Patent Description:
Implantable medical devices may be used to monitor a variety of conditions of patients and/or to deliver a variety of therapies to patients. Some implantable medical devices include electrodes to sense electrical signals and/or deliver electrical therapies. Some implantable medical devices include elongated leads to position the electrodes proximate to target tissue for sensing or therapy delivery. For example, an implantable medical device may deliver anti-tachyarrhythmia (e.g., defibrillation) shocks via one or more coil electrodes that are part of one or more leads and are located within or proximate to the heart. <CIT> realtes to an implantable electrode and a method of fabrication. <CIT> relates to a transvenous defibrillation lead.

The techniques of this disclosure generally relate to assembling implantable medical leads including coil electrodes and, more particularly, to securing the windings of a coil electrode, e.g., preserving intra-winding spacing, by an "inside-out" approach. In some existing implantable medical leads, coil electrodes are secured using an adhesive applied from the outside of the coil electrode. In contrast, the techniques of the present disclosure secure the coil electrode using an insulative tube disposed within a lumen defined by the coil electrode, which may increase the surface area of the coil electrode available for blood/tissue contact to interact with relative to the existing implantable medical leads.

The insulative tube within the lumen is transitioned to an expanded state to make contact with the coil electrode, e.g., such that the coil electrode is partially embedded within the insulative tube, and thus secure the spacing between the windings. The expansion of the tube may be done through the application of heat and/or air pressure to the inside of the tube. In some examples, prior to expanding the insulative tube, transition rings are connected at the ends of the coil electrode and the tube to maintain them in place relative to one another during expansion of the tube.

In some examples, the coil electrode assembly may be constructed as a subassembly for the implantable medical leads. Making the implantable medical lead using such a subassembly process can help reduce waste, because if one subassembly part needs to be scrapped, the remaining portion of the lead does not need to be scrapped as well. Examples in which the coil electrode assembly includes one or more conductive transition rings may also facilitate electrical connection of the coil electrode to a conductor of the implantable medical lead via the transition ring.

In one example, the present disclosure provides an implantable medical lead configured to be coupled to an implantable medical device, the implantable medical lead comprising a coil electrode assembly. The coil electrode assembly comprises a coil electrode 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, and the coil electrode comprising a plurality of windings. The coil electrode assembly further comprises an insulative tube extending from a tube proximal end to a tube distal end, the insulative tube extending within the electrode lumen such that the coil electrode extends along an outer surface of the insulative tube, the coil electrode partially embedded within the insulative tube when the insulative tube is in an expanded state to maintain a spacing between the windings. The coil electrode assembly further comprises a first transition ring at the electrode distal end and the tube distal end, wherein a portion of the first transition ring is within the electrode lumen, wherein the first transition ring defines a first transition ring lumen, and wherein a distal portion of the insulative tube including the tube distal end is within the first transition ring lumen. The coil electrode assembly further comprises a second transition ring at the electrode proximal end and the tube proximal end, wherein a portion of the second transition ring is within the electrode lumen, wherein the second transition ring defines a second transition ring lumen, and wherein a proximal portion of the insulative tube including the tube proximal end is within the second transition ring lumen.

In another example, the disclosure provides a system comprising an implantable medical device configured to generate an antitachyarrhythmia shock, and an implantable medical lead extending from a lead proximal end to a lead distal end, the lead proximal end configured to be coupled to the implantable medical device, the implantable medical lead comprising a coil electrode assembly between the lead proximal end and the lead distal end. The coil electrode assembly comprises a coil electrode 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, and the coil electrode comprising a plurality of windings, wherein the coil electrode is configured to deliver the antitachyarrhythmia shock. The coil electrode assembly further comprises an insulative tube extending from a tube proximal end to a tube distal end, the insulative tube extending within the electrode lumen such that the coil electrode extends along an outer surface of the insulative tube, the coil electrode partially embedded within the insulative tube when the insulative tube is in an expanded state to maintain a spacing between the windings. The coil electrode assembly further comprises a first transition ring at the electrode distal end and the tube distal end, wherein a portion of the first transition ring is within the electrode lumen, wherein the first transition ring defines a first transition ring lumen, and wherein a distal portion of the insulative tube including the tube distal end is within the first transition ring lumen. The coil electrode assembly further comprises a second transition ring at the electrode proximal end and the tube proximal end, wherein a portion of the second transition ring is within the electrode lumen, wherein the second transition ring defines a second transition ring lumen, and wherein a proximal portion of the insulative tube including the tube proximal end is within the second transition ring lumen.

