stent

Abstract

Provide is a stent having a two-layer structure capable of appropriately expanding a biological lumen even when the relative position in the circumferential direction between an outer stent body and an inner stent body has shifted.　A stent 1 comprises: an outer stent body 10 in which a plurality of outer cells 12 are arranged in the circumferential direction OD and are continuous in the central axis direction LD; and an inner stent body 20 in which a plurality of inner cells 22 are arranged in the circumferential direction and are continuous in the central axis direction LD, the inner stent body 20 being inserted into the outer stent body 10 at least in a region for expanding a biological lumen. The stent 1 has a same shape region A in which cells having the same shape when viewed from the radial direction among the outer cells 12 and the inner cells 22 are arranged adjacent to each other. The same shape region A includes a region in which outer overlapping portions 14 and inner overlapping portions 24 are arranged with the relative positions thereof has shifted in the axial direction of the stent 1.

Description

stents

[0001] The present disclosure relates to stents.

[0002] 2. Description of the Related Art Catheter therapy is known in the art, in which a stent is deployed at a lesion site in a blood vessel lumen.

[0003] However, in conventional single-layer stents such as those disclosed in Patent Document 1, the surface area in contact with the blood vessel lumen is small, so increasing the expansion force of the stent increases the pressure with which the stent presses against the blood vessel lumen, increasing the risk of blood vessel damage.

[0004] Furthermore, a stent having an outer stent body and an inner stent body inserted into the outer stent body (hereinafter also referred to as a two-layer structure stent) has been disclosed as a stent with a larger surface area and excellent shape-following properties to the vascular structure and diameter reduction properties (see Patent Document 2).

[0005] A conventional two-layer stent such as that disclosed in Patent Document 2 has a larger surface area in contact with the blood vessel lumen than a single-layer stent, making it possible to reduce the risk of blood vessel damage even if the stent's expansion force is increased. In the conventional two-layer stent disclosed in Patent Document 2, the region in which cells of the same shape are located on the inner and outer stent bodies accounts for the majority of the region in which blood vessels or the like are expanded. These cells of the same shape are staggered in the circumferential direction, thereby increasing the surface area in contact with the inner wall of the blood vessel.

[0006] U.S. Patent No. 10,390,982 International Publication No. 2022 / 085313

[0007] However, if the relative circumferential positions of the outer stent body and the inner stent body are misaligned, causing the outer cells and the inner cells to overlap at approximately the same position, the opening area of ​​the mesh formed by the outer stent body and the inner stent body will become larger, causing the inner wall of the blood vessel to protrude into the stent and the stent body to become embedded in the inner wall of the blood vessel, which could prevent the blood vessel from being sufficiently expanded.

[0008] The object of the present disclosure is to provide a two-layer stent that can appropriately expand a biological lumen even if the relative circumferential positions of the outer stent body and the inner stent body are misaligned.

[0009] The present disclosure solves the above-mentioned problems by the following means: For ease of understanding, the following description will be given with reference numerals corresponding to the embodiments of the present disclosure, but the present disclosure is not limited to these.

[0010] The first disclosure relates to a stent (1) that is inserted into a catheter, and is taken out of the catheter in a biological lumen to be used for expanding the biological lumen, and includes an outer stent body (10) in which a plurality of outer cells (12) surrounded by outer struts (11) and outer overlapping portions (14) where the outer struts (11) cross are arranged in the circumferential direction and are continuous in the central axis direction, and a plurality of inner cells (22) surrounded by inner struts (21) and inner overlapping portions (24) where the inner struts (21) cross are arranged in the circumferential direction. and an inner stent body (20) that is inserted into the outer stent body (10) at least in a region that expands a biological lumen, the outer cells (12) and the inner cells (22) having a uniform shape region (A) in which cells of the same shape are arranged adjacent to each other when viewed from the radial direction, and the uniform shape region (A) has a region in which the relative positions of the outer overlapping portion (14) and the inner overlapping portion (24) are shifted in the axial direction of the stent (1).

[0011] The second disclosure is a stent (1) according to the first disclosure, wherein the outer overlapping portion (14) and the inner overlapping portion (24) within the identical shape region (A) are arranged with a shift of half a period of the arrangement period in which the outer cells (12) and the inner cells (22) are arranged in the circumferential direction when viewed from the radial direction.

[0012] A third disclosure is a stent (1) according to the first or second disclosure, wherein the outer overlapping portion (14) and the inner overlapping portion (24) within the identically shaped region (A) are arranged such that the axial position and the circumferential position of the stent (1) in the outer cell (12) and the inner cell (22) are shifted, respectively.

