WO2016178126A1

WO2016178126A1 - Mitral valve implant

Info

Publication number: WO2016178126A1
Application number: PCT/IB2016/052470
Authority: WO
Inventors: Shmuel Banai; Eyal Benjamin BEN ASSA
Original assignee: The Medical Research Infrastructure And Health Services Fund Of The Tel-Aviv Medical Center
Priority date: 2015-05-05
Filing date: 2016-05-01
Publication date: 2016-11-10

Abstract

A prosthetic heart valve includes a frame (40, 52, 62, 82, 102, 122), which is configured for implantation in an annulus between first and second chambers (24, 26) of a heart (48). Two or more leaflets (32, 34, 58, 64, 72, 84, 86, 104, 106, 108, 112, 114, 116, 124, 126) are held within the frame and configured to open so as to admit blood from the first chamber into the second chamber and to close so as to prevent blood flow from the second chamber to the first chamber. The frame and leaflets are configured to direct blood flowing from the first chamber through the valve into the second chamber in a direction that is angled obliquely relative to a plane of the annulus.

Description

MITRAL VALVE IMPLANT

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Patent Application 62/156,919, filed May 5, 2015, which is incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates generally to implantable medical devices, and particularly to prosthetic mitral valves for surgical or trans-catheter implantation.

BACKGROUND

The native heart valves serve critical functions in assuring forward flow of blood through the cardiovascular system. Dysfunction of a heart valve can result in cardiovascular compromise and even death. For example, mitral regurgitation (MR) is the most prevalent heart valve disease in western countries, affecting almost 10% of individuals over 75 years of age. The definitive treatment for a dysfunctional heart valve is surgical or percutaneous repair or replacement of the valve. Prosthetic cardiac valves have been used for many years to treat cardiac valvular disorders, including MR.

For example, U.S. Patent Application Publication 2013/0053950 describes a prosthetic mitral valve assembly is disclosed. The assembly comprises a radially-expandable stent including a lower portion sized for deployment between leaflets of a native mitral valve and an upper portion having a flared end. The upper portion is sized for deployment within the annulus of the mitral valve and the flared end is configured to extend above the annulus. The stent is formed with a substantially D-shape cross-section for conforming to the native mitral valve. The assembly further includes a valve portion formed of pericardial tissue and mounted within an interior portion of the stent for occluding blood flow in one direction.

As another example, U.S. Patent Application Publication 2014/0379074 describes systems, devices and methods associated with the placement of a dock or anchor for a prosthetic mitral valve. The anchor may take the form of a helical anchor having multiple coils and/or a stent-like structure. U.S. Patent Application Publication 2014/0296971 describes an alignment device for providing the correct valve alignment during deployment of an asymmetrical transcatheter valve while it is being deployed in a patient in need thereof. SUMMARY

Embodiments of the present invention that are described hereinbelow provide improved devices and methods for mitral valve repair and replacement.

There is therefore provided, in accordance with an embodiment of the invention, a prosthetic heart valve, including a frame, which is configured for implantation in an annulus between first and second chambers of a heart. Two or more leaflets are held within the frame and configured to open so as to admit blood from the first chamber into the second chamber and to close so as to prevent blood flow from the second chamber to the first chamber. The frame and leaflets are configured to direct blood flowing from the first chamber through the valve into the second chamber in a direction that is angled obliquely relative to a plane of the annulus.

In a disclosed embodiment, the frame is configured for implantation in a mitral annulus between a left atrium and a left ventricle of the heart, and the frame and leaflets are configured to direct the blood toward a posterior wall of the left ventricle during diastole. Typically, the valve is configured to create a vortex, which directs the blood from the mitral annulus toward an outflow tract of the left ventricle.

