Local reentry is located within which structures and leads to which tachycardias?

• A. Within atria or ventricles; atrial or ventricular tachycardia
• B. Within AV node; SVT only
• C. Within the ventricles; ventricular fibrillation
• D. Within the SA node; sinus tachycardia

Answer: (A)

Local reentry is a circulating wavefront that stays within a single chamber of the heart, typically the atria or the ventricles. When a reentrant circuit forms in atrial tissue, it drives atrial tachycardia; when it forms in ventricular tissue, it drives ventricular tachycardia. This differs from reentry within the AV node, which causes AV nodal reentrant tachycardia presenting as a narrow-complex SVT, and from sinus tachycardia or ventricular fibrillation, which are not driven by a single local reentrant circuit. The SA node–based reentry and sinus tachycardia aren’t the mechanisms here, whereas a localized atrial or ventricular circuit directly explains a tachycardia arising from within those chambers.