Balloon catheter

Abstract

Provided is a balloon catheter which includes: a shaft extending in the longitudinal direction from the proximal side to the distal side; an inner balloon disposed at a distal part of the shaft; and a balloon group composed of a plurality of outer balloons arranged side by side in the circumferential direction of the inner balloon, in the radially outward direction of the inner balloon. In manufacturing the balloon catheter, welding defects are less likely to occur, thereby reducing the rate of defective products.　In the balloon catheter: a distal-side sleeve part of an inner balloon and a distal-side sleeve part of an outer balloon are connected to a distal-side shaft part; a proximal-side sleeve part of the outer balloon is connected to a proximal-side shaft part; and the total light transmittance of the proximal-side shaft part and the distal-side shaft part measured on the basis of JIS K7361-1 is lower than the total light transmittance of a proximal-side sleeve part of the inner balloon, the distal-side sleeve part of the inner balloon, the proximal-side sleeve part of the outer balloon, and the distal-side sleeve part of the outer balloon measured on the basis of JIS K7361-1.

Description

Balloon Catheter

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

[0002] Diseases such as angina pectoris and myocardial infarction are caused by the formation of a stenotic site hardened by calcification or the like on the inner wall of a blood vessel. As one of the therapeutic methods for these conditions, there is angioplasty in which a stenotic site is dilated using a balloon catheter. Angioplasty is sometimes referred to as Percutaneous Transluminal Angioplasty (PTA) or Percutaneous Transluminal Coronary Angioplasty (PTCA). Angioplasty is a minimally invasive therapy that does not require thoracotomy like bypass surgery, and is widely performed.

[0003] A balloon catheter used for angioplasty includes a shaft extending longitudinally from a proximal side to a distal side, and a balloon disposed at a distal portion of the shaft. An example of such a balloon catheter is described in Patent Document 1. FIG. 42 of Patent Document 1 describes an expansion device including an inner balloon member and a plurality of outer balloon members.

[0004] US Patent Application Publication No. 2012 / 0209375

[0005] Incidentally, in a balloon catheter having a balloon, the balloon is fixed by welding to a shaft extending longitudinally from the proximal side to the distal side. In this case, as described in Patent Document 1, when a balloon catheter includes a plurality of balloons, the number of fixation sites to the shaft increases. As a result, welding defects are likely to occur, leading to an increased defective product rate.

[0006] The problem to be solved by this disclosure is to provide a balloon catheter that is less prone to welding defects and can reduce the rate of defective products when manufacturing a balloon catheter having a shaft extending longitudinally from the proximal to the distal end of the shaft, an inner balloon disposed at the distal end of the shaft, and a balloon group consisting of a plurality of outer balloons arranged radially outward of the inner balloon and aligned in the circumferential direction of the inner balloon.

[0007] The present disclosure is as follows: [1] A balloon catheter comprising: a shaft extending longitudinally from proximal to distal; an inner balloon disposed at the distal end of the shaft; and a balloon group comprising a plurality of outer balloons arranged radially outward of the inner balloon and aligned circumferentially with respect to the inner balloon, wherein the inner balloon and the outer balloon each have a straight tube portion, a proximal tapered portion located proximal to the straight tube portion, a proximal sleeve portion located proximal to the proximal tapered portion, a distal tapered portion located distal to the straight tube portion, and a distal sleeve portion located distal to the distal tapered portion, the shaft having a proximal shaft portion located proximal to the inner balloon and a distal shaft portion located distal to the inner balloon, the distal sleeve portion of the inner balloon and the distal sleeve portion of the outer balloon are each connected to the distal shaft portion, A balloon catheter in which the proximal sleeve portion of the outer balloon is connected to the proximal shaft portion, and the total light transmittance of the proximal shaft portion and the distal shaft portion, as measured according to JIS K 7361-1, is lower than the total light transmittance of the proximal sleeve portion of the inner balloon, the distal sleeve portion of the inner balloon, the proximal sleeve portion of the outer balloon, and the distal sleeve portion of the outer balloon, as measured according to JIS K 7361-1. [2] The balloon catheter in which the brightness of the proximal shaft portion and the distal shaft portion is lower than the brightness of the proximal sleeve portion of the inner balloon, the distal sleeve portion of the inner balloon, the proximal sleeve portion of the outer balloon, and the distal sleeve portion of the outer balloon, as described in [1].[3] The balloon catheter according to [1] or [2], wherein the position where the proximal sleeve portion of the inner balloon is connected to the proximal shaft portion is distal to or the same as the position where the proximal sleeve portion of the outer balloon is connected, and the position where the distal sleeve portion of the inner balloon is connected to the distal shaft portion is proximal to or the same as the position where the distal sleeve portion of the outer balloon is connected. [4] The balloon catheter according to any one of [1] to [3], wherein the length of the proximal sleeve portion of the outer balloon in the extending direction is the same as or longer than the length in the extending direction from the distal end of the proximal sleeve portion of the inner balloon to the position where the proximal sleeve portion of the inner balloon is directly or indirectly connected to the proximal shaft portion. [5] The balloon catheter according to any one of [1] to [4], wherein the length of the distal sleeve portion of the outer balloon in the extending direction is the same as or longer than the length of the distal sleeve portion of the inner balloon in the extending direction from the proximal end of the distal sleeve portion of the inner balloon to the position where the distal sleeve portion of the inner balloon is connected to the distal shaft portion. [6] The balloon catheter according to any one of [1] to [5], further comprising an outer shaft extending in the longitudinal direction, wherein the position of the distal end of the outer shaft is the same as or distal to the position of the proximal end of the proximal sleeve portion of the inner balloon and the position of the proximal end of the proximal sleeve portion of the outer balloon. [7] The balloon catheter according to [6], wherein the total light transmittance of the outer shaft measured according to JIS K 7361-1 is higher than the total light transmittance of the proximal sleeve portion of the inner balloon and the proximal sleeve portion of the outer balloon measured according to JIS K 7361-1. [8] The balloon catheter according to any one of [1] to [7], wherein the length in the longitudinal direction of the straight tube portion of the inner balloon is shorter than the length in the longitudinal direction of the straight tube portion of the outer balloon. [9] The balloon catheter according to any one of [1] to [8], wherein when the inner balloon and the balloon group are expanded, adjacent outer balloons constituting the balloon group are in contact with each other.

[10] A balloon catheter according to any one of [1] to [9], wherein, when the inner balloon and the balloon group are expanded, at least one of the multiple outer balloons constituting the balloon group is in contact with the outer surface of the inner balloon.

[11] A balloon catheter according to any one of [1] to

[10] , wherein, when the inner balloon and the balloon group are expanded, the maximum outer diameters of all the outer balloons constituting the balloon group are the same, and the maximum outer diameter of the outer balloons is the same as the maximum outer diameter of the inner balloon.

