JP2002045432A - Stent - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a stent for being provided with appropriate bendability and flexibility in a reduced diameter state, being provided with an excellent insertion property, being easily, smoothly and uniformly expanded in a radial direction, being provided with sufficient radial direction strength after expansion and suppressing the growth of re-constriction. SOLUTION: This stent 2 in a cylindrical shape as the whole is expandable in the radial direction and is detained inside the lumen of a living body. It is provided with a spiral stent element 4 wound continuously for one round or more and the stent element 4 is the continuous body of a plurality of cells 40 connected along a spiral direction. The stent 2 is further provided with an axial direction connection element 6 for interconnecting the stent elements 4 adjacent to each other along an axial direction.

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 using 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, for example, in a contracted state outside the balloon portion in a contracted state, and is inserted into a body cavity together with the balloon portion. After the balloon portion is positioned at the stenosis portion, the stent is inflated by inflating the balloon portion to expand the stenosis portion. The stent is kept in an expanded state, and only the balloon catheter is withdrawn.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 reduced diameter state, has excellent insertability into a body cavity, and can be easily and uniformly expanded in the radial direction. After expansion, it must not be easily collapsed 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 (Japanese Patent Application Laid-Open No. 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 coil-shaped stent, the wire is simply wound in a coil shape (spiral shape). And axial length)
However, it changes from the reduced diameter state, and it is difficult to forcibly expand the balloon. This is because it is not practical to expand a coiled stent having a large number of turns and having an elongated shape in an axial direction in a radial direction while sliding along a spiral direction around the outer periphery of the balloon, requiring a considerable expansion force. .

[0006] There has also been proposed an attempt to construct a conventional coiled stent from a shape memory alloy or the like and to self-expand the stent by using a change in temperature. Occasionally, the number of turns and the axial length of the coil change, making uniform expansion difficult. Moreover,
Since the axial length of the stent becomes shorter in accordance with the change from the reduced diameter state to the expanded diameter state, it is difficult to expand the stent at an accurate position corresponding to the stenosis.

A stent has also been proposed in which a plurality of ring-shaped stent elements, each of which is expandable in the cell itself, are arranged continuously in the circumferential direction, and a plurality of ring-shaped stent elements are connected in the axial direction.
In the reduced diameter state of the stent, the flexibility (flexibility) is small, the insertability when inserting the stent is poor, and the burden on the patient is large.

The present invention has been made in view of such circumstances, has appropriate flexibility and flexibility in a reduced diameter state, has excellent insertability, and is easy to expand smoothly and uniformly in the radial direction. It is an object of the present invention to provide a stent having sufficient radial strength and capable of suppressing the growth of restenosis.

[0009]

In order to achieve the above object, a stent according to the present invention is a generally cylindrical stent which is expandable in a radial direction and is placed in a lumen of a living body. , A spiral-shaped stent element wound continuously for at least one round, and the stent element is a continuous body of a plurality of cells connected along the spiral direction.

Each cell is not particularly limited as long as each cell can be expanded in the spiral direction, and may be a closed loop shape or a non-closed loop shape. It has a closed loop shape in which a space is formed at the center when expanded. The closed-loop-shaped cell is preferable because, even when the wire diameter of the wire constituting the cell is made smaller than the non-closed-loop-shaped cell, the cell has excellent radial proof stress after stent expansion and a high effect of suppressing restenosis. It is. It is also conceivable that a stent composed of a continuous body of cells having a closed loop shape may abut on the surface of the stenosis at a loop shape portion having a relatively large area.

The closed loop-shaped cell is not particularly limited, and may be a polygonal ring-shaped cell, a circular ring-shaped cell, an elliptical ring-shaped cell, etc. in the expanded state, but is preferably a hexagonal ring-shaped cell. The set of hexagonal ring-shaped cells constitutes a honeycomb structure in the expanded state, has excellent strength, makes it difficult for the stent after expansion to be crushed, and easily expands along the spiral direction in the reduced diameter state of the stent. This is because the shape becomes crushed. Further, the non-closed loop shape cell is not particularly limited, and examples thereof include a zigzag shape, a valley shape, and the like.

In the present invention, the spirally wound stent elements may be arranged in a single line in the same stent, or may be arranged in two or more lines.

[0013] The stent according to the present invention preferably further includes an axial connection element that connects the adjacent stent elements along the axial direction. By further providing the axial connection element, the axial dimensional stability of the stent when the stent changes from the reduced diameter state to the expanded diameter state can be further improved.

