Catheter

Abstract

Provided is a catheter which includes: an outer shaft 10 having a lumen; an inner shaft 22 slidably inserted into the lumen; and a spline 16 in which a proximal end part 42 is connected to a distal end side of the outer shaft 10, a distal end part 32 is connected to a distal end side of the inner shaft 22, and an electrode 18 is disposed. The spline 16 has a linear part 40 extending obliquely and linearly with respect to a radius line R of the inner shaft 22 which passes through the distal end part 32 in a distal end region 34 that is continuous from the distal end part 32 of the spline 16 when viewed from an axial direction of the outer shaft 10.

Description

Catheter

[0001] The present disclosure relates to a catheter.

[0002] Conventionally, there has been known a catheter in which a curved spline having an electrode is provided on the distal end side of a shaft. In this catheter, the distal end portion of the spline is connected to a surface of a connecting member provided at the distal end of the shaft, the surface facing the proximal end side of the shaft. Therefore, the connecting member is located at the most distal end of the catheter.

[0003] Japanese National Publication of International Patent Application No. 2016-507349

[0004] For example, when performing left atrial posterior wall isolation after pulmonary vein isolation (PVI), ablation may be performed by pressing the spline against biological tissue like pressing a stamp. In contrast, in conventional catheters, since the connecting member is located at the most distal end of the catheter, contact of the electrode with biological tissue may be hindered by the connecting member. As a method for solving this problem, it is conceivable to extend the spline toward the distal end direction of the catheter beyond the connecting member, then fold it back toward the proximal end direction, and connect the distal end portion of the spline to a surface of the connecting member facing the distal end direction of the shaft. According to this configuration, the spline can be arranged at the most distal end of the catheter, and it is possible to easily avoid that the contact of the electrode with biological tissue is hindered by the connecting member.

[0005] On the other hand, generally a catheter is inserted into a living body through a sheath that has been inserted into the living body in advance. At this time, since the spline expands in a direction away from the shaft, it is difficult to insert the catheter into the sheath when the spline remains expanded. For this reason, generally a catheter has been inserted into the sheath together with an inserter in a state where the spline is housed in a cylindrical sheath called an inserter.

[0006] The present inventors have conducted intensive studies on the above-mentioned situation, and as a result, have found that there is room for reducing the load applied to the spline and improving the reliability of the catheter in a catheter that has a folded portion of the spline at the most distal end and is inserted into an inserter.

[0007] This disclosure is made in light of these circumstances, and its purpose is to provide a novel technology that improves the reliability of catheters.

[0008] One aspect of the present disclosure is a catheter. The catheter comprises an outer shaft having a lumen, an inner shaft slidably inserted into the lumen, and at least one spline whose proximal end is connected to the tip of the outer shaft and whose tip is connected to the tip of the inner shaft, and on which at least one electrode is positioned. The spline has a linear portion that extends diagonally and linearly with respect to the radius line of the inner shaft passing through the tip, in a predetermined tip region continuous with respect to the tip of the spline when viewed from the axial direction of the outer shaft.

[0009] Another aspect of the present disclosure is a catheter. This catheter comprises an outer shaft having a lumen, an inner shaft slidably inserted into the lumen, and at least one spline whose proximal end is connected to the tip of the outer shaft and whose tip is connected to the tip of the inner shaft and on which at least one electrode is positioned. The spline satisfies at least one of the following: the cross-sectional area of ​​the cross section perpendicular to the axis of the spline has a small cross-sectional area portion continuous from the tip of the spline in a predetermined tip region having a cross-sectional area smaller than the cross-sectional area of ​​the proximal end and continuous from the tip; and the radial dimension of the inner shaft in the cross-sectional shape perpendicular to the axis of the inner shaft has a small dimension portion in the tip region having a dimension smaller than the dimension of the proximal end and continuous from the tip.

[0010] Any combination of the above components, as well as any conversion of the expressions of this disclosure between methods, apparatus, systems, etc., are also valid forms of this disclosure.

[0011] This disclosure provides a novel technology for improving the reliability of catheters.

[0012] This is a schematic diagram of the ablation system. Figure 3(A) shows the electrode assembly in its extended state, viewed from the radial direction of the outer shaft. Figure 3(B) shows the electrode assembly in its flattened state, viewed from the radial direction of the outer shaft. Figure 4(A) is an enlarged view of the tip side of the electrode assembly. Figure 4(B) is a perspective view of the electrode assembly inserted into the inserter. This figure shows a portion of the electrode assembly viewed from the axial direction of the outer shaft. Figure 6(A) is a cross-sectional view perpendicular to the axis of the inner shaft and the axis of the spline, and passing through the base end of the spline. Figure 6(B) is a cross-sectional view perpendicular to the axis of the inner shaft and the axis of the spline, and passing through the tip end of the spline.

