Surgery – Instruments – Electrical application
Reexamination Certificate
1999-07-19
2002-10-29
Dvorak, Linda C. M. (Department: 3739)
Surgery
Instruments
Electrical application
C606S046000, C606S047000, C607S101000, C607S122000
Reexamination Certificate
active
06471697
ABSTRACT:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not Applicable
REFERENCE TO A MICROFICHE APPENDIX
Not Applicable
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is a surgical device. More particularly, it is a medical catheter assembly that has an ablation element which is adapted to have its two ends anchored at predetermined locations on a body space wall such that the ablation element is adapted to firmly contact the length of tissue between predetermined locations for the purpose of forming a long linear lesion therebetween.
2. Description of the Background Art
Atrial Fibrillation
Cardiac arrhythmias, and atrial fibrillation in particular, remain a persistent medical condition in modern society. In the United States alone, approximately 1% of the total adult population is afflicted by atrial fibrillation, currently more than 2.5 million people, with prevalence increasing as a function of age. The resulting loss of blood flow due to incomplete cardiac contractions along with a rapid heart rate can lead to shortness of breath, dizziness, limited physical endurance, and chest pains. Persistence of atrial fibrillation renders an individual susceptible to congestive heart failure, stroke, other thromboembolic events, and myocardial ischemia. Considerable information is evolving regarding the conditions of the heart which contribute to the appearance of atrial fibrillation, factors which may be exacerbated by stress, anxiety, high blood pressure, heart valve disorders, and heart muscle dysfunction. An initial overview of the clinical phenomena associated with atrial arrhythmia is as follows.
The mammalian heart is composed of three different categories of cardiac tissue namely, atrial, ventricular, and excitatory conduction types. Normally, the atrial and ventricular muscles of the heart are electrically excited in a synchronous, patterned fashion. The cardiac cycle commences with the generation of action potentials by the sino-atrial (SA) node, located in the lateral wall of the right atrium. These action potentials propagate through the atrial chamber, possibly along preferential conduction pathways leading to the atrioventricular (AV) node. Potentials emanating from the AV node travel through the His-Purkinje bundle to the ventricular tissue, causing a synchronous contraction of the ventricles following that of the atria.
Pathological conditions of the cardiac tissue may lead to asynchronous cardiac rhythms, resulting in an overall elevation in the heart rate, inclusive of paroxysmal or chronic tachycardias. Tachycardias may initiate in the AV node, the bundle of His, or more generally in the atrial or ventricular tissues. The aforementioned tachycardias may manifest as a multiwavelet reentrant mechanism, resulting in asynchronous eddies of electrical impulses scattered about the atrial chamber. The fibrillation may also be more focal in nature, caused by the rapid, repetitive firing of an isolated center within the atria, but so rapidly that the remainder of the atrium cannot follow in a synchronized fashion.
Presently, many categories of tachycardia may be detected using the electrocardiogram (EKG). An alternative, more sensitive procedure commonly used to detect localized aberrations in electrical activity, and thus confirm the presence of arrhythmias such as atrial fibrillation, is the mapping of the cardiac chambers as disclosed in U.S. Pat. Nos. 4,641,649 and 4,699,147 and WO 96/32897.
Numerous cardiac arrhythmias, such as atrial fibrillation, were once thought untreatable except by pharmacological or surgical intervention, both capable of manifesting undesirable side effects. Recently, the emergence of less invasive catheter ablation methods have expanded the field of cardiac electrophysiology to provide limited percutaneous solutions to the medical conditions just described. A brief description of the aforementioned conventional therapies for atrial fibrillation and approaches to cardiac ablation thereof is found below.
Regimes of Conventional Treatment
Episodes of tachycardia may be responsive to treatment by antiarrhythmic medication, as disclosed in U.S. Pat. No. 4,673,563 to Berne et al. and further described in U.S. Pat. No. 4,569,801. In addition, pharmacological intervention for treating atrial arrhythmias has been disclosed in the Hindricks, et al. in “Current Management of Arrhythmias” (1991). However, the administration of such medications sometimes does not restore normal cardiac hemodynamics, and may ultimately exacerbate the arrhythmic condition through the occurrence of proarrhythmia.
Specific clinical circumstances may necessitate invasive surgical intervention for multiwavelet tachycardias, including the placement of implantable atrial defibrillators to maintain sinus rhythms as disclosed in U.S. Pat. Nos. 4,316,472; 5,209,229; 5,411,524 or alternatively, by the mechanical destruction of atrial electrical conduction pathways, as described by Cox, J L et al. in “The surgical treatment of atrial fibrillation. I. Summary”
Thoracic and Cardiovascular Surgery
101 (3), pp. 402-405 (1991) or Cox, J L “The surgical treatment of atrial fibrillation. IV. Surgical Technique”,
Thoracic and Cardiovascular Surgery
101 (4), pp. 584-592 (1991).
Described by the Cox procedure, as referenced above, is a strategy to incur patterned surgical incisions within the atrial chambers, creating a maze by which propagating electrical waves are extinguished at the lines of suture. In this way, reentrant wavelets are not sustained, arrhythmia cannot persist, and normal sinus rhythm is restored. Curative efforts for atrial arrhythmias were initially focused on the right atrium, with mixed results. However, procedures which combine right and left atrial treatments have been observed to have dramatically increased success rates. In the left atrium, a common protocol includes vertical incisions from the two superior pulmonary veins and terminating just posterior to the mitral valve annulus, transversing the inferior pulmonary veins en route. An additional horizontal line also connects the superior ends of the two vertical incisions. Thus, the region of the pulmonary vein ostia is isolated from the other atrial tissue. By severing electrical conduction pathways within the atrial tissues, the fibrillatory process is eliminated.
Transcatheter Cardiac Ablation
Alternative, less invasive approaches have recently been adopted for the treatment of cardiac arrhythmias in a clinical setting. These catheter-based transvascular approaches include procedures and associated devices for the treatment of ventricular or supraventricular tachycardias, as described in Lesh, MD in “Interventional Electrophysiology—State of the Art, 1993”
American Heart Journal
, 126, pp. 686-698 (1993).
The initial approach to the ablative procedure used catheters responsive to high energy direct current (DC) to either disrupt the AV node function or to create a heart block by disruption of the His bundle. However, it has been more recently observed that radio frequency (RF) is often a more desirable energy source as disclosed in WO 93/20770. Alternative ablation techniques have also been disclosed. For example, an ablative catheter responsive to microwave frequencies is described in WO 93/20767. Other catheter based ablation technologies which have also been disclosed to render the aberrant cells electrically silent include freezing, ultrasound, and laser energy as disclosed in U.S. Pat. Nos. 5,147,355; 5,156,157 and 5,104,393, respectively.
Ablation procedures have typically involved the incremental application of electrical energy to the endocardium to form focal lesions to interrupt the inappropriate conduction pathways. Methods and devices for using percutaneous ablative techniques intended to remedy cardiac fibrillation or arrhythmias have been disclosed in U.S. Pat. Nos. 5,231,995; 5,487,385; WO 94/21165 and WO 96/10961 in addition to U.S. Pat. Nos. 5,228,442 and 5,324,284 to Imran. The disclosures of these references are herein incorporated in their entirety by re
Dvorak Linda C. M.
O'Banion John P.
Peacock, III James C.
Ruddy David M.
The Regents of the University of California
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