Catheter and catheter manufacturing method

Abstract

The present invention provides: a catheter with a novel structure allowing a more flexible leading end portion to be achieved while ensuring performance such as pushability and kink resistance when inserted into a body lumen such as a more distal and narrow blood vessel; and a novel catheter manufacturing method.　A catheter 10 comprises a lumen 14 extending in a length direction, with reinforcing materials 24 being provided in an embedded state in a peripheral wall of the lumen 14. An inner peripheral surface of the lumen 14 has, between the reinforcing materials 24, a concave curved surface 30 that is concave toward the outer peripheral side.

Description

Catheter and method of manufacturing the same

[0001] The present invention relates to a catheter used, for example, for administering a medicinal solution or for suctioning a blood clot, and a method for manufacturing the catheter.

[0002] Catheters that are percutaneously inserted into blood vessels and used, for example, to aspirate and remove thrombi or to administer medicinal solutions to patients have been known. As disclosed in International Publication No. 2019 / 004100 (Patent Document 1), for example, the catheter has a lumen extending in the longitudinal direction, and it is possible to administer medicinal solutions into blood vessels, aspirate thrombi, insert a therapeutic instrument, and the like through the lumen.

[0003] The catheter of Patent Document 1 is provided with a reinforcing structure that reinforces the peripheral wall of the lumen in order to achieve the necessary properties, such as pushability, torque performance, flexible bending, recovery, and kink resistance, required for reaching the treatment site from the arm, leg, etc. The reinforcing structure is made of, for example, a coil-shaped or braided reinforcing material.

[0004] International Publication No. 2019 / 004100

[0005] However, catheters may be required to have different characteristics along their length. Specifically, for example, the base end portion may be required to have a higher level of pushability, which allows the operating force applied to the proximal end of the catheter to be efficiently transmitted to the tip portion, while the tip portion, which is inserted into a thin blood vessel, may be required to have a high level of flexibility so that it can follow the complex curvature of the blood vessel. In particular, catheters inserted into deep blood vessels, for example, are inserted into thin blood vessels with more complex curvatures, and therefore are required to have the above-mentioned characteristics that differ from those of relatively large-diameter catheters.

[0006] However, when a reinforcing structure is provided around the lumen to achieve the pushability and other performance required for the base end, it is difficult to achieve the high flexibility required for the tip end. In order to satisfy the different required characteristics along the length of the catheter, it is possible to provide a reinforcing member partially along the length, but this creates a problem in that the difference in hardness between the reinforcing member and the non-reinforcing member becomes large, making the catheter more susceptible to bending due to stress concentration, etc.

[0007] An object of the present invention is to provide a catheter having a novel structure that can achieve greater flexibility while maintaining performance such as pushability and kink resistance.

[0008] Another object of the present invention is to provide a novel method for manufacturing a catheter that can achieve greater flexibility while maintaining performance such as pushability and kink resistance.

[0009] The following describes preferred embodiments for understanding the present invention, but the embodiments described below are merely examples and may be appropriately combined with one another. Multiple components described in each embodiment may be recognized and employed independently to the greatest extent possible, and may also be appropriately combined with any of the components described in other embodiments. Accordingly, the present invention is not limited to the embodiments described below, and various other embodiments may be realized.

[0010] The first aspect is a catheter having a lumen extending in the longitudinal direction, with a reinforcing material embedded in the peripheral wall of the lumen, and the inner peripheral surface of the lumen has a concave curved surface recessed toward the outer periphery between the reinforcing materials.

[0011] According to a catheter constructed in accordance with this aspect, the reinforcing material is embedded in the peripheral wall of the lumen, thereby effectively achieving pushability, kink resistance, and the like.

[0012] Furthermore, the concave curved surface ensures a large free length of the inner circumferential surface of the lumen between the reinforcing members. This prevents the bending deformation of the catheter from being restricted by tension on the inner circumferential surface of the lumen, improving the flexibility of the catheter. Therefore, when inserting the catheter into a curved blood vessel, for example, the catheter can more accurately follow the curved shape of the blood vessel, improving the ease of insertion into the blood vessel.

[0013] In a second aspect, in the catheter according to the first aspect, the reinforcing member has a coil-shaped reinforcing member extending in a spiral shape.

