Surgery: light – thermal – and electrical application – Light – thermal – and electrical application – Thermal applicators
Reexamination Certificate
1998-05-06
2003-02-18
Kearney, Rosiland S. (Department: 3739)
Surgery: light, thermal, and electrical application
Light, thermal, and electrical application
Thermal applicators
C607S104000, C607S105000, C606S041000
Reexamination Certificate
active
06522930
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is a surgical device. More specifically, the present invention relates to a tissue ablation device assembly with an irrigated ablation member which is adapted to produce a lesion within tissue. The present invention also relates to the construction of the ablation member.
2. Description of Related Art
Cardiac arrhythmias, and atrial fibrillation in particular, remain a persistent medical condition in modern society. Persistence of atrial fibrillation has been observed to cause or at least contribute to various medical conditions including congestive heart failure, stroke, other thromboembolic events, and myocardial ischemia.
Several surgical approaches have been developed for the purpose of treating or preventing cardiac arrhythmias, and in particular more recently with the intention of treating atrial fibrillation, such as according to one example known as the “maze procedure,” as disclosed 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); and also by Cox, J L in “The surgical treatment of atrial fibrillation. IV. Surgical Technique”,
Thoracic and Cardiovascular Surgery
101(4), pp. 584-592 (1991). In general, the “maze” procedure is designed to relieve atrial arrhythmia by restoring effective atrial systole and sinus node control through a prescribed pattern of incisions about the cardiac tissue wall. In the early reported clinical experiences, the “maze” procedure included surgical incisions in both the right and the left atrial chambers. However, more recent reports predict that the surgical “maze” procedure may be substantially efficacious when performed only in the left atrium, such as is disclosed in Sueda et al., “Simple Left Atrial Procedure for Chronic Atrial Fibrillation Associated With Mitral Valve Disease” (1996).
The “maze procedure” as performed in the left atrium generally includes forming vertical incisions from the two superior pulmonary veins and terminating in the region of the mitral valve annulus, traversing the inferior pulmonary veins en route. An additional horizontal line also connects the superior ends of the two vertical incisions. Thus, the atrial wall region bordered by the pulmonary vein ostia is isolated from the other atrial tissue. In this process, the mechanical sectioning of atrial tissue eliminates the precipitating conduction to the atrial arrhythmia by creating conduction blocks within the aberrant electrical conduction pathways.
While surgical intervention such as the “maze” procedure has been moderately successful in treating atrial arrhythmia, this highly invasive methodology is believed to be prohibitive in many cases. However, these procedures have provided the principle that electrically isolating faulty cardiac tissue may successfully prevent atrial arrhythmia, and particularly atrial fibrillation caused by perpetually wandering reentrant wavelets or focal regions of arrhythmogenic conduction. Hence the development of less invasive catheter-based approaches to treat atrial fibrillation through cardiac tissue ablation intended to emulate the maze-type procedures.
In general, known catheter-based therapies for cardiac arrhythmias involve introducing a catheter within a cardiac chamber, such as in a percutaneous translumenal procedure, such that an energy sink on the catheter's distal end portion is positioned at or adjacent to the aberrantly conductive tissue. The energy sink is activated according to various known modes of operation such that the targeted tissue adjacent thereto is ablated and rendered non-conductive as to the propagation of cardiac rhythm.
One particular type of energy sink which has been disclosed for use as an ablation element as such is a heat sink which ablates tissue by use of thermal conduction, for example by means of a resistive wire which heats upon application of a current in a closed loop system within an ablation catheter. A threshold temperature which has been disclosed for ablating tissue according to a thermal conduction mode of ablation is generally above 45 degrees, usually from 45 to 70 degrees, usually 50 to 65 degrees C., and preferably from about 53 to 60 degrees C. It has also been observed that high temperatures, such as temperatures above 70 degrees, may produce charring at the tissue-ablation element interface. It has been further observed that such charring may cause adverse medical results such as thrombosis on the tissue wall in the case of tissue ablation of the cardiac chambers including the atrium.
Another previously disclosed energy sink for use as an ablation element includes an electrode which emits direct current (DC), such as from an electrode on the distal end of a catheter placed adjacent to the targeted tissue and coupled by way of the body's own conductivity to a return electrode. However, more modem current-based ablation elements which have been disclosed for use in tissue ablation devices and procedures instead use radio frequency (RF) current driven electrodes. According to RF electrode ablation, the electrode is placed adjacent to the target tissue and is electrically coupled to a return electrode which may be provided on the same or another invasive device, or more generally is provided as a large surface area conductive patch provided on the patient. Current flowing between the electrode and the patch is at its highest density at the tissue adjacent to the treatment electrode and therefore causes ablation of the tissue. It is believed that this arrangement is adapted to ablate tissue both by way of thermal conduction at the electrode-tissue interface, in addition to thermal ablation caused by resistive or dielectric heating of the tissue itself as it resides in the high current density region of the RF current path.
In addition to the energy sinks just described for use as tissue ablation elements, other energy sources which have been disclosed for use in catheter-based ablation procedures include microwave energy sources, cryoblation energy sources, light energy sources, and ultrasound energy sources.
Various specific catheter-based tissue ablation devices and methods have also been disclosed for forming lesions of specific geometry or patterns in the target tissue. In particular, various known tissue ablation devices have been adapted to form either focal or linear (including curvilinear) lesions in the wall tissue which defines the atrial chambers. Less-invasive percutaneous catheter ablation devices and techniques have been disclosed which use variations of “end-electrode” catheter designs for delivering a point source of energy to ablate the area of abnormal electrical activity, such as where atrial fibrillation is believed to be focal in nature, such as where a focal arrhythmia originates from a pulmonary veins of the left atrium. The end electrodes form localized lesions that ablate the focus, thus ablating and thereby treating such focal arrhythmias, such as in the pulmonary veins. Examples of previously disclosed therapeutic focal ablation procedures for ablating foci in the pulmonary vein may be found in the following references: “Right and Left Atrial Radiofrequency Catheter Therapy of Paroxysmal Atrial Fibrillation”, Haissaguerre et al.,
Journal of Cardiovascular Electrophysiology
7(12), pp. 1132-1144 (1996); and “A focal source of atrial fibrillation treated by discrete radiofrequency ablation”, Jais et al.,
Circulation
95:572-576 (1997).
Focal tissue ablation, however, is not generally believed to be appropriate for many cases of atrial fibrillation of the “multi-wavelet” type which involve multiple reentrant loops which are believed to arise from various arrhythmogenic sources. These multiple excitation waves would simply circumnavigate a focal ablative lesion within the cardiac tissue. Therefore, similar to the surgical “maze” procedure described above, continuous linear lesions are believed to be necessary in order to completely segment the atrial tissue so as to bl
Schaer Alan K.
Valencia Aurelio
Atrionix, Inc.
Kearney Rosiland S.
Knobbe Martens Olson & Bear LLP
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