JP2005342105A - Stent - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a stent occluding aneurysms easily. <P>SOLUTION: The stent 3 comprises a first annular structure 1 and a second annular structure 2 branching off in the middle of the structure 1 in the longitudinal direction. The structure 1 is formed of a main body 10 of the stent and a polymer layer 12. The upstream side 1a of the structure 1 is placed in an upstream area of a branching part of a blood vessel, and the downstream side 1b of the structure 1 is placed in one blood vessel in a downstream area of the branching part of the blood vessel. The structure 2 is placed in the other blood vessel. An area near an intersecting corner 4 where the down stream side 1b of the structure 1 and the structure 2 cross occludes the aneurysm. The polymer layer makes close contact with the entire outer surface of the main body of the stent and covers it. Since the soft polymer layer makes close contact with and covers not only the outer peripheral surface of the main body of the stent but also the entire outer surface, the stent is free from problems such as metal allergy, stimulations of cells by a metal, and rust. Moreover, since the inner peripheral surface of the stent is a smooth surface covered with the polymer layer, the formation of thrombi is sufficiently prevented. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a stent (intraluminal graft) which is placed in a blood vessel and used for occlusion of an aneurysm or the like. Specifically, the present invention relates to a stent placed in the vicinity of a blood vessel bifurcation.

  Aneurysms are still a representative example of serious vascular diseases that have developed clinical medicine. Most aneurysms occur when the crotch portion of the blood vessel bifurcation is overloaded and torn, but once aneurysms do not shrink naturally, in many cases about 5% to 10% per year It has been reported to grow.

  There is a correlation between the diameter of the aneurysm and the risk of rupture, and when the diameter is 5 cm to 6 cm, the risk of rupture is high, and the success rate of emergency surgery in case of rupture is as low as 50% even in specialized emergency hospitals, It is very important to treat aneurysms before rupture.

  On the other hand, a method for medically treating an aneurysm, such as medication, has not been established, and is generally treated surgically. These surgical treatment methods include artificial blood vessel replacement for the abdomen and thoracic aorta, and occlusion with a platinum clip for intracranial blood vessels.

  In recent years, embolization with a coil has been developed as a percutaneous transluminal therapy.

  However, surgical operations such as artificial blood vessel replacement and occlusion with a platinum clip are all very invasive with laparotomy, thoracotomy, and cranial perforation. Furthermore, in the case of an abdominal aortic aneurysm, there are many cases that can be performed relatively safely and have good results. Sometimes used together. In addition, it may cause surgical complications such as heart failure, pneumonia, renal failure, cerebral infarction, etc., or when the site of occurrence is beyond the diaphragm, it may be accompanied by operations that cut blood vessels that feed the spinal cord or stop blood flow There are also cases in which sequelae such as inferior lower body due to spinal cord injury remain.

  Recently developed aneurysm occlusion with a coil has attracted attention as a percutaneous transluminal minimally invasive therapy, but if the opening of the aneurysm is large, the coil may be exposed to the blood vessel. When is large, it has a problem that it is difficult to fill with a coil, and it is not always perfect.

  On the other hand, as a percutaneous transluminal minimally invasive therapy, aneurysm closure treatment by stent graft is being studied in many medical facilities.

  A stent is an intraluminal graft that is carried through a lumen such as a blood vessel and supported by action from the inside by expanding its diameter at the treatment site of the lumen. Since metal stents have thrombogenicity, when exposed to blood, they contact plasma proteins such as albumin and fibrinogen and aggregate due to platelet adhesion. There are also indications that placing a metal stent body promotes thickening of the intima and causes restenosis. Japanese Patent Application Laid-Open No. 11-299901 describes that the outer peripheral surface of a metal stent body is covered with a flexible polymer film having fine holes.

  FIG. 3 is a perspective view showing a mesh-shaped metal stent main body 10 used in such a stent, and FIG. 4 is a perspective view showing a state 10 ′ in which the diameter of the stent main body 10 of FIG. 3 is expanded. . FIG. 5 is a perspective view showing a stent 20 in which the outer peripheral surface of the stent main body 10 is covered with a flexible polymer film 19 having fine holes, and FIG. 6 shows a state in which the stent 20 is expanded. It is a perspective view.

