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.