GB2239690A

GB2239690A - Heart valve prosthesis.

Info

Publication number: GB2239690A
Application number: GB8928792A
Authority: GB
Inventors: Gianni Angelini; Claudio Pistolesi
Original assignee: Cardio Carbon Co Ltd
Current assignee: Cardio Carbon Co Ltd
Priority date: 1989-12-20
Filing date: 1989-12-20
Publication date: 1991-07-10
Also published as: GB8928792D0; WO1991008719A1; EP0506779A1; AU7030591A

Abstract

A bileaflet heart valve prosthesis has two leaflets (2, 3) which are pivotally mounted in an annular housing (1). The leaflets are pivotable between a closed position and an open position in which the flow of blood through the valve is substantially unrestricted. Pivot formations (4, 5) are provided on respective leaflets and are movable, in respective pivot seats (6, 7) provided in the annular housing, in the direction of blood flow. The upstream facing surface defined by the leaflets (2, 3) in their closed position is concave and smoothly curved in two mutually perpendicular directions.

Description

Heart Valve Prosthesis The present invention is concerned with heart valve prostheses.

Various types of synthetic heart prosthesis are known which operate haemodynamically when used in the surgical replacement of a heart valve, such as the mitral or aortic valve.

One known type of heart valve prosthesis is the St. Jude valve, which comprises a valve body having a passageway for the flow of blood therethrough from upstream to downstream, and a pair of flat leaflets which are pivotally supported in the passageway and movable between a closed position inhibiting blood flow and an open position permitting blood flow therethrough.

Another known type of heart valve prosthesis is the Duramedics valve which is a bileaflet valve in which the leaflets are curved in a plane parallel to the pivot axis of the leaflets.

Such heart valve prostheses have peripheral pivot points, the pivot axes being substantially parallel to the junction between the two leaflets, and each axis defining a chord on the respective leaflet. Such heart valve prostheses all have points of weakness at the pivot points, which can cause catastrophic failure and/or promote blood coagulation.

Moreover, the leaflets provide obstructions to the flow of blood through the valve and substantially disturb the laminarity of such blood flow.

The present invention seeks to provide an improved bileaflet heart valve prosthesis. According to the present invention therefore, there is provided a heart valve prosthesis comprising: a) a unitary annular valve body having a passageway for the flow of blood therethrough; b) a pair of rigid, pivotally mounted leaflets, which are pivotally movable between a closed position and an open position, in which closed position said leaflets lie adjacent to or abut one another along a common sealing edge so as to substantially obturate said passageway to the flow of blood therethrough, said leaflets having first curved surfaces which in said closed position define a concave upstream-facing surface in which said sealing edge is smoothly curved along its length, said upstream-facing surface being smoothly curved transversely across said sealing edge, and in which open position said curved surfaces are spaced from and face one another such that the flow of blood through said passageway in use is substantially unrestricted; c) pivot seat formations provided integral with said annular body, which formations are so dimensioned and shaped to receive complementary pivot formations provided integrally on respective leaflets such that said pivot formations are movable relative to respective pivot seats in the direction of blood flow as said leaflets are pivotally moved from said closed position to said open position.

The heart valve prosthesis according to the invention is generally such that the passageway is substantially free of any transverse obstruction to blood flow when the leaflets are in the open position. It is particularly preferred that in the open position, the leaflets are arranged such that the minimum spacing between the first curved surfaces is substantially no less than the spacing between the axes about which the leaflets pivot.

The leaflets are preferably symmetrical and generally semi-circular or semi-elliptical when viewed in plan.

It is preferred that the leaflets h#ave obverse surfaces which are substantially parallel to the first curved surfaces.

In the closed position it is preferred that the leaflets are substantially wholly contained within the upstream and downstream limits of the body.

Preferably, the pivot seats are provided in diametrically opposed portions of the annular valve body. It is preferred that the pivot formations provided on respective leaflets are substantially parallel to the common sealing edge when the leaflets are in the closed position.

Advantageously, the pivot formations may be ovaloid in cross-section, in which case the respective pivot seats are preferably generally triangular in cross-section.

It is preferred that in the closed position, the sealing edge is of a continuous radius of curvature along its length. It is particularly preferred that the radius of curvature of the sealing edge is greater than the internal radius of curvature of the annular valve body.

The leaflets, the valve body and the pivot formations (that is, substantially the entire valve) may be of any suitable non-thrombogenic material. Examples of suitable materials include pyrolytic carbon, certain ceramics (such as silicon nitride), stainless steel, glass or vitreous carbon.

It is particularly preferred to employ vitreous carbon, which can be made by careful, controlled pyrolysis of resin mouldings (for example, using a method as described in "Polymeric Carbons, Carbon Fibre, Glass and Char" by G. Jenkins and K.

Kawamura, Cambridge University Press, 1976). In this method, the resin material (such as a phenolic resin or a furan resin) is moulded, baked while in the mould and then slowly pyrolysed over a prolonged period.

