A bare stent that can be compressed and stretched along the axial direction

Abstract

The present application relates to a bare stent that is axially compressible and stretchable. The bare stent is used in the aorta and has at least two layers of braided mesh, characterized in that the bare stent has a non-sparse mesh area and a sparse mesh area, the non-sparse mesh area is formed by overlapping and interweaving at least two first wires and second wires of different diameters, wherein the first wire has a diameter of 20 to 150 μm, and the second wire has a diameter of 150 to 600 μm, the sparse mesh area is only composed of the second wire, and is arranged at a location with branched arteries in the corresponding treatment site after the bare stent is released, wherein, in a naturally released state, except for the sparse mesh area, the bare stent has a metal coverage rate of at least 60%. The bare stent is used to treat aortic aneurysms and / or aortic dissection lesions, especially type A aortic dissection, and can be axially stretched and radially compressed in the released state to obtain a delivery configuration with a suitable size so that surgery can be performed using a conventional delivery catheter delivered through the femoral artery.

Description

Technical Field

[0001] The present invention relates to a bare stent, and in particular to a bare stent used for treating aortic diseases such as aortic aneurysm or aortic dissection. Background Art

[0002] The arterial wall is composed of the intima, media, and adventitia that fit tightly together. When the inner wall of the artery is partially damaged, the media of the arterial wall gradually peels off under the strong impact of arterial blood flow, allowing blood to enter between the media and adventitia of the blood vessel wall, forming two true and false cavities. The most common is aortic dissection. Aortic dissection weakens the arterial wall and is at risk of rupture at any time. Once the dissection ruptures, it will cause the patient's death within a few minutes.

[0003] Aortic dissection is divided into type A and type B according to the site and extension of the intimal tear (ie, Stanford classification). Type A refers to lesions involving the ascending aorta, where the arterial wall dissection starts from the ascending aorta, and can also occur in the aortic arch or the proximal part of the descending aorta but involves the ascending aorta. Type B refers to the site of arterial wall dissection occurring in the descending aorta, not exceeding the proximal end of the opening of the left subclavian artery.

[0004] Aortic aneurysm is an abnormal dilation of the aorta. A rupture of an aortic aneurysm can be fatal.

[0005] Therefore, early diagnosis and timely treatment of aortic dissection and aortic aneurysm are very necessary.

[0006] Currently, there are three common options for the treatment of aortic dissection or aortic aneurysm.

[0007] One option is to use open surgery to replace artificial blood vessels. This option is currently used for type A aortic dissection. Its disadvantages are high intraoperative mortality, residual dissection (i.e. type B dissection) after surgery, and the proportion of patients who need reoperation within 10 years is as high as 9-67%. In addition, the cost of treatment is very high, and relatively few hospitals have mastered this surgical technique. In addition, open surgery is not suitable for all patients, so the proportion of patients who can benefit from this option is very small.

[0008] Another option is EVAR, which is also known as covered stent implantation. This option has the advantages of less trauma, faster recovery, and low mortality, but because the stent placement site often involves the aortic arch and / or abdominal aorta, the three major branch arteries on the convex side of the aortic arch, as well as the main branch arteries such as the left renal artery, right renal artery, celiac trunk, and superior mesenteric artery in the abdominal aorta cannot be blocked during and after the entire operation. The conventional practice is to make a hole on-site at the site of the covered stent corresponding to the important branch artery. On the one hand, this increases the difficulty of the operation and requires experienced surgeons to implement it; on the other hand, if the positioning is inaccurate during placement, or the stent shifts during the release process, blocking important branch blood vessels will cause serious consequences. In addition, if the stent is modified before the operation, the manufacturer may refuse to provide warranty services on this basis.

[0009] The third option is a recently proposed total intraluminal aortic intervention using a dense mesh stent (i.e., TEVAR intervention). Unlike the EVAR intraluminal intervention, this option does not use a mechanical occlusion mechanism for the false lumen, and the dense mesh stent does not significantly impede blood flow. Instead, it achieves the therapeutic purpose by forming an obstruction to blood flow on the inner wall of the diseased blood vessel, changing the hemodynamics in the false lumen, reducing the pressure therein, and promoting intraluminal thrombosis. Compared with the EVAR intraluminal intervention, this option uses a dense mesh stent, which not only has the advantages of less trauma, faster recovery, and lower mortality, but also the dense mesh stent will not significantly block blood flow to the branch arteries, thereby greatly reducing the difficulty of the operation. Therefore, doctors with ordinary experience can implement it.

[0010] However, the therapeutic effect of this type of stent is not ideal, because the rupture of the vascular wall is not completely blocked, and an ideal intraluminal thrombus cannot always be formed. In addition, the current dense mesh stent is still difficult to apply to all types of aortic dissection and aortic aneurysm, especially type A aortic lesions.

[0011] Type A aortic dissection involves the ascending aorta, where the inner diameter of the blood vessel is significantly increased due to the lesion, usually up to 38 to 55 mm. Such a large diameter dense mesh stent cannot be radially compressed to a very small diameter, so a thicker transmission system is often required. This makes it difficult to place the transmission system through the relatively thin femoral artery, especially for Asians with relatively thinner blood vessels, and even makes it impossible to implement. In order to reduce the diameter of the stent in the compressed state, thinner wires can be used to weave the stent, but this results in the radial support force of the stent being insufficient to play a therapeutic role. Summary of the invention

[0012] In view of this, the main purpose of the present invention is to provide a stent, a delivery system containing the stent, and a stent placement method that can solve or improve at least one of the above-mentioned prior art problems. Specifically, the purpose of the present invention is to provide a stent for treating aortic dissection or aortic aneurysm, especially type A aortic lesions, with a diameter suitable for delivery through the femoral artery in the delivery state. The stent may have a large diameter suitable for the aorta, especially the ascending aorta. It is axially stretched and radially compressed in the released state to obtain a delivery configuration with a suitable size so that the operation can be performed using a conventional delivery catheter delivered through the femoral artery. At the same time, after release at the treatment site, appropriate liquid-impermeability and radial support force can be obtained by axial compression, but it does not affect the blood supply to the branch arteries.

[0013] To this end, a first aspect of the present invention provides a bare stent for use in the aorta, the bare stent having at least two layers of woven mesh, characterized in that the bare stent includes a non-sparse mesh area, the non-sparse mesh area is formed by overlapping and interweaving at least two first wires and second wires of different diameters, wherein the first wire has a diameter of 20 to 150 μm, and the second wire has a diameter of 150 to 600 μm; and an optional sparse mesh area, the sparse mesh area is composed only of the second wire, and is arranged at a location with a branch artery in a corresponding treatment site after the bare stent is released, wherein, in a naturally released state, the bare stent has a metal coverage rate of at least 60% except for the sparse mesh area.