[12] A balloon catheter according to any one of [1] to

[10] , wherein, when the balloon group is expanded, there are two or more outer balloons constituting the balloon group that have different maximum outer diameters.

[13] A balloon catheter according to

[12] , wherein, when the inner balloon and the balloon group are expanded, two types of outer balloons with different maximum outer diameters are arranged circumferentially around the outer circumference of the inner balloon, and the outer balloon with the smaller maximum outer diameter is sandwiched between the outer balloons with the larger maximum outer diameter.

[14] A balloon catheter according to any one of [1] to

[10] , wherein, when the inner balloon and the balloon group are expanded, the maximum outer diameters of all the outer balloons constituting the balloon group are the same, and the maximum outer diameter of the outer balloons is different from the maximum outer diameter of the inner balloon.

[15] A balloon catheter according to

[14] , wherein the maximum outer diameter of the outer balloons constituting the balloon group is smaller than the maximum outer diameter of the inner balloon.

[0008] According to this disclosure, when manufacturing a balloon catheter having a shaft extending longitudinally from the proximal to the distal end, an inner balloon positioned at the distal end of the shaft, and a balloon group consisting of a plurality of outer balloons arranged radially outward from the inner balloon and aligned circumferentially with the inner balloon, it is possible to provide a balloon catheter that can reduce the rate of defective balloon catheters due to welding defects.

[0009] Figure 1 is a side view (partially a fluoroscopic view) of a balloon catheter. Figure 2 is a magnified view of the balloon shown in Figure 1. Figure 3 is a cross-sectional view of the balloon shown in Figure 1 at position III-III. Figure 4 is a cross-sectional view of a balloon different from the balloons shown in Figures 1 and 2. Figure 5 is a cross-sectional view of a balloon different from the balloons shown in Figures 1 and 2.

[0010] An embodiment of a balloon catheter comprises: a shaft extending longitudinally from proximal to distal; an inner balloon positioned at the distal end of the shaft; and a balloon group consisting of a plurality of outer balloons arranged radially outward from the inner balloon and aligned circumferentially with respect to the inner balloon, wherein the inner balloon and the outer balloon each have a straight tube portion, a proximal tapered portion located proximal to the straight tube portion, a proximal sleeve portion located proximal to the proximal tapered portion, a distal tapered portion located distal to the straight tube portion, and a distal sleeve portion located distal to the distal tapered portion, respectively; the shaft has a proximal shaft portion located proximal to the inner balloon and a distal shaft portion located distal to the inner balloon, and the distal sleeve portion of the inner balloon and the distal sleeve portion of the outer balloon are each connected to the distal shaft portion. The gist of this invention is that the proximal sleeve portion of the outer balloon is connected to the proximal shaft portion, and the total light transmittance measured according to JIS K 7361-1 for the proximal shaft portion and the distal shaft portion is lower than the total light transmittance measured according to JIS K 7361-1 for the proximal sleeve portion of the inner balloon, the distal sleeve portion of the inner balloon, the proximal sleeve portion of the outer balloon, and the distal sleeve portion of the outer balloon.

[0011] The balloon catheter will be described in detail below with reference to the drawings, but the contents of this disclosure are not limited to the illustrated examples, and modifications can be made to the extent that they are in line with the spirit described above and below, and all such modifications are included in the technical scope of this disclosure. In each drawing, hatching and reference numerals may be omitted for convenience, in which case refer to the specification or other drawings. Also, the dimensions of various parts in the drawings may differ from the actual dimensions, as priority is given to helping to understand the features of this disclosure.

[0012] Figure 1 is a side view (partially a fluoroscopic view) showing an embodiment of a balloon catheter. Hereafter, the same components will be denoted by the same reference numerals to avoid redundant explanations. Figure 2 is an enlarged view of the balloon shown in Figure 1. Figure 3 is a cross-sectional view of the balloon shown in Figure 1 at the line III-III. In Figures 1 and 2, the left side of the figure is the proximal side (operator side), and the right side is the distal side (affected area side).

[0013] The balloon catheter 1 has a shaft 10 extending longitudinally x from the proximal to the distal end, and an inner balloon A and a plurality of outer balloons b1 to b4 etc. arranged at the distal end of the shaft 10. In this specification, the plurality of outer balloons b1 to b4 etc. may be collectively referred to as "balloon group B". In this specification, the inner balloon A and balloon group B may be collectively referred to as "balloon 2". The plurality of outer balloons b1 to b4 etc. are arranged radially outward of the inner balloon A, aligned in the circumferential direction z of the inner balloon A.

[0014] The shaft 10 has a longitudinal direction x, a radial direction y connecting the centroid of the outer edge of the shaft 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 shaft 10 in a cross section perpendicular to the longitudinal direction x. In this specification, the direction toward the user's hand in the longitudinal direction x is referred to as the proximal side, and the direction opposite to the proximal side, i.e., toward the person being treated, is referred to as the distal side. Other members and parts 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 shaft 10. However, for ease of understanding, in this specification, all members and parts are described as having the same longitudinal direction x, radial direction y, and circumferential direction z as the shaft 10.

[0015] The shaft 10 has a proximal shaft portion 10p located proximal to the inner balloon A, and a distal shaft portion 10d located distal to the inner balloon A.

[0016] As shown in Figure 2, the inner balloon A has a straight tube section 23, a proximal tapered section 22 located proximal to the straight tube section 23, a distal tapered section 24 located distal to the straight tube section 23, a proximal sleeve section 21 located proximal to the proximal tapered section 22, and a distal sleeve section 25 located distal to the distal tapered section 24.

[0017] As shown in Figure 2, each outer balloon constituting balloon group B has a straight tube section 23, a proximal tapered section 22 located proximal to the straight tube section 23, a distal tapered section 24 located distal to the straight tube section 23, a proximal sleeve section 21 located proximal to the proximal tapered section 22, and a distal sleeve section 25 located distal to the distal tapered section 24.

[0018] As shown in Figure 2, the distal sleeve portion 25 of the inner balloon A and the distal sleeve portion 25 of the outer balloon are connected to the distal shaft portion 10d, respectively. As shown in Figure 2, the proximal sleeve portion 21 of the outer balloon is connected to the proximal shaft portion 10p.

[0019] The balloon catheter 1 has a total light transmittance of the proximal shaft portion 10p and distal shaft portion 10d measured according to JIS K 7361-1 which is lower than the total light transmittance of the proximal sleeve portion 21 of the inner balloon A, the distal sleeve portion 25 of the inner balloon A, the proximal sleeve portion 21 of the outer balloon, and the distal sleeve portion 25 of the outer balloon measured according to JIS K 7361-1. Thus, because the total light transmittance of the proximal and distal shaft portions 10p and 10d is lower than the total light transmittance of the proximal sleeve portion 21 and the distal sleeve portion 25 of the inner and outer balloons, the shaft 10 can be seen through the sleeve portions of the inner and outer balloons when welding the shaft 10 to the sleeve portions of the inner and outer balloons. As welding progresses and the air between the shaft 10 and the sleeve portions 21 and 25 disappears, the refraction of light changes, and when welding is complete, the color of the shaft 10 appears darker through the sleeve portions 21 and 25. By visually observing this change in color, it is possible to confirm that welding between the shaft 10 and the sleeve portions 21 and 25 is complete, thereby reducing the rate of defective balloon catheters 1 due to welding defects.

