RU2353290C2 - Pre-delivery fetal diagnostic unit - Google Patents

Abstract

FIELD: medicine. ^ SUBSTANCE: invention refers to medicine, specifically to obstetrics and can be used for pregnancy fetal diagnostics. A unit comprises electrocardiographic electrodes arranged on anterior abdominal wall of a pregnant woman to record abdominal electrocardiogram and electrically connected to the input of a low-pass filter with its output connected to the input of high-pass filter with its output connected to the input of a band-elimination filter with its output connected to the first input of an abdominal electrocardiogram amplifier. The second input of the amplifier is connected to the output of a fetal RR interval detector with its input connected to the output of an ultrasonic signal transmitter established on anterior abdominal wall of a pregnant woman. The output of the abdominal electrocardiogram amplifier is connected to the input of a fetal R-wave cardiocomplex detector. The output of the ultrasonic signal transmitter is connected to the first input of a fetal heart rate estimator with its second input connected to the fetal R-wave cardiocomplex detector. The output of the fetal heart rate estimator and the fetal R-wave cardiocomplex detector are connected to the inputs of information medium. The latter is computerised with possibility to record precise time of R-wave and adjusted fetal heart rate signal. ^ EFFECT: higher diagnostic accuracy of heart activity in a pregnant woman and a fetus. ^ 4 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 the state of the circulatory system of the fetus. The invention simultaneously records a joint ECG of the pregnant woman and the fetus from the anterior abdominal wall of the mother and an ultrasound signal (US) of the fetal heartbeat.

There is a method of 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 when abdominally placing an ultrasound probe during a certain interval of monitor observation (20 ... 60 min). [one]

The disadvantage of this method of measuring heart rate, which many experts call routine, is the imposition of a methodical interference on the ultrasonic signal. The ultrasound scan, reflecting the cardiocomplex of the fetus, often represents 2-3 pulses (figure 1), each of which reflects the movement of any cardiostructure.

When the fetus moves, the maximum impulse of the cardiocomplex may “shift”, and the calculation of the heart interval will be incorrect. For slowly changing heart rate characteristics, such as the basal rhythm, this inaccuracy will be insignificant, but for such “short heart rate variations”, measured in units of milliseconds, these errors can be very significant. Due to these and similar inaccuracies in the calculation of heart rate by ultrasonic testing in the past few years, many experts have come to the conclusion that it is necessary to calculate the heart rate of the fetus by ECG of the fetus. In addition, for accurate diagnosis, especially of pregnant risk groups, fetal electrocardiocomplexes are necessary.

There is a lot of information about research, but so far there are no such devices in wide clinical practice.

The aim of the invention is to obtain accurate information for the diagnosis of cardiac activity of the pregnant woman and the fetus - rhythmograms of heart rate measured "from shock to shock", and fetal electrocardiocomplexes recorded with sufficient accuracy for calculating the teeth and intervals.

The technical result is achieved through the simultaneous recording of two signals, one of which is an abdominal ECG taken from the anterior abdominal wall of a pregnant woman with a high resolution ECG recorder (up to 1 μV), and the other is an ultrasound signal reflected from the fetal cardiostructures (Fig. 2).

As studies have shown, the isolation of the cardiocomplex from the abdominal ECG by analyzing only the abdominal ECG and filtering it is not effective.

The spectra of the electrocardiocomplex of the fetus, as well as their amplitude-time characteristics, on the one hand, are very variable, on the other hand, they differ very little from other biopotentials recorded from the abdomen of a pregnant woman, therefore, the automatic recognition of cardiocomplexes by reference, which is the basis of patent RU 2226982 C2, A61B 5/0452, 5/0444, according to the authors, is not effective. Also, a method based on the “blind separation of potentials” is not effective, since the indicators and characteristics of the secreted “source of potential” (fetal heart) change over time. The authors are not aware of devices that are widely used in practice, built on a similar principle.

In the proposed device, synchronization with an ultrasound signal allows for additional independent filtering, highlighting the time intervals from the abdominal ECG signal in which the fetal ECG is reliably present. At the same time, filters 2, 3, 4 (Fig. 3) do not solve the problem of isolating the fetal complex from an abdominal ECG. They eliminate the influence of interference (high-pass filters), mirams (notch filter) and “swing” of the isoline (low-pass filter). When filtering from a pregnant woman’s abdominal ECG, the isolation of the fetal ECG from the joint signal inevitably introduces significant distortions of the fetal ECG signal, which will lead to errors both in the calculation of heart rate and in the calculation of teeth and intervals of cardiac complexes. The use of an ultrasound signal allows more clearly to exclude from the abdominal ECG potentials that are not associated with the fetal ECG.

The device operates as follows. The combined ECG of the pregnant woman and the fetus and the ultrasound scan of the fetal heartbeat are recorded simultaneously. The joint ECG signal is passed through the filters. The filter parameters are chosen so that the QRS complexes of the fetus and the pregnant woman become very clear, while the amplitude of the R wave of the fetal ECG can vary from 5 to 30 μV. The amplitude of the R-wave of the ECG of a pregnant woman in a joint ECG taken from the front wall of the mother’s abdomen is from 100 to 300 μV. An ultrasound signal is passed through the fetal heart rate interval detector, which at the peaks of the ultrasound scan emits a “rough” cardio interval. The output of the cardiointervalue detector is fed to the resolving input of the abdominal ECG signal amplifier, which amplifies and “passes” the abdominal ECG signal only during the cardiointerval determined by the CCI detector.

