Patent Application
20250213169
The present invention is in the field of signal processing of physiological signals and particularly relates to measurement of heart tissue activation signals such as intracardiac-electrograms (IEGM) used in electrocardiographic monitoring or mapping during medical procedures.
A wide range of medical procedures involve placing probes, such as catheters, within a patient's body. One medical procedure in which these types of probes or catheters have proved extremely useful is in the treatment of cardiac arrhythmias. Cardiac arrhythmias and atrial fibrillation in particular, persist as common and dangerous medical ailments, especially in the aging population.
Diagnosis and treatment of cardiac arrhythmias include mapping the electrical properties of heart tissue, especially the endocardium and the heart volume, and selectively ablating cardiac tissue by application of energy. Catheters are inserted into the heart chamber and optionally around the heart chamber during such procedures. In most procedures, multiple catheters are inserted into the patient. Catheters may include mapping, ablation, temperature sensing and image sensing catheters. Some catheters are dedicated for placement in specific parts of the anatomy, e.g., coronary sinus, esophagus, atrium, ventricle. The catheters have multiple electrical channels, some more than others depending on the number of sensors and electrodes included in each catheter. The number and type of catheters depends on the procedure and on the physician preferred workflow. During a procedure, the electrical activity of the heart is monitored/mapped from the catheter's electrodes and as well as optionally from body surface electrodes that are attached to the patient's skin.
In order to better understand the subject matter that is disclosed herein and to exemplify how it may be carried out in practice, embodiments will now be described, by way of non-limiting example only, with reference to the accompanying drawings, in which:
Like reference numerals are used in the figures to designate similar modules/elements of the present invention or elements/modules having like functionalities. Accordingly, unless otherwise specified, the description of modules/elements with reference to a certain embodiment of the invention should be understood to apply to all embodiments of the present invention, in which such module/element is incorporated.
There is a need in the art for a novel and inventive technique to accurately determine cardiac tissue activation signals.
Widely used conventional technologies for measuring or mapping the electrical properties of a heart tissue, often utilize catheters with volumetric distal end assemblies, such as basket or balloon catheters or otherwise catheters having multiple splines at their distal end that surrounding a certain volume. In such catheters, typically electrode(s) which are located on outer/external surface(s) of the distal end (e.g., on external surfaces of the catheter's splines), are operated to measure intracardiac-electrograms (IEGM) from tissue regions in contact therewith, and another electrode, which is typically located within the volume enclosed by the volumetric distal end and thus within the intracardiac cavity but remote from the intracardiac tissue, is operated measure a far-field components of the IEGM. Accordingly, the far-field components of the IEGM may than be used to suppress the far-field IEGM component in the IEGM signals obtained from the electrode(s) contacting the tissue (e.g. by subtracting far-field IEGM component from the IEGM signals obtained from the contacting electrode(s)), to thereby obtain near-field IEGM component(s) of the IEGM signals sensed by the contacting electrode(s). The development of the near-field component of IEGM signal sensed by a respective electrode contacting a tissue region overtime is indicative of the activation signal in the tissue region being in contact with the respective electrode.
Intra-cardiac catheters are typically disposable elements designated for single-use in an intracardiac operation. There is therefore a need in the art to reduce the fabrication costs of such catheters. As will be appreciated by the below description, one approach for reducing fabrication costs of catheters for measuring/mapping the electrical properties of a heart tissue, is to use catheters having planar distal end assembly. This significantly lowers the fabrication costs, as such planar distal end assembly can be formed by a flexible printed circuit board (PCB) with the electrodes printed thereon.
However, a challenge in using such catheters having the planar distal end assembly, for measuring or mapping the electrical properties of a heart tissue, arises from the fact that there is no specific location in the planar configuration of the distal end for placing an electrode designated for measuring the far-field IEGM signal component. Indeed, any of the electrodes on the planar distal end assembly may occasionally touch or not touch the heart tissue during operation, or be proximal thereto, and therefore the far-field IEGM signal component cannot be obtained reliably from any specific electrode.
