System for cardiac electrography, electrode assembly, use and method

Abstract

System for cardiac electrography, comprising: an electrode arrangement comprising at least one set of a primary electrode and three secondary electrodes, the three secondary electrodes being arranged to define respective three vertices of an imaginary triangle in which the primary electrode is arranged centrally; a signal acquisition unit electrically connectable or connected to the electrode arrangement and configured, when connected, to acquire electrographic signals from the at least one set of electrodes; and a signal processing unit configured to process the acquired electrographic signals to determine, for one or more sets of the at least one set of electrodes, a difference signal between on the one hand an electrographic signal from the primary electrode and on the other hand an average electrographic signal from the three secondary electrodes.

Description

[0001] P137803PC00

[0002] Title: System for cardiac electrography, electrode assembly, use and method

[0003] FIELD

[0004] The invention relates to a system for cardiac electrography, as well as to an electrode assembly for cardiac electrography, a use of the system and / or the electrode assembly, and a method of cardiac electrography.

[0005] BACKGROUND

[0006] In cardiac electrography, various electrode arrangements and associated signal processing schemes are known. In so-called coaxial cardiac electrography, it is known to arrange a primary electrode at the center of an imaginary square, with four secondary electrodes being arranged at the square’s vertices. The signals acquired from the secondary electrodes are combined into one average signal, which is then subtracted from the signal acquired from the primary electrode to produce a so-called coaxial electrogram. Variations using more than four secondary electrodes are also known. Compared to unipolar electrograms, such a coaxial electrogram can provide similar morphological information while remote components like the effect of gradual voltage gradients of repolarization can be reduced.

[0007] As a further known type of cardiac electrograms, bipolar electrograms are sensitive to the direction of the activation front relative to the electrode arrangement, and do not allow precise localization. In so-called omnipolar electrograms, two orthogonally arranged bipolar electrograms are combined to reduce the directional sensitivity with respect to amplitude, however without reducing the directional sensitivity with respect to morphology, and without providing more precise localization. In view thereof, coaxial electrograms are preferred when localized signal morphology is important, such as for cardiac activation and voltage mapping. Spatially distributed sets of simultaneous coaxial electrograms are known to be recorded using an electrode assembly in which electrodes are arranged at the vertices of a square grid, see for example Coronel et al., J Cardiovasc Electrophysiol 2000, 11:1119-1128 (https: / / doi.org / 10.llll / j.1540-8167.2000. tb01758.x). In such an approach, the required total number of electrodes depends on the outer shape of the grid and on the required number of coaxial electrogram locations within the grid. It has been found that, compared to other known types of electrograms, this can make the acquisition of sets of coaxial electrograms, e.g. for activation and voltage mapping, relatively inefficient in terms of the resulting number of different electrograms in relation to the number of electrodes of the electrode assembly. This applies in particular for relatively small grids and / or grids with a relatively noncircular outer shape.

[0008] SUMMARY

[0009] An object is to enable more efficient acquisition of cardiac electrograms for cardiac activation and voltage mapping, in particular while maintaining or improving advantages of known coaxial cardiac electrograms. An object is to enable acquisition of a higher number of spatially distributed coaxial cardiac electrograms using a same number of electrodes, or a same number of spatially distributed coaxial cardiac electrograms using a smaller number of electrodes. An object is to at least provide an alternative system for cardiac electrography, in particular for cardiac activation and voltage mapping.

[0010] Thereto, an aspect provides system for cardiac electrography, comprising an electrode arrangement, a signal acquisition unit and a signal processing unit. The electrode arrangement is configured for cardiac electrography and comprises at least one set of a primary electrode and three secondary electrodes. The three secondary electrodes are arranged to define respective three vertices of an imaginary triangle in which the primary electrode is arranged centrally. The signal acquisition unit is electrically connectable or connected to the electrode arrangement and configured, when connected, to acquire electrographic signals from the primary electrode and the secondary electrodes. The signal processing unit is configured to process the acquired electrographic signals to determine, for one or more sets of the at least one set, a difference signal between on the one hand an electrographic signal from the primary electrode and on the other hand an average electrographic signal from the three secondary electrodes.

[0011] Advantageously, it has been found that in this way, compared to known forms of coaxial electrography, highly similar electrograms can be obtained using a smaller number of electrodes. Thus, cardiac electrography can be performed more efficiently, in particular in the context of cardiac activation and voltage mapping. The electrographic signals from the respective electrodes may initially be obtained as respective unipolar electrograms, to be subsequently combined, e.g. digitally, into the difference signal.

