A cardiac pacing device with full automatic magnetic resonance compatibility

Abstract

The application discloses a kind of heart pacing device with full-automatic magnetic resonance compatibility function, belong to medical instrument technical field, comprising: magnetic field detection module, motion detection module, attitude detection module are respectively used to detect static magnetic field characteristics, motion characteristics and attitude characteristics;Perception detection module, acquisition includes cardiac electrophysiological signal and magnetic resonance interference signal perception signal sequence and carries out perception event identification and signal intensity analysis to determine perception event trigger signal and magnetic resonance scanning active characteristics;Digital signal processing module, based on all characteristics, multi-dimensional physical constraint cascade decision, full-automatic conversion to magnetic resonance mode and output trigger instruction;Charge pump and pacing output module, according to trigger instruction dynamic adjustment pacing pulse timing, based on charge pump adjustment pacing pulse energy, and pulse output path, to avoid rectification effect and direct current component accumulation risk, truly realize full-automatic magnetic resonance compatible safe physiological pacing.

Description

Technical Field

[0001] This invention belongs to the field of implantable medical device technology, specifically relating to a cardiac pacing device with fully automated magnetic resonance compatible function. Background Technology

[0002] Cardiac pacemakers are widely used in clinical practice to treat heart diseases such as bradycardia and conduction disorders. A typical pacing system consists of an interpulse generator (IPG) sealed in a titanium alloy housing and electrode leads implanted into the heart chambers via a vein. The IPG typically contains precision electronic components, a dedicated ASIC chip, and a battery. The physical properties of its ferromagnetic or highly conductive metallic materials determine its high sensitivity in strong electromagnetic environments. Since pacemakers can have a service life of up to 10 years, more than half of implanted patients will have a clear indication for MRI examination during the device's lifespan. With the increasing prevalence of comorbidities such as heart disease, cancer, and neurodegenerative diseases, the urgent need for MRI examinations among pacemaker patients is becoming increasingly apparent.

[0003] However, MRI generates extreme electromagnetic environments, including strong static magnetic fields (such as 1.5T or 3T), rapidly changing gradient magnetic fields (around 1kHz), and radio frequency fields (such as 64MHz or 128MHz). These fields interact violently with the pacemaker's metal casing, internal ASIC chip, and slender lead loops. MRI was once considered an absolute contraindication for such patients, and this conflict between the need for medical diagnostics and the safety of implants is a major challenge in implantable device development.

[0004] The harmful effects of the MRI environment on pacemakers are not one-dimensional, but rather the result of multi-field coupling: 1. Risks of radiofrequency fields include: (1) Tissue thermal damage: The radiofrequency energy (B1 field) of MRI will generate induced current in the implant lead, especially at the end of the lead (the contact point between the electrode and the myocardium). This will cause a significant increase in local temperature, which may lead to thermal necrosis of myocardial tissue, and thus increase the pacing threshold or even pacing failure. (2) Unintended stimulation: The induced current induced by the radiofrequency field is rectified to DC level by the nonlinear components inside the pacemaker. If the rectified voltage exceeds the cardiac excitation threshold, it will cause unintended cardiac capture, which may induce tachyarrhythmias. (3) Sensitive hypersensitivity and false inhibition: The sensing circuit of the pacemaker may misidentify the high-frequency radiofrequency signal as a P wave or R wave. This sensitive hypersensitivity will inhibit the normal delivery of pacing pulses, causing the patient to experience long pauses or pauses during the scan.

[0005] 2. Risks arising from static magnetic fields include: (1) Magnetic torque and displacement force: Strong static magnetic fields (1.5T / 3T) can exert a huge attraction on the ferromagnetic materials in the pacemaker casing, battery, and internal electronic components, which may cause the pacemaker to shift within the pocket or change the lead tension, resulting in lead dislocation or micro-displacement. (2) Failure of magnetically sensitive components: Traditional pacemakers use magnetically sensitive switches (such as reed switches) to enter magnet mode. Strong static magnetic fields will continuously close this switch, forcing the device into a specific asynchronous pacing mode, which cannot be adjusted according to the patient's actual physiological needs.

[0006] 3. Gradient magnetic field risks, specifically including: (1) Gradient induced potential: A rapidly changing gradient field (dB / dt) will induce a low-frequency voltage in the lead loop. This voltage frequency is close to the cardiac electrophysiological signal, which can easily interfere with the pacemaker's sensing decision. (2) Vibration: The Lorentz force generated by the interaction between the gradient field and the static magnetic field will cause microscopic vibration in the internal components of the device (such as ceramic capacitors and inductors), leading to malfunction. (3) Unintended cardiac stimulation: If the potential induced by the gradient field is strong enough, it may even directly generate an induced current exceeding the threshold in the cardiac tissue, leading to unintended cardiac capture. (4) Eddy current heating: When a high-frequency switching gradient field penetrates the pacemaker shell, a closed loop current (i.e., eddy current) will be induced on the conductive shell surface. Due to the internal resistance of the metal shell itself, the eddy current will convert electrical energy into heat energy through the Joule heating effect.

[0007] 4. System-level risks in the comprehensive field include: (1) Power management anomalies: Strong magnetic fields and radio frequency interference may affect the working efficiency of DC-DC converters or charge pumps, leading to abnormal battery power consumption or internal power supply voltage drops, which in turn triggers system reset. (2) Electromagnetic compatibility (EMC) limit failure: In the extreme environment of MRI, conventional EMC filtering circuits may saturate or fail, causing the equipment to completely lose its protective capabilities. (3) Artifacts: The magnetic susceptibility of the metal materials (even non-ferromagnetic metals) contained in the pacemaker shell, internal electronic components, and wires differs significantly from that of human soft tissue. This difference distorts the local magnetic field, resulting in severe artifacts in the image.

[0008] To address these issues, most mainstream MRI-compatible pacemakers on the market currently offer both manual and automatic MRI modes. For the existing manual MRI mode, before entering the MRI scanning room, a professional pacemaker programmer must manually switch the device to MRI mode (usually asynchronous pacing, such as VOO, DOO, or AOO) using a programmer; after the examination, it must be manually switched back to the original programming mode (such as DDD or VVI). This process is inefficient in emergency situations and involves a risk window of several hours, during which the patient is in a fixed-frequency pacing state, lacking cardiac sensing and at risk of inducing competing arrhythmias.

