JP4323102B2 - Flexible stent - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an indwelling stent used for improving a stenosis or occlusion occurring in a lumen of blood vessels, bile ducts, trachea, esophagus, urethra, and other organs, and more particularly, a balloon-expandable stent. It relates to a stent.
[0002]
[Prior art]
In order to treat various diseases caused by stenosis or occlusion of blood vessels or other in-vivo lumens, stents are expanded at the site of stenosis or occlusion and placed at that site to secure the lumen. Generally, it is a tubular medical device.
[0003]
Among such stents, the balloon-expandable stent does not have a self-expanding function like a self-expandable stent, and after being inserted into a target site, the balloon is expanded within the stent, and the stent is expanded (plastic deformation) by the expansion force of the balloon. ) And fixed in close contact with the inner surface of the target lumen.
[0004]
[Problems to be solved by the invention]
In general, the basic functions that a stent should have are delivery performance and restenosis prevention function. Delivery performance is a function of a stent that can be delivered to a target intraluminal site, and since it cannot be naturally placed unless it can be delivered to the target site, it is a basic function. Regarding balloon expandable stents in particular, factors involved in this delivery performance include the stent diameter when mounted on the balloon catheter, the adhesion between the balloon and stent when mounted on the balloon catheter, etc. In particular, the flexibility of the stent when mounted on a balloon catheter is important.
[0005]
The flexibility when mounted on the balloon catheter is a physical property necessary for following the guide wire that is indwelling, particularly for a blood vessel that is bent or meandering. A stent with poor axial flexibility may not be able to follow the guidewire and deliver to the lesion site. This is especially true for long stents. In addition, when passing through a lesion that is bent and further calcified, the stent may be caught by a hard calcified intima and not advance further. In particular, when the stent is bent, a portion of the strut protrudes outward and does not advance against the hard lesion. In addition, it is a problem that often arises in clinical practice. When the stent is pulled back into the guiding catheter because the stent does not pass through the lesion, a part of the stent is caught on the tip of the guiding catheter and cannot be recovered. May fall off the balloon catheter.
[0006]
On the other hand, the restenosis prevention function is a function capable of preventing the portion where the stent is placed from becoming restenosis. The mechanism of restenosis has not been fully elucidated, and the structure of lesions has been complicated and diverse in clinical studies. The fact is that whether stents contribute to a reduction in the rate of restenosis has not been fully elucidated. However, stents with poor axial flexibility are said to be prone to restenosis at the edge of the stent, which is thought to be due to stress on the edge and irritation of the blood vessels because it is stiff. Yes. Thus, it is considered that the stent should be flexible even after the stent is expanded and placed. However, since a stent having no free portion is generally hard in the axial direction, it is said that the restenosis rate at the end edge of the stent is high.
[0007]
Accordingly, an object of the present invention is to provide an axially flexible stent before and after expansion.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the present invention is formed in a tubular shape as a whole, has a first outer diameter that can be inserted into a living body lumen, and is given a radially outward expansion force inside. A plurality of stents, sometimes expandable to a second outer diameter that is larger than the first outer diameter, each comprising a plurality of corrugated elements spaced apart from each other with a constant gap along the axial direction of the stent. An annular expansion member; All of A plurality of corrugated connecting members that connect adjacent annular expanding members to each other at the peaks and peaks and / or valleys and valleys of the corrugated element, the plurality of annular expanding members are arranged in the axial direction of the stent. Are arranged so as not to substantially cause a phase difference between the waves of the corrugated elements, and each corrugated connecting member has a plurality of waves inside each wave of the corrugated elements, and is adjacent to each other. In the gap between the annular expansion members, the corrugated element has a wave having a larger amplitude than the other waves, and the largest wave in each corrugated connecting member is the corrugated element in a state where the stent has the first outer diameter. Larger than the width of the mountain or valley of And inside the largest wave of the corrugated connecting member adjacent in the circumferential direction of the stent, The corrugated element is composed of a plurality of linear segments and a curved segment connecting two adjacent linear segments, and the plurality of waves of the corrugated connecting member are the two adjacent straight lines. Between the segments The width of each corrugated connecting member is ½ or less of the width of the corrugated element, and the total extension of the corrugated connecting members is the peak and peak or valley of the corrugated elements of adjacent annular expansion members. More than 1.3 times the straight line distance to the valley An expandable flexible stent is provided.
