Method for manufacturing stent delivery system

Abstract

To provide a stent delivery system achieving improvement of retention of a balloon catheter to which a stent is crimped.SOLUTION: The method for manufacturing a stent delivery system 200 includes: a first diameter reduction process for compressing a stent 2 inwards in a radial direction of the stent 2, with a balloon 1 inserted into a cylinder of the cylindrically formed stent 2, reducing the diameters of the stent 2 and the balloon 1 and then releasing the compression; a second diameter reduction process for compressing the stent 2 inwards in the radial direction of the stent 2 to reduce the diameters of the stent 2 and the balloon 1 and then releasing the compression, after the first diameter reduction process; and a pressurizing process for inflating the balloon 1 by supplying a liquid to the balloon 1 and pressing the balloon 1 to the inside of the stent 2.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a method of manufacturing a stent delivery system. [Background technology]

[0002] Patent Document 1 discloses a method for manufacturing a stent delivery system in which a stent is crimped onto a balloon catheter. In this method, a prepared stent is pre-shrunk to a second diameter, which has an inner diameter equal to or smaller than the outer diameter of the folded balloon, and a folded balloon is inserted into the stent. Further, pressure is applied radially inward from the outer surface of the stent to shrink the stent to a third diameter, which is the diameter at which crimping is completed. This method is said to be capable of manufacturing a stent delivery system that can prevent the stent from falling off or moving. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Publication 2012-070912 Summary of the Invention [Problem to be solved by the invention]

[0004] In a stent delivery system, if the retention force of a stent crimped onto the balloon of a balloon catheter, i.e., retention, is weak, the stent may fall off the balloon. However, conventional techniques such as those disclosed in Patent Document 1 have not always been able to achieve sufficient retention. Therefore, there is a need for an improved retention force for a stent on a balloon in a balloon catheter, i.e., improved retention.

[0005] The present disclosure has been made in consideration of the above circumstances, and its purpose is to provide a manufacturing method for a stent delivery system that improves the retention of a balloon catheter onto which a stent is crimped. [Means for solving the problem]

[0006] In order to achieve the above object, the manufacturing method of the stent delivery system according to the present disclosure is as follows.

[0007] [1] A first diameter reduction step of compressing the stent radially inward to reduce the diameters of the stent and the balloon in a state in which a balloon is inserted into a tubular stent formed in a cylindrical shape, and then releasing the compression; a second diameter reduction step, which is performed after the first diameter reduction step, in which the stent is compressed inward in the radial direction of the stent to reduce the diameters of the stent and the balloon, and then the compression is released; a pressurizing step of supplying a fluid to the balloon to inflate it and press the balloon against the inside of the stent.

[0008] [2] The first diameter reduction step a first compression step of compressing the stent radially inward to reduce the stent to a first diameter; a first maintaining step of maintaining the stent at the first diameter; a first releasing step of releasing the compression after the first maintaining step, The second diameter reduction step is repeated two or more times, The pressurizing step includes: a pre-pressurizing step carried out before the start of the first diameter reduction step; a medium pressure step carried out during the first compression step; A method for manufacturing the stent delivery system described in [1] above, which includes a post-pressurizing step performed during the first maintaining step.

[0009] [3] A method for manufacturing a stent delivery system according to [2] above, wherein the pressurizing step is continued from before the start of the first compressing step until the first maintaining step is completed.

[0010] [4] The second diameter reduction step is repeated two or more times, The method for manufacturing a stent delivery system according to any one of [1] to [3] above, wherein the pressurizing step is carried out during the second diameter reduction step from the second time onwards.

[0011] [5] The second diameter reduction step a second compression step of compressing the stent radially inward to reduce the stent to a second diameter; a second maintaining step of maintaining the stent at the second diameter; a second releasing step of releasing the compression after the second maintaining step, The method for manufacturing a stent delivery system according to [4] above, wherein the pressurizing step includes a post-pressurizing step carried out during the second maintaining step.

[0012] [6] A method for manufacturing a stent delivery system according to the above [5], wherein the second diameter reduction step in which the pressurizing step is performed is followed by the second diameter reduction step in which the pressurizing step is not performed. [Effects of the Invention]

[0013] According to the present disclosure, it is possible to provide a method for manufacturing a stent delivery system that improves retention of a balloon catheter onto which a stent is crimped. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is an explanatory diagram of a stent delivery system. [Figure 2] FIG. 2 is a cross-sectional view taken along the line II-II in FIG. [Figure 3] 1 is a cross-sectional view of a balloon, a stent, a portion of a shaft supporting the balloon, and the surrounding area. [Figure 4] FIG. 1 is a development view of a stent. [Figure 5] 1 is an explanatory diagram of the state of the balloon, stent, and crimp head before the stent is reduced in diameter during the crimping operation. FIG. [Figure 6] 10 is an explanatory diagram of the state of the balloon, stent, and crimp head after the stent has been reduced in diameter during the crimping operation. FIG. [Figure 7] 1 is a graph showing a method for manufacturing a stent delivery system in terms of the relationship between the opening diameter of the crimp head and the elapsed time of the process. [Figure 8] FIG. 1 is a cross-sectional view of another stent delivery system. DETAILED DESCRIPTION OF THE INVENTION

[0015] A method for manufacturing a stent delivery system according to an embodiment of the present disclosure will be described with reference to the drawings.

[0016] FIG. 1 shows a stent delivery system 200 realized by the method for manufacturing a stent delivery system according to this embodiment.

[0017] Figure 2 shows a cross-sectional view taken along the line II-II in Figure 1. First, an outline of the stent delivery system 200 and its manufacturing method will be described.

[0018] As shown in FIG. 1, the stent delivery system 200 comprises a balloon catheter 100 having a balloon 1 that is inflated or deflated by supplying or discharging a fluid, and a stent 2 that is placed on the balloon 1 and formed into a cylindrical shape.

[0019] As shown in Figure 2, the stent 2 has a balloon 1 inserted into its cylinder, and is fixed onto the outer circumferential surface of the balloon 1. In other words, the stent 2 is crimped onto the balloon 1. In Figures 1 and 2, the balloon 1 is in a deflated state.