In another example, the disclosure provides a coil electrode assembly for an implantable medical lead configured to be coupled to an implantable medical device. The coil electrode assembly comprises a coil electrode 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, and the coil electrode comprising a plurality of windings. The coil electrode assembly further comprises an insulative tube extending from a tube proximal end to a tube distal end, the insulative tube extending within the electrode lumen such that the coil electrode extends along an outer surface of the insulative tube, the coil electrode partially embedded within the insulative tube when the insulative tube is in an expanded state to maintain a spacing between the windings. The coil electrode assembly further comprises a first transition ring at the electrode distal end and the tube distal end, wherein a portion of the first transition ring is within the electrode lumen, wherein the first transition ring defines a first transition ring lumen, and wherein a distal portion of the insulative tube including the tube distal end is within the first transition ring lumen. The coil electrode assembly further comprises a second transition ring at the electrode proximal end and the tube proximal end, wherein a portion of the second transition ring is within the electrode lumen, wherein the second transition ring defines a second transition ring lumen, and wherein a proximal portion of the insulative tube including the tube proximal end is within the second transition ring lumen.

In another example, a method comprises inserting an insulative tube within an electrode lumen defined by a coil electrode of a coil electrode assembly such that the coil electrode extends along an outer surface of the insulative tube, the insulative tube extending from a tube proximal end to a tube distal end and the coil electrode extending from an electrode proximal end to an electrode distal end, and the coil electrode comprising a plurality of windings. The method further comprises connecting a first transition ring to the coil electrode at the electrode distal end and to the insulative tube at the tube distal end, and connecting a second transition ring to the coil electrode at the electrode proximal end and to the insulative tube at the tube proximal end. The method further comprises applying at least one of heat and gas pressure to the insulative tube to transition the insulative tube from a non-expanded state to an expanded state such that the coil electrode is partially embedded within the insulative tube and a spacing between the windings is maintained.

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 within the accompanying drawings and description below. Other features, objects, and advantages of the techniques described in this disclosure will be apparent from the description and drawings. The present invention provides a coil electrode assembly according to claim <NUM>, an implantable medical lead according to claim <NUM> and a method according to claim <NUM>.

Electrodes used to deliver relatively higher-energy (e.g., compared to cardiac pacing) anti-tachyarrhythmia (e.g., defibrillation) shocks can take the form of a wound coil with the outside surface exposed to the blood or other bodily fluid. The windings of these coils are typically secured in their axial position with respect to the underlying lead body tube and each other (e.g., to avoid filar dislocation, fracture, or fibrosis tissue ingrowth) through depositing silicone adhesive or silicone rubber in an outside-in direction to cover the wound coil and the space between the coils. Due to this deposition of the silicone adhesive or silicone rubber, an exterior surface of wound coil, including the spaces between the electrodes, can be fully or partially covered with a thin coating.

While the thin coating can lock the wound coils in place, preventing movement of the defibrillation coil electrode, the coating may potentially reduce the performance of the coil electrode due to reduced available surface area of the coil electrode. In some examples, in order to counteract the reduction of available surface area of the coil electrode, the excess adhesive is removed from the outer surface of the coil. However, removing the adhesive requires relatively skilled labor and adds a step to the process of making the implantable medical lead including the coil electrode. Also, using conventional lead assembly techniques, errors in the application of the adhesive or the removal of the thin coating may lead to scrapping the entire implantable medical lead.

A coil electrode assembly according to this disclosure includes an insulative tube within a lumen defined by the coil electrode, and the insulative tube is transitioned to an expanded state to partially embed the coil electrode to secure the coil windings in place via an inside-out approach. In this manner, the coil electrode assembly described herein may have increased outer surface area for delivery of anti-tachyarrhythmia shocks. Increasing the available surface areas of the coil can increase the effectiveness of the shock delivered, e.g., during ventricular tachycardia (VT) and ventricular fibrillation (VF). Additionally, manufacturing an implantable medical lead including a coil electrode assembly, as described herein, can reduce operator variability and provide cost savings by creating subassemblies that are to be assembled together to create the final product. For example, if the coil electrode assembly is not assembled correctly, only the coil electrode assembly needs to be scrapped.

<FIG> is a conceptual diagram illustrating an example medical device system <NUM> including an implantable medical device (IMD) <NUM> coupled to one or more coil electrodes on one or more implantable medical leads. In the example of <FIG>, IMD <NUM> is coupled to leads <NUM> and <NUM>. IMD <NUM> may be, for example, an implantable pacemaker, cardioverter, and/or defibrillator that provides electrical signals to heart <NUM> via electrodes coupled to one or more of leads <NUM> and <NUM>.

In the example of <FIG>, leads <NUM> and <NUM> extend into the heart <NUM> to sense electrical activity of a heart <NUM> and/or deliver electrical therapy to heart <NUM>. Right ventricular (RV) lead <NUM> extends through one or more veins (not shown), the superior vena cava (not shown), and right atrium <NUM>, and into right ventricle <NUM>. Right atrial (RA) lead <NUM> extends through one or more veins and the vena cava, and into the right atrium <NUM> of heart <NUM>. Although example system <NUM> includes intravascular leads and intracardiac electrodes, extravascular leads including extravascular coil electrodes may include coil electrode assemblies according to the techniques of this disclosure.

