Method for manufacturing a medical electrical lead connector ring

A method of manufacturing a medical electrical device is presented. An inner diameter and an outer diameter of a connector ring is machined to form a first and a second flange extending from the inner diameter. An electric discharge machining wire burner is used to form a conductor channel in the inner diameter of the connector ring. A conductor is positioned within the conductor channel. A first distal end of the first flange is coupled to a second distal end of the second flange.

TECHNICAL FIELD

The invention relates to implantable medical devices, and, more particularly, to configurations of implantable medical lead connectors.

BACKGROUND

In the medical field, implantable medical leads are used with a wide variety of therapeutic or monitoring devices. For example, implantable leads are commonly used to form part of implantable cardiac pacemaker systems that provide therapeutic stimulation to the heart by sensing electrical activity of the heart and delivering pacing, cardioversion, or defibrillation pulses via electrodes disposed on the leads, typically near the distal ends of the leads. Electrodes or sensors carried by the lead are generally coupled to a conductor extending to a proximal connector assembly for facilitating electrical coupling of the electrodes or sensors to a therapy delivery or monitoring device. A number of challenges exist with respect to such medical leads. As implantable medical device technology continues to be downsized and more advanced therapeutic techniques are developed, new lead arrangements are required. As such, new configurations for electrically coupling an electrode or other sensor carried by a lead to an associated monitoring or therapy delivery device are needed. In particular, electrical coupling configurations are needed that are reliable and can be manufactured in a cost-effective manner.

DETAILED DESCRIPTION

The following detailed description provides a practical illustration for implementing various embodiments of the invention and is not intended to limit the scope, applicability, or configuration of the invention in any way.

FIG. 1is a plan view of a medical electrical device according to an embodiment of the present invention. As illustrated inFIG. 1, a medical electrical device according to an embodiment of the present invention includes a lead10embodied as a cardiac pacing lead having electrodes that can be used for sensing cardiac electrogram signals and delivering electrical stimulation pulses to myocardial tissue for pacing, cardioverting or defibrillating the heart. Lead10includes an elongated lead body12having a proximal end14and a distal end16. Lead10is provided with a distal tip electrode18located at or near distal end16of lead body12, a ring electrode20located proximal to tip electrode18, and two coil electrodes22and24. Distal tip electrode18and ring electrode20are commonly used for pacing and sensing the heart. Coil electrodes22and24are commonly used for delivering high-voltage cardioversion and defibrillation pulses to the heart. While a particular electrode arrangement is shown inFIG. 1, it is recognized that various embodiments of the invention may include a variety of lead types, including neuromuscular stimulation leads, monitoring leads, or any other medical electrical leads. Such leads may be provided with a variety of electrode arrangements, which may include one or more electrodes included on lead body12. Furthermore, different types of electrodes, such as an active fixation electrode, or any other electrode or sensor known for use with implantable medical leads may be included on lead10.

Lead body12includes at least one lumen13through which insulated conductors15extend between each of the respective electrodes18,20,22, and24and a proximal connector assembly28located at proximal body end14. Connector assembly28is adapted for connection to a connector bore included in an associated medical device, such as a pacemaker or neurostimulator device. Such connector assembly configurations for mating with a medical device connector bore are known in the art.

Connector assembly28includes a pin connector30and three ring connectors32,34and36. Each of pin connector30and ring connectors32,34and36are coupled to a respective conductor extending to one of tip electrode18, ring electrode20and coil electrodes22and24such that each electrode is electrically coupled to one of pin connector30or ring connectors32,34and36but remain electrically isolated from each other. Upon proper insertion of connector assembly28into an associated medical device connector bore, electrodes18,20,22, and24become electrically coupled to the medical device circuitry via the respective pin connector30and ring connectors32,34, and36and associated insulated conductors extending between the connectors and the electrodes.

Connector assembly28includes an insulative sheath35mounted around connector pin30and terminating prior to a proximal end31of connector pin30. Connector rings32,34, and36are mounted on insulative sheath35and are thereby insulated from connector pin30. Connector rings32,34and36are insulated from each other by intervening insulative segments38, which may include sealing rings39for forming fluid-tight seals with a corresponding connector bore between each of connector rings32,34and36. It is recognized that connector assembly28may be embodied in a variety of ways, including varying configurations of insulative members for supporting and insulating the required number of connectors needed to electrically couple electrodes or sensors carried by the lead to an associated medical device. Examples of arrangements of a connector pin and one or more connector rings on a connector assembly are generally disclosed in U.S. Pat. No. 4,951,687 issued to Ufford et al., and U.S. Pat. No. 5,007,435 issued to Doan et al.

