Automatically identify abnormal LAT differences

Abstract

The present invention is entitled "Automatic Identification of Abnormal LAT Differences". The present invention provides a device, which is composed of a catheter, the catheter is configured to be inserted into a chamber of the heart, and has one or more electrodes, the one or more electrodes are configured to contact the myocardial tissue at multiple locations in the chamber. The one or more electrodes receive electrical signals in response to conductive waves traveling through the tissue. The device includes a display and a processor, the processor is configured to receive the electrical signals from the catheter and present a map of the chamber to the display in response to the electrical signals, the map of the chamber including an indication of the local time of occurrence of the conductive waves at the multiple locations. The processor is also configured to calculate the velocity of the conductive waves between the locations in response to the local time of occurrence, and mark on the map one or more areas of the chamber where the velocity is below a preset threshold.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This patent application claims the benefit of U.S. Provisional Patent Application No. 62 / 723,218, filed on August 27, 2018, which is incorporated herein by reference. Technical Field

[0003] The present invention relates generally to electrophysiological potentials and, more particularly, to the identification of tissue having abnormal electrophysiological potentials. Background Art

[0004] A standard method for cardiac research involves generating a map of the local activation time (LAT) of the chambers of a beating heart. A "normal" heart operating in sinus rhythm generates well-defined LAT maps for the different chambers. Deviations from these maps allow a physician to examine the map to identify chamber areas that may be problematic. However, such identification may not be obvious from the LAT map itself. Summary of the invention

[0005] One embodiment of the present invention provides a device comprising a catheter configured to be inserted into a chamber of the heart and having one or more electrodes configured to contact myocardial tissue at multiple locations in the chamber and receive electrical signals in response to conducted waves traveling through the tissue.

[0006] The device also has a display and a processor configured to receive the electrical signal from the catheter and present to the display a map of the chamber in response to the electrical signal, the map of the chamber including an indication of the local time of occurrence of the conducted waves at the plurality of locations. The processor also calculates the velocity of the conducted waves between the locations in response to the local time of occurrence and marks on the map one or more regions of the chamber where the velocity is below a preset threshold.

[0007] In one disclosed embodiment, the processor is configured to calculate an interpolated local time of occurrence at a corresponding location between the plurality of locations and mark an indication of the interpolated local time of occurrence on the map at the corresponding location. Typically, the processor is configured not to mark an indication of the interpolated local time of occurrence on the map at the one or more regions.

[0008] In another disclosed embodiment, the processor is configured to divide the chamber into contiguous surfaces, each surface surrounding a respective one of the plurality of locations, and the one or more regions are located at a boundary between two contiguous surfaces.

[0009] The processor may be configured to divide the chamber into adjacent surfaces by forming the surface of the chamber into groups of voxels and, for each given position in the plurality of positions, iteratively and simultaneously add adjacent voxels to a previous voxel that initially included a local primitive voxel corresponding to the given position so as to form a given adjacent surface.

[0010] The processor may be further configured to calculate the speed of the conducted wave at the zone by finding the sum of the distances of the zone on the boundary to corresponding locations of the two adjoining surfaces, and dividing the sum by the time difference between the local times of occurrence at the corresponding locations.

[0011] In another disclosed embodiment, the electrical signal comprises an electrocardiogram (ECG) signal, and the local time of occurrence corresponds to a local activation time (LAT) derived from the ECG signal. Typically, the processor is configured to incorporate into the mapping a color from a color scale having a corresponding color corresponding to a value of the LAT. The processor may be configured to color the one or more regions with a color different from the color of the color scale.

[0012] In an alternative embodiment, the preset threshold is between 0.01 mm / ms and 1 mm / ms.

[0013] In another alternative embodiment, the preset threshold is 0.1 mm.

[0014] In yet another alternative embodiment, the catheter comprises a position sensor configured to provide a signal indicative of the plurality of positions to the processor.Typically, the position sensor comprises one or more coils that provide a signal in response to a magnetic field passing through the coils.

