Membrane body for stent graft and method of manufacture

Abstract

To provide a membrane body for a tubular treatment device that ensures low liquid permeability and exhibits resistance to tearing or rupture when sutured.SOLUTION: A membrane body for a tubular treatment device includes a tubular membrane portion (12). The membrane portion forms a multi-layer structure having a first layer (21) formed of a fiber and a second layer (22) having liquid permeability lower than that of the first layer.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a membrane for a tubular therapeutic device and a tubular therapeutic device. [Background technology]

[0002] For example, stent grafts have been known as tubular medical devices used to treat aortic aneurysms and aortic dissections that occur in the aorta (see, for example, Patent Documents 1 and 2). The stent graft includes, for example, a skeleton made of metal wires and a coating covering the skeleton, and has an overall tubular shape. The stent graft expands when an external force is applied radially outward from the inside at a predetermined position within the blood vessel, and is placed within the blood vessel in a state of close contact with the blood vessel. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6131441 [Patent Document 2] Patent No. 5824759 Summary of the Invention [Problem to be solved by the invention]

[0004] The membrane of the stent graft preferably has low liquid permeability in order to suppress the inflow of blood into the lesion during use. On the other hand, when the membrane is fixed to the framework by suturing, the membrane may tear or break at the suture depending on the material of the membrane.

[0005] An object of the present invention is to provide a membrane for a tubular therapeutic device, which ensures low liquid permeability and is less susceptible to tearing or rupturing at the suturing, and a tubular therapeutic device. [Means for solving the problem]

[0006] One aspect of the present invention is a membrane body for a tubular therapeutic device having a tubular coating portion, the coating portion having a multilayer structure having a first layer made of fibers and a second layer having lower liquid permeability than the first layer.

[0007] Another aspect of the present invention is a tubular therapeutic device comprising a tubular coating portion and a skeletal portion sutured to one side of the coating portion, the coating portion having a multilayer structure including a first layer made of fiber and a second layer having lower liquid permeability than the first layer. Effect of the Invention

[0008] According to the present invention, it is possible to ensure low liquid permeability while making it difficult for tears or rips to occur at the seams. [Brief description of the drawings]

[0009] [Figure 1] 1 is a perspective view of a stent graft according to one embodiment of the present invention. [Diagram 2] FIG. 2 is a diagram showing a schematic configuration of a coating portion. [Diagram 3] FIG. 2 is a diagram showing a schematic cross-sectional structure of a portion surrounded by a dashed line in FIG. [Figure 4] FIG. 3 is a cross-sectional view taken along line IIIb-IIIb in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In each of the drawings described below, a configuration example of a stent graft 10 as one embodiment of a tubular therapeutic device is shown typically. The shape, dimensions, etc. of the stent graft 10 in the drawings are shown typically and do not represent the actual shape, dimensions, etc.

[0011] Fig. 1 is a perspective view showing a schematic configuration of a stent graft 10 according to one embodiment. Fig. 1 shows the stent graft 10 indwelled in a blood vessel (in use).

[0012] The stent graft 10 shown in Fig. 1 is a stent graft for blood vessels, and has a tubular overall shape. The stent graft 10 has openings at both ends in the axial direction Ax that communicate with each other, and has a tubular flow path therein through which the patient's blood passes when in use. 1 shows a straight tubular stent graft 10. However, the stent graft 10 of the present embodiment may have, for example, an arched shape (for example, a shape corresponding to the aortic arch of a patient) or a twisted shape.

[0013] The stent graft 10 has a so-called self-expanding configuration in which the shape of the expanded state is memorized. The stent graft 10 is housed in a cylindrical sheath (not shown) and introduced into the blood vessel 30 in a state (not shown) in which it is contracted radially inward. After being transported to a predetermined position in the blood vessel 30 (e.g., a lesion site 31 where an aortic aneurysm or the like has occurred), the stent graft 10 is released from the sheath and expands radially outward. The expanded stent graft 10 is placed in the blood vessel 30 in a state of intimate contact with the inner wall of the blood vessel 30 as shown in FIG. 1.

