Ventricular propagation map with areas showing segmented electrograms

Abstract

To provide a method for characterizing cardiac arrhythmia.SOLUTION: A method includes storing an anatomical map of at least a portion of a surface of a heart. Respective electrogram (EGM) signal amplitudes measured at respective positions on the surface of the heart are stored. Based on the EGM signal amplitudes, defined are: one or more first regions of the surface in which the EGM signal amplitudes are fractionated, and one or more second regions of the surface in which the EGM signal amplitudes are non-fractionated. A first surface representation is generated for the fractionated EGM signal amplitudes in the first regions. Propagation times are extracted from the non-fractionated EGM signal amplitudes in the second regions, and a second surface representation of the propagation times is derived. The first and second surface representations of the respective first and second regions of the surface, overlaid on the anatomical map, are simultaneously presented.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates generally to electrophysiological mapping, and more particularly to visualization of cardiac electrophysiological maps. [Background technology]

[0002] In electrophysiological (EP) cardiac mapping, visualization methods previously proposed in the patent literature may be used to facilitate interpretation of EP maps. For example, U.S. Pat. No. 8,838,216 describes a method for generating a model of a cardiac surface having a plurality of images representative of electrogram voltages at a plurality of measurement points within the heart. The method includes measuring electrogram voltages at a plurality of points within the heart, generating a first model of the cardiac surface of the heart, generating images representative of each electrogram voltage, each image having a feature representative of the electrogram voltage, and generating a further model of the cardiac surface. The images representative of the electrogram voltages project from the further model of the cardiac surface at points on the further model corresponding to the points at which the electrogram voltages were measured. An apparatus for generating a model of the cardiac surface is also disclosed.

[0003] As another example, U.S. Patent Application Publication No. 2009 / 0192393 describes software and apparatus for automatically detecting and mapping ganglionated plexi found within the area of ​​complex fractionated atrial electrograms (CFAEs) in the ventricles when atrial fibrillation (AFib) occurs. The electrogram signals are analyzed to measure the number of complexes whose amplitudes and peak-to-peak intervals meet certain criteria. Functional maps showing the spatial distribution of the ganglionated plexi and the relative number of complex fractionated electrograms are generated for display.

[0004] US Patent Application Publication No. 2014 / 0005563 describes a method for visualization of electrophysiological information that may include electroanatomical data representing electrical activity on an anatomical region within a patient's body over a period of time. An interval within the period is selected in response to a user's selection. A visual representation of the physiological information for the user-selected interval may be generated by applying at least one analysis method to the electroanatomical data. The visual representation may be spatially superimposed on a graphical representation of the anatomical region within the patient's body. In one embodiment of the present invention, the granularity may be displayed spatially as a 3D complex granularity electrogram map. The granularity from lowest to highest may be visually identified by a color map. Summary of the Invention [Means for solving the problem]

[0005] An embodiment of the invention provides a method including storing an anatomical map of at least a portion of a surface of the heart. Respective electrogram (EGM) signal amplitudes measured at respective locations on the surface of the heart are stored. One or more first regions of the surface in which the EGM signal amplitudes are subdivided and one or more second regions of the surface in which the EGM signal amplitudes are not subdivided are defined based on the EGM signal amplitudes. A first surface representation for the subdivided EGM signal amplitudes in the first regions is generated. Propagation times are extracted from the unsubdivided EGM signal amplitudes in the second regions, and a second surface representation of the propagation times is derived. The first and second surface representations of each of the first and second regions of the surface are simultaneously presented, superimposed on the anatomical map.

[0006] In some embodiments, the method further comprises generating a third surface representation for signals that are not defined as being subdivided and that cannot be defined in terms of propagation time.

[0007] In one embodiment, generating a first surface representation for the refined EGM signal amplitudes includes selecting a subset of the refined EGM signal amplitudes and generating a surface for the subset.

[0008] In some embodiments the first surface representation comprises geometric shapes protruding from the surface, hi some embodiments the protruding geometric shapes comprise one of ripples and bars.

[0009] In one embodiment, the second surface representation includes a color scale.

