Balloon catheter

Abstract

To provide a balloon catheter capable of achieving both of improvement in pull-in property to a guiding catheter and excellent expansion accuracy when the diameter of a balloon is expanded.SOLUTION: A balloon 140 includes a straight portion 141 and a tapered portion 142 inclined from the straight portion 141 toward a connecting portion with a shaft 110, having the same diameters along the axial direction. An outer diameter of the straight portion 141 at the time of NP dilation is greater than 4 mm and equal to or less than 6 mm. A taper length D1 which is an axial length of the tapered portion 142 is 4-6 mm. A ratio of the taper length D1 to a distance D2 (farthest end portion distance D2) from a central axis C of the shaft 110 to a farthest end portion of the balloon 140 when the balloon 140 deflated in a state where a plurality of blade portions 150 are formed in the straight portion 141 and the tapered portion 142 in the circumferential direction is viewed in the axial direction is 2-4.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a balloon catheter. [Background technology]

[0002] Balloon catheters are widely known as devices used in procedures to dilate lesions (such as narrowed areas) formed in biological lumens such as blood vessels, and for placing stents and the like.

[0003] A balloon catheter is a medical device that has a radially expandable balloon attached to the distal end of a shaft. The balloon has a tapered proximal end that expands in diameter from the proximal end where it connects to the long shaft toward the distal end, a straight portion with the same diameter along the axial direction, and a tapered distal end that reduces in diameter from the proximal end toward the distal end where it connects to the shaft. A balloon catheter can be inserted into a blood vessel through a guiding catheter in a deflated state, and can reach the lesion, where it can be expanded to widen the lesion (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2019 / 234784 Summary of the Invention [Problem to be solved by the invention]

[0005] Balloon catheters are expanded and contracted within a specified range based on the characteristics of the lesion and blood vessels. Therefore, by increasing the inflation diameter of the balloon, the range of expansion and contraction of the balloon (the range over which the balloon can be expanded and contracted) can be widened, thereby increasing the flexibility of the procedure.

[0006] For example, if the outer diameter of a balloon catheter for PTCA treatment is expanded to increase the flexibility of the PTCA procedure, this balloon catheter is introduced into a blood vessel using a PTCA guiding catheter. However, when the balloon of the balloon catheter is expanded at the lesion and then deflated and retracted into the guiding catheter, the expanded balloon increases the outer diameter of the reduced diameter part, creating significant retraction resistance and potentially delaying the procedure.

[0007] One way to reduce the resistance to retraction of the guiding catheter is to increase the axial length (taper length) of the balloon's tapered section. However, increasing the balloon's tapered length reduces the slope of the tapered section, making it easier for the distal tapered section and parts of the proximal tapered section (especially near the junction with the straight section) to change to straight sections. When part of the tapered section changes to a straight section, the effective length of the balloon is extended, which increases the risk of dilating blood vessels in locations other than the intended dilatation site, reducing dilatation accuracy (the degree to which only the intended dilatation site can be accurately dilated).

[0008] At least one embodiment of the present invention has been made in consideration of the above-mentioned circumstances, and specifically, an object of the present invention is to provide a balloon catheter that can achieve both improved retractability into a guiding catheter when the balloon is expanded in diameter and good expansion accuracy. [Means for solving the problem]

[0009] As a result of extensive research into solving the problems that arise when expanding the diameter of a balloon, the inventors of the present application discovered that when the "taper sharpness" calculated from two parameters, "the balloon taper length" which can affect retractability and expansion accuracy, and "the distance from the central axis of the shaft to the farthest end of the balloon when viewed axially of a deflated balloon," falls within a specified range, it is possible to achieve both improved retractability and good expansion accuracy, and thus arrived at the present invention.

[0010] The present invention provides (1) a balloon catheter comprising a long shaft and a balloon disposed at the tip of the shaft and having an expandable and contractable membrane-like body, wherein the balloon has a straight portion of the same diameter along the axial direction and a tapered portion that slopes from the straight portion toward the connection with the shaft, the outer diameter of the straight portion when expanded is greater than 4 mm and not greater than 6 mm, the tapered portion has an axial length that is the taper length of 4 mm or more and not greater than 6 mm, and the ratio of the tapered length to the distance from the central axis of the shaft to the farthest end of the balloon when viewed in the axial direction after deflation with multiple wing portions formed circumferentially on the straight portion and the tapered portion is 2 or more and not greater than 4.

[0011] Here, the embodiment of the present invention can be configured as follows.

[0012] (2) In the balloon catheter of (1) above, the number of the blades is preferably four or more and six or less.

[0013] (3) In the balloon catheter of (1) above, it is preferable that the number of the blades is five.

[0014] (4) In the balloon catheter of (1) above, it is preferable that the number of the blades is odd.

[0015] (5) In the balloon catheter of (1) above, when the balloon has five wing portions and the taper length is 6 mm, it is preferable that the film thickness of the main body after blow molding is 33.0 μm or more and 35.0 μm or less.

[0016] (6) In the balloon catheter of any one of (1) to (5) above, the main body of the balloon preferably has a three-layer structure in which an inner layer, a middle layer, and an outer layer are laminated.

[0017] (7) In the balloon catheter of (6) above, the elongation at break of the intermediate layer is preferably lower than those of the inner layer and the outer layer.

[0018] (8) In the balloon catheter of (6) or (7) above, the elongation at break of the outer layer is preferably equal to or greater than the elongation at break of the inner layer.

[0019] (9) In the balloon catheter of (8) above, it is preferable that the elongation at break of the inner layer and the outer layer be equal.

