JP6428050B2 - Stent - Google Patents

Description

  The present invention relates to a stent that is inserted and placed in a body lumen such as a blood vessel.

  Conventionally, when an abnormality such as stenosis or occlusion occurs in a lumen such as a blood vessel, for example, a stent treatment is performed in which a stent is inserted into the lumen and the lumen is held in an expanded state. The stent has a cylindrical shape as a whole, and has a small diameter when inserted into a lumen, but is expanded and placed in the lumen. As a method for expanding the diameter of the stent in the lumen, there are self-expansion using a shape memory material and the like, mechanical expansion, and the like in addition to expansion using a balloon.

  The stent can be expanded and contracted as described above, and has a porous structure or a linear shape in which a large number of through holes are provided in the peripheral wall portion in consideration of reducing the burden on the living body and improving biofusion. The strut structure is connected to Specifically, as described in, for example, Japanese Patent Application Laid-Open No. 2007-267844 (Patent Document 1) and the like, a metal tube such as stainless steel or platinum is cut into an appropriate length, and the peripheral wall is cut. By forming through holes and struts by laser processing, a stent having a simple rectangular cross-sectional shape is formed.

  However, with a stent with a conventional structure with struts having a simple rectangular cross-section, it is still difficult to obtain sufficient design flexibility to realize compatibility with each patient. It was hard to say that I was able to respond sufficiently.

  Specifically, for example, when a stent with a conventional structure is placed in a stenotic site of an arteriosclerotic patient and the stent treatment is performed, the expanded state of the blood vessel is maintained immediately after the placement of the stent. After a month, blood vessels may restenect at the indwelling position of the stent due to adhesion of thrombus to the stent. The presence or absence or degree of restenosis varies depending on the site where the stenosis occurs, the state of the stenosis site, the patient, etc., and it has been difficult to improve and cope with the conventional stent.

  On the other hand, when the stent is expanded with a balloon or the like and placed in the blood vessel, the stent may be displaced in the length direction in the blood vessel. The presence / absence and extent of stent misalignment in the blood vessel also varies depending on the site and state of the stent, the patient, and the like, and it has been difficult to improve and cope with the stent with the conventional structure.

JP 2007-267844 A

  The present invention has been made in the background of the above-mentioned circumstances, and the problem to be solved is a stent according to a site where a stenosis occurs in a lumen where the stent is placed, a state of the stenosis site, or the like. It is an object of the present invention to provide a stent having a novel structure capable of adjusting the performance and the like with a greater degree of design freedom.

A first aspect of the present invention is a stent that is formed into a cylindrical shape by a structure of a skeleton that can be expanded and contracted in a radial direction, and is placed in a body lumen, and the skeleton is deformed by a change in the thickness direction of a cross-sectional shape The cross-sectional shape of the skeleton is an approximately inverted triangular shape whose width increases from the inner peripheral surface toward the outer peripheral surface, and extends from the outer peripheral surface of the skeleton to the inner peripheral side and intersects. Both side surfaces in the circumferential direction are straight in cross-sectional shape, and the skeleton is a laminated structure of a plurality of types of metals, and the metal of the outer layer portion of the laminated structure is different from the metal of the inner layer portion , And

  In the stent having the structure according to this aspect, the skeleton has a cross-sectional shape different from a conventional simple rectangular cross-sectional shape, so that the stenosis occurs in the lumen where the stent is placed, the state of the stenosis, or the like. Accordingly, the stent performance and the like can be adjusted efficiently with a large degree of design freedom. The specific adjustment mode can be realized by each mode of the present invention described below, for example.

In addition, in the stent having the structure according to this aspect, the cross-sectional width dimension of the portion exposed to the fluid in the lumen such as blood is made smaller than that of the conventional structure having a skeleton having a simple rectangular cross section. Can do. As a result, blood or the like can flow more easily in the placement position of the stent in the lumen of a blood vessel or the like than a stent having a conventional structure, and stagnation or turbulence of blood or the like can be suppressed. As a result, troubles such as formation of thrombus and restenosis of the blood vessel at the indwelling position of the stent due to the attachment of the thrombus to the stent can be effectively avoided.

  In addition, since the cross-sectional width of the skeleton is relatively large in the circumferential direction on the outer peripheral surface of the stent, the pressing force on the inner surface of the lumen such as a blood vessel can be dispersed, resulting in local force concentration. The generation of cracks can be suppressed, and the healing period of cracks generated in the lumen wall can be shortened. Thereby, for example, restenosis caused by enlargement of vascular endothelial cells in a cracked portion of the blood vessel can be effectively suppressed. Further, even if the vascular endothelial cells are enlarged, a relatively large gap is provided between the skeletons having a reduced cross-sectional width on the inner peripheral surface side of the stent, so that the vascular endothelial cells can be Further enlargement inward from the surface is suppressed, and a further inhibitory effect on the restenosis of the blood vessel is exhibited.

Further, in the stent having a structure according to this aspect, the circumferential width dimension in the skeleton cross section is reduced toward the inner peripheral side, so that when the diameter is reduced by being attached to the delivery catheter, The problem that adjacent skeletons contact each other on the inner peripheral side having a small peripheral length and the amount of diameter reduction is limited is solved. Therefore, while ensuring the cross-sectional area of the skeleton and realizing the required strength and the like, it is possible to improve the delivery performance by setting the size capable of reducing the diameter sufficiently small. Furthermore, the stent according to this embodiment can be combined with a ninth embodiment of the present invention described later to form a laminated structure of a plurality of types of metals, for example, by electroforming. For example, by adopting a metal material with a larger ductility in the outer layer than in the inner layer, it is possible to relieve stress on the surface during expansion / contraction and deformation of the stent while preventing the occurrence of cracks etc. while securing the stent strength in the inner layer. Is also possible. In addition, by adopting a metal material with a smaller ionization tendency in the outer layer than in the inner layer, it is possible to achieve biocompatibility, radiopacity, etc. by the outer layer while ensuring the required strength characteristics in the inner layer. Become. In this embodiment, it is sufficient that at least a part of the skeleton has a laminated structure, and the entire skeleton does not have to have a laminated structure.

In the stent according to this aspect, the cross-sectional shape of the skeleton is not particularly limited as long as the width dimension is increased from the inner peripheral surface toward the outer peripheral surface, but it is particularly preferable that the skeleton is an approximately inverted triangle. More preferably, the cross-sectional shape is an approximately inverted isosceles triangle.
According to a second aspect of the present invention, in the stent according to the first aspect, in the cross-sectional shape of the skeleton, the corner on the inner peripheral side is an arcuate curved surface.

