Aortic Stent

Abstract

The invention relates to a stent for placement at an aortic annulus that is expandable from an undeployed state to a deployed state comprising a stent frame having rows of cells with a proximal section and a distal section at a longitudinal axis of the stent, the stent frame being formed by a plurality of arms, the arms being connected to one another at connection points, and wherein the plurality of arms forms a plurality of diamond-shaped stent cells, in particular the rows of cells, formed of vertices at said connection points between the arms, a dry valve made out bovine pericardium arranged at least at the distal 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 one or more eyelets arranged at a distal end of some of the arms, with the eyelets being configured to fix the valve to the stent frame.

Claims

1. A stent for placement at an aortic annulus that is expandable from an undeployed state to a deployed state, the stent comprising: a stent frame having rows of cells with a proximal section and a distal section at a longitudinal axis of the stent, the stent frame being formed by a plurality of arms, the arms being connected to one another at connection points, and wherein the plurality of arms forms a plurality of diamond-shaped stent cells, in particular the rows of cells, formed of vertices at said connection points between the arms, a dry valve made out bovine pericardium arranged at least at the distal 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 one or more eyelets arranged at a distal end of some of the arms, with the eyelets being configured to fix the dry valve to the stent frame.

2. The stent in accordance with claim 1, wherein two eyelets are provided at each one of said arms of said some of the arms.

3. The stent in accordance with claim 1, wherein the dry valve comprises between two and six leaflets, preferably three or four leaflets, with the leaflets being connected to the stent frame at said eyelets.

4. The stent according to claim 1, wherein the stent comprises four rows of cells along the longitudinal axis.

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

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

7. The stent in accordance with claim 1, wherein the dry bovine pericardium has a calcium content selected in the range of 0.01 to 0.1 g/Kg.

8. The stent according to claim 1, wherein the dry bovine pericardium is formed using a method of treatment comprising the following steps: soaking of the bovine pericardium treated with a crosslinking agent with a saline solution; contacting the soaked bovine pericardium with an aqueous solution comprising Hydrogen Peroxide; contacting the bovine pericardium with an aqueous solution comprising PBS and EDTA; contacting the bovine pericardium with a solution comprising glycerol, ethanol and EDTA; and contacting the bovine pericardium with a glycerol solution.

9. The stent according to claim 1, wherein the skirt is arranged to cover at least the distal section of the stent frame from within.

10. The stent according to claim 1, wherein the skirt is arranged to cover at least the proximal section of the stent frame from within.

11. The stent according to claim 1, wherein the skirt is arranged to cover the whole stent from within.

12. The stent according to claim 1, wherein all ends of the arms at the distal and the proximal section lie in a common plane.

13. The stent according to claim 12, wherein the eyelets of the distal end project beyond said common plane at the ends of the arms.

14. The stent according to claim 13, wherein the eyelets lie in a further common plane.

15. The stent according to claim 14, wherein ends of the eyelets remote from the ends of the arms lie in said further common plane.

16. The stent according to claim 1, wherein the stent further comprises means for attaching the stent frame to an artery at at least one of the distal end and a proximal end of the stent frame.

17. The stent according to claim 16, wherein the means for attaching the stent frame to an artery are configured to be attached to the aortic artery.

18. The stent according to claim 1, wherein the stent frame is made out of at least one of chromium, cobalt and Nitinol.

19. The stent according to claim 1, wherein a diameter of the distal section and the proximal section is larger than a diameter of a middle section arranged between the distal section and the proximal section.

20. The stent according to claim 1, wherein a radius of curvature between the proximal section, the middle section and the distal section lies in the range of 5 to 50 mm.

21. The stent according to claim 1, wherein a radius of curvature between the proximal section, the middle section and the distal section lies in the range of 10 to 40 mm.

22. The stent according to claim 1, wherein a radius of curvature between the proximal section, the middle section and the distal section lies in the range of 20 to 30 mm.

