Patent Publication Number: US-2021177583-A1

Title: Prosthetic valve with improved washout

Description:
FIELD 
     The present disclosure relates generally to prosthetic valves and more specifically flexible leaflet-type prosthetic heart valve devices. 
     BACKGROUND 
     Prosthetic valves are used to replace natural valves in a cardiovascular system when the natural valve no longer functions properly. A flexible leaflet prosthetic valve comprises one or more leaflets that move under the influence of fluid pressure. 
     Prosthetic leaflets are attached to a support structure to form a valve. In operation, the flexible leaflets open when the inflow fluid pressure exceeds the outflow fluid pressure and close when the inflow fluid pressure drops below the outflow fluid pressure. The free edges of the leaflets coapt under the influence of outflow fluid pressure closing the valve to prevent outflow blood from flowing retrograde through the valve.  FIGS. 1A and 1B  are perspective and axial views, respectively, of a closed prosthetic valve  10  that includes a frame  20  that supports leaflets  30 , in accordance to what is known in the art. The closed prosthetic valve  10  represents when the outflow pressure downstream of the prosthetic valve  10  is greater than the inflow pressure upstream of the prosthetic valve  10 , wherein the leaflets  30  close to prevent regurgitant flow through the prosthetic valve  10 . 
       FIGS. 1C and 1D  are a perspective view and axial view, respectively, of the prosthetic valve  10  where the leaflets  30  are open such as when the inflow pressure upstream of the prosthetic valve  10  is greater than the outflow pressure, wherein the leaflets  30  open to allow fluid to proceed in the forward flow direction  402  through the prosthetic valve  100 . 
       FIGS. 1E and 1F  are cross-sectional views of the closed prosthetic valve  10  of  FIG. 1B  along outline  1 E- 1 E and the open prosthetic valve  10  of  FIG. 1D  along cut line  1 F- 1 F, respectively.  FIG. 1E  shows the retrograde flow direction  404  where the outflow pressure of the prosthetic valve  10  is greater than the inflow pressure thus closing the leaflet  30 .  FIG. 1F  shows the fluid moving in the forward flow direction  402  through the prosthetic valve  10  where the inflow pressure is greater than the outflow pressure thus opening the flexible leaflet  30  away from the valve axis X. Behind the leaflet  30  the fluid follows a recirculating direction, referred to as recirculating flow  406 , including flow in the retrograde flow direction  404  between the leaflet  30  and a structure behind the leaflet  30 , such as, but not limited to, the frame  20 , a prosthetic conduit, and native tissue. 
     The lack of or insufficient fluid in the retrograde flow direction  404  or recirculating flow  406  can result in the fluid flow slowing or stagnating behind the leaflet  30  and in particular, at the leaflet base  308  where the leaflet  30  intersects the frame  20 . The slowing or stagnation of fluid flow is known to cause the blood to clot and form thrombus. Thrombus is detrimental in that it can hinder the leaflet  30  opening and closing dynamics which in turn leads to increased pressure gradients that negatively affect valve performance. Thrombus may also flow downstream which can lead to stroke, heart attack or pulmonary embolism. 
     There remains a need for a prosthetic valve that reduces or eliminates the reduced or stagnated flow behind an open prosthetic valve leaflet. 
     SUMMARY 
     Described embodiments are directed to apparatus, system, and methods for valve replacement, such as cardiac valve replacement. More specifically, described embodiments are directed toward flexible leaflet valve devices having biological or synthetic leaflet material and a support structure, and methods of making and implanting the valve devices. 
     According to one example (Example 1), a valve having a leaflet moveable between an open position that permits antegrade flow through the prosthetic valve and a closed position that prevents regurgitant flow through the prosthetic valve, the leaflet comprising an aperture or gap, or a separation of portions of the leaflet to allow a flow or exchange of fluid between the front and back of the leaflet, when the leaflet is not in the closed position. 
     According to another example (Example 2), further to Example 1, the aperture, gap or separation is operable to close to prevent flow of exchange of fluid between the back and the front of the leaflet, when the leaflet is in the closed position. 
     According to another example (Example 3), further to Examples 1 or 2, comprising a support structure, wherein the leaflet is coupled to the support structure. 
     According to another example (Example 4), further to of Examples 1-3, the leaflet includes a first leaflet component and a second leaflet component. 
     According to another example (Example 5), further to Example 4, the first leaflet component is upstream of the second leaflet component, or wherein the first leaflet component is downstream of the second leaflet component. 
     According to another example (Example 6), further to Examples 4 or 5, said flow or exchange of fluid is via an aperture, gap or separation of the first and second components, when the leaflet is not in the closed position. 
     According to another example (Example 7), further to any one of Examples 4 to 6, and in accordance with Example 1, the second leaflet component comprises an inflow free edge; and defines a gap between the second leaflet component and the support structure. 
     According to another example (Example 8), further to any one of Examples 4 to 7, the first leaflet component or the second leaflet component defines an aperture therethrough; and wherein the other of the first leaflet component or the second leaflet component is operable to occlude the aperture. 
     According to another example (Example 9), further to any one of Examples 4 to 8, the first leaflet component and the second leaflet component partially overlap. 
     According to another example (Example 10), further to Example 9, the first leaflet component comprises a first overlap region and the second leaflet component comprises a second overlap region; wherein the first and second overlap regions are in sealing engagement with one another, when the leaflet is in the closed position. 
     According to another example (Example 11), further to Example 10, the first and second overlap regions each extend from a free edge of the respective first and second leaflet component. 
     According to another example (Example 12), further to Example 11, the first overlap region extends from an outflow free edge of the first leaflet component and the second overlap region extends from an inflow free edge of the second leaflet component. 
     According to another example (Example 13), further to any one of Examples 10 or 11, the first leaflet component comprises apertures in the first overlap region, or wherein the second leaflet component comprises apertures in the second overlap region. 
     According to another example (Example 14), further to any one of Examples 4 to 13, the first leaflet component is stationary relative to the second leaflet component, or vice versa. 
     According to another example (Example 15), further to any one of Examples 4 to 13, and in accordance with Example 3, the first leaflet component, or the second leaflet component is stationary relative to the support structure. 
     According to another example (Example 16), further to any one of Examples 4 to 13, the first leaflet component is configured to move more slowly than the second leaflet component. 
     According to another example (Example 17), further to Example 16, the first leaflet component has a higher bending stiffness than the second leaflet component. 
     According to another example (Example 18), further to any one of Examples 16 or 17, the first leaflet component is upstream of the second leaflet component. 
     According to another example (Example 19), further to any one of Examples 4 to 13, the second leaflet component is configured to move more slowly than the first leaflet component. 
     According to another example (Example 20), further to Example 19, the second leaflet component has a higher bending stiffness than the first leaflet component. 
     According to another example (Example 21), further to any one of Examples 19 or 20, the second leaflet component is upstream of the first leaflet component. 
     According to another example (Example 22), further to any one of Examples 9 to 21, and in accordance with Example 3, the first and second leaflet components overlap and define an overlap region which tapers in width towards the support structure. 
     According to another example (Example 23), further to Example 22, when the leaflet is in the closed position, there is a regurgitant gap or gaps of a predetermined size between the first and second leaflet components, extending away from the support structure. 
     According to another example (Example 24), further to any one of Examples 1-23, the leaflet comprises multiple apertures, gaps or separations of portions of the leaflet, to allow a flow or exchange of fluid between the front and back of the leaflet, when the leaflet is not in the closed position. 
     According to another example (Example 25), further to any one of Examples 4 to 23, the leaflet comprises multiple first leaflet components and/or wherein the leaflet comprises a first leaflet component comprising multiple outflow free edges. 
     According to another example (Example 26), further to Example 25, further includes a tether element which couples the multiple first leaflets or multiple outflow free edges to tether element may prevent prolapse. 
     According to another example (Example 27), further to any one of Examples 25 or 26, in further of example 3, the second leaflet component comprises multiple inflow free edges, defining multiple gaps between the second leaflet component and the support structure, corresponding to one of the said multiple first leaflet components or outflow free edges. 
     According to another example (Example 28), further to any one of Examples 24 to 26, the second leaflet component defines multiple apertures therethrough, wherein the first leaflet component is operable to occlude the apertures, or wherein one said multiple first leaflet components is operable to occlude each said aperture. 
     According to another example (Example 29), further to any one of Examples 1-28, wherein the shape of the shape of the leaflet, and, and in further of Example 3, the shape of a corresponding attachment region to a support structure, is generally that of a parabola or of an isosceles trapezoid. 
     According to another example (Example 30), further to any one of Examples 1-23, the leaflet comprises a porous polymer membrane and a material present in pores of the porous polymer membrane such that the or each leaflet is impermeable. 
     According to another example (Example 31), further to Examples 30, the porous polymer membrane is expanded polytetrafluoroethylene. 
     According to another example (Example 32), further to any one of Examples 30 or 31, the material present in the pores is an elastomer or an elastomeric material or a non-elastomeric material. 
     According to another example (Example 33), further to any one of Examples 30 to 32, the material present in the pores is a TFE/PMVE copolymer. 
     According to another example (Example 34), further to any one of Examples 1-33, the leaflet comprises a biological tissue. 
     According to another example (Example 35), further to any one of Examples 30 to 34, the leaflet comprises when in further of any one of Examples 4 to 13, wherein the or each first leaflet component and/or the second leaflet component comprises said porous polymer membrane and a material present in pores of the porous polymer membrane such that the or each first leaflet component and/or the second leaflet component is impermeable. 
     According to another example (Example 36), further to Example 35, wherein at least one of the first leaflet component and the second leaflet component comprises a biological tissue. 
     According to another example (Example 37), further to any one of Examples 1-36, the leaflet is coupled to a support structure in the form of a frame. 
     According to another example (Example 38), further to Example 38, the frame defines a generally open pattern of apertures operable to allow the frame to be compressed and expanded between different diameters. 
     According to another example (Example 39), further to any one of Examples 1 to 38, comprising a plurality of leaflets. 
     According to another example (Example 40), further to Example 39, comprising valve may comprise three leaflets. 
     According to another example (Example 41), further to any one of Examples 39 or 40, wherein each leaflet comprises a leaflet free edge, wherein leaflet free edges may coapt under the influence of retrograde fluid pressure; thereby closing the valve. 
     According to another example (Example 42), further to any one of Examples 1 to 41, wherein the valve is a prosthetic valve. 
     According to another example (Example 43), further to Examples 42, wherein the prosthetic valve is a prosthetic heart valve. 
     The foregoing Examples are just that, and should not be read to limit or otherwise narrow the scope of any of the inventive concepts otherwise provided by the instant disclosure. 
