise conveying the first wedge member, the second wedge member, and the first leaflet tab through a commissure window of an expandable annular frame of the prosthetic heart valve. The commissure window can have upper and lower openings separated from each other along an axial direction of the annular frame by a crossbar. The conveying can be along a radial direction of the annular frame from a radially inner-side of the commissure window to a radially-outer side of the commissure window. The conveying can be such that the upper tab portion of the first leaflet tab and the first wedge member are inserted through the upper opening and the lower tab portion of the first leaflet tab and the second wedge member are inserted through the lower opening. The method can also comprise conveying a second tab of the pair of tabs of the second leaflet through the commissure window. The conveying can be along the radial direction from the radially inner-side of the commissure window to the radially-outer side of the commissure window and such that the upper tab portion of the second leaflet tab is inserted through the upper opening and the lower tab portion of the second leaflet tab is inserted through the lower opening. The method can further comprise folding the upper tab portion of the second leaflet tab around the upper tab portion of the first leaflet tab, and folding the lower tab portion of the second leaflet tab around the lower tab portion of the first leaflet tab. The method can also comprise stitching together the first wedge member, and the upper tab portions of the first and second leaflet tabs, and stitching together the second wedge member and the lower tab portions of the first and second leaflet tabs. 
     In another representative embodiment, an assembly method for a prosthetic heart valve is provided. The method can comprise providing first and second leaflets for a valvular structure of the prosthetic heart valve. Each leaflet can have a pair of tabs, and one of the tabs can be on an opposite side from the other of the tabs with respect to a centerline of the leaflet. Each tab can have an upper tab portion and a lower tab portion separated from the upper tab portion along a direction parallel to the centerline by a gap. The method can further comprise conveying a first tab of the pair of tabs of the first leaflet through a commissure window of an expandable annular frame of the prosthetic heart valve, and conveying a second tab of the pair of tabs of the second leaflet through the commissure window. The commissure window can have upper and lower openings separated from each other along an axial direction of the annular frame by a crossbar. The conveying can be along a radial direction of the annular frame from a radially inner-side of the commissure window to a radially-outer side of the commissure window. The conveying can be such that the upper tab portions are inserted through the upper opening and the lower tab portions are inserted through the lower opening. The method can also comprise disposing the upper and lower tab portions of the first leaflet tab to surround at least a portion of a circumference of one or more wedge members. The method can further comprise folding the upper tab portion of the second leaflet tab around the upper tab portion of the first leaflet tab, and folding the lower tab portion of the second leaflet tab around the lower tab portion of the first leaflet tab. The method can also comprise stitching together the one or more wedge members and the upper tab portions of the first and second leaflet tabs, and stitching together the one or more wedge members and the lower tab portions of the first and second leaflet tabs. 
     In another representative embodiment, an assembly method for a prosthetic heart valve is provided. The method can comprise providing first and second leaflets for a valvular structure of the prosthetic heart valve. Each leaflet can have a pair of tabs, and one of the tabs can be on an opposite side from the other of the tabs with respect to a centerline of the leaflet. Each tab can have an upper tab portion and a lower tab portion separated from the upper tab portion along a direction parallel to the centerline by a gap. The method can further comprise disposing the upper tab portion of a first tab of the pair of tabs of the first leaflet to surround at least a portion of a circumference of a first wedge member. The method can also comprise stitching together the first wedge member and at least the upper tab portion of the first leaflet tab. The method can further comprise conveying a lower tab portion of the first leaflet tab through a commissure window of an expandable annular frame of the prosthetic heart valve. The commissure window can have upper and lower openings separated from each other along an axial direction of the annular frame by a crossbar. The conveying can be along a radial direction of the annular frame from a radially-inner side of the commissure window to a radially-outer side of the commissure window. The conveying can be such that the lower tab portion of the first leaflet tab extends through the lower opening. The method can also comprise conveying the first wedge member and the upper tab portion of the first leaflet tab from the radially-inner side of the commissure window through or over the upper opening of the commissure window to the radially-outer side of the commissure window, such that the upper tab portion of the first leaflet tab extends through the upper opening. The method can further comprise folding the lower tab portion of the first leaflet tab around the first wedge member. The method can also comprise conveying a second tab of the pair of tabs of the second leaflet through the commissure window. The conveying the second tab can be along the radial direction from the radially inner-side of the commissure window to the radially-outer side of the commissure window. The conveying the second tab can be such that the upper tab portion of the second leaflet tab is inserted through the upper opening and the lower tab portion of the second leaflet tab is inserted through the lower opening. The method can further comprise folding the upper tab portion of the second leaflet tab around the upper tab portion of the first leaflet tab, and folding the lower tab portion of the second leaflet tab around the lower tab portion of the first leaflet tab. The method can also comprise stitching together the first wedge member and the upper and lower tab portions of the first and second leaflet tabs. 
     In another representative embodiment, a prosthetic heart valve can comprise an expandable annular frame and a valvular structure. The expandable annular frame can have a plurality of commissure windows. The valvular structure can be coupled to the commissure windows. The valvular structure can comprise a plurality of leaflets. The tabs of adjacent leaflets can be coupled to a respective one of the commissure windows according to any of the disclosed assembly methods. 
     In another representative embodiment, a prosthetic heart valve can comprise an expandable annular frame and a valvular structure. The expandable annular frame can have a plurality of commissure windows. The valvular structure can comprise a plurality of leaflets. Each leaflet can have a pair of tabs, one of which can be on an opposite side from the other with respect to a centerline of the leaflet. Each tab can have an upper tab portion and a lower tab portion separated from the upper tab portion along a direction parallel to the centerline by a gap. The valvular structure can have a plurality of commissures formed by paired tabs of adjacent leaflets. Each commissure can be coupled to a corresponding one of the commissure windows to support the valvular structure within the annular frame. Each commissure window can have upper and lower openings separated from each other along an axial direction of the annular frame by a respective crossbar. The upper and lower tab portions for each tab can extend through the upper and lower openings, respectively, to a radially-outer side of the respective commissure window. The annular frame can be expandable between a crimped state having a first diameter and an expanded state having a second diameter greater than the first diameter. 
     The various innovations of this disclosure can be used in combination or separately. This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. The foregoing and other objects, features, and advantages of the invention will become more apparent from the following detailed description, which proceeds with reference to the accompanying figures. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a perspective view of an exemplary prosthetic heart valve with H-shaped commissure windows. 
         FIG.  2    is a perspective view of an exemplary frame of the prosthetic valve of  FIG.  1   . 
         FIGS.  3 A- 3 B  are side and detail views, respectively, of an exemplary H-shaped commissure window of the prosthetic heart valve frame of  FIG.  2   . 
         FIG.  3 C  is a detail view of a section of the H-shaped commissure window of  FIG.  3 A  and surrounding angled struts, when the prosthetic heart valve is at a configuration midway between the fully-expanded and crimped configurations. 
         FIGS.  4 A- 4 B  are side views of the prosthetic heart valve frame of  FIG.  2    in crimped and expanded configurations, respectively. 
         FIG.  5    is a plan view of an individual leaflet used to form a leaflet assembly for a prosthetic heart valve. 
         FIG.  6    is a simplified perspective view showing an exemplary assembly of a commissure to the H-shaped commissure window of the prosthetic heart valve frame of  FIG.  2   . 
         FIG.  7 A- 7 B  are simplified top-down and perspective views, respectively, that illustrate coupling of a pair of leaflet tabs of a commissure prior to insertion through an H-shaped commissure window, according to a first exemplary assembly method. 
         FIGS.  8 - 10    are simplified top-down views that illustrate insertion of the leaflet tabs of  FIGS.  7 A- 7 B  through the H-shaped commissure window, insertion of a wedge member, and further attachment of the leaflet tabs, respectively, according to the first exemplary assembly method. 
         FIGS.  11 - 13    are simplified top-down views that illustrate insertion of the leaflet tabs through an H-shaped commissure window, insertion of a wedge member, and further attachment of the leaflet tabs, respectively, according to a second exemplary assembly method. 
         FIG.  14    is a simplified top-down view that illustrates coupling of a pair of leaflet tabs of a commissure and a wedge member prior to insertion through an H-shaped commissure window, according to a third exemplary assembly method. 
         FIG.  15    is a simplified perspective view that illustrates the commissure and wedge of  FIG.  14    after insertion through the H-shaped commissure window, according to the third exemplary assembly method. 
         FIG.  16    is a side view of an embodiment of a prosthetic valve being implanted within a native aortic valve of a heart, which is partially shown. 
         FIGS.  17 A- 17 B  are side and detail views, respectively, of another exemplary H-shaped commissure window of the prosthetic heart valve frame of  FIG.  2   . 
         FIG.  18    is a plan view of an individual leaflet that can be incorporated in any of the prosthetic valves disclosed herein. 
     
    
    
     DETAILED DESCRIPTION 
     For purposes of this description, certain aspects, advantages, and novel features of the embodiments of this disclosure are described herein. The disclosed methods, apparatus, and systems should not be construed as being limiting in any way. Instead, the present disclosure is directed toward all novel and nonobvious features and aspects of the various disclosed embodiments, alone and in various combinations and sub-combinations with one another. The methods, apparatus, and systems are not limited to any specific aspect or feature or combination thereof, nor do the disclosed embodiments require that any one or more specific advantages be present, or problems be solved. The technologies from any example can be combined with the technologies described in any one or more of the other examples. In view of the many possible embodiments to which the principles of the disclosed technology may be applied, it should be recognized that the illustrated embodiments are only preferred examples and should not be taken as limiting the scope of the disclosed technology. 
     Although the operations of some of the disclosed embodiments are described in a particular, sequential order for convenient presentation, it should be understood that this manner of description encompasses rearrangement, unless a particular ordering is required by specific language set forth below. For example, operations described sequentially may in some cases be rearranged or performed concurrently. Moreover, for the sake of simplicity, the attached figures may not show the various ways in which the disclosed methods can be used in conjunction with other methods. Additionally, the description sometimes uses terms like “provide” or “achieve” to describe the disclosed methods. These terms are high-level abstractions of the actual operations that are performed. The actual operations that correspond to these terms may vary depending on the particular implementation and are readily discernible by one of ordinary skill in the art. 
     As used herein with reference to the prosthetic heart valve assembly and implantation and structures of the prosthetic heart valve, “proximal” refers to a position, direction, or portion of a component that is closer to the user and a handle of the delivery system that is outside the patient, while “distal” refers to a position, direction, or portion of a component that is further away from the user and the handle and closer to the implantation site. The terms “longitudinal” and “axial” refer to an axis extending in the proximal and distal directions, unless otherwise expressly defined. 
     The terms “axial direction,” “radial direction,” and “circumferential direction” have been used herein to describe the arrangement of components and assembly of commissures to respective windows, relative to the geometry of the frame of the prosthetic heart valve. Such terms have been used for convenient description, but the disclosed embodiments are not strictly limited to the description. In particular, where a component or action is described relative to a particular direction, directions parallel to the specified direction as well as minor deviations therefrom. Thus, a description of a component extending along an axial direction of the frame does not require the component to be aligned with a center of the frame; rather, the component can extend substantially along a direction parallel to a central axis of the frame. 
     As used herein, the terms “integrally formed” and “unitary construction” refer to a construction that does not include any welds, fasteners, or other means for securing separately formed pieces of material to each other. 
     As used herein, operations that occur “simultaneously” or “concurrently” occur generally at the same time as one another, although delays in the occurrence of operation relative to the other due to, for example, spacing between components, are expressly within the scope of the above terms, absent specific contrary language. 
     As used in this application and in the claims, the singular forms “a,” “an,” and “the” include the plural forms unless the context clearly dictates otherwise. Additionally, the terms “have” or “includes” means “comprises.” Further, the terms “coupled” and “connected” generally mean electrically, electromagnetically, and/or physically (e.g., mechanically or chemically) coupled or linked and does not exclude the presence of intermediate elements between the coupled or associated items absent specific contrary language. As used herein, “and/or” means “and” or “or,” as well as “and” and “or.” 
     Directions and other relative references may be used to facilitate discussion of the drawings and principles herein, but are not intended to be limiting. For example, certain terms may be used such as “inner,” “outer,” “upper,” “lower,” “inside,” “outside,”, “top,” “bottom,” “interior,” “exterior,” “left,” right,” and the like. Such terms are used, where applicable, to provide some clarity of description when dealing with relative relationships, particularly with respect to the illustrated embodiments. Such terms are not, however, intended to imply absolute relationships, positions, and/or orientations. For example, with respect to an object, an “upper” part can become a “lower” part simply by turning the object over. Nevertheless, it is still the same part and the object remains the same. 
     Described herein are examples of prosthetic heart valves, annular frames with commissure windows and leaflets for prosthetic heart valves, and methods for assembling leaflets to commissure windows of annular frames to form prosthetic heart valves. A valvular structure, which is formed by multiple leaflets, is supported by an expandable annular frame of the prosthetic heart valve. Each tab of the leaflet can have upper and lower portions separated from each other by a gap. Commissures formed by paired tabs of adjacent leaflets are coupled to corresponding commissure windows to support the valvular structure within the frame. Each commissure window can have upper and lower openings separated from each other by a crossbar. The upper and lower tab portions can extend through the upper and lower openings, respectively, of the corresponding commissure window. One or more wedge members coupled to the tab portions can prevent the leaflet tab from passing back through the commissure window, thereby retaining the valvular structure to the annular frame. As a result, a position of the leaflet assembly for a prosthetic heart valve may be effectively locked in place during assembly and use of the prosthetic heart valve, and a time and effort for securing the leaflet assembly to the frame of the prosthetic heart valve may be reduced. 
     In some embodiments, each commissure window can be substantially H-shaped in respective side view, with the crossbar connecting between a pair of struts extending along an axial direction of the valve. A thickness of each axially-extending strut of the H-shaped commissure window and a location of the crossbar along the axial direction can be selected such that the H-shape does not deform, or experiences minimal deformation, as the frame transitions between fully-expanded and crimped states, thereby reducing the risk of damage to the leaflets and/or detachment of the leaflets from the frame. 
       FIGS.  1 - 4 B  illustrate various features of an exemplary prosthetic heart valve  100 , according to one or more embodiments of the disclosed subject matter. The prosthetic heart valve  100  can be radially compressible and expandable between a radially compressed configuration for delivery (e.g., a crimped state) into a patient, for example, as illustrated in  FIG.  4 A , and a radially expanded configuration (e.g., a deployed state), for example, as illustrated in  FIGS.  1  and  4 B . In particular embodiments, the prosthetic heart valve  100  can be implanted within the native aortic annulus, although it also can be implanted at other locations in the heart, including within the native mitral valve, the native pulmonary valve, or the native tricuspid valve. 
     The prosthetic heart valve  100  can include an annular stent or frame  102 . The frame  102  can have a first axial end  116  and a second axial end  118 . In the depicted embodiment, the first axial end  116  can be an outflow end, and the second axial end  118  can be an inflow end. The outflow end  116  can be coupled to a delivery apparatus for delivering and implanting the prosthetic heart valve  100  within the native aortic valve using a transfemoral, retrograde delivery approach. Thus, in the delivery configuration of the prosthetic heart valve, the outflow end  116  can be considered the proximal-most end of the prosthetic valve. In other embodiments, the inflow end  118  can instead be coupled to the delivery apparatus, depending on the particular native valve being replaced and the delivery technique that is used (e.g., trans-septal, transapical, etc.). For example, the inflow end  118  can be coupled to the delivery apparatus (and therefore would be the proximal-most end of the prosthetic heart valve in the delivery configuration) when delivering the prosthetic heart valve to the native mitral valve via a trans-septal delivery approach. 
     In some embodiments, the frame  102 , or components thereof (e.g., struts and/or fasteners), can be made of any of various suitable plastically-expandable materials (e.g., stainless steel, etc.) or self-expanding materials (e.g., nickel titanium alloy (NiTi), such as nitinol), as known in the art. Suitable plastically-expandable materials that can be used to form the frame  102  include, without limitation, stainless steel, biocompatible high-strength alloys (e.g., a cobalt-chromium or a nickel-cobalt-chromium alloys), polymers, or combinations thereof. In particular embodiments, frame  102  is made of a nickel-cobalt-chromium-molybdenum alloy, such as MP35N® alloy (SPS Technologies, Jenkintown, Pa.), which is equivalent to UNS R30035 alloy (covered by ASTM F562-02). MP35N® alloy/UNS R30035 alloy comprises 35% nickel, 35% cobalt, 20% chromium, and 10% molybdenum, by weight. 
     When constructed of a plastically-expandable material, the frame  102  (and thus the prosthetic valve  100 ) can be crimped to a radially collapsed configuration on a delivery catheter and then expanded inside a patient by an inflatable balloon or equivalent expansion mechanism. For example,  FIGS.  4 A- 4 B  illustrates expansion of the frame  102  from a crimped state (e.g.,  FIG.  4 A ) to a deployed state (e.g.,  FIG.  4 B ) using inflatable balloon  154 . When constructed of a self-expandable material, the frame  102  (and thus the prosthetic valve  100 ) can be crimped to a radially collapsed configuration and restrained in the collapsed configuration by insertion into a sheath or equivalent mechanism of a delivery catheter. Once inside the body, the prosthetic valve can be advanced from the delivery sheath, which allows the prosthetic valve to expand to its functional size. 
     For example, referring to  FIG.  16   , a delivery apparatus  900  including a handle  902  can be used to deliver and implant the prosthetic valve  100  in the following exemplary manner. The prosthetic valve  100  can be disposed on a distal end portion  906  of the delivery apparatus  900  in a radially compressed state. The prosthetic valve  100  can be crimped on an inflatable balloon  904  (e.g., balloon  154 ) or another type of expansion member that can be used to radially expand the prosthetic valve  100 . The distal end portion  906  of the delivery apparatus  900 , including prosthetic valve  100 , can be advanced through the vasculature to a selected implantation site (e.g., within a previously implanted host valve and/or within a native valve). In the illustrated embodiment, the distal end portion of the delivery apparatus  900  and the prosthetic valve  100  are inserted into a femoral artery and advanced through the femoral artery and the aorta and positioned within the native aortic valve  800  or a host valve previously implanted within the native aortic valve  800 . The prosthetic valve  100  can then be deployed at the implantation site, such as by inflating the balloon  904 . Further details of delivery apparatuses that can be used to deliver and implant plastically expandable prosthetic valves, such as the prosthetic valve  100  (or any other prosthetic valves disclosed herein), are disclosed in U.S. Patent Application Publication Nos. 2017/0065415, 2016/0158497, and 2013/0030519, which are incorporated herein by reference. 
     If the prosthetic valve  100  being implanted is a self-expandable prosthetic valve, the prosthetic valve can be retained in a radially compressed state within a delivery capsule or sheath of the delivery apparatus when inserted into and advanced through the patient&#39;s vasculature to the desired implantation site. Once positioned at the desired implantation site, the prosthetic valve can be deployed from the delivery capsule, which allows the prosthetic valve to self-expand to its radially-expanded, functional size within the native valve or a previously implanted host valve. Further details of delivery apparatuses that can be used to deliver and implant self-expandable prosthetic valves (including any of the prosthetic valves disclosed herein when the frames are constructed of a self-expandable material such as Nitinol) are disclosed in U.S. Patent Application Publication Nos. 2014/0343670 and 2010/0049313, which are incorporated herein by reference. 
