In vivo stent and stent delivery system

Abstract

A stent 1 for in-vivo indwelling comprises: a plurality of annular bodies 2 which are formed in an annular shape from linear constituent components, and which are disposed in the axial direction; and a linking part 3 for linking the annular bodies disposed adjacent to each other. The annular bodies 2 have connecting linear parts 23, 24 that link one end-side bend section 21 and another end-side bend section 22. One of the connecting linear parts of the annular bodies 2 positioned towards the center of the stent comprises: an axial direction linear section 25 that has, as a starting end, one end-side vertex 21a of the one end-side bend section, and that extends in parallel with the axial direction of the stent 1; and a fold section 26 that has a starting end at a terminating end 25a of the axial direction linear section, and that extends in the circumferential direction of the stent 1. The linking part 3 connects the terminating end of the axial direction linear section to the one end-side vertex of an annular body adjacent to the axial direction linear section on another end side.

Description

[Technical field]

[0001] The present invention relates to a stent for placement in a living body and a stent delivery system used to improve narrowed or blocked areas occurring in biological lumens such as blood vessels, bile ducts, tracheas, esophagus, and urethra. [Background technology]

[0002] Stents for placement in vivo are used to treat various diseases caused by narrowing or occlusion of blood vessels or other lumens in the body. Stents are formed in a tubular shape to expand the narrowed or occluded area and secure the lumen.

[0003] Below, a blood vessel will be used as an example for explanation, but the present invention is not limited to this. A stent is inserted into the body from outside, so that it has a small diameter when inserted, and expands at the target stenosis or obstruction site to increase its diameter and maintain the lumen intact.

[0004] Stents are generally cylindrical metal wires or tubes that are thinned and attached to catheters and inserted into the body. They are expanded at the target site by some method and fixed to the inner wall of the lumen to maintain the lumen shape.

[0005] Stents are divided into self-expanding stents and balloon-expanding stents according to their function and placement method. Balloon-expanding stents do not have an expansion function themselves, and after the stent is mounted on a balloon and inserted into the target site, the balloon is expanded, and the stent is expanded (plastically deformed) by the expansion force of the balloon, adhering to the inner surface of the target lumen and fixed in place. This type of stent requires the stent expansion process described above. On the other hand, self-expanding stents have an expansion function themselves, and are inserted into the body in a thin, contracted state, and when released at the target site, they return to their original expanded state by themselves, adhering to and fixing to the inner wall of the lumen to maintain the lumen shape.

[0006] The current purpose of stent placement is to restore blood vessels that have become narrowed for some reason to their original patent state. Most self-expanding stents are used in peripheral areas such as the blood vessels of the lower limbs and the carotid arteries. In the coronary and cerebrovascular areas, there is a demand for stents that can be thinned during insertion.

[0007] The applicant of the present application has proposed JP 2011-115634 A (Patent Document 1). The stent 1 in Patent Document 1 is provided with a connecting section 5 in which a plurality of annular units 4, each of which is made up of a plurality of annular linear bodies 2 and a connecting section 3, are arranged in the axial direction of the stent. Both the starting and ending ends of the connecting section 5 are connected to the vertices of the bent portions of the annular linear bodies. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Patent Publication No. 2011-115634 Summary of the Invention [Problem to be solved by the invention]

[0009] In the stent of Patent Document 1, as described above, both the start and end of the connecting portion 5 are connected to the vertices of the bent portion of the annular filament. At the connecting portion, the annular filament extending in the circumferential direction is bent, but is connected to the connecting portion before and after the bent portion, and intersects with the connecting portion in a cross shape. When this stent is reduced in diameter, it is difficult to reduce the diameter at the connecting portion.

[0010] Therefore, the object of the present invention is to provide a tubular stent for placement in the body in which multiple annular bodies formed by wavy and annular linear elements each having a plurality of one-end side bent portions with apexes at one axial end side and a plurality of other-end side bent portions with apexes at the other axial end side of the stent are arranged in the axial direction, and adjacent annular bodies are connected by connecting portions, and which has good radial compressibility and sufficient expansive force, and a stent delivery system for placement in the body. [Means for solving the problem]

[0011] The above objectives are achieved by the following: A stent for placement in vivo, in which a plurality of annular bodies formed in an annular shape by a single endless linear element are arranged in an axial direction, and adjacent annular bodies are connected by a connecting portion, the annular bodies have a plurality of one-end bent portions located on one end side of the stent in the axial direction, a plurality of other-end bent portions located on the other end side of the stent in the axial direction, and a plurality of connecting linear portions connecting the one-end bent portions and the other-end bent portions, and further, when the stent is in an expanded state, one of the connecting linear portions of the plurality of annular bodies located in a central portion of the stent is connected to one end side of the one-end bent portion. a connecting portion connecting the end of the axial linear portion to the annular body having an axial linear portion, the connecting portion connecting the end of the axial linear portion to the annular body having an axial linear portion, the connecting portion connecting the end of the axial linear portion to the annular body having an axial linear portion and the one end apex of the annular body adjacent to the other end of the stent in the axial direction.

[0012] The above object is also achieved by the following: A stent delivery system comprising a sheath, the above-mentioned stent housed within the tip of the sheath, and a shaft for inserting through the sheath and releasing the stent from the tip of the sheath, wherein the stent is formed in a roughly cylindrical shape, is compressed in the direction of its central axis when inserted into the body, and expands outwardly and restores to its pre-compressed shape when placed in the body. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is a development view of a stent for placement in a living body according to one embodiment of the present invention during production. [Diagram 2]FIG. 2 is a partially enlarged view of the stent for placement in a living body shown in FIG. [Diagram 3] FIG. 3 is an explanatory view for explaining the ring-shaped body of the stent to be placed in a living body in FIG. [Figure 4] FIG. 4 is an external view of the in-vivo stent of FIG. 1 when expanded. [Diagram 5] FIG. 5 is an external view of the stent for placement in a living body shown in FIG. 1 when its diameter is contracted. [Figure 6] FIG. 6 is a partially enlarged view of the stent for placement in a living body shown in FIG. [Figure 7] FIG. 7 is an external view of a stent for placement in a living body according to another embodiment of the present invention when expanded. [Figure 8] FIG. 8 is a front view of a stent delivery system according to an embodiment of the present invention. [Figure 9] FIG. 9 is an enlarged, partially cutaway view of the distal end portion of the stent delivery system shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] The in-vivo stent of the present invention will be described with reference to the embodiments shown in the drawings. As shown in Figures 1 and 2, the stent 1 for placement in the body of the present invention is a stent for placement in the body in which a plurality of annular bodies 2 formed in a ring shape by a single endless linear element (strut) are arranged in the axial direction, and adjacent annular bodies 2 (2a, 2b, 2c, 2d, 2e, 2f, 2g, 2h) are connected by connecting portions 3. The annular bodies 2a, 2b, 2c, 2d, 2e, 2f, 2g, and 2h have a plurality of one-end bent portions 21 located on one end side in the axial direction of the stent (left side in Figure 1), a plurality of other-end bent portions 22 located on the other end side in the axial direction of the stent (right side in Figure 1; direction in which the stent is inserted into the body), and a plurality of connecting linear portions 23, 24 connecting the one-end bent portions 21 and the other-end bent portions 22.