[0020] The total light transmittance of the proximal shaft portion 10p and the distal shaft portion 10d, measured according to JIS K 7361-1, may be 10% or more smaller, preferably 20% or more smaller, more preferably 30% or more smaller, and may be 70% or less smaller than the total light transmittance of the proximal sleeve portion 21 of the inner balloon A, the distal sleeve portion 25 of the inner balloon A, the proximal sleeve portion 21 of the outer balloon, and the distal sleeve portion 25 of the outer balloon, measured according to JIS K 7361-1.

[0021] The total light transmittance of the proximal shaft portion 10p, measured according to JIS K 7361-1, may be, for example, 1 to 30%. The total light transmittance of the distal shaft portion 10d, measured according to JIS K 7361-1, may be, for example, 1 to 30%. The total light transmittance of the proximal sleeve portion 21 of the inner balloon A, measured according to JIS K 7361-1, may be, for example, 60 to 90%. The total light transmittance of the distal sleeve portion 25 of the inner balloon A, measured according to JIS K 7361-1, may be, for example, 60 to 90%. The total light transmittance of the proximal sleeve portion 21 of the outer balloon, measured according to JIS K 7361-1, may be, for example, 60 to 90%. The total light transmittance of the distal sleeve portion 25 of the outer balloon, measured according to JIS K 7361-1, may be, for example, 60 to 90%.

[0022] The brightness of the proximal shaft portion 10p and distal shaft portion 10d of the balloon catheter 1 may be lower than the brightness of the proximal sleeve portion 21 of the inner balloon A, the distal sleeve portion 25 of the inner balloon A, the proximal sleeve portion 21 of the outer balloon, and the distal sleeve portion 25 of the outer balloon. This makes it easier to observe the color change when the shaft 10 is welded to the sleeve portions 21 and 25 of the inner and outer balloons, and allows for efficient welding of the shaft 10 to the sleeve portions 21 and 25. Brightness is expressed according to JIS Z 8721.

[0023] The difference between the brightness of the proximal shaft portion 10p and the distal shaft portion 10d as expressed in accordance with JIS Z 8721 and the brightness of the proximal sleeve portion 21 of the inner balloon A, the distal sleeve portion 25 of the inner balloon A, the proximal sleeve portion 21 of the outer balloon, and the distal sleeve portion 25 of the outer balloon as expressed in accordance with JIS Z 8721 may be 3 or more, preferably 5 or more, more preferably 7 or more, and may be 9 or less.

[0024] As shown in Figure 2, in the balloon catheter 1, the most proximal position xp1 to which the proximal sleeve portion 21 of the inner balloon A is connected in the proximal shaft portion 10p is distal to or the same as the most proximal position xp2 to which the proximal sleeve portion 21 of the outer balloon is connected, and the most distal position xd1 to which the distal sleeve portion 25 of the inner balloon A is connected in the distal shaft portion 10d is proximal to or the same as the most distal position xd2 to which the distal sleeve portion 25 of the outer balloon is connected.

[0025] The position xp1 where the proximal sleeve portion 21 of the inner balloon A is connected to the proximal shaft portion 10p is distal to the position xp2 where the proximal sleeve portion 21 of the outer balloon is connected, and the position xd1 where the distal sleeve portion 25 of the inner balloon A is connected to the distal shaft portion 10d is proximal to the position xd2 where the distal sleeve portion 25 of the outer balloon is connected. As a result, the position xp1 where the proximal sleeve portion 21 of the inner balloon A is connected to the proximal shaft portion 10p and the position xp2 where the proximal sleeve portion 21 of the outer balloon is connected to the proximal shaft portion 10p are at different positions in the longitudinal direction x, and the position xd1 where the distal sleeve portion 25 of the inner balloon is connected to the distal shaft portion 10d and the position xd2 where the distal sleeve portion 25 of the outer balloon is connected to the distal shaft portion 10d are at different positions in the longitudinal direction x. As a result, the welding state between the inner balloon A and the shaft 10, and the welding state between the outer balloon and the shaft 10 can be checked individually, thereby reducing the rate of defective balloon catheters due to poor welding. In addition, it becomes easier to weld multiple outer balloons to the shaft 10 after welding the inner balloon A to the shaft 10.

[0026] In the proximal shaft portion 10p, the position xp1 where the proximal sleeve portion 21 of the inner balloon A is connected and the position xp2 where the proximal sleeve portion 21 of the outer balloon is connected are at the same position in the longitudinal direction x. Similarly, in the distal shaft portion 10d, the position xd1 where the distal sleeve portion 25 of the inner balloon A is connected and the position xd2 where the distal sleeve portion 25 of the outer balloon is connected are at the same position in the longitudinal direction x. As a result, the proximal sleeve portion 21 of the inner balloon A, the proximal sleeve portion 21 of the outer balloon, and the proximal shaft portion 10p can be welded simultaneously, and the distal sleeve portion 25 of the inner balloon A, the distal sleeve portion 25 of the outer balloon, and the distal shaft portion 10d can be welded simultaneously. Consequently, the welding state between the inner balloon A and the shaft 10 and the welding state between the outer balloon and the shaft 10 can be checked simultaneously, thereby reducing the rate of defective balloon catheters due to welding defects. Furthermore, the number of welding operations can be reduced, thereby increasing the manufacturing efficiency of the balloon catheter 1.

[0027] The length of the proximal sleeve portion 21 of the outer balloon in the extending direction may be the same as, or longer than, the length of the proximal sleeve portion 21 of the inner balloon A from its distal end 21b to position xp1 where the proximal sleeve portion 21 of the inner balloon A is directly or indirectly connected to the proximal shaft portion 10p. By having the length of the proximal sleeve portion 21 of the outer balloon in the extending direction be the same as the length of the proximal sleeve portion 21 of the inner balloon A from its distal end 21b to position xp1 where the proximal sleeve portion 21 of the inner balloon A is directly or indirectly connected to the proximal shaft portion 10p, the strength applied to the sleeve portion becomes constant, making it less susceptible to damage. The length of the proximal sleeve portion 21 of the outer balloon in the extending direction is longer than the length of the proximal sleeve portion 21 of the inner balloon A from the distal end 21b of the proximal sleeve portion 21 of the inner balloon A to position xp1 where the proximal sleeve portion 21 of the inner balloon A is directly or indirectly connected to the proximal shaft portion 10p. This makes it easier to weld multiple outer balloons to the shaft 10 after welding the inner balloon A to the shaft. The proximal sleeve portion 21 of the inner balloon A may be directly connected to the proximal shaft portion 10p, or it may be indirectly connected to the proximal shaft portion 10p. If the proximal sleeve portion 21 of the inner balloon A is indirectly connected to the proximal shaft portion 10p, for example, the proximal sleeve portion 21 may be connected to an inflation tube, and this inflation tube may be connected to the proximal shaft portion 10p.