A third aspect of the present invention, in the stent according to the first or second aspect, in the cross-sectional shape of the skeleton, the included angle of the circumferential side surfaces, are larger than the center angle in the arc of the outer peripheral surface Is.

  In the stent having the structure according to the present aspect, both side surfaces in the circumferential direction in the skeleton cross section enter a direction approaching each other toward the inner circumferential side rather than the radial line in a state before the diameter reduction. Therefore, even when the diameter is reduced, it is avoided that the skeletons adjacent in the circumferential direction come into contact with each other on the inner circumference side at an early stage and the amount of diameter reduction is limited. As a result, it is possible to realize a stent that can be deformed to a smaller diameter while ensuring the circumferential length of the skeleton on the outer peripheral surface of the stent and avoiding the action of a local pressing force on a blood vessel or the like.

  A fourth aspect of the present invention is the stent according to any one of the first to third aspects, wherein the rigidity at at least one end in the axial direction is greater than that of the central part.

  In the stent having the structure according to this aspect, the rigidity of the axial end portion that is easily deformed is increased, so that restenosis of the lumen is effectively suppressed. That is, the rigidity of the axial end of the stent is improved because, for example, when the axial end of the stent is left in the blood vessel, the blood flow is disturbed and a thrombus is formed. By enlarging and stably indwelling in the blood vessel, restenosis at the stent indwelling position can be effectively prevented.

  According to a fifth aspect of the present invention, in the stent according to the fourth aspect, the end portion whose rigidity is increased compared to the central portion is reduced in rigidity at the end portion on the axially outer side. is there.

  In the stent having the structure according to this aspect, since the rigidity of the end portion at the end of the stent is reduced, the load exerted on the lumen by the end portion of the stent can be suppressed. Preferably, the rigidity of the end portion is set to be substantially the same as or smaller than that of the central portion.

According to a sixth aspect of the present invention, in the stent according to any one of the first to fifth aspects, a weakened portion partially reduced in strength is formed on the skeleton by at least one of electroforming and etching. It is what.

  In a stent having a structure according to this aspect, by providing a weakened portion in the skeleton, for example, it is divided after placement to obtain a stent shape that conforms to the lumen shape, or is cut or deformed during placement treatment for branching. Forming the opening by a technique can be easily realized.

  In particular, by forming such a fragile portion by electroforming or etching, there is no need for a troublesome operation such as making it separately from other portions of the skeleton and then fixing them. In addition, the position and shape of the fragile portion can be arbitrarily set, and the degree of freedom in design can be improved.

According to a seventh aspect of the present invention, in the stent according to the sixth aspect, the fragile portion is easily deformed with a smaller cross-sectional area than other portions of the skeleton.

  In the stent having the structure according to this aspect, the fragile portion is stably cut by making the cross-sectional area of the fragile portion smaller than other portions in the skeleton to further facilitate the bending.

An eighth aspect of the present invention is the stent according to any one of the first to seventh aspects, wherein the skeleton is provided with a recess on the surface.

  In a stent having a structure according to this embodiment, a concave portion or a convex portion is formed on the surface of the skeleton to provide a relative recess, for example, to improve the positioning performance with respect to the surface of the lumen, It is also possible to retain the drug and place it in the lumen. In addition, the recess in this aspect can be formed in any surface of the inner peripheral surface of the stent peripheral wall made into the cylindrical shape, and an outer peripheral surface. Further, the recess in this embodiment may be a through hole as well as a bottomed shape.

  In addition, it is desirable that the size of the recess in this aspect is an opening size of about 10 to 30 μm, thereby further reducing the patient's foreign body feeling and adversely affecting the strength of the stent as much as possible. To be avoided.

According to a ninth aspect of the present invention, in the stent according to any one of the first to eighth aspects, the skeleton is a metal skeleton formed by at least one of electroforming and etching. .

  In the stent having the structure according to this aspect, the shape of the skeleton is formed by electroforming or etching, so that the shape corresponds to the shape of the lumen from the beginning. Therefore, the portion to be excised can be reduced as compared with the stent manufactured by laser processing, and the stent can be manufactured with a good yield.

Further, in combination with the fourth aspect, the adjustment of the rigidity at the end can be realized by increasing the thickness dimension or changing the material. Further, in combination with the sixth aspect, the weakened portion can be formed simultaneously with other portions of the skeleton by electroforming or etching, and the weakened portion is provided with high dimensional accuracy without the need for post-processing. Is possible. According to a tenth aspect of the present invention, in the stent according to any one of the first to ninth aspects, metals having different rigidity are used in the central portion and both end portions.

  The stent according to the present invention has a greater degree of design freedom than a conventional simple rectangular cross-sectional stent, thereby producing, for example, a patient-specific or symptomatic stent. can do.

  In particular, by making the cross-sectional shape of the skeleton of the stent an approximately inverted triangle, the portion protruding into the lumen can be made smaller compared to a conventional stent having a simple rectangular cross section, and the fluid in the lumen can be reduced. Turbulence can be suppressed. Furthermore, when a stent is placed in a blood vessel, the formation of a thrombus associated with turbulent flow is avoided, and the risk of blood vessel restenosis at the stent placement position associated with the attachment of the thrombus to the stent may be reduced. . Further, when the stent is mounted with a reduced diameter on a delivery catheter or the like, the diameter can be further reduced as compared with a conventional stent, and the delivery performance can be improved.

