CN113116612B

CN113116612B - Covered stent

Info

Publication number: CN113116612B
Application number: CN201911418430.4A
Authority: CN
Inventors: 肖本好; 何里明
Original assignee: Lifetech Scientific Shenzhen Co Ltd
Current assignee: Lifetech Scientific Shenzhen Co Ltd
Priority date: 2019-12-31
Filing date: 2019-12-31
Publication date: 2023-01-17
Anticipated expiration: 2039-12-31
Also published as: CN113116612A

Abstract

The invention belongs to the technical field of interventional medical devices, and particularly relates to a covered stent, which comprises: an inner stent and an outer stent. The inner-layer support comprises a first radial structure and a second radial structure which are connected, the outer-layer support is sleeved outside the inner-layer support and is in sealing connection with the outer surface of the inner-layer support, the outer-layer support comprises a third radial structure and a fourth radial structure which are connected, and the fourth radial structure is connected to the second radial structure; the bend radius of the second radial structure is less than the bend radius of the fourth radial structure, and the radial strength of the fourth radial structure is less than the radial strength of the third radial structure. According to the film-coated stent provided by the embodiment of the invention, the second radial structure has better flexibility, can better conform to a twisted blood vessel, ensures normal blood supply, and meanwhile, the connection part of the fourth radial structure and the second radial structure can effectively prevent the second radial structure from continuously shortening towards the first radial structure, so that the risk of separation of the first radial structure from the short branch is reduced.

Description

Covered stent

Technical Field

The invention belongs to the technical field of interventional medical instruments, and particularly relates to a covered stent.

Background

This section provides background information related to the present disclosure only and is not necessarily prior art.

Abdominal aortic aneurysm (AAA abdominal aortic aneurysm) with common iliac artery dilatation lesion is one of common diseases, AAA cannot be cured by the existing medicines, and the treatment method mainly comprises the traditional open surgery and the endoluminal repair (EVAR). The traditional treatment mode is to perform aneurysm excision and then artificial blood vessel reconstruction, but because the iliac artery is positioned behind the peritoneum, the anatomical part is deep, the tumor body is often large, the separation is difficult, the wound is large, the complications are more, and the iliac artery is replaced by endovascular repair of aneurysm (EVAR).

Abdominal aortic aneurysms are often accompanied by dilation of the common iliac artery and even involvement of the internal iliac artery. Conventional intervention treatment releases the main tectorial membrane support of abdomen earlier in abdominal aortic aneurysm pathological change department, and the unsettled stagnation of short branch is stayed abdominal aortic aneurysm department, and long branch and common iliac artery vessel wall laminating anchor release iliac artery support again, one end and the main short branch of abdomen cup joint, and the other end and the laminating of healthy vessel wall to make blood reach the isolated effect of moving abdominal aortic aneurysm.

Because common iliac arteries are easy to distort, in practical application, if a stent with poor flexibility is selected, the stent is difficult to conform to blood vessels at the distorted iliac artery lesion positions, the stent is easy to be broken, and the risk of occlusion exists in the long term. If the iliac artery stent with better flexibility is selected, the stent can well conform to the distorted blood vessel, and the normal blood supply is ensured. However, the flexibility of the stent is mainly realized by adjusting the axial constraint between the waveforms, and in the process of bending the stent to conform to the blood vessel, if the axial constraint of adjacent waveforms is small, the stent can be bent between the waveform stents, so that the effect of conforming to the blood vessel is achieved. But because of no axial constraint, the stent is easy to shrink under the pulsation of the blood vessel, so that the distal end of the stent is not anchored enough to form endoleaks. If the stent is shortened towards the distal end, the iliac artery stent can even be separated from the abdominal main short branch stent, which causes the failure of the operation.

Disclosure of Invention

It is an object of the present invention to solve at least one of the problems of the prior art. The purpose is realized by the following technical scheme:

the invention provides a covered stent, which comprises: an inner stent comprising a first radial structure and a second radial structure connected;

the outer layer support is sleeved outside the inner layer support and is in sealing connection with the outer surface of the inner layer support, the outer layer support comprises a third radial structure and a fourth radial structure which are connected, and the fourth radial structure is connected to the second radial structure;

the second radial structure has a bend radius that is less than a bend radius of the fourth radial structure, and the fourth radial structure has a radial strength that is less than a radial strength of the third radial structure.

