Ring connector for implantable medical devices

An electrical contact for use in the header assembly of an implantable tissue stimulator includes a metal housing having a base and a sidewall where the opening in the base is adapted to receive the terminal of a medical lead therethrough. An electrical contact support member is welded to the edge of the sidewall and affixed to the support member are a plurality of spring members that are tangent to an imaginary circle whose diameter is slightly less than the outside diameter of the lead terminal contact rings. When the contacts are axially aligned in the device header, the terminal of an electrical lead may be longitudinally inserted into the header to establish electrical contact with device feedthrough wires that are joined to the electrical contacts in the header.

BACKGROUND OF THE INVENTION

I. Field of the Invention

This invention relates generally to implantable electronic tissue stimulating apparatus of the type including a pulse generator that is coupled through a medical lead to target tissue, and more particularly to the design of electrical contacts used in a header of such a pulse generator to mechanically and electrically couple the pulse generator's input/output pins to a proximal terminal of a medical lead.

II. Discussion of the Prior Art

Over the past 30 years great strides have been made in increasing the functional performance of and decreasing the physical size of implantable medical devices, such as those designed for cardiac rhythm management and neural stimulation. Generally speaking, current state-of-the-art implantable medical tissue stimulating devices incorporate a battery power supply and a microprocessor-based controller that is designed to control a pulse generator, causing it to issue pulses at times determined by the microprocessor-based controller. The pulses are conveyed to target tissue on or in the heart by means of one or more medical leads having sensing/stimulating electrodes at a distal end and the electrodes are connected by lead conductors to electrical contacts on a connector pin located at the proximal end of the lead. The lead connector connects the lead to the pulse generator.

While a variety of lead connectors have been devised, a major improvement in lead connectors has been the low profile, in-line bipolar design. An in-line connector places both electrical terminals on a single lead pin, with an insulating barrier separating the anode contact from the cathode contact. To facilitate compatibility between pulse generators and leads of differing manufacturers, standards have been developed. More particularly, a collaborative effort between IEC and International Standards Organization has defined the parameters of a low-profile connector referred to as IS-1 for unipolar and bipolar leads and DF-1 for defibrillator leads. Additionally, there is ongoing work to develop AAMI and potentially ISO standards for connectors for tripolar and quadrapolar leads.

As those skilled in the art appreciate, the lead connector must be mechanically and electrically secured to the implantable device in a way that remains secure following implantation, but which can be readily detached if and when it becomes necessary to install a new pulse generator. The Persuitti et al. U.S. Pat. No. 6,044,302 describes a connector port for an implantable pulse generator that can accommodate a plurality of in-line lead terminal pin having multiple contacts. In the '302 patent, a lead port has one or more connector blocks each including a set screw to lock the lead connector in contact with the connector block. The connector blocks are, in turn, connected to a feed-through wire. A single elastomeric seal is provided within the port such that when the connector pin is inserted therethrough, it precludes ingress of body fluids into the bore in the header. It is also known in the art to provide sealing rings on the lead terminal connector itself for creating a fluid impervious seal upon insertion of the lead's terminal into a connector port. In this regard, reference is made to the Hawkins et al. U.S. Pat. No. 6,029,089.

Copending application Ser. No. 10/222,151 filed on Aug. 16, 2002, and entitled “Connector Port Construction Technique for Implantable Medical Device”, which application is assigned to the assignee of the present application, there is described a connector port for an implantable medical device that is capable of accommodating multiple feedthrough wires and lead connector contacts and that is small in size, easy to assembly and which exhibits a low insertion force. The lead connector contacts described in the aforereferenced application (referred to herein as a toroidal spring design) comprise a metal housing having a circular bore formed through the thickness dimension thereof The wall defining the bore includes an annular recess for containing a canted-coil spring that is formed as a ring. A number of such electrical contacts are concentrically aligned in a molded plastic header with elastomeric seals disposed between each such contact. A feedthrough wire on the pulse generator is then welded to the housing containing the canted-coil spring. Upon insertion of a lead terminal, the spring is spread to receive a terminal contact therein and the coil spring engages the terminal contact at a multiplicity of points around its circumference.

The use of the currently available spring design is not optimal. The toroidal spring “floats” within the bore of the housing comprising the contact and makes connection between the terminal and spring, and in turn, between the spring and contact housing only through physical interference. This can lead to an unnecessarily high resistance connection between the connector contact member and the contacts on the lead's terminal pin. Other spring designs for this application are too large to fit within the required space or also float within their housing.

It is accordingly a principal object of the present invention to provide a small, improved, cost effective connector contact for use in the header of an implantable pulse generator and which provides a more positive connection between a feedthrough wire of the pulse generator and a lead terminal.

SUMMARY OF THE INVENTION

The present invention provides an electrical connector contact for use in the header assembly of an implantable cardiac rhythm management device for mating with a terminal pin of a tissue stimulating/sensing lead. The contact connector comprises a metal housing that has a base and a sidewall. A central opening in the base is sized to receive a terminal pin of a medical lead therethrough with a predetermined non-contact clearance. A plurality of spring members are attached to an electrical contact support member where the support member has an outside shape permitting placement on an exposed edge of the sidewall of the housing. The spring members are attached to the contact support member such that they project inwardly of the inside opening of the electrical contact support member to provide an interference fit with a lead terminal pin that is inserted through the opening in the base of the housing and through the electrical contact support member.

