stent

Abstract

Provided is a stent with which it is possible to safely and easily perform appropriate expansion of a stenosed site.　A stent 10 comprises a self-expanding cylindrical part 11 that is used for expanding a stenosed site of a biological lumen. The cylindrical part 11 has a mesh pattern structure composed of a plurality of struts. The cylindrical part 11 includes a radiopaque coating layer formed over a range of the effective length VL thereof. The expansion force is different between a central portion 11a and opposite end portions 11b, 11c of the range of the effective length VL.

Description

stents

[0001] The present invention relates to a stent.

[0002] Conventionally, catheter treatment has been performed in which a stent or balloon is deployed at the site of stenosis and left in place.

[0003] Special Publication No. 2015-532188

[0004] The thickness and stenosis rate of a stenotic site vary depending on the affected area. Therefore, by selecting a stent with an expansion force appropriate for the thickness and stenosis rate of the stenotic site, the stenotic site can be properly opened. However, if the expansion force is the same throughout the stent, the same force will be applied to normal blood vessels or areas with a low stenosis rate as to areas with a high stenosis rate. Excessive force applied to normal blood vessels or areas with a low stenosis rate may cause the blood vessel to expand more than necessary, potentially resulting in damage or dissection of the blood vessel. On the other hand, if the expansion force of the stent is set low throughout the entire stent to avoid such an event, it is possible that the stenotic site will not be properly opened. Here, metals (e.g., Ni-Ti alloys) that are commonly used as stent materials have high X-ray transparency and low visibility in X-ray images. Therefore, it is difficult to accurately determine whether the stent has properly expanded the stenotic site within the blood vessel, making the procedure for opening the stenotic site even more difficult.

[0005] An object of the present invention is to provide a stent that can safely and easily perform appropriate dilation of a stricture site.

[0006] The first disclosure is a stent having a self-expanding cylindrical portion used to expand a narrowed portion of a biological lumen, the cylindrical portion having a mesh pattern structure made up of a plurality of struts, an X-ray opaque coating layer formed within the effective length range of the cylindrical portion, and the stent having different expansion forces at the center and both ends of the effective length range.

[0007] A second disclosure is the stent according to the first disclosure, wherein the expansion force of the cylindrical portion is smaller at the two ends than at the central portion.

[0008] A third disclosure is a stent according to either the first or second disclosure, wherein the thickness of the coating layer is smaller at the two ends than at the central portion.

[0009] A fourth disclosure is the stent according to any one of the first to third disclosures, wherein the thickness of the coating layer varies continuously between the central portion and the both end portions.

[0010] A fifth disclosure is a stent according to any one of the first to fourth disclosures, wherein the width of the struts is narrower at the both ends than at the central portion.

[0011] A sixth disclosure is a stent according to any one of the first to fifth disclosures, wherein the width of the struts varies continuously between the central portion and the both end portions.

[0012] A seventh disclosure is the stent according to any one of the first to sixth disclosures, wherein the struts are made of a superelastic material that has a shape memory function at a temperature equal to or higher than its transformation point.

[0013] An eighth disclosure is a stent according to any one of the first to seventh disclosures, wherein the coating layer is a plated layer of a radiopaque metal.

[0014] A ninth disclosure is a stent according to any one of the first to eighth disclosures, wherein the metal plating layer is a gold plating layer.

[0015] A tenth disclosure is the stent according to any one of the first to ninth disclosures, wherein the open area of ​​the cells forming the mesh pattern structure is 80 to 120% of the reference open area.

[0016] The eleventh disclosure is a stent having a self-expanding cylindrical portion used to expand a narrowed portion of a biological lumen, the cylindrical portion comprising: a first cylindrical portion having a mesh pattern structure made up of a plurality of struts; and a second cylindrical portion having a mesh pattern structure made up of a plurality of struts and inserted into the first cylindrical portion, wherein an X-ray opaque coating layer is formed within the effective length range of the first cylindrical portion and / or the second cylindrical portion, and the first cylindrical portion and / or the second cylindrical portion has different expansion forces at the center and both ends of the effective length range.

[0017] A twelfth disclosure is a stent according to any one of the first to eleventh disclosures, wherein the stent is used for applications in which it is temporarily placed in a biological lumen and then retrieved outside the body.

[0018] The thirteenth disclosure is a method for expanding a biological organ having a tubular structure using a stent, the stent being a stent having a self-expanding cylindrical portion, the cylindrical portion having a mesh pattern structure made up of a plurality of struts, an X-ray opaque coating layer formed within an effective length range of the cylindrical portion, and different expansion forces at the center and both ends of the effective length range, the method comprising: delivering the stent housed in a catheter in a contracted state together with the catheter through the biological organ to a planned position of expansion of the biological organ; withdrawing the catheter proximally and starting expansion of the stent from the distal side; completing expansion of the stent; and re-accommodating the expanded stent into the catheter.

[0019] According to the present invention, a stent can be provided that can safely and easily perform appropriate dilation of a stricture site.

