Surgery – Instruments – Electrical application
Reexamination Certificate
1999-07-23
2003-09-23
Kearney, Rosiland S. (Department: 3739)
Surgery
Instruments
Electrical application
C606S042000, C607S101000, C607S113000
Reexamination Certificate
active
06623480
ABSTRACT:
TECHNICAL FIELD
The present invention relates to the field of interventional cardiology and, more particularly, to a catheter and a related method for the ablation of atrial flutter utilizing radio frequency energy.
BACKGROUND OF THE INVENTION
Many advances have been made in interventional therapy for cardiac arrhythmias, as devices such as catheters for mapping and ablation of target areas have improved. Many arrhythmias are now frequently treated by using specially adapted radio frequency (RF) catheters. The successful treatment rate of RF catheters may reach >90% for certain cardiac arrhythmias. Moreover, RF ablation using a catheter does not require general anesthesia and recovery from the procedure is rapid.
Electrical conduction problems such as ventricular tachycardia and artioventricular node reentrant tachycardia are also routinely treated without general anesthesia utilizing radio frequency ablation. However, for those patients in whom maintenance of sinus rhythm is not possible (approximately 20% of patients over 60 years old), control of ventricular rate is achieved with AV nodal blockers such as digoxin, &bgr;-blockers, or calcium channel blockers. Although prior to the present invention, a “cure” of atrial fibrillation with catheter ablation techniques appeared not to be possible, various attempts had been made at permanent modification of the AV conduction such that rapid conduction could be eliminated, but normal conduction (fewer than 100 beats per minute) remains, thereby avoiding the need for a permanent pacemaker. Unfortunately, these attempts have been unsuccessful. See, Vogel & King, The Practice of Interventional Cardiology, 2
nd
Ed., pages 671-683 (1993).
Accordingly, specially adapted radio frequency ablation catheters designed for either general purpose or specific application are known in the art, some of which are widely used. For example, U.S. Pat. No. 5,507,802 to Irman, for “METHOD OF MAPPING AND/OR ABLATION USING A CATHETER HAVING A TIP WITH FIXATION MEANS.” (Irman '802) generally discloses a mapping and/or ablation catheter 11 having a flexible elongate tubular member 12, with a large central lumen 16 and a plurality of additional lumens 17 (see, column 2, lines 7-35). Anchoring or fixation means are carried by the distal tip 21 with means for selective engagement and disengagement of the fixation means. Irman '802 also discloses plural ring platinum electrodes 46, 47 near the distal tip and conducting means 48, 49 which extend through the additional lumens of the catheter for connection to a remote source of radio frequency energy (see, column 3, lines 14-20).
U.S. Pat. No. 5,673,695 to McGee et al. for “METHODS FOR LOCATING AND ABLATING ACCESSORY PATHWAYS IN THE HEART” (McGee et al. '695) discloses an ablation catheter having a multifunction element 40 (ring electrodes E1-E10) spaced apart and located near the distal tip for location/ablation of accessory electrical pathways of the heart (see, column 6, lines 7-52). The body 42 of the catheter can be constructed from a variety of flexible resilient materials and also may include an inner core of a suitable metal or super elastic material such as Nitinol® (see, column 5, lines 48-67).
U.S. Pat. No. 5,582,609 to Swanson et al., for “SYSTEMS AND METHODS FOR FORMING LARGE LESIONS IN BODY TISSUE USING CURVILINEAR ELEMENTS” (Swanson et al. '609) describes generally the need for catheters designed especially for treatment of atrial fibrillation and atrial flutter, having “the larger ablating mass required for these electrodes among separate multiple electrodes spaced apart along a flexible body” (see, column 1, lines 42-61). The '609 reference discloses both spaced apart ring electrodes and coiled spring configurations (see, FIGS. 36, and columns 6-7) and at column 8, lines 23-31 further describes the use of a sliding sheath 50 (FIG. 12). However, this sheath 50 slides within the lumen of catheter body 12 and is used to vary the impedance and the surface area contact of the coil electrode 46. The '609 reference specifically discloses the lesion patterns attainable with the device for treatment of atrial flutter and discloses how lesion characteristics can be controlled (see, column 9, lines 5-30).
U.S. Pat. No. 5,111,811 to Smits, for “CARDIOVERSION AND DEFRIBRILLATION LEAD SYSTEM WITH ELECTRODE EXTENSION INTO THE CORONARY SINUS AND GREAT VEIN.” discloses a screw anchor fixation assembly 76 having a rotatable corkscrew electrode 78 (see, FIG. 4 and column 6, lines 33-44.
U.S. Pat. No. 5,578,067 to Elkwall et al., for “MEDICAL ELECTRODE SYSTEM HAVING A SLEEVE.BODY AND CONTROL ELEMENT THEREFOR FOR SELECTIVELY POSITIONING AN EXPOSED CONDUCTOR AREA” discloses a sleeve like body 19 (sheath) having a window-like opening 18. The sheath 19 slides along the electrode cable 3 to vary the location of the exposed electrode 6a (see, FIG. 4, and column 5, lines 28-45).
Atrial flutter is a rapid abnormal rhythm of the atrium with the electrical impulse traveling around the orifice of the right atrium at the junction with the inferior vena cava, the major vein collecting blood from the lower body and returning it to the heart. This abnormal electrical impulse travels through a strip of heart muscle, termed the isthmus, located between this orifice and another orifice between the right atrium and right ventricle.
A total interruption of this pathway, i.e. the isthmus, by an interventional procedure such as RF ablation has been shown play a key role in successfully curing atrial flutter. The current technique utilizes a general purpose RF ablation catheter. The tip of the catheter is dragged across the entire width of the isthmus under fluoroscopic guidance to create a complete linear cut by RF energy. Using this technique requires a high skill level and may necessitate multiple attempts to achieve a proper cut. Thus, the procedure may be time consuming and result in heavy X-ray exposure. Furthermore, its availability is limited to selected major medical centers having a large patient population.
As should be appreciated, creation of a consistent and complete linear lesion requires full and stable contact between the electrode and the endocardial surface along the entire length of the cut. Currently available catheters including those described in the above-cited patents lack the ability to maintain such contact without either dragging the catheter or repositioning it several times during the procedure. Therefore, the procedure remains time consuming and highly dependent on the operator's skill level.
Accordingly, a need is identified for a radio frequency ablation catheter that is specially adapted for the treatment of atrial flutter that makes the treatment less time consuming and less dependent on the operator's skill. The catheter would be flexible to facilitate the bending necessary to place the electrodes used for ablation over the target area for treatment. Anchoring means would also be included to anchor the catheter in position to facilitate the bending operation and to ensure that the catheter remains in the proper position over the target area during the procedure, thereby avoiding the need for dragging or repositioning of the catheter during the procedure. Overall, such a catheter would be simpler to operate and thus require a lower skill level to successfully perform the ablation procedure.
OBJECTS OF THE INVENTION
It is a primary object of the present invention to provide a radio frequency ablation catheter and a related method of catheterization that overcomes the limitations and shortcomings of the above-referenced prior art devices and methods.
It is another object of the present invention to provide a radio frequency ablation catheter specially adapted for the treatment of atrial flutter that is simpler to operate, thereby making a successful outcome less dependent upon the skill of the operator.
Another object of the invention is to provide a catheter electrode for the purpose of ablative procedures using radio frequency energy that is more flexible than
Gurley John C.
Kuo Chien-Suu
Kearney Rosiland S.
King & Schickli PLLC
University of Kentucky Research Foundation
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