Balloon catheter

Abstract

Provided is a balloon catheter (1) having an inner tube (2) and an outer balloon group (150) including n number of outer balloons (where n is an integer of 3 or more). The maximum outer diameter RO of the outer proximal sleeve part (175) satisfies the following requirements 1 and 2.　(Requirement 1) Smaller than the maximum outer diameter R of the outer proximal sleeve parts (175) when the outer proximal sleeve parts (175) of adjacent outer balloons contact each other in a first virtual outer balloon group (151) composed of n number of outer balloons.　(Requirement 2) Larger than the maximum outer diameter r of the outer proximal sleeve parts (175) when the outer proximal sleeve parts (175) of adjacent outer balloons contact each other in a second virtual outer balloon group (152) composed of (n +1) number of outer balloons.

Description

Balloon catheter

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

[0002] The formation of hardened stenotic areas due to calcification and other factors on the inner walls of blood vessels can lead to diseases such as angina pectoris and myocardial infarction. One of the treatments for these conditions is angioplasty, which uses a balloon catheter to dilate the stenotic area. Angioplasty is a minimally invasive treatment that does not require open chest surgery like bypass surgery, and is widely used.

[0003] Aortic stenosis is a condition in which the aortic valve becomes hardened due to calcification, making it difficult to open and obstructing blood flow. Treatment for aortic stenosis involves surgical open-chest surgery and catheter placement to replace the hardened aortic valve with a biological valve (artificial valve).

[0004] An implanted bioprosthetic valve deteriorates over time due to calcification, wear, and other factors. When an implanted bioprosthetic valve deteriorates, it must be replaced. To replace a bioprosthetic valve, high pressure is applied to the implanted bioprosthetic valve using a braided balloon catheter or multiple balloon catheters, causing it to deform or break. The valve's lumen is then expanded, and a new bioprosthetic valve is then placed inside the deformed or broken bioprosthetic valve using a procedure such as transcatheter aortic valve replacement.

[0005] As balloon catheters used for dilating hardened stenotic lesions or placing biological valves, for example, Patent Document 1 discloses a catheter having an expansion means composed of multiple expansion elements, the walls of which together form a substantially circular cross section when the expansion means is inflated. Patent Document 2 discloses a balloon catheter having multiple balloon members, with multiple outer balloon members arranged to surround the outer surface of an inner balloon member. Patent Document 3 discloses a balloon catheter having multiple balloons that expand independently without being affected by the other balloons and that are separated from the other balloons after expansion. Patent Document 4 discloses a device having a perfusion balloon with an internal passage and a balloon disposed in the internal passage of the perfusion balloon. Patent Document 5 discloses a catheter including first, second, and third balloons that can be inflated and deflated independently of each other.

[0006] Japanese Patent Publication No. 03-013907 U.S. Patent Application Publication No. 2012 / 0209375 JP 2018-175550 A JP 2018-536474 A International Publication No. 2021 / 054189

[0007] However, in the conventional balloon catheters described above, the relative positions of the multiple balloons can shift when the balloons are inflated, resulting in a distorted shape of the balloon in the inflated state. When the balloon has a distorted shape in the inflated state, the balloon may damage the stenosis or the biological valve, or it may be difficult to apply a load uniformly around the balloon, making it difficult to inflate the stenosis or the biological valve.

[0008] Therefore, there has been a demand for balloon catheters with multiple balloons to optimize the arrangement of the balloons at the design stage and to predict the possibility of damage to the balloons, thereby ensuring appropriate arrangement and size of the balloons. There has also been a demand for a system that can predict whether or not a balloon catheter with multiple balloons will be displaced before inflation, making it easier to perform the procedure appropriately.

[0009] In view of the above circumstances, an object of the present invention is to provide a balloon catheter that makes it easy to arrange multiple balloons uniformly and that is less likely to cause deviation in the relative positions of the multiple balloons when the balloons are inflated.

[0010] The balloon catheter according to the embodiment of the present invention that has solved the above problems is as follows: [1] A balloon catheter having an inner tube and an outer balloon group including n outer balloons (n ​​is an integer of 3 or more) arranged radially outward of the inner tube, wherein the outer balloon has an outer straight tube section, an outer distal tapered section located distal to the outer straight tube section, an outer distal sleeve section located distal to the outer distal tapered section, an outer proximal tapered section located proximal to the outer straight tube section, and an outer proximal sleeve section located proximal to the outer proximal tapered section, and wherein the maximum outer diameter R of the outer proximal sleeve section in a cross section perpendicular to the longitudinal direction is 1 / 2. Ｏ is a balloon catheter that satisfies the following requirements 1 and 2. (Requirement 1) The maximum outer diameter is R ＩＴ The outer proximal sleeve portion is circumscribed around the inner tube, and the outer proximal sleeve portion of each of the outer balloons adjacent to each other in the circumferential direction is in contact with each other in a first imaginary outer balloon group consisting of n outer balloons arranged radially outward from the inner tube. (Requirement 2) The maximum outer diameter R is smaller than the maximum outer diameter R of the outer proximal sleeve portion when the outer proximal sleeve portion of each of the outer balloons adjacent to each other in the circumferential direction is in contact with each other. ＩＴ[2] An inner balloon is arranged radially inward of the outer balloon group, and the inner balloon has an inner straight tube portion, an inner distal tapered portion located distal to the inner straight tube portion, an inner distal sleeve portion located distal to the inner distal tapered portion, an inner proximal tapered portion located proximal to the inner straight tube portion, and an inner proximal sleeve portion located proximal to the inner proximal tapered portion, and the maximum outer diameter R of the outer proximal sleeve portion is Ｏ The balloon catheter according to [1] satisfies the following requirements 3 and 4. (Requirement 3) The maximum outer diameter is R ＩＢ The outer proximal sleeve portion is circumscribed on the inner proximal sleeve portion, and the outer proximal sleeve portion is smaller than the maximum outer diameter R of the outer proximal sleeve portion when the outer proximal sleeve portions of the outer balloons adjacent to each other in the circumferential direction are in contact with each other in a first imaginary outer balloon group consisting of n outer balloons arranged radially outward of the inner balloon. (Requirement 4) The maximum outer diameter is R ＩＢ [3] The balloon catheter according to [1] or [2], wherein the number of outer balloons constituting the outer balloon group is 20 or less. [4] In a cross section perpendicular to the longitudinal direction, the maximum outer diameter R of the outer proximal sleeve portion is greater than the maximum outer diameter r of the outer proximal sleeve portion when the outer proximal sleeve portions of the outer balloons adjacent to each other in the circumferential direction are in contact with each other in a second virtual outer balloon group composed of (n+1) outer balloons arranged radially outward of the inner balloon. Ｏ The balloon catheter according to any one of [1] to [3], wherein R satisfies the following formula (1): Ｏ ≦R ＩＴ ...(1) [In formula (1), R ＩＴis the maximum outer diameter of the inner tube.] [5] The device further includes a shaft having a longitudinal direction, the shaft having a tubular member proximal to the outer proximal tapered portion, the tubular member being connected to the inner tube and the plurality of outer proximal sleeve portions, and the maximum inner diameter R of the tubular member Ｃ The balloon catheter according to any one of [1] to [4], wherein R satisfies the following formula (2): Ｃ >R ＩＴ +2R...(2) [In formula (2), R Ｃ is the maximum inner diameter of the cylindrical member, and R ＩＴ is the maximum outer diameter of the inner tube, and R is the maximum outer diameter R ＩＴ [6] In a cross section perpendicular to the longitudinal direction, the outer proximal sleeve portion is circumscribed about an inner tube having a diameter of n, and the outer proximal sleeve portion of each of the outer balloons adjacent to each other in the circumferential direction among a first imaginary outer balloon group consisting of n outer balloons arranged radially outward of the inner tube is in contact with each other. Ｏ The balloon catheter according to [2], wherein R satisfies the following formula (3): Ｏ ≦R ＩＢ ...(3) [In formula (3), R ＩＢ is the maximum outer diameter of the inner proximal sleeve portion.] [7] A catheter further comprising a shaft having a longitudinal direction, the shaft having a tubular member proximal to the inner proximal tapered portion and the outer proximal tapered portion, the tubular member being connected to the inner proximal sleeve portion and the plurality of outer proximal sleeve portions, and the maximum inner diameter R of the tubular member Ｃ The balloon catheter according to [2] or [6], wherein R satisfies the following formula (4): Ｃ >R ＩＢ +2R...(4) [In formula (4), R Ｃ is the maximum inner diameter of the cylindrical member, and R ＩＢ is the maximum outer diameter of the inner proximal sleeve portion, and R is the maximum outer diameter R ＩＢ

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[0011] The balloon catheter described above facilitates uniform placement of the outer balloon, reducing the likelihood of misalignment between the inner and outer balloons, thereby enabling a uniform load to be applied circumferentially to the balloon when it is inflated, reducing the risk of damaging the stenosis or the biological valve, and facilitating the expansion of the stenosis or the biological valve.

[0012] 1 shows an overall view of a balloon catheter according to one embodiment of the present invention.

[0033] FIG. 1 shows an enlarged view of a portion of the balloon catheter shown in FIG. 1 where a balloon is arranged.

[0034] FIG. 2 shows a III-III cross-sectional view of the balloon catheter shown in FIG. 1.

[0035] FIG. 3 shows a IV-IV cross-sectional view of the balloon catheter shown in FIG. 1.

[0036] FIG. 4 shows a cross-sectional view perpendicular to the longitudinal direction of a first imaginary outer balloon group of the balloon catheter shown in FIG. 1.

