Patent Publication Number: US-2023149165-A1

Title: Commissure assemblies formed from tabs of asymmetric leaflets

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of International Application No. PCT/US2021/042000, filed Jul. 16, 2021, which claims benefit of U.S. Provisional Application No. 63/053,176, filed on Jul. 17, 2020, the contents of each of which are herein incorporated by reference in their entirety. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to implantable prosthetic devices, such as prosthetic heart valves, and to leaflet designs and commissure assembly configurations of such implantable prosthetic devices. 
     BACKGROUND OF THE INVENTION 
     Native heart valves, such as the aortic, pulmonary and mitral valves, function to assure adequate directional flow from, and to, the heart, and between the heart&#39;s chambers, to supply blood to the whole cardiovascular system. Various valvular diseases can render the valves ineffective and require replacement with artificial valves. Surgical procedures can be performed to repair or replace a heart valve. Since surgeries are prone to an abundance of clinical complications, alternative less invasive techniques of delivering a prosthetic heart valve over a catheter and implanting it over the native malfunctioning valve have been developed over the years. 
     Different types of prosthetic heart valves are known to date, including balloon expandable valve, self-expandable valves and mechanically-expandable valves. Different methods of delivery and implantation are also known, and may vary according to the site of implantation and the type of prosthetic valve. One exemplary technique includes utilization of a delivery assembly for delivering a prosthetic valve in a crimped state, from an incision which can be located at the patient&#39;s femoral or iliac artery, toward the native malfunctioning valve. Once the prosthetic valve is properly positioned at the desired site of implantation, it can be expanded against the surrounding anatomy, such as an annulus of a native valve, and the delivery assembly can be retrieved thereafter. 
     A prosthetic valve conventionally includes a circumferential frame, and a leaflet assembly composed of a plurality of leaflets attached to the frame via a plurality of commissure assemblies, and configured to regulate blood flow through the prosthetic valve. There is an ongoing need to provide improved leaflet designs and commissure assembly configurations, for improvement of long-term durability within the patient&#39;s body after valve implantation. 
     SUMMARY OF THE INVENTION 
     The present disclosure is directed toward prosthetic heart valves that include an expandable frame and a leaflet assembly mounted therein, wherein the leaflet assembly is coupled to the frame via a plurality of commissure assemblies, formed from tabs of adjacent asymmetrical leaflets secured to each other, wherein at least one of the leaflet tabs includes a vertical tab portion folded over the tab of an adjacent leaflet. 
     According to one aspect of the invention, there is provided a prosthetic valve comprising a frame movable between a radially compressed configuration and a radially expanded configuration, and a leaflet assembly mounted within the frame and comprising a plurality of leaflets configured to regulate flow through the prosthetic valve. Each leaflet comprises a pair of oppositely-directed tabs, wherein each of the tabs comprises a lateral tab portion. At least one of the tabs of each leaflet comprises a vertical tab extension, extending at a non-zero angle from the lateral tab portion. The leaflet is asymmetrical with respect to a leaflet central axis thereof. The at least one vertical tab extension of each leaflet is folded over a lateral tab portion of an adjacent leaflet to form a plurality of annularly spaced commissure assemblies of the leaflet structure 
     According to some embodiments, the vertical tab portions of all commissure assemblies are positioned radially inward with respect to the frame. 
     According to some embodiments, the at least one vertical tab extension is orthogonal with respect to the lateral tab portion it extends from. 
     According to some embodiments, each leaflet comprises two vertical tab extensions, extending from both lateral tab portions in opposite vertical directions with respect to each other. 
     According to some embodiments, each vertical tab extension of two adjacent vertical tab extension within each commissure assembly, is folded over a lateral tab portion of an adjacent leaflet of the same commissure assembly. 
     According to some embodiments, at least one suture is stitched through both vertical tab extensions and both lateral tab portions of each commissure assembly, in an in and out pattern. 
     According to some embodiments, the length of both vertical tab extensions of each leaflet is identical. 
     According to some embodiments, the length of the at least one vertical tab extension is at least as great as 50% of the width of the lateral tab portion. 
     According to some embodiments, the length of the at least one vertical tab extension is at least as great as the width of the lateral tab portion. 
     According to some embodiments, the length of the at least one vertical tab extension is at least as great as the sum of the width of the lateral tab portion and the thickness of the tab. 
     According to some embodiments, each leaflet comprises a single vertical tab extension, vertically extending from one of the lateral tab portions. 
     According to some embodiments, each vertical tab extension within each commissure assembly, is folded over a lateral tab portion of an adjacent leaflet of the same commissure assembly, and folded back over the lateral tab portion from which the vertical tab extension is extending. 
     According to some embodiments, at least one suture is stitched through both folded portions of the vertical tab extension and both lateral tab portions of each commissure assembly, in an in and out pattern. 
     According to some embodiments, the length of the at least one vertical tab extension is at least as great as 200% of the width of the lateral tab portion. 
     According to some embodiments, the length of the at least one vertical tab extension is at least as great as the sum of the 200% of the width of the lateral tab portion and 200% of the thickness of the tab. 
     According to some embodiments, each leaflet is cut from bovine pericardium. 
     According to another aspect of the invention, there is provided a leaflet assembly a plurality of leaflets. Each leaflet comprises a pair of oppositely-directed tabs. Each of the tabs comprises a lateral tab portion, wherein at least one of the tabs of each leaflet comprises a vertical tab extension extending at a non-zero angle from the lateral tab portion. Each leaflet is asymmetrical with respect to a leaflet central axis thereof. 
     According to some embodiments, the at least one vertical tab extension is orthogonal with respect to the lateral tab portion it extends from. 
     According to some embodiments, each leaflet comprises two vertical tab extensions, extending from both lateral tab portions in opposite vertical directions with respect to each other. 
     According to some embodiments, each vertical tab extension of two adjacent vertical tab extensions within each commissure assembly, is folded over a lateral tab portion of an adjacent leaflet of the same commissure assembly. 
     According to some embodiments, at least one suture is stitched through both vertical tab extensions and both lateral tab portions of each commissure assembly, in an in and out pattern. 
     According to some embodiments, the length of both vertical tab extensions of each leaflet is identical. 
     According to some embodiments, the length of the at least one vertical tab extension is at least as great as 50% of the width of the lateral tab portion. 
     According to some embodiments, the length of the at least one vertical tab extension is at least as great as the width of the lateral tab portion. 
     According to some embodiments, the length of the at least one vertical tab extension is at least as great as the sum of the width of the lateral tab portion and the thickness of the tab. 
     According to some embodiments, each leaflet comprises a single vertical tab extension, vertically extending from one of the lateral tab portions. 
     According to some embodiments, each vertical tab extension within each commissure assembly, is folded over a lateral tab portion of an adjacent leaflet of the same commissure assembly, and folded back over the lateral tab portion from which the vertical tab extension is extending. 
     According to some embodiments, at least one suture is stitched through both folded portions of the vertical tab extension and both lateral tab portions of each commissure assembly, in an in and out pattern. 
     According to some embodiments, the length of the at least one vertical tab extension is at least as great as 200% of the width of the lateral tab portion. 
