This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Medicine
Prolongation of QRS complex in ECG represents: 
Select and explain. 
A. Acute cor pulmonale, B. Chronic cor pulmonale, C. Left ventricular hypertrophy, D. Bundle branch block
D: Bundle branch block
Answer: D: Bundle branch block 
Explanation: Intrinsic impairment of conduction in either the right or the left bundle system (intraventricular conduction disturbances) leads to prolongation of the QRS interval.

With complete bundle branch blocks, the QRS interval is >120 ms in duration.
With incomplete blocks, the QRS interval is between 100 and 120 ms.