[0009] For existing automated MRI modes, the recognition logic often relies solely on a single static magnetic field strength (B0) determination. However, in daily life, patients inevitably encounter strong magnetic environments (such as magnetic phone cases, magnetic tablet holders, audio equipment, or industrial magnetic fields), where the local magnetic field strength can reach the level of the MRI scanner's edge magnetic field. This single determination mechanism can lead to erroneous pacemaker switching in non-scanning environments, disabling sensing functions, increasing pacing energy, posing unnecessary clinical risks to non-dependent patients, and significantly increasing battery consumption.

[0010] Most existing technologies can only sense the presence of a magnetic field, but cannot accurately determine whether the pacemaker is within the effective working area of ​​the scanning aperture (Bore). This makes it difficult for the equipment to distinguish whether a patient is merely walking through the scanning room door or is already lying on the examination table ready to begin the scan. Furthermore, current equipment cannot collaboratively analyze the patient's motion state and posture. During an MRI scan, the patient must remain still and is usually in a supine position, and existing automatic switching mechanisms do not consider these physiological signs as decision factors, making true zero-intervention, precise identification difficult. Moreover, MRI examinations are not continuous radiofrequency emission processes. In an MRI examination cycle of 30-60 minutes, the active scanning time, which actually includes radiofrequency field and gradient field interference, accounts for only about 20%-30%, with the remaining time consisting only of a static magnetic field. Traditional automatic modes maintain asynchronous pacing throughout the entire scan once activated. In fact, during non-scanning periods (blank periods), the equipment is fully capable of resuming normal physiological sensing pacing to provide treatment options that better meet hemodynamic requirements. Existing solutions lack real-time monitoring and precise dynamic response capabilities during the scanning sequence.

[0011] Furthermore, the impedance characteristics of traditional pacemakers' port networks are fixed when dealing with MRI environments. Under strong gradient or radio frequency fields, the induced current in the leads often converges entirely at the electrode tips due to the lack of an effective physical discharge and impedance reconstruction path. Existing solutions lack an integrated network at the circuit level that can balance pacing charge balance and impedance transformation in the MRI environment, making it difficult to avoid the risk of thermal damage at the physical level. Summary of the Invention

[0012] In view of the above, the purpose of this invention is to solve the problems of automated management and physical safety of long-cycle implantable devices in the MRI environment, specifically including: low efficiency of manual mode switching and the existence of risk window period; simple automatic mode recognition logic, which is easily interfered by magnetic objects in daily life; and the inability to restore physiological pacing during the interval of MRI scanning, and the lack of an effective impedance reconstruction network at the physical level to avoid the risk of radiofrequency thermal damage and unexpected stimulation.

[0013] To achieve the above-mentioned objectives, this invention provides a cardiac pacing device with fully automated magnetic resonance imaging (MRI) compatibility, comprising: a magnetic field detection module, a motion detection module, and a posture detection module, respectively used to detect static magnetic field characteristics, motion characteristics, and posture characteristics; and further comprising: The sensing and detection module is used to acquire sensing signal sequences containing cardiac electrophysiological signals and magnetic resonance interference signals, and to perform sensing event identification and signal intensity analysis to determine sensing event trigger signals and magnetic resonance scan activity characteristics. The digital signal processing module is used to make cascaded decisions on multi-dimensional physical constraints based on static magnetic field characteristics, motion characteristics, attitude characteristics, and magnetic resonance scanning activity characteristics, and automatically switch to magnetic resonance mode and output trigger commands. The charge pump and pacing output module are used to dynamically adjust the timing of the pacing pulses that match the magnetic resonance mode, the pacing pulse energy based on the charge pump adjustment, and the pulse output path according to the trigger command, so as to avoid the rectification effect and the risk of DC component accumulation.

[0014] Preferably, the magnetic field detection module includes a magnetic field sensor, a precision current source, and a comparator; the precision current source is configured as a current mirror structure, wherein a first current source generates a controlled pulse driving current and acts on the magnetic field sensor to generate an analog sampling voltage, and a second current source works with a digital-to-analog converter to establish a preset reference threshold voltage; the comparator is used to compare the analog sampling voltage with the reference threshold voltage in real time, and generates a logic jump signal as the static magnetic field characteristics of the magnetic resonance scan when the analog sampling voltage exceeds the reference threshold voltage.

[0015] Preferably, the magnetic field detection module adopts a periodic pulse scanning method, combined with a microampere-level pulse drive current, to achieve low-energy magnetic field detection.

[0016] Preferably, the motion detection module detects motion features in the following manner: The three-axis acceleration vector is acquired synchronously and dynamic differential calculation is performed to filter out the gravity component to obtain the acceleration change vector. Then, the absolute value of the acceleration change vector is compared with the acceleration gear threshold. A motion score flag is assigned to the sampling time that is less than or equal to the acceleration gear threshold to obtain the motion feature. Within a preset sliding window time, the motion feature is integrally evaluated. When the integral value reaches the preset evaluation threshold, it is identified as a motion state; otherwise, it is identified as a stationary state.

[0017] Preferably, the attitude detection module detects attitude features in the following manner: The system acquires the triaxial acceleration reference value in a static upright state and calculates the rotation vector; it also acquires the triaxial acceleration vector at the current sampling moment in real time and calculates the dot product of the rotation vector and the triaxial acceleration vector as the posture feature. This posture feature is used to identify the spatial body position. Specifically, when the posture feature is less than or equal to a preset judgment threshold, the patient is determined to be in a non-upright state; otherwise, the patient is identified as being in an upright state.

