Handling Ectopic Beats in Electroanatomical Mapping of the Heart

Abstract

The present invention is entitled "Processing Ectopic Beats in Electroanatomical Mapping of the Heart". The present invention discloses a medical device that includes a probe configured to be inserted into a chamber of a patient's heart and includes one or more intracardiac electrodes. An interface circuit acquires intracardiac electrogram signals from the intracardiac electrodes and acquires electrocardiogram (ECG) signals from body surface electrodes fixed to the patient's body surface. A processor detects a P wave in each heartbeat in a sequence of heartbeats in the acquired ECG signals and identifies one or more heartbeats in the sequence of heartbeats as ectopic beats in response to the morphology of the detected P wave in the heartbeat. The processor extracts electrophysiological parameters from the intracardiac electrogram signals acquired during the sequence of heartbeats and generates a map of the extracted electrophysiological parameters while excluding the intracardiac electrogram signals received during the ectopic beats from the map.

Description

Technical Field

[0001] The present invention generally relates to invasive medical diagnostic systems and methods, and more particularly, to electroanatomical mapping of the heart. Background Art

[0002] Electroanatomical maps of the chambers of the heart show both the physical structure of the walls of the heart chamber and the distribution of electrophysiological parameters such as local activation time (LAT) over the walls. LAT is, for example, the time interval between a reference time determined from a body surface ECG or intracardiac electrogram and the time of a local depolarization event in the heart wall. Electroanatomical maps are typically based on intracardiac electrical measurements made by a suitable transvascular catheter. Many systems for electroanatomical mapping are commercially available, such as those produced by Biosense Webster, Inc. (Irvine, California). System.

[0003] In some diagnostic procedures, intracardiac electrical measurements are combined with simultaneous body surface measurements of electrocardiogram (ECG) signals. For example, U.S. Patent Application Publication 2019 / 0223808 describes a method for classifying heartbeats based on the time series and morphology of intracardiac (IC) and body surface (BS) ECG signals, the disclosure of which is incorporated herein by reference in its entirety as if fully set forth. The IC-ECG signals are classified as atrial (A-) activity or ventricular (V-) activity, and the IC annotations are designated as IC-A annotations or IC-V annotations, respectively. Corresponding A / V time series comparisons of the IC annotations reflecting the sensed heartbeats are made using one or more time series templates for heartbeat classification. Morphological comparisons of the BS-ECG oscillatory signal segments reflecting the morphology templates of the sensed heartbeats can also be made for classification.

[0004] As described in the above publication, the morphology of the ECG can be a useful tool in heartbeat classification and arrhythmia identification. In this regard, U.S. Patent Application Publication 2018 / 0008203 describes a method for automatically classifying beats based on the similarity of the morphological characteristics of the beats to members of a set of templates, the disclosure of which is incorporated herein by reference in its entirety as if fully set forth. Figures 4 and 5 in that publication show morphological matching filters that can be used for such classification, while Figures 6 and 7 show specific algorithms for implementing morphological correlation in such filters. These morphological filters and associated calculations are described in detail in paragraphs 〖0058〗 to 〖0070〗 of that publication.

[0005] Documents incorporated by reference into this patent application are to be considered an integral part of this patent application, except for any terms defined in these incorporated documents in a manner that conflicts with the definitions expressly or implicitly given in this specification, in which case only the definitions in this specification shall be considered. Specifically, as used in the following description and claims, the terms "electrocardiogram" and "ECG" refer to electrical signals collected from skin electrodes on the body surface, while the term "intracardiac electrogram" refers to electrical signals collected by a probe within the heart. The term "morphology" is used in this specification and claims to refer to the shape characteristics of an ECG, including the amplitude, width, and profile of the waves that make up the ECG signal. Summary of the Invention

[0006] The exemplary embodiments of the invention described below provide improved methods and systems for electroanatomical mapping.

[0007] Thus, according to an exemplary embodiment of the invention, there is provided a medical device that includes a probe configured to be inserted into a chamber of a patient's heart and includes one or more intracardiac electrodes configured to sense electrical potential in tissue within the chamber during a sequence of heartbeats. An interface circuit is configured to acquire intracardiac electrogram signals from the one or more intracardiac electrodes and electrocardiogram (ECG) signals from body surface electrodes fixed to the patient's body surface. A processor is configured to: detect a P wave in the acquired ECG signals in each heartbeat of the sequence of heartbeats; and identify one or more heartbeats in the sequence of heartbeats as ectopic beats in response to the morphology of the P wave detected in one or more heartbeats of the sequence; and extract electrophysiological parameters from the intracardiac electrogram signals acquired during the sequence of heartbeats; and generate a map of the extracted electrophysiological parameters while excluding intracardiac electrogram signals received during ectopic beats from the map.