[0014] The stent of the present invention is a bare stent having at least two layers of braided mesh formed by overlapping and interweaving at least two wires of different diameters, namely the first wire and the second wire as defined above. This overlapping braiding method makes the stent stretchable and compressible in its axial direction. According to the present invention, a bare stent woven from the first and second wires within the above-mentioned diameter range can obtain a relatively high radial support force when it has a braid density within a specified range in a naturally released state (i.e., without axial compression or extension).

[0015] According to one embodiment, the bare stent has a radial supporting force of no less than 100N in a naturally released state.

[0016] According to a more specific embodiment, the bare stent has a radial support force of 100-600N and a metal coverage rate of 70-90% except for the sparse mesh area.

[0017] The bare stent with this characteristic has a large axial extensibility. Therefore, despite having a much higher braid density and radial support force than a conventional bare stent, it can still be easily radially compressed to a suitable size after axial extension to reduce the density of the braided wire per unit length, so as to be assembled into a suitable delivery system. This also enables the bare stent of the present invention to obtain an acceptable delivery configuration size when the diameter is as high as 38 to 60 mm, so that it can even be suitable for the treatment of type A dissection involving the ascending aorta. Specifically, the bare stent of the present invention can be delivered through the femoral artery using a delivery system with a conventional outer diameter (such as about 5 to about 10 mm, preferably about 5 to about 7 mm), without the need to use a delivery system with a larger outer diameter.

[0018] The stent of this embodiment has a large radial support force and braid density after partial release without compression, which is convenient for immediately supporting and expanding the true lumen of the blood vessel and blocking the breach to a certain extent. Furthermore, by axially compressing the local section of the stent, the radial support force and braid density can be further strengthened to form the necessary radial support force and braid density that meet the above requirements, so as to more effectively block the breach in the inner wall of the blood vessel.

[0019] Therefore, when the bare stent is placed in the aorta, it has different degrees of compression along its length.

[0020] The bare stent of the present invention has a relatively high braid density in the naturally released state, which may cause a certain obstruction to the blood flow from the aorta to the branch arteries. To this end, the bare stent has a sparse mesh area over the entire area with branch arteries in the corresponding treatment site. The sparse mesh area is composed only of the second wire, thereby greatly reducing the braid density, so that the blood flow in the area with the sparse mesh area is not obstructed. Unlike the covered stent that opens a window for each branch artery, the bare stent of the present invention has a sparse mesh area on the greater curvature side such as the aortic arch, and the openings of the three branch arteries on the greater curvature side on the aorta are all within the range of the sparse mesh area, thereby reducing the difficulty of the operation. In this way, the bare stent of the present invention can, on the one hand, effectively block the tear of the vascular endothelium like a covered stent, but does not require an experienced doctor to open a window and modify it on site like a conventional covered stent, and does not cause any risk of branch blood vessels being blocked.

[0021] According to the present invention, when the bare stent is placed in the aorta, it has different compression degrees along its length. Except for the sparse mesh area, the first wire and the second wire are woven into the bare stent in a uniformly distributed manner.

[0022] According to one embodiment, the bare stent has a metal coverage of 90-100%, preferably 90-95%, when in a released and axially maximally compressed state.

[0023] According to one embodiment, the stent has a radial supporting force of not less than 500N, preferably 500-1000N, when it is released and in a state of maximum axial compression.

[0024] Within the above-defined range of braid density and radial support force under the maximum axial compression state, the stent of the present invention can effectively support the narrowed vascular lumen even with a maximum diameter suitable for the ascending aorta (such as 38-60 mm). In particular, the radial support force within the preferred range is particularly beneficial for the affected area that has been formed for a certain period of time, in which the torn vascular endothelial sheet becomes hard and requires a greater force to open.

[0025] Therefore, in practical applications, when the stent of the present invention is released in a blood vessel (especially the aorta), the radial supporting force at different parts thereof may vary within the range of 100-1000N according to the compression ratio.

[0026] The aorta to which the bare stent of the present invention is applicable particularly refers to the area from the ascending aorta to the abdominal aorta, including at least the ascending aorta. According to one embodiment, the treatment site includes the aortic arch. The sparse mesh area of ​​the bare stent of the present invention includes a first sparse mesh area corresponding to the aortic arch, and the central angle corresponding to the first sparse mesh area is about 120° to about 180°.

[0027] The first sparse mesh area specifically corresponds to the greater curvature of the aortic arch, especially to the branch arteries on the aortic arch: the brachiocephalic trunk, the left common carotid artery and the left subclavian artery. Specifically, the length of the first sparse mesh area is greater than the length of the branch artery area on the aortic arch, for example, 6 to 8 cm.

[0028] According to another embodiment, the treatment site further includes the abdominal aorta. The sparse mesh area of ​​the bare stent of the present invention further includes a second sparse mesh area corresponding to the branch artery site in the abdominal aorta, wherein the branch artery in the abdominal aorta is the left renal artery, the right renal artery, the celiac trunk and the superior mesenteric artery on the abdominal aorta, and the central angle corresponding to the second sparse mesh area is about 180°. Specifically, the length of the second sparse mesh area is greater than the length of the above-mentioned branch artery distribution area on the abdominal aorta, for example, 2 to 4 cm.

[0029] According to another embodiment, the bare stent is used for the area from the ascending aorta to the abdominal aorta, including at least the abdominal aorta. The treatment site relates to a site on the abdominal aorta with branched blood vessels. The dredging area of ​​the bare stent includes a second dredging area corresponding to the site of the branched arteries in the abdominal aorta, wherein the branched arteries in the abdominal aorta are the left renal artery, the right renal artery, the celiac trunk and the superior mesenteric artery on the abdominal aorta, and the central angle corresponding to the second dredging area is 180°. Similarly, the length of the second dredging area is greater than the length of the above-mentioned branched artery distribution area on the abdominal aorta, for example, 2 to 4 cm.

[0030] According to another embodiment, the bare stent of the present invention is used in the area without branch vessels in the descending aorta. The bare stent used in this area may only include a non-sparse mesh area.

[0031] In the case where the treatment site of the bare stent of the present invention involves the abdominal aorta, the bare stent is provided with two common iliac artery stent fixing parts for fixing the left and right common iliac artery stents in the internal space. The common iliac artery stent fixing parts are arranged inside the bare stent at the bifurcation of the left and right common iliac arteries corresponding to the abdominal aorta, and the two common iliac artery stent fixing parts are arranged in a tangent ring shape and are formed integrally with the inner wall of the bare stent.