     In some embodiments, struts of the frame  102  are pivotable or bendable relative to each other to permit radial expansion and contraction of the frame  102 . For example, the frame  102  can be formed (e.g., via laser cutting, electroforming or physical vapor deposition) from a single piece of material (e.g., a metal tube). In other embodiments, the frame  102  can be constructed by forming individual components (e.g., the struts and fasteners of the frame) and then mechanically assembling and connecting the individual components together. For example, instead of the strut structure illustrated in  FIGS.  1 - 4 B , the frame can have individual diagonally-extending struts pivotably coupled to one another at one or more pivot joints along the length of each strut, as described in U.S. Patent Application Publication Nos. 2018/0153689, 2018/0344456, and 2019/0060057, all of which are incorporated herein by reference. Further details regarding exemplary constructions of frame  102  and/or prosthetic heart valve  100  are described in U.S. Patent Application Publication Nos. 2012/0123529 and 2019/0365530, U.S. Provisional Application No. 62/869,948, International Publication No. WO-2020/081893, and International Application No. PCT/US2019/056865, all of which are incorporated herein by reference. 
     As illustrated in  FIGS.  2 - 3 A , frame  102  can include a plurality of struts that are angled with respect to an axial direction (A) of the frame  102  so as to extend along a circumferential direction (C) of the frame  102 . The struts can be organized into circumferentially-extending rows, for example, a first row  171  of angled struts  138  and angled struts  130  arranged end-to-end and extending circumferentially at the outflow end  116  of the frame  102 ; a second row  173  of angled struts  132  and  140  arranged end-to-end and extending circumferentially; a third row  175  of angled struts  142  arranged end-to-end and extending circumferentially; and a fourth row  177  of angled struts  148  arranged end-to-end and extending circumferentially at the inflow end  118  of the frame  102 . In some embodiments, a magnitude of the angle with respect to the axial direction for the struts  130 ,  138  in the first row  171  can be the same as, or substantially similar to (e.g., within  10 %), that for the struts  148  in the fourth row  177 . In some embodiments, a magnitude of the angle with respect to the axial direction for the struts  132 ,  140  in the second row  173  and/or the struts  142  in the third row  175  can be different than that for the struts  130 ,  138  in the first row  171  and/or the struts  148  in the fourth row  177 . 
     Within first row  171 , angled struts  130 ,  138  can connect to (e.g., by joining or integrally formed with) adjacent angled struts  130 ,  138  via joint or union  134 . Similarly, within fourth row  177 , angled struts  148  can connect to (e.g., by joining or integrally formed with) adjacent angled struts  148  via joint or union  150 . Angled struts  132 ,  140  of the second row  173  and angled struts  142  of the third row  175  can connect to (e.g., by joining or integrally formed with) each other via joint or union  144 . Angled struts  142  of the third row  175  and angled struts  148  of the fourth row  177  can connect to (e.g., by joining or integrally formed with) each other via joint or union  146 . 
     Between the first row  171  and the second row  173 , the frame  102  can further include a plurality of support struts  136  and a plurality of commissure windows  114 . Each support strut  136  can extend substantially parallel to the axial direction (A) of the frame  102 . Each support strut  136  can connect to (e.g., by joining or integrally formed with) an adjacent pair of the angled struts  138  of the first row  171  at its first end (e.g., closest to outflow end  116  of the frame  102 ) and can connect to (e.g., by joining or integrally formed with) an adjacent pair of the angled struts  140  of the second row  173  at its opposite second end (e.g., closest to inflow end  118  of the frame  102 ). Similarly, each commissure window  114  can connect to (e.g., by joining or integrally formed with) an adjacent pair of angled struts  130  of the first row  171  at its first end (e.g., closest to outflow end  116  of the frame  102 ) and can connect to (e.g., by joining or integrally formed with) an adjacent pair of angled struts  132  of the second row  173  at its opposite second end (e.g., closest to inflow end  118  of the frame  102 ). 
     The angled struts, support struts, commissure windows, and other frame portions collectively define an open-cell lattice structure, with each of the cells  200 - 208  being open along a radial direction (R) of the annular frame. At the outflow end  116  of the valve  100 , each cell  200  can be defined, at least in part, by a pair of angled struts  138  of the first row  171 , a pair of support struts  136 , and a pair of angled struts  140  of the second row  173 . Also at the outflow end  116  of the valve  100 , each cell  206  can be defined, at least in part, by angled strut  130  and angled strut  138  of the first row  171 , a support strut  136 , a commissure window  114 , and angled strut  132  and angled strut  140  of the second row  173 . At the inflow end  118  of the valve, each cell  202  can be defined, at least in part, by a pair of angled struts  142  of the third row  175  and a pair of angled struts  148  of the fourth row  177 . In between cells  200  at the outflow end and cells  202  at the inflow end along the axial direction, each cell  204  can be defined, at least in part, by a pair of angled struts  140  of the second row  173  and a pair of angled struts  142  of the third row  175 . In between cells  206  at the outflow end and cells  202  at the inflow end along the axial direction, each cell  208  can be defined, at least in part, by a pair of angled struts  132  of the second row  173  and a pair of angled struts  142  of the third row  175 . 
     In the illustrated embodiment, each cell  200 ,  206  at the outflow end  116  has a respective open area that is greater than that of the cells  202  at the inflow end  118 . Each of the cells  204 ,  208  can have a respective open area that is between that of the outflow end cells  200 ,  206  and the inflow end cells  202 . The relatively-larger openings of cells  200 ,  206  at the outflow end  116  can allow portions of the leaflets of the valvular structure to protrude or bulge into and/or through the openings of the cells when the frame  102  is crimped, for example, to minimize crimping profile of the valve  100 . In other embodiments, cells  200 - 208  can have substantially the same open areas, the cells  202  at the inflow end  118  can have the largest open area instead of cells  200 ,  206 , or the intermediate cells  204 ,  208  can have the largest open area instead of cells  200 ,  206 . 
     The frame  102  can be formed with a plurality of circumferentially-spaced commissure windows  114  that are adapted to couple the valvular structure  106  to the frame  102 . In particular, each commissure  112  of the valvular structure  106  is mounted to a respective one of the commissure windows  114 . The support struts  136  and the commissure windows  114  can be disposed at equal intervals along the circumferential direction of the frame  102 . In the illustrated embodiment, the valvular structure  106  comprises three leaflets  110  (e.g., a tricuspid configuration), and the commissure windows  114  are equally spaced at 120° intervals (i.e., 0°, 120°, and 240°) along the circumference of the frame  102 . A pair of support struts  136  are disposed along the circumference of the frame between each sequential pair of the commissure windows  114  and equally spaced from each other. Thus, either a support strut  136  or a commissure window  114  can be disposed at regular intervals around the circumference of the frame  102 , for example, at each 40° interval. 
     Other spacings and numbers of supports struts  136  and commissure windows  114  are also possible according to one or more contemplated embodiments. For example, a single support strut  136  can be disposed between each sequential pair of commissure windows  114 . In such an example, either a support strut  136  or a commissure window  114  can be disposed at 60° intervals around the circumference of the frame  102 . In another example, the valvular structure  106  comprises two leaflets  110  (e.g., a bicuspid configuration), and the commissure windows  114  are disposed on opposite sides of the frame (e.g., aligned on a same diameter of the frame). Multiple support struts  136  can be disposed along the circumference of the frame between the pair of commissure windows  114 , and each support strut  136  may be disposed on an opposite side of the frame from another support strut  136  (e.g., both aligned on a same diameter of the frame). 
     As shown in  FIGS.  2 A- 3 B , each commissure window  114  can be formed by a pair of window struts  122 ,  124  and a crossbar  120 . Window struts  122 ,  124  can extend substantially parallel to the axial direction of the frame  102 . Each window strut  122 ,  124  can connect to (e.g., by joining or integrally formed with) an adjacent angled strut  130  at its first end (e.g., closest to the outflow end  116  of the frame  102 ) and connect to (e.g., by joining or integrally formed with) an adjacent angled strut  132  at its second end (e.g., closets to the inflow end  118  of the frame  102 ). The crossbar  120  can extend between the window struts  122 ,  124  along the circumferential direction and connect with the window struts  122 ,  124 , thereby dividing a spacing between the window struts  122 ,  124  into an upper window or opening  126  and a lower window or opening  128 . For example, each commissure window  114  is constructed to have a substantially H-shape in respective side view. 
     The upper opening  126 , which is defined by facing surfaces of portions of the window struts  122 ,  124  at the first end and an upper surface of the crossbar  120 , can be open to the outflow end  116  along the axial direction of the valve  100 . The lower opening  128 , which is defined by facing surfaces of portions of the window struts  122 ,  124  at the second end and a lower surface of the crossbar  120 , can be open to an adjacent cell  208  along the axial direction of the valve  100 . Lower opening  128  of the window  114  is closed to the inflow end  118  of the valve  100  by virtue of union  146 , which closes cell  208  to the inflow end  118  of the valve  100 . However, in other embodiments, union  146  of cell  208  can be omitted, thereby allowing lower opening  128  of commissure window  114  to be open to the inflow end  118  while upper opening  126  of commissure window  114  is open to the outflow end  118 . In still other embodiments, lower opening  128  of commissure window  114  can be open to the inflow end  118  (e.g., via removal of union  146  of cell  208 ) while upper opening  126  of commissure window  114  can be closed to the outflow end  116  (e.g., by providing another crossbar or union between angled struts  130  at an end of the upper opening  126 ). 
     The window struts  122 ,  124  can be spaced from each other along the circumferential direction by a gap width, Wi. The size of the upper and lower openings  126 ,  128  is thus defined by the spacing between struts  122 ,  124  and the position of the crossbar  120 . Alternatively, the upper opening  126  can have a different gap width than that of the lower opening  128 . In some embodiments, the gap width W 1  can be defined based on the size of leaflet tabs that are inserted into the openings  126 ,  128  of the commissure window  114 . For example, the gap width W 1  can be greater than twice a thickness of a leaflet tab, and/or less than four times the thickness of the leaflet tab. A commissure  112  formed by a pair of leaflet tabs can thus be inserted through the gap width W 1  of each opening  126 ,  128 , but is prevented from passing back through the opening upon folding of the leaflet tab in combination with one or more wedge members, as described in further detail below. 
     The commissure window  114  can have a length, L, along the axial direction of the frame  102  between first ends of the window struts  122 ,  124  (e.g., ends closest to the outflow end  116 ) and second ends of the window struts  122 ,  124  (e.g., ends closest to the inflow end  118 ). In some embodiments, the crossbar  120  can be offset from a midpoint of the window struts  122 ,  124  (e.g., L/2) along the axial direction of the frame  102 , for example, between the outflow end  116  and the window strut midpoints. For example, a length, L 1 , of the upper opening  126 , as measured from the first ends of the window struts  122  to a middle of the crossbar  120 , is less than a length, L 2 , measured from the second ends of the window struts  122 ,  124  to the middle of the crossbar  120 , such that the upper opening  126  is smaller (e.g., in terms of dimension along the axial direction or open area) than the lower opening  128 . For example, a ratio of L 1  to L 2  (e.g., L 1 /L 2 ) can be in a range of 0.25 to 0.35, inclusive. 
     In some embodiments, each window strut  122 ,  124  can have a width, W 2 , along the circumferential direction of the frame  102  that is relatively larger than that of the surrounding angled struts  130 ,  132 . For example, each angled strut  130 ,  132  can have a width, W 3 , measured in a direction perpendicular to its direction of extension, and W 2  may be greater than W 3 . In some embodiments, the other angled struts  138 ,  140 ,  142 , and  148  can each have a width that is the same as or substantially similar (e.g., within 10%) to the width W 3  of angled struts  130 ,  132 . Thus, each window strut  122 ,  124  can be wider than the angled struts of the frame  102 . 
     In some embodiments, the sizing and/or location of components of the commissure window  114  can be tailored to avoid formation of convex or concave contours along the struts  122 ,  124  during transition between crimped ( FIG.  4 A ) and fully expanded ( FIG.  4 B ) configurations of the valve  100 . For example, by increasing widths W 2  of the window struts  122 ,  124 , the stiffness of the window struts can be increased such that the struts maintain a substantially linear contour during the transition. Alternatively or additionally, the sizing and/or location of components of the commissure window  114  can be tailored such that the gap widths W 1  of the upper opening  126  and/or the lower opening  128  remain substantially constant (e.g., variations of 10% or less) as the valve  100  transitions between crimped ( FIG.  4 A ) and fully expanded ( FIG.  4 B ) configurations. For example, by positioning the crossbar  120  at a particular location along the axial direction, circumferentially-directed forces acting on the first ends of the struts  122 ,  124  can be balanced with circumferentially-directed forces acting on the second ends of the struts  122 ,  124 . In combination with the increased widths of the window struts  122 ,  124 , the balancing can allow the widths W 1  of the upper and lower openings to remain substantially constant during the transition. 
     For example, both the location of the crossbar  120  along the axial direction of the frame  102  and the widths W 2 of the window struts  122 ,  124  can be selected such that the shape of the commissure window  114  does not deform, or experiences only minimal deformation (e.g., no more than 10% variation), as the frame  102  transitions between fully expanded and crimped states, in order to reduce the risk of damage to and/or detachment of the leaflets. In some embodiments, finite element analysis (FEA) can be used to determine optimal values for the widths for the struts  122 ,  124  and axial location of crossbar  120 , which values may depend on the particular construction of the valve frame  102  (e.g., material composition, number and geometry of open cells, sizes and angles of adjacent struts  130 ,  132 , etc.). 
     Alternatively, or additionally, the axial location for the crossbar  120  can be based on relative positions along the axial direction of the angled struts  130 ,  132 .  FIG.  3 C  shows a section view for a commissure window  114  and surrounding angled struts  130 ,  132 , when the valve  100  is at a configuration midway between the fully-expanded and crimped states. In  FIG.  3 C , h 1  represents a relative length along the axial direction for angled strut  130  as measured from one end of strut  130  (adjacent to the first end of window strut  122 ) to an opposite end of strut  130  (at union  134 ), and h 2  represents a relative length along the axial direction for angled strut  132  as measured from one end of strut  132  (adjacent to the second end of the window strut  122 ) to an opposite end of strut  132  (at union  144 ). The angled strut  130  is associated with a relative distance y 1 , measured along the axial direction from a middle of crossbar  120  to the end of strut  130  at union  134 . The angled strut  132  is also associated with a relative distance y 2 , measured along the axial direction from the middle of crossbar  120  to the end of strut  132  at union  144 . To avoid (or at least reduce) deformation of the commissure window  114 , the location of the crossbar  120  can be selected such that the (h 1 ×y 2 )/(h 2 ×y 1 ) is within a range of 0.8-1.2, inclusive, preferably  0 . 9 - 1 . 1 , inclusive. For example, the location of the crossbar  120  can be selected such that (h 1 ×y 2 )/(h 2 ×y 1 )≈1. Note that the values recited above are for h 1 , h 2 , y 1 , and y 2  measured when the frame  102  is midway (e.g., at a mean diameter, D 3 =(D 2 −D 1 )/2) between the fully-expanded (D 2 ) and crimped (D 1 ) states. 
     Using the crossbar location, the width W 2  of the window strut  122  can be derived based on forces applied by angled struts  130 ,  132 , for example, such that the maximum force applied along the circumferential direction to the angled strut  130  (e.g., Fi) during transition between crimped and expanded states results in minimal deflection of the first end of the window strut  122  and such that the maximum force applied along the circumferential direction to the angle strut  132  (e.g., F 2 ) during the transition between states results in minimal deflection of the second end of the window strut  122 . In some embodiments, the other window strut  124  of the commissure window  114  can have dimensions (e.g., width W 2  and length along the axial direction) identical to that of window strut  122  for symmetrical application of forces. 
     In some embodiments, each support strut  136  can also have a width along the circumferential direction of the frame  102  that is relatively larger than the of the surrounding angled struts  138 ,  140 . For example, the angled struts  138 ,  140  can also have a width, W 3 , measured in a direction perpendicular to its direction of extension, and a minimum width of the support strut  136  can be greater than W 3 . In the illustrated embodiment, each support strut  136  can have a width (as measured along the circumferential direction) that varies along the axial direction of the frame  102 . For example, opposite ends of the support strut  136  can have a relatively larger width while a mid-portion between the opposite ends can have a relatively smaller width. Thus, each support strut  136  can have a dog-bone shape in respective side view, with a recess  152  being formed between the larger-width ends of the strut  136 . When the frame  102  is in the crimped configuration (e.g., as shown in  FIG.  4 A ), the dog-bone shape of the support strut  136  can complement a shape of a facing strut  122 ,  124  of the adjacent commissure window  114 , with a portion of the facing strut  122 ,  124  fitting into recess  152 . The dog-bone shape of the support strut  136  can thus allow the frame  102  to achieve a minimum crimping profile despite the presence of the commissure windows  114 . In some embodiments, some of the support struts  136  may have a width that is substantially constant along the axial direction while other of the support struts  136  that are immediately adjacent to one of the commissure windows may have the dog-bone shape. 
     The prosthetic valve  100  also includes a valvular structure  106  configured for allowing blood flow through the frame  102  in one direction, for example, to regulate the flow of blood through the prosthetic heart valve  100  from the inflow end  118  to the outflow end  116 . The valvular structure  106  can include, for example, a leaflet assembly formed by one or more leaflets  110  (three leaflets illustrated in  FIG.  1   ) made of a flexible material. Tabs of adjacent leaflets  110  can be arranged together to form commissures  112  that are coupled (directly or indirectly) to respective commissure windows  114  of the frame  102 , thereby securing at least a portion of the valvular structure  106  to the frame  102 . 
     As shown in  FIG.  5   , each leaflet  110  can comprise a main, cusp edge portion  160 , two leaflet tabs (also referred to herein as commissure tabs)  162  at opposing ends of the leaflet  110 , and an upper edge portion  158 . The cusp edge portion  160 , leaflet tabs  162 , and upper edge portion  158  may be arranged around an outer perimeter of the leaflet  110 . The upper edge portion  158  can extend between the two leaflet tabs  162  at an upper edge of the leaflet  110 , and the cusp edge portion  160  can extend between the two leaflet tabs  162  at a lower edge of the leaflet  110 . As used here, “upper” and “lower” may be relative to a central longitudinal axis of the prosthetic heart valve  100  when the valvular structure is installed and coupled to frame  102 , with upper being closer to the outflow end of the valve  100  and lower being closer to the inflow end of the valve  100 . The upper edge of the leaflet  110  can be referred to as the “free edge” or the “coaptation edge” of the leaflet. 
     In some embodiments, the cusp edge portion  160  has a curved, scalloped shape (as shown in  FIG.  5   ). Thus, the cusp edge portion  160  may curve between the two leaflet tabs  162 .  FIG.  5    further illustrates a centerline  156  for each of the individual leaflets  110 , which may also be a centerline of the leaflet assembly. For example, when assembled, the centerlines  156  for each of the leaflets  110  may overlap. Further, as shown in  FIG.  5   , the leaflet tabs  162  may be arranged at opposing ends of the leaflet  110 , across the centerline  156  from one another. In some embodiments, the leaflets and/or components of the leaflet assembly may have symmetry with respect to the centerline  156 . 
