JP2001238964A - Stent - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide moderate flexibility, to easily and smoothly expand in a radial direction, to have sufficient radial strength after expansion, and to suppress the growth of restenosis. Provide a stent. SOLUTION: A substantially cylindrical stent 2 to be indwelled in a lumen of a living body, in which a plurality of gaps 6 are formed, and a primary stent structure 4 defining an outer shape of the stent 2,
A secondary stent structure 8 connected to the primary stent structure 4 and having a secondary repeating unit 8a having a similar shape and a smaller size than the primary repeating unit of the primary stent structure 4; At least have.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stent to be placed in a stenosis in a body cavity such as a blood vessel, a gallbladder, an esophagus, an intestine, and a ureter.

[0002]

2. Description of the Related Art A stent is used, for example, together with a balloon catheter. When a stenosis occurs in a body cavity such as a blood vessel, the stent is deployed after the stenosis is expanded by a balloon catheter, and the stent is supported from the inside. It is used to prevent restenosis and the like. When the stent is inserted, the stent is mounted in a contracted state, for example, outside the balloon part in a contracted state, and is inserted into a body cavity together with the balloon part. After the balloon portion is positioned at the stenosis portion, the stent is expanded by inflating the balloon portion to expand the stenosis portion, the stent is left in an expanded state, and only the balloon catheter is withdrawn.

[0003] The characteristics required for a stent used in such a method of use are that it is flexible in a contracted state, has excellent insertability into a body cavity, and can be easily and uniformly expanded in the radial direction. Later it is necessary that it does not collapse easily in the radial direction.

As conventional stents, pantograph-shaped stents, coil-shaped stents, stitches or lattice-shaped stents, cylindrical stents having slits formed in the longitudinal direction, and the like are known (JP-A-9-1175).
No. 12, Japanese Unexamined Patent Application Publication No. 11-99207, Tokuheihei 1
2-501328, JP-A-7-531, JP-A-12-5321, etc.).

[0005]

However, in the conventional stent, in order to smoothly and uniformly expand in the radial direction, it is necessary to make the stitch of the stent largely sparse. The radial strength of the later stent is reduced, increasing the potential for restenosis. Also, if the stitches of the stent are large and sparse, the stenotic portion may regrow from the stitches, resulting in restenosis.

[0006] Therefore, if the stitches are made dense or the wire diameter of the members constituting the stitches is increased in order to prevent restenosis, the stent becomes hard and becomes difficult to expand with a balloon or the like. If the stent is too hard, the inner wall of a body cavity such as a blood vessel is easily stimulated, and the restenosis is more likely to occur due to inflammation or the like.

The present invention has been made in view of such circumstances, has appropriate flexibility, is easy to expand smoothly and uniformly in the radial direction, has sufficient radial strength after expansion, and has a restenosis. An object is to provide a stent that can suppress growth.

[0008]

In order to achieve the above object, a stent according to the present invention is a substantially cylindrical stent to be placed in a lumen of a living body. A first stent structure defining an outer shape of the first stent structure; and a first stent structure connected to the first stent structure.
And a secondary stent structure having a secondary repeating unit that is substantially similar in shape and smaller than the primary repeating unit of the secondary stent structure.

In the gap between the primary stent structure and the secondary stent structure, there is provided a third repeating unit having a tertiary repeating unit having a shape substantially similar to that of the secondary repeating unit.
The next stent structure may be deployed. Similarly, a higher-order stent structure having the fourth and subsequent repeating units may be arranged.

[0010] Preferably, at least one of the gaps in the primary stent structure has a through hole in which the secondary stent structure or the tertiary structure is not arranged. Is also good.

[0011]

The present inventor has conducted intensive studies on medical stents. As a result, by adopting a so-called fractal structure for the stent in accordance with the natural world, even a stent having a dense stitch has appropriate flexibility, It has been found that it is easy to expand smoothly and uniformly in the radial direction, has sufficient radial strength after expansion, and suppresses the growth of restenosis.

[0012] By simply connecting a higher-order microstructure having no relation to the primary stent structure, when the stent is expanded, the higher-order microstructure is deformed due to the deformation of the primary stent structure. Excessive deformation is given to the microstructure, and a higher-order microstructure may be broken.

On the other hand, in the present invention, the primary stent structure has secondary and subsequent repeating units that are substantially similar in shape to the primary repeating units of the primary stent structure. The higher order stent structures are connected to realize a so-called fractal structure. Therefore, in the stent according to the present invention, when the stent is expanded, the higher-order stent structure also deforms at the same deformation rate following the deformation of the primary stent structure, and No deformation is given. Therefore, the stent has a moderate flexibility and expands smoothly and uniformly in the radial direction.

Moreover, after expansion of the stent of the present invention,
It has sufficient radial strength to withstand the forces of restenosis, and the higher order stent structure can inhibit the growth of restenosis.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on embodiments shown in the drawings. 1 (A) is a side view of a main part of a stent according to one embodiment of the present invention, and FIG. 1 (B) is a schematic diagram showing a repeating unit of the secondary stent structure shown in FIG. 1;
2C is a schematic view showing a repeating unit of the tertiary stent structure, FIGS. 2A and 2B are cross-sectional views of a main part showing a use state of the stent, and FIG. 3 is another embodiment of the present invention. It is a principal part side view of the stent which concerns on a form.

