Covered stent

Abstract

This invention provides a covered stent, comprising a main body segment having a tubular body and a branch segment. The branch segment includes a first branch and a second branch. The axial length of the first branch is greater than or equal to the axial length of the second branch. The first branch includes a first parallel portion that can be arranged alongside the second branch. The first parallel portion includes a proximal portion on the proximal side and a distal portion on the distal side along the axial direction. The axial deformation resistance of at least the distal portion of the first branch is greater than or equal to the axial deformation resistance of the proximal portion. By enabling at least the distal portion of the first branch implanted in the external iliac vessel to have good axial deformation resistance, occlusion of the lumen due to covered extension can be avoided at least at this location. Furthermore, the entire axial segment of the covered stent can be provided with good axial deformation resistance, thereby preventing stent lumen narrowing from affecting blood flow.

Description

Technical Field

[0001] This invention relates to the field of medical device technology, and more particularly to a covered stent. Background Technology

[0002] Aortoiliac artery occlusion refers to ischemic diseases of the lower limbs and pelvic tissues and organs caused by stenosis or occlusion of the aorta and iliac arteries in the lower abdomen. Clinical manifestations include pain in the gluteal muscles or lower limbs after activity, i.e., intermittent claudication. If the condition continues to worsen, it can cause chronic severe lower limb ischemia, affecting quality of life and even endangering life. Increasing literature indicates that endovascular interventional therapy has a significant advantage over open surgery in the treatment of aortoiliac artery occlusion due to its minimal invasiveness. For patients with occlusion extending from the lower border of the renal artery to both iliac arteries, the lumen morphology can be reconstructed by implanting a bifurcated covered stent and a branch covered stent. Existing bifurcated stents are anchored proximally to the lower border of the renal artery and have two branch channels. The distal end of one branch channel can be anchored to one external iliac artery, while the other branch channel is generally connected to the branch covered stent, which is anchored distally to the other internal iliac artery.

[0003] Because PTFE membranes are unlikely to cause restenosis, they are generally used as the membrane material for stents. However, due to their strong ductility, during the process of inserting the stent into the sheath, it is generally necessary to use a lead wire to pull the distal end of the stent into the sheath. This process can easily cause the stent to elongate, leading to lumen contraction or even membrane rupture. The elongated stent has no support in the absence of a metal skeleton, and the lumen is prone to blockage. Summary of the Invention

[0004] Therefore, it is necessary to provide a covered stent that, through the design of the covered structure and the stent structure, minimizes or even avoids the axial extension of the covered stent during the process of pulling the distal end of the stent into the sheath with a lead wire, thereby preventing lumen shrinkage or covered stent rupture.

[0005] A covered stent includes a main segment having a tubular body and a branch segment. The branch segment includes a first branch and a second branch. The axial length of the first branch is greater than or equal to the axial length of the second branch. The first branch includes a first parallel portion that can be arranged side by side with the second branch. The first parallel portion includes a proximal portion located on a proximal side and a distal portion located on a distal side along the axial direction. In the first branch, at least the axial deformation resistance of the distal portion is greater than or equal to the axial deformation resistance of the proximal portion.

[0006] In one embodiment, the first branch includes an axially disposed first support frame and a first covering, wherein the radial thickness of the first covering at the proximal portion is less than or equal to the radial thickness of the first covering at the distal portion.

[0007] In one embodiment, the first support frame includes a plurality of first corrugated coils spaced apart axially, and the covering bracket includes an axial connector that connects at least two axially adjacent first corrugated coils located at the distal portion.

[0008] In one embodiment, the outer surface of the first side-by-side portion is covered with a second film, the second film having a greater resistance to deformation than the first film.

[0009] In one embodiment, the second branch is fixedly connected to the first parallel portion after being placed side by side, and the axial deformation resistance of the second branch is greater than that of the first parallel portion.

[0010] In one embodiment, the second branch is fixedly connected to the first parallel portion at least to the side closest to the first branch, or the second branch is fixedly connected to the distal portion at least to the side closest to the first branch.

[0011] In one embodiment, the second branch includes a second support frame and a third cover film arranged along the axial direction, wherein the third cover film is fixedly connected to the first cover film and / or the second support frame is fixedly connected to the first support frame.

[0012] In one embodiment, the first support frame and the second support frame of the first side-by-side portion are integrally formed, and the first film and the third film are integrally formed, so that the inner cavity of the first side-by-side portion is connected to the inner cavity of the second branch.

[0013] In one embodiment, the branch segment includes a thickened film, and the outer side of the position where the first side-by-side portion and the second branch are close to each other includes an adhesion gap, wherein the thickened film at least covers and fills the adhesion gap.

[0014] In one embodiment, the first branch includes a first connecting rod that extends axially from the proximal side to the distal side of the first branch and is fixedly connected to the first support frame and / or the first covering film; the radial dimension of the first connecting rod on the distal side is greater than or equal to the radial dimension on the proximal side.

[0015] In one embodiment, the main body segment includes an axially arranged main body support frame, a main body covering film, and a second connecting rod. The second connecting rod extends from the proximal end to the distal end along the axial direction of the main body segment and is fixedly connected to the main body support frame and / or the main body covering film. The radial dimension of the second connecting rod is less than or equal to the minimum radial dimension of the first connecting rod.

