Stent

Abstract

Provided is a stent that is highly safe and that has excellent expandability.　A stent 1 comprises: an outer stent body 10 in which a plurality of outer cells 12 surrounded by an outer strut 11 are arranged at least in the central axis direction; and an inner stent body 20 in which a plurality of inner cells 22 surrounded by an inner strut 21A, 21B are arranged in at least the central axis direction and which is inserted into the outer stent body 10 in at least a region for expanding a biological lumen. In a cylindrical shape part 1a of which the diameter expands to form a cylindrical shape in a free state in which the diameter of the stent 1 is freely expanded, the outer outermost surface has a blade part which has an area smaller than that of the inner outermost surface and makes an incision into a lesion site in the biological lumen.

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] Furthermore, as a stent with a larger surface area and excellent shape-conforming properties to the vascular structure and diameter reduction properties, a stent comprising 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 (see Patent Document 2). In the two-layer structure stent described in Patent Document 2, the outer stent body and the inner stent body have the same stent pattern.

[0004] Also known are medical devices called cutting balloon catheters and scoring balloon catheters, which are used to treat narrowed areas caused by calcified lesions in blood vessels and the like, by dilating them (see Patent Document 3).

[0005] US Patent No. 10,390,982 International Publication No. 2022 / 085313 JP 2008-519654 A

[0006] However, the cutting balloon catheter disclosed in Patent Document 3 is manufactured by attaching a cutting element to a balloon, which makes manufacturing difficult, and there is a risk that the cutting element may fall off the balloon.

[0007] An object of the present disclosure is to provide a stent that is highly safe and has excellent expandability.

[0008] 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.

[0009] The first disclosure relates to a stent (1), comprising an outer stent body (10, 10B) in which a plurality of outer cells (12) surrounded by outer struts (11) are arranged at least in the central axis direction, and an inner stent body (20, 20B) in which a plurality of inner cells (22, 22A, 22B, 22C) surrounded by inner struts (21, 21A, 21B) are arranged at least in the central axis direction, and which is inserted into the outer stent body (10, 10B) at least in a region where the body lumen is expanded. and in a cylindrical portion (1a) where the stent (1, 1B) expands in diameter into a cylindrical shape when the stent (1, 1B) is in a free state where the diameter of the stent (1, 1B) is freely expanded, the surface located outermost in the radial direction of the inner stent body (20, 20B) is defined as the inner outermost surface, and the surface located outermost in the radial direction of the outer stent body (10, 10B) is defined as the outer outermost surface, the outer outermost surface having an area smaller than that of the inner outermost surface, and having a blade portion for making an incision into a lesion site in a biological lumen.

[0010] The second disclosure is a stent (1, 1B) in which, in the stent (1) described in claim 1, the outer struts (11) are arranged in a range of the cylindrical portion (1a) where the mesh pattern of the outer stent body (10) is coarser than the mesh pattern of the inner stent body (20), and the outer struts (11) function as the blade portion.

[0011] The third disclosure is a stent (1B) according to claim 1, wherein a partly twisted portion of the outer strut (11) functions as the blade portion.

[0012] The fourth disclosure is a stent (1B) according to claim 3, wherein in a cylindrical portion (1a) that expands into a cylindrical shape in a free state when freely expanded in diameter, the blade portions where the outer struts (11) are partially twisted protrude outward from the cylindrical shape formed by the surface of the outer struts (11) other than the blade portions.

[0013] The fifth disclosure is a stent (1, 1B) according to any one of claims 1 to 4, wherein the width of the outer stent body (10, 10B) in a direction perpendicular to the extension direction of the blade portion as viewed from the radial direction is 0.5 mm or less.

[0014] The sixth disclosure is a method for expanding a biological organ having a luminal structure using a stent (1, 1B), the stent (1, 1B) comprising: an outer stent body (10, 10B) in which a plurality of outer cells (12) surrounded by outer struts (11) are arranged at least in the central axis direction; and an inner stent body (20, 20B) in which a plurality of inner cells (22, 22A, 22B, 22C) surrounded by inner struts (21, 21A, 21B) are arranged at least in the central axis direction, the inner stent body (20, 20B) being inserted into the outer stent body (10, 10B) at least in a region where a biological lumen is expanded, and in a cylindrical portion (1a) in which the stent (1, 1B) expands into a cylindrical shape in a free state in which the diameter of the stent (1, 1B) is freely expanded, the outermost portion in the radial direction of the inner stent body (20, 20B) being arranged at least in the central axis direction. When the surface located on the side closest to the stent body (10, 10B) is defined as the inner outermost surface and the surface located most outside in the radial direction of the outer stent body (10, 10B) is defined as the outer outermost surface, the outer outermost surface has an area smaller than that of the inner outermost surface and has a blade portion for making an incision at a lesion site in a biological lumen, and the method includes: delivering the stent (1, 1B) housed in a catheter (50) in a contracted state together with the catheter (50) through the biological organ to a planned position in the biological organ to 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).

