Collet spring for high voltage electrical contacts in ICD headers

A connector assembly includes a conductive collet spring with an annular base and integral circumferentially spaced cantilevered generally parallel arms terminating at tip members diametrically spaced closer than the diameter of the base. A conductive housing overlying and electrically and mechanically engaged with the collet spring engageably receives the electrical terminal of a medical stimulating device and includes a distal mounting flange. A non-conductive barrel is fittingly attached to the distal mounting flange of the housing and has an inner bore for receiving a medical electrical lead. A non-conductive header encapsulates the connector assembly, is mounted on the casing, and has a header bore aligned with the inner bore for receiving the medical electrical lead which, when inserted and sufficiently advanced through the header bore, the inner bore, and the annular base, the tip members firmly engage the proximal terminal pin thereof.

FIELD OF THE INVENTION

The present invention relates generally to a technique for interconnecting electrical leads and electrical medical devices, and more particularly, for interconnecting implantable electrical leads and implantable medical electrical devices such as implantable cardioverter-defibrillators (ICDs) without requiring currently employed components of a connector block, setscrew, and septum to operate successfully.

BACKGROUND OF THE INVENTION

ICDs are devices which are capable of recognizing ventricular tachycardia or ventricular fibrillation and delivering electrical therapy to terminate such an arrhythmia and may also be used to treat the atria. Advantageously, such devices are relatively small, light-weight and implantable. In order to sense and stimulate the heart, however, such ICDs must be used with an ICD lead—an electrical conductor that carries electrical signals between the heart and the ICD. Advantageously, the ICD lead can be inserted into the heart transvenously through a relatively simple and well-known surgical procedure. Disadvantageously, one end of the lead (sometimes designated herein as the “connecting end”) must be electrically and mechanically secured to the ICD in a way that provides for a long-term safe and secure, yet detachable, connection. Those skilled in the art of ICDs have long sought after a simple, yet reliable and safe, technique for making this detachable electrical and mechanical connection between the ICD and the connecting end of the ICD lead.

In order to appreciate the advantages of the present invention, it will help first to have a basic understanding of the manner in which the mechanical and electrical connection functions are carried out in known ICDs. The main components associated with the connection function of known ICDs are shown inFIG. 1. An ICD10electrically includes a battery14that powers electronic circuitry12. The ICD electronic circuitry12and battery14are mechanically housed and hermetically sealed in a suitable housing16. Typically, this casing16is shaped to include a flat side or platform20to which a suitable epoxy header22can be bonded. At least one feedthru terminal18, in electrical contact with the electronic circuitry12, passes through the casing16and protrudes out from the platform20. This feedthru terminal18is electrically isolated from the casing16. A platinum wire24, or other suitable conductive element, connects the terminal18to a conductive connector block26that is fitted within the header22. An ICD lead28, having a proximal electrode30, connects to the ICD electronic circuitry by inserting the proximal electrode30into a receiving channel31of the header22until the electrode30is in contact with the connector block26. A set screw32is then securely tightened using a torque wrench34to firmly hold the electrode30in both mechanical and electrical connection with the connector block26. A septum35is typically placed over the set screw32in order to prevent body fluids from seeping through the set screw hole. Further, sealing ribs or ridges36on the connecting end of the ICD lead are designed to tightly engage the inside edges of the receiving channel31in order to prevent any body fluids from entering into the receiving channel31once the connecting end of the lead has been pushed into the header22.

Typically, known headers22are cast in place from epoxy to the platform20of the ICD, or a premolded header is bonded to the platform20using a suitable sealing and bonding agent. Further, once the electrical connection is made from the terminal post18to the connector block26, and the header22is attached to the housing, all remaining voids within the header, not including the receiving channel31into which the proximal end of the lead is to be inserted, must be filled with a suitable filler material, such as a two-component epoxy or silicone rubber.

