WO2017154512A1 - Stent and stent delivery system - Google Patents

Abstract

This stent 2 has a tubular shape, is inserted from the distal end side into a living organism lumen so as to be mounted in an indwelling position, and supports, in the indwelling state, a lesioned part of the living organism lumen. Also, the stent 2 has: a distal end section 5; a proximal end section 6 located on the side opposite the distal end section 5; and an intermediate section 7 located between the distal end section 5 and the proximal end section 6 and supporting the lesioned part. Further, the distal end section 5, the proximal end section 6, and the intermediate section 7 contain a biodegradable material which degrades and dissolves when coming in contact with bodily fluid. The intermediate section 7 takes a longer degradation time period than at least one of the distal end section 5 and the proximal end section 6, the degradation time period being the time from when the intermediate section 7 and at least one of the distal end section 5 and the proximal end section 6 come in contact with the bodily fluid to when the intermediate section 7 and the at least one of the distal end section 5 and the proximal end section 6 degrade and disappear.

Description

Stent and stent delivery system

The present invention relates to a stent and a stent delivery system.

A medical device called a stent is used to improve a lesion site such as a stenosis or an obstruction occurring in a body lumen such as a blood vessel, a bile duct, a trachea, an esophagus, or a urethra. This stent is a hollow tubular medical device in which a lesion site is expanded in order to maintain the patency state of the living body lumen, and is placed in the living body lumen in the expanded diameter state. Stents are used, for example, in the coronary arteries of the heart to prevent restenosis after percutaneous coronary angioplasty (PTCA). By placing a stent, the incidence of acute vascular occlusion and restenosis can be reduced.

This stent is present in the body lumen even after the healing of the lesion site is completed. Therefore, in recent years, a stent made of a biodegradable material that is indwelled in a living body for a predetermined period of time as described in Patent Document 1 and then decomposes and elutes by contacting with a body fluid such as blood has been used. Yes.

Examples of the biodegradable material include biodegradable metal materials and biodegradable polymer materials. Although the biodegradable metal material depends on the type, generally, the biodegradable metal material has a high decomposition rate when it comes into contact with a body fluid and tends to shorten the time in which it is left in the living body. For this reason, there is a possibility that a sufficient period for supporting the lesion site cannot be secured.

On the other hand, although the biodegradable polymer material depends on the type, generally, the degradation rate when it comes into contact with a body fluid is slow, and the time in which it is left in the living body tends to be long. For this reason, although a lesioned part can be supported for a long period of time compared with a biodegradable metal material, the period during which a load is applied to a normal part around the lesioned part becomes longer.

Thus, when the stent is composed of a biodegradable material, it is difficult to prevent the normal site from being unnecessarily loaded while supporting the lesion site for a sufficiently long period.

JP 2008-220811 A

The purpose of the present invention is to prevent the lesion from remaining in the body after the healing of the lesion has been completed, to support the lesion for a sufficiently long period of time, and to load a normal site more than necessary. It is an object of the present invention to provide a stent and a stent delivery system capable of preventing both of them.

Such an object is achieved by the present inventions (1) to (10) below.
(1) A stent that has a tubular shape, is placed in a living body lumen from a distal end side, and supports a lesion site of the living body lumen in the indwelling state,
The tip,
A proximal end opposite to the distal end;
An intermediate portion located between the distal end portion and the proximal end portion and supporting the lesion site;
The distal end portion, the proximal end portion, and the intermediate portion include a biodegradable material that is decomposed and eluted by contact with a body fluid,
The stent according to claim 1, wherein the intermediate portion has a longer disassembly period from contact with the body fluid to disassembly and disappearance than at least one of the distal end portion and the proximal end portion.

(2) The stent according to (1), wherein the tube thickness of the intermediate portion is thicker than the tube thickness of the one end portion.

(3) The stent according to (1) or (2), wherein the molecular weight per unit volume of the intermediate portion is larger than the molecular weight per unit volume of the one end portion.

(4) When the decomposition period of the intermediate portion is Ta and the decomposition period of the one end is Tb,
Ta / Tb is 1.1 or more and 30 or less, The stent in any one of said (1) thru | or (3).

(5) The stent according to any one of (1) to (4), wherein the intermediate portion has higher rigidity than the distal end portion and the proximal end portion.

(6) The stent according to any one of (1) to (5), wherein the distal end portion has lower rigidity than the proximal end portion.

(7) The intermediate portion includes a biodegradable polymer material,
The stent according to any one of (1) to (6), wherein the distal end portion and the proximal end portion include a biodegradable metal material.

(8) The stent according to any one of (1) to (7), wherein the distal end portion, the proximal end portion, and the intermediate portion have a net shape.

(9) The stent according to any one of (1) to (8), wherein a length of the distal end portion and a length of the proximal end portion are 0.5 mm or more and 5.0 mm.