[0014] In a catheter constructed according to this embodiment, the reinforcing material is a helically extending coiled reinforcing material, which makes it easier to achieve superior flexibility compared to a braided reinforcing material (braid). In particular, when a coiled reinforcing material is used, the reinforcing material-free portion of the circumferential wall of the lumen continues in a helical pattern between the pitches of the coiled reinforcing material, and by providing a concave curved surface between the pitches of the coiled reinforcing material, the flexibility of the catheter can be efficiently improved. Note that, in this embodiment, when multiple reinforcing materials are provided, it is desirable to position the helically extending coiled reinforcing material closest to the inner circumferential surface of the lumen.

[0015] In a third aspect, in the catheter according to the first or second aspect, the peripheral wall of the lumen comprises an inner layer and an outer layer, and the inner layer is made of a harder material than the outer layer.

[0016] When the inner layer constituting the inner circumferential surface of the lumen is made of a harder material than the outer layer, as in the present embodiment, tension or the like of the inner layer can be a factor in reducing the flexibility of the catheter. However, in the catheter according to the present embodiment, even if the inner layer is made of a harder material than the outer layer, the provision of a concavely curved surface in the inner layer reduces the adverse effects on flexibility caused by tension or the like of the inner layer. Therefore, for example, even when a soft outer layer is used in consideration of contact with the human body, and an inner layer harder than the outer layer is used in consideration of chemical resistance and slidability, the catheter can be made highly flexible.

[0017] In a fourth aspect, in the catheter described in the third aspect, the inner layer of the tip portion where the concave curved surface is formed is made of polytetrafluoroethylene, and the outer layer of the tip portion where the concave curved surface is formed is made of polyurethane.

[0018] In a catheter constructed according to this embodiment, the inner layer is formed from polytetrafluoroethylene, which makes it possible to fully obtain the performance required of the inner layer, such as chemical resistance and sliding properties. Furthermore, by employing an outer layer formed from polyurethane, which is more flexible than the inner layer, the outer layer is less likely to injure the human body even if it comes into contact with a blood vessel or the like.

[0019] In a fifth aspect, in the catheter according to any one of the first to fourth aspects, the concave curved surface is provided at a distal end portion in the longitudinal direction of the lumen.

[0020] With a catheter constructed according to this aspect, the flexibility of the tip portion, which has a significant effect on the ease of insertion into blood vessels, etc., can be increased by forming a concavely curved surface, thereby efficiently improving the ease of insertion into blood vessels, etc. In this aspect, the concavely curved surface may or may not be provided in the base end portion as long as it is provided in the tip portion in the longitudinal direction of the lumen, but for example, if it is not provided in the base end portion, it is easier to make the bending rigidity of the base end portion higher than that of the tip portion, making it easier to achieve performance such as pushability and kink resistance that is particularly required in the base end portion.

[0021] In a sixth aspect, in the catheter according to any one of the first to fifth aspects, the surface roughness of the outer surface of the peripheral wall of the lumen in the portion where the concave curved surface is formed is rougher than the surface roughness of the outer surface in the portion outside the concave curved surface.

[0022] With a catheter constructed in accordance with this aspect, it is possible to determine the position of the concave curved surface based on the surface roughness of the outer surface without having to check the inner surface shape of the lumen using a CT image or the like.

[0023] The concave curved surface between the reinforcing members can be formed, for example, by bending the catheter in advance, and in this case, after bending, the surface roughness of the outer surface at the portion where the concave curved surface is formed will be greater than the surface roughness of the outer surface in other portions. Therefore, the presence and position of the concave curved surface can be easily determined based on the difference in surface roughness of the outer surface.

[0024] In a seventh aspect, in the catheter according to any one of the first to sixth aspects, the concave curved surface is provided so as to extend in the circumferential direction.

[0025] In a catheter constructed according to this aspect, the circumferentially extending concave curved surface ensures a long free length of the inner circumferential surface of the lumen over a wider range in the circumferential direction, thereby more advantageously improving the flexibility of the lumen due to the concave curved surface.

[0026] This embodiment can be expected to have even better effects when combined with the second embodiment. That is, by providing a spirally extending concave curved surface in the circumferential direction between the pitches of the spirally extending coiled reinforcing material, the concave curved surface can more easily accommodate changes in the pitch of the coiled reinforcing material, thereby efficiently increasing the flexibility of the catheter.

[0027] An eighth aspect is a method for manufacturing a catheter having a lumen extending in the longitudinal direction and a reinforcing material embedded in the peripheral wall of the lumen, which includes a softening step of inserting the curved portion of a mandrel into the lumen and then removing the mandrel from the lumen.

