RU2387370C2 - Device of non-invasive diagnostics of fetus cardiac activity and methods of its application - Google Patents

Abstract

FIELD: medicine.

SUBSTANCE: inventions relate to medicine, namely to device and method for diagnostics of fetus state during pregnancy. Device contains successively connected electrodes for registering abdominal ECG, ADC, filter and amplifier, whose outlet is connected with unit of second derivative calculation and first inlet of unit of abdominal ECG memory, display device and sensor of one-dimension ultra-sound signal. Amplifier outlet is additionally connected with first inlet of display device and first inlet of unit of measurement of cardiointerval duration, and sensor of one-dimension ultra-sound signal is connected with first inlet of unit of comparison, whose second inlet is connected with outlet of unit of etalon ultra-sound signals memory. Outlet of unit of comparison is connected with second inlet of display device, second inlet of unit of measurement of cardiointerval duration and first inlet of unit of accurate measurement of heartbeat rate, outlet of calculation of second derivative being connected with second inlet of unit of accurate measurement of heartbeat rate, outlet of unit of measurement of cardiointerval duration is connected with third inlet of unit of accurate measurement of heartbeat rate, outlet of display device is connected with first inlet of analysis device, whose second inlet is connected with outlet of unit of abdominal ECG memory, and two outlets of unit of accurate measurement of heartbeat rate are connected with inlets of display device. Method of cardiodiagnostics of prenatal state of fetus includes registration of abdominal ECG, rhythmograms of fetus and pregnant woman, analogue-digital conversion, filtration and amplification of fetus ECG signals, calculation of amplitude of teeth and cardiocomplex intervals. By means of ultra-sound signal zone of fetus location, characterised by two-, three-peak complexes of ultra-sound signal testifying to "direct" directing of ultra-sound signal sensor at fetus heart, is localised, ECG electrodes being placed at 10-12 cm distance from sensor.

EFFECT: application of inventions allows to increase reliability and efficiency of prenatal cardiodiagnostics of fetus and pregnant woman.

3 cl, 10 dwg

Description

The invention relates to medicine, more specifically to the field of obstetrics, and can be used to diagnose the condition of the fetus during pregnancy by analyzing its electrocardiogram (ECG). A mother and fetus joint ECG (abdominal ECG) from the front surface of the woman’s skin and an ultrasound signal (US) of the fetal heart beat are recorded synchronously.

There is a method for diagnosing the condition of the fetus during pregnancy, which is the most accessible and common method for monitoring the functional state of the fetus during pregnancy and consists in directly registering the fetal heart rate (HR) of the fetus by ultrasound sounding based on the Doppler effect, with the abdominal placement of the ultrasound probe during a certain interval of monitor observation (20 ... 60 min) - the method of cardiotocography.

The disadvantages of cardiotocography are well known:

- The ultrasonic signal captures large vessels in addition to the cardiac structures of the fetus. The amplitude of the Doppler signal reflected from them can be no less than the amplitude of the signal reflected from the cardiac structures and it is impossible to distinguish them with filters.

- The ultrasonic signals used by cardiotocographs are not regulated and are not certified (unlike an ECG). Calculation of heart rate is built, as a rule, only taking into account peak values of signals.

- To increase the reliability of the measured fetal heart rate, autocorrelation filters are used, which exclude the possibility of registering the rhythm on a “beat to beat” basis and do not allow diagnosing instant extrasystoles of cardiac activity in risk groups.

Non-invasive methods for registering an abdominal ECG and rhythm calculation, proposed in a number of sources [1-5], also have several disadvantages:

- It is recommended to use from 8 to 16 electrodes of the abdominal ECG, which is very cumbersome, inconvenient and prevents the widespread introduction of the proposed devices into clinical practice.

- Since it is proposed to use electrocardiographs with conventional amplification, the required scale is achieved by combinatorial addition of leads with filtration, which inevitably shifts and distorts the original ECG signals.

- Filters excluding the maternal ECG also distort the fetal ECG, and, as will be shown later, the mother's ECG has useful diagnostic and algorithmic information.

- The instruments and methods described in [2, 4, 5] are intended only for measuring the rhythm of the fetal heart rate, while in [2] the necessity of measuring the teeth and intervals of the fetal cardiocomplexes is emphasized.