[0013] The fourth disclosure is a method for expanding a biological organ having a luminal structure using a stent (1), the stent (1) comprising: an outer stent body (10) in which a plurality of outer cells (12) surrounded by outer struts (11) and outer overlapping portions (14) where the outer struts (11) intersect are arranged in the circumferential direction and are continuous in the central axis direction; and an inner stent body (20) in which a plurality of inner cells (22) surrounded by inner struts (21) and inner overlapping portions (24) where the inner struts (21) intersect are arranged in the circumferential direction and are continuous in the central axis direction, the inner stent body (20) being inserted into the outer stent body (10) at least in a region where the biological lumen is to be expanded, and the outer cells (12) and the inner cells (22) are contiguous when viewed in the radial direction. The stent (1) has a uniformly shaped region (A) in which cells of one shape are arranged adjacently, and in the uniformly shaped region (A), there is a region in which the relative positions of the outer overlapping portion (14) and the inner overlapping portion (24) are shifted in the axial direction of the stent (1). The method includes: delivering the stent (1, 1B) housed in a catheter (50) in a reduced diameter state together with the catheter (50) through a biological organ to a planned position in the biological organ where it will be expanded; withdrawing the catheter (50) proximally and starting to expand the stent (1, 1B) from the distal side; completing the expansion of the stent (1, 1B); and re-accommodating the expanded stent (1, 1B) into the catheter (50).

[0014] According to the present disclosure, it is possible to provide a two-layer stent that can appropriately expand a biological lumen even if the relative circumferential positions of the outer stent body and the inner stent body are misaligned.

[0015] FIG. 1 is a side view of a stent 1 of a first embodiment. FIG. 2 is a virtual development view of a portion of an outer stent body 10 of the first embodiment. FIG. 3 is a virtual development view of a portion of an inner stent body 20 of the first embodiment. FIG. 4 is a virtual development view of a portion of a stent 1 of the first embodiment, with the relative circumferential positions of the outer stent body 10 and the inner stent body 20 at the target design positions. FIG. 5 is a virtual development view of a portion of a stent 1 of the first embodiment, with the relative circumferential positions of the outer stent body 10 and the inner stent body 20 deviated from the target design positions. FIG. 6 is a diagram illustrating the outer diameter D1 of a single outer stent body 10. FIG. 7 is a diagram illustrating the outer diameter D2 of a single inner stent body 20. FIG. 8 is a diagram illustrating the process of inserting the inner stent body 20 into the outer stent body 10. FIG. 9 is a virtual development view of a portion of a stent 1 of a second embodiment, with the relative circumferential positions of the outer stent body 10 and the inner stent body 20 at the target design positions. Fig. 1 is a virtual development view of a portion of the stent 1 of the second embodiment in a state where the relative circumferential positions of the outer stent body 10 and the inner stent body 20 are deviated from the intended design positions. Fig. 2 is a schematic diagram showing the procedure for dilating a stenotic site in a blood vessel using the stent 1. Fig. 3 is a schematic diagram showing the procedure for dilating a stenotic site in a blood vessel using the stent 1. Fig. 4 is a schematic diagram showing the procedure for dilating a stenotic site in a blood vessel using the stent 1. Fig. 5 is a schematic diagram showing the procedure for dilating a stenotic site in a blood vessel using the stent 1.

[0016] Hereinafter, an embodiment of a stent according to the present invention will be described. Note that the drawings attached to this specification are all schematic diagrams, and the shape, scale, aspect ratio, etc. may be modified or exaggerated from the actual product. Furthermore, hatching indicating the cross section of a component may be omitted as appropriate in the drawings.

[0017] In this specification, terms specifying the shape, geometric conditions, and the degree of these, such as "orthogonal" and "direction," include not only the strict meaning of the terms but also the range in which they can be considered to be nearly orthogonal or the range in which they can be considered to be roughly in that direction. In this specification, the axial direction (longitudinal direction) LD refers to the side closer to the practitioner (proximal) as the LD1 side (or proximal LD1 side), and the side farther from the practitioner as the LD2 side (or distal LD2 side), and the direction orthogonal to the axial direction LD is referred to as the radial direction RD. Also, in this specification, the direction in which the cells are arranged is referred to as the circumferential direction OD.

[0018] (First embodiment) Fig. 1 is a side view of a stent 1 of a first embodiment. Fig. 2A is a virtual developed view of a portion of an outer stent body 10 of the first embodiment. Fig. 2B is a virtual developed view of a portion of an inner stent body 20 of the first embodiment. Fig. 2C is a virtual developed view of a portion of the stent 1 of the first embodiment in a state where the relative circumferential positions of the outer stent body 10 and the inner stent body 20 are at the design target positions.

[0019] In the drawings showing the first embodiment and other embodiments, to easily distinguish between the outer stent body 10 and the inner stent body 20, the struts of the outer stent body 10 are shown in black, and the struts of the inner stent body 20 are shown in white. Furthermore, in this specification and the like, a "cell" refers to a portion surrounded by strut material (struts) that forms the stent. The "cells" may have the same shape and size as each other, or they may differ. A "strut" refers to a portion made of the wire-like material. In this specification and the like, the opening of a cell is also referred to as an "opening portion," and the portion where struts of adjacent cells are connected or overlapped is also referred to as an "overlapping portion."

[0020] The stent 1 of the first embodiment can be used, for example, to dilate a narrowed or blocked blood vessel by being housed in a catheter and being pushed out of the catheter in the lumen of the blood vessel to expand its diameter. The stent 1 is used in applications where it is temporarily placed in the blood vessel and then retrieved from the body, but it can also be used in applications where it is left in the blood vessel without being retrieved from the body. When used in such applications, it is preferable that the wire 2 and the stent 1 can be separated by an operator's operation.