The present invention thus provides a novel technique for measuring the far-field IEGM signal component in a manner suitable for use in catheters designated for measurement or mapping of electrical properties of a heart tissue. The invention may be for example used to determine far-field component of IEGM signals sensed by catheters, which do not have an electrode (e.g. dedicated electrode) that is specifically adapted/dedicated to sense the far-field comments of the IEGM signals (e.g. while without, or with substantially suppressed, sensing of “noise” such as near-field IEGM from its surroundings). A non-limiting example of such a catheter is the catheter described herein below which has a planar distal end assembly, but the invention is not limited to this specific type of catheter and may be used for determining the far-field component of IEGM signals sensed by other catheter types which do not have any specific electrode suited for far-field IEGM sensing. Accordingly, the present invention provides a solution to the above challenge, facilitating the accurate measurement of tissue activation signals, by such catheters.
Reference is made to
Catheter 14 is an exemplary catheter that includes multiple electrodes 26 at distal end portion 28 thereof for sensing IEGM signals from a heart tissue proximal thereto. Catheter 14 may additionally include a position sensor 29 embedded in or near distal end assembly 28 for tracking position and orientation of distal end assembly 28. Optionally and preferably, position sensor 29 is a magnetic based position sensor including three magnetic coils for sensing three-dimensional (3D) location and/or orientation.
Magnetic based position sensor 29 may be operated together with a location pad 25, which includes a plurality of magnetic coils 32 configured to generate magnetic fields in a predefined working volume. Real time position of distal end assembly 28 of catheter 14 may be tracked based on magnetic fields generated with location pad 25 and sensed by magnetic based position sensor 29. System 10 optionally also includes one or more patches 38 positioned for skin contact on patient 23 to establish location reference for location pad 25. Details of the magnetic based position sensing technology are described for example 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.
A recorder 11 records and displays electrograms 21 captured with body surface electrocardiogram (ECG) electrodes 18 and 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.
In some embodiments the system 10 may be further adapted to perform tissue ablation. In such embodiments the system 10 may include an ablation energy generator 50 and a catheter dedicated for tissue ablation (not specifically shown). To this end, the system 10 may include a one or more catheters including catheter(s) dedicated for IEGM sensing and/or catheter(s) dedicated for ablating and/or catheter(s) dedicated for both IEGM and ablating. For ablation, physician 24 may similarly place a distal end of an ablation catheter in contact with a target site for ablating a tissue there. The ablation energy generator 50 is adapted to conduct ablative energy to one or more of electrodes at a distal end of the ablation catheter. 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. In embodiments, the catheter 14 may also be configured and operable for tissue ablation, and may thus be adapted for both IEGM sensing and ablating.
Patient interface unit (PIU) 30 is an interface configured to establish electrical communication between medical devices, such as catheters and/or other electrophysiological equipment, and a workstation 55 for controlling operation of system 10. The medical devices of system 10 may for example include electrophysiological equipment such as one or more 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/IEMG signal-processing and/or calculations.
Workstation 55 includes one or more processors with memory and/or storage with appropriate operating software stored 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 (or other data) compiled from recorded electrograms 21 in representative visual indicia or imagery superimposed on the rendered anatomical map, (3) displaying real-time location and orientation of one or more catheters within the heart chamber, and (4) displaying, on display device 27, sites of interest such as places where activations signals are measured/mapped, or 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.
