CN113499168B

CN113499168B - Valve prosthesis and valve prosthesis system

Info

Publication number: CN113499168B
Application number: CN202110786587.3A
Authority: CN
Inventors: 王广卉; 黎鹏; 谢建
Original assignee: Shanghai Yiqiao Medical Instrument Co ltd
Current assignee: Shanghai Yiqiao Medical Instrument Co ltd
Priority date: 2021-07-12
Filing date: 2021-07-12
Publication date: 2024-05-14
Anticipated expiration: 2041-07-12
Also published as: CN113499168A; WO2023284663A1

Abstract

The invention discloses a valve prosthesis and a valve prosthesis system, the valve prosthesis comprises: valve support, valve support include outer support and inner support, and outer support is connected and is located the periphery of inner support with the inner support, and outer support includes: an atrial matching part, the atrial matching part comprising: the first support rods are distributed in the circumferential direction and are connected in sequence, and each first support rod is provided with a movable end; a leaflet secured to the inner stent; a skirt which is coated on the inner surface and/or the outer surface of the valve bracket; and the connectors are arranged at the movable ends of the first support rods and allow the first support rods to move between a contracted position and an expanded position. The connectors are arranged at the movable ends of the first support rods, so that the first support rods can move between the contracted position and the expanded position, and the first support rods can be smoothly expanded or contracted.

Description

Valve prosthesis and valve prosthesis system

Technical Field

The invention relates to the technical field of medical instruments, in particular to a valve prosthesis and a valve prosthesis system.

Background

The mitral valve is a valve in the heart that separates the left atrium from the left ventricle. The mitral valve, like a "one-way valve", ensures that blood flows in one direction by opening or closing. Normally, the mitral valve will allow blood to flow from the left atrium to the left ventricle, but if the mitral valve is not closed, a portion of the blood flow will return to the left atrium when the heart contracts, which is called "mitral regurgitation". Mitral regurgitation causes increased load on the heart, lungs, and other organs, and the heart of some patients becomes larger due to the need for more forceful contraction and relaxation to allow blood to be delivered throughout the body. As the condition becomes more severe, other more serious heart problems (such as total heart failure) eventually occur, and may lead to irregular heartbeats, cerebral hemorrhage, sudden death, etc.

In recent years, transcatheter prosthetic heart valve replacement has been rapidly developed and applied clinically as minimally invasive interventional techniques progress. The technology implants a prosthetic heart valve into the native mitral valve of the heart through an interventional procedure to replace the native mitral valve and restore its original function. The interventional operation process does not need to open chest, has small wound and quick postoperative recovery, provides a new treatment mode for patients with high risk of surgical operation, and can prolong the lives of the patients.

Currently, the upper ends of most valve prostheses are open structures and are not joined as a unit. The nodes of the open structure are relatively sharp and may cause damage to the tissue against which they are placed after implantation in the valve prosthesis.

In the related art, in order to avoid damage to the attached tissue caused by the nodes of the open structure, all the nodes at the upper end of the valve prosthesis are connected together to form a round closed structure, so that the damage to the attached tissue is avoided. However, during delivery, the valve prosthesis as a whole needs to be crimped to a small delivery size and constrained within the lumen of a delivery tube of a few millimeters. In the pressing and holding process, the fixed connection point at the upper end can play a limiting role on the support rod, so that the pressing and holding of the support rod is hindered. In addition, after the press-holding is completed, the upper end of the support rod is in a bending state, and the strain at the part is large and possibly exceeds the elastic deformation range which can be born by the support rod material, so that the support rod is easy to break or the fatigue life is easy to influence.

Disclosure of Invention

The present invention aims to solve at least one of the technical problems existing in the prior art. Therefore, the invention provides a valve prosthesis, and the movable ends of the first struts are provided with connectors, so that a plurality of first struts can move between a contracted position and an expanded position, and the valve prosthesis can be conveniently and smoothly expanded or contracted.

The invention also provides a valve prosthesis system.

An embodiment of a valve prosthesis according to the first aspect of the invention comprises: a valve stent, the valve stent comprising: the outer support with the inner support is connected and is located the periphery of inner support, the outer support includes: an atrial mating portion, the atrial mating portion comprising: the first support rods are distributed in the circumferential direction and are connected in sequence, and each first support rod is provided with a movable end;

a leaflet secured to the inner stent;

a skirt, the skirt being wrapped around the inner and/or outer surface of the valve holder;

The connector is arranged at the movable ends of the first struts and allows the first struts to move between a contracted position and an expanded position, the first struts are adjacent to the inner support when the first struts are in the contracted position, and the first struts are far away from the inner support to be supported in an atrium when the first struts are in the expanded position.

According to the valve prosthesis provided by the embodiment of the invention, the movable ends of the first support rods are enabled to move between the contracted position and the expanded position by arranging the connector at the movable ends of the first support rods, so that the first support rods can be smoothly expanded or contracted, and the first support rods cannot be excessively stressed to break or influence the fatigue life after the compression is completed.

According to some embodiments of the invention, the connector is formed with a movable slot, and the movable ends of the plurality of first struts are rotatably disposed in the movable slot.

According to some embodiments of the invention, the connector further forms a first escape groove, the first escape groove is communicated with the movable groove, the first strut further comprises a main body part and a connecting part arranged between the main body part and the movable end, and the connecting part is positioned in the first escape groove when the plurality of first struts are in the contracted position.

According to some embodiments of the invention, the width of the movable slot is greater than the width of the movable end, which is greater than the width of the connecting portion.

According to some embodiments of the invention, the movable groove is configured as a spherical groove, the first relief groove is configured as a rectangular groove, and the movable end is configured as a sphere or a disc.

According to some embodiments of the invention, the connector comprises: the movable groove and the first avoidance groove are formed in the connecting seat, and the cover body is arranged on the connecting seat and partially covers the movable groove.

According to some embodiments of the invention, a second avoidance groove is formed on the cover body, the second avoidance groove is opposite to the first avoidance groove and is communicated with the movable groove, and when the plurality of first struts are in the unfolding position, the connecting portion is located in the second avoidance groove.

According to some embodiments of the invention, the connecting seat and the cover are provided with a threaded shaft hole.

According to some embodiments of the invention, the plurality of first struts together form a spherical shape in the circumferential direction when the plurality of first struts are in the deployed position.

