WO2015098629A1

WO2015098629A1 - Stent

Info

Publication number: WO2015098629A1
Application number: PCT/JP2014/083308
Authority: WO
Inventors: 佐野　嘉彦; 大山　靖; 比恵島　徳寛; 孝次秋本
Original assignee: 二プロ株式会社
Priority date: 2013-12-24
Filing date: 2014-12-16
Publication date: 2015-07-02

Abstract

　Provided is a stent having a novel structure, whereby the performance, etc., of the stent can be adjusted with an even greater degree of freedom of design in accordance with the location at which stenosis occurs in the lumen in which the stent is placed, the state of the stenosis location, etc. Also provided is a stent having a novel structure, whereby a shape corresponding to a lumen such as a blood vessel can be realized with good yield. A stent (32) placed in a body lumen and having a cylindrical shape formed by a structure of a radially expandable skeleton (18, 19), the skeleton (18, 19) having a heteromorphic structure due to variation of the cross-sectional shape thereof in the thickness direction. A stent (10) placed in a body lumen and configured so as to be radially expandable, the stent (10) having a heteromorphic cylindrical shape, the cross-sectional shape of which varies in the length direction, and having a metal-made skeleton (18, 19) formed by electroforming and/or etching.

Description

Stent

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 of a blood vessel or the like, 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 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, and required characteristics in the medical field. 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 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 longitudinal 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.

Furthermore, in such a stent having a conventional structure, since the metal tube as a raw tube has a simple straight cylindrical shape, it is difficult to form a shape corresponding to an indwelling site in a lumen such as a blood vessel. . Therefore, there is a problem that it is difficult to prepare a stent that accurately matches the shape of the lumen in a lumen, for example, in a portion where the inner diameter dimension changes in a tapered shape or a branch portion such as a bifurcation.

Moreover, when forming the through holes and struts by applying laser processing to the tube, there is a problem that the yield is poor when the area to be excised is large. In order to improve the yield, a stent obtained by laser processing of a small-diameter cylindrical tube is reduced in diameter and inserted into the lumen, and then expanded to a diameter larger than the initial tube diameter. Although it is conceivable to indwell, there is a possibility that strain and residual stress increase in a diameter-expanded state and it becomes difficult to obtain a stable shape and durability.

In addition, since the burr-like roughness tends to occur in the laser-processed part and chemical or mechanical post-processing is required, the manufacturing becomes complicated and the accuracy control of the post-processing is also performed. There was a problem that it was difficult.

JP 2007-267844 A

The present invention has been made in the background of the above-mentioned circumstances, and a problem to be solved by the invention according to claim 1 is that a stenosis site or a stenosis site in a lumen where a stent is placed is generated. It is an object of the present invention to provide a stent having a novel structure capable of adjusting the performance and the like of the stent with a greater degree of design freedom in accordance with the state of the above.

The problem to be solved by the invention described in claim 5 is to provide a stent having a novel structure in which a shape corresponding to a lumen such as a blood vessel can be realized with a good yield.

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 It is said that it is said.

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.

A second aspect of the present invention is the stent according to the first aspect, wherein the width dimension is increased from the inner peripheral surface toward the outer peripheral surface in the cross-sectional shape of the skeleton.

In the stent having the structure according to the present aspect, the cross-sectional width dimension of the portion exposed to the fluid in the lumen such as blood can be reduced as compared with the stent having the conventional structure having a skeleton having a simple rectangular cross section. . 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 occurrence of cracks in the lumen wall can be suppressed, and the healing period of the 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. 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 are separated from the inner peripheral surface of the stent. Further, the enlargement toward the inside is suppressed, and a further inhibitory effect is exerted on the restenosis of the blood vessel.

Further, in the stent having the structure according to the present 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.

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 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 angles on both sides in the circumferential direction are made larger than the central angle in the arc of the outer peripheral surface. It is.

In the stent having the structure according to this aspect, both side surfaces in the circumferential direction of 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.

According to a fourth aspect of the present invention, in the stent according to any one of the first to third 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 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.

Also, by combining with the eighth aspect described later, the adjustment of the rigidity at the end can be realized by increasing the thickness dimension or changing the material. Furthermore, by combining with the eleventh aspect to be described later, the fragile portion can be formed simultaneously with other portions of the skeleton by electroforming or etching, and the fragile portion is provided with high dimensional accuracy without the need for post-processing. It becomes possible.

A fifth aspect of the present invention is a stent that can be expanded and contracted in the radial direction and is placed in a body lumen, and has a deformed cylindrical shape whose cross-sectional shape changes in the length direction, and It has a metal skeleton formed by at least one of electroforming and etching.

Unlike the stent obtained by laser processing a conventional elemental tube, the stent according to this embodiment gives a shape corresponding to the shape of the lumen from the beginning by a skeleton formed by electroforming or etching. It is done. Therefore, the portion to be excised can be reduced as compared with the conventional laser-processed stent, and the stent can be manufactured with a good yield.

Therefore, even when placed in an irregularly shaped lumen such as a blood vessel, the shape corresponding to the lumen is realized with high accuracy, reducing the labor burden of the procedure for the practitioner and the burden on the living body for the patient. Etc. are reduced. Further, even in the stent itself placed in a shape corresponding to the lumen, distortion and residual stress are reduced, and good shape stability and durability can be realized.

A sixth aspect of the present invention is a stent according to the fifth aspect, wherein a branched portion is provided and the number of tubular portions is changed in the length direction.

In the stent having the structure according to this aspect, a stent that can be easily applied to a bifurcation portion such as a bifurcation in a lumen such as a blood vessel can be realized.