With reference to
The shaft 14H includes a reference electrode 22 arranged on the shaft 14H near the distal end assembly 28. As described in more details below, the reference electrode 22 facilitates measurement of distances between the electrodes 26 and the heart tissue and thereby enables to assess a far-field component of the IEGM signal sensed thereby according to the technique of the present invention as described in more detail below. As will be appreciated by those versed in the art, in order to measure cardiac tissue activation signal at region of interest of a heart tissue, a far field component of the IEGM signals, should generally be measured (e.g. by electrode sufficiently distanced from the heart tissue yet still within the blood pool of the heart) The far-field component should then be subtracted/suppressed from the IEGM signals measured by each electrode touching the heart tissue at the region of interest, to thereby obtain a near-field component of the IEGM signals at that region of interest, which overtime is indicative of the cardiac tissue activation signal at the tissue region of interest. However, in some catheters, such as catheter 14 whose distal end assembly 28 is planar, there may be no specific electrode(s) dedicated for measuring the far-field component of the IEGM signals, and more specifically there is no specific electrode that is a priory maintained distanced from the tissue wall of the heart such that it can accurately measure the far field component of the IEGM signals sensed by the electrodes 26. For example, during operation with the planar distal end assembly 28 of catheter 14, all or some of the electrodes located on one surface (e.g. P1) of the planar distal end assembly 28 may touch the tissue of the heart wall, while all or some of the electrodes 26 located on the opposite surface (e.g. P2) may not touch the heart tissue. As the distal end assembly 28 in this catheter example 14 is planar (i.e. not volumetric as for instance in basket or balloon catheter types), there is no specific location on the distal end assembly 28 at which an electrode can be placed to verifiably not touch the heart tissue. Thus, in such type of catheter, in which there is no specific electrode designated for sensing the far-field IEGM, there is a need to dynamically identify and select, during the operation, electrode(s) of the plurality of electrodes 26, which are not touching the heart tissue and are sufficiently distanced therefrom, and use the signals from those selected electrode(s) to determine the far-field EGM signal. To achieve that, the reference electrode 22 is furnished on the catheter 14 and adapted/dedicated for implementation of tissue proximity sensing/measurements based on impedance between each one of electrodes 26 and the reference electrode 22, to thereby assess the distances of one or more of the electrodes 26 from the heart tissue.
In this non-limiting example, the reference electrode 22 is arranged on the shaft 14H of the catheter 14, and is adapted to facilitate the tissue proximity measurements. Then IEGM signals, which are acquired/measured by a subset of the electrodes 26 that were identified as being sufficiently distanced from the tissue, are used to determine/assess the far-field component of the IEGM signals that is sensed by one or more of the electrodes 26 that are in contact with the tissue. In order to facilitate the tissue proximity measurement(s), the reference electrode 22 in this example is arranged on the shaft 14H of the catheter in a manner such that during intracardiac operation of the catheter 14 within the heart it contacts body fluids (for example the blood when the catheter is inserted through patient's vascular system), while typically maintained distanced from, and not in contact with, the tissue/heart-tissue. This arrangement enables using the reference electrode 22 for the impedance-based tissue proximity measurements, by which the impedance between it and each respective electrode of electrodes 26 can be used to assess the distance of the respective electrode from the heart tissue. Preferably, in some embodiments the reference electrode 22 is configured with a ring like shape (e.g. surrounds the shaft 14H).
Indeed, although the reference electrode 22, in this case is on the shaft 14H, is arranged such as it typically does not contact the tissue, it may still not be suitable to provide accurate measurement of the far-field IEGM component. One reason for that may be that the reference electrode is typically relatively large and therefore it may capture both near-field and far-field components in case it brought close to the tissue wall. One reason for that may be that as the reference electrode 22 is placed on the shaft 14H (and is typically relatively large) it is generally too close to the tissue (e.g. tissue of the vascular system through which the catheter may be inserted, thus not suited for accurate sensing of the far-field signals), and thus may capture both far-field component of the IEGM signal as well as near-field components thereof from the tissue region proximal thereto. Another reason is that in some cases, where the catheter 14 is delivered via a delivery sheath, the reference electrode 22 which is located on the shaft 14H, may remain within the delivery sheath and thereby substantially masked from sensing the far-field component of the IEGM signal.
Nonetheless, according to embodiments of the invention, the reference electrode 22 may be used to assess the distances of one or more of the electrodes 26 from the heart tissue and thereby facilitate the identification and dynamic selections of subsets of electrodes 26, which are sufficiently distant from the tissue, and by which the far-field signal can be measured with accuracy. As described in more detail below, the distance measurements of the electrodes 26, also referred to herein as tissue proximity measurement(s), and or tissue proximity index/indices, may be performed by measuring the impedances of respective electrode(s) 26 whose tissue proximity is to be assessed (e.g. impedances between each respective electrode and the reference electrode 22) and determine the tissue proximities of one or more of the electrodes 26 based on their impedances. Example for tissue proximity measurements/techniques which may be implemented according to the present invention to assess the tissue proximities of one or more of the electrodes 26 are disclosed for example in U.S. Patent Application Publication No. 2021/0177504 which is incorporated herein by reference.
Optionally, the shaft 14H also includes a position sensor 29 which is typically embedded at or near the catheter's distal end assembly 28 to enable tracking position of the distal end assembly 28 (e.g. and the electrodes 26 thereon) by system 100, and thereby enable special mapping of the activation signals sensed by electrodes 26 or some of them.