[0028] According to the method for manufacturing a catheter having a structure according to this aspect, the resistance (bending rigidity) of the lumen peripheral wall to bending is reduced by the softening step of pre-bending the lumen peripheral wall by inserting the bending portion of the mandrel, and therefore, the softening of the lumen peripheral wall can be achieved without, for example, changing the material of the lumen peripheral wall.

[0029] Furthermore, in the softening process, the peripheral wall of the lumen is curved by inserting the mandrel into the lumen, which prevents the peripheral wall of the lumen from kinking during the softening process, allowing the softening process to be carried out stably.

[0030] According to the present invention, it is possible to achieve greater flexibility in a catheter while ensuring performance such as pushability and kink resistance.

[0031] FIG. 1 is a plan view showing a catheter according to a first embodiment of the present invention; FIG. 2 is a longitudinal cross-sectional view of the catheter shown in FIG. 1; FIG. 3 is a view explaining the softening process of the catheter shown in FIG. 1, showing the state before the mandrel is inserted into the lumen; FIG. 4 is a view explaining the softening process of the catheter shown in FIG. 1, showing the state after the mandrel is inserted into the lumen;

[0032] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0033] Figure 1 shows a suction catheter 10 as a first embodiment of a catheter according to the present invention. The suction catheter 10 includes a catheter body 12. In the following description, the distal end generally refers to the left side in Figure 1, which is distal, and the proximal end generally refers to the right side in Figure 1, which is proximal.

[0034] The catheter body 12 is a small-diameter, elongated tube that is capable of elastic bending deformation. As shown in Figure 2, the catheter body 12 has a lumen 14 that has a substantially circular cross section and runs through it in the longitudinal direction. The catheter body 12, which forms the peripheral wall of the lumen 14, has a tubular inner layer 16 that provides the inner circumferential surface of the lumen 14, and a tubular outer layer 18 that covers the inner layer 16 from the outer periphery.

[0035] The inner layer 16 is made of a resin, such as polytetrafluoroethylene (PTFE). In this embodiment, the inner layer 16 is entirely made of a single type of resin material. However, the inner layer 16 may be made of multiple types of resin materials along its length. In this case, it is preferable that the distal end portion is made of a resin material with a lower flexural modulus. The inner layer 16 is made of a ductile material that plastically stretches when tensile.

[0036] A radiopaque marker 20 is disposed at the distal end of the inner layer 16. The radiopaque marker 20 is, for example, in the form of a coil, and is attached in an externally inserted state to the distal end of the inner layer 16, and is disposed between the inner layer 16 and the outer layer 18. The radiopaque marker 20 is formed of a metal such as gold, tungsten, or platinum. The radiopaque marker 20 is located further distal than the distal end portion 34 of the catheter body 12, on which the concave curved surface 30, described below, is provided.

[0037] The outer layer 18 is made of resin, such as polyamide, polyamide elastomer, polyurethane, or a synthetic resin material containing a mixture of these. While the entire outer layer 18 may be made of a single type of resin material, it is preferable that the outer layer 18 be made of multiple types of resin material along its length. In this case, the distal end is preferably made of a resin material with a lower flexural modulus. In this embodiment, the outer layer 18 is made of multiple types of resin along its length, and from the proximal end to the distal end, the outer layer 18 is made of polyamide, polyamide elastomer, polyurethane, low-hardness polyurethane, and polyurethane. In this embodiment, the outer layer 18 is made of increasingly harder resin material toward the proximal end, except for the tip portion 22 (described below) at the most distal end, which is made of polyurethane. The outer layer 18 is made of a material with elasticity that allows it to reversibly expand and contract under tension.

[0038] In the distal end portion 34 (described below) of the catheter body 12, the inner layer 16 is made of a harder material than the outer layer 18. That is, in the distal end portion 34 of the catheter body 12, the inner layer 16 made of PTFE is made of a harder material than the outer layer 18 made of polyurethane (low-hardness polyurethane). Therefore, the flexibility (bending rigidity) of the distal end portion 34 of the catheter body 12 is more affected by the inner layer 16 than by the outer layer 18.

[0039] The distal end of the outer layer 18 is a tip portion 22. The tip portion 22 has a tapered shape that decreases in diameter toward the distal end. The tip portion 22 protrudes distally beyond the inner layer 16 and, together with the inner layer 16, forms the wall surface of the lumen 14. The tip portion 22 may be a separate member from the outer layer 18, or may be fixed to the distal end sides of the inner layer 16 and the outer layer 18.

[0040] A low-friction coating layer such as a hydrophilic coating or a fluororesin coating may be provided on the outer peripheral surface of the outer layer 18. This reduces the sliding resistance against the inner surface of the blood vessel wall when the catheter body 12 is inserted into a blood vessel, etc., thereby improving ease of insertion into the blood vessel.

