Covered stent

Abstract

The covered stent comprises a grid skeleton and a covering film, the grid skeleton comprises a covered stent section and a near-end bare stent section which are sequentially arranged from the far end to the near end in the axial direction of the grid skeleton, the whole outer surface of the covered stent section is covered with the covering film, the length of the covered stent section ranges from 4 mm to 30 mm, the length of the near-end bare stent section ranges from 2 mm to 10 mm, and the length of the covering film ranges from 2 mm to 10 mm. Therefore, the multi-aspect performance of the covered stent is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of medical devices, and particularly to a covered stent. Background Art

[0002] Cardiovascular and cerebrovascular diseases are important diseases affecting human health, among which aneurysms are the most common, constantly endangering human health. Covered stents have become stents with increasingly wide applications due to their innate advantage of being able to block, especially applied to pathological locations such as the thoracic aorta, abdominal aorta, heart valves, carotid arteries, etc., to isolate aneurysms and guide blood to flow along the direction of normal blood vessels.

[0003] Most current covered stents are fully covered stents, where the stent is completely covered by the film, or double-layer films are used. The fully covered method is likely to affect the flexibility and stretchability of the stent, and the film is also prone to problems such as rupture, reducing the effectiveness of the film. The double-layer film will greatly increase the thickness of the stent, which is not conducive to the delivery of the stent and entering smaller blood vessels. In addition, if the release position is inappropriate, it is not convenient for the existing covered stent to be recovered, readjusted in position and then released. Moreover, the covered stent may also have problems such as non-adherence to the proximal wall or blocking of branch blood vessels.

[0004] Therefore, for those skilled in the art, how to design a covered stent that can balance various performances is an urgent problem to be solved currently.

[0005] It should be noted that the information disclosed in the background art part of the present application is only intended to deepen the understanding of the general background art of the present application, and should not be regarded as an admission or any form of suggestion that this information constitutes the prior art known to those skilled in the art. Summary of the Invention

[0006] The purpose of the present invention is to provide a covered stent, aiming to improve various performances of the covered stent, especially the anchoring performance, recovery performance, wall-adhering performance, and not easily blocking branch blood vessels.

[0007] To achieve the above purpose, the present invention provides a covered stent, including a grid skeleton and a film. The grid skeleton includes a covered stent segment and a proximal bare stent segment arranged in sequence along its own axis from the distal end to the proximal end. The film covers the entire outer surface of the covered stent segment. The length of the covered stent segment is 4 mm to 30 mm, and the length of the proximal bare stent segment is 2 mm to 10 mm.

[0008] Preferably, the grid skeleton further includes a distal bare stent segment arranged along its own axis. The distal bare stent segment is located at the distal end of the covered stent segment, and the length of the distal bare stent segment does not exceed 4 mm.

[0009] Preferably, the grid skeleton further includes a distal flare section and a proximal flare section arranged along its own axis. The distal flare section is located at the distal end of the distal bare stent section, and the proximal flare section is located at the proximal end of the proximal bare stent section. The diameters of both the distal flare section and the proximal flare section are greater than the diameter of the covered stent section and the diameter of the proximal bare stent section, and the diameter of the distal bare stent section is smaller than the diameters of the distal flare section and the proximal flare section.

[0010] Preferably, the lengths of the distal flare section and the proximal flare section are 1 mm to 4 mm.

[0011] Preferably, the diameter of the distal flare section is 1.2 to 4 times the diameter of the distal bare stent section, and the diameter of the proximal flare section is 1.2 to 4 times the diameter of the proximal bare stent section.

[0012] Preferably, the diameters of the distal bare stent section and the proximal bare stent section are 1.0 to 1.5 times the diameter of the covered stent section.

[0013] Preferably, a plurality of radiopaque markers are provided on both the distal flare section and the proximal flare section.

[0014] Preferably, the covering film forms wrinkles on the covered stent section.

[0015] Preferably, the grid skeleton is woven from a plurality of braided wires, and the plurality of braided wires intersect with each other to form grids and intersection points;

[0016] The covered stent further includes a plurality of membrane sheets. All the membrane sheets are arranged in the inner cavity of the grid skeleton. The axial two ends of the covering film are respectively heat-melted and connected to a plurality of the membrane sheets. The plurality of membrane sheets connected to any one end of the covering film are distributed circumferentially along the grid skeleton, and each membrane sheet covers the braided wires between two adjacent intersection points.

[0017] Preferably, each membrane sheet is not fixed to the braided wire covering the membrane sheet.

[0018] Preferably, the braided wire covering the membrane sheet presses on another braided wire at the corresponding intersection point, so that the other braided wire pressed by the braided wire covering the membrane sheet can block the membrane sheet during the axial stretching process of the covered stent.

[0019] Preferably, a plurality of radiopaque markers are provided at both the proximal end and the distal end of the covered stent section.

[0020] Preferably, the length of the proximal bare stent section is 2 mm to 5 mm.

[0021] Compared with the prior art, the covered stent provided by the present invention has at least the following advantages:

[0022] In the above covered stent, the length of the proximal bare stent segment is 2 mm to 10 mm. With this length, the retrievability and repositioning of the covered stent can be achieved, and it can be avoided that the covered stent blocks the branch vessels after complete release. It should be understood that if the proximal bare stent segment is too short, it will be difficult to retrieve the covered stent segment after complete release. Therefore, the proximal bare stent segment cannot be too short. After the covered stent segment and the covering are completely released, the proximal bare stent segment can still be used to retrieve the covered stent again. After repositioning, the covered stent can be released again to ensure the effectiveness and accuracy of isolating the blood vessel and blood flow. At the same time, the length of the proximal bare stent segment is not too long, and it does not block the branch vessels after the covered stent is completely released, ensuring the smooth blood flow of the branch vessels.