[0012] A further aspect provides a method of cardiac electrography, comprising: providing an electrode arrangement comprising at least one set of a primary electrode and three secondary electrodes, the three secondary electrodes being arranged to define respective three vertices of an imaginary triangle in which the primary electrode is arranged centrally; acquiring electrographic signals from the at least one set of electrodes; and processing the acquired electrographic signals to determine, for one or more sets of the at least one set of electrodes, a difference signal between on the one hand an electrographic signal from the primary electrode and on the other hand an average electrographic signal from the three secondary electrodes.

[0013] Such a method can provide advantages corresponding to those described above with respect to the system. A further aspect provides an electrode assembly for cardiac electrography, comprising an electrode arrangement and a support structure for the electrode arrangement. The electrode arrangement is configured for cardiac electrography and comprises at least six sets of a primary electrode and three secondary electrodes. The three secondary electrodes are arranged to define respective three vertices of an imaginary equilateral triangle in which the primary electrode is arranged centrally. The support structure is configured to mutually fix the electrodes in the electrode arrangement. Within the electrode arrangement of the electrode assembly, one or more groups of six of the primary electrodes are arranged to each define respective six vertices of respective one or more imaginary regular hexagons. For at least one, preferably each, of the one or more imaginary hexagons, the electrode arrangement is free from electrodes between the electrodes arranged at the vertices of the hexagon.

[0014] Such an electrode assembly can advantageously be used as part of a system as described herein, wherein in particular the support structure can facilitate handling and placement of the electrode arrangement, for example against an endocardial surface.

[0015] In the electrode assembly, and preferably in the system, the equilateral triangular arrangement of the secondary electrodes allows resulting coaxial electrograms to be particularly insensitive to orientation of the electrode arrangement, in particular when a respective distance between the respective secondary electrode and the primary electrode is the same for each of the three secondary electrodes. In known electrode assemblies in which electrodes are arranged at the vertices of a square grid, secondary electrodes cannot be arranged at vertices of an imaginary equilateral triangle while being sufficiently close to each other and to their primary electrode for meaningful activation and voltage mapping.

[0016] In the electrode assembly, and preferably in the system, the regular hexagonal arrangement of the primary electrodes allows coverage of a relatively large area using a relatively small interelectrode distance and a relatively small number of electrodes. US11771373B2 discloses an electrode assembly for bipolar electrography having an electrode arrangement in which electrode-free areas between adjacent electrodes are triangular as opposed to hexagonal, resulting in a relatively dense electrode arrangement. Although less preferred, such a dense electrode arrangement and assembly may nevertheless be used in a system and method as described herein. US11771373B2 does not disclose the advantageous signal processing of the present disclosure.

[0017] Optional advantageous elaborations of the above aspects are indicated and explained in the below detailed description.

[0018] DETAILED DESCRIPTION

[0019] In the following, the invention will be explained further using examples of embodiments and drawing. The drawings are schematic and merely show examples. Explanation of embodiments herein can also be understood without reference to the drawings. In the drawings, corresponding elements are provided with corresponding reference signs. In the drawings:

[0020] Fig. 1 shows a diagram of a system for cardiac electrography;

[0021] Fig. 2 shows a plan view of an electrode arrangement;

[0022] Fig. 3 shows a plan view of a more extensive electrode arrangement;

[0023] Fig. 4 shows a plan view of an even more extensive electrode arrangement;

[0024] Fig. 5 shows a plan view of an electrode assembly;

[0025] Fig. 6 shows a plan view of a further electrode assembly;

[0026] Fig. 7 shows a flow chart illustrating a method of cardiac electrography; Fig. 8 shows a plan view of a portion of an experimental electrode arrangement; and

[0027] Fig. 9 shows an experimental cardiac electrographic result obtained using the experimental electrode arrangement of Fig. 8.

[0028] Fig. 1 schematically shows an example of a system 1 for cardiac electrography. The system 1 comprises an electrode arrangement 2 configured for cardiac electrography, a signal acquisition unit 4 and a signal processing unit 5.

