Electrophysiology Unit (EPU) Practice Exam

The key idea is how a ventricular pacing maneuver alters the tachycardia circuit. If SVT ends when pacing is stopped and you don’t see any atrial activation afterward, there’s no retrograde conduction from the ventricles back to the atria via an accessory pathway. That retrograde pathway is essential for AVRT. Without it, AVRT cannot sustain or reinitiate after the last paced beat, so this observation excludes AVRT as the mechanism.

AVNRT and atrial tachycardia don’t rely on that ventriculoatrial conduction through an accessory pathway to continue, so their mechanisms remain plausible. In AVNRT the reentrant circuit is within the AV node itself, and termination can occur without immediate atrial activation after pacing. In atrial tachycardia, the atria drive the rhythm, and the pacing maneuver may terminate without producing a new atrial response post-pacing.

So the pacing finding specifically rules AVRT out.