[0015] According to the present disclosure, a stent that is highly safe and has excellent expandability can be provided.

[0016] 1. A side view of a stent 1 of a first embodiment. FIG. 2. A virtual development view of a portion of the cylindrical portion 1a of the outer stent body 10 and the inner stent body 20 of the first embodiment. FIG. 3. A virtual development view of a portion of the cylindrical portion 1a of the outer stent body 10 of the first embodiment. FIG. 4. A virtual development view of a portion of the cylindrical portion 1a of the inner stent body 20 of the first embodiment. FIG. 5. An explanatory view of the outer diameter D1 of the outer stent body 10 before assembly. FIG. 6. An explanatory view of the outer diameter D2 of the inner stent body 20 before assembly. FIG. 7. A diagram showing the process of inserting the inner stent body 20 into the outer stent body 10. A cross-sectional view taken along line s1-s1 of FIG. 1. FIG. 1 is a schematic side view of a stent 1B of a second embodiment. FIG. 8. An explanatory view of a portion of the cylindrical portion 1a of the outer stent body 10B and the inner stent body 20B of the second embodiment. FIG. 9. An explanatory view of a portion of the cylindrical portion 1a of the outer stent body 10B of the second embodiment. FIG. 11. An explanatory view of a portion of the cylindrical portion 1a of the inner stent body 20B of the second embodiment. 1 is a perspective view showing an enlarged view of the twisted portion 16; FIG. 2 is a view showing a state before the twisted portion 16 is twisted; FIG. 3 is a view of a stent 1B of a second embodiment as viewed from the distal LD2 side; FIG. 4 is a view showing a modified form of the second embodiment; FIG. 5 is a side view of a stent 1C of a third embodiment; FIG. 6 is a schematic view showing a procedure for dilating a stenotic site in a blood vessel using the stent 1; FIG. 7 is a schematic view showing a procedure for dilating a stenotic site in a blood vessel using the stent 1; FIG. 8 is a schematic view showing a procedure for dilating a stenotic site in a blood vessel using the stent 1;

[0017] Hereinafter, an embodiment of a stent 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, in the drawings, hatching indicating the cross section of a member may be omitted as appropriate.

[0018] 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 (distal) 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. The circumferential direction may be the radial direction RD or a direction inclined relative to the radial direction RD.

[0019] (First embodiment) Fig. 1 is a side view of a stent 1 of the first embodiment. Fig. 2A is a virtual developed view of a portion of the cylindrical portion 1a of the outer stent body 10 and the inner stent body 20 of the first embodiment. Fig. 2B is a virtual developed view of a portion of the cylindrical portion 1a of the outer stent body 10 of the first embodiment. Fig. 2C is a virtual developed view of a portion of the cylindrical portion 1a of the inner stent body 20 of the first embodiment.

[0020] In the drawings, to make it easier to 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, etc., a "cell" refers to a portion surrounded by struts that form a stent. The "cells" may have the same shape and size as one another, or they may differ from one another. A "strut" refers to a portion made of the wire-like material. In this specification, etc., the opening of a cell is referred to as an "opening portion," and the portion where struts of adjacent cells are connected or overlapped is referred to as an "overlapping portion."

[0021] 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 outside the body, but it can also be used to leave the stent 1 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.

[0022] The stent 1 includes a cylindrical portion 1a and a converging portion 1b. In a free state where the cylindrical portion 1a is freely expanded, the cylindrical portion 1a has a cylindrical shape as shown in FIGS. 3A and 3B (described later), and has a mesh pattern structure composed of outer cells 12 and inner cells 22 (described later). The converging portion 1b is a portion where the proximal LD1 side of the cylindrical portion 1a converges toward the wire 2. The stent 1 is configured to have a substantially cylindrical shape when extended in a free state after being removed from the catheter (see FIGS. 3A and 3B (described later)). Although not shown, the stent 1 has an elongated cylindrical shape in a contracted state. Furthermore, the wire 2 is connected to the end of the stent 1 on the proximal LD1 side. The connection between the proximal end of the stent 1 and the wire 2 can be any connection method commonly used in medical devices, including, for example, welding, UV bonding, and infiltration with silver brazing.

[0023] The wire 2 is a member that is operated by the practitioner when moving the stent 1. The practitioner advances or retreats the stent 1 within the catheter or blood vessel by pushing or pulling the wire 2 via an 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).

[0024] The stent 1 comprises an outer stent body 10 and an inner stent body 20, which are substantially cylindrical structures. The stent 1 is configured as a two-layer stent in which the inner stent body 20 is inserted into the outer stent body 10 at least in the region where the stenotic site of the biological lumen is dilated. Here, the region where the stenotic site of the biological lumen is dilated refers to the region that substantially contributes to dilating the stenotic site 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 where the stenotic site is dilated. 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 cylindrical portion 1a 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.

