What is the definition of AVNERP?

• A. The longest A1 A2 measurement from the His electrogram that fails to conduct to the His
• B. The shortest A1 A2 measurement from the His electrogram that conducts to the His
• C. The longest S1 S2 that fails to conduct to the His
• D. The longest A1 A2 measurement from the RA electrogram that fails to conduct to the His

Answer: (A)

AVNERP measures how long the AV node remains refractory after a premature atrial impulse. In an EP study you deliver a baseline atrial beat (A1) and then a premature atrial stimulus (A2) at progressively shorter coupling intervals, checking with the His bundle electrogram to see whether conduction to the His bundle occurs. AVNERP is defined as the longest A1–A2 interval that fails to conduct to the His. This boundary shows the AV node’s effective refractoriness: if the premature impulse arrives earlier than this interval, it won’t reach the His; if it’s longer, conduction can occur. Measuring from the His electrogram is essential because it directly shows whether the impulse propagates to the His. The other options describe different measurements or sites (such as the RA and S1–S2 paradigms) that do not define the AV node’s effective refractory period in the same way.