Typically, the catheter 14 is implemented as a disposable catheter. In some embodiments, the planar distal end assembly 28 of catheter 14 is configured with a flexible printed circuit board (PCB) and with the first and second electrode pluralities of the electrodes 26 furnished/fabricated on opposite sides/surfaces, P1 and P2 of the flexible PCB. This inter-alia provides for cost effective fabrication of the catheter 14, reducing its production costs of and thus also costs of medical procedures, such as epicardial procedures, in which it may be utilized.
Turning back to
According to the present invention the system 10 includes a IEGM signal measurement system 100 (subsystem of system 10) capable of at least determining a far-field component of IEGM signals sensed by electrode(s) 26 of a catheter, such as catheter 14, which may have no specific electrode designated for measuring the far field IEGM signal component. The IEGM signal measurement system 100 may further be adapted to determine near-field component(s) of IEGM signal(s) measured by one or more of the electrodes 26 of the catheter, and optionally thereby determine the activations signals AS in the tissue regions proximal to the one or more electrodes 26. In various implementation the system 100 is implemented as a subsystem of system 10, and components of the system 100 may be included or implemented in any one or more of the: workstation 55, PIU 30 and recorder 11 of system 10 or distributed between them (e.g. implemented by one or more processors and/or signal processors of those sub-systems).
Reference is now made together to
In operation 210 of method 200, a catheter, such as catheter 14, is provided, having a plurality of electrodes 26 arranged at a distal end assembly 28 thereof, in a manner suitable for sensing IEGM signals from tissue regions in contact therewith respectively. The electrodes 26 may for example be arranged at outer surfaces of the distal end assembly 28 of the catheter 14. Optionally the catheter also includes a reference electrode 22 as described above. Alternatively, in some implementation the reference electrode 22 may not necessarily reside on the catheter 14 and may be arranged in a different manner to contacts body fluids while maintained distanced from be body/heart tissue.
Operation 220 of method 200, is carried out to determine a far-field component FF of the IEGM signals E sensed by the electrode(s) 26 of the catheter 14. To achieve that, in operation 220a a tissue proximity measurement is applied to each respective electrode of a multitude of the electrodes 26 to assess respective distances D of electrodes of the multitude from the surface of the tissue (e.g., heart tissue). The multitude of electrodes, whose tissue proximities are assessed in this case may include one or more of the plurality of electrodes 26 at the distal end assembly 28 of the catheter 14, and typically preferably more than one electrode. In some embodiments the tissue proximity measurements are implemented for example by a technique similar to that disclosed in U.S. Patent Application Publication No. 2021/0177504.
For instance, the tissue proximity measurements, may be implemented by tissue proximity processor/processing 110 of system 100. For example, the tissue proximity processing 110 may be carried out by a signal processor which is associated with the system and connected to the multitude of the electrodes 26 and the reference electrode 22. The signal processor implementing the tissue proximity processing 110 may deliver current including one or more frequency components in between each respective of the electrode of the multitude of the electrodes 26 and the reference electrode 22, and measure the respective impedance between them (e.g. optionally the measured impedance(s) per each frequency component in the delivered current). As the tissue has typically significantly different impedance than body fluids/blood, the respective impedance measured in this way, between each respective electrode of and the reference electrode 22, provides indication D of the distance between the respective electrode and the tissue.
More specifically, as the impedance readings are generally very sensitive to tissue proximity and may vary from patient to patient, in some embodiments the relation between impedances and respective distances D of the electrodes, may be inferred dynamically during the medical procedure. In such embodiments, optionally in operation 220a (e.g. in at least one iteration of this operation), the impedance values from each electrode whose impedance is being measured, may be stored by the system 100. Then, based on properties of the distribution of the measured impedance values (e.g. for example based on the maximal and minimal impedances measured), a relation between measured impedance of an electrode and its distance D from the tissue, and/or an impedance threshold indicative of whether the electrode contacts the tissue or not, may be determined in real time during the medical procedure. Accordingly, based on this relation or impedance-threshold, the distances D of the respective electrodes may be assessed in 220a from their measured impedances.
