Balloon catheter and method for manufacturing balloon catheter

Abstract

A balloon (100) of a balloon catheter (10) according to the present embodiment has an oblateness of 0.6204% or less in an axially orthogonal cross section of a straight portion (105), as determined by equation (1) when the balloon (100) is expanded at 4 to 14 atm (inclusive). (Equation 1) Oblateness = (maximum outer diameter - minimum outer diameter) / maximum outer diameter × 100 (%)

Description

Balloon Catheter and Method for Manufacturing Balloon Catheter

[0001] The present invention relates to a balloon catheter and a method for manufacturing a balloon catheter.

[0002] Conventionally, a balloon catheter including a balloon having a drug coating layer formed on the outer surface thereof is known (e.g., Patent Document 1).

[0003] In a procedure using a balloon catheter, the balloon is delivered to a lesion in a biological lumen such as a blood vessel, and the balloon is expanded in the vicinity of the lesion to treat the lesion. After the treatment with the balloon is completed, an operator or the like deflates the balloon and pulls the balloon catheter into the lumen of a delivery medical device such as a guide catheter. In order to reduce the pull-in resistance of the balloon, when manufacturing the balloon, shaping is performed on the balloon to enable smooth and easy folding when the balloon is deflated.

[0004] Japanese Patent Application Publication No. 2018-153282

[0005] For example, if an appropriate folded shape is not imparted to the balloon, when the balloon is deflated, part of the drug coating layer formed on the outer surface of the balloon will peel off. This causes non-uniform thickness of the drug coating layer. In addition, if an appropriate folded shape is not imparted to the balloon, the passability of the balloon when passing through a stenotic site or the like in a blood vessel is reduced. As a result, when delivering the balloon to the lesion, the drug coating peels off from the outer surface of the balloon.

[0006] On the other hand, when a folded shape is imparted to the balloon, the shape of the balloon is set with a habit, so that the roundness of the cross-sectional shape of the balloon during expansion decreases. When a balloon having a cross-sectional shape with extremely reduced roundness due to shaping is expanded in a biological lumen, it becomes difficult to uniformly apply the drug contained in the drug coating layer to the lesion formed in the biological lumen along the circumferential direction of the cross-section of the blood vessel.

[0007] The present invention has been made in view of the above-mentioned problems, and aims to provide a balloon catheter that has a balloon with a straight section having high roundness, thereby achieving high delivery performance and uniform administration of a drug to a lesion, and a method for manufacturing a balloon catheter.

[0008] The present invention can be achieved by any of the following means (1) to (4).

[0009] (1) A balloon catheter comprising a balloon having a drug-coated layer formed thereon, and a shaft portion to which the balloon is connected, wherein the balloon, when expanded, comprises a tip tapered portion whose outer diameter gradually decreases toward the tip, a base tapered portion whose outer diameter gradually decreases toward the base, and a straight portion formed between the tip tapered portion and the base tapered portion, extending substantially linearly along the axial direction of the shaft portion, wherein when the balloon is expanded at 4 atm or more and 14 atm or less, the flattening ratio of the cross-section perpendicular to the axis of the straight portion, which can be determined by the following formula (1), is 0.6204% or less; Flattening ratio = (Maximum outer diameter - Minimum outer diameter) ÷ Maximum outer diameter × 100 [%] (Formula 1) In the above formula (1), a balloon catheter in which the largest of the first outer diameter along the first straight line passing through the center position of the straight portion in the cross section perpendicular to the axis and the second outer diameter along the second straight line perpendicular to the first straight line is defined as the maximum outer diameter, and the smallest of the two outer diameters is defined as the minimum outer diameter.

[0010] (2) A method for manufacturing a balloon catheter comprising a balloon on which a drug coating layer is formed, comprising: a shaping step of shaping a foldable protrusion on the balloon while heating the balloon; and a drug coating layer forming step of forming a drug coating layer on at least the outer surface of the straight portion of the balloon while the balloon on which the protrusion has been shaped is expanded.

[0011] (3) The method for manufacturing a balloon catheter according to claim 2, further comprising a welding step of welding the balloon to the shaft portion after the shaping step and before the drug coating layer formation step.

[0012] (4) The method for manufacturing a balloon catheter according to (2) or (3), wherein the shaping step involves heating the balloon to a temperature above the glass transition temperature and below the melting point of the balloon.

