Artificial blood vessel and method for manufacturing artificial blood vessel

Abstract

This artificial blood vessel comprises weft threads and warp threads composed of a multifilament yarn. The artificial blood vessel has first regions where the weft threads and the warp threads are woven in plain weave, second regions each having second region-side first portions where a warp thread crosses over a plurality of weft threads and second region-side second portions where the warp thread extends while crossing over one weft thread, and third regions each having third region-side first portions where a warp thread crosses over a plurality of weft threads and third region-side second portions where the warp thread extends while crossing over one weft thread. The second region-side first portions and the third region-side first portions have a covering portion. The covering portion is configured to be relatively movable with respect to the surface of the warp thread located between the pair of second region-side first portions and the warp thread located between the pair of third region-side first portions. Such a structure makes it possible to provide an artificial blood vessel that can achieve an improvement in blood leakage resistance while maintaining flexibility.

Description

Artificial blood vessel and method for manufacturing the same

[0001] The present invention relates to a vascular graft and a method for producing the same.

[0002] Artificial blood vessels are used, for example, to replace diseased biological blood vessels. As shown in Patent Document 1, for example, artificial blood vessels are constructed with a woven structure of warp and weft threads. Artificial blood vessels are required to have low blood leakage from the artificial blood vessel, i.e., high blood leakage resistance. The blood leakage resistance of artificial blood vessels can be improved by increasing the weave density of the warp and weft threads.

[0003] JP 2012-139498 A

[0004] However, although increasing the weave density of an artificial blood vessel can improve the resistance to blood leakage, it impairs the flexibility required of the artificial blood vessel.

[0005] Therefore, an object of the present invention is to provide an artificial blood vessel that can improve blood leakage resistance while maintaining flexibility, and a method for manufacturing the artificial blood vessel.

[0006] The artificial blood vessel of the present invention has weft yarns and warp yarns made of multifilament yarns, and the artificial blood vessel has a first region in which the warp yarns and the weft yarns are woven in a plain weave, a second region on one side of the artificial blood vessel having a first portion on a second region side where the warp yarns cross multiple weft yarns and a second portion on the second region side where the warp yarns extend across one weft yarn, and a third region on one side of the artificial blood vessel having a first portion on a second region side where the warp yarns cross multiple weft yarns. a third region having a third region side first portion and a third region having a third region side second portion in which the warp extends across one weft, the third region having a third region side first portion in which the warp extends across one weft, the second region side first portion being adjacent to the third region side second portion in the extension direction of the weft, the second region side second portion being adjacent to the third region side first portion in the extension direction of the weft, the second region side first portion and the third region side first portion being adjacent to the second region side first portion and the The artificial blood vessel has a covering portion formed by a melted and solidified multifilament yarn on the surface of the third region side first portion, or a resin layer coated on the surface of the multifilament yarn, and the covering portion covers the multifilament yarn in the second region side first portion and the third region side first portion in a planar manner, and the covering portion extends in the extension direction of the weft yarn so as to cover at least a portion of the surface of the warp yarn arranged between the pair of second region side first portions in the extension direction of the weft yarn and the surface of the warp yarn arranged between the pair of third region side first portions in the extension direction of the weft yarn, and the covering portion is configured to be able to move radially of the artificial blood vessel relative to the surface of the warp yarn arranged between the pair of second region side first portions in the extension direction of the weft yarn and the surface of the warp yarn arranged between the pair of third region side first portions in the extension direction of the weft yarn in accordance with the movement of the artificial blood vessel.

[0007] The method for producing an artificial blood vessel of the present invention is a method for producing an artificial blood vessel having weft yarns and warp yarns made of multifilament yarns, the method comprising: a first region in which the warp yarns and the weft yarns are woven in a plain weave; a second region on one side of the artificial blood vessel having a first portion on a second region side where the warp yarns cross a plurality of weft yarns and a second portion on the second region side where the warp yarns extend across a single weft yarn; a third region on one side of the artificial blood vessel having a first portion on a third region side where the warp yarns cross a plurality of weft yarns and a second portion on the third region side where the warp yarns extend across a single weft yarn; a third region having a third region-side second portion extending across the weft yarn, and a base material having these third regions alternately arranged in the extending direction of the weft yarn; and a heating medium is brought into contact with a surface of the base material that will become the outer surface of the artificial blood vessel, thereby melting and solidifying the multifilament yarns on the surfaces of the second region-side first portion and the third region-side first portion, or by coating a resin layer on the surfaces of the second region-side first portion and the third region-side first portion. the covering portion extends in the direction of extension of the weft yarn so as to cover at least a portion of the surface of the warp yarn disposed between the pair of second-region-side first portions in the direction of extension of the weft yarn and at least a portion of the surface of the warp yarn disposed between the pair of third-region-side first portions in the direction of extension of the weft yarn, and the covering portion is configured to be movable in the radial direction of the artificial blood vessel relative to the surface of the warp yarn disposed between the pair of second-region-side first portions in the direction of extension of the weft yarn and the surface of the warp yarn disposed between the pair of third-region-side first portions in the direction of extension of the weft yarn in accordance with the movement of the artificial blood vessel.

[0008] According to the artificial blood vessel and the method for producing the artificial blood vessel of the present invention, it is possible to improve the resistance to blood leakage while maintaining flexibility.

[0009] 6A is a side view of an artificial blood vessel according to one embodiment of the present invention; FIG. 1B is a partially enlarged view of region II in FIG. 1; FIG. 2 is a woven fabric structure diagram showing an example of the woven structure of the base material used in the artificial blood vessel of FIG. 1; FIG. 3 is a schematic view of a cross section of the base material obtained by cutting the base material along line IV-IV in FIG. 3; FIG. 4 is a schematic view of a cross section of the base material obtained by cutting the base material along line V-V in FIG. 3; FIG. 5 is a 30x SEM photograph of the surface of the artificial blood vessel of this embodiment taken in the radial direction of the artificial blood vessel; FIG. 6B is a 100x SEM photograph of the surface of the artificial blood vessel of FIG. 6A taken in an oblique direction; FIG. 6C is a 30x SEM photograph of the surface of the artificial blood vessel of another embodiment taken in the radial direction of the artificial blood vessel; FIG. 6D is a schematic view showing a state in which a covering portion provided on one warp thread covers another warp thread; FIG. 8 is a schematic view showing a state in which a covering portion provided on one warp thread covers another warp thread when a force is applied radially outward to the inner surface of the artificial blood vessel from the state shown in FIG. 8A. 1 is a photograph of the artificial blood vessel of the present embodiment when visible light is transmitted through it. FIG. 2 is a schematic diagram showing a state in which a cylindrical body is placed on the outside of a molding core material and a winding member is partially wrapped around the outside of the cylindrical body in order to form peaks and valleys in the artificial blood vessel. FIG. 3 is a schematic diagram showing a state in which a cylindrical body is placed on the outside of a molding core material, as viewed in the axial direction. FIG. 4 is a diagram showing an example of the configuration of a housing member that houses a cylindrical body and a compression element placed on the outside of the molding core material in order to pressurize the cylindrical body. FIG. 5 is a schematic diagram showing the interior of a housing member.

[0010] An artificial blood vessel according to one embodiment of the present invention will be described below with reference to the drawings. Note that the embodiment described below is merely an example, and the artificial blood vessel of the present invention is not limited to the following embodiment.

[0011] In this specification, expressions such as "perpendicular to A" and similar expressions do not refer only to a direction that is completely perpendicular to A, but also refer to a direction that is approximately perpendicular to A. In this specification, expressions such as "parallel to B" and similar expressions do not refer only to a direction that is completely parallel to B, but also refer to a direction that is approximately parallel to B. In this specification, expressions such as "C-shape" and similar expressions do not refer only to a perfect C-shape, but also refer to a shape that visually resembles a C-shape (approximately a C-shape).

[0012] Fig. 1 is a side view of an artificial blood vessel according to one embodiment of the present invention. Fig. 2 is a partially enlarged view of region II of the artificial blood vessel in Fig. 1. Fig. 3 is a woven fabric diagram showing an example of the woven structure of a base material used in the artificial blood vessel in Fig. 1.

[0013] Artificial blood vessels are used, for example, to replace diseased biological blood vessels or to bypass the biological blood vessels. As shown in Figures 1 and 2, the artificial blood vessel VE of this embodiment has peaks M and valleys V alternately formed in the direction of the axis X (see Figure 1) of the artificial blood vessel VE. When peaks M and valleys V are alternately formed in the artificial blood vessel VE, the artificial blood vessel VE can be made flexible and is less likely to kink when bent. For convenience of explanation, in this specification, the portion radially outward (upper side in Figure 2) from the midpoint between the crests Mt of the peaks M (see Figure 2) and the bottoms Vb of the valleys V (see Figure 2) in the radial direction of the artificial blood vessel VE will be referred to as the peak M, and the portion radially inward (lower side in Figure 2) from the midpoint between the crests Mt of the peaks M and the bottoms Vb of the valleys V will be referred to as the valley V. In this embodiment, the artificial blood vessel VE is formed in a cylindrical shape with peaks M and valleys V formed in a spiral shape, but the artificial blood vessel does not have to have peaks M and valleys V.