[0015] Furthermore, in the expanded state of the stent 1, one (e.g., 23) of the connecting linear portions (including axial linear portions 25 and bent portions 26 described later) 23, 24 of the multiple annular bodies 2 located in the central portion of the stent includes an axial linear portion 25 having a start end at one end apex 21a of the one-end bent portion 21, extending parallel to the axial direction of the stent 1 compared to other portions of the connecting linear portions 23, 24 and having a length shorter than the axial length of the annular body 2, and a bent portion 26 having a start end at a terminal end 25a of the axial linear portion 25, extending in the circumferential direction of the stent 1 and in a direction away from the one-end apex 21a, and having a terminal end connected to the remaining portion of one of the connecting linear portions 23 (24). The connecting portion 3 connects the terminal end 25a of the axial linear portion 25 to the annular body 2 having the axial linear portion 25 and the one-end apex 21a of the annular body 2 adjacent to the other end side of the stent 1 in the axial direction. This stent 1 can be effectively used as a stent for dilating cerebral arteries.

[0016] The stent 1 of this embodiment is formed in a substantially cylindrical shape, is compressed in the direction of its central axis when inserted into the body, and is a so-called self-expanding stent that expands outward when placed in the body and restores to its pre-compression shape. 1 to 6, the stent 1 of this embodiment has a configuration in which a plurality of ring-shaped bodies 2a, 2b, 2c, 2d, 2e, 2f, 2g, and 2h are arranged in parallel in the axial direction so as to be adjacent to each other in the axial direction, and adjacent ring-shaped bodies are connected to each other. Each of the ring-shaped bodies 2b, 2c, 2d, 2e, 2f, 2g, and 2h is formed of a wavy and ring-shaped linear component having a plurality of one-end side bent portions 21 having an apex 21a at one end side in the axial direction and a plurality of other-end side bent portions 22 having an apex 22a at the other end side in the axial direction of the stent 1. The number of the annular bodies 2 in the stent 1 is preferably 5 to 30, and more preferably 6 to 20. The number of the annular bodies 2 in the stent 1 in this embodiment is 8.

[0017] The annular bodies 2a, 2b, 2c, 2d, 2e, 2f, 2g, and 2h in the stent 1 of this embodiment have a plurality of one-end bent portions 21 and other-end bent portions 22 at approximately the same pitch, as shown in Fig. 1. The number of one-end bent portions 21 (or other-end bent portions 22) in each of the annular bodies 2a, 2b, 2c, 2d, 2e, 2f, 2g, and 2h is preferably 4 to 10, and more preferably 4 to 8.

[0018] In the stent 1 of this embodiment, when the stent 1 is formed and in its expanded state, as shown in Figures 1, 2 and 4, one of the connecting linear portions 23, 24 of the multiple annular bodies 2 located in the central portion of the stent has an axial linear portion 25 that begins at the one-end vertex 21a of the one-end bent portion 21 and extends parallel to the axial direction of the stent 1 compared to the other portions of the connecting linear portions 23, 24 and is shorter than the axial length of the annular body 2, and a bent portion 26 that has a starting end at the end 25a of the axial linear portion 25, extends circumferentially of the stent 1 and in a direction away from the one-end vertex 21a, and has an end connected to the remainder of one of the connecting linear portions 23, 24.

[0019] The axially linear portion 25 extends from inside one end vertex 21a (the portion located closest to one end in the one-end bent portion) of the annular body 2 in the axial direction and toward the other end of the stent 1. The bent portion 26 is bent from the terminal end 25a of the axially linear portion 25 and has a circumferentially extending portion that extends a short distance in the circumferential direction of the stent, and a bent portion that is formed at the terminal end of the circumferentially extending portion and extends obliquely toward the other end of the stent 1. The terminal end of the bent portion of the bent portion 26 is connected to the remaining portion of the connecting linear portion 23.

[0020] The number of annular bodies 2 located in the central portion of the stent and having the above-mentioned axial linear portions 25 and bent portions 26 is preferably 5 to 30, and more preferably 6 to 20. The number of the above-mentioned type of annular bodies 2 in the stent 1 of this embodiment is 5. It is also preferable that all of the annular bodies 2 located in the central portion of the stent are annular bodies having axial linear portions 25 and bent portions 26.

[0021] Furthermore, in the stent 1 of this embodiment, as shown in Figure 1, in the annular bodies 2b, 2c, 2d, 2e, 2f having the above-mentioned axial linear portions 25 and bent portions 26, one side of each of the connecting linear portions 23, 24 is all provided with an axial linear portion 25 and a bent portion 26, and further, a connecting portion 3 is connected to the end of each of the axial linear portions 25.

[0022] In the stent 1 of this embodiment, the axial linear portion 25 is an axially straight portion. The axial linear portion 25 extends parallel to the axial direction of the stent 1 compared to other portions of the connecting linear portion 23 (24). Specifically, the axial linear portion 25 is substantially parallel to the axial direction of the stent 1, but is slightly inclined with respect to the central axis of the stent.

[0023] As shown in FIG. 3, the one-end bent portion 21 of the annular body 2 (2b, 2c, 2d, 2e, 2f) having the axial linear portion 25 and the bent portion 26 has a first inflection point formed by the apex 21a and a second inflection point formed by the bent portion 26. The second inflection point (bent portion 26) is located on the other end side from the first inflection point (apex 21a) by a predetermined length (specifically, the length of the axial linear portion 25). The one-end bent portions 21 having the axial linear portion 25 and the bent portion 26 are arranged in a plurality of circumferential directions. Also, as shown in FIG. 3, the other-end bent portion 22 has a single inflection point formed by the apex 22a, and the other-end bent portions 21 are arranged in a plurality of circumferential directions. Therefore, in the annular body 2 having the axial linear portion 25 and the bent portion 26, the one end side bent portion 21 and the other end side bent portion 22 have different shapes.