[0008] In one exemplary embodiment, the electrophysiological parameter includes a local activation time (LAT) extracted from intracardiac electrogram signals acquired from multiple locations within a chamber of the heart.

[0009] In the disclosed exemplary embodiment, the device includes a position tracking subsystem configured to acquire position coordinates of the probe within the chamber, wherein the processor is configured to apply the position coordinates in generating the map.

[0010] In some exemplary embodiments, the probe is configured to be inserted into an atrium of the heart, and the processor is configured to map the extracted electrophysiological parameters over the atrium while identifying ectopic beats occurring due to premature atrial contractions and excluding the ectopic beats from the map. Typically, the processor is configured to identify ectopic beats occurring due to premature atrial contractions and exclude the ectopic beats from the map even when the RR interval of the ectopic beats is not significantly different from the previous heartbeat in the sequence.

[0011] In the disclosed exemplary embodiments, the processor is configured to: create a template of the P wave based on a series of acquired ECG signals; and identify ectopic beats by comparing the ECG signals with the template.

[0012] According to an exemplary embodiment of the present invention, there is also provided a method for electrophysiological measurement, the method comprising: acquiring intracardiac electrogram signals from tissue in a chamber of a patient's heart during a heartbeat sequence; and acquiring electrocardiogram (ECG) signals from body surface electrodes fixed to the patient's body surface during the heartbeat sequence. Detecting P waves in the digitized ECG signals in each heartbeat in the sequence, and identifying one or more heartbeats in the sequence as ectopic beats in response to the morphology of the P waves detected in one or more heartbeats in the sequence. Extracting electrophysiological parameters from the intracardiac electrogram signals acquired during the heartbeat sequence, and generating a map of the extracted electrophysiological parameters while excluding the intracardiac electrogram signals received during the ectopic beats from the map. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The present invention will be more fully understood from the following detailed description of embodiments of the present invention in conjunction with the accompanying drawings, in which:

[0014] Figure 1 is a schematic illustration of a system for electrophysiological measurement and mapping of the heart according to an exemplary embodiment of the present invention; and

[0015] Figure 2 is a flow chart schematically showing a method for electroanatomical mapping of the heart according to an exemplary embodiment of the present invention. DETAILED DESCRIPTION

[0016] The P wave in the ECG typically occurs in each heartbeat due to atrial depolarization (which causes atrial contraction). Typically, the depolarization front in the heart starts from the sinoatrial node in the right atrium and then travels through the left atrium to the ventricles. Depolarization of the ventricles produces a QRS complex in the ECG, which typically occurs after a short delay after the P wave.

[0017] However, abnormal conduction in the atrium can sometimes cause atrial ectopic beats, and during ectopic beats, the synchronization between atrial contraction and ventricular contraction is lost. Atrial ectopic beats are associated with premature atrial complexes in the ECG, which can be identified based on corresponding changes in the morphology of the P wave. Although there are premature atrial complexes, the P wave in atrial ectopic beats is usually followed by a normal QRS complex, and occasionally the RR interval (i.e., the duration of the heartbeat) of atrial ectopic beats may not be significantly different from the previous heartbeat in the sequence. The term "significant" is used in this specification and the claims in a statistical sense to denote a difference outside the expected bounds of random variation; for example, if the RR interval of a heartbeat differs from the average RR interval of the previous sequence by more than twice the standard deviation of the RR intervals in the previous sequence or by more than a given fraction (such as 10%) of the average, then the RR interval of the heartbeat can be considered significantly different from the previous heartbeat sequence.

[0018] For example, in the electroanatomical mapping performed in the above Carto system, intracardiac electrograms are acquired from multiple locations within the chambers of the heart over a period of multiple heartbeats. When mapping temporal characteristics such as LAT, the electrogram signals acquired within multiple heartbeats are typically synchronized with each other using a reference point in the ECG such as the peak of the R wave. However, when an ectopic beat occurs during electroanatomical mapping of a heart chamber, the synchronization of the electrogram signal with the reference point is lost; and the combination of signals acquired during the ectopic beat can thus introduce noise and errors into the map. To this end, when the electroanatomical mapping system detects that the RR interval of a given heartbeat is significantly different from the RR intervals of the previous heartbeat sequence, the system typically discards the electrogram signal acquired during the given heartbeat.