[0015] Another embodiment of the present invention provides a method comprising:

[0016] inserting a catheter into a chamber of the heart, the catheter having one or more electrodes configured to contact myocardial tissue at a plurality of locations in the chamber and to receive electrical signals responsive to conducted waves traveling through the tissue;

[0017] Provide a display;

[0018] receiving an electrical signal from the catheter;

[0019] presenting to a display a map of the chamber in response to the electrical signal, the map of the chamber including indications of local times of occurrence of the conducted waves at the plurality of locations;

[0020] calculating a velocity of the conducted wave between the locations in response to the local times of occurrence; and marking on the map one or more regions of the chamber where the velocity is below a preset threshold.

[0021] The present disclosure will be more fully understood through the following detailed description of the embodiments of the present disclosure in conjunction with the accompanying drawings, in which: BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is a schematic diagram of an invasive medical procedure using a device according to an embodiment of the present invention;

[0023] Figure 2 is a schematic diagram of a distal end portion of a probe used in a device according to an embodiment of the present invention;

[0024] Figure 3 is a flow chart of steps performed during operation of an apparatus according to an embodiment of the present invention; and

[0025] Figure 4A , Figure 4B and Figure 5 Some steps of a flow chart according to an embodiment of the invention are shown. DETAILED DESCRIPTION

[0026] Overview

[0027] Typically, when generating a local activation time (LAT) map of a chamber of the heart, multiple points on the surface of the chamber are sampled, and the LAT value for each of these points is calculated from the sampled data. The LAT value for a point on the surface intermediate the sampled points is typically found by interpolation from the sampled points. The LAT values ​​are typically incorporated into a 3D map of the chamber in different colors, and the colored map including the sampled and interpolated LAT values ​​can then be presented to the physician for analysis.

[0028] However, the colored map itself does not necessarily provide an indication of an abnormal region of the chamber, particularly because in the case of an abnormal region, the above-mentioned interpolation may give an erroneous result and thus hide any abnormal LAT value. For example, inspection of the colored map may not give any indication that the velocity of the conductive waves traveling through the chamber is reduced, and such reduced velocity indicates an abnormal region.

[0029] Embodiments of the present invention provide a method of using further analysis of the sampled data to indicate abnormal areas by estimating the velocity of the conduction waves. This indication is provided on a "conventional" LAT colored map, so that there is no need to generate or view a different map showing the conduction wave velocity.

[0030] First, a probe is inserted into the chamber of interest and used to collect position data signals that are analyzed to give the three-dimensional (3D) position of the chamber surface. One or more electrodes on the probe or on another probe are also used to collect timing data signals, typically electrocardiogram (ECG) signals, at selected locations on the surface. The ECG signals can be analyzed to calculate the LAT values ​​at the selected locations, and a map of the 3D chamber location can be generated, with the LAT values ​​incorporated into the map as colors.

[0031] In addition to generating the map, the selected locations and their corresponding LAT values ​​are analyzed to calculate the velocity of the conducted wave at the surface region between the selected locations. When the velocity of a portion of one of the regions is below a preset threshold, a visual indication is placed on the map for that portion of the region. DETAILED DESCRIPTION

[0033] Figure 1 is a schematic diagram of an invasive medical procedure using the device 12, and Figure 2 Schematic diagram of the distal end 22 of the catheter 20 used in the device according to an embodiment of the present invention. The catheter 20 is also referred to herein as the probe 20. The procedure is performed by a medical professional 14, and in the following description, it is assumed that the procedure includes an electrode potential (EP) study of a three-dimensional (3D) surface 17 of a chamber 15 of a heart 16 of a human patient 18.

[0034] To conduct the study, the professional 14 inserts the probe 20 into a sheath 21 that has been pre-positioned in the patient's lumen. The sheath 21 is positioned so that the distal end 22 of the probe enters the patient's heart. The distal end 22 includes a position sensor 24 that can track the position and orientation of the distal end. The distal end 22 also includes one or more electrodes 30 for collecting electrode potentials from the surface 17, as described below. For clarity and simplicity, the following description assumes that only one electrode 30 is present.