[0025] 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 part of the inner stent body 20 may be radially outer than the inner surface of the outer stent body 10, or may be outer than the surface (outer surface) of the outer stent body 10. As described above, a part of the outer stent body 10 may be radially outer than the surface (outer surface) of the inner stent body 20.

[0026] When the inner stent body 20 is inserted into the outer stent body 10, 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 connected via the wire 2, but are not connected in other regions. Therefore, the stent 1 allows the outer stent body 10 and the inner stent body 20 to deform independently in their respective layers. 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 connected (connected) to each other 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.

[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 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.

[0028] 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.

[0029] 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, into the outer stent body 10 in a contracted state. As a result, in the stent 1 in both the contracted and expanded states, the inserted inner stent body 20 is constantly pressing the outer stent body 10 outward in the radial direction RD. Therefore, the stent 1 can more firmly adhere the outer stent body 10 and the inner stent body 20 to each other while maintaining a state in which the outer stent body 10 and the inner stent body 20 can deform independently on their respective layers.

[0030] As shown in Figure 1, on the proximal LD1 side of the stent 1, the outer stent body 10 and the inner stent body 20 have converging portions 1b at their ends, which gradually reduce in diameter toward the wire 2 side and are connected to the wire 2. This restricts the axial movement of the inner stent body 20 relative to the outer stent body 10.

[0031] The stent 1 is provided with a first wire marker portion 31 and a second wire marker portion 32 as markers. 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 made of 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.

[0032] 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.

[0033] 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.

[0034] The first wire marker portion 31 is a coil marker formed by coiling a linear member made of a highly radiopaque material, and is fixed by welding in a position covering the end of the outer strut 11 on the proximal LD1 side. The second wire marker portion 32 is a ring marker formed by soldering a marker component made of a highly radiopaque material in a cylindrical shape to the strut, and is fixed by solder in a position covering the end of the inner stent body 20 on the proximal LD1 side. Note that the first wire marker portion 31 and the second wire marker portion 32 in this embodiment are examples of some of the specific forms of markers, and their locations and numbers can be changed as appropriate. For example, markers may also be provided on the stent portion.

[0035] As shown in Fig. 2B , 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 predetermined shape. 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. Adjacent outer cells 12 in the circumferential direction OD are connected at overlapping portions 14.

[0036] The overlapping portion 14 is a portion where the outer struts 11 of four adjacent outer cells 12 are connected. The 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 overlapping portion 14. Each outer strut 11 has a curved portion 15 formed at the portion where it is connected to the overlapping portion 14. Therefore, when the expanded stent 1 is bent into a generally U-shape, each outer strut 11 connected to the 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.

[0037] 2C , the inner stent body 20 has a plurality of inner cells (22A, 22B, 22C) arranged in the circumferential direction OD, each of which is made up of inner struts 21A, 21B arranged to surround an area in a predetermined shape. More specifically, a first inner cell 22A, a second inner cell 22B, and a third inner cell 22C are arranged in the circumferential direction OD.

[0038] 2A , the first inner cell 22A has a shape similar to that of the outer cell 12, is surrounded by inner struts 21A, and is smaller than the outer cell 12. The width of the first inner cell 22A in the circumferential direction OD may be, for example, 20% to 60% of the width of the outer cell 12 in the circumferential direction OD. The first inner cell 22A is arranged such that the center position of the first inner cell 22A and the center position of the outer cell 12 coincide when viewed in the radial direction RD.

[0039] As shown in FIG. 2A , the second inner cell 22B is surrounded by inner struts 21B and is formed in a shape similar to that of the outer cell 12 of the outer stent body 10, but is smaller than the outer cell 12. Also, as shown in FIGS. 2A and 2B , the second inner cell 22B is formed in a shape similar to that of the outer cell 12, but is larger than the first inner cell 22A. The second inner cell 22B is disposed such that the center position of the first inner cell 22A coincides with the center position of the overlapping portion 14 of the outer stent body 10 when viewed in the radial direction RD. Furthermore, both ends of the second inner cell 22B in the circumferential direction OD are connected to the first inner cell 22A at overlapping portions 24A provided at both ends of the second inner cell 22B in the circumferential direction OD. In other words, the size of the second inner cell 22B is such that both ends of the second inner cell 22B in the circumferential direction OD can be connected to the first inner cell 22A at the overlapping portions 24A provided at both ends of the first inner cell 22A in the circumferential direction OD. Therefore, the size of the second inner cell 22B is set to match the size of the first inner cell 22A. In the present embodiment, as described above, the second inner cell 22B is formed to have a shape similar to that of the outer cell 12, which is larger than the first inner cell 22A. However, conversely, the second inner cell 22B may be formed to have a shape similar to that of the outer cell 12, which is smaller than the first inner cell 22A, or the second inner cell 22B may be formed to have the same size as the first inner cell 22A.