[0014] The diameter of the artificial blood vessel VE can be varied depending on the site of use, etc., and is not particularly limited. For example, the artificial blood vessel VE may be a large-diameter artificial blood vessel with an inner diameter of 10 mm or more (for the thoracic and abdominal aorta), a medium-diameter artificial blood vessel with an inner diameter of 6 mm or more but less than 10 mm, such as 6 mm or 8 mm (for arteries in the lower limbs, neck, and axillary regions), or a small-diameter artificial blood vessel with an inner diameter of less than 6 mm. The thickness of the artificial blood vessel VE can be varied appropriately depending on the inner diameter and length of the artificial blood vessel to be used, and is not particularly limited. For example, the thickness of the artificial blood vessel VE can be 0.1 to 2 mm.

[0015] The length of the artificial blood vessel VE in the axial direction X can be changed depending on the site where it is used, and is not particularly limited. For example, the length of the artificial blood vessel VE in the axial direction X can be 100 to 1000 mm. When the artificial blood vessel VE is to be transplanted into a desired site, it is cut to a predetermined length by a doctor or the like. Depending on the site where it is to be transplanted, the artificial blood vessel VE may be cut perpendicular to the axial direction X, or may be cut obliquely at a predetermined angle relative to the axial direction X.

[0016] When the artificial blood vessel VE has peaks M and valleys V, the number of peaks M (or valleys V) (the number of pleats) of the artificial blood vessel VE is not particularly limited and can be appropriately set depending on the required kink resistance. For example, in the case of an artificial blood vessel with an outer diameter of 15 mm, the number of peaks M (the number of pleats) of the artificial blood vessel VE can be 20 to 70, preferably 25 to 35, per 100 mm of length in the axial X direction. Furthermore, the spacing (pitch) in the axial X direction between the apex Mt of a peak M of the artificial blood vessel VE (see FIG. 2 ) and the apex Mt of an adjacent peak M of the artificial blood vessel VE is not particularly limited and can be, for example, 10 to 30%, preferably 15 to 25%, of the outer diameter of the artificial blood vessel VE (the outer diameter at the apex Mt of the peak M). Furthermore, the depth from the top Mt of the peak M to the bottom Vb of the valley V (see Figure 2) is not particularly limited, but can be, for example, 5 to 20%, preferably 5 to 15%, of the outer diameter of the artificial blood vessel VE.

[0017] In this embodiment, the curvature at the crests Mt of the peaks M is smaller than the curvature at the bottoms Vb of the valleys V (in this embodiment, the radius of curvature at the crests Mt of the peaks M is larger than the radius of curvature at the bottoms Vb of the valleys V). Note that "the curvature at the crests Mt is smaller than the curvature at the bottoms Vb of the valleys V" means that the degree of curvature of the crests Mt of the peaks M along the axial direction X is smaller than the degree of curvature of the bottoms Vb of the valleys V along the axial direction X (the curve of the peaks M is gentler than the curve of the valleys V), and the peaks M and the valleys V do not necessarily form perfect arc surfaces. If the curvature at the crests Mt of the peaks M is smaller than the curvature at the bottoms Vb of the valleys V, stress will be concentrated at the valleys V when an external force is applied to the artificial blood vessel VE, making the artificial blood vessel VE more likely to bend from the valleys V. The curvatures of the peaks M and valleys V are not particularly limited. For example, the radius of curvature of the tops Mt of the peaks M can be 5 to 8% of the diameter of the artificial blood vessel VE (and larger than the radius of curvature of the bottoms Vb of the valleys V). The radius of curvature of the bottoms Vb of the valleys V can be 2 to 3% of the diameter of the artificial blood vessel VE (and smaller than the radius of curvature of the tops Mt of the peaks M). By making the artificial blood vessel VE more easily bendable, the bent artificial blood vessel VE is less likely to return to its original shape, and the load on the connection site between the artificial blood vessel VE and a blood vessel, etc., can be reduced.

[0018] The curved portions at the peaks Mt of the peaks M and the curved portions at the bottoms Vb of the valleys V can be connected by flat portions PL (see FIG. 2). This allows for improved flexibility and kink resistance compared to when the curved portions are directly connected to each other. The angle θ between the flat portion PL1 on one side and the flat portion PL2 on the other side can be set to 20° to 40°, preferably 30°. The angle θ between the flat portion PL1 on one side and the flat portion PL2 on the other side can be set appropriately depending on the diameter of the artificial blood vessel, the height of the peaks, the height of the valleys, the pitch, etc.

[0019] Next, the structure of the base material that constitutes the artificial blood vessel VE will be described.

[0020] The artificial blood vessel VE of this embodiment has a predetermined weave structure in which warp threads 1 and weft threads 2 are woven. In this embodiment, the artificial blood vessel VE has weft threads 2 and warp threads 1 made of multifilament yarns. In this embodiment, of the warp threads 1 and weft threads 2 that make up the artificial blood vessel VE, at least the warp threads 1 are made of multifilament yarns containing multiple filament yarns. The weft threads 2 may be made of multifilament yarns or monofilament yarns. The predetermined weave structure of the artificial blood vessel VE will be described later.

[0021] In this embodiment, as shown in FIG. 3 , the artificial blood vessel VE has warp threads 1a-1l (hereinafter collectively referred to as warp threads 1) extending along the axial X direction (the vertical direction in FIG. 3 ) and weft threads 2a-2l (hereinafter collectively referred to as weft threads 2) extending along the circumferential direction of the artificial blood vessel VE (the horizontal direction in FIG. 3 ). More specifically, as shown in FIG. 3 , the artificial blood vessel VE has a plurality of warp threads 1a-1l and a plurality of weft threads 2a-2l, and has a woven structure in which the warp threads 1 and the weft threads 2 are intertwined. Note that in FIG. 3 , the warp threads 1 extend in the vertical direction, and the extending direction of the warp threads 1 (the axial X direction of the artificial blood vessel VE) is referred to as D1. Also, in FIG. 3 , the weft threads 2 extend in the horizontal direction, and the extending direction of the weft threads 2 (the circumferential direction of the artificial blood vessel VE) is referred to as D2. In Figure 3, the black (dotted) areas indicate the areas where the warp threads 1 emerge on the outer surface (front surface) of the artificial blood vessel VE, and the white areas indicate the areas where the weft threads 2 emerge on the outer surface of the artificial blood vessel VE. Note that the loom for manufacturing the artificial blood vessel VE is not particularly limited.

[0022] As will be described later, in this embodiment, the warp threads 1 have portions R21 and R31 that extend across multiple weft threads 2 (see Figs. 3 and 5). Specifically, as shown in Fig. 3, the warp threads 1 have portions R21 and R31 that extend across multiple weft threads 2, and portions R1, R22, and R32 that extend across a single weft thread 2. Furthermore, the woven structure of the artificial blood vessel VE is not necessarily limited to the woven structure shown in Fig. 3, and other woven structures may be used.

[0023] 3, the artificial blood vessel VE has a first region R1 in which warp threads 1 and weft threads 2 are woven in a plain weave. The artificial blood vessel VE also has, on one surface of the artificial blood vessel VE (in this embodiment, the outer surface (front surface) of the artificial blood vessel VE), a second region R2 having a second region-side first portion R21 (a portion extending across multiple weft threads 2) in which the warp threads 1 extend across multiple weft threads 2, and a second region-side second portion R22 (a portion extending across one weft thread 2) in which the warp threads 1 extend across one weft thread 2. Furthermore, the artificial blood vessel VE has a third region R3 on one surface of the artificial blood vessel VE (in this embodiment, the outer surface (surface) of the artificial blood vessel VE). The third region R3 has a first portion R31 (a portion extending across multiple wefts 2) on the third region side where the warp threads 1 cross multiple wefts 2, and a second portion R32 (a portion extending across one weft 2) on the third region side where the warp threads 1 cross multiple wefts 2. As shown in FIG. 3 , the first region R1, the second region R2, and the third region R3 are alternately formed in the extending direction D2 of the wefts 2. That is, the first region R1, the second region R2, and the third region R3 are repeatedly arranged in this order in the extending direction D2 of the wefts 2. The second-region-side first portion R21 is adjacent to the third-region-side second portion R32 in the extending direction D2 of the weft yarn 2, and the second-region-side second portion R22 is adjacent to the third-region-side first portion R31 in the extending direction D2 of the weft yarn 2. When the artificial blood vessel VE of this embodiment has the above-described configuration, as described below, the warp yarns 1 made of multifilament yarns that extend long and unconstrained in the second-region-side first portion R21 or the third-region-side first portion R31 spread into the plain-weave first region R1. Due to the three-dimensional structure of the warp yarns 1, when blood seeps through the fiber gaps that occur in the plain-weave first region R1, the blood is prevented from leaking and is retained within the three-dimensional structure. Coagulation of the blood in this retained state improves blood leakage resistance. The configuration and weaving structure of each part of the artificial blood vessel VE are described below.

