Cardiac catheter imaging system

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No. 60/325,707, filed Sep. 28, 2001.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable.

REFERENCE TO A “SEQUENTIAL LISTING,” A TABLE, OR A COMPUTER PROGRAM LISTING APPENDIX SUBMITTED ON A COMPACT DISC

Not Applicable.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention involves catheters usable in medical evaluations of a condition of a living body, and more particularly, catheters that can detect based on electric, ultrasonic, or other types of sensing methods.

2. Description of Related Art

The related art can be reviewed via published patent applications, issued patents, and scholarly articles published in various medical and scientific journals. First, the following are the published applications and issued patents.

Published Patent Applications

The full disclosures of the following published patent applications are all incorporated herein by this reference:

• 20010021841 Title: “Automated longitudinal position translator for ultrasonic imaging probes, and methods of using same”

This discloses a longitudinal position translator that includes a probe drive module and a linear translation module. The probe drive module is coupled operatively to an ultrasonic imaging probe assembly having a distally located ultrasound transducer subassembly in such a manner that longitudinal shifting of the transducer subassembly may be effected.

• 20010021811 Title: “Method and apparatus for intravascular two-dimensional ultrasonography”

This discloses a catheter for insertion in the blood vessel of a patient for ultrasonically imaging the vessel wall. The catheter includes a tubular element and an internally housed drive cable for effective circumferential scan about the catheter of an ultrasonic generating means.

• 20010021805 Title: “Method and apparatus using shaped field of repositionable magnet to guide implant

This discloses methods and apparatuses for displaying and using a shaped field of a repositionable magnet to move, guide, and/or steer a magnetic seed or catheter in living tissue for medicinal purposes.

• 20010020149 Title: “Safety mechanism and methods to prevent rotating imaging device from exiting a catheter”

This discloses systems and methods to prevent rotation of an imaging device if the imaging device is advanced beyond a distal end of a catheter.

• 20010020126 Title: “Systems And Methods For Visualizing Tissue During Diagnostic Or Therapeutic Procedures”

This discloses a catheter tube that carries an imaging element for visualizing tissue. The catheter tube also carries a support structure, which extends beyond the imaging element for contacting surrounding tissue away from the imaging element. The support element stabilizes the imaging element, while the imaging element visualizes tissue in the interior body region. The support structure also carries a diagnostic or therapeutic component to contact surrounding tissue.

• 20010016687 Title: “Ultrasound imaging guidewire with static central core and tip”

This discloses an ultrasound imaging guidewire, that is inserted into a patient's body. The guidewire has a static central core and an imaging guidewire body comprising an acoustical scanning device. The acoustical scanning device can be rotated to obtain 360 degree acoustical images of a site of interest in the patient's body.

• 20010011889 Title: “Magnetic resonance imaging device”

This discloses an imaging probe having all components necessary to allow magnetic resonance measurements and imaging of local surroundings of the probe.

• 20010009976 Title: “Systems for recording use of structures deployed in association with heart tissue”

This discloses an image controller that generates an image of a structure while in use with heart tissue in a patient.

• 20010007940 Title: “Medical device having ultrasound imaging and therapeutic means”

This discloses an ultrasound transducer for ultrasound imaging, RF thermal therapy, cryogenic therapy and temperature sensing, for treating a tissue or lesion.

Issued Patents

The full disclosures of the following patents are all incorporated herein by this reference:

• U.S. Pat. No. 6,283,920 Ultrasound transducer assembly
• U.S. Pat. No. 6,277,077 Catheter including ultrasound transducer with emissions attenuation
• U.S. Pat. No. 6,267,727 Methods and apparatus for non-uniform rotation distortion detection in an intravascular ultrasound imaging system
• U.S. Pat. No. 6,266,564 Method and device for electronically controlling the beating of a heart
• U.S. Pat. No. 6,263,229 Miniature magnetic resonance catheter coils and related methods
• U.S. Pat. No. 6,251,078 Preamplifier and protection circuit for an ultrasound catheter
• U.S. Pat. No. 6,246,899 Ultrasound locating system having ablation capabilities
• U.S. Pat. No. 6,233,477 Catheter system having controllable ultrasound locating means
• U.S. Pat. No. 6,216,026 Method of navigating a magnetic object, and MR device
• U.S. Pat. No. 6,210,356 Ultrasound assembly for use with a catheter
• U.S. Pat. No. 6,200,269 Forward-scanning ultrasound catheter probe
• U.S. Pat. No. 6,192,144 MR method for the image-assisted monitoring of the displacement of an object, and MR device for carry out the method
• U.S. Pat. No. 6,178,346 Infrared endoscopic imaging in a liquid with suspended particles: method and apparatus
• U.S. Pat. No. 6,173,205 Electrophysiology catheter
• U.S. Pat. No. 6,165,127 Acoustic imaging catheter and the like
• U.S. Pat. No. 6,162,179 Loop imaging catheter
• U.S. Pat. No. 6,152,878 Intravascular ultrasound enhanced image and signal processing
• U.S. Pat. No. 6,149,598 Ultrasound endoscope
• U.S. Pat. No. 6,149,596 Ultrasonic catheter apparatus and method
• U.S. Pat. No. 6,240,307 Endocardial mapping system
• U.S. Pat. No. 5,662,108 Electrophysiology mapping system
• U.S. Pat. No. 5,713,946 Apparatus and method for intrabody mapping
• U.S. Pat. No. 5,546,951 Method and apparatus for studying cardiac arrhythmias
• U.S. Pat. No. 5,480,422 Apparatus for treating cardiac arrhythmias
• U.S. Pat. No. 6,277,077 Catheter including ultrasound transducer with emissions attenuation
• U.S. Pat. No. 6,216,027 System for electrode localization using ultrasound
• U.S. Pat. No. 6,014,579 Endocardial mapping catheter with movable electrode
• U.S. Pat. No. 6,443,894 Medical diagnostic ultrasound system and method for mapping surface data for three dimensional imaging

The following related art comes from scholarly articles published in various medical and scientific journals. The numbers in brackets refer to the reference numbers listed at the end of the specification.

Heart rhythm disorders (atrial and ventricular arrhythmias) result in significant morbidity and mortality. Atrial fibrillation is the most common cardiac arrhythmia: it affects more than two million Americans, is responsible for one-third of all strokes over the age of 65 years, and annually costs 9 billion dollars to manage [1]. Furthermore, about 300,000 Americans die of sudden cardiac death annually, primarily due to ventricular tachyarrhythmias (ventricular tachycardia and fibrillation) which result in intractable, extremely rapid heartbeats [2]. Unfortunately, current pharmacological therapy for managing cardiac arrhythmias is often ineffective and, at times, can cause arrhythmias [3,4], thereby shifting emphasis to nonpharmacological therapy (such as ablation, pacing, and defibrillation) [5–8]. Catheter ablation has been successful in managing many atrial and a few ventricular tachyarrhythmias [9]. However, due to limitations in present mapping techniques, brief, chaotic, or complex arrhythmias such as atrial fibrillation and ventricular tachycardia cannot be mapped adequately, resulting in unsuccessful elimination of the arrhythmia. In addition, localizing abnormal beats and delivering and quantifying the effects of therapy such as ablation are very time consuming. Selecting appropriate pharmacological therapies and advancing nonpharmacological methods to manage cardiac arrhythmias are contingent on developing mapping techniques that identify mechanisms of arrhythmias, localize their sites of origin with respect to underlying cardiac anatomy, and elucidate effects of therapy. Therefore, to successfully manage cardiac arrhythmias, electrical-anatomical imaging on a beat-by-beat basis, simultaneously, and at multiple sites is required.

Electrical mapping of the heartbeat, whereby multielectrode arrays are placed on the exterior surface of the heart (epicardium) to directly record the electrical activity, has been applied extensively in both animals and humans [10–13]. Although epicardial mapping provides detailed information on sites of origin and mechanisms of abnormal heart rhythms (arrhythmias), its clinical application has great limitation: it is performed at the expense of open-chest surgery. In addition, epicardial mapping does not provide access to interior heart structures that play critical roles in the initiation and maintenance of abnormal heartbeats.

Many heart rhythm abnormalities (arrhythmias) originate from interior heart tissues (endocardium). Further, because the endocardium is more safely accessible (without surgery) than the epicardium, most electrical mapping techniques and delivery of nonpharmacological therapies (e.g. pacing and catheter ablation) have focused on endocardial approaches. However, current endocardial mapping techniques have certain limitations. Traditional electrode-catheter mapping performed during electrophysiology procedures is confined to a limited number of recording sites, is time consuming, and is carried out over several heartbeats without accounting for possible beat-to-beat variability in activation [14]. While newly introduced catheter-mapping approaches provide important three-dimensional positions of a roving electrode-catheter through the use of “special” sensors, mapping is still performed over several heartbeats [15–17]. On the other hand, although multielectrode basket-catheters [18,19] measure endocardial electrical activities at multiple sites simultaneously by expanding the basket inside the heart so that the electrodes are in direct contact with the endocardium, the basket is limited to a fixed number of recording sites, may not be in contact with the entire endocardium, and may result in irritation of the myocardium.