[0010] In some embodiments, the propagation time comprises a local activation time (LAT) value.

[0011] In one embodiment, the method further includes assigning a local activation time (LAT) value to the EGM signal even when the EGM signal is segmented, and generating a third surface representation that visualizes the third surface representation for the segmented EGM signal.

[0012] In another embodiment, the propagation time includes a cycle length value.

[0013] According to another embodiment of the present invention, there is further provided a system including a memory and a processor, the memory configured to store an anatomical map of at least a portion of a surface of the heart and to store respective electrogram (EGM) signal amplitudes measured at respective locations on the surface of the heart, the processor configured to (i) define, based on the EGM signal amplitudes, one or more first regions of the surface in which the EGM signal amplitudes are subdivided and one or more second regions of the surface in which the EGM signal amplitudes are not subdivided, (ii) generate a first surface representation for the subdivided EGM signal amplitudes in the first regions, (iii) extract a propagation time from the unsubdivided EGM signal amplitudes in the second regions to derive a second surface representation of the propagation time, and (iv) simultaneously present the first and second surface representations of each of the first and second regions of the surface superimposed on the anatomical map. [Brief description of the drawings]

[0014] The invention will be more fully understood from consideration of the following detailed description taken in conjunction with the drawings, in which: [Figure 1] FIG. 1 is a schematic, pictorial diagram of a catheter-based cardiac navigation and electrophysiological (EP) signal analysis system, in accordance with an exemplary embodiment of the present invention. [Diagram 2] 1 is a graph that illustrates a schematic representation of a sharply defined electrogram (EGM) signal and a segmented electrogram signal, in accordance with an exemplary embodiment of the present invention; [Diagram 3] 1 is a schematic pictorial volume rendering of a mixed representation EP map superimposed on a ventricular anatomy, in accordance with an exemplary embodiment of the present invention; [Figure 4] 4 is a flow chart that generally illustrates a method and algorithm for generating the mixed representation EP map of FIG. 3, according to an exemplary embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Overview Cardiac arrhythmias are a class of conditions in which the heart beats irregularly. Among these cardiac arrhythmia conditions are the important classes, several types of ventricular tachycardia, atrial tachycardia, and several types of fibrillation.

[0016] To characterize a patient's cardiac arrhythmias, a catheter-based electrophysiological (EP) mapping system may be used to generate an EP map of at least a portion of the patient's heart, such as an EP map of a ventricle. In a typical catheter-based EP mapping procedure, a distal end of a catheter with one or more sensing electrodes is inserted into a ventricle to sense EP signals. As a physician operating the system moves the distal end inside the ventricle, the EP mapping system acquires EP signals at various locations on the inner surface of the ventricle, as well as the respective positions of the distal end. Based on these acquired signals, a processor of the mapping system generates the required EP map, such as a map including local activation times (LATs) superimposed on an anatomical map of the ventricle.

[0017] LAT maps typically contain regions exhibiting normal periodic electrical activity (e.g., sinus rhythm), regions exhibiting abnormal rapid cycling electrical activity (e.g., rotators), and regions exhibiting complex fractionated electrograms in pathological tissues. Over time, however, occurrences of normal electrogram cycles, episodes of rapid cycling electrograms, and complex fractionated electrograms can be observed in areas mostly exhibiting sinus rhythm, and in tachycardias.

[0018] Thus, LAT maps may indicate the occurrence of abnormal, yet well-defined, propagation characteristics of the EP signal. For example, LAT maps may indicate reentry of tachycardia (RT) by showing regions where EP activation waves propagate in closed loops with well-defined, yet pathological cycle lengths (e.g., time between successive peaks of the electrogram).

[0019] In some cases, however, EP abnormalities may be manifested by episodes in which the electrogram is fragmented (e.g., produced in irregular patterns such as bursts of very rapid deflections of the signal), making it impossible to define (or in fact never to occur) the time at which the EP wave passes under the capture electrode. In this context, the term "fragmented electrogram" refers to aperiodic electrograms that do not have a characteristic cycle time, and in some cases, do not even have a definable peak from which to derive a LAT value.