- All researchers emphasize that in the period from 26 to 36 weeks the fetal ECG is not recorded, that is, during this period the electrocardiograph does not allow to diagnose the antenatal condition of the fetus.

- Fetal mobility during the session (15-20 minutes) does not allow to register the required number of fetal cardiac intervals for accurate diagnosis of the fetus, which is especially important for the risk group;

- The device [4], which uses a synchronously recorded abdominal ECG and ultrasound signals of the fetal pulse for diagnosis, does not allow calculating the fetal heart rate from shock to shock during pregnancy, during which the fetal ECG is not recorded (22-33 weeks), when it is absolutely necessary to diagnose the condition of the fetus;

In the course of our research, we also established previously unknown shortcomings of the devices and methods used:

- Parallel registration of the ECG of the abdominal and ultrasonic signal (US) of the fetal pulse showed that the cardiac complexes of the fetus very often do not coincide with the peaks of the ultrasound, which leads to a large error in calculating heart rate on cardiotocographs. This was confirmed by direct comparisons of heart rate calculations on the proposed device and cardiotocograph.

- Studies of the effect of electrocardiograph filters on measuring R-R intervals of ECGs were carried out, it turned out that the shift between the initial and filtered ECGs can be different for different teeth - P, Q, R, since each of these teeth has a different spectrum. It follows that when calculating the intervals with an accuracy of 1 ms, it is necessary to take into account the amplitude and duration of the R wave itself in order to ensure the necessary accuracy in calculating heart rate (this applies not only to fetal heart rate calculations).

- Exclusion from a pregnant woman’s abdominal ECG does not allow the construction of two synchronous rhythmograms of the pregnant woman and the fetus with high accuracy (up to 2-3 ms) in order to assess the presence of the mutual influence of the pregnant woman’s heart rhythm on the fetal heart rhythm, which is a sign of fetal heart failure and affiliation to risk group.

In general, cardiotocography does not allow direct diagnosis of cardiostructures and cardiofunctions of the fetus, necessary for the accurate diagnosis of a pregnant woman, especially at risk. Cardiotocography, confirming the “routine” of the method, allows you to diagnose by indirect averaged characteristics. The same can be said about the method of "blind separation" of potentials when registering an ECG of the fetus. Averaging 8-16 signals, the variability of which is very high, also leads to a significant decrease in accuracy.

Closest to the proposed device is a device that can be considered the closest analogue - a device for diagnosing cardiac activity of the fetus in the antenatal period (application No. 2006106476 A, class A61B 5/00, 09/01/2007) [4], which, like the claimed device, contains electrodes for removal of the abdominal ECG of the pregnant woman and the fetus, a filter connected to the amplifier, as well as an ultrasonic sensor, a display device (made in the form of a monitor of a hardware-software complex - PAK), to which signals from an ultrasonic sensor and an amplifier are received and performed with the ability to analyze the incoming signals, as well as a means of accurately measuring the heart rate, which also allows you to diagnose the cardiac activity of both the fetus and mother both by rhythmography methods and by methods that evaluate the shape of the ECG, the values of the P, Q, R, S teeth and PQ intervals , QT, QRS.

The disadvantage of the analogue is as follows.

An analog device that uses a synchronously recorded abdominal ECG and ultrasound signals (US) of the fetal pulse for diagnosis does not allow calculating the fetal heart rate from shock to shock during pregnancy, during which the fetal ECG is not recorded (22-33 weeks), when necessary for diagnosing the condition of the fetus; including for making decisions on forced delivery. In this case (in the absence of a fetus in the abdominal ECG), the method for calculating fetal heart rate by an ultrasonic signal, adopted in an analog device and other cardiotocographs, does not allow calculating heart rate “from shock to shock”, which is necessary for diagnosis.

It should be noted that the above drawbacks of cardiotocographs are recognized not only by obstetricians, but also by leading manufacturers of devices, the well-known Oxford company (England) proposed a new Sonicaid FM800ADAPT device in advertisements, which announced the use of new ultrasonic processing methods that allow conduct accurate calculation of fetal heart rate [3].

“... The fetal heart rate estimation algorithm. The new ADAPT technology uses the most advanced signal processing principles and pattern recognition methods in the SonicaidFM800 series. ADAPT technology has been developed and comprehensively tested using: a database for synchronized Doppler ultrasound signals of heart rate and ECG signals, created in the United Kingdom in collaboration with the Royal Center (Nottingham) and the School of Electrical and Electronics of the University of Nottingham in the United Kingdom ... ".

