Recording equipment noise reduction

Abstract

The present invention is entitled "Recording Device Noise Reduction". The present invention provides an electrical activity measurement system, in one embodiment, the electrical activity measurement system includes: a catheter, the catheter is inserted into a body part and includes at least one electrode; a signal processing circuit, the signal processing circuit is coupled to receive an intracardiac electrogram (IEGM) signal from the at least one electrode and processes the IEGM signal for output to a recording device via a cable, the cable picking up ambient electrical noise; and a feedback circuit, the feedback circuit is configured to receive at least some of the electrical noise picked up by the cable and provide a feedback signal indicative of the received electrical noise to the signal processing circuit, the signal processing circuit is configured to compensate at least partially for electrical noise that is not yet in the IEGM signal but will be added to the IEGM signal in the cable in response to the feedback signal, thereby generating a noise-compensated IEGM signal for output to the recording device via the cable.

Description

[0001] Related application information

[0002] This application claims the benefit of U.S. Provisional Patent Application No. 62 / 877,218, filed on July 22, 2019, under 35 U.S.C. 119, which is hereby incorporated by reference as if fully set forth herein. Technical Field

[0003] The present invention relates to medical devices and particularly, but not exclusively, to noise reduction of electrogram signals. Background Art

[0004] Electrical noise can be a significant problem when recording electrophysiological signals.

[0005] U.S. Patent 9,591,981 issued to Levin et al. provides a method for acquiring electrical signals from a living subject, the method comprising: injecting a known calibration signal into the subject via an injection electrode attached to the subject; and measuring a corresponding level of an output signal generated at an input electrode attached to the subject in response to the calibration signal. The method also includes deriving a corresponding weight factor for the input electrode in response to the corresponding level, and then applying the corresponding weight factor to a physiological signal acquired by the input electrode to generate a corresponding corrected physiological signal.

[0006] Donofrio et al., U.S. Patent Publication 2010 / 0114201, describes methods for evaluating and, in some examples, mitigating electrical crosstalk between two implantable medical devices or two different therapeutic modules of a common implantable medical device. In some examples, one of the implantable medical devices or therapeutic modules delivers electrical stimulation to a non-myocardial tissue site or a non-vascular cardiac tissue site, and the other implantable medical device or therapeutic module delivers cardiac rhythm management therapy to the patient's heart.

[0007] Connelly's U.S. Patent Publication 2002 / 0133208 describes an electromagnetic immunotissue invasive system including a main device housing. The main device housing has control circuitry therein. A shield is formed around the main device housing to shield the main device housing and any circuitry therein from electromagnetic interference. A lead system transmits and receives signals between the main device housings. The lead system is a fiber optic system or an electrically shielded electrical lead system.

[0008] U.S. Patent Publication 2017 / 0112405 to Sterrett et al. describes an integrated electrode structure including a catheter shaft including a proximal end and a distal end, the catheter shaft defining a longitudinal axis of the catheter shaft. A flexible end portion may be located near the distal end of the catheter shaft, the flexible end portion including a flexible frame. A plurality of microelectrodes may be disposed on the flexible frame and may form a flexible microelectrode array adapted to conform to tissue. A plurality of conductive traces may be disposed on the flexible frame, each of the plurality of conductive traces being electrically coupled to a corresponding one of the plurality of microelectrodes.

[0009] Landy et al., U.S. Patent Publication 2018 / 0303414, describes systems, devices, and methods for performing precise treatment, mapping, and / or testing of tissue, for administering an agent to one or more precise regions within a tissue mass, and for treating a target region within a tissue mass. The present invention discloses systems, devices, and methods for identifying, locating, monitoring neural communication near a target region within a tissue mass, quantifying neural communication near a target region within a tissue mass, and mapping neural communication near a target region within a tissue mass. Summary of the invention

[0010] According to one embodiment of the present disclosure, an electrical activity measurement system is provided, which includes: a catheter configured to be inserted into a body part of a living subject and including a distal end, the distal end including at least one electrode; a signal processing circuit coupled to the at least one electrode and configured to receive an intracardiac electrogram (IEGM) signal from the at least one electrode and process the IEGM signal for output to a recording device via a cable, the cable picking up ambient electrical noise; and a feedback circuit configured to receive at least some of the electrical noise picked up by the cable and provide a feedback signal indicative of the received electrical noise to the signal processing circuit, the signal processing circuit being configured to at least partially compensate for electrical noise that is not yet in the IEGM signal but will be added to the IEGM signal in the cable in response to the feedback signal, thereby generating a noise-compensated IEGM signal for output to the recording device via the cable.

[0011] Further in accordance with one embodiment of the present disclosure, the feedback circuit includes a sensor configured to sense at least some of the electrical noise picked up by the cable, and the signal processing circuit includes: an analog-to-digital converter coupled to receive the IEGM signal from at least one electrode as an input analog IEGM signal and configured to convert the input analog IEGM signal into a digital IEGM signal; a digital signal filtering device coupled to receive the digital IEGM signal and configured to filter noise from the received digital IEGM signal; a digital-to-analog converter coupled to receive the filtered digital IEGM signal and configured to convert the filtered digital IEGM signal into a filtered analog IEGM signal; and a compensation circuit coupled to receive the feedback signal and the filtered analog IEGM signal and configured to at least partially compensate for electrical noise that is not in the filtered analog IEGM signal but will be added to the cable in response to the feedback signal, thereby generating a noise-compensated analog IEGM signal for output to a recording device via the cable.