  In living tissue, inner surfaces such as blood vessels, that is, portions that come into contact with blood are covered with a cell layer called endothelial cells. These endothelial cells have thrombomodulin, a membrane protein with anticoagulant and fibrinolysis-promoting effects on their surface, and the endothelial cells themselves secrete substances that suppress platelet activation, such as prostaglandins. Therefore, thrombus and the like hardly occur in living tissue. In the stent disclosed in JP-A-11-299901, by coating the outer peripheral surface of a metal stent body with a polymer film, it is possible to promote moderate cell endothelialization and reduce thrombosis.

In JP-A-11-299901, the polymer film covering the outer peripheral surface of the stent body is formed as follows. That is, first, a cover strip mandrill is impregnated with a polymer solution, dried and perforated, and then the mandrill is removed to form a thin film cover strip (bag-shaped cover film). Gas is fed into the bag-shaped cover film, the stent body is inserted into the bag-shaped cover film with the cover film fully opened, and then the air blowing is stopped to shrink the cover film. By doing so, an outer film of the polymer film is formed on the outer peripheral surface of the stent body.
JP 11-299901 A

  In a straight blood vessel, it is expected to be a very good treatment because an aneurysm can be reliably closed with a single device. However, many aneurysms occur in the crotch region at the bifurcation. There are many cases where stent graft therapy, which is limited to vascular sites, cannot be applied.

  An object of the present invention is to provide a stent used for minimally invasive therapy of an aneurysm that has occurred in a crotch portion where a blood vessel branches.

  In the above-mentioned stent of JP-A-11-299901, the inner peripheral surface of the stent body is not covered with the polymer film, and the metal stent main body remains exposed. There are problems of thrombus generation, metal allergy, cell irritation by metal, and rust generation. In particular, since the stent struts constituting the mesh-shaped stent main body project as convex ridges on the inner peripheral surface of the stent, the blood flow is disturbed and thrombus tends to occur. The thrombus that has occurred peels off and flies downstream (flows along the bloodstream to the peripheral side) to infarction of the small blood vessels on the downstream side, or platelet-derived growth factor released from platelets in the thrombus, etc. Since this stimulates vascular cells to cause thickening of the intima, the problem of thrombus formation in this area is significant.

  Moreover, simply inserting the stent body into the bag-shaped cover film and simply shrinking the bag-shaped cover film to form an outer film of the polymer film on the outer peripheral surface of the stent body has the following problems. That is, as shown in FIGS. 2 and 3, the stent body 10 used in Japanese Patent Application Laid-Open No. 11-299901 has an oblique grid-like mesh shape. When the outer film of the polymer film was formed, this outer film was fixed at the contact portion to each of the stent struts 11 constituting the mesh stent main body on the outer peripheral surface of the mesh stent main body as shown in FIG. Therefore, the integrity of the polymer film 19 and the stent body is low.

  For this reason, when the diameter of the stent body is expanded, the contact portion between the stent strut 11 and the polymer film 19 slides. That is, the position of the polymer film 19 covering the outer peripheral surface of the stent body is shifted when the stent is expanded.

  In Japanese Patent Application Laid-Open No. 11-299901, fine holes are arranged in the polymer film 19 at substantially uniform intervals. Since the micropores are perforated for the purpose of suppressing the generation of thrombus and the thickening of the intima by engrafting endothelial cells on the stent inner wall, it is thought that the micropores are perforated avoiding the position directly above the stent skeleton, If the position of the polymer film with respect to the stent body shifts when the stent is expanded as described above, the micropores may be blocked by the stent struts. It will be a thing.

  JP-A-11-299901 also describes that this polymer film is coated with a biodegradable polymer or drug. When such a functional agent is coated on the inner peripheral surface of the stent body, Although the coating layer of the functional agent is not formed on the portion of the inner peripheral surface of the polymer film where the struts of the mesh-shaped stent body are present, the position of the polymer film is shifted with respect to the stent body when the stent is expanded. As a result, the surface on which the functional agent is not coated is exposed, and this coating is also meaningless.