The front view which shows the whole shape in the shaping | molding state of the stent as the 1st Embodiment of this invention. (A) is a perspective view which expands and shows the cross section of the axis orthogonal direction in the stent shown by FIG. 1, (b) is a principal part enlarged view in the axial direction view of (a). Explanatory drawing which shows schematically the position of the suitable link part in the thickness direction in the stent of this invention. It is explanatory drawing which shows the position of the suitable link part in the width direction in the stent of this invention roughly, Comprising: The figure corresponded in the IV-IV cross section of FIG. FIG. 2 is a transverse sectional view of a skeleton constituting the stent shown in FIG. 1. Explanatory view for explaining the magnitude of the included angle of the center angle and the circumferential side surfaces of the outer peripheral surface in a cross-sectional view of the skeleton shown in FIG. Explanatory drawing for demonstrating the principal part of the diameter-reduced state of the stent shown by FIG. (A) is an axial view in the diameter-reduced state of the stent shown by FIG. 7, Comprising: (b) is explanatory drawing which expands and shows the principal part of (a). The front view which shows the whole shape of the stent as the 2nd Embodiment of this invention. The front view which shows the whole shape of the stent as the 3rd Embodiment of this invention. It is explanatory drawing which shows the stent as an Example of this invention, Comprising: The figure corresponding to FIG. It is explanatory drawing which shows the stent as a comparative example of this invention, Comprising: The figure corresponding to FIG. It is explanatory drawing for demonstrating the principal part of the diameter-reduced state of the stent shown by FIG. 11, Comprising: The figure corresponding to FIG. It is explanatory drawing for demonstrating the principal part of the diameter-reduced state of the stent shown by FIG. 13, Comprising: The figure corresponding to FIG. It is explanatory drawing for demonstrating the principal part of the diameter-reduced state of the stent shown by FIG. 12, Comprising: The figure corresponding to FIG. It is explanatory drawing for demonstrating the principal part of the diameter-reduced state of the stent shown by FIG. 15, Comprising: The figure corresponding to FIG. It is explanatory drawing for demonstrating the result of having confirmed the flow velocity using the stent shown by FIG. 1 as an Example of this invention, Comprising: (a) has shown the velocity distribution near the blood vessel wall surface as a vector, (B) shows the velocity distribution in the vicinity of the blood vessel wall surface. It is explanatory drawing for demonstrating the result of having confirmed the flow velocity using the stent shown by FIG. 11 as another Example of this invention, Comprising: The figure corresponding to FIG. It is explanatory drawing for demonstrating the result of having confirmed the flow velocity using the stent shown by FIG. 12 as a comparative example of this invention, Comprising: The figure corresponding to FIG. The front enlarged view which shows the structural example of the recess employable in the stent of this invention.

  Embodiments of the present invention will be described below with reference to the drawings.

  First, FIGS. 1 and 2 show a stent 10 as a first embodiment of the present invention in a molded state before being contracted or expanded. The stent 10 is delivered to a stenotic site of a body lumen such as a blood vessel and is placed in an expanded state at the stenotic site, so that the body lumen is maintained in an expanded state. In the following description, the axial direction refers to the vertical direction in FIG.

  More specifically, the stent 10 of the present embodiment is linearly extended in a generally cylindrical shape as a whole, and includes a plurality of annular portions 12 provided at a predetermined distance in the axial direction. . Each of the annular portions 12 is formed by one strut 14 extending continuously in the circumferential direction by repeatedly bending or bending in a wavy shape.

  The annular portions 12 and 12 that are adjacent in the axial direction are connected to each other by a link portion 16 that extends substantially in the axial direction, thereby forming a tubular stent 10 having a predetermined length. Thereby, in this embodiment, the skeleton of the stent 10 is constituted by each strut 14 and each link portion 16. Such a skeleton can be expanded and contracted in the radial direction of the stent 10. In the present embodiment, the struts 14 are folded at both axial ends of each annular portion 12, and the folded portions of the struts 14, 14 facing each other in the axial direction are connected by the link portion 16. As a result, the strength and the degree of freedom of deformation of the stent 10 are improved, and local deformation such as buckling of the struts 14 during deformation is prevented.

  The specific shapes of the annular portion 12 and the link portion 16 are not limited in the present invention, and the wave shape of the strut 14 and the connecting portion by the link portion 16 are considered in consideration of the characteristics required for the stent 10. The number of link portions 16 on the circumference of the annular portion 12 can be appropriately set.

  Further, the position of the link portion 16 provided between the annular portions 12 and 12 is not limited in any way, but each link portion 16 has a thickness between the struts 14 and 14 as shown in FIGS. It is preferably formed at the center of the vertical direction (vertical direction in FIG. 3) or the width direction (horizontal direction in FIG. 4). In the present embodiment, the link portion 16 is located at the center in the width direction of the folded portion of the strut 14, that is, at the top of the folded portion of the strut 14. 3 and 4 merely show the relative positions of the link portion 16 and the strut 14 and do not limit the cross-sectional shape of the link portion 16 in any way. The cross-sectional shape of 16 is a substantially inverted triangle like the cross-sectional shape of the strut 14 described later.

  Here, the link portion 16 may be a weakened portion having a thickness or width smaller than that of the strut 14. That is, in the skeleton of the stent 10, the cross-sectional area of the link portion 16 can be made smaller than that of the strut 14, so that it can be formed as a weakened portion having a partially reduced strength. Then, by forming the fragile portion, the stent 10 may be easily deformed or broken at the fragile portion.

  In addition, although the width dimension and thickness dimension of the annular part 12 and the link part 16 are not particularly limited, the strut 14 constituting the annular part 12 is about 30 to 200 μm in order to ensure the strength. The width dimension and the thickness dimension are desirable, and the link part 16 is desirably a width dimension and a thickness dimension of about 10 to 100 μm.

  Here, the strut 14 of this embodiment is formed as a deformed structure having a different cross-sectional shape in the thickness direction (vertical direction in FIG. 5) as shown in FIG. The width dimension (the lateral dimension in FIG. 5) is increased toward. In FIG. 5, the upper side is the outer peripheral side of the stent 10, and the lower side is the inner peripheral side of the stent 10.

  That is, in this embodiment, the cross-sectional shape of the strut 14 is a substantially inverted triangle. Further, in this embodiment, the edge portion in the inverted trapezoidal cross-sectional shape shown in FIG. 2B is subjected to chamfering such as sand blasting, chemical polishing, and electrolytic polishing, so that the outline shown in FIG. An inverted triangular cross-sectional shape is formed. In the cross-sectional shape before chamfering shown in FIG. 2B, if the width dimension of the outer peripheral surface is W, 60 mm ≦ W ≦ 180 mm is preferable, and 80 mm ≦ W ≦ 130 mm is more preferable. It is set within the range, and in this embodiment, W = 125 mm.

  Therefore, in this embodiment, as shown in FIG. 6, the central angle β in the arc of the inner peripheral surface is made smaller than the central angle α in the arc of the outer peripheral surface of the strut 14 (β <α). . That is, with respect to two points A and B on the outer peripheral surface where the width dimension is the largest in the cross-sectional shape of the strut 14 before chamfering processing (thick one-dot chain line in FIG. 6), the outer periphery passes through these points A and B. An arc Co that is convex to the side and a center of curvature O located on the inner peripheral side of the strut 14 are assumed as the center of curvature of the arc Co. In addition, assuming an arc Ci having a center of curvature at the point O in the cross-sectional shape of the strut 14 before the chamfering process, two points on the inner peripheral surface of the strut 14 that are located on the arc Ci and have the smallest width dimension. Let D, E. Here, when ∠AOB is the central angle α in the arc of the outer peripheral surface of the strut 14 and ∠DOE is the central angle β in the arc of the inner peripheral surface of the strut 14, the central angle β in the strut 14 is greater than the central angle α. It is also small.

