Patent Application
20240197234
This disclosure relates generally to analysis of electrophysiological (EP) signals, and specifically to a method for identifying tissue sources of focal arrhythmia.
Identifying arrhythmogenic tissue regions in the heart using a mapping catheter was previously proposed in the patent literature. For example, U.S. Pat. No. 10,582,894 describes a method of atrial rotational activity pattern (RAP) source detection, where RAP is one of the proposed mechanisms for atrial fibrillation maintenance. The method includes detecting, via a plurality of sensors, electro-cardiogram (ECG) signals over time, each ECG signal detected via one of the plurality of sensors and indicating electrical activity of a heart. The method also includes determining, for each of the plurality of ECG signals, one or more local activation times (LATs) each indicating a time of activation of a corresponding ECG signal. The method further includes detecting whether one or more RAP source areas of activation in the heart is indicated based on the detected ECG signals and the one or more local LATs. Mapping information of the detected RAP source areas of activation in the heart is also generated for providing one or more maps.
The present disclosure will be more fully understood from the following detailed description of the examples thereof, taken together with the drawings, in which:
In order to characterize an arrhythmia of a patient, such as atrial fibrillation (AF), a catheter-based electrophysiology (EP) mapping system may be used to generate an EP map of least part of the heart of the patient, such as of an atrium. Typically, such EP map comprises local EP tissue characteristics (e.g., local activation time (LAT), or local cycle time (CL) between activations) overlaid on an anatomical map of the cardiac chamber. The EP map is meant to show arrhythmogenic sources and pathways in the atrium wall tissue, so as to guide a physician to the best locations at which to ablate tissue in order to suppress the arrhythmia.
Typically, in treatment of AF, the physician will look in the EP map for isolated areas with one or more tissue locations of focal arrhythmia (also called hereinafter “focal sources”), and consider such areas as candidates for ablation. Such “spots” of arrhythmogenic focal sources with a characteristic time stamp are targets as they are sources of arrhythmogenic activity leading to the AF.
In a typical catheter-based EP mapping procedure, a distal end of a catheter, which comprises multiple sensing electrodes, is inserted into the cardiac chamber to sense EP signals, such as unipolar and/or bipolar electrograms (EGM). As a physician operating the system moves the distal end inside the cardiac chamber, the EP-mapping system acquires EP signals at numerous locations on the inner surface of the cardiac chamber. At the same time the system records the respective positions of the distal end.
A multi-electrode catheter, such as a multi-arm catheter, has about 100 electrodes that can capture at a given instance a hundred intracardiac ECG signals even over a limited area. Therefore, such EP mapping procedure may generate a vast amount of information to analyze, up to few tens of thousands of data points (each comprising an EP signal and a position). Cardiac wave propagation analysis based on output from all the electrodes may yield a chaotic pattern, because this is how AF is electrophysiologically manifested when observed over a large area.
The interpretation of an EP map is therefore not always straightforward. For example, in AF, propagation of the cardiac action potential appears chaotic in time, and fractionated actional potentials (e.g., irregular patterns such as bursts of highly rapid deflections of the EGM) may be observed. One reason for such disordered signals is due to a plurality of arrhythmogenic focal sources concurrently initiating activation. Another reason may be due to scar tissue. Cycle length in a region of scar tissue may be longer than the cycle length associated with sinus rhythm. In the process, the focal sources themselves are not readily apparent in the chaotic propagation. It is therefore difficult to make any sense (e.g., identify the required time stamp) out of this seemingly random pattern. Without identifying the focal sources, a physician will have difficulty in understanding where to ablate.
Examples of the present disclosure that are described herein provide a technique in which a processor runs a program to search for organized patterns within the seemingly-chaotic propagation patterns of the EP map. To this end, the processor separately examines outputs from sub-groups of contiguous electrodes of a multi-electrode EP mapping catheter. When identifying an organized pattern, the processor uses the organized pattern to direct the physician to one or more focal sources. Optionally, the physician can choose to ablate these.
In the present context, the term “organized pattern” refers to a set of EP measurements (e.g., cycle lengths, activation frequencies or local activation times) that are measured by a contiguous sub-group of electrodes and are self-consistent with one another according to a defined consistency test, such as sharing a same CL within tight tolerance (e.g., all presenting a sinus rhythm).
