The junctional rhythm originates from which region?

• A. AV node or bundle of His
• B. Right atrial appendage
• C. Purkinje fibers in ventricles
• D. Sinoatrial node

Answer: (A)

Junctional rhythm comes from the atrioventricular (AV) node region—the AV junction, including the bundle of His. This occurs when the SA node isn’t driving the heart (or conduction from atria to ventricles is blocked), so the AV node takes over as the pacemaker, with an intrinsic rate around 40–60 beats per minute. On ECG, the atrial depolarization (P waves) may be absent, inverted, or occur after the QRS when the impulse travels retrogradely into the atria; the QRS is usually narrow because ventricular activation proceeds through the normal His-Purkinje system. This distinguishes it from sinus rhythm (which originates in the SA node and has normal P waves before each QRS) and from ventricular pacemaking (which has wide QRS from Purkinje/ventricular escape). So the origin is the AV node region.