Local reentry within the AV node leads to which arrhythmia?

• A. SVT
• B. Atrial tachycardia
• C. Ventricular tachycardia
• D. Ventricular fibrillation

Answer: (A)

Local reentry within the AV node produces a fast, regular, narrow-complex tachycardia called AV nodal reentrant tachycardia, a form of supraventricular tachycardia. The AV node can have dual conduction pathways (a fast and a slow pathway). In reentry, a wavefront travels down one pathway and re-enters through the other, creating a self-sustaining circuit trapped in or around the AV node. Because the impulse ultimately travels to the ventricles through the normal His-Purkinje system, the QRS complexes stay narrow, distinguishing this as a supraventricular, not ventricular, tachycardia.

Clinically, AVNRT often presents with abrupt onset and termination of a rapid rhythm, typically around 150 beats per minute, and is frequently amenable to vagal maneuvers or adenosine.

Atrial tachycardia would originate from atrial tissue outside the AV node, usually with a different atrial activation pattern. Ventricular tachycardia and ventricular fibrillation originate below the AV node in the ventricles and usually produce wide QRS complexes (and can be unstable), not a narrow-complex SVT.