Methods of manufacturing implantable medical devices with one or more undermolded features are disclosed. An example method includes injection molding an annular-shaped member onto an inner surface of a sacrificial mold insert, and then undermolding an elongate medical device body directly to the member. The member is directly coupled to the device body without the use of adhesives or bonding agents, thus eliminating the presence of gaps or surface irregularities that can affect device performance.

TECHNICAL FIELD

The present disclosure relates generally to methods of manufacturing implantable medical devices. More specifically, the present disclosure pertains to methods of manufacturing implantable medical devices with undermolded features such as steroid-eluting drug collars, visual aids, and/or radioscopic traceable members.

BACKGROUND

Various types of medical electrical leads for use in cardiac rhythm management (CRM) and neurostimulation applications are known. In CRM applications, for example, such leads are frequently delivered intravascularly to an implantation location on or within a patient's heart, typically under the aid of fluoroscopy. Once implanted, the lead is coupled to a pulse generator or other implantable device for sensing cardiac electrical activity, delivering therapeutic stimuli, and/or for performing other desired functions within the body. Such leads typically include a distal conductor end with one or more electrodes that contact the heart tissue, and a proximal terminal end that is connected to a pacemaker or defibrillator. The conductor end of the lead can include one or more features such as an active fixation helix or a number of passive tines to facilitate securing the lead to the heart tissue. The terminal end of the lead, in turn, includes one or more electrical contacts that are electrically connected to the electrodes via a number of lead conductors.

An increase in the stimulation threshold required to electrically stimulate the body can result from the interaction of the electrodes with the body tissue at the site of implantation. In CRM applications involving leads implanted in or near the heart, for example, the capture threshold of the lead can increase due to the formation of scar tissue at the location where the electrodes contact the body tissue. Approaches to reducing the capture threshold have included the incorporation of drug-eluting collars or plugs containing a therapeutic drug such as dexamethasone acetate, which reduces inflammation at the site of contact.

The incorporation of drug-eluting collars or plugs into medical electrical leads is typically accomplished via an injection molding process in which the collar or plug is pre-formed as a separate component, and then subsequently bonded to the lead body via an adhesive or glue. In the fabrication of medical electrical leads used in CRM and neurostimulation applications, for example, the drug-eluting collar is typically formed in a mold and then adhesively bonded onto a distal portion of the lead, typically adjacent to an electrode located at the distal end of the lead body. In some cases, variability in the contact surface area at the location of the adhesive can cause the rate at which the drug is eluted into the body tissue to vary. Some drug collar bonding techniques can also result in yield fallout and other manufacturing issues.

SUMMARY

The present disclosure relates to methods of manufacturing implantable medical devices with undermolded features such as steroid-eluting drug collars, visual aids, and/or radioscopic traceable members.

In Example 1, a method of manufacturing an implantable medical device comprises: inserting a mold insert into a molding tool and molding a member onto an interior surface within an interior cavity of the mold insert; inserting an elongate medical device body into an interior lumen of the member; undermolding the elongate medical device body directly to the member; and removing the mold insert from the member.

In Example 2, the method according to Example 1, wherein molding a member onto an interior surface of the mold insert comprises: inserting an elongate rod into the interior cavity of the mold insert; and injection molding an annular-shaped ring onto the interior surface of the mold insert.

In Example 3, the method according to either Example 1 or 2, wherein the mold insert comprises a sacrificial disk.

In Example 4, the method according to Example 3, wherein the sacrificial disk comprises a polymeric or metallic material.

In Example 5, the method according to any of Examples 1-4, wherein undermolding the elongate medical device body directly to the member comprises molding the body onto an interior surface of the member.

In Example 6, the method according to any of Examples 1-5, wherein undermolding the elongate medical device body directly to the member comprises molding the device body onto an interior surface of the member.

In Example 7, the method according to any of Examples 1-6, wherein removing the mold insert from the member comprises cutting the mold insert away from the member.

In Example 8, the method according to any of Examples 1-7, wherein the medical device is an implantable medical electrical lead, and wherein the elongate medical device body is a lead body.

In Example 9, the method according to any of Examples 1-8, wherein the member comprises a drug-eluting collar.

In Example 10, a method of manufacturing an implantable medical electrical lead comprises: inserting a mold insert into a molding tool and molding a collar onto an interior surface within an interior cavity of the mold insert; inserting an elongate lead body into an interior lumen of the collar; undermolding the lead body directly to the collar; and removing the mold insert from the collar.