     The leaflets  110  of the valvular structure  106  can be made from in whole or part, biological materials, bio-compatible synthetic materials, or other such materials. Suitable biological materials can include, for example, bovine pericardium (or pericardium from other sources). Further details regarding transcatheter prosthetic heart valves, including the manner in which the valvular structure can be coupled to the frame  102  of the prosthetic heart valve  100 , can be found, for example, in U.S. Provisional Application No.  62 / 959 , 723 , U.S. Pat. Nos. 6,730,118, 7,393,360, 7,510,575, 7,993,394, and 8,652,202, and U.S. Patent Application Publication No. 2018/0325665, all of which are incorporated herein by reference in their entireties. 
     The tabs  162  of adjacent leaflets  110  can be arranged together to form commissures  112  that can be coupled to respective commissure windows  114 , thereby securing at least a portion of the valvular structure  106  to the frame  102 . Each tab  162  of the leaflet  110  can have an upper tab portion  164  and a lower tab portion  166 . A gap  168  along a direction parallel to centerline  156  can separate the upper tab portion  164  from the lower tab portion  166 . Thus, the upper tab portion  164  extends from an end surface  176  of gap  168  outward (e.g., in a direction away from centerline  156 ) and terminates at free end  172 . Similarly, the lower tab portion  166  extends from end surface  176  of gap  168  outward and terminates at free end  174 . In some embodiments, the upper and lower tab portions extend substantially parallel to each other, thereby forming a sideways U-shape or C-shape in side view. A length of the upper tab portion  164  along a direction perpendicular to centerline  156  can be substantially the same as that of the lower tab portion  166 . However, the height of the upper tab portion  164  along a direction parallel to centerline  156  may be different than that of the lower tab portion  166 . For example, upper tab portion  164  can have a height that corresponds to a size of upper opening  126  (e.g., length L 1  minus part of the thickness of crossbar  120  in  FIG.  3 B ) of commissure window  114 , while lower tab portion  166  can have a height that corresponds to a size of the lower opening  128  (e.g., length L 2  minus part of the thickness of crossbar  120  in  FIG.  3 B ) of commissure window  114 . 
       FIG.  6    shows an exemplary arrangement of leaflets  110   a ,  110   b  assembled to an H-shaped commissure window  114 , according to one or more embodiments of the disclosed subject matter. Tabs  162  of adjacent leaflets  110   a ,  110   b  can be paired together and inserted into commissure window  114  (e.g., by conveying from a radially-inner side to a radially-outer side of the window  114 ), with upper tab portions  164   a ,  164   b  of each leaflet  110   a ,  110   b  extending through the upper opening  126  and lower tab portions  166   a ,  166   b  of each leaflet extending through the lower opening  128 . The gaps separating the upper and lower tabs portions (of which, only gap  168   b  is visible in  FIG.  6   ) can correspond to a location of the crossbar  120  of the window  114 , and the end surface  176  of each gap  168  can be arranged to abut, or at least approach, a radially-inner surface of the crossbar  120  once the commissure is fully installed to the window  114 . 
     The upper tab portions  164   a ,  164   b  and the lower tab portions  166   a ,  166   b  can be wrapped around a wedge member  170  (or multiple wedge members) and coupled thereto. For example, the leaflet tabs and the wedge member  170  can be coupled to each other using one or more sutures, adhesive, welding, and/or any other means for attaching leaflets to wedge members. In some embodiments, a thickness of the combination of the wrapped tab portions and the wedge member  170  is greater than width W 1  of the openings  126 ,  128  of commissure window  114 , thereby preventing the combination from sliding radially inward and back through commissure window  114 . Alternatively, or additionally, the wedge member  170  can be a single continuous member that extends along the axial direction between the upper tab portions  164  and the lower tab portions  166 . In such configurations, the wedge member  170  may interact with the radially-outer side of the crossbar  120  to prevent the combination from sliding radially inward and back through commissure window  114 . 
     The one or more wedge members  170  can be formed from a relatively thick, multi-filament or monofilament suture, yarn or cable (e.g., a braided, polyester suture, such as an Ethibond suture), a piece of cloth or fabric folded one or more times to increase its thickness, or any other structure. For example, the disclosed wedge members, or sutures coupled thereto, can be formed of a material that does not encourage tissue ingrowth, such as ultra-high molecular weight polyethylene (UHMPE), polyethylene terephthalate (PET), polyurethane (PU), or polytetrafluoroethylene (PTFE). Alternatively, or additionally, any other material that is minimally porous, configured to prevent or minimize neo-vascularization, or does not allow tissue anchoring can be used for the disclosed wedge members. Alternatively, or additionally, the disclosed wedge members can be a coated or laminated polymeric material. In some embodiments, the material for the disclosed wedge members can be a polymer material that is processed in a manner, or otherwise configured, to reduce the likelihood for tissue ingrowth. For example, if exposure of the material to certain levels of heat may induce thrombogenicity, the materials for the disclosed wedge members may be processed in a manner that avoids or reduces such heating steps. 
     In the illustrated embodiment, commissure windows  114  are formed as part of the lattice structure of the frame  102 . In other embodiments, commissure windows  114  may instead be formed in another structure of the frame  102  or as a separate structure attached to the frame  102 . For example, in some embodiments, the prosthetic valve includes one or more actuators coupled to the frame to cause transition of the valve between crimped and expanded configurations, and/or one or more locking mechanisms that maintains a shape of the frame after expansion or contraction. In addition to or in place of commissure windows provided in the lattice structure of the frame, at least one of the actuators or locking mechanisms can include an H-shaped commissure window formed therein and can be used to mount a commissure of the valvular assembly thereto. Further details of the actuators, locking mechanisms and delivery apparatuses for actuating the actuators can be found in U.S. Patent Application Publication Nos. 2018/0153689, 2018/0325665, and 2019/0060057, each of which is incorporated herein by reference in its entirety. Any of the actuators and locking mechanisms disclosed in the previously filed applications can be incorporated in any of the prosthetic valves disclosed herein. Further, any of the delivery apparatuses disclosed in the previously filed applications can be used to deliver and implant any of the prosthetic valves discloses herein. 
     Alternatively, or additionally, the prosthetic valve can include one or more support members that form a part of or are coupled to the annular frame and that include an H-shaped commissure window. For example, the support member can be an axially extending member that is attached to a radially-inner surface of the frame, and the H-shaped commissure window can be formed in the support member (e.g., an axially-extending commissure post coupled to the frame, an actuator, or a locking mechanism). Alternatively, or additionally, the H-shaped commissure window can be formed by a wireform (e.g., bent piece of wire) or clamp coupled to the frame, actuator, locking mechanism, or support member. Further details regarding commissure windows formed from wireforms and commissure windows formed in or on actuators, locking mechanisms, and support members can be found in U.S. Provisional Applications No. 62/959,723 and International Publication No. WO-2020/102487, both of which are incorporated herein by reference in their entireties. 
     As shown in  FIG.  1   , the prosthetic heart valve  100  can also include one or more skirts or sealing members. For example, the prosthetic heart valve  100  can include an inner skirt  108  mounted on an inner surface of the frame  102  and/or an outer skirt  104  mounted on an outer surface of the frame  102 . The inner skirt  108  can be a circumferential inner skirt that spans an entire circumference of the inner surface of the frame  102 . The inner skirt  108  can function as a sealing member to prevent or decrease perivalvular leakage (e.g., when the valve is placed at the implantation site) and as an attachment surface to anchor a portion of the leaflets  110  to the frame  102 . For example, the cusp edge portions  160  of the leaflets  110  (see  FIG.  5   ) can be sutured to the inner skirt  108 , which in turn can be sutured to selected struts  142  of the frame  102 . The outer skirt  104  can function as a sealing member by sealing against the tissue of the native valve annulus and helping to reduce paravalvular leakage past the prosthetic valve  100 . The inner and outer skirts  108 ,  104  can be formed from any of various suitable biocompatible materials, including any of various synthetic materials (e.g., polyethylene terephthalate (PET)) or natural tissue (e.g., pericardial tissue). The inner and outer skirts  108 ,  104  can be mounted to the frame  102  using sutures, adhesive, welding, and/or other means for attaching the skirts to the frame. Further details regarding the inner and outer skirts, techniques for assembling the leaflets to the inner skirt, and techniques for assembling the skirts on the frame are disclosed in U.S. Patent Application Publication Nos. 2012/0123529, 2019/0192296, and 2019/0365530, and International Patent Application Nos. PCT/US2020/014701 and PCT/US2020/024559, each of which is incorporated herein by reference. 
     Once each commissure  112  of the valvular structure  106  has been secured to a respective one of the commissure windows  114 , the lower edges of the leaflets  110  between commissures  112  can be sutured to the inner skirt  108 . For example, the sutures can be in-and-out sutures extending through each leaflet, inner skirt, and optionally a reinforcing strip (not shown). Each leaflet and respective reinforcing strip can be sewn separately to the inner skirt. In this manner, the lower edges of the leaflets  110  can be secured to the frame  102  via the inner skirt  108 . In some embodiments, the lower edges of the leaflets  110  can be secured to the skirt with blanket sutures that extend through each reinforcing strip, leaflet, and the inner skirt while looping around edges of the reinforcing strips and leaflets. 
     In some embodiments, adjacent leaflet tabs of a commissure can be coupled together prior to insertion through the commissure window. A first leaflet tab of the commissure can be folded and attached to a second leaflet tab, which can remain unfolded. Once the upper and lower tab portions of the first and second leaflet tabs are passed through the upper and lower openings, respectively, to the radially-outer side of the commissure window, one or more wedge members can be inserted between folded portions of the first leaflet tab. Prior to or after insertion of the wedge member(s), the second leaflet tab can be wrapped around the folded first leaflet tab. The wedge member(s) can increase a width of the combination of first and second folded leaflet tabs such that the leaflet tabs cannot pass back through the window. 
     For example,  FIGS.  7 A- 10    illustrate a first exemplary method of installing a commissure  112  to an H-shaped commissure window  114 . Referring to  FIGS.  7 A- 7 B , a first leaflet tab  162   a  and a second leaflet tab  162   b  can be disposed adjacent to each other. The first leaflet tab  162   a  can have an upper tab portion  164   a  with free end  172   a , a lower tab portion  166   a  with free end  174   a , and a gap  168   a  with end surface  176   a  separating the upper and lower tab portions. Similarly, the second leaflet tab  162   b  can have an upper tab portion  164   b  with free end  172   b , a lower tab portion  166   b  with free end  174   b , and a gap  168   b  with end surface  176   b  separating the upper and lower tab portions. Each upper tab portion  162   a,b  can have a first part  193   a,b  that is adjacent to a free end  172   a,b  of the upper tab portion and a second part  191   a,b  that is between the first part  193   a,b  and the centerline of the leaflet (or the respective end surface  176   a,b  of the gap  168   a,b  along a direction perpendicular to the centerline). Similarly, each lower tab portion  164   a,b  can have a first part that is adjacent to a free end  174   a,b  of the lower tab portion and a second part that is between the first part and the centerline of the leaflet (or the respective end surface  176   a,b  of the gap  168   a,b  along a direction perpendicular to the centerline). 
     In some embodiments, each of the upper tab portions  164   a,b  and the lower tab portions  166   a,b  can optionally be provided with one or more holes, through which one or more sutures can be passed to couple the tab portions and/or a wedge member together. For example, the first parts  193   a  of the upper and lower tab portions  164   a ,  166   a  of the first leaflet tab  162   a  can have through-holes  182   a , while the second parts  191   a  of the upper and lower tab portions  164   a ,  166   a  of the first leaflet tab  162   a  can have through-holes  180   a . Similarly, the first parts  193   b  of the upper and lower tab portions  164   b ,  166   b  of the second leaflet tab  162   b  can have through-holes  182   b , while the second parts of the upper and lower tab portions  164   b ,  166   b  of the second leaflet tab  162   b  can have through-holes  180   b . One or more sutures  184  can be passed through the holes  182   a  in the first leaflet tab  162   a  and the holes  180   b  in the second leaflet tab  162   b  to couple the leaflet tabs  162   a,b  together. In other embodiments, only some or none of the first and second parts of the tab portions are provided with holes  180 ,  182 . In such embodiments, a suture can pierce through the first or second parts of the leaflet tab portions, or a means for attachment other than a suture can be used to couple the leaflet tab portions together, for example, by welding or adhesive. 
     As illustrated in  FIGS.  7 A- 7 B , the first leaflet tab  162   a  can be folded onto itself, for example, by passing the free ends  172   a ,  174   a  of the upper and lower tab portions  164   a ,  166   a  between the first leaflet tab  162   a  and the second leaflet tab  162   b . Thus, the first part  193   a  of the upper tab portion  164   a  of the first leaflet tab  162   a  contacts, or at least faces, the second part  191   b  of the upper tab portion  164   b  of the second leaflet tab  162   b , and the first part of the lower tab portion  166   a  of the first leaflet tab  162   a  contacts, or at least faces, the second part of the lower tab portion  166   b  of the second leaflet tab  162   b . The folded portions of the first leaflet tab  162   a  also creates a gap or recess  178  between the facing surfaces of the first part  193   a  and second part  193   a  of the upper tab portion  164   a  and between the facing surfaces of the first and second parts of the lower tab portion  166   a.    
     In some embodiments, one or more sutures  184  can be used to couple the leaflet tabs  162   a ,  162   b  together after the folding of the first leaflet tab  162   a . Alternatively, the one or more sutures  184  can be used to couple the leaflet tabs  162   a ,  162   b  together before the folding of the first leaflet tab  162   a . For example, the first leaflet tab  162   a  can be disposed in a substantially flat configuration on the second leaflet tab  162   b  and extending in an opposite direction from the second leaflet tab  162   b , such that the centerlines of the leaflets are on opposite sides of overlapping portions of the first and second leaflet tabs  162   a ,  162   b . Thus, the first parts  193   a  of the upper and lower tab portions  164   a ,  166   a  of the first leaflet tab  162   a  can be aligned with the second parts  191   b  of the upper and lower tab portions  164   b ,  166   b  of the second leaflet tab  162   b , and the first parts  193   b  of the upper and lower tab portions  164   b ,  166   b  of the second leaflet tab  162   b  can be aligned with the second parts  191   a  of the upper and lower tab portions  164   a ,  166   a  of the first leaflet tab  162   a . In this overlapping configuration, the one or more first sutures  184  can be passed through the first parts  193   a  of the upper and lower tab portions  164   a ,  166   a  of the first leaflet tab  162   a  (e.g., via through-holes  182   a ) and through the second parts  191   b  of the upper and lower tab portions  164   b ,  166   b  of the second leaflet tab  162   b  (e.g., via through-holes  180   b ) to couple together the leaflet tabs  162   a ,  162   b . After the leaflet tabs are coupled together, the upper and lower tab portions  164   a ,  166   a  can then be folded, as described above. In some embodiments, a single suture  184  can be used to couple both the upper and lower tab portions of the first and second leaflet tabs  162   a ,  162   b , so long as the portion of the suture  184  extending between the upper tab portions  164   a ,  164   b  and the lower tab portions  166   a ,  166   b  does not otherwise interfere with crossbar  120  as the leaflet tabs  162   a ,  162   b  are inserted into the commissure window  114 . 
     With the upper and lower tab portions  164   a ,  166   a  of the first leaflet tab  162   a  folded, the coupled-together first and second leaflet tabs  162   a ,  162   b  can then be conveyed from a radially-inner side through respective openings  126 ,  128  to a radially-outer side of the commissure window  114 . For example, as shown in  FIG.  8   , the free end  172   b  of the upper tab portion  166   b  of the second leaflet tab  162   b  can be inserted into the upper opening  126  of the commissure window, followed by the remainder of the upper tab portion  166   b  of the second leaflet tab  162   b  and the folded portions of the upper tab portion  164   a  of the first leaflet tab  162   a . Similarly, the free end  174   b  of the lower tab portion  166   b  of the second leaflet tab  162   b  can be inserted into the lower opening  128  of the commissure window, followed by the remainder of the lower tab portion  166   b  of the second leaflet tab  162   b  and the folded portions of the lower tab portion  166   a  of the first leaflet tab  162   a . In some embodiments, the insertion of the upper tab portions  164   a ,  164   b  into the upper opening  126  and the insertion of the lower tab portions  166   a ,  166   b  into the lower opening  128  can occur simultaneously or substantially at the same time. In other embodiments, the lower tab portions  166   a ,  166   b  can be fully inserted through the lower opening  128  prior to insertion of the upper tab portions  164   a ,  164   b  into the upper opening  126 , or vice versa. 
     Once the upper and lower tab portions of the first and second leaflet tabs  162   a ,  162   b  have been inserted through the respective openings  126 ,  128  of the commissure window, one or more wedge members can be added to the assembly at the radially-outer side of the commissure window. For example, a wedge member  170  can be inserted into the recess  178  formed by the upper and lower tab portions  164   a ,  166   a  of the first leaflet tab  162   a , as illustrated in  FIG.  9   . The wedge member  170  can be conveyed parallel to the axial direction of the frame (e.g., from the outflow end  116  to the inflow end  118  or vice versa) in between the facing surfaces of the first and second parts  191   a ,  193   a  of the upper and lower tab portions  164   a ,  166   a  of the first leaflet tab  162   a . The wedge member  170  can extend between the upper and lower tab portions  164   a ,  166   a  and thus prevent, or at least restrain, the leaflet tabs  162   a ,  162   b  from passing back through the commissure window  114  (e.g., from the radially-outer side of the window back to the radially-inner side of the window) due to interaction between an intermediate portion of the wedge member  170  (e.g., between the upper tab portion  164   a  and the lower tab portion  164   b  along the axial direction of the frame) and the crossbar  120  of the window. The wedge member  170  may also cause a width (along the circumferential direction) of the combination of the first and second leaflet tabs  162   a ,  162   b  at the radially-outer side of the window  114  to be greater than that of the upper opening  126  and/or lower opening  128 . Thus, the increased width can also prevent, or at least restrain, leaflet tabs  162   a ,  162   b  from passing back through the commissure window  114 . 
     Alternatively, multiple wedge members can be provided, for example, a first wedge member for the upper tab portion  164   a  of the first leaflet tab  162   a  and a separate second wedge member for the lower tab portion  166   a  of the first leaflet tab. In such configurations, a gap  168   a  between the upper tab portion  164   a  and lower tab portion  166   a  would remain after insertion of the first and second wedge members. However, each wedge member causes a width (along the circumferential direction) of the combination of the first and second leaflet tabs  162   a ,  162   b  at the radially-outer side of the window  114  to be greater than that of the upper opening  126  and/or lower opening  128 , thereby preventing, or at least restraining, the leaflet tabs  162   a ,  162   b  from passing back through the commissure window  114 . In such embodiments, the multiple wedge members can be coupled together (e.g., via stitching using one or more sutures) and/or the upper and lower tab portions on the radially-outer side of the commissure window  114  can be coupled together (e.g., via stitching using one or more sutures), for example, to prevent sliding along the axial direction of the respective tab portions. 
     Once the one or more wedge members have been positioned with respect to the first leaflet tab  162   a , the upper tab portion  164   b  of the second leaflet tab  162   b  can be wrapped around the upper tab portion  164   a  of the first leaflet tab  162   a , as shown in  FIG.  10   . Before, during, or after the wrapping of the upper tab portion  164   b , the lower tab portion  166   b  of the second leaflet  162   b  can also be wrapped around the lower tab portion  166   a  of the first leaflet tab  162   a . Alternatively, in some embodiments, the upper tab portion  164   b  and/or the lower tab portion  166   b  of the second leaflet tab  162   b  can be wrapped around the respective tab portions of the first leaflet tab  162   a  prior to positioning of the wedge members. In either case, after positioning of the one or more wedge members, the tab portions of each leaflet tab  162   a ,  162   b  can be arranged such that free ends  172   a ,  172   b  of the upper tab portions  164   a ,  164   b  and free ends  174   a ,  174   b  of the lower tab portions  166   a ,  166   b  are disposed between the wedge member  170  and a radially-outer side of the commissure window  114  along a radial direction of the frame  102 . 