In some embodiments, the leaflets have an asymmetrical shape chosen so that when open, at least one of the leaflets directs the blood in the obliquely- angled direction. In some of these embodiments, the leaflets include at least first and second leaflets of different, respective sizes. In one embodiment, the first leaflet is larger than the second leaflet, and at least the first leaflet includes flexible, resilient ribs on a side of the first leaflet that is configured to face into the second chamber. Additionally or alternatively, the leaflets include at least first and second leaflets of different, respective shapes and/or different, respective angulations, relative to the plane of the annulus, when the leaflets are open.

In some embodiments, the frame includes a ring. In a disclosed embodiment, the ring has a non-uniform cross-sectional shape, which is selected so as to conform to the annulus. Additionally or alternatively, the ring has an asymmetrical shape chosen so as to direct the blood in the obliquely- angled direction. In one embodiment, the ring has a first side configured to face into the first chamber and a second side configured to face into the second chamber, wherein the second side is angled obliquely relative to the first side.

Additionally or alternatively, the frame includes a high-porosity surface, which is mounted in an oblique orientation, relative to the plane of the annulus so as to direct the blood in the obliquely- angled direction.

In some embodiments, the two or more leaflets include at least three leaflets. There is also provided, in accordance with an embodiment of the invention, a method for treatment of a heart of a living subject. The method includes implanting a prosthetic heart valve in an annulus between first and second chambers of the heart, while orienting the implanted heart valve so as to direct blood flowing from the first chamber through the valve into the second chamber in a direction that is angled obliquely relative to a plane of the annulus.

In some embodiments, the prosthetic heart valve is implanted between a left atrium and a left ventricle of the heart, and the implanted heart valve is oriented so as to direct the blood toward a posterior wall of the left ventricle during diastole. Typically, the prosthetic heart valve is configured to create vortices, which direct a flow of the blood from an inlet to an outflow tract of the left ventricle.

In one embodiment, implanting the prosthetic heart valve includes mounting the prosthetic heart valve, in a crimped state, at an end of a catheter, and inserting the catheter via a vascular system of the subject so as deliver the valve to the annulus, and expanding the prosthetic heart valve at the annulus.

In an alternative embodiment, implanting the prosthetic heart valve includes inserting the prosthetic heart valve through an apex of the heart into the annulus.

In some embodiments, the prosthetic heart valve includes leaflets having an asymmetrical shape chosen so that when open, at least one of the leaflets directs the blood in the obliquely- angled direction.

Additionally or alternatively, the prosthetic heart valve includes a frame, including a ring having an asymmetrical shape chosen so as to direct the blood in the obliquely- angled direction.

Further additionally or alternatively, the prosthetic heart valve includes a frame, including a high-porosity surface, which is mounted in an oblique orientation, relative to the plane of the annulus so as to direct the blood in the obliquely- angled direction.

The present invention will be more fully understood from the following detailed description of the embodiments thereof, taken together with the drawings in which:

BRIEF DESCRIPTION OF THE DRAWINGS

Figs. 1A and IB are schematic, anterior sectional views of a heart showing a mitral valve prosthesis during systole and diastole, respectively, in accordance with an embodiment of the invention;

Figs. 2A and 2B are schematic sectional and top views, respectively, of a mitral valve prosthesis in a closed configuration, in accordance with an embodiment of the invention; Fig. 2C is a schematic side view of the mitral valve prosthesis of Figs. 2A and 2B in an open configuration, in accordance with an embodiment of the invention;

Fig. 3 is a schematic, posterior sectional view of a heart in which the mitral valve prosthesis of Figs. 2A-C has been implanted, in accordance with an embodiment of the invention;

Fig. 4A is a schematic side view of a mitral valve prosthesis, in accordance with another embodiment of the invention;

Fig. 4B is a schematic, posterior sectional view of a heart in which the mitral valve prosthesis of Fig. 4A has been implanted, in accordance with an embodiment of the invention;

Figs. 5A and 5B are schematic top and sectional views, respectively, of a mitral valve prosthesis, in accordance with a further embodiment of the invention;

