Automatically switching patient-triggered and magnetic resonance compatible modes of an implantable cardiac electrical monitor system

Abstract

The application discloses an implantable electrocardio monitoring system capable of automatically switching patient trigger and magnetic resonance compatible mode, belongs to the technical field of medical devices, and uses a pulse driving current mirror mode to realize multi-stage detection of trigger magnetic field and MRI magnetic field; based on the multi-stage detection magnetic field result and the posture result, a magnetic resonance special monitoring mode is realized; based on the electrocardio signal collected by an electrocardio sensing module, magnetic resonance noise parameters and electrocardio reliability parameters are calculated, and when the signal is reliable, electrocardio segments, heart rate information or rhythm trend are recorded; according to the magnetic resonance signal interference response quantity collected, when the interference caused by the current scanning process to the implanted device exceeds the preset allowed range, warning information corresponding to the interference type and the interference degree is generated and sent to an external receiving device. In this way, the magnetic field source can be accurately distinguished, false positives and power waste caused by strong magnetic interference can be avoided, medical staff or magnetic resonance operators can be reminded to review the scanning conditions in time, and the device can be protected.

Description

Technical Field

[0001] This invention belongs to the field of medical device technology, specifically relating to an implantable electrocardiogram monitoring system that automatically switches between patient triggering and magnetic resonance compatible modes. Background Technology

[0002] Implantable cardiac monitoring systems (ICMs) are widely used for the monitoring and diagnosis of long-term arrhythmias. Existing systems typically include a patient trigger function, whereby a patient can trigger the system to record the current electrocardiogram by placing a small magnet at the implantation site on their chest when experiencing symptoms such as palpitations or syncope. Meanwhile, with the development of imaging technology, an increasing number of implanted patients require magnetic resonance imaging (MRI) scans.

[0003] The main shortcomings of existing technologies are: 1. Inability to accurately distinguish the source of the magnetic field: Most existing magnetic sensors are single-threshold detectors, making it difficult to distinguish between the weak magnetic field generated by a small magnet triggered by a patient's hand and the extremely strong static magnetic field generated by MRI equipment (such as 1.5T or 3.0T). This can easily lead to the system misidentifying the triggering event as a continuous patient event in the MRI environment, resulting in a large number of invalid records. 2. Strong magnetic interference causing false positives and wasted power: If silence protection or special anti-interference discrimination strategies for MRI are not adopted during MRI scanning, the strong electromagnetic noise generated by the radio frequency field and gradient magnetic field may be misidentified by the system as serious arrhythmias such as tachycardia or ventricular fibrillation. This not only consumes a lot of storage space and equipment power, but also places a great burden on doctors in subsequent data evaluation for false positive screening.

[0004] Patent application CN106110503A discloses an implantable medical device and a method for automatically switching MRI working modes, including the following steps: Step S11, detecting an external strong magnetic field and determining whether the external strong magnetic field is detected; if yes, proceed to step S12; if no, continue repeating step S11; Step S12, recording the time when the external strong magnetic field is detected and the state of the implanted device, marking it as being in a strong magnetic field environment, and proceeding to step S13; Step S13, switching to MRI mode, marking the MRI mode switching event, and proceeding to step S14; Step S14, determining whether the external strong magnetic field has disappeared; if yes, proceeding to step S15; if no, repeating step S14; Step S15, recording the time when the external strong magnetic field disappears and the state of the implanted device, marking it as leaving the strong magnetic field environment, and proceeding to step S16; and Step S16, switching to normal mode, marking the MRI mode switching event, and returning to step S11.

[0005] The existing technical solution can achieve simple switching between normal mode and MRI working mode, but it cannot accurately distinguish between the patient trigger magnetic field and the MRI magnetic field, and it has a strong exit mechanism for the MRI magnetic field, which is not conducive to patient monitoring. Summary of the Invention

[0006] In view of the above, the purpose of this invention is to provide an implantable electrocardiogram monitoring system that automatically switches between patient-triggered and magnetic resonance compatible modes, which can provide an automatic mode switching scheme based on multi-level magnetic field detection, patient posture recognition and programmable magnetic resonance mode configuration.

[0007] To achieve the above-mentioned objectives, an embodiment provides an implantable electrocardiogram (ECG) monitoring system that automatically switches between patient-triggered and MRI-compatible modes, characterized in that it includes: an ECG sensing module, a magnetic field detection module, an attitude detection module, a control module, a communication module, a clock / timing module, and a storage module; The magnetic field detection module uses a pulse-driven current mirror to achieve multi-level detection of the trigger magnetic field and the MRI magnetic field. The control module automatically switches between patient trigger mode and MRI-compatible mode based on the results of multi-level magnetic field detection or the results of posture detection by the posture detection module. The magnetic resonance compatible mode includes a special magnetic resonance monitoring mode: based on the electrocardiogram (ECG) signal collected by the ECG sensing module, the magnetic resonance noise parameters and ECG reliability parameters are calculated, and when the signal is deemed reliable, ECG segments, heart rate information, or rhythm trends are recorded; furthermore, based on the interference response of the collected magnetic resonance signal, when it is indirectly determined that the interference caused to the implanted device by the current scanning process exceeds the preset allowable range, a warning message corresponding to the type and degree of interference is generated and sent through the communication module to inform medical personnel or magnetic resonance operators of the current interference status and suggested handling measures, thereby realizing abnormal monitoring and safety warnings based on the interference response at the implanted device end.

[0008] Preferably, the pulse-driven current mirror method is based on an ultra-low power circuit including a pulse-driven current mirror, a dual-channel programmable DAC, and a dual-threshold comparator. It includes: synchronously driving the magnetoresistor and the dual-channel programmable DAC with pulse current to convert the resistance fluctuation caused by the change of external magnetic field into a sensing voltage, and comparing the sensing voltage with two independent and programmable reference voltages generated by the first DAC and the second DAC based on the pulse current in real time. Finally, the combination of logic levels output by the two threshold comparators is compared with the threshold to realize multi-level layered detection of the patient's trigger magnetic field and MRI magnetic field.

