WO2011007444A1

WO2011007444A1 - Coaxial multi-layered stent

Info

Publication number: WO2011007444A1
Application number: PCT/JP2009/062955
Authority: WO
Inventors: 浩二森
Original assignee: 株式会社メドバン・アイ・ピー
Priority date: 2009-07-17
Filing date: 2009-07-17
Publication date: 2011-01-20

Abstract

Provided is a coaxial multi-layered stent which has a radial rigidity almost equivalent to a single layer stent, can be fabricated by a medical doctor by him/herself in clinical practice without forming a special supporting strut member, is free from the separation of the stent in the course of the delivery to a lesion site, enables a side branch treatment, and ensures a space for storing a large amount of a drug. Use is made of a coaxial multi-layered stent comprising a component stent A forming the inner layer in which a supporting strut member constituting the same has uniform diameter and which is provided with a supporting strut member (accommodation port) engageable with a radially running supporting strut member of a supporting strut member of another stent, and another component stent B forming the outer layer which has a supporting strut member located at a larger radial position than the stent A, a supporting strut member located at a smaller radial position and a supporting strut member (radially running supporting strut member) connecting the two supporting strut members as described above, wherein the stent A is inserted in the longitudinal direction to the stent B so as to provide supporting strut members arranged at three radial positions formed by engaging the supporting strut member of the stent B with the accommodation port of the stent A and a single supporting strut member the radius of which varies continuously.

Description

Coaxial multilayer stent

The present invention relates to coaxial multi-layer stents and to intraluminal endoprostheses and endoprostheses having similar or similar support structures.

There are diseases in which tubular organs such as blood vessels in the body cause stenosis and the like, and these diseases sometimes have a serious effect on life. As an example, when a stenosis or the like occurs in a coronary artery, the blood flow to the myocardium is reduced, and the function of the heart is lowered, thereby threatening life. As a device for treating such a disease, there is a device called a stent that has been attracting attention in recent years in order to enable non-invasive treatment. This is a cylindrical structure with open ends or a coiled type, and is composed of a metal material that can be plastically deformed, such as stainless steel, and has properties such as shape memory and superelasticity. Some of them are composed of Nitinol (Ni-Ti) alloy, etc., some are composed of metal materials, biopolymer materials, ceramics, biodegradable plastics, etc. that have superplasticity and melting characteristics in vivo. is there.
Of these, stents made of a plastically deformable metal material such as stainless steel are most frequently used, and will be described below by taking this as an example. It should be noted that those skilled in the art can easily guess that the same applies to stents made of other materials.

(General usage of stent)
Usually, the stent is attached to the balloon part at the tip of the catheter, which is called a balloon catheter and a delivery device called a catheter together with a small radius so that it can be placed in a tubular organ inside the body in advance. It has been. If the radius of the stent can be reduced when attached to the balloon catheter, it can be very easily transported to the lesion during and after insertion into the body.

This is inserted into a blood vessel or the like from a part where a small part of the living body is incised, and is carried from there to the lesioned part. The stent is delivered to the lesion site, where the tip of the balloon catheter is expanded. A stent is attached to the distal end portion of the balloon catheter, but the portion to which the stent is attached has a balloon shape and can be expanded. The stent is also expanded in the body by the expansion of the balloon catheter. When the stent is a plastic material, the stent is expanded to cause plastic deformation and the deformation is retained permanently. When the balloon catheter is removed after the balloon portion is deflated after the stent is expanded, only the plastically deformed stent remains in a state where the lesion site where the stenosis or the like has occurred is expanded.

(General requirements for stents)
Conventionally, various functions and structures have been proposed as stents. Many functions are required for a stent. Among them, the most basic required functions are expansion of a tubular organ, radial rigidity that supports the tubular organ from the inside, and tubular organ that runs in the long axis direction. It is flexible enough to follow complex shapes.
In many cases, the stent is basically constituted by repeating the same shape in the circumferential direction and the major axis direction. As shown in FIG. 1, a typical stent structure includes a portion called a “cell” 2 that expands a tubular organ and supports the organ, and a “link” 3 that gives the stent flexibility in the longitudinal direction. A stent having a structured structure (see, for example, Patent Document 14). Such a stent is called a closed cell structure and is characterized in that a portion called a link has an S-shape or an N-shape.

On the other hand, a structure is proposed in which “cells” 2 for expanding and supporting tubular organs are connected by struts called “connectors” (also referred to as links) that are substantially parallel to the long axis direction of the stent. (For example, see Patent Document 12). This is called an open cell structure.
In addition, it has a stent in which the wire is formed in a coil shape (called a “coil stent”), and a strut called the spine that is almost parallel to the long axis direction of the stent. On the other hand, there is a stent (see, for example, Patent Document 13) in which struts are arranged vertically, that is, in a circumferential direction.

However, since the coil stent has a relatively low radial rigidity (see, for example, Non-Patent Document 1), the blood vessel cannot be sufficiently expanded, and the treatment results are inferior. Such a problem also exists in the stent of Patent Document 13. Therefore, at present, stents such as Patent Documents 12 and 14 are often used. Such stents are typically fabricated from a single material hollow tube, referred to herein as a single-layer stent.

Among such single-layer stents, there are stents intended to improve the mechanical properties of a stent by combining a plurality of materials. For example, Patent Document 1 and Patent Document 2 propose a stent including an inner layer and an outer layer. These are a shape memory alloy superelastic material and a malleable material (elastic plastic material) such as stainless steel, which are processed into one tube shape and then processed into a stent shape. However, it is a stent formed so that the material composition of the struts has a layered structure in the radial direction, and intended to improve the stent function (mainly to improve flexibility) by the material properties of the struts provided with the layered structure. Is. However, the basic characteristics of these stents are the same as those of the single layer stent described above, and do not solve the essential problems caused by the structural reasons of the single layer stent.

As described above, single-layer stents mainly have a structure called a closed cell structure and an open cell structure. The closed cell structure and the open cell structure are characterized by the difference in the size of the repeating structural unit, in addition to the above-described characteristics. In general, the closed cell structure has a smaller size of the repeating structural unit.

Also, as described in Non-Patent Document 2, the closed cell structure and the open cell structure have advantages and disadvantages. For example, the closed cell structure has a preferable characteristic that it can expand and support a tubular organ with a uniform stress distribution while it has little change in shape when bent, but has a problem that it is difficult to use in a portion where the tubular organ is branched. On the other hand, the open cell structure is suitable for use in a branched part of a tubular organ, and is highly flexible, but when bent, a part of the stent may be unexpectedly deformed excessively. Therefore, there is a problem that uneven stress distribution may be given to the tubular organ.

In general, a conventional single-layer stent has a structure in which cells and links (or connectors) are alternately arranged in a row when viewed in the longitudinal direction, and the tubular organ is expanded and supported in the link or connector portion. There is a problem that almost no function can be expected. This is particularly noticeable in the closed cell structure, and also appears in the open cell structure when expanded.

(Organ shape following)
In addition, the stent is required to have followability to the shape of the tubular organ to be applied (shape followability). This followability means that a stent placed in a tubular organ that meanders in the long axis direction can faithfully follow the organ shape even after expansion and placement. At the same time, it is desirable to follow the radial cross-sectional shape of the tubular organ, that is, to expand and support the tubular organ into a circular shape.

If the stent has insufficient ability to follow the shape of the tubular organ, when the stent is expanded and placed in the tubular organ, there is a problem that the expandability of the tubular organ becomes non-uniform with respect to the long axis direction. It develops into the problem of non-uniformity of stress distribution in the organ and damage of the tubular organ at the stress concentration site and the occurrence of restenosis.

(Vessel part with side branch)
By the way, there is a demand for enabling treatment with a stent 1 'to a blood vessel portion having a side branch 2b as shown in FIG. 2 such as a coronary artery which is an important application site of a stent. For this purpose, the number of struts of the stent 1 at the (corresponding) portion disposed on the side branch branch portion (side branch base) 2a is reduced (that is, the area of the cell portion of the stent 1 is widened to reduce the mesh). Reduce the number of links), and increase the gap. This facilitates the introduction of the stent 1 ′ into the side branch 2 b from this gap of the stent 1 (and the introduction of the balloon catheter thereby), etc. (In this sense, the open cell structure has an excellent approach to the side branch. It is said.) FIGS. 2 (i)-(iv) illustrate this state, and thus a high therapeutic effect can be expected.

However, there are two difficulties in realizing this. First, when a stent is to be placed in a side branch, there is usually a stenosis or the like at the branch of the side branch. The areas where sufficient radial stiffness is required to expand the part where the erosion occurs are in close proximity. Second, in the treatment with a stent, since the treatment is usually performed under fluoroscopy, even if the number of stent struts at a specific location is reduced, the location cannot be reliably positioned on the side branch portion. (For positioning, it is necessary to specify the position in the major axis direction and the angle in the circumferential direction.) For this reason, the site where the stent struts are reduced is not accurately placed in a site such as a stenosis of the blood vessel, There is a possibility that the stenosis site etc. cannot be expanded sufficiently.

In order to solve such problems, Patent Document 3 and Patent Document 4 disclose a stent applied to a portion having a side branch and a dedicated balloon catheter. This balloon catheter is provided with a special side branch discriminating device and can specify the position of the side branch in the long axis direction and the angle in the circumferential direction. The stent has a structure that allows easy opening of one portion outward so that the balloon catheter can be easily introduced into the side branch. However, in order to enhance the therapeutic effect of the bifurcation as described above, there is a problem that it is necessary to prepare a special stent or a special delivery device.

(Combination of multiple stents / composite stent)
In order to solve the problems of these single layer stents, a method of combining a plurality of stents has been proposed.
For example, the proposal which intends to provide more functions to a stent by connecting a plurality of stents in the major axis direction has been made (see Patent Document 6). That is, in order to ensure flexibility in the long axis direction, the stent is connected in the long axis direction. This means that there are more links than links made from one metal tube, and it is said that high flexibility can be imparted to the stent.

In another proposal, there is disclosed a stent intended to improve flexibility and transportability to a lesion site by providing an engagement portion capable of connecting and separating two stents in the longitudinal direction. (For example, see Patent Document 7).

In these stents, it is possible to improve the flexibility to some extent, but the problem that the stents are separated from each other by an external force such as friction between the stent and the living tissue generated during transportation to the lesion site has not been solved. That is, when the stent is transported, friction with the living tissue is generated, and the friction force acts in the major axis direction or the circumferential direction. However, generally, the frictional force in the major axis direction is larger and occurs for a longer time. Therefore, it is necessary to fix the stent so as not to move in the longitudinal direction of the delivery device. In Patent Document 6 and Patent Document 7, since the mechanical connection is made in the long axis direction, a force derived from the frictional force is applied to the connecting portion in relation to the force acting in the long axis direction of such a stent. Act directly on. If the force exceeds the connection force, the connection is broken and broken.

In Patent Document 5, a stent (“coil stent”) in which metal wires of a single material are formed in a spiral shape are overlapped, and the overlapping strut portions are joined by welding or the like. A method of enhancing the radial rigidity, which is a weak point of a coil stent, is disclosed. However, it must also be taken into account that the thinner the stent struts, the lower the restenosis rate. In other words, superimposing stents in the radial direction in order to enhance the radial rigidity is rational in engineering, but medically, on the contrary, it does not provide useful results. This is because, as shown in Non-Patent Document 3, the restenosis rate is reduced as the struts of the stent are thinner.

In Patent Document 11, a stent having a plurality of thin struts having slightly different radii (hereinafter referred to as “thin stent”) is prepared, and the other thin stent is inserted into one thin stent in the long axis direction. A multi-layered stent suitable for treatment of a side branch or the like is disclosed by superimposing them on the same axis and joining a part of struts at both ends (see FIG. 3 of Patent Document 11). However, for the joining of thin stents, joining utilizing resistance welding or thermocompression bonding is assumed (refer to paragraph [0040] and FIG. 5 (b) of Patent Document 11 for this). In addition, these bonding methods may change the properties of the materials used in thin stents, so what are the cells (functions that expand blood vessels) and links (functions that give flexibility) necessary for stent treatment? A method of joining two thin stents by separately providing unrelated joining struts and joining the two thin stent joining struts to each other has been unavoidable.

