Surgery – Diagnostic testing – Cardiovascular
Reexamination Certificate
2001-03-13
2003-06-24
Schaetzle, Kennedy (Department: 3762)
Surgery
Diagnostic testing
Cardiovascular
C128S901000
Reexamination Certificate
active
06584345
ABSTRACT:
FIELD OF THE INVENTION
This invention is directed to apparatus and methods for measuring a plurality of electrical signals from an electrode array preferably situated in the body of a patient, and is especially suited for measuring a plurality of weak electrical signals emanating from a patient's heart using intracardiac non-contact electrodes.
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.
Commonly assigned U.S. Pat. No. 5,546,951; and PCT application WO 96/05768 and its corresponding U.S. patent application Ser. No. 08/793,371 filed on May 14, 1997, all of which are incorporated herein in their entirety by reference, disclose methods for sensing an electrical property of 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 having electrical and location sensors in their distal tips that are advanced into the heart. Electrical signals are generally acquired with an electrode located at the catheter distal tip after determining that the tip is in stable and steady contact with the endocardium. 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. Nos. 09/122,137 and 09/357,559 filed on Jul. 24, 1998 and Jul. 22, 1999, respectively, 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 is often combined with data taken at additional points in order to generate a more comprehensive map of the heart's electrical activity. In clinical settings, it is not uncommon to accumulate data at 100 or more sites to generate a detailed, comprehensive map of heart chamber electrical activity. The generated detailed map 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 motion characteristics such as the contractility of the tissue. As disclosed in U.S. Pat. No. 5,738,096 which is incorporated herein in its entirety by reference, maps depicting such motion characteristics may be constructed when the trajectory information is sampled at a sufficient number of points in the heart.
A drawback with mapping a cardiac chamber using a catheter containing only a single, distal tip electrode is the long period of time required to accumulate data on a point-by-point basis over the requisite number of points required for a detailed map of the chamber as a whole. Accordingly, multiple-electrode catheters have been developed to simultaneously measure electrical activity at multiple points in the heart chamber. Cardiac electrical activity data has been acquired with multi-electrode catheters using contact as well as non-contact methods.
U.S. Pat. No. 5,487,391, directed to systems and methods for deriving and displaying the propagation velocities of electrical events in the heart, is illustrative of contact methods found in the art. In the system disclosed in the '391 patent, the electrical probe is a three-dimensional structure that takes the form of a basket. In the embodiment illustrated in the '391 patent, the basket is composed of 8 splines, each of which carries eight electrodes, for a total of 64 electrodes in the probe. The basket structure is designed such that when deployed, its electrodes are held in intimate contact against the endocardial surface. A problem with the catheters disclosed in the '391 patent is that they are both difficult and expensive to produce. The large number of electrodes in such catheters is also very demanding of the data recording and processing subsystem. There are additional complexities associated with the deployment and withdrawal of these catheters, and increased danger of blood coagulation.
U.S. Pat. No. 5,848,972 to Triedman et al. discloses a method for endocardial activation mapping using a multi-electrode catheter. In the method of the '972 patent, a multi-electrode catheter, preferably, a 50-electrode Webster-Jenkins™ basket catheter from Cordis-Webster of Baldwin Park, Calif., is advanced into a chamber of the heart. Anteroposterior (AP) and lateral fluorograms are obtained to establish the position and orientation of each of the electrodes. Electrograms are recorded from each of the electrodes in contact with the cardiac surface relative to a temporal reference such as the onset of the P-wave in sinus rhythm from a body surface ECG. Interestingly, Triedman et al. differentiate between those electrodes that register electrical activity and those that do not due to absence of close proximity to the endocardial wall. After the initial electrograms are recorded, the catheter is repositioned, and fluorograms and electrograms are once again recorded. An electrical map is then constructed from the above information.
U.S. Pat. No. 4,649,924 to Taccardi discloses a method for the detection of intracardiac electrical potential fields. The '924 patent is illustrative of the non-contact methods that have been proposed to simultaneously acquire a large amount of cardiac electrical information. In the method of the '924 patent, a catheter having a distal end portion is provided with a series of sensor electrodes distributed over its surface. The electrodes are connected to insulated electrical conductors for connection to signal sensing and processing means. The size and shape of the catheter distal end portion are such that the electrodes are spaced substantially away from the wall of the cardiac chamber. The electrodes are preferably distributed on a series of circumferences lying in planes spaced from each other and perpendicular to the major axis of the end portion of the catheter. At least two additional electrodes are provided adjacent the ends of the major axis of the end portion. The '924 patent discloses a single exemplary embodiment in which the catheter comprises eight electrodes spaced equiangularly on each of four circumferences. Thus, in that exemplary embodiment, the catheter comprises 34 electrodes (32 circumferential and two end electrodes). The method of the '924 patent is said to detect the intracardiac potential fields in only a single cardiac beat.
PCT application WO 99/06112 to Rudy, the disclosure of which is incorporated herein by reference, discloses an electrophysiological cardiac mapping system and method based on a non-contact, non-expanded multi-electrode catheter. Electrograms are obtained with catheters having from 42 to 122 electrodes. In addition to the above-described problem of complexity of multi-electrode catheters, the Rudy method requires prior knowledge of the relative geometry of the probe and the endocardium, which must be obtained via an independent imaging modality such as transesophogeal echocardiography. In the Rudy method, after the independent imaging, non-contact electrodes are used to measure cardiac surface potentials and construct maps therefrom.
U.S. Pat. No. 5,297,549 to Beatty et al., the disclosure of which is incorporated herein by reference, discloses a method and apparatus for mapping the electrical potential distribution of a heart chamber. In the Beatty method, an intra
Biosense Inc.
Capezzuto Louis J.
Droesch Kristen
Herman Frederick L.
Schaetzle Kennedy
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