[0009] Preferably, the control module automatically switches the patient trigger mode based on the results of multi-level detection magnetic fields, including: When the detected magnetic field strength is higher than the patient trigger magnetic field strength threshold but lower than the MRI strength threshold, the system enters the patient trigger confirmation state. The control module controls the clock / timing module to start the patient trigger confirmation timing. If the detected magnetic field strength still meets the criteria of being higher than the patient trigger magnetic field strength threshold but lower than the MRI strength threshold after the timing period expires, the patient trigger process is initiated, and a patient trigger event is recorded. The ECG waveform, rhythm information, and trigger time of the previous period are stored together in the storage module. If the detected magnetic field strength does not meet the criteria of being higher than the patient trigger magnetic field strength threshold but lower than the MRI strength threshold after the timing period expires, the patient trigger confirmation fails, and the system switches to the non-patient trigger state without recording the patient trigger event.

[0010] Preferably, the control module automatically switches between magnetic resonance compatible modes based on multi-level detected magnetic field results and attitude results detected by the attitude detection module, including: When the patient is in a supine position and the magnetic field strength is higher than the MRI intensity threshold, the MRI will enter the confirmation state. If the magnetic field strength is still higher than the MRI intensity threshold and the patient is in a supine position when the confirmation time ends, the MRI will enter the MRI process state and enter the corresponding working mode according to the MRI mode configuration. Otherwise, it will switch to the non-MRI state. If, during MRI, the magnetic field strength is detected to be below the MRI exit threshold and the patient is not in a supine position, the MRI exit confirmation state is entered. If, at the end of the exit timer, the magnetic field strength is still below the MRI exit threshold and the patient is still not in a supine position, the MRI compatibility mode is exited, and the ECG sensing and automatic arrhythmia detection functions are restored.

[0011] Preferably, after entering the MRI state, the special MRI monitoring mode is confirmed according to the programmable MRI mode configuration. The ECG sensing module collects ECG signals in a conventional manner, while adding special MRI judgments during the collection process: analyzing the waveform morphology, frequency characteristics, amplitude characteristics, periodicity, saturation degree, noise envelope and / or spectral energy of the ECG signal, calculating MRI noise parameters to distinguish MRI noise signals generated during MRI scanning, calculating ECG reliability parameters and determining the ECG signal in the low-interference monitoring window by judging the reliability of the signal, and recording ECG segments, heart rate information or rhythm trends in the low-interference monitoring window.

[0012] Furthermore, the control module uses the differences between MRI scan noise and the patient's actual ECG signal in the time domain, frequency domain, and label consistency to make a distinction. MRI scan noise typically manifests as high-amplitude pulse trains that appear or disappear abruptly, saturated segments with sample values ​​close to the upper and lower limits of the analog-to-digital converter, large derivative jumps with significantly increased amplitude differences between adjacent sample points, stable periodic components or spectral peaks in non-electrophysiological frequency bands, and high coupling between sensing labels and high-amplitude spikes or saturated sample points. In contrast, the patient's actual ECG signal typically exhibits a relatively stable QRS morphology, RR interval variations within the physiological range, continuous cardiac cycle relationships, and repeatable morphological features between adjacent heartbeats. Based on these characteristics, the system can establish noise confidence and ECG reliability scores, and determine whether the current segment is scan noise, a low-interference monitorable segment, or an unreadable segment.

[0013] Preferably, the magnetic resonance compatible mode also includes a silent protection mode. If the silent protection mode is confirmed to be entered according to the programmable magnetic resonance mode configuration, the ECG sensing and automatic arrhythmia detection functions will be turned off, while the necessary magnetic field, posture, timing and communication monitoring will be retained.

[0014] Preferably, the magnetic resonance signal interference response includes one or more of the following: peak-to-peak value, saturation ratio, continuous saturation duration, large derivative jump ratio, window signal energy, pulse packet duration, pulse packet repetition interval, interference duty cycle, spectral main peak, non-ECG frequency band energy ratio, noise envelope period, and noise score.

[0015] Preferably, the method further includes: monitoring device status quantities; when the monitored device status quantities exceed a preset threshold, or multiple consecutive analysis windows meet the strong interference conditions, it is determined that the interference caused by the current magnetic resonance scanning process to the implanted device exceeds a preset safe or monitorable range, and a warning message corresponding to the type and degree of interference is generated. The device status parameters include device temperature, instantaneous battery voltage drop, prolonged saturation of the front-end amplifier, continuous full-amplitude state of the ADC, abnormal density of sensing markers, and the duration for which the output of the magnetic monitoring module is continuously higher than the magnetic resonance threshold.

[0016] Preferably, the warning information includes one or more of the following: interference level, interference type, out-of-limit parameter, out-of-limit duration, and recommended handling measures; the recommended handling measures include one or more of the following: recommending review or reduce radio frequency load, recommending review or reduce gradient load, recommending insert a scan interval or perform segmented scanning, recommending pausing the current scan or exiting the inspection.

[0017] Compared with the prior art, the beneficial effects of the present invention include at least the following: 1. Intelligent and seamless switching, reducing clinical intervention: Combining magnetic field strength and patient position (supine / non-supine) with a time window confirmation mechanism, it greatly improves the accuracy of entering and exiting MRI-compatible modes. Automatic switching of the implanted device's operating mode can be achieved without the need for physician intervention using programmed equipment.

[0018] 2. Configurable MRI-compatible mode, balancing safety and monitoring needs: After confirming entry into MRI mode, a silent protection mode or a special MRI monitoring mode can be selected according to the program settings. For ordinary patients or scenarios with low monitoring needs, the silent protection mode with sensing turned off can be used; for scenarios that require preserving the patient's ECG information as much as possible during the MRI examination or require monitoring of the scanning process, the special MRI monitoring mode can be used, thereby improving the clinical adaptability of the system.

