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Direct fetal electrocardiography

 
, medical expert
Last reviewed: 19.10.2021
 
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Apparatus and methods. It is recommended to use the BMT 9141 fruit monitor in conjunction with the recording and recording device. Screw electrodes are used as electrodes. Electrodes are applied to the protruding part of the fetus (head, buttocks), taking into account contraindications: placenta previa (partial or full), umbilical cord loosening, rupture of the bladder with a high head. A connector plate is placed on the mother's thigh, which is practically the closing link of the circuit between the electrode and the monitor. To record the direct ECG of the fetus, the speed of the 5O mm / s tape is recommended, and to increase the number of components in a number of obstetric situations, it is advisable to increase the tape speed to 100 mm / s. Among the complications with direct ECG in rare cases (0.6-0.8%) in the fetus are possible: scalp abscesses, bleeding, necrosis, sepsis. With rotational movement of the fetal head, the screw electrodes can be skewed, so that sometimes their partial displacement (separation) occurs, which can damage the soft tissues of the mother's birth canal. Therefore, you must follow the rules of asepsis in pregnancy and in childbirth:

  • sanitation of the vagina during pregnancy;
  • strict adherence to aseptic and antiseptic rules when applying electrodes;
  • after giving birth, immediate treatment of the site of application of electrodes with alcohol solution.

The shape of the fetal electrocardiogram consists of two parts - atrial and ventricular. As an empirical rule, it can be assumed that the time norms in the fetal ECG are% of the ECG time of the adult person.

It is important to determine the electrical axis of the heart by Larks:

  • if the vector of the electrical axis of the heart lies in the zone between 180 "and 330", it is in the critical zone;
  • if there is no pathology of the umbilical cord, we can assume a heart disease;
  • this information is made available to the neonatologist;
  • it is advisable to perform the calculation of the axis of the heart, so that the position of the axis of the heart can be determined immediately.

It is advisable to compare (ways of determining) the position of the intranatal and postnatal axis of the heart. For example, with a tight cord around the neck of the fetus, a meconium admixture, when the fetal heartbeat was found in the birth in the critical zone, we can assume the persistence of this pathological axis of the heart in the first 2 days after birth. Therefore, the intranatal pathological axis of the heart requires a postnatal ECG.

Possibilities of erroneous conclusions (deviations from the norm):

  • technical equipment malfunctions;
  • layering of the mother's pulses in the ECG with intrauterine fetal death;
  • maternal impulses in a normal fetal electrocardiogram;
  • incorrect connection (polarization) of electrodes from the skin of the fetal head;
  • the superposition of alternating currents on the ECG curve of the fetus.

Recommended:

  • Before each decoding of the fetal electrocardiogram, it is necessary to check additionally whether free from disturbing effects, a purely recorded and technically correlated ECG;
  • in unclear, doubtful cases, other data (CTG, analysis of the acid-base and gas composition of the blood, the mother's ECG) should be of primary importance. Fetal ECG - there is always an additional way to diagnose.

Fetal abnormalities:

  • reversible or persistent negative P-teeth may be a sign of umbilical cord pathology. Differential diagnosis: migratory pacemaker;
  • rhythm disturbances in the intranatal ECG of the fetus are mainly caused by hypoxia and congenital malformations;
  • with persistent persistent sinus tachycardia, there is a risk of heart failure in the fetus, therefore, with an attempt to prevent transplacental cardioversion with certain precautions;
  • the upper rhythm of the AV node may be a symptom of hypoxia and / or umbilical pathology;
  • in some cases, emerging ventricular extrasystoles are most often harmless and safe. Regularly alternating extrasystoles (bi-, tri- and quadrigemini) are warning signals. Postnatal monitoring with ECG is necessary.
  • supraventricular tachycardia is a serious rhythm disturbance and perinatal pharmacology of the fetal heart is shown (adrenergic agents, calcium antagonists, etc.). In the postnatal period intensive therapy is mandatory. If there are no congenital malformations, the prognosis of supraventricular tachycardia is good;
  • with AV blockade of I-III degree post-natal should be excluded heart disease. Newborn children with AV blockade require intensive observation by a neonatologist;
  • the serration and splitting of the P wave in the sense of the delay of the upper point of the junction or blockade of the legs of the Hiss bundle is almost always a symptom of the pathology of the umbilical cord. It is also necessary to exclude heart disease and in the postnatal period to remove the ECG.

Intratonal therapy of rhythm disorders. When persisting tachycardia of the fetus is recommended:

  • establishment of supraventricular origin of tachycardia by ECG analysis;
  • registration of the mother's electrocardiogram to exclude contraindications regarding the prescribed therapy;
  • control of blood pressure and pulse in the mother;
  • 1 tablet anaprilina (obzidan, propranolol) - 25 mg inside the mother (or 1 tablet - 0.25 mg digoxin);
  • constant monitoring of the fetal electrocardiogram;
  • postnatal ECG and intensive observation of the neonatologist, postnatal therapy with digoxin is possible.

The rise and fall of the ST segment. A decrease in the ST segment may indicate the following pathology:

  • violation of the regulation (dysregulation) of cerebral-vagotropic effects of blood circulation due to compression of the head during passage through the birth canal;
  • pathology of the umbilical cord (abutment, nodes, vascular anomalies);
  • shift of electrolyte balance (hyperkalemia);
  • Bland-White-Garland syndrome;
  • myocarditis.

There are three forms of reduction of the ST segment in the fetal ECG:

  • trough-like lowering of the ST segment ,
  • horizontal depression (depression) of the ST segment ,
  • oblique upward slope of the ST segment .

Thus, a sharp and prolonged decrease in the ST segment is mostly a symptom of hypoxia and / or umbilical pathology. Therefore, it is necessary to try to involve other methods to determine the state of the fetus - acid-base state and blood gases.

Tine T during the excitation process in the fetal ECG, in particular, a decrease or increase in the T wave, should never be done in isolation and there should be a cautious interpretation of these changes.

ECG of a dying fetus. The most characteristic features:

  • high, sharp two-phase inverted tooth P;
  • jagged, mostly unusual shape QRS complex;
  • lowering of the ST segment ,
  • shortening of the PR interval ;
  • inversion of the T wave .

It is important to take into account the ECG indicators and medications that the mother received during pregnancy and childbirth.

A program has been developed for computer analysis of the fetal ECG in childbirth in various obstetric situations. With the increase in the technical equipment of maternity hospitals and the simplification of the automation of the fetal ECG, the amount of information which is still far from being exhausted, the obstetrician will receive important information about the fetal condition in childbirth.

trusted-source[1], [2], [3], [4], [5], [6], [7], [8], [9], [10], [11], [12], [13], [14]

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