Covered stent

Abstract

To provide a covered stent resistant to rupture, cracking, and pinhole formation in a covering film due to friction with the sheath of a placement device.SOLUTION: A covered stent 1 configured to be placed in a body lumen comprises a tubular framework part 11 that is expandable and contractible in a radial direction while being stretchable and contractible in a longitudinal direction, and a covering part 12 that covers the framework part 11 in a tubular form. The covering part 12 comprises a first layer 13 having a thin-film structure and covering the framework part 11 from the inner circumferential side, and a second layer 14 that has a nonwoven structure formed by lamination on the outer circumferential side of the first layer 13 by electrospinning and is fused to the outer circumferential surface of the first layer 13 to cover the framework part 11 from the outer circumferential side. The first layer 13 has lower liquid permeability than the second layer 14, and the second layer 14 has lower elongation at breakage and higher breaking strength than the first layer 13.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a covered stent. [Background technology]

[0002] Conventionally, stents are known that are placed in narrowed or obstructed areas in biological lumens such as blood vessels, bile ducts, and digestive tracts to expand the diameter of the lesion and maintain the patency of the biological lumen. Generally, stents are delivered to the target placement site using an indwelling device such as a catheter. The indwelling device carries the stent in a radially contracted state to the affected area, and then radially expands the stent at the affected area, thereby placing the stent in the affected area.

[0003] As an example of this type of stent, it has been proposed to cover the inner and / or outer periphery of the stent with a coating such as a graft (for example, Patent Document 1, etc.). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-217487 Summary of the Invention [Problem to be solved by the invention]

[0005] Covered stents, in which the gaps in the framework are covered, may be susceptible to leakage due to friction with the sheath of the placement device when the device is loaded or released, causing tears, cracks, pinholes, etc. in the coating.

[0006] The present invention has been made in view of the above circumstances, and aims to provide a covered stent in which the coating is less likely to break, crack, or develop pinholes due to friction with the sheath of the placement device. [Means for solving the problem]

[0007] One aspect of the present invention is a covered stent to be placed in a biological lumen, comprising a tubular skeleton that is radially expandable and contractable and longitudinally stretchable, and a covering that covers the skeleton in a tubular shape. The covering comprises a first layer having a thin film structure that covers the skeleton from the inside, and a second layer having a nonwoven fabric structure formed by electrospinning on the outer periphery of the first layer and welded to the outer periphery of the first layer to cover the skeleton from the outside. The first layer has lower liquid permeability than the second layer, and the second layer has a lower breaking elongation than the first layer and a higher breaking strength than the first layer. [Effects of the Invention]

[0008] According to one aspect of the present invention, a covered stent can be provided that is less susceptible to breakage, cracks, pinholes, and the like in the coating due to friction with the sheath of the placement device. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a perspective view showing an example of the configuration of a covered stent according to an embodiment of the present invention. [Figure 2] 1 is a diagram schematically illustrating a state in which the covered stent of this embodiment is placed in a biological lumen and used. FIG. [Figure 3] 1A and 1B are diagrams showing a schematic diagram of a covered stent in an expanded state and a contracted state. [Figure 4] 4(a) is a view showing a cross section along the axial direction of the covered stent of this embodiment, and FIG. 4(b) is a cross section taken along line AA of FIG. 4(b). [Figure 5] FIG. 2 is a partially enlarged cross-sectional view of the covered stent of this embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, examples of the configuration of a covered stent according to an embodiment will be described with reference to the drawings. Note that the shapes, dimensions, etc. of each part in the drawings are shown schematically and do not represent the actual shapes, dimensions, etc.

[0011] In the drawings, the longitudinal axis direction Ax of the covered stent is indicated by an arrow as appropriate. The direction substantially perpendicular to the longitudinal axis direction Ax is defined as the radial direction, and the rotation direction around the longitudinal axis direction Ax is defined as the circumferential direction.

[0012] FIG. 1 is a perspective view showing an example of the configuration of a covered stent 1 of this embodiment. FIG. 2 is a diagram schematically showing a covered stent of this embodiment in use, placed in a biological lumen. FIG. 3 is a diagram schematically showing the covered stent in an expanded state and a contracted state. FIG. 4(a) is a diagram showing a cross section of the covered stent of this embodiment along the axial direction, and FIG. 4(b) is a cross section taken along line AA of FIG. 4(b). FIG. 5 is a partially enlarged view of the cross section of the covered stent of this embodiment.