As is evident from the above description, placing a header on an ICD housing is a very labor-intensive process involving many components. What is needed is a simpler manner of lead attachment that provides the requisite mechanical and electrical connection functions using fewer components and less labor yet providing higher reliability. As mentioned above, many known ICDs use a setscrew connector block assembly to make electrical contact between leads and device. The surgeon secures leads in the header by tightening the setscrew(s) with a torque wrench inserted through the septum. The septum is installed over the setscrew in the header to seal the connector block from body fluid. This process of tightening setscrews establishes electrical contact between lead and device and starts delivery of therapy.

Occasionally, the septum gets damaged either by the torque wrench or the setscrew, creating a leak path for body fluid to come in contact with the connector block. This may result in device malfunction and/or connector block corrosion. Additionally, the quality of electrical contact between the lead and device is compromised due to presence of body fluid.

Damage to setscrews is one of the main reasons for field return of devices. In many devices where the cause of failure is indeterminate, the septum is observed to be damaged.

In order to assemble the septum, a cavity is created in the header. The cavity raises the profile of header surfaces. This raised profile tends to rub against body tissue after implant and is a primary source of irritation and patient discomfort.

Low septums, however, are a cause of rejects in manufacturing. In this regard, it is noteworthy to explain that during normal header manufacturing operation, a cylindrical cavity is created in the side of the header and the septum is installed in the cavity such that the top surface of the septum is flush with the rim of the cylindrical cavity. Sometimes the cavity is created excessively deep, with the result that the septum sits low in the cavity. In this case the top surface of the septum lies below the rim of the cylindrical cavity. This condition is known as a low septum and is a cause of rejects.

This is one of the reasons for often low yield of the casting process when manufacturing ICD headers and, frequently, devices require rework on account of this problem. Further, during quality inspection, septums can get damaged due to insertion of torque wrench.

The present invention addresses these and other needs and it was in light of the foregoing that the present invention was conceived and has now been reduced to practice.

SUMMARY

A connector assembly includes a conductive collet spring with an annular base and integral circumferentially spaced cantilevered generally parallel arms extend from the annular base terminating at tip members which are diametrically spaced closer than the diameter of the base. A conductive housing overlying and electrically engaged with the collet spring is connected to the electrical terminal of a medical stimulating device and includes a distal mounting flange. A non-conductive barrel is fittingly attached to the distal mounting flange of the housing and has an inner bore for receiving a medical electrical lead. A non-conductive header encapsulates the connector assembly, is mounted on the casing, and has a header bore aligned with the inner bore for receiving the medical electrical lead which, when inserted and sufficiently advanced through the header bore, the inner bore, and the annular base, the tip members firmly engage the proximal terminal pin thereof and assure electrical continuity with the device's electronic circuitry.

Other and further features, advantages, and benefits of the invention will become apparent in the following description taken in conjunction with the following drawings. It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory but are not to be restrictive of the invention. The accompanying drawings which are incorporated in and constitute a part of this invention, illustrate one of the embodiments of the invention, and together with the description, serve to explain the principles of the invention in general terms. Like numerals refer to like parts throughout the disclosure.

DETAILED DESCRIPTION

Refer again to the drawings and, this time, toFIGS. 2 and 3.FIG. 2illustrates a detail perspective view of a header assembly40, embodying the invention, for an ICD41. The header assembly40is shown in position mounted on a mounting surface42of a casing44of the ICD41containing a battery and electronic circuitry, not here shown, but generally provided in the manner illustrated inFIG. 1.FIG. 3is a longitudinal cross section view in elevation of a connector assembly46of which one is seen inFIG. 2within the header assembly40and to which is coupled a body implantable medical electrical or ICD lead48. Although the present invention will be described with reference to the embodiments shown in the drawings, it should be understood that the present invention can be embodied in many alternate forms or embodiments. In addition, any suitable size, shape or type of elements or materials could be used.

