Multilayer coil body and medical device using same

Abstract

The purpose of the present disclosure is to provide a multilayer coil body which is capable of smoothly transmitting a large torque applied to a base end toward a tip end side, and a medical device using the same. This multilayer coil body 1 comprises: an outer coil 11 which has a lumen 11h in which a plurality of element wires w11, w12 are helically wound, wherein the element wires w11, w12 adjacent to each other in a long axis direction are in close contact with each other so as to have an initial tension; and an inner coil 21 which is disposed in the lumen 11h of the outer coil 11 so as to be in close contact with the inner periphery 11a of the outer coil 11, and in which the element wire w2 is helically wound.

Description

Multilayer coil body and medical device using the same

[0001] The present disclosure relates to a multilayer coil body and a medical device using the same.

[0002] For example, a technique using a torque shaft has been proposed as a device for delivering a medical device such as a leadless pacemaker to a predetermined site within a body cavity (see, for example, Patent Document 1).

[0003] By using such a torque shaft, a medical device can be delivered to a predetermined site.

[0004] Special Publication No. 2020-518376

[0005] An object of the present disclosure is to provide a multilayer coil body that can smoothly transmit a large torque applied to the base end toward the tip side, and a medical device using the same.

[0006] The multilayer coil body of the present disclosure includes: (1) an outer coil having an inner cavity in which a plurality of wires are spirally wound, the outer coil having adjacent wires in the longitudinal direction in close contact with each other so as to have an initial tension; and an inner coil in which the wires are spirally wound and disposed in the inner cavity of the outer coil in close contact with the inner periphery of the outer coil. This configuration can increase the torsional rigidity of the outer coil, and can smoothly transmit a large torque applied to the base end of the multilayer coil body toward the tip side.

[0007] (2) In the multilayer coil body of (1), when the inner coil and the outer coil are separated, the outer diameter of the inner coil may be larger than the inner diameter of the outer coil. With this configuration, the outer coil is supported from the radially inner side by the expansion force of the inner coil, thereby further increasing the torsional rigidity of the outer coil.

[0008] (3) In the multilayer coil body of (1) or (2), the inner coil may be formed of a single-filament coil in which a single wire is wound in a spiral shape. With this configuration, since a single-filament coil has higher flexibility than a multi-filament coil, the inner coil can be tightly attached to the outer coil, and the inner coil can effectively support the outer coil.

[0009] The medical device of the present disclosure (4) includes the multilayer coil body described above in (1) to (3). With this configuration, the multilayer coil body can smoothly transmit a large torque applied to the proximal end toward the distal end. Therefore, the multilayer coil body can be applied to medical devices that require the smooth transmission of large torque.

[0010] In this specification, "distal side" refers to the direction along the long axis of the multilayer coil body (longitudinal direction) and the direction toward deeper insertion (distal) into the body cavity. "Proximal end side" refers to the direction along the long axis of the multilayer coil body and the opposite direction to the "distal side." "Distal" refers to the distal end of any component. "Proximal end" refers to the proximal end of any component. "Longitudinal direction" refers to the longitudinal direction of the multilayer coil body. "Radial direction" refers to the radial direction perpendicular to the longitudinal axis of the multilayer coil body. "Initial tension" refers to the load (force) that balances the torsional stress (initial stress) that occurs between the wires in the coil that are in close contact with each other.

[0011] Fig. 1 is a schematic cross-sectional view showing a first embodiment; Fig. 2 is a schematic cross-sectional view showing an enlarged portion of Fig. 1; Fig. 3 is an explanatory view of an exploded state of the multilayer coil body of Fig. 1; Fig. 4 is a schematic cross-sectional view showing a second embodiment; Fig. 5 is a schematic view showing an example of a tensile test;

[0012] Hereinafter, first and second embodiments of the present disclosure will be described with reference to the drawings. The present disclosure is not limited to the embodiments shown in the drawings. The dimensions of each part shown in the drawings are shown to facilitate understanding of the implementation content and do not necessarily correspond to the actual dimensions.