[0013] 2, a covered stent 1 is placed at a lesion 3 such as a stenosis or obstruction in a biological lumen 2 such as a blood vessel, esophagus, bile duct, trachea, or ureter, and is used to expand the lesion 3. In this embodiment, a covered stent 1 placed at a lesion 3 in, for example, a bile duct will be described.

[0014] The covered stent 1 has openings at both ends in the longitudinal direction Ax that communicate with each other, and forms a tubular flow path 4 therein through which a fluid flows through a biological lumen 2 when in use. In this embodiment, the covered stent 1 has an overall straight tubular shape as an example, but the covered stent 1 may be pre-shaped, for example, into an arched curved shape or a twisted shape. The specifications of the covered stent 1, such as the dimensions, are set appropriately depending on, for example, the diameter of the biological lumen 2 in which the covered stent 1 is to be placed, the length of the range in which the covered stent 1 is to be placed, and the like.

[0015] The covered stent 1 is a so-called self-expanding type that memorizes the shape of its expanded state, and is expandable from a contracted state in which it contracts radially inward to an expanded state in which it expands radially outward, as shown in Fig. 3. In the contracted state, the covered stent 1 is displaced so as to be elongated in the longitudinal direction compared to the expanded state.

[0016] The covered stent 1 of this embodiment is introduced into a biological lumen 2 using a catheter (not shown) in a contracted state in which it contracts radially inward and extends in the longitudinal direction. After being delivered to a lesion site 3 in the biological lumen 2, the covered stent 1 is released from the sheath of the catheter and is placed in a state of intimate contact with the inner wall of the biological lumen 2 as shown in Figure 2 by contracting radially inward and expanding radially outward. The covered stent 1 released from the catheter may be expanded radially outward by expanding and pressing a balloon (not shown) from the inside.

[0017] As shown in FIGS. 1 and 2, the covered stent 1 includes a skeletal portion 11 having a cylindrical overall shape, and a covering portion 12 attached to the skeletal portion 11.

[0018] The skeleton 11 is formed, for example, by spirally winding a thin metal wire (wire material). For example, the skeleton 11 is formed by spirally winding the thin metal wire while folding it back and forth in a zigzag pattern so that peaks and valleys are alternately formed. In the contracted state, the skeleton 11 is displaced so that the spacing between adjacent peaks and valleys is narrower than in the expanded state. As a result, in the contracted state, the tilt of the thin metal wire in the longitudinal direction at the peaks and valleys is smaller, and the skeleton 11 is stretched in the longitudinal direction compared to the expanded state.

[0019] Examples of materials constituting the fine metal wires of the skeleton 11 include known metals or metal alloys such as Ni-Ti alloy (nitinol), cobalt-chromium alloy, titanium alloy, and stainless steel. When a Ni-Ti alloy is used as the material of the skeleton 11, the skeleton 11 can memorize the expanded shape by adjusting the skeleton 11 to the expanded shape and then subjecting it to a predetermined heat treatment. The skeleton 11 may also be made of a material other than metal (for example, ceramic, resin, etc.).

[0020] In the skeleton portion 11, parameters such as the number of folds and fold shape (number of ridges and shape of ridges) of the thin metal wire, and the cross-sectional area and cross-sectional shape of the thin metal wire can be set to appropriate values ​​depending on the specifications of the biological lumen 2 in which it is to be placed.

[0021] The configuration of the skeleton 11 is not limited to the spiral configuration described above. For example, the cylindrical skeleton 11 may be formed by weaving thin metal wires in a fence-like pattern. Alternatively, the cylindrical skeleton 11 may be formed by arranging a plurality of skeleton pieces in the longitudinal direction, the skeleton pieces being folded back in a zigzag pattern in the longitudinal direction so that peaks and valleys are alternately formed.

[0022] The covering portion 12 is a flexible membrane that is stretchable and biocompatible. The covering portion 12 forms the above-mentioned tubular flow path 4 and is attached to the skeleton portion 11 so as to cylindrically cover the skeleton portion 11 and block any gaps. The covering portion 12 prevents re-blockage due to infiltration of the lesion portion 3 into the biological lumen 2, and also suppresses the in-growth of cellular tissue into the skeleton portion 11, thereby ensuring the ease of removal of the covered stent 1.