In this method, alignment in the major axis direction and the circumferential direction is necessary in the joining process. In order to align the positions of the struts, it is necessary to match the joining struts formed on the two thin stents with respect to the major axis direction (position z) and the circumferential direction (angle θ). Furthermore, since the strut of the outer thin stent must be brought into contact with the strut of the inner thin stent, the position of the radius r must be strictly controlled. In order to achieve this, the two thin stents have the same position and direction of the central axis (long axis) of each stent when they are joined, and the outer diameter (ri_out) of the inner thin stent is There was a need to match the inner diameter (ro_in) of the outer thin stent. Since the dimensions of the joining struts are about 0.1-0.5 mm, the required accuracy is the precision below this strut, specifically, the precision is 0.1 mm or less. In order to achieve this, alignment under a microscope is necessary. For resistance welding and thermocompression bonding, it is necessary to prepare a dedicated machine for development.

Furthermore, in Patent Document 11, a joining method by fitting is also disclosed. However, the details are not specifically disclosed, and there is only a description that “a concave portion and a convex portion are formed, and both are press-fitted and fitted”. From this description, it is only presumed that a support column for fitting is provided in addition to the cell and the link. In addition, in order to implement | achieve joining by this fitting, as mentioned above, precise alignment using a microscope is required. Moreover, in order to complete the fitting, the support column must be deformed (to press fit), and the operation amount (deformation amount) is assumed to be a very fine operation amount from the thickness and width of the support column. Is done. To achieve this, it is necessary to support a special device under a microscope. The manufacturer also needs special training. There is a problem that these constraints lead to an increase in manufacturing cost, and it is difficult to actually realize them.

Generally, stents are folded to a small diameter and transported to a lesion site such as a luminal organ. Therefore, the designer designs the stent by assuming a small folded state. For this reason, as disclosed in Patent Document 11, if a support column that is not necessary for treatment and is merely used for conjugation is provided, there is a restriction on the design of the support column that has a function essential for the treatment of cells and links. Or, due to the presence of the extra struts, smooth folding (warping) is hindered, and the stent does not fold sufficiently small.

An object of the present invention is to provide a thin, coaxial multi-layered stent that eliminates such constraints and does not require a dedicated machine such as a welding machine and does not require precise alignment. It is what.

Japanese translation of PCT publication No. 2002-537027 Japanese Patent Laid-Open No. 11-332998 Special table 2003-532447 gazette Special table 2003-532446 gazette US Patent Application Publication No. 2005/278017 Special table 2003-503152 gazette JP 2005-118571 A US Pat. No. 5,716,698 Special table 2004-511297 gazette Japanese Patent No. 3713488 JP 2008-301923 A JP-T-2001-50149 US Pat. No. 5,282,824 Japanese Patent No. 3236628 JP 2000-42119 A Special table 2008-503264

In the present invention, the radial rigidity is almost the same as that of a conventional single-layer stent, and it can be easily assembled by a doctor without any special struts at a medical site and inserted into the body. Providing a new coaxial multi-layered stent that does not separate the stent during delivery to the lesion in the blood vessel, enables side branch treatment without using a special delivery device, and can secure a space for storing a large amount of drug. It is intended to do.

Therefore, as a result of intensive studies to solve the above problems, the present inventor has reached the following invention.
[1] According to the present invention,
A planar structure consisting of multiple struts (Supporting Strut Members (SSM or Just SM)) arranged to form a mesh structure is rolled into a cylindrical shape, and consists of a cylindrical body with a long axis at the center. Coaxial multi-layer stent that forms two component stents A and B (hereinafter sometimes referred to as CSA and CSB) that can be reduced and expanded, and is arranged and configured coaxially with the CSA as the inner layer and CSB as the outer layer. (Coaxial Multi-Layered Stent) (CMLS)

The column is composed of a plurality of cells, each of which has a bent portion, and at least one link connecting the cells in the long axis direction.
The CSA and CSB are each composed of a main body part (Main Body Portion (MBP) occupying most of the center and both side (left and right) ends (LEP, REP) of the main body part,
The radii of the body portions are Ra and Rb (where Ra <Rb),
The component stent A (CSA) and the component stent B (CSB) are composed of the component stent A (CSA) strut (SSM) and the component stent B at least at the left end (LEP) of the both ends of the CMLS. The crossing of the columns (CSB) of the

And at the left end (LEP),
(I) The radius (Ra, in) of the cylindrical body of the component stent A (CSA) is the same as the radius Ra of the main body portion, and the struts can receive the struts of other component stents. Part (Accommodation Port or Portion (AP))

(Ii) The component stent B (CSB) is
(A) A support column arranged at the same radial position (Rb, in) as the radius (Rb) of the main body,
(A) a strut disposed at a radius position (Rb, df) smaller than the main body radius (Ra) of the component stent A; and
(C) A strut (Radially-running SM (RRSM)) (running or disposed in the radial direction of the cylindrical body connecting the two struts arranged at the two radial positions (Rb, in Rb, df). Or Radially-disposed SM (RDSM), Radially-arranged SM (RASM))

The component stent A (CSA) is inserted in the longitudinal direction of the cylindrical body of the component stent B with respect to the component stent B (CSB), and the strut (RRSM) of the component stent B (CSB) is inserted into the component stent B (CSB). A coaxial multi-layer stent characterized in that the two component stents A and B are engaged with each other by inserting and fitting the stent A (CSA) into the receiving portion (AP) so as to penetrate the radial direction. Is provided.

[2] According to the present invention,
A planar structure consisting of multiple struts (Supporting Strut Members (SSM or Just SM)) arranged to form a mesh structure is rolled into a cylindrical shape, and consists of a cylindrical body with a long axis at the center. A coaxial multi-layered stent in which two component stents A and B (hereinafter sometimes referred to as CSA and CSB) that can be contracted and expanded are formed and arranged coaxially with the CSA as an inner layer and the CSB as an outer layer. (Coaxial Multi-Layered Stent) (CMLS)

The column is composed of a plurality of cells, each of which has a bent portion, and at least one link connecting the cells in the long axis direction.
The CSA and CSB are each composed of a main body part (Main Body Portion (MBP) occupying most of the center and both side (left and right) ends (LEP, REP) of the main body part.
The radii of the body portions are Ra and Rb (where Ra <Rb),
The component stent A (CSA) and the component stent B (CSB) intersect the strut (SSM) of the component stent A (CSA) and the strut (CSB) of the component stent B at the right end (REP) of the CMLS. Is performed,

And at the right end (REP),
(I) The component stent A (CSA) is
(A) A support column arranged at the same radial position (Ra, in) as the radius (Ra) of the main body,
(A) a strut disposed at a radius position (Ra, df) larger than the main body radius (Rb) of the component stent B; and
(C) A strut (Radially-running SM (RRSM)) running or arranged in the radial direction of the cylinder connecting the two struts arranged at the two radial positions (Ra, in Ra, df) (Or Radially-disposed SM (RDSM), Radially-arranged SM (RASM))

(Ii) The radius (Rb, in) of the cylindrical body of the component stent B (CSB) is the same as the radius Rb of the main body portion, and the struts are capable of receiving struts of other component stents. Department (Accommodation Port Portion (AP)) is formed,

The component stent A is inserted into the component stent B (CSB) in the longitudinal direction of the cylindrical body of the component stent B, and the RRSM of the component stent A (CSA) is inserted into the component stent B (CSB). A coaxial multi-layer stent is provided in which the two component stents A and B are engaged with each other by inserting and fitting the receiving portion so as to penetrate the receiving portion in the radial direction.

[3] Also, according to the present invention,
At the left and right ends, the strut (SSM) and the component stent B strut (CSB) of the component stent A (CSA) are crossed, respectively, and the coaxial stent in which the two component stents A and B are engaged. A layered stent, wherein the engagement at the left end (LEP) is performed as defined in [1], and the engagement at the right end (REP) is performed as defined in [2]. A coaxial multi-layer stent is provided.

[4] According to the present invention,
A part of the strut of the component stent A or B partially surrounds the long axis by connecting a plurality of cells having bent portions capable of reducing and extending the circumferential length of the cylindrical body in the vertical direction. It is composed of a ring-shaped support (Ring-shaped SM) configured by arranging a plurality of the same and at least one link connecting the adjacent ring-shaped support in the major axis direction [ [1] The coaxial multilayer stent according to any one of [3].

[5] Also, according to the present invention,
The receiving portion AP of the component stent A or B is provided as a part of the cell having the bent portion, and a part thereof is opened in the direction of the left end portion (LEP) and / or the right end portion (REP), The coaxial multilayer stent according to any one of [1] to [4], wherein the opening defines a passage for introducing a strut.

[6] According to the present invention,
The receiving portion AP of the component stent A or B includes the passage and a locking holder (Latch Holder) having a circular opening (Round-Rectangular Aperture) communicating with the passage. In the opening, the radius of curvature of the column that forms the opening located at a position opposite to the passage is longer than the radius of the bent portion of the cell, and forms the passage of the passage communicating with the holder. The distance between the two opposing struts (SM) is narrower than the strut width forming the bent portion of the holder or cell, according to any one of [1]-[5] A layer stent is provided.

[7] Also, according to the present invention,
In the receiving portion AP of the component stent A or B, the holder is symmetrical with respect to a straight vertical bisector connecting the cell bent portions in the circumferential direction, but the opposing struts forming the passage are The coaxial multilayer stent according to [6], which is disposed at a position shifted in the circumferential direction from the perpendicular bisector thereof.

[8] According to the present invention,
The receiving portion AP of the component stent A or B is provided as a part of a cell having a bent portion, and at least two of the receiving portions (AP) are part of at least two or more cells. The coaxial multilayer stent according to any one of [1] to [7], characterized in that each is provided.

[9] Also, according to the present invention,
The receiving portion AP of the component stent A or B is characterized in that at least one receiving portion (AP) has a mirror image relationship with the other receiving portion (AP) with respect to the major axis of the stent A or B [ 8] is provided.

[10] According to the present invention,
The component stent A or B has a radially running or arranged strut (Radially-running SM (RRSM)) (or Radially-disposed SM (RDSM), Radially-arranged SM (RASM)). The coaxial multilayer stent according to any one of [1] to [9], wherein the coaxial multilayer stent is provided as a part of a link portion.

[11] According to the present invention,
Struts (Radially-running SM (RRSM), Radially-arranged, Radially-running SM (RRSM)) provided in the link portion of the component stent A or B. SM (RASM))), the length in the major axis direction of the link part is longer than the length in the major axis direction of the link part of the pillar without the strut (RRSM) traveling in the radial direction. The coaxial multilayer stent according to [10] is provided.

[12] Also, according to the present invention,
[1] In the coaxial multi-layered stent (CMLS) according to any one of [11], a gap in the main body between the two component stents A and B (CSA, CSB) The drug elution is characterized by the fact that the part can be preferably used as a site for storing or holding a drug reservoir (Drug Reserver or Holder) (Said space is favorably used for, or serves as, a DR) A coaxial multi-layer stent is provided.

[13] According to the present invention,
[1] In the coaxial multi-layered stent (CMLS) according to any one of [11], a gap in the main body between the two component stents A and B (CSA, CSB) A drug-eluting coaxial multi-layer stent (DE-CMLS) is provided in which the drug to be eluted is accommodated or accommodated in a part as a drug reservoir.

The present invention has the following advantageous effects.
In the coaxial multilayer stent of the present invention, it is possible to assemble the coaxial multilayer stent without using a dedicated machine such as a welding machine and without requiring precise alignment. The cells located at the end of the stent have a wide interval between the opposing struts, and the cell struts are formed so as to gradually narrow toward the struts for engagement. This eliminates the need for an assembly machine (manufacturer) or a dedicated joining machine, and enables engagement by simply moving and sliding a plurality of thin stents (component stents) in the longitudinal direction. The coaxial multilayer stent of the present invention can be assembled.

