Surgery: light – thermal – and electrical application – Light – thermal – and electrical application – Electrical therapeutic systems
Reexamination Certificate
2000-10-12
2001-08-28
Kamm, William E. (Department: 3762)
Surgery: light, thermal, and electrical application
Light, thermal, and electrical application
Electrical therapeutic systems
Reexamination Certificate
active
06280462
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to an implantable cardiac stimulation lead and electrode system for applying electrical energy to an abnormally functioning heart and more particularly to an implantable pulse generator housing having electrically conductive walls serving as a defibrillation discharge electrode.
Electrodes implanted in the body for electrical stimulation of muscle or body organs are well known. More specifically, electrodes implanted on or about the heart have been used to reverse certain abnormal and life-threatening arrhythmias. Electrical energy is applied to the heart via the electrodes to return the heart to normal sinus rhythm.
Common abnormal cardiac arrhythmias include bradycardia (slower than normal heartbeat rhythm), ventricular tachycardia (faster than normal heartbeat rhythm), and ventricular fibrillation (sporadic and uncoordinated beating of the heart). The latter two arrhythmias generally are fatal if left untreated.
To control the heartbeat rhythm and prevent fatalities from ventricular tachycardia and fibrillation, several devices have been designed having the ability to stimulate the heart according to a sensed cardiac signal such as a sensed ECG signal. See for example U.S. Pat. No. 4,603,705 to Speicher et al. The Speicher et al. patent discloses a multiple electrode unitary intravascular cardiac catheter having a distal electrode for sensing and pacing, an intermediate electrode for sensing, pacing and cardioverting, and a proximal electrode for sensing and cardioverting. This multiple electrode catheter maintains the ability for heart rate sensing and low threshold pacing immediately following cardioversion.
There are many types of defibrillation cardioversion electrodes in the art. U.S. Pat. No. 4,825,871 to Cansell discloses a defibrillation/cardioversion shock system in which the box housing the pulse generator circuitry serves as a support for a discharge electrode. Specifically, the metal box is enclosed by a plastics material and a metal plate is attached to the metal box and electrically connected therewith. Charges collected by the metal plate are transmitted to the metal box, which serves as a collector. The metal box itself is not used as an electrode in the Cansell system.
The need therefore exists for implantable cardiac stimulation lead system capable of performing standard pacing, such as anti-bradycardia pacing, anti-tachycardia pacing, low-energy cardioversion, and high-energy defibrillation.
SUMMARY OF THE INVENTION
It is a primary object of this invention to provide an implantable cardiac stimulation lead system having pacemaking, cardioversion and higher energy defibrillation capabilities.
It is an additional object of this invention to provide an implantable cardiac stimulation lead system having pacemaking, cardioversion and defibrillation capabilities via a selectable defibrillation electrode configuration.
It is yet a further object of this invention to provide an implantable cardiac stimulation lead system utilizing a relatively small number of implantable parts.
It is still another object of the present invention to provide an implantable pulse generator housing made entirely or partially but in a selective manner, of electrically conductive material, serving as a defibrillation electrode.
It is yet a further object of the invention to provide an electrically conductive portion of an implantable pulse generator housing which, together with electrical discharge surfaces extending therefrom, serve as an electrode.
It is still another object of the present invention to reduce the size of the pulse generator housing by eliminating one terminal on the housing.
Briefly, the implantable cardiac stimulation lead system of the present invention comprises a transvenous endocardial or epicardial lead having a plurality of electrodes. Typically, the lead electrodes are capable of sensing and performing standard anti-bradycardia pacing, anti-tachycardia pacing, cardioversion and defibrillation. The transvenous lead is connected to a pulse generator having full-function pacing capabilities as well as cardioversion and defibrillation capabilities. The housing of the pulse generator (together with, as desired, electrical discharge surfaces extending therefrom) is conductive and is connected to the pulse generator circuitry so that it may selectively serve as a discharge electrode. The outer surface of the pulse generator could be of a special configuration to facilitate its discharge capabilities. Typically, the pulse generator is implanted in the pectoral or abdominal region of the body proximate the heart. A programmable switch or other type of circuitry is provided to select the electrode configuration which may include or exclude the pulse generator housing electrode. As a result, different electrode configurations can be obtained for specific types of cardiac stimulations.
In a first embodiment, the electrode surface of the pulse generator housing comprises a portion of the conductive wall of the housing.
In a second embodiment, the electrode surface comprises conductive mesh attached to the pulse generator housing.
In a third embodiment, the pulse generator housing is a metal housing, all or selective ones of the surfaces of which, together with, as desired, electrical discharge surfaces extending therefrom, are conductive.
In accordance with a fourth embodiment, the other surface of the conductive pulse generator housing is platinum.
The fifth embodiment relates to dedicating isolated conductive surface regions from one another, such isolated regions may serve for separately sensing, pacing and shocking.
In accordance with the sixth embodiment, an insulative mask is disposed over a conductive surface of the pulse generator housing.
In a seventh embodiment, a sensing switch is used to determine when the pulse generator is implanted and when it is outside the body of the patient.
The above objects and advantages of the present invention can be further understood when reference is made to the following description, taken in conjunction with the accompanying drawings.
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Dahl Roger W.
Hauser Robert G.
KenKnight Bruce H.
Cardiac Pacemakers Inc.
Kamm William E.
Schwegman Lundberg Woessner & Kluth P.A.
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