Identification and Delineation of Cardiac Regions Showing Progressive Slow Activation (PSA)

Abstract

The method includes receiving a cardiac signal sensed by electrodes at a location within a patient's heart, the cardiac signal including signal components induced by respective activations. The signal components within the cardiac signal are found and annotated. Respective time differences between the annotations and corresponding activations are calculated. Based on the time differences, one or more cardiac tissue locations exhibiting progressive slow activation (PSA) are identified. An EP map of at least a portion of the heart is presented to a user, including providing a graphical indication of the one or more tissue locations exhibiting PSA.

Description

[Technical Field]

[0001] The present invention relates generally to electrophysiological (EP) signals, and specifically to methods for the assessment of electrical propagation within the heart. [Background technology]

[0002] Estimation of electrophysiological signals to determine local activation time (LAT) has previously been proposed in the patent literature. For example, U.S. Pat. No. 5,954,661 describes cardiac tissue characterized using pacing without inducing ventricular tachycardia (VT). Tissue characterization can be used to determine a patient's risk of developing VT and to determine slow conduction zones in the patient's heart. Characterization involves pacing the patient's heart by applying a pacing signal having a varying pacing cycle interval to the patient's cardiac chambers. Response signals generated by the paced heart are received and used as a basis for characterizing the patient's cardiac tissue.

[0003] A more complete understanding of the present disclosure will be obtained from the following detailed description of the embodiments of the present disclosure when read in conjunction with the drawings. [Brief explanation of the drawings]

[0004] [Figure 1] 1 is a schematic, pictorial, illustrative illustration of a catheter-based system for electrophysiological (EP) mapping and ablation, according to an embodiment of the present disclosure; [Figure 2] 2 shows an exemplary graph of a bipolar electrogram acquired using the system of FIG. 1 with progressively slowing activation (PSA) potentials annotated on the bipolar signal, in accordance with an embodiment of the present invention. [Figure 3]1 is a flowchart that generally illustrates a method and algorithm for finding heart chamber tissue locations indicative of PSA, according to an embodiment of the present disclosure. [Figure 4] 1 is a schematic pictorial volume rendering of an EP map graphically showing left atrial locations found to exhibit PSA, according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0005] overview To characterize arrhythmias (e.g., reentry arrhythmias) in a heart chamber, a physician may use a multi-electrode mapping catheter to perform electrophysiological (EP) mapping of suspected tissue pathways and circuits within the heart chamber.

[0006] In EP mapping, tissue EP characteristics, such as local activation time (LAT), are measured under sinus rhythm or rapid pacing and then correlated with local tissue arrhythmogenicity. A dedicated pacing catheter can be used to pace the heart chamber, while the EP mapping catheter acquires bipolar electrograms from various tissue locations. A processor can execute algorithms to identify tissue with unhealthy electrophysiological properties, such as locations exhibiting low bipolar potentials (relative to the timing of the pacing signal) and / or abnormal conduction times.

[0007] Once arrhythmogenic tissue is identified, specialized ablation catheters may be used to eliminate the possibility of arrhythmia (eg, by ablation interrupting aberrant conduction pathways that give rise to reentry circuits).

[0008] However, in practice, it can be difficult to identify the unique EP patterns (eg, temporal patterns) of arrhythmogenic sites or pathways due to, for example, inherent variability and signal noise.

[0009] The authors of this disclosure noted that during pacing, activation time measured at remote tissue distances from the pacing site sometimes progressively increases with pacing cycles. This progressive increase, hereafter referred to as progressive slow activation (PSA), typically indicates the presence of arrhythmogenic tissue (arrhythmogenicity can be either local or manifest as arrhythmogenic tissue pathways between the pacing site and the measurement site). The presence of abnormal tissue may be related to the arrhythmogenicity of this tissue as part of a reentrant arrhythmia.