Further explaining that the coaxial multi-layer stent of the present invention can be easily assembled, even if the circumferential position is inappropriate before joining, only the length of the long axis of the cell in the long axis direction ( If it slides about 1.0mm-2.5mm), as will be described later, the struts that run in the radial direction are guided to an appropriate position. The moving length slide amount is the long axis length of the cell (or the long axis length of the receiving part receiving the column) (approximately 1.0mm-2.5mm), so the joining operation is performed manually without using a special machine. it can.

As will be described later, in the component stent B constituting the outer layer, the struts that run in the radial direction are engaged with the struts (receiving portions) for engaging the component stent A constituting the inner layer. The positions of the central axes of the two component stents A and B do not have to coincide with each other. The thickness of the struts radially running in the outer component stent B is different from the thickness radius difference of the struts of the inner component stent A. A gap error is allowed as much as the thickness is subtracted. In this regard, in the prior art, the two stent central axes are in sharp contrast to the fact that they had to be exactly coincident.

Even if the circumferential position (angle θ) is inadequate before joining, if the cell is moved and slid in the long axis direction by the length of the long axis of the cell (approximately 1.0mm-2.5mm), the struts of the component stent B ( The struts that run in the radial direction are naturally guided to the struts (receiving portions) for engaging the component stent A with the struts of the component stent B serving as a guide. This indicates that the required accuracy regarding the angle θ at the time of joining can be relaxed as compared with the conventional coaxial multilayer stent. These contribute to or contribute to eliminating the need for precise alignment during bonding in the radial direction and the circumferential direction. Moreover, since the moving amount of the component stent in the major axis direction is about 1.0 mm to 2.5 mm, it has a great effect that it can be easily assembled without using a microscope.

Moreover, if the point which the fall of the component stent B of the outer side at the time of conveyance is effectively prevented is demonstrated, the coaxial multilayer stent of this invention was mounted in the balloon, and it was overlapped on the way of conveying to a lesioned part. A force to pull the struts often acts. This force is a force in the r direction in the stent coordinate system. For example, it occurs when the stent passes through a bend in a blood vessel.

In the coaxial multi-layer stent of the present invention, the struts involved in the engagement of the inner component stent A and the outer component stent B intersect with each other at the radial positions in the engaging portions as will be described later. is doing. When a radial force (r-force) is applied to the inner component stent A, the strut of the component stent B is arranged on the outer side of the component stent A by the strut of the component stent A. Prevent separation from the column. Similarly, when a force in the r direction acts on the outer component stent B, the strut of the component stent B is disposed outside the component stent B, so that the strut of the component stent B becomes the component stent. Prevents from leaving the A column.

The coaxial multi-layer stent of the present invention has a novel engagement mechanism in which struts that run in the radial direction are formed in each of the inner component stent A and the outer component stent B, thereby engaging with each other. Therefore, the problem of dropping off the outer component stent during transportation, which is one of the biggest problems in the conventional coaxial multilayer stent, has been essentially solved.

As for the foldability of the stent, it is not necessary to newly provide struts for engagement formed on both ends of the component stents A and B as elements different from the cells as in the prior art. Since it is fused with the cell and is provided as a part of the cell, it is possible to fold the stent after joining, for example, in a contraction time without being disturbed.

Regarding the rigidity, flexibility and side opening of the coaxial multilayer stent of the present invention, in the stent of the present invention, the number of links affecting the flexibility is the same as the total number of inner layers and outer layers. Although the number is the same as that of a single-layer stent, the thickness of the struts at the link site is thinner than that of a conventional stent, so that it has excellent flexibility. In addition, regarding the radial rigidity, the thickness of the stacked struts is designed to be the same as that of the conventional stent, so that the radial rigidity is comparable to that of the conventional stent.

Each component stent before overlapping has a large mesh (pattern consisting of cells and links). Each stent has a strut joined at its end, but the other portions do not affect the deformation of the stent struts. Therefore, the coaxial multilayer stent of the present invention can make a large hole in the side surface.

The component stent constituting the present invention is provided with a connector fused with a cell or a link, and is thereby joined. In addition, since work such as welding can be omitted for the joining, it is expected that productivity can be improved by facilitating assembly work and preventing assembly errors. Moreover, since it is not necessary to prepare the support | pillar for joining, the design method equivalent to the conventional single layer stent can be applied. Therefore, the coaxial multilayer stent of the present invention can be realized without complicating the design process.

At present, DES (Drug Eluting Stent), in which a drug such as a thrombolytic agent is applied to the surface of the stent, is attracting attention. However, the coaxial multi-layer stent of the present invention has a function of holding such a drug. If it mentions, since the said stent of this invention is the state in which the some component stent was piled up, the space exists in the radial direction between each component stent. It is possible to store a drug reservoir formed in a spiral shape or the like that is stored in the shape of the space with a polymer mixed with the drug. The drug reservoir (shape and capacity) is formed regardless of the shape and structure of each component stent. Therefore, the shape and structure of the component stent and the multi-layer stent do not affect the amount of drug mixed in the drug reservoir. This means that the drug loading can be set independently from the shape and structure of the component stent and the multilayer stent.

In particular, in a conventional drug-eluting stent, the drug is applied to the surface of the stent cell or link as it is or together with a binder, and the amount of the drug is regulated by the surface area and can be changed (increased) significantly. It was difficult. However, in the present invention, since the drug is stored not in the stent surface but in the space between the layers of the coaxial multi-layer stent, the degree of freedom is extremely large, and the drug can be eluted for a long time. The effect is very great. The configuration of the drug reservoir by the coaxial multilayer stent of the present invention and the accommodation mechanism thereof will be described in detail later.

FIG. 1 is a developed view of a general stent. FIG. 2 is a schematic view of a bifurcation treatment. FIG. 3 is a conceptual diagram showing a method for assembling a coaxial stent. FIG. 4 is an explanatory diagram showing the definition of the coordinate system. FIG. 5 is a development view of the cell. FIG. 6 is a photograph showing a state before and after expansion of the stent. FIG. 7 is a photograph showing a state when the stent is expanded when there is no cell bent portion on the cell central axis. FIG. 8 is an explanatory view of a receiving portion (female connector FC). FIG. 9 is an explanatory view showing the receiving portion and the locking holder. FIG. 10 is a diagram illustrating the passage portion in detail. FIG. 11 is a diagram illustrating the definition of the angle of the passage portion and another embodiment of the passage portion. FIG. 12 is an explanatory diagram showing a receiving portion and a receiving portion that is in a mirror image relationship with the receiving portion. FIG. 13 is a schematic view showing a cell and a receiving portion. FIG. 14 is a conceptual diagram showing a radial traveling strut in the mail connector MC. FIG. 15 is a conceptual diagram showing a component stent in which a mail connector MC is formed on a part of a link. FIG. 16 is a conceptual diagram showing a component stent in which both a receiving portion and a mail connector are formed. FIG. 17 is a cross-sectional view of component stents A and B. FIG. 18 is a cross-sectional view showing a state where the end portions of the component stents A and B are deformed for joining. FIG. 19 is a cross-sectional view showing a state where the end portions of the component stents A and B are deformed for joining. FIG. 20 is a diagram showing a state in the middle of the crossing of the component stents, where (i) is a cross-sectional view and (ii) is a development view. FIG. 21 is a diagram showing a state where the crossing process of the component stent has further progressed (immediately before joining), where (i) is a sectional view and (ii) is a developed view. FIG. 22 is a diagram illustrating a state where the crossing of the component stents is completed (after joining), where (i) is a cross-sectional view and (ii) is a developed view. FIG. 23 is an enlarged view showing the receiving portion and the radial traveling strut in a state where the intersection is completed and joined. FIG. 24 is a developed view showing the positions of the struts when the joined component stents are displaced in the circumferential direction. FIG. 25 is a cross-sectional view of a coaxial multilayer stent mounted on a balloon catheter. FIG. 26 is a development view showing stents having the same shape and different strut thicknesses t. FIG. 27 is a developed view showing stents that differ only in the number n of links in the circumferential direction. FIG. 28 is a graph showing a change in radius during pressurization of a coaxial multilayer stent and a conventional single layer stent. FIG. 29 is a developed view showing two coarse component stents A and B. (However, the connector is omitted.) FIG. 30 shows a development view (i) when the component stents A and B of FIG. 29 are joined, and a development view (ii) when a hole is made in the side wall thereof. (However, the connector is omitted.) FIG. 31 is an explanatory view showing a preferable shape of the medicine reservoir.

Planar structure of a stent A composed of a plurality of struts arranged so as to form an A ₀ network structure B Planar structure of a stent B composed of a plurality of struts arranged so as to form a A ₀ network structure A A component stent B forming an inner layer Component stent forming the outer layer MBP (Main Body Portion))
LEP Left side end of main body part REP Left side end part of main body part Ra Radius of main part of stent A Ra, in Radius of cylindrical body of stent A (before forming a step)
Ra, df Radius of cylindrical body of stent A (after forming a step)
Rb Radius of stent B main body radius Rb, in Radius of cylindrical body of stent B (before forming a step)
Rb, df Radius of the stent B cylinder (after forming the step)
AP Stent Receptor AP ^* Receptor in a mirror image relationship with AP AP (A) Stent A Receptor AP (B) Stent B Receptor Ld Stent Long Axis ld Cell Central Axis RRSM Runs in Radial Direction Prop (radial travel prop)
Vab gap in the body FC Female connector MC Mail connector DR Drug reservoir

01 Planar structure of a stent composed of a plurality of struts 1, 1 'Stent 7 Stent central axis 2a Side branch base 2b Side branch 10A Stent A strut 12A Stent A strut 14A Strut 14 A connecting section 14 running in the radial direction of stent A '' Radial Deformation 14 '''Radial Deformation 10B Stent B Strut 12B Stent B Strut 14B Stent B Radial Strut 16A Stent A Passage 18A Stent A Opening
16B passage of stent B 18B opening of stent B
30 Cell-like corrugated body 31j J-side cell bent portion 32j J-side cell bent portion 34j J-side cell central long side portion 31k K-side cell bent portion 32k K-side cell bent portion 34k J-side cell side Long side of cell center 36 Arc 38 Locking holder 50 Balloon catheter

Hereinafter, the present invention will be described in detail with reference to the drawings. First, the meanings of terms used in the present specification are clarified as follows.
(Definition of terms)
(A) Strut In this specification, “strut” (Supporting Strut Member) (SSM or Just SM)) is an element (element) that constitutes the network structure of a stent, and mainly connects cells and cells. Although it consists of a link, it may contain other elements.

(A) Joining, adhering, connecting In this specification, “joining” refers to bringing two struts into contact with each other. “Fixation” refers to a state where two struts are in contact and the two struts do not change their relative position and angle at the contacted portion. A fixed state can be created by joining the struts by welding. “Attachment” refers to a state in which two struts are in contact with each other and the relative position of the two struts does not change, but the relative angle changes. A joined state can be created by joining the struts by engagement.

(C) Engagement “Engagement” means that in two parts or elements, a claw part, a projecting part, or a convex part (hereinafter referred to as a claw part or the like) of one part or element is formed. Other parts or elements are provided with a locking part or a hook-like part (hereinafter referred to as a locking part or the like) having a space part for fixing the claw part or the like corresponding to the claw part or the like. When the or element is brought close to each other, the claw portion or the like is received by the space portion such as the locking portion, the two engage with each other, and the two parts or elements are connected. In the present specification, engagement and fitting are used interchangeably.

As an example of a specific mode of engagement, in a set of one part having a projecting portion formed of elastic metal and another part having a space portion and a narrow passage communicating with the space portion, When the protrusion is press-fitted into the part having the space through the passage, the protrusion is elastically deformed at the time of insertion and passes through the gap while expanding the passage so that the inside of the space Is inserted into the space portion, and the protruding portion that has returned to its original shape is caught by a part of the space portion, and the gap of the passage is returned to the narrow width. Since the passage cannot be reversed, the two are stably connected. Here, if the space is formed larger than the protrusion, the protrusion is movable “with play” in the space, so that it engages in a so-called “free fit” state. It will be.