[0040] The first inner cells 22A and second inner cells 22B, which are connected and arranged in the circumferential direction OD, are arranged in the axial direction LD. In the axial direction LD, the first inner cells 22A and the second inner cells 22B are connected at overlapping portions 24B. That is, the inner stent body 20 has a mesh pattern in which a plurality of first inner cells 22A and second inner cells 22B are arranged in the circumferential direction OD and the axial direction LD. In this mesh pattern, the region surrounded by the first inner cells 22A and the second inner cells 22B is a third inner cell 22C, which is a cell with an irregular shape that is dissimilar to the first inner cell 22A and the second inner cell 22B.

[0041] The first inner cell 22A has a first opening portion 23A and overlapping portions 24A at both ends in the circumferential direction OD. The overlapping portions 24A are portions where the inner struts 21A, 21B of four adjacent cells are connected. The overlapping portions 24A have a generally rectangular shape that is elongated in the axial direction LD. The second inner cell 22B has a second opening portion 23B and is connected to the first inner cell 22A at overlapping portions 24A at both ends in the circumferential direction OD. The third inner cell 22C has a third opening portion 23C and overlapping portions 24B at both ends in the circumferential direction OD. The overlapping portions 24B are portions where the inner struts 21A, 21B of four adjacent cells are connected. The overlapping portions 24B have a generally rectangular shape that is elongated in the axial direction LD. Each inner strut 21A, 21B is connected to the four corners of the overlapping portion 24A or 24B. Each inner strut 21A, 21B has a curved portion 25 formed at the portion where it is connected to the overlapping portion 24A or the overlapping portion 24B. Therefore, when the expanded stent 1 is bent into a generally U-shape, each inner strut 21A, 21B connected to the overlapping portion 24 or the overlapping portion 24B can be deformed independently. This allows the first inner cell 22A, the second inner cell 22B, and the third inner cell 22C, which are arranged in the circumferential direction OD, to bend more flexibly. In this way, the inner stent body 20 has excellent shape conformability and diameter reduction properties because it allows the first inner cell 22A, the second inner cell 22B, and the third inner cell 22C, which are arranged in the circumferential direction OD, to bend more flexibly.

[0042] Fig. 3A is a diagram illustrating the outer diameter D1 of a single outer stent body 10. Fig. 3B is a diagram illustrating the outer diameter D2 of a single inner stent body 20. Fig. 4 is a diagram illustrating the procedure for inserting the inner stent body 20 into the outer stent body 10. As shown in Figs. 3A and 3B , in the first embodiment, the relationship between the outer diameter D1 of the single outer stent body 10 and the outer diameter D2 of the single inner stent body 20 is set so that D1 < D2. Therefore, by following the procedure indicated by the arrows in Fig. 4 , the inner stent body 20, which has an outer diameter larger than that of the outer stent body 10, is reduced in diameter to form the inner stent body 20A, and then inserted into the outer stent body 10, a two-layered stent 1 can be fabricated in which the inner stent body 20 is tightly attached to the inside of the outer stent body 10 due to the self-expansion force of the inner stent body 20. 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.

[0043] In the stent 1 fabricated as described above, the outer stent body 10 and the inner stent body 20 are in close contact with each other in the radial direction RD due to the self-expansion force of the inner stent body 20 (see Fig. 5 described later). 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 of the stent 1 (see Fig. 1).

[0044] In the first embodiment, the inner stent body 20 inserted into the outer stent body 10 in a contracted state is itself a self-expanding body (elastic body). Therefore, the inner stent body 20 constantly presses the outer stent body 10 outward in the radial direction RD. Therefore, even if the outer stent body 10 and the inner stent body 20 are not connected to each other in the radial direction, the outer stent body 10 and the inner stent body 20 can be more firmly adhered to each other. Furthermore, because the outer stent body 10 and the inner stent body 20 are not connected to each other in the radial direction, the outer stent body 10 and the inner stent body 20 can maintain a state in which they can deform independently on each layer. Furthermore, the two-layer stent 1 has an expansion force that is the sum of the expansion force of the outer stent body 10 and the expansion force of the inner stent body 20. Therefore, even with the same surface area, the expansion force can be greater than that of a single-layer stent.

[0045] The stent 1 (outer stent body 10, inner stent body 20) may be made of a highly biocompatible material. While not particularly limited, a material with superelastic properties, such as a nickel-titanium (Ni-Ti) alloy, is preferred. The outer stent body 10 and inner stent body 20 can be fabricated, for example, by laser processing a substantially cylindrical tube made of the above material.

