CN1172630C - Device for detecting T wave alternation in exercise electrocardiogram - Google Patents

Abstract

The present invention belongs to the technical field of medicine detection, and relates to a method and a device thereof for detecting the alternation of T waves of an exercise electrocardiogram. The present invention has the method that the exercise electrocardiogram is divided into an adjustment period, a first-stage heart rate period, a second-stage heart rate period and a recovery period according to the range of heart rate valves; each stage is set to sustain a period of time, the movement speed and the gradient of a flat plate are controlled, the heart rates of testers orderly enter the four stages of the heart rate values, and electrocardio signals of the first-stage heart rate period and the second-stage heart rate period are respectively recorded. The device comprises a lead device, an input protective circuit, an amplifier system, an analog to digital, a microcomputer, a flat plate and a flat plate control interface circuit, wherein the amplifier system is composed of a pre-amplying circuit, a stopping circuit, a main amplifier, trapped waves of 50Hz, an optoelectronic isolating amplifier and a low-pass filter circuit. The present invention can be used for detecting the alternation of T waves which can not detected by naked eyes in a microvolt magnitude, and can also be used for detecting, processing and researching the alternation of T waves, and the present invention provides a reliable tool for relevant clinical research.

Description

Device for detecting T wave alternation in exercise electrocardiogram

technical field

The invention belongs to the technical field of medical detection, in particular to the design of a detection device for T wave alternation in exercise electrocardiograms.

Background technique

Malignant ventricular arrhythmia is a heart disease that poses a great threat to human life safety. It is a major factor in the loss of life in developed countries such as Europe and the United States. Therefore, the prediction of malignant ventricular arrhythmia in these countries has always been at the forefront Discussion questions. At present, the relatively accepted predictive method is electrophysiological examination of cardiac catheterization, which uses a programmed stimulator to deliver 2 or 3 electrical stimuli under program control to the right atrium through cardiac catheter electrodes. If ventricular tachycardia (VT) can be induced, then Indicates that there is a material basis for the occurrence of ventricular tachycardia and ventricular fibrillation (Vf), and this method is called intracardiac programmed electrical stimulation (PES). This method has certain risks and may cause harm to patients. Therefore, many studies have tried to find an effective non-invasive prediction method, and thus developed a T wave alternation detection technology based on digital ECG to predict malignant ventricular arrhythmia.

The ECG signal of a typical cardiac cycle is composed of P wave, QRS wave and T wave, etc., forming the ECG waveform shown in Figure 1, wherein P wave represents the depolarization process of the atrium, QRS wave represents the depolarization process of the ventricle, and T wave represents the depolarization process of the ventricle. Waves represent the repolarization process of the ventricles.

T wave alternation means that on the body surface ECG, the shape or amplitude of T wave changes beat by beat on the basis of repeated intervals, that is, the shape or amplitude of T wave appears regularly in the form of ABABAB... between consecutive heart beats. Figure 2 is a case of surface ECG with visible T wave alternation.

Studies in some countries have shown that in the higher heart rate range of 90bpm-110bpm, the appearance of T wave alternation can predict the occurrence of malignant ventricular arrhythmia. However, T wave alternation visible to the naked eye is relatively rare, so predicting the occurrence of malignant ventricular arrhythmias by observing T wave alternation has not yet been applied in practice.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies of the prior art, to propose a method for detecting T-wave alternation in exercise electrocardiogram and its device, which can be used to detect the T-wave alternation that is invisible to the naked eye, that is, the microvolt level, and can be used For the detection and treatment of T wave alternation, it also provides a reliable tool for related clinical research.

The present invention proposes a kind of detection method of T wave alternation in exercise electrocardiogram, comprises the following steps:

1) According to the range of heart rate value, it is divided into four stages, which are: the adjustment period, when the heart rate is below 90bpm; the first-level heart rate period, when the heart rate is 90-105bpm; Heart rate below 90bpm;

2) Set the duration of the first-level heart rate period and the second-level heart rate period to 3-6 minutes respectively;

3) Control the movement speed and slope of the tablet so that the heart rate of the tester enters the four stages of the heart rate value in turn, and maintain the duration set for the first-level heart rate period and the second-level heart rate period;

4) Record the electrocardiographic signals of the first-level heart rate period and the second-level heart rate period respectively.