[0020] FIG. 1 is a side view of the stent system 1 according to the first embodiment. FIG. 2 is a virtual development view of the main body portion 11 of the stent 10. FIG. 3 is a cross-sectional view taken along the line s1-s1 of FIG. 2. FIG. 4 is a cross-sectional view taken along the line s2-s2 and s3-s3 of FIG. 2. FIG. 5 is a schematic view showing a procedure for dilating a stenotic site in a blood vessel using the stent system 1. FIG. 6 is a schematic view showing a procedure for dilating a stenotic site in a blood vessel using the stent system 1. FIG. 7 is a schematic view showing a procedure for dilating a stenotic site in a blood vessel using the stent system 1. FIG. 8 is a schematic view showing a procedure for dilating a stenotic site in a blood vessel using the stent system 1. FIG. 9 is a diagram corresponding to the cross-sectional view taken along the line s1-s1 of FIG. 2. FIG. 10 is a diagram corresponding to the cross-sectional views taken along the line s2-s2 and s3-s3 of FIG. 2. FIG. 11 is a side view of a stent system 1B according to a third embodiment.

[0021] The following describes an embodiment of a stent system including a stent. The drawings attached to this specification are all schematic diagrams, and the shape, scale, aspect ratio, and other aspects may be modified or exaggerated from the actual product. In this specification, terms specifying the shape, geometric conditions, and the extent of these, such as "direction," include not only the strict meaning of the term but also the range that can be roughly considered to be that direction. Furthermore, in this specification, the longitudinal direction of the stent when extended linearly is referred to as the "axial direction LD" or simply "axial direction," and the direction perpendicular to the axial direction LD is referred to as the "radial direction RD" or simply "radial direction." Furthermore, in the axial direction LD of the stent or the direction of extension of the biological lumen, the side closer to the practitioner (proximal) is referred to as "D1," and the side farther from the practitioner (distal) is referred to as "D2."

[0022] (First embodiment) Fig. 1 is a side view of a stent system 1 according to a first embodiment. Fig. 1 is a side view of a stent 10 in its natural state. The natural state refers to a state in which the stent 10 has not been contracted (unloaded state). Fig. 2 is a virtual development view of the main body portion 11 of the stent 10. Fig. 2 schematically shows the planar shape of the main body portion 11. Fig. 3A is a cross-sectional view taken along s1-s1 in Fig. 2. Fig. 3B is a cross-sectional view taken along s2-s2 and s3-s3 in Fig. 2. Fig. 3B is a common cross-sectional view showing the cross section of a strut 15 forming the proximal portion 11b and the cross section of a strut 15 forming the distal portion 11c.

[0023] The stent system 1 shown in Fig. 1 is housed in a catheter (not shown), and is used to dilate a narrowed or blocked blood vessel by withdrawing the stent 10 from the catheter and deploying it in the lumen of the blood vessel. The blood vessels of the biological lumen in which the stent system 1 is used may be blood vessels of the brain, coronary arteries, upper and lower limbs (arteries, veins), organs, etc. In the following description, the biological lumen may also be simply referred to as a "blood vessel."

[0024] As shown in FIG. 1 , the stent system 1 includes a stent 10, a pusher wire 20, and a connecting portion 30. The stent 10 is a structure to be placed at a stenotic site (described later) in a blood vessel. The stent 10 is configured to have a generally cylindrical shape when expanded. Although not shown, the stent 10 has a more elongated cylindrical shape when contracted (stored in a catheter). The stent 10 includes a main body portion 11 and an antenna portion 12.

[0025] The main body 11 is a self-expanding cylindrical portion. The main body 11 expands into a cylindrical shape within the blood vessel due to its self-expansion force, thereby dilating the narrowed or blocked portion. The self-expansion force of the main body 11 acts as a force pushing the inner wall of the blood vessel from the inside to the outside in the radial direction. Therefore, the stent 10 expanded within the blood vessel can be retained in place. The main body 11 has a mesh pattern structure in which multiple cells 13 are arranged in the axial and radial directions. A "cell," also referred to as an opening or compartment, refers to a frame-shaped portion surrounded by struts that form the mesh pattern structure. In the following description, the cells are collectively referred to as "cell 13," and cells located in specific positions are identified by a symbol, for example, "cell 13f." A "strut" refers to a long, thin, rod-shaped or strip-shaped portion made of a wire-like material.

[0026] The cell structure is not particularly specified, but may be entirely open cells or entirely closed cells. Furthermore, the cell structure may include both open and closed cells. In this specification, the definitions of open and closed cells are not uniquely specified. For example, in a closed cell including a free end, half of the region surrounded by the two sides (struts) that form the free end may be specified as an open cell (part), and the other half may be specified as a closed cell (part). Alternatively, a closed cell including a free end may be specified as an open cell, and a closed cell not including a free end may be specified as a closed cell.

[0027] As shown in FIG. 1 , the range of the main body portion 11 in the axial direction LD corresponds to the range of the effective length VL of the stent 10. As shown in FIG. 2 , the range of the effective length VL refers to the range between the distal end 131 of the cell 13f located on the most distal side D2 of the main body portion 11 and the proximal end 132 of the cell 13n located on the most proximal side D1. The main body portion 11 can support the inner wall of the blood vessel by expanding in diameter within the range of the effective length VL. The effective length VL of the stent 10 is preferably longer than the axial length of the stenosis site CS and is long enough to contact normal blood vessels located near the stenosis site CS. The effective length VL of the stent 10 is preferably, for example, approximately 1.3 to 2.0 times the axial length of the stenosis site CS.