[0023] In the above covered stent, the length of the covered stent segment is 4 mm to 30 mm. This length enables the covered stent to isolate the vast majority of aneurysms and ensures its scope of application. Also, since the covering is a single layer and is locally covered, it can reduce the influence of the covering on the grid skeleton, ensure the flexibility of the covered stent and the effectiveness of the covering, and can also not increase the thickness of the stent, enabling the covered stent to be delivered and enter smaller blood vessels.

[0024] On the above basis, the above covered stent can further be provided with a proximal flared segment and a distal flared segment to improve the anchoring performance of the covered stent by using the proximal flared segment and the distal flared segment. Also, by using the proximal bare stent segment to transition between the covered stent segment and the proximal flared segment, the wall attachment performance of the covered stent at the proximal end can be improved, thereby preventing endoleakage, and thus ensuring the anchoring force and wall attachment of the covered stent.

[0025] Furthermore, in the above covered stent, the wall attachment performance of the covered stent at the distal end can be further improved by using a distal bare stent segment to transition the covered stent segment, further preventing endoleakage. Also, by setting the length of the distal bare stent segment not exceeding 4 mm, the positioning performance at the distal end of the covering is ensured, which is beneficial for the operator (such as a doctor) to determine the position of the distal end of the covering, and then quickly and accurately occlude the aneurysm.

[0026] Furthermore, in the above covered stent, on the premise of ensuring that the covered stent has sufficient anchoring force, by setting the lengths of the distal flared segment and the proximal flared segment to be 1 mm to 4 mm, the lengths of the distal flared segment and the proximal flared segment are made short enough to reduce the length of the entire covered stent and lower the delivery difficulty. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Those of ordinary skill in the art will understand that the provided drawings are used to better understand the present invention and do not constitute any limitation to the scope of the present invention. Among them:

[0028] Figure 1 Schematic diagram of the overall structure of the covered stent based on the braided skeleton in the preferred embodiment of the present invention;

[0029] Figure 2 Schematic diagram of the partial structure of the covered stent with the film covered by heat-melting connection of multiple film sheets in the preferred embodiment of the present invention;

[0030] Figure 3 Schematic diagram of the partial structure of the covered stent for positioning the film in the preferred embodiment of the present invention, where the vertical line L represents the proximal edge of the film, and the part to the left of the proximal edge is the film;

[0031] Figure 4 Schematic diagram of the structure of the covered stent based on the cut skeleton in the preferred embodiment of the present invention. Detailed implementation manners

[0032] To make the objectives, advantages and features of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that the accompanying drawings are all in very simplified forms and not drawn to scale, and are only used to facilitate and clearly assist in explaining the objectives of the embodiments of the present invention. In addition, the structures shown in the accompanying drawings are often part of the actual structures. In particular, the accompanying drawings need to show different emphases, and sometimes different scales are used. As used in this specification, the singular forms "a", "an" and "the" include plural objects unless the context clearly indicates otherwise. As used in this specification, the term "or" is generally used in the sense of including "and / or" unless the context clearly indicates otherwise.

[0033] In this application, "diameter" refers to "outer diameter", "axial direction" refers to the longitudinal axis direction of the covered stent, "circumferential direction" refers to the direction around the longitudinal axis of the covered stent, and "radial direction" refers to the direction perpendicular to the longitudinal axis of the covered stent, that is, the diameter direction. In this application, "proximal end" refers to the end of the covered stent close to the surgeon during delivery, and "distal end" refers to the end of the covered stent far from the surgeon during delivery. The "length" and "diameter" described in this application document are the dimensions of the covered stent in the deployed and expanded state. In addition, "not exceeding" described in this application document means less than or equal to.

[0034] The core idea of the present invention is to provide a covered stent that can be re-recovered and re-positioned after the covered stent segment and the film are completely released. On this basis, more performances can be further considered, such as performances in terms of thickness, flexibility, anchoring property, wall attachment property, recovery performance, positioning performance, delivery performance, etc.

[0035] The covered stent of the present invention can be self-expanded or expanded by means of external force, and there is no requirement for this. During actual use, the covered stent has a folded and contracted state and an expanded state, and can switch between the folded and contracted state and the expanded state. Generally, the covered stent is in a folded and contracted state when being transported in a delivery system. In the folded and contracted state, the covered stent is axially elongated to facilitate transportation; while the covered stent is in an expanded state after being released from the delivery system; however, when the covered stent is not restricted by external force, it is also in an expanded state, and this expanded state should be understood as the natural state.

[0036] The following will be described with reference to the accompanying drawings.

[0037] As Figures 1 to 4 shown, the covered stent provided in the embodiment of the present invention includes a mesh skeleton 10 and a covering film 20. The mesh skeleton 10 is a braided stent or a cut stent, and the present invention is not limited thereto. In this embodiment, a braided stent is taken as an example for illustrative description. The braided stent is braided by a plurality of braided wires 101. The cut stent can be integrally cut from a pipe, such as formed by laser engraving. In any case, the mesh skeleton 10 is a tubular mesh structure, having a plurality of meshes 102 and a plurality of intersection points 103.

