Balloon catheter and balloon catheter system

Abstract

In order to maintain a constant surface temperature of a balloon in a safe manner, this balloon catheter (15) comprises a balloon (25), an outer cylinder shaft (30) connected to the proximal end of the balloon, an inner cylinder shaft (35) passing through the outer cylinder shaft and connected to the distal end of the balloon, a heating member (40) for heating a liquid inside the balloon, a first temperature sensor (31) secured to an end of the heating member, and a liquid passage (LP) formed between the outer cylinder shaft and the inner cylinder shaft, and communicating with the interior of the balloon. The balloon can be expanded or loosened by movement of the inner cylinder shaft relative to the outer cylinder shaft, the heating member is arranged inside the balloon and is configured so as to be secured only to the outer cylinder shaft.

Description

Balloon catheter and balloon catheter system

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

[0002] Catheter ablation therapy is a treatment method in which a target site within the body is ablated using a catheter inserted into the body. For example, by destroying the target site through ablation, diseases such as arrhythmia due to atrial fibrillation, endometriosis, and cancer are treated. As disclosed in Patent Documents 1 and 2, balloon catheters having a balloon at the distal end are known as catheters used in catheter ablation therapy.

[0003] When the balloon catheter is inserted into the body, the balloon is deflated and stretched in the longitudinal direction of the balloon catheter. Next, a liquid is injected into the balloon catheter inserted into the body, causing the balloon to expand. The liquid inside the balloon is temperature-regulated, which allows the surface temperature of the balloon to be controlled. By contacting the balloon, which has been regulated to a predetermined surface temperature, with a circumferential target region, such as a vein connecting to the atrium, the circumferential target region can be ablated in one go.

[0004] Patent No. 3611799 Patent No. 4747141 WO2021 / 201078

[0005] In treatments using balloon catheters, it is important to accurately grasp the balloon's surface temperature and safely maintain a constant surface temperature. In this regard, the balloon catheters disclosed in Patent Documents 1 and 2 are equipped with a temperature sensor for measuring the balloon's surface temperature. Patent Document 1 uses a temperature sensor attached to the inner surface of the balloon. However, it is not easy to stably install a temperature sensor on the surface of a balloon that expands from a deflated state. In this regard, Patent Document 2 proposes a two-layer balloon structure with a temperature sensor located between the layers. However, due to practical manufacturing difficulties in terms of fabricating the balloon, installing the temperature sensor's heat-sensing unit, and handling the temperature sensor's lead wires, the balloon catheter of Patent Document 2 has not yet become widespread. In other words, it has been difficult to accurately determine the balloon's surface temperature with conventional balloon catheters.

[0006] Patent Document 3 proposes a catheter that measures the balloon surface temperature with high accuracy by placing a temperature sensor in the balloon catheter's fluid supply path. However, with this balloon catheter, the balloon surface temperature varies significantly depending on the contact state between the balloon and the object, making it difficult to maintain a constant balloon surface temperature. Patent Document 3 also describes a method for controlling the balloon surface temperature using a temperature sensor placed in the balloon catheter's fluid supply path. However, if the temperature of the heating element placed in the balloon differs significantly from the temperature of the balloon surface, it is difficult to obtain the desired balloon surface temperature from a safety standpoint.

[0007] The present invention has been made in consideration of the above points, and an object of the present invention is to provide a balloon catheter and a balloon catheter system that can safely maintain a constant surface temperature of the balloon.

[0008] As a result of intensive research to solve the above problems, the inventors have discovered the following inventions (1) to (3): (1) A balloon catheter comprising: a balloon, an outer cylindrical shaft connected to the proximal end of the balloon, an inner cylindrical shaft passing through the outer cylindrical shaft and connected to the distal end of the balloon, a heating element for heating a liquid within the balloon, a first temperature sensor fixed to an end of the heating element, and a liquid supply path formed between the outer cylindrical shaft and the inner cylindrical shaft and leading to the inside of the balloon, wherein the balloon can be expanded or relaxed by moving the inner cylindrical shaft relative to the outer cylindrical shaft, and the heating element is disposed within the balloon and fixed only to the outer cylindrical shaft. (2) A balloon catheter according to (1), wherein the outer cylindrical shaft has an extension extending into the balloon, and the heating element is fixed to the extension. (3) A balloon catheter system comprising: a balloon catheter according to (1) or (2); a supply device that supplies liquid to the liquid feed path; a stirring device that stirs the liquid in the balloon by repeatedly supplying liquid to the liquid feed path and discharging liquid from the liquid feed path; and a heating device that is electrically connected to the heating element and applies electrical energy to the heating element, wherein the heating device applies electrical energy to the heating element based on information related to the temperature acquired by the first temperature sensor.

[0009] According to the present invention, the surface temperature of the balloon can be safely maintained constant.

[0010] 1 is a diagram for explaining a first embodiment, showing a balloon catheter system and a balloon catheter.

[0023] FIG. 1 is a diagram showing the distal end portion of the balloon catheter of FIG. 1 with the balloon inflated.

[0024] FIG. 2 is a diagram showing the distal end portion of the balloon catheter of FIG. 1 with the balloon in a deflated and extended state.

[0025] A cross-sectional view taken along line IV-IV in FIG. 2. A cross-sectional view taken along line V-V in FIG. 2.

[0026] A diagram showing the distal end portion of the balloon catheter of FIG. 1 with the balloon inflated according to a second embodiment.

[0027] A diagram showing the distal end portion of the balloon catheter of FIG. 1 with the balloon inflated according to a third embodiment.

[0028] A diagram showing a comparative example of a balloon catheter in which a heating element is not fixed to the outer cylindrical shaft.

[0029] Temperature distribution at the distal end portion of a balloon catheter in a coaxial state, obtained by thermal fluid analysis using CAE. Temperature distribution at the distal end portion of a balloon catheter in a non-coaxial state, obtained by thermal fluid analysis using CAE.

[0029] A diagram for explaining an experimental method using a balloon catheter system.

[0029] A diagram showing the distal end portion of a balloon catheter, showing the catheter being pressed firmly against a treatment site. Graph showing measurement data of the difference between the temperature of the heating element and the surface temperature of the balloon. A diagram showing the distal end portion of a balloon catheter, illustrating the flow of liquid when discharging liquid from the liquid feed path into the balloon in a coaxial state. A diagram showing the distal end portion of a balloon catheter, illustrating the flow of liquid when aspirating liquid from inside the balloon into the liquid feed path in a coaxial state. A diagram showing the distal end portion of a balloon catheter, illustrating the flow of liquid when discharging liquid from the liquid feed path into the balloon in a non-coaxial state. A diagram showing the distal end portion of a balloon catheter, illustrating the flow of liquid when aspirating liquid from inside the balloon into the liquid feed path in a non-coaxial state. A diagram showing the distal end portion of a balloon catheter of a comparative example, illustrating the flow of liquid when aspirating liquid from inside the balloon into the liquid feed path in a coaxial state. A diagram showing the distal end portion of a balloon catheter of a comparative example, illustrating the flow of liquid when aspirating liquid from inside the balloon into the liquid feed path in a coaxial state. FIG. 10 is a diagram showing the distal end portion of a balloon catheter of a comparative example, illustrating the flow of liquid when liquid is discharged from the liquid delivery path into the balloon in a non-coaxial state.FIG. 10 is a diagram showing the distal end portion of a balloon catheter of a comparative example, illustrating the flow of liquid when liquid is aspirated from inside the balloon into the liquid feed path in a non-coaxial state.

