Patent Description:
Cardiac arrhythmias such as atrial fibrillation are an important cause of morbidity and death. Commonly assigned <CIT>, and <CIT>, both issued to Ben Haim and <CIT>, 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. Data are acquired with one or more catheters having electrical and location sensors in their distal tips, which are advanced into the heart. Methods of creating a map of the electrical activity of the heart based on these data are disclosed in commonly assigned <CIT>, and <CIT>, both issued to Reisfeld. As indicated in these patents, location and electrical activity is typically initially measured on about <NUM> to about <NUM> points on generate a preliminary reconstruction or map of the cardiac surface. 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. Indeed, in clinical settings, it is not uncommon to accumulate data at <NUM> 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 <CIT>, issued to Ben Haim, maps depicting such motion characteristics may be constructed when the trajectory information is sampled at a sufficient number of points in the heart.

Electrical activity at a point in the heart is typically measured by advancing a multiple-electrode catheter to measure electrical activity at multiple points in the heart chamber simultaneously. A record derived from time varying electrical potentials as measured by one or more electrodes is known as an electrogram. Electrograms may be measured by unipolar or bipolar leads, and are used, e.g., to determine onset of electrical propagation at a point, known as local activation time.

However, determination of local activation time as an indicator of electrical propagation becomes problematic in the presence of conduction abnormalities. For example, atrial electrograms during sustained atrial fibrillation have three distinct patterns: single potential, double potential and a complex fractionated atrial electrograms (CFAE's). Thus, compared to a normal sinus rhythm signal, an atrial fibrillation signal is extremely complex, as well as being more variable. While there is noise on both types of signal, which makes analysis of them difficult, because of the complexity and variability of the atrial fibrillation signal the analysis is correspondingly more difficult. On the other hand, in order to overcome the atrial fibrillation in a medical procedure, it is useful to establish possible paths of activation waves travelling through the heart representing atrial fibrillation. Once these paths have been identified, they may be blocked, for example, by appropriate ablation of a region of the heart. The paths may be determined by analysis of intra-cardiac atrial fibrillation signals, and embodiments of the present invention facilitate the analysis.

<CIT>, <CIT> and <CIT>describe systems which process electrogram data.

The present invention is defined by appended claim <NUM>. Embodiments are disclosed in the dependent claims.

While the description herein is, for simplicity, directed to situations where atrial fibrillation is occurring, those having ordinary skill in the art will be able to adapt the description for other types of fibrillation.

Embodiments of the present invention simultaneously acquire electropotential signals in the heart using a catheter having a multiplicity of electrodes at its distal end, each electrode generating a respective unipolar signal. The signals may be considered as unipolar signals, or in combination with another electrode, as bipolar signals. Unipolar signals may be calculated with respect to the Wilson central terminal (WCT), or with respect to another intracardiac electrode.

In a first part of the analysis of the signals, significant features, typically sections of the signals having a large numerical slope, are identified. The analysis is performed for the unipolar signals (using the bipolar signals to improve the analysis). The analysis identifies the electrical activations, herein termed annotations, and assigns respective quality factors to each of the annotations.

In a second part of the analysis, the atrial fibrillation signals are further investigated to identify blocked regions of the heart, i.e., regions of the heart where cells have been temporarily saturated (refractory), so that they are unable to sustain, or are only partly able to sustain, passage of an activation wave and subsequent detection of annotations. The analysis can identify cells that are permanently non-conducting, such as cells of scar tissue.

The results of the two parts of the analysis may be incorporated into a dynamic 3D map of the heart, showing progress of the activation wave through the heart, as well as blocked regions of the heart, i.e., regions through which an activation wave does not pass.

The present invention is related to software for implementing methods described herein. The methods themselves are not independently claimed. There is provided herein a method, which is carried out by inserting a probe having electrodes into a heart of a living subject, recording a bipolar electrogram and a unipolar electrogram from one of the electrodes at a location in the heart, and defining a time interval including a window of interest wherein a rate of change in a potential of the bipolar electrogram exceeds a predetermined value. The method is further carried out by establishing an annotation in the unipolar electrogram, wherein the annotation denotes a maximum rate of change in a potential of the unipolar electrogram within the window of interest, assigning a quality value to the annotation, and generating a <NUM>-dimensional map of a portion of the heart that includes the annotation and the quality value thereof.

