Assessment of the Severity of Heart Failure in Fetuses with Fetal Arrhythmias

Abstract

Fetal arrhythmia is a known cause of fetal heart failure that can lead to fetal death. Although assessment of the severity of heart failure is important for managing affected fetuses, it is often difficult in fetuses with arrhythmias. Usually, Doppler waveform, which is accepted in the cardiovascular profiling (CVP) score, is the most useful finding for assessing cardiac function. However, arrhythmia changes the Doppler waveform regardless of the cardiac function, so many of these waveforms may not reveal heart failure. Hence, other fetal echocardiographic findings, such as cardiomegaly assessed by the cardiothoracic area ratio, presence of atrioventricular valve regurgitation, and assessment of cardiac output calculated from the velocity-time integral, are used to detect early signs of cardiac failure. The Biophysical Profiling Score is another method useful for assessing the well-being of affected fetuses. Regarding the fetal heart rate, fetuses often develop heart failure with a fetal heart rate ＞220 bpm in fetal supraventricular tachycardia, ＞200 bpm in fetal ventricular tachycardia, and ＜55 bpm in fetal bradycardia. However, most fetuses with arrhythmia also have cardiac dysfunction, such as tachycardia-induced cardiomyopathy in fetal tachycardia and myocarditis caused by anti-SS-A antibody in fetal bradycardia. Hence, fetal heart rate may not reflect the severity of heart failure in many fetuses. Assessment by combining multiple assessment strategies and sequential follow-up of these findings are essential for assessing heart failure in fetuses with arrhythmias.