[0011] An embodiment of the present invention will be described below with reference to the drawings. In this specification, terms such as "parallel," "orthogonal," and "identical," which specify shapes and geometric conditions and their degrees, as well as values ​​of lengths and angles, are not limited to their strict meanings but are interpreted to include a range within which similar functions can be expected.

[0012] 1 includes a balloon catheter 15, a control device 70, and a stirring device 75 connected to the balloon catheter 15. The balloon catheter 15 also includes a catheter body 20 having a longitudinal direction LD, and a handle 50 connected to the proximal end of the catheter body 20.

[0013] The catheter main body 20 shown in Fig. 2 includes a balloon 25, an outer cylindrical shaft 30 connected to the proximal end 25b of the balloon 25, an inner cylindrical shaft 35 connected to the distal end 25a of the balloon 25, a heating member 40 disposed within the balloon 25, and a first temperature sensor 31 connected to the proximal end 40a of the heating member 40. The inner cylindrical shaft 35 passes through the outer cylindrical shaft 30 and extends into the balloon 25. A liquid delivery path LP leading to the inside of the balloon 25 is formed proximally of the inside of the balloon 25 and between the outer cylindrical shaft 30 and the inner cylindrical shaft 35. The heating member 40 heats the liquid within the balloon 25.

[0014] The catheter main body 20 can accurately determine the surface temperature of the balloon 25 into which the heated liquid has been injected using a second temperature sensor 45 installed in the liquid supply path LP. In particular, the catheter main body 20 according to this embodiment is devised to maintain a constant surface temperature of the balloon 25 determined using the second temperature sensor 45. Specifically, by fixing the outer cylindrical shaft 30 and the heating member 40, the length DY between the heating member 40 and the proximal end 25b of the balloon 25 is always constant. Furthermore, the positional relationship between the hole 44 formed in the tapered transition portion 43a of the fixing member 43 and the heating member 40 is constant. This makes it possible to maintain a constant temperature between the temperature detected by the first temperature sensor 31 installed at the proximal end 40a of the heating member and the temperature detected by the second temperature sensor installed in the liquid supply path LP for determining the surface temperature of the balloon 25.

[0015] The longitudinal direction LD of the catheter main body 20 is specified as the direction in which the central axes of the outer cylindrical shaft 30 and the inner cylindrical shaft 35 extending from the outer cylindrical shaft 30 extend. In this specification, the "distal" side used with respect to each component of the balloon catheter 15 and the catheter main body 20 means the side away from the operator (surgeon) of the handle 50 and the balloon catheter 15 along the longitudinal direction LD of the catheter main body 20, or in other words, the tip side. In addition, the "proximal" side used with respect to each component of the balloon catheter 15 and the catheter main body 20 means the side close to the operator (surgeon) of the handle 50 and the balloon catheter 15 along the longitudinal direction LD of the catheter main body 20, or in other words, the base end side.

[0016] The balloon catheter system 10 and the balloon catheter 15 will now be described in detail. First, the catheter main body 20 constituting the balloon catheter 15 will be described in detail. As described above, the catheter main body 20 constituting the balloon catheter 15 according to this embodiment includes the balloon 25, the outer cylindrical shaft 30, the inner cylindrical shaft 35, the heating element 40, the first temperature sensor 31, and the second temperature sensor 45.

[0017] Of these, the outer cylindrical shaft 30 and the inner cylindrical shaft 35 are both configured as a tube, typically a cylinder. Therefore, the outer cylindrical shaft 30 and the inner cylindrical shaft 35 each form a lumen as an internal space. For example, a guidewire (not shown) can be inserted into the lumen formed by the inner cylindrical shaft 35. The inner cylindrical shaft 35 is inserted into the lumen formed by the outer cylindrical shaft 30. That is, the outer cylindrical shaft 30 and the inner cylindrical shaft 35 have a double-tube shaft configuration. The inner diameter of the outer cylindrical shaft 30 is larger than the outer diameter of the inner cylindrical shaft 35. Therefore, a lumen remains between the outer cylindrical shaft 30 and the inner cylindrical shaft 35. This lumen between the outer cylindrical shaft 30 and the inner cylindrical shaft 35 forms a liquid delivery path LP. As shown in FIG. 2 , the liquid delivery path LP communicates with the balloon 25. The liquid delivery path LP also extends into the handle 50.

[0018] The length of the outer cylindrical shaft 30 is preferably 500 mm or more and 1700 mm or less, and more preferably 600 mm or more and 1200 mm or less, and the length of the inner cylindrical shaft 35 is preferably 500 mm or more and 1700 mm or less, and more preferably 600 mm or more and 1200 mm or less. By making the outer cylindrical shaft 30 shorter than the inner cylindrical shaft 35 by 0 mm to 40 mm, the outer cylindrical shaft 30 can be used as an extension that extends into the interior of the balloon 25.

[0019] The outer cylindrical shaft 30 and the inner cylindrical shaft 35 are preferably made of a flexible material with excellent antithrombogenicity. Examples of flexible materials with excellent antithrombogenicity include, but are not limited to, fluoropolymers, polyamides, polyurethane-based polymers, and polyimides. Furthermore, the outer cylindrical shaft 30 is preferably made by laminating layers of different flexible materials to achieve both slidability with the inner cylindrical shaft 35 and adhesive or thermal welding properties with the balloon 25. Here, the outer diameter of the inner cylindrical shaft 35 is preferably 1.4 mm or more and 1.7 mm or less. The inner diameter of the inner cylindrical shaft 35 is preferably 1.1 mm or more and 1.3 mm or less.

[0020] A balloon 25 is connected to the side surface of the outer cylindrical shaft 30 and the tip of the inner cylindrical shaft 35. The balloon 25 is configured to be inflatable by injecting a liquid and to be deflated by discharging the liquid. The balloon 25 preferably has a shape that can fit the target site (e.g., a blood vessel) to be treated. As an example, a spherical shape with a diameter of 15 mm to 40 mm can be adopted as the shape of the balloon 25 that fits the pulmonary vein junction of the left atrium. Here, the spherical shape includes a perfect sphere, an oblate spheroid, an elongated spheroid, and a nearly spherical shape.

[0021] The thickness of the balloon 25 is preferably 10 μm or more and 200 μm or less. Furthermore, a stretchable material with excellent antithrombotic properties is preferred as the material for the balloon 25, and specifically, a polyurethane-based polymer material or the like can be used. Examples of polyurethane-based polymer materials that can be used for the balloon 25 include thermoplastic polyether urethane, polyether polyurethane urea, fluorine polyether urethane urea, polyether polyurethane urea resin, and polyether polyurethane urea amide.

[0022] 2 and 3, in the illustrated catheter main body 20, the distal end (tip) 25a of the balloon 25 is fixed to the distal end (tip) 35a of the inner cylindrical shaft 35. The proximal end (base end) 25b of the balloon 25 is fixed to the side surface of the outer cylindrical shaft 30. The balloon 25 can be connected to the outer cylindrical shaft 30 and the inner cylindrical shaft 35 by adhesive or thermal welding.

[0023] In the first embodiment, the proximal end (base end) 25b of the balloon 25 is fixed to the side surface of the outer cylindrical shaft 30, and the outer cylindrical shaft 30 extends beyond that into the interior of the balloon 25 to form an extension 36 of the outer cylindrical shaft 30. Here, the extension refers to the portion of the outer cylindrical shaft that extends into the balloon.

