Expansion of the electrocardiogram (ECG) acquisition ability of a catheter-based cardiac system

Abstract

To remove the influence of a presystolic period and improve the measurement accuracy of pulse wave propagation times.SOLUTION: A method includes receiving an analog body-surface signal from a body-surface electrode, and multiple analog unipolar signals from multiple unipolar electrodes of an invasive probe. A first unipolar electrode is assigned to serve as a common electrical ground and a common timing reference for the analog unipolar signals and the analog body-surface signal. The analog unipolar signals are digitized to produce digital unipolar signals sampled relative to a digital ground. Defined are an analog bipolar signal between the first unipolar electrode and a second unipolar electrode of the probe, and a digital bipolar signal formed from the first unipolar electrode and the second unipolar electrode. Ground and timing offsets between the analog bipolar signal and the digital bipolar signal are estimated while the first unipolar electrode is connected to the digital ground. The ground offset and the timing offset are applied in measuring a third unipolar signal, sensed by a third unipolar electrode.SELECTED DRAWING: Figure 1

Description

[Technology Field]

[0001] (Cross-reference of related applications) This application claims the benefit of U.S. Provisional Patent Application No. 62 / 863,679, filed June 19, 2019, the disclosure of which is incorporated herein by reference.

[0002] (Field of invention) The present invention generally relates to the acquisition and processing of electrophysiological signals, and more specifically to the processing of electrocardiogram (ECG) signals acquired using a catheter. [Background technology]

[0003] Electrocardiography (ECG) is a well-established cardiac diagnostic technique. Various techniques for measuring ECG signals have been proposed in the patent literature. For example, U.S. Patent No. 9,398,862 describes a method, in some embodiments, that includes measuring a unipolar signal at one or more electrodes in response to electrical activity within the cardiac chambers. In some embodiments, the signal is measured over several heartbeats at either a single catheter location or several locations within the cardiac chambers. The method also includes determining bipolar physiological information at multiple locations on the surface and at the locations of one or more electrodes on the surface based at least in part on the Laplace equation.

[0004] As another example, Chinese Patent Application Publication No. 2018 / 11333583 describes a method and apparatus for measuring ECG pulse wave propagation time. The synchronized acquisition method measures the pulse wave signal, extracts the pulse wave signal and ECG feature points, and calculates the pulse transition time. This method obtains the pulse wave propagation time by subtracting the pre-systolic period from the calculated pulse transition time, according to the pre-systolic ECG calculation. [Overview of the project] [Problems that the invention aims to solve]

[0005] This invention eliminates the influence of presystole and improves the accuracy of pulse wave propagation time measurement. [Means for solving the problem]

[0006] The method includes (i) receiving analog surface signals from one or more surface electrodes attached externally to the patient's body, and (ii) receiving multiple analog monopolar signals from multiple monopolar electrodes of a probe inserted into the patient's organs. A first monopolar electrode is assigned from among the multiple monopolar electrodes to function as a common electrical ground and a common timing reference for the analog monopolar signals and the analog surface signals. The analog monopolar signals are digitized and each digital monopolar signal is generated by sampling the analog monopolar signals against a digital ground. Below, (i) an analog bipolar signal between the first and second monopolar electrodes of the probe, and (ii) a digital bipolar signal formed from the respective digital monopolar signals derived from the first and second monopolar electrodes are defined. While the first monopolar electrode is connected to the digital ground, a ground offset and timing offset between the analog bipolar signal and the digital bipolar signal are estimated.

[0007] Grounding offset and timing offset are applied when measuring the third unipolar signal sensed by the third unipolar electrode of the catheter in relation to the body surface signal.

[0008] In some embodiments, the analog unipolar signal and the digital unipolar signal include an electrocardiogram.

[0009] In some embodiments, the analog body surface signal includes a Wilson central terminal (WCT) signal.

