JP7778677B2 - Electrode catheter - Google Patents

Description

The present disclosure relates to an electrode catheter.

Patent Document 1 discloses an electrode catheter comprising an outer shaft with a lumen formed therein, an inner shaft that is inserted into the lumen so as to be able to advance and retreat, and an electrode assembly that is provided distal to the distal end of the outer shaft. The electrode assembly comprises multiple splines connected to both the outer shaft and the inner shaft. The shape of the electrode assembly can be adjusted by the multiple splines deforming in response to the advance and retreat of the inner shaft.

JP 2015-057093 A

The inventors have come up with a new idea to increase the degree of freedom in the shape of the electrode assembly, which is adjusted by moving the inner shaft back and forth.

One of the objectives of this disclosure is to provide technology that increases the degree of freedom in the shape of the electrode assembly, which is adjusted by moving the inner shaft back and forth.

The electrode catheter of the first item of the present disclosure comprises an outer shaft having a lumen formed therein, an inner shaft that is inserted into the lumen so as to be able to advance and retreat, and an electrode assembly at least a portion of which is provided distal to the distal end of the outer shaft, the electrode assembly having a plurality of splines, one end of which is connected to the outer shaft and the other end of which is connected to the inner shaft, and the inner shaft is capable of advancing and retreating between a protruding position where it protrudes from a distal end opening provided at the distal end of the lumen and a retracted position where it is retracted to the rear of the distal end opening.

The electrode catheter of the second aspect of the present disclosure comprises an outer shaft having a lumen formed therein, an inner shaft inserted into the lumen so as to be able to advance and retract, and an electrode assembly having at least a portion disposed distal to the distal end of the outer shaft, the electrode assembly having a plurality of splines, one end of which is connected to the outer shaft and the other end of which is connected to the inner shaft, each of the plurality of splines having a distal folded end that folds back at the distal end of the spline in the advance and retraction direction of the inner shaft when the inner shaft is positioned anywhere within its advance and retraction range, and each of the plurality of splines is flexibly deformable so as to change the distance in the advance and retraction direction from the inner shaft to the distal folded end in accordance with the advance and retraction of the inner shaft.

This disclosure allows for greater freedom in the shape of the electrode assembly, which can be adjusted by moving the inner shaft back and forth.

FIG. 2 is an explanatory diagram illustrating the state of use of the electrode catheter of the first embodiment. FIG. 1 is a side view schematically showing an electrode catheter of a first embodiment. FIG. 2 is a schematic diagram showing the electrode assembly of the first embodiment together with the surrounding structure. FIG. 2 is a schematic diagram of the electrode assembly of the first embodiment viewed from the forward/backward direction together with the surrounding structure. 4 is a cross-sectional view taken along line AA in FIG. 3. FIG. 4 is a first explanatory diagram schematically illustrating the operation of the electrode assembly of the first embodiment. FIG. 10 is a second explanatory diagram schematically illustrating the operation of the electrode assembly of the first embodiment. FIG. 10 is a third explanatory diagram schematically illustrating the operation of the electrode assembly of the first embodiment. FIG. 1 is a diagram schematically illustrating an electrode assembly according to a reference embodiment. 10A to 10C are explanatory diagrams relating to the operation of the electrode assembly of the reference embodiment. 10A and 10B are explanatory diagrams illustrating a state in which an electrode assembly according to a reference embodiment is used. FIG. 2 is an explanatory diagram of an irrigation port according to the first embodiment. FIG. 10 is a schematic view of the electrode assembly of the second embodiment, viewed from the forward/backward direction together with the surrounding structure. FIG. 10 is a schematic view showing an electrode assembly according to a second embodiment, viewed obliquely together with its surrounding structure. 10A to 10C are explanatory diagrams relating to the operation of the electrode assembly of the second embodiment.

Embodiments for implementing the present disclosure are described below. Identical or equivalent components are designated by the same reference numerals, and redundant explanations will be omitted. For the sake of clarity, components in each drawing are omitted, enlarged, or reduced in size as appropriate. The drawings should be viewed in accordance with the orientation of the reference numerals.

(First embodiment) Refer to Figure 1. The following description begins with a usage scenario for the electrode catheter 10. The electrode catheter 10 is inserted into the body to treat a living organism. "Treatment" here refers to an action related to the medical treatment or examination of the living organism. Treatment here refers to, for example, ablation (PFA (Pulsed Field Ablation), radiofrequency ablation, etc.) and defibrillation. Examination here refers to, for example, an electrocardiogram. Here, an example is described in which the treatment target 16 is the terminal end of a pulmonary vein 14 that opens into the left atrium 12 of the living organism. In other words, the treatment target 16 of the living organism is the terminal end of a second organ (here, the pulmonary vein) that opens into a first organ (here, the heart) of the living organism. This treatment target 16 has a tapered portion 16a that tapers toward the back when viewed from the first organ. This treatment target 16 is merely an example, and various parts of the living organism may be the treatment target 16, regardless of whether or not it has a tapered portion 16a.

Refer to Figures 2, 3, and 4. The electrode catheter 10 comprises a cylindrical outer shaft 22 having a lumen 20 formed therein, and an inner shaft 24 that is inserted into the lumen 20 and is capable of advancing and retracting. The electrode catheter 10 also comprises a handle 26 that is attached to the proximal portion of the outer shaft 22 and supports the outer shaft 22, and an electrode assembly 28, at least a portion of which is located distal to the distal end of the outer shaft 22. As described herein, the condition "located distal to the distal end of the outer shaft 22" is satisfied by at least a portion of the electrode assembly 28. For example, in this embodiment, this condition is satisfied by the entire electrode assembly 28 when the inner shaft 24 is located distal to a settling start position Pb (described below) within the advance/retract range of the inner shaft 24. Conversely, this condition is satisfied by a portion of the electrode assembly 28 when the inner shaft 24 is located proximal to the settling start position Pb within the advance/retract range of the inner shaft 24.