[0019] 3. Effectively avoids false positives and improves diagnostic efficiency: In silent protection mode, the system actively shuts down the ECG sensing module and automatic arrhythmia detection function. This strategy cuts off the path where strong magnetic interference causes noise to be misjudged as abnormal ECG events, protecting the equipment circuitry and significantly reducing the burden on doctors to exclude invalid event records later. In special MRI monitoring mode, the system avoids directly storing MRI noise as arrhythmia events through signal reliability analysis, helping to reduce invalid events.

[0020] 4. Intermittent ECG monitoring during scanning enhances information retention: In special monitoring modes of MRI, the system attempts to distinguish between MRI scan noise signals and the patient's real ECG signals, recording valuable ECG fragments, heart rate information, or rhythm information during scan intervals, sequence switching intervals, or low-interference windows, so that the implantable device can still retain some clinically valuable information during MRI examinations.

[0021] 5. Repeatable noise feature identification reduces MRI spurious events: The system uses features such as saturation ratio, large derivative jump, non-ECG cycle frequency, pulse packet burst boundary, and R-mark coupling with noise peaks to identify pseudotachycardia or other pseudoarrhythmic events caused by MRI scan noise, which helps reduce the burden on doctors to screen for invalid events after MRI examination.

[0022] 6. Abnormal graded warning to improve the safety of MRI examination: The system can determine whether the interference caused to the implanted device during the current scanning process exceeds the preset allowable range based on the interference response characteristics collected by the implanted device itself under MRI conditions. When an abnormality occurs, the system will output warning information to the external receiving device through the communication module, so that medical staff or MRI operators can know the type of interference, the level of interference, the parameters exceeding the limit and the recommended handling measures. They can promptly review the scanning conditions and, if necessary, manually reduce the radio frequency load, reduce the gradient load, insert scanning intervals, perform segmented scanning, pause the scanning or exit the examination, thereby providing proactive safety warnings for the MRI scanning process.

[0023] 7. Ultra-low power consumption design to extend the life of implanted devices: The magnetic field detection adopts a pulse current mirror architecture for synchronous driving, avoiding continuous static current consumption; at the same time, in different magnetic resonance modes, the sensing function is turned off in the silent protection mode, and invalid event confirmation and interference fragment storage are suppressed in the special monitoring mode to optimize the overall power consumption of the device. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is a schematic diagram of the implantable electrocardiogram monitoring system with automatic switching between patient-triggered and magnetic resonance compatible modes provided in the embodiment. Figure 2 This is a schematic diagram of the circuit structure of the magnetic field detection module provided in the embodiment; Figure 3 This is a state transition diagram of the patient triggering mode provided in the embodiment; Figure 4 This is a state transition diagram of the magnetic resonance compatible mode provided in the embodiment; Figure 5 This is a flowchart illustrating the magnetic resonance imaging process during the implementation of the embodiment. Figure 6 This is a flowchart of the magnetic resonance interference anomaly classification warning provided in the embodiment. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not limit the scope of protection of this invention.

[0027] Existing technologies have the following limitations: Current implantable devices cannot automatically distinguish between trigger magnets and strong MRI magnetic fields; they cannot solve the cumbersome and easily overlooked clinical procedures caused by manually setting MRI modes; they cannot resolve the issue of electromagnetic noise in strong magnetic environments being misinterpreted as arrhythmia, leading to a large number of false positives and a sharp increase in power consumption; they cannot further address the problem that existing implantable devices typically cease sensing completely after entering MRI mode, making it impossible to acquire patient ECG information during scan intervals or low-interference windows; and they cannot simultaneously address the lack of implant-side monitoring and timely alerts for the actual interference response caused by the MRI scanning process to the implantable device.

[0028] To address the aforementioned issues, embodiments of the present invention provide an implantable electrocardiogram (ICM) monitoring system that automatically switches between patient-triggered and MRI-compatible modes. This system is applicable to the medical device field, particularly to implantable electrocardiogram monitors (ICMs), implantable pacemakers, implantable cardioverter defibrillators, and other active implantable devices that require consideration of patient subjective event marking, MRI scan compatibility, and MRI process monitoring.

[0029] like Figure 1 As shown, the implantable electrocardiogram (ECG) monitoring system of the present invention includes an ECG sensing module, a clock / timing module, a magnetic field detection module, an attitude detection module, a control module, a storage module, and a communication module. The ECG sensing module senses the patient's subcutaneous ECG waveform and rhythm information to form an ECG signal. The control module analyzes the patient's ECG state based on the ECG signal, detects arrhythmia events, and stores the corresponding ECG waveform, rhythm information, and event information in the storage module when an arrhythmia event is detected. The clock / timing module is responsible for timing and timer functions.

[0030] In this embodiment, the posture detection module is used to detect the patient's motion state and posture, where patient posture detection is divided into supine and non-suppressive states. In this invention, the posture detection module uses a low-power triaxial accelerometer, and its operation is as follows: the triaxial acceleration is processed into posture data, which is determined by the magnitude of the acceleration component of gravitational acceleration along the vertical axis of the human body. When the patient is stationary, they are only affected by gravitational acceleration; if they are moving, motion acceleration is superimposed. Therefore, only when the patient is stationary and in a supine position is the acceleration component along the vertical axis of the human body at its minimum of 0; otherwise, a motion acceleration component is superimposed for a non-stationary position, and a gravitational acceleration component is superimposed for a non-suppressive position. In this invention, the actual three-axis coordinate system of the accelerometer does not necessarily coincide perfectly with the ideal coordinate axes in reality. Considering that the device remains relatively constant with the human body after implantation, the three-axis coordinate system of the accelerometer can be regarded as the ideal coordinate system having undergone rotation. During the first programmed follow-up after the implantation surgery, the doctor sends a position calibration command through an external programmer. At this time, the patient remains upright and still. The control module collects the current three-axis acceleration data and calculates the transformation matrix, which is then stored in the storage module. After determining the transformation matrix, the control module transforms the collected three-axis acceleration values ​​according to the transformation matrix to detect and distinguish the patient's upright / lying posture.