[0012] According to yet further an embodiment of the present disclosure, the sensor is an antenna or a coil.

[0013] Additionally, according to an embodiment of the present disclosure, the compensation circuit is configured to generate a compensation signal in response to the feedback signal, and add the compensation signal to the filtered analog IEGM signal.

[0014] Furthermore, according to one embodiment of the present disclosure, the compensation circuit is configured to generate the compensation signal based on changing the phase of the feedback signal to be 180 degrees out of phase.

[0015] Further in accordance with one embodiment of the present disclosure, the signal processing circuit includes: an analog-to-digital converter, which is coupled to receive an IEGM signal from at least one electrode as an input analog IEGM signal and is configured to convert the input analog IEGM signal into a digital IEGM signal; a digital signal filtering device, which is coupled to receive the digital IEGM signal and is configured to filter noise from the received digital IEGM signal; a compensation circuit, which is coupled to receive the filtered digital IEGM signal and a feedback signal; a feedback circuit, which includes an electrical connection extending from a cable (running) back to the compensation circuit, and the compensation circuit is configured to at least partially compensate for electrical noise that is not in the digital IEGM signal but will be added to the cable in response to the feedback signal, thereby generating a noise-compensated digital IEGM signal; and a digital-to-analog converter, which is coupled to receive the noise-compensated digital IEGM signal and is configured to convert the noise-compensated digital IEGM signal into a noise-compensated analog IEGM signal for output to a recording device via the cable.

[0016] Still further in accordance with an embodiment of the present disclosure, the compensation circuit is configured to generate a compensation signal in response to the feedback signal, and add the compensation signal to the filtered digital IEGM signal.

[0017] In addition, according to one embodiment of the present disclosure, the compensation circuit is configured to transform a time window of a feedback signal into a frequency domain, analyze the transformed time window for the presence of at least one frequency associated with electrical noise, and generate a compensation signal in response to a transformed time window in which at least one frequency associated with electrical noise exists in the transformed time window.

[0018] Furthermore, according to one embodiment of the present disclosure, the compensator circuit is configured to transform a transform time window into a time domain signal, and generate a compensation signal based on changing a phase of the time domain signal to be 180 degrees out of phase.

[0019] According to another embodiment of the present disclosure, a method for measuring electrical activity is also provided, the method comprising receiving an intracardiac electrogram (IEGM) signal from at least one electrode of a catheter configured to be inserted into a body part of a living subject, processing the IEGM signal for output to a recording device via a cable that picks up ambient electrical noise, receiving at least some of the electrical noise picked up by the cable, providing a feedback signal indicative of the received electrical noise, and in response to the feedback signal at least partially compensating for electrical noise that is not yet in the IEGM signal but will be added to the IEGM signal in the cable, thereby generating a noise-compensated IEGM signal for output to the recording device via the cable.

[0020] Further in accordance with one embodiment of the present disclosure, the method includes sensing at least some of the electrical noise picked up by the cable, receiving an IEGM signal from at least one electrode as an input analog IEGM signal, converting the input analog IEGM signal to a digital IEGM signal, filtering noise from the digital IEGM signal, converting the filtered digital IEGM signal to a filtered analog IEGM signal, and in response to a feedback signal at least partially compensating for electrical noise that is not in the filtered analog IEGM signal but will be added to the cable, thereby generating a noise compensated analog IEGM signal for output to a recording device via the cable.

[0021] Still further in accordance with an embodiment of the present disclosure, the method includes generating a compensation signal in response to the feedback signal, and adding the compensation signal to the filtered analog IEGM signal.

[0022] Additionally, according to an embodiment of the present disclosure, generating includes generating the compensation signal based on changing the phase of the feedback signal to be 180 degrees out of phase.

[0023] In addition, according to one embodiment of the present disclosure, the method includes receiving an IEGM signal from at least one electrode as an input analog IEGM signal, converting the input analog IEGM signal into a digital IEGM signal, filtering noise from the received digital IEGM signal, at least partially compensating for electrical noise that is not in the digital IEGM signal but will be added to the cable in response to a feedback signal, thereby generating a noise-compensated digital IEGM signal, and converting the noise-compensated digital IEGM signal into a noise-compensated analog IEGM signal for output to a recording device via a cable.

[0024] Further in accordance with an embodiment of the present disclosure, the method includes generating a compensation signal in response to the feedback signal, and adding the compensation signal to the filtered digital IEGM signal.

[0025] Further according to one embodiment of the present disclosure, the method includes transforming a time window of the feedback signal into the frequency domain, analyzing the transformed time window for the presence of at least one frequency associated with electrical noise, and wherein generating includes generating a compensation signal in response to the presence of at least one frequency associated with electrical noise in the transformed time window.

