Method and apparatus for mapping a chamber of a heart

Surgery – Diagnostic testing – Cardiovascular

Reexamination Certificate

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C606S130000, C382S131000, C382S173000, C382S174000

Reexamination Certificate

active

06368285

ABSTRACT:

FIELD OF THE INVENTION
The invention relates generally to methods and apparatus for mapping a condition or property of an organ of a subject, and particularly to methods and apparatus for mapping the electrical and/or the mechanical activity of one or more chambers of the heart.
BACKGROUND OF THE INVENTION
Cardiac arrhythmias, the most common of which is ventricular tachycardia (VT), are a leading cause of death. In a majority of patients, VT originates from a 1 mm to 2 mm lesion located close to the inner surface of the heart chamber. One of the treatments for VT comprises mapping the electrical pathways of the heart to locate the lesion followed by ablation of the active site.
U.S. Pat. No. 5,546,951 and U.S. patent application Ser. No. 08/793,371 and its corresponding application filed under the Patent Cooperation Treaty and published as WO 96/05768, which are incorporated herein in their entirety by reference, disclose methods for sensing an electrical property of the heart tissue, for example, local activation time, as a function of the precise location within the heart. The data are acquired with one or more catheters that are advanced into the heart, the catheters having electrical and location sensors in their distal tips. Methods of creating a map of the electrical activity of the heart based on these data are disclosed in commonly assigned U.S. patent application Ser. No. 09/122,137 filed on Jul. 24, 1998 and in its corresponding published European Patent Application no. EP 974,936, as well as in U.S. patent application Ser. No. 09/357,559 filed on Jul. 22, 1999, the disclosures of which are also incorporated herein in their entirety by reference. As indicated in these applications, location and electrical activity is preferably initially measured at about 10 to about 20 points on the interior surface of the heart. These data points are then generally sufficient to generate a preliminary reconstruction or map of the cardiac surface to a satisfactory quality. The preliminary map may be combined with data taken at additional points in order to generate a more comprehensive map of the heart's electrical activity. The detailed map so obtained may then serve as the basis for deciding on a therapeutic course of action, for example, tissue ablation, to alter the propagation of the heart's electrical activity and to restore normal heart rhythm.
Catheters containing position sensors may be used to determine the trajectory of points on the cardiac surface. These trajectories may be used to infer the motion characteristics such as the contractility of the tissue. As disclosed in U.S. Pat. Nos. 5,738,096 and 6,066,094, incorporated herein in depicting such motion characteristics may be constructed when the trajectory information is sampled at a sufficient number of points in the heart. A high quality preliminary map of motion characteristics is dependent on acquiring a sufficient number of points representatively spaced about the heart chamber volume.
In constructing these preliminary maps, it is desirable that the data are sampled at points sufficiently spaced to outline the entire volume of the chamber under study. If the preliminary map adequately outlines the heart volume, acquisition of additional points will generally enable the detailed reconstruction to permit accurate diagnosis and treatment. Occasionally however, incomplete sampling, as, for example, by localizing the sample points to only a portion of the heart volume, will result in the generation of an incomplete map. Further sampling may lead to a more detailed map of the partial cardiac volume, but this may be inadequate for proper diagnosis and treatment.
In creating maps of the heart using the above-referenced systems, the initial data points for the preliminary reconstruction are generally acquired under the guidance of an imaging modality such as fluoroscopy that permits the cardiologist to observe the placement of the catheter tip within the heart chamber. Once the preliminary map is generated, subsequent points may then be acquired under the guidance of the preliminary map and a location system based on, for example, electromagnetic or acoustic sensors. Unfortunately, unassisted fluoroscopy provides relatively poor visualization of topographical features within the heart. While contrast-assisted fluoroscopy, in which a contrast agent is injected into the heart chamber under examination, significantly improves the observation of topography, the contrast agent obscures the observation of the catheter tip. Thus, fluoroscopy is insufficient to properly guide the cardiologist to the points on the interior of the heart necessary for the generation of a preliminary map of the electrical activity that roughly encompasses the complete heart volume. The potentially harmful effects of the contrast agent and of ionizing radiation to the patient also limit the amount of data that can be collected under fluoroscopy.
Electrical activity at a point in the heart is typically measured by advancing a catheter containing an electrical sensor (an electrode) at or near its distal tip to that point in the heart, firmly contacting the tissue with the electrode and acquiring data at that point. Alternatively, electrical activity may be measured with catheters containing multiple electrodes. In the case of catheters with multiple electrodes, one or more electrodes are generally present at the catheter tip and other electrodes may be present along the catheter body.
It is generally important to maintain good electrical contact between the electrodes and the tissue in order to obtain a reliable and stable electrical reading. Fluoroscopy produces images that are lacking in topographical detail. Accordingly, in taking measurements under the guidance of this imaging modality, the catheter tip may not actually be in effective contact with the tissue. Alternatively, it may be possible to bruise the intracardial tissue by excessive pressure of the catheter tip against the tissue while making such measurements.
PCT application WO 98/35720 discloses an x-ray guided surgical location system with extended mapping volume. The application does not teach or suggest navigation of a catheter tip for the purpose of mapping a chamber of a heart guided by topological information contained in acquired images of the chamber.
U.S. Pat. No. 5,391,199 discloses an apparatus and method for treating cardiac arrhythmias. The method of the '199 patent comprises obtaining a perspective image of the organ to be mapped; advancing one or more catheters to sites adjacent to or within the organ; sensing the location of each of the catheter's distal tips with a non-ionizing field; sensing local information of the organ; processing the local information to create one or more data points; and superimposing the one or more data points on the perspective image of the organ or structure. The '199 patent does not teach or suggest the registration of the image with a positional frame of reference of a position sensor contained in or proximate to the catheter tip. Furthermore, the '199 patent does not teach or suggest navigating the catheter tip under the guidance of topological information contained in acquired images of the chamber.
U.S. Pat. No. 5,433,198 discloses an apparatus and method for cardiac ablation. The apparatus and method of the '198 patent includes a multi-electrode catheter introduced percutaneously into a subject's heart and deployable adjacent to various endocardial sites. The electrodes are connectable to a mapping unit, an ablation power unit and a pacing unit, all of which are under computer control. Intracardiac electrogram signals emanated from a tachycardia site of origin are detectable by the electrodes. Their arrival times are processed to generate various visual maps to purportedly provide real-time guidance for steering the catheter to the tachycardia site of origin. In one aspect, the apparatus of the '198 patent also includes a physical imaging system which is capable of providing different imaged ph

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