     According to another example (Example 44), a method of making a prosthetic valve, comprising: obtaining a support structure such as a leaflet frame or conduit, obtaining a leaflet including a first leaflet component and a second leaflet component; coupling the first leaflet component adjacent to an inlet portion of the support structure; and coupling the second leaflet component adjacent to an outlet portion of the support structure such that a second overlap region of a second inflow free edge of the second leaflet component overlaps a first overlap region of a first outflow free edge of the first leaflet component such that a portion of a second inflow side of the second leaflet component is in contact and in sealing engagement with a portion of a first outflow side of the first leaflet component when the leaflet is in a closed position defining a leaflet overlap region preventing fluid flow through a lumen in a retrograde direction, and wherein the first overlap region and the second overlap region are not in contact therewith wherein the first outflow free edge and the second inflow free edge define a gap therebetween when the leaflet is not in the closed position, wherein fluid adjacent a second outflow side can pass through the gap during fluid flow in a forward direction. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings are included to provide a further understanding of the present disclosure and are incorporated in and constitute a part of this specification, illustrate embodiments described herein, and together with the description serve to explain the principles discussed in this disclosure. 
         FIG. 1A  is a perspective view of a closed prosthetic valve that includes a frame that supports leaflets, in accordance to what is known in the art; 
         FIG. 1B  is an axial view of the closed prosthetic valve of  FIG. 1A  that includes a frame that supports leaflets, in accordance to what is known in the art; 
         FIG. 1C  is a perspective view of the prosthetic valve of  FIG. 1A  where the leaflets are open such as when the inflow pressure upstream of the prosthetic valve is greater than the outflow pressure, in accordance to what is known in the art; 
         FIG. 1D  is an axial view of the prosthetic valve of  FIG. 1C  where the leaflets are open such as when the outflow pressure upstream of the prosthetic valve is greater than the outflow pressure, wherein the leaflets open to allow forward flow through the prosthetic valve, in accordance to what is known in the art; 
         FIG. 1E  is a cross-sectional view of the closed valve of  FIG. 1B  along cutline  1 E- 1 E, in accordance to what is known in the art; 
         FIG. 1F  is a cross-sectional view of the open valve of  FIG. 1D  along cutline  1 F- 1 F, in accordance to what is known in the art; 
         FIG. 2A  is a perspective view of a prosthetic valve in a closed position, in accordance with an embodiment; 
         FIG. 2B  is an axial view of the prosthetic valve of  FIG. 2A  in a closed position, in accordance with an embodiment; 
         FIG. 2C  is a perspective view of the prosthetic valve of  FIG. 2A  in an open position, in accordance with an embodiment; 
         FIG. 2D  is an axial view of the prosthetic valve  FIG. 2C  in an open position, in accordance with an embodiment; 
         FIG. 2E  is a cross-sectional view of the closed valve of  FIG. 2B  along cutline  2 E- 2 E, in accordance with an embodiment; 
         FIG. 2F  is a cross-sectional view of the open valve of  FIG. 2D  along cutline  2 F- 2 F, in accordance with an embodiment; 
         FIG. 3A  is perspective view of a prosthetic valve, in accordance with another embodiment; 
         FIG. 3B  is an axial view of the prosthetic valve of  FIG. 3A  in a closed position, in accordance with an embodiment; 
         FIG. 3C  is a perspective view of the prosthetic valve of  FIG. 3A  in an open position, in accordance with an embodiment; 
         FIG. 3D  is an axial view of the prosthetic valve  FIG. 3C  in an open position, in accordance with an embodiment; 
         FIG. 3E  is a cross-sectional view of the closed valve of  FIG. 3B  along cutline  3 E- 3 E, in accordance with an embodiment; 
         FIG. 3F  is a cross-sectional view of the open valve of  FIG. 3D  along cutline  3 F- 3 F, in accordance with an embodiment; 
         FIG. 4A  is perspective view of a prosthetic valve, in accordance with another embodiment; 
         FIG. 4B  is an axial view of the prosthetic valve of  FIG. 4A  in a closed position, in accordance with an embodiment; 
         FIG. 4C  is a perspective view of the prosthetic valve of  FIG. 4A  in an open position, in accordance with an embodiment; 
         FIG. 4D  is an axial view of the prosthetic valve  FIG. 4C  in an open position, in accordance with an embodiment; 
         FIG. 4E  is a cross-sectional view of the closed valve of  FIG. 4B  along cutline  4 E- 4 E, in accordance with an embodiment; 
         FIG. 4F  is a cross-sectional view of the open valve of  FIG. 4D  along cutline  4 F- 4 F, in accordance with an embodiment; 
         FIG. 5  is a perspective view of a prosthetic valve wherein the leaflet overlap region has a non-uniform width, in accordance with an embodiment; 
         FIG. 6A  is a perspective view of a prosthetic valve having a frame and a plurality of leaflets each having a first leaflet component and a second leaflet component defining a shape substantially that of an isosceles trapezoid, in accordance with an embodiment; 
         FIG. 6B  is a perspective view of a prosthetic valve having a frame and a plurality of leaflets each having a first leaflet component and a second leaflet component defining a shape substantially that of an isosceles trapezoid, in accordance with an embodiment; 
         FIG. 7  is a plan view of the frame of the embodiment of  FIGS. 6A and 6B  unrolled to a flat profile; 
         FIG. 8  is a plan view of a leaflet pattern comprising a plurality of first leaflet components and second leaflet components, in accordance with an embodiment; 
         FIG. 9  is a plan view of a leaflet pattern comprising a plurality of first leaflet components, in accordance with an embodiment; 
         FIG. 10  is a plan view of a leaflet pattern comprising a plurality of second leaflet components, in accordance with an embodiment; 
         FIG. 11A  is a perspective view a prosthetic valve having a frame and a plurality of leaflets each having a plurality of first leaflet components that overlap the second inflow side of a second leaflet component, in accordance with an embodiment; 
         FIG. 11B  is a perspective view a prosthetic valve having a frame and a plurality of leaflets each having a plurality of first leaflet components that overlap the second outflow side of a second leaflet component, in accordance with another embodiment; 
         FIG. 11C  is a cross-sectional view along cut-line  110  of the embodiment of  FIG. 11B  when the leaflet is in the closed position; 
         FIG. 11D  is a cross-sectional view along cut-line  110  of the embodiment of  FIG. 11B  when the leaflet is in the open position; 
         FIG. 12A  is a plan view of a leaflet pattern comprising a plurality of first leaflet components, in accordance with an embodiment; 
         FIG. 12B  is a plan view of a leaflet pattern comprising a plurality of first leaflet components, in accordance with an embodiment; 
         FIG. 12C  is a plan view of a leaflet pattern comprising a plurality of first leaflet components, in accordance with an embodiment; 
         FIG. 13  is a plan view of a leaflet pattern comprising a plurality of second leaflet components, in accordance with an embodiment; 
         FIG. 14  is a prosthetic valve with a second leaflet component with a relatively narrow strip that attaches as the base of the frame, in accordance with an embodiment; 
         FIG. 15  is another prosthetic valve similar to the embodiment of  FIG. 14  that includes one first leaflet component that overlaps both second inflow free edges, in accordance with another embodiment; 
         FIG. 16A  is perspective view of a prosthetic valve, in accordance with another embodiment; 
         FIG. 16B  is an axial view of the prosthetic valve of  FIG. 16A  in a closed position, in accordance with an embodiment; 
         FIG. 16C  is a perspective view of the prosthetic valve of  FIG. 16A  in an open position, in accordance with an embodiment; 
         FIG. 16D  is an axial view of the prosthetic valve  FIG. 16C  in an open position, in accordance with an embodiment; 
         FIG. 16E  is a cross-sectional view of the closed valve of  FIG. 16B  along cutline  16 E- 16 E, in accordance with an embodiment; 
         FIG. 16F  is a cross-sectional view of the open valve of  FIG. 16D  along cutline  16 F- 16 F, in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Persons skilled in the art will readily appreciate that various aspects of the present disclosure can be realized by any number of methods and apparatus configured to perform the intended functions. Stated differently, other methods and apparatus can be incorporated herein to perform the intended functions. It should also be noted that the accompanying drawing figures referred to herein are not necessarily drawn to scale, but may be exaggerated to illustrate various aspects of the present disclosure, and in that regard, the drawing figures should not be construed as limiting. 
     Although the embodiments herein may be described in connection with various principles and beliefs, the described embodiments should not be bound by theory. For example, embodiments are described herein in connection with prosthetic valves, more specifically cardiac prosthetic valves. However, embodiments within the scope of this disclosure can be applied toward any valve or mechanism of similar structure and/or function. Furthermore, embodiments within the scope of this disclosure can be applied in non-cardiac applications. 
     The term “leaflet” as used herein in the context of prosthetic valves is a flexible component of a one-way valve wherein the leaflet is operable to move between an open and closed position under the influence of a pressure differential. In an open position, the leaflet allows blood to flow through the valve. In a closed position, the leaflet substantially blocks retrograde flow from passing through the valve. In embodiments comprising multiple leaflets, each leaflet cooperates with at least one neighboring leaflet to block the retrograde flow from becoming regurgitant. The pressure differential in the blood is caused, for example, by the contraction of a ventricle or atrium of the heart, or the drainage of blood from the ventricle or atrium. As the pressure on the inflow side of the valve rises above the pressure on the outflow side of the valve, the leaflets are caused to open and blood flows therethrough. As blood flows through the valve into a neighboring chamber or blood vessel, the pressure on the inflow side equalizes with the pressure on the outflow side. As the pressure on the inflow side of the valve drops below the pressure on the outflow side of the valve, the leaflets are caused to return to the closed position generally preventing regurgitant flow of blood through the valve. 
     As used herein, “inflow fluid pressure” refers to a fluid pressure at an upstream location of the valve. “Outflow fluid pressure” refers to a fluid pressure at a downstream location of the valve. 
     As used herein, “retrograde” and “retrograde flow” refers to fluid flow at a downstream location of the valve that is moving toward the valve. Retrograde flow may be encountered, by way of example, but not limited to, in turbulent or recirculatory flow that is downstream of the valve, and during the pressure transition of the inflow fluid pressure dropping below the outflow fluid pressure tending to change the flow pattern away from a forward flow direction. 
     As used herein, “regurgitant”, “regurgitation”, and “regurgitant flow” refers to flow through a valve when the leaflets are in the close position. A valve that is exhibiting regurgitation is commonly said to be leaking. Regurgitant flow is differentiated from retrograde flow in that regurgitant flow is fluid flow that passes through the valve from a downstream location to an upstream location whereas retrograde flow is flow in a downstream location that does not necessarily pass through the valve. 
     The term “biocompatible material” as used herein generically refers to any material with biocompatible characteristics including synthetic, such as, but not limited to, a biocompatible polymer, or a biological material, such as, but not limited to, human, bovine, and pig tissue. 
     The terms “native valve” orifice and “tissue orifice” refer to an anatomical structure into which a prosthetic valve can be placed. Such anatomical structure includes, but is not limited to, a location wherein a cardiac valve may have been surgically removed. It is understood that other anatomical structures that can receive a prosthetic valve include, but are not limited to, veins, arteries, ducts and shunts. It is further understood that a valve orifice or implant site may also refer to a location in a synthetic or biological conduit that may receive a valve. 