Below, the positional relationship of each component will be explained based on the assumption that the outer shaft 22 and inner shaft 24 are not bent and extend linearly. The circumferential direction and radial direction around the center line (not shown) of the outer shaft 22 are simply referred to as the "circumferential direction" and "radial direction." The "distal side" refers to the side of the outer shaft 22 that is farther from the surgeon's hand holding the handle 26 in the axial direction, and the "proximal side" refers to the side opposite the distal side in the axial direction. The most distal position within the range in which the inner shaft 24 can be advanced or retreated is referred to as the most distal position Pa. Figure 3 shows the inner shaft 24 in the most distal position Pa.

The handle 26 is held by the surgeon. The handle 26 is provided with an advance/retract operation unit 26a, such as a slide knob, which is operated to advance/retract the inner shaft 24.

See Figures 3, 4, and 5. The outer shaft 22 is inserted into the body at least on its distal side. The distal end of the lumen 20 of the outer shaft 22 is provided with a distal end opening 30 that opens to the distal end of the outer shaft 22.

The inner shaft 24 is composed of at least one shaft member 24A-24D. In this embodiment, the inner shaft 24 is illustrated as being composed of four shaft members 24A-24D, but the number is not particularly limited. The four shaft members 24A-24D include, from distal to proximal, the most distal shaft member 24A, the distal shaft member 24B, the intermediate shaft member 24C, and the proximal shaft member 24D. The multiple shaft members 24A-24D are integrated by welding, adhesive bonding, or the like. The most distal shaft member 24A is composed of a member with a higher hardness than the distal shaft member 24B. This ensures the strength of the distal end of the inner shaft 24. Alternatively, the most distal shaft member 24A and the distal shaft member 24B may be composed of a single shaft member.

The outer shaft 22 and inner shaft 24 are flexible and bendable. The outer shaft 22 and inner shaft 24 (shaft members 24A-24D) are made of various materials, including well-known materials used to make catheter shafts. Examples of such materials include synthetic resins such as polyether block ether, polyamide, polyolefin, and polytetrafluoroethylene.

The electrode assembly 28 includes a plurality of splines 32 and a plurality of electrodes 34 provided on each of the splines 32. Here, an example is shown in which there are four splines 32 in total, but the number is not particularly limited. In Figure 3, only two splines 32 are shown, with the remaining splines 32 omitted.

A plurality of electrodes 34 corresponding to each spline 32 are provided on each spline 32 at intervals along the length of the spline 32. The electrodes 34 are ring-shaped. The electrodes 34 are made of a metal (including alloys) with good electrical conductivity, such as platinum, gold, or silver.

Each of the multiple splines 32 is configured as a flexible linear body that can be bent and deformed. The multiple splines 32 are spaced circumferentially around the centerline of the outer shaft 22. Each of the multiple splines 32 has one longitudinal end (hereinafter referred to as the outer end 32a) connected to the outer shaft 22 and the other longitudinal end (hereinafter referred to as the inner end 32b) connected to the inner shaft 24. To achieve this, the splines 32 of this embodiment are connected to each shaft 22, 24 via their core wires 42 (described below). The splines 32 are connected to each shaft 22, 24 by adhesive bonding, welding, or the like. To achieve this, the splines 32 may be connected to each shaft 22, 24 directly or via another member fixed to each shaft 22, 24. The splines 32 of this embodiment are inserted into first insertion holes 36 provided in the outer shaft 22, and their outer end 32a is connected to the outer shaft 22. In this embodiment, the spline 32 is inserted into a second insertion hole 38 provided in the inner shaft 24, and its inner end 32b is connected to the intermediate shaft member 24C.

The spline 32 has an exposed portion 40 that is exposed outside the inner shaft 24 and the outer shaft 22. The term "exposed" here refers to the condition that the inner shaft 24 is positioned anywhere within its retractable range. For example, when the inner shaft 24 is in retracted position P2 (described below), a specific portion of the spline 32 located within the lumen 20 of the outer shaft 22 is located on the spline 32. In this case, if the inner shaft 24 is in protruding position Pa1 (described below), and that specific portion of the spline 32 is exposed outside the lumen 20 of the outer shaft 22, that specific portion is treated as part of the exposed portion 40. The portion of the spline 32 that constitutes the exposed portion 40 does not change depending on the position of the inner shaft 24 within its retractable range. Hereinafter, the end of the exposed portion 40 of the spline 32 facing the outer shaft 22 will be referred to as the outer-side exposed end 32c, and the end facing the inner shaft 24 will be referred to as the inner-side exposed end 32d.

The spline 32 includes a core wire 42 that forms the core of the spline 32 and an outer tube 44 that covers the core wire 42. The core wire 42 is made of, for example, metal, resin, etc. The outer tube 44 is made of, for example, resin, etc. A plurality of conductors (not shown) are inserted through the outer tube 44 and are connected to each of the plurality of electrodes 34 corresponding to the spline 32. The plurality of conductors are drawn into the outer shaft 22 via the outer end 32a of the spline 32 and electrically connected to an external electrical device. The external electrical device cooperates with the plurality of electrodes 34 to supply electricity for treatment to the treatment target portion 16 of the living body, process biosignals (such as cardiac potentials) from the treatment target portion 16, and so on.

Please refer to Figures 6 to 8. Figure 6 shows the inner shaft 24 at its most distal position Pa, Figure 8 shows the inner shaft 24 at its retraction start position Pb, which will be described later, and Figure 7 shows the inner shaft 24 in a state between the most distal position Pa and the retraction start position Pb.

The inner shaft 24 can be advanced and retracted between a protruding position P1, where the inner shaft 24 protrudes from the distal end opening 30 of the outer shaft 22, and a retracted position P2, where the inner shaft 24 is retracted to the rear of the distal end opening 30. Here, "retracted position P2" refers to the position rearward of the position where the distal end 24a of the inner shaft 24 and the distal end opening 30 of the outer shaft 22 overlap. When the inner shaft 24 is retracted, the position where the inner shaft 24 begins to retract to the rear of the distal end opening 30 is called the retraction start position Pb. The retraction start position Pb is part of the retraction position P2. Figure 8 shows an example where the inner shaft 24 is at the retraction start position Pb, but the inner shaft 24 of this embodiment can be retracted further rearward than the retraction start position Pb.