[0041] A hard coil-shaped reinforcing member 24 is disposed on the outer peripheral surface of the inner layer 16 as a reinforcing material. The coil-shaped reinforcing member 24 is formed in the shape of a coil that extends in a spiral shape as a whole. The coil-shaped reinforcing member 24 is preferably made of metal, such as stainless steel or a nickel-titanium (Ni-Ti) alloy. As shown in FIG. 2 , the coil-shaped reinforcing member 24 of this embodiment is configured by a flat-bundle wire 28 consisting of three wires 26, 26, 26 arranged in the longitudinal direction of the catheter main body 12. The coil-shaped reinforcing member 24 of this embodiment extends with a substantially constant cross section, but the cross-sectional shape, cross-sectional area, number of wires 26 constituting the flat-bundle wire 28, etc. may be different between the proximal end and distal end.

[0042] The inner layer 16 and the outer layer 18 are fixed to each other. That is, the outer layer 18 is disposed so as to cover the outer periphery of the inner layer 16 onto which the radiopaque marker 20 and the coil-shaped reinforcing material 24 are inserted, and the two layers are fixed to each other by means of adhesion, heat welding, or the like, to form the catheter main body 12. In this embodiment, the inner periphery of the outer layer 18 is heated by a laser or the like, and is welded to the inner layer 16, the radiopaque marker 20, and the coil-shaped reinforcing material 24, thereby forming the catheter main body 12. As a result, the radiopaque marker 20 and the coil-shaped reinforcing material 24 are disposed in an embedded state in the circumferential wall of the lumen 14 formed by the inner layer 16 and the outer layer 18.

[0043] As shown in Figure 2, the inner circumferential surface of the inner layer 16 that constitutes the inner circumferential surface of the lumen 14 is provided with a concave curved surface 30 that is concave toward the outer periphery. The concave curved surface 30 has a concave longitudinal cross-sectional shape that opens toward the inner periphery between the pitches of the flat bundled wires 28 that constitute the coiled reinforcing member 24. The concave curved surface 30 extends circumferentially between the pitches of the flat bundled wires 28, and extends in a spiral shape over a length of at least one revolution in the circumferential direction. In the portion where the concave curved surface 30 is formed, the inner layer 16 forms a flexible portion 32 that is curved in a shape that is concave toward the outer periphery, and the outer circumferential surface is also concave toward the outer periphery.

[0044] The radial depth dimension D of the concave curved surface 30 is preferably at least ⅓, and more preferably at least ⅔, of the radial thickness dimension T of the inner layer 16. The radial depth dimension D of the concave curved surface 30 is preferably within a range of 3 to 30 μm, for example, and more preferably within a range of 5 to 10 μm.

[0045] The concavely curved surface 30 is provided at the distal end portion 34 of the catheter body 12, but is not provided at the proximal end portion of the catheter body 12 in this embodiment. The inner layer 16 has a longer free length per unit axial length at the distal end portion 34 where the concavely curved surface 30 is formed than at the proximal end portion where the concavely curved surface 30 is not formed. The length L of the distal end portion 34 where the concavely curved surface 30 is formed is not particularly limited, but is preferably within a range of 10 to 100 mm, for example, and more preferably within a range of 15 to 30 mm. At the portion of the distal end portion 34 where the concavely curved surface 30 is formed, the inner circumferential surface of the inner layer 16 is located more radially outward than at the proximal end portion where the concavely curved surface 30 is not formed, and the inner diameter is larger. The inner diameter of the inner layer 16 at the distal end portion 34, outside the concavely curved surface 30 located at the inner periphery of the flat-bundle wire 28, is approximately the same as that of the inner layer 16 at the proximal end portion. In short, the concave curved surface 30 is not formed by the portion of the inner layer 16 located on the inner periphery of the flat-bundle wires 28 protruding toward the inner periphery, but by the inner layer 16 being recessed toward the outer periphery between the pitches of the flat-bundle wires 28.

[0046] The concave curved surface 30 of the inner layer 16 may be formed during molding of the inner layer 16, but is preferably formed by performing a softening step, as shown in Figures 3A and 3B, on the inner layer 16 that has been molded into a straight tubular shape during the manufacturing process of the suction catheter 10. The manufacturing method of the suction catheter 10 will be described below.

[0047] First, the inner layer 16 and the outer layer 18 are prepared. Then, the metallic contrast marker 20 and the coil-shaped reinforcing member 24 are prepared. The manufacturing methods for these are well known, so a description thereof will be omitted here.