[0020] The stent delivery system 200 can be manufactured by a method for manufacturing a stent delivery system that includes a diameter reduction process in which, with a balloon 1 inserted inside a tubular stent 2 formed in a cylindrical shape, the stent 2 is compressed radially inward to reduce the diameter of the stent 2 and the balloon 1, and then the compression is released.

[0021] The stent delivery system and its manufacturing method will be described in detail below.

[0022] A stent delivery system 200 having a balloon catheter 100 shown in FIG. 1 is a medical device used in a procedure (e.g., PCI) to open a lesion (stenosis) formed in a biological lumen such as a blood vessel. In a procedure using the stent delivery system 200, an operator inserts a stent 2 crimped onto a balloon 1 disposed at the distal end of a shaft 5 into the biological lumen. The operator expands the balloon 1 on the inner periphery of a stenosis formed in the biological lumen, expanding the stent 2 together with the balloon 1. The operator places the expanded stent 2 on the inner periphery of the stenosis, thereby keeping the stenosis open.

[0023] The balloon catheter 100 is used to deliver the stent 2 to the narrowed area, but it can also be configured to be used for the purpose of treating and improving narrowed areas formed in biological organs such as blood vessels, bile ducts, tracheas, esophagus, other digestive tracts, urethras, ear and nose cavities, and other organs.

[0024] As shown in Figures 1 to 3, the balloon catheter 100 has a flexible, long shaft 5, a balloon 1 disposed at the distal end of the shaft 5, and a hub 8 (see Figure 1) disposed at the proximal end of the shaft 5. In a stent delivery system 200 (see Figure 1), a stent 2 is crimped onto the balloon 1 of the balloon catheter 100. Note that Figure 3 is a cross-sectional view taken along the arrows III-III in Figure 1, showing the balloon 1 in an expanded state, the stent 2, the portion of the shaft 5 supporting the balloon 1, and their surroundings. Figure 3 shows a cross-section overlapping the axial center of the shaft 5.

[0025] The balloon catheter 100 may be provided with a guidewire port 51 near the distal end of the shaft 5, through which a guidewire or the like can be led out.

[0026] 3, the shaft 5 has an inner tube 7 formed with a lumen 71 through which a guidewire or the like is inserted, and an outer tube 6 forming a lumen 61 between the inner tube 7 and the outer tube 6, through which a pressurized medium (e.g., a fluid such as physiological saline or a contrast agent) can flow. By inserting the inner tube 7 into the outer tube 6, the shaft 5 has a double-tube structure in which the inner tube 7 and the outer tube 6 are concentrically arranged.

[0027] The shaft 5 supports the balloon 1. The inner tube 7 of the shaft 5 passes through the balloon 1. The shaft 5 supplies the above-mentioned fluid to the space inside the balloon 1 or discharges the fluid from the balloon 1, thereby inflating or deflating the balloon 1.

[0028] The balloon 1 is liquid-tightly and air-tightly joined to the tip of the inner tube 7 by welding or the like. The tip of the balloon 1 in the extension direction of the shaft 5 is joined to the inner tube 7 by fusion or the like. The base of the balloon 1 in the extension direction of the shaft 5 is liquid-tightly and air-tightly joined to the outer tube 6 by fusion or the like. In FIG. 3, the part of the balloon 1 where the tip of the balloon 1 and the inner tube 7 are joined is shown as a tip-side joint 17. The part of the balloon 1 where the base of the balloon 1 and the outer tube 6 are joined is shown as a base-side joint 16. The diameter D of the base-side joint 16 is larger than the diameter (outer diameter) of the tip-side joint 17.

[0029] A distal tip 79 can be attached to the distal end of the inner tube 7. This tip 79 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 79 can be made of a resin material that is more flexible than the inner tube 7.

[0030] A pressurized medium can flow into the space between the balloon 1 and the inner tube 7 (hereinafter referred to as the internal space).

[0031] The balloon 1 is inserted into a biological lumen and is folded to maintain passability through the biological lumen until it reaches a stricture in the biological lumen.

[0032] The balloon 1 expands when a pressurized medium is introduced into the internal space (see FIG. 3). When the balloon 1 expands, the balloon catheter 100 expands the diameter of the balloon 1 so that a portion of the balloon 1 presses the stent 2 against a stricture formed in a biological lumen. The stent 2 is placed in the expanded state by the balloon 1, pushing open the stricture.

[0033] The balloon 1 is inserted into a biological lumen and is folded in a deflated state to maintain its passability through the biological lumen until it reaches the narrowed part of the biological lumen (see Figure 2). The deflated state of the balloon 1 refers to a state in which no pressurized medium is flowing into the internal space.

[0034] As shown in Figure 2, the balloon 1 may be divided into three or more regions and folded along the circumferential direction (direction C in Figure 2) of the inner tube 7. In Figure 2, each region of the balloon 1 is folded to have a wing base 11 adjacent to the inner tube 7 and aligned along the inner tube 7, and a wing 12 superimposed on the wing base 11.

[0035] The blade portions 12 in each region are superimposed on the blade base 11 along the same circumferential direction. The blade portions 12 have inner portions 12a superimposed adjacent to each other on the blade base 11, and outer portions 12b superimposed on the inner portions 12a.

[0036] The boundary between the blade base 11 and the blade portion 12, that is, the boundary between the blade base 11 and the blade portion 12 superposed on the blade base 11, is a fold portion 13 along the axial direction (direction Z in FIG. 3) of the inner tube 7. The fold portion 13 is located more inward than the outer portion 12b in the radial direction (direction R in FIG. 3) of the inner tube 7.

[0037] The boundary between the inner portion 12a and the outer portion 12b, at the end of the inner portion 12a opposite the fold portion 13 in the circumferential direction of the inner tube 7, is a fold portion 14 that runs along the axial direction of the inner tube 7.