(Definition of coordinate system)
The coordinate system used in the present invention will be described with reference to FIG. In the figure, the global coordinate system Og-XYZ is a general three-dimensional coordinate system. The stent coordinate system Os-rθz (FIG. 4 (i)) is a coordinate system used to represent the position and orientation of the stent, and is the same as the cylindrical coordinate system, and has a radius r, a circumferential angle θ, and a length. It consists of an axis z. The long axis z coincides with the central axis of the stent. Reference numeral 7 denotes a central axis of the stent.

The stent development coordinate system Oe-θz (FIG. 4 (ii)) is a two-dimensional coordinate system. It is used to describe the shape of the struts that are placed at any radius of the stent when it is deployed. The direction perpendicular to the plane of the paper coincides with the radius r in the stent coordinate system. FIG. 4 also shows the relationship between the coordinate systems.

(Assembly of coaxial multi-layer stent)
The multi-layer stent of the present invention is configured by stacking two stents. The basic configuration of each stent (component stent) is schematically shown in FIG. A planar structure 01 composed of a plurality of support columns arranged so as to form a mesh structure is rolled into a cylindrical shape, has a long axis at the center, and its circumferential length can be reduced and expanded as shown in FIG. It consists of a cylindrical stent 1 as shown in c). FIG. 1B is an enlarged view of a part of the column, and shows that the cell 2 and the link 3 connecting the cells are included as elements.

FIGS. 17 to 22 are diagrams showing the process of assembling the laminated stent of the present invention.
Reference is first made to FIG. FIGS. 19A and 19B show planar structures A ₀ and B ₀ composed of a plurality of support columns arranged so as to form a mesh structure, and FIGS. 19A and 19B show this structure. Two component stents A and B (hereinafter referred to as CSA and CSB, respectively), each of which is formed by a cylindrical body having a long axis at the center, and whose circumferential length can be reduced and expanded, Yes.) (The figure is a longitudinal sectional view.)

The component stent A (CSA) is used as an inner layer, and the component stent B (CSB) is used as an outer layer to be coaxially disposed and configured to form a coaxial multi-layered stent (CMLS) as follows. . (Hereinafter, component stent A may be simply referred to as stent A, and component stent B may be referred to as stent B.)

As shown in FIGS. 19 (a ′) and 19 (b ′) (and FIG. 17-18 which is an enlarged view thereof), the CSA and CSB each have a main body portion (Main Body Portion (MBP)) that occupies most of the center. And end portions on both sides (left and right) of the main body, that is, a left end portion (LEP) and a right end portion (REP).
The radii of the main body portions are Ra and Rb (where Ra <Rb), respectively. (Of course, this means that the radius of the body portion of the component stent B forming the outer layer is larger than the radius of the body portion of the component stent A forming the inner layer.)

Here, it is important that the component stent A (CSA) and the component stent (B) (CSB) are at least the left end (LEP) or the right end (REP) of the both ends of the CMLS. In any case, the strut (SSM) of the component stent A (CSA) and the strut (CSB) of the component stent B are configured to be crossed.

The most characteristic point of the present invention is that the stent A and the stent B are connected by performing the “crossing of the struts”. For this purpose, first, stents A and B as shown in FIG. 17 are used as starting stents, and as shown in FIG. 18 (i), the stent A (main body radius Ra) is directed outward at the right end thereof. A step is formed, and its radius is Ra, df (note that the radius immediately before forming the step is Ra, in, and Ra = Ra, in). Further, as shown in FIG. 18 (ii), the stent B (main body radius Rb) is formed with a step in the radial direction at the left end thereof, and the radius is defined as Rb, df (The radius immediately before forming is Rb, in, and Rb = Rb, in.)

(Left end crossing / Before crossing)
First, the case where a support | pillar crossing is performed in a left end part (LEP) by the style like FIG. 20 is demonstrated.
(I) As shown in FIG. 20 (i), the radius (Ra, in) of the cylindrical body of the component stent A (CSA) constituting the inner layer is the same as the radius Ra of the main body at the left end. (That is, the component stent A is not particularly provided with a “step” at the left end portion thereof, and the left end portion and the main body portion are on the same plane.) A receiving port (Accommodation Port or Portion (AP (A))) that can receive the column is formed. (The receiving unit AP (A) consists of a passage for introducing the column and an opening for holding the introduced column.) An example of a typical shape is as shown in the left side view of Fig. 20 (ii), which will be described in detail later.

(Ii) Further, the component stent B (CSB) constituting the outer layer is formed with a “step” that extends downward from the main body at the left end thereof. That is, the step is
(A) A column 10B arranged at the same radial position (Rb, in) as the radius (Rb) of the main body,
(A) a strut 12B disposed at a radius position (Rb, df) smaller than the main body radius (Ra) of the component stent A; and
(C) A strut 14B (Radially-running SM (RRSM)) running or arranged in the radial direction of the cylindrical body connecting the two struts arranged at the two radial positions (Rb, in Rb, df). (Or also referred to as Radially-disposed SM (RDSM) or Radially-arranged SM (RASM)).

In such a state, the component stent A constituting the inner layer is inserted into the component stent B constituting the outer layer in the direction indicated by IN along the long axis Ld. The figure shows a state in which the receiving portion AP (A) at the left end of the inner component stent A is approaching the “step” of the component stent B, that is, the strut 14B that runs in the radial direction, at the left end LEP. Show. (The left view of FIG. 20 (ii) shows the support 14B and the receiving portion AP (A) in this state as seen from the radial direction.)

(Intersection)
FIG. 21 shows a stage where the component stents A and B are in the middle of crossing at the left end thereof.
That is, as shown in FIG. 21 (i), the supporting portion AP (A) (the supporting strut) at the left end portion of the inner component stent A intersects the strut 14B traveling in the radial direction. (In other words, it is understood that the columns cross in a cross section.)
Specifically, as shown in the left diagram of FIG. 21 (ii), the receiving portion AP (A) is composed of a passage 16A for introducing a support column and an opening 18A for holding the introduced support column. The state where the column 14B is entering the passage is shown.

(Intersection completed)
FIG. 22 shows a state in which the component stents A and B have completed the crossing process at the left end thereof.
That is, as shown in the left end of FIG. 22 (i), the intersection of the strut 14B traveling in the radial direction and the receiving portion AP (A) (the strut constituting the left end of the inner component stent) is completed. Thereafter, the intersection cannot be solved (that is, this state does not return to the state of FIG. 21 or FIG. 20).

Specifically, as shown in the left diagram of FIG. 21 (ii), the column 14B introduced from the passage 16A is trapped in the opening 18A of the receiving portion AP (A). Because it is. The column 14B is movable in the opening (in other words, in a loosely fitted state), but is configured not to run backward to the passage. The mechanism by which the receiving portion traps the support will be described in detail later.

As described above, in the present invention, the component stent A (CSA) that forms the inner layer is arranged in the major axis direction of the cylindrical body of the component stent B with respect to the component stent B (CSB) that forms the outer layer. Inserting and fitting the strut (RRSM) of the component stent B (CSB) into the receiving portion AP of the component stent A (CSA) so as to penetrate the component stent A (CSA) in the radial direction. , B are formed into a coaxial multilayer stent.

(Right end crossing / Before crossing)
Similarly, the case where the pillars cross at the right end will be described.
(I) As shown in FIG. 20 (i), at the right end, the radius (Rb, in) of the cylindrical body of the component stent B (CSB) constituting the outer layer is the same as the radius Rb of the main body. (That is, the component stent B is not particularly provided with a “step” at the right end thereof, and the left end portion and the main body portion are on the same plane.) A receiving portion (Accommodation Port or Portion (AP (B))) capable of receiving the support is formed (the receiving portion AP (B) includes a passage for introducing the support and an opening for holding the introduced support. An example of a typical shape is as shown in the right diagram of Fig. 20 (ii), which will be described in detail later.

(Ii) Further, the component stent A (CSA) constituting the inner layer is formed with a “step” toward the upper side from the main body at the right end thereof. That is, the step is
(A) A support 10A disposed at the same radial position (Ra, in) as the radius (Ra) of the main body,
(A) a column 12A disposed at a radial position (Ra, df) larger than the main body radius (Ra) of the component stent (A); and
(C) A strut 14A (Radially-running SM (RRSM)) that travels or is arranged in the radial direction of the cylindrical body connecting the two struts arranged at the two radial positions (Ra, in Ra, df). , (Or Radially-disposed SM (RDSM), Radially-arranged SM (RASM)).

In such a state, the component stent A constituting the inner layer is inserted into the component stent B constituting the outer layer in the direction indicated by IN along the long axis Ld. The figure shows a state in which the receiving portion AP (B) at the right end portion of the outer component stent is approaching the “step” of the component stent A, that is, the strut 14A running in the radial direction at the right end portion thereof. . (The right side view of FIG. 20 (ii) is a view of the column 14A and the receiving portion AP (B) in this state from the radial direction.)

(Intersection)
FIG. 21 shows a stage in which the component stents A and B are in the middle of crossing at the right end thereof.
That is, in the right end portion of FIG. 21 (i), the receiving portion AP (B) (the supporting strut) of the right end portion of the outer layer component stent B is disposed on the strut 14A running in the radial direction of the inner layer component stent A. Crossed. (In other words, it is understood that the columns cross in a cross section.)
Specifically, as shown in the right diagram of FIG. 21 (ii), the receiving portion AP (B) is composed of a passage 16B for introducing a support column and an opening 18B for holding the introduced support column. However, a state in which the column 14A is entering the passage is shown.

(Intersection completed)
FIG. 22 shows a state in which the crossing process of the component stents A and B is completed at the right end portion thereof.
That is, as shown in the right end portion of FIG. 22 (i), the struts constituting the struts 14A that run in the radial direction of the inner layer component stent A and the receiving portions AP (B) (at the right end portion of the outer layer component stents). ) Is completed and the intersection cannot be solved (that is, this state does not return to the state of FIG. 21 or FIG. 20).

Specifically, as shown in the right side view of FIG. 22 (ii), the column 14A introduced from the passage 16B is trapped in the opening 18B of the receiving portion AP (B). Because it is. The support column 14A is movable in the opening, but is configured not to run backward to the passage.

As described above, in the present invention, the component stent A (CSA) is inserted into the major axis direction of the cylindrical body of the component stent B with respect to the component stent B (CSB). By inserting and fitting the RRSM of (CSA) into the receiving portion of the component stent B (CSB) so as to penetrate in the radial direction, and engaging the two component stents A and B, A layered stent is formed.

In the coaxial multi-layer stent of the present invention, as described above, at least the left end or the right end is crossed, but preferably both the left end and the right end. In Fig. 3, the intersection is performed.

Also, the coaxial multilayer stent of the present invention can be defined as follows. That is, a component stent A that forms an inner layer having a strut (receiving portion) that can engage a strut that is configured in the radial direction of struts of other stents and that has a uniform strut radius, and a stent Outer layer having struts arranged at larger radial positions, struts arranged at smaller radii, and struts (struts running in the radial direction) for connecting the struts arranged at the two radii as compared to A The stent A is inserted in the longitudinal direction relative to the stent B, and the struts of the stent B are arranged at three radial positions formed by engaging the receiving portion of the stent A. A coaxial multi-layer stent having a strut and a strut having a continuously changing radius.

Hereinafter, the present invention will be described more specifically.
(cell)
In the present invention, one of the elements constituting the support column is a cell. A typical cell shape is shown in FIGS. 5A and 5B as development views. That is, FIG. 5 (a) shows a state in which a plurality of cells 30 having bent portions are connected in a waveform in the radial direction (circumferential direction). A ring is formed that surrounds the long axis.

FIG. 5B is an enlarged view of the shape of the one cell. The cell has a cell center axis ld, two above the cell center axis (J side), Two cell bent portions (cell bent portion 31j, cell bent portion 31k, cell bent portion 32j, cell bent 32k) and two cell central

long side portions

34j, 34k are formed on the side (K side). A straight bisector of a straight line connecting the cell bent portion 31j and the cell bent portion 31k in the circumferential direction is the cell center axis ld.
(That is, in one cell, the elements constituting it extend from 31j → 34j → 32j → 32k → 34k → 31k to form one cell. In this case, the cell bent portion 32j and the cell bent 32k are directly Are connected to form one arc 36 as a whole.)