[0013] According to the present invention, a balloon catheter is provided that has a balloon with a straight section having high roundness, thereby achieving high delivery performance and uniform administration of a drug to a lesion site, and a method for manufacturing a balloon catheter is also provided.

[0014] This figure shows a balloon catheter according to an embodiment. This is a cross-sectional view showing the vicinity of the tip of the balloon catheter. This is a cross-sectional view perpendicular to the axis to illustrate the roundness (flatness) of the balloon. This figure shows the results of Example 1. This figure shows the results of Example 2. This figure shows the results of Example 3. This is a flowchart for explaining the manufacturing method of the balloon catheter according to an embodiment. This is a simplified cross-sectional view

[0015] Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. The embodiments shown herein are illustrative examples to embody the technical idea of ​​the present invention and do not limit the present invention. Furthermore, all other implementable forms, examples, and operational techniques that can be conceived by those skilled in the art without departing from the spirit of the present invention are included in the scope and spirit of the present invention, as well as in the claims and their equivalents.

[0016] Furthermore, the drawings attached to this specification may be schematically represented with changes to scale, aspect ratio, shape, etc., from the actual object for the sake of illustration and ease of understanding, but these are merely examples and do not limit the interpretation of the present invention.

[0017] Furthermore, in the following explanations, ordinal numbers such as "first" and "second" are used, but unless otherwise specified, they are used for convenience and do not prescribe any particular order.

[0018] For the sake of clarity, the following directions are defined in this specification.

[0019] The "axial direction" of the balloon catheter 10 is parallel to the central axis c1 of the shaft portion 200. The "circumferential direction" is the rotational direction with respect to the central axis c1 of the shaft portion 200 as the reference axis.

[0020] The arrows X1-X2 in each figure indicate the axial direction of the shaft portion 200, the arrows Y1-Y2 indicate the depth direction perpendicular to the axial direction, and the arrows Z1-Z2 indicate the height perpendicular to both the axial direction and the depth direction. The cross section perpendicular to the axial direction (the Y1-Y2 / Z1-Z2 cross section shown in Figures 3, 6 to 11) is defined as the orthogonal cross section.

[0021] In the balloon catheter 10, the side where the hub portion 250 is located is referred to as the "proximal end" (the side indicated by arrow X2). The side of the balloon catheter 10 that is located opposite the proximal end and is introduced into the body is referred to as the "proximal end" (the side indicated by arrow X1). Furthermore, "proximal end" refers to the portion that includes a certain range extending from the tip (extent) towards the proximal end, and "proximal end" refers to the portion that includes a certain range extending from the proximal end (very basal end) towards the proximal end.

[0022] <Embodiment> Figures 1 and 2 show the balloon catheter 10 according to this embodiment, and Figures 3, 4A to 4C are diagrams for explaining the flattening ratio of the straight portion 105 of the balloon 100. Figures 5 to 11 are diagrams for explaining the manufacturing method of the balloon catheter 10.

[0023] (Balloon catheter 10) As shown in Figures 1 and 2, the balloon catheter 10 comprises a balloon 100 on which a drug coating layer 110 is formed, and a shaft portion 200 to which the balloon 100 is connected.

[0024] In this embodiment, the balloon catheter 10 is configured as a medical device (Drug Eluting Balloon (DEB) catheter) that administers a drug contained in the drug coating layer 110 formed on the balloon 100 to a lesion formed in a biological lumen (e.g., a blood vessel) by expanding the balloon 100, which is positioned at the tip of the shaft portion 200, at the lesion.

[0025] There are no particular restrictions on the type of biological lumen or specific disease for which the balloon catheter 10 can be used. For example, examples of biological lumens include blood vessels, bile ducts, trachea, esophagus, and urethra.

[0026] Figure 2 shows a simplified cross-section along the axial direction of the balloon 100 when it has been expanded with a predetermined pressure.

[0027] In its expanded state, the balloon 100 comprises a tip tapered portion 102 whose outer diameter gradually decreases toward the tip, a base tapered portion 104 whose outer diameter gradually decreases toward the base, and a straight portion 105 formed between the tip tapered portion 102 and the base tapered portion 104, which extends substantially linearly along the axial direction of the shaft portion 200.

[0028] The straight section 105 has a cross-sectional shape that extends with a substantially constant outer diameter between the tapered tip section 102 and the tapered base section 104.