[0031] In this embodiment, the magnetic field detection module uses a pulse-driven current mirror to achieve multi-level detection of the trigger magnetic field and the MRI magnetic field. For example... Figure 2 As shown, the pulse-driven current mirror method is based on an ultra-low-power circuit that includes a pulse-driven current mirror, a dual-channel programmable DAC (digital-to-analog converter), and dual threshold comparators. Specifically, the circuit synchronously drives the magnetoresistor and the dual-channel programmable DAC with a pulse current (I_sensor) to convert the resistance (R_sensor) fluctuation caused by changes in the external magnetic field into a sensing voltage (V_sensor). This voltage is then compared in real time with two independent and programmable reference voltages (Vth1, Vth2) generated by DAC1 and DAC2 based on the pulse current. Finally, the analog magnetic field strength is accurately converted into a digital signal by combining the logic levels output by the two threshold comparators. This enables precise multi-level layered detection of different magnetic field environments (patient-triggered magnetic field and MRI magnetic field). With extremely low static power consumption, the magnetic field environment can be reliably divided into multi-level layered states such as normal without triggering, patient-triggered, and MRI.

[0032] Specifically, the output of threshold comparator 1 corresponds to the detection of the patient-triggered magnetic field strength, and the output of threshold comparator 2 corresponds to the detection of MRI intensity. The control module detects the outputs of the two threshold comparators. When threshold comparator 1 outputs a low level, it confirms that the current device has detected a magnetic field strength lower than the patient-triggered magnetic field strength threshold, which is a normal state. When threshold comparator 1 outputs a high level and threshold comparator 2 outputs a low level, it confirms that the current device has detected a magnetic field strength higher than the patient-triggered magnetic field strength threshold but lower than the MRI intensity threshold, which is a trigger magnetic field state. When threshold comparator 2 outputs a high level, it confirms that the device has detected a magnetic field strength higher than the MRI intensity threshold, which is an MRI magnetic field state.

[0033] In this embodiment, the control module interacts with all modules to realize multiple functions of the implantable ECG monitoring system. For example... Figure 3 As shown, the control module can automatically switch patient trigger modes based on multi-level magnetic field detection results. For the patient trigger function, when the detected magnetic field strength is higher than the patient trigger magnetic field strength threshold but lower than the MRI strength threshold, it enters the patient trigger confirmation state. The control module controls the clock / timing module to start the patient trigger confirmation timing Ttrigger. After the patient trigger confirmation timing time expires, if the detected magnetic field strength still meets the requirement of being higher than the patient trigger magnetic field strength threshold but lower than the MRI strength threshold, the patient trigger process is initiated, and a patient trigger event is recorded, storing the ECG waveform, rhythm information, and trigger time of the previous period in the storage module. If, after the patient trigger confirmation timing time expires, the detected magnetic field strength does not meet the requirement of being higher than the patient trigger magnetic field strength threshold but lower than the MRI strength threshold, the patient trigger confirmation fails, and it switches to the non-patient trigger state without recording the patient trigger event. In this embodiment of the invention, the patient trigger confirmation timing duration is 2 seconds.

[0034] like Figure 4 As shown, the control module automatically switches between magnetic resonance compatible modes based on the results of multi-level magnetic field detection and the attitude detection results detected by the attitude detection module. In this invention, the states related to the magnetic resonance compatible mode include non-magnetic resonance state, magnetic resonance entry confirmation state, magnetic resonance in progress state, and magnetic resonance exit confirmation state.

[0035] In the non-MRI state, the system's related sensing and automatic arrhythmia detection functions operate in normal mode. If a magnetic field strength higher than the MRI intensity threshold is detected, and the patient is in a supine position, the system enters the MRI entry confirmation state and initiates the MRI entry confirmation timer Tmri_in. After the MRI confirmation timer expires, the system detects the magnetic field strength and the patient's posture. If the magnetic field strength is higher than the MRI intensity threshold and the patient is in a supine position, the system confirms entry into the MRI process and enters the corresponding working mode according to the MRI mode configuration; otherwise, the MRI entry confirmation fails, and the system transitions to the non-MRI state.

[0036] If, during MRI operation, a magnetic field strength below the MRI exit threshold is detected and the patient is not in a supine position, the system enters the MRI exit confirmation state and initiates the MRI exit confirmation timer Tmri_out. After the MRI exit confirmation timer expires, the magnetic field strength and patient posture are checked. If the magnetic field strength is below the MRI exit threshold and the patient is not in a supine position, the system confirms exit from MRI compatibility mode and restores ECG sensing and automatic arrhythmia detection functions. If, after the MRI exit confirmation timer expires, the magnetic field strength is not below the MRI exit threshold and the patient is not in a supine position, the MRI exit confirmation fails, and the system returns to the MRI operation state. In this embodiment of the invention, the MRI entry confirmation timer lasts 10 seconds, and the MRI exit confirmation timer lasts 1 minute.

[0037] After confirming entry into the MRI confirmation state, the control module reads the pre-saved MRI mode configuration from the storage module. This configuration can be set by the doctor, patient management device, or external programming device before the MRI examination, or it can be saved as the device's default parameters. Based on the MRI mode configuration, the control module selects to enter either the silent protection mode or the MRI special monitoring mode.

