Atrioventricular Nodal Reentrant Tachycardia

Presentation

This is the commonest pediatric arrhythmia presenting in around the age of 7 years or late after cardiac surgery. Children usually complain of intermittent palpitations. Characteristically these have a sudden onset with no obvious precipitating cause and they may also feel a little faint. Although the arrhythmia may spontaneously stop suddenly the patient notices only a gradual reduction in heart rate as it takes time for haemodynamic stability to return.

Mechanism

In patients with atrioventricular nodal reentrant tachycardia (AVNRT) the AV node has two functionally discrete pathways (a fast and slow pathway). Normal conduction is down the fast pathway. The refractory period of the fast pathway is longer than that of the slow, so premature atrial beats preferentially conduct down the slow pathway. This slow conduction may allow the fast pathway to recover excitability and permit retrograde conduction up the fast pathway to the atria. The circuit is then completed by anterograde conduction down the slow pathway.

ECG

The surface ECG is similar to that in atrioventricular reentrant tachycardia although the rate may be a little lower. It is common to see a negative p wave in children in contrast to adults.

Management

Management of both the acute attack and the prevention of recurrence is similar to the management of atrioventricular reentrant tachycardia.

Prognosis

This arrhythmia tends to persist with periods of exacerbations and remissions unlike the infant presentation of atrioventricular reentrant tachycardia. Despite this with current treatment including radiofrequency ablation the prognosis is excellent in the vast majority of patients.

This page was last edited 14/2/2004

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