Said method for processing the electrocardiographic signal may be sequentially performing steps such as amplification, filtering, and analog-to-digital conversion.

The detection device for the alternation of T waves in the exercise electrocardiogram proposed by the present invention comprises the following parts: a lead device connected to the subject to be tested, an input protection circuit connected with the output signal of the lead device, and the protection circuit A connected amplifier system, and an analog-to-digital conversion circuit connected to the output of the amplifier system, the analog-to-digital conversion circuit is connected to a microcomputer, a flat panel control interface circuit is connected to the computer, and the control interface circuit is connected to be tested The said amplifier system is composed of a preamplifier circuit, a DC blocking circuit, a main amplifier, a 50Hz notch wave, a photoelectric isolation amplifier and a low-pass filter circuit connected in sequence.

The working principle of the present invention is described as follows:

According to the current clinical research results, it is generally believed that within the heart rate range of 90 to 110bpm, the appearance of T wave alternation has diagnostic value, and the occurrence of significant T wave alternation at 90 to 105bpm is positive, and there is still no significant T wave alternation at a heart rate above 105 Then it is negative, and according to this standard heart rate range, the present invention has newly created the detection method of T wave alternation in exercise electrocardiogram.

The subject is on the tablet, and the computer outputs control commands through the interface circuit controlled by the tablet to control the movement of the sports tablet. The program sets the described detection method, and the program controls the motion of the panel according to the method, and the subject is forced to move along with the panel motion, and the human body motion ECG signal (voltage) passes through the protection circuit from the Mason-Likar lead system (for The patient's safety and the reliable work of the system), enter the amplification system, and the hardware circuit blocks, filters, and amplifies. After analog-to-digital conversion, it becomes a digital signal and enters the computer. In the computer, the ECG signal is digitally filtered to suppress the base drift, power frequency interference and electromyographic interference, reduce the noise of the exercise ECG, and then determine the QRS complex wave, so as to select the T wave, and then perform power spectrum analysis on the T wave. The moving window was used to analyze the T wave alternation of the whole 12 leads, and the detection results of T wave alternation were obtained.

Features and effects of the present invention:

According to the characteristics of T-wave alternation, the present invention designs a set of detection method and its device, collects exercise ECG signals, can detect T-wave alternation of microvolt level, and can be used for the detection and processing research of T-wave alternation , also provides a reliable tool for related clinical research.

Description of drawings

Figure 1 shows the basic waveform of an electrocardiogram.

Figure 2 is a case of surface electrocardiogram with visible T wave alternation.

Fig. 3 is a schematic structural diagram of a T-wave alternate detection device.

Fig. 4 is a flow chart for controlling the running of the tablet and alternately detecting T waves.

Figure 5 is the preamplifier.

Figure 6 is the main amplifier.

Figure 7 is a 50Hz trap circuit.

Figure 8 is a photoelectric isolation amplifier.

Figure 9 is a low-pass filter circuit.

Figure 10 is the panel control interface circuit.

FIG. 11 is a heart rate change trend curve in the results of T wave alternate detection.

Figure 12 shows the T wave alternation trend in the test results.

Detailed ways

A kind of detection method and device embodiment thereof of electrocardiogram T wave alternation that the present invention proposes are described in detail as follows in conjunction with each accompanying drawing:

A kind of detection device embodiment of T wave alternation in exercise electrocardiogram proposed by the present invention, as shown in Fig. Computer, tablet and its control interface circuit. The amplifier system consists of six parts: preamplifier, DC blocking circuit, main amplifier stage, 50Hz notch wave, photoelectric isolation amplifier, and low-pass filter. The specific implementation structure and working principle of each part are described in detail as follows:

The lead device of this embodiment is composed of a Mason-Likar improved limb lead and a Wilson resistance network, and receives ECG signals from the lead electrodes.

The DC blocking circuit of this embodiment is used to eliminate the polarization voltage generated when the electrodes are in contact with the human body.