[0048] Next, the radiopaque marker 20 and the coil-shaped reinforcing material 24 are placed on the inner layer 16 in an externally fitted state, and then the outer layer 18 is placed on top of it, and the inner periphery of the outer layer 18 is welded to the inner layer 16. In this way, the inner layer 16, the outer layer 18, the radiopaque marker 20, and the coil-shaped reinforcing material 24 are integrally fixed to each other, thereby obtaining the catheter body 12'. A previously prepared hub 40 (described below) is attached to the proximal end of the catheter body 12'. Note that the inner layer 16 of the catheter body 12' does not have a concave curved surface 30 formed thereon.

[0049] Next, a softening step is performed to increase the flexibility of the distal end portion 34 of the catheter body 12'. The softening step is performed using a mandrel 36, as shown in Figures 3A and 3B. The mandrel 36 is a metal round rod and has a curved portion 38 that is curved in an arc. The mandrel 36 has an outer diameter that allows it to be inserted into the lumen 14 of the aspiration catheter 10. In particular, the curved portion 38 of the mandrel 36 has an outer diameter that allows it to be inserted into the lumen 14 of the distal end portion 34 of the catheter body 12. The radius r of the curved portion 38 is not particularly limited, but is preferably within a range of 0.5 to 5 mm, and more preferably within a range of 1 to 3 mm.

[0050] In the softening step, first, as shown in FIG. 3A , a mandrel 36 is placed at the distal end of the catheter body 12′ where the concavely curved surface 30 is not formed, and the mandrel 36 is inserted into the lumen 14 from the distal end. Next, as shown in FIG. 3B , the curved portion 38 of the mandrel 36 is inserted into the distal end 34 of the catheter body 12′ where the concavely curved surface 30 is formed. As a result, the distal end 34 of the catheter body 12′ is curved and deformed along the curved portion 38 of the mandrel 36, and the inner layer 16 of the catheter body 12′ is stretched in the axial direction on the outer periphery of the curved deformation, forming a partially stretched portion in the circumferential direction of the inner layer 16. The ductile inner layer 16 is plastically stretched by inserting the curved portion 38 into the lumen 14. The inner layer 16 can be stretched more reliably by repeatedly inserting and removing the curved portion 38 of the mandrel 36 into and from the lumen 14 of the distal end 34 of the catheter body 12′.

[0051] Next, the mandrel 36 is pulled out from the lumen 14 toward the distal end, returning the catheter body 12' to its initial straight shape as shown in Fig. 1. At this time, the inner layer 16, which has been stretched by the insertion of the curved portion 38 of the mandrel 36, remains stretched without returning to its initial shape before stretching. Therefore, when the catheter body 12' returns to its initial straight shape, a bend occurs in the stretched portion of the inner layer 16, and the stretched portion of the inner layer 16 becomes a bent portion 32 that is recessed outward.

[0052] Next, the mandrel 36 and the catheter body 12' are rotated relative to each other in the circumferential direction, and then the mandrel 36 is inserted into the lumen 14 of the catheter body 12', and the curved portion 38 is reinserted into the distal end portion 34 of the catheter body 12'. This stretches the inner layer 16 at different positions in the circumferential direction, forming concavely recessed curved portions 32 in the inner layer 16 at different positions in the circumferential direction.

[0053] By repeating the process of rotating the mandrel 36 and the catheter body 12' relatively in the circumferential direction and then inserting and removing the curved portion 38 of the mandrel 36 into and from the lumen 14, a concave, bent portion 32 is formed in the inner layer 16 over a wider circumferential range. In this embodiment, for example, by rotating the mandrel 36 and the catheter body 12' relatively in 90° increments in the circumferential direction and repeating the above process four times, a concave, bent portion 32 is formed over the entire circumference of the inner layer 16. This makes it possible to obtain a catheter body 12 in which a concave, curved surface 30 that continues spirally in the circumferential direction is formed on the inner surface of the inner layer 16. Note that by reducing the relative rotation angle between the mandrel 36 and the catheter body 12' and repeating the process of inserting and removing the curved portion 38 more times, the shape of the concave, curved surface 30 can be stabilized and the flexibility of the catheter body 12 can be further improved. The relative rotation of the mandrel 36 and the catheter body 12' may be performed with the mandrel 36 completely removed from the catheter body 12', or may be performed with, for example, the straight portion of the mandrel 36 inserted at least partially into the catheter body 12'.