In one embodiment, a ratio of a radius of curvature of the fourth radial structure to a radius of curvature of the second radial structure is 1.3-2.5.

In one embodiment, the ratio of the radial strength of the third radial structure to the radial strength of the fourth radial structure is 1.5-2.8.

In one embodiment, the radial strength of the second radial structure is less than the radial strength of the third radial structure.

In one embodiment, the ratio of the radial strength of the third radial structure to the radial strength of the second radial structure is 1.2-2.

In one embodiment, the radial strength of the second radial structure is less than the radial strength of the first radial structure.

In one embodiment, the ratio of the radial strength of the first radial structure to the radial strength of the second radial structure is 1.2-2.

In one embodiment, the inner stent further comprises a fifth radial structure, the first segment of the second radial structure, the fifth radial structure and the second segment of the second radial structure are sequentially connected along the axial direction, the fourth radial structure is connected with the fifth radial structure, and the bending radius of the fifth radial structure is smaller than that of the second radial structure.

In one embodiment, the ratio of the bending radius of the second radial structure to the bending radius of the fifth radial structure is 1.3-2.5.

In one embodiment, the radial strength of the fifth radial structure is less than the radial strength of the second radial structure.

According to the covered stent of the embodiment, the inner layer stent at least comprises a first radial structure and a second radial structure which are connected, the outer layer stent comprises a third radial structure and a fourth radial structure which are connected, the bending radius of the second radial structure is smaller than that of the fourth radial structure, namely, the flexibility of the second radial structure is superior to that of the fourth radial structure, and the arrangement is that the second radial structure has better flexibility, can better conform to a twisted blood vessel, ensures normal blood supply and reduces the risk of occlusion. Because the compliance of second radial structure for the second radial structure probably has the distal end to shift and increases the risk of interior hourglass, or the risk that near-end and short branch break away from, through setting up outer support, outer support can carry out the shutoff to the interior hourglass that second radial structure leads to, and because the bending radius of second radial structure is less, fourth radial structure and second radial structure junction have the ability of anti displacement, when the second radial structure shortens to the distal end, fourth radial structure and second radial structure junction can effectively prevent the second radial structure to continue to shorten toward first radial structure's direction, reduce the risk that first radial structure and short branch break away from. Radial intensity through setting up third radial structure is greater than fourth radial intensity, can increase the anchoring nature of third radial structure and common iliac artery expansion vascular wall, avoids displacement or deformation that outer support leads to because of vascular pulsation, causes the shutoff failure, realizes the secondary shutoff of the blood that all descends by a wide margin to pressure and velocity of flow, avoids interior hourglass.

Drawings

Various additional advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The drawings are only for purposes of illustrating the preferred embodiments and are not to be construed as limiting the invention. Also, like reference numerals are used to refer to like parts throughout the drawings. In the drawings:

FIG. 1 is a schematic diagram of a prior art abdominal aorta affected by a lesion;

FIG. 2 is a schematic view of a prior art primary therapeutic implant stent graft;

FIG. 3 is a schematic structural view showing that the treatment implanted abdominal main covered stent and the iliac artery stent are broken in the prior art;

FIG. 4 is a schematic structural view showing the foreshortening of a main abdominal stent graft and an iliac artery stent graft in the prior art;

FIG. 5 is a schematic structural view of the stent graft implanted in the abdominal aorta in accordance with the embodiment of the present invention;

FIG. 6 is a schematic perspective view of a stent graft according to a first embodiment of the present invention;

FIG. 7 is a schematic view of the deployment of the inner stent of the stent graft shown in FIG. 6;

FIG. 8 is a schematic view of the outer stent of FIG. 6 in a fourth radial configuration;

fig. 9 is an expanded view of the inner stent according to the second embodiment of the present invention.

Detailed Description

Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

It is to be understood that the terminology used herein is for the purpose of describing particular example embodiments only, and is not intended to be limiting. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms "comprises," "comprising," "including," and "having" are inclusive and therefore specify the presence of stated features, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and/or groups thereof.

