Adenosine will terminate AVNRT tachycardia.

• A. True
• B. False
• C. Only if there is pre-excitation
• D. It is unpredictable

Answer: (A)

Adenosine terminates AVNRT by transiently blocking conduction through the AV node and increasing its refractory period. AVNRT relies on a reentrant circuit that uses the AV node as part of the pathway, so when adenosine briefly halts AV nodal conduction, the circuit can no longer propagate and the tachycardia stops, returning to normal rhythm. This effect is independent of whether there is pre-excitation; AVNRT does not require an accessory pathway, so adenosine can terminate it reliably. The other choices aren’t correct because termination doesn’t depend on pre-excitation, and the response is not unpredictable—adenosine is a known, effective acute therapy for AVNRT.