Embedding of medical lead coil electrodes

Abstract

In some examples, a coil electrode assembly includes a coil electrode including a plurality of windings and extending from an electrode proximal end to an electrode distal end, the coil electrode defining an electrode lumen from the electrode proximal end to the electrode distal end. The coil electrode assembly further includes an insulating tube extending within the lumen of the coil electrode such that the coil electrode extends along an outer surface of the insulating tube. When the insulating tube is in an inflated state, the coil electrode is partially embedded within the insulating tube to maintain spacing between the windings.

Description

Technical Field

[0001] This disclosure generally relates to implantable medical devices. Background Technology

[0002] Implantable medical devices can be used to monitor a variety of patient conditions and / or provide patients with a variety of therapies. Some implantable medical devices include electrodes to sense electrical signals and / or provide electrotherapy. Some implantable medical devices include elongated leads to position the electrodes near target tissue for sensing or treatment. For example, an implantable medical device can deliver an anti-tachyarrhythmic (e.g., defibrillation) shock via one or more coil electrodes that are part of one or more leads and are located inside or near the heart. Summary of the Invention

[0003] The technology disclosed herein generally relates to assembling implantable medical leads comprising coil electrodes, and more specifically to securing windings of coil electrodes using an "inside-out" approach, such as maintaining internal spacing within the windings. In some existing implantable medical leads, the coil electrodes are secured using an adhesive coated from the outside. In contrast, the technology of this disclosure uses an insulating tube disposed within a cavity defined by the coil electrodes to secure them, which increases the surface area of ​​the coil electrodes available for blood / tissue contact and interaction compared to existing implantable medical leads.

[0004] The insulating tube within the cavity transforms into an expanded state to contact the coil electrodes, for example, by partially embedding the coil electrodes within the insulating tube, thus fixing the spacing between the windings. This expansion of the tube can be accomplished by applying heat and / or air pressure to the interior of the tube. In some instances, a transformation ring is attached to the ends of the coil electrodes and the tube before the insulating tube is expanded to hold them in place relative to each other during the expansion of the tube.

[0005] In some instances, the coil electrode assembly can be configured as a subassembly for implantable medical leads. Using this subassembly in the manufacture of implantable medical leads helps reduce waste because if a subassembly part needs to be discarded, the remaining portion of the lead is also discarded. Examples where the coil electrode assembly includes one or more conductive transition rings also facilitate the electrical connection of the coil electrodes to the conductors of the implantable medical lead via the transition rings.

[0006] In one example, this disclosure provides an implantable medical lead configured to be coupled to an implantable medical device, the implantable medical lead including a coil electrode assembly. The coil electrode assembly includes coil electrodes extending from a proximal end to a distal end of an electrode, the coil electrodes defining an electrode cavity from the proximal end to the distal end of the electrode, and the coil electrodes including a plurality of windings. The coil electrode assembly further includes an insulating tube extending from a proximal end to a distal end of a tube, the insulating tube extending within the electrode cavity such that the coil electrodes extend along an outer surface of the insulating tube, the coil electrodes being partially embedded within the insulating tube in an expanded state to maintain spacing between the windings. The coil electrode assembly further includes a first transition ring at the distal end of the electrode and the distal end of the tube, wherein a portion of the first transition ring is within the electrode cavity, wherein the first transition ring defines a first transition ring cavity, and wherein a distal portion of the insulating tube including the distal end of the tube is within the first transition ring cavity. The coil electrode assembly further includes a second transition ring at the proximal end of the electrode and the proximal end of the tube, wherein a portion of the second transition ring is within the electrode cavity, wherein the second transition ring defines a second transition ring cavity, and wherein the proximal portion of the insulating tube, including the proximal end of the tube, is within the second transition ring cavity.

[0007] In another embodiment, this disclosure provides a system comprising: an implantable medical device configured to generate an anti-tachyarrhythmic shock; and an implantable medical lead extending from a proximal end to a distal end, the proximal end of the lead being configured to be coupled to the implantable medical device, the implantable medical lead including a coil electrode assembly between the proximal and distal ends of the lead. The coil electrode assembly includes coil electrodes extending from the proximal to the distal end of the electrodes, the coil electrodes defining an electrode cavity from the proximal to the distal end of the electrodes, and the coil electrodes including a plurality of windings, wherein the coil electrodes are configured to deliver an anti-tachyarrhythmic shock. The coil electrode assembly further includes an insulating tube extending from a proximal end to the distal end of the tube, the insulating tube extending within the electrode cavity such that the coil electrodes extend along an outer surface of the insulating tube, the coil electrodes being partially embedded within the insulating tube when the insulating tube is in an expanded state to maintain spacing between the windings. The coil electrode assembly further includes a first transition ring at the distal end of the electrode and the distal end of the tube, wherein a portion of the first transition ring is within the electrode cavity, wherein the first transition ring defines a first transition ring cavity, and wherein the distal portion of the insulating tube, including the distal end of the tube, is within the first transition ring cavity. The coil electrode assembly further includes a second transition ring at the proximal end of the electrode and the proximal end of the tube, wherein a portion of the second transition ring is within the electrode cavity, wherein the second transition ring defines a second transition ring cavity, and wherein the proximal portion of the insulating tube, including the proximal end of the tube, is within the second transition ring cavity.

[0008] In another embodiment, this disclosure provides a coil electrode assembly for an implantable medical lead configured to be coupled to an implantable medical device. The coil electrode assembly includes coil electrodes extending from a proximal end to a distal end of an electrode, the coil electrodes defining an electrode cavity from the proximal end to the distal end of the electrode, and the coil electrodes including a plurality of windings. The coil electrode assembly further includes an insulating tube extending from a proximal end to a distal end of a tube, the insulating tube extending within the electrode cavity such that the coil electrodes extend along an outer surface of the insulating tube, the coil electrodes being partially embedded within the insulating tube when the insulating tube is in an expanded state to maintain spacing between the windings. The coil electrode assembly further includes a first transition ring at the distal end of the electrode and the distal end of the tube, wherein a portion of the first transition ring is within the electrode cavity, wherein the first transition ring defines a first transition ring cavity, and wherein a distal portion of the insulating tube including the distal end of the tube is within the first transition ring cavity. The coil electrode assembly further includes a second transition ring at the proximal end of the electrode and the proximal end of the tube, wherein a portion of the second transition ring is within the electrode cavity, wherein the second transition ring defines a second transition ring cavity, and wherein the proximal portion of the insulating tube, including the proximal end of the tube, is within the second transition ring cavity.