[0038] Among them, the mesh skeleton 10 includes a distal bell mouth section 11, a distal bare stent section 12, a covered stent section 13, a proximal bare stent section 14, and a proximal bell mouth section 15 which are sequentially arranged along its own axis from the distal end to the proximal end. It should be recognized that the distal bell mouth section 11, the distal bare stent section 12, and the proximal bell mouth section 15 are not necessary. In some cases, the mesh skeleton 10 does not include the distal bell mouth section 11, the distal bare stent section 12, and the proximal bell mouth section 15. In other cases, the mesh skeleton 10 includes at least one of the distal bell mouth section 11, the distal bare stent section 12, and the proximal bell mouth section 15. The following takes the inclusion of the distal bell mouth section 11, the distal bare stent section 12, and the proximal bell mouth section 15 for illustrative description, but those skilled in the art should be able to modify the following description to obtain the covered stent without the distal bell mouth section 11, the distal bare stent section 12, and the proximal bell mouth section 15.

[0039] In this embodiment, the diameters of both the distal bell mouth section 11 and the proximal bell mouth section 15 are larger than the diameters of the distal bare stent section 12, the covered stent section 13, and the proximal bare stent section 14. The diameter of the distal bell mouth section 11 becomes smaller from the distal end to the proximal end, forming a bell mouth, while the diameter of the proximal bell mouth section 15 becomes larger from the distal end to the proximal end, also forming a bell mouth. In this way, through the distal bell mouth section 11 and the proximal bell mouth section 15, the covered stent can play a better anchoring role after being opened, thereby improving the anchoring performance of the covered stent, especially improving the supporting performance of the braided stent and making it not easy to shift.

[0040] Compared with the prior art, in the embodiment of the present invention, a single-layer film covering is used to replace the traditional double-layer film, and local film covering is also used to replace the traditional full film covering. For this purpose, the film covering 20 only covers the entire outer surface of the film-covered stent section 13 to completely enclose the film-covered stent section 13, and the remaining stent sections are not film-covered. By doing so, the influence of the film covering 20 on the grid skeleton 10 can be reduced, and problems such as rupture of the film covering 20 are not likely to occur. Furthermore, the flexibility of the film-covered stent and the effectiveness of the film covering 20 can be ensured, and the thickness of the stent can be not increased, enabling the film-covered stent to be delivered and inserted into smaller blood vessels.

[0041] Since the film covering 20 will, to a certain extent, restrict the film-covered stent section 13, at least the proximal bare stent section 14 is used to transition between the film-covered stent section 13 and the proximal flared section 15, so that the proximal part of the film-covered stent can adhere well to the blood vessel wall after release to prevent endoleakage. Further, the distal bare stent section 12 can be used to transition between the film-covered stent section 13 and the distal flared section 11, so that the distal part of the film-covered stent can adhere well to the blood vessel wall after release to further prevent endoleakage.

[0042] In order to improve the retrievability of the film-covered stent, in the embodiment of the present invention, the proximal bare stent section 14 is also used to achieve the retrievability and repositioning of the film-covered stent, and at the same time, it can also prevent the film-covered stent from blocking the branch blood vessels after complete release. Thus, the length of the proximal bare stent section 14 is set to be 2 mm to 10 mm, and more preferably 2 mm to 5 mm; this length makes the proximal bare stent section 14 neither too long nor too short. At the same time, the length of the proximal bare stent section 14 is such that after the film-covered stent section 13 and the film covering 20 are completely released, the film-covered stent can still be retrieved using the proximal bare stent section 14, repositioned and then released, ensuring the effectiveness and accuracy of isolating the blood vessel and blood flow. Specifically, after the film-covered stent section 13 and the film covering 20 are completely released and the film covering 20 needs to adhere to the wall, and the proximal bare stent section 14 has not been released from the delivery system, at this time, contrast agent can be injected to observe whether the film covering 20 has blocked the aneurysm. If not, the film-covered stent can be retrieved, repositioned and then released. At the same time, the proximal bare stent section 14 cannot be too long to avoid blocking the branch blood vessels after the film-covered stent is completely released and ensure the smooth blood flow of the branch blood vessels.

[0043] The length of the film-covered stent section 13 can be determined according to the length range of the aneurysm neck opening that needs to be covered in actual clinical applications, so that the film-covered stent can be used to isolate most aneurysms and ensure its scope of application. Therefore, the length of the film-covered stent section 13 is set to be 4 mm to 30 mm, and this length can cover the length of the aneurysm neck opening of most aneurysms.

[0044] Compared with the prior art, the covered stent according to the embodiments of the present invention can achieve the retrievability and repositioning of the covered stent through the proximal bare stent segment 12. On this basis, the anchoring performance and wall attachment performance of the covered stent can be improved through at least one of the distal flared segment 11, the proximal flared segment 15, and the distal bare stent segment 12, so that the covered stent can take into account various performances. As introduced above, it can take into account at least the performances such as the stent thickness, flexibility, effectiveness, anchoring performance, wall attachment performance, retrievability, influence on branch vessels, and application range. Therefore, the comprehensive performance of the covered stent is better.

[0045] Further, when the distal bare stent segment 12 is provided on the covered stent, the distal bare stent segment 12 should not be too long. Preferably, the length of the distal bare stent segment 12 does not exceed 4 mm to ensure the positioning performance at the distal end of the covering, which is beneficial for doctors to determine the position of the distal end of the covering, and then quickly and accurately occlude the aneurysm. It can be understood in this way that imaging points are usually provided on the distal flared segment 11 and the distal end of the covering 20 to position the covered stent. During the delivery process, the covered stent will be axially stretched, and during the release process, the covered stent will contract again. If the distal bare stent segment 12 is short enough, the distance change between the imaging point on the distal flared segment 11 and the imaging point at the distal end of the covering will be small enough during delivery and after release, which is beneficial for doctors to determine the distal position of the covering 20 to occlude the aneurysm. Therefore, the distal bare stent segment 12 should be short enough, or even the distal bare stent segment 12 is not provided.