Although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms may be only used to distinguish one element, component, region, layer or section from another region, layer or section. Terms such as "first," "second," and other numerical terms when used herein do not imply a sequence or order unless clearly indicated by the context. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the example embodiments.

For convenience in description, the relationship of one element or feature to another element or feature as illustrated in the figures may be described herein using spatially relative terms, such as "inner", "outer", "lower", "below", "upper", "over", and the like. This spatially relative term is intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as "below" or "beneath" other elements or features would then be oriented "above" or "over" the other elements or features. Thus, the example term "in 8230 \8230; below" may include both upper and lower orientations. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

In the field of stents, one end of a blood flow flowing into a blood vessel is generally referred to as a "proximal end" of the stent, and one end of the blood flow flowing out of the blood vessel is generally referred to as a "distal end" of the stent, and "proximal end" and "distal end" of any member of the stent are defined according to this principle. "axial" generally refers to the length of the stent as it is delivered, and "radial" generally refers to the direction of the stent perpendicular to its "axial" direction, and defines both "axial" and "radial" directions for any component of the stent graft according to this principle.

The stent graft provided in this embodiment is used for treating aorta, such as ascending aorta, aortic arch, descending aorta, and abdominal aorta 1, etc., and is described below as treating abdominal aortic aneurysm 11, as shown in fig. 1 to 4, arrows indicate the direction of blood flow, fig. 1 is a schematic view of the lesion of existing abdominal aortic aneurysm 11, as shown in fig. 1, including abdominal aortic aneurysm 11, common iliac artery dilation 12, external iliac artery 13, and internal iliac artery 14, and region a in the drawing is a common iliac artery kinking section. As shown in fig. 2, when treatment is performed, the main abdominal stent graft 2 is released at the lesion site of the abdominal aortic aneurysm 11, the short branch 21 is suspended and stayed at the abdominal aortic aneurysm 11, the long branch 22 is anchored by being attached to the wall of the common iliac artery, the iliac artery stent 3 is released again, one end of the main abdominal branch 21 is sleeved, and the other end of the main abdominal branch is attached to the wall of the healthy blood vessel, so that blood can achieve the effect of isolating the abdominal aortic aneurysm 11. If the iliac artery stent 3 with poor flexibility is selected, as shown in fig. 3, the stent is difficult to conform to the blood vessel, and the A area is easy to be broken, and the occlusion risk exists in the long term.

To accommodate the twisted common iliac artery, one approach is to conform to the vessel morphology by increasing the compliance of the iliac stent 3, ensuring normal blood supply. The compliance of the stent is generally achieved by adjusting the axial constraint between the waveforms. In the process of conforming the stent to the blood vessel, if the axial constraint between adjacent waveforms is small, the stent can be bent between the waveforms, so that the function of conforming the blood vessel is achieved. However, due to less axial constraint, as shown in the area B in fig. 4, the stent is likely to be shortened under the action of pulsating external force, and if the stent is shortened towards the proximal end, the anchoring force at the distal end of the stent is insufficient, so that endoleak is formed. If the stent is shortened distally, there is even a risk of the iliac artery stent 300 becoming detached from the short branch 21, resulting in a failure of the operation.

Example one

As shown in fig. 5 to 9, the present embodiment provides a covered stent, which is the iliac artery stent 3 used in the above text, and includes an inner stent 4 and an outer stent 5, wherein the inner stent 4 includes a first radial structure 41 and a second radial structure 42 connected to each other, the outer stent 5 is sleeved outside the inner stent 4 and is connected to the outer surface of the inner stent 4 in a sealing manner, the outer stent 5 includes a third radial structure 51 and a fourth radial structure connected to each other, the fourth radial structure 52 is connected to the second radial structure 42, the bending radius of the second radial structure 42 is smaller than that of the fourth radial structure, and the radial strength of the fourth radial structure 52 is smaller than that of the third radial structure 51.

