Heart valve prosthesis and method of manufacture

Abstract

A cardiac valve prosthesis having a frame and two or more leaflets (preferably three) attached to the frame. The leaflets are attached to the frame between posts, with a free edge which can seal the leaflets together when the valve is closed under back pressure. The leaflets are created in a mathematically defined shape allowing good wash-out of the whole leaflet orifice, including the area close to the frame posts, thereby relieving the problem of thrombus deposition under clinical implant conditions.

What is claimed is:  
     
         1 . A cardiac valve prosthesis comprising: 
 a frame defining a blood flow axis; and    at least two flexible leaflets attached to the frame, the at least two leaflets being configured to be movable from an open to a closed position, the at least two leaflets having a blood inlet side and a blood outlet side, the at least two leaflets being in the closed position when fluid pressure is applied to the outlet side, being in the open position when fluid pressure is applied to the inlet side and being in a neutral position intermediate the open and closed position, in the absence of fluid pressure being applied to the leaflets, the at least two leaflets including a first leaflet having a surface contour such that when the first leaflet is in the neutral position an intersection of the first leaflet with at least one plane perpendicular to the blood flow axis forms a first composite wave, the first composite wave being substantially defined by a first wave combined with at least a second wave superimposed over the first wave, the first wave having a first frequency, the second wave having a second frequency, the first frequency being different from the second frequency,    wherein the frame is substantially cylindrical having first and second ends, one of the ends defining at least two scalloped edge positions separated by at least two posts, each post having a tip,    wherein each leaflet has a fixed edge joined to a respective scalloped edge portion of the frame and a free edge extending substantially between the tips of two posts, and    wherein when the at least two leaflets are in the neutral position the valve prosthesis has partially open commissures defined by an included angle between adjacent leaflet free edges that is in the range of 10 to 55°.    
     
     
         2 . The valve prosthesis of  claim 1  wherein the first composite wave is defined by a first wave combined with second and third waves superimposed over the first wave, the third wave having a third frequency which is different from the first frequency.  
     
     
         3 . The valve prosthesis of  claim 1  wherein the first wave is symmetric about a plane parallel to and intersecting the blood flow axis and bisecting the first leaflet.  
     
     
         4 . The valve prosthesis of  claim 1  wherein the first wave is asymmetric about a plane parallel to and intersecting the blood flow axis and bisecting the first leaflet.  
     
     
         5 . The valve prosthesis of  claim 1  wherein the second wave is symmetric about a plane parallel to and intersecting the blood flow axis and bisecting the first leaflet.  
     
     
         6 . The valve prosthesis of  claim 1  wherein the second wave is asymmetric about a plane parallel to and intersecting the blood flow axis and bisecting the first leaflet.  
     
     
         7 . The valve prosthesis of  claim 3  wherein the second wave is symmetric about a plane parallel to and intersecting the blood flow axis and bisecting the first leaflet.  
     
     
         8 . The valve prosthesis of  claim 3  wherein the second wave is asymmetric about a plane parallel to and intersecting the blood flow axis and bisecting the first leaflet.  
     
     
         9 . The valve prosthesis of  claim 4  wherein the second wave is symmetric about a plane parallel to and intersecting the blood flow axis and bisecting the first leaflet.  
     
     
         10 . The valve prosthesis of  claim 4  wherein the second wave is asymmetric about a plane parallel to and intersecting the blood flow axis and bisecting the first leaflet.  
     
     
         11 . The valve prosthesis of  claim 1  wherein the first composite wave is symmetric about a plane parallel to and intersecting the blood flow axis and bisecting the first leaflet.  
     
     
         12 . The valve prosthesis of  claim 1  wherein the composite wave is asymmetric about a plane parallel to and intersecting the blood flow axis and bisecting the first leaflet.  
     
     
         13 . The valve prosthesis of  claim 1  wherein the at least two leaflets further include second and third leaflets and wherein an intersection of the second and third leaflets with the plane perpendicular to the blood flow axis forms second and third composite waves, respectively, the second and third composite waves being substantially the same as the first composite wave.  
     
