Patent Description:
Electrophysiological mapping, and more particularly electrocardiographic mapping, is a part of numerous cardiac diagnostic and therapeutic procedures. As the complexity of such procedures increases, however, the electrophysiology maps must increase in quality and in data density.

To increase the quality and density of electrophysiology maps, medical devices and systems (e.g., electrophysiology catheters, electroanatomical mapping systems) that simultaneously collect many (e.g., more than ten) intracardiac electrogram signals can be used. Extant devices and systems, however, often do not provide a practitioner with a quick, visual confirmation of the quality of the electrograms being collected. <CIT> relates to electrophysiological mapping, in particular generating an electrophysiology map from data collected by a roving electrophysiology probe by including only those data which satisfy a predetermined inclusion criteria. <CIT> relates to the determination and representation of physiological information relating to a heart surface, such as electroanatomical mapping and annotation.

Disclosed herein is a system of determining signal quality of an electrophysiological signal according to the subject-matter of claim <NUM>. Further developments of the invention are given in the dependent claims.

The information regarding proximal stability include: information regarding a distance between the electrophysiology catheter and the anatomical surface at the acquisition time; and optionally information regarding a velocity of the electrophysiology catheter at the acquisition time. It is also contemplated that the information regarding proximal stability further include information regarding contact force between the electrophysiology catheter and the anatomical surface at the acquisition time.

According to the instant disclosure, the distance between the electrophysiology catheter and the anatomical surface can be measured using a geometric model of the anatomical region.

The system can also include outputting a graphical representation of the signal quality score. For example, a graphical representation of the electrophysiological signal can be colored to represent the signal quality score.

Receiving, at a signal processor, information regarding proximal stability, relative to an anatomical region, of an electrophysiology catheter used to measure the electrophysiological signal at an acquisition time of the electrophysiological signal and information regarding temporal stability of the electrophysiological signal; and computing a signal quality score using the information regarding proximal stability and the information regarding temporal stability can be repeated for a plurality of electrophysiological signals to create a signal quality map. In turn, it is contemplated that a graphical representation of the signal quality map can be output. For example, the graphical representation of the signal quality map can be output on a geometric model of the anatomical region.

The disclosure also relates to repeating the step of computing a signal quality score for the received electrophysiological signal as a function of two or more of a surface proximity parameter, a contact force parameter, and a signal temporal stability parameter for a plurality of received electrophysiological signals, to create a signal quality map. In turn, the method can further include outputting a graphical representation of the signal quality map, for example on a geometric model of an anatomical region from which the plurality of received electrophysiological signals originated.

The surface proximity parameter can be based at least in part upon a distance from an electrophysiology catheter receiving the received electrophysiological signal and an anatomical region from which the received electrophysiological signal originated at an acquisition time of the received electrophysiological signal. The surface proximity parameter can additionally or alternatively be based at least in part upon a velocity of the electrophysiology catheter at the acquisition time.

In embodiments, the function is a function of all of the surface proximity parameter, the contact force parameter, and the signal temporal stability parameter. For example, the function can be of form QS=TS* [CF+(<NUM>-CF)*PS], where QS is the signal quality score; TS is the signal temporal stability parameter; CF is the contact force parameter; and PS is the surface proximity parameter.

The invention provides a system for determining signal quality of an electrophysiological signal measured at an acquisition time from an anatomical region using electrophysiology catheter according to claim <NUM>.

The foregoing and other aspects, features, details, utilities, and advantages of the present invention will be apparent from reading the following description and claims, and from reviewing the accompanying drawings.

While multiple embodiments are disclosed, still other embodiments of the present disclosure will become apparent to those skilled in the art from the following detailed description, which shows and describes illustrative embodiments.

The instant disclosure provides systems for determining electrophysiological signal quality. For purposes of illustration, aspects of the disclosure will be described in connection with a cardiac electrophysiological study. It should be understood, however, that the teachings herein can be applied to good advantage in other contexts.

<FIG> shows a schematic diagram of an exemplary electroanatomical mapping system <NUM> for conducting cardiac electrophysiology studies by navigating a cardiac catheter and measuring electrical activity occurring in a heart <NUM> of a patient <NUM> and three-dimensionally mapping the electrical activity and/or information related to or representative of the electrical activity so measured. System <NUM> can be used, for example, to create an anatomical model of the patient's heart <NUM> using one or more electrodes. System <NUM> can also be used to measure electrophysiology data at a plurality of points along a cardiac surface and store the measured data in association with location information for each measurement point at which the electrophysiology data was measured, for example to create a diagnostic data map of the patient's heart <NUM>. In some embodiments, and as discussed further herein, the system <NUM> can determine the signal quality of measured electrophysiological data and compute a corresponding signal quality score.