[0046] Further, on the premise of ensuring that the covered stent has sufficient anchoring force, by setting the lengths of the distal flared segment 11 and the proximal flared segment 15 to be 1 mm to 4 mm, the lengths of the distal flared segment 11 and the proximal flared segment 15 are made short enough to reduce the length of the entire covered stent and lower the delivery difficulty. In this way, the covered stent can further take into account the delivery performance. The lengths of the distal flared segment 11 and the proximal flared segment 15 can be the same or different.

[0047] In terms of the diameter of the covered stent, the diameters of the distal flared segment 11 and the proximal flared segment 15 can be the same or different, and there is no limitation in this regard. The diameter of the distal flared segment 11 is preferably 1.2 times to 4 times the diameter of the distal bare stent segment 12. Correspondingly, the diameter of the proximal flared segment 15 is preferably 1.2 times to 4 times the diameter of the proximal bare stent segment 14. Thereby, the covered stent can be better anchored in the blood vessel after release, reducing the risk of its displacement.

[0048] The diameters of the distal bare stent segment 12 and the proximal bare stent segment 14 may be the same or different. Preferably, the diameters of the distal bare stent segment 12 and the proximal bare stent segment 14 are 1 to 1.5 times the diameter of the covered stent segment 13, which can enable better wall attachment at the distal and proximal ends after the covered stent is released and achieve a better effect of preventing endoleakage. The diameter of the covered stent segment 13 should be understood as the diameter after the covered stent segment 13 is sleeved with the covering film 20.

[0049] In this embodiment, a plurality of radiopaque points are provided on both the distal flared segment 11 and the proximal flared segment 15, which is convenient for doctors to locate the position of the covered stent during the operation. The radiopaque points described herein can all be radiopaque under X-ray irradiation. The material of the radiopaque points can be any known metal radiopaque material, such as platinum tungsten or other materials.

[0050] As Figure 1 shown, a plurality of radiopaque springs 104 are provided on the distal flared segment 11. The plurality of radiopaque springs 104 are arranged circumferentially on the distal flared segment 11 in sequence. Preferably, 3 to 4 radiopaque springs 104 are provided. At the same time, a plurality of radiopaque sleeves 105 are provided on the proximal flared segment 15. The plurality of radiopaque sleeves 105 are arranged circumferentially on the proximal flared segment 15 in sequence, such as at least 3 to 4 radiopaque sleeves 105. In some embodiments, the radiopaque sleeve 105 here can not only be radiopaque but also connect to the wire ends of the braided wire 101 to avoid the exposure or formation of tips of the proximal wire ends. Actually, only by helically winding a radiopaque metal wire on the braided wire 101 and then further bonding and fixing it, the radiopaque spring 104 can be formed, and the radiopaque sleeve 105 itself is tubular, and the wire ends of at least two braided wires 101 are inserted into the radiopaque sleeve 105 for bonding and fixing.

[0051] Preferably, a plurality of radiopaque points are provided at both the proximal and distal ends of the covered stent segment 13. As Figure 3 shown, in this embodiment, the radiopaque points on the covered stent segment 13 are the radiopaque springs 104. A plurality of radiopaque springs 104 are provided at both the proximal and distal ends of the covered stent segment 13, such as 3 to 4 radiopaque springs 104. The plurality of radiopaque springs 104 at any one end of the covered stent segment 13 are arranged circumferentially. The radiopaque springs 104 on the covered stent segment 13 need to be fixed at the end edge of the covering film 20. At least part of the radiopaque springs 104 on the covered stent segment 13 can be covered by the covering film 20, and it is best to be completely covered by the covering film 20, which can better determine the position of the covering film 20. However, it should be understood that the proximal end of the covered stent segment 13 is the distal end of the proximal bare stent segment 14, and the distal end of the covered stent segment 13 is the proximal end of the distal bare stent segment 12, which is equivalent to providing a plurality of radiopaque points at the distal end of the proximal bare stent segment 14 and the proximal end of the distal bare stent segment 12 respectively.

[0052] However, there are various ways to set the developing points on the grid skeleton 10, including but not limited to the developing points prepared by the above-mentioned developing spring 104 and developing sleeve 105. Developing points in other structural forms can also be adopted, and the present application does not limit this. The developing points at both ends of the covered stent segment 13 and the developing points on any one of the flared segments can be set alternatively or simultaneously.

[0053] As Figure 1 shown, in this embodiment, the grid skeleton 10 is a braided stent, and there is no exposed wire end or tip at both its proximal and distal ends. That is, the braided wires 101 at both the proximal and distal ends form closed loops. For example, the braided wires 101 at the distal end wind around to form a closed loop, and the braided wires 101 at the proximal end are constrained by the developing sleeve 105. In this way, damage to blood vessels caused by both ends of the grid skeleton 10 can be avoided. The number of braided wire heads on the grid skeleton 10 is not limited. Common numbers of braided wire heads are 8, 12, 16, 24, 32, 48, or 64.

[0054] The grid skeleton 10 is prepared from common materials, such as one material or a combination of multiple materials selected from cobalt-based alloys, stainless steels, nitinol alloys, platinum alloys, iridium alloys, bioactive ceramics, and carbon, or composite materials selected from these materials.