     According to some embodiments, the length of the at least one vertical tab extension is at least as great as the sum of the 200% of the width of the lateral tab portion and 200% of the thickness of the tab. 
     According to some embodiments, each leaflet is cut from bovine pericardium. 
     According to yet another aspect of the invention, there is provided a method of assembling a leaflet assembly. The method comprises a step of providing a plurality of asymmetrical leaflets, wherein each leaflet comprises a pair of oppositely-directed tabs, wherein each of the tabs comprises a lateral tab portion, and wherein at least one of the tabs of each leaflet comprises a vertical tab extension extending at a non-zero angle from the lateral tab portion. 
     The method further comprises a step of folding a vertical tab extension of one of the leaflets over a lateral tab portion of an adjacent leaflet to form a plurality of annularly spaced commissure assemblies of the leaflet structure. 
     According to some embodiments, at least one vertical tab extension is orthogonal with respect to the lateral tab portion it extends from. 
     According to some embodiments, each leaflet comprises two vertical tab extensions, extending from both lateral tab portions in opposite vertical directions with respect to each other. 
     According to some embodiments, the step of folding vertical tab extension of one of the leaflets over a lateral tab portion of an adjacent leaflet, comprises folding each vertical tab extension of two adjacent vertical tab extensions within each commissure assembly, over a lateral tab portion of an adjacent leaflet of the same commissure assembly. 
     According to some embodiments, the method further comprises a step of stitching a suture through both vertical tab extensions and both lateral tab portions of each commissure assembly. 
     According to some embodiments, the stitching is performed in an in and out pattern. 
     According to some embodiments, the length of both vertical tab extensions of each leaflet is identical. 
     According to some embodiments, the length of the at least one vertical tab extension is at least as great as 50% of the width of the lateral tab portion. 
     According to some embodiments, the length of the at least one vertical tab extension is at least as great as the width of the lateral tab portion. 
     According to some embodiments, the length of the at least one vertical tab extension is at least as great as the sum of the width of the lateral tab portion and the thickness of the tab. 
     According to some embodiments, each leaflet comprises a single vertical tab extension, vertically extending from one of the lateral tab portions. 
     According to some embodiments, the step of folding vertical tab extension of one of the leaflets over a lateral tab portion of an adjacent leaflet, comprises folding each vertical tab extension within each commissure assembly, a lateral tab portion of an adjacent leaflet of the same commissure assembly, and then folding it back over the lateral tab portion from which the vertical tab extension is extending. 
     According to some embodiments, the method further comprises a step of stitching a suture through both folded portions of the vertical tab extension and both lateral tab portions of each commissure assembly. 
     According to some embodiments, the stitching is performed in an in and out pattern. 
     According to some embodiments, the length of the at least one vertical tab extension is at least as great as 200% of the width of the lateral tab portion. 
     According to some embodiments, the length of the at least one vertical tab extension is at least as great as the sum of the 200% of the width of the lateral tab portion and 200% of the thickness of the tab. 
     According to some embodiments, each leaflet is cut from bovine pericardium. 
     According to some embodiments, the method further comprises a step of mounting the leaflet assembly within a frame of a prosthetic valve. 
     According to some embodiments, the step of mounting comprises positioning the vertical tab portions of all commissure assemblies radially inward with respect to the frame. 
     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 FIGURES 
       Some embodiments of the invention are described herein with reference to the accompanying figures. The description, together with the figures, makes apparent to a person having ordinary skill in the art how some embodiments may be practiced. The figures are for the purpose of illustrative description and no attempt is made to show structural details of an embodiment in more detail than is necessary for a fundamental understanding of the invention. For the sake of clarity, some objects depicted in the figures are not to scale. 
       In the Figures: 
         FIG.  1 A . shows a side view of a frame of a prosthetic valve, according to some embodiments. 
         FIG.  1 B . shows an enlarged side view of one type of an axially extending window frame portion. 
         FIG.  1 C . shows an enlarged side view of another type of an axially extending window frame portion. 
         FIG.  2    shows a view in perspective of a prosthetic valve, according to some embodiments. 
         FIG.  3    shows a single leaflet, according to some embodiments. 
         FIG.  4 A  shows an enlarged view in perspective of a commissure assembly mounted within a commissure window, according to some embodiments. 
         FIG.  4 B  shows cross-sectional view of a commissure assembly mounted within a commissure window, according to some embodiments. 
         FIG.  5    shows a plan view of a prosthetic valve, according to some embodiments. 
         FIG.  6    shows a leaflet having two vertical tab extensions, oriented in opposite directions with respect to each other, according to some embodiments. 
         FIG.  7 A  shows an enlarged view in perspective of a commissure assembly comprising tabs of adjacent leaflets of the type shown in  FIG.  6    secured to each other, according to some embodiments. 
         FIG.  7 B  shows a cross sectional view along plane  7 B- 7 B of  FIG.  7 A . 
         FIG.  8    shows a leaflet having a single vertical tab extension, according to some embodiments. 
         FIG.  9 A  shows an enlarged view in perspective of a commissure assembly comprising tabs of adjacent leaflets of the type shown in  FIG.  8    secured to each other, according to some embodiments. 
         FIG.  9 B  shows a cross sectional view along plane  9 B- 9 B of  FIG.  7 A   
     
    
    
     DETAILED DESCRIPTION OF SOME EMBODIMENTS 
     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. Furthermore, well-known features may be omitted or simplified in order not to obscure the disclosure. In order to avoid undue clutter from having too many reference numbers and lead lines on a particular drawing, some components will be introduced via one or more drawings and not explicitly identified in every subsequent drawing that contains that component. 
     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 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.” 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. 
     Reference is now made to  FIGS.  1 A- 2   , showing a prosthetic valve  100 , including various components thereof, according to some embodiments.  FIG.  1    shows a bare frame  106  of an exemplary prosthetic valve  100 .  FIGS.  1 B and  1 C  show two exemplary types of window frame portions  112  of a prosthetic valve  100 .  FIG.  2    shows the prosthetic valve  100  of  FIG.  1 A , including soft components, such as a leaflet assembly  130  and an inner skirt  122 , attached to the frame  106 . 
     The prosthetic valve  100  is deliverable to a patient&#39;s target site over a catheter (not shown), and is radially expandable and compressible between a radially compressed, or crimped, state, and a radially expanded state—shown in  FIGS.  1 A and  2   . The expanded state may include a range of diameters to which the valve  100  may expand, between the compressed state and a maximal diameter reached at a fully expanded state. Thus, a plurality of partially expanded states may relate to any expansion diameter between radially compressed or crimped state, and maximally expanded state. A prosthetic valve  100  of the current disclosure may include any prosthetic valve configured to be mounted within the native aortic valve, the native mitral valve, the native pulmonary valve, and the native tricuspid valve. 
     The term “plurality”, as used herein, means more than one. 
     As stated above, a prosthetic valve  100  can be delivered to the site of implantation via a delivery assembly carrying the valve  100  in a radially compressed or crimped state, toward the target site, to be mounted against the native anatomy, by expanding the valve  100  via various expansion mechanisms.  FIG.  1    shows an exemplary frame  106  of a balloon expandable valve. Balloon expandable valves generally involve a procedure of inflating a balloon within a prosthetic valve, thereby expanding the prosthetic valve  100  within the desired implantation site. Once the valve is sufficiently expanded, the balloon is deflated and retrieved along with the delivery apparatus. 