[0037] FIG. 5 shows a cross-sectional view perpendicular to the longitudinal direction of a second imaginary outer balloon group of the balloon catheter shown in FIG. 1.

[0038] FIG. 6 shows an overall view of a balloon catheter according to another embodiment of the present invention.

[0039] FIG. 7 shows an enlarged view of a portion of the balloon catheter shown in FIG. 7 where a balloon is arranged.

[0039] FIG. 8 shows a IX-IX cross-sectional view of the balloon catheter shown in FIG. 7.

[0039] FIG. 9 shows an X-X cross-sectional view of the balloon catheter shown in FIG. 7.

[0039] FIG. 10 shows a cross-sectional view perpendicular to the longitudinal direction of a first imaginary outer balloon group of the balloon catheter shown in FIG. 7.

[0039] FIG. 11 shows a cross-sectional view perpendicular to the longitudinal direction of a second imaginary outer balloon group of the balloon catheter shown in FIG. 7.

[0013] The present invention will be described below based on the embodiments, but the present invention is not limited to the following embodiments and can be implemented with appropriate modifications within the scope of the above and below-described purposes, and all such modifications are included within the technical scope of the present invention. In addition, hatching and component symbols may be omitted in each drawing for convenience. In such cases, please refer to the specification or other drawings. Furthermore, the dimensions of various components in the drawings may differ from the actual dimensions, as priority is given to helping understand the features of the present invention.

[0014] A balloon catheter according to an embodiment of the present invention is a balloon catheter having an inner tube and an outer balloon group including n outer balloons (n ​​is an integer of 3 or more) arranged radially outward of the inner tube, wherein the outer balloon has an outer straight tube section, an outer distal tapered section located distal to the outer straight tube section, an outer distal sleeve section located distal to the outer distal tapered section, an outer proximal tapered section located proximal to the outer straight tube section, and an outer proximal sleeve section located proximal to the outer proximal tapered section, and the maximum outer diameter R of the outer proximal sleeve section in a cross section perpendicular to the longitudinal direction is Ｏ The following requirements 1 and 2 are satisfied: (Requirement 1) The maximum outer diameter is R ＩＴ The outer proximal sleeve portion is circumscribed around the inner tube, and the outer proximal sleeve portion of each of the outer balloons adjacent to each other in the circumferential direction is in contact with each other in a first imaginary outer balloon group consisting of n outer balloons arranged radially outward from the inner tube. (Requirement 2) The maximum outer diameter R is smaller than the maximum outer diameter R of the outer proximal sleeve portion when the outer proximal sleeve portion of each of the outer balloons adjacent to each other in the circumferential direction is in contact with each other. ＩＴ The outer proximal sleeve portion is circumscribed around the inner tube, and the outer proximal sleeve portion of each of the outer balloons adjacent to each other in the circumferential direction of the second virtual outer balloon group, which is composed of (n+1) outer balloons arranged radially outward from the inner tube, is larger than the maximum outer diameter r of the outer proximal sleeve portion when the outer proximal sleeve portion is in contact with each other.

[0015] Hereinafter, a balloon catheter according to an embodiment of the present invention will be described with reference to Figures 1 to 12. Figure 1 is an overall view of a balloon catheter according to an embodiment of the present invention, and Figure 2 is an enlarged view of a portion of the balloon catheter shown in Figure 1 where a balloon is disposed. Figure 3 is a III-III cross-sectional view of the balloon catheter shown in Figure 1, and Figure 4 is a IV-IV cross-sectional view of the balloon catheter shown in Figure 1, each showing a cross-sectional view perpendicular to the longitudinal direction of a portion where a balloon group is present when the balloon group is in an expanded state. Figure 5 is a cross-sectional view perpendicular to the longitudinal direction of a first imaginary outer balloon group of the balloon catheter shown in Figure 1, and Figure 6 is a cross-sectional view perpendicular to the longitudinal direction of a second imaginary outer balloon group of the balloon catheter shown in Figure 1. Figure 7 is an overall view of a balloon catheter according to another embodiment of the present invention, and Figure 8 is an enlarged view of a portion of the balloon catheter shown in Figure 7 where a balloon is disposed. Figure 9 is a cross-sectional view taken along line IX-IX of the balloon catheter shown in Figure 7, and Figure 10 is a cross-sectional view taken along line X-X of the balloon catheter shown in Figure 7, each showing a cross-section perpendicular to the longitudinal direction at the portion where the balloon groups are present when the balloon groups are in an expanded state. Figure 11 shows a cross-sectional view perpendicular to the longitudinal direction of a first imaginary outer balloon group in the balloon catheter shown in Figure 7, and Figure 12 shows a cross-sectional view perpendicular to the longitudinal direction of a second imaginary outer balloon group in the balloon catheter shown in Figure 7.

[0016] As shown in Figures 1 to 4, the balloon catheter 1 includes an inner tube 2 and an outer balloon group 150 including n outer balloons 50 arranged radially outward from the inner tube 2, where n is an integer greater than or equal to 3. That is, the balloon catheter 1 includes the inner tube 2 and the outer balloon group 150, and the outer balloon group 150 includes three or more outer balloons 50 arranged radially outward from the inner tube 2. Preferably, the distal ends of the inner tube 2 and the outer balloon 50 are fixed to each other, and the proximal ends of the inner tube 2 and the outer balloon 50 are fixed to each other. For fixation, welding or adhesive fixation can be used. The balloon catheter 1 includes an inner tube 2 and an outer balloon group 150 including n outer balloons 50. The inner tube 2 and the outer balloons 50 are fixed to each other at their distal ends and at their proximal ends, so that the inner tube 2 suppresses radial inward expansion of the outer balloon group 150 caused by each of the outer balloons 50. As a result, the inner tube 2 suppresses the expansion of the outer balloons 50, making the outer balloon group 150 more pressure-resistant. This increases the hardness of the outer balloons 50 constituting the outer balloon group 150 and improves their expansion force. Furthermore, the inner tube 2 suppresses the expansion of the outer balloons 50, making the outer balloons 50 constituting the outer balloon group 150 less likely to expand. Therefore, even when high pressure is applied to each of the outer balloons 50 constituting the outer balloon group 150, overexpansion of the outer balloon group 150 is suppressed, preventing the outer balloon group 150 from expanding beyond a desired outer diameter. This reduces damage to intravascular lumens such as the aortic valve and improves safety.

[0017] 7 to 10, the balloon catheter 1 preferably further includes an inner balloon 40 disposed radially inward of the outer balloon group 150. That is, the balloon catheter 1 preferably includes an outer balloon group 150 and an inner balloon 40, and the outer balloon group 150 preferably includes n outer balloons 50 disposed radially outward of the inner balloon 40. Preferably, the distal ends of the inner tube 2 and the outer balloon 50 are fixed to each other, the proximal ends of the inner tube 2 and the outer balloon 50 are fixed to each other, the distal ends of the inner tube 2 and the inner balloon 40 are fixed to each other, and the proximal ends of the inner tube 2 and the inner balloon 40 are fixed to each other. For fixation, welding or adhesive fixation can be used.

[0018] The balloon catheter 1 has an inner balloon 40 and an outer balloon group 150 including n outer balloons 50, and the distal ends of the inner tube 2 and the outer balloon 50 are fixed to each other, the proximal ends of the inner tube 2 and the outer balloon 50 are fixed to each other, the distal ends of the inner tube 2 and the inner balloon 40 are fixed to each other, and the proximal ends of the inner tube 2 and the inner balloon 40 are fixed to each other, so that the outer balloons 50 restrain the radially outward expansion of the inner balloon 40, and the inner balloon 40 restrains the radially inward expansion of the outer balloons 50. As a result, the inner balloon 40 and the outer balloons 50 mutually restrain each other from expanding, so that the balloon group 11 composed of the plurality of balloons 10 including the inner balloon 40 and the outer balloon 50 has a high pressure resistance, and the hardness of the plurality of balloons 10 constituting the balloon group 11 is increased, thereby further improving the expansion force. Furthermore, the inner balloon 40 and the outer balloons 50 mutually suppress the expansion of each other, making it more difficult for the balloons 10 constituting the balloon group 11 to expand. Therefore, even when high pressure is applied to each of the balloons 10 constituting the balloon group 11, overexpansion of the balloons 10 is suppressed, preventing the balloon group 11 from expanding beyond the intended outer diameter, and improving the effect of reducing damage to intravascular lumens such as the aortic valve and increasing safety.

[0019] Hereinafter, when describing the common configuration of the inner balloon 40 and the outer balloon 50, they may be referred to simply as the balloon 10. Furthermore, the plurality of balloons 10 including the inner balloon 40 and the outer balloon 50 possessed by the balloon catheter 1 may be referred to as the balloon group 11.

[0020] The balloon 10 has a longitudinal direction x, a radial direction y connecting the centroid of the outer edge of the balloon 10 to a point on the outer edge in a cross section perpendicular to the longitudinal direction x, and a circumferential direction z along the outer edge of the balloon 10 in a cross section perpendicular to the longitudinal direction x. In this specification, the direction toward the user in the longitudinal direction x is referred to as the proximal side, and the direction opposite the proximal side, i.e., toward the patient, is referred to as the distal side. Furthermore, when each component or part of the balloon 10 is divided into two equal parts in the longitudinal direction x, the distal part of each component or part is referred to as the distal portion of each component or part, and the proximal part of each component or part is referred to as the proximal part of each component or part. The distal end of each component or part is the most distal end of each component or part. The proximal end of each component or part is the most proximal end of each component or part. The term "end" includes the peripheral portion of the end. That is, the distal end refers to the distal end and the area surrounding the distal end, and the proximal end refers to the proximal end and the area surrounding the proximal end.