Figs. 6A and 6B are schematic top and sectional views, respectively, of a mitral valve prosthesis, in accordance with an alternative embodiment of the invention;

Fig. 7 is a schematic, pictorial illustration of a mitral valve prosthesis, in accordance with yet another embodiment of the invention;

Figs. 8-10 are schematic top views of mitral valve prostheses, in accordance with additional embodiments of the invention;

Figs. 11A and 1 IB are schematic top and bottom pictorial views, respectively, of a mitral valve prosthesis in a closed configuration, in accordance with an embodiment of the invention; and

Fig. 11C is a schematic top pictorial view of the mitral valve prosthesis of Figs. 11 A and 1 IB in an open configuration, in accordance with an embodiment of the invention.

DETAILED DESCRIPTION OF EMBODIMENTS

Inflow dynamics of blood entering the left ventricle feature the formation of vortices associated with the smooth redirection of flow from the inlet to the outflow tract. The inventor has found that the physiologic asymmetrical blood flow in the left ventricle is essential in optimizing cardiac function by preserving kinetic energy, maintaining ventricular structure and enabling enhanced output during strenuous exertion. Every deviation from the normal flow pattern can cause increased energy loss.

The mitral valve controls the flow direction from the left atrium into left ventricle of the heart. During the early diastolic phase, the blood that flows from the left atrium into the left ventricle passes through the relatively narrow mitral valve. As a result, a pressure gradient is imposed across the mitral valve annulus. From the point of view of fluid dynamics, the flow direction fulfills the rule of minimum system energy loss. In the case of blood flow through the mitral valve, the natural structure of the valve, including the asymmetrical sizes and shapes of the two leaflets of the valve, is such that minimum energy loss is achieved when the flow is directed toward the posterior wall of the left ventricle, thus giving rise to the desired vortex formation.

Replacing a dysfunctional native mitral valve with a prosthetic valve restores the unidirectional blood flow through the valve and eliminates mitral regurgitation. It fails, however, to restore the unique, asymmetrical spiral inflow dynamics of blood entering the left ventricle during diastole. Mitral valve prostheses that are known in the art cause distortion of the normal intraventricular flow pattern, and therefore increase energy dissipation and raise oxygen consumption of the myocardium. These factors can eventually lead to deterioration in left ventricular function and thus to poor clinical outcomes.

Embodiments of the present invention that are described herein provide a prosthetic mitral valve assembly that is designed to create inflow patterns and intra- ventricular blood flow dynamics that preserve kinetic energy of the blood, by creating intra-ventricular vortices that redirect the flow from the inlet to the outflow tract of the left ventricle. The inflow patterns created by this mitral prosthesis mimic the normal flow dynamics that are created by the native mitral valve. The resulting asymmetrical spiral flow optimizes cardiac function, maintains ventricular structure, and enables enhanced output during strenuous exertion.

The disclosed prosthetic mitral valve assemblies fit the contour of the native mitral apparatus and can be inserted by a trans-catheter approach or by a surgical approach. The assembly comprises an outer support frame with tissue leaflets mounted therein, each having one end coupled to the frame and the opposite end free. In diastole the free ends of the prosthetic valve leaflets are disposed away from one another to open the valve orifice and allow antegrade blood flow from the left atrium into the left ventricle. The configuration of the frame and/or the leaflets is such that when the valve opens in diastole, it directs the blood flow towards the posterior wall of the left ventricle. This configuration creates an asymmetrical spiral flow of blood into the left ventricle, forming vortices that redirect the flow from the inlet to the outflow tract of the left ventricle, thus preserving kinetic energy. These vortices can help to maintain efficient cardiac output under various physiologic and pathologic conditions.