  In the present embodiment, the depression angle θ on both side surfaces is made larger (α <θ) than the central angle α of the arc on the outer peripheral surface of the strut 14. The depression angle θ is formed by the intersection of the straight line AD and the straight line BE in FIG. 6 in the cross-sectional shape of the strut 14 before the chamfering process.

  The central angle α of the outer peripheral surface is preferably 1 ° ≦ α ≦ 45 °, and more preferably 4 ° ≦ α ≦ 15 °. On the other hand, the central angle β of the inner peripheral surface is preferably set to 0 ° ≦ β ≦ 30 °, and more preferably set within a range of 0 ° ≦ β ≦ 10 °. Further, the depression angle θ on both side surfaces is preferably set to 15 ° ≦ θ ≦ 150 °, and more preferably set within a range of 30 ° ≦ θ ≦ 100 °. By setting the center angles α and β of the outer peripheral surface and the inner peripheral surface and the depression angles θ of both side surfaces within the above ranges, the effect of preventing fluid turbulence and the effect of reducing the outer diameter at the time of diameter reduction are stabilized. Can be demonstrated.

  The stent 10 of this embodiment having such a shape is manufactured as a metal skeleton in which the struts 14 and the link portions 16 as the skeleton are integrally formed by electroforming.

  Specifically, a molding base having the shape and size of the target stent 10 is prepared by using a conductor such as stainless steel. Then, on the surface of the molding base, an exposed surface is formed in a shape corresponding to each of the plurality of annular portions 12 and link portions 16, and a non-conductive mask is applied to the other regions. Then, it is immersed in an electrolytic bath in which a predetermined metal is ionized, and metal ions are electrodeposited on the exposed surface of the molding base to perform electroforming. After obtaining a metal having a predetermined thickness, the mask 10 is removed, and the molded base is removed or dissolved, whereby the stent 10 having the above-described target structure can be obtained.

  The stent 10 of the present embodiment can be expanded and contracted in the radial direction, and is mechanically contracted from a state before contraction shown in FIG. 1 to a predetermined size, and contracted as shown in FIGS. The diameter state is assumed. In use, the stent 10 is delivered to, for example, a stenosis portion of a blood vessel by a delivery catheter or the like. Thereafter, the stent 10 is expanded by a balloon catheter, or when the stent 10 is formed of a shape memory material, the stent 10 is automatically expanded by being released from the delivery catheter. It is placed in a body lumen such as a blood vessel. FIG. 7 shows one of the annular parts 12 constituting the stent 10, and the illustration of the other annular part 12 and the link part 16 connecting the annular parts 12, 12 is omitted.

  Here, the cross-sectional shape of the struts 14 is an approximately inverted triangle as shown in FIG. 5, and by being reduced in diameter, adjacent to each other in the circumferential direction of the struts 14 at both axial end portions of the annular portion 12. Part abuts. At that time, as shown in FIG. 8 (b), the peripheral end portions on the outer peripheral side in the cross-sectional shape of the struts 14 are in contact with each other, so that the diameter reduction of the stent 10 is limited, and in the reduced diameter state. The outer diameter dimension of the stent 10 is defined.

  In the stent 10 of the present embodiment configured as described above, the cross-sectional shape of the struts 14 is a substantially inverted triangle. Therefore, for example, the stent 10 has a skeleton having a rectangular cross section compared to a stent having a rectangular structure. A portion exposed to the blood flow on the inner peripheral side can be reduced. Thereby, it is suppressed that the stent 10 inhibits the blood flow, and it is avoided that the blood flow becomes slow or the blood flow is disturbed (turbulent flow) due to the stent 10 being placed in the blood vessel. Is done. Therefore, formation of a thrombus in a blood vessel or a heart due to turbulence is suppressed, and restenosis at the indwelling position of the stent 10 due to the attachment of the thrombus to the stent 10 is effectively prevented. obtain.

  Moreover, since the area exposed from the blood vessel wall is reduced, it is buried in the vascular endothelial cell at an early stage. That is, since the blood vessel wall that has cracked due to the placement of the stent 10 can be healed in a relatively short time, the enlargement of the vascular endothelial cells is suppressed and a thrombus adheres to the enlarged vascular endothelial cells. Thus, restenosis at the indwelling position of the stent 10 can be avoided. However, even if the vascular endothelial cells are enlarged, a lot of gaps are formed on the inner peripheral side of the stent 10, so that the vascular endothelial cells enter the gaps and the growth of the vascular endothelial cells to the inner peripheral side is suppressed. Thus, the risk of restenosis at the placement position of the stent 10 can be further reduced.

  Furthermore, for example, in a stent in which the skeleton of the conventional structure has a rectangular cross section, when the diameter is reduced, the corners on the inner peripheral side in the skeleton cross section quickly contact each other, and further reduction in diameter is limited. In the form of the stent 10, since the cross-sectional shape of the strut 14 is a substantially inverted triangle, the strut 14 does not abut on the inner peripheral side but abuts on the outer peripheral side. As a result, the stent 10 of the present embodiment is not further restricted in diameter compared to a stent having a conventional structure, and the outer diameter at the time of diameter reduction can be further reduced. In particular, as in this embodiment, by increasing the depression angle θ on both sides compared to the central angle α of the outer peripheral surface, the possibility of contact on the inner peripheral side is further reduced. The dimensions can be reliably reduced. As a result, the delivery of the stent 10 and the delivery catheter equipped with the stent 10 can be improved.

  In the present embodiment, the annular portions 12, 12 adjacent in the axial direction are connected by the link portion 16. The link portion 16 can also be a weakened portion having a smaller cross-sectional area than the strut 14 and thus being easily deformable. Thereby, for example, when an opening is formed in the stent 10 corresponding to a branched blood vessel or the like, the operator can easily perform an operation of cutting or expanding the fragile portion 16.

  In particular, in the present embodiment, since the link portion 16 is also formed by electroforming simultaneously with the strut 14, it is not necessary to form the link portion separately and to be fixed to the strut afterwards, and has high dimensional accuracy. The manufacturing can be facilitated while ensuring the above. In addition, since the link portion 16 is formed by electroforming, it is easier to form the link portion 16 thinner and thinner than the strut 14.