[0028] The cells 13 constituting the main body 11 are formed to have substantially the same shape. Specifically, the opening area of ​​each cell 13 is formed to be 80 to 120% of the reference opening area (design opening area). The opening area of ​​a cell 13 can be, for example, a value calculated by arithmetic average of the opening areas of all the cells 13 constituting the main body 11.

[0029] As shown in FIG. 2 , in the main body 11 of the first embodiment, multiple cells 13f located on the most distal side D2 and multiple cells 13n located on the most proximal side D1 are present in the radial direction RD. However, there may be only one cell 13f located on the most distal side and / or one cell 13n located on the most proximal side. That is, the cell 13f located on the most distal side D2 may be a cell that protrudes only one cell toward the distal side D2 from the other cells 13. Similarly, the cell 13n located on the most proximal side D1 may be a cell that protrudes only one cell toward the proximal side D1 from the other cells 13. Note that the radial direction RD (a direction perpendicular to the axial direction LD) shown in FIG. 2 corresponds to the circumferential direction (circumferential direction) of the main body 11 when virtually unfolded in a plane.

[0030] As shown in Figures 1 and 2, the main body portion 11 is divided into a central portion 11a, a proximal portion 11b, and a distal portion 11c in the axial direction LD. The central portion 11a is a region located approximately in the middle of the main body portion 11 in the axial direction. The proximal portion 11b is a region located on the proximal side D1 of the central portion 11a in the axial direction of the main body portion 11. The distal portion 11c is a region located on the distal side D2 of the central portion 11a in the axial direction of the main body portion 11. In the following description, the proximal portion 11b and the distal portion 11c are also referred to as "both ends" of the main body portion 11.

[0031] Within the effective length VL of the main body portion 11, the proportions occupied by the central portion 11a, the proximal portion 11b, and the distal portion 11c are determined based on the length, thickness, and stenosis rate of the stenotic region. In the main body portion 11 of this embodiment, the central portion 11a, the proximal portion 11b, and the distal portion 11c have different expansive forces when the coating layer 16 (described below) is not formed. The expansive force is also called radial force and refers to the reaction force generated when the stent is uniformly compressed in the radial direction. The expansive force can be measured, for example, by a radial force test method conforming to ISO 25539-2.

[0032] In FIG. 2, the diagonally shaded struts 15 are struts that form the central portion 11a of the main body portion 11. The width W1 (see FIG. 3A) of the struts 15 that form the central portion 11a of the main body portion 11 is wider than the width W2 (see FIG. 3B) of the struts 15 that form the proximal portion 11b and the distal portion 11c. In other words, the width of the struts 15 that form the main body portion 11 is narrower at the proximal portion 11b and the distal portion 11c, which are both ends of the main body portion 11, than at the central portion 11a. The width W1 of the struts 15 that form the main body portion 11 and the width W2 of the struts 15 that form the proximal portion 11b and the distal portion 11c are not particularly specified. The width ratio W1 / W2 is preferably, for example, approximately 1.0 to 1.5. Note that, because FIG. 2 is a schematic diagram, all struts 15 are shown with the same width.

[0033] In the stent 10 (main body portion 11), by making the width W1 of the struts 15 forming the central portion 11a wider than the width W2 of the struts 15 forming the proximal portion 11b and the distal portion 11c, the bending rigidity of the central portion 11a can be made greater than the bending rigidity of the both end portions, and therefore the expansive force of the central portion 11a can be made greater than the expansive force of the proximal portion 11b and the distal portion 11c. In other words, the expansive force of the proximal portion 11b and the distal portion 11c can be made smaller than the expansive force of the central portion 11a. Note that, as shown in Figures 3A and 3B, in this embodiment, the thickness T of the struts 15 forming the central portion 11a, the proximal portion 11b, and the distal portion 11c are the same.

[0034] The stent 10 has a radiopaque coating layer 16 formed within the effective length VL (the range of the main body 11). The coating layer 16 is formed so that the shape of the stent 10 can be seen in an X-ray radiographic image obtained by irradiating the stent 10 with X-rays. By forming the coating layer 16 within the effective length VL of the stent 10, the visibility of the stent 10 in an X-ray radiographic image can be further improved. As shown in FIGS. 3A and 3B , the coating layer 16 is formed so as to cover the outer circumferential surface of the struts 15. In the stent 10 of this embodiment, the thicknesses of the coating layers 16 formed on the central portion 11a, proximal portion 11b, and distal portion 11c are the same. The thickness of the coating layer 16 is not particularly limited, but is preferably, for example, approximately 1 to 10% of the thickness T of the struts 15. Note that the coating layer 16 does not have to be formed so as to cover the entire outer circumferential surface of the struts 15, as long as the shape of the struts 15 can be seen in an X-ray radiographic image. For example, the coating layer 16 may be formed only on the surface of the strut 15 located on the outer side in the radial direction RD.