[0024] 2 and 3 , the outer cylindrical shaft 30 in the first embodiment may have the extension portion 36 formed as a separate member. In this case, the outer cylindrical shaft 30 is made up of a cylindrical intermediate member 46 and a fixing member 43 fixed to the distal end (tip) of the cylindrical intermediate member 46, and the fixing member 43 forms the extension portion 36 of the outer cylindrical shaft 30. In another embodiment, the outer cylindrical shaft 30 may be formed as an integral shaft.

[0025] Here, the outer diameter of the cylindrical intermediate member 46 is preferably 3.0 mm or more and 4.0 mm or less, and the inner diameter of the cylindrical intermediate member 46 is preferably 2.5 mm or more and 3.5 mm or less.

[0026] The fixing member 43 shown in Figures 2 and 3 has a large-diameter cylindrical portion 43b on the proximal side and a small-diameter cylindrical portion 43c on the distal side, with a tapered transition portion 43a between them that connects the large-diameter cylindrical portion and the small-diameter cylindrical portion.

[0027] In the fixing member 43, the outer diameter of the large-diameter cylindrical portion 43b, which is the portion connected to the cylindrical intermediate member 46, is preferably 3.0 mm or more and 4.0 mm or less, and the inner diameter of the large-diameter cylindrical portion 43b is preferably 2.5 mm or more and 3.5 mm or less. Furthermore, the outer diameter of the small-diameter cylindrical portion 43c, which fixes the heating member 40, is preferably 1.5 mm or more and 3.0 mm or less, and the inner diameter of the small-diameter cylindrical portion 43c is preferably 1.5 mm or more and 2.0 mm or less. Furthermore, the tapered transition portion 43a preferably has one or more holes 44 through which a conductor is passed and which serve as a liquid transfer path, and the hole 44 has a diameter of 0.5 mm or more. ２ More than 2 mm ２ The following is preferred:

[0028] The balloon 25 connected to the outer cylindrical shaft 30 and the inner cylindrical shaft 35 is deformed by the relative movement of the outer cylindrical shaft 30 and the inner cylindrical shaft 35 in the longitudinal direction LD. Furthermore, the balloon 25 can be stretched or relaxed by the relative movement of the outer cylindrical shaft 30 with respect to the inner cylindrical shaft 35, thereby adjusting the dimensions of the balloon 25 in the longitudinal direction LD. Here, "stretched" refers to a state in which the width of the balloon 25 in the longitudinal direction LD is stretched and tension is applied to the balloon 25, and "relaxed" refers to a state in which tension is not applied to the balloon 25.

[0029] As shown in Fig. 3, when the inner cylindrical shaft 35 moves distally in the longitudinal direction LD relative to the outer cylindrical shaft 30, the balloon 25 stretches in the longitudinal direction LD and becomes more tense. In the illustrated example, the range of distal movement of the inner cylindrical shaft 35 relative to the outer cylindrical shaft 30 in the longitudinal direction LD is restricted by the balloon 25. When the inner cylindrical shaft 35 moves proximally in the longitudinal direction LD relative to the outer cylindrical shaft 30 from the state shown in Fig. 3, the balloon 25 becomes relaxed.

[0030] Furthermore, by injecting a fluid into the relaxed balloon 25, the balloon 25 can be expanded as shown in FIG. 2, and the dimensions of the balloon 25 in the short direction can be adjusted.

[0031] Next, the heating member 40 will be described. The heating member 40 is disposed inside the balloon 25 and is fixed only to the outer cylindrical shaft 30. The heating member 40 is a member for heating the fluid injected into the balloon 25.

[0032] The heating member 40 is disposed within the balloon 25 and is only required to be fixed to the outer cylindrical shaft 30. Specifically, as shown in Figures 2 and 3, the heating member 40 is formed on the extension portion 36 of the outer cylindrical shaft 30 connected to the balloon 25, and is provided so as to surround the inner cylindrical shaft 35 extending within the balloon 25.

[0033] In another embodiment, an outer cylindrical shaft 30 may be used that does not have an extension 36 that extends into the interior of the balloon 25. In this case, the outer cylindrical shaft 30 does not have the extension 36, and the proximal end of the balloon 25 and the distal end of the outer cylindrical shaft 30 are connected, so the outer cylindrical shaft 30 does not enter the interior of the balloon 25. On the other hand, the proximal end of the heating member 40 is fixed only to the distal end of the outer cylindrical shaft 30, and is provided so as to surround the inner cylindrical shaft 35 that extends inside the balloon 25. In this case, the outer cylindrical shaft 30 and the heating member 40 can be fixed using techniques such as adhesive bonding or welding.

[0034] As an example, a nichrome wire that generates heat by electrical resistance can be used as the heating element 40. As another example of the heating element 40, a coil electrode can be used, as shown in Figures 2 and 3. When high-frequency electricity is applied to the heating element 40, a high-frequency current flows between the heating element 40 and an externally disposed counter electrode 77 (Figure 1), causing Joule heat to be generated in the liquid located between the heating element 40 and the counter electrode 77. The counter electrode 77 is placed, for example, on the back of the patient.

[0035] In the example shown in Figures 2 and 3, the heating element 40 is formed on the extension 36 of the outer cylindrical shaft 30 connected to the balloon 25 and is arranged to surround the inner cylindrical shaft 35 extending within the balloon 25. The heating element 40, which is a coil electrode, may be formed of a wound conductive wire. The heating element 40 is electrically connected to wiring 42 for high-frequency current application. The wiring 42 extends to the handle 50 through the liquid delivery path LP, which serves as a lumen between the outer cylindrical shaft 30 and the inner cylindrical shaft 35. As a specific example of a coil electrode, the insulation-coated lead wire used for the wiring 42 may be stripped, wound around a mandrel, connected to the outer cylindrical shaft 30, and arranged to surround the inner cylindrical shaft 35. Because such a coil electrode is integrally formed with the wiring 42, it is possible to effectively prevent problems such as wire breakage.

[0036] 2, the outer cylindrical shaft 30 is made up of a cylindrical intermediate member 46 and a fixed member 43 fixed to the distal end (tip) of the cylindrical intermediate member 46. A tapered transition portion 43a of the fixed member 43 has a hole 44 through which a conductor wire passes and which serves as a liquid delivery path. The coil electrode is made up of a conductor wire wound around the fixed member 43.

[0037] The diameter of the coil electrode and wiring 42 is preferably 0.1 mm or more and 1 mm or less, and more preferably 0.1 mm or more and 0.4 mm or less. Examples of conductive materials that form the coil electrode and wiring 42 include copper, silver, gold, platinum, and alloys thereof. To prevent short circuits, the wiring 42 is preferably configured such that a conductor made of a conductive material is coated with an insulating coating such as a fluoropolymer (see FIGS. 4 and 5).

[0038] A first temperature sensor 31 is installed at the proximal end of the heating member 40, which is made of a coil electrode, and the first temperature sensor 31 acquires the temperature of the heating member 40. By managing and controlling the temperature of the heating member 40, which is the hottest part of the balloon catheter, safer treatment is possible.

[0039] Next, the second temperature sensor 45 will be described. The second temperature sensor 45 acquires information regarding the temperature of the liquid. In this embodiment, the second temperature sensor 45 is disposed in the liquid feed path LP, which is located closer to the proximal end than the balloon 25 and between the outer cylindrical shaft 30 and the inner cylindrical shaft 35. The second temperature sensor 45 can acquire information regarding the temperature of the liquid in the liquid feed path LP.