[0009] In another example, a method includes inserting an insulating tube into an electrode cavity defined by coil electrodes of a coil electrode assembly, such that the coil electrodes extend along the outer surface of the insulating tube from a proximal end to a distal end of the tube and the coil electrodes extend from the proximal end to the distal end of the electrode, the coil electrodes comprising a plurality of windings. The method further includes connecting a first transition ring at the distal end of the electrode to the coil electrode and at the distal end of the tube to the insulating tube, and connecting a second transition ring at the proximal end of the electrode to the coil electrode and at the proximal end of the tube to the insulating tube. The method further includes applying at least one of heat and gas pressure to the insulating tube to transition the insulating tube from a non-expanded state to an expanded state, such that the coil electrodes are partially embedded within the insulating tube and the spacing between the windings is maintained.

[0010] This summary is intended to provide an overview of the subject matter described in this disclosure. It is not intended to provide an exclusive or exhaustive explanation of the methods and systems described in detail in the following drawings and specification. Details of one or more aspects of this disclosure are set forth in the drawings and the following description. Other features, objectives, and advantages of the techniques described in this disclosure will be apparent from the description and drawings and from the claims. Attached Figure Description

[0011] Figure 1 This is a conceptual diagram illustrating an example medical device system, which includes an implantable medical device comprising one or more coil electrodes coupled to one or more implantable medical leads.

[0012] Figure 2 This is a cross-sectional view showing an example coil electrode assembly.

[0013] Figure 3 It is to further demonstrate Figure 2 A cross-sectional view of region A of the first end portion of the example coil electrode assembly.

[0014] Figure 4 It is to further demonstrate Figure 2 A cross-sectional view of region B of the second end portion of the example coil electrode assembly.

[0015] Figure 5 It is shown Figure 2 A conceptual diagram of an exploded view of an example coil electrode assembly.

[0016] Figure 6A and 6B They are shown separately as similar to Figure 2 Cross-sectional views of region A of another example coil electrode assembly, showing the region before and after expansion.

[0017] Figure 7A and 7B They are shown separately as similar to Figure 2 Cross-sectional views of region B of another example coil electrode assembly before and after expansion.

[0018] Figure 8 This is a flowchart illustrating an example technique for manufacturing a coil electrode assembly to be attached to an implantable medical lead. Detailed Implementation

[0019] Electrodes used to deliver relatively high-energy (e.g., compared to cardiac pacing) shocks against rapid arrhythmias (e.g., defibrillation) can take the form of wound coils with their outer surfaces exposed to blood or other bodily fluids. These coils are typically fixed in their axial position relative to an underlying lead body and to each other (e.g., to prevent wire misalignment, breakage, or inward growth of fibrous tissue) by depositing silicone adhesive or silicone rubber in an outside-to-inward direction to cover the wound coils and the spaces between them. Due to this deposition of silicone adhesive or silicone rubber, the outer surface of the wound coils, including the spaces between the electrodes, can be completely or partially covered by a thin coating.

[0020] While a thin coating can lock the wound coil in place and prevent displacement of the defibrillator coil electrodes, it can potentially degrade the performance of the coil electrodes due to the reduced usable surface area. In some instances, excessive adhesive has been removed from the outer surface of the coil to counteract the reduced usable surface area. However, removing adhesive requires relatively skilled manual labor and adds a step to the process of manufacturing the implantable medical lead containing the coil electrodes. Furthermore, using conventional lead assembly techniques, errors in the adhesive application or thin coating removal process can render the entire implantable medical lead unusable.

[0021] The coil electrode assembly according to this disclosure includes an insulating tube within a cavity defined by coil electrodes, and the insulating tube transforms into an expanded state to partially embed the coil electrodes, thereby securing the coil winding in place via an inside-out method. In this way, the coil electrode assembly described herein can have increased external surface area for delivering anti-tachyarrhythmic shocks. Increasing the available surface area of ​​the coil can, for example, increase the effectiveness of the delivered shock during ventricular tachycardia (VT) and ventricular fibrillation (VF). Furthermore, manufacturing an implantable medical lead including a coil electrode assembly as described herein can reduce operational variability and provide cost savings by forming sub-assemblies to be assembled together to form a final product. For example, if the coil electrode assembly is not assembled correctly, only the coil electrode assembly needs to be discarded.

[0022] Figure 1 This is a conceptual diagram illustrating an example medical device system 10, which includes an implantable medical device (IMD) 16 coupled to one or more coil electrodes connected to one or more implantable medical leads. Figure 1 In this example, IMD 16 is coupled to leads 18 and 22. IMD 16 can be an implantable pacemaker, cardioverter, and / or defibrillator that provides electrical signals to the heart 12, for example, via electrodes coupled to one or more of leads 18 and 22.

[0023] exist Figure 1 In this example, leads 18 and 22 extend into the heart 12 to sense electrical activity of the heart 12 and / or deliver electrical therapy to the heart 12. Right ventricular (RV) lead 18 extends through one or more veins (not shown), the superior vena cava (not shown), and the right atrium 26, and enters the right ventricle 28. Right atrial (RA) lead 22 extends through one or more veins and the vena cava, and enters the right atrium 26 of the heart 12. Although example system 10 includes intravascular leads and intracardiac electrodes, extravascular leads including extravascular coil electrodes may include coil electrode assemblies according to the technology of this disclosure.

[0024] The IMD 16 can sense electrical signals accompanying depolarization and repolarization of the heart 12 via electrodes coupled to at least one of leads 18 and 22. In some instances, the IMD 16 delivers pacing pulses to the heart 12 based on the electrical signals sensed within the heart 12. The electrodes of the IMD 16 for sensing and pacing can be configured as unipolar or bipolar. The IMD 16 can detect arrhythmias of the heart 12, such as tachycardia or fibrillation of the atria (including the right atrium 26) and / or ventricles (including the right ventricle 28), and can also deliver anti-tachyarrhythmic shocks, such as defibrillation and / or cardioversion shocks, via electrodes located on at least one of leads 18 and 22. In some instances, the IMD 16 can be programmed to deliver therapeutic processes, such as pulses with increasing energy levels, until fibrillation of the heart 12 ceases. The IMD 16 can detect fibrillation using one or more fibrillation detection techniques known in the art.