Thus, as illustrated the none-limiting example of
In parallel, however not necessarily concurrently with the tissue proximity measurement operation 220a but typically following it, IEGM signal measurements, referenced E in
In some none-limiting embodiments, the tissue proximity processing 110 and the IEGM signal measurement processing 120 may be implemented by a signal processor, which may be a part of the PIU 30 of system 10 described above. The signal processor, e.g. PIU 30, may be for example in signal communication with the electrodes 26, as well as optionally with the reference electrode 22 (used for the tissue proximity processing), and optionally also with the another electrode e.g. 18, which may be used for unipolar IEGM signal measurements. The signal processor may implement various signal processing capabilities, for instance impedance and/or voltage measurements between electrodes coupled thereto, signal/noise filtering, analog-to-digital conversion and/or other signal processing as will be appreciated by those versed in the art. As will be described in more detail below the tissue proximity processing 110 and the IEGM signal measurement processing 120 may be performed repeatedly during successive time frames (e.g. each being in the order of for example of 50 milliseconds (ms)), in order to assess the tissue proximities D for multitudes of the electrodes 26 and the IEGM signal measurements E for some or all of them as described above, for each successive time frame. In case analog-to-digital conversion is implemented, each such time frame may include for instance 50 samples, e.g. assuming a sampling rate in the order of 1 kHz is applied.
In order to determine/assess the far-field IEGM component FF sensed (e.g. commonly) by the electrodes 26, operation 220 of method 200 further includes the sub-operations 220b and 220c. In operation 220b, subset of electrodes 26 whose respective tissue distances/proximities D were assessed in operation 220a to be above a certain distance threshold DTH, are selected (e.g. dynamically selected per each time frame) for further processing of their IEGM signals E to determine based thereon the (common) far-field IEGM component FF in the IEGM signals. The minimal distance threshold DTH, above which the electrodes are selected is generally such that the IEGM signals sensed thereby is expected to be mostly composed of the far-field component FF and to lesser degree of near-field IEGM components NF. For instance, the distance threshold DTH may be selected as at least DTH>5 millimeters.
In operation 220c the far-field component FF of the IEGM signal is determined (e.g. for the respective time frame) by averaging (or otherwise aggregating by a different aggregation scheme) the IEGM signal measurements E from the respective electrodes 26 of the subset selected in 220b whose respective distances D from the tissue surface are above the minimal distance threshold DTH. The aggregation/averaging of the signals from the plurality of electrodes provide for suppressing/averaging-out noise components (e.g. near-field signal residues which may still be weakly sensed by the electrodes of the subset in spite of their relative distance from the tissue) to thereby reliably obtain the far-field component FF substantially “clean” from noise.
For some time-frames, operation 220b may not yield any selected electrodes. For example, in case the reference electrode 22 happens to touch a tissue near it during a time-frame, the distance measurements D obtained in operation 220a for all/any of the electrodes 26 may provide values below the threshold DTH for all the electrodes 26. Therefore, in operation 220c, in cases where a number of the electrodes identified as sufficient tissue distance is below a certain predetermined minimal number of electrodes (e.g. the minimal number being at least one and typically more than one), the previous value of the far-field IEGM signal FF measured for a preceding timeframe may be used in the consecutive timeframe. This generally does not introduce significant artifacts to the measured far-field IEGM signal FF since these cases are typically rare due to the location/configuration of the reference electrode 22, and also because the timeframes are typically of duration smaller than a characteristic time interval for change in the far-field component FF of the IEGM signal.
For example, in operation 220a impedances of all, or of a plurality of, electrodes 26 from both sides of the planar distal end assembly 28, may be measured with reference to electrode 22. In case all the impedances being measured in 220a are indicative of the respective electrodes being in contact with the tissue wall (e.g., being relatively high impedances), then in this case, in operation 220b the system 100 may assert the that the origin of the high impedance is that the reference electrode 22 is touching the cavity/tissue wall (since it would be typically impossible for pluralities of electrodes on both sides of the planar distal end assembly 28 to simultaneously touch the tissue wall), and no electrode will be dynamically selected as being distant from the tissue. Therefore, in this case, in operation 220c the previous value of the far-field IEGM signal FF will be provided as representative of the far-field IEGM signal FF also for the current timeframe.