[0010] In another embodiment of the present invention, an apparatus including a circuit and a processor is further provided. The circuit is configured to (a) receive analog surface signals from one or more surface electrodes attached outside the patient's body; (b) receive multiple analog monopolar signals from multiple monopolar electrodes of a probe inserted into the patient's organs; (c) assign a first monopolar electrode from among the multiple monopolar electrodes to function as a common electrical ground and a common timing reference for the analog monopolar signals and analog surface signals; (d) generate each digital monopolar signal by digitizing the analog monopolar signals and sampling the analog monopolar signals against a digital ground; and (e) define (i) an analog bipolar signal between the first monopolar electrode and the second monopolar electrode of the probe, and (ii) a digital bipolar signal formed from each digital monopolar signal derived from the first and second monopolar electrodes. The processor is configured to estimate the grounding offset and timing offset between the analog bipolar signal and the digital bipolar signal while the first unipolar electrode is connected to the digital ground, and to apply the grounding offset and timing offset to the body surface signal when measuring the third unipolar signal sensed by the third unipolar electrode of the probe.

[0011] This invention will be more fully understood by considering the following "Modes for Carrying Out the Invention" in conjunction with the drawings. [Brief explanation of the drawing]

[0012] [Figure 1] This is a schematic diagram of a catheter-based electrophysiological sensing system according to one embodiment of the present invention. [Figure 2A] Figure 1 shows a diagram and electrical circuit diagram of a device that enables the measurement of a unipolar signal from a catheter, according to one embodiment of the present invention. [Figure 2B] Figure 1 shows a diagram and electrical circuit diagram of a device that enables the measurement of a unipolar signal from a catheter, according to one embodiment of the present invention. [Figure 2C] Figure 1 shows a diagram and electrical circuit diagram of a device that enables the measurement of a unipolar signal from a catheter, according to one embodiment of the present invention. [Figure 3] This flowchart schematically illustrates a method for measuring multiple unipolar signals from a catheter using the system shown in Figure 1, according to one embodiment of the present invention. [Modes for carrying out the invention]

[0013] Overview Legacy catheter-based cardiac systems may be configured to measure a limited number of signals, such as up to a few dozen electrocardiogram (ECG) channels. However, modern diagnostic catheters can have many more electrodes, such as 256 electrodes inside the target organ (e.g., the heart). To accommodate the additional channels of modern diagnostic catheters, signals from such catheters (e.g., a basket catheter with 256 channels) can be transmitted to a legacy catheter-based system via a digital communication link to process all of the channels.

[0014] To obtain analog signals from a catheter transmitted via a digital link, an analog-to-digital converter (ADC) module (referred herein to as an "ADC dongle" or simply a "dongle") is inserted between the diagnostic catheter and a legacy catheter-based system.

[0015] Several clinical applications require acquiring the catheter signal as a unipolar signal against a Wilson-coupled electrode (WCT) ground, which is connected to a legacy system formed from three surface electrodes attached to the patient's skin. The WCT ground is obtained by averaging the voltages of three external active limb electrodes measured with respect to the return ground electrode, as described in "True Unipolar ECG Machine for Wilson Central Terminal Measurements" by Gaetano D. Gargiulo, The MARCS Institute, University of Western Sydney, Kingswood, NSW2747, Australia, May 2015, and "Wilson's Central Terminal, the keystone to electrogram recording—What, where and why?" published April 23, 2013 by John Silberbauer, EP Fellow, San Raffaele Hospital, Milan, which are incorporated by reference in the appendix.

[0016] Two problems arise when a legacy system processor uses digitized signals from any of the 256 ECG channels of an internally positioned catheter to derive and analyze a unipolar signal relative to the WCT ground.

[0017] The first problem is that the electrical grounding of the ADC dongle, where the unipolar signal is digitized, is different from the grounding of the legacy catheter-based system (e.g., WCT grounding). Therefore, the digitized unipolar amplitude input from the catheter will have an incorrect amplitude relative to the legacy catheter-based system.

[0018] The second problem is that the timing of the digitized signal (e.g., signal phase) and the timing of the WCT ground of the legacy catheter-based system are irrelevant. Therefore, the desynchronized signals (digitized catheter signal vs. analog ground signal) cannot be related to other signals (even if there is no problem with the ground amplitude).

[0019] The embodiments of the present invention described below provide an apparatus and method for overcoming the lack of common ground and the lack of signal synchronization between a legacy system and a modern diagnostic catheter connected via a digital link. The disclosed technology enables, for example, accurate measurement of a plurality of unipolar ECG signals using a legacy system.

