Which description best differentiates AVNERP from VANERP?

• A. AVNERP shows pacing with His capture; VANERP shows no His conduction.
• B. AVNERP involves atrial capture; VANERP involves ventricular capture.
• C. AVNERP shows pacing without His signal but ventricular capture; VANERP shows ventricular capture with no retrograde atrial conduction.
• D. AVNERP indicates retrograde conduction; VANERP indicates bidirectional conduction.

Answer: (C)

AVNERP and VANERP are distinguished by how the pacing impulse interacts with the AV conduction system and whether retrograde atrial activation occurs. When you pace near the AV node and you capture the ventricle but do not observe a His bundle signal, you are activating ventricular tissue without engaging the His bundle. This pattern identifies AV nodal effective refractory period properties, hence AVNERP. In contrast, when pacing the ventricle results in capture but there is no retrograde atrial conduction (the impulse fails to travel back to the atria), you’re assessing VA conduction without atrial activation, which points to VANERP. Therefore, the scenario where pacing yields ventricular capture without a His signal best differentiates AVNERP from VANERP.