     As used herein, “couple” means to join, connect, attach, adhere, affix, or bond, whether directly or indirectly, and whether permanently or temporarily. 
     Embodiments herein include various apparatus, systems, and methods for a prosthetic valve, such as, but not limited to, cardiac valve replacement devices. The valve is operable as a one-way valve wherein the valve defines a valve orifice into which one or more flexible leaflets open to permit flow and close so as to occlude the valve orifice and prevent regurgitant flow in response to a differential fluid pressure. In accordance with embodiments, the leaflet is configured so as to increase the motion of fluid behind an open leaflet so as, but not limited to, reducing the likelihood of fluid stagnation and potential thrombus formation behind the open leaflet. 
     In accordance with embodiments, each of the one or more flexible leaflets comprise a means for allowing a flow or exchange of fluid between the front and back of the leaflet when the leaflet is not in the closed position through the leaflet via an aperture, gap or separation of portions of the leaflet. This flow or exchange of fluid may include fluid from in front of the leaflet passing through the leaflet to the back of the leaflet which displaces the existing fluid that is behind the leaflet and keeps that fluid in motion. This exchange of fluid may also include fluid from behind the leaflet passing through the leaflet to the front of the leaflet which displaces the existing fluid that is behind the leaflet and keeps it in motion. 
     In accordance with embodiments, a prosthetic valve includes at least one leaflet and a support structure supporting the leaflet so that it may operate as a one-way valve. As described in the embodiments presented below, the support structure is described as a frame and used herein as an example, and used interchangeably with support structure. It is understood that other support structures are anticipated, including, but not limited to, conduits, that are operable to support the leaflet for its intended function. 
       FIGS. 2A and 2B  are perspective and axial views, respectively, of a prosthetic valve  100  in a closed position, in accordance with an embodiment.  FIGS. 2C and 2D  are perspective and axial views, respectively, of the prosthetic valve  100  in an open position, in accordance with an embodiment.  FIGS. 2E and 2F  are cross-sectional views of the closed prosthetic valve  100  of  FIG. 2B  along cutline  2 E- 2 E and of the prosthetic valve  100  of  FIG. 2D  along cutline  2 F- 2 F, respectively. 
     Frame 
     As shown in  FIG. 2A , a frame  200  is operable to hold and support a plurality of leaflets  300 . The frame  200  is annular, that is, it defines a cylinder having a lumen  214  having an axis X and a plurality of commissure posts  210  extending parallel to the axis X that are spaced from one another. Between the commissure posts  210  is a leaflet attachment region  212  that is operable to couple with and support the leaflet  300  about a perimeter of the leaflet  300  except for a leaflet free edge  306 . 
     The frame  200  defines a cylinder having a frame inner side  202  and a frame outer side  204  opposite the frame inner side  202 . The frame  200  further defines a plurality of commissure posts  210 . 
     Although the frame  200  in the instant embodiment defines a cylinder of constant diameter along the axis X, it is understood that the diameter may vary along the axis X. Such variation may be advantageous, such as, but not limited to, to better fit the anatomy of the tissue orifice and adjacent upstream and downstream anatomy. Similarly, the frame  200  may not necessarily be circular along the axis X but, by way of example, but not limited thereto, may be oval and lobed. Such variation may be advantageous, such as, but not limited to, to better fit the anatomy of the tissue orifice and adjacent upstream and downstream anatomy, and/or to control the flow dynamics through the valve and around the leaflets. 
     In accordance with an embodiment, the frame  200  is annular about a central longitudinal axis X of the prosthetic valve  100  as shown in  FIGS. 2A-2D . The frame  200  has an inflow end  206  and an outflow end  208  opposite the inflow end  206  and defines a lumen  110  therebetween along an axis X. The frame  200  has at least one leaflet attachment region  212  for each leaflet  300 . The leaflet attachment region  212  has an inflow portion  232  and an outflow portion  234 . 
     The frame  200  can be etched, cut, laser cut, stamped, three-dimensional printed, among other suitable processes, into an annular structure or a sheet of material, with the sheet then formed into an annular structure. Wires and strands may also be used to form into an annular structure. 
     The frame  200  can comprise, such as, but not limited to, any metallic or polymeric material that is generally biocompatible. The frame  200  can comprise a shape-memory material, such as Nitinol, a nickel-titanium alloy. Other materials suitable for the frame  200  include, but not limited to, other titanium alloys, stainless steel, cobalt-nickel alloy, polypropylene, acetyl homopolymer, acetyl copolymer, other alloys or polymers, elastomers and elastomeric materials, other shape memory and/or superelastic materials, polymers, and composite materials, or any other material that is generally biocompatible having adequate physical and mechanical properties to function as a leaflet frame  200  as described herein. Suitable frames can be made from a variety of materials and need only be biocompatible or able to be made biocompatible. 
     It is appreciated that  FIG. 2A  shows a frame  200  that is operable to be used in a surgical procedure, wherein the frame  200  has a fixed diameter both pre- and post-implant. It is appreciated that the frame  200  may be configured for use in a transcatheter procedure, wherein the frame  200  can be expanded from a smaller pre-deployment diameter to a larger deployed diameter. 
     A wide variety of frames are known in the medical technology arts, and any suitable frame can be utilized. One requirement is that the frame provide a surface to which the leaflet can be attached and function as described herein. 
     As described below, in accordance with an embodiment, the frame has radially compressed and radially expanded configurations. Such a frame can be implanted at a point of treatment within a body vessel by minimally invasive techniques, such as delivery and deployment with an intravascular catheter. The frame can optionally provide additional function to the medical device. For example, the frame can provide a stenting function, i.e., exert a radially outward force on the interior wall of a vessel in which the medical device is implanted. By including a frame that exerts such a force, a medical device according to the invention can provide both a stenting and a valving function at a point of treatment within a body vessel. 
     The stent art provides numerous frames acceptable for use in the present invention, and any suitable stent can be used as the frame. The specific frame chosen will depend on numerous factors, including the body vessel in which the medical device is being implanted, the axial length of the treatment site within the vessel, the number of valves desired in the medical device, the inner diameter of the vessel, the delivery method for placing the medical device, and other considerations. Those skilled in the art can determine an appropriate frame based on these and other considerations. 
     The frame can be self-expandable or balloon expandable. The structural characteristics of both of these types of frames are known in the art, and are not detailed herein. Each type of frame has advantages and for any given application, one type may be more desirable than the other based on a variety of considerations. For example, in the peripheral vasculature, vessels are generally more compliant and typically experience dramatic changes in their cross-sectional shape during routine activity. Medical devices for implantation in the peripheral vasculature should retain a degree of flexibility to accommodate these changes of the vasculature. Accordingly, medical devices according to the invention intended for implantation in the peripheral vasculature, such as prosthetic venous valves, advantageously include a self-expandable frame. These frames, as is known in the art, are generally more flexible than balloon-expandable frames following deployment. 
     Suitable frames can also have a variety of shapes and configurations, including being comprised of wire, strands, braided strands, helically wound strands, ring members, consecutively attached ring members, zig-zag members, tubular members, and frames cut from solid tubes and flat sheets. Frames may define a generally open pattern of apertures operable to allow the frame to be compressed and expanded between different diameters, in accordance with embodiments. 
     Leaflet 
     As shown in  FIGS. 2A-2F , the leaflet  300  is coupled to each of the at least one leaflet attachment region  212  of the frame  200 . 
     The leaflet  300  includes a first leaflet component  310  and a second leaflet component  320 , in accordance with an embodiment. The first leaflet component  310  has a first inflow side  312  and a first outflow side  314  opposite the first inflow side  312  that defines a first thickness. The term “inflow side” is that side which is facing the inflow end  206  of the frame  200  when the leaflet  300  is in the closed position. The term “outflow side” is that side which is facing the outflow end  208  of the frame  200  when the leaflet  300  is in the closed position. The first leaflet component  310  has a first frame attachment edge  319  and a first outflow free edge  316 . 
     The second leaflet component  320  has a second inflow side  322  and a second outflow side  324  opposite the second inflow side  322  defining a second thickness. The second leaflet component  320  has a plurality of second frame attachment edges  329 , a second inflow free edge  327  and a second outflow free edge  326  opposite the second inflow free edge  327 . The second leaflet component  320  is configured to be movable between an open position to allow fluid flow in a forward flow direction through the lumen  214  and a closed position in cooperative engagement with the first leaflet component  310  that prevents regurgitant flow. 
     The first frame attachment edge  319  of the first leaflet component  310  is coupled to the inflow portion  232  of the leaflet attachment region  212  with the first inflow side  312  facing the axis X. The inflow portion  232  is that portion adjacent to the inflow end  206  of the frame  200 . 
     The second frame attachment edges  329  of the second leaflet component  320  is coupled to the outflow portion  234  of the leaflet attachment region  212  with the second inflow side  322  facing the axis X. The outflow portion  234  is that portion adjacent to the outflow end  208  of the frame  200 . 
     The first leaflet component  310  and the second leaflet component are arranged on the frame  200  such that they at least partially overlap. A second overlap region  325  adjacent to the second inflow free edge  327  overlaps a first overlap region  315  adjacent to the first outflow free edge  316  such that a portion of the second inflow side  322  of the second leaflet component  320  is in contact and in sealing engagement with a portion of the first outflow side  314  of the first leaflet component  310  when the leaflet  300  is in the closed position defining a leaflet overlap region  335  operable to prevent regurgitant flow through the leaflet  300  at the leaflet overlap region  335 , as shown in  FIG. 2E . 
     During fluid flow in the forward flow direction  402  when the leaflet  300  is not in the closed position, as shown in  FIG. 2F , when the inflow pressure is greater than the outflow pressure, the first overlap region  315  and the second overlap region  325  move away from each other wherein the first outflow free edge  316  and the second inflow free edge  327  define a gap  330  therebetween. The gap  330  formed between the first leaflet component  310  and the second leaflet component  320  when the leaflet  300  is not in the closed position allows fluid adjacent the first outflow side  314  and the second outflow side  324  to pass through the gap  330  when the fluid is moving in the forward flow direction  402  through the lumen  214 . That is, recirculating flow  406  from behind the leaflet  300  may pass through the gap  330  preventing the recirculating flow  406  from stagnating behind the leaflet  300 . Further, the gap  330  also allows fluid flow in the forward flow direction  402  to pass through the gap  330  from the first inflow side  312  and the second inflow side  322  further disrupting and displacing the recirculating flow  406  behind the leaflet  300  to downstream of the leaflet  300 . Thus, blood behind the leaflet  300  is less likely to clot or form thrombus, particularly at the leaflet base  308  and where it attaches to the frame  200 . 
     In accordance with an embodiment, the first leaflet component  310  is stationary relative to the second leaflet component  320  such that the gap  330  may be formed between the second leaflet component  320  moving away from the first leaflet component  310  under fluid pressure during fluid flow in the forward flow direction  402 . 