[0029] The tip tapered portion 102 and the base tapered portion 104 can be configured to have a greater wall thickness than, for example, the straight portion 105. By configuring it in this way, when adding the foldable protrusion 108 to the balloon 100 as described later, the protrusion 108 can be shaped more strongly relative to each tapered portion 102 and 104 than to the straight portion 105. As a result, when the balloon 100 is deflated after being expanded once, each tapered portion 102 and 104 can be folded to a shape close to its shape before expansion. Therefore, it becomes possible to improve the delivery of the balloon catheter 10 within the biological lumen.

[0030] The balloon 100 has an internal space 106 into which fluid can be injected. The internal space 106 is partitioned around the outer surface of the inner tube 210 of the shaft portion 200. The internal space 106 is in fluid communication with the lumen 225 of the outer tube 220 of the shaft portion 200 via the tip opening 221a of the outer tube 220 of the shaft portion 200.

[0031] As materials for the balloon 100, for example, polyethylene, polypropylene, ethylene-propylene copolymer polyolefin, polyester such as polyethylene terephthalate, polyvinyl chloride, ethylene-vinyl acetate copolymer, cross-linked ethylene-vinyl acetate copolymer, thermoplastic resins such as polyurethane, polyamide, polyamide elastomer, polystyrene elastomer, silicone rubber, latex rubber, etc. can be used.

[0032] The drug coating layer 110 can be provided on the outer surface 100a of the balloon 100 in a location (range) where at least the straight portion 105 is formed. By placing the drug coating layer 110 on the straight portion 105, the drug can be efficiently administered to the lesion from the straight portion 105 by expanding the balloon 100 with the balloon 100 positioned near the lesion. In this specification, the "effective length" of the balloon 100 means the length that actually contacts the lesion and administers the drug when expanded, and is usually a region that includes at least the entire length of the straight portion 105. The drug coating layer 110 is preferably formed in a range corresponding to at least this effective length, and may extend to a part of the tip tapered portion 102 and the base tapered portion 104 as needed.

[0033] The drug used in the drug coating layer 110 can be arbitrarily selected according to the procedure using the balloon catheter 10 (such as the type of biological lumen or the type of lesion). Examples of drugs that can be used in the drug coating layer 110 include anticancer drugs, immunosuppressants, antibiotics, antirheumatic drugs, antithrombotic drugs, HMG-CoA reductase inhibitors, ACE inhibitors, calcium channel blockers, antihyperlipidemic drugs, integrin inhibitors, antiallergic drugs, antioxidants, GPIIbIIIa antagonists, retinoids, flavonoids, carotenoids, lipid-improving drugs, DNA synthesis inhibitors, tyrosine kinase inhibitors, antiplatelet drugs, anti-inflammatory drugs, bio-derived materials, interferon, mucolytic agents, etc.

[0034] The drug coating layer 110 can be formed by coating the outer surface 100a of the balloon 100 with a drug or the like exemplified above, supported on a biocompatible polymer.

[0035] The shaft portion 200 includes an inner tube 210 having a lumen 215 through which a guide wire GW can be inserted, and an outer tube 220 having a lumen 225 that is in fluid communication with the internal space 106 of the balloon 100.

[0036] The inner tube 210 and the outer tube 220 are arranged coaxially. The tip 211 of the inner tube 210 is positioned to protrude further forward than the tip 221 of the outer tube 220.

[0037] The tip portion 101 located on the tip side of the tapered tip portion 102 of the balloon 100 can be connected to the tip portion 211 and tip tip 260 of the inner tube 210.

[0038] In the balloon 100, the base end portion 103, located on the base end side of the base end tapered portion 104, can be connected to the tip portion 221 of the outer tube 220.

[0039] The balloon 100 can be welded to the shaft portion 200 (inner tube 210, outer tube 220), for example.

[0040] As shown in Figure 1, a hub portion 250 can be connected to the base end of the shaft portion 200, which has a port configured to fluidly communicate with the internal space 106 of the balloon 100 via the lumen 225 of the outer tube 220.

[0041] The hub portion 250 can be connected to a device (such as a syringe) for controlling the supply and discharge of the expansion fluid (for example, a liquid such as physiological saline) used to expand the balloon 100. The hub portion 250 can be of a structure known in the catheter field.

[0042] As shown in Figure 1, a tip 260 made of a flexible resin material can be attached to the portion of the inner tube 210's tip 211 that protrudes further forward than the outer tube 220.