According to another aspect of the method, recording a bipolar electrogram includes establishing a double bipolar electrode configuration of electrodes. The double bipolar electrode configuration includes a first differential signal from a first pair of unipolar electrodes and a second differential signal from a second pair of unipolar electrodes, wherein the bipolar electrogram is measured as a time-varying difference between the first differential signal and the second differential signal.

According to the method, establishing an annotation includes computing a wavelet transform of the unipolar electrogram.

An additional aspect of the method includes producing a scalogram of the wavelet transform and determining the maximum rate of change in the scalogram.

Yet another aspect of the method includes determining from the quality value that the annotation is a qualified annotation that meets predetermined blocking criteria, and indicating on the map that the qualified annotation is at or near a blocked region of the heart.

According to still another aspect of the method, establishing an annotation includes removing ventricular far field components from the unipolar electrogram.

According to one aspect of the method, establishing an annotation includes determining if a temporal cycle length of the unipolar electrogram at the annotation lies within predefined statistical bounds for temporal cycle lengths of other annotations.

An additional aspect of the method includes adjusting the quality value of the annotation according to at least one of a quality value, inter-annotation distance and timing of another annotation.

According to another aspect of the method, the other annotation was generated from another unipolar electrogram that was read from another of the electrodes.

A further aspect of the method includes filtering the unipolar electrogram by an amount sufficient to reduce noise to a predetermined level, wherein assigning a quality value includes determining the amount.

There is further provided according to embodiments of the invention an apparatus, including an intra-body probe having a plurality of electrodes. The probe is configured to contact tissue in a heart. The apparatus includes a display, and a processor, which is configured to receive an electrical signal from the electrodes and to perform the steps of recording a bipolar electrogram and a unipolar electrogram from one of the electrodes at a location in the heart, defining a time interval including a window of interest wherein a rate of change in a potential of the bipolar electrogram exceeds a predetermined value, establishing an annotation in the unipolar electrogram, wherein the annotation denotes a maximum rate of change in a potential of the unipolar electrogram within the window of interest, assigning a quality value to the annotation, and generating on the display a <NUM>-dimensional map of a portion of the heart wherein the map includes the annotation and the quality value thereof.

According to a further aspect of the apparatus, the probe has multiple rays, and each of the rays has at least one electrode.

According to one aspect of the apparatus, the probe is a basket catheter having multiple rib s, and each of the rib s has at least one electrode.

For a better understanding of the present invention, reference is made to the detailed description of the invention, by way of example, which is to be read in conjunction with the following drawings, wherein like elements are given like reference numerals, and wherein:.

In the following description, numerous specific details are set forth in order to provide a thorough understanding of the various principles of the present invention. It will be apparent to one skilled in the art, however, that not all these details are necessarily needed for practicing the present invention. In this instance, well-known circuits, control logic, and the details of computer program instructions for conventional algorithms and processes have not been shown in detail in order not to obscure the general concepts unnecessarily.

"Annotations" or "annotation points" refer to points or candidates on an electrogram that are considered to denote events of interest. In this disclosure the events are typically onset (local activation time) of the propagation of an electrical wave as sensed by the electrode.

"Activity" in an electrogram is used herein to denote a distinct region of bursty or undulating changes in an electrogram signal. Such a region may be recognized as being outstanding between regions of baseline signals. In this disclosure "activity" more often refers to a manifestation on an electrogram of one or more electrical propagation waves through the heart.

Turning now to the drawings, reference is initially made to <FIG>, which is a pictorial illustration of a system <NUM> for detecting areas of electrical activity in a heart <NUM> of a living subject <NUM> in accordance with a disclosed embodiment of the invention. The system comprises a probe, typically a catheter <NUM>, which is percutaneously inserted by an operator <NUM>, who is typically a physician, through the patient's vascular system into a chamber or vascular structure of the heart. The operator <NUM> brings the catheter's distal tip <NUM> into contact with the heart wall at a target site that is to be evaluated. Unipolar and bipolar electrograms are recorded using mapping electrodes on the distal segment of the catheter. Electrical activation maps based on the electrograms are then prepared, according to the methods disclosed in the above-noted <CIT>, and <CIT>, and in commonly assigned <CIT>.