[0021] Components and parts other than the balloon 10 also have longitudinal, radial, and circumferential directions, which may or may not be the same as the longitudinal direction x, radial direction y, and circumferential direction z of the balloon 10. However, for ease of understanding, this specification will be described as assuming that all components and parts have the same longitudinal, radial, and circumferential directions as the longitudinal direction x, radial direction y, and circumferential direction z of the balloon 10.

[0022] A balloon group 11 having a plurality of balloons 10 is located at the distal portion of the balloon catheter 1. The balloons 10 can be expanded by introducing a fluid into the lumen of the balloons 10, and can be deflated by discharging the fluid from the lumen of the balloons 10. To control the expansion and contraction of the balloons 10, an indeflator (a balloon pressurizer) can be used to introduce or discharge the fluid. The fluid may be, for example, saline or a mixture of a contrast agent and saline. The fluid may also be a pressurized fluid pressurized by a pump or the like.

[0023] Examples of materials that can be used to form the balloon 10 include polyamide resins such as nylon 11 and nylon 12, polyester resins such as polyethylene terephthalate and polybutylene terephthalate, polyurethane resins, and thermoplastic elastomers such as polyether block amide copolymers.

[0024] As shown in Figure 8, the inner balloon 40 has an inner straight tube section 161, an inner distal tapered section 162 located distally of the inner straight tube section 161, an inner distal sleeve section 164 located distally of the inner distal tapered section 162, an inner proximal tapered section 163 located proximal to the inner straight tube section 161, and an inner proximal sleeve section 165 located proximal to the inner proximal tapered section 163.

[0025] As shown in Figures 2 and 8, the outer balloon 50 has an outer straight tube section 171, an outer distal tapered section 172 located distally of the outer straight tube section 171, an outer distal sleeve section 174 located distally of the outer distal tapered section 172, an outer proximal tapered section 173 located proximal to the outer straight tube section 171, and an outer proximal sleeve section 175 located proximal to the outer proximal tapered section 173.

[0026] The inner straight tube section 161 and the outer straight tube section 171 are preferably substantially cylindrical and have approximately the same diameter in the longitudinal direction x, but may have different diameters in the longitudinal direction x. The inner distal tapered section 162 and the inner proximal tapered section 163 are sections that decrease in diameter as they move away from the inner straight tube section 161 and are formed into a substantially conical or truncated conical shape. Similarly, the outer distal tapered section 172 and the outer proximal tapered section 173 are sections that decrease in diameter as they move away from the outer straight tube section 171 and are formed into a substantially conical or truncated conical shape. Because the inner straight tube section 161 and the outer straight tube section 171 each have a maximum diameter, when the balloon group 11 is expanded at a lesion such as a stenosis, the straight tube sections of the balloons 10 constituting the balloon group 11 can sufficiently contact the lesion, facilitating treatment such as dilation of the lesion. Furthermore, since the inner distal tapered portion 162, the inner proximal tapered portion 163, the outer distal tapered portion 172, and the outer proximal tapered portion 173 are reduced in diameter, when the balloon group 11 is deflated, the outer diameters of the proximal and distal ends of the balloons 10 that make up the balloon group 11 can be reduced, making it easier to insert the balloon catheter 1 into a body cavity.

[0027] In the inner balloon 40, the inner straight tube section 161, the inner distal tapered section 162, and the inner proximal tapered section 163 are sections that expand when a fluid is introduced into the inner balloon 40, whereas the inner distal sleeve section 164 and the inner proximal sleeve section 165 are sections that do not expand. Similarly, in the outer balloon 50, the outer straight tube section 171, the outer distal tapered section 172, and the outer proximal tapered section 173 are sections that expand when a fluid is introduced into the outer balloon 50, whereas the outer distal sleeve section 174 and the outer proximal sleeve section 175 are sections that do not expand. Note that if tubular members are integrated with both ends of the balloon 10 by welding or the like and do not expand when a fluid is introduced into the balloon 10, these tubular members may also be included in the sleeve sections.

[0028] As shown in FIGS. 4 to 6, in a cross section perpendicular to the longitudinal direction x, the outer proximal sleeve portion 175 has a maximum outer diameter R ＯThe following requirements 1 and 2 are satisfied: (Requirement 1) The maximum outer diameter is R ＩＴ The outer proximal sleeve portion 175 is circumscribed on the inner tube 2, and the outer proximal sleeve portion 175 of each of the outer balloons 50 adjacent to each other in the circumferential direction z of the first imaginary outer balloon group 151 is in contact with each other in the first imaginary outer balloon group 151. The first imaginary outer balloon group 151 is composed of n outer balloons 50 arranged radially outward from the inner tube 2. The outer proximal sleeve portion 175 is smaller than the maximum outer diameter R of the outer proximal sleeve portion 175 when the outer proximal sleeve portion 175 is in contact with each other in the first imaginary outer balloon group 151. (Requirement 2) The maximum outer diameter is R ＩＴ The outer proximal sleeve portion 175 is circumscribed on the inner tube 2, and is larger than the maximum outer diameter r of the outer proximal sleeve portion 175 when the outer proximal sleeve portions 175 of the outer balloons 50 adjacent to each other in the circumferential direction z are in contact with each other in the second virtual outer balloon group 152 consisting of (n+1) outer balloons 50 arranged radially outward from the inner tube 2.

[0029] Fig. 5 shows a cross-sectional view of the outer proximal sleeve portion 175 perpendicular to the longitudinal direction x in the first imaginary outer balloon group 151. The first imaginary outer balloon group 151 shown in Fig. 5 is composed of n=6 outer balloons 50. As shown in Fig. 5, in the first imaginary outer balloon group 151, the maximum outer diameter of the outer proximal sleeve portion 175 when the outer proximal sleeve portions 175 of the outer balloons 50 adjacent to each other in the circumferential direction z are in contact with each other is R.

[0030] Fig. 6 shows a cross-sectional view of the outer proximal sleeve portion 175 perpendicular to the longitudinal direction x in the second imaginary outer balloon group 152. The second imaginary outer balloon group 152 shown in Fig. 6 is composed of (n+1)=(6+1)=7 outer balloons 50. As shown in Fig. 6, in the second imaginary outer balloon group 152, the maximum outer diameter of the outer proximal sleeve portion 175 when the outer proximal sleeve portions 175 of the outer balloons 50 adjacent to each other in the circumferential direction z are in contact with each other is r.

[0031] As shown in FIGS. 4 to 6, in a cross section perpendicular to the longitudinal direction x, the outer proximal sleeve portion 175 has a maximum outer diameter R Ｏis smaller than the maximum outer diameter R of the outer proximal sleeve portion 175 in the first imaginary outer balloon group 151 and is larger than the maximum outer diameter r of the outer proximal sleeve portion 175 in the second imaginary outer balloon group 152. In other words, in the balloon catheter 1 of the present invention, the maximum outer diameter R of the outer proximal sleeve portion 175 of the n outer balloons 50 constituting the outer balloon group 150 is Ｏ is smaller than the maximum outer diameter R of the outer proximal sleeve portions 175 when the outer proximal sleeve portions 175 of n outer balloons 50 adjacent to one another in the circumferential direction z in the first imaginary outer balloon group 151 are in contact with one another, and is larger than the maximum outer diameter r of the outer proximal sleeve portions 175 when the outer proximal sleeve portions 175 of (n+1) outer balloons 50 adjacent to one another in the circumferential direction z in the second imaginary outer balloon group 152 are in contact with one another. Note that in Figure 4, the maximum outer diameter R of the outer proximal sleeve portions 175 in the first imaginary outer balloon group 151 and the maximum outer diameter r of the outer proximal sleeve portions 175 in the second imaginary outer balloon group 152 are indicated by dashed lines.

[0032] Maximum outer diameter R of outer proximal sleeve portion 175 Ｏ is smaller than the maximum outer diameter R of the outer proximal sleeve portion 175 in the first imaginary outer balloon group 151 and is larger than the maximum outer diameter r of the outer proximal sleeve portion 175 in the second imaginary outer balloon group 152, the outer balloons 50 are evenly arranged in the outer proximal sleeve portion 175, and misalignment is less likely to occur between the multiple outer balloons 50 and the inner tube 2 arranged radially inward of the multiple outer balloons 50. As a result, misalignment of the balloon 10 is less likely to occur when the outer balloon group 150 is inflated, and stenosis sites, biological valves, etc. are less likely to be damaged when the balloon group 11 is inflated. In addition, a load can be more easily applied evenly in the circumferential direction z to the balloon group 11, making it easier to dilate stenosis sites, biological valves, etc. with the balloon catheter 1.

[0033] As shown in FIG. 4, in a cross section perpendicular to the longitudinal direction x, the outer proximal sleeve portion 175 has a maximum outer diameter R Ｏ It is preferable that R satisfies the following formula (1): Ｏ ≦RＩＴ ...(1) [In formula (1), R ＩＴ is the maximum outer diameter of the inner tube 2.]