[0040] Furthermore, according to the inventors' investigations, it is possible to determine with high accuracy the surface temperature of the balloon 25, which is important in ablation treatment using the balloon catheter system 10, based on the information obtained by the second temperature sensor 45. Installing the second temperature sensor 45 in the liquid feed path LP can greatly simplify the manufacture of the catheter body 20 compared to installing the second temperature sensor 45 inside the balloon 25.

[0041] Furthermore, the second temperature sensor 45 can be protected from external stress and stably supported by being disposed in the liquid feed path LP, as compared to being disposed in the balloon 25. In other words, by disposing the second temperature sensor 45 in the liquid feed path LP, the quality and reliability of the balloon catheter system 10 and the balloon catheter 15 can be significantly improved.

[0042] For the purpose of determining the surface temperature of the balloon 25 with high accuracy, the length DX between the proximal end 25b of the balloon 25 and the second temperature sensor 45 in the longitudinal direction LD strictly depends on the amount of liquid supplied and discharged by the stirring device 75, which will be described later. However, considering the dimensions of the catheter main body 20 typically used in cardiac ablation treatment and the amount of liquid supplied and discharged from the stirring device 75, the length DX (see FIG. 2) between the proximal end 25b of the balloon 25 and the second temperature sensor 45 is preferably 5 mm or more and 150 mm or less, and more preferably 10 mm or more and 20 mm or less.

[0043] Unless otherwise specified, the length DX between the proximal end 25b of the balloon 25 and the second temperature sensor 45 is the length determined when the balloon 25 shown in Figure 2 is inflated with liquid.

[0044] The first temperature sensor 31 and the second temperature sensor 45 can be a thermocouple or a thermistor. Furthermore, a T-type thermocouple is particularly suitable for the first temperature sensor 31 and the second temperature sensor 45. Using a T-type thermocouple reduces the thermal capacity of the heat-sensing unit. Furthermore, employing a T-type thermocouple for the first temperature sensor 31 and the second temperature sensor 45 stabilizes the thermoelectromotive force. Furthermore, a T-type thermocouple can detect temperatures in the range of 50°C to 80°C with high accuracy, making it particularly suitable for cardiac ablation treatment. The temperature-related information acquired by the first temperature sensor 31 and the second temperature sensor 45 is, for example, a potential acquired from a thermocouple or a resistance value acquired from a thermistor.

[0045] 2 and 3, the first temperature sensor 31 and the second temperature sensor 45 typically have a heat-sensing portion and a lead wire 47 electrically connected to the heat-sensing portion. In the case of a thermocouple, the heat-sensing portion of the first temperature sensor 31 and the second temperature sensor 45 is formed by a portion where dissimilar metals are connected. In the case of a thermistor, the heat-sensing portion of the first temperature sensor 31 and the second temperature sensor 45 is formed by a ceramic element. The lead wire 47 extends to the handle 50 through the liquid transfer path LP, which serves as a lumen between the outer cylindrical shaft 30 and the inner cylindrical shaft 35.

[0046] The diameter of the lead wire 47 is preferably 0.05 mm or more and 0.5 mm or less, and more preferably 0.05 mm or more and 0.3 mm or less. In the first temperature sensor 31 and the second temperature sensor 45 serving as a thermocouple, for example, one lead wire 47 may be made of copper and the other lead wire 47 may be made of constantan. In order to prevent short-circuiting between the pair of lead wires 47, it is preferable that an electrically insulating coating such as a fluoropolymer or enamel be provided, as shown in Figures 4 and 5.

[0047] 2 to 4, the second temperature sensor 45 is fixed to the inner cylindrical shaft 35 via the lead wire 47 by using a fixing means 48 to fix the lead wire 47. The second temperature sensor 45 is separated from both the outer cylindrical shaft 30 and the inner cylindrical shaft 35. In other words, the second temperature sensor 45 is not in contact with the outer cylindrical shaft 30 and the inner cylindrical shaft 35. This makes it possible to avoid deterioration of the responsiveness of the second temperature sensor 45 due to the temperatures of the outer cylindrical shaft 30 and the inner cylindrical shaft 35, which have large heat capacities. This allows the second temperature sensor 45 to evaluate the temperature of the liquid in the liquid transfer path LP with high accuracy and high responsiveness.

[0048] Note that various means can be used as the fixing means 48 for fixing the lead wire 47 to the inner cylindrical shaft 35 without any particular limitation. In the illustrated example, a heat shrink tube that shrinks when heated is used as the fixing means 48. However, the fixing means 48 is not limited to this example, and various types of shrink tubes, adhesive tape, adhesives, etc. can be used as the fixing means 48.

[0049] In the illustrated example, the wiring 42 is not attached to either the outer tube shaft 30 or the inner tube shaft 35, but this is not limited to this example, and the wiring 42 may be attached to the outer tube shaft 30.

[0050] 3 , even when the inner cylindrical shaft 35 moves distally relative to the outer cylindrical shaft 30 in the longitudinal direction LD to the maximum extent possible so that the balloon 25 expands, the second temperature sensor 45 is located proximal to the balloon 25 and within the liquid feed path LP located between the outer cylindrical shaft 30 and the inner cylindrical shaft 35. According to this specific example, the second temperature sensor 45 can be located within the liquid feed path LP regardless of the relative position of the inner cylindrical shaft 35 with respect to the outer cylindrical shaft 30. Therefore, the second temperature sensor 45 can be stably protected by the outer cylindrical shaft 30 regardless of the relative position of the inner cylindrical shaft 35 with respect to the outer cylindrical shaft 30.

[0051] On the other hand, unlike the illustrated example, the second temperature sensor 45 may be attached to the inner surface of the outer cylindrical shaft 30. According to this specific example, the second temperature sensor 45 can be stably protected by the outer cylindrical shaft 30, regardless of the relative position of the inner cylindrical shaft 35 with respect to the outer cylindrical shaft 30.

[0052] Next, the handle 50 connected to the proximal side of the catheter main body 20 described above will be described. The handle 50 is the part that is grasped by the operator (surgeon) while using the balloon catheter system 10. Therefore, it is preferable that the handle 50 has a design that allows the operator to easily grasp and operate it with their hands. The material that constitutes the handle 50 is preferably a highly chemical-resistant material, such as polycarbonate or acrylonitrile-butadiene-styrene copolymer (hereinafter referred to as ABS resin).

[0053] The handle 50 shown in Fig. 1 has a first handle portion 51 and a second handle portion 52 that are slidable relative to each other. The first handle portion (front handle portion) 51 is connected to the outer cylindrical shaft 30 of the catheter main body 20. The second handle portion (rear handle portion) 52 is connected to the inner cylindrical shaft 35 of the catheter main body 20. By moving the second handle portion 52 relative to the first handle portion 51, the inner cylindrical shaft 35 can be moved relative to the outer cylindrical shaft 30.

[0054] As shown in FIG. 1, the handle 50 also serves as a connection point between the balloon catheter 15 and other devices included in the balloon catheter system 10.

[0055] First, a connector 56 extends from the second handle portion 52. This connector 56 electrically connects the wiring 42 of the catheter main body 20 and the lead wire 47 of the temperature sensor 45 to an external control device 70. The connector 56 extends from one of multiple branch portions 52a provided on the second handle portion 52. When the wiring 42 and the lead wire 47 are connected to an external device (control device 70) via the same handle portion, it is preferable that the wiring 42 and the lead wire 47 be the same as each other, either the outer cylindrical shaft 30 or the inner cylindrical shaft 35, as described above, and that they are attached to the shaft (in the illustrated example, the inner cylindrical shaft 35) connected to the handle portion (in the illustrated example, the second handle portion 52). In this case, tangling and disconnection of the wiring 42 and the lead wire 47 can be more effectively avoided.