23. The stent according to claim 1, wherein the stent frame has a shape that corresponds to or at least substantially corresponds to the shape of a nucleus of a torus.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0080] 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:

[0081] FIG. 1: a perspective view of an aortic stent;

[0082] FIG. 2: a side view of the aortic stent of FIG. 1;

[0083] FIG. 3: a side view of a stent frame;

[0084] FIG. 4: a top view of the stent of FIG. 1;

[0085] FIG. 5: a top view of a stent including a native artery and a marked inner space;

[0086] FIG. 6: a part of a delivery device delivering the stent;

[0087] FIG. 7: CT pictures of a delivered stent; and

[0088] FIG. 8: CT pictures of the delivered stent of FIG. 7.

DETAILED DESCRIPTION

[0089] FIG. 1 shows a perspective view of a stent 10 according to the invention with a stent frame 12 composed of a plurality of arms 14. The stent 10 can be a balloon-expandable or a self-expandable stent 10, both configured to be placed at the aortic artery and the aortic valve of a patient. The stent frame 12 can be composed of Chromium and Cobalt, in the case of a balloon-expandable stent 10, or Nitinol if a self-expandable stent 10 is desired. Both versions of the stent 10 can be delivered in a compressed state to a point of interest such as the aortic artery of a human, where it then can be (self-)expanded once it is deployed.

[0090] The frame 12 further comprises at least two sections, i.e. a proximal section PS and a distal section MS, arranged at a longitudinal axis A. Often the stent further comprises a third section, i.e. a middle section MS, which is arranged between the proximal section PS and the distal section DS respectively. All sections DS, MS, PS are interconnected with each other. In this connection it is noted that the terms “distal” and “proximal” refer to said end of the stent which is farther away or closer to the heart of the patient, respectively, once the stent 10 is put in place.

[0091] The frame 12 is further characterized in that the arms 14 are connected one to another at a plurality of connection points 16 such that they form a web-like structure of diamond-shaped cells 18. In the embodiment of FIG. 1 the stent 10 is composed of four rows of cells 18 arranged along the longitudinal axis A of the stent 10. Generally, the stent 10 can also comprise more or less rows of cells 18 depending on the application, the anatomical conditions of the patient etc.

[0092] Each stent cell 18 in the present example is formed of four sides and four vertices. The four sides of the stent cells 18 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 16.

[0093] The distal section DS of the stent 10 further comprises a valve 20 made out of dry bovine pericardium as well as a skirt 22 made out of dry bovine pericardium and polyester. The valve 20 comprises three leaflets 24 which are attached to the stent frame 12 at eyelets 26 arranged at some arms 14 at a distal end DE of the frame 12 (FIG. 1 and FIG. 4). In the depicted embodiment three arms 14—corresponding to the three leaflets 24—are provided with eyelets 26, wherein each one of said arms 14 comprises two eyelets 26 to which the leaflets 26 can be attached to, i. e. sutured, i.e. an eyelet is provided per leaflet. As one can also see, said eyelets 26 are provided at the position where two adjacent leaflets 24 meet such that both of said leaflets 20 can be sutured to one arm 14.

[0094] The eyelets 26 are arranged such that they are positioned at apexes between two directly adjacent leaflets 26, with the region of the respective leaflets at the apexes being fixed to the eyelets in order to stabilize the dry valve 20 in this region to ensure a correct functioning, i.e. opening and closing, of the leaflets 26 even in the region of the apexes.

[0095] Generally speaking, also every arm 14 could be provided with eyelets 26. The exact number of arms 14 which will be provided with eyelets 26 may be chosen according to the application. For example, if a valve 20 with only two leaflets 24 is chosen to be placed inside the stent 10, only two arms 14 may be provided with eyelets 26. In some embodiments, on the other hand, the eyelets 26 can always be provided at two adjacent arms 14 in order to fix two adjacent leaflets 24 to the stent frame 12 (see FIG. 3).