[0034] That is, in a cross section perpendicular to the longitudinal direction x, the maximum outer diameter R of the outer proximal sleeve portion 175 is Ｏ is the maximum outer diameter R of the inner tube 2 ＩＴ or the maximum outer diameter R of the inner tube 2 ＩＴ The maximum outer diameter R of the outer proximal sleeve portion 175 is preferably equal to Ｏ is R Ｏ ≦R ＩＴ By satisfying the above formula, the outer proximal sleeve portions 175 of the multiple outer balloons 50 are more likely to be lined up evenly along the outer circumference of the inner tube 2, and the multiple outer balloons 50 are more likely to be arranged evenly.

[0035] As shown in FIGS. 10 to 12, in a cross section perpendicular to the longitudinal direction x, the outer proximal sleeve portion 175 has a maximum outer diameter R Ｏ It is preferable that the following requirements 3 and 4 are satisfied: (Requirement 3) The maximum outer diameter is R ＩＢ The outer proximal sleeve portion 175 is circumscribed on the inner proximal sleeve portion 165, and the outer proximal sleeve portion 175 is smaller than the maximum outer diameter R of the outer proximal sleeve portion 175 when the outer proximal sleeve portions 175 of the outer balloons 50 adjacent to each other in the circumferential direction z are in contact with each other in a first imaginary outer balloon group 151 composed of n outer balloons 50 arranged radially outward of the inner balloon 40. (Requirement 4) The maximum outer diameter is R ＩＢ The outer proximal sleeve portion 175 is circumscribed around the inner proximal sleeve portion 165, and is larger than the maximum outer diameter r of the outer proximal sleeve portion 175 when the outer proximal sleeve portions 175 of adjacent outer balloons 50 in the circumferential direction z are in contact with each other among the second virtual outer balloon group 152 consisting of (n+1) outer balloons 50 arranged radially outward of the inner balloon 40.

[0036] Fig. 11 shows a cross-sectional view of the outer proximal sleeve portion 175 perpendicular to the longitudinal direction x in the first imaginary outer balloon group 151. The first imaginary outer balloon group 151 shown in Fig. 11 is composed of n=6 outer balloons 50. As shown in Fig. 11 , in the first imaginary outer balloon group 151, the maximum outer diameter of the outer proximal sleeve portion 175 when the outer proximal sleeve portions 175 of the outer balloons 50 adjacent to each other in the circumferential direction z are in contact with each other is R.

[0037] Fig. 12 shows a cross-sectional view of the outer proximal sleeve portion 175 perpendicular to the longitudinal direction x in the second imaginary outer balloon group 152. The second imaginary outer balloon group 152 shown in Fig. 12 is composed of (n+1)=(6+1)=7 outer balloons 50. As shown in Fig. 12 , in the second imaginary outer balloon group 152, the maximum outer diameter of the outer proximal sleeve portion 175 when the outer proximal sleeve portions 175 of the outer balloons 50 adjacent to each other in the circumferential direction z are in contact with each other is r.

[0038] As shown in FIGS. 10 to 12, the balloon catheter 1 further includes an inner balloon 40, and the outer proximal sleeve portion 175 has a maximum outer diameter R Ｏ is preferably smaller than the maximum outer diameter R of the outer proximal sleeve portion 175 in the first imaginary outer balloon group 151 and larger than the maximum outer diameter r of the outer proximal sleeve portion 175 in the second imaginary outer balloon group 152. In other words, the maximum outer diameter R of the outer proximal sleeve portion 175 of the n outer balloons 50 constituting the outer balloon group 150 is Ｏis preferably smaller than the maximum outer diameter R of the outer proximal sleeve portions 175 when the outer proximal sleeve portions 175 of n outer balloons 50 adjacent to each other in the circumferential direction z in the first imaginary outer balloon group 151 are in contact with each other, and is greater than the maximum outer diameter r of the outer proximal sleeve portions 175 when the outer proximal sleeve portions 175 of (n+1) outer balloons 50 adjacent to each other in the circumferential direction z in the second imaginary outer balloon group 152 are in contact with each other. In Figure 10, the maximum outer diameter R of the outer proximal sleeve portions 175 in the first imaginary outer balloon group 151 and the maximum outer diameter r of the outer proximal sleeve portions 175 in the second imaginary outer balloon group 152 are indicated by dashed lines.

[0039] In the balloon catheter 1 having the inner balloon 40, the maximum outer diameter R of the outer proximal sleeve portion 175 Ｏ However, since the maximum outer diameter R of the outer proximal sleeve portion 175 in the first virtual outer balloon group 151 is smaller than the maximum outer diameter r of the outer proximal sleeve portion 175 in the second virtual outer balloon group 152, the outer balloons 50 are more easily arranged in the outer proximal sleeve portion 175, which makes it possible to further enhance the effect of preventing misalignment in the respective positional relationships between the multiple outer balloons 50 and the inner balloons 40 arranged radially inward of the multiple outer balloons 50.

[0040] As shown in FIG. 10, in a cross section perpendicular to the longitudinal direction x, the outer proximal sleeve portion 175 has a maximum outer diameter R Ｏ It is preferable that R satisfies the following formula (3): Ｏ ≦R ＩＢ ...(3) [In formula (3), R ＩＢ is the maximum outer diameter of inner proximal sleeve portion 165.]

[0041] That is, in a cross section perpendicular to the longitudinal direction x, the maximum outer diameter R of the outer proximal sleeve portion 175 is Ｏ is the maximum outer diameter R of the inner proximal sleeve portion 165 ＩＢ or the maximum outer diameter R of the inner proximal sleeve portion 165 ＩＢ The maximum outer diameter R of the outer proximal sleeve portion 175 is preferably equal to Ｏis R Ｏ ≦R ＩＢ By satisfying the above formula, the outer proximal sleeve portions 175 of the multiple outer balloons 50 are more likely to be aligned evenly along the outer periphery of the inner proximal sleeve portion 165 of the inner balloon 40, and the multiple outer balloons 50 are more likely to be arranged evenly.

[0042] The number of outer balloons 50 constituting the outer balloon group 150 may be three or more, preferably four or more, more preferably five or more, and even more preferably six or more. That is, the value of n of the n outer balloons 50 included in the outer balloon group 150 may be an integer of three or more, preferably four or more, more preferably five or more, and even more preferably six or more. In particular, in a cross section perpendicular to the longitudinal direction x, the maximum outer diameter R Ｏ is the formula (2) R Ｏ ≦R ＩＢ In the case where the configuration satisfies the above condition, the number of outer balloons 50 constituting the outer balloon group 150 is preferably six or more. By setting the lower limit of the number of outer balloons 50 constituting the outer balloon group 150 within the above range, the positions of the multiple outer balloons 50 constituting the outer balloon group 150 are easily fixed, and it is possible to make it less likely for the multiple outer balloons 50 to shift in position in the circumferential direction z.

[0043] The number of outer balloons 50 constituting the outer balloon group 150 is preferably 20 or less. In other words, the value of n of the n outer balloons 50 included in the outer balloon group 150 is preferably an integer between 3 and 20. By constituting the outer balloon group 150 with a number of outer balloons 50 of 20 or less, the multiple outer balloons 50 can be more easily arranged evenly along the outer periphery of the inner balloon 40.

[0044] The number of outer balloons 50 constituting the outer balloon group 150 is preferably 20 or less, more preferably 12 or less, even more preferably 10 or less, and even more preferably 8 or less. By setting the upper limit of the number of outer balloons 50 constituting the outer balloon group 150 within the above range, the multiple outer balloons 50 constituting the outer balloon group 150 are more likely to be evenly arranged radially outward of the inner balloon 40, which makes it easier to prevent the balloons 10 from shifting position.

[0045] The number of inner balloons 40 may be multiple, but is preferably one. That is, the balloon group 11 preferably includes one inner balloon 40 and n outer balloons 50. By including only one inner balloon 40, the inner balloon 40 is less likely to move radially inward of the multiple outer balloons 50 when the balloon group 11 is inflated. As a result, the inner balloon 40 is more likely to suppress the inflation of the multiple outer balloons 50, and the hardness of the multiple balloons 10 that make up the balloon group 11 is increased, making it easier to increase the inflation force.

[0046] The material constituting the outer balloon 50 may be the same as or different from the material constituting the inner balloon 40. The materials constituting each of the n outer balloons 50 included in the outer balloon group 150 may be different, but are preferably the same. In other words, the outer balloon group 150 preferably includes n outer balloons 50 made of the same material. By making each of the n outer balloons 50 out of the same material, the degree of expansion, hardness, etc. of each of the n outer balloons 50 in the circumferential direction z can be made to be approximately the same.

[0047] In the expanded state of the balloon group 11, the maximum outer diameters of the n outer balloons 50 included in the outer balloon group 150 may be different but are preferably the same. The same maximum outer diameter of the n outer balloons 50 included in the outer balloon group 150 means that the maximum outer diameters of the n outer balloons 50 are approximately the same. Specifically, it means that the maximum outer diameter of one outer balloon 50 is 90% to 110% of the maximum outer diameters of all the other outer balloons 50. In the expanded state of the balloon group 11, the same maximum outer diameter of the n outer balloons 50 included in the outer balloon group 150 makes it easier to synchronize the timing of expansion of all n outer balloons 50 included in the outer balloon group 150, making it easier to control the expansion of the balloon group 11. The expanded state of the balloon group 11 can be rephrased as the state when the balloon group 11 is expanded, and refers to a state in which a fluid is introduced into the lumen of each of the multiple balloons 10 that constitute the balloon group 11, and all of the balloons 10 that constitute the balloon group 11 are expanded.