[0035] The device 12 is controlled by a system processor 46, which is located in an operating console 48 of the device. The console 48 includes controls 49 used by the professional 14 to communicate with the processor. Software for the processor 46 can be downloaded to the processor in electronic form, for example, over a network. Alternatively or in addition, the software can be provided via non-transitory tangible media such as optical, magnetic or electronic storage media.

[0036] Electrode potential (3D) data derived from EP signals acquired by electrodes 30 is presented on a three-dimensional (3D) representation 60 of the heart of patient 18 formed on display 62. EP signals are generated in response to conducted waves traveling through myocardial tissue of the heart.

[0037] In an embodiment of the present invention, a color scale 64 is used to present a 3D representation, wherein different colors are assigned corresponding different values ​​of a parameter derived from the EP data in a one-to-one manner. The parameter used herein is the local activation time (LAT) of a zone of the surface 17, the LAT corresponding to the local time of occurrence of the conduction wave. In one embodiment, the LAT varies from a low value of about -150 ms to a high value of about 90 ms, as measured relative to a baseline reference signal, which is typically derived from a probe positioned in the coronary sinus of the heart 16. In this case, the color scale 64 is preset to red for low LAT values, purple for high LAT values, and the preset colors for medium LAT values ​​are hues such as orange, yellow, green, blue.

[0038] The system processor 46 includes a real-time noise reduction circuit 45, typically configured as a field programmable gate array (FPGA), followed by an analog-to-digital (A / D) signal conversion integrated circuit 47. The processor may pass signals from the A / D circuit 47 to another processor, and / or may be programmed to execute at least one algorithm disclosed herein, which includes the steps disclosed below and is stored in a memory 72 in communication with the processor 46. The processor uses the circuits 45 and 47, as well as the features of the modules described in detail below, in order to execute the algorithm.

[0039] To operate the device 12, the algorithm of the processor 46 communicates with a module library 50, which has a plurality of modules used by the processor to operate the device. Thus, the library 50 includes an electrocardiogram (ECG) module 56 that collects and analyzes signals from the electrode 30, and a tracking module 58 that receives and analyzes signals from the position sensor 24 and uses signal analysis to generate the position and orientation of the distal end 22. In some embodiments, the sensor 24 includes one or more coils that provide sensor signals in response to a magnetic field passing through the coil. In these embodiments, in addition to receiving and analyzing signals from the sensor 24, the tracking module 58 also controls radiators 32, 34, and 36 that radiate magnetic fields passing through the sensor 24. These radiators are positioned close to the heart 16 and are configured to radiate alternating magnetic fields into an area close to the heart. Manufactured by Biosense Webster (33 Technology Drive, Irvine, CA 92618 USA) The system uses this type of magnetic tracking system.

[0040] Figure 3 is a flow chart of the steps of an algorithm executed by processor 46 and professional 14 during operation of device 12 according to an embodiment of the present invention, Figure 4A , Figure 4B and Figure 5Some steps according to an embodiment of the present invention are shown. The flowchart describes the steps of mapping the 3D surface 17 of the chamber 15, and also describes the steps of acquiring signals from the surface. Although in some embodiments, these two functions are performed by separate probes, for simplicity, in the following description, it is assumed that these two functions are performed by the probe 20. Specific implementations of the embodiment for the case of different probes for different functions are also considered to be within the scope of the present invention.

[0041] In an initial step 100, a 3D map of the surface 17 of the chamber 15 of the heart of the patient 18 is generated. This is typically produced by inserting the distal tip 22 into the chamber and moving the distal tip into the chamber. As the distal tip is moved, the tracking module 58 acquires adjacent data position signals from the position sensor 24, and the module, together with the processor 46, analyzes each signal to generate a corresponding 3D position for the distal tip.

[0042] Processor 46 analyses the set of 3D positions, effectively a point cloud, to produce a mesh enclosing the point cloud, and the processor generates the surface 17 of the chamber from the mesh as a set of voxels. Methods for generating enclosing meshes and corresponding surfaces for point clouds are well known in the art.