[0024] Furthermore, as shown in Figures 1 to 3, the connecting linear portions 23, 24 (connecting linear portion 23 in the annular bodies 2b, 2d, 2f) having the axial linear portion 25 and the bent portion 26 have a longer length of linear component (strut) than the connecting linear portions 23, 24 (connecting linear portion 24 in the annular bodies 2b, 2d, 2f) which do not have the axial linear portion 25 and the bent portion 26 and connect the one end vertex 21a of the one end bend portion 21 and the other end vertex 22a of the other end bend portion 22.

[0025] 1 to 3, the connecting linear portions 23, 24 (connecting linear portion 23 in the annular body 2d) of the portion (including the bent portion 26) connecting the terminal end 25a of the axial linear portion 25 and the other end vertex 22a of the other end bent portion 22 have a shorter length of linear component (strut) than the connecting linear portions 23, 24 (connecting linear portion 24 in the annular body 2d) that directly connects the one end vertex 21a of the one end bent portion 21 and the other end vertex 22a of the other end bent portion 22. This makes it possible to reduce the risk of the other end vertex 22a coming into contact with the connecting portion inclined portion 32 and the stent being deformed when the stent is placed in the bent portion.

[0026] The distance between the one end vertex 21a and the end 25a of the axial linear portion 25 or the start of the bent portion 26 (the length of the axial linear portion 25) is preferably 1 / 16 to 1 / 2, and more preferably 1 / 8 to 1 / 4, of the length of the connecting linear portion (the connecting linear portion not including the axial linear portion 25 and the bent portion 26) extending from the one end vertex 21a. The axial length of the axial linear portion 25 is preferably 1 / 16 to 1 / 2, and more preferably 1 / 8 to 1 / 4, of the axial length of the annular body 2.

[0027] In the stent 1 of this embodiment, the annular body 2 located in the central portion of the above-mentioned stent 1 has a plurality of bent portions 26, as shown in Figures 1 to 3, and the circumferential direction in which each bent portion 26 extends is the same. 1 and 2, in the stent 1 of this embodiment, the one-end bent portion 21 of the annular body 2 (2d) having the axial linear portion 25 and the bent portion 26 includes a first branch portion A formed by the other end of the connecting portion 3, the apex 21a, and the axial linear portion 25, and a second branch portion B formed by the axial linear portion 25, one end of the connecting portion 3, and the bent portion 26 at a position shifted toward the other end by a predetermined length (the length of the axial linear portion 25) from the first branch portion A. The connecting linear portions 23, 24 (connecting linear portion 24 in the annular body 2d) having the first branch portion A are connected to the connecting linear portions 23, 24 (connecting linear portion 23 in the annular body 2d) having the second branch portion B at the other-end bent portion 22.

[0028] In other words, in the stent 1 of the present invention, the connecting linear portions 23, 24 (connecting linear portion 24 in the annular body 2d) having the one-end bent portion 21 and the connecting linear portion 23, 24 (connecting linear portion 23 in the annular body 2d) having the axial direction linear portion 25 and the bent portion 26 are connected at the other-end bent portion 22. There is no connecting portion between the two.

[0029] The first branch portion A and the second branch portion B are branched portions that do not intersect in a crisscross pattern. The first branch portion A and the second branch portion B are shifted toward the other end by a predetermined length (the length of the axial linear portion 25), which improves the radial deformability (diameter reduction) of the bent portion on one end of the ring-shaped body having the first branch portion A and the second branch portion B when the stent is compressed (diameter reduction) as shown in Figs. 5 and 6.

[0030] More specifically, when the stent is compressed (reduced in diameter), the stent 1 is in a state as shown typically in Figures 5 and 6. When the stent 1 is compressed in the radial direction, the linear components (struts) are such that, as shown in Figure 6, the connecting linear portions 23, 24 (connecting linear portion 24 in the annular body 2d) having a first branch portion A and the connecting linear portions 23, 24 (connecting linear portion 23 in the annular body 2d) having a second branch portion B directly connected thereto are brought into close proximity.

[0031] The deformed first branch A forms a curved portion extending in the first circumferential direction, and similarly, the deformed second branch B forms a curved portion extending in the opposite direction to the first circumferential direction. Since the second branch B is shifted toward the other end side from the first branch A by a predetermined length (the length of the axial linear portion 25), the curved portion formed by the deformed second branch B does not overlap with the curved portion formed by the deformed first branch A, and is located on the other end side. In particular, in the stent 1 of this embodiment, the curved portion formed by the deformed second branch B enters the other end side of the curved portion formed by the deformed first branch A. As a result, the first branch portion A and the second branch portion B of the stent 1 are less likely to become obstacles when the stent 1 is reduced in diameter, ensuring good radial deformability (reduced diameter) when the stent is compressed (reduced in diameter).

[0032] 1 and 2, in the stent 1 of this embodiment, the circumferential directions in which the bent portions 26 adjacent to each other in the axial direction of the stent 1 extend are different in the adjacent annular bodies 2 located in the center of the stent 1. In the stent of this embodiment, the connecting linear portion having the one-end bend portion 21 (connecting linear portion 24 in the annular bodies 2b, 2d, and 2f) and the connecting linear portion having the axial linear portion 25 and the bent portion 26 (connecting linear portion 23 in the annular bodies 2b, 2d, and 2f) are connected at the other-end bent portion 22. In addition, the connecting linear portion having the one-end bend portion 21 (connecting linear portion 23 in the annular bodies 2c and 2e) and the connecting linear portion having the axial linear portion 25 and the bent portion 26 (connecting linear portion 24 in the annular bodies 2c and 2e) are connected at the other-end bent portion 22.

[0033] By doing so, a uniform expansive force can be exerted throughout the entire stent. Although the above is preferable, as in the case of a stent 1a shown in Fig. 7, in adjacent annular bodies 2 located in the center of the stent 1a, the circumferential directions in which adjacent bent portions 26 in the axial direction of the stent 1a extend may all be the same.