[0013] The present disclosure will be described below with reference to the drawings, based on preferred embodiments. The embodiments are illustrative and not limiting, and not all features or combinations thereof described in the embodiments are necessarily essential to the present disclosure. The same or equivalent components, members, and processes shown in each drawing are denoted by the same reference numerals, and redundant descriptions are omitted where appropriate. The scale and shape of each part shown in each drawing are set for convenience to facilitate explanation and are not to be interpreted restrictively unless otherwise specified. Furthermore, where terms such as "first," "second," etc. are used in this specification or claims, unless otherwise specified, these terms do not indicate any order or importance, but are used to distinguish one configuration from another. In addition, some components that are not important for explaining the embodiments are omitted in each drawing.

[0014] First, an example of an ablation system 1 in which the catheter 4 according to the embodiment is used will be described. Figure 1 is a schematic diagram of the ablation system 1. In Figure 1, some of the components of the ablation system 1 are depicted as functional blocks. At least some of these functional blocks can be realized in hardware configurations using elements and circuits such as the CPU and memory of a computer, and in software configurations using computer programs, etc. It will be understood by those skilled in the art that these functional blocks can be realized in various forms by combinations of hardware and software.

[0015] The ablation system 1 performs a predetermined ablation on the patient's affected area 2. Examples of the affected area 2 include organs where arrhythmias occur. The ablation system 1 can also be used for ablation of other affected areas 2. The ablation system 1 comprises a catheter 4, a counter electrode plate 6, and a power supply unit 8.

[0016] The catheter 4 comprises an outer shaft 10, an electrode assembly 12, and a handle 14. The outer shaft 10 is composed of a flexible tubular body, and at least its tip is inserted into the patient's body via a blood vessel or the like. The outer shaft 10 is made of a known flexible material, including resins such as polyolefin, polytetrafluoroethylene, polyether block amide, and polyamide. The outer shaft 10 has at least one lumen. The inner shaft 22 (see Figure 2), described later, of the catheter 4 is slidably inserted through the lumen. The outer shaft 10 also has a lumen through which various thin wires (not shown), such as conductors and operating wires, are inserted.

[0017] In this disclosure, the direction along the centerline or central axis of the outer shaft 10 or inner shaft 22 is referred to as the "axial direction," and the radial and circumferential directions of a circle centered on the said centerline are referred to as the "radial direction" and "circumferential direction," respectively. In this embodiment, the axial direction of the outer shaft 10 and the axial direction of the inner shaft 22, the radial direction of the outer shaft 10 and the radial direction of the inner shaft 22, and the circumferential direction of the outer shaft 10 and the circumferential direction of the inner shaft 22 coincide with each other. An electrode assembly 12 is provided at the tip of the outer shaft 10. The electrode assembly 12 is inserted into the patient's body and positioned at the affected area 2. The structure of the electrode assembly 12 will be described in detail later.

[0018] The handle 14 is provided on the proximal end of the outer shaft 10 and is positioned outside the body when the catheter 4 is in use, and is grasped or operated by the operator. The handle 14 has a main body that is grasped by the operator and an operating part for advancing and retracting the inner shaft 22. A connector (not shown) is provided on the main body. The proximal end of a conductor (not shown) is connected to the connector. The conductor is passed through the lumen of the outer shaft 10, and its tip is connected to the electrode 18 (see Figure 2) of the electrode assembly 12. The power supply 8 is also electrically connected to the conductor via the connector. The power supply 8 applies an ablation voltage to the electrode 18.

[0019] The counter electrode plate 6 is attached to the patient's body surface during ablation. The counter electrode plate 6 is also electrically connected to the power supply unit 8. The power supply unit 8 applies the ablation voltage to the counter electrode plate 6.

[0020] The power supply unit 8 comprises an input unit 24, a power supply unit 26, a control unit 28, and a display unit 30. The input unit 24 is composed of, for example, a dial, buttons, a touch panel, etc., and is operated by the operator of the ablation system 1. The operator can input various setting values ​​and signals to instruct operations to the power supply unit 8 via the input unit 24. Note that various setting values ​​may be pre-set and stored in the power supply unit 8 at the time of product shipment, etc. Signals indicating the setting values, etc., are sent from the input unit 24 to the control unit 28.