[0054] Finally, the mandrel 36 is removed from the catheter body 12 to complete the softening process and obtain the aspiration catheter 10. As can be seen from the above description of the softening process, the concave curved surface 30 is not necessarily formed in a constant shape or size, and changes (variations) in shape may occur in the circumferential and axial directions.

[0055] Figures 4A and 4B show CT images (computed tomography images) of actual prototype catheter bodies 12', 12. In the catheter body 12' before the softening process shown in Figure 4A, no concavely curved surface 30 is formed in the inner layer 16, and the inner circumferential surface of the inner layer 16 has a substantially straight shape. In contrast, in the catheter body 12 after the softening process shown in Figure 4B, concavely curved surfaces 30 are formed on the inner circumferential surface of the inner layer 16 between the pitches of the coiled reinforcing material 24. The CT images of the prototypes also confirm that the concavely curved surfaces 30 of the inner layer 16 are formed between the pitches of the coiled reinforcing material 24 by the softening process described above.

[0056] Furthermore, since the outer layer 18 is made of a material that is more flexible than the inner layer 16, even if the inner layer 16 deforms on the inner side of the outer layer 18 so as to be recessed toward the outer periphery, the outer diameter dimension of the outer layer 18 hardly changes due to the radial compression deformation of the outer layer 18.

[0057] Because the outer layer 18 is made of a flexible material, traces of deformation during the softening process remain in the form of fine wrinkles on the outer peripheral surface. As a result, the outer layer 18 has a rougher surface at the distal end 34, where the curved portion 38 of the mandrel 36 is inserted to form the concavely curved surface 30 on the inner layer 16, than at the proximal end, where the inner layer 16 does not have the concavely curved surface 30. Therefore, the difference in surface roughness of the outer peripheral surface of the outer layer 18 makes it possible to easily determine the portion of the inner peripheral surface of the inner layer 16 where the concavely curved surface 30 is formed, without cutting the catheter body 12 or taking a CT image of the catheter body 12. The difference in surface roughness on the outer peripheral surface of the outer layer 18 can be confirmed by measurement using a surface roughness measuring instrument or a digital microscope that measures ten-point average roughness or centerline average roughness. More simply, the difference can also be determined visually, for example, based on the difference in scattering of reflected light when light is irradiated onto the outer peripheral surface of the outer layer 18. These traces of the softening process remaining on the outer surface of the outer layer 18 are very fine wrinkles, etc., and therefore do not substantially affect the performance of the catheter body 12, such as its sliding ability against the blood vessel wall. In Figure 1, the difference in surface roughness on the outer surface of the outer layer 18 is illustrated by coloring the rougher surface area (tip portion 34) with light ink.

[0058] As shown in Fig. 1, a hub 40 is attached to the proximal end of the catheter body 12. The hub 40 is made of hard resin or metal, and its proximal end is connected to an external circuit (not shown), thereby connecting the lumen 14 of the catheter body 12 to the external circuit. The specific structure of the hub 40 is not particularly limited, but the hub 40 of this embodiment is integrally provided with a tubular portion 42 connected to the proximal end of the catheter body 12 and a plurality of operating wings 44 protruding radially outward from the tubular portion 42. A strain relief 46 is attached to the end of the catheter body 12 on the hub 40 side to prevent kinking of the catheter body 12.

[0059] The aspiration catheter 10 having such a structure is used, for example, for aspiration of thrombi in cerebral blood vessels. In this case, a negative pressure pump for aspiration (not shown) that applies negative pressure to the lumen 14 is connected to the hub 40 via an external circuit. Then, for example, the catheter main body 12 is percutaneously inserted into a blood vessel from the leg or the like, and the tip of the catheter main body 12 is delivered to an affected area of ​​the cerebral blood vessel, where the thrombi are aspirated from the tip opening of the lumen 14.

[0060] The aspiration catheter 10 has a catheter body 12 that is long enough to reach the cerebral blood vessels, and a small diameter at the distal end of the catheter body 12 that allows it to be inserted into narrow cerebral blood vessels. Furthermore, because the deep parts of cerebral blood vessels are complexly curved, the distal end portion 34 of the catheter body 12 must be flexible enough to follow the complex shape of the cerebral blood vessels.

[0061] Therefore, the catheter body 12 of the aspiration catheter 10 has a coiled reinforcing member 24 embedded between the inner layer 16 and the outer layer 18, so that the pushing force input from the proximal to the distal end is effectively transmitted to the tip side of the catheter body 12. The excellent pushability and kink resistance provided by this coiled reinforcing member 24 allows the pushing force to be effectively transmitted to the tip portion 34 of the long catheter body 12, which reaches deeper into the cerebral blood vessels.