[0020] In some embodiments, the disclosed apparatus is provided to overcome the lack of common ground and the lack of signal synchronization described above. The apparatus includes an interface circuit of a legacy system configured to receive an analog body surface signal (e.g., a WCT ground signal) from one or more body surface electrodes attached outside the patient's body.

[0021] The disclosed apparatus further includes an additional (e.g., add-on or stand-alone) circuit including an ADC module, the additional circuit receiving a plurality of analog unipolar signals from a plurality of unipolar electrodes of a probe inserted into a patient's organ, assigning a first unipolar electrode from among the plurality of unipolar electrodes to function as a common electrical ground and a common timing reference for the analog unipolar signals and the analog body surface signal, digitizing the analog unipolar signals, and sampling the analog unipolar signals with respect to the digital ground to generate respective digital unipolar signals, and configured to define (i) an analog bipolar signal between a first unipolar electrode and a second unipolar electrode of the probe, and (ii) a digital bipolar signal formed from the respective digital unipolar signals derived from the first unipolar electrode and the second unipolar electrode.

[0022] The disclosed apparatus further comprises a legacy system processor configured to estimate a grounding offset and a timing offset between an analog bipolar signal and a digital bipolar signal while a first unipolar electrode is connected to digital ground, and to apply the grounding offset and timing offset to a body surface signal when measuring a third unipolar signal sensed by a third unipolar electrode of a probe (e.g., a catheter).

[0023] In other words, the disclosed technique sacrifices one of the probe's electrodes and uses this electrode to function as a common ground and common timing reference between the digitized signals and the original analog signal.

[0024] To estimate the timing offset, the legacy system's processor instructs the interface circuit to apply high-pass filtering (i.e., "skew") to both the analog bipolar signal input and the digital bipolar signal. The two bipolar signals are then routed to the legacy system's cross-correlation circuit to cross-correlate them. In one embodiment, the cross-correlated bipolar signals are used by the processor to synchronize the legacy system's clock and the dongle's signals to cancel the timing offset between the analog and digital bipolar signals.

[0025] After the timing offset is applied, the legacy system's processor calculates each monopolar signal acquired by the probe's third electrode in order to apply the grounding offset when measuring the third monopolar signal. The processor calculates V from any third catheter electrode X. x -V WCT The unipolar voltage can be calculated by calculating for the values ​​X=1, 2, ..., 256, i.e., for the digitized signals from any catheter electrode transmitted via the digital link, as described below.

[0026] Typically, a processor is programmed with software that includes specific algorithms that enable it to perform each of the processor-related processes and functions outlined above.

[0027] The disclosed technology provides a simple and effective means that enables legacy systems to accurately measure multiple unipolar signals acquired by multiple electrodes of a modern catheter. Therefore, the disclosed technology can increase the availability of modern catheter-based diagnostic services.

[0028] System Description Figure 1 is a schematic diagram of a catheter-based electrophysiological sensing system 20 according to one embodiment of the present invention. The system 20 may be, for example, the CARTO® 3 system produced by Biosense Webster (Irvine, California). The system 20 comprises a catheter 21 having a shaft 22, which is navigated by a physician 30 into the heart 26 of a patient 28. In the drawn example, the physician 30 inserts the shaft 22 through the sheath 23 while manipulating the shaft 22 using a manipulator 32 near the proximal end of the catheter.

[0029] In the embodiments described herein, the catheter 21 may be used for any preferred diagnostic purpose, such as electrophysiological mapping of the heart 26. The ECG recorder 35 can receive various types of ECG signals sensed by the system 20 during the process.

[0030] As shown in inset 25, a multi-electrode basket catheter 40 is attached to the distal end of the shaft 22 of the catheter 21. Inset 45 shows the arrangement of multiple sensing electrodes 48 (i.e., 256 or more channels) of the basket catheter 40. The proximal end of the catheter 21 is connected to the control console 24 by an ADC dongle 50. The ADC dongle 50 accommodates additional channels from the multiple electrodes 48 by digitizing all catheter channels and transmitting the digitized signals to the digital link 51 of the control console 24.