In the disclosed technique, the processor selects one or more sub-groups of electrodes, from among the numerous electrodes of the mapping catheter. In one example of the disclosed method, the processor examines local cycle lengths (or activation frequencies, if implementation is in the frequency domain using unit of HR=60,000/CL [BPM] for CL given in milliseconds) to find areas that are being activated from a same focal source. Electrograms possessing peaks at long cycle lengths that are constant in time and space can be considered to be activated from such same source. If frequency domain analysis is used by, for example, applying FFT to electrograms, then the criterion is specified in terms of frequency. This way, electrograms possessing peaks low at frequencies (lower than characteristic frequency of sinus rhythm) that are constant in time and space can be considered to be activated from such source. A same frequency domain chart of representative power spectrum (e.g., sum or average of FFT power spectrum over a subgroup of electrodes) can be presented in Hz units, where center heart rate in Hz is given using 1000/t [1/sec] for t given in milliseconds.
To this end, the processor may apply a consistency test to the sub-group of CL values, such as by defining a criterion for a sub-group of CL values to be considered as constant in time and space. In one example, the criterion is based on a histogram of the sub-group CL values about a representative CL value (median or maximal CL value) being narrow enough, e.g., below a defined width threshold. Another criterion may be based on a histogram of the sub-group LAT values being narrow enough, e.g., below a defined width threshold. In this disclosure, a representative CL in time domain is equivalent to a representative heart rate in the frequency domain, using the aforementioned time-frequency conversion.
For each local organized pattern detected, the focal source of such a pattern may then be identified by a processor by the aforementioned comparison to sinus rhythm and acceptability testing. The processor may compare the local cycle length (or local frequency of activation) to that of a normal, global, sinus rhythm cycle length (or heart rate frequency) of the heart. If a sub-group of contiguous electrodes exhibit a same frequency (or cycle length) that is other than the sinus rhythm, the processor may provide indication of this region on a map of the chamber. When the local cycle length found is other than the sinus CL, the processor indicates this region in association with its cycle length to the user on an EP map.
In some examples, to best identify such areas, the processor attempts different divisions into sub-groups (including different sized and shaped sub-groups) to search for regions with a same cycle length. If the processor cannot find such organized pattern, the processor divides at least portion of the numerous electrodes into differently shaped sub-group, and/or divides the sub-groups into smaller sub-groups and tries again. The process may be iterative, to find a sub-group of electrodes that best meets the above set criteria. Based on this division, the processor may build a map of the chamber and indicate the areas that have the same cycle length and thereby may be activated by the same focal source.
System 10 includes multiple catheters, which are percutaneously inserted by physician 24 through the patient's vascular system into a chamber or vascular structure of a heart 12. Typically, a delivery sheath catheter is inserted into the left or right atrium near a desired location in heart 12. Thereafter, a plurality of catheters can be inserted into the delivery sheath catheter so as to arrive at the desired location. The plurality of catheters may include catheters dedicated for sensing Intracardiac Electrogram (IEGM) signals, catheters dedicated for ablating and/or catheters dedicated for both sensing and ablating. An example catheter 14 that is configured for sensing IEGM is illustrated herein. Physician brings a distal tip 28 (also called hereinafter “distal end assembly 28”) of catheter 14 into contact with the heart wall for sensing a target site in heart 12. For ablation, physician 24 would similarly bring a distal end of an ablation catheter to a target site for ablating.
Catheter 14 is an exemplary catheter that includes one and preferably multiple electrodes 26 optionally distributed over a plurality of splines 22 at distal tip 28 and configured to sense the IEGM signals. Catheter 14 may additionally include a position sensor 29 embedded in or near distal tip 28 for tracking position and orientation of distal tip 28. Optionally and preferably, position sensor 29 is a magnetic based position sensor including three magnetic coils for sensing three-dimensional (3D) position and orientation.
Magnetic based position sensor 29 may be operated together with a location pad 25 including a plurality of magnetic coils 32 configured to generate magnetic fields in a predefined working volume. Real time position of distal tip 28 of catheter 14 may be tracked based on magnetic fields generated with location pad 25 and sensed by magnetic based position sensor 29. Details of the magnetic based position sensing technology are described in U.S. Pat. Nos. 5,5391, 199; 5,443,489; 5,558,091; 6,172,499; 6,239,724; 6,332,089; 6,484,118; 6,618,612; 6,690,963; 6,788,967; 6,892,091.
System 10 includes one or more electrode patches 38 positioned for skin contact on patient 23 to establish location reference for location pad 25 as well as impedance-based tracking of electrodes 26. For impedance-based tracking, electrical current is directed toward electrodes 26 and sensed at electrode skin patches 38 so that the location of each electrode can be triangulated via the electrode patches 38. Details of the impedance-based location tracking technology are described in U.S. Pat. Nos. 7,536,218; 7,756,576; 7,848,787; 7,869,865; and 8,456,182.