     Other types of valves may include other expansion mechanisms, such as mechanical expansion mechanisms or self-expandable mechanisms (not shown). Mechanically expandable valves are a category of prosthetic valves that rely on a mechanical actuation mechanism for expansion. The mechanical actuation mechanism usually includes a plurality of expansions and locking assemblies, releasably coupled to respective actuation assemblies of a delivery apparatus, controlled via a handle for actuating the actuation assemblies to expand the prosthetic valve to a desired diameter. The expansions and locking assemblies may optionally lock the valve&#39;s position to prevent undesired recompression thereof, and disconnection of the actuation assemblies from the expansions and locking assemblies, to enable retrieval of the delivery apparatus once the prosthetic valve is properly positioned at the desired site of implantation. 
     Self-expandable valves include a frame that is shape-set to automatically expand as soon as an outer retaining structure, such as a capsule or a portion of a shaft, is withdrawn proximally relative to the prosthetic valve. 
     A prosthetic valve  100  can comprise an inflow end  104  and an outflow end portion  102 . In some instances, the outflow end  102  is the distal end of the prosthetic valve  100 , and the inflow end  104  is the proximal end of the prosthetic valve  100 . Alternatively, depending for example on the delivery approach of the valve, the outflow end can be the proximal end of the prosthetic valve, and the inflow end can be the distal end of the prosthetic valve. 
     The term “proximal”, as used herein, generally refers to a position, direction, or portion of any device or a component of a device, which is closer to the user and further away from the implantation site. 
     The term “distal”, as used herein, generally refers to a position, direction, or portion of any device or a component of a device, which is further away from the user and closer to the implantation site. 
     The term “outflow”, as used herein, refers to a region of the prosthetic valve through which the blood flows through and out of the valve  100 . 
     The term “inflow”, as used herein, refers to a region of the prosthetic valve through which the blood flows into the valve  100 . 
     The valve  100  comprises an annular frame  106  movable between a radially compressed configuration and a radially expanded configuration, and a leaflet assembly  130  mounted within the frame  106 . The frame  106  can be made of various suitable materials, including plastically-deformable materials such as, but not limited to, stainless steel, a nickel based alloy (e.g., a cobalt-chromium or a nickel-cobalt-chromium alloy such as MP35N alloy), polymers, or combinations thereof. When constructed of a plastically-deformable materials, the frame  106  can be crimped to a radially compressed state on a delivery shaft (not shown), and then expanded inside a patient by an inflatable balloon or equivalent expansion mechanisms. Alternatively or additionally, the frame can be made of shape-memory materials such as, but not limited to, nickel titanium alloy (e.g., Nitinol). When constructed of a shape-memory material, such as the case for mechanically expandable valves, the frame can be crimped to a radially compressed state and restrained in the compressed state by insertion into a shaft or equivalent mechanism of a delivery apparatus (not shown). 
     In the examples illustrated in  FIGS.  1 A and  2   , the frame  106  is an annular, stent-like structure comprising a plurality of intersecting struts  110 . In this application, the term “strut” encompasses vertical struts, angled struts, attachment posts, commissure windows, and any similar structures described by U.S. Pat. Nos. 7,993,394 and 9,393,110, which are incorporated herein by reference. A strut  110  may be any elongated member or portion of the frame  106 . The frame  106  can have one or more multiple rows of cells  108  defined by intersecting struts  110 . The frame  106  can have a cylindrical or substantially cylindrical shape having a constant diameter from the inflow end portion  104  to the outflow end portion  102  of the frame as shown, or the frame can vary in diameter along the height of the frame, as disclosed in U.S. Pat. No. 9,155,619, which is incorporated herein by reference. 
     The end portions of the struts  110  are forming outflow apices  120  at the outflow end  102  and inflow apices  118  at the inflow end  104 . The struts  110  can intersect at additional junctions  116  formed between the outflow apices  120  and the inflow apices  118 . The junctions  116  can be equally or unequally spaced apart from each other, and/or from the apices  118 ,  120 , between the outflow end  102  and the inflow end  104 . 
     According to some embodiments, the struts  110  include a plurality of angled struts and vertical struts. In the exemplary embodiment illustrated in  FIG.  1 A , the frame  106  comprises a plurality of angled struts  110 , and axially extending struts  114 . The struts may be pivotable or bendable relative to each other, so as to permit frame expansion or compression. In some implementations, the frame  106  can be formed from a single piece of material, such as a metal tube, via various processes such as, but not limited to, laser cutting, electroforming, and/or physical vapor deposition, while retaining the ability to collapse/expand radially. 
     The leaflet assembly  130  comprises a plurality of leaflets  132  (e.g., three leaflets), positioned at least partially within the frame  106 , and configured to regulate flow of blood through the prosthetic valve  100  from the inflow end  104  to the outflow end  102 . While three leaflets  132  arranged to collapse in a tricuspid arrangement, are shown in the exemplary embodiment illustrated in  FIGS.  2   , it will be clear that a prosthetic valve  100  can include any other number of leaflets  132 . The leaflets  132  are made of a flexible material, derived from biological materials (e.g., bovine pericardium or pericardium from other sources), bio-compatible synthetic materials, or other suitable materials as known in the art and described, for example, in U.S. Pat. Nos. 6,730,118, 6,767,362 and 6,908,481, which are incorporated by reference herein. 
       FIG.  3    shows a single representative leaflet  132  in a flattened configuration. The leaflet  132  has a rounded cusp edge  134 , and a pair of generally oppositely-directed tabs  138  separating the cusp edge  134  and the free edge  136 . The cusp edge  134  forms a single scallop. When the leaflets  132  are coupled to the frame and to each other, the lower edge of the resulting leaflet assembly  130  desirably has an undulating, curved scalloped shape. By forming the leaflets with this scalloped geometry, stresses on the leaflets  132  are reduced which, in turn, improves durability of the valve. Moreover, by virtue of the scalloped shape, folds and ripples at the belly of each leaflet ( 132 ), which can cause early calcification in those areas, can be eliminated or at least minimized. The scalloped geometry also reduces the amount of tissue material used to form the leaflet assembly, thereby allowing a smaller, more even crimped profile at the inflow end of the valve. 
     A conventional leaflet, such as leaflet  132  shown in  FIG.  3   , is symmetrical with respect to a leaflet central axis  20  extending vertically along it&#39;s center, such that if the leaflet  132  is theoretically folded over itself along the leaflet central axis  20 , both tabs  138  are congruent with respect to each other. 
     The leaflets  132  define a non-planar coaptation plane (not annotated) when their free edges  136  co-apt with each other to seal blood flow through the prosthetic valve  100 . In some implementations, the free edge  136  of a leaflet  132  can extend along a straight line between the tabs  138 . In other implementations, as shown in  FIG.  3   , the free edge  136  between the tabs  138  is concave with either one or more curvatures (i.e., simple or complex curves). 