(10) The stent according to any one of (1) to (9) above,
A stent delivery system comprising: a delivery device that removably holds the stent and that delivers the stent into the living body lumen.

According to the present invention, since the entire stent is made of a biodegradable material, it can be prevented from remaining in the living body after the healing of the lesion site is completed.

In addition, since the intermediate portion that supports the lesion site has a long degradation period from contact with the body fluid until it is degraded and disappears, the lesion site can be supported for a long period of time. And since the decomposition | disassembly period until the edge part which contacts the periphery of a lesioned part contacts with a bodily fluid until it decomposes | disassembles and it lose | disappears is short, it disappears faster than an intermediate part. Thereby, it is possible to prevent a normal part from being loaded more than necessary.

As described above, according to the present invention, it is possible to simultaneously support a lesion site for a sufficiently long period and to prevent a normal site from being unnecessarily burdened.

FIG. 1 is a side view showing a first embodiment of the stent and stent delivery system of the present invention. 2A and 2B are diagrams showing the stent shown in FIG. 1, where FIG. 2A is an enlarged side view and FIG. 2B is a longitudinal sectional view. FIG. 3 is a diagram for explaining the operation of the stent shown in FIG. 1 and shows a state when the stent is in an indwelling state. FIG. 4 is a view for explaining the operation of the stent shown in FIG. 1 and shows a state in which the distal end portion and the proximal end portion are disassembled and disappeared before the intermediate portion. FIG. 5 is a view for explaining the operation of the stent shown in FIG. 1 and shows a state in which the intermediate portion is disassembled and disappears. FIG. 6 is an enlarged cross-sectional view showing a connecting portion of the stent shown in FIG. FIG. 7 is a view seen from the direction of arrow A in FIG. FIG. 8 is an enlarged cross-sectional view of a connecting portion provided in the second embodiment of the stent and stent delivery system of the present invention. FIG. 9 is a view seen from the direction of arrow B in FIG. FIG. 10 is a view showing a third embodiment of the stent and stent delivery system of the present invention. FIG. 11 is a diagram showing a third embodiment of the stent and stent delivery system of the present invention. FIG. 12 is a diagram showing a third embodiment of the stent and stent delivery system of the present invention.

Hereinafter, a stent and a stent delivery system of the present invention will be described in detail based on preferred embodiments shown in the accompanying drawings.

<First Embodiment>
FIG. 1 is a side view showing a first embodiment of the stent and stent delivery system of the present invention. 2A and 2B are diagrams showing the stent shown in FIG. 1, where FIG. 2A is an enlarged side view and FIG. 2B is a longitudinal sectional view. FIG. 3 is a diagram for explaining the operation of the stent shown in FIG. 1 and shows a state when the stent is in an indwelling state. FIG. 4 is a view for explaining the operation of the stent shown in FIG. 1 and shows a state in which the distal end portion and the proximal end portion are disassembled and disappeared before the intermediate portion. FIG. 5 is a view for explaining the operation of the stent shown in FIG. 1 and shows a state in which the intermediate portion is disassembled and disappears. FIG. 6 is an enlarged cross-sectional view showing a connecting portion of the stent shown in FIG. FIG. 7 is a view seen from the direction of arrow A in FIG.

In the following, for convenience of explanation, the upper side of FIGS. 1 to 7 (the same applies to FIGS. 8 to 12) is “upper” or “upper”, the lower side is “lower” or “lower”, and the left side is “ The “left side” or “front end side” and the right side are referred to as “right side” or “proximal side”.

A stent delivery system 1 shown in FIG. 1 includes a stent 2 placed in a living body lumen, and a stent delivery catheter 3 (transport device) that transports the stent 2.

The stent 2 is a medical device for supporting a lesion site such as a stenosis portion or an obstruction portion generated in a living body lumen such as a blood vessel, a bile duct, a trachea, an esophagus, or a urethra from the inside and maintaining a patent state. Hereinafter, as an example, the stent 2 will be described as supporting the stenosis site 101 generated in the blood vessel 100 (see FIGS. 3 and 4).

Prior to describing the stent 2, the stent delivery catheter 3 will be described.

The stent delivery catheter 3 includes a tubular catheter body 31, a hub 32 provided at the proximal end of the catheter body 31, and a balloon 33 provided near the distal end of the catheter body 31. The outer diameter of the balloon 33 is expanded when a working fluid is supplied through a flow path (not shown). The stent 2 is disposed on the outer peripheral portion of the balloon 33 with the outer diameter reduced.

The stent delivery catheter 3 is inserted into a living body, for example, so as to be inserted through a guide wire previously inserted into the blood vessel 100. When the stenosis region 101 is reached, the balloon 33 is expanded. Thereby, the stent 2 is pushed and expanded by the balloon 33, and becomes a diameter-expanded state. In this expanded diameter state, the stenosis region 101 can be supported from the inside, and the patency state of the stenosis region 101 can be maintained. Then, the stent delivery catheter 3 is removed from the blood vessel 100, and only the stent 2 is left in the living body.