[0055] The covering film 20 is a common polymer material, usually selected from expanded polytetrafluoroethylene (ePTFE), polyester (PET), polyurethane (TPU), and polylactic acid (PLA). The covering film 20 usually has no elasticity or little elasticity and cannot expand and contract together with the grid skeleton 10. To further reduce the influence of the covering film 20 on the grid skeleton 10, preferably, the covering film 20 forms folds on the covered stent segment 13. That is, the length of the covering film 20 installed on the grid skeleton 10 is less than the length of the covering film 20 before installation. The covering film 20 forms folds during installation, which can also reduce the risk of rupture and the like of the covering film 20 when the grid skeleton 10 expands and contracts, thereby further improving the effectiveness of the covering film 20. It can be understood that the covering film 20 forming folds on the covered stent segment 13 means that when the stent is in the compressed state, the covering film 20 has no folds in the length direction but has folds in the circumferential direction, and when the stent is in the natural state, the covering film 20 has no folds in the circumferential direction but has folds in the length direction; the folding ratio of the covering film 20 is the shortening rate of the grid skeleton 10, and the shortening rate is generally 10% - 50%.

[0056] The forming method of the covering film 20 on the grid skeleton 10 is not limited. For example, the covering film 20 is directly electrospun on the grid skeleton 10, or a sheet-shaped covering film raw material is first prepared and then wound around the grid skeleton 10 to obtain the covering film 20, or a tubular covering film raw material is first prepared and then sleeved on the grid skeleton 10 to obtain the covering film 20.

[0057] The following further describes the fixing method of the film 20 on the grid framework 10. Compared with the prior art, in the embodiment of the present invention, small diaphragms are used to replace the traditional suture stitching and double-layer film, so as to further control the thickness of the film-covered stent and further reduce the influence of the film on the flexibility and appearance of the stent.

[0058] As Figure 2 and Figure 3 shown, in a preferred embodiment, the film-covered stent further includes a plurality of diaphragms 30. All the diaphragms 30 are arranged in the inner cavity of the grid framework 10 without affecting the appearance of the stent. After the film 20 is installed on the grid framework 10, the axial two ends of the film 20 are respectively heat-melted and connected with a plurality of diaphragms 30 to fix the position of the film 20 on the grid framework 10. More specifically, the proximal end of the film 20 is heat-melted and connected with a plurality of diaphragms 30 arranged in sequence in the circumferential direction of the grid framework 10, and the distal end of the film 20 is also heat-melted and connected with another plurality of diaphragms 30 arranged in sequence in the circumferential direction of the grid framework 10. During heat melting, the diaphragm 30 and the film 20 can be directly heat-melted through the grid 102, and the diaphragm 30 is kept flat, so that the edge of the diaphragm 30 is completely fused with the external film 20, and finally the two ends of the film 20 are fixed on the grid framework 10.

[0059] The size of the diaphragm 30 is much smaller than that of the film 20 and will not significantly increase the thickness of the stent. In addition, when the grid framework 10 is a braided stent, each diaphragm 30 preferably only covers the braided wires 101 between two adjacent intersection points 103 and does not cover the intersection points 103. Because the two braided wires 101 forming the intersection point 103 will move, if the diaphragm 30 covers the intersection point 103, it is easily affected by the two braided wires 101, and thus is not firm and easily falls off. If the grid framework 10 is a cut stent, the diaphragm 30 is not limited to only covering the intersection point 103.

[0060] Furthermore, each diaphragm 30 is not fixed (i.e., movable) to the braided wire 101 or the cut stent rod covering the diaphragm 30, which reduces the influence of the diaphragm 30 and the film 20 on the flexibility of the stent and can also avoid problems such as more wrinkles and ruptures of the film 20. When the diaphragm 30 is not fixed to the braided wire 101, it can also avoid affecting the sliding of the braided wire 101.

[0061] Preferably, the braided wire 101 covering the diaphragm 30 presses on another braided wire 101 at the corresponding intersection point 103, so that the other braided wire 101 pressed by the braided wire 101 covering the diaphragm 30 can block the diaphragm 30 during the axial stretching process of the film-covered stent, and thus the diaphragm 30 also only moves on the braided wires 101 between two adjacent intersection points 103 and will not produce a large displacement. It can be understood that if the grid framework 10 is a cut stent, then the intersection point 103 of the cut stent can naturally block the diaphragm 30.

[0062] It should be understood that when the covered stent is axially stretched, the membrane 30 has a tendency to slip towards the midline direction of the grid skeleton 100 (the midline can be understood as the symmetry line perpendicular to the longitudinal axis). At this time, the membrane 30 will be blocked by the braided wire 101 below it and cannot further displace. Thus, it can be ensured that the external covering film 20 does not undergo obvious displacement during the axial stretching of the covered stent, so that the relative position between the covering film 20 and the grid skeleton 10 does not change significantly. On the contrary, if the braided wire 101 covering the membrane 30 is pressed below by another braided wire 101 intersecting with it, during the axial stretching process, when the membrane 30 slips towards the midline direction of the grid skeleton 100, the membrane 30 may slip out between the two intersecting braided wires 101, resulting in a large displacement. Therefore, the braided wire 101 covering the membrane 30 is preferably pressed on another braided wire 101 intersecting with it to prevent the membrane 30 from slipping out between the two braided wires 101.