[0029] With reference to Fig. 2 as an elementary example, the electrode arrangement 2 comprises at least one set 3 of a primary electrode 3-1 and three secondary electrodes 3-2, the three secondary electrodes 3-2 being arranged to define respective three vertices of an imaginary triangle T in which the primary electrode 3-1 is arranged centrally. Figs. 3 - 6 show more extensive examples of the electrode arrangement 2, in particular with multiple sets 3 of electrodes, as explained further elsewhere herein.

[0030] In embodiments, including in the shown examples, the system 1 comprises a support structure 6 for the electrode arrangement 2, wherein the support structure 6 is configured to mutually fix the electrodes 3-1, 3-2 in the electrode arrangement 2. The electrode arrangement 2 and the support structure 6 may together form, or at least be comprised by, an electrode assembly 8 that may be comprised by the system 1.

[0031] The signal acquisition unit 4 is electrically connectable or connected to the electrode arrangement 2 and configured, when connected, to acquire electrographic signals from the at least one set 3 of electrodes 3-1, 3-2. In embodiments, including in the shown examples, the system 1 further comprises a reference electrode 7 operatively connectable or connected to the signal acquisition unit 4, wherein the signal acquisition unit 4 is configured, when connected, to acquire the electrographic signals 4 from the primary and secondary electrodes 3-1, 3-2 using the reference electrode 7. The reference electrode 7 is preferably arranged for its potential to be substantially indifferent to the cardiac cycle. Various possible arrangements for such a reference electrode 7 known as such in cardiac electrography may be used, including compound arrangements in which a combination of spatially distributed electrodes is used to represent a virtual reference electrode 7, for example a so-called Wilson’s central terminal. In embodiments, including in the shown examples, the electrographic signals are acquired as respective unipolar electrograms from each of the primary and secondary electrodes 3-1, 3-2 using the reference electrode as a remote common reference. This allows subsequent processing to determine one or more coaxial electrograms, as explained further elsewhere herein, in particular while allowing to retain the original unipolar signals as well, e.g. for reference or additional analysis.

[0032] The signal processing unit 5 is configured to process the acquired electrographic signals to determine, for one or more sets 3 of the at least one set 3 of electrodes 3-1, 3-2, a difference signal between on the one hand an electrographic signal from the primary electrode 3-1 and on the other hand an average electrographic signal from the three secondary electrodes 3-2. The resulting difference signal may be regarded as a type of coaxial electrogram associated with the location of the respective primary electrode 3-1. In case of a more extensive electrode arrangement 2 (see e.g. Figs. 3 - 6), multiple such coaxial electrograms can be obtained simultaneously for different locations, as explained further elsewhere herein.

[0033] Although not necessarily required or advantageous, in some embodiments, one, some or all of the unipolar electrograms or other initially acquired electrographic signals may be normalized and / or filtered, before subsequently being combined to determine the average electrographic signal and / or the difference signal. Thus, the processing of the acquired electrographic signals may comprise normalizing and / or filtering of the acquired electrographic signals, wherein the average electrographic signal and / or the difference signal may be determined from the normalized and / or filtered signals, or such normalized and / or filtered signals may otherwise be used for determining the difference signal. The normalizing may in particular be a normalizing of an amplitude or gain of the respective signal. The filtering may for example be a high-pass filtering.

[0034] In embodiments, including in the shown examples, the signal acquisition unit 4 is configured to acquire the electrographic signals in digital form, in particular using an analog-to-digital converter. In embodiments, including in the shown examples, the signal processing unit 5 is configured to process the acquired electrographic signals in digital form.

[0035] Fig. 7 illustrates an associated method of cardiac electrography, comprising: providing (Si) an electrode arrangement 2 comprising at least one set 3 of a primary electrode 3-1 and three secondary electrodes 3-2, the three secondary electrodes 3-2 being arranged to define respective three vertices of an imaginary triangle T in which the primary electrode 3-1 is arranged centrally; acquiring (S2) electrographic signals from the at least one set 3 of electrodes; and processing (S3) the acquired electrographic signals to determine, for one or more sets 3 of the at least one set 3 of electrodes, a difference signal between on the one hand an electrographic signal from the primary electrode 3-1 and on the other hand an average electrographic signal from the three secondary electrodes 3-2.