The system <NUM> may comprise a general purpose or embedded computer processor, which is programmed with suitable software for carrying out the functions described hereinbelow. Thus, although portions of the system <NUM> shown in other drawing figures herein are shown as comprising a number of separate functional blocks, these blocks are not necessarily separate physical entities, but rather may represent, for example, different computing tasks or data objects stored in a memory that is accessible to the processor. These tasks may be carried out in software running on a single processor, or on multiple processors. The software may be provided to the processor or processors on tangible non-transitory media, such as CD-ROM or non-volatile memory. Alternatively or additionally, the system <NUM> may comprise a digital signal processor or hard-wired logic.

The catheter <NUM> typically comprises a handle <NUM>, having suitable controls on the handle to enable the operator <NUM> to steer, position and orient the distal end of the catheter as desired to the ablation. To aid the operator <NUM>, the distal portion of the catheter <NUM> contains position sensors (not shown) that provide signals to a positioning processor <NUM>, located in a console <NUM>. The catheter <NUM> may be adapted, from the ablation catheter described in commonly assigned <CIT>. The console <NUM> typically contains an ECG processor <NUM> and a display <NUM>.

The positioning processor <NUM> measures location and orientation coordinates of the catheter <NUM>. In one embodiment, the system <NUM> comprises a magnetic position tracking system that determines the position and orientation of the catheter <NUM>. The system <NUM> typically comprises a set of external radiators, such as field generating coils <NUM>, which are located in fixed, known positions external to the patient. The coils <NUM> generate electromagnetic fields in the vicinity of the heart <NUM>. These fields are sensed by magnetic field sensors located in the catheter <NUM>.

Typically, the system <NUM> includes other elements, which are not shown in the figures for the sake of simplicity. For example, the system <NUM> may include an electrocardiogram (ECG) monitor, coupled to receive signals from one or more body surface electrodes, so as to provide an ECG synchronization signal to the console <NUM>. The system <NUM> typically also includes a reference position sensor, either on an externally-applied reference patch attached to the exterior of the subject's body, or on an internally-placed catheter, which is inserted into the heart <NUM> maintained in a fixed position relative to the heart <NUM>. Conventional pumps and lines for circulating liquids through the catheter <NUM> for cooling an ablation site may be provided.

One system that embodies the above-described features of the system <NUM> is the CARTO® <NUM> System, available from Biosense Webster, Inc. , <NUM> Diamond Canyon Road, Diamond Bar, CA <NUM>. This system may be modified by those skilled in the art to embody the principles of the invention described herein. Multi-electrode basket and spline catheters are known that are suitable for obtaining unipolar and bipolar electrograms. An example of such a spline catheter is the Pentaray® NAV catheter, available from Biosense Webster.

In order to better illustrate the difficulties that can be solved by application of the principles of the invention, reference is now made to <FIG>, which is a group of bipolar electrograms, in accordance with an embodiment of the invention, in which a simulated bipolar electrode has been positioned in eight directions. The bipolar electrograms have been calculated from the difference of unipolar electrograms e.g., squares <NUM>, <NUM>, shown in distinctive hatching patterns in an electroanatomic map <NUM>, in which one pole is fixedly positioned at the square <NUM> and the other pole is rotated in <NUM> steps (<NUM> perpendicular and four oblique positions) around the position of the fixed pole. On the map <NUM>, an activation wave propagates slightly obliquely from right to left. The morphology observed from the eight bipolar complexes differs. This group shows a complex activation, resulting from fusion of two waves, which leads to large differences in morphology and amplitude of the bipolar complexes within windows of interest <NUM>. <FIG> illustrates ambiguities in detection of activation. The local activation time at which the activation wave passes a point is calculated by locating an event on an electrogram meeting criteria to be described below and subtracting the time of a fiducial reference from the time of the event. The time of the reference event may be defined using another intracardiac signal or body surface electrocardiogram.

The following two figures are schematic illustrations of distal ends of catheters used to acquire electropotentials from the heart, according to an embodiment of the present invention:.

Reference is now made to <FIG>, which is a diagram of a basket cardiac chamber mapping catheter <NUM> for use in accordance with an embodiment of the invention. The catheter <NUM> is similar in design to the basket catheter described in <CIT>, et al. , which is assigned to the assignees of the present invention. The catheter <NUM> has multiple ribs, each rib having at multiple electrodes. In one embodiment the catheter <NUM> has <NUM> unipolar electrodes, and can be configured with up to <NUM> bipolar pairs per spline. For example rib <NUM> has unipolar electrodes M1 - M8, with bipolar configurations B1 - B7. The inter-electrode distance is <NUM>.