[0010] Examples of the present disclosure described below provide a PSA mapping method and system that automatically identifies PSA behavior without inducing actual arrhythmia. The method and system analyzes, displays, and notifies the physician of PSA behavior using visual, auditory, and / or tactile means. In one example, the processor displays PSA behavior by overlaying a graphical indicator of clusters of PSA locations on a cardiac EP map.

[0011] The disclosed automated PSA mapping method includes receiving a pacing signal applied to a patient's heart. The pacing signal includes a sequence of regular pacing stimuli having the same cycle length (CL) between stimuli that is shorter than naturally occurring sinus rhythm. (CL can range between a value close to the normal sinus rhythm CL and a value much shorter than CL.) In the context of this description, the term "regular pacing stimuli" includes equidistant pulses up to a predefined variation. Typically, the predefined variation is limited to the order of 1% of the specified equidistant interval, although in some cases, a larger deviation, e.g., 5%, may be acceptable. Pacing is typically applied by a dedicated pacing catheter that contacts cardiac tissue at a fixed location.

[0012] The response signal of the propagating cardiac activation wave is received and sensed by electrodes of the multi-electrode mapping catheter in contact with cardiac tissue locations. For each intracardiac bipolar channel of the multi-electrode mapping catheter, a processor finds and annotates activation after each pace. The time difference (e.g., LAT value) between each evoked potential and a fixed timing reference in the pacing pulse, e.g., the timing of the preceding pacing spike, is calculated. This bipolar potential LAT measurement is performed at multiple locations within the cardiac chamber. Tissue locations that exhibit increasing time differences for at least two consecutive beats (i.e., over three consecutive pacing cycles) are identified as potential PSA locations.

[0013] The processor constructs and presents to the user an EP map of at least a portion of the heart, along with a graphical indication of the locations where PSA activity was found. Optionally, a boundary around the cluster of PSA sites is shown. The physician may choose to ablate the indicated boundary or a location on a particular PSA site.

[0014] The spatial stability of the catheter may also be monitored to ensure there is no significant catheter movement that could cause changes in LAT between pacing cycles.

[0015] Finally, naturally occurring sinus rhythm activation can also be used to identify PSA without pacing (although with less accuracy).

[0016] Thus, in one embodiment, a system is provided that includes an interface and a processor. The interface receives cardiac signals sensed by electrodes at locations within a patient's heart, the cardiac signals including signal components evoked by respective activations. The processor analyzes the evoked signal components to find signal components within the cardiac signals and annotates the signal components. The processor then calculates respective time differences between the annotations and corresponding activations. Based on the time differences, the processor identifies one or more cardiac tissue locations indicative of PSA. The processor presents an EP map of at least a portion of the heart to a user, including providing a graphical indication of the one or more tissue locations indicative of PSA.

[0017] Typically, the processor is programmed with software that contains specific algorithms that enable the processor to perform each of the processor-related steps and functions outlined above.

[0018] The disclosed PSA mapping technique introduces a new and unique EP mapping tool relative to many existing EP mapping tools, thereby potentially increasing the sensitivity and uniqueness of EP mapping.

[0019] System Description FIG. 1 is a schematic, pictorial, illustrative diagram of a catheter-based electrophysiological (EP) mapping and ablation system 10, according to an embodiment of the present disclosure.

[0020] The system 10 includes multiple catheters that are percutaneously inserted by a physician 24 through the patient's vascular system into a chamber or vasculature of the heart 12. Typically, a delivery sheath catheter is inserted into a heart chamber, such as the left or right atrium, near a desired location within the heart 12. Multiple catheters may then be inserted into the delivery sheath catheter to reach the desired location. The multiple catheters may include catheters dedicated to pacing, catheters for sensing intracardiac electrogram signals, and catheters dedicated to ablation, and / or catheters dedicated to both EP mapping and ablation. An exemplary catheter 14 configured to sense bipolar electrograms is illustrated herein. The physician 24 brings a distal tip 28 (hereinafter also referred to as the "distal end assembly 28") of the catheter 14 into contact with the heart wall to sense a target site in the heart 12. For ablation, the physician 24 similarly brings the distal end of an ablation catheter to the target site for ablation.