[0024] The warp threads 1 are fibers that extend in one direction among the fibers that make up the artificial blood vessel VE. In this embodiment, the warp threads 1 extend along the length of the artificial blood vessel VE (the direction of the axis X). The warp threads 1 are made of a material that is applicable to fabric artificial blood vessels formed by a woven fiber structure. The material of the warp threads 1 is not particularly limited as long as it is applicable to fabric artificial blood vessels. For example, the material of the warp threads 1 can be polyester, polytetrafluoroethylene, polyamide, etc. Furthermore, the material of the warp threads 1 can be a composite material composed of two or more applicable materials with different properties, such as melting points and stretch rates. For example, the material of the warp threads 1 can be a synthetic fiber in which polyethylene terephthalate (PET) and polytrimethylene terephthalate (PTT), etc., are combined during the spinning process to form a single long fiber with a spiral crimp. For example, when a composite material having a spiral crimp and composed of two types of materials with different melting points and elasticity is used as the material for warp thread 1, the three-dimensional structure formed by warp thread 1 described below tends to expand in the extension direction D2 of weft thread 2, thereby improving the blood retention performance and improving resistance to blood leakage.

[0025] In this embodiment, the warp yarns 1 are made of multifilament yarns. The fineness of the warp yarns 1 can be, for example, 0.25 to 2.50 dtex for the single yarn fineness of the warp yarns 1, preferably 0.50 to 2.00 dtex, and 2 to 2500 dtex for the total fineness of the warp yarns 1, preferably 6 to 1600 dtex, more preferably 10 to 540 dtex, and even more preferably 30 to 200 dtex. By setting the single yarn fineness of the warp yarns 1 and the total fineness of the warp yarns 1 within the above ranges, the warp yarns 1 in the second region R2 and the third region R3 can be effectively spread toward the first region R1. Therefore, when blood seeps out from the gaps in the first region R1, the warp yarns 1 in the second region R2 and the third region R3 prevent the blood from leaking out and are held in place by the three-dimensional structure of the warp yarns 1. The blood coagulates in this held state, thereby improving blood leakage resistance. The "single yarn fineness" is the fineness per filament constituting the warp yarn 1, and the "total fineness" is the product of the single yarn fineness and the number of filaments constituting the warp yarn 1. The number of filaments constituting one warp yarn (hereinafter referred to as the number of filaments) is not particularly limited, but for example, as will be described later, when the total number of filaments in the warp yarn 1 is 1.5 times or more the number of filaments per weft yarn 2, and the number of warp yarns 1 spanning multiple weft yarns 2 in the second region R2 is one, the number of filaments per warp yarn 1 can be 8 to 1,000, preferably 12 to 800, more preferably 20 to 270, and even more preferably 60 to 100. As will be described later, when the number of filaments per warp thread 1 is 0.8 to 1.2 times the number of filaments per weft thread 2 and the number of warp threads 1 spanning multiple weft threads 2 in the second region R2 is two or more, the number of filaments per warp thread 1 can be 4 to 500, preferably 6 to 400, more preferably 10 to 135, and even more preferably 30 to 50.

[0026] The weft threads 2 are fibers that make up the artificial blood vessel VE and extend in a direction that intersects with the warp threads 1. In this embodiment, the weft threads 2 are fibers that extend in the circumferential direction of the artificial blood vessel VE. The weft threads 2 are made of a material that is applicable to a fabric artificial blood vessel that is formed with a woven fiber structure. The material of the weft threads 2 is not particularly limited as long as it is applicable to a fabric artificial blood vessel. For example, the material of the weft threads 2 can be polyester, polytetrafluoroethylene, polyamide, etc.

[0027] Each of the weft yarns 2 may be a monofilament yarn or a multifilament yarn, but in this embodiment, the weft yarn 2 is made of a multifilament yarn. The fineness of the weft yarn 2 is not particularly limited, but for example, when the weft yarn 2 is a monofilament yarn, the single yarn fineness of the weft yarn can be 15 to 100 dtex, preferably 20 to 75 dtex. Furthermore, when each of the weft yarns 2 is made of a multifilament yarn, the single yarn fineness of the weft yarn 2 can be 0.25 to 2.50 dtex, preferably 0.50 to 2.00 dtex, and the total fineness of the weft yarns 2 can be 1 to 1250 dtex, preferably 3 to 800 dtex, more preferably 5 to 270 dtex, and even more preferably 15 to 100 dtex. The "single yarn fineness" is the fineness per filament (monofilament or multifilament) constituting the weft yarn 2, and the "total fineness" is the product of the single yarn fineness and the number of filaments constituting the weft yarn 2. When the weft yarn 2 is composed of a multifilament yarn, the number of filament yarns constituting one weft yarn can be 4 to 500, preferably 6 to 400, more preferably 10 to 135, and even more preferably 30 to 50.

[0028] The first region R1 is a plain-woven portion of the artificial blood vessel VE, where the warp yarns 1 and the weft yarns 2 are interwoven. In FIG. 3 , the first region R1 is a region where the warp yarns 1a, 1b, 1e, 1f, 1i, and 1j intersect with the weft yarns 2 (weft yarns 2a to 2l). In the plain-woven first region R1, as shown in FIG. 4 , the warp yarns 1 extend from one side of the artificial blood vessel VE (the outer surface (surface) of the artificial blood vessel VE; the upper surface in FIG. 4 ) to the other side (the inner surface of the artificial blood vessel VE; the lower surface in FIG. 4 ) and from the other side to the one side, crossing only one weft yarn 2 (without crossing multiple weft yarns 2). The first region R1 improves the strength of the artificial blood vessel VE, particularly its tensile strength (in the axial direction X of the artificial blood vessel VE). The first region R1 extends along the extending direction D1 of the warp yarns 1 and in the axial direction X of the artificial blood vessel VE. A plurality of first regions R1 are arranged at predetermined intervals in the extension direction D2 of the weft yarn 2. A second region R2 and a third region R3 are arranged between one first region R1 and another first region R1 in the extension direction D2 of the weft yarn 2.

[0029] In this embodiment, as shown in FIG. 3 , the first region R1 is formed by plain weaving two warp threads 1a and 1b (warp threads 1e and 1f or warp threads 1i and 1j) and multiple weft threads 2a to 2l (and weft threads not shown). The number of warp threads 1 provided in one first region R1 can be 2 to 4, preferably 2 to 3, and more preferably 2. In this specification, when the warp threads 1 are multifilament yarns, the term "number of warp threads" does not refer to the number of filaments constituting the multifilament yarn, but rather refers to the number of warp threads 1 formed by a group of multiple filament yarns. By setting the number of warp threads 1 within the above-mentioned range, the area of ​​the first region R1 that is not covered by the warp threads 1 of the second-region-side first portion R21 and the warp threads 1 of the third-region-side first portion R31 can be reduced. Therefore, the plain weave first region R1 is more likely to be three-dimensionally covered by the warp yarns 1 of the second-region-side first portion R21 and the warp yarns 1 of the third-region-side first portion R31, and when blood seeps out of the first region R1, the three-dimensional structure of the warp yarns 1 of the second-region-side first portion R21 and the warp yarns 1 of the third-region-side first portion R31 holds the blood and causes it to clot while held, thereby reducing the amount of blood leaking from the artificial blood vessel VE. Furthermore, in the artificial blood vessel VE, the ratio of the number of warp yarns 1 in the first region R1 to the total number of warp yarns 1 arranged in the extension direction D2 of the weft yarns 2 in the first to third regions R1 to R3 (number of warp yarns in the first region R1 / total number of warp yarns) is not particularly limited, but may be, for example, 0.2 to 0.4 (1 / 3 in this embodiment). By setting the number of warp threads 1 and the ratio of the number of warp threads in the first region R1 within the above range, the strength of the artificial blood vessel VE can be increased while reducing the amount of blood leaking from the artificial blood vessel VE.

[0030] The second region R2 has a second-region-side first portion R21 where the warp yarn 1 crosses multiple weft yarns 2, and a second-region-side second portion R22 where the warp yarn 1 crosses a single weft yarn 2. The second-region-side first portion R21 and the second-region-side second portion R22 are alternately arranged in the extending direction D1 of the warp yarn 1, as shown in FIG. 3 . The second region R2 having the second-region-side first portion R21 and the second-region-side second portion R22 allows the artificial blood vessel VE to be more flexible than an artificial blood vessel VE entirely having a plain weave structure. The portion of the warp yarn 1c in the second region R2 may be composed of a single warp yarn or multiple warp yarns. The number of warp yarns 1 in the second region R2 may be, for example, 1 to 4, preferably 2 to 3, and more preferably 2.