[0035] The coating layer 16 is preferably a plated layer of a radiopaque metal, more preferably a gold plated layer. Examples of materials for forming the coating layer 16 include gold, platinum, tantalum, tungsten, iridium, platinum tungsten, and alloys thereof. The coating layer 16 is not limited to a plated layer, and may be formed from, for example, a polymer material having radiopaque properties to which a radiopaque filler or the like has been added.

[0036] An X-ray image of the stent 10 guided into the biological lumen is taken by an X-ray imaging device (not shown). The X-ray imaging device is a device that captures X-ray transmission images as moving or still images. By displaying the moving X-ray transmission images taken by the X-ray imaging device on a monitor screen, the practitioner can visually confirm the behavior of the stent 10 (main body 11) within the biological lumen in real time. In addition, by displaying the still X-ray transmission images taken by the X-ray imaging device on a monitor screen, the practitioner can visually confirm the state of the stent 10 within the biological lumen.

[0037] Returning to Fig. 1 , the antenna portion 12 is a portion where the proximal side D1 of the main body portion 11 converges to the distal side D2 of the pusher wire 20, and is formed integrally with the main body portion 11 in the axial direction. The antenna portion 12 has a mesh pattern structure similar to the main body portion 11, but the cells that form the antenna portion 12 are designed not to support the inner wall of the blood vessel when expanded within the blood vessel. The end of the proximal side D1 of the antenna portion 12 is connected to the pusher wire 20 (described below) via a connection portion 30.

[0038] The stent 10, which includes the main body 11 and the antenna 12, is preferably formed from a material that is highly rigid and biocompatible. While not particularly limited, such a material is preferably a material with superelastic properties, such as a nickel-titanium (Ni-Ti) alloy. The stent 10 can be fabricated, for example, by laser processing a substantially cylindrical tube made of the above material.

[0039] The practitioner can advance and retract the stent 10 in a catheter, blood vessel, stenosis site, etc. by pushing and pulling the pusher wire 20 via an ex vivo operating member (not shown) connected to the proximal side D1 of the pusher wire 20.

[0040] The connecting portion 30 is a member that connects the pusher wire 20 and the stent 10. As shown in Fig. 1 , the connecting portion 30 is provided between the distal side D2 of the pusher wire 20 and the proximal side D1 of the stent 10. As will be described later, when the stent 10 is to be left in place without being retrieved from the biological lumen, the connecting portion 30 may be configured to connect the pusher wire 20 and the stent 10 in a separable manner.

[0041] Next, an example of how the stent system 1 including the stent 10 of this embodiment is used will be described. Figures 4A to 4D are schematic diagrams showing the procedure for dilating a stenotic site in a blood vessel using the stent system 1. Here, a procedure for widening a stenotic site CS formed in a blood vessel BV to ensure blood flow will be described. The following procedure is performed by identifying the position of the stent, etc., using a visible marker (radiopaque marker).

[0042] First, as shown in Fig. 4A, a guidewire 40 is passed through the stenosis site CS. A catheter 50 is fitted onto the guidewire 40. Next, as shown in Fig. 4B, the tip of the catheter 50 fitted onto the guidewire 40 is inserted into the stenosis site CS along the passed guidewire 40 and passed through until it reaches the distal side D2 of the stenosis site CS. Next, although not shown, the guidewire 40 is pulled out of the living body and recovered from the catheter 50. Then, the stent system 1 is inserted from the proximal side D1 of the catheter 50. In the stent system 1, the stent 10 is inserted into the catheter 50 in a contracted state.

[0043] Next, as shown in Figure 4C, the stent 10 of the stent system 1 is deployed from the tip of the catheter 50 at the distal side D2 of the stenosis site CS. The tip of the catheter 50 is positioned at the distal side D2 of the stenosis site CS, and the catheter 50 is retracted to the proximal side D1, thereby deploying the stent 10 from the tip of the catheter 50. When the stent 10 is deployed from the tip of the catheter 50, the stent 10 expands by its own expansion force, thereby pushing open the stenosis site CS from the inside. By pushing open the stenosis site CS from the inside with the expanded stent 10, blood flow in the blood vessel BV can be ensured.

[0044] After it is confirmed that blood flow in the blood vessel BV has been secured, the patient is observed for, for example, 5 to 60 minutes. After the observation, as shown in FIG. 4D , the tip of the catheter 50 is advanced to the distal side D2 of the stent 10, and the entire stent 10 is retracted into the catheter 50. This allows the stent 10 and the catheter 50 to be retrieved outside the body.