[0043] In a signal acquisition step 102 , the electrode 30 of the distal end 22 is touched at different points of the surface 17 , and at each point, the position P of the touched point is deduced from the signal acquired from the sensor 24 .

[0044] At the same time, the signal generated at the touched point is collected from the electrode 30 by the ECG module 56, which also records the signal. For any given point "a", the collected signal is a set of voltage-time ordered pairs: {(V t ,t)} a , where V t is the electrode potential at time t. In some embodiments, {(V t ,t)} a The technician 14 is presented as a graph of voltage versus time on the display 62 .

[0045] ECG module 56 and processor 46 analyze each of the recorded signals, {(V t ,t)} to derive the corresponding local activation time (LAT) for each point touched by electrode 30. This analysis is represented by formula (1):

[0046] LAT a =f[{(V t ,t)} a ] (1)

[0047] Where a is the identifier of the point on the surface 17, and f represents the point applied to {(V t ,t)} at point a, LAT a Function to derive local activation time.

[0048] As mentioned above, LAT a The value of is typically a time measured relative to a predetermined reference time signal, such as the time provided by a reference probe inserted into the coronary sinus of heart 16 .

[0049] Therefore, for a given point a, step 102 finds the ordered pair (position, local activation time): (P a ,LAT a ).

[0050] Due to the beating of heart 16, the surface mapped in step 100 is not a stationary surface, so that the location of the point touched by electrodes 30 and derived in step 102 may generally not coincide with the surface generated in step 100. Projection step 104 resolves this point.

[0051] In a projection step 104 , processor 46 projects each position found in step 102 onto voxel surface 17 derived in step 100 . Figure 4A is a schematic diagram of a projection, and shows by way of example the positions P of three points a, b, c close to the 3D surface 17 a , P b and P c The projection corresponds to the corresponding voxel V on the surface a 、V b and V c In step 104, the processor stores the set of voxels found by projecting all the points determined in step 102. The voxels derived from the projection are referred to herein as local primitive voxels.

[0052] The local primitive voxels are colored using the corresponding LAT value of the projected location according to scale 64. The LAT values ​​of intermediate voxels on surface 17 (i.e., voxels that are not local primitive voxels) are typically determined by interpolation, and the intermediate voxels are also colored according to scale 64. In one embodiment, the interpolation of the intermediate voxels finds the average of the LAT values ​​of the nearest local primitive voxels, which is weighted according to the distance from the local primitive voxel.

[0053] In a propagation step 106, the processor 46 defines a corresponding zone in the 3D surface 17, ie, a corresponding group of voxels surrounding each local primitive voxel. To define each zone, the processor defines a common identifier V for each voxel in the zone. id, where id is a numeric identifier for the region and is also a numeric identifier for the local primitive voxel in the region. As described below, the processor also measures the distance D of each voxel in the region from the local primitive voxel in the region above the 3D surface 17. Thus, each voxel in a given region has associated with it an ordered pair (voxel identifier, distance to the local primitive voxel), denoted herein by (V id ,D). The ordered pair of each local primitive element in the region is (V id ,0).

[0054] After defining the ordered pair (V1, 0), (V2, 0), (V3, 0), ... for each local primitive voxel, the processor assigns the other voxels of the surface 17 to have a temporary ordered pair, thereby enabling the processor to distinguish the non-local primitive voxels from the local primitive voxels. By way of example, in the following description, all non-local primitive voxels are assigned the ordered pair (0, 0); that is, the identifier of the non-local primitive voxel is assigned the value 0. However, it is assumed that other methods of distinguishing non-local primitive voxels from local primitive voxels are considered to be included in the scope of the present invention.

[0055] Once all voxels of the surface 17 have been assigned ordered pairs as described above, the processor proceeds to "propagate" the identifiers of each of the local primitive voxels. To achieve this propagation, for each voxel with an identifier V g For a given local primitive voxel, the processor determines the immediately neighboring voxels and checks whether the first item of the ordered pair (the identifier of the voxel) is 0.