A seventh aspect of the present invention is a stent according to the fifth or sixth aspect, wherein the stent has a deformed cylindrical shape whose diameter is changed in the length direction.

In the stent having the structure according to this aspect, a stent that can be applied satisfactorily to a site where the inner diameter changes in the length direction in a lumen such as a blood vessel can be realized. In addition, the stent of this mode can be combined with the sixth mode, so that at least one tube portion of the stent having a branch portion can have a tapered tube shape or the like.

According to an eighth aspect of the present invention, in the stent according to any one of the first to seventh aspects, rigidity at at least one end in the axial direction is greater than that of the central portion.

In the case of a stent having a structure according to this aspect, for example, when it is formed by electroforming, the rigidity can be adjusted by increasing the thickness dimension of a specific portion in the length direction or changing the material. It becomes possible. In particular, in the stent of this aspect, the rigidity of the axial end portion that is easily deformed is increased for structural reasons, so that the axial end portion is separated from the lumen while being placed in the lumen. It can also be effectively prevented from causing stenosis.

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.

A ninth aspect of the present invention is the stent according to the eighth aspect, wherein the end portion whose rigidity is increased as compared with the central portion is reduced in rigidity at the end portion on the axially outer side. Is.

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. When the skeleton is made of metal, the rigidity adjustment at the end portion is realized by forming only the end portion of the stent with a soft metal, or by reducing the thickness or width. obtain. Preferably, the rigidity of the end portion is set to be substantially the same as or smaller than that of the central portion.

A tenth aspect of the present invention is the stent according to any one of the first to ninth aspects, wherein the skeleton has a laminated structure of a plurality of types of metals.

In a stent having a structure according to this aspect, a laminated structure of a plurality of types of metals can be formed by, for example, electroforming. For example, by adopting a metal material whose surface layer is more ductile than the core layer, the core layer ensures the strength of the stent while relaxing the stress on the surface when the stent expands or contracts and prevents cracks from occurring It is also possible to do. In addition, by adopting a metal material with a smaller ionization tendency in the surface layer than in the core layer, it is possible to achieve biocompatibility, radiopacity, etc. by the surface layer while ensuring the required strength characteristics in the core layer. It becomes possible. 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.

According to an eleventh aspect of the present invention, in the stent according to any one of the first to tenth aspects, a weakened portion partially reduced in strength is formed in 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, it is possible to provide it with a high degree of dimensional accuracy without the need for troublesome operations such as making it separately from other parts of the skeleton and fixing it later. It becomes possible. In addition, the position and shape of the fragile portion can be arbitrarily set, and the degree of freedom in design can be improved.

In a twelfth aspect of the present invention, in the stent according to the eleventh 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 forming the fragile portion thinner than other portions of the skeleton, for example, to further facilitate the bending of the stent. In particular, when the fragile portion is formed by electroforming, for example, it is possible to reduce the thickness of the fragile portion only in the thickness direction, change the material, or the like.

A thirteenth aspect of the present invention is the stent according to any one of the first to twelfth aspects, wherein the skeleton is provided with a recess on the surface.

In the case of a stent having a structure according to this aspect, for example, when formed by electroforming, a recess is provided at the same time as molding on the surface of the skeleton, or a convex is provided at the same time as molding, so that a relatively concave Can be provided. The surface uneven structure can improve the positioning performance with respect to the surface of the lumen, for example, or can retain the medicine in the recess and place it in the lumen. In addition, the recessed part in this aspect can be formed in any surface of the internal peripheral surface and outer peripheral surface of the surrounding wall made into the cylinder shape. Moreover, the recess in this aspect may be not only a bottomed shape but also a through hole formed by electroforming, etching, or the like.

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 feeling of foreign objects and adversely affecting the strength of the stent as much as possible. To be avoided.

A fourteenth aspect of the present invention is the stent according to any one of the first to thirteenth aspects, wherein the skeleton has a cross-sectional shape whose width dimension changes from the inner peripheral surface toward the outer peripheral surface. is there.

In the stent having the structure according to this aspect, for example, the design freedom of the shape of the outer peripheral surface of the stent peripheral wall pressed against the living body, the inner peripheral surface of the stent peripheral wall exposed to blood flow, and the like is improved.

According to the first aspect of the present invention, the degree of freedom in design is greatly improved as compared to a conventional stent having a simple rectangular cross-sectional shape, whereby, for example, a stent corresponding to a patient or a symptom can be provided. Can be manufactured.

In particular, in the first aspect of the present invention, for example, by making the cross-sectional shape of the skeleton of the stent an approximately inverted triangle, the portion protruding into the lumen is made smaller than a conventional simple rectangular cross-section stent. And turbulence of fluid in the lumen 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.

Further, in the stent having the structure according to the invention described in claim 5, for example, when an irregular shape is given by a skeleton formed by electroforming or etching, for example, it corresponds to a branch portion of a blood vessel from the beginning. A stent can be obtained in the shape obtained. In addition, since the stent shape accurately corresponds to the lumen of a blood vessel or the like, the treatment is facilitated, compatibility with a living body is improved, and strain and residual stress of the placed stent itself can be reduced. . In addition, since a portion to be excised is reduced as compared with a conventional laser-processed stent, the stent can be formed with a good yield.