[0031] The second-region-side first portion R21 is a woven portion in which the warp yarns 1 cross multiple weft yarns 2. In this embodiment, warp yarns 1c, 1g, 1k, etc. cross multiple weft yarns 2. In the second-region-side first portion R21, the warp yarns 1 cross multiple weft yarns 2, making the artificial blood vessel VE more flexible in that portion than in a plain weave structure. Furthermore, if the warp yarns 1 in the second-region-side first portion R21 are made of multifilament yarns, both ends of the second-region-side first portion R21 in the extending direction D1 of the warp yarns 1 are bound by the weft yarns 2 of the second-region-side second portion R22 (see portion P1 in Figure 3 ). In this case, the second-region-side first portion R21 of the warp yarns 1, which are made of multifilament yarns with both ends bound, forms a three-dimensional structure in which the center portion in the extending direction D1 of the warp yarns 1 extends in the extending direction D2 of the weft yarns 2 (note that this three-dimensional structure also extends left and right and toward the front of the page in Figure 3 ). That is, in the second-region-side first portion R21 of the warp yarn 1, the width of the central portion in the extension direction D1 of the warp yarn 1 is larger than the width of the end portion in the extension direction D1 of the warp yarn 1 (see FIG. 10 ). Therefore, the plain-weave first region R1 adjacent to the second-region-side first portion R21 in the extension direction D2 of the weft yarn 2 is partially covered by the expanded multifilament yarns of the second-region-side first portion R21. Due to this three-dimensional structure of the warp yarn 1, when blood seeps through the fiber gaps generated in the plain-weave first region R1, the exuded blood is retained in the gaps between the filaments of the three-dimensional structure formed by the multifilaments. As a result, the blood coagulates in the retained state, improving blood leakage resistance. Furthermore, in this embodiment, the third-region-side second portion R32 adjacent to the second-region-side first portion R21 in the extension direction D2 of the weft yarn 2 is also partially covered by the expanded multifilament yarns of the second-region-side first portion R21. As a result, any gaps that occur in the third region side second portion R32 are also covered by the multifilament yarn of the second region side first portion R21, making it less likely that blood in the artificial blood vessel VE will leak to the outside.

[0032] In the second region-side first portion R21 (from when the warp threads 1 emerge from the other surface of the artificial blood vessel VE to one surface (the surface shown in FIG. 3) to when they reach the other surface), the number of weft threads 2 that the warp threads 1 cross over is not particularly limited, but may be, for example, 2 to 5, preferably 3 to 4, and more preferably 3 (as shown in FIG. 3). By setting the number of weft threads 2 that the warp threads 1 cross over to the above range in the second region-side first portion R21, the multifilament yarns of the warp threads 1 can be easily spread in the extending direction D2 of the weft threads 2, and the artificial blood vessel VE can be maintained at a predetermined strength.

[0033] The number of warp threads 1 constituting the second-region-side first portion R21 is not particularly limited as long as the warp threads 1 have a portion where they cross over multiple weft threads 2. For example, the second-region-side first portion R21 (second region R2) may be composed of multiple (two) warp threads (each of warp threads 1c, 1g, and 1k is composed of multiple warp threads). Furthermore, the second-region-side first portion R21 (second region R2) may have at least one warp thread 1 extending across (only) one weft thread 2 and at least one warp thread 1 crossing multiple weft threads 2.

[0034] The second-region-side second portion R22 is a portion woven so that the warp thread 1 crosses only one weft thread 2 (the warp thread 1 does not cross multiple weft threads 2 from the time it exits from the other surface of the artificial blood vessel VE to one surface (the surface shown in FIG. 3) until it reaches the other surface). The second-region-side second portion R22 has a length approximately equal to that of the second-region-side first portion R21 in the extending direction D1 of the warp thread 1. That is, the number of weft threads in the second-region-side first portion R21 (three in FIG. 3) is equal to the number of weft threads in the second-region-side second portion R22 (three in FIG. 3).

[0035] The third region R3 has a third-region-side first portion R31, where the warp yarn 1 crosses multiple weft yarns 2, and a third-region-side second portion R32, where the warp yarn 1 crosses a single weft yarn 2. The third-region-side first portion R31 and the third-region-side second portion R32 are alternately arranged in the extending direction D1 of the warp yarn 1, as shown in FIG. 3 . The third region R3 has the third-region-side first portion R31 and the third-region-side second portion R32, which allows the artificial blood vessel VE to be more flexible than an artificial blood vessel VE entirely having a plain weave structure. The portion of the warp yarn 1d in the third region R3 may be composed of a single warp yarn or multiple warp yarns. The number of warp yarns 1 in the third region R3 may be, for example, 1 to 4, preferably 2 to 3, and more preferably 2.

[0036] The third-region-side first portion R31 is a woven portion in which the warp yarns 1 cross multiple weft yarns 2. In this embodiment, warp yarns 1d, 1h, 1l, etc. cross multiple weft yarns 2. In the third-region-side first portion R31, the warp yarns 1 cross multiple weft yarns 2, making the artificial blood vessel VE more flexible in that portion than in a plain weave structure. Furthermore, if the warp yarns 1 in the third-region-side first portion R31 are made of multifilament yarns, both ends of the third-region-side first portion R31 in the extending direction D1 of the warp yarns 1 are bound by the weft yarns 2 in the third-region-side second portion R32 (see portion P2 in Figure 3 ). In this case, the third-region-side first portion R31 of the warp yarns 1, made of multifilament yarns with both ends bound, forms a three-dimensional structure in which the center portion in the extending direction D1 of the warp yarns 1 expands in the extending direction D2 of the weft yarns 2. That is, in the third-region-side first portion R31 of the warp yarn 1, the width of the central portion in the extension direction D1 of the warp yarn 1 is larger than the width of the end portion in the extension direction D1 of the warp yarn 1 (see FIG. 10 ). Therefore, the plain-weave first region R1 adjacent to the third-region-side first portion R31 in the extension direction D2 of the weft yarn 2 is partially covered by the expanded multifilament yarns of the third-region-side first portion R31. Due to this three-dimensional structure of the warp yarn 1, when blood seeps through the fiber gaps generated in the plain-weave first region R1, the exuded blood is retained in the gaps between the filaments of the three-dimensional structure formed by the multifilaments. As a result, the blood coagulates in the retained state, improving blood leakage resistance. Furthermore, in this embodiment, the second-region-side second portion R22 adjacent to the third-region-side first portion R31 in the extension direction D2 of the weft yarn 2 is also partially covered by the expanded multifilament yarns of the third-region-side first portion R31. As a result, any gaps that occur in the second region side second portion R22 are also covered by the multifilament yarn of the third region side first portion R31, making it less likely that blood in the artificial blood vessel VE will leak to the outside.

[0037] In the third region-side first portion R31 (from when the warp threads 1 emerge from the other surface of the artificial blood vessel VE to one surface (the surface shown in FIG. 3) to when they reach the other surface), the number of weft threads 2 crossed by the warp threads 1 is not particularly limited, but may be, for example, 2 to 5, preferably 3 to 4, and more preferably 3 (as shown in FIG. 3). By setting the number of weft threads 2 crossed by the warp threads 1 within the above range in the third region-side first portion R31, the multifilament yarns of the warp threads 1 can be easily spread in the extending direction D2 of the weft threads 2, and the artificial blood vessel VE can be maintained at a predetermined strength.

[0038] The number of warp threads 1 constituting the third-region-side first portion R31 is not particularly limited as long as the warp threads 1 have a portion where the warp threads 1 cross over multiple weft threads 2. For example, the third-region-side first portion R31 (third region R3) may be composed of multiple (two) warp threads (each of warp threads 1d, 1h, and 1l is composed of multiple warp threads). Furthermore, the third-region-side first portion R31 (third region R3) may have at least one warp thread 1 extending across (only) one weft thread 2 and at least one warp thread 1 crossing multiple weft threads 2.

[0039] The third-region-side second portion R32 is a portion woven so that the warp thread 1 crosses only one weft thread 2 (the warp thread 1 does not cross multiple weft threads 2 from the time it emerges from the other surface of the artificial blood vessel VE to one surface (the surface shown in FIG. 3 ) until it reaches the other surface). The third-region-side second portion R32 has a length approximately equal to that of the third-region-side first portion R31 in the extending direction D1 of the warp thread 1. That is, the number of weft threads in the weft thread 2 in the third-region-side first portion R31 (three in FIG. 3 ) is the same as the number of weft threads in the weft thread 2 in the third-region-side second portion R32 (three in FIG. 3 ).

[0040] As shown in Figures 5 and 6A to 6C, the artificial blood vessel VE of this embodiment has a plurality of covered portions C that are provided in multiple locations on the surface of the artificial blood vessel VE and each cover the multifilament yarn in a planar manner, and uncovered portions UC that are provided between the multiple covered portions C on the surface of the artificial blood vessel VE and are not covered by the covered portions C.

