Mitral Stent

Abstract

The invention relates to a self-expendable stent for placement at a mitral annulus that is self-expandable from an undeployed state to a deployed state comprising a stent frame having at least a first section and a second section arranged at a longitudinal axis of the stent, wherein the stent frame is formed by a plurality of endless arms, the arms being connected to one another at connection points forming a web-like structure with diamond-shaped cells; a dry valve made out of bovine pericardium arranged at least at the second section of the stent with the dry bovine pericardium being configured to be rehydrated with a solution, a skirt surrounding the dry valve and comprising at least one of bovine pericardium and polyester, and wherein, in the expanded state, a maximum outer diameter of the first section is larger than a maximum outer diameter of the second section, and wherein at least at a transition between the first section and the second section some of the endless arms extend outwardly beyond the web-like structure to form a hook, which faces the first section.

Claims

1. A self-expendable stent for placement at a mitral annulus that is self-expandable from an undeployed state to a deployed state comprising: a stent frame having at least a first section and a second section arranged at a longitudinal axis of the stent, wherein the stent frame is formed by a plurality of endless arms, the arms being connected to one another at connection points forming a web-like structure with diamond-shaped cells; a dry valve made out of bovine pericardium arranged at least at the second section of the stent with the dry bovine pericardium being configured to be rehydrated with a solution, a skirt surrounding the dry valve and comprising at least one of bovine pericardium and polyester, and wherein, in the expanded state, a maximum outer diameter of the first section is larger than a maximum outer diameter of the second section, and wherein at least at a transition between the first section and the second section some of the endless arms extend outwardly beyond the web-like structure to form a hook, which faces the first section.

2. The self-expendable stent according to claim 1, wherein the hooks are formed by two adjacent arms, which are interconnected.

3. The self-expendable stent according to claim 2, wherein a tip of the hook is formed by a vertex of the respective diamond shaped cell.

4. The self-expendable stent according to claim 1, wherein the stent frame further comprises additional struts arranged at least at the second section and/or at a transition between the first and the second section, which extend outwardly beyond the web-like structure and face the first section to form additional anchors.

5. The self-expendable stent according to claim 4, wherein said additional struts are fixed at the connection points of the arms.

6. The self-expendable stent according to claim 1, wherein, at the transition between the first and second sections, all of the arms of the first section extend outwardly with respect to the second section.

7. The self-expendable stent according to claim 1, wherein the first section comprises part of a generally balloon like outer shape.

8. The self-expendable stent according to claim 1, wherein the second section comprises a generally cylindrical shape.

9. The self-expendable stent according to claim 1, wherein ends of the arms of the first section face radially inwards.

10. The self-expendable stent according to claim 1, wherein ends of the arms of the second section are arranged coaxially with the longitudinal axis, i.e. parallel to the longitudinal axis.

11. The self-expendable stent according to claim 1, wherein at least some of the cells of the first section are larger than the cells of the second section.

12. The self-expendable stent according to claim 1, wherein the dry valve comprises between two and six leaflets, with the leaflets being fixed to the stent frame at fixation points at the second section.

13. The self-expendable stent according to claim 12, wherein the dry valve comprises three or four leaflets.

14. The self-expendable stent according to claim 1, wherein the dry bovine pericardium has a maximum tensile stress selected in the range of 20 to 25 MPa.

15. The self-expendable stent according to claim 1, wherein the rehydrated bovine pericardium has a tensile stress selected in the range of 12 to 15 MPa.

16. The self-expendable stent according to claim 1, wherein the dry bovine pericardium has a calcium content selected in the range of 0.01 to 0.1 g/Kg.

17. The self-expendable stent according to claim 1, wherein the skirt is arranged to cover at least the second section from within.

18. The self-expendable stent according to claim 17, wherein the skirt is arranged to cover also the first section from within.

19. The self-expendable stent according to claim 17, wherein the skirt is arranged to cover the whole stent frame from within.

20. The self-expendable stent according to claim 1, wherein all ends of the arms at a first end and a second end lie in a common plane.

21. The self-expendable stent according to claim 1, wherein the stent further comprises eyelets arranged at a first end of the first section for attaching the stent to a delivery device, wherein the eyelets lie in a further common plane.

22. The self-expendable stent according to claim 21, wherein the eyelets are arranged to project beyond said common plane of the ends of the arms.

23. The self-expendable stent according to claim 21, wherein the eyelets of the first section project inwardly with respect to the longitudinal axis.