[0016] The beneficial effects of the present invention are as follows: Compared with the prior art, the present invention provides a covered stent, including a main body segment having a tubular body and a branch segment. The branch segment includes a first branch and a second branch. The axial length of the first branch is greater than or equal to the axial length of the second branch. The first branch includes a first parallel portion that can be arranged alongside the second branch. The first parallel portion includes a proximal portion located on the proximal side and a distal portion located on the distal side along the axial direction. The axial deformation resistance of at least the distal portion of the first branch is greater than or equal to the axial deformation resistance of the proximal portion. By making at least the distal portion of the first branch implanted in the external iliac vessel have good axial deformation resistance, the occlusion of the lumen caused by the covered stent due to the extension of the covered stent can be avoided at least at this position. Furthermore, the entire axial segment of the covered stent can be provided with good axial deformation resistance, thereby avoiding the narrowing of the stent lumen from affecting blood flow. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the structure of the film-coated stent of the present invention.

[0018] Figure 2 This is a schematic diagram of the first parallel section of the film-coated support structure of the present invention.

[0019] Figure 3 This is a schematic diagram of the structure in Embodiment 1 of the present invention, in which the thickness of the distal portion of the first coating is greater than that of the proximal portion.

[0020] Figure 4 This is a schematic diagram of the structure of the first branch with an axial connecting member in one embodiment of the present invention.

[0021] Figure 5 This is a schematic diagram of the structure of the first branch with an axial connecting member in one embodiment of the present invention.

[0022] Figure 6 This is a schematic diagram of the structure of the first branch with an axial connecting member in one embodiment of the present invention.

[0023] Figure 7 This is a schematic diagram of the structure of a polymer connecting wire as the axial connecting member in another embodiment of the present invention.

[0024] Figure 8This is a schematic diagram of a second coating structure where the first side-by-side portion covers and connects to the second coating structure in another embodiment of the present invention.

[0025] Figure 9 This is a schematic diagram of a fixed connection between the first branch and the second branch in Embodiment 2 of the present invention, wherein the second branch is a mesh support structure.

[0026] Figure 10 This is a schematic diagram of the second branch connecting the developing wire in one embodiment of the second embodiment of the present invention.

[0027] Figure 11 This is a schematic diagram of the fully stitched connection structure of the first branch and the second branch in Embodiment 2 of the present invention.

[0028] Figure 12 This is a schematic diagram of the suture connection structure of the first branch and the second branch at the distal end in another embodiment of the second embodiment of the present invention.

[0029] Figure 13 This is a schematic diagram of the structure in Embodiment 2 of the present invention in which the first support frame and the second support frame are fixedly connected by a metal sleeve.

[0030] Figure 14 This is a schematic diagram of a thickened coating structure provided for the bonding gap between the first branch and the second branch in another embodiment of the present invention.

[0031] Figure 15 This is a schematic diagram of an integrally formed structure of the first side-by-side portion and the second branch in another embodiment of the present invention.

[0032] Figure 16 This is a schematic diagram of the first and second support frames in another embodiment of the second embodiment of the present invention;

[0033] Figure 17 This is a schematic diagram of a first and third coating structure with different diameters in another embodiment of the second embodiment of the present invention;

[0034] Figure 18 This is a schematic diagram of the connection structure between the first branch and the second branch via a developing ring in another embodiment of the present invention.

[0035] Figure 19 This is a schematic diagram of the structure in Embodiment 3 of the present invention, in which the first branch is fully connected to the first connecting rod.

[0036] Figure 20 This is a schematic diagram of the structure in Embodiment 3 of the present invention, in which the main body segment is connected to the second connecting rod. Detailed Implementation

[0037] To better understand the concept of this application, the implementation methods of this application will be described in detail below with reference to the accompanying drawings. The following specific embodiments are only some embodiments of this application and are not intended to limit this application.

[0038] For ease of description, spatial relative terms may be used in the text to describe the relationship of one element or feature relative to another element or feature, as shown in the figure. These relative terms include, for example, "inside," "outside," "middle," "outer," "below," "below," "above," "over," etc. Such spatial relative terms are intended to include different orientations of the device in use or operation, other than those depicted in the figure. For example, if the device in the figure is flipped, an element described as "below other elements or features" or "below other elements or features" would subsequently be oriented as "above other elements or features" or "above other elements or features." Therefore, the example term "below" can include both upper and lower orientations. The device may be otherwise oriented (rotated 90 degrees or in other directions), and the spatial relative descriptors used in the text will be interpreted accordingly.

[0039] Although terms such as first, second, third, etc., may be used in this document to describe multiple elements, components, regions, layers, and / or segments, these elements, components, regions, layers, and / or segments should not be limited by these terms. These terms may be used only to distinguish one element, component, region, layer, or segment from another. Unless the context clearly indicates otherwise, terms such as "first," "second," and other numerical terms used herein do not imply order or sequence. Therefore, the first element, component, region, layer, or segment discussed below may be referred to as the second element, component, region, layer, or segment without departing from the teachings of the exemplary embodiments.