As shown in FIG. 1, a stent 2 according to the present embodiment is a substantially cylindrical stent to be placed in a lumen of a living body, and has a plurality of gaps 6 formed therein. And a primary stent structure 4 defining the following.
The primary stent structure 4 has axially connected primary repeating units meandering along the circumferential direction. Note that the specific shape of the primary repeating unit is not particularly limited, and a waveform shape, a sine / cosine curve shape, a zigzag shape, a bead shape, a sawtooth shape, a valley shape, a pulse shape, or a circumferential shape are provided. A combination of these or other repetitive shapes may be used.

In the gap 6 of the primary stent structure 4, the first stent structure 4 is connected to the first stent structure 4. Second having the secondary repeating unit 8a (FIG. 1B)
The next stent structure 8 is arranged. In this embodiment,
Although the secondary stent structures 8 are arranged in all the gaps 6 of the primary stent structure 4, in FIG. A secondary stent structure 8 is located. Of course, in the present invention, the secondary stent structures 8 are not necessarily formed in all the gaps 6 of the primary structure 4, but are arranged in the gaps 6 in a predetermined arrangement pattern such as every other. May be.

Further, in the present invention, the secondary repeating unit 8a shown in FIG.
Alternatively, a tertiary stent structure having a tertiary repeating unit 8b shown in FIG. Such a structure is called a fractal structure in nature. Note that a stent structure having a higher-order microstructure may be disposed in the gap between the tertiary stent structures.

The primary representative width L1 of the primary repeating unit of the primary stent structure 4 is not particularly limited, but is, for example, about 1 to 5 mm. The similarity ratio (L2 / L) of the representative width L2 of the secondary repeating unit 8a to the primary representative width L1
1) is not particularly limited, but preferably ranges from 0.1 to 0.1.
3. The similarity ratio (L3 / L2) of the representative width L3 of the tertiary repeating unit 8b to the secondary representative width L2 is:
It is not particularly limited, and may be the same or different from the similarity ratio L2 / L1.

The cross section of the wire constituting the primary stent structure 4 is not particularly limited, and may be circular, rectangular, or any other shape. Typically, stents are fabricated from metal tubing, with a tube thickness of 30-300 μm. Further, the wire diameter and the width of the wire constituting the primary stent structure 4 after processing are not particularly limited.
It is preferably about μm. The wire diameter of the wire constituting the secondary stent structure 8 is different from the wire diameter of the wire constituting the primary stent structure 4 by the similarity ratio (L2 / L1 or L3).
/ L2) is preferably as thin as the same ratio.

The overall dimensions of the stent 2 are appropriately determined according to the purpose of use, and are not particularly limited. For example, when the stent 2 is used for treating a coronary artery, the outer diameter of the stent 2 when expanded is preferably 2 mm. ~ 5mm, axial length 15 ~ 4
0 mm. In the case of a stent for peripheral vascular treatment, the outer diameter of the stent 2 when expanded is preferably 3 to 10 mm.
mm, and the axial length is 15 to 40 mm. In the case of an aortic treatment stent, the outer diameter of the stent 2 when expanded is preferably 5 to 30 mm, and the axial length is 30 to 100.
mm.

The materials of the primary stent structure 4, the secondary stent structure 8, and the tertiary stent structure constituting the stent 2 are all made of the same material from the viewpoint of ease of manufacture and the like. Although it is preferable that they are provided, they may be made of different materials. The material of the stent 2 is not particularly limited, and stainless steel, nickel, titanium, tantalum, cobalt, platinum, gold, an alloy thereof, or the like is used. However, metals generally elute ions in vivo,
This causes a metal inflammatory reaction and allergy. Therefore, it is preferable that the surface of the metal constituting the stent 2 is covered with a coating layer.

As the coating layer, ordinary polymers used for medical purposes such as olefins such as polyethylene, nitrogen-containing polymers such as polyimide and polyamide, and siloxane polymers are used. Further, the coating layer is not limited to the polymer, and may be an inorganic coating layer such as carbon such as silicon carbide, pyrolite carbon, and diamond-like carbon. Further, the surface of the stent 2 may be subjected to a hydrophilic treatment, or an enzyme, a biological component, or a drug for preventing restenosis may be fixed on the surface of the stent 2.

The method for producing the stent 2 is not particularly limited, and examples thereof include a machining method, a method of cutting a tubular material by a laser, and an etching method, and the etching method is particularly preferable. Specifically, first, a large original that is several tens of times or more of the product size is prepared, and an original plate for photosensitivity is prepared using the original. Next, a metal tube serving as a raw material for the stent is coated with a photosensitive cross-linking resist, and the original prepared above is used as a photomask, and is exposed by a reduction projection exposure apparatus to transfer the pattern of the original to the resist.
In this case, the exposure is performed while rotating the metal tube. Thereafter, a non-crosslinked portion of the resist is eluted by a usual method, a fractal structure pattern is formed on the resist, and unnecessary metal portions of the metal tube are removed by etching to produce a fractal structure stent.

