Heart valve prosthesis and method of manufacture
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.
1. 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 in a neutral position, 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 composite wave providing multiple curves in the leaflet free edge; 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 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 method of claim 1 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.
3. The method of claim 1 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.
4. The method of claim 1 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.
5. The method of claim 1 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.
6. The method of claim 1 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.
7. The method of claim 3 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.
8. The method of claim 3 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.
9. The method of claim 4 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.
10. The method of claim 4 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.
11. The method of claim 1 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.
12. The method of claim 1 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.
13. The method of claim 1 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.
14. The method of claim 1 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.
15. The method of claim 1 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.
16. The method of claim 11 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.
17. The method of claim 12 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.
18. The method of claim 1 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.
19. The method of claim 1 where the included angle between adjacent leaflet free edges at the partially open commissures is in the range of 25 to 55°.
20. The method of claim 1 where the included angle between adjacent leaflet free edges at the partially open commissures is in the range of 40 to 55°.