[0040] To more clearly describe the structure of this application, the terms "proximal" and "distal" are used here as conventional terms in the field of interventional medicine. Specifically, "proximal" refers to the end of the blood vessel closer to the heart, and "distal" refers to the end of the blood vessel farther from the heart; "axial" refers to its length direction, and "radial" refers to the direction perpendicular to the "axial" direction; "upper end" and "lower end" are two relatively distant ends, and when one end is defined as "upper end", the other distant end is "lower end".

[0041] This application provides a covered stent 100; please refer to [link / reference]. Figure 1 and Figure 2This is mainly used for implantation in bifurcation vessels within human blood vessels. Bifurcation vessels typically include a main vessel and at least two branch vessels connected to the main vessel. The covered stent 100 of this application includes a main segment 1 with a tubular body and a branch segment 2. During implantation, the main segment 1 is anchored within the main vessel, and the branch segment 2 is anchored within the branch vessel. Specifically, the branch segment 2 includes a first branch 21 and a second branch 22. The axial length H1 of the first branch 21 is greater than or equal to the axial length H2 of the second branch 22. Here, the first branch 21 can be set to the same axial length as the second branch 22 to anchor the branch vessel. Setting the first branch 21 to be greater than the axial length H1 of the second branch 22 is generally suitable for cases where a small stent needs to be implanted within the second branch 22 to achieve treatment of a branch vessel with a larger length range, such as the treatment of the internal iliac artery of the iliac bifurcation. The first branch 21 includes an axially arranged first support frame 211 and a first membrane 212. The first support frame 211 is used to support and maintain the tube structure of the first branch 21, and the first membrane 212 is used to isolate blood. The main body segment 1 may include an axially arranged main support frame 11 and a main membrane 12. The main support frame 11 is used to support and maintain the tube structure of the main body segment 1, and the main membrane 12 is used to isolate blood. The first branch 21 includes a first parallel portion 210 that can be arranged alongside the second branch 22. When the first branch 21 and the second branch 22 are set to the same axial length, the first parallel portion 210 of the first branch 21 is the entire first branch 21 itself, and the first parallel portion 210 of the first branch 21 is the part connected to the main body segment 1.

[0042] In order to improve long-term blood patency after implantation and to reduce radial compression size when the covered stent 100 is compressed into the sheath for delivery, this application selects a PTFE membrane with lower roughness and porosity as the first cover 212 and the main cover 12. It should be understood that the PTFE membrane has good extensibility. Typically, when compressing and inserting the covered stent 100 into the sheath, the distal end of the covered stent 100 is pulled in conjunction with the proximal end to push the covered stent 100, thereby compressing the covered stent. When the covered stent 100 is inserted into the sheath, the PTFE membrane will be stretched and extended axially during the pulling process. This stretching is more severe closer to the stretching point along the axial direction of the covered stent 100, exhibiting a distribution pattern of milder stretching proximally and more severe stretching distally. This stretching can lead to a reduction in the radial dimension of the lumen when the stretched area unfolds again within the blood vessel, thus affecting blood flow to the stent and causing unpredictable impacts on the long-term use of the covered stent 100. To reduce the stretching during the insertion of the covered stent 100 into the sheath... To minimize the impact, at least as much as possible, on the first branch 21, the first side-by-side portion 210 of the first branch 21 includes a proximal portion 213 on the proximal side and a distal portion 214 on the distal side. The axial deformation resistance of the first covering 212 at least in the distal portion 214 is greater than or equal to the axial deformation resistance of the proximal portion 213. Here, in the embodiment, the axial deformation resistance of the covering directly affects the deformation of the covering under axial tension, and the first side-by-side portion 210 is the main area where bending occurs after the covered stent 100 is implanted into the blood vessel. Therefore, in bending... There is a risk of occlusion when the lumen narrows simultaneously. Therefore, the axial deformation resistance of the first membrane 212 at least in the distal portion 214 is greater than or equal to the axial deformation resistance of the proximal portion 213. The axial deformation resistance of the first membrane 212 can be reasonably set according to the severe extension from the proximal end to the distal end component. This allows the first membrane 212 to better resist axial extension at least in the first parallel portion 210. At the same time, when extension occurs, the axial lumen change is uniform and there is no lumen distribution with drop, thereby ensuring the smoothness of blood flow in the lumen.

[0043] In this application, the resistance to axial deformation can be characterized by tensile strength, hardness, or stiffness. The change in tensile strength can be achieved by setting up a support frame with different materials and structural changes and a surface coating. Therefore, when this application mentions having good resistance to axial deformation, it usually refers to having higher tensile strength, material hardness, or stiffness.