Reference is now made to <FIG>, which is a diagram of a spline catheter <NUM> for use in accordance with an embodiment of the invention. An example of such a spline catheter is the Pentaray® NAV catheter, available from Biosense Webster. The catheter <NUM> has multiple splines, each spline having several electrodes. In one embodiment the catheter <NUM> has <NUM> unipolar electrodes, which can be configured as either two or three bipolar pairs per spline. For example, spline <NUM> has a first pair of unipolar electrodes <NUM>, <NUM> and a second pair of unipolar electrodes <NUM>, <NUM> (M1 - M4). Respective differences between the unipolar electrode pairs are calculated in blocks <NUM>, <NUM>. The outputs of blocks <NUM>, <NUM> (B1, B2) can be associated with one another to constitute a hybrid bipolar electrode configuration, an arrangement referred to herein as a "double bipolar configuration". The double bipolar configuration is used to establish a bipolar window of interest as described below Possible inter-electrode distances are <NUM>-<NUM>-<NUM> or <NUM>-<NUM>-<NUM>. Similar bipolar configurations can be established in the catheter <NUM> (<FIG>).

Both of the catheters <NUM>, <NUM> have multiple electrodes and are examples of distal ends with multiple electrodes in their individual splines, spokes or branches, and the distal ends may be inserted into the heart of a patient. Embodiments of the present invention use catheters such as the catheters <NUM>, <NUM> to acquire time-varying electropotentials simultaneously from different regions of the heart. In the case where the heart may be undergoing atrial fibrillation the acquired electropotentials are analyzed in order to characterize their transit within the heart.

Reference is now made to <FIG>, which is a flow chart of a method, presently claimed as software implementing the method, of annotating an electroanatomic map of the heart in accordance with an embodiment of the invention. The process steps are shown in a particular linear sequence for clarity of presentation. However, it will be evident that many of them can be performed in parallel, asynchronously, or in different orders. Those skilled in the art will also appreciate that a process could alternatively be represented as a number of interrelated states or events, e.g., in a state diagram. Moreover, not all illustrated process steps may be required to implement the method.

The method comprises analyzing the electropotentials acquired by multiple catheter electrodes while the subject is experiencing a conduction disturbance, e.g., atrial fibrillation. Initially electropotential signals are acquired as bipolar potentials plotted over time, typically by finding the differential signal between pairs of adjacent electrodes. However, there is no necessity that the pairs of electrodes be adjacent, and in some embodiments bipolar signals from non-adjacent electrodes are used. For the bipolar signals information on the <NUM>-dimensional position of the electrodes may be used; alternatively or additionally information on the electrode arrangement in the catheter may be used.

In initial step <NUM> the bipolar signals are analyzed to determine initial time periods, or windows, during which there is a relatively large change in potential, i.e., a maximum value of <MAT>.

Reference is now made to <FIG>, which is a block diagram of a method of unipolar local activation time (LAT) detection in accordance with an embodiment of the invention. A unipolar electrogram (EGM) input <NUM> is processed for removal of ventricular far field effects in a block <NUM>. Far field reduction can be accomplished using the teachings of commonly assigned Application No. <NUM>/<NUM>,<NUM>. Prefiltering occurs in block <NUM>, and may be accomplished using high and low pass filters, e.g. FIR and IIR filters. The output of block <NUM> is then processed in wavelet detection block <NUM>, details of which are described below.

The output of block <NUM> forms an input <NUM> of double bipolar electrogram calculation block <NUM>. Another input <NUM> ofblock <NUM> carries the identification of the electrodes being used for calculation of a bipolar electrogram, as an output signal <NUM>. Each member of a bipolar pair is constructed as described with reference to the catheter <NUM> (<FIG>). For example the inputs <NUM>, <NUM> of block <NUM> could be unipolar electrodes <NUM>, <NUM> (<FIG>) of the catheter <NUM>. Block <NUM> of <FIG> corresponds to block <NUM> of <FIG>. Bipolar EGM onset and termination are established in block <NUM>. This may be accomplished using the teachings of commonly assigned <CIT>. Windows of interest for the bipolar electrogram are established using the outputs ofblock <NUM> and block <NUM> in block <NUM>.