[0021] Stent 1 is configured to have a substantially cylindrical shape when extruded from the catheter and expanded in its free state (see Figures 4A and 4B described below). Although not shown, stent 1 has an elongated cylindrical shape when contracted. Furthermore, a wire 2 is connected to the end of stent 1 on the proximal LD1 side. The method for connecting the proximal end of stent 1 to wire 2 is not particularly limited as long as it is a connection method used in general medical devices, and examples include welding, UV bonding, and infiltration with silver solder.

[0022] The practitioner advances or retreats the stent 1 within the catheter or blood vessel by pushing or pulling the wire 2 via an ex vivo operating unit (not shown) connected to the proximal LD1 side of the wire 2. The practitioner can also extend the stent 1 out of the catheter and expand its diameter, or retract it into the catheter, by pulling (retreating) or pushing (advancing) the catheter without moving the wire 2 (stent 1).

[0023] The stent 1 comprises an outer stent body 10 and an inner stent body 20, which are substantially cylindrical structures. The stent 1 is a two-layer structure (two-layer structure) in which the inner stent body 20 is inserted into the outer stent body 10 at least in the region that dilates the narrowed portion of the biological lumen. Here, the region that dilates the narrowed portion of the biological lumen refers to the region that substantially contributes to dilating the narrowed portion during use, and in the case of the stent 1 of this embodiment, it refers to the region that is expanded into a substantially cylindrical shape in the expanded state shown in Fig. 1 . The above-mentioned "at least" means that the inner stent body 20 must be inserted into the outer stent body 10 in the region that dilates the narrowed portion. The range in which the inner stent body 20 is inserted into the outer stent body 10 is not limited to the region that substantially expands the narrowed area described above (in this embodiment, the region that expands into an approximately cylindrical shape), and in this embodiment, the inner stent body 20 is inserted into the outer stent body 10 up to the point where it is connected to the wire 2.

[0024] Furthermore, the statement that the inner stent body 20 is disposed inside (or inserted inside) the outer stent body 10 does not mean that the inner stent body 20 is completely inside the outer stent body 10 at all positions of the stent. That is, even in a region where the inner stent body 20 is disposed inside (internalized inside) the outer stent body 10, a portion of the inner stent body 20 may be radially outer than the inner surface of the outer stent body 10 or outer than the surface (outer surface) of the outer stent body 10. As will be described later, in this embodiment, a portion of the inner stent body 20 is intentionally configured to be radially outer than the inner surface of the outer stent body 10 or outer than the surface (outer surface) of the outer stent body 10. Note that, similar to the above, a portion of the outer stent body 10 may be radially inner than the surface (outer surface) of the inner stent body 20.

[0025] The outer stent body 10 and the inner stent body 20 are not connected to each other in the radial direction. Specifically, the outer stent body 10 and the inner stent body 20 are indirectly connected via the wire 2, but are not connected in other regions. Therefore, the outer stent body 10 and the inner stent body 20 can flexibly deform independently. Furthermore, even in the expanded diameter state, the outer stent body 10 and the inner stent body 20 are merely in close contact with each other in the radial direction and are not linked (connected) together in the radial direction. Therefore, the outer stent body 10 and the inner stent body 20 are independently deformable and do not restrict each other's deformation.

[0026] The proximal LD1 side of the outer stent body 10, the proximal LD1 side of the inner stent body 20, and the distal LD2 side of the wire 2 are directly connected. Here, "directly connected" means, for example, that the proximal LD1 side of the outer stent body 10 is connected to the distal LD2 side of the wire 2, and that the proximal LD1 side of the inner stent body 20 is connected to the distal LD2 side of the wire 2. In this case, the position where the proximal LD1 side of the outer stent body 10 is connected to the wire 2 and the position where the proximal LD1 side of the inner stent body 20 is connected to the wire 2 may be the same as or different from each other.

[0027] The proximal LD1 side of the outer stent body 10, the proximal LD1 side of the inner stent body 20, and the distal LD2 side of the wire 2 may be indirectly connected. Here, "indirectly connected" refers to, for example, a configuration in which the proximal LD1 side of the outer stent body 10 is connected to the distal LD2 side of the wire 2, and the proximal LD1 side of the outer stent body 10 is connected to the proximal LD1 side of the inner stent body 20 (or a configuration in which the connections between the two stent bodies are reversed). In this case, the proximal LD1 side of the inner stent body 20 is indirectly connected to the wire 2 via the proximal LD1 side of the outer stent body 10. Alternatively, the proximal LD1 side of the outer stent body 10 and the proximal LD1 side of the inner stent body 20 are connected via a pipe-shaped sleeve (not shown) fitted onto the distal LD2 side of the wire 2. In this case, the proximal LD1 side of the outer stent body 10 and the proximal LD1 side of the inner stent body 20 are indirectly connected to the distal LD2 side of the wire 2 via the sleeve. Thus, in this specification, "indirectly connected" includes a configuration in which one of the proximal LD1 side of the outer stent body 10 or the proximal LD1 side of the inner stent body 20 is directly connected to the wire 2, and the other stent body is indirectly connected to the wire 2 via the directly connected stent body. Methods for connecting the proximal end of each stent body to the wire 2 include, for example, welding, UV bonding, impregnation with silver solder, etc., but are not particularly limited as long as they are connection methods used in general medical devices.