As one of ordinary skill in the art will recognize, and as will be further described below, system <NUM> determines the location, and in some aspects the orientation, of objects, typically within a three-dimensional space, and expresses those locations as position information determined relative to at least one reference.

For simplicity of illustration, the patient <NUM> is depicted schematically as an oval. In the embodiment shown in <FIG>, three sets of surface electrodes (e.g., patch electrodes) are shown applied to a surface of the patient <NUM>, defining three generally orthogonal axes, referred to herein as an x-axis, a y-axis, and a z-axis. In other embodiments the electrodes could be positioned in other arrangements, for example multiple electrodes on a particular body surface. As a further alternative, the electrodes do not need to be on the body surface, but could be positioned internally to the body.

In <FIG>, the x-axis surface electrodes <NUM>, <NUM> are applied to the patient along a first axis, such as on the lateral sides of the thorax region of the patient (e.g., applied to the patient's skin underneath each arm) and may be referred to as the Left and Right electrodes. The y-axis electrodes <NUM>, <NUM> are applied to the patient along a second axis generally orthogonal to the x-axis, such as along the inner thigh and neck regions of the patient, and may be referred to as the Left Leg and Neck electrodes. The z-axis electrodes <NUM>, <NUM> are applied along a third axis generally orthogonal to both the x-axis and the y-axis, such as along the sternum and spine of the patient in the thorax region, and may be referred to as the Chest and Back electrodes. The heart <NUM> lies between these pairs of surface electrodes <NUM>/<NUM>, <NUM>/<NUM>, and <NUM>/<NUM>.

An additional surface reference electrode (e.g., a "belly patch") <NUM> provides a reference and/or ground electrode for the system <NUM>. The belly patch electrode <NUM> may be an alternative to a fixed intra-cardiac electrode <NUM>, described in further detail below. It should also be appreciated that, in addition, the patient <NUM> may have most or all of the conventional electrocardiogram ("ECG" or "EKG") system leads in place. In certain embodiments, for example, a standard set of <NUM> ECG leads may be utilized for sensing electrocardiograms on the patient's heart <NUM>. This ECG information is available to the system <NUM> (e.g., it can be provided as input to computer system <NUM>). Insofar as ECG leads are well understood, and for the sake of clarity in the figures, only a single lead <NUM> and its connection to computer <NUM> is illustrated in <FIG>.

A representative catheter <NUM> having at least one electrode <NUM> is also shown. This representative catheter electrode <NUM> is referred to as the "roving electrode," "moving electrode," or "measurement electrode" throughout the specification. Typically, multiple electrodes <NUM> on catheter <NUM>, or on multiple such catheters, will be used. In one embodiment, for example, the system <NUM> may comprise sixty-four electrodes on twelve catheters disposed within the heart and/or vasculature of the patient. Of course, this embodiment is merely exemplary, and any number of electrodes and catheters may be used.

Likewise, it should be understood that catheter <NUM> (or multiple such catheters) are typically introduced into the heart and/or vasculature of the patient via one or more introducers and using familiar procedures. For purposes of this disclosure, a segment of an exemplary multi-electrode catheter <NUM> is shown in <FIG>. In <FIG>, catheter <NUM> extends into the left ventricle <NUM> of the patient's heart <NUM> through a transseptal sheath <NUM>. The use of a transseptal approach to the left ventricle is well known and will be familiar to those of ordinary skill in the art, and need not be further described herein. Of course, catheter <NUM> can also be introduced into the heart <NUM> in any other suitable manner (e.g., via epicardial access).

Catheter <NUM> includes electrode <NUM> on its distal tip, as well as a plurality of additional measurement electrodes <NUM>, <NUM>, <NUM> spaced along its length in the illustrated embodiment. Typically, the spacing between adjacent electrodes will be known, though it should be understood that the electrodes may not be evenly spaced along catheter <NUM> or of equal size to each other. Since each of these electrodes <NUM>, <NUM>, <NUM>, <NUM> lies within the patient, location data may be collected simultaneously for each of the electrodes by system <NUM>.

