Photo and electrocardiography of the fetus

The most common methods of assessing the cardiac activity of the fetus are electrocardiographic (ECG) and phonocardiography (FKG) studies. The use of these methods makes it possible to significantly improve the diagnosis of fetal hypoxia and umbilical cord pathology, as well as antenatally diagnose congenital disorders of the heart rhythm.

Allocate a direct and indirect ECG of the fetus. Indirect ECG is performed when the electrodes are applied to the anterior abdominal wall of the pregnant (the neutral electrode is located on the surface of the thigh) and is used primarily in the antenatal period. Normally, the ECG clearly identifies the ventricular complex QRS, sometimes the tooth R. The mother complexes are differentiated by simultaneous registration of the mother's ECG. Fetal electrocardiogram can be registered starting from 11-12 weeks of pregnancy, but in 100% of cases it is possible only by the end of the third trimester. Thus, an indirect ECG is used after the 32nd week of pregnancy.

A direct ECG is recorded directly from the fetal head during delivery when the cervix is opened 3 cm or more. A direct ECG is characterized by the presence of the atrial P wave, the ventricular complex PQ, and the T wave.

When analyzing the antenatal ECG, the heart rate and p. The nature of the rhythm, the magnitude and duration of the ventricular complex, as well as its shape. Normally, the rhythm of the fetus is correct, the heart rate fluctuates between 120-160 / min, the tooth P is pointed, the duration of the ventricular complex is 0.03-0.07 sec, and its voltage varies from 9 to 65 microvolts. With an increase in gestation, there is a gradual increase in the voltage of the ventricular complex.

FKG of the fetus is recorded when the microphone is placed in the best listening position with the stethoscope of its heart tones. A phonocardiogram is usually represented by two groups of oscillations that reflect the I and II heart tones. Sometimes III and IV tones are determined. Variations in the duration and amplitude of heart tones are very variable in the III trimester of pregnancy and are on average: I tone - 0.09 sec (0.06-0.13 sec), II tone - 0.07 sec (0.05-0.09 sec).

With the simultaneous registration of the ECG and FGF of the fetus, the duration of the phases of the cardiac cycle can be calculated: the phases of asynchronous contraction (AC), mechanical systole (Si), total systole (So), diastole (D). The phase of asynchronous contraction is revealed between the beginning of the Q and I wave in a tone, its duration is in the range of 0.02-0.05 sec. The mechanical systole reflects the distance between the start of the I and II tone and lasts from 0.15 to 0.22 seconds. The total systole includes a mechanical systole and an asynchronous contraction phase and is 0.17-0.26 sec. Diastole (the distance between the II and I tones) lasts for 0.15-0.25 seconds. It is important to establish the ratio of the duration of the total systole to the duration of diastole, which at the end of uncomplicated pregnancy is an average of 1.23.

In addition to analyzing the cardiac activity of the fetus at rest, functional tests are of great help in assessing the reserve possibilities of the fetoplacental system with antenatal CTG. The most common are non-stress (NST) and stress (oxytocin) tests.

The essence of the stress test is to study the reaction of the fetal cardiovascular system in response to its movement. In the normal course of pregnancy, in response to the fetal movement, the heart rate increases by an average of 10 min or more. In this case, the test is considered positive. If in response to fetal movements, the ac- celeration occurs in less than 80% of the observations, the test is regarded as negative. In the absence of changes in the heart rate in response to the perturbation of the fetus, the NST is negative, which indicates the presence of intrauterine hypoxia of the fetus. The appearance of bradycardia and monotony of the heart rhythm also indicate the suffering of the fetus.

The oxytocin test is based on the study of the reaction of the fetal cardiovascular system in response to induced uterine contractions. To conduct the test, intravenously inject a solution of oxytocin (0.01 ED / 1 ml of a 0.9% solution of sodium chloride or 5% glucose solution). The test is evaluated as positive if at least 3 contractions of the uterus are observed during 10 min at the rate of administration of oxytocin 1 ml / min. With sufficient compensatory possibilities of the fetoplacental system, in response to uterine contraction, there is an inconspicuous short-term ac- celeration or early short-term deceleration. The detection of late, especially W-shaped, decelerations indicates fetoplacental insufficiency.

Contraindications to the oxytocin test are: an anomaly of placenta attachment, its partial premature detachment, the threat of termination of pregnancy, the presence of a scar on the uterus.

The task of monitoring in the process of childbirth is to timely recognize the deterioration of the fetus, which allows for adequate therapeutic measures, and, if necessary, accelerate delivery.

To assess the condition of the fetus in childbirth, the following parameters of the cardiotocogram are studied: the basal rhythm of the heart rate, the variability of the curve, and the nature of the slow accelerations (accelerations) and decelerations (de-ulations) of the heart rhythm, comparing them with data reflecting the contractile activity of the uterus.

In uncomplicated births, all types of basal rhythm variability can occur, but most often there are slightly undulating and undulating rhythms.

The criteria for a normal cardiacogram in the intranatal period are:

• basal rhythm of heart rate 110-150 beats per minute;
• amplitude of basal rhythm variability 5-25 beats per minute.

The signs of a suspicious cardiotocogram in childbirth include:

• basal rhythm of 170-150 beats / min and 110-100 beats / min;
• amplitude of basal rhythm variability 5-10 beats / min in more than 40 minutes of recording or more than 25 beats / min;
• variable decelerations.

Diagnosis of the pathological cardiotocogram in childbirth is based on the following criteria:

• basal rhythm is less than 100 or more than 170 beats / min;
• variability of basal rhythm is less than 5 beats per minute for more than 40 minutes of follow-up;
• pronounced variable declerations or pronounced recurring early de- celerations;
• prolonged decelerations;
• late decelerations;
• sinusoidal type of curve.

It should be emphasized that when using CTG during childbirth, a monitor principle is needed, that is, constant dynamic observation during childbirth. The diagnostic value of the method is enhanced by careful comparison of CTG data with the obstetric situation and other methods of assessing the fetus.

It is important to emphasize the need to examine all women in labor who enter the maternity ward. In the subsequent recording cardiocograms can be made periodically, if the primary record is estimated as normal for 30 minutes or more, and the birth takes place without complications. Continuous recording of a cardiotocogram is performed in pathological or suspicious types of the primary curve, as well as in pregnant women with a burdened obstetric anamnesis.

[1], [2], [3], [4], [5]