24. The self-expendable stent according to claim 23, wherein the eyelets follow the same contour as the ends of the arms of the first section remote from the transition.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0085] The invention will be described in detail by means of embodiments and with reference to the drawings. These show preferred embodiments. The features described may be configured in various combinations, which are encompassed in this document. The drawings show:

[0086] FIG. 1: a stent frame according to a first embodiment;

[0087] FIG. 2: the stent frame according to a second embodiment and further including a dry valve and a skirt;

[0088] FIG. 3: different views of the stent of FIG. 2;

[0089] FIG. 4: CT reconstruction pictures of a deployed stent; and

[0090] FIG. 5: CT reconstruction pictures of the deployed stent of FIG. 4 from different angles.

DETAILED DESCRIPTION

[0091] FIGS. 1 to 3 show different views of a self-expandable stent 10 configured to be placed at the mitral valve of a patient, with the stent 10 having a stent frame 12 composed of a plurality of different arms 14. The stent frame 12 is composed of Nitinol, which is a flexible material comprising shape-memory such that the stent 10 is able to self-expand once it is deployed. Hence, the stent 10 can be delivered in a compressed state to the mitral valve before it self-expands at a delivery site.

[0092] The frame 12 further comprises at least two sections, i. e. a first section 16A and second section 16B, arranged at a longitudinal axis A. The terms “first” and “second” refer to the direction of the blood flow through the stent once it is deployed at its intended place. Hence, once put in place, blood flows first through the first section 16A and then through the second section 16B of the stent 10. Additionally, the stent 10 comprises a transition T between the first section 16A and the second section 16B. All sections 16A, 16B and T are interconnected with each other.

[0093] The frame 12 is further characterized in that the arms 14 are connected to one another at a plurality of connection points 18 such that they form a web-like structure of diamond-shaped cells 20. As one can see in FIGS. 1 to 3 the stent 10 can be composed of rows of cells 20 arranged at the longitudinal axis A. The amount of rows of cells 20 can be chosen according to the anatomical conditions of the patient etc.

[0094] Each stent cell 20 in the present embodiments is formed of four sides and four vertices. The four sides of stent cells 20 are respectively formed by sections of the arms 14 and the vertices are either formed by an end of an arm 14 or a connection point 18.

[0095] As can be seen in FIGS. 1 to 3 some of the arms 14 of the stent 10 extend outwardly beyond the web-like structure of a main body of the stent frame 12 to form a hook 40 which faces the first section 16A. The cells 21, which are arranged underneath said hooks 40, comprise an, in particular significantly, larger area than the rest of the cells 20 of the stent frame. Said hooks 40 can act as anchors in order to attach the stent more tightly at the position of a native mitral valve which is supposed to be treated and/or replaced.

[0096] It can further be seen that the hooks 40 originate at the transition T between the first section 16A and the second section 16B. They are built by two adjacent arms 14, which are interconnected. In particular, a tip 41 of the hook 40 is formed by a vertex of the respective diamond-shaped cell 20. Furthermore, the shape of the hooks 40 generally follows the balloon-like shape of the first section 16A albeit comprising a larger diameter than the first section 16A.

[0097] In the embodiment of FIG. 1 the stent 10 further comprises additional struts 42 which are formed at the second section 16B and at the transition T. Said struts 42 also extend outwardly such that they function like barbs in order to fix the stent more accurately and securely to the heart. The struts 42 of the shown embodiment comprise a linear shape and a comparatively short length.

[0098] The length of the struts can be selected from the range of lengths comprising 25 to 75%, in particular 40 to 60% of a length of the respective cell 20 between two apexes of the cell 20 in parallel to the longitudinal axis A.

[0099] It can further be seen in FIG. 1 that the struts 42 are fixed at the connection points 18 of the arms 14. For this reason, said connection points may comprise eyelets (not shown) to which the struts 42 can be fixed to.

[0100] The second section 16B further comprises a valve 22 made out of dry bovine pericardium as well as a skirt 24 made out of dry bovine pericardium and polyester. The valve 24 usually comprises between two and six leaflets 26 which can be attached to the stent frame 12, for example, at eyelets 28 (see FIGS. 1 and 2) arranged at some 14 at a second end 17B of the stent frame 12. Consequently, the stent 10 further comprises a first end 17A at the first section 16A. In the depicted embodiment the valve 22 comprises three leaflets 26 which are attached to three arms 14 at the second end 17B of the stent 10. As one can see in FIG. 1 it can be possible to provide two eyelets 28 at each arm 14. As one can also see, said eyelets 28 are provided at the position where two adjacent leaflets 26 meet such that both of said leaflets 26 can be sutured to one arm 14. Hence, with the two eyelets being provided at said one arm 14, the stent 10 comprises one eyelet 28 per leaflet 26 at each one of said arms 14.