[0026] Additionally, according to an embodiment of the present disclosure, the method includes transforming a transform time window into a time domain signal, wherein generating includes generating a compensation signal based on changing a phase of the time domain signal to be 180 degrees out of phase. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The present invention will be understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

[0028] Figure 1 is a partially schematic, partially block diagram illustration of an electrical activity measurement device constructed and operative in accordance with an embodiment of the present invention;

[0029] Figure 2 For use Figure 1 A schematic diagram of a catheter in a device;

[0030] Figure 3 is a schematic diagram of an electrical activity measurement system connected to a recording device according to an embodiment of the present invention;

[0031] Figure 4 To include Figure 3 A flowchart of the steps in the method of operation of the system;

[0032] Figure 5 To include in Figure 3 A view of a circuit in a compensation circuit of a system;

[0033] Figure 6 is a schematic diagram of an electrical activity measurement system connected to a recording device according to an alternative embodiment of the present invention;

[0034] Figure 7 To include Figure 6 A flowchart of the steps in the method of operation of the system;

[0035] Figure 8 and Fig. 9 To show Figure 7 a view of the electrical signal of the method; and

[0036] Fig.10 To include Figure 7 A flowchart of sub-steps of a step within a method step. DETAILED DESCRIPTION

[0037] Overview

[0038] As used herein, the term "about" or "approximately" for any numerical value or range indicates a suitable dimensional tolerance that allows a collection of parts or elements to achieve its intended purpose as described herein. More specifically, "about" or "approximately" can refer to a range of values ​​± 20% of the recited value, for example, "about 90%" can refer to a range of values ​​from 71% to 99%. In addition, as used herein, the terms "patient", "host", "user", and "subject" refer to any human or animal subject, and are not intended to limit systems or methods to human use, but the use of the subject invention in human patients represents a preferred embodiment.

[0039] As mentioned previously, during a cardiac electrophysiology (EP) study or ablation procedure, the patient is physically connected to the electrical system used for the procedure, such as The leads between the Carto system (Biosense Webster, Inc., of Irvine CA) and / or the external recording system can pick up noise. Even in the case where the noise comes from a known device, it may be difficult or even impossible to remove the device. For example, the Carto system can use an external uninterruptible power supply (UPS) that cannot be removed but generates electrical noise. The Carto system typically uses filtering techniques to clean the signal of noise. However, the signal recorded by the external recording system can be very noisy, which can be a significant problem due to the very small voltages associated with the electrophysiological signals.

[0040] Embodiments of the present invention reduce problems associated with electrical noise pickup in the cable between the catheter and a recording system by routing intracardiac electrogram (IEGM) signals captured by the catheter through a signal processing circuit (e.g., as part of a Carto system) that compensates for expected noise pickup before outputting the IEGM signals to an external recording system.

[0041] The catheter is connected to the signal processing circuit via a first cable and then connected to an external recording system using a second cable from the signal processing circuit. The signal processing circuit typically receives the IEGM signal as an analog signal via the first cable and then converts the analog signal into a digital signal by the signal processing circuit. At this stage, the signal processing circuit can filter the noise picked up in the first cable from the digital signal using any suitable digital filtering technique. The digital filtering can focus on removing signal components associated with electrical noise generated by surrounding electrical equipment, which is typically based on frequencies of about 50 Hz and possible harmonic frequencies of 100 Hz and 150 Hz, etc. At a later stage, the digital signal is converted back to an analog signal by the signal processing circuit for output to an external recording system via the second cable.

[0042] Electrical noise may also be picked up in the second cable. The external recording system is typically an analog device without noise filtering capabilities and therefore cannot filter noise from the received IEGM signal via the second cable. Therefore, the signal processing circuit compensates for this expected noise that is not yet in the IEGM signal (while the IEGM signal is in the signal processing circuit) but will be added to the IEGM signal of the second cable. In some embodiments, a sensor disposed near the second cable senses at least some of the electrical noise picked up by the second cable, and a feedback signal indicating the sensed electrical noise is provided to the signal processing circuit. In other embodiments, the electrical connector feeds back the signal in the cable to the signal processing circuit. In both embodiments, the signal processing circuit at least partially compensates for the electrical noise of the IEGM signal that is not yet in the IEGM signal but will be added to the IEGM signal in the second cable in response to the feedback signal, thereby generating a noise-compensated IEGM signal for output to the recording device via the second cable.

[0043] In some implementations, compensation for expected noise is performed when the IEGM signal is in analog form.

[0044] System Description

[0045] Documents incorporated herein by reference shall be considered to be an integral part of this application, except that, to the extent that any term is defined in these incorporated documents in a manner that contradicts a definition explicitly or implicitly made in this specification, only the definition in this specification shall prevail.

[0046] Reference now Figure 1 and Figure 2 . Figure 1 2 is a partially schematic, partially block diagram illustration of an electrical activity measurement device 12 constructed and operative in accordance with an embodiment of the present invention. Figure 2 For use Figure 1 Schematic diagram of a catheter 20 in a device 12 of a human patient 18. The catheter 20 has a distal end 22 and is configured to be inserted into a body part (e.g., a heart) of a living subject. The procedure is performed by a physician 14, and in the following description, it is assumed that the procedure includes a mapping procedure and / or ablation of a portion of tissue 15 of a myocardium 16 of a heart of a human patient 18.

[0047] To perform the procedure, the physician 14 inserts the catheter 20 into a sheath 21 that has been pre-positioned in the lumen of the patient 18, so that the catheter 20 is inserted into a chamber of the heart. The sheath 21 is positioned so that the distal end 22 of the catheter 20 enters the heart of the patient 18. The distal end 22 includes a position sensor 24 that enables the position and orientation of the distal end 22 to be tracked, a force sensor 26 that measures the force applied by the distal end 22 when contacting the myocardium 16, and one or more temperature sensors 28 that measure the temperature at the corresponding position of the distal end 22. The distal end 22 also includes one or more electrodes 30 for applying radiofrequency power to the myocardium 16 in the chamber so as to ablate the myocardium 16. The electrodes 30 can also be used to collect electrical potentials from the myocardium 16.