IMD <NUM> may sense electrical signals attendant to the depolarization and repolarization of heart <NUM> via electrodes coupled to at least one of the leads <NUM> and <NUM>. In some examples, IMD <NUM> provides pacing pulses to heart <NUM> based on the electrical signals sensed within heart <NUM>. The configurations of electrodes used by IMD <NUM> for sensing and pacing may be unipolar or bipolar. IMD <NUM> may detect arrhythmia of heart <NUM>, such as tachycardia or fibrillation of the atria (including right atrium <NUM>) and/or the ventricles (including right ventricle <NUM>), and may also provide anti-tachyarrhythmia shocks, e.g., defibrillation and/or cardioversion shocks, via electrodes located on at least one of the leads <NUM> and <NUM>. In some examples, IMD <NUM> may be programmed to deliver a progression of therapies, e.g., pulses with increasing energy levels, until a fibrillation of heart <NUM> is stopped. IMD <NUM> may detect fibrillation employing one or more fibrillation detection techniques known in the art.

As shown in <FIG>, the proximal ends of leads <NUM> and <NUM> are connected to a connector block <NUM> of IMD <NUM> to electrically couple the electrodes on the leads to circuitry within the housing <NUM> of IMD <NUM>. In some examples, proximal ends of leads <NUM> and <NUM> may include electrical contacts that electrically couple to respective electrical contacts within connector block <NUM> of IMD <NUM>. Each of the leads <NUM> and <NUM> includes an elongated insulative lead body, which may carry a number of conductors, e.g., a conductor for each electrode on the lead, each of which may be connected to a respective contact at the proximal end of the lead. Bipolar electrodes <NUM> and <NUM> are located adjacent to a distal end of lead <NUM> in right ventricle <NUM>. In addition, bipolar electrodes <NUM> and <NUM> are located adjacent to a distal end of lead <NUM> in right atrium <NUM>.

Electrodes <NUM> and <NUM> may take the form of ring electrodes, and electrodes <NUM> and <NUM> may take the form of helix tip electrodes mounted, e.g., with a fixed screw, within insulative electrode heads <NUM> and <NUM>, respectively. Some helix tip electrodes can include a mechanism for an extendable/retractable helix. In other examples, one or more of electrodes <NUM> and <NUM> may take the form of small circular electrodes at the tip of a tined lead or other fixation element. Leads <NUM> and <NUM> also include elongated electrodes <NUM> and <NUM>, respectively, each of which may take the form of a coil. Each of the electrodes <NUM>, <NUM>, <NUM>, <NUM>, <NUM> and <NUM> may be electrically coupled to a respective one of the conductors within the lead body of its associated lead <NUM> and <NUM>, and thereby coupled to respective ones of the electrical contacts on the proximal end of leads <NUM> and <NUM>.

In the example of <FIG>, IMD <NUM> includes a housing electrode <NUM>, which may be formed integrally with an outer surface of hermetically-sealed housing <NUM> of IMD <NUM>, or otherwise coupled to housing <NUM>. In some examples, housing electrode <NUM> is defined by an uninsulated portion of an outward facing portion of housing <NUM> of IMD <NUM>. Other division between insulated and uninsulated portions of housing <NUM> may be employed to define two or more housing electrodes. In some examples, housing electrode <NUM> comprises substantially all of housing <NUM>.

IMD <NUM> may sense electrical signals attendant to the depolarization and repolarization of heart <NUM> via electrodes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>. The electrical signals are conducted to IMD <NUM> from the electrodes via the respective leads <NUM> and <NUM>. IMD <NUM> may sense such electrical signals via any bipolar combination of electrodes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>. Furthermore, any of the electrodes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> may be used for unipolar sensing in combination with housing electrode <NUM>. The combination of electrodes used for sensing may be referred to as a sensing configuration or electrode vector.

In some examples, IMD <NUM> delivers pacing pulses via bipolar combinations of electrodes <NUM>, <NUM>, <NUM> and <NUM> to produce depolarization of cardiac tissue of heart <NUM>. In some examples, IMD <NUM> delivers pacing pulses via any of electrodes <NUM>, <NUM>, <NUM> and <NUM> in combination with housing electrode <NUM> in a unipolar configuration. Furthermore, IMD <NUM> may deliver antitachyarrhythmia shocks, e.g., defibrillation shocks, to heart <NUM> via any combination of elongated electrodes <NUM> and <NUM>, and housing electrode <NUM>. IMD <NUM> may also use electrodes <NUM>, <NUM>, and <NUM> to deliver cardioversion shocks to heart <NUM>. Electrodes <NUM> and <NUM> may be fabricated from any suitable electrically conductive material, such as, but not limited to, platinum, platinum alloy or other materials known to be usable in implantable defibrillation electrodes.

