CN109464212B

CN109464212B - Covered stent

Info

Publication number: CN109464212B
Application number: CN201811533707.3A
Authority: CN
Inventors: 肖本好; 浦文俊
Original assignee: Shenzhen Xianjian Changtong Medical Co ltd
Current assignee: Lifetech Scientific Shenzhen Co Ltd
Priority date: 2018-12-14
Filing date: 2018-12-14
Publication date: 2022-04-05
Anticipated expiration: 2038-12-14
Also published as: CN109464212A

Abstract

The invention relates to a covered stent, which comprises a covered unit and an exposed unit connected with the covered unit, wherein the covered unit comprises a first area, the first area is arranged at one end, close to the exposed unit, of the covered unit, the first area is connected with the exposed unit, and the rigidity of the first area is greater than that of the exposed unit. According to the covered stent, because the rigidity of the exposed unit is smaller than that of the first area, the exposed unit can be bent and deformed to enable the first area to be completely attached to the vessel wall in the releasing process, the risk of displacement of the covered stent in the releasing process is prevented, and the releasing precision is improved; and because the rigidity of the first area is higher, a larger axial supporting force can be provided, and the risk of the tectorial membrane stent displacing after being implanted is reduced.

Description

Covered stent

Technical Field

The invention relates to the field of medical instruments, in particular to a covered stent.

Background

Thoracic aortic aneurysm refers to aneurysm occurring in aortic sinus, ascending aorta, aortic arch or descending aorta, and is an abnormal expansion, deformation, or neoplastic protrusion of the thoracic aorta. The thoracic aorta is irreversibly dilated or expanded locally or at multiple positions due to various reasons to form a "tumor-like" mass, which is called aneurysm.

Thoracic aortic intraluminal repair Therapy (TEVAR) was first proposed by Parodi and used for treatment of thoracic aortic distensive disease, followed by a gradual treatment of Stanford B-type aortic dissection (TBAD). Through recent research and technological improvement, the method has become the first treatment method for various types of TBAD, including acute stage, chronic stage, stable type and unstable type, and basically replaces the traditional open thoracic aorta replacement operation.

The thoracic aorta intraluminal repair treatment technology can only be used for treating descending aortic dissection or aneurysm before, and with the development of interventional technology, the treatment of aortic diseases affecting the aortic arch and the branch arteries thereof is continuously reported by adopting a chimney technology, an in-situ windowing technology and the like. When these new techniques are used to reconstruct an upper branch of the aortic arch, it is often necessary to advance the proximal anchoring region of the stent graft from the descending aorta to the aortic arch.

The problem of accurate anchoring of the covered stent at the aortic arch part is solved, the distance between three branches on the aortic arch is small, and the problem is summarized by students: the average distances between the innominate artery and the left common carotid artery and the left subclavian artery are respectively 4.39 +/-2.49 mm and 6.43 +/-3.98 mm. Most common thoracic aorta covered stents in the market adopt a structure that a naked stent is arranged at the proximal end, so that the anchoring area can be finely adjusted after a part of the anchoring part at the proximal end is released, and the proximal end can be anchored more accurately. However, when the anchoring area is small, the anchoring precision of the existing covered stent is insufficient, if the anchoring position deviates to the far end, the blocking effect of the covered stent is reduced, even type I internal leakage is caused, and if the anchoring position deviates to the near end, partial or complete coverage of the branch blood vessel is easily caused, which affects blood flow.

Disclosure of Invention

The object of the present invention is to solve at least one of the problems of the prior art mentioned above, and the object is achieved by the following technical solutions:

the utility model provides a covered stent, including the tectorial membrane unit and with the exposed unit that the tectorial membrane unit links to each other, the tectorial membrane unit includes first region, first region set up in the tectorial membrane unit is close to the one end of exposed unit, first region with exposed unit connects, the rigidity in first region is greater than the rigidity of exposed unit.

According to the covered stent, because the rigidity of the exposed unit is smaller than that of the first area, the exposed unit can be bent and deformed to enable the first area to be completely attached to the vessel wall in the releasing process, the risk of displacement of the covered stent in the releasing process is prevented, and the releasing precision is improved; and because the rigidity of the first area is higher, a larger axial supporting force can be provided, and the risk of the tectorial membrane stent displacing after being implanted is reduced.