[0031] The console 24 includes a processor 41, which is typically a general-purpose computer, and includes a suitable front-end and interface circuit 38 for receiving ECG signals, as well as non-ECG signals (such as position signals) from the sensing electrodes 48 of the catheter 21. The electrodes 48 may include 256 or more n sensing electrodes, each electrode of the electrodes 48 would be referred to as “electrode 48 #1, #2, #3...#n” located inside or near the heart. For this purpose, the processor 41 is connected to the sensing electrodes 48 via wires extending into the shaft 22. The interface circuit 38 is further configured to receive ECG signals and non-ECG signals from surface electrodes 49. Typically, the electrodes 49 are attached to the skin around the chest and legs of the patient 28. The processor 41 is connected to the electrodes 49 by wires extending through the cable 39 to receive signals from the electrodes 49.

[0032] Four of the body surface electrodes 49 are named according to the standard ECG protocol: MA (right arm), LA (left arm), ML (right leg), and LL (left leg). A Wilson coupled electrode (WCT) can be formed by three of the four named body surface electrodes 49, and the resulting ECG signal V WCT This is received by the interface circuit 38.

[0033] To overcome the lack of synchronization between signals acquired by the catheter electrode 48 and body surface electrode 49 described above, the system 20 has two of the catheter electrodes that are also connected to the interface circuit 38 via a first split cable 52. In this way, the legacy system directly receives the analog bipolar signal. In addition, the two catheter electrodes described above provide a digital bipolar signal to a digital ground formed by a second split cable 54 that electrically grounds one of the electrodes to the ground of the dongle 50. The wiring 52 and 54 allows the processor 41 of the legacy system 20 to synchronize the two bipolar signals and subsequently accurately derive and present the catheter unipolar ECG signal from the electrode 48 on the legacy system 20, as described below.

[0034] The processor 41 is typically programmed with software to perform the functions described herein. The software may be downloaded to the processor in electronic form, for example, over a network, or it may be provided and / or stored on a non-temporary tangible medium such as magnetic, optical, or electronic memory. In particular, the processor 41 executes a dedicated algorithm, such as the one shown in Figure 3, which enables the processor 41 to perform the disclosed steps, as will be further described below.

[0035] Expanding the ECG acquisition capabilities of catheter-based cardiac systems Figures 2A to 2C are a diagram and electrical circuit diagram of a device 100, according to one embodiment of the present invention, which enables the system of Figure 1 to measure a unipolar signal from the catheter 21.

[0036] As shown in FIG. 2A, interface circuit 38 receives an electrical signal from body surface electrode 49 via cable 39. Electrodes 49 are typically attached to the skin of the patient around the chest and legs of patient 28. Four of electrodes 49: MA (right arm), LA (left arm), ML (right leg), LL (left leg) are shown. The Wilson combination electrode (WCT) is formed by three of the four shown body surface electrodes 49, and the resulting ECG signal, V WCT is received by interface circuit 38, as shown in FIG. 2B.

[0037] As further seen in FIG. 2B, electrodes #1 and #2 of electrode 48 are wired to the input socket of interface circuit 38 by cable 52, and this input socket thus directly receives the analog bipolar signal V 12 . Any other two electrodes 48 of the 256 or more electrodes of catheter 21 may be used, and it should be noted that there is no loss of generality when using electrodes #1 and #2. All 256 or more of electrodes 48 including electrodes #1 and #2 are connected to interface circuit 38 via a dongle 50 plugged into the socket of digital link 51. As seen, electrode #1 is grounded to the ground of ADC dongle 50 inside dongle 50 via cable 54.

[0038] Processor 41 receives a set of input signals (V x -V1), X = 2,..., n (where n is 256 or more) including a set of measured and digitized bipolar signals via ADC dongle 50 through digital link 51 within interface circuit 38. Processor 41 further directly receives the measured ground offset signal (V1 - V WCT ) via interface circuit 38, and can derive a unipolar signal in addition to the bipolar signal (V x -V1) of the synchronized digitized signal of the processor. Processor 41 calculates the remaining 255 unipolar signals V x -V WCT (i.e., V WCTDerive each of the following (for each of the above). formula 1 V x -V WCT =(V x -V1)+(V1-V WCT ), X=2, ..., n

[0039] As shown in Figure 2C, the schematic configuration shown in Figure 2A (for the CARTO® 3 system in Figure 1) can be implemented with a patient-interface unit (PIU) connected to a body surface sensor "BS". The PIU is also connected to a dongle 50 along with a diagnostic catheter 48. In this prototype, both the circuit 38 and the processor 41 are integrated into the PIU.