[0009]
In the present invention, it is preferable that the crests and crests and the troughs and troughs of the corrugated elements of all adjacent annular expansion members are connected by a corrugated connection member.
[0010]
The width of each corrugated connecting member is preferably ½ or less of the width of the corrugated element. Specifically, the width of each corrugated connecting member is in the range of 0.03 mm to 0.08 mm. Is preferred.
[0011]
Moreover, it is preferable that the largest wave in each corrugated connecting member is larger than the width of the peak or valley of the corrugated element in a state where the stent has the first outer diameter. Furthermore, it is preferable that the total extension of the corrugated connecting member is 1.3 times or more the linear distance between the peaks and peaks or the valleys and valleys of the corrugated elements of the adjacent annular expansion members.
[0012]
The flexible stent according to any one of claims 1 to 6, wherein a width of a gap between adjacent annular expansion members is 0.4 to 0.8 mm.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the drawings.
[0014]
The flexible stent of the present invention is formed in a tubular shape as a whole, has a first outer diameter that can be inserted into a living body lumen, and has a first outer diameter when an expansion force is applied radially outward. It can be expanded to a second outer diameter larger than the outer diameter.
[0015]
FIG. 1 shows one embodiment of the present invention in a state in which the stent of the present invention is mounted on a balloon catheter, that is, in a state having a first outer diameter that is sufficiently small so as to be inserted into a living body lumen (non-expanded state). It is an expansion expanded view of the stent which concerns on a form. FIG. 2 is an enlarged view showing a part of the stent shown in FIG.
[0016]
A stent 10 shown in FIG. 1 includes a corrugated connecting member 12 that connects a plurality of (for example, ten) annular expanding members 11 and adjacent annular expanding members 11.
[0017]
Each of the annular expansion members 11 expands to a second outer diameter larger than the first outer diameter when a force spreading radially outward is applied therein, and when the force is removed, The expanded shape is retained, and each is constituted by a corrugated element 111. Each corrugated element 111 is formed in an annular shape so that peaks and troughs of the waves appear periodically so as to intersect the circumferential direction of the expansion member 11. All the wave elements 111 preferably have the same shape as shown in FIG. As shown in FIG. 1, the annular expansion member 11 composed of the corrugated elements 111 has a predetermined distance d in parallel with each other without substantially causing a wave phase difference between adjacent corrugated elements 111. Are arranged in the (longitudinal) axial direction of the stent 10 (indicated by X in FIG. 1). That is, the annular expansion member 11 is disposed such that the peaks and peaks, and the valleys and valleys in the adjacent annular expansion members 11 are aligned in parallel to the axial direction of the stent 10 (the wave peaks and valleys are corrugated. When the bent portion on one side of the element 111 is a mountain, the bent portion on the other side is defined as a trough.Hereinafter, for convenience, in FIG. (Indicated as M in FIG. 2), the right bent portion is referred to as a trough (indicated as V in FIG. 2). In the embodiment shown in FIG. 1, each corrugated element 111 has six peaks M and six valleys V.
[0018]
Although there is no restriction | limiting in particular in the waveform of the waveform element 111 which comprises the cyclic | annular expansion member 11, As shown in FIG.1 and FIG.2, it is preferable that it is substantially U-shaped. More specifically, referring to FIG. 2, the U-shaped corrugated element 111 is composed of a substantially straight segment 111a and a curved segment 111b connecting the straight segment 111a. 111a is alternately connected by one curved segment 111b at their ends.
[0019]
As shown in FIG. 2, the corrugated connecting member 12 is a wave connecting the corrugated mountain connecting element 121 and the trough and the valley in the corrugated element 111 of the adjacent annular expansion members 11 and connecting the peaks and the mountains. And a mold valley coupling element 122. In the case of this stent, the mountain connecting element 121 is connected from the left mountain M to the right mountain M. The mountain connecting element 121 has a plurality of (for example, two) small waves 121a and 121b in the gap between the adjacent linear segments 111a, and between the adjacent annular expansion members 11, another wave 121a. , 121b has a larger wave 121c than that of 121b. By having the wave 121c having a larger amplitude than the other waves in the gap between the adjacent annular expansion members 11, the flexibility of the stent 10 is increased. The wave shape of the mountain connecting element may be V-shaped, but the S-shape is preferred because it is difficult to bend when bent. It is preferable that all the mountain coupling elements 121 have the same shape. 1 and 2, the mountain coupling element 121 has two small waves between adjacent linear segments 111 a and one large wave between adjacent annular expansion members 11. However, the present invention is not limited to this, and the mountain connecting element has a plurality of waves and a wave having a larger amplitude than the other waves in the gap between adjacent annular expansion members. do it.