     Leaflets  132  can be secured to one another at their tabs  138  to form commissure assemblies  144  (see, for example,  FIG.  4 A ) of the leaflet assembly  130 , which can be secured, directly or indirectly, to structural elements connected to the frame  106  or formed therein, such as commissure posts (not shown) or axially extending window frame portion  112 . When secured to two other leaflets  132  to form leaflet assembly  130 , the cusp edges  134  of the leaflets  132  collectively form the scalloped shaped lower edge portion of the leaflet assembly  130 , which may be coupled, directly or indirectly, to the frame  106 , via a scallop-line suture  126  (see  FIG.  2   ). 
     According to some embodiments, the upper row of cells comprises a plurality of axially extending window frame portions  112  which define commissure windows  170 , and a plurality of axially extending struts  114 . Each axial strut  114  and each window frame portion  112  extends from a junction  116  defined by the convergence of the lower ends of two angled struts  110  to another junction  116  defined by the convergence of the upper ends of two angled struts  110 ″. Each commissure window frame portion  112  mounts a respective commissure assembly  144  assembly of the leaflet assembly  130 . 
       FIGS.  1 B and  1 C  show enlarged views of two exemplary two types of window frame portions  112 . It will be appreciated that reference numerals with prime marks (′) or double prime marks (″) are used to denote different embodiments of the same elements. Embodiments of the disclosed devices and systems may include any combination of different embodiments of the same elements. Specifically, any reference to an element without single or double prime marks may refer to any alternative embodiment of the same element denoted with a single prime mark or double prime marks. 
       FIG.  1 B  shows an exemplary window frame portion  112 ′ defining a closed commissure window  170 ′, wherein all reference numerals with prime marks (′) shown in  FIG.  1 B  refer to like elements comprised within such a window frame portion  112 ′. The commissure window  170 ′ is enclosed between a base strut  174 ′ at its bottom, two lateral struts  172 ′ extending axially from the base strut  174 ′. And an outflow lateral strut  176 ′ opposite to, and parallel with, the base strut  174 ′. A commissure assembly  144  may be coupled to a window frame portion  112 ′ in such a manner that portions of the commissure assembly  144 , such as leaflet tabs  138 , extend through the closed window  170 ′. This may be achieved, for example, by placement of the leaflet assembly  130  within the inner space defined by the frame ( 106 ), and extending the tabs  138  radially outward through the closed window  170 ′. 
       FIG.  1 C  shows an exemplary window frame portion  112 ″ defining a closed commissure window  170 ″, wherein all reference numerals with double prime marks (″) shown in  FIG.  1 C  refer to like elements comprised within such a window frame portion  112 ″. The commissure window  170 ″ is defined between a base strut  174 ″ at its bottom, and two lateral struts  172 ″ extending axially from the base strut  174 ″. However, unlike the window frame portion  112 ′, the window frame portion  112 ″ does not include an outflow lateral strut ( 176 ), thus forming an open-ended commissure window  170 ″. This configuration advantageously allows commissure assemblies ( 144 ) to be pre-assembled prior to mounting the commissure assembly within the commissure window  170 ″, which advantageously simplifies the assembly process. 
     In the illustrated embodiment, each commissure window  170 ″ is substantially U-shaped. However, in other embodiments, the commissure window ( 170 ) can have any of various shapes configured to accept the leaflets  132 . For example, the commissure windows ( 170 ) can be ovular, square, rectangular, triangular, L-shaped, T-shaped, etc. 
     Additional frame configurations may include commissure posts attached to the frame, configured to accept commissures  144  extending either through window portions defined therein, or supporting commissure attachment thereto in various other manners. Alternatively, some of the cells  108  may be configured to receive commissure assemblies  144  attached thereto. For example, the uppermost row of cells  108  can be configured to receive tabs  138  of the leaflets  132 . Further details regarding prosthetic valves, including the manner in which commissures may be mounted to their frames, are described in U.S. Pat. Nos. 6,730,118, 7,393,360, 7,510,575, 7,993,394, 8,252,202, and 9,393,110; U.S. Publication Nos. 2018/0325665, 2019/0105153, U.S. Application Nos. 62/869,948 and 62/813,643; and PCT Application No. PCT/US2019/61392, all of which documents are incorporated herein by reference. Any of the techniques and mechanisms disclosed in the prior documents can be used to connect the commissure assemblies  144 , directly or indirectly, to the frame  106 . 
     According to some embodiments, the prosthetic valve  100  further comprises an inner skirt  122  that can be secured to the inner surface of the frame  106 , for example by sutures  124 . The inner skirt  122  is configured to assist in securing the leaflet assembly  130  to the frame  106  and to assist in forming a good seal between the valve ( 100 ) and the native annulus by blocking the flow of blood through the open cells  108  of the frame ( 106 ) below the cusp edges  134  of the leaflets ( 132 ). The leaflets  132  may be sutured to the inner skirt  122  via a scallop-line suture  126  that tracks their lower cusp edges  134 , while the inner skirt  122  can be sutured to the frame  106  at locations away from the scallop-line suture  126  so that the inner skirt  122  can be more pliable in that area. This can avoid stress concentrations at the scallop-line suture  126 . 
     According to some embodiments, the prosthetic valve  100  can further comprise an outer skirt (not shown) mounted on the outer surface of the frame  106 , configure to function, for example, as a sealing member retained between the frame  106  and the surrounding tissue of the native annulus against which the prosthetic valve  100  is mounted, thereby reducing risk of paravalvular leakage past the prosthetic valve  100 . Either one of the inner skirt ( 122 ) or the outer skirt can be made of various suitable biocompatible materials, such as, but not limited to, various synthetic materials (e.g., PET) or natural tissue (e.g. bovine pericardium). 
       FIG.  4 A  shows a perspective view of a window frame portion  112  defining a commissure window  170 , including a commissure assembly  144  mounter thereto.  FIG.  4 B  shows a cross-sectional view of a commissure assembly  144  mounted within the commissure window  170  of  FIG.  4 A . As shown, two tabs  138  of leaflets  132  can be inserted into the commissure window  170 , either by insertion of the tabs  138  from an inner side of the commissure window  170  to its outer side, such that they may extend radially outward from the commissure window  170 , or by sliding both tabs from an upper opening of a commissure window, for example in the case of open commissure windows  170 ″. 
     A wedge  148  can be inserted between the portions of the tabs  138  that extend through the commissure window  170 . The wedge  148  can press portions of the tabs  138  against the outer surfaces of the lateral struts  172 . In some implementations, the wedge  148  can be inserted between the tabs  138  after extending the tabs  138  through the commissure window  170 . In other implementations, the wedge  148  can be attached first to, and between, the outer portions of the tabs  138 , followed by sliding the pre-assembled commissure assembly  144  into the commissure window from an upper opening thereof, for example in the case of an open commissure window  170 ″. 
     According to some embodiments, as shown, the wedge  148  is an elongated member having a circular shape in cross-section. However, in other embodiments, the wedge can have any of various shapes in cross-section, such as, for example, triangular, ovular, square, rectangular, C-shaped, semi-circular, etc. The wedge  148  can be provided in the form of a wire, chord, sleeve, fabric or suture. 