     
         14 . The valve prosthesis of  claim 1  wherein the first wave is defined by an equation which is one of trigonometric, elliptical, hyperbolic, parabolic, circular, a smooth analytic function and a table of values.  
     
     
         15 . The valve prosthesis of  claim 1  wherein the second wave is defined by an equation which is one of trigonometric, elliptical, hyperbolic, parabolic, circular, a smooth analytic function and a table of values.  
     
     
         16 . The valve prosthesis of  claim 1  wherein the at least two leaflets are configured such that they are substantially free of bending stresses when in the neutral position.  
     
     
         17 . The valve prosthesis of  claim 11  wherein the first and second waves are symmetric about a plane parallel to and intersecting the blood flow axis and bisecting the first leaflet.  
     
     
         18 . The valve prosthesis of  claim 12  wherein at least one of the first and second waves is asymmetric about a plane parallel to and intersecting the blood flow axis and bisecting the first leaflet.  
     
     
         19 . The valve prosthesis of  claim 1  wherein the first leaflet has a surface contour such that when the first leaflet is in the neutral position an intersection of the first leaflet with a plane parallel to and intersecting the blood flow axis and bisecting the first leaflet forms a fourth wave.  
     
     
         20 . The valve prosthesis of  claim 1  wherein the included angle between adjacent leaflet free edges at the partially open commissures is in the range of 25 to 55°.  
     
     
         21 . The valve prosthesis of  claim 1  wherein the included angle between adjacent leaflet free edges at the partially open commissures is in the range of 40 to 55°.  
     
     
         22 . A method of making a cardiac valve prosthesis which includes a frame defining a blood flow axis substantially parallel to the flow of blood through the valve prosthesis and at least two flexible leaflets attached to the frame, the method comprising: 
 providing a forming element having at least two leaflet forming surfaces;    engaging the forming element to the frame;    applying a coating over the frame and engaged forming element, the coating binding to the frame, the coating over the leaflet forming surfaces forming the at least two flexible leaflets, the at least two leaflets being configured to be movable from an open to a closed position, the at least two leaflets having a blood inlet side and a blood outlet side, the at least two leaflets being in the closed position when fluid pressure is applied to the outlet side, being in the open position when fluid pressure is applied to the inlet side and being in a neutral position intermediate the open and closed position, in the absence of fluid pressure being applied to the leaflets, the at least two leaflets including a first leaflet having a surface contour such that when the first leaflet is in the neutral position an intersection of the first leaflet with at least one plane perpendicular to the blood flow axis forms a first composite wave, the first composite wave being substantially defined by a first wave combined with at least a second superimposed wave, the first wave having a first frequency, the second wave having a second frequency, the first frequency being different from the second frequency; and    disengaging the forming element from the frame, and 
 wherein the frame is substantially cylindrical having first and second ends, one of the ends defining at least two scalloped edge positions separated by at least two posts, each post having a tip,  
   wherein each leaflet has a fixed edge joined to a respective scalloped edge portion of the frame and a free edge extending substantially between the tips of two posts, and    wherein when the at least two leaflets are in the neutral position the valve prosthesis has partially open commissures defined by an included angle between adjacent leaflet free edges that is in the range of 10 to 55°.    
     
     
         23 . The method of  claim 22  wherein the first composite wave formed in the coating step is defined by a first wave combined with second and third waves superimposed over the first wave, the third wave having a third frequency which is different from the first frequency.  
     
     
         24 . The method of  claim 22  wherein the first wave formed in the coating step is symmetric about a plane parallel to and intersecting the blood flow axis and bisecting the first leaflet.  
     
     
         25 . The method of  claim 22  wherein the first wave formed in the coating step is asymmetric about a plane parallel to and intersecting the blood flow axis and bisecting the first leaflet.  
     
     
         26 . The method of  claim 22  wherein the second wave formed in the coating step is symmetric about a plane parallel to and intersecting the blood flow axis and bisecting the first leaflet.  
     