However, even in these devices the USM is not output to the display means, it is not described with what reference signals the USM compares the current USM signal, or by what principle is the analysis of the current USM used to calculate the heart rate using the “from shock to shock” method. It should be noted that the devices were tested using databases synchronously recorded by the fetal ultrasound and ECG, but in the diagnostics with the Somcaid FM800ADAPT instrument, fetal ECG was not registered in a non-invasive way. Thus, the diagnostic value of synchronous ultrasound scan and fetal ECG is confirmed, but the implementation of such an algorithm apparently causes problems.

The device proposed in this application uses synchronously recorded ultrasound signals (USS) and an abdominal ECG to diagnose the condition of the fetus. It should be noted that the use of the proposed devices will allow the creation in the Russian Federation of a similar database as indicated above, which is currently not available in the Russian Federation, since there are no devices and devices for the simultaneous recording of ECG and USS in the Russian Federation.

Using the proposed device, studies were conducted that showed:

- with parallel recording of an abdominal ECG and an ultrasound signal (US) of the fetal pulse, the fetal electrocardiocomplexes coincide with two-, three-peak pulses of the ultrasound and do not coincide with most single-peak pulses, as shown in Fig. 1.

This indicates that two-, three-peak pulses of the ultrasound scan are the result of reflection of the ultrasound signal (ultrasound scan) from the heart structures (myocardium and ventricles), and single-pulse ones from large vessels (for example, the aorta). And the presence of only two-, three-peak pulses in the USG signal indicates the “correct” direction of the USM sensor on the fetal heart. Due to the fact that the shape of the ultrasonic signal (USG) is not regulated (in contrast to the ECG) and not a single tocography device informs the operator of the USG curve and its requirements for accurate calculation of heart rate, it can be argued that the calculation of heart rate using USG, including “all” signal peaks in itself gives a very large error, because contains both the peaks of the reflected signal from the cardiac structures and from the vessels, comparable in amplitude and width. This is especially characteristic of the most popular multichip sensors now, providing "good" capture of the heart, they inevitably capture non-cardiac structures. Heart rate calculated by the cardiotocograph and ECG recorder, and can vary significantly, as can be seen from figure 2;

- to localize the position of the fetus, any ultrasound cardiotocograph with sound indication of the ultrasound signal (USS) can be used. If you place the sensor on the pregnant woman’s abdomen at the point of maximum signal, with a high degree of certainty, to get the fetal ECG, it’s enough to place 3 or 4 sensors at a distance of 10-12 cm from the USG sensor on mutually perpendicular axes, which is much simpler than placing 12 or 16 electrodes proposed by researchers in England and the USA. If the ECG is recorded with MAK devices that display an ultrasonic signal (USS) on the monitor screen, the USS signal should contain only two-, three-peak pulses, i.e. the sensor should be aimed directly at the fetal heart;

- fetal electrocardiocomplexes can be present in any of 4 signals taken from the electrodes, as shown in the diagrams shown in figure 3;

- the signal of the abdominal ECG contains complexes of the pregnant woman and the fetus. Their frequency properties are such that, after the second differentiation, the peak amplitudes are aligned, because the peaks of the ECG of the mother are reduced, and the fetus is increased and become comparable. This allows you to build a simple logical algorithm for separating the complexes of the pregnant woman and the fetus and calculate two rhythmograms - the pregnant woman and the fetus. It should be noted that the registration filters do not allow interference to sharply increase during the second differentiation, as evidenced by the diagrams in Fig. 4;

- Comparison of the rhythmograms of the pregnant woman and the fetus showed their complete independence. This confirms the claims of specialists that the “connectedness” of rhythmograms indicates that the pregnant woman and the fetus belong to the risk group, the use of the proposed device enables the operator of the diagnostic complex to determine the presence of pathology and compare accurate synchronized rhythmograms that cannot be made by existing instruments;

- synchronous comparison of rhythmograms is necessary for risk groups;

- filters of the registration device allow you to accurately calculate the teeth and ECG intervals of the fetus, which follows from the diagrams in figure 5;