  Next, FIG. 9 shows a stent 18 as a second embodiment of the present invention. Similar to the first embodiment, the stent 18 of the present embodiment has a skeletal structure including struts 14 and link portions 16, and the cross-sectional shape of the struts 14 is the same as that of the first embodiment shown in FIG. The shape shown in FIG. In the following description, the same members and parts as those of the first embodiment are denoted by the same reference numerals as those of the first embodiment in the drawings, and detailed description thereof is omitted.

  The stent 18 of the present embodiment has a deformed cylindrical shape in which the outer diameter dimension at both end portions in the axial direction (vertical direction in FIG. 9) is larger than the outer diameter dimension at the central portion in the axial direction. The stent 18 of the present embodiment has, for example, a plurality of annular portions 12 located at both axial end portions relative to the straight cylindrical stent 10 shown in FIG. It can be formed by increasing the number of times of electroforming to make it thicker. That is, the stent can have a laminated structure of a plurality of layers. In such a case, it is preferable that the stent has a laminated structure made of a plurality of types of metals. Such a laminated structure does not need to be formed over the entire stent, and a specific portion of the stent may be a laminated structure. Moreover, the shape of the inner hole of the stent 18 is not limited at all, and may be, for example, a straight shape extending in the axial direction, or both end portions may be larger in diameter than the central portion in the axial direction.

  Specifically, after forming a non-conductive mask on the surface of the molding base as described above and performing the first electroforming, the electroforming is performed in the second electrolytic bath of another metal ion. By performing the casting, a metal layer of another material can be formed on the surface of the metal formed by the first electroforming by the second electroforming. By repeating this a plurality of times, the stent 18 of the present embodiment having a laminated structure of a plurality of types of metals is configured.

  Such a laminated structure of metals can be performed any number of times. For example, a structure in which an outer layer is provided by coating another metal so as to cover an inner layer formed of a specific metal can also be used. . In that case, for example, it is preferable that the outer layer metal has a higher ductility than the inner layer metal. As a result, the followability when the stent is bent is improved, and in particular, the occurrence of cracks and peeling during expansion deformation is prevented.

  Further, it is preferable that the outer layer metal has a smaller ionization tendency than the inner layer metal. Specifically, for example, the inner layer is formed of stainless steel (SUS316L), CrCo alloy, tantalum, NiTi or the like, while the outer layer is particularly preferably Ni, NiCo, Cu, NiW, Pt, Au, Ag, Cr, Zn, or the like. Can also be formed of Au or Pt. Accordingly, it is possible to improve biocompatibility by suppressing the potential difference from the living body with the metal of the outer layer while efficiently ensuring strength and rigidity with the metal constituting the inner layer. Moreover, since the ionization tendency of Au, Pt, etc. is very low, metal elution can be suppressed. Furthermore, elution of metal ions that cause metal allergy such as Ni used in the inner alloy layer can be suppressed. Moreover, since Au, Pt, etc. have a large specific gravity and good radiopacity, the visibility of a stent using X-rays can be improved.

  In addition, after performing the first electroforming, it is also possible to re-form the mask and perform the second electroforming. Accordingly, for example, the annular portion and the link portion can be formed of different metal materials, and the material of the annular portion can be partially different in the length direction and the circumferential direction of the stent.

  Further, the stent 18 of the present embodiment has both end portions in the axial direction being thicker than the central portion in the axial direction, so that the rigidity of both end portions is increased compared to the central portion. Furthermore, it is preferable that the rigidity of the end portions that are axially outer of these both end portions is substantially the same as or smaller than that of the central portion in the axial direction. Such a rigid end portion can be realized, for example, by forming only the end portion with a soft metal, or by adjusting the number of times of electroforming, a mask or the like to reduce the thickness or width of the end portion.

  Also in the stent 18 of the present embodiment having the above-described shape, the same effect as that of the first embodiment is exhibited because the cross-sectional shape of the skeleton is the same as that of the first embodiment. Can be done. In addition, in this embodiment, since both end portions in the axial direction are larger in outer diameter than the central portion in the axial direction and have increased rigidity, the axial end portions of the stent 18 are lifted from the blood vessel. Is suppressed, and it is stably placed at the stenosis site of the blood vessel. In particular, when the axial end portion of the stent is separated from the blood vessel in the state where it is placed in the blood vessel, the risk of blood flow disturbance and the formation of a thrombus is improved. Therefore, as shown in this embodiment, lifting from the blood vessel is suppressed at both axial ends of the stent 18, so that restenosis at the stent placement position can be more effectively prevented. Furthermore, by reducing the rigidity of the axial end portion, the load exerted on the blood vessel wall by the axial end portion of the stent placed so as to bite can be reduced.

  Next, FIG. 10 shows a stent 20 as a third embodiment of the present invention. The stent 20 of the present embodiment has a skeletal structure composed of the struts 14 and the link portions 16 as in the previous embodiment, and the cross-sectional shape of the struts 14 is the shape shown in FIG.

  The stent 20 of the present embodiment includes a main cylinder portion 22 and a branch cylinder portion 24 that are each substantially cylindrical and linearly extend, and are located on the side from a branch portion 26 provided in an intermediate portion in the axial direction of the main cylinder portion 22. As a whole, the branch cylinder portion 24 is inclined so as to be substantially Y-shaped. In other words, in the stent 20 of the present embodiment, the number of cylindrical portions is different in the axial direction, and the stent 20 has an irregular cylindrical shape whose cross-sectional shape changes in the axial direction.

  In the stent 20 of the present embodiment, for example, the main cylinder portion 22 and the branch cylinder portion 24 may be formed separately and joined together by means such as welding, but the main cylinder portion 22 is formed by electroforming. The branch cylinder portion 24 is integrally formed.

  Also in the stent 20 of this embodiment having such a shape, since the cross-sectional shape of the skeleton is the same as that of the first embodiment, the same effect as the stent 10 of the first embodiment is obtained. Can be demonstrated. In particular, the stent 20 of the present embodiment has a bifurcated shape and can correspond to a complicated shape such as a blood vessel of a living body, and blood flow disturbance is suppressed even at the bifurcated portion of the blood vessel, so that the restenosis of the blood vessel is further improved. It can be prevented more effectively.