     
         27 . The method of  claim 22  wherein the second wave formed in the coating step is asymmetric about a plane parallel to and intersecting the blood flow axis and bisecting the first leaflet.  
     
     
         28 . The method of  claim 24  wherein the second wave formed in the coating step is symmetric about a plane parallel to and intersecting the blood flow axis and bisecting the first leaflet.  
     
     
         29 . The method of  claim 24  wherein the second wave formed in the coating step is asymmetric about a plane parallel to and intersecting the blood flow axis and bisecting the first leaflet.  
     
     
         30 . The method of  claim 25  wherein the second wave formed in the coating step is symmetric about a plane parallel to and intersecting the blood flow axis and bisecting the first leaflet.  
     
     
         31 . The method of  claim 25  wherein the second wave formed in the coating step is asymmetric about a plane parallel to and intersecting the blood flow axis and bisecting the first leaflet.  
     
     
         32 . The method of  claim 22  wherein the first composite wave formed in the coating step is symmetric about a plane parallel to and intersecting the blood flow axis and bisecting the first leaflet.  
     
     
         33 . The method of  claim 22  wherein the first composite wave formed in the coating step is asymmetric about a plane parallel to and intersecting the blood flow axis and bisecting the first leaflet.  
     
     
         34 . The method of  claim 22  wherein the at least two leaflets formed in the coating step include second and third leaflets and wherein an intersection of the second and third leaflets with the plane perpendicular to the blood flow axis forms second and third composite waves, respectively, the second and third composite waves being substantially the same as the first composite wave.  
     
     
         35 . The method of  claim 22  wherein the first wave formed in the coating step is defined by an equation which is one of trigonometric, elliptical, hyperbolic, parabolic, circular, a smooth analytic function and a table of values.  
     
     
         36 . The method of  claim 22  wherein the second wave formed in the coating step is defined by an equation which is one of trigonometric, elliptical, hyperbolic, parabolic, circular, a smooth analytic function and a table of values.  
     
     
         37 . The method of  claim 32  wherein the first and second waves formed in the coating step are symmetric about a plane parallel to and intersecting the blood flow axis and bisecting the first leaflet.  
     
     
         38 . The method of  claim 33  wherein at least one of the first and second waves formed in the coating step is asymmetric about a plane parallel to and intersecting the blood flow axis and bisecting the first leaflet.  
     
     
         39 . The method of  claim 22  wherein the at least two leaflets formed in the coating step are configured such that they are substantially free of bending stresses when in the neutral position.  
     
     
         40 . The method of  claim 22  where the included angle between adjacent leaflet free edges at the partially open commissures is in the range of 25 to 55°.  
     
     
         41 . The method of  claim 22  where the included angle between adjacent leaflet free edges at the partially open commissures is in the range of 40 to 55°.  
     
     
         42 . A cardiac valve prosthesis comprising: 
 a frame defining a blood flow axis; and    at least two leaflets attached to the frame including a first leaflet having an internal surface facing the blood flow axis and an external surface facing away from the blood flow axis, the first leaflet being configured such that a mean thickness of a first half of the first leaflet is different than a mean thickness of a second half of the first leaflet, the first leaflet being divided into first and second halves by a plane parallel to and intersecting the blood flow axis and bisecting the first leaflet.    
     
     
         43 . The cardiac valve prosthesis of  claim 42  wherein the first leaflet is further configured such that a thickness of the first leaflet between the internal and external surfaces along a cross section defined by the intersection of a plane perpendicular to the blood flow axis and the first leaflet increases gradually and substantially continuously from a first end of the cross section to a second end of the cross section.  
     