[0036] It shall be appreciated that, using digital processing, the difference signal may be determined directly from the signals from the individual electrodes, in particular without necessarily first explicitly determining the average signal from the secondary electrodes. It shall also be appreciated that, by definition, an average electrographic signal from the three secondary electrodes of a set having only three secondary electrodes does not contain any contribution from any further secondary electrode. An average electrographic signal may generally be determined from multiple electrodes by multiplying respective signals from the electrodes by respective weights, e.g. equal weights, and summing the thus weighted signals. The total of the weights is preferably one, although as an alternative the signal from the primary electrode may be multiplied by the total of the weights for the secondary electrodes before the difference signal is determined, e.g. in case the absolute amplitudes of the difference signal are not of interest. In general, signal amplitude values may be mapped back and forth to different scales, e.g. to facilitate digital processing and / or storage.

[0037] It shall be appreciated that the system 1 as described herein may thus be used for cardiac electrography, for example in the method as described herein. In particular: the electrode arrangement 2 of the system 1 may be used as the electrode arrangement 2 in the method; the acquiring of the electrographic signals may be performed using the signal acquisition unit 4; and / or the processing of the acquired electrographic signals may be performed using the signal processing unit 5. Similarly, the system 1 may be configured to perform one or more parts of the method. Options and advantages described herein with reference to the system may thus correspondingly be applied to the method, and vice versa.

[0038] The cardiac electrography as mentioned herein is preferably endocardial electrography. In embodiments, including in the shown examples, the support structure 6 is configured for the electrode arrangement 2 to be held against an endocardial surface of a subject for electrical contact of the electrodes 3-1, 3-2 with the endocardial surface. The endocardial electrography may comprise cardiac activation mapping and / or cardiac voltage mapping.

[0039] Other possible types of cardiac electrography include epicardial electrography, esophageal cardiac electrography and non-invasive cardiac electrography. Although non-invasive cardiac electrography is not excluded, it is considered that the invention can be particularly beneficial in the context of invasive cardiac electrography, in particular in scenarios where activation and voltage mapping are applied today. It shall be appreciated that the support structure may be configured in accordance with the intended type of cardiac electrography.

[0040] In embodiments, including in the shown examples, the imaginary triangle T is an equilateral triangle. In embodiments, including in the shown examples, a respective interelectrode distance d between the respective secondary electrode 3-2 and the primary electrode 3-1 is the same for each of the three secondary electrodes 3-2. In embodiments, including in the shown examples, respective electrographic signals from each of the three secondary electrodes 3-2 have a same weight in the average electrographic signal. In this way, the secondary electrodes 3-2 can be relatively evenly distributed around the primary electrode 3-1, and the resulting difference signal as coaxial electrogram can be particularly insensitive to the direction of the activation front relative to the electrode arrangement while also allowing relatively precise localization, in particular in an efficiently and well-scalable manner. As a possible alternative, different weights may be used for respective signals from different secondary electrodes 3-2, for example to compensate for estimated or determined differences in electrode impedance and / or to compensate for slight deviations in actual relative positions of the electrodes compared to designed ideal relative positions. A calibration procedure may be performed to adjust weights to actual conditions. Weights may be varied over time, e.g. using a dynamic calibration procedure.

[0041] To illustrate the efficiency gain provided by the electrode arrangement of the present disclosure, it is observed that using the electrode arrangement of Fig. 3, as many as six coaxial electrograms can be obtained simultaneously using only twelve electrodes. By contrast, in known coaxial electrography using four secondary electrodes, at most four coaxial electrograms can be obtained simultaneously using twelve electrodes. Similar theoretical evaluations can be made to show efficiency gains for larger numbers of electrodes. Meanwhile, the different types of coaxial electrograms can be similarly insensitive to the direction of the activation front relative to the electrode arrangement, and allow similarly precise localization. Thus, the efficiency gain does not affect usability of the acquired coaxial electrograms, e.g. for cardiac activation and voltage mapping.

[0042] In embodiments, including in the shown examples, an interelectrode distance d among the electrodes of the electrode arrangement 2 is in the range of 0.1 to 12 mm, preferably in the range of 0.2 to 6 mm, more preferably in the range of 0.6 to 2.4 mm, for example about 1.2 mm. In embodiments, including in the shown examples, the interelectrode distance d, i.e. the distance between mutually associated primary and secondary electrodes 3-1, 3-2, is uniform across the electrode arrangement 2. In this way, a relatively favorable balance can be provided between on the one hand localized examination and on the other hand meaningful electrogram characteristics. Moreover, a relatively favorable balance can be provided between one the one hand localized examination across a relatively large area and on the other hand a relatively small number of electrodes, as explained further elsewhere herein.