The front view which shows the whole shape of the stent as the 1st Embodiment of this invention. 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 sectional drawing which shows the specific example of the frame | skeleton employable in the stent of this invention, Comprising: The figure which shows a substantially triangular shape (a) and a substantially inverted triangular shape (b). Explanatory drawing which shows schematically the position of the weak part employable in the stent of this invention. Explanatory drawing which shows schematically the position of the suitable weak part in the stent of this invention. The front view which shows the whole shape in the shaping | molding state of the stent as the 4th Embodiment of this invention. (A) is a perspective view which expands and shows the cross section of the axis-perpendicular direction in the stent shown by FIG. 7, (b) is a principal part enlarged view in the axial direction view of (a). Explanatory drawing for demonstrating the magnitude | size of the center angle of the outer peripheral surface and the depression angle of the circumferential direction both sides in sectional drawing of the frame | skeleton shown by FIG.4 (b). 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. 10, 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 5th Embodiment of this invention. The front view which shows the whole shape of the stent as the 6th 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. 14, 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. 16, 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 principal part of the diameter-reduced state of the stent shown by FIG. 18, Comprising: The figure corresponding to FIG. It is explanatory drawing for demonstrating the result of having confirmed the flow velocity using the stent shown in FIG. 7 as an Example of this invention, Comprising: (a) has shown the velocity distribution near the blood vessel wall surface with 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. 14 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. 15 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.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

First, FIG. 1 shows 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.

The stent 10 of the present embodiment includes a trunk cylinder portion 12 and a branch cylinder portion 14 that are each substantially cylindrical and extend linearly. From the branch portion 13 provided in an intermediate portion in the length direction of the trunk cylinder portion 12. The branch cylinder part 14 is inclined to the side and extends so as to form a substantially Y-shaped branch shape as a whole. In other words, in the stent 10 of the present embodiment, the number of tube portions is different in the length direction (vertical direction in FIG. 1) by the branch portion 13, that is, the stent 10 has a cross-sectional shape in the length direction. It is an irregularly shaped cylinder shape that changes.

Each of the trunk tube portion 12 and the branch tube portion 14 is provided with a plurality of annular portions 16 that are continuously bent in the circumferential direction by repeatedly curving or bending in a wavy shape with a predetermined distance from each other in the axial direction. Thereby, a series of struts 19a constituting the trunk cylinder part 12 and a series of struts 19b constituting the branch cylinder part 14 are respectively formed. And the

annular parts

16 and 16 adjacent to each other in the axial direction in the

struts

19a and 19b are respectively connected by the link parts 18 extending in the substantially axial direction, thereby forming a cylindrical shape having a predetermined length.

Particularly in the present embodiment, the annular portion 16 constituting the trunk portion 12 and the annular portion 16 constituting the branch cylinder portion 14 are continuously provided on the circumference of the trunk cylinder portion 12 and the branch cylinder portion 14 in the branch portion. It extends. Thereby, in the branch part of the basic cylinder part 12 and the branch cylinder part 14, the integral structure of each

strut

19a, 19b is implement | achieved, and the continuous strut 19 is comprised. In the strut 19, the

annular portions

16 and 16 adjacent in the axial direction are connected by the link portion 18, so that the skeleton of the stent 10 of the present embodiment is configured. 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 strut 19 during deformation is prevented.

The specific shapes of the annular portion 16 and the link portion 18 are not limited in the present invention, and the wave shape of the annular portion 16 and the connection by the link portion 18 are considered in consideration of the characteristics required for the stent 10. A part, the number of the link parts 18 on the periphery of the annular part 16, etc. can be set suitably.

Further, the width dimension and thickness dimension of the annular portion 16 and the link portion 18 are not particularly limited, but the strut 19 constituting the annular portion 16 is about 30 to 200 μm for the purpose of ensuring the strength. The width dimension and the thickness dimension are desirable, and the link portion 18 is desirably a width dimension and a thickness dimension of about 10 to 100 μm.

Then, such a branched stent 10 is manufactured by integrally forming a plurality of annular portions 16 and link portions 18 constituting the strut 19 by electroforming.

Specifically, a molded base having the shape and size of the target trunk cylinder 12 and branch cylinder 14 is prepared by using a conductor such as stainless steel. Then, an exposed surface is formed in a shape corresponding to each of the plurality of annular portions 16 and the link portions 18 on the surface of the molding base, and a non-conductive mask is applied to 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 having the above-described structure is capable of expanding and contracting in the radial direction in the trunk cylinder portion 12 and the branch cylinder portion 14, and is in a predetermined state from the state before contraction shown in FIG. 1. The diameter is mechanically reduced to the size. 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, and in the state shown in FIG. Etc. are placed in the body lumen.

Since the stent 10 of the present embodiment is manufactured by electroforming, a branched shape having the trunk cylinder portion 12 and the branch cylinder portion 14 can be integrally formed. Therefore, compared to the case where two stents obtained by laser processing straight cylindrical metal fittings as in the conventional structure are joined to form a branched shape, the portion to be excised can be reduced, The yield can be improved and a complicated branch shape can be obtained with high accuracy. Therefore, it is possible to realize the stent 10 that accurately corresponds to a complicated shape portion such as a blood vessel of a living body with a good yield.

In addition, since it is manufactured by electroforming as described above, the degree of freedom in design of the shape is greatly improved while ensuring the integral formability of the stent 10, so that a straight cylindrical metal fitting having a conventional structure is laser processed. Compared to the obtained stent, it is possible to obtain a stent with various irregular initial shapes.

For example, as shown in FIG. 2, the stent 20 as the second embodiment of the present invention having a tapered cylindrical shape whose inner and outer diameter dimensions change in the axial direction also has an initial shape with a target taper angle. It can be integrally formed by casting. The stent 20 of the present embodiment has such a tapered shape and a deformed cylindrical shape whose cross-sectional shape changes in the length direction. 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.

Since such a stent 20 is tapered in an initial shape when placed in a blood vessel or the like whose diameter size changes, it is possible to suppress strain and residual stress in the placed state.