     As shown in  FIGS.  4 A- 4 B , each lateral strut  172  can comprise one or more chamfered surfaces. In the illustrated embodiment, each lateral strut  172  comprises a chamfered surface angled radially outwardly, which may help in securing the leaflets  132  within the commissure window ( 170 ). In such configurations, the wedge  148  presses portions of the tabs  138  against the chamfered surfaces. While not shown, it will be clear that each lateral strut ( 172 ) can similarly include a chamfered surface angled radially inwardly, which can assist in mitigating frictional contact between the leaflets ( 132 ) and the lateral struts  172  during systole. Furthermore, it is to be understood that the lateral struts  172  can be rounded instead of chamfered, to achieve the same potential advantages. 
     A commissure assembly  144  may further include reinforcement members  150  disposed vertically along the inner side of the window frame portion ( 112 ), on both sides of the leaflets  132 , such as on both sides of the inner portions of the tabs  138 . The reinforcement members  150  are more resistant to bending, or articulating, than the portions of the leaflets  132  that are radially inward of the tabs  138 , and can be provided in the form of wires, chords, sleeves, fabrics or sutures. 
     As shown in  FIG.  4 B , a fabric strip or cloth  152  can be used to interconnect pairs of adjacent tabs  138  with the reinforcement members  150  and the wedge  148  (cloth removed from view in  FIG.  4 A  for clarity). Cloth  152  can be made from a piece of woven PET fabric, although other synthetic and/or natural materials can be used. 
     The commissure assembly  144  can then be coupled to window frame portion ( 112 ) using, for example, one or more sutures. Further details regarding various attachments techniques and mechanisms for attaching commissures to expansion and locking mechanisms are disclosed in U.S. Publication No. 2018/0325665; U.S. Publication No. 2019/0105153; U.S. Application No. 62/869,948; U.S. Application No. 62/813,643; and PCT Application No. PCT/US2019/61392, all of which documents are incorporated herein by reference. Any of the techniques and mechanisms disclosed in the prior documents can be used to connect the commissure assemblies ( 144 ) formed by tabs ( 138 ) to an axially extending window frame portion ( 112 ), to a commissure post attachable to the frame, to commissure clamps attachable to the frame, and/or to commissure windows formed within expansion and locking assemblies of mechanically expandable valves. 
     During valve cycling, the leaflets can articulate about articulation axes  154 , between an open state during systole and coaptation state during diastole. Placement of reinforcement members  150  at the interface of the tabs  138  and the inner surface of the frame  106 , helps space the articulation axes  154  away from the frame  106  during normal operation of the prosthetic valve, as further shown in  FIG.  5   . By having the leaflets  132  flex against reinforcement members  150 , contact between the moving portions of the leaflets  132  (especially the free edges  136  of the leaflets) and the frame  106  can be avoided during working cycles, which in turn improves the durability of the valve. 
     Despite the advantages of utilizing offsetting structures attached to the leaflets  132 , such as reinforcement members (e.g., reinforcement members  150 ) and/or fabric strips (e.g., cloth  152 ), to space the articulation axes  154  of the leaflets radially inward, with respect to the frame  106 , the moving sections of the leaflets  132  may be subject to wear due to abrasion of against such materials. 
     According to some embodiments, each leaflet is provided as an asymmetrical leaflet having at least one vertical tab extension, extending at a non-zero angle, preferably orthogonal to, a lateral portion of at least one tab. The at least one vertical tab extension of one leaflet is folded over a lateral tab portion of an adjacent leaflet, and attached thereto, to form a commissure assembly. 
     Reference is now made to  FIGS.  6 - 7 B , showing an exemplary embodiment of commissures  244  formed from tabs  238  of leaflets  232 .  FIG.  6    shows a flattened view of one exemplary type of leaflet  232 , which can be similar to leaflet  132 , except when noted. The leaflet  232  has a rounded cusp edge  234 , and a pair of generally oppositely-directed tabs  238  separating the cusp edge  234  and the free edge  236 . Tabs  238  differ from tabs  138  in that each of the tabs  238  further comprises a lateral tab portion  240 , which extends in a lateral direction away from the cusp edge  234  and the free edge  236 , and a vertical tab extension  242  extending vertically from the corresponding lateral tab portion  240 . Each lateral tab portion  240  comprises a lateral outer portion  241 , defined as the sub-portion of the lateral tab portion  240  projecting away from the vertical tab extension  242 , and having a non-zero length. 
     Unlike the case with most conventional leaflets, such as leaflet  132  shown in  FIG.  3   , the leaflet  232  is asymmetrical with respect to a leaflet central axis  20 , since the vertical tab extensions  242  on both sides of the leaflet central axis  20  extend in opposite vertical directions with respect to each other. In other words, if the leaflet  232  is theoretically folded over itself along the leaflet central axis  20 , both vertical tab extensions  242  extend in opposite directions from each other. 
       FIG.  7 A  shows an enlarged view of a commissure  244  mounted within a commissure window  170 .  FIG.  7 B  shows a cross-section view of the commissure  244  across plane  7 B- 7 B of  FIG.  7 A . A commissure  244  is formed by attaching tabs  238  of adjacent leaflets  232  to each other, such that the vertical tab extension  242  of each tab  238  is folded over the adjacent tab  238 , and more specifically, over the lateral tab portion  240  of the adjacent tab  238 . A suture  156  can be used to couple the adjacent lateral tab portions  240  and the vertical tab extensions  242  folded thereover, to form a four-layered structure as shown in  FIG.  7 B , extending from the inner surface of the window frame portion  112 . 
     The resulting four layered structure is more resistant to bending, or articulating, than the portions of the leaflets  232  that are radially inward of the tabs  238 , and serves to offset the articulation axes  254  radially inward, away from the frame  106 . By having the leaflets  232  flex against the inner edges of the vertical tab extensions  242 , contact between the moving portions of the leaflets  232  (especially the free edges  236  of the leaflets) and the frame  106  can be avoided during working cycles, which in turn improves the durability of the valve. 
     According to some embodiments, the leaflets  232 , including their tabs  238  with the vertical tab extensions  242 , are cut out from bovine pericardium as a single component. 
     Advantageously, since the vertical tab extensions  242  constitute integral portions of the leaflets  232 , the moving portions of the leaflets  232  articulate about portions of the leaflets  232  made of the same material (e.g., bovine pericardium), instead of articulating about external components such as reinforcement members ( 150 ) or cloth ( 152 ), which can comprise other materials (e.g., textiles, polymeric materials, and the like). The absence of such materials can significantly reduce abrasion and wear of the leaflet material. 
     As further shown in  FIG.  6   , each lateral tab portion  240  may have a width W 1 , and each vertical tab extension  242  may have a length L 1 . Each tab  238  may also have a thickness t 1  (see  FIG.  7 A ). According to some embodiments, the length L 1  of both vertical tab extension  242  on both sides of the leaflet  232  is identical. According to some embodiments, the length L 1  of the vertical tab extension  242  is at least as great as 50% of the width W 1  of the lateral tab portion  240 . According to some embodiments, the length L 1  of the vertical tab extension  242  is at least as great as 70% of the width W 1  of the lateral tab portion  240 . According to some embodiments, the length L 1  of the vertical tab extension  242  is at least as great as the width W 1  of the lateral tab portion  240 . According to some embodiments, the length L 1  of the vertical tab extension  242  is at least as great as the sum of the width W 1  of the lateral tab portion  240  and the thickness t 1  of the tab  238 . 