The material of the stent element and / or the axial connection element is not particularly limited, but is preferably made of a superelastic alloy or a shape memory alloy. By configuring these elements with these alloys, the flexibility and / or flexibility of the stent in the reduced diameter state is further improved, and the insertability is further improved.

In the present invention, the superelastic metal is not particularly limited, but examples thereof include nickel-titanium, iron-manganese-silicon, and copper-aluminum-nickel. In the present invention, the term “superelasticity” means that a recoverable elastic strain range is large.
% To 10%, including pseudoelasticity that causes twin deformation and the like. In general, a superelastic metal has an elastic modulus in a superelastic region that is extremely small as compared with that of iron or stainless steel, and is excellent in flexibility.

[0016]

The stent according to the present invention has a spiral-shaped stent element wound continuously for at least one round, so that it has appropriate flexibility and flexibility in a reduced diameter state and is excellent in insertability. . Further, in the stent according to the present invention, since the stent element is a continuous body of a plurality of cells connected along the spiral direction, when expanding the diameter of the stent, each cell extends along the spiral direction. Thus, the diameter of the stent can be expanded without changing the number of turns of the spiral. Therefore, the stent according to the present invention is easy to expand smoothly and uniformly in the radial direction, has sufficient radial strength after expansion, and can suppress the growth of restenosis. Further, even if the stent of the present invention changes from the reduced diameter state to the expanded diameter state, it hardly changes in the axial direction, so that the stenotic portion can be expanded at an accurate position.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on embodiments shown in the drawings. FIG. 1 is a schematic perspective view of a stent according to an embodiment of the present invention, FIG. 2 is a schematic view showing an arrangement relationship of axial connection elements in the stent shown in FIG.
FIGS. 4A to 4D are schematic views showing a modification of the cell shape of the stent element in the stent, and FIGS.
(B) is a principal part schematic sectional drawing which shows the example of use of a stent.

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 is continuous for at least one round that defines the outer shape of the stent 2. It has a wound spiral stent element 4. The stent element 4 is, as shown in FIG.
The stent is composed of a continuous body of a plurality of hexagonal ring-shaped cells 40 connected along the spiral direction in the expanded state of the stent.

Each of the hexagonal ring-shaped cells 40 is a kind of a closed-loop-shaped cell that is crushed when contracted and has a space formed in the center when expanded. These cells 40 are continuously arranged along the spiral direction 52 at a predetermined angle θ1 with respect to the axis 50 of the stent 2 so that adjacent cells are displaced from each other.

The predetermined angle θ1 is not particularly limited, but when expressed as tan θ1, preferably 1 to
0.1, more preferably 0.5 to 0.2. If the angle θ1 is too small, the number of spiral turns of the stent element becomes too small for a predetermined length in the axial direction of the stent 2, and the radial strength of the stent in the expanded state tends to decrease. If the angle θ1 is too close to 90 degrees, the number of spiral turns of the stent element becomes too large for a predetermined length in the axial direction of the stent 2,
When the diameter of the stent is reduced, the flexibility and flexibility of the stent tend to decrease, and the insertion characteristics tend to deteriorate.

The size of each hexagonal ring-shaped cell 40 is not particularly limited. For example, the outer diameter of a circle circumscribing the hexagonal ring is preferably 1/4 to 1/1 / of the expanded diameter of the stent.
20, particularly preferably about 1/8 to 1/12. If the outer diameter is too small, the size of the cell 40 will be too small, the dimensional change from the contracted state to the expanded state will be small, and the degree of change of the stent 2 from the contracted state to the expanded state will tend to be small. It is in. If the outer diameter is too large, the size of each cell 40 becomes too large, and the stent 2
In the expanded state, the strength in the radial direction tends to be insufficient.

As shown in FIGS. 1 and 2, the stent 2 according to the present embodiment has a structure in which cells 40 adjacent to each other in the axial direction are arranged.
And an axial connecting element 6 for interconnecting the two. The number of the axial connection elements 6 is not particularly limited, but is preferably about one to several per one or several turns of the stent elements 4 arranged in a spiral shape, and particularly preferably one to one per one turn.
About the number is preferable. Moreover, it is preferable that the axial connection elements 6 adjacent to each other in the axial direction are displaced from each other by a predetermined angle θ2 when viewed from the axial center direction of the stent 2 as shown in FIG. As the predetermined angle θ2, for example, 90 to 150
Degree is preferable.