     
         44 . A method of making a cardiac valve prosthesis which includes a frame defining a blood flow axis substantially parallel to the flow of blood through the valve prosthesis and at least two flexible leaflets attached to the frame, the method comprising: 
 providing a mold having a cavity sized to accommodate the frame;    inserting the frame into the mold;    inserting the mold into an injection molding machine;    injecting molten polymer into the cavity of the mold to form the at least two leaflets and band the at least two leaflets to the frame, the cavity being shaped to form the at least two leaflets in a desired configuration, the at least two leaflets being configured to be movable from an open to a closed position, the at least two leaflets having a blood inlet side and a blood outlet side, the at least two leaflets being in the closed position when fluid pressure is applied to the outlet side, being in the open position when fluid pressure is applied to the inlet side and being in a neutral position intermediate the open and closed position, in the absence of fluid pressure being applied to the leaflets, the at least two leaflets including a first leaflet having a surface contour such that when the first leaflet is in the neutral position an intersection of the first leaflet with at least one plane perpendicular to the blood flow axis forms a first composite wave, the first composite wave being substantially defined by a first wave combined with at least a second superimposed wave, the first wave having a first frequency, the second wave having a second frequency, the first frequency being different from the second frequency, and    wherein the frame is substantially cylindrical having first and second ends, one of the ends defining at least two scalloped edge positions separated by at least two posts, each post having a tip,    wherein each leaflet has a fixed edge joined to a respective scalloped edge portion of the frame and a free edge extending substantially between the tips of two posts, and    wherein when the at least two leaflets are in the neutral position the valve prosthesis has partially open commissures defined by an included angle between adjacent leaflet free edges that is in the range of 10 to 55°.    
     
     
         45 . The method of  claim 44  wherein the first composite wave formed in the injecting step is defined by a first wave combined with second and third waves superimposed over the first wave, the third wave having a third frequency which is different from the first frequency.  
     
     
         46 . The method of  claim 44  wherein the first wave in the injecting step is symmetric about a plane parallel to and intersecting the blood flow axis and bisecting the first leaflet.  
     
     
         47 . The method of  claim 44  wherein the first wave in the injecting step is asymmetric about a plane parallel to and intersecting the blood flow axis and bisecting the first leaflet.  
     
     
         48 . The method of  claim 44  wherein the second wave in the injecting step is symmetric about a plane parallel to and intersecting the blood flow axis and bisecting the first leaflet.  
     
     
         49 . The method of  claim 44  wherein the second wave in the injecting step is asymmetric about a plane parallel to and intersecting the blood flow axis and bisecting the first leaflet.  
     
     
         50 . The method of  claim 46  wherein the second wave in the injecting step is symmetric about a plane parallel to and intersecting the blood flow axis and bisecting the first leaflet.  
     
     
         51 . The method of  claim 46  wherein the second wave in the injecting step is asymmetric about a plane parallel to and intersecting the blood flow axis and bisecting the first leaflet.  
     
     
         52 . The method of  claim 47  wherein the second wave in the injecting step is symmetric about a plane parallel to and intersecting the blood flow axis and bisecting the first leaflet.  
     
     
         53 . The method of  claim 47  wherein the second wave in the injecting step is asymmetric about a plane parallel to and intersecting the blood flow axis and bisecting the first leaflet.  
     
     
         54 . The method of  claim 44  wherein the first composite wave in the injecting step is asymmetric about a plane parallel to and intersecting the blood flow axis and bisecting the first leaflet.  
     
     
         55 . The method of  claim 44  wherein the first composite wave in the injecting step is asymmetric about a plane parallel to and intersecting the blood flow axis and bisecting the first leaflet.  
     
     
         56 . The method of  claim 44  wherein the at least two leaflets formed in the injecting step include second and third leaflets and wherein an intersection of the second and third leaflets with the plane perpendicular to the blood flow axis forms second and third composite waves, respectively, ht second and third composite waves being substantially the same as the first composite wave.  
     
     
         57 . The method of  claim 44  wherein the first wave in the injecting step is defined by an equation which is one of trigonometric, elliptical, hyperbolic, parabolic, circular, a smooth analytic function and a table of values.  
     
     
         58 . The method of  claim 44  wherein the second wave in the injecting step is defined by an equation which is one of trigonometric, elliptical, hyperbolic, parabolic, circular, a smooth analytic function and a table of values.  
     
