Surgery: light – thermal – and electrical application – Light – thermal – and electrical application – Electrical energy applicator
Reexamination Certificate
2001-04-05
2004-07-20
Jastrzab, Jeffrey R. (Department: 3762)
Surgery: light, thermal, and electrical application
Light, thermal, and electrical application
Electrical energy applicator
Reexamination Certificate
active
06766203
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to lead assemblies for coupling implantable pulse generating medical devices with selected body tissue to be stimulated, and particularly, to tip electrodes forming part of such lead assemblies.
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 medical 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. However, the appended claims are not intended to be limited to any specific example or embodiment described herein.
Pacemaker leads form the electrical connection between the cardiac pacemaker pulse generator and the heart tissue which is to be stimulated. As is well known, the leads connecting such pulse generators with the heart may be used for pacing, or for sensing electrical signals produced by the heart and representing cardiac activity, or for both pacing and sensing in which case a single lead serves as a bidirectional pulse transmission link between the pacemaker and the heart. An endocardial type lead, that is, a lead which is inserted into a vein and guided therethrough into a cavity of the heart, includes at its distal end a tip electrode designed to intimately contact the endocardium, the tissue lining the inside of the heart. An epicardial type lead includes a tip electrode in direct contact with the outside of the heart, that is, the epicardium. A myocardial lead has a tip electrode inserted into heart muscle, that is, the myocardium. In one typical form thereof, these leads include a proximal end having a connector pin adapted to be received by a mating socket in the pulse generator. A flexible, conductor, typically having a coiled configuration, is surrounded by an insulating tube or sheath and couples the connector pin at the proximal end of the lead and the tip electrode at the distal end of the lead.
The design of an implantable pacemaker pacing and sensing lead has a significant influence on the cost of its manufacture. For example, conventional pacing/sensing leads typically comprise several individual components which are assembled and welded together in a series of labor- and time-intensive, and therefore costly, steps in order to provide a reliable electrical and mechanical connection between the tip electrode and the associated electrical conductor.
With reference to
FIG. 1
, there is shown a simplified, axial cross section of an example of a conventional prior art lead assembly in the form of a unipolar, passive endocardial lead assembly
10
including a distal end portion
12
. The lead assembly
10
includes an elongated lead body
14
extending along a central longitudinal axis
16
and covered by a tubular, flexible, biocompatible, biostable insulative sheath or housing
18
fabricated of silicone rubber, polyurethane, or other suitable polymer. As is known, the lead assembly's proximal end portion (not shown in
FIG. 1
) is adapted to be electrically coupled to the receptacle of an implantable tissue stimulation pulse generator or pacemaker by means of a connector including an electrically conductive hollow pin. At the distal end portion
12
of the lead assembly, the insulative sheath
18
carries a plurality of outwardly extending tines
20
of known design for cooperating with the fibrous myocardial tissue to passively retain a tip electrode
22
, comprising part of a tip electrode assembly
24
, in position against the endocardium, in a fashion well known in the pacing art. The tip electrode
22
includes a proximal end
26
and a distal end
28
, the latter having a distal extremity
29
defining an active tissue stimulating electrode surface
30
which, in the particular example shown, is generally hemispherical in shape. The tip electrode
22
includes a generally tubular section
31
having an interior chamber
32
which extends between the proximal and distal ends
26
,
28
of the tip electrode. The distal end
28
of the tip electrode
22
may include one or more grooves
34
extending transversely of the longitudinal axis
16
. A central bore
36
provides communication between the grooves
34
and the chamber
32
to form an elution path for the passage of a drug stored in a drug impregnated plug
38
enclosed within the chamber
32
of the tubular section of the tip electrode adjacent the distal end
28
thereof. The drug may be one intended to counter thrombus formation, fibrosis, inflammation or arrhythmias, or any combination thereof, or to accomplish any desired localized purpose. For example, the drug dispensing plug may be loaded with a steroidal anti-inflammatory such as dexamethasone serving to reduce the stimulation threshold by minimizing fibrotic encapsulation or fibrosis. The typical prior art tip electrode assembly
24
shown in
FIG. 1
further includes a weld element
40
secured to the proximal end
26
of the tip electrode
22
by resistance or laser welding or the like. The weld element
40
has a first or distal projection
42
extending into the chamber
32
and a second projection
44
, longer than the first projection
42
, extending proximally. The second projection
44
includes a flange
46
and a tubular portion
48
extending proximally therefrom. The proximally extending tubular portion
48
of the weld element
40
extends into the lumen
50
of a coiled electrical conductor
52
which is held in place by means of a crimp tube
54
, welds, or a combination thereof. As is known in the art, the coiled electrical conductor
52
extends through the lead body
14
to the proximal end of the lead assembly and is coupled to the aforementioned, hollow connector pin. Also, as is known in the art, the insertion and placement of the lead assembly
10
into the heart is aided by means of a stylet (not shown) passed through the hollow connector pin and lumen
50
of the conductor coil
52
and into the tubular portion
48
of the weld element
40
to enable the distal end portion
12
of the lead assembly
10
to be positioned at a desired location in the heart.
It will be seen that the prior art tip electrode assembly
24
, which includes the weld element
40
, comprises a lengthy, rigid structure making difficult the insertion of the lead transvenously into the heart and its maneuvering and placement therein. It will also be appreciated that there are substantial labor and material costs associated with the fabrication of the multiple component tip electrode assembly
24
of the prior art. For example, considerable time must be spent on resistance or laser welders in order to join the various components with the attendant costs of the skilled labor required.
Thus, there continues to be a need for pacemaker leads having tip electrode assemblies that comprise fewer parts, are simpler and less costly to manufacture and are smaller than existing tip electrode assemblies so as to facilitate insertion and placement of the tip electrode within the heart.
SUMMARY OF THE INVENTION
Tip electrodes in accordance with the present invention are extremely easy to manufacture and accordingly very cost effective in comparison to conventional tip electrodes. Indeed, the minimal expense of fabricating tip electrodes with superior electrical characteristics is a primary advantage of the present invention.
A feature of the present invention is the provision of a tip electrode which can be inexpensively manufactured while maintaining the performance achieved by much more expensive electrode designs.
In accordance with one, specific exemplary embodiment of the present invention, there is provided a body implantable lead adapted to transmit electrical signals between a proximal end portion of the lead and a distal end portion of the lead to thereby stimulate selected body tissue and/or sense electrical signals therefrom. The lead extends i
Chitre Yougandh
Doan Phong D.
Helland John R.
Jastrzab Jeffrey R.
Oropeza Frances P.
Pacesetter Inc.
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