InFIG. 2, an electrical terminal50connected to the electronic circuitry within the casing44projects out of the mounting surface42. While only one electrical terminal is shown, there may be several, depending on the specific construction of the ICD41.

Continuing to viewFIG. 3together withFIGS. 4 and 5, the connector assembly46is illustrated in relation to a longitudinal axis52and includes an electrically conductive collet spring54(FIGS. 3,5,6,7,8,9, and12) composed of a biocompatible metal such as titanium, stainless steel, platinum, or MP35N. Collet spring54is constructed with an annular base56lying in a plane transverse of the longitudinal axis52(FIGS. 4,5, and12). A plurality of circumferentially spaced cantilevered arms58integral with the annular base56extend away from the annular base and are generally parallel to the longitudinal axis52. Each of the arms58terminate at a tip member60and the plurality of the tip members60are at a uniform radial distance from the longitudinal axis52which, as clearly seen inFIGS. 5-9is less than a radial distance between the annular base56and the longitudinal axis52.

Turning now especially toFIGS. 10,11, and12, an electrically conductive housing62overlies, and is mechanically and electrically engaged, as by spot welding, with the collet spring54. The housing62has an annular groove63lying in a plane transverse of the longitudinal axis52for engageably receiving the electrical terminal50(FIG. 2) of the medical stimulating device, or ICD41. At an appropriate stage of the fabrication of the header assembly40, the electrical terminal50is welded to the groove63of the housing62. The housing62extends between a proximal annular mounting flange64generally coextensive with the tip members60of the collet spring54and a distal annular mounting flange66generally coextensive with the annular base56.

A non-conductive barrel member68(FIGS. 3,4, and5) extends between proximal and distal ends70,72, respectively, and is aligned with the longitudinal axis52. The barrel member68has an annular flange74at its proximal end70and has an inner bore75for receiving a proximal terminal pin76(FIG. 3) of the medical electrical lead48. The proximal annular flange74is fittingly attached to the distal mounting flange66of the housing62.

A non-conductive end cap78, as seen especially well inFIGS. 3,4,5,13,14, and15, includes an annular mounting flange80and has a receptive cavity82. The mounting flange80of the end cap78is fittingly attached to the proximal mounting flange64of the housing62at the receptive cavity to thereby enclose the proximal end of the connector assembly46.

As seen inFIG. 2, an electrically non-conductive header84encapsulates the connector assembly46and is mounted on the mounting surface42of the casing44and has a header bore86(FIG. 2) aligned with the inner bore75of the barrel member68. The header bore86extends between a bore entrance88and the inner bore75of the barrel member68for receiving the proximal terminal pin76of the medical electrical lead48. With this construction, when the proximal terminal pin76of the medical electrical lead48is inserted through the header bore86and through the inner bore75and is sufficiently advanced through the annular base56of the collet spring54, the tip members60of the plurality of cantilevered arms58firmly engage the proximal terminal pin76and assure electrical continuity between the proximal terminal pin and the electronic circuitry of the medical stimulating device, or ICD,41.

The header84may be molded in place on the mounting surface42of the casing44encapsulating the connector assembly46comprised of the end cap78, the collet spring54, the housing62, and the barrel member68. Alternatively, the header84may be pre-molded with an outer peripheral surface90and an undersurface92for mounting engagement on the mounting surface42of the ICD41. During the procedure of molding the header84, the end cap78, the housing62, and the barrel member68protect the interior of the connector assembly46against the intrusion of the fluid plastic or epoxy material and also provide for electrical insulation during the operation of the resulting medical stimulating device.

It should be understood that the foregoing description is only illustrative of the invention. Various alternatives and modifications can be devised by those skilled in the art without departing from the invention. For example, although the foregoing description has referred primarily to the application of the invention to a DF-1 lead pin, it can also be beneficially employed with respect to other lead pin designs such as IS-1, IS-4, and DF-4. Accordingly, the present invention is intended to embrace all such alternatives, modifications and variances which fall within the scope of the appended claims.