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October 23, 2016 23:01

Photo and fetal electrocardiography

most common methods of assessment of fetal cardiac activity are electrocardiographic (ECG) and fonokardiograficheskoe (PCG) study.Using these methods can significantly improve the diagnosis of fetal hypoxia and pathology of the umbilical cord, as well as prenatally diagnosed congenital cardiac arrhythmia.

There are direct and indirect fetal ECG.Indirect ECG is performed when applying the electrodes to the anterior abdominal wall of the pregnant (neutral electrode is placed on the surface of the thighs), and is used predominantly in the antenatal period.Normally the ECG clearly identified ventricular complex QRS, sometimes tooth R. Motherboard complexes differentiated by simultaneous ECG mother.Fetal ECG can register starting from 11-12 weeks of pregnancy, but in 100% of cases it is possible only by the end of III trimester.Thus, indirect ECG is used after 32 weeks of gestation.

Direct ECG is recorded directly to the fetal head during delivery at the opening of the cervix is ​​3 cm or more.Direct EC

G is characterized by the presence of atrial P wave, ventricular complex P-Q and T wave

In the analysis of ECGs antenatal determine heart rate and reduced p.the nature of rhythm, the magnitude and duration of the ventricular complex, as well as its shape.In normal rhythm correct fetal heart rate varies between 120-160 / min, P pointed tooth, the duration of the ventricular complex is 0.03-0.07 sec, and its voltage varies from 9 to 65 mV.With increasing gestational age there is a gradual increase in the voltage of the ventricular complex.

PCG fetus register when applying the microphone at the point of best stethoscope listening to his heart sounds.Phonocardiogram, as a rule, it is represented by two groups of oscillations that represent I and II heart sounds.Sometimes determined III and IV tones.Fluctuations in duration and amplitude of heart sounds is very variable in the III trimester of pregnancy and, on average: I tone - 0.09 sec (0,06-0,13 sec), II tone - 0.07 seconds (0.05-0.09s).

When simultaneous ECG and PCG fetus can calculate the duration of the cardiac cycle phases: phase asynchronous reduction (AU), the mechanical systole (of Si), general systole (for So), diastolic (D).Phase asynchronous contraction is detected between the start of I and Q wave tone, its duration is between 0.02-0.05 sec.Mechanical systole reflects the distance between the beginning of I and II and tone extends from 0.15 to 0.22 seconds.The total includes the mechanical systole systole phase and asynchronous contractions and is 0,17-0,26 sec.Diastole (the distance between I and II tones) lasts for 0.15-0.25 seconds.It is important to establish the duration of systole to the total duration of diastole, which is at the end of uncomplicated pregnancy is on average 1.23.

addition to the analysis of fetal heart rate at rest, a lot of help in the evaluation of reserve possibilities of fetoplacental system using antenatal CTG provide functional tests.The most widely nonstress (HCT) and stress (oxytocin) tests.

essence of non-stress test is to study the reaction of the cardiovascular system of the fetus in response to his motion.In normal pregnancy, in response to a perturbation in the fetal heart rate increases on average 10 minutes or more.In this case, the test is considered positive.If in response to fetal movement aktseleratsii having less than 80% of cases, the test is regarded as negative.In the absence of changes in heart rate in response to fetal movements HCT is negative, which indicates the presence of fetal hypoxia.The appearance of bradycardia and cardiac rhythm monotony also indicate fetal distress.

oxytocin test is based on a study of the reaction of the cardiovascular system of the fetus in response to induced uterine contractions.For the test solution was intravenously administered oxytocin (0.01 U / 1 ml 0.9% sodium chloride or 5% glucose solution).The test is evaluated as positive if for 10 minutes at oxytocin 1 ml / min is observed for at least 3 uterine contractions.When sufficient compensatory possibilities of fetoplacental system in response to uterine contractions observed mild or severe short-term aktseleratsiya brief early decelerations.Identification later, especially W-shaped, decelerations evidence of placental insufficiency.

contraindications for oxytocin test are: placental abnormality, its partial abruptio, the threat of termination of pregnancy, the presence of uterine scar.

task monitor surveillance during labor is a timely recognition of the deterioration of fetal condition that allows for adequate therapeutic measures, and accelerate the delivery is as required.

for fetal assessment during labor study the following parameters kardiotokogrammy: basal rhythm of heart rate variability of the curve, as well as the nature of the slow acceleration (aktseleratsy) and decelerations (decelerations), heart rate, comparing them with the datareflecting the uterine contractile activity.

In uncomplicated childbirth can meet all types of basal rate variability, but is most often present slightly undulating and undulating rhythms.

normal criteria kardiotokogrammy in intrapartum period considered:

  • basal rhythm of the heart rate of 110-150 beats / min;
  • amplitude variability of the basal rate 5-25 beats / min.

Signs suspicious kardiotokogrammy in labor include:

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

pathological diagnosis kardiotokogrammy in labor based on the following criteria:

  • basal rate of less than 100 or more than 170 beats / min;
  • variability of the basal rate of less than 5 beats / min for more than 40 minutes of observation;
  • denominated variable decelerations or severe recurrent early decelerations;
  • prolonged decelerations;
  • late decelerations;
  • sinusoidal curve type.

should be noted that when using the CTG during labor requires monitor principle, ie. F. Constant dynamic observation during childbirth.The diagnostic value of the method is increased by carefully comparing the data with CTG obstetric situation and other methods of fetal assessment.

It is important to emphasize the need for a survey of all pregnant women coming to the maternity ward.Subsequently kardiotokogramm recording may be performed periodically if the primary entry evaluated as normal for 30 minutes or more, and labor is adequate.Continuous recording kardiotokogrammy conducted at pathological or suspicious curve type of primary as well as in pregnant women with burdened obstetric history.