Which statement about AV node conduction is true?

• A. It slows conduction from the atria to the ventricles to allow time for atrial contraction and ventricular filling.
• B. It speeds conduction directly from the atria to the ventricles.
• C. It is the primary site of automaticity with the highest firing rate.
• D. It is located in the left ventricle near the aortic valve.

Answer: (A)

The AV node serves as a gatekeeper between the atria and ventricles, introducing a deliberate delay in the conduction of electrical impulses. This pause gives the atria time to depolarize and contract, pushing blood into the ventricles and allowing optimal ventricular filling before the ventricles squeeze.

This delay is a hallmark of AV nodal conduction. The impulse then travels to the His-Purkinje system to activate the ventricles, but the key step is the slow conduction through the AV node itself. On an ECG, this timing shows up as the PR interval, which reflects how long the AV node takes to pass the impulse to the ventricles.

The statement is correct because it captures that slowing of conduction between the atria and ventricles is the primary job of the AV node to coordinate timing of heartbeats. The AV node is not the fastest pathway (that would be the Purkinje system), and its primary pacemaking tissue is the SA node, not the AV node. It is also located in the right atrium near the interatrial septum, close to the tricuspid valve—not in the left ventricle near the aortic valve.