[0040] Figure 3 is a flowchart illustrating a schematic method for measuring multiple unipolar signals from a catheter using the system of Figure 1, according to one embodiment of the present invention. The algorithm according to this embodiment performs a process that begins in a first wiring step 70 by directly wiring electrode #1 (i.e., the first electrode) of the catheter 21 electrode 48 and electrode #2 (e.g., from among the 256 electrodes of the catheter 21) to the interface circuit 38 of the system 20, before the signals from the two electrodes are digitized. In a second wiring step 72, electrode #1 of electrode 48 is grounded to the ground of the ADC dongle 50.

[0041] In the ground offset extraction step 73, the analog potential of electrode #1 of electrode 48 is measured by the interface circuit 38 and compared with the WCT potential to obtain the ground offset V1-V WCT Derive the following.

[0042] Simultaneously, in the bipolar signal measurement step 76, the interface circuit 38 measures the analog bipolar signal and the digital bipolar signal digitized from the same source as the analog bipolar signal.

[0043] Using the measured analog and digital bipolar signals, the interface circuit 38 synchronizes the clocks of the system 20 and the ADC dongle 50 in the clock synchronization step 76.

[0044] In sampling step 78, the catheter signal from each electrode is digitally sampled for electrode #1 of electrode 48 by the ADC dongle 50.

[0045] Finally, in the unipolar signal calculation step 80, for a third digitized signal from any electrode 48 different from electrodes #1 and #2 of electrode 48, the processor 41 uses equation 1 to calculate the respective unipolar signals for WCT ground.

[0046] The configuration examples shown in the figures are selected solely for the purpose of clarifying the concept. In alternative embodiments, the disclosed technology may use other suitable configurations, including other wiring schemes, different standalone interfaces, and other types of catheters other than basket catheters.

[0047] The embodiments described above are illustrative examples, and it should be understood that the present invention is not limited to those specifically shown and described above. Rather, the scope of the present invention includes both combinations of the various features described above and combinations of some thereof, as well as variations and modifications thereof that can be conceived by a person skilled in the art by reading the above description and that are not disclosed in the prior art. Documents incorporated by reference in this patent application shall be deemed to be part of this application, except that if any term is defined in such incorporated documents in a manner that contradicts the definitions expressed or implied herein, only the definitions herein shall be considered.

[0048] [Implementation Method] (1) A method, (i) receiving analog surface signals from one or more surface electrodes attached outside the patient's body, and (ii) receiving multiple analog unipolar signals from multiple unipolar electrodes of a probe inserted into the patient's organs, Assigning a first monopolar electrode from among the plurality of monopolar electrodes so that it functions as a common electrical ground and a common timing reference for the analog monopolar signal and the analog surface signal, The analog single-pole signal is digitized, and each digital single-pole signal is generated by sampling the analog single-pole signal against a digital ground. (i) define the analog bipolar signal between the first monopolar electrode and the second monopolar electrode of the probe, and (ii) define the digital bipolar signal formed from the respective digital monopolar signals derived from the first monopolar electrode and the second monopolar electrode. While the first unipolar electrode is connected to the digital ground, the ground offset and timing offset between the analog bipolar signal and the digital bipolar signal are estimated. A method comprising applying the grounding offset and the timing offset when measuring a third unipolar signal sensed by the third unipolar electrode of the probe to the body surface signal. (2) The method according to Embodiment 1, wherein the analog single-pole signal and the digital single-pole signal include an electrocardiogram. (3) The method according to Embodiment 1, wherein the analog body surface signal includes a Wilson coupled electrode (WCT) signal. (4) A device, It is a circuit, Receiving analog surface signals from one or more surface electrodes attached outside the patient's body, The process involves receiving multiple analog monopolar signals from multiple monopolar electrodes of a probe inserted into the organs of the patient, Assigning a first monopolar electrode from among the plurality of monopolar electrodes so that it functions as a common electrical ground and a common timing reference for the analog monopolar signal and the analog surface signal, The analog single-pole signal is digitized, and each digital single-pole signal is generated by sampling the analog single-pole signal against a digital ground. A circuit configured to (i) define an analog bipolar signal between the first and second monopolar electrodes of the probe, and (ii) define a digital bipolar signal formed from the respective digital monopolar signals derived from the first and second monopolar electrodes, It is a processor, While the first unipolar electrode is connected to the digital ground, the ground offset and timing offset between the analog bipolar signal and the digital bipolar signal are estimated. A device comprising: a processor configured to apply the grounding offset and the timing offset when measuring a third unipolar signal sensed by the third unipolar electrode of the probe to the body surface signal. (5) The apparatus according to Embodiment 4, wherein the interface circuit and the processor are included in a legacy system.