[0063] For reference Figure 2 , the braided wire 101 covering the membrane 30 is defined as the upper layer wire 101a, that is, when observing from the inside to the outside of the grid skeleton 10, the braided wire 101 covering the membrane 30 is the upper layer wire 101a, and the one pressed under the upper layer wire 101a is the lower layer wire 101b. Furthermore, during the stretching process, the membrane 30 slips towards the midline direction until the membrane 30 is blocked by the lower layer wire 101b. It should be understood that the braided wire 101 covering the membrane 30 is the upper layer wire 101a at the current intersection point 103, but is the lower layer wire 101b at another intersection point 103. Therefore, the upper layer wire 101a of the covering membrane 30 only refers to the intersection point 103 that needs to be able to block the membrane 30.

[0064] Therefore, when the braided wire 101 covering the membrane 30 is the upper layer wire 101a at the corresponding intersection point 103, it can avoid large displacements of the two axial ends of the covering film 20 relative to the grid skeleton 10, can better fix the position of the covering film 20 on the grid skeleton 10, prevent the covering film 20 from aggregating and wrinkling towards the midline direction due to the expansion and contraction of the grid skeleton 10, and further avoid excessive wrinkling of the covering film 20 resulting in thrombosis. In addition, when the covering film 20 does not undergo large displacements, it can ensure that the two end edges of the covering film 20 basically do not deviate from the imaging points on the covered stent section 13, which is convenient for doctors to determine the position of the covering film 20, and then quickly and accurately release the covering film 20 at the aneurysm neck opening, providing convenience for immediately blocking the aneurysm.

[0065] The material of the membrane 30 is a common polymer material, and its material may be the same as or different from that of the covering film 20. When the material of the membrane 30 is the same as that of the covering film 20, the bonding strength during heat melting between the membrane 30 and the covering film 20 is more excellent. While ensuring the heat melting strength, it can improve the effectiveness of fixing the covering film 20. In addition, after adding the membrane 30, there is no need to increase the biological evaluation test, which is convenient to use.

[0066] The thickness of the diaphragm 30 is substantially the same as that of the coating film 20. The diaphragm 30 can have various shapes, including but not limited to the illustrated rectangle, as long as the diaphragm 30 can be thermally fused to the external coating film 20 to ensure the connection strength. Preferably, the diaphragm 30 is rectangular, which is convenient for processing and manufacturing and also for thermal fusion connection. The size of the diaphragm 30 is mainly set according to the size of the grid 102. Generally, the width of the diaphragm 30 does not exceed the length of the braided wire 101 between two adjacent intersection points 103. In this embodiment, the diaphragm 30 is rectangular. Preferably, the length of the diaphragm 30 is 0.2 mm to 5.0 mm, and the width is 0.2 mm to 5.0 mm.

[0067] Most of the grids 102 are diamond-shaped. Each grid 102 is surrounded by four braided wires 101 or cutting support rods. The diaphragm 30 can be covered on any one of the braided wires 101 or cutting support rods of the grid 102. The same diaphragm 30 can cover one or more braided wires 101 or cutting support rods. Preferably, only one braided wire 101 or cutting support rod is covered. The diaphragms 30 do not overlap and are all arranged independently of each other. However, in any case, for the braided coating stent, each braided wire 101 covering the diaphragm 30 is preferably pressed on the corresponding other braided wire 101 at the corresponding intersection point 103.

[0068] The multiple diaphragms 30 connected to any one end of the coating film 20 are all distributed in sequence along the circumferential direction of the grid framework 10 and are spaced apart from each other in the circumferential direction. The multiple diaphragms 30 connected to any one end of the coating film 20 are distributed evenly or unevenly along the circumferential direction of the grid framework 10. Preferably, they are evenly distributed so that the coating film 20 is stressed evenly and is not likely to have more wrinkles. There is no special requirement for the number of diaphragms 30 connected to any one end of the coating film 20. On the premise of meeting the connection strength, the number of diaphragms 30 is minimized to avoid increasing the thickness of the stent. Optionally, 4 diaphragms 30 are connected to any one end of the coating film 20.

[0069] The multiple diaphragms 30 connected to any one end of the coating film 20 are sequentially spaced N grids 102 apart in the circumferential direction of the grid framework 10. N is a natural number that is zero or greater than zero. That is, the diaphragm 30 can be spaced one or more grids 102 apart, or the diaphragm 30 can be provided at each grid 102 (i.e., without spacing).

[0070] Such as Figure 2As shown, in this embodiment, a plurality of diaphragms 30 connected to any one end of the film coating 20 are sequentially arranged at intervals of one grid 102 in the circumferential direction of the grid skeleton 10. All the diaphragms 30 cover the inner side of the braided wire 101 or the cutting support rod and are heat-melted with the external film coating 20 at high temperature. If a diaphragm 30 is arranged at an interval of one grid 102, while ensuring the connection strength of the film coating 20, the thickness of the stent can be in a relatively small state.

[0071] A plurality of diaphragms 30 connected to any one end of the film coating 20 are sequentially distributed in the circumferential direction of the grid skeleton 10. These diaphragms 30 can be aligned or staggered in the axial direction of the grid skeleton 10. Axial alignment means that a plurality of diaphragms 30 are arranged on the same circumference. At this time, a plurality of diaphragms 30 can be arranged at the same position of a plurality of grids 102 in the circumferential direction. Axial staggering means that a plurality of diaphragms 30 are arranged on different circumferences, so that a plurality of diaphragms 30 are arranged at different positions of a plurality of grids 102 in the circumferential direction. Preferably, a plurality of diaphragms 30 connected to the same end of the film coating 20 are axially aligned, which can avoid the risk of the film coating 20 warping due to uneven ends and reduce the thrombus risk.