     
         59 . The method of  claim 54  wherein the first and second waves in the injecting step are symmetric about a plane parallel to and intersecting the blood flow axis and bisecting the first leaflet.  
     
     
         60 . The method of  claim 55  wherein at least one of the first and second waves in the injecting step is asymmetric about a plane parallel to and intersecting the blood flow axis and bisecting the first leaflet.  
     
     
         61 . The method of  claim 44  wherein the at least two leaflets in the injecting step are configured such that they are substantially free of bending stresses when in the neutral position.  
     
     
         62 . The method of  claim 44  where the included angle between adjacent leaflet free edges at the partially open commissures is in the range of 25 to 55°.  
     
     
         63 . The method of  claim 44  where the included angle between adjacent leaflet free edges at the partially open commissures is in the range of 40 to 55°.  
     
     
         64 . A method of designing a cardiac valve prosthesis which includes a frame and at least two flexible leaflets attached to the frame, the method comprising: 
 defining a first desired shape of the leaflets in a first position;    defining a second desired shape of the leaflets in a second position different from the first position; and    conducting a draping analysis to identify values of adjustable parameters defining at least one of the first and second shapes to ensure that the leaflets are comprised of a sufficient amount and distribution of material for the leaflets to assume both the first and second desired shapes.    
     
     
         65 . The method of  claim 64  wherein at least one of the first and second positions in the defining steps is a closed position and the other of the first and second positions is a partially open position.  
     
     
         66 . A cardiac valve prosthesis comprising: 
 a frame defining a blood flow axis; and    at least two flexible leaflets attached to the frame, the at least two leaflets being configured to be movable from an open to a closed position, the at least two leaflets having a blood inlet side and a blood outlet side, the at least two leaflets being in the closed position when fluid pressure is applied to the outlet side, being in the open position when fluid pressure is applied to the inlet side and being in a neutral position intermediate the open and closed position, in the absence of fluid pressure being applied to the leaflets,    wherein the frame is substantially cylindrical having first and second ends, one of the ends defining at least two scalloped edge positions separated by at least two posts, each post having a tip,    wherein each leaflet has a fixed edge joined to a respective scalloped edge portion of the frame and a free edge extending substantially between the tips of two posts, and    wherein when the at least two leaflets are in the neutral position the valve prosthesis has partially open commissures defined by an included angle between adjacent leaflet free edges that is in the range of 10 to 55°.    
     
     
         67 . A method of making a cardiac valve prosthesis which includes a frame defining a blood flow axis substantially parallel to the flow of blood through the valve prosthesis and at least two flexible leaflets attached to the frame, the method comprising: 
 providing a forming element having at least two leaflet forming surfaces;    engaging the forming element to the frame;    applying a coating over the frame and engaged forming element, the coating binding to the frame, the coating over the leaflet forming surfaces forming the at least two flexible leaflets, the at least two leaflets being configured to be movable from an open to a closed position, the at least two leaflets having a blood inlet side and a blood outlet side, the at least two leaflets being in the closed position when fluid pressure is applied to the outlet side, being in the open position when fluid pressure is applied to the inlet side and being in a neutral position intermediate the open and closed position in the absence of fluid pressure being applied to the leaflets; and    disengaging the forming element from the frame, and    wherein the frame is substantially cylindrical having first and second ends, one of the ends defining at least two scalloped edge portions separated by at least two posts, each post having a tip,    wherein each leaflet has a fixed edge joined to a respective scalloped edge portion of the frame and a free edge extending substantially between the tips of the at least two posts, and    wherein when the at least two leaflets are in the neutral position the valve prosthesis has partially open commissures defined by an included angle between adjacent leaflet free edges that is in the range of 10 to 55°.    
     