[0019] However, in atrial ectopic beats, the RR interval is not significantly different from the RR intervals of the previous heartbeats in many cases. The abnormal atrial conduction occurring during such heartbeats can introduce errors into the electroanatomical map of the atrium, and filtering out heartbeats based solely on the RR interval will not eliminate this source of error.

[0020] To alleviate this problem, the exemplary embodiments of the invention described herein identify changes in the morphology of the P wave acquired in the ECG signal by surface electrodes. When a certain aspect of the P wave morphology in a given heartbeat is significantly different from the P waves in the previous heartbeat sequence, the atrial electrogram signal acquired during the given heartbeat is excluded from the map.

[0021] Accordingly, the disclosed exemplary embodiments provide a medical device and diagnostic method in which a probe (such as a catheter) is inserted into a chamber of a patient's heart (such as one of the atria). Intracardiac electrodes on the probe sense the electrical potential in the myocardial tissue in the chamber during a heartbeat sequence. An interface circuit (such as an analog front end and digitizing circuitry) acquires intracardiac electrogram signals from the intracardiac electrodes and simultaneously acquires ECG signals from body surface electrodes fixed to the patient's body surface.

[0022] The processor detects the P wave in the acquired ECG signals in each heartbeat of the heartbeat and identifies ectopic beats based on the morphology of the detected P wave. The processor also extracts electrophysiological parameters (such as LAT) from the intracardiac electrogram signals acquired during the heartbeat sequence and generates a mapping diagram combining these parameters, while excluding the intracardiac electrogram signals received during the identified ectopic beats from the mapping diagram. Specifically, even when the RR interval of the ectopic beat is not significantly different from the previous heartbeat in the sequence, the processor can exclude the ectopic beats occurring due to premature atrial contractions in this way.

[0023] Figure 1 FIG. 7 is a schematic illustration of a catheter-based system 20 for electrophysiological (EP) sensing and mapping of the heart according to an exemplary embodiment of the present invention. System 20 includes a catheter 21 that includes an insertion tube 22 for percutaneous insertion into a patient 28's heart 26, the patient being shown lying on a table 29. The distal end 25 of the insertion tube 22 (as Figure 1 seen in the inset) includes one or more electrodes 38 that contact and sense the electrical potential in the myocardial tissue in the heart 26. Although, for simplicity, the distal end 25 is shown in Figure 1 as a single linear structure, in alternative embodiments, the distal end of the catheter 21 may have other features and shapes known in the art, such as, for example, multiple arms or a basket configuration. The distal end 25 also includes a magnetic position sensor 40, the function of which is further described below.

[0024] The proximal end of the catheter 21 is connected to a catheter interface circuit 44 in a console 24. The interface circuit 44 generally includes an analog front end that includes suitable amplifiers and filters for acquiring intracardiac electrogram signals from the electrodes 38 and one or more analog-to-digital converters for converting the signals into digital samples. In addition, an ECG interface circuit 45 in the console 24 receives, amplifies, filters, and digitizes the ECG signals from body surface electrodes 49 fixed to the body surface of the patient 28. The digital samples from the interface circuits 44, 45 are input to a processor 41 in the console 24.

[0025] To perform a diagnostic mapping procedure, physician 30 first inserts sheath 23 into patient 28's heart 26 and then advances insertion tube 22 through the sheath. Physician 30 manipulates catheter 21 by using a manipulator 32 near the proximal end of the catheter to advance the distal end 25 of insertion tube 22 toward a target location in heart 26, such as within the left atrium 51 of the heart. Once the distal end 25 of insertion tube 22 has reached the left atrium in heart 26, physician 30 retracts sheath 23 and manipulates catheter 21 so that electrodes 38 contact myocardial tissue at multiple locations. Console 24 can verify good contact between the electrodes and the tissue by measuring the impedance between each of these electrodes and the tissue.

[0026] During this procedure, the position tracking subsystem in system 20 applies magnetic position sensing in tracking the position and orientation of the distal end 25 of insertion tube 22 within heart 26. To this end, as shown in the illustration of Figure 1 , the distal end 25 of insertion tube 22 contains a magnetic position sensor 40, which includes, for example, a micro wire coil or multiple coils. One or more magnetic field generators 36 are fixed, for example, beneath the bed 29 at known positions close to the body of patient 28, as shown in Figure 1 . Drive circuit 34 in console 24 applies drive signals to the magnetic field generators so as to generate multiple magnetic field components oriented along different respective axes. During navigation of the distal end 25 within heart 26, magnetic sensor 40 outputs electrical signals in response to the magnetic field components. A position sensing circuit, such as processor 41 in console 24, receives these signals through interface circuit 44 and processes these signals to find the position (position and orientation) coordinates of the distal end 25. These coordinates also indicate the corresponding positions of electrodes 38.