[0044] Example 1:

[0045] In this embodiment, please refer to Figure 2 and Figure 3 The axial deformation resistance of the coating can be improved by increasing the thickness of the coating itself. Specifically, the radial thickness L2 of the first coating 212 in the proximal portion 213 can be less than or equal to the radial thickness L1 of the first coating 212 in the distal portion 214. When the radial thickness of the first coating 212 in the proximal portion 213 is set to be equal to the radial thickness of the first coating 212 in the distal portion 214, the radial thickness of the first coating 212 and the radial thickness of the second coating 216 in the proximal portion 213 should be able to resist most of the axial tensile force, thereby achieving good axial deformation resistance to resist deformation. For example, with a coating thickness of 0.1 mm and a diameter of 18 mm... Taking a 1 mm stent as an example, the stent membrane can withstand a tensile force of about 40 N. Beyond this value, the deformation increases with the increase of tensile force. Here, the axial tensile force that the stent will withstand when pulled into the sheath is about 10 N to 60 N. Therefore, the stent needs to be able to resist a tensile force of at least 60 N to reduce or avoid membrane stretching. If the membrane thickness is increased to 0.15 mm, the tensile force can be increased by about 20 N, so that the stent membrane can withstand a tensile force of about 60 N. Therefore, in the distal part of the region where stretching is more severe, the membrane thickness should be set to be at least greater than 0.15 mm, specifically between 0.15 mm and 1.0 mm, to provide sufficient resistance to axial deformation.

[0046] In this embodiment, please refer to Figure 3 The radial thickness L2 of the first covering 212 at the proximal portion 213 is set to be less than the radial thickness L1 of the first covering 212 at the distal portion 214. Here, the variation in covering thickness can be adapted to the variation law of the covering in axial extension. In this way, the covering thickness can be reasonably set to avoid setting too much thick covering, which would lead to an increase in the radial dimension of the stent after compression, and thus affect the compression and delivery of the covered stent 100 into the sheath. Furthermore, the radial thickness of the first covering 212 in the first parallel portion 210 can be made to gradually increase from the proximal portion 213 to the distal portion 214, so as to better adapt to the trend of the axial extension becoming more severe from the proximal portion 213 to the distal portion 214, while effectively reducing the amount of covering used to reduce the radial dimension of the covered stent 100 after compression.

[0047] In this embodiment, the radial thickness variation of the coating can be set at intervals between multiple adjacent first support frames 211 arranged along the axial direction. The coating at other positions, since it covers the first support frame 211, will provide a certain support force to prevent extension when it occurs. The coating at the interval positions, since there is no support, is the main area where extension occurs. Therefore, setting the coating with varying thickness at these positions can avoid the increase in the radial compression dimension of the coating support 100 due to too much unnecessary coating, and at the same time slow down the occurrence of coating extension.

[0048] In one embodiment, see Figure 4 The axial deformation resistance of the covering can be improved by increasing its tensile strength in the axial direction. Specifically, to ensure that the first support frame 211 can provide lumen support for the stent while also giving the first branch 21 good flexibility, the first support frame 211 can include multiple first wave coils 2110. The multiple first wave coils 2110 are spaced apart along the axial direction. The first support frame 211 is configured as a wave coil structure. The wave coil structure has elastic self-expansion capability to provide sufficient vascular lumen support. At the same time, the spaced first wave coils 2110 can have good bending flexibility due to the spacing. However, the covering at the spaced positions is often the main location where extension occurs. Therefore, to minimize the occurrence of extension, the covered stent 100 can include an axial connector 215. The axial connector 215 has at least The axial connector 215 connects any two axially adjacent first corrugated coils 2110 located in the distal portion 214. When extension occurs, it is usually accompanied by axial displacement between the two adjacent first corrugated coils 2110. Therefore, by connecting the two first corrugated coils 2110 together through the axial connector 215, relative axial displacement is avoided as much as possible, thereby avoiding axial extension of the first coating 212 connected to its surface. Furthermore, by providing the axial connector 215 at least at any two axially adjacent first corrugated coils 2110 in the distal portion 214, axial extension of the first coating 212 in the distal portion 214 can be avoided at least, thereby avoiding lumen closure of the first branch 21 at the bendable position.

[0049] In one embodiment, please refer to Figure 5 and Figure 6The axial connector 215 can be a metal connecting wire 2151. The metal connecting wire 2151 connects two adjacent first coils 2110 by welding or metal sleeve connection. Specifically, the metal connecting wire 2151 can be connected to the crests and troughs of two adjacent first coils 2110, or it can be connected to the wave rod. Using the metal connecting wire 2151, due to its good rigidity, it can provide both anti-extension and anti-shortening functions in the axial direction. Here, the metal connecting wire 2151 can be made of a developable material, and with the special positional design of the metal connecting wire 2151, it can serve as a guide for the orientation of the support within the human body.

[0050] In another embodiment, please refer to Figure 7 The axial connector 215 can be a polymer connecting wire 2152. The polymer connecting wire 2152 is connected between two adjacent first coils 2110 by sewing or wrapping. Specifically, the polymer connecting wire 2152 can be connected to the crests and troughs of two adjacent first coils 2110, or it can be connected to the wave rod. Compared with the metal connecting wire 2151, the polymer connecting wire 2152 has a smaller radial dimension and better flexibility, while also providing axial anti-stretch capability. Furthermore, the polymer connecting wire 2152 can be connected between two adjacent first coils 2110 by forming a mesh cover, thereby providing sufficient axial anti-stretch capability. Here, the polymer connecting wire 2152 can be a connecting wire made of PET material or a connecting wire made of PTFE material. Using a connecting wire made of PTFE material can have better compatibility with the first coating 212, so that after connecting to two adjacent first wave coils 2110, the polymer connecting wire 2152 made of PTFE material can be embedded and stored in the first coating 212.

