Introduction
Fetal AF is a serious and threatening form of tachyarrhythmia, as it may
cause fetal hydrops and associated with fetal mortality and neurological
complications. The incidence of fetal tachyarrhythmia in less than 1%
of pregnancies, and the two commonest forms are AF (10-30%) and
supraventricular tachycardia (SVT) (66-90%).1
Fetal AF is characterised by a rapid regular atrial contraction (300-600
beats/minute).2 This makes the ventricles unable to
respond to this rapid speed in a 1:1 fashion leading to a 2:1 or
variable atrioventricular (AV) block or 2:1 conduction. It commonly
develops in the third trimester and should not be confused with fetal
tachycardia or distress. The proposed underlying mechanism causing fetal
AF is the reentrant circuit causing premature atrial
impulses.3 The use of M-mode ultrasound establishes
the diagnosis followed by fetal echocardiogram to rule out structural
heart anomalies. The outcome of fetal tachyarrhythmia is dependent on
the presence of hydrops and cardiac disease, and not the type of
tachyarrhythmia.4 Treatment is individualised with
factors like gestational age, structural heart problems and hydrops
taken into significant consideration. Early detection and treatment
improved clinical outcome significantly.5
We present a case of fetal atrial flutter in a 24-year-old low risk
pregnancy at 37 weeks gestation. There was no fetal history of hydrops
or cardiac disease and she had emergency caesarean section. Neonatal
sinus rhythm was restored with single electrocardioversion and some
course of digitalisation.