Drawings

FIG. 1 is a schematic structural view of a stent graft according to a first embodiment of the present application;

FIG. 2 is a schematic illustration of the stent graft of FIG. 1 being released from the delivery device;

FIG. 3 is a schematic illustration of a prior art stent graft release process in a conveyor;

FIG. 4 is a schematic structural view of a stent graft according to a second embodiment of the present application;

FIG. 5 is a schematic structural view of a stent graft according to a third embodiment of the present application;

FIG. 6 is a partial schematic structural view of the stent graft shown in FIG. 5.

Detailed Description

In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein, but rather should be construed as broadly as the present invention is capable of modification in various respects, all without departing from the spirit and scope of the present invention.

It will be understood that when an element is referred to as being "secured to" or "disposed on" another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present. The terms "vertical," "horizontal," "left," "right," and the like as used herein are for illustrative purposes only and do not represent the only embodiments.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

In this application, the "proximal end" is the proximal end, i.e., the end close to the heart after implantation, and the "distal end" is the distal end, i.e., the end far from the heart after implantation. "axial" generally refers to the length of the stent graft as it is delivered, and "radial" generally refers to the direction perpendicular to its "axial" direction, and defines both "axial" and "radial" directions for any component of the stent graft in accordance with this principle.

Referring to fig. 1, a stent graft 10 according to a first embodiment of the present application includes a stent graft unit 11 and an exposed unit 12 connected to the stent graft unit 11. The surface of the film covering unit 11 is adhered with a film to form a tubular structure with two open ends and a closed middle part, when the covered stent 10 is implanted into a blood vessel, the film on the film covering unit 11 can isolate lesions such as aneurysm on the blood vessel from blood. The bare cell 12 is not covered with a membrane. The film covering unit 11 comprises a first area 111, the first area 111 is arranged at one end, close to the exposed unit 12, of the film covering unit 11, the first area 11 is connected with the exposed unit 12, and the rigidity of the first area 11 is larger than that of the exposed unit 12.

Please refer to FIG. 2, which is a schematic view of the release process of the stent graft 10 at the designated position of the blood vessel by the transporter. As shown in FIG. 2A, the bare cell 12 is tethered to the anchoring structure of the delivery device through which the stent graft 10 is passed to the desired location in the vessel; the sheath of the withdrawing conveyor starts to release the stent graft, as shown in fig. 2B, the proximal end of the stent graft 10 is partially released, the proximal end of the stent graft 10 is tapered, only a small part of the proximal end is attached to the vessel wall, and at this time, the anchoring force of the stent graft 10 is weak, and the proximal end of the stent graft 10 can be moved to an accurate anchoring position by operating the conveyor; the sheath of the conveyor is further withdrawn, and the stent graft 10 is further released, as shown in fig. 2C, most of the first region 111 of the stent graft 10 is adhered to the wall, so that a larger anchoring force can be provided, and the support can bear a certain axial force without displacement; the proximal ends of the exposed units 12 are moved backwards by operating the conveyor, as shown in D in fig. 2, the rigidity of the exposed units 12 is small, the proximal ends of the exposed units 12 can be moved backwards by a small axial force, at this time, the whole covered stent 10 cannot be displaced due to the large anchoring force of the first region 111, the proximal ends of the covered stent 10 can be attached to the vessel wall, and meanwhile, the axial force of the exposed units 12 for moving backwards can be compensated by the bending of the exposed units 12; in this step, if the position of the proximal end of the stent graft unit 12 after being attached to the wall is inaccurate, the proximal end of the bare cell 11 can be moved forward to withdraw part of the stent graft unit 12, and the anchoring position is adjusted again after the proximal end of the bare cell 11 is moved forward to the state shown in C in fig. 2, after the proximal end of the first region 111 is anchored as shown in D in fig. 2, the proximal end of the stent graft 10 is not affected by the subsequent release operation, and finally the bare cell 12 is released from the conveyor, as shown in E in fig. 2, the proximal end of the stent graft unit 12 does not move, that is, the stent graft 10 can not move any more, which is beneficial to realizing accurate release of the stent graft 10.