[0020] (10) In any of the balloon catheters (6) to (9) above, it is preferable that the main body of the balloon has the inner layer formed of a nylon elastomer, the middle layer formed of nylon, and the outer layer formed of a nylon elastomer. [Effects of the Invention]

[0021] According to at least one embodiment of the present invention, it is possible to provide a balloon catheter that can achieve both improved retractability into a guiding catheter when the balloon is expanded in diameter and good expansion accuracy. [Brief explanation of the drawings]

[0022] [Figure 1] 1 is a schematic diagram of a balloon catheter according to an embodiment of the present invention. FIG. [Figure 2] FIG. 2 is a cross-sectional view of the vicinity of the tip of the balloon catheter according to the present embodiment. [Figure 3] FIG. 2 is a cross-sectional view perpendicular to the axis of the balloon according to the present embodiment. [Figure 4A] FIG. 1 is a schematic cross-sectional view of the balloon after deflation as viewed in the axial direction. [Figure 4B] FIG. 1 is a schematic cross-sectional view of the balloon after expansion in an axial view. [Figure 5] 10A and 10B are diagrams for explaining the taper length and the distance to the farthest end required when obtaining the taper sharpness. [Figure 6A] FIG. 10 is a schematic cross-sectional view showing a state in which there is no misalignment of the inner tube in a deflated balloon with an odd number of blades (five) as viewed in the axial direction. [Figure 6B]FIG. 10 is a schematic cross-sectional view showing the state in which the inner tube is misaligned in a deflated balloon with an odd number of blades (five) as viewed in the axial direction. [Figure 7A] FIG. 10 is a schematic cross-sectional view showing a state in which there is no misalignment of the inner tube in a deflated balloon with an even number (four) of blades as viewed in the axial direction. [Figure 7B] FIG. 10 is a schematic cross-sectional view showing a state in which the inner tube is misaligned in a deflated balloon with an even number (four) of blades as viewed in the axial direction. [Figure 8] 10 is a graph showing the measurement results measured by an outer diameter measuring device. [Figure 9] 10 is a graph showing the test results of Test 2. [Figure 10] 10 is a graph showing the results of outer diameter measurement when NP is expanded (dotted line) and when RBP is expanded (solid line) in an example in Test 3. [Figure 11] 10 is a graph showing the results of outer diameter measurement when NP is expanded (dotted line) and when RBP is expanded (solid line) in a comparative example in Test 3. [Figure 12] FIG. 10 is a diagram showing the configuration of the pull-in test device used in Tests 2 and 4. DETAILED DESCRIPTION OF THE INVENTION

[0023] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The embodiments shown here are merely examples for embodying the technical concept of the present invention and are not intended to limit the present invention. Furthermore, all other embodiments, 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 within the scope and spirit of the present invention, as well as within the scope of the claims and their equivalents.

[0024] Furthermore, for the convenience of illustration and ease of understanding, the drawings attached to this specification may be represented schematically with the scale, aspect ratio, shape, etc. appropriately changed from the actual product, but these are merely examples and do not limit the interpretation of the present invention.

[0025] Furthermore, in the following description, when ordinal numbers such as "first" and "second" are used, unless otherwise specified, they are used for convenience and do not stipulate any particular order.

[0026] [composition] First, the configuration of the balloon catheter 100 according to this embodiment will be described.

[0027] As shown in Figure 1 or Figure 2, the balloon catheter 100 is a medical device that expands a lesion, such as a stenosis formed in a biological lumen, by expanding a balloon 140 located at the tip of the shaft 110 at the lesion.

[0028] The balloon catheter 100 can be configured as a PTCA treatment balloon catheter used, for example, to widen a lesion in a coronary artery. However, the balloon catheter 100 can also be configured as a catheter used for the purpose of treating and improving lesions formed in other biological organs, such as other blood vessels, the bile duct, the trachea, the esophagus, other digestive tracts, the urethra, the ear and nose cavities, and other organs.

[0029] In the following description, the side where the balloon 140 is disposed is referred to as the "distal side" of the balloon catheter 100, the side where the hub 160 is disposed is referred to as the "proximal side" of the balloon catheter 100, and the direction in which the shaft 110 extends is referred to as the "axial direction." Furthermore, unless otherwise specified, the "distal portion" refers to a certain range including the distal end (the most distal end) and its surroundings, and the "proximal end" refers to a certain range including the proximal end (the most proximal end) and its surroundings.

[0030] The balloon catheter 100 is configured as a so-called "rapid exchange catheter device" in which a guidewire port 111 through which a guidewire G is led out is provided near the distal end of the shaft 110. The balloon catheter 100 can also be configured as a so-called "over-the-wire catheter device" in which a guidewire lumen 121 is formed to extend from the distal end to the proximal end of the shaft 110.

[0031] 1, the balloon catheter 100 can be provided with a hub 160 at the proximal end of the shaft 110. The hub 160 is configured to be connectable to a connector (Y connector) known in the medical field, and can be connected in a liquid-tight and air-tight manner via the connector to a supply device such as an indeflator for supplying a pressurized medium.

[0032] Figure 2 is a cross-sectional view of the balloon catheter 100 taken along the axial direction of the distal end periphery (the inflated balloon 140 and its surroundings). As shown in Figure 2, the shaft 110 has an inner tube 120 having a guidewire lumen 121 through which a guidewire G is inserted, and an outer tube 130 having a pressurized medium lumen 131 between the inner tube 120 and the outer tube 130, through which a pressurized medium can flow. The shaft 110 has a double-tube structure in which the inner tube 120 and the outer tube 130 are concentrically arranged by inserting the inner tube 120 into the outer tube 130.

[0033] The balloon 140 is liquid-tightly and airtightly joined to the distal end of the inner tube 120 by a known method such as welding. The distal end of the balloon 140 is joined to the inner tube 120, and the proximal end is joined to the outer tube 130.

[0034] A distal tip 170 can be attached to the distal end of the inner tube 120. The distal tip 170 prevents damage to a biological organ (such as the inner wall of a blood vessel) when the distal end of the balloon catheter 100 comes into contact with the biological organ. The distal tip 170 can be made of a resin material that is more flexible than the inner tube 120.

[0035] The inner tube 120 may be provided with a radiopaque marker section 180. The radiopaque marker section 180 may be disposed, for example, at a position on the inner tube 120 that indicates the boundary with the distal end side of the balloon 140, and at a position on the inner tube 120 that indicates the boundary with the proximal end side of the balloon 140.

[0036] Materials that can be used to form the inner tube 120 and the outer tube 130 include, for example, polyolefins such as polyethylene, polypropylene, ethylene-propylene copolymer, and ethylene-vinyl acetate copolymer, thermoplastic resins such as soft polyvinyl chloride, various rubbers such as silicone rubber and latex rubber, various elastomers such as polyurethane elastomer, polyamide elastomer, and polyester elastomer, and crystalline plastics such as polyamide, crystalline polyethylene, and crystalline polypropylene. These materials can also be blended with antithrombotic substances such as heparin, prostaglandin, urokinase, and arginine derivatives to create antithrombotic materials.

