A method for automatically detecting the pacing threshold of a cardiac pacemaker and a pacemaker

Abstract

The present invention discloses an automatic detection method of a pacing threshold of a cardiac pacemaker and a pacemaker, comprising: when the pacing threshold is automatically detected, the cardiac pacemaker issues pacing pulses according to the current pacing output voltage, and at the end of the pacing pulse issuance, the sensing time and the sensing circuit are turned on to detect the myocardial depolarization wave, wherein the sensing time is set to the time required to detect the myocardial depolarization wave, and depolarization discharge is performed at the end of the sensing time, and the cardiac pacemaker determines whether capture is successful according to the detection result of the myocardial depolarization wave; when capture is successful, backup pacing is not issued, and the current pacing output voltage is updated by reducing one level, and the above pacing threshold automatic detection process is repeated until it is determined that the capture is unsuccessful, and the previous level pacing output voltage corresponding to the unsuccessful capture is used as the detected pacing threshold; when capture is unsuccessful, backup pacing is performed after the last discharge. In this way, automatic and accurate detection of the pacing threshold can be achieved at a low cost.

Description

Technical Field

[0001] The invention belongs to the technical field of implantable active medical devices, and in particular relates to an automatic detection method for a pacing threshold of a cardiac pacemaker and a pacemaker. Background Art

[0002] Cardiac pacemakers are active implantable medical devices that are widely used in the treatment of bradyarrhythmias. The cardiac pacing system consists of pacing electrode leads and a pulse generator. The pulse generator can emit pulses of set frequency on demand, which are transmitted through the electrode leads to the myocardium (atrium or ventricle) that the electrode contacts, so that local myocardial cells are electrically stimulated and excited, and spread to the surrounding myocardium through the connection between cells, so that the entire atrium or ventricle is excited and then produces contraction activity, restoring the normal rhythm of the heart.

[0003] Automatic detection of pacing thresholds makes pacemakers more intelligent, safer and more energy-efficient. 1) The pacing output voltage is set according to the automatically detected threshold to extend the life of the pacemaker; 2) The threshold changes dynamically, and a reliable pacing output voltage is provided based on the automatically detected pacing threshold; the pacing output voltage setting affects the service life of the pacemaker; after the pacemaker is implanted, the pacing threshold will change under different cardiac conditions, so a fixed pacing output voltage cannot ensure that the myocardium is always captured, and even a higher fixed pacing output voltage may be unsafe. The setting of pacing output based on the automatic detection of the pacing threshold not only ensures the effectiveness and safety of cardiac pacing, but also greatly reduces the energy consumption of the pacemaker and extends the life of the pacemaker.

[0004] The pacing threshold set by the pacemaker includes the pacing pulse voltage amplitude and width, such as Figure 1 As shown, the voltage amplitude of the pacing pulse is generated by the charging pump Vpump, and the energy is stored in the capacitor Cs. The pacing switch (S_ring / S_tip) is turned on to output the pacing pulse through the capacitor to the positive Tip and negative Ring ports of the pacemaker, and the electrodes stimulate the heart to beat. The width of the pacing pulse is controlled by the conduction time of the electronic switch, which is usually around 0.4ms. After pacing, depolarization discharge is required to eliminate electrode polarization and electrical corrosion. In the circuit, the pacing switch S_ring is disconnected, the depolarization discharge switch S_dischange and the pacing switch S_tip are turned on, and reverse discharge is performed through the capacitor Cp to achieve electrode depolarization, neutralization of positive and negative charges, and myocardial recovery.

[0005] The pacing threshold changes dynamically. It is tested by issuing pacing pulses of different outputs to determine whether it is captured (stimulating cardiac pacing). The basis for determining whether pacing capture is detected is whether there is a pacing-induced myocardial depolarization wave in the post-pacing potential sensed by the terminal electrode after the pacing pulse is issued. The specific pacing capture detection method is as follows: Figure 2The pacing pulse is delivered by the pacing delivery equivalent circuit shown in the figure. Figure 3 As shown, when the pacing capacitor ends releasing the pulse, a detection window of a set duration is opened, and at the same time, the depolarization discharge switch S_dis and the pacing switch S_tip are turned on to perform depolarization discharge, and the sensing switches S_sen1 and S_sen2 are turned on to form a sensing circuit for capture detection, as shown in FIG. Figure 4 As shown, the depolarization fusion wave signal of myocardial depolarization and depolarization discharge is specifically detected, the depolarization electrical signal is removed through various algorithms, the myocardial depolarization wave is detected, and it is determined whether the myocardial depolarization is captured. If there is no myocardial depolarization signal, it means that the myocardial depolarization is not captured, and a backup pacing signal with a higher threshold needs to be sent subsequently to ensure capture.