When the stent is expanded at a lesion site, the

cell bending portions

32j and 32k that continuously form an arc are deformed, so that the circumferential distance between the cell bending portions 31i-31k is increased. Since the distance between the bent portions 31i-31k is a part of the circumference of the stent having a cylindrical shape, the longer distance between the cell bent portions 31i-31k means that the circumference of the stent becomes longer, in other words, This means that the radius of the stent is increased.

Regarding the expanded state of the stent, FIGS. 6A and 6B show photographs of the stent actually produced by the present inventors. At this time, according to the findings of the present inventors, when the arc formed by the cell bent portion 31i and the cell bent portion 31k is offset in the circumferential direction from the cell central axis ld, the stent is twisted during expansion. It was found that this phenomenon was observed.

FIGS. 7 (i)-(iii) are photographs showing the result of expanding an actually produced stent based on the drawing disclosed in Patent Document 15 (FIG. (Iv)). As can be easily understood, it was confirmed that twisting occurred during expansion, and further expansion might not be possible. Therefore, the arc formed by the cell bent portion 32j and the cell bent portion 32k is preferably located on the cell center axis ld that passes through the midpoint between the cell bent portion 31i and the cell bent portion 31k. It is understood that a symmetrical shape with respect to the axis is preferred.

The radial stiffness of the stent is largely governed by the length of the cell in the long axis direction. Therefore, the shape of the strut of the cell central long side portion (also simply referred to as the cell central portion) other than the cell bent portion forming the corrugation hardly affects the radial rigidity of the stent (for example, Stent design using sensitivity analysis, see Koji Mori, Ken Ikeuchi, Kazuaki Mitsudo, Journal of Japanese Society for Clinical Biomechanics, 22, 381-387, 2001). Therefore, it is possible to change the shape of the column in the central part of the cell so that the column in the central part of the cell plays the role of a claw or protrusion necessary for realizing the engagement mechanism by crossing as described above. preferable.

In the cell bent portion 32j and the cell bent portion 32k (and the cell bent portion 31j and the cell bent portion 31k), strain concentrates when the stent expands. If this concentrated strain maximum exceeds the fracture strain of the material used for the stent, the stent will break. According to the analysis by the present inventors, the maximum strain when expanding the stent with the same cell length and changing the radius of curvature to 0.09 mm, 0.12 mm, and 0.16 mm is 33.4%, 29.1%, and 25.1, respectively. %. As described above, the maximum value of strain concentrated at the time of expansion generally decreases as the radius of curvature increases.

In order to transport the stent to the lesioned part, the radius of the stent is usually further reduced from an unexpanded state (for example, FIG. 6A). This is because the smaller the radius of the stent, the easier it is to pass through the blood vessel. In such a case, as for the shape of the cell, the circumferential distance between the cell bent portion 31j and the cell bent portion 31k is reduced, but the curvature radius of the bent portion is hardly reduced.

(Specific configuration of receiving part)
In the present invention, it is practical to form the receiving portion (AP (A), AP (B), etc.) for receiving the struts that run in the radial direction in a part of the cell, but by forming the receiving portion, From the above-mentioned knowledge, in order to maintain or achieve the function as the original link without obstructing the function required as the link (also referred to as a connector), the shape as shown in the developed view of FIG. It is preferable to form. (Note that the receiving portion is also referred to as a “female connector” (FC) from the viewpoint that it is an element that receives a strut that travels in the radial direction and functions as a link.)

That is, in FIG. 8, the receiving portion AP is composed of the

cell bending portions

31 j and 31 k, the cell center

long side portions

34 j and 34 k, the passage portion 16, and the locking holder 38 having the opening 18. In FIG. 8, the opening 18 is divided into a J-side opening 18j and a K-side opening 18k.

Since it is configured in this manner, for example, in the receiving portion AP shown in FIG. 8, the struts of the component stent moving in the radial direction moving from the left are already assembled at the time of assembling (in the crossing process), It is smoothly guided to the opening 18. The opening 18 is preferably circular.

Then, as shown in FIG. 9, when the locking holder 38 (referring to a column that forms the opening 18) is divided into its constituent elements, a J-side bent portion 38'j and a K-side bent portion 38'k. (This is the portion corresponding to the arc portion of the circular opening.) The straight portion 38 ″ j on the J side and the straight portion 38 ″ k on the K side (this is the shape of the circular opening. It is a part corresponding to a square part.).

FIG. 10 shows the passage portion 16 divided according to the function. The entrance portion (Inlet Port j, k) ((i)), the taxiway (Guide Path j, k) ((ii) ), Outlet part (Outlet Port j, k) ((iii)), and locking part (Locking Port j, k) ((iv)). Here, the cell center

long side portions

34j, 34k and the entrance portion 16 of the passage portion are smoothly connected to each other.

Next, attention is focused on FIGS. 11 (a)-(c).
As shown in FIG. 11 (a), the angle formed between the J-side inlet and the cell center axis ld in the support of the inlet (Inlet Port) (j, k) and outlet (Outlet Port) (j, k) The relationship between α and the angle β between the J-side outlet portion (Outlet Port) (j) and the cell center axis ld is formed such that α <β. The relationship between the angle γ formed by the other K-side inlet (Inlet Port) and the cell center axis ld and the angle K between the K-side outlet (Otelet Port) (k) and the cell center axis ld is γ <δ. It forms so that it may become.

Here, the passage 16 is preferably formed at a position offset in either of the circumferential directions with respect to the cell center axis ld. Therefore, the relationship between the angle α and the angle γ in FIG. 11A is preferably α ≠ γ. However, even if α = γ, it is possible to form the passage so that it is offset in either of the circumferential directions with respect to the central axis. That is, α ≠ γ is a necessary condition for offsetting in the circumferential direction with respect to the central axis. Moreover, it is preferable to form the position of the long axis direction of the channel | path 16 in the position near the said opening part 18 rather than the intermediate point of the square-shaped opening part 18 and the

cell bending parts

31j and 31k.

10 (iv), the locking portions 18′j and 18′k of the passage 16, and the 38 ″ j and 38 ″ k (38 ″ k) of the central column of the locking holder (the column forming the opening). It is preferable that the major axis direction interval of the square portion of the circular opening shown in FIG. 9 is close to the thickness of the struts of the component stent to be joined. By comprising in this way, the support | pillar which runs to the radial direction of one component stent can be fixed with respect to the longitudinal direction in the latching holder of the receiving part of another component stent.

According to the fixing mechanism of the strut running in the radial direction by the receiving portion or the locking holder in the present invention, a long-axis direction (friction with living tissue) force generated when the stent is transported to the lesioned part. On the other hand, the stent can be prevented from shifting in the long axis direction. Moreover, it is preferable that the space | interval of the support | pillar of the opening part which opposes regarding cell center axis | shaft ld is near the width | variety of the support | pillar of the component stent to join. In FIG. 11 (a), the passage portion is formed by a column having a constant thickness. However, as shown in FIG. 11 (b), the passage portion is formed by locally changing the thickness of the column. However, the same function can be achieved by maintaining the relationship of the angles α, β, γ, and δ. Furthermore, as shown in FIG. 11C, it is obvious that the same function can be exhibited even if the passage is formed by branching the support.

The opening 18 in the locking holder reduces its expansion strain and allows its radius of curvature to be received by the receiving portion (or locking holder) in order to secure space for holding another component stent strut. It is preferable to form the cell larger than the

bent portions

32j and 32k of the cell in which no is formed. The larger the opening 18, the greater the tolerance in the assembly process when manufacturing the stent including the locking holder (or receiving part), and the ease of assembly and the yield are improved. However, if the radius of curvature is too large, restrictions on the cell shape and the link shape, which are other structural parts of the stent, are not preferable.

One of the objects of the present invention is to prevent the overlapped stent from falling off due to frictional force with the living tissue generated in the longitudinal direction when the stent is transported to the lesion. The shape is preferably short in the long axis direction and long in the circumferential direction. (This is why it is preferable that the opening 18 has a circular shape.) By adopting such a shape, the radius of curvature at the center of the opening is increased, and strain concentration during expansion can be reduced. The following effects can also be expected. Also, the opening 18 plays the same role as the cell bent

portions

32j and 32k in the cell (where no receiving portion or locking holder is formed) when the stent is expanded. A symmetrical shape is preferred, which can prevent twisting during expansion.

From the above, as shown in FIGS. 12 (a) and 12 (b), the receiving portion AP (female connector) has two types of shapes depending on the direction of the channel offset. It is understood that the portion is preferably formed to be AP and AP ^* (AP having a mirror image relationship with respect to the cell center axis ld).

In the present invention, it is preferable to replace the cell 2 in which the receiving portion AP having such a shape is formed with at least two or more of the cells arranged at the end of the stent. At this time, not all the receiving parts are formed in the same type of receiving part AP, but at least one of the receiving parts AP ^* (that is, a mirror image of the AP) is different as shown in FIG. It is preferable to replace with.

(Stands that run in the radial direction)
In the present invention, the struts of the component stent inserted into the opening of the receiving portion AP (or AP ^* ) are the struts having the configuration described below, whereby the stent forming the inner layer and the two struts forming the outer layer are formed. The binding force of the stent can be further increased. In the present invention, the strut RRSM that travels in the radial direction may be referred to as a “mail connector” (MC), focusing on its function.
Such a mail connector MC is preferably formed in the portion of the link 3, and more preferably, the link shape thereof is formed in such a shape that the engagement with the receiving portion is more reliably performed. desirable.

Basically, as shown in FIG. 14, it is preferable that the link portion 3 as a support is connected in series with a function as a radial traveling support RRSM (mail connector MC). That is, at the time of assembling the stent, preferably, a connecting portion 14 ′ is provided at a position (corresponding) to the opening 18 of the receiving portion AP, and this is connected to the link 3 in series. The connecting portion 14 ′ is an element that finally constitutes the radial traveling strut RRSM, and is also a portion that constitutes a mail connector.

As shown in FIG. 14, the post of the mail connector MC, that is, the radial running post RRSM is located on the cell center axis of the adjacent cell, and when the coaxial multi-layer stent described above is assembled, the mail connector MC The post is deformed in the radial direction so that the radially deformed portion (RDP) 14 ″ is positioned between the link 3 and the connecting portion 14 ′. Further, it is understood that the connecting portion 14 ′ is connected to the cell 2 through another radial deformation portion 14 ″ ″.

The struts of the mail connector, that is, the radial traveling struts RRSM, are preferably wider than the interval (circumferential direction) of the passage portion of the receiving portion. In general, the link portion 3 is typically narrower than the cell portion 2. However, with respect to the mail connector formed in the link portion, it is preferable that a part or all of the struts be formed wider than the other ordinary link portions 3 as shown by 14 'in the figure. . Thus, as for a connection part, it is preferable that the support | pillar width is wider than another link part.

In FIG. 14, the portion indicated by the dotted line S has the same width as the normal link portion 3. Basically, as shown in the dotted line S, it is essential to form the link portion 3 to be long (L) as the post of the mail connector. However, in order to ensure a more reliable engagement with the AP, it is preferable not only to make it as long as L but also to have a wide configuration as shown in FIG.
Note that the radially deforming portions 14 ″, 14 ′ ″ in the struts that run in the radial direction bend greatly when the mail connector is deformed in the radial direction. Therefore, it is preferable that this portion has a relatively narrow column width compared to the connecting portion, and it is preferable to make this column the same as the column width of the other link 3.

As already mentioned in the assembly section, when joining two component stents, at the part of the mail connector (in FIG. 20, the

struts

14A, 14B at the left or right end of the stent) By changing the radius of the stent, the struts are configured to run radially (RRSM).

Further, as shown in FIG. 15, the mail connector MC is preferably configured to be replaced with some of the links 3 in the stent, like the receiving portion AP.
As described above, the part L of the mail connector MC that forms the struts that run in the radial direction is preferably longer than the other links. That is, the length of the component stent in this case is such that the length of the component stent can be easily understood by changing the radius of part of the component stent for joining and forming struts that run in the radial direction. Since the length of the component stent without the connector is approached, it is desirable that the length of the two component stents be equal when the component stents are joined.

