Filtering intracardiac electrograms in presence of pacing spikes

Abstract

The name of the invention of the present disclosure is "filtering intracardiac electrograms in the presence of pacing spikes". A method for removing pacing artifacts includes registering a pacing location at which a pacing signal has been applied into a patient's heart. The first electrode and the second electrode are respectively positioned at a first position and a second position close to the pacing position. First and second circuits having different respective first and second transfer functions are coupled to receive respective first and second ECG signals generated in response to a pacing signal from the first and second electrodes. A first derived ECG signal and a second derived ECG signal are recorded from the first circuit and the second circuit in response to the first ECG signal and the second ECG signal. In response to registering the pacing signal, at least one of the first derived ECG signal and the second derived ECG signal is analyzed. In response to the analysis, pacing artifacts are removed from at least one of the first derived ECG signal and the second derived ECG signal.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of U.S. Provisional Patent Application 63 / 528,709, filed on July 25, 2023, which is incorporated herein by reference. Technical Field

[0003] The present disclosure relates generally to electrophysiology, and in particular to signal acquisition during electrophysiology procedures. Background Art

[0004] During electrophysiology procedures, such as during mapping of the electrical properties of one or more chambers of the heart, it may be advantageous to apply a pacing signal to the heart.Such a signal injects electrical current into the heart. BRIEF DESCRIPTION OF THE DRAWINGS

[0005] The present disclosure will be understood from the following detailed description in conjunction with the accompanying drawings, in which:

[0006] Figure 1 A catheter-based electrophysiology mapping and ablation system according to an example of the present disclosure is shown;

[0007] Figure 2A and Figure 2B is a schematic block diagram illustrating elements of a system for use during a pacing procedure performed on a heart according to an example of the present disclosure;

[0008] Figure 3 Schematic diagram showing pacing artifacts of a balanced system and an unbalanced system according to an example of the present disclosure;

[0009] Figure 4 is a block diagram illustrating the functionality of a signal analysis and pacing artifact removal block according to an example of the present disclosure;

[0010] Figure 5 is a flow chart illustrating steps performed by a processor to implement DC correction in a DC correction block according to an example of the present disclosure;

[0011] Figure 6 shows a graph illustrating the operation of a DC correction block according to an example of the present disclosure;

[0012] Figure 7 A flowchart showing steps performed by a processor in calculating a point in time of an Artifact Reference Time (ART) according to an example of the present disclosure; and

[0013] Figure 8 is a flow chart showing steps of calculating a fitting function and applying a decay function for baseline correction according to an example of the present disclosure. DETAILED DESCRIPTION

[0014] Overview

[0015] During an electrophysiology procedure, pacing provides a means of characterizing the myocardium for the professional performing the procedure. Pacing involves injecting electrical pulses (called pacing signals) into a location in the myocardium and detecting intracardiac electrophysiological (EP) signals generated in areas of the myocardium other than the injection location. In this document, unless otherwise specified, unipolar EP signals are assumed to be included, otherwise intracardiac EP signals are generated due to the action of the pacing signal on the myocardium. Pacing can be provided by electrodes of the catheter, and unipolar EP signal detection can be performed by one or more other electrodes, which can be located on the catheter or on other catheters, referred to herein as acquisition electrodes.

[0016] In addition to the detected EP signal, pacing can generate electrical signals other than the EP signal on the acquisition electrodes. Such signals (referred to herein as pacing artifacts) are typically caused by changes in the electrical potential field in the heart, due to the pacing signal, where the acquisition electrodes are placed. The EP signal is typically recorded along with the artifact on an intracardiac electrocardiogram (ECG) generated during the procedure, and the ECG can be analyzed to achieve a variety of clinical needs, such as, for example, determining local activation time (LAT) and wavefront mapping.

[0017] However, the presence of pacing artifacts in the ECG may lead to errors in ECG analysis.

[0018] In an example of the present disclosure, it is assumed that ECG analysis includes analysis of two unipolar EP signals collected from two collection electrodes, and analysis of bipolar EP signals derived from the two unipolar signals. The two collection electrodes are connected to an ECG recording system through respective transmission circuits. Each transmission circuit applies a corresponding transmission function to the signal it receives, so that two derived unipolar EP signals are provided to the ECG recording system. The recording system analyzes the derived bipolar EP signal and formulates the derived bipolar EP signal by calculating the difference between the two derived unipolar EP signals.

[0019] In some examples, the two transmission circuits for the two electrodes are nominally identical, with components having the same nominal values ​​arranged in the same manner so that the two circuits have the same nominal transfer function. While pacing artifacts can be significantly reduced in ECG analysis of the derived bipolar EP signal, deviations from the component nominal values ​​and the fact that the two acquisition electrodes cannot acquire exactly the same pacing artifacts due to their different spatial locations relative to the pacing source and / or differences in the electrodes themselves typically leave residual pacing artifacts in the derived bipolar signal. The residual pacing artifacts are referred to herein as common transfer function pacing artifacts.