[0038] like Figure 5 As shown, after determining the corresponding working mode based on the MRI mode configuration, if configured as a silent protection mode, the ECG sensing and automatic arrhythmia detection functions are disabled to prevent increased power consumption and erroneous event recording caused by noise from the MRI radio frequency field, gradient field, and strong magnetic environment, thereby reducing power consumption, protecting the equipment, and reducing the burden on doctors in assessing false positive events. At the same time, necessary magnetic field, posture, timing, and necessary communication monitoring are retained. If configured as a special MRI monitoring mode, ECG signal acquisition is maintained, and MRI noise parameters and ECG reliability parameters are calculated. Based on this, the current time window is divided into a scan noise window, a low-interference monitorable window, or an uninterpretable window. Finally, the magnetic field and posture are continuously monitored, and the MRI exit confirmation process is initiated when the exit conditions are met.

[0039] Specifically, in the special monitoring mode of magnetic resonance imaging (MRI), the system maintains the ECG sensing module in normal sampling operation. While routinely acquiring ECG signals, the control module adjusts or enables anti-interference discrimination parameters under MRI conditions, including but not limited to filtering parameters, saturation detection threshold, noise feature threshold, ECG reliability threshold, and anti-interference discrimination algorithm, and performs ECG reliability judgment on the acquired ECG signals. The control module analyzes the waveform morphology, amplitude, frequency, periodicity, saturation time, pulse envelope, spectral energy, and temporal continuity of the acquired ECG signals, identifying noise signals generated by radio frequency fields, gradient fields, or strong magnetic environments during MRI scanning, and identifying possible real patient ECG signals during scan intervals, sequence switching intervals, or low-interference windows. When the signal meets the preset ECG reliability conditions, the system can extract and store the corresponding ECG segment, heart rate information, or rhythm information; when the signal does not meet the reliability conditions, the system can only store a summary of interference features or not perform arrhythmia event judgment.

[0040] In one embodiment, interference waveforms acquired during an MRI scan may appear as multiple high-amplitude pulse packets with clear boundaries. These pulse packets contain saturation points near the upper and lower limits of sampling and numerous large jumps between adjacent samples. In other scan intervals or low-interference segments, the waveform baseline is relatively restored, but narrow, high spikes may still be superimposed. The system can identify the former as active scanning noise and further perform spike removal and QRS reliability assessment on the latter, thereby preserving as much valuable ECG information as possible without completely disabling sensing.

[0041] The following is an embodiment of a quantitative discrimination method under a special monitoring mode of magnetic resonance imaging (MRI). After confirming that the device is in MRI mode and the special monitoring mode of MRI is selected in the programmable configuration, the control module processes the electrocardiogram (ECG) signals collected by the ECG sensing module according to the following steps.

[0042] Step S1, Acquisition and Windowing. The ECG sensing module outputs an ADC sampling sequence x(n). The control module acquires the ADC sampling sequence at a preset sampling frequency Fs (Fs is preferably 128Hz) and forms a sliding analysis window according to a preset window length W (W is preferably 4 seconds) and a window step size S (S is preferably 1 second). Each window contains N = Fs × W sampling points. The control module independently calculates the magnetic resonance noise parameters and ECG reliability parameters for each window.

[0043] Step S2: Calculate the magnetic resonance noise parameters. The control module calculates at least one or more of the following parameters in each window: (1) the saturation ratio (SatRatio) where the sampled value reaches or approaches the upper / lower limit of the ADC (preferably 8-bit sampling), defined as the ratio of the number of sampling points that satisfy x(n)≤Lsat or x(n)≥Hsat to the total number of sampling points N in the window, where Lsat is the low saturation threshold (Lsat is preferably 5) and Hsat is the high saturation threshold (Hsat is preferably 250); (2) the peak-to-peak value (P2P) within a certain time window, defined as the difference between the maximum value max(x(n)) and the minimum value min(x(n)) in the sampling sequence within the window, i.e. max(x(n))-min(x(n)); (3) the ratio of the large derivative of the absolute value of the difference between adjacent sampling points that exceeds the preset threshold (DiffRatio), defined as the ratio of the number of adjacent sampling points that satisfy |x(n)-x(n-1)|≥Dth to the total number of adjacent sampling points in the window, where Dth is the difference threshold (Dth is preferably 80 ADC counts). (4) BurstFeature: The duration, number of repetitions, repetition interval, and burst start and end boundaries of the noise envelope of a pulse segment that continuously meets the conditions of high amplitude, saturation, or large derivative. (5) FreqFeature: The main peak frequency, main peak energy ratio, or stable periodic component in the window spectrum located in the preset non-ECG frequency band (preferably 10Hz to 50Hz). (6) MarkerCoupling: The time coupling degree parameter between the sensing marker and the high amplitude spike / saturation sampling point is defined as the proportion of the number of markers with high amplitude spikes, saturation sampling points, or large derivative jumps within the preset time range before and after the R marker or sensing marker (preferably 40ms before and after the R marker) to the total number of markers in the window. (7) RR physiological rationality parameter: Whether the RR interval formed by adjacent R markers in the window falls within the preset physiological range, and whether the short RR interval lacks the corresponding stable QRS morphology, that is, whether it lacks the regularity of being synchronized with the scanning pulse.

[0044] Step S3: Determine the magnetic resonance noise score. The control module generates a noise score based on the parameters obtained in step S2. The noise score increases when the saturation ratio is greater than the first saturation threshold (preferably 5%); when the peak-to-peak value is greater than the first peak-to-peak value threshold (preferably 200 ADC counts); when the large derivative ratio is greater than the first derivative threshold (preferably 8%); when the pulse packet parameters show the presence of repetitive high-amplitude pulse packets or sudden start-end boundaries; when the spectrum parameters show the presence of a stable main peak in a non-ECG frequency band; when the marker coupling parameter is greater than the first coupling threshold (preferably 60%); and when the RR physiological rationality parameter shows multiple consecutive (e.g., 3) RR intervals shorter than the physiological lower limit (preferably 350ms) and the corresponding waveform lacks a stable QRS morphology, an RRPhysio abnormality is determined, and the noise score increases. When the noise score reaches the preset noise score threshold (preferably 3 points, i.e., 3 or more of the above noise conditions are met), the control module determines the window as an active magnetic resonance scanning noise window, determines the corresponding segment as a magnetic resonance scanning noise segment, and suppresses the automatic determination of arrhythmia events such as tachycardia, atrial fibrillation, and cardiac arrest in the segment or stores it as a magnetic resonance interference segment.