A recorder 11 displays electrograms 21 captured with body surface ECG electrodes and 18 intracardiac electrograms (IEGM) captured with electrodes 26 of catheter 14. Recorder 11 may include pacing capability for pacing the heart rhythm and/or may be electrically connected to a standalone pacer.
System 10 may include an ablation energy generator 50 that is adapted to conduct ablative energy to one or more of electrodes at a distal tip of a catheter configured for ablating. Energy produced by ablation energy generator 50 may include, but is not limited to, radiofrequency (RF) energy or pulsed-field ablation (PFA) energy, including monopolar or bipolar high-voltage DC pulses as may be used to effect irreversible electroporation (IRE), or combinations thereof.
Patient interface unit (PIU) 30 is an interface configured to establish electrical communication between catheters, electrophysiological equipment, power supply and a workstation 55 for controlling operation of system 10. Electrophysiological equipment of system 10 may include for example, multiple catheters, location pad 25, body surface ECG electrodes 18, electrode patches 38, ablation energy generator 50, and recorder 11. Optionally and preferably, PIU 30 additionally includes processing capability for implementing real-time computations of location of the catheters and for performing ECG calculations.
Workstation 55 includes memory 57, processor 56 unit with memory or storage with appropriate operating software loaded therein, and user interface capability. Workstation 55 may provide multiple functions, optionally including (1) modeling the endocardial anatomy in three-dimensions (3D) and rendering the model or anatomical map 20 for display on a display device 27, (2) displaying on display device 27 activation sequences (or other data) compiled from recorded electrograms 21 in representative visual indicia or imagery superimposed on the rendered anatomical map 20, (3) displaying real-time location and orientation of multiple catheters within the heart chamber, and (5) displaying on display device 27 sites of interest such as places where ablation energy has been applied. One commercial product embodying elements of the system 10 is available as the CARTO™ 3 System, available from Biosense Webster, Inc., 31A Technology Drive, Irvine, CA 92618.
Identifying Focal Sources of Arrhythmia with Multi Electrode Catheter
Flat distal end assembly 240 is seen being attached to a portion 257 of a wall tissue of a left atrium, with electrodes 248 acquiring EP signals, such as bipolar electrograms.
As described above, during analysis, processor 56 runs a program to examine output from contiguous sub-groups of electrodes 248, such as within areas 260 and 262 of flat catheter's distal end assembly 240.
The processor extracts, using FFT, power spectrum of electrograms for each electrode in these areas, the representative power spectrum seen in graph 270. The schematically shown spectra are generated by accumulating spectrums of individual EGMs acquired each from individual electrodes of a same area.
Analysis of EP signals from area 262 reveals a well-defined peak centered about a global sinus rhythm value 272 of the accumulated spectrum. This means normal, healthy, tissue region was mapped under area 262. A well-defined peak 273 of the accumulated spectrum, on the other hand, reveals a consistent frequency range that has a representative frequency value 274 (e.g., mean activation frequency value). Such a peak (narrowly distributed, but around an exceedingly small representative frequency value) is typically indicative of an arrhythmogenic tissue region that was mapped under area 262 at the time the EP signals were acquired. Representative frequency value 274 is distinctively lower than the normal heart rate value.
Analysis of EGMs from acquired from another region of cardiac tissue, under area 264 of contiguous electrodes, reveals a high frequency well-defined peak 275.
As catheter 14 is equipped with position sensor 29, seen in
In another example, processor 56 runs an algorithm that divides the area of catheter's distal end assembly 240 by grid 230 areas 233, to examine output from sub-groups of electrodes 248 inside areas 233. The FFT analysis is performed as above, in search of at least one area 233 with a representative power spectrum that shows a narrowly distributed peak, that is spread around an exceedingly small representative frequency value.
If none is found, the processor can change grid 230 parameters (e.g., periodicities), to, for examples, examine representative power spectra from smaller areas 233.
In catheter electrode array virtual division step, the processor divides the electrode array (e.g., the set of electrodes) into sub-groups of contiguous electrodes, as demonstrated in
In EP data analysis step 306, processor 56 runs a program to examine output from the sub-groups of contiguous electrodes 248 by calculating a representative power spectrum for each sub-group, such as demonstrated in
Next, processor 56 performs FFT on the output to identify whether one or more of the sub-groups of contiguous electrodes 248 that exhibit a common frequency component, e.g., substantive peak in the power spectrum. In one example, processor 56 checks if the accumulated sensed voltage in each area of contiguous electrodes shows a well-defined peak, such as any of the peaks shown in
Based on Step 308, the processor iterates the analysis by reducing the size of the sub-group in an attempt to receive a well-defined peak. The iterations may stop at a minimal size of a subgroup, or by another conditions, such as reaching a maximal number of iterations. An iteration may also include changing a shape of an area, like to into different shapes, some of which are seen in
For peaks in representative power spectra that passed the test, e.g., showing in analysis step 310 a well-defined peak, processor 56 compares the representative frequency detected to a frequency associated with sinus rhythm. The frequency associated with sinus rhythm may be determined from a region that is known to be healthy and the value may be stored in memory.