[0056] The connector 56 preferably has a configuration that can effectively prevent incorrect connection. The connector 56 also preferably has excellent waterproof properties. The configuration of the connector 56 can be determined taking into consideration the convenience for the surgeon and design considerations. Similarly to the handle 50, the connector 56 is preferably made of a material with high chemical resistance, such as polycarbonate or ABS resin.

[0057] The connector 56 may have a high conductivity metal pin therein. The wiring 42 and the lead wire 47 can be electrically connected to the control device 70 serving as a high frequency power supply means by connecting to this high conductivity metal pin. However, the lead wire 47 of the second temperature sensor 45 may be electrically connected to a device other than the control device 70 serving as a high frequency power supply means, such as a temperature indicator.

[0058] The material of the high-conductivity metal pin included in the connector 56 is not particularly limited as long as it is a metal with high conductivity. Examples of high-conductivity metal pins included in the connector 56 include copper, silver, gold, platinum, and alloys thereof. In addition, it is preferable that the exterior of the high-conductivity metal pin is protected with an electrically insulating and chemical-resistant material. Examples of electrically insulating and chemical-resistant materials include polysulfone, polyurethane-based polymers, polypropylene, and polyvinyl chloride.

[0059] The second handle portion 52 has branches 52b and 52c in addition to the branch 52a to which the connector 56 is connected. These branches 52b and 52c function as portions for supplying liquid to the lumen, which is the internal space of the inner cylindrical shaft 35, and as portions from which a guidewire inserted through the lumen of the inner cylindrical shaft 35 extends. During cardiac ablation treatment, a small amount of saline solution, approximately 100 ml per hour, is typically discharged into the body through the lumen of the inner cylindrical shaft 35. Discharging saline solution effectively prevents backflow of blood into the lumen of the inner cylindrical shaft 35.

[0060] 1, an extension tube 57 extends from the first handle portion 51. This extension tube 57 connects the liquid feed path LP of the catheter main body 20 to an external supply device 74 and agitator 75. The extension tube 57 extends from a branch portion 51a provided in the first handle portion 51. The extension tube 57 is connected to the supply device 74 and the agitator 75 via a valve 58. In the illustrated example, by operating the valve 58, it is possible to select either the supply device 74 or the agitator 75 to be connected to the liquid feed path LP. A three-way stopcock can be used as the valve 58.

[0061] Next, the devices that constitute the balloon catheter system 10 together with the balloon catheter 15 described above, specifically the control device 70, the supply device 74, and the stirring device 75, will be described.

[0062] The illustrated control device 70 is electrically connected to the heating member 40, which is made up of a coil electrode, via wiring 42. The control device 70 has a high-frequency current control unit (not shown) that controls the application of high-frequency current to the heating member 40. In the illustrated example, the high-frequency current control unit controls the application of high-frequency current to the heating member 40, thereby adjusting the output from the counter electrode 77. The high-frequency current control unit can control the application of high-frequency current to the heating member 40 based on the temperature of the heating member 40 determined by the first temperature sensor and the surface temperature of the balloon 25 determined by a temperature calculation unit (described later), or according to preset processing, or according to input from the operator.

[0063] When control is performed based only on the temperature of the heating element 40 identified by the first temperature sensor, for example, if the set temperature of the first temperature sensor is 70°C, the high-frequency current control unit controls so that high-frequency current continues to be applied until the temperature of the heating element 40 identified by the first temperature sensor 31 reaches 70°C, regardless of the surface temperature of the balloon 25 identified by the temperature obtained by the second temperature sensor 45.

[0064] On the other hand, when control is performed based only on the surface temperature of the balloon 25 determined by the temperature acquired by the second temperature sensor 45, for example, when the set temperature of the surface temperature of the balloon 25 determined by the temperature acquired by the second temperature sensor 45 is set to 65°C, the high-frequency current control unit controls so that high-frequency power continues to be applied until the surface temperature of the balloon 25 determined by the temperature acquired by the second temperature sensor 45 reaches 65°C, regardless of the temperature of the heating element 40 determined by the first temperature sensor 31.

[0065] Furthermore, we will explain the control performed using both the temperature of the heating element 40 determined from the first temperature sensor 31 and the surface temperature of the balloon 25 determined by the temperature acquired by the second temperature sensor 45.

[0066] For example, if the set temperature of the heating element 40 determined by the first temperature sensor 31 is 70°C and the set temperature of the surface temperature of the balloon 25 determined by the temperature acquired by the second temperature sensor 45 is 65°C, when the temperature acquired by the first temperature sensor 31 reaches 70°C but the temperature acquired by the second temperature sensor 45 does not reach 65°C, the high-frequency current control unit controls so that no further high-frequency current is applied, even though the temperature acquired by the second temperature sensor 45 has not yet reached the set temperature. Also, when the temperature acquired by the first temperature sensor 31 does not reach 70°C but the temperature acquired by the second temperature sensor 45 reaches 65°C, the high-frequency current control unit controls so that no further high-frequency current is applied, even though the temperature acquired by the first temperature sensor 31 has not yet reached the set temperature.

[0067] The control device 70 is also electrically connected to the lead wire 47 of the first temperature sensor 31 and the lead wire 47 of the second temperature sensor 45. The control device 70 has a temperature calculation unit (not shown) that calculates information related to the temperature acquired by the second temperature sensor 45. The temperature calculation unit calculates the liquid temperature in the liquid feed path LP based on the information related to the temperature acquired by the second temperature sensor 45, and further estimates the surface temperature of the balloon 25 based on the calculated liquid temperature. The temperature calculation unit may display the identified surface temperature of the balloon 25 on the display unit 71.

[0068] Furthermore, the control device 70 has an agitator control unit (not shown) that controls the agitator 75. The agitator control unit may display the control conditions of the agitator 75 on the display unit 71.

[0069] The control device 70 is configured with hardware such as a CPU, for example. One or more of the high-frequency current control unit, the temperature calculation unit, and the stirring device control unit included in the control device 70 may be configured as separate hardware, or a portion may be provided. At least a portion of the control device 70 may be configured with software. A portion of the control device 70 may be physically located separately. In addition, some of the components of the control device 70 may be capable of cooperating with other components by communication via a network. In addition, some of the components of the control device 70 may be located on a device that can communicate with other components via an external network, such as a server or database on a cloud.

[0070] Next, the supply device 74 will be described. The supply device 74 supplies liquid into the liquid feed path LP. By injecting liquid from the supply device 74 into the balloon 25 via the liquid feed path LP, the balloon 25 can be inflated as shown in FIG. 2. On the other hand, by discharging liquid from the balloon 25 via the liquid feed path LP from the supply device 74, the balloon 25 can be deflated. The liquid supplied into the liquid feed path LP can typically be physiological saline. As shown in the figure, a syringe can be used as the supply device 74. However, a pump or the like can also be used as the supply device 74.

[0071] Next, the agitator 75 will be described. The agitator 75 is provided to agitate the liquid in the balloon 25. By agitating the liquid in the balloon 25, the heat supplied to the balloon 25 can be dispersed or uniformized, thereby adjusting the surface temperature of the balloon 25. The agitator 75 repeatedly supplies liquid to the liquid feed path LP and discharges liquid from the liquid feed path LP. As the agitator 75, a pump selected from the group consisting of a roller pump, a diaphragm pump, a bellows pump, a vane pump, a centrifugal pump, and a pump formed by a combination of a piston and a cylinder can be used.