[0028] As will be described later, the stent 1 of the first embodiment is produced by inserting an inner stent body 20, which has an outer diameter larger than that of the outer stent body 10 in its natural state, into the outer stent body 10 in a contracted state. The inner stent body 20 constantly presses the outer stent body 10 outward in the radial direction RD, bringing the outer stent body 10 and the inner stent body 20 into close contact. Furthermore, as will be described later, in an expanded diameter state, a portion of the inner stent body 20 can be located radially outside the inner surface of the outer stent body 10.

[0029] As shown in Fig. 1, the proximal ends LD1 of the outer stent body 10 and the inner stent body 20 are tapered and connected to a wire 2. This restricts the inner stent body 20 from moving in the axial direction relative to the outer stent body 10.

[0030] The stent 1 is equipped with markers, including a first wire marker portion 31, a second wire marker portion 32, an outer stent marker portion 111, and an inner stent marker portion 121. These markers are components that serve as landmarks for confirming the position and state of the stent 1 under radiographic observation within a tubular organ such as a blood vessel, and are formed from a material that is highly radiopaque (highly contrast-enhancing). Here, radiopaque refers to a material that is more radiopaque than portions of the stent 1 other than the markers (other portions that do not have radiopaque properties) under radiographic observation during a procedure, and is radiopaque to the extent that the markers can be observed as an image. "Radiopaque" is necessary to obtain "visibility" and "contrast" under radiographic observation.

[0031] Highly radiopaque materials that can be used as markers may be metals or synthetic resins. Examples of metal materials include gold, tantalum, platinum, tungsten, iridium, platinum tungsten, etc., and alloys thereof. Other examples include radiopaque polymer materials to which a radiopaque filler or the like has been added. When the marker is configured as a linear member, for example, a composite wire having a core material made of the aforementioned metal material coaxially within a nickel-titanium wire can be used.

[0032] Furthermore, as a method for attaching the marker to the stent 1, any processing method that has been conventionally used to place a marker on a known stent can be used as appropriate, such as soldering laser welding of gold-tin or silver-tin, mechanical crimping, or adhesive bonding with resin.

[0033] The first wire marker portion 31 is a coil marker made of a wire-shaped member formed into a coil from a highly radiopaque material, and is welded and fixed in a position covering the end of the proximal LD1 side of the outer strut 11. The second wire marker portion 32 is a ring marker made of a tubular marker component formed from a highly radiopaque material and fixed to the strut by soldering, and is fixed in a position covering the end of the proximal LD1 side of the inner stent body 20 by soldering. The outer stent marker portion 111 is a crimped marker formed in a generally square pipe shape and fixed by crimping to the end of the distal LD2 side of the first stent body 10. The inner stent marker portion 121 is a crimped marker formed in a generally square pipe shape and fixed by crimping to the end of the distal LD2 side of the second stent body 20 in a similar form to the outer stent marker portion 111. In addition, the first wire marker portion 31, the second wire marker portion 32, the outer stent marker portion 111, and the inner stent marker portion 121 in this embodiment are examples of some of the specific forms of the markers, and their locations and numbers can be changed as appropriate.

[0034] As shown in FIG. 2A , the outer stent body 10 has a plurality of outer cells 12 arranged in the circumferential direction OD, each of which is made up of outer struts 11 arranged to surround a region in a generally diamond shape, excluding the proximal LD1 side and the distal LD2 side. In the outer stent body 10, the outer cells 12 arranged in the circumferential direction OD are also arranged in the axial direction LD. That is, the outer stent body 10 has a mesh pattern in which the outer cells 12 are arranged in the circumferential direction OD and the axial direction LD. Openings 13 are formed in the outer cells 12. Furthermore, adjacent outer cells 12 in the circumferential direction OD are connected at outer overlapping portions 14. As described above, the proximal LD1 side of the outer stent body 10 gradually converges toward the wire 2 side and is connected to the wire 2. In this embodiment, the distal LD2 side of the outer stent body 10 converges at two outer stent marker portions 111.

[0035] The outer overlapping portion 14 is a portion where the outer struts 11 of four adjacent outer cells 12 are connected. The outer overlapping portion 14 has a generally rectangular shape that is elongated in the axial direction LD. Each outer strut 11 is connected to one of the four corners of the outer overlapping portion 14. Each outer strut 11 has a curved portion 15 formed at the portion where it is connected to the outer overlapping portion 14. Therefore, when the expanded stent 1 is bent into a generally U-shape, each outer strut 11 connected to the outer overlapping portion 14 can be deformed independently. This allows the outer cells 12 arranged in the circumferential direction OD to bend more flexibly. In this way, the outer stent body 10 allows the outer cells 12 arranged in the circumferential direction OD to bend flexibly, thereby providing excellent shape conformability and diameter reduction properties.