In the prior art, in order to improve the anchoring force of the exposed unit, the stiffness of the exposed unit is generally greater than that of the membrane unit, or the stiffness of the exposed unit is also substantially equal to that of the membrane unit, please refer to fig. 3, when the exposed unit is loaded on a conveyor and bound, the proximal end of the membrane unit is suspended, the profile of the proximal end of the membrane unit is a curved surface (the position indicated by an arrow in fig. 3), when the exposed unit is released, the proximal end of the membrane unit is attached to a blood vessel, and the profile of the proximal end of the membrane unit is a straight tube type, so that the proximal ends of the membrane unit are axially different before and after release, if the proximal end of the membrane unit is used for positioning, the stent is completely released, and the anchoring is often inaccurate, for example, the proximal end moves forward to cause partial coverage of an aortic branch, or the proximal end moves backward to cause insufficient anchoring length of the stent; if the operation of moving the bare stent backward after local release enables the near end of the covered stent to be anchored in advance, the rigidity of the bare unit is high, a large axial force is needed to bend the bare unit, the covered stent may move backward integrally at the moment, and the joint of the covered unit and the bare unit may tilt, which may cause the risk of scratching the vascular wall.

According to the covered stent, because the rigidity of the exposed unit 12 is smaller than that of the first area 111, in the releasing process, the exposed unit 12 can enable the first area 111 to be completely attached to the vessel wall through deformation, the risk of displacement of the covered stent 10 in the releasing process is prevented, and the releasing precision is improved; moreover, because the first region 111 is relatively rigid, a relatively large axial support force may be provided to reduce the risk of the stent graft 10 becoming dislodged after implantation.

In one embodiment, the exposed unit 12 has a stiffness A and the first region 111 has a stiffness B, where A/B is 0.02 ≦ A/B ≦ 0.8. if the A/B value is too small, the exposed unit 12 is less stiff and is not fully deployed, resulting in a release failure that is more difficult to disengage from the conveyor. If the value of a/B is too large, the first region 111 has a large rigidity and causes a large stimulation to the blood vessel wall, which may cause a risk of damaging the blood vessel wall. Specifically, in the present embodiment, the ratio of the stiffness a of the exposed unit 12 to the stiffness B of the first region 111 is 0.03-0.5, i.e. a/B is greater than or equal to 0.03 and less than or equal to 0.5. In other embodiments, the value of A/B may also be 0.10, 0.15, 0.20, 0.25, 0.30, 0.35, 0.40, 0.45, 0.50, etc. In the application, the rigidity is the axial counter force of the measured section of the support when compressing a unit distance in the process that one end of the measured section of the support is fixed and the other end of the measured section of the support is compressed towards the fixed end along the axial direction. In one embodiment, the rigidity of the exposed unit 12 is 0.01-0.2N/mm during the compression process. It should be noted that in the present application, a/B refers to the ratio of stiffness in the same process between the exposed unit 12 and the first region 111, for example, the ratio of stiffness in the rebound process between the exposed unit and the first region. The stiffness is the average stiffness of the region.

Referring to fig. 1, the film covering unit 11 further includes a first region 112 connected to an end of the first region 111 away from the exposed unit 12, and the rigidity of the second region 112 is less than that of the first region 111. Specifically, the ratio of the rigidity a of the bare cell 12, the rigidity B of the first region 111, and the rigidity C of the second region 112, a: b: c ═ 0.02 to 0.8: 1: (0.4-0.9), the exposed unit 12 has low rigidity, the first area 111 can be attached to the wall sufficiently through deformation, the first area 111 can provide high anchoring force to ensure that the covered stent 10 does not shift in the backward moving process of the exposed unit 12, and the second area 112 can be anchored normally. Specifically, in this embodiment, a: b: c ═ 0.03 to 0.5: 1: (0.5-0.8). In other embodiments, the value of A/B may also be 0.10, 0.15, 0.20, 0.25, 0.30, 0.35, 0.40, 0.45, 0.50, etc., and the value of B/C may also be 0.50, 0.55, 0.60, 0.65, 0.70, 0.75, 0.80, etc.