Thus, embodiments of the present invention that are described herein mimic the functionality of the natural mitral valve in directing blood flow towards the posterior wall of the left ventricle. The disclosed valve prostheses shift and/or direct the blood flow in a direction that is angled obliquely (i.e., neither perpendicular nor parallel) relative to the plane of the valve annulus by imposing additional forces on the blood. These forces include inertial (velocity) force, shear force, and pressure force. The present embodiments can use one or more of three principal means to induce these forces on the blood flow from the left atrium into the left ventricle:

• Configuring and implanting the prosthetic mitral valve such that its orifice (narrowest cross- section) direction is in the desired flow direction.

• Using a flow-diverting surface downstream from the prosthetic mitral valve ring (i.e., on the ventricular side of the mitral annulus) to divert the blood flow away from that surface and direct it toward another surface. This technique involves manipulation mainly by shear and inertial forces.

• Mounting a highly-porous surface normal to the desired flow direction, downstream from the mitral valve (i.e., in the left ventricle). The porous surface creates a further small pressure gradient and thus shifts the flow. This technique involves manipulation mainly by shear and pressure forces.

Some example embodiments illustrating implementations of these principles are described below. These implementations are suited particularly for mitral valve repair but may alternatively be adapted, mutatis mutandis, for replacement of other heart valves. Although each of these implementations is shown separately, the principles of these embodiments may alternatively be combined in a single prosthetic valve.

In the disclosed embodiments, a prosthetic heart valve comprises a frame, which is implanted in the natural valve annulus between two chambers of a heart, such as the left atrium and left ventricle. Two or more leaflets, held within the frame, open so as to admit blood from the first chamber into the second chamber and close so as to prevent blood flow from the second chamber to the first chamber. The frame and leaflets are configured to direct blood flowing from the first chamber through the valve into the second chamber in a direction that is angled obliquely relative to the plane of the annulus.

Figs. 1A and IB are schematic, anterior sectional views of a heart showing a mitral valve prosthesis 20 during systole and diastole, respectively, in accordance with an embodiment of the invention. An outer solid stent or other frame comprises a ring, which anchors prosthesis 20 to fit the contour and shape of a native mitral annulus 22, between a left atrium 24 and a left ventricle 26. During systole, as shown in Fig. 1A, contraction of left ventricle 26 pumps blood out through an aortic valve 28 into an ascending aorta 30, and leaflets 32 and 34 of prosthesis close to prevent regurgitation of blood into atrium 24. During diastole, as shown in Fig. IB, leaflets 32 and 34 open to allow blood flow from atrium 24 into ventricle 26, as illustrated by an arrow 36.

Prosthesis 20 is positioned so that the native leaflets of the mitral valve (not shown in the figures) are held in the open position. Within the solid frame or stent of prosthesis 20, flexible leaflets 32 and 34 open and close the prosthetic valve orifice. Leaflets 32 and 34 are asymmetric and different in size and shape, as well as in the angulation in which each leaflet opens relative to the plane of mitral annulus 22. During diastole, as shown by arrow 36, the configuration and shape of the leaflets directs the inflow of blood towards the posterior wall of left ventricle 26 in an asymmetrical spiral flow, which creates intra-ventricular vortices that redirect the flow from the inlet to the outflow tract of the left ventricle, i.e., toward aortic valve 28.

As noted earlier, prosthesis 20, as well as valves of other designs that are described hereinbelow, may be implanted by either open-heart or less invasive approaches. In the latter category, the prosthetic valve may be mounted in a crimped state on the end portion of a flexible catheter (not shown) and advanced through the patient's vascular system. For example, the catheter may be passed through the vena cava, into the right atrium, crossing the septum between the right and left atria until the valve is delivered to the implantation site. The valve at the catheter tip is then expanded to its functional size at the site of the defective native mitral valve.

Another technique that may be used is a transapical approach, in which a small incision is made in the chest wall of a patient. The catheter is advanced through the apex into the left ventricle, where it is expanded in place of the native mitral valve, either using a balloon or using a self-expandable ring or stent as the prosthetic valve housing.

