AV reentrant tachycardia (AVRT)

This particular symptom complex, also referred to as Wolff-Parkinson-White-Syndrome, is characterized by an additional pathway, termed an accessory conduction pathway, connecting the atria and ventricles. This is situated next to the AV node, which is normally the only electrical pathway between the atria and ventricles. Conduction of electrical activity along this pathway may be anterograde, i.e. from the atria to the ventricles, retrograde, i.e. from the ventricles to the atria, or bidirectional.

In patients with pathways capable of anterograde conduction, surface ECGs will show premature stimulation of the ventricles, i.e. the ventricles are "pre-excited" before the normal electrical stimulus has passed via the AV node. On the ECG trace, this phenomenon is referred to as a "delta wave". If a premature beat from the atria or ventricles reaches the AV node or the accessory pathway at the wrong moment, the impulse can continue to travel in a circular pattern between the atria and ventricles, resulting in AV reentrant tachycardia. The result is a very rapid heartbeat, which the affected person experiences as palpitations.

Most accessory pathways are located between the left atrium and the left ventricle, but sometimes these may also occur between the right atrium and the inter-atrial septum.