With continued reference to fig. 1, the distal end surface of the bare cell 12 coincides with the proximal end surface of the first region 111. The bare cell 12 includes a bare wave ring 121, and the wave troughs/wave crests of the bare wave ring 121 are connected to the proximal end of the first region 111, for example, the bare wave ring 121 is sewn to the proximal end face of the first region 111 at the positions of the wave troughs by a suture. The wave ring 121 is made of a metallic material with good biocompatibility (such as nickel titanium, stainless steel, etc.) to form a Z-wave structure or other wave shape that can be radially compressed to a smaller size. In the illustrated embodiment, the bare cell 12 includes a bare wave coil 121, and the number of peaks of the bare wave coil 121 is 3-8. In one embodiment, the number of peaks of the bare wave ring 121 is 5-8.

Specifically, the length of the bare cell 12 in the axial direction of the stent graft 10 is L1, the diameter of the bare cell 12 is D1, wherein 0.25 is equal to or less than L1/D1 is equal to or less than 0.8, and in the illustrated embodiment, the ratio of the wave height of the bare wave ring 121 to the diameter of the bare wave ring 121 is 0.25-0.8. The value of L1/D1 is too small, the length of the exposed unit 12 is too short, and the exposed unit 12 is difficult to make the first region 111 completely adhere to the wall when the conveyor is withdrawn, so that the release effect of the covered stent 10 is influenced. Too large a value of L1/D1, and too long a length of the bare cell 12, increases the risk of the bare cell 12 penetrating the branch vessel. In one embodiment, 0.3 ≦ L1/D1 ≦ 0.7. In another embodiment, 0.3 ≦ L1/D1 ≦ 0.6. The ratio of L1/D1 can be 0.3, 0.35, 0.4, 0.45, 0.5, or 0.55, etc. It should be noted that, in this embodiment, the curved surface where the outer circumferential surface of the exposed unit 12 is located is a cylindrical shape, the diameters of the exposed units 12 are all equal, and the diameter of the exposed unit 12 is the diameter of the cylindrical shape. In other embodiments, the curved surface of the outer circumferential surface of the exposed unit 12 may have other shapes, such as a truncated cone shape, and the diameter of the exposed unit 12 is the average diameter of the exposed unit 12. The length of the exposed unit 12 in the axial direction of the stent graft 10 is also the exposed unit 12 in the stent graft.

Referring to fig. 1, the first region 111 includes at least one axially disposed proximal wave ring 1111, wherein the proximal wave ring 1111 is formed of a metallic material (e.g., nitinol, stainless steel, etc.) with good biocompatibility to form a Z-wave structure or other wave structure that can be radially compressed to a smaller size. The bare wave ring 121 and the near wave ring 1111 are made of metal wires made of the same material. For example, the bare wave ring 121 and the proximal wave ring 1111 are each braided from a single nickel-titanium wire or are each cut from a nickel-titanium tube. The sectional area S1 of the metal wire adopted by the naked wave ring 121 and the sectional area S2 of the metal wire adopted by the near-end wave ring 1111 are respectively, wherein S1/S2 is more than or equal to 0.05 and less than or equal to 0.8. Preferably, 0.10 is less than or equal to S1/S2 is less than or equal to 0.8. The value of S1/S2 may also be 0.15, 0.20, 0.30, 0.40, 0.50, 0.60, 0.70, etc. By adjusting the cross-sectional area of the exposed unit 12 and the wires of the first area 111, different requirements of the exposed unit 12 and the first area 111 on rigidity are realized. Of course, the difference in rigidity between the exposed unit 12 and the first region 111 may be satisfied by adjusting the metal coverage of the two.