[0028] The length of the distal sleeve portion 25 of the outer balloon in the extending direction may be the same as, or longer than, the length of the distal sleeve portion 25 of the inner balloon A from the proximal end 25a to the position xd1 where the distal sleeve of the inner balloon A is connected to the distal shaft portion 10d. By making the length of the distal sleeve portion 25 of the outer balloon in the extending direction the same as the length of the distal sleeve portion 25 of the inner balloon A from the proximal end 25a to the position xd1 where the distal sleeve of the inner balloon A is connected to the distal shaft portion 10d, the strength applied to the sleeve portion becomes constant, making it less susceptible to damage. The length of the distal sleeve portion 25 of the outer balloon in the extending direction is longer than the length of the distal sleeve portion 25 of the inner balloon A from the proximal end 25a to the position xd1 where the distal sleeve of the inner balloon A is connected to the distal shaft portion 10d. This makes it easier to weld multiple outer balloons to the shaft 10 after welding the inner balloon A to the shaft 10.

[0029] The length of the proximal sleeve portion 21 of the outer balloon in the extending direction is the same as, or may be longer than, the length of the proximal sleeve portion 21 of the inner balloon A from the distal end 21b to position xp1 where the proximal sleeve of the inner balloon A is directly or indirectly connected to the proximal shaft portion 2, and the length of the distal sleeve portion 25 of the outer balloon in the extending direction is the same as, or may be longer than, the length of the distal sleeve portion 25 of the outer balloon from the proximal end 25a to position xd1 where the distal sleeve of the inner balloon A is connected to the distal shaft portion 10d.

[0030] As shown in Figure 2, the balloon catheter 1 further has an outer shaft 80 extending in the longitudinal direction x, and the distal end 80b of the outer shaft 80 may be at the same position as the proximal end 21a of the proximal sleeve portion 21 of the inner balloon A and the proximal end 21a of the proximal sleeve portion 21 of the outer balloon, or it may be distal. This allows the outer shaft 80 to protect the proximal welded portion between the inner and outer balloons and the shaft 10, thereby increasing the strength of the welded portion and improving pushability.

[0031] If the balloon catheter 1 has an outer shaft 80, the total light transmittance of the outer shaft 80, as measured according to JIS K 7361-1, may be higher than the total light transmittance of the proximal sleeve portion 21 of the inner balloon A and the proximal sleeve portion 21 of the outer balloon, as measured according to JIS K 7361-1. In this way, because the total light transmittance of the outer shaft 80 is higher than the total light transmittance of the proximal sleeve portions 21 of the inner and outer balloons, when the outer shaft 80 and the proximal sleeve portions 21 of the inner and outer balloons are welded together, the proximal sleeve portions 21 of the inner and outer balloons can be seen through the outer shaft 80. As welding progresses, the air between the outer shaft 80 and the proximal sleeve portions 21 of the inner and outer balloons decreases, changing the refraction of light. When welding is complete, the color of the proximal shaft 10p appears darker through the outer shaft 80 and the proximal sleeve portions 21 of the inner and outer balloons. By visually observing this color change, it is possible to confirm that the welding between the outer shaft 80, the sleeve portion 21 of the inner and outer balloons, and the proximal shaft 10p has been completed, thereby reducing the rate of defective balloon catheters due to poor welding.

[0032] The total light transmittance of the outer shaft 80, measured according to JIS K 7361-1, may be 10% or more greater, preferably 20% or more greater, more preferably 30% or more greater, and may be 70% or less greater than the total light transmittance of the proximal sleeve portion 21 of the inner balloon A and the proximal sleeve portion 21 of the outer balloon, measured according to JIS K 7361-1.

[0033] The total light transmittance of the outer shaft 80, measured according to JIS K 7361-1, may be 10% or more greater than the total light transmittance of the proximal shaft portion 10p, preferably 20% or more greater, more preferably 30% or more greater, and may be 70% or less greater. For example, the color of the proximal shaft portion may be blue and the color of the outer shaft may be yellow.

[0034] As shown in Figure 2, the length ALe of the straight tube portion 23 of the inner balloon A in the longitudinal direction x may be shorter than the length BLE of the straight tube portion 23 of the outer balloon in the longitudinal direction x. This allows the positions of the tapered portion of the inner balloon A and the tapered portion of the outer balloon to be offset in the longitudinal direction x, thereby reducing the outer diameter when the balloon 2 is deflated and reducing the extraction load.

[0035] The length ALe of the straight tube portion 23 of the inner balloon A 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 BLE of the straight tube portion 23 of the outer balloon in the longitudinal direction x. The length ALe of the straight tube portion 23 of the inner balloon A in the longitudinal direction x is preferably 20% or more, more preferably 25% or more, and even more preferably 30% or more of the length BLE of the straight tube portion 23 of the outer balloon in the longitudinal direction x. That is, the length ALe of the straight tube portion 23 of the inner balloon A in the longitudinal direction x may be 20 to 95%, 25 to 90%, or 30 to 85% of the length BLE of the straight tube portion 23 of the outer balloon in the longitudinal direction x.

[0036] The length ALe of the straight tube portion 23 of the inner balloon A in the longitudinal direction x may be, for example, 10 to 30 mm, 15 to 25 mm, or 18 to 23 mm. The length BLE of the straight tube portion 23 of the outer balloon in the longitudinal direction x may be, for example, 30 to 50 mm, 25 to 45 mm, or 28 to 43 mm.

[0037] As shown in Figures 1 to 3, the balloon catheter 1 has multiple outer balloons, and the multiple outer balloons (balloon group B) are arranged radially outward from the inner balloon A, aligned in the circumferential direction z of the inner balloon A. The arrangement of the inner balloon A and balloon group B will be explained using Figures 3, 4, and 5. Figure 3 is a cross-sectional view of the balloon 2 shown in Figures 1 and 2 at the position of line III-III. Figures 4 and 5 are cross-sectional views of the balloon 2 at the position of line III-III with a different configuration from the balloon 2 shown in Figures 1 and 2.

[0038] The balloon catheter 1 shown in Figure 3 consists of one inner balloon A and six outer balloons, with the six outer balloons forming balloon group B. In Figure 3, for the sake of explanation, four of the six outer balloons are labeled b1 to b4. When inner balloon A and outer balloon b1 are expanded, the maximum outer diameter of inner balloon A is denoted as Da, and the maximum outer diameter of outer balloon b1 is denoted as Db1 (the same applies hereafter).

