The "slow pathway" potential: fact or fiction?

The exact electroanatomic circuit responsible for atrioventricular nodal reentrant tachycardia (AVNRT) remains poorly understood. Initially, the pathological substrate was thought to be a small reentry circuit within the compact AV node (AVN).1 However, through a series of detailed histological studies,2 computer modeling,3 optical mapping,4 and uniquely insightful observations of tachycardia behavior, with the introduction of critically timed and placed premature atrial complexes,5–7 the determinative role played by the atrial inputs to the AVN has been established.