Surgery – Instruments – Electrical application
Reexamination Certificate
1998-06-25
2001-06-26
Cohen, Lee (Department: 3739)
Surgery
Instruments
Electrical application
C600S374000, C600S549000, C607S099000, C607S113000, C607S122000
Reexamination Certificate
active
06251107
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention generally relates to the detection and elimination of cardiac arrhythmia and particularly atrial fibrillation and atrial flutter.
Atrial fibrillation is the disorganized depolarization of a patient's atrium with little or no effective atrial contraction. This condition may be chronic or intermittent, and it presently affects approximately 2 million people in the United States alone. Prior methods for treating a patient's arrhythmia include the use of antiarrhythmic drugs such as sodium and calcium channel blockers-or drugs which reduce the Beta-adrenergic activity. Other methods include surgically sectioning the origin of the signals causing the arrhythmia or the conducting pathway for such signals. However, the surgical technique is quite traumatic and is unacceptable to a large number of patients. A more frequently used technique to terminate the arrhythmia involves destroying the heart tissue which causes the arrhythmia by heat, e.g., applying a laser beam or high frequency electrical energy, such as RF or microwave, to a desired arrhythmogenic site on the patient's endocardium. In the latter method, intravascular electrophysiological (EP) devices can be used to form contiguous lesions within a patient's atrial chamber to provide results similar to the surgical segregation techniques in terminating atrial fibrillation but with significantly reduced trauma.
Typically, the EP device is advanced within a patient's vasculature and into a heart chamber, and a lesion is formed at the endocardium when RF electrical energy is emitted from electrodes of the device. RF ablation techniques produce lesions of a significantly smaller area. Consequently, several lesions are typically formed to completely ablate an area than the average arrhythmogenic site. A major problem of RF ablation techniques is forming a lesion of the requisite size, which completely ablates the area of interest but does not unnecessarily destroy surrounding healthy tissue.
What has been needed is an ablation device which allows for improved monitoring of the creation of a lesion, to generate linear lesions of a requisite length. The present invention satisfies these and other needs.
SUMMARY OF THE INVENTION
This invention is directed to a low profile electrophysiology (EP) device suitable for forming linear ablations within a chamber of a patient's heart. The EP device of the invention has electrodes and temperature sensors along an outer surface of the device. The configuration results in a low profile and improved control over lesion size due to improved monitoring of lesion formation. The lesions from such linear ablations are particularly suitable for eliminating or minimizing atrial fibrillation and flutter by isolating sections of the patient's atrial wall.
The EP device of the invention generally comprises an elongated shaft with a proximal section, a distal section, and a plurality of at least partially exposed electrodes disposed on an outer surface of the distal section. The electrodes are spaced along a length of the distal section with at least one temperature sensor located between adjacent electrodes.
The electrodes on the distal shaft section form a lesion from within a patient's heart chamber when electrical energy, preferably RF energy, is emitted therefrom. The electrodes may be combination sensing and ablation electrodes which are capable of ablation and detection of electrical activity from within a lumen of the patient's body. In a preferred embodiment, the electrodes on the device shaft are independent, for monopolar mode use with an electrode in contact with the exterior of the patient's body. Alternatively, the electrodes may be bipolar, for use as a pair of electrodes on the shaft. A presently preferred electrode is in the form of a helical coil for improved device flexibility, although other designs are suitable including cylindrical bands, arcuate bands or ribbons or the like. For high resolution sensing, the electrodes may be spaced in a first compact array of electrodes mounted on the distal shaft section and a second expanded array of sensing electrodes mounted on the distal shaft section with an interelectrode spacing greater than that of the first compact array, such as described in copending application Ser. No. 08/443,657, entitled High Resolution Intravascular Signal Detection, filed on May 18, 1995, which is incorporated herein in its entirety.
A presently preferred temperature sensor is a thermocouple, although other suitable temperature sensors may be used, such as thermisters or other temperature sensing means. The presently preferred thermocouple is a T-type formed of copper and constantan wire. A conducting member may be provided on an outer surface of the temperature sensor. The conducting member is formed from a conducting material, such as gold, which rapidly equilibrates the temperature around the catheter circumference to the temperature at the patient's heart wall.
The location of the temperature sensors on an outer surface of the device between the electrodes allows for a low profile device. The low profile facilitates maneuvering and positioning the operative distal end of the device within the patient. The maximum outer diameter of the distal shaft section of the device is about 1.0 mm (3.0 French) to about 1.3 mm (4 French). In contrast to the EP device of the invention, EP devices having temperature sensors radially spaced in the shaft, at a location intermediate the electrodes and the central axis of the device, require a larger diameter shaft than the EP device of the invention.
Moreover, the EP device of the invention provides more effective lesion formation through improved monitoring of the temperature during lesion formation. To effectively ablate an arrhythmogenic site, the individual lesions formed by adjacent electrodes must come together, in order to form one continuous lesion that completely ablates an area of interest. However, if lesion formation is prematurely stopped, the lesions will not be continuous and thus may not terminate the arrhythmia. EP devices having temperature sensors located distal or proximal to the section of the shaft on which the electrodes are located, or radially spaced from the electrodes within the device shaft, cannot accurately measure the temperature of the heart wall between adjacent electrodes, and consequently do not effectively monitor the ablation to ensure a continuous lesion. In contrast, with the EP device of the invention, the temperature sensors monitor the temperature of the heart wall at the edge of the adjacent lesions which meet or overlap to form one continuous lesion. By thus monitoring the temperature, the physician is able to ensure that adequate heating is produced, while avoiding over heating which could cause coagulation of blood and charring of tissue. Thus, the physician applies ablation energy to adjacent electrodes so that the heart wall between the electrodes reaches a given temperature for a given time. In this way, the physician can monitor lesion formation and determine when one continuous lesion of the desired size has been formed.
The wall of the distal section is formed at least in part of individually insulated electrical conductors which are electrically connected to individual electrodes on the distal section. Preferably the electrical conductors are braided. Individual conductor wires in the distal section wall are also connected to the temperature sensors, or, in the case of thermocouple temperature sensors, have a distal end which forms the temperature sensor. A plurality of polymer strands formed of nylon, DACRON® (Dupont) and the like may also be braided either with the electrical conductors as they are braided or braided separately on the exterior of the tubular member formed by the braided conductors. The proximal ends of the electrical corductors are electrically connected to individual pins of a multi-pin connector on the proximal end of the shaft which facilitate transmission of hi
Cardima, Inc.
Cohen Lee
Heller Ehrman White & McAuliffe LLP
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