[0023] The liquid permeability required for the covering portion 12 is appropriately set depending on the type of the biological lumen 2 in which the covered stent 1 is to be placed. As an example, when the covered stent 1 is a bile duct stent, the normal range of intrabile duct pressure is 0 to 200 mmH2O, so if the liquid permeability of the covering portion 12 is 0 at an internal pressure of 200 mmH2O (29.4 mmHg) or less, leakage of bodily fluids between the inside and outside of the covered stent 1 can be sufficiently suppressed. Therefore, when the covered stent 1 is a bile duct stent, it is preferable that the liquid permeability of the covering portion 12 is 0 when the internal pressure is 200 mmH2O or less.

[0024] As shown in FIGS. 4 and 5, the covering portion 12 has a multi-layer structure, and has a first layer 13 and a second layer 14 disposed on either side of the skeletal portion 11 in the radial direction.

[0025] The first layer 13 is a coating that covers the inner periphery of the framework 11. The first layer 13 has a liquid-impermeable, thin-film structure and functions to prevent leakage of bodily fluids between the inside and outside of the covered stent 1. In other words, while bodily fluids flow inside the covered stent 1 when it is placed in the biological lumen 2, the liquid-impermeable first layer 13 prevents the bodily fluids inside the covered stent 1 from leaking out to the outside of the covered stent 1.

[0026] The thickness of the first layer 13 is equal to or greater than the thickness of the second layer 14, and is preferably, for example, 20 μm or more and 100 μm or less from the viewpoint of liquid impermeability that suppresses leakage of body fluids.

[0027] The material of the first layer 13 is selected from the group consisting of polyvinylidene fluoride, urethane, and silicone. As an example, the coating of the first layer 13 is formed by immersing the skeleton 11 in a solution of the above material using a dipping method. The coating of the first layer 13 may also be formed by fixing a film made of the above material, which has been stretched or rolled, to the skeleton 11 by adhesive or the like.

[0028] The second layer 14 is formed by laminating on the outer peripheral side of the first layer 13, and is a coating that covers the outer periphery of the skeleton 11. The second layer 14 expands and contracts together with the liquid-impermeable first layer 13, and serves to reinforce the first layer 13 from the outer peripheral side.

[0029] The second layer 14 is a film formed by electrospinning, and has a nonwoven fabric-like structure in which nanofibers 14a are irregularly oriented, as shown in Figure 5. Since the nonwoven fabric-like second layer 14 has many fine pores formed in the gaps between the nanofibers 14a, the second layer 14 has higher liquid permeability than the thin film-like first layer 13 which does not have such pores.

[0030] In electrospinning, a high voltage is applied to a polymer solution in a spinning nozzle, and the charged polymer solution is drawn out of the spinning nozzle to spin fibers. The fluid from the spinning nozzle becomes a spiral flow due to air resistance, and fiberization due to entanglement of molecular chains and nano-sizing of the fiber diameter due to electrostatic repulsion simultaneously occur, resulting in the formation of a nonwoven fabric-like coating of nanofibers 14a as the second layer 14.

[0031] The material used to spin the nanofibers 14a of the second layer 14 by electrospinning is selected from the group consisting of polyvinylidene fluoride, urethane, and silicone, similar to the material of the first layer 13. The material of the first layer 13 and the material of the second layer 14 may be the same or different.

[0032] At the interface between the first layer 13 and the second layer 14 of the covering portion 12, as shown in Figure 5, the nanofibers 14a of the second layer 14 are welded to the outer peripheral surface of the first layer 13 by the residual solvent 14b that remains during spinning by the electrospinning method. The residual solvent 14b is a portion of the residual solvent 14b from the polymer solution that is scattered from the spinning nozzle and reaches the first layer 13 without evaporating, and adheres to the first layer 13 together with the nanofibers 14a. As a result, in the manufacturing process of the covered stent 1, the second layer 14 can be welded to the outer peripheral surface of the first layer 13 at the same time as the second layer 14 is formed, thereby integrating the first layer 13 and the second layer 14.