With reference to the system 100 illustrated in
In view of the above, in operation 220 the far-field FF component of the IEGM signal may be determined based on the IEGM signals E measured by the electrodes 26, while generally obviating a need to have a dedicated electrode arranged in the catheter 14 for sensing the intra-cardiac far-field IEGM component FF.
As indicated above the operation 220 may be carried out for assessing determining the far-field FF component of the IEGM signal per respective time frames (successive/consecutive time frames), at which the IEGM signals E are measured by the electrodes 26. Accordingly, as illustrated in the optional operation 230 of method 200, the operation 220 may be repeated for multiple successive or consecutive time frames, in order to update the value of the far-field IEGM component FF for multiple time-frames over a desired time duration of a medical operation at which the IEGM signals are to be monitored. As indicated above, for timeframes (e.g. generally rare) where the field IEGM component FF cannot be assessed (e.g. in case reference electrode 22 touches the tissue), the far-field IEGM component FF assessed for the respectively preceding time frame may be used. To this end, system 100 may include a buffer (data or signal buffer not specifically shown) holding the value of the last updated field IEGM component FF in the preceding timeframe, to enable this value to be used in such cases).
Optionally, method 200 further includes operation 240 for assessing a near field components NF of an IEGM signal sensed by certain one or more electrodes of interest SE of the electrodes 26 (typically some of the electrodes 26 which are in contact with the cardiac tissue). The set of the certain electrodes for which the near-field component NF is to be determined, may in various implementations be automatically selected by the system 10 (e.g. in accordance with cardiac electrical activity being mapped or measured thereby, possibly based on the tissue regions of interest being mapped/measured and the position of the catheter 14 as may be determined by position sensor 29), and/or it may be selected in some implementations by physician 24 operating the system 10.
Operation 240 optionally includes sub-operation 240a, in which IEGM signal(s) E measured by the certain one or more electrodes of interest SE are obtained (at least one electrode is illustrated in the none-limiting example of
To implement the optional operation 240, system 100 as illustrated in
Generally, operation 240, may be performed per each respective time frame of interest at which the near field components NF of certain electrodes of interest SE are to be assessed. To this end, as will be appreciated from the above description, the operation 240 may be performed in synchronization with operation 220, such that the far-field component FF obtained for a respective time frame is suppressed from the IEGM signal E obtained from each electrode of interest SE, for the corresponding/same time frame to thereby yield the near-field signal NF sensed by that electrode SE during that time frame.
Optionally method 200 may also further include operation 250 by which operation 240 is repeated for multiple time frames to determine/record the tissue activation signal AS sensed by each electrode of interest SE from the tissue in its vicinity. The tissue activation signal AS is used herein to designate an aggregation/accumulation of the near-field signal NF components measured by each respective measured electrode of interest SE in each time frame for over a time duration one of multiple time frames. Operation 250 may for example be performed by a recorder 170 of system 100 illustrated in
To this end, system 100 and method 200 described above exemplify implementations of the technique of the present invention to assess far-field signal components FF of IEGM signals E sensed by a plurality of electrodes 26 on a distal end assembly of a catheter, such as catheter 14, which may not have a suitable electrode dedicated for sensing intra-cardiac far-field IEGM signal FF. For clarity the system 100 is illustrated in
Example 1. A method 220 to determine cardiac tissue activation signals, the method includes:
Example 2. The method 200 according to example 1, further includes:
Example 3. The method 200 according to example 2, further includes repeating (230, 250) the operations II and III to determine development of the near-field NF component of the EGM signal E over time and thereby obtaining a cardiac tissue activation signal of the tissue near said at least one electrode.
Example 4. The method 200 according to example 1, wherein applying the tissue proximity measurement (220a) to the respective electrode includes applying an excitation current through the respective electrode and measuring an impedance of the electrode and thereby assessing the tissue proximity D based on said impedance.
Example 5. The method 200 according to example 4, wherein the impedance is measured between the respective electrode and a reference electrode 22 arranged near an end of a shaft 14H of the catheter 14 proximal to the distal end assembly 28, such that it typically remains spaced from the tissue during operation of the catheter 14.
Example 6. The method 200 according to example 1, wherein the far-field component FF of IEGM signal E is repeatedly updated (230) by repeating operation II (220).