[0037] The balloon 140 is disposed on the distal end side of the shaft 110 (the distal end side of the inner tube 120), and has a space between it and the inner tube 120 into which a pressurized medium can flow. The balloon 140 expands when a pressurized medium flows into the space. When the balloon 140 expands, the balloon catheter 100 presses a portion of the balloon 140 against a lesion formed in a biological lumen, thereby expanding and widening the lesion.

[0038] 2, the balloon 140 has a straight portion 141 of constant diameter along the axial direction, a tapered portion 142 inclined from the straight portion 141 toward the distal end (or proximal end) of the balloon 140, and a connecting portion 143 joined to the inner tube 120 of the shaft 110. The tapered portion 142 is composed of a proximal tapered portion 142a that expands in diameter from the distal end of a proximal connecting portion 143a that is disposed on the proximal end side of the straight portion 141 and that joins with the inner tube 120 toward the distal end, and a distal tapered portion 142b that expands in diameter from the proximal end of a distal connecting portion 143b that is disposed on the distal end side of the straight portion 141 and that joins with the inner tube 120 toward the proximal end. The connecting portion 143 is composed of a base end connecting portion 143a that extends from the base end of the base end tapered portion 142a toward the base end and joins with the inner tube 120, and a tip end connecting portion 143b that extends from the tip end of the tip end tapered portion 142b toward the tip end and joins with the inner tube 120.

[0039] For example, an organic polymer material can be used as the material for forming the balloon 140. Specifically, polymer materials such as polyolefin (e.g., polyethylene, polypropylene, polybutene, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, ionomer, or a mixture of two or more of these), polyvinyl chloride, polyamides (e.g., nylons such as nylon 6, nylon 6·6, nylon 6·10, and nylon 12), polyamide elastomer, nylon elastomer, polyurethane, polyurethane elastomer, polyimide, and fluororesin, or a mixture of these, or an elastic resin such as two or more of the above polymer materials, can be used.

[0040] The balloon 140 has a multi-layer structure including at least an inner layer 140a and an outer layer 140c.

[0041] As shown in FIG. 3, the balloon 140 may have a three-layer structure including an inner layer 140a, a middle layer 140b, and an outer layer 140c. In the balloon 140 shown in FIG. 3, the inner layer 140a may be formed of a nylon elastomer, the middle layer 140b may be formed of nylon, and the outer layer 140c may be formed of a nylon elastomer. If the balloon 140 has a three-layer structure in which each layer is made of the above-mentioned materials, the balloon 140 can fully stretch in the axial direction before expanding circumferentially when inflated, thereby reducing the risk of lateral cracking (the risk of circumferential burst). Note that the material composition of each layer of the balloon 140 is not limited to the above-mentioned composition.

[0042] A pressurized medium (e.g., a fluid such as saline or contrast agent) used to inflate the balloon 140 can be flowed into the pressurized medium lumen 131 of the shaft 110 via the internal space (lumen) of the hub 160. The pressurized medium is supplied to the space of the balloon 140 via the pressurized medium lumen 131.

[0043] A coating can be formed on the outer surface of the balloon 140. The coating can be, for example, a hydrophilic coating layer that improves the sliding properties of the balloon 140, or a drug coating layer that contains a predetermined drug. There are no particular limitations on the specific materials that can be used to form the hydrophilic coating layer or drug coating layer.

[0044] The balloon 140 is manufactured by extrusion molding a tubular parison (original tube) made of the above-mentioned elastic resin, and this tubular parison is preformed by known stretch blow molding (for example, biaxial stretch blow molding). The preformed balloon 140 then undergoes a shaping process using a mold, forming a plurality of wings 150 that protrude radially from the inner tube 120 and fold around the outer circumference when deflated (see FIG. 4A). As a result, when the balloon is deflated after expansion, the wings 150 fold and reduce in diameter, thereby improving passability through blood vessels and guiding catheters.

[0045] FIG. 4A is an orthogonal cross-sectional view of the balloon 140 after deflation, and FIG. 4B is an orthogonal cross-sectional view of the balloon 140 after expansion. In FIG. 4A, one of the five blades 150 is hatched, and in FIG. 4B, the portion corresponding to the blade 150 hatched in FIG. 4A is hatched with similar dots. As shown in FIG. 4A, multiple blades 150 (five in the figure) are arranged at equal intervals around the circumference of the inner tube 120. As shown in FIG. 4B, when the balloon 140 is expanded, the blades 150 unfold from their folded shape to form part of the outer periphery of the balloon 140. Because the balloon 140 in FIG. 4A has five blades 150, each blade 150 in FIG. 4B has a length of approximately 1 / 5 of the entire circumference of the balloon.

[0046] The balloon 140 has an outer diameter when expanded (outer diameter when expanded at recommended expansion pressure (NP), hereinafter also referred to as "NP expanded outer diameter") that is greater than 4.0 mm and not greater than 6.0 mm, preferably not less than 5.0 mm and not greater than 6.0 mm, more preferably not less than 5.5 mm and not greater than 6.0 mm, and most preferably 6.0 mm.

[0047] The balloon catheter 100 of this embodiment is a catheter that can achieve both improved retractability and good expansion accuracy when the balloon 140 is expanded (for example, when the balloon outer diameter of a PTCA treatment balloon catheter is expanded from 4.00 mm to 6.00 mm during NP expansion).

[0048] In order to reduce the increase in retraction resistance that accompanies the expansion of the balloon 140, if the tapered length D1 of the tapered portion 142 of the balloon 140 is increased, the retraction resistance will be reduced, but there is a problem in that part of the tapered portion 142 will change into a straight portion 141, extending the effective length of the balloon 140 and reducing the expansion accuracy.

[0049] Therefore, the inventors of the present application conducted extensive research to solve the above-mentioned problems, and as a result, they found that when the "taper sharpness" of the balloon 140, a newly discovered parameter, falls within a certain range, it is possible to achieve both improved retractability into the guiding catheter when the balloon 140 is expanded in diameter and good expansion accuracy.