  In paragraph [0040] of JP-A-11-299901, when the stent body is covered with a cover strip, a heated gas is sent to ensure close contact with the outer periphery of the stent body 10 by thermal fusion. Although there is a statement that the contact point between the polymer film 19 and the stent strut 11 constituting the mesh-shaped stent body is increased by this operation, the stent strut 11 is planarized with the polymer film 19. It cannot be coated. In general, since the stent body is made by laser processing of a metal tube, the sharp edge of the cut stent strut portion is rounded by chemical polishing and sonic treatment, and the surface of the stent body itself is often mirror-finished. Just as it is difficult to bond a resin material to a smooth surface metal material, it is not easy to bond the stent body and the polymer film. In order to coat the stent strut 11 in a planar shape with the polymer film 19 and further improve the adhesion by the polymer film 19, it is necessary to melt the cover strip even momentarily and press it against the stent body. In order to achieve this, it is necessary to feed a considerably high temperature gas, while the cover strip is a thin film having fine pores, and a high temperature gas that melts the polymer film is fed to the polymer. The film cannot maintain its shape, leading to the occurrence of defects such as rupture, breakage, pinholes and cracks.

  In one aspect, the present invention eliminates the drawbacks of the stent disclosed in JP-A-11-299901, and more reliably prevents thrombus generation by covering the stent body with a polymer layer with good adhesion. In addition, an object of the present invention is to provide a stent in which the problem of displacement between the stent body and the covering layer is also solved.

  The stent of the present invention has a first annular structure having a tubular stent body that can be expanded and a flexible polymer layer that covers the stent body, and branches in the form of branches from the middle of the first annular structure. And at least a second annular structure made of a polymer having a flexible surface.

  In the stent of the present invention, the second annular structure is branched from the side surface of the first annular structure, and is placed in the vicinity of the branch portion of the blood vessel. In general, when a blood vessel branches into two hands, an aneurysm tends to occur at the branching crotch portion. In the stent of the present invention, the upstream side of the branch portion of the first annular structure is placed in the upstream region of the branch portion of the blood vessel. The first annular structure is detained in one of the blood vessel downstream areas branched downstream from the branch portion, and the second annular structure is detained in the other of the branched blood vessel downstream areas. By placing the stent of the present invention in the vicinity of such a blood vessel bifurcation, an aneurysm generated in the blood vessel crotch portion can be occluded.

  The first annular structure of the stent of the present invention preferably has an expandable tubular stent body and a flexible polymer layer covering the stent body, the polymer layer being entirely outside the stent body. It is in close contact with the surface and covers it. In this aspect of the stent, not only the outer peripheral surface of the stent body but also the entire outer surface thereof is covered with a flexible polymer layer so that there is no problem of metal allergy, metal irritation, and rust generation. Moreover, since the inner peripheral surface of the stent is a smooth surface covered with a polymer layer and there is no protruding protrusion of the stent base material, thrombus generation can be sufficiently suppressed without disturbing blood flow. Further, there is no problem of displacement between the stent body and the polymer layer at the time of stent expansion, and the positional relationship between the stent body and the polymer layer is maintained before and after expansion.

  Hereinafter, embodiments will be described with reference to the drawings.

  FIG. 1A is a perspective view of a stent 3 according to the embodiment, and FIG. 1B is a cross-sectional view in the longitudinal direction of the stent. FIG. 2 is an enlarged view in the vicinity of II of the first annular structure of FIG.

  The stent 3 includes a first annular structure 1 and a second annular structure 2 branched from the middle of the first annular structure 1 in the longitudinal direction. The first annular structure 1 includes a stent body 10 and a polymer layer 12. The stent body 10 has a cylindrical shape made of a mesh whose diameter can be expanded as shown in FIG. The polymer layer 12 is in close contact with and covers the entire outer surface of the stent body 10.

  The stent 3 has a main stent body 10 on one end side (left end side in the figure, hereinafter sometimes referred to as an upstream side) 1a from a branch portion between the first annular structure 1 and the second annular structure 2. Has been placed. The other part of the stent 3 consists of a polymer only. The second annular structure 2 is arranged such that the first annular structure 1 is inclined to the other end side (the right end side in the figure, hereinafter referred to as the downstream side) 1b side from the branch portion of the first annular structure 1. The ring structure 1 is crossed. The second annular structure 2 communicates with the first annular structure 1.

  The first annular structure 1 and the second annular structure 2 may have the same or different diameters.

  In this stent 3, the first annular structure 1 has a straight tube shape and is shaped like a toroid. However, the downstream side 1 b and the second annular structure body with respect to the upstream side 1 a of the first annular structure 1. Each of 2 may be a Y-shape that is oblique.