[0043] A contrast marker 270, which is visible on X-ray images, can be attached to the outer surface of the inner tube 210 at a predetermined position (for example, a position that coincides with the axial center position of the straight section 105 in the circumferential direction). The contrast marker 270 can be made of a ring-shaped member made of a metal such as platinum, gold, silver, iridium, titanium, or tungsten, or an alloy thereof.

[0044] As shown in Figure 1, the shaft portion 200 is in communication with the tip opening 211a and lumen 215 of the inner tube 210 and is equipped with a guide wire port 227 through which the guide wire GW can be drawn out. The guide wire port 227 is provided at a predetermined position on the proximal end side of the balloon 100.

[0045] As described above, the balloon catheter 10 has a so-called rapid exchange type catheter structure in which a guidewire port is formed in the middle of the shaft portion 200. Note that the balloon catheter 10 may also have a so-called over-the-wire type catheter structure.

[0046] The inner tube 210 and the outer tube 220 can be made of resin materials, for example, polyolefins such as polyethylene, polypropylene, ethylene-propylene copolymer, and ethylene-vinyl acetate copolymer; thermoplastic resins such as soft polyvinyl chloride; various elastomers such as polyurethane elastomer, polyamide elastomer, and polyester elastomer; and crystalline plastics such as polyamide, crystalline polyethylene, and crystalline polypropylene.

[0047] (Ovality of Balloon 100) Next, the ovality of the balloon 100 according to the present embodiment will be described with reference to FIG. 3.

[0048] FIG. 3 is a diagram for explaining ovality, created based on an axial cross-sectional view of the straight portion 105 taken along arrows 2A-2A shown in FIG. 2.

[0049] The balloon 100 can be configured such that when expanded at a pressure of 4 atm to 14 atm, the ovality of the axial cross-section of the straight portion 105 obtained by the following formula (1) is 0.6204% or less.

[0050] Ovality = (maximum outer diameter - minimum outer diameter) ÷ maximum outer diameter × 100 [%] (Formula 1) In the above formula (1), among the first outer diameter along the first straight lines H1, H1' passing through the center position of the straight portion 105 in the axial cross-section shown in FIG. 3 (which is the same position as the position where the central axis c1 is arranged in the axial cross-sectional view in the present embodiment) and the second outer diameter along the second straight lines H2, H2' orthogonal to the first straight lines H1, H1', the largest outer diameter is defined as the maximum outer diameter, and the smallest outer diameter is defined as the minimum outer diameter.

[0051] The above-mentioned flattening ratio of 0.6204% is the "mean + 3σ" (= 99.7% normal distribution) value calculated from the flattening ratios measured when the product was expanded under multiple different pressure conditions, as will be explained in the examples described later. This "mean + 3σ" value was calculated based on the measurement results in Example 2, which will be described later.

[0052] The first straight line H1 used as the basis for calculating the aspect ratio can be defined as any straight line passing through the center position. Furthermore, the second straight line H2, which is perpendicular to the first straight line H1, is not particularly limited as long as the angle between it and the first straight line H1 is a right angle (90°). In the embodiments described later, the aspect ratio is calculated using the maximum and minimum outer diameter values ​​calculated using the first straight line H1 and the second straight line H2 shown in Figure 3, and the maximum and minimum outer diameter values ​​calculated using the first straight line H1' and the second straight line H2'. Note that the aspect ratio according to the present invention is a value that can be calculated based on at least one pair of first and second straight lines passing through the center position in the cross-section perpendicular to the axis of the straight section 105. In the embodiments, as shown in Figure 3, aspect ratio 1 and aspect ratio 2 are calculated based on two pairs of mutually perpendicular straight lines (first straight line H1 and second straight line H2, and first straight line H1' and second straight line H2'), but these are just examples of the measurement direction of the aspect ratio and do not limit the scope of the present invention.

[0053] In Figure 3, for the purpose of understanding the method for calculating the flatness ratio, balloon 100A, which has the largest outer diameter, balloon 100B, which has the smallest outer diameter, and balloon 100C, which is the balloon to be measured, are schematically shown.

[0054] The flattening ratio, as defined by equation (1) above, is a value that represents how flat an ellipse or ellipsoid is compared to a circle (perfect circle) or sphere (how much difference there is between the length along the major axis of the ellipse and the length along the minor axis). The flattening ratio is 0 for a circle (perfect circle) or sphere, and approaches 1 as the shape becomes flatter.

[0055] The balloon 100 can exhibit the following effects because the flattening ratio of the straight section 105 is 0.6204% or less.