[0032] Different from the fixing parts that form two cylindrical branches at the lower part of the abdominal aorta stent, the two fixing parts of the bare stent of the present invention are arranged inside the bare stent, so that the outer part of the bare stent still maintains a cylindrical shape, which is more conducive to opening the blood vessel without deteriorating the support near the common iliac artery. Moreover, the common iliac artery fixing part is formed integrally with the stent, which can more stably fix the left and right iliac artery stents.

[0033] In different embodiments, the support may have the first open mesh area, or may have the first and second open mesh areas, or may have only the second open mesh area.

[0034] Due to the overlap weaving, any mesh of the open mesh area is expandable, thereby allowing the branch stent to be placed through the expanded mesh.

[0035] The bare stent of this embodiment can be woven according to the braiding density requirements of the parts of the stent except the sparse mesh area. After the weaving is completed, the first wire is removed in the area where the sparse mesh area is predetermined to be formed, thereby forming the sparse mesh area.

[0036] According to the present invention, the bare stent may have a varying diameter, and the diameter is in the range of 20 to 60 mm, preferably 20 to 55 mm.

[0037] According to another embodiment, a portion of the bare stent has a diameter in the range of 38 to 60 mm, preferably 38 to 55 mm. The bare stent in this embodiment may have a first section located at the proximal end of the bare stent in the released state. The first section may have a diameter of 38 to 60 cm, preferably 38 to 55 mm, to be suitable for the ascending aorta. The length of the first section is 8-11 cm, preferably 8-10 cm. The bare stent may further have a second section adjacent to the first section. The second section may have a diameter of, for example, 20 to 35 mm to be suitable for the aortic arch, or even extend to a portion of the abdominal aorta. The second section extends to the distal end of the bare stent following the first section. The length of the second section may be 20-35 cm, preferably 25-30 cm. The above two sections may also be formed into two stents respectively, and the second section stent portion extends to the interior of the first section stent when placed. The second method is more flexible. If necessary, three independent stents may also be formed to facilitate operation.

[0038] The bare stent of the present invention is particularly advantageous for type A aortic dissection involving the ascending aorta. As is known, the inner diameter of the ascending aorta is large, but the straight portion is relatively short, and the distal end is the aortic arch that turns nearly 180 degrees. This makes it more difficult to release the stent in the ascending aorta. The bare stent of the present invention has a certain braid density and radial support force in the naturally released state, so only a small axial compression is required to obtain the expected effective occlusion of the aortic intima tear site. It can be seen in the stent release method detailed below in conjunction with the specific implementation method that the expected effect can be obtained after releasing a shorter section of the stent in the ascending aorta and performing a lower proportion of compression. Therefore, the bare stent of the present invention is particularly beneficial for the treatment of the ascending aorta with a relatively short straight portion.

[0039] According to other embodiments, the bare stent may have only a portion corresponding to the descending aorta to the auxiliary aorta, and thus has a diameter of, for example, 20 to 35 mm and a length of 20 to 30 cm.

[0040] According to one embodiment, the bare stent is woven from wires having three different diameters, wherein the second wire may include a first thick wire and a second thick wire having different diameters. According to a specific embodiment, the first thick wire may have a diameter of 150 to 300 μm, and the second thick wire may have a diameter of 300 to 600 μm.

[0041] According to another embodiment, the bare stent is woven from wires having three different diameters, wherein the first wire may include a first filament and a second filament having different diameters. According to a specific embodiment, the first filament may have a diameter of 50 to 100 μm, and the second filament may have a diameter of 100 to 150 μm.

[0042] According to another embodiment, the bare stent may be woven from the first and second thin filaments and the first and second thick filaments, four types of filaments having different diameters.

[0043] The number of wires used to braid the bare stent may be 96 to 202, preferably 96 to 156. The number of second wires may be 4 or more, such as 4 to 30, 4 to 24, and the rest are first wires.

[0044] According to one embodiment, when thick wires of two different diameters are used, the second wires include 6 to 12 first thick wires and 4 to 12 second thick wires, and the rest are first wires.

[0045] Too many thick wires (i.e., second wires) will result in the stent being unable to be effectively compressed into an ideal delivery state, while too few thick wires will result in the stent being unable to provide the expected radial support force even after compression, and unable to maintain the expected structure and shape of the stent in the released state.

[0046] According to another embodiment, when two filaments of different diameters are used (first filaments), the number of second filaments is 4 to 30, preferably 4 to 24, and the rest are first filaments, wherein the first filaments include 32 to 166 of the first filaments and 32 to 166 of the second filaments, provided that the total number of the first filaments and the second filaments does not exceed 198.

[0047] In order to obtain the braid density and radial support force of the bare stent of the present invention while taking into account the radial compression rate, this can be achieved by increasing the number of braided mesh layers.

[0048] According to one embodiment, the bare stent is composed of at least two layers of braided mesh. According to one embodiment, the stent has 2 to 4 layers of braided mesh, preferably 4 layers of braided mesh.

[0049] There is no particular limitation on the braiding method of the stent of the present invention. Conventional overlapping braiding (ie, no binding at the intersection of the wires) can be used as long as the stent can be easily compressed and stretched in the axial direction.

[0050] It should be understood that according to the radial support force range and braid density range required for a specific treatment type, those skilled in the art can select appropriate braiding materials under specific equipment conditions, determine a reasonable number of layers, further select appropriate wire diameters, numbers, etc., and determine an appropriate braiding scheme based on the description herein to obtain a stent with the required radial support force range and metal coverage range. For example, a suitable braiding scheme can be designed using dedicated software.

[0051] According to a further embodiment, the end of the bare stent of the present invention (especially the proximal end, where the radial support force of the stent is the largest) can be formed by a back-weaving method. For the other end, if there is a burr that cannot be back-weaved again, the burr can be located on the inner side of the bare stent by selecting a suitable arrangement of each layer; or if there are two layers of burrs, one layer of burrs can be back-weaved a short distance and the other burr can be wrapped in the back-weaving section, or when multiple stents are used in combination, a single layer or two layers of burrs can be overlapped and placed in another dense mesh stent. The bare stent of this embodiment has a smooth end, thereby avoiding mechanical damage to the inner wall of the blood vessel by the exposed wire end (burr).