- filters of any electrocardiograph “shift” individual teeth of electrocardiograms. And since each tooth has its own spectrum, this shift can be different. In Fig.6 it is shown that the P wave is shifted by 1 ms, and R - by 5 ms (Fig.6). This shift is especially significant in the R wave, according to which the rhythm and its variability are most often considered. Since the width and amplitude of the R wave can vary during the session of the subject, the shift will also change. Therefore, for accurate measurement of the rhythm of heart contractions (not only in the pregnant woman and the fetus, but in any person), it is necessary to make a correction determined by the spectrum of the R wave (for example, the Rm / T ratio);

- studies have shown that for reliable registration of the ECG of fetal complexes, long-term monitoring of the abdominal ECG is necessary. The proposed registration device can solve this problem when replacing a PC with a PDA. Registration can last at least 6 hours, followed by decryption of the entire abdominal ECG.

Cardiotocography as a principle for diagnosing the intrauterine condition of the fetus does not allow direct diagnosis of the cardiostructures and cardiofunctions of the fetus, which are necessary for the accurate diagnosis of pregnant women, especially at-risk groups. Cardiotocography does not allow assessing heart rate variability “from shock to shock”. This method allows diagnosis only by indirect averaged characteristics of the fetal heart rate variability. In this case, the causes of rhythm changes are not determined. The reliability of the diagnosis in cardiotocography is very conditional; to increase it, it is necessary to significantly increase the session time - up to 40-60 minutes or more, which is most often unacceptable. In the proposed device, it is proposed to introduce the reference characteristics of the ultrasonic signal (USS), allowing with significantly greater reliability to assess the variability of heart rate, including “from shock to shock”, in cases where the fetal ECG is not released non-invasively.

Due to the fact that the shape of the ultrasonic signal (USG) is not regulated (in contrast to the ECG) and not a single tocography device informs the operator of the USG and its requirements for accurate calculation of heart rate, it can be argued that the calculation of heart rate by USG, including “All” signal peaks gives a very large error, because contains both the peaks of the reflected signal from the cardiac structures and from the vessels, comparable in amplitude and width. This is especially characteristic of the most popular multichip sensors now, providing "good" capture of the heart, they inevitably capture non-cardiac structures. The heart rate calculated by the cardiotocograph and ECG recorder can vary significantly, as can be seen from figure 2.

Two-, three-peak pulses of an ultrasonic signal (US) are the result of the reflection of signals from the cardiac structures (myocardium and ventricles), and single-pulse from large vessels (for example, the aorta). And the presence of only two, three-peak pulses in the USG signal indicates the “correct” direction of the USM sensor on the fetal heart.

Two-, three-pulse complexes with intervals “inside” the complex from 40 to 100 ms and the interval between complexes from 300 ms to 900 ms can only characterize the movement of the fetal cardiostructures, because individual vessels will form single impulses after 300-900 ms, and uterine contractions indicated in the request can occur at significantly longer time intervals - 60-90 s. Similar impulses can be formed only when reflected from the pregnant woman’s heart, which is almost impossible when the sensor is located on the front wall of the pregnant woman’s abdomen, and is also easily recognized by the operator, since the frequency of these contractions is much lower and can be determined by the pregnant woman’s cardiac complexes in an abdominal ECG.

Own research and the study of publications of scientific papers have made it possible to formulate requirements for the complexes of antenatal cardiac diagnostics of the fetus:

- it is necessary to register signals that ensure accurate calculation of the fetal heart rate on a shock-to-shock basis (accuracy not worse than 1 ms);

- it is necessary to provide the ability to compare synchronous rhythmograms of the heart rate of the pregnant woman and the fetus (especially for risk groups);

- it is necessary to ensure reliable registration of the fetal ECG in the intervals of at least 20-30 s;

- it is necessary to provide visual observation of the ECG for a qualitative analysis of the teeth and ECG intervals;

- it is necessary to ensure the ability to accurately calculate the teeth of the intervals of cardiocomplexes (especially the parameters P and ST);

- it is necessary to ensure the possibility of long-term monitoring of the ECG of the fetus and subsequent computer analysis of the ECG.

