Electrical connectors – Medical use or attached to human body
Reexamination Certificate
2001-03-26
2002-08-06
Paumen, Gary (Department: 2833)
Electrical connectors
Medical use or attached to human body
C607S037000
Reexamination Certificate
active
06428368
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to connector assemblies for receiving implantable leads and connecting such leads to electronic circuits within an implantable stimulation device, such as a cardiac pacemaker, and more particularly to a side actuated connector assembly having at least one lead receptacle within which an implantable lead is fixed and sealed.
BACKGROUND OF THE INVENTION
Although it will become evident to those skilled in the art that the present invention is applicable to a variety of implantable tissue stimulation devices utilizing pulse generators to stimulate selected body tissue, the invention and its background will be described principally in the context of a specific example of such devices, namely, cardiac pacemakers for providing precisely controlled stimulation pulses to the heart and for receiving sensed cardiac signals via an external connector assembly having one or more lead-receiving receptacles. The appended claims are not intended to be limited, however, to any specific example or embodiment described herein.
Cardiac pacemakers, and other implantable stimulation devices such as cardiac defibrillators, are hermetically packaged to isolate the device from the body environment. Such devices require that electrical signals be reliably passed between the packaged device and its external connectors, without compromising the hermeticity of the package. Depending on the configuration of the implantable device, there may be multiple electrical paths required between the device and its external connectors for delivering, for example, multi-chamber or multi-site stimulation and shock therapy, and receiving sensed cardiac signals. These paths must be electrically and mechanically integrated with the device to provide a safe, long-term connector assembly which does not compromise the hermetic package.
Typically, a hermetic housing feedthrough electrically couples the electronic circuits contained within the device housing to a connector assembly. The feedthrough assembly extends through the hermetically sealed outer wall of the housing and into the connector assembly so as to couple the electronic circuits within the housing to lead-receiving receptacles within the connector assembly. Each lead has one or more terminals, typically in the form of a pin and one or more conductive rings. The pin is electrically coupled to a distal tip electrode and is therefore sometimes called the “tip terminal.” When inserted into the lead receptacle of a connector assembly, contacts within the receptacle come into contact with corresponding terminals on the lead so as to couple the lead to the electronic circuits within the implantable stimulation device via the feedthrough assembly. Needless to say, it is imperative that completely dependable electrical contact be made between the lead and the connector assembly. At the same time, the connector assembly must be capable of releasing the lead from the lead receptacle during a subsequent surgical procedure, and must also tightly seal against the entry of body fluids.
It is known in prior art connector assemblies to make electrical connection to one or more terminals on the lead by means of a variety of connector assemblies including a captive fastening screw/collet arrangement; a setscrew; and a spring or other compliant electrical contact. It is also known to use a prefabricated connector assembly to hold the electrical contacts together with a series of nonconductive spacers which are made from plastic. The resulting connector subassembly is attached to the pacemaker, or other implantable device, by fixturing it over the pacemaker and having epoxy molded around the subassembly. Alternatively, the connector subassembly may be inserted into a pre-molded connector top and bonded to the pacemaker.
In those prior art connector assemblies in which the lead is fixed within the lead receptacle using a setscrew, the setscrew is often threaded into a connector block within the connector assembly. When the screw is advanced, it comes into physical contact with the tip terminal of the lead. The resulting physical connection is often used as the electrical contact as well. However, this can present one or more problems. For example, the lead is sometimes damaged by the force produced when the setscrew is tightened. Such damage must be controlled, inasmuch as the life of the lead is often longer than that of the pacemaker. Additionally, setscrews in prior art connector assemblies have a history of stripping out of the threaded block. Particularly where relatively small setscrews are used, the threads, or the hex flats, may strip. To minimize or eliminate such problems, setscrews of a certain minimum physical size are necessary. The result is often a hump on the side of the connector assembly as the physical size of the pacemaker and its connector assembly are reduced.
A further problem of prior art setscrew type connector assemblies arises from the need to isolate the setscrew and the setscrew block from bodily fluids. One solution has been to use a silicone seal called a septum. The septum forms an insulation barrier between the setscrew and bodily fluids. However, the septum must permit a wrench to pass through it so that the screw can be tightened. Frequently, the septum is damaged by the wrench resulting in a loss of the insulation barrier.
U.S. Pat. No. 5,951,595 issued Sep. 14, 1999, and incorporated herein by reference in its entirety, discloses a connector assembly mounted on an implantable cardiac stimulation device having an actuator mechanism for fixing and tightly sealing electrical leads inserted into lead receptacles within the connector assembly without the use of setscrews. Fixing and sealing of the leads is accomplished by compressing resilient lead lock seals of O-ring shape, disposed in annular recesses, with lip portions of a plunger drawn toward a molded support by the actuator mechanism. In a first embodiment of the actuator mechanism of the '595 patent, rotation of a cam actuator transversely journaled within the support, using a torque wrench or similar tool, moves a cam slide attached to the plunger through a fixed displacement between lock and unlock positions as an offset camming portion of the actuator engages the surfaces of a slot within the cam slide. In a second embodiment of the actuator mechanism of the '595 patent, constant-force compression of the lead lock seals by the plunger is provided by using a torque wrench to rotate a screw actuator having one end coupled to the plunger and an opposite threaded end received within a screw block transversely disposed within the support. The screw actuator is oriented longitudinally, that is, its axis is parallel with the longitudinal axes of the lead receptacles, and includes an enlarged driver end projecting from the front end of the plunger in between the leads extending from the lead receptacles. In a third embodiment of the actuator mechanism of the '595 patent, the actuator comprises a rotatable toothed pinion engages a toothed slot within a slidable rack to provide incremental advancement of the rack, and thereby stepped displacement and applied force, with a resulting increased resolution. In a fourth embodiment of the mechanism of the '595 patent, compliance provided by either a spring formed within the cam slide, or a spring nut mounted thereon, prevents excessive force from being exerted on leads of larger diameter.
The connector assembly of the '595 patent overcomes the disadvantages of earlier connector assemblies employing lead fixation techniques using setscrews. In addition, unlike the second embodiment of the '595 patent utilizing a front actuated, longitudinally extending screw actuator, the first embodiment of the '595 patent employing a cam actuator transversely journaled within the support has the advantage of providing unobstructed access to the actuator from the side of the assembly thereby speeding the fixation of the leads in the lead receptacles as well as their removal. A s
Hawkins Rodney J.
Lim Wisit
Truex Buehl E.
McCamey Ann
Pacesetter Inc.
Paumen Gary
LandOfFree
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