[0052] The bare stent of the present invention is self-expandable or capsule-expandable. The materials of the first wire and the second wire of the bare stent can be different, but preferably the same. Usually the material of the wire can be metal, such as shape memory alloy (such as Nitinol), cobalt-chromium alloy, tungsten or tantalum. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 A single-layer schematic diagram of a bare stent according to an embodiment of the present invention;

[0054] Figure 2 for Figure 1 The schematic diagram of the axial compression and stretching of a local section of a bare stent, and the radial compression after the axial stretching;

[0055] Figure 3 A schematic diagram of a bare stent according to another embodiment of the present invention;

[0056] Figure 4 A schematic diagram of a bare stent according to another embodiment of the present invention;

[0057] Figure 5 A partially enlarged schematic diagram of a bare stent according to an embodiment of the present invention;

[0058] Figure 6 It is a schematic cross-sectional view of a multi-layer stent wall of a bare stent according to the present invention;

[0059] Figure 7 is a schematic diagram of a stent delivery system for a bare stent of the present invention;

[0060] Figure 8 A schematic diagram of placing a bare stent of the present invention in type A aortic dissection using a stent delivery system; and

[0061] Fig. 9 It is a schematic diagram of placing the bare stent of the present invention at the aortic intimal rupture using a stent delivery system. DETAILED DESCRIPTION

[0062] The technical solutions in the embodiments of the present invention will be described clearly and completely below in combination with the embodiments of the present invention and the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. In the absence of conflict, the technical solutions recorded in the embodiments of the present invention can be implemented in any combination. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0063] Throughout the specification, unless otherwise specifically stated, the terms used herein should be understood as meanings commonly used in the art. Therefore, unless otherwise defined, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art to which the present invention belongs. In the event of a conflict, the present specification takes precedence.

[0064] The same reference numerals in the drawings refer to the same components. The shapes and sizes of the components in the schematic drawings are for illustration only and should not be considered to reflect the actual shapes, sizes and absolute positions.

[0065] It should be noted that, in the present invention, the terms "comprises", "includes" or any other variations thereof are intended to cover non-exclusive inclusion, so that a method or apparatus including a series of elements includes not only the elements explicitly stated, but also includes other elements not explicitly listed, or also includes elements inherent to the implementation of the method or apparatus.

[0066] It should be noted that the terms "first\second" involved in the embodiments of the present invention are only used to distinguish similar objects, and do not represent a specific order for the objects. It is understandable that "first\second" can be interchanged with a specific order or sequence where permitted. It should be understood that the objects distinguished by "first\second" can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein.

[0067] In order to describe the present invention more clearly, the terms "proximal end" and "distal end" are commonly used in the field of interventional medicine, wherein the "distal end" refers to the end away from the heart during the surgical operation, and the "proximal end" refers to the end close to the heart during the surgical operation.

[0068] Herein, the terms "bare stent" and "stent" are used interchangeably and have the same meaning, unless otherwise specified, referring to a bare stent. The present invention provides a bare stent for use in an aorta, the bare stent having at least two layers of braided mesh, and formed by overlapping and interweaving at least two first and second wires of different diameters, wherein the first wire has a diameter of 20 to 150 μm, and the second wire has a diameter of 150 to 600 μm, wherein the bare stent has a metal coverage of at least 60% in a naturally released state except for the sparse mesh area, and the bare stent may further have at least one sparse mesh area, which is composed only of the second wire and is arranged at a location with a branch artery in a corresponding treatment site after the bare stent is released.

[0069] Figure 1 FIG. 1 shows a single-layer schematic diagram of a bare stent 10 of the present invention according to one embodiment. Figure 1 As shown, the bare stent 10 has a section 18 suitable for the ascending aorta and a section 19 suitable for the aortic arch, wherein the section 18 suitable for the ascending aorta has a diameter of about 38 mm to about 60 mm, and the diameter of the section 19 suitable for the aortic arch is reduced to about 25 mm to about 35 mm. The bare stent 10 can have multiple layers, such as 4 layers, to obtain the desired braid density. To clearly illustrate the specific structure of the bare stent, Figure 1 Only the single-layer situation is shown in the figure. Each layer of the bare stent 10 is interwoven by the first wire (thin wire) 13 and the second wire (thick wire) 14. There is a sparse mesh area 16 in the section 19 suitable for the aortic arch. The sparse mesh area 16 only has the second wire (i.e., thick wire) 14. The sparse mesh area 16 is arranged at the position corresponding to the greater curvature of the aortic arch after the stent is released, and has an area larger than the opening of the branch blood vessels on the greater curvature side in the artery. Typically, the sparse mesh area 16 may have a length of about 6-8 cm, and a width of about 1 / 3-1 / 2 of the arc length of the circumference of the section 19 of the stent 10, or the corresponding central angle is about 120° to about 180°.

[0070] Since the bare stent is braided from wires having at least two different diameters, the stent body is configured to be at least partially compressible and extendable along the axial direction of the stent in a released state.

[0071] The bare stent 10 of the present invention is woven by overlapping, and the intersections between the filaments can produce any relative movement, so any mesh on the stent 10 of the present invention can be easily expanded or compressed. The bare stent formed in this way can be axially compressed or stretched along its central axis when one end is fixed.

[0072] See also Figure 2 , which schematically shows Figure 1The local segment 18 of the bare stent 10 shown is axially compressed 18', axially stretched 18", and the axially stretched segment 18" is further radially compressed 18'".

[0073] The "axial direction" of the stent mentioned in this article refers to Figure 1 The direction along AA shown is the direction of the central axis of the cylindrical shape of the stent. The "radial direction" of the stent mentioned in this article refers to the direction along the AA direction. Figure 1 The direction shown is along DD, which is the diameter direction of the circle of the cylindrical shape of the stent. Generally, "compression / stretching along the axial direction" herein refers to compression / stretching along the AA axis; "compression along the radial direction" refers to compression from the circumference to the center of the circle.