     As shown in  FIGS.  7 A- 7 B , two adjacent tabs  238   a  and  238   b  of respective leaflets  232   a  and  232   b , may be secured to each other such that the vertical tab extension  242   a  is folded over lateral tab portion  240   b , while the vertical tab extension  242   b  is folded over lateral tab portion  240   a . Since both vertical tab extension  242   a  and  242   b  extend from their respective lateral tab portion  240  at opposite directions relative to each other, it is possible to fold them over the adjacent lateral tab portion  240  from opposite sides, thereby preventing any interference there-between during the folding procedure. 
     Once in the folded position shown in  FIGS.  7 A- 7 B , a suture  156  may be used to stitch all four layers, including the vertical tab extension  242   a , the lateral tab portion  240   b , the lateral tab portion  240   a  and the vertical tab extension  242   b , together. It is noted that suture  156  is used by way of illustration and not limitation, and that other securement means may be used to attach the four layers to each other. Moreover, more than one suture  156  may be used, and while shown to pass through the layers in an in-and-out pattern, any other stitching pattern is contemplated. 
     As shown in  FIG.  7 A , the folded vertical tab extensions  242  of the commissure assembly  244  are positioned radially inward with respect to the frame  106 . The remaining portions of the lateral tab portions  240 , extending beyond the vertical tab extension  242 , may project radially outward through a commissure window  170 , and a wedge  148  may be disposed between the portions of the lateral tab portion  240  projecting radially outward from the commissure window  170 , and more specifically, between the lateral outer portion  241 . While not shown explicitly, a cloth ( 152 ) may be used to cover the wedge  148  and portions of the lateral tab portion  240 . However, even when a cloth is used to further cover and assist in attachment of components of a commissure assemble  244 , the cloth will not extend radially inward beyond the inner edges of the vertical tab extensions  242 , so as to avoid potential contact between the moving portions of the leaflets  232  and the cloth, thereby minimizing or eliminating risk of leaflet abrasion. 
     Reference is now made to  FIGS.  8 - 9 B , showing an exemplary embodiment of commissures assembly  344  formed from tabs  338  of leaflets  332 .  FIG.  8    shows an exemplary type of leaflet  332 , which can be similar to leaflet  232 , except when noted. The leaflet  332  has a rounded cusp edge  334 , and a pair of generally oppositely-directed tabs  338  separating the cusp edge  334  and the free edge  336 . Both tabs  338  include lateral tab portions  340 , which extends in a lateral direction away from the cusp edge  234  and the free edge  236 . Unlike leaflet  232 , the leaflet  332  comprises only one vertical tab extension  342  extending vertically from one of the tabs  338 . Similarly, unlike the case with most conventional leaflets, such as leaflet  132  shown in  FIG.  3   , the leaflet  332  is asymmetrical with respect to a leaflet central axis  20 , since only one tab  138  on one side of the leaflet central axis  20  includes a vertical tab extension  342 . 
     It will be clear that any reference to lateral tab portions ( 240 ,  340 ) extending in lateral directions away from the cusp edge, and any reference to a vertical tab extensions ( 242 ,  342 ), extending vertically from the lateral tab extensions, refer to flattened configurations of the leaflets ( 232 ,  332 ) as shown in  FIGS.  6  and  8   , and that the lateral tab portions ( 240 ,  340 ) and/or the vertical tab extensions ( 242 ,  342 ) may assume other orientations once assembled within respective commissures ( 244 ,  344 ) and coupled to the frame ( 106 ). 
       FIG.  8    shows a leaflet  332  having two tabs  338   aa  and  338   ab , provided with corresponding lateral tab portions  340   aa  and  340   ab  extending laterally from both sides thereof (at opposite directions). Both lateral tab portions  340  may have the same width W 2 , which may be identical to the width W 1  of lateral tab portions  240 . A vertical tab extension  342  extends from the lateral tab portion  340   aa , preferably orthogonal thereto, while the opposite lateral tab portion  340   ab  is devoid of a vertical tab extension. The lateral tab portion  340   aa  comprises a lateral outer portion  341 , defined as the sub-portion of the lateral tab portion  340   aa  projecting away from the vertical tab extension  342 , and having a non-zero length. 
     While the vertical tab extension  342  is illustrated extending from the lateral tab portion  340   aa , it will be clear that in other implementations, the vertical tab extension  342  can extend from the lateral tab portion  340   ab , while the lateral tab portion  340   aa  is devoid of a vertical tab extension. While the vertical tab extension  342  is illustrated as extending upward, it will be clear that this is for illustrative purpose only, and that in other implementations, the vertical tab extension  342  may extend downward. 
       FIG.  9 A  shows an enlarged view of a commissure  344  mounted within a commissure window  170 .  FIG.  9 B  shows a cross-section view of the commissure  344  across plane  9 B- 9 B of  FIG.  9 A . A commissure  344  is formed by attaching tabs  338  of adjacent leaflets  332  to each other, such that the vertical tab extension  342  of one tab  338  is folded over the tab  338  of the adjacent leaflet, which is devoid of a vertical tab extension  342 . The vertical tab extension  342  can be long enough to be further folded over the lateral tab portion  340  it is extending from. 
     A suture  156  can be used to couple the adjacent lateral tab portions  340  and the vertical tab extension  342  folded thereover, to form a four-layered structure as shown in  FIG.  9 B , extending from the inner surface of the window frame portion  112 . The resulting four layered structure is more resistant to bending, or articulating, than the portions of the leaflets  332  that are radially inward of the tabs  338 , and serves to offset the articulation axes  354  radially inward, away from the frame  106 . By having the leaflets  332  flex against the inner edges of the vertical tab extension  342 , contact between the moving portions of the leaflets  332  (especially the free edges  336  of the leaflets) and the frame  106  can be avoided during working cycles, which in turn improves the durability of the valve. 
     Advantageously, since the vertical tab extension  342  constitutes an integral portion of the leaflet  232 , the moving portions of the leaflets  232  articulate about portions of the leaflets  332  made of the same material (e.g., bovine pericardium), instead of articulating about external components such as reinforcement members ( 150 ) or cloth ( 152 ), which can comprise other materials (e.g., textiles, polymeric materials, and the like). The absence of such materials can significantly reduce abrasion and wear of the leaflet material. 
     The vertical tab extension  342  may have a length L 2  (see  FIG.  8   ), and the tabs  338  may have a thickness t 1  (see  FIG.  9 B ). According to some embodiments, the length L 2  of the vertical tab extension  342  is greater than the length L 1  of the vertical tab extension  242 . According to some embodiments, the length L 2  of the vertical tab extension  342  is at least as great as the width W 2  of the lateral tab portion  340 . According to some embodiments, the length L 2  of the vertical tab extension  342  is at least as great as 200% of the width W 1  of the lateral tab portion  340 . According to some embodiments, the length L 2  of the vertical tab extension  342  is at least as great as the sum of 200% of the width W 1  of the lateral tab portion  340 , and 200% of the thickness t 1  of the tab  238 . 
