Artificial valve prosthesis with improved flow dynamics
An expandable venous valve having a support structure that configured to enlarge the area adjacent to the valve structure such that the flow patterns of retrograde flow are modified in a way that facilitates the flushing of the pockets at the base of the valve area to prevent stagnation of bodily fluid, which in the venous system, can lead to thrombus formation. The enlarged pocket areas can be created by forming an artificial sinus adjacent the valve structure in an unsupported section of vessel wall between two support frame section or the support frame can comprise an expanded-diameter intermediate or proximal section that forms an artificial sinus adjacent the valve structure. In another group of embodiments, the attachment pathway between opposing leaflets and the support frame and/or vessel wall comprises a proximal portion that places the leaflets in extended contact with one another and a distal portion forms a large angle with respect to the adjacent walls such that a large pocket is created at the base of the leaflets. In one embodiment, the attachment pathway extends distally along a pair of substantially parallel longitudinal attachment struts to create an extended leaflet contact area, then angles circumferentially and distally from the former along distal attachment struts to define the bottom edge of the leaflets.
1. A radially expandable artificial valve prosthesis for implantation in a vessel having a vessel wall comprising:
a support structure having a longitudinal axis, a first end that includes a first and a second commissure, and a second end located distal thereto, the first and second commissures disposed substantially opposite each other with respect to the longitudinal axis, the support structure defining first and second attachment pathways, the first attachment pathway including a first proximal portion extending from the first commissure, a second proximal portion extending from the second commissure, a first distal portion angling obliquely from the first proximal portion and a second distal portion angling obliquely from the second proximal portion, the first and second distal portions cooperatively defining a first distal commissure at the second end of the support structure, the second attachment pathway including a third proximal portion extending from the first commissure, a fourth proximal portion extending from the second commissure, a third distal portion angling obliquely from the third proximal portion and a fourth distal portion angling obliquely from the fourth proximal portion, the third and fourth distal portions cooperatively defining a second distal commissure at the second end of the support structure, the first, second, third, and fourth proximal portions extending along a substantial portion of the length of the prosthesis and having a substantially parallel orientation with respect to the longitudinal axis of the support structure, the first and second distal commissures disposed substantially opposite each other with respect to the longitudinal axis;
a plurality of leaflets, each leaflet of the plurality of leaflets having an outer edge that includes a first lateral edge extending distally from the first commissure and a second lateral edge extending distally from the second commissure, the first and second lateral edges generally converging about the second end of the support structure such that the plurality of leaflets is configured to collectively form a seal with said vessel wall and restrict fluid flow through said vessel; and
wherein the first and second lateral edges of a first leaflet of the plurality of leaflets are each attached to the support structure along the first attachment pathway and the first and second lateral edges of a second leaflet of the plurality of leaflets are each attached to the support structure along the second attachment pathway such that each leaflet of the plurality of leaflets has a coaptable area and a basal portion, the coaptable area and basal portion configured to cooperate with said vessel wall to define a valve pocket;
wherein the coaptable areas of the plurality of leaflets are configured to coapt with each other while said valve prosthesis is in a resting state and wherein each coaptable area of each leaflet of the plurality of leaflets has a length that is between 10% and 80% of the length of said valve prosthesis.
2. The radially expandable artificial valve prosthesis of claim 1 , wherein the support structure comprises a superelastic material.
3. The radially expandable artificial valve prosthesis of claim 2 , wherein the superelastic material comprises nitinol.
4. The radially expandable artificial valve prosthesis of claim 1 , wherein each coaptable area of each leaflet of the plurality of leaflets has a length that is between 30% and 60% of the length of said valve prosthesis.
5. The radially expandable artificial valve prosthesis of claim 1 , wherein each coaptable area of each leaflet of the plurality of leaflets has a length that is between 35% and 55% of the length of said valve prosthesis.
6. The radially expandable artificial valve prosthesis of claim 1 , wherein each coaptable area of each leaflet of the plurality of leaflets has a length that is greater than 50% of the length of said valve prosthesis.