[0048] When the balloon group 11 is in an expanded state, the maximum outer diameter of the inner balloon 40 may be the same as or different from the maximum outer diameter of each of the n outer balloons 50 included in the outer balloon group 150. The maximum outer diameter of the inner balloon 40 being the same as the maximum outer diameter of each of the n outer balloons 50 included in the outer balloon group 150 means that the maximum outer diameter of the inner balloon 40 and the maximum outer diameter of each of the n outer balloons 50 included in the outer balloon group 150 are approximately the same, specifically, means that the maximum outer diameter of the inner balloon 40 is 90% or more and 110% or less of the average value of the maximum outer diameters of the n outer balloons 50. When the balloon group 11 is in an expanded state, the maximum outer diameter of the inner balloon 40 being the same as the maximum outer diameter of each of the n outer balloons 50 included in the outer balloon group 150 makes it easier to balance the force that tends to expand the inner balloon 40 with the force that tends to suppress the expansion of the inner balloon 40 due to the expansion of the multiple outer balloons 50. As a result, the hardness of the balloon group 11 increases, making it easier to increase the expansion force of the balloon group 11.

[0049] When the balloon group 11 is in an expanded state, the maximum outer diameter of the inner balloon 40 is preferably larger than the maximum outer diameter of the n outer balloons 50 included in the outer balloon group 150. When the balloon group 11 is in an expanded state, the maximum outer diameter of the inner balloon 40 is larger than the maximum outer diameter of the n outer balloons 50 included in the outer balloon group 150, which makes it easier to evenly arrange the multiple outer balloons 50 along the outer periphery of the expanded inner balloon 40. Therefore, when the balloon group 11 is deflated, the multiple outer balloons 50 are easily folded, making it possible to reduce the outer diameter of the balloon catheter 1 at the portion where the balloon group 11 is located.

[0050] When the balloon group 11 is inflated, the maximum outer diameter of the inner balloon 40 is preferably 1.10 times or more, more preferably 1.15 times or more, and even more preferably 1.20 times or more, the maximum outer diameter of the n outer balloons 50 included in the outer balloon group 150. By setting the lower limit of the ratio of the maximum outer diameter of the inner balloon 40 to the maximum outer diameter of the outer balloon 50 when the balloon group 11 is inflated within the above range, it becomes easier to evenly arrange the multiple outer balloons 50 along the outer periphery of the inner balloon 40. Furthermore, when the balloon group 11 is inflated, the maximum outer diameter of the inner balloon 40 is preferably 3.0 times or less, more preferably 2.5 times or less, and even more preferably 2.0 times or less, the maximum outer diameter of the n outer balloons 50 included in the outer balloon group 150. By setting the upper limit of the ratio between the maximum outer diameter of the inner balloon 40 and the maximum outer diameter of the outer balloon 50 when the balloon group 11 is in the expanded state within the above range, it becomes easier to reduce the outer diameter of the portion of the balloon catheter 1 where the balloon group 11 is located when the balloon 10 is in the contracted state, making the balloon catheter 1 less invasive.

[0051] When the balloon group 11 is in an expanded state, the length L50 from the distal end 50d of the outer balloon 50 to the proximal end 50p of the outer balloon 50 in the longitudinal direction x of each of the n outer balloons 50 included in the outer balloon group 150 may be different, but is preferably the same. The length L50 from the distal end 50d of the outer balloon 50 to the proximal end 50p of the outer balloon 50 in the longitudinal direction x of each of the n outer balloons 50 included in the outer balloon group 150 being the same means that the lengths L50 in the longitudinal direction x of each of the n outer balloons 50 included in the outer balloon group 150 are approximately the same, and more specifically, this means that the length L50 in the longitudinal direction x of one outer balloon 50 is 90% to 110% of the lengths L50 in the longitudinal direction x of all the other outer balloons 50. Since the length L50 in the longitudinal direction x of the n outer balloons 50 included in the outer balloon group 150 when the balloon group 11 is in an expanded state is the same, it becomes easier to align the timing at which all of the outer balloons 50 expand, making it easier to control the expansion of the balloon group 11.

[0052] When the balloon group 11 is in an inflated state, the length L40 from the distal end 40d of the inner balloon 40 to the proximal end 40p of the inner balloon 40 in the longitudinal direction x is preferably shorter than the length L50 from the distal end 50d of the outer balloon 50 to the proximal end 50p of the outer balloon 50 in the longitudinal direction x. By making the length L40 of the inner balloon 40 shorter than the length L50 of the outer balloon 50, the inner balloon 40 is restrained by the outer balloon 50, making it less likely for the inner balloon 40 to shift position when the balloon group 11 is in an inflated state. This makes it easier for the balloon group 11 to expand more in the area where the inner balloon 40 is present than in the area where the inner balloon 40 is not present, making it easier to apply pressure to the area where the inner balloon 40 is present, and enabling accurate application of pressure to the target location. Furthermore, the balloon group 11 is less likely to expand more in the area where the inner balloon 40 is not present, making it harder to apply pressure, making it less likely for stress to be applied to areas other than the target location, thereby improving the minimally invasive nature of the balloon catheter 1.

[0053] When the balloon group 11 is in an expanded state, the length L40 from the distal end 40d of the inner balloon 40 to the proximal end 40p of the inner balloon 40 in the longitudinal direction x is preferably 95% or less, more preferably 90% or less, and even more preferably 85% or less of the length L50 from the distal end 50d of the outer balloon 50 to the proximal end 50p of the outer balloon 50 in the longitudinal direction x. By setting the upper limit of the ratio of the length L40 of the inner balloon 40 to the length L50 of the outer balloon 50 within the above range, the balloon catheter 1 can be made to easily apply high pressure accurately to the target location. Furthermore, when the balloon group 11 is in an expanded state, the length L40 from the distal end 40d of the inner balloon 40 to the proximal end 40p of the inner balloon 40 in the longitudinal direction x is preferably at least 20%, more preferably at least 25%, and even more preferably at least 30% of the length L50 from the distal end 50d of the outer balloon 50 to the proximal end 50p of the outer balloon 50 in the longitudinal direction x. By setting the lower limit of the ratio of the length L40 of the inner balloon 40 to the length L50 of the outer balloon 50 within the above range, it becomes easier to apply pressure to a sufficient area of ​​the target site using the balloon catheter 1, making it easier to efficiently dilate a stenotic site and deform or destroy a biological valve.

[0054] 7 and 8 , it is preferable that the distal end 40d of the inner balloon 40 is located proximal to the distal end 50d of the outer balloon 50, and that the proximal end 40p of the inner balloon 40 is located distal to the proximal end 50p of the outer balloon 50. By configuring the distal end 40d of the inner balloon 40 to be proximal to the distal end 50d of the outer balloon 50 and the proximal end 40p of the inner balloon 40 to be distal to the proximal end 50p of the outer balloon 50, the distal end of the inner balloon 40 and the proximal end of the outer balloon 50 are less likely to overlap. Also, the proximal end of the inner balloon 40 and the proximal end of the outer balloon 50 are less likely to overlap. As a result, when the balloon group 11 is in a deflated state, the outer diameter of the portion of the balloon catheter 1 where the balloon group 11 is located can be easily reduced.

[0055] In the expanded state of the balloon group 11, it is preferable that the distal end of the inner distal tapered portion 162 of the inner balloon 40 is proximal to the proximal end of the outer distal tapered portion 172 of the outer balloon 50, and the proximal end of the inner proximal tapered portion 163 of the inner balloon 40 is distal to the distal end of the outer proximal tapered portion 173 of the outer balloon 50. The distal end of the inner distal tapered portion 162 of the inner balloon 40 is located proximal to the proximal end of the outer distal tapered portion 172 of the outer balloon 50, and the proximal end of the inner proximal tapered portion 163 of the inner balloon 40 is located distal to the distal end of the outer proximal tapered portion 173 of the outer balloon 50. This results in a configuration in which the positions of the inner distal tapered portion 162 of the inner balloon 40 and the outer distal tapered portion 172 of the outer balloon 50 do not overlap, and the positions of the inner proximal tapered portion 163 of the inner balloon 40 and the outer proximal tapered portion 173 of the outer balloon 50 do not overlap. Therefore, the outer diameter of the balloon group 11 is less likely to increase when the balloon group 11 is in an expanded state, making it easier to improve minimal invasiveness.

[0056] The distance from the distal end 40d of the inner balloon 40 to the distal end 50d of the outer balloon 50 in the longitudinal direction x is preferably approximately the same as the distance from the proximal end 40p of the inner balloon 40 to the proximal end 50p of the outer balloon 50 in the longitudinal direction x. In other words, the distance from the distal end 40d of the inner balloon 40 to the distal end 50d of the outer balloon 50 in the longitudinal direction x is preferably 90% or more and 110% or less of the distance from the proximal end 40p of the inner balloon 40 to the proximal end 50p of the outer balloon 50 in the longitudinal direction x. By making the distance from the distal end 40d of the inner balloon 40 to the distal end 50d of the outer balloon 50 approximately the same as the distance from the proximal end 40p of the inner balloon 40 to the proximal end 50p of the outer balloon 50, the inner balloon 40 is more likely to be positioned in the central portion of the balloon group 11 in the longitudinal direction x. As a result, the portion to which the load is applied by the expansion of the balloon group 11 is more likely to be the center of the balloon group 11, and it becomes easier to adjust the location to which pressure is applied by the balloon group 11.