[0020] In some examples, the two transmission circuits for the two electrodes are different, so that each circuit applies a different transfer function to the signal it receives. In this case, the pacing artifact (referred to herein as a different transfer function pacing artifact) is generally larger than the common transfer function pacing artifact.

[0021] Examples of the present disclosure provide an algorithm that analyzes the derived EP signal to identify and compensate for the presence of the two types of pacing artifacts described above.

[0022] Artifacts typically alter the signal collected by the collection electrodes in a variety of ways, including altering the DC (direct current) voltage level of the signal and altering the slope of the signal's baseline, i.e., imparting a baseline drift to the signal. The algorithm corrects for any altered DC level and any baseline drift, and further corrects for any remaining alterations to the signal.

[0023] Apply the algorithm:

[0024] Minimize the impact of artifacts on ECG presentation;

[0025] Eliminate incorrect bipolar voltage measurements that may be caused by artifacts; and

[0026] Eliminate false candidate annotations on ECG.

[0027] System Description

[0028] In the following description, similar elements are identified by the same reference numerals and are distinguished by adding letters as suffixes after the numerals where necessary.

[0029] Reference now Figure 1 , shows a catheter-based electrophysiology mapping and ablation system 10 according to an example of the present disclosure. The system 10 includes a plurality of catheters that are inserted into a chamber or vascular structure of a heart 12 by a physician 24 through the patient's vascular system via the skin. Typically, a delivery sheath catheter is inserted into the left atrium or right atrium near a desired location in the heart 12. Multiple catheters may then be inserted into the delivery sheath catheter in order to reach the desired location. The multiple catheters may include a catheter dedicated to sensing intracardiac electrogram (IEGM) signals, a catheter dedicated to ablation, and / or a catheter dedicated to both sensing and ablation. An example catheter 14 configured for sensing is shown herein. The physician 24 brings the distal end 28 of the catheter 14 into contact with the heart wall for sensing the electrical potential (EP) at a target location in the heart 12.

[0030] The catheter 14 is an exemplary multi-ridge catheter that includes a plurality of electrodes 26 distributed on the spines of the catheter. The catheter 14 may additionally include a position sensor 29 embedded in or near the distal tip 28 for tracking the position and orientation of the distal tip 28. Optionally and preferably, the position sensor 29 is a magnetically based positioning sensor that includes three magnetic coils for sensing three-dimensional (3D) position and orientation.

[0031] The magnetic-based position sensor 29 can operate with the positioning pad 25, which includes a plurality of magnetic coils 32 configured to generate a magnetic field in a predefined working space. The real-time position of the distal tip 28 of the catheter 14 can be tracked based on the magnetic field generated by the positioning pad 25 and sensed by the magnetic-based position sensor 29. The details of the magnetic-based position sensing technology are described in U.S. Patent Nos. 5,539,199, 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.

[0032] The system 10 includes one or more electrode patches 38 positioned in contact with the skin of the patient 23 to establish a position reference for impedance-based tracking of the positioning pad 25 and at least some of the electrodes 26. For impedance-based tracking, current is directed toward the electrodes 26 and sensed at the electrode skin patches 38 so that the position of each electrode can be triangulated via the electrode patches 38. Details of impedance-based position tracking techniques are described in U.S. Patent Nos. 7,536,218, 7,756,576, 7,848,787, 7,869,865, and 8,456,182.

[0033] The recorder 11 displays an electrogram 21 captured using the surface ECG electrodes 18 and an intracardiac electrogram (IEGM) that may be captured using electrodes 26 of the catheter 14. The recorder 11 may include pacing capabilities for pacing the cardiac rhythm and / or may be electrically connected to a separate pacemaker. As further described below, in some examples, a pacing signal may be delivered via one of the electrodes 26 or via another intracardiac electrode.

[0034] The system 10 may include an ablation energy generator 50 adapted to conduct ablation energy to one or more of the electrodes 26. The energy generated by the ablation energy generator 50 may include, but is not limited to, radio frequency (RF) energy or pulsed field ablation (PFA) energy (including monopolar or bipolar high voltage DC pulses that may be used to achieve irreversible electroporation (IRE)), or a combination thereof.