Further, since the skeletons of the

stents

10 and 20 as described above, that is, the struts 19 and the link portions 18 are manufactured by electroforming, it is possible to have a laminated structure of different materials. 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.

Such a laminated structure of metals can be performed any number of times, for example, a structure in which a surface layer portion is provided by coating another metal so as to cover a core portion formed of a specific metal is also possible. It is. In that case, for example, it is preferable that the metal of the surface layer portion has a higher ductility than the metal of the core portion. As a result, the followability when the stent is bent is improved, and the concentration of strain and stress in the surface layer portion is avoided.

Further, it is preferable that the metal in the surface layer portion has a smaller ionization tendency than the metal in the core portion. Specifically, for example, the core portion is formed of stainless steel (SUS316L), CrCo alloy, tantalum, NiTi, etc., while the surface layer portion is Ni, NiCo, Cu, NiW, Pt, Au, Ag, Cr, Zn, etc. Preferably, it can 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 in the surface layer portion while efficiently ensuring strength and rigidity with the metal constituting the core member. 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 alloy as the core material 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 16 and the link portion 18 can be formed of different metal materials, and the material of the annular portion 16 can be partially different in the length direction and the circumferential direction of the stent 10. become.

Specifically, as shown in FIG. 3, as a third embodiment of the present invention, in a straight cylindrical stent 30, one or a plurality of annular portions positioned at the axial ends thereof Only 16 can be made thicker by increasing the number of times of electroforming than the other annular portion 16 located in the central portion in the axial direction. That is, in the stent 30 of the present embodiment, the cross-sectional shape changes in the length direction with a shape in which the thickness dimension changes in the length direction. In addition, by making the axial end portion thicker than the central portion, the axial end portion may have a larger outer diameter size, a smaller inner diameter size, or both than the central portion. . Moreover, this thick part may be provided in one edge part of an axial direction, and may be provided in an axial direction both ends.

As described above, in the deformed cylindrical stent 30 in which the axial end is thicker than the central portion, the rigidity of the axial end is made larger than that of the central portion, so that deformation in the central portion is achieved. It is also possible to prevent restenosis by suppressing the lifting from the blood vessel at the axial end while securing the degree of freedom.

In addition, after the first electroforming, the mask is formed again, and the second electroforming is performed so as to straddle the

annular portions

16 and 16 located at the end portions in the axial direction and adjacent to each other. It is also possible to form the annular portion 16 shifted by a half pitch in the axial direction so as to cover the outer periphery. 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.

In addition, in the stent 30 of this embodiment, it is preferable that the rigidity of the axially outer end portion is substantially the same as or smaller than that of the central portion at the axial end portion where the rigidity is increased compared to the central portion. . Thereby, the load which the axial direction terminal part of the stent detained so that it may bite into the blood vessel wall can exert on the blood vessel wall can be reduced. 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.

Furthermore, since the

stents

10, 20, and 30 as described above are manufactured by electroforming, the design freedom of the cross-sectional shape of the strut 19 constituting the skeleton is also a simple rectangular cross-section in the conventional laser processing. On the other hand, a large degree of freedom can be secured. For example, FIGS. 4A and 4B show a cross-sectional shape of the strut 19 in which the width dimension changes from the inner peripheral surface toward the outer peripheral surface. 4 (a) and 4 (b), the upper side is the side in contact with the blood vessel wall, and the lower side is the side located in the blood vessel lumen.

Specifically, as shown in FIG. 4A, a strut 19 having a substantially triangular cross section can also be used. In the strut 19 having such a shape, the side in contact with the blood vessel wall is gradually narrowed, so that the pressing force against the blood vessel wall of the stent can be concentrated on the tapered portion of the strut 19 when the stent is expanded. As a result, the blood vessel can be expanded with a smaller pressing pressure of the stent, in other words, with the expansion pressure of the stent. In addition, even when the blood vessel wall is hard, such as a calcified lesion of a blood vessel, the taper portion of the strut 19 bites in and breaks against the calcified lesion portion. Vascularized vessels can also be dilated.

Further, as shown in FIG. 4 (b), a strut 19 having a substantially inverted triangular cross section can also be used. In the strut 19 having such a shape, since the side located in the blood vessel lumen is gradually narrowed, the area in contact with the blood flow is reduced, and the foreign body reaction can be suppressed as much as possible. Moreover, since it is difficult for stagnation to occur in the blood flow, the risk of blood clots and the like being generated can be reduced. Further, since the area exposed to the blood vessel lumen is small, the period until it is covered with the vascular endothelial cells can be shortened, and the strut 19 is buried in the blood vessel at an early stage. From this, the enlargement of the vascular endothelium can be suppressed, and the stent placement portion can be cured in a relatively short period of time.

The strut 19 having such a shape can be formed by adjusting the shape of the mask during electroforming to a desired shape by etching or the like, and can greatly improve the degree of freedom of setting the cross-sectional shape. However, the cross-sectional shape of the strut 19 is not limited to the approximate triangular shape or the generally inverted triangular shape shown in FIGS. 4A and 4B, and for example, a semicircular shape or a double tapered shape is also employed. Can be done.

Furthermore, since the

stents

10, 20, and 30 as described above are manufactured by electroforming, the cross-sectional shape of the link portion 18 that connects the

annular portions

16 and 16 and the degree of freedom in designing the strength and brittleness are also large. Can be secured. In this way, by providing a partially low-strength portion in the skeleton of the stent, the fragile portion applied when the expanded stent is bent is easily deformed or cut, so that the stent has a shape of a body lumen. It is easy to follow. In addition, when an opening is formed in a stent corresponding to a branched blood vessel or the like, an operator can easily perform an operation of cutting or expanding the fragile site.