The length of the first region 111 in the axial direction of the stent graft 10 is L2, the diameter of the first region 111 is D2, wherein 0.2 is equal to or less than L2/D2 is equal to or less than 2, if the value of L2/D2 is too small, the first region 111 is difficult to realize local anchoring, the first region 111 is difficult to make the first region 111 adhere to the wall completely by adjusting the proximal end of the exposed unit 12, if the value of L2/D2 is too large, the length of the first region 111 is large, the anchoring region is too large, and the position of the stent graft 10 is difficult to adjust in the releasing process. In one embodiment, 0.5 ≦ L2/D2 ≦ 1.5. The value of L2/D2 may also be 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, or 1.4, etc. In this embodiment, the curved surface of the outer peripheral surface of the first region 111 is a cylindrical shape, the diameters of the first region 111 are equal, and the diameter of the first region 111 is the diameter of the cylindrical shape. Of course, if the curved surface of the outer peripheral surface of the first region 111 is of a structure having unequal diameters, such as a truncated cone, the diameter of the first region 111 is the average diameter of the first region 111.

With continued reference to fig. 1, in order to prevent the first region 111 from shrinking, an axial connecting element 1112 is further disposed between the proximal wave rings 1111, and the axial connecting element 1112 connects two adjacent proximal wave rings 1111. By providing the axial connecting member 1112, the axial strength of the first region 111 can be improved, and the first region 111 can be prevented from being wrinkled and moved backward when the exposed unit 12 moves backward, thereby further improving the release accuracy. The number of the axial connectors 1112 may be two or more, and the two axial connectors 1112 may be uniformly distributed in the circumferential direction of the first region 111.

Referring to FIG. 4, the stent graft 20 provided in the second embodiment of the present application has substantially the same structure as the stent graft 10, but the exposed unit 22 of the stent graft 20 includes a plurality of bare-wave loops 221 formed by twisting or braiding a plurality of wires. After twisting or weaving, the ends of the multi-strand wires can be fixed together by steel sleeves or welding and the like.

Specifically, the multi-strand wire can be formed by directly winding a plurality of metal wires with each other; or dividing a plurality of metal wires into a plurality of parts, wherein the number of the metal wires in each part is not less than 2, mutually winding the metal wires in each part into one strand, and twisting the plurality of strands of metal wires into one strand; or the multi-strand wires can also be formed by mixed weaving of partial metal wires and partial polymer wires. In this embodiment, the bare unit 22 uses a plurality of strands of nickel-titanium wires to form the bare wave ring 221 by weaving or twisting, and the overall outer diameter of the plurality of strands of nickel-titanium wires is 0.2-0.5 mm.

In one embodiment, the exposed unit 22 is made of 2-20 Ni-Ti wires by weaving or twisting. Compared with a single nickel-titanium wire with the same diameter, the smaller the number of the nickel-titanium wires, the lower the structural rigidity after weaving or twisting, and the lower the winding stability, the larger the number of the nickel-titanium wires, the larger the structural rigidity after weaving or twisting, and the better the winding stability, but as the number of the nickel-titanium wires is larger, the diameter of each nickel-titanium wire participating in weaving or twisting is also smaller, so that fatigue fracture is easy, and the structural looseness of weaving or twisting can be caused. In one embodiment, the exposed unit 22 is made of 3-12 Ni-Ti wires by weaving or twisting. In another embodiment, the exposed unit 22 is made of 3-8 Ni-Ti wires by weaving or twisting.

In the illustrated embodiment, the bare cell 22 employs wires that are round in cross-sectional area to improve bending fatigue resistance. For round metal wires made of the same material, the rigidity of the round metal wires is generally proportional to the fourth power of the diameter of the round metal wires, and in order to obtain proper rigidity, the diameter of each nickel-titanium wire is 0.05-0.2 mm. In one embodiment, each Ni-Ti wire has a diameter of 0.07-0.12 mm.

Referring to fig. 5, the stent graft 30 provided in the third embodiment of the present application has substantially the same structure as the stent graft 10, but the difference is that the exposed unit 32 extends to partially cover the first region 311, and the exposed unit 32 is located on the outer surface of the first region 311. The exposed unit 32 can wrap the membrane of the first region 311, so that the phenomenon that the near end of the first region 311 is warped can be well avoided, the possibility that the stent graft 30 scratches the blood vessel wall is reduced, and the risk of damaging the blood vessel wall is reduced.