[0048] The device 12 is controlled by a system processor 46, which is located in an operating console 48 of the device. The operating console 48 includes controls for at least one user input device 49 used by the physician 14 to communicate with the processor 46. Software for the processor 46 may be downloaded to the processor 46 in electronic form, for example, over a network. Alternatively or in addition, the software may be provided via non-transitory tangible media such as optical, magnetic or electronic storage media.

[0049] The processor 46 may include a digital signal filtering device 45, which is typically configured as a field programmable gate array (FPGA), and an analog-to-digital (A / D) converter integrated circuit 47. The processor 46 may pass signals from the A / D converter 47 to another processor and / or may be programmed to execute at least one algorithm disclosed herein, which includes the steps described below. The processor 46 uses the features of the digital signal filtering device 45 and the A / D converter 47 and the modules described in more detail below to execute the algorithm.

[0050] To operate the device 12, the algorithm of the processor 46 communicates with a module library 50 having a plurality of modules used by the processor 46 to operate the device 12. Thus, the module library 50 includes an electrocardiogram (ECG) module 56 coupled to receive signals from the body surface electrodes 31 and / or electrodes 30 so as to provide ECG signals to the processor 46. The body surface electrodes 31 and / or electrodes 30 are configured to be applied to the body of a subject (e.g., patient 18) and are configured to output signals in response to the electrical activity of the heart of the subject. The electrodes 30 are applied to the heart of the body via the catheter 20. The module library 50 also includes a tracking module 58 that receives and analyzes signals from the position sensor 24 and utilizes the signal analysis to generate the position and orientation of the distal end 22. In some embodiments, the position sensor 24 includes one or more coils that provide sensor signals in response to a magnetic field passing through the coils. In these embodiments, in addition to receiving and analyzing signals from the sensor 24, the tracking module 58 also controls the radiators 32, 34 and 36 that radiate the magnetic field that passes through the position sensor 24. The radiators 32, 34, 36 are positioned close to the myocardium 16 and are configured to radiate the alternating magnetic field into the area close to the myocardium 16. A plurality of wire connections 35 connect the operating console 48 with the surface electrodes 31 and other components (such as the radiators 32, 34, 36 and the sensor 24) so ​​that the tracking module 58 can measure the position and orientation coordinates of the catheter 20. In some embodiments, the tracking module 58 is configured to calculate the relative position and relative orientation of the catheter 20 relative to the heart. Magnetic position and orientation tracking is described in U.S. Patents 7,756,576 and 7,536,218, which are hereby incorporated by reference. The Carto system manufactured by Biosense Webster (33 Technology Drive, Irvine, CA 92618 USA) uses such a magnetic tracking system. Tracking module 58 is not limited to using magnetic-based position and orientation tracking. Any suitable position and orientation tracking may be used, such as impedance-based or image-based tracking.

[0051] The device 12 may receive image data from an external imaging modality (such as an MRI unit, a CT unit, etc.) and include an image processor that may be incorporated into or called by the processor 46 to generate and display images. The image data may be registered with the tracking module 58, and a user interface screen 70 combining the received data with the position of the probe 20 may be displayed to the physician 14 on the display 61. For example, the trajectory of the distal end 22 of the catheter 20 may be shown on a three-dimensional (3D) representation of the heart of the patient 18 displayed on the display 61. In some embodiments, the 3D representation of the heart may be calculated at least in part based on the mapping performed by the catheter 20.

[0052] Electrode 30 and body surface electrode 31 may be used to measure tissue impedance at the ablation site as taught in US Pat. No. 7,536,218 to Govari et al., which is incorporated herein by reference.

[0053] The module library 50 also includes a force module 60, a power module 62, a flushing module 64, and a temperature module 66. The functions of these modules are explained below. The modules in the module library 50 and the processor 46 are referred to herein as processing circuitry 51.

[0054] The force module 60 receives the signal from the force sensor 26 and generates, based on the signal, a magnitude of the contact force applied by the distal end 22 on the tissue 15 (herein assumed to be measured in grams). In some embodiments, the force sensor 26 is configured so that the signal it provides to the force module 60 enables the force module 60 to assess the direction of the force applied by the distal end 22 on the tissue 15.

[0055] The power module 62 includes a radio frequency (RF) signal generator 63 that generates the radio frequency power applied by the electrodes 30 to ablate the tissue 15 of the myocardium 16. The processor 46 and the power module 62 are capable of regulating the power level delivered by the electrodes 30 (herein assumed to be measured in watts) and the length of time during which the power is delivered (measured in seconds).

[0056] The irrigation module 64 controls the flow rate (herein assumed to be measured in mL / min) of the irrigation fluid (typically saline) provided to the distal end 22 by the pump 65 disposed in the operating console 48. The catheter 20 includes an irrigation channel through which the myocardium 16 is irrigated. The irrigation fluid is discharged from the irrigation hole 69 in the distal end 22. The pump 65 is configured to selectively pump the irrigation fluid into the irrigation channel at an idle rate and one or more non-idle rates (higher than the idle rate) according to the state of the ablation procedure.

[0057] The temperature module 66 receives a temperature signal provided by the temperature sensor 28 (or by each temperature sensor 28). The temperature signal indicates the temperature of the myocardium at a plurality of different times. The temperature module 66 determines the temperature recorded by each of the sensors 28. Typically, where there are multiple sensors 28, the temperature module 66 determines an average temperature of the distal end 22. Additionally, where there are multiple sensors, the temperature module 66 may generate a map of the temperature distribution of the distal end 22.

