How are typical and atypical AVNRT named?

How are typical and atypical AVNRT named?

• A. Typical AVNRT is slow-fast
• B. Typical AVNRT is fast-slow
• C. Atypical AVNRT is slow-fast
• D. Atypical AVNRT is fast-slow

Answer: (A)

The key idea is how the impulse travels through the two AV nodal pathways during the tachycardia. AVNRT uses a slow pathway and a fast pathway. In the typical form, the impulse travels antegrade through the slow pathway to activate the ventricles, then returns (retrograde) via the fast pathway back to the atria. This sequence is described as slow-fast. In the atypical form, the antegrade conduction uses the fast pathway and the retrograde return uses the slow pathway, yielding a fast-slow pattern. So the statement that typical AVNRT is slow-fast matches the usual antegrade–retrograde conduction pattern, making it the correct description.

The key idea is how the impulse travels through the two AV nodal pathways during the tachycardia. AVNRT uses a slow pathway and a fast pathway. In the typical form, the impulse travels antegrade through the slow pathway to activate the ventricles, then returns (retrograde) via the fast pathway back to the atria. This sequence is described as slow-fast. In the atypical form, the antegrade conduction uses the fast pathway and the retrograde return uses the slow pathway, yielding a fast-slow pattern. So the statement that typical AVNRT is slow-fast matches the usual antegrade–retrograde conduction pattern, making it the correct description.