Next, the stent 2 will be described.
The stent 2 includes a large number of ring-shaped strands 21 and a large number of connecting portions 22 that are coupled to the respective strands 21, and is configured as a net-like tube as a whole. For this reason, the stent 2 can support the stenosis site 101 as uniformly as possible.

The strand 21 has a wavy shape that is curved many times. Each strand 21 is concentrically arranged in one direction. In the stent 2, a skeleton is formed by these strands 21.

The connecting part 22 maintains the arrangement state of the strands 21. Moreover, the connection part 22 has connected the part 211 which becomes a wavy peak in the adjacent strand 21, ie, the part which mutually approached. Thereby, the length of the connection part 22 can be made comparatively short. Therefore, it can suppress that the whole stent is twisted, and can maintain the whole shape. In addition, the connection part 22 may connect the part 211 used as a peak, and the part used as a trough.

In addition, the stent 2 is not limited to the mesh-like tube body. For example, the stent 2 has a coil shape in which one strand is wound spirally, or a mesh shape in which a number of strands are folded into a mesh shape. It may be done.

This stent 2 can take the reduced diameter state shown in FIGS. 2A and 2B and the expanded state in which the inner diameter and the outer diameter are larger than the reduced diameter state. The stent 2 is in a reduced diameter state when stored in the stent delivery catheter 3.

Further, the stent 2 is expanded in diameter by the balloon 33 and is placed in the blood vessel 100 in the expanded diameter state. In the expanded diameter state, the undulations of the strands 21 are deformed, and adjacent apexes are separated from each other than in the reduced diameter state. Thus, the stent 2 is a so-called “balloon expandable stent”.

The stent 2 may be constituted by a so-called “self-expanding stent” that expands by its own elasticity. In this case, in a double-tube catheter having an outer tube and an inner tube, the stent 2 is disposed between the outer tube and the inner tube to maintain the reduced diameter state, that is, the outer tube is brought into an expanded state. And is inserted into the living body in this state. Then, by moving the outer tube relative to the inner tube relative to the proximal side of the catheter, the restriction by the outer tube can be canceled and the diameter can be increased.

The stent 2 is composed of a biodegradable material that is biodegraded by contact with blood (body fluid) and elutes into the blood. For this reason, the stent 2 is placed in the stenotic region 101 for a predetermined period to support the stenotic region 101 and gradually elute. Therefore, it is possible to prevent the stent 2 from remaining in the living body after the treatment of the stenosis region 101 is completed. As a result, for example, the risk of developing chronic inflammation due to mechanical stress on the blood vessel 100 can be avoided.

Here, as shown in FIGS. 2 and 3, the stent 2 can be divided into a distal end portion 5, a proximal end portion 6, and an intermediate portion 7 located therebetween.

As shown in FIG. 3, the distal end portion 5 is a portion of the blood vessel 100 that is in contact with and supported by the normal portion 102 on the front side (tip end side) of the stenosis portion 101 in the indwelling state. In the indwelling state, the proximal end portion 6 is a portion of the blood vessel 100 that is in contact with and supported by the normal portion 103 on the rear side (the proximal end side) of the stenosis portion 101. The intermediate part 7 is a part that contacts and supports the stenosis part 101 in the indwelling state.

In the stent 2, the distal end portion 5, the proximal end portion 6, and the intermediate portion 7 are different from each other in a portion of the blood vessel 100 that contacts (supports) each other. When a long period is required for the distal end portion 5 and the proximal end portion 6 to be decomposed, there is a possibility that mechanical stress is applied to the normal portions 102 and 103 more than necessary. On the other hand, when the period during which the intermediate part 7 is disassembled is short, the period for supporting the stenotic region 101 is insufficient, and the stenotic region 101 may not be completely cured and may be restenulated.

Therefore, the stent 2 has an effective configuration for solving the above problem. This will be described below.

First, the distal end portion 5 and the proximal end portion 6 will be described.
The distal end portion 5 and the proximal end portion 6 are made of a biodegradable metal material that is decomposed and eluted by contact with a body fluid such as blood.

As the biodegradable metal, for example, pure magnesium or a magnesium alloy, calcium, zinc, lithium or the like can be used, and preferably pure magnesium or a magnesium alloy can be used.

The magnesium alloy contains magnesium as a main component and contains at least one element selected from a biocompatible element group consisting of Zr, Y, Ti, Ta, Nd, Nb, Zn, Ca, Al, Li, and Mn. Those that do are preferred. Thereby, even if it decomposes | dissolves and elutes, it can prevent having a bad influence on a human body.