According to the stent graft of the embodiment, the inner stent 4 comprises at least two parts of a first radial structure 41 and a second radial structure 42 which are connected, the outer stent 5 comprises a third radial structure 51 and a fourth radial structure 52 which are connected, the bending radius of the second radial structure 42 is smaller than that of the fourth radial structure 52, namely the compliance of the second radial structure 42 is better than that of the fourth radial structure 52, so that the second radial structure has better compliance and can better conform to a twisted blood vessel, ensure normal blood supply and reduce the risk of occlusion, the second radial structure may have a risk of distal displacement and increase inner leakage or a risk of proximal separation from a short branch due to the compliance of the second radial structure, the outer stent 5 can block the inner leakage caused by the second radial structure by arranging the outer stent 5, and the connection between the fourth radial structure 52 and the second radial structure 42 has the capability of resisting displacement due to the smaller bending radius of the second radial structure 42, when the second radial structure 42 is shortened distally, the effective connection between the fourth radial structure 52 and the second radial structure 42 can prevent the risk of the first radial structure 41 from being further separated from the short branch 21. Radial intensity through setting up third radial structure 41 is greater than fourth radial intensity, can increase the anchoring nature of third radial structure 51 and common iliac artery expansion 12 vascular walls, avoids displacement or deformation that outer support 5 leads to because of the pulsation of blood vessel, causes the shutoff failure, realizes the secondary shutoff of the blood that all descends by a wide margin to pressure and velocity of flow, avoids interior hourglass.

In one embodiment, after the stent graft is advanced into the blood vessel, a portion of the second radial structure 42 is positioned in the common iliac artery 12, and to accommodate the tortuous iliac artery and mitigate the risk of distal occlusion, the second radial structure 42 is configured with a bend radius of 5-25mm to accommodate most of the tortuous iliac artery. In the present application, the bending radius, taking the second radial structure 42 as an example, refers to the minimum radius that the second radial structure 42 can reach on the premise of ensuring the radial shape of the second radial structure 42 by bending the two ends of the second radial structure 42 towards the middle.

In one embodiment, the ratio of the bend radius of the fourth radial structure 52 to the bend radius of the second radial structure 42 is 1.3-2.5. Because the bending radius of the second radial structure 42 is smaller, the joint of the fourth radial structure 52 and the second radial structure 42 has the capability of resisting displacement, when the second radial structure 42 is shortened towards the distal end, the joint of the fourth radial structure 52 and the second radial structure 42 can effectively prevent the second radial structure 42 from being shortened towards the first radial structure 41, and the risk that the first radial structure 41 is separated from the short branch 21 is reduced. In one embodiment, the fourth radial structure 52 includes a plurality of wave structures arranged at intervals along the axial direction, and adjacent wave structures are connected by a connecting rod, and the connecting rod can reduce the axial shrinkage of the fourth radial structure 42, thereby improving the displacement resistance of the fourth radial structure 42. In another embodiment, the fourth radial structure 52 may employ a crest and trough interengagement to reduce axial shortening of the fourth radial structure 42.

In one embodiment, the inner stent 4 is a hollow lumen structure and has a radial expansion capability, and can be compressed under an external force and released to return to an expanded state after the external force is removed and maintain the expanded state, and can realize anchoring with a blood vessel wall, the inner stent 4 has a proximal end 44 and a distal end 45, and defines that blood flows from the proximal end 44 to the distal end 45 after implantation, the proximal end 44 is formed on a first radial structure 41, the distal end 45 is formed on a second radial structure 42, the outer stent 5 is hermetically connected with the inner stent 4 at a position close to the proximal end 44, the outer stent 5 and the inner stent 4 form a skirt structure at a position close to the distal end 45, the first radial structure 41 and the second radial structure 42 can be a plurality of wave structures arranged along the axial direction, can also be a mesh structure formed by weaving metal wires, and can also be a mesh structure formed by cutting metal tubes, the inner stent 4 further includes a first coating film, the first coating film is coated on the first radial structure 41 and the second radial structure 42, and may be a PET (polyethylene terephthalate) film or a PTFE (Poly tetra fluoro ethylene) film, the first radial structure 41 and the second radial structure 42 are connected with the first coating film by sewing or heat fusing, in one embodiment, each of the first radial structure 41 and the second radial structure 42 includes at least one wave-shaped structure, the number of the wave-shaped structures may be selected by those skilled in the art according to requirements, the illustrated number is merely used for illustration and is not a limitation of the embodiment, the wave-shaped structure may be formed by winding a metal wire, for example, by winding a memory alloy wire according to a predetermined waveform, the memory alloy may be a nickel-titanium alloy, the wire diameter of the metal wire is 0.15-0.4mm, the wave structure can be formed by cutting a metal pipe, the wire diameter of the metal rod forming the wave structure is 0.15-0.4mm, the wave crest and the wave trough of the wave structure are set to be round corners, the round corners are too large and can increase the sheathing difficulty, the round corners are too small, stress concentration at the round corners can be more obvious, and fracture is easily caused, so that the sizes of the round corners R1 at the wave crest and the wave trough of the first radial structure 41 and the round corners R2 at the wave crest and the wave trough of the second radial structure 42 are 0.5-2mm, and balance between the sheathing difficulty and the wire breakage risk is ensured.