     In accordance with another embodiment, the first leaflet component  310  has a bending stiffness that is greater than the second leaflet component  320  such that the second leaflet component  320  may move more quickly relative to the first leaflet component  310  such that the gap  330  may be formed between the second leaflet component  320  moving away from the first leaflet component  310  under fluid pressure during fluid flow in the forward flow direction  402 . Examples of providing a predetermined bending stiffness include, but not limited to, using a material having a predetermined modulus and providing a component of predetermined thickness. 
     In accordance with another embodiment,  FIGS. 3A and 3B  are perspective and axial views, respectively, of a prosthetic valve  100  in a closed position.  FIGS. 3C and 3D  are perspective and axial views, respectively, of the prosthetic valve  100  in an open position, in accordance with the embodiment of  FIGS. 3A and 3B .  FIGS. 3E and 3F  are cross-sectional views of the closed prosthetic valve  100  of  FIG. 3B  along cutline  3 E- 3 E and of the prosthetic valve  100  of  FIG. 3D  along cutline  3 F- 3 F, respectively. The first overlap region  315  comprises a plurality of apertures  350  extending from the first inflow side  312  to the first outflow side  314  operable to allow upstream flow to pass through the apertures  350  from the first inflow side  312  to the first outflow side  314  during fluid flow in the forward flow direction  402  when the leaflet  300  is not in the closed position. The apertures  350  in the first overlap region  315  provides, in part, that the first leaflet component  310  moves to the open position at a slower rate than the second leaflet component  320  ensuring that the gap  330  is formed therebetween. During retrograde flow, the second overlap region  325  is in sealing engagement with the apertures  350  when the leaflet  300  is in the closed position preventing fluid flow through the apertures  350  in the retrograde flow direction  404 . Leakage of the fluid when the leaflet  300  is closed is known as regurgitation, or regurgitent flow. 
     In accordance with another embodiment,  FIGS. 4A and 4B  are perspective and axial views, respectively, of a prosthetic valve  100  in a closed position.  FIGS. 4C and 4D  are perspective and axial views, respectively, of the prosthetic valve  100  in an open position, in accordance with the embodiment of  FIGS. 4A and 4B .  FIGS. 4E and 4F  are cross-sectional views of the closed prosthetic valve  100  of  FIG. 3B  along cutline  4 E- 4 E and of the prosthetic valve  100  of  FIG. 4D  along cutline  4 F- 4 F, respectively. The second overlap region  325  comprises a plurality of apertures  350  extending from the second inflow side  322  to the second outflow side  324  operable to allow fluid adjacent the second outflow side  324  to pass through the apertures  350  from the second outflow side  324  to the second inflow side  322  during fluid flow when the leaflet  300  is not in the closed position. 
     The apertures  350  in the second overlap region  325 , in part, augments the benefit of the gap  330  to further allow the flow of the fluid adjacent the second outflow side  324  to pass to the second inflow side  322 . During reverse flow, the second overlap region  325  is in sealing engagement with the apertures  350  when the leaflet  300  is in the closed position preventing fluid flow through the apertures  350  in the retrograde flow direction  404 , preventing regurgitation. 
     In the embodiments of  FIGS. 2A, 3A, and 4A , the leaflet overlap region  335  has a relatively uniform width. The first overlap region  315  and the second overlap region  325  defines a leaflet overlap region  335  that is relatively consistent in width from adjacent the frame  200  to away from the frame  200 .  FIG. 5  is a perspective view of a prosthetic valve  100  wherein the leaflet overlap region  335  has a non-uniform width, in accordance with an embodiment. In the embodiment of  FIG. 5 , the first overlap region  315  and the second overlap region  325  defines a leaflet overlap region  335  that tapers in width from a minimum adjacent the frame  200  to a maximum farthest away from the frame  200 . As shown in  FIG. 5 , the leaflet overlap region  335  defines a width and a length, wherein the width has a non-uniform dimension along the width as defined by the first outflow free edge  316  having a concave profile. It is understood that the width of the overlap region  335 , as defined by the degree of overlap between first overlap region  315  and the second overlap region  325  is predetermined for, among other things, to prevent prolapse of the second inflow free edge  327  and to ensure a sufficient sealing engagement between the first overlap region  315  and the second overlap region  325  when the leaflet  300  is in the closed position to prevent regurgitant flow due to downstream fluid pressure. Under certain downstream fluid pressure conditions, the first overlap region  315  and the second overlap region  325  may slip relative to each other with the potential of slipping out of engagement, or prolapsing, if the overlap region  335  is not sufficiently wide. It is understood that the frame  200  and/or the leaflet  300  will elastically deform under fluid pressure. Further, it is understood that the elastic deformation at the first outflow free edge  316  and the second inflow free edge  327  may be greater away from the attachment point to the frame  200 . Therefore, the width of the overlap region  325  is predetermined to accommodate for the increase in deformation further away from the support provided by the frame  200 . 
     As will be described later in reference to the embodiment of  FIG. 6B , the first overlap region  315  and the second overlap region  325  define a leaflet overlap region  335  that tapers in width such that there is no overlap between the first leaflet component  310  and the second leaflet component  320  adjacent to and a predetermined distance away from the frame  200  which defines a regurgitant gap  331  of a predetermined size. 
     It is also understood that the degree of overlap between first overlap region  315  and the second overlap region  325  will also affect the size of the gap  330  and the degree of separation between the first outflow free edge  316  and the second inflow free edge  327  when the leaflet  300  is not in the closed position. 
     The relative size of the first leaflet component  310  and the second leaflet component  320  is predetermined for a particular purpose. In accordance with an embodiment, the first leaflet component  310  is made relatively small so as to not excessively extend into the lumen  214  of the frame  200 , particularly if the first leaflet component  310  is relatively inflexible, so as to minimize the impediment to flow in the forward flow direction  402  through the prosthetic valve  100  when in the open position. It is understood that the relative size of the first leaflet component  310  and the second leaflet component  320  will determine, in part, the characteristics of the pattern of flow in the forward flow direction  402  and the pattern of flow in the recirculating direction, that is, recirculating flow  406 , which will also, in part, determine the dynamics of the first leaflet component  310  and the second leaflet component  320 . It has been found in some embodiments that as the first leaflet component  310  extends further into the lumen  214 , the second leaflet component  320  may begin to flutter when in the open position during forward flow conditions. 
     Related to the relative size of the first leaflet component  310  and the second leaflet component  320  is the axial location X 1  of the overlap region  335  relative to the upstream-most location of the leaflet base  308 . In general, wherein the axial location X 1  increases away from the inflow end  206  and closer to the outflow end  208 , the first leaflet component  310  will extend further into the lumen  214  of the frame  200  and thus affect the characteristics of the flow in the forward flow direction  402 . 
     The shape of the leaflets  300  are defined, at least in part, by the shape of the frame  200  at the leaflet attachment region  212  and the leaflet free edge  306 , as shown in  FIG. 2A . In the embodiments of the prosthetic valve  100  shown in  FIGS. 2A-2F, 3A-3F, 4A-4F, and 5 , the shape of the leaflet  300 , and corresponding leaflet attachment region  212  of the frame  200 , is substantially that of a parabola. The leaflet  300  may define a shape that is predetermined for a particular purpose.  FIG. 6A  is a perspective view of a prosthetic valve  102  having a frame  200  and a plurality of leaflets  300  each having a first leaflet component  310  and a second leaflet component  320  defining a shape substantially that of an isosceles trapezoid, in accordance with an embodiment. It has been found that leaflets  300  defining a shape substantially that of an isosceles trapezoid has improved bending dynamics as compared to that of a parabola. Improved bending dynamics of thin, flexible leaflets may include, but are not limited to, reduced creasing and wrinkling and faster opening and closing response to fluid pressure changes. 
       FIG. 6B  is a perspective view of a prosthetic valve  102  having a frame  200  and a plurality of leaflets  300  each having a first leaflet component  310  and a second leaflet component  320  defining a shape substantially that of an isosceles trapezoid, in accordance with an embodiment. The first overlap region  315  and the second overlap region  325  define a leaflet overlap region  335  that tapers in width such that there is no overlap adjacent to and a predetermined distance away from the frame  200  defining a regurgitant gap  331  of a predetermined size. The regurgitant gap  331  allows a predetermined amount of retrograde flow to pass through the regurgitant gap  331  when the prosthetic valve  102  is closed. The regurgitant gap  331  is operable to prevent pinching or creasing of the first outflow free edge  316  and the second inflow free edge  327  at the frame attachment location adjacent the regurgitant gap when the leaflet  300  is in the closed position. Additionally, the regurgitant gap  331  may assist in preventing fluid stagnation at the location of the regurgitant gap  331  so at to prevent thrombus formation. 
       FIG. 7  is a plan view of a frame  200  unrolled to a flat profile to better visualize the shape of the frame components, in accordance with the embodiment of  FIG. 6 . The frame  200  comprises a leaflet attachment region  212  that has substantially the shape of three sides of an isosceles trapezoid having two leaflet attachment sides  223 , and a leaflet attachment base  224 . 
     The leaflets  300  comprising the first leaflet component  310  and the second leaflet component  320  may be made in a number of different ways. In accordance with an embodiment, each leaflet  300  is made as a single pair including a first leaflet component  310  and a second leaflet component  320 . In accordance with another embodiment, as shown in  FIG. 8 , a plurality of leaflets  300 , and in particular, a plurality of second leaflet components  320 , may be made from a single leaflet pattern. By way of example, a leaflet pattern comprising a plurality of leaflets can be made by starting with a cylinder of biological or synthetic material and cutting the cylinder into a pattern that defines the leaflets. 
       FIG. 8  is a plan view of a leaflet pattern  360  comprising a plurality of first leaflet components  310  and second leaflet components  320 , in accordance with an embodiment. The leaflet pattern  360  may be made from a flat sheet of material cut into a leaflet pattern  360  and subsequently rolled into a cylindrical shape or cut from a cylindrical component to correspond to the cylindrical shape of the frame  200 . In accordance with another embodiment, the leaflet pattern  360  may be formed is by compression or injection molding. The second leaflet components  320  may be linked together via second tabs  364 . 
     Referring to  FIG. 8 , the first leaflet component  310  comprises a first frame attachment edge  319  and a first outflow free edge  316 . The first frame attachment edge  319  includes a plurality of first tabs  362  that couple to components of the frame  200  in a wrap-around fashion in accordance with an embodiment, as shown by way of example in  FIG. 6 . The second leaflet component  320  comprises a second inflow free edge  327 , a second outflow free edge  326 , and second frame attachment edges  329 . The second frame attachment edge  329  includes a plurality of second tabs  364  that couple to components of the frame  200  in a wrap-around fashion. 
     Although some of the embodiments described herein provide, by way of example, attachment edges including tabs that couple to the frame, it is understood and appreciated that the leaflets may be coupled to the frame in many ways known in the art. By way of example, but not limited thereto, the leaflets may be coupled to the frame using mechanical elements, such as, but not limited to, those associated with posts, hooks, and suture, and using other means such as, but not limited to, heat bonding, gluing, molding and crimping. Embodiments presented herein are not limited by the particular coupling means used to couple the leaflet, and corresponding leaflet components, to the frame or other support structure. 