[0036] As shown in FIG. 2B , the inner stent body 20 has a plurality of inner cells 22 arranged in the circumferential direction OD, each of which is made up of inner struts 21 arranged to surround a region in a generally diamond shape, excluding the proximal LD1 side and the distal LD2 side. In the inner stent body 20, the inner cells 22 arranged in the circumferential direction OD are also arranged in the axial direction LD. That is, the inner stent body 20 has a mesh pattern in which the inner cells 22 are arranged in the circumferential direction OD and the axial direction LD. Openings 23 are formed in the inner cells 22. Furthermore, adjacent inner cells 22 in the circumferential direction OD are connected at inner overlapping portions 24. As described above, the proximal LD1 side of the inner stent body 20 gradually converges toward the wire 2 and is connected to the wire 2. In this embodiment, the distal LD2 side of the inner stent body 20 converges at two inner stent markers 121.

[0037] The inner overlapping portion 24 is a portion where the inner struts 21 of four adjacent inner cells 22 are connected. The inner overlapping portion 24 has a generally rectangular shape that is elongated in the axial direction LD. Each inner strut 21 is connected to one of the four corners of the inner overlapping portion 24. Each inner strut 21 has a curved portion 25 formed at the portion where it connects to the inner overlapping portion 24. Therefore, when the expanded stent 1 is bent into a generally U-shape, each inner strut 21 connected to the inner overlapping portion 24 can be deformed independently. This allows the inner cells 22 arranged in the circumferential direction OD to bend more flexibly. In this way, the inner stent body 20 allows the inner cells 22 arranged in the circumferential direction OD to bend flexibly, thereby providing excellent shape conformability and diameter reduction properties.

[0038] As shown in Fig. 2C, the stent 1 of the first embodiment has an identical shape region A in which the outer cells 12 and the inner cells 22 are arranged adjacent to each other and have the same shape (same size and shape) when viewed from the radial direction, excluding the proximal LD1 side and the distal LD2 side. That is, the mesh pattern of the outer stent body 10 shown in Fig. 2A and the mesh pattern of the inner stent body 20 shown in Fig. 2B are substantially the same pattern within the same shape region A, excluding the proximal LD1 side and the distal LD2 side. Here, cells of the same shape (same size and shape) mean substantially the same pattern, and are considered to have the same shape even if there are manufacturing errors or minor differences in size or shape.

[0039] As shown in Figure 2C, in the stent 1, the outer stent body 10 and the inner stent body 20 are overlapped such that the inner overlapping portions 24 of the inner cells 22 (inner stent body 20) are disposed in the openings 13 of the outer cells 12 (outer stent body 10). Specifically, in the identical shape region A, the inner overlapping portions 24 of the inner cells 22 are disposed in the openings 13 of the outer cells 12, and the outer overlapping portions 14 of the outer cells 12 are disposed in the openings 23 of the inner cells 22. The outer overlapping portions 14 and the inner overlapping portions 24 within the identical shape region A are offset by half a period of the arrangement period of the outer cells 12 and the inner cells 22 in the circumferential direction OD when viewed from the radial direction. Therefore, the inner overlapping portions 24 complement the openings 13 of the outer cells 12, and the outer overlapping portions 14 complement the openings 23 of the inner cells 22. Four outer struts 11 and four inner struts 21 are gathered in each of the outer overlapping portion 14 and the inner overlapping portion 24. Therefore, the above arrangement allows the struts 21 and struts 11 to abut against the inner wall of the blood vessel, also in the opening portion 13 and the opening portion 23. Here, the arrangement period at which the outer cells 12 and the inner cells 22 are arranged in the circumferential direction OD corresponds to the width of one cell (outer cell 12 or inner cell 22) in the circumferential direction OD.

[0040] In the identical shape region A, the outer overlapping portion 14 of the outer cell 12 and the inner overlapping portion 24 of the inner cell 22 are arranged so that their relative positions are offset in the axial direction LD of the stent 1. In other words, the inner overlapping portion 24 is arranged so as not to overlap on a virtual straight line V drawn from the outer overlapping portion 14 in the circumferential direction OD.

[0041] Fig. 3 is a virtual planar development view of a portion of the stent 1 of the first embodiment, in which the relative circumferential positions of the outer stent body 10 and the inner stent body 20 are displaced from their intended positions. The example shown in Fig. 3 illustrates a case in which the relative circumferential positions of the outer stent body 10 and the inner stent body 20 are displaced to the point where the outer overlapping portion 14 and the inner overlapping portion 24 are closest to each other. The amount of displacement in Fig. 3 corresponds to half the period of the arrangement of the outer cells 12 and the inner cells 22 in the circumferential direction OD. As shown in Fig. 3, in the stent 1 of this embodiment, even if there is an identical-shape region A in which the outer cells 12 and the inner cells 22 have substantially the same shape, they do not completely overlap when the relative circumferential positions of the outer stent body 10 and the inner stent body 20 are displaced. Therefore, the opening area of ​​the mesh formed by the outer stent body 10 and the inner stent body 20 can be prevented from increasing, thereby enabling appropriate expansion of the biological lumen. Furthermore, both the outer struts 11 and the inner struts 21 can come into contact with the inner wall of a biological lumen, such as the inner wall of a blood vessel, preventing an extreme increase in expansion pressure when the stent 1 expands the inner wall of a blood vessel, etc. Therefore, the stent 1 is highly safe even if the relative circumferential positions of the outer stent body 10 and the inner stent body 20 are misaligned, because the outer overlapping portion 14 and the inner overlapping portion 24 are arranged with a deviation in the axial direction LD.

