Surgery – Diagnostic testing – Detecting nuclear – electromagnetic – or ultrasonic radiation
Reexamination Certificate
1999-08-09
2001-05-15
Casler, Brian L. (Department: 3737)
Surgery
Diagnostic testing
Detecting nuclear, electromagnetic, or ultrasonic radiation
C607S122000
Reexamination Certificate
active
06233477
ABSTRACT:
FIELD OF THE INVENTION
The present invention generally relates to improved constructions for a catheter system. More particularly, this invention relates to catheters and methods for mapping cardiac arrhythmias and ablative cardiac tissues via a steerable catheter system having ultrasound locating capabilities, comprising a locator catheter and an ultrasound receiver catheter having location-controllable transducers, resulting in an effective electrophysiology procedure without undesired side effects of using a conventional x-ray imaging system.
BACKGROUND OF THE INVENTION
Symptoms of abnormal heart rhythms are generally referred to as cardiac arrhythmas, with an abnormally rapid rhythm being referred to as a tachycardia. The present invention is concerned with the treatment of tachycardias which are frequently caused by the presence of an “arrhythmogenic site” or “accessory atrioventricular pathway” close to the inner surface of the chambers of a heart. The heart includes a number of nonnal pathways which are responsible for the propagation of electrical signals from the upper to the lower chambers necessary for performing normal systole and diastole function. The presence of arrhythmogenic site or accessory pathway can bypass or short circuit the normal pathway, potentially resulting in very rapid heart contractions, referred to herein as tachycardias.
Treatment of tachycardias may be accomplished by a variety of approaches, including drugs, surgery, implantable pacemakers/defibrillators, and catheter ablation. While drugs may be the treatment of choice for many patients, they only mask the symptoms and do not cure the underlying causes. Implantable devices only correct the arrhythmia after it occurs. Surgical and catheter-based treatments, in contrast, will actually cure the problem, usually by ablative the abnormal arrhythmogenic tissue or accessory pathway responsible for the tachycardia. It is important for a physician to accurately steer the catheter to the exact site for ablation. Once at the site, it is important for a physician to control the emission of energy to ablate the tissue within the heart.
Of particular interest to the present invention are radiofrequency (RF) ablation protocols which have proven to be highly effective in tachycardia treatment while exposing a patient to minimal side effects and risks. Radiofrequency catheter ablation is generally performed after conducting an initial mapping study where the locations of the arrhythmogenic site and/or accessory pathway are determined. After a mapping study, an ablation catheter is usually introduced to the target heart chamber and is manipulated so that the ablation tip electrode lies exactly at the target tissue site. Radiofrequency energy or other suitable energy is then applied through the electrodes to the cardiac tissue in order to ablate the tissue of arrhythmogenic site or the accessory pathway. By successfully destroying that tissue, the abnormal signal patterns responsible for the tachycardia may be eliminated.
The mapping and ablation procedures require means to locate the catheter, especially the tip section of said catheter, to the exact site of the arrhythmogenic sources. The conventional method uses x-ray fluoroscope to image the location of the catheter. While x-ray imaging is quite successful, some patients, such as the pregnant women, the fluoro-phobic patients and the like, can tolerate little x-ray exposure. It is imperative that other imaging means be used to locate the catheter within the body of a patient.
Ultrasound imaging has been used extensively to reveal the existence of a device having the ultrasound emitter. In the U.S. Pat. No. 4,794,931, there has been disclosed a catheter and system which can be utilized for ultrasonic imaging. However, there is no disclosure on the technique of using ultrasound locating means to generate the three-dimensional location data. Based on recent advances in computer data analysis capability, the speed of analyzing the data obtained from a 3-D ultrasound locating system becomes feasible.
Though a 3-D ultrasound locating system is useful, sometimes one of the multiple signal receivers may approximately overlap on the other signal receiver so that the locating capability is compromised. To alleviate this potential weakness, a location-controllable signal receiver of ultrasound transducers that are movable with known location coordinates becomes important.
While an electrophysiology mapping and/or ablation procedure using an existing catheter has had promising results under x-ray imaging, reduction or elimination of x-ray exposure becomes a clinical need and a health issue to certain types of patients undergoing the catheter-based treatment. Therefore there is a need for an improved catheter system having ultrasound locating capabilities that comprises a location-controllable signal means for optimizing the 3-D locating of a catheter system.
SUMMARY OF THE INVENTION
In general, it is an object of the present invention to provide an improved catheter system for positioning the mapping and/or ablation catheter. It is another object of the present invention to provide a catheter system having the capability to generate three-dimensional location coordinates for the mapping and/or ablation catheter. It is still another object of the present invention to provide a catheter system using the ultrasound locating technique that comprises at least one location-controllable signal receiver of ultrasound transducers that are movable with known location three-dimensional coordinates. It is another object of the present invention to provide a catheter system with ultrasound receiving means inserted in the body of a patient for three-dimensional locating capabilities. It is another object of the present invention to provide a catheter system with ultrasound receiving means external of the body of a patient for three-dimensional locating capabilities.
It is still another object of the present invention to provide a catheter system comprising a locator catheter and a reference receiver catheter, wherein a plurality of ultrasound crystal beacons are secured on said catheters having emitting and receiving ultrasonic signals capabilities. In one embodiment, at least one ultrasound crystal is secured on the locator catheter and at least three crystals are secured on the reference catheter. To further identify and calibrate the location of the locator catheter, at least four crystals are secured on the reference catheter in an alternate embodiment. At least one crystal beacon is movable by a beacon deployment mechanism at the handle, said ultrasound crystal beacons having coordinates that are pre-set with reference to an external location calibration system, wherein said beacons can emit and receive ultrasound signals.
REFERENCES:
patent: 5480422 (1996-01-01), Ben-Haim
patent: 5722402 (1998-03-01), Swanson et al.
patent: 5735280 (1998-04-01), Sherman et al.
patent: 5840031 (1998-11-01), Crowley
patent: 5868673 (1999-02-01), Vesely
patent: 5954649 (1999-09-01), Chia et al.
Chia Weng-Kwen Raymond
Tu Hosheng
Casler Brian L.
Irvine Biomedical , Inc.
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