Similarly, each of electrodes <NUM>, <NUM>, <NUM>, and <NUM> can be used to gather electrophysiological data from the cardiac surface. The ordinarily skilled artisan will be familiar with various modalities for the acquisition and processing of electrophysiology data points (including, for example, both contact and non-contact electrophysiological mapping), such that further discussion thereof is not necessary to the understanding of the techniques disclosed herein. Likewise, various techniques familiar in the art can be used to generate a graphical representation from the plurality of electrophysiology data points. Insofar as the ordinarily skilled artisan will appreciate how to create electrophysiology maps from electrophysiology data points, the aspects thereof will only be described herein to the extent necessary to understand the instant disclosure.

Returning now to <FIG>, in some embodiments, an optional fixed reference electrode <NUM> (e.g., attached to a wall of the heart <NUM>) is shown on a second catheter <NUM>. For calibration purposes, this electrode <NUM> may be stationary (e.g., attached to or near the wall of the heart) or disposed in a fixed spatial relationship with the roving electrodes (e.g., electrodes <NUM>), and thus may be referred to as a "navigational reference" or "local reference. " The fixed reference electrode <NUM> may be used in addition or alternatively to the surface reference electrode <NUM> described above. In many instances, a coronary sinus electrode or other fixed electrode in the heart <NUM> can be used as a reference for measuring voltages and displacements; that is, as described below, fixed reference electrode <NUM> may define the origin of a coordinate system.

Each surface electrode is coupled to a multiplex switch <NUM>, and the pairs of surface electrodes are selected by software running on a computer <NUM>, which couples the surface electrodes to a signal generator <NUM>. Alternately, switch <NUM> may be eliminated and multiple (e.g., three) instances of signal generator <NUM> may be provided, one for each measurement axis (that is, each surface electrode pairing).

The computer <NUM> may comprise, for example, a conventional general-purpose computer, a special-purpose computer, a distributed computer, or any other type of computer. The computer <NUM> may comprise one or more processors <NUM>, such as a single central processing unit ("CPU"), or a plurality of processing units, commonly referred to as a parallel processing environment, which may execute instructions to practice the various aspects described herein.

Generally, three nominally orthogonal electric fields are generated by a series of driven and sensed electric dipoles (e.g., surface electrode pairs <NUM>/<NUM>, <NUM>/<NUM>, and <NUM>/<NUM>) in order to realize catheter navigation in a biological conductor. Alternatively, these orthogonal fields can be decomposed and any pairs of surface electrodes can be driven as dipoles to provide effective electrode triangulation. Likewise, the electrodes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> (or any number of electrodes) could be positioned in any other effective arrangement for driving a current to or sensing a current from an electrode in the heart. For example, multiple electrodes could be placed on the back, sides, and/or belly of patient <NUM>. Additionally, such non-orthogonal methodologies add to the flexibility of the system. For any desired axis, the potentials measured across the roving electrodes resulting from a predetermined set of drive (source-sink) configurations may be combined algebraically to yield the same effective potential as would be obtained by simply driving a uniform current along the orthogonal axes.

Thus, any two of the surface electrodes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> may be selected as a dipole source and drain with respect to a ground reference, such as belly patch <NUM>, while the unexcited electrodes measure voltage with respect to the ground reference. The roving electrodes <NUM> placed in the heart <NUM> are exposed to the field from a current pulse and are measured with respect to ground, such as belly patch <NUM>. In practice the catheters within the heart <NUM> may contain more or fewer electrodes than the sixteen shown, and each electrode potential may be measured. As previously noted, at least one electrode may be fixed to the interior surface of the heart to form a fixed reference electrode <NUM>, which is also measured with respect to ground, such as belly patch <NUM>, and which may be defined as the origin of the coordinate system relative to which system <NUM> measures positions. Data sets from each of the surface electrodes, the internal electrodes, and the virtual electrodes may all be used to determine the location of the roving electrodes <NUM> within heart <NUM>.

The measured voltages may be used by system <NUM> to determine the location in three-dimensional space of the electrodes inside the heart, such as roving electrodes <NUM> relative to a reference location, such as reference electrode <NUM>. That is, the voltages measured at reference electrode <NUM> may be used to define the origin of a coordinate system, while the voltages measured at roving electrodes <NUM> may be used to express the location of roving electrodes <NUM> relative to the origin. In some embodiments, the coordinate system is a three-dimensional (x, y, z) Cartesian coordinate system, although other coordinate systems, such as polar, spherical, and cylindrical coordinate systems, are contemplated.