     One or more sutures can be used to couple together the wedge members and the folded leaflet tabs  162   a ,  162   b . For example, one or more second sutures  188  can be passed through the first part  193   b  of the upper tab portion  164   b  of the second leaflet tab  162   b  (e.g., via through-holes  182   b ), the second part  191   a  of the upper tab portion  164   a  of the first leaflet tab  162   a  (e.g., via through-holes  180   a ), the wedge member  170 , the first part  193   a  of the upper tab portion  164   a  of the first leaflet tab  162   a  (e.g., via through-holes  182   a ), and the second part  191   a  of the upper tab portion  164   b  of the second leaflet tab  162   b  (e.g., via through-holes  180   b ), in order or vice versa. The one or more second sutures  188  can be passed through the first and second parts of the lower tab portions  166   a ,  166   b  of the first and second leaflet tabs  162   a ,  162   b  and the wedge member  170  in a similar manner. 
     If the valvular structure includes other commissures to be attached to commissure windows of the frame, the method of  FIGS.  7 A- 10    can be repeated for the other commissures. In some embodiments, the valvular structure can have a tricuspid configuration with three leaflets, and the three commissures of the valvular structure are coupled to respective commissure windows of the frame by performing the method of  FIGS.  7 A- 10    three separate times. In other embodiments, the valvular structure can have a bicuspid configuration with two leaflets, and the two commissures of the valvular structure are coupled to respective commissure windows of the frame by performing the method of  FIGS.  7 A- 10    two separate times. In any of the embodiments with multiple commissures and commissure windows, performance of some or all of the method for the respective commissures can occur in parallel. For example, the leaflet tabs for each commissure can be folded and coupled together at the same time, after which the coupled leaflet tabs can be inserted into their respective windows. Other variations for parallel assembly of multiple commissures to multiple commissure windows are also possible according to one or more contemplated embodiments. 
     The method of assembly described with respect to  FIGS.  7 A- 10    provides a simple and cost-effective methodology for installing commissure assemblies to respective windows of the valve frame. For example, the configuration of  FIGS.  7 A- 7 B  can allow the leaflet tabs  162   a ,  162   b  to be quickly and easily coupled together in a flat configuration, followed by a simple sliding/insertion of the upper and lower tab portions into the respective upper and lower openings of the commissure window. Moreover, the assembly of the leaflet tabs and subsequent mounting to the window using one or more wedge members involves a relatively small number of distinct components and assembly stages. 
     In some embodiments, adjacent leaflet tabs of a commissure can be inserted through the commissure window prior to any folding of the leaflet tabs and/or the coupling of leaflet tabs to each other. The upper and lower tab portions of the first and second leaflet tabs can be passed (simultaneously or sequentially) through the upper and lower openings, respectively, to the radially-outer side of the commissure window. The first leaflet tab can then be folded around one or more wedge members and coupled thereto. Prior to or after the coupling of the first leaflet tab and the wedge member(s), the second leaflet tab can be wrapped around the folded first leaflet tab. The wedge member(s) can increase a width of the combination of first and second folded leaflet tabs such that the leaflet tabs cannot pass back through the window. 
     For example,  FIGS.  11 - 13    illustrate a second exemplary method of installing a commissure  112  to an H-shaped commissure window  114 . While  FIGS.  11 - 13    illustrate only the upper tab portions  164   a ,  164   b  of the first and second leaflet tabs  162   a ,  162   b , it should be noted that the installation of the lower tab portions  166   a ,  166   b  of the first and second leaflet tabs  162   a ,  162   b  would be handled in a similar manner simultaneously with, or substantially at a same time as, the illustrated installation of the upper tab portions  164   a ,  164   b.    
     In  FIG.  11   , a first leaflet tab  162   a  and a second leaflet tab  162   b  can be disposed adjacent to each other. As described in detail above, each leaflet tab  162   a ,  162   b  can have respective upper tab portions  164   a ,  164   b  and lower tab portions  166   a ,  166   b  separated by a gap  168   a ,  168   b . Each upper tab portion  162   a,b  can have a first part  193   a,b  that is adjacent to a free end  172   a,b  of the upper tab portion and a second part  191   a,b  that is between the first part  193   a,b  and the centerline of the leaflet, and each lower tab portion can have a first part that is adjacent to a free end of the lower tab portion and a second part that is between the first part and the centerline of the leaflet. In some embodiments, the respective first and second parts of the upper tab portions  164   a,b  and the lower tab portions  166   a,b  can optionally be provided with one or more holes (e.g., through-holes  180   a,b  and  182   a,b ), through which one or more sutures can be passed to couple the tab portions and/or a wedge member together. 
     The first leaflet tab  162   a  can be conveyed from a radially-inner side through respective openings  126 ,  128  to a radially-outer side of the commissure window  114 . Before, after, or during the conveying of the first leaflet tab  162   a  into commissure window  114 , the second leaflet tab  162   b  can be conveyed from the radially-inner side through respective openings  126 ,  128  to the radially-outer side of the commissure window  114 . For example, as shown in  FIG.  12   , the free end  172   a  of the upper tab portion  164   a  of the first leaflet tab  162   a  can be inserted into the upper opening  126  of the commissure window, and the free end  172   b  of the upper tab portion  164   b  of the second leaflet tab  162   b  can be inserted into the upper opening of the commissure window. Similarly, the free end  174   a  of the lower tab portion  166   a  of the first leaflet tab  162   a  can be inserted into the lower opening  128  of the commissure window, and the free end  174   b  of the lower tab portion  166   b  of the second leaflet tab  162   b  can be inserted into the lower opening of the commissure window. In some embodiments, the insertion of the upper tab portions  164   a ,  164   b  into the upper opening  126  and the insertion of the lower tab portions  166   a ,  166   b  into the lower opening  128  can occur simultaneously or substantially at the same time. In other embodiments, the lower tab portions  166   a ,  166   b  can be fully inserted through the lower opening  128  prior to insertion of the upper tab portions  164   a ,  164   b  into the upper opening  126 , or vice versa. 
     After insertion through respective openings  126 ,  128  of the commissure window  114 , the first leaflet tab  162   a  can be wrapped around one or more wedge members at the radially-outer side of the commissure window. For example, the upper and lower tab portions  164   a ,  166   a  of the first leaflet tab  162   a  can be wrapped around (e.g., folded around) a single wedge member  170 , as illustrated in  FIG.  12   . The wedge member  170  can extend between the upper and lower tab portions  164   a ,  166   a  and thus prevent, or at least restrain, the leaflet tabs  162   a ,  162   b  from passing back through the commissure window  114  (e.g., from the radially-outer side of the window back to the radially-inner side of the window) due to interaction between an intermediate portion of the wedge member  170  (e.g., between the upper tab portion  164   a  and the lower tab portion  164   b  along the axial direction of the frame) and the crossbar  120  of the window. The wedge member  170  may also cause a width (along the circumferential direction) of the combination of the first and second leaflet tabs  162   a ,  162   b  at the radially-outer side of the window  114  to be greater than that of the upper opening  126  and/or lower opening  128 . Thus, the increased width can also prevent, or at least restrain, leaflet tabs  162   a ,  162   b  from passing back through the commissure window  114 . 
     Alternatively, multiple wedge members can be provided, for example, a first wedge member for the upper tab portion  164   a  of the first leaflet tab  162   a  and a separate second wedge member for the lower tab portion  166   a  of the first leaflet tab. In such configurations, a gap  168   a  between the upper tab portion  164   a  and lower tab portion  166   a  would remain after insertion of the first and second wedge members. However, each wedge member causes a width (along the circumferential direction) of the combination of the first and second leaflet tabs  162   a ,  162   b  at the radially-outer side of the window  114  to be greater than that of the upper opening  126  and/or lower opening  128 , thereby preventing, or at least restraining, the leaflet tabs  162   a ,  162   b  from passing back through the commissure window  114 . In such embodiments, the multiple wedge members can be coupled together (e.g., via stitching using one or more sutures) and/or the upper and lower tab portions on the radially-outer side of the commissure window  114  can be coupled together (e.g., via stitching using one or more sutures), for example, to prevent sliding along the axial direction of the respective tab portions. 
     One or more sutures can be used to couple together the wedge members and the wrapped upper and lower tab portions  164   a ,  166   a  of the first leaflet tab  162   a . For example, as illustrated in  FIG.  12   , one or more first sutures  190  can be passed through the first part  193   a  of the upper tab portion  164   a  of the first leaflet tab  162   a  (e.g., via through-hole  182   a ), the wedge member  170 , and the second part  191   a  of the upper tab portion  164   a  of the first leaflet tab  162   a  (e.g., via through-hole  180   a ), in order or vice versa. The one or more first sutures  190  can be passed through the first and second parts of the lower tab portion  166   a  of the first leaflet tab  162   a  in a similar manner. 
     Once the one or more wedge members have been positioned with respect to the first leaflet tab  162   a , the upper tab portion  164   b  of the second leaflet tab  162   b  can be wrapped around the upper tab portion  164   a  of the first leaflet tab  162   a , as shown in  FIG.  13   . Before, during, or after the wrapping of the upper tab portion  164   b , the lower tab portion  166   b  of the second leaflet  162   b  can also be wrapped around the lower tab portion  166   a  of the first leaflet tab  162   a . Alternatively, in some embodiments, the upper tab portion  164   b  and/or the lower tab portion  166   b  of the second leaflet tab  162   b  can be wrapped around the respective tab portions of the first leaflet tab  162   a  prior to positioning of the wedge members. In either case, after positioning of the one or more wedge members, the tab portions of each leaflet tab  162   a ,  162   b  can be arranged such that free ends  172   a ,  172   b  of the upper tab portions  164   a ,  164   b  and free ends  174   a ,  174   b  of the lower tab portions  166   a ,  166   b  are disposed between the wedge member  170  and a radially-outer side of the commissure window  114  along a radial direction of the frame  102 . 
     One or more sutures can be used to couple together the wedge members and the wrapped leaflet tabs  162   a ,  162   b . For example, as illustrated in  FIG.  13   , one or more second sutures  192  can be passed, through the first part  193   b  of the upper tab portion  164   b  of the second leaflet tab  162   b  (e.g., via through-holes  182   b ), the second part  191   a  of the upper tab portion  164   a  of the first leaflet tab  162   a  (e.g., via through-holes  180   a ), the wedge member  170 , the first part  193   a  of the upper tab portion  164   a  of the first leaflet tab  162   a  (e.g., via through-holes  182   a ), and the second part  191   a  of the upper tab portion  164   b  of the second leaflet tab  162   b  (e.g., via through-holes  180   b ), in order or vice versa. The one or more second sutures  192  can be passed through the first and second parts of the lower tab portions  166   a ,  166   b  of the first and second leaflet tabs  162   a ,  162   b  and the wedge member  170  in a similar manner. In some embodiments, the second leaflet tab  162   b  can be wrapped around the first leaflet tab  162   a  and the one or more wedge members prior to coupling the first leaflet tab  162   a  to the wedge member(s)  170 . In such embodiments, the first suture(s)  190  can be omitted in favor of coupling together the first and second leaflet tabs  162   a ,  162   b  and the wedge member(s)  170  using just the second suture(s)  192 . 
     If the valvular structure includes other commissures to be attached to commissure windows of the frame, the method of  FIGS.  11 - 13    can be repeated for the other commissures. In some embodiments, the valvular structure can have a tricuspid configuration with three leaflets, and the three commissures of the valvular structure are coupled to respective commissure windows of the frame by performing the process of  FIGS.  11 - 13    three separate times. In other embodiments, the valvular structure can have a bicuspid configuration with two leaflets, and the two commissures of the valvular structure are coupled to respective commissure windows of the frame by performing the method of  FIGS.  11 - 13    two separate times. In any of the embodiments with multiple commissures and commissure windows, performance of some or all of the method for the respective commissures can occur in parallel. For example, the leaflet tabs for each commissure can be inserted into their respective windows and then the first leaflet tabs can be wrapped around and coupled to respective wedge members. Other variations for parallel assembly of multiple commissures to multiple commissure windows are also possible according to one or more contemplated embodiments. 
     The method of assembly described with respect to  FIGS.  11 - 13    provides a simple and cost-effective methodology for installing commissure assemblies to respective windows of the valve frame. For example, the arrangement of  FIG.  11    can allow the leaflet tabs  162   a ,  162   b  to be quickly and easily inserted through the respective upper and lower openings of the commissure window. Moreover, the assembly of the leaflet tabs and subsequent mounting to the window using one or more wedge members involves a relatively small number of distinct components and assembly stages. 
     In some embodiments, adjacent leaflet tabs of a commissure can be coupled a wedge member prior to insertion through the commissure window. An upper tab portion of the first leaflet tab of the commissure can be wrapped around a wedge member, and then coupled to an upper tab portion of the second leaflet tab. The lower tab portion of the first leaflet tab and the upper and lower tab portions of the second leaflet tab can remain unfolded. The lower tab portions of the first and second leaflet tabs can be passed through the lower opening of the commissure window from the radially-inner side to the radially-outer side of the commissure window, and the upper tab portion of the second leaflet tab can be passed through the upper opening of the commissure window from the radially-inner side to the radially-outer side of the commissure window. The wedge member and the upper tab portion of the first leaflet tab can be passed over the open end of the upper opening of the commissure window to the radially outer-side of the commissure window, such that a portion of the upper tab slides into the upper opening of the commissure window. The lower tab portion of the first leaflet tab can then be wrapped around the wedge member, and the upper and lower tab portions of the second leaflet tab can be wrapped around the respective portions of the first leaflet tab. The wedge member can increase a width of the combination of the first and second folded leaflet tabs such that the leaflet tabs cannot pass back through the window. 
     For example,  FIGS.  14 - 15    illustrate a third exemplary method of installing a commissure  112  to an H-shaped commissure window  114 . As described in detail above, each leaflet tab  162   a ,  162   b  for the commissure can have respective upper tab portions  164   a ,  164   b  and lower tab portions  166   a ,  166   b  separated by a gap  168   a ,  168   b . Each upper tab portion  162   a,b  can have a first part  193   a,b  that is adjacent to a free end  172   a,b  of the upper tab portion and a second part  191   a,b  that is between the first part  193   a,b  and the centerline of the leaflet, and each lower tab portion can have a first part that is adjacent to a free end of the lower tab portion and a second part that is between the first part and the centerline of the leaflet. In some embodiments, the respective first and second parts of the upper tab portions  164   a,b  and the lower tab portions  166   a,b  can optionally be provided with one or more holes (e.g., through-holes  180   a,b  and  182   a ,b), through which one or more sutures can be passed to couple the tab portions and/or a wedge member together. 
     The upper tab portion  164   a  of the first leaflet tab  162   a  can be wrapped around a wedge member  170 . The wrapped upper tab portion  164   a  of the first leaflet tab  162   a  can then be disposed adjacent to the upper tab portion  164   b  of the second leaflet tab  162   b , which remains unfolded. Thus, the first part  193   a  of the upper tab portion  164   a  of the first leaflet tab  162   a  can contact, or at least face, the second part  191   b  of the upper tab portion of the second leaflet tab  162   b , as shown in  FIG.  14   . Simultaneously or sequentially, the lower tab portions of the first and second leaflet tabs  162   a ,  162   b  can be disposed adjacent to each other and unfolded. One or more sutures can be used to couple together the wedge member  170  and the upper tab portions  164   a ,  164   b  of the first and second leaflet tabs  162   a ,  162   b . For example, as illustrated in  FIG.  14   , one or more first sutures  194  can be passed through the second part  191   b  of the upper tab portion  164   b  of the second leaflet tab  162   b  (e.g., via through-holes  180   b ), the first part  193   a  of the upper tab portion  164   a  of the first leaflet tab  162   a  (e.g., via through-holes  182   a ), the wedge member  170 , and the second part  191   a  of the upper tab portion  164   a  of the first leaflet tab  162   a  (e.g., via through-holes  180   a ), in order or vice versa. 
     Alternatively, the one or more sutures  194  can be used to couple the leaflet tabs  162   a ,  162   b  together before the wrapping of the first leaflet tab  162   a . For example, the first leaflet tab  162   a  can be disposed in a substantially flat configuration on the second leaflet tab  162   b  and extending in an opposite direction from the second leaflet tab  162   b , such that the centerlines of the leaflets are on opposite sides of overlapping portions of the first and second leaflet tabs  162   a ,  162   b . Thus, the first parts  193   a  of the upper and lower tab portions  164   a ,  166   a  of the first leaflet tab  162   a  can be aligned with the second parts  191   b  of the upper and lower tab portions  164   b ,  166   b  of the second leaflet tab  162   b , and the first parts  193   b  of the upper and lower tab portions  164   b ,  166   b  of the second leaflet tab  162   b  can be aligned with the second parts  191   a  of the upper and lower tab portions  164   a ,  166   a  of the first leaflet tab  162   a . The wedge member  170  can be disposed atop the first part  193   a  of the upper tab portion  162   a  of the first leaflet tab  162   a . In this overlapping configuration, the one or more first sutures  194  may be passed through the wedge member  170 , the first part  193   a  of the upper tab portion  164   a  of the first leaflet tab  162   a , and the second part  191   b  of the upper tab portion  164   b  of the second leaflet tab  162   b , in order or vice versa. After the leaflet tabs are coupled together, the upper tab portions  164   a  can then be wrapped around the wedge member  170 , as described above. 
     The wedge member  170  can extend to the lower tab portions  166   a ,  166   b  of the first and second leaflet tabs  162   a ,  162   b , and attaching the wedge member  170  to the lower tab portions  166   a ,  166   b  would prevent the commissure from passing through the commissure window due to the intervening crossbar  120 . Thus, the lower tab portions  166   a ,  166   b  can remain unattached to the wedge member  170  at this stage. This allows the lower tab portions  166   a ,  166   b  to be inserted through the lower opening  128  of commissure window  114 , for example, in a manner similar to that described above with respect to  FIG.  11   . Before, during, or after the insertion of the lower tab portions  166   a ,  166   b , the wedge member  170  can be passed over the upper end of upper opening  126  of the commissure window  114  (e.g., by passing over the outflow end  116  of the valve frame  102 , from the radially-inner side of the window  114  to the radially-outer side of the window  114 ). The upper tab portions  164   a ,  164   b  can thus be inserted into the upper opening  126 , for example, along a direction parallel to the axial direction of the frame  102  or a combination of axial and radial components. Alternatively or additionally, a cross-sectional dimension of the wedge member  170  can be such that the combination of wrapped upper tab portion  164   a  of the first leaflet tab  162   a , the unfolded upper tab portion  164   b  of the second leaflet tab  162   b , and the wedge member  170  is able to fit through the upper opening  126 . To avoid the crossbar  120  as the upper tab portions pass through the upper opening  126 , the wedge member  170  may be temporarily tilted to extend along the radial direction of the frame and can pass through the upper opening  126  prior to or with the free end  172   b  of the upper tab portion  164   b  of the second leaflet tab  162   b . In either case, the wedge member  170  avoids the crossbar  120  of the window  114 , thereby allowing the wedge member  170  to be attached to the upper tab portions  162   a ,  162   b  at the radially-inner side of the commissure window while still permitting the upper tab portions  162   a ,  162   b  to inserted through the upper opening  126  of the commissure window  114 . 