[0006] from Figure 4 It was observed that capture detection is difficult. First, the electrode signal detected is a fused electrical signal of myocardial depolarization and depolarization discharge, which is a superposition signal of the two signals. At the same time, the depolarization capacitor discharges and is connected in parallel to the electrode detection input port. The myocardial depolarization wave signal is greatly attenuated, which adds considerable difficulty to signal detection.

[0007] Since the myocardial depolarization wave signal is greatly attenuated by the capacitor Cp, the myocardial depolarization wave signal is very small and cannot be collected by the sensing module. For this reason, a special low-noise and high-gain circuit module is designed to collect the fused electrical signal. Of course, it is also very difficult to detect the myocardial depolarization signal from the fused electrical signal. For this reason, various algorithms are designed to judge the capture situation. The most common method is to count the area corresponding to the discharge curve after the pacing pulse is issued. The pacing capture detection function is configured with specially designed special circuits and algorithm resources to achieve it. The corresponding high-difficulty pacing capture detection uses a very high cost, and its accuracy and correctness cannot be fully guaranteed. Summary of the invention

[0008] In view of the above, an object of the present invention is to provide a method for automatic detection of the pacing threshold of a cardiac pacemaker and a pacemaker, which can realize automatic and accurate detection of the pacing threshold at a low cost, and then obtain an accurate pacing threshold to reduce pacing energy, ensure pacing safety, and extend the service life of the cardiac pacemaker.

[0009] To achieve the above-mentioned object of the invention, an embodiment of the present invention provides a method for automatically detecting a pacing threshold of a cardiac pacemaker, comprising the following steps:

[0010] When the pacing threshold is automatically detected, the cardiac pacemaker issues pacing pulses according to the current pacing output voltage. When the pacing pulse is issued, the sensing time and sensing circuit are turned on to detect the myocardial depolarization wave. The sensing time is set to the time required to detect the myocardial depolarization wave. When the sensing time ends, the depolarization discharge is performed. The cardiac pacemaker determines whether the capture is successful based on the detection result of the myocardial depolarization wave.

[0011] When it is determined that the capture is successful, the backup pacing is not issued, and the current pacing output voltage is updated by reducing one level, and the above pacing threshold automatic detection process is repeated until it is determined that the capture is unsuccessful, and the previous level of pacing output voltage corresponding to the unsuccessful capture is used as the pacing threshold for detection;

[0012] When capture is judged to be unsuccessful, backup pacing is performed after the last discharge.

[0013] Preferably, the method further comprises: when it is determined that capture is unsuccessful, preparing to deliver backup pacing while performing depolarization discharge, wherein the pacing output voltage of the backup pacing is at least greater than the detected current pacing threshold. Alternatively, the pacing output voltage of the backup pacing is set to a sufficiently large value, such as greater than 5V, to ensure effective pacing and successfully capture the myocardium.

[0014] Preferably, judging whether the capture is successful or not according to the detection result of the myocardial depolarization wave includes: judging that the capture is successful when the sensing circuit detects the myocardial depolarization wave, and judging that the capture is unsuccessful when the sensing circuit does not detect the myocardial depolarization wave signal.

[0015] Preferably, the perception time is 40-50 ms, and more preferably, the perception time is 45 ms.

[0016] An embodiment of the present invention further provides a cardiac pacemaker, which adopts the above-mentioned method for automatically detecting the pacing threshold of the cardiac pacemaker.