[0038] As shown in Figure 3, the balloon 1 has an expanded size in which, for example, the outer diameter of the straight portion 10 is about 1 to 20 mm, preferably about 1 to 10 mm, and the length in the axial direction (direction Z) is about 5 to 100 mm, preferably about 5 to 60 mm. The outer diameter of the distal joint portion 17 is about 0.3 to 1.5 mm, preferably about 0.5 to 1.3 mm, and the length in the axial direction is about 0.5 to 5 mm, preferably about 0.5 to 3 mm. The outer diameter of the proximal joint portion 16 is about 0.5 to 1.8 mm, preferably about 0.6 to 1.3 mm, and the length in the axial direction is about 1 to 8 mm, preferably about 1 to 6 mm. The axial lengths of the distal tapered portion 19 and the proximal tapered portion 18 are about 1 to 10 mm, preferably about 3 to 7 mm.

[0039] For example, an organic polymer material can be used as the material for forming the balloon 1. Specific examples of the organic polymer material for forming the balloon 1 include 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, polyamide, polyamide elastomer, polyurethane, polyurethane elastomer, polyimide, and fluororesin, or a mixture of these, or an elastic resin material such as two or more of the above polymer materials, and polyamide resin is particularly suitable as the main material.

[0040] The stent 2 is a member formed into a cylindrical shape as shown in FIG. 3. The stent 2 is formed, for example, from a metal alloy. The stent 2 is, for example, a wire mesh member formed into a cylindrical shape. A balloon 1 is inserted into the cylindrical interior of the stent 2. The stent 2 is fixed (crimped) onto the outer surface of the balloon 1. When the stent 2 is fixed onto the outer surface of the balloon 1, the radial direction of the stent 2 and the radial direction of the inner tube 7 are the same. Hereinafter, the radial direction of the stent 2 and the radial direction of the inner tube 7 may be collectively referred to simply as the radial direction.

[0041] Fig. 4 shows a developed view of the stent 2. As shown in Fig. 4, the stent 2 has a plurality of annular portions 21 that extend in a wave-like pattern in the circumferential direction of the inner tube 7 (see Fig. 2) and are arranged at predetermined intervals in the axial direction of the inner tube 7, and a plurality of link portions 22 that connect adjacent annular portions 21 in the axial direction. The stent 2 is configured in a cylindrical shape. A balloon 1 is inserted inside the cylinder of the stent 2 (see Figs. 2 and 3).

[0042] The stent 2 is designed to remain fixed (crimped) on the outer surface of the balloon 1 and to maintain its expanded diameter once expanded by the balloon 1. Therefore, the material of the stent 2 can be selected to be one that undergoes plastic deformation upon expansion of the balloon 1 and maintains its shape.

[0043] The metal alloy forming the stent 2 may contain at least one selected from the group consisting of cobalt, chromium, nickel, tungsten, molybdenum, iron, and platinum as an alloy component. A particularly suitable metal alloy forming the stent 2 is the L-605 alloy, which is an alloy containing cobalt, chromium, tungsten, and nickel.

[0044] The expanded diameter of the stent 2 is not particularly limited, but is, for example, 1 to 30 mm in outer diameter. The stent 2 according to this embodiment is used to treat lesions such as strictures and obstructions that occur in blood vessels, bile ducts, tracheas, esophagus, urethra, or other biological lumens. The expanded diameter of the stent 2 is set according to the diameter of the target lesion.

[0045] The diameter of the stent 2 before expansion and when attached to the balloon catheter 100 is not particularly limited, but is, for example, an outer diameter of 0.5 to 3 mm. If the diameter of the lumen in which the target lesion exists is small, the diameter of the stent when attached to the delivery catheter must also be small.

[0046] The diameter of the stent 2 before expansion and before attachment to the balloon catheter 100 is not particularly limited, but may be, for example, an outer diameter of 1 to 5 mm. The stent 2 is manufactured using known techniques, for example, by removing unnecessary portions from a pipe material other than the regions that will become the struts, followed by polishing. The stent 2 is then contracted and attached to the balloon catheter 100; in this case, the outer diameter before attachment to the balloon catheter 100 is the outer diameter of the stent 2 after polishing, which is approximately the same as the outer diameter of the pipe material.

[0047] The thickness of the stent 2 is not particularly limited, but is, for example, 0.05 to 1 mm.

[0048] The line width of the stent 2 is not particularly limited, but is, for example, 0.05 to 1 mm.

[0049] The angle formed by the curved portion (hereinafter referred to as the curved portion) in the annular portion 21 of the stent 2 is not particularly limited, but is, for example, 10 to 120° when uniformly expanded.

[0050] The axial length of the link portion 22 is not particularly limited, but is, for example, 0.05 to 50 mm. The link portion 22 may have a component extending in the circumferential direction, but in that case, the circumferential length is not particularly limited, but is, for example, 0.05 to 50 mm.

[0051] The surface of the stent 2 may be coated with a drug such as an immunosuppressant, thereby preventing restenosis in the biological lumen after the stent is placed. Because stress concentration occurs at the curved portion during expansion, which may cause the drug to peel off, the curved portion does not need to be coated with a drug.

[0052] Also, for example, like a stent graft, a cover member made of a fibrous material, a sheet-like material, or the like may be disposed on the outer or inner surface of the stent 2. The cover member may have high or low permeability to liquids and gases, or may be impermeable.

[0053] The stent 2 is crimped onto the balloon 1 as follows. Below, a method for crimping the stent 2 onto the balloon 1 by caulking (hereinafter referred to as the crimping method) will be described as a method for manufacturing the stent delivery system 200.

[0054] The crimping method according to this embodiment includes a first diameter reduction step in which, with the balloon 1 inserted inside the stent 2, the stent 2 is compressed inward in the radial direction of the stent 2 to reduce the diameters of the stent 2 and the balloon 1, and then this compression is released. The crimping method according to this embodiment may also include a second diameter reduction step, which is performed after the first diameter reduction step, in which the stent 2 is compressed inward in the radial direction of the stent 2 to reduce the diameters of the stent 2 and the balloon 1, and then this compression is released. The first diameter reduction step and the second diameter reduction step are operations for crimping the stent 2 to the balloon 1.