[0018] Preferably, the sensing and detection module performs sensing and detection through the following continuous signal processing link: A sensing signal sequence containing cardiac electrophysiological signals and magnetic resonance interference signals is input via an electrode port that supports programmable switching between unipolar and bipolar differential modes. A controlled variable capacitor is connected across the electrode port, and the capacitance of the controlled variable capacitor is automatically adjusted by the trigger command output by the digital signal processing module based on the magnetic resonance scan activity characteristics. The signal processed by the controlled variable capacitor is then DC isolated between the external electrode and the subsequent circuit through an input coupling capacitor connected in series in the signal path, and guided into the analog front-end processing unit via a channel switching switch. In the analog front-end processing unit, the signal is sequentially amplified by high gain, bandpass filtered, and converted from analog to digital before being synchronously guided to a dual-path discrimination architecture consisting of an amplitude detection unit and a threshold comparison unit. In the amplitude detection unit, the amplitude index of the signal envelope energy is calculated in real time to determine the magnetic resonance scan activity characteristics. In the threshold comparison unit, the signal is compared with a dynamic threshold in real time, and a sensing event trigger signal is output.

[0019] Preferably, the controlled variable capacitor is automatically adjusted in capacitance by a trigger command output by the digital signal processing module based on the magnetic resonance scan activity characteristics, including: Based on the trigger command, during a high-activity magnetic resonance (MRI) scan, the capacitance value of the controlled variable capacitor is adjusted to optimize the resonant impedance characteristics of the front-end filter and improve the attenuation capability of MRI radio frequency interference signals. During non-scanning intervals or in normal living environments, the capacitance value of the controlled variable capacitor is adjusted to the optimal reference to ensure that the morphological characteristics of the ECG waveform are not distorted and to maintain the sensitivity of the sensor.

[0020] Preferably, in the digital signal processing module, the cascaded decision-making based on multi-dimensional physical constraints according to static magnetic field characteristics, motion characteristics, attitude characteristics, and magnetic resonance scanning activity characteristics includes: First, the first level of physical constraint conditions is determined based on the static magnetic field characteristics, motion characteristics, and posture characteristics to determine whether the environmental magnetic field exceeds the standard, whether the patient is in a static state, and whether the patient is in a non-upright posture. Under the premise that the magnetic field exceeds the limit, the object is stationary and not in an upright position, a second-level condition judgment is performed based on the activity characteristics of magnetic resonance scanning. When it is determined that the magnetic resonance scanning process is in progress, a trigger command for magnetic resonance mode is generated. This trigger command is used to drive the sensing and detection module to adjust the capacitance of the controlled variable capacitor to enhance filtering, and also to drive the charge pump and pacing output module to switch to asynchronous stimulation mode and lock the bipolar differential output path; otherwise, a safety countdown program is started, and the magnetic resonance mode is automatically exited after confirming that the environment remains safe.

[0021] Preferably, the digital signal processing module is further used for rapid identification of invalid sensing events based on static magnetic field characteristics, motion characteristics, attitude characteristics, and sensing signals, including: First, the first level of physical constraint conditions is determined based on the static magnetic field characteristics, motion characteristics, and posture characteristics to determine whether the environmental magnetic field exceeds the standard, whether the patient is in a static state, and whether the patient is in a non-upright posture. If, under the premise that the magnetic field exceeds the limit, the object is stationary and not in an upright position, the sensing signal exhibits high synchronicity on the time axis and shows circuit saturation characteristics in amplitude, it is determined to be a false sensing event and the original pacing sequence is maintained; otherwise, it is determined to be a valid sensing event and the pacing sequence is reset to restore physiological sensing pacing function.

[0022] Preferably, the charge pump and pacing output module employs an output network with dynamic path switching, rapid charge balancing, and physical impedance reconstruction functions, specifically including: The energy source is connected to the input of the charge pump via a DC power supply. The output of the charge pump is connected in parallel with an energy storage capacitor, the negative terminal of which is connected to the system reference ground. In the output path, the positive terminal of the energy storage capacitor is led out through the first and second switches to two branches, which are connected to the CAN port and the RING port via the first and second output capacitors, respectively. At the same time, the third and fourth switches are connected across the nodes before the first and second output capacitors to the system reference ground, respectively. The fifth switch is connected in series in the loop between the system reference ground and the TIP port. One end of the first and second internal resistors are connected to the paths before the first and second output capacitors, respectively, and the other end is connected together to the TIP port after the fifth switch. During the pacing phase, the first or second switch, together with the fifth switch, is turned on to deliver pacing pulses; then, the rapid charge recovery phase begins, where the third or fourth switch, together with the fifth switch, is turned on simultaneously, so that the two ends of the output capacitor form a rapid discharge circuit through the system reference ground, thereby achieving rapid charge recovery. The internal first and second resistors are connected across the output path and the TIP port to achieve physical impedance reconstruction, providing a discharge path for the induced current in the magnetic resonance environment. When the magnetic resonance scanning activity characteristics are detected, the switch state is forcibly locked so that the TIP port and the RING port form a bipolar differential output path.

[0023] Compared with the prior art, the beneficial effects of the present invention include at least the following: 1. By using a cascaded determination based on magnetic field, motion, attitude, and signal characteristics, the risk of accidental switching caused by magnetic objects in daily life is eliminated.

[0024] 2. It achieves dynamic response to the MRI scan cycle, only entering MRI mode during interference periods and automatically resuming physiological sensing pacing during interference-free intervals, thus maximizing the protection of the patient's hemodynamic needs.

[0025] 3. By utilizing physical impedance reconstruction and bipolar output locking mechanisms, induced current and rectification effects are effectively suppressed, and electrode thermal damage and unintended stimulation are avoided. Attached Figure Description

[0026] 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.

[0027] Figure 1This invention provides a system architecture block diagram of a cardiac pacing device with fully automated magnetic resonance imaging (MRI) compatibility. Figure 2 This is a schematic diagram of the circuit principle of the magnetic field detection module in an embodiment of the present invention; Figure 3 This is a block diagram of the algorithm execution logic of the motion detection module in this embodiment of the invention; Figure 4 This is a block diagram of the algorithm execution logic of the attitude detection module in an embodiment of the present invention; Figure 5 This is a schematic diagram of a sensing and detection circuit framework with a controlled variable capacitor in an embodiment of the present invention; Figure 6 This is a topology diagram of a charge pump and pacing output circuit with impedance reconstruction function in an embodiment of the present invention; Figure 7 This is a flowchart illustrating a fully automatic mode switching process performed by the digital signal processing module in an embodiment of the present invention. Figure 8 This is a simplified flowchart of a fully automatic mode switching performed by the digital signal processing module in an embodiment of the present invention; Figure 9 This is a schematic diagram illustrating the acquisition, comparison, and feature extraction of magnetic resonance interference signals and normal cardiac electrophysiological signals in an embodiment of the present invention. Detailed Implementation

[0028] 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.