     As provided above, the shape of the leaflets  300  are defined, at least in part, by the shape of the frame  200  at the leaflet attachment region  212  and the leaflet free edge  306 . The shape of the leaflets  300  can also be defined by the processes used to manufacture the prosthetic valve  100 , such as, but not limited, those described below. For example, in accordance with an embodiment, the shape of the leaflets  300  depends in part on making the leaflets  300  using molding and trimming processes to impart a predetermined shape to the leaflets  300 . 
       FIGS. 9 and 10  are plan views of a leaflet pattern  360  comprising a first leaflet component  310  and a second leaflet component  320 , respectively, in accordance with an embodiment. The first leaflet component  310  comprises a first frame attachment edge  319  and a first outflow free edge  316 . The first frame attachment edge  319  includes a plurality of first tabs  362  that are operable to couple to components of the frame  200  adjacent the leaflet attachment base  224  and at least a portion of the two leaflet attachment sides  223 , as shown in  FIGS. 2A, 6 and 7 . The first frame attachment edge  319  defines a shape of a portion of the leaflet sides  307  and the leaflet base  308 , in that the two leaflet sides  307  diverge from the leaflet base  308 .  FIG. 9  shows two alternative embodiments for the leaflet base  308  in dashed lines, a straight first frame attachment edge  319   a , corresponding to the frame  200  of  FIG. 7 , and a parabolic first frame attachment edge  319   b , suitable for a parabolic leaflet attachment base  224  corresponding to the frame  200  of  FIG. 2A . During the opening and closing of the leaflet  300 , the first leaflet component  310  will bend about the leaflet base  308 . Bending about the straight first frame attachment edge  319   a  may be in a more controlled manner that may reduce wrinkling and/or fluttering of the first leaflet component  310  as compared with bending about the parabolic first frame attachment edge  319   b.    
     The second leaflet component  320  comprises a second inflow free edge  327 , a second outflow free edge  326 , and two second frame attachment edges  329  that diverge from the second inflow free edge  327 . The second frame attachment edges  329  include a plurality of second tabs  364  that couple to components of the frame  200  adjacent each of the two leaflet attachment sides  223 . The first outflow free edge  316  of the first leaflet component  310  is operable to overlap the second inflow side  322  of the second inflow free edge  327  of the second leaflet component  320  to define an overlap region  315 , as shown in the embodiment of  FIG. 6 , and similarly for the embodiment of  FIG. 2A . The shape of the second inflow free edge  327  is predetermined by the shape of the first outflow free edge  316  and the desired width of the overlap region  315 , suitable for a particular purpose. 
     In accordance with embodiments, as exemplified in  FIGS. 2A, 3A, 4A, 5, 6A , wherein the second leaflet component  320  has a second inflow free edge  327  being not coupled to the leaflet attachment base  224  of the frame  200 , it has been found that the second leaflet component  320  has improved bending dynamics as compared to that of a parabolic leaflet  30  such as shown in  FIG. 1A . The benefits of improved bending dynamics of the leaflet second component  320  may include, but are not limited to, reduced creasing and wrinkling, reduced fluttering, faster opening and closing response to fluid pressure changes, and an increase in durability. 
     In the previous embodiments, the first leaflet component  310  and the second leaflet component  320  are generally located upstream and downstream on the frame  200 , respectively, defining a single gap  330  generally extending across the leaflet  300  perpendicular to the axis X of the prosthetic valve  100 , as shown in  FIG. 2F . It may be advantageous to provide a leaflet with more than one gap  330  for a predetermined flow dynamic behind the leaflet. 
       FIG. 11A  is a perspective view a prosthetic valve  600  having a frame  200  and a plurality of leaflets  630  each having a plurality of first leaflet components  610  that overlap a second inflow side  622  of a second leaflet component  620 , in accordance with an embodiment. Similarly to the embodiment of  FIGS. 2E and 2F , a gap  330  formed between the first leaflet component  610  and the second leaflet component  620  when the leaflet  630  is not in the closed position allows fluid adjacent the first outflow side  614  and the second outflow side  624  to pass through the gap  330  during fluid flow in the forward flow direction  402  through the lumen  214 . That is, the recirculating flow  406  behind the leaflet  630  may pass through the gap  330  preventing the recirculating flow  406  from slowing down or stagnating behind the leaflet  300 . Further, the gap  330  also allows fluid flow in the forward flow direction  402  to pass through the gap  330  from the first inflow side  612  and the second inflow side  622  further disrupting and displacing the recirculating flow  406  behind the leaflet  630  to downstream of the leaflet  630 . Thus, fluid behind the leaflet  630  is less likely to clot or form thrombus, particularly at the leaflet base  608  and where it attaches to the frame  200 . In this embodiment, the first leaflet component  610  comprises a material with a high modulus such that it resists bending under the anticipated flow conditions. Since the first leaflet component  610  is not supported by the second leaflet component  320  at the overlap region  625  when in the closed position, the first leaflet component  610  must resist the back pressure of the fluid when in the closed position to prevent prolapse. 
       FIGS. 12A and 13  are plan views of a leaflet pattern  660  comprising a plurality of first leaflet components  610  and second leaflet components  620 , respectively, in accordance with an embodiment. Referring to  FIG. 12A , each of the first leaflet components  610  comprise a first frame attachment edge  619  and a first outflow free edge  616 . The first frame attachment edge  619  includes a plurality of first tabs  662  that couple to components of the frame  200 . 
     The second leaflet component  620  comprises a plurality of second inflow free edges  627 , a second outflow free edge  626 , and three second frame attachment edges  629 . The second frame attachment edges  629  include a plurality of first tabs  662  that couple to components of the frame  200 . Alignment of each of the first leaflet components  610  relative to the second leaflet component  620  is provided by locating first tab apertures  611  on first tabs  662  with second tab apertures  621  on second tabs  664 . 
     The leaflets  630  comprise multiple first leaflet components  610 , in this embodiment, two first leaflet components  610 , and a second leaflet component  620  defining two second inflow free edges  627 . The second leaflet component  620  is coupled to the frame  200  along second frame attachment edges  629 . A first leaflet component  610  is coupled to the frame  200  along the first frame attachment edge  619  adjacent each of the second inflow free edges  627  so as to define a gap  330  therebetween when the leaflet  630  is open. In accordance with an embodiment, the first outflow free edge  616  of the first leaflet component  610  is located adjacent to and overlaps the second inflow side  622  of the second inflow free edge  627  to define the overlap region  625 . Because of the specific location of the gap  330 , the gap  330  will close in sealing engagement at the overlap region  625 , shown in  FIG. 11B , to prevent regurgitent flow when the leaflet  630  is in the closed position. 
     In accordance with the embodiment of  FIG. 11A , the upstream-most second frame attachment edge  629   a  provides additional support to the second inflow free edges  627  such that they do not prolapse when in the closed position resisting downstream flow pressure. The length of the upstream-most second frame attachment edge  629   a  is sized for a particular purpose. 
       FIG. 11B  is a perspective view a prosthetic valve  600  having a frame  200  and a plurality of leaflets  630  each having a plurality of first leaflet components  610  that overlap a second outflow side  624  of a second leaflet component  620 , in accordance with an embodiment. The first outflow free edge  616  of the first leaflet component  610  is located adjacent to and overlaps with the second outflow side  624  of the second inflow free edge  627  to define the overlap region  625 . The gap  633  will close in sealing engagement at the overlap region  625  to prevent regurgitent flow when the leaflet  630  is in the closed position.  FIG. 11C  is a cross-sectional view along cut-line  110  of the embodiment of  FIG. 11B  when the leaflet  630  is in the closed position.  FIG. 11D  is a cross-sectional view along cut-line  110  of the embodiment of  FIG. 11B  when the leaflet  630  is in the open position. A gap  330  formed between the first leaflet component  610  and the second leaflet component  620  when the leaflet  630  is not in the closed position allows fluid flow in the forward flow direction  402  to pass through the gap  330  from the first inflow side  612  and the second inflow side  622  disrupting and displacing the recirculating flow  406  behind the leaflet  630 . Thus, blood behind the leaflet  630  is less likely to clot or form thrombus, particularly at the leaflet base  608  and where it attaches to the frame  200 . Under certain flow conditions, the gap  330  also allows fluid adjacent the first outflow side  614  and the second outflow side  624  to pass through the gap  330  during fluid flow in the forward flow direction  402  through the lumen  214 . That is, the recirculating flow  406  behind the leaflet  630  may pass through the gap  330  preventing the recirculating flow  406  from slowing down or stagnating behind the leaflet  630 . 
       FIG. 12B  is another embodiment of a first leaflet component  610  that may be used in cooperation with the second leaflet component  620  of  FIG. 13 . The first leaflet component  610  comprises two a first frame attachment edges  619  and two first outflow free edges  616 . The first frame attachment edges  619  includes a plurality of first tabs  662  that couple to components of the frame  200 . This embodiment is similar to the embodiment of  FIG. 12A  wherein the two first leaflet components  610  are coupled together as one component. 
       FIG. 12C  is another embodiment of a first leaflet component  610  that may be used in cooperation with the second leaflet component  620  of  FIG. 13 . This embodiment is similar to the embodiment of  FIG. 12B  wherein the two first leaflet components  610  are coupled together as one component. The first leaflet component  610  comprises two a first frame attachment edges  619  and two first outflow free edges  616 . The first frame attachment edges  619  includes a plurality of first tabs  662  that couple to components of the frame  200 . The first leaflet component  610  further comprises a tether element  640  that couples the two first outflow free edges  616  to the frame via a plurality of first tabs  662 . The tether element  640  is operable to prevent prolapse of the two first outflow free edges  616  when the leaflets are in the closed position. 
       FIG. 14  is a perspective view a prosthetic valve  700  having a frame  200  and a plurality of leaflets  730  each having a plurality of first leaflet components  610  that overlap a second leaflet component  620 , in accordance with an embodiment. The second leaflet component  620  has a relatively narrow upstream-most second frame attachment edge  629   a  providing the benefit of providing relatively large gaps between the two first leaflet components  610  and the second leaflet component  620  when the leaflet is not in the closed position while providing tethered support of the second inflow free edges  627  that prevents prolapse when in the closed position resisting downstream flow pressure. 
       FIG. 15  is a perspective view a prosthetic valve  800  having a frame  200  and a plurality of leaflets  830  each having one first leaflet component  610  that overlaps a second leaflet component  620  that defines two second inflow free edges  627 , in accordance with another embodiment. The second leaflet component  620  is similar to the embodiment of  FIG. 14  in that the second leaflet component  620  has a relatively narrow upstream-most second frame attachment edge  629   a  providing the benefit of providing relatively large gaps between the first leaflet component  610  and the second leaflet component  620  when the leaflet is not in the closed position while providing tethered support of the second inflow free edges  627  that prevents prolapse when in the closed position resisting downstream flow pressure. 