[0034] 1 to 6, the stent 1 includes terminal ends 25a of the axial linear portions 25 and connecting portions 3 that connect the annular bodies 2 having the axial linear portions 25 to one end vertices 21a of the annular bodies 2 adjacent to the other axial end side of the stent 1. In the stent 1 of this embodiment, the terminal ends 25a of all the axial linear portions 25 of the annular bodies 2 having the axial linear portions 25 are connected to the connecting portions 3.

[0035] In the stent 1 of this embodiment, the connecting portion 3 has one end at the terminal end 25a of the axial linear portion 25, and is equipped with a connecting portion parallel portion 31 extending approximately parallel to the axial direction of the stent 1, and a connecting portion inclined portion 32 extending diagonally in the circumferential direction and axial direction of the stent 1 from the other end of the connecting portion parallel portion 31, and the terminal end of the connecting portion inclined portion 32 is connected to the one-end side vertex 21a other than the closest one-end side vertex of an adjacent annular body 2.

[0036] Specifically, in the stent 1 of this embodiment, the axial linear portion 25 and the connecting portion parallel portion 31 of the connecting portion 3 are continuous and linear. Also, in the stent 1 of this embodiment, the end of the connecting portion inclined portion 32 is connected to the one-end vertex 21a that is adjacent to the one-end vertex 21a closest to the one-end vertex 21a of the adjacent annular bodies 2 in the circumferential direction.

[0037] In the stent 1 of this embodiment, as shown in Fig. 1, all of the connection inclined portions 32 between adjacent annular bodies 2 are inclined in the same direction. In particular, in the stent 1, all of the connection inclined portions 32 between adjacent annular bodies 2 are substantially parallel. Furthermore, the connection inclined portions 32 adjacent in the axial direction of the stent are inclined in different directions in the circumferential direction of the stent 1. In the stent 1, the connection inclined portions 32 adjacent in the axial direction have different inclination directions and have substantially the same inclination angle with respect to the central axis of the stent 1.

[0038] In the stent 1 of this embodiment, the connecting portion inclined portion 32 of the connecting portion 3 is inclined in the axial direction of the stent and curved in the circumferential direction. Therefore, as shown in FIG. 4, which is an external view of the stent 1 when expanded, the connecting portion inclined portion 32 is curved with the center of the connecting portion inclined portion 32 bulging outward when the stent 1 is expanded. In the expanded state of the stent, this stent is located between the adjacent ring-shaped bodies and has a convex portion that protrudes to the outside of the stent. This convex portion is formed by the middle portion of the connecting portion protruding outward. In addition, the protrusion amount increases from both ends of the connecting portion toward the center, and the center is the apex of the convex portion. If the space between the convex portions is considered as a concave portion, unevenness occurs on the outside of the stent, and the period of this unevenness in the axial direction is the distance in the axial direction between the apexes on one end side or the apexes on the other end side of the adjacent ring-shaped bodies. Therefore, the adhesion to the inserted biological site is improved, and movement is restricted. In addition, the axial linear portion 25 and the connecting portion 3 form one wavy linear portion extending in the axial direction. In order to ensure sufficient adhesion of the stent to the living body site, it is desirable that the height of the above-mentioned convex portions (distance between the convex and concave portions) is 50 μm or more.

[0039] In the stent 1 of this embodiment, the end 31a of the parallel portion 31 of the connecting portion 3 is located at the same position as the other end vertex 22a of the annular body 2 having the axial linear portion 25 to which one end of the connecting portion 3 is connected, or slightly toward the other end of the stent 1 in the axial direction of the stent 1 when the stent 1 is in an expanded state. In this way, when the stent is reduced in diameter, the connecting portion inclined portion 32 connected to the end 31a of the connecting portion parallel portion 31 of the connecting portion 3 does not come into contact with the other end side bent portion 22 of the annular body 2, resulting in good diameter reduction. Note that the end 31a of the connecting portion parallel portion 31 of the connecting portion 3 is preferably located closer to the other end side of the stent 1 than the other end side apex 22a of the annular body 2.

[0040] In addition, it is preferable that the end 31a of the parallel portion 31 of the connecting portion 3 is located at the same position as the other end vertex 22a of the annular body 2 having the axial linear portion 25 to which one end of the connecting portion 3 is connected, or slightly toward the one end of the stent 1 relative to the other end vertex 22a, in the axial direction of the stent 1 when the stent 1 is in a contracted state. By doing this, when the stent is contracted and stored in the sheath, the connecting portion inclined portion 32 becomes closer to being parallel to the axial direction, making it easier to transmit axial forces and increasing the axial rigidity.

[0041] 1, the stent 1 of this embodiment includes a one-end annular body connector 3a connecting the other end apex 22a of the annular body 2a located at one end to the one end apex 21a of the adjacent annular body 2b, and an other-end annular body connector 3b connecting the one end apex 21a of the annular body 2h located at the other end to the other end apex 22a of the adjacent annular body 2g. Therefore, both ends of the stent 1 are in a so-called closed cell state, and have high axial rigidity.

[0042] In the stent 1 of this embodiment, the apexes 21a of the one-end bent portions 21 of the adjacent ring-shaped bodies 2b, 2c, 2d, 2e, 2f, 2g, and 2h, except for the ring-shaped body 2a located at one end of the stent 1, are connected to the connecting portions 3, 3a, and 3b. Therefore, the stent 1 of this embodiment does not have the one-end bent portion 21 whose apex 21a is a free end, except for the ring-shaped body 2a located at one end of the stent 1. Furthermore, in the stent 1 of this embodiment, each of the ring-shaped bodies 2b, 2c, 2d, 2e, 2f, and 2h, except for the ring-shaped body 2a and 2g, has a plurality of other-end bent portions 22 whose other-end apexes 22a are free ends.

[0043] The stent of this embodiment has a single wavy line portion formed by the axial line portion 25 and the connecting portion 3, and is provided with a plurality of wavy line portions arranged approximately evenly in the circumferential direction. This allows the stent to deform as a whole favorably when compressed or pulled, and also provides favorable blood vessel tracking ability when placed in a curved blood vessel.