The configuration of system <NUM> illustrated in <FIG> is merely one example. In other examples, a system may include extravascular leads and electrodes instead of or in addition to the transvenous leads <NUM> and <NUM> illustrated in <FIG>. Further, IMD <NUM> need not be implanted within the patient. In examples in which IMD <NUM> is not implanted in the patient, IMD <NUM> may sense electrical signals and/or deliver antitachyarrhythmia shocks and other therapies to heart <NUM> via percutaneous leads that extend through the skin of a patient to a variety of positions within or outside of heart <NUM>.

<FIG> is a cross-sectional diagram that illustrates an example coil electrode assembly <NUM>. <FIG> is a cross-sectional diagram that further illustrates a view of a first end portion <NUM> (region A from <FIG>) of coil electrode assembly <NUM>. <FIG> is a cross-sectional diagram that further illustrates a view of a second end portion <NUM> (region B from <FIG>) of coil electrode assembly <NUM>. <FIG> is a conceptual diagram illustrating an exploded view of the example coil electrode assembly of <FIG>.

Coil electrode assembly <NUM> includes a coil electrode <NUM>, an insulative tube <NUM>, a first transition ring <NUM>, and a second transition ring <NUM>. When assembled as shown in <FIG>, lumen respectively defined by each of insulative tube <NUM>, first transition ring <NUM> and second transition ring <NUM> collectively define a lumen <NUM> of coil electrode assembly <NUM>. Either or both of elongated electrodes <NUM> and <NUM> on leads <NUM> and <NUM>, respectively, may be assembled according to the techniques described herein with respect to coil electrode assembly <NUM>. In general, coil electrode assembly <NUM> may be included in an implantable medical lead at a desired position between a proximal end and a distal end of the lead.

Although inclusion on an implantable medical lead is described herein as an example, coil electrode assembly <NUM> can be used with other medical devices and/or therapies. In general, coil electrode assembly <NUM> can be used in any medical device or non-medical device.

In the example of <FIG>, coil electrode <NUM> includes a plurality of windings <NUM> that extend from a coil electrode distal end <NUM> to a coil electrode proximal end <NUM>. Windings <NUM> define a coil lumen <NUM> from a distal end <NUM> to a proximal end <NUM> of coil electrode <NUM>. As shown in <FIG>, insulative tube <NUM> extends from a tube proximal end <NUM> to a tube distal end <NUM>. Insulative tube <NUM> extends within coil lumen <NUM>, e.g., from the electrode distal end <NUM> to the electrode proximal end <NUM>, such that coil electrode <NUM> extends along an outer surface <NUM> (<FIG>) of insulative tube <NUM>. When insulative tube <NUM> is in an expanded state to maintain a spacing <NUM> (as shown in <FIG>) between windings <NUM>, coil electrode <NUM> is partially embedded within insulative tube <NUM>.

Insulative tube <NUM> may include a polymer including polyurethane and/or silicone. Inclusion of a polyurethane may provide desirable mechanical properties, such as relatively increased tensile and tear strength in at least the expanded state, compared to a similar thickness tube made from other materials. In some examples, the polymer or other material of insulative tube <NUM> may have a durometer hardness of at least <NUM> Shore D, such as approximately <NUM> Shore D.

First transition ring <NUM> is connected to coil electrode <NUM> at coil electrode distal end <NUM>, and second transition ring <NUM> is connected to coil electrode <NUM> at coil electrode proximal end <NUM>. In some examples, a first transition ring junction <NUM> defines a surface for the coil electrode to abut for the connection between first transition ring <NUM> and coil electrode <NUM>, and a second transition ring junction <NUM> defines a surface for the coil electrode to abut for the connection between second transition ring <NUM> and coil electrode <NUM>. The connection can be provided by multiple methods including welding, crimping, and staking, as examples. In some examples, each of first transition ring junction <NUM> and second transition ring junction <NUM> can withstand a tensile pull force of at least <NUM> pound.

First transition ring <NUM> defines an inner lumen <NUM> (<FIG> and <FIG>) and second transition ring <NUM> defines an inner lumen <NUM> (<FIG> and <FIG>). Insulative tube <NUM> defines an insulative tube lumen <NUM> (<FIG> and <FIG>). At least a portion of first transition ring <NUM> and second transition ring <NUM> are disposed within coil lumen <NUM>, and in some examples between coil electrode <NUM> and an outer surface, e.g., outer surface <NUM> (<FIG>), of insulative tube <NUM>. Inner lumen <NUM> of first transition ring <NUM>, insulative tube lumen <NUM>, and inner lumen <NUM> of second transition ring <NUM> form lumen <NUM> of coil electrode assembly <NUM>.