[Example]
As Example 1 of the present invention, a stent 10 having the structure according to the first embodiment shown in FIGS. 1 and 2 was virtually manufactured on a computer. Further, as Example 2 of the present invention, as shown in FIG. 11, a stent 28 is adopted in which the cross-sectional shape of the skeleton is reduced to a width from the inner peripheral surface to the outer peripheral surface to make an approximate triangle. As a comparative example, a stent 30 having a conventional structure with a rectangular cross section as shown in FIG. 12 was employed, and each was virtually fabricated on a computer. In addition, while Example 2 and the stents 28 and 30 of a comparative example shown by FIG. 11, 12 are the things of the shaping | molding state before diameter reduction, these stents 1, 2, and the stent 10 of a comparative example are shown. 28 and 30 were prepared assuming that the edge portions were not chamfered.

  In addition, the outer diameters of the stents 10, 28, and 30 of Examples 1 and 2 and the comparative example before the diameter reduction were each set to φ = 3 mm (see FIG. 1). Furthermore, while the width dimension of the outer peripheral surface of the cross section of the strut 14 in the first embodiment is W = 125 mm (see FIG. 2B), the width dimension of the inner peripheral surface of the cross section of the strut 32 in the second embodiment (FIG. 11B). )) Was also designated W. Furthermore, the width dimension of the outer peripheral surface of the cross section of the strut 34 in the comparative example was W1 = 100 mm (see FIG. 12B). The thickness dimensions of the struts 14, 32, and 34 of Examples 1 and 2 and the comparative example were set to the same T = 0.1 mm (see FIG. 2B and the like).

  Then, diameter reduction processing was performed on the stents 10, 28, and 30 of Examples 1 and 2 and Comparative Example that were virtually manufactured on a computer, and the respective outer diameter dimensions were compared. A perspective view and an axial view of the annular portion 12 obtained by reducing the diameter of the stent 10 of Example 1 are shown in FIGS. 7 and 8, and the stent 28 of Example 2 and the comparative example are shown in FIGS. , 30 are a perspective view and an axial view of the annular portion 12 subjected to the diameter reduction processing, as shown in FIGS. Thus, the outer diameter dimensions of the stents 10, 28 and 30 of Examples 1 and 2 and the comparative example subjected to the diameter reduction treatment are φ ′ (see FIG. 8A), φ1 (see FIG. 14), and φ2, respectively. (See FIG. 16). In addition, “ANSYS R14.5” manufactured by ANSYS was used as software for performing analysis by performing such a diameter reduction process.

  As a result, φ1 = 1.80 mm and φ2 = 1.70 mm, whereas φ ′ = 1,68 mm. That is, the stent 10 in which the cross-sectional shape of the struts 14 is a substantially inverted triangle is compared with the stent 28 in which the cross-sectional shape of the struts 32 is a general triangle and the stent 30 in which the cross-sectional shape of the struts 34 of the conventional structure is a rectangular shape. Thus, it is shown that the outer diameter dimension when the diameter reduction treatment is performed becomes smaller.

  The reason why the outer diameter of the stent 10 of Example 1 is smaller than that of the stent 28 of Example 2 and the stent 30 of Comparative Example after the diameter reduction process is as follows. As shown in FIG. 14B and FIG. 16B, when the diameter reduction process is performed, the inner peripheral sides of the skeletons adjacent in the circumferential direction come into contact with each other quickly, and further diameter reduction is limited. Is done. On the other hand, as shown in FIG. 8B, the stent 10 of the example has a width dimension of the inner peripheral surface smaller than a width dimension of the outer peripheral surface. It is presumed that the diameter reduction is not limited until the outer peripheral sides come into contact with each other, and the outer diameter dimension becomes smaller.

  As a result, the outer diameter of the stent 10 of the first embodiment can be made smaller than that of the stent 28 having the substantially triangular cross section of the second embodiment and the stent 30 having the rectangular cross section of the conventional structure. Since the outer diameter at the time of mounting can be reduced, good delivery can be exhibited.

  Moreover, the flow velocity in the vicinity of each strut was confirmed using the stents 10, 28, and 30 of Examples 1 and 2 and the comparative example. The results of Examples 1 and 2 are shown in FIGS. 17 and 18, respectively, and the result of the comparative example is shown in FIG. In addition, the stents 10, 28, and 30 shown in FIGS. 17 to 19 are in the molded state shown in FIGS. 2, 11, and 12, respectively, and each outer diameter dimension is set to φ = 3 mm. 17 (a), 18 (a) and 19 (a) show the velocity distribution in the vicinity of the blood vessel wall surface as vectors, and FIGS. 17 (b), 18 (b) and 19 (b) show blood vessels. The velocity distribution in the vicinity of the wall surface is shown by a plane. 17 to 19 are difficult to see because the analysis result output and displayed as a colored image is displayed in gray scale for patent application, but the flow is fast in the dark gray portion in the figure. On the other hand, the light color portion indicates that the flow is slow, and the flow velocity changes stepwise corresponding to the change from the dark gray portion to the light color portion. This analysis was performed using software “ANSYS R14.5” manufactured by ANSYS.

As a result of comparing FIGS. 17 to 19, compared to FIGS. 18 (a) and 19 (a), FIG. . The reason why the number of vector lines is small in FIGS. 18 (a) and 19 (a) is that the line color is thin and the flow is slow so that it is not displayed as a large vector line or there is almost no flow itself. This is because there seems to be no vector line. On the other hand, compared with FIGS. 18 (b) and 19 (b), 17 (b) shows many dark portions as a whole. From this, it is shown that the flow velocity of the fluid passing through the vicinity of the strut of the stent 10 of Example 1 is faster than the flow velocity of the fluid passing through the vicinity of the strut of the stent 28 of Example 2 and the stent 30 of the comparative example. . As a result, in the stent 10 of Example 1, the fluid can flow without stagnation at the stent placement position in the lumen compared to the stent 28 of Example 2 and the stent 30 of Comparative Example. In particular, when the stent 10 is indwelled in a blood vessel, the effect of preventing the occurrence of thrombus due to blood retention or turbulence and the restenosis at the stent indwelling position due to the thrombus adhering to the stent is further improved. It is suggested that it can be demonstrated.

  The reason for exhibiting such an effect is that the cross section of the strut 14 of the stent 10 of the first embodiment is an approximately inverted triangle, so that the strut 32 having a generally triangular section as in the second embodiment and the strut having a rectangular section as in the comparative example. It can be inferred that the portion projecting to the inner peripheral side can be made smaller than 34, and the inhibition of the flow of fluid passing through the inside of the stent 10 is suppressed as much as possible.

