Method for manufacturing stent delivery system

Abstract

To provide a stent delivery system achieving stabilization 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 which includes a first compression step 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, to reduce the diameters of the stent 2 and the balloon 1 and a first releasing step for releasing the compression after the first compression step; and a pressurizing process for inflating the balloon 2 by supplying a liquid to the balloon 2 and pressing the balloon 2 to the inside of the stent 1. The pressurizing process is conducted during the first releasing step or after the first releasing step.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 there is a large variation in the retention force of a stent crimped onto the balloon of a balloon catheter, that is, in retention, a stent with poor retention may fall off the balloon. However, conventional techniques such as those disclosed in Patent Document 1 have not always been able to sufficiently reduce retention variation. Therefore, it is desirable to reduce the variation in the retention force of a stent on a balloon in a balloon catheter, that is, to stabilize 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 achieves stable 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 process including a first compression process in which, with a balloon inserted into a tubular stent formed in a cylindrical shape, the stent is compressed inward in the radial direction of the stent to reduce the diameter of the stent and the balloon, and a first release process thereafter in which 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; A method for manufacturing a stent delivery system, wherein the pressurizing step is performed during or after the first releasing step.

[0008] [2] The method further includes a second diameter reduction step, which is performed after the first diameter reduction step, and includes a second compression step of compressing the stent inward in the radial direction of the stent to reduce the diameter of the stent and the balloon, and a second release step of releasing the compression thereafter, The method for manufacturing a stent delivery system according to [1] above, wherein the pressurizing step is carried out during the second compressing step.

[0009] [3] A method for manufacturing a stent delivery system according to [2] above, wherein the pressurizing step is carried out from the first releasing step through the second compressing step immediately after the first releasing step.

[0010] [4] A method for manufacturing a stent delivery system according to [2] above, wherein the pressurizing step is carried out from before the first releasing step until after the second compressing step immediately after the first releasing step.

[0011] [5] A method for manufacturing a stent delivery system according to [2] above, wherein the pressurizing step is carried out after the first releasing step and before the second compressing step immediately after the first releasing step.

[0012] [6] A method for manufacturing a stent delivery system described in any one of [3] to [5] above, wherein the pressurizing step includes a holding step of keeping the pressure of the fluid supplied to the balloon and the diameter of the stent constant for a predetermined period of time.

[0013] [7] A method for manufacturing a stent delivery system described in any one of [2] to [6] above, wherein the second diameter reduction step is repeated two or more times.

[0014] [8] A method for manufacturing a stent delivery system described in any one of [1] to [7] above, wherein in the first release step, the pressurizing step expands the diameter of the stent to a diameter greater than the recoil diameter to which the stent recoils in the first release step. [Effects of the Invention]

[0015] According to the present disclosure, it is possible to provide a method for manufacturing a stent delivery system that achieves stable retention of a balloon catheter onto which a stent is crimped. [Brief explanation of the drawings]

[0016] [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 an example of 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] 10 is a graph showing another example of a method for manufacturing a stent delivery system, showing the relationship between the opening diameter of the crimp head and the elapsed time of the process. DETAILED DESCRIPTION OF THE INVENTION

[0017] A method for manufacturing a stent delivery system according to an embodiment of the present disclosure will be described with reference to the drawings.

[0018] FIG. 1 shows a stent delivery system 200 realized by the method for manufacturing a stent delivery system according to this embodiment.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] The stent delivery system and its manufacturing method will be described in detail below.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] The balloon 1 is liquid-tightly and airtightly joined to the distal end of the inner tube 7 by welding or the like. The distal end 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 proximal end of the balloon 1 in the extension direction of the shaft 5 is joined to the outer tube 6 by fusion or the like. In FIG. 3, the portion of the balloon 1 where the distal end of the balloon 1 and the inner tube 7 are joined is shown as distal joint 17. The portion of the balloon 1 where the proximal end of the balloon 1 and the outer tube 6 are joined is shown as proximal joint 16. The diameter D of the proximal joint 16 is larger than the diameter (outer diameter) of the distal joint 17.

[0031] 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.