[0021] Catheter 14 is an exemplary catheter that includes one, and preferably multiple, electrodes 26 optionally distributed across multiple splines 22 at distal tip 28 and configured to sense IEGM signals. Catheter 14 may additionally include a position sensor 29 embedded in or near distal tip 28 for tracking the 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.

[0022] The magnetic-based position sensor 29 may operate in conjunction with a location pad 25 that includes a plurality of magnetic coils 32 configured to generate a magnetic field within a predetermined working volume. The real-time position of the distal tip 28 of the catheter 14 may be tracked based on the magnetic fields generated by the location pad 25 and sensed by the magnetic-based position sensor 29. Details of magnetic-based position sensing technology are described in U.S. Patent 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; and 6,892,091.

[0023] System 10 includes one or more electrode patches 38 positioned for skin contact on patient 23 to establish a position reference for location pads 25 and impedance-based tracking of electrodes 26. For impedance-based tracking, current is directed to electrodes 26 and sensed at electrode skin patches 38, allowing the location of each electrode to be triangulated via electrode patches 38. Details of impedance-based position tracking techniques are described in U.S. Patent Nos. 7,536,218, 7,756,576, 7,848,787, 7,869,865, and 8,456,182.

[0024] Recorder 11 displays electrograms 21 captured by body surface ECG electrodes 18 and intracardiac electrograms captured by electrodes 26 on catheter 14. Recorder 11 may include pacing capability for pacing the cardiac rhythm and / or may be electrically connected to a stand-alone pacer.

[0025] The system 10 may include an ablation energy generator 50 adapted to conduct ablation energy to one or more electrodes at the distal tip of a catheter configured for ablation. The energy generated by the 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, such as may be used to effect irreversible electroporation (IRE), or a combination thereof.

[0026] The patient interface unit (PIU) 30 is an interface configured to establish electrical communication between the catheters, the electrophysiology equipment, the power supply, and the workstation 55 to control the operation of the system 10. The electrophysiology equipment of the system 10 may include, for example, multiple catheters, location pads 25, body surface ECG electrodes 18, electrode patches 38, an ablation energy generator 50, and a recorder 11. Optionally and preferably, the PIU 30 additionally includes processing capability to perform real-time calculations of catheter position and to perform ECG calculations.

[0027] The workstation 55 includes a memory 57, a processor 56 unit having memory or storage loaded with appropriate operating software, and user interface functionality. The workstation 55 may optionally provide multiple functions, including (1) modeling the endocardial anatomical structure in three dimensions (3D) and rendering a model or anatomical map 20 for display on the display device 27, (2) displaying activation sequences (or other data) compiled from recorded electrograms 21 on the display device 27 with representative visual indicators or images superimposed on the rendered anatomical map 20, (3) displaying the real-time location and orientation of multiple catheters within the cardiac chambers, and (5) displaying sites of interest, such as locations where ablation energy has been applied, on the display device 27. One commercially available 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.

[0028] In some embodiments, processor 56 typically comprises a general-purpose computer that is programmed with software to perform the functions described herein. The software may be downloaded to the computer in electronic form, for example, over a network, or alternatively or additionally, may be provided and / or stored on non-transitory, tangible media, such as magnetic, optical, or electronic memory.

[0029] This particular configuration of system 10 is presented as an example to illustrate the particular problem addressed by embodiments of the present disclosure and to demonstrate the application of these embodiments in improving the performance of such systems. However, embodiments of the present disclosure are in no way limited to this particular type of exemplary system, and the principles described herein may be applied to other types of medical systems as well. For example, other types of multi-electrode catheters, such as OCTARAY™ catheters or basket catheters, may be used.