In Example 11, the method according to Example 10, wherein molding a collar onto an interior surface of the mold insert comprises: inserting an elongate rod into the interior cavity of the mold insert; and injection molding an annular-shaped collar onto the interior surface of the mold insert.

In Example 12, the method according to either Example 10 or 11, wherein the mold insert comprises a sacrificial disk.

In Example 13, the method according to Example 12, wherein the sacrificial disk comprises a polymeric or metallic material.

In Example 14, the method according to any of Examples 10-13, wherein undermolding the lead body directly to the collar comprises injection molding the lead body onto an interior surface of the collar.

In Example 15, the method according to any of Examples 10-14, wherein undermolding the lead body directly to the collar comprises molding the lead body onto an interior surface of the collar.

In Example 16, the method according to any of Examples 10-15, wherein removing the mold insert from the collar comprises cutting the mold insert away from the collar.

In Example 17, a medical electrical lead comprises: a lead body having a proximal section, a distal section, and an outer periphery; and at least one annular-shaped collar undermolded directly to the outer periphery of the lead body.

In Example 18, the medical electrical lead according to Example 17, wherein the collar is directly coupled to the outer periphery of the lead body via an adhesiveless bond.

In Example 19, the medical electrical lead according to Example 17, wherein the lead body is molded onto an interior surface of the collar.

In Example 20, the medical electrical lead according to any of Examples 17-19, wherein the at least one annular-shaped collar comprises a plurality of collars undermolded to the outer periphery of the lead body.

DETAILED DESCRIPTION

FIG. 1is a perspective view showing an implantable medical device10including an undermolded member. The device10, illustratively an implantable cardiac lead configured for providing electrical stimulus therapy to and/or for sensing electrical activity within a patient's heart, comprises a lead body12having a proximal section14and a distal section16. The proximal section14of the lead10includes a terminal pin18and a number of terminal ring contacts22,24,26that connect to a pacemaker, implantable cardioverter defibrillator (ICD), cardiac resynchronization therapy (CRT) device, or other pulse generator. The distal section16of the lead10includes a number of electrodes28,30,32,34each coupled to a corresponding lead conductor within the interior of the lead body12. In the embodiment ofFIG. 1, for example, the lead10includes three ring electrodes28,30,32each electrically connected to a corresponding terminal contact22,24,26on the lead10. A distal tip electrode34on the implantable lead10is electrically coupled to the terminal pin18, and is located at or near the distal end36of the lead10. A number of fixation tines38can be used to secure the distal end36of the lead10to cardiac tissue during the implantation process.

During operation, the pulse generator supplies electrical pulses to the electrodes28,30,32,34for pacing the heart and/or for sensing cardiac electrical activity. A number of members40,42,44coupled to the lead body12are configured to delivery therapy to the body tissue, to serve as a visual aid or radioscopically traceable member for visualizing and/or locating the lead10within the body, and/or for performing other desired functions within the body. In some embodiments, for example, the members40,42,44each comprise a drug-eluting collar that delivers a therapeutic drug (e.g., dexamethasone acetate) into the body tissue adjacent to the ring electrodes28,30,32. In the embodiment ofFIG. 1, for example, each member40,42,44is disposed on the lead body12adjacent to an associated electrode28,30,32, and is configured to deliver a drug to the body over a period of time in order to reduce inflammation at the site of contact between the electrodes28,30,32and the surrounding tissue. The members40,42,44can be configured to deliver other drugs and/or provide other types of therapy in addition to, or in lieu of, steroids used for the purpose of reducing insertion site inflammation. Other types of members can include, for example, ablation electrodes for providing ablation therapy to the body and radiopaque markers for fluoroscopically imaging the lead within the body.

FIG. 2is a cross-sectional view of the lead10along line2-2inFIG. 1showing one of the members42coupled to the lead body12. As can be further seen inFIG. 2, the lead body12comprises an elongate, tubular shaped body including one or more interior lumens44,46for housing several lead conductors50a,50b,50cused for supplying electrical currents to the ring electrodes28,30,32and the distal tip electrode34. The lead body12may also contain other lead components such as steering wires, fluid lumens, and/or a drive mechanism for engaging a fixation helix.