[0043] In embodiments, including in the examples of Figs. 3 - 6, the number of sets 3 of the at least one set 3 of electrodes is at least two, more preferably at least three, more preferably at least four, more preferably at least five, more preferably at least six. In this way, coaxial electrograms can be obtained for multiple locations simultaneously.

[0044] In embodiments, including in the examples of Figs. 3 - 6, two or more, preferably each, of the sets 3 shares at least one electrode 3-1, 3-2 with another one of the sets 3. In embodiments, including in the examples of Figs. 3 - 6, at least one electrode 3-1, 3-2 of the electrode arrangement 2 is arranged to serve both as the primary electrode 3-1 in one of the sets 3 and as one of the secondary electrodes 3-2 in at least one other of the sets 3. In this way, the electrode arrangement 2 can be particularly efficient in terms of the number of coaxial electrograms that can be obtained relative to the total number of electrodes in the electrode arrangement 2. In embodiments, including in the examples of Figs. 3 - 6, at least one further electrode 3-2 of the electrode arrangement 2 is arranged to serve only as one of the secondary electrodes 3-2 and not as any of the primary electrodes 3-1.

[0045] As an illustrative example, Fig. 3 shows how here six electrodes that are shown as filled circles can serve both as the primary electrode 3-1 in one set 3 and as one of the secondary electrodes 3-2 in two other sets 3, whereas six further electrodes that are shown as unfilled circles can serve only as one of the secondary electrodes 3-2 and not as any of the primary electrodes 3-1. Essentially the same applies for the examples of Figs. 4 - 6, except that there several of the electrodes shown as filled circles can serve as one the secondary electrodes 3-2 in three rather than two other sets 3.

[0046] For clarity of the figures, references signs 3-1 and 3-2 have been omitted in Figs. 5 and 6, and are only shown for some electrodes in Figs. 3 and 4. Also for clarity, each of the sets 3 is provided with a reference sign in Fig. 3, while only one of the sets 3 in Fig. 4 and none of the sets in Figs. 5 and 6 is provided with a reference sign. The triangles T are not explicitly indicated in Fig. 5 and 6, and only one triangle T is indicated in each of Figs. 3 and 4. In Figs. 2 - 6 and 8, dashed lines between the electrodes merely serve to more clearly show their spatial arrangement relative to each other. The same interelectrode distance d as indicated in Fig. 2 applies along each of the dashed lines between the electrodes in the examples of Figs. 3 - 6. It shall thus be appreciated how the electrode arrangements 2 of Figs. 3 - 6 are essentially configured as progressively extended variations of the electrode arrangement 2 of Fig. 2, and that a wide variety of electrode arrangements can thus be provided by such extensions.

[0047] In embodiments, including in the examples of Figs. 3 - 6, the number of sets 3 is at least six, wherein, within the electrode arrangement 2, one or more groups of six of the primary electrodes 3-1 are arranged to define respective six vertices of respective one or more imaginary hexagons H, preferably regular hexagons. Primary electrodes may be shared among such groups. For example, a same primary electrode may be part of three of such groups. In embodiments, including in the examples of Figs. 4 - 6, the number of groups of the one or more groups and imaginary hexagons H is at least three, wherein the imaginary hexagons H are mutually joined along sides thereof to define an imaginary honeycomb pattern P, i.e. an imaginary regular hexagonal grid. In this way, the elementary triangular arrangement of secondary electrodes 3-2 with a primary electrode 3-1 centrally therewithin (see e.g. Fig. 2) can be extended across a flat or curved plane to essentially any shape and size, in particular in a regular manner using a uniform interelectrode distance d. Meanwhile, many of the electrodes (shown as filled circles in Figs. 3 - 6) can serve both as a primary electrode 3-1 in one set 3 and as a respective secondary electrode 3-2 in one, two or three other sets 3, as explained elsewhere herein, so that the total number of electrodes can be relatively low compared to the number of simultaneous coaxial electrogram locations. Efficient and effective cardiac voltage and activation mapping can be facilitated thereby.