[0051] In other embodiments, please refer to Figure 8The axial extension of the first membrane 212 at the distal end of the first branch 214 can be reduced or avoided by covering and connecting the first parallel portion 210 of the first branch 21 with the second membrane 216, which has a lower deformability. Specifically, the second membrane 216 can be applied to the surface of the first membrane 212 at this location by sewing or bonding, and both ends can be fixed to the first corrugated coil 2110 by sewing. Thus, when axial tension is applied at this location, the tension that was originally applied entirely to the first membrane 212 is reduced. Part of the tension is distributed onto the second film 216, reducing the tensile force on the first film 212. At the same time, the second film 216 has better resistance to deformation, thus resisting deformation caused by tension. Specifically, the second film 216 can be made of PET material. The tensile strength of PET material is between 50 and 200 MPa, while the tensile strength of PTFE material is between 20 and 30 MPa. Therefore, using the second film 216 made of PET material with higher tensile strength can better help the first film 212 resist axial tension.

[0052] Example 2:

[0053] In this embodiment, please refer to Figure 9 The structural configuration of the main body segment 1 and the first branch 21 is largely the same as in Embodiment 1. The difference is that the first parallel portion 210 of the first branch 21 and the second branch 22 arranged side by side can be connected to disperse the axial tensile force on the first parallel portion 210 of the first branch 21. Here, when the first branch 21 and the second branch 22 are connected side by side and subjected to axial tensile force, the second branch 22 can at least at the connection position distribute part of the axial tensile force on the first branch 21. When the axial deformation resistance of the second branch 22 is greater than the axial deformation resistance of the first parallel portion 210, the second branch 22 can help at least the first parallel portion 210 of the first branch 21 resist part of the axial tensile force to reduce the axial extension of the first film 212. Specifically, the second branch 22 includes a second support frame 221 and a third film 222 arranged along the axial direction. The second support frame 221 can be set as a mesh support. The mesh support has better tensile strength than the wave coil support, thereby providing better axial deformation resistance for the second support.

[0054] In one embodiment, see Figure 10The second support frame 221 can be configured as a plurality of second wave coils 223 arranged along the axial direction, thereby providing good bending flexibility at the second branch 22 position. With this configuration, developing wires 220 arranged continuously along the axial direction can be arranged between the plurality of second wave coils 223 arranged at axial intervals. The developing wires 220 connect each second wave coil 223, which can play a role in directional development and axial tension restriction at the same time, thereby giving the second branch 22 better resistance to axial deformation.

[0055] In this embodiment, please refer to Figure 11 When the second branch 22 is fixedly connected to the first branch 21 side by side, the position of the connection point can affect the location where the tension is dispersed when the first branch 21 is subjected to axial tension. The number of connection points can affect the total amount of tension that is dispersed from the first branch 21 to the second branch 22. Specifically, the second branch 22 can be fixedly connected to the first parallel part 210 at least on the side closest to the first branch 21. Here, the second branch 22 is completely fixedly connected to the first parallel part 210 of the first branch 21. After the connection, when the first branch 21 is subjected to axial tension, the second branch 22 can disperse the tension of the first parallel part 210 to the second branch 22, thereby reducing the axial tension of the first branch 21 at least the first parallel part 210.

[0056] In other embodiments, please refer to Figure 12 This allows the second branch 22 to be fixedly connected to the distal portion 214 of the first parallel portion 210 at least on the side closest to the first branch 21. Here, the distal portion 214 of the first parallel portion 210 is the easily bendable position when the covered stent 100 is implanted into the bifurcation vessel. Therefore, by connecting the second branch 22 to the first branch 21 at the distal portion 214, the axial tension it receives can be dispersed to the second branch 22 at least at the distal portion 214 position, thereby reducing the axial tension at that position and thus at least reducing or preventing the second branch 22 from undergoing excessive covered extension at that position, which could lead to lumen occlusion after bending.

[0057] In this embodiment, the first branch 21 and the second branch 22 can be fixedly connected by the third covering film 222 and the first covering film 212, and / or by the second support frame 221 and the first support frame 211. When the third covering film 222 and the first covering film 212 are fixedly connected, they can be fixed by suturing with suture 224 or by adhesive bonding. By covering and fixing, when the first covering film 212 is subjected to axial tension, since it is connected to the other third covering film 222 in the radial direction, the third covering film 222 has a radial tension on it, thereby dispersing and offsetting the axial tension by the radial tension, thereby reducing the force on the first covering film 212 at the fixed connection position, and thus reducing the degree of film extension. When the second support frame 221 is fixedly connected to the first support frame 211, and the first branch 21 is about to undergo elongation and deformation of the first film 212 under axial tension, causing a change in the axial distance between the first support frames 211, the second support frame 221's radial fixing effect on the first support frame 211 restricts the axial displacement of the first support frame 211 to a certain extent, thereby limiting the axial elongation and deformation of the first film 212. Furthermore, the third film 222 can be fixedly connected to the first film 212 and the second support frame 221 can be fixedly connected to the first support frame 211 simultaneously. In this way, at least the side-by-side film and frame of the first branch 21 establish a stable fixed connection with the second branch 22, allowing the second branch 22 to maximize the dispersion and offset of the axial tension, reducing the degree of film elongation of the first side-by-side portion 210 of the first branch 21.