[0056] If it is 0, the processor assigns the voxel an identifier V g , and also calculates the distance D to the local original voxel, which is assigned to the second item of the ordered pair of this voxel.

[0057] If the voxel's identifier is not 0, the processor checks another immediately neighboring voxel, and continues until all immediately neighboring voxels have been checked.

[0058] The processor continues to check for additional non-local voxels adjacent to the immediately adjacent voxels already checked, in each case checking whether the voxel identifier is 0. For each voxel whose identifier is 0, the processor assigns the voxel an identifier V g The processor also compares the distance between the two voxels to be compared with the voxels with the identifier V already present. g The distance D of the local original voxel above the 3D surface 17 is calculated by adding the distances of the voxels of the local original voxel. It should be understood that the distance assigned to any particular voxel is equal to the cumulative distance between all immediately adjacent voxels.

[0059] The above process is iterated so that the neighboring region of the voxel grows around the local original voxel. Each voxel in the growing region has an identifier V that is identical to the local original voxel.g A common identifier, and a distance D equal to the distance above the 3D surface 17 calculated from the local primitive voxel.

[0060] Processor 46 applies the above process to all local primitive voxels simultaneously, so that there are multiple growing regions, each region originating from a local primitive voxel, in the process implemented by step 106. It should be understood that each region stops growing when the processor no longer finds additional neighboring voxels with an identifier of 0, and when at least one of the neighboring voxels has an identifier different from that of the local primitive voxel.

[0061] The condition 108 checks whether all voxels of the surface 17 have been assigned an identifier and a distance to the local primitive voxel. If the condition returns a negative value, the processor continues with the propagation step 106.

[0062] If the condition returns a positive value, control continues with the distance calculation step 110 as described below. It should be understood that upon completion of the method described above for step 106, the surface 17 is divided into a set of adjacent regions that are touching, i.e., there are no gaps between the regions. Each region includes a set of adjacent voxels having a common voxel identifier corresponding to the identifier of the local primitive voxel of the region. As described above, each voxel of a given region is also associated with a distance measured above the 3D surface 17 from the local primitive voxel of the given region.

[0063] Figure 4B The conclusion of step 106 is schematically shown, showing by way of example the local primitives V on the surface 17, respectively. a 、V b and V c There are three zones 150, 154, and 158 associated. Each zone is adjoined by at least one other zone, and in the example shown, each zone is adjoined by two zones. Thus, there is a border 160 between zones 150 and 154, a border 164 between zones 154 and 158, and a border 168 between zones 158 and 150.

[0064] exist Figure 4B , zone boundaries 160, 164, and 168 are shown as solid lines for clarity; however, it should be understood that in implementation, the boundaries of the zones around the local primitive voxels are not visible on the representation of surface 17 presented on display 62. Furthermore, it should be understood that because the zone boundaries generated in step 106 are not associated with the LAT values ​​of the boundary voxels, there is generally no relationship between the interpolated color of the boundary voxels (as shown in step 104) and the location of the boundary voxels.

[0065] The region boundary includes a set of n voxels, where n is a positive integer, each of which has an identifier that is the same as the identifier of the local primitive voxel. In addition, each of the boundary voxels has at least one nearest neighbor voxel that has an identifier that is different from the local primitive voxel. Thus, if the local primitive voxel V of region 150 a has identifier A, and if the local primitive element V of zone 154 b With identifier B, each of the n boundary voxels in region 150 at boundary 160 has identifier A, and each of these boundary voxels has a nearest boundary with identifier B. There is a corresponding group of voxels in region 154 at boundary 160, each of these voxels has identifier B and a nearest boundary with identifier A.

[0066] When condition 108 returns a positive value, the processor records the positions of all n voxels of each boundary.