[0030] Identifying PSA-indicating locations 2 illustrates an exemplary graph of a bipolar electrogram 200 obtained using the system 10 of FIG. 1, with PSA potentials annotated 204 on the bipolar signal, according to an embodiment of the present disclosure. Dashed lines 202 indicate the timing of equidistant 203 pacing stimuli (e.g., each of the activations discussed above).

[0031] As can be seen, over the five pacing cycles, the annotations 204 made by the processor to the evoked signal components occur as five consecutive PSA time differences 206: 387, 396, 410, 418, and 424 milliseconds. The processor then calculates each sequence of time difference changes. For the electrogram of FIG. 2, this corresponds to a sequence of four increments resulting from the PSA having values ​​of +9, +14, +8, and +6 milliseconds. As found by applicant, such consistent PSA behavior is highly predictive of an arrhythmogenic region where the electrogram 200 was acquired.

[0032] 2 is presented as an example, and the method can be applied to different types of electrograms. In particular, the method can annotate PSA on unipolar or multipolar electrograms.

[0033] How to identify and display areas that indicate PSA 3 is a flow chart that generally illustrates a method and algorithm for finding cardiac chamber tissue locations indicative of PSA, according to an embodiment of the present disclosure. According to the embodiment shown, the algorithm executes a process that begins with system 10 applying a pacing signal in the form of equidistant (203) pacing pulses at pacing step 302.

[0034] In an EP data receive step 304, processor 56 receives the pacing signals, the bipolar signals (eg, waveforms) from catheter 14, and the respective ECG signals from the body surface (BS) electrodes.

[0035] Next, in an EP response extraction step 306, the processor 56 annotates 204 the evoked potentials. The processor may use an annotation algorithm created by Biosense Webster to identify late potentials.

[0036] Using the pacing stimulus timing 202 and the processor-generated annotations 204 , the processor 56 calculates the time difference 206 in a time difference calculation step 308 .

[0037] In PSA analysis step 310, processor 56 calculates each sequence of changes in time difference 206 as done in Figure 2 and uses criteria to identify chamber locations indicative of PSA. One example of a criterion is that a tissue location exhibits an increasing time difference of at least two consecutive beats (i.e., beats over three consecutive pacing cycles) to be identified as a potential PSA location.

[0038] Finally, as shown below in FIG. 4, in a PSA location registration step 312, processor 28 displays the PSA location on the EP map.

[0039] The exemplary flowchart shown in Figure 3 has been chosen purely for purposes of conceptual clarity. This embodiment may also include additional algorithmic steps, such as receiving multiple bipolar and ECG signals simultaneously, and receiving an indication of the degree of physical contact of the electrodes with the tissue being diagnosed from a force sensor. This and other possible steps have been intentionally omitted from the disclosure herein to provide a more simplified flowchart.

[0040] PSA Map FIG. 4 is a schematic pictorial volume rendering of an EP map 400 graphically illustrating left atrial regions 404 found to be indicative of PSA, according to an embodiment of the present disclosure. EP map 400 shows an anatomical surface onto which a graphically encoded EP parameter 402, such as bipolar potential amplitude or LAT, is superimposed. Alternatively, FIG. 4 may show only the anatomical surface. In FIG. 4, dark regions 404 are encoded to indicate one or more locations (e.g., clusters of locations) identified by the disclosed techniques to be indicative of PSA. As can be seen, processor 56 has delineated a boundary 405 around each region 404 containing a cluster of locations indicative of PSA. A physician can use delineation 405 to plan an ablation to eliminate the arrhythmia in that region.

[0041] When the PSA index is superimposed on another EP layer, such as the EP layer of bipolar potential, physicians can evaluate the correlation between proarrhythmic regions to improve ablation planning. For example, a region exhibiting both PSA potential and low bipolar potential can be considered a scar region that should be homogenized to eliminate slow conduction pathways therein. [Example]

[0042] Example 1 The method includes receiving a cardiac signal (21) sensed by electrodes (26) at a location within a patient's heart (12), the cardiac signal (21) including signal components evoked by respective activations. The signal components in the cardiac signal (21) are found and the signal components are annotated (204). Respective time differences (206) between the annotations and corresponding activations are calculated. Based on the time differences (206), one or more cardiac tissue locations exhibiting progressive slow activation (PSA) are identified. An EP map (400) of at least a portion of the heart (12) is presented to a user, including providing a graphical indication (405) of the one or more tissue locations exhibiting PSA.