[0020] Where fractionated electrograms are presented, EP propagation maps based on LAT values ​​or cycle times are not used in practice due to the difficulty of calculating meaningful LAT values ​​from such electrogram signals. Nevertheless, the occurrence of fractionated electrograms has been found to be clinically significant, and therefore presenting them on an EP map is considered important for accurate assessment of the underlying EP pathology.

[0021] One possible way to incorporate segmented signals into an EP map is to use a time-dependent "ripple" map in which instantaneous EP amplitude is shown as a function of time, for example by being presented as a time-varying bar protruding from the ventricular surface. In such a presentation, the length (height) of each bar indicates the voltage measured at the corresponding location on the ventricular surface at a given time. However, applying ripple mapping to the entire ventricle is usually computationally intensive and visually too complex to interpret, and may also compromise the clarity of the presentation of other important EP information (e.g., LAT information), as other information may be omitted or obscured in such a map.

[0022] To overcome the above problems, the exemplary embodiments of the present invention described below separate the ventricular map into segmented and non-segmented areas and incorporate two different types of display simultaneously into the map. In some exemplary embodiments, a mixed representation EP map is provided in which clearly defined EP propagation characteristics (e.g., LAT values) and segmented EP signal amplitudes are each superimposed on the cardiac anatomical structure using different graphical representations, without either of them obscuring the other. The process typically follows a processor performing the following: 1. Generate an EP map including an anatomical map encoded with one or more first regions of segmented EP activity and one or more second regions of sharply defined EP activity, and delineate the various regions on the anatomical structure using data analysis methods such as deep learning or clustering. The one or more first regions and one or more second regions of the surface are defined using a processor based on electrogram (EGM) signal amplitudes, as described below. The processor then generates a first surface representation for the segmented EGM signal amplitudes in the first regions, extracts propagation times from the unsegmented EGM signal amplitudes in the second regions, and derives a second surface representation of the propagation times. Finally, the processor simultaneously presents the first and second surface representations of the respective first and second regions of the surface superimposed on the anatomical map. 2. When the user requests a propagation map, the processor displays, for example, a conventional propagation map, as derived from the LAT values, over the non-subdivision areas and simultaneously displays a ripple map over the subdivision areas.

[0023] A conventional propagation map consists of a moving highlight, hue, color, or some other visual indicator that propagates according to the LAT value of each point. Typically, each point has one LAT value, but some points may also have multiple LAT values, e.g., a dual-potential point may have two LAT values. If the system is designed to have at most one LAT value for each point, then the conventional propagation map will highlight each point at most once. If the system is designed to assign multiple LAT values ​​to some points, then the conventional propagation map may highlight some points multiple times.

[0024] In another exemplary embodiment, the processor generates a third surface representation for signals that are not defined as subdivided and cannot be defined in terms of propagation time, such as for dual potential presentations.

[0025] In yet another exemplary embodiment, the processor selects only a subset of the signals that it considers to be subdivided for representation by the first surface representation.

[0026] In some cases, even if a particular EGM signal is subdivided, it is possible to approximate or otherwise assign LAT values ​​to the EGM signal. In an exemplary embodiment, the processor is further configured to generate different surface representations for such subdivided EGM signals. In this exemplary embodiment, the subdivided signals may be represented by map representations based on ripples and / or LAT values.

[0027] The disclosed mixed representation EP maps are dynamic in nature and are capable of showing areas exhibiting time-dependent segmented and non-segmented electrogram (EGM) behavior, for example in a video mode of the mixed map.

[0028] By displaying segmented and non-segmented EGM signatures on cardiac anatomical structures using different graphical means (e.g., ripple and color scaling), the disclosed mixed representation EP mapping technique may improve the diagnostic value of catheter-based EP mapping procedures.