The exposed portion 40 of the spline 32 can expand or contract radially in response to the advancement and retreat of the inner shaft 24. The exposed portion 40 contracts by shrinking radially inward and expands by bulging radially outward. When the inner shaft 24 is in the protruding position P1, the multiple splines 32 in this embodiment form a basket structure that can expand or contract in response to the advancement and retreat of the inner shaft 24. The basket structure is formed by the multiple splines 32 surrounding an inner space. It can also be said that the multiple splines 32 form a basket structure when the inner shaft 24 is positioned anywhere within the advancement and retreat range.

The outer diameter of the electrode assembly 28 in this embodiment can be adjusted by expanding or contracting the multiple splines 32 in response to the advancement and retreat of the inner shaft 24. Here, the outer diameter of the electrode assembly 28 refers to the radius of a circle circumscribing the electrode assembly 28, with the center line (not shown) of the outer shaft 22 as its center, when viewed from the advancement and retreat direction Da of the inner shaft 24.

The position of the inner shaft 24 when the outer diameter of the basket-structured electrode assembly 28 is at its maximum is referred to as the maximum outer diameter position Pc. Also, consider an end range Rb located at the end of the movable range Ra of the inner shaft 24, from the most distal position Pa to the beginning retraction position Pb, closer to the beginning retraction position Pb. The end range Rb here refers to the range from the beginning retraction position Pb to the length of the movable range Ra in the forward/retraction direction, divided into four equal parts. In Figure 6, each position Pa, Pb, and Pc is indicated by 24a (at Pa), etc., using the position of the distal end 24a of the inner shaft 24. For example, 24a (at Pc) indicates the position of the distal end 24a when the inner shaft 24 is at the maximum outer diameter position Pc. When the distal end 24a of the inner shaft 24 is located within the end range Rb in Figure 6, this means that the inner shaft 24 is in the end range Rb.

The inventors of the present application have discovered that when the multiple splines 32 are configured to expand or contract in response to the advancement or retreat of the inner shaft 24, the maximum outer diameter position Pc is located somewhere within the end range Rb, although this may vary due to factors such as the flexibility of the splines 32. In particular, they have discovered that in many cases, the maximum outer diameter position Pc of the inner shaft 24 is located very close to the retraction start position Pb within the end range Rb of the inner shaft 24. When the electrode assembly 28 is configured as described above, as the inner shaft 24 retracts from the distal-most position Pa to the maximum outer diameter position Pc, the multiple splines 32 expand, increasing its outer diameter. Furthermore, as the inner shaft 24 retracts from the maximum outer diameter position Pc, the multiple splines 32 each contract, decreasing its outer diameter. Note that the maximum outer diameter position Pc of the inner shaft 24 may also be the retraction start position Pb.

When the inner shaft 24 is positioned anywhere within its range of movement, each of the multiple splines 32 is shaped to fold back at its distal end in the direction of movement Da of the inner shaft 24. In this embodiment, this condition is met when the inner shaft 24 is positioned at any position within its range of movement. Here, the "distal end 32h of the spline 32" does not refer to the longitudinal end of the spline 32, but rather to the point located most distally in the direction of movement Da of the spline 32. By folding back the spline 32 in the direction of movement Da of the inner shaft 24 in this manner, a distal folded end 32e is formed at the distal end 32h of the spline 32. This "distal folded end 32e" refers to the boundary between two portions 36A, 36B extending longitudinally of the spline 32 from both ends of the spline 32 toward the distal end 32h. The portion of these two portions 36A, 36B that extends further in the longitudinal direction of the spline 32 and toward the proximal side than the boundary between the two portions is not included in the distal folded end portion 32e.

Each of the multiple splines 32 is flexibly deformable to change the forward/backward distance La from the inner shaft 24 to the distal flap portion 32e of the spline 32 in accordance with the forward/backward movement of the inner shaft 24. This forward/backward distance La increases as the inner shaft 24 moves back from the distalmost position Pa to the maximum outer diameter position Pc, and decreases as the inner shaft 24 moves back from the maximum outer diameter position Pc. This forward/backward distance La refers to the distance from the distal end of the inner shaft 24 to the distal end 32h of the spline 32. The forward/backward distance when the inner shaft 24 is at the forward/backward position (here, the distalmost position Pa) where the forward/backward distance La is smallest within the forward/backward range of the inner shaft 24 is referred to as the reference distance. In this case, "changing the advance/retract direction distance La" does not mean that the advance/retract direction distance La changes within a small range relative to the reference distance (for example, a range of the reference distance x 1.1 or less), but rather that the advance/retract direction distance La changes within a certain range relative to the reference distance (for example, a range of the reference distance x 1.5 or more).

As the inner shaft 24 retracts from the distalmost position Pa to the maximum outer diameter position Pc, each of the multiple splines 32 deforms such that the position of the distal folded end 32e relative to the inner shaft 24 shifts radially outward. At this time, the distal folded end 32e of the spline 32 can shift from an extension range Sa, which is an extension of the outer shaft 22 in the forward/backward direction Da, to a position radially outward beyond that extension range Sa. Here, the extension range Sa refers to the range obtained by extending the entire portion of the outer shaft 22 radially inward from the outer circumferential surface in the forward/backward direction Da. Furthermore, as the inner shaft 24 retracts from the distalmost position Pa to the maximum outer diameter position Pc, each of the multiple splines 32 deforms such that the position of the outermost peripheral end 32f relative to the inner shaft 24 shifts radially outward. As a result, the outer diameter of the electrode assembly 28 increases. Here, the outermost peripheral end 32f refers to the radially outermost point of the exposed portion 40 of the spline 32.

To achieve the aforementioned flexible deformation of the spline 32, the spline 32 has a shape that does not have any bent portions within the aforementioned extension range Sa. A bent portion here refers to a portion that maintains a bent state (folded state) even when the spline 32 deforms in response to the advancement and retreat of the inner shaft 24, as in the reference embodiment described below. If a bent portion exists within the longitudinal range of such an exposed member, the flexible deformation of the spline 32 at that bent portion will be significantly restricted.