     With the upper and lower tab portions of the first and second leaflets  162   a ,  162   b  inserted through the respective openings  126 ,  128  and the wedge member  170  on the radially-outer side of the window  114  as shown in  FIG.  14   , the lower tab portion  166   a  can be wrapped around the wedge member  170 . The upper tab portion  164   b  of the second leaflet tab  162   b  can be wrapped around the upper tab portion  164   a  of the first leaflet tab  162   a , and the lower tab portion  166   b  of the second leaflet  162   b  can be wrapped around the lower tab portion  166   a  of the first leaflet tab  162   a , resulting in a configuration similar to that illustrated in  FIG.  13   . Similar to the above described embodiments, one or more sutures can be used to couple together the wedge member  170  and the folded leaflet tabs  162   a ,  162   b . For example, similar to the configuration of  FIG.  13   , one or more second sutures  192  can be passed, through the first part  193   b  of the upper tab portion  164   b  of the second leaflet tab  162   b  (e.g., via through-holes  182   b ), the second part  191   a  of the upper tab portion  164   a  of the first leaflet tab  162   a  (e.g., via through-holes  180   a ), the wedge member  170 , the first part  193   a  of the upper tab portion  164   a  of the first leaflet tab  162   a  (e.g., via through-holes  182   a ), and the second part  191   a  of the upper tab portion  164   b  of the second leaflet tab  162   b  (e.g., via through-holes  180   b ), in order or vice versa. The one or more second sutures  192  can be passed through the first and second parts of the lower tab portions  166   a ,  166   b  of the first and second leaflet tabs  162   a ,  162   b  and the wedge member  170  in a similar manner. 
     If the valvular structure includes other commissures to be attached to commissure windows of the frame, the method of  FIGS.  14 - 15    can be repeated for the other commissures. In some embodiments, the valvular structure can have a tricuspid configuration with three leaflets, and the three commissures of the valvular structure are coupled to respective commissure windows of the frame by performing the process of  FIGS.  14 - 15    three separate times. In other embodiments, the valvular structure can have a bicuspid configuration with two leaflets, and the two commissures of the valvular structure are coupled to respective commissure windows of the frame by performing the method of  FIGS.  14 - 15    two separate times. In any of the embodiments with multiple commissures and commissure windows, performance of some or all of the method for the respective commissures can occur in parallel. For example, the leaflet tabs for each commissure can be wrapped around respective wedge members and then coupled together at the same time, after which the coupled leaflet tabs can be inserted into their respective windows. Other variations for parallel assembly of multiple commissures to multiple commissure windows are also possible according to one or more contemplated embodiments. 
     The method of assembly described with respect to  FIGS.  14 - 15    provides a simple and cost-effective methodology for installing commissure assemblies to respective windows of the valve frame. For example, the arrangement of  FIG.  11    can allow the leaflet tabs  162   a ,  162   b  to be quickly and easily inserted through the respective upper and lower openings of the commissure window. Moreover, the assembly of the leaflet tabs and subsequent mounting to the window using one or more wedge members involves a relatively small number of distinct components and assembly stages. 
     In some embodiments, upper and lower tab portions of adjacent leaflet tabs can be coupled to separate wedge members prior to insertion through the commissure window. For example, an upper tab portion of the first leaflet tab of the commissure can be wrapped around a first wedge member, and then coupled to an upper tab portion of the second leaflet tab, which remains unfolded. Similarly, a lower tab portion of the first leaflet tab of the commissure can be wrapped around a second wedge member, and then coupled to a lower tab portion of the second leaflet tab, which remains unfolded. The configuration for upper and lower tab portions can be similar to that illustrated in  FIG.  14   , but with upper tab portion having a wedge member  170  separate from that of the lower tab portion. 
     The cross-sectional dimension of each wedge member can be such that the combination of wrapped upper tab portion of the first leaflet tab, first wedge member, and unfolded upper tab portion of the second leaflet tab fits through the upper opening of the commissure window, and the combination of wrapped lower tab portion of the first leaflet tab, second wedge member, and unfolded lower tab portion of the second leaflet tab fits through the lower opening of the commissure window. Since there is no wedge member extending between the upper and lower tab portions that would otherwise obstruct passage of the commissure through the window due to crossbar  120 , the upper and lower tab portions of the first and second leaflet tabs can be passed through the upper and lower openings of the commissure window, respectively, from the radially-inner side to the radially-outer side of the commissure window. 
     The second leaflet tab can then be wrapped around and further coupled to the first leaflet tab and the wedge members, resulting in a structure similar to that described above with respect to  FIG.  6 ,  10   , or  13 . Each wedge member can increase a width of the combination of the wrapped first and second leaflet tabs such that the leaflet tabs is prevented, or at least restrained, from passing back through the window. In such embodiments, the multiple wedge members can be coupled together (e.g., via stitching using one or more sutures) and/or the upper and lower tab portions on the radially-outer side of the commissure window  114  can be coupled together (e.g., via stitching using one or more sutures), for example, to prevent sliding along the axial direction of the respective tab portions. As with the other described embodiments, if the valvular structure includes other commissures to be attached to commissure windows of the frame, the method can be repeated for the other commissures. 
     In some embodiments, the upper tab portion of the first and second leaflet tabs can be inserted through the upper opening and attached to the commissure window  114  and/or the lower tab portion of the first and second leaflet tabs can be inserted through the lower opening and attached to the commissure window  114 , using any of the assembly techniques disclosed in U.S. Provisional Application No. 62/959,723, which is incorporated herein by reference. 
     In some embodiments, the leaflet tabs of each leaflet of the valvular structure can be formed without separate upper and lower tab portions, for example, without gaps  168 . In such embodiments, the leaflet tabs can have a configuration similar to those described in U.S. Provisional Application No. 62/959,723 and the other applications and publications incorporated by reference above. In some embodiments, these leaflet tabs can be inserted into either the upper opening or the lower opening of the commissure window  114 . Since the leaflet tabs are only inserted into half of the H-shaped commissure window  114 , the commissure window  114  may be considered a U-shaped window in such embodiments. 
     In any of the disclosed examples or embodiments, a coupling member, such as a flexible cloth or fabric, can be disposed around surfaces of the leaflet tabs and or the wedge member(s). For example, the coupling member can be attached to the wedge member(s) and the tabs prior to installation in the commissure window. In some embodiments, the coupling member can be wrapped around portions of the commissure window (e.g., struts  122 ,  124 ) to further secure the leaflet tabs to the commissure window and/or protect portions of the leaflets from abrasion. 
       FIGS.  17 A and  17 B  illustrate an alternative frame  102 ′ with commissure windows  114 ′ according to another example. In some embodiments, the prosthetic valve  100  can include the frame  102 ′ instead of the previously described frame  102 . The frame  102 ′ is similar in many respects to the frame  102  except for the details of the commissure windows. Similar reference numbers are used for parts of the frame  102 ′ that are similar or the same as parts of the frame  102 . For purposes of illustration, only the bare frame  102 ′ is shown in  FIGS.  17 A and  17 B . It should be understood that any of the other components of the prosthetic valve  100  (e.g., leaflets  100 , inner skirt  108 , outer skirt  104 , etc.) can be assembled onto the frame  102 ′ in the manner shown in  FIG.  1    and described above. 
     In the example illustrated in  FIGS.  17 A and  17 B , each commissure window  114 ′ can include window struts  122 ,  124 , which extend along the axial direction of the frame  102 ′ and are spaced along the circumferential direction of the frame  102 ′. Each commissure window  114 ′ can include a crossbar  120  extending between and connected to the window struts  122 ,  124 . Each commissure window  114 ′ can include a first, upper opening  126  (or upper window portion or downstream window portion) formed on one side of the crossbar  120  and a second, lower opening  128  (or lower window portion or upstream window portion) formed on the other side of the crossbar  120 . 
     Each commissure window  114 ′ can further include an upper lateral strut portion  131  extending between the upper ends of the window struts  122 ,  124  and forming a closed end of the upper opening  126 . In one example, an upper angled strut  130   a  is connected to an upper end of the window strut  122 , and an upper angled strut  130   b  is connected to an upper end of the window strut  124 . The upper lateral strut portion  131  extends between the junction formed between the upper angled strut  130   a  and the window strut  122  and the junction formed between the upper angled strut  130   b  and the window strut  124 . The upper lateral strut portion  131  can thereby increase the stability of the window struts  122 ,  124  at the upper ends. 
     Each commissure window  114 ′ can further include a lower lateral strut portion  133  extending between the lower ends of the window struts  122 ,  124  and forming a closed end of the lower opening  128 . In one example, a lower angled strut  132   a  is connected to a lower end of the window strut  122 , and a lower angled strut  132   b  is connected to a lower end of the window strut  124 . The lower lateral strut portion  133  extends between the junction formed between the lower angled strut  132   a  and the window strut  122  and the junction formed between the lower angled strut  132   a  and the window strut  124 . The lower lateral strut portion  133  can thereby increase the structural stability of the window struts  122 ,  124  at the lower ends. 
     The lateral strut portions  131 ,  133  are spaced in the axial direction of the frame  102 ′ and extend in the circumferential direction of the frame  102 ′. The upper opening  126  is enclosed by the window struts  122 ,  124 , the upper lateral strut portion  131 , and the crossbar  120 . The lower opening  128  is enclosed by the window struts  122 ,  124 , the lower lateral strut portion  133 , and the crossbar  120 . The resulting commissure window  114 ′ can be described as having an H-shape with closed ends, where the window struts  122 ,  124  and the crossbar  120  form the H-shape (as in the previously described commissure window  114 ) and the lateral strut portions  131 ,  133  form the closed ends. 
     The inner surface  131   a  of the upper lateral strut portion  131  that faces the upper opening  126  can be flat as shown, or it can be curved (e.g., concave) in other examples. The outer surface  131   b  of the upper lateral strut portion  131  that extends between the upper angled struts  131   a ,  131   b  can be curved. In some cases, the outer surface  131   b  may include a notch (e.g., a U-shaped notch), as shown, for example, at the ends of the struts  136 . The inner surface  133   a  of the lower lateral strut portion  133  that faces the opening  128  can be flat as shown, or it can be curved (e.g., concave) in other examples. The outer surface  133   b  of the lateral strut portion  133  that extends between the lower angled struts  132   a ,  132   b  can be curved. In some cases, the outer surface  133   b  may include a notch (e.g., U-shaped notch), as shown, for example, at the ends of the struts  136 . 
     An axial distance measured from the inner surface  131   a  of the upper lateral strut portion  131  to a midline of the crossbar  120  can be represented by the length L 1 . An axial distance measured from the inner surface  133   a  of the lower lateral strut portion  133  to the midline of the crossbar  120  can be represented by the length L 2 . The axial distance measured from the inner surface  131   a  of the upper lateral strut portion  131  to the inner surface  133   a  of the lower lateral strut portion  131  can be represented by the length L, which is the sum of the lengths L 1  and L 2 . The thickness of the crossbar  120  in the axial direction can be represented by the length L 3 . 
     The ratio L 1 /L 2  determines the axial position of the crossbar  120  relative to the window struts  112 ,  124  (or the relative to the lateral strut portions  131 ,  133 ). In one example, the ratio L 1 /L 2  can be greater than or equal to  1 . When L 1 /L 2  is equal to 1, the crossbar  120  is positioned at the midpoint of each window strut  122 ,  124  along the axial direction. When L 1 /L 2  is greater than 1, the upper opening  126  is taller than the lower opening  128 , and the crossbar  120  is positioned closer to the lower lateral strut portion  133  than to the upper lateral strut portion  131 . L 1 /L 2  greater than 1 may allow the commissure window  114 ′ to carry a higher load in the upper window portion. In one example, L 1 /L 2  can be in a range from 1 to 3. 
     The length of the upper opening  126  is L 1 −½L 3 . The length of the lower opening  128  is L 2 −½L 3 . The leaflets can experience greater stress along the upper opening  126  since the leaflet free edge (i.e., the edge of the leaflet that coapts with the free edges of the other leaflets to close the prosthetic valve and moves away from the free edges of the other leaflets to open the prosthetic valve) is attached to this opening. In some cases, a longer L 1  can help prevent tearing at the portion of the commissure formed in the upper opening  126 . In other cases, a longer L 1  can allow use of a high tab, which is a commissure tab that is slightly higher than the leaflet outflow. A high tab can allow better stress distribution at the top of the commissure. 
       FIG.  18    illustrates an example of a leaflet  210  with a relatively high commissure tab. The leaflet  210  can include a main, cusp edge portion  260 , two leaflet tabs  262  (or commissure tabs), and a leaflet free edge  258  (or coaptation edge). In the orientation of the drawing, the cusp edge portion  260  forms a lower edge portion of the leaflet  210 , and the leaflet free edge  258  forms an upper edge of the leaflet  210 . The leaflet tabs  262  project from opposite side edges of the leaflet  210 . In some cases, the leaflet tabs  262  can be symmetrical about a centerline  256  of the leaflet. Each of the tabs  262  can include an upper tab portion  264  and a lower tab portion  266  separated by a notch  268  (or slit). In one example, the height Z 1  of each upper tab portion  264  can be greater than the height Z 2  of the respective lower tab portion  266 . In one example, the upper tab portions  264  can extend slightly above the leaflet free edge  258  by a height Z 3 &gt;0. For example, height Z 3  can be in a range from 0.5 to 2 mm. 
     A leaflet assembly composed of a plurality of leaflets  210  (e.g., three leaflets  210 ) can be coupled to an annular frame using the commissure windows  114 ′ (shown in  FIGS.  17 A and  17 B ). The assembly can include extending the high upper tab portions  264  of adjacent leaflets  210  through the upper openings  126  of the commissure windows  114 ′ to form upper portions of the commissures and extending the lower tab portions  266  through the lower openings  128  of the commissure windows  114 ′ to form the lower portions of the commissures. The process of forming the commissures can be as previously described with respect to commissure window  114 . In the example where the upper tab portions  264  extend above the leaflet free edge  258 , as shown in  FIG.  18   , bumps will be formed at the entrance of the commissure windows  114 ′. These bumps can allow better stress distribution at the top of the commissures formed at the commissure windows  114 ′ by the leaflet tabs  262 . 
     Returning to  FIG.  17 B , the length L 3  (i.e., the thickness of the crossbar  120  in the axial direction) is normally significantly less than each of lengths L 1  and L 2 . At the same time, the length L 3  should be large enough to provide the crossbar  120  with sufficient strength to prevent the window struts  122 ,  124  from buckling too much under load. The length L 3  can be determined by analysis of the forces acting on the commissure window  114 ′ during transition of the frame  102 ′ from the crimped configuration to the fully expanded configuration. In one example, the length L 3  can have a minimum value of 0.2 mm. In another example, the length L 3  can have a minimum value of 0.4 mm. 
     The minimum thickness of the lateral strut portion  131  in the axial direction can be represented by the length L 4 , and the minimum thickness of the lateral strut portion  133  in the axial direction can be represented by the length L 5 . The lengths L 4  and L 5  can be the same or can be different, and each length L 4 , L 5  should be large enough to provide the respective lateral strut portion with sufficient strength to prevent the window struts  122 ,  124  from buckling too much under load. The lengths L 4  and L 5  can be determined by analysis of the forces acting on the commissure window  114 ′ during transition of the frame  102  from the crimped configuration to the fully expanded configuration. In one example, each of the lengths L 4  and L 5  can have a minimum value of 0.2 mm. In another example, each of the lengths L 4  and L 5  can have a minimum value of 0.4 mm. 
     The openings  124 ,  126  (or the gap between the window struts  122 ,  124 ) can have a width W 1 . The size of the width W 1  can be selected to accommodate two leaflet tabs, sutures, and/or fabric involved in forming commissures, while taking into account compression of the leaflet tabs. In one example, the width W 1  can be in a range from 0.5 to 1 mm. The width of the window struts  122 ,  124  can be represented by W 2 . The width W 2  is selected based on strength considerations. In one example, the width W 2  is selected such that the window struts  122 ,  124  do not bend during crimping/expansion and during cycling. The size of the width W 2  can be determined by force analysis (e.g., using finite element analysis) of the frame  102 ′ when the frame  102 ′ transitions between the crimped and fully expanded configurations and when the leaflets of the valvular structure attached to the frame are cycling between open and closed potions. In one example, the width W 2  can be in a range from 0.2 to 0.5 mm. 
     The crossbar  120  and the lateral strut portions  131 ,  133  can enable the commissure window  114 ′ to be elongated in form. Elongated commissure windows can accommodate longer leaflet tabs (the length being measured in the axial direction), which are useful in relieving stresses applied to the leaflets during the transition between the systolic and diastolic phases. The crossbar  120  divides the commissure window into sub-windows such that the window strut portions of each sub-window extend over a shorter length, allowing the sub-window to retain its structural integrity and resist bending/plastic deformation under load, such as when the prosthetic valve is crimped to a radially compressed state. The lateral strut portions  131 ,  133  affixed to the ends of the window struts  122 ,  124  advantageously increase the structural stability of the window struts  122 ,  124 . 
     The prosthetic valve  100  (shown in  FIG.  1   ) can be constructed by disposing the valvular structure  106  (shown in  FIG.  1   ) within the frame  102 ′ and installing commissures at the commissure windows  114 ′ to attach the leaflets of the valvular structure to the frame, as previously described and illustrated in  FIGS.  6 - 15   . The dimensions of the commissure window  114 ′ as defined by W 1 , W 2 , L 1 , L 2 , L 3 , L 4 , L 5  in  FIG.  17 B  can be tailored to avoid formation of convex or concave contours along the window struts  122 ,  124  when the frame  102 ′ is under load (such as during crimping of the prosthetic valve or during transition of the prosthetic valve from the crimped configuration to the fully expanded configuration or during cycling of the leaflets). The dimensions can be determined, for example, by modeling the forces acting on the window struts  122 ,  124  when the frame  102 ′ is under load. 
     In view of the above described implementations of the disclosed subject matter, this application discloses the additional examples enumerated below. It should be noted that one feature of an example in isolation or more than one feature of the example taken in combination and, optionally, in combination with one or more features of one or more further examples are further examples also falling within the disclosure of this application. 
     EXAMPLE 1 
     An assembly method for a prosthetic heart valve comprises (a) providing first and second leaflets for a valvular structure of the prosthetic heart valve, each leaflet having a pair of tabs, one of the tabs being on an opposite side from the other of the tabs with respect to a centerline of the leaflet, each tab having an upper tab portion and a lower tab portion separated from the upper tab portion along a direction parallel to the centerline by a gap; (b) disposing the upper and lower tab portions of a second tab of the pair of tabs of the second leaflet adjacent to the upper and lower tab portions of a first tab of the pair of tabs of the first leaflet, respectively; (c) stitching together the upper tab portions of the first and second leaflet tabs, and stitching together the lower tab portions of the first and second leaflet tabs; (d) folding the upper and lower tab portions of the first leaflet tab; (e) conveying the first and second leaflet tabs through a commissure window of an expandable annular frame of the prosthetic heart valve, the commissure window having upper and lower openings separated from each other along an axial direction of the annular frame by a crossbar, the conveying being along a radial direction of the annular frame from a radially inner-side of the commissure window to a radially-outer side of the commissure window and such that the upper tab portions are inserted through the upper opening and the lower tab portions are inserted through the lower opening; (f) inserting one or more wedge members between facing surfaces of the folded upper tab portion of the first leaflet tab and between facing surfaces of the folded lower tab portion of the first leaflet tab; (g) folding the upper tab portion of the second leaflet tab around the folded upper tab portion of the first leaflet tab, and folding the lower tab portion of the second leaflet tab around the folded lower tab portion of the first leaflet tab; and (h) after inserting the one or more wedge members as described in (f), stitching together the one or more wedge members and the upper tab portions of the first and second leaflet tabs, and stitching together the one or more wedge members and the lower tab portions of the first and second leaflet tabs. 