As should be clear from the foregoing discussion, the data used to determine the location of the electrode(s) within the heart is measured while the surface electrode pairs impress an electric field on the heart. The electrode data may also be used to create a respiration compensation value used to improve the raw location data for the electrode locations as described, for example, in <CIT>. The electrode data may also be used to compensate for changes in the impedance of the body of the patient as described, for example, in <CIT>.

Therefore, in one representative embodiment, system <NUM> first selects a set of surface electrodes and then drives them with current pulses. While the current pulses are being delivered, electrical activity, such as the voltages measured with at least one of the remaining surface electrodes and in vivo electrodes, is measured and stored. Compensation for artifacts, such as respiration and/or impedance shifting, may be performed as indicated above.

In some embodiments, system <NUM> is the EnSite™ Velocity™ or EnSite Precision™ cardiac mapping and visualization system of Abbott Laboratories. Other localization systems, however, may be used in connection with the present teachings, including for example the CARTO navigation and location system of Biosense Webster, Inc. , the AURORA® system of Northern Digital Inc. , Sterotaxis' NIOBE® Magnetic Navigation System, as well as MediGuide™ Technology from Abbott Laboratories.

The localization and mapping systems described in the following patents can also be used with the present invention: <CIT>; <CIT>; <CIT>; <CIT>; <CIT>; <CIT>; <CIT>; and <CIT>.

Aspects of the disclosure relate to computing signal quality scores (e.g., indices of the quality of the electrophysiology signals collected by electrodes <NUM>, <NUM>, <NUM>, <NUM>). System <NUM> can therefore also include a signal quality module <NUM> (e.g., executing on processor <NUM>) that can be used to determine signal quality scores.

One exemplary method of determining signal quality indices according to the present teachings will be explained with reference to the flowchart <NUM> of representative steps shown in <FIG>. In some embodiments, for example, flowchart <NUM> may represent several exemplary steps that can be carried out by electroanatomical mapping system <NUM> of <FIG> (e.g., by processor <NUM> and/or signal quality module <NUM>). It should be understood that the representative steps described below can be either hardware- or software-implemented. For the sake of explanation, the term "signal processor" is used herein to describe both hardware- and software-based implementations of the teachings herein.

It should also be understood that the representative steps described below can be carried out in real time (e.g., upon an intracardiac electrogram at the time of collection during an electrophysiology study) or as post-processing (e.g., upon an intracardiac electrogram that was collected during an electrophysiology study performed at an earlier time). That is, the electrogram signal received in block <NUM> of <FIG> can be a real-time electrogram signal or an electrogram signal that is part of a data set undergoing post processing.

In block <NUM>, the signal processor receives information regarding the proximal stability of an electrophysiology catheter (e.g., catheter <NUM>) used to measure the electrogram signal received in block <NUM> at the time that signal was acquired. The proximal stability information is determined relative to an anatomical region, such as the cardiac surface being studied.

For example, the proximal stability information can include a distance between catheter <NUM> and the cardiac surface at the signal acquisition time. In some aspects of the disclosure, the distance between catheter <NUM> and the cardiac surface is measured using a geometric model of the anatomical region (e.g., a cardiac geometry generated by electroanatomical mapping system <NUM>), but it is also regarded as within the scope of the instant disclosure to measure the distance in other ways (e.g., ultrasound, fluoroscopy).

As another example, in additional embodiments of the disclosure, the proximal stability information can also include information regarding contact force between catheter <NUM> and the cardiac surface at the signal acquisition time.

The proximal stability information can also include information regarding the velocity of catheter <NUM> at the signal acquisition time.

In block <NUM>, the proximal stability information is used to generate a surface proximity signal quality parameter ("PS") and a contact force signal quality parameter ("CF"). For example, PS can be defined as follows: <MAT> where d is the distance between catheter <NUM> and the cardiac surface at the signal acquisition time and v is the velocity of catheter <NUM> at the signal acquisition time. Other definitions of PS, including non-linear functions, are also contemplated as within the scope of the instant disclosure.

Likewise, CF can be defined as follows: <MAT> where F is the contact force between catheter <NUM> and the cardiac surface. Those of ordinary skill in the art will understand that, according to the foregoing equation, CF will also be set to <NUM> if catheter <NUM> lacks a contact force sensor. Other definitions of CF, including non-linear functions, are also contemplated as within the scope of the instant disclosure.