[0101] The eyelets 28 are arranged such that they are positioned at apexes between two directly adjacent leaflets 26, with the region of the respective leaflets 26 at the apexes being fixed to the eyelets 28 in order to stabilize the dry valve 22 in this region to ensure a correct functioning, i. e. opening and closing, of the leaflets 26 even in the region of the apexes.

[0102] Generally speaking, also every arm 14 could be provided with eyelets 28. The exact number of arms 14 which will be provided with eyelets 28 may be chosen according to the application. For example, if a valve 22 with only two leaflets 26 is chosen to be placed inside the stent 10, only two arms 14 may be provided with eyelets 28. In some embodiments, on the other hand, the eyelets 28 can always be provided at two adjacent arms 14 in order to fix two adjacent leaflets 26 to the stent frame 12 (see FIG. 2).

[0103] Due to anatomical reasons of the left ventricle and left atrium of the heart, the skirt 24 does not only surround the valve 22 at the second section 16B but may cover up to 100% of the stent 10 to prevent leakage between the stent 10 and the heart of the patient. In the embodiments of FIGS. 2 and 3, for example, most of the cells 20 are covered by the skirt 24. Only some of the cells 20 of the second section 16B are covered by the skirt 24 while others are being left out, namely the ones between the leaflets 26.

[0104] An outer contour of the stent 10 according to the invention can be described as being balloon shaped at the first section 16A and cylindrical at the second section 16B. Starting from the first end 17A the first section 16A then transitions into the transition T into the second section 16B. It can be seen that the maximum outer diameter of the first section 16A is significantly larger than the maximum outer diameter of the second section 16B.

[0105] Generally speaking the outer contour is selected to adapt to the shape of the valve into which it is fitted in order to be adapted to create a tight interference fit with the mitral valve to ensure that the positioning of the stent 10 does not vary in time. This interference fit may add minor, but additional, stability to the valve 22 once positioned.

[0106] In order to attach the stent 10 at its respective point of interest, i. e. the mitral valve, the stent 10 can comprise further eyelets (not shown) at its respective first and second ends 17A, 17B. That is, after being expanded, the stent 10 does not only hold itself in place by fitting into the mitral valve but also by being sutured to the walls of the heart. The exact attachment point and technique can be chosen according to the different conditions inside the different hearts which are being treated with the invention.

[0107] The ends 30 of the arms 14 at both ends of the stent 10 can lie in a common plane. The eyelets, which are used to attach the stent to the mitral valve (not shown) can comprise a rectangular outer shape with a rectangular opening for suturing the stent 10 to the aortic artery. Generally, said eyelets can also comprise a different shape, e. g. a circular shape, for both their outer and inner shape. The eyelets 28 as well as the eyelets for suturing the stent 10 to the artery can project beyond sad common plane of the ends 30 of the arms 14 and span another common plane.

[0108] Additionally, the stent 10 comprises eyelets 32 for attaching the stent 10 to a delivery device (see FIG. 1) which also project beyond the common plane of the ends 30 of the arms 14.

[0109] Finally, in FIGS. 4 and 5 one can see different CT pictures of a stent 10, which has been deployed at the mitral valve of a patient, preferably using a delivery device as described in the foregoing. Such delivery devices are common state of the art and are therefore not described in detail. The different pictures in FIGS. 4 and 5 show the same stent 10 from different angles. As one can see in those CT pictures, the stent 10 is in the expanded state and has been deployed at the native mitral valve of the patient in order to replace it.

REFERENCE LISTING

[0110] 10 stent [0111] 12 frame [0112] 14 arms [0113] 16A first section [0114] 16B second section [0115] 17A first end [0116] 17B second end [0117] 18 connection point [0118] 20 cell [0119] 21 bigger cell [0120] 22 valve [0121] 24 skirt [0122] 26 leaflet [0123] 28 eyelet [0124] 30 end of arms [0125] 32 eyelets [0126] 40 hooks [0127] 41 tip [0128] 42 struts [0129] A longitudinal axis [0130] T transition