     EXAMPLE 2 
     An assembly method according to any example herein, particularly example 1, wherein the upper and lower openings of the commissure window are disposed to form an H-shape in side view; the H-shaped commissure window has a pair of struts that each extend along the axial direction of the annular frame; and the crossbar extends along a circumferential direction of the annular frame between the pair of struts. 
     EXAMPLE 3 
     An assembly method according to any example herein, particularly example 2, wherein the crossbar is offset from a midpoint of each strut along the axial direction. 
     EXAMPLE 4 
     An assembly method according to any example herein, particularly example 3, wherein each strut has a first end adjacent to the upper opening and a second end adjacent to the lower opening, a distance, L 1 , along the axial direction from the first end of each strut to a middle of the crossbar along the axial direction is less than a distance, L 2 , along the axial direction from the middle of the crossbar to the second end of each strut, and L 1 /L 2  is within a range of 0.25 to 0.35, inclusive. 
     EXAMPLE 5 
     An assembly method according to any example herein, particularly any of examples 1 to 4, wherein the stitching in (c) is by at least one first suture. 
     EXAMPLE 6 
     An assembly method according to any example herein, particularly example 5, wherein the at least one first suture is a single first suture that stitches together the upper tab portions of the first and second leaflet tabs and the lower tab portions of the first and second leaflet tabs. 
     EXAMPLE 7 
     An assembly method according to any example herein, particularly example 5, wherein the at least one first suture is a pair of first sutures, one of the pair of first sutures stitching together the upper tab portions of the first and second leaflet tabs, and the other of the pair of first sutures stitching together the lower tab portions of the first and second leaflet tabs. 
     EXAMPLE 8 
     An assembly method according to any example herein, particularly any of examples 1 to 7, wherein the stitching in (h) is by at least one second suture. 
     EXAMPLE 9 
     An assembly method according to any example herein, particularly example 8, wherein the at least one second suture is a single second suture that stitches together the one or more wedge members, the upper tab portions of the first and second leaflet tabs, and the lower tab portions of the first and second leaflet tabs. 
     EXAMPLE 10 
     An assembly method according to any example herein, particularly example 8, wherein the at least one second suture is a pair of second sutures, one of the pair of second sutures stitching together the one or more wedge members and the upper tab portions of the first and second leaflet tabs, and the other of the pair of second sutures stitching together the one or more wedge members and the lower tab portions of the first and second leaflet tabs. 
     EXAMPLE 11 
     An assembly method according to any example herein, particularly any of examples 1 to 10, wherein the upper tab portion of each leaflet tab has a first part that is adjacent to a free end of said upper tab portion and a second part that is between the first part and the centerline of the leaflet; and wherein the lower tab portion of each leaflet tab has a third part that is adjacent to a free end of said lower tab portion and a fourth part that is between the third part and the centerline of the leaflet. 
     EXAMPLE 12 
     An assembly method according to any example herein, particularly example 11, wherein the stitching in (c) comprises stitching the first part of the upper tab portion of the first leaflet tab to the second part of the upper tab portion of the second leaflet tab and stitching the third part of the lower tab portion of the first leaflet tab to the fourth part of the lower tab portion of the second leaflet tab; and wherein after the stitching in (c) and before the stitching in (h), the first part of the upper tab portion of the second leaflet tab, the second part of the upper tab portion of the first leaflet tab, the third part of the lower tab portion of the second leaflet tab, and the fourth part of the lower tab portion of the first leaflet tab are not stitched. 
     EXAMPLE 13 
     An assembly method according to any example herein, particularly any of examples 11 and 12, wherein after the folding in (g), the first part of the upper tab portion of the second leaflet tab contacts the second part of the upper tab portion of the first leaflet tab, and the third part of the lower tab portion of the second leaflet tab contacts the fourth part of the lower tab portion of the first leaflet tab. 
     EXAMPLE 14 
     An assembly method according to any example herein, particularly any of examples 11 to 13, wherein after the stitching in (h), the first part of the upper tab portion of the second leaflet tab, the second part of the upper tab portion of the first leaflet tab, the one or more wedge members, the first part of the upper tab portion of the first leaflet tab, and the second part of the upper tab portion of the second leaflet tab are disposed in order along the circumferential direction and stitched together. In addition, the third part of the lower tab portion of the second leaflet tab, the fourth part of the lower tab portion of the first leaflet tab, the one or more wedge members, the third part of the lower tab portion of the first leaflet tab, and the fourth part of the lower tab portion of the second leaflet tab are disposed in order along the circumferential direction and stitched together. 
     EXAMPLE 15 
     An assembly method according to any example herein, particularly any of examples 11 to 14, wherein after the folding in (g), the free ends of the upper tab portions of the first and second leaflet tabs and the free ends of the lower tab portions of the first and second leaflet tabs are disposed along the radial direction between the one or more wedge members and the radially-outer side of the commissure window. 
     EXAMPLE 16 
     An assembly method according to any example herein, particularly any of examples 11 to 15, wherein the folding in (d) is such that the second part of the upper tab portion of the first leaflet tab faces or is in contact with the first part of the upper tab portion of the first leaflet tab, and the fourth part of the lower tab portion of the first leaflet tab faces or is in contact with the third part of the lower tab portion of the first leaflet tab. 
     EXAMPLE 17 
     An assembly method according to any example herein, particularly any of examples 1 to 16, further comprises (i) providing a third leaflet for the valvular structure, the third leaflet also having a pair of tabs, one of the tabs being on an opposite side from the other of the tabs with respect to a centerline of the third leaflet, each tab having an upper tab portion and a lower tab portion separated from the upper tab portion along a direction parallel to the centerline by a gap; (j) disposing the upper and lower tab portions of a fourth tab of the pair of tabs of either the first leaflet or the second leaflet adjacent to the upper and lower tab portions of a third tab of the pair of tabs of the third leaflet, respectively; (k) stitching together the upper tab portions of the third and fourth tabs, and stitching together the lower tab portions of the third and fourth tabs; ( 1 ) folding the upper and lower tab portions of the third leaflet tab; (m) conveying the third and fourth tabs through a second commissure window of the annular frame, the second commissure window having second upper and second lower openings separated from each other along the axial direction by a second crossbar, the conveying being along the radial direction from a radially inner-side of the second commissure window to a radially-outer side of the second commissure window and such that the upper tab portions are inserted through the second upper opening and the lower tab portions are inserted through the second lower opening; (n) inserting one or more second wedge members between facing surfaces of the folded upper tab portion of the third tab and between facing surfaces of the folded lower tab portion of the third tab; (o) folding the upper tab portion of the fourth tab around the folded upper tab portion of the third tab, and folding the lower tab portion of the fourth tab around the folded lower tab portion of the third tab; and (p) after (n), stitching together the one or more second wedge members and the upper tab portions of the third and fourth tabs, and stitching together the one or more second wedge members and the lower tab portions of the third and fourth tabs. 
     EXAMPLE 18 
     An assembly method according to any example herein, particularly any of examples 1 to 17, wherein each wedge member comprises at least one of a braided suture, a braided cable, or a folded piece of cloth. 
     EXAMPLE 19 
     An assembly method according to any example herein, particularly any of examples 1 to 18, wherein each commissure window is an integral part of the expandable annular frame of the prosthetic heart valve. 
     EXAMPLE 20 
     An assembly method according to any example herein, particularly any of examples 1 to 18, wherein each commissure window is a part of a respective support member that forms a part of or is coupled to the expandable annular frame of the prosthetic heart valve. 
     EXAMPLE 21 
     An assembly method according to any example herein, particularly example 20, wherein the support member comprises a portion of an actuator or locking mechanism of the prosthetic heart valve, or is coupled to an actuator or locking mechanism of the prosthetic heart valve. 
     EXAMPLE 22 
     An assembly method according to any example herein, particularly any of examples 11 to 21, wherein one or more of the first through fourth parts includes one or more through-holes therein. 
     EXAMPLE 23 
     An assembly method according to any example herein, particularly example 22, wherein the stitching in (c) comprises passing one or more sutures through the through-holes of the first part of the upper tab portion of the first leaflet tab and of the second part of the upper tab portion of the second leaflet tab, and passing one or more sutures through the through-holes of the third part of the lower tab portion of the first leaflet tab and of the fourth part of the lower tab portion of the second leaflet tab. 
     EXAMPLE 24 
     An assembly method according to any example herein, particularly any of examples 22 and 23, wherein the stitching in (h) comprises passing one or more sutures through the through-holes of the first and second parts of the upper tab portion of the second leaflet tab, and passing one or more sutures through the through-holes of the third and fourth parts of the lower tab portion of the second leaflet tab. 
     EXAMPLE 25 
     An assembly method according to any example herein, particularly any of examples 1 to 24, wherein the one or more wedge members comprises a single continuous wedge member. 
     EXAMPLE 26 
     An assembly method according to any example herein, particularly any of examples 1 to 24, wherein the one or more wedge members comprises separate first and second wedge members, the first wedge member being inserted with respect to the upper tab portion of the first leaflet tab, the second wedge member being inserted with respect to the lower tab portion of the first leaflet tab. 
     EXAMPLE 27 
     An assembly method according to any example herein, particularly any of examples 1 to 26, wherein the conveying of (e) is performed prior to the disposing of (b) or (c), and/or wherein the folding of (g) is performed prior to the inserting of (f). 
     EXAMPLE 28 
     An assembly method for a prosthetic heart valve comprises (a) providing first and second leaflets for a valvular structure of the prosthetic heart valve, each leaflet having a pair of tabs, one of the tabs being on an opposite side from the other of the tabs with respect to a centerline of the leaflet, each tab having an upper tab portion and a lower tab portion separated from the upper tab portion along a direction parallel to the centerline by a gap; (b) disposing the upper tab portion of a first tab of the pair of tabs of the first leaflet to surround at least a portion of a circumference of a first wedge member, and disposing the lower tab portion of the first leaflet tab to surround at least a portion of a circumference of a second wedge member; (c) stitching together the first wedge member and at least the upper tab portion of the first leaflet tab, and stitching together the second wedge member and at least the lower tab portion of the first leaflet tab; (d) conveying the first wedge member, the second wedge member, and the first leaflet tab through a commissure window of an expandable annular frame of the prosthetic heart valve, the commissure window having upper and lower openings separated from each other along an axial direction of the annular frame by a crossbar, the conveying being along a radial direction of the annular frame from a radially inner-side of the commissure window to a radially-outer side of the commissure window, and such that the upper tab portion of the first leaflet tab and the first wedge member are inserted through the upper opening and the lower tab portion of the first leaflet tab and the second wedge member are inserted through the lower opening; (e) conveying a second tab of the pair of tabs of the second leaflet through the commissure window, the conveying being along the radial direction from the radially inner-side of the commissure window to the radially-outer side of the commissure window and such that the upper tab portion of the second leaflet tab is inserted through the upper opening and the lower tab portion of the second leaflet tab is inserted through the lower opening; ( 0  folding the upper tab portion of the second leaflet tab around the upper tab portion of the first leaflet tab, and folding the lower tab portion of the second leaflet tab around the lower tab portion of the first leaflet tab; and (g) after (f), stitching together the first wedge member, and the upper tab portions of the first and second leaflet tabs, and stitching together the second wedge member and the lower tab portions of the first and second leaflet tabs. 
     EXAMPLE 29 
     An assembly method according to any example herein, particularly example 28, wherein the upper tab portion of each leaflet tab has a first part that is adjacent to a free end of said upper tab portion and a second part that is between the first part and the centerline of the leaflet; and wherein the lower tab portion of each leaflet tab has a third part that is adjacent to a free end of said lower tab portion and a fourth part that is between the third part and the centerline of the leaflet. 
     EXAMPLE 30 
     An assembly method according to any example herein, particularly example 29, wherein, after the folding in (f), the first part of the upper tab portion of the second leaflet tab contacts the second part of the upper tab portion of the first leaflet tab, and the third part of the lower tab portion of the second leaflet tab contacts the fourth part of the lower tab portion of the first leaflet tab. 
     EXAMPLE 31 
     An assembly method according to any example herein, particularly any of examples 29 and 30, wherein the stitching in (c) comprises stitching together the first part of the upper tab portion of the first leaflet tab, the first wedge member, and the second part of the upper tab portion of the first leaflet tab; and wherein stitching together the third part of the lower tab portion of the first leaflet tab, the second wedge member, and the fourth part of the lower tab portion of the first leaflet tab. 
     EXAMPLE 32 
     An assembly method according to any example herein, particularly any of examples 29 and 30, further comprises prior to the stitching of (c), disposing the upper and lower tab portions of a second tab of the pair of tabs of the second leaflet adjacent to the upper and lower tab portions of the first leaflet tab, respectively. In the stitching of (c), the first wedge member and the upper tab portions of the first and second leaflet tabs are stitched together, and the second wedge member and the lower tab portions of the first and second leaflet tabs are stitched together. The conveying of (e) is performed simultaneously with the conveying of (d). 
     EXAMPLE 33 
     An assembly method according to any example herein, particularly example 32, wherein the stitching in (c) comprises stitching together the first part of the upper tab portion of the first leaflet tab, the first wedge member, the second part of the upper tab portion of the first leaflet tab, and the second part of the upper tab portion of the second leaflet tab. The stitching in (c) further comprises stitching together the third part of the lower tab portion of the first leaflet tab, the second wedge member, the fourth part of the lower tab portion of the first leaflet tab, and the fourth part of the lower tab portion of the second leaflet tab 
     EXAMPLE 34 
     An assembly method according to any example herein, particularly of any of examples 28 to 33, wherein after the stitching of (c) and before the stitching of (g), at least the first part of the upper tab portion of the second leaflet tab and the third part of the lower tab portion of the second leaflet tab are not stitched. 
     EXAMPLE 35 
     An assembly method according to any example herein, particularly example 28, wherein the stitching of (c) is performed after the conveying of (d) or prior to the disposing of (b). 
     EXAMPLE 36 
     An assembly method according to any example herein, particularly any of examples 28 to 35, wherein in the conveying of (d), a dimension along the circumferential direction of a combination of the first wedge member and the upper tab portion of the first leaflet tab is less than a width along the circumferential direction of the upper opening of the commissure window; and wherein after the folding of (f), a dimension along the circumferential direction of a combination of the first wedge member and the upper tab portions of the first and second leaflet tabs is greater than the width along the circumferential direction of the upper opening. 
     EXAMPLE 37 
     An assembly method according to any example herein, particularly any of examples 28 to 36, wherein in the conveying of (d), a dimension along the circumferential direction of a combination of the second wedge member and the lower tab portion of the first leaflet tab is less than a width along the circumferential direction of the lower opening of the commissure window; and wherein after the folding of (f), a dimension along the circumferential direction of a combination of the second wedge member and the lower tab portions of the first and second leaflet tabs is greater than the width along the circumferential direction of the lower opening. 
     EXAMPLE 38 
     An assembly method according to any example herein, particularly any of examples 28 to 37, wherein the disposing the upper tab portion of (b) comprises folding the upper tab portion of the first leaflet tab inserting the first wedge member between facing surfaces of the folded upper tab portion of the first leaflet tab; and/or wherein the disposing the lower tab portion of (b) comprises folding the lower tab portion of the first leaflet tab and inserting the second wedge member between facing surfaces of the folded lower tab portion of the first leaflet tab. 
     EXAMPLE 39 
     An assembly method according to any example herein, particularly any of examples 28 to 38, wherein the disposing the upper tab portion of (b) comprises wrapping the upper tab portion of the first leaflet tab around the first wedge member, and/or the disposing the lower tab portion of (b) comprises wrapping the lower tab portion of the first leaflet tab around the second wedge member. 
     EXAMPLE 40 
     An assembly method according to any example herein, particularly any of examples 28 to 39, wherein the upper and lower openings of the commissure window are disposed to form an H-shape in side view, the H-shaped commissure window has a pair of struts that each extend along the axial direction of the annular frame, and the crossbar extends along a circumferential direction of the annular frame between the pair of struts. 
     EXAMPLE 41 
     An assembly method according to any example herein, particularly example 40, wherein the crossbar is offset from a midpoint of each strut along the axial direction. 
     EXAMPLE 42 
     An assembly method according to any example herein, particularly example 41, wherein each strut has a first end adjacent to the upper opening and a second end adjacent to the lower opening, a distance, L 1 , along the axial direction from the first end of each strut to a middle of the crossbar along the axial direction is less than a distance, L 2 , along the axial direction from the middle of the crossbar to the second end of each strut, and L 1 /L 2  is within a range of 0.25 to 0.35, inclusive. 
     EXAMPLE 43 
     An assembly method according to any example herein, particularly any of examples 28 to 42, wherein in the folding of (d), the stitching together the first wedge member and the upper tab portions is by at least one first suture, and the stitching together the second wedge member and the lower tab portions is by at least one second suture. 
     EXAMPLE 44 
     An assembly method according to any example herein, particularly any of examples 28-43, wherein, in (d), the stitching together the first wedge member and the upper tab portions and the stitching together the second wedge member and the lower tab portions is by a single suture. 
     EXAMPLE 45 
     An assembly method according to any example herein, particularly any of examples 28-44, wherein, after the stitching of (g): the first part of the upper tab portion of the second leaflet tab, the second part of the upper tab portion of the first leaflet tab, the first wedge member, the first part of the upper tab portion of the first leaflet tab, and the second part of the upper tab portion of the second leaflet tab are disposed in order along the circumferential direction and stitched together; and/or the third part of the lower tab portion of the second leaflet tab, the fourth part of the lower tab portion of the first leaflet tab, the second wedge member, the third part of the lower tab portion of the first leaflet tab, and the fourth part of the lower tab portion of the second leaflet tab are disposed in order along the circumferential direction and stitched together. 
     EXAMPLE 46 
     An assembly method according to any example herein, particularly any of examples 28-45, wherein, after the folding of (f): the free ends of the upper tab portions of the first and second leaflet are disposed along the radial direction between the first wedge member and the radially-outer side of the commissure window; and/or the free ends of the lower tab portions of the first and second leaflet tabs are disposed along the radial direction between the second wedge member and the radially-outer side of the commissure window. 