[0044] The axial length of the connecting portion 3 during expansion of the stent is preferably 5 / 4 to 3 times, and more preferably 3 / 2 to 2 times, the axial length of the annular body 2 during expansion of the stent. The axial length of the connecting portion parallel portion 31 of the connecting portion 3 during expansion of the stent is preferably 1 / 2 to 2 times, and more preferably 3 / 4 to 5 / 4 times, the axial length of the annular body 2 during expansion of the stent. The axial length of the connecting portion inclined portion 32 of the connecting portion 3 is preferably 1 / 4 to 2 times, and more preferably 1 / 2 to 3 / 2 times, the axial length of the annular body 2 during expansion of the stent. The axial length of the connecting portion inclined portion 32 of the connecting portion 3 during expansion of the stent is preferably longer than the axial length of the connecting portion parallel portion 31. The inclination angle of the connecting portion inclined portion 32 of the connecting portion 3 with respect to the central axis of the stent 1 is preferably 35 degrees to 65 degrees, and more preferably 40 degrees to 60 degrees. The stent of the present embodiment can be made thin and can be stably placed in bent sections, and is therefore suitable for placement in cerebral arteries which have a small inner diameter and many bends, making it suitable as a stent for treating cerebral artery stenosis.

[0045] A superelastic metal is suitable as a material for forming the stent. A superelastic alloy is preferably used as the superelastic metal. The superelastic alloy referred to here is generally called a shape memory alloy, and exhibits superelasticity at least at the temperature of the living body (around 37°C). Particularly preferred are superelastic alloys such as a Ti-Ni alloy containing 49 to 53 atomic % Ni, a Cu-Zn alloy containing 38.5 to 41.5 weight % Zn, a Cu-Zn-X alloy containing 1 to 10 weight % X (X = Be, Si, Sn, Al, Ga), and a Ni-Al alloy containing 36 to 38 atomic % Al. Particularly preferred is the Ti-Ni alloy. In addition, the mechanical properties can be appropriately changed by replacing a part of the Ti-Ni alloy with 0.01-10.0% X to make a Ti-Ni-X alloy (X=Co, Fe, Mn, Cr, V, Al, Nb, W, B, etc.), or by replacing a part of the Ti-Ni alloy with 0.01-30.0% Y to make a Ti-Ni-Y alloy (Y=Cu, Pb, Zr), and by selecting the cold working rate and / or the final heat treatment conditions. In addition, the mechanical properties can be appropriately changed by using the above Ti-Ni alloy, Ti-Ni-X alloy, or Ti-Ni-Y alloy and selecting the cold working rate and / or the final heat treatment conditions. The buckling strength (yield stress under load) of the superelastic alloy used is 5-200 kgf / mm 2 (22°C), more preferably 8 to 150 kgf / mm 2 , the recovery stress (yield stress when unloaded) is 3 to 180 kgf / mm 2 (22°C), more preferably 5 to 130 kgf / mm 2 The term "superelasticity" used here means that even if it is deformed (bent, stretched, compressed) to the extent that normal metals would undergo plastic deformation at the operating temperature, it will recover to almost its original shape after the deformation is released without the need for heating.

[0046] For example, when the stent 1 is used for dilating cerebral blood vessels, the diameter when expanded (uncompressed) is preferably about 0.5 to 6.0 mm, more preferably 0.9 to 5.0 mm, and the length when expanded (uncompressed) is preferably about 5 to 50 mm.

[0047] The wall thickness of the stent is preferably about 0.05 to 0.15 mm, and more preferably 0.06 to 0.13 mm. The width of the linear elements constituting the stent is preferably about 0.04 to 0.15 mm, and more preferably 0.05 to 0.13 mm.

[0048] The stent of the present invention may contain a physiologically active substance in a releasable manner. For example, a method for releasably containing a physiologically active substance includes coating the surface of the stent with a polymer (e.g., a biodegradable polymer) containing the physiologically active substance. The biodegradable polymer is not particularly limited as long as it is degraded enzymatically or non-enzymatically in the body and the decomposition products are not toxic. For example, polylactic acid, polyglycolic acid, polylactic acid-polyglycolic acid copolymer, polycaprolactone, polylactic acid-polycaprolactone copolymer, polyorthoester, polyphosphazene, polyphosphate ester, polyhydroxybutyric acid, polymalic acid, poly-α-amino acid, collagen, gelatin, laminin, heparan sulfate, fibronectin, vitronectin, chondroitin sulfate, hyaluronic acid, polypeptide, chitin, chitosan, etc. can be used.

[0049] In addition, as the physiologically active substance, a substance that promotes the dissolution or metabolism of thrombus or thrombus complex, a substance that suppresses the increase of thrombus or thrombus complex, a substance that suppresses intimal thickening, an anticancer drug, an immunosuppressant, an antibiotic, an antirheumatic drug, an antithrombotic drug, an HMG-CoA reductase inhibitor, an ACE inhibitor, a calcium antagonist, an antihyperlipidemic drug, an antiinflammatory drug, an integrin inhibitor, an antiallergic drug, an antioxidant, a GPIIbIIIa antagonist, a retinoid, a flavonoid and a carotenoid, a lipid improving drug, a DNA synthesis inhibitor, a tyrosine kinase inhibitor, an antiplatelet drug, a vascular smooth muscle proliferation inhibitor, a biological material, an interferon, and an epithelial cell produced by genetic engineering can be used. A mixture of two or more of the above substances can also be used.

[0050] As a substance for promoting the dissolution or metabolism of thrombus or thrombus complexes or a substance for inhibiting the increase of thrombus or thrombus complexes, streptokinase, plasminogen activator, urokinase, staphinokinase, lumbrokinase, nattokinase, or analogs thereof can be used. As a substance for inhibiting the increase of thrombus or thrombus complexes, antiplatelet drugs represented by acetylsalicylic acid, ticlopidine, dipyridamole, cilostazol, beraprost Na, limaprost alfatex, ethyl icosapentaenoate, sarvogrelate hydrochloride, trapidil, clopidogrel, prasugrel, and analogs thereof, or anticoagulants represented by GP IIb / IIIa antagonists, heparin, and warfarin potassium can be used.

[0051] Next, a stent delivery system according to an embodiment of the present invention will be described with reference to the drawings. Fig. 8 is a partially omitted front view of a stent delivery system according to an embodiment of the present invention, and Fig. 9 is an enlarged longitudinal sectional view of the distal end portion of the stent delivery system shown in Fig. 8. The stent delivery system 10 of this embodiment comprises a sheath 12, a stent 1 housed within the distal end of the sheath 12, and an inner tube 14 that is slidably inserted through the sheath 12 and used to release the stent 1 from the distal end of the sheath 12. In the stent delivery system 10 of this embodiment, the stent 1 is the above-mentioned self-expanding stent which is formed in a cylindrical shape, compressed in the central axis direction when inserted into the body, and expands outward when placed in the body, and can restore to its pre-compression shape.