Here, in the

stents

10, 20, and 30, in the skeleton, the link portion 18 forms a weakened portion whose strength is smaller than that of the annular portion 16. By producing such a link portion 18 by electroforming, only a thin shape can be formed in the width direction of the strut 19 by the laser processing of the conventional structure, but not only the thin shape but also the thickness of the strut 19 is formed. Thin shapes can also be formed in the vertical direction. Further, the cross-sectional shape of the link portion 18 is only a simple rectangular cross-section in the conventional laser processing, but a shape other than the rectangular shape can be formed.

Specifically, for example, as shown in FIGS. 5A to 5C, the position of the link portion 18 in the thickness direction can be appropriately changed with respect to the

annular portions

16 and 16. In FIG. 5, the upper side indicates the blood vessel wall side, and the lower side indicates the blood vessel lumen side. That is, in FIG. 5 (a), the

annular portions

16, 16 are connected by the link portion 18 on the blood vessel wall side, while in FIG. 5 (b), the

annular portions

16, 16 are the link portion at the central portion in the thickness direction. 18 are connected. In FIG. 5C, the annular portions 16 are connected by a link portion 18 on the blood vessel lumen side. Furthermore, it is possible to combine the link portions 18 located on the blood vessel wall side, the central portion, and the blood vessel lumen side. In FIG. 5, the strut 19 and the link portion 18 are shown as a rectangular cross section, but FIG. 5 merely shows the relative positions of the

annular portions

16 and 16 and the link portion 18, and the strut 19 and the link portion 18. The shape of is not limited in any way.

As described above, in the conventional laser processing, since one pipe is formed penetrating in the thickness direction, the annular portion and the link portion can only be formed with the same thickness. , 20, and 30 can be manufactured by electroforming to reduce the thickness of the link portion 18. Thereby, the link part 18 can be formed thinly and thinly, and when the link part 18 is cut | disconnected, it is made easy to cut | disconnect more easily than before. Conventionally, a method in which the annular portion 16 and the link portion 18 are formed separately and then fixed together has been adopted. However, by manufacturing the

stents

10, 20, and 30 by electroforming, The link portion 18 is integrally formed, and manufacturing can be facilitated while ensuring high dimensional accuracy. Furthermore, since the cut surface of the link part 18 is made small, irritation | stimulation by a cut surface contacting a blood vessel wall etc. can be suppressed as much as possible.

Further, the position of the link portion 18 can be appropriately changed in design with respect to the width direction of the strut 19 and can be formed at the end portion in the width direction with respect to the strut 19, but is shown in FIG. As described above, the link portion 18 is preferably formed in the center portion in the width direction of the strut 19, that is, in the center portion in the width direction in the bent portion of the annular portion 16 in the above-described embodiment. In particular, as shown in FIG. 6, the link portion 18 is preferably located at the central portion of the strut 19 even in the thickness direction. Thereby, the possibility that the cut surface of the link portion 18 contacts the blood vessel wall is further reduced, and the discomfort given to the patient can be further reduced.

6, the strut 19 and the link portion 18 are shown as a rectangular cross section, but FIG. 6 merely shows the relative positions of the annular portion 16 and the link portion 18. The shape is not limited at all.

Next, FIGS. 7 and 8 show a stent 32 as a fourth embodiment of the present invention. The stent 32 is generally cylindrical and extends linearly as a whole.

Here, the cross-sectional shape of the strut 19 in the stent 32 of the present embodiment is formed as a deformed structure that is different in the thickness direction (vertical direction in FIG. 4B) as shown in FIG. 4B. The width dimension (the lateral dimension in FIG. 4B) is increased from the inner peripheral surface toward the outer peripheral surface.

That is, in this embodiment, the cross-sectional shape of the strut 19 is a substantially inverted triangle. Further, in this embodiment, the edge portion in the inverted trapezoidal cross-sectional shape shown in FIG. 8B is subjected to chamfering such as sand blasting, chemical polishing, electrolytic polishing, etc., so that FIG. The generally inverted triangular cross-sectional shape shown is formed. In the cross-sectional shape before chamfering shown in FIG. 8B, 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. 9, 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 19 (β <α). . That is, two points A and B on the outer peripheral surface having the largest width dimension in the cross-sectional shape of the strut 19 before chamfering processing (thick one-dot chain line in FIG. 9) pass through these points A and B and An arc Co that is convex to the side and a center of curvature O located on the inner peripheral side of the strut 19 are assumed as the center of curvature of the arc Co. Further, assuming the arc Ci having the center of curvature at the point O in the cross-sectional shape of the strut 19 before the chamfering process, two points on the inner peripheral surface of the strut 19 that are located on the arc Ci and have the smallest width dimension are shown. Let D, E. Here, when ∠AOB is the central angle α in the arc of the outer peripheral surface of the strut 19, and ∠ DOE is the central angle β in the arc of the inner peripheral surface of the strut 19, the central angle β in the strut 19 is greater than the central angle α. It is also small.

Further, in this embodiment, the depression angle θ on both side surfaces is made larger (α <θ) than the central angle α in the arc of the outer peripheral surface of the strut 19. The depression angle θ is formed by the intersection of the straight line AD and the straight line BE in FIG. 9 in the cross-sectional shape of the strut 19 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 during diameter reduction described later are Can be demonstrated.

The stent 32 of this embodiment having such a shape is manufactured as a metal skeleton in which the struts 19 and the link portions 18 as the skeleton are integrally formed by electroforming.