[0046] The stent 1 may be loaded with a drug such as a physiologically active substance (such as a drug that suppresses intimal hyperplasia), and specifically, may carry the drug so that the drug is eluted in the lumen structure.

[0047] The outer stent body 10 and the inner stent body 20 are fabricated, for example, by laser processing a tube with an outer diameter of approximately 0.4 to 3 mm to form a mesh pattern, and then stretching it radially to achieve the desired diameter. As described above, a two-layered stent 1 can be fabricated by inserting the inner stent body 20 into the outer stent body 10. This two-layered stent 1 is housed in the lumen of a catheter (not shown) in a state where its diameter is reduced in the radial direction from its natural state. If the stent is made of an elastic material such as a superelastic alloy or a shape-memory alloy, pushing the stent 1 housed in the catheter out will cause it to expand in diameter by its own expansion force.

[0048] In this embodiment, as described above, the first inner cells 22A are formed in a similar shape to the outer cells 12, which are smaller than the outer cells 12, and are arranged so that the center positions of the first inner cells 22A and the outer cells 12 coincide when viewed in the radial direction RD. In other words, the mesh pattern of the outer stent body 10 is coarser than the mesh pattern of the inner stent body 20. Furthermore, when the stent 1 is viewed in the radial direction RD, the width of the outer struts 11 of the outer stent body 10 is approximately equal to the width of the inner struts 21A and 21B of the inner stent body 20, or is narrower than the width of the inner struts 21A and 21B of the inner stent body 20.

[0049] In the cylindrical portion 1a of the stent 1, which expands into a cylindrical shape when the stent 1 is in a free state, the surface located outermost in the radial direction of the inner stent body 20 is referred to as the inner outermost surface, and the surface located outermost in the radial direction of the outer stent body 10 is referred to as the outer outermost surface. In the first embodiment, the outer outermost surface is the surface of the shape of the outer stent body 10 within the range of the cylindrical portion 1a shown in the developed view of FIG. 2B. Similarly, the inner outermost surface is the surface of the shape of the inner stent body 20 within the range of the cylindrical portion 1a shown in the developed view of FIG. 2C. In the first embodiment, the mesh pattern of the outer stent body 10 is coarser than the mesh pattern of the inner stent body 20. Therefore, the area of ​​the outer outermost surface is smaller than that of the inner outermost surface. As a result, the outer struts 11, mainly part of the outer outermost surface of the outer stent body 10, function as a blade for cutting into a lesion in a biological lumen.

[0050] Figure 5 is a cross-sectional view taken along line s1-s1 in Figure 1. Because the mesh pattern of the outer stent body 10 is coarser than that of the inner stent body 20, the outermost surface area of ​​the outer struts 11 of the outer stent body 10, which come into contact first with the inner wall of the biological lumen, is small, and the expansion force of the entire stent 1 is concentrated on this small surface area. The expansion force of the entire stent 1 is the sum of the expansion forces of the outer stent body 10 and the inner stent body 20. Therefore, a large expansion force is concentrated on the outer struts 11 of the outer stent body 10, which have a small surface area and come into contact first with the inner wall of the biological lumen. This allows the outer struts 11 to act as cutting edges, pressing very thin linear bodies firmly against the inner wall of the biological lumen, making it possible to cut, for example, calcified lesions in blood vessels during the expansion process of the stent 1. Here, in order to make it easier to cut into calcified lesions and the like in blood vessels, it is desirable that the width of the blade portion (outer strut 11) in the expanded state in the direction perpendicular to the extension direction when viewed from the radial direction of the outer stent body 10 is 0.5 mm or less.

[0051] On the other hand, the mesh pattern of the inner stent body 20 is finer than the mesh pattern of the outer stent body 10. Furthermore, when the stent 1 is viewed in the radial direction RD, the widths of the inner struts 21A and 21B of the inner stent body 20 are equal to or wider than the widths of the outer struts 11 of the outer stent body 10. Therefore, when the inner stent body 20 abuts against the inner wall of the biological lumen, the outer struts 11 are prevented from cutting into the inner wall of the biological lumen more than necessary. Therefore, in hard areas such as calcified lesions in blood vessels, the outer struts 11 can make cuts to promote expansion, while in situations where the inner stent body 20 abuts against the inner wall of the biological lumen, cutting by the outer struts 11 is suppressed. As such, the stent 1 of this embodiment has high expandability and is highly safe.

[0052] Next, a method for using the stent 1 of the first embodiment in a blood vessel lumen will be described. When the stent 1 of the first embodiment is expanded in the same manner as a conventional stent, the outer struts 11, which act as blades, strike first, applying concentrated force, cutting into and fracturing the lesion. By making the cuts, the stent can be expanded with less force than a conventional stent, even in hard lesions, and by making the cuts, it can be expanded smoothly without being distorted by the lesion. The stent 1 of the first embodiment has a self-expanding structure, and the operation itself is the same as that of a conventionally known two-layered stent, and it self-expands when deployed from a microcatheter.