     
         68 . A method of making a cardiac valve prosthesis which includes a frame defining a blood flow axis substantially parallel to the flow of blood through the valve prosthesis and at least two flexible leaflets attached to the frame, the method comprising: 
 providing a mold having a cavity sized to accommodate the frame;    inserting the frame into the mold;    inserting the mold into an injection molding machine;    injecting molten polymer into the cavity of the mold to form the at least two leaflets and bond the at least two leaflets to the frame, the cavity being shaped to form the at least two leaflets in a desired configuration, the at least two leaflets being configured to be movable from an open to a closed position, the at least two leaflets having a blood inlet side and a blood outlet side, the at least two leaflets being in the closed position when fluid pressure is applied to the outlet side, being in the open position when fluid pressure is applied to the inlet side and being in a neutral position intermediate the open and closed position in the absence of fluid pressure being applied to the leaflets, and    wherein the frame is substantially cylindrical having first and second ends, one of the ends defining at least two scalloped edge portions separated by at least two posts, each post having a tip,    wherein each leaflet has a fixed edge jointed to a respective scalloped edge portion of the frame and a free edge extending substantially between the tips of the at least two posts, and    wherein when the at least two leaflets are in the neutral position the valve prosthesis has partially open commissures defined by an included angle between adjacent leaflet free edges that is in the range of 10 to 55°.    
     
     
         69 . A cardiac valve prosthesis comprising: 
 a substantially cylindrical frame defining a blood flow axis, the frame having first and second ends, one of the ends defining at least two scalloped edge positions separated by at least two posts, each post having a tip; and    at least two flexible leaflets attached to the frame, the at least two leaflets being configured to be movable from an open to a closed position, the at least two leaflets having a blood inlet side and a blood outlet side, the at least two leaflets being in the closed position when fluid pressure is applied to the outlet side, being in the open position when fluid pressure is applied to the inlet side and being in a neutral position intermediate the open and closed position, in the absence of fluid pressure being applied to the leaflets, each leaflet having a fixed edge joined to a respective scalloped edge portion of the frame and a free edge extending substantially between the tips of two posts.    
     
     
         70 . The valve prosthesis of  claim 69  wherein the at least two leaflets include a first leaflet having a surface contour such that when the first leaflet is in the neutral position an intersection of the first leaflet with at least one plane perpendicular to the blood flow axis forms a first composite wave, the first composite wave being substantially defined by a first wave combined with at least a second wave superimposed over the first wave, the first wave having a first frequency, the second wave having a second frequency different than the first frequency, the first wave comprising a circular arc.  
     
     
         71 . The valve prosthesis of  claim 70  wherein the first wave is defined by a first wave combined with second and third waves superimposed over the first wave, the third wave having a third frequency which is different from the first and second frequencies.  
     
     
         72 . The valve prosthesis of  claim 70  wherein the second wave is symmetric about a plane parallel to and intersecting the blood flow axis and bisecting the first leaflet.  
     
     
         73 . The valve prosthesis of  claim 70  wherein the second wave is asymmetric about a plane parallel to and intersecting the blood flow axis and bisecting the first leaflet.  
     
     
         74 . The valve prosthesis of  claim 70  wherein the first composite wave is symmetric about a plane parallel to and intersecting the blood flow axis and bisecting the first leaflet.  
     
     
         75 . The valve prosthesis of  claim 70  wherein the first composite wave is asymmetric about a plane parallel to and intersecting the blood flow axis and bisecting the first leaflet.  
     
     
         76 . The valve prosthesis of  claim 70  wherein the at least two leaflets further include second and third leaflets and wherein an intersection of the second and third leaflets with the plane perpendicular to the blood flow axis forms second and third composite waves, respectively, the second and third composite waves being substantially the same as the first composite wave.  
     
     
         77 . The valve prosthesis of  claim 70  wherein the second wave is defined by an equation which is one of trigonometric, elliptical, hyperbolic, a smooth analytic function and a table of values.  
     
     
         78 . The valve prosthesis of  claim 69  wherein the at least two leaflets are configured such that they are substantially free of bending stresses when in the neutral position.  
     