Example 7. The method 200 according to example 6, wherein updates of the far-field component FF of IEGM signal E are skipped in repetitions (230) of operation II in which a number of the electrodes identified by the dynamic selection (220b) as having the respective distances D from the tissue surface above the certain threshold DTH, is below a certain predetermined minimal number of electrodes. For example, the predetermined minimal number of electrodes with distance D above the certain threshold DTH, that below this number the far-field component FF is not updated and its preceding value remains being one or more electrodes.
Example 8. The method 200 according to example 7, wherein applying said tissue proximity measurement to said respective electrode (220a) includes measuring an impedance between the respective electrode and a reference electrode 22 that is arranged on the catheter 14, such that it typically remains spaced from the tissue; and wherein in repetitions (230) in which the number of the electrodes is below the certain predetermined minimal number, the reference electrode 22 is assumed to be in contact with the tissue, therefore skipping the updates of the far-field component of EGM signal in those repetitions.
Example 9. The method 200 according to example 1, wherein the distal end assembly 28 of the catheter 14 has a planar configuration, and the plurality of EGM electrodes 26 includes a first and second pluralities of the EGM electrodes arranged respectively on opposite surfaces, P1 and P2, of the distal end assembly 28.
Example 10. The method 200 according to example 1, adapted to enable the assessment of the far-field component FF of the EGM signals E while without the catheter 14 having a dedicated electrode arranged in its distal end assembly 28 for sensing the far-field component FF.
Example 11. The method 200 according to example 9, wherein the distal end assembly of the catheter 14 includes a flexible printed circuit board (PCB) with the first and second electrode pluralities at opposite sides of the PCB.
Example 12. A system 100 to determine cardiac tissue activation signals, the system 100 being connectable to a catheter 14 having a plurality of electrodes 26 arranged at a distal end assembly 28 thereof;
Example 13. The system 100 according to example 12, wherein the one or more processors are adapted to further assess a near-field component NF of the IEGM signal E sensed by at least one of the electrodes 26 by subtracting the far-field component FF from the IEGM signal measurement obtained from the at least one electrode.
Example 14. The system 100 according to example 13, wherein the one or more processors are adapted to determine cardiac tissue activation signal AS in a tissue near said at least one electrode by repeatedly (230, 250) determining (230, 250) the far-field and near-field components, FF and NF, and thereby determining development of the near-field component NF of the IEGM signal over time, whereby the development being indicative of the cardiac tissue activation signal AS.
Example 15. The system 100 according to example 12, wherein the one or more processors are adapted to apply the tissue proximity measurement (220a) to the respective electrode by delivering an excitation current through the respective electrode and measuring an impedance of the electrode, to thereby assess the tissue proximity based on the impedance.
Example 16. The system 100 according to example 15, wherein the delivery of the excitation current is made between the respective electrode and a reference electrode 22 arranged near an end of the shaft 14H proximal to the distal end assembly 28 of the catheter 14, such that it typically remains spaced from the tissue.
Example 17. The system 100 according to example 12 wherein the one or more processor are adapted to repeatedly update (230) the far-field component of IEGM signal by repeating method operations 220a to 220c; and wherein updates of the far-field component of IEGM signal are skipped in repetitions of these in which a number of the electrodes identified by the dynamic selection operation 220b as having the respective distances D from the tissue surface above the certain threshold DTH, is below a certain predetermined minimal number of electrodes (the mini number may be one or in some cases more than one to facilitate improved measurement/assessment of the far-field components by averaging the signals of several electrodes).
Example 18. A catheter 14 for Intracardiac Electrogram (IEGM) mapping. The catheter 14 includes a shaft 14H and a distal end assembly 28 connected at one end of the shaft 14H; wherein the distal end assembly 28 has a planar configuration and includes a plurality of electrodes 26 including a first and second pluralities of the electrodes arranged respectively on opposite surfaces, P1 and P2, of the planar configuration of the distal end assembly 28, and a reference electrode 22 arranged on the shaft 14H in vicinity of the distal end assembly 28 to enable conduction of respective tissue proximity measurement for one or more respective electrodes of the plurality by measuring an impedances between the reference electrode 22 and the respective electrodes 26.
Example 19. The catheter 14 according to example 18, wherein at least one of the following:
Example 20. The catheter 14 according to example 18 configured as a disposable catheter.