First transition ring <NUM> is connected to insulative tube <NUM> at tube distal end <NUM>, and second transition ring <NUM> is connected to insulative tube <NUM> at tube proximal end <NUM>. In some examples, a distal recess <NUM> (<FIG>, <FIG> and <FIG>) is formed in a distal portion <NUM> (<FIG> and <FIG>) of insulative tube <NUM>, and a proximal recess <NUM> (<FIG>, <FIG> and <FIG>) in a proximal portion <NUM> (<FIG> and <FIG>) of insulative tube <NUM>. Portions of first transition ring <NUM> and second transition ring <NUM> extending medially from junctions <NUM> and <NUM>, respectively, can receive the portions of insulative tube <NUM> defining the respective one of the recesses <NUM> and <NUM>. Distal recess <NUM> can help provide a secure fit between first transition ring <NUM> and insulative tube <NUM>. Distal recess <NUM> and proximal recess <NUM> of insulative tube <NUM> can be reciprocally shaped to transition rings <NUM> and <NUM> so there is a substantially smooth transition from insulative tube <NUM> to transition rings <NUM> and <NUM>. As illustrated in <FIG>, the combined thickness of insulative tube <NUM> at recesses <NUM> and <NUM> and the mated portions of transition rings <NUM> and <NUM> may define a substantially similar thickness to the thickness of the remainder of insulative tube <NUM>.

In some examples, insulative tube <NUM> need not include recesses <NUM> and <NUM>. Nevertheless, in such examples, distal portion <NUM> of insulative tube <NUM> including distal tube end <NUM> may be received within distal ring lumen <NUM>, and proximal portion <NUM> of insulative tube <NUM> including proximal tube end <NUM> may be received within proximal ring lumen <NUM>. An example of a coil electrode assembly in which an insulative tube does not include recesses at the distal and proximal portions is described with respect to <FIG>.

First transition ring <NUM> and second transition ring <NUM> may be made of a conductive material. In some examples, coil electrode assembly <NUM> can have one or more electrical conductors. A first electrical conductor 144a of an implantable medical lead (e.g., lead <NUM> or <NUM>) may be electrically coupled to coil electrode <NUM> via at least one of the first transition ring <NUM> and second transition ring <NUM>. In the example illustrated by <FIG>, first electrical conductor 144a is coupled to second transition ring <NUM>. First electrical conductor 144a may connect coil electrode <NUM>, via transition ring <NUM> to the proximal end of the implantable medical lead.

In some examples, as shown in <FIG>, a second conductors 144b may connect one or more electrodes distal of coil electrode assembly <NUM> to the proximal end of the implantable medical lead and, thus to the IMD (conductors 144a and 144b collectively as conductors <NUM>). For example, with respect to the example of <FIG>, second conductor 144b may extend through lumen <NUM> to connect electrodes <NUM> and <NUM> (or <NUM> and <NUM>) to IMD <NUM> through coil electrode assembly <NUM> in which coil electrode <NUM> corresponds to electrode <NUM> and <NUM> (shown in <FIG>).

As illustrated in <FIG>, first transition ring <NUM> may include a proximal end <NUM> and a distal end <NUM>. The proximal and distal sides extend from respective ends, <NUM> and <NUM>, to an increased diameter shoulder <NUM>. The proximal and distal sides of shoulder <NUM> can have different shapes and sizes. For example, proximal side of shoulder <NUM> can include a curved corner, and distal side of shoulder <NUM> can include a <NUM>-degree (<NUM>°) corner. Proximal side of shoulder <NUM> provides first transition ring junction <NUM> which may include a surface for coil electrode <NUM> to engage. In some examples, coil electrode <NUM> may be welded to first transition ring <NUM> at proximal side of shoulder <NUM>. Distal side of shoulder <NUM> provides a surface for coil electrode assembly <NUM> to connect with a remainder of a lead body of an implantable medical lead.

<FIG> is a conceptual diagram that illustrates an example proximal portion of coil electrode assembly <NUM> including second transition ring <NUM>. Second transition ring <NUM> may be similar to first transition ring <NUM>. In the illustrated example, second transition ring <NUM>, with a proximal end <NUM> and a distal end <NUM>, includes two increased diameter portions, defining a first shoulder <NUM> and a second shoulder <NUM>. A distal side of shoulder <NUM> can include a curved corner, and proximal side of shoulder <NUM> can include an approximately <NUM>-degree (<NUM>°) corner. Distal side of shoulder <NUM> provides second transition ring junction <NUM> which may include a surface for coil electrode <NUM> to engage. In some examples, coil electrode <NUM> may be welded to second transition ring <NUM> at proximal side of shoulder <NUM>. In some examples, second shoulder <NUM> can provide a transition to the body of the implantable medical lead. Similar, to first transition ring <NUM>, second transition ring <NUM> has holes 176A, 176B, 184A, 184B and grooves <NUM> and <NUM> to increase structural integrity of the joint by, e.g., adding additional locations/geometries for mechanical fixation of components. Similar to recess <NUM> at distal end of insulative tube <NUM>, proximal end of insulative tube <NUM> also has a proximal recess <NUM> and functions to provide a connection between insulative tube <NUM> and second transition ring <NUM>.

