Which finding indicates a Bundle Branch Block?

• A. Normal QRS complex
• B. Short PR interval
• C. Atrial flutter
• D. Wide QRS complex with delayed conduction in the ventricles

Answer: (D)

The finding points to a slowdown or blockage in the ventricular conduction pathway, specifically a bundle branch. In normal hearts, ventricular activation travels quickly through the His-Purkinje system, producing a narrow QRS complex. When a bundle branch is blocked, one ventricle is activated later through slower cell-to-cell conduction, causing desynchronization and a longer depolarization time, which makes the QRS complex wide (usually longer than 120 ms). This widened QRS with delayed intraventricular conduction is the hallmark of a bundle branch block, and you can see characteristic patterns depending on whether the left or right branch is affected. The other findings—normal QRS, short PR interval, or atrial flutter—do not reflect this intraventricular conduction delay.