According to some embodiments of the invention, each of the first struts comprises: one end of each first pole segment of a plurality of first poles is close to each other, and the quantity of first pole segment is n, n satisfies the relation: n is more than or equal to 3 and less than or equal to 15; the width of the first pole segment is d1, and d1 satisfies the relation: d1 is more than or equal to 0.3mm and less than or equal to 5mm.

According to some embodiments of the invention, each of the first struts further comprises: the other end of each first pole section is connected with at least two second pole sections, and the second pole sections of the plurality of first poles are sequentially connected in the circumferential direction.

According to some embodiments of the invention, each of the first struts further comprises: the transition pole section, every the other end of first pole section is passed through the transition pole section is connected with two at least second pole section, a plurality of the transition pole section of first branch is connected gradually in the circumference.

An embodiment of a valve prosthesis system according to the second aspect of the invention comprises: the valve prosthesis and delivery assembly described above, the delivery assembly comprising: a delivery sheath and a guidewire, a delivery lumen disposed within the delivery sheath for loading and delivering the valve prosthesis.

Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention.

Drawings

The foregoing and/or additional aspects and advantages of the invention will become apparent and may be better understood from the following description of embodiments taken in conjunction with the accompanying drawings in which:

FIG. 1 is a schematic illustration of a valve prosthesis (with connectors omitted) implanted in the left atrium according to an embodiment of the invention;

FIG. 2 is a schematic structural view of a valve prosthesis according to an embodiment of the present invention;

FIG. 3 is a top view of a valve prosthesis (with leaflets and skirts omitted) according to an embodiment of the present invention;

FIG. 4 is a schematic structural view of a valve stent according to an embodiment of the present invention;

FIG. 5 is a schematic view of the structure of an inner stent according to an embodiment of the present invention;

FIG. 6 is a schematic view of a first strut in a compressed position according to an embodiment of the present invention;

FIG. 7 is a schematic view of a first strut in a deployed position according to an embodiment of the present invention;

fig. 8 is a cross-sectional view of a connector according to an embodiment of the present invention;

fig. 9 is a cross-sectional view of a connection socket according to an embodiment of the present invention;

FIG. 10 is a bottom view of a connection block according to an embodiment of the present invention;

Fig. 11 is a cross-sectional view of a cover according to an embodiment of the present invention;

FIG. 12 is a schematic illustration of a valve prosthesis according to an embodiment of the present invention when contracted;

FIG. 13 is a schematic illustration of a valve prosthesis, as it is implanted in the right atrium, according to an embodiment of the invention;

Fig. 14 is a schematic view of a valve prosthesis centered from the left atrium and the annulus into the left ventricle according to an embodiment of the invention.

Reference numerals:

100. A valve prosthesis;

10. a valve stent;

11. An outer bracket; 111. an atrial matching part; 112. a first strut; 113. a first pole segment; 114. a transition rod section; 115. a second pole segment; 116. an annulus matching section; 117. a second strut; 118. a third pole segment; 119. a fourth pole segment;

12. An inner bracket; 121. a grid; 122. a fifth pole segment; 123. a sixth pole segment; 124. a leaflet attachment section;

22. a skirt edge; 23. an annulus; 24. atrial wall; 25. the left atrium;

30. A connector; 31. a movable groove; 32. a first avoidance groove; 33. a connecting seat; 34. a cover body; 35. a second avoidance groove; 36. a shaft hole;

210. a delivery sheath; 220. a guide wire.

Detailed Description

Embodiments of the present invention will be described in detail below, with reference to the accompanying drawings, which are exemplary.

The valve prosthesis 100 according to an embodiment of the present invention is described below with reference to fig. 1 to 14, and the present invention also proposes a valve prosthesis system having the valve prosthesis 100 described above.

The valve prosthesis 100 of the present invention may be used to replace native valve structures such as mitral valve, tricuspid valve, aortic valve, and pulmonary valve, as exemplified below.

As shown in fig. 1-5, a valve prosthesis 100 according to an embodiment of the first aspect of the present invention includes: valve stent 10, leaflets, skirt 22 and connector 30, valve stent 10 comprises: an outer stent 11 and an inner stent 12, the outer stent 11 is connected with the inner stent 12 and is positioned at the periphery of the inner stent 12, the valve leaflet is fixed on the inner stent 12, the skirt 22 is coated on the inner surface and/or the outer surface of the valve stent 10, and the connector 30 is arranged on the top of the outer stent 11.

Wherein the valve holder 10 is the main body structure of the valve prosthesis 100, providing support to the leaflets by means of the inner holder 12 and to the skirt 22 by means of at least one of the outer holder 11 and the inner holder 12, while the mounting, positioning and fixation of the valve prosthesis 100 in the left atrium 25 and at the annulus 23 of the native mitral valve is achieved by means of the outer holder 11. In addition, the outer stent 11 and the inner stent 12 may be manufactured by an integral process, such as pipe integral cutting or wire integral braiding, and then shaped into the valve stent 10 by a heat treatment process; alternatively, the outer stent 11 and the inner stent 12 may be separately manufactured, and then the respective portions may be connected by welding and/or riveting to form the integral valve stent 10.

The skirt 22 serves to perform a sealing function, ensuring that the passage of blood from the left atrium 25 into the left ventricle is only the passage after the leaflets are opened, preventing leakage of blood from the peripheral side of the valve prosthesis 100 or from the interior of the valve prosthesis 100, affecting the hemodynamic effect of the valve prosthesis 100.

Skirt 22 may be made of animal derived pericardial tissue or may be made of biocompatible polymers such as polyethylene terephthalate, polytetrafluoroethylene or expanded polytetrafluoroethylene. By means of suturing, the skirt 22 is sutured integrally with the valve holder 10, the leaflets, preventing blood leakage from the interstices of the mesh of the valve holder 10 and the gaps between the outer holder 11 and the inner holder 12, thus ensuring good hemodynamics. Meanwhile, the surface of the skirt edge 22 has a micropore structure, which is favorable for climbing human endothelial cells, can accelerate endothelialization of the valve prosthesis 100, is favorable for long-term fixation of the valve prosthesis 100, and can improve thrombus condition of the valve prosthesis 100. Alternatively, skirt 22 may be attached to valve holder 10 by heat staking.