[0041] The covering portion C partially covers the multiple filament yarns of the multifilament yarns constituting one warp yarn or one weft yarn on the surface of the artificial blood vessel VE. "Coating the multifilament yarns in a planar manner" means that the covering portion C extends on the surface of the artificial blood vessel VE in the extension direction of the multifilament yarns (extension direction D1 of warp yarn 1) and in a direction perpendicular to the extension direction of the multifilament yarns (extension direction D2 of weft yarn 2) so as to close gaps on the surface side of the artificial blood vessel VE between the multiple adjacent filament yarns constituting the multifilament yarn. As will be described in detail later, the provision of the covering portion C closes gaps on the surface of the artificial blood vessel VE between the multiple filament yarns located inside the covering portion C in the radial direction of the artificial blood vessel VE. This improves the blood leakage resistance of the artificial blood vessel VE.

[0042] As shown in Figures 5 and 6A to 6C, the covered portions C are provided in multiple locations on the surface of the artificial blood vessel VE. Here, "multiple locations" refers to the covered portions C being provided in multiple locations when the entire surface of the artificial blood vessel VE is divided into multiple sections. The covered portions C may be provided in multiple locations that are separate from each other (see Figure 6A), or may be provided in multiple locations that are continuous with each other in the axial direction (extension direction D1 of the warp yarns 1) and / or circumferential direction (extension direction D2 of the weft yarns 2) of the artificial blood vessel VE (with uncovered portions UC scattered therein; see Figure 6C). The covered portions C are not regularly distributed, but may have some areas where they are concentrated and some areas where they are not.

[0043] As shown in Figures 6A to 6C, the uncovered portions UC are the remaining portions of the surface of the artificial blood vessel VE that are not covered by the covered portions C. As shown in Figures 6A to 6C, the uncovered portions UC are arranged between the covered portions C provided at multiple locations. The uncovered portions UC are arranged between the covered portions C, for example, in the axial direction (extension direction D1 of warp yarns 1) and / or circumferential direction (extension direction D2 of weft yarns 2) of the artificial blood vessel VE. As will be described in detail later, the uncovered portions UC are arranged between the covered portions C on the surface of the artificial blood vessel VE, thereby contributing to maintaining the flexibility of the artificial blood vessel VE. In this embodiment, the multifilament yarns of the warp yarns 1 and weft yarns 2 in the regions of the uncovered portions UC are exposed on the surface of the artificial blood vessel VE with gaps maintained between adjacent filament yarns (see Figures 6A and 6B).

[0044] As described above, in this embodiment, the artificial blood vessel VE has a plurality of covered portions C that are provided at a plurality of locations on the surface of the artificial blood vessel VE, each covering a plurality of multifilament yarns in a planar manner, and uncovered portions UC that are provided on the surface of the artificial blood vessel VE between the plurality of covered portions C and are not covered by the covered portions C. In this case, as will be described later, the visible light transmittance can be reduced by the covered portions C, and for example, it becomes easy to set the visible light transmittance of the artificial blood vessel VE in the range of 1.5 to 4%, making it easy to achieve both flexibility and resistance to blood leakage in the artificial blood vessel VE.

[0045] In this embodiment, as shown in FIG. 5 , the artificial blood vessel VE has an inner woven portion IW, in which multiple filament yarns of a multifilament yarn extend in a separated state, radially inward of the artificial blood vessel VE relative to the covering portion C (lower side in FIG. 5 ). The inner woven portion IW constitutes part of the woven structure of the artificial blood vessel VE and is covered by the covering portion C with multiple filament yarns separated from each other with gaps between them. The multiple filament yarns of the inner woven portion IW, which are shown schematically in FIG. 5 , extend in a bundle such that multiple adjacent filament yarns are arranged in the radial direction of the artificial blood vessel VE (up and down direction in FIG. 5 ) and in the extension direction D2 of the weft yarn 2 (depth direction in FIG. 5 ). Although the inner woven portion IW is not visible in FIGS. 6A and 6C because it is covered by the covering portion C, it is located in the depth direction relative to the covering portion C. The structure of the inner woven portion IW is not particularly limited as long as multiple filament yarns extend in a separated state radially inward of the artificial blood vessel VE relative to the covering portion C. In this embodiment, the inner woven portion IW has a structure in which the multifilament yarns in the region corresponding to the second region-side first portion R21 (and the third region-side first portion R31) are spread in the extension direction D2 of the weft yarns 2, and the multiple filament yarns constituting the multifilament yarns of the inner woven portion IW extend in a dispersed state along the extension direction D1 of the warp yarns 1. Note that in this embodiment, as shown in Fig. 5, the warp yarns 1 have a two-layer structure in the region corresponding to the second region-side first portion R21 (and the third region-side first portion R31) consisting of a covering portion C which is a planar resin layer on the surface side of the artificial blood vessel VE, and an inner woven portion IW which is a multifilament layer located radially inward of the covering layer C.

[0046] By providing the inner woven portion IW radially inward of the covering portion C, multiple filament yarns extend radially inward of the planar covering portion C in a separated state with gaps between them. Therefore, the inner woven portion IW, which is made of multifilament yarns covered by the covering portion C, extends while maintaining a predetermined flexibility. Therefore, even with the planar covering portion C, the flexibility of the artificial blood vessel VE as a whole is unlikely to be impaired, and the artificial blood vessel VE can achieve both flexibility and blood leakage resistance. Furthermore, the presence of the inner woven portion IW allows the inner structure of the artificial blood vessel to maintain its woven structure and suppress the impairment of cell invasion.

[0047] Furthermore, it is preferable that the covered portions C and the uncovered portions UC are alternately arranged in the axial direction (extension direction D1 of warp yarn 1) and / or circumferential direction (extension direction D2 of weft yarn 2) of the artificial blood vessel VE on a portion of the surface of the artificial blood vessel VE. In this case, the covered portions C and the uncovered portions UC are arranged in a balanced manner in the axial and / or circumferential directions of the artificial blood vessel VE. This improves the flexibility and blood leakage resistance of the artificial blood vessel VE in a balanced manner, thereby preventing the artificial blood vessel VE from becoming locally stiff or prone to localized blood leakage. In particular, when the covered portions C and the uncovered portions UC are alternately arranged in the axial direction of the artificial blood vessel VE, the artificial blood vessel VE becomes easier to bend, facilitating its placement in the body. Furthermore, when the covered portions C and the uncovered portions UC are alternately arranged in the circumferential direction of the artificial blood vessel VE, the artificial blood vessel VE becomes easier to twist, preventing deformation (collapse) when twisted. Therefore, even if the artificial blood vessel VE is subjected to a twisting force, for example, by screwing when connected to an artificial heart-lung machine, the artificial blood vessel VE is prevented from being crushed by twisting. Therefore, adverse effects of twisting of the artificial blood vessel VE, such as blood clotting at the crushed area and occlusion of the artificial blood vessel VE, are prevented. In this embodiment, the artificial blood vessel VE has covered portions C and uncovered portions UC alternately provided in both the axial and circumferential directions of the artificial blood vessel VE. In this case, the flexibility and leakage resistance of the artificial blood vessel VE are improved in a balanced manner throughout the entire artificial blood vessel VE.

[0048] The region where the covering portion C is provided is not particularly limited, as long as the covering portion C is provided in multiple locations over a predetermined area on the surface of the artificial blood vessel VE. In this embodiment, as shown in Figures 5 and 7, the covering portion C is provided on portions R21 and R31 of the warp yarns 1 that extend across multiple weft yarns 2 (only portion R21 that extends across multiple weft yarns 2 is shown in Figures 5 and 7). More specifically, the covering portion C is provided on portions corresponding to the second-region-side first portion R21 and the third-region-side first portion R31. Note that the covering portion C does not necessarily need to cover all of the multiple filament yarns provided in the portions that extend across multiple weft yarns 2 (the second-region-side first portion R21 and the third-region-side first portion R31), but it is sufficient that the covering portion C covers most of the multiple filament yarns (for example, but not limited to, 50% or more, preferably 80% or more).

[0049] The structure of the covering portion C is not particularly limited as long as it can cover the multifilament yarn in a planar manner. In this embodiment, the covering portion C is formed by melting and solidifying the multifilament yarn or by a resin layer coated on the surface of the multifilament yarn. "Melting and solidifying the multifilament yarn" refers to a state in which a portion of the multifilament yarn constituting the warp yarn 1 and / or the weft yarn 2 is melted by heating or the like and then solidified to form a planar resin layer. In this case, the surface of the artificial blood vessel VE is covered with the planar covering portion C, which is a melted and solidified resin layer. Furthermore, "a resin layer coated on the surface" refers to a resin layer formed by planarly coating the multifilament yarn constituting the warp yarn 1 and / or the weft yarn 2 with a resin material.

[0050] In this embodiment, the artificial blood vessel VE may have the first region R1, second region R2, and third region R3 described above, and may be configured so that the artificial blood vessel VE has a visible light transmittance of 1.5 to 4%. In this case, as described below, it is possible to achieve a high level of both flexibility and blood leakage resistance of the artificial blood vessel VE. By setting the lower limit of the visible light transmittance of the artificial blood vessel VE to 1.5%, more preferably 2%, the flexibility of the artificial blood vessel VE can be increased. Furthermore, by setting the upper limit of the visible light transmittance of the artificial blood vessel VE to 4%, more preferably 3%, the blood leakage resistance of the artificial blood vessel VE can be increased.

