Abstract

Fetal dysrhythmias are common, usually manifesting as irregular rhythms. Whilst most irregularities are benign and caused by isolated atrial ectopics, in a few cases, rhythm irregularity may indicate partial atrioventricular block, which has different aetiological and prognostic implications. We provide a flowchart for initial management of irregular rhythm, to help select cases requiring urgent specialist referral. Tachycardias and bradycardias are less frequent, can lead to haemodynamic compromise and may require in-utero therapy. Pharmacological treatment of tachycardia depends on type (supraventricular tachycardia or atrial flutter) and presence of hydrops, with digoxin, flecainide and sotalol being commonly used. An ongoing randomized trial may best inform about their efficacy. Bradycardia due to blocked bigeminy normally resolves spontaneously, but if due to established complete heart block there is no effective treatment. Ongoing research suggests hydroxychloroquine may reduce the risk of auto-immune atrioventricular block. Sinus bradycardia (rate < 3rd centile) may be a prenatal marker for long QT syndrome.