[0033] Here, it is generally known that the following parameters have an effect on film formation by the electrospinning method. (1) Concentration of polymer solution used for spinning If the concentration of the polymer solution is too low, the polymer solution will atomize at the tip of the spinning nozzle and disperse into the air, whereas if the concentration of the polymer solution is too high, the polymer solution will solidify due to its strong surface tension, making it difficult to spray the polymer solution from the spinning nozzle. (2) Spinning nozzle (needle) If there are burrs on the spinning nozzle, the stability of the nanofibers will decrease. Also, the smaller the diameter of the spinning nozzle, the smaller the diameter of the nanofibers will be. (3) Spinning distance (distance from spinning nozzle to collector) If the distance between the spinning fibers is too short, arcing occurs and the polymer solution does not diffuse sufficiently into the jet, reaching the collector as a solution.On the other hand, if the distance between the spinning fibers is too long, the jet does not reach the collector, and the nanofibers do not form a layer. (4) Humidity It is desirable to keep the humidity low (a rough guideline is 40% RH or less) so that the solvent can evaporate. (5) Applied voltage The appropriate relationship between the applied voltage and the distance between the needle and the collector is 1.0 to 2.0 kV / cm. (6) Membrane strength For the same thickness of the membrane, the thicker the fiber diameter, the stronger the mechanical strength.

[0034] For example, during film formation by the electrospinning method, it is believed that by adjusting the concentration of the polymer solution, the ambient humidity, and the applied voltage and appropriately controlling the evaporation rate of the solvent in the polymer solution, it is possible to adhere the remaining solvent 14b to the outer peripheral surface of the first layer 13. Furthermore, it is believed that the shorter the spinning distance and the higher the boiling point of the electrospinning solvent, the more easily the polymer solution will reach the collector, making it easier to increase the amount of remaining solvent 14b that adheres to the first layer 13.

[0035] Furthermore, if the fiber diameter of the nanofibers 14a in the second layer 14 is less than 500 nm, the nanofibers 14a will be less likely to weld to the first layer 13, reducing the adhesion of the second layer 14 to the first layer 13 and reducing the mechanical strength of the second layer 14 against elongation. On the other hand, if the fiber diameter of the nanofibers 14a is greater than 1500 nm, the gaps between the nanofibers 14a in the second layer 14 will be larger, making it easier for the density of the nanofibers 14a to decrease and increasing unevenness in the nanofibers 14a at each position in the second layer 14. For the reasons stated above, although not particularly limited, the fiber diameter of the nanofibers 14a forming the nonwoven fabric structure of the second layer 14 is preferably 500 nm or more and 1500 nm or less, and particularly preferably 700 nm or more and 1000 nm or less.

[0036] Furthermore, if the thickness of the second layer 14 is less than 10 μm, the mechanical strength of the second layer 14 cannot be sufficiently ensured, and the second layer 14 is prone to tearing. On the other hand, if the thickness of the second layer 14 is more than 20 μm, it becomes difficult to fill the covered stent 1 into the sheath of the catheter. For the above reasons, although there are no particular limitations, the thickness of the second layer 14 is preferably 10 μm or more and 20 μm or less.

[0037] The second layer 14 has a lower breaking elongation (elongation percentage) than the first layer 13 and a higher breaking strength than the first layer 13. The first layer 13 is thin and easily stretches in the planar direction, but is also prone to breaking when stretched. In contrast, the second layer 14 has irregularly oriented nanofibers 14a intricately entangled. When the second layer 14 stretches, the nonwoven-like gaps between the nanofibers 14a displace to narrow, allowing it to follow the deformation caused by stretching, but the fibers of the nanofibers 14a provide resistance to stretching in the planar direction. Therefore, the second layer 14 is less stretchable than the first layer 13 and has a lower breaking elongation, but has a higher breaking strength than the first layer 13.

[0038] Although not particularly limited, for example, the breaking elongation of the first layer 13 is preferably in the range of 400% or more and less than 1000%, and the breaking elongation of the second layer 14 is preferably in the range of 300% or more and less than 400%.

[0039] The operation of the covered stent 1 of this embodiment will be described below. In this embodiment, a covered stent 1 to be placed in a biological lumen 2 includes a tubular skeletal portion 11 that is radially expandable and contractable and longitudinally stretchable, and a covering portion 12 that tubularly covers the skeletal portion 11. The covering portion 12 has a thin-film structure and includes a first layer 13 that covers the skeletal portion 11 from the inner periphery, and a second layer 14 that has a nonwoven fabric structure formed by electrospinning on the outer periphery of the first layer 13 and is welded to the outer periphery of the first layer 13 to cover the skeletal portion 11 from the outer periphery. The first layer 13 has lower liquid permeability than the second layer 14, and the second layer 14 has a lower breaking elongation than the first layer 13 and a higher breaking strength than the first layer 13.