[0072] As Figure 2 shown, in a preferred embodiment, the diaphragm 30 has an avoidance area 31 and a heat-melting area 32. The heat-melting area 32 is located on the periphery of the avoidance area 31, so that the diaphragm 30 contacts and abuts against the covered braided wire 101 or the cutting support rod through the avoidance area 31, but the avoidance area 31 is not fixed to the braided wire 101 or the cutting support rod. In particular, the area near the braided wire 101 should not be heat-melted to avoid affecting the flexibility and compliance of the grid skeleton 10. After setting the avoidance area 31, the range that does not need to be heat-melted near the braided wire 101 can be more accurately controlled, without affecting the sliding of the braided wire 101, and the influence on the braided stent can be minimized as much as possible. The heat-melting area 32 is used for heat-melting with the film coating 20 to ensure the connection strength. The sizes and shapes of the avoidance area 31 and the heat-melting area 32 can be set according to actual needs and should not be limited to those shown in the drawings. The diaphragm 30 can be arranged centered or off-centered on the braided wire 101 or the cutting support rod.

[0073] In this embodiment, the diaphragm 30 is rectangular, and this kind of diaphragm will not significantly increase the thickness of the stent. Preferably, the length of the avoidance area 31 is 1 / 4 to 1 / 3 of the total length of the diaphragm 30, and the width of the avoidance area 31 is equal to the width of the heat-melting area 32.

[0074] It should also be noted that in addition to heat-melting and connecting the diaphragms 30 at both axial ends of the film coating 20, a plurality of diaphragms 30 can be further heat-melted at a suitable position (such as the middle position) between the proximal end and the distal end of the film coating 20 to better fix the film coating 20.

[0075] The present invention will be further illustrated by the following exemplary embodiments. However, these exemplary embodiments are merely illustrative and are intended to enable those skilled in the art to understand the present invention, rather than to limit the scope of protection of the present invention.

[0076]

Embodiment 1

[0077] In this embodiment, the grid skeleton 10 is a braided stent, and the number of braided filaments is 16. The film covering 20 is made of expanded polytetrafluoroethylene (ePTFE) material. The material of the membrane sheet 30 is the same as that of the film covering 20. Any one end of the film covering 20 is heat-melted with a plurality of axially aligned and circumferentially distributed membrane sheets 30. And, in the circumferential direction of the grid skeleton 10, one membrane sheet 30 is provided at every other grid 102. Each membrane sheet 30 only covers one braided filament 101. The braided filament 101 covered by the membrane sheet 30 is the upper layer filament 101a at the corresponding intersection point 103. Then, local heat melting is performed to completely fuse the edge of the membrane sheet 30 with the external film covering 20 until the boundary of the membrane sheet 30 is no longer visible, which not only ensures the heat-melting strength but also does not affect the appearance. Finally, a covered stent with four membrane sheets 30 connected to each of the proximal and distal ends is obtained.

[0078]

Embodiment 2

[0079] The difference between the covered stent provided in Embodiment 2 and Embodiment 1 is that a plurality of membrane sheets 30 connected to any one end of the film covering 20 are arranged at intervals of multiple grids 102 or without intervals of grids 102 in the circumferential direction of the grid skeleton 10. And, the number of intervals of grids 102 can be the same or different. For example, intervals of 1 grid 102, intervals of 2 grids 102, intervals of 3 grids 103, etc. However, it should be recognized that all the braided filaments 101 covered by the membrane sheet 30 are preferably the upper layer filaments 101a at the corresponding intersection points 103.

[0080]

Embodiment 3

[0081] The difference between the covered stent provided in Embodiment 3 and Embodiment 1 is that the membrane sheet 30 covers multiple braided filaments 101 simultaneously.

[0082]

Embodiment 4

[0083] The difference between the covered stent provided in Embodiment 4 and Embodiment 1 is that multiple membrane sheets 30 are covered on one braided filament 101.

[0084]

Embodiment 5

[0085] The difference between the covered stent provided in Embodiment 5 and Embodiment 1 is that any one end of the film covering 20 is heat-melted with a plurality of axially offset and circumferentially distributed membrane sheets 30. If the multiple membrane sheets 30 connected to the same end of the film covering 20 are axially offset, they can be partially offset or completely offset, and various arrangement forms can exist, such as "zigzag", "wavy", etc. In this regard, the present application is not limited.

[0086]

Example VI

[0087] The difference between the covered stent provided in Example VI and Example I is that the materials of the covering 20 and the membrane sheet 30 are different. For example, the membrane sheet 30 is made of ePTFE material, and the covering 20 is made of other polymer materials such as polyester (PET), polyurethane (TPU), or polylactic acid (PLA).

[0088]

Example VII

[0089] The difference between the covered stent provided in Example VII and Example I is that in addition to arranging the membrane sheets 30 at both axial ends of the covering 20, a plurality of membrane sheets 30 are also thermally connected at the intermediate position between the proximal end and the distal end of the covering 20. Of course, all the membrane sheets 30 are arranged in the inner cavity of the grid framework 10.

[0090]

Example VIII

[0091] The difference from the above Examples I to VII is that, as shown in Figure 4 , the covered stent provided in this example is a cutting stent, and the implementation method of the membrane sheet 30 can refer to the braided stent, which will not be elaborated here.

[0092] In summary, compared with the prior art, the covered stent provided by the present invention has at least the following advantages:

[0093] (1) Ensure the anchoring performance of the covered stent through the proximal flared section and the distal flared section.