Finally, the processor graphically indicates (e.g., colors) any region having a common frequency on an anatomical map of the chamber in step 312. The indication is relative to the frequency associated with sinus rhythm. This way the physician can see what regions are being activated by a focal source, what regions are scar tissue regions and what regions are activated by sinus rhythm. Based on the map, the physician can readily depict areas that have a cycle length that is greater than sinus and regions that are less than sinus. Also, the degree at which the cycle is different than sinus can be depicted. This would be evident on the EP map of
The flow chart shown in
The map graphically indicates (e.g., colors) regions with the same cycle length (up to a tolerance) with the same color. In one example, sinus rhythm is represented by a defined color 412 and the other regions are different colors depending on their characteristic cycle length as compared to sinus cycle length. A color scale 405 assist user to read the map. In another example, the color scale can be a rainbow scale so that a physician can easily identify where each color is in the range.
EP map 400 can be a CL map or equivalently, a frequency map. Regions 414, 416, and 418 of respective long CL values Normal tissue regions 412 will be associated with the characteristic sinus CL 412. Regions 420 and 422 are regions with short cycle lengths.
Based on EP map 400, a physician 30 can plan and perform a careful, selective ablation to eliminate AF with minimal hazard to the patient.
A system (10) includes a processor (56) and a display (27). The processor is configured to receive electro-physiological (EP) signals (21) from a plurality of electrodes (26) on a distal end assembly (28) of a catheter in the chamber, (b) apply a consistency test to the EP signals acquired by the contiguous sub-group to determine if the EP signals from the sub-group of the electrodes display a common cycle length (c) when the consistency test is successful, identify a region in the chamber from which the EP signals have been acquired by the contiguous sub-group. The display (27) is configured to render an electro-anatomical (EA) map (20) of the chamber and to indicate the region on the rendered EA map (20).
The system according to example 1, wherein the processor (56) is configured to calculate power spectra (270) for the EP signals acquired by the electrodes in the sub-group, and to apply the consistency test to the power spectra.
The system according to any of examples 1 and 2, wherein, when the consistency test is successful, the processor (56) is configured to compare a representative frequency value (274, 275) of the sub-group to a sinus frequency value (272) of the heart, and provide indication (420, 422) if the representative frequency value is smaller than the sinus frequency by a minimum amount.
The system according to any of examples 1 and 2, wherein, when the consistency test is unsuccessful, the processor (56) is further configured to select a smaller contiguous sub-group of the electrodes of the catheter and apply a consistency test to the EP signals acquired by the electrodes (26) in the smaller sub-group.
The system according to any of examples 1 and 2, wherein the processor (56) is configured to apply the consistency test by estimating a width of a peak of a representative power spectrum peak (274, 275) for the sub-group.
The system according to any of examples 1 through 5, wherein the processor (56) is configured to calculate local Cycle Length (CL) values for the EP signals acquired by the electrodes in the sub-group, and to apply the consistency test to the local CL values.
The system according to any of examples 1 through 6, wherein, when the consistency test is successful, the (56) processor is configured to compare a representative CL value of the sub-group to a sinus CL value of the heart, and provide indication (414, 416, 418) if the representative CL value is larger than the sinus CL value by a minimum amount.
The system according to any of examples 1 through 6, wherein the processor (56) is further configured to graphically encode (405) on an EP map (400), regions (414, 416, 418, 420, 422) with representative CL values that larger or smaller compared to a representative sinus CL value.
The system according to any of examples 1 through 6, wherein the processor (56) is configured to apply the consistency test by estimating a width of a histogram of the CL values of the sub-group.
The system according to any of examples 1 through 10, wherein EP signals are one of unipolar and bipolar electrograms (21).
A method for rendering and electro-anatomical (EA) map of signals from tissue inside a chamber of a patient's heart, the method includes:
Although the examples described herein mainly address cardiac diagnostic applications, the methods and systems described herein can also be used in other medical applications.
It will be appreciated that the examples described above are cited by way of example, and that the present disclosure is not limited to what has been particularly shown and described hereinabove. Rather, the scope of the present disclosure includes both combinations and sub-combinations of the various features described hereinabove, as well as variations and modifications thereof which would occur to persons skilled in the art upon reading the foregoing description and which are not disclosed in the prior art.