[0020]
The corrugated valley coupling element 122 is coupled from the left valley V to the right valley V. Like the mountain coupling element 121, the valley coupling element 122 has a plurality of (for example, two) small waves 122a and 122b in the gap between the linear segments 111a adjacent to each other. In between, there is a wave 122c having a larger amplitude than the other waves 122a and 122b. By having the wave 122c having a larger amplitude than the other waves in the gap between the adjacent annular expansion members 11, the flexibility of the stent 10 is increased. The large wave 122c preferably has a wave height greater than the width of the gap between adjacent linear segments 111a. The wave shape of the valley coupling element 122 may be V-shaped, but the S-shape is preferred because the directionality when bent is difficult. Moreover, as shown in FIG. 1, it is preferable that all the valley connection elements 122 are the same shape. 1 and 2, the valley coupling element 122 has two small waves between the adjacent linear segments 111 a and one large wave between the adjacent annular expansion members 11. Although shown as, but not limited to this, the valley coupling element 122 has a plurality of waves and a wave having a larger amplitude than the other waves in a gap between adjacent annular expansion members. Just have it. In a particularly preferred embodiment of the present invention, the peak connecting element 121 and the valley connecting element 122 are all the same shape and only have different orientations, as shown in FIG. Moreover, it is preferable that all the peaks and ridges and valleys and valleys of the corrugated elements constituting the adjacent expansion members 11 are connected by the connecting member 12.
[0021]
In the present invention, from the viewpoint of further increasing the flexibility before and after expansion, the wave of the corrugated connecting member (the wave existing in the gap between adjacent expansion members 12) has a wave height H (see FIG. 2), It is preferable that the width W of the peak M or valley V of the corrugated element 111 constituting the annular expansion member 11 is larger. The width w of the peak M or the valley V is a distance between two points P1 and P2 where one curved segment connects to two linear segments 111a in a state where the stent is deployed.
[0022]
The annular expansion member 11 is deformed when expanded, and needs to exhibit a counter force sufficient to counteract the force when the blood vessel contracts while maintaining the deformed state. It is preferable to have a thickness. On the other hand, the connecting member 12 may have a considerably narrow width as long as the connecting member 12 only needs to have a role of keeping a constant distance without separating the annular expansion members 11 from each other. However, if the connecting member 12 is to have a function of expanding and holding the blood vessel, it needs to have the same width and thickness as the expansion member, so that the expansion holding force is high, but relatively flexible. Become a scarce stent.
[0023]
However, it is an object of the present invention to provide a stent that is axially flexible both before and after expansion. As a result of various studies on such flexibility, the present inventors have determined that the width of the connecting member 12 (the mountain connecting element 121 and the valley connecting element 122) is ½ of the width of the corrugated element 111 constituting the annular expansion member 11. It has been found that by making the following, the flexibility can be further increased, and the distance between the annular expansion members 11 can be kept constant, and the function of the stent can be sufficiently exerted. Specifically, it was found that the width of the connecting member 12 is preferably 0.03 mm to 0.08 mm, and more preferably 0.04 mm to 0.06 mm.
[0024]
If the gap d between the annular expansion members 11 is too wide, the flexibility of the stent 10 increases, but the number of expansion members 11 having the function of expanding and holding decreases per unit length. Extended holding power is reduced. On the other hand, if the gap d between the expansion members 11 is too narrow, the number of expansion members 11 per unit length increases, so that the expansion holding force is relatively increased, but the flexibility is relatively poor. Therefore, as a result of research to appropriately balance the contradictory requirements of expansion retention and flexibility, the width of the gap d is preferably 0.4 mm to 0.8 mm, and more preferably 0.5 mm to 0.7 mm. It turned out to be more preferable.