[0032] A pressurized medium can flow into the space between the balloon 1 and the inner tube 7 (hereinafter referred to as the internal space).

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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).

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] The thickness of the stent 2 is not particularly limited, but is, for example, 0.05 to 1 mm.

[0050] The line width of the stent 2 is not particularly limited, but is, for example, 0.05 to 1 mm.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] 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, and a pressurizing step in which a fluid is supplied to the balloon 2 to inflate it and press the balloon 1 against the inside of the stent 2. 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.

[0057] The first diameter reduction step is an operation that includes compressing and releasing 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 compressing and releasing the stent 2 after the first diameter reduction step. The first diameter reduction step and 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.

[0058] 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.

[0059] The first diameter reduction step may include a first maintaining step of maintaining the stent 2 at a first diameter. That is, the first diameter reduction step may include a first compression step of compressing the stent 2 inward in the radial direction of the stent 2 to reduce the stent 2 to a first diameter, a first maintaining step of maintaining the stent 2 at the first diameter, and a first releasing step of releasing the compression after the first maintaining step. The first compression step, first maintaining step, and first releasing step are performed in this order.

[0060] In the first release step, the diameter of the stent 2 expands (so-called recoil) due to the release of compression. Recoil refers to the natural expansion of the diameter of the stent 2 by an amount equal to the deformation due to elastic deformation when the diameter of the stent 2 is contracted. In the first release step, the pressurizing step described below expands the diameter of the stent 2 beyond the recoil diameter of the stent 2 when it is fully recoiled in the first release step. The pressurizing step will be described later. The first release step may be repeated two or more times by repeating the second diameter contraction step. In this embodiment, the complete recoil of the stent 2 means that the stent 2 is expanded to its maximum diameter by recoil, and the recoil diameter refers to the maximum diameter to which the stent 2 is expanded by recoil.

[0061] 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 13, 14 (see FIG. 2 ) of the balloon 1 become more even, or the space inside the balloon 1 is reduced, thereby enabling the stent 2 to have a smaller diameter than when only the first diameter reduction step is performed. This makes the cross-sectional shapes of the balloon 1 and the stent 1 uniform, reducing variation in the retention force that holds the stent 2 to the balloon 1 and stabilizing retention. 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 stably securing the stent 2 to the balloon 1. This reduces variation in the retention force that holds the stent 2 to the balloon 1 in the balloon catheter 100 and stabilizing retention.

[0062] Hereinafter, the reduction of the variation in the holding force that holds the stent 2 to the balloon 1 in the balloon catheter 100 may be simply referred to as "stabilized retention" or "stabilized retention."

[0063] The second diameter reduction step is preferably repeated two or more times. This allows for further diameter reduction and stable retention. If the second diameter reduction step is performed three to 20 times, sufficient diameter reduction and stable retention can be achieved.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] 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.

[0068] 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.

[0069] The first maintaining step is a step in which, after the diameter of stent 2 reaches the first diameter in the first compression step, compression is stopped in this state and the diameter of stent 2 is maintained at the first diameter for a certain period of time. This increases the amount of clamping of stent 2 between balloon 1 and balloon 1, thereby more firmly fixing stent 2 to balloon 1 and stabilizing retention. In the first maintaining step, a load of 5 N to 10 N per 1 mm of length in the axial direction of stent 2 may be applied inward along the radial direction to stent 2.

[0070] 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.

[0071] 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, 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 uniformizes the cross-sectional shapes of the balloon 1 and the stent 1, stabilizing 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.

[0072] 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.

[0073] The final diameter may be equal to or smaller than the diameter D of the proximal junction 16. The final diameter (particularly the second diameter) is preferably smaller than (less than) the diameter D of the proximal junction 16. This allows for a thinner 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 and 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.

[0074] Of the final diameters, the first diameter may be larger than the diameter D (greater than the diameter D), and the second diameter may be smaller than the diameter D (less than the diameter D). This may shorten the process time for the first compression step and the first release step in the first diameter reduction step, thereby shortening the manufacturing time for the stent delivery system 200.

[0075] 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.