     As shown in  FIGS.  9 A- 9 B , two adjacent tabs  338   a  and  338   b  of respective leaflets  332   a  and  332   b , may be secured to each other such that the vertical tab extension  342  is wrapped around both lateral tab portions  340   a  and  340   b  of the commissure  344 . More specifically, the vertical tab extension  342  may be folded over the adjacent lateral tab portion  340   b , and then further folded backward over the lateral tab portion  340   a  it extends from. 
     Once in the folded position shown in  FIGS.  9 A- 9 B , a suture  156  may be used to stitch all four layers, including both folded portions of the vertical tab extension  342 , the lateral tab portion  340   b , the lateral tab portion  340   a , together. It is noted that suture  156  is used by way of illustration and not limitation, and that other securement means may be used to attach the four layers to each other. Moreover, more than one suture  156  may be used, and while shown to pass through the layers in an in-and-out pattern, any other stitching pattern is contemplated. 
     As shown in  FIG.  9 A , the folded vertical tab extension  342  of the commissure assembly  344  is positioned radially inward with respect to the frame  106 . The remaining portions of the lateral tab portions  340  extending beyond the vertical tab extension  242 , including the lateral outer portion  341 , may project radially outward through a commissure window  170 , and a wedge  148  may be disposed between the portions of the lateral tab portion  340  at the radially outer side of the commissure window  170 . While not shown explicitly, a cloth ( 152 ) may be used to cover the wedge  148  and portions of the lateral tab portion  340 . However, even when a cloth is used to further cover and assist in attachment of components of a commissure assemble  344 , the cloth will not extend radially inward beyond the inner edges of the vertical tab extension  342 , so as to avoid potential contact between the moving portions of the leaflets  332  and the cloth, thereby minimizing or eliminating risk of leaflet abrasion. 
     It will be appreciated that placement of the commissure assemblies  244  and  344  within commissure windows  170  of axially extending window frame portions  112 , as shown throughout the Figures, is show by way of illustration and not limitation, and that commissure assemblies  244 ,  344  comprising tabs  238 ,  338  with at least one vertical tab extension  242 ,  342 , secured to each other, may be used in combination with any other commissure attachment configuration known in the art, to secure commissures to a frame of a prosthetic valve. For example, the lateral tab portion  240 ,  340 , including lateral outer portions  241 ,  341  thereof, can be folded over or wrapped around vertical strut portions of a frame, and/or around commissure posts or rods attached to a frame. Similarly, commissure windows may be formed not only within integral structures of the frame, such as axially extending window frame portions ( 112 ), but may be similarly formed by clip members attached to the frame, and/or within outflow portions of expansion and locking assemblies of mechanically expandable valves. 
     Additional Examples of the Disclosed Technology 
     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. A prosthetic valve, comprising: 
     a frame movable between a radially compressed configuration and a radially expanded configuration, and 
     a leaflet assembly mounted within the frame and comprising a plurality of leaflets configured to regulate flow through the prosthetic valve, wherein each leaflet comprises a pair of oppositely-directed tabs, wherein each of the tabs comprises a lateral tab portion, and wherein at least one of the tabs of each leaflet comprises a vertical tab extension extending at a non-zero angle from the lateral tab portion; 
     wherein each leaflet is asymmetrical with respect to a leaflet central axis thereof; and 
     wherein the at least one vertical tab extension of each leaflet is folded over a lateral tab portion of an adjacent leaflet to form a plurality of annularly spaced commissure assemblies of the leaflet assembly. 
     Example 2. The prosthetic valve of any example herein, particularly example 1, wherein the vertical tab portions of all commissure assemblies are positioned radially inward with respect to the frame. 
     Example 3. The prosthetic valve of any example herein, particularly any one of examples 1 to 2, wherein the at least one vertical tab extension is orthogonal with respect to the lateral tab portion it extends from. 
     Example 4. The prosthetic valve of any example herein, particularly any one of examples 1 to 2, wherein each leaflet comprises two vertical tab extensions, extending from both lateral tab portions in opposite vertical directions with respect to each other. 
     Example 5. The prosthetic valve of any example herein, particularly example 4, wherein each vertical tab extension of two adjacent vertical tab extensions within each commissure assembly, is folded over a lateral tab portion of an adjacent leaflet of the same commissure assembly. 
     Example 6. The prosthetic valve of any example herein, particularly example 5, wherein at least one suture is stitched through both vertical tab extensions and both lateral tab portions of each commissure assembly, in an in and out pattern. 
     Example 7. The prosthetic valve of any example herein, particularly any one of examples 4 to 6, wherein the length of both vertical tab extensions of each leaflet is identical. 
     Example 8. The prosthetic valve of any example herein, particularly any one of examples 1 to 7, wherein the length of the at least one vertical tab extension is at least as great as 50% of the width of the lateral tab portion. 
     Example 9. The prosthetic valve of any example herein, particularly any one of examples 1 to 7, wherein the length of the at least one vertical tab extension is at least as great as the width of the lateral tab portion. 
     Example 10. The prosthetic valve of any example herein, particularly any one of examples 1 to 7, wherein the length of the at least one vertical tab extension is at least as great as the sum of the width of the lateral tab portion and the thickness of the tab. 
     Example 11. The prosthetic valve of any example herein, particularly any one of examples 1 to 4, wherein each leaflet comprises a single vertical tab extension, vertically extending from one of the lateral tab portions. 
     Example 12. The prosthetic valve of any example herein, particularly example 11, wherein each vertical tab extension within each commissure assembly, is folded over a lateral tab portion of an adjacent leaflet of the same commissure assembly, and folded back over the lateral tab portion from which the vertical tab extension is extending. 
     Example 13. The prosthetic valve of any example herein, particularly example 12, wherein at least one suture is stitched through both folded portions of the vertical tab extension and both lateral tab portions of each commissure assembly, in an in and out pattern. 
     Example 14. The prosthetic valve of any example herein, particularly any one of examples 1 to 3 or 11 to 13, wherein the length of the at least one vertical tab extension is at least as great as 200% of the width of the lateral tab portion. 
     Example 15. The prosthetic valve of any example herein, particularly any one of examples 1 to 3 or 11 to 13, wherein the length of the at least one vertical tab extension is at least as great as the sum of 200% of the width of the lateral tab portion and 200% of the thickness of the tab. 
     Example 16. The prosthetic valve of any example herein, particularly any one of examples 1 to 15, wherein each leaflet is cut from bovine pericardium. 
     Example 17. A leaflet assembly comprising: 
     a plurality of leaflets, wherein each leaflet comprises:
         a pair of oppositely-directed tabs, wherein each of the tabs comprises a lateral tab portion, and wherein at least one of the tabs of each leaflet comprises a vertical tab extension extending at a non-zero angle from the lateral tab portion;       

     wherein each leaflet is asymmetrical with respect to a leaflet central axis thereof; and 
     wherein the at least one vertical tab extension of each leaflet is folded over a lateral tab portion of an adjacent leaflet to form a plurality of annularly spaced commissure assemblies of the leaflet assembly. 