[0056] As mentioned above, a small flattening ratio of the straight portion 105 of the balloon 100 means that the straight portion 105 of the balloon 100 has a high degree of roundness. As will be described later, in the manufacturing method of this embodiment, when forming the drug coating layer 110 on the balloon 100, the balloon 100 can be deformed into an expanded state (see Figure 10). By applying the material for forming the drug coating layer 110 to the outer surface 100a (outer surface of the straight portion 105) of the balloon 100 while the balloon 100 is expanded, it becomes possible to form a drug coating layer 110 of uniform thickness on each part of the circumferential direction of the outer surface 100a of the straight portion 105 of the balloon 100. In this case, as in the balloon 100 of this embodiment, the straight portion 105 is formed with a high degree of roundness, which makes it possible to form a drug coating layer 110 of more uniform thickness on each part of the circumferential direction of the outer surface of the straight portion 105.

[0057] Furthermore, because the balloon 100 has a highly rounded straight section 105, when the straight section 105 is pressed against a lesion formed in a biological lumen such as a blood vessel, it becomes possible to uniformly administer (apply) the drug contained in the drug coating layer 110 along the circumferential direction of the cross-section of the blood vessel. This improves the therapeutic effect of the balloon 100.

[0058] Next, a preferred aspect ratio for the straight section 105 will be described based on the examples.

[0059] Figures 4A to 4C show the results of measuring the flattening ratio of the straight portion 105 of the balloon 100 manufactured by the manufacturing method of this embodiment, which will be described later.

[0060] Each balloon according to Examples 1 to 3 shown in Figures 4A to 4C has the following configuration: • Example 1: Balloon expansion diameter φ2.5 mm, balloon effective length 40 mm, balloon film thickness (wall thickness) 11.5 μm to 19.5 μm. • Example 2: Balloon expansion diameter φ2.5 mm, balloon effective length 15 mm, balloon film thickness (wall thickness) 11.5 μm to 19.5 μm. • Example 3: Balloon expansion diameter φ4.0 mm, balloon effective length 15 mm, balloon film thickness (wall thickness) 15.5 μm to 25.5 μm. • Polyamide elastomer (nylon 12-polytetramethylene glycol copolymer) was used as the constituent material for the balloons in Examples 1 to 3. The above expansion diameter refers to the nominal outer diameter (so-called nominal diameter) when the balloon is expanded at a specified pressure (6 atm).

[0061] The outer diameters of measurement points H1, H2, H1', ​​and H2' in Figures 4A to 4C represent the outer diameter (first outer diameter or second outer diameter) of the straight section 105 of the balloon 100, measured at the point where each straight line shown in Figure 3 intersects with the outer surface 100a of the straight section 105. As described above, in each of the embodiments 1 to 3, the flattening ratio is calculated based on the maximum and minimum outer diameter values ​​measured based on the first straight line H1 and the second straight line H2, and the maximum and minimum outer diameter values ​​measured based on the first straight line H1' and the second straight line H2'.

[0062] In Figures 4A to 4C, the flattening ratio calculated using the first straight line H1 and the second straight line H2 is shown as "Flattening Ratio 1," and the flattening ratio calculated using the first straight line H1' and the second straight line H2' is shown as "Flattening Ratio 2."

[0063] In Figures 4A to 4C, "Minimum Outer Diameter" and "Maximum Outer Diameter" represent the minimum and maximum outer diameters measured at each measurement point H1, H2, H1', ​​and H2'. In Figures 4A to 4C, "Average Outer Diameter" represents the average outer diameter calculated from the values ​​measured at each measurement point H1, H2, H1', ​​and H2'.

[0064] The values ​​shown in Figures 4A to 4C are the values ​​of the straight section 105 measured in the state described later in the manufacturing method of this embodiment, where the balloon 100 is molded, given a folded shape in the shaping process (S11), and expanded before forming the chemical coating layer 110 (the state shown in Figure 9). The measurement point was set to the axial center position of the straight section 105.

[0065] In Examples 1 to 3, the flattening ratio of the straight section 105 of the balloon 100 and the value of the "average + 3σ" of the measured flattening ratios were calculated when the internal pressure of the balloon 100 was increased to 4 atm, 6 atm, and 14 atm.

[0066] In Example 1, the "average + 3σ" of both flatness ratio 1 and flatness ratio 2 was 0.5191% or less when the pressurized force was within the range of 4 atm to 14 atm. It is believed that the balloon 100 according to Example 1 can appropriately exhibit the above-mentioned effects because the straight section 105 has a high degree of roundness. The maximum value of the individual flatness measured under each pressure was 0.3965%.