Each member42comprises an annular-shaped collar disposed about an outer periphery52of the lead body12. The member42is spaced longitudinally apart from the ring electrode30via a longitudinal distance D1. In some embodiments, the distance D1may be selected so as to permit drugs to be delivered to the contact site where the ring electrode30contacts the surrounding tissue. In some embodiments, for example, the member42is spaced longitudinally apart from the ring electrode30by a distance D1of between about 0.1 millimeters to about 10 millimeters, and more specifically, about 0.5 millimeters to about 0.7 millimeters. The length D2of the member42can vary from about 0.5 millimeters to about 10 millimeters, and more specifically, about 0.8 millimeters to about 2.5 millimeters. The thickness D3of the member42, in turn, can vary from about 0.1 millimeters to about 1.0 millimeters, and more specifically, about 0.2 millimeters to about 0.3 millimeters. Other lengths D1, D2and a thickness D3greater or lesser than these ranges are also possible depending on the configuration of the lead10.

The member42is coupled directly to the lead body12via an undermolding process such that no gaps or spaces exist at the interface54between the member42and the lead body12. The other members40,44can also have a similar configuration so as to eliminate the presence of gaps or surface irregularities at other locations along the length of the lead body12. As used herein, the term “directly coupled” indicates that the member42is in contact with the lead body12without any interstitial layers or members disposed in between the two components12,42. In some embodiments, for example, the interface54between the member42and the lead body12does not contain an adhesive or bonding agent, as is typically used in securing many conventional drug collars to the lead. As a result, the interface54is substantially devoid of any gaps or surface irregularities that can result from adhesive bonding. Several example steps that can be used for manufacturing an implantable medical device such as the lead10ofFIGS. 1-2are further described herein with respect to FIGS.3and5A-5D.

In some embodiments, the material used in fabricating the lead body12and/or members40,42,44can be selected to facilitate thermal bonding of the members40,42,44directly onto the lead body12during an undermolding process. In some embodiments, for example, the members40,42,44are each formed from a base polymeric material that, when sufficiently heated onto the outer periphery52of the lead body12at a temperature below the melting point of the material, causes the lead body material to thermally bond with the member40,42,44material at the interface54. An example polymeric material that can be used for this purpose is silicone, which can be thermally bonded to lead body materials such as silicone or polyether ether ketone (PEEK).

FIG. 3is a flow diagram showing an example method56of manufacturing an implantable medical device.FIG. 3may represent, for example, several example manufacturing steps that can be used for molding one or more drug-eluting collars onto a medical electrical lead such as the lead10ofFIG. 1.

The method56may begin generally at block58in which a sacrificial mold insert is inserted into a molding tool such as a multi-cavity injection mold. In certain embodiments, for example, the sacrificial mold insert comprises a disk-shaped member that is used for initially forming an annular-shaped member independent of the lead body. During later steps, the mold insert also serves to facilitate undermolding of the lead body directly to an interior lumen of the member. An example sacrificial mold insert that can be used for this purpose is further described herein with respect toFIG. 4.

Once the mold insert is placed within the molding tool, an elongate member such as an elongate rod (e.g., a core pin) is then inserted into an interior cavity of the mold insert (block60). The outer extent of the rod is suitably sized so that an annular-shaped space is formed within the molding tool in between the outer periphery of the elongate member and an interior surface formed by an interior cavity of the mold insert. With the elongate member disposed within the mold insert, a plastic resin containing the steroid is then injection molded into the space formed by the interior cavity of the mold insert (block62). The mold insert along with the annular-shaped member are then removed from the molding tool.

Upon injection molding the member to the inner surface of the mold insert, an elongate medical device body is then inserted into an interior lumen of the annular-shaped member while the member is still attached to the mold insert (block64). The medical device body and mold insert are then subjected to an undermolding process in order to undermold the medical device body directly to the annular-shaped member (block66). During this process, the second molding tool is maintained at a suitable temperature to cause the material of the annular-shaped member to thermally bond to the material forming the medical device body without causing the two components to melt, thus forming an interface layer between the two components that is devoid of any gaps or surface irregularities.

Once the medical device body is undermolded to the annular-shaped member, the mold insert is then removed from about the member (block68). In certain embodiments, for example, removal of the member from the mold insert can be accomplished by cutting the mold insert and then peeling the insert away from the member. In other embodiments, a press can be used to force the member out from within the interior cavity of the mold insert.