[0040] For example, consider a comparative example in which a typical covered stent having only the first layer 13 as the covering portion 12 is loaded into the sheath of a placement device by contracting and expanding the framework 11. When the covered stent of the comparative example is loaded, the first layer 13 is stretched and thinned (in a state of low mechanical strength), causing it to rub directly against the inner periphery of the sheath. Furthermore, when the loaded covered stent of the comparative example is released / deployed from the sheath, it also rubs against the inner surface of the sheath. Therefore, the friction with the sheath makes the first layer 13 of the comparative example prone to tearing, cracking, pinholes, and the like.

[0041] On the other hand, in the covering 12 of this embodiment, as described above, the nonwoven second layer 14 formed by electrospinning is welded and laminated to the outer periphery of the impermeable, thin-film first layer 13. The first layer 13 is more stretchable and has a lower breaking strength than the second layer 14, so when the covering 12 stretches, the first layer 13 is constrained from the outer periphery by the second layer 14. Therefore, when the covering 12 of this embodiment stretches, a decrease in thickness due to stretching of the first layer 13 is suppressed, and the strength of the first layer 13 can be maintained during, for example, loading of a sheath. Furthermore, in the covering 12 of this embodiment, the nonwoven second layer 14 located on the outer periphery contacts the inner surface of the sheath, so the stretched first layer 13 does not rub directly against the sheath. Therefore, the covered stent 1 of this embodiment is less likely to suffer tears, cracks, pinholes, etc. in the coating due to friction with the sheath of the placement device, and can be placed within the biological lumen 2 without reducing the water impermeability (anti-leakage performance of body fluids) of the first layer 13.

[0042] Furthermore, the covering portion 12 of this embodiment has a second layer 14 on the outer periphery that is nonwoven fabric, and many fibrous projections and recesses are formed on the surface of the second layer 14. As a result, the covering portion 12 of this embodiment has a relatively smaller contact area with the sheath than the comparative example, which reduces resistance during release and makes it less likely for the covering portion 12 to become blocked within the sheath. As a result, the covered stent 1 of this embodiment can also improve the operability of the placement device during procedures.

[0043] Furthermore, the second layer 14 of this embodiment is welded to the outer peripheral surface of the first layer 13 via the residual solvent 14b from the electrospinning method. As a result, in this embodiment, the second layer 14 can be welded to the first layer 13 at the same time that the second layer 14 is formed by the electrospinning method, thereby improving the productivity of the covered stent 1.

[0044] Furthermore, the first layer 13 of this embodiment is a thin film formed by a dipping method. Generally, when a thin film is formed on the skeleton 11 by a dipping method, it is difficult to achieve a uniform film thickness due to the surface tension of the dipping liquid, and thin portions of the thin film are generated, making the thin film prone to tearing when stretched. On the other hand, the covering 12 of this embodiment has the nonwoven fabric-like second layer 14 laminated on the outer periphery, so that a covering 12 that is resistant to tearing can be provided even when the first layer 13 is formed by a dipping method.

[0045] (Example) In the examples, a silicone sheet piece (Specimen 1) and a polyurethane sheet piece formed by electrospinning (Specimen 2) were stretched while held in a chuck using a tensile testing machine (AGX-V manufactured by Shimadzu Corporation), and the breaking strength and breaking elongation were measured.

[0046] The silicone sheet piece of the specimen 1 can be obtained by applying a silicone solution to a core material having a predetermined size by dipping it in the silicone solution, and then evaporating the solvent present on the core material. The dimensions of specimen 1 were 10 mm wide x 14 mm long x 62±6 μm thick. The test conditions for specimen 1 were a load of 20 N, a chuck distance of 10 mm, and a test speed of 40 mm / min. The breaking strength of specimen 1 was 10.2±1.6 (MPa), and the breaking elongation of specimen 1 was 959±55 (%). Therefore, it can be seen that the breaking elongation of specimen 1 in this example falls within a practical range of 400% or more and less than 1000%.

[0047] The polyurethane sheet piece used as specimen 2 was formed by cutting open a cylindrical membrane formed by electrospinning. The dimensions of specimen 2 were a fiber diameter of 958±352 nm, a width of 10 mm, a length of 60 mm, and a thickness of 15 μm. The test conditions for specimen 2 were a load of 20 N, a chuck distance of 20 mm, and a test speed of 20 mm / min. For the test of specimen 2, six specimens 2 corresponding to the longitudinal direction (TD direction) of the cylindrical membrane and six specimens 2 corresponding to the circumferential direction (MD direction) of the cylindrical membrane were prepared, and the average values ​​of their breaking strength and breaking elongation were obtained.