[0045] Step S4: Determine the ECG Confidence Score. For windows not identified as noise windows in the MRI active scan, the control module further calculates the ECG Confidence Score. The ECG Confidence Score increases when the saturation percentage within the window is below the second saturation threshold (preferably 1%), the large derivative percentage is below the second derivative threshold (preferably 2%), the peak-to-peak value is not close to the full ADC range, there is no significant saturation drift at the baseline, the candidate QRS complex has a repeatable morphology, the QRS width and slope fall within a preset range, the RR interval between adjacent heartbeats falls within the patient's physiological range, and the R label is consistent with the candidate QRS complex. When the MRI noise score is lower than the noise score threshold and the ECG reliability score reaches the preset reliability threshold (preferably 4 points, i.e., meeting 4 or more of the following criteria: low saturation, low derivative, not close to full scale, repeatable QRS morphology, physiologically reasonable RR interval, and R label consistent with QRS), the control module determines the window as a low-interference monitorable window and performs heart rate information estimation, rhythm trend recording, or ECG segment saving within the window; when the ECG reliability score does not reach the preset ECG reliability threshold, the control module marks the window as an unreadable window or only stores a summary of interference features.

[0046] In this embodiment, pseudotachycardia fragments caused by MRI noise can be characterized by a saturated sample ratio of approximately 6% to 14%, a large derivative ratio of approximately 8% to 33%, a peak-to-peak value close to the full scale of the ADC, and a non-ECG dominant frequency component of approximately 16Hz to 44Hz. The corresponding R markers can form non-physiological short RR intervals of approximately 240ms to 320ms, and are highly correlated with high-amplitude spikes or saturated pulse packets. The above values ​​are the parameter values ​​or discrimination ranges of this embodiment. In other embodiments, calibration or adaptive adjustment can be performed based on the ADC bit width, sampling frequency, implantation site, patient's normal ECG amplitude, scanning field strength, scanning sequence, and programming settings.

[0047] like Figure 6 As shown, in the special monitoring mode of magnetic resonance imaging (MRI), the system does not directly read the actual scanning parameters of the MRI scanner. The control module determines whether the interference caused to the implanted device by the current scanning process is within a preset allowable range based on the acquired MRI interference signal. This determination does not require the implanted device to directly obtain the actual sequence parameters of the MRI scanner, but rather uses the signal interference response quantity obtainable by the implanted device as the basis for judgment. The signal interference response quantity includes one or more of the following: peak-to-peak value, saturation ratio, continuous saturation duration, large derivative jump ratio, window signal energy or root mean square amplitude, pulse packet duration, pulse packet repetition interval, interference duty cycle, spectral main peak, non-ECG frequency band energy proportion, noise envelope period, and noise score.

[0048] Optionally, when the implanted device hardware has corresponding detection capabilities, the control module can also comprehensively judge based on device status parameters such as device temperature, instantaneous battery voltage drop, prolonged saturation of the front-end amplifier, continuous full-amplitude state of the ADC, abnormal density of sensing markers, and the duration of the magnetic monitoring module output exceeding the magnetic resonance threshold. If the control module determines that the above signal interference response or device status parameters exceed a preset threshold, or that multiple consecutive analysis windows meet strong interference conditions, it determines that the interference caused by the current magnetic resonance scanning process to the implanted device exceeds a preset safe or monitorable range, and generates corresponding warning information based on the type and degree of interference. In this embodiment, the communication module includes a Bluetooth communication module, and the warning information can be sent to an external receiving device, a programmable device, a relay device, and / or a doctor's client via a Bluetooth wireless link; after receiving the warning information, the external receiving device can prompt medical personnel or magnetic resonance operators through display, sound, vibration, indicator lights, recording, and / or forwarding. The warning information is received by medical personnel or magnetic resonance operators, who then manually determine whether to review or adjust the magnetic resonance scanning conditions; the magnetic resonance scanning system does not need to be configured with a control interface for receiving and automatically executing the output information of the implanted device.

[0049] If the signal interference response exhibits a stable spectral peak, increased window signal energy, and an increased saturation ratio, the control module classifies it as radio frequency (RF) related interference. For interference scenarios where RF related interference is predominant, the control module generates RF related interference warning information. This warning information may include suggestions for MRI operators to review one or more of the following: RF transmit power, RF energy limits, flip angle or refocusing flip angle, RF field strength related limits, repetition time, echo train length, or scan sequence.

[0050] Specifically, the control module calculates the signal interference response using a 4-second analysis window and a 1-second window step. When the magnetic resonance noise score reaches the preset noise score threshold for three consecutive analysis windows, or when any two of the following conditions are met simultaneously: saturation ratio greater than 5%, continuous saturation duration greater than 200ms, or large derivative jump ratio greater than 8%, the control module determines that the current scanning process exceeds the first warning threshold and generates a Level 1 radio frequency related interference warning. In this embodiment, the Level 1 radio frequency related interference warning may include a suggestion for the magnetic resonance operator to lower the radio frequency energy limit or the whole-body average SAR target value by 20%, or to limit the upper limit of the whole-body average SAR to no more than 1.5W / kg, lower the B1+rms related limit by 20%, and lower the flip angle or refocusing flip angle by 10% to 20%. If the strong interference conditions are met for three consecutive analysis windows after the warning is issued, a Level 2 radiofrequency-related interference warning will be generated, indicating that the interference is still ongoing. It may be recommended that the MRI operator further reduce the radiofrequency energy limit or the whole-body average SAR target value by 20% from the previous setting, or limit the upper limit of the whole-body average SAR to no more than 1.0 W / kg, and increase the repetition time by 10% to 30% or reduce the echo train length by 10% to 30%. The above values ​​are only examples of suggested measures in the warning message; whether to adjust and the specific amount of adjustment should be determined by the MRI operator based on the allowable range of the MRI equipment, the purpose of the scan, and the patient's condition.