Reference is now made to Figs. 2A-C and 3, which schematically show details of mitral valve prosthesis 20, in accordance with an embodiment of the invention. Figs. 2A and B are top and sectional views, respectively, with leaves 32 and 34 in a closed (systolic) configuration, while Fig. 2C is a side view of prosthesis 20 in an open (diastolic) configuration. Fig. 3 is a schematic, posterior sectional view of a heart 48 in which prosthesis 20 has been implanted.

As shown in the figures, prosthesis 20 comprises a frame in the form of a rigid or semirigid ring 40, which is sized and shaped to fit within the mitral annulus. Asymmetrical leaflets 32 and 34 are attached within the ring. The surface plane vector of ring 40 is marked in Fig. 2C by an arrow 42, while another arrow 44 marks a tangent to the surface of the larger leaflet 32. Thus, leaflets 32 and 34 have different sizes, different shapes, and different angulations (as illustrated by arrow 44) when open, all chosen to give the desired, oblique flow direction, which is marked by an arrow 46. As shown in Fig. 3, prosthesis 20 is oriented in the mitral annulus in heart 48 so that this flow direction points toward the posterior wall of ventricle 26. As a result, the blood flows through ventricle 26 along a spiral path indicated by an arrow 49, thus mimicking the flow pattern induced by the natural mitral valve in a healthy heart.

Ring 40 (as well as the prosthetic valve housings or bodies used in other embodiments) can be made from any suitable biocompatible metallic material, such as Nitinol, stainless steel or a cobalt chromium alloy, or a plastic, such as polyethylene terephthalate (PET), polyamide or polyimide. Although ring 40 is shown in Fig. 2A as circular, a ring with a non-circular shape, such as a D-shaped ring (to conform to the natural shape of the mitral valve annulus) or other shape may alternatively be used, as shown in some of the figures that follow. The ring is typically covered with a woven or non- woven fabric (such as PET), which serves as a sewing ring to anchor the prosthetic valve in place. Alternatively, the ring can be made from a metal or plastic wire mesh, which is radially collapsible and expandable for use in minimally-invasive implantation techniques.

Leaflets 32 and 34, as well as the leaflets shown in the embodiments that follow, can be made from soft, elastic materials, such as bovine, porcine or equine pericardium, or suitable biocompatible elastomers, such as polyurethane, or hard elastic materials, such as carbon fiber. The leaflets are cut to their pre-defined shapes and sewn to ring 40. Alternatively, the ring and leaflets may be cast or molded as one piece. As another option, prosthesis 20 can be made from a xenograft heart valve (such as a porcine xenograft valve), which is shaped in accordance with one of the described embodiments.

Figs. 4A and 4B schematically illustrate a mitral valve prosthesis 50, in accordance with another embodiment. Fig. 4A is a side view of prosthesis 50, while Fig. 4B is a posterior sectional view of heart 48 in which prosthesis 50 has been implanted. Prosthesis 50 comprises a rigid or semi-rigid ring 52 with symmetrical leaflets 58. Ring 52 has a lower side 54, which faces into left ventricle 26 and is oriented obliquely (i.e., not parallel) relative to an upper side 56 of the ring, which faces into left atrium 24. The surface plane vector of upper side 56, which is mounted on the mitral annulus between left atrium 24 and left ventricle 26, is marked by arrow 42. The surface plane vector of lower side 54, where leaflets 58 are mounted, is marked by an arrow 57, which is angled relative to arrow 42 and is roughly parallel to the desired flow direction. The shape and orientation of ring 52 thus cause the blood to flow through prosthesis 50 toward the posterior wall of ventricle 26, as marked by arrow 46 in Fig. 4B. Figs. 5A and 5B are schematic top and sectional views, respectively, of a mitral valve prosthesis 60, in accordance with a further embodiment of the invention. The frame of prosthesis 60 comprises a ring 62, having upper and lower sides that are oriented obliquely relative to one another, with two leaflets 64 mounted within the ring. The frame of prosthesis 60 also comprises a high-porosity surface 66, which is mounted on the lower side of ring 62, in an oblique orientation, relative to the valve annulus, facing into the left ventricle. The surface plane vector of surface 66, marked by an arrow 68, is angled relative to arrow 42 and is approximately parallel to the desired flow direction, marked by arrow 46. Surface 66 can be made from the sorts of biocompatible metal or polymeric materials that are mentioned above, in the form of woven wires or a thin plate with an array of slits or holes. For example, in one embodiment, surface 66 contains slits that are in the range of 1-4 cm long and 2-5 mm wide.

