WO2004008998A1

WO2004008998A1 - Mechanical heart valve prosthesis with improved occluding kinematics

Info

Publication number: WO2004008998A1
Application number: PCT/EP2003/007769
Authority: WO
Inventors: Anselm Steegers; Bernd Holder
Original assignee: Lsmedcap Gmbh
Priority date: 2002-07-19
Filing date: 2003-07-17
Publication date: 2004-01-29
Also published as: AU2003260311A1

Abstract

The present invention relates to an improved mechanical heart valve prosthesis, more particular to a prosthetic valve working according to physiologic kinematics, i.e. the leaflets of those valves open centrally as native valves do. The occluders (521, 522) of the invented valve design are equipped with so called 'winglets' (561, 562), i.e. the peripheral corners of the trailing edges (541, 542) of the leaflets show a distinct curvature, which for the leaflets in opened position is located in a plane perpendicular to the main axis (flow direction) of the valve.

Description

Mec anica! heart valve prosthesis with improved occiu iπg kinematics

The present invention relates to heart valve prostheses.

Mechanical heart valve prostheses are according to their definition valves made entirely from technical materials. This results in good durability on the one hand, while the major drawbacks of these products currently on the market are in the limited hemocompatibility primarily due to the suboptimal flow pattern of the blood within the valve and its direct neighborhood, where turbulent and laminar shear stresses damage the erythrocytes and thrombocytes. This leads to the need of lifetime anticoagulation medication to reduce the risk of thromboembolic events, on the other hand entailing hemorrhagic risk and increased follow up cost. These disadvantages are addressed by the present invention. The above mentioned drawbacks of mechanical heart valves according to the state of the art could not be overcome by detail modifications as can be seen from the valves emerging on the market within the last 50 years. The construction of heart valve prostheses developed from ballvallves to lifting disc valves to tilting disc valves and finally to bileaflet valves which comprise of two hinged occluder bodies. Although the performance of those turns out to be superior compared to the former embodiments, the above mentioned drawbacks could not be overcome. Bileaflet valves itself have been modified in a wide range during the last 20 years however, regarding the occluder kinematics, all the valves currently available show an antiphysilogical working principle. Hence, the hemodynamics were only slightly improved without any significant impact on clinical outcome.

Native aortic valves, however, are working in a different way, the physiologic working principle. The leaflets open centrally, i.e. the downstream edges move from the center of the valve to the periphery giving free a large central opening area. All valves currently available work vice versa. During opening movement, the leaflets rotate in a way that the downstream edges move from the periphery to the center, i.e. an anti-physiological working principle. This results in two larger lateral opening areas and a small central on. Severe flow disturbance can be seen for those valves.

Several publications describe the idea of heart valve prostheses which try to mimic the characteristic physiologic kinematics of native heart valves. The occluders of those valves open centrally, i.e. from the center of the valve to the periphery. This is supposed to result in superior hemodynamics as well as advantageous kinematics of the occluders of those heart valve prostheses entailing a significantly reduced risk of thromboembolic and hemorrhagic events. Such valves are for instance disclosed in US 4,078,268 (1978); US 4,363,142 (1982); US 4,676,789 (1987); EP0283413A1 (1988); US 4,808,180 (1989); US 5,405,381 (1995); US 5,814,099 (1998).

Unfortunately, till this day, bileaflet valves according to this principle could not be realized. The reason for this is the highly complex flow pattern during the phase of the opening and closing movement of the occluders. These flow phenomena make it impossible for these valves to work adequately due to principle interrelations between flow pattern and occluder movement. Despite the fact that the first disclosure of that principle took place some quarter century ago these problems could not be overcome - physiologically working bileaflet mechanical heart valves could not be realized.

An object of the present invention is to overcome the above cited problems by providing a heart valve prosthesis according to claim 1.

The valve according to the invention makes possible a physiologic kinematics of the occluders by leading the blood flow around the occluders in a way that results in flow forces, which cause an opening (resp. closing) moment during the entire phase of movement of the occluders.

Beside making the physiologic kinematics (central opening) of bileaflet valves possible in principle, the invented design results in several more hemodynamic advantages of the heart valve prostheses. With the valve according to the invention the achieved flow of bileaflet valves becomes substantially more laminar, more even and essentially free of disturbances. The flow does not show any more regions of separation as known for prior art designed valves within the wake of the leaflets. Thereby this results in a substantially less degree of blood damage with the known problems of thromboembolic and hemolytic risks. Moreover, the design according to the present invention results in superior energetic efficacy (i.e. pressure drop, closure volume loss) and excellent leaflet kinematics. Leaflets are significantly less fluttering.