[0039] The balloon catheter 1 shown in Figure 4 consists of one inner balloon A and eight outer balloons, with the eight outer balloons forming balloon group B. In Figure 4, for the sake of explanation, four of the eight outer balloons are labeled b11 to b14.

[0040] The balloon catheter 1 shown in Figure 5 consists of one inner balloon A and 20 outer balloons, with the 20 outer balloons forming balloon group B. In Figure 5, for the sake of explanation, three of the 20 outer balloons are labeled b21 to b23.

[0041] As shown in Figure 3, the balloon catheter 1 has a balloon group B consisting of multiple outer balloons located radially outward of the inner balloon A and circumferentially z-directly of the inner balloon A. By expanding both the inner balloon A and the balloon group B, the outer diameter of the balloon 2 can be increased. As a result, the stenotic portion can be reliably expanded.

[0042] As shown in Figure 3, when the inner balloon A and balloon group B of the balloon catheter 1 are expanded, it is preferable that adjacent outer balloons b1 and b2 among the multiple outer balloons constituting the balloon group B are in contact with each other. When adjacent outer balloons b1 and b2 are in contact with each other, the outer balloons suppress each other's expansion, thereby increasing pressure resistance and thus increasing the expansion force of balloon group B. In addition, when adjacent outer balloons b1 and b2 are in contact with each other, even if balloon group B comes into contact with the stenosis, it is less likely to shift in the circumferential direction z of the outer circumference of the inner balloon A, so that the stenosis can be reliably expanded.

[0043] When the inner balloon A and balloon group B are expanded, the multiple outer balloons constituting balloon group B only need to have at least one pair of adjacent outer balloons in contact with each other, preferably two or more pairs of adjacent outer balloons in contact with each other, and more preferably all adjacent outer balloons in contact with each other. When all adjacent outer balloons are in contact with each other, the outer balloons can be expanded uniformly.

[0044] When the inner balloon A and balloon group B are expanded, the outer balloons constituting balloon group B do not need to be in contact with the outer surface of the inner balloon A, but it is preferable that at least one of the multiple outer balloons constituting balloon group B is in contact with the outer surface of the inner balloon A. Because at least one of the multiple outer balloons is in contact with the outer surface of the inner balloon A, even if the outer balloon is pressed against the constricted area, the outer balloon remains in contact with the outer surface of the inner balloon A, making it less likely for the outer balloon to shift in the radial direction y of the inner balloon A, and ensuring that the constricted area is reliably expanded. It is even more preferable that all of the multiple outer balloons constituting balloon group B are in contact with the outer surface of the inner balloon A. Because all of the multiple outer balloons are in contact with the outer surface of the inner balloon A, even if the outer balloon is pressed against the constricted area, the inner balloon A and the outer balloons expand against each other, thus enabling balloon group B to withstand high pressure.

[0045] The number of outer balloons constituting the balloon group B is preferably 3 or more, more preferably 4 or more, and still more preferably 5 or more. By setting the lower limit of the number of outer balloons constituting the balloon group B within the above range, the balloon group B can easily surround the outer circumference of the inner balloon A, and the balloon group B can easily suppress the expansion of the inner balloon A. As a result, when fluid is introduced into both the inner balloon A and the balloon group B, the inner balloon A and the outer balloons mutually suppress each other's expansion, whereby the pressure resistance of the balloon 2 is increased, the hardness of the balloon 2 is increased, and the expansion force can be improved. In addition, since the inner balloon A and the outer balloons mutually suppress each other's expansion, the balloon 2 becomes less likely to inflate. Therefore, even when a high pressure is applied to the balloon 2, overexpansion of the balloon 2 is suppressed, the balloon 2 is prevented from inflating beyond a target outer diameter, damage to a luminal tissue in a living body such as an aortic valve is reduced, and safety can be improved. The upper limit of the number of outer balloons constituting the balloon group B is not particularly limited, but for example, it is preferably 20 or less, more preferably 12 or less, still more preferably 10 or less, and particularly preferably 8 or less. By setting the upper limit of the number of outer balloons constituting the balloon group B within the above range, the outer balloons constituting the balloon group B are less likely to shift in the radial direction y and the circumferential direction z of the inner balloon A, and the balloon group B can easily suppress the expansion of the inner balloon A.

[0046] When the inner balloon A and the balloon group B are expanded, the maximum outer diameter of the circumscribed circle of the balloon 2 is not particularly limited, but for example, a range of 5 mm to 60 mm is preferred.

[0047] The relationship between the maximum outer diameter of the inner balloon A and the maximum outer diameter of the outer balloons constituting the balloon group B is preferably any one of the following (1) to (3), for example. (1) When the inner balloon A and the balloon group B are expanded, all of the outer balloons constituting the balloon group B have the same maximum outer diameter, and the maximum outer diameter of the outer balloons is the same as the maximum outer diameter of the inner balloon A. (2) When the balloon group B is expanded, there are two or more types of outer balloons constituting the balloon group B having different maximum outer diameters. (3) When the inner balloon A and the balloon group B are expanded, all of the outer balloons constituting the balloon group B have the same maximum outer diameter, and the maximum outer diameter of the outer balloons is different from the maximum outer diameter of the inner balloon A.

[0048] The maximum outer diameter of the inner balloon A refers to the maximum equivalent circular diameter of the inner balloon A in a cross section perpendicular to the longitudinal direction x of the inner balloon A. The maximum outer diameter of the outer balloon refers to the maximum equivalent circular diameter of the outer balloon in a cross section perpendicular to the longitudinal direction x of the outer balloon.

[0049] (1) will be described with reference to FIG. 3. As shown in FIG. 3, when the inner balloon A and the balloon group B are expanded, all of the outer balloons constituting the balloon group B have the same maximum outer diameter, and the maximum outer diameter of the outer balloons is the same as the maximum outer diameter of the inner balloon A. This makes it easy to achieve a balance between the force by which the inner balloon A attempts to expand and the force by which the expansion of the outer balloon attempts to suppress the expansion of the inner balloon A. As a result, the hardness of the inner balloon A and the balloon group B increases, the expansion force of the balloon group B can be easily increased, and the stenotic site can be uniformly expanded.

[0050] When the maximum outer diameter of inner balloon A and all outer balloons are the same, the maximum outer diameter of inner balloon A and the outer balloons is preferably, for example, 3 mm to 8 mm. When the maximum outer diameters of the multiple outer balloons constituting balloon group B are all the same, it means that the maximum outer diameters of the multiple outer balloons constituting balloon group B are approximately the same, specifically that the maximum outer diameter of the outer balloon with the largest maximum outer diameter among the outer balloons constituting balloon group B is 100% to 110% of the maximum outer diameter of the outer balloon with the smallest maximum outer diameter among the outer balloons constituting balloon group B. When the maximum outer diameter of inner balloon A is the same as the maximum outer diameter of the multiple outer balloons constituting balloon group B, it means that the maximum outer diameter of inner balloon A and the maximum outer diameters of the multiple outer balloons constituting balloon group B are approximately the same, specifically that the maximum outer diameter of inner balloon A is 90% to 110% of the maximum outer diameter (for example, the average value) of the outer balloons.