[0029] System Description FIG. 1 is a schematic pictorial diagram of a catheter-based cardiac navigation and electrophysiological (EP) signal analysis system 20, according to an exemplary embodiment of the present invention. The system 20 may be configured to analyze virtually any physiological parameter or combination of such parameters. In the present description, by way of example, it is assumed that the analyzed signals are potential-time relationships of intracardiac electrograms (EGMs) and / or extracardiac (body surface) electrocardiograms (ECGs). To fully characterize such relationships, the signals at various locations need to be cross-referenced in time, as is done, for example, during local activation time (LAT) map generation. Time referencing is achieved by measuring relative to a reference time (e.g., a time point), such as the start of each QRS complex (i.e., the start of each heart beat) of an ECG reference signal. In an exemplary embodiment, the reference signal is received from a catheter placed in the coronary sinus. A method for generating LAT maps is described in U.S. Pat. No. 9,050,011, the disclosure of which is incorporated herein by reference.

[0030] For simplicity and clarity, the following description assumes, unless otherwise noted, an investigation procedure in which the system 20 uses a probe 24 to measure actual electrical activity of the heart 34. The distal end 32 of the probe is assumed to have an electrode 22. The measured signals are used, among other things, to create a LAT map of at least a portion of the wall tissue of the heart 34 of the patient 26.

[0031] Typically, probe 24 comprises a catheter that is inserted into the body of patient 26 during a mapping procedure performed by a physician 28 using system 20. It is assumed that a ground electrode 23 is attached to the patient 26 during the procedure. In addition, an electrode 29 is assumed to be attached to the skin of patient 26 in the region of the heart 34.

[0032] In an exemplary embodiment, EGMs are acquired as the probe 24 is moved across a portion of the ventricle. At the times when abnormal EP activation waves pass under the catheter electrodes, some features of the measured EGM trace are annotated. At these times, the location of the probe 24 is also recorded.

[0033] System 20 may be controlled by a system processor 40, which includes a processing unit 42 in communication with a memory 44. In some embodiments, system processor 40 includes memory 44 that stores a LAT and / or voltage map 62 of at least a portion of the wall tissue of heart 34 of patient 26. Processor 40 is typically mounted in a console 46, which includes operating controls 38, which typically include a pointing device 39, such as a mouse or trackball, used by physician 28 to interact with the processor.

[0034] The processor 40 (particularly the processing unit 42) executes software including the probe tracking module 30, the ECG module 36, and the EP activation analysis module 35 to operate the system 20 and / or the EP activation analysis module 35 to model arrhythmias and perform at least a portion of the disclosed analyses (e.g., using the LAT or adjusted LAT map 62 stored in memory 44).

[0035] The ECG module 36 is connected to receive the actual electrical signals from the electrodes 22 and 29. The module is configured to analyze the actual signals and is able to present the results of the analysis on a display 48, typically in the standard ECG format of a graphical representation that varies over time.

[0036] The probe tracking module 30 typically tracks the location of the distal end 32 of the probe 24 within the heart 34 of the patient 26. The tracking module 30 may use any probe position tracking method known in the art. For example, the module 30 may operate a magnetic field based position tracking subsystem. For simplicity, components of such a subsystem are not shown in FIG. 1 .

[0037] Alternatively or additionally, tracking module 30 may track probe 24 by measuring the impedance between electrodes 23, 29 and 22, as well as the impedance to other electrodes that may be located on the probe. In this case, electrodes 22 and / or 29 may provide both ECG and position tracking signals. The Carto3® system, manufactured by Biosense Webster (Irvine, California), uses both magnetic field position tracking and impedance measurements for position tracking.

[0038] The processor 40 can use the tracking module 30 to determine the location of the distal tip 32. Additionally, by using both the tracking module 30 and the ECG module 36, the processor can determine not only the location of the distal tip, but also the LAT of the actual electrical signal detected at these specific locations. As mentioned above, the electrical tracking signals from the individual electrodes 22 can be combined with the magnetic tracking signals so that the location of each electrode is recorded. Such a mixed (i.e. magnetic / electrical) tracking system and method is implemented in various medical applications, for example, in the CARTO™ Advanced Current Location (ACL) system manufactured by Biosense-Webster Inc., and is described in detail in U.S. Pat. No. 8,456,182, the disclosure of which is incorporated herein by reference.