[0050] FIG. 5 is a diagram illustrating the taper length D1 and the farthest end distance D2 of the deflated balloon 140. As shown in FIG. 5, "taper sharpness" is a physical property calculated as the ratio (D1 / D2) of the taper length D1, which is the axial length of the tapered portion 142 of the deflated balloon 140, to the distance D2 from the central axis C of the shaft 110 to the farthest end of the balloon 140 when the deflated balloon 140 is viewed in the axial direction (hereinafter simply referred to as "farthest end distance D2"). The larger the taper sharpness value, the sharper the balloon 140. Note that the central axis C of the shaft 110 coincides with the central axes of the inner tube 120, the outer tube 130, and the balloon 140.

[0051] The condition for obtaining the farthest end distance D2, "a state in which the balloon 140 is deflated (deflation state)", is a state in which, after inflation at the recommended inflation pressure (NP), the pressurized medium is removed from inside the balloon 140 and negative pressure continues to be applied (the amount of pressurized medium is less than 0.005 g) and / or the indeflator is filled with 5±1 mL of pressurized medium (water), connected to the balloon 140 so that the contained gas is less than 0.1 mL, the indeflator maintains a specified pressure (e.g., maximum inflation pressure: RBP) for 10 seconds or more (e.g., 30 seconds), and then the indeflator is pulled to its maximum and deflated for 30 seconds or more (e.g., 30 seconds) to maintain the reduced pressure state.

[0052] The taper sharpness increases as the taper length D1 increases. The taper sharpness also changes depending on the number of wing portions 150 formed on the balloon 140, and the value increases as the number of wing portions 150 increases. In other words, the taper sharpness can be said to be a value that has a correlation between the taper length D1 of the tapered portion 142 and the number of wing portions 150.

[0053] The greater the taper sharpness, the sharper the balloon 140, which can suppress deformation of the distal tip when retracting the balloon 140 into the guiding catheter and improve the retractability of the balloon 140. However, if the taper length D1 of the balloon 140 is made too long in pursuit of a sharper taper, the expansion precision will decrease, and if the number of wings 150 is too large, new problems will arise, such as unstable shaping of the wings 150 or a lack of flexibility due to the large number of folds.

[0054] Taking these parameter characteristics into consideration, the inventors of the present application have determined an appropriate range for the taper sharpness of the balloon 140 of the balloon catheter 100. The taper sharpness is between 2 and 4, preferably between 2.12 and 3.82, more preferably between 2.55 and 3.82, and most preferably 3.18.

[0055] When the taper sharpness of the balloon 140 is set to 2 or more and 4 or less, the taper length D1 is preferably set to 4.0 mm or more and 6.0 mm or less, and the number of blades 150 is preferably set to 4 or more and 6 or less. When the taper sharpness of the balloon 140 is set to 2.12 or more and 3.82 or less, the number of blades 150 is preferably set to 5 or 6 when the taper length D1 is 4.0 mm, and 4 or more and 6 or less when the taper length D1 is 6.0 mm. When the taper sharpness of the balloon 140 is set to 2.55 or more and 3.82 or less, the number of blades 150 is preferably set to 6 when the taper length D1 is 4.0 mm, and 4 or more and 6 or less when the taper length D1 is 6.0 mm. When the balloon 140 has a taper sharpness of 3.18, the taper length D1 is preferably 6.0 mm and the number of the wing portions 150 is preferably five.

[0056] Here, if the taper sharpness is less than 2, the retraction load increases, resulting in high retraction resistance to the guiding catheter and poor passage through stenotic lesions. Furthermore, if the taper sharpness exceeds 4, the taper length D1 also increases, making it easier for the tapered portion 142 to change to the straight portion 141, reducing expansion accuracy. Furthermore, the length of the rigid balloon portion increases, reducing passage through bends in the blood vessel. If the taper length D1 of the balloon 140 is less than 4.0 mm, the expansion accuracy increases, but the retraction resistance increases, preventing the desired performance. Furthermore, if the taper length D1 of the balloon 140 exceeds 6.0 mm, the taper sharpness increases, potentially improving retraction, but the expansion accuracy decreases, preventing the desired performance. Furthermore, if the balloon 140 has seven or more blades 150, the radial length of the blades 150 becomes too short, making shaping unstable, and the increased number of blades 150 also increases the number of folds, reducing flexibility, making the balloon unsuitable as a product. Details regarding the sharpness of the taper of the balloon 140 will be described in the Examples.

[0057] It is preferable that the balloon 140 have an odd number of blades 150. Fig. 6A shows the deflated balloon 140 with five (odd number) blades 150 as viewed from the axial direction, and Fig. 6B shows the state in which the inner tube 120 in Fig. 6A is shifted 1 mm from its specified position. Fig. 7A shows the deflated balloon 140 with four (even number) blades 150 as viewed from the axial direction, and Fig. 7B shows the state in which the inner tube 120 in Fig. 7A is shifted 1 mm from its specified position.

[0058] As shown in Fig. 6A, when the number of blades 150 is odd and the farthest-end distance D2 is 2.3 mm, if the inner tube 120 shifts 1 mm toward the turned-back portion, which is the apex of the blades 150, as shown in Fig. 6B, the farthest-end distance D2 becomes 3.0 mm, and the shift amount becomes 0.7 mm. On the other hand, as shown in Fig. 7A, when the number of blades 150 is even and the farthest-end distance D2 is 2.0 mm, if the inner tube 120 shifts 1 mm toward the turned-back portion, which is the apex of the blades 150, as shown in Fig. 7B, the farthest-end distance D2 becomes 3.0 mm, and the shift amount becomes 1.0 mm. In this way, if the balloon 140 has an odd number of blades 150, the influence of the shift can be reduced even if the inner tube 120 shifts during deflation, for example.

[0059] 8 is a graph showing the results of outer diameter measurement using an outer diameter measuring device that has an LED light source or laser light source as a measuring means and measures the outer diameter from the length of the deflated balloon 140 that blocks the light source. Each line in the graph represents the degree of inclination of the outer peripheral surface of balloon 140 from the tip of tip connecting portion 143b to straight portion 141 via tip tapered portion 142b.

[0060] When the number of blades 150 in balloon 140 is increased from three to five, the distance D2 to the farthest end of the balloon 140 is theoretically 3 / 5. However, as shown in Figure 8, when a sample with three blades 150 is compared to a sample with five blades 150, the outer diameter is smaller but does not reach 3 / 5. This is thought to be due to factors such as the size of inner tube 120, wrinkles in balloon 140, bending of blades 150 due to shaping, and deformation of blades 150 during contraction.