[0021] The power supply unit 26 applies an ablation voltage V to the electrode 18 and the counter electrode plate 6 according to the control signal CTL sent from the control unit 28. ｏｕｔ A voltage is applied. The power supply unit 26 is composed of a predetermined power supply circuit, such as a switching regulator. The control unit 28 controls the operation of the entire power supply device 8 and performs predetermined calculation processing. The control unit 28 is composed of a microcomputer, for example. The control unit 28 controls the application of voltage from the power supply unit 26 to the electrode 18 and the counter electrode plate 6 by sending a control signal CTL to the power supply unit 26. The display unit 30 displays various information to the outside. The display unit 30 is composed of a liquid crystal display, a CRT display, an organic EL display, etc.

[0022] As an example, the power supply unit 8 performs ablation on the affected area 2 using irreversible electroporation (IRE). Since IRE is non-thermal, it can minimize damage to surrounding tissues and nerves. For example, when performing pulmonary vein dissection to treat atrial fibrillation, it can suppress damage to the esophagus and phrenic nerve around the affected area, thereby preventing complications such as esophageal fistula and phrenic nerve paralysis.

[0023] In IRE, pulsed electric field ablation (PFA) is performed. PFA is an ablation technique that kills cells by using a pulsed electric field generated by applying a high voltage between the electrode 18 and the counter electrode plate 6, or between the electrodes 18 if the electrode assembly 12 has multiple electrodes 18, thereby forming a region (lesion) in the affected area 2. The electric field tends to reflect at the boundary between tissues. Therefore, when the affected area is ablated, damage to adjacent tissues can be suppressed.

[0024] The control unit 28 can control the power supply unit 26 to apply a voltage between one or more electrodes 18 and one or more other electrodes 18. In other words, the control unit 28 can control the power supply unit 26 to perform bipolar application. The control unit 28 can also control the power supply unit 26 to apply a voltage between one or more electrodes 18 and the counter electrode plate 6. In other words, the control unit 28 can control the power supply unit 26 to perform monopolar application (also called unipolar application). With monopolar application, regions can be formed deeper into the tissue more easily than with bipolar application. On the other hand, with bipolar application, regions can be formed over a wide area in the direction of the tissue surface (i.e., the direction in which the surface spreads) more easily than with monopolar application.

[0025] In this embodiment, the power supply unit 26 applies voltage to the electrodes 18 and the counter electrode plate 6 to generate biphase pulses (bipolar pulses). Therefore, in the case of bipolar application, a voltage phase pulse of one polarity, either a positive voltage phase pulse or a negative voltage phase pulse, is applied to one electrode 18. A voltage phase pulse of the other polarity is applied to the other electrode 18. The polarity of one electrode 18 and the other electrode 18 alternates. In the case of monopolar application, a voltage phase pulse of one polarity, either a positive voltage phase pulse or a negative voltage phase pulse, is applied to one electrode 18. A voltage phase pulse of the other polarity is applied to the counter electrode plate 6. The polarity of one electrode 18 and the counter electrode plate 6 alternates. The voltage amplitude value Am is, for example, 1000V to 4000V. The pulse width Δp is, for example, 0.1μs to 100μs. The power supply unit 26 may also apply voltage to each electrode 18 and the counter electrode plate 6 to generate single-phase pulses.

[0026] The control unit 28 may perform either monopolar or bipolar voltage application, or a combination of both. When monopolar and bipolar voltage application are performed in combination, a uniform region can be easily formed over a wide area. The voltage application methods in monopolar and bipolar voltage application can be appropriately set based on the designer's empirical knowledge or experiments and simulations conducted by the designer. Furthermore, if the control unit 28 performs only bipolar voltage application, the counter electrode plate 6 can be omitted. In addition, even if the power supply unit 26 is electrically connected to the catheter 4 and the counter electrode plate 6, the control unit 28 may control the power supply unit 26 to perform only bipolar voltage application.

[0027] Next, the structure of the electrode assembly 12 will be described in detail. Figure 2 is a view of the electrode assembly 12 in its extended state, seen from the radial direction of the outer shaft 10. Figure 3(A) is a view of the electrode assembly 12 in its flattened state, seen from the radial direction of the outer shaft 10. Figure 3(B) is a view of the electrode assembly 12 in its extended state, seen from the axial direction of the outer shaft 10. When the electrode assembly 12 is viewed from the axial direction of the outer shaft 10, the electrode assembly 12 has roughly the same shape in both the extended and flattened states, although the contours differ slightly.

[0028] The electrode assembly 12 has at least one spline 16. The electrode assembly 12 of this embodiment has multiple splines 16. Each spline 16 is a linear body extending in the axial direction of the outer shaft 10 and is made of the same flexible material as the outer shaft 10. An example electrode assembly 12 has a first spline 16a, a second spline 16b, a third spline 16c, a fourth spline 16d, a fifth spline 16e, and a sixth spline 16f, but the number of splines 16 is not limited to six, and may be multiple other than six or just one. In this disclosure, when there is no need to distinguish between the first splines 16a to the sixth splines 16f, they may simply be referred to as "spline 16".