[0058] Please see here. Figure 13 When the second support frame 221 is fixedly connected to the first support frame 211, the first support frame 211 and the second support frame 221 can overlap each other on one side. After overlapping, they are fixedly connected by fitting together with a metal sleeve 225.

[0059] In another embodiment, please refer to Figure 14The side-by-side fixed connection between the second branch 22 and the first branch 21 can be achieved by adding an additional covering at their close-to-each position. Specifically, the branch segment 2 includes a thickened covering 3. The outer side of the close-to-each position of the first side-by-side portion 210 and the second branch 22 includes a bonding gap. The thickened covering 3 at least covers and fills the bonding gap. The thickened covering 3 can provide a connection relationship between the two branches at the connection position to disperse the axial tension of the first branch 21, while increasing the thickness of the covering at the connection position of the first branch 21 and the second branch 22, thereby enhancing the resistance of the first covering 212 to axial elongation deformation at this position. Furthermore, the thickened covering 3 can also fill the bonding gap to increase the contact area between the first branch 21 and the second branch 22 and the vessel wall after they are side-by-side fixedly connected, thereby enhancing the stability of the covered stent 100 after it is anchored to the vessel wall.

[0060] In another embodiment, please refer to Figure 15 Increasing the coating thickness and adding connectors can improve the axial elongation resistance of the first branch 21. However, this also results in the coating support 100 having a larger radial dimension when compressed radially at the location where the coating thickness and connectors are added. This may make it difficult to compress into the sheath. Therefore, to further address this issue, the second branch 22 and the first branch 21 can be connected side-by-side by integrally forming the first support frame 211 and the second support frame 221 of the first side-by-side portion 210 at their close proximity, and by integrally forming the first coating 212 and the third coating 222. Here, integrally forming the first support frame 211 and the second support frame 221 means forming them in one piece by weaving or cutting, without using stitches or metal sleeves. Integral forming of the first coating 212 and the third coating 222 means forming them as a single sheet of coating or by heat treatment. After forming, the first side-by-side portion 210 and the second branch 22 are formed with interconnected cavities. Here, the one-piece molded support frame and membrane, compared to two independently set supports, can at least reduce the size of the support frame and membrane located at the close-fitting position of the first parallel portion 210 and the second branch 22, thereby effectively reducing the volume after radial compression. Furthermore, the one-piece molded first support frame 211 and second support frame 221 have stronger overall integrity, and their mutual support and counteracting of radial tension are better. Specifically, the one-piece molded first parallel portion 210 and second branch 22 form a radial cross-section with a figure-eight shape, or an elliptical or sausage-shaped radial cross-section with a central cutout.

[0061] For further details, please refer to Figure 16 and Figure 17To ensure that the intermediate segment 2 provides better anchoring force for the small stent in the second branch 22 while providing better blood flow in the first parallel section 210, it should be understood that blood flow in the human body has blood pressure, and blood vessels are elastic, expanding and contracting with changes in blood pressure. Therefore, in the second branch 22 section where better anchoring force is desired, the second branch 22 can resist vascular dilation without radial size increase, thus ensuring long-term stability of the small stent anchorage. In the first parallel section 210 section where better blood flow is desired, the first parallel section 210 can expand or contract with changes in blood pressure and blood vessels, thus providing better blood flow. Specifically, the maximum expansion diameter r2 of the third covering 222 is less than or equal to the natural expansion diameter r1 of the second support frame 221, and the maximum expansion diameter R2 of the first covering 212 is greater than or equal to the natural expansion diameter R1 of the first support frame 211. Here, the second support frame 221 and the first support frame... The frame 211 provides radial support for the second branch 22 and the first parallel section 210 respectively. At the same time, since the wave coil structure itself is elastic and can be compressed or expanded, the coating covering the surface of the wave coil structure has low elasticity. Under the condition of reasonably setting the maximum expansion diameter, it can limit the further expansion of the wave coil structure. The maximum expansion diameter r2 of the third coating 222 covering the second support frame 221 and the maximum expansion diameter R2 of the first coating 212 covering the first support frame 211 are set to different sizes, so that the maximum expansion diameter r2 of the third coating 222 is less than or equal to the expansion diameter r1 of the second support frame 221 in its natural state. In this way, when the middle section 2 is implanted into the blood vessel and expands, after the second support frame 221 expands to the lumen size in its natural state, the third coating 222 expands to its maximum diameter. Thus, under the impact of blood flow, even if the second support frame 221 has a tendency to expand outward, it is restricted by the third coating 222 and cannot expand, thereby ensuring the stability of the second branch 22 anchoring the small stent 4. The maximum expansion diameter R3 of the first membrane 212 is greater than or equal to the natural expansion diameter R2 of the first support frame 211. This ensures that after the first support frame 211 expands to its natural lumen, the first membrane 212 is not fully expanded. This allows the first support frame 211 to better adapt to the shape of the blood vessel as it expands and contracts with the pulsation of the blood vessel, thus enabling smoother blood flow. Through the above structural design, even a one-piece continuously formed support wave coil, after forming the second branch 22 and the first parallel portion 210, exhibits completely different characteristics due to the different restrictions imposed on the two channels by the membrane. At the same time, the pleated structure of the third membrane can also resist axial tensile stretching to a certain extent.