A conventional single-layer stent is composed of cells 2 and links 3. On the other hand, in the present invention, as shown in FIG. 16, in addition to the cell 2 and the link 3, it is composed of a stent to which a mail connector MC and / or a female connector FC is added. Such a stent is a component stent, and in the above-described one, the component stent A forms the inner layer and the component stent B forms the outer layer, and forms a coaxial bilayer stent. The component stent A, the component stent B, the component stent C,... Are formed as coaxial multilayer (coaxial multilayer) stents.

The coaxial multi-layer stent of the present invention is configured by coaxially laminating a plurality of component stents as described above in the assembly section. In this case, it should be noted that the strut thickness of one component stent is about 1/2 to 1/4 of the strut thickness of a single layer stent. The radial stiffness of the component stent is greatly affected by the strut thickness. Thus, a single component stent alone does not reach the radial stiffness of a single layer stent. This suggests that the component stent alone is incomplete as a therapeutic device. In the present invention, by combining (combining) a plurality of component stents as coaxial multi-layer stents, the present invention provides a therapeutic instrument that exhibits strength in the radial direction equivalent to that of a conventional single-layer stent. It is.

As shown in FIG. 22, when the crossing process of the two component stents A and B is completed, the strut RRSM that finally travels in the radial direction of the mail connector MC passes through the passage portion 16 completely. The opening 18 of the female connector (AP) is reached. When the support column reaches the opening, the gap in the passage portion is restored. And the support | pillar of the latching | locking part of the channel | path part of a mail connector and the support | pillar of the connection part of a mail connector mutually mesh, and the said support | pillar is prevented from passing a channel | path again (namely, reverse running). . FIG. 23 is an enlarged view three-dimensionally showing how the female connector (that is, the receiving portion AP) and the male connector (radial travel strut 14 thereof) thus joined are locked.

Further, when this state is analyzed, in the state of FIG. 22 and FIG. 23, the component stent B forming the outer layer is determined in the major axis direction and the circumferential direction by the openings of the component stent B constituting the inner layer. The radial position of the stent B is determined by the radial position of the struts of the component stent A. The tolerance of these positions can be controlled by the size of the opening 18 and the amount of deformation of the mail connector in the radial direction (that is, the size of the “step”). If these are reduced, the tolerance is reduced and the relative position of the two component stents can be determined precisely. On the other hand, if these are increased, the accuracy of the relative positions of the two component stents is lowered. Maintaining low positioning accuracy allows for relative movement of the two component stent struts.

The coaxial multi-layer stent of the present invention allows treatment impossible with a conventional single-layer stent by preventing deformation of one layer of struts from interfering with struts of other layers. Therefore, allowing low positioning accuracy contributes to stronger properties of the coaxial multilayer stent.

¡Sliding amount in the long axis direction for engaging and joining the component stent is almost equal to the long axis length of the cell or the female connector. Specifically, it is about 1.0 mm-2.5 mm. This slide amount can be realized manually without the assistance of a special device. If the state shown in FIG. 22 or FIG. 23 is realized, when the component stent is moved in either of the circumferential directions relatively, as shown in FIG. It should be noted that the mail connector post 14 is not located at the exit of the AP) passage.

That is, in at least one female connector, the struts of the joined component stent have moved away from the outlet (in the circumferential direction) and are in contact with the lock. Accordingly, the two component stents once joined are less likely to be released when they are relatively displaced in the circumferential direction. This is because, when the coaxial multi-layer stent of the present invention is transported in a blood vessel, even if the component stent is displaced in the circumferential direction due to a frictional force with a living tissue, the component stent does not easily fall off. Means.
The multi-layer stent of the present invention is composed of two component stents in which two component stents are joined (engaged) at this position. At this time, the radius of the component stent strut is, for example, as shown in FIG. As shown, there are four different radii (Ra, Ra, df, Rb, Rb, df).

(Compression of multi-layer stent and advantageous effects)
When applied to actual treatment, the two component stents (coaxial multi-layer stent) connected to each other are placed on a balloon catheter, and the two components are utilized by utilizing the device disclosed in, for example, Patent Document 16. The stent (multi-layer stent) is compressed radially. This force causes the two component stents (multilayer stent) to be mounted on the balloon catheter 50. FIG. 25 shows the mounted state.

Referring to FIG. 25, in the present invention, the radius of the struts of the component stent (multi-layer stent) at this time becomes two, Ra_mount and Rb_mount. In this way, the component stent strut (which forms part of the cell or link) straddles (intersects) the other component stent strut, so that the radial force in the stent coordinate system is reduced. When acting, it has the effect that the struts of the two component stents are difficult to separate.

∙ When transported to a lesioned part, the compressed multilayer stent needs to pass through the bent part of the blood vessel. Generally, when a stent is bent, it tries to return to a straight state. When this force is expressed in the stent coordinate system in the radial direction and bent, the struts located on the outside try to separate from each other.

In this state, in the coaxial multilayer stent of the present invention, when a radial (r direction) force is applied to the inner component stent A, the component stent A is supported by the struts of the component stent B arranged on the outer side. Acts to prevent it from leaving the strut of the component stent B. Similarly, when a force in the r direction acts on the component stent B of the outer layer, the strut of the component stent A is separated from the strut of the component stent A by the strut of the component stent A arranged outside the component stent B. Acts to prevent separation.

In the coaxial stent of Patent Document 11, the struts of the component stents of each other are joined but do not intersect in the radial direction. Therefore, when the radial force exceeds the bonding force of the bonding portion, bonding is canceled. That is, at this time, since the struts do not cross each other, the struts of the outer component stent cannot be prevented from being separated.

On the other hand, the coaxial multi-layer stent according to the present invention is bonded to the component stent as described above even if a force is generated in the major axis direction, the circumferential direction, or the radial direction of the stent at the time of transportation to the lesioned part. Will not separate. Moreover, as described above in detail in the assembly section, a strong connection can be achieved by simply inserting the two component stents from the longitudinal direction and intersecting them, as described above in detail in the assembly section. ing. Also, the manufacturer can easily perform this simple operation manually without the assistance of a microscope.

It is also worth noting that such a simplified assembly procedure is feasible in the operating room, and because of the simplified assembly procedure, the physician himself can do so without special training. is there. In this way, the doctor has the great advantage of being able to select the component stent (s) suitable for the patient's medical condition at any time and to assemble it in a short time and with ease. There is nothing too much to emphasize.

(More advantageous effects, compared with single-layer stent)
The coaxial multilayer stent of the present invention has further advantages over conventional single layer stents. As shown in FIG. 29, the meshes of the component stents A and B in the present invention are large. Thus, it is essentially understood that it can be used to treat side branches as shown in FIG.

That is, when combining these component stents A and B, the positions of the meshes of the two component stents can be slid in the circumferential direction and joined. As shown in FIG. 30 (i), the mesh of the composite stent after assembly is small. This means that blood vessels can be expanded uniformly. In addition, as shown in FIG. 30 (ii), the central portions of the two component stents can be deformed independently of each other. Therefore, large holes can be drilled in the side walls of the combined multilayer stent to ensure side branch blood flow.

In contrast, in conventional single-layer stents, it was common to use open-cell (single-layer) stents with a large mesh for the treatment of bifurcations. It has a weak point that it has a large mesh and is not good at expanding blood vessels uniformly. However, in the composite stent of the present invention, the mesh size is the same as that of the closed cell structure, and as described above, as shown in FIG. 30 (ii), a large hole is formed in the side wall of the composite stent. I can open it.

Furthermore, between the female connector and the male connector, it is possible to make a hole in the side wall at any position in both the long axis direction and the circumferential direction. Therefore, in the coaxial multilayer stent of the present invention, the side branch can be treated without precisely controlling the indwelling position in the lesion. Thus, there is an advantage that a device for examining the indwelling position is not required as in Patent Document 3 and Patent Document 4.

It should be noted that such advantages do not exist in the multilayered stents already disclosed and proposed, as well as single-layered stents. The reason for this is that in the conventional multi-layered stent, the struts of each layer are not essentially intersecting, but most of the struts overlap each other, and all the overlapping struts are joined together. Because.

In contrast, the coaxial multi-layer stent of the present invention differs from the conventional multi-layer stent in that most of the struts overlap each other, but the overlapping struts are not joined. Alternatively, even when the struts of each layer intersect, bonding at the intersecting portion is not performed. As already mentioned in the assembly section, it is characterized in that only specific struts of specific parts of the stent end are joined.

This configuration has the great advantage that the struts of each layer in the central part (in the longitudinal direction) of the stent used for treatment can be deformed without being interfered with the struts of the other layers. Since such deformation is possible, a therapeutic effect that is impossible with a normal stent can be exhibited. For example, in the side branch treatment at the bifurcation as described above, it is possible to make a large hole on the side wall of the stent as compared with a normal stent.
In other words, the coaxial multi-layer stent of the present invention has a high degree of freedom in the struts of each layer with respect to the overlapping portion, so that a treatment function that cannot be realized by a single-layer stent or other conventional multi-layer stents Can be expressed.

In conventional multilayer stents, as described in Patent Document 11 and the like, struts are fixed by welding or the like, and component stents of respective layers are joined (welded). On the other hand, in the coaxial multilayer stent of the present invention, the component stents of the respective layers are joined (engagement joined) by engagement. As already described, since the struts are connected in joining by engagement, the degree of freedom of deformation in the struts of each layer is much greater than that of a composite stent that is firmly joined by welding or the like. More specifically, there is a great difference that the fixed struts are not only restricted in relative position but also the relative angle, whereas the connected struts in the present invention are not restricted in relative angle. Therefore, since the coaxial multilayer stent of the present invention has a greater degree of freedom of deformation of the struts, specifically, in the treatment of the bifurcation, a larger hole can be formed in the side wall as needed. This greatly contributes to further reducing the influence of the inhibition of the blood flow of the branched blood vessels as a result of the treatment.

(Mechanical properties and characteristics)
FIG. 3 shows an example of a coaxial multilayer stent of the present invention as a three-dimensional view. FIG. 3 (i) shows a case where the stent A constituting the inner layer is inserted into the component stent B constituting the outer layer. FIG. 3 is an explanatory view showing an assembling process constituting a laminated stent, and FIG. 3 (ii) is an enlarged view of a part of the constructed multilayer stent.
In the case of this stent, each component stent is composed of component stents having half the number of links in the circumferential direction and half the strut thickness as compared with a general stent (single-layer stent). In the following, the mechanical properties of the coaxial multilayer stent composed of such component stents will be considered.

First, one of the mechanical properties required for a stent is flexibility.
Stent flexibility can be evaluated by bending stiffness. Small bending stiffness means high flexibility. Such bending stiffness can be measured by a bending test.
The present inventors measured the bending rigidity of stents having two same stent shapes and different thicknesses t as shown in FIG. That is, the bending stiffness of a stent having a thickness of 0.100 mm (FIG. 26 (i)) and a stent having a thickness t of 0.080 mm (FIG. 26 (ii)) was measured. As a result, the bending rigidity of the stent having a thickness t = 0.100 mm was 67.0 Nmm2, and the bending rigidity of the stent having a thickness t = 2,0.08 mm was 21.6 Nmm2. This result shows that the thinner the stent is, the more the bending rigidity of the stent can be reduced and the flexibility is improved.

Also, the number n of links in the circumferential direction affects the flexibility of the stent. The bending stiffness of two stents as shown in FIG. 27 was measured. The stent with 8 links n (FIG. 27 (ii)) had a flexural rigidity of 80.9 Nmm2, and the stent with 6 links n (FIG. 27 (i)) had 43.6 Nmm2. This result shows that a stent having a smaller number of links n has higher flexibility. Here, a stent having a small number of links means a stent having a large mesh.
From the above results, it was shown that a stent having a small thickness and a small number of links in the circumferential direction has excellent flexibility.

Based on the results of the thickness t and the number of links n, the coaxial multi-layered stent of the present invention is made by connecting two male and female stents A and B having thin struts and connecting the male connector and the female connector. To do. The assembly method has already been described in detail.