Referring to fig. 5, the exposed unit 32 includes a bare wave ring 321, the first region 311 includes a first proximal wave ring 3111 disposed closest to the exposed unit 32 and a membrane 3113 covering the first proximal wave ring 3111, the bare wave ring 321 and the first proximal wave ring 3111 both have a wave peak, a wave valley and a wave rod connecting the wave peak and the wave valley, a distance from the wave peak to an end of the film covering unit 31 away from the exposed unit 32 is greater than a distance from the wave valley to an end of the film covering unit 31 away from the exposed unit 32, the wave valley of the bare wave ring 321 intersects at least a portion of the wave valley of the first proximal wave ring 3111, the bare wave ring 321 can be fixed at the wave valley position with the wave valley position of the first proximal wave ring 3111 by stitching or the like, the structure is stable, and the risk of the bare wave ring 321 shifting relative to the film covering bracket 30 can be reduced. In an embodiment, the first proximal wave ring 3111 is located on the inner surface of the diaphragm 3113, and the bare wave ring 321 is located on the outer surface of the diaphragm 3113, so that scraping of the first proximal wave ring 3111 on a blood vessel wall can be reduced, a risk of warping at the proximal end of the first region 311 is reduced, and a risk of losing the blood vessel wall is further reduced. It should be noted that in other embodiments, the first proximal wave ring 3111 may be sandwiched between two membranes 3113, that is, the inner and outer surfaces of the first proximal wave ring 3111 are provided with membranes 3113, such as PTFE membranes, and the first proximal wave ring 3111 is wrapped between the membranes 3113 by lamination.

Referring to fig. 6, the wave rod of the bare wave ring 321 intersects the wave peak of the first proximal wave ring 3111 at the wave peak of the first proximal wave ring 3111, that is, the wave peak of the first proximal wave ring 3111 can be pressed by the wave rod of the bare wave ring 321, when the bare wave ring 321 is bound, the wave rod of the bare wave ring 321 can bend to the center by pressing the wave peak of the first proximal wave ring 3111, so as to better avoid the wave peak of the first proximal wave ring 3111 from warping during local release, and reduce the stimulation to the blood vessel wall during the release process. In one embodiment, all the peaks of the first proximal wave ring 3111 intersect the wave rod of the bare wave ring 321.

With reference to fig. 5, the length of the exposed portion of the exposed unit 32 in the first region 311 in the axial direction of the stent graft 30 is L3, and the diameter of the exposed portion of the exposed unit 32 in the first region 311 is D3, wherein L3/D3 is 0.3 ≤ and 0.8. The L3/D3 value is too small, the length of the part of the exposed unit 32, which is exposed out of the first area 311, is too short, and the exposed unit 32 is difficult to ensure that the first area 311 is completely attached to the wall when the conveyor is retracted, so that the release effect of the stent graft 30 is influenced. Too large a value of L3/D3, and too long an exposed length of the exposed unit 32 in the first region 311, increases the risk of the exposed unit 32 penetrating the branch vessel. In one embodiment, 0.3 ≦ L3/D3 ≦ 0.7. In another embodiment, 0.3 ≦ L3/D3 ≦ 0.6. The ratio of L3/D3 can be 0.3, 0.35, 0.4, 0.45, 0.5, or 0.55, etc. In this embodiment, the curved surface of the outer circumferential surface of the portion of the exposed unit 32 exposed out of the first region 311 is a cylindrical shape, the diameters of the portions of the exposed unit 32 exposed out of the first region 311 are all equal, and the diameter of the portion of the exposed unit 32 exposed out of the first region 311 is the diameter of the cylindrical shape. In other embodiments, the curved surface of the outer circumferential surface of the portion of the exposed unit 32 exposed out of the first region 311 may have other shapes, such as a truncated cone shape, and the diameter of the portion of the exposed unit 32 exposed out of the first region 311 is the average diameter of the portion.