[0014] As shown in Fig. 1, the stent graft 10 includes a skeleton 11 and a coating 12 fixed to the skeleton 11. The coating 12 is an example of a membrane body for a tubular therapeutic device. A bare portion 14 made of, for example, a metal skeleton is formed at one end of the stent graft 10 in the axial direction Ax. The bare portion 14 generates friction between the stent graft 10 and the inner wall of the blood vessel 30 when the stent graft 10 is placed, and serves to suppress displacement (migration) of the stent graft 10.

[0015] The skeleton 11 is formed, for example, by winding a thin metal wire (wire material) in a spiral shape. For example, the thin metal wire is wound in a spiral shape while being bent so that peaks and valleys are alternately formed, thereby forming the skeleton 11. The cross-sectional shape of the thin metal wire of the skeleton 11 is, for example, circular or elliptical.

[0016] The skeleton 11 is configured to be deformable so as to self-expand from a contracted state in which it is contracted radially inward to an expanded state in which it is expanded radially outward.

[0017] Examples of materials constituting the thin metal wires of the skeleton 11 include known metals or metal alloys such as Ni-Ti alloy (nitinol), cobalt-chromium alloy, titanium alloy, stainless steel, etc. The skeleton 11 may be formed of a material other than metal (e.g., ceramic, resin, etc.).

[0018] In addition, for example, the material of the skeletal portion 11 (Nitinol, etc.), the cross-sectional area and cross-sectional shape of the thin metal wire of the skeletal portion 11 (circular wire material such as wire, or angular wire material by laser cutting), the number of folds and the fold shape of the skeletal portion 11 in the circumferential direction (the number of peaks and the shape of the peaks), and the helical pitch of the skeletal portion 11 in the axial direction (the amount of the skeleton per unit length of the stent graft 10) can be set to appropriate values ​​depending on the diameter of the blood vessel in which it is placed, etc. A detailed description of these parameters will be omitted.

[0019] The coating portion 12 is a tubular flexible membrane body that forms the above-mentioned tubular flow path, and is attached to the skeleton portion 11 so as to close gaps in the skeleton portion 11. In this embodiment, as shown in Fig. 1, the coating portion 12 is attached to the inside of the skeleton portion 11. In addition, outer coating portions 12a that partially cover the skeleton portion 11 from the outside are attached to both ends of the stent graft 10 in the axial direction Ax. The outer coating portion 12a may be formed, for example, by folding back the coating portion 12 from the inside to the outside of the skeleton portion 11. Alternatively, the outer coating portion 12a may be formed by overlapping a band-shaped coating portion 12 formed on the outside of the skeleton portion 11.

[0020] The outer coating portion 12a may be attached so as to entirely cover the skeletal portion 11 from the outside, that is, so as to sandwich and cover the skeletal portion 11 from the inside and outside using two coating portions 12. Moreover, the coating portion 12 may be attached only to the outside of the skeleton portion 11 .

[0021] 3 and 4, the skeleton 11 of this embodiment is sewn to the membrane 12 with thread 13. The skeleton 11 and the membrane 12 may be fixed to each other by, for example, adhesion, welding, or taping.

[0022] Fig. 2 is a diagram showing a schematic configuration of the coating portion 12. Fig. 3 is a diagram showing a schematic cross-sectional structure of a portion surrounded by a dashed line in Fig. 1. Fig. 4 is a cross-sectional view taken along line IIIb-IIIb in Fig. 3.

[0023] The membrane portion 12 is a membrane body with a multi-layer structure in which a first layer 21 made of fibers and a second layer 22 having lower liquid permeability than the first layer 21 are laminated. In addition, an adhesive layer 23 is formed between the first layer 21 and the second layer 22 as an intermediate layer to bond the first layer 21 and the second layer 22 together.