Each component stent has a large mesh, that is, a component stent with a small number of links. Therefore, in the assembled coaxial multilayer stent of the present invention, the number of links (the total number of links of the inner layer and the outer layer) is equal to that of the conventional single layer stent, but the thickness t of the link strut is thin. Thus, it is clear that the flexibility is superior to that of single layer stents.

(Numerical analysis of radial stiffness)
The radial stiffness of the coaxial multilayer stent of the present invention was examined by numerical analysis. An elastic tube simulating a vascular wall with a single-layer stent (strut thickness: 0.070 mm) and a coaxial multi-layer stent (combination of two component stents with strut thickness: 0.035 mm) with the same cell shape A pressure p of 0.5 atm was applied via Each stent was pressurized after expanding to a radius of about 1.5 mm. Radius after the addition of pressure, in a single layer stent, a 1.50 mm (in pre-compression p ₀ 1.56 mm), a coaxial multilayer stent was 1.47 mm (the pre-compression p ₀ 1.59 mm) .

The results are shown in FIG. (In the figure, the vertical axis indicates the radius before and after pressurization.) The difference in radius after pressurization was 2%. This indicates that the radius of the blood vessel expanded by the coaxial multilayer stent of the present invention is approximately the same radius as that of the blood vessel expanded by the single layer stent.

In the present invention, the material constituting the stent may be known per se and is not particularly limited, but is basically a metal material that can be plastically deformed, preferably stainless steel such as SUS316L, In addition, shape memory alloys such as Ni-Ti alloys and Cu-Al-Mn alloys already described, Cu-Zn alloys, Ni-Al alloys, titanium, titanium alloys, tantalum, tantalum alloys, platinum, platinum alloys, tungsten, tungsten Alloys can be appropriately employed depending on the purpose.

For processing from these metal bases to stents, generally known means are employed, and a mesh pattern before the stent is expanded from a tube or pipe (substantially tubular body) of the metal base by a laser or the like. Cut out and made. Further, the flat plate of the metal material may be laser-processed to form a mesh pattern, which is subsequently rounded into a tubular shape.

In addition, in terms of the dimensions of the stent of the present invention, the stent of the present invention is a very fine and complicated structure, and the struts constituting the stent are generally strut widths of 0.050 mm-0.300 mm, The strut thickness is about 0.050 mm-0.300 mm, and the diameter is about 1.0 mm-1.5 mm (before expansion) and the length is about 10.0 mm-30.0 mm for coronary arteries, although there are individual differences. Generally, as described above, a mesh pattern before expansion of a stent is cut out from a metal tube or the like with a laser or the like.

(Use as a drug-eluting stent)
The coaxial multilayer stent of the present invention described in detail above can be suitably used as a drug-eluting coaxial multilayer stent. This point has already been briefly described, but will be explained in more detail here.
That is, in the coaxial multi-layer stent according to the present invention, the gap Vab (see FIGS. 21-22) in the main body between the two component stents A and B is a reservoir for storing a drug such as a thrombolytic agent (see FIG. 21-22). Drug Reserver, DR) can be preferably used as a site for accommodating.

More specifically, in the coaxial multi-layer stent of the present invention, a drug containing a drug to be eluted as a drug holding reservoir in the void portion Vab in the main body between the two component stents A and B. An eluting coaxial multi-layer stent (DE-CMLS) can be formed.

(Problems of conventional drug-eluting stents)
Conventionally, a method of adding and combining drugs to a stent is known as a method for enhancing stent treatment. That is, using a stent, the drug is delivered to the lesion site, and the effect of the stent treatment is enhanced by the effect of the drug.
In the prior art, for example, Patent Document 8, it is disclosed that a therapeutic effect is enhanced when a stent is placed in a blood vessel by applying a drug to the stent by application or the like. Therefore, in Patent Document 8, the drug is fixed to the stent by applying a biodegradable polymer mixed with the drug to the stent strut. Such a stent is called a drug-eluting stent (DES). Non-patent document 2 shows that the rate of restenosis is significantly reduced in a drug-eluting stent compared to a stent (Bare Stent) in which no drug is applied and the drug is not eluted. In this way, the therapeutic effect can be enhanced by the drug-eluting stent, so that it is expected to be applied to the treatment of restenosis of blood vessels and the like, which are conventionally considered difficult to treat, and the treatment of blood vessels with narrow occlusions and branches. ing.

(I) However, since the stent used for the drug-eluting stent is a conventional single-layer stent, the above structural problem remains.
(Ii) Another problem of the drug eluting stent is a method of loading the drug on the stent as the base material. Since the loading of the drug is performed by application (coating) to the stent strut, the loading amount of the drug is physically limited by the surface area of the stent strut. Therefore, only drugs that exhibit a therapeutic effect with a limited loading amount can be used, or treatment must be performed with an insufficient amount of loading agent, which narrows treatment options. (Iii) Further, since the sustained release speed of the drug depends on the diffusion of the drug, there is a problem that the sustained release speed cannot be precisely controlled. In this case, in order to coat a sufficient amount of drug on the stent, it is necessary to make the thickness of the coating film not negligible compared to the thickness of the stent strut (0.070 mm-0.100 mm is common). There is (0.005mm-0.008mm). Therefore, when the coating film is thickened, the restenosis rate may increase.

(Iv) Furthermore, if the coating film of the drug is formed excessively thick, part of the coating film may fall off due to contact with the blood vessel wall during the transportation of the drug eluting stent. If a part of the strut is greatly deformed during the expansion of the stent, the coating film formed thickly may not follow the deformation and may peel from the stent. In addition, when the bonding force between the coating film and the stent is inappropriate, there is also a problem that the drug cannot be gradually released to the blood vessel wall uniformly.

Patent Document 9 discloses a method in which a number of holes for storing a drug are formed in a stent column and the drug is stored there. This is a technique intended to enhance the therapeutic effect by controlling the sustained release speed of the drug. In addition, this method has an advantage that, unlike the coating, there is no possibility of the drug falling off during transportation. However, this method still has the problem that the loading amount is limited by the surface area of the stent strut.

Patent Document 10 discloses a method for enhancing a therapeutic effect by forming a stent itself with a biodegradable polymer and mixing a drug with the polymer in advance. Compared with Patent Document 8 and Patent Document 9, this method determines the loading amount of drug (content in the volume of the stent) not by the surface area of the stent but by the volume of the stent. Can be installed.
However, biodegradable polymers are significantly inferior in material properties such as Young's modulus compared to metals, and the stent has a mechanical problem in that the radial rigidity is reduced. Non-Patent Document 4 discloses a treatment result of a stent using a biodegradable polymer in which a drug is premixed. Even in this case, the restenosis rate is inferior to that of a stent made by the method as described in Patent Document 8.

(Drug reservoir)
In the coaxial multi-layer stent of the present invention, the gap Vab in the main body between the two component stents A and B, more specifically, most of the center, not the end where the struts intersect. In the main body portion that occupies, the struts of the two stents are arranged in a separated state, and this portion forms a void portion Vab. A drug-eluting coaxial multi-layer stent (DE-CMLS) can be formed in which the drug to be eluted is preferably accommodated as a drug reservoir (Drug Rseaver, DR).

The drug reservoir DR is formed in advance so as to mix the drug to be eluted and the polymer (preferably, those having biocompatibility) and to match the shape of the cavity of the coaxial multilayer stent.・ Processed. For example, it is preferably processed into a spiral shape as shown in FIG.

There are various methods for producing the drug reservoir, and one method is based on a thin film. This is because a base material (polymer composition containing a biodegradable material such as polylactic acid and containing a drug) placed on a flat plate (because the base material on the flat plate has low viscosity) When the temperature is high), the flat plate is rotated at a high speed, and when the base material temperature decreases, a thin and uniform film can be formed. This is a method called spin coating (or double spin coating) and is one of the manufacturing methods generally used in the semiconductor field.

Furthermore, in the production of a thin film containing a drug, another method is used so that the drug is evenly distributed throughout the thin film. The used thin film may be formed.

The thin film formed by the above method is cut out with a certain width (about 0.05 to 1.0 mm). The length is appropriately determined depending on the length of the stent used as the carrier. Thus, a rectangular thin film having a determined width and length is wound around the component stent (in the middle) of the coaxial multilayer stent so as to be spiral in the long axis direction. In this case, it may be directly wound around the component stent, or separately wound around a rod having the same circular cross section as that of the component stent, spirally formed, and then combined with the component stent.

Other methods include substances produced in human bodies (substances such as hyaluronic acid and collagen) themselves, or polymeric substances to which a thickener is added to increase the viscosity (preferably biocompatible). It is also possible to use a technique in which a drug or the like is contained in a thin sheet processed and sandwiched between coaxial multilayer stents.
Furthermore, a polymer or the like (preferably biocompatible material is desirable) is processed into a sheet shape by containing a drug or the like, but a microneedle is formed on one surface of the sheet and this is directly inserted into the inner wall of the blood vessel. However, it is also possible to create a shape in which the drug contained in the sheet main body is injected into the blood vessel wall from the micro needle just like the function of the syringe.

As the drug reservoir, it is generally preferable that the drug reservoir does not become a deformation resistance when the stent is expanded, and does not overlap in the radial direction in the contracted state.
As such a shape, even if it is basically a cylindrical shape, a plurality of incisions are made in the circumferential direction and the long axis direction, and cracks progress from there in the expansion direction. A shape that can lower the thickness is preferable. That is, at the time of expansion, a plurality of holes and cuts are opened in the drug reservoir. Therefore, it can be said that the above-described spiral shape is one of preferable shapes.

Note that this drug reservoir is a structure for actively leaking sufficient blood from the side wall of the stent (for blood flowing in the stent). Is fundamentally different. This is because the stent graft is a kind of artificial blood vessel and blood should not leak through the side wall of the stent.

Examples of drugs in the drug reservoir of the present invention include, for example, anticoagulants, antithrombotic agents, antiplatelet agents, cytokines, steroids and nonsteroids, antibiotics, anticancer agents, anticholesterol agents, anticholesterol agents, Immunity agent, antiallergic agent, regeneration promoting or inhibiting factor substance in the field of regenerative medicine, intracellular substance, extracellular matrix, drug such as cell growth or inhibiting factor or gene in the field of gene therapy, genetic factor or gene, inhibitor or more Derivatives such as drugs, analogs, metabolites, by-products, etc., or combinations of these drugs and the like, heparin which is a substance that effectively reduces the degree of intimal hyperplasia in animal models and Heparin fragment, colchicine taxol, angiotensin converting enzyme (ACE) inhibitor, angiopeptin, chic Includes rosporin A, goat-anti-rabbit PDGF antibody, terbinafine, trapidil, tranilast, interferon- gamma, rapamycin, steroids, ionizing radiation, fusion toxins, antisense oligonucleotides and gene vectors. Heparin and heparin conjugates that have antiproliferative effects on smooth muscle cells in vitro, taxol, tranilast, colchicine, ACE inhibitors, fusiontoxins, antisense oligonucleotides, rapamycin And a substance containing ionizing radiation.

These drugs are dispersed and held in the polymer molded in the above-mentioned form as DR, and when the outer surface comes into contact with the bloodstream in the living body, diffusion, dissolution, and other mass transfer mechanisms, It is gradually released (released) from the surface of the reservoir, and functions to suppress the formation of thrombus and the like in the vicinity of the stent and to exert other desired effects.

As a polymer mixed with a drug to form a reservoir (preferably, a biocompatible polymer is desirable), the stent is compressed, expanded, bent or deformed while being accommodated in a coaxial multilayer stent. The polymer material (preferably having biocompatibility) that can follow the deformation when subjected to is preferable. In addition, an effective amount of an anticoagulant or the like that is a polymer that is not soluble in blood or physiological saline (preferably having biocompatibility is desirable) and that can inhibit blood coagulation is obtained in vivo. There is no particular limitation as long as it can be gradually eluted (slow release) from the surface of the coating layer.
Examples of such polymers include polyvinyl acetate, (meth) acrylic ester polymers, polyester elastomers, polyamide elastomers, polyurethane elastomers, poly (ethylene-vinyl alcohol) copolymers, and 2-methacryloyloxy. Ethyl phosphorylcholine (MPC), (2-hydroxyethyl-methacrylate) -styrene block copolymer is exemplified as a preferable one.