In one embodiment, the spring members are generally shaped to provide an interference fit with minimal drag, allowing compression thereof when the terminal pin of the tissue stimulating lead is inserted. In an alternative embodiment, the electrical contacts are bent cylindrical bars having one end welded to the contact support member and a straight section oriented tangent to a circle that is centered with respect to the opening in the base and of a lesser diameter than the opening in the base.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring toFIG. 1, there is shown a ring connector for use in the header of an implantable tissue stimulator, such as a cardiac pacemaker or an automatic implantable cardiac defibrillator. The ring connector may be used in the manner fully described in the aforereferenced co-pending application Ser. No. 10/222,151, which is hereby incorporated by reference. It is seen to comprise a housing member12made of a suitable metal. It had a base14and a sidewall16, where the base14includes an opening18that is of a predetermined size slightly larger than the diameter of a lead terminal that is to be inserted therethrough. As a result, there is a predetermined non-contact clearance between the opening and the lead terminal. Resting atop the exposed edge20of the metal contact housing12is a washer-like plate22that is welded to the exposed edge20of the housing. The central opening24of the washer22is generally sized such that a lead terminal will also have a non-contact clearance with the washer22.

As seen in the cross-sectional view ofFIG. 2, a spring contact member26is welded to the washer22. Referring momentarily toFIG. 4, the spring contact member26is made of a suitable metal, such as MP35N. In a preferred form, the contact members are formed with the ring28in a stamping and bending operation.

The cross-sectional view ofFIG. 5shows that the contacts30of the member26are generally shaped to provide interference with minimal drag, having a straight back portion32that is generally perpendicular of the plane of the ring28and an arcuate front portion34. The curvature of the front portion34is such that it is tangent to an imaginary circle that is of a lesser diameter than the opening in member28and the openings18and24seen inFIG. 1.

Referring next to the cross-sectional view ofFIG. 3, it can be seen that the contact member26ofFIG. 4is welded at points represented by the black dots38in the drawing to the washer22and that the contacts30encroach into the opening defined by the aperture of the contact support member26. The tolerances are such that when a lead terminal is inserted through the opening18in the housing member12with a predetermined force, it will deflect the springs30which then intimately engage a contact ring on the lead terminal to establish electrical contact at a multiplicity of points, resulting in a low impedance connection.

While the embodiment described illustrates six contacts30on the spring contact member26, a greater or a fewer number of such contacts may be utilized. As a minimum, however, there should be at least three such contacts, but with six such contacts being preferred. The contacts30will be deflected as the lead terminal is inserted through the ring connector10. While the embodiment reflected inFIGS. 1–5show the contact ring28spot-welded to the underside of washer22, it is also possible to insert the contact ring28into the housing with the contacts30projecting upward from the base14.

FIGS. 6–9illustrate an alternative embodiment of the ring connector of the present invention. The ring connector, indicated generally by numeral40, again comprises a metal contact housing42having a sidewall44supported on a base46. The base has an opening48formed therethrough that is sized to receive a lead terminal with non-contact clearance. Again, the size of the opening48is slightly greater than the diameter of a ring contact on a medical lead to be inserted through that aperture. The aperture48is preferably beveled, as at50, to facilitate or guide the insertion of a lead's terminal therethrough. Welded to an exposed edge52of the wall44is a contact plate54in the form of a washer having an opening56that is seized to receive a lead terminal with non-contact clearance. At regular intervals, e.g., every 60°, a small hole, as at58, is drilled through the contact support member54. Fitted into each of these holes is one end60of a generally bent cylinder contact62. An isometric view of one such bent cylinder contact is shown inFIG. 9.

Referring toFIG. 8, before being welded in place within the holes58, the contacts62are aligned in a manufacturing jig (not shown) so that the straight section66of the bent cylinder is tangent to an imaginary circle represented by the broken line68inFIG. 8and bent end portion64is directed away from that circle. When a lead terminal is inserted through the contact member assembly40, the cylindrical bar contact62will be deflected so as to press against a contact surface of the lead's terminal to establish a low resistance path between the pulse generator (not shown) that attaches to the housing42and the aforesaid lead contact surface.

When the ring contact assemblies10and40ofFIG. 1orFIG. 6, respectively, are axially aligned in the header of an implantable medical device of the type concerned here, they electrically couple the device's high or low voltage output to a corresponding medical lead terminal. No outside mechanical actuation or tools are required, such as set screws or Allen wenches. In addition, the contact assemblies of the present invention are less costly than known prior art ring contact arrangements.

The physical geometry of the contacts disclosed herein is quite different from known prior art approaches. The spring tabs or bent cylinders of the present invention, instead of the canted toroidal springs of the prior art, yield improved results. The prior art competitive contact has an inherent disadvantage in that its toroidal spring “floats” within the housing and makes connection between the terminal and housing only through physical interference. The contacts disclosed in the present application are solidly connected (i.e., welded) to the housing, thus improving the electrical quality of the connection.