[0025] like Figure 1 As shown, the proximal ends of leads 18 and 22 are connected to connector block 34 of IMD 16 to electrically connect electrodes on the leads to a circuit system within housing 60 of IMD 16. In some instances, the proximal ends of leads 18 and 22 may contain electrical contacts that are electrically connected to corresponding electrical contacts within connector block 34 of IMD 16. Each of leads 18 and 22 includes an elongated insulated lead body that can carry a plurality of conductors, such as conductors for each electrode on the lead, each of which can be connected to a corresponding contact at the proximal end of the lead. Additionally, bipolar electrodes 40 and 42 are positioned adjacent to the distal end of lead 18 in right ventricle 28. Furthermore, bipolar electrodes 48 and 50 are positioned adjacent to the distal end of lead 22 in right atrium 26.

[0026] Electrodes 40 and 48 may be in the form of ring electrodes, and electrodes 42 and 50 may be in the form of helical tip electrodes, which are mounted, for example, within insulated electrode heads 52 and 56 using fixing screws. Some helical tip electrodes may include mechanisms for extending / retracting helices. In other instances, one or more of electrodes 42 and 50 may be in the form of small circular electrodes at the tip of tin-plated leads or other fixing elements. Leads 18 and 22 also include elongated electrodes 62 and 66, each of which may be in the form of a coil. Each of electrodes 40, 42, 48, 50, 62, and 66 may be electrically connected to a corresponding conductor within the lead body of its associated lead 18 and 22, and thereby connected to a corresponding electrical contact in an electrical contact at the proximal end of leads 18 and 22.

[0027] exist Figure 1In some examples, the IMD 16 includes a housing electrode 58, which may be integrally formed with or otherwise coupled to the outer surface of the hermetically sealed housing 60 of the IMD 16. In some examples, the housing electrode 58 is defined by a non-insulated portion of the outward-facing portion of the housing 60 of the IMD 16. Other divisions between the insulating and non-insulated portions of the housing 60 may be used to define two or more housing electrodes. In some examples, the housing electrode 58 substantially encompasses the entire housing 60.

[0028] The IMD 16 can sense electrical signals associated with the depolarization and repolarization of the heart 12 via electrodes 40, 42, 48, 50, 62, and 66. These electrical signals are conducted from the electrodes to the IMD 16 via corresponding leads 18 and 22. The IMD 16 can sense these electrical signals via any bipolar combination of electrodes 40, 42, 48, 50, 62, and 66. Furthermore, any one of electrodes 40, 42, 48, 50, 62, and 66 can be combined with housing electrode 58 for unipolar sensing. The combination of electrodes used for sensing may be referred to as a sensing configuration or electrode vector.

[0029] In some instances, the IMD 16 delivers pacing pulses via a bipolar combination of electrodes 40, 42, 48, and 50 to induce depolarization of the myocardial tissue of the heart 12. In some instances, the IMD 16 delivers pacing pulses in a monopolar configuration with housing electrode 58 via any of electrodes 40, 42, 48, and 50. Furthermore, the IMD 16 can deliver anti-tachyarrhythmic shocks, such as defibrillation shocks, to the heart 12 via any combination of extended electrodes 62 and 66 with housing electrode 58. The IMD 16 can also deliver cardioversion shocks to the heart 12 using electrodes 58, 62, and 66. Electrodes 62 and 66 can be made of any suitable conductive material, such as, but not limited to, platinum, platinum alloys, or other materials known for use in implantable defibrillator electrodes.

[0030] Figure 1 The configuration of system 10 shown is only one example. In other examples, the system may include external vascular leads and electrodes, as... Figure 1 Alternatives or supplements to the transvenous leads 18 and 22 shown. Furthermore, the IMD 16 need not be implanted in the patient. In instances where the IMD 16 is not implanted in the patient, the IMD 16 can sense electrical signals and / or deliver anti-tachyarrhythmic shocks and other therapies to the heart 12 via percutaneous leads extending through the patient's skin to various locations inside or outside the heart 12.

[0031] Figure 2 This is a cross-sectional view showing the example coil electrode assembly 100. Figure 3 This further illustrates the first end portion 134 of the coil electrode assembly 100 (from... Figure 2A cross-sectional view of area A). Figure 4 This further illustrates the second end portion 136 of the coil electrode assembly 100 (from... Figure 2 A cross-sectional view of area B). Figure 5 It is shown Figure 2 A conceptual diagram of an exploded view of an example coil electrode assembly.

[0032] The coil electrode assembly 100 includes a coil electrode 112, an insulating tube 122, a first transition ring 124, and a second transition ring 126. When... Figure 2 As shown in the assembly, the cavity 102 of the coil electrode assembly 100 is jointly defined by cavities defined by each of the insulating tube 122, the first transition ring 124, and the second transition ring 126. Either or both of the elongated electrodes 62 and 66 on the leads 18 and 22 can be assembled according to the techniques described herein with respect to the coil electrode assembly 100. Generally, the coil electrode assembly 100 can be included in an implantable medical lead at a desired location between the proximal and distal ends of the lead.

[0033] Although described herein as an example within an implantable medical lead, the coil electrode assembly 100 can be used with other medical devices and / or therapies. In general, the coil electrode assembly 100 can be used in any medical or non-medical device.

[0034] exist Figure 2 In one example, coil electrode 112 includes a plurality of windings 114 extending from a distal end 118 of the coil electrode to a proximal end 120 of the coil electrode. The windings 114 define a coil cavity 116 from the distal end 118 to the proximal end 120 of the coil electrode 112. Figure 5 As shown, the insulating tube 122 extends from the proximal end 138 to the distal end 139 of the tube. The insulating tube 122 extends within the coil cavity 116, for example, from the distal end 118 to the proximal end 120 of the electrode, such that the coil electrode 112 extends along the outer surface 141 of the insulating tube 122. Figure 5 ) extension. When the insulating tube 122 is in an expanded state to maintain the spacing 168 between the windings 114 (e.g. Figure 3 As shown, the coil electrode 112 is partially embedded in the insulating tube 122.

[0035] The insulating tubing 122 may comprise a polymer containing polyurethane and / or silicone. The inclusion of polyurethane provides desired mechanical properties, such as a relatively increased tensile and tear strength, at least in the expanded state, compared to tubing of similar thickness made of other materials. In some instances, the polymer or other material of the insulating tubing 122 may have a hardness of at least 50 Shore D, for example, approximately 55 Shore D.