The spline 32 of this embodiment has a shape that is free of bends in the longitudinal range from the distal folded end 32e of the spline 32 to the inner end 32b. The spline 32 of this embodiment also has a shape that is free of bends in the longitudinal range from the distal folded end 32e of the spline 32 to the outermost end 32f. This shape allows the spline 32 to deform in response to the advancement and retreat of the inner shaft 24 when the inner shaft 24 is in the protruding position P1, while maintaining a smooth curved shape that is convex distally in the longitudinal range including the distal folded end 32e. In this embodiment, the spline 32 deforms in the longitudinal range from the inner end 32b of the spline 32 to the outermost end 32f while maintaining a smooth curved shape that is convex distally. Here, "smooth curved shape" means a shape that is free of bends in that longitudinal range.

The effects of the electrode catheter 10 described above will now be explained.

(A) In addition to the aforementioned protruding position P1, the inner shaft 24 can also be advanced and retracted to the retracted position P2. Therefore, compared to when the inner shaft 24 can only be advanced and retracted to the protruding position P1, the range in which the inner shaft 24 can be advanced and retracted can be expanded to the retracted position P2. Consequently, compared to when the inner shaft 24 can only be advanced and retracted to the protruding position P1, the amount of deformation of the multiple splines 32 can be increased, and the degree of freedom in the shape of the electrode assembly 28 that can be adjusted by advancing and retracting the inner shaft 24 can be increased.

(B) The outer diameter of the electrode catheter 10 can be adjusted by expanding or contracting the multiple splines 32 in response to the advancement and retraction of the inner shaft 24. With this structure, as described above, typically, a maximum outer diameter position Pc, where the outer diameter of the electrode assembly 28 is at its maximum, exists somewhere within the end range Rb of the movable range Ra of the inner shaft 24. As described above, the inner shaft 24 of this embodiment can expand the advancement and retraction range of the inner shaft 24 from the protruding position P1 to the retracted position P2 (retraction start position Pb). Therefore, compared to when the inner shaft 24 can only advance and retract to the protruding position P1, the inner shaft 24 can be reliably positioned at the maximum outer diameter position Pc. Consequently, the shape of the electrode assembly 28 can be adjusted so that the outer diameter of the electrode assembly 28 is reliably at its maximum outer diameter.

(C) The spline 32 is flexibly deformable so as to change the distance La of the distal folded end 32e relative to the inner shaft 24 in accordance with the advancement and retreat of the inner shaft 24. Therefore, compared to a case in which the distance La of the distal folded end 32e of the spline 32 relative to the inner shaft 24 is constant, as in the following reference embodiment, the degree of freedom in the shape of the electrode assembly 28, which is adjusted by the advancement and retreat of the inner shaft 24, can be increased.

Referring to Figures 9A and 9B, an electrode catheter 100 of the reference embodiment will be described. This electrode catheter 100 differs from the electrode catheter 10 of the first embodiment in the splines 32 of the electrode assembly 28. The multiple splines 32 of the reference embodiment have a bent portion 102 in the aforementioned extension range Sa, and this bent portion 102 forms the distal folded end 32e.

In this case, even when the inner shaft 24 is advanced or retracted, the bend 102 at the distal folded end 32e of the spline 32 inhibits flexible deformation of the spline 32. As a result, the portion of the spline 32 from the distal folded end 32e to the inner exposed end 32d cannot flexibly deform, while the portion between the distal folded end 32e and the outer exposed end 32c can flexibly deform. In other words, with the structure of the reference embodiment, the multiple splines 32 cannot flexibly deform to change the advance/retract directional distance La from the inner shaft 24 to the distal folded end 32e of the spline 32 in response to the advance/retraction of the inner shaft 24. Therefore, as the inner shaft 24 is retracted, the advance/retract directional distance Lb from the distal folded end 32e of the spline 32 to the outer exposed end 32c of the spline 32 uniformly shortens. As a result, the multiple splines 32 as a whole assume a flattened shape in the advance/retract direction Da. As a result, as shown in Figure 10, when the outer diameter of the electrode assembly 28 is increased, the electrode assembly 28 can only come into contact with the tapered portion 16a of the treatment target area 16 of the living body at a localized location near the outermost edge 32f of the electrode assembly 28.

In this regard, each of the multiple splines 32 in this embodiment is flexibly deformable to change the advance/retraction direction distance La from the inner shaft 24 to the distal folded end 32e of the spline 32 in response to the advance/retraction of the inner shaft 24. Therefore, when the inner shaft 24 is retracted, the spline 32 can flexibly deform so as to increase the advance/retraction direction distance La from the inner shaft 24 to the distal folded end 32e of the spline 32. This prevents the advance/retraction direction distance Lb from the distal folded end 32e of the spline 32 to the outer exposed end 32c of the spline 32 from uniformly shortening as the inner shaft 24 is retracted, and allows the advance/retraction direction distance Lb to be maintained at a certain length. This makes it less likely that the multiple splines 32 as a whole will become flattened in the advance/retraction direction Da. Furthermore, as shown in FIG. 1, when the outer diameter of the electrode assembly 28 is increased, the electrode assembly 28 can contact the tapered portion 16a of the treatment target portion 16 of the living body at locations other than the outermost peripheral end 32f of the electrode assembly 28. Therefore, even when the outer diameter of the electrode assembly 28 is increased, it is easier to ensure the contact area of the electrode assembly 28 with the treatment target portion 16 of the living body.

Other features of the electrode catheter 10 will now be described. Refer to Figures 3 and 11. At least one of the outer shaft 22 and the inner shaft 24 has irrigation ports 50A, 50B for injecting irrigation fluid. In this embodiment, the outer shaft 22 has a first irrigation port 50A, and the inner shaft 24 has a second irrigation port 50B. The first irrigation port 50A opens at the distal end surface of the outer shaft 22 and serves as the distal end opening 30 of the outer shaft 22. The second irrigation port 50B opens at the distal end surface of the inner shaft 24. Irrigation fluid is injected distally from each irrigation port 50A, 50B. Irrigation fluid is supplied to each irrigation port 50A, 50B from an external fluid supply device through irrigation fluid supply paths (not shown) provided in the handle 26, each shaft 22, 24, etc.