[0055] The first diameter reduction step is an operation that includes initial compression and release of the stent 2. In the first diameter reduction step, folds 13, 14 (see Figure 2) are formed in the balloon 1 (to give the balloon 1 a folded shape). The second diameter reduction step is an operation that includes compression and release of the compression that is performed after the first diameter reduction step. The second diameter reduction step may be repeated two or more times. The operation of reducing the diameter of the stent 2 and the balloon 1 in the first diameter reduction step and the operation of reducing the diameter of the stent 2 and the balloon 1 in the second diameter reduction step are basically the same operation, but there are some differences.

[0056] The first diameter reduction step includes a first compression step in which the stent 2 is compressed radially inward to reduce the stent 2 to a first diameter, and a first release step in which the compression is released after the first compression step.

[0057] The first diameter reduction step may include a first maintenance step of maintaining the stent 2 at a first diameter. That is, the first diameter reduction step may include a first compression step in which the stent 2 is compressed inward in the radial direction of the stent 2 to reduce the diameter of the stent 2 to a first diameter, a first maintaining step in which the stent 2 is maintained at the first diameter, and a first releasing step in which the compression is released after the first maintaining step. The first compression step, first maintaining step, and first releasing step are performed in this order.

[0058] The second diameter reduction step includes a second compression step in which the stent 2 is compressed radially inward to reduce the stent 2 to a second diameter, and a second release step in which the compression is released after the second compression step. By performing the second diameter reduction step in addition to the first diameter reduction step, the folds of the folds 13, 14 (see FIG. 2 ) of the balloon 1 become more even, or the space within the balloon 1 is reduced, making it possible to further reduce the diameter of the stent 2 compared to when only the first diameter reduction step is performed. Furthermore, the second diameter reduction step increases the amount of clamping of the stent 2 between the balloon 1 and the balloon 1, thereby more firmly securing the stent 2 to the balloon 1. In other words, the retention of the stent 2 on the balloon 1 in the balloon catheter 100 is improved.

[0059] Hereinafter, an improvement in the force of holding the stent 2 on the balloon 1 in the balloon catheter 100 may be simply referred to as "improved retention."

[0060] The second diameter reduction step is preferably repeated two or more times. This results in a thinner diameter or improved retention. If the second diameter reduction step is performed three to 20 times, sufficient thinning and improved retention can be achieved.

[0061] The second diameter reduction step may include a second maintaining step of maintaining the stent 2 at the second diameter. That is, the second diameter reduction step may include a second compression step of compressing the stent 2 inward in the radial direction of the stent 2 to reduce the stent 2 to the second diameter, a second maintaining step of maintaining the stent 2 at the second diameter, and a second releasing step of releasing the compression after the second maintaining step. The second compression step, second maintaining step, and second releasing step are performed in this order.

[0062] The diameter of the stent 2 is reduced in the first diameter reduction step (first compression step) and the second diameter reduction step (first compression step) by a crimping operation using a crimp head 9 of a crimping device, as shown in Figures 5 and 6. Figures 5 and 6 are explanatory diagrams showing the image of the state of the balloon 1, the stent 2, and the crimp head 9 before and after the diameter of the stent 2 is reduced in the crimping operation, respectively.

[0063] The crimp head 9 has a straight-bore hole 90 whose inner diameter can be reduced or expanded. The diameter of the stent 2 can be reduced by inserting the balloon 1 to which the stent 2 is fixed into the hole 90 and reducing the diameter of the hole 90 (hereinafter sometimes referred to as the opening diameter of the crimp head 9), thereby pressing, i.e., compressing, the outer circumferential surface of the stent 2 in the radial direction. The stent 2 can be released from compression by expanding the opening diameter of the crimp head 9.

[0064] The diameter of the stent 2 in the first diameter-reducing step and the second diameter-reducing step may be reduced by applying a load of 5 N to 10 N per mm of length in the axial direction of the stent 2 (direction Z in FIG. 3 ) inward along the radial direction. This allows the stent 2 to be crimped to the balloon 1 without damaging the balloon 1, and also reduces the diameter (outer diameter) of the stent 2 and the balloon 1. Hereinafter, reducing the diameter of the stent 2 may be simply referred to as "diameter reduction" or "diameter reduction." The concepts of "diameter reduction" and "diameter reduction" include reducing the diameter of the stent 2 and the balloon 1. In the following description, when the term "diameter of the stent 2" is simply referred to, this refers to the outer diameter of the stent 2.

[0065] In the first diameter reduction step, the opening diameter of the crimp head 9 may be reduced to a first diameter. This allows the diameter of the stent 2 to be reduced until the diameter of the stent 2 reaches the first diameter.

[0066] The first maintaining step is a step in which, after the diameter of the stent 2 reaches the first diameter in the first compression step, compression is stopped in this state and the diameter of the stent 2 is maintained at the first diameter for a certain period of time. This increases the amount of clamping of the balloon 1 into the stent 2, thereby more firmly fixing the stent 2 to the balloon 1. In other words, retention is improved. In the first maintaining step, a load of 5 N to 10 N per 1 mm of length in the axial direction of the stent 2 may be applied inward along the radial direction to the stent 2.

[0067] In the second diameter reduction step, the opening diameter of the crimp head 9 may be reduced to the second diameter. That is, in the second diameter reduction step, the stent 2 may be compressed until the diameter of the stent 2 becomes the second diameter. In this way, the diameter of the stent 2 can be reduced until the diameter of the stent 2 becomes the second diameter.

[0068] The second maintaining step is a step in which, after the diameter of the stent 2 reaches the second diameter in the second compression step, the compression is stopped in this state and the diameter of the stent 2 is maintained at the second diameter for a certain period of time. This improves retention. In the second maintaining step, a load of 5 N to 10 N per 1 mm of length in the axial direction of the stent 2 may be applied inward along the radial direction.

[0069] The second diameter may be equal to or smaller than the first diameter. That is, the second diameter may be the same as the first diameter. The second diameter may also be smaller than the first diameter. The second diameter may be, for example, 3.0 mm or less. Hereinafter, the target diameter reduction value in each diameter reduction step, such as the first diameter and the second diameter, may be referred to as the final diameter.