[0076] 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 enlarging the opening diameter of the crimp head 9 from the final diameter. When the opening diameter of the crimp head 9 is enlarged, the diameter of the stent 2 and the balloon 1 increases (recoil).

[0077] After the first diameter reduction step (after the first release step), the diameter of the stent 2 and 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) is sufficient to be equal to or smaller than the diameter of the hole 90 at the start of the first diameter reduction step (the opening diameter of the crimp head 9 at the start of the first compression step of the first release step; hereinafter referred to as the first starting diameter). Note that the first starting diameter of the initial (first) first diameter reduction step is the opening diameter of the crimp head 9 at the start of the first diameter reduction step, 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 start of compression of the stent 2.

[0078] The first initial diameter from the second time onward is preferably set larger than the diameter D of the proximal joint portion 16. This prevents irregular folding of the balloon 2 and improves retention.

[0079] Furthermore, as described above, since the diameter of the stent 2 and 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 first 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 releasing diameter of the first releasing step, which is performed immediately before.

[0080] 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) needs to be 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).

[0081] 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 be the same as or larger than the first starting diameter to make it easier to remove the stent 2 and balloon 1 from the crimp head 9.

[0082] 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:

[0083] 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.

[0084] 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.

[0085] 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.

[0086] 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.

[0087] 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.

[0088] 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.

[0089] In the crimping method according to this embodiment, as described above, a pressurizing step is performed in the process of crimping the stent 2 onto the balloon 1, in which a fluid is supplied to the balloon 1 to inflate it, and the outer surface of the balloon 1 is pressed against the inside of the stent 2. The pressurizing step increases the amount of clamping of the balloon 1 onto the stent 2, improving and stabilizing retention. In addition, the adhesive force between the radially inner surface of the stent 2 and the outer surface of the balloon 1 is improved, stabilizing retention.

[0090] The pressurizing step may be performed in a state in which the stent 2 is recoiled by the first releasing step. By performing the pressurizing step in a state in which the stent 2 is recoiled, the way in which the balloon 2 is folded can be made uniform, resulting in more stable retention.

[0091] The pressurizing step is preferably performed in a state in which the stent 2 is expanded to a diameter greater than the recoil diameter (the maximum diameter to which the stent 2 naturally expands) of the stent 2 when recoiled in the first releasing step. This may result in a more uniform folding of the balloon 2 and stable retention. In the pressurizing step, the stent 2 is preferably expanded to a diameter greater than the recoil diameter and equal to or smaller than the first starting diameter.

[0092] The periods during which the stent 2 is in a recoiled state due to the first releasing step include the period during the first releasing step, the period immediately after the first releasing step and immediately before the first compression step of the subsequent first diameter reducing step, the period during the first compression step of the first diameter reducing step performed immediately after the first releasing step, the period immediately after the first releasing step and immediately before the second compression step of the second diameter reducing step, and the period during the second compression step of the second diameter reducing step performed immediately after the first releasing step. In other words, the pressurizing step may be performed during these steps.

[0093] As described above, the pressurizing step may be performed during the first releasing step, which allows the balloon 1 to be sandwiched between the stent 2 after the first compressing step has been performed to create creases in the balloon 1 (after the balloon 1 has been given a folded shape), resulting in uniform folding of the balloon 2 and stable retention.

[0094] As described above, the pressurizing step may be performed from the first release step through the first compression step or the second compression step immediately after the first release step. Alternatively, the pressurizing step may be performed from before the first release step through the first compression step or the second compression step immediately after the first release step. This allows the pressurizing step time to be extended without extending the overall process time, thereby improving retention stability.

[0095] As described above, the pressurization step may be performed immediately after the first release step and immediately before the first compression step of the subsequent first diameter reduction step, or immediately after the first release step and immediately before the second compression step of the second diameter reduction step. Even in these cases, the balloon 1 can be sandwiched between the stent 2 after the first compression step has been performed to create creases in the balloon 1 (after the balloon 1 has been given a folded shape), improving retention and reducing variation in retention.