[0051] Here, the "visible light transmittance" of the artificial blood vessel VE refers to the ratio of light transmitted from one surface (inner surface) of the artificial blood vessel VE to the other surface (outer surface) when the artificial blood vessel VE is irradiated with visible light in the wavelength range of 380 to 780 nm (see Figure 10). The calculation method involves photographing the surface of the artificial blood vessel VE using a digital microscope at maximum light (e.g., 255 in a 256-level grayscale image), determining the maximum light (255) as the portion through which light is transmitted, and calculating the light transmittance as the ratio of the number of pixels with maximum light to the total number of pixels. The visible light transmittance is the visible light transmittance of the artificial blood vessel VE in a predetermined region (e.g., a region including 10 warp yarns 1 and 10 weft yarns 2) having a predetermined area or greater, including the peaks M and valleys V. For example, the visible light transmittance in this predetermined region can be calculated at multiple locations and then averaged. The visible light transmittance of the artificial blood vessel VE is not limited to the above-mentioned range. Furthermore, when the visible light transmittance of the artificial blood vessel VE is within the above-mentioned range, even if the visible light transmittance in a portion of the artificial blood vessel VE is locally outside the range of 1.5 to 4%, it is acceptable as long as the average transmittance is within that range. The visible light transmittance can be measured, for example, by cutting a portion of the artificial blood vessel VE as a sample and measuring it with a commercially available spectrophotometer. There are no particular limitations on the method for measuring the visible light transmittance, but for example, the sample of the artificial blood vessel VE to be measured can be moved while measuring the spectral transmittance at multiple locations (e.g., 10 locations), and the visible light transmittance can be calculated as the arithmetic average of the multiple measurements.

[0052] The visible light transmittance corresponds to the size of the gaps that occur in the intersection regions of the warp yarns 1 and weft yarns 2 in the woven structure of the artificial blood vessel VE. Normally, if the woven structure has a visible light transmittance in the above-mentioned range of 1.5 to 4%, the artificial blood vessel will have a dense weave and will become stiff. On the other hand, in this embodiment, if the specific woven structure having the above-mentioned first region R1, second region R2, and third region R3 has a visible light transmittance of 1.5 to 4%, it will be possible to achieve a high level of both flexibility and resistance to blood leakage in the artificial blood vessel VE, as will be described later.

[0053] In this embodiment, as shown in Fig. 7 , the covering portion C extends in the extending direction D2 of the weft yarn 2 so as to cover at least a portion of the surface of the warp yarn 1 disposed between a pair of second-region-side first portions R21 in the extending direction D2 of the weft yarn 2. In this embodiment, the covering portion C is configured to cover at least a portion of the warp yarns 1d, 1e, and 1f other than the warp yarn 1c including the second-region-side first portion R21 on which the covering portion C is provided. More specifically, the covering portion C is configured to cover at least a portion of the warp yarns 1d, 1e, and 1f in the first region R1 or the second-region-side second portion R22. Although not shown in Fig. 7 , the covering portion C extends in the extending direction D2 of the weft yarn 2 so as to cover at least a portion of the surface of the warp yarn 1 disposed between a pair of third-region-side first portions R31 in the extending direction D2 of the weft yarn 2. In this embodiment, the covering portion C is configured to cover at least a portion of a warp thread other than the one warp thread including the third-region-side first portion R31 on which the covering portion C is provided. More specifically, the covering portion C is configured to cover at least a portion of the warp thread of the first region R1 or the third-region-side second portion R32.

[0054] In this case, as shown in FIG. 7 , the covering C of one warp thread 1c, 1g covers another warp thread adjacent to it in the extending direction D2 of the weft thread 2 (for example, warp threads 1d, 1e, 1f in the case of FIG. 7 ). This suppresses not only blood leakage through gaps between the multifilament yarns of one warp thread 1 but also blood leakage through gaps between the multifilament yarns of other warp threads 1 different from the one warp thread 1. Therefore, the blood leakage resistance of the artificial blood vessel VE is improved. Furthermore, the covering C is provided on the surface of one warp thread 1 that is on the radially outer side of the artificial blood vessel VE, while the multifilament yarns are in a loose state in the radially inner part. Therefore, the loose multifilament yarns of one warp thread 1 provided with the covering C and the other warp threads 1 face each other in the radial direction of the artificial blood vessel VE, and are prevented from adhering to each other (note that partial adhesion may occur due to individual differences, temperature conditions, etc.). Therefore, the covering portion C can move radially relative to the surface of the warp yarn 1 disposed between a pair of second-region-side first portions R21 in the extending direction D2 of the weft yarn 2 and the surface of the warp yarn 1 disposed between a pair of third-region-side first portions R31 in the extending direction D2 of the weft yarn 2 in response to the movement of the artificial blood vessel VE. Specifically, as shown in FIG. 8 , the covering portion C is formed on the surface of one warp yarn 1, and the multifilament yarns in a loose state come into contact with the surfaces of the other warp yarns 1. In this state, for example, when the artificial blood vessel VE is placed in a body, a radially outward force may be applied to the inside of the artificial blood vessel VE due to blood flow pulsation or the like. In this case, the artificial blood vessel VE deforms to increase its diameter. In this embodiment, one warp yarn 1 is not fixed to the other warp yarns 1, so one warp yarn 1 can move radially relative to the other warp yarns 1 in the extending direction D2 of the weft yarn 2. Therefore, for example, when the artificial blood vessel VE expands, the covering C suppresses blood leakage, while the relative movement of one warp thread 1 with the other warp threads 1 allows the artificial blood vessel VE to flexibly deform in accordance with the blood flow within the artificial blood vessel VE. This allows the artificial blood vessel VE to have both resistance to blood leakage and flexibility.

[0055] In this embodiment, as shown in Figures 2 and 6A, the artificial blood vessel has peaks M and valleys V alternately formed in the direction of axis X, and is configured so that the visible light transmittance of the valleys V is lower than that of the peaks M. In this case, the valleys V have low transmittance, which increases blood leakage resistance but also makes the vessel harder. However, the peaks M are more flexible than the valleys V, ensuring flexibility for the entire vessel VE. Furthermore, since the artificial blood vessel VE has the above-described transmittance, the blood leakage resistance of the entire vessel VE is ensured, while the valleys V have low transmittance (small gaps) and therefore high strength. Therefore, when a medical instrument such as a guidewire or catheter is inserted through the artificial blood vessel VE, the valleys V, which come into contact with the medical instrument, have high strength, which can prevent damage to the artificial blood vessel VE due to contact with the medical instrument. The visible light transmittance of the peaks M and valleys V is not limited, but for example, the visible light transmittance of the valleys V can be set to 1 to 3%, and the visible light transmittance of the peaks M can be set to 2 to 4.5%. The visible light transmittance of the valleys V and the visible light transmittance of the peaks M may be approximately the same.

[0056] An example of a method for producing the artificial blood vessel VE of this embodiment will be described below. However, the following description is merely an example, and the artificial blood vessel VE of the present invention is not limited to the following method for producing it.

[0057] First, a base material for the artificial blood vessel VE having the above-described woven structure is prepared. Specifically, as shown in Fig. 3, the base material includes a first region R1 in which warp yarns 1 and weft yarns 2 are woven in a plain weave, a second region R2 having a second-region-side first portion R21 and a second-region-side second portion R22, and a third region R3 having a third-region-side first portion R31 and a third-region-side second portion R32. At this stage, the base material is not cylindrical but sheet-like.