[0051] (2) will be explained using Figure 4. As shown in Figure 4, when balloon group B is expanded, since there are two or more outer balloons with different maximum outer diameters that make up balloon group B, multiple outer balloons with different maximum outer diameters are arranged in the circumferential direction z of the outer circumference of inner balloon A. As a result, the outer balloons b11 and b12 with the larger maximum outer diameters of balloon group B come into contact with the inner wall of the blood vessel, while the outer balloons b13 and b14 with the smaller maximum outer diameters do not come into contact with the inner wall of the blood vessel. Therefore, a space is easily created between the inner wall of the blood vessel and the outer balloons b13 and b14 that do not come into contact with the inner wall of the blood vessel, allowing blood to perfuse. In addition, because the outer balloons b11 and b12 with the larger maximum outer diameters of balloon group B come into contact with the inner wall of the blood vessel, the number of outer balloons in contact with the inner wall of balloon group B is limited to a portion, so the contact points between the outer balloons and the inner wall of the blood vessel are reduced, and the stress applied from the outer balloons to the inner wall of the blood vessel can be concentrated. As a result, the stenosis can be reliably expanded.

[0052] As shown in Figure 4, when balloon group B consists of at least three outer balloons, and when inner balloon A and balloon group B are expanded, two types of outer balloons b with different maximum outer diameters are arranged in the circumferential direction z radially outward from inner balloon A, it is preferable that the outer balloon b13 with the smaller maximum outer diameter is sandwiched between the outer balloons b11 and b12 with the larger maximum outer diameters. By sandwiching the outer balloon b13 with the smaller maximum outer diameter between the outer balloons b11 and b12 with the larger maximum outer diameters in the circumferential direction z radially outward from inner balloon A, the space formed between the inner wall of the blood vessel and the outer balloon that does not contact the inner wall of the blood vessel is distributed in the circumferential direction z on the outer circumference of inner balloon A, thereby enabling stable blood perfusion.

[0053] When balloon group B is expanded, the maximum outer diameter of the multiple outer balloons constituting balloon group B may be, for example, two different sizes, three different sizes, or four or more different sizes. In particular, it is preferable that the maximum outer diameter of the outer balloons constituting balloon group B be two different sizes.

[0054] As shown in Figure 4, when the inner balloon A and balloon group B are expanded, if there are two types of outer balloons constituting balloon group B with different maximum outer diameters, the ratio of the maximum outer diameter Db11 of the outer balloon b11 with a larger maximum outer diameter to the maximum outer diameter Db13 of the outer balloon b13 with a smaller maximum outer diameter (Db11 / Db13) is preferably greater than 1 and 5 or less, more preferably 1.1 or more, even more preferably greater than 1.1, particularly preferably 2 or more, most preferably 2.5 or more, more preferably 4.5 or less, and even more preferably 4 or less. That is, the ratio of the maximum outer diameter Db11 to the maximum outer diameter Db13 (Db11 / Db13) may be greater than 1 and 5 or less, may be between 1.1 and 4.5, may be greater than 1.1 and 4 or less, may be between 2 and 4, or may be between 2.5 and 4.

[0055] As shown in Figure 4, when the inner balloon A and balloon group B are expanded, if there are two types of outer balloons constituting balloon group B with different maximum outer diameters, the maximum outer diameter Db13 of the outer balloon b13 with the smaller maximum outer diameter is preferably, for example, 3 mm to 5 mm, and the maximum outer diameter Db11 of the outer balloon b11 with the larger maximum outer diameter is preferably, for example, 3.1 mm to 25 mm (particularly greater than 3.3 mm and 25 mm or less).

[0056] (3) will be explained using Figure 5. As shown in Figure 5, when the inner balloon A and balloon group B are expanded, the maximum outer diameters of the multiple outer balloons constituting balloon group B are all the same, but the maximum outer diameter of the outer balloons is different from the maximum outer diameter of the inner balloon A. This makes it easier to adjust the maximum outer diameter of balloon group B by appropriately combining and adjusting the inner balloon A and the outer balloons which have different maximum outer diameters. The fact that the maximum outer diameters of the multiple outer balloons constituting balloon group B are all the same means that the maximum outer diameters of the multiple outer balloons constituting balloon group B are approximately the same. Specifically, this means that the maximum outer diameter of the outer balloon with the largest maximum outer diameter among the outer balloons constituting balloon group B is between 100% and 110% of the maximum outer diameter of the outer balloon with the smallest maximum outer diameter among the outer balloons constituting balloon group B.

[0057] In case (3), when the inner balloon A and balloon group B are expanded, the maximum outer diameter of the multiple outer balloons constituting balloon group B may be larger than or smaller than the maximum outer diameter of the inner balloon A, but it is preferable that it be smaller. By making the maximum outer diameter of the multiple outer balloons constituting balloon group B smaller than the maximum outer diameter of the inner balloon A, the inner balloon A can be expanded at high pressure, thereby ensuring that the constricted area is expanded.

[0058] When the maximum outer diameter of the multiple outer balloons constituting balloon group B is greater than the maximum outer diameter of inner balloon A, the ratio of the maximum outer diameter Db21 of outer balloon b21 to the maximum outer diameter Da of inner balloon A (Db21 / Da) is preferably greater than 1 and 4.5 or less, more preferably 1.1 or more, even more preferably greater than 1.1, particularly preferably 1.2 or more, more preferably 4 or less, and even more preferably 3 or less. That is, the ratio of the maximum outer diameter Db21 to the maximum outer diameter Da (Db21 / Da) may be greater than 1 and 4.5 or less, 1.1 to 4, greater than 1.1 and 3 or less, or 1.2 to 3.

[0059] When the maximum outer diameter of the multiple outer balloons constituting balloon group B is greater than the maximum outer diameter of inner balloon A, the maximum outer diameter Da of inner balloon A is preferably, for example, 3 mm to 5 mm, and the maximum outer diameter Db21 of outer balloon b21 is preferably, for example, 3.1 mm to 13.5 mm (particularly greater than 3.3 mm and 13.5 mm or less).