[0027] The methods and apparatus for magnetic position sensing implemented in system 20 are based on those used in the above-described Carto system. The operating principles of such magnetic sensing are described in detail in, for example, U.S. Patents 5391199, 6690963, 6484118, 6239724, 6618612, and 6332089, in PCT Patent Publication WO 96 / 05768, and in U.S. Patent Application Publications 2002 / 0065455A1, 2003 / 0120150 A1, and 2004 / 0068178 A1, the disclosures of which are hereby incorporated by reference in their entireties as if fully set forth herein.

[0028] Alternatively or additionally, system 20 can implement other position sensing techniques known in the art, including both magnetic sensing modalities and other position sensing techniques. For example, processor 41 can measure and analyze the electrical impedance between intracardiac electrode 38 and body surface electrode 49 to find the position coordinates of the intracardiac electrode.

[0029] In some exemplary embodiments, processor 41 includes a general-purpose computer having suitable interface circuits 44, 45 for receiving signals from catheter 21 and body surface electrodes 49 (including low-noise amplifiers and analog-to-digital converters), and for receiving signals from and controlling the operation of other components of system 20. Processor 41 generally performs these functions under the control of software stored in memory 48 of system 20. The software may be downloaded electronically to the computer via a network, for example, or alternatively or additionally, it may be set up and / or stored on a non-transitory tangible medium such as magnetic memory, optical memory, or electronic memory. Additionally or alternatively, at least some of the functions of processor 41 may be performed by dedicated or programmable hardware logic.

[0030] Based on the intracardiac electrogram signals acquired from the electrodes within the heartbeat sequence, processor 41 generates an electroanatomical map 50 and, in the illustrated example, renders the map onto display 27. Map 50 includes electrophysiological parameters extracted at each point within a heart chamber (such as within left atrium 51), such as LAT or peak voltage measured at each point. The parameter values may be overlaid on the map as numerical values or as corresponding color codings, for example.

[0031] As described above, processor 41 also acquires ECG signal 52 from the body surface electrodes (and, in the illustrated example, also presents the ECG signal on display 27). Processor 41 detects P wave 54 in each heartbeat of the acquired ECG signal and analyzes the morphology of the P wave to identify ectopic beats. When generating map 50, processor 41 excludes the intracardiac electrogram signals acquired from electrode 38 during ectopic beats.

[0032] Figure 2 FIG. is a flow chart schematically showing a method for electroanatomical mapping of the heart according to an exemplary embodiment of the present invention. For clarity and conciseness, the method is described hereinafter with reference to the elements of system 20 as Figure 1 shown. Alternatively, with the necessary modifications, the principles of this method of mapping are applied in other kinds of electroanatomical mapping configurations.

[0033] At probe positioning step 60, physician 30 advances catheter 21 through the vascular system of patient 28 until the distal end 25 is positioned within atrium 51 of heart 26. At electrogram acquisition step 62, processor 41 acquires intracardiac electrogram signals from electrode 38 on distal end 25 via catheter interface circuit 44. At ECG acquisition step 64, processor 41 simultaneously acquires ECG signals from body surface electrodes 49 via ECG interface circuit 45.

[0034] At the morphological analysis step 66, the processor 41 analyzes the morphology of the ECG signal, and specifically, the morphology of the P wave in each heartbeat. For example, the processor 41 can create a template of the P wave by averaging the ECG signal over a specific number of heartbeats in which the ECG signal is stable, and then can calculate the correlation between subsequent heartbeats and this template. Template creation and subsequent correlation can be performed on any or all signals from various ECG leads; however, these operations are most advantageously applied to signals from leads II and V1, where the P wave is typically most prominent.

[0035] In one exemplary embodiment, for the purposes of step 66, an operator such as the physician 30 identifies a time window in which the P wave appears in a series of heartbeats. The time window can be defined relative to an annotation point such as the peak of the R wave in the ECG signal. The processor 41 accumulates the ECG signals during an initial reference period and verifies that they have an expected overall shape (in the case of the P wave, typically a shallow jump) and are consistent between beats, for example where the signal-to-noise ratio is higher than a predefined minimum level and the variance between beats is lower than a maximum limit. The processor 41 combines the accumulated signals, for example by averaging the signals, to create a template that then serves as a kernel for comparing subsequent heartbeats. This comparison can be performed, for example, by calculating the cross-correlation between the kernel and the portion of the ECG signal that falls within the P wave time window defined by the operator. Alternatively or additionally, the processor 41 can apply a specific transform to the template and the subsequent signals, such as, for example, a Fourier transform, a wavelet transform, or a multi-pole transform, and then can compare the transform coefficients at step 66.