The irrigation fluid is, for example, saline solution. The irrigation fluid is irrigated, for example, to cool the treatment target area 16 and the electrode assembly 28 of the living body, and to promote blood flow around the electrode assembly 28. When ablation is performed using the electrode assembly 28, the treatment target area 16 and the electrode assembly 28 are heated by the electricity output from the electrode assembly 28. Cooling the heated treatment target area 16, etc. with irrigation fluid can prevent excessive temperature rise. When the electrode assembly 28 is placed in an area where blood is present, such as the heart or blood vessels, blood stagnation around the complex-shaped electrode assembly 28 increases the risk of thrombus formation. By using irrigation fluid to promote the flow of blood that would otherwise stagnate, the risk of thrombus formation can be reduced.

Let's consider a case where the inner shaft 24 can only move back and forth between the protruding position P1. In this case, for example, when the inner shaft 24 is at the distalmost position Pa (see FIG. 6), the inner exposed end 32d of the spline 32 moves away from the first irrigation port 50A of the outer shaft 22. This poses a problem in that irrigation fluid injected from the first irrigation port 50A has difficulty reaching the area around the inner exposed end 32d of the spline 32. Furthermore, in this case, the outer exposed end 32c of the spline 32 moves away from the second irrigation port 50B (not shown) of the inner shaft 24. This poses a problem in that irrigation fluid injected from the second irrigation port 50B has difficulty reaching the area around the outer exposed end 32c of the spline 32.

(D) In this regard, as described above, the inner shaft 24 of this embodiment can be advanced and retracted to the retracted position P2 in addition to the protruding position P1. Therefore, as shown in FIG. 11, by positioning the inner shaft 24 at the retracted position P2 (particularly the retraction start position Pb), the exposed ends 32c, 32d of the splines 32 can be brought closer to the irrigation ports 50A, 50B of the outer shaft 22 and the inner shaft 24. This in turn makes it easier for the irrigation fluid injected from the irrigation ports 50A, 50B to sufficiently reach the areas around the exposed ends 32c, 32d of the splines 32. In relation to the effect of (D), only one of the outer shaft 22 and the inner shaft 24 needs to have the irrigation ports 50A, 50B.

(E) As described above, the spline 32 can flexibly deform so as to change the relative position of the distal folded end 32e with respect to the inner shaft 24 in response to the advancement and retreat of the inner shaft 24. This allows the portion of the spline 32 from the inner exposed end 32d to the outermost end 32f to have a smooth curved shape. When irrigation fluid is injected distally from the irrigation ports 50A, 50B of the outer shaft 22 and inner shaft 24 into the curved portion of the spline 32, the curved portion allows the irrigation fluid to be smoothly guided in direction Db. In particular, the irrigation fluid can be guided more smoothly than when the spline 32 has a bent portion. Therefore, the irrigation fluid injected from the irrigation ports 50A, 50B can reach a wider area. In relation to the effect of (E), only one of the outer shaft 22 and the inner shaft 24 needs to have irrigation ports 50A, 50B. Additionally, although the case where the inner shaft 24 is in the retracted position P2 has been illustrated and described here, this effect (E) can also be obtained when the inner shaft 24 is in the protruding position P1.

Other features of the electrode catheter 10 will now be described. See Figure 6. The distal folded end 32e of each of the multiple splines 32 is located distally of the distal end 24b of the inner shaft 24 or a member integral with the distal end 24b of the inner shaft 24. Here, "integral member" refers, for example, to a member that is integrally attached to the inner shaft 24 and to which the inner ends 32b of each of the multiple splines 32 are connected. In cases where there is no member integral with the distal end 24b of the inner shaft 24, as in this embodiment, the distal folded end 32e of each of the multiple splines 32 may be located distally of the distal end 24b. Furthermore, in cases where there is a member integral with the distal end 24b of the inner shaft 24, the distal folded end 32e of each of the multiple splines 32 may be located distally of the integral member.

(F) This results in a structure in which other components of the electrode catheter 10 do not protrude distally beyond the distal folded end 32e of each of the multiple splines 32. Therefore, compared to when the components of the electrode catheter 10 protrude distally beyond the multiple splines 32, the electrode assembly 28 can be brought into contact with the distal treatment target portion 16 of the living body without interfering with those components. This in turn makes it easier to increase the contact area of the electrode assembly 28 with the treatment target portion 16 of the living body.

(G) The core wire 42 is exposed and not covered by the outer tube 44 at least at the inner-side exposed end 32d of the spline 32. The exposed portion of the core wire 42 is more flexible and deformable than the portion of the core wire 42 covered by the outer tube 44. Therefore, by exposing the core wire 42 at the inner-side exposed end 32d of the spline 32, the flexibility of the inner-side exposed end 32d can be increased. Therefore, when the inner shaft 24 approaches the most distal position Pa, the inner-side exposed end 32d of the spline 32 is more likely to bend and deform significantly. Accordingly, the portion of the exposed portion 40 of the spline 32 closer to the outer shaft 22 than the distal folded end 32e can be more easily brought closer to the inner shaft 24, making it easier to reduce the outer diameter of the electrode assembly 28. As a result, when the electrode assembly 28 is housed within the sheath, reducing the outer diameter of the electrode assembly 28 also reduces the outer diameter of the sheath. This sheath is used to store the electrode assembly 28 before inserting it close to the treatment target area 16 of the living body.

A step 32g is formed on the spline 32 by the end surface of the outer tube 44 facing the inner shaft 24. Blood tends to stagnate around this step 32g of the spline 32. Therefore, it is preferable to provide the step 32g of the spline 32 as close as possible to the inner shaft 24-side end of the exposed portion 40 of the spline 32, where irrigation fluid injected from the irrigation ports 50A, 50B can easily reach. From this perspective, the exposed portion of the core wire 42 is preferably provided only on the inner shaft 24 side of the distal folded end 32e of the spline 32. This condition only needs to be met when the inner shaft 24 is at its most distal position Pa. This makes it easier for irrigation fluid injected from the irrigation ports 50A, 50B to reach the step 32g of the core wire 42, thereby suppressing thrombosis around the step 32g.

