The invention generally relates to systems and methods for guiding or locating diagnostic or therapeutic electrode elements in the interior regions of the body. More particularly, the invention relates to guiding or locating diagnostic or therapeutic electrode elements inside the heart for treatment of cardiac conditions.
Physicians make use of catheters today in medical procedures to gain access into interior regions of the body f or diagnostic and therapeutic purposes. It is important for the physician to be able to precisely position the catheter within the body to gain contact with a desired tissue location.
The need for precise control over the catheter is especially critical during procedures that ablate myocardial tissue from within the heart. These procedures, called ablation therapy, are used to treat cardiac rhythm disturbances.
During these procedures, a physician steers a catheter through a main vein or artery into the interior region of the heart that is to be treated. The physician then further manipulates a steering mechanism to place the electrode carried on the distal tip of the catheter into direct contact with the endocardial tissue. The physician directs energy from the electrode through myocardial tissue either to an indifferent electrode (in a uni-polar electrode arrangement) or to an adjacent electrode (in a bipolar electrode arrangement) to ablate the tissue.
Before ablating heart tissue, physicians often examine the propagation of electrical impulses in heart tissue to locate aberrant conductive pathways and to identify the arrhythmia foci, which are ablated. The techniques used to analyze these pathways and locate foci are commonly called xe2x80x9cmapping.xe2x80x9d
Conventional cardiac tissue mapping techniques use multiple-electrodes positioned in contact with heart tissue to obtain multiple electrograms. These conventional mapping techniques require invasive open-heart surgical techniques to position the electrodes on the interior or exterior surfaces of the heart.
An alternative technique of introducing multiple-electrode arrays into the. heart through venous or arterial accesses to map myocardial tissue is known. Compared to conventional, open heart mapping techniques, endocardial mapping techniques, being comparatively noninvasive, hold great promise. Multiple electrogram signals obtained from within the heart can be externally processed to detect local electrical events and identify likely foci.
Once mapping identifies the foci, an ablation electrode is steered into position in contact with a focus site. At least, in theory, this is the goal sought to be achieved. In actuality, though, the task of remotely guiding an ablation element within the blood pool of a beating heart to a particular focus site can be, at best, problematic.
There is the need to provide simple, yet reliable, ways of guiding electrode elements within the, heart, or within other interior parts of the body, to precise locations targeted for diagnosis or treatments.
This invention has as its principal objective the realization of safe and efficacious systems and methods for remotely locating electrode elements at precise locations within the body.
One aspect of the invention provides a system and related method for guiding a movable electrode within an array of multiple-electrodes located within the body. The system and method couple an emitting electrode to an electrical energy-generating element. The emitting electrode comprises either the movable electrode or at least one of the electrodes in the array. The generating element conditions the emitting electrode to emit electrical energy while the movable electrode is located within the array.
According to this aspect of the invention, the system and method couple a sensing electrode to a sensing element. The sensing electrode comprises either the movable electrode or at least one of the electrodes in the array. The sensing element conditions the sensing electrode to sense electrical energy emitted by the emitting electrode.
Further in accordance with this aspect of the invention, the system and method couple a processing element to the sensing element. The processing element analyzes sensed electrical energy and generates, based upon its analysis, an output that locates the movable electrode within the array.
Another aspect of the invention provides a system and method for ablating tissue within the heart. The system and method are usable in conjunction with an array of multiple-electrodes located within the heart to locate foci appropriate for ablation and an ablation electrode that is movable within the array for applying ablating energy to the foci.
According to this aspect of the invention, the system and method condition an emitting electrode to emit electrical energy while the ablation electrode is present within the array. The emitting electrode comprises either the ablation electrode or at least one of the electrodes in the array. While the ablation electrode is present within the array, the system and method also sense the emitted electrical energy with a sensing electrode. The sensing electrode comprises either the ablation electrode or at least one of the electrodes in the array. The system and method process the sensed electrical energy to generate an output locating the ablation electrode relative to the multiple-electrodes on the array.
In a preferred embodiment, the system and method continuously generate the location indicating output while the physician moves the ablation electrode within the array. In this way, the system and method aid the physician in guiding the ablation electrode to the targeted ablation site.
In a preferred embodiment, the systems and methods that incorporate either aspect of the invention generate an electric field within the array, while sensing electrode electric potentials in the electric field. In this embodiment, the processing element generates the output by analyzing spatial variations in the electrical potentials within the array. The variations can comprise variations in phase, variations in amplitude, or both. Alternatively, the processing element generates the output by analyzing spatial variations in impedances between the emitting and sensing electrodes.
In a preferred embodiment, the systems and methods that incorporate either aspect of the invention inject electrical energy into body tissue, while sensing tissue response to the injected electrical energy. In. this embodiment, the processing element generates the output by analyzing differences in the sensed tissue response. In one implementation, the processing element analyzes time differences in the sensed tissue response. In another implementation, the sensing element senses the depolarization of myocardial tissue, and the processing element analyses time differences in sensed tissue depolarization.
Yet another aspect of the invention provides a system and method for ablating tissue within the heart. The system and method locate an array of multiple-electrodes in contact with tissue within the heart to sense electrical activity in heart tissue to locate foci appropriate for ablation. The system and method also locates a movable ablation electrode within the array. The system and method condition an emitting electrode comprising either the ablation electrode or at least one of the electrodes in the array to emit ultrasonic energy while the ablation electrode is located within the array. While the ablation electrode is located within the array, the system and method also sense the emitted ultrasonic energy with a sensing electrode. The sensing electrode comprises the ablation electrode, if the ablation electrode is not the emitting electrode, or, otherwise, at least one of the electrodes in the array. The system and method process the sensed ultrasonic energy to generate an output locating the ablation electrode relative to the multiple-electrodes in the array.
In a preferred embodiment of this aspect of the invention, the system and method move the ablation electrode within the array while repeating the emitting, sensing, and processing steps just described. The result is an output that continuously locates the ablation electrode as it moves within the array.
Other features and advantages of the inventions are set forth in the following Description and Drawings, as well as in the appended Claims.