Defects in the ventricular conduction system typically produce which electrocardiographic change?

• A. AV block primarily affects PR interval.
• B. P wave height increases.
• C. Bundle branch blocks or other conduction delays within ventricles slow spread of impulses, causing prolonged QRS.
• D. T wave inversion.

Answer: (C)

When the ventricular conduction system is defective, the impulse spreads through the ventricles more slowly, so ventricular depolarization takes longer. This appears on the ECG as a wider, prolonged QRS complex because the entire ventricle is activated over an extended period rather than quickly via the normal His-Purkinje pathway.

The best choice describes bundle branch blocks or other intraventricular conduction delays, which slow the spread of impulses within the ventricles and produce a prolonged QRS duration. Normal QRS is brief; when conduction within the ventricles is delayed, the QRS widens.

Other options don’t fit this pattern: AV block mainly alters the PR interval since it concerns atrioventricular conduction; increasing P wave height relates to atrial activity; T wave inversion reflects repolarization changes and is not a specific indicator of intraventricular conduction delay.