[0029] Each spline 16 is arranged at intervals from each other in the circumferential direction of the inner shaft 22 or outer shaft 10. The base end 42 of each spline 16 is connected to the tip side of the outer shaft 10. For example, the base end 42 of each spline 16 is inserted into the outer shaft 10 from the tip and fixed to the outer shaft 10. The tip 32 of each spline 16 is connected to the tip side of the inner shaft 22 that protrudes from the tip of the outer shaft 10. The inner shaft 22 is made of the same flexible material as the outer shaft 10. As an example, the inner shaft 22 has an annular restraining member 23 at its tip. The tip 32 of each spline 16 is inserted into the restraining member 23 and fixed to the inner shaft 22. As an example, the tip 32 is the part of the spline 16 that is exposed outside the restraining member 23 at the tip side of the spline 16. Furthermore, the base end portion 42 is the portion of the spline 16 that is closest to the base end and is exposed to the outside of the outer shaft 10 at the base end side of the spline 16.

[0030] Furthermore, the tip 32 of each spline 16 is connected to the tip side of the inner shaft 22 at a position offset from the base end 42 in the circumferential direction of the outer shaft 10. The direction in which each tip 32 is offset from each base end 42 may be clockwise or counterclockwise when viewed from the axial direction of the outer shaft 10. For example, when viewed from the axial direction of the outer shaft 10, the tip 32 of the first spline 16a roughly overlaps with the base end 42 of the third spline 16c.

[0031] The inner shaft 22 is passed through the lumen of the outer shaft 10, and its base end is connected to the handle 14. The inner shaft 22 can move forward and backward toward the tip and base end of the outer shaft 10 by operating the operating part of the handle 14. This allows the electrode assembly 12 to switch between an extended state, where it extends in the axial direction of the outer shaft 10, as shown in Figure 2, and a flattened state, where it is crushed in the axial direction of the outer shaft 10, as shown in Figure 3(A).

[0032] In other words, when the electrode assembly 12 is in an extended state and the inner shaft 22 is pulled into the outer shaft 10, the base end 42 and tip end 32 of each spline 16 move closer to each other. As a result, each spline 16 expands radially on the outer shaft 10, and the electrode assembly 12 switches from an extended state to a flattened state. Also, when the electrode assembly 12 is in a flattened state and the inner shaft 22 is pushed out toward the tip of the outer shaft 10, the base end 42 and tip end 32 of each spline 16 move further apart. As a result, each spline 16 that has expanded radially on the outer shaft 10 narrows, and the electrode assembly 12 switches from a flattened state to an extended state.

[0033] In this embodiment, the tip portion 32 of each spline 16 is offset relative to the base portion 42 in the circumferential direction of the outer shaft 10. Therefore, when the electrode assembly 12 is in a flattened state, each spline 16 has a tip-side region and a base-side region that protrude radially in the radial direction of the outer shaft 10, and an intermediate region located between the tip-side region and the base-side region that extends in the circumferential direction of the outer shaft 10. Thus, each spline 16 is loop-shaped when viewed from the axial direction of the outer shaft 10. Furthermore, each loop-shaped spline 16 overlaps with an adjacent spline 16 when viewed from the axial direction of the outer shaft 10. For example, the loop-shaped first spline 16a overlaps with the loop-shaped second spline 16b and the loop-shaped sixth spline 16f. Also, when the electrode assembly 12 is in a flattened state, the electrode assembly 12 takes on a trumpet shape or conical shape that widens radially in the outer shaft 10 from the base end to the tip end. Furthermore, each spline 16 has a petal shape that expands radially in the direction of the outer shaft 10.

[0034] Each spline 16 is provided with at least one electrode 18. In this embodiment, each spline 16 is provided with multiple electrodes 18. The multiple electrodes 18 are arranged at predetermined intervals from each other in the longitudinal direction of the spline 16. Each electrode 18 is ring-shaped and is made of a highly conductive metal such as platinum, gold, silver, copper, aluminum, or stainless steel, or an alloy thereof. In this embodiment, as an example, each spline 16 is provided with a first electrode 18a, a second electrode 18b, a third electrode 18c, and a fourth electrode 18d in order from the tip side, but the number of electrodes 18 is not limited to four and can be at least one. In this disclosure, when it is not necessary to distinguish between the first electrode 18a to the fourth electrode 18d, they may simply be referred to as "electrode 18".