     It is appreciated that embodiments of the prosthetic valve having one or more first leaflet components and one or more second leaflet components, and where the overlap region is on the inflow side or outflow side of the second leaflet component, are predetermined for a particular purpose to provide flow through the gap therebetween when the leaflet is in the open position and to prevent regurgitent flow through the gap therebetween when the leaflet is in the closed position. The gap formed between the first leaflet component and the second leaflet component when the leaflet is not in the closed position allows fluid adjacent the first outflow side and the second outflow side to pass through the gap during fluid flow in the forward direction through the lumen. That is, the recirculating flow behind the leaflet may pass through the gap  330  preventing the recirculating flow from slowing down or stagnating behind the leaflet. Further, the gap also allows forward flow to pass through the gap from the first inflow side and the second inflow side further disrupting and displacing the recirculating flow behind the leaflet to downstream of the leaflet. Thus, blood behind the leaflet is less likely to clot or form thrombus, particularly where the leaflet attaches to the frame. 
     In accordance with another embodiment, as shown in  FIGS. 16A-16F , a prosthetic valve  900  comprises a leaflet  930  having a second leaflet component  320  defining a second leaflet aperture  850  therethrough and a first leaflet component  310  operable to close the second leaflet aperture  850  when the leaflet  930  is in the closed position.  FIGS. 16A and 16B  are perspective and axial views, respectively, of a prosthetic valve  900  in a closed position, in accordance with an embodiment.  FIGS. 16C and 16D  are perspective and axial views, respectively, of the prosthetic valve  900  in an open position, in accordance with an embodiment.  FIGS. 16E and 16F  are cross-sectional views of the closed prosthetic valve  900  of  FIG. 16B  along cutline  16 E- 16 E and of the prosthetic valve  900  of  FIG. 16D  along cutline  16 F- 16 F, respectively. 
     As shown in  FIG. 16A , a frame  200  is operable to hold and support a plurality of leaflets  930 . The frame  200  is annular, that is, it defines a cylinder having a lumen  214  having an axis X and a plurality of commissure posts  210  extending parallel to the axis X that are spaced from one another. Between the commissure posts  210  is a leaflet attachment region  212  that is operable to couple with and support the leaflet  930  about a perimeter of the leaflet  930 . 
     The leaflet  930  includes a first leaflet component  310  and a second leaflet component  320 , in accordance with an embodiment. The first leaflet component  310  has a first inflow side  312  and a first outflow side  314  opposite the first inflow side  312  that defines a first thickness. The first leaflet component  310  has a first frame attachment edge  319  and a first outflow free edge  316 . The first leaflet component  310  defines a second leaflet aperture  850  adjacent the leaflet base  308 . 
     The second leaflet component  320  has a second inflow side  322  and a second outflow side  324  opposite the second inflow side  322  defining a second thickness. The second leaflet component  320  has a plurality of second frame attachment edges  329  and an aperture occluder  382  therebetween that is operable to occlude the second leaflet aperture  850  when the leaflet  930  is in the closed position. The first leaflet component  310  and the second leaflet component  320  are configured to be movable between an open position to allow fluid flow in a forward flow direction through the lumen  214  and a closed position in cooperative engagement that prevents regurgitant flow. 
     The first leaflet component  310  and the second leaflet component are arranged on the frame  200  such that they at least partially overlap. A second overlap region  325  adjacent to the second inflow free edge  327  overlaps a first overlap region  315  adjacent to the first outflow free edge  316  such that a portion of the second inflow side  322  of the second leaflet component  320  is in contact and in sealing engagement with a portion of the first outflow side  314  of the first leaflet component  310  when the leaflet  300  is in the closed position defining a leaflet overlap region  335  operable to prevent regurgitant flow through the leaflet  300  at the leaflet overlap region  335 , as shown in  FIG. 16E . 
     During fluid flow in the forward flow direction  402  when the leaflet  930  is not in the closed position, as shown in  FIG. 16F , when the inflow pressure is greater than the outflow pressure, the first overlap region  315  and the second overlap region  325  move away from each other wherein the first leaflet component  310  uncovers the second leaflet aperture  850  allowing fluid to flow therethrough. The second leaflet aperture  850  in the second leaflet component  320  when the leaflet  300  is not in the closed position allows fluid adjacent the second inflow side  322  to pass through the second leaflet aperture  850  when the fluid is moving in the forward flow direction  402  through the lumen  214 . The aperture occluder  382  to move downstream from the second leaflet aperture  850 . Recirculating flow  406  from behind the leaflet  930 , including the first leaflet component  310  may pass in front of the aperture occluder  382  so as to prevent the recirculating flow  406  from stagnating behind the leaflet  930 . Thus, blood behind the leaflet  930  is less likely to clot or form thrombus, particularly at the leaflet base  308  and where it attaches to the frame  200 . 
     Leaflet Material 
     In accordance with some embodiments herein, the leaflet  300  can comprise a biocompatible material that is not of a biological source and that is sufficiently compliant and strong for the particular purpose, such as a biocompatible polymer. In accordance with some embodiments, the first leaflet component  310  and the second leaflet component  320  comprise the same material and exhibit the same material properties. In accordance with other embodiments, the first leaflet component  310  has a bending stiffness that is greater than the second leaflet component  320 . Examples of providing a predetermined bending stiffness include, but not limited to, using a material having a predetermined modulus and providing a component of predetermined thickness. 
     In an embodiment, the leaflet  300  comprises a membrane that is combined with an elastomer or elastomeric material to form a composite material. In accordance with other embodiments, the biocompatible material that makes up the leaflet  300  comprises a biological material, such as, but not limited to, human, bovine, and pig tissue. 
     The leaflet  300  can comprise any biocompatible material sufficiently compliant and flexible, such as a biocompatible polymer. Either one or both of the first leaflet component  310  and the second leaflet component  320  can comprise a membrane that is combined with an elastomer or elastomeric material to form a composite material. The leaflet  300  can comprise, according to an embodiment, a composite material comprising an expanded fluoropolymer membrane, which comprises a plurality of spaces within a matrix of fibrils, and an elastomeric material. It should be appreciated that multiple types of fluoropolymer membranes and multiple types of elastomeric materials can be combined to form a composite material while remaining within the scope of the present disclosure. It should also be appreciated that the elastomeric material can include multiple elastomers, multiple types of non-elastomeric components, and include such things as inorganic fillers, therapeutic agents, radiopaque markers, and the like while remaining within the scope of the present disclosure. 
     In accordance with an embodiment, the composite material includes an expanded fluoropolymer material made from porous ePTFE membrane, for instance as generally described in U.S. Pat. No. 7,306,729 to Bacino. 
     The expandable fluoropolymer, used to form the expanded fluoropolymer material described, can comprise PTFE homopolymer. In alternative embodiments, blends of PTFE, expandable modified PTFE and/or expanded copolymers of PTFE can be used. Non-limiting examples of suitable fluoropolymer materials are described in, for example, U.S. Pat. No. 5,708,044, to Branca, U.S. Pat. No. 6,541,589, to Baillie, U.S. Pat. No. 7,531,611, to Sabol et al., U.S. patent application Ser. No. 11/906,877, to Ford, and U.S. patent application Ser. No. 12/410,050, to Xu et al. 
     The expanded fluoropolymer membrane can comprise any suitable microstructure, such as pores, for achieving the desired leaflet performance. Other biocompatible polymers which can be suitable for use in leaflet include but are not limited to the groups of urethanes, silicones (organopolysiloxanes), copolymers of silicon-urethane, styrene/isobutylene copolymers, polyisobutylene, polyethylene-co-poly(vinyl acetate), polyester copolymers, nylon copolymers, fluorinated hydrocarbon polymers and copolymers or mixtures of each of the foregoing. 
     In accordance with embodiments, the first leaflet component and the second leaflet component may be formed of at least one of Polyether ether ketone (PEEK), expanded Polytetrafluoroethylene (ePTFE), Fluorinated ethylene propylene (FEP), copolymers of tetrafluoroethylene (TFE) and perfluoromethyl vinyl ether (PMVE) (TFE-PMVE copolymer), urethanes, polyimides, thermoplastics, thermosets, 3D printable metals and polymers (stainless steel, titanium, etc.) nylon, or any other biocompatible material suitable for long term blood contact that is dimensionally stable, and does not leech contaminates. 
     Further examples of leaflet construct materials include: wherein the leaflet construct comprises at least one fluoropolymer membrane layer; wherein the leaflet construct comprises a laminate having more than one fluoropolymer membrane layer; wherein the at least one fluoropolymer membrane layer is an expanded fluoropolymer membrane layer; wherein an elastomer, elastomeric, non-elastomer, or a copolymer of TFE-PMVE material is contained within the expanded fluoropolymer membrane layer; wherein the elastomer or elastomeric material comprises perfluoromethyl vinyl ether and tetrafluoroethylene; wherein the expanded fluoropolymer membrane layer comprises ePTFE; wherein the leaflet construct comprises a composite material having at least one fluoropolymer membrane layer having a plurality of pores and an elastomer or elastomeric material present in the pores of at least one of the fluoropolymer membrane layers; wherein the composite material comprises fluoropolymer membrane by weight in a range of about 10% to 90%; wherein the elastomer comprises (per)fluoroalkylvinylethers (PAVE); wherein the elastomer or elastomeric material comprises a copolymer of tetrafluoroethylene and perfluoromethyl vinyl ether; wherein the elastomer is silicone; wherein the elastomer is a fluoroelastomer; wherein the elastomer is a urethane; and wherein the elastomer or elastomeric material is a TFE/PMVE copolymer; wherein the TFE/PMVE copolymer comprises essentially of between about 40 and 80 weight percent perfluoromethyl vinyl ether and complementally 60 and 20 weight percent tetrafluoroethylene; and wherein the leaflet construct comprises silicone. 
     The leaflet comprises a section of material, such as a sheet, that is attached to the frame. The leaflet can be formed of any suitable material, and need only be biocompatible or be able to be made biocompatible. The material can advantageously be formed of a flexible material. Examples of suitable materials for the valve leaflet include natural materials, synthetic materials, and combinations of natural and synthetic materials. Examples of suitable natural materials include extracellular matrix (ECM) materials, such as small intestine submucosa (SIS), and other bioremodellable materials, such as bovine pericardium. Other examples of ECM materials that can be used in the prosthetic valves of the invention include stomach submucosa, liver basement membrane, urinary bladder submucosa, tissue mucosa, and dura mater. Examples of suitable synthetic materials include polymeric materials, such as expanded polytetrafluoroethylene and polyurethane. ECM materials are particularly well-suited materials for use in the leaflet, at least because of their abilities to remodel and become incorporated into adjacent tissues. These materials can provide a scaffold onto which cellular in-growth can occur, eventually allowing the material to remodel into a structure of host cells. 
     In accordance with an embodiment, the first leaflet component and the second leaflet component comprise a porous polymer membrane and an elastomeric material present in pores of the porous polymer membrane such that the first leaflet component and the second leaflet components are impermeable. Further, in another embodiment, the porous polymer membrane is expanded polytetrafluoroethylene. Further, in another embodiment, the elastomeric material is an elastomer. Further, in another embodiment, the elastomeric material is TFE/PMVE copolymer. Further, in another embodiment, the elastomer is TFE/PMVE copolymer. 