[0049] (6) The apparatus according to Embodiment 4, wherein the analog single-pole signal and the digital single-pole signal include an electrocardiogram. (7) The apparatus according to Embodiment 4, wherein the analog body surface signal includes a Wilson coupled electrode (WCT) signal. (8) The apparatus according to Embodiment 4, wherein the interface circuit includes a multi-channel digital link configured to receive a digitized signal from the probe.

Claims

1. 1. A method comprising: receiving (i) an analog body surface signal from one or more body surface electrodes attached to the outside of a patient's body, and (ii) a plurality of analog unipolar signals from a plurality of unipolar electrodes of a probe inserted into an organ of the patient; assigning a first unipolar electrode from among the plurality of unipolar electrodes to serve as a common electrical ground and a common timing reference for the analog unipolar signal and the analog body surface signal; digitizing the analog unipolar signal and generating a respective digital unipolar signal by sampling the analog unipolar signal with respect to digital ground; defining (i) an analog bipolar signal between the first unipolar electrode and a second unipolar electrode of the probe, and (ii) a digital bipolar signal formed from respective digital unipolar signals derived from the first unipolar electrode and the second unipolar electrode; estimating a ground offset and a timing offset between the analog bipolar signal and the digital bipolar signal while the first unipolar electrode is connected to the digital ground; applying the ground offset and the timing offset when measuring a third unipolar signal sensed by a third unipolar electrode of the probe relative to the body surface signal.

2. The method of claim 1 , wherein the analog unipolar signal and the digital unipolar signal comprise an electrocardiogram.

3. 10. The method of claim 1, wherein the analog body surface signal comprises a Wilson's Coupled Electrode (WCT) signal.

4. 1. An apparatus comprising: A circuit comprising: receiving an analog body surface signal from one or more body surface electrodes attached externally to the patient; receiving a plurality of analog unipolar signals from a plurality of unipolar electrodes of a probe inserted into an organ of the patient; assigning a first unipolar electrode from among the plurality of unipolar electrodes to serve as a common electrical ground and a common timing reference for the analog unipolar signal and the analog body surface signal; digitizing the analog unipolar signal and generating a respective digital unipolar signal by sampling the analog unipolar signal with respect to digital ground; a circuit configured to: (i) define an analog bipolar signal between the first and second unipolar electrodes of the probe; and (ii) define a digital bipolar signal formed from the respective digital unipolar signals derived from the first and second unipolar electrodes; 1. A processor, comprising: estimating a ground offset and a timing offset between the analog bipolar signal and the digital bipolar signal while the first unipolar electrode is connected to the digital ground; and applying the ground offset and the timing offset to the body surface signal when measuring a third unipolar signal sensed by a third unipolar electrode of the probe.

5. The apparatus of claim 4 , wherein the interface circuit and the processor are included in a legacy system.

6. 5. The apparatus of claim 4, wherein the analog unipolar signal and the digital unipolar signal comprise an electrocardiogram.

7. 5. The apparatus of claim 4, wherein the analog body surface signal comprises a Wilson coupled electrode (WCT) signal.

8. 5. The apparatus of claim 4, wherein the interface circuitry includes a multi-channel digital link configured to receive digitized signals from the probe.

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