[0074] like Figure 2 As shown, the above characteristics of the bare stent of the present invention can bring a variety of benefits. According to the stent placement method detailed below, the bare stent of the present invention can be partially released (for example, releasing the segment 18 at the ascending aorta) and axially compressed during the placement process, and the compressed stent segment 18' forms a high braid density, and the density of the second wire per unit length is increased to obtain a high radial support force. The high radial support force can achieve effective expansion of the narrowed part of the blood vessel, and the high braid density can achieve very low fluid permeability, thereby effectively blocking the damaged part of the vascular endothelium. At this time, the second wire 4 in the segment 18' at the ascending aorta plays the role of supporting the skeleton, and the first wire fills the gap between the second wires, playing a role similar to the fabric membrane of the coated stent. Unlike the coated stent, the bare stent of the present invention can provide a relatively high radial support force after axial compression, which is difficult to achieve with the coated stent, and can even be effectively used for the treatment of type A aortic dissection involving the ascending aorta. In addition, since the stent can be stretched axially, the stent after appropriate stretching (see Figure 2 The density of the braided wires, especially the second wire, per unit length is significantly reduced, so that the braided wires are radially compressed (see Figure 2 The segment 18"') shown is easily compressed to a smaller diameter so as to be assembled into a delivery system with a conventional outer diameter (such as 5-10 cm, preferably 5-7 cm). Therefore, the bare stent of the present invention solves the problem in the prior art that large-sized, high-support stents cannot be assembled into a delivery system with a suitable diameter, and the problem that conventional dense mesh stents or covered stents are difficult to apply to the ascending aorta.

[0075] The bare stent of the present invention can have a radial supporting force of not less than 100N in a naturally released state; and can have a radial supporting force of not less than 500N in a state of maximum axial compression.

[0076] The "natural release state" of the stent mentioned herein refers to the state in which the stent is not axially compressed and released when fixed in a 37±2°C water bath.

[0077] The "maximum axial compression state" of the stent mentioned herein refers to a state in which the stent is axially compressed to the point where it cannot be further compressed when in a naturally released state.

[0078] The "radial support force" of the stent mentioned in this article refers to the force required to compress the stent to 85% of its original diameter along the diameter direction after the stent is fixed in the natural release state.

[0079] In contrast to the radial support force, the stent of the present invention also needs a high degree of liquid impermeability in order to effectively block the rupture of the vascular intima. This property can be represented by the density of the braid. The stent 1 of the present invention can have a metal coverage of more than 60%, up to 90%, in the natural release state; and can have a metal coverage of 90-100%, preferably 90-95%, in the axial maximum compression state.

[0080] The "metal coverage" of the stent mentioned in this article refers to the metal coverage ratio per unit area measured by electron microscope scanning. The sum of the metal coverage and void ratio per unit area should be 100%.

[0081] Figure 1 Although only a single layer is shown, the stent of the present invention has a multi-layer structure, for example, 2 to 4 layers. For example, the multi-layer structure can be formed by back-braiding.

[0082] According to the present invention, the stent 1 can be woven with a total of 96 to 202 wires. For example, the stent of the present invention can be woven with 96, 128, 160, or 196 wires. The number of wires can be determined according to the diameter of the stent, the number of layers, and the material of the wires used.

[0083] The material used for the stent of the present invention can be any suitable material used for peripheral vascular stents, as long as the material can provide sufficient radial support and has a certain fineness. Usually, metal wires are preferably used, such as nickel-titanium alloy wires, cobalt-chromium alloy wires, tungsten wires, tantalum wires, etc., and nickel-titanium alloy wires are more preferably used.

[0084] The second wire 4 as a thick wire is at least 4, usually not more than 30, for example, 8, 10, 12, 14, 16, 20, 24, 28. The diameter of the second wire 4 is between 150 and 800 μm, preferably between 150 and 600 μm, for example, 150 μm, 200 μm, 250 μm, 300 μm, 350 μm, 400 μm, 450 μm, 500 μm, 550 μm or 600 μm. The second wire 4 provides basic support and complete structure for the stent 1. However, the number of second wires cannot be too much. For example, even if only 300 μm diameter wires are used, when it reaches about 32, especially for the ultra-large diameter stent part greater than about 40 mm, it is difficult to compress it to a suitable delivery size, resulting in it being unusable.

[0085] In the stent 1, except for the thick wire, the rest are the first wire 3 as thin wires. The first wire 3 used in the present invention can have a diameter of 20 to 150 μm, preferably 50 to 150 μm, for example: 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, 110 μm, 1120 μm, 130 μm, 140 μm and 150 μm. The first wire 3 plays the role of auxiliary support for the stent 1 and fills the gap of the second wire 4. And the first wire 3, because the number is much larger than the second wire 4, also plays the role of maintaining the shape of the stent 1. The inventors found that although it seems feasible in theory, in fact, using the overlapping interlacing method of the present invention, it is impossible to form a large-diameter stent with a certain shape and sufficient supporting force by the second wire (i.e., thick wire) alone. And the large-diameter stent fixed by the intersection of the wire and the wire formed by laser engraving technology, for example, has much smaller supporting force even if the diameter of the wire is the same, and cannot meet the requirements of the present invention for aortic blood vessels.

[0086] According to another example, the bare stent of the present invention can be applied to the entire arterial region from the ascending aorta to the abdominal aorta.

[0087] See also Figure 3 , which schematically shows a single-layer schematic diagram of a bare stent 20 having two sparse mesh areas according to another embodiment of the present invention. Figure 3 Although only a single-layer structure is shown in the figure, the bare stent 20 of this embodiment may have 2 to 4 braided layers woven in the same manner.

[0088] like Figure 3As shown, the bare stent 20 includes a section 28 corresponding to the ascending aorta, a section 29 corresponding to the aortic arch, and a section 25 corresponding to the descending aorta to the abdominal aorta. The section 28 corresponding to the ascending aorta may have a diameter of 38 to 60 mm, for example, 38 to 55 mm, and a length of 8 to 11 cm. The section 29 corresponding to the aortic arch may have a diameter of 20 to 45 mm, for example, a diameter that gradually decreases within the range of about 20 to 35 mm. The section 25 corresponding to the descending aorta to the abdominal aorta may extend from the area behind the aortic arch to the area of ​​the abdominal aorta, and the diameter may vary from about 25 mm to about 30 mm to about 20 mm to about 25 mm. The section 29 corresponding to the aortic arch may have a length of 8-11 cm, and the section 25 corresponding to the descending aorta to the abdominal aorta may have a length of, for example, 20 to 35 cm.

[0089] The bare stent 20 in this embodiment is also formed by interweaving the first wire 23 and the second wire 24 .

[0090] According to a modified embodiment, the three sections can be made into three independent stents respectively, so that they can be used in combination flexibly. When used, the proximal end of the stent farther from the heart is inserted into the distal end of the stent closer to the heart, so that the relative positions of the stents are fixed.

[0091] The bare stent 20 may include two dredge regions consisting only of the second wire 24, namely, a first dredge region 26 corresponding to the branch arteries at the aortic arch (brachiocephalic trunk, left common carotid artery and left subclavian artery), and a second dredge region 27 corresponding to the branch arteries at the abdominal aorta (mainly the left renal artery, right renal artery, celiac trunk and superior mesenteric artery). The first dredge region may have the following features: Figure 1 Dimensions of the illustrated embodiment. The second open mesh region may have a length of about 2-4 cm and a width occupying about 1 / 2 of the arc length of the circumference of the region.