[0051] If the interference response exhibits an increased proportion of large derivative jumps, a pulse packet repetition interval correlated with the gradient switching rhythm, and a short saturation duration, the control module classifies it as gradient-related interference. For interference scenarios dominated by gradient-related interference, the control module generates gradient-related interference warning information. This warning information may include suggestions for MRI operators to review one or more of the following: gradient amplitude, gradient switching rate, gradient rise time, fast sequence factor, echo interval, or scan sequence.

[0052] Specifically, when the interference response exceeds the first warning threshold within three consecutive analysis windows, and the interference characteristics include one or more of the following: an increased proportion of large derivative jumps, a correlation between the pulse packet repetition interval and the gradient switching rhythm, and a short saturation duration, a first-level gradient-related interference warning is generated. This may include a suggestion to the MRI operator to lower the upper limit of the gradient switching rate by 20% to 30%, lower the upper limit of the gradient amplitude by 10% to 20%, or increase the gradient rise time by 20% to 50%. If the interference response still exceeds the preset range after the warning is issued, a second-level gradient-related interference warning is generated, indicating that the interference is still ongoing. This may suggest that the MRI operator lower the fast sequence factor by 10% to 30%, increase the echo interval by 10% to 30%, or switch to a preset low-gradient load scan sequence. The above values ​​are only examples of suggested measures in the warning information; whether to adjust and the specific adjustment amount are determined by the MRI operator.

[0053] For persistent strong interference or abnormal equipment status, the control module generates high-level warning information. Specifically, if the second warning threshold is exceeded for more than five consecutive analysis windows, or if the equipment temperature, instantaneous battery voltage drop, prolonged saturation of the front-end amplifier, or continuous full-amplitude state of the ADC reaches preset abnormal conditions, the control module generates a level three emergency warning. In this embodiment, the level three emergency warning may include suggesting that the MRI operator pause the current scan for 30 to 120 seconds, insert a cooling interval of no less than 30 seconds, split the current scan into segmented scans of no more than 3 minutes, or exit the current scan sequence.

[0054] The specific values ​​mentioned above are the default values ​​in this embodiment. In actual products, they can be preset, programmed, or adaptively calibrated according to the MR conditions of the implanted device, magnetic resonance field strength, scanning site, coil type, patient body size, and clinical scanning protocol.

[0055] After the warning message is issued, the implanted device continues to collect ECG sensing front-end signals and reassess the signal interference response. If the signal interference response characteristics return to the preset allowable range, a warning cancellation message is sent or the warning level is lowered. If the interference response characteristics still exceed the preset range, the warning level is upgraded, and the MRI operator is prompted to consider pausing the scan or exiting the examination, thus forming a continuous monitoring and graded warning mechanism for the implanted device based on its own interference response.

[0056] When the magnetic field weakens and the patient returns to a non-recumbent position for a certain period of time, the system automatically exits the MRI-compatible mode and resumes normal ECG sensing and automatic arrhythmia detection functions, thereby achieving efficient, safe and fully automatic switching between multiple modes such as patient triggering, MRI silent protection and MRI special monitoring.

[0057] In this embodiment, the storage module is responsible for storing automatically detected arrhythmia events, patient-triggered event information, and magnetic resonance monitoring data obtained under special magnetic resonance monitoring modes.

[0058] In this embodiment, the communication module is responsible for communicating with external devices. The communication module may include a Bluetooth communication module and can send arrhythmia events, patient-triggered events, magnetic resonance monitoring data, and warning information to the programmable device, doctor's client, or external relay device via a Bluetooth wireless link.

[0059] The specific embodiments described above illustrate the technical solution and beneficial effects of the present invention in detail. It should be understood that the above description is only the most preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, additions, and equivalent substitutions made within the scope of the principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An implantable electrocardiogram monitoring system that automatically switches between patient-triggered and magnetic resonance imaging (MRI) compatible modes, characterized in that, include: The system includes an ECG sensing module, a magnetic field detection module, an attitude detection module, a control module, a communication module, a clock / timing module, and a storage module. The magnetic field detection module uses a pulse-driven current mirror to achieve multi-level detection of the trigger magnetic field and the MRI magnetic field. The control module automatically switches between patient trigger mode and MRI-compatible mode based on the results of multi-level magnetic field detection or the results of posture detection by the posture detection module. The magnetic resonance compatible mode includes a special magnetic resonance monitoring mode: based on the electrocardiogram (ECG) signal collected by the ECG sensing module, the magnetic resonance noise parameters and ECG reliability parameters are calculated, and when the signal is deemed reliable, ECG segments, heart rate information, or rhythm trends are recorded; furthermore, based on the interference response of the collected magnetic resonance signal, when it is indirectly determined that the interference caused to the implanted device by the current scanning process exceeds the preset allowable range, a warning message corresponding to the type and degree of interference is generated and sent through the communication module to inform medical personnel or magnetic resonance operators of the current interference status and suggested handling measures, thereby realizing abnormal monitoring and safety warnings based on the interference response at the implanted device end.

2. The implantable ECG monitoring system with automatic switching between patient triggering and MRI-compatible modes according to claim 1, characterized in that, The pulse-driven current mirror method is based on an ultra-low power circuit that includes a pulse-driven current mirror, a dual-channel programmable DAC, and a dual-threshold comparator. It includes: synchronously driving the magnetoresistor and the dual-channel programmable DAC with pulse current to convert the resistance fluctuation caused by the change of external magnetic field into a sensing voltage, and comparing the sensing voltage with two independent and programmable reference voltages generated by the first DAC and the second DAC based on the pulse current in real time. Finally, the combination of logic levels output by the two threshold comparators is compared with the threshold to realize multi-level layered detection of the patient's trigger magnetic field and MRI magnetic field.

