Surgery – Instruments – Cyrogenic application
Reexamination Certificate
1998-06-17
2001-06-05
Dvorak, Linda C. M. (Department: 3739)
Surgery
Instruments
Cyrogenic application
C606S021000, C606S020000
Reexamination Certificate
active
06241722
ABSTRACT:
FIELD OF THE INVENTION
The invention relates generally to a cryogenic catheter and a method of using same. More particularly, this invention relates to a cryogenic catheter which may be used to map cardiopulmonary tissue, and/or to produce lesions in biological tissue. The cryogenic catheter and method of using same are particularly useful in the treatment of tachycardia.
BACKGROUND OF THE INVENTION
Catheters which include a variety of electrode means for the ablation of biological tissue are known. For example, most of the catheters used for the ablation of cardiac tissue employ electrodes which are energized by a radio-frequency (“RF”) electrical current. That is, the cardiac tissue is heated by the RF-energized electrodes until a lesion is formed in the desired location. Generally, the RF-electrode catheters are also used to map, or to record, the electrical conduction pathways of the cardiac tissue.
Examples of such RF-energized electrode catheters for use in the treatment of cardiac arrhythmia appear in U.S. Pat. No. 5,720,775 to Larnard; U.S. 5,676,693 to LaFontaine; U.S. Pat. No. 5,555,883 to Avitall; U.S. Pat. No. 5,545,193 to Fleischman et al.; U.S. Pat, No. 5,281,213 to Milder et al.; and U.S. Pat. No. 5,281,215 to Milder.
Generally, in the treatment of tachycardia, electrode mapping is used to locate the originating site of the disturbance in the electrical activity or rhythm of the heart. A focal lesion is formed at the originating site of the arrhythmia to interrupt the abnormal electrical activity. Generally, in the treatment of atrial fibrillation, electrode mapping is used to record the electrical conduction system of the atria in order to ensure that the ablation electrode does not reach the normal conduction system. In such treatment, elongated, continuous lesions are formed in the atrial tissue to block reentry circuits which disrupt the normal electrical activity of the atria.
Use of RF-energized electrode catheters to form such cardiac lesions has significant disadvantages. For example, often when using such a catheter to form a cardiac lesion, the cardiac tissue becomes charred from the RF-energized heating of the tissue, blood in the vicinity of the cardiac tissue undergoing treatment becomes coagulated, and the cardiac tissue undergoes separation and/or popping. Further, it is often difficult to form an effective lesion having sufficient length, continuity and/or depth to interrupt or to block electrical conduction across the lesion, when using an RF-energized electrode catheter.
Theoretical consideration and experimental testing have indicated that the formation of cardiac lesions by cryogenic means overcomes many of the disadvantages associated with the use of RF-energized electrode catheters. Yet, cryogenic means have not become the means of choice, for lack of development of a desirable and effective cryogenic system and technique for the treatment of cardiac conditions.
By way of example, Milder (above) discloses a cryogenic catheter for performing “ice-mapping” and cryogenic ablation of cardiac tissue. The catheter is designed for cryoablation at its tip, such that focal lesions are formed. The catheter of Milder is not suitable for the formation of the elongated, continuous, and/or deep lesions that are desirable in the treatment of various cardiac conditions, such as atrial fibrillation.
There is a need for a cryogenic system, and a method of using same, that provides for efficacious treatment of biological tissue by forming an efficacious lesion in the tissue. There is a particular need for same for the treatment of abnormal conditions in cardiopulmonary tissue.
SUMMARY OF THE INVENTION
According to a primary aspect of the present invention, briefly and generally, a cryogenic device for treating biological tissue is provided, which includes at least two media-flow lumens and a media-expansion element for cooling media flowing within the device. The device is particularly adapted, and/or adaptable, to the tissue being treated, such that good contact between a cooling portion of the device and the tissue is achieved. For example, according to one embodiment, the cooling portion is located along a bellows portion of one of the media-flow lumens, which bellows portion is of a fixed or selectable shape or dimension, suitable for good contact with the selected tissue. In this manner, the device is capable of contacting tissue that is difficult to access, is of a complicated shape and/or of a small size, for the desired treatment of the tissue.
The device may be employed in the treatment of a variety of tissue, such as tissue affected with an undesirable condition, whether benign or malignant, tissue of an organ, and particularly, tissue within a body which is accessible via percutaneous or intravenous means. The device is especially suitable for the treatment of cardiopulmonary tissue, as it may be employed to effect not only deep focal lesions, but also elongated, continuous and/or deep lesions that may be desirable in the treatment of such tissue.
In the device of the present invention, a medium flowing in a first lumen thereof is pressurized and at a first temperature just distal of the expansion element. Upon passage through the expansion element, the medium now flowing into a second lumen is comparatively of a lower pressure and temperature. This cooled medium is sufficient for cooling the tissue when the second lumen is appropriately placed in relation to the tissue.
According to a preferred embodiment of the present invention, the second lumen includes a bellows portion for contacting the tissue and a cooling portion along the bellows portion for cooling the tissue. The bellows portion is constructed to facilitate contact between the cooling portion, or contact portion, of the device and the tissue. To this end, the bellows portion may be longitudinally fixed, or longitudinally expandable or contractible. In a preferred embodiment, at least the contact portion is composed of a super-elastic metal alloy, such as nitinol, which has desirable flexibility, strength and longevity. Given these desirable properties, the entire bellows portion may be composed of this material.
According to one aspect of the present invention, the expansion means is a media-flow restriction means, preferably, an orifice sufficient for Joule-Thomson expansion of the medium flowing therethrough. Preferably, the expansion means is longitudinally moveable so that the contact portion can be moved to a desirable longitudinal position along the bellows portion for optimal cooling of the selected tissue.
The device of the present invention may be advantageously employed over an operating temperature range of from about normal body temperature, for example, when the device is being placed in contact with the tissue, to a desirable cooling temperature. For example, the cooling temperature at the contact portion may be at less than or equal to about 0° C. for adhesion of the contact portion to the selected tissue. Further by way of example, the cooling temperature may be at about −10° C. for the cold-mapping of cardiopulmonary tissue. This cooling temperature may be lower, generally, from about −20° C. to about −150° C., and preferably, from about −70° C. to about −120° C., for forming an efficacious lesion in biological tissue, such as cardiopulmonary tissue.
According to a particular aspect of the invention, the medium supplied to the first lumen may be pre-cooled so that it is at a desirably low temperature before it reaches the expansion means for further cooling. That is, a conduit having a pre-cooling medium flowing therethrough may be disposed in an efficacious heat-exchange relationship with the first lumen to pre-cool the medium flowing in the first lumen. According to yet another aspect of the invention, the second lumen may be in an efficacious heat-exchange relationship with the first lumen for further cooling of the medium flowing in the first lumen. With such heat-exchange relationships, the device can achieve a very low cooling temper
Dobak John D.
Li Hong
CryoGen, Inc.
Dvorak Linda C. M.
Gibson Roy
Skjerven Morrill & MacPherson LLP
LandOfFree
Cryogenic device, system and method of using same does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Cryogenic device, system and method of using same, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Cryogenic device, system and method of using same will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2491726