In AVRT, which activation pattern characterizes septal pathways?

• A. CS distal early eccentric activation
• B. HRA earliest concentric activation
• C. CS proximal late activation
• D. HIS earliest concentric activation

Answer: (D)

In AVRT, where the activation starts in the atria relative to the ventricles helps pinpoint the location of the accessory pathway. Septal pathways sit right near the AV node and His bundle, so the retrograde impulse tends to enter the atria first at the region of the His bundle. This produces an activation pattern where the His bundle region is the earliest site and the activation then spreads concentrically to surrounding atrial tissue. That is why the correct pattern is His-early, concentric activation.

Patterns that show earliest activation at the coronary sinus areas (distal or proximal) or at the high right atrium reflect non-septal, more lateral or different regional pathways, not septal ones.