An alternative mapping approach utilizes a noncontact, multielectrode cavitary probe [20] that measures electrical activities (electrograms) from inside the blood-filled heart cavity from multiple directions simultaneously. The probe electrodes are not necessarily in direct contact with the endocardium; consequently, noncontact sensing results in a smoothed electrical potential pattern [21]. Cavitary probe mapping was also conducted on experimental myocardial infarction [22]. More recently, nonsurgical insertion of a noncontact, multielectrode balloon-catheter, that does not occlude the blood-filled cavity, has been reported in humans [23]. This catheter was used to compute electrograms on an ellipsoid that approximated the endocardium.

Present mapping systems cannot provide true images of endocardial anatomy. Present systems often delineate anatomical features based on (1) extensive use of fluoroscopy; (2) deployment of multiple catheters, or roving the catheters, at multiple locations; and (3) assumptions about properties of recorded electrograms in relation to underlying anatomy (e.g. electrograms facing a valve are low in amplitude). However, direct correlation between endocardial activation and cardiac anatomy is important in order to clearly identify the anatomical sources of abnormal heartbeats, to understand the mechanisms of cardiac arrhythmias and their sequences of activation within or around complex anatomical structures, and to deliver appropriate therapy.

Early applications of the “inverse problem” of electrocardiography sought to noninvasively reconstruct (compute) epicardial surface potentials (electrograms) and activation sequences of the heartbeat based on noncontact potentials measured at multiple sites on the body surface [24,25]. The computed epicardial potentials were in turn used to delineate information on cardiac sources within the underlying myocardium [26,27]. To solve the “inverse problem”, numeric techniques have been repeatedly tested on computer, animal, and human models [28–38]. Similarly, computing endocardial surface electrical potentials (electrograms) based on noncontact potentials (electrograms) measured with the use of a multielectrode cavitary probe constitutes a form of endocardial electrocardiographic “inverse problem.”

The objective of the endocardial electrocardiographic “inverse problem” is to compute virtual endocardial surface electrograms based on noncontact cavitary electrograms measured by multielectrode probes. Preliminary studies have demonstrated that methods for acquisition of cavitary electrograms and computation of endocardial electrograms in the beating heart have been established and their accuracy globally confirmed [39–50]. Determining the probe-endocardium geometrical relationship (i.e. probe position and orientation with respect to the endocardial surface) is required to solve the “inverse problem” and a prerequisite for accurate noncontact electrical-anatomical imaging. In initial studies, fluoroscopic imaging provided a means for beat-by-beat global validation of computed endocardial activation in the intact, beating heart [46–50]. Furthermore, epicardial echocardiography [45] was used to determine the probe-cavity geometrical model. However, complex geometry, such as that of the atrium, may not be easily characterized by transthoracic or epicardial echocardiography.

Accurate three-dimensional positioning of electrode-catheters at abnormal electrogram or ablation sites on the endocardium and repositioning of the catheters at specific sites are important for the success of ablation. The disadvantages of routine fluoroscopy during catheterization include radiation effects and limited three-dimensional localization of the catheter. New catheter-systems achieve better three-dimensional positioning by (1) using a specialized magnetic sensor at the tip of the catheter that determines its location with respect to an externally applied magnetic field [15], (2) calculating the distances between a roving intracardiac catheter and a reference catheter, each carrying multiple ultrasonic transducers [16], (3) measuring the field strength at the catheter tip-electrode, while applying three orthogonal currents through the patient's body to locate the catheter [17]; and (4) emitting a low-current locator signal from the catheter tip and determining its distance from a multielectrode cavitary probe [51]. With these mapping techniques true three-dimensional imaging of important endocardial anatomical structures is not readily integrated (only semi-realistic geometric approximations of the endocardial surface), and assumptions must often be made about properties of recorded electrograms in relation to underlying anatomy (e.g. electrograms facing the tricuspid and mitral annuli are low in amplitude).

