AV nodal reentrant tachycardia

AV nodal reentrant tachycardia (AVNRT) is a type of reentrant tachycardia (fast rhythm) of the heart. It is a supraventricular tachycardia, meaning that it involves the atria (upper chambers) of the heart.

In AVNRT, the fast pathway and the slow pathway are both in the AV node.

Types of AVNRT

There are two types of AVNRT, called the common form and the uncommon form.

Common AVNRT

In common AVNRT, the anterograde conduction is via the slow pathway and the retrograde conduction is via the fast pathway.

Because the retrograde conduction is via the fast pathway, stimulation of the atria (which produces the inverted P wave) will occur at the same time as stimulation of the ventricles (which causes the QRS complex). As a result, the inverted P waves may not be seen on the surface ECG since they are buried with the QRS complexes.

Uncommon AVNRT

In uncommon AVNRT, the anterograde conduction is via the fast pathway and the retrograde conduction is via the slow pathway.

Because the retrograde conduction is via the slow pathway, stimulation of the atria will be delayed by the slow conduction tissue and will typically produce an inverted P wave that falls after the QRS complex on the surface ECG.

Treatment

An episode of supraventricular tachycardia (SVT) due to AVNRT can be terminated by any action that transiently blocks the AV node. This is because the AV node is an essential portion of the reentrant circuit in AVNRT.

Related topics

• AV Reentrant tachycardia
• Supraventricular tachycardia