Ultrasound diagnosis and monitoring of irregular fetal heart rhythm
Aim. The work is devoted to the development of ultrasound differential diagnostic criteria for assessing of fetal heart rhythm and a complex of practical indicators for fetal hemodynamics assessment, as well as algorithms of dynamic observation of the fetuses with different types of arrhythmia, which is necessary for optimization of antenatal care.
Material and Methods. Reports of 2073 ultrasound examinations of fetal heart from 1996 to 2016 were retrospectively studied, and 213 diagnosed cases of fetal arrhythmias were analyzed. All the examinations were carried out according to the general protocol. The evaluation of the fetal heart anatomy was based on segmental analysis. The rhythm assessment was performed by reconstructing the fetal EGC using ultrasound techniques and foreseeing the determination of the heart rate of the fetus, atrioventricular ratio, duration and ratio of cardiac cycle intervals. According to the results of the work, algorithms for differential diagnosis of fetal arrhythmias have been developed. To determine hemodynamic complications, a scoring scale was created. For the statistical processing of the obtained results, all the subjects were divided into groups based on the age of pregnant women, and onthe term of pregnancy. All arrhythmias were divided into groups based on the types of detected arrhythmias, duration, clinical significance and thedegree of hemodynamic complications. Based on the obtained findings, the prognostic significance of the fetal arrhythmias was determined, and the algorithms of pregnancy maintenance were developed.
Results and Discussion. The total frequency of fetal arrhythmias was 10.3 %. Irregular rhythm is the largest group of arrhythmias - 143 cases, which amounts to 6,9% of the total number of examined patients and 67% of the number of arrhythmias. Supraventricular extrasystoles was the most numerous occurrence- 132 cases (92.3%). Sinus arrhythmia and ventricular extrasystoles were significantly less commonly diagnosed; in 5 cases (3,5%) and 6 cases (4,2%) respectively. The results of statistical treatment indicate that the probability of fetal irregular rhythm is lower among women over 30 years (p<0.0003). Frequency of arrhythmia up to 20 and after 36 weeks of gestation is significantly higher than duriingother periods, and from 26 to 30 weeks - the lowest (p<0.01). Elevenfetuses (7.7%) had irregular rhythm combined with structural heart defect. In more than 60% of cases, arrhythmia was short-lived and prognostically benign, while in 141 fetuses (98.6%) no disorders of fetal hemodynamic were detected. Hemodynamic complications have been documented twice: as a result of fetal tachyarrhythmias and in combination with congenital heart disease. In cases of prolonged allorithmic (bi-, tri-, quadrigeminia) blocked supraventricular extrasystoles (approximately 2%), which caused a significant decrease frequency of ventricular contractions, differential diagnosis with an atrientricular block of the II degree has been performed. This is necessary because of different predictive value of arrhythmias and important for choosing the correct prenatal strategy. In cases of frequent supraventricular extrasystoles, tighter fetal control has been performed due to a higher (up to 15%) risk of induction of fetal tachyarrhythmia, which could provoke significant hemodynamic complications and fetal death. Thus, in the absolute majority of fetuses of group I, there was an uncomplicated course of arrhythmia, which was manifested by the absence of hemodynamic effects (p<0.00001), and it was clearly observed in comparison with other types of arrhythmias (p<0.002).
Conclusions. Irregular rhythm is the largest group of fetal arrhythmias. The majority of the disturbances in this group, about 90%, is due to supraventricular extrasystoles. Irregular rhythm has a benign course, since it does not cause any fetal hemodynamic disorders; it usually disappears before the baby is born, and therefore does not require treatment. Certain types of arrhythmias in this group require a differential diagnosis with atrioventricular blockade, second degree, or control over the fetal rhythm because of the possibility of occurrence of super-ventricular tachycardia. Irregular rhythm is predominantly found in a structurally normal fetal heart. In cases of combination of arrhythmia with congenital heart disease, the risk of hemodynamic complications may increase, so it is necessary to conduct control tests for monitoing of fetal condition. In uncomplicated cases, delivery should be performednaturally. The need for the follow-up after birth is determined according to the clinical situation.
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