Surgery – Instruments – Electrical application
Reexamination Certificate
1999-09-10
2001-11-13
Dvorak, Linda C. M. (Department: 3739)
Surgery
Instruments
Electrical application
C606S046000, C606S047000, C607S101000, C607S122000
Reexamination Certificate
active
06315778
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to medical devices for performing ablative procedures and, more particularly, to a medical device which is capable of ablating a continuous ring of tissue in a single step.
BACKGROUND OF THE INVENTION
The human heart is a very complex organ, which relies on both muscle contraction and electrical impulses to properly function. The electrical impulses travel through the heart walls, first through the atria and then the ventricles, causing the corresponding muscle tissue in the atria and ventricles to contract. Thus, the atria contract first, followed by the ventricles. This order is essential for proper functioning of the heart.
Over time, the electrical impulses traveling through the heart can begin to travel in improper directions, thereby causing the heart chambers to contract at improper times. Such a condition is generally termed a cardiac arrhythmia, and can take many different forms. When the chambers contract at improper times, the amount of blood pumped by the heart decreases, which can result in premature death of the person.
Non-surgical procedures, for example, management with drugs, are favored in the treatment of cardiac arrhythmias. However, some arrhythmias are not treatable with drugs. For example, drug therapy to combat certain types of cardiac arrhythmias has been found to be successful in only 30 to 50 percent of patients. Because of this low success rate, another conventional remedy is to perform a surgical procedure. According to these procedures, various incisions are made in the heart to block conduction pathways in an effort to abolish the arrhythmia.
Minimally invasive techniques have been developed which are used to locate cardiac regions responsible for the cardiac arrhythmia, and also to disable the short-circuit function of these areas. According to these techniques, electrical energy is applied to a portion of the heart tissue to ablate that tissue and produce scars which interrupt the reentrant conduction pathways. The regions to be ablated are usually first determined by endocardial mapping techniques. Mapping typically involves percutaneously introducing a catheter having one or more electrodes into the patient, passing the catheter through a blood vessel (e.g. the femoral vein or aorta) and into an endocardial site (e.g., the atrium or ventricle of the heart), and inducing a tachycardia so that a continuous, simultaneous recording can be made with a multichannel recorder at each of several different endocardial positions. When a tachycardia focus is located, as indicated in the electrocardiogram recording, it is marked by means of a fluoroscopic image so that cardiac arrhythmias at the located site can be ablated. An ablation catheter with one or more electrodes can then transmit electrical energy to the tissue adjacent the electrode to create a lesion in the tissue. One or more suitably positioned lesions will typically create a region of necrotic tissue which serves to disable the propagation to the errant impulse caused by the tachycardia focus.
Ablation is carried out by applying energy to the catheter electrodes once the electrodes are in contact with the cardiac tissue. The energy can be, for example, RF, DC, ultrasound, microwave, or laser radiation. When RF energy is delivered between the distal tip of a standard electrode catheter and a backplate, there is a localized RF heating effect. This creates a well-defined, discrete lesion slightly larger than the tip electrode (i.e., the “damage range” for the electrode), and also causes the temperature of the tissue in contact with the electrode to rise.
It has been found that to overcome focal arrhythmias (a form of cardiac arrhythmia), it is often necessary to create a continuous, annular lesion around the ostia (i.e., the openings) of either veins or arteries leading to or from the atria. Conventional techniques include applying multiple point sources around the ostia in an effort to create a continuous lesion. Such a technique is relatively involved, and requires significant skill and attention from the clinician performing the procedure.
Accordingly, it will be apparent that there continues to be a need for a device for performing ablations which facilitates the creation of continuous, annular lesions. In addition, there exists the need for such a device which may pass through relatively narrow passageways to arrive at the site of interest. The instant invention addresses these and other needs.
SUMMARY OF THE INVENTION
According to one aspect of the invention, a deformable electrode structure is extended over a tubular inner member, such as a catheter shaft, guide wire, or the like. The electrode structure is deformable to assume a distally facing, ablative ring, to simultaneously ablate a ring of tissue, and is also collapsible to facilitate manipulation of the device through a patient's vasculature.
In one illustrative embodiment, the electrode structure is in the form of an elongated, braided electrode which is slidably extended over the inner member. An actuating member is also slidably extended over the inner member and is connected to the braided electrode. Advancement of the actuating member distally relative to the inner member causes the braided electrode structure to expand radially outwardly and assume a generally disk shape. Further advancement of the actuating member causes the braided electrode structure to buckle and thereby assume a generally conical shape which defines the distally facing, ablative ring.
In another illustrative embodiment, the invention includes a stabilizing and centering member which is configured for insertion into a patient's vessel (e.g., an artery or vein leading to or from a chamber of interest) and is expandable inside the lumen to center the device relative to the lumen, and to anchor the device in place for reliable deployment of the ablating electrode.
Thus, in one illustrative embodiment, the present invention is directed to a medical device which includes: an inner tubular member; a braided, electrically conductive member slidably extended over the tubular member; first and second sheaths slidably extended over the tubular member and connected to respective ends of the braided conductive member; a stop formed on the inner tubular member at a location distal of the distal-most sheath; wherein the first sheath is advanceable distally over the inner tubular member to force the second sheath against the stop and cause the conductive member to assume a generally conical configuration and define a distally facing ablative ring.
In another illustrative embodiment, the invention is directed to a medical device for ablating a ring of tissue, including: an elongated inner member; a braided, electrically conductive member slidably extended over the tubular member; and means for deforming the braided, electrically conductive member to define a ring of ablative material.
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patent
Falwell Gary S.
Forde Sean
Gambale Richard
Haissaguerre Michel
Patterson Donald
C. R. Bard Inc.
Darby & Darby
Dvorak Linda C. M.
Ruddy David
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