Surgery: light – thermal – and electrical application – Light – thermal – and electrical application – Electrical therapeutic systems
Reexamination Certificate
2001-11-21
2004-06-22
Getzow, Scott M. (Department: 3762)
Surgery: light, thermal, and electrical application
Light, thermal, and electrical application
Electrical therapeutic systems
Reexamination Certificate
active
06754528
ABSTRACT:
FIELD OF THE INVENTION
The subject invention relates generally to implantable cardioverter/defibrillators and, more particularly, to detection of cardiac arrhythmias with subcutaneous implantable cardioverter/defibrillators.
BACKGROUND OF THE INVENTION
Defibrillation/cardioversion is a technique employed to counter arrhythmic heart conditions including some tachycardias or fast heart rhythms originating 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. A variety of shock waveforms are used for both defibrillation and pacing, including truncated exponentially decaying monophasic and biphasic waveform pulses as well as pulses where the waveform maintains a relatively constant current over the duration of delivery to the myocardium.
Defibrillation/cardioversion systems include body implantable electrodes that are connected to a hermetically sealed container housing the electronics, battery supply and capacitors. The entire system is referred to as an implantable cardioverter/defibrillators (ICD). The electrodes used in ICDs can be in the form of patches applied directly to epicardium, or, more commonly, the electrodes are located on the distal regions of small cylindrical insulated catheters that typically enter the subclavian venous system, pass through the superior vena cava and, into one or more endocardial areas of the heart. Such electrode systems are called intravascular or transvenous electrodes. 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, in combination with other intravascular or transvenous electrodes, or in combination with an epicardial patch or subcutaneous electrodes. 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 sensing and defibrillation aspects of such a system.
Recent efforts to improve the efficiency of ICDs have led manufacturers to produce ICDs that are small enough to be implanted in the infraclavicular pectoral region, a site allowing access to the subclavian venous system. 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 (VF) and also ventricular tachycardia (VT). ICDs are very effective at treating VF and VT, but traditional ICD implantation still requires significant surgery and surgical skill, especially regarding lead insertion into the venous system and lead positioning in the heart.
As ICD therapy becomes more prophylactic in nature and used in progressively less ill individuals, including children, the requirement of ICD therapy to use intravenous catheters and transvenous leads is a major impediment to very long term management as most individuals will develop complications related to lead system malfunction, fracture or infection sometime in the 5-10 year time frame, often earlier. In addition, chronic transvenous lead systems, their removal and reimplantation, 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 known 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 a related therapy, the automatic external defibrillator (AED). AEDs employ the use of cutaneous patch electrodes, rather than implantable lead systems, to effect defibrillation under the direction of a bystander user who treats the patient suffering from VF with a portable device containing the necessary electronics and power supply that allows defibrillation. AEDs can be nearly as effective as an ICD for defibrillation if applied to the victim of ventricular fibrillation promptly, i.e., within 2 to 3 minutes of the onset of the ventricular fibrillation. AEDs, unlike ICDs, only make shock
o shock decisions, as they are relieved of the burden of needing to deliver complicated tiered therapeutic responses that the ICD encumbers as a consequence of detecting and treating a multitude of rhythm problems with a multitude of therapies. AEDs either shock for a life-threatening event or they do not shock. ICDs, on the other hand, are designed for a variety of interventions and use a different technological approach for arrhythmia detection, redetection, assessment of effectiveness and therapy.
AED therapy has great appeal as a tool for diminishing the risk of death in public venues such as in airplanes. However, an AED must be used by another individual, not the person suffering from the potential 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 ID 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 for life-threatening arrhythmias, especially for children and for prophylactic long term use for adults at risk of cardiac arrest, is a novel 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 harboring most of the simpler diagnostic and therapeutic technological approaches of an AED. What is also needed is a cardioverter/defibrillator that is of simple design and can be comfortably implanted in a patient for many years.
Further, an ICD is needed that can detect various types of cardiac arrhythmias to provide a patient with adequate therapy according to the type of cardiac arrhythmia experienced by the patient. Although ICDs have multiple secondary functions, they primarily have two key functions: detection and therapy of life threatening cardiac arrhythmias. ICDs constantly monitor a patient's cardiac activity and analyze the card
Allavatam Venugopal
Bardy Gust H.
Erlinger Paul J.
Ostroff Alan H.
Rissmann William J.
Cameraon Health, Inc.
Crompton Seager & Tufte LLC
Getzow Scott M.
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