[0029] This embodiment provides a cardiac pacing device with fully automated MRI compatibility. It features fully automated environmental awareness, real-time identification of MRI scan sequence activity, and dynamic adjustment of the operating mode. This aims to address the risks of accidental triggering, radiofrequency thermal damage, and unexpected stimulation associated with long-term implantable devices in complex electromagnetic environments, as well as MRI-related issues. It also enables the restoration of physiological pacing benefits during scan intervals. This device is not only suitable for single-chamber or dual-chamber cardiac pacemakers (IPGs) used to treat bradyarrhythmias, but also widely applicable to implantable cardioverter-defibrillators (ICDs) with pacing functions and cardiac resynchronization therapy devices (CRT-D / P) for heart failure treatment. Furthermore, this invention can be extended to implantable electronic medical devices such as implantable neurostimulators that utilize electrical stimulation principles for treatment.

[0030] Figure 1 This is a schematic diagram of a cardiac pacing device with fully automated magnetic resonance imaging (MRI) compatibility provided in an embodiment of the present invention. Figure 1As shown, the cardiac pacemaker 100 integrates multiple collaborative sensing and decision-making modules to achieve safety protection and working mode switching with zero human intervention in strong electromagnetic environments. Specifically, it includes a magnetic field detection module 110, a motion detection module 120, a posture detection module 130, a sensing detection module 140, a digital signal processing module 150, and a charge pump and pacing output module 160. In the hardware collaborative logic, the magnetic field detection module 110, motion detection module 120, posture detection module 130, and sensing detection module 140 jointly construct a multi-source information input network, which is communicatively connected to the digital signal processing module 150. The output of the digital signal processing module 150 is connected to the charge pump and pacing output module 160, and finally, a discharge pulse signal is sent to the patient's heart through the pacing pulse output terminal 170.

[0031] In this embodiment, the magnetic field detection module 110 is mainly used to periodically detect the external environmental magnetic field, accurately identify static magnetic field (BO) characteristics, and determine whether the device has entered a strong magnetic field-restricted area. The motion detection module 120 is responsible for assessing the intensity of the patient's physical activity, obtaining motion characteristics by detecting acceleration vectors, and using this information to analyze and determine whether the patient is in a static state that meets the scanning conditions. The posture detection module 130 is used to identify the patient's spatial position and shape, obtaining posture characteristics through dot product operations, and accurately identifying whether the patient is in a non-upright state (such as a supine position), providing crucial physical state constraints for entering MRI mode. The sensing detection module 140 is responsible for acquiring and processing sensing signal sequences containing cardiac electrophysiological signals and sequential magnetic resonance interference signals from MRI scans, providing raw signal streams for evaluating the effectiveness of sensing events, and performing sensing event identification and signal intensity analysis to determine sensing event trigger signals and magnetic resonance scan activity characteristics. The digital signal processing module 150, as the core decision-making center of the system, executes cascaded decision logic based on multi-dimensional physical constraints according to static magnetic field characteristics, motion characteristics, posture characteristics, and magnetic resonance scan activity characteristics. It comprehensively determines whether to activate or deactivate the magnetic resonance mode and outputs trigger commands, driving the dynamic reset of system operating parameters (such as pacing mode, parameters, etc.) in real time. The charge pump and pacing output module 160 is the terminal hardware that executes the pacing pulse delivery. According to the real-time trigger commands from the digital signal processing module 150, it adjusts the timing and energy of charge release. When magnetic resonance scan activity characteristics are detected, it outputs stable asynchronous stimulation pulses through physical impedance reconstruction and bipolar differential path locking, ensuring the continuity of treatment while ensuring physical safety.

[0032] Figure 2The circuit principle of the magnetic field detection module in this embodiment of the invention is shown. In a specific implementation, the magnetic field detection module 110 includes a magnetic field sensor, a precision current source, and a comparator. The magnetic field sensor senses the external environmental magnetic field signal and converts it into an analog electrical signal. Depending on the detection dimension and accuracy requirements, the magnetic field sensor 203 (i.e., R_Sensor) can be a single-axis, two-axis, or three-axis sensor structure. This magnetic field sensor can employ magnetoresistive effect elements such as anisotropic magnetoresistive (AMR), giant magnetoresistive (GMR), or tunneling magnetoresistive (TMR), accurately identifying the intensity characteristics of the MRI static magnetic field B0 by sensing the shift in resistance value. The core circuit inside this module adopts a precision current mirror architecture. Specifically, the first current source 201 (I_Sensor) is controlled to generate an extremely low-power pulsed drive current that acts on the magnetic field sensor 203, thereby generating an analog sampling voltage V_Sensor reflecting the magnetic field strength at the sampling point 202. To achieve optimal power consumption management, the amplitude and pulse width of the pulse current source (e.g., 100µA / 100µs) are dynamically set according to the impedance characteristics of the magnetic field sensor itself. The reference side of the current mirror is formed by a second current source 204 and a digital-to-analog converter (DAC) 206 working together. The second current source, in conjunction with the DAC, establishes a preset reference threshold voltage. The DAC 206 is essentially a settable resistor network, and its resistance value is controlled by a preset digital value in the digital signal processing module 150 (with an internal register). When the current from the second current source 204 flows through the DAC 206, it is converted at the comparison point 205 to establish a reference threshold voltage V_th corresponding to the preset digital value. Comparator 207 compares the analog sampling voltage with the reference threshold voltage in real time. Once the analog sampling voltage V_sensor exceeds the reference threshold voltage V_th, the output terminal 208 generates a logic jump signal as the static magnetic field characteristics of the magnetic resonance scan and transmits it to the digital signal processing module 150, thereby determining that the device has entered a strong magnetic field area such as the MRI scanning chamber.