[0057] The position of the midpoint of the length L40 in the longitudinal direction x from the distal end 40d of the inner balloon 40 to the proximal end 40p of the inner balloon 40 preferably coincides with the position of the midpoint of the length L50 in the longitudinal direction x from the distal end 50d of the outer balloon 50 constituting the outer balloon group 150 to the proximal end 50p of the outer balloon 50. By having the position of the midpoint of the length L40 of the inner balloon 40 coincide with the position of the midpoint of the length L50 of the outer balloon 50 constituting the outer balloon group 150 in the longitudinal direction x, the balloon 10 is likely to expand most greatly at the midpoint of the length of the balloon group 11 in the longitudinal direction x, making it easier for the balloon group 11 to apply high pressure to the target site.

[0058] 1, 2, 7, and 8, the balloon catheter 1 preferably further includes a shaft 70 having a longitudinal direction x. The distal portion of the shaft 70 is connected to the balloon 10, and a fluid for inflating and deflating the balloon 10 is preferably introduced and discharged through the lumen of the shaft 70.

[0059] The shaft 70 is preferably made of resin, metal, or a combination of resin and metal. Using a resin as the material for the shaft 70 facilitates imparting flexibility and elasticity to the shaft 70. Furthermore, using a metal as the material for the shaft 70 can improve the deliverability of the balloon catheter 1. Examples of resins that can be used to form the shaft 70 include polyamide resins, polyester resins, polyurethane resins, polyolefin resins, fluorine-containing resins, vinyl chloride resins, silicone resins, natural rubber, and synthetic rubber. These materials may be used alone or in combination. Examples of metals that can be used to form the shaft 70 include stainless steels such as SUS304 and SUS316, platinum, nickel, cobalt, chromium, titanium, tungsten, gold, Ni-Ti alloys, Co-Cr alloys, and combinations thereof. The shaft 70 may also have a layered structure made of different or the same materials.

[0060] The inner tube 2 is preferably a guidewire tube 192 for inserting a guidewire through its lumen. By using the inner tube 2 as the guidewire tube 192, the balloon catheter 1 can be easily transported to the target site along the guidewire.

[0061] 1 and 7 show a so-called rapid exchange type balloon catheter 1 having a guidewire port 191 midway from the distal side to the proximal side of the shaft 70 and a guidewire tube 192 that functions as a guidewire passage from the guidewire port 191 to the distal side of the shaft 70. When the balloon catheter 1 is a rapid exchange type, the balloon catheter 1 preferably has a distal shaft 75 and a proximal shaft 76. The distal shaft 75 and the proximal shaft 76 may be separate members, and the proximal end of the distal shaft 75 may be connected to the distal end of the proximal shaft 76 to form the shaft 70 that extends from the balloon 10 to the proximal end of the balloon catheter 1. When the shaft 70 is composed of the distal shaft 75 and the proximal shaft 76 that are separate members, the distal shaft 75 may be made of resin and the proximal shaft 76 may be made of metal, for example. Alternatively, one shaft 70 may extend from the balloon 10 to the proximal end of the balloon catheter 1, and the distal shaft 75 and the proximal shaft 76 may be made up of multiple tubular members.

[0062] Alternatively, although not shown, the present invention can also be applied to a so-called over-the-wire balloon catheter, which has a guidewire passage extending from the distal side to the proximal side of the shaft. When the balloon catheter is an over-the-wire type, it is preferable that the inflation lumen and the guidewire lumen extend to a hub located on the proximal side, and that the proximal openings of each lumen are provided in a bifurcated hub.

[0063] It is preferable that the shaft 70 has a fluid flow path and a guidewire insertion path therein. To configure the shaft 70 to have a fluid flow path and a guidewire insertion path therein, for example, a guidewire tube 192 disposed inside the shaft 70 can function as the guidewire insertion path, and the space between the shaft 70 and the guidewire tube 192 can function as a fluid flow path. In such a configuration, it is preferable that the guidewire tube 192 extends from the distal end of the shaft 70 and passes through the balloon 10, with the distal side of the balloon 10 connected to the guidewire tube 192 and the proximal side of the balloon 10 connected to the shaft 70.

[0064] As shown in FIGS. 1, 2, and 4 to 6, the shaft 70 has a tubular member 180 on the proximal side of the outer proximal tapered portion 173, and the tubular member 180 is connected to the inner tube 2 and a plurality of outer proximal sleeve portions 175. The maximum inner diameter R Ｃ It is preferable that R satisfies the following formula (2): Ｃ >R ＩＴ +2R...(2) [In formula (2), R Ｃ is the maximum inner diameter of the cylindrical member 180, and R ＩＴ is the maximum outer diameter of the inner tube 2, and R is the maximum outer diameter R ＩＢ The outer proximal sleeve portion 175 is in circumscribing contact with the inner tube 2, and the outer proximal sleeve portion 175 of each of the outer balloons 50 adjacent to each other in the circumferential direction z of the first imaginary outer balloon group 151 is composed of n outer balloons 50 arranged radially outward of the inner tube 2. This is the maximum outer diameter of the outer proximal sleeve portion 175 when these outer proximal sleeve portions 175 are in contact with each other.]

[0065] That is, in a cross section perpendicular to the longitudinal direction x, the maximum inner diameter R Ｃ is the maximum outer diameter R of the inner tube 2 ＩＴ and twice the maximum outer diameter R of the outer proximal sleeve portion 175 of the first imaginary outer balloon group 151. Ｃ is R Ｃ >R ＩＴBy satisfying the formula +2R, the size of the lumen of the tubular member 180 can be made larger than the outer diameter of the balloon group 11 when the multiple outer proximal sleeve portions 175 are arranged radially outward of the inner tube 2 so as to surround the periphery of the inner tube 2. As a result, the tubular member 180 can appropriately fix the positions of the outer proximal sleeve portions 175 of the multiple outer balloons 50 relative to the inner tube 2, making it easier to stabilize the shape of the balloon group 11 in its expanded state.

[0066] As shown in FIGS. 7, 8, and 10 to 12, the shaft 70 has a tubular member 180 proximal to the inner proximal tapered portion 163 and the outer proximal tapered portion 173, and the tubular member 180 is connected to the inner proximal sleeve portion 165 and the plurality of outer proximal sleeve portions 175. The maximum inner diameter R Ｃ It is preferable that R satisfies the following formula (4): Ｃ >R ＩＢ +2R...(4) [In formula (4), R Ｃ is the maximum inner diameter of the cylindrical member 180, and R ＩＢ is the maximum outer diameter of the inner proximal sleeve portion 165, and R is the maximum outer diameter R ＩＢ The outer proximal sleeve portion 175 is circumscribing the inner proximal sleeve portion 165, and the outer proximal sleeve portion 175 is the maximum outer diameter of the outer proximal sleeve portion 175 when the outer proximal sleeve portions 175 of the outer balloons 50 adjacent to each other in the circumferential direction z of the first imaginary outer balloon group 151 are in contact with each other. The first imaginary outer balloon group 151 is composed of n outer balloons 50 arranged radially outward of the inner balloon 40.

[0067] That is, in a cross section perpendicular to the longitudinal direction x, the maximum inner diameter R Ｃ is the maximum outer diameter R of the inner proximal sleeve portion 165 ＩＢ and twice the maximum outer diameter R of the outer proximal sleeve portion 175 of the first imaginary outer balloon group 151. Ｃ is R Ｃ >R ＩＢBy satisfying the formula +2R, the size of the lumen of the tubular member 180 can be made larger than the outer diameter of the balloon group 11 when the multiple outer proximal sleeve portions 175 are arranged radially outward of the inner proximal sleeve portion 165 so as to surround the inner proximal sleeve portion 165. As a result, the tubular member 180 can fix the inner proximal sleeve portion 165 of the inner balloon 40 and the outer proximal sleeve portions 175 of the multiple outer balloons 50 in appropriate positions, making it easier to stabilize the shape of the balloon group 11 in its expanded state.

[0068] The constituent material of the tubular member 180 is preferably a resin. Examples of resins that may be used to constitute the tubular member 180 include polyamide resins, polyester resins, polyurethane resins, polyolefin resins, fluorine-based resins, vinyl chloride resins, silicone resins, natural rubber, and synthetic rubber. These may be used alone or in combination of two or more. Using a resin as the constituent material of the tubular member 180 makes it easier to increase the bonding strength between the tubular member 180 and the inner proximal sleeve portion 165 and the outer proximal sleeve portion 175. The tubular member 180 may also have a layered structure made of different materials or the same material.

[0069] The tubular member 180 and the inner proximal sleeve portion 165 and the outer proximal sleeve portion 175 can be joined by adhesive bonding, welding, or the like. Among these, the tubular member 180 and the inner proximal sleeve portion 165 and the outer proximal sleeve portion 175 are preferably joined by welding. By joining the tubular member 180 and the inner proximal sleeve portion 165 and the outer proximal sleeve portion 175 by welding, the joining between the tubular member 180 and the inner proximal sleeve portion 165 and the outer proximal sleeve portion 175 is less likely to come loose even when the balloon 10 is repeatedly inflated or deflated, thereby increasing the joining strength.

[0070] The inner tube 2 and the plurality of outer proximal sleeve portions 175 are preferably disposed within the lumen of the tubular member 180. By disposing the inner tube 2 and the plurality of outer proximal sleeve portions 175 within the lumen of the tubular member 180, the tubular member 180 can easily fix the respective positional relationships between the inner tube 2 and the plurality of outer proximal sleeve portions 175 as appropriate, thereby making it possible to stabilize the shape of the balloon group 11 in its expanded state.