The stent 32 of this embodiment can be expanded and contracted in the radial direction, and is mechanically reduced in diameter from a state before contraction shown in FIG. 7 to a predetermined size, and contracted as shown in FIGS. The diameter state is assumed. 10 shows one of the annular portions 16 constituting the stent 32, and the illustration of the other annular portion 16 and the link portion 18 connecting the

annular portions

16, 16 is omitted.

Here, the cross-sectional shape of the strut 19 is an approximately inverted triangle as shown in FIG. 4B, and when the diameter is reduced, the circumferential direction of the strut 19 is formed at both axial end portions of the annular portion 16. Adjacent parts abut. At that time, as shown in FIG. 11 (b), the peripheral end portions on the outer peripheral side in the cross-sectional shape of the strut 19 are in contact with each other, so that the diameter reduction of the stent 32 is limited, and in the reduced diameter state. The outer diameter dimension of the stent 32 is defined.

In the stent 32 of the present embodiment having the above-described structure, the cross-sectional shape of the strut 19 is a substantially inverted triangle. Therefore, for example, the stent 32 has a skeleton having a rectangular cross section compared with a stent having a rectangular cross section. A portion exposed to the blood flow on the inner peripheral side can be reduced. Thereby, it is suppressed that the stent 32 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 32 being placed in the blood vessel. Is done. Therefore, formation of a thrombus in a blood vessel or a heart due to turbulent flow is suppressed, and restenosis at the indwelling position of the stent 32 due to the attachment of the thrombus to the stent 32 is effectively prevented. obtain.

Moreover, since the area exposed from the blood vessel wall is reduced, it is buried in the vascular endothelial cells at an early stage. That is, since the blood vessel wall that has cracked due to the placement of the stent 32 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 placement position of the stent 32 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 32, so that the vascular endothelial cells enter the gap and the growth of the vascular endothelial cells to the inner peripheral side is suppressed. Thus, the risk of restenosis at the indwelling position of the stent 32 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 stent 32 of the form, since the cross-sectional shape of the strut 19 is an approximately inverted triangle, the strut 19 does not abut on the inner peripheral side but abuts on the outer peripheral side. As a result, the stent 32 of the present embodiment is not further restricted in diameter as compared with 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 32 and the delivery catheter equipped with the stent 32 can be improved.

Next, FIG. 12 shows a stent 34 as a fifth embodiment of the present invention. The stent 34 of the present embodiment has a skeletal structure composed of the struts 19 and the link portions 18 as in the fourth embodiment, and the cross-sectional shape of the struts 19 is the same as that of the fourth embodiment as shown in FIG. The shape shown in FIG.

The stent 34 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. 12) is larger than the outer diameter dimension at the central portion in the axial direction. In the stent 34 of the present embodiment, for example, with respect to the straight cylindrical stent 32 shown in FIG. 7, the plurality of annular portions 16 positioned at both axial end portions are annular portions 16 positioned at the central portion in the axial direction. It can be formed by increasing the number of times of electroforming to make it thicker. That is, it is preferable that the stent 34 of this embodiment 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 34 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.

Furthermore, the stent 34 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.

Also in the stent 34 of the present embodiment having the above-described shape, the same effect as that of the fourth embodiment is exhibited because the cross-sectional shape of the skeleton is the same as that of the fourth embodiment. Can be done. In addition, in this embodiment, both end portions in the axial direction are larger in outer diameter than the central portion in the axial direction and have increased rigidity, so that the axial end portions of the stent 34 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 in this embodiment, the lift from the blood vessel is suppressed at both ends in the axial direction of the stent 34, 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. 13 shows a stent 36 as a sixth embodiment of the present invention. The stent 36 of the present embodiment has a substantially Y-shaped skeleton structure composed of the struts 19 and the link portions 18 as in the first embodiment, and the cross-sectional shape of the struts 19 is the same as that of the fourth embodiment. The shape shown in FIG. 4B is the same as in the embodiment.

In the stent 36 of the present embodiment, for example, the basic cylinder portion 38 and the branch cylinder portion 40 may be formed separately and joined together by means such as welding. The part 38 and the branch cylinder part 40 may be formed integrally.

Also in the stent 36 of this embodiment having such a shape, since the cross-sectional shape of the strut 19 is the same as that of the fourth embodiment, the same effect as the stent 32 of the fourth embodiment is obtained. Can be demonstrated. In particular, the stent 36 of the present embodiment has a bifurcated shape and can correspond to a complex shape such as a blood vessel of a living body, and blood flow disturbance is also suppressed at the bifurcated portion of the blood vessel, thereby further reducing the restenosis of the blood vessel. It can be prevented more effectively.

[Example]
As Example 1 of the present invention, a stent 32 having the structure according to the fourth embodiment shown in FIGS. 7 and 8 was virtually manufactured on a computer. Further, as Example 2 of the present invention, as shown in FIG. 14, a stent 42 is adopted in which the cross-sectional shape of the skeleton is reduced from the inner peripheral surface to the outer peripheral surface so that the width dimension is reduced to an approximate triangle. As a comparative example, as shown in FIG. 15, a stent 44 having a rectangular skeleton having a conventional structure was adopted, and each was virtually manufactured on a computer. The

stents

42 and 44 of Example 2 and the comparative example shown in FIGS. 14 and 15 are in a molded state before the diameter reduction, and the

stents

32 and 40 of Examples 1 and 2 and the comparative example are shown. 42 and 44 were prepared assuming that the edge portions had not been chamfered.