Alternatively, the following method may be adopted. That is, after coating the photosensitive cross-linkable resist on the mandrel, exposure is performed in the same manner as described above, a fractal structure pattern is formed on the resist, and electroless plating is performed.
By VD method, metal is deposited on the outer peripheral surface of the mandrel,
By extracting the mandrel, a stent having a fractal structure may be obtained.

Next, an example of use of the stent according to the present embodiment will be described. As shown in FIG. 2A, the stent 2
First, the balloon catheter 12 is contracted in the radial direction.
The balloon catheter 12 is inserted into a body cavity such as a blood vessel 20 in this state. The balloon portion 10 of the balloon catheter 12 is positioned up to the stenosis portion 22 of the blood vessel 20, and the balloon portion 10 is moved outward in the radial direction by sending a fluid into the balloon portion.
To expand.

As a result, as shown in FIG. 2 (B), the stenosis portion 22 expands together with the expansion of the balloon portion 10, and the stent 2 also expands radially outward at the same time. Thereafter, only the balloon catheter 12 is withdrawn from the blood vessel 20, and only the expanded stent 2 is placed in the expanded stenotic portion 22 to prevent restenosis.

In the stent 2 according to the present embodiment, the primary stent structure 4 has the second and subsequent repetitions which are smaller than the primary repeating unit of the primary stent structure 4 in a substantially similar shape. A higher order stent structure having units is connected to realize a so-called fractal structure. Therefore, in the stent 2 according to the present embodiment, when the stent 2 is expanded, the higher-order stent structure 8 also deforms at the same deformation rate following the deformation of the primary stent structure 4, The stent structure 8 is not excessively deformed. Therefore, the stent 2 has appropriate flexibility and expands smoothly and uniformly in the radial direction.

Moreover, after expansion of the stent 2 of the present embodiment, the stent 2 has sufficient radial strength, can sufficiently withstand the force for restenosis, and has a high-order stent structure 8 through which the stent gap can be removed. Growth of restenosis can be suppressed.

The present invention is not limited to the above-described embodiment, but can be variously modified within the scope of the present invention.

For example, as shown in FIG.
Are also within the scope of the present invention. In this stent 32, primary stent structures 34 each having a meandering primary repeating unit along the circumferential direction are arranged at predetermined intervals in the axial direction, and the axial distance between these primary stent structures 34 is determined. Direction gap, the second
The secondary stent structure 38 is arranged, and the primary stent structures 34 are connected to each other to realize a fractal structure. The configuration, material, dimensional relationship, and the like of the repeating units of the primary stent structure 34 and the secondary stent structure 38 are the same as those of the stent 2 shown in FIG. FIG.
In the embodiment shown in FIG.
The positional relationship with the next stent structure is different from that shown in FIG.

In the present embodiment, the meandering gap 36 of the primary stent structure 34 is provided with the secondary stent structure 3.
8 or higher stent structures are not deployed,
The through hole penetrates the inside and outside of the stent. Through this through hole, a branch stent that branches to the stent 32 may be passed. If necessary, a third or higher order stent structure may be arranged in all or a part of the meandering gap 36 in the primary stent structure 34.

[0033]

As described above, according to the present invention, the present invention has appropriate flexibility, is easy to expand smoothly and uniformly in the radial direction, has sufficient radial strength after expansion, and has good A stent capable of suppressing the growth of stenosis can be provided.

[Brief description of the drawings]

1 (A) is a side view of a main part of a stent according to an embodiment of the present invention, and FIG. 1 (B) is a schematic view showing a repeating unit of the secondary stent structure shown in FIG. 1; FIG. (C) is a schematic view showing a repeating unit of the tertiary stent structure.

FIGS. 2A and 2B are cross-sectional views of a main part showing a use state of a stent.

FIG. 3 is a side view of a main part of a stent according to another embodiment of the present invention.

[Explanation of symbols]

 2, 32 ... stent 4, 34 ... primary stent structure 6, 36 ... gap 8, 38 ... secondary stent structure 8a ... secondary repeating unit 8b ... tertiary repeating unit 10 ... balloon part 12 ... Balloon catheter 20 ... Blood vessel 22 ... Stenosis

Claims (3)

[Claims] 1. A substantially cylindrical stent to be placed in a lumen of a living body, a primary stent structure having a plurality of gaps formed therein and defining an outer shape of the stent; A secondary stent structure having a secondary repeating unit connected to the structure and having a secondary repeating unit that is substantially similar in shape to the primary repeating unit of the primary stent structure. 2. A tertiary stent structure having a tertiary repeating unit smaller in a substantially similar shape than the secondary repeating unit in a gap between the primary stent structure and the secondary stent structure. The stent according to claim 1, wherein the body is disposed. 3. A through hole in which at least one of the gaps in the primary stent structure is not provided with the secondary stent structure or the tertiary structure. 3. The stent according to 1 or 2.