[0061] As a result of extensive research into methods for suppressing deformation that can occur as the number of blades 150 increases, the inventors of the present application discovered that deformation that can occur as the number of blades 150 increases can be suppressed when the film thickness of the balloon 140 is within a specific range.

[0062] When balloon 140 has five blade portions 150 and a taper length D1 of 6 mm, the film thickness of the main body of balloon 140 after blow molding is 33.0 μm or more and 35.0 μm or less, preferably 33.9 μm or more and 34.8 μm or less, and most preferably 33.9 μm.

[0063] For a balloon 140 having five blade portions 150 and a taper length D1 of 6 mm, if the film thickness after blow molding is within the above range, deformation during contraction can be effectively prevented, and the reduced diameter portion during contraction does not become large, thereby keeping retraction resistance low.

[0064] Here, when the thickness of the balloon 140 with five blades 150 and a taper length D1 of 6.0 mm exceeds 35.0 μm, the retraction resistance increases due to the thick film thickness. On the other hand, when the thickness of the balloon 140 falls below 33.0 μm, the retraction resistance decreases, but the shape easily collapses when repeatedly expanding and contracting, making it unusable.

[0065] The balloon 140 has, at least outside the inner layer 140a, a layer whose elongation at break is lower than that of the inner layer 140a. In the balloon 140, the outer layer 140c has a higher elongation at break than the middle layer 140b (middle layer < outer layer), and the inner layer 140a has a higher elongation at break than the middle layer 140b (inner layer > middle layer). That is, the elongation at break of the middle layer 140b is lower than that of the inner layer 140a and the outer layer 140c. In addition, the elongation at break of the inner layer 140a and the outer layer 140c may be equal to each other, or the outer layer 140c may have a higher elongation at break. Furthermore, since the balloon 140 only needs to have a layer outside the inner layer 140a that has a lower elongation rate at break than the inner layer 140a, it can be configured to include a layer that has a lower elongation rate at break than the inner layer 140a, for example, between the inner layer 140a and the intermediate layer 140b, between the intermediate layer 140b and the outer layer 140c, or further outside the outer layer 140c.

[0066] [Action and effect] As described above, the balloon catheter 100 according to this embodiment includes a long shaft 110 and a balloon 140 disposed at the distal end of the shaft 110 and having an expandable and contractible membrane-like main body. The balloon 140 has a straight portion 141 of constant diameter along the axial direction and a tapered portion 142 that slopes from the straight portion 141 toward the connection with the shaft 110. The outer diameter of the straight portion 141 when expanded is greater than 4 mm and not greater than 6 mm, the tapered portion 142 has a taper length D1 that is the axial length of the tapered portion 142 that is not less than 4 mm and not greater than 6 mm, and the ratio of the taper length D1 to the distance D2 from the central axis C of the shaft 110 to the distal end of the balloon 140 (distant end distance D2) D2 when the balloon 140 is deflated with multiple wing portions 150 formed circumferentially on the straight portion 141 and the tapered portion 142 is not less than 2 and not greater than 4.

[0067] As a result, the balloon 140 has a moderately sharp taper that improves retractability even when the diameter is expanded, while maintaining sufficient expansion accuracy. Therefore, even when applied to a balloon catheter for PTCA treatment and the outer diameter during NP expansion is expanded from 4.0 mm to 6.0 mm, good expansion accuracy is ensured and retraction resistance to the guiding catheter is reduced, allowing for smooth procedure.

[0068] Furthermore, in the balloon catheter 100 according to this embodiment, the number of wing portions 150 is preferably four or more and six or less, and more preferably five.

[0069] Therefore, by having four to six, and more preferably five, wing portions 150, the taper sharpness approaches the optimum value, thereby providing a balloon catheter 100 with better retractability and expandability.

[0070] Furthermore, the balloon catheter 100 according to this embodiment may have an odd number of wings 150.

[0071] As a result, even if the inner tube 120 is displaced when the balloon is deflated, the influence of the displacement can be reduced by providing an odd number of blade portions 150.

[0072] Furthermore, in the balloon catheter 100 according to this embodiment, when the balloon 140 has five blade portions 150 and a taper length D1 of 6 mm, the film thickness of the main body after blow molding can be configured to be 33.0 μm or more and 35.0 μm or less.

[0073] This prevents the balloon 140 from losing its shape when deflated, and further improvements in retractability and expansion accuracy are expected.

[0074] In the balloon catheter 100 according to this embodiment, the main body of the balloon 140 may have a three-layer structure in which an inner layer 140a, a middle layer 140b, and an outer layer 140c are laminated in this order. The elongation at break of the middle layer 140b may be lower than that of the inner layer 140a and the outer layer 140c, or the elongation at break of the outer layer 140c may be equal to or greater than that of the inner layer 140a, or the elongation at break of the inner layer 140a and the outer layer 140c may be equal to each other.

[0075] By providing the balloon 140 with a three-layer structure, the balloon 140 can fully stretch in the axial direction before expanding in the circumferential direction when expanded, thereby reducing the risk of lateral cracking.

[0076] In addition, in the balloon catheter 100 according to this embodiment, the main body of the balloon 140 can be configured such that the inner layer 140a is formed from a nylon elastomer, the middle layer 140b is formed from nylon, and the outer layer 140c is formed from a nylon elastomer.

[0077] This allows the balloon 140 to fully stretch in the axial direction before expanding in the circumferential direction, resulting in a balloon catheter 100 with a reduced risk of lateral cracking. [Example]

[0078] The present invention will be described in more detail below with reference to examples, but the scope of the present invention is not limited to the following examples.

[0079] [Test 1. Taper sharpness measurement test] The taper sharpness measurement test was carried out as follows.

[0080] <1-1. Sample Production> The number of samples to be measured for taper sharpness was 20 in total, including four patterns of taper length D1: 3.0 mm, 4.0 mm, 6.0 mm, and 10.0 mm, and five patterns of the number of blades: 3, 4, 5, 6, and 7.