  In the stent 28 of the second embodiment, the cross-sectional shape of the struts 32 is approximately triangular, and the inner peripheral sides of the struts contact with each other relatively early. There is a possibility that the effect of reducing the outer diameter cannot be fully enjoyed. Further, when the stent 28 is indwelled in the lumen, a portion that protrudes from the lumen wall to the inner peripheral side becomes relatively large, and the protruding portion serves as a barrier for the fluid. There is a risk that the flow of

  However, the outer peripheral side is tapered in the cross-sectional shape of the strut 32, and the stent 28 is positioned so that the tapered tip of the stent 28 bites into the lumen wall, thereby effectively exerting the positioning action of the stent 28 in the lumen. Can be done. In particular, even in the case where the blood vessel wall is hardened like a calcified lesion and the skeleton of the conventional structure has a rectangular cross section, it is difficult to expand the blood vessel, and the tapered portion on the outer peripheral side of the strut 32 is applied. A blood vessel that has been difficult to expand with a conventional rectangular cross section can be expanded by adopting the stent 28 as in the second embodiment because it has an effect of splitting on a lesion site.

  Therefore, depending on the state of the patient and the lesion site, a stent having a substantially triangular cross-sectional shape can be suitably employed. Thus, since the stent corresponding to the state of the stenosis site or the site where the stenosis has occurred can be manufactured with a large degree of design freedom, the stents 10, 18, 20, and 28 of the present invention have excellent technical significance. It is what you are doing.

  Although the embodiments and examples of the present invention have been described in detail above, the present invention is not limited to the specific descriptions, and various changes, modifications, improvements, and the like have been added based on the knowledge of those skilled in the art. Any embodiment may be implemented within the scope of the present invention without departing from the spirit of the present invention.

  For example, the surface of the stent may have an appropriate shape such as embossing, and when the stent is manufactured by electroforming, the shape of the molding base and mask used for electroforming is appropriately set. Thus, an appropriate shape such as emboss can be easily transferred to the surface. Thus, by providing unevenness on the outer peripheral surface of the stent, for example, it can be effectively used as a drug-eluting stent. That is, for example, by applying or depositing a drug that suppresses cell growth or a resin layer containing such a drug on the outer peripheral surface of a stent with irregularities, the drug can be eluted from the blood vessel wall. it can. At that time, the wettability is improved by such unevenness, and the applied drug or the resin layer can be easily attached to the outer peripheral surface of the stent and can be made difficult to peel off.

  Further, as shown in FIG. 20, a recess 36 may be formed in the skeleton of the stent, that is, the strut 14 or the link portion 16. Such a recess can be formed in an arbitrary shape and size, such as a groove shape extending in the length direction of the strut 14 and the link portion 16 as shown in FIG. It may be a hole. When such a stent is produced by electroforming, it is possible to form a recess of any size on the surface by appropriately setting the shape of the molding base and mask used for electroforming. The design freedom can be greatly secured.

  Further, when the stent is formed by electroforming, for example, using a eutectoid plating technique using an electrolytic solution in which a non-conductive powder is dispersed, a porous structure or microporous corresponding to the eutectoid fine particles is used. It is also possible to give the structure to the strut 14 and the link part 16.

  By forming the struts 14 and the link portions 16 with the recesses 36 and the porous structure in this way, the amount of metal constituting the stent can be reduced. Further, by loading the drug in the recess 36 or the porous structure, for example, a drug-eluting stent as described above can be formed, and the drug can be effectively eluted into the blood vessel wall.

  Furthermore, the recess 36 formed in the stent may be not only a bottomed shape but also a through hole. By forming the through hole in the stent in this way, the loading of the drug can be further facilitated and the amount of the drug loaded can be increased. In addition, since the through-hole becomes hollow after the drug or the like is eluted, blood can pass through the through-hole. For example, blood flow is inhibited as compared with the case where the recess is bottomed. Therefore, the turbulent flow and restenosis prevention effect of the present invention can be further exhibited.

  Further, the drug may be directly placed in the recess 36, or a biodegradable resin cotton impregnated with the drug or a capsule encapsulating the drug may be placed in the recess 36, for example.

  Furthermore, the unevenness formed on the stent may be formed directly on the surface of the stent. For example, by forming a convex portion on the surface of the stent, a relatively concave portion is formed. May be.

  In addition, when the stent is formed by electroforming, for example, after performing the first electroforming, the mask is formed again, and the second electroforming is performed so that they are positioned at the end portions in the axial direction. It is also possible to form the annular portion 12 shifted by a half pitch in the axial direction so as to cover the outer periphery across the adjacent annular portions 12 and 12. Since it is possible to reinforce the rigidity of the axial end portion with such a complicated structure, a large degree of freedom in design is realized.

  However, the stent does not need to be formed by electroforming, and may be formed, for example, by applying laser processing to a metal tube. In such a case, struts having a cross-sectional shape of a quadrangle ADEB as shown in FIG. 6 can be directly obtained by laser processing. Alternatively, laser processing is first performed on the metal tube so as to have a large central angle α on the outer peripheral surface to obtain a strut having a cross-sectional shape of a quadrangle AD′E′B, and then on the side surface of the strut. On the other hand, a strut having a quadrangular ADEB in cross-sectional shape may be formed by performing laser processing so that the central angle of the inner peripheral surface is β, in other words, the depression angle of both side surfaces is θ. Then, by performing chamfering on the edge portion of the strut obtained in this way, it is possible to obtain a strut having a substantially inverted triangular cross section as shown in FIG. In FIG. 6, arcs Co and Ci are the outer peripheral surface and the inner peripheral surface of the metal tube, respectively. Further, for example, after forming by electroforming so as to have a large central angle α on the outer peripheral surface, laser cutting may be performed so that the inner peripheral surface has a small central angle β, or the both side surfaces have a depression angle θ. In the production of the stent, either electroforming or laser cutting may be performed. Furthermore, the recess 36 formed in the stent does not need to be formed by electroforming. For example, a through-hole as a recess may be formed by laser processing or the like simultaneously with or after the formation of the stent.

  Furthermore, the stents 10, 18, and 20 described in the above embodiments all have an initial shape, and when inserted into a lumen such as a blood vessel, the stent 10 is deformed in diameter and delivered by a catheter. When these stents 10, 18 and 20 are of a balloon expandable type, they are inflated using a balloon and are placed in a state of being pressed against the inner peripheral surface of the blood vessel, while being self-expanded as a metal material. If it is a mold, it is automatically expanded when released from the delivery catheter. It is also possible to have an almost initial shape in such an expanded state. In this case, the shape in the expanded state is stably expressed, and strain and residual stress in the expanded indwelling state are also generated. Effectively suppressed. However, the present invention is not limited to such an embodiment, and can be formed with an initial shape having a diameter different from the shape at the time of indwelling.