[0052] As shown in FIG. 8, the stent delivery system 10 of this embodiment comprises a sheath 12, a self-expanding stent 1, and an inner tube 14. As shown in Figures 8 and 9, the sheath 12 is a tubular body with openings at the distal and proximal ends. The distal opening functions as an outlet for the stent 1 when the stent 1 is placed in a stricture in a body cavity. The stent 1 is released from this distal opening by sliding the sheath 12 towards the proximal end, where the stress load is released and the stent 1 expands and returns to its pre-compression shape. The distal end of the sheath 12 serves as a stent storage region 15 for storing the stent 1 therein. The sheath 12 also has a side hole 41 provided on the proximal side of the storage region 15. The side hole 41 is for leading out a guide wire to the outside.

[0053] The outer diameter of the sheath 12 is preferably about 0.4 to 4.0 mm, and more preferably about 0.5 to 3.0 mm. The inner diameter of the sheath 12 is preferably about 0.3 to 2.0 mm. The length of the sheath 12 is preferably about 300 to 2500 mm, and more preferably about 300 to 2000 mm. 8, a sheath hub 16 is fixed to the base end of the sheath 12. The sheath hub 16 includes a sheath hub body and a valve body (not shown) that is housed in the sheath hub body and holds the inner tube 14 slidably and liquid-tight. The sheath hub 16 also includes a side port 18 that branches obliquely rearward from near the center of the sheath hub body. The sheath hub 16 also preferably includes an inner tube locking mechanism that restricts movement of the inner tube 14.

[0054] As shown in Figures 8 and 9, the inner tube 14 comprises a shaft-shaped inner tube main body portion 40, a tip portion 47 provided at the tip of the inner tube main body portion 40 and protruding from the tip of the sheath 12, and an inner tube hub 17 fixed to the base end of the inner tube main body portion 40. The tip portion 47 preferably projects beyond the tip of the sheath 12 and is formed in a tapered shape that gradually reduces in diameter toward the tip, as shown in Fig. 9. Forming it in this manner facilitates insertion into a stricture. The inner tube 14 is also preferably provided with a stopper that is located on the tip side of the stent 1 and prevents the sheath from moving toward the tip. The base end of the tip portion 47 is capable of abutting against the tip of the sheath 12 and functions as the stopper.

[0055] As shown in Fig. 9, the inner tube 14 has two protrusions 43, 45 for holding the self-expanding stent 1. The protrusions 43, 45 are preferably annular protrusions. A stent holding protrusion 43 is provided on the base end side of the tip portion 47 of the inner tube 14. A stent pushing protrusion 45 is provided a predetermined distance on the base end side from the stent holding protrusion 43. The stent 1 is disposed between these two protrusions 43, 45. The outer diameters of these protrusions 43, 45 are large enough to abut against the compressed stent 1.

[0056] Therefore, the movement of the stent 1 toward the distal end is restricted by the protrusion 43, and the movement toward the proximal end is restricted by the protrusion 45. The stent 1 is ejected from the sheath 12 by moving the sheath 12 toward the proximal end and by moving the inner tube 14 toward the distal end. Furthermore, the proximal end side of the stent pushing protrusion 45 preferably has a tapered section 46 that gradually reduces in diameter toward the proximal end, as shown in Fig. 9. Similarly, the proximal end side of the stent holding protrusion 43 preferably has a tapered section 44 that gradually reduces in diameter toward the proximal end, as shown in Fig. 9.

[0057] This prevents the inner tube 14 from protruding from the tip of the sheath 12, and the inner tube 14 from getting caught on the tip of the sheath when the stent 1 is released from the sheath 12 and then re-stored in the sheath 12. As described above, the stent 1 of the present invention does not have the one-end bent portion 21 that is a free end, except for the annular body 2a located at one end of the stent 1, and even if the stent is exposed to some extent, it can be re-stored in the sheath 12. The protruding portions 43 and 45 may be formed of separate members made of an X-ray contrast material. This allows the position of the stent to be accurately grasped under X-ray contrast, making the procedure easier.

[0058] As shown in Fig. 9, the inner tube 14 has a lumen 48 extending from the tip to at least the base end side of the stent storage site 15 of the sheath 12, and an inner tube side hole 42 communicating with the lumen 48 on the base end side of the stent storage site. In the stent delivery system 10 of this embodiment, the lumen 48 terminates at the side hole 42 formation site. The lumen 48 is for inserting one end of a guide wire from the tip of the stent delivery system 10, passing it partially through the inner tube, and then leading it to the outside from the side surface of the inner tube. The inner tube side hole 42 is located slightly distal to the stent delivery system 10 from the sheath side hole 41. The center of the inner tube side hole 42 is preferably 0.5 to 10 mm distal from the center of the sheath side hole 41.

[0059] The stent delivery system is not limited to the above-mentioned type, and the lumen 48 may extend to the base end of the inner tube. In this case, the side hole 41 of the sheath is not necessary. The inner tube 14 passes through the sheath 12 and protrudes from the proximal end opening of the sheath 12. An inner tube hub 17 is fixed to the proximal end of the inner tube 14, as shown in FIG.

[0060] The stent of the present invention is a stent for placement in a living body, in which a plurality of annular bodies formed into a ring shape by a single endless linear element are arranged in the axial direction, and adjacent annular bodies are connected by a connecting portion. The annular bodies have a plurality of one-end bent portions located on one axial end side of the stent, a plurality of other-end bent portions located on the other axial end side of the stent, and a plurality of connecting linear portions connecting the one-end bent portions and the other-end bent portions. Furthermore, when the stent is in an expanded state, one of the connecting linear portions of the plurality of annular bodies located in the central portion of the stent has an axial linear portion that has a start end at the one-end apex of the one-end bent portion, extends parallel to the axial direction of the stent compared to other portions of the connecting linear portion, and is shorter than the axial length of the annular body, and has a start end at an end of the axial linear portion, extends in the circumferential direction of the stent and away from the one-end apex, and has an end connected to the remaining portion of one of the connecting linear portions. The connecting portion connects the end of the axially linear portion to the annular body having the axially linear portion and to the apex of one end of the annular body adjacent to the other axial end of the stent. In particular, in the multiple annular bodies located in the central portion of the stent, when the stent is in an expanded state, one of the connecting linear portions has an axial linear portion that has a start end at one end apex of the one-end bent portion, extends so as to be parallel to the axial direction of the stent compared to the connecting linear portion and is shorter than the axial length of the annular body, and has a start end at an end of the axial linear portion, extends in the circumferential direction of the stent and in a direction away from the one-end apex, and has an end connected to the remainder of one of the connecting linear portions. The connecting portion connects the end of the axial linear portion to the annular body having the axial linear portion and the one-end apex of the adjacent annular body on the other axial end side of the stent. Therefore, one end of the connecting portion is connected to the end of the axial linear portion of the annular body, and is not connected to the apex of the bent portion of the annular body. Therefore, instead of intersecting in a cross shape with the connecting portion as the intersection point, the intersection is divided into two branching intersections that are offset in the axial direction. Therefore, when the diameter is reduced, the annular body has good radial deformability, and can be made smaller in diameter. [Industrial Applicability]