[0062] In this embodiment, after the intermediate segment 2 with different maximum expansion diameters of the coating is formed, in the natural state of the coating support 100, on the outer surface of the intermediate segment 2, the third coating 222 on the second branch 22 has a relatively smooth coating surface, while the first coating 212 on the first parallel portion 210 forms an uneven surface with more wrinkles. Here, since the maximum expansion diameter of the third coating 222 is greater than the expansion diameter of the second support frame 221 in the natural state, the first corrugated portion 2530 of the second branch 22 is in a compressed and taut state. Therefore, in the natural state of the coating support 100, when the second branch 22 is expanded from the inner cavity of the second branch 22, no significant radial expansion of the channel size occurs. However, when the first parallel portion 210 is expanded from the inner cavity of the first parallel portion 210, a more significant radial expansion of the channel size can be observed.

[0063] In this embodiment, please refer to Figure 18 The parallel fixed connection between the second branch 22 and the first branch 21 can also be achieved by setting a figure-eight shaped developing ring 226 at the distal end of the first parallel portion 210 of the first branch 21 and the distal end of the second branch 22. The developing ring 226 can be connected to the coating by stitching. After connection, at least the distal end of the first parallel portion of the first branch 21 and the second branch 22 are connected. When subjected to axial tension, the tension at least at this position is partially dispersed radially to the second branch 22, thereby dispersing the tension and reducing the tension on the first coating 212, thus reducing the coating stretching.

[0064] Example 3:

[0065] In this embodiment, please refer to Figure 19 and Figure 20The structural configuration of the main body segment 1, the first branch 21, and the second branch 22 is largely the same as in Embodiments 1 and 2. The difference lies in the fact that, because the first branch 21 has a longer axial length, when the covered stent 100 is compressed and pulled into the sheath distally, the covered stent 100 is typically pulled by the distal side of the first branch 21. Here, the entire first branch 21 is subjected to axial tension, resulting in covered stent stretching deformation, which becomes more pronounced from the proximal side to the distal side. When the covered stent 100 of this application is applied to the iliac bifurcation vessel, the first branch 21 is usually located within the external iliac vessel. The long-term patency of the external iliac vessel is crucial for the entire iliac bifurcation vessel; therefore, the lumen size of the entire first branch 21 is optimized. Stability is essential. Here, a first connecting rod 4 is provided on the first branch 21. The first connecting rod 4 extends from the proximal end to the distal end along the axial direction of the first branch 21 and is fixedly connected to the first support frame 211 and / or the first membrane 212. The first connecting rod 4 can be connected to the first membrane 212 or the first support frame 211. After connection, the first connecting rod 4 can act like a keel to connect the first membranes 212 of the entire first branch 21 together. The first connecting rod 4 can be set as a metal wire or polymer wire with stiffness or tensile strength much greater than that of the first membrane 212, so that when the first branch 21 is subjected to axial tension, it can effectively resist axial tension and minimize or avoid the occurrence of axial extension of the first membrane 212. In one embodiment, the first connecting rod 4 can be connected to both the first membrane 212 and the first support frame 211 simultaneously. Specifically, the first connecting rod 4 can be axially connected to the first metal frame by welding or by metal sleeve connection. Here, the first membrane 212 adopts a double-layer structure with an inner membrane and an outer membrane formed by heat treatment. After connection, the first connecting rod 4 is embedded between the inner and outer membranes of the first membrane 212 and connected to the first membrane 212. In this way, the first connecting rod 4 connects the first membrane 212 and the first support frame 211 simultaneously, which can limit the axial displacement between the first support frames 211 and prevent the extension of the first membrane 212, thus better reducing the occurrence of extension.

[0066] Furthermore, in order to minimize the impact of the first connecting rod 4 on the radial dimension of the first branch 21 after compression, the radial dimension L3 of the first connecting rod 4 on the distal side can be greater than or equal to the radial dimension L4 on the proximal side. Here, it can be understood that the first film 212 on the distal side is the area where film stretching is most severe when under tension, and it gradually weakens towards the proximal side. Therefore, according to the characteristics of this stretching, the first connecting rod 4 with different radial dimensions can be set along the axial direction to make reasonable use of the increased number of connecting rods to prevent the increase of radial dimension in solving the stretching problem. Therefore, the first connecting rod 4 with a smaller radial dimension L4 is used in the proximal side area where the stretching is relatively mild, while the first connecting rod 4 with a larger radial dimension L3 is used in the distal side area where the stretching is more severe. This can achieve the same anti-stretching effect in the axial direction while minimizing the increase of radial dimension of the first branch 21 after compression.