[0092] Figure 1 and Figure 3 The bare stents shown can be woven in a conventional manner, and then open mesh areas 16, 26, 27 are formed by removing the first wires 13, 23 in predetermined areas.

[0093] According to a further embodiment, the bare stent of the present invention may have two common iliac artery stent fixing parts for receiving and fixing the left and right common iliac artery stents in the portion corresponding to the treatment site of the abdominal aorta. Figure 4 , in which a bare stent of this embodiment is schematically shown. Figure 4 The stent 20' shown is suitable for the abdominal aorta segment and has a sparse mesh area 27'. The interior of the lower part of the stent 20' has a common iliac artery stent fixing portion 22' arranged as two adjacent circular channels. For clarity, Figure 4The fixing portion 22' is shown as a plane in the figure, but in fact the fixing portion 22' has a certain thickness. In some examples, the fixing portion 22' of the common iliac artery stent may extend downward to the lower end of the stent 20'.

[0094] The common iliac artery stent fixing portion 22' is also woven from the same first and second wires as the stent 20' (the first and second wires are not shown), and is formed integrally with the bare stent. The two annular outer portions are woven integrally with the inner wall of the stent 20'. The sizes of the two annular inner diameters are adapted to the outer diameters of the left and right common iliac artery stents to be received and fixed, and are usually slightly smaller than the outer diameters of the left and right common iliac artery stents, so as to be able to fix the common iliac artery stent.

[0095] According to one embodiment, the stent of the present invention can also be woven from three wires with different diameters. Figure 5 As shown, a partially enlarged schematic diagram of a single layer of the stent of this embodiment is shown. The stent is woven from a first wire 33 and two second wires 34a, 34b. The first wire 33 is a thin wire, which may have a diameter of 50 to 150 μm; the second wire includes a first thick wire 34a, which may have a diameter of 150 to 300 μm, and a second thick wire 34b, which may have a diameter of 300 to 600 μm. Among them, 6 to 12 first thick wires can be used, and more than 4 second thick wires can be used, but no more than 12, and the rest are first wires. This embodiment may also have other variations, such as a stent composed of two first wires (for example, with diameters in the range of 20 to 100 μm and 100 to 150 μm, respectively) and a second wire, or two first wires and two second wires, but is not limited thereto.

[0096] The radial supporting force of a stent formed by three or more wires of different diameters is more uniform throughout the stent, and the flexibility of the stent may also be enhanced.

[0097] As described above, the bare stent of the present invention has multiple layers, and the three-dimensional bare stent has two layers, three layers or four layers. According to a preferred embodiment, the multi-layer bare stent can be formed by back-weaving a single-layer braided mesh. Figure 6 As shown in A to C, a cross-sectional schematic diagram of 2 to 4 layers of the support wall is shown. Figure 6 Figure A is a double-layer structure, in which the upper layer 42 is located on the inner side of the stent, and the lower layer 44 is located on the outer side of the stent (i.e., the side in contact with the blood vessel wall). In this structure, the proximal end 41 is braided back to form a smooth port. At the distal end 43, the lower layer 44 facing the outside of the stent is braided back for a distance, and the open edge (burr) of the distal end of the upper layer 42 facing the inside of the stent is wrapped inside the lower layer 44. Thus, a port with smooth ends is formed. Similarly, Figure 6The upper layer 52 in B is woven back at the proximal end 51 to form the lower layer 54, and further woven back at the distal end 53 to form the middle layer 56. The lower layer 54 and the middle layer 56 at the distal end 53 are slightly longer than the upper layer 52, so that the open edge of the distal end of the upper layer is located inside the bare stent. In this way, both ends of the bare stent are smooth ports. Figure 6 The same is true for the four layers in C. The two layers 62 and 68 on the inner side of the bare stent are shorter than the edges formed by the two layers 64 and 66 on the outer side of the bare stent at the distal end 63, while the proximal end 61 forms the bottom layer 64 by weaving the top layer 62 back to wrap the two middle layers 68 and 66 in the middle. A modified method can be to weave a small section back at the distal end of the top layer 62 or the middle layer 68 to wrap the open edge of another layer in the middle. In this way, both ends of the bare stent are completely smooth ports.

[0098] The above is a detailed description of the stent of the present invention by way of examples. Those skilled in the art should understand that the above examples are used to illustrate the advantages of the stent of the present invention rather than to limit the scope of the present invention, and the features in the examples can be applied to the stents of other examples individually or in combination under appropriate circumstances. Obvious deformations and modifications made to the stent by those skilled in the art based on the disclosure herein are also within the scope of the present invention as long as they conform to the concept of the present invention.

[0099] The following is an exemplary description of a stent delivery system for placing a bare stent of the present invention and a method for placing the bare stent.

[0100] Although the bare stent of the present invention has a diameter as high as 38 to 60 mm and a braid density of 60 to 90%, it can still be compressed to a delivery configuration of a suitable diameter as described above so as to be assembled in a delivery system with a conventional outer diameter. In the delivery system, the stent of the present invention as described above is assembled in the system in a delivery configuration, and both ends of the stent are removably restrained, and the restraint is removed only when the other parts of the stent are completely released, thereby completely releasing the stent.

[0101] refer to Figure 7 , which shows a schematic diagram of a stent delivery system 100 according to the present invention in a semi-released state. The stent delivery system 100 includes a delivery catheter 120 and a stent 150.

[0102] The delivery catheter 120 includes an outer catheter 130, an inner catheter 140 and a push rod 170 which are coaxially arranged from outside to inside along the longitudinal axis XX. The delivery catheter 120 has a distal end 123 and a proximal end 122. The delivery catheter 120 also has a hemostatic valve 125. The outer catheter 130 has a proximal end 180 and a distal end 190, and a first hollow cavity 133 runs through the entire outer catheter 130. The inner catheter 140 is coaxially arranged with the outer catheter 130 along the longitudinal axis XX in the first hollow cavity 133 of its distal end 190, and has a second hollow cavity 143. The push rod 170 extends from the proximal end 123 in the first hollow cavity of the outer catheter 130 and passes through the second hollow cavity 143 of the inner catheter 140 to the outside of the distal end port 135. The push rod 170 may have a third hollow cavity (not shown) for a guide wire to pass through.