Figs. 6A and 6B are schematic top and sectional views, respectively, of a mitral valve prosthesis 70, in accordance with an alternative embodiment of the invention. Prosthesis 70 is similar in it construction and principle of operation to prosthesis 60, but contains three symmetrical leaflets 72, instead of the two shown in Fig. 5A. In other embodiments (not shown in the figures), mitral valve prostheses implementing the principles described herein may have four or five leaflets, for example.

Fig. 7 is a schematic, pictorial illustration of a mitral valve prosthesis 80, in accordance with yet another embodiment of the invention. Prosthesis 80 is based on a D-shaped ring 82, which may conform better than the circular rings shown above to the shape of the natural mitral annulus. Asymmetrical leaflets 84 and 86 are attached within ring 82, in the manner described earlier.

Figs. 8-10 are schematic top views of mitral valve prostheses 90, 100 and 110, respectively, in accordance with additional embodiments of the invention. These embodiments illustrate various possible configurations of asymmetrical leaflets: Prosthesis 90 comprises two asymmetrical leaflets 92 and 94 within D-shaped ring 82; prosthesis 100 comprises three asymmetrical leaflets 104, 106 and 108 within a circular ring 102; and prosthesis 110 comprises three asymmetrical leaflets 112, 114 and 116 with D-shaped ring 82. These particular examples are shown solely by way of illustration, and other asymmetrical leaflet designs implementing the principles described above will be apparent to those skilled in the art after reading the present description and are considered to be within the scope of the present invention.

Reference is now made to Figs. 11A-C, which schematically illustrate a mitral valve prosthesis 120, in accordance with yet another embodiment of the invention. Figs. 11A and 11B are top and bottom pictorial views, showing prosthesis 120 in a closed configuration, while Fig. 11C is a schematic top pictorial view of prosthesis 120 in an open configuration.

Prosthesis 120 comprises a D-shaped ring 122, with a large leaflet 124 and a small leaflet 126, which operate in the manner described above. For added strength and limiting the motion of the valve, flexible ribs 128 are fixed to the bottom of leaflet 124. Ribs 128 typically comprise a suitable resilient metal or plastic material, which is molded together with leaflet 124 or fabricated separately and then fastened to the leaflet. During diastole, as shown in Fig. 11C, ribs 128 collapse (and thus shorten) as the valve opens, but then return to their original shape during systole, as shown in Fig. 11B.

The principles of the present invention may also be applied for diagnostic purposes. For such purposes, the direction of blood flow through the mitral valve may be evaluated, using Doppler imaging or implanted flow sensors, for example. The extent to which the blood flow deviates from the desired direction (toward the posterior wall of the ventricle) can serve as a prognostic indicator with regard to future heart failure, as well as guiding the cardiologist in prescribing appropriate surgery or other treatment.

It will thus be appreciated that the embodiments described above are cited by way of example, and that the present invention is not limited to what has been particularly shown and described hereinabove. Rather, the scope of the present invention includes both combinations and subcombinations of the various features described hereinabove, as well as variations and modifications thereof which would occur to persons skilled in the art upon reading the foregoing description and which are not disclosed in the prior art.