  The stent 3 is placed in the vicinity of the branch portion of the blood vessel. In this case, the upstream side 1a of the first annular structure 1 is placed in the upstream region from the branch portion of the blood vessel, and the downstream side of the first annular structure 1 is placed in one blood vessel in the downstream region from the branch portion. 1b is placed, and the second annular structure 2 is placed in the other blood vessel.

  An aneurysm is likely to occur at the crossing corner of the two downstream blood vessels (ie, the crotch portion sandwiched between the two downstream blood vessels).

  The stent 3 is placed in the blood vessel so that the vicinity of the crossing corner 4 between the downstream side 1b of the first annular structure 1 and the second annular structure 2 closes the aneurysm.

  In order to place the stent 3 in the blood vessel, the upstream side 1a is arranged in the upstream region from the branching portion of the blood vessel, and then the stent body 10 is expanded in diameter, and the outer peripheral surface of the upstream side 1a and the inner peripheral surface of the blood vessel To fix the upstream side 1a.

  A balloon may be used to expand the diameter of the stent body 10. When the stent body 10 is made of a shape memory material, the stent body 10 may be inserted into a blood vessel, and the diameter may be increased by raising the temperature according to body temperature.

  After fixing the upstream side 1a of the first annular structure 1 to the upstream region of the blood vessel, the downstream side 1b and the second annular structure 2 may be guided to each downstream region where the blood vessel branches, the upstream side 1a, After the downstream side 1b and the second annular structure 2 are arranged in the upstream area in the vicinity of the blood vessel branching portion and the predetermined positions in the respective downstream areas, the stent body 10 may be expanded in diameter.

  In the downstream region from the branch portion of the blood vessel, a straight tubular stent different from the stent of the present invention is inserted into the downstream side 1b and the second annular structure 2, and each annular structure is formed by the straight tubular stent. The ends of 1 and 2 may be fixed. Instead of using such a separate straight tubular stent, the end of each annular structure 1, 2 is provided with a stent body similar to the stent body 10, and the stent body is expanded to expand the annular structure 1, The two end portions may be fixed.

  The stent body is preferably a tube having a length of about 2 to 40 mm and a diameter of about 1/10 to 1/2 of the length. Further, the thickness of the stent body (thickness of the tubular portion) is preferably 11 to 2000 μm, more preferably 51 to 500 μm, and particularly preferably 101 to 300 μm. The stent body is preferably in the form of a mesh so that the diameter of the stent can be expanded flexibly, and in particular, the stent body 10 having an oblique lattice shape as shown in FIG.

  The stent body is preferably made of a biocompatible metal. Examples of the biocompatible metal include stainless steel, titanium, tantalum, aluminum, tungsten, nickel / titanium alloy, cobalt / chromium / nickel / iron alloy, and the like. The metal stent body is preferably subjected to heat treatment in order to memorize the shape. By this heat treatment, self-expandability can be imparted to the stent body.

  The stent body may be disposed only in the first annular structure 1 as illustrated in FIG. 1, and may be disposed in both the first annular structure 2 and the second annular structure 2, although not illustrated. . When the stent body is provided only on the first annular structure, the stent body may be provided on the entire first annular structure (excluding the communication portion to the second annular structure). The stent body may be provided only in the portion.

  When the stent body is provided only in a part of the first annular structure like the latter, as shown in FIG. 1, by providing the stent body 10 on the upstream side 1a from the branch portion of the first annular structure 1, By expanding the diameter of the stent body 10, the outer peripheral surface of the upstream side 1a and the inner peripheral surface of the blood vessel can be brought into close contact with each other.

  In the case where the stent body is disposed entirely within the first annular structure, a plurality of stent bodies are disposed at intervals in the longitudinal direction within the first annular structure in order to increase the flexibility of the stent. Is preferred.

  The stent body may be disposed in both the first annular structure 1 and the second annular structure 2, in which case the stent body in the first annular structure and the stent body in the second annular structure. May be continuous or may be divided.

  These stent bodies are also expanded in diameter after the stent is inserted into the blood vessel.

  In the stent of the present invention, a radiopaque substance may be disposed on the whole or a part of the stent, thereby making it easy to detect the position of the stent by X-ray during endovascular therapy. It becomes.

  The radiopaque material may be disposed in the vicinity of a portion where the second annular structure branches from the first annular structure, whereby the crotch portion of the blood vessel having an aneurysm, the branch portion of the stent, It is easy for the surgeon to adjust the position of the stent so that they match. The same effect can be expected even if the radiopaque substance is disposed only in the second tubular structure.