(H) Refer to Figure 3. Of the core wire 42 and outer tube 44, only the core wire 42 is inserted into at least one of the inner shaft 24 and the outer shaft 22. This means that the outer tube 44 is not inserted into at least one of the inner shaft 24 and the outer shaft 22. In this embodiment, only the core wire 42 is inserted into both the inner shaft 24 and the outer shaft 22. To meet this condition, the core wire 42 is inserted into the first insertion hole 36 of the outer shaft 22 toward the rear, and into the second insertion hole 38 of the inner shaft 24 toward the rear. Alternatively, only the core wire 42 may be inserted into only one of the inner shaft 24 and the outer shaft 22. This avoids the need for a shaft without the outer tube 44 inserted therethrough, compared to when the outer tube 44 is inserted in addition to the core wire 42. In this embodiment, it is possible to avoid the need for a shaft with a large outer diameter without the outer tube 44 inserted therethrough.

(I) The inner shaft 24 has a protruding region 24c that protrudes from the outer shaft 22 when the inner shaft 24 is at its distalmost position Pa. The spline 32 is inserted into the inner shaft 24 over at least the entire range of the forward/backward direction in which the protruding region 24c is located. To satisfy this condition, it is sufficient that one of the components of the spline 32 is inserted into the protruding region 24c of the inner shaft 24. In this embodiment, the core wire 42 of the spline 32 is inserted into the protruding region 24c. Alternatively, both the core wire 42 and the outer tube 44 of the spline 32 may be inserted into the protruding region 24c, or the outer tube 44 may be inserted into the protruding region 24c. By inserting the spline 32 over such a range of the forward/backward direction that includes the protruding region 24c, the protruding region 24c can be reinforced by the spline 32.

(Second embodiment) See Figures 12 and 13. The electrode catheter 10 of this embodiment differs from the first embodiment mainly in the configuration of the multiple splines 32. The same configuration as the first embodiment applies except for the electrode assembly 28. Although not shown here, the inner shaft 24 can be moved back and forth between the protruding position P1 and the retracted position P2, just like in the first embodiment.

The electrode assembly 28 of this embodiment has a total of four splines 32. Hereinafter, when distinguishing between the four splines 32, the splines 32 will be prefixed with "first, second, third, fourth" and the reference numerals will be suffixed with "-A, -B, -C, -D."

The splines 32-A to 32-D can form a flower structure when the inner shaft 24 is positioned anywhere within its range of movement. In this embodiment, this condition is met when the inner shaft 24 is in any position within its range of movement. When the splines 32-A to 32-D form a flower structure, each of them has a petal-shaped portion 60 that protrudes radially outward. Splines 32-A to 32-D that have the petal-shaped portion 60 are folded back radially to form an outer circumferential folded end 62 at the outermost end 32f of the spline 32. The "outer circumferential folded end 62" here refers to the boundary between two portions 64A, 64B that extend longitudinally from both ends of the spline 32 toward the outermost end 32f. Each of the splines 32-A to 32-D has two such portions 64A, 64B: a first end portion 64A extending from the outer circumferential folded end 62 toward the first end, and a second end portion 64B extending from the outer circumferential folded end 62 toward the second end. When viewed from the forward/backward direction Da (as viewed from the perspective of FIG. 12), the petal-shaped portion 60 has a hoop shape with a notched radially inward portion. At the base of the petal-shaped portion 60, the first end portion 64A is located to one circumferential side (here, clockwise) of the second end portion 64B.

Each spline 32-A to 32-D is positioned so that it can intertwine with at least one adjacent spline 32-A to 32-D on one circumferential side from the circumferential inner side. It can also be said that each spline 32-A to 32-D is positioned so that it intersects with at least one adjacent spline 32-A to 32-D on one circumferential side when viewed from the forward/backward direction Da (as viewed from the perspective of FIG. 12). In this embodiment, the splines 32-A to 32-D are positioned so that they can intertwine with each of the other individual splines 32-A to 32-D adjacent to them on both circumferential sides from the circumferential inner side. For example, the first end portion 64A of the first spline 32-A is positioned so that it can intertwine with the second end portion 64B of the other adjacent second spline 32-B on one circumferential side from the circumferential inner side. Furthermore, the second end portion 64B of the first spline 32-A is positioned so that it can intertwine with the first end portion 64A of another adjacent fourth spline 32-D from the circumferentially inner side. Here, "circumferentially inner" refers to the side (counterclockwise) of the second end portion 64B of the same spline 32-A to 32-D in the case of the first end portion 64A, and the side (clockwise) of the second end portion 64B in the case of the second end portion 64B of the same spline 32-A to 32-D in the case of the first end portion 64A. All of the multiple splines 32-A to 32-D that make up the electrode assembly 28 satisfy the conditions described above. Furthermore, the first end portions 64A and second end portions 64B of adjacent splines 32-A to 32-D are positioned so that they can intertwine with each other in the exposed portion 40.

Assuming an angular range θ from the end of the exposed portion 40 of the first end portion 64A of one spline 32 to the end of the exposed portion 40 of the second end portion 64B of another adjacent spline 32, as viewed from the forward/backward direction Da. This angular range θ is centered on the center line of the outer shaft 22 and is defined by two radial lines that touch the ends of the two referenced exposed portions 40 from the circumferential outside. This angular range θ is the same size for all splines 32. Here, "same size" means identical or approximately identical.

The effects of the electrode catheter 10 described above will now be explained. Consider the case where an external force F1 acts on a first spline 32-A that is positioned so that it can intertwine with the second spline 32-B, moving the first spline 32-A away from the second spline 32-B in the circumferential direction. In this case, the first spline 32-A intertwines with the second spline 32-B in the circumferential direction, restricting the movement of the first spline 32-A away from the second spline 32-B in the circumferential direction. This makes it difficult for the first spline 32-A to move away from the second spline 32-B in the circumferential direction, making it easier to maintain the circumferential spacing between adjacent first splines 32-A and second splines 32-B. While the effects achieved in the relationship between the first spline 32-A and the second spline 32-B adjacent to it on one circumferential side have been described here, similar effects can also be achieved in the relationship between any other spline 32 and another spline 32 adjacent to it on one circumferential side.