In block <NUM>, the signal processor receives information regarding the temporal stability of the electrogram signal received in block <NUM>. Then, in block <NUM>, the temporal stability information is used to generate a temporal stability signal quality parameter ("TS").

One approach to generating TS will be described with reference to the flowchart <NUM> of <FIG>. Decision block <NUM> determines whether the received electrogram signal is part of a stable rhythm (e.g., sinus rhythm; stable tachycardia) or an unstable rhythm. For an unstable rhythm, TS = <NUM> (block <NUM>).

For a stable rhythm, decision block <NUM> determines whether the signal has a temporal reproducibility above a reproducibility threshold (e.g., <NUM>%). If not, TS = <NUM> (block <NUM>). If so, TS =<NUM> (block <NUM>). This reduces the likelihood that ectopic beats and/or noise signal artifacts will be acquired.

Once the signal quality parameters are generated, they can be used to compute a signal quality score for the received electrogram in block <NUM>. For example, a quality score ("QS") can be computed according to the equation QS = TS * [CF + (<NUM> - CF) * PS].

In block <NUM>, a graphical representation of the signal quality score can be output (e.g., to display <NUM>). A visual trace of the received electrogram signal is displayed using a color scale that corresponds to the computed quality score (e.g., high quality signals (e.g., quality scores greater than or equal to about <NUM>) can be colored white, while low quality signals (e.g., quality scores less than or equal to about <NUM>) can be colored red). It is contemplated that the thresholds for high and low quality scores can be user-defined and/or user-adjustable.

As another example, the numerical quality score can be shown on display <NUM> adjacent the corresponding visual trace of the received electrogram. To enhance the visibility of the quality score, progressively larger fonts can be used to display the numerical quality score as the quality score increases. Analogous font scaling can also be applied to other displayed text associated with the received electrogram (e.g., a lead designator) in addition to or as an alternative to the displayed numerical quality score.

The teachings above, which are described with reference to a single electrogram, can be applied to multiple electrograms, thereby creating a signal quality map. The signal quality map can also be output as a graphical representation in a manner analogous to other electrophysiology maps, which techniques will be familiar to those of ordinary skill in the art. For example, <CIT>, discloses, among other things, the use of glyphs to graphically represent biological attributes. In embodiments of the disclosure, one or more glyph attributes (e.g., color, size, transparency, or the like) can be used to display signal quality.

By providing the practitioner with a visual indication of signal quality, the practitioner will be able to ascertain, in real time, whether a particular electrophysiology data point should be stored and/or if catheter <NUM> should be repositioned prior to storing an electrophysiology data point. The techniques described herein can also be used to remove undesirable electrophysiology data points (e.g., ectopic beats; noise artifacts) from an electrophysiology map in post-processing, thereby improving the quality of the electrophysiology map.

Although several embodiments have been described above with a certain degree of particularity, those skilled in the art could make numerous alterations to the disclosed embodiments.

All directional references (e.g., upper, lower, upward, downward, left, right, leftward, rightward, top, bottom, above, below, vertical, horizontal, clockwise, and counterclockwise) are only used for identification purposes to aid the reader's understanding. Joinder references (e.g., attached, coupled, connected, and the like) may include intermediate members between a connection of elements and relative movement between elements.

Claim 1:
A system (<NUM>) for determining signal quality of an electrophysiological signal measured at an acquisition time from an anatomical region using electrophysiology catheter (<NUM>), the system comprising:
a signal quality processor configured to:
receive as input information regarding proximal stability of the electrophysiology catheter relative to the anatomical region at the acquisition time, wherein the information regarding proximal stability comprises:
information regarding a distance between the electrophysiology catheter and the anatomical surface at the acquisition time; and
information regarding contact force between the electrophysiology catheter and the anatomical surface at the acquisition time;
receive as input information regarding temporal stability of the electrophysiological signal; and
compute a numerical signal quality score as a mathematical function of the information regarding proximal stability and the information regarding temporal stability; and
a mapping processor configured to output a graphical representation of the numerical signal quality score, wherein the graphical representation of the numerical signal quality score comprises outputting a visual trace of the electrophysiology signal to a display (<NUM>) using a color scale that corresponds to the computed numerical quality score.