In the embodiment of the present invention, the skirt 22 is coated on the outer surface of the outer stent 11 and the inner surface of the inner stent 12 to prevent leakage of blood. That is, by providing the skirt 22 on the outer surface of the outer stent 11 and the inner surface of the inner stent 12, it is possible to prevent blood from leaking from the outer stent 11, the inner stent 12, and the gaps between the outer stent 11 and the inner stent 12, to affect the hemodynamic effect of the interventional valve prosthesis 100, and to ensure that the passage of blood from the left atrium 25 into the left ventricle is only the passage after the leaflet is opened.

The valve leaflet can simulate the native valve leaflet, realize the closing when the left ventricle contracts and opening when the left ventricle expands, and replace the function of the native valve leaflet. Alternatively, the leaflets are prepared from animal-derived pericardial tissue, preferably porcine pericardium or bovine pericardium tissue, and are sutured to the valve stent 10 after treatment by an inactivation, anti-calcification process, or the like. Alternatively, the leaflets are prepared from valve tissue of animal origin, such as porcine aortic valve, porcine pulmonary valve, etc. Alternatively, the petals She Xuan are made of biocompatible polymers, such as polyethylene terephthalate, polytetrafluoroethylene, polyethylene, and the like, and are easier to process and manufacture than animal-derived tissues.

In the embodiment of the invention, the valve blades are in a blade type structure, and 3 valve blades are sewn on the inner bracket 12 by adopting a sewing process mode. The 3 valve leaves are mutually matched and have good hydrodynamic effect, so that the hemodynamics are more stable when the valve leaves are opened or closed. Alternatively, the number of leaflets may be 2, the same as the number of leaflets of the native mitral valve. Or the valve blades can be 4 or more, and can be correspondingly arranged according to actual requirements. Instead of being sewn, the leaflets may be secured to the inner frame 12 in other ways, such as by adhesive or welding.

As shown in fig. 3 and 4, the outer bracket 11 includes: an atrial matching part 111. The atrial mating part 111 is formed in a spherical or spheroid shape to match the shape of the heart chamber of the left atrium 25, so that the atrial mating part 111 is supported on the atrial wall 24 in a spheroid or spheroid-like form, achieving the fixation of the valve prosthesis 100 in the left atrium 25. Specifically, the spherical or spheroid-like atrium matching portion 111 cooperates with the atrium wall 24, and the two portions abut against each other, so that the atrium matching portion 111 can be effectively abutted against and supported on the atrium wall 24 during heart beating, and displacement of the valve prosthesis 100 caused by movement in the front-back, left-right and up-down directions can be avoided, so that the valve prosthesis 100 is reliably fixed in the left atrium 25.

Among them, the atrium matching section 111 includes: the plurality of first struts 112, the plurality of first struts 112 are distributed in the circumferential direction, and the plurality of first struts 112 are sequentially connected to constitute a spherical or spheroid-like atrial mating part 111. The plurality of first struts 112 abut the atrial wall 24 and, depending on the support of the atrial wall 24, prevent the valve prosthesis 100 from moving in the anterior-posterior, lateral-lateral, and superior-inferior directions, so that the valve prosthesis 100 is reliably fixed in the left atrium 25. The number of the first struts 112 may be between 3 and 15, and in the embodiment of the present invention, 6. In the present invention, a plurality means three or more.

The upper ends of the plurality of first struts 112 constitute the top of the atrial mating part 111, i.e., the top of the outer stent 11. The upper ends of the first struts 112 are movable ends, and the connector 30 is disposed at the movable ends of the plurality of first struts 112 and allows the plurality of first struts 112 to rotate relative to the connector 30 such that the plurality of first struts 112 are movable between a retracted position and an extended position. As shown in FIG. 12, with the plurality of first struts 112 in the contracted position, the first struts 112 are adjacent the inner stent 12, and the valve prosthesis 100 is now of relatively small radial size, and is conveniently received within the delivery sheath and delivered through the delivery sheath into the left atrium 25; as shown in fig. 1,2 and 4, the first plurality of struts 112 are distal from the inner stent 12 when the first plurality of struts 112 are in the deployed position, and the first plurality of struts 112 are spherical or spheroid-shaped, thereby facilitating support of the valve prosthesis 100 within the left atrium 25. That is, the connection between the connector 30 and the first strut 112 is a multi-directional movement, i.e., the first strut 112 is rotatable relative to the connector 30 between the expanded position and the contracted position after the first strut 112 is combined with the connector 30, so as to facilitate the change of the shape of the valve prosthesis 100 without damaging the first strut 112. As such, the connector 30 does not interfere with the collapsing and expanding of the first strut 112 nor cause excessive strain of the first strut 112 to fracture or interfere with fatigue life when the first strut 112 is in the collapsed position. In addition, the open upper ends of the plurality of first struts 112 are connected by the connector 30 to form a closed structure that prevents damage to the atrial wall 24 from the open upper ends of the plurality of first struts 112.

Wherein the entire valve prosthesis 100 is constrained in a cylindrical state with the first struts 112 in the contracted position, the first struts 112 are adjacent to each other with the first struts 112 extending in the axial direction of the valve prosthesis 100, and the first struts 112 remain integrally connected by the connector 30. And, with the first struts 112 in the deployed position, the valve prosthesis 100 is deployed with the plurality of first struts 112 spaced apart from one another, while the plurality of first struts 112 remain integrally connected by the connector 30.

Thus, by providing the connectors 30 on the first struts 112, the plurality of first struts 112 can move between the contracted position and the expanded position, so that the first struts 112 can be smoothly expanded or contracted, and the first struts 112 cannot be broken or the fatigue life is not affected due to excessive strain after compression.

Referring to fig. 6 to 9, the connector 30 is formed with a movable groove 31, and a plurality of first struts 112 are rotatably disposed in the movable groove 31. That is, the movable groove 31 is provided on the connector 30, the plurality of first struts 112 may extend into the movable groove 31, and the movable end may rotate up and down, left and right with respect to the movable groove 31, so that the valve prosthesis 100 may be restrained in a cylindrical state when the valve prosthesis 100 is delivered, that is, the valve prosthesis 100 is in a contracted state, the outer stent 11 and the inner stent 12 may abut against each other, and the plurality of first struts 112 may be close to each other, in this state, the upper ends of the first struts 112 may be close to a vertical state in the movable groove 31, that is, the ends of the first struts 112 do not need to be forcibly bent, so that the first struts 112 may not be excessively strained to break or affect the fatigue life.