[0043] Example 2 2. The method of example 1, wherein the activation comprises a pacing stimulus applied to the heart (12).

[0044] Example 3 3. The method of any one of the preceding claims, wherein the activation comprises naturally occurring sinus rhythm activation of the heart (12).

[0045] Example 4 The method of any one of Examples 1 to 3, wherein identifying tissue locations indicative of PSA comprises identifying one or more tissue locations that exhibit a monotonically increasing time difference (206) over at least three consecutive cardiac cycles.

[0046] Example 5 The method of any one of Examples 1 to 4, wherein providing the graphical indication (405) comprises delineating a boundary around a cluster of tissue locations exhibiting PSA.

[0047] Example 6 The method of any one of claims 1 to 5, wherein receiving cardiac signals (21) comprises receiving unipolar and bipolar electrograms acquired using a catheter (14).

[0048] Example 7 7. The method of any one of Examples 1 to 6, wherein annotating 204 the signal 21 components comprises annotating a bipolar electrogram, a unipolar electrogram, or a multipolar electrogram.

[0049] Example 8 The system includes an interface (30) and a processor (56). The interface (30) is configured to receive a cardiac signal (21) sensed by electrodes (26) at locations within a patient's heart (12), the cardiac signal (21) including signal components evoked by respective activations. The processor (56) is configured to (i) locate and annotate (204) the signal components within the cardiac signal (21), (ii) calculate respective time differences (206) between the annotations (204) and corresponding activations, (iii) identify one or more cardiac tissue locations exhibiting progressive slow activation (PSA) based on the time differences (206), and (iv) present to a user an EP map (400) of at least a portion of the heart (12), including providing a graphical indication (405) of the one or more tissue locations exhibiting PSA.

[0050] It will be understood that the above-described embodiments are given by way of example, and that the present disclosure is not limited to what is particularly shown and described hereinabove. Rather, the scope of the present disclosure includes both combinations and subcombinations of the various features described hereinabove, as well as variations and modifications thereof not disclosed in the prior art that would occur to one skilled in the art upon reading the foregoing description.

[0051] [Embodiment] (1) A method comprising: receiving a cardiac signal sensed by an electrode at a location within the patient's heart, the cardiac signal including a signal component induced by each activation; Finding the signal components in the cardiac signal and annotating the signal components; calculating respective time differences between the annotations and the corresponding activations; identifying one or more cardiac tissue locations exhibiting progressively slowing activation (PSA) based on the time difference; and presenting to a user an EP map of at least a portion of the heart, the EP map comprising providing a graphical indication of the one or more tissue locations indicative of the PSA. (2) The method of embodiment 1, wherein the activation includes a pacing stimulus applied to the heart. (3) The method of embodiment 1, wherein the activation comprises naturally occurring sinus rhythm activation of the heart. (4) The method of embodiment 1, wherein identifying the tissue locations indicative of the PSA comprises identifying one or more tissue locations that exhibit a monotonically increasing time difference over at least three consecutive cardiac cycles. (5) The method of embodiment 1, wherein providing the graphical indicator comprises delineating a boundary around a cluster of tissue locations exhibiting the PSA.