[0042] Furthermore, the outer overlapping portion 14 and the inner overlapping portion 24 are arranged with a shift of half a period of the arrangement period of the outer cells 12 and the inner cells 22 in the circumferential direction OD, as viewed from the radial direction. Therefore, the amount of shift in the circumferential direction OD up to the position where the outer overlapping portion 14 and the inner overlapping portion 24 are closest to each other, as shown in Figure 3, can be made equal in both directions in the circumferential direction OD, resulting in an ideal arrangement with respect to relative positional shifts in the circumferential direction between the outer stent body 10 and the inner stent body 20, which are difficult to predict.

[0043] Furthermore, because the outer overlapping portion 14 and the inner overlapping portion 24 are wider than the outer struts 11 and the inner struts 21, the outer diameter of the stent 1 in its most contracted state is determined by the outer diameter at the locations of the outer overlapping portion 14 and the inner overlapping portion 24. In the stent 1 of this embodiment, the outer overlapping portion 14 and the inner overlapping portion 24 are arranged with a relative offset in the axial direction LD of the stent 1, so the outer overlapping portion 14 and the inner overlapping portion 24 do not overlap at the same position when contracted. Therefore, the stent 1 of this embodiment can have a smaller outer diameter in its most contracted state than a conventional stent in which the outer overlapping portion 14 and the inner overlapping portion 24 overlap at the same position when contracted, and is therefore more easily accommodated in a catheter or the like.

[0044] Furthermore, the outer overlapping portion 14 and the inner overlapping portion 24 are wider than the outer struts 11 and the inner struts 21, and therefore have higher rigidity than the outer struts 11 and the inner struts 21 compared to other portions. Therefore, if the outer overlapping portion 14 and the inner overlapping portion 24 were positioned so as to overlap in the axial direction LD, the stiffness would be locally increased, deteriorating the overall flexibility of the stent 1 and potentially making it difficult for the stent 1 to pass through curved sections of a blood vessel or the like when delivered using a catheter. However, in the stent 1 of this embodiment, the outer overlapping portion 14 and the inner overlapping portion 24 are positioned so as to be offset relative to each other in the axial direction LD of the stent 1, preventing localized increases in stiffness, improving the overall flexibility of the stent 1 and resulting in excellent shape-following ability.

[0045] Furthermore, overlapping the mesh patterns of the stent bodies as described above increases the density of the mesh pattern throughout the stent, thereby increasing the surface area of ​​the stent 1. Furthermore, the stent 1 of this embodiment has excellent shape-following ability and diameter reduction properties because the outer overlapping portions 14 of the outer cells 12 have the configuration shown in Fig. 2A and the inner overlapping portions 24 of the inner cells 22 have the configuration shown in Fig. 2B. Furthermore, since the outer cells 12 and the inner cells 22 of the stent 1 have the above-described configurations, it is possible to easily accommodate the stent 1 in a catheter after it has been reduced in diameter, and also to easily accommodate the stent 1 in a catheter after it has been expanded in a blood vessel.

[0046] FIG. 4A is a diagram illustrating the outer diameter D1 of the outer stent body 10 before assembly. FIG. 4B is a diagram illustrating the outer diameter D2 of the inner stent body 20 before assembly. FIG. 5 is a diagram illustrating the process of inserting the inner stent body 20 into the outer stent body 10. As shown in FIGS. 4A and 4B , in the first embodiment, the relationship between the outer diameter D1 of the outer stent body 10 alone and the outer diameter D2 of the inner stent body 20 alone is D1<D2. Therefore, as shown in FIG. 5 , the inner stent body 20A, in which the inner stent body 20 has been reduced in diameter, is inserted into the outer stent body 10. Then, due to the self-expansion force of the inner stent body 20, the inner stent body 20 is tightly fitted to the inside of the outer stent body 10 in the radial direction RD. Therefore, the outer stent body 10 and the inner stent body 20 are less likely to be misaligned relative to each other in the axial direction LD (see FIG. 1 ) of the stent 1. In Figure 4, for ease of understanding, only the annular cell rows arranged in the circumferential direction are shown in each stent body, and the number of cells is made larger than in other figures and the shape of the cells is simplified to make it easier to understand the tubular shape.