Meanwhile, when the valve prosthesis 100 is implanted in the left atrium 25, the valve prosthesis 100 is in a deployed state, and at this time, the atrium-matching portion 111 is in a spherical or spheroid shape, and the upper ends of the first struts 112 are in a nearly horizontal state in the movable groove 31 of the connector 30. Because heart beats, the atrium wall 24 can produce the extrusion effect of all directions to valve prosthesis 100, at this moment, first branch 112 can atress take place to the deformation for the form of first branch 112 upper end changes, and the movable slot 31 structure that the inside of connector 30 set up can adapt to the various deformation of first branch 112, guarantees that the movable end is in the connector 30 all the time inside, and the cooperation of first branch 112 and connector 30 is the active state all the time, the unsteady restraint, thereby when valve support 10 takes place the deformation by heart beats influence, first branch 112 can not receive the excessive restraint of connector 30, forms bigger deformation. In this way, when the first strut 112 is in service in the left atrium 25 by the connector 30, the first strut 112 can deform according to the external force, the connection between the first strut 112 and the connector 30 is free from stress concentration, the first strut 112 is not easy to crack, and the fatigue performance of the valve stent 10 can be remarkably improved. In addition, the upper end of the first strut 112 cooperates with the connector 30 to form a closed structure that prevents the upper end of the first strut 112 from damaging the atrial wall 24 in the open state.

As shown in fig. 6 to 10, the connector 30 is further formed with a first escape groove 32, the first escape groove 32 is in communication with the movable groove 31, and when the plurality of first struts 112 are in the retracted position, a rod portion of the first struts 112 adjacent to the movable end is located in the first escape groove 32. The portion of the first strut 112 adjacent the movable end is a connection portion connecting the movable end and the main body portion of the first strut 112. That is, when the first struts 112 are in a compressed state, the plurality of first struts 112 are close to each other, and the connection portions of the plurality of first struts 112 are received in the first avoidance groove 32, so that the radial dimension of the valve stent 10 when the first struts 112 are in the contracted position can be reduced, and the delivery of the valve stent 10 is facilitated. Specifically, when the first strut 112 is in the retracted position, the movable end of the first strut 112 may be accommodated in the movable slot 31, and the connection portion of the first strut 112 is located in the first avoidance slot 32, where the first strut 112 may be in an upright state without deformation.

Wherein, the width of the movable groove 31 is larger than the width of the movable end, and the width of the movable end is larger than the width of the connecting part. That is, the movable end has a smaller outer dimension than the movable slot 31, so that the movable end can be flipped up and down, left and right in the movable slot 31 to accommodate the various deflection forces experienced by the valve holder 10 when in service in the left atrium 25, and to facilitate the switching of the first struts 112 between the collapsed and expanded positions. And the width of the movable end is larger than the width of the connecting portion, so that it can be restricted that the movable end is not separated from the opening of the movable groove 31 when the movable end is disposed in the movable groove 31, so that the connector 30 can be rationally disposed.

Referring to fig. 6 to 9, the movable groove 31 is configured as a spherical groove, and the movable end is configured as a sphere or a disc. Wherein, the movable groove 31 is configured as a spherical groove, so that the movable end can be smoothly turned over in the movable groove 31, for example, turned up and down, left and right, so as to facilitate the morphological change of the outer bracket 11. And the movable end is configured in a sphere or wafer shape, which also allows the movable end to flip up and down, left and right, within the movable slot 31 to accommodate the various deflection forces experienced by the valve holder 10 when in service within the heart chamber. The movable end is preferably in a round plate shape, and the round plate shape is convenient to process and shape and is also convenient to install.

Further, as shown in connection with fig. 8 and 9, the first escape groove 32 is configured as a rectangular groove that can facilitate the receiving of the connection portion of the first strut 112 in the first escape groove 32. And, the depth of the rectangular groove exactly matches the thickness of the connecting portion of the first strut 112, or is greater than the thickness of the connecting portion of the first strut 112, and the width of the rectangular groove should be greater than or equal to the width of the connecting portion of the first strut 112, when the first strut 112 is in the contracted position, the connecting portion of the first strut 112 can be exactly received into the rectangular groove, so that the first strut 112 can be in an upright state without deformation, and the external dimension does not exceed the dimension of the connector 30, without affecting the use of the connector 30, or additionally increasing the radial dimension of the valve prosthesis 100.

Referring to fig. 6, the connector 30 includes: the connection seat 33 and the cover 34, the movable groove 31 and the first escape groove 32 are formed at the connection seat 33, the cover 34 is provided at the connection seat 33, and the cover 34 partially covers the movable groove 31. That is, the connector 30 is composed of a cover 34 and a connection seat 33, and a movable slot 31 matched with the first support rod 112 is provided on the connection seat 33, which can be used to accommodate the movable end of the first support rod 112 and allow the movable end to move in the movable slot 31. The cover 34 mainly prevents the first supporting rod 112 from falling out when moving in the connecting seat 33, i.e. the freedom of movement of the first supporting rod 112 can be limited. When assembling, the movable end of the first supporting rod 112 is placed in the movable groove 31, and then the cover 34 is fastened on the connecting seat 33 to prevent the movable end from sliding out of the movable groove 31, so that the cover 34 and the connecting seat 33 can form an effective and reliable movable connection structure.

The connecting seat 33 and the cover 34 can be made of nickel-titanium alloy, cobalt-chromium alloy, titanium alloy, stainless steel or polyether-ether-ketone and other materials with better biocompatibility and better processing performance. The connecting seat 33 and the cover 34 can be made of the same material or different materials. Preferably, the connecting seat 33 and the cover 34 are made of the same material. The connection between the connection seat 33 and the cover 34 can be welded, glued or screwed.