Specific examples of magnesium alloys include, for example, magnesium 50 to 98%, lithium (Li) 0 to 40%, iron 0 to 5%, other metals or rare earth elements (cerium, lanthanum, neodymium, praseodymium, etc.) In which 0 is from 5 to 5%. For example, magnesium is 79 to 97%, aluminum is 2 to 5%, lithium (Li) is 0 to 12%, and rare earth elements (cerium, lanthanum, neodymium, praseodymium, etc.) are 1 to 4%. be able to. Further, for example, magnesium is 85 to 91%, aluminum is 2%, lithium (Li) is 6 to 12%, and rare earth elements (cerium, lanthanum, neodymium, praseodymium, etc.) are 1%. For example, magnesium is 86 to 97%, aluminum is 2 to 4%, lithium (Li) is 0 to 8%, and rare earth elements (cerium, lanthanum, neodymium, praseodymium, etc.) are 1 to 2%. be able to. Also, for example, aluminum is 8.5 to 9.5%, manganese (Mn) is 0.15 to 0.4%, zinc is 0.45 to 0.9%, and the remainder is magnesium. it can. Further, for example, aluminum is 4.5 to 5.3%, manganese (Mn) is 0.28 to 0.5%, and the remainder is magnesium. In addition, for example, magnesium is 55 to 65%, lithium (Li) is 30 to 40%, and other metals and / or rare earth elements (cerium, lanthanum, neodymium, praseodymium, etc.) are 0 to 5%. Can do.

By using pure magnesium or a magnesium alloy, the rigidity of the distal end portion 5 and the proximal end portion 6 can be increased. The rigidity of the distal end portion 5 and the proximal end portion 6 is required when the stent 2 is expanded and placed in the blood vessel 100. For example, in the procedure in which the stent 2 is placed in the blood vessel 100 to secure the diameter of the blood vessel and then the device is additionally delivered toward the distal end side of the place where the stent 2 is placed, the proximal end portion 6 is the device. The tip of is easy to get caught. On the other hand, the distal end portion 5 is easily caught when the device advanced to the distal end side with respect to the stent 2 is retracted to the proximal end side with respect to the stent 2. Therefore, the distal end portion 5 and the base end portion 6 are made of pure magnesium or a magnesium alloy, and the rigidity of the distal end portion 5 and the base end portion 6 is increased, so that the distal end portion 5 and the proximal end portion 6 are caught by the device. Can be prevented or suppressed.

Further, the tube thickness (the thickness of the strand 21 in the radial direction of the stent 2) t of the distal end portion 5 and the proximal end portion 6 is not particularly limited, but is preferably 30 μm or more and 120 μm or less, for example, 30 μm or more. 80 μm or less is more preferable. As a result, the strength of the distal end portion 5 and the proximal end portion 6 can be sufficiently secured, and the above-described hooking with other devices to be additionally inserted and the accompanying change in the shape of the stent 2 can be suppressed. Can do.

Further, the distal end portion 5 and the proximal end portion 6 may have the same or different rigidity. When the distal end portion 5 and the proximal end portion 6 are different in rigidity, the distal end portion 5 is preferably lower in rigidity than the proximal end portion 6. Thereby, the effect which improves the intravascular passage property of the whole stent can be acquired. In the case where the distal end portion 5 and the proximal end portion 6 have the same rigidity, for example, when the stent 2 is installed on the outer periphery of the balloon 33, it can be installed regardless of the front-rear direction.

The difference in rigidity between the distal end portion 5 and the proximal end portion 6 is, for example, that the constituent materials of the distal end portion 5 and the proximal end portion 6 are different, or the distal end portion 5 and the proximal end portion 6 are made of the same material, It can be expressed by varying the tube thickness t of the distal end portion 5 and the proximal end portion 6 and the width w of the strand 21 (see FIG. 2).

Such a distal end portion 5 and a proximal end portion 6 have a high decomposition rate when contacted with blood (hereinafter simply referred to as “decomposition rate”). For this reason, the disassembly period until the distal end portion 5 and the proximal end portion 6 are disassembled and disappear after the stent 2 is in an indwelling state is relatively short. Thereby, the period when the front-end | tip part 5 and the base end part 6 are contacting with the normal parts 102 and 103, respectively can be shortened. Therefore, it is possible to prevent excessive mechanical stress from being applied to the normal parts 102 and 103.

In the present specification, the “decomposition period” means that each part of the distal end part 5, the proximal end part 6 and the intermediate part 7 is placed in an indwelling state, and each part is decomposed and disappears. The period until.
Moreover, you may comprise the front-end | tip part 5 and the base end part 6 with the below-mentioned biodegradable polymer material.