[0036] A first transition ring 124 is connected to a coil electrode 112 at its distal end 118, and a second transition ring 126 is connected to a coil electrode 112 at its proximal end 120. In some embodiments, a first transition ring engagement 130 defines a surface for coil electrode mating to connect between the first transition ring 124 and the coil electrode 112, and a second transition ring engagement 132 defines a surface for coil electrode mating to connect between the second transition ring 126 and the coil electrode 112. The connection can be provided by a variety of methods, including welding, crimping, and bracing. In some embodiments, each of the first transition ring engagement 130 and the second transition ring engagement 132 can withstand a tensile force of at least 1.0 pound.

[0037] The first transformation ring 124 defines the inner cavity 125 ( Figure 3 and 5 ), and the second transition ring 126 defines the inner cavity 127 ( Figure 4 and 5 Insulating fitting 122 defines the insulating fitting cavity 123. Figure 2 and 5 At least a portion of the first transition ring 124 and the second transition ring 126 are disposed within the coil cavity 116, and in some instances, on the outer surface of the coil electrode 112 and the insulating tube 122 (e.g., outer surface 141). Figure 5 Between )) The inner cavity 125 of the first transition ring 124, the insulating tube cavity 123, and the inner cavity 127 of the second transition ring 126 form the cavity 102 of the coil electrode assembly 100.

[0038] A first transition ring 124 connects to an insulating fitting 122 at the distal end 139 of the fitting, and a second transition ring 126 connects to the insulating fitting 122 at the proximal end 138 of the fitting. In some examples, a distal notch 166 ( Figure 2 , 3 (and 5) are formed on the distal portion 140 of the insulating tube 122. Figure 3 and 5 In ), and the near-side notch 186 ( Figure 2 , 4 (and 5) are formed in the proximal portion 142 of the insulating tube 122. Figure 4 and 5 In the first transition ring 124 and the second transition ring 126, the portions extending centrally from the joints 130 and 132, respectively, can receive portions of a corresponding notch in one of the defined notches 166 and 186 of the insulating tube 122. The distal notch 166 helps to provide a tight fit between the first transition ring 124 and the insulating tube 122. The distal notch 166 and the proximal notch 186 of the insulating tube 122 can be shaped opposite to those of the transition rings 124 and 126, such that there is a generally smooth transition from the insulating tube 122 to the transition rings 124 and 126. Figure 2-4 As shown, the combined thickness of the insulating tube 122 at notches 166 and 186 with the mating portions of the transition rings 124 and 126 can be defined to be substantially similar to the thickness of the remaining portion of the insulating tube 122.

[0039] In some instances, the insulating tube 122 need not include notches 166 and 186. Nevertheless, in these instances, the distal portion 140 of the insulating tube 122, including the distal end 139, may be received within the distal annular cavity 125, and the proximal portion 142 of the insulating tube 122, including the proximal end 138, may be received within the proximal annular cavity 127. Relative to Figures 6A-7B Describe an example of a coil electrode assembly in which the insulating tubing does not include notches at the distal and proximal portions.

[0040] The first transition ring 124 and the second transition ring 126 may be made of a conductive material. In some instances, the coil electrode assembly 100 may have one or more electrical conductors. A first electrical conductor 144a of an implantable medical lead (e.g., lead 18 or 22) may be electrically connected to the coil electrode 112 via at least one of the first transition ring 124 and the second transition ring 126. Figure 4 In the example shown, a first conductor 144a is coupled to a second transition ring 126. The first conductor 144a can connect the coil electrode 112 to the proximal end of an implantable medical lead via the transition ring 126.

[0041] In some instances, such as Figure 2 As shown, the second conductor 144b can connect one or more electrodes on the distal side of the coil electrode assembly 100 to the proximal end of the implantable medical lead, and thus to the IMD (conductors 144a and 144b are collectively referred to as conductor 144). For example, relative to Figure 2 In one example, the second conductor 144b may extend through the cavity 102 to connect electrodes 40 and 42 (or 48 and 50) to the IMD 16 via the coil electrode assembly 100, wherein coil electrode 112 corresponds to electrodes 62 and 66. Figure 1 (as shown in the image).

[0042] like Figure 3As shown, the first transition ring 124 may include a proximal end 162 and a distal end 164. The proximal and distal ends extend from the respective ends 162 and 164 to an increased diameter shoulder 150. The proximal and distal ends of the shoulder 150 may have different shapes and sizes. For example, the proximal end of the shoulder 150 may include a curved corner, and the distal end of the shoulder 150 may include a 90-degree (90°) corner. The proximal end of the shoulder 150 provides a first transition ring engagement 130, which may include a surface for engagement of the coil electrode 112. In some embodiments, the coil electrode 112 may be soldered to the first transition ring 124 at the proximal end of the shoulder 150. The distal end of the shoulder 150 provides a surface for connection of the coil electrode assembly 100 to the remainder of the lead body of an implantable medical lead.

[0043] Figure 4 This is a conceptual diagram showing an example of the proximal portion of a coil electrode assembly 100 including a second transition ring 126. The second transition ring 126 may be similar to the first transition ring 124. In the example shown, the second transition ring 126, having a proximal end 180 and a distal end 182, includes two increasing diameter portions defining a first shoulder 170 and a second shoulder 172. The distal side of the shoulder 170 may include a curved corner, and the proximal side of the shoulder 170 may include a generally 90-degree (90°) corner. The distal side of the shoulder 170 provides a second transition ring engagement 132, which may include a surface for engagement of a coil electrode 112. In some examples, the coil electrode 112 may be soldered to the second transition ring 126 proximal to the shoulder 170. In some examples, the second shoulder 172 may provide a transition to the body of an implantable medical lead. Similar to the first transition ring 124, the second transition ring 126 has holes 176A, 176B, 184A, 184B and grooves 178 and 188 to increase the structural integrity of the joint by, for example, adding additional locations / geometry for mechanical fastening of the assembly. Similar to the notch 166 at the distal end of the insulating tube 122, the proximal end of the insulating tube 122 also has a proximal notch 186 for providing a connection between the insulating tube 122 and the second transition ring 126.

[0044] The first transition ring 124 is connected to the distal portion 140 of the insulating tube 122. Figure 3 The second transition ring 126 is connected to the proximal portion 142 of the insulating tube 122. Figure 4 Adhesive 146 is disposed on the distal portion 140 and the proximal portion 142 of the insulating tube 122, for example on the outer surface 141 of the insulating tube 122 at these portions. Adhesive 146 connects a first transition ring 124 to the distal portion 140 of the insulating tube 122 and a second transition ring 126 to the proximal portion 142 of the insulating tube 122.