FIG. 2is an end view of a connector ring according to an embodiment of the present invention included in the medical electrical device ofFIG. 1. Connector ring32is a generally cylindrical member having an outer diameter40and inner diameter42. Connector ring32is formed with a conductor channel44extending longitudinally along the inner diameter42of connector ring32. Conductor channel44is provided for receiving an uninsulated proximal portion of a conductor. The term “channel” as used herein refers to a passage having one open side, such as a generally “U”-shaped or “C”-shaped passage, in contrast to a fully enclosed or annular passage, such as a generally “O”-shaped or “D”-shaped passage. InFIG. 2, conductor channel is shown as a generally “U”-shaped passage formed by two flanges46and48adapted to be crimped closed around a conductor extending through conductor channel lumen50. Thus the conductor channel44is provided initially as an open passage having open side49formed by flanges46and48. The closed side52of channel44can be formed as a generally curved surface as shown inFIG. 2. Conductor channel lumen50is sized to approximately match the outer diameter of a conductor. The proximal portion of the conductor can be positioned in conductor channel44by either threading the conductor into conductor channel lumen50or by threading the conductor through lumen82of connector ring32then dropping the conductor down into conductor channel44through open side49.

Connector ring32is fabricated from a conductive material, such as MP35N, titanium, or stainless steel. Connector ring32is formed during a machining process that includes machining the inner diameter42from round stock. In one method, a pilot hole is machined so that an electrical discharge machining wire burner can be threaded through the round stock. The wire burner is then used to form inner diameter42and conductor channel44in one machining process. The use of electric discharge machining (EDM) wire burner for machining conductor channel44reduces the number of machining steps required to machine connector rings as compared to past practice, which used EDM hole popper methods. The EDM wire burner step for forming conductor channel44can be performed on multiple, stacked connector ring piece parts to further reduce manufacturing time.

FIG. 3is a side, cut-away view of a connector ring according to an embodiment of the present invention. Conductor channel44is shown extending longitudinally along substantially the entire length of connector ring32. In alternative embodiments, conductor channel44may extend along the inner diameter42of connector ring32for any portion of the length of connector ring32. Connector ring32may be provided with a contoured outer diameter41to accommodate outer insulation sheaths used in assembling a lead connector.

FIG. 4is a side cut-away view of a connector ring according to an embodiment of the present invention. As illustrated inFIG. 4, according to an embodiment of the present invention, flange46of conductor channel44may be formed to include chamfered ends54and56. Similarly, flange48, not seen in the cut away view ofFIG. 4, would also be formed to include chamfered ends similar to ends54and56of flange46. In a manufacturing process that involves threading the proximal end of a conductor into conductor channel lumen50, the threading step may be more readily performed when ends54and56are chamfered since the end openings51and53to conductor channel lumen50will have a larger cross-sectional area than when distal ends of the flanges extend straight up as shown inFIG. 3.

A conductor may be threaded into lumen50through either conductor channel end opening51or53. As shown inFIGS. 3 and 4, connector ring32provided as a piece part with identically machined ends does not have a designated proximal or distal end. InFIG. 4, flange46is provided with chamfered ends54and56at both end openings51and53. During an assembly process, which may be manual or automated, the connector ring32can be oriented in either direction when a conductor is threaded into either end opening51or53of conductor channel44. In particular, automated assembly of a conductor onto connector ring32is facilitated by providing connector ring32with identically machined ends51and53. It is recognized, however, that in other embodiments flanges46and48can be provided with chamfered ends at only one end opening,51or53. During assembly, the connector ring would need to be properly oriented for a conductor to be threaded into the chamfered end51or53.

FIG. 5is an end view of a connector ring according to an embodiment of the present invention. As illustrated inFIG. 5, according to an embodiment of the present invention, a connector ring80is formed as described above, with a conductor60positioned to extend through lumen50of conductor channel44. Conductor60is shown as a cable conductor, however, connector ring sub-assembly80may be formed using other conductor types, such as a wire, stranded, bundled, or coiled conductor. A crimping tool70is pressed down over conductor channel44to advance flanges46and48together such that a distal end72of flange46is positioned adjacent to or engaged against a distal end74of flange48to close formerly open side49(shown inFIG. 2). Conductor60becomes enclosed within conductor channel lumen50such that conductor60and connector ring40are electrically and mechanically coupled.