[0058] In some embodiments, the catheter 20 may include any suitable catheter, such as, but not limited to, a focal catheter, a fancy catheter with several deflectable arms, a balloon catheter, a lasso catheter, or a basket catheter. The catheter may include an electrode 30 for collecting electrical potentials, but may exclude or include one or more of the following: a force sensor; a temperature sensor; and an irrigation channel.

[0059] Reference now Figure 3 and Figure 4 . Figure 3 is a schematic diagram of an electrical activity measurement system 120 connected to a recording device 82 according to an embodiment of the present invention. Figure 4 To include Figure 3 Flowchart 130 of steps in a method of operation of system 120.

[0060] The electrical activity measurement system 120 includes Figure 1 The electrical activity measurement system 120 further includes a compensation circuit 122 and a digital-to-analog (D / A) converter 84. The digital signal filtering device 45, the A / D converter 47, the compensation circuit 122, and the D / A converter 84 are collectively referred to herein as a signal processing circuit 86. The electrical activity measurement system 120 further includes a feedback circuit 85, which includes a sensor 88 and a cable 87, which electrically connects the sensor 88 to the compensation circuit 122. By way of example only, the sensor 88 may include an antenna or a coil. The sensor 88 provides a feedback signal to the analog compensation circuit 122.

[0061] Signal processing circuit 86 is coupled to catheter 20 ( Figure 2 ) of the electrode 30( Figure 2 ), and is configured to be from electrode 30 ( Figure 2 ) receives one or more intracardiac electrogram (IEGM) signals 125 and processes the IEGM signals 125 for output to a recording device 82 via a cable 90 that picks up ambient electrical noise 92. The catheter 20 may also pick up ambient electrical noise 94, which may be identified and filtered by a digital signal filtering device 45, as described in more detail below.

[0062] The sensor 88 of the feedback circuit 85 is configured to sense and thereby receive at least some of the electrical noise 92 picked up by the cable 90, and to provide a feedback signal indicative of the sensed (and received) electrical noise to the compensation circuit 122. The compensation circuit 122 is configured to at least partially compensate for the electrical noise 92 that is not already in the IEGM signal but will be added to the IEGM signal in the cable 90 in response to the feedback signal, thereby generating a noise-compensated IEGM signal for output to the recording device 82 via the cable 90.

[0063] Compensation for electrical noise 92 may be performed by adding a compensation signal having the same frequency and amplitude as the feedback signal and generated to interfere with the electrical noise so as to cancel the electrical noise added to the IEGM signal of cable 90. The compensation signal may be based on changing the phase of the feedback signal to be 180 degrees out of phase. The electrical activity measurement system 120 is now described in more detail.

[0064] A / D converter 47 is coupled to receive the data from electrode 30 ( Figure 2 ) receives the IEGM signal 125 as an input analog IEGM signal (block 132) and is configured to convert the input analog IEGM signal into a digital IEGM signal (block 134).

[0065] The digital signal filtering device 45 is coupled to receive the digital IEGM signal and is configured to filter noise from the received digital IEGM signal (block 136). The digital signal filtering device 45 may include various filtering circuits, such as, but not limited to, a low pass filter 96 for removing signals having frequencies above a threshold frequency (e.g., 60 Hz or 100 Hz), and / or a band stop filter 98 for removing signals having frequencies within a certain frequency range (e.g., 100 Hz-200 Hz). The IEGM signal may include frequencies similar to noise, such as in the 50 Hz range, and thus simply filtering out the 50 Hz component using a low pass or band stop filter may not produce acceptable results. Therefore, other filtering methods may also be applied to remove noise associated with external sources without adversely affecting the IEGM signal. Such methods refer to Figures 8 to 10 47. At least some of the functions of the digital signal filtering device 45 and / or the A / D converter 47 may be performed by one or more computers or processors executing software. The software may be downloaded to the computer or processor in electronic form, for example, over a network. Alternatively or in addition, the software may be provided via non-transitory tangible media such as optical, magnetic or electronic storage media.

[0066] The D / A converter 84 is coupled to receive the filtered digital IEGM signal and is configured to convert the filtered digital IEGM signal to a filtered analog IEGM signal (block 138 ).

[0067] The compensation circuit 122 is coupled to receive the feedback signal (from the sensor 88) and the filtered analog IEGM signal (from the D / A converter 84). The compensation circuit 122 is configured to at least partially compensate for electrical noise that is not in the filtered analog IEGM signal but would be added to the cable 90 in response to the feedback signal (block 140), thereby generating a noise compensated analog IEGM signal for output to the recording device 82 via the cable 90.

[0068] In some embodiments, the compensation circuit 122 may be configured to generate a compensation signal (block 142) in response to the feedback signal, the compensation signal having the same frequency and amplitude as the feedback signal and being generated to interfere with the electrical noise so as to cancel the electrical noise added to the IEGM signal of the cable 90. In some embodiments, the compensation circuit 122 is configured to generate the compensation signal based on changing the phase of the feedback signal to be 180 degrees out of phase. The compensation circuit 122 is configured to add the compensation signal to the filtered analog IEGM signal (block 144), thereby generating a noise compensated analog IEGM signal for output to the recording device 82 via the cable 90.

[0069] Reference now Figure 5 , which is included in Figure 3 1 is a diagram of a circuit 124 in a compensation circuit 122 of a system 120.