[0062] The distal end section 34 of the catheter body 12 is provided with excellent flexibility by virtue of the outer layer 18 being made of flexible polyurethane.

[0063] Furthermore, the inner layer 16, which is made of harder PTFE than the outer layer 18, has a free length that is increased in advance between the pitches of the flat-bundled wires 28 by concave curved surfaces 30 formed between the pitches of the flat-bundled wires 28 of the coiled reinforcing member 24, forming a bent flexible portion 32. Therefore, when the distal end portion 34 of the catheter body 12 is bent, the force used to stretch the inner layer 16 is reduced or eliminated, and the flexibility of the distal end portion 34 of the catheter body 12 is increased.

[0064] That is, when the tip section 34 of the catheter body 12 is bent, a tensile force acts in the axial direction on the inner layer 16 located on the opposite side of the center of curvature of the bend of the catheter body 12 (on the outer periphery of the bend), but because the inner layer 16 is curved so as to be concave toward the outer periphery at the flexible section 32, which forms the concavely curved surface 30, the inner layer 16 deforms in such a way that the curvature of the concavely curved surface 30 (flexible section 32) decreases, thereby allowing the bending deformation of the catheter body 12 without significantly stretching the inner layer 16. Therefore, when the tip section 34 of the catheter body 12 is bent, a strong force to stretch the inner layer 16, which is harder than the outer layer 18, is not needed, and the flexibility of the tip section 34 of the catheter body 12 is improved.

[0065] In this way, the catheter body 12 of this embodiment is less likely to be inhibited in bending and deformation at the tip portion 34 by the inner layer 16, which is harder than the outer layer 18, and exhibits excellent flexibility at the tip portion 34, making it possible to insert the catheter body 12, for example, deeper into the cerebral blood vessels.

[0066] The catheter body 12 is made of a coiled reinforcing material 24 that extends in a spiral shape, and has reduced bending rigidity compared to a braided reinforcing material. Moreover, since the pitches of the flat bundled wires 28 of the coiled reinforcing material 24 are continuous in the circumferential direction, the concavely curved surface 30 is formed continuously around the entire circumference, and the concavely curved surface 30 advantageously improves the flexibility of the distal end portion 34 of the catheter body 12.

[0067] The depth dimension D of the concavely curved surface 30 is set to at least one-half, and more preferably at least two-thirds, of the thickness dimension T of the inner layer 16, thereby ensuring a sufficiently large deflection of the inner layer 16 due to the concavely curved surface 30 between the pitches of the coiled reinforcing material 24. Therefore, when the distal end portion 34 of the catheter body 12 is bent, tension or the like of the inner layer 16 is sufficiently reduced, and good blood vessel followability can be achieved due to improved bending flexibility.

[0068] Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the specific descriptions. For example, the concave curved surface may be provided partially in the circumferential direction of the inner layer, or may be provided at multiple locations in the circumferential direction. Furthermore, the concave curved surface may be provided at a location where improved flexibility is desired, for example, at a location other than the distal end of the catheter body.

[0069] The reinforcing material is not limited to the coil-shaped reinforcing material 24. For example, a braided reinforcing material in which wires having any cross-sectional shape are woven in a cross-like pattern, or a reinforcing material in which multiple rings are partially connected in the circumferential direction by means such as welding, can also be used. Furthermore, the coil-shaped reinforcing material 24 is not limited to a structure formed by a flat-bundle wire 28 consisting of multiple wires 26. A single wire 26 may also be spirally wound. The cross-sectional shape of the wire 26 is not limited to the circular shape shown in the first embodiment, but may be polygonal, irregular, or other shapes. The lead angle, pitch, and other configurations of the coil-shaped reinforcing material extending in a spiral shape as a whole can be appropriately set depending on the required characteristics of the catheter. However, to stably provide a concave curved surface, it is preferable to provide a continuous gap between adjacent coil-shaped reinforcing materials in the catheter length direction, for example, a portion having a width equal to or greater than the diameter of a single wire constituting the coil-shaped reinforcing material, or a portion having a width equal to or greater than 0.05 mm, for example. Furthermore, it is desirable that the gap between adjacent coil-shaped reinforcing members in the length direction of the catheter be 0.5 mm or less, which more effectively improves the flexibility of the catheter body by forming a concave curved surface.