[0067] In Example 2, the "average + 3σ" of both flatness ratio 1 and flatness ratio 2 was 0.6204% or less when the pressurized force was within the range of 4 atm to 14 atm. It is believed that the balloon 100 according to Example 2 can appropriately exhibit the above-mentioned effects because the straight section 105 has high roundness. The maximum value of the individual flatness measured under each pressure was 0.4452%.

[0068] In Example 3, the "average + 3σ" of both flatness ratio 1 and flatness ratio 2 was 0.3182% or less when the pressurized force was within the range of 4 atm to 14 atm. It is believed that the balloon 100 according to Example 3 can appropriately exhibit the above-mentioned effects because the straight section 105 has high roundness. The maximum value of the individual flatness measured under each pressure was 0.2163%.

[0069] From the results of each of Examples 1 to 3, it is possible to provide a highly round balloon 100 with a flattening ratio of 0.6204% or less (preferably 0.5191% or less, more preferably 0.3182% or less) when pressurized at 4 atm to 14 atm by employing the manufacturing method described later.

[0070] (Method for manufacturing the balloon catheter 10) Next, the method for manufacturing the balloon catheter 10 according to this embodiment (hereinafter referred to as the "manufacturing method") will be described.

[0071] Referring to Figure 5, the manufacturing method comprises a molding step (S10) for forming the balloon 100, a shaping step (S11) for giving the balloon 100 a predetermined shape, a welding step (S12) for welding the balloon 100 to the shaft portion 200, a drug coating layer forming step (S13) for forming a drug coating layer 110 on the balloon 100, and a folding step (S14) for folding the balloon 100.

[0072] Specifically, the manufacturing method is a method for manufacturing a balloon catheter 10 comprising a balloon 100 on which a drug coating layer 110 is formed. The manufacturing method includes a shaping step (S11) in which a foldable protrusion 108 is formed on the balloon 100 while the balloon 100 is heated, and a drug coating layer forming step (S13) in which the drug coating layer 110 is formed on the outer surface 100a of the balloon 100 while the balloon 100, which has been shaped into a folded shape, is expanded.

[0073] Furthermore, the manufacturing method may optionally include the following additional steps.

[0074] The process includes a welding step (S12) in which the balloon 100 is welded to the shaft portion 200 after the shaping step (S11) and before the drug coating layer formation step (S13).

[0075] The shaping process (S11) is carried out at a temperature above the glass transition temperature of the balloon 100 and below its melting point.

[0076] The following describes each step in detail with reference to Figures 6 to 11. Note that explanations of known aspects of balloon catheter manufacturing methods will be omitted as appropriate in the description of each step.

[0077] In the manufacturing method, the balloon 100 is formed using a predetermined balloon molding die 310 (S10).

[0078] In forming the balloon 100, the hollow member (parison) 100' that will be the material for the balloon 100 is set in the balloon molding die 310, and the hollow member 100' is pressurized from the inside. This process adds shapes such as the straight section 105 and the tapered sections 102, 104 to the balloon 100.

[0079] In the above process, annealing of the balloon 100 can be performed. Annealing can be performed, for example, at a temperature of around 125° to 135°. Annealing can be performed, for example, using a heating device (such as a heater) capable of heating the balloon mold 310.

[0080] As described above, by performing annealing, the hollow member 100' can be molded into a balloon 100 of a predetermined shape. When annealing is performed, the balloon 100 does not have a chemical coating layer 110. Therefore, the chemical coating layer 110 is not affected by heat, and annealing can be performed at the predetermined temperature. As a result, a straight portion 105 with a smaller flattening ratio (higher roundness) in cross-sectional shape can be added to the balloon 100.

[0081] Next, a foldable protrusion 108 is formed on the balloon 100 (S11).

[0082] In the manufacturing method, a shaping mold 320 having three divided molds is used to create three protrusions 108 (parts that function as wings when folded) on the balloon 100. There are no particular restrictions on the number of divided molds included in the shaping mold 320, the cavity shape, the number of protrusions 108, or the cross-sectional shape.

[0083] In the manufacturing method, during step (S11) described above, the balloon 100 is heated while shaping it. The balloon 100 can be heated, for example, using a heating device (such as a heater) capable of heating the shaping mold 320.