     In accordance with an embodiment, the first leaflet component and the second leaflet component comprise a porous polymer membrane and an elastomer present in pores of the porous polymer membrane such that the first leaflet component and the second leaflet components are impermeable. Further, in another embodiment, the porous polymer membrane is expanded polytetrafluoroethylene. Further, in another embodiment, the elastomer is TFE/PMVE copolymer. 
     In accordance with an embodiment, the first leaflet component or the second leaflet component comprise a porous polymer membrane and an elastomeric material present in pores of the porous polymer membrane such that the first leaflet component or the second leaflet component, respectively, is impermeable. 
     In accordance with an embodiment, the first leaflet component and the second leaflet component comprise expanded polytetrafluoroethylene membrane and TFE/PMVE copolymer present in pores of the expanded polytetrafluoroethylene membrane such that the first leaflet component and the second leaflet component, respectively, are impermeable. 
     In accordance with an embodiment, at least one of the first leaflet component and the second leaflet component comprise a biological tissue. 
     In accordance with an embodiment, a prosthetic valve comprises a frame and a plurality of leaflets each including one or more first valve components that overlap a second valve component. The frame includes an inflow end and an outflow end and leaflet attachment portions. Each first leaflet component includes a first inflow end portion and a first outflow end portion wherein the first inflow end portion is coupled to a leaflet attachment portion adjacent the inflow end of the frame. The second leaflet portion has a second inflow end portion, a second outflow end portion, a plurality of side attachment portions, a lumen facing side and a frame facing side. At least two side attachment portions are coupled to the leaflet attachment portions of the frame. A portion of the first leaflet outflow end portion overlaps with a portion of the second leaflet inflow end portion of the leaflet on the lumen facing side defining an overlap region. The leaflet being movable between an open position to allow fluid flow in a forward direction through the lumen and a closed position in cooperative engagement with the valve component in sealing engagement at the overlap region that prevents fluid flow in a retrograde direction through the frame. A gap is formed between the overlap region to allow fluid flow therethrough during fluid flow in a forward direction through the frame. 
     In accordance with another embodiment, a prosthetic valve comprises a first leaflet component and a second leaflet component. The second leaflet component being disposed downstream of the first leaflet component. The first leaflet component and the second leaflet component are in operable engagement configured to allow forward fluid flow through the prosthetic valve in a first direction extending downstream and prevent retrograde fluid flow through the prosthetic valve in an opposite direction extending upstream, and in operable engagement configured to allow fluid flow between a gap defined by the first leaflet component and the second leaflet component during forward fluid flow through the prosthetic valve. 
     In accordance with another embodiment, a prosthetic valve comprises a frame and a leaflet component coupled to the frame being moveable between a first position that permits fluid to forward flow in a first direction through the prosthetic valve and a second position that hinders retrograde flow in a second direction opposite the first direction through the prosthetic valve. The leaflet component includes a means for opening an aperture during forward flow to enable fluid flow therethrough during forward flow and to close the aperture during retrograde flow. 
     In accordance with another embodiment, a prosthetic valve, comprises a frame and a leaflet coupled to the frame being moveable between a first position that permits antegrade flow through the prosthetic valve and a second position that prevents retrograde flow through the prosthetic valve. The leaflet component includes a recirculation aperture operable to open to enable recirculation flow therethrough during antegrade flow through the prosthetic valve and operable to close to prevent retrograde flow therethrough through the prosthetic valve. 
     In accordance with another embodiment, a prosthetic valve comprises a frame, a first leaflet component coupled to the frame, and a second leaflet component coupled to the frame and at least partially overlapping the first leaflet component defining an overlap region. The second leaflet component being moveable between a first position that brings the first leaflet component and the second leaflet component into sealing engagement at the overlap region that prevents retrograde flow through the prosthetic valve and moveable between a second position that allows antegrade flow through the prosthetic valve and separates the first leaflet component and the second leaflet component at the overlap region defining a recirculation aperture that allows recirculation flow through the recirculation aperture. 
     In accordance with another embodiment, a prosthetic valve comprises a frame and at least one leaflet. The frame has an inflow end and an outflow end opposite the inflow end and defining a lumen therebetween defining an axis, the frame having at least one leaflet attachment region having an inflow portion and an outflow portion. A leaflet is coupled to each of the at least one leaflet attachment regions. Each leaflet includes at least one first leaflet component and a second leaflet component. Each first leaflet component has a first inflow side and a first outflow side opposite the first inflow side, a first frame attachment edge and a first outflow free edge. The second leaflet component has a second inflow side and a second outflow side opposite the second inflow side. The second leaflet component has a plurality of second frame attachment edges, at least one second inflow free edge and a second outflow free edge opposite the at least one second inflow free edge. The second leaflet component being movable between an open position to allow fluid flow in a forward direction through the lumen and a closed position in cooperative engagement with the at least one first leaflet component that prevents fluid flow in a retrograde direction through the lumen. The first frame attachment edge of the at least one first leaflet component being coupled to the inflow portion of the leaflet attachment region with the first inflow side facing the axis. The frame attachment edges of the second leaflet component being coupled to at least the outflow portion of the leaflet attachment region with the second inflow side facing the axis. Wherein a second overlap region of the second inflow free edge overlaps a first overlap region of the first outflow free edge of the at least one first leaflet component when the leaflet is in the closed position defining a leaflet overlap region preventing fluid flow through the lumen in the retrograde direction. Wherein the first overlap region of the at least one first leaflet component and the second overlap region are not in contact therewith wherein the first outflow free edge of the at least one first leaflet component and the second inflow free edge define a gap therebetween when the leaflet is not in the closed position, wherein fluid adjacent the second outflow side can pass through the gap during fluid flow in the forward direction. 
     In accordance with another embodiment, a prosthetic valve comprises a frame and a plurality of leaflets. The frame has an inflow end and an outflow end opposite the inflow end and defines a lumen therebetween defining an axis. The frame has at least one leaflet attachment region having an inflow portion and an outflow portion. Each leaflet being coupled to each of the at least one leaflet attachment regions. The at least one leaflet includes at least one first leaflet component and a second leaflet component. The at least one first leaflet component has a first inflow side and a first outflow side opposite the first inflow side. The at least one first leaflet component has a first frame attachment edge and a first outflow free edge. The second leaflet component has a second inflow side and a second outflow side opposite the second inflow side. The second leaflet component has a plurality of second frame attachment edges, at least one second inflow free edge and a second outflow free edge opposite the at least one second inflow free edge. The second leaflet component being movable between an open position to allow fluid flow in a forward direction through the lumen and a closed position in cooperative engagement with the at least one first leaflet component that prevents fluid flow in a retrograde direction through the lumen. The first frame attachment edge of each first leaflet component being coupled to the inflow portion of the leaflet attachment region with the first inflow side facing the axis. The frame attachment edges of the second leaflet component being coupled to at least the outflow portion of the leaflet attachment region with the second inflow side facing the axis. Wherein a second overlap region of the second leaflet component adjacent the second inflow free edge overlaps a first overlap region of the first leaflet component adjacent the first outflow free edge such that they are in sealing engagement therewith when the leaflet is in the closed position defining a leaflet overlap region preventing fluid flow through the lumen in the retrograde direction. Wherein the first overlap region of each first leaflet component and the second overlap region are not in contact therewith wherein the first outflow free edge of the each of the first leaflet component and the second inflow free edge define a gap therebetween when the leaflet is not in the closed position, wherein fluid adjacent the second outflow side can pass through the gap during fluid flow in the forward direction. 
     In accordance with embodiments, the valve may comprise the following properties, singularly or in combination. 
     The leaflet may comprise a means for allowing a flow or exchange of fluid between the front and back of the leaflet when the leaflet is not in the closed position. Said flow or exchange of fluid may be through the leaflet via an aperture, gap or separation of portions of the leaflet. Said aperture, gap or separation may be operable to close to prevent flow of exchange of fluid between the back and the front of the leaflet, when the leaflet is in the closed position. 
     The valve may comprise a support structure, such as a frame or a conduit; wherein the leaflet is coupled to the support structure. 
     The leaflet may include a first leaflet component and a second leaflet component. 
     The first leaflet component and the second leaflet component may be coupled to the support structure. 
     The first leaflet component may be upstream of the second leaflet component. 
     The first leaflet component may be downstream of the second leaflet component. 
     Said flow or exchange of fluid may be via an aperture, gap or separation of the first and second components, when the leaflet is not in the closed position. 
     In some embodiments, the second leaflet component comprises an inflow free edge, and defines a gap between the second leaflet component and the support structure. In some embodiments, the first leaflet component or the second leaflet component defines an aperture therethrough, and wherein the other of the first leaflet component or the second leaflet component is operable to occlude the aperture. 
     The first leaflet component and the second leaflet component may be partially overlapping. 
     Respective first and second overlap regions of the first leaflet component and the second leaflet component may be in sealing engagement with one another, when the leaflet is in the closed position. The first leaflet component may comprise a first overlap region and the second leaflet component may comprise a second overlap region, wherein the first and second overlap regions together define a leaflet overlap region, when the first and second leaflet components are in sealing engagement with one another. 
     The first and second overlap regions may extend from a free edge of the respective leaflet component. 
     The first overlap region may extend from, and typically upstream from, an outflow free edge. The second overlap region may extend from, and typically downstream from, an inflow free edge. 
     The first and second leaflet components may be brought into sealing engagement with one another by fluid pressure, under the action of retrograde flow. 
     The first leaflet component may be stationary relative to the second leaflet component, or vice versa. The first leaflet component, or the second leaflet component may be relatively stationary relative to the support structure. 
     The first leaflet component may be configured to move more slowly than the second leaflet component, or vice versa. In some embodiments, the first leaflet component is downstream of the second leaflet component and the second leaflet component is configured to move more slowly than the first leaflet component. In some embodiments the first leaflet component is upstream of the second leaflet component and the first leaflet component is configured to move more slowly than the second leaflet component. 
     In some embodiments, the first leaflet component may have a higher, or a lower, bending stiffness than the second leaflet component. 
     The first leaflet component may comprise apertures in the first overlap region. In some embodiments, the second leaflet component may comprise apertures in the second overlap region. During forward flow (i.e. downstream flow) the apertures in the first or second overlap region may provide, at least in part, that the respective first or second leaflet component moves to the open position at a slower rate than the other said leaflet component, such that a gap is formed therebetween. 
     In some embodiments, apertures are provided in the first or second overlap regions to augment regurgitant blood flow. In some embodiments, the leaflet component configured to move more slowly is provided with apertures in its overlap region. In some embodiments, the leaflet component configured to move more quickly is provided with apertures in its overlap region. 
     The apertures in the first or second overlap region may be sealed by the other said overlap region, during retrograde blood flow when the leaflet is in the closed position. 