The Cardio Interval Detector detects the peak values of the ultrasonic scan and, according to the time intervals measured between the peaks, determines the time of the cardiocomplex (if this interval is less than 200 ms) or the time of the cardiointerval (if the interval is more than 250 ms). A similar algorithm is accepted in cardiotocographs.

The “missed” and amplified ECG signal is fed to the input of the R-wave detector of the cardiosignal, which records the exact time of the R-wave and refines the cardio interval of the fetal heartbeat (R-R interval).

The fetal ECG R-wave detector detects the position of the R-wave by the maximum ECG values during the cardio interval. A similar algorithm is used in all rhythmocardiographs (figure 4).

At the same time, the measurement of fetal heart rate by an ultrasonic signal is recorded by a mark on the monitor screen of the device. If, for one reason or another, the R-wave detector did not detect the R-wave of the fetal ECG in a missed enhanced ECG, heart rate calculation is continued by the ultrasound of the fetal heart rate without a mark on the exact measurement of heart rate. Clarification can be carried out during registration of each subsequent cardiocycle, i.e. in real time. The doctor (operator) receives a set of measured fetal cardiac intervals specified for accurate calculations and analysis with information about the exact measurement and decides to continue and stop the session or to change the position of the electrodes and ultrasound sensor.

From the initial abdominal ECG, time intervals are excluded in which the fetal cardiocomplexes and electric potentials not known to be associated with the cardiocomplexes of the fetus are not detected by the ultrasound signal.

As a result of the operation of the fetal condition diagnostic device, divided synchronous accurate ECG diagrams of the fetus were prepared, which allow to diagnose the fetal cardiac activity with high accuracy both by rhythmocardiography and methods that evaluate the shape of the ECG, the values of the P, Q, R, S, T teeth, the duration of the intervals PQ, QRS, ST segments.

In the proposed device, at the output of the amplifier, a clear fetal ECG signal is obtained, sufficient for analyzing rhythm variability on a “from shock to shock” principle, including for analyzing “short variations” (STV), which are very “accurate” (up to 3, 5 ms) and very important for the diagnosis of fetal heart activity.

Such an analysis does not carry out any known device for diagnosing the intrauterine condition of the fetus. The device can be installed in maternity wards, antenatal clinics.

The device for diagnosing the condition of the pregnant woman and the fetus during the prenatal period (Fig. 3) contains an I pair of electrodes recording a joint ECG of the pregnant woman and the fetus, filters 2, 3 and 4 connected in series, an amplifier 7 and a display and memory device 8, the software of which contains diagnostic programs, analyzing the variability of the rhythm of cardiac activity, the amplitude of the teeth and the intervals of the QRS ECG complexes.

The first input of the amplifier 7 is connected to the output of the filters of the signal of the abdominal ECG containing the signal of the abdominal ECG containing the cardiac complexes of the pregnant woman and the fetus (Fig. 4), the second input of the amplifier 7 is connected to the output of the cardiointerval detector of the fetus 5, the input of which is connected to the ultrasonic sensor, the output of the amplifier 7 connected to the input of the detector of the R-wave ECG of the fetus 9, the output of which is connected to the calculation unit of the fetal heart rate 6 and the display and storage device 8.

Used sources

1. Markin L.B., Pavlovsky M.P. and other Monitor systems in obstetric care. - Kiev: Health, 1992, p.13, 127, 25, 109-112, 114, 23, 30, 31, 56.

2. Voronin K.V., Potapov V.A. Fundamentals of cardiotocography. - Dnepropetrovsk, Dnepropetrovsk Medical Institute, 1986, p.16-19, 40.

3. USSR Copyright Certificate No. 624602, 1978

4. Copyright certificate RU 2226982 C2, A61B 5/0452, 2002

Claims (1)

A device for diagnosing the condition of the fetus in the prenatal period, characterized in that the electrocardiographic electrodes mounted on the front wall of the pregnant abdomen to register an abdominal ECG are electrically connected to the input of the low-pass filter, the output of which is connected to the input of the high-pass filter, the output of which is connected to the input of the notch filter, the output of which is connected to the input of the abdominal ECG amplifier, the permitting input of which is connected to the output of the fetal cardiointerval detector, the input of which is connected to by the ultrasonic signal sensor for detecting fetal heart contractions installed on the front wall of the pregnant abdomen, the output of the abdominal ECG amplifier is connected to the input of the R-wave detector of the fetal cardiocomplex, the output of the ultrasonic signal sensor is connected to the input of the fetal heart rate calculation unit, the other input of which is connected to the R detector - teeth of the fetal cardiocomplex, the outputs of the fetal heart rate calculation unit and the detector of the R-tooth of the fetal cardiocomplex are connected to the inputs of the information carrier made on a personal computer with possibility of fixing the exact time at the outputs R-wave and proximate FHR signal.

Images