[0060] When the maximum outer diameter of the multiple outer balloons constituting balloon group B is smaller than the maximum outer diameter of inner balloon A, the ratio of the maximum outer diameter Db21 of the outer balloon to the maximum outer diameter Da of inner balloon A (Db21 / Da) is preferably, for example, 0.01 or more and less than 1, more preferably 0.03 or more, even more preferably 0.05 or more, more preferably less than 0.9, even more preferably 0.2 or less, and particularly preferably 0.1 or less. That is, the ratio of the maximum outer diameter Db21 to the maximum outer diameter Da (Db21 / Da) may be, for example, 0.01 or more and less than 1, 0.03 or more and less than 0.9, 0.05 to 0.2, or 0.05 to 0.1.

[0061] When the maximum outer diameter of the multiple outer balloons constituting balloon group B is smaller than the maximum outer diameter of inner balloon A, the maximum outer diameter Da of inner balloon A is preferably, for example, 3 mm to 20 mm, and the maximum outer diameter Db21 of outer balloon b21 is preferably, for example, 1.0 mm to 5 mm.

[0062] Examples of materials that make up the inner balloon A and the outer balloon include polyolefin resins such as polyethylene, polypropylene, and ethylene-propylene copolymer; polyester resins such as polyethylene terephthalate and polyester elastomer; polyurethane resins such as polyurethane and polyurethane elastomer; polyphenylene sulfide resin; polyamide resins such as polyamide and polyamide elastomer; fluororesin; silicone resin; natural rubber such as latex rubber; and the like. Only one of these may be used, or two or more may be used in combination. In particular, at least one of polyamide resins, polyester resins, and polyurethane resins is preferred for the materials that make up the inner balloon A and the outer balloon.

[0063] For the materials constituting the inner balloon A and the outer balloon, it is preferable to use elastomer resins from the viewpoint of thinness and flexibility. For example, among polyamide resins, nylon 12 and nylon 11 are suitable as materials for constituting the inner balloon A and the outer balloon. Nylon 12 is more preferable because it can be molded relatively easily during blow molding. Furthermore, from the viewpoint of thinness and flexibility of the inner balloon A and the outer balloon, polyamide elastomers such as polyether ester amide elastomers and polyamide ether elastomers are preferably used. Among these, polyether ester amide elastomers are preferably used because they have high yield strength and provide good dimensional stability for the inner balloon A and the outer balloon.

[0064] The materials constituting the inner balloon A and the outer balloon may be the same, but are preferably different. When the pressure resistance value of the outer balloon is P2 and the pressure resistance value of the inner balloon A is P1, it is preferable to select the materials such that the pressure resistance value P2 of the outer balloon is greater than the pressure resistance value P1 of the inner balloon A. The materials constituting multiple outer balloons may each be different, but are preferably the same. By being the same, the degree of expansion and hardness of each outer balloon can be made to be of a similar degree.

[0065] Examples of materials that make up the shaft 10 include polyamide resin, polyester resin, polyurethane resin, polyolefin resin, fluororesin, vinyl chloride resin, silicone resin, natural rubber, etc. Only one of these may be used, or two or more may be used in combination. In particular, at least one of polyamide resin, polyolefin resin, and fluororesin is preferred as the material that makes up the shaft 10. By using any of polyamide resin, polyolefin resin, or fluororesin, the slipperiness of the surface of the shaft 10 is increased, which improves the insertion of the balloon catheter 1 into the blood vessel.

[0066] As shown in Figure 1, an example of a balloon catheter 1 is a so-called rapid exchange type balloon catheter 1, which has a guidewire port 50 located midway from the distal to the proximal end of the shaft 10, and a guidewire insertion passage from the guidewire port 50 to the distal end of the shaft 10. As shown in Figure 1, the balloon catheter 1 may also have a hub 5 at the proximal end, and the hub 5 may be provided with a fluid injection section 6 for injecting fluid to expand or deflate the balloon 2.

[0067] In the case of a rapid exchange type balloon catheter 1, the shaft 10 of the balloon catheter 1 preferably has a distal shaft and a proximal shaft positioned proximal to the distal shaft, and the distal shaft and the proximal shaft may be made of separate components. If the distal shaft and the proximal shaft are made of separate components, the proximal shaft may be made of resin or metal.

[0068] In the case of a rapid exchange type balloon catheter 1, the outer walls of the proximal shaft and / or distal shaft may be coated, or both the proximal and distal shafts may be coated. The coating can be hydrophilic or hydrophobic depending on the purpose, and can be applied by immersing the shaft 10 in a hydrophilic or hydrophobic coating agent, applying a hydrophilic or hydrophobic coating agent to the outer wall of the shaft 10, or covering the outer wall of the shaft 10 with a hydrophilic or hydrophobic coating agent. The coating agent may contain drugs or additives.

[0069] Examples of hydrophilic coating agents include hydrophilic polymers such as polyvinyl alcohol, polyethylene glycol, polyacrylamide, polyvinylpyrrolidone, and methyl vinyl ether maleic anhydride copolymer, or hydrophilic coating agents made from any combination thereof. Examples of hydrophobic coating agents include polytetrafluoroethylene (PTFE), ethylene fluoride propylene (FEP), perfluoroalkoxyalkanes (PFA), silicone oil, hydrophobic urethane resins, carbon coatings, diamond coatings, diamond-like carbon (DLC) coatings, ceramic coatings, and substances with low surface free energy terminated with alkyl groups or perfluoroalkyl groups.

[0070] Although not shown in the figures, the balloon catheter 1 may be a so-called over-the-wire type balloon catheter 1 having a guidewire insertion passage extending from the distal to the proximal end of the shaft 10. In the case of an over-the-wire type balloon catheter 1, it is preferable that the inflation lumen and guidewire lumen extend to a hub 5 located on the proximal end, and that the proximal opening of each lumen is provided in a bifurcated hub 5. In the case of an over-the-wire type balloon catheter 1, it is preferable that the outer wall of the shaft 10 is coated. For details on the materials and coatings constituting the shaft 10, refer to the description of the rapid-exchange type balloon catheter 1.

[0071] A tip member 60 may be provided at the distal end of the balloon catheter 1. The tip member 60 may be provided at the distal end of the balloon catheter 1 by being connected to the distal end of the inner balloon A as a separate member from the shaft 10, or the distal end of the shaft 10 may function as the tip member 60 by extending distally beyond the distal end 24d of the inner balloon A.

[0072] The balloon catheter 1 can be used, for example, to dilate blood vessels. The balloon catheter 1 can also be used, for example, to dilate the aortic valve, deform a bioprosthetic valve implanted in the heart, or destroy the bioprosthetic valve. Vascular stenosis can occur, for example, in the aortic valve. When stenosis occurs in the aortic valve, the aortic valve is removed and a new bioprosthetic valve is implanted. However, implanted bioprosthetic valves deteriorate over time and need to be replaced every 5 to 10 years. When a new bioprosthetic valve (artificial valve) is implanted transcatheterally due to deterioration of a surgically implanted bioprosthetic valve (artificial valve), the valve orifice area may become smaller. Therefore, the size of the new bioprosthetic valve must be smaller than the deteriorated bioprosthetic valve, leading to decreased blood flow, a pressure difference before and after the bioprosthetic valve, and a strain on the heart. Therefore, by using the balloon catheter 1 to deform or destroy a bioprosthetic valve implanted in the heart, a larger bioprosthetic valve can be implanted, improving the pressure difference before and after the bioprosthetic valve.