[0096] The pressurizing step may include a holding step in which the pressure of the fluid supplied to the balloon 1 and the diameter of the stent 2 are kept constant for a predetermined time (between 10 and 45 seconds, for example, 30 seconds). This ensures that the balloon 2 is folded uniformly and retention is stable. The holding step may be performed during the period immediately after the first releasing step and immediately before the first compressing step of the next first diameter reducing step, or during the period immediately after the first releasing step and immediately before the second compressing step of the second diameter reducing step.

[0097] In this holding step, it is preferable that the stent 2 be expanded to a diameter larger than the recoil diameter, which may result in the balloon 2 being folded uniformly and the retention being more stable.

[0098] In this embodiment, the pressurizing step may be performed during a period other than the above-mentioned periods or steps. For example, the pressurizing step may be performed before the first diameter reduction step, during the first diameter reduction step, during the first maintaining step, and during the second maintaining step.

[0099] When a pressurizing step is performed, it is preferable to repeat the second diameter reduction step two or more times. This may result in more stable 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 result in more stable retention.

[0100] 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.

[0101] In Fig. 7, the symbol S1 indicates the first diameter reduction step. In the example shown in Fig. 7, the first diameter reduction step is performed M times (where M is a natural number). j Symbol S11 denotes the first compression step (j is a natural number equal to or less than M) of the j-th first diameter reduction step. Symbol S13 denotes the first release step.

[0102] Symbol Q indicates the start of the first first diameter reduction step. In the example shown in FIG. 7, the first starting diameter in the second and subsequent first diameter reduction steps is the same as the first released diameter in the immediately preceding release step. The first starting diameter in the first diameter reduction step is larger than the diameter D of the base-end joint portion 16. The first released diameter is also larger than the recoil diameter.

[0103] The symbol H indicates a holding step. Symbols H such as H1 j indicates the j-th holding step. The holding step is performed immediately after the first releasing step. The holding step is performed before the first compressing step or the second compressing step of the first releasing step. The symbol P indicates the period during which the pressurizing step is performed. The symbols P such as symbol P1 j indicates the j-th pressurizing step. In the example shown in Fig. 7, the period during which the pressurizing step was performed is the same as the period during which the holding step was performed.

[0104] 7 shows a case where a first diameter reduction step in which the final diameter is a first diameter is performed M times, and then a second diameter reduction step in which the final diameter is a second diameter is performed N times (where N is a natural number). In the example shown in Fig. 7, the first diameter is larger than the diameter D (see Fig. 3) of the base-end joint portion 16, and the second diameter is smaller than the diameter D.

[0105] In FIG. 7, the symbol S2 indicates the second diameter reduction step. i indicates the i-th (where i is a natural number equal to or less than N) second diameter reduction step. Reference symbol S21 indicates the second compression step. Reference symbol S23 indicates the second release step.

[0106] 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 Figure 7, the second released diameters in the second release steps except for the last one are the same as the first diameter. That is, the second released diameter is larger than the diameter D of the base-end joint portion 16 (see Figure 3).

[0107] The second released diameter in the final second diameter reduction step is set to, for example, equal to or larger than the first starting diameter, and crimping is completed.

[0108] Figure 8 shows a graph illustrating another example of the above-described manufacturing method (crimping method) of the stent delivery system, 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. As with Figure 7, in the graph of Figure 8, the vertical axis represents the opening diameter of the crimp head 9 (opening diameter in Figure 8), and the horizontal axis represents the elapsed time of the process in the manufacturing method of the stent delivery system. In the graph of Figure 8, the solid line L represents the opening diameter of the crimp head 9.

[0109] In FIG. 8, symbol S1 indicates the first diameter reduction step. Symbol S11 indicates the first compression step. Symbol S12 indicates the first maintenance step. Symbol S13 indicates the first release step. Symbol Q indicates the start of the first diameter reduction step. In the example shown in FIG. 8, the first release diameter in the first release step is the same as the first start diameter. In addition, the first release diameter is larger than the recoil diameter.