Next, the intermediate part 7 will be described.
The intermediate portion 7 is made of a biodegradable polymer material that is decomposed and eluted by contact with a body fluid such as blood. Examples of the biodegradable polymer material include polylactic acid, polyglycolic acid, a copolymer of lactic acid and glycolic acid, polycaprolactone, polyhydroxybutyric acid, polyhydroxybutyrate valeric acid, polymalic acid, and poly-α-amino acid. At least one polymer selected from the group consisting of polyorthoesters, cellulose, collagen, laminin, heparan sulfate, fibronectin, vitronectin, chondroitin sulfate, hyaluronic acid, cinnamic acid, and cinnamic acid derivatives. The copolymer is preferably a copolymer obtained by arbitrarily copolymerizing a monomer, and a mixture of a polymer and a copolymer. Among these, polylactic acid (PLA), polyglycolic acid (PGA), or lactic acid-glycolic acid copolymer (PLGA) is more preferable from the viewpoint of biocompatibility.

Polylactic acid (PLA), polyglycolic acid (PGA), or lactic acid-glycolic acid copolymer (PLGA) may be purchased or synthesized commercially. In the case of synthesis, for example, L-lactic acid It can be obtained by dehydrating polycondensation using D-lactic acid and glycolic acid having a required structure as a raw material. Preferably, it can be obtained by ring-opening polymerization by selecting one having a required structure from lactide, which is a cyclic dimer of lactic acid, and glycolide, which is a cyclic dimer of glycolic acid. Lactide includes L-lactide, which is a cyclic dimer of L-lactic acid, D-lactide, which is a cyclic dimer of D-lactic acid, meso-lactide obtained by cyclic dimerization of D-lactic acid and L-lactic acid, and D-lactide. There is DL-lactide, which is a racemic mixture of lactide and L-lactide. Any lactide can be used in the present invention.

Further, the biodegradable polymer material may contain a plasticizer. If a plasticizer is contained, the ductility of the biodegradable polymer material is improved, the bending flexibility of the strand 21 is improved, and cracks that may occur when the strand 21 is deformed can be prevented.

The plasticizer is not particularly limited as long as it does not adversely affect the human body, but polyethylene glycol, polyoxyethylene polyoxypropylene glycol, polyoxyethylene sorbitan monooleate, polyethylene glyceryl triricinoleate, sorbitan sesquioleate At least one selected from the group consisting of triethyl citrate, acetyl tributyl citrate, acetyl trihexyl citrate, butyryl trihexyl citrate, medium chain fatty acid triglycerides, monoglycerides, and acetylated monoglycerides, or a mixture thereof It is preferable.

The content of such a plasticizer is preferably 0.01 to 80% by mass, more preferably 0.1 to 60% by mass with respect to the biodegradable polymer material, and 1 to 40% by mass. % Is more preferable.

Further, the tube thickness (the thickness of the strand 21 in the radial direction of the stent 2) T of the intermediate portion 7 is not particularly limited, but is preferably 50 μm or more and 150 μm or less, for example, 50 μm or more and 100 μm or less. Is more preferable. The tube thickness T of the intermediate portion 7 is preferably the same as the tube thickness t of the distal end portion 5 and the proximal end portion 6, but after the stent 2 is placed in the blood vessel, the effect of supporting the lesion site by the stent 2 is achieved. In order to increase the thickness, the tube thickness t of the distal end portion 5 and the proximal end portion 6 may be thicker. Thereby, the rigidity of the intermediate part 7 can be made comparatively high, and the constriction site | part 101 can fully be supported.

In addition, when the front-end | tip part 5 and the base end part 6 are biodegradable polymer materials, the molecular weight per unit volume of the intermediate part 7 becomes larger than the molecular weight per unit volume of the front-end | tip part 5 and the base end part 6. Yes.

2B, in the stent 2, the outer diameters of the distal end portion 5, the intermediate portion 7, and the proximal end portion 6 are constant along the longitudinal direction of the stent 2, and the distal end portion 5 The intermediate portion 7 and the base end portion 6 have different inner diameters. Thereby, for example, compared with a case where the inner diameter is constant and the outer diameter is different, for example, the distal end portion of the catheter body 31 shown in FIG.

In such a stent 2, the intermediate portion 7 has a slower decomposition rate (hereinafter simply referred to as “decomposition rate”) when contacting the blood than the distal end portion 5 and the proximal end portion 6. The base end portion 6 is configured to have a shorter period until it is disassembled and disappears than the intermediate portion 7.

Thus, when a predetermined time elapses from the indwelling state shown in FIG. 3, the distal end portion 5 and the proximal end portion 6 are disassembled before the intermediate portion 7 and disappear as shown in FIG. In this state, the normal portions 102 and 103 are prevented from being loaded, and the stenosis portion 101 is supported from the inside. And when predetermined time passes further from the state shown in FIG. 4, the intermediate part 7 will also be decomposed | disassembled and will lose | disappear.

Thus, according to the stent 2, it is possible to prevent the stent 2 from remaining in the living body after the healing of the stenotic region 101 is completed. Further, it is possible to prevent both the distal end portion 5 and the proximal end portion 6 from applying unnecessary mechanical stress to the normal portions 102 and 103 and to support the stenosis portion 101 sufficiently by the intermediate portion 7. be able to.