[0033] To further improve detection reliability, the system employs a multi-measurement strategy for jitter reduction, using logical algorithms to eliminate false interference caused by stray magnetic fields or electromagnetic glitches in the instantaneous environment. To meet the low-power consumption requirements of long-cycle implantation products, magnetic field sampling uses a periodic pulse scanning method with a fixed sampling rate of 10 Hz (sampling interval 100ms). Combined with microampere-level pulse current, this minimizes overall module power consumption, ensuring the device can automatically and reliably identify the magnetic resonance scanning environment while maximizing battery life.

[0034] Figure 3The algorithm execution logic of the motion detection module 120 in this embodiment of the invention is illustrated in detail. This process aims to accurately assess the intensity of a patient's physical activity through acceleration features, extract motion features, and use these features as a key decision factor for switching fully automated MRI modes. The specific execution steps are as follows: S301: Multi-axis signal acquisition. At each sampling time... The output values ​​of the triaxial MEMS accelerometer are acquired synchronously and denoted as the triaxial acceleration vector. .

[0035] S302: Dynamic differential calculation. Calculates the current sampling time. Compared with the previous sampling time acceleration change vector Differential processing can effectively filter out the static component of gravitational acceleration and extract the dynamic signal reflecting body motion.

[0036] S303: Instantaneous threshold determination. The absolute value of the acceleration change vector... Compare with a preset acceleration level threshold (preferably set to 200mg depending on clinical needs).

[0037] S304a / S304b: Flag assignment. If If the set acceleration level threshold is met (i.e., less than or equal to the acceleration level threshold), then the motion score flag at the current sampling time will be updated. Assign the corresponding weight value of 1 (step S304a); if not satisfied, then The value is assigned to 0 (step S304b), thereby obtaining the motion features.

[0038] S305: Exercise volume integral assessment. Based on a preset sliding window time. (For example, select the 6-second interval before the current time) and assign all sports score flags within that interval. The values ​​are accumulated to calculate the current exercise volume assessment value. k is the time index.

[0039] S306: Exercise Status Decision. Determining Exercise Volume Assessment Values. Is it greater than or equal to the set evaluation threshold (e.g., the set threshold can be set to 2)?

[0040] S307a / S307b: Status locked. If Meeting the standard means If the value is greater than or equal to the evaluation threshold, it is identified as a motion state (step S307a); if it does not meet the threshold, i.e. If the value is below the evaluation threshold, the patient is identified as being in a stationary state (step S307b). Determining the patient to be in a stationary state is an important constraint for entering MRI mode, which can effectively exclude non-scanning environment interference caused by the patient's daily walking or strenuous activities.

[0041] S308: Loop Waiting. The system enters the next sampling cycle (the sampling frequency is preferably 5Hz, i.e., waits for 200ms), and returns to step S301 to continue the new round of feature extraction and judgment.

[0042] The motion detection module 120 achieves extremely low static power consumption through an extremely low sampling frequency and microsecond-level computational logic. Simultaneously, through the integration processing mechanism in step S305, the algorithm possesses excellent anti-transient jitter capability, ensuring the stability and high reliability of the long-cycle implantation device in complex physical environments.

[0043] Figure 4 This document details the specific algorithm execution logic of the posture detection module 130 in this embodiment of the invention. This module aims to identify the patient's spatial position and obtain posture characteristics (such as upright or supine posture), providing crucial physical constraints for fully automated mode switching, thereby effectively distinguishing between normal daily life activities and the MRI scanning environment. The following is a detailed description of the algorithm's steps: S401: Initial Calibration to Obtain Baseline Values. After device implantation or during follow-up, triaxial acceleration samples are first acquired when the patient is in a static, upright position, and these are used as triaxial acceleration baseline values. This step establishes a gravity vector reference for the individual patient.

[0044] S402: Calculate the rotation vector Based on the obtained baseline value Calculate the rotation vector The calculation formula is: ,in, The rotation vector This represents the projection of the direction of gravity in the patient's standard upright position.

[0045] S403: Real-time acquisition of the three-axis acceleration vector at the current sampling moment. At the current sampling time Obtain real-time triaxial acceleration vectors And calculate the rotation vector. With the current triaxial acceleration vector The dot product is used as a pose feature.

[0046] S404: Perform threshold determination. The result is compared with a preset judgment threshold (which, based on clinical experience, is preferably set to 1 / 2).

[0047] S405a / S405b: Status output. If the dot product result... If the result is less than or equal to the threshold, the patient is determined to be in a non-upright position (step S405a). A non-upright position (such as supine position) is a key criterion for determining whether the patient has entered the MRI examination table. If the dot product result is greater than the threshold, the patient is determined to be in an upright position (step S405b).

[0048] S406: Loop Waiting. The system enters the next sampling cycle (to optimize power consumption, the waiting time is preferably 1 second), and then returns to step S403 to continue execution. The system enters the next sampling cycle (e.g., after 1 second), and returns to step S403 to continue execution.

[0049] To reduce the power consumption of long-term implantable products, the sampling period of the posture detection module 130 can be set to once per second. At the same time, multiple measurement and jitter reduction processes are performed through algorithmic logic to ensure that the state transition is only triggered when the patient's body position undergoes a stable change (such as from standing to lying down), effectively eliminating the false interference of instantaneous shaking in daily life on posture recognition.

[0050] Figure 5 This paper details the implementation of the sensing and detection module 140 in this invention. The sensing and detection module 140 acquires and precisely processes cardiac electrophysiological signals and radio frequency and gradient field interference signals from an external magnetic resonance imaging (MRI) environment in real time. Its signal input section is illustrated by equivalent signal sources 501 and 502, supporting both unipolar and bipolar differential physical input modes. Specifically, a unipolar input link can be formed by combining electrode ports 503 (CAN) and 504 (TIP), while a bipolar differential input link can be formed by combining ports 504 (TIP) and 505 (RING). This allows clinicians to programmatically select the most suitable sensing signal acquisition combination based on the patient's electrode lead implantation type and cardiac chamber sensing needs. To cope with the intense electromagnetic wave fluctuations in the MRI environment, the circuit front end is designed with a crucial impedance matching and filtering adjustment mechanism, namely, controlled variable capacitors 506 and 507 connected across the electrode port input path.

