Surgery – Instruments – Electrical application
Reexamination Certificate
2000-08-04
2004-06-08
Peffley, Michael (Department: 3739)
Surgery
Instruments
Electrical application
C604S095040
Reexamination Certificate
active
06746446
ABSTRACT:
FIELD OF THE INVENTION
This relates to the elimination of cardiac arrhythmia, particularly, atrial flutter by interrupting signals crossing the so-called isthmus region of the heart through electrophysiological (EP) treatment.
BACKGROUND OF THE INVENTION
Cardiac arrhythmia presently affects approximately 2 million people in the United States alone. A first type of arrhythmia, atrial fibrillation, is the disorganized depolarization of a patient's atrium, with little or no effective atrial contraction. Various uncoordinated stages of depolarization and repolarization, due to multiple reentry circuits within the atria, cause, instead of intermittent contraction, quivering in a chaotic pattern that results in an irregular and often rapid ventricular rate. A second type, atrial flutter, is a condition in which atrial contractions are rapid (250 to 300 beats per minute), but regular. In many instances, a circus movement caused by reentry is probably present. The condition is such that the ventricles are unable to respond to each atrial impulse so that at least a partial atrioventricular block develops. Either condition may be chronic or intermittent. It is atrial flutter that the present invention is most intended to address.
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 (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 the arrhythmia but with significantly reduced trauma.
Typically, an EP device is advanced within a patient's vasculature and into a heart chamber and a lesion is formed at the site of interest when RF electrical energy is emitted from electrodes of the device. RF ablation techniques produce lesions of a generally small area. Consequently, several lesions are typically needed to completely ablate the area of the average arrhythmogenic site. As such, 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. There has been a need for ablation devices which allow for improved monitoring of the creation of a lesion, to generate linear lesions of a requisite length. The present invention satisfies this need.
It is well known that in order to effectively produce lesions using EP devices that contact with or proximity to target tissues is key. Various devices used to improve contact with sites of interest in the heart other than the isthmus region are known in the art. Basket-shaped or volume filling devices like basket-shaped catheters which expand to contact opposing heart wall sections, such as that disclosed in U.S. Pat. Nos. 5,228,442 and 5,908,446 to Imran and U.S. Pat. No. 5,465,717 to Imran et al., are known. Another device to provide efficient contact between the treatment device and a site of interest is disclosed in U.S. Pat. No. 5,482,037 to Borghi where a catheter having an electrode on a flexible member which is shaped by a control wire forms a manipulable unit adapted to achieve configurations advantageous for providing a section capable of improved contact of the electrode with tissue. U.S. Pat. No. 5,879,295 to Li et al. discloses a device having multiple electrodes that may be manipulated in a similar manner, except that the two control wires are connected apart from each other near the distal end of the device. Such a configuration allows for the formation of more complex shapes in using the device. Further, U.S. Pat. No. 5,895,417 to Pomeranz et al. discloses a catheter having a resilient, looped end with a section with electrodes. Either end of the loop may be advanced or drawn back to provide various shapes in order that the effective section of the catheter may better conform to a region. The non-active section of the loop may be used to bias the loop against a wall opposite the ablating electrodes portion to press the electrodes into improved contact with the wall it abuts.
Also, steerable or deflectable tip catheters and catheters with preformed curved sections that may be straightened for delivery purposes have been used to provide an electrode interface region conformable with particular regions in the heart. EP devices having simple J or C-shaped curved sections are known. U.S. Pat. No. 5,170,787 to Lindegren discloses a catheter utilizing a J-shaped preformed wire wherein the device has an ablating electrode at the tip. Also, there are EP devices where the curved shape is extended. U.S. Pat. Nos. 5,673,695 and 5,860,920 to McGee et al. disclose a device with a generally-circular or pigtail electrode array that may conform to the circumferential geometry of a selected annulus region in the heart. Both preformed and deflectable means of achieving the desired shape are disclosed therein. U.S. Pat. No. 5,462,545 to Wang et al. discloses a device having electrodes where the device may be formed in a planar spiral and a corkscrew configuration in addition to a generally circular shape. Further, U.S. Pat. No. 5,823,955 to Kuck et al. discloses an EP device with a distal end portion curving in one direction and switching back in an opposite direction. In all, such shapes are provided to enable improved accessibility to and/or interface with a treatment site in the heart.
The present invention also addresses the need for improved accessibility to and/or interface with the heart wall. However, the present invention meets the challenges presented in the treatment of arrhythmia by forming lesions between the tricuspid annulus and the inferior vena cava, i.e., in the “isthmus” region of the heart. Such lesions may be highly effective in treating atrial flutter by breaking abnormal circuits. While the isthmus has become an area of increasing interest, treating the region is complicated by the irregularity of the anatomical geometry and variation of the region from one patient to another. Ridges, crevasses, bumps and the like make uniform contact with the atrial wall for ablation and/or mapping in this region difficult. None of the devices noted above can perform effectively in RF ablation of the isthmus region.
The present invention provides a device and methods specifically adapted to face the challenges in ablating the isthmus region. An EP device utilizing variations on a shape having particular functional advantages is provided. The advantageous shape of the device allows it to be manipulated in a new manner which forms part of the invention.
SUMMARY OF THE INVENTION
This invention is directed to a electrophysiology (EP) device suitable for mapping functions and/or forming ablations or lesions in the isthmus region of a human patient's heart. The EP device of the invention has electrodes along the outer surface of the device and may have temperature sensors to work in concert with the electrodes. When prepared for use the catheter-like device assumes a shape specialized to advantageously interface with the isthmus region to form lesions. Lesions formed may be made in the form of linear ablations particularly suitable for eliminating or minimizing atrial flutter and/or fibrillation by isolating sections of the patient's atrial wall.
The EP device of the invention generally comprises an elongated shaft having a lumen and a proximal section, a distal section, and a plurality of at leas
Chun Sung
Hilario Reynaldo P.
Hill, III E. Richard
Huynh Tim Ngeo
Obara Robert
Cardima, Inc.
Fitch Even Tabin & Flannery
Peffley Michael
Vrettakos Peter J
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