What mapping strategy is used for Orthodromic AVRT?

• A. Pace A map to earliest V
• B. Pace V map to earliest A
• C. Pace A map to earliest H
• D. Pace V map to latest A

Answer: (B)

In orthodromic AVRT, conduction travels antegradely through the AV node and retrogradely through the accessory pathway from ventricle to atrium. To locate the accessory pathway, you want to reproduce that retrograde flow and find where the atrium is activated earliest by ventricular pacing. Pacing the ventricle and mapping the atrium to the earliest atrial activation pinpoint the atrial insertion of the pathway, which is where ablation is most effective. Pacing the atrium or focusing on the earliest ventricular or His activation would not specifically reveal the retrograde pathway location, since the retrograde connection is what you’re trying to map.