The axial connecting element 6 is preferably a straight line parallel to the axial direction, but may be a non-parallel straight line, a curved line, or another shape and inclination angle. The length of the axial connection element 6 along the axial direction is determined according to the predetermined angle θ1 shown in FIG.

In the present embodiment, the cells 40 and the axial connection elements 6 constituting the stent element 4 are all integrally formed of a shape memory alloy or a superelastic metal of the same material, and the width and thickness of the wire constituting the same are used. The (wire diameter) is not particularly limited, but is preferably 20 to 400 μm, and more preferably 30 to 100 μm.

The method for manufacturing the stent 2 shown in FIG. 1 is not particularly limited. For example, by etching a metal tube in a predetermined pattern, the cell 40 and the axial connection element 6 constituting the stent element 4 are integrally formed. An example of a method for obtaining a failed stent 2 is illustrated. Also, a vapor deposition method such as sputtering is performed on the surface of the core material in a predetermined pattern to deposit a metal thin film having the pattern shown in FIG. 1 and then the core material is removed. Can be obtained.

The stent element 4 and the axial connection element 6
And can be composed of different materials, in which case,
The diameters of these wires may be different. For example, the wire diameter of the wire of the stent element 4 is preferably 30 to 400
μm, more preferably 50-100 μm, and the wire diameter of the wire of the connecting element 6 is preferably 20-100 μm.
m, more preferably 30 to 60 μm.

When the stent element 4 and the axial connection element 6 are made of different materials, it is preferable that the stent element 4 be made of a material that is not easily crushed after the outer diameter of the stent is expanded. The material that is not easily crushed after the outer diameter is expanded is not particularly limited, and examples thereof include a metal that undergoes plastic deformation such as stainless steel (for example, annealed SUS316), gold, platinum, or an alloy thereof.

In that case, the connecting element 6 is
It may be made of a superelastic metal such as a nickel-titanium alloy. The superelastic metal has a property that a recoverable elastic strain range is large, for example, reaches 3% to 10% or more, and in a superelastic region, a force required for deformation is substantially constant even when strain increases. In general, a superelastic metal has an elastic modulus in an elastic region that is about several times smaller than that of iron or stainless steel, and is excellent in flexibility.

Thus, the stent element 4 and the connecting element 6
By making the materials different from each other, it is possible to realize a stent that is excellent in flexibility and flexibility in the contracted state of the stent and hard to be crushed in the radial direction in the expanded state of the stent.

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 a stent for aortic treatment, 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 surfaces of the stent element 4 and the connecting element 6 constituting the stent 2 are preferably coated with a plating film and / or a biocompatible coating film. This is for improving biocompatibility. Further, a platinum or gold plating film is used as the plating film. Examples of the biocompatible coating film include, but are not particularly limited to, ordinary polymers used for medical purposes, such as olefins such as polyethylene, nitrogen-containing polymers such as polyimide and polyamide, and siloxane polymers. Further, the coating film is not limited to the polymer, and may be an inorganic coating film such as silicon carbide, carbon such as 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. Although the thickness of these is not particularly limited, the thickness of the plating film is, for example, about 0.05 to 5 μm,
The thickness of the biocompatible coating film is 0.1 to 10 μm
Degree, preferably 0.5 to 5 μm.

Next, an example of use of the stent 2 of the embodiment shown in FIG. 1 will be described. As shown in FIG. 4 (A), first, the stent 2 is mounted on the outer periphery of the balloon portion 10 of the balloon catheter 12 in a radially contracted state. Inserted inside. Thereafter, the stent 2 and the balloon portion 10 of the balloon catheter 12 are combined with the strongly bent blood vessel 2.
0, and finally the stenosis 22 of the blood vessel 20
To reach. In the stent 2 according to the present embodiment, since the stent element 4 has a spiral shape, the stent element 4 easily bends in accordance with the bent shape of the blood vessel 20, and the desired stenosis 22
After repositioning, recover its original shape. Therefore, the bending followability and insertion characteristics of the stent 2 are improved. In particular, when the stent element 4 and the connection element 6 are made of a shape memory alloy or a superelastic alloy, the shape recovery effect after the stent 2 is located at the target stenosis 22 is enhanced.