[0058] Next, a covering portion C is formed on the substrate. Specifically, a heating medium (not shown) is brought into contact with the surface of the substrate that will become the outer surface (surface) of the artificial blood vessel VE, melting a portion of the substrate (a portion of the multifilament yarn), and the melted portion is cooled and solidified. In the above-described substrate, the second-region-side first portion R21 and the third-region-side first portion R31 protrude further toward the outer surface of the artificial blood vessel VE in the thickness direction of the substrate than other portions (e.g., the first region R1, the second-region-side second portion R22, and the third-region-side second portion R32). Therefore, the multifilament yarn on the surface of the second-region-side first portion R21 and the third-region-side first portion R31 melts first. By adjusting the temperature of the heating medium, the heating time, etc., it is possible to melt only the surface of the substrate. Specifically, the multifilament yarns of the second region-side first portion R21 and the third region-side first portion R31 are melted only in the surface layer portion that faces the outer surface of the artificial blood vessel VE in the thickness direction of the substrate, while the portions that face the inner surface of the artificial blood vessel VE are not melted. This forms a covering portion C that covers the multifilament yarns of the second region-side first portion R21 and the third region-side first portion R31 in a planar manner. In this case, the portion of the multifilament yarns of the substrate that faces the inner surface of the artificial blood vessel VE remains in a state where multiple filament yarns are separated. This results in a substrate having a two-layer structure consisting of the covering portion C and the inner woven portion IW. Since the insides (inner woven portion IW) of the multifilament yarns of the second-region-side first portion R21 and the third-region-side first portion R31 are not melted, when the covering portions C of the warp yarns 1c and 1g cover the surfaces of the warp yarns 1d, 1e, and 1f arranged between the second-region-side first portions R21 and R21 of a pair of warp yarns 1c and 1g, the covering portions C (inner woven portion IW) are not fixed to the covered warp yarns 1d, 1e, and 1f, as shown in Fig. 7. Therefore, as described above, the covering portions C can move relative to the warp yarns 1 covered by the covering portions C in the radial direction of the artificial blood vessel VE and in the extending direction D2 of the weft yarns 2 in response to the movement of the artificial blood vessel VE (e.g., movement when the artificial blood vessel VE expands radially outward), as shown in Figs. In this way, in this embodiment, even if the artificial blood vessel VE moves, one warp thread 1 provided with the covering portion C and another warp thread 1 covered by the covering portion C can move relative to each other and flexibly deform while maintaining a high level of resistance to blood leakage.Therefore, the artificial blood vessel VE of this embodiment can improve its resistance to blood leakage while maintaining its flexibility. Instead of melting the substrate, a resin layer may be coated on the multifilament yarn on the surface of the substrate. When coating the surface of the multifilament yarn with a resin layer, instead of the above-mentioned substrate heating step (a step of melting a portion of the multifilament yarn), a resin material can be applied to the surface of the multifilament yarn in a desired pattern using a known method to form the covering portion C.

[0059] Next, the substrate is processed into a cylindrical shape to form a cylindrical body CY (see FIG. 11). At this point, the ridges M and valleys V have not yet been formed in this cylindrical body CY. A known method for manufacturing a cylindrical artificial blood vessel having a predetermined woven structure (an artificial blood vessel without pleats) can be used to form the cylindrical body CY, and therefore a detailed description thereof will be omitted. The step of forming the cylindrical body CY may be performed before the step of bringing the heating medium into contact with the substrate.

[0060] After the substrate is processed into a cylindrical shape to form the cylindrical body CY, peaks M and valleys V are formed in the cylindrical body CY, as shown in FIG. 11 . Specifically, the cylindrical body CY is placed on the outside of a molding core 3 (see FIG. 11 ), which has peaks 31 and valleys 32 corresponding to the peaks M and valleys V. The molding core 3 has a size and shape corresponding to the artificial blood vessel VE, which has peaks M and valleys V of the desired size and shape. In this embodiment, the molding core 3 is configured so that it can cover the outside of the cylindrical body CY. The outer diameter of the peaks 31 of the molding core 3 is preferably the same as or smaller than the inner diameter of the cylindrical body CY, but the outer diameter of the peaks 31 may be slightly larger than the inner diameter of the cylindrical body CY. In this embodiment, the molding core 3 is supported rotatably about axis X by a support (not shown) of a molding device including the molding core 3.

[0061] When the tubular body CY is placed outside the forming core 3, as shown in Figure 11, with the tubular body CY placed outside the forming core 3, the winding member 4 is wound around part of the circumferential direction of the tubular body CY along the recess 32 of the forming core 3. The winding member 4 is a member for pressing the part of the tubular body CY placed outside the forming core 3 against the recess 32 of the forming core 3 to form a part in the tubular body CY corresponding to the valley V. The winding member 4 is not particularly limited as long as it can form the valley V in the tubular body CY. In this embodiment, it can be a wire having a size that can fit between a pair of protrusions 31 corresponding to a pair of peaks M. In this embodiment, the winding member 4 is stretched under tension (see FIG. 12 ), and the forming core 3 is rotated about the axis X, whereby the winding member 4 is wound spirally around the outer periphery of the tubular body CY, thereby forming valleys V in the tubular body CY. Alternatively, the forming core 3 may not be rotated, and the winding member 4 may be moved so as to wind spirally around the forming core 3, thereby forming valleys V in the tubular body CY.

[0062] Next, the tubular body CY is pressed radially inward in a point-like manner. Specifically, the tubular body CY, which is disposed outside the molding core 3 and has the winding member 4 wrapped around it, is housed in the housing member 5 (see FIGS. 13 and 14 ). The housing member 5 has compression elements PR (indicated by dots in FIG. 14 ) disposed between the inner surface of the housing member 5 and the outside of the tubular body CY. In this embodiment, the compression elements PR pressurize the tubular body CY radially inward. In this embodiment, the compression elements PR are composed of a plurality of granular bodies. In this embodiment, because the compression elements PR are composed of a plurality of granular bodies, the granular compression elements PR come into point-like contact with the warp yarns 1 and weft yarns 2 of the tubular body CY. In this case, force is applied more evenly to the warp threads 1 and weft threads 2 than with a wire-shaped compression element (for example, a wire-shaped compression element that is wound around the entire tubular body CY along the extension direction of the ridges M (circumferential direction of the artificial blood vessel VE)) that makes linear contact with the tubular body CY. Therefore, when the tubular body CY is compressed by the compression element PR, a large force is applied locally, causing the warp threads 1 and weft threads 2 to shift position, which prevents localized gaps from becoming larger.

[0063] In this embodiment, as shown in FIG. 14 , a tubular body CY, which is formed by wrapping a molding core 3 and a winding member 4, is housed in a housing member 5. A plurality of granular compression elements PR are filled in the clearance between the tubular body CY and the inner surface of the housing member 5. In this embodiment, the housing member 5 is configured to reduce its internal volume. As the internal volume decreases, the compression elements PR press the tubular body CY radially inward. This applies a radially inward force to the second-region-side first portion R21 and the third-region-side first portion R31 of the warp yarns 1, which are made of multifilament yarns. Therefore, the second-region-side first portion R21 and the third-region-side first portion R31 are pressed by the compression elements PR and tightly adhere to the surface of the warp yarns 1, which are located radially inside the artificial blood vessel VE relative to the covering portion C. This further improves the leakage resistance of the artificial blood vessel VE.

[0064] The material and size of the compression element PR are not particularly limited as long as it is configured to be able to press the cylindrical body CY radially inward. The compression element PR can be configured, for example, from a metallic material that has a predetermined rigidity and is capable of conducting heat.

[0065] The configuration of the accommodating member 5 is not particularly limited as long as the granular compression elements PR can press the cylindrical body CY radially inward. In this embodiment, as shown in FIG. 13 , the accommodating member 5 includes a cylindrical main body 51 and a lid 52 configured to screw onto the end of the main body 51. Screwing the lid 52 onto the main body 51 moves the lid 52 in the axial direction of the main body 51 relative to the main body 51. When the lid 52 moves in the axial direction of the main body 51, the lid 52 presses the pressing body 53 in the axial direction of the main body 51, thereby reducing the internal volume of the main body 51. As a result, the granular compression elements PR housed within the accommodating member 5 are pressed, and the cylindrical body CY is pressed radially inward by the compression elements PR. The accommodating member may have other configurations. For example, the cylindrical body CY may be pressed by a pressure member such as a weight instead of the lid 52 of the accommodating member. Specifically, with a granular compression element PR arranged around a cylindrical body CY within a storage member, a load may be applied to the compression element PR from outside the storage member by a pressure member such as a weight, thereby pressing the cylindrical body CY radially inward.

[0066] Next, the compression element PR is heated while the tubular body CY is compressed by the compression element PR within the housing member 5 (see FIG. 14 ). In this embodiment, the housing member 5 is placed in a heating furnace and heated, thereby heating the compression element PR via the housing member 5. As a result, the tubular body CY is heated by heat transfer from the compression element PR. The tubular body CY is heated while the portions of the tubular body CY that are in contact with the compression element PR (particularly the second-region-side first portion R21 and the third-region-side first portion R31) are compressed in a point-like manner, causing the tubular body CY to deform so as to conform closely to the surface shape of the warp yarns 1 covered by the covering portion C. The tubular body CY is then removed from the housing member 5 and maintained in the shape of the point-like compressed state, completing the artificial blood vessel VE. In this embodiment, the point-like compression of the tubular body CY causes the covering portion C to have a recess that is concave radially inward of the artificial blood vessel VE (see FIG. 6B ). As described above, the recesses reduce the gap between the warp threads 1 and the other warp threads 1 covered by the covering C. In addition, the plurality of recesses makes the artificial blood vessel VE more flexible and easier to bend. The temperature in the heating step is not particularly limited, and the artificial blood vessel VE may be heated to a temperature sufficient to deform the covering C.

[0067] Instead of placing the accommodating member 5 in a heating furnace, the compression element PR may be made of a conductive material, and an electric current may be passed through the compression element PR to heat it, thereby heating the cylindrical body CY.

[0068] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments. Note that the above-described embodiments mainly describe the invention having the following configurations.