The difference in the decomposition speed between the intermediate portion 7 and the distal end portion 5 and the proximal end portion 6 can be determined by using materials having different decomposition speeds in the intermediate portion 7 and the distal end portion 5 and the proximal end portion 6, It can be expressed by varying the thickness or the width of the strand 21.

Further, the intermediate portion 7 may be higher or lower in rigidity than the distal end portion 5 and the proximal end portion 6, or may be the same.

When the rigidity of the intermediate part 7 is lower than that of the distal end part 5 and the proximal end part 6, the intermediate part 7 is easily deformed, so that it can be easily transported when the stent 2 is transported. Furthermore, when the intermediate portion 7 follows the bent shape of the stenotic region 101 in the indwelling state, an effect of improving the crimped state after expansion can be obtained.

On the other hand, when the rigidity of the intermediate portion 7 is higher than that of the distal end portion 5 and the proximal end portion 6, the stenotic region 101 can be more effectively supported and the patency state of the blood vessel 100 can be more effectively maintained.

The rigidity of the distal end portion 5, the proximal end portion 6, and the intermediate portion 7 can be determined by, for example, changing the thickness of the strand 21 (the thickness of the tube wall), the width, the density of the strand 21, etc. It can be set by changing.

If the decomposition period Ta of the intermediate part 7 is too short, there is a possibility that a sufficient period for supporting the stenosis site 101 cannot be secured. On the other hand, if the decomposition period Ta of the intermediate portion 7 is too long, there is a possibility that a load is applied to the completely constricted region 101 even after the constricted region 101 is completely cured.

In addition, if the decomposition period Tb of the distal end portion 5 and the proximal end portion 6 is too short, there is a possibility that the uniformity of the blood vessel lumens of the stenotic region 101 immediately after placement and the surrounding normal regions 102 and 103 cannot be ensured. On the other hand, if the disassembly period Tb of the distal end portion 5 and the proximal end portion 6 is too long, mechanical stress may be applied to the normal portions 102 and 103 more than necessary.

When the decomposition period of the intermediate part 7 is Ta and the decomposition period of the tip part 5 and the base end part 6 is Tb, the ratio Ta / Tb is preferably 1.1 or more and 30 or less, preferably 1.5 or more. , 25 or less is more preferable. As a result, it is possible to secure a sufficient period for supporting the stenotic region 101 and to prevent the normal regions 102 and 103 from being subjected to unnecessary mechanical stress.

Specifically, the decomposition period Ta of the intermediate part 7 is preferably 3 months or more and 24 months or less, and more preferably 6 months or more and 12 months or less. Further, the decomposition period Tb of the distal end portion 5 and the proximal end portion 6 is specifically preferably 1 month or more and 12 months or less, and more preferably 3 months or more and 6 months or less. preferable. Thereby, it is possible to sufficiently secure a period from when the distal end portion 5 and the proximal end portion 6 are disassembled and disappeared until the intermediate portion 7 is disassembled and disappeared.

Further, the length L5 of the distal end portion 5 and the length L6 of the proximal end portion 6 are preferably 0.5 mm or more and 5.0 mm or less, and more preferably 0.5 mm or more and 3.0 mm or more. preferable. If the length L5 and the length L6 are too long, the area in contact with the normal portions 102 and 103 is increased, and the burden on the normal portions 102 and 103 may be increased. On the other hand, if the length L5 and the length L6 are too short, when the indwelling state is set, the area in contact with the normal sites 102 and 103 is too small, and the positioning of the stent 2 with respect to the stenosis site 101 tends to be difficult.

Further, the length L7 of the intermediate portion 7 is arbitrary, and the user can select a stent having an appropriate length according to the length of the lesion. If the length L7 is too long, there is a possibility that the intermediate portion 7 comes into contact with the normal parts 102 and 103 in the indwelling state. In this case, there is a possibility that mechanical stress is applied to a portion of the normal portions 102 and 103 that is in contact with the intermediate portion 7. On the other hand, if the length L7 is too short, it may be difficult for the intermediate portion 7 to support the entire stenotic region 101.

Further, the thickness of the strand 21 is constant at the distal end portion 5, the thickness of the strand 21 is constant at the proximal end portion 6, and the thickness of the strand 21 at the intermediate portion 7. Is constant. Thereby, in the front-end | tip part 5, when the strand 21 is decomposed | disassembled, it will lose | disappear simultaneously (same also about the base end part 6 and the intermediate part 7). Therefore, it is possible to prevent as much as possible that a part of the strand 21 is released into the blood in a solid state during the decomposition.

Next, the configuration of the boundary portion between the distal end portion 5 and the intermediate portion 7 and the connecting portion 22 located at the boundary portion between the intermediate portion 7 and the proximal end portion 6 will be described with reference to FIGS. 6 and 7. In addition, since the connection part 22 located in each boundary part is the same structure, respectively, below, it is one of the connection parts 22 located in the boundary part of the base end part 6 and the intermediate part 7 (henceforth, this this) The connecting portion 22 will be described as a representative of “referred to as a connecting portion 22A”).