[0053] Furthermore, although the stent 1 of the first embodiment can make an incision into the lesion, making an incision is not its purpose. The stent 1 of the first embodiment can be expanded appropriately by making an incision. Therefore, the expanded state of the stent 1 of the first embodiment can be confirmed in the same manner as in the past using a conventional confirmation method using X-rays. For example, during treatment using the stent 1 of the first embodiment, the state of the lesion and the stent 1 can be observed by angiography before, during, and after expansion. The state of the stent 1 may also be confirmed using cone-beam CT.

[0054] Furthermore, the stent 1 of the first embodiment can incise the lesion, but does not require any special operation compared to conventional stents that cannot incise the lesion. Therefore, even after expanding the stent 1, the lesion can be treated by expanding it and maintaining the state of resuming blood flow for a certain period of time, just as in the conventional case.

[0055] Alternatively, after expanding and deploying the stent 1 for a certain period of time, the stent 1 may be temporarily retrieved into the microcatheter, and the stent 1 may be rotated around the central axis within the microcatheter or together with the microcatheter, and then the microcatheter alone may be moved toward the proximal LD1 side to re-expand the stent 1. This allows incisions to be made at multiple locations, making it possible to expand even harder lesions.

[0056] Furthermore, depending on the state of the lesion, it may be expected that fragments of the lesion site will be generated due to the incision made by the stent 1. In such a case, a filter member may be placed on the LD2 side distal to the stent 1, or a suction catheter may be placed on the LD1 side proximal to the stent 1 to perform suction.

[0057] Furthermore, the retrieval (resheathing) of the stent 1 of the first embodiment can be performed in the same manner as a conventionally known two-layered stent. That is, instead of pulling the stent 1 toward the proximal LD1 side, the microcatheter is advanced toward the distal LD2 side to retrieve the stent 1 into the microcatheter. This operation prevents the blade portion from damaging the inner wall of the blood vessel, allowing the stent 1 to be retrieved safely.

[0058] By deploying the stent 1 of the first embodiment at a lesion site in the lumen of a blood vessel, the lumen of the blood vessel is expanded, ensuring patency of the lesion site. By removing (retrieving) the stent 1 from the lumen of the blood vessel after a predetermined period of time has passed, 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 is therefore highly blood-friendly. 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.

[0059] 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.

[0060] 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 there. 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 mesh of the aneurysm treatment stent. Furthermore, because the stent 1 has a fine mesh, it can also be used alone without the use of a coil to reduce blood flow into the aneurysm and induce thrombosis within the aneurysm for treatment.

[0061] Furthermore, an application of placing a stent in a blood vessel includes, for example, 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. Examples of ischemic cerebrovascular disorders include cerebral infarction such as atherothrombotic cerebral infarction, lacunar infarction, and cardiogenic cerebral embolism, while examples of hemorrhagic cerebrovascular disorders include cerebral hemorrhage and subarachnoid hemorrhage. Furthermore, the stent 1 can be used to treat cerebral vasospasm and the like. Note that a stent placed in a blood vessel or the like is removed after a predetermined period of time has elapsed or after the purpose of placing the stent has been achieved.

[0062] Second Embodiment Fig. 6 is a schematic side view of a stent 1B of a second embodiment. Fig. 7A is a development view of a portion of the cylindrical portion 1a of an outer stent body 10B and an inner stent body 20B of a second embodiment, which is virtually unfolded into a plane. Fig. 7B is a development view of a portion of the cylindrical portion 1a of the outer stent body 10B of the second embodiment, which is virtually unfolded into a plane. Fig. 7C is a development view of a portion of the cylindrical portion 1a of the inner stent body 20B of the second embodiment, which is virtually unfolded into a plane. The stent 1B of the second embodiment is similar to the stent 1 of the first embodiment, except that the mesh patterns of the outer stent body 10B and the inner stent body 20B are different from those of the first embodiment and that the stent 1B includes a twisted portion 16. Therefore, parts that perform the same functions as those of the first embodiment described above are designated by the same reference numerals, and redundant description will be omitted as appropriate.