[0067] In this embodiment, please refer to Figure 20 When the PTFE-coated support 100 is subjected to axial tension, the axial elongation of the coating occurs along the entire length of the support 100 subjected to the tensile force. Therefore, the main body segment 1 of the support 100 is also affected by the elongation of the coating. Thus, a second connecting rod 5 can be provided in the main body segment 1 to limit the occurrence of axial elongation. Specifically, the main body segment 1 includes an axially arranged main support frame 11 and a main coating 12. The second connecting rod 5 extends axially from the proximal end to the distal end of the main body segment 1, and connects with the first connecting rod 4 in the first... The same setting method is used for branch 21. The second connecting rod 5 can be connected to the main body film 12 or to the first support frame 211. After connection, the second connecting rod 5 can play a role similar to a keel to connect the main body film 12 of the entire main body segment 1 together. The second connecting rod 5 can be set as a metal wire or polymer wire with stiffness or tensile strength greater than the main body film 12 and less than the first connecting rod 4. In this way, when the main body segment 1 is subjected to axial tension, it can resist the axial tension well and reduce or avoid the occurrence of axial extension of the main body film 12 as much as possible. In one embodiment, the second connecting rod 5 can be connected to both the main body film 12 and the first support frame 211 simultaneously. Specifically, the second connecting rod 5 can be axially connected to the first metal frame by welding or by metal sleeve connection. Here, the main body film 12 adopts a double-layer structure with an inner film and an outer film formed by heat treatment. After connection, the second connecting rod 5 is embedded between the inner and outer films of the main body film 12 and connected to the main body film 12. In this way, the second connecting rod 5 connects the main body film 12 and the first support frame 211 simultaneously, which can limit the axial displacement of the first support frame 211 while avoiding the extension of the main body film 12, thus better reducing the occurrence of extension.

[0068] In this embodiment, since the extension of the main body segment 1 is usually less severe than that of the first branch 21, the degree of film extension that the second connecting rod 5 needs to resist is less than that that the first connecting rod 4 needs to resist. Therefore, the radial dimension L5 of the second connecting rod 5 can be smaller than the radial dimension L3 of the first connecting rod 4, so as to resist the film extension while minimizing the increase in radial compression dimension.

[0069] In one embodiment, the first connecting rod 4 can be configured as a multi-strand metal filament, while the second connecting rod can be configured as a polymer thread. The diameter of the multi-strand metal filament of the first connecting rod 4 is smaller than the diameter of a single skeleton of the first support skeleton 211. Simultaneously, the number of multi-strand metal filaments on the proximal side of the first connecting rod 4 can be reduced by the number of multi-strand metal filaments on the distal side, thereby achieving a change in the radial dimension of the first connecting rod 4. Furthermore, the radial dimension L5 of the second connecting rod 5 can be smaller than the minimum radial dimension L4 of the first connecting rod 4 on the proximal side.

[0070] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A covered stent, characterized in that, The device includes a main body segment with a tubular body and branch segments. The branch segments include a first branch and a second branch. The axial length of the first branch is greater than or equal to the axial length of the second branch. The first branch includes a first parallel portion that can be placed alongside the second branch. The first parallel portion includes a proximal portion located on the proximal side and a distal portion located on the distal side along the axial direction. In the first branch, at least the axial deformation resistance of the distal portion is greater than or equal to the axial deformation resistance of the proximal portion.

2. The covered stent according to claim 1, characterized in that, The first branch includes an axially arranged first support frame and a first covering film, wherein the radial thickness of the first covering film at the proximal portion is less than or equal to the radial thickness of the first covering film at the distal portion.

3. The covered stent according to claim 2, characterized in that, The first support frame includes a plurality of first corrugated coils, which are spaced apart along the axial direction. The film-coated bracket includes an axial connector, which connects at least two axially adjacent first corrugated coils located at the distal portion.

4. The covered stent according to claim 1, characterized in that, The outer surface of the first side-by-side portion is covered with a second film, and the second film has a greater resistance to deformation than the first film.

5. The covered stent according to any one of claims 1-4, characterized in that, The second branch is fixedly connected to the first parallel part after being placed side by side, and the axial deformation resistance of the second branch is greater than that of the first parallel part.

6. The covered stent according to claim 5, characterized in that, The second branch is fixedly connected to the first parallel portion at least to the side closest to the first branch, or the second branch is fixedly connected to the distal portion at least to the side closest to the first branch.

7. The covered stent according to claim 6, characterized in that, The second branch includes a second support frame and a third covering film arranged along the axial direction, wherein the third covering film is fixedly connected to the first covering film and / or the second support frame is fixedly connected to the first support frame.

8. The covered stent according to claim 7, characterized in that, The first and second support frames of the first side-by-side portion are integrally formed, and the first and third films are integrally formed, so that the inner cavity of the first side-by-side portion is connected to the inner cavity of the second branch.

9. The covered stent according to claim 1, characterized in that, The branch segment includes a thickened film, and the outer side of the first side-by-side portion and the second branch close to each other includes a bonding gap, and the thickened film at least covers and fills the bonding gap.

10. The covered stent according to claim 1, characterized in that, The first branch includes a first connecting rod that extends from the proximal side to the distal side along the axial direction of the first branch and is fixedly connected to the first support frame and / or the first covering film; the radial dimension of the first connecting rod on the distal side is greater than or equal to the radial dimension on the proximal side.

11. The covered stent according to claim 10, characterized in that, The main body segment includes an axially arranged main support frame, a main body membrane, and a second connecting rod. The second connecting rod extends from the proximal end to the distal end along the axial direction of the main body segment and is fixedly connected to the main support frame and / or the main body membrane. The radial dimension of the second connecting rod is less than or equal to the minimum radial dimension of the first connecting rod.

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