The connecting portion 22A has a cylindrical portion 221A and a rod-shaped portion 222A inserted into the cylindrical portion 221A. The cylindrical portion 221A extends from the strand 21 of the intermediate portion 7 toward the proximal end side. The rod-shaped portion 222A extends from the strand 21 of the base end portion 6 toward the distal end side.

The cylindrical portion 221A is made of a biodegradable polymer material. The rod-shaped portion 222 </ b> A is made of the same material as the base end portion 6. Further, a groove 223A extending in the radial direction of the stent 2 is formed on the outer peripheral portion of the rod-like portion 222A. The groove 223A has a rounded inner periphery.

In addition, a part of the cylindrical portion 221A is inserted inside the groove 223A. Thereby, it is possible to make it difficult for the rod-shaped portion 222A to come out of the tubular portion 221A.

Further, the base end portion of the cylindrical portion 221A is a tapered portion 225A having a tapered shape with an outer diameter gradually decreasing toward the base end side.

Such a connecting part 22 can be obtained, for example, by melting or softening a part of the strand 21 of the intermediate part 7 and, in that state, bringing it into contact with the outer peripheral part of the rod-like part 222A and cooling it. it can.

Second Embodiment
FIG. 8 is an enlarged cross-sectional view of a connecting portion provided in the second embodiment of the stent and stent delivery system of the present invention. FIG. 9 is a view seen from the direction of arrow B in FIG.

Hereinafter, the second embodiment of the stent and stent delivery system of the present invention will be described with reference to these drawings, but the description will focus on the differences from the above-described embodiment, and the description of the same matters will be omitted. .
This embodiment is substantially the same as the first embodiment described above except that the configuration of the connecting portion is different.

As shown in FIGS. 8 and 9, the connecting portion 22 has a cylindrical portion 221B and a rod-like portion 222B. Further, the rod-like portion 222B is formed with a large number of through holes 224B penetrating in the radial direction of the stent 2.

These through holes 224 </ b> B are arranged at predetermined intervals along the longitudinal direction of the connecting portion 22. Further, in the rod-like portion 222B, portions where two through holes 224B are arranged in the circumferential direction of the stent 2 and portions where one through hole 224B is arranged are alternately arranged.

In addition, a part of the cylindrical portion 221B is inserted inside each through hole 224B. According to such this embodiment, it can prevent more reliably that the rod-shaped part 222B comes off from the cylindrical part 221B. Therefore, for example, in the indwelling state, it is possible to more reliably prevent the distal end portion 5 and the intermediate portion 7 and the proximal end portion 6 and the intermediate portion 7 from being separated.

<Third Embodiment>
10 to 12 are views showing a third embodiment of the stent and stent delivery system of the present invention.

Hereinafter, the third embodiment of the stent and stent delivery system of the present invention will be described with reference to these drawings, but the description will focus on the differences from the above-described embodiment, and the description of the same matters will be omitted. .
This embodiment is substantially the same as the first embodiment described above except that the configuration of the intermediate portion is different.

As shown in FIG. 10, the intermediate portion 7 </ b> A can be divided into both end portions 71 and a central portion 72. The thickness of the strand 21 at both ends 71 is smaller than the thickness of the strand 21 at the central portion 72. For this reason, the disassembly period of the center part 72 can be made longer than the both end parts 71. Such a configuration has the following advantages.

FIG. 10 is a view showing a state in which the distal end portion 5 and the proximal end portion 6 are disassembled and disappeared in the stent 2. In this state, the intermediate portion 7A is not disassembled and is supporting the stenosis region 101.

FIG. 11 shows a state in which a predetermined time has elapsed from the state shown in FIG. 10 and the distal region and the proximal region of the stenosis region 101 have been treated to become normal regions 104 and 105. FIG. At this time, in the intermediate portion 7A, both end portions 71 are disassembled before the central portion 72 and disappear. As a result, it is possible to prevent excessive mechanical stress from being applied to the region of the stenosis portion 101 that becomes the normal portions 104 and 105 first.

Then, as shown in FIG. 12, when the stenosis site 101 is completely cured, the central portion 72 of the intermediate portion 7A is disassembled and disappears.

Thus, according to the present embodiment, not only excessive mechanical stress is not applied to the normal parts 102 and 103, but also the region that becomes the normal parts 104 and 105 ahead of the stenosis part 101. In addition, excessive mechanical stress can be prevented. As a result, the burden on the blood vessel 100 can be further reduced.

As described above, the stent and the stent delivery system of the present invention have been described with respect to the illustrated embodiment. However, the present invention is not limited to this, and each part constituting the stent and the stent delivery system exhibits the same function. It can be replaced with any configuration obtained. Moreover, arbitrary components may be added.