[0073] This application claims the benefit of priority based on Japanese Patent Application No. 2025-057073, filed on 28 March 2025. The entire contents of the specification of the above Japanese Patent Application No. 2025-057073 are incorporated herein by reference.

[0074] 1 Balloon catheter 2 Balloon 5 Hub 6 Fluid injection section 10 Shaft 10p Proximal shaft section 10d Distal shaft section 21 Proximal sleeve section 21a Proximal end of proximal sleeve section 21b Distal end of proximal sleeve section 22 Proximal tapered section 23 Straight section 24 Distal tapered section 24d Distal end of distal tapered section 25 Distal sleeve section 25a Proximal end of distal sleeve section 50 Guidewire port 60 Tip member 80 Outer shaft 80b Distal end of outer shaft A Inner balloon ALe Length of the straight section of the inner balloon in the longitudinal direction B Balloon group BLE Length of the straight section of the outer balloon in the longitudinal direction b1, b2, b3, b4, b11-b14, b21-b23 Outer balloon Da Maximum outer diameter of inner balloon Db1, Db2, Db11-Db14, Db21-Db23 Maximum outer diameter of outer balloon x Longitudinal direction xp1 Position where the proximal sleeve of the inner balloon is directly or indirectly connected to the proximal shaft xp2 Position where the proximal sleeve of the outer balloon is connected to the proximal shaft xd1 Position where the distal sleeve of the inner balloon is connected to the distal shaft xd2 Position where the distal sleeve of the outer balloon is connected to the distal shaft y Radial direction z Circumferential direction

Claims

1. A balloon catheter comprising: a shaft extending longitudinally from proximal to distal; an inner balloon positioned at the distal end of the shaft; and a balloon group comprising a plurality of outer balloons arranged radially outward from the inner balloon and aligned circumferentially with respect to the inner balloon, wherein the inner balloon and the outer balloon each have a straight section, a proximal tapered section located proximal to the straight section, a proximal sleeve section located proximal to the proximal tapered section, a distal tapered section located distal to the straight section, and a distal sleeve section located distal to the distal tapered section, respectively; the shaft has a proximal shaft section located proximal to the inner balloon and a distal shaft section located distal to the inner balloon, and the distal sleeve section of the inner balloon and the distal sleeve section of the outer balloon are each connected to the distal shaft section. A balloon catheter in which the proximal sleeve portion of the outer balloon is connected to the proximal shaft portion, and the total light transmittance of the proximal shaft portion and the distal shaft portion, as measured according to JIS K 7361-1, is lower than the total light transmittance of the proximal sleeve portion of the inner balloon, the distal sleeve portion of the inner balloon, the proximal sleeve portion of the outer balloon, and the distal sleeve portion of the outer balloon, as measured according to JIS K 7361-1.

2. The balloon catheter according to claim 1, wherein the brightness of the proximal shaft portion and the distal shaft portion is lower than the brightness of the proximal sleeve portion of the inner balloon, the distal sleeve portion of the inner balloon, the proximal sleeve portion of the outer balloon, and the distal sleeve portion of the outer balloon.

3. The balloon catheter according to claim 1 or 2, wherein the position where the proximal sleeve portion of the inner balloon is connected in the proximal shaft portion is distal to or the same as the position where the proximal sleeve portion of the outer balloon is connected, and the position where the distal sleeve portion of the inner balloon is connected in the distal shaft portion is proximal to or the same as the position where the distal sleeve portion of the outer balloon is connected.

4. The balloon catheter according to claim 1 or 2, wherein the length of the proximal sleeve portion of the outer balloon in the extending direction is the same as, or longer than, the length of the proximal sleeve portion of the inner balloon in the extending direction from the distal end of the proximal sleeve portion of the inner balloon to the position where the proximal sleeve portion of the inner balloon is directly or indirectly connected to the proximal shaft portion.

5. The balloon catheter according to claim 1 or 2, wherein the length of the distal sleeve portion of the outer balloon in the extending direction is the same as, or longer than, the length of the distal sleeve portion of the inner balloon in the extending direction from the proximal end of the distal sleeve portion of the inner balloon to the position where the distal sleeve portion of the inner balloon is connected to the distal shaft portion.

6. The balloon catheter according to claim 1 or 2, further comprising an outer shaft extending in the longitudinal direction, wherein the distal end of the outer shaft is located at the same position as, or distal to, the proximal end of the proximal sleeve portion of the inner balloon and the proximal end of the proximal sleeve portion of the outer balloon.

7. The balloon catheter according to claim 6, wherein the total light transmittance of the outer shaft, as measured according to JIS K 7361-1, is higher than the total light transmittance of the proximal sleeve portion of the inner balloon and the proximal sleeve portion of the outer balloon, as measured according to JIS K 7361-1.

8. The balloon catheter according to claim 1 or 2, wherein the length in the longitudinal direction of the straight tube portion of the inner balloon is shorter than the length in the longitudinal direction of the straight tube portion of the outer balloon.

9. The balloon catheter according to claim 1 or 2, wherein, when the inner balloon and the balloon group are expanded, adjacent outer balloons constituting the balloon group are in contact with each other.

10. The balloon catheter according to claim 1 or 2, wherein, when the inner balloon and the balloon group are expanded, at least one of the plurality of outer balloons constituting the balloon group is in contact with the outer surface of the inner balloon.

11. The balloon catheter according to claim 1 or 2, wherein, when the inner balloon and the balloon group are expanded, the maximum outer diameters of all the outer balloons constituting the balloon group are the same, and the maximum outer diameter of the outer balloons is the same as the maximum outer diameter of the inner balloon.

12. The balloon catheter according to claim 1 or 2, wherein, when the balloon group is expanded, there are two or more outer balloons constituting the balloon group that have different maximum outer diameters.

13. The balloon catheter according to claim 12, wherein, when the inner balloon and the balloon group are expanded, two types of outer balloons with different maximum outer diameters are arranged circumferentially around the outer circumference of the inner balloon, and the outer balloon with the smaller maximum outer diameter is sandwiched between the outer balloons with the larger maximum outer diameter.

14. The balloon catheter according to claim 1 or 2, wherein, when the inner balloon and the balloon group are expanded, the maximum outer diameters of all the outer balloons constituting the balloon group are the same, and the maximum outer diameter of the outer balloons is different from the maximum outer diameter of the inner balloon.

15. The balloon catheter according to claim 14, wherein the maximum outer diameter of the outer balloon constituting the balloon group is smaller than the maximum outer diameter of the inner balloon.

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