In an embodiment, the radial strength of the first radial structure 41 is greater than that of the second radial structure 42, and the arrangement is such that the first radial structure 41 has sufficient radial expansion capability, and can be connected with a stent in the abdominal aorta 1, thereby preventing connection failure, and can be anchored with a blood vessel wall by the radial supporting force generated by radial expansion, reducing the risk of inner leakage, and being not easy to deform, avoiding the blockage of blood flowing into the stent, reducing the radial strength of the second radial structure 42 relative to the first radial structure 41, increasing the adherence between the second radial structure 42 and the inner wall of the blood vessel, and being capable of adapting to blood vessel structures of different forms, thereby further reducing the risk of inner leakage.

In an embodiment, the ratio of the radial strength of the first radial structure 41 to the radial strength of the second radial structure 42 is 1.2-2, the arrangement mode enables the first radial structure 41 to have sufficient radial expansion capacity, and can be connected with a stent in the abdominal aorta 1 to prevent connection failure, and can be anchored with a blood vessel wall through the radial supporting force generated by radial expansion, so that the risk of internal leakage is reduced, deformation is not easy to occur, and the blockage of blood flowing into the stent is avoided.

In one embodiment, the first radial structure 41 has a radial strength of 0.12N/mm or more, and the first radial structure 41 has a radial expansion capability capable of connecting to a stent in the abdominal aorta 1, preventing connection failure, and anchoring to a vessel wall by radial support force generated by radial expansion. However, as the radial strength increases, the rigidity after radial expansion is stronger, and when the rigidity is too high, the compliance and adherence with the blood vessel wall are reduced, thereby causing internal leakage, so that it is necessary to determine the radial strength of the first radial structure 41 within a range that ensures the balance between the rigidity and the compliance of the first radial structure 41, and determine the radial strength of the first radial structure 41 to be 0.12N/mm to 0.4N/mm.

In the present application, the radial strength may be measured using a radial support force tester, such as a Machine Solution Inc (MSI) model RX550-100 radial support force tester. For example, taking the first radial structure as an example, the inner layer stent 4 is implanted in a radial gripper, the radial gripper is uniformly radially compressed until the lumen is compressed by 20% all the time during the test, and the radial strength value of the first radial structure 41 at this moment is tested.

In one embodiment, the outer stent 5 is a hollow lumen structure and has a radial expansion capability, and can be compressed under an external force and released to return to an expanded state after the external force is removed, and the expanded state is maintained, so as to achieve anchoring with a blood vessel wall, each of the third radial structure 51 and the fourth radial structure 52 can be a plurality of wave structures arranged along the axial direction, and can also be a mesh structure formed by weaving metal wires, and can also be a mesh structure formed by cutting metal tubes, the outer stent 5 further comprises a second covering film, the second covering film is covered on the third radial structure 51 and the fourth radial structure 52, and can be a PET film or a PTFE film, the third radial structure 51 and the fourth radial structure 52 are connected with the second covering film through sewing or hot melting, in one embodiment, each of the third radial structure 51 and the fourth radial structure 52 comprises at least one wave structure, the number of the wave-shaped structures can be selected by those skilled in the art according to the needs, the number shown in the figure is only used as an example and is not limited to this embodiment, the wave-shaped structures can be formed by winding metal wires, for example, memory alloy wires are wound according to a predetermined waveform, the memory alloy can be nickel titanium alloy, so that the self-expansion capability of the metal wires is achieved, the wave shapes can be Z-shaped waves, U-shaped waves or sine waves, the wave-shaped structures of the third radial structure 51 can be formed by cutting metal tubes, the wire diameter of the metal wires used in the fourth radial structure 52 is 0.05-0.35mm, the wave-shaped structures can also be formed by cutting metal tubes, the wire diameter of the metal rods forming the wave-shaped structures is 0.05-0.35mm, the wave-shaped structures are provided with rounded corners at the peaks and valleys, the rounded corners are too large rounded corners, which increases the sheathing difficulty, and the stress concentration at the rounded corners is more obvious, easily lead to the fracture, therefore the fillet R4 size of crest and trough department of fourth radial structure 52 is 0.5-2mm to guarantee the balance of the sheath degree of difficulty and disconnected silk risk, the connection between outer support 5 and the inlayer support 4 is realized through first tectorial membrane and second tectorial membrane, realize sealing connection through sewing up or sealed mode between first tectorial membrane and the second tectorial membrane, the suitable sealed mode of technical staff can select as required, no longer describe herein.