[0081] Each sample was produced by extrusion molding a three-layer tubular parison: an inner layer (inner diameter: 0.80 mm) made of nylon elastomer (product name: Grilflex ELG6260, manufactured by EMS), a middle layer (inner diameter: 1.07 mm, outer diameter: 1.55 mm) made of nylon (product name: Grilamid L25, manufactured by EMS), and an outer layer (outer diameter: 1.72 mm) made of nylon elastomer (product name: Grilflex ELG6260, manufactured by EMS). This tubular parison was placed in a mold and blow-molded (mold temperature: 115°C, heating time: 30 seconds, pressure: 3.0 MPa) to form the desired number of blades. A sample with an expanded NP outer diameter of 6.0 mm was produced. The blades were shaped using a mold molded according to the number of blades. The elongation at break of each sample was in the following relationship: inner layer > intermediate layer, intermediate layer < outer layer, inner layer = outer layer.

[0082] 1-2. Test Method As shown in Figure 5, the taper sharpness of each sample was a physical property calculated as the ratio (D1 / D2) of the taper length D1, which is the axial length of the tapered portion 142, to the distance D2 (farthest end distance D2) from the central axis C of the shaft 110 to the farthest end of the balloon 140 when the deflated balloon 140 is viewed in the axial direction. To determine the taper sharpness, the taper length D1 of each sample was measured using a digital microscope (product name: VHX-5000, manufactured by Keyence Corporation). The distance D2 from the central axis of each sample to the farthest end of the balloon was measured using a laser dimension measuring device (product name: LS-5040R, manufactured by Keyence Corporation).

[0083] The balloon's contracted state (deflation state) when obtaining the farthest end distance D2 was determined as follows: each sample was inflated at the recommended inflation pressure (NP) using an indeflator (product name: Demax Indeflator 20 ml, 30 atm, manufactured by Kaneka Corporation), and then the pressurized medium was removed from each sample and negative pressure was continued to be applied (the amount of pressurized medium was less than 0.005 g); and / or each sample was filled with 5 ± 1 mL of pressurized medium (water), and the indeflator was connected to each sample so that the contained gas was less than 0.1 mL. The specified pressure (maximum inflation pressure: RBP) was maintained with the indeflator for 10 seconds, and then the indeflator was pulled to its maximum and deflated for 30 seconds, maintaining the reduced pressure.

[0084] The measurement results are shown in Table 1 below. Each sample was evaluated based on the retractability and expansion accuracy, with samples that had a taper sharpness of 2 or more and 4 or less being considered good products (samples in bold and surrounded by a double line in the table), and samples that fell outside this range were considered defective.

[0085] [Table 1]

[0086] <1-3.Results> As shown in Table 1, good samples with a taper sharpness of 2 to 4 had five or six blades when the taper length D1 was 4.0 mm, and four to six when the taper length D1 was 6.0 mm. Among the good samples, samples with a taper sharpness of 2.55 to 3.82 (six blades when the taper length D1 was 4.0 mm, and four to six when the taper length D1 was 6.0 mm) were confirmed to have higher retractability and expansion accuracy than the other samples. Among the good samples, the sample with a taper sharpness of 3.18 had a taper length D1 of 6.0 mm and five blades, and was confirmed to have the highest retractability and expansion accuracy (bold and underlined in the table).

[0087] On the other hand, for samples with a taper length D1 of less than 4.0 mm, the shorter taper length improved dilation accuracy, but the taper sharpness was low, resulting in increased retraction resistance. Furthermore, samples with a taper length D1 of more than 6.0 mm generally had a high taper sharpness of 4 or higher, which is expected to improve retraction performance, but increasing the taper length D1 to 10 mm reduced dilation accuracy. Furthermore, for samples with seven blades, regardless of the taper length D1, the radial length of the blades was too short, making shaping unstable. Increasing the number of blades increased the number of folds, reducing flexibility, making them unsuitable for use as a product. From the above, it was found that samples with a taper sharpness of less than 2 had a high retraction load, resulting in high retraction resistance to the guiding catheter and poor passability through stenotic lesions, making them unsuitable for use as a product. Furthermore, when the taper sharpness exceeds 4, the taper length D1 also becomes longer, which makes it easier for the tapered section to change to a straight section, reducing the expansion accuracy, and the length of the hard balloon portion becomes longer, which makes it less able to pass through the bends in the blood vessel, making it unsuitable as a product.

[0088] [Test 2. Pull-in load test] The pull load test was carried out as follows.

[0089] <2-1. Sample Production> Example A1 In Example A1, the sample produced in Test 1 (taper length D1: 6.0 mm, number of blades: 5, taper sharpness: 3.18) was used. Example A2 In Example A2, the sample produced in Test 1 (taper length D1: 6.0 mm, number of blades: 4, taper sharpness: 2.55) was used. Comparative Example A1 In Comparative Example A1, the sample produced in Test 1 (taper length D1: 6.0 mm, number of blade portions: 3, taper sharpness: 1.91) was used.

[0090] <2-2. Test Method> The measurement of the pull load was carried out using a pull test device 300 shown in FIG.

[0091] As shown in FIG. 12 , the retraction test device 300 connects a transparent tube 310 with an inner diameter of 6.5 mm to a transparent resin tube 320 with an inner diameter of 6.5 mm via a tubular connecting member 330, and a Y connector 340 is connected to the proximal end of the transparent resin tube 320. A guiding catheter 200 is inserted into the lumen of the transparent resin tube 320 via the Y connector 340. The guiding catheter 200 is inserted into the transparent resin tube 320 via the Y connector 340 until its distal end reaches the interior of the transparent tube 310. A first conduit 351 of a three-way stopcock 350 is connected to the proximal end of the shaft 110 of the balloon catheter 100. A second conduit 352 of the three-way stopcock 350 is connected to an indeflator 360 for supplying a pressurized medium to the balloon 140. The third conduit 353 of the three-way stopcock 350 is connected to a push-pull gauge 380 that is movably mounted on a linear slider 370 that extends along the axial direction of the balloon catheter 100 .

[0092] 12, the longitudinal directions of the transparent tube 310, transparent resin tube 320, Y connector 340, three-way stopcock 350, and guiding catheter 200 that make up the pull-in test device 300 are arranged so as to coincide with the central axis C of the balloon catheter 100. In addition, when the balloon catheter 100 is pulled, the push-pull gauge 380 moves on a linear slider 370 so that the pulling direction does not deviate from the axial direction of the balloon catheter 100.