  Examples of the radiopaque substance include metal salts such as barium sulfate, metal powders such as silver and tungsten, iodine compounds such as iodoxamic acid, metrizoic acid, iodamide, and iodinated fatty acid alkyl ester.

  Although illustration is omitted, in the stent of the present invention, a portion other than the stent body may be formed of a cylindrical body and a polymer that covers the cylindrical body. This polymer constitutes the surface of the annular structure. By disposing this cylindrical body, the stent is given a firmness (waist), and the stent is easily guided to a target position in the blood vessel. This cylindrical body is preferably made of metal, and in particular, a braided metal thin wire (for example, a mesh cylinder) is preferable. This cylindrical body is preferably made of nickel / titanium alloy, cobalt / chromium / nickel / iron alloy or the like in order to memorize the shape. Self-expanding can be imparted to the stent by heat-treating the cylindrical body and storing the shape.

  In the stent of the present invention, as the material used as the flexible polymer layer, a high-flexibility polymer elastomer is suitable. For example, polystyrene, polyolefin, polyester, polyamide, silicone, urethane, fluororesin In addition, various elastomers such as natural rubber and copolymers thereof or polymer alloys thereof can be used. Among them, segmented polyurethane, polyolefin polymer, and silicone polymer are preferable. Particularly, segmented polyurethane having high flexibility and high strength is optimal.

  A segmented polyurethane polymer has a flexible polyether portion as a soft segment and a portion rich in aromatic rings and urethane bonds as a hard segment, and the soft segment and the hard segment are phase-separated to form a fine structure. It is what. This segmented polyurethane polymer is excellent in antithrombotic properties. Moreover, it is excellent in properties such as strength and elongation, and can be sufficiently expanded without breaking even when the stent is expanded in diameter.

  The coating thickness of the polymer layer such as the segmented polyurethane polymer (d in FIG. 1 described later) preferably has a thickness of 1 μm to 100 μm, particularly 5 μm to 50 μm.

  This polymer layer is preferably provided with a plurality of micropores. The fine holes may be randomly arranged, but preferably the fine holes are perforated at substantially uniform intervals. The fact that the micropores are perforated at a substantially uniform interval does not mean that the intervals are the same, but that the micropores are arranged at a substantially constant interval by a controlled method. Accordingly, the substantially uniform interval includes diagonal, circular, and elliptical arrangements that appear to be randomly arranged at first glance. The micropore may have any size and shape as long as the endothelial cells can enter and exit. Preferably, it is a circle having a diameter of 5 to 500 μm, most preferably 10 to 100 μm. Needless to say, other shapes such as an ellipse, a square, and a rectangle are also included. These are the states before expansion, and when the stent body is expanded and placed in the lumen, the circle is deformed into an oval shape, and the diameter changes accordingly. Moreover, as an arrangement | positioning space | interval of a micropore, it arrange | positions on a some straight line by the space | interval of 51-10000 micrometers, Preferably 101-8000 micrometers, More preferably, 201-5000 micrometers. The plurality of straight lines include, for example, 10 to 50 straight lines arranged at a predetermined constant angular interval in the axial direction of the stent.

  The polymer layer may be coated with a biodegradable polymer (bioabsorbable polymer). Examples of such biodegradable polymers include gelatin, polylactic acid, polyglycolic acid, caprolactone, lactic acid-glycolic acid copolymer, polygioxanone, and chitin.

  The biodegradable polymer may contain a therapeutic agent such as an antiplatelet agent, an antithrombotic agent, a growth promoter, a growth inhibitor, or an immunosuppressant. This therapeutic agent is released into the body as the biodegradable polymer degrades, suppressing the formation of thrombus, preventing the proliferation of smooth muscle cells to prevent stenosis, and the growth of cancerous cells. It is effective in suppressing or promoting endothelial cell proliferation and obtaining endothelialization at an early stage.

  This treatment includes heparin, low molecular weight heparin, hirudin, argatroban, formacholine, bapiprost, prostamorin, prostakyrin congeners, dextran, lofepro-algchloromethylketone, dipyridamole, glycoprotein platelet membrane receptor antibody, combination Reversible hirudin, thrombin inhibitor, vascular peptin, vascular tensin converting enzyme inhibitor, steroid, fibroblast growth factor antagonist, fish oil, omega-3 fatty acid, histamine, antagonist, HMG-CoA reductase inhibitor, ceramine, Examples include serotonin blocking antibodies, thioprotein inhibitors, trimazole pyridimine, interferon, vascular endothelial growth factor (VEGF), rapamycin, FK506, and the like.