[0072] The amount of liquid supplied to the liquid transfer path LP and the amount of liquid discharged from the liquid transfer path LP can be set to a constant amount (e.g., 5 ml to 30 ml). Furthermore, the supply of liquid to the liquid transfer path LP and the discharge of liquid from the liquid transfer path LP may be repeated at a constant cycle (e.g., 1 to 5 times per second). The amount of liquid supplied to the liquid transfer path LP and the amount of liquid discharged from the liquid transfer path LP may be adjusted by a control signal from the above-mentioned agitation device control unit or by direct input from the operator. Similarly, the cycle of the supply of liquid to the liquid transfer path LP and the discharge of liquid from the liquid transfer path LP may be adjusted by a control signal from the above-mentioned agitation device control unit or by direct input from the operator.

[0073] Next, an example of how to use the balloon catheter system 10 configured as above will be described.

[0074] First, the valve 58 is operated to connect the supply device 74 to the liquid feed path LP of the catheter main body 20 via the handle 50. The supply device 74 is then operated to introduce liquid into the liquid feed path LP, filling the balloon, the liquid feed path LP, and the extension tube 57 with liquid. Next, the inner cylindrical shaft 35 is moved distally (toward the tip) in the longitudinal direction LD relative to the outer cylindrical shaft 30, thereby expanding the balloon 25 as shown in FIG. 3 . At this time, the outer cylindrical shaft 30 and the inner cylindrical shaft 35 can be moved relative to each other by operating the first handle portion 51 and the second handle portion 52 of the handle 50. The catheter main body 20 with the balloon 25 expanded is then inserted into the body.

[0075] Once the distal end of the catheter main body 20 has been guided to the vicinity of the target site (affected area), the inner cylindrical shaft 35 is moved proximally (toward the base end) relative to the outer cylindrical shaft 30 in the longitudinal direction LD to relax the balloon 25. Next, the valve 58 is operated to connect the supply device 74 to the liquid feed path LP of the catheter main body 20 via the handle 50. Thereafter, the supply device 74 is operated to inject liquid into the liquid feed path LP, thereby inflating the balloon 25 with the liquid, as shown in FIG.

[0076] Next, the valve 58 is operated to disconnect the supply device 74 from the liquid transfer path LP and connect the agitator 75 to the liquid transfer path LP. The agitator 75 is controlled by a control signal from the agitator control section of the control device 70. The agitator 75 repeatedly supplies a fixed amount of liquid to the liquid transfer path LP and discharges a fixed amount of liquid from the liquid transfer path LP at a fixed cycle. As a result, a fixed amount of liquid is discharged from the liquid transfer path LP into the balloon 25 and a fixed amount of liquid is sucked from the balloon 25 into the liquid transfer path L at a fixed cycle. This agitates the liquid in the balloon 25.

[0077] Furthermore, the high-frequency current control unit of the control device 70 controls the heating member 40 to adjust the temperature of the liquid in the balloon 25. Specifically, the control device 70 applies high-frequency current between the heating member 40, which is made up of a coil electrode, and a counter electrode 77, which is placed outside the patient's body. As a result, a high-frequency current is generated between the heating member 40 and the counter electrode 77. However, by making the longitudinal width of the coil electrode smaller than the width of the counter electrode, the current density around the heating member 40 increases, and the surrounding liquid and contrast agent are heated by Joule heating.

[0078] In this manner, the liquid in the balloon 25 is heated and stirred. Then, the balloon 25 containing the heated liquid is pressed against the target site, and the target site is ablated. During ablation, the second temperature sensor 45 disposed in the liquid supply path LP acquires information regarding the temperature of the liquid in the liquid supply path LP. The acquired information is calculated by the temperature calculation unit of the control device 70. In particular, the temperature calculation unit not only determines the temperature of the liquid in the area where the second temperature sensor 45 is disposed, but also can accurately determine the surface temperature of the balloon 25, as described below. The surface temperature of the balloon 25 determined with high accuracy by the temperature calculation unit is displayed, for example, on the display unit 71.

[0079] In other words, by using this balloon catheter system 10, the operator can perform ablation treatment while preventing excessive heating of the hottest part of the balloon catheter and accurately monitoring the surface temperature of the balloon 25 at all times.

[0080] When ablation of the target area is complete, the energy supply to the heating element 40 is stopped. The valve 58 is also operated to connect the supply device 74 to the liquid feed path LP of the catheter main body 20 via the handle 50, and the agitator 75 is disconnected from the liquid feed path LP. The supply device 74 is then used to discharge the liquid from the liquid feed path LP, thereby deflating the balloon 25. Next, the second handle portion 52 is operated to expand the deflated balloon 25 as shown in FIG. 3. The catheter main body 20 with the expanded balloon 25 is then removed from the body. This completes the procedure using the balloon catheter system 10.

[0081] A second embodiment of the distal end portion of a balloon catheter is shown in Figure 6. The proximal end of the balloon 25 is connected to the side surface of the outer cylindrical shaft 30, and the distal end (tip) of the outer cylindrical shaft 30 protrudes into the balloon 25. The outer cylindrical shaft 30 has a large-diameter cylindrical portion 30b on the proximal side and a small-diameter cylindrical portion 30c on the distal side, with a tapered transition portion 30a between them that connects the large-diameter cylindrical portion and the small-diameter cylindrical portion.

[0082] In this case, the extension 36, which is the portion that protrudes into the balloon 25, is formed from the small-diameter tubular portion 30c of the outer tubular shaft 30 and a part of the tapered transition portion 30a. The tapered transition portion 30a has a hole 44 through which a conductor passes and which serves as a liquid delivery path. The heating member 40, which is a coil electrode, is formed from a conductor wound around the small-diameter tubular portion 30c.

[0083] In the outer cylindrical shaft 30 of the second embodiment, the outer diameter of the large-diameter cylindrical portion 30b is preferably 3.0 mm or more and 4.0 mm or less, and the inner diameter of the large-diameter cylindrical portion 30b is preferably 2.5 mm or more and 3.5 mm or less. The outer diameter of the small-diameter cylindrical portion 30c is preferably 1.5 mm or more and 3.0 mm or less, and the inner diameter of the small-diameter cylindrical portion 30c is preferably 1.5 mm or more and 2.0 mm or less. The tapered transition portion 30a of the outer cylindrical shaft 30 has one or more holes 44, and the diameter of the hole 44 is 0.5 mm or more. ２ More than 2 mm ２ The following is preferred:

[0084] A third embodiment of the distal end portion of the balloon catheter is shown in Figure 7. In this embodiment, the outer tubular shaft 30 has a single inner and outer diameter, and the outer tubular shaft 30 connected to the proximal end of the balloon 25 does not protrude into the balloon 25. The heating element 40, which is a coil electrode, is composed of a free-standing conductor formed into a coil shape. The proximal end (base end) 25b of the balloon 25 is fixed to the side of the outer tubular shaft 30, and the proximal end (base end) 40a of the heating element 40 is fixed to the distal end (tip end) of the outer tubular shaft 30. The heating element 40 is formed by winding wiring 42 in a coil shape around a mandrel and fixing both ends of the coil by soldering, welding, or the like.

[0085] In the third embodiment, the outer diameter of the coil electrode is preferably 3.0 mm or more and 4.0 mm or less, and the inner diameter of the coil electrode is preferably 2.5 mm or more and 3.5 mm or less.