[0051] In a preferred embodiment of the present invention, the sensing front-end circuit, designed for 1.5T (corresponding to approximately 64MHz of radio frequency interference) and 3.0T (corresponding to approximately 128MHz of radio frequency interference) environments, employs a variable capacitor array as its internal controlled variable capacitor. Driven by digital trigger commands output from the digital signal processing module, the variable capacitor array performs nonlinear capacitance switching. Because capacitors exhibit self-resonance in high-frequency environments, the control unit does not employ a blind strategy of simply increasing the capacitance value. Instead, it precisely adjusts the equivalent capacitance value of the controlled variable capacitor to a specific target point by switching combinations of capacitor grid switches. This specific point ensures that the current magnetic resonance radio frequency interference frequency (e.g., 64MHz or 128MHz) falls precisely within the series resonant low-impedance window of the capacitor array, thereby constructing an extremely low-impedance discharge path. This fundamentally prevents large-amplitude high-frequency interference signals from entering subsequent circuits, thus avoiding abnormal rectified stimulation currents or causing device malfunctions. Accordingly, during non-scanning intervals or in normal living environments, the capacitance value of the controlled variable capacitor is adjusted to the optimal reference (e.g., a typical value of 4.7 nF) to ensure that the morphological characteristics of the electrocardiogram waveform (e.g., R wave or P wave) are not distorted and to maintain the sensitivity of the sensing.

[0052] The signal, after dynamic processing by the front-end controlled variable capacitor, is guided into the analog front-end processing unit 514 via coupling capacitors 508, 509, and 510 connected in series in the signal path and channel switching switches 511, 512, and 513. Within the analog front-end processing unit 514, the weak electrophysiological signal undergoes high-gain, low-noise amplification, bandpass filtering in a specific frequency band, and high-bit-width analog-to-digital conversion (ADC) to be converted into a digital signal stream suitable for subsequent logic operations. Subsequently, the signal stream is synchronously transmitted to a dual-path discrimination architecture consisting of an amplitude detection unit and a threshold comparison unit: the amplitude detection unit 515 is responsible for calculating the envelope energy of the signal in real time and outputting an amplitude index 517, which serves as a key feature for determining the magnetic resonance scanning activity in the current sensing signal sequence, i.e., the magnetic resonance scanning activity feature; while the threshold comparison unit 516 accurately outputs a sensing event trigger signal 518 by comparing the signal with the dynamic threshold of sensing recognition in real time. Through this series of sophisticated hardware configurations and dynamic adjustment mechanisms, the sensing and detection module 140 provides robust and accurate data support for the cascading determination of effective / ineffective sensing events of the pacing device in complex magnetic resonance environments.

[0053] Figure 6The hardware architecture and circuit topology of the charge pump and pacing output module 160 in this embodiment of the invention are shown in detail. This charge pump and pacing output module 160 is constructed as an output network with dynamic path switching, rapid charge balancing, and physical impedance reconstruction functions. Its specific circuit connection and functional implementation logic are as follows: The DC power supply 601 of this module is connected to a charge pump 602 with bidirectional adjustment capability. The charge pump 602 can not only perform boost charging but also perform buck adjustment according to programmable requirements, thereby storing energy in an energy storage capacitor 603 connected in parallel at its output terminal with its negative terminal grounded. This achieves precise adjustment of the pacing voltage amplitude to ensure constant output energy. On the output link, the positive terminal of the energy storage capacitor 603 is led out through a first switch 604 and a second switch 605, respectively connected to port CAN 503 via the first output capacitor 611 and to port RING 505 via the second output capacitor 612. Meanwhile, at the nodes before the first output capacitor 611 and the second output capacitor 612, a third switch 606 and a fourth switch 607 are respectively connected across to the system reference ground. A fifth switch 608 is connected in series in the loop between the system reference ground and port TIP 504. One end of the internal first resistor 609 and the second resistor 610 are respectively connected to the paths before the second output capacitor 612 and the first output capacitor 611, and the other end is connected together to port TIP after the fifth switch 608.

[0054] Pacing Phase: According to the programmed command, the first switch 604 or the second switch 605, together with the fifth switch 608, is turned on, allowing the energy in the energy storage capacitor 603 to be released to the equivalent cardiac tissue impedance 614 or 613 through the selected output capacitor. Subsequently, a rapid charge recovery phase begins, where the third switch 606 or the fourth switch 607, together with the fifth switch 608, is simultaneously turned on, forming a rapid discharge circuit across the output capacitor via the system reference ground. Furthermore, the internal first resistor 609 and the second resistor 610, connected across the output path and the TIP port, achieve physical impedance reconstruction, providing a discharge path for the induced current in a magnetic resonance environment, greatly reducing the energy accumulation density at the electrode tip. When an active magnetic resonance scan sequence is confirmed according to the trigger command, the system forcibly locks the switch state, causing the TIP port and the RING port to form a bipolar differential output path to avoid rectification effects and the risk of DC component accumulation, ensuring the physical safety and pacing reliability of the device in extremely high electromagnetic field environments.

[0055] Figure 7The core control logic of the digital signal processing module 150 in the cardiac pacing device of this invention is illustrated in detail. This process realizes closed-loop management of the device's fully automatic entry and exit from MRI mode, ensuring safety during scanning and physiological benefits during non-scanning intervals. The specific execution steps and logic are as follows: Multidimensional environmental monitoring: Periodic monitoring tasks (S701a-S701d) are performed in parallel across four dimensions: magnetic field, motion, posture, and perception, and features are extracted from the acquired signals. Among them, magnetic field detection is used to identify static magnetic field features, motion and posture detection is used to detect motion features, and posture features are used to identify whether the patient is in a lying, static scan preparation state. Perception detection is used to capture scan sequence features such as radiofrequency pulses.