[0035] Figure 4(A) is an enlarged view of the tip side of the electrode assembly 12. Figure 4(B) is a perspective view of the electrode assembly 12 inserted into the inserter 38. Figure 5 is a view of a portion of the electrode assembly 12 as seen from the axial direction of the outer shaft 10. Figure 6(A) is a cross-sectional view perpendicular to the axis of the inner shaft 22 and the axis of the spline 16, and passing through the base end 42 of the spline 16. Figure 6(B) is a cross-sectional view perpendicular to the axis of the inner shaft 22 and the axis of the spline 16, and passing through the tip 32 of the spline 16.

[0036] Next, the structure of the electrode assembly 12 will be described in more detail. As shown in Figure 4(A), each spline 16 has a folded portion 36 in a predetermined tip region 34 that is continuous with the tip portion 32 connected to the restraining member 23. The tip region 34 is, for example, the region from the tip portion 32 to the tip end of the electrode 18 located at the very tip. The electrode 18 that serves as the reference for the range of the tip region 34 is the electrode used to apply voltage to biological tissue. The folded portion 36 is the part of each spline 16 that extends from the tip portion 32 in the direction D toward the tip of the catheter 4 and folds back in the direction P toward the proximal end of the catheter 4. Therefore, the folded portion 36 is located on the tip side of the catheter 4, relative to the restraining member 23.

[0037] Furthermore, as shown in Figure 4(B), the electrode assembly 12 is inserted into the inserter 38 prior to insertion into the patient's body. The inserter 38 is a flexible cylindrical sheath member. By inserting the electrode assembly 12 into the inserter 38, each spline 16, which is curved in a direction away from the inner shaft 22, can be brought closer to the inner shaft 22. The catheter 4 is inserted into the body via a sheath (not shown) that has been previously inserted into the body, with the electrode assembly 12 housed in the inserter 38. The housing of the electrode assembly 12 in the inserter 38 makes it possible to easily insert the catheter 4 into the sheath.

[0038] If the tip of the catheter 4 has a folded portion 36 of the spline 16, inserting the electrode assembly 12 into the inserter 38 and forcibly moving the spline 16 towards the inner shaft 22 will cause the folded portion 36 to bend sharply. This can place an excessive load on the folded portion 36. In addition, the spline 16 may have a core wire (not shown) for shape memory inserted into it. If the folded portion 36 is bent sharply and its radius of curvature becomes small, an excessive load can also be placed on the core wire.

[0039] In contrast, each spline 16 in this embodiment has a straight section 40 in its tip region 34, as shown in Figure 5. The straight section 40 extends linearly and obliquely to the radius line R of the inner shaft 22 passing through the tip section 32, when viewed from the axial direction of the outer shaft 10. In other words, the tip section 32 of each spline 16 is connected to the inner shaft 22 at a position offset from the radius line R that extends parallel to the straight section 40. For this reason, the straight section 40 extends obliquely to the radius line R passing through the tip section 32. The radius line R passing through the tip section 32 is, for example, the radius line R passing through the geometric center of the tip section 32 in a cross-section along the tip surface of the restraining member 23. The straight section 40 may be provided so as to be continuous with the tip section 32. Alternatively, the straight section 40 may be provided in only a part of the tip region 34. For example, the straight section 40 may be longer than the thickness of the tip section 32, or it may be in the range of 1 / 2 of the tip region 34, or it may be in the range of 3 / 4 of the tip region 34.

[0040] The straightness of the center line 40CL of the straight section 40 may be, for example, 0 mm or more and 5 mm or less. Also, the angle θ between the center line 40CL of the straight section 40 and the radius line R passing through the tip section 32 may be greater than 0 degrees and less than 90 degrees, for example, 30 degrees or more and 85 degrees or less.

[0041] In this way, by providing a straight section 40 in the tip region 34 of the spline 16 and rotating the straight section 40 around the tip 32 so that the straight section 40 is oblique to the radius line R, the radius of curvature of the folded section 36 can be increased when the spline 16 is pressed towards the inner shaft 22 by the inserter 38. This reduces the load on the folded section 36. Furthermore, when a core wire is inserted into the spline 16, the load on the core wire can also be reduced. As a result, damage to the spline 16 can be suppressed, and the reliability of the catheter 4 can be improved.

[0042] Furthermore, each spline 16 satisfies at least one of the following conditions: Condition I, which relates to the cross-sectional area of ​​the section perpendicular to the axis of the spline 16 (hereinafter referred to as "spline axis cross-sectional area" as appropriate); and Condition II, which relates to the radial dimension of the inner shaft 22 in the cross-sectional shape perpendicular to the axis of the inner shaft 22 (hereinafter referred to as "shaft axis cross-sectional dimension" as appropriate).