[0035] The patient interface unit (PIU) 30 is an interface configured to establish electrical communication between catheters, electrophysiology equipment, a power source, and a workstation 55 for controlling the operation of the system 10. The electrophysiology equipment of the system 10 may include, for example, multiple catheters, a positioning pad 25, surface ECG electrodes 18, electrode patches 38, an ablation energy generator 50, and a recorder 11. Optionally and preferably, the PIU 30 additionally includes processing capabilities for enabling real-time calculation of the position of the catheter and for performing ECG calculations.

[0036] A system processing unit (SPU) 60 between the PIU 30 and the catheter 14 couples the PIU to the electrodes 26 of the catheter via a cable 65 between the PIU and the SPU and a cable 63 between the SPU and the electrodes. In some examples, the SPU 60 includes corresponding front-end circuitry 64, which is assumed herein to include a low-noise preamplifier, an analog-to-digital (A / D) converter, and filtering circuits, which are applied to the EP signals collected by each electrode 26 before they are transmitted to the PIU. In some examples, the SPU includes corresponding modified front-end circuitry 68, which, in addition to the circuitry of circuitry 64, also includes other elements that enable current to be injected into the corresponding electrode 26 so that the electrode can be used for impedance-based tracking, as described above.

[0037] In the examples of the present disclosure, it is assumed that the A / D converters mentioned above sample and digitize their analog signals at a rate of 1 ms.

[0038] The workstation 55 includes a memory, a processor 22 with a memory or storage device loaded with appropriate operating software, and user interface capabilities. The workstation 55 can provide multiple functions, optionally including: (1) three-dimensional (3D) modeling of the endocardial anatomy and rendering the model or anatomical map (20) for display on the display device 27; (2) displaying the activation sequence (or other data) compiled from the recorded electrograms 21 on the display device 27 as representative visual markers or images superimposed on the rendered anatomical map 20; (3) displaying the real-time position and orientation of the distal tip 28 within the heart chamber; and (4) displaying on the display device 27 a site of interest, such as where ablation energy has been applied. A commercial product embodying elements of the system 10 can be CARTO TM The 3 system was purchased from Biosense Webster, Inc., 31A Technology Drive, Irvine, CA 92618.

[0039] Pacing by System 10

[0040] Figure 2A and Figure 2Bis a schematic block diagram showing elements of system 10 used during a pacing procedure performed by the system on heart 12 according to an example of the present disclosure. In the procedure, a pacing signal is injected into a region of the heart, and a resulting intracardiac EP signal generated in response to the pacing signal is acquired by electrodes on a distal tip 28 of catheter 14 that contacts heart 12. The accompanying drawings show two such electrodes, electrodes 26A, 26B, which are assumed herein by way of example to be on a common ridge of the distal tip. However, in other examples of the present disclosure, electrodes 26A, 26B are not on a common ridge of the distal tip 28. Electrodes 26A, 26B are also referred to herein as acquisition electrodes 26A, 26B. As described below, the signals acquired by electrodes 26A, 26B are used to calculate a bipolar EP signal between the two electrodes.

[0041] exist Figure 2A , each acquisition electrode 26A, 26B is connected to a signal analysis and pacing artifact removal block 76 via a respective transmission circuit 72A, 72B. The structure and function of block 76 are described below, and by way of example, it is assumed that the elements of the block are installed in PIU 30. The output of block 76 includes the resulting unipolar and bipolar signals derived from the corresponding signals acquired by electrodes 26A, 26B, wherein the pacing artifacts present on the acquired signals are removed. The resulting signals from block 76 may be provided to a workstation 55, which may use the resulting signals, for example, to display and analyze the corresponding IEGMs from which the pacing artifacts have been removed.

[0042] exist Figure 2A , transmission circuits 72A and 72B have identical physical components. Thus, circuit 72A includes cable 63A coupling electrode 26A to front-end circuit 64A, front-end circuit 64A, and cable 65A coupling front-end circuit 64A to block 76; and circuit 72B includes cable 63B coupling electrode 26B to front-end circuit 64B, front-end circuit 64B, and cable 65B coupling front-end circuit 64B to block 76.

[0043] Figure 2A The components of the two transmission circuits shown in are connected in the same configuration in both circuits, so that the figure illustrates a balanced system. However, while the physical components of the two transmission circuits may have the same nominal values, it should be understood that because the corresponding components of the circuits (such as their corresponding preamplifiers) are physically different, the actual electrical parameters associated with the components (such as their gain and / or impedance) are typically different.

[0044] Due to differences in the actual electrical parameters of the components of circuits 72A and 72B, including differences in the characteristics of individual electrodes, the respective signal transfer functions associated with each circuit are different. The signal transfer function of a given transmission circuit includes a function that defines the resulting signal generated by the transmission circuit for a given input signal.