[0093] The procedure for measuring the pull load is as follows: Step 1 A pull-in test device 300 shown in FIG. 12 was prepared. Step 2 The transparent tube 310 and the guiding catheter 200 (product name: Mach1 6Fr.JR4.0, inner diameter: 1.79 mm, manufactured by Boston Scientific) were filled with water. Step 3 The guiding catheter 200 with the balloon catheter 100 inserted therein was inserted from the Y connector 340 into the transparent resin tube 320 until the tip reached the inside of the transparent tube 310. With the balloon 140 protruding from the tip of the guiding catheter 200, the indeflator 360 connected to the three-way stopcock 350 was used to apply a maximum inflation pressure (18 atm) to the balloon 140 for 30 seconds. Step 4 Next, the indeflator 360 was pulled to its maximum to deflate the balloon 140 for 30 seconds, and the three-way stopcock 350 was operated to maintain the balloon 140 at negative pressure. Step 5 The indeflator 360 was removed, and the third pipe 353 of the three-way stopcock 350 was connected to the hub of the push-pull gauge 380. Step 6 The push-pull gauge 380 was moved toward the proximal end of the balloon catheter 100 at a constant speed (600 mm / s), and the retraction load (N) when the balloon 140 was retracted into the guiding catheter 200 was measured four times. In order to prevent damage to the guiding catheter 200 and the retraction test device 300, the test was terminated when the retraction load exceeded 8N.

[0094] <2-3.Results> Figure 9 is a graph showing the measurement results of the retraction load. As shown in Figure 9, Example A1 had a retraction load of 1.30 N. Example A2 had a retraction load of 1.69 N. On the other hand, Comparative Example A1 had a retraction load of 4.13 N. Both Example A1 and Example A2 had a taper sharpness of 2 or more, but Comparative Example A1 had a taper sharpness of 2 or less. This confirmed that when the balloon taper sharpness is 2 or more, the retraction load decreases, and when it is 2 or less, the retraction load increases.

[0095] [Test 3. Balloon stretch test] The balloon stretch test was performed as follows.

[0096] <3-1. Sample Production> Example B1 Example B1 was produced by extrusion molding a three-layer tubular parison, with an inner layer (inner diameter: 0.80 mm) made of nylon elastomer (product name: Grilflex ELG6260, manufactured by EMS), a middle layer (inner diameter: 1.07 mm, outer diameter: 1.55 mm) made of nylon (product name: Grilamid L25, manufactured by EMS), and an outer layer (outer diameter: 1.72 mm) made of nylon elastomer (product name: Grilflex ELG6260, manufactured by EMS). This tubular parison was placed in a mold and blow-molded (mold temperature: 115°C, heating time: 30 seconds, pressure: 3.0 MPa) to form five blades, resulting in a sample with an NP expanded outer diameter of 6.0 mm and a taper length of 6.0 mm. Comparative Example B1 Comparative Example B1 was NC EMERGE (model: H7493926715600, NP outer diameter when expanded: 6.0 mm, taper length: 10.0 mm) manufactured by Boston Scientific.

[0097] <3-2. Test Method> The procedure for the balloon stretch test is as follows: Step 1 A balloon catheter was made by joining the balloon of each sample to a shaft, and an indeflator (product name: Demax Indeflator 20 ml, 30 atm, manufactured by Kaneka Corporation) was connected to the hub on the proximal end. Each sample was pressurized at the recommended inflation pressure (NP) for 30 seconds, and the pressurized state of each sample was maintained. Step 2 The outer diameter of each sample during NP expansion was measured using a laser dimension measuring device (product name: LS-5040R, manufactured by Keyence Corporation). Step 3 Using the indeflator, each sample was pressurized at maximum expansive pressure (RBP) for 30 seconds and maintained in the pressurized state. Step 4 The outer diameter of each sample during RBP expansion was measured using the above-mentioned outer diameter measuring device.

[0098] <3-3.Results> Figure 10 is a graph showing the results of outer diameter measurements during NP expansion (dotted line) and RBP expansion (solid line) in Example B1. Figure 11 is a graph showing the results of outer diameter measurements during NP expansion (dotted line) and RBP expansion (solid line) in Comparative Example B1. The length of the straight section was determined by first calculating the average outer diameter of a continuous region where the axial difference in the balloon outer diameter was sufficiently small (here, measurements were taken at 0.1 mm intervals in the axial direction, with the outer diameter difference between intervals being -0.005 to 0.005 mm) and where the outer diameter was 2 mm or greater, based on the measurement results during NP expansion. The axial length was then determined as the length of a continuous region that exceeded a value 0.1 mm smaller than the calculated outer diameter.

[0099] As shown in Figure 10, the length of the straight portion of Example B1 was 12.9 mm when the NP was expanded and 15.4 mm when the RBP was expanded, resulting in an elongation rate of 19.3%. On the other hand, as shown in Figure 11, the length of the straight portion of Comparative Example B1 was 11.5 mm when the NP was expanded and 15.8 mm when the RBP was expanded, resulting in an elongation rate of 38.5%. Since the taper length of the Example was 6.0 mm and the taper length of the Comparative Example was 10.0 mm, it was confirmed that shortening the taper length made it difficult for the tapered portion to change to a straight portion during expansion. This confirmed that the balloon of Example B1 had a higher expansion accuracy because the tapered portion was less likely to change to a straight portion compared to the balloon of Comparative Example B1.

[0100] [Test 4. Film Thickness Evaluation Test] The film thickness evaluation test was carried out as follows.