Also, consider the case where an external force F2 acts on the first spline 32-A, causing it to approach the second spline 32-D in the circumferential direction. In this case, the first spline 32-A becomes entangled with the fourth spline 32-D in the circumferential direction, restricting the movement of the first spline 32-A away from the fourth spline 32-D in the circumferential direction. This makes it difficult for the first spline 32-A to approach the second spline 32-B in the circumferential direction, making it easier to maintain the circumferential spacing between the second spline 32-B and the first spline 32-A. The same applies to the circumferential spacing between the first spline 32-A and the fourth spline 32-D. Here, we have described the effect that is achieved in the relationship between the first spline 32-A and the fourth spline 32-D adjacent to it on the other circumferential side. However, a similar effect can be achieved in the relationship between any other spline 32 and another spline 32 adjacent to it on the other circumferential side.

Another feature of the electrode catheter 10 of this embodiment will now be described. Consider a first end portion 64A of one spline 32-A to 32-D and a second end portion 64B of another spline 32-A to 32-D that are adjacent in the circumferential direction. For example, the first end portion 64A of the first spline 32-A and the second end portion 64B of the second spline 32-B. One of these (in this example, the first end portion 64A of the first spline 32-A) is connected to the outer shaft 22. The other of these (in this example, the second end portion 64B of the second spline 32-B) is connected to the inner shaft 24. The outer shaft 22 is connected to the aforementioned outer end portion (not shown), which forms part of the end portion 64A of the spline 32 in question. The inner shaft 24 is connected to the aforementioned inner end portion (not shown), which forms part of the end portion 64B of the spline 32 in question.

See Figure 14. The inner shaft 24 can be retracted further back than the distal end opening 30 of the outer shaft 22. In other words, the inner shaft 24 can be advanced and retracted from the retracted position P2. By retracting the inner shaft 24 in this manner, the second end portion 64B of the spline 32 connected to the inner shaft 24 can be retracted into the lumen 20 of the outer shaft 22. This reduces the outer diameter of the petal-shaped portion 60 of the spline 32, allowing the outer diameter of the entire electrode assembly 28 to be reduced. In other words, the outer diameter of the electrode assembly 28 can be adjusted.

Furthermore, the first end portion 64A of the spline 32 connected to the outer shaft 22 can guide the second end portion 64B of the spline 32 connected to the inner shaft 24 in the direction Dc (counterclockwise in this case) toward the circumferential inside of the spline 32. As a result, by returning the inner shaft 24 to its original position before retraction (for example, the retraction start position Pb in Figure 13), even if the spacing between adjacent splines 32 near the outer circumferential folded end 62 is excessively wide, it is easy to correct this so that the spacing becomes closer.

Note that this embodiment can also achieve the same effects as those described in (A). Furthermore, the configurations described in (B) to (I) of the first embodiment may also be applied to this embodiment.

When the above flower structure is adopted, the inner shaft 24 may be rotatable relative to the outer shaft 22. In this case, the handle 26 may be provided with a rotation operating part that is operated when rotating the inner shaft 24. This makes it possible to adjust the width and outer diameter of the petal-shaped portion 60 of the spline 32 by rotating the inner shaft 24.

Alternatively, the inner shaft 24 may be configured to be non-rotatable relative to the outer shaft 22. To achieve this, the lumen 20 of the outer shaft 22 and the outer periphery of the inner shaft 24 may be shaped (e.g., oval-shaped) to limit the rotation of the inner shaft 24 relative to the outer shaft 22.

Incidentally, even when multiple splines 32 form a basket structure, as in the first embodiment, the inner shaft 24 may be provided to be rotatable. In this case, by rotating the inner shaft 24, it is possible to form both a basket structure and a flower structure.

Next, we will explain variations of each of the components described above.

The electrode catheter 10 may not include irrigation ports 50A, 50B. The multiple splines 32 may have a bent shape within the extension range Sa of the inner shaft 24. The distal folded end 32e of each of the multiple splines 32 may not be located distally of the distal end 24b of the inner shaft 24 or a member integral with the distal end of the inner shaft 24. The splines 32 may be inserted within the inner shaft 24 only in a portion of the forward/backward direction range where the protruding region 24c is located, or may not be inserted within the inner shaft 24 at all.

The spline 32 may have only the outer tube 44 without the core wire 42. Both the core wire 42 and the outer tube 44 may be inserted through both the inner shaft 24 and the outer shaft 22. The core wire 42 may also be covered by the outer tube 44 at the inner exposed end 32d of the spline 32. This allows the inner exposed end 32d of the spline 32 to be reinforced by the outer tube 44. In this case, too, only the core wire 42 of the spline 32 may be inserted through the outer tube 44.

In the second embodiment, the splines 32 may be positioned so that they can intertwine only with other adjacent splines 32 on one circumferential side from the inside in the circumferential direction. It is sufficient that at least some of the multiple splines 32 are positioned so that they can intertwine with other adjacent splines 32 on one circumferential side; it is not necessary for all splines 32 to meet this condition. In the second embodiment, the inner shaft 24 may be unable to retract further beyond the distal end opening 30 of the lumen 20.

The above embodiments and variations are merely examples. The abstract technical concepts behind them should not be interpreted as being limited to the content of the embodiments and variations. Many design changes are possible in the contents of the embodiments and variations, such as changing, adding, or deleting components. In the above embodiments, the terms "embodiment" are used to emphasize content that allows for such design changes. However, design changes are also permitted even in content that does not have such a notation. Hatching on cross sections in the drawings does not limit the material of the hatched objects. The structures and numerical values referred to in the embodiments and variations naturally include those that can be considered identical when manufacturing errors, etc. are taken into account.

The technical ideas embodied in the above embodiments and variations can be generalized to include the technical ideas described in the following third item in addition to the first and second items mentioned above.

The third item comprises an outer shaft having a lumen formed therein, an inner shaft inserted into the lumen so as to be able to advance and retract, and an electrode assembly at least a portion of which is provided distal to the distal end of the outer shaft, the electrode assembly having a plurality of splines, one end of which is connected to the outer shaft and the other end of which is connected to the inner shaft, each of which has a petal-shaped portion protruding radially outward when viewed from the advance and retract direction when the inner shaft is at any position within the advance and retract range, and one of the splines is provided in a position where it can intertwine with another spline adjacent to it on at least one circumferential side from the circumferential inside.