[0043] Regarding condition I, each spline 16 has a small cross-sectional area portion 44 in its tip region 34. The small cross-sectional area portion 44 is provided in at least a part of the tip region 34 and in a region continuous with the tip portion 32. The small cross-sectional area portion 44 is the portion in which the spline axial cross-sectional area 44A is smaller than the spline axial cross-sectional area 42A of the base portion 42. Since each spline 16 is curved, the axial direction of the spline 16 may differ at each position of the spline 16.

[0044] Regarding Condition II, each spline 16 has a small-sized portion 46 in a distal end region 34. The small-sized portion 46 is provided in at least a part of the distal end region 34 and in a region continuous from the distal end portion 32. The small-sized portion 46 is a portion where a shaft axial cross-sectional dimension 46S is smaller than a shaft axial cross-sectional dimension 42S of a base end portion 42. In the present disclosure, the "shaft axial cross-sectional dimension" is, for example, the distance between a straight line Lo that passes through the outermost point of the shaft axial cross-sectional shape, is perpendicular to a radial line R of the inner shaft 22 passing through a geometric center C of the shaft axial cross-sectional shape, and a straight line Li that passes through the innermost point of the shaft axial cross-sectional shape.

[0045] The range in which the small cross-sectional area portion 44 extends and the range in which the small-sized portion 46 extends may each be longer than the thickness of the distal end portion 32, may be 1 / 2 of the distal end region 34, or may be 3 / 4 of the distal end region 34. Further, for the small cross-sectional area portion 44, the average value of a spline axial cross-sectional area 44A may be smaller than a spline axial cross-sectional area 42A at the base end portion 42. Furthermore, the average value of the spline axial cross-sectional area 44A may be smaller than the average value of spline axial cross-sectional areas in a range from the base end portion 42 to an electrode 18 located on the most proximal side of the spline 16. Further, for the small-sized portion 46, the average value of a shaft axial cross-sectional dimension 46S may be smaller than the shaft axial cross-sectional dimension 42S of the base end portion 42. Furthermore, the average value of the shaft axial cross-sectional dimension 46S may be smaller than the average value of shaft axial cross-sectional dimensions in a range from the base end portion 42 to an electrode 18 located on the most proximal side of the spline 16. The average value described above is an average of values measured at a plurality of points spaced at predetermined intervals in the extending direction of the spline 16.

[0046] When each spline 16 satisfies at least one of Condition I and Condition II, the distal end region 34 including the folded-back portion 36 can be easily bent when the spline 16 is pressed toward the inner shaft 22 side by the inserter 38. This makes it possible to reduce the load applied to the folded-back portion 36. Further, when a core wire is inserted into the spline 16, the load applied to the core wire can also be reduced. Therefore, damage to the spline 16 can be suppressed, and the reliability of the catheter 4 can be improved.

[0047] The small cross-sectional area portion 44 of the present embodiment is also a small dimension portion 46. Accordingly, each spline 16 of the present embodiment satisfies both condition I and condition II. This makes the distal end region 34 even more bendable. Therefore, damage to the spline 16 can be further suppressed, and the reliability of the catheter 4 can be further improved.

[0048] Furthermore, in the present embodiment, the straight portion 40 is continuous from the distal end portion 32. The entire straight portion 40 has substantially the same spline shaft cross-sectional area as the distal end portion 32, and also has substantially the same shaft cross-sectional dimension as the distal end portion 32. For this reason, each spline 16 satisfies condition I and condition II over the entire straight portion 40. That is, the spline shaft cross-sectional area of the straight portion 40 is smaller than the spline shaft cross-sectional area 42A of the proximal end portion 42. In addition, the shaft cross-sectional dimension of the straight portion 40 is smaller than the shaft cross-sectional dimension 42S of the proximal end portion 42. This makes the distal end region 34 even more bendable. Therefore, damage to the spline 16 can be further suppressed, and the reliability of the catheter 4 can be further improved. Note that the straight portion 40 may satisfy only one of condition I and condition II.

[0049] Furthermore, by providing the small cross-sectional area portion 44 and the small dimension portion 46 only in the distal end region 34, the thickness of the portion of the spline 16 where the electrode 18 is provided can be maintained. This maintains the ease of bringing the electrode 18 into contact with a biological tissue. Therefore, the operability of the catheter 4 can be improved. As an example, each spline 16 has substantially the same spline shaft cross-sectional area and shaft cross-sectional dimension from the proximal end portion 42 to the electrode 18 disposed on the most distal side of the spline 16.