[0071] Furthermore, the inner proximal sleeve portion 165 and the plurality of outer proximal sleeve portions 175 are preferably disposed in the lumen of the tubular member 180. Disposing the inner proximal sleeve portion 165 and the plurality of outer proximal sleeve portions 175 in the lumen of the tubular member 180 can enhance the effect of appropriately positioning the inner proximal sleeve portion 165 and the plurality of outer proximal sleeve portions 175 and fixing them by the tubular member 180. Therefore, the positions of the inner balloon 40 and the plurality of outer balloons 50 can be appropriately positioned, making it easier to stabilize the shape of the balloon group 11 in its expanded state.

[0072] When the inner balloon 40 and the outer balloon group 150 are in an inflated state, it is preferable that there be a portion where the outer surface of the inner balloon 40 and the outer surfaces of the multiple outer balloons 50 constituting the outer balloon group 150 are in contact. That is, when the balloon group 11 is in an inflated state, it is preferable that at least one outer balloon 50 of the multiple outer balloons 50 constituting the outer balloon group 150 is in contact with the outer surface of the inner balloon 40. When the inner balloon 40 and the outer balloon group 150 are in an inflated state, there is a portion where the outer surface of the inner balloon 40 and the outer balloon 50 are in contact, which makes it easier for the inner balloon 40 and the outer balloon 50 to mutually suppress the expansion of each other when the balloon group 11 is in an inflated state. As a result, it becomes difficult for both the inner balloon 40 and the outer balloon 50 to inflate, making it easier to increase the expansion force of the balloon group 11. Furthermore, by the inner balloon 40 and the outer balloon 50 mutually suppressing expansion, when fluid is introduced into both the inner balloon 40 and the outer balloon 50 to put the balloon group 11 into a high-pressure state, the effect of preventing the inner balloon 40 and the outer balloon 50 from expanding too much can be achieved.

[0073] It is more preferable that, when the inner balloon 40 and the outer balloon group 150 are in an expanded state, all of the outer balloons 50 constituting the outer balloon group 150 are in contact with the outer surface of the inner balloon 40. When the inner balloon 40 and the outer balloon group 150 are in an expanded state, all of the outer balloons 50 constituting the outer balloon group 150 are in contact with the outer surface of the inner balloon 40, which tends to enhance the effect of the inner balloon 40 and the outer balloon 50 in suppressing each other's expansion, and makes it easier to further increase the expansion force of the balloon group 11.

[0074] As shown in Fig. 3 , the balloon group 11 preferably includes a first outer balloon 51 and a second outer balloon 52 adjacent to the first outer balloon 51 on one side of the inner tube 2 in the circumferential direction z. Also, as shown in Fig. 9 , the balloon group 11 preferably includes a first outer balloon 51 and a second outer balloon 52 adjacent to the first outer balloon 51 on one side of the inner balloon 40 in the circumferential direction z. When the balloon group 11 is in an expanded state, the first outer balloon 51 and the second outer balloon 52 are preferably in contact with each other. That is, when the balloon group 11 is in an expanded state, the outer surfaces of at least one pair of adjacent outer balloons 50 are preferably in contact with each other. Because the first outer balloon 51 and the second outer balloon 52 are in contact with each other when a fluid is introduced into the balloons 10 constituting the balloon group 11 to expand the balloons 10, the adjacent first outer balloon 51 and second outer balloon 52 mutually suppress the expansion of each other. As a result, the pressure of the fluid pumped into the inner cavities of the first outer balloon 51 and the second outer balloon 52 increases, and the hardness of both the first outer balloon 51 and the second outer balloon 52 increases, thereby increasing the expansion force of the balloon group 11.

[0075] When the balloon group 11 is in an expanded state, it is preferable that all of the outer balloons 50 constituting the outer balloon group 150 are in contact with adjacent outer balloons 50. Specifically, in the case of a balloon catheter 1 configured as shown in Figures 3 and 9, it is preferable that each outer balloon 50 be in contact with the outer balloons 50 located on both sides of the outer balloon 50 in the circumferential direction z. When the balloon group 11 is in an expanded state, all of the outer balloons 50 constituting the outer balloon group 150 are in contact with adjacent outer balloons 50. As a result, when the balloon group 11 is in an expanded state, all of the outer balloons 50 constituting the outer balloon group 150 suppress each other's expansion, and the internal pressure of all of the outer balloons 50 increases. This increases the hardness of the balloon group 11 as a whole, further increasing the expansion force of the balloon group 11.

[0076] The shaft 70 has a guidewire lumen 93 extending in the longitudinal direction x and through which a guidewire is inserted, and further has a guidewire tube 192 having an inner cavity communicating with the guidewire lumen 93, the guidewire tube 192 preferably being disposed in the inner cavity of the inner balloon 40. Since the balloon catheter 1 has the guidewire tube 192 having an inner cavity communicating with the guidewire lumen 93, it becomes easy to insert a guidewire into the balloon catheter 1, and the balloon catheter 1 can be transported into the body along the guidewire. Furthermore, inserting the guidewire into the guidewire tube 192 prevents the guidewire from damaging the balloon 10, etc.

[0077] Examples of materials constituting the guidewire tube 192 include synthetic resins such as polyolefin resins (e.g., polyethylene, polypropylene, etc.), polyamide resins (e.g., nylon, etc.), polyester resins (e.g., PET), aromatic polyetherketone resins (e.g., PEEK, etc.), polyetherpolyamide resins, polyurethane resins, polyimide resins, fluorine-based resins (e.g., PTFE, PFA, ETFE, etc.), and polyvinyl chloride resins. Among these, polyimide resins are preferred as the material constituting the guidewire tube 192. Using polyimide resin as the material constituting the guidewire tube 192 improves the lubricity of the guidewire tube 192. This facilitates inserting a guidewire through the lumen of the guidewire tube 192 and feeding the balloon catheter 1 into the body along the guidewire. The guidewire tube 192 may also have a multi-layer structure including a braided layer (e.g., a metal braid). The multi-layer structure of the guidewire tube 192 can improve the strength of the guidewire tube 192, its lubricity relative to the guidewire, and its kink resistance.

[0078] 1 and 7, the proximal end of the guidewire tube 192 is preferably connected to the distal end of the shaft 70. When the shaft 70 has a distal shaft 75 and a proximal shaft 76, the proximal end of the guidewire tube 192 is preferably connected to the distal end of the distal shaft 75. Connecting the proximal end of the guidewire tube 192 to the distal end of the shaft 70 prevents the outer diameter of the balloon catheter 1 from becoming large, thereby improving minimal invasiveness.

[0079] The balloon 10 and the shaft 70 can be joined by adhesive bonding, welding, or by attaching a ring-shaped member to the overlapping portion of the end of the balloon 10 and the shaft 70 and crimping the end. Of these, it is preferable that the balloon 10 and the shaft 70 be joined by welding. By joining the balloon 10 and the shaft 70 by welding, the bond between the balloon 10 and the shaft 70 is less likely to come loose even when the balloon 10 is repeatedly expanded or contracted, and the bond strength can be improved.

[0080] A tip member 193 is preferably provided at the distal end of the balloon catheter 1. The tip member 193 may be provided at the distal end of the balloon catheter 1 as a separate member from the guidewire tube 192 and connected to the distal end of the balloon 10, or the guidewire tube 192 extending distally of the distal end of the balloon 10 may function as the tip member 193.

[0081] As shown in Figures 7 and 8, a radiopaque marker 194 may be placed on the guidewire tube 192 inside the balloon 10 at the location where the balloon 10 is located in the longitudinal axis direction x so that the position of the balloon 10 can be confirmed under X-ray fluoroscopy.

[0082] Examples of positions on the guidewire tube 192 where the radiopaque marker 194 is located include the midpoint of the length L40 from the distal end 40d of the inner balloon 40 to the proximal end 40p of the inner balloon 40, the proximal and distal ends of the inner straight tube portion 161 of the inner balloon 40, and the proximal and distal ends of the outer straight tube portion 171 of the outer balloon 50. Among these, the positions on the guidewire tube 192 where the radiopaque marker 194 is located are preferably the proximal and distal ends of the inner straight tube portion 161 of the inner balloon 40. By locating the radiopaque marker 194 on the guidewire tube 192 at the proximal and distal ends of the inner straight tube portion 161 of the inner balloon 40, it becomes easier to confirm the positions where the balloon group 11 will be greatly expanded by the inner balloon 40. As a result, the balloon catheter 1 can be configured to easily apply pressure to the target location.

[0083] 1 and 7 , a hub 5 may be provided on the proximal side of the shaft 70. The hub 5 may also be provided with a fluid injecting section 6 that communicates with a flow path for fluid supplied to the interior of the balloon 10.

[0084] The shaft 70 and the hub 5 can be joined by, for example, bonding with an adhesive or welding. Among these, it is preferable that the shaft 70 and the hub 5 are joined by adhesive. By joining the shaft 70 and the hub 5 by adhesive, the bond strength between the shaft 70 and the hub 5 can be increased and the durability of the balloon catheter 1 can be improved when the shaft 70 and the hub 5 are made of different materials, for example, when the shaft 70 is made of a highly flexible material and the hub 5 is made of a highly rigid material.

[0085] When the balloon catheter 1 is of a rapid exchange type, a coating may be applied to the outer wall of at least one of the distal shaft 75 and the proximal shaft 76, or may be applied to the outer walls of both the distal shaft 75 and the proximal shaft 76. When the balloon catheter 1 is of an over-the-wire type, a coating may be applied to the outer wall of the outer shaft.