[0063] The outer stent body 10B of the second embodiment is similar to the outer stent body 10 of the first embodiment, except that it has a twisted portion 16 instead of the overlapping portion 14 of the first embodiment. The twisted portion 16 is formed to be longer in the axial direction LD than the overlapping portion 14 of the first embodiment. The twisted portion 16 has a configuration in which the outer struts 11 are partially twisted. Figure 8 is an enlarged perspective view of the twisted portion 16. Figure 9 is a diagram showing the state of the twisted portion 16 before it is twisted. The twisted portion 16 is formed by twisting a wide portion 160, which is a portion of the width of which is increased at the overlapping portion where multiple outer struts 11 gather, by approximately 90 degrees, to form the configuration shown in Figure 8. Therefore, when the stent 1 is in its expanded state, the twisted portion 16 partially protrudes outward from the cylindrical shape formed by the surfaces of the outer struts 11 other than the twisted portion 16. The surface formed on the outermost side of this twisted portion 16 is the outermost surface, and its area is smaller than that of the innermost surface. As a result, in the outer stent body 10B of the second embodiment, the twisted portion 16 functions as a blade portion that cuts into a lesion within a biological lumen. Here, in order to make it easier to cut into calcified lesions and the like in blood vessels, the width of the twisted portion 16 in the direction perpendicular to the extending direction of the blade portion (twisted portion 16) as viewed from the radial direction of the outer stent body 10B in the expanded state is desirably 0.5 mm or less.

[0064] As shown in Figure 7C, the inner stent body 20B 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 predetermined shape. In the inner stent body 20B, the inner cells 22 arranged in the circumferential direction OD are also arranged in the axial direction LD. That is, the inner stent body 20B 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, the inner cells 22 adjacent to each other in the circumferential direction OD are connected at overlapping portions 24.

[0065] The overlapping portion 24 is where the inner struts 21 of four adjacent inner cells 22 are connected. The overlapping portion 24 has a generally rectangular shape elongated in the axial direction LD. Each inner strut 21 is connected to one of the four corners of the overlapping portion 24. Each inner strut 21 has a curved portion 25 formed at the portion where it connects to the overlapping portion 24. Therefore, when the expanded stent 1 is bent into a generally U-shape, each inner strut 21 connected to the overlapping portion 24 can deform independently. This allows the inner cells 22 arranged in the circumferential direction OD to bend more flexibly. In this way, the inner stent body 20B has excellent shape-following ability and diameter reduction ability because it allows the inner cells 22 arranged in the circumferential direction OD to bend flexibly. In the second embodiment, the innermost surface is the surface of the shape of the inner stent body 20B within the range of the cylindrical portion 1a shown in the developed view of FIG. 7C.

[0066] As shown in Fig. 7A , the outer stent body 10B and the inner stent body 20B of the second embodiment have the same mesh pattern except for the twisted portions 16 and overlapping portions 24, and are positioned such that the relative positions of the two are shifted so that the twisted portions 16 and overlapping portions 24 do not overlap. That is, as shown in Fig. 7A , in stent 1B, the outer stent body 10B and the inner stent body 20B are overlapped such that the overlapping portions 24 of the inner cells 22 (inner stent body 20B) are positioned in the openings 13 of the outer cells 12 (outer stent body 10B). Specifically, in a configuration in which the overlapping portions 24 of the inner cells 22 are positioned in the openings 13 of the outer cells 12, the overlapping portions 24 of one inner cell 22 are positioned in the openings 13 of one outer cell 12.

[0067] Figure 10 is a view of a stent 1B of the second embodiment as seen from the distal end LD2. As shown in Figure 10, when the stent 1 is in an expanded state, the twisted portion 16 partially protrudes outward from the outer shape of the outer struts 11, constituting the outermost surface. Therefore, the twisted portion 16 functions as a blade for cutting into a lesion within a biological lumen. The twisted portion 16 of the second embodiment forms an outermost surface with an even smaller surface area than the outer struts 11 of the first embodiment, thereby further enhancing its ability to cut into a lesion within a biological lumen. Therefore, the stent 1B of the second embodiment can provide a stent with even greater expandability than the first embodiment and with the same high level of safety as the first embodiment.

[0068] (Third Embodiment) Figure 12 is a schematic side view of a stent 1C of a third embodiment. The third embodiment differs from the stent 1 of the first embodiment in that the outer stent body 10B and the inner stent body 20B have the same stent pattern and that a distal end shaft 3 is connected to the end of the distal side LD2. The stent 1C of the third embodiment also differs from the stent 1 of the first embodiment in that it includes sub-struts 51. The other configuration of the stent 1C of the third embodiment is similar to that of the stent 1 of the first embodiment, so repeated explanations will be omitted.

[0069] The distal end shaft 3 is a mark for identifying the position of the distal LD2 side of the stent 1 in an X-ray image, and at least a portion of the distal end shaft 3 is made of a material that is opaque to radiography. The ends of the outer stent body 10 and the inner stent body 20 are gradually tapered in diameter toward the distal end shaft 3 and are connected to the distal end shaft 3.