[0048] The average breaking strength of specimen 2 corresponding to the TD direction was 68.79 (MPa), and the average breaking elongation of specimen 2 corresponding to the TD direction was 361.05 (%). The average breaking strength of specimen 2 corresponding to the MD direction was 53.44 (MPa), and the average breaking elongation of specimen 2 corresponding to the MD direction was 356.88 (%). Therefore, it can be seen that the breaking elongation of specimen 2 in this example is in the range of 300% or more and less than 400%.

[0049] The present invention is not limited to the above-described embodiment, and various improvements and design changes may be made without departing from the spirit of the present invention.

[0050] Furthermore, the embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims.

[0051] The disclosure of the above embodiment encompasses the following technical ideas. (1) A covered stent to be placed in a biological lumen, comprising: a tubular skeleton that is expandable and contractable in the radial direction and stretchable in the longitudinal direction; and a covering that covers the skeleton in a tubular shape, wherein the covering has a thin film structure and comprises a first layer that covers the skeleton from the inside; and a second layer that has a nonwoven fabric structure formed by electrospinning on the outer periphery of the first layer and is welded to the outer surface of the first layer to cover the skeleton from the outside; wherein the first layer has lower liquid permeability than the second layer, and the second layer has lower breaking elongation than the first layer and higher breaking strength than the first layer. (2) The covered stent according to (1) above, wherein the second layer is welded to the outer peripheral surface of the first layer via the residual solvent from the electrospinning method. (3) The covered stent according to (2) above, wherein the first layer is a thin film formed by a dipping method. (4) A covered stent according to any one of (1) to (3) above, wherein the materials of the first layer and the second layer are each selected from polyvinylidene fluoride, urethane, and silicone. (5) A covered stent according to any one of (1) to (4) above, wherein the breaking elongation of the first layer is in the range of 400% or more and less than 1000%, and the breaking elongation of the second layer is in the range of 300% or more and less than 400%. (6) A covered stent according to any one of (1) to (5) above, wherein the fiber diameter of the fibers forming the nonwoven fabric structure of the second layer is 500 nm or more and 1500 nm or less. (7) A covered stent according to any one of (1) to (6) above, wherein the thickness of the second layer is 10 μm or more and 20 μm or less. (8) The covered stent according to any one of (1) to (7), wherein the covering portion has a liquid permeability of 0 when the internal pressure is 200 mmH2O or less. [Explanation of symbols]

[0052] 1...covered stent, 2...biological lumen, 3...lesion site, 4...tubular flow channel, 11...skeleton portion, 12...covering portion, 13...first layer, 14...second layer, 14a...nanofiber, 14b...residual solvent

Claims

1. A covered stent to be placed in a biological lumen, a cylindrical skeleton portion that is expandable and contractable in the radial direction and expandable and contractible in the longitudinal direction; a covering portion that covers the skeleton portion in a cylindrical shape, The covering portion is a first layer having a thin film structure and covering the skeleton from the inner periphery; a second layer having a nonwoven fabric structure formed by laminating the first layer on the outer periphery side by an electrospinning method, the second layer being welded to the outer periphery of the first layer to cover the outer periphery of the skeleton; the first layer being less liquid permeable than the second layer; The second layer has a lower breaking elongation than the first layer and a higher breaking strength than the first layer. Covered stent.

2. The second layer is welded to the outer peripheral surface of the first layer via the residual solvent in the electrospinning method. The covered stent of claim 1 .

3. The first layer is a thin film formed by a dipping method. The covered stent of claim 2.

4. The materials of the first layer and the second layer are each selected from polyvinylidene fluoride, urethane, and silicone. A covered stent according to any one of claims 1 to 3.

5. The breaking elongation of the first layer is in the range of 400% or more and less than 1000%, The breaking elongation of the second layer is in the range of 300% or more and less than 400%. A covered stent according to any one of claims 1 to 3.

6. The fiber diameter of the fibers forming the nonwoven fabric structure of the second layer is 500 nm or more and 1500 nm or less. A covered stent according to any one of claims 1 to 3.

7. The thickness of the second layer is 10 μm or more and 20 μm or less. A covered stent according to any one of claims 1 to 3.

8. The covering portion has an internal pressure of 200 mmH ２ When the temperature is 0 or less, the liquid permeability is 0. A covered stent according to any one of claims 1 to 3.

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