     EXAMPLE 47 
     An assembly method according to any example herein, particularly any of examples 28-46, further comprising: (h) providing a third leaflet for the valvular structure, the third leaflet also having a pair of tabs, one of the tabs being on an opposite side from the other of the tabs with respect to a centerline of the third leaflet, each tab having an upper tab portion and a lower tab portion separated from the upper tab portion along a direction parallel to the centerline by a gap; (i) disposing the upper tab portion of a third tab of the pair of tabs of the third leaflet to surround at least a portion of a circumference of a third wedge member, and disposing the lower tab portion of the third leaflet tab to surround at least a portion of a circumference of a fourth wedge member; (j) stitching together the third wedge member and at least the upper tab portion of the third leaflet tab, and stitching together the fourth wedge member and at least the lower tab portion of the third leaflet tab; (k) conveying the third wedge member, the fourth wedge member, and the third leaflet tab through a second commissure window of the annular frame, the second commissure window having second upper and second lower openings separated from each other along the axial direction by a second crossbar, the conveying being along the radial direction from a radially inner-side of the second commissure window to a radially-outer side of the second commissure window, and such that the upper tab portion of the third leaflet tab and the third wedge member are inserted through the second upper opening and the lower tab portion of the third leaflet tab and the fourth wedge member are inserted through the second lower opening; (l) conveying a fourth tab of the pair of tabs of either the first leaflet or the second leaflet through the second commissure window, the conveying being along the radial direction from the radially inner-side of the second commissure window to the radially-outer side of the second commissure window and such that the upper tab portion of the fourth tab is inserted through the upper opening and the lower tab portion of the fourth tab is inserted through the lower opening; (m) folding the upper tab portion of the fourth tab around the upper tab portion of the third leaflet tab, and folding the lower tab portion of the fourth tab around the lower tab portion of the third leaflet tab; and (n) after (m), stitching together the third wedge member, and the upper tab portions of the third and fourth tabs, and stitching together the fourth wedge member and the lower tab portions of the third and fourth tabs. 
     EXAMPLE 48 
     An assembly method according to any example herein, particularly any of examples 28-47, wherein each wedge member comprises at least one of a braided suture, a braided cable, or a folded piece of cloth. 
     EXAMPLE 49 
     An assembly method according to any example herein, particularly any of examples 28-48, wherein each commissure window is an integral part of the expandable annular frame of the prosthetic heart valve. 
     EXAMPLE 50 
     An assembly method according to any example herein, particularly any of examples 28-48, wherein each commissure window is a part of a respective support member that forms a part of or is coupled to the expandable annular frame of the prosthetic heart valve. 
     EXAMPLE 51 
     An assembly method according to any example herein, particularly example 50, wherein the support member comprises a portion of an actuator or locking mechanism of the prosthetic heart valve, or is coupled to an actuator or locking mechanism of the prosthetic heart valve. 
     EXAMPLE 52 
     An assembly method according to any example herein, particularly any of examples 29-51, wherein one or more of the first through fourth parts includes one or more through-holes therein. 
     EXAMPLE 53 
     An assembly method according to any example herein, particularly example 52, wherein the stitching in (c) comprises passing one or more sutures through the through-holes of the second part of the upper tab portion of the first leaflet tab and of the second part of the upper tab portion of the first leaflet tab, and passing one or more sutures through the through-holes of the fourth part of the lower tab portion of the first leaflet tab and of the fourth part of the lower tab portion of the second leaflet tab. 
     EXAMPLE 54 
     An assembly method according to any example herein, particularly any of examples 52-53, wherein the stitching in (g) comprises passing one or more sutures through the through-holes of the first and second parts of the upper tab portion of the second leaflet tab, and passing one or more sutures through the through-holes of the third and fourth parts of the lower tab portion of the second leaflet tab. 
     EXAMPLE 55 
     An assembly method for a prosthetic heart valve comprises: (a) providing first and second leaflets for a valvular structure of the prosthetic heart valve, each leaflet having a pair of tabs, one of the tabs being on an opposite side from the other of the tabs with respect to a centerline of the leaflet, each tab having an upper tab portion and a lower tab portion separated from the upper tab portion along a direction parallel to the centerline by a gap; (b) conveying a first tab of the pair of tabs of the first leaflet through a commissure window of an expandable annular frame of the prosthetic heart valve, and conveying a second tab of the pair of tabs of the second leaflet through the commissure window, the commissure window having upper and lower openings separated from each other along an axial direction of the annular frame by a crossbar, the conveying being along a radial direction of the annular frame from a radially inner-side of the commissure window to a radially-outer side of the commissure window and such that the upper tab portions are inserted through the upper opening and the lower tab portions are inserted through the lower opening; (c) after (b), disposing the upper and lower tab portions of the first leaflet tab to surround at least a portion of a circumference of one or more wedge members; (d) folding the upper tab portion of the second leaflet tab around the upper tab portion of the first leaflet tab, and folding the lower tab portion of the second leaflet tab around the lower tab portion of the first leaflet tab; and (e) stitching together the one or more wedge members and the upper tab portions of the first and second leaflet tabs, and stitching together the one or more wedge members and the lower tab portions of the first and second leaflet tabs. 
     EXAMPLE 56 
     An assembly method according to any example herein, particularly example 55, wherein: the upper tab portion of each leaflet tab has a first part that is adjacent to a free end of said upper tab portion and a second part that is between the first part and the centerline of the leaflet, and the lower tab portion of each leaflet tab has a third part that is adjacent to a free end of said lower tab portion and a fourth part that is between the third part and the centerline of the leaflet. 
     EXAMPLE 57 
     An assembly method according to any example herein, particularly any of examples 55-56, further comprises: after (c) and prior to (d), stitching together the one or more wedge members and the upper tab portions of the first leaflet tab, and stitching together one or more wedge members and the lower tab portions of the first leaflet tab. 
     EXAMPLE 58 
     An assembly method according to any example herein, particularly example 57, wherein: the stitching together the one or more wedge members and the upper tab portions of the first leaflet tab comprises stitching together the first part of the upper tab portion of the first leaflet tab, the one or more wedge members, and the second part of the upper tab portion of the first leaflet tab; and the stitching together one or more wedge members and the lower tab portions of the first leaflet tab comprises stitching together the third part of the lower tab portion of the first leaflet tab, the one or more wedge members, and the fourth part of the lower tab portion of the first leaflet tab. 
     EXAMPLE 59 
     An assembly method according to any example herein, particularly any of examples 55-58, wherein in (b), the conveying the second leaflet tab through the commissure window occurs simultaneously with the conveying the first leaflet tab through the commissure window. 
     EXAMPLE 60 
     An assembly method according to any example herein, particularly any of examples 55-58, wherein in (b), the conveying the second leaflet tab through the commissure window occurs before or after the conveying the first leaflet tab through the commissure window. 
     EXAMPLE 61 
     An assembly method according to any example herein, particularly any of examples 55-60, wherein, after (d): the first part of the upper tab portion of the second leaflet tab contacts the second part of the upper tab portion of the first leaflet tab, the second part of the upper tab portion of the second leaflet tab contacts the first part of the upper tab portion of the first leaflet tab, the third part of the lower tab portion of the second leaflet tab contacts the fourth part of the lower tab portion of the first leaflet tab, and the fourth part of the lower tab portion of the second leaflet tab contacts the third part of the lower tab portion of the first leaflet tab. 
     EXAMPLE 62 
     An assembly method according to any example herein, particularly example 55, wherein the folding of (d) occurs prior to the disposing of (c). 
     EXAMPLE 63 
     An assembly method according to any example herein, particularly any of examples 55-62, wherein prior to (e), the upper and lower tab portions of the second leaflet tab are not stitched. 
     EXAMPLE 64 
     An assembly method according to any example herein, particularly any of examples 55-63, wherein, after (d): a dimension along the circumferential direction of a combination of the one or more wedge members and the upper tab portions of the first and second leaflet tabs is greater than a width along the circumferential direction of the upper opening, and/or a dimension along the circumferential direction of a combination of the one or more wedge members and the lower tab portions of the first and second leaflet tabs is greater than the width along the circumferential direction of the lower opening. 
     EXAMPLE 65 
     An assembly method according to any example herein, particularly any of examples 55-64, wherein the disposing the upper tab portion of (c) comprises: folding the upper tab portion of the first leaflet tab; and inserting the one or more wedge members between facing surfaces of the folded upper tab portion of the first leaflet tab; and/or wherein the disposing the lower tab portion of (c) comprises: folding the lower tab portion of the first leaflet tab; and inserting the one or more wedge members between facing surfaces of the folded lower tab portion of the first leaflet tab. 
     EXAMPLE 66 
     An assembly method according to any example herein, particularly any of examples 55-65, wherein: the disposing the upper tab portion of (c) comprises wrapping the upper tab portion of the first leaflet tab around the one or more wedge members, and/or the disposing the lower tab portion of (c) comprises wrapping the lower tab portion of the first leaflet tab around the one or more wedge members. 
     EXAMPLE 67 
     An assembly method according to any example herein, particularly any of examples 55-66, wherein the one or more wedge members comprises a single continuous wedge member. 
     EXAMPLE 68 
     An assembly method according to any example herein, particularly any of examples 55-66, wherein the one or more wedge members comprises separate first and second wedge members, the upper tab portion of the first leaflet tab being disposed around the first wedge member, the lower tab portion of the first leaflet tab being disposed around the second wedge member. 
     EXAMPLE 69 
     An assembly method according to any example herein, particularly any of examples 55-68, wherein: the upper and lower openings of the commissure window are disposed to form an H-shape in side view, the H-shaped commissure window has a pair of struts that each extend along the axial direction of the annular frame, and the crossbar extends along a circumferential direction of the annular frame between the pair of struts. 
     EXAMPLE 70 
     An assembly method according to any example herein, particularly example 69, wherein the crossbar is offset from a midpoint of each strut along the axial direction. 
     EXAMPLE 71 
     An assembly method according to any example herein, particularly example 70, wherein: each strut has a first end adjacent to the upper opening and a second end adjacent to the lower opening, a distance, L 1 , along the axial direction from the first end of each strut to a middle of the crossbar along the axial direction is less than a distance, L 2 , along the axial direction from the middle of the crossbar to the second end of each strut, and L 1 /L 2  is within a range of 0.25 to 0.35, inclusive. 
     EXAMPLE 72 
     An assembly method according to any example herein, particularly any of examples 55-71, wherein the stitching in (e) is by at least one first suture. 
     EXAMPLE 73 
     An assembly method according to any example herein, particularly example 72, wherein the at least one first suture is a single first suture that stitches together the one or more wedge members, the upper tab portions of the first and second leaflet tabs, and the lower tab portions of the first and second leaflet tabs. 
     EXAMPLE 74 
     An assembly method according to any example herein, particularly example 72, wherein the at least one first suture is a pair of first sutures, one of the pair of first sutures stitching together the one or more wedge members and the upper tab portions of the first and second leaflet tabs, and the other of the pair of first sutures stitching together the one or more wedge members and the lower tab portions of the first and second leaflet tabs. 
     EXAMPLE 75 
     An assembly method according to any example herein, particularly any of examples 56-74, wherein, after (d): the free ends of the upper tab portions of the first and second leaflet are disposed along the radial direction between the one or more wedge members and the radially-outer side of the commissure window; and/or the free ends of the lower tab portions of the first and second leaflet tabs are disposed along the radial direction between the one or more wedge members and the radially-outer side of the commissure window. 
     EXAMPLE 76 
     An assembly method according to any example herein, particularly any of examples 55-75, further comprises: (f) providing a third leaflet for the valvular structure, the third leaflet also having a pair of tabs, one of the tabs being on an opposite side from the other of the tabs with respect to a centerline of the third leaflet, each tab having an upper tab portion and a lower tab portion separated from the upper tab portion along a direction parallel to the centerline by a gap; (g) conveying the third leaflet tab through a second commissure window of the annular frame, and conveying a fourth tab of the pair of tabs of either the first leaflet or the second leaflet through the second commissure window, the second commissure window having second upper and second lower openings separated from each other along the axial direction by a second crossbar, the conveying being along the radial direction from a radially inner-side of the second commissure window to a radially-outer side of the second commissure window and such that the upper tab portions are inserted through the second upper opening and the lower tab portions are inserted through the second lower opening; (h) after (g), disposing the upper and lower tab portions of the third tab to surround at least a portion of a circumference of one or more second wedge members; (i) folding the upper tab portion of the fourth tab around the upper tab portion of the third tab, and folding the lower tab portion of the fourth tab around the folded lower tab portion of the third tab; and (j) after (i), stitching together the one or more second wedge members and the upper tab portions of the third and fourth tabs, and stitching together the one or more second wedge members and the lower tab portions of the third and fourth tabs. 
     EXAMPLE 77 
     An assembly method according to any example herein, particularly any of examples 55-76, wherein each wedge member comprises at least one of a braided suture, a braided cable, or a folded piece of cloth. 
     EXAMPLE 78 
     An assembly method according to any example herein, particularly any of examples 55-77, wherein each commissure window is an integral part of the expandable annular frame of the prosthetic heart valve. 
     EXAMPLE 79 
     An assembly method according to any example herein, particularly any of examples 55-77, wherein each commissure window is a part of a respective support member that forms a part of or is coupled to the expandable annular frame of the prosthetic heart valve. 
     EXAMPLE 80 
     An assembly method according to any example herein, particularly example 79, wherein the support member comprises a portion of an actuator or locking mechanism of the prosthetic heart valve, or is coupled to an actuator or locking mechanism of the prosthetic heart valve. 
     EXAMPLE 81 
     An assembly method according to any example herein, particularly any of examples 56-79, wherein one or more of the first through fourth parts includes one or more through-holes therein. 
     EXAMPLE 82 
     An assembly method according to any example herein, particularly example 81, wherein the stitching in (e) comprises passing one or more sutures through the through-holes of the first part of the upper tab portion of the second leaflet tab and of the second part of the upper tab portion of the second leaflet tab, and passing one or more sutures through the through-holes of the third part of the lower tab portion of the second leaflet tab and of the fourth part of the lower tab portion of the second leaflet tab. 
     EXAMPLE 83 
     An assembly method for a prosthetic heart valve comprises: (a) providing first and second leaflets for a valvular structure of the prosthetic heart valve, each leaflet having a pair of tabs, one of the tabs being on an opposite side from the other of the tabs with respect to a centerline of the leaflet, each tab having an upper tab portion and a lower tab portion separated from the upper tab portion along a direction parallel to the centerline by a gap; (b) disposing the upper tab portion of a first tab of the pair of tabs of the first leaflet to surround at least a portion of a circumference of a first wedge member; (c) stitching together the first wedge member and at least the upper tab portion of the first leaflet tab; (d) conveying a lower tab portion of the first leaflet tab through a commissure window of an expandable annular frame of the prosthetic heart valve, the commissure window having upper and lower openings separated from each other along an axial direction of the annular frame by a crossbar, the conveying being along a radial direction of the annular frame from a radially-inner side of the commissure window to a radially-outer side of the commissure window and such that the lower tab portion of the first leaflet tab extends through the lower opening; (e) conveying the first wedge member and the upper tab portion of the first leaflet tab from the radially-inner side of the commissure window through or over the upper opening of the commissure window to the radially-outer side of the commissure window, such that the upper tab portion of the first leaflet tab extends through the upper opening; (f) folding the lower tab portion of the first leaflet tab around the first wedge member; (g) conveying a second tab of the pair of tabs of the second leaflet through the commissure window, the conveying being along the radial direction from the radially inner-side of the commissure window to the radially-outer side of the commissure window and such that the upper tab portion of the second leaflet tab is inserted through the upper opening and the lower tab portion of the second leaflet tab is inserted through the lower opening; (h) folding the upper tab portion of the second leaflet tab around the upper tab portion of the first leaflet tab, and folding the lower tab portion of the second leaflet tab around the lower tab portion of the first leaflet tab; and (i) after (h), stitching together the first wedge member and the upper and lower tab portions of the first and second leaflet tabs. 
     EXAMPLE 84 
     An assembly method according to any example herein, particularly example 83, wherein: the upper tab portion of each leaflet tab has a first part that is adjacent to a free end of said upper tab portion and a second part that is between the first part and the centerline of the leaflet, and the lower tab portion of each leaflet tab has a third part that is adjacent to a free end of said lower tab portion and a fourth part that is between the third part and the centerline of the leaflet. 
     EXAMPLE 85 
     An assembly method according to any example herein, particularly any of examples 83-84, further comprises: after (f) and prior to (h), stitching together the first wedge member and the lower tab portion of the first leaflet tab. 
     EXAMPLE 86 
     An assembly method according to any example herein, particularly any of examples 83-85, wherein, in (c), the first wedge member, the upper tab portion of the first leaflet tab, and the upper portion of the second leaflet tab are stitched together, and the conveying of (g) is performed together with the conveying of (d) and/or (e). 
     EXAMPLE 87 
     An assembly method according to any example herein, particularly any of examples 83-85, wherein the conveying of (g) is performed before or with the conveying of (d) and/or (e). 
     EXAMPLE 88 
     An assembly method according to any example herein, particularly any of examples 83-87, wherein the conveying of (e) is performed before or with the conveying of (d). 
     EXAMPLE 89 
     An assembly method according to any example herein, particularly any of examples 83-88, wherein the folding of (f) is performed together with the folding of (h). 
     EXAMPLE 90 
     An assembly method according to any example herein, particularly any of examples 84-89, wherein, after (h): the first part of the upper tab portion of the second leaflet tab contacts the second part of the upper tab portion of the first leaflet tab, the second part of the upper tab portion of the second leaflet tab contacts the first part of the upper tab portion of the first leaflet tab, the third part of the lower tab portion of the second leaflet tab contacts the fourth part of the lower tab portion of the first leaflet tab, and the fourth part of the lower tab portion of the second leaflet tab contacts the third part of the lower tab portion of the first leaflet tab. 
     EXAMPLE 91 
     An assembly method according to any example herein, particularly any of examples 83-90, wherein, after (h): a dimension along the circumferential direction of a combination of the first wedge member and the upper tab portions of the first and second leaflet tabs is greater than a width along the circumferential direction of the upper opening, and/or a dimension along the circumferential direction of a combination of the first wedge member and the lower tab portions of the first and second leaflet tabs is greater than the width along the circumferential direction of the lower opening. 
     EXAMPLE 92 
     An assembly method according to any example herein, particularly any of examples 83-91, wherein the disposing the upper tab portion of (b) comprises: folding the upper tab portion of the first leaflet tab, and inserting the first wedge member between facing surfaces of the folded upper tab portion of the first leaflet tab; or wrapping the upper tab portion of the first leaflet tab around the one or more wedge members. 
     EXAMPLE 93 
     An assembly method according to any example herein, particularly any of examples 83-92, wherein: the upper and lower openings of the commissure window are disposed to form an H-shape in side view, the H-shaped commissure window has a pair of struts that each extend along the axial direction of the annular frame, and the crossbar extends along a circumferential direction of the annular frame between the pair of struts. 
     EXAMPLE 94 
     An assembly method according to any example herein, particularly example 93, wherein the crossbar is offset from a midpoint of each strut along the axial direction. 
     EXAMPLE 95 
     An assembly method according to any example herein, particularly example 94, wherein: each strut has a first end adjacent to the upper opening and a second end adjacent to the lower opening, a distance, L 1 , along the axial direction from the first end of each strut to a middle of the crossbar along the axial direction is less than a distance, L 2 , along the axial direction from the middle of the crossbar to the second end of each strut, and L 1 /L 2  is within a range of 0.25 to 0.35, inclusive. 
     EXAMPLE 96 
     An assembly method according to any example herein, particularly any of examples 83-95, wherein the stitching in (i) is by at least one first suture. 
     EXAMPLE 97 
     An assembly method according to any example herein, particularly example 96, wherein the at least one first suture is a single first suture that stitches together the first wedge member, the upper tab portions of the first and second leaflet tabs, and the lower tab portions of the first and second leaflet tabs. 