[0017] Compared with the prior art, the present invention adopts the above-mentioned automatic detection method for the threshold of the cardiac pacemaker, and the beneficial effects of the present invention include at least:

[0018] The depolarization wave sensing time is set and the sensing circuit is turned on during this time to detect a single myocardial depolarization wave, and the depolarization discharge is delayed until the sensing time is over. In this way, by separating the myocardial depolarization wave and the depolarization discharge signal in timing after the pacing pulse is issued, and turning on the sensing circuit to detect a single myocardial depolarization wave during the delayed depolarization discharge time, the difficulty of pacing capture detection judgment is solved, and the accuracy of capture detection is improved. The detection can be realized by using a general sensing circuit, and no special pacing capture detection circuit is required, which reduces the cost of circuit materials; if the myocardial depolarization wave signal is not detected, it is judged that the capture is unsuccessful. After the sensing is over, a pacing pulse with a higher pacing output is issued for backup pacing, so that the pacing threshold is dynamically tracked, the pacing is effective and safe, the pacing output required for safe pacing is accurately set, the pacing energy is reduced, and the service life of the pacemaker is extended. The above automatic detection method is suitable for implantable cardiac pacemakers and cardiac defibrillators and other products. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0020] Figure 1 is a schematic diagram of an existing pacing sensing structure provided by an embodiment;

[0021] Figure 2 It is an existing pacing delivery equivalent circuit provided by the embodiment;

[0022] Figure 3 It is an existing capture detection equivalent circuit provided by the embodiment;

[0023] Figure 4 It is a schematic diagram of existing capture detection provided by an embodiment;

[0024] Figure 5 is a flow chart of a method for automatically detecting a pacing threshold of a cardiac pacemaker provided in an embodiment;

[0025] Figure 6 is a schematic diagram of capture detection of the present invention provided in an embodiment;

[0026] Figure 7 The pacing release equivalent circuit of the present invention provided by the embodiment;

[0027] Figure 8 is a capture detection equivalent circuit of the present invention provided by an embodiment;

[0028] Fig. 9 The depolarization discharge equivalent circuit of the present invention provided by the embodiment;

[0029] Fig.10 The backup pacing equivalent circuit of the present invention provided by the embodiment;

[0030] Fig.11 is an electrical schematic diagram of a simulated pacing system of the present invention provided in an embodiment;

[0031] Fig.12 It is a waveform diagram of the simulation signal output of the present invention provided in an embodiment. DETAILED DESCRIPTION

[0032] To make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific implementation methods described herein are only used to explain the present invention and do not limit the scope of protection of the present invention.

[0033] The inventive concept of the present invention is: in view of the technical problems that the capture detection and judgment in the existing capture detection scheme are relatively difficult, and the detection accuracy and correctness are very limited, the embodiment of the present invention provides an automatic detection method for the pacing threshold of a cardiac pacemaker, which delays the depolarization discharge after the pacing pulse is issued, and starts the depolarization wave detection for a certain period of time, which solves the problem of superposition of detection signals. At the same time, there is no large attenuation of the depolarization wave signal by the depolarization discharge circuit, and there is no need to specially design a depolarization fusion wave detection circuit. The myocardial depolarization wave signal can be easily detected using the existing sensing circuit. After the capture detection, the depolarization discharge process is started, and the backup pacing is prepared to be issued. If the myocardial depolarization wave signal is detected, it means that it has been captured, and there is no need to issue the backup pacing. If there is no capture, a larger output backup pacing pulse needs to be issued to ensure capture.

[0034] like Figure 5 and Figure 6 As shown, the method for automatically detecting the pacing threshold of a cardiac pacemaker provided in the embodiment comprises the following steps:

[0035] S1, when the pacing threshold is automatically detected, the pacemaker issues pacing pulses according to the current pacing output voltage. When the pacing pulse is completed, the sensing time and sensing circuit are turned on to detect the myocardial depolarization wave, and depolarization discharge is performed when the sensing time ends.

[0036] In the embodiment, the pacemaker is as follows Figure 7 The pacing pulse delivery equivalent circuit shown is used to deliver pacing pulses. Specifically, the sensing switch (S_sen) is disconnected, the depolarization discharge switch (S_dis) is disconnected, the pacing switch (S_ring / S_tip) is turned on, and the pacing pulses are delivered through the capacitor Cp.

[0037] In the embodiment, a sensing time is started at the same time as the pacing pulse is released, and the sensing circuit is turned on to detect the myocardial depolarization wave. The sensing time is set to be able to detect the myocardial depolarization wave at least when the myocardial depolarization wave exists, preferably 45ms. Figure 8 The sensing circuit for capture detection is turned on as shown, specifically the sensing switch (S_sen) is turned on, the pacing switch (S_ring / S_tip) is turned off, the depolarization discharge switch (S_dis) is turned off, and the myocardial depolarization wave is detected through the sensing circuit.