[0024] The first layer 21 is, for example, a fabric in which fibers are arranged in a mesh pattern, and is made of a woven, knitted, or nonwoven fabric made of a biocompatible fiber material. This first layer 21 mainly functions to prevent tears or rips in the portion sewn with the thread 13. Examples of fiber materials for the first layer 21 include polyester resins such as polyethylene terephthalate and fluororesins such as PTFE (polytetrafluoroethylene). 3 and 4 show an example in which the first layer 21 is formed of a woven fabric, but as described above, the coating portion 12 may be a knitted fabric or a nonwoven fabric. The weaving method of the fabric of the first layer 21 may be any of plain weave, twill weave, and satin weave.

[0025] The second layer 22 is composed of a liquid-impermeable film formed by stretching, rolling, etc., a biocompatible material. Examples of materials for the second layer 22 include fluororesins such as PTFE (polytetrafluoroethylene), but polyester resins such as polyethylene terephthalate may also be used.

[0026] The second layer 22 has the function of suppressing leakage of bodily fluids between the inside and outside of the stent graft 10. When the stent graft 10 is in use, blood flows inside the stent graft 10, but the presence of the liquid-impermeable second layer 22 suppresses the blood inside the stent graft 10 from flowing into the diseased site 31 on the outside of the stent graft 10. In addition, while minute pores are formed in gaps between fibers in the fabric of the first layer 21, there are no gaps between fibers like in the fabric on the surface of the second layer 22. Therefore, the second layer 22 has lower liquid permeability than the first layer 21.

[0027] The adhesive layer 23 may be any material that can bond the fabric of the first layer 21 to the second layer 22. When heating is performed during bonding, the adhesive layer 23 is made of a material that has a lower melting point than the first layer 21 and the second layer 22. Examples of materials for the adhesive layer 23 include silicone, urethane, and polyethylene. As an example, silicone can be attached to at least the adhesive surface of the fabric of the first layer 21 facing the second layer 22 by dipping or the like, and the fabric of the first layer 21 with the silicone attached and the film of the second layer 22 can be overlapped and then heated, thereby bonding the first layer 21 and the second layer 22 together with silicone.

[0028] The adhesive layer 23 in the coating portion 12 is not essential, and the first layer 21 and the second layer 22 may be fixed to each other by a method other than adhesion. For example, the adhesive layer 23 may be omitted by subjecting the surface of either the first layer 21 or the second layer 22 to a surface modification treatment to increase the affinity between the first layer 21 and the second layer 22 and bond them together.

[0029] In this embodiment, the skeleton 11 is sewn to the membrane 12, which has a multi-layer structure in which a first layer 21 of fabric and a second layer 22 of film are laminated together. At this time, the thread 13 sewing the skeleton 11 and the membrane 12 together passes through gaps between the fibers in the first layer 21 of the membrane 12 and penetrates the second layer 22 of the membrane 12. Therefore, when the thread 13 is passed through the second layer 22 by sewing, an opening 15 is formed in the second layer 22 as shown in Figures 3 and 4.

[0030] Here, since the stent graft 10 expands radially outward when in use, a force that stretches in the circumferential direction acts on the coating portion 12 of the stent graft 10 when in use. Furthermore, when the stent graft 10 is subjected to periodic vibrations due to vascular pulsation during use, such vibrations may cause misalignment of the skeletal portion 11 and the coating portion 12 on the circumferential surface of the stent graft 10. The force that causes such misalignment causes a shear force to act between the coating portion 12 and the thread 13 that sutures the skeletal portion 11 and the coating portion 12.