[0069] (1) An artificial blood vessel having weft yarns and warps made of multifilament yarns, the artificial blood vessel having: a first region in which the warps and weft yarns are woven in a plain weave; a second region on one surface of the artificial blood vessel having second region-side first portions where the warps cross multiple weft yarns and second region-side second portions where the warps extend across a single weft yarn; and a third region on one surface of the artificial blood vessel having third region-side first portions where the warps cross multiple weft yarns and third region-side second portions where the warps extend across a single weft yarn, the second region-side first portions being adjacent to the third region-side second portions in the extension direction of the weft yarns, and the second region-side second portions being adjacent to the third region-side first portions in the extension direction of the weft yarns, an artificial blood vessel, the second region side first portion and the third region side first portion having a covering portion formed by melted and solidified multifilament yarns on the surfaces of the second region side first portion and the third region side first portion, or by a resin layer coated on the surface of the multifilament yarns, the covering portion covering the multifilament yarns in a planar manner in the second region side first portion and the third region side first portion, the covering portion extending in the direction of extension of the weft yarn so as to cover at least a portion of the surface of the warp yarns arranged between the pair of second region side first portions in the direction of extension of the weft yarn and the surface of the warp yarns arranged between the pair of third region side first portions in the direction of extension of the weft yarn, and the covering portion being configured to be able to move in the radial direction of the artificial blood vessel relative to the surface of the warp yarns arranged between the pair of second region side first portions in the direction of extension of the weft yarn and the surface of the warp yarns arranged between the pair of third region side first portions in the direction of extension of the weft yarn in accordance with the movement of the artificial blood vessel.

[0070] (2) The artificial blood vessel described in (1), wherein the artificial blood vessel has an inner woven portion in which the multiple filament yarns of the multifilament yarn extend separately from each other, radially inward of the artificial blood vessel relative to the covering portion.

[0071] (3) The artificial blood vessel according to (1) or (2), wherein the covering portion has a recessed portion that is recessed radially inward of the artificial blood vessel.

[0072] (4) A method for manufacturing an artificial blood vessel having weft yarns and warp yarns made of multifilament yarns, the method comprising the steps of: preparing a base material having, alternately in the extending direction of the weft yarns, a first region in which the warp yarns and the weft yarns are woven in a plain weave; a second region on one side of the artificial blood vessel, having a first portion on a second region side where the warp yarns cross over a plurality of weft yarns and a second portion on the second region side where the warp yarns extend across a single weft yarn; and a third region on one side of the artificial blood vessel, having a first portion on a third region side where the warp yarns cross over a plurality of weft yarns and a second portion on the third region side where the warp yarns extend across a single weft yarn; the step of bringing a heating medium into contact with the surface of the base material that will become the outer surface of the artificial blood vessel, thereby melting and solidifying the multifilament yarns on the surface of the second region side first portion and the third region side first portion, or by coating the surface of the second region side first portion and the third region side first portion with a resin layer, thereby forming a covering portion that covers the multifilament yarns on the surface of the second region side first portion and the third region side first portion in a planar manner; the step of forming a tubular body by processing the base material into a tubular shape; the step of accommodating the tubular body in a containing member having a compression element, and applying spot-like pressure to the tubular body radially inward by the compression element arranged between the inner surface of the containing member and the outside of the tubular body; and the step of heating the compression element while the tubular body is pressed in spot-like pressure radially inward, thereby deforming the surface of the covering portion into a shape in a compressed state, The covering portion extends in the direction of extension of the weft thread so as to cover at least a portion of the surface of the warp thread arranged between the pair of second region side first portions in the direction of extension of the weft thread and the surface of the warp thread arranged between the pair of third region side first portions in the direction of extension of the weft thread, and the covering portion is configured to be able to move radially of the artificial blood vessel relative to the surface of the warp thread arranged between the pair of second region side first portions in the direction of extension of the weft thread and the surface of the warp thread arranged between the pair of third region side first portions in the direction of extension of the weft thread in accordance with the movement of the artificial blood vessel.

[0073] 1, 1a, 1b, 1c, 1d, 1e, 1f, 1g, 1h, 1i, 1j, 1k, 1l: warp threads 2, 2a, 2b, 2c, 2d, 2e, 2f, 2g, 2h, 2i, 2j, 2k, 2l: weft threads 3: molding core material 31: convex portion 32: concave portion 4: winding member 5: containing member 51: main body 52: lid portion 53: pressing body C: covering portion CY: cylindrical body D1: extension direction of warp threads (axial direction of artificial blood vessel) D2: extension direction of weft threads (circumferential direction of artificial blood vessel) IW: inner woven portion M: peak portion Mt: peak portion of peak portion P1: portion of weft threads binding both ends of the first portion on the second region side P2: portion of weft threads binding both ends of the first portion on the third region side PL, PL1, PL2: flat portion PR Compression element R1 First region R2 Second region R21 First portion on the second region side (portion extending across multiple wefts) R22 Second portion on the second region side (portion extending across one weft) R3 Third region R31 First portion on the third region side (portion extending across multiple wefts) R32 Second portion on the third region side (portion extending across one weft) UC Uncovered portion V Valley portion Vb Bottom of valley portion VE Artificial blood vessel X Axis of artificial blood vessel θ Angle between the flat portion on one side and the flat portion on the other side

Claims

1. An artificial blood vessel having weft yarns and warps made of multifilament yarns, the artificial blood vessel having: a first region in which the warps and the weft yarns are woven in a plain weave; a second region on one side of the artificial blood vessel having a second region side first portion in which the warps cross a plurality of weft yarns and a second region side second portion in which the warps extend across a single weft yarn; and a third region on one side of the artificial blood vessel having a third region side first portion in which the warps cross a plurality of weft yarns and a third region side second portion in which the warps extend across a single weft yarn, the second region side first portion being adjacent to the third region side second portion in the extension direction of the weft yarn, and the second region side second portion being adjacent to the third region side first portion in the extension direction of the weft yarn, an artificial blood vessel, the second region side first portion and the third region side first portion having a covering portion constituted by a melted and solidified state of multifilament yarns on the surfaces of the second region side first portion and the third region side first portion, or a resin layer coated on the surfaces of the multifilament yarns, the covering portion covering the multifilament yarns of the second region side first portion and the third region side first portion in a planar manner, the covering portion spreading in the extension direction of the weft yarn so as to cover at least a portion of a surface of a warp yarn arranged between the pair of second region side first portions in the extension direction of the weft yarn and a surface of a warp yarn arranged between the pair of third region side first portions in the extension direction of the weft yarn, and the covering portion being configured to be movable in a radial direction of the artificial blood vessel relative to the surface of the warp yarn arranged between the pair of second region side first portions in the extension direction of the weft yarn and the surface of the warp yarn arranged between the pair of third region side first portions in the extension direction of the weft yarn in response to a movement of the artificial blood vessel.

2. The artificial blood vessel as described in claim 1, wherein the artificial blood vessel has an inner woven portion in which the multiple filament yarns of the multifilament yarn extend separately from one another, radially inward of the artificial blood vessel relative to the covering portion.

3. The artificial blood vessel according to claim 1, wherein the covering portion has a recess that is concave on the radially inner side of the artificial blood vessel.

4. A method for manufacturing an artificial blood vessel having weft yarns and warp yarns made of multifilament yarns, said method comprising the steps of: preparing a base material having a first region in which the warp yarns and the weft yarns are woven in a plain weave; a second region on one side of the artificial blood vessel, the second region having a first portion on a second region side where the warp yarns cross over a plurality of weft yarns and a second portion on a second region side where the warp yarns extend across a single weft yarn; and a third region on one side of the artificial blood vessel, the third region having a first portion on a third region side where the warp yarns cross over a plurality of weft yarns and a second portion on a third region side where the warp yarns extend across a single weft yarn, the third region being alternately arranged in the extending direction of the weft yarns; the step of contacting a surface of the base material that will become the outer surface of the artificial blood vessel with a heating medium to melt and solidify the multifilament yarns on the surface of the second region side first portion and the third region side first portion, or by coating the surface of the second region side first portion and the third region side first portion with a resin layer to form a covering portion that covers the multifilament yarns on the second region side first portion and the third region side first portion in a planar manner; the step of forming a tubular body by processing the base material into a tubular shape; the step of housing the tubular body in a housing member having a compression element, and applying spot-like pressure to the tubular body radially inward by the compression element disposed between the inner surface of the housing member and the outside of the tubular body; and the step of heating the compression element in a state in which the tubular body is pressed in spot-like manner radially inward, thereby deforming the surface of the covering portion into a shape in a pressurized state, The covering portion extends in the extension direction of the weft so as to cover at least a portion of the surface of the warp yarn arranged between the pair of first portions on the second region side in the extension direction of the weft yarn and the surface of the warp yarn arranged between the pair of first portions on the third region side in the extension direction of the weft yarn, and the covering portion is configured to be able to move radially of the artificial blood vessel relative to the surface of the warp yarn arranged between the pair of first portions on the second region side in the extension direction of the weft yarn and the surface of the warp yarn arranged between the pair of first portions on the third region side in the extension direction of the weft yarn in response to the movement of the artificial blood vessel.

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