[0048] In embodiments, including in the examples of Figs. 3 - 6, within at least one, preferably each, of the imaginary hexagons H, the electrode arrangement 2 is free from electrodes. In this way, the electrode arrangement 2 can advantageously cover a relatively large area using a relatively small uniform interelectrode distance and a relatively small number of electrodes. Although adding an electrode at the center of each imaginary hexagon H would enable additional coaxial electrograms to be obtained, it is considered that this would in most cases provide only little additional diagnostic information in proportion to the additional cost and complexity. Nevertheless, such optional additional electrodes are not excluded in the context of the system and method as described herein. An example of an electrode assembly comprising such additional electrodes, resulting in a relatively dense electrode arrangement with triangular electrode-free areas between adjacent electrodes, is known from US11771373B2. In an electrode arrangement of the present disclosure, such electrode-free areas are preferably hexagonal, as explained above.

[0049] In embodiments, including in the examples of Figs. 5 and 6, the support structure 8 comprises a series of elongate support members 9 arranged side-to-side in a rigid mutual arrangement, wherein the support members 9 preferably extend from a common base (not shown). In embodiments, including in the examples of Figs. 5 and 6, at least some of the support members 9 are straight. In embodiments, including in the example of Fig. 6, at least some of the support members 9 extend along a meandering or zig-zag path, in particular to substantially coincide with zigzag paths within the honeycomb pattern P. To promote rigidity of the support structure 6, adjacent ones of the support members 9 may be laterally interconnected at distributed positions along their length, for example at some or all of the dashed lines between the electrodes in Figs. 5 and 6. Thus, in some variations, the support structure may form a hexagonal grid coinciding with the imaginary honeycomb pattern P of the electrode assembly 2. This may be particularly advantageous in case the electrode arrangement extends across a curved plane, for example a concave plane. Configuring the electrode arrangement to extend across a curved plane, in particular a double curved plane, may facilitate electrical contact with a curved surface such as a curved endocardial surface.

[0050] Although the invention has been explained herein using examples of embodiments and drawings, these do not limit the scope of the invention as defined by the claims. Within said scope, many variations, combinations and extensions are possible. Examples thereof have been provided herein. EXPERIMENTAL EXAMPLE

[0051] With reference to Figs. 8 and 9, an experimental example will now be presented showing a comparison between a known type of coaxial electrogram and an alternative type of coaxial electrogram obtained in accordance with the present invention.

[0052] An experimental electrode assembly, having an electrode arrangement including a portion as schematically shown in Fig. 8, was designed and built to enable simultaneous recording of two types of coaxial electrograms using a same primary electrode A at a same location. The support structure of the experimental electrode assembly was 3D printed, after which holes for electrodes were drilled therein in accordance with the arrangement of Fig. 8. Silver wires of 0.125 mm diameter, insulated with polyimide, were extended through cylinders placed in the drilled holes and were jacketed together in a cable and soldered onto a connector for connection to a signal acquisition unit. The silver wires at the support structure surface were then cut and polished, leaving the cross section of the silver wires exposed for recording. The uniform interelectrode distance d, as indicated in Fig. 8, was 1.2 mm. Electrodes B, D and F were arranged at vertices of an imaginary equilateral triangle. Electrodes B, C, E and G were arranged at vertices of an imaginary square. Electrode A was arranged at the center of the triangle and the square, at same distances d from each of the electrodes B-G.

[0053] After required regulatory approval was obtained, a pig was anesthetized and euthanized, and heparin 25.000 IU was administered intravenously. After about 600 mL was drained from the femoral artery, ventricular fibrillation was induced by touching the right ventricular myocardium with the terminals of a 9V battery. The heart was then rapidly excised and submerged in ice-cold Tyrode’s solution. The aorta was then cannulated and connected to a Langendorff setup. The heart was then perfused with approximately 1.4 L of a recirculating blood-Tyrode’s mixture that was gassed with 95% O2 / 5% CO2 and kept at a constant temperature by running the perfusate through a coil shaped glass heat exchanger.

[0054] A reference electrode was then connected to the aortic root. The reference electrode and the experimental electrode assembly were connected to an ActiveTwo acquisition set-up (BioSemi, Amsterdam, The Netherlands). Recordings were made at a sampling rate of 16 kHz.

[0055] After an equilibration period, the heart was defibrillated using a single direct current shock. Recordings were made from the left ventricular anterolateral and right ventricular outflow tract epicardium during spontaneous rhythm.