[0039] The results of the operations performed by processor 40 are displayed to physician 28 on display 48, which typically presents a graphic user interface to the physician, a visual representation of the ECG signals sensed by electrodes 22, and / or an image or map of the heart 34 under examination.

[0040] The software executed by processor 40 may be downloaded to processor 40 in electronic form, for example over a network, but alternatively or additionally, the software may be provided and / or stored on a non-transitory tangible medium, such as a magnetic, optical or electronic memory. In particular, processor 40 executes dedicated algorithms that enable processor 40 to perform the disclosed steps, as described below.

[0041] Fractionated electrogram (EGM) signal 2 is a graph that diagrammatically illustrates (i) a well-defined electrogram (EGM) signal 50 and (ii) a segmented electrogram signal 55, according to an exemplary embodiment of the present invention. As shown, the well-defined EGM signal allows for definition of a temporal cycle length 52, whereas cardiac locations that exhibit segmented episodes of EGM signals may not allow for a defined temporal cycle length. Such cardiac locations that exhibit disorganized EGM signals may be sources of proarrhythmic activity that require ablation to treat the resulting arrhythmia. Complicating matters, however, both cardiac locations that exhibit well-defined cycle lengths and cardiac locations that present segmented episodes of EGM signals have significant clinical value in diagnosing arrhythmias.

[0042] To answer this challenge, exemplary embodiments of the disclosed invention provide graphical techniques for presenting both types of EP information on the same EP map so that physicians can more easily analyze and diagnose complex abnormal cardiac activity.

[0043] Ventricular propagation map with areas showing segmented electrograms 3 is a schematic pictorial volume rendering of a mixed representation EP map 60 superimposed on ventricular anatomy, in accordance with an exemplary embodiment of the present invention. As shown, the mixed representation EP map 60 includes a first surface representation 61 of segmented areas and a second surface representation 62 of non-segmented (i.e., sharply defined) areas.

[0044] In areas such as area 61 where temporal analysis is not possible due to the EGM signal being acquired at a segmented surface location, the mixed representation EP map 60 provides a visualization of the segmented amplitude superimposed on the anatomical structures in the form of bars 63 protruding from the surface, where the height of the bar represents the magnitude of the EGM amplitude at that location at a given time.

[0045] The second surface representation 62 encodes propagation time values, e.g., LAT values, in the form of a color scale rendering 64 (shown in grayscale) over an area, such as area 62 of the anatomical map, where the color of a surface location gives the LAT value at that location at a given time.

[0046] The mixed representation EP map 60 should be understood as a “snapshot” of time-dependent EP activity, and typically a video mode is used to display the mixed representation EP map 60 .

[0047] Figure 4 is a flow chart that generally illustrates a method and algorithm for generating the mixed representation EA map 60 of Figure 3, according to an exemplary embodiment of the present invention. The algorithm, according to the exemplary embodiment presented, executes a process that begins with processor 40 uploading from memory 44 an anatomical map of the ventricle and EP mapping data (e.g., a set of EGMs from surface locations above the mapped anatomy) at an anatomical and EP data upload step 70.

[0048] Next, in an EGM analysis step 72, processor 40 determines which of the uploaded EGMs are segmented and which are well-defined (eg, unsegmented).

[0049] In an EP map generation step 74, processor 40 generates an EP map that includes an anatomical map encoded with one or more first regions of segmented EP activity and one or more second regions of sharply defined EP activity, depicting various regions across the anatomical structure.

[0050] At a present EP map step 76, the processor 40 presents the rendered EP map of step 74 on the display 48 to a user, such as the physician 28. At this point, the physician 28 may require more information, such as to display a propagation map including LAT values ​​or cycle lengths, at a request propagation map step 78.

[0051] To maintain fine-grained EP activity information without obscuring the propagation information, processor 40 derives the mixed representation EP map 60 described above.

[0052] In EP data analysis step 80, processor 40 extracts signal amplitudes from the segmented EGMs and amplitude propagation times, such as LAT values ​​or cycle lengths, from the unsegmented EGM signals. Finally, in step 82, processor 40 constructs a mixed representation EP map 60, where parts of the anatomy are overlaid with discrete representations (e.g., projecting bars 68) to show segmented EP activity and other parts of the anatomy are overlaid with continuous time information of sharply defined EP activation (e.g., color-scaled areas 64).