Reference is now made to <FIG>, which is a detailed block diagram illustrating the operation of block <NUM> (<FIG>) in accordance with an embodiment of the invention. Two EGM inputs <NUM>, <NUM> are pre-filtered and far-field components removed in blocks <NUM>, <NUM>. The inputs <NUM>, <NUM> are typically generated from pairs of neighboring electrodes, each member of a pair itself constituting a bipolar source, as shown in <FIG>. For example, the input <NUM> could be from unipolar electrode <NUM> (<FIG>). The outputs of blocks <NUM>, <NUM> are subtracted in block <NUM>, generating a double bipolar output signal <NUM>. The signal <NUM> is subjected to another pre-filtering step in block <NUM>, denotched in block <NUM>, and an output signal <NUM> submitted to block <NUM> wherein a bipolar window of interest is determined. An output signal <NUM> is produced by block <NUM>.

Reference is now made to <FIG>, which is a detailed block diagram illustrating a portion of the operation of block <NUM> (<FIG>) in accordance with an embodiment of the invention. Signals <NUM>, <NUM>, which represent successive tentative window determinations (signal <NUM> (<FIG>)) are evaluated in window detection blocks <NUM>, <NUM>, which generate output signals <NUM>, <NUM>, respectively. A maximum between two minima is detected. The signals <NUM>, <NUM> are processed in block <NUM>, where overlap of the detected windows is determined. In block <NUM> the windows found in blocks <NUM>, <NUM> are fused, provided that there is an overlap that exceeds <NUM>%. A signal <NUM> indicative of a window of interest is output by block <NUM>.

Reference is now made to <FIG>, which is a chart illustrating signals that are processed according to the arrangement of <FIG> in accordance with an embodiment of the invention. Graphs <NUM>, <NUM> represent outputs of blocks <NUM>, <NUM> and show the morphology of the electrograms and respective detected windows. For example, windows <NUM>, <NUM> extensively overlap and are therefore fused, as shown in graph <NUM>. Graph <NUM> indicates a superimposition of the electrograms of the graphs <NUM>, <NUM> and a fusion of the windows <NUM>, <NUM> to form a larger window <NUM>. Window <NUM> begins at point <NUM>, which is the minimum of the onset times of the windows <NUM>, <NUM> and ends at point <NUM>, which is the maximum of the termination times of the windows <NUM>, <NUM>.

Reference is now made to <FIG>, which is a detailed block diagram illustrating the operation of wavelet detection block <NUM> (<FIG>) in accordance with an embodiment of the invention. Wavelet transformation provides decomposition of a signal as a combination of a set of (orthonormal) basis functions derived from a mother wavelet by dilation and translation. If the wavelet is the derivative of a smoothing function, the wavelet coefficients represent the slope of the input signal. The wavelet parameters used in the arrangement of <FIG> comprise: (<NUM>) a continuous wavelet transform (CWT); (<NUM>) the first derivative of a Gaussian wavelet; and (<NUM>) decomposition over <NUM> linear scales in blocks <NUM>, <NUM>, followed by ratings and peak detection in blocks <NUM>, <NUM>.

Reference is now made to <FIG>, which is a diagram illustrating signals produced by the arrangement shown in <FIG> in accordance with an embodiment of the invention. Scalogram <NUM> is produced in wavelet transform block <NUM> from electrogram <NUM> by chaining maxima and minima; i.e., forming an ordered set of curves by an iterative filtering process. For example intervals <NUM>, <NUM> show readily identifiable maxima and minima in the scalogram <NUM>, whereas these are much less distinct in the electrogram <NUM>.

Reference is now made to <FIG>, which is a diagram illustrating the operation of wavelet transform block <NUM> (<FIG>) in different arrhythmias in accordance with an embodiment of the invention. Regional electroanatomic maps <NUM> indicate various types of atrial arrhythmic abnormalities that can be associated with atrial fibrillation. The maps <NUM> are shown with corresponding electrograms <NUM> and scalograms <NUM>. The scalograms <NUM> have distinct morphologies that relate to respective electrograms <NUM>. Generally the peaks in the electrograms <NUM> are more clearly isolated in the scalograms <NUM>, particularly when the activations become less distinct, for example in the cases <NUM>, <NUM> at the right of the figure.