[0084] As described above, by shaping the protrusion 108 on the balloon 100 while heating the balloon 100, the protrusion 108 can be more reliably shaped on the balloon 100. This makes it possible to reduce the size (thinner diameter) of the balloon 100's profiling when the balloon 100 is folded by wrapping the protrusion 108 around the outer circumference of the shaft 200.

[0085] Furthermore, by heating the balloon 100 in the above step (S11), the protrusions 108 on the balloon 100 can be more firmly shaped. This makes it possible to improve the recovery of the balloon 100 to its contracted shape when the balloon 100 is expanded and then contracted again during a procedure using the balloon catheter 10. As a result, it becomes possible to reduce the size of the profiling when the balloon 100 is contracted after being expanded once. This prevents the drug coating layer 110 formed on the outer surface 100a of the balloon 100 from rubbing against the guide catheter and peeling off when the balloon 100 is placed in a guide catheter or the like after being contracted after being expanded once.

[0086] Furthermore, in this embodiment, since the convex portion 108 is shaped on the balloon 100 before forming the drug coating layer 110 on the straight portion 105 of the balloon 100, the heating of the balloon 100 does not affect the drug contained in the drug coating layer 110. Therefore, it is possible to heat the balloon 100 to a predetermined temperature or higher.

[0087] For example, in the shaping process, the balloon 100 can be heated to a temperature above its glass transition temperature but below its melting point. By heating the balloon 100 to such a temperature, it becomes possible to more firmly shape the protrusions 108 on the balloon 100 while preventing the balloon 100 from melting.

[0088] The heating temperature during shaping can be, for example, set to about 80% of the annealing temperature during the molding process. For example, if the balloon 100 is made of polyamide elastomer, the temperature can be set to 90° to 140°, which is above the glass transition temperature of the polyamide elastomer (30° to 55°) and below the melting point of the polyamide elastomer (160° to 180°). The heating temperature during the shaping process should be within the range of the glass transition temperature and below the melting point of the balloon 100 material, but it may also be set in relation to the annealing temperature during the molding process. For example, if the annealing temperature during the molding process is about 125° to 135°, it is preferable to set the heating temperature during the shaping process to a range of approximately 80% or more of the annealing temperature and below the annealing temperature, for example, 90° to 140°. By setting the temperature in this way, the shape of the protrusions 108 can be sufficiently retained while preventing the balloon 100 from melting.

[0089] Next, as shown in Figure 8, the balloon 100 with the convex portion 108 formed on it is released from the shaping mold 320.

[0090] Next, the balloon 100 released from the shaping mold 320 is welded to the shaft portion 200 (S12).

[0091] In this embodiment, the welding of the balloon 100 to the shaft portion 200 is performed before the drug coating layer formation step (S13), so that the drug coating layer 110 does not peel off or melt out from the balloon 100 during welding. The welding temperature when welding the balloon 100 to the shaft portion 200 is, for example, 160° to 200°.

[0092] Next, as shown in Figure 9, the balloon 100 is expanded, thereby deforming the straight portion 105 of the balloon 100 into a roughly circular cross-sectional shape.

[0093] Next, as shown in Figure 10, with the balloon 100 expanded, a material for forming the drug coating layer 110 is applied to at least the straight portion 105 of the balloon 100 (S13). For example, a known spray can be used to apply the material for forming the drug coating layer 110. In this manufacturing method, since the material for the drug coating layer 110 is applied to the straight portion 105 with a small flatness while it is expanded, it becomes possible to form a drug coating layer 110 of uniform thickness on each part of the outer surface of the straight portion 105.

[0094] Next, as shown in Figure 11, the balloon 100 is folded so as to wrap around the shaft portion 200 (S14).

[0095] In the above process, the balloon 100 is folded so that the protrusion 108 formed in the shaping process (S11) is wrapped around the shaft portion 200. As mentioned above, the balloon 100 is heated when forming the protrusion 108 to more firmly shape the protrusion 108 onto the balloon 100, so the profiling of the folded balloon 100 can be made smaller. This improves the delivery of the balloon catheter 10. Furthermore, because the profiling of the folded balloon 100 is made smaller, when the balloon catheter 10 is delivered to a predetermined position in the biological lumen using a guide catheter or the like, the drug coating layer 110 formed on the outer surface 100a of the balloon 100 can be effectively prevented from rubbing against the guide catheter or the like and peeling off.

