Defect in ventricular repolarization affects which ECG component?

• A. Affects the P wave.
• B. Affects the QT interval.
• C. No ECG changes.
• D. Affects the T wave.

Answer: (D)

Ventricular repolarization is reflected on the ECG by the T wave. A defect in this phase alters how the ventricles reset their electrical state after contraction, leading to changes in the T wave’s shape, direction, or amplitude (such as inversion or flattening). The P wave comes from atrial depolarization, so it wouldn’t primarily reflect a ventricular repolarization defect. The QT interval spans from the start of ventricular depolarization to the end of repolarization (including the T wave); while repolarization problems can prolong it, the direct component signaling the repolarization process is the T wave. Therefore, the best answer is that ventricular repolarization affects the T wave.