In addition, as shown in fig. 6, 8 and 11, the cover 34 is formed with a second avoidance groove 35, the second avoidance groove 35 is disposed opposite to the first avoidance groove 32, and the second avoidance groove 35 is communicated with the movable groove 31, and when the plurality of first struts 112 are in the expanded position, the connection portion of the first struts 112 is located in the second avoidance groove 35. When the first struts 112 are in the unfolded position, the connection portions of the first struts 112 are approximately horizontally arranged, and the second avoidance groove 35 is formed in the cover 34, so that the connection portion of the first struts 112 can be allowed to extend into the connector 30 from the second avoidance groove 35, and the movable end is matched with the connector 30, so that the first struts 112 can be unfolded smoothly, and the first struts 112 can be prevented from sliding out of the connector 30. The length and width of the second avoidance groove 35 should be not less than those of the first avoidance groove 32, so that the connection portion of the first strut 112 can flexibly move in the second avoidance groove 35 and the first avoidance groove 32.

As shown in fig. 8 to 11, the connection seat 33 and the cover 34 are provided with a shaft hole 36 with threads. By providing the shaft hole 36 on the connection base 33 and the cover 34, the connection base 33 and the cover 34 can be detachably engaged with the conveying member of the conveying assembly. In particular, the valve prosthesis 100 may be pushed out of the delivery sheath when the delivery member is connected to the connector 30. After implantation is complete, the delivery member is separated from connector 30 so that the delivery assembly can be withdrawn from the left atrium 25. Other detachable connection modes can be arranged between the connector 30 and the conveying member. For example, the connector 30 and the conveying member are provided with a clamping groove and a clamping buckle, when the connector 30 and the conveying member are in clamping fit, and after the implantation is completed, the connector 30 and the conveying member are in clamping fit.

As shown in fig. 1 and 4, the valve stent 10 further comprises: an annulus matching part 116 provided at the lower end of the atrium matching part 111. The annulus matching portion 116 is matched with the annulus 23 of the native mitral valve, specifically, the annulus matching portion 116 is inserted into the annulus 23, and the positioning of the valve prosthesis 100 is achieved by means of the radial supporting force of the annulus matching portion 116, so that the valve prosthesis 100 is prevented from deflecting. Thus, in combination with the foregoing, the valve prosthesis 100 is substantially located in the heart chamber of the left atrium 25, and the anchoring of the valve prosthesis 100 in the left atrium 25 is achieved by means of the mutual abutment of the atrial mating part 111 and the atrial wall 24, so that torsion and displacement during heart beating can be avoided. At the same time, the valve prosthesis 100 is supported at the annulus 23 by means of the radial supporting force of the valve annulus matching part 116, which is matched with the annulus 23 and the native valve leaflets, so that the valve prosthesis 100 is further prevented from deflecting and shifting. Thus, by the two morphological designs of the outer stent 11, the valve prosthesis 100 is reliably fixed after implantation by means of two fixing mechanisms.

As shown in fig. 4, each first strut 112 includes: a first pole segment 113 and at least two second pole segments 115. The upper ends of the first pole sections 113 of each first pole 112 are arranged close to each other to form the top of the atrial matching part 111, i.e. the upper ends of the first pole sections 113 are movable ends of the first pole 112, and the parts of the first pole sections 113 close to the upper ends thereof are connecting parts of the first pole 112. At least two second pole segments 115 are connected to the lower end of each first pole segment 113, and the second pole segments 115 of the plurality of first poles 112 are sequentially connected in the circumferential direction. That is, each first pole segment 113 is connected to at least two second pole segments 115, and adjacent two second pole segments 115 are connected in the circumferential direction,

Wherein the number of the first pole segments 113 is identical to the number of the first struts 112, i.e. the number of the first pole segments 113 is 3-15, in the embodiment of the present invention 6. In addition, the stem width of the first stem section 113 is greatest throughout the valve stent 10, the stem width d1 of the first stem section 113 being designed to be 0.5-3mm. By rationally designing the number and the stem width of the first stem segments 113 such that the number and the stem width of the first stem segments 113 cooperate with each other, the valve prosthesis 100 is sufficiently rigid in the expanded state and sufficiently flexible in the contracted state.

Specifically, in the deployed state of the valve prosthesis 100, the number of the first stem segments 113 is not too small, so that the outer stent 11 can be spherically or spherically-like supported in the left atrium 25, and, as shown in fig. 1, the number of the first stem segments 113 is not too large, i.e., the whole first stem segments 113 are sparse, so that the valve prosthesis 100 can be prevented from endothelialising to block the pulmonary veins and affect the blood flow paths of the pulmonary veins. In addition, during the suturing of the valve leaflet, the sparse first stem segment 113 has little shielding of the suturing operation, facilitating the suturing operation of the valve leaflet and the inner stent 12 by the needle and line passing through the sparse first stem segment 113. Further, by providing the first stem segments 113 with a suitable stem width, each first stem segment 113 has a certain rigidity and thus a certain supporting force, so that each first stem segment 113 can be effectively supported on the atrium wall 24 during heart beating, and thus the whole valve prosthesis 100 is supported by the atrium wall 24, and the valve prosthesis 100 is prevented from moving and shifting.

As shown in fig. 13 and 14, the valve prosthesis 100 is adapted to be delivered into the left atrium 25 via a delivery sheath in a contracted state. In the contracted state of the valve prosthesis 100, all of the first stem segments 113 are combined to form a single body. With the above arrangement of the shaft widths of the first shaft segments 113, such that each first shaft segment 113 has a certain rigidity with respect to the contraction and expansion of the atrial wall 24 during heart beating, in fact, each first shaft segment 113 can still bend under a large external force by virtue of the shaft width of the present invention. Further, the number of the first pole segments 113 is relatively small, and although all the first pole segments 113 are combined to form a whole body to be rigidly overlapped, the first pole segments have certain flexibility, are easy to bend and have good bending performance. In this way, the valve prosthesis 100 is in the flexible delivery sheath, and the combination of all the first stem segments 113 results in a flexible overall body, which has less impact on the performance of the flexible delivery sheath, facilitates the passage of the valve prosthesis 100 along the delivery sheath through the curved vascular path and across the atrial septum into the left atrium 25, and avoids damage to the vessel wall during delivery. More importantly, by properly designing the number and the width of the first pole segments 113, the combined integration of all the first pole segments 113 is flexible enough to withstand approximately 90 ° bending. As shown in fig. 14, by bending approximately 90 °, the annulus mating portion 116 can be centered with the annulus 23, thereby enabling the annulus mating portion 116 to be aligned over the annulus 23 after deployment of the valve prosthesis 100. It should be noted that after the valve prosthesis 100 is deployed, the outer stent 11 is matched to the heart chamber of the left atrium 25, and it is difficult to adjust the position of the valve prosthesis 100. In the present invention, however, the first stem segment 113 may be bent approximately 90 ° in the contracted state of the valve prosthesis 100, thereby centering the valve annulus mating portion 116, avoiding inaccurate positioning during release, so that the valve annulus mating portion 116 may be ensured to be released in the valve annulus 23, and the valve annulus mating portion 116 may be mated with the valve annulus 23 after being expanded. In addition, the annulus mating portion 116, when mated with the annulus 23, serves to locate the rest of the valve prosthesis 100, ensuring that the valve prosthesis 100 is installed in place. Moreover, the first stem segment 113 generates less deflection force on the annulus 23 during release and deployment, and once positioned, no deflection or displacement of the valve prosthesis 100 occurs.