In an embodiment, the radial strength of the third radial structure 51 is greater than the radial strength of the second radial structure 42. The reduction of radial strength has increased the compliance of second radial structure 42, has improved the laminating nature of second radial structure 42 and the vascular wall of external iliac artery 13, makes the plaque on the vascular wall that second radial structure 42 can laminate, further reduces the risk of interior hourglass. Because the flow velocity and the pressure of the blood are greatly reduced after the inner-layer stent is plugged once, the smaller the pressure and the flow velocity are, the greater the difficulty for the blood to pass between the covered stent and the blood vessel wall is, namely, the requirement for the adherence of the third radial structure 51 and the common iliac artery expansion 12 blood vessel wall is lower than the requirement for the adherence of the second radial structure 42 and the external iliac artery 13. In an embodiment, the ratio of the radial strength of the third radial structure 51 to the radial strength of the second radial structure 42 is set to be 1.2-2, so that the anchoring property of the third radial structure 51 to the common iliac artery expansion 12 blood vessel wall is increased, the failure of plugging caused by displacement or deformation of the outer stent 5 due to pulsation of the blood vessel is avoided, secondary plugging of blood with greatly reduced pressure and flow rate is realized, and internal leakage is avoided.

In an embodiment, the fourth radial structure 52 serves as a connecting transition between the third radial structure 51 and the second radial structure 42, the third radial structure 51 is attached to the vessel wall, the fourth radial structure 52 provides an auxiliary function for the expansion of the third radial structure 51, and the radial strength of the fourth radial structure 52 is set to be smaller than that of the third radial structure 51, which can reduce the difficulty of sheathing. In an embodiment, the ratio of the radial strength of the third radial structure 51 to the fourth radial structure 52 is 1.5-2.8.

In an embodiment, the outer stent 5 is sleeved outside the inner stent 4, and an overlapping region exists between the outer stent 5 and the inner stent 4, the longer the overlapping region is, the greater the sheathing difficulty is, but the longer the overlapping region is, the better the blood backflow blocking effect is, so that the blood backflow blocking effect is smoothly unfolded and attached to the vascular wall, and the sum of the length L1 of the third radial structure 51 and the length L2 of the fourth radial structure 52 is 15mm-30mm, so as to ensure the balance of the sheathing difficulty and the blocking effect.

Example two

The first radial structure 41, the second radial structure 42, the third radial structure 51 and the fourth radial structure 52 in this embodiment are the same as those in the first embodiment, as shown in fig. 10, except that the inner stent 4 further includes a fifth radial structure 43, when the inner stent 4 includes the fifth radial structure 43, the inner stent 4 sequentially includes the first radial structure 41, the first section of the second radial structure 42, the fifth radial structure 43 and the second section of the second radial structure 42 along the axial direction, two ends of the fifth radial structure 43 are respectively connected to one of the second radial structures 42, the fourth radial structure 52 is connected to a connection between the first section of the second radial structure 42 and the fifth radial structure 43, and the outer stent 5 and the inner stent 4 are overlapped with each other on the fifth radial structure 43. Because the cross-sectional area of the region of outer support 5 and the coincidence of inlayer support 4 increases gradually, set for the radial strength that is less than second radial structure 42 with the radial strength of fifth radial structure 43, on the one hand, reduced the sheath degree of difficulty of the region of coincidence, on the other hand, the both ends of fifth radial structure 43 are provided with second radial structure 42 respectively, also can not influence the adherence with the vascular wall, only need keep blood can normally pass through in the position of fifth radial structure 43 can. In one embodiment, the ratio of the radial strength of the second radial structure 42 to the radial strength of the fifth radial structure 43 is 1.3-2.