[0013] <Multilayer coil body> The multilayer coil body of the present disclosure includes an outer coil having an inner cavity in which a plurality of wires are spirally wound, in which adjacent wires in the longitudinal direction are in close contact with each other so as to have an initial tension, and an inner coil in which the wires are spirally wound and which is disposed in the inner cavity of the outer coil so as to be in close contact with the inner circumference of the outer coil.

[0014] 1 and 2 are schematic diagrams showing a first embodiment. As shown in Fig. 1 and Fig. 2, a multilayer coil body 1 includes, for example, an outer coil 11 and an inner coil 21.

[0015] The outer coil 11 is a coil having an inner cavity 11h in which a plurality of wires are wound helically, and adjacent wires in the longitudinal direction are in close contact with each other so as to have an initial tension. Specifically, the outer coil 11 can be formed, for example, as a multi-filament coil in which two single wires w11, w12 are combined into a set and wound helically around the longitudinal axis of the multilayer coil body 1. A single wire means one single wire.

[0016] The initial tension of the outer coil 11 refers to a force that balances the torsional stress that occurs between the wires w11 and w12 that are in close contact with each other in the outer coil 11. Because the outer coil 11 has an initial tension, the wires w11 and w12 of the outer coil 11 that are adjacent in the longitudinal direction are wound in a state in which they are in strong contact with each other (see arrow A in Figure 2).

[0017] The initial tension of the outer coil 11 may be set, for example, in the range of 0.01 N to 10.0 N, or in the range of 0.50 N to 5.0 N. By setting the initial tension within the above range, torque can be effectively transmitted toward the distal end while maintaining the flexibility of the outer coil 11.

[0018] The load per wire of the outer coil 11 may be set, for example, in the range of 0.0010 N to 5.0 N, or in the range of 0.00167 N to 2.50 N. Setting the load per wire within the above range makes it possible to effectively transmit torque toward the distal end while maintaining the flexibility of the outer coil 11. The load per wire can be calculated by dividing the initial tension of the outer coil 11 by the number of wires in the outer coil 11.

[0019] The initial tension of the outer coil 11 can be measured, for example, by the following method: First, the outer coil 11 alone is held at both ends and subjected to a tensile test in the axial direction of the outer coil 11 at a tension rate of 10 mm / min, and a graph is created with the test force (N) on the vertical axis and the displacement (mm) on the horizontal axis.

[0020] FIG. 5 is a schematic diagram showing an example of a tensile test. As the displacement of the outer coil body increases from zero, an elastic region with a steep slope influenced by the initial tension appears, as shown in FIG. 5. Then, as the displacement increases, the elastic region transitions to a gentle slope where the influence of the initial tension is eliminated. At this time, the value of the test force obtained by extrapolating the gentle slope elastic region where the influence of the initial tension is eliminated to a displacement of 0 mm is considered to be the initial tension. If no steep slope elastic region influenced by the initial tension appears, only a gentle slope elastic region where the influence of the initial tension is eliminated appears when the tensile test is started. In this case, the value of the test force at the intercept of the vertical axis can be considered to be the initial tension.

[0021] The inner coil 21 is disposed in the inner cavity 11h of the outer coil 11 so as to be in close contact with the inner periphery 11a of the outer coil 11, and is a coil in which the wires w2 are wound helically. Specifically, the inner coil 21 may be formed, for example, as a single-filament coil in which a single wire is used as the wire w2 and the single wire is wound helically around the longitudinal axis of the multilayer coil body 1 along the longitudinal axis direction. The inner coil 21 may be formed as a multi-filament coil in which a set of two or more single wires is wound helically around the longitudinal axis of the multilayer coil body 1 along the longitudinal axis direction. The inner coil 21 may be configured such that adjacent wires w2 in the longitudinal direction are in close contact with each other (closely wound). The inner coil 21 may be configured such that adjacent wires w2 in the longitudinal direction have gaps between them (openly wound). In this embodiment, the inner coil 21 is a single-filament coil formed in a close-wound configuration.