Referring again to fig. 4, the number of second pole segments 115 is 2-6 times the number of first pole segments 113. In the embodiment of the invention, 24 first pole segments 113 are 4 times the number of the first pole segments 113, namely, 4 second pole segments 115 are connected to the lower end of each first pole segment 113. In addition, the second pole segment 115 has a pole width d2 of 0.1-0.8mm, and d2 < d1. Through the design of the number and the rod width of the second rod segment 115, the corresponding position of the second rod segment 115 is compact and soft, has better compliance, after the valve prosthesis 100 is implanted, the segment structure is in contact with the lower edge of the atrial wall 24, and the compact and soft second rod segment 115 has good mechanical property and morphological adaptability, so that the segment of the valve stent 10 can be tightly attached to the atrial wall 24, the leakage of blood from the gap between the valve stent 10 and the atrial wall 24 is avoided, the perivalvular leakage can be effectively reduced, and meanwhile, the excessive support to the atrial wall 24 is not caused, and the contraction function of the atrial wall 24 is not influenced.

In embodiments of the present invention, the second pole segment 115 is arranged in 1 row, it being understood that the second pole segment 115 may also be arranged in 2 or 3 rows. But should not exceed 3 rows in order not to affect compliance. In addition, the number of second pole segments 115 refers to the number of rows.

Each first strut 112 further comprises: a transition pole segment 114. The lower end of each first pole segment 113 is connected to at least two second pole segments 115 via a transition pole segment 114, the transition pole segments 114 being connected in turn in the circumferential direction. By transition of the transition bar segment 114, isolated bar segments or nodes can be avoided, thereby ensuring a closed-loop envelope of the entire outer stent 11. In the embodiment of the present invention, the number of the transition pole segments 114 is 12, so that each first pole segment 113 corresponds to two transition pole segments 114, and each of the two transition pole segments 114 corresponds to two second pole segments 115, so as to avoid isolated pole segments or nodes. The transition segment 114 serves as a connecting rod segment between the first segment 113 and the second segment 115, and on the one hand, needs to have a certain rigidity to ensure good supporting performance, and on the other hand, needs to have a certain flexibility to gradually conform against the atrial wall 24 in a direction approaching the second segment 115. Thus, the stem width d3 of the transition stem section 114 is designed to be 0.2-1mm, and d 1> d3 > d2. The number of transition pole segments 114 is adaptively adjusted according to the number of first pole segments 113 and second pole segments 115 to avoid isolated pole segments or nodes.

As shown in fig. 4, the height of the annulus matching portion 116 is H, which satisfies the relation: h is more than or equal to 5 and less than or equal to 15mm. That is, the size of the annulus mating portion 116 in the axial direction is H and is set between 5-15mm, such that the annulus mating portion 116 not only mates with the annulus 23, but also extends partially through the annulus 23 into the left ventricle to mate with the native valve leaflet. The valve annulus matching part 116 extends into the left ventricle, so that when the valve prosthesis 100 is released, the valve annulus matching part 116 is matched with the valve annulus 23, a pre-positioning function is provided, and the situation that the rest part of the valve prosthesis 100 shifts or tilts in the releasing and unfolding processes to influence the final implantation effect is avoided. After implantation is complete, the annulus mating portion 116 extends partially into the left ventricle, which may enhance the fixation of the valve prosthesis 100. In addition, the partial extension of the annulus mating portion 116 into the left ventricle may push away the native leaflets, limit the movement of the native leaflets, prevent the movement of the native leaflets from interfering with the operation of the valve prosthesis 100, e.g., avoid the valve prosthesis 100 operating simultaneously with the native leaflets, causing hemodynamic disturbances. In addition, as described above, the valve prosthesis 100 adopts two fixing mechanisms, and in the case that the atrial matching part 111 can also play a role in fixing, the valve annulus matching part 116 does not need to extend into the left ventricle too much, the main structure of the valve prosthesis 100 is located in the left atrium 25, the depth of the valve annulus matching part 116 extending into the left ventricle is shallow, the native valve leaflet can be ensured to be pushed open, the function of the left ventricular outflow tract cannot be affected, and the obstruction of the left ventricular outflow tract can be avoided.

As shown in fig. 4, the annulus matching portion 116 is matched with the annulus 23, the annulus matching portion 116 is connected to the second shaft section 115, and the annulus matching portion 116 is connected to the inner stent 12 to constitute a connecting section of the outer stent 11 and the inner stent 12.

The annulus matching section 116 includes: a plurality of second struts 117, the plurality of second struts 117 being distributed in the circumferential direction. The number of second struts 117 may be 6-24. The second strut 117 includes: a third pole segment 118 and a fourth pole segment 119, the third pole segment 118 being connected between the second pole segment 115 and one end of the fourth pole segment 119, the other end of the fourth pole segment 119 being connected to the inner support 12, the third pole segment 118 extending in the axial direction of the inner support 12, and the fourth pole segment 119 extending in the radial direction of the inner support 12. That is, after implantation of the valve prosthesis 100, the third stem section 118 mates with the annulus 23, such that the valve prosthesis 100 may be secured at the annulus 23, while the outer and inner stents 11, 12 are fixedly connected by means of the fourth stem section 119. The stem width d4 of the third stem section 118 is 0.3-0.8mm so that the third stem section 118 has sufficient radial support force to bear against the annulus 23.