Additional processing steps can then be performed to fabricate the remaining portion of the device, as is well known in the art. If desired, one or more additional members (e.g., drug collars) can also be coupled to other locations along the medical device body by repeating the process of injection molding an annular-shaped member within an interior cavity of a mold insert, and then undermolding the medical device body directly to the member.

FIG. 4is a perspective view showing a sacrificial mold insert72that can be used in conjunction with the method56ofFIG. 3. As shown inFIG. 4, the mold insert72comprises a disk-shaped insert body74having a first side76, a second side78, and a peripheral edge80. A number of notches82,84projecting inwardly from the peripheral edge80are used for aligning the mold insert within the molding tool, and to facilitate later removal of the mold insert72from the member during later processing steps.

An interior cavity86extending through the mold insert72from the first side76to the second side78defines an inner surface88that is sized to form the outer periphery of the member, once molded therein. The inner diameter of the interior cavity86will typically vary depending on the size of the medical device body. In medical electrical leads for use in cardiac and neurostimulation applications, for example, the inner diameter of the interior cavity86may vary in size from between about 1.0 millimeters to about 3.0 millimeters. Other sizes greater or smaller than these values are also contemplated. Although the mold insert72shown inFIG. 4comprises a circular-shaped interior cavity86, other shaped cavities are also possible in other embodiments. For example, in some embodiments the interior cavity86can have an oval, rectangular, or other non-symmetric cross-sectional shape.

The thickness of the mold insert72between the first and second sides76,78defines the length of the member (as indicated by dimension D2inFIG. 2). For medical electrical leads, a suitable thickness of the mold insert72is between about 0.5 millimeters to about 10 millimeters, and more specifically, about 0.8 millimeters to about 2.5 millimeters. The thickness of the mold insert72can vary, however, depending on the specific length D2of the member to be fabricated.

In some embodiments, the mold insert72comprises a polymeric material having a melting point that is greater than that of the materials forming the lead body12and member42. In one embodiment, for example, the mold insert comprises PEEK. In other embodiments, the mold insert is formed from a metal or a metal-polymer composite having a melting point greater than that of the materials forming the lead body12and member42.

FIGS. 5A-5Dare several views showing an example implementation of the method56ofFIG. 3for use in manufacturing a medical electrical lead10with one or more members.

In a first view shown inFIG. 5A, the sacrificial mold insert72is first inserted into the cavity90of a multi-cavity molding tool92. In some embodiments, the molding tool92comprises a number of mold plates94,96and one or more nozzles (not shown) for injecting plastic resin into the interior cavity86of the mold insert72once the insert72is placed into the mold cavity90.

FIG. 5Bis a view showing the insertion of an elongate member98(e.g., an elongate rod) into the interior cavity86of the mold insert72. With the elongate member98inserted into the interior cavity86, and as further shown inFIG. 5C, plastic resin is then injected into the mold92and into the space100located between the inner surface88of the mold insert72and the outer periphery102of the elongate member98. This annular-shaped space100, when injected with the plastic resin, corresponds in size and shape to the final member later assembled to the lead body.

FIG. 5Cis a view showing the formation of an annular-shaped member (e.g., member42ofFIG. 2) after the elongate member98has been removed from within the mold insert72, and once the mold insert72and accompanying member42have been removed from the molding tool92.

FIG. 5Dis a view showing the mold insert72and member42inserted into the interior cavity106of another molding tool108including a number of mold plates110,112. As can be seen inFIG. 5D, the lead body12is inserted into the interior lumen of the member42, and the mold plates110,112are brought together while applying heat, causing the lead body12to undermold to the inner surface114of the member42. During this step, the lead body12and member42are both maintained at a temperature sufficient to cause the member42to thermally bond to the lead body12, but without melting. In certain embodiments, for example, the molding tool108is maintained at a temperature of about 130° C. for a period of about 60 seconds to about 300 seconds when a polymeric material such as silicone is used in forming the lead body12and member42. The temperature and duration will typically vary depending on the material or materials used in forming the lead body12and/or the member42.

FIG. 6is a perspective view showing a portion of the lead body12once undermolded to the member42inFIG. 5D.FIG. 7, in turn, is a cross-sectional view showing the lead body12and member42across line7-7inFIG. 6. As can be seen inFIG. 7, the member42is directly coupled about a circumferential interface120to the outer periphery52of the lead body12without the use of any adhesives or bonding agents. As a result, the outer surface52of the lead body12at the location of the member42is substantially devoid of any gaps or surface irregularities that can affect the desired performance characteristics of the lead10.