[0045] The input signal acquired by a given electrode 26 is composed of two sub-signals: a unipolar EP signal generated at least in part in response to a pacing signal injected into the heart 12; and a pacing artifact that is also generated by direct conduction, induction, and / or radiation in response to the pacing signal. Due to the physical separation of electrodes 26A, 26B, the unipolar EP signal component acquired by electrode 26A is different from the unipolar EP signal component acquired by electrode 26B. Similarly, the pacing artifact acquired by electrode 26A is different from the artifact acquired by electrode 26B.

[0046] In an example of the present disclosure, block 76 receives the resulting unipolar EP signals of circuit 72A and circuit 72B (also referred to herein as raw or derived unipolar EP signals of circuit 72A and circuit 72B) and initially calculates a difference in the derived signals to form a raw bipolar EP signal. As described below, block 76 is configured to remove pacing artifacts from both the raw unipolar EP signal and the raw bipolar EP signal output by the block.

[0047] Reference now Figure 2B . Except for the differences described below, Figure 2B The operation of the elements shown in FIG. 1 is generally similar to that of Figure 2A , and elements indicated by the same reference numerals in the two figures are generally similar in structure and operation.

[0048] and Figure 2A In contrast to the balanced system shown in Figure 2B The system shown in is an unbalanced system. Figure 2B In the embodiment shown in FIG. 1 , electrode 26A is connected to block 76 via transmission circuit 72A, which includes cable 63A, front end circuit 64A, and cable 65A, as described above. However, electrode 26B is connected to block 76 via transmission circuit 80B. Transmission circuit 80B includes modified front end circuit 68B, cable 63B connecting circuit 68B to electrode 26B, and cable 65B connecting circuit 68B to block 76.

[0049] As for Figure 2A The balance system, Figure 2B In an unbalanced system, block 76 receives the raw unipolar EP signal of circuit 72A and the raw unipolar EP signal of circuit 80B and initially calculates the difference in the raw signals to form a raw bipolar EP signal. As for a balanced system, block 76 is configured to remove pacing artifacts from the two raw unipolar EP signals and the raw bipolar EP signal output by the block. Typically, the pacing artifacts in the raw bipolar EP signal of the unbalanced system are larger than the pacing artifacts in the raw bipolar EP signal of the balanced system.

[0050] Figure 3Schematic diagrams of pacing artifacts for a balanced system and an unbalanced system according to an example of the present disclosure are shown. Graph 90 is a voltage versus time graph of the raw bipolar EP signal for the balanced system, as initially calculated by block 76, and graph 94 is a voltage versus time graph of the raw bipolar EP signal for the unbalanced system. The pacing artifacts occur approximately between time T1 and T2, and it is apparent from the figure that the pacing artifacts for the unbalanced system (referred to herein as different transfer function pacing artifacts) are larger than the pacing artifacts for the balanced system (referred to herein as common transfer function pacing artifacts).

[0051] In the example of the present disclosure, block 76 is configured to Figure 2A The balance system shown and Figure 2B The unbalanced system shown is removed from the signal output by this block Figure 3 Pacing artifacts are shown.

[0052] Figure 4 is a block diagram illustrating the functionality of the signal analysis and pacing artifact removal block 76 according to an example of the present disclosure. The pacing artifacts applied to each raw unipolar EP signal derived from the electrodes 26 and to the raw bipolar EP signals formed from the unipolar signals generally include the following elements:

[0053] DC level changes

[0054] Baseline slope change

[0055] Residual signal changes.

[0056] For each of the three raw signals (i.e., two raw unipolar EP signals and a raw bipolar EP signal), the examples of the present disclosure analyze the signals received from the electrodes 26 to calculate a DC level change, and use the calculation to correct for the change in the DC correction block 100. The DC corrected signal is then transmitted to the baseline correction block 104. In block 104, the baseline slope is measured at two different times, and the measured slope is used to generate a function that is applied to the baseline to correct for the slope change. The baseline corrected signal is transmitted to the filtering block 108, where the remaining signal changes (although typically small) are removed by applying a filtering network to the baseline correction signal.

[0057] The following sections describe the operation of each block in the signal analysis and pacing artifact removal block 76. These operations are performed under the overall control of the processor 22.

[0058] DC Correction

[0059] Figure 5 is a flowchart 120 illustrating steps performed by the processor 22 to implement the DC correction of the block 100 according to an example of the present disclosure, and Figure 6A diagram illustrating the operation of blocks according to examples of the present disclosure is shown. A processor operates on a sampled digitized signal to compute a DC correction.

[0060] In an initial pacing registration step 124, processor 22 registers that a pacing signal has been injected into heart 12, and uses the registration time as a pacing indication, also referred to herein as a reference time point. The processor also identifies the sample at the reference time point as a reference sample. The injection of a pacing signal typically generates a voltage on electrode 26 of catheter 14 other than electrodes 26A, 26B, or on an electrode of another catheter positionable in heart 12. The generated voltage is typically at least twice the typical maximum EP voltage generated by heart 12, so the processor can assume that the voltage is caused by the injection of a pacing signal.