[0045] The stent 10 of the first embodiment described above exhibits, for example, the following effects. The stent 10 of the first embodiment has different expansive forces in the central portion 11a and the proximal and distal portions 11b and 11c within the effective length VL. Therefore, for example, for a stenosis site CS having a shape as shown in FIG. 4A , by making the expansive force of the central portion 11a of the stent 10 greater than that of the proximal and distal portions 11b and 11c, the stenosis site CS can be more appropriately opened in the central portion 11a. On the other hand, because the expansive force of the proximal and distal portions 11b and 11c of the stent 10 is smaller than that of the central portion 11a, it is possible to prevent a force equivalent to that applied to a region with a high stenosis rate from acting on a normal blood vessel or a region with a low stenosis rate where the proximal and distal portions 11b and 11c, which are both ends of the stent 10, are in contact. This reduces the risk of blood vessel damage or dissection caused by the stent 10. In this way, the stent 10 of the first embodiment can safely and easily dilate the stenotic site appropriately.

[0046] Furthermore, the stent 10 of the first embodiment has a radiopaque coating layer 16 formed within the effective length VL. This configuration provides excellent visibility in X-ray images, allowing for more accurate determination of whether the stent 10 has adequately expanded the stenotic site. Furthermore, the X-ray images can also be used to confirm defects such as excessive localized expansion force within the blood vessel, insufficient opening of the stenotic site, and kinking of the stent 10 placed in a curved blood vessel. Thus, the stent 10 of the first embodiment provides excellent visibility in X-ray images, reducing the risk of vascular damage or dissection, restenosis, re-occlusion, or thrombus formation due to kinking after placement.

[0047] In the stent 10 of the first embodiment, the central portion 11a, the proximal portion 11b, and the distal portion 11c are configured so that the expansion force varies depending on the width of the strut 15. Therefore, for example, when the stent 10 is produced by laser processing a metal tube, it is easy to set the expansion force at each of the central portion 11a, the proximal portion 11b, and the distal portion 11c.

[0048] In the stent 10 of the first embodiment, the coating layer 16 is a gold-plated layer, which provides better visibility in X-ray images. In the stent 10 of the first embodiment, the opening area of ​​each of the cells 13 constituting the central portion 11a, the proximal portion 11b, and the distal portion 11c is formed to be 80 to 120% of the reference opening area (design opening area). Therefore, even if the expansion forces of the central portion 11a, the proximal portion 11b, and the distal portion 11c are different, the stent 10 can be expanded more appropriately.

[0049] Second Embodiment A stent system 1A of a second embodiment differs from the first embodiment in that the expansive force of each portion of the stent 10A is adjusted by the thickness of the coating layer 16. The other configurations of the stent 10A of the second embodiment are the same as those of the first embodiment. Therefore, in the second embodiment, only a cross-sectional view of a strut 15 on which a coating layer 16 is formed is shown, and the stent 10A and stent system 1A are not shown (see FIG. 1). Furthermore, in the description and drawings of the second embodiment, components equivalent to those of the first embodiment are designated by the same reference numerals as those of the first embodiment, and redundant description will be omitted.

[0050] Figure 5A is a view corresponding to the s1-s1 cross-sectional view in Figure 2. Figure 5B is a view corresponding to the s2-s2 and s3-s3 cross-sectional views in Figure 2. Figure 5B is a common cross-sectional view showing the cross-section of struts 15 forming the proximal portion 11b and the cross-section of struts 15 forming the distal portion 11c.

[0051] In the stent 10A of the second embodiment, the width W and thickness T of the struts 15 in the central portion 11a (see FIG. 5A) are the same as the width W and thickness T of the struts 15 in the proximal and distal portions 11b and 11c (see FIG. 5B). That is, the width W and thickness T of the struts 15 forming the main body portion 11 are the same overall. Meanwhile, the thickness t1 (see FIG. 5A) of the coating layer 16 formed on the struts 15 in the central portion 11a is configured to be greater than the thickness t2 (see FIG. 5B) of the coating layer 16 formed on the struts 15 in the proximal and distal portions 11b and 11c. In other words, the thickness t2 of the coating layer 16 at the proximal and distal portions 11b and 11c, which are both ends, is smaller than the thickness t1 of the central portion 11a. The thicknesses t1 and t2 of the coating layer 16 are not particularly limited, but are preferably, for example, approximately 1 to 10% of the thickness T of the struts 15. The thickness ratio t1 / t2 is preferably, for example, about 1.0 to 3.0 The material and method for forming the coating layer 16 may be the same as those in the first embodiment.

[0052] In Figures 5A and 5B, the thicknesses t1 and t2 of the coating layer 16 are the same around the outer periphery (four sides) of the strut 15. However, the thicknesses t1 and t2 of the coating layer 16 may be partially different in the central portion 11a, proximal portion 11b, and distal portion 11c as long as the designed expansive force can be obtained. For example, in the strut 15 shown in Figure 5A, the thickness of the coating layer 16 formed on the sides corresponding to the side surfaces (sides positioned horizontally in the figure) may be thinner than the thickness of the coating layer 16 formed on the other sides (sides positioned vertically in the figure). Note that in Figures 5A and 5B, the thicknesses t1 and t2 of the coating layer 16 are exaggerated relative to the cross section of the strut 15. However, it is desirable to set the thicknesses t1 and t2 of the coating layer 16 within a range of approximately 10 to 20% of the thickness T of the strut 15. Setting the thickness of the coating layer 16 to approximately 10 to 20% of the thickness of the strut 15 facilitates insertion into a small-diameter catheter. Furthermore, it is possible to prevent a decrease in operability when advancing and retracting the stent 10 inside the catheter.

