Response to Atrial Extrastimulus During Supraventricular Tachycardia: What Is the Mechanism?

Arrhythmia Rounds. We describe a case illustrating the potential challenges in distinguishing AV nodal reentry tachycardia (AVNRT) from automatic junctional tachycardia (JT). While an early atrial extrastimulus advanced the next His and ventricular depolarization without tachycardia termination, suggesting JT, other features indicated the correct diagnosis of AVNRT. This teaching case demonstrates a novel exception to a recently reported diagnostic pacing maneuver and illustrates the importance of considering response to multiple maneuvers in reaching a diagnosis of SVT mechanism. (J Cardiovasc Electrophysiol, Vol. 24, pp. 359-363, March 2013)