One of the purposes of the electrode catheter in the third item is to provide technology that makes it easier to maintain the circumferential spacing between adjacent splines.

When realizing the electrode catheter of the first item, it is not necessary for each of the multiple splines to have a distal folded end, as in the second item. When realizing the electrode catheter of the second item, it is not necessary for the inner shaft to be able to advance and retract between the extended position and the retracted position, as in the first item. For example, the inner shaft may be able to advance and retract only in the extended position. When realizing the electrode catheter of the third item, it is not necessary for the inner shaft to be able to advance and retract between the extended position and the retracted position, as in the first item. For example, to achieve this, the inner shaft may be able to advance and retract only in the retracted position. When realizing the electrode catheter of the third item, it is not necessary for each of the multiple splines to have a distal folded end, as in the second item. For example, each of the multiple splines may only have a shape with the petal-shaped portion described above.

Any combination of the above components is also valid. For example, any description of another embodiment may be combined with this embodiment, or any description of an embodiment and another modified embodiment may be combined with this modified embodiment. The same applies to realizing the electrode splines of items 1 to 3.

10...electrode catheter, 20...lumen, 22...outer shaft, 22...shaft, 24...inner shaft, 24a...distal end, 24b...distal end, 24c...protruding region, 28...electrode assembly, 30...distal end opening, 32...spline, 32e...distal folded end, 34...electrode, 40...exposed portion, 42...core wire, 44...outer tube, 50A, 50B...irrigation port, 60...petal-shaped portion, 64A...first end portion, 64B...second end portion.

Claims (16)

an outer shaft having a lumen formed therein;
an inner shaft that is inserted into the lumen so as to be able to advance and retreat;
an electrode assembly at least partially disposed distal to the distal end of the outer shaft;
the electrode assembly includes a plurality of splines, one end of which is connected to the outer shaft and the other end of which is connected to the inner shaft;
The electrode catheter is configured such that the inner shaft is movable between a protruding position where it protrudes from a distal end opening provided at the distal end of the lumen and a retracted position where it is retracted to the rear side of the distal end opening. An electrode catheter as described in claim 1, wherein the outer diameter of the electrode assembly is adjustable by the multiple splines expanding or contracting radially in response to the advancement or retreat of the inner shaft. The electrode catheter of claim 1, wherein at least one of the outer shaft and the inner shaft is provided with an irrigation port for injecting irrigation fluid. An electrode catheter as described in claim 1, wherein each of the plurality of splines is shaped so that it folds back at the distal end in the direction of advancement and retraction of the inner shaft when the inner shaft is positioned anywhere within its range of advancement and retraction. An electrode catheter as described in claim 4, wherein each of the multiple splines is flexibly deformable so as to change the distance from the inner shaft to the distal folded end of the spline in the advancing/retracting direction in response to the advancing/retracting movement of the inner shaft. 6. The electrode catheter according to claim 5 , wherein the spline has a shape that has no bends in a range extending in the advancing/retracting direction of the outer shaft when the inner shaft is in the protruding position. 2. The electrode catheter of claim 1 , wherein at least one of the outer shaft and the inner shaft includes an irrigation port for injecting irrigation fluid distally from a distal end thereof. The electrode catheter according to claim 4, wherein the distal folded end of each of the plurality of splines is located at a position distal to the distal end of the inner shaft or a member integral with the distal end of the inner shaft. The spline includes a core wire and an outer tube that covers the core wire,
the spline includes an exposed portion that is exposed to the outside of the inner shaft and the outer shaft,
The electrode catheter according to claim 1 , wherein the core wire is exposed at least at an end of the exposed portion on the inner shaft side. The spline includes a core wire and an outer tube that covers the core wire,
The electrode catheter according to claim 1 , wherein only the core wire of the core wire and the outer tube is inserted inside at least one of the inner shaft and the outer shaft. the inner shaft includes a protruding region that protrudes from the outer shaft when the inner shaft is at the distalmost position within a range in which the inner shaft can be advanced or retreated,
The electrode catheter according to claim 1 , wherein the spline is inserted through the inner shaft at least over the entire range of the protruding region in the advancing and retracting direction. When the inner shaft is positioned anywhere within a range in which the inner shaft can be advanced or retreated, each of the plurality of splines has a shape including petal-shaped portions that protrude radially outward in a radial direction as viewed from the direction in which the inner shaft is advanced or retreated,
2. The electrode catheter according to claim 1 , wherein one of the splines is provided at a position where it can be entangled with another of the splines adjacent to at least one side in the circumferential direction from the circumferentially inner side. The electrode catheter according to claim 12, wherein one of the splines is entangled with another of the splines from the circumferentially inner side, thereby restricting movement of the one of the splines away from the other of the splines in the circumferential direction. The electrode catheter according to claim 12 , wherein the first spline is provided at a position where it can be entangled with other splines adjacent to it on both sides in the circumferential direction from the inside in the circumferential direction. the spline includes a first end portion located closer to the first end than the outer circumferential folded end of the spline, and a second end portion located closer to the second end than the outer circumferential folded end,
a first end portion of the one spline is provided at a position where it can be entangled with a second end portion of the other spline from the circumferentially inner side,
one of a first end portion of the one spline and a second end portion of the other spline is connected to the outer shaft, and the other is connected to the inner shaft;
The electrode catheter according to claim 12 , wherein the inner shaft is retractable further back than the distal end opening of the lumen. an outer shaft having a lumen formed therein;
an inner shaft that is inserted into the lumen so as to be able to advance and retreat;
an electrode assembly at least partially disposed distal to the distal end of the outer shaft;
the electrode assembly includes a plurality of splines, one end of which is connected to the outer shaft and the other end of which is connected to the inner shaft;
When the inner shaft is positioned anywhere within a range in which the inner shaft can be advanced or retreated, each of the plurality of splines has a shape including petal-shaped portions that protrude radially outward in a radial direction as viewed from the direction in which the inner shaft is advanced or retreated,
one spline is provided at a position where it can be entangled with another spline adjacent to at least one side in the circumferential direction from the inner side in the circumferential direction ,
An electrode catheter in which one of the splines is entangled with another of the splines from the circumferentially inner side, thereby restricting movement of the one of the splines away from the other of the splines in the circumferential direction .