  Further, the polymer layer on the outer peripheral surface side of the stent may be coated with a lubricious substance on the outer surface in order to smoothly move the fine blood vessel in the human body. Such lubricating substances include low molecular weight hydrophilic substances such as glycerin, biocompatible substances such as hyaluronic acid and gelatin, synthetic hydrophilic polymers such as polyethylene glycol, polyacrylamide, polydimethylacrylamide, and polyvinylpyrrolidone. Can be mentioned.

  The stent of the present invention in which the entire outer surface of the stent body is closely adhered and coated with the polymer layer can be manufactured, for example, by the following method, but the manufacturing method of the stent body is not limited to the following method.

  First, a mandrill having a G shape or a Y shape is prepared by detachably connecting two straight bars. The mandrill is slowly immersed in a polymer solution so that bubbles are not caught, and then pulled up vertically, and if necessary, is subjected to a curing treatment such as drying or ultraviolet irradiation to form an inner polymer layer. When this polymer solution is a polymer solution, drying is suitable as the curing treatment, and when the polymer solution is a monomer polymerizable solution, ultraviolet irradiation or heat curing is suitable as the curing treatment.

  Next, the stent body is mounted so as to be externally fitted to the mandrill having the inner polymer layer, the mandrill having the stent body mounted thereon is slowly immersed in the polymer solution, and then pulled up vertically to the outer polymer layer. Form. After the outer polymer layer is cured, the mandrill is pulled out to produce a stent body. In the manufactured stent element body, the inner polymer layer and the outer polymer layer usually protrude longer than both ends of the stent body, so that the excess protruding polymer layer is cut off.

  In the case of forming the biodegradable polymer layer, the mandrill is immersed in the biodegradable polymer solution prior to the formation of the inner polymer layer or after the outer polymer layer is formed, and the coating treatment is performed in the same manner as described above. Just do it. If a therapeutic agent is added to the biodegradable polymer solution, a coating containing the therapeutic agent can be formed, and the type, molecular weight, coating thickness, etc. of the biodegradable polymer are adjusted. As a result, it is possible to set the time and period for releasing the therapeutic agent into the body. The lubricating polymer layer can be formed in the same manner.

  The fine holes of the polymer layer can be provided by laser processing or the like so as to penetrate the inner polymer layer and the outer polymer layer before or after the mandrill is drawn.

  When pulling out a mandrill from a molded stent body, the mandrill can be easily immersed in an organic solvent that swells slightly, preferably swells with a volume expansion rate of 10% or less. It can be pulled out. Depending on the material of the polymer film, for example, when a segmented polyurethane resin is used for the polymer film, the mandrill is used in a lower alcohol, preferably methanol or ethanol, particularly preferably methanol, preferably 1 to 30 hours, particularly preferably 5 It is preferable to soak for ~ 20 hours. As a result, the mandrill can be easily pulled out. The reason for this is not necessarily clear, but the polymer film slightly swells and weakly adheres to the mandrill and has a low affinity for both the metal and polymer layers and is a low surface tension liquid. It is inferred that alcohol penetrates into the interface between the metal mandrill and the inner polymer layer to reduce the adhesion between the mandrill surface and the polymer layer and at the same time improve the slidability.

  The stent of the present invention manufactured in this way has a polymer layer 12 in close contact with the entire outer surface of the stent strut 11 constituting the mesh-shaped stent body as shown in FIG. The inner peripheral surface A of the stent is a smooth surface formed by the polymer layer 12. With such a stent, since there is no exposed surface of the metal stent body, the problems of metal allergy, metal irritation, and rust generation are eliminated. In addition, thrombus is prevented from being generated, and in particular, since the inner peripheral surface is a smooth surface without unevenness, the occurrence of thrombus in the uneven portion is eliminated. Moreover, there is no problem of misalignment between the polymer layer and the stent body before and after expansion of the stent.

  In addition, the coating thickness of the above-mentioned polymer layer shows the thickness part of the polymer layer 12 which has directly covered the stent strut 11 shown by d in FIG.