Claims

1. A prosthetic heart valve, comprising:

a frame, which is configured for implantation in an annulus between first and second chambers of a heart; and

two or more leaflets held within the frame and configured to open so as to admit blood from the first chamber into the second chamber and to close so as to prevent blood flow from the second chamber to the first chamber,

wherein the frame and leaflets are configured to direct blood flowing from the first chamber through the valve into the second chamber in a direction that is angled obliquely relative to a plane of the annulus.

2. The valve according to claim 1, wherein the frame is configured for implantation in a mitral annulus between a left atrium and a left ventricle of the heart, and the frame and leaflets are configured to direct the blood toward a posterior wall of the left ventricle during diastole.

3. The valve according to claim 2, wherein the valve is configured to create a vortex, which directs the blood from the mitral annulus toward an outflow tract of the left ventricle.

4. The valve according to claim 1, wherein the leaflets have an asymmetrical shape chosen so that when open, at least one of the leaflets directs the blood in the obliquely- angled direction.

5. The valve according to claim 4, wherein the leaflets comprise at least first and second leaflets of different, respective sizes.

6. The valve according to claim 5, wherein the first leaflet is larger than the second leaflet, and at least the first leaflet comprises flexible, resilient ribs on a side of the first leaflet that is configured to face into the second chamber.

7. The valve according to claim 4, wherein the leaflets comprise at least first and second leaflets of different, respective shapes.

8. The valve according to claim 4, wherein the leaflets comprise at least first and second leaflets of different, respective angulations, relative to the plane of the annulus, when the leaflets are open.

9. The valve according to any of claims 1-8, wherein the frame comprises a ring.

10. The valve according to claim 9, wherein the ring has a non-uniform cross-sectional shape, which is selected so as to conform to the annulus.

11. The valve according to claim 9, wherein the ring has an asymmetrical shape chosen so as to direct the blood in the obliquely-angled direction.

12. The valve according to claim 11, wherein the ring has a first side configured to face into the first chamber and a second side configured to face into the second chamber, wherein the second side is angled obliquely relative to the first side.

13. The valve according to any of claims 1-8, wherein the frame comprises a high-porosity surface, which is mounted in an oblique orientation, relative to the plane of the annulus so as to direct the blood in the obliquely-angled direction.

14. The valve according to any of claims 1-8, wherein the two or more leaflets comprise at least three leaflets.

15. A method for treatment of a heart of a living subject, the method comprising:

implanting a prosthetic heart valve in an annulus between first and second chambers of the heart, while orienting the implanted heart valve so as to direct blood flowing from the first chamber through the valve into the second chamber in a direction that is angled obliquely relative to a plane of the annulus.

16. The method according to claim 15, wherein the prosthetic heart valve is implanted between a left atrium and a left ventricle of the heart, and wherein the implanted heart valve is oriented so as to direct the blood toward a posterior wall of the left ventricle during diastole.

17. The method according to claim 16, wherein the prosthetic heart valve is configured to create vortices, which direct a flow of the blood from an inlet to an outflow tract of the left ventricle.

18. The method according to claim 15, wherein implanting the prosthetic heart valve comprises mounting the prosthetic heart valve, in a crimped state, at an end of a catheter, and inserting the catheter via a vascular system of the subject so as deliver the valve to the annulus, and expanding the prosthetic heart valve at the annulus.

19. The method according to claim 15, wherein implanting the prosthetic heart valve comprises inserting the prosthetic heart valve through an apex of the heart into the annulus.

20. The method according to any of claims 15-19, wherein the prosthetic heart valve comprises leaflets having an asymmetrical shape chosen so that when open, at least one of the leaflets directs the blood in the obliquely-angled direction.

21. The method according to any of claims 15-19, wherein the prosthetic heart valve comprises a frame, comprising a ring having an asymmetrical shape chosen so as to direct the blood in the obliquely-angled direction.

22. The method according to any of claims 15-19, wherein the prosthetic heart valve comprises a frame, comprising a high-porosity surface, which is mounted in an oblique orientation, relative to the plane of the annulus so as to direct the blood in the obliquely- angled direction.