     Example 18. The leaflet assembly of any example herein, particularly example 17, wherein the at least one vertical tab extension is orthogonal with respect to the lateral tab portion it extends from. 
     Example 19. The leaflet assembly of any example herein, particularly any one of examples 17 to 18, wherein each leaflet comprises two vertical tab extensions, extending from both lateral tab portions in opposite vertical directions with respect to each other. 
     Example 20. The leaflet assembly of any example herein, particularly example 19, wherein each vertical tab extension of two adjacent vertical tab extensions within each commissure assembly, is folded over a lateral tab portion of an adjacent leaflet of the same commissure assembly. 
     Example 21. The leaflet assembly of any example herein, particularly example 20, wherein at least one suture is stitched through both vertical tab extensions and both lateral tab portions of each commissure assembly, in an in and out pattern. 
     Example 22. The leaflet assembly of any example herein, particularly any one of examples 19 to 21, wherein the length of both vertical tab extensions of each leaflet is identical. 
     Example 23. The leaflet assembly of any example herein, particularly any one of examples 17 to 22, wherein the length of the at least one vertical tab extension is at least as great as 50% of the width of the lateral tab portion. 
     Example 24. The leaflet assembly of any example herein, particularly any one of examples 17 to 22, wherein the length of the at least one vertical tab extension is at least as great as the width of the lateral tab portion. 
     Example 25. The leaflet assembly of any example herein, particularly any one of examples 17 to 22, wherein the length of the at least one vertical tab extension is at least as great as the sum of the width of the lateral tab portion and the thickness of the tab. 
     Example 26. The leaflet assembly of any example herein, particularly any one of examples 17 to 18, wherein each leaflet comprises a single vertical tab extension, vertically extending from one of the lateral tab portions. 
     Example 27. The leaflet assembly of any example herein, particularly example 26, wherein each vertical tab extension within each commissure assembly, is folded over a lateral tab portion of an adjacent leaflet of the same commissure assembly, and folded back over the lateral tab portion from which the vertical tab extension is extending. 
     Example 28. The leaflet assembly of any example herein, particularly example 27, wherein at least one suture is stitched through both folded portions of the vertical tab extension and both lateral tab portions of each commissure assembly, in an in and out pattern. 
     Example 29. The leaflet assembly of any example herein, particularly any one of examples 17 to 18 or 26 to 28, wherein the length of the at least one vertical tab extension is at least as great as 200% of the width of the lateral tab portion. 
     Example 30. The leaflet assembly of any example herein, particularly any one of examples 17 to 18 or 26 to 28, wherein the length of the at least one vertical tab extension is at least as great as the sum of 200% of the width of the lateral tab portion and 200% of the thickness of the tab. 
     Example 31. The leaflet assembly of any example herein, particularly any one of examples 17 to 30, wherein each leaflet is cut from bovine pericardium. 
     Example 32. A method of assembling a leaflet assembly, comprising the steps of: 
     providing a plurality of asymmetrical leaflets, wherein each leaflet comprises a pair of oppositely-directed tabs, wherein each of the tabs comprises a lateral tab portion, and wherein at least one of the tabs of each leaflet comprises a vertical tab extension extending at a non-zero angle from the lateral tab portion; and 
     folding a vertical tab extension of one of the leaflets over a lateral tab portion of an adjacent leaflet to form a plurality of annularly spaced commissure assemblies of the leaflet assembly. 
     Example 33. The method of any example herein, particularly example 32, wherein at least one vertical tab extension is orthogonal with respect to the lateral tab portion it extends from. 
     Example 34. The method of any example herein, particularly any one of examples 32 to 33, wherein each leaflet comprises two vertical tab extensions, extending from both lateral tab portions in opposite vertical directions with respect to each other. 
     Example 35. The method of any example herein, particularly example 34, wherein the step of folding vertical tab extension of one of the leaflets over a lateral tab portion of an adjacent leaflet, comprises folding each vertical tab extension of two adjacent vertical tab extensions within each commissure assembly, over a lateral tab portion of an adjacent leaflet of the same commissure assembly. 
     Example 36. The method of any example herein, particularly example 35, further comprising a step of stitching a suture through both vertical tab extensions and both lateral tab portions of each commissure assembly. 
     Example 37. The method of any example herein, particularly example 36, wherein the stitching is performed in an in and out pattern. 
     Example 38. The method of any example herein, particularly any one of examples 35 to 37, wherein the length of both vertical tab extensions of each leaflet is identical. 
     Example 39. The method of any example herein, particularly any one of examples 32 to 38, wherein the length of the at least one vertical tab extension is at least as great as 50% of the width of the lateral tab portion. 
     Example 40. The method of any example herein, particularly any one of examples 32 to 38, wherein the length of the at least one vertical tab extension is at least as great as the width of the lateral tab portion. 
     Example 41. The method of any example herein, particularly any one of examples 32 to 38, wherein the length of the at least one vertical tab extension is at least as great as the sum of the width of the lateral tab portion and the thickness of the tab. 
     Example 42. The method of any example herein, particularly any one of examples 32 to 33, wherein each leaflet comprises a single vertical tab extension, vertically extending from one of the lateral tab portions. 
     Example 43. The method of any example herein, particularly example 42, wherein the step of folding vertical tab extension of one of the leaflets over a lateral tab portion of an adjacent leaflet, comprises folding each vertical tab extension within each commissure assembly, a lateral tab portion of an adjacent leaflet of the same commissure assembly, and then folding it back over the lateral tab portion from which the vertical tab extension is extending. 
     Example 44. The method of any example herein, particularly example 43, further comprising a step of stitching a suture through both folded portions of the vertical tab extension and both lateral tab portions of each commissure assembly. 
     Example 45. The method of any example herein, particularly example 44, wherein the stitching is performed in an in and out pattern. 
     Example 46. The method of any example herein, particularly any one of examples 32 to 33 or 42 to 45, wherein the length of the at least one vertical tab extension is at least as great as 200% of the width of the lateral tab portion. 
     Example 47. The method of any example herein, particularly any one of examples 32 to 33 or 42 to 45, wherein the length of the at least one vertical tab extension is at least as great as the sum of 200% of the width of the lateral tab portion and 200% of the thickness of the tab. 
     Example 48. The method of any example herein, particularly any one of examples 32 to 47, wherein each leaflet is cut from bovine pericardium. 
     Example 49. The method of any example herein, particularly any one of examples 32 to 48, wherein further comprising a step of mounting the leaflet assembly within a frame of a prosthetic valve. 
     Example 50. The method of any example herein, particularly example 49, wherein the step of mounting comprises positioning the vertical tab portions of all commissure assemblies radially inward with respect to the frame. 
     It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable sub-combination or as suitable in any other described embodiment of the invention. No feature described in the context of an embodiment is to be considered an essential feature of that embodiment, unless explicitly specified as such. 
     In view of the many possible embodiments to which the principles of the disclosure may be applied, it should be recognized that the illustrated embodiments are only preferred examples and should not be taken as limiting the scope. Rather, the scope is defined by the following claims. We therefore claim all that comes within the scope and spirit of these claims.