In the embodiment of the present invention, the number of the second struts 117 is 12, and one second strut 117 is connected to the node of each two connected second rod segments 115. Specifically, two transition pole segments 114 connected to the same first pole segment 113 extend in a direction away from each other, two second pole segments 115 connected to the same transition pole segment 114 extend in a direction away from each other, two adjacent second pole segment 115 ends on two different transition pole segments 114 are connected, and two adjacent second pole segments 115 are connected with a third pole segment 118. That is, the number of the third pole segments 118 is less than half of the number of the second pole segments 115, that is, the number of the third pole segments 118 is 12, and the number of the fourth pole segments 119 is also 12, the third pole segments 118 are in one-to-one correspondence with the fourth pole segments 119, the number of the second struts 117 is less, the mutual interval is larger, the second struts 117 are facilitated to be bent and molded during the processing of the valve stent 10, the L-shaped valve ring matching part 116 is formed, the valve ring matching part 116 is conveniently connected with the inner stent 12, and the valve ring matching part 116 is conveniently abutted with the valve ring 23.

In addition, the third pole segment 118 is folded relative to the fourth pole segment 119, with the angle θ being set at 90-180, but not including 180, to accommodate the annulus 23. And, third pole section 118 and fourth pole section 119 junction be the fillet to can have the roundness excessively, avoid forming sharp bump, can effectively avoid damaging the tissue. Preferably, the radius of the fillet is 1-2mm.

Referring to fig. 4, the sum of the heights of the second pole segment 115 and the second strut 117 is h1, and the height of the inner frame 12 is h2, h1 and h2 satisfy the relationship: h1 is less than or equal to h2. As such, the second stem segment 115 and the second struts 117 overlap the inner stent 12 when the valve prosthesis 100 is crimped to the delivery sheath, i.e., when the valve prosthesis 100 is in a compressed state. Although each second pole segment 115 is more flexible, the greater number of second pole segments 115, when combined together, rigidly overlap to form a stiffer, inflexible portion a. While the inner stent 12 is used to support the leaflets, greater rigidity is required and the inner stent 12 forms a stiffer, inflexible portion B after compression of the valve prosthesis 100. It should be noted that the inner stent 12 is more difficult to adjust based on the proper height of the leaflet, i.e., the height of the inflexible portion B. Thus, in order to relatively minimize the axially stiff portion of the valve prosthesis 100 in the compressed state, and relatively maximize the pliable portion, it is necessary to have the non-pliable portion B axially overlap the non-pliable portion a, and thus, it is necessary to have: h1 is less than or equal to h2.

The outer bracket 11 can be manufactured by a pipe cutting mode or by wire braiding. The outer bracket 11 is preferably made of nickel-titanium memory alloy, and is shaped into a sphere or sphere-like shape by utilizing the characteristics of the nickel-titanium memory alloy.

As shown in fig. 5, the inner bracket 12 includes: the plurality of mesh frames 121 are connected in an array manner in the circumferential direction and constitute a cylindrical or conical shape. That is, the inner frame 12 is a supporting frame composed of a plurality of grids 121, and has a cylindrical or conical profile, and at least a portion of the grids 121 are provided with fixing interfaces for fixing the leaflets, through which the leaflets are sutured, and support for the leaflet opening and closing movement. Wherein the grid frame 121 is of a quadrilateral structure, and the design of the grid frame 121 into a quadrilateral shape is beneficial to the compression and expansion of the inner bracket 12.

The inner support 12 includes at least three rows of grids 121 along the axial direction, in this embodiment, the inner support 12 includes three rows of grids 121 along the axial direction, and each row is composed of 12 grids 121 distributed circumferentially, it will be understood that in other embodiments not shown, the number of rows of grids 121 and the number of each row may be adjusted according to actual use requirements.

Further, as shown in fig. 5, at the boundary between the adjacent two grid frames 121, the grid frames 121 include in the axial direction: the fifth and sixth pole segments 122, 123, and in particular the lattice frame 121, are quadrilateral in configuration, the lattice frame 121 being designed to facilitate compression and expansion of the inner frame 12. Each grid 121 comprises two sixth pole segments 123 and two fifth pole segments 122. Since the inner frame 12 includes at least three rows of the lattice frames 121 connected in an array in the circumferential direction, there is a case where two adjacent rows of lattice frames 121 are co-bordered, for example, the sixth pole segment 123 of the lattice frame 121 of the first row is the fifth pole segment 122 of the lattice frame 121 of the second row. For convenience of description and understanding, for the single lattice frame 121, the fifth pole section 122 located above and the sixth pole section 123 located below, the upper ends of the two fifth pole sections 122 are connected to each other, the lower ends of the two sixth pole sections 123 are connected to each other, and the lower ends of the fifth pole sections 122 are connected to the upper ends of the corresponding sixth pole sections 123. The fourth pole segment 119 is in one-to-one correspondence with the lowermost grid 121 and is connected to the lower ends of the corresponding two sixth pole segments 123.

As shown in fig. 5, the fifth pole segment 122 has a height h3, the sixth pole segment 123 has a height h4, and the second pole segment 115 has a height h5, h3, h4, and h5 satisfy the relationship: h3 is less than h5, and h4 is less than h5. That is, the fifth and sixth stem segments 122, 123 are each smaller in axial dimension than the second stem segment 115, which ensures a high rigidity of the inner frame 12, giving sufficient support to the leaflets. Further, the fifth and sixth pole segments 122, 123 may be set to be equal in size or unequal in height in the axial direction.

And the fifth pole segment 122 has a width d5, the sixth pole segment 123 has a width d6, and the second pole segment 115 has a width d2, d5, and d6 satisfying the relationship: d2 < d5, d2 < d6. That is, the rod width of the fifth rod segment 122 and the rod width of the sixth rod segment 123 are both greater than the rod width of the second rod segment 115, so that the inner support 12 formed by the lattice frame 121 has better rigidity and strength, has stability enough to support the movement of the valve leaflet, avoids the great deformation of the inner support 12 during the movement of the valve leaflet, and ensures the normal opening and closing of the valve leaflet and the hydrodynamic effect. The rod width of the fifth rod segment 122 and the rod width of the sixth rod segment 123 may be equal or different, and the rod widths d5 and d6 are between 0.3 mm and 1 mm.