[0031] When the above forces act on the coating 12 in a compound manner, for example, rips or tears are likely to occur at the opening 15 of the second layer 22 where stress is likely to concentrate. However, since the coating 12 has a multi-layer structure of the first layer 21 and the second layer 22 made of fibers, the fibers arranged in a mesh pattern in the first layer 21 provide resistance to the force that tries to widen the opening 15 of the second layer 22. Therefore, the strength of the area around the opening 15 of the second layer 22 is supplemented by the first layer 21, making it less likely that the second layer 22 will rip or tear due to stitching.

[0032] Regarding the positional relationship between the coating part 12 and the skeleton 11, the coating part 12 may be attached so that the first layer 21 faces the skeleton 11, or the coating part 12 may be attached so that the second layer 22 faces the skeleton 11. For example, by attaching the coating part 12 so that the second layer 22 faces the inside, the second layer 22, which is smoother and has higher antithrombotic properties than the first layer 21, is more likely to come into contact with blood. This makes it possible to make the stent graft 10 less likely to become clogged with a thrombus. This is particularly useful for small-diameter stent grafts that are thought to be more susceptible to clogging. In this embodiment, as shown in Figs. 3 and 4, the coating portion 12 is attached to the inside of the skeleton portion 11 such that the first layer 21 faces the skeleton portion 11.

[0033] As described above, the application of periodic vibrations to the stent graft 10 due to vascular pulsation can cause misalignment between the skeletal portion 11 and the coating portion 12 on the circumferential surface of the stent graft 10. However, when the first layer 21 faces the skeletal portion 11, the fabric of the first layer 21 contacts the skeletal portion 11, and the skeletal portion 11 and the second layer 22 do not directly contact each other. Therefore, when the above-mentioned misalignment between the skeletal portion 11 and the coating portion 12 occurs, it is possible to suppress the second layer 22, which is responsible for the liquid impermeability function, from rubbing against the skeletal portion 11 and wearing away. Furthermore, when the first layer 21 faces the outside of the stent graft 10, the surface of the first layer 21 has a relatively large surface roughness due to the unevenness of the fibers, and therefore the contact area between the skeletal portion 11 and the coating portion 12 is reduced compared to when the coating portion 12 has a smooth surface. Therefore, even if the position of the skeletal portion 11 and the coating portion 12 is shifted due to vascular pulsation or the like, the coating portion 12 can be made less susceptible to wear.

[0034] On the other hand, although not shown, when the coating portion 12 is attached to the inside of the skeleton portion 11 such that the second layer 22 faces the skeleton portion 11, the second layer 22 faces the outer periphery of the stent graft 10. In this case, when the stent graft 10 is used, the second layer 22, which has a liquid impermeability function, is pressed against the inner wall of the blood vessel, and the inner wall of the blood vessel and the second layer 22 are easily brought into close contact with each other. For example, at the end of the stent graft 10, a gap is less likely to occur between the inner wall of the blood vessel and the second layer 22, which makes it easier to suppress blood flow from the end of the stent graft 10 to the lesion site 31.

[0035] As described above, the stent graft 10 of this embodiment includes the tubular coating portion 12 and the framework portion 11 sutured to one surface of the coating portion 12. The coating portion 12 is a multilayer membrane body having a first layer 21 made of fiber and a second layer 22 having lower liquid permeability than the first layer 21. According to this embodiment, the coating portion 12 has a second layer 22 with low liquid permeability, thereby suppressing leakage of bodily fluids between the inside and outside of the stent graft 10 and preventing blood on the inside of the stent graft 10 from flowing into the lesion site 31 on the outside. Furthermore, since the coating portion 12 has a multi-layer structure of the first layer 21 and the second layer 22 made of fibers, the fibers arranged in a mesh pattern in the first layer 21 provide resistance to a force that attempts to widen the opening 15 in the second layer 22 formed by passing the thread 13 through. Therefore, according to this embodiment, the second layer 22 is less likely to tear or break due to sewing.

[0036] Furthermore, according to the stent graft 10 having a coating portion 12 with a multilayer structure of this embodiment, the overall thickness of the coating portion 12 can be made smaller than when the coating portion is made of only fabric or only a film-like membrane body.