Further, as the polymer, a biodegradable polymer is more preferable. Such polymers include PLA (polylactic acid), PLGA (lactic acid / glycolic acid copolymer), PLGAC (lactic acid / glycolic acid / ε-caprolactone copolymer), and in-vivo products, which are usually used for DDS. Hyaluronic acid, collagen, extracellular matrix, etc. and inorganic substances (for example, magnesium, calcium, etc.) are desirable.

In the present invention, when two component stents are combined, this pre-formed drug reservoir is sandwiched in a void Vab formed by the inner component stent A and the outer component stent B, and is narrowed by both component stents. (See Figures 21-22). For example, as shown in FIG. 31, the drug reservoir DR is formed in a spiral shape, and is formed of a polymer that can follow the deformation of the stent. Can follow deformation (expansion).

In the present invention, the shape and structure of the coaxial multilayer stent and the drug reservoir are basically separate elements and are independent of each other. Therefore, the amount of medicine loaded in the medicine reservoir depends only on the shape and structure of the medicine reservoir. Thus, if the volume of the medicine reservoir is increased, the amount of medicine loaded can be easily increased.
The concentration of the drug in the drug reservoir can be appropriately selected. For example, in the drug reservoir (based on the total mass), 0.01-80% by mass, preferably 0.1-60% by mass, more preferably 1. It is about 0-50% by mass.

The method for forming the drug reservoir (molded body) DR has been described in detail above. However, the method is not limited to this. For example, the shape of the void Vab formed by the target component stent A and the component stent B is used. In addition, a mold is prepared as a split mold, and in the split mold, a resin composition composed of a drug and a polymer (preferably those having biocompatibility is desirable) is melted in an injection molding machine, It is injected into the mold and cured, or a solvent of at least the polymer (preferably biocompatible) is added to the composition to obtain a resin solution containing a drug, This may be poured into the split mold, and then the solvent may be removed by drying. The drug and the monomer of the resin can be injected into a split mold together with a polymerization initiator or the like, and polymerized in the mold.

For the drug reservoir housed in the coaxial multilayer stent of the present invention, the volume of the drug reservoir is not affected by the structural characteristics of the stent. Thus, the volume of the drug reservoir can be increased or decreased independently of the stent structure. For example, a large volume drug reservoir is combined with a coaxial multilayer stent using an open cell component stent, or a small volume drug reservoir is combined with a coaxial multilayer stent composed of a closed cell structure component stent. You can also

The drug reservoir of the present invention is also housed in the void portion Vab of the coaxial multilayer stent composed of the two component stents A and B, and is guided to the lesioned portion in a sandwiched state. Therefore, it is unlikely that the drug reservoir comes into contact with the blood vessel wall or the like during transportation and a part of the drug reservoir falls off. During delivery, the coaxial multilayer stent protects the drug reservoir held by it.

The present invention has the following industrial applicability.
In the coaxial multilayer stent of the present invention, it is possible to assemble the coaxial multilayer stent without using a dedicated machine such as a welding machine and without requiring precise alignment. That is, engagement can be realized by simply moving and sliding a plurality of thin stents (component stents) in the long axis direction, and the coaxial multilayer stent of the present invention can be assembled. Further, since the moving amount of the component stent in the major axis direction is about 1.0 mm-2.5 mm, it can be easily assembled without using a microscope.

While the stent is mounted on the balloon and is transported to the lesion, a force for separating the superimposed struts often acts. In the coaxial multilayer stent of the present invention, the inner component stent A and the outer stent One of the biggest problems in the conventional coaxial multi-layer stent is that it has a new engagement mechanism that forms struts that run in the radial direction in each of the component stents B, and thereby performs engagement. The problem of falling out of the outer component stent during transportation is essentially solved.

In the coaxial multilayer stent of the present invention, each component stent before overlapping has a large mesh (pattern composed of cells and links). Each stent has a strut joined at its end, but the other portions do not affect the deformation of the stent struts. Therefore, the coaxial multilayer stent of the present invention can make a large hole in the side surface and can be effectively applied to the treatment of a blood vessel portion having a side branch.

In the coaxial multilayer stent of the present invention, a drug eluting stent can be formed by having a space part that can suitably store a drug reservoir between component stents. That is, in the drug-eluting coaxial multi-layer stent of the present invention, since the drug is stored in the space between the layers, the degree of freedom is extremely large, and the drug can be eluted for a long time. The availability is very large.

Claims

A planar structure consisting of multiple struts (Supporting Strut Members (SSM or Just SM)) arranged to form a mesh structure is rolled into a cylindrical shape, and consists of a cylindrical body with a long axis at the center. Two component stents (A, B) (hereinafter sometimes referred to as CSA and CSB) that can be reduced and expanded are formed, and the coaxial composite is constructed and configured coaxially with the CSA as the inner layer and the CSB as the outer layer. Coaxial Multi-Layered Stent (CMLS)
The column is composed of a plurality of cells, each of which has a bent portion, and at least one link connecting the cells in the long axis direction.
The CSA and CSB are each composed of a main body part (Main Body Portion (MBP) occupying most of the center and both side (left and right) ends (LEP, REP) of the main body part,
The radii of the body portions are Ra and Rb (where Ra <Rb),
The component stent (A) (CSA) and the component stent (B) (CSB) are the struts of the component stent (A) (CSA) at least at the left end (LEP) of the both ends of the CMLS. SSM) and strut (CSB) of component stent (B) are performed,
And at the left end (LEP),
(I) The radius (Ra, in) of the cylindrical body of the component stent (A) (CSA) is the same as the radius Ra of the main body portion, and the struts of other component stents can be received in the struts. A possible receiving part (Accommodation Port or Portion (AP)) is formed,
(Ii) The component stent (B) (CSB) is
(A) A support column arranged at the same radial position (Rb, in) as the radius (Rb) of the main body,
(A) a strut disposed at a radius position (Rb, df) smaller than the main body radius (Ra) of the component stent (A); and
(C) Two struts arranged at the two radial positions (Rb, in Rb, df), or struts (Radially-running SM (RRSM), )
The component stent (A) (CSA) is inserted into the component stent (B) (CSB)) in the longitudinal direction of the cylindrical body of the component stent (B), and the component stent (B) (CSB) ) Of the two component stents (A, B) are inserted and fitted to the receiving part (AP) of the component stent (A) (CSA) in a radial direction. A coaxial multi-layer stent characterized by engaging.
A planar structure consisting of multiple struts (Supporting Strut Members (SSM or Just SM)) arranged to form a mesh structure is rolled into a cylindrical shape, and consists of a cylindrical body with a long axis at the center. Two component stents (A, B) (hereinafter sometimes referred to as CSA and CSB) that can be reduced and expanded are formed, and the coaxial composite is constructed and configured coaxially with the CSA as the inner layer and the CSB as the outer layer. Coaxial Multi-Layered Stent (CMLS)
The column is composed of a plurality of cells, each of which has a bent portion, and at least one link connecting the cells in the long axis direction.
The CSA and CSB are each composed of a main body part (Main Body Portion (MBP) occupying most of the center and both side (left and right) ends (LEP, REP) of the main body part.
The radii of the body portions are Ra and Rb (where Ra <Rb),
The component stent (A) (CSA) and the component stent (B) (CSB) are arranged at the right end (REP) of the CMLS at the strut (SSM) and the component stent (B) of the component stent (A) (CSA). ) Struts (CSB) crossing,
And at the right end (REP),
(I) The component stent (A) (CSA) is
(A) A support column arranged at the same radial position (Ra, in) as the radius (Ra) of the main body,
(A) a strut disposed at a radial position (Ra, df) larger than the radius (Rb) of the main body of the component stent (B); and
(C) Two struts arranged at the two radial positions (Ra, in Ra, df) are connected in a radial direction of the cylinder to be connected (Radially-running SM (RRSM), )
(Ii) The radius (Rb, in) of the cylindrical body of the component stent (B) (CSB) is the same as the radius Rb of the main body, and the struts of the other component stents can be received in the struts. A possible receiving part (Accommodation Port or Portion (AP)) is formed,
The component stent (A) is inserted into the major axis of the cylindrical body of the component stent (B) with respect to the component stent (B) (CSB), and the RRSM of the component stent (A) (CSA) is inserted. Coaxially characterized in that the two component stents (A, B) are engaged with each other by inserting and fitting the component stents (B) (CSB) so as to penetrate the radial direction. Multi-layer stent.
At the left and right ends, the strut (SSM) and the component stent (B) strut (CSB) of the component stent (A) (CSA) are respectively intersected, and the two component stents (A, B) are engaged. A coaxial multi-layered stent, wherein the engagement at the left end (LEP) is as defined in claim 1 and the engagement at the right end (REP) is as defined in claim 2 A coaxial multi-layer stent.
A part of the strut of the component stent (A,) or (B) is a part of which connects a plurality of cells having bent portions capable of reducing and extending the circumferential length of the cylindrical body in the vertical direction. A ring-shaped strut (Ring-shaped SM) configured by arranging a plurality of rings so as to surround the shaft, and at least one link connecting the adjacent ring-shaped struts in the longitudinal direction. The coaxial multilayer stent according to any one of claims 1-3.
The receiving portion (AP) of the component stent (A) or (B) is provided as a part of the cell having the bent portion, and is directed in the direction of the left end portion (LEP) and / or the right end portion (REP). The coaxial multilayer stent according to any one of claims 1 to 4, wherein a part thereof is opened and the opening defines a passage for introducing a strut.
The receiving portion (AP) of the component stent (A) or (B) includes the passage and a latch holder having a round-shaped aperture (Round-Rectangular Aperture) communicating with the passage. In the circular opening, the radius of curvature of the column that forms the opening located at a position opposite to the passage is longer than the radius of the bent portion of the cell, and the passage communicating with the holder The space between two opposing struts (SM) forming the passage is narrower than the strut width forming the bent portion of the holder or cell. The coaxial multi-layer stent as described.
In the receiving portion (AP) of the component stent (A) or (B), the holder is symmetric with respect to a straight vertical bisector connecting the cell bent portions in the circumferential direction, The coaxial multi-layer stent according to claim 6, wherein the opposing struts to be formed are arranged at positions shifted in the circumferential direction from the perpendicular bisector.
The receiving part (AP) of the component stent (A) or (B) is provided as a part of a cell having a bent part, and at least two of the receiving parts (AP) are at least two or more. The coaxial multilayer stent according to claim 1, wherein the coaxial multilayer stent is provided as a part of each cell.
The receiving part (AP) of the component stent (A) or (B) has at least one receiving part (AP) mirrored with respect to the other receiving part (AP) and the long axis of the stent (A) or (B). The coaxial multilayer stent according to claim 9, wherein:
Radially-disposed SM (RDSM), Radially-arranged SM (RASM) of the component stent (A) or (B) that runs or is arranged radially (radially-running SM (RRSM)) The coaxial multilayer stent according to any one of claims 1 to 9, wherein the coaxial multilayer stent is provided as a part of a link portion.
In the strut (Radially-running SM (RRSM)) provided in the link portion of the component stent (A) or (B), the length in the major axis direction of the link portion is: The coaxial multi-layer stent according to claim 10, wherein a length of the link portion of the strut where the strut (RRSM) traveling in the radial direction does not exist is longer than a length in a major axis direction.
12. A coaxial multi-layered stent (CMLS) according to any one of claims 1-11, wherein the body portion is between the two component stents (A) and (B) (CSA, CSB). The voids in the drug can be preferably used as a site that contains a drug reservoir (Drug Reserver or Holder) (Said space is favorably used for, or serves as, a DR) Type coaxial multilayer stent.
12. A coaxial multi-layered stent (CMLS) according to any one of claims 1-11, wherein the body portion is located between the two component stents (A) and (B) (CSA, CSB). A drug-eluting coaxial multi-layer stent (DE-CMLS), in which a drug to be eluted is accommodated or held as a drug reservoir in the void portion in FIG.