[0086] Next, the relationship between the temperature of the heating member 40 detected by the first temperature sensor 31 and the surface temperature of the balloon 25 that can be detected by the second temperature sensor 45 will be described in detail using examples and comparative examples.

[0087] Example 1 To produce the balloon catheter 15 of Example 1, a polyurethane balloon 25 having a diameter of 30 mm and a thickness of 20 μm was produced by blow molding.

[0088] The cylindrical intermediate member 46 was a polyurethane tube having an outer diameter of 3.6 mm, an inner diameter of 3.0 mm, and a total length of 1000 mm. The inner cylindrical shaft 35 was a polyamide tube having an outer diameter of 1.6 mm, an inner diameter of 1.2 mm, and a total length of 1100 mm. The fixing member 43 was connected to the distal end (tip) of the cylindrical intermediate member 46 to form the outer cylindrical shaft 30. The small-diameter cylindrical portion 43c of the fixing member 43 had an outer diameter of 2.0 mm and an inner diameter of 1.7 mm, and the large-diameter cylindrical portion 43b had an outer diameter of 2.9 mm and an inner diameter of 2.7 mm. In addition, a tapered transition portion 43a connecting the large-diameter cylindrical portion and the small-diameter cylindrical portion had a hole diameter of 1 mm. ２ Four holes were formed.

[0089] Furthermore, a portion of the electrically insulating protective coating applied to the wiring 42 and the lead wire 47 was stripped off, and the wiring 42 was wound in a coil shape around a fixing member 43 with the lead wire 47 sandwiched therebetween, thereby forming one electrode with an electrode length of 13 mm, a heating member 40 consisting of a coil electrode, and a first temperature sensor 43. Furthermore, the wiring 42 and the lead wire 47 were welded and fixed to the inner cylindrical shaft near the heating member 40, thereby forming a second temperature sensor 45.

[0090] The inner cylindrical shaft 35 was slidably inserted into the lumen of the outer cylindrical shaft 30. Then, the distal end 25a of the balloon 25 was fixed to the distal end 35a of the inner cylindrical shaft 35. Furthermore, the distal end 30a of the outer cylindrical shaft 30 was inserted into the balloon 25 from the proximal end 25b of the balloon 25, and the proximal end 25b of the balloon 25 was fixed proximal to the distal end 30a of the outer cylindrical shaft 30.

[0091] In addition, a polycarbonate handle 50 is provided at the rear end of the outer cylindrical shaft 30 and the inner cylindrical shaft 35. The handle 50 is composed of a first handle portion (front handle portion) 51 connected to the outer cylindrical shaft 30 and a second handle portion (rear handle portion) 52 connected to the inner cylindrical shaft 35. By sliding the second handle portion 52 relative to the first handle portion 51, the inner cylindrical shaft 35 slides inside the outer cylindrical shaft 30, thereby enabling the shape of the balloon 25 to be deformed.

[0092] In this example, the outer cylindrical shaft 30 was a stepped shaft whose diameter changed via a taper. The dimensions of the stepped shaft were such that the outer diameter of the thin-diameter cylindrical portion 30c protruding into the balloon 25 was 2.0 mm and the inner diameter was 1.7 mm, and the outer diameter of the thick-diameter cylindrical portion 30b was 3.6 mm and the inner diameter was 3.0 mm. In addition, a hole with a diameter of 1 mm was provided at the connection portion with the balloon 25. ２ A balloon catheter 15 was produced in the same manner as in Example 1, except that four holes were formed.

[0093] Example 3 A portion of the electrically insulating protective coating applied to the wiring 42 and the lead wire 47 was stripped, and the wiring 42 was wound around a mandrel with the lead wire 47 sandwiched therebetween into a coil shape. Both ends of the coil were fixed by soldering, forming one electrode with an electrode length of 13 mm, a heating element 40 consisting of a coil electrode, and a first temperature sensor 43. The mandrel was then removed, and the wiring 42 and the lead wire 47 were fixed to the distal end 30a of the outer tubular shaft 30 using an adhesive. A balloon catheter 15 was fabricated in the same manner as in Example 1, except that the length between the heating element 40 and the distal end 30a of the outer tubular shaft 30 remained constant even when the outer tubular shaft 30 was inserted into the balloon 25. In this example, the outer tubular shaft 30 did not have an extension at its distal end that extended into the balloon.

[0094] Comparative Example Referring to FIG. 8, a balloon catheter 15 was produced in the same manner as in Example 1, except that the fixing member 43 was not used and the heating member 40 was formed on the inner cylindrical shaft 35.

[0095] First, FIGS. 9 and 10 show the results of a simulation of the temperature distribution in the balloon 25 using computer-assisted engineering (CAE) for a comparative example. FIG. 6 shows the simulation results for a state in which the balloon 25 is pressed against the target site along the longitudinal direction LD (hereinafter, also referred to simply as the "coaxial state"). In the example shown in FIG. 9, the outer cylindrical shaft 30 is aligned substantially in a straight line with the inner cylindrical shaft 35 and the heating element 40 inside the balloon 25. On the other hand, FIG. 10 shows the simulation results for a state in which the balloon 25 is pressed against the target site from a direction inclined relative to the longitudinal direction LD (hereinafter, also referred to simply as the "non-coaxial state"). In the comparative example shown in FIG. 8, the outer cylindrical shaft 30 is significantly inclined with respect to the inner cylindrical shaft 35 and the heating element 40 inside the balloon 25, as shown in FIG. 10.

[0096] The simulation results show that even if the liquid in the balloon 25 is stirred using the stirring device 75, a temperature gradient occurs in the liquid in the balloon 25 due to the arrangement of the heating element 40. When the heating element 40 made of a coil electrode is used, this temperature distribution shows a tendency similar to the current density distribution. The temperature distribution in the balloon 25 is 5°C or more in the coaxial state shown in Figure 6, and is about 10°C in the non-coaxial state shown in Figure 10. As such, it can be seen that the temperature distribution in the balloon 25 changes depending on factors such as the state in which the balloon 25 is pressed against the target site.

[0097] 11 shows the balloon catheter system 10 used in an experiment conducted to confirm the relationship between the surface temperature of the heating element 40 detected by the first temperature sensor 31 and the surface temperature of the balloon 25 that can be detected by the second temperature sensor 45. In this experiment, the actual measured value of the surface temperature of the balloon 25 was compared with the actual measured value of the temperature of the liquid in the liquid feed path LP, which was identified based on the information acquired by the temperature sensor 45. In this experiment, the balloon catheter system 10 shown in FIG. 1 and described above was used.

[0098] 11 , the detection result of the first temperature sensor 31 was taken in by the temperature calculation unit of the control device 70. The high-frequency current control unit received the calculation result of the temperature calculation unit and controlled the high-frequency current supply to the heating member 40 based on the information acquired by the first temperature sensor 31.

[0099] In this experiment, ablation treatment was performed on a simulated living body 99 simulating the orifice of the left atrium and pulmonary vein of a human body. The simulated living body 99 was immersed in physiological saline solution held in a water bath 85. During the experiment, a water bath stirrer 86 was used to stir the physiological saline solution in the water bath 85. A counter electrode 77, which generates a high-frequency current between itself and the heating member 40, which is made of a coil electrode of the catheter main body 20, was placed on the side wall of the water bath 85. The physiological saline solution in the water bath 85 was prepared by dissolving 0.9 wt % salt (sodium chloride) in water.