     
         79 . The valve prosthesis of  claim 74  wherein the first and second waves are symmetric about a plane parallel to and intersecting the blood flow axis and bisecting the first leaflet.  
     
     
         80 . The valve prosthesis of  claim 75  wherein at least one of the first and second waves is asymmetric about a plane parallel to and intersecting the blood flow axis and bisecting the first leaflet.  
     
     
         81 . The valve prosthesis of  claim 70  wherein the first leaflet has a surface contour such that when the first leaflet is in the neutral position an intersection of the first leaflet with a plane parallel to and intersecting the blood flow axis and bisecting the first leaflet forms a fourth wave.  
     
     
         82 . A method of making a cardiac valve prosthesis which includes a substantially cylindrical frame defining a blood flow axis substantially parallel to the flow of blood through the valve prosthesis and at least two flexible leaflets attached to the frame, the method comprising: 
 forming at least two scalloped edge portions on the frame, the shape of each scalloped edge portion being defined by the intersection of the frame with a plane inclined with respect to the blood flow axis;    treating the frame to raise its surface energy to above about 64 mN/m;    providing a forming element having at least two leaflet forming surfaces;    engaging the forming element to the frame;    applying a coating over the frame and engaged forming element, the coating binding to the frame, the coating over the leaflet forming surfaces forming the at least two flexible leaflets, the at least two leaflets being configured to be movable from an open to a closed position, the at least two leaflets having a blood inlet side and a blood outlet side, the at least two leaflets being in the closed position when fluid pressure is applied to the outlet side, being in the open position when fluid pressure is applied to the inlet side and being in a neutral position intermediate the open and closed position, in the absence of fluid pressure being applied to the leaflets, the at least two leaflets including a first leaflet having a surface contour such that when the first leaflet is in the neutral position an intersection of the first leaflet with at least one plane perpendicular to the blood flow axis forms a first composite wave, the first composite wave being substantially defined by a first wave combined with at least a second superimposed wave, the first wave having a first frequency, the second wave having a second frequency, the first frequency being different from the second frequency, the first wave comprising a circular arc; and    disengaging the forming element from the frame.    
     
     
         83 . The method of  claim 82  wherein the first composite wave formed in the coating step is defined by a first wave combined with second and third waves superimposed over the first wave, the third wave having a third frequency which is different from the first frequency.  
     
     
         84 . The method of  claim 82  wherein the second wave formed in the coating step is symmetric about a plane parallel to and intersecting the blood flow axis and bisecting the first leaflet.  
     
     
         85 . The method of  claim 82  wherein the second wave formed in the coating step is asymmetric about a plane parallel to and intersecting the blood flow axis and bisecting the first leaflet.  
     
     
         86 . The method of  claim 82  wherein the first composite wave formed in the coating step is symmetric about a plane parallel to and intersecting the blood flow axis and bisecting the first leaflet.  
     
     
         87 . The method of  claim 82  wherein the first composite wave formed in the coating step is asymmetric about a plane parallel to and intersecting the blood flow axis and bisecting the first leaflet.  
     
     
         88 . The method of  claim 82  wherein the at least two leaflets formed in the coating step include second and third leaflets and wherein an intersection of the second and third leaflets with the plane perpendicular to the blood flow axis forms second and third composite waves, respectively, the second and third composite waves being substantially the same as the first composite wave.  
     
     
         89 . The method of  claim 82  wherein the second wave formed in the coating step is defined by an equation which is one of trigonometric, elliptical, hyperbolic, a smooth analytic function and a table of values.  
     
     
         90 . The method of  claim 86  wherein the first and second waves formed in the coating step are symmetric about a plane parallel to and intersecting the blood flow axis and bisecting the first leaflet.  
     
     
         91 . The method of  claim 87  wherein at least one of the first and second waves formed in the coating step is asymmetric about a plane parallel to and intersecting the blood flow axis and bisecting the first leaflet.  
     
     
         92 . The method of  claim 82  wherein the at least two leaflets formed in the coating step are configured such that they are substantially free of bending stresses when in the neutral position.