What is the QRS duration in a standard junctional rhythm?

• A. ≤0.10 s
• B. >0.12 s
• C. 0.12-0.16 s
• D. Not specified

Answer: (A)

QRS duration shows how long it takes for ventricular depolarization. In a standard junctional rhythm, the impulse still uses the heart’s normal conduction system to activate the ventricles, so the QRS complex remains narrow. A normal QRS duration is up to 0.10 second (100 ms), so the QRS in a junctional rhythm is typically 0.10 seconds or less. That makes the ≤0.10 s range the best match. The other ranges imply a wider QRS, which would indicate abnormal ventricular conduction such as bundle branch block or an ectopic/ventricular rhythm, not a standard junctional one.