[0070] The sub-strut 51 is spirally wound around the outer stent body 10C located outside the stent 1C. One end 51a of the sub-strut 51 is connected to the proximal LD1 side of the outer stent body 10C. The other end 51b of the sub-strut 51 is connected to the distal LD2 side of the outer stent body 10C. The wire diameter of the sub-strut 51 is desirably narrower than the width of the outer strut 11 in a direction perpendicular to the extension direction. By spirally winding the sub-strut 51 around the outer stent body 10C, when the sub-strut 51 first abuts against a lesion on the inner wall of the blood vessel, the small contact area can be used to cut into the lesion. Note that multiple sub-struts 51 may be wound around the outer stent body 10C. Note that the sub-strut 51 may be connected to the outer struts 11 of the outer stent body 10C by welding or the like. The sub-strut 51 may also be formed from a material with high contrast properties. In addition, in this embodiment, the outer stent body 10C and the inner stent body 20C have the same stent pattern, but the outer stent body 10C and the inner stent body 20C may have different stent patterns.

[0071] The stent 1C of the third embodiment can be a highly expandable stent that can make an incision into a lesion site without being affected by the stent patterns of the outer stent body 10C and the inner stent body 20C.

[0072] (Method of Use) Next, an example of a method of using the stents 1, 1B, and 1C of each embodiment will be described. Here, the stent 1 of the first embodiment will be described, but the same applies to the stents 1B and 1C of the other embodiments. Figures 13A to 13D are schematic diagrams showing the procedure for dilating a stenotic site in a blood vessel using the stent 1. Figures 13C and 13D 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 while the position of the stent, etc., is grasped using a visible marker (radiopaque marker).

[0073] First, as shown in Fig. 13A, a guidewire 40 is passed through the stenosis site CS. A catheter 50 is fitted onto the guidewire 40. Next, as shown in Fig. 13B, 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.

[0074] 13C , 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.

[0075] After it is confirmed that blood flow in the blood vessel BV has been secured, the patient is observed for, for example, 5 to 60 minutes. After the observation, as shown in Fig. 13D, 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.

[0076] (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.

[0077] Figure 11 shows a modified version of the second embodiment. In the second embodiment, a twisted portion 16 is provided at the portion where multiple outer struts 11 gather. This is not limiting, and for example, as shown in Figure 11 , a twisted portion 16B may be provided by twisting a wide portion 160B provided midway along one outer strut 11 by approximately 90 degrees. Furthermore, twisted portions 16B of this modified version may also be provided on outer struts 11 other than the positions illustrated in Figure 11 to increase the density of twisted portions 16B. Furthermore, twisted portions 16B of this modified version may be arranged together with the twisted portions 16 of the second embodiment.

[0078] 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.

[0079] DESCRIPTION OF SYMBOLS 1 Stent 1B Stent 1a Cylindrical portion 1b Converging portion 2 Wire 10 Outer stent body 10B Outer stent body 11 Outer strut 12 Outer cell 13 Opening portion 14 Overlapping portion 15 Curved portion 16 Twisted portion 16B Twisted portion 20 Inner stent body 20A Inner stent body 20B Inner stent body 21 Inner strut 21A Strut 21B Strut 22 Inner cell 22A First inner cell 22B Second inner cell 22C Third inner cell 23 Opening portion 23A First opening portion 23B Second opening portion 23C Third opening portion 24 Overlapping portion 24A Overlapping portion 24B Overlapping portion 25 Curved portion 31 First wire marker portion 32 Second wire marker portion 51 Substrut 160 Wide portion 160B Wide portion

Claims

1. A stent, comprising: an outer stent body in which a plurality of outer cells surrounded by outer struts are arranged at least in the central axis direction; and an inner stent body in which a plurality of inner cells surrounded by inner struts are arranged at least in the central axis direction and which is inserted into the outer stent body in at least a region for expanding a biological lumen. In a cylindrical portion that expands in a cylindrical shape in a freely expanded state where the stent expands in diameter freely, when the surface located most outward in the radial direction of the inner stent body is defined as the inner outermost surface and the surface located most outward in the radial direction of the outer stent body is defined as the outer outermost surface, the outer outermost surface has an area smaller than that of the inner outermost surface and has a blade portion for making an incision in a diseased site within a biological lumen.

2. The stent according to claim 1, wherein, among the outer struts, in the cylindrical portion, the outer struts provided in a range where the mesh pattern of the outer stent body is coarser than the mesh pattern of the inner stent body function as the blade portion.

3. The stent according to claim 1, wherein, among the outer struts, a portion that is partially twisted functions as the blade portion.

4. The stent according to claim 3, wherein, in a cylindrical portion that expands in a cylindrical shape in a freely expanded state where the stent expands in diameter freely, the blade portion where the outer strut is partially twisted protrudes outward from the cylindrical shape formed by the surface of the outer strut other than the blade portion.

5. The stent according to any one of claims 1 to 4, wherein the width in a direction orthogonal to the extending direction of the blade portion as viewed from the radial direction of the outer stent body is 0.5 mm or less.

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