The proposed device and methods provide an increase in the reliability, convenience and informational content of cardiac diagnostics of the fetus in the antenatal period. This is achieved by generating a signal that contains an abdominal ECG taken from the anterior abdominal wall of a pregnant woman using an ECG recorder with high resolution and accuracy (up to 1 μV), and can be used to accurately calculate the heart rhythms of the pregnant woman and the fetus, calculating the teeth and ECG intervals of the fetus, as well as joint analysis with ultrasound signals (US) reflected from the cardiac structures of the fetus, including for the accurate calculation of fetal heart rate.

In general, the device and methods make it possible to diagnose the condition of the fetus by directly monitoring the electrocardiogram or the mechanical movement of the fetal cardiostructures during the antenatal period and assessing heart rate variability “from shock to shock”.

The invention solves the problem of increasing the reliability and effectiveness of prenatal cardiac diagnostics of the fetus and the pregnant woman by directly registering the dynamics of the fetal cardiostructures and the ECG of the pregnant woman and the fetus.

The problem is solved using the antenatal cardiac diagnostic device, which is shown in Fig. 8 and contains serially connected electrodes for ECG removal (1), an analog-to-digital converter (ADC) (2), a filter (3) and an amplifier (4), the output of which is connected with the first input of the display device (monitor) (5), the calculation unit of the second derivative (10), the first input of the accurate heart rate measurement unit (11) and the input of the abdominal ECG memory unit (12), characterized in that the sensor is a one-dimensional ultrasonic signal (USS) (7) connected to the first input of the cp block avonii (9), the second input of which is connected to the output of the memory block of the standard ultrasonic testing device (8), the output of block 9 is connected to the 2 input of the device 5 and the third input of the accurate heart rate measurement unit 11; the output of block 10 is connected to the second input of the measurement unit 11, and the output of device 5 is connected to the first input of the analysis device 6; two outputs of block 11 are connected to 3 and 4 inputs of device 5, the output of memory device 12 is connected to the second input of analysis device 6.

The device operates as follows:

The signal of the abdominal ECG, taken by 4 electrodes from the anterior abdominal wall of the pregnant woman, filtered and amplified, is fed to the 1 input of the accurate heart rate measurement unit and to the input of the formation unit of the 2nd derivative of the abdominal ECG, in which the ECG amplitudes of the mother and fetus are “aligned” ( figure 4). This signal is fed to the 2 input of the accurate heart rate measurement unit. The accurate heart rate measurement unit fixes the time intervals between the maximum values of the input signal and generates Δ-pulses at the output through time intervals corresponding to the maximum values of the input signal (see the diagram of Fig. 9 and the block diagram of the algorithm of Fig. 10). If an abdominal ECG signal is fed to 1 input, then at the I output the intervals between Δ-pulses correspond to the pregnant woman’s cardiointervals (R-R), since the pregnant woman’s ECG amplitudes are several times greater than the fetal ECG amplitudes in the abdominal ECG.

The signal 2 of the derivative of the abdominal ECG is fed to the 2 input of the accurate heart rate measurement unit. In the block, Δ-pulses are formed at time points corresponding to the R-teeth of the pregnant woman's ECG and fetal ECG. At the 2 output of the accurate heart rate measurement unit, output pulses are formed at time instants at which the input pulses at 1 and 2 inputs do not coincide in time. If the pulses at the 1st and 2nd inputs coincide, there are no pulses at the 2nd output, thus, registration of the cardiocomplexes of the pregnant woman is excluded from the signal. Pulses at the 2nd output correspond to the R-teeth of the fetal ECG.

The comparison unit “compares” the ultrasonic signal (USS) at input 1 with the reference signal supplied to input 2, when they are “similar”, generates a signal to the input of the display device and to the 3rd input of the accurate heart rate measurement unit. Comparison of the current USS with the reference can be carried out both by the operator in the form of the signal and in parameters, since the reference signal is characterized by a complex of amplitude-time parameters, as shown in Fig. 7 with certain tolerances.

The accurate heart rate measurement unit, at the 3 input of which a signal is sent corresponding to the beginning of the ultrasound complex corresponding to the standard, calculates the exact heart rate of the fetus from the beginnings of two-, three-peak complexes, forming Δ-pulses at the beginning of each complex.

The operator selects a signal for accurate heart rate calculation. If he chooses an ECG, then the calculation is based on the ECG and ECG ^// , if the heart rate is calculated using an ultrasonic signal (US), then the operator selects the signals corresponding to the beginning of the current US complexes, corresponding to the standard.