[0061] The following description applies to the analysis performed on each of the three signals received by block 76 (ie, the two raw monopolar EP signals and the raw bipolar EP signal).

[0062] In a prior DC level step 128, the processor measures the average DC level of the raw EP signal within a preset prior time window prior to the reference time point. In one example, the prior time window has a fixed width of 3 ms, between 5 ms and 2 ms prior to the reference time point. The time window boundaries are typically selected to be as close to the reference time point as possible.

[0063] In a subsequent DC level step 132, the processor measures the DC level at a dynamic time point within a subsequent time window after the reference time point. In one example, the subsequent time window is between 10 ms and 20 ms after the reference time point and may be referred to as follows Figure 7 The algorithm described in flowchart 160 in FIG. 1 is used to find the dynamic time point within the window (also referred to herein as the Artifact Reference Time (ART)).

[0064] In a final step 136 , the processor finds the difference between the DC levels of step 132 and step 128 and applies the difference to correct the raw EP signal after the reference time point. The DC correction signal formed in step 136 is transmitted to the baseline correction block 104 .

[0065] Figure 6 A DC correction applied to a raw bipolar EP signal according to an example of the present disclosure is shown. Graph 148 is a voltage versus time graph of the raw EP bipolar signal before the DC correction is applied, and graph 152 is a voltage versus time graph after the correction is applied (translated parallel to the voltage axis for clarity). As shown in the graphs, the DC correction shifts the baseline after an input signal including a pacing response and artifacts so that the shifted baseline starts at the same voltage level as the baseline before the input signal.

[0066] Reference now Figure 7 , a flowchart 160 showing steps performed by processor 22 in calculating a time point of an Artifact Reference Time (ART) according to an example of the present disclosure. In contrast to the above-described preset time window using a preset time point, as described above, the ART is a dynamic time point that can vary from signal to signal.

[0067] As described above, to correct for the presence of pacing artifacts, examples of the present disclosure apply DC correction and baseline correction. ART acts as a dynamic time point for separating the application of DC correction from the application of baseline correction, and ART provides a balance between a short artifact period from a reference time point (i.e., pacing indication) to ART and a period after ART with a small residual voltage artifact.

[0068] In an initial step 164, the processor delineates preset boundaries of the time window within which the ART is calculated. In one example, the first boundary is set at 10 ms after the pacing indication and the last boundary is set at 20 ms after the pacing indication, but the preset boundaries may be different in other examples.

[0069] In a first calculation step 168, the processor calculates the absolute value of the running average of the means of the differences between the sample subsets until the last window boundary. In one example, the processor uses subsets of three consecutive samples and calculates the mean of each difference for each subset according to the following equation:

[0070]

[0071] Where P is the reference time point,

[0072] sig(n) is the signal value of the nth sample, and

[0073] M(n) is the absolute value of the mean assigned to the nth sample.

[0074] It should be understood that equation (1) is one method for calculating the mean, and one of ordinary skill in the art will know other methods. It is assumed that all such methods are included within the scope of the present disclosure.

[0075] In a second calculation step 172, the processor finds the difference between the mean calculated in step 168 and the mean of the last window boundary according to equation (2):

[0076]

[0077] In a final step 176, the processor searches backwards from the last boundary difference to find the first sample that crosses a preset threshold and occurs after the first window boundary. In one example, the preset threshold is 0.5 mV / ms.

[0078] The processor uses the time of the sample found in this step as the ART.

[0079] Baseline correction

[0080] In addition to the DC changes described above, pacing artifacts include changes in the slope of the EP baseline. To compensate for this, examples of the present disclosure analyze the baseline and, in response to the analysis, generate a baseline fit function and a decay function. The fit function is designed to eliminate baseline slope artifacts, while the decay function is designed to ensure that the fit function decreases over time and eventually eliminates the effects of the fit function.

[0081] Examples of the present disclosure use a fitting function of the form given by equation (3) below: Equation (3) is an exponential function that decays with time, corresponding to the charge / discharge characteristics of a fixed impedance RC circuit.

[0082]

[0083] Where n is the number of samples of the signal,

[0084] α is the decay rate, and

[0085] γ is the gain.

[0086] α and γ are real numbers and are chosen such that F(n) is monotonic.

[0087] The examples of the present disclosure use a high pass infinite impulse response (IIR) filter on the acquired signal, and the filter effectively generates the derivative of the signal being filtered for low frequencies. To accommodate this, the derivative of the fitted function is matched to the measured derivative of the EP signal. By performing this matching, the IIR filter does not introduce any further artifacts in the signal.