[0070] The final diameter should be equal to or smaller than the diameter D of the proximal junction 16. The final diameter is preferably smaller than the diameter D of the proximal junction 16. This allows for a smaller diameter. For example, it may be possible to provide a stent delivery system 200 in which the diameter of the stent 2 is equal to or smaller than the diameter D of the proximal junction 16 but equal to or larger than the diameter of the inner tube 7. Note that when the final diameter is equal to or smaller than the diameter D of the proximal junction 16, it is preferable that the stent 2 and the outer tube 6 do not overlap in the radial direction.

[0071] As described above, the second diameter reduction step may be repeated two or more times. In this case, the second diameter in one second diameter reduction step may be smaller than the second diameter in the second diameter reduction step performed immediately before it. That is, the final diameter may be successively smaller as the second diameter reduction step is repeated.

[0072] The first and second release steps are steps in which the stent 2 is compressed to its final diameter and then released. Here, releasing the compression means ending the pressing and relaxing the stent 2 and the balloon 1; specifically, this is done by expanding the opening diameter of the crimp head 9 beyond the final diameter. When the opening diameter of the crimp head 9 is expanded, the diameter of the stent 2 and the balloon 1 increases (so-called recoil). Note that recoil refers to the natural expansion of the stent 2 in diameter by an amount equal to the deformation caused by elastic deformation when the stent 2 is contracted.

[0073] After the first diameter reduction step (after the first release step), the diameter of the stent 2 and the balloon 1 (the diameter after recoil) is smaller than at the start of the first diameter reduction step. Therefore, when releasing the compression in the first diameter reduction step, i.e., in the first release step, the diameter of the hole 90 at the end of the first release step (hereinafter referred to as the first release diameter) needs to be smaller than the diameter of the hole 90 at the start of the first diameter reduction step (hereinafter referred to as the starting diameter). The starting diameter refers to the opening diameter of the crimp head 9 at the time when the inner surface of the hole 90 comes into contact with the entire outer peripheral surface of the stent 2, in other words, the opening diameter of the crimp head 9 at the time when compression of the stent 2 begins.

[0074] Furthermore, as described above, since the diameter of the stent 2 and the balloon 1 (the diameter after recoil) after the first diameter reduction step is smaller than at the start of the first diameter reduction step, the opening diameter of the crimp head 9 (the diameter of the hole 90, hereinafter referred to as the second starting diameter) at the start of the second diameter reduction step is smaller than the starting diameter. In this embodiment, the second starting diameter of the second diameter reduction step, which is performed first, is the same as the first release diameter.

[0075] The second starting diameter may be equal to or smaller than the diameter D of the base-end joint 16. The second starting diameter is preferably less than the diameter D of the base-end joint 16. This allows for a thinner diameter. It may also be possible to shorten the manufacturing time of the stent delivery system 200. When the second starting diameter is equal to or smaller than the diameter D of the base-end joint 16, it is preferable that the stent 2 and the outer tube 6 do not overlap in the radial direction.

[0076] After the second diameter reduction step (after the second release step), the diameter (post-recoil diameter) of the stent 2 and balloon 1 is smaller than the second starting diameter of the second diameter reduction step. Therefore, when releasing the compression in the second diameter reduction step, i.e., in the second release step, the diameter of the hole 90 at the end of the second release step (hereinafter referred to as the second release diameter) is sufficient if it is equal to or smaller than the diameter of the hole 90 at the start of the second diameter reduction step (hereinafter referred to as the second starting diameter).

[0077] In addition, in the second release step of the final second diameter reduction step, the opening diameter of the crimp head 9 may be expanded to the same as or greater than the starting diameter to make it easier to remove the stent 2 and balloon 1 from the crimp head 9.

[0078] As described above, the second diameter reducing step may be repeated two or more times, but the repetition of the second diameter reducing step may be terminated in the following cases:

[0079] For example, the repetition of the second diameter reduction step may be terminated when the diameter of the stent 2 after recoil that occurs after the second diameter reduction step becomes equal to or less than a predetermined value (for example, 1.02 mm). In other words, once the diameter of the stent 2 has been reduced to a predetermined target value, the repetition of the second diameter reduction step may be terminated. This allows for efficient diameter reduction.

[0080] Furthermore, the repetition of the second diameter reduction step may be terminated when the rate of change (rate of reduction) in the diameter of the stent 2 when a load of 5 N to 10 N per 1 mm of length in the axial direction of the stent 2 is applied inward along the radial direction of the stent 2 is equal to or less than a predetermined amount x (%). This allows for efficient diameter reduction.

[0081] Here, the rate of change in the diameter of stent 2 is the absolute value of the difference Δd obtained by subtracting the diameter d2 of stent 2 after the application of the above load from the diameter d1 of stent 2 before the application of the above load, divided by the diameter d1 and multiplied by 100.

[0082] In addition, when the second compression step in the second diameter reduction step is performed by applying a load of 5 N or more and 10 N or less per 1 mm of axial length of the stent 2 in an inward direction along the radial direction to the stent 2, the diameter d1 is the diameter of the stent 2 immediately before the start of the second diameter reduction step, and the diameter d2 is the diameter of the stent 2 after the recoil that occurs after the second diameter reduction step.

[0083] The predetermined amount x is 1.54% or less, preferably 1.44% or less, more preferably 0.66% or less, and even more preferably 0.60% or less. The predetermined amount x is allowed to be 0.08% or more.

[0084] In addition, when the diameter of stent 2 is reduced in the second diameter reduction step with a load of 5 N or more and 10 N or less per 1 mm of length in the axial direction of stent 2, the amount of reduction in the diameter of stent 2 in that step corresponds to the difference Δd, and diameter d2 is the diameter of stent 2 immediately after that step.

[0085] In the crimping method according to this embodiment, a pressurizing step may be performed in the process of crimping the stent 2 to the balloon 1, in which a fluid is supplied to the balloon 1 to inflate it and press the outer circumferential surface of the balloon 1 against the inside of the stent 2. The pressurizing step increases the amount of clamping of the balloon 1 into the stent 2, improving retention. In addition, the adhesion between the inner surface of the stent 2 in the radial direction and the outer surface of the balloon 1 is improved, improving retention.