BRIEF SUMMARY OF THE INVENTION

A system and methods are described that make possible the combined use of (1) a lumen-catheter carrying a plurality of sensing electrodes (multielectrode catheter-probe) for taking multiple noncontact measurements from different directions of the electrical characteristics of interior tissue such as the heart (endocardium) and (2) an internal coaxial catheter carrying one or more imaging elements for visualizing the anatomical characteristics of the tissue. A middle, coaxial lumen-catheter (sheath) provides structural support and serves as a conduit for advancing or withdrawing the multielectrode catheter over its surface, or inserting the anatomical imaging catheter through its lumen. The imaging catheter is inserted inside the multielectrode catheter-probe (or the supporting lumen-catheter when in use) and is moved to detect the tissue from inside the lumen using different modalities such as ultrasound, infrared, and magnetic resonance. Both the electrical and anatomical measurements are sent to a data acquisition system that in turn provides combined electrical and anatomical graphical or numerical displays to the operator.

In another feature of the present invention, the catheter imaging system simultaneously maps multiple interior heart surface electrical activities (endocardial electrograms) on a beat-by-beat basis and combines three-dimensional activation-recovery sequences with endocardial anatomy. Electrical-anatomical imaging of the heart, based on (1) cavitary electrograms that are measured with a noncontact, multielectrode probe and (2) three-dimensional endocardial anatomy that is determined with an integrated anatomical imaging modality (such as intracardiac echocardiography), provides an effective and efficient means to diagnose abnormal heartbeats and deliver therapy.

In another feature of the present invention, the integrated electrical-anatomical imaging catheter system contains both a multielectrode probe and an anatomical imaging catheter, which can be percutaneously introduced into the heart in ways similar to standard catheters used in routine procedures. This “noncontact” imaging approach reconstructs endocardial surface electrograms from measured probe electrograms, provides three-dimensional images of cardiac anatomy, and integrates the electrical and anatomical images to produce three-dimensional isopotential and isochronal images.

In another feature of the present invention, the method improves the understanding of the mechanisms of initiation, maintenance, and termination of abnormal heartbeats, which could lead to selecting or developing better pharmacological or nonpharmacological therapies. Mapping is conducted with little use of fluoroscopy on a beat-by-beat basis, and allows the study of brief, rare, or even chaotic rhythm disorders that are difficult to manage with existing techniques.

In another feature of the present invention, there is a means to navigate standard diagnostic-therapeutic catheters, and accurately guide them to regions of interest within an anatomically-realistic model of the heart that is derived from ultrasound, infrared, or magnetic resonance. The present invention provides considerable advantages in guiding clinical, interventional electrophysiology procedures, such as imaging anatomical structures, confirming electrode-tissue contact, monitoring ablation lesions, and providing hemodynamic assessment.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 illustrates the system of the present invention in use with a human patient.

FIG. 2 illustrates a lumen sheath with a pig-tail at its distal end and a guide wire inside its lumen.

FIG. 3A illustrates a multielectrode catheter-probe with a lumen inside its shaft.

FIG. 3B illustrates an alternative embodiment of a multielectrode lumen catheter-probe whereby a grid of electrodes can be expanded.

FIG. 3C illustrates an alternative embodiment of a multielectrode lumen catheter-probe with a pig-tail at its distal end for structural support.

FIG. 4 illustrates an anatomical imaging catheter such as intracardiac echocardiography catheter.

FIG. 5A illustrates a configuration that combines the sheath (of FIG. 2) with the multielectrode catheter-probe (of FIG. 3A) over its surface at the proximal end and the anatomical imaging catheter (of FIG. 4) advanced inside the lumen at the distal end.

FIG. 5B illustrates an alternative embodiment that combines the sheath (of FIG. 2) with the multielectrode catheter-probe (of FIG. 3B) advanced over its surface to the distal end and the anatomical imaging catheter (of FIG. 4) inside the lumen at the proximal end.

FIG. 6 illustrates an alternative embodiment that combines the multielectrode catheter-probe (of FIG. 3C) with the anatomical imaging catheter (of FIG. 4) inside its lumen.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates an electrical-anatomical imaging catheter-system 10 in use in a human patient. The catheter is percutaneously inserted through a blood vessel (vein or artery) and advanced into the heart cavity. The catheter detects both electrical and anatomical properties of interior heart tissue (endocardium).