The memory unit of the abdominal ECG by the signal of the operator remembers the signal supplied to the input, and by the signal of the operator passes the specified signal to the output, which is associated with the input of the analysis unit.

To adjust the measured values of the fetal heart rate according to the decision of the operator in block 6, the width of the R-teeth for the ECG of the pregnant woman and the fetus is measured and the calculations of the cardiac intervals in the rhythmograms are adjusted.

The method is implemented in the following sequence:

With the help of an ultrasonic signal sensor (USS), the fetal area is localized, which is characterized by two-, three-peak complexes of USS corresponding to the reference ones, as studies have shown that the USS sensor is directed directly to the fetal heart, and not to the vessels, the operator monitors the USS signal and abdominal ECG and can move the electrodes to obtain a clearer signal of the abdominal ECG on the monitor screen, while the most reliable fetal ECG signals are observed if the electrodes are located on a distance of 10-12 cm from the sensor signals of the abdominal ECG are pre-filtered and transmitted through the ADC to the PAK monitor, in which they are differentiated twice to calculate the synchronous rhythmograms of the pregnant woman and the fetus, and the amplitude and duration of the R-waves are measured.

Used sources

1. Karagulyan Ruslan Rubenovich "Diagnostic value of direct electrocardiography of the fetus in childbirth", abstract of the dissertation for the degree of candidate of medical sciences.

2. Academician of RAS M. P. Roshchevsky, N. L. Kolomeets, A. S. Kuzivanova, O. N. Lebedeva, M. A. Murashko, I. M. Roshchevskaya, “Opportunities for assessing the condition of the fetus by the method of isolation and analysis of electric heart activity. " Komi Scientific Medical Center of the Northwest Branch of the Russian Academy of Medical Sciences, Laboratory of Comparative Cardiology, Komi Scientific Center of the Ural Branch of the Russian Academy of Sciences, Syktyvkar.

3. Advertising at Oxford, England, “Fetal heart rate estimation algorithm. New ADAPT Technology. ”

4. Patent RU 23532290 C2, A61B 5/0444, application 2006106476/14 of 02.03.2006.

5. Copyright certificate RU 2226982 C2 A61B 5/0452 (2002).

Claims (3)

1. A prenatal cardiac diagnostic device containing serially connected electrodes for abdominal ECG removal, an analog-digital converter, a filter and an amplifier, the output of which is connected to the second derivative calculation unit and the first input of the abdominal ECG memory unit, a display device and a one-dimensional ultrasonic signal sensor, characterized in that the output of the amplifier is additionally connected to the first input of the display device and the first input of the unit for measuring the duration of the cardio interval, the sensor is one-dimensional the ultrasonic signal is connected to the first input of the comparison unit, the second input of which is connected to the output of the memory unit of the reference ultrasonic signals, the output of the comparison unit is connected to the second input of the display device, the second input of the unit for measuring the duration of the cardio interval and the first input of the unit for accurate measurement of heart rate, while the output of the unit calculating the second derivative is connected to the second input of the accurate heart rate measuring unit, the output of the cardio interval duration measuring unit is connected to by the input of the accurate heart rate measurement unit, the output of the display device is connected to the first input of the analysis device, the second input of which is connected to the output of the abdominal ECG memory unit, and the two outputs of the accurate heart rate measurement unit are connected to the inputs of the display device. 2. A method for cardiodiagnostics of the prenatal state of the fetus, including registration of an abdominal electrocardiogram (ECG), rhythm and cardiogram of the fetus and a pregnant woman, analog-to-digital conversion, filtering and amplification of the fetal ECG signal, calculation of the amplitude of teeth and intervals of cardiocomplexes, characterized in that with the help of an ultrasound signal (US ) localize the fetal location zone, which is characterized by two-, three-peak complexes of ultrasonic testing, indicating the "direct" direction of the ultrasonic scanning sensor to the fetal heart, while the ECG electrodes placed at a distance of 10-12 cm from the sensor of the USS. 3. The method of cardiodiagnosis of the prenatal state of the fetus according to claim 2, characterized in that the signal of the abdominal ECG is twice differentiated, the synchronous rhythmograms of the fetus and the pregnant woman are calculated, and the amplitudes and durations of R teeth are measured.

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