Further, the outer diameter dimensions of the

stents

32, 42, and 44 of Examples 1 and 2 and the comparative example before the diameter reduction were each set to φ = 3 mm (see FIG. 7). Furthermore, while the width dimension of the outer peripheral surface of the cross section of the strut 19 in the first embodiment is W = 125 mm (see FIG. 8B), the width dimension of the inner peripheral surface of the cross section of the strut 19 ′ in the second embodiment (see FIG. b) was also designated W. Furthermore, the width dimension of the outer peripheral surface of the cross section of the strut 46 in the comparative example was set to W1 = 100 mm (see FIG. 15B). In addition, the thickness dimensions of the

struts

19, 19 'and 46 of Examples 1 and 2 and the comparative example were set to the same T = 0.1 mm (see FIG. 8B and the like).

Then, diameter reduction processing was performed on the

stents

32, 42, and 44 of Examples 1 and 2 and the 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 16 obtained by reducing the diameter of the stent 32 of Example 1 are those shown in FIGS. 10 and 11 described above, and the stent 42 of Example 2 and the comparative example. , 44 are a perspective view and an axial view of the annular portion 16 in which the diameter reduction processing is performed. Thus, the outer diameter dimensions of the

stents

32, 42, and 44 of Examples 1 and 2 and the comparative example subjected to the diameter reduction treatment are φ ′ (see FIG. 11A), φ1 (see FIG. 17), and φ2, respectively. (See FIG. 19). Note that “ANSYS R14.5” manufactured by ANSYS was used as software for performing the analysis by reducing the diameter.

As a result, φ1 = 1.80 mm and φ2 = 1.70 mm, whereas φ ′ = 1,68 mm. That is, the stent 32 in which the cross-sectional shape of the strut 19 is an approximately inverted triangle is changed to the stent 42 in which the cross-sectional shape of the strut 19 ′ is an approximate triangle or the stent 44 in which the cross-sectional shape of the strut 46 of the conventional structure is a rectangle. On the other hand, it is shown that the outer diameter size when the diameter reduction process is performed becomes smaller.

The reason why the outer diameter of the stent 32 of Example 1 is smaller than that of the stent 42 of Example 2 and the stent 44 of Comparative Example after the diameter reduction processing is that in the

stents

42 and 44 of Example 2 and Comparative Example, FIG. As shown in FIGS. 17 (b) and 19 (b), when the diameter reducing process is performed, the inner peripheral sides of the skeletons adjacent to each other in the circumferential direction are brought into contact with each other quickly, and further diameter reduction is limited. Is done. On the other hand, as shown in FIG. 11B, the stent 32 of Example 1 has a skeleton that is adjacent in the circumferential direction because the width of the inner peripheral surface is smaller than the width of the outer peripheral surface. It is surmised that the diameter reduction is not limited until the outer peripheral sides of the two come into contact with each other, and the outer diameter dimension becomes smaller.

As a result, the stent 32 of the first embodiment can have a smaller outer diameter than the stent 42 of the general triangular cross section of the second embodiment and the stent 44 of 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.

In addition, the flow velocity in the vicinity of each strut was confirmed using the

stents

32, 42, and 44 of Examples 1 and 2 and the comparative example. The results of Examples 1 and 2 are shown in FIGS. 20 and 21, respectively, and the result of the comparative example is shown in FIG. The

stents

32, 42, and 44 shown in FIGS. 20 to 22 are in the molded state shown in FIGS. 8, 14, and 15, respectively, and their outer diameters are set to φ = 3 mm. 20 (a), 21 (a), and 22 (a) show the velocity distribution in the vicinity of the blood vessel wall surface as vectors, and FIGS. 20 (b), 21 (b), and 22 (b) show blood vessels. The velocity distribution in the vicinity of the wall surface is shown by a plane. 20 to 22 are difficult to see because the analysis results output and displayed as colored images are displayed in gray scale for patent application, but the flow is fast in the dark gray part 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. 20 to 22, compared to FIGS. 21 (a) and 22 (a), FIG. 20 (a) has large and many dark gray vector lines representing a generally fast flow. . The reason why the number of vector lines is small in FIGS. 21 (a) and 22 (a) is that the line color is thin and the flow is slow, so it is not displayed large as a vector line, or there is almost no flow itself. This is because there seems to be no vector line. On the other hand, as compared with FIGS. 21 (b) and 22 (b), 20 (b) shows many lighter portions as a whole. From this, it is shown that the flow velocity of the fluid passing near the strut of the stent 32 of Example 1 is faster than the flow velocity of the fluid passing near the strut of the stent 42 of Example 2 and the stent 44 of the comparative example. . As a result, in the stent 32 of Example 1, the fluid can flow without stagnation at the stent placement position in the lumen compared to the stent 42 of Example 2 and the stent 44 of Comparative Example. In particular, when the stent 32 is indwelled in a blood vessel, the effect of preventing the occurrence of thrombus due to blood retention or turbulence, and restenosis at the stent indwelling position due to the thrombus adhering to the stent is further enhanced. It is suggested that it can be demonstrated.

The reason for exhibiting such an effect is that the cross section of the strut 19 of the stent 32 of the first embodiment is a substantially inverted triangle, so that the strut 19 ′ having a cross section of the general triangle as in the second embodiment and a rectangular cross section as in the comparative example. Compared to the struts 46, it is presumed that the portion protruding to the inner peripheral side can be made smaller, and the inhibition of the flow of fluid passing through the inside of the stent 32 is suppressed as much as possible.

In the stent 42 of the second embodiment, the cross-sectional shape of the strut 19 'is an approximate triangle, and the inner peripheral sides of the struts contact with each other relatively early. There is a possibility that the outer diameter reduction effect at the time cannot be fully enjoyed. Further, when the stent 42 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 19 ′, and the stent 42 is positioned so that the tapered tip of the stent 42 bites into the lumen wall, thereby effectively positioning the stent 42 in the lumen. Can be demonstrated. 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. Since the effect of splitting on the lesion site is exerted, a blood vessel that is difficult to expand with a conventional rectangular cross section can be expanded by employing the stent 42 as in the second embodiment.

