Idiopathic Neonatal Atrial Flutter

Idiopathic neonatal atrial flutter (AFL) is a rare rhythm disorder, characterized by sustained tachycardia in newborns and infants with an atrial rate often at around 440 beats/minute (range 340-580). AFL may manifest as asymptomatic tachycardia, congestive heart failure or hydrops.

Epidemiology

AFL is rare with an approximate incidence of around 1/50,000 live births in Europe.

Clinical description

AFL has a neonatal onset and the majority (72%) of patients present with symptoms within the first 48 h of life. Onset during the fetal period may be associated with hydrops fetalis and death. AFL manifests with tachycardia and congestive heart failure. AFL is sustained although conversion from atrial flutter to sinus rhythm may occur spontaneously (<24 hours). Some patients are asymptomatic and tachycardia may be noted on routine examination and monitoring.

Etiology

The etiology of AFL is unknown but immaturity of the myocardium and the high pressure in the right atrium during the perinatal period may be factors that favor the appearance of atrial re-entry.

Diagnostic methods

The diagnosis of AFL relies on surface electrocardiogram (ECG) which usually shows an atrial rate of around 440 beats/min, most often with 2:1 atrioventricular conduction (sometimes with variable AV conduction and an irregular ventricular rate of 125-280 beats/min), and saw tooth P waves in leads II, III, and aVF. The echocardiogram may show impaired ventricular function after prolonged tachycardia.

Differential diagnosis

Differential diagnosis includes multifocal atrial tachycardia (see this term) and other forms of supraventricular tachycardia.

Antenatal diagnosis

AFL may be diagnosed prenatally by fetal echocardiogram which will show an atrial rate of over 400 per minute and most often 2:1 AV conduction to give a ventricular rate of over 200 per minute.

Management and treatment

The first aim of treatment is the restoration of sinus rhythm. This is most easily achieved by transoesophageal overdrive pacing or synchronised low energy DC cardioversion using around 0.5-1 J/kg. The response to drug treatment is variable and unpredictable. Recurrence of atrial flutter in neonates is rare and prophylactic medication is usually not required. Sotalol is said to be an effective agent in the treatment of AFL in the fetus as it has excellent transplacental passage.

Prognosis

In the absence of additional arrhythmias, infants with AFL have an excellent prognosis once in sinus rhythm, with a low risk of recurrence, and chronic anti arrhythmic therapy is unlikely to be necessary.