[0103] In the proximal end 180 of the outer catheter 130, the stent 150 is releasably held in the first hollow cavity 133 between the push rod 170 and the outer catheter 130 in a delivery configuration. The first restraint 161 restrains the proximal end 154 of the stent 150 at the proximal end of the push rod 170. The first restraint 161 can be a conventional stopper, which can be removed from the stent 150 when necessary, so that the proximal end 154 of the stent 150 is released. The second restraint 162 restrains the distal end 156 of the stent 150 at the proximal end of the inner catheter 140. Similarly, the second restraint 162 can be a conventional stopper, which can be removed from the stent 150 when necessary, so that the distal end 156 of the stent 150 is released.

[0104] According to the delivery system 100 of this embodiment, the proximal end 131 of the outer catheter 130 can be separated from the proximal end 122 of the delivery catheter 120. By pushing the push rod 170 toward the proximal end or by pulling the outer catheter 130 toward the distal end, the outer catheter 130, the inner catheter 140 and the push rod 170 can be moved relative to each other.

[0105] Figure 7 The system 100 shown in the figure pushes the push rod 170 toward the proximal end 122, so that the proximal end 122 of the delivery catheter 120 drives the push rod 170 fixedly connected thereto and the stent 150 bound to the end of the push rod 170 to move toward the proximal end relative to the outer catheter 130. In this way, the stent 150 starts to be released from its proximal end 154.

[0106] The stent delivery system of the present invention is particularly advantageous for the treatment of type A aortic dissection.

[0107] Combination Figure 8, which shows a schematic diagram of using the stent delivery system 100 of the present invention to place a stent 150 in type A aortic dissection lesions, to illustrate the therapeutic advantages of the stent delivery system of the present invention for type A aortic dissection. Figure 8 It is shown that there is a breach 93 in the ascending aorta 81, so a false lumen 92 is formed from the ascending aorta 81 through the aortic arch 83 to the descending aorta 84. The stent delivery system 100 of the present invention has been guided into the true lumen 91 of the aorta by the guidewire 101. When the stent 150 begins to be released, the operator pushes the push rod 170 toward the proximal end, wherein the thrust is represented by f1, and the direction of the thrust is represented by an arrow upward along the descending aorta. The thrust f1 is transmitted along the push rod 170 to the proximal end 122 of the delivery catheter. At this time, since the delivery system 100 bends nearly 180° after passing through the aortic arch 83, the force f2 acting on the proximal end 122 of the delivery catheter is almost opposite to the direction of the thrust at f1 (as shown by the arrow). This makes it difficult to control the thrust required for the initial release. In the stent delivery system 100 of the present invention, see Figure 8 The proximal end of the stent 150 is temporarily restrained by a member such as a stopper at the proximal end of the push rod 170, thereby significantly reducing the external expansion force of the stent 150 at the proximal end, thereby reducing the friction between the stent 150 and the inner wall of the outer catheter 130. Therefore, the thrust required for the initial release of the stent by the delivery system 100 of the present invention is significantly reduced, and the proximal end of the push rod 170 can be pushed out of the outer catheter 130 more easily.

[0108] Further integration Fig. 9 , which shows a schematic diagram of placing a stent at an aortic intimal rupture using the stent delivery system of the present invention. Fig. 9 A of FIG. 1 shows a section of an aorta 91 including a rupture 93 in the intima of the blood vessel, which causes a tear in the intima to form a false lumen 92. The stent delivery system 100 of the present invention has been guided to the rupture 93, and while keeping the position of the outer catheter 130 unchanged, a section of the stent 151 has been released by pushing the push rod in the direction indicated by the arrow. Fig. 9 In middle B, the inner and outer catheters of the delivery system 100 are kept in position, and the push rod is pulled back in the direction of the arrow in the figure, so that the released stent segment 151 is compressed back and finally abuts against the blood vessel area where the rupture 93 of the vascular endothelium is located, forming a compressed segment 151'. When designing a stent, the diameter of the stent is usually designed to be slightly larger than the diameter of the blood vessel at the placement site, so that the compressed segment 151' tightly abuts against the inner wall of the segment of the blood vessel, blocks the rupture 93, and expands the true lumen of the segment of the blood vessel. Due to the inward contraction force of the blood vessel wall, the compressed segment 151' is maintained in the segment of the blood vessel in the compressed shape.

[0109] then, Fig. 9As shown in FIG. 1C, the outer catheter 130 is pulled toward the distal end in the direction indicated by the arrow in the figure (the inner catheter 140 and the push rod 170 remain stationary) to further release the remaining stent segments 152. Finally, when the stent 150 is completely released, the restraints on both ends of the stent by the stopper are removed, so that the entire stent 150 is released to the treatment site, and the delivery catheter is withdrawn from the blood vessel (see FIG. 1B ). Fig. 9 D). The stent 150 placed at the lesion site has two sections, one is a compression section 151', and the other is a natural release section 152. The compression section 151' has a blocking effect on the rupture 93 and a strong radial support effect on the blood vessel, and the natural release section 152 has a proper support effect on other parts of the blood vessel and does not hinder the flow of blood, especially does not hinder the flow of blood to the branch blood vessels.

[0110] According to the present invention, after the stent segment 151 is released (ie, Fig. 9 The position of the stent can be confirmed in the state shown in A in the middle, so that the compressed section can accurately block the breach 93. If the position is not ideal, it can be adjusted, or even the released section 151 can be retracted into the outer catheter again, and the position of the delivery system can be adjusted before it is released again.

[0111] Similarly, the position of the stent can be confirmed after any section is released to obtain the best placement effect. Finally, before removing the restraints on both ends of the stent, the position of the stent is confirmed again, because at this time, if the placement position is found to be unsatisfactory, the stent can be recovered and released again. When the restraints on both ends of the stent are removed, the position of the stent can no longer be adjusted.

[0112] In addition, the compression patterns of other sections of the stent are similar to Fig. 9 Similar to that shown in B. For example, after the front part of the stent is released and has already abutted against the vessel wall, a section of the stent is continuously released. Since the end of the subsequently released stent is bounded by the outer catheter, the outer catheter and the inner catheter can be simultaneously moved toward the proximal end by keeping the push rod stationary, so that a section of the stent that is newly released but has not yet abutted against the vessel wall is compressed and abuts against the vessel wall, forming a section with high metal coverage and high radial support force.

[0113] The above examples illustrate the detailed scheme of the stent delivery system of the present invention and the method of placing the stent in a blood vessel using the system. Those skilled in the art can easily make deformations and modifications based on the above content to adapt to actual application needs without departing from the spirit of the present invention, and these deformations and modifications are also within the scope of the present invention.