[0056] Unipolar electrograms from each of the electrodes A to G (see Fig. 8) were recorded. No filtering was applied. A portion of the unipolar electrogram VA from electrode A is shown at the bottom in Fig. 9. These unipolar electrograms VA to VG served as the basis for two types of coaxial electrograms that were calculated using Matlab R2021a (Mathworks Inc., Natick, MA), namely a known type of coaxial electrogram I using electrode A as the primary electrode and four electrodes B, C, E and G as secondary electrodes, and an alternative type coaxial electrogram II using the same electrode A as the primary electrode but only three electrodes B, D and F as secondary electrodes. For both types of coaxial electrograms I and II, the unipolar electrograms Vx from the relevant secondary electrodes were combined into an average signal using equal weights, whereafter the resulting average signal was subtracted from the unipolar electrogram VA from primary electrode A. So, electrogram I was determined from unipolar electrograms according to the expression VA - ((VB+VC+VE+VG) / 4), and electrogram II was determined from unipolar electrograms according to the expression VA - ((VB+VD+VF) / 3).

[0057] Fig. 9 shows corresponding portions of the resulting coaxial electrograms I and II synchronously above a portion of the associated unipolar electrogram VA. It was observed that both coaxial electrograms I and II retained the morphological features of a positive deflection followed by a negative deflection of the unipolar electrogram VA, and that the coaxial electrograms I and II showed a high degree of mutual similarity in shapes, amplitudes and timing.

[0058] Additionally, the obtained coaxial electrogram II was compared to three associated bipolar electrograms (not shown), determined according to the expressions VA - VB, VA - VD and VA - VF. Moments of activation were determined from the bipolar electrograms (namely as the time stamp at the largest amplitude), from the coaxial electrogram (namely as the time stamp at the largest negative slope) and from the unipolar electrogram (namely as the time stamp at the largest negative slope). The moment of activation from the unipolar electrogram was taken as a standard for the comparison. It was observed that overall, the moment of activation from the coaxial electrogram tended to be closer to that standard than the moments of activation from the bipolar electrograms.

[0059] Further recordings were made at the same location after an approximately 90 degree rotation of the experimental electrode assembly about a rotation axis extending normal to the plane of the electrode assembly, with the same signal processing as described above being performed thereon. It was observed that the resulting altered orientation of the experimental electrode arrangement relative to the activation front had relatively little effect on both coaxial electrograms I and II, and that both essentially maintained the same signal morphology and amplitude.

[0060] LIST OF REFERENCE SIGNS

[0061] 1. System

[0062] 2. Electrode arrangement

[0063] 3. Set of electrodes

[0064] 3-1. Primary electrode

[0065] 3-2. Secondary electrode

[0066] 4. Signal acquisition unit

[0067] 5. Signal processing unit

[0068] 6. Support structure

[0069] 7. Reference electrode

[0070] 8. Electrode assembly

[0071] 9. Support member d. Interelectrode distance

[0072] A-G. Electrodes of experimental electrode arrangement

[0073] H. Imaginary hexagon

[0074] P. Imaginary honeycomb pattern

[0075] S1-S3. Method steps

[0076] T. Imaginary triangle

Claims

Claims1. System (1) for cardiac electrography, comprising: an electrode arrangement (2) configured for cardiac electrography, comprising at least one set (3) of a primary electrode (3-1) and three secondary electrodes (3-2), the three secondary electrodes (3-2) being arranged to define respective three vertices of an imaginary triangle (T) in which the primary electrode (3-1) is arranged centrally; a signal acquisition unit (4) electrically connectable or connected to the electrode arrangement (2) and configured, when connected, to acquire electrographic signals from the at least one set (3) of electrodes (3-1, 3-2); and a signal processing unit (5) configured to process the acquired electrographic signals, to determine, for one or more sets (3) of the at least one set (3) of electrodes (3-1, 3-2), a difference signal between on the one hand an electrographic signal from the primary electrode (3-1) and on the other hand an average electrographic signal from the three secondary electrodes (3-2).

2. System according to claim 1, wherein the imaginary triangle (T) is an equilateral triangle.

3. System according to claim 1 or 2, wherein a respective interelectrode distance (d) between the respective secondary electrode (3-2) and the primary electrode (3-1) is the same for each of the three secondary electrodes (3-2).

4. System according to claims 2 and 3, wherein respective electrographic signals from each of the three secondary electrodes (3-2) have a same weight in the average electrographic signal.