[0052] (6) The method of embodiment 1, wherein receiving the cardiac signal includes receiving unipolar and bipolar electrograms obtained using a catheter. (7) The method of embodiment 1, wherein annotating the signal components includes annotating a bipolar electrogram, a unipolar electrogram, or a multipolar electrogram. (8) A system comprising: an interface configured to receive cardiac signals sensed by electrodes at locations within the patient's heart, the cardiac signals including signal components induced by respective activations; 1. A processor, comprising: Finding the signal components in the cardiac signal and annotating the signal components; calculating respective time differences between said annotations and said corresponding activations; identifying one or more cardiac tissue locations exhibiting progressive slow activation (PSA) based on the time difference; and a processor configured to present to a user an EP map of at least a portion of the heart, including providing a graphical indication of the one or more tissue locations indicative of the PSA. (9) The system of embodiment 8, wherein the activation includes a pacing stimulus applied to the heart. (10) The system described in embodiment 8, wherein the activation includes naturally occurring sinus rhythm activation of the heart.

[0053] (11) The system of embodiment 1, wherein the processor is configured to identify the tissue locations exhibiting the PSA by identifying one or more tissue locations exhibiting a monotonically increasing time difference over at least three consecutive cardiac cycles. (12) The system of embodiment 8, wherein the processor is configured to provide the graphical indication by drawing a boundary around a cluster of tissue locations that exhibit the PSA. (13) The system of embodiment 8, wherein the interface is configured to receive the cardiac signals by receiving unipolar and bipolar electrograms acquired using a catheter. (14) The system of embodiment 8, wherein the processor is configured to annotate the signal components by annotating a bipolar electrogram, a unipolar electrogram, or a multipolar electrogram.

Claims

1. 1. A system comprising: an interface configured to receive cardiac signals sensed by electrodes at locations within the patient's heart, the cardiac signals including signal components induced by respective activations; 1. A processor, comprising: Finding the signal components in the cardiac signal and annotating the signal components; calculating respective time differences between said annotations and said corresponding activations; identifying one or more cardiac tissue locations exhibiting progressive slow activation (PSA) based on the time difference; a processor configured to present an EP map of at least a portion of the heart to a user, including providing a graphical indication of the one or more tissue locations indicative of the PSA.

2. The system of claim 1 , wherein the activation comprises a pacing stimulus applied to the heart.

3. The system of claim 1 , wherein the activation comprises naturally occurring sinus rhythm activation of the heart.

4. 2. The system of claim 1, wherein the processor is configured to identify the tissue locations indicative of the PSA by identifying one or more tissue locations that exhibit a monotonically increasing time difference over at least three consecutive cardiac cycles.

5. The system of claim 1 , wherein the processor is configured to provide the graphical indication by delineating a boundary around a cluster of tissue locations indicative of the PSA.

6. The system of claim 1 , wherein the interface is configured to receive the cardiac signals by receiving unipolar and bipolar electrograms acquired using a catheter.

7. The system of claim 1 , wherein the processor is configured to annotate the signal components by annotating a bipolar, unipolar, or multipolar electrogram.

8. 1. A method comprising: receiving a cardiac signal sensed by an electrode at a location within the patient's heart, the cardiac signal including a signal component induced by each activation; Finding the signal components in the cardiac signal and annotating the signal components; calculating respective time differences between the annotations and the corresponding activations; identifying one or more cardiac tissue locations exhibiting progressive slow activation (PSA) based on the time difference; presenting to a user an EP map of at least a portion of the heart, the EP map comprising providing a graphical indication of the one or more tissue locations indicative of the PSA.

9. The method of claim 8 , wherein the activation comprises a pacing stimulus applied to the heart.

10. The method of claim 8 , wherein the activation comprises naturally occurring sinus rhythm activation of the heart.

11. 9. The method of claim 8, wherein identifying the tissue locations indicative of the PSA comprises identifying one or more tissue locations that exhibit a monotonically increasing time difference over at least three consecutive cardiac cycles.

12. The method of claim 8 , wherein providing the graphical indication comprises delineating a boundary around a cluster of tissue locations indicative of the PSA.

13. 10. The method of claim 8, wherein receiving the cardiac signals comprises receiving unipolar and bipolar electrograms acquired using a catheter.

14. The method of claim 8 , wherein annotating the signal components comprises annotating a bipolar electrogram, a unipolar electrogram, or a multipolar electrogram.

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