[0067] In a distance calculation step 110, the processor analyzes the parameters associated with the boundary voxels in order to calculate the distance between adjacent local primitive voxels measured above the 3D surface 17. In the boundary 160, the n boundary voxels of the region 150 have corresponding ordered pairs: (A, D Va1 )、(A,D Va2 )、(A,D Va3 )、…、(A,D Van ), where D Van The nth boundary voxel of the boundary 160 and the local primitive voxel V a Each of the n boundary voxels of the boundary 160 has at least one nearest neighbor voxel with identifier B. Therefore, there is also a corresponding ordered pair (B, D) in the region 154. Vb1 )、(B,D Vb2 )、(B,D Vb3 )、…、(B,D Vbn ) is a set of n boundary voxels, where D Vbn The nth boundary voxel of the boundary 160 and the local primitive voxel V b distance.

[0068] For boundary 160, processor 46 selects pairs of adjacent boundary voxels. For a given pair, one voxel is located in region 150 and the other voxel is located in region 154. Each pair has parameters (A, D Vak )、(B,Dvbk) Vbk ), where k is an integer between 1 and n. From the local primitive V a To local protocell V b The distance is calculated by using the parameters (A,D Vak )、(B,D Vbk) is given by:

[0069] D abk =D vak +D vbk (2)

[0070] Step 110 ends when the processor has calculated all distances between adjacent local primitive voxels of all boundaries generated in step 106 via corresponding boundary voxel pairs using formula (2). For two generic neighboring regions p, q, these distances are generally referred to herein as D pq .

[0071] In a timing step 112, the processor calculates the difference in local activation times between adjacent local primitive voxels. To calculate this difference, the processor first estimates the median cycle length CL of the heart 16, that is, the median time period between consecutive ventricular activations. The processor can estimate CL in any convenient manner, such as analyzing the time pushed out from the above-mentioned coronary sinus reference probe, or analyzing the time from the body surface electrode.

[0072] To account for the cyclic nature of the LAT values, the processor then calculates the LAT difference between adjacent local primitive voxels according to the following formula:

[0073] ΔLAT pq =min(|LAT p -LAT q |,[CL-|LAT p -LAT q |]) (3)

[0074] Among them, LAT p , LAT q is the LAT of the corresponding local voxel of the adjacent regions p, q, and

[0075] ΔLAT pq is the difference in LAT.

[0076] In step 112, the processor calculates the ΔLATpq values ​​for all pairs of neighboring regions p, q on the surface.

[0077] In a comparison step 114, for each boundary voxel pair, as determined in step 110, the processor calculates the ratio It will be appreciated that this ratio corresponds to the speed of the propagated wave as it transfers between the local primitive voxels of regions p, q via the considered pair of boundary voxels.

[0078] The processor then checks whether the calculated speed is below a preset threshold speed V 阈值 , that is, the processor checks whether expression (4) is valid. 阈值The typical value of V is about 0.1 mm / ms, while V 阈值 A typical range is from about 0.01 mm / ms to about 1 mm / ms.

[0079]

[0080] If the comparison of expression (4) returns a positive value, i.e., the calculated speed is below the preset threshold speed, then in a color-differentiation step 116, the processor colors the boundary voxel pair with consideration of a color-differentiation color that is different from the color of the scale 64. For example, if brown is not in the color scale 64, the processor may color the boundary voxel pair brown if expression (4) is positive.

[0081] Figure 5 The case where the comparison of expression (4) returns a positive value is shown. Figure 5 Roughly similar to Figure 4B , but with Figure 4B In contrast, boundaries 160, 164, 168 are not shown in solid lines; however, the boundaries still exist.

[0082] exist Figure 5 In , line 180 is assumed to include boundary voxel pairs in boundary 160 for which expression (4) returns a positive value. Therefore, starting from step 116, the voxel pairs of line 180 are colored with a distinguishing color different from the color of scale 64.

[0083] Presenting differently colored zones, such as for line 180, helps the professional 14 determine the direction of travel of the conducted waves through the heart. The line effectively shows a blockage of a wave that might be traveling from zone 150 to zone 154. Thus, the conducted wave might be traveling along a path similar to solid arrow 188, rather than along dashed arrow 184 as a possible wave path.