[0088] Figure 8 is a diagram showing the steps performed by the processor 22 to calculate the fitting function and apply the decay function to perform block 104 ( Figure 4 ) is a flowchart 200 of steps for baseline correction.

[0089] In an initial pacing registration step 204, the processor identifies an artifact reference time (ART) of the EP signal, as described above with reference to flowchart 160 ( Figure 7 ) as described.

[0090] In a sample selection step 208, the processor selects a preset number of sample EP signals that follow the ART from the DC correction signal received from block 100. In the disclosed example described herein, ten samples s[1], s[2], ..., s

[10] are selected, but other examples may have more or less than ten samples.

[0091] In calculation step 212, based on the selected samples, the processor calculates the mean of the derivatives of the first samples of the selected set and the mean of the derivatives of the last samples of the selected set. In one example, assume that there are three first samples with values ​​s[1], s[2], s[3], and there are three last samples with values ​​s[8], s[9], s

[10] .

[0092] The first three samples have a mean derivative, referred to herein as K1, given by equation (4):

[0093]

[0094] The last three samples have a mean derivative, referred to herein as K9, given by equation (5):

[0095]

[0096] The processor 22 uses the calculated values ​​K1, K9 to find the values ​​of α and γ in equation (3), as explained below.

[0097] According to equation (3), the partial derivative of F(n) with respect to n is given by:

[0098]

[0099] For n = 0, And this corresponds to K1, that is,

[0100]

[0101] For n = 9, And this corresponds to K9, that is,

[0102]

[0103] Equations (7) and (8) can be used to solve for α and γ, yielding:

[0104]

[0105] as well as

[0106]

[0107] In an application step 216, the processor substitutes the values ​​of α and γ calculated in equations (9) and (10) into equation (3), resulting in the following expression for the baseline fit function:

[0108]

[0109] To ensure that the baseline fit function decreases, eventually decreasing to zero for larger values ​​of n, the processor applies a decay function D to the fit function. The decay function prevents the EP signal from exceeding the allowable dynamic range and also prevents the signal from having baseline drift in the system's IIR filter.

[0110] In one example, the decay function D is defined according to the following equation:

[0111]

[0112] Where a is a preset parameter, which is assumed to be 0.5 in this paper, and τ depends on the baseline signal B p The variable time constant of the value of , i.e., the baseline signal of the pacing event p. p Defined by equation (13):

[0113] B p = signal p (prior)-signal p (post)+Res p-1 (13)

[0114] Among them, signal p (prior) is the baseline signal at the time just before the preset prior time window defined in step 128 of flowchart 120,

[0115] signal p (post) is the baseline signal at the time just after the dynamic time point ART found in flow chart 160, and

[0116] Res p-1 is the residual baseline signal remaining after the (p-1) pace estimate.

[0117] The time constant τ is set to be equal to B according to equation (14). p Proportional:

[0118]

[0119] where K is a constant.

[0120] In one example, K is equal to the product of a time interval corresponding to the maximum possible pacing rate in a clinical setting and a maximum saturation value of the ECG signal. In the disclosed example, the time interval is about 300 ms and the maximum saturation value is about 50 mV.

[0121] The processor calculates the correction value C(n) according to the following equation:

[0122] C(n)=(B p -F(n))·D (15)

[0123] Among them B p As defined in equation (13),

[0124] F(n) is defined as in equation (11),

[0125] D is defined as in equation (12), and

[0126] n is the sample number, relative to ART (flowchart 160).

[0127] In step 216, to implement the baseline correction signal, the processor subtracts the correction value C(n) from each sample n of the DC correction signal.

[0128] Return to Figure 4 As shown, the results from the baseline correction block 104 (ie, the results produced by step 216 of the flowchart 200 ) are transmitted to the filtering block 108 .

[0129] In block 108, processor 22 applies a filter to the signal received from baseline correction block 104. However, to avoid introducing anomalies into the signal through the use of the filter, the received signal is first "chopped" to separate the pacing signal, and the remaining signal is filtered, as explained below.

[0130] In one example of the present disclosure, the processor performs chopping as follows:

[0131] The processor identifies and clips pacing peaks from the signal received from the baseline correction block 104 and stores the clipped pacing peaks in a memory of the workstation 55 .

[0132] The cut peak leaves a "hole" in the signal. The processor interpolates the area of ​​this hole.

[0133] The processor then filters the signal including the interpolated portion, for example using a high pass IIR filter.

[0134] After filtering, processor 22 accesses memory to restore the ablated pacing signal to a filtered signal to produce a pacing signal without significant artifacts.