(A) The figure is a perspective view of the stent which concerns on embodiment, (b) The figure is sectional drawing of this stent. It is an expanded sectional view of the II section of Drawing 1 showing the covering state by the polymer layer of the stent of the present invention. It is a perspective view of a stent main body. It is a perspective view of the stent main body expanded in diameter. It is a perspective view of the conventional stent. FIG. 6 is a perspective view of the stent of FIG. 5 having an enlarged diameter. It is typical sectional drawing which shows the covering state by the polymer film of the stent of Unexamined-Japanese-Patent No. 11-299901.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 1st tubular structure 1a Upstream side 1b Downstream side 2 2nd tubular structure 3 Stent 10 Stent body 11 Stent strut 12 Polymer layer

Claims (26)

A first annular structure having an expandable tubular stent body and a flexible polymer layer covering the stent body;
A stent having a second annular structure that is branched from the middle of the first annular structure and is made of a polymer having a flexible surface at least.   2. The stent according to claim 1, wherein the stent body is disposed in a partial region of the first annular structure.   3. The stent according to claim 2, wherein the stent body is disposed on one end side of a first annular structure that is placed upstream when the stent is placed in a blood vessel.   The stent according to any one of claims 1 to 3, wherein a radiopaque substance is disposed in a part or all of the stent.   The stent according to claim 4, wherein the radiopaque substance is disposed in the vicinity of a branch portion between the first annular structure and the second annular structure.   The stent according to claim 4, wherein the radiopaque material is disposed only in the second annular structure.   7. The structure according to claim 1, wherein at least a part of the stent other than a portion where the stent body is disposed forms a cylindrical body and the surface of the annular structure covering the cylindrical body. A stent comprising the polymer.   The stent according to claim 7, wherein the cylindrical body is made of metal.   9. The stent according to claim 8, wherein the cylindrical body is formed of a braided body of fine metal wires.   The stent according to claim 8 or 9, wherein the metal is nickel, titanium alloy, or cobalt-chromium-nickel-iron alloy.   The stent according to any one of claims 1 to 9, wherein the polymer is in close contact with and covers the entire outer surface of the stent body.   The stent according to any one of claims 1 to 11, wherein the stent body is made of a mesh-like metal member.   The stent according to claim 12, wherein the mesh-shaped metal member is made of a cobalt-chromium-nickel-iron alloy.   The stent according to claim 12, wherein the mesh-shaped metal member is made of a nickel-titanium alloy.   The stent according to any one of claims 1 to 14, wherein a plurality of micropores are formed in the polymer layer.   The stent according to claim 15, wherein the micropores are arranged at substantially uniform intervals.   The stent according to claim 15 or 16, wherein the micropores are provided at intervals of 51 to 10000 µm and have a diameter of 5 to 500 µm.   18. A stent according to any one of claims 1 to 17, wherein the polymer comprises segmented polyurethane.   The stent according to any one of claims 1 to 17, wherein the polymer comprises a polyolefin-based polymer.   The stent according to any one of claims 1 to 17, wherein the polymer is a silicone polymer film.   The stent according to any one of claims 1 to 20, wherein the coating thickness of the polymer is 10 to 100 µm.   The stent according to any one of claims 1 to 21, wherein the polymer is further coated with a biodegradable polymer.   The stent according to claim 22, wherein the biodegradable polymer contains a drug.   24. The platelet membrane receptor of claim 23, wherein the drug is heparin, low molecular weight heparin, hirudin, argatroban, formacholine, bapiprost, prostamorin, prostaquilin homologue, dextran, lofepro-alguchloromethyl ketone, dipyridamole, glycoprotein Antibody, recombinant hirudin, thrombin inhibitor, vascular peptin, vascular tensin converting enzyme inhibitor, steroid, fibroblast growth factor antagonist, fish oil, omega-3 fatty acid, histamine, antagonist, HMG-CoA reductase inhibitor , Seramine, serotonin blocking antibody, thioprotease inhibitor, trimazole pyridimine, interferon, vascular endothelial growth factor (VEGF), rapamycin, and FK506 Stent, wherein Kutomo is one.   25. The stent according to any one of claims 1 to 24, wherein the stent is placed in a blood vessel near a blood vessel bifurcation and used for occlusion of an aneurysm.   26. The stent according to claim 25, wherein the stent is used so that the main stent body is located in an upstream region of a blood vessel bifurcation.

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