[0037] For example, if the membrane portion is made of fabric only, it is necessary to make the membrane portion thicker in order to reduce the liquid permeability. In addition, when the membrane part is made of only a film-like membrane, it is relatively easy to ensure liquid impermeability, but when it is sewn to the skeleton, for example, there is a possibility that bodily fluids may leak due to tears or breaks at the sewn parts. Therefore, even when the membrane part is made of only a film-like membrane, it is necessary to make the membrane part thicker to prevent tears or breaks. If the coating portion is made thick as described above, there is a concern that the tubular therapeutic instrument may become less easily stored in the sheath and may become less easily released from the sheath.

[0038] In contrast, according to this embodiment, the coating portion 12 has a multi-layer structure, with the first layer 21 ensuring strength against rips and tears, and the second layer 22 ensuring liquid impermeability. Therefore, it is not necessary to make the first layer 21 and the second layer 22 thick, and as a result, the overall thickness of the coating portion 12 can be reduced. As a result, according to this embodiment, it becomes possible to perform a stent graft placement procedure using a sheath with a smaller diameter than conventionally, and the burden (invasiveness) on the patient during surgery can be further reduced.

[0039] Moreover, according to this embodiment, the coating part 12 is attached to the inside of the skeletal part 11 so that the first layer 21 faces the skeletal part 11 (FIGS. 3 and 4). Therefore, the skeletal part 11 comes into contact with the fabric of the first layer 21 but does not come into contact with the second layer 22, so that the second layer 22 can be prevented from rubbing against the skeletal part 11 and becoming worn.

[0040] Furthermore, according to this embodiment, outer coating portions 12a are formed on both ends of the stent graft 10 in the axial direction Ax to partially cover the skeleton portion 11 from the outside (FIG. 1). Here, by arranging the outer coating portion 12a of the stent graft 10 such that the second layer 22 faces the outer periphery of the stent graft 10, the inner wall of the blood vessel and the second layer 22 come into close contact with each other, making it difficult for a gap to form between the inner wall of the blood vessel and the second layer 22. This makes it easier to further suppress the inflow of blood from the ends of the stent graft 10 to the lesion site 31.

[0041] As described above, 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.

[0042] For example, in the above embodiment, the coating portion 12 has one each of the first layer 21 and the second layer 22, but the coating portion 12 may have a plurality of either the first layer 21 or the second layer 22. For example, the coating portion 12 may be a multi-layered film body in which the second layer 22 is disposed between two first layers 21, or a multi-layered film body in which the first layer 21 is disposed between two second layers 22.

[0043] Furthermore, in the coating portion 12, the first layer 21, which is responsible for ensuring strength against rips and tears, does not have to be disposed over the entire coating portion 12. For example, the first layer 21 may be provided partially on the circumferential surface of the coating portion 12 in accordance with the position where the skeletal portion 11 is disposed, so that the stitched portions of the skeletal portion 11 are partially reinforced.

[0044] The first layer 21 may contain a polymeric compound such as polyethylene (particularly, ultra-high molecular weight polyethylene having a molecular weight of about 1 to 6 million). This can impart slipperiness to the first layer 21, and can reduce the resistance when the stent graft 10 is loaded into the sheath or released from the sheath. The polymeric compound may be filled and blocked in gaps between the fibers of the first layer 21, thereby reducing the liquid permeability of the first layer 21.

[0045] In addition, the embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present invention is defined by the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0046] 10 Stent graft (tubular treatment device) 11 Skeleton 12 Membrane 12a Outer membrane part 13. Thread 21 1st layer 22 2nd layer 23 Adhesive layer

Claims

[Claim 1] A membrane body for a tubular medical device having a tubular coating portion, The coating portion is A first layer made of fibers; A second layer having a lower liquid permeability than the first layer. Membrane body for tubular treatment devices.

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