[0038] At the end of the sensing time, a depolarization discharge is performed. The equivalent circuit of the depolarization discharge is as follows Fig. 9 As shown, the sensing switch (S_sen) is disconnected, the pacing switch (S_ring) is disconnected, the pacing switch S_tip is turned on, and the depolarization discharge switch (S_dis) is turned on. The depolarization voltage is released through the capacitor Cp to perform depolarization discharge, thereby achieving electrode depolarization, neutralization of positive and negative charges, and myocardial recovery.

[0039] S2, the pacemaker determines whether the capture is successful based on the detection results of the myocardial depolarization wave. When it is determined that the capture is successful, the backup pacing is not issued, and the current pacing output voltage is updated by reducing one level, and the above-mentioned pacing threshold automatic detection process is repeated until it is determined that the capture is unsuccessful. The previous level of pacing output voltage corresponding to the unsuccessful capture is used as the pacing threshold for detection.

[0040] In the embodiment, when the sensing circuit detects the myocardial depolarization wave and determines that the capture is successful, there is no need to issue backup pacing when the capture is successful. At this time, it is considered that the current pacing output voltage is capable of successfully pacing the heart. Therefore, in order to reduce energy consumption, the pacing output voltage needs to be appropriately reduced. Specifically, the pacing output voltage can be reduced by reducing the voltage by one level each time, and then the current pacing output voltage is updated. At this point, it can be considered that a complete cardiac pacing and automatic detection of the pacing threshold are completed, and then the updated current pacing output voltage is used to perform the next automatic detection of the pacing threshold. This cycle is repeated until it is determined that the capture is unsuccessful, that is, it is considered that the current pacing output voltage corresponding to the unsuccessful capture cannot successfully pace the heart. Therefore, it is necessary to use the previous level pacing output voltage corresponding to the unsuccessful capture as the pacing threshold for detection, thereby realizing automatic detection of the pacing threshold.

[0041] S3, when it is determined that capture is unsuccessful, backup pacing is prepared to be delivered while depolarization discharge is being performed, wherein the pacing output voltage of the backup pacing is at least greater than the detected current pacing threshold, and the backup pacing is delivered after the depolarization discharge time is over.

[0042] In an embodiment, the pacing output voltage of the backup pacing is set according to the pacing output voltage of the previous level before the loss of capture (that is, the current pacing threshold), and is specifically set to be at least greater than the detected current pacing threshold, or directly set to a larger value (such as 5V) to ensure safe pacing.

[0043] In the embodiment, according to Fig.10 The backup pacing release equivalent circuit shown releases backup pacing pulses. Specifically, the sensing switch (S_sen) is disconnected, the pacing switch (S_ring / S_tip) is turned on, and the depolarization discharge switch (S_dis) is disconnected. A voltage pulse with a higher pacing output that can ensure the capture of the heart is released through capacitor Cs. When the backup pacing pulse is completed, a sensing time is started, and myocardial depolarization wave detection and depolarization discharge are performed according to the processes of S1 and S2.

[0044] In order to verify the above automatic capture detection method, the following Fig.11 The electrical schematic diagram of the pacemaker system simulation is shown in the figure. The timing control and switch descriptions of each part of the circuit are as follows:

[0045] Pacing part: pacing voltage source V_Cs;

[0046] The pacing switch is S_ring, and the pacing pulse control source is Tim-pace (V2);

[0047] Discharge part: the depolarization discharge switch is S_dis, and the timing control source is Tim-dis (V3);

[0048] Sensing part: the sensing switch is S_sen, and the timing control source is Tim-ER (V1);

[0049] Myocardial depolarization signal: The myocardial depolarization signal switch is S_er, and the timing control source is Tim-ER (V1);

[0050] Perception module: The perception signal is processed through the active bandpass filter composed of U1 and U2.

[0051] Specifically, the simulation process is described as follows:

[0052] Issue pacing pulse: The pacing pulse controls the S_ring switch to turn on, and the pacing voltage source V_Cs outputs the V-pace pacing pulse. Through the capacitor Cp, the V-Ring pulse is issued to simulate the heart load R_heart (500Ω) to obtain the pacing pulse. The simulated pacing pulse control signal is as follows Fig.12 As shown in the red waveform of tim-pace, the pacing pulse is applied to the simulated heart. Fig.12 5Vp-p blue positive pulse in the middle v-ring.