[0086] The pressurizing step may be carried out before the first diameter reducing step, during the first diameter reducing step, or during the second diameter reducing step. As an example, the pressurizing step may include a pre-pressurizing step carried out before the start of the first diameter reducing step (first compression step), an intermediate pressurizing step carried out during the first compression step, a post-pressurizing step (first post-pressurizing step) carried out during the first maintaining step, and a post-pressurizing step (second post-pressurizing step) carried out during the second maintaining step.

[0087] The pressurizing step preferably includes a pre-pressurizing step, a middle pressurizing step, and a first post-pressurizing step. This effectively improves retention. In this case, the pre-pressurizing step, the middle pressurizing step, and the first post-pressurizing step are preferably a series of pressurizing steps that continue from before the start of the first compression step until during the first maintaining step. This effectively improves retention. Hereinafter, the series of pressurizing steps that continue from before the start of the first compression step until during the first maintaining step may be referred to as the first pressurizing step.

[0088] The pressurizing step preferably includes a second post-pressurizing step, which improves retention.

[0089] The pressurizing step may include a first pressurizing step and a second post-pressurizing step, which may further improve retention.

[0090] When a pressurizing step is performed, it is preferable to repeat the second diameter reduction step two or more times. This may improve retention. When a first pressurizing step or a second post-pressurizing step is performed, it is preferable to further perform a second diameter reduction step without a pressurizing step after these pressurizing steps. It is preferable that the second diameter reduction step without a pressurizing step performed after a pressurizing step is repeated two or more times, preferably three to five times. This may further improve retention.

[0091] Figure 7 shows a graph illustrating an example of the manufacturing method (crimping method) for the stent delivery system described above, showing the relationship between the opening diameter of the crimp head 9 of the crimping device (see Figures 5 and 6 above) and the elapsed time of the process. In the graph of Figure 7, the vertical axis represents the opening diameter of the crimp head 9 (opening diameter in Figure 7), and the horizontal axis represents the elapsed time of the process in the manufacturing method for the stent delivery system. In the graph of Figure 7, the solid line L represents the opening diameter of the crimp head 9.

[0092] In Fig. 7, symbol S1 indicates a first diameter reduction step, symbol S11 indicates a first compression step, symbol S12 indicates a first maintenance step, symbol S13 indicates a first release step, and symbol Q1 indicates the start of the first diameter reduction step.

[0093] In Fig. 7, the symbol S2 indicates the second diameter reduction step. In the example shown in Fig. 7, the second diameter reduction step is performed N+M times (where N and M are natural numbers). The symbols S2, such as S21, i indicates the i-th second diameter reduction step (where i is a natural number equal to or less than N+M). Symbol S21 indicates the second compression step. Symbol S22 indicates the second maintenance step. Symbol S23 indicates the second release step. Symbol Q2 i indicates the start of the i-th second diameter reduction step.

[0094] The second starting diameter in the first (initial) second diameter reduction step is the same as the first released diameter in the first diameter reduction step. In the example shown in FIG. 7, the final diameter (second diameter) in the second diameter reduction step is the same as the final diameter (first diameter) in the first diameter reduction step. Also, in the example shown in FIG. 7, the second released diameters in the second diameter reduction steps except for the last one are the same as the second starting diameter in the second diameter reduction step. The second released diameter in the last second diameter reduction step is set to be equal to or larger than the first starting diameter, and crimping is completed.

[0095] In Fig. 7, symbol P1 indicates a first pressurizing step. Symbol P2 indicates a second post-pressurizing step. In the example shown in Fig. 7, the first pressurizing step includes a pre-pressurizing step, a middle pressurizing step, and a first post-pressurizing step. The first pressurizing step is a series of pressurizing steps that continues from before the start of the first compression step until during the first maintenance step.

[0096] In the example shown in FIG. 7, the second diameter reduction step (S2 N After that, the second diameter reduction step (S2 N+1 ~S2 N+M ) is performed M times.

[0097] (Example) Hereinafter, a stent delivery system and a method for manufacturing the same will be described based on examples.

[0098] Example 1 In this example, according to the crimping method described above, a balloon mounted on a shaft having an inner tube and an outer tube was inserted into the cylindrical stent having a diameter (outer diameter) of 2.0 mm, and the stent and balloon were then inserted into the crimping head of a crimping device and crimped to crimp the stent to the balloon. The diameter of the crimped stent was then measured. The balloon and stent were crimped using an "Ultimaster Nagomi (registered trademark)" manufactured by Terumo Corporation.

[0099] The balloon used in this example has its proximal end fused to the outer periphery of the outer tube, with a diameter (outer diameter) of 1.0 mm at the proximal end. The distal end of this balloon is fused to the outer periphery of the inner tube, with a diameter (outer diameter) of 0.6 mm at the distal end. The balloon was pre-folded to have three wings before insertion into the stent. This balloon was made of polyamide resin. The outer diameter of the inner tube was 0.25 mm, and the outer diameter of the outer tube was 0.65 mm.

[0100] The stent used in this example was a wire mesh stent made of L-605 alloy.

[0101] Before starting the first diameter reduction step, the stent was temporarily attached to the balloon by inserting the balloon, which was placed on the shaft, into the stent tube, and then inserting the stent and balloon into the crimp head of the crimping device and lightly crimping them together.

[0102] The starting diameter in the first diameter reduction step is the same as the outer diameter of the stent after the temporary fixing, and is smaller than the diameter (2 mm) of the stent before the temporary fixing.

[0103] The final diameter in the first compression step was 0.48 mm, which was smaller than the diameter of the base-end joining portion.

[0104] The first compression step was performed by gradually reducing the hole diameter of the crimp head, applying a load of 5 to 10 N per 1 mm of axial length of the stent inward along the radial direction of the stent while maintaining this state until the final diameter was reached. The first compression step took approximately 30 seconds. In this example, the first maintenance step was omitted. After the first compression step, a first release step was performed. The first release diameter was 1.2 mm, which was larger than the diameter of the proximal joint.