[0084] return Figure 3 , if the comparison of expression (4) returns a negative value, that is, the calculated speed is equal to or higher than the preset threshold speed, then in the standard coloring step 118, the processor colors the boundary voxel pairs according to the scale 64, that is, by selecting the corresponding color from the scale using their interpolated LAT values.

[0085] As used herein, the term "about" for any numerical value or range indicates a suitable dimensional tolerance that allows a collection of parts or elements to achieve its intended purpose as described herein. More specifically, "about" may refer to a range of ±10% of the value of the recited value, for example, "about 90%" may refer to a range of values ​​from 81% to 99%.

[0086] It should be understood that applying a distinguishing color in step 116 is only one method of indicating that a group of boundary voxels have a velocity below a preset threshold, and other distinguishing methods (such as overlaying a dashed line on the voxels) are assumed to be included within the scope of the present invention.

[0087] It should therefore be understood that the embodiments described above are cited by way of example, and that the present invention is not limited to what is specifically shown and described above. On the contrary, the scope of the present invention includes combinations and sub-combinations of the various features described above, as well as variations and modifications thereof, which should occur to those skilled in the art upon reading the above description, and which are not disclosed in the prior art.

Claims

1. An apparatus for automatically identifying abnormal LAT differences, comprising: a catheter configured to be inserted into a chamber of the heart and comprising one or more electrodes configured to contact myocardial tissue at a plurality of locations in the chamber and to receive electrical signals responsive to conducted waves traveling through the tissue; monitor; and a processor configured to: receive the electrical signal from the catheter; and presenting to the display a map of the chamber in response to the electrical signal, the map of the chamber including indications of local times of occurrence of the conducted waves at the plurality of locations; and calculating the velocity of the conducted wave between the positions in response to the local time of the occurrence; and dividing the chamber into adjacent surfaces, each surface surrounding a corresponding one of the plurality of positions, and marking on the mapping map one or more regions of the chamber where the velocity is below a preset threshold, and wherein the one or more regions are located at a boundary between two adjacent surfaces.

2. The apparatus of claim 1, wherein the processor is configured to calculate an interpolated local time of occurrence at a corresponding position between the plurality of positions, and to mark an indication of the interpolated local time of occurrence on the mapping map at the corresponding position. 3 . The apparatus of claim 2 , wherein the processor is configured to not mark the indication of the local time of occurrence of the interpolation on the map at the one or more regions.

4. An apparatus according to claim 1, wherein the processor is configured to divide the chamber into the adjacent surfaces by forming the surface of the chamber into groups of voxels, and, for each given position in the plurality of positions, iteratively and simultaneously add adjacent voxels to previous voxels that initially include local primitive voxels corresponding to the given position so as to form a given adjacent surface.

5. An apparatus according to claim 1, wherein the processor is configured to calculate the speed of the conducted wave at the zone by finding the sum of the distances of the zone on the boundary to the corresponding positions of the two adjacent surfaces, and dividing the sum by the time difference between the local times of the occurrences at the corresponding positions.

6. The apparatus of claim 1, wherein the electrical signal comprises an electrocardiogram (ECG) signal, and wherein the local time of the occurrence corresponds to a local activation time (LAT) derived from the ECG signal.

7. The apparatus of claim 6, wherein the processor is configured to incorporate into the map colors from a color scale having respective colors that correspond one-to-one with values ​​of the LAT. 8 . The device of claim 7 , wherein the processor is configured to color the one or more regions in a color different from a color of the color scale.

9. The apparatus according to claim 1, wherein the preset threshold is between 0.01 mm / ms and 1 mm / ms.

10. The device according to claim 1, wherein the preset threshold is 0.1 mm / ms.

11. The apparatus of claim 1, wherein the catheter comprises a position sensor configured to provide a signal indicative of the plurality of positions to the processor.

12. The apparatus of claim 11, wherein the position sensor comprises one or more coils that provide the signal in response to a magnetic field passing through the coils.

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