     EXAMPLE 98 
     The method of claim 96, wherein the at least one first suture is a pair of first sutures, one of the pair of first sutures stitching together the first wedge member and the upper tab portions of the first and second leaflet tabs, and the other of the pair of first sutures stitching together the first wedge member and the lower tab portions of the first and second leaflet tabs. 
     EXAMPLE 99 
     An assembly method according to any example herein, particularly any of examples 84-98, wherein, after (h): the free ends of the upper tab portions of the first and second leaflet are disposed along the radial direction between the first wedge member and the radially-outer side of the commissure window; and the free ends of the lower tab portions of the first and second leaflet tabs are disposed along the radial direction between the first wedge member and the radially-outer side of the commissure window. 
     EXAMPLE 100 
     An assembly method according to any example herein, particularly any of examples 83-99, further comprising: (j) providing a third leaflet for the valvular structure, the third leaflet also having a pair of tabs, one of the tabs being on an opposite side from the other of the tabs with respect to a centerline of the third leaflet, each tab having an upper tab portion and a lower tab portion separated from the upper tab portion along a direction parallel to the centerline by a gap; (k) disposing the upper tab portion of a third tab of the pair of tabs of the third leaflet to surround at least a portion of a circumference of a second wedge member; (l) stitching together the third wedge member and at least the upper tab portion of the third tab; (m) conveying a lower tab portion of the third tab through a second commissure window of the annular frame, the second commissure window having second upper and second lower openings separated from each other along the axial direction by a second crossbar, the conveying being along the radial direction from a radially inner-side of the second commissure window to a radially-outer side of the second commissure window and such that the lower tab portion of the third tab extends through the second lower opening; (n) conveying the second wedge member and the upper tab portion of the third tab from the radially-inner side of the second commissure window through or over the upper opening of the second commissure window to the radially-outer side of the second commissure window, such that the upper tab portion of the third tab extends through the second upper opening; (o) folding the lower tab portion of the third tab around the second wedge member; (p) conveying a fourth tab of the pair of tabs of either the first leaflet or the second leaflet through the second commissure window, the conveying being along the radial direction from the radially inner-side of the second commissure window to the radially-outer side of the second commissure window and such that the upper tab portion of the fourth tab is inserted through the upper opening and the lower tab portion of the fourth tab is inserted through the lower opening; (q) folding the upper tab portion of the fourth tab around the upper tab portion of the third tab, and folding the lower tab portion of the fourth tab around the folded lower tab portion of the third tab; and (r) after (q), stitching together the second wedge member and the upper and lower tab portions of the third and fourth tabs. 
     EXAMPLE 101 
     An assembly method according to any example herein, particularly any of examples 83-100, wherein each wedge member comprises at least one of a braided suture, a braided cable, or a folded piece of cloth. 
     EXAMPLE 102 
     An assembly method according to any example herein, particularly any of examples 83-101, wherein each commissure window is an integral part of the expandable annular frame of the prosthetic heart valve. 
     EXAMPLE 103 
     An assembly method according to any example herein, particularly any of examples 83-101, wherein each commissure window is a part of a respective support member that forms a part of or is coupled to the expandable annular frame of the prosthetic heart valve. 
     EXAMPLE 104 
     An assembly method according to any example herein, particularly example 103, wherein the support member comprises a portion of an actuator or locking mechanism of the prosthetic heart valve, or is coupled to an actuator or locking mechanism of the prosthetic heart valve. 
     EXAMPLE 105 
     An assembly method according to any example herein, particularly any of examples 83-104, wherein one or more of the first through fourth parts includes one or more through-holes therein. 
     EXAMPLE 106 
     An assembly method according to any example herein, particularly example 105, wherein the stitching in (h) comprises passing one or more sutures through the through-holes of the first part of the upper tab portion of the second leaflet tab and of the second part of the upper tab portion of the second leaflet tab, and passing one or more sutures through the through-holes of the third part of the lower tab portion of the second leaflet tab and of the fourth part of the lower tab portion of the second leaflet tab. 
     EXAMPLE 107 
     A prosthetic heart valve comprises: an expandable annular frame having a plurality of commissure windows; and a valvular structure coupled to the commissure windows. The valvular structure comprises a plurality of leaflets. The tabs of adjacent leaflets are coupled to a respective one of the commissure windows according to the assembly method of any of examples 1-106. 
     EXAMPLE 108 
     A prosthetic heart valve comprises: an expandable annular frame having a plurality of commissure windows; and a valvular structure comprising a plurality of leaflets, each leaflet having a pair of tabs, one of the tabs being on an opposite side from the other of the tabs with respect to a centerline of the leaflet, each tab having an upper tab portion and a lower tab portion separated from the upper tab portion along a direction parallel to the centerline by a gap. The valvular structure has a plurality of commissures formed by paired tabs of adjacent leaflets. Each commissure is coupled to a corresponding one of the commissure windows to support the valvular structure within the annular frame. Each commissure window has upper and lower openings separated from each other along an axial direction of the annular frame by a respective crossbar. The upper and lower tab portions for each tab extend through the upper and lower openings, respectively, to a radially-outer side of the respective commissure window. The annular frame is expandable between a crimped state having a first diameter and an expanded state having a second diameter greater than the first diameter. 
     EXAMPLE 109 
     The prosthetic heart valve of any example herein, particularly example 108, further comprises a plurality of wedge members corresponding to the plurality of commissures. Each wedge member is disposed on the radially-outer side of the respective commissure window, with the tabs of the corresponding commissure wrapping around the wedge member. 
     EXAMPLE 110 
     The prosthetic heart valve of any example herein, particularly example 109, wherein each wedge member is coupled to one or more of the wrapped tabs of the corresponding commissure by one or more sutures. 
     EXAMPLE 111 
     The prosthetic heart valve of any example herein, particularly example 108, further comprises: a plurality of first and second wedge members corresponding to the plurality of commissures. Each first wedge member is disposed on the radially-outer side of the respective commissure window, with the upper tab portions of the tabs of the corresponding commissure wrapping around said first wedge member. Each second wedge member is disposed on the radially-outer side of the respective commissure window with the lower tab portions of the tabs of the corresponding commissure wrapping around said second wedge member. 
     EXAMPLE 112 
     The prosthetic heart valve of any example herein, particularly example 111, wherein: each first wedge member is coupled to one or more of the wrapped upper tab portions of the tabs of the corresponding commissure, and each second wedge member is coupled to one or more of the wrapped lower tab portions of the tabs of the corresponding commissure by one or more sutures. 
     EXAMPLE 113 
     The prosthetic heart valve of any example herein, particularly any of examples 109-112, wherein each wedge member comprises at least one of a braided suture, a braided cable, or a folded piece of cloth. 
     EXAMPLE 114 
     The prosthetic heart valve of any example herein, particularly any of examples 108-113, wherein each commissure window is an integral part of the expandable annular frame. 
     EXAMPLE 115 
     The prosthetic heart valve of any example herein, particularly any of examples 108-113, further comprises a plurality of support members that form a part of or are coupled to the expandable annular frame. Each commissure window is a part of a respective one of the support members. 
     EXAMPLE 116 
     The prosthetic heart valve of any example herein, particularly example 115, further comprises an actuator constructed to expand or contract the annular frame, or a locking mechanism constructed to maintain a shape of the annular frame after expansion or contraction thereof. At least one of the support members is a portion of the actuator or locking mechanism, or is coupled to the actuator or locking mechanism. 
     EXAMPLE 117 
     The prosthetic heart valve of any example herein, particularly any of examples 108-116, wherein the upper and lower openings of each commissure window are disposed to form an H-shape in respective side view, each commissure window has a pair of struts, each strut extending along the axial direction of the annular frame, and for each commissure window, the corresponding crossbar extends along a circumferential direction of the annular frame between the pair of struts. 
     EXAMPLE 118 
     The prosthetic heart valve of any example herein, particularly example 117, wherein the crossbar is offset from a midpoint of each strut along the axial direction. 
     EXAMPLE 119 
     The prosthetic heart valve of any example herein, particularly example 118, wherein, for each commissure window: each strut has a first end adjacent to the upper opening and a second end adjacent to the lower opening, a distance, L 1 , along the axial direction from the first end of each strut to a middle of the crossbar along the axial direction is less than a distance, L 2 , along the axial direction from the middle of the crossbar to the second end of each strut. 
     EXAMPLE 120 
     The prosthetic heart valve of any example herein, particularly example 119, wherein L 1 /L 2  is within a range of 0.25 to 0.35, inclusive. 
     EXAMPLE 121 
     The prosthetic heart valve of any example herein, particularly any of examples 107-120, wherein the annular frame comprises a plurality of first struts that are angled with respect to the axial direction so as to extend along a circumferential direction of the annular frame, the first struts connect together at adjacent ends to form an open-cell lattice structure, each cell being open along the radial direction of the annular frame, and the struts of each commissure window are disposed within the lattice structure and coupled to adjacent ones of the first struts. 
     EXAMPLE 122 
     The prosthetic heart valve of any example herein, particularly any of examples 107-121, wherein for each commissure window, each strut has: a first end adjacent to the upper opening and connected to a third end of a respective first angled strut of the annular frame, the first angled strut having a fourth end connected to an adjacent angled strut of the annular frame; and a second end adjacent to the lower opening and connected to a fifth end of a respective second angled strut of the annular frame, the second angled strut having a sixth end connected to another adjacent angled strut of the annular frame. For each commissure window, (h 1 y 2 )/(h 2 y 1 ) is within a range of 0.8-1.2, inclusive, when the annular frame is at a third diameter midway between the crimped state and the expanded state, where h 1  is a distance along the axial direction from the third end to the fourth end of the first angled strut, h 2  is a distance along the axial direction from the fifth end to the sixth end of the second angled strut, y 1  is a distance along the axial direction from the fourth end to a middle of the crossbar, and y 2  is a distance along the axial direction from the sixth end to the middle of the crossbar. 
     EXAMPLE 123 
     The prosthetic heart valve of any example herein, particularly example 122, wherein (h 1 y 2 )/(h 2 y 1 ) is within a range of 0.9-1.1, inclusive. 
     EXAMPLE 124 
     The prosthetic heart valve of any example herein, particularly example 123, wherein (h 1 y 2 )/(h 2 y 1 ) is approximately 1. 
     EXAMPLE 125 
     The prosthetic heart valve of any example herein, particularly any of examples 121-124, wherein the annular frame further comprises a plurality of second struts that extend substantially parallel to the axial direction, each second strut being disposed within the lattice structure and coupled to adjacent ones of the first struts. 
     EXAMPLE 126 
     The prosthetic heart valve of any example herein, particularly 125, wherein at least one of the second struts is disposed between a pair of the commissure windows along the circumferential direction of the annular frame. 
     EXAMPLE 127 
     The prosthetic heart valve of any example herein, particularly any of examples 125-126, wherein at equal intervals along the circumferential direction of the annular frame, one of the second struts or one of the commissure windows is disposed within the lattice structure. 
     EXAMPLE 128 
     The prosthetic heart valve of any example herein, particularly any of examples 125-127, wherein each second strut has a width along the circumferential direction that is greater than a width of each first strut. 
     EXAMPLE 129 
     The prosthetic heart valve of any example herein, particularly any of examples 125-128, wherein each second strut has end portions and a middle portion between the end portions along a direction parallel to the axial direction of the annular frame, a width of the middle portion along the circumferential direction being less than that of the end portions. 
     EXAMPLE 130 
     The prosthetic heart valve of any example herein, particularly any of examples 125-129, wherein each second strut has a dog-bone shape in respective side view that complements a shape of a facing strut of one of the commissure windows when the annular frame is in a crimped configuration. 
     EXAMPLE 131 
     The prosthetic heart valve of any example herein, particularly any of examples 121-130, wherein the struts of each commissure window have widths along the circumferential direction greater than respective widths of the first struts. 
     EXAMPLE 132 
     The prosthetic heart valve of any example herein, particularly any of examples 121-131, wherein the commissure windows and the lattice structure are constructed such that, for each commissure window: a first distance along the circumferential direction between the struts at their first ends remains substantially the same in the deployed state as in the crimped state, and/or a second distance along the circumferential direction between the struts at their second ends remains substantially the same in the deployed state as in the crimped state. 
     EXAMPLE 133 
     The prosthetic heart valve of any example herein, particularly any of examples 107-132, wherein the annular frame has an inflow end and an outflow end, and the upper opening of each commissure window is disposed between the outflow end and the lower opening along the axial direction. 
     EXAMPLE 134 
     The prosthetic heart valve of any example herein, particularly example 133, wherein the lattice structure is constructed such that: the upper opening of each commissure window opens to the outflow end of the annular frame along a direction parallel to the axial direction of the annular frame, and/or the lower opening of each commissure window opens along a direction parallel to the axial direction of the annular frame to a respective one of the cells of the lattice structure that is closed to the inflow end of the annular frame by one of the first struts or a joint between adjacent first struts that form said one of the cells. 
     EXAMPLE 135 
     The prosthetic heart valve of any example herein, particularly any of examples 133-134, wherein an open area of one of the cells formed adjacent to the outflow end of the annular frame is greater than an open area of one of the cells formed adjacent to the inflow end of the annular frame. 
     EXAMPLE 136 
     The prosthetic heart valve of any example herein, particularly any of examples 117-135, wherein, for each commissure window, a maximum width of each strut along the circumferential direction is at a portion between the first and second ends of the strut. 
     EXAMPLE 137 
     The prosthetic heart valve of any example herein, particularly any of examples 107-136, wherein the valvular structure is a bicuspid structure with two leaflets and two commissures, and the annular frame has two commissure windows on diametrically opposite sides from each other. 
     EXAMPLE 138 
     The prosthetic heart valve of any example herein, particularly any of examples 107-136, wherein the valvular structure is a tricuspid structure with three leaflets and three commissures, and the annular frame has three commissure windows equally spaced along a circumferential direction of the annular frame. 
     EXAMPLE 139 
     The prosthetic heart valve of any example herein, particularly any of examples 107-138, wherein the annular frame is formed of a plastically-expandable material or a self-expanding material. 
     EXAMPLE 140 
     The prosthetic heart valve of any example herein, particularly any of examples 108-116, wherein at least one of the commissure windows comprises: a first strut and a second strut extending along the axial direction of the annular frame and spaced apart from each other in a circumferential direction of the annular frame, each of the first strut and the second strut having first and second ends spaced apart along an axial direction of the annular frame; a first lateral strut portion connected to the first ends of the first strut and the second strut; and a second lateral strut portion connected to the second ends of the first strut and the second strut. The crossbar of the at least one of the commissure windows is connected to the first and second struts and positioned between the first and second lateral strut portions. The upper opening of the at least one of the commissure windows is defined between the first and second struts, the first lateral strut portion, and the crossbar. The lower opening of the at least one of the commissure windows is defined between the first and second struts, the second lateral strut portion, and the crossbar. 
     EXAMPLE 141 
     The prosthetic heart valve of any example herein, particularly example 140, wherein a ratio of a first distance measured from the first lateral strut portion to a midline of the crossbar to a second distance measured from the second lateral strut portion to the midline of the crossbar is in a range from 1 to 3. 
     EXAMPLE 142 
     A delivery assembly comprises a delivery apparatus having a handle at a proximal end thereof and a prosthetic heart valve according to any of examples 108-141 coupled to a distal end portion of the delivery apparatus. 
     EXAMPLE 143 
     A method comprises inserting the prosthetic heart valve according to any of examples 108-141 and 144-146 into a body of a patient, wherein the prosthetic heart valve is inserted with the annular frame in a crimped configuration. The method comprises advancing the prosthetic heart valve to an implantation site within the body of the patient. The method includes radially expanding the prosthetic heart valve to a functional size at the implantation site. 
     EXAMPLE 144 
     A prosthetic heart valve comprises an expandable annular frame having a first window strut portion and a second window strut portion extending in an axial direction of the frame and a crossbar extending in a circumferential direction of the frame and connected at opposite ends to the first and second window strut portions. The crossbar and the first and second window strut portions define a commissure window having an H-shape. The commissure window has a first commissure window portion upstream of the crossbar and a second commissure window downstream of the crossbar. The prosthetic heart valve further comprises a valvular structure disposed within the expandable annular frame. The valvular structure comprises a first leaflet and a second leaflet. The first leaflet has a first tab on a first side edge thereof, and the second leaflet has a second tab on a second side edge thereof. The first tab and the second tab extend through at least one of the first and second commissure window portions to form at least a portion of a commissure that couples the first leaflet and the second leaflet to the expandable annular frame. 
     EXAMPLE 145 
     The prosthetic heart valve of any example herein, particularly example 144, wherein each of the first tab and the second tab comprises a first tab portion and a second tab portion, wherein the first tab portions of the first tab and the second tab extend through the first commissure window portion to form a first portion of the commissure, and wherein the second tab portions of the first tab and the second tab extend through the second commissure window portion to form a second portion of the commissure. 
     EXAMPLE 146 
     The prosthetic heart valve of any example herein, particularly any one of examples 144 and 145, further comprises a first lateral strut portion disposed upstream of the crossbar and connected at opposite ends to the first and second window strut portions and a second lateral strut portion disposed downstream of the crossbar and connected at opposite ends to the first and second window strut portions. The first lateral strut portion forms a closed end of the first commissure window portion. The second lateral strut portion forms a closed end of the second commissure window portion. 
     EXAMPLE 147 
     A prosthetic heart valve comprises an expandable annular frame having a plurality of commissure windows and a valvular structure comprising a plurality of leaflets. Each leaflet has a pair of tabs, one of the tabs being on an opposite side from the other of the tabs with respect to a centerline of the leaflet. Each tab has an upper tab portion and a lower tab portion. The valvular structure has a plurality of commissures formed by paired tabs of adjacent leaflets. Each commissure is coupled to a corresponding one of the commissure windows to support the valvular structure within the annular frame. Each commissure window has upper and lower openings separated from each other along an axial direction of the annular frame by a respective crossbar. The upper and lower tab portions for each tab extend through the upper and lower openings, respectively, to a radially-outer side of the respective commissure window. The annular frame is expandable between a crimped state having a first diameter and an expanded state having a second diameter greater than the first diameter. 
     EXAMPLE 148 
     An assembly method for a prosthetic heart valve comprises providing first and second leaflets for a valvular structure of the prosthetic heart valve, each leaflet having a pair of tabs, one of the tabs being on an opposite side from the other of the tabs with respect to a centerline of the leaflet, each tab having an upper tab portion and a lower tab portion. The method comprises disposing the upper and lower tab portions of a second tab of the pair of tabs of the second leaflet adjacent to the upper and lower tab portions of a first tab of the pair of tabs of the first leaflet, respectively. The method comprises conveying the first and second leaflet tabs through a commissure window of an expandable annular frame of the prosthetic heart valve, the commissure window having upper and lower openings separated from each other along an axial direction of the annular frame by a crossbar, the conveying being along a radial direction of the annular frame from a radially inner-side of the commissure window to a radially-outer side of the commissure window and such that the upper tab portions are inserted through the upper opening and the lower tab portions are inserted through the lower opening. The method further comprises securing the first and second leaflet tabs on the radially-outer side of the commissure window. 
     In view of the many possible embodiments to which the principles of the disclosed invention may be applied, it should be recognized that the illustrated embodiments are only preferred examples of the invention and should not be taken as limiting the scope of the invention. Rather, the scope of the invention is defined by the following claims. We therefore claim as our invention all that comes within the scope and spirit of these claims.