Surgery – Instruments – Electrical application
Reexamination Certificate
1997-10-02
2001-07-31
Dvorak, Linda C. M. (Department: 3739)
Surgery
Instruments
Electrical application
C607S101000, C607S122000
Reexamination Certificate
active
06267757
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention is directed to the ablation of tissue in the wall of a patient's heart and particularly to form channels within the heart wall in order to perform transmyocardial revascularization (TMR), to deliver therapeutic or diagnostic agents to various locations in the patient's heart wall or for a variety of other utilities.
As presently used, TMR involves forming a plurality of channels in a ventricular wall of a patient's heart by means of laser energy. The first clinical trials of the TMR procedure using laser energy were performed by Mirhoseini et al. See for example the discussions in Lasers in General Surgery (Williams & Wilkins; 1989), pp 18 216-223. Other early disclosures of the TMR procedure are found in an article by Okada et al. in Kobe J. Med. Sci 32, 151-161, October 1986 and in U.S. Pat. No. 4,658,817 (Hardy). These early references describe intraoperative TMR procedures which require an opening in the chest wall and include formation of channels completely through the heart wall starting from the epicardium.
U.S. Pat. No. 5,554,152 which issued on Dec. 20, 1994 (Aita et al.), which is incorporated herein in its entirety, describes a system for TMR which is introduced through the chest wall either as an intraoperative procedure where the chest is opened up or as a minimally invasive procedure where the system is introduced into the patient's chest cavity through small openings in the chest by means of a thoroscope. In U.S. Pat. No. 5,389,096 (Aita et al.) a percutaneous TMR procedure is described wherein an elongated flexible laser based optical fiber device is introduced through the patient's peripheral arterial system, e.g. the femoral artery, and advanced through the aorta until the distal end of the device extends into the patient's left ventricle. Within the left ventricle, the distal end of the optical fiber device is directed toward a desired location on the patient's endocardium and urged against the endocardial surface while a laser beam is emitted from its distal end to form the channel.
The laser based revascularization procedure has been shown to be clinically beneficial to a variety of patients, particularly patients who were, for the most part, not suitable candidates for by-pass surgery or for minimally invasive procedures such as angioplasty or atherectomy. However, to date the equipment for laser based systems has been quite expensive. What has been needed is a system which is cheaper than but as clinically effective as laser based systems. The present invention satisfies these and other needs.
SUMMARY OF THE INVENTION
The present invention is directed to a method and system for the revascularization of a region of a patient's heart by ablating tissue in said region with emissions of radio frequency (RF) energy over discrete intervals and is particularly directed to the method and system to ablate tissue in the patient's heart wall to form channels therein by means of such RF energy.
In accordance with one embodiment of the invention, tissue is ablated within a patient's heart wall by means of one or more bursts of RF emissions over intervals of about one to about 500 msec and preferably about 30 to about 130 msec. An RF burst may comprise a continuous emission or discontinuous emission, i.e. be pulsatile, and, if pulsatile, may involve a plurality or train of pulses which may or may not be of the same width (duration), frequency or amplitude.
The RF emissions is preferably controlled so that heart tissue is exposed to the RF energy over a desired period and particularly over a period which will avoid interfering with the patient's heart beat, e.g. just after the R wave but before the T wave. One to about 10 bursts of RF energy may be required to effectively form the desired channel within the patient's heart wall and preferably one burst of RF emission is delivered per heart cycle. The RF energy source generally should have a peak power output of about 150 to about 500 watts, preferably about 200 to about 300 watts.
One presently preferred system for forming the channels in the patient's heart wall includes an RF energy transmitting member which has a proximal end, an elongated shaft insulated along a length thereof and an uninsulated distal tip configured to emit RF energy. The system is introduced into the patient and advanced within the patient until the uninsulated distal tip thereof is disposed adjacent to a surface of the patient's heart wall. At least one burst of RF energy from an RF energy source is transmitted through the RF energy transmitting member to the uninsulated distal tip thereof and from which transmitted RF energy transmitted is emitted to the surface of the heart wall in contact with said distal tip. The channel formed in the heart wall preferably has an aspect ratio, i.e. depth to width, of at least 1, preferably at least 2.
One embodiment of the invention involves a percutaneous approach wherein a flexible elongated RF energy delivery system is advanced through the patient's vasculature until a distal portion of the system enters a heart chamber such as the left ventricle. The RF energy delivery system is advanced so that the uninsulated distal tip thereof which emits RF energy contacts the interior surface of the heart wall which defines in part the heart chamber. At least one burst of RF energy is emitted from the uninsulated distal tip of the system into the patient's heart wall wherein tissue is ablated, resulting in the revascularization of the heart wall region.
Another embodiment of the invention involves a minimally invasive approach where a small incision is made in the patient's chest and with or without the benefit of a trocar sheath, an elongated RF energy transmitting system is advanced into the patient's chest cavity until the uninsulated distal tip of the RF transmitting system contacts the exterior of the patient's heart. One or more bursts of RF energy are emitted from the uninsulated distal tip so as to ablate tissue within the patient's heart wall causing the revascularization thereof as in the previously discussed embodiment of the invention. A similar procedure may be used in conjunction with an open chest procedure such as coronary by-pass surgery.
The RF energy transmitting system preferably includes an elongated electrical conducting shaft which is insulated along its length except for the distal tip thereof which is uninsulated and which is configured to contact the surface of the heart wall and to emit bursts of RF energy therefrom into adjacent tissue of the heart wall. The uninsulated distal tip has a diameter of about 0.025 to about 0.2 inch (0.64-5.1 mm), preferably about 0.04 to about 0.08 inch (1-2 mm) and a length of about 0.1 to about 5 mm, preferably about 1.5 to about 3.5 mm. The distal tip may be solid or hollow and may be relatively sharp or blunt. However, it should not be sharp enough to penetrate the tissue of the heart wall when pressed against the wall to maintain contact during the emission of RF energy bursts. The average power level should be about 50 to about 500 watts, preferably about 100 to about 300 watts. The frequency of the RF current should not be less than 100 khz and preferably is about 250 to about 500 khz.
The method and system of the invention effectively ablates tissue within the patient's heart wall to revascularize the ablated region and particularly can be used to form channels within the heart wall. These and other advantages of the invention will become more apparent from the following detailed description of the invention and the accompanying exemplary drawings.
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patent: 5197963 (199
Aita Michael
Aron Kenneth P.
Burkhoff Daniel
Danek Christopher J.
Taimisto Miriam H.
Dvorak Linda C. M.
Eclipse Surgical Technologies Inc.
Gibson Roy
Heller Ehrman White & McAuliffe LLP
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