[0070] A second reinforcing material that exerts a supplementary reinforcing effect can also be provided separately from the reinforcing material. The second reinforcing material is made of synthetic fibers such as polyamide, polyester, or polyacrylonitrile, and is arranged in a state where it is wrapped around the outer periphery of the reinforcing material so as to cover it in contact with or at a distance from the reinforcing material, thereby exerting a supplementary reinforcing effect.

[0071] The catheter body is not limited to a two-layer structure consisting of an inner layer and an outer layer. For example, the catheter body may have an intermediate layer between the inner and outer layers, or may have a coating layer or the like provided on the outer periphery of the outer layer.

[0072] For example, by using a mandrel 36 with multiple curved portions 38 that curve in different directions, it is possible to form concave curved surfaces 30 at multiple locations circumferentially on the inner layer 16 by inserting the mandrel 36 into the lumen 14 once. Furthermore, by using a mandrel 36 with multiple curved portions 38 and varying the number of curved portions 38 passing through the distal end and the proximal end of the distal portion 34 of the catheter body 12, it is possible to manufacture a catheter body 12 whose flexibility gradually changes, becoming more flexible toward the distal end. This avoids a sudden change in stiffness along the length of the catheter body 12 and prevents breakage due to stress concentration in the stiffness change portion. For example, in a mandrel 36 with multiple curved portions 38, by making the radius of curvature of the curved portions 38 located more distally smaller or by making the curved portions 38 curve in different directions, it is possible to more advantageously obtain a catheter body 12 that is more flexible toward the distal end.

[0073] In the softening step, the formation of the concavely curved surface 30 in the inner layer 16 can be further promoted by inserting the curved portion 38 of the mandrel 36 into the lumen 14 under temperature control, for example, by preheating the mandrel 36 or by preheating the catheter body 12'. It is also preferable to insert the curved portion 38 of the mandrel 36 from the distal opening into the distal section 34 of the catheter body 12 and then remove the mandrel 36 from the distal opening. However, if the concavely curved surface 30 can be formed only in the distal section 34 due to, for example, a difference in hardness along the length of the outer layer 18, the mandrel 36 may be passed through the entire catheter body 12 and then removed from the proximal opening.

[0074] The present invention is not limited to being applied to suction catheters used for suctioning thrombi and the like, but can also be applied to various known catheters, such as catheters used for delivering medicinal solutions or stents to lesions, balloon catheters with a balloon at the tip, and measurement catheters for measuring the concentration of nitric oxide and the like in the blood.

[0075] 10 Suction catheter (first embodiment catheter) 12, 12' Catheter body 14 Lumen 16 Inner layer 18 Outer layer 20 Contrast marker 22 Tip portion 24 Coiled reinforcing material (reinforcing material) 26 Wire rod 28 Flat bundled wire 30 Concave curved surface 32 Flexure portion 34 Tip portion 36 Mandrel 38 Curved portion 40 Hub 42 Cylindrical portion 44 Operation blade portion 46 Strain relief D Depth dimension of concave curved surface T Thickness dimension of inner layer L Length dimension of tip portion r Radius of curved portion

Claims

1. A catheter having a lumen extending in the longitudinal direction, with a reinforcing material embedded in the peripheral wall of the lumen, wherein the inner peripheral surface of the lumen has a concave curved surface recessed toward the outer periphery between the reinforcing materials.

2. The catheter of claim 1, wherein said stiffener comprises a helically extending coiled stiffener.

3. A catheter according to claim 1 or 2, wherein the peripheral wall of the lumen comprises an inner layer and an outer layer, and the inner layer is made of a harder material than the outer layer in the portion forming the concave curved surface.

4. A catheter according to claim 3, wherein the inner layer is made of polytetrafluoroethylene in the area where the concave curved surface is formed, and the outer layer is made of polyurethane in the area where the concave curved surface is formed.

5. A catheter according to claim 1 or 2, wherein the concave curved surface is provided at the distal end portion of the lumen in the longitudinal direction.

6. A catheter as described in claim 1 or 2, wherein the surface roughness of the outer peripheral surface of the portion of the peripheral wall of the lumen where the concave curved surface is formed is rougher than the surface roughness of the outer peripheral surface of the portion outside the concave curved surface.

7. A catheter according to claim 1 or 2, wherein the concave curved surface extends in the circumferential direction.

8. A method for manufacturing a catheter having a lumen extending in the longitudinal direction and having a reinforcing material embedded in the peripheral wall of the lumen, the method comprising a softening step of inserting a curved portion of a mandrel into the lumen and then removing the mandrel from the lumen.

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