Atrioventricular nodal reentry tachycardia

**Definition:** A reentrant supraventricular tachycardia that uses multiple slow atrioventricular nodal pathways or a slow atrioventricular nodal pathway in conjunction with a fast atrioventricular nodal pathway in a reentry circuit.

**Long definition:** Atrioventricular nodal reentry tachycardia involves reciprocation between two functionally and anatomically distinct pathways. In most cases, the fast pathway appears to be located near the apex of Koch’s triangle. The slow pathway extends inferoposterior to the compact AV-node tissue and stretches along the septal margin of the tricuspid annulus at the level of, or slightly superior to, the coronary sinus (the righward inferior extension of the AV node). The slow pathway may be formed from the leftward inferior extension of the AV node with the earliest retrograde activation at the roof of the proximal coronary sinus (1-3 cm from the ostium).