[0045] Adhesive 146 may be applied at one or more locations. In some instances, adhesive 146 is applied at only two locations on the insulating tube 122. The first location of adhesive 146 is between the surface of the first transition ring 124 and the distal portion 140 of the insulating tube 122. The second location of adhesive 146 is between the surface of the second transition ring 126 and the proximal portion 142 of the insulating tube 122. At each location, adhesive 146 may be applied continuously or discontinuously as beads, spray, parallel lines, or various patterns. For example, adhesive 146 may be applied continuously to the distal portion 140 of the insulating tube 122 and discontinuously to the proximal portion 142 of the insulating tube 122.

[0046] The amount of adhesive 146 applied to the coil electrode assembly 100 can vary over a wide range. The composition of adhesive 146 can also vary and may include silicone adhesive. In some instances, adhesive 146 may be a mixture of heptane and an adhesive. Adhesive 146 with different compositions can be applied to different portions of the insulating tube 122. For example, some portions of the coil electrode assembly 100 may contain a stronger adhesive 146 than others. In some instances, the connection of the transition rings 124 and 126 to the tube 122 can be achieved by various means, as a supplement to or alternative to the adhesive 146.

[0047] Some areas of the coil electrode assembly 100 may be free of adhesive 146. For example, the outer surface of the coil electrode 112 may be substantially free of adhesive 146. At least a portion of the first transition ring 124, the first region 145, may be free of adhesive 146. Similarly, at least a portion of the second transition ring 126, the second region 147, may be free of adhesive 146. Both the first transition ring 124 and the second transition ring 126 may contain multiple regions free of adhesive 146. By reducing the amount of adhesive 146 on the outer surface of the coil electrode 112, the surface area of ​​the coil electrode 112 available for patient interaction is increased, thereby potentially increasing the effectiveness of the implantable medical lead comprising the coil electrode assembly 100.

[0048] The groove 154 and holes 156A and 156B (collectively referred to as "holes 156") secure the first transition ring 124 to the insulating tube 122. The groove 154 facilitates bonding using adhesives. The holes 156 can also be used for inspection and verification. For example, the holes 156 can be used to visually ensure that the insulating tube 122 is properly positioned within the first transition ring 124. Holes 156A and 156B are on opposite sides of the first transition ring 124. The holes 156 extend from the outer surface of the first transition ring 124 to the inner cavity 125 of the first transition ring 124. In some instances, instead of two holes 156A and 156B, one or more holes 156 may be present. In some instances, a plurality of holes 156 may be circumferentially arranged around the first transition ring 124. The plurality of holes 156 may be evenly or irregularly spaced. A plurality of holes 156 spaced longitudinally along the first transition ring 124 may also be present as a replacement or supplement to the circumferentially spaced holes 156.

[0049] The groove 154 may extend circumferentially around the first transition ring 124. In some embodiments, the groove 154 may not extend completely circumferentially around the first transition ring 124. For example, the groove 154 may extend only partially around the circumference of the first transition ring 124. Furthermore, the angle between the groove 154 and the longitudinal axis of the first transition ring 124 may vary. For example, the groove 154 may extend perpendicular to the longitudinal axis of the first transition ring 124 or at an angle to the longitudinal axis of the first transition ring 124.

[0050] Recess 158 and holes 160A and 160B (collectively referred to as “hole 160”) may be the same as, substantially similar to, or different from recess 154 and holes 156A and 156B. In some instances, recesses 154 and 158 may be substantially similar, and hole 156 may differ from hole 160, or vice versa. Recesses 158 and holes 160 provide connection members for connecting the first transition ring 124 and the coil electrode assembly 100 to other components and / or assemblies of the implantable medical lead, respectively. Recess 158 may be used with an adhesive to provide a connection between the first transition ring 124 and the lead body. In some instances, recess 158 may be used, for example, to facilitate adhesive bonding to other components by increasing adhesive strength. Other connection members may also be used as alternatives to or supplements to recesses 154, 158 and holes 156, 160. Holes 156 and 160 allow the second conductor 144b to make an electrical connection from the inner cavity 125 of the first transition ring 124 to the outside of the first transition ring 124. Similar to the first transition ring 124, the second transition ring 126 ( Figure 4 It has holes 176A, 176B, 184A, 184B and grooves 178 and 188, which can provide connection with the first transition ring 124. Figure 3The holes 156 and 160, and the grooves 154 and 158, are generally similar in functionality. In some instances, the transition rings 124 and 126 may use holes 156, 160, 176, and 184 to facilitate adhesion to attached components and provide inspection / verification features. In some instances, the transition rings 124 and 126 may not contain holes 160 and 176.

[0051] Figure 6A and 6B They are shown separately as similar to Figure 2 Cross-sectional views of region A of another example coil electrode assembly, showing the region before and after expansion. Figure 6A and 6B The first end portion 200 is similar to the first end portion 134, except for the differences described herein. For example, similar to the first end portion 134, the first end portion 200 includes a first transition ring 210, a coil electrode 224, and an insulating tube 226. The first transition ring 210 is connected to the distal portion of the lead body 202. A conductor 208 extends through the middle of the first end portion 200. A first insulating layer 206 and a second insulating layer 204 surround the conductor 208. In some instances, the first insulating layer 206 is a cable sheath that helps protect the conductor 208 from abrasion during or after assembly. In some instances, the second insulating layer 204 is a conduit and may be made of any suitable insulating layer, such as (but not limited to) polymers containing polyurethane, silicone, or other materials known for use as insulating layers for conductors in medical applications.

[0052] In some instances, cable conductor 208 can be used as a pacemaker conductor, such as a stranded cable conductor, and can be substantially similar to the second conductor 144b. The first transition ring 210 can be substantially similar to the first transition ring 124. The first transition ring 210 has grooves 216 and 222 and holes 212, 214, 218, and 220. The insulating tube 226 can expand so that the coil electrode 224 can be partially embedded within the insulating tube 226, for example... Figure 6B As shown, this is to maintain the spacing between the windings of the coil electrodes.