Furthermore, as shown in fig. 5, the side of the inner frame 12 facing away from the fourth pole section 119 in the axial direction is further provided with a leaflet attachment section 124, to which the leaflet is attached, specifically the part between the attachment interface and the node at which the two fifth pole sections 122 of the first row of lattice frames 121 of the inner frame 12 are attached is the leaflet attachment section 124. The axial dimension of the leaflet attachment section 124 is h6, and in this embodiment, the profile shape of the inner stent 12 is cylindrical, and the radial dimension of the inner stent 12 is D1, h6 satisfies the relationship: h6 is more than or equal to 8mm and less than or equal to 20mm, and D1 satisfies the relation: d1 is more than or equal to 21mm and less than or equal to 34mm. In this way, the valve prosthesis 100 may be conveniently adapted to the anatomy of the human body and the size of the native valve leaflets to perform the function of the native mitral valve.

The inner stent 12 may be manufactured by cutting a tube or by braiding wires. The material of the inner stent 12 is preferably nickel titanium shape memory alloy, which is shaped to a corresponding form by utilizing its characteristics. The material of the inner bracket 12 can also be cobalt-chromium alloy, stainless steel, titanium alloy and other materials with better biocompatibility.

An embodiment of a valve prosthesis system according to the second aspect of the invention comprises: the valve prosthesis 100 and delivery assembly described above, the delivery assembly comprising: a delivery sheath 210 and a guidewire 220, a delivery lumen being disposed within the delivery sheath 210 for loading and delivering the valve prosthesis 100.

A delivery member (not shown) is connected to the connector 30 prior to implantation of the valve prosthesis 100. The valve prosthesis 100 is then compressed together and loaded into the delivery lumen along with the guide wire 220 and the delivery member, with the plurality of first struts 112 in the contracted position and the plurality of first struts 112 disposed in a relatively parallel arrangement. It will be appreciated that the delivery lumen may be one lumen or multiple lumens, and that when the delivery lumen is multiple lumens, the valve prosthesis 100, the guidewire 220, the delivery member, and other related components may be loaded into different lumens.

As shown in fig. 12 and 14, first, a delivery path from a blood vessel to a left ventricle is established by using a guide wire 220, and a delivery sheath 210 is guided and supported by the guide wire 220 to deliver the valve prosthesis 100 to a right atrium along the guide wire 220. The first stem segment 113 is then bent to facilitate extension of the valve prosthesis 100 into the left atrium 25. Then, after entering the left atrium 25, the valve mating portion 116 is brought into direct opposition to the annulus 23 by bending the first shaft segment 113 approximately 90 again. Then, the valve prosthesis 100 is passed through the annulus 23, partially protruding into the left ventricle. The delivery member then pushes the valve prosthesis 100 out of the delivery lumen, effecting release of the valve prosthesis 100, and expansion of the valve prosthesis 100. Finally, delivery sheath 210, delivery member, and delivery assembly related components such as guidewire 220 are removed.

In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings are merely for convenience in describing the present invention and simplifying the description, and do not indicate or imply that the device or element being referred to must have a specific orientation, be configured and operated in a specific orientation, and therefore should not be construed as limiting the present invention.

In the description of the present specification, reference to the terms "one embodiment," "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiments or examples.

While embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that: many changes, modifications, substitutions and variations may be made to the embodiments without departing from the spirit and principles of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A valve prosthesis, comprising:

a valve stent, the valve stent comprising: the outer support with the inner support is connected and is located the periphery of inner support, the outer support includes: an atrial mating portion, the atrial mating portion comprising: the first support rods are distributed in the circumferential direction and are connected in sequence, and each first support rod is provided with a movable end;

a leaflet secured to the inner stent;

A connector disposed at the movable ends of the plurality of first struts and allowing the plurality of first struts to move between a contracted position, in which the plurality of first struts are adjacent the inner stent, and an expanded position, in which the plurality of first struts are distal from the inner stent for support within the atrium;

the connector is provided with a movable groove, the movable ends of the first support rods are rotatably arranged in the movable groove, the connector is also provided with a first avoiding groove, the first avoiding groove is communicated with the movable groove, the first support rods are further provided with a main body part and a connecting part arranged between the main body part and the movable ends, and when the first support rods are positioned at the contraction positions, the connecting part is positioned in the first avoiding groove; and

The connector includes: the movable groove and the first avoidance groove are formed in the connecting seat, and the cover body is arranged on the connecting seat and partially covers the movable groove.

2. The valve prosthesis of claim 1, wherein the width of the active slot is greater than the width of the active end, the width of the active end being greater than the width of the connection.

3. The valve prosthesis of claim 1, wherein the movable slot is configured as a spherical slot, the first relief slot is configured as a rectangular slot, and the movable end is configured as a sphere or a disc.

4. Valve prosthesis according to claim 1, characterized in that the connecting seat and the cover are provided with threaded shaft holes.

5. The valve prosthesis of claim 1, wherein the plurality of first struts together form a spherical shape in the circumferential direction when the plurality of first struts are in the deployed position.

6. The valve prosthesis of claim 1, wherein a second avoidance groove is formed in the cover, the second avoidance groove is disposed opposite the first avoidance groove and is in communication with the movable groove, and the connection portion is disposed in the second avoidance groove when the plurality of first struts are in the deployed position.

7. The valve prosthesis of claim 1, wherein each of the first struts comprises: one end of each first pole segment of a plurality of first poles is close to each other, and the quantity of first pole segment is n, n satisfies the relation: n is more than or equal to 3 and less than or equal to 15;

The width of the first pole segment is d1, and d1 satisfies the relation: d1 is more than or equal to 0.3mm and less than or equal to 5mm.

8. The valve prosthesis of claim 7, wherein each of the first struts further comprises: the other end of each first pole section is connected with at least two second pole sections, and the second pole sections of the plurality of first poles are sequentially connected in the circumferential direction.

9. The valve prosthesis of claim 8, wherein each of the first struts further comprises: the transition pole section, every the other end of first pole section is passed through the transition pole section is connected with two at least second pole section, a plurality of the transition pole section of first branch is connected gradually in the circumference.

10. A valve prosthesis system, comprising:

The valve prosthesis of any one of claims 1-9;

a delivery assembly, the delivery assembly comprising: a delivery sheath and a guidewire, a delivery lumen disposed within the delivery sheath for loading and delivering the valve prosthesis.