In another embodiment, the first film of the inner stent 4 also covers the fifth radial structure 43, and the fifth radial structure 43 and the first film are connected by sewing or heat-melting. Of course, in an embodiment, the surface of the fifth radial structure may also be not covered by the first cover film, that is, the surface of the fifth radial structure is not covered by the cover film, so that the cross-sectional area of the region where the outer stent 5 and the inner stent 4 are overlapped can be further reduced, the sheathing difficulty is reduced, and the function of the cover stent for isolating blood is not affected due to the plugging effect of the outer stent 5. The fifth radial structure 43 includes at least one wave structure, the number of the wave structures can be selected by those skilled in the art according to the requirement, the number shown is only used as an example and not a limitation to the embodiment, the wave structure can be formed by winding a metal wire, for example, a memory alloy wire wound according to a predetermined wave shape, the memory alloy can be a nickel-titanium alloy, so that the memory alloy has self-expansion capability, the wave shape can be a Z-wave, a U-wave or a sine wave, and the wire diameter of the metal wire is 0.05-0.35mm. The wave-shaped structure can also be formed by cutting a metal pipe, and the wire diameter of the metal rod forming the wave-shaped structure is 0.05-0.35mm. Wave structure's crest and trough department set up to the fillet, and the fillet is too big can increase the dress sheath degree of difficulty, and the fillet undersize can make the stress concentration of fillet department more obvious, leads to the fracture easily, and consequently the fillet R3 size of fifth radial structure crest and trough department is 0.5-2mm to guarantee the dress sheath degree of difficulty and the balance of disconnected silk risk.

It should be noted that, when the stent graft provided in the first embodiment is implanted, the stent graft provided in the second embodiment may be used alone, or the stent grafts provided in the first and second embodiments may be used together to mate with each other.

While the invention has been described with reference to specific preferred embodiments, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the following claims. Therefore, the protection scope of the present invention shall be subject to the protection scope of the appended claims.

Claims

1. A stent graft, comprising:

an inner stent comprising a first radial structure and a second radial structure connected;

the bend radius of the second radial structure is less than the bend radius of the fourth radial structure, and the radial strength of the fourth radial structure is less than the radial strength of the third radial structure;

the inner support further comprises a fifth radial structure, the first section, the second radial structure, the fifth radial structure and the second section are sequentially connected along the axial direction, the first section is respectively connected to the two ends of the fifth radial structure, the second radial structure and the second section are connected to the second radial structure, the fourth radial structure is connected to the first section, the second radial structure is connected to the junction of the fifth radial structure, the outer support is coincided with the inner support in the fifth radial structure, and the radial strength of the fifth radial structure is smaller than that of the second radial structure.

2. The stent graft as recited in claim 1, wherein the ratio of the bend radius of the fourth radial structure to the bend radius of the second radial structure is 1.3-2.5.

3. The stent graft as recited in claim 1, wherein the ratio of the radial strength of the third radial structure to the radial strength of the fourth radial structure is 1.5-2.8.

4. The stent-graft of claim 1, wherein the radial strength of the second radial structure is less than the radial strength of the third radial structure.

5. The stent-graft of claim 4, wherein the ratio of the radial strength of the third radial structure to the radial strength of the second radial structure is 1.2-2.

6. The stent-graft of claim 1, wherein the radial strength of the second radial structure is less than the radial strength of the first radial structure.

7. The stent graft of claim 6, wherein the ratio of the radial strength of the first radial structure to the radial strength of the second radial structure is 1.2-2.

8. The stent graft as recited in claim 1, wherein the fifth radial structure has a radius of curvature that is less than the radius of curvature of the second radial structure.

9. The stent graft of claim 8, wherein a ratio of the bend radius of the second radial structure to the bend radius of the fifth radial structure is 1.3-2.5.