[0053] The stent 10A of the second embodiment described above also has the same functions and actions as the stent 10 of the first embodiment, and therefore can safely and easily dilate the stenotic site. Furthermore, because the stent 10A has excellent visibility in X-ray images, it is possible to more accurately determine in the X-ray images whether the stenotic site has been appropriately dilated by the stent 10A.

[0054] In the stent 10A of the second embodiment, the central portion 11a, the proximal portion 11b, and the distal portion 11c are configured so that their expansion forces differ depending on the thickness of the coating layer 16. This configuration makes it easier to set the expansion force than the configuration of the first embodiment, in which the expansion force is set by adjusting the width of the struts 15. Furthermore, because the coating layer 16 is a plated layer of a radiopaque metal, thickness control can be performed more easily and simply.

[0055] (Third Embodiment) A stent system 1B of the third embodiment differs from the first and second embodiments in that a stent 10B has a two-layer structure. The other configurations of the stent 10B of the third embodiment are the same as those of the first or second embodiment. Therefore, in the third embodiment, only the stent system 1B is illustrated, and the first stent body 101 and the second stent body 102 (described later) that constitute the stent 10B are not illustrated individually. Furthermore, in the description and drawings of the first embodiment, the same reference numerals as in the first embodiment are used for components, parts, etc. that are equivalent to those of the first embodiment, and redundant description will be omitted.

[0056] FIG. 6 is a side view of a stent system 1B according to the third embodiment. Like FIG. 1 of the first embodiment, FIG. 6 is a side view of a stent 10B in its natural state. As shown in FIG. 6 , the stent system 1B includes a stent 10B, a pusher wire 20, and a connecting portion 30. The stent 10B includes a main body portion 11 having a two-layer structure and an antenna portion 12. The main body portion 11 having a two-layer structure is composed of a first main body portion (first cylindrical portion) 111 of a first stent main body 101 (described below) and a second main body portion (second cylindrical portion) 112 of a second stent main body 102 (described below). The antenna portion 12 having a two-layer structure is composed of a first antenna portion 121 of the first stent main body 101 and a second antenna portion 122 of the second stent main body 102.

[0057] The stent 10B has a substantially cylindrical structure and includes a first stent body 101 and a second stent body 102. In Fig. 6, to easily distinguish between the first stent body 101 and the second stent body 102, the first stent body 101 is shown with a black background and the second stent body 102 is shown with a black frame. The stent 10B of the third embodiment is a stent with a double-layer structure in which the second stent body 102 is inserted into the first stent body 101.

[0058] The first stent body 101 and the second stent body 102 are not connected to each other in the radial direction RD. More specifically, the proximal side D1 ends of the first stent body 101 and the second stent body 102 are indirectly connected to the pusher wire 20 via the connecting portion 30, but are not connected in any other portion. Therefore, the first stent body 101 and the second stent body 102 can flexibly deform independently in the radial direction RD.

[0059] The stent 10B of the third embodiment is produced by inserting a second stent body 102, which has a larger outer diameter than the first stent body 101 in its natural state, into the first stent body 101 in a contracted state. As a result, the second stent body 102 constantly presses the first stent body 101 outward in the radial direction RD. "Constantly pressing" means that the stent 10B is constantly pressing not only in its contracted state but also in its expanded state. This results in stronger adhesion between the first stent body 101 and the second stent body 102.

[0060] 6 , in a stent 10B of the third embodiment, a first stent body 101 includes a first body portion 111 and a first antenna portion 121. In the first stent body 101, the first body portion 111 includes a central portion 111a, a proximal portion 111b, and a distal portion 111c. The second stent body 102 includes a second body portion 112 and a second antenna portion 122. In the second stent body 102, the second body portion 112 includes a central portion 112a, a proximal portion 112b, and a distal portion 112c.

[0061] 6, the central portion 111a, proximal portion 111b, and distal portion 111c of the first stent body 101 and the central portion 112a, proximal portion 112b, and distal portion 112c of the second stent body 102 are provided at the same positions in the axial direction LD of the stent 10B. In the first stent body 101 and the second stent body 102, the positions and ranges of the above-mentioned respective portions may be the same as shown in FIG. 6, or may be different in the axial direction LD.

[0062] In the stent 10B of the third embodiment, the central portion 11a, the proximal portion 11b, and the distal portion 11c also have different expansive forces. Specifically, the expansive force of the central portion 11a of the stent 10B is configured to be greater than the expansive forces of the proximal portion 11b and the distal portion 11c. The expansive force of the central portion 11a of the stent 10B is set from the expansive force of the central portion 111a of the first stent body 101 and the expansive force of the central portion 112a of the second stent body 102. The expansive force of the proximal portion 11b of the stent 10B is set from the expansive force of the proximal portion 111b of the first stent body 101 and the expansive force of the proximal portion 112b of the second stent body 102. Furthermore, the expansion force of the distal portion 11 c of the stent 10 B is set by the expansion force of the distal portion 111 c of the first stent body 101 and the expansion force of the distal portion 112 c of the second stent body 102 .