[0025]
FIG. 3 is a development view in a state in which the stent 10 shown in FIG. 1 is expanded to have the second outer diameter. The corrugated element 111 constituting the annular expansion member 11 is deformed from a U shape at the time of non-expansion shown in FIG. 1 to a V shape, and the diameter of the stent 10 is expanded accordingly. If the connecting member 12 is a stent expansion in a straight blood vessel that is not curved, its shape and length basically do not change. That is, when the stent is expanded, the axial length of the expansion member 11 changes, but adjacent peaks or valleys connected by the connection member 12 change by the same length in the same direction. The length of 12 will not change. On the other hand, if the wave of the wave element 111 of the expansion member 11 is 180 degrees out of phase, that is, if the wave crest and valley of the wave element 111 are connected, the expansion member And the connecting member 12 extends. In the stent of the present invention, since the expansion members 11 are arranged in the axial direction so that there is no phase difference between the waves of the corrugated element 111, the total length changes even when the stent is extremely expanded. The advantage of being difficult (substantially unchanged) is obtained. If the overall length of the stent is shortened due to expansion, the entire stenosis of the target blood vessel cannot be expanded, or there is a gap between the assumed placement site under the X-ray imaging and the actual stent placement state. In some cases, effective stenosis cannot be improved.
[0026]
Further, when the connecting member 12 is corrugated, not only the flexibility of the stent is increased as described above, but also the advantage that the treatment of the side branch can be easily performed. The advantage is particularly remarkable in a stent placed in a coronary artery. The coronary artery has various side branches (blood vessels in which a blood vessel thinner than the main tube branches from the main tube) in a main thick blood vessel (hereinafter referred to as a main tube). If the stenosis is at the branch between the main branch and the side branch, the stent may be placed including the branch. At that time, as a result of placing the stent, the degree of stenosis of the side branch may be further increased or occluded. In many cases, since the side branch is a thin blood vessel, clinical symptoms and myocardial infarction do not occur, but sometimes chest pain and infarction symptoms are present and some treatment is required.
[0027]
In that case, a guide wire is inserted into the side branch through the gap 21 of the stent shown in FIG. 3, and a balloon catheter is delivered to the stenosis portion along the guide wire to be expanded and treated. In most cases, the stenosis will be at the entrance of the side branch, so the stent wall will expand together. In addition, in order to exert a sufficient expansion effect, it is necessary to expand with a balloon that is as close as possible to the blood vessel diameter of the side branch. When the balloon is expanded, the half portion 111h of the corrugated element 111 defining the gap 21 of the stent, the mountain connecting element 121 and the valley connecting element 122 adjacent to each other in the circumferential direction, and the half portion 111h1 of the corrugated element 111 adjacent to each other in the axial direction. The half portion 111h2 of the corrugated element 111 is deformed into a substantially circular shape as the balloon is expanded. Since it is preferable to expand with a balloon as large as possible as described above, it is better that the perimeter is longer. In the present invention, since the connecting member 12 is corrugated, the circumferential length of the gap 21 is longer than that of a straight line, so that a large balloon can be used. From this point of view, it is particularly preferable that each corrugated connecting member 12 has a total extension of 1.3 times or more of the linear distance between the peaks and peaks or the valleys and valleys of adjacent annular expansion members 11. .
[0028]
The material for forming the stent 10 is preferably biocompatible, and examples thereof include stainless steel, tantalum or a tantalum alloy, platinum or a platinum alloy, gold or a gold alloy, and a cobalt base alloy. In addition, noble metal plating (gold, platinum) may be applied after the stent shape is produced. As stainless steel, SUS316L having the most corrosion resistance is suitable. Furthermore, it is preferable to anneal after creating the final shape of the stent 10. By performing the annealing, the flexibility and plasticity of the entire stent are improved, and the indwellability in the bent blood vessel is improved. Compared to the case where annealing is not performed, the force to restore the shape before expansion after expanding the stent, particularly the force to return to the linear shape that appears when expanding at a bent blood vessel site, The physical stimulation applied to the bent inner wall of the blood vessel is reduced, and the factor of restenosis can be reduced. Annealing is preferably performed by heating to 900 to 1200 ° C. in an inert gas atmosphere (for example, argon gas) and then slowly cooling so that an oxide film is not formed on the stent surface.
[0029]
The stent 10 of the present invention can be preferably manufactured by using a method of hollowing out a portion of the stent from a metal pipe. Various methods can be adopted as a method of hollowing out the stent from the pipe. For example, there is an etching method using chemicals and masking called photofabrication, an electric discharge machining method using a mold, and a mechanical cutting method.