[0022] In this embodiment, the inner coil 21 is formed as a single-filament coil in which a single wire w2 is wound spirally. A single-filament coil has higher flexibility than a multi-filament coil. This allows the inner coil 21 to be tightly attached to the outer coil 11, and the inner coil 21 can effectively support the outer coil 11.

[0023] The wires forming the outer coil 11 and the inner coil 21 may be flexible, antithrombogenic, and biocompatible, since the multilayer coil body 1 is applied to a living body. Examples of the wires w11, w12, and w2 include metal materials, resin materials, and composite materials thereof. Examples of metal materials include stainless steel such as SUS316, superelastic alloys such as Ni-Ti alloys, and radiopaque metals such as platinum and tungsten. Examples of resin materials include nylon and polyethylene.

[0024] As shown in FIG. 3 , when the inner coil 21 and the outer coil 11 are separated, the outer diameter D2 of the inner coil 21 may be larger than the inner diameter D1 of the outer coil 11. In other words, when the multilayer coil body 1 is in a state where the inner coil 21 is disposed in the lumen 11h of the outer coil 11, the inner coil 21 may be formed to have a force tending to expand radially outward (hereinafter also referred to as "expansion force") (see arrow B in FIGS. 2 and 3 ). The expansion force may be generated, for example, by springback of the inner coil 21. Because the expansion force of the inner coil 21 supports the outer coil 11 from the radially inner side, the torsional rigidity of the outer coil 11 can be further increased. Furthermore, the interaction between the expansion force of the inner coil 21 and the initial tension of the outer coil 11 can also reduce elongation in response to tension in the longitudinal direction.

[0025] The winding direction of the wires w11 and w12 of the outer coil 11 and the winding direction of the wire w2 of the inner coil 21 may be opposite to each other. That is, one of the outer coil 11 and the inner coil 21 may be S-twisted and the other Z-twisted. When the multilayer coil body 1 is rotated, the direction of the force in the longitudinal direction applied to the wires w11 and w12 of the outer coil 11 and the wire w2 of the inner coil 21 can be made to be opposite to each other. This allows smooth transmission of torque regardless of the direction in which the multilayer coil body 1 is rotated.

[0026] As described above, the multilayer coil body 1 has the above-described configuration, which increases the torsional rigidity of the outer coil 11 and enables a large torque applied to the base end to be smoothly transmitted toward the distal end. As a result, it is possible to prevent delays in rotation between the distal and proximal ends of the multilayer coil body 1 and prevent kinking of the multilayer coil body 1. Because kinking can be prevented, pushability (the ability to push the multilayer coil body 1 into a body cavity) is improved. This is presumably due mainly to the rapid interlocking of adjacent strands w11 and w12 caused by the initial tension of the outer coil 11.

[0027] <Medical Device> A medical device according to the present disclosure includes the multilayer coil body according to the present disclosure. Hereinafter, one embodiment of the medical device will be described, taking the multilayer coil body 1 as an example.

[0028] Second Embodiment Fig. 4 is a schematic diagram showing a second embodiment. A medical device 100 exemplified in this embodiment is a medical device that delivers a leadless pacemaker to the heart within a blood vessel. As shown in Fig. 4, the medical device 100 includes, for example, a multilayer coil body 1, an equipment mounting member 2, and a gripping member 3. The multilayer coil body 1 is similar to that of the first embodiment, and therefore the same components are designated by the same reference numerals and detailed description thereof will be omitted.

[0029] The multilayer coil body 1 is an outer coil having an inner cavity in which a plurality of wires are wound helically, and is provided with an outer coil 11 in which adjacent wires in the longitudinal direction are in close contact with each other so as to have an initial tension, and an inner coil 21 in which the wires are wound helically and which is arranged in the inner cavity of the outer coil 11 so as to be in close contact with the inner circumference of the outer coil 11.