[0135] Example

[0136] Embodiment 1. A method for removing pacing artifacts, comprising:

[0137] registering that a pacing signal has been applied to a pacing location in the patient's heart;

[0138] positioning a first electrode in a first location proximate to the pacing location and coupling a first circuit having a first transfer function to receive a first electrocardiogram (ECG) signal generated in response to the pacing signal from the first electrode;

[0139] recording a first derived ECG signal from the first circuit in response to the first ECG signal;

[0140] positioning a second electrode in a second location proximate to the pacing location and coupling a second circuit having a second transfer function different from the first transfer function to receive a second ECG signal generated in response to the pacing signal from the second electrode;

[0141] recording a second derived ECG signal from the second circuit in response to the second ECG signal;

[0142] responsive to registering the pacing signal, analyzing at least one of the first derived ECG signal and the second derived ECG signal; and

[0143] Responsive to the analyzing, the pacing artifact is removed from the at least one of the first derived ECG signal and the second derived ECG signal.

[0144] Embodiment 2. The method of embodiment 1, wherein the first circuit and the second circuit include common circuit components arranged in a common configuration.

[0145] Embodiment 3. The method of embodiment 2, wherein one of the common circuit components of the first circuit has an electrical parameter value that is different from an electrical parameter value of a corresponding component of the second circuit.

[0146] Embodiment 4. The method of embodiment 1, wherein the first circuit and the second circuit include different circuit components.

[0147] Embodiment 5. The method of Embodiment 1, wherein the first circuit and the second circuit include common circuit components arranged in different configurations.

[0148] Example 6. A method according to Example 1, wherein analyzing at least one of the first derived ECG signal and the second derived ECG signal includes: calculating its direct current (DC) voltage level, and wherein removing the pacing artifact includes: applying the DC voltage level as a DC correction to the at least one of the first derived ECG signal and the second derived ECG signal.

[0149] Example 7. A method according to Example 1, wherein analyzing at least one of the first derived ECG signal and the second derived ECG signal includes: calculating a baseline fitting function to compensate for changes in the baseline slope of at least one of the first derived ECG signal and the second derived ECG signal.

[0150] Embodiment 8. The method of embodiment 7, and comprising applying a decay function to the baseline fit function.

[0151] Example 9. A method according to Example 1, wherein analyzing at least one of the first derived ECG signal and the second derived ECG signal includes: calculating a bipolar ECG signal based on the first derived ECG signal and the second derived ECG signal, and wherein removing the artifact includes: removing the artifact from the bipolar ECG signal.

[0152] Embodiment 10. A method according to embodiment 1, wherein analyzing at least one of the first derived ECG signal and the second derived ECG signal includes: cutting out pacing peaks therefrom to produce a chopped signal; interpolating and filtering the chopped signal to produce a filtered signal; and restoring the pacing peaks to the filtered signal.

[0153] Embodiment 11. A device for removing pacing artifacts, comprising:

[0154] a first electrode positioned at a first location in a patient's heart proximate to a pacing location, wherein a pacing signal has been applied;

[0155] a first circuit having a first transfer function, the first circuit being coupled to receive a first electrocardiogram (ECG) signal generated in response to the pacing signal from the first electrode;

[0156] a second electrode positioned at a second location proximate to the pacing location;

[0157] a second circuit having a second transfer function different from the first transfer function, the second circuit being coupled to receive a second ECG signal generated in response to the pacing signal from the second electrode; and

[0158] A processor, the processor being configured to:

[0159] recording a first derived ECG signal from the first circuit in response to the first ECG signal,

[0160] recording a second derived ECG signal from the second circuit in response to the second ECG signal,

[0161] registering that the pacing signal has been applied,

[0162] responsive to registering the pacing signal, analyzing at least one of the first derived ECG signal and the second derived ECG signal, and

[0163] Responsive to the analyzing, the pacing artifact is removed from the at least one of the first derived ECG signal and the second derived ECG signal.

[0164] The above embodiments are cited by way of example, and the present disclosure is not limited by what is specifically shown and described above. On the contrary, the scope of the present disclosure includes combinations and sub-combinations of the various features described above, as well as variations and modifications thereof, which will occur to those skilled in the art upon reading the above description and which are not disclosed in the prior art.

Claims

1. A method for removing pacing artifacts, comprising: registering that a pacing signal has been applied to a pacing location in the patient's heart; positioning a first electrode in a first location proximate to the pacing location and coupling a first circuit having a first transfer function to receive a first electrocardiogram (ECG) signal generated in response to the pacing signal from the first electrode; recording a first derived ECG signal from the first circuit in response to the first ECG signal; positioning a second electrode in a second location proximate to the pacing location and coupling a second circuit having a second transfer function different from the first transfer function to receive a second ECG signal generated in response to the pacing signal from the second electrode; recording a second derived ECG signal from the second circuit in response to the second ECG signal; responsive to registering the pacing signal, analyzing at least one of the first derived ECG signal and the second derived ECG signal; as well as Responsive to the analyzing, the pacing artifact is removed from the at least one of the first derived ECG signal and the second derived ECG signal.