Reverting to <FIG>, in a signal adjustment step <NUM> interfering signals are removed from the unipolar fibrillation signals, in order to expose the fibrillation signals. The interfering signals include ventricular far field signals or components that are projected from the ventricle. In one way of removing these components, the signal emanating from the ventricle is detected, and a mean QRS signal is subtracted, at the time of generation of the ventricle signal, from the fibrillation signal.

Reference is now made to <FIG>, which is a set of diagrams illustrating a process for removing an interfering signal from a unipolar fibrillation signal, in accordance with an embodiment of the invention. As shown in a first part <NUM>, a fibrillation signal initially includes a ventricular far-field portion. A mean QRS signal is generated, typically from a set of QRS signals, as is shown in a second part <NUM>, and, as shown in third and fourth parts <NUM>, the fibrillation signal is corrected by subtraction of the mean QRS signal.

Alternatively or additionally, template matching to a predefined ventricle signal, and/or a template based on an estimation from the fibrillation signal, at times where the signal is only ventricular, may be used for prediction of the ventricular far field signal for the unipolar fibrillation signals. Typically, times for expected occurrence of the ventricular signals may be determined from body ECG signals, ventricular intra-cardiac signals, or coronary sinus signals. Using the template, the ventricular far field signals or components may be estimated and subtracted from the fibrillation signal.

Those having ordinary skill in the art will be able to adapt the description above, , for other methods of removal of the ventricular far field signal. In addition, interfering signals other than the ventricular far field signals may be removed by similar methods to those described above for the ventricular signals.

Other adjustments that may be performed in the signal adjustments step include noise reduction (including <NUM>/<NUM> signal induced noise), reduction of electro-magnetic interference (EMI), and correcting for baseline drift, by any methods known in the art.

Returning to the flowchart of <FIG>, in a further analysis step <NUM> performed on the adjusted unipolar fibrillation signal, times, herein termed annotations, a maximum <MAT> value is detected are determined. The process of determining the maximum <MAT> value is applied to the adjusted signal within the windows found in the initial analysis initial step <NUM>, and further includes a process of noise reduction. In one embodiment, the noise reduction applied to the corrected fibrillation signal comprises forming a composition of different wavelet transforms with the corrected fibrillation signal. The different wavelet transforms effectively generate filters of differing bandwidths, and the composition of these filters with the corrected fibrillation signal reduces noise in the signal.

Additionally or alternatively, other methods for noise reduction, such as by applying one or more different bandwidth filters to the signal, within the windows referred to above, may be applied to the corrected fibrillation signal.

In a quality estimation step <NUM>, each maximum <MAT> annotation may be assigned a parameter measuring the goodness of the annotation, depending on the amount and type of filtering required to determine the annotation in step <NUM>. For example, an annotation assigned with a high parameter value may be returned for both low and high levels of filtering, whereas an annotation assigned with a low parameter value may be returned only for low or high filter levels, but not for both.

The annotations are further characterized to estimate a final quality of the annotation. The characterization is according to the position of the electrodes generating their signal. The characterization may further be according to the location in the heart from where the signal was acquired, the timing of the annotation, the goodness parameter of the annotation (determined in the previous step), and/or whether the annotation is at or close to a time where signal adjustments, described above in the signal adjustment step, have been made. These parameters are assigned a numerical value. From the position of a first electrode it may be considered that it is physiologically unlikely that the signal acquired by the electrode will comprise an annotation, in which case the annotation final quality is downgraded. For a second electrode it may be considered likely that the signal comprises an annotation, in which case the annotation final quality may be upgraded.

In addition to the variables described above for estimating the quality of a given annotation, the quality, inter-annotation distance and timing of neighboring spatial annotations may be checked, and the quality of the given annotation adjusted accordingly. For example, if a given electrode is surrounded by electrodes generating annotations with a high quality, then in some cases the quality of the given electrode annotation may be increased (in other cases, described below with reference to step <NUM>, there may be a blocking effect). Alternatively, if a given electrode is surrounded by electrodes generating annotations with a low quality, then the quality of the given electrode annotation may be decreased. In addition, if a given electrode is surrounded by electrodes generating quality annotations significantly outside a physiological range, then the quality of the given electrode may be further decreased.