[0030]
The simplest method with high processing accuracy is based on the laser processing method. As the laser processing machine, a YAG laser (trade name SL116E) manufactured by NEC Corporation can be used. The metal pipe is set on a jig with a rotary motor with a chuck mechanism so that the shaft does not shake, and this is set on an XY table that can be numerically controlled. Then, the XY table and the rotation motor are connected to the personal computer, and the output of the personal computer is set to be input to the numerical control controller and the rotation motor of the XY table. Drawing software is stored in the personal computer, and a developed drawing of the stent having the composition as shown in FIG. 1 is input thereto. Based on the drawing data output from the personal computer, the XY table and the rotary motor are driven. By irradiating a laser there, a stent structure having a shape as shown in FIG. 1 is created. In addition to such a system, a so-called laser marker (galvanometer method) driven by a laser processing machine may be used.
[0031]
Here, as a typical stent placement technique when using a balloon expandable stent, a brief description will be given of the placement technique of a coronary stent. First, in order to secure various blood vessels in order to introduce various catheters into the blood vessels, Place the sheath in the appropriate blood vessels (mainly the femoral, elbow, and radial arteries). The sheath is a device provided with a valve at the end of a thin plastic tube that prevents blood leakage and allows catheters to be inserted and removed. A catheter called a guiding catheter is inserted through this sheath, and its tip is fixed to the right or left coronary artery ostium. As a result, a passage from outside the body to the coronary artery is formed.
[0032]
Next, a thin guide wire having a diameter of, for example, about 0.36 mm (0.014 inch) is inserted into the guiding catheter, and after passing through the stenosis of the coronary artery, a balloon is provided at the tip along the guide wire. The balloon catheter is inserted, the balloon is expanded at the stenosis part to widen the stenosis part, and then the balloon catheter is removed. Thereafter, a contrast medium is injected from the guiding catheter, and the degree of expansion of the stenosis is confirmed. If the stenosis is sufficiently expanded and there are no defects, the procedure is completed. If the expansion is insufficient or the intima is peeled off, the next step is to place the stent. To do.
[0033]
That is, the stent is mounted on the balloon of the balloon catheter (in a folded state), and the balloon catheter is advanced along the guide wire to the stenosis in the same manner as described above. The tip is positioned in the stenosis and the position is confirmed. Thereafter, a contrast medium is injected into the balloon at a high pressure, and the balloon is expanded by the force. By expanding the balloon, the stent is plastically deformed so that its diameter expands in the radial direction, expands (expands) as shown in FIG. 3, and pushes the stenosis. The balloon pressure is then removed and deflated. Since the stent has an expansion retention force (shape retention force) due to plastic deformation, the stent does not contract and stays in that position, and maintains the expanded state of the blood vessel, thereby improving the blood flow disorder.
[0034]
【Example】
Hereinafter, the present invention will be further described with reference to specific examples.
[0035]
A long pipe of stainless steel (SUS316L) having a diameter of 1.4 mm and a wall thickness of 0.10 mm was cut to a length of 100 mm, and a desired stent was manufactured from this stainless steel pipe piece by a laser processing method. A YAG laser (trade name SL116E) manufactured by NEC was used as the laser processing machine. The stainless steel pipe piece was set on a jig with a rotary motor with a chuck mechanism so that the shaft would not shake, and this was set on an XY table capable of numerical control. Then, the XY table and the rotary motor were connected to a personal computer, and the output of the personal computer was set to be input to the numerical control controller and the rotary motor of the XY table. Drawing software is stored in the personal computer, and a developed drawing of a stent having a composition as shown in FIG. 1 is input thereto. Thus, on the basis of the drawing data output from the personal computer, the XY table and the rotary motor are driven, and the stainless steel pipe piece that moves with the XY table is irradiated with the laser, whereby the stent structure having the shape as shown in FIG. I made a thing. A mandrel was inserted into the pipe to prevent laser light from penetrating the pipe. The laser processing conditions were a current value of 25 A, an output of 1.5 W, and a driving speed of 10 mm / min.