[0105] After the first diameter reduction step, the second diameter reduction step was repeated 15 times. The second starting diameter in all second diameter reduction steps was 1.2 mm, the same as the first released diameter. That is, the second released diameter in the first to fourteenth second diameter reduction steps was 1.2 mm, the same as the first released diameter. The second released diameter in the fifteenth second diameter reduction step was larger than the starting diameter. In this example, the second maintaining step was omitted in all second diameter reduction steps.

[0106] The second compression step in the second diameter reduction step was carried out in the same manner as the first compression step, by gradually reducing the hole diameter of the crimp head, while applying a load of 5 to 10 N per mm of axial length of the stent inward along the radial direction of the stent, until the final diameter was reached. Each second compression step took approximately 20 seconds.

[0107] After the first diameter reduction step and each second diameter reduction step, the diameter of the stent crimped onto the balloon was measured. The measurement results are shown in Table 1. Note that the number of crimping operations in Table 1 is counted with the first diameter reduction step as the first operation and the second diameter reduction step and subsequent operations as the second operation and subsequent operations. That is, in Table 1, each compression and release in the first diameter reduction step and the second diameter reduction step constitute one cycle of the crimping operation, and the cumulative number of such crimping operations is shown as the number of crimping operations. That is, the diameter of the first crimping operation in Table 1 is the diameter of the stent immediately after the first diameter reduction step. Furthermore, the diameter of the second crimping operation in Table 1 is the diameter of the stent immediately after the first second diameter reduction step, and the same applies for the third and subsequent operations.

[0108] [Table 1]

[0109] Table 1 also shows the percentage change (%) before and after each crimping operation. This percentage change is calculated by dividing the absolute value (absolute value in Table 1) of the difference (the difference in Table 1) obtained by subtracting the diameter of the stent after each crimping operation from the diameter of the stent immediately before each crimping operation by the diameter of the stent immediately before the crimping operation, and multiplying the result by 100. For example, the percentage change after the third crimping operation is calculated by dividing the absolute value of the difference (the diameter of the stent immediately before the third crimping operation, i.e., after the second crimping operation, minus the diameter of the stent after the third crimping operation) by the diameter of the stent after the second crimping operation, and multiplying the result by 100.

[0110] As shown in Table 1, the rate of change decreases to approximately 1.44% after the third crimping, indicating that the stent is thinned. Therefore, in order to thin the stent, it is necessary for the rate of change to be at least 1.54% or less. For the stent to be thinned appropriately, it is preferable that the rate of change be 1.44% or less. Furthermore, when the stent is sufficiently thinned, the balloon is sufficiently sandwiched between the stent 2, and it can be determined that the balloon retention has reached a level required for practical use.

[0111] In this example, the final diameter of the first compression step is 0.48 mm, which is smaller than the diameter of the base-end joint, and is therefore smaller than the diameter of the base-end joint. Setting the final diameter of the first compression step in this manner is also thought to have contributed to the thinning of the stent after the third crimping.

[0112] Furthermore, in this embodiment, the final diameter of the second compression step is set to 0.48 mm, which is smaller than the diameter of the base-end joint, and is therefore smaller than the diameter of the base-end joint. Setting the final diameter of the second compression step in this manner is also thought to have contributed to the thinning of the stent after the third crimping.

[0113] After the fourth crimping, the rate of change reaches approximately 0.66% or less, and the stent is sufficiently thinned. Therefore, it is considered that a stent can be sufficiently thinned if the rate of change is 0.66% or less.

[0114] After the fifth crimping, the change rate reached approximately 0.60% or less, and the stent was further thinned. Therefore, if the change rate is 0.60% or less, it is believed that the stent can be further thinned. Furthermore, after the ninth crimping, the change rate was 0.08% or more.

[0115] Considering the rate of change after the fifth crimping, it is believed that sufficient thinning of the stent can be achieved even if the repetition of the second diameter reduction step is terminated when the rate of change reaches 0.60% or less.

[0116] When considering the number of times of crimping, the rate of change becomes roughly constant after the fifth crimping, and even after the ninth crimping. Therefore, it is considered that performing the second diameter reduction step four or more times, preferably eight or more times, is sufficient for sufficient thinning, and nine or more times is sufficient.

[0117] For example, if the second diameter reduction step is performed four or more times and the rate of change is controlled to 0.60% or less, it is believed that reliable thinning can be achieved.

[0118] The final diameter of the stent was less than the diameter of the proximal junction and greater than the diameter of the inner tube.

[0119] Furthermore, no pinholes were observed in the balloon in the final second diameter reduction step.

[0120] Example 2 In Example 2, the stent and balloon lots were changed, and the procedure was otherwise the same as in Example 1, up to the 15th second diameter reduction step, and the stent was crimped onto the balloon. In Example 2, the diameter and retention (holding force) of the stent after the 15th second diameter reduction step were measured. In Example 2, six crimped stents were manufactured using the same manufacturing method, and the average diameters of five of the stents and the average retention (holding force) of four of the stents were obtained. The diameter variation and retention variation of the crimped stents were also evaluated based on the standard deviation. Table 2 shows the average diameter (mm), standard deviation of diameter (mm), average retention (N), and standard deviation of retention (N) of the crimped stents.

[0121] [Table 2]

[0122] The retention is the retention force of the stent when it is crimped onto the balloon. In this example, the retention is a value measured in accordance with ASTM F2394-07 (initial peak displacement force as described in Reapproved 2022), and is the tensile force at which the stent falls off the balloon when the stent is pulled in the axial direction relative to the balloon.

[0123] Example 3 Example 3 differs from Example 2 in that the second maintaining step was performed only in the 15th second diameter reduction step, and that a pressurizing step was performed during this second maintaining step, in which a fluid was supplied to the balloon to inflate it and press the balloon against the inside of the stent. Otherwise, the average stent diameter and average retention (retention force) were obtained in the same manner as Example 2, and the variations in these values ​​were evaluated. Table 2 also shows these results.

[0124] In this example, the second maintaining step in the 15th second diameter reduction step was performed for 30 seconds. That is, in the 15th second diameter reduction step, after the compression step, the hole diameter of the crimping device was maintained at the final diameter for 30 seconds as the second maintaining step. After the second maintaining step, a second releasing step was performed to increase the hole diameter of the crimping device from the initial diameter.

