Ultrasonоgraphic analysis of the fetal heart rhythm: clinical significance and differential diagnosis of bradyarrhythmias

Abstract

The aim – 1) to evaluate the possibilities of ultrasound fetal heart examination in the detection and differential diagnosis of bradyarrhythmias; 2) to study the influence of arrhythmias on fetal hemodynamics; 3) to examine the role of fetal echocardiography in the management of prenatally diagnosed bradyarrhythmias for determining the optimal pregnancy and delivery tactics.Material and methods. The analysis of echocardiographic examinations of the fetal heart from April 1996 to July 2016 has been performed. During this period 2073 pregnant women were examined and 213 cases of fetal heart arrhythmias were detected. Ultrasound examination of the fetal heart was conducted according to the general protocol. The anatomy of the fetal heart was assessed based on segmental analysis. Rhythm of the fetal heart was determined by simultaneous recording of mechanical events (contractions of the atria and ventricles), which are the consequence of electrical activity, with estimation of the ratio between them, as well as the measured time intervals of the cardiac cycle with calculation of their ratio. For this purpose, various ultrasound techniques (M-method, color, pulse-wave and tissue Doppler) have been used.Results. During the study period 45 cases of fetal bradyarrhythmias were detected, (2.2 % of the number of all patients examined and 21.1 % of all arrhythmias). They included 20 cases (44.5 %) of periodic bradycardia of different duration, 9 cases (20 %) of sustained sinus bradycardia, 9 cases (20 %) of complete atrioventricular block, 5 cases (11 %) of blocked atrial bigeminy and 2 cases (4.5 %) of 2nd degree atrioventricular block. Persistent fetal bradycardia requires a complete echocardiographic examination to exclude structural pathology and assess possible hemodynamic complications. Bradyarrhythmias with a frequency of ventricular contractions of more than 60 bpm are well tolerated by the fetuses due to various adaptive mechanisms. Permanent forms of arrhythmia with a frequency less than 55 bpm, as usual, lead to serious hemodynamic comromise even in the absence of fetal congenital heart defects.Conclusions. Ultrasound fetal heart examination provides not only the identification and reliable differential diagnosis of various types of fetal bradyarrhythmia, but also an assessment of its hemodynamic consequences and prenatal period monitoring of the fetal condition. This makes possible to choose the tactics of pregnancy management, determine the frequency of follow-up examinations, plan the time, place and route of delivery. The majority of fetal brady­­arrhythmias are non-threatening rhythm disorders.