[0047] On the other hand, in the circumferential direction centered on the axial direction LD of the stent 1 (see FIG. 1 ), the positions of the outer stent body 10 and the inner stent body 20 may be misaligned relative to each other. However, as described above, in the stent 1 of this embodiment, the outer overlapping portion 14 and the inner overlapping portion 24 are arranged with a relative misalignment in the axial direction LD of the stent 1. Therefore, even if the positions of the outer stent body 10 and the inner stent body 20 are misaligned relative to each other in the circumferential direction, the biological lumen can be appropriately expanded. Furthermore, a reduction in the surface area of ​​the stent 1 that abuts against the inner wall of the blood vessel can be suppressed, thereby improving safety.

[0048] By deploying the stent 1 of the first embodiment described above at a lesion site in a blood vessel lumen, the blood vessel lumen is expanded, ensuring patency of the lesion site. By removing (retrieving) the stent 1 from the blood vessel lumen after a predetermined period of time, complications due to the placement of the stent, such as restenosis, re-occlusion, and thrombosis, can be prevented. Furthermore, the stent 1 of the first embodiment has excellent shape-following properties, and therefore is highly protective of the blood vessel. Note that the stent 1 of the first embodiment can be used not only for the treatment of blood vessels, but also for the treatment of luminal structures in general, such as the esophagus and large intestine.

[0049] The stent 1 of the first embodiment can also be used to treat cerebral vasospasm. Note that the stents of other embodiments described below also exhibit the same effects as the stent 1 of the first embodiment.

[0050] The stent 1 of the first embodiment may also be used for applications requiring placement in a blood vessel for a predetermined period of time or permanently. An example of an application requiring placement of a stent in a blood vessel is a stent for treating an aneurysm. The aneurysm treatment stent is deployed at a target location and placed in place. The purpose of placing the aneurysm treatment stent at a target location is, for example, to reduce blood flow into an aneurysm present at the target location or to retain an embolic coil placed in the aneurysm. After the aneurysm treatment stent is placed at the target location, an embolic coil (neither of which is shown) can be delivered to the distal LD2 side via a microcatheter inserted into the catheter, allowing the embolic coil to be placed in the aneurysm through the meshwork of the aneurysm treatment stent.

[0051] Furthermore, an example of an application for placing a stent in a blood vessel is a stent for placement in a cerebrovascular vessel, and the stent 1 of the first embodiment can be used to treat cerebrovascular disorders. Cerebrovascular disorders are mainly classified into ischemic cerebrovascular disorders and hemorrhagic cerebrovascular disorders. Ischemic cerebrovascular disorders include cerebral infarction such as atherothrombotic cerebral infarction, lacunar infarction, and cardiogenic cerebral embolism, while hemorrhagic cerebrovascular disorders include cerebral hemorrhage and subarachnoid hemorrhage.

[0052] Second Embodiment Figure 6 is a development view of a portion of a stent 1 of a second embodiment, unfolded virtually in a plane, with the relative circumferential positions of the outer stent body 10 and the inner stent body 20 at the design target positions. The stent 1 of the second embodiment is similar to the stent 1 of the first embodiment, except that the outer cells 12 and the inner cells 22 are substantially parallelogram-shaped. Therefore, a description of the same parts as in the first embodiment will be omitted. The outer cells 12 are arranged in such a manner that cells of the same shape are adjacent to each other in the circumferential direction OD and the axial direction LD at outer overlapping portions 14 at the four corners of the substantially parallelogram-shaped outer cells 12. The inner cells 22 are arranged in such a manner that cells of the same shape are adjacent to each other in the circumferential direction OD and the axial direction LD at inner overlapping portions 24 at the four corners of the substantially parallelogram-shaped inner cells 22.

[0053] In the stent 1 of the second embodiment, similarly to the stent 1 of the first embodiment, the relative positions of the outer overlapping portion 14 and the inner overlapping portion 24 are shifted in the axial direction LD of the stent 1. Furthermore, in the stent 1 of the second embodiment, the relative positions of the outer overlapping portion 14 and the inner overlapping portion 24 are also shifted in the circumferential direction OD of the stent 1. Furthermore, similarly to the first embodiment, the stent 1 has an identical shape region A in which outer cells 12 and inner cells 22 are arranged adjacent to each other and have the same shape when viewed in the radial direction, except on the proximal LD1 side and the distal LD2 side.

[0054] Fig. 7 is a virtual planar development view of a portion of the stent 1 of the second embodiment, in which the relative circumferential positions of the outer stent body 10 and the inner stent body 20 are displaced from their intended positions. The example shown in Fig. 7 illustrates a case in which the relative circumferential positions of the outer stent body 10 and the inner stent body 20 are displaced to the point where the outer overlapping portion 14 and the inner overlapping portion 24 are closest to each other. In the stent 1 of the second embodiment, the outer overlapping portion 14 and the inner overlapping portion 24 within the identical shape region A are displaced in both the axial direction LD and the circumferential direction OD of the stent 1 in the outer cell 12 and the inner cell 22, respectively. Therefore, as shown in Fig. 7, in the stent 1 of this embodiment, even if there is an identical shape region A in which the outer cell 12 and the inner cell 22 have substantially the same shape, they will not completely overlap when the relative circumferential positions of the outer stent body 10 and the inner stent body 20 are displaced. Therefore, both the outer struts 11 and the inner struts 21 can come into contact with the inner wall of a biological lumen, such as the inner wall of a blood vessel, and an extreme increase in expansion pressure can be prevented when the stent 1 expands the inner wall of a blood vessel, etc. Therefore, because the outer overlapping portion 14 and the inner overlapping portion 24 of the stent body 1 are arranged with a deviation in the axial direction LD, the stent body 1 can appropriately expand a biological lumen even if the relative circumferential positions of the outer stent body 10 and the inner stent body 20 are misaligned, and this also provides a high level of safety.