[0070] Circuit 124 has two inputs (input 1 and input 2) and one output. Input 1 (box 129) takes the feedback signal from sensor 88 as input. Input 2 is usually a constant DC voltage input (box 127). Gain control is controlled by controlling the resistance K of variable resistor 126. The variable resistor can be manually controlled by a user who is viewing the signal on a monitor (not shown) of recording device 82 to minimize the noise shown in the signal shown on the monitor. This adjustment is usually performed once at the beginning of a medical procedure. The output provides a compensation signal with an amplitude equal to input 1 minus (input 2 / K). The variable resistor can be set by the user viewing the signal received at the recording device 82 via an oscilloscope and adjusting the gain until the noise is minimized.

[0071] Reference now Figure 6 and Figure 7 . Figure 6 is a schematic diagram of an electrical activity measurement system 150 connected to a recording device 82 according to an alternative embodiment of the present invention. Figure 7 To include Figure 6 Flowchart 200 of steps in a method of operation of system 150.

[0072] The electrical activity measurement system 150 includes Figure 1The electrical activity measurement system 150 further includes a compensation circuit 152 and a digital-to-analog (D / A) converter 154. In some embodiments, the compensation circuit 152 and / or the D / A converter 154 may be disposed in the operating console 48. The digital signal filtering device 45, the A / D converter 47, the compensation circuit 152, and the D / A converter 154 are collectively referred to herein as a signal processing circuit 156. The electrical activity measurement system 150 further includes a feedback circuit 158, which includes an electrical connection 160 extending from a cable 90 back to the compensation circuit 152. The cable 90 connects the D / A converter 154 to the recording device 82.

[0073] Signal processing circuit 156 is coupled to catheter 20 ( Figure 2 ) of the electrode 30( Figure 2 ), and is configured to be from electrode 30 ( Figure 2 ) receives one or more intracardiac electrogram (IEGM) signals 125 and processes the IEGM signals 125 for output to a recording device 82 via a cable 90 that picks up ambient electrical noise 92. The catheter 20 may also pick up ambient electrical noise 94, which may be identified and filtered by a digital signal filtering device 45, as described in more detail below.

[0074] The electrical connection 160 of the feedback circuit 85 is configured to receive at least some of the electrical noise 92 picked up by the cable 90 and to provide a feedback signal indicative of the received electrical noise to the compensation circuit 152. The electrical connection 160 may be connected to any suitable point along the cable 90, as the electrical noise 92 is generally picked up by the signal along the length of the cable 90. The compensation circuit 152 is configured to at least partially compensate for the electrical noise 92 that is not already in the IEGM signal but will be added to the IEGM signal in the cable 90 in response to the feedback signal, thereby generating a noise compensated IEGM signal for output to the recording device 82 via the cable 90.

[0075] Compensation for the electrical noise 92 may be performed by adding a compensation signal having the same frequency and amplitude as the noise in the feedback signal and generated to interfere with the electrical noise so as to cancel the electrical noise added to the IEGM signal of the cable 90. Generation of the compensation signal Figures 8 to 10 The electrical activity measurement system 120 is now described in more detail.

[0076] A / D converter 47 is coupled to receive the data from electrode 30 ( Figure 2) receives the IEGM signal 125 as an input analog IEGM signal (block 202). The A / D converter 47 is configured to convert the input analog IEGM signal into a digital IEGM signal (block 204).

[0077] The digital signal filtering device 45 is coupled to receive the digital IEGM signal and is configured to filter noise from the received digital IEGM signal (block 206). The digital signal filtering device 45 may include various filtering circuits, such as, but not limited to, a low pass filter 96 for removing signals having frequencies above a threshold frequency (e.g., 100 Hz), and / or a band stop filter 98 for removing signals having frequencies within a certain frequency range (e.g., 100 Hz-200 Hz). The IEGM signal may include frequencies similar to noise, such as in the 50 Hz range, and thus simply filtering out the 50 Hz component using a low pass or band stop filter may not produce acceptable results. Therefore, other filtering methods may also be applied to remove noise associated with external sources without adversely affecting the IEGM signal. Such methods refer to Figures 8 to 10 Described in more detail.

[0078] The compensation circuit 152 is coupled to receive the filtered digital IEGM signal (from the digital signal filtering device 45) and the feedback signal (via the electrical connection 160 from the cable 90). The compensation circuit 152 is configured to at least partially compensate for electrical noise that is not in the digital IEGM signal but would be added to the cable 90 in response to the feedback signal (block 208), thereby generating a noise compensated digital IEGM signal. The steps of block 208 refer to Figures 8 to 10 Described in more detail.

[0079] At least some of the functions of the digital signal filtering device 45 and / or the A / D converter 47 and / or the compensation circuit 152 may be performed by one or more computers or processors executing software. The software may be downloaded to the computer or processor in electronic form, for example, over a network. Alternatively or in addition, the software may be provided via non-transitory tangible media such as optical, magnetic or electronic storage media.

[0080] The D / A converter 154 is coupled to receive the noise compensated digital IEGM signal from the compensation circuit 152 and is configured to convert the noise compensated digital IEGM signal to a noise compensated analog IEGM signal for output to the recording device 82 via the cable 90 (block 210).

[0081] See now Figure 8 and Fig. 9 , which shows Figure 7 A view of the electrical signal of the method. Figure 8A noise-free IEGM signal 212 and a noise IEGM signal 214 are shown. The noise in the noise IEGM signal 214 may have any one or more frequencies. In some cases, the noise IEGM signal 214 may include 50 Hz noise from surrounding electrical appliances, and harmonics associated with the noise from surrounding electrical appliances, such as 100 Hz and 150 Hz. However, due to the presence of the electrode 30 ( Figure 2 ) The IEGM signal detected by electrode 30 may include frequencies similar to noise, for example, in the 50 Hz range, and simply filtering out the 50 Hz component using a low-pass or band-stop filter may also destroy some of the IEGM signals detected by electrode 30.