[0050] Furthermore, the shaft axis cross-sectional shape of the small dimension section 46 in this embodiment is flattened in the direction X from which the tip portion 32 extends to the tip region 34, or in other words, in the direction X from which the straight portion 40 extends, when viewed from the axial direction of the outer shaft 10. That is, the dimension of the shaft axis cross-sectional shape of the small dimension section 46 in the direction X from which the straight portion 40 extends is smaller than the dimension in the direction perpendicular to the straight portion 40. For example, the shaft axis cross-sectional shape of the small dimension section 46 may be elliptical, oblong, or oval. Alternatively, the shaft axis cross-sectional shape of the small dimension section 46 may be a rounded rectangle or the like, having a pair of straight lines perpendicular to the direction X from which the straight portion 40 extends and aligned in that direction X. This makes the tip region 34 easier to bend. Therefore, damage to the spline 16 can be further suppressed, and the reliability of the catheter 4 can be further improved.

[0051] Furthermore, the straight section 40 may be connected to the portion of the spline 16 closer to the base end of the straight section 40 such that the central axis of the straight section 40 is offset radially outward from the central axis of the base end portion of the inner shaft 22. This prevents interference between the straight section 40 and the restraining member 23 when the electrode assembly 12 is housed in the inserter 38, when the diameter of the restraining member 23 is larger than the diameter of the inner shaft 22, making it easier to house the electrode assembly 12 in the inserter 38. The outer circumferential surface of the straight section 40 and the outer circumferential surface of the base end portion may be smoothly continuous.

[0052] As described above, in the catheter 4 of this embodiment, when viewed from the axial direction of the outer shaft 10, the straight section 40 provided in the tip region 34 of the spline 16 extends diagonally in a straight line with respect to the radius line R of the inner shaft 22 passing through the tip portion 32. Furthermore, the catheter 4 of this embodiment has a small cross-sectional area section 44 in the tip region 34 in which the spline axial cross-sectional area is smaller than the spline axial cross-sectional area of ​​the base portion 42. In addition, the catheter 4 has a small dimension section 46 in the tip region 34 in which the shaft axial cross-sectional dimension is smaller than the shaft axial cross-sectional dimension of the base portion 42. As a result, the load on the folded portion 36 can be reduced, and the reliability of the catheter 4 can be improved. Note that even if only one of the straight section 40, small cross-sectional area section 44, and small dimension section 46 is present, the reliability improvement effect of the catheter 4 can be obtained, but by combining two or more, the effect can be obtained more reliably or even more effectively.

[0053] The embodiments of this disclosure have been described in detail above. The embodiments described above are merely examples of how to implement this disclosure. The content of the embodiments does not limit the technical scope of this disclosure, and many design changes, such as changes, additions, and deletions of components, are possible, as long as they do not deviate from the idea of ​​this disclosure as defined in the claims. A new embodiment with design changes will have the effects of both the combined embodiment and the variation. In the embodiments described above, the content in which such design changes are possible is emphasized with notations such as "of this embodiment" or "in this embodiment," but design changes are also permitted even if there are no such notations. Any combination of components included in each embodiment is also valid as an embodiment of this disclosure. The hatching applied to the cross-section in the drawings does not limit the material of the object to which the hatching is applied.

[0054] The configuration of the catheter 4 and the power supply 8 can be changed as appropriate. For example, the tip 32 and proximal 42 of the spline 16 do not have to be offset in the circumferential direction of the inner shaft 22. The electrode assembly 12 may also be basket-shaped or the like. The term "basket shape" in this disclosure is derived from the fact that the shape of the multiple splines 16 in the deployed state resembles the curved pattern on the surface of a basketball. Some electrodes 18 may also be excluded from the application of the ablation voltage. Electrodes 18 excluded from the application of the voltage can be used for potential measurement or as spares when the ablation range is wide. The catheter 4 may also have an irrigation mechanism that sprays an irrigation fluid such as physiological saline from the tip side during ablation.

[0055] Furthermore, the catheter 4 may be bendable in one direction or multiple directions at the tip of the outer shaft 10 by operating the handle 14. The control of the power supply unit 26 by the control unit 28 may be implemented by hardware (circuit) or by software (program). If implemented by software, the software consists of a group of programs that cause a computer to execute each function. Each program may be pre-installed in the computer or installed on the computer from a network or recording medium.