Referring now to FIG. 2, the electrical-anatomical imaging catheter-system 10 includes a lumen sheath 12 (about 3 mm in diameter) which has a pig tail distal end 14 to minimize motion artifacts inside the heart cavity. A guide wire 15 is advanced to a tip 13 to guide the sheath 12. The sheath 12 provides structural support for a coaxial multielectrode catheter-probe 16 (illustrated in FIG. 3A and FIG. 3B) that slides over the surface of the sheath 12, and records noncontact cavitary electrical signals (electrograms) from multiple directions. The sheath 12 also functions as a conduit for inserting an anatomical imaging catheter 18 (illustrated in FIG. 4) such as a standard intracardiac echocardiography (ICE) catheter that records continuous echocardiographic images of the heart interior. With this approach, the sheath 12 maintains the same imaging axis and direction over several deployments inside the heart cavity of both the probe 16 and the anatomical imaging catheter 18. Radiopaque and sonopaque ring marker 20 at the distal end of the sheath 12 and radiopaque and sonopaque ring marker 22 at the proximal end of the sheath 12 aid in verifying the probe 16 and the anatomical imaging catheter 18 locations.

Referring now to FIG. 3A, the electrical-anatomical imaging catheter-system 10 includes a lumen catheter which carries a plurality of sensing electrodes 24 on its surface that make up the multielectrode probe 16. The electrodes 24 are arranged in columns. The diameter of the probe 16 is similar to that of shaft 23 of the probe 16(on the order of 3 mm). The sheath 12 and the anatomical imaging catheter 18 both coaxially fit inside the lumen of the probe 16. The catheter-probe 16 has a straight distal end 45 that permits sliding the probe 16 over the coaxial lumen sheath 12. In this state the probe 16 is easily inserted percutaneously by the operator through a blood vessel and advanced into the heart cavity. By sliding the catheter-probe 16 over the central sheath 12, it is possible to place the probe 16 along the axis of the cavity. The shaft 23 of the probe 16 is shorter than the central sheath 12 so that it slides easily over the sheath 12 in and out of the heart cavity.

FIG. 3B illustrates another embodiment of part of the electrical-anatomical imaging catheter-system 10 of the present invention, in which for the probe 16, the electrodes 24 are laid on a central balloon 26 that is inflated to a fixed diameter without the electrodes 24 necessarily touching the interior surface of the heart. The balloon is similar to angioplasty catheters used in routine catheterization procedures. The balloon 26 is inflated inside the heart cavity to enlarge the probe 16. The sheath 12 and the anatomical imaging catheter 18 (illustrated in FIG. 4) fit inside the lumen 50. The probe 16 has a straight distal end 45 that permits sliding the probe 16 over the coaxial lumen sheath 12. By sliding the probe 16 over the central sheath 12, it is possible to place the probe 16 along the axis of the heart cavity. In its collapsed state the size of the probe 16 is similar to that of the sheath 12. Thus, the operator is able to insert the probe percutaneously and inflate it inside the heart without occluding the cavity. The shaft 23 of the probe 16 is shorter than the central sheath 12 so that the probe 16 slides easily over the sheath 12 in and out of the cavity.

In another embodiment of the electrical-anatomical imaging catheter-system 10, FIG. 3C illustrates the probe 16 with a pig-tail 46 at its distal end to minimize motion artifacts of the probe 16. In this embodiment, the probe 16 is used independently of the lumen sheath 12. The anatomical imaging catheter 18 (illustrated in FIG. 4) fits inside the lumen of the probe 16.

Referring now to FIG. 4, the anatomical imaging catheter 18 is used to image interior structures of the heart. In the preferred embodiment, the catheter 18 is a 9-MHz intracardiac echocardiography catheter (Model Ultra ICE, manufactured by Boston Scientific/EPT, located in San Jose, Calif.). To acquire echocardiographic images, the catheter 18 connects to an imaging console (Model ClearView, manufactured by Boston Scientific/EPT, located in San Jose, Calif.). The catheter 18 has a distal imaging window 30 and a rotatable imaging core 32 with a distal transducer 34 that emits and receives ultrasound energy. Continuous rotation of the transducer provides tomographic sections of the heart cavity. The design of the present invention allows for integrating other anatomical imaging catheters presently under development such as echocardiography catheters carrying multiple phased-array transducers, infrared, and magnetic resonance imaging catheters. While the anatomical imaging catheter 18 is in use, the three-dimensional anatomical reconstruction assumes that the catheter 18 is straight and thus straightens the image of the heart cavity. If the catheter 18 curves, the image is distorted, or, if the catheter 18 rotates during pullback, the image is twisted. Therefore, in the preferred embodiment, a position and orientation sensor 40 is added to the catheter 18.