[0125] The pressurization step started simultaneously with the start of the second maintenance step and ended simultaneously with the end of the second maintenance step. That is, the pressurization step was carried out for 30 seconds. During the pressurization step, the pressure inside the balloon was pressurized to 1.4 MPa and maintained, and at the end of the pressurization step, the pressure inside the balloon was released.

[0126] Example 4 In Example 4, the second diameter reduction step was carried out in the same manner as in Example 3 up to the second maintaining step in the 15th second diameter reduction step and the pressurizing step carried out simultaneously with this second maintaining step. Thereafter, unlike in Example 3, the second diameter reduction step was carried out in the 15th second diameter reduction step and the pressurizing step carried out simultaneously with this second maintaining step, and then the second diameter reduction step was repeated four more times. The final (19th) second diameter reduction step was carried out in the same manner as the final (15th) second diameter reduction step in Example 2. The stents crimped onto the balloon were evaluated by obtaining the average stent diameter and average retention (retention force) values ​​in the same manner as in Examples 2 and 3, and evaluating the variability therein. Table 2 also shows these results.

[0127] As shown in Table 2, a comparison of Examples 2 to 4 shows that the stent diameter was reduced regardless of whether or not a pressurizing process was performed. However, Examples 3 and 4, in which a pressurizing process was performed, had higher retention values ​​than Example 2, in which a pressurizing process was not performed, demonstrating the effect of improving retention. Furthermore, Examples 3 and 4, in which a pressurizing process was performed, also showed less variation in retention than Example 2, in which a pressurizing process was not performed, demonstrating the effect of stabilizing retention.

[0128] These results suggest that the pressurization process increased the amount of the balloon clamped to the stent, improving retention. It is also believed that the pressurization process improved the adhesion between the inner surface of the stent in the radial direction and the outer surface of the balloon, improving retention.

[0129] Furthermore, when considering whether or not a second diameter reduction step was performed after the pressurizing step, Example 4, in which a second diameter reduction step was performed after the pressurizing step, had a higher retention value than Example 3, in which a second diameter reduction step was not performed after the pressurizing step, and it can be seen that the effect of improving retention can be obtained by performing a second diameter reduction step without a pressurizing step after a second diameter reduction step with a pressurizing step.

[0130] These results suggest that the second diameter reduction step after the pressurization step further increased the amount of clamping of the balloon into the stent, improving retention. Also, the second diameter reduction step after the pressurization step further improved the adhesion between the radially inner surface of the stent and the outer surface of the balloon, improving retention.

[0131] As described above, it is possible to provide a stent delivery system and a manufacturing method thereof that realizes a reduction in the diameter of a balloon catheter having a crimped stent.

[0132] [Another embodiment] (1) In the above embodiment, the stent delivery system 200 (see FIG. 1, etc.) has been described as an example in which the diameter of the stent 2 exceeds the diameter D of the base-end joint 16 when the balloon 1 is folded (before the stent 2 is expanded). However, as shown in FIG. 8, the stent delivery system 200 may have a diameter of the stent 2 that is equal to or smaller than the diameter D of the base-end joint 16 when the balloon 1 is folded. Note that FIG. 8 shows a cross section similar to that of FIG. 2. In this case, the diameter of the stent 2 is equal to or larger than the diameter of the inner tube 7.

[0133] It should be noted that the embodiments disclosed in this specification are merely examples, and the embodiments of the present disclosure are not limited to these, and can be modified as appropriate within the scope of the purpose of the present disclosure. [Industrial Applicability]

[0134] The present disclosure is applicable to methods of manufacturing stent delivery systems. [Explanation of symbols]

[0135] 1: Balloon 100: Balloon catheter 10: Straight section 11: Wing base 12: Blade part 12a:Inner part 12b:Outer part 13: Folding part 14: Folding part 16: Proximal joint (junction) 17: Tip side joint 18: Base end tapered section 19: Tapered tip 2: Stent 200: Stent delivery system 21: Annular section 22: Link section 5: Shaft 51: Guidewire port 6:Outer tube 61: lumen 7: Inner tube 71: lumen 79: Tip 8: Hub 9: Crimp head 90: Hole C: Direction D: Diameter R: Direction Z: Direction

Claims

1. a first diameter reduction step of compressing the stent radially inward to reduce the diameters of the stent and the balloon in a state in which a balloon is inserted into a tubular stent formed in a cylindrical shape, and then releasing the compression; a second diameter reduction step, which is performed after the first diameter reduction step, in which the stent is compressed inward in the radial direction of the stent to reduce the diameters of the stent and the balloon, and then the compression is released; a pressurizing step of supplying a fluid to the balloon to inflate it and press the balloon against the inside of the stent.

2. The first diameter reduction step a first compression step of compressing the stent radially inward to reduce the stent to a first diameter; a first maintaining step of maintaining the stent at the first diameter; a first releasing step of releasing the compression after the first maintaining step, The second diameter reduction step is repeated two or more times, The pressurizing step includes: a pre-pressurizing step carried out before the start of the first diameter reduction step; a medium pressure step carried out during the first compression step; The method for manufacturing a stent delivery system according to claim 1 , further comprising a post-pressurizing step performed during the first maintaining step.

3. The method for manufacturing a stent delivery system according to claim 2 , wherein the pressurizing step is continued from before the start of the first compressing step until the first maintaining step is completed.

4. The second diameter reduction step is repeated two or more times, The method for manufacturing a stent delivery system according to claim 1 , wherein the pressurizing step is performed during the second diameter reduction step from the second time onward.

5. The second diameter reduction step a second compression step of compressing the stent radially inward to reduce the stent to a second diameter; a second maintaining step of maintaining the stent at the second diameter; a second releasing step of releasing the compression after the second maintaining step, The method for manufacturing a stent delivery system according to claim 4 , wherein the pressurizing step includes a post-pressurizing step performed during the second maintaining step.

6. The method for manufacturing a stent delivery system according to claim 5, wherein the second diameter reduction step in which the pressurizing step is performed is followed by the second diameter reduction step in which the pressurizing step is not performed.

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