[0094] (2) Ensure the wall attachment performance of the covered stent at the proximal end by means of the proximal bare stent section to transition the covered stent section and the proximal flared section, thereby preventing endoleakage.

[0095] (3) On the basis of ensuring the anchoring force and wall attachment property, through the length of the proximal bare stent section of 2 mm to 10 mm, the recoverability and repositioning of the covered stent are realized, and the blockage of the branch blood vessels after the complete release of the covered stent is avoided.

[0096] (4) By setting the length of the covered stent section to 4 mm to 30 mm, the covered stent can be used to isolate most aneurysms and ensure its scope of application.

[0097] (5) Since the covering is single-layer and locally covered, it can reduce the influence of the covering on the grid framework, ensure the flexibility of the covered stent and the effectiveness of the covering, and can also not increase the thickness of the stent, enabling the covered stent to be delivered and enter smaller blood vessels.

[0098] (6) Instead of using sutures for stitching or double-layered membranes, a single membrane is thermally fixed to the mesh skeleton through multiple small membrane pieces, and all the small membrane pieces are only arranged in the inner cavity of the mesh skeleton, thereby realizing the combination of the membrane and the mesh skeleton, which can maximally avoid increasing the thickness of the stent, providing conditions for the covered stent to enter the small delivery system and reach the smaller blood vessels at the farther end, without affecting the appearance of the stent, and can also reduce the influence of the membrane on the stent, ensuring the flexibility of the stent.

[0099] (7) When the mesh skeleton adopts a braided stent, the braided wires can be used to block the small membrane pieces to prevent the large displacement of the small membrane pieces, so that the two ends of the membrane can only move within a relatively small area, and the relative position of the membrane on the braided stent can be better fixed. The method of thermally fusing the external membrane with the small membrane pieces can also adapt to the elongation and shortening rates of more than 100% of the braided stent, without affecting the movement of the braided wires, and will not cause stent deformation due to the membrane. The risk of stent deformation is reduced, the reliability and stability are better, and the performance is more excellent.

[0100] Compared with the traditional membrane covering method, the membrane covering method with small membrane pieces is simpler and easier for mechanized operation, which is convenient for simplifying the manufacturing process of the covered stent and improving the production efficiency.

[0101] The above description is only a description of the preferred embodiments of the present invention, and does not limit the scope of the present invention in any way. Any changes and modifications made by those of ordinary skill in the art of the present invention according to the above disclosure shall fall within the protection scope of the technical solution of the present invention.

Claims

1. A covered stent, characterized in that, it includes a grid skeleton and a covering film. The grid skeleton includes a covered stent section and a proximal bare stent section arranged in sequence along its own axis from the distal end to the proximal end. The covering film covers the entire outer surface of the covered stent section. The length of the covered stent section is 4 mm to 30 mm, and the length of the proximal bare stent section is 2 mm to 10 mm.

2. The covered stent according to claim 1, characterized in that, the grid skeleton further includes a distal bare stent section arranged along its own axis. The distal bare stent section is located at the distal end of the covered stent section, and the length of the distal bare stent section does not exceed 4 mm.

3. The covered stent according to claim 2, characterized in that, the grid skeleton further includes a distal flared section and a proximal flared section arranged along its own axis. The distal flared section is located at the distal end of the distal bare stent section, and the proximal flared section is located at the proximal end of the proximal bare stent section. The diameters of the distal flared section and the proximal flared section are both larger than the diameters of the covered stent section and the proximal bare stent section, and the diameter of the distal bare stent section is smaller than the diameters of the distal flared section and the proximal flared section.

4. The covered stent according to claim 3, characterized in that, the lengths of the distal flared section and the proximal flared section are 1 mm to 4 mm.

5. The covered stent according to claim 3, characterized in that, the diameter of the distal flared section is 1.2 times to 4 times the diameter of the distal bare stent section, and the diameter of the proximal flared section is 1.2 times to 4 times the diameter of the proximal bare stent section.

6. The covered stent according to claim 2, characterized in that, the diameters of the distal bare stent section and the proximal bare stent section are 1.0 to 1.5 times the diameter of the covered stent section.

7. The covered stent according to claim 3, characterized in that, a plurality of radiopaque points are provided on both the distal flared section and the proximal flared section.

8. The covered stent according to claim 1 or 2, characterized in that, the covering film forms wrinkles on the covered stent section.

9. The covered stent according to claim 1 or 2, characterized in that, the grid skeleton is woven by a plurality of braided wires, and the plurality of braided wires intersect with each other to form grids and intersection points; the covered stent further includes a plurality of membrane sheets. All the membrane sheets are arranged in the inner cavity of the grid skeleton. The axial two ends of the covering film are respectively heat-melted and connected to a plurality of the membrane sheets. The plurality of membrane sheets connected to any one end of the covering film are distributed along the circumference of the grid skeleton. Each membrane sheet covers the braided wires between two adjacent intersection points.

10. The covered stent according to claim 9, characterized in that, each membrane sheet is not fixed to the braided wires covering the membrane sheet.

11. The covered stent according to claim 10, characterized in that, The braided wires covering the diaphragm are pressed against another braided wire at the corresponding intersection points, so that the other braided wire pressed by the braided wire covering the diaphragm can block the diaphragm during the axial stretching of the covered stent.

12. The covered stent according to claim 1 or 2, wherein, a plurality of radiopaque points are provided at both the proximal end and the distal end of the covered stent segment.

13. The covered stent according to claim 1 or 2, wherein, the length of the proximal bare stent segment is 2 mm to 5 mm.

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