[0056] The embodiments may be specified by the following items. [Item 1] A catheter (4) comprising: an outer shaft (10) having a lumen; an inner shaft (22) slidably inserted into the lumen; and at least one spline (16) whose proximal end (42) is connected to the tip side of the outer shaft (10) and whose tip (32) is connected to the tip side of the inner shaft (22) and on which at least one electrode (18) is arranged, wherein the spline (16) has a straight section (40) that extends diagonally in a straight line with respect to the radius line (R) of the inner shaft (22) passing through the tip (32) in a predetermined tip region (34) continuous with the tip (32) of the spline (16) when viewed from the axial direction of the outer shaft (10). [Item 2] The catheter (4) of Item 1, wherein the angle (θ) between the straight section (40) and the radius line (R) is 30 degrees or more and 85 degrees or less. [Item 3] A catheter (4) that satisfies at least one of the following conditions: the spline (16) has a cross-sectional area perpendicular to the axis of the spline (16) such that the cross-sectional area of ​​the straight section (40) is smaller than the cross-sectional area of ​​the proximal end (42), and the radial dimension of the inner shaft (22) in a cross-sectional shape perpendicular to the axis of the inner shaft (22) such that the dimension of the straight section (40) is smaller than the dimension of the proximal end (42).[Item 4] The device comprises an outer shaft (10) having lumens, an inner shaft (22) slidably inserted into the lumens, and at least one spline (16) whose base end (42) is connected to the tip side of the outer shaft (10) and whose tip (32) is connected to the tip side of the inner shaft (22) and on which at least one electrode (18) is arranged, wherein the spline (16) is A catheter (4) that satisfies at least one of the following conditions: [Item 5] The shape of the small dimension portion (46) is flattened in the direction (X) in which the tip region (34) extends from the tip (32) of the outer shaft (10). [Item 6] The catheter (4) is any catheter (4) according to item 1 to 5, having a plurality of splines (16) arranged in the circumferential direction of the inner shaft (22). [Item 7] The tip region (34) is any catheter (4) according to item 1 to 6, having a folded portion (36) that extends from the tip portion (32) toward the tip (D) of the catheter (4) and folds back toward the proximal end (P) of the catheter (4).

[0057] This disclosure can be used in catheters.

[0058] 4 Catheter, 10 Outer shaft, 16 Spline, 18 Electrode, 22 Inner shaft, 32 Tip, 34 Tip region, 36 Folded section, 40 Straight section, 42 Base end, 42A Spline axial cross-sectional area, 42S Shaft axial cross-sectional dimensions, 44 Small cross-sectional area section, 44A Spline axial cross-sectional area, 46 Small dimension section, 46S Shaft axial cross-sectional dimensions.

Claims

1. A catheter comprising: an outer shaft having a lumen; an inner shaft slidably inserted into the lumen; and at least one spline whose base end is connected to the tip side of the outer shaft and whose tip is connected to the tip side of the inner shaft and on which at least one electrode is disposed, wherein the spline has a straight portion that extends diagonally in a straight line with respect to the radius line of the inner shaft passing through the tip, in a predetermined tip region continuous with respect to the tip of the spline when viewed from the axial direction of the outer shaft.

2. The catheter according to claim 1, wherein the angle between the straight portion and the radius line is 30 degrees or more and 85 degrees or less.

3. The catheter according to claim 1 or 2, wherein the spline satisfies at least one of the following: the cross-sectional area of ​​the straight portion of the spline perpendicular to the axis of the spline is smaller than the cross-sectional area of ​​the base end; and the radial dimension of the inner shaft in the cross-sectional shape perpendicular to the axis of the inner shaft is smaller than the dimension of the straight portion of the inner shaft.

4. A catheter comprising: an outer shaft having a lumen; an inner shaft slidably inserted into the lumen; and at least one spline having a base end connected to the tip side of the outer shaft and a tip end connected to the tip side of the inner shaft, on which at least one electrode is disposed, wherein the spline satisfies at least one of the following: the cross-sectional area of ​​the cross section perpendicular to the axis of the spline has a small cross-sectional area portion in a predetermined tip region continuous with the tip of the spline, where the cross-sectional area is smaller than the cross-sectional area of ​​the base end and continuous with the tip; and the radial dimension of the inner shaft in the cross-sectional shape perpendicular to the axis of the inner shaft has a small dimension portion in the tip region where the dimension is smaller than the dimension of the base end and continuous with the tip.

5. The catheter according to claim 4, wherein the shape of the small portion is flattened in the direction in which the tip portion extends from the tip region when viewed from the axial direction of the outer shaft.

6. The catheter according to any one of claims 1, 2, 4, and 5, wherein the catheter has a plurality of splines arranged in the circumferential direction of the inner shaft.

7. The catheter according to any one of claims 1, 2, 4, and 5, wherein the tip region has a folded portion that extends from the tip portion toward the tip of the catheter and folds back toward the proximal end of the catheter.

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