[0086] The coating applied to the shaft 70 can be a hydrophilic coating or a hydrophobic coating depending on the purpose, and can be applied by immersing the shaft 70 in a hydrophilic coating agent or a hydrophobic coating agent, applying a hydrophilic coating agent or a hydrophobic coating agent to the outer wall of the shaft 70, covering the outer wall of the shaft 70 with a hydrophilic coating agent or a hydrophobic coating agent, etc. The coating agent may contain drugs, additives, etc.

[0087] Examples of hydrophilic coating agents include hydrophilic polymers such as polyvinyl alcohol, polyethylene glycol, polyacrylamide, polyvinylpyrrolidone, methyl vinyl ether maleic anhydride copolymer, and the like, or hydrophilic coating agents made from any combination thereof.

[0088] Examples of hydrophobic coating agents include polytetrafluoroethylene (PTFE), fluorinated ethylene propylene (FEP), perfluoroalkoxyalkane (PFA), silicone oil, hydrophobic urethane resin, carbon coat, diamond coat, diamond-like carbon (DLC) coat, ceramic coat, and substances terminated with alkyl groups or perfluoroalkyl groups and having low surface free energy.

[0089] The balloon catheter 1 of the present invention is preferably used for dilating an aortic valve, deforming a biological valve placed in the heart, or destroying a biological valve. Specifically, the balloon catheter 1 of the present invention is preferably used for dilating an aortic valve that has hardened due to calcification or the like, or for deforming or destroying an artificial valve annulus of a biological valve to replace a deteriorated biological valve placed in the heart. The balloon catheter 1 of the present invention is preferably used for dilating a hardened aortic valve and deforming or destroying a biological valve, which cannot be sufficiently dilated with conventional balloon catheters, because it is easy to apply high pressure to the portion where the inner balloon 40 is located.

[0090] This application claims the benefit of priority based on Japanese Patent Application No. 2024-047088, filed on March 22, 2024. The entire contents of the specification of Japanese Patent Application No. 2024-047088, filed on March 22, 2024, are incorporated herein by reference.

[0091] 1: Balloon catheter 2: Inner tube 5: Hub 6: Fluid injection section 10: Balloon 11: Balloon group 40: Inner balloon 40d: Distal end of inner balloon 40p: Proximal end of inner balloon 50: Outer balloon 50d: Distal end of outer balloon 50p: Proximal end of outer balloon 51: First outer balloon 52: Second outer balloon 70: Shaft 75: Distal shaft 76: Proximal shaft 93: Guidewire lumen 150: Outer balloon group 151: First virtual outer balloon group 152: Second virtual outer balloon group 161: Inner straight tube section 162: Inner distal tapered section 163: Inner proximal tapered section 164: Inner distal sleeve section 165: Inner proximal sleeve section 171: Outer straight tube section 172: Outer distal tapered section 173: Outer proximal tapered section 174: Outer distal sleeve portion 175: Outer proximal sleeve portion 180: Cylindrical member 191: Guidewire port 192: Guidewire tube 193: Distal tip member 194: X-ray opaque marker R Ｏ : Maximum outer diameter of outer proximal sleeve R ＩＴ : Maximum outer diameter of inner tube R ＩＢ : Maximum outer diameter of the inner proximal sleeve portion R: Maximum outer diameter of the outer proximal sleeve portion in the first virtual outer balloon group r: Maximum outer diameter of the outer proximal sleeve portion in the second virtual outer balloon group L40: Length of the inner balloon L50: Length of the outer balloon

Claims

1. A balloon catheter having an inner tube and an outer balloon group including n outer balloons (n ​​is an integer of 3 or more) arranged radially outward of the inner tube, wherein the outer balloon has an outer straight tube section, an outer distal tapered section located distal to the outer straight tube section, an outer distal sleeve section located distal to the outer distal tapered section, an outer proximal tapered section located proximal to the outer straight tube section, and an outer proximal sleeve section located proximal to the outer proximal tapered section, and the maximum outer diameter R of the outer proximal sleeve section in a cross section perpendicular to the longitudinal direction Ｏ is a balloon catheter that satisfies the following requirements 1 and 2. (Requirement 1) The maximum outer diameter is R ＩＴ The outer proximal sleeve portion is circumscribed around the inner tube, and the outer proximal sleeve portion of each of the outer balloons adjacent to each other in the circumferential direction is in contact with each other in a first imaginary outer balloon group consisting of n outer balloons arranged radially outward from the inner tube. (Requirement 2) The maximum outer diameter R is smaller than the maximum outer diameter R of the outer proximal sleeve portion when the outer proximal sleeve portion of each of the outer balloons adjacent to each other in the circumferential direction is in contact with each other. ＩＴ The outer proximal sleeve portion is circumscribed around the inner tube, and the outer proximal sleeve portion of each of the outer balloons adjacent to each other in the circumferential direction of the second virtual outer balloon group, which is composed of (n+1) outer balloons arranged radially outward from the inner tube, is larger than the maximum outer diameter r of the outer proximal sleeve portion when the outer proximal sleeve portion is in contact with each other.

2. An inner balloon is disposed radially inward of the group of outer balloons, and the inner balloon has an inner straight tube portion, an inner distal tapered portion located distally of the inner straight tube portion, an inner distal sleeve portion located distally of the inner distal tapered portion, an inner proximal tapered portion located proximal to the inner straight tube portion, and an inner proximal sleeve portion located proximal to the inner proximal tapered portion, and the maximum outer diameter R of the outer proximal sleeve portion in a cross section perpendicular to the longitudinal direction Ｏ The balloon catheter according to claim 1, wherein the maximum outer diameter R is 0.01 mm or less and the maximum outer diameter R is 0.01 mm or less. ＩＢ The outer proximal sleeve portion is circumscribed on the inner proximal sleeve portion, and the outer proximal sleeve portion is smaller than the maximum outer diameter R of the outer proximal sleeve portion when the outer proximal sleeve portions of the outer balloons adjacent to each other in the circumferential direction are in contact with each other in a first imaginary outer balloon group consisting of n outer balloons arranged radially outward of the inner balloon. (Requirement 4) The maximum outer diameter is R ＩＢ The outer proximal sleeve portion is circumscribed by an outer proximal sleeve portion circumscribed by an inner proximal sleeve portion, and the outer proximal sleeve portion is larger than the maximum outer diameter r of the outer proximal sleeve portion when the outer proximal sleeve portions of the outer balloons adjacent to each other in the circumferential direction are in contact with each other in a second virtual outer balloon group consisting of (n+1) outer balloons arranged radially outward of the inner balloon.

3. A balloon catheter according to claim 1 or 2, wherein the number of outer balloons constituting the outer balloon group is 20 or less.

4. The maximum outer diameter R of the outer proximal sleeve portion in a cross section perpendicular to the longitudinal direction Ｏ The balloon catheter according to claim 1, wherein R satisfies the following formula (1): Ｏ ≦R ＩＴ ...(1) [In formula (1), R ＩＴ is the maximum outer diameter of the inner tube.

5. The device further includes a shaft having a longitudinal direction, the shaft having a tubular member proximal to the outer proximal tapered portion, the tubular member being connected to the inner tube and the plurality of outer proximal sleeve portions, and the tubular member having a maximum inner diameter R Ｃ The balloon catheter according to claim 1, wherein R satisfies the following formula (2): Ｃ >R ＩＴ +2R...(2) [In formula (2), R Ｃ is the maximum inner diameter of the cylindrical member, and R ＩＴ is the maximum outer diameter of the inner tube, and R is the maximum outer diameter R ＩＴ The outer proximal sleeve portion is in circumferential contact with an inner tube having an inner tube diameter of n, and the outer proximal sleeve portion is the maximum outer diameter of the outer proximal sleeve portion when the outer proximal sleeve portions of the outer balloons adjacent to each other in the circumferential direction are in contact with each other in a first imaginary outer balloon group consisting of n outer balloons arranged radially outward from the inner tube.

6. The maximum outer diameter R of the outer proximal sleeve portion in a cross section perpendicular to the longitudinal direction Ｏ The balloon catheter according to claim 2, wherein R satisfies the following formula (3): Ｏ ≦R ＩＢ ...(3) [In formula (3), R ＩＢ is the maximum outer diameter of the inner proximal sleeve portion.

7. A method for treating a vascular disease, comprising: a shaft having a longitudinal direction; the shaft having a tubular member proximal to the inner proximal tapered portion and the outer proximal tapered portion; the tubular member being connected to the inner proximal sleeve portion and a plurality of the outer proximal sleeve portions; and a maximum inner diameter R of the tubular member. Ｃ The balloon catheter according to claim 2, wherein R satisfies the following formula (4): Ｃ >R ＩＢ +2R...(4) [In formula (4), R Ｃ is the maximum inner diameter of the cylindrical member, and R ＩＢ is the maximum outer diameter of the inner proximal sleeve portion, and R is the maximum outer diameter R ＩＢ The outer proximal sleeve portion is circumscribing an inner proximal sleeve portion such that the outer proximal sleeve portion is in contact with the outer proximal sleeve portion of each of the outer balloons adjacent to each other in the circumferential direction in a first imaginary outer balloon group consisting of n outer balloons arranged radially outward of the inner balloon.] 8. The balloon catheter according to claim 7, wherein the inner proximal sleeve portion and the plurality of outer proximal sleeve portions are disposed within the lumen of the tubular member.

9. A balloon catheter as described in claim 2, wherein when the inner balloon and the outer balloon group are in an expanded state, there is a portion where the outer surface of the inner balloon is in contact with the outer surfaces of the multiple outer balloons that make up the outer balloon group.

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