[0055] (Method of Use) Next, an example of a method of using the stent 1 of each embodiment will be described. Figures 8A to 8D are schematic diagrams showing the procedure for dilating a stenotic site in a blood vessel using the stent 1. Figures 8C and 8D show a simplified shape of the stent 1. Here, a procedure for widening a stenotic site CS formed in a blood vessel BV to ensure blood flow will be described. Note that the following procedure is performed by identifying the position of the stent, etc., using a visible marker (radiopaque marker).

[0056] First, as shown in Fig. 8A, a guidewire 40 is passed through the stenosis site CS. A catheter 50 is fitted onto the guidewire 40. Next, as shown in Fig. 8B, the tip of the catheter 50 fitted onto the guidewire 40 is inserted into the stenosis site CS along the passed guidewire 40 and passed through until it reaches the distal LD2 side of the stenosis site CS. Next, although not shown, the guidewire 40 is pulled out of the living body and recovered from the catheter 50. Then, a stent 1 is inserted from the proximal LD1 side of the catheter 50. The stent 1 is inserted into the catheter 50 in a contracted state.

[0057] Next, as shown in Figure 8C, the stent 1 is deployed from the tip of the catheter 50 on the distal LD2 side of the stenosis site CS. The tip of the catheter 50 is positioned on the distal LD2 side of the stenosis site CS, and the catheter 50 is retracted toward the proximal LD1 side, thereby deploying the stent 1 from the tip of the catheter 50. When the stent 1 is deployed from the tip of the catheter 50, the stent 1 expands by its own expansion force, thereby pushing open the stenosis site CS from the inside. By pushing open the stenosis site CS from the inside with the expanded stent 1, blood flow in the blood vessel BV can be ensured.

[0058] After it is confirmed that blood flow in the blood vessel BV is ensured, follow-up observation is performed for, for example, about 5 to 60 minutes. After the follow-up observation, as shown in Figure 8D, the tip of the catheter 50 is advanced toward the distal end LD2 of the stent 1, and the entire stent 1 is retracted into the catheter 50. This allows the stent 1 and the catheter 50 to be retrieved outside the body.

[0059] (Modifications) The present disclosure is not limited to the above-described embodiment, and various modifications and variations are possible, and these are also within the scope of the present disclosure.

[0060] For example, in each embodiment, the outer cells 12 and the inner cells 22 are generally rhombic or parallelogram-shaped. However, the shapes of the outer cells 12 and the inner cells 22 may be, for example, generally hexagonal, and can be modified as appropriate.

[0061] The embodiments and modifications may be used in combination as appropriate, but detailed description thereof will be omitted. The present disclosure is not limited to the embodiments described above.

[0062] REFERENCE SIGNS LIST 1 Stent 2 Wire 10 Outer stent body 11 Outer strut 12 Outer cell 13 Opening portion 14 Outer overlapping portion 15 Curved portion 20 Inner stent body 20A Inner stent body 21 Inner strut 22 Inner cell 23 Opening portion 24 Inner overlapping portion 25 Curved portion 31 First wire marker portion 32 Second wire marker portion 111 Outer stent marker portion 121 Inner stent marker portion

Claims

1. A stent inserted into a catheter and used to be taken out of the catheter in a body lumen to expand the body lumen, comprising: an outer stent body in which a plurality of outer cells surrounded by an outer strut and an outer overlapping portion where the outer struts intersect are arranged in the circumferential direction and are continuous in the central axis direction; an inner stent body in which a plurality of inner cells surrounded by an inner strut and an inner overlapping portion where the inner struts intersect are arranged in the circumferential direction and are continuous in the central axis direction, and the inner stent body is inserted into the outer stent body at least in a region for expanding the body lumen; wherein the outer cells and the inner cells have a same-shaped region where cells of the same shape are arranged adjacent to each other when viewed in the radial direction; and in the same-shaped region, there is a region where the relative positions of the outer overlapping portion and the inner overlapping portion are displaced in the axial direction of the stent.

2. The stent according to claim 1, wherein the outer overlapping portion and the inner overlapping portion in the same-shaped region are displaced by a half period of the arrangement period in which the outer cells and the inner cells are arranged in the circumferential direction when viewed in the radial direction.

3. The stent according to claim 1 or claim 2, wherein the outer overlapping portion and the inner overlapping portion in the same-shaped region are each displaced in both the axial position and the circumferential position of the stent in the outer cells and the inner cells.

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