[0110] 8 illustrates an example in which the final diameter (first diameter) in the first diameter reduction step and the final diameter (second diameter) in the second diameter reduction step are the same, and these final diameters are smaller than the diameter D of the base-end joint portion 16 (see FIG. 3).

[0111] In Fig. 8, the symbol S2 indicates the second diameter reduction step. In the example shown in Fig. 8, the second diameter reduction step is performed N times (where N is a natural number). The symbols S21, S22, etc. i indicates the i-th (where i is a natural number equal to or less than N) second diameter reduction step. In this example, the second diameter reduction step is performed N times after the first diameter reduction step. Reference symbol S21 indicates the second compression step. Reference symbol S22 indicates the second maintaining step. Reference symbol S23 indicates the second releasing step. Reference symbol S23 indicates the second releasing step. Figure 8 shows a case where the second maintaining step is performed only in the first second diameter reduction step.

[0112] In FIG. 8, the second released diameter in the second releasing step in the second diameter reduction step is smaller than the first released diameter and larger than the diameter D of the base-end joint portion 16 (see FIG. 3).

[0113] The symbol H denotes a holding step, which is carried out in the period between the first releasing step in the first diameter reduction step and the second compressing step in the (first) second diameter reduction step immediately thereafter.

[0114] The symbol P indicates the period during which the pressurizing step was performed. In the example shown in Fig. 8, the period during which the pressurizing step was performed extends from before the start of the holding step to after it ended. More specifically, the pressurizing step is performed before the first releasing step, i.e., during the first maintaining step in the first diameter reduction step, and during the second maintaining step in the (first) second diameter reduction step immediately thereafter.

[0115] (Example) Hereinafter, a stent delivery system and a method for manufacturing the same will be described based on examples.

[0116] Example 1 In this example, a balloon mounted on a shaft having an inner tube and an outer tube was inserted into the cylindrical stent with a diameter (outer diameter) of 2.0 mm. The stent and balloon were then inserted into the crimping head of a crimping device and crimped together, and the stent was crimped onto the balloon using the crimping method described below. The retention and variability of the crimped stent were then measured. The balloon and stent were made using an "Ultimaster Nagomi (registered trademark)" manufactured by Terumo Corporation.

[0117] 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.

[0118] The stent used in this example was a wire mesh stent made of L-605 alloy.

[0119] In Example 1, the stent was crimped onto the balloon using a crimping method similar to the example shown in FIG. 8 above.

[0120] Before 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.

[0121] The first diameter reduction step was carried out once.

[0122] The first starting diameter in the first diameter reduction step is 2.0 mm, which is the same as the diameter of the stent.

[0123] The final diameter (first diameter) in the first diameter reduction step was set to 1.8 mm, which was smaller than the diameter of the base-end side joint portion.

[0124] 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. 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 1.3 mm, smaller than the first starting diameter and larger than the recoil diameter.

[0125] As will be described later, the first releasing step was followed by a holding step, after which the second diameter reducing step was repeatedly carried out.

[0126] The pressurization step was carried out from the first maintaining step in the first diameter reduction step to the second maintaining step in the (first) second diameter reduction step immediately thereafter. During the pressurization step, the pressure inside the balloon was pressurized to 1.4 MPa and maintained, and the pressure inside the balloon was released at the end of the pressurization step.

[0127] The holding step was performed between the first release step in the first diameter reduction step and the second compression step in the (first) second diameter reduction step immediately thereafter. During the holding step, the diameter of the stent was maintained at the first release diameter (1.3 mm). As a result, during the holding step, the stent expanded to a diameter greater than the recoil diameter due to the pressurization of the balloon.

[0128] After the holding step, the second diameter reduction step was repeated 15 times. The second released diameter in the first to fourteenth second diameter reduction steps was 1.2 mm, smaller than the first released diameter. That is, the second released diameter in the second to fifteenth second diameter reduction steps was 1.2 mm. The second released diameter in the fifteenth second diameter reduction step was larger than the first starting diameter. In this example, the second maintaining step was performed only in the first first diameter reduction step, and the second maintaining step was omitted in the second and subsequent second diameter reduction steps.