[0101] <4-1. Sample Production> Example C1 Example C1 was produced by injection molding a three-layer tubular parison with an inner layer (inner diameter 0.86 mm) made of nylon elastomer (product name: Grilflex ELG6260, manufactured by EMS), a middle layer (inner diameter 1.07 mm, outer diameter 1.55 mm) made of nylon (product name: Grilamid L25, manufactured by EMS), and an outer layer (outer diameter 1.72 mm) made of nylon elastomer (product name: Grilflex ELG6260, manufactured by EMS). This tubular parison was placed in a mold and blow-molded (mold temperature: 115°C, heating time: 30 seconds, pressure: 3.0 MPa) to form five blades, resulting in a sample with an NP outer diameter of 6.0 mm when expanded. Example C2 Example C2 was the same as Example B1 prepared in Test 3. Comparative Example C1 Comparative Example C1 was prepared by injection molding a three-layer tubular parison with an inner layer (inner diameter 0.86 mm) made of nylon elastomer (product name: Grilflex ELG6260, manufactured by EMS), a middle layer (inner diameter 1.07 mm, outer diameter 1.63 mm) made of nylon (product name: Grilamid L25, manufactured by EMS), and an outer layer (outer diameter 1.84 mm) made of nylon elastomer (product name: Grilflex ELG6260, manufactured by EMS). This tubular parison was placed in a mold and blow-molded (mold temperature: 115°C, heating time: 30 seconds, pressure: 3.0 MPa) to form five wing portions, resulting in a sample with an NP outer diameter of 6.0 mm when expanded. Comparative Example C2 Comparative Example C2 was prepared by injection molding a three-layer tubular parison with an inner layer (inner diameter 0.80 mm) made of nylon elastomer (product name: Grilflex ELG6260, manufactured by EMS), a middle layer (inner diameter 1.07 mm, outer diameter 1.55 mm) made of nylon (product name: Grilamid L25, manufactured by EMS), and an outer layer (outer diameter 1.67 mm) made of nylon elastomer (product name: Grilflex ELG6260, manufactured by EMS). This tubular parison was placed in a mold and blow-molded (mold temperature: 115°C, heating time: 30 seconds, pressure: 3.0 MPa) to form five wing sections, resulting in a sample with an NP outer diameter of 6.0 mm when expanded. Comparative Example C3 Comparative Example C3 was NC EMERGE (model name: H7493926715600, NP outer diameter when expanded: 6.0 mm, taper length: 10.0 mm) manufactured by Boston Scientific, and was used as a reference product for obtaining a reference value of the retraction load (N).

[0102] <4-2. Test Method> The retraction load test was carried out in the same manner as the retraction load test carried out in Test 2. The retraction load test was carried out three times, and the retraction loads of each sample were measured three times.

[0103] The measurement results and evaluation results are shown in Table 2 below. The "average retraction load (N)" in the table is the average value of the retraction load values ​​obtained by repeating the retraction load test three times. The "maximum retraction load (N)" is the maximum retraction load value obtained when the retraction load test was performed three times.

[0104] [Table 2]

[0105] <4-3.Results> As shown in Table 2, Example C1 had an average retraction load of 1.56 N and a maximum retraction load of 1.74 N, and Example C2 had an average retraction load of 1.85 N and a maximum retraction load of 1.98 N. Since the retraction resistance load of Comparative Example 3, which serves as the reference value, was 1.98 N, Example C1 had a retraction load equal to or less than Comparative Example C3, and Example C2 had a retraction load at least equal to or less than Comparative Example C3, confirming that the retraction resistance was reduced compared to the reference product, resulting in a product with excellent operability.

[0106] On the other hand, Comparative Example C1 had an average retraction load of 2.14 N and a maximum retraction load of 2.25 N, which were higher than the retraction load of Comparative Example 3. Comparative Example C1 had a film thickness after molding of 37.8 μm, which was thicker than Examples C1 and C2, and it is presumed that this resulted in a larger outer diameter of the reduced diameter portion after shrinkage, resulting in a higher retraction load. Comparative Example C2 had an average retraction load of 1.89 N and a maximum retraction load of 2.27 N, which were higher than the retraction load of Comparative Example 3. Comparative Example C2 had a film thickness after molding of 31.3 μm, which was thinner than Examples C1 and C2, and therefore was more susceptible to deformation after shrinkage. Repeated expansion and contraction operations presumably caused the shape of the reduced diameter portion to collapse, increasing the diameter of the reduced diameter portion and resulting in a higher retraction load.

[0107] As described above, it was found that for a balloon with a taper length D1 of 6.0 mm and five blades, if the membrane thickness is set to 33.0 μm or more and 35.0 μm or less, preferably 33.9 μm or more and 34.8 μm or less, it is possible to achieve both improved retractability and expansion accuracy even when the balloon diameter is expanded. [Explanation of symbols]

[0108] 100 balloon catheters, 110 shaft, 120 inner tube, 130 outer tube, 140 balloon (140a inner layer, 140b middle layer, 140c outer layer), 141 straight section, 142 tapered portion (142a base end tapered portion, 142b tip end tapered portion) 143 connection portion (143a base end connection portion, 143b tip end connection portion), 150 blade section, 160 hub, 200 guiding catheter, 300 Pull-in test equipment, C center axis, G Guidewire.

Claims

1. A long shaft and a balloon disposed at a distal end of the shaft and having an expandable and contractible membrane-like body, The balloon is a straight portion having the same diameter along the axial direction and a tapered portion inclined from the straight portion toward a connection portion with the shaft, The straight portion has an expanded outer diameter of more than 4 mm and not more than 6 mm, The tapered portion has an axial length of 4 mm or more and 6 mm or less, a balloon catheter in which the ratio of the taper length to the distance from the central axis of the shaft to the farthest end of the balloon when the balloon is deflated with multiple wing portions formed circumferentially on the straight portion and the tapered portion, as viewed in the axial direction, is 2 or more and 4 or less.

2. The balloon catheter according to claim 1 , wherein the number of the wings is between four and six.

3. The balloon catheter according to claim 1 , wherein the number of the wings is five.

4. The balloon catheter of claim 1 , wherein the number of wings is odd.

5. 2. The balloon catheter according to claim 1, wherein when the balloon has five wing portions and the taper length is 6 mm, the film thickness of the main body after blow molding is 33.0 μm or more and 35.0 μm or less.

6. 6. The balloon catheter according to claim 1, wherein the main body of the balloon has a three-layer structure in which an inner layer, a middle layer, and an outer layer are laminated.

7. The balloon catheter of claim 6, wherein the intermediate layer has a lower elongation at break than the inner layer and the outer layer.

8. 7. The balloon catheter according to claim 6, wherein the elongation at break of the outer layer is equal to or greater than the elongation at break of the inner layer.

9. The balloon catheter of claim 8 , wherein the inner layer and the outer layer have equivalent elongation at break.

10. 7. The balloon catheter according to claim 6, wherein the balloon body has the inner layer formed of a nylon elastomer, the intermediate layer formed of nylon, and the outer layer formed of a nylon elastomer.

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