[0096] As described above, the balloon catheter 10 according to this embodiment comprises a balloon 100 on which a drug coating layer 110 is formed, and a shaft portion 200 to which the balloon 100 is connected. When the balloon 100 is expanded, it comprises a tip tapered portion 102 whose outer diameter gradually decreases toward the tip, a base tapered portion 104 whose outer diameter gradually decreases toward the base, and a straight portion 105 formed between the tip tapered portion 102 and the base tapered portion 104, extending substantially linearly along the axial direction of the shaft portion 200. When the balloon 100 is expanded at 4 atm or more and 14 atm or less, the flattening ratio of the cross-section perpendicular to the axis of the straight portion 105, which can be determined by the following formula (1), is 0.6204% or less: Flattening ratio = (Maximum outer diameter - Minimum outer diameter) ÷ Maximum outer diameter × 100 [%] (Formula 1) In the above formula (1), the largest of the first outer diameter along the first straight line passing through the center position of the straight portion 105 in the cross section perpendicular to the axis and the second outer diameter along the second straight line perpendicular to the first straight line is defined as the maximum outer diameter, and the smallest of the two outer diameters is defined as the minimum outer diameter.

[0097] Furthermore, the manufacturing method according to this embodiment is a method for manufacturing a balloon catheter 10 comprising a balloon 100 on which a drug coating layer 110 is formed, and comprises a shaping step (S11) in which a foldable protrusion 108 is formed on the balloon 100 while the balloon 100 is heated, and a drug coating layer forming step (S13) in which the drug coating layer 110 is formed on the outer surface 100a of the balloon 100 while the balloon 100 on which the protrusion 108 has been formed is expanded.

[0098] According to this embodiment, a balloon catheter 10 is provided that has high delivery performance and uniform administration of the drug to the lesion site by having a balloon 100 with a straight portion 105 having high roundness, and a method for manufacturing the balloon catheter 10 is also provided.

[0099] Although the balloon catheter and method for manufacturing the balloon catheter according to the present invention have been described above through embodiments, the present invention is not limited to the configuration described in the specification and can be arbitrarily and additionally modified based on the claims.

[0100] This application is based on Japanese Patent Application No. 2025-053062, filed on 27 March 2025, the disclosures of which are incorporated herein by reference in their entirety.

[0101] 10 Balloon catheter 100 Balloon 100a Outer surface of the balloon 102 Tapered tip 104 Tapered base 105 Straight section 106 Internal space 108 Convex section 110 Drug coating layer 200 Shaft section 250 Hub section 310 Balloon molding die 320 Shaping mold H1 First straight line H1' First straight line H2 Second straight line H2' Second straight line GW Guide wire c1 Central axis

Claims

1. A balloon catheter comprising a balloon having a drug-coated layer formed thereon, and a shaft portion to which the balloon is connected, wherein the balloon, when expanded, comprises a tip tapered portion whose outer diameter gradually decreases toward the tip, a base tapered portion whose outer diameter gradually decreases toward the base, and a straight portion formed between the tip tapered portion and the base tapered portion, extending substantially linearly along the axial direction of the shaft portion, wherein when the balloon is expanded at 4 atm or more and 14 atm or less, the flattening ratio of the cross-section perpendicular to the axis of the straight portion, which can be determined by the following formula (1), is 0.6204% or less: Flattening ratio = (maximum outer diameter - minimum outer diameter) ÷ maximum outer diameter × 100 [%] (Formula 1) In the above formula (1), the balloon catheter wherein the largest outer diameter among the first outer diameter along the first straight line passing through the center position of the straight portion in the cross-section perpendicular to the axis and the second outer diameter along the second straight line perpendicular to the first straight line is defined as the maximum outer diameter, and the smallest outer diameter is defined as the minimum outer diameter.

2. A method for manufacturing a balloon catheter comprising a balloon on which a drug coating layer is formed, comprising: a shaping step of shaping a foldable protrusion on the balloon while heating the balloon; and a drug coating layer forming step of forming a drug coating layer on at least the outer surface of the straight portion of the balloon while the balloon with the shaped protrusion is expanded.

3. The method for manufacturing a balloon catheter according to claim 2, further comprising a welding step of welding the balloon to the shaft portion after the shaping step and before the drug coating layer formation step.

4. The method for manufacturing a balloon catheter according to claim 2 or 3, wherein the shaping step involves heating the balloon to a temperature above the glass transition temperature and below the melting point of the balloon.

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