[0036] Further alternatively or additionally, other kinds of morphological calculations can be applied to the ECG signal, such as those described in the above-mentioned U.S. Patent Application Publication 2018 / 0008203. The processor 41 can not only test and apply the morphology of the P wave to determine which signals to include and which signals to exclude from the electroanatomical map, but can also test and apply other features of the ECG signal.

[0037] At classification step 68, the processor 41 examines the results of the morphological analysis in order to classify the current heartbeat as a normal heartbeat or an ectopic heartbeat. For example, when the correlation of the P wave in a given heartbeat significantly drops below a specific baseline correlation level with a morphological template, the processor 41 identifies the given heartbeat as an ectopic beat. In such a case, at mapping exclusion step 70, the intracardiac electrogram signals acquired during the given heartbeat are excluded from the map. Even when the RR interval of the ectopic beat is not significantly different from the previous heartbeat in the sequence, the processor 41 will identify and exclude such ectopic beats that are clearly due to premature atrial contractions. (In addition, regardless of the P wave morphology, the processor 41 will generally exclude from the map heartbeats in which the RR interval is significantly different from the previous heartbeat or exhibits other abnormal characteristics.) The excluded data may be discarded, or alternatively, the processor 41 may incorporate the excluded data into another map or other reports on the arrhythmic behavior of the heart.

[0038] On the other hand, when it is found at step 68 that the ECG signals in a given heartbeat have a normal morphology, at mapping addition step 72, the processor 41 derives electrophysiological parameters of interest from the intracardiac electrogram signals and incorporates these parameters into the map.

[0039] At mapping completion step 74, after optionally updating the electroanatomical map, the processor 41 determines whether the map includes sufficient data. (This decision may be made, for example, in response to a corresponding input from the physician 30.) If so, Figure 2 the process terminates. Otherwise, the processor 41 returns to step 62 and repeats the cycle of acquisition, analysis, and mapping.

[0040] It should be understood that the above embodiments are cited by way of example, and 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 their variations and modifications, which would occur to those skilled in the art upon reading the above description and which are not disclosed in the prior art.

Claims

1. A medical device for electroanatomical mapping of the heart, the medical device comprising: A probe configured to be inserted into a chamber of a patient's heart and comprising one or more intracardiac electrodes configured to sense electrical potential in tissue in the chamber during a sequence of heartbeats; An interface circuit configured to acquire intracardiac electrogram signals from the one or more intracardiac electrodes and electrocardiogram ECG signals from body surface electrodes fixed to the body surface of the patient; And A processor configured to: Detect a P wave in the acquired ECG signal in each heartbeat of the sequence of heartbeats; Calculate the correlation between each detected P wave in the detected P waves of the sequence of heartbeats and a template; Identify one or more heartbeats in the sequence of heartbeats as ectopic beats based on identifying a significant drop in the correlation over the sequence of heartbeats; Extract electrophysiological parameters from the intracardiac electrogram signals acquired during the sequence of heartbeats; And Generate a map of the extracted electrophysiological parameters while excluding the intracardiac electrogram signals received during the ectopic beats from the map.

2. The medical device according to claim 1, wherein, The electrophysiological parameters include local activation time LAT extracted from the intracardiac electrogram signals acquired from multiple positions in the chamber of the heart.

3. The medical device according to claim 1 and comprising a position tracking subsystem configured to acquire position coordinates of the probe in the chamber, wherein the processor is configured to apply the position coordinates in generating the map.

4. The medical device according to claim 1, wherein, The probe is configured to be inserted into the atrium of the heart, and the processor is configured to map the extracted electrophysiological parameters over the atrium while identifying the ectopic beats occurring due to atrial premature contractions and excluding the ectopic beats occurring due to atrial premature contractions from the map.

5. The medical device according to claim 4, wherein, The processor is configured to identify the ectopic beats occurring due to atrial premature contractions and exclude the ectopic beats occurring due to atrial premature contractions from the map even when the RR interval of the ectopic beats is not significantly different from the previous heartbeat in the sequence.

6. The medical device according to claim 1, wherein, The processor is configured to: create a template of the P wave based on a series of acquired ECG signals.

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