[0063] In the stent 10B of the third embodiment, the configuration of the stent 10 shown in the first embodiment or the configuration of the stent 10A shown in the second embodiment can be applied as a configuration for making the expansive force of the central portion 11a greater than the expansive force of the proximal portion 11b and the distal portion 11c. That is, as in the stent 10 of the first embodiment, the expansive force may be adjusted by changing the width of the struts 15 in the central portion 11a (111a, 112a), the proximal portion 11b (111b, 112b), and the distal portion 11c (111c, 112c), or as in the stent 10A of the second embodiment, the expansive force may be adjusted by changing the thickness of the coating layer 16 in the central portion 11a (111a, 112a), the proximal portion 11b (111b, 112b), and the distal portion 11c (111c, 112c).

[0064] In the stent 10B of the third embodiment, the expansion force of each of the central portion 111a, proximal portion 111b, and distal portion 111c of the first stent body 101 may be adjusted by changing the width of the struts 15, and the expansion force of each of the central portion 112a, proximal portion 112b, and distal portion 112c of the second stent body 102 may be adjusted by changing the thickness of the struts 15. Furthermore, the expansion force of the central portion 111a, proximal portion 111b, and distal portion 111c of the first stent body 101 may be adjusted by changing the thickness of the struts 15, and the expansion force of the central portion 112a, proximal portion 112b, and distal portion 112c of the second stent body 102 may be adjusted by changing the width of the struts 15.

[0065] In the stent 10B of the third embodiment, the above-described configuration for adjusting the expansive force of the central portion 11a, proximal portion 11b, and distal portion 11c may be applied only to the central portion 111a, proximal portion 111b, and distal portion 111c of the first stent body 101, or may be applied only to the central portion 112a, proximal portion 112b, and distal portion 112c of the second stent body 102. In the stent 10B of the third embodiment, as a configuration for adjusting the expansive force of the central portion 11a, proximal portion 11b, and distal portion 11c, the configuration of the stent 10 shown in the first embodiment may be applied to the first stent body 101, and the configuration of the stent 10A shown in the second embodiment may be applied to the second stent body 102. Alternatively, the configuration of the stent 10A shown in the second embodiment may be applied to the first stent body 101, and the configuration of the stent 10 shown in the first embodiment may be applied to the second stent body 102.

[0066] The stent 10B of the third embodiment described above also exhibits the same functions and actions as the stent 10 of the first embodiment, allowing for safe and easy appropriate dilation of the stenotic site. Furthermore, because the stent 10B has excellent visibility in X-ray radiographic images, it is possible to more accurately determine in X-ray radiographic images whether the stent 10B has appropriately dilated the stenotic site. Because the stent 10B of the third embodiment has a double-layer structure, the mesh pattern density is higher than that of a stent with a single-layer structure, allowing for a larger stent surface area. Therefore, the stent 10B of the third embodiment can more appropriately dilate the stenotic site, normal blood vessels, and areas with a low stenosis rate.

[0067] In the stent 10B of the third embodiment, the first stent body 101 and the second stent body 102 are not connected to each other. This allows the first stent body 101 and the second stent body 102 to deform independently in the radial direction, thereby improving the flexibility of the stent as a whole. The stent 10B of the third embodiment has excellent surface area and shape conformability to the vascular structure.

[0068] In the stent 10B of the third embodiment, the first stent body 101 and the second stent body 102 can be deformed independently in the radial direction, allowing the struts of each body to be reduced in diameter without interfering with each other. The stent 10B of the third embodiment has an excellent balance between surface area and ease of storage in a small-diameter catheter. Therefore, the stent 10B of the third embodiment has an excellent balance between surface area, ability to conform to the shape of the vascular structure, and ability to reduce in diameter.

[0069] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications and variations, such as those described below, are possible, and are also within the technical scope of the present invention. Furthermore, the effects described in the embodiments are merely a list of the most preferable effects resulting from the present invention, and are not limited to those described in the embodiments. Note that the above-described embodiments and the modifications described below can also be used in appropriate combinations, but detailed description thereof will be omitted.

[0070] (Modifications) In the stent 10 of the first embodiment, the width of the struts 15 constituting the main body portion 11 may be varied continuously in the axial direction. For example, in FIG. 2, the width of the struts 15 located near the boundary between the central portion 11a and the proximal portion 11b may be set to a width approximately midway between the width (predetermined value) of the struts 15 in the central portion 11a and the width (predetermined value) of the struts 15 in the proximal portion 11b. The same applies to the width of the struts 15 located near the boundary between the central portion 11a and the distal portion 11c. The above-described variation in the width of the struts 15 may be made more subtle. With this configuration, an expansion force appropriate for the thickness of the stenotic portion can be obtained in a shape in which the thickness of the stenotic portion gradually slopes from the central portion 11a to both ends.