  Further, the shape of the stent is not limited to the simple straight shape, the thick end shape, and the Y-shaped branch shape as exemplified in the above embodiment, but the stent or the main cylinder portion having a tapered cylindrical shape as a whole. And stents having different diameters of the branch cylinders, stents in which at least one of the trunk cylinder part and the branch cylinder part is tapered, a stent partially tapered in the length direction, The present invention is applicable to various types of irregularly shaped stents, such as a stent having a thick portion at the end or central portion.

  Furthermore, in the second embodiment, the rigidity is increased by thickening both end portions in the axial direction. However, in the straight stent in the first embodiment, the rigidity is increased as both end portions in the axial direction. By adopting a metal having a large rigidity, or by adopting a metal having a large rigidity as both end portions in the axial direction, with the thickness dimension of the stent according to the second embodiment being substantially constant over the entire length in the axial direction. The rigidity may be increased.

  Furthermore, in the skeleton of the stent, the cross-sectional shapes of the struts 14 and the link portions 16 may be different. However, in the stent of the present invention, the link portion is not essential, and the annular portions adjacent in the axial direction of the stent may be continuously connected in a spiral structure. In this way, when the link portion is not provided, the skeleton of the stent is configured only by the struts.

  Furthermore, the strut thickness need not be uniform over the entire length. For example, it may be partially thick or thin in the length direction of the strut. Moreover, when not providing a link part as mentioned above, a weak part may be formed of the thin part of the strut.

  In the above-described embodiment, the generally inverted triangle is exemplified as the shape in which the circumferential width dimension in the cross-sectional shape of the strut 14 gradually decreases from the outer peripheral side toward the inner peripheral side. A semicircular shape that protrudes toward the circumferential side may be used. However, in the present invention, like the stent 28 of Example 2 described above, it is also possible to have a deformed structure in which the circumferential width dimension of the skeleton cross section gradually increases from the outer peripheral side toward the inner peripheral side. In addition to the illustrated approximate triangle, the shape may be a trapezoid or a semicircular shape that protrudes toward the outer periphery. This reduces the pressing area of the outer peripheral surface of the stent to the blood vessel in the skeleton and concentrates the pressing force, thereby improving the positioning action of the stent on the blood vessel and Misalignment can also be suppressed. In addition, since the pressing force is concentrated on the blood vessel wall, not only can an effective expansion action be exerted on a hardened blood vessel such as a calcified lesion, but also a non-hardened blood vessel However, it is possible to expand to a desired dimension with a smaller expansion force.

  Furthermore, in the present invention, a deformed structure in which the circumferential width dimension of the skeleton cross section is increased at the intermediate portion in the radial direction of the stent and gradually decreases toward both the outer peripheral side and the inner peripheral side, that is, for example, a rhombic cross section or a circular shape. A cross section or an elliptical cross section is also possible. This makes it possible to concentrate the pressing force on the blood vessel on the outer peripheral surface of the skeleton while suppressing mutual interference in the circumferential direction at the inner peripheral ends of the skeletons adjacent to each other in the circumferential direction, which tends to be an obstacle when the stent is reduced in diameter. Therefore, it is possible to improve positioning performance and blood vessel expansion performance.

  Further, in the present invention, a stent may be manufactured using an etching technique instead of the laser cutting or electroforming described above. Examples of the etching technique include the following techniques. A molded base having the desired stent shape and size is prepared. And on the surface of this shaping | molding base, a corrosion-resistant mask is given in the shape corresponding to each some annular part and link part, and the non-masked part exposes a shaping | molding base. Thereafter, it is immersed in a polishing liquid composed of strong acid, strong alkali, strong oxidizing agent, etc., and the unmasked portion of the molding base is corroded and dissolved to obtain a stent having the target structure as described above. Can do.

  Since the etching technology produces the stent by corrosive dissolution of the unmasked part of the molded base, the thickness of the molded base is almost the same as the thickness of the finished product, and the thickness of the finished product takes time. Can be set larger. In addition, since the etching technique does not require a liquid sample dedicated to electroforming, the material selectivity is increased. Furthermore, since the etching technique does not require a current to flow, it is not necessary to electrically adjust the current density, voltage, etc., and manufacturing conditions can be easily set and managed. In the present invention, a skeleton can be formed by appropriately combining laser cutting, electroforming, and etching. For example, a skeleton formed by electroforming can be partially etched.

10, 18, 20, 28: stent, 12: annular portion, 14: strut, 16: link portion (fragile portion), 36: recess

Claims (10)

It is a stent that is made into a cylindrical shape by a skeletal structure that can be expanded and contracted in a radial direction and is placed in a body lumen,
The skeleton is an irregular structure by a change in the thickness direction of the cross-sectional shape,
The cross-sectional shape of the skeleton is an approximately inverted triangular shape whose width increases from the inner peripheral surface toward the outer peripheral surface, and both circumferential side surfaces extending and intersecting from the outer peripheral surface of the skeleton to the inner peripheral side are The cross-sectional shape is straight and
A stent characterized in that the skeleton has a laminated structure of a plurality of kinds of metals, and the metal in the outer layer portion of the laminated structure is different from the metal in the inner layer portion .   The stent according to claim 1, wherein, in the cross-sectional shape of the skeleton, a corner portion on the inner peripheral side is an arcuate curved surface.   The stent according to claim 1 or 2, wherein, in the cross-sectional shape of the skeleton, a depression angle on both side surfaces in the circumferential direction is larger than a central angle in an arc of the outer circumferential surface.   The stent according to any one of claims 1 to 3, wherein rigidity at at least one end in the axial direction is larger than that of the central portion.   The stent according to claim 4, wherein the end portion whose rigidity is increased as compared with the central portion is reduced in rigidity at a terminal portion on the outer side in the axial direction. The stent according to any one of claims 1 to 5 , wherein a weakened portion having a partially reduced strength is formed in the skeleton by at least one of electroforming and etching. The stent according to claim 6 , wherein the fragile portion is easily deformed with a smaller cross-sectional area than other portions of the skeleton. The stent according to any one of claims 1 to 7 , wherein a recess is provided on a surface of the skeleton. The stent according to any one of claims 1 to 8 , wherein the skeleton is a metal skeleton formed by at least one of electroforming and etching. The stent according to any one of claims 1 to 9, wherein metals having different rigidity from each other are used in the central portion and both end portions.