Crimping tool70is an elongated tool that can be inserted through connector ring lumen82. Crimping tool70is provided with a crimping notch76that extends along crimping tool70for a length corresponding to the length of conductor channel44. Crimping notch76is sized such that when crimping tool70is pressed down over conductor channel44, flanges46and48will be crimped together within notch76along the entire length of conductor channel44. A mechanical and electrical crimp joint between conductor ring32and conductor60is thereby formed, extending approximately the entire length of conductor channel44, which has been shown to extend approximately the entire length of connector ring32. It is expected that by providing a crimp joint extending the entire length of connector ring32, a reliable mechanical and electrical coupling between connector ring32and conductor60can be formed which is capable of withstanding a higher tensile force than a crimp joint extending along only a portion of connector ring32. However, depending on the application, a crimp joint that extends only a portion of the length of connector ring32may also provide adequate tensile strength for acceptable lead reliability.

After crimping conductor channel44around conductor60, inspection of the crimp joint is performed. The crimp joint is readily verified by inspecting if distal ends72and74meet along the entire length of conductor channel44.

FIG. 6is a side view of the connector ring ofFIG. 5. Crimping tool70may be inserted into lumen82of connector ring32from either end84or86for crimping conductor channel44around conductor60. The proximal portion of conductor60that extends through lumen50of conductor channel44is stripped of insulation64. Connector ring80can be utilized in manufacturing a medical electrical lead.

FIG. 7Ais an end view of a connector ring according to an embodiment of the present invention. As illustrated inFIG. 7A, according to an embodiment of the present invention, a connector ring100is provided with a conductor channel102having a generally “C”-shaped cross-section with open side106, and extending along connector ring inner surface101. A flange104forms a conductor channel lumen108through which a conductor110is threaded. As shown inFIG. 7B, an end105of flange104is advanced toward inner surface101to close open side106, thereby enclosing conductor110within lumen108and forming a mechanical and electrical coupling between connector ring100and conductor110.

FIG. 8is an end view of a connector ring of a medical electrical device according to an embodiment of the present invention. Connector ring32of the embodiment ofFIG. 8is shown having a generally “U”-shaped conductor channel44adapted for crimping around a conductor extending through conductor channel lumen50. In this embodiment, flanges46and48are provided with beveled distal ends120and122, respectively. The distal ends120and122may be provided as rounded, beveled, canted or otherwise modified tips to promote complete and stable closure of open side49of conductor channel44after crimping. In particular, when connector ring32is fabricated from Titanium, beveled distal ends120and122promote a more reliable crimp joint.

FIG. 9is a flow chart of a method for manufacturing a medical electrical device according to an embodiment of the present invention. At step202, fabrication of a connector ring is initiated, including machining the inner diameter and outer diameter contours of the connector ring from solid, round stock of a selected, conductive metal material. At step204, partially machined connector rings can be stacked for machining the conductor channel into multiple connector rings simultaneously at subsequent step206. At step206, the conductor channel is machined on the inner diameter of the connector ring using an EDM wire burner method.

After completion of connector ring fabrication, a connector ring sub-assembly is assembled. At step208, a proximal, uninsulated portion of a conductor is inserted through the lumen of the conductor channel. This insertion step may be performed by threading the conductor through an open end of the conductor channel lumen or by threading the conductor through an open end of the connector ring lumen then dropping the conductor down into the conductor channel through the open side of the conductor channel.

After inserting the conductor in the conductor channel, a crimping tool is used to crimp the conductor channel to close the open side of the conductor channel at step210. The resulting crimp joint formed between the conductor and the conductor channel provides mechanical and electrical coupling between the connector ring and the conductor. The connector ring sub-assembly is then ready to use in assembling a lead connector assembly at step212. The lead connector assembly can then be used in assembling a medical electrical lead at step214.

Thus, a connector ring and associated methods for assembling a connector ring sub-assembly, a connector assembly and a medical electrical lead including the connector ring, have been presented in the foregoing description with reference to specific embodiments. It is appreciated that various modifications to the referenced embodiments may be made without departing from the scope of the invention as set forth in the following claims.