[0114] Example

[0115] This embodiment provides Figure 1The bare stent of the structure shown is used in the ascending aorta to the aortic arch area. The bare stent is made of nickel-titanium material and is interwoven with 120 first wires with a diameter of 100 μm and 8 second wires with a diameter of 400 μm. The bare stent is woven in a back-braiding manner with a total of 4 layers. The back-braiding manner is as follows Figure 5 As shown in C, the proximal end is a completely braided smooth end, the distal end has two layers of burrs placed on the inner side of the stent, and two layers of braided edges placed on the outer side of the stent to prevent the burrs from being exposed and damaging the blood vessel wall.

[0116] The diameter of the bare stent corresponding to the ascending aorta is 45mm and the length is 9cm; the diameter of the bare stent corresponding to the aortic arch is 32mm and the length is 6cm. A dredging area is set 30mm away from the proximal end of the bare stent. The length of the dredging area is 6cm and the arc length is 1 / 3 of the circumference.

[0117] Scanning electron microscope detection shows that the metal coverage of the stent in this embodiment is 80% in the natural state except for the sparse mesh area, and the metal coverage is 98% after the maximum axial compression. Detected by a radial support force tester, the radial support force of the stent in this embodiment corresponding to the thicker part of the ascending aorta in the natural state is about 400N, the radial support force of the part with the sparse mesh area is about 100N, and the radial support force after the maximum axial compression is greater than 400N, and can even reach more than 500N.

[0118] In addition, in order to simulate the axial bending stress of the stent when it is fixed at the aortic arch, the radial recoil force of the stent was measured between 0.4 and 1.0N.

[0119] The above descriptions are only some specific embodiments of the present invention, and are not intended to limit the patent scope of the present invention. All equivalent structural changes made using the contents of the present invention's specification and drawings, or directly / indirectly applied in other related technical fields, are included in the patent protection scope of the present invention.

Claims

1. A bare stent that is compressible and stretchable along the axial direction, the bare stent is used in the aorta, characterized in that: The bare stent has at least two layers of woven mesh formed in a back-woven manner, and the bare stent includes: A non-sparse mesh area, wherein the non-sparse mesh area is formed by overlapping and interweaving at least two first wires and second wires of different diameters, wherein the first wire has a diameter of 20 μm to 150 μm, and the second wire has a diameter of 150 μm to 600 μm; and an optional sparse mesh area, which is composed only of the second wire and is arranged at a location with branched arteries in a corresponding treatment site after the bare stent is released, Wherein, in the natural release state, the bare stent has a metal coverage rate of at least 60% except for the sparse mesh area; The bare stent is woven from 96 to 202 wires, wherein the second wires are 4 to 30 and the rest are first wires; The bare stent has a radial support force of not less than 100N in a naturally released state; When the bare stent is released and in a state of maximum axial compression, it has a radial supporting force of not less than 500N.

2. The bare stent according to claim 1, characterized in that: The bare stent has a radial support force of 100N-600N and a metal coverage rate of 70%-90% except for the sparse mesh area in a naturally released state.

3. The bare stent according to claim 1, characterized in that: When the bare stent is placed in the aorta, it has different degrees of compression along its length.

4. The bare stent according to claim 1, characterized in that: Except for the sparse mesh area, the first wire and the second wire are woven into the bare stent in a uniformly distributed manner.

5. The bare stent according to claim 1 or 2, characterized in that: The bare stent has a metal coverage of 90%-100% when it is released and in a state of maximum axial compression.

6. The bare stent according to claim 5, characterized in that: When the bare stent is released and in a state of maximum axial compression, it has a radial supporting force of 500N-1000N.

7. The bare stent according to claim 1, characterized in that: The bare stent is used in the area from the ascending aorta to the abdominal aorta, including at least the ascending aorta, and the sparse mesh area includes a first sparse mesh area corresponding to the aortic arch, and the central angle corresponding to the first sparse mesh area is 120°~180°.

8. The bare stent according to claim 7, characterized in that: The sparse mesh area also includes a second sparse mesh area corresponding to the branch artery location in the abdominal aorta, wherein the branch arteries in the abdominal aorta are the left renal artery, the right renal artery, the celiac trunk and the superior mesenteric artery on the abdominal aorta, and the central angle corresponding to the second sparse mesh area is 180°.

9. The bare stent according to claim 7, characterized in that: The bare stent uses an area from the ascending aorta to the abdominal aorta, including at least the abdominal aorta. The bare stent has a second sparse mesh area corresponding to the branch artery location in the abdominal aorta. The branch arteries in the abdominal aorta are the left renal artery, the right renal artery, the celiac trunk and the superior mesenteric artery on the abdominal aorta. The central angle corresponding to the first sparse mesh area is 180°.

10. The bare stent according to claim 8 or 9, characterized in that: The bare stent is provided with two common iliac artery stent fixing parts in the internal space for fixing the left and right common iliac artery stents.

11. The bare stent according to claim 10, characterized in that: The common iliac artery stent fixing portion is arranged inside the bare stent at the bifurcation of the abdominal aorta close to the left and right common iliac arteries. The two common iliac artery stent fixing portions are arranged in tangent rings and are formed integrally with the inner wall of the bare stent.

12. The bare stent according to claim 1, characterized in that: The bare stent has a varying diameter, and the diameter is in the range of 20 mm to 60 mm.

13. The bare stent according to claim 12, characterized in that: A portion of the bare stent has a diameter in the range of 38 mm to 60 mm.

14. The bare stent according to claim 1, characterized in that: The second filament includes a first thick filament and a second thick filament having different diameters, wherein the first thick filament has a diameter of 150 μm to 300 μm, and the second thick filament has a diameter of 300 μm to 600 μm.

15. The bare stent according to claim 1, characterized in that: The first filament includes a first filament and a second filament having different diameters, wherein the first filament has a diameter of 50 μm to 100 μm, and the second filament has a diameter of 100 μm to 150 μm.

16. The bare stent according to claim 14, characterized in that: The bare stent is woven from 96 to 202 wires, wherein the second wires include 6 to 12 first thick wires and 4 to 12 second thick wires, and the rest are first wires.

17. The bare stent according to claim 15, characterized in that: The first filaments include 32 to 166 of the first filaments and 32 to 166 of the second filaments, provided that the total number of the first filaments and the second filaments does not exceed 198.

18. The bare stent according to claim 1, characterized in that: The bare stent has 4 layers of woven mesh.

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