[0061] The stent for placement in a living body according to the present invention is as follows. (1) A stent for placement in a living body, in which a plurality of annular bodies formed in an annular shape by a single endless linear element are arranged in an axial direction, and adjacent annular bodies are connected by a connecting portion, the annular bodies have a plurality of one-end bent portions located on one end side of the axial direction of the stent, a plurality of other-end bent portions located on the other end side of the axial direction of the stent, and a plurality of connecting linear portions connecting the one-end bent portions and the other-end bent portions, and further, when the stent is in an expanded state, one of the connecting linear portions of the plurality of annular bodies located in a central portion of the stent is connected to one end side of the one-end bent portion. a connecting portion connecting the end of the axial linear portion to the annular body having an axial linear portion, the connecting portion connecting the end of the axial linear portion to the annular body having an axial linear portion, the connecting portion connecting the end of the axial linear portion to the annular body having an axial linear portion and the one end apex of the annular body adjacent to the other end of the stent in the axial direction.

[0062] This stent for placement in vivo is a stent for placement in vivo in which a plurality of annular bodies formed into a ring shape by a single endless linear element are arranged in the axial direction, and adjacent annular bodies are connected by a connecting portion. The annular bodies have a plurality of one-end bent portions located on one axial end side of the stent, a plurality of other-end bent portions located on the other axial end side of the stent, and a plurality of connecting linear portions connecting the one-end bent portions and the other-end bent portions. Furthermore, when the stent is in an expanded state, one of the connecting linear portions of the plurality of annular bodies located in the central portion of the stent has an axial linear portion that has a start end at the one-end apex of the one-end bent portion, extends parallel to the axial direction of the stent compared to other portions of the connecting linear portion, and is shorter than the axial length of the annular body, and has a start end at an end of the axial linear portion, extends in the circumferential direction of the stent and in a direction away from the one-end apex, and has an end connected to the remaining portion of one of the connecting linear portions. The connecting portion connects the end of the axially linear portion to the annular body having the axially linear portion and to the apex of one end of the annular body adjacent to the other axial end of the stent. In particular, in the multiple annular bodies located in the central portion of the stent, when the stent is in an expanded state, one of the connecting linear portions has an axial linear portion that has a start end at one end apex of the one-end bent portion, extends so as to be parallel to the axial direction of the stent compared to the connecting linear portion and is shorter than the axial length of the annular body, and has a start end at an end of the axial linear portion, extends in the circumferential direction of the stent and in a direction away from the one-end apex, and has an end connected to the remainder of one of the connecting linear portions. The connecting portion connects the end of the axial linear portion to the annular body having the axial linear portion and the one-end apex of the adjacent annular body on the other axial end side of the stent. Therefore, one end of the connecting portion is connected to the end of the axial linear portion of the annular body, and is not connected to the apex of the bent portion of the annular body. Therefore, instead of intersecting in a cross shape with the connecting portion as the intersection point, the intersection is divided into two branching intersections that are offset in the axial direction. Therefore, when the diameter is reduced, the annular body has good radial deformability, and can be made smaller in diameter.

[0063] The above embodiment may also be as follows. (2) A stent for placement in vivo as described in (1) above, wherein the connecting portion has one end at the terminal end of the axially linear portion, and comprises a connecting portion parallel portion extending approximately parallel to the axial direction of the stent, and a connecting portion inclined portion extending obliquely in the circumferential direction and axial direction of the stent from the other end of the connecting portion parallel portion, and the terminal end of the connecting portion inclined portion is connected to an end side vertex other than the one end side vertex that is closest to the one end side vertex of an adjacent annular body. (3) The stent for placement in a living body according to (1) or (2) above, wherein the axially linear portion is an axially straight portion. (4) The stent for placement in a living body according to (2) or (3) above, wherein the axially linear portion and the connecting portion parallel portion of the connecting portion are continuous and linear. (5) A stent for placement in vivo as described in any of (2) to (4) above, wherein an end of the parallel portion of the connecting portion is located at the same position as the apex of the other end of the annular body including the axially linear portion to which one end of the connecting portion is connected, or slightly toward the other end of the stent, in the axial direction of the stent when the stent is in an expanded state, and wherein an end of the parallel portion of the connecting portion is located at the same position as the apex of the other end of the annular body including the axially linear portion to which one end of the connecting portion is connected, or slightly toward the one end of the stent, in the axial direction of the stent when the stent is in a contracted state. (6) A stent for placement in a living body as described in any one of (1) to (5) above, wherein the connecting linear portion connecting the end of the axial linear portion and the other end vertex of the other end bent portion is shorter than the connecting linear portion connecting the one end vertex of the one end bent portion and the other end vertex of the other end bent portion. (7) A stent for placement in a living body as described in any one of (1) to (6) above, wherein the distance between the apex on one end side and the end of the axial linear portion or the start of the bent portion is 1 / 16 to 1 / 2 of the length of the connecting linear portion extending from the apex on one end side. (8) A stent for placement in vivo as described in any one of (1) to (7) above, wherein the annular body located in the central portion of the stent has a plurality of the bent portions, and the circumferential direction in which each bent portion extends is the same. (9) A stent for placement in vivo as described in (8) above, wherein the circumferential directions in which the bent portions adjacent to each other in the axial direction of the stent extend are different in adjacent annular bodies located in the central portion of the stent. (10) A stent for placement in a living body as described in any one of (1) to (9) above, wherein the stent does not have a bent portion on one end side that is a free end, except for the annular body located at one end. (11) A stent for placement in a living body as described in any one of (1) to (10) above, wherein ends of all of the axially linear portions of the annular body having the axially linear portions are connected to the connecting portions. (12) The stent comprises a one end annular body connecting portion connecting the other end vertex of the annular body located at one end to the one end vertex of the annular body adjacent to the annular body located at the one end, and an other end annular body connecting portion connecting the one end vertex of the annular body located at the other end to the other end vertex of the annular body located at the other end, and the one end vertex of all the annular bodies except for the annular body located at one end is connected to the connecting portion, the one end annular body connecting portion or the other end annular body connecting portion. A stent for placement in a living body as described in any of (1) to (11) above. (13) A stent for placement in a living body as described in any one of (1) to (12) above, wherein the stent has a protrusion that is located between adjacent annular bodies and protrudes outward from the stent in an expanded state. (14) A stent for placement in a living body as described in any one of (1) to (13) above, which is formed in an approximately cylindrical shape, is compressed in the direction of its central axis when inserted into the living body, and expands outwardly and restores to its pre-compressed shape when placed in the living body.