First transition ring <NUM> is connected to a distal portion <NUM> (<FIG>) of insulative tube <NUM>, and second transition ring <NUM> is connected to proximal portion <NUM> (<FIG>) of insulative tube <NUM>. Adhesive <NUM> is disposed on distal portion <NUM> of insulative tube <NUM> and proximal portion <NUM> of insulative tube <NUM>, e.g., outer surface <NUM> of insulative tube <NUM> at these portions. Adhesive <NUM> connects first transition ring <NUM> to distal portion <NUM> of insulative tube <NUM> and second transition ring <NUM> to proximal portion <NUM> of insulative tube <NUM>.

Adhesive <NUM> can be disposed in one location or multiple locations. In some examples, adhesive <NUM> is disposed only on two locations of insulative tube <NUM>. The first location for adhesive <NUM> is located between a surface of first transition ring <NUM> and the distal portion <NUM> of insulative tube <NUM>. The second location for adhesive <NUM> is between a surface of second transition ring <NUM> and the proximal portion <NUM> of insulative tube <NUM>. In each location, adhesive <NUM> may be applied continuously or discontinuously as beads, a spray, parallel lines, or various patterns. For example, adhesive <NUM> can be applied in a continuous coating to the distal portion <NUM> of insulative tube <NUM> and applied in a discontinuous coating to the proximal portion <NUM> of insulative tube <NUM>.

The amount of adhesive <NUM> applied to coil electrode assembly <NUM> may vary over a wide range. The composition of adhesive <NUM> can vary as well and can include silicone adhesive. In some examples, adhesive <NUM> can be a mixture of heptane and adhesive. Different compositions of adhesive <NUM> can be applied to different parts of insulative tube <NUM>. For example, some portions of coil electrode assembly <NUM> may include a stronger adhesive <NUM> than other parts. In some examples, the connection of transition rings <NUM> and <NUM> to tube <NUM> may be by a variety of means in addition to or instead of adhesive <NUM>.

Some areas of coil electrode assembly <NUM> can be free of adhesive <NUM>. For example, an outer surface of coil electrode <NUM> may be substantially free of adhesive <NUM>. At least part of first transition ring <NUM>, a first area <NUM>, can be free of adhesive <NUM>. Similarly, at least part of second transition ring <NUM>, a second area <NUM>, can be free of adhesive <NUM>. Both first transition ring <NUM> and second transition ring <NUM> can include multiple areas free of adhesive <NUM>. By reducing the amount of adhesive <NUM> on the outer surface of coil electrode <NUM>, the surface area of coil electrode <NUM> that is available to interact with the patient is increased, thereby potentially increasing the effectiveness of an implantable medical lead including coil electrode assembly <NUM>.

Grooves <NUM> and holes 156A and 156B (collectively "holes <NUM>") secure first transition ring <NUM> to insulative tube <NUM>. Grooves <NUM> can facilitate connection with the use of adhesive. Holes <NUM> can also be used for inspection and verification. For example, holes <NUM> can be used to visually ensure insulative tube <NUM> is properly positioned in first transition ring <NUM>. Holes 156A and 156B are on opposite sides of first transition ring <NUM>. Holes <NUM> extend from outer surface of first transition ring <NUM> to inner lumen <NUM> of first transition ring <NUM>. In some examples, instead of two holes 156A and 156B, there could be one hole or more than two holes <NUM>. In some examples, multiple holes <NUM> could be placed circumferentially around first transition ring <NUM>. Multiple holes <NUM> could be evenly or irregularly spaced. There could also be multiple holes <NUM> spaced longitudinally along first transition ring <NUM>, instead of or in addition to holes <NUM> spaced circumferentially.

Grooves <NUM> can extend circumferentially around first transition ring <NUM>. In some examples, grooves <NUM> may not extend completely circumferentially around first transition ring <NUM>. For example, grooves <NUM> may extend only partially around the circumference of first transition ring <NUM>. In addition, the angle of grooves <NUM> to the longitudinal axis of first transition ring <NUM> may vary. For example, grooves <NUM> may extend perpendicular or at an angle to a longitudinal axis of first transition ring <NUM>.

Grooves <NUM> and holes 160A and 160B (collectively "holes <NUM>") may be the same or substantially similar or different than grooves <NUM> and holes 156A and 156B. In some examples, grooves <NUM> and <NUM> may be substantially similar, and holes <NUM> may be different than holes <NUM>, or vice versa. Grooves <NUM> and holes <NUM> provide connection means for first transition ring <NUM> and coil electrode assembly <NUM>, respectively, to connect with other components and/or assemblies of the implantable medical lead. Grooves <NUM> can be used with adhesive to provide a connection between first transition ring <NUM> and a lead body. In some examples, grooves <NUM> can be used to promote an adhesive connection to other components, e.g., by increasing bond strength. Other connection means besides or in addition to grooves <NUM>, <NUM> and holes <NUM>, <NUM> could be used as well. Holes <NUM> and <NUM> can enable second conductor 144b to make an electrical connection from inner lumen <NUM> of first transition ring <NUM> to the exterior of first transition ring <NUM>. Similar, to first transition ring <NUM>, second transition ring <NUM> (<FIG>) has holes 176A, 176B, 184A, 184B and grooves <NUM> and <NUM>, which may provide substantially similar functionality to holes <NUM> and <NUM> and grooves <NUM> and <NUM> of first transition ring <NUM> (<FIG>). In some examples, transition rings <NUM> and <NUM> can use holes <NUM>, <NUM>, <NUM>, and <NUM> to promote adhesion to an attached component and provide an inspection/verification feature. In some examples, transition rings <NUM> and <NUM> may be free of holes <NUM> and <NUM>.