3. The implantable ECG monitoring system with automatic switching between patient triggering and MRI-compatible modes according to claim 1, characterized in that, The control module automatically switches the patient trigger mode based on the results of multi-level magnetic field detection, including: When the detected magnetic field strength is higher than the patient trigger magnetic field strength threshold but lower than the MRI strength threshold, the system enters the patient trigger confirmation state. The control module controls the clock / timing module to start the patient trigger confirmation timing. If the detected magnetic field strength still meets the criteria of being higher than the patient trigger magnetic field strength threshold but lower than the MRI strength threshold after the timing period expires, the patient trigger process is initiated, and a patient trigger event is recorded. The ECG waveform, rhythm information, and trigger time of the previous period are stored together in the storage module. If the detected magnetic field strength does not meet the criteria of being higher than the patient trigger magnetic field strength threshold but lower than the MRI strength threshold after the timing period expires, the patient trigger confirmation fails, and the system switches to the non-patient trigger state without recording the patient trigger event.

4. The implantable ECG monitoring system with automatic switching between patient triggering and MRI-compatible modes according to claim 1, characterized in that, The control module automatically switches between magnetic resonance compatible modes based on multi-level detected magnetic field results and attitude results detected by the attitude detection module, including: When the patient is in a supine position and the magnetic field strength is higher than the MRI intensity threshold, the MRI will enter the confirmation state. If the magnetic field strength is still higher than the MRI intensity threshold and the patient is in a supine position when the confirmation time ends, the MRI will enter the MRI process state and enter the corresponding working mode according to the MRI mode configuration. Otherwise, it will switch to the non-MRI state. If, during MRI, the magnetic field strength is detected to be below the MRI exit threshold and the patient is not in a supine position, the MRI exit confirmation state is entered. If, at the end of the exit timer, the magnetic field strength is still below the MRI exit threshold and the patient is still not in a supine position, the MRI compatibility mode is exited, and the ECG sensing and automatic arrhythmia detection functions are restored.

5. The implantable ECG monitoring system with automatic switching between patient triggering and MRI-compatible modes according to claim 1, characterized in that, After entering the MRI state, the special MRI monitoring mode is confirmed according to the programmable MRI mode configuration. The ECG sensing module collects ECG signals as usual, and at the same time, special MRI judgments are added during the collection process: the waveform morphology, frequency characteristics, amplitude characteristics, periodicity, saturation degree, noise envelope and / or spectral energy of the ECG signal are analyzed, the MRI noise parameters are calculated to distinguish the MRI noise signals generated during the MRI scan, the ECG reliability parameters are calculated and the ECG signal in the low interference monitoring window is determined by judging the reliability of the signal, and the ECG segments, heart rate information or rhythm trend in the low interference monitoring window are recorded at the same time.

6. The implantable ECG monitoring system with automatic switching between patient triggering and MRI-compatible modes according to claim 1, characterized in that, The magnetic resonance compatible mode also includes a silent protection mode. When the programmable magnetic resonance mode configuration is confirmed to enter the silent protection mode, the ECG sensing and automatic arrhythmia detection functions are turned off, while the necessary magnetic field, posture, timing and communication monitoring are retained.

7. The implantable ECG monitoring system with automatic switching between patient triggering and MRI-compatible modes according to claim 1, characterized in that, The magnetic resonance signal interference response includes one or more of the following: peak-to-peak value, saturation ratio, continuous saturation duration, large derivative jump ratio, window signal energy, pulse packet duration, pulse packet repetition interval, interference duty cycle, main peak of the spectrum, energy proportion of non-ECG frequency bands, noise envelope period, and noise score.

8. The implantable ECG monitoring system with automatic switching of patient triggering and MRI-compatible modes according to claim 1 or 7, characterized in that, Also includes: The system monitors the status of the device. When the monitored status exceeds a preset threshold, or when multiple consecutive analysis windows meet the strong interference conditions, it determines that the interference caused by the current magnetic resonance scanning process to the implanted device exceeds the preset safe or monitorable range, and generates warning information corresponding to the type and degree of interference. The device status parameters include device temperature, instantaneous battery voltage drop, prolonged saturation of the front-end amplifier, continuous full-amplitude state of the ADC, abnormal density of sensing markers, and the duration for which the output of the magnetic monitoring module is continuously higher than the magnetic resonance threshold.

9. The implantable ECG monitoring system with automatic switching between patient triggering and MRI-compatible modes according to claim 1, characterized in that, The warning information includes one or more of the following: interference level, interference type, out-of-limit parameters, out-of-limit duration, and recommended handling measures; the recommended handling measures include one or more of the following: recommending review or reduce radio frequency load, recommending review or reduce gradient load, recommending insert a scan interval or perform segmented scanning, recommending pausing the current scan or exiting the inspection.

10. The implantable ECG monitoring system with automatic switching between patient triggering and MRI-compatible modes according to claim 9, characterized in that, For interference scenarios where radio frequency (RF) related interference is the primary cause, the warning information includes an RF related interference identifier and a recommendation for an MRI operator to review one or more of the following: RF transmit power, RF energy limits, flip angle or refocusing flip angle, RF field strength related limits, repetition time, echo train length, or scan sequence. For interference scenarios where gradient-related interference is the primary cause, the warning information includes a gradient-related interference identifier and a recommendation for the MRI operator to review one or more of the following: gradient amplitude, gradient switching rate, gradient rise time, fast sequence factor, echo interval, or scan sequence. In the event of persistent strong interference or abnormal equipment status, the warning information includes an indicator of persistent strong interference or abnormal equipment status, and a suggestion for the MRI operator to insert a scan interval, increase a cooling interval, perform segmented scanning, pause the current scan, or exit the inspection.

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