Referring now to FIG. 5A, an integrated, noncontact, electrical-anatomical imaging catheter-system 10 is illustrated that combines the sheath 12 with the multielectrode catheter-probe 16 over its surface at the proximal end, and the anatomical imaging catheter 18 inside the lumen at the distal end. In operation, the probe 16 is preloaded over the central sheath 12, thereby enabling the probe 16 to move in and out of the heart cavity in small increments over a fixed axis. The guide wire 15 is placed inside the central sheath 12 to ensure the pig-tail end 14 remains straight during insertion through a blood vessel. With the probe 16 loaded on the sheath 12 and pulled back, the sheath 12 is advanced through a blood vessel and placed inside the heart cavity under the guidance of fluoroscopy, and the guide wire 15 is then removed. The anatomical imaging catheter 18 is then inserted through the lumen of the central sheath 12, replacing the guide wire 15, and advanced until a tip 19 of the catheter 18 is situated at the pre-determined radiopaque and sonopaque distal marker 20 on the sheath 12. The catheter 18 is pulled back from the distal marker 20 to the proximal marker 22 on the sheath 12 at fixed intervals, and noncontact anatomical images are continuously acquired at each interval.

Referring now to FIG. 5B, under the guidance of fluoroscopy, the probe 16 is advanced over the central sheath 12 until a tip 17 is at the distal marker 20, and the balloon 26 (if used) is inflated to unfold the probe 16. The probe 16 then simultaneously acquires noncontact cavitary electrograms.

Referring now to FIG. 6, an alternate embodiment of the integrated electrical-anatomical imaging catheter system 10 is illustrated, labeled as an integrated electrical-anatomical imaging catheter system 11, in which the lumen sheath 12 is eliminated. A multielectrode lumen catheter-probe 16 with a pig-tail 46 at its distal end is inserted inside the heart cavity and is used to acquire noncontact electrograms. The anatomical imaging catheter 18 is inserted inside the lumen of the catheter-probe 16, and imaging is performed from inside the probe 16.

Unipolar cavitary electrograms sensed by the noncontact multielectrode probe 16 with respect to an external reference electrode 55 (shown in FIG. 1) along with body surface electrocardiogram signals, are simultaneously acquired with a computer-based multichannel data acquisition mapping system, which, in the preferred embodiment, is the one built by Prucka Engineering-GE Medical Systems, located in Milwaukee, Wis. The mapping system amplifies and displays the signals at a 1 ms sampling interval per channel. The mapping system displays graphical isopotential and isochronal maps that enable evaluation of the quality of the data acquired during the procedure and interaction with the study conditions. The multiple anatomical images (such as ICE) are digitized, and the interior heart borders automatically delineated. The cavity three-dimensional geometry is rendered in a virtual reality environment, as this advances diagnostic and therapeutic procedures.

To reconstruct the electrical activities (electrical potentials, V) on the interior heart surface (endocardium) based on electrical information measured by the cavitary multielectrode probe 16 and anatomical information derived from the anatomical imaging catheter 18, Laplace's equation (∇²V=0) is numerically solved in the blood-filled cavity between the probe 16 and the endocardium (similar to previous studies [40–50]). The boundary element method is employed in computing the electrical potentials in a three-dimensional geometry [52]. A numeric regularization technique (filtering) based on the commonly used Tikhonov method [30] is employed to find the electrical potentials on the endocardium. Here, the electrical potentials are uniquely reconstructed on the real endocardial anatomy derived from the anatomical imaging catheter 18.

Nonfluoroscopic three-dimensional positioning and visualization of standard navigational electrode-catheters is clinically necessary for (1) detailed and localized point-by-point mapping at select interior heart regions, (2) delivering nonpharmacological therapy such as pacing or ablation, (3) repositioning the catheters at specific sites, and (4) reducing the radiation effects of fluoroscopy during catheterization. To guide three-dimensional positioning and navigation of standard electrode-catheters, a low-amplitude location electrical signal is emitted between the catheter tip-electrode and the external reference electrode 55, and sensed by multiple electrodes 24 on the surface of the probe 16. Similar to previous work [53], the catheter tip is localized by finding the x, y, and z coordinates of a location point p. The location of the emitting electrode is determined by minimizing [F(p)−V(p)]^T[F(p)−V(p)] with respect to p, where V(p) are the electrical potentials measured on the probe 16, and F(p) are the electrical potentials computed on the probe 16 using an analytical (known) function and assuming an infinite, homogeneous conducting medium. This process also constructs the shape of the catheter within the cavity by determining the locations of all catheter electrodes. Alternatively, the location and shape of the roving electrode-catheter is determined with respect to the underlying real anatomy by direct visualization with the anatomical imaging catheter 18.