[0036]
In this way, a stent having the shape shown in FIG. 1 was produced. The produced stent had a total length of 15 mm and an outer diameter of 1.4 mm, the width of the corrugated element constituting each expansion member was 0.11 mm, and the width of each connection member was 0.05 mm. When this stent is mounted on a delivery balloon, the outer diameter of the stent is about 1.0 mm, the peak / valley width of the corrugated element is 0.36 mm, and the height of the largest wave of the connecting member is 0.50 mm. The wave height was larger than the peak / valley width of the wave element. Moreover, the distance between adjacent expansion members was 0.51 mm. The total extension of each connecting member was 2.13 mm. And the linear distance of the peak and peak in an adjacent expansion member, or a valley and a valley was 1.55 mm.
[0037]
The perimeter of the aforementioned gap 21 of the stent was 6.35 mm. This is 2.02 mm when converted into a circle diameter. On the other hand, if it is assumed that the peaks are connected by a straight connecting member, the peripheral length of the gap of the stent at that time is 4.80 mm. This is 1.53 mm when converted into a circle diameter. Therefore, when the stent of the present invention is used, a 2.0 mm balloon can be used for the side branch, but when the connecting member is a straight line, only a 1.5 mm balloon can be used. In terms of the cross-sectional area, the diameter of 2.0 mm is 1.7 times the diameter of 1.5 mm, which is advantageous in this respect. This is considered to be due to the fact that when the balloon is expanded, it is easily deformed along the balloon because the corrugated connecting member has a small width.
[0038]
【The invention's effect】
The stent of the present invention is particularly excellent in axial flexibility before and after expansion because the annular expansion members are connected by corrugated connection members having a plurality of waves. Therefore, when delivering the stent of the present invention, it is possible to deliver even difficult lesions that are bent and calcified, and the flexibility that the stent bends easily even when placed in a bent lesion. Therefore, it can be expected to prevent restenosis at the stent edge. Furthermore, the stent of the present invention includes a corrugated connecting member having a plurality of waves, and since the total extension thereof is longer than a straight line, it has an advantage that a larger balloon can be applied to the side branch.
[Brief description of the drawings]
FIG. 1 is an enlarged development view of a stent before expansion according to an embodiment of the present invention.
FIG. 2 is an expanded view showing a part of the stent shown in FIG.
FIG. 3 is a development view after expansion of the stent shown in FIG. 1;
[Explanation of symbols]
11 ... annular expansion member
12 ... Wave connecting member
111 ... Wavy elements
111a ... Linear segment of corrugated element
111b ... Curved segment of corrugated element
111h1, 111h2 ... Half part of corrugated element
121 ... Wave type mountain connecting element
122 ... Wave type valley connecting element
121a, 121b, 122a, 122b ... small wave of corrugated connecting member
121c, 122c ... Big wave of corrugated connecting member
21 ... Gap during stent expansion
M ... Pile of wave elements
V ... Valley valley
X: Axial direction of stent

Claims (3)

The first outer diameter is formed into a tubular shape as a whole and can be inserted into a living body lumen. When an expansion force is applied to the inside in the radial direction, the first outer diameter is larger than the first outer diameter. A plurality of annular expansion members of corrugated elements, each of which is expandable to two outer diameters and spaced apart from each other with a certain gap along the axial direction of the stent, and all adjacent annular expansions A plurality of corrugated connecting members that interconnect the members at the peaks and / or peaks and / or valleys of the corrugated elements, wherein the plurality of annular expansion members are mutually connected along the axial direction of the stent. Arranged so as not to substantially cause a phase difference in the wave of the mold element, each corrugated connecting member has a plurality of waves inside each wave of the corrugated element, and between adjacent annular expansion members Having a wave with a larger amplitude than other waves in the gap Most big waves in undulating connecting member, in a state where the stent has said first outer diameter greater than the width of the peak or valley of the corrugated element, and most corrugated connecting member adjacent to the circumferential direction of the stent The corrugated element is composed of a plurality of linear segments and a curved segment connecting two adjacent linear segments to each other, and the corrugated coupling member includes the plurality of corrugated elements. It is Ri near between the phase Tonariru two straight segments, the width of each wave-type connecting member is less than half the width of the corrugated element, the total length of the wave type connection member, Neighboring An expandable flexible stent characterized in that it is at least 1.3 times the linear distance between the peaks and peaks of the corrugated elements of the annular expansion member . The flexible stent according to claim 1 , wherein the width of each corrugated connecting member is in the range of 0.03 mm to 0.08 mm. The flexible stent according to claim 1 or 2 , wherein a width of a gap between adjacent annular expansion members is 0.4 to 0.8 mm.

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