The length of the exposed unit 32 in the axial direction of the covered stent 30 is L1, wherein L3/L1 is more than or equal to 0.1 and less than 1. In one embodiment, 0.3 ≦ L3/L1 < 1. In another embodiment, 0.3 ≦ L3/L1 < 0.7. The value of L3/L1 may also be 0.4, 0.5, 0.6, etc. The wave height (i.e., the length of the adjacent wave crests and wave troughs in the axial direction of the stent graft) of the bare wave ring 321 is 5-20 mm, and in the embodiment, the wave height of the bare wave ring 321 is the length L1 of the bare wave unit 32 in the axial direction of the stent graft 30, i.e., 5mm & ltL 1 & ltL 20 mm. If the wave height is too low, the wave number of the bare wave ring 321 is large, which increases the sheathing difficulty of the covered stent 30, and if the wave height is too high, the wave number of the bare wave ring 321 is small, which affects the wall sticking effect of the bare wave ring 321. In one embodiment, the wave height of the wave-shaped bare ring 321 is 8-12 mm.

The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.

The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.

Claims

1. A covered stent comprises a covering membrane unit and an exposed unit connected with the covering membrane unit, and is characterized in that the covering membrane unit comprises a first area, the first area is arranged at one end, close to the exposed unit, of the covering membrane unit, the first area is connected with the exposed unit, the far end face of the exposed unit is overlapped with the near end face of the first area, the length of the exposed unit in the axial direction of the covered stent is L1, the diameter of the exposed unit is D1, and L1/D1 is not more than 0.25 and not more than 0.8; the distal end face of the exposed unit is flush with the proximal end face of the first area, the length of the first area in the axial direction of the covered stent is L2, the diameter of the first area is D2, and L2/D2 is more than or equal to 0.2 and less than or equal to 2; the rigidity of the first area is larger than that of the exposed unit, the rigidity is the axial counter force of the measured section of the support when the measured section of the support is compressed for a unit distance in the process that one end of the measured section of the support is fixed and the other end of the measured section of the support is compressed towards the fixed end along the axial direction.

2. The stent graft of claim 1, wherein the bare cell is connected to a proximal end of the stent graft unit.

3. The stent graft of claim 1 or 2, wherein the bare cell has a stiffness of A and the first region has a stiffness of B, wherein 0.02 ≦ A/B ≦ 0.8.

4. The stent graft as claimed in claim 1 or 2, wherein the exposed unit and the first region are made of the same metal wire, the cross-sectional area of the metal wire used in the exposed unit is S1, the cross-sectional area of the metal wire used in the first region is S2, and 0.05 ≦ S1/S2 ≦ 0.8.

5. The stent graft of claim 1 or 2, wherein the exposed unit comprises a bare wave formed by twisting or braiding a plurality of filaments.

6. The stent graft of claim 1 or 2, wherein the graft unit further comprises a second region connected to an end of the first region distal to the bare cell, the second region having a stiffness less than a stiffness of the first region.

7. The stent graft of claim 6, wherein the bare cell has a stiffness of A, the first region has a stiffness of B, and the second region has a stiffness of C, wherein A: b: c ═ 0.02 to 0.8: 1: (0.4-0.9).

8. The stent graft of claim 1 or 2, wherein the exposed elements extend to partially cover the first region and the exposed elements are located on an outer surface of the first region.

9. The stent graft of claim 8, wherein the exposed element comprises a bare wave ring, the first region comprises a first proximal wave ring disposed closest to the exposed element, the bare wave ring and the first proximal wave ring each have a peak and a trough, the peak is further from an end of the stent graft distal from the exposed element than the trough is from the end of the stent graft distal from the exposed element, and the trough of the bare wave ring at least partially intersects the trough of the first proximal wave ring.

10. The stent graft of claim 8, wherein the exposed element comprises a bare wave ring, the first region comprises a first proximal wave ring disposed closest to the exposed element, the bare wave ring and the first proximal wave ring each have a peak, a trough, and a beam connecting the peak and the trough, the peak is further from an end of the stent graft distal from the exposed element than the trough is from the end of the stent graft distal from the exposed element, and the beam of the bare wave ring intersects the peak of the first proximal wave ring at the peak of the first proximal wave ring.

11. The stent graft of claim 8, wherein the exposed unit comprises a bare wave ring, the first region comprises a first proximal wave ring disposed closest to the exposed unit and a membrane covering the first proximal wave ring, the first proximal wave ring is disposed on an inner surface of the membrane, and the bare wave ring is disposed on an outer surface of the membrane.