[0100] The liquid supplied from the supply device 74 to the liquid feed path LP and the balloon 25 was physiological saline solution, which was made by dissolving 0.9 wt% salt (sodium chloride) in water, and further mixed with a contrast agent for X-ray imaging. The amount of liquid injected into the balloon 25 was two levels: 10 mL and 20 mL, which are commonly used in actual ablation treatments. The contrast agent mixed in the liquid was Omnipaque (registered trademark; manufactured by GE Healthcare Pharma, Ltd.).

[0101] The high-frequency current control section of the control device 70 controlled the high-frequency current so that the temperature of the heating member 40 was 70° C. The driving power was 150 W.

[0102] In the experiment, the amount of liquid injected into the balloon 25 was changed between two levels: 10 ml and 20 ml, and the contact state of the balloon 25 was changed between two levels: coaxial and non-coaxial. Furthermore, when the balloon catheter 15 is pressed against the target site during ablation, the outer cylindrical shaft 30 advances distally in the longitudinal direction LD, thereby pushing the balloon rear end 25b, as shown in Figure 12, and shortening the length DY between the heating element 40 and the proximal end 25b of the balloon 25. To reproduce this, two levels of DY length were selected: 5 mm and 9 mm. Furthermore, to reproduce a state in which the balloon catheter 15 is not pressed against the target site, a level of DY length of 13 mm was selected, and a total of three levels of DY length were used: 5 mm, 9 mm, and 13 mm.

[0103] Simulation tests were conducted using the balloon catheter system 10 on a simulated living organism 99 under a total of 24 different conditions, with the amount of liquid injected, the state of contact of the balloon, and the length DY between the heating element and the proximal end of the balloon being changed for each of Examples 1 to 3 and the Comparative Example. The difference between the temperature measured by the first temperature sensor 31 and the second temperature sensor 45 for each experimental condition is shown in Figure 13. Figure 13 shows the average temperature measured after the surface temperature of the balloon 25 has sufficiently stabilized since the start of application of high-frequency power, specifically, from 150 to 200 seconds after the start of application of power.

[0104] The following findings were obtained from the experimental results shown in Figure 13. When the heating element 40 is fixed to the inner cylindrical shaft 35 as in the comparative example, the surface temperature of the balloon is significantly affected by the amount of liquid injected, the state of contact with the balloon, and the length DY between the heating element and the proximal end of the balloon, and it becomes necessary to increase the temperature of the heating element 40 in order to maintain a constant surface temperature of the balloon. On the other hand, when the heating element 40 is fixed to the outer cylindrical shaft 30 as in the example, it was found that the surface temperature of the balloon is less affected by the amount of liquid injected and the state of contact with the balloon, and does not change with the length DY between the heating element and the proximal end of the balloon.

[0105] The reason for this result is presumably that, when the heating element 40 is fixed only to the outer cylindrical shaft 30, as shown in Figures 14 to 17, even if the contact state of the balloon changes, the flow of the stirring flow inside the balloon 25 is unlikely to change, the positional relationship between the heating element 40 and the outer cylindrical shaft 30 is always constant, and the cooling effect of the heating element by the liquid supplied from the liquid supply path LP into the balloon 25 is always the same.

[0106] On the other hand, when the heating element 40 is fixed only to the inner cylindrical shaft 35, as shown in Figures 18 to 21, if the contact state of the balloon or the like changes, the flow of the stirring flow inside the balloon 25 easily changes, and it is presumed that the cooling effect of the heating element by the liquid supplied from the liquid supply path LP into the balloon 25 is not constant.

[0107] In order to safely maintain a constant balloon surface temperature, it is considered extremely important to maintain a constant cooling effect of the heating element 40 by the liquid supplied from the liquid supply path LP into the balloon 25. This makes it possible to provide a balloon catheter that can stably and efficiently diffuse the heated liquid inside the balloon without being affected by catheter operation, and that can safely obtain a stable balloon surface temperature (the balloon surface temperature does not change whether the balloon is in a coaxial or non-coaxial state), as well as a catheter system that includes such a balloon catheter.

[0108] Although one embodiment has been described using a number of examples, these examples are not intended to limit the embodiment. The embodiment described above can be implemented in various other examples, and various omissions, substitutions, changes, additions, etc. can be made without departing from the spirit of the embodiment.

[0109] For example, in the example of one embodiment described above, one liquid supply path LP is provided between the outer tube shaft 30 and the inner tube shaft 35, and liquid is supplied into the balloon 25 and discharged from the balloon 25 via this one liquid supply path LP.

[0110] However, without being limited to this example, two or more liquid transfer paths LP may be provided between the outer cylindrical shaft 30 and the inner cylindrical shaft 35. In this modification, the two or more liquid transfer paths LP may include a liquid supply path for supplying liquid into the balloon 25 and a liquid discharge path for discharging liquid from the balloon 25.

[0111] Even in this modified example, since the heating member 40 is fixed only to the outer tube shaft 30, the relationship between the temperature of the heating member 40 detected by the first temperature sensor 31 and the surface temperature of the balloon 25 detected by the second temperature sensor 45 can be maintained constant, thereby providing a highly safe ablation catheter.

[0112] INDUSTRIAL APPLICABILITY The present invention can be used in a balloon catheter system and a balloon catheter for treating arrhythmia such as atrial fibrillation, endometriosis, cancer, and the like.

[0113] 10... Balloon catheter system, 15... Balloon catheter, 20... Catheter body, 25... Balloon, 25a... Distal end, 25b... Proximal end, 30... Outer cylindrical shaft, 30a... Tapered transition section, 30b... Large diameter cylindrical section, 30c... Thin diameter cylindrical section, 31... First temperature sensor, 35... Inner cylindrical shaft, 40... Heating member, 42... Wiring, 43... Fixing member, 43a... Tapered transition section, 43b... Large diameter cylindrical section, 43c... Thin diameter cylindrical section, 44... Hole, 45... Second temperature sensor, 46... Cylindrical intermediate member, 47... Lead wire, 50... Handle, 70... Control device, 75... Stirring device, 77... Counter electrode, 99... Simulated living body, LD... Longitudinal direction, LP... Fluid delivery path, DX... Length between the proximal end of the balloon and the second temperature sensor, DY... Length between the heating member and the proximal end of the balloon

Claims

1. A balloon catheter comprising: a balloon; an outer cylindrical shaft connected to the proximal end of the balloon; an inner cylindrical shaft passing through the outer cylindrical shaft and connected to the distal end of the balloon; a heating element for heating a liquid within the balloon; a first temperature sensor fixed to an end of the heating element; and a liquid supply path formed between the outer cylindrical shaft and the inner cylindrical shaft and leading to the inside of the balloon, wherein the balloon can be expanded or relaxed by moving the inner cylindrical shaft relative to the outer cylindrical shaft, and the heating element is disposed within the balloon and is fixed only to the outer cylindrical shaft.

2. The balloon catheter according to claim 1, wherein the outer cylindrical shaft has an extension portion extending into the balloon, and the heating element is fixed to the extension portion.

3. A balloon catheter system comprising: a balloon catheter according to claim 1 or 2; a supply device that supplies liquid to the liquid feed path; a stirring device that stirs the liquid in the balloon by repeatedly supplying liquid to the liquid feed path and discharging liquid from the liquid feed path; and a heating device that is electrically connected to the heating element and applies electrical energy to the heating element, wherein the heating element applies electrical energy to the heating element based on information related to the temperature acquired by the first temperature sensor.