Thereafter, as shown in FIG. 4 (B), the stenosis portion 22 expands along with the expansion of the balloon portion 10, and the stent 2
Also expand radially outward. At that time, in the stent 2 according to the present embodiment, since the stent element 4 is a continuous body of a plurality of cells 40 connected along the spiral direction, each cell 40 is extended along the spiral direction. , Without changing the number of spiral turns
The diameter of the stent 2 can be expanded. Therefore, the stent 2 according to the present embodiment is easy to expand smoothly and uniformly in the radial direction, has sufficient radial strength after expansion, and can suppress the growth of restenosis. Further, even if the diameter of the stent 2 is changed from the reduced diameter state to the expanded diameter state, it hardly changes in the axial direction, so that the stenotic portion 22 can be expanded at an accurate position. is there.

After expanding the diameter of the stent 2, only the balloon catheter 12 is extracted from the blood vessel 20, and only the stent 2 is placed inside the expanded stenosis portion 22 to prevent restenosis. In the present embodiment, the stent element 4 of the stent 2 is a portion that suppresses a force of the stenotic portion after expansion to return to its original state, and is a continuous body of a plurality of hexagonal ring-shaped cells 40 arranged in a spiral shape. Because it is configured, it does not collapse easily, and can effectively prevent restenosis.

It should be noted that 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, the shape and arrangement of the cells constituting the stent element are not particularly limited. As shown in FIG. 3A, by displacing one side of the hexagonal ring-shaped cell 40 to be connected, The spiral stent element 4 may be configured, or may be configured as shown in FIG. In the configuration of the stent element 4a shown in FIG. 3 (B), each hexagonal ring-shaped cell 40a is inclined at a predetermined axis θ1 to connect the hexagonal ring-shaped cells 40a to be connected.
One side of a is completely matched.

The stent element 4b shown in FIG.
Then, each circular ring-shaped cell 40b, which is a kind of closed loop cell, is connected by a spiral connecting wire 42,
The cells 40b are arranged in a spiral direction at a predetermined angle θ1 with respect to the axis 50 of the stent. The outer diameter and the wire diameter of the ring-shaped cell 40b are substantially the same as the circumscribed circle diameter and the wire diameter of the hexagonal ring-shaped cell 40 shown in FIG.

The spiral direction connecting wire 42 is
It may be arranged between the hexagonal ring-shaped cells 40 or 40a shown in FIGS. 3 (A) and 3 (B). The wire 42 need not be a straight line, but may be a curve or a zigzag shape.

In the stent element 4c shown in FIG.
A zigzag-shaped cell 40c, which is a kind of non-closed-loop-shaped cell other than a closed-loop-shaped cell, is spirally arranged along a direction at a predetermined angle θ1 with respect to the axis 50 of the stent.

Further, in the present invention, such a spiral stent element 4, 4a, 4b, 4c may be arranged in a double or more spiral form in a single stent. Further, different stent elements may be combined.
Furthermore, in a single spiral stent element,
Each cell may be connected in two or more rows in the axial direction.

In the above-described embodiment, the wires constituting the cell 40 and the axial connection element 6 are integrally formed of a shape memory alloy or a superelastic alloy. However, the present invention is not limited to this. It may be made of metal, tungsten, platinum, molybdenum, or an alloy thereof, or a metal and other composite material.

[0042]

As described above, according to the present invention, it has appropriate flexibility and flexibility in the reduced diameter state, is excellent in insertability, and is easy to expand smoothly and uniformly in the radial direction. It is possible to provide a stent having sufficient radial strength after expansion and capable of suppressing the growth of restenosis.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view of a stent according to one embodiment of the present invention.

FIG. 2 is a schematic diagram showing an arrangement relationship of axial connection elements in the stent shown in FIG.

3 (A) to 3 (D) are schematic views showing a modification of the cell shape of the stent element in the stent.

4 (A) and 4 (B) are schematic cross-sectional views of main parts showing an example of use of a stent.

[Explanation of symbols]

 2 ... Stent 4, 4a, 4b, 4c ... Stent element 6 ... Axial connection element 40, 40a, 40b, 40c ... Cell

Claims (4)

[Claims] Claims: 1. An overall tubular stent that is radially expandable and is placed in a lumen of a living body, the spiral stent element having a spiral shape wound continuously for at least one round, The stent, wherein the stent element is a continuum of a plurality of cells connected along a spiral direction. 2. The method according to claim 2, wherein each of the cells is crushed when contracted.
The stent according to claim 1, wherein the stent is a closed-loop-shaped cell in which a space is formed in a central portion when expanded. 3. The stent according to claim 1, further comprising an axial connection element that interconnects the stent elements adjacent to each other along the axial direction. 4. The stent according to claim 1, wherein the stent element and / or the axial connection element is made of a superelastic alloy or a shape memory alloy.