[0053] Unlike Figure 3 The insulating tube 122, and the insulating tube 226, do not include a notch similar to the distal notch 166 of the first end portion 134. In fact, the insulating tube 226 has a substantially uniform wall thickness along its entire length. The insulating tube 226 may require simpler manufacturing than the insulating tube 122 which includes the notch 166, for example, fewer steps. Figure 6B The insulating tube 226 is shown in an expanded state, such that the coil electrode 224 is partially embedded in the expanded insulating tube 226.

[0054] Figure 7A and 7B They are shown separately as similar to Figure 2 Cross-sectional views of region B of another example coil electrode assembly, showing the region before and after expansion. Figure 7A and 7B The second end portion 240 is similar to Figure 2 The second end portion 136, except for the differences described herein. For example, the second end portion 240 includes an insulating tube 226, a coil electrode 224, a second transition ring 250, a coil conductor 260, and a lead body 272. The conductor 208 is surrounded by a first insulating layer 206 and a second insulating layer 204.

[0055] In some instances, the second transformation ring 250 differs from... Figure 2 The second transition ring 126. For example, the second transition ring 250 lacks a second shoulder. Furthermore, the size of the groove 258 can vary along the longitudinal length of the second transition ring 250. For example, the groove 258 on one portion of the second transition ring 250 can be sized to facilitate an adhesive connection between the second transition ring 250 and the lead body 272. On a second, different portion of the second transition ring 250, the groove 258 can be sized to provide a connection between the first transition ring 250 and the coil conductor 260.

[0056] In the pre-expansion state, the inner diameter of the insulating fitting can remain substantially constant from the distal end to the proximal end of the fitting, for example... Figure 6A and 7A As shown relative to insulating tube 226. In the expanded state, the inner diameter of the insulating tube can be increased, for example in the longitudinal position, where the tube is not restricted by the transition ring and extends into the electrode coil, as... Figure 6B and 7B As shown relative to insulating fitting 226. In some instances, in the expanded state, the inner diameter of the insulating fitting at its center is larger than the inner diameters of the insulating fitting at its distal and proximal ends.

[0057] Figure 8 This is a flowchart illustrating an example technique for manufacturing a coil electrode assembly 100 to be attached to an implantable medical lead. Reference will also be made to the portion having a first end 134 ( Figure 3 ) and the second end 136 ( Figure 4 ) coil electrode assembly 100 ( Figure 2-5 )describe Figure 8 The technology is described, but those skilled in the art will understand that reference can be made to the first end 200 (…). Figure 6A and 6B ) and the second end 240 ( Figure 7A and 7BThe technique is performed by an electrode assembly, another electrode assembly, another implantable medical lead, or any other medical device.

[0058] Figure 8 Method 200 includes attaching an insulating tube 122 to a second transition ring 126 (302). The insulating tube 122 with the attached second transition ring 126 is inserted into a coil cavity 116 defined by a winding 114 of coil electrodes 112 (304). The insulating tube 122 is attached to a first transition ring 124 (306). In some instances, the insulating tube 122 is attached to the first and second transition rings 124 and 126 using an adhesive 146. The adhesive 146 may be applied along a distal portion 140 and a proximal portion 142 of the outer surface of the insulating tube 122. The adhesive 146 may also be applied to the outer surface of the insulating tube 122 before or after placement inside the coil cavity 116. In some instances, instead of applying the adhesive 146 to the insulating tube 122, the adhesive 146 may be applied to the inner surfaces of the first and second transition rings 124 and 126.

[0059] In some instances, the order of steps 302, 304, and 306 can be rearranged without affecting the finished product (e.g., step 304, followed by steps 302 and 306). Steps 302, 304, and 306 may need to be completed before the welding and heat application steps. For example, the insulating tube 122 may be inserted into the coil cavity 116 before attaching the first or second transition rings 124 and 126 (e.g., switching steps 302 and 304). In some instances, steps 306 and 302 may also be switched.

[0060] Once the insulating tube 122 is within the coil cavity 116 defined by the coil electrode 112 and the first and second transition rings 124 and 126 are attached to the insulating tube 122, the coil electrode 122 is welded to the first and second transition rings 124 and 126 (308). The insulating tube 122 can then be transformed into an expanded state to partially embed the coil electrode 112 within the insulating tube 122 (310). The insulating tube 122 can be transformed into an expanded state by applying heat and / or air (or other gas or liquid) pressure. The parameters of the heat and / or air pressure can be selected to ensure that the insulating tube 122 does not break or overflow, or otherwise damage. The applied pressure can consist of applying air or another fluid or gas to the interior of the insulating tube 122 at an internal pressure of less than approximately 6900 Pa for a range of approximately 60 seconds to approximately 90 seconds. Applying heat may involve applying heat to the insulating fitting 122, for example, the interior of the fitting, at approximately 180 degrees Celsius (°C) for approximately 60 to approximately 90 seconds. In one example, heat is slowly applied to the insulating fitting 122 at approximately 180°C for approximately 60 to 90 seconds, and internal pressure is applied within the insulating fitting 122 at a low pressure, for example, less than 6900 Pa. In some examples, heat and pressure are applied together, more specifically in the form of a heated gas, such as air, delivered at the desired pressure, for example, through a nozzle.

[0061] In some instances, based on the anticipated application and material properties of the coil electrode assembly 100, different temperatures and / or pressures can be used to modify the expansion of the insulating tube 122. After the insulating tube 122 is expanded, its outer diameter is smaller than that of the coil electrode 112. After expansion, the temperature of the insulating tube 122 is allowed to cool down. The first and second transition rings 124 and 126 can be attached to a high-voltage conductor extending within the insulating tube 122. After the coil electrode assembly 100 is completed, it can be attached to a lead (312), such as an implantable medical lead.

[0062] It should be understood that the various aspects disclosed herein can be combined with combinations different from those specifically presented in the specification and drawings. It should also be understood that, depending on the example, the actions or events of any process or method described herein can be performed in a different order, and can be added, combined, or excluded entirely (e.g., all described actions and events may not be necessary for performing the technique). Furthermore, although certain aspects of this disclosure are described for clarity as being performed by a single module or unit, it should be understood that the techniques of this disclosure can be performed by a combination of units or modules associated with, for example, a medical device.

[0063] Additionally, it should be noted that the system described herein is not limited to the treatment of human patients. In alternative instances, the system can be implemented in non-human patients, such as primates, canines, equines, pigs, and felines. These other animals may undergo clinical or research treatments that may benefit from the subject matter of this disclosure.

[0064] Various examples have been described. These and other examples are within the scope of the following claims and examples.