A preferred embodiment of the present invention will now be described with reference to the accompanying drawings, in which: Figures la and lb are, respectively, plan and side elevations of an exemplary heart valve according to the invention, with a pair of leaflets in the fully closed position; Figures 2a and 2b are, respectively, plan and side elevations of the heart valve of Figures la and lb with the leaflets just separated; Figures 3a and 3b are, respectively, plan and side elevations showing the leaflets slightly further open; Figures 4a and 4b are, respectively, plan and side elevations showing the leaflets in the fully open position; and Figures Sa and 5b are scrap sectional views showing a preferred construction of pivot formations and pivot seats, with leaflets respectively in a closed and an open position.

The illustrated embodiment comprises a valve occluder ring 1 having a pair of generally semi-circular leaflets 2,3 each having a peripheral extension 4,5 beyond the root thereof. Each peripheral extension is integral with the main leaflet structure and connected in sessile fashion (that is, without any intervening constriction or "stalk").

Extensions 4,5 are each seated on respective seating structures 6,7 in a freely-floating manner so that the leaflets can pivot by sliding movement of the extension and the associated leaflet. The seating structures and the associated leaflet. The seating structures are upstream of the median plane X-X of the occluder ring 1.

Leaflets 2,3 are concave when viewed in the direction of arrow A (from the upstream direction) and convex when viewed from downstream. Each face of each leaflet is in the form of a smooth continuous curve, such that blood can flow in a non-turbulent manner over both faces.

Figures la and lb show the leaflets in fully closed position with the free edges 8,9 in close juxtaposition. In the fully closed position, the leaflets are wholly within the upstream and downstream limits 10,11 of the occluder ring.

Figures 2a and 2b show the leaflets in slightly open position (about 109 relative to the median plane X-X) with the free edges 8,9 slightly separated.

Figures 3a and 3b show the leaflets in slightly more open position (about 309 relative to the median plane X-X).

Figures 4a and 4b show the leaflets in the fully open position; in this position it will be noted that the free edges 8,9 are separated by an amount equal to the spacing between the pivot structures. In this position, the passageway 12 is, as shown, free of any transverse obstruction to the flow of blood. Blood flowing through the valve need only come into contact with smoothly curved surfaces.

Figures 5a and Sb show a pivot formation of ovaloid cross-section, pivotable in a generally triangular pivot seat, the corners of which are radiused. Shaping the pivot seats and pivot formations in this way inhibits the accumulation of blood in the pivot seats, since the leaflets moving from a closed position (Figure 5a) to an open position (Figure 5b) cause the ovaloid pivot formations to 'squeeze' any accumulated blood clear of the pivot seat, ensuring circulation of 'fresh' blood around the pivot formations.

Claims

Claims:

1. A heart valve prosthesis comprising: 4 a) a unitary annular valve body having a passageway for the flow of blood therethrough; b) a pair of rigid, pivotally mounted leaflets, which are pivotally movable between a closed position and an open position, in which closed position said leaflets lie adjacent to or abut one another along a common sealing edge so as to substantially obturate said passageway to the flow of blood therethrough, said leaflets having first curved surfaces which in said closed position define a concave upstream-facing surface in which said sealing edge is smoothly curved along its length, said upstream-facing surface being smoothly curved transversely across said sealing edge, and in which open position said curved surfaces are substantially spaced from and face one another such that the flow of blood through said passageway in use is substantially unrestricted; c) pivot seat formations provided integral with said annular body, which formations are so dimensioned and shaped to receive complementary pivot formations provided integrally on respective leaflets such that said pivot formations are movable relative to respective pivot seats in the direction of blood flow as said leaflets are pivotally moved from said closed position to said open position.

2. A heart valve prosthesis according to claim 1, wherein said passageway is substantially free of any transverse obstruction to blood flow when said leaflets are in said open position.

3. A heart valve prosthesis according to claim 1 or claim 2, wherein said leaflets when in said open position are arranged such that the minimum spacing between said first curved surfaces is not substantially less than the spacing between the axes about which the leaflets pivot.

4. A heart valve prosthesis according to any preceding claim, wherein said leaflets are symmetrical and generally semi-circular or semi-elliptical when viewed in plan.

5. A heart valve prosthesis according to any preceding claim, wherein said leaflets have obverse surfaces which are substantially parallel to said first curved surfaces.

6. A heart valve prosthesis according to any preceding claim, wherein said leaflets are substantially wholly contained within the upstream and downstream limits of the valve body.

7. A heart valve prosthesis according to any preceding claim, wherein said pivot seats are provided in diametrically opposed portions of the annular valve body.

8. A heart valve prosthesis according to any preceding claim, wherein said pivot formations provided on respective leaflets are substantially parallel to the common sealing edge when the the leaflets are in the closed position.

9. A heart valve prosthesis according to any preceding claim, wherein said pivot formations are ovaloid in cross-section, with respective pivot seats being generally triangular in cross-section.

10. A heart valve prosthesis according to any preceding claim, wherein in said closed position, said sealing edge is of a continuous radius of curvature along its length.

11. A heart valve prosthesis according to any preceding claim, wherein the radius of curvature of said sealing edge is greater than the internal radius of curvature of said annular valve body.

12. A heart valve prosthesis according to any preceding claim, wherein substantially the entire valve is of vitreous carbon.

13. A heart valve prosthesis as substantially described herein with reference to the accompanying drawings.