[0082] Figure 8 The time window 216 showing the noise-free IEGM signal 212 is flat and does not have any amplitude associated with the IEGM signal detected by the electrode 30. In the same time window 216, the noisy IEGM signal 214 includes noise, which can be assumed to correspond to isolated noise.

[0083] Above Fig. 9 2, which shows two time windows of the selected noisy IEGM signal 214. A portion of the noisy IEGM signal 214 in the first time window 218 is transformed using a suitable transform such as a discrete Fourier transform (DFT) from the time domain to the frequency domain. The result of the transform is shown in a graph 220, which shows that the portion of the noisy IEGM signal 214 in the first time window 218 includes components of 50 Hz, 100 Hz, 150 Hz, and many other frequency components. It can therefore be inferred that the portion of the noisy IEGM signal 214 in the first time window 218 includes noise as well as the noise generated by the electrode 30 ( Figure 2 ) detected IEGM signal.

[0084] The portion of the noisy IEGM signal 214 in the second time window 222 is transformed using any suitable transform such as a discrete Fourier transform (DFT) from the time domain to the frequency domain. The result of the transform is shown in a graph 224, which shows that the portion of the noisy IEGM signal 214 in the second time window 222 only includes frequency components of 50 Hz, 100 Hz, and 150 Hz. It can therefore be inferred that the portion of the noisy IEGM signal 214 in the second time window 222 only includes noise and does not include the frequency components generated by the electrode 30 ( Figure 2) detected IEGM signal. The portion of the noisy IEGM signal 214 in the second time window 222 can then be transformed from the frequency domain back to the time domain using any suitable transform (e.g., using an inverse DFT). The time domain signal can then be used to generate a compensation signal based on changing the phase of the time domain signal to be 180 degrees out of phase. The compensation signal can then be added to the filtered digital IEGM signal, as referenced Fig.10 Describe in more detail.

[0085] Since the electrode 30 ( Figure 2 ) is generally not obvious from the noisy IEGM signal 214, so different time windows of the noisy IEGM signal 214 are analyzed using the above method to determine which time windows do not include the IEGM signal detected by the electrode 30. In some embodiments, many time windows of the noisy IEGM signal 214 may include some frequencies other than noise (e.g., other than the 50 Hz component and its harmonics), and the system may select a time window that includes some frequencies other than noise to form the basis of a compensation signal if the magnitude of the frequencies other than noise is below a given threshold.

[0086] See now Fig.10 , the figure includes Figure 7 208 of the method of FIG. 200 . The compensation circuit 152 is configured to transform the time window of the feedback signal into the frequency domain (block 226), for example using a DFT. The step size between the time windows and the size of the time windows may be set to any suitable value. In some embodiments, by way of example only, the step size between the time windows may be in the range of 0.1 seconds to 0.4 seconds, and the size of the time window may be in the range of 0.1 seconds to 0.5 seconds.

[0087] The compensation circuit 152 is configured to analyze the transformed time window of the feedback signal for at least one frequency associated with electrical noise (block 228) without being associated with the electrical noise as determined by the electrode 30 ( Figure 2 ) or has a frequency associated with an IEGM signal detected by electrode 30 but below a given threshold magnitude. Compensation circuit 152 selects one of the transformed time windows that does not have a frequency associated with an IEGM signal detected by electrode 30 ( Figure 2 ) or has a frequency associated with an IEGM signal detected by electrode 30 but below a given threshold magnitude. Compensation circuit 152 is configured to transform the selected transformed time window of the feedback signal into a time domain signal, for example using an inverse DFT (block 230).

[0088] The compensation circuit 152 is configured to generate a compensation signal in response to the time domain signal (block 232), the time domain signal being based on transforming a selected transform time window (of the feedback signal) in which at least one frequency associated with electrical noise of the feedback signal is present (without other frequencies or with other frequencies but below a given threshold). In some embodiments, the compensation circuit 152 is configured to generate the compensation signal based on changing the phase of the time domain signal to be 180 degrees out of phase. The compensation circuit 152 is configured to add the compensation signal to the filtered digital IEGM signal (block 234).

[0089] Since the feedback signal may vary continuously, the compensation signal may be generated from the feedback signal repeatedly, for example but not limited to once every second or every two seconds.

[0090] See again Figure 3 and Figure 5 . It has been previously mentioned that the electrical activity measurement system 120 uses circuit 124 as part of the compensation circuit 122, and the gain control of circuit 124 can be controlled by manually controlling the resistance K of the variable resistor 126. In other embodiments, the gain control of circuit 124 can be automatically controlled by the digital signal filtering device 45 using a signal from the digital signal filtering device 45 to adjust the variable resistor 126. The digital signal filtering device 45 can calculate the gain control for setting the variable resistor 126 as follows. The gain control is the ratio of the electrical noise 92 included in the signal in the cable 90 to the electrical noise 92 sensed by the sensor 88. The electrical noise 92 included in the signal in the cable 90 can be determined by using an electrical connection from the cable 90 to the digital signal filtering device 45, where the gain control is automatically controlled in a "flat area" of the IEGM signal, such as the time window 216 ( Figure 8 ) in the measurement signal. The “flat region” can be referred to as Figure 8 and Fig. 9 The method described is determined by acquiring various time windows of the signal and analyzing the frequency components of the time windows until a "flat area" is identified. The electrical noise 92 sensed by the sensor 88 can be determined by using an electrical connection from the sensor 88 to a digital signal filtering device 45, which measures the noise level in the signal received from the sensor 88. The calculation of the gain ratio and the setting of the variable resistor 126 can be performed at the beginning of the medical procedure or at any suitable time.