[0065] Example 1. An implantable medical lead configured to connect to an implantable medical device, the implantable medical lead comprising: a coil electrode assembly including coil electrodes extending from a proximal end to a distal end of an electrode, the coil electrodes defining an electrode cavity from the proximal end to the distal end of the electrode, and the coil electrodes including a plurality of windings; an insulating tube extending from a proximal end to a distal end of the tube, the insulating tube extending within the electrode cavity such that the coil electrodes extend along an outer surface of the insulating tube, the coil electrodes being partially embedded within the insulating tube when the insulating tube is in an expanded state. To maintain the spacing between the windings; a first transition ring at the distal end of the electrode and the distal end of the tube, wherein a portion of the first transition ring is within the electrode cavity, wherein the first transition ring defines a first transition ring cavity, and wherein the distal portion of the insulating tube including the distal end of the tube is within the first transition ring cavity; and a second transition ring at the proximal end of the electrode and the proximal end of the tube, wherein a portion of the second transition ring is within the electrode cavity, wherein the second transition ring defines a second transition ring cavity, and wherein the proximal portion of the insulating tube including the proximal end of the tube is within the second transition ring cavity.

[0066] Example 2. The implantable medical lead of Example 1 further includes an adhesive disposed on the distal portion of the insulating tube and the proximal portion of the insulating tube, wherein the adhesive is configured to attach a first transition ring to the distal portion of the insulating tube and a second transition ring to the proximal portion of the insulating tube.

[0067] Example 3. An implantable medical lead of Example 2, wherein the adhesive is disposed on the insulating tube only between the surface of the first transition ring and the distal portion of the insulating tube, and between the surface of the second transition ring and the proximal portion of the insulating tube.

[0068] Example 4. An implantable medical lead of either Example 2 or 3, wherein the outer surface of the coil electrode is substantially free of adhesive.

[0069] Example 5. An implantable medical lead of any of Examples 1-4, wherein each of the first and second transition rings is welded to the coil electrode.

[0070] Example 6. An implantable medical lead of any of Examples 1-5, wherein the insulating tubing comprises a polymer and is configured to transform into the expanded state by applying heat and air pressure.

[0071] Example 7. Implantable medical lead of Example 6, wherein the polymer comprises polyurethane.

[0072] Example 8. An implantable medical lead of any one of Examples 6 or 7, wherein the polymer has a hardness of at least 50 Shore D.

[0073] Example 9. An implantable medical lead of any of Examples 1-8, wherein, in the pre-expansion state, the inner diameter of the insulating tube is substantially constant from the distal end to the proximal end of the tube, and wherein, in the expanded state, the inner diameter of the insulating tube at its center is greater than the inner diameter of the insulating tube at both the distal and proximal ends of the tube.

[0074] Example 10. A system comprising an implantable medical device configured to generate an anti-tachyarrhythmic shock, and an implantable medical lead extending from a proximal end of a lead to a distal end of a lead, the proximal end of the lead being configured to be coupled to the implantable medical device, the implantable medical lead comprising: a coil electrode assembly between the proximal end and the distal end of the lead, the coil electrode assembly including coil electrodes extending from the proximal end to the distal end of the lead, the coil electrodes defining an electrode cavity from the proximal end to the distal end of the lead, and the coil electrodes including a plurality of windings, wherein the coil electrodes are configured to deliver the anti-tachyarrhythmic shock; an insulating tube extending from a proximal end of the tube to the distal end of the tube, the insulating tube extending within the electrode cavity such that the coil electrodes are along... The outer surface of the insulating tube extends such that, when the insulating tube is in an expanded state, the coil electrode is partially embedded within the insulating tube to maintain the spacing between the windings; a first transition ring is located at the distal end of the electrode and the distal end of the tube, wherein a portion of the first transition ring is within the electrode cavity, wherein the first transition ring defines a first transition ring cavity, and wherein the distal portion of the insulating tube including the distal end of the tube is within the first transition ring cavity; and a second transition ring is located at the proximal end of the electrode and the proximal end of the tube, wherein a portion of the second transition ring is within the electrode cavity, wherein the second transition ring defines a second transition ring cavity, and wherein the proximal portion of the insulating tube including the proximal end of the tube is within the second transition ring cavity.

[0075] Example 11. The system of Example 10, wherein the implantable medical lead further includes an electrical conductor configured to electrically connect the coil electrode to the implantable medical device, wherein the first and second transition rings are conductive, and the electrical conductor is connected to at least one of the first and second transition rings.

[0076] Example 12. A system of any one of Examples 10 or 11, wherein the implantable medical lead further includes another electrode distal to the coil electrode assembly and at least one electrical conductor configured to electrically connect the other electrode to the implantable medical device, wherein the inner surface of the insulating tube defines a cavity of the coil electrode assembly, and wherein the at least one electrical conductor extends through the cavity of the coil electrode assembly.

[0077] Example 14. A method includes: inserting an insulating tube into an electrode cavity defined by coil electrodes of a coil electrode assembly, such that the coil electrodes extend along an outer surface of the insulating tube from a proximal end to a distal end of the tube and the coil electrodes extend from the proximal end to the distal end of the electrode, and the coil electrodes include a plurality of windings; connecting a first transition ring at the distal end of the electrode to the coil electrode and at the distal end of the tube to the insulating tube; connecting a second transition ring at the proximal end of the electrode to the coil electrode and at the proximal end of the tube to the insulating tube; and applying at least one of heat and gas pressure to the insulating tube to transition the insulating tube from a non-expanded state to an expanded state, such that the coil electrodes are partially embedded within the insulating tube and the spacing between the windings is maintained.

[0078] Example 15. The method of Example 14 further includes securing the coil electrode assembly to an implantable medical lead.

[0079] Example 16. The method of Example 15, wherein the transition ring is conductive, the method further comprising connecting at least one of the transition rings to an electrical conductor to electrically connect the coil electrode to the proximal end of the implantable medical lead.

[0080] Example 17. A method of any one of Examples 15 or 16, wherein the inner surface of the insulating tube defines a cavity of the coil electrode assembly, the method further comprising connecting an electrical conductor extending through the cavity of the coil electrode assembly to another electrode at a distal end of the coil electrode assembly on the implantable medical lead to electrically connect the other electrode to a proximal end of the implantable medical lead.

[0081] Example 18. The method of any one of Examples 14-17, wherein applying gas pressure includes applying gas to the interior of the insulating tube for a period of approximately 60 to approximately 90 seconds at an internal pressure of less than approximately 6900 Pascals (Pa).

