Surgery – Means for introducing or removing material from body for... – Treating material introduced into or removed from body...
Reexamination Certificate
1999-02-25
2001-10-02
Seidel, Richard K. (Department: 3763)
Surgery
Means for introducing or removing material from body for...
Treating material introduced into or removed from body...
Reexamination Certificate
active
06296630
ABSTRACT:
FIELD OF THE INVENTION
The inventions described below relate to the field of cardiovascular surgery, including systems and methods for temporarily introducing a conduction block between the atria and ventricles in a mammalian heart for the purpose of fine control over cardiac contraction. This would allow surgeons to temporarily stop the heart, and/or alter the heart rate to reduce the motion associated with cardiac contraction. This provides substantial advantage to delicate surgical techniques that are performed on the heart.
BACKGROUND OF THE INVENTION
Atrial fibrillation is a form of heart disease that afflicts millions of people. It is a condition in which the normal contraction of the heart is interrupted, primarily by abnormal and uncontrolled action of the atria of the heart. The heart has four chambers: the right atrium, right ventricle, the left ventricle, and the left atrium. The right atrium pumps de-oxygenated blood from the vena cava to the right ventricle, which pumps the blood to the lungs, necessary for return flow of de-oxygenated blood from the body. The right atrium contracts to squeeze blood into the right ventricle, and expands to suck blood from the vena cava. The contractions normally occur in a controlled sequence with the contractions of the other chambers of the heart. When the right atrium fails to contract, contracts out of sequence, or contracts ineffectively, blood flow within the heart is disrupted. The disruption of the normal rhythm of contraction is referred to as an arrhythmia. The arrhythmia known as atrial fibrillation can cause weakness due to reduced ventricular filling and reduced cardiac output, stroke due to clot formation in a poorly contracting atria (which may lead to brain damage and death), and even other life threatening ventricular arrhythmias.
Atrial defibrillator is a therapy being developed for atrial fibrillation. Atrial defibrillators are typically implantable electrical therapy devices which deliver defibrillating energy to the atrium to terminate arrhythmias. They sense the electrical activity of the atrium and deliver an electrical shock to the atrium when the electrical activity indicates that the atrium is in fibrillation. Electrical defibrillation has two major problems: the therapy causes substantial pain and has the potential to initiate a life threatening ventricular arrhythmia. The pain associated with the electrical shock is severe and unacceptable for many patients. Unlike electrical ventricular defibrillators where the patient loses consciousness prior to receiving therapy, the patient who suffers an atrial arrhythmia is conscious and alert when the device delivers electrical therapy.
The potential exists for inappropriate induction of ventricular fibrillation by the shock intended to defibrillate the atrium. The induction of ventricular fibrillation has great potential to result in death in just a few minutes if no intervening therapy is provided. Careful algorithms to deliver shocks to the periods in the ventricular contraction cycle when the heart is not susceptible to shock induced ventricular fibrillation have been developed to reduce the potential of this risk. If the problem of patient pain can be overcome, atrial defibrillators could be used in a large portion of the patient population that suffer from atrial fibrillation.
Pharmacological Atrial Defibrillators
For some time, doctors have treated atrial fibrillation with drugs injected intravenously or administered orally. Recent literature describes the potential for the delivery of drugs to the heart on demand to terminate arrhythmias. The concept has been suggested for use in the atrium to treat atrial fibrillation. Arzbaecher, Pharmacologic Atrial Defibrillator and Method, U.S. Pat. No. 5,527,344 (Jun. 18, 1996) describes a pharmacological atrial defibrillator and method for automatically delivering a defibrillating drug into the bloodstream of a patient upon detection of atrial arrhythmias in order to terminate the atrial arrhythmias. Arzbaecher teaches that unspecified defibrillating drugs should be injected into the bloodstream with a large initial dose followed by delivery of a continuous smaller dose (this is the “two-compartment pharmacokinetic model” discussed in the Arzbaecher patent). By delivering agents to a blood vessel and maintaining a therapeutic level of drugs in the blood stream, Arzbaecher requires systemic effects to be achieved in order to terminate atrial arrhythmias. In other words, if drugs injected according to Arzbaecher are to have any effective concentrations within the heart, a large amount must be injected in the blood stream to ensure that an adequate dose will be delivered to the affected area of the heart. While the drugs are in the blood stream, they are available throughout the body to cause side effects on all other organs.
There are several disadvantages to the transient introduction of systemic drug levels by an implantable device. Systemic effects resulting from such delivery may result in detrimental effects to ventricular cardiac conduction. These detrimental effects could be life threatening. The large amount of drugs required for systemic delivery of therapeutic doses demands a larger, less comfortable device than smaller dosages would allow. The large quantity of drug in the implantable reservoir of such a system is potentially more dangerous if it develops a leak or is ruptured. Such a large single dosage will require a reservoir that requires frequent follow ups for refilling post therapy by a clinician. Lastly, the large quantities of drug required to obtain therapeutic levels in the entire body may cost substantially more than that required to treat a specific site within the heart. The system described by Arzbaecher has one primary advantage over electrical atrial defibrillation: the delivery of therapy to terminate an arrhythmia does not cause patient pain, and some recent abstracts have appeared in the literature which suggest that this technique is viable. See Arzbaecher, et al., Development Of An Automatic Implanted Drug Infusion System For The Management Of Cardiac Arrhythmias, 76 IEEE Proc. 1204 (1991); Bloem, et al., Use Of Microprocessor Based Pacemaker To Control An Implantable Drug Delivery System, Computers in Cardiology 1 (1993); Bloem, et al., Microprocessor Based Automatic Drug Infusion System For Treatment Of Paroxysmal Atrial Fibrillation, 26S J. Electrocardiogr. 60 (1993); and Wood, et al., Feedback control of antiarrhythmic agents, in
Molecular Interventions and Local Drug Delivery,
(W B Saunders 1995).
Drug delivery directly into the heart has been proposed for other conditions. In my own prior patent, Altman, Implantable Device for the Effective Elimination of Cardiac Arrythmogenic Sites, U.S. Pat. No. 5,551,427 (Sep. 3, 1996) I describe an implantable substrate for local drug delivery at a depth within the heart. The patent shows an implantable helically coiled injection needle which can be screwed into the heart wall in the ventricles and connected to an implanted drug reservoir outside the heart. This system allows injection of drugs directly into the wall of the heart by merely the injection of drugs through the skin into the reservoir. The patent also shows a helical coil coated with a coating which releases drug into the myocardium. This drug delivery may be performed by a number of techniques, among them infusion through a fluid pathway, and delivery from controlled release matrices at a depth within the heart. Co-pending application Ser. No. 08/881,685 by Altman and Altman, describes some additional techniques for delivering local pharmacological agents to the heart.
Other implanted drug delivery systems have been proposed. Levy, System for Controlled Release of Antiarrhythmic Agents, U.S. Pat. No. 5,387,419 (Feb. 7, 1995), describes the placement of controlled release matrices on the surface of the epicardium (on the outside of the heart) for delivery of antiarrhythmic agents, but all dosage forms described are for steady state drug delivery and do not address the advant
Altman John D.
Altman Peter A.
Biocardia, Inc.
Crockett & Crockett
Crockett, Esq. K. David
Hayes Michael
Seidel Richard K.
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