5. System according to any of the preceding claims, wherein the number of sets (3) of the at least one set (3) is at least two, more preferably at least three, more preferably at least four, more preferably at least five, more preferably at least six.

6. System according to claim 5, wherein two or more, preferably each, of the sets (3) shares at least one electrode (3-1, 3-2) with another one of the sets (3).

7. System according to claim 5 or 6, wherein at least one electrode (3-1, 3-2) of the electrode arrangement (2) is arranged to serve both as the primary electrode (3-1) in one of the sets (3) and as one of the secondary electrodes (3-2) in at least one other of the sets (3).

8. System according to claim 7, wherein at least one further electrode (3-2) of the electrode arrangement (2) is arranged to serve only as one of the secondary electrodes (3-2) and not as any of the primary electrodes (3-1).

9. System according to any of claims 5 - 8, wherein the number of sets (3) is at least six, wherein, within the electrode arrangement (2), one or more groups of six of the primary electrodes (3-1) are arranged to define respective six vertices of respective one or more imaginary hexagons (H), preferably regular hexagons.

10. System according to claim 9, wherein the number of groups of the one or more groups and imaginary hexagons (H) is at least three, wherein the imaginary hexagons (H) are mutually joined along sides thereof to define an imaginary honeycomb pattern (P).

11. System according to claim 9 or 10, wherein, for at least one, preferably each, of the one or more imaginary hexagons (H), the electrode arrangement (2) is free from electrodes between the electrodes (3-1) arranged at the vertices of the hexagon (H).

12. System according to any of the preceding claims, wherein an interelectrode distance (d) among the electrodes of the electrode arrangement (2) is in the range of 0.1 to 12 mm, preferably in the range of 0.2 to 6 mm, more preferably in the range of 0.6 to 2.4 mm, for example about 1.2 mm.

13. System according to any of the preceding claims, comprising a support structure (6) for the electrode arrangement (2), wherein the support structure (6) is configured to mutually fix the electrodes (3-1, 3-2) in the electrode arrangement (2).

14. System according to any of the preceding claims, wherein the support structure (6) is configured for the electrode arrangement (2) to be held against an endocardial surface of a subject for electrical contact of the electrodes (3-1, 3-2) with the endocardial surface.

15. System according to any of the preceding claims, comprising a reference electrode (7) operatively connectable or connected to the signal acquisition unit (4), wherein the signal acquisition unit (4) is configured, when connected, to acquire the electrographic signals (4) from the primary and secondary electrodes (3-1, 3-2) using the reference electrode (7).

16. System according to any of the preceding claims, wherein the signal processing unit (5) is configured to process the acquired electrographic signals in digital form.

17. Electrode assembly (8) for cardiac electrography, comprising: an electrode arrangement (2) configured for cardiac electrography, comprising at least six sets (3) of a primary electrode (3-1) and three secondary electrodes (3-2), the three secondary electrodes (3-2) being arranged to define respective three vertices of an imaginary equilateral triangle (T) in which the primary electrode (3-1) is arranged centrally; and a support structure (6) for the electrode arrangement (2), wherein the support structure (6) is configured to mutually fix the electrodes (3-1, 3- 2) in the electrode arrangement (2), wherein, within the electrode arrangement (2), one or more groups of six of the primary electrodes (3-1) are arranged to each define respective six vertices of respective one or more imaginary regular hexagons (H), characterized in that, within at least one, preferably each, of the one or more imaginary hexagons (H), the electrode arrangement (2) is free from electrodes.

18. Electrode assembly (8) according to claim 17, wherein the electrode arrangement (2) and / or the support structure (6) is as further specified in any of claims 1 - 16.

19. Use of a system (1) according to any of claims 1 - 16, and / or an electrode assembly (8) according to claim 17 or 18, for cardiac electrography.

20. Method of cardiac electrography, comprising: providing (S 1) an electrode arrangement (2) comprising at least one set (3) of a primary electrode (3-1) and three secondary electrodes (3-2), the three secondary electrodes (3-2) being arranged to define respective three vertices of an imaginary triangle (T) in which the primary electrode (3-1) is arranged centrally;acquiring (S2) electrographic signals from the at least one set (3) of electrodes; and processing (S3) the acquired electrographic signals to determine, for one or more sets (3) of the at least one set (3) of electrodes, a difference signal between on the one hand an electrographic signal from the primary electrode (3-1) and on the other hand an average electrographic signal from the three secondary electrodes (3-2).

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