Furthermore, the trailing edge of the leaflets now can be designed in the ideal orientation parallel to the main flow direction. This leads in a further improved hemodynamic, reduction of wake and flow separation areas, early reattachment to the aortic wall, decreased peripheral vortex street. A parallel orientation of the trailing edge up to now could only be achieved by a special hinge design to force leaflet rotation by a translatory movement which potentially causes an increased risk of thromboembolic events as known from the Medtronic Parallel valve (see literature). The presented valve characteristics makes free design of the hinges possible.

The invented valve allows the design of a further increased opening area which is strongly related to the pressure drop and the valve efficacy.

Summarizing the advantages achieved by the invented design characteristics: • Central flow

• Reduced vortex- and turbulence- areas

• Reduced areas of flow separation

• Reducing leaflet fluttering (fig 5)

• Decreased thromboembolic and hemolytic risk • Decreased pressure drop of the valve

• Fast opening

• Early and fast closure with a concurrent reduction of the leaflet velocity at the instant of closure resulting in an attenuation of the impact

• Significantly reduced closure volume (backflow during closing movement) • Significantly reduced elastic rebound of the leaflets (cavitation)

• Reduced wear within the hinges and at the leaflet / ring contact areas

• Reduced proneness to cavitation

• Reduced proneness to HITS with a reduced incidence of neurocognitive impairment in the long term outcome

The leaflets are designed in a way that the peripheral ends of the trailing edge comprise so called "winglets" (Figures No. 5 and 6), i.e. the peripheral ends of the leaflets have curvatures which for the leaflets in opened position are located within a plane perpendicular to the main flow direction. In contrast to that, valves of the prior art have leaflets which are essentially flat or leaflets which are curved or cambered in a plane parallel to the main flow direction or which are substantially evenly curved within the plane perpendicular to the main flow direction. The latter leaflet curvatures of the prior art, which might be located in a plane perpendicular to the main flow direction show a grade of curvature which is essentially constant over the length of the trailing edge. The novel geometry, however, involves a curvature where the grade of curvature is increased in a region nearby the tip of the trailing edge to built so called "winglets". It is to be noted that the invention is not limited to a specific winglet shape or to a specific orientation of the winglets. It is also not limited to a specific number of winglets or to a specific location where the winglets should be fixed to the leaflet. Nor is the present invention limited to aortic valve replacements.

A non limitative example of the invention will be discussed hereafter with the help of the following drawings:

Fig. 1. Prior art valve. Fig. 2 Native aortic valve principle Fig. 3 Prior art physiological working valve draft. Fig. 4 Working principles. Fig. 5 Perspective view of a bileaflet valve equipped with the novel occluders according to the present invention

Fig. 6: Perspective view of a leaflet equipped with the novel winglets according to the present invention.

Fig. 7: Leaflet curvature. Fig. 8 Leaflet cambering Fig. 9. Leaflet curvature.

Detailed description of the preferred embodiment

A drawing of the prior art valve is given in Figure No. 1 (100). The valve comprises of a valve ring (120) defined by the leading edge where the blood enters the valve body (121) and the trailing edge (122), where the blood emerges from the valve. The valve body carries two leaflet occluders (130) being adapted to rotate between an open and an closed position by means of suitable hinge mechanisms (110). Leaflet occluders are defined by a leading edge (131 ) and a trailing edge (132) according to the blood flow direction (101). Due to the design principle, the leaflet occluders are to move in a way that the trailing edge closes at the ring, while the leading edges defines the central diameter of the valve. Figure No. 2 on the other hand depicts the native aortic valve. Comprising of the aortic root (210) and three leaflets (221, 222, 223). Blood flows from the ventricular side (201) towards the aortic side (202). The leaflets move according to the given direction (231, 232, 233) as seen from the aortic side.

Figure No. 3 shows a draft of a valve according to the physiological kinematics principle. The leaflets (321, 322) defined by a leading edge (331, 332) and a trailing edge (341, 342) according to the main flow direction (301) are received by the ring (310) in a way that the trailing edges (341 , 342) move from the center towards the lateral ring area.