2. The method according to claim 1, wherein: The first circuit and the second circuit include common circuit components arranged in a common configuration.

3. The method according to claim 2, wherein: One of the common circuit components of the first circuit has an electrical parameter value that is different from the electrical parameter value of the corresponding component of the second circuit.

4. The method according to claim 1, wherein: The first circuit and the second circuit include different circuit components.

5. The method according to claim 1, wherein: The first circuit and the second circuit include common circuit components arranged in different configurations.

6. The method according to claim 1, wherein: Analyzing at least one of the first derived ECG signal and the second derived ECG signal includes calculating a direct current (DC) voltage level thereof, and wherein removing the pacing artifact includes applying the DC voltage level as a DC correction to the at least one of the first derived ECG signal and the second derived ECG signal.

7. The method according to claim 1, wherein: Analyzing the at least one of the first derived ECG signal and the second derived ECG signal includes calculating a baseline fit function to compensate for changes in a baseline slope of the at least one of the first derived ECG signal and the second derived ECG signal.

8. A method according to claim 7, and comprising applying a decay function to the baseline fit function.

9. The method according to claim 1, wherein: Analyzing the at least one of the first derived ECG signal and the second derived ECG signal includes calculating a bipolar ECG signal from the first derived ECG signal and the second derived ECG signal, and wherein removing the artifact includes removing the artifact from the bipolar ECG signal.

10. The method according to claim 1, wherein: Analyzing the at least one of the first derived ECG signal and the second derived ECG signal comprises: cutting pacing peaks therefrom to produce a chopped signal; interpolating and filtering the chopped signal to produce a filtered signal; and restoring the pacing peaks to the filtered signal.

11. A device for removing pacing artifacts, comprising: a first electrode positioned in a first location in a heart of a patient proximate to a pacing location, wherein a pacing signal has been applied; a first circuit having a first transfer function, the first circuit being coupled to receive a first electrocardiogram (ECG) signal generated in response to the pacing signal from the first electrode; a second electrode positioned in a second location proximate to the pacing location; a second circuit having a second transfer function different from the first transfer function, the second circuit being coupled to receive a second ECG signal generated in response to the pacing signal from the second electrode; and A processor, the processor being configured to: recording a first derived ECG signal from the first circuit in response to the first ECG signal, recording a second derived ECG signal from the second circuit in response to the second ECG signal, registering that the pacing signal has been applied, responsive to registering the pacing signal, analyzing at least one of the first derived ECG signal and the second derived ECG signal, and Responsive to the analyzing, the pacing artifact is removed from the at least one of the first derived ECG signal and the second derived ECG signal.

12. The device according to claim 11, wherein The first circuit and the second circuit include common circuit components arranged in a common configuration.

13. The device according to claim 12, wherein: One of the common circuit components of the first circuit has an electrical parameter value that is different from the electrical parameter value of the corresponding component of the second circuit.

14. The device according to claim 11, wherein: The first circuit and the second circuit include different circuit components.

15. The apparatus according to claim 11, wherein: The first circuit and the second circuit include common circuit components arranged in different configurations.

16. The apparatus according to claim 11, wherein: Analyzing at least one of the first derived ECG signal and the second derived ECG signal includes calculating a direct current (DC) voltage level thereof, and wherein removing the pacing artifact includes applying the DC voltage level as a DC correction to the at least one of the first derived ECG signal and the second derived ECG signal.

17. The apparatus according to claim 1, wherein: Analyzing the at least one of the first derived ECG signal and the second derived ECG signal includes calculating a baseline fit function to compensate for changes in a baseline slope of the at least one of the first derived ECG signal and the second derived ECG signal.

18. Apparatus according to claim 17 and comprising applying a decay function to the baseline fit function.

19. The apparatus according to claim 11, wherein: Analyzing the at least one of the first derived ECG signal and the second derived ECG signal includes calculating a bipolar ECG signal from the first derived ECG signal and the second derived ECG signal, and wherein removing the artifact includes removing the artifact from the bipolar ECG signal.

20. The apparatus of claim 11, wherein: Analyzing the at least one of the first derived ECG signal and the second derived ECG signal includes: cutting pacing peaks therefrom to produce a chopped signal; interpolating and filtering the chopped signal to produce a filtered signal; and restoring the pacing peaks to the filtered signal.

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