In each of the above-described embodiments, the stent is described as being placed at a stenosis site in a blood vessel as an example. However, the present invention is not limited thereto. It may be indwelled at the lesion site.

Moreover, in each said embodiment, although both the front-end | tip part and the base end part were a thing whose decomposition period is shorter than an intermediate part, in this invention, it is not limited to this, One of a front-end | tip part and a base end part If the decomposition period of the end of the is shorter than the decomposition period of the intermediate part, the effect of the present invention is obtained.

Further, the distal end portion, the proximal end portion and the intermediate portion may be made of the same material. Thereby, manufacture becomes easy. In particular, when the distal end portion, the proximal end portion, and the intermediate portion are made of a biodegradable polymer material, there are the following advantages.

The process of joining the connecting parts becomes easy. Further, the intravascular permeability is improved by improving the flexibility of the entire stent. Furthermore, the decomposition period can be easily controlled by controlling the molecular weight and the crystallinity.

The stent of the present invention has a tubular shape, is placed in a living body lumen from the distal end side, and supports the lesion site of the living body lumen in the placed state, and the distal end portion is opposite to the distal end portion. A proximal end portion on the side, and an intermediate portion that is located between the distal end portion and the proximal end portion and supports the lesion site, and the distal end portion, the proximal end portion, and the intermediate portion, A biodegradable material that decomposes and elutes upon contact with a body fluid, and the intermediate portion is decomposed after being in contact with the body fluid rather than at least one of the distal end portion and the proximal end portion; The decomposition period until it disappears is long. According to the present invention, since the entire stent is made of a biodegradable material, it can be prevented from remaining in the living body after the healing of the lesion site is completed. In addition, since the intermediate portion that supports the lesion site has a long degradation period from contact with the body fluid until it is degraded and disappears, the lesion site can be supported for a long period of time. And since the decomposition | disassembly period until the edge part which contacts the periphery of a lesioned part contacts with a bodily fluid until it decomposes | disassembles and it lose | disappears is short, it disappears faster than an intermediate part. Thereby, it is possible to prevent a normal part from being loaded more than necessary. As described above, according to the present invention, it is possible to simultaneously support a lesion site for a sufficiently long period and to prevent a normal site from being unnecessarily burdened.

DESCRIPTION OF SYMBOLS 1 Stent delivery system 2 Stent 21 Strand 211 Part 22 Connection part 22A Connection part 221A Tubular part 221B Tubular part 222A Rod-like part 222B Rod-like part 223A Groove 224B Through-hole 225A Tapered part 3 Stent delivery catheter 31 Catheter body 32 Hub 33 Balloon 5 Tip portion 6 Base end portion 7 Intermediate portion 7A Intermediate portion 71 Both ends 72 Central portion 100 Blood vessel 101 Stenotic region 102 Normal region 103 Normal region 104 Normal region 105 Normal region L5 Length L6 Length L7 Length t Tube thickness T Tube thickness w width

Claims (10)

A stent that has a tubular shape, is placed in the body lumen from the distal end side, and supports the lesion site of the body lumen in the indwelling state,
The tip,
A proximal end opposite to the distal end;
An intermediate portion located between the distal end portion and the proximal end portion and supporting the lesion site;
The distal end portion, the proximal end portion, and the intermediate portion include a biodegradable material that is decomposed and eluted by contact with a body fluid,
The stent according to claim 1, wherein the intermediate portion has a longer disassembly period from contact with the body fluid to disassembly and disappearance than at least one of the distal end portion and the proximal end portion. The stent according to claim 1, wherein the tube thickness of the intermediate portion is thicker than the tube thickness of the one end portion. The stent according to claim 1 or 2, wherein a molecular weight per unit volume of the intermediate portion is larger than a molecular weight per unit volume of the one end portion. When the decomposition period of the intermediate portion is Ta and the decomposition period of the one end is Tb,
The stent according to any one of claims 1 to 3, wherein Ta / Tb is 1.1 or more and 30 or less. The stent according to any one of claims 1 to 4, wherein the intermediate portion has higher rigidity than the distal end portion and the proximal end portion. The stent according to any one of claims 1 to 5, wherein the distal end portion has lower rigidity than the proximal end portion. The intermediate portion includes a biodegradable polymer material;
The stent according to any one of claims 1 to 6, wherein the distal end portion and the proximal end portion include a biodegradable metal material. The stent according to any one of claims 1 to 7, wherein the distal end portion, the proximal end portion, and the intermediate portion have a mesh shape. The stent according to any one of claims 1 to 8, wherein a length of the distal end portion and a length of the proximal end portion are 0.5 mm or more and 5.0 mm. A stent according to any one of claims 1 to 9,
A stent delivery system comprising: a delivery device that removably holds the stent and that delivers the stent into the living body lumen.

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