[0071] In the stent 10 of the first embodiment, the thickness of the coating layer 16 formed on the main body portion 11 may be continuously varied in the axial direction. For example, in FIG. 2, the thickness of the coating layer 16 formed near the boundary between the central portion 11a and the proximal portion 11b may be set to a thickness approximately midway between the thickness (predetermined value) of the coating layer 16 formed in the central portion 11a and the thickness (predetermined value) of the coating layer 16 formed in the proximal portion 11b. The same applies to the thickness of the coating layer 16 formed near the boundary between the central portion 11a and the distal portion 11c. The thickness of the coating layer 16 may be varied more finely. In this configuration, too, a shape in which the thickness of the stenotic portion gradually slopes from the central portion 11a toward both ends can provide an expansion force appropriate for the thickness of the stenotic portion.

[0072] In the stent 10 (10A, 10B), the expansion forces of the central portion 11a, the proximal portion 11b, and the distal portion 11c can be set appropriately depending on the thickness, stenosis rate, shape, etc. of the stenotic site. For example, the expansion force of either the proximal portion 11b or the distal portion 11c may be set smaller than the expansion force of the central portion 11a, or the expansion force of the central portion 11a may be set smaller than the expansion force of the proximal portion 11b and / or the distal portion 11c. In addition, the expansion forces of the central portion 11a, the proximal portion 11b, and the distal portion 11c can be combined appropriately.

[0073] In the stent 10A of the second embodiment, an intermediate layer for adjusting the expansive force may be formed (laminated) between the struts 15 and the coating layer 16. For example, by making the thickness of the intermediate layer formed on the struts 15 in the central portion 11a thicker than the thickness of the intermediate layer formed on the struts 15 in the proximal portion 11b and the distal portion 11c, it is possible to configure the central portion 11a to have a different expansive force from the proximal portion 11b and the distal portion 11c. A metal material is preferable as the material for forming the intermediate layer, and for example, the material used to form the stent 10 described above can be used. The thickness of the coating layer 16 formed on the surface of the intermediate layer may be uniform in the central portion 11a, the proximal portion 11b, and the distal portion 11c, or may vary depending on the thickness of the intermediate layer.

[0074] The stent 10 (10A, 10B) is used in applications where it is temporarily placed in a blood vessel and then retrieved outside the body, but it can also be used in applications where the stent 10 (10A, 10B) is left in the blood vessel without being retrieved from the body. When used in such applications, for example, the connection portion 30 may be formed of a heater coil, filament, or the like, and configured to be cut (melted) when electricity is applied to the pusher wire 20. Alternatively, the connection portion 30 may be configured to be mechanically cut when a rotational force is applied to the pusher wire 20 in the circumferential direction. The connection portion 30 is not limited to the above example, and may have any configuration as long as the pusher wire 20 and the stent 10 can be separated by an operation by a practitioner.

[0075] DESCRIPTION OF SYMBOLS 1, 1A, 1B Stent system 10, 10A, 10B Stent 11 Main body portion 11a, 111a, 112a Central portion 11b, 111b, 112b Proximal portion 11c, 111c, 112c Distal portion 12 Antenna portion 13 Cell 15 Strut 16 Coating layer 20 Pusher wire 30 Connection portion 50 Catheter 101 First stent body 102 Second stent body 111 First main body portion 112 Second main body portion

Claims

1. A stent having a self-expanding cylindrical shape for use in expanding a stenotic portion of a biological lumen, wherein the cylindrical shape has a mesh pattern structure composed of a plurality of struts, an X-ray impermeable coating layer is formed in the range of the effective length of the cylindrical shape, and the stent has different expansion forces at the central portion and both end portions in the range of the effective length.

2. The stent according to claim 1, wherein the expansion force of the cylindrical shape is smaller at both end portions than at the central portion.

3. The stent according to claim 2, wherein the thickness of the coating layer is smaller at both end portions than at the central portion.

4. The stent according to claim 3, wherein the thickness of the coating layer continuously changes between the central portion and both end portions.

5. The stent according to claim 2, wherein the width of the strut is narrower at both end portions than at the central portion.

6. The stent according to claim 5, wherein the width of the strut continuously changes between the central portion and both end portions.

7. The stent according to any one of claims 1 to 6, wherein the strut is made of a superelastic material having a shape memory function at a temperature equal to or higher than a transformation point.

8. The stent according to any one of claims 1 to 6, wherein the coating layer is an X-ray impermeable metal plating layer.

9. The stent according to claim 8, wherein the metal plating layer is a gold plating layer.

10. The stent according to any one of claims 1 to 6, wherein the opening area of the cell forming the mesh pattern structure is 80 to 120% of the reference opening area.

11. A stent having a self-expanding cylindrical shape for use in expanding a stenotic portion of a biological lumen, wherein the cylindrical shape includes a first cylindrical shape having a mesh pattern structure composed of a plurality of struts and a second cylindrical shape having a mesh pattern structure composed of a plurality of struts and inserted into the first cylindrical shape, an X-ray impermeable coating layer is formed in the range of the effective length of the first cylindrical shape and / or the second cylindrical shape, and the first cylindrical shape and / or the second cylindrical shape have different expansion forces at the central portion and both end portions in the range of the effective length.

12. The stent according to any one of claims 1 to 6 or 11, which is used for a purpose of being retrieved outside the body after being temporarily placed in a living body lumen.

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