[0129] The final diameter (second diameter) in each second diameter reduction step was set to 0.75 mm, which was smaller than the diameter of the base-end side joint portion.

[0130] In the second compression step, similar to the first compression step, the hole diameter of the crimp head was gradually reduced to apply a load of 5 N to 10 N per 1 mm of axial length of the stent inward along the radial direction of the stent, while maintaining this load, until the final diameter was reached.

[0131] Two stents were manufactured by crimping them onto a balloon in this way, and the average retention (holding force) of these stents was obtained. The average retention was 1.76 (N). The variance in retention (standard deviation σ) was 0.027 (N).

[0132] 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.

[0133] (Comparative Example 1) Comparative Example 1 differs from Example 1 in that the first released diameter in the first releasing step performed in Example 1 was 1.2 mm, the same as the second released diameter, a pressurizing step was performed in which the inside of the balloon was pressurized to and maintained at 1.4 MPa from before the start of the first diameter reduction step until halfway through the first maintaining step, and the maintaining step and all second maintaining steps were omitted; otherwise, the stent was crimped onto the balloon in the same manner as Example 1. Then, the retention of the crimped stent was measured.

[0134] Two stents were manufactured by crimping them onto a balloon in this way, and the average retention (holding force) of these stents and their variance were obtained. The average retention was 2.32 (N). The variance (standard deviation σ) of retention was 0.175 (N).

[0135] From the results of Example 1 and Comparative Example 1, it was found that the variation in retention was reduced by performing the pressurization step during or after the first release step. This result is thought to be due to the fact that the balloon 2 is folded uniformly because it can be sandwiched between the stent once the first compression step has been performed and creases have been formed in the balloon (after the balloon has been given a folded shape).

[0136] Furthermore, it was found that the stent's retention variability was reduced by expanding the stent to a diameter smaller than the recoil diameter during the pressurization process. This is thought to be because the balloon's folding was made uniform or irregularities in the folding were suppressed, which increased the amount of the balloon clamped onto the stent, stabilizing the state of the stent's retention by the balloon. Furthermore, the pressurization process is thought to improve the adhesion between the inner surface of the stent in the radial direction and the outer surface of the balloon, stabilizing the state of the stent's retention by the reballoon.

[0137] 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.

[0138] 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]

[0139] The present disclosure is applicable to methods of manufacturing stent delivery systems. [Explanation of symbols]

[0140] 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 27: Tip side joint 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 including a first compression step in which, with a balloon inserted into a cylindrical stent formed in a cylindrical shape, the stent is compressed inward in the radial direction of the stent to reduce the diameters of the stent and the balloon, and a first release step thereafter in which 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; A method for manufacturing a stent delivery system, wherein the pressurizing step is performed during or after the first releasing step.

2. a second diameter reduction step, which is performed after the first diameter reduction step, and which includes a second compression step of compressing the stent inward in the radial direction of the stent to reduce the diameter of the stent and the balloon, and a second release step of releasing the compression thereafter; The method for manufacturing a stent delivery system according to claim 1 , wherein the pressurizing step is performed during the second compressing step.

3. The method for manufacturing a stent delivery system according to claim 2, wherein the pressurizing step is carried out from the first releasing step through the second compressing step immediately after the first releasing step.

4. The method for manufacturing a stent delivery system according to claim 2, wherein the pressurizing step is performed from before the first releasing step until after the second compressing step immediately after the first releasing step.

5. The method for manufacturing a stent delivery system according to claim 2, wherein the pressurizing step is performed after the first releasing step and before the second compressing step immediately after the first releasing step.

6. 4. The method for manufacturing a stent delivery system according to claim 3, wherein the pressurizing step includes a holding step of keeping the pressure of the fluid supplied to the balloon and the diameter of the stent constant for a predetermined time.

7. The method for manufacturing a stent delivery system according to claim 2 , wherein the second diameter reduction step is repeated two or more times.

8. 7. A method for manufacturing a stent delivery system according to claim 2, wherein in the first releasing step, the pressurizing step expands the diameter of the stent to a diameter greater than the recoil diameter of the stent recoiled in the first releasing step.

Images