[0053] Delayed depolarization discharge: When the pacing pulse is released, a sensing time (about 45mS) is turned on. At this time, the S_ring switch and S_dis switch are in the off state, and there is no voltage on the simulated heart load R_heart. Fig.12 In the blue waveform of the v-ring, we can see that there is a 45ms delay after the pacing pulse is delivered. This sensing time turns on the sensing circuit and shows that there is no influence of any residual charge after pacing during the sensing time.

[0054] Turn on the sensing circuit: When the pacing pulse is released, a sensing time (about 45mS) is started and the sensing circuit channel S-sen switch is turned on. Any tiny signal on the simulated heart load R_heart can be detected by the sensing circuit. Fig.12 In the blue waveform of the v-ring, the sensing circuit is turned on after a delay after the pacing pulse is delivered.

[0055] Myocardial depolarization wave: The pacing pulse stimulates the myocardium, captures the ventricle or atrium to generate a myocardial depolarization wave signal, and the Tim-ER myocardial depolarization wave controls the S_er switch to turn on. Fig.12During the time period of the green waveform pulse in the middle tim-er, a myocardial depolarization wave signal is sent to the simulated heart load R_heart, such as Fig.12 As shown in the green waveform of v-sen.

[0056] Sensing capture: The above-mentioned opened sensing circuit channel detects myocardial depolarization signals. If the pacing pulse captures the myocardium, a depolarization wave signal is generated. If the pacing pulse energy is insufficient, the myocardium cannot be captured and no depolarization wave signal is generated. The detection of the depolarization wave is the same as the detection of the sensing signal. Fig.12 The brown signal in v-sen-out shows the depolarization wave signal after being processed by the sensing circuit.

[0057] Depolarization discharge: After the pacing pulse is released, a sensing time (about 45ms) is started to detect the myocardial depolarization signal. After the detection is completed, the depolarization discharge is started. Fig.12 The negative pulse discharge waveform is shown in the blue waveform of the v-ring.

[0058] The above simulation circuit test verifies the correctness of the innovative pacing threshold detection scheme. It uses the delayed depolarization discharge method to decompose the mixed signal and split the timing to solve the technical problems of pacing capture detection, improves the accuracy of pacing capture detection and the accuracy of dynamically setting the pacing output based on the pacing threshold, and provides innovative ideas for the threshold capture detection scheme of active implantable cardiac pacemakers.

[0059] The automatic capture detection method provided above solves the complexity of the threshold analysis of the dynamic tracking function of the pacing threshold, making pacing effective and safe. The problem of excessive margin in the pacing output setting is solved by automatically adjusting the pacing output based on the pacing threshold. Accurate pacing output reduces unnecessary pacing energy consumption and prolongs the service life of the pacemaker.

[0060] The specific implementation methods described above provide a detailed description of the technical solutions and beneficial effects of the present invention. It should be understood that the above is only the most preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, supplements and equivalent substitutions made within the scope of the principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A cardiac pacemaker, characterized in that: The cardiac pacemaker adopts the following automatic detection method of pacing threshold, comprising the following steps: When the pacing threshold is automatically detected, the cardiac pacemaker issues pacing pulses according to the current pacing output voltage. When the pacing pulse is issued, the sensing time and sensing circuit are turned on to detect the myocardial depolarization wave. The sensing time is set to the time required to detect the myocardial depolarization wave. When the sensing time ends, the depolarization discharge is performed. The cardiac pacemaker determines whether the capture is successful based on the detection result of the myocardial depolarization wave. When it is determined that the capture is successful, the backup pacing is not issued, and the current pacing output voltage is updated by reducing one level, and the above pacing threshold automatic detection process is repeated until it is determined that the capture is unsuccessful, and the previous level of pacing output voltage corresponding to the unsuccessful capture is used as the pacing threshold for detection; When it is determined that capture is unsuccessful, backup pacing is prepared to be delivered while depolarization discharge is in progress, wherein the pacing output voltage of the backup pacing is at least greater than the detected current pacing threshold, and the backup pacing is performed after the depolarization discharge.

2. The cardiac pacemaker according to claim 1, characterized in that: Judging whether the capture is successful or not according to the detection result of the myocardial depolarization wave includes: judging that the capture is successful when the sensing circuit detects the myocardial depolarization wave signal, and judging that the capture is unsuccessful when the sensing circuit does not detect the myocardial depolarization wave signal.

3. The cardiac pacemaker according to claim 1, characterized in that: The perception time is 40-50ms.

4. The cardiac pacemaker according to claim 1, characterized in that: The perception time is 45ms.

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