Figure No. 4 makes the difference between physiological and anti-physiological principle clear: figure No. 4a gives the prior art anti-physiological kinematics while Figure No. 4b depicts the physiological working principle. Blood direction is defined by (410) and (420). Opening movement is given by (411) and (421). Leaflet rotation center is given at (415) and (425), respectively.

The preferred embodiment of the present invention is given in Figure No. 5. The valve ring (510) is defined by a leading edge (511) and a trailing edge (512) according to the main flow direction (501). The ring carries two leaflet occluders (521 and 522) which are defined by a leading edge (531 and 532) and a trailing edge (541 and 542). Leaflets are received by hinge mechanisms (551 and 552). The leaflets are equipped with winglets (561 and 562)

One leaflet of the preferred embodiment is given in Figure No. 6. The leaflet body (611) is defined by the leading edge (621) and a trailing edge (631) according to the main flow direction (601). The leaflet is symmetrically equipped with winglets (651 and 661).

Another embodiment is given in Figure No. 7a as seen from the valve outflow side, where the leaflet body (711) with its skeleton line (721) is flat regarding the cross section in the plane substantially orthogonal io the main flow direction (701). Winglets (751 and 761) might be adapted as seen from the drawing. On the other hand a curved leaflet body might be advantageous as given in Figure No. 7b. Leaflet body (712) might be curved in the main valve area as illustrated by the skeleton line (722) regarding the cross section in the plane substantially orthogonal to the main flow direction (702). The winglets might be adapted as shown (752 and 762). Another embodiment of the valve leaflets is given in Figure No. 8; where Figure 8a gives a leaflet (811) defined by leading edge (821) and trailing edge (831) which is cambered (871) in a plane substantially parallel to the main flow direction (801) but equipped with winglets (851 and 861). In comparison Figure 8b gives the flat leaflet body in the same view. The valve body (812) defined by leading edge (822) and trailing edge (832) is equipped with winglets (852 and 862). Whereas the skeleton lines are substantially not curved (881 and 882)

A further embodiment which might be advantageous is given in Figure No. 9. The leaflet body (911) defined by leading edge (921) and trailing edge (931) is curved in a plane substantially parallel to the main flow direction (901). The curvature is defined by the leaflets body skeleton line (981) The orientation of that curvature might be towards the valve center (901) ), see Figure 9a or vice versa (902) ), see Figure 9b. The winglets of this leaflet embodiment might be integrated as shown (951 and 961) or (952 and 962), respectively.

Claims

1. A heart valve prosthesis comprising:

- a substantially annular valve body essentially defined within a plane x-y, said valve body having an interior surface defining a central passageway through which blood may flow substantially along a direction z perpendicular to said plane ^χ-y.

- a pair of opposed leaflet occluders adapted to be received within said valve body and being rotatable around an axis which is parallel to said plane x-y, said leaflet occluders being adapted to rotate between an open position permitting blood flow in a downstream direction and a closed position blocking the reverse flow of blood in an upstream direction, each leaflet occluder furthermore comprising a trailing edge disposed on its downstream side, each trailing edge being defined in a plane parallel to said plane x-y when the valve is open and both trailing edges being in contact when the valve is closed, characterized by the fact that each leaflet occluder comprises two winglets, each one being located at one end of said trailing edge and being defined in a plane substantially parallel to the z direction when the valve is open.

2. A heart valve prosthesis according to claim 1 characterized by the fact that each leaflet occluder or its winglets are not curved regarding a skeleton line defined in a plane substantially parallel to the main flow direction.

3. A heart valve prosthesis according to claim 1 characterized by the fact that each leaflet occluder or its winglets are curved regarding a skeleton line defined in a plane substantially parallel to the main flow direction.

4. A heart valve prosthesis according to claim 1 characterized by the fact that each leaflet occluder body is not curved regarding a skeleton line defined in a plane substantially orthogonal to the main flow direction.

5. A heart valve prosthesis according to claim 1 characterized by the fact that each leaflet occluder body is curved regarding a skeleton line defined in a plane substantially orthogonal to the main flow direction.

6. A heart valve prosthesis according to claim 1 characterized by the fact that each leaflet occluder or its winglets are not cambered regarding the leaflet body or the winglets.

7. A heart valve prosthesis according to claim 1 characterized by the fact that each leaflet occluder or its winglets are cambered regarding the leaflet body or the winglets.