As a further check to determine the quality of an annotation, the annotation is evaluated with respect to a statistic describing other annotations. For example, a histogram of temporal cycle lengths of each annotation may be generated. Only those annotations lying within predefined bounds of the histogram may be considered to be valid, and those outside the bounds are assumed to be erroneous.

In a blocking identification step <NUM>, the annotations meeting the criteria assigned in step <NUM> are considered to identify regions of the heart where the activation of the heart muscle appears to have been "blocked. " Such a blockage occurs when activation waves collide or are dissociated, causing heart muscle cells at the position of collision to saturate temporarily, so that they are unable to reactivate. These are known as "refractory cells". Blocked regions may be identified by considering the signal on a given electrode, as well as on the surrounding electrodes. Typically, if the annotation signal on the given electrode is significantly smaller, has a different morphology, and/or has a lower quality, than the annotation signals on surrounding electrodes, then the given electrode may be considered to be located at or near a blocked region of the heart. A block may be temporary (functional block) or permanent (e.g., a scar).

In a presentation step <NUM>, the results from the two previous steps, i.e., good quality annotations and regions identified as being blocked, are presented on a dynamic <NUM>-dimensional map of the heart, or a chamber of the heart. Typically, the dynamic map illustrates the relative timing and the quality of the annotations in the heart, as well as an estimated "flow" of the annotations, i.e., time intervals between successive annotations. The dynamic map also illustrates regions of the heart that are assumed to be blocked. The dynamic map may also indicate regions of the heart, or of a chamber of the heart, from which no information was obtained.

Reference is now made to <FIG>, which is a graphic diagram presenting an annotation of an electrogram <NUM> in accordance with an embodiment of the invention. The lower portion of the figure details the process applied to a representative complex <NUM>. Hybrid bipolar windows <NUM>, <NUM> are obtained from two unipolar electrodes as described above. Tracings <NUM>, <NUM> represent the first derivatives of the signals from the two unipolar electrodes. A scalogram <NUM> was developed from wavelet transformations computed based on the electrogram <NUM>. A series of annotations <NUM> is shown on the scalogram <NUM>.

Reference is now made to <FIG>, which is a graphic diagram presenting annotations of electrical activity <NUM> in a case of atrial fibrillation in accordance with an embodiment of the invention. Tracings <NUM> are superimposed body surface electrode signals. Annotations are shown for several complexes in a scalogram <NUM> in the lower portion of the figure, and further indicated by the number of triangles in the lower portion of the figure. For example an annotation indicated by arrow <NUM> is associated with only two triangles <NUM> and is of relatively low quality compared to an annotation indicated by arrow <NUM>, which is associated with a larger number of triangles <NUM>. The quality of the annotations is further graphically shown in middle portion <NUM>. The technique has successfully annotated a complex fractionated portion <NUM> of the activity <NUM>.

Reference is now made to <FIG>, which is a graphic diagram presenting annotations of electrical activity in accordance with an embodiment of the invention. The presentation is similar to <FIG>. The quality of the annotations is further indicated by dots <NUM>. Dots <NUM> represent chains starting from the finest scale and progressing to coarser scales. Inspection of the chains indicated by the dots <NUM> together with the chains indicated by the triangles that progress in the opposite direction permits the operator to distinguish the various activation patterns shown by scalograms <NUM>(<FIG>).

Claim 1:
Software for carrying out a method of determining quality of annotations of unipolar electrical signals from a heart when executed by a processor comprising:
receiving bipolar signals and unipolar signals from the heart;
receiving signals indicative of positions of unipolar electrodes generating the unipolar signals;
analyzing the bipolar signals to find time windows with a large numerical slope;
removing interfering signals from the unipolar signals; and
performing wavelet transformation and annotating maximum numerical slope of the unipolar signals with removed interfering signals within the time windows, thereby identifying a plurality of annotations;
for each of the annotations:
estimating a quality of the annotation based on the position of the unipolar electrode generating its signal;
assigning a numerical quality value to the position of the unipolar electrode generating its signal; and
downgrading the numerical quality value when, from the position of the unipolar electrode, it is physiologically unlikely that the signal from the unipolar electrode will comprise an annotation.