[0053] It will be understood that the above described embodiments are given by way of example, and the present invention is not limited to what is specifically shown and described herein above. Rather, the scope of the present invention includes both combinations and subcombinations of the various features described in the above specification, as well as variations and modifications thereof that would occur to a person skilled in the art upon reading the foregoing description, and that are not disclosed in the prior art. Documents incorporated by reference into this patent application are to be considered as part of this application, except that if any term is defined in these incorporated documents in a manner that is inconsistent with the definition expressly or impliedly given herein, then only the definition in this specification shall be considered.

[0054] [Embodiment] (1) A method for characterizing cardiac arrhythmia, comprising: storing an anatomical map of at least a portion of a surface of the heart; storing each electrogram (EGM) signal amplitude measured at each location on the surface of the heart; defining, based on the EGM signal amplitude, one or more first regions of the surface in which the EGM signal amplitude is subdivided and one or more second regions of the surface in which the EGM signal amplitude is not subdivided; generating a first surface representation for the refined EGM signal amplitudes in the first region; extracting a propagation time from the unrefined EGM signal amplitude in the second region and deriving a second surface representation of the propagation time; and simultaneously presenting the first and second surface representations of the first and second regions of the surface, respectively, superimposed on the anatomical map. (2) The method of embodiment 1, comprising generating a third surface representation for signals that are not defined as being subdivided and that cannot be defined in terms of propagation time. (3) The method of embodiment 1, wherein generating the first surface representation for the subdivided EGM signal amplitudes includes selecting a subset of the subdivided EGM signal amplitudes and generating the surface for the subset. (4) The method of claim 1, wherein the first surface representation includes geometric shapes protruding from the surface. (5) The method of claim 2, wherein the protruding geometric shape includes one of a ripple and a bar.

[0055] (6) The method of embodiment 1, wherein the second surface representation includes a color scale. (7) The method of embodiment 1, wherein the propagation time comprises a local activation time (LAT) value. (8) The method of embodiment 1, comprising assigning a local activation time (LAT) value to the EGM signal even when the EGM signal is segmented, and generating a third surface representation that visualizes a third surface representation for the segmented EGM signal. (9) The method of embodiment 1, wherein the propagation time includes a cycle length value. (10) A system for characterizing cardiac arrhythmia, comprising: A memory, storing an anatomical map of at least a portion of a surface of the heart; and storing each electrogram (EGM) signal amplitude measured at each location on the surface of the heart. 1. A processor comprising: defining, based on the EGM signal amplitude, one or more first regions of the surface in which the EGM signal amplitude is subdivided and one or more second regions of the surface in which the EGM signal amplitude is not subdivided; generating a first surface representation for the refined EGM signal amplitudes in the first region; extracting a propagation time from the unrefined EGM signal amplitude in the second region and deriving a second surface representation of the propagation time; and simultaneously presenting the first and second surface representations of respective first and second regions of the surface superimposed on the anatomical map.

[0056] (11) The system of embodiment 10, wherein the processor is further configured to generate a third surface representation for signals that are not defined as subdivided and cannot be defined in terms of propagation time. (12) The system of embodiment 10, wherein the processor is configured to generate the first surface representation for the subdivided EGM signal amplitudes, and generating the first surface representation includes selecting a subset of the subdivided EGM signal amplitudes and generating the surface for the subset. (13) The system of embodiment 10, wherein the first surface representation includes a geometric shape protruding from the surface. (14) The system of embodiment 11, wherein the protruding geometric shape includes one of a ripple and a bar. (15) The system of embodiment 10, wherein the second surface representation includes a color scale.

[0057] (16) The system of embodiment 10, wherein the propagation time includes a local activation time (LAT) value. (17) The system of embodiment 10, wherein the processor is configured to assign a local activation time (LAT) value to the EGM signal even when the EGM signal is segmented, and to generate a third surface representation that visualizes a third surface representation for the segmented EGM signal. (18) The system of embodiment 10, wherein the propagation time includes a cycle length value.