[0064] The stent delivery system of the present invention is as follows. (15) A stent delivery system comprising: a sheath; the stent according to (14) housed in a distal end of the sheath; and a shaft for passing through the sheath and releasing the stent from the distal end of the sheath.

[0065] The above embodiment may also be as follows. (16) The stent delivery system described in (15) above, wherein the stent is released from the tip of the sheath by moving the sheath toward the base end, and the stent, which is partially exposed from the sheath, can be re-stored within the sheath by moving the sheath toward the tip end relative to the stent.

Claims

1. A stent for placement in a living body, comprising a plurality of annular bodies each formed into an annular shape by a single endless linear element, arranged in an axial direction, and adjacent annular bodies connected to each other by a connecting portion, the annular body has a plurality of one-end bent portions located on one end side in the axial direction of the stent, a plurality of other-end bent portions located on the other end side in the axial direction of the stent, and a plurality of connecting linear portions connecting the one-end bent portions and the other-end bent portions, Furthermore, when the stent is in an expanded state, one of the connecting linear portions of the multiple annular bodies located in the central portion of the stent comprises an axial linear portion having a starting end at the one-end apex of the one-end bent portion, extending parallel to the axial direction of the stent compared to other portions of the connecting linear portion and shorter than the axial length of the annular bodies, and a bent portion having a starting end at an end terminal of the axial linear portion, extending in the circumferential direction of the stent and in a direction away from the one-end apex, the end terminal being connected to the remainder of the one of the connecting linear portions, A stent for placement in a living body, characterized in that the connecting portion connects the end of the axially linear portion to the annular body having the axially linear portion and the apex of one end of the annular body adjacent to the other axial end of the stent.

2. 2. The stent for placement in vivo according to claim 1, wherein the connecting portion has one end at the terminal end of the axially linear portion, and comprises a connecting portion parallel portion extending approximately parallel to the axial direction of the stent, and a connecting portion inclined portion extending obliquely in the circumferential direction and axial direction of the stent from the other end of the connecting portion parallel portion, and the terminal end of the connecting portion inclined portion is connected to a one-end vertex other than the one-end vertex that is closest to the adjacent annular body.

3. 3. The stent for placement in a living body according to claim 1, wherein the axially linear portion is an axially straight portion.

4. 4. The stent for placement in a living body according to claim 2, wherein the axially linear portion and the connecting portion parallel portion of the connecting portion form a continuous straight line.

5. 5. A stent for placement in vivo according to claim 2, wherein an end of the parallel portion of the connecting portion is located, in the axial direction of the stent when the stent is in an expanded state, at the same position as the apex of the other end of the annular body comprising the axially linear portion to which one end of the connecting portion is connected or slightly toward the other end of the stent from the apex of the other end, and wherein, in the axial direction of the stent when the stent is in a contracted state, the apex of the other end of the annular body comprising the axially linear portion to which one end of the connecting portion is connected or slightly toward the one end of the stent from the apex of the other end.

6. 6. A stent for placement in a living body as described in any one of claims 1 to 5, wherein the connecting linear portion connecting the end of the axial linear portion and the other end vertex of the other end bent portion is shorter than the connecting linear portion connecting the one end vertex of the one end bent portion and the other end vertex of the other end bent portion.

7. 7. A stent for placement in a living body as described in any one of claims 1 to 6, wherein the distance between the apex on one end side and the end of the axial linear portion or the start of the bent portion is 1 / 16 to 1 / 2 of the length of the connecting linear portion extending from the apex on one end side.

8. 8. A stent for placement in a living body according to claim 1, wherein the annular body located in the central portion of the stent has a plurality of the bent portions, and the bent portions extend in the same circumferential direction.

9. 9. The stent for placement in a living body according to claim 8, wherein in adjacent annular bodies located in a central portion of the stent, the circumferential directions in which the bent portions adjacent to each other in the axial direction of the stent extend are different.

10. 10. The stent for placement in a living body according to claim 1, wherein the stent has no bent portion on one end side that serves as a free end, except for the annular body located at one end.

11. 11. The stent for placement in a living body according to claim 1, wherein all ends of the axially linear portions of the annular body having the axially linear portions are connected to the connecting portion.

12. The stent comprises a one end annular body connecting portion connecting the other end vertex of the annular body located at one end to the one end vertex of the annular body adjacent to the annular body located at the one end, and an other end annular body connecting portion connecting the one end vertex of the annular body located at the other end to the other end vertex of the annular body located at the other end to the other end vertex of the annular body adjacent to the annular body located at the other end, and the one end vertices of all of the annular bodies except for the annular body located at one end are connected to the connecting portion, the one end annular body connecting portion or the other end annular body connecting portion. A stent for placement in a living body as described in any one of claims 1 to 11.

13. 13. The stent for placement in a living body according to claim 1, wherein the stent has protrusions which are positioned between adjacent annular bodies and protrude outwardly of the stent when the stent is in an expanded state.

14. 14. A stent for placement in a living body according to any one of claims 1 to 13, which is formed in a substantially cylindrical shape, is compressed in the direction of its central axis when inserted into the living body, and expands outwardly and restores to its pre-compressed shape when placed in the living body.

15. A stent delivery system comprising a sheath, a stent according to claim 14 housed in a distal end portion of the sheath, and a shaft for passing through the sheath and releasing the stent from the distal end of the sheath.

16. The stent delivery system of claim 15, wherein the stent delivery system releases the stent from the tip of the sheath by moving the sheath toward the base end, and the stent, which is partially exposed from the sheath, can be re-stored within the sheath by moving the sheath toward the tip end relative to the stent.

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