The microcomputer Pentium III of this embodiment outputs control commands through the interface circuit controlled by the flat panel to control the motion of the flat panel. The program sets the motion scheme for detecting T wave alternation, and the program controls the movement of the tablet according to the motion scheme. The subject is forced to move along with the movement of the tablet, and the ECG signal during his movement enters the amplification system and computer through the electrodes through the leads. The flow chart of the computer controlling the motion plate and detecting the alternation of T waves is shown in Figure 4.

First of all, the system is initialized, setting the electronic medical records, amplifier magnification, starting analog-to-digital conversion and other preparations. The computer resets the initial state of the tablet through the tablet control interface, the tablet is in a horizontal and static state, and collects 2-minute rest period ECG data. Then, control the tablet to start exercising and enter the adjustment period to collect the ECG data until the heart rate reaches 90bpm. Control the speed and slope of the tablet, enter the first-level heart rate period, and collect ECG data for 5 minutes. Continue to control the speed and slope of the tablet exercise. When the heart rate reaches above 105bpm, enter the second-level heart rate period and collect ECG data for 5 minutes. Then, stop the exercise tablet and enter the recovery period. Continue to record ECG data until the heart rate drops below 90bpm . Finally, the obtained electrocardiographic data are analyzed and processed to obtain an analysis result of T wave alternation.

The input protection circuit of this embodiment is composed of two-stage limiter protection circuits. The first stage uses neon bulbs to limit the voltage to 60-70V, and the second stage uses bidirectional series diodes to keep the input terminal voltage from not exceeding 7V.

The preamplifier of this embodiment is shown in Fig. 5, which is composed of instrument amplifier INA118, resistors R2, R3, Rg capacitors CN1, CN2. The preamplifier has the characteristics of high common mode rejection ratio, high input impedance, low noise and strong anti-interference ability.

In order to be able to adapt to different amplitudes of ECG signals, the main amplifier of this embodiment adopts a program-controlled variable gain amplifier circuit shown in FIG. 6 to adapt to exercise ECG signals with different amplitudes. The main amplifier is composed of 7650 operational amplifier, analog multi-way switch 4051, multiple resistors R8-R14, R22 and multiple capacitors C12-C14, CN3, CN4. The analog multiplexer 4051 selects different resistors to select different amplification factors.

The 50Hz notch circuit in this embodiment is a band-stop filter, mainly used to filter out power frequency interference. A typical double-T network composed of two operational amplifiers A1, A2, three resistors R1, R2, R3 and three capacitors C1, C2, C3 is used, as shown in Figure 7, its amplitude-frequency characteristics are:

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In the formula, k is the voltage division ratio of the potentiometer W.

In order to ensure the safety of the patient, the photoelectric isolation amplifier of this embodiment adopts the floating ground technology to realize the complete isolation of the human body and the electricity. The circuit is composed of a complementary optocoupler TLP-521, as shown in Figure 8, two-stage operational amplifiers A1 and A2 are used, and the coupling is realized through optocouplers PH1 and PH2 working in the linear region, where W1 and W2 are potentials to adjust the operating point and gain of the amplifier.

The low-pass filter circuit of this embodiment is used to suppress high-frequency interference generated by the circuit, including a second-order voltage-controlled voltage source low-pass filter composed of an operational amplifier A1, resistors R1, R2, and R4, and capacitors C1 and C2. And a passive RC low-pass filter circuit composed of R3 and C3, as shown in Figure 9.

In the analog-to-digital conversion circuit of this embodiment, the analog-to-digital conversion chip is MAX122, the sampling rate is 12×500 Hz, and the sampling accuracy is 12 bits.

The flat plate of this embodiment adopts known commercially available products.

The tablet control interface circuit of the present embodiment, as shown in Figure 10, is made up of analog multi-way switch 4051, counter 74LS169, and the analog multi-way switch connects or disconnects each control button of motion flat panel, and the count value of counter determines concrete button. For example, the operation of the DOWN switch starts to simulate the disconnection of the switch, then gives the counter a pulse to clear it to zero, then counts 3, and the analog switch corresponding to DOWN is closed for 50 milliseconds, which is equivalent to closing the DOWN switch once and then disconnecting the analog switch, the counter is cleared.

