If you suspect AVNRT for an SVT EPS, which observations are consistent with typical AVNRT?

• A. AH jump, echo beat
• B. Short PR interval only
• C. Prolonged QT interval
• D. No change in AV conduction

Answer: (A)

Recognizing dual AV nodal physiology with a reentrant circuit inside the AV node is what EPS looks for in typical AVNRT. When pacing or delivering premature atrial stimuli, you can see an abrupt lengthening of the AH interval—the AH jump—indicating a switch from fast to slow pathway conduction within the AV node. That sudden change is a hallmark of two distinct AV nodal pathways.

If the premature impulse then travels down the slow pathway and retrogradely uses the fast pathway to reach the atria, you may observe an echo beat on the tracing. This retrograde atrial activation following the initial impulse demonstrates the loop involving the slow antegrade and fast retrograde limb, which is the reentrant mechanism behind AVNRT.

So the combination of an AH jump and an echo beat best fits typical AVNRT, reflecting the dual-pathway setup and intra-nodal reentry. A short PR interval alone, a prolonged QT interval, or no change in AV conduction do not specifically indicate this dual-pathway reentry pattern.