[0056] Fully automatic entry determination: The digital signal processing module executes cascaded determination logic. When four conditions are simultaneously met—environmental magnetic field exceeding the limit (S702a-S703a), patient in a static state (S702b-S703b), patient in a non-upright posture (S702c-S703c), and the sensed signal conforming to MRI scan activity characteristics (S702d-S703d)—entry into the MRI scanning environment is confirmed. If the current mode is determined to be MRI (S707), the MRI mode is maintained (S710). If the current mode is determined to be non-MRI (S707), parameter changes after entering MRI mode are executed: Once MRI mode is determined to be entered, the parameter change command is immediately executed (S711). Key execution actions include: forcibly changing the stimulation polarity to bipolar mode to prevent rectification effects under strong radio frequency fields; simultaneously, automatically switching the pacing mode to asynchronous stimulation modes such as DOO, AOO, or VOO to ensure that pacing delivery is not suppressed by perception under strong interference environments and to ensure continuous pacing output; and synchronously driving the sensing and detection module 140 to adjust the controlled variable capacitor to enhance the high-frequency filtering effect.

[0057] Automatic Exit and Delayed Recovery Logic: When any of the above conditions are no longer met (such as the detection of magnetic field disappearance or the patient getting up), and the system is determined to be in programmed working mode (S704), the programmed working mode is maintained (S708). If the system is determined not to be in programmed working mode (S704), the system enters the delay timing (S705) and delay determination (S706) stages. The delay mechanism is introduced to filter out transient interference caused by environmental fluctuations and scanning intervals, ensuring the continuity of environmental changes.

[0058] Fully automatic mode recovery: When the delay time expires (S706) and the environment remains safe, the system executes the parameter change command (S709), automatically cancels the asynchronous pacing configuration, restores the device to the original programmed working mode (S709), and finally completes the mode recovery, so that the pacemaker returns to the physiological sensing pacing state.

[0059] This fully automated process, through multi-physical quantity constraints and delayed confirmation technology, enables seamless entry into protection mode and reliable exit after scanning in the MRI environment, greatly reducing the risk of accidental triggering and improving the convenience of clinical operation.

[0060] Figure 8 This paper demonstrates a simplified and efficient implementation of the decision logic for the digital signal processing module 150. Its core lies in utilizing... Figure 9 The physical characteristics of the magnetic resonance interference signal shown enable rapid identification of invalid sensing events: such as Figure 9 As shown, during active MRI scanning (i.e., when the radio frequency field and gradient field are on), the pseudo ventricular fibrillation (VF) and pseudo atrial fibrillation (AF) signals captured by the unipolar sensing link are essentially interference generated by the coupling of the radio frequency and gradient field. These interference signals exhibit high synchronicity on the time axis (i.e., VF and AF appear almost synchronously) and show obvious circuit saturation characteristics in amplitude. Based on this, they are determined to be invalid sensing events, and the S802 procedure is executed to maintain the original pacing sequence and prevent pacing from being erroneously suppressed. Conversely, if the sensing signal does not have the above synchronous saturation characteristics (such as during the scanning interval), the system executes the S801 procedure to determine it as a valid sensing event and resets the pacing sequence to restore the physiological sensing pacing function. This ensures the real-time response speed and judgment robustness of the device in extreme electromagnetic environments with simpler logic.

[0061] The aforementioned cardiac pacing device can solve the problems of low clinical workflow efficiency, susceptibility to false interference from living magnetic fields, and lack of physiological benefits during scanning intervals caused by the reliance on manual switching or single magnetic field recognition logic in traditional MRI modes. Simultaneously, it avoids physical safety risks such as tissue thermal damage, unexpected stimulation, and sensory inhibition caused by radiofrequency and gradient fields through a multi-dimensional cascaded decision and impedance reconstruction network.

[0062] 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. A cardiac pacing device with fully automated magnetic resonance imaging (MRI) compatibility, comprising: The magnetic field detection module, motion detection module, and attitude detection module are used to detect static magnetic field characteristics, motion characteristics, and attitude characteristics, respectively; the feature is that it further includes: The sensing and detection module is used to acquire sensing signal sequences containing cardiac electrophysiological signals and magnetic resonance interference signals, and to perform sensing event identification and signal intensity analysis to determine sensing event trigger signals and magnetic resonance scan activity characteristics. The digital signal processing module is used to make cascaded decisions on multi-dimensional physical constraints based on static magnetic field characteristics, motion characteristics, attitude characteristics, and magnetic resonance scanning activity characteristics, and automatically switch to magnetic resonance mode and output trigger commands. The charge pump and pacing output module are used to dynamically adjust the timing of the pacing pulses that match the magnetic resonance mode, the pacing pulse energy based on the charge pump adjustment, and the pulse output path according to the trigger command, so as to avoid the rectification effect and the risk of DC component accumulation.

2. The cardiac pacing device with fully automatic magnetic resonance compatible function according to claim 1, characterized in that, The magnetic field detection module includes a magnetic field sensor, a precision current source, and a comparator. The precision current source is configured as a current mirror structure, wherein a first current source generates a controlled pulse driving current and acts on the magnetic field sensor to generate an analog sampling voltage, and a second current source works with a digital-to-analog converter to establish a preset reference threshold voltage. The comparator is used to compare the analog sampling voltage with the reference threshold voltage in real time. When the analog sampling voltage exceeds the reference threshold voltage, a logic jump signal is generated as the static magnetic field characteristic of the magnetic resonance scan.

3. The cardiac pacing device with fully automatic magnetic resonance compatible function according to claim 2, characterized in that, The magnetic field detection module uses a periodic pulse scanning method, combined with a microampere-level pulse drive current, to achieve low-energy magnetic field detection.

4. The cardiac pacing device with fully automatic magnetic resonance compatible function according to claim 1, characterized in that, The motion detection module detects motion features in the following ways: The three-axis acceleration vector is acquired synchronously and dynamic differential calculation is performed to filter out the gravity component to obtain the acceleration change vector. Then, the absolute value of the acceleration change vector is compared with the acceleration gear threshold. A motion score flag is assigned to the sampling time that is less than or equal to the acceleration gear threshold to obtain the motion feature. Within a preset sliding window time, the motion feature is integrally evaluated. When the integral value reaches the preset evaluation threshold, it is identified as a motion state; otherwise, it is identified as a stationary state.