<FIG> are cross-sectional diagrams illustrating a pre-expansion state and a post-expansion state, respectively, of a region of another example coil electrode assembly similar to region A of the example coil electrode assembly of <FIG>. First end portion <NUM> of <FIG> is similar to first end portion <NUM>, except for the differences described herein. For example, like first end portion <NUM>, first end portion <NUM> includes a first transition ring <NUM>, a coil electrode <NUM>, and an insulative tube <NUM>. First transition ring <NUM> is connected to a distal portion of a lead body <NUM>. A conductor <NUM> extends through the middle of first end portion <NUM>. A first insulator layer <NUM> and a second insulator layer <NUM> surround conductor <NUM>. In some examples, first insulator layer <NUM> is a cable jacket, which can help protect conductor <NUM> from abrasion during or after assembly. In some examples, second insulator layer <NUM> is a tubing and can be made from any suitable insulative layer, such as, but not limited to, a polymer including polyurethane, silicone, or other materials known to be usable for insulative layers for conductors in medical applications.

In some examples, cable conductor <NUM> can be used as a pacing conductor, e.g., a cable conductor such as a stranded cable, and can be substantially similar to second conductor 144b. First transition ring <NUM> can be substantially similar to first transition ring <NUM>. First transition ring <NUM> has grooves <NUM> and <NUM> and holes <NUM>, <NUM>, <NUM>, and <NUM>. Insulative tube <NUM> can be expanded so coil electrode <NUM> can be partially embedded within insulative tube <NUM>, e.g., as shown in <FIG>, to maintain a spacing between the windings of coil electrode.

Unlike insulative tube <NUM> of <FIG>, insulative tube <NUM> does not include a recess similar to distal recess <NUM> of first end portion <NUM>. Instead, insulative tube <NUM> has a substantially uniform wall thickness along its entire length. Insulative tube <NUM> may require simpler manufacturing, e.g., fewer steps, then insulative tube <NUM> that includes recess <NUM>. <FIG> shows insulative tube <NUM> in an expanded state such that coil electrode <NUM> is partially embedded within the post-expansion insulative tube <NUM>.

<FIG> are cross-sectional diagrams illustrating a pre-expansion state and a post-expansion state, respectively, of a region of the other example coil electrode assembly similar to region B of the example coil electrode assembly of <FIG>. A second end portion <NUM> of <FIG> is similar to second end portion <NUM> of <FIG>, except for the differences described herein. For example, second end portion <NUM> includes insulative tube <NUM>, coil electrode <NUM>, second transition ring <NUM>, a coil conductor <NUM>, and a lead body <NUM>. Conductor <NUM> is surrounded by a first insulator layer <NUM> and a second insulator layer <NUM>.

In some examples, second transition ring <NUM> differs from second transition ring <NUM> of <FIG>. For example, second transition ring <NUM> lacks a second shoulder. Further, grooves <NUM> can vary in size along a longitudinal length of second transition ring <NUM>. For examples, grooves <NUM> on one portion of second transition ring <NUM> can be sized to promote an adhesive connection between second transition ring <NUM> and lead body <NUM>. On a second, different portion of second transition ring <NUM> grooves <NUM> can be sized to provide connection between first transition ring <NUM> and coil conductor <NUM>.

In a pre-expanded state, an inner diameter of an insulative tube may be substantially constant from the tube distal end to the tube proximal end, e.g., as illustrated with respect to insulative tube <NUM> in <FIG> and <FIG>. In the expanded state, the inner diameter of the insulative tube may increase, e.g., at longitudinal positions where the tube is not constrained by the transition rings and expands into the electrode coil, as illustrated with respect to insulative tube <NUM> in <FIG> and <FIG>. In some examples, in the expanded state, the inner diameter of the insulative tube at a center of the insulative tube is greater than the inner diameter of the insulative tube at the tube distal end and the tube proximal end.

<FIG> is a flow diagram of an example technique for manufacturing a coil electrode assembly <NUM> to be attached to an implantable medical lead. The technique of <FIG> will be described with concurrent reference to coil electrode assembly <NUM> (<FIG>) having a first end <NUM> (<FIG>) and a second end <NUM> (<FIG>), although a person having ordinary skill in the art will understand that the technique may be performed in reference to an electrode assembly having a first end <NUM> (<FIG>) and a second end <NUM> (<FIG>), another electrode assembly, another implantable medical lead, or any other medical device.