The method of the present invention senses the location signal by multiple probe electrodes 24 simultaneously, thereby localizing the roving catheter more accurately than prior art methods. Furthermore, the method of the present invention reconstructs the shape of the roving catheter during navigation by emitting a location signal from each of the catheter electrodes and determining their locations within the cavity. With this approach, online navigation of standard electrode-catheters is performed and displayed within an anatomically-correct geometry derived from ultrasound, infrared, or magnetic resonance, and without extensive use of fluoroscopy.

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• 22. Hilger A L, Claydon F J, Ingram L A, Mirvis D M. Quantitative effects of acute myocardial infarction on intracavitary potentials. Proc 14th IEEE/EMBS 1992, pp 537–539.
• 23. Schilling R J, Peters N S, Davies D W. Simultaneous endocardial mapping in the human left ventricle using a noncontact catheter: Comparison of contact and reconstructed electrograms during sinus rhythm. Circulation 1998;98:887–898.
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• 25. Colli-Franzone P, Guerri L, Tentoni S, Viganotti C, Baruffi S, Spaggiari S, Taccardi B. A mathematical procedure for solving the inverse problem of electrocardiography: analysis of the time-space accuracy from in vitro experimental data. Math Biosci 1985;77:353–396.
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• 28. Messinger-Rapport B J, Rudy Y. Regularization of the inverse problem in electrocardiography: a model study. Math Biosci 1988;89:79–118.
• 29. Messinger-Rapport B J, Rudy Y. Computational issues of importance to the inverse recovery of epicardial potentials in a realistic heart-torso geometry. Math Biosci 1989;97:85–120.
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• 32. Messinger-Rapport B J, Rudy Y. Noninvasive recovery of epicardial potentials in a realistic heart-torso geometry. Normal sinus rhythm. Circ Res 1990;66:1023–1039.
• 33. Gulrajani R M. The forward and inverse problems of electrocardiography. IEEE Eng Med Biol 1998;17(5):84–122.
• 34. MacLeod R S, Brooks D H. Recent progress in inverse problems in electrocardiology. IEEE Eng Med Biol 1998;17(1):73–83.
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• 36. Oster H S, Rudy Y. Regional regularization of the electrocardiographic inverse problem: a model study using spherical geometry. IEEE Trans Biomed Eng 1997;44:188–199.
• 37. Oster H S, Rudy Y. The use of temporal information in the regularization of the inverse problem of electrocardiography. IEEE Trans Biomed Eng 1992;39:65–75.
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• 40. Khoury D S. Recovery of endocardial potentials from intracavitary potential data [Dissertation]. Cleveland, Ohio: Case Western Reserve University, 1993, 174 p.
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• 44. Khoury D S, Taccardi B, Lux R L, Ershler P R, Rudy Y. Reconstruction of endocardial potentials and excitation sequences from intracavitary probe measurements. Localization of pacing sites and effects of myocardial structure. Circulation 1995;91:845–863.
• 45. Khoury D S, Berrier K L, Badruddin S M, Zoghbi W A. Three-dimensional electrophysiologic imaging of the intact dog left ventricle using a noncontact multielectrode cavitary probe. Study of sinus, paced, and spontaneous premature beats. Circulation 1998;97:399–409.
• 46. Velipasaoglu E O, Sun H, Berrier K L, Khoury D S. Spatial regularization of the electrocardiographic inverse problem and its application to endocardial mapping. IEEE Trans Biomed Eng 2000;47:327–337.
• 47. Sun H, Velipasaoglu E O, Berrier K L, Khoury D S. Electrophysiological imaging of the right atrium using a noncontact multielectrode cavitary probe: study of normal and abnormal rhythms. PACE 1998;21[Pt. II]:2500–2505.
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MOST RELEVANT PUBLICATIONS

