Which statement best distinguishes AVRT from AVNRT?

• A. AVRT uses an accessory pathway; AVNRT uses AV node circuits
• B. AVNRT uses an accessory pathway; AVRT uses AV node circuits
• C. Both rely on AV node; no difference
• D. AVNRT involves ventricles only

Answer: (A)

The key distinction is where the reentrant circuit forms. AVRT relies on an accessory pathway outside the AV node to complete the loop between atria and ventricles, so the rhythm uses this extra tract in addition to the normal conduction system. AVNRT, by contrast, is a reentry circuit contained entirely within the AV node, typically due to dual AV nodal pathways, with no external accessory pathway involved. This is why the statement that AVRT uses an accessory pathway and AVNRT uses AV node circuits best captures the fundamental difference.

The other options misstate the locations or involvement: AVNRT does not rely on an accessory pathway, and AVRT does not involve only AV nodal circuits.