[0091] For the sake of clarity, various features of the present invention described in the context of independent embodiments may also be provided in combination in a single embodiment. Conversely, for the sake of simplicity, various features of the present invention are described in the context of a single embodiment and may also be provided separately or in any suitable sub-combination.

[0092] The above embodiments are cited by way of example, and the present invention is not limited by what is specifically shown and described above. On the contrary, the scope of the present invention includes combinations and sub-combinations of the various features described above, as well as variations and modifications thereof, which should occur to those skilled in the art when reading the above description, and which are not disclosed in the prior art.

Claims

1. An electrical activity measurement system, comprising: a catheter configured to be inserted into a body part of a living subject and comprising a distal end including at least one electrode; a signal processing circuit coupled to the at least one electrode and configured to receive an intracardiac electrogram (IEGM) signal from the at least one electrode and process the intracardiac electrogram (IEGM) signal for output to a recording device via a cable that picks up ambient electrical noise; and A feedback circuit configured to: receive at least some of the electrical noise picked up by the cable; and provide a feedback signal indicative of the received electrical noise to the signal processing circuit, the signal processing circuit configured to compensate at least partially for the electrical noise that is not yet in the intracardiac electrogram (IEGM) signal but will be added to the intracardiac electrogram (IEGM) signal in response to the feedback signal, thereby generating a noise-compensated intracardiac electrogram (IEGM) signal for output to the recording device via the cable.

2. The system of claim 1, wherein: the feedback circuit comprising a sensor configured to sense the at least some of the electrical noise picked up by the cable; and The signal processing circuit comprises: an analog-to-digital converter coupled to receive the intracardiac electrogram (IEGM) signal from the at least one electrode as an input analog intracardiac electrogram (IEGM) signal and configured to convert the input analog intracardiac electrogram (IEGM) signal into a digital intracardiac electrogram (IEGM) signal; a digital signal filtering device coupled to receive the digital intracardiac electrogram (IEGM) signal and configured to filter noise from the received digital intracardiac electrogram (IEGM) signal; a digital-to-analog converter coupled to receive the filtered digital intracardiac electrogram (IEGM) signal and configured to convert the filtered digital intracardiac electrogram (IEGM) signal into a filtered analog intracardiac electrogram (IEGM) signal; and a compensation circuit coupled to receive the feedback signal and the filtered simulated intracardiac electrogram (IEGM) signal and configured to at least partially compensate for the electrical noise that is not in the filtered simulated intracardiac electrogram (IEGM) signal but would be added to the cable in response to the feedback signal, thereby generating a noise compensated simulated intracardiac electrogram (IEGM) signal for output to the recording device via the cable. The system of claim 2 , wherein the sensor comprises an antenna or a coil.

4. The system of claim 2, wherein the compensation circuit is configured to: generate a compensation signal in response to the feedback signal; and add the compensation signal to the filtered simulated intracardiac electrogram (IEGM) signal. 5 . The system of claim 4 , wherein the compensation circuit is configured to generate the compensation signal based on changing the phase of the feedback signal to be approximately 180 degrees out of phase.

6. The system of claim 1, wherein the signal processing circuit comprises: an analog-to-digital converter coupled to receive the intracardiac electrogram (IEGM) signal from the at least one electrode as an input analog intracardiac electrogram (IEGM) signal and configured to convert the input analog intracardiac electrogram (IEGM) signal into a digital intracardiac electrogram (IEGM) signal; a digital signal filtering device coupled to receive the digital intracardiac electrogram (IEGM) signal and configured to filter noise from the received digital intracardiac electrogram (IEGM) signal; a compensation circuit coupled to receive the filtered digital intracardiac electrogram (IEGM) signal and the feedback signal, the feedback circuit including an electrical connection extending from the cable back to the compensation circuit, the compensation circuit being configured to at least partially compensate for the electrical noise that is not in the digital intracardiac electrogram (IEGM) signal but would be added to the cable in response to the feedback signal, thereby producing a noise compensated digital intracardiac electrogram (IEGM) signal; and a digital-to-analog converter coupled to receive the noise compensated digital intracardiac electrogram (IEGM) signal and configured to convert the noise compensated digital intracardiac electrogram (IEGM) signal into a noise compensated analog intracardiac electrogram (IEGM) signal for output to the recording device via the cable.

7. The system of claim 6, wherein the compensation circuit is configured to: generate a compensation signal in response to the feedback signal; and add the compensation signal to the filtered digital intracardiac electrogram (IEGM) signal.

8. The system of claim 7, wherein the compensation circuit is configured to: transforming the time window of the feedback signal into the frequency domain; analyzing the transformed time window for the presence of at least one frequency associated with the electrical noise; and The compensation signal is generated in response to a transformed time window in which the at least one frequency associated with the electrical noise is present in the transformed time windows.

9. The system of claim 8, wherein the compensation circuit is configured to: transforming the one transform time window into a time domain signal; and The compensation signal is generated based on changing the phase of the time domain signal to be approximately 180 degrees out of phase.

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