Surgery: light – thermal – and electrical application – Light – thermal – and electrical application – Electrical therapeutic systems
Reexamination Certificate
2000-09-18
2004-04-13
Schaetzle, Kennedy (Department: 3762)
Surgery: light, thermal, and electrical application
Light, thermal, and electrical application
Electrical therapeutic systems
C607S005000, C128S898000
Reexamination Certificate
active
06721597
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an apparatus and method for performing electrical cardioversion/defibrillation and optional pacing of the heart via a totally subcutaneous non-transvenous system.
BACKGROUND OF THE INVENTION
Defibrillation/cardioversion is a technique employed to counter arrhythmic heart conditions including some tachycardias in the atria and/or ventricles. Typically, electrodes are employed to stimulate the heart with electrical impulses or shocks, of a magnitude substantially greater than pulses used in cardiac pacing.
Defibrillation/cardioversion systems include body implantable electrodes and are referred to as implantable cardioverter/defibrillators (ICDs). Such electrodes can be in the form of patches applied directly to epicardial tissue, or at the distal end regions of intravascular catheters, inserted into a selected cardiac chamber. U.S. Pat. Nos. 4,603,705, 4,693,253, 4,944,300, 5,105,810, the disclosures of which are all incorporated herein by reference, disclose intravascular or transvenous electrodes, employed either alone or in combination with an epicardial patch electrode. Compliant epicardial defibrillator electrodes are disclosed in U.S. Pat. Nos. 4,567,900 and 5,618,287, the disclosures of which are incorporated herein by reference. A sensing epicardial electrode configuration is disclosed in U.S. Pat. No. 5,476,503, the disclosure of which is incorporated herein by reference.
In addition to epicardial and transvenous electrodes, subcutaneous electrode systems have also been developed. For example, U.S. Pat. Nos. 5,342,407 and 5,603,732, the disclosures of which are incorporated herein by reference, teach the use of a pulse monitor/generator surgically implanted into the abdomen and subcutaneous electrodes implanted in the thorax. This system is far more complicated to use than current ICD systems using transvenous lead systems together with an active can electrode and therefore it has no practical use. It has in fact never been used because of the surgical difficulty of applying such a device (3 incisions), the impractical abdominal location of the generator and the electrically poor defibrillation aspects of such a system.
Recent efforts to improve the efficiency of ICDs have led manufacturers to produce ICDs which are small enough to be implanted in the pectoral region. In addition, advances in circuit design have enabled the housing of the ICD to form a subcutaneous electrode. Some examples of ICDs in which the housing of the ICD serves as an optional additional electrode are described in U.S. Pat. Nos. 5,133,353, 5,261,400, 5,620,477, and 5,658,321, the disclosures of which are incorporated herein by reference.
ICDs are now an established therapy for the management of life threatening cardiac rhythm disorders, primarily ventricular fibrillation (V-Fib). ICDs are very effective at treating V-Fib, but are therapies that still require significant surgery.
As ICD therapy becomes more prophylactic in nature and used in progressively less ill individuals, especially children at risk of cardiac arrest, the requirement of ICD therapy to use intravenous catheters and transvenous leads is an impediment to very long term management as most individuals will begin to develop complications related to lead system malfunction sometime in the 5-10 year time frame, often earlier. In addition, chronic transvenous lead systems, their reimplantation and removals, can damage major cardiovascular venous systems and the tricuspid valve, as well as result in life threatening perforations of the great vessels and heart. Consequently, use of transvenous lead systems, despite their many advantages, are not without their chronic patient management limitations in those with life expectancies of >5 years. The problem of lead complications is even greater in children where body growth can substantially alter transvenous lead function and lead to additional cardiovascular problems and revisions. Moreover, transvenous ICD systems also increase cost and require specialized interventional rooms and equipment as well as special skill for insertion. These systems are typically implanted by cardiac electrophysiologists who have had a great deal of extra training.
In addition to the background related to ICD therapy, the present invention requires a brief understanding of automatic external defibrillator (AED) therapy. AEDs employ the use of cutaneous patch electrodes to effect defibrillation under the direction of a bystander user who treats the patient suffering from V-Fib. AEDs can be as effective as an ICD if applied to the victim promptly within 2 to 3 minutes.
AED therapy has great appeal as a tool for diminishing the risk of death in public venues such as in air flight. However, an AED must be used by another individual, not the person suffering from the potentially fatal rhythm. It is more of a public health tool than a patient-specific tool like an ICD. Because >75% of cardiac arrests occur in the home, and over half occur in the bedroom, patients at risk of cardiac arrest are often alone or asleep and can not be helped in time with an AED. Moreover, its success depends to a reasonable degree on an acceptable level of skill and calm by the bystander user.
What is needed therefore, especially for children and for prophylactic long term use, is a combination of the two forms of therapy which would provide prompt and near-certain defibrillation, like an ICD, but without the long-term adverse sequelae of a transvenous lead system while simultaneously using most of the simpler and lower cost technology of an AED. We call such a device a sub-cutaneous only ICD (S-ICD) and is described in detail below.
SUMMARY OF THE INVENTION
The preferred embodiment for the subcutaneous only ICD (S-ICD) with optional pacing consists of five basic components: 1) an electrically active canister housing a battery supply, capacitor and operational circuitry wherein the housing serves as an electrode and replaces one conventional lead of the prior art systems; 2) one or more subcutaneous combined high voltage/sense/pace electrodes emanating from the S-ICD housing; 3) sense circuitry suitable to an ICD or AED V-FIB detection algorithm; 4) an application system for simple insertion of the subcutaneous lead; and 5) a cutaneous test system designed to estimate the best location of the S-ICD for each patient. Therefore, no transvenous lead system is necessary, eliminating a significant impediment to broader scale prophylactic use and especially use in children.
The active canister housing will provide energy and voltage intermediate to that available with ICD and AEDs. The typical maximum voltage necessary for ICDs using most biphasic waveforms is approximately 750 V and associated maximum energy of approximately 40 J. The typical maximum voltage necessary for AEDs is approximately 2000-5000 V with an associated maximum energy of approximately 150-360 J. The S-ICD of the present invention will use voltages in the range of 800 to 2000 V and associated with energies of approximately 40-150 J. The canister could be employed as either a cathode or an anode.
In the preferred embodiment only one subcutaneous high voltage electrode, of opposite polarity to the canister, will be used but no limit is placed on the number of subcutaneous electrodes that may be required to achieve optimal S-ICD function. The subcutaneous electrode, composed of silicone or polyurethane insulation, will have a minimum of 1 electrode but, in the preferred embodiment, will have 3: a high voltage, low-impedance coil electrode approximately 5-10 cm length and two low voltage, high impedance sense electrodes at the tip. The spacing of the sense electrodes will be approximately 4 cm to provide a reasonable QRS signal from a subcutaneous extracardiac sampling location but may be of variable length to allow for sense optimization. In the preferred embodiment, the sense electrodes are placed proximal to the high voltage lead, contrary to typical transvenous ICD lead systems, but alternative locations are al
Bardy Gust H.
Cappato Riccardo
Cameron Health, Inc.
Crompton Seager & Tufte LLC
Droesch Kristen
Schaetzle Kennedy
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