[0082] Example 19. The method of any one of Examples 14-18, wherein applying heat comprises applying heat to the interior of the insulating tube at about 180 degrees Celsius for a period of about 60 seconds to about 90 seconds.

[0083] Example 20. The method of any one of Examples 14-19, wherein after the insulating tube is transformed into the expanded state, the outer diameter of the insulating tube is smaller than the outer diameter of the coil electrode.

[0084] Example 21. The method of any one of Examples 14-20, wherein in the pre-expansion state, the inner diameter of the insulating tube is substantially constant from the distal end to the proximal end of the tube, and wherein in the expanded state, the inner diameter of the insulating tube at its center is greater than the inner diameter of the insulating tube at both the distal and proximal ends of the tube.

[0085] Example 22. A method of any one of Examples 14-21, wherein the first transition ring defines a first transition ring cavity and the second transition ring defines a second transition ring cavity, wherein connecting the first transition ring includes connecting the first transition ring such that a portion of the first transition ring is within the electrode cavity and a distal portion of the insulating tube including the distal end of the tube is within the first transition ring cavity, wherein connecting the second transition ring includes connecting the second transition ring such that a portion of the second transition ring is within the electrode cavity and a proximal portion of the insulating tube including the proximal end of the tube is within the second transition ring cavity.

[0086] Example 23. The method of Example 22, wherein connecting the transition ring to the insulating tube comprises connecting the transition ring to the insulating tube using an adhesive disposed only between the surface of the first transition ring and the distal portion of the insulating tube, and between the surface of the second transition ring and the proximal portion of the insulating tube.

Claims

1. A coil electrode assembly, comprising: A coil electrode extending from a proximal end to a distal end of an electrode, the coil electrode defining an electrode cavity from the proximal end to the distal end of the electrode, and the coil electrode including a plurality of windings; An insulating tube extending from a proximal end to a distal end of the tube, the insulating tube extending within the electrode cavity such that the coil electrode extends along the outer surface of the insulating tube, and when the insulating tube is in an expanded state, the coil electrode is partially embedded within the insulating tube to maintain the spacing between the windings; A first transition ring is located at the distal end of the electrode and the distal end of the tubing, wherein a portion of the first transition ring is within the electrode cavity, wherein the first transition ring defines a first transition ring cavity, and wherein the distal portion of the insulating tubing including the distal end of the tubing is within the first transition ring cavity. as well as A second transition ring is located at the proximal end of the electrode and the proximal end of the tubing, wherein a portion of the second transition ring is within the electrode cavity, wherein the second transition ring defines a second transition ring cavity, and wherein the proximal portion of the insulating tubing including the proximal end of the tubing is within the second transition ring cavity.

2. The coil electrode assembly of claim 1, further comprising an adhesive disposed on the distal portion of the insulating tube and the proximal portion of the insulating tube, wherein the adhesive is configured to connect the first transition ring to the distal portion of the insulating tube and to connect the second transition ring to the proximal portion of the insulating tube.

3. The coil electrode assembly of claim 2, wherein the adhesive is disposed on the insulating tube only between the surface of the first transition ring and the distal portion of the insulating tube, and between the surface of the second transition ring and the proximal portion of the insulating tube.

4. The coil electrode assembly according to any one of claims 2 or 3, wherein the outer surface of the coil electrode is free of adhesive.

5. The coil electrode assembly according to any one of claims 1-3, wherein each of the first and second transition rings is welded to the coil electrode.

6. The coil electrode assembly according to any one of claims 1-3, wherein the insulating tube comprises a polymer and is configured to transform into the expanded state by applying heat and air pressure.

7. The coil electrode assembly of claim 6, wherein the polymer comprises polyurethane.

8. The coil electrode assembly of claim 6, wherein the polymer has a hardness of at least 50 Shore D.

9. The coil electrode assembly according to any one of claims 1-3, In the pre-expansion state, the inner diameter of the insulating tube is substantially constant from the distal end to the proximal end of the tube, and In the expanded state, the inner diameter of the insulating tube at its center is greater than the inner diameter of the insulating tube at its distal end and the inner diameter of the insulating tube at its proximal end.

10. An implantable medical lead, comprising: It is configured to connect to the proximal end and the distal end of a lead in an implantable medical device; as well as The coil electrode assembly according to any one of claims 1-9 is located at a position between the proximal end and the distal end of the lead.

11. The implantable medical lead of claim 10, further comprising: At least one electrical contact at the proximal end of the lead is configured to be electrically connected to the implantable medical device when the proximal end of the lead is connected to the implantable medical device. Insulated lead body; as well as At least one electrical conductor within the insulated lead body is electrically connected to the electrical contact at the proximal end of the lead and to the coil electrode of the electrode assembly.

12. The implantable medical lead of claim 11, wherein the first and second transition rings are conductive, and the electrical conductor is connected to at least one of the first and second transition rings.

13. The implantable medical lead of any one of claims 11-12, wherein the implantable medical lead further comprises another electrode distal to the coil electrode assembly and at least one electrical conductor configured to electrically connect the other electrode to the implantable medical device, wherein the inner surface of the insulating tube defines a cavity of the coil electrode assembly, and wherein the at least one electrical conductor extends through the cavity of the coil electrode assembly.

14. A medical system comprising: An implantable medical device configured to generate an anti-tachyarrhythmic electric shock; as well as Implantable medical leads according to any one of claims 10-13.

15. A method for manufacturing a coil electrode assembly, comprising: An insulating tube is inserted into an electrode cavity defined by a coil electrode of a coil electrode assembly, such that the coil electrode extends along the outer surface of the insulating tube from a proximal end to a distal end of the tube and the coil electrode extends from a proximal end to a distal end of the electrode, and the coil electrode includes a plurality of windings. The first transition ring is connected to the coil electrode at the distal end of the electrode and to the insulating tube at the distal end of the tube, such that the distal portion of the insulating tube including the distal end of the tube is within the cavity of the first transition ring. The second transition ring is connected to the coil electrode at the proximal end of the electrode and to the insulating tube at the proximal end of the tube, such that the proximal portion of the insulating tube including the proximal end of the tube is within the cavity of the second transition ring. as well as At least one of heat and gas pressure is applied to the insulating tube to change the insulating tube from a non-expanded state to an expanded state, such that the coil electrodes are partially embedded in the insulating tube and the spacing between the windings is maintained.

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