Claims

1. 1. A method of operation of a system for characterizing cardiac arrhythmias, comprising: a memory of the system, storing an anatomical map of at least a portion of a surface of the heart; storing each electrogram (EGM) signal amplitude measured at each location on the surface of the heart; a processor of the system, defining, based on the EGM signal amplitude, one or more first regions of the surface in which the EGM signal amplitude is subdivided and one or more second regions of the surface in which the EGM signal amplitude is not subdivided; generating a first surface representation for the subdivided EGM signal amplitudes in the first region; extracting a propagation time from the unrefined EGM signal amplitude in the second region and deriving a second surface representation of the propagation time; simultaneously presenting the first and second surface representations of respective first and second regions of the surface superimposed on the anatomical map, the first surface representation consisting of geometric shapes protruding from the surface, a height of the protruding geometric shapes representing a magnitude of the EGM signal amplitude at an associated location on the surface at a given time, and the second surface representation consisting of a color scale, a color of a location on the surface representing the propagation time at the location on the surface at a given time; superimposing the protruding geometric shape on the first region where temporal analysis is not possible; A method of operation comprising:

2. 2. A method according to claim 1, further comprising the processor generating a third surface representation for signals not defined as being subdivided and not defined in terms of the propagation time.

3. The method of claim 1, wherein the processor generating the first surface representation for the subdivided EGM signal amplitudes includes selecting a subset of the subdivided EGM signal amplitudes and generating the surface for the subset.

4. The method of claim 2 , wherein the protruding geometric shape comprises one of a ripple and a bar.

5. The method of claim 1 , wherein the propagation time comprises a local activation time (LAT) value.

6. 2. The method of claim 1, further comprising: assigning a local activation time (LAT) value to the EGM signal even when the EGM signal is segmented; and generating a third surface representation that visualizes a third surface representation for the segmented EGM signal.

7. The method of claim 1 , wherein the propagation time includes a cycle length value.

8. 1. A system for characterizing cardiac arrhythmias, comprising: A memory, storing an anatomical map of at least a portion of a surface of the heart; and storing each electrogram (EGM) signal amplitude measured at each location on the surface of the heart.

1. A processor comprising: defining, based on the EGM signal amplitude, one or more first regions of the surface in which the EGM signal amplitude is subdivided and one or more second regions of the surface in which the EGM signal amplitude is not subdivided; generating a first surface representation for the subdivided EGM signal amplitudes in the first region; extracting a propagation time from the unrefined EGM signal amplitude in the second region and deriving a second surface representation of the propagation time; simultaneously presenting the first and second surface representations of respective first and second regions of the surface superimposed on the anatomical map, the first surface representation consisting of geometric shapes protruding from the surface, a height of the protruding geometric shapes representing a magnitude of the EGM signal amplitude at an associated location on the surface at a given time, and the second surface representation consisting of a color scale, a color of a location on the surface representing the propagation time at the location on the surface at a given time; superimposing said protruding geometric shape on said first region where temporal analysis is not possible; and a processor configured to perform the steps.

9. The system of claim 8 , wherein the processor is further configured to generate a third surface representation for signals that are not defined as being subdivided and that cannot be defined in terms of the propagation time.

10. 9. The system of claim 8, wherein the processor is configured to generate the first surface representation for the subdivided EGM signal amplitudes, and generating the first surface representation includes selecting a subset of the subdivided EGM signal amplitudes and generating the surface for the subset.

11. The system of claim 9 , wherein the protruding geometric shape comprises one of a ripple and a bar.

12. The system of claim 8 , wherein the propagation time comprises a local activation time (LAT) value.

13. 10. The system of claim 8, wherein the processor is configured to assign a local activation time (LAT) value to the EGM signal even when the EGM signal is segmented, and to generate a third surface representation that visualizes a third surface representation for the segmented EGM signal.

14. The system of claim 8 , wherein the propagation time comprises a cycle length value.

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