The method for the alternate detection of T waves of the present embodiment is described as follows:

The design exercise program is divided into four stages: adjustment period (including buffer time), first-level heart rate period, second-level heart rate period and recovery period.

Record 2-minute resting ECG data before exercise, and record 3-minute recovery ECG data after exercise. Due to the relatively large individual differences of the subjects, if some subjects have a phenomenon of rapid heart rate in the early stage of exercise, in order to avoid affecting the subsequent grading feedback, a buffer time of one minute is arranged. The operator adjusts this time according to the specific conditions of the subject, such as whether the exercise posture is correct or whether the heart rate is stable, and gives specific guidance to the subject. Afterwards, the program began to adjust the exercise parameters of the movable tablet according to the subject's heart rate. Due to the large individual differences in the basic heart rate and heart rate rate, the time of the adjustment period will fluctuate greatly among individuals. The adjustment period ended after the subject's heart rate exceeded 90 bpm.

At present, the positive heart rate recognized abroad is 110bpm, that is, below 110bpm, if T wave alternation occurs, it is a symptom of the disease, and above 110bpm, T wave alternation does not have diagnostic value, because above this heart rate, even normal people often There are T waves appearing alternately. The negative heart rate is 105bpm, that is, there is no T wave alternation above this heart rate, and it can be considered as T wave alternation negative. According to the above standard, the present invention adopts a two-level heart rate control strategy, the first-level heart rate is 90-105bpm, and the second-level heart rate is above 105bpm. Level 1 heart rate is considered positive for detection of T wave alternation, while level 2 heart rate is considered negative for detection of T wave alternation. After the adjustment period, the subject's heart rate was controlled within the first-level heart rate range for 5 minutes, and if the heart rate was too low, the amount of exercise was increased. If it is too high, reduce the amount of exercise. After the first-level heart rate period is over, it will directly enter the second-level heart rate period. During the period, the subject's heart rate will reach the second-level heart rate by increasing the amount of exercise, and the duration is also 5 minutes. After the second-level heart rate period is over, stop the active tablet and end the exercise state.

After T-wave alternation detection, analysis and judgment, the result is displayed on the display screen, which consists of heart rate variation trend curve during the experiment, T-wave alternation amplitude curve of twelve leads and corresponding noise level estimation curve.

Taking 16 beats as the basic time unit, draw a curve with the corresponding average heart rate at each moment, so as to understand the approximate change trend curve of the heart rate during the whole experiment, as shown in Figure 11, where the ordinate is the heart rate value, and the unit is bpm ( times/minute), the abscissa is time, 2 cells are 1 minute, and the vertical dotted line divides different exercise stages.

The analysis results of each lead have two curves, one curve reflects the change of noise level during the exercise test; the other curve is the change curve of T wave alternating amplitude. Figure 12 is a T-wave alternating trend diagram of a tester's V5 lead. In the figure, the vertical dotted line divides different motion stages, the abscissa is time, 2 cells are 1 minute, the upper part is noise, and the ordinate is Noise level, the unit is microvolts, the lower part is the T wave alternation trend, the black part indicates that the T wave alternation detection result is significant, the gray indicates that the T wave alternation detection is pending, and the blank indicates that the T wave alternation test is negative, the ordinate unit for microvolts.

Claims (1)

1, a kind of detection device of T wave alternation in exercise electrocardiogram, it is characterized in that, comprises following part: the lead device that is connected with the person being tested, the input protection circuit that is connected with the signal output end of this lead device, and this protection An amplifier system connected to the circuit, and an analog-to-digital conversion circuit connected to the output of the amplifier system, the analog-to-digital conversion circuit is connected to a microcomputer, a panel control interface circuit connected to the computer, and the control interface circuit is connected to be used The flat panel on which the tester moves; said amplifier system is composed of a preamplifier circuit, a DC blocking circuit, a main amplifier, a 50Hz notch wave, a photoelectric isolation amplifier and a low-pass filter circuit connected in sequence.

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