[0030] 1 and 2, in the multilayer coil body 1 of this embodiment, the outer coil 11 is formed by helically winding two wires w11 and w12. The outer coil 11 has an inner cavity 11h in which the inner coil 21 is disposed. The initial tension of the outer coil 11 is set to 0.4 to 0.5 N. The inner coil 21 is formed as a single-filament coil in which adjacent wires w2 in the longitudinal direction are in close contact with each other.

[0031] The device mounting member 2 is a member for mounting a device such as a leadless pacemaker. The device mounting member 2 is disposed at the distal end of the medical device 100. The device mounting member 2 has an attachment portion 2a to which a device C, indicated by a two-dot chain line, is detachably attached.

[0032] The gripping member 3 is a member with which the operator operates the medical device 100. The gripping member 3 is connected to the base end of the multilayer coil body 1. The gripping member 3 has an operation unit (not shown). When the operator operates the operation unit, the instrument C is released from the attachment unit 2a into the body.

[0033] A description will be given of a usage mode of the medical device 100. In this description, a leadless pacemaker (hereinafter also referred to as "leadless pacemaker C") will be exemplified as the device C.

[0034] First, a catheter is inserted into a blood vessel and advanced so that its tip reaches near the heart.

[0035] Next, the leadless pacemaker C is delivered to the heart. Specifically, the medical device 100 is prepared, with the leadless pacemaker C attached to the attachment portion 2a of the equipment mounting member 2. Next, the medical device 100 is inserted into the lumen of the catheter, and under X-ray fluoroscopy, the medical device 100 is pushed forward until the leadless pacemaker C attached to the tip of the medical device 100 reaches the right ventricle of the heart.

[0036] Next, the leadless pacemaker C is placed on the wall of the right ventricle. Specifically, by operating the operating portion of the grasping member 3, the leadless pacemaker C is released from the attachment portion 2 a of the device mounting member 2 and fixed to the wall of the right ventricle.

[0037] When the leadless pacemaker C is transported within a blood vessel or placed in the heart, the medical device 100 may be rotated. In this case, by rotating the gripping member 3, torque is reliably transmitted to the leadless pacemaker C via the multilayer coil body 1, allowing the leadless pacemaker C to be smoothly rotated in response to the operator's operation.

[0038] Next, it is confirmed whether the leadless pacemaker C is operating normally. If there is no abnormality, the medical device 100 and the catheter are removed from the body. This completes the procedure using the medical device 100.

[0039] As described above, the medical device 100 includes the multilayer coil body 1. The multilayer coil body 1 can smoothly transmit a large torque applied to the proximal end toward the distal end. Therefore, the multilayer coil body 1 can be applied to, for example, a medical device 100 for leadless pacemaker delivery, which requires smooth transmission of a large torque.

[0040] The present disclosure is not limited to the configurations of the above-described embodiments, but is intended to include all modifications within the meaning and scope of the claims as defined by the claims. Part of the configurations of the above-described embodiments may be deleted or replaced with other configurations, or other configurations may be added to the configurations of the above-described embodiments.

[0041] For example, in the first embodiment described above, the multilayer coil body 1 is provided with the inner coil 21 formed of a single-filament coil and a densely wound coil. The inner coil may be a multi-filament coil. The inner coil may be a loosely wound coil.

[0042] In the above-described first embodiment, the multilayer coil body 1 has been described in which the inner coil 21 has an expansible force. The inner coil does not necessarily have to have an expansible force as long as it can support the outer coil from the inside.

Claims

1. A multilayer coil body comprising: an outer coil having an inner cavity in which a plurality of wires are wound helically, in which adjacent wires in the longitudinal direction are in close contact with each other so as to have an initial tension; and an inner coil in which the wires are wound helically, and which is disposed in the inner cavity of the outer coil so as to be in close contact with the inner circumference of the outer coil.

2. The multilayer coil body according to claim 1, wherein the outer diameter of the inner coil is larger than the inner diameter of the outer coil when the inner coil and the outer coil are separated.

3. A multilayer coil body according to claim 1 or claim 2, wherein the inner coil is formed of a single wire coil wound in a spiral shape.

4. A medical device comprising a multilayer coil body according to any one of claims 1 to 3.

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