     The leaflet overlap region may be of any suitable shape or configuration. In some embodiments, the leaflet overlap region tapers in width towards the support structure. For example, in some embodiments there is no overlap at and optionally to a predetermined distance away from the support structure. 
     In some embodiments, when the leaflet is in the closed position, there is a regurgitant gap or gaps of a predetermined size between the first and second leaflet components, for example extending away from the support structure. The regurgitant gap or gaps allow a predetermined amount of retrograde flow to pass therethrough, when the valve is closed. 
     The relative sizes of the first and second leaflet components may determine the axial location of the leaflet overlap region. 
     The leaflet may provide for flow or exchange of fluid may be via multiple (e.g. two, or three or more) apertures, gaps or separations, when the leaflet is not in the closed position. 
     The leaflet may comprise multiple first leaflet components. The leaflet may comprise a first leaflet component comprising multiple outflow free edges. 
     In some embodiments, the second leaflet component may comprise multiple inflow free edges, defining multiple gaps between the second leaflet component and the support structure, corresponding to one of the said multiple first leaflet components or free edges. 
     In some embodiments, the second leaflet component defines multiple apertures therethrough. The first leaflet component may be operable to occlude the apertures, or one of the said multiple first leaflet components may be operable to occlude each said aperture. 
     Where there are multiple outflow free edges (either of multiple first leaflet components or of a first leaflet component having multiple outflow free edges), the leaflet may comprise a tether element, which couples said outflow free edges. The tether element may prevent prolapse. 
     The leaflet may comprise a porous polymer membrane and a material present in pores of the porous polymer membrane such that the or each leaflet is impermeable. 
     The porous polymer membrane may for example be a fluoropolymer such as expanded polytetrafluoroethylene, or may be a polymer such as polyethylene. 
     The material present in the pores may be an elastomer or an elastomeric material or may be a non-elastomeric material. The material present in the pores may be a TFE/PMVE copolymer. 
     The leaflet may alternatively or in addition comprise a biological tissue, such as native valve tissue, or porcine tissue. 
     Where the valve comprises one or more first leaflet components and a second leaflet component, the or each first leaflet component and/or the second leaflet component may comprise said porous polymer membrane and a material present in pores of the porous polymer membrane such that the or each first leaflet component and/or the second leaflet component is impermeable. 
     In some embodiments, wherein at least one of the first leaflet component (or components) and the second leaflet component comprises a biological tissue. 
     The leaflet may have any suitable shape or configuration. For example, the shape of the leaflet, and of a corresponding attachment region to a support structure, may be generally that of a parabola or of an isosceles trapezoid. 
     The valve may comprise a plurality of leaflets, for example two leaflets, three leaflets or four leaflets. The valve may comprise three leaflets. 
     Each leaflet may comprise a leaflet free edge. The leaflet free edges may coapt under the influence of outflow (i.e. retrograde) fluid pressure; thereby closing the valve. 
     The valve may be a prosthetic valve. The valve may be a prosthetic heart valve. 
     The valve may comprise a leaflet including a first leaflet component and a second leaflet component being disposed downstream of the first leaflet component, the first leaflet component and the second leaflet component are in operable engagement configured to allow forward fluid flow through the prosthetic valve in a first direction extending downstream and prevent regurgitant fluid flow through the prosthetic valve in an opposite direction extending upstream, and in operable engagement configured to allow fluid flow between a gap defined by the first leaflet component and the second leaflet component during forward fluid flow through the prosthetic valve. 
     The valve may comprise a frame; and a leaflet including a first leaflet component coupled to the frame and a second leaflet component coupled to the frame and at least partially overlapping the first leaflet component defining an overlap region, the second leaflet component being moveable between a first position that brings the first leaflet component and the second leaflet component into sealing engagement at the overlap region that prevents regurgitant flow through the prosthetic valve and moveable between a second position that allows antegrade flow through the prosthetic valve and separates the first leaflet component and the second leaflet component at the overlap region defining a recirculation aperture that allows recirculation flow through the recirculation aperture. 
     The valve may comprise a frame; and a leaflet including a leaflet component coupled to the frame being moveable between a first position that permits fluid to forward flow in a first direction through the prosthetic valve and a second position that hinders regurgitant flow in a second direction opposite the first direction through the prosthetic valve, the leaflet component including a means for opening an aperture during forward flow to enable fluid flow therethrough during forward flow and to close the aperture during retrograde flow. 
     The valve may comprise a frame; and a leaflet coupled to the frame being moveable between a first position that permits antegrade flow through the prosthetic valve and a second position that prevents regurgitant flow through the prosthetic valve, the leaflet including a recirculation aperture operable to open to enable recirculation flow therethrough during antegrade flow through the prosthetic valve and operable to close to prevent retrograde flow therethrough through the prosthetic valve. 
     A method for treating a human patient with a diagnosed condition or disease associated with valve insufficiency or valve failure of a native valve, the method comprising implanting a prosthetic valve at the location of the native valve. The prosthetic valve comprises a frame and a plurality of leaflets. The frame has an inflow end and an outflow end opposite the inflow end and defines a lumen therebetween defining an axis. The frame has at least one leaflet attachment region having an inflow portion and an outflow portion. Each leaflet being coupled to each of the at least one leaflet attachment regions. The at least one leaflet includes at least one first leaflet component and a second leaflet component. The at least one first leaflet component has a first inflow side and a first outflow side opposite the first inflow side. The at least one first leaflet component has a first frame attachment edge and a first outflow free edge. The second leaflet component has a second inflow side and a second outflow side opposite the second inflow side. The second leaflet component has a plurality of second frame attachment edges, at least one second inflow free edge and a second outflow free edge opposite the at least one second inflow free edge. The second leaflet component being movable between an open position to allow fluid flow in a forward direction through the lumen and a closed position in cooperative engagement with the at least one first leaflet component that prevents fluid flow in a retrograde direction through the lumen. The first frame attachment edge of each first leaflet component being coupled to the inflow portion of the leaflet attachment region with the first inflow side facing the axis. The frame attachment edges of the second leaflet component being coupled to at least the outflow portion of the leaflet attachment region with the second inflow side facing the axis. Wherein a second overlap region of the second leaflet component adjacent the second inflow free edge overlaps a first overlap region of the first leaflet component adjacent the first outflow free edge such that they are in sealing engagement therewith when the leaflet is in the closed position defining a leaflet overlap region preventing fluid flow through the lumen in the retrograde direction. Wherein the first overlap region of each first leaflet component and the second overlap region are not in contact therewith wherein the first outflow free edge of the each of the first leaflet component and the second inflow free edge define a gap therebetween when the leaflet is not in the closed position, wherein fluid adjacent the second outflow side can pass through the gap during fluid flow in the forward direction. 
     A method for reducing incidents of thrombus or reducing thrombus formation associated with treating a human patient with a diagnosed condition or disease associated with valve insufficiency or valve failure of a native valve, the method comprising implanting a prosthetic valve at the location of the native valve. The prosthetic valve comprises a frame and a plurality of leaflets. The frame has an inflow end and an outflow end opposite the inflow end and defines a lumen therebetween defining an axis. The frame has at least one leaflet attachment region having an inflow portion and an outflow portion. Each leaflet being coupled to each of the at least one leaflet attachment regions. The at least one leaflet includes at least one first leaflet component and a second leaflet component. The at least one first leaflet component has a first inflow side and a first outflow side opposite the first inflow side. The at least one first leaflet component has a first frame attachment edge and a first outflow free edge. The second leaflet component has a second inflow side and a second outflow side opposite the second inflow side. The second leaflet component has a plurality of second frame attachment edges, at least one second inflow free edge and a second outflow free edge opposite the at least one second inflow free edge. The second leaflet component being movable between an open position to allow fluid flow in a forward direction through the lumen and a closed position in cooperative engagement with the at least one first leaflet component that prevents fluid flow in a retrograde direction through the lumen. The first frame attachment edge of each first leaflet component being coupled to the inflow portion of the leaflet attachment region with the first inflow side facing the axis. The frame attachment edges of the second leaflet component being coupled to at least the outflow portion of the leaflet attachment region with the second inflow side facing the axis. Wherein a second overlap region of the second leaflet component adjacent the second inflow free edge overlaps a first overlap region of the first leaflet component adjacent the first outflow free edge such that they are in sealing engagement therewith when the leaflet is in the closed position defining a leaflet overlap region preventing fluid flow through the lumen in the retrograde direction. Wherein the first overlap region of each first leaflet component and the second overlap region are not in contact therewith wherein the first outflow free edge of the each of the first leaflet component and the second inflow free edge define a gap therebetween when the leaflet is not in the closed position, wherein fluid adjacent the second outflow side can pass through the gap during fluid flow in the forward direction. 
     Applications 
     The prosthetic valve of the embodiments provided herein can be used as a prosthetic heart valve. In this capacity, the prosthetic valve is placed in an orifice collocated with a native heart valve or in place of an excised heart valve to regulate the flow of blood through the heart. It is believed that the leaflet moves to the first position, for example, as illustrated in  FIG. 2B , during systole in which the heart forces blood through the artery or vein in a forward flow direction  402 . During diastole, the leaflet  300  moves to the closed position, illustrated in  FIG. 2A , to substantially prevent fluid flow in the second, opposite direction referred to as retrograde flow. It is believed that a pressure change and reversal of flow direction occurs during the change from systole to diastole, and the leaflet  300  changes position in response to these changes. 
     The prosthetic valve of the embodiments provided herein can also be used as a prosthetic venous valve. In this capacity, the prosthetic valve is placed in a vein to regulate the flow of blood through the vein. 
     In accordance with an embodiment, a method of making a prosthetic valve comprises obtaining a leaflet frame, and a leaflet including a first leaflet component and a second leaflet component. Coupling the first leaflet component adjacent to an inlet portion of the leaflet frame. Coupling the second leaflet component adjacent to an outlet portion of the leaflet frame such that a second overlap region of a second inflow free edge of the second leaflet component overlaps a first overlap region of a first outflow free edge of the first leaflet component such that a portion of a second inflow side of the second leaflet component is in contact and in sealing engagement with a portion of a first outflow side of the first leaflet component when the leaflet is in a closed position defining a leaflet overlap region preventing fluid flow through the lumen in the retrograde direction. And wherein the first overlap region and the second overlap region are not in contact therewith wherein the first outflow free edge and the second inflow free edge define a gap therebetween when the leaflet is not in the closed position, wherein fluid adjacent the second outflow side can pass through the gap during fluid flow in the forward direction. 
     Numerous characteristics and advantages have been set forth in the preceding description, including various alternatives together with details of the structure and function of the devices and/or methods. The disclosure is intended as illustrative only and as such is not intended to be exhaustive. It will be evident to those skilled in the art that various modifications can be made, especially in matters of structure, materials, elements, components, shape, size and arrangement of parts including combinations within the principles of the disclosure, to the full extent indicated by the broad, general meaning of the terms in which the appended claims are expressed. To the extent that these various modifications do not depart from the spirit and scope of the appended claims, they are intended to be encompassed therein.