[0096] The eyelets 26 are provided at the distal end DE of the stent 10 in order to maximize the area inside the stent, especially at the middle section MS (see FIG. 5). By placing the eyelets 26 at the distal end DE the suturing does not decrease the effective area inside the stent 10.

[0097] Due to anatomical reasons of the aortic artery and of the right ventricle of the heart, the skirt 22 does not only surround the valve 20 at the distal section DS but may cover up to 100% of the stent 10 to prevent leakage between the stent 10 and the ventricle of the patient's heart (see FIG. 2). In the embodiment of FIG. 2, for example, three out of four rows of cells 18 are covered by the skirt 22. Only some of the cells 18 of the last row at the distal end DE of the stent 10, namely the ones which are right underneath the eyelets 26 are provided with a skirt 22.

[0098] An outer contour of the stent 10 of FIGS. 1 to 5 can be described as having the following shapes, an approximately cylindrical shape in both the proximal section PS and the distal section DS with the distal end DE and a proximal end PE both having a slightly convex outer surface 28. Starting from the proximal end PE the proximal section PS then transitions into the middle section MS which then transitions into the distal section DS. The respective transitions T correspond to a mathematical turning point such that the outer surface 28 of the stent comprises a radius of curvature which lies in the range of 20 to 30 mm.

[0099] Hence, a maximum outer diameter of both the distal and the proximal section DS, PS is larger than a maximum outer diameter of the middle section MS. Preferably the maximum outer diameters of the distal and the proximal sections are the same. In some cases it may nevertheless be advantageous to provide with different diameters, such as a bigger diameter for the distal section DS than for the proximal section PS. The middle section MS comprises the smallest diameter in order to avoid compression of the coronary arteries, which wrap the whole heart, can be prevented.

[0100] Generally speaking the outer contour is selected to adapt to the shape of the blood vessel into which it is fitted with the distal section PS being adapted to create a tight interference fit with the blood vessel to ensure that the positioning of the stent 10 does not vary in time. The proximal section is designed to have an interference fit with the aorta superior to the aortic annulus. This interference fit may add minor, but additional, stability to the valve 20 once positioned.

[0101] In order to be able to attach the stent 10 at its respective point of interest, i.e. the aortic artery, the stent 10 can comprise further eyelets (not shown) at its respective proximal and/or distal ends PE, DE. That is, after being expanded, the stent 10 does not only hold itself in place by into the aortic artery but also by being sutured. This way, it may also be possible to attach the proximal end PE of the stent 10 at the transition of the aortic artery and the right ventricle of the heart or at the wall of the right ventricle itself such that the stent 10 protrudes inside the ventricle. The exact attachment point and technique can thus be chosen according to the different conditions at the different hearts which are being treated with the invention.

[0102] 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 artery (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 the outer and the inner shape. The eyelets 26 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.

[0103] FIG. 6 shows a delivery device 32 for delivering the (balloon-) expandable stent 10 also known as catheter. Such a delivery device can be configured to inflate a balloon which then expands the stent once it is put in place. Such delivery devices are common state of the art and are thus not described in detail.

[0104] In FIGS. 7 and 8 one can see different MRI pictures of a stent 10, which has been deployed at the aortic artery of a patient, preferably using the delivery device 32 of FIG. 6. The different pictures in FIGS. 7 and 8 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 transition between the aortic artery and the right ventricle of the patient.

REFERENCE LISTING

[0105] 10 stent [0106] 12 frame [0107] 14 arms [0108] 16 connection point [0109] 18 cell [0110] 20 valve [0111] 22 skirt [0112] 24 leaflet [0113] 26 eyelet [0114] 28 outer surface [0115] 30 end of arms [0116] 32 delivery device [0117] A longitudinal axis [0118] DE distal end [0119] DS distal section [0120] MS middle section [0121] PE proximal end [0122] PS proximal section [0123] T transition