5. The cardiac pacing device with fully automatic magnetic resonance compatible function according to claim 1, characterized in that, The attitude detection module detects attitude features in the following ways: The system acquires the triaxial acceleration reference value in a static upright state and calculates the rotation vector; it also acquires the triaxial acceleration vector at the current sampling moment in real time and calculates the dot product of the rotation vector and the triaxial acceleration vector as the posture feature. This posture feature is used to identify the spatial body position. Specifically, when the posture feature is less than or equal to a preset judgment threshold, the patient is determined to be in a non-upright state; otherwise, the patient is identified as being in an upright state.

6. The cardiac pacing device with fully automatic magnetic resonance compatible function according to claim 1, characterized in that, The sensing and detection module performs sensing and detection through the following continuous signal processing link: The sensing signal sequence, which includes cardiac electrophysiological signals and magnetic resonance interference signals, is input through an electrode port that supports programmable switching between unipolar or bipolar differential modes. A controlled variable capacitor is connected across the electrode port. The controlled variable capacitor is automatically adjusted by the digital signal processing module based on the trigger command output by the magnetic resonance scan activity characteristics. The signal, after being processed by a controlled variable capacitor, is then DC isolated between the external electrodes and the subsequent circuitry by an input coupling capacitor connected in series in the signal path, and guided into the analog front-end processing unit via a channel switching switch. In the analog front-end processing unit, the signal is sequentially amplified by high gain, bandpass filtered, and converted from analog to digital before being synchronously guided to a dual-path discrimination architecture consisting of an amplitude detection unit and a threshold comparison unit. In the amplitude detection unit, the amplitude index of the signal envelope energy is calculated in real time to determine the magnetic resonance scanning activity characteristics. In the threshold comparison unit, the signal is compared with a dynamic threshold in real time, and a sensing event trigger signal is output.

7. The cardiac pacing device with fully automatic magnetic resonance compatible function according to claim 6, characterized in that, The controlled variable capacitor automatically adjusts its capacitance based on trigger commands output by the digital signal processing module according to the magnetic resonance scan activity characteristics, including: Based on the trigger command, during a high-activity magnetic resonance (MRI) scan, the capacitance value of the controlled variable capacitor is adjusted to optimize the resonant impedance characteristics of the front-end filter and improve the attenuation capability of MRI radio frequency interference signals. During non-scanning intervals or in normal living environments, the capacitance value of the controlled variable capacitor is adjusted to the optimal reference to ensure that the morphological characteristics of the ECG waveform are not distorted and to maintain the sensitivity of perception.

8. The cardiac pacing device with fully automatic magnetic resonance compatible function according to claim 1, characterized in that, The digital signal processing module performs cascaded decision-making based on static magnetic field characteristics, motion characteristics, attitude characteristics, and magnetic resonance scanning activity characteristics, including: First, the first level of physical constraint conditions is determined based on the static magnetic field characteristics, motion characteristics, and posture characteristics to determine whether the environmental magnetic field exceeds the standard, whether the patient is in a static state, and whether the patient is in a non-upright posture. Under the premise that the magnetic field exceeds the limit, the object is stationary and not in an upright position, a second-level condition judgment is performed based on the activity characteristics of magnetic resonance scanning. When it is determined that the magnetic resonance scanning process is in progress, a trigger command for magnetic resonance mode is generated. This trigger command is used to drive the sensing and detection module to adjust the capacitance of the controlled variable capacitor to enhance filtering, and also to drive the charge pump and pacing output module to switch to asynchronous stimulation mode and lock the bipolar differential output path; otherwise, a safety countdown program is started, and the magnetic resonance mode is automatically exited after confirming that the environment remains safe.

9. The cardiac pacing device with fully automatic magnetic resonance compatible function according to claim 1, characterized in that, The digital signal processing module is also used for rapid identification of invalid sensing events based on static magnetic field characteristics, motion characteristics, attitude characteristics, and sensing signals, including: First, the first level of physical constraint conditions is determined based on the static magnetic field characteristics, motion characteristics, and posture characteristics to determine whether the environmental magnetic field exceeds the standard, whether the patient is in a static state, and whether the patient is in a non-upright posture. If, under the premise that the magnetic field exceeds the limit, the object is stationary and not in an upright position, the sensing signal exhibits high synchronicity on the time axis and shows circuit saturation characteristics in amplitude, it is determined to be a false sensing event and the original pacing sequence is maintained; otherwise, it is determined to be a valid sensing event and the pacing sequence is reset to restore physiological sensing pacing function.

10. The cardiac pacing device with fully automatic magnetic resonance compatible function according to claim 1, characterized in that, The charge pump and pacing output module employs an output network with dynamic path switching, rapid charge balancing, and physical impedance reconstruction capabilities, specifically including: The energy source is connected to the input of the charge pump via a DC power supply. The output of the charge pump is connected in parallel with an energy storage capacitor, the negative terminal of which is connected to the system reference ground. In the output path, the positive terminal of the energy storage capacitor is led out through the first and second switches to two branches, which are connected to the CAN port and the RING port via the first and second output capacitors, respectively. At the same time, the third and fourth switches are connected across the nodes before the first and second output capacitors to the system reference ground, respectively. The fifth switch is connected in series in the loop between the system reference ground and the TIP port. One end of the first and second internal resistors are connected to the paths before the first and second output capacitors, respectively, and the other end is connected together to the TIP port after the fifth switch. During the pacing phase, the first or second switch, together with the fifth switch, is turned on to deliver pacing pulses; then, the rapid charge recovery phase begins, where the third or fourth switch, together with the fifth switch, is turned on simultaneously, so that the two ends of the output capacitor form a rapid discharge circuit through the system reference ground, thereby achieving rapid charge recovery. The internal first and second resistors are connected across the output path and the TIP port to achieve physical impedance reconstruction, providing a discharge path for the induced current in the magnetic resonance environment. When the magnetic resonance scanning activity characteristics are detected, the switch state is forcibly locked so that the TIP port and the RING port form a bipolar differential output path.

Images