Therefore, depending on the condition of the patient and the lesion site, a stent having a substantially triangular cross-sectional shape can be suitably employed. As described above, the

stents

32, 34, 36, and 42 of the present invention have excellent technical significance because the stent corresponding to the state of the stenosis site and the site where the stenosis has occurred can be manufactured with a large degree of design freedom. It is what you do.

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. 23, a recess 48 may be formed in the skeleton of the stent, that is, the strut 19 or the link portion 18. Specifically, when the stent is formed by electroforming, for example, by treating the surface of the molding base with a protrusion or the like, the inner peripheral surface of the stent formed by electrodeposition on the surface A recess having a size corresponding to can be formed by transferring. In addition, by forming an island-shaped mask on the central portion of the surface of the skeleton formed in advance by electroforming and performing electroforming, a peripheral wall surrounding the island-shaped mask portion is formed by electroforming, It is also possible to form a recess opening in the outer peripheral surface of the stent in the mask portion. Such a recess 48 can be formed in an arbitrary shape and size. In addition to the groove shape extending in the length direction of the strut 19 and the link portion 18 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 19 and the link part 18.

Thus, by forming the strut 19 and the link portion 18 with the recess 48 and the porous structure, the amount of metal constituting the stent can be reduced. In addition, by loading a drug in the recess 48 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.

Further, the recess 48 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 put directly into the recess 48, or for example, a biodegradable resin cotton impregnated with the drug or a capsule filled with the drug may be put into the recess 48.

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.

However, the stent does not need to be formed by electroforming, and may be formed, for example, by performing laser processing on a metal tube. In such a case, a strut having a quadrangular ADEB in cross-sectional shape as shown in FIG. 9 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 applying chamfering to the edge portion of the strut thus obtained, a strut having a cross-section of a generally inverted triangle as shown in FIG. 4B can be obtained. In FIG. 9, 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. Further, the recess 48 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, 20, 30, 32, 34, 36, and 42 described in the above embodiments all have an initial shape, and when inserted into a lumen such as a blood vessel, the diameter of the stent is reduced and deformed. Delivered with. When these

stents

10, 20, 30, 32, 34, 36, 42 are of a balloon expandable type, they are expanded by using a balloon, and are placed in a state of being pressed against the inner peripheral surface of the blood vessel. On the other hand, if the metal material is a self-expanding type, it is automatically expanded by being 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.

In addition, the shape of the stent is not limited to the Y-shaped branch shape, the tapered cylindrical shape, the thick end shape, the simple straight shape, etc., as exemplified in the above embodiment. Stents with different diameter dimensions, stents in which at least one of the basic cylinder part and the branch cylinder part is tapered, a stent partially tapered in the length direction, the end or center in the length direction The present invention is applicable to various types of irregularly shaped stents, such as a stent having a thick-walled portion.

Furthermore, in the fifth embodiment, the rigidity is increased by making both end portions in the axial direction thick, but in the straight-shaped stent in the fourth 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 axial end portions in the stent according to the fifth embodiment, the thickness dimension is substantially constant over the entire axial length. The rigidity may be increased.

Further, in the skeleton of the stent, the cross-sectional shapes of the strut 19 and the link portion 18 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 fourth to sixth embodiments, the generally inverted triangle is exemplified as the shape in which the circumferential width dimension in the cross-sectional shape of the strut 19 gradually decreases from the outer peripheral side toward the inner peripheral side. A trapezoid may be sufficient and the semicircle shape which becomes convex on the inner peripheral side may be sufficient. However, in the present invention, like the stent 42 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 by 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, 20, 30, 32, 34, 36, 42: stent, 13: branching portion, 16: annular portion, 18: link portion (fragile portion), 19: strut, 48: recess

Claims

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,
A stent characterized in that the skeleton has a deformed structure by a change in the thickness direction of the cross-sectional shape.
The stent according to claim 1, wherein in the cross-sectional shape of the skeleton, the width dimension is increased from the inner peripheral surface toward the outer peripheral surface.
The stent according to claim 1 or 2, wherein in the cross-sectional shape of the skeleton, the depression angles on both sides in the circumferential direction are made larger than the central angle in the arc on the outer circumferential surface.
The stent according to any one of claims 1 to 3, wherein the skeleton is a metal skeleton formed by at least one of electroforming and etching.
A stent that is radially expandable and contracted and is placed in a body lumen,
A stent having a deformed cylindrical shape whose cross-sectional shape changes in the length direction and a metal skeleton formed by at least one of electroforming and etching.
6. The stent according to claim 5, wherein the stent has a deformed cylindrical shape in which a branch portion is provided and the number of the cylindrical portions is changed in the length direction.
The stent according to claim 5 or 6, wherein the stent has a deformed cylindrical shape whose diameter is changed in the length direction.
The stent according to any one of claims 1 to 7, wherein rigidity at at least one end in the axial direction is larger than that of the central portion.
The stent according to claim 8, wherein the end portion whose rigidity is increased compared to the central portion is reduced in rigidity at an end portion on the outer side in the axial direction.
The stent according to any one of claims 1 to 9, wherein the skeleton has a laminated structure of a plurality of types of metals.
The stent according to any one of claims 1 to 10, wherein the skeleton is formed with at least one of electroforming and etching in which a weakened portion having a partially reduced strength is formed.
The stent according to claim 11, 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 12, wherein the skeleton is provided with a recess in the surface.