Method <NUM> of <FIG> includes attaching insulative tube <NUM> to second transition ring <NUM> (<NUM>). Insulative tube <NUM>, with second transition ring <NUM> attached, is inserted within coil lumen <NUM> defined by windings <NUM> of coil electrode <NUM> (<NUM>). Insulative tube <NUM> is attached to first transition ring <NUM> (<NUM>). In some examples, insulative tube <NUM> is attached to first and second transition rings <NUM> and <NUM> with adhesive <NUM>. Adhesive <NUM> can be applied along distal portion <NUM> and proximal portion <NUM> of the exterior surface of insulative tube <NUM>. Adhesive <NUM> can also be applied to an exterior surface of insulative tube <NUM> before or after placement inside coil lumen <NUM>. In some examples, instead of applying adhesive <NUM> to insulative tube <NUM>, adhesive <NUM> can be applied to an internal surface of first and second transition rings <NUM> and <NUM>.

In some examples, the order of steps <NUM>, <NUM>, and <NUM> can be rearranged without impacting the finished product (e.g., step <NUM> then steps <NUM> and <NUM>). Steps <NUM>, <NUM>, and <NUM> may need to be completed before the steps welding and applying heat. For example, insulative tube <NUM> can be inserted into coil lumen <NUM> before attaching either first or second transition <NUM> and <NUM>, e.g., switching steps <NUM> and <NUM>. In some examples, steps <NUM> and <NUM> may also be switched.

Once insulative tube <NUM> is within coil lumen <NUM> defined by coil electrode <NUM> and first and second transition rings <NUM> and <NUM> are attached to insulative tube <NUM>, coil electrode <NUM> is welded to first and second transition rings <NUM> and <NUM> (<NUM>). Insulative tube <NUM> can then be transitioned to the expanded state to partially embed coil electrode <NUM> within insulative tube <NUM> (<NUM>). Insulative tube <NUM> can be transitioned to the expanded state by application of heat and/or air (or other gas or liquid) pressure. The parameters of heat and/or air pressure may be selected to ensure insulative tube <NUM> does not rupture or overflow, or is otherwise damaged. Applying pressure may include applying air or another fluid or gas to an inside of insulative tube <NUM> over a range of between approximately <NUM> seconds to approximately <NUM> seconds at less than approximately <NUM> Pascal (Pa) of internal pressure. Applying heat may include applying heat to insulative tube <NUM>, e.g., the inside of the tube, over a range of between approximately <NUM> seconds to approximately <NUM> seconds at about <NUM> degrees Celsius (°C). In one example, heat is applied to insulative tube <NUM> slowly for approximately <NUM> to <NUM> seconds at approximately <NUM>, and internal pressure within insulative tube <NUM> is applied at a low pressure, such as less than <NUM> Pa. In some examples, the heat and pressure are applied together and, more particularly, applied in the form of heated gas, e.g., air, delivered at a desired pressure, e.g., via a nozzle.

In some examples, based on predicted applications of coil electrode assembly <NUM> and material properties, different temperatures and/or pressures can be used to modify the expansion of insulative tube <NUM>. After expanding insulative tube <NUM>, an outer diameter of insulative tube <NUM> is less than an outer diameter of coil electrode <NUM>. The temperature of insulative tube <NUM> is allowed to cool down after expansion. First and second transition rings <NUM> and <NUM> can be attached to a high-voltage conductor that extends within insulative tube <NUM>. After coil electrode assembly <NUM> is complete, coil electrode assembly <NUM> can be attached to a lead, e.g., an implantable medical lead (<NUM>).

Claim 1:
A coil electrode assembly (<NUM>) for implantable medical leads, the assembly comprising:
a coil electrode (<NUM>) extending from an electrode proximal end (<NUM>) to an electrode distal end (<NUM>), the coil electrode defining an electrode lumen (<NUM>) from the electrode proximal end to the electrode distal end, and the coil electrode comprising a plurality of windings (<NUM>);
an insulative tube (<NUM>) extending from a tube proximal end (<NUM>) to a tube distal end (<NUM>), the insulative tube extending within the electrode lumen such that the coil electrode extends along an outer surface (<NUM>) of the insulative tube, the coil electrode partially embedded within the insulative tube when the insulative tube is in an expanded state to maintain a spacing between the windings;
a first transition ring (<NUM>) at the electrode distal end and the tube distal end,
wherein a portion of the first transition ring is within the electrode lumen, wherein the first transition ring defines a first transition ring lumen (<NUM>), and wherein a distal portion (<NUM>) of the insulative tube including the tube distal end is within the first transition ring lumen; and
a second transition ring (<NUM>) at the electrode proximal end and the tube proximal end, wherein a portion of the second transition ring is within the electrode lumen, wherein the second transition ring defines a second transition ring lumen (<NUM>), and wherein a proximal portion (<NUM>) of the insulative tube including the tube proximal end is within the second transition ring lumen.