• 1. Taccardi B, Arisi G, Macchi E, Baruffi S, Spaggiari S. A new intracavitary probe for detecting the site of origin of ectopic ventricular beats during one cardiac cycle. Circulation 1987;75:272–281.
• 2. Gepstein L, Hayam G, Ben-Haim S A. A novel method for nonfluoroscopic catheter-based electroanatomical mapping of the heart. In vitro and in vivo accuracy results. Circulation 1997;95:1611–1622.
• 3. De Groot N M S, Bootsma M, Van Der Velde E T, Schalij M J. Three-dimensional catheter positioning during radiofrequency ablation in patients: first application of a real-time position management system. J Cardiovasc Electrophysiol 2000;11:1183–1192.
• 4. Wittkampf F H M, Wever E F D, Derksen R, Wilde A A M, Ramanna H, Hauer R N W, Robles de Medlina E O. LocaLisa. New technique for real-time 3-dimensional localization of regular intracardiac electrodes. Circulation 1999;99:1312–1317.
• 5. Jenkins K J, Walsh E P, Colan S D, Bergau D M, Saul J P, Lock J E. Multipolar endocardial mapping of the right atrium during cardiac catheterization: description of a new technique. J Am Coll Cardial 1993;22:1105–1110.
• 6. Eldar M, Fitzpatrick A P, Ohad D, Smith M F, Hsu S, Whayne J G, Vered Z, Rotstein Z, Kordis T, Swanson D K, Chin M, Scheinman M M, Lesh M D, Greenspon A J. Percutaneous multielectrode endocardial mapping during ventricular tachycardia in the swine model. Circulation 1996;94:1125–1130.
• 7. Derfus D L, Pilkington T C, Simpson E W, Ideker R E. A comparison of measured and calculated intracavitary potentials for electrical stimuli in the exposed dog heart. IEEE Trans Biomed Eng 1992;39:1192–1206.
• 8. Schilling R J, Peters N S, Davies D W. Simultaneous endocardial mapping in the human left ventricle using a noncontact catheter: Comparison of contact and reconstructed electrograms during sinus rhythm. Circulation 1998;98:887–898.
• 9. Ren J F, Schwartzman D, Callans D J, Brode S E, Gottlieb C D, Marchlinski F E. Intracardiac echocardiography (9 MHz) in humans: methods, imaging views and clinical utility. Ultrosound Med Biol 1999;25:1077–1086.
• 10. Ladd M E, Quick H H, Debatin J F. Interventional MRI and intravascular imaging. J Magn Reson Imaging 2000;12:534–546.
• 11. Khoury D S. Recovery of endocardial potentials from intracavitary potential data [Dissertation]. Cleveland, Ohio: Case Western Reserve University, 1993, 174 p.
• 12. Khoury D S, Taccardi B, Lux R L, Ershler P R, Rudy Y. Reconstruction of endocardial potentials and excitation sequences from intracavitary probe measurements. Localization of pacing sites and effects of myocardial structure. Circulation 1995;91:845–863.
• 13. Khoury D S , Berrier K L, Badruddin S M, Zoghbi W A. Three-dimensional electrophysiologic imaging of the intact dog left ventricle using a noncontact multielectrode cavitary probe. Study of sinus, paced, and spontaneous premature beats. Circulation 1998;97:399–409.
• 14. Sun H, Velipasaoglu E O, Berrier K L, Khoury D S. Electrophysiological imaging of the right atrium using a noncontact multielectrode cavitary probe: study of normal and abnormal rhythms. PACE 1998;21[Pt. II]:2500–2505.
• 15. Velipasaoglu E O, Sun H, Berrier K L, Khoury D S. Spatial regularization of the electrocardiographic inverse problem and its application to endocardial mapping. IEEE Trans Biomed Eng 2000;47:327–337.
• 16. Khoury D S, Sun H, Velipasaoglu E O, Dupree D, McMillan A, Panescu D. Four-dimensional, biatrial mapping in the intact beating heart [Abstract]. PACE 2000;23:750.
• 17. Rao L, Sun H, Khoury D S. Global Comparisons between contact and noncontact mapping techniques in the right atrium: role of cavitary probe size. Ann Biomed Eng 2001;29:493–500.
• 18. Khoury D S, Sun H, Velipasaoglu E O, Dupree D, McMillan A, Panescu D. Four-dimensional, biatrial mapping in the intact beating heart [Abstract]. Pacing and Clinical Electrophysiology (PACE) 2000;23:750. Presented as a poster at the 21st Annual Scientifc Sessions of the North American Society of Pacing and Electrophysiology, Washington, D.C.