QT prolongation increases the risk of which arrhythmia?

• A. QT prolongation increases risk of torsades de pointes
• B. It reduces risk of arrhythmias
• C. It only affects AV conduction
• D. It causes hyperkalemia

Answer: (A)

Prolonged QT interval means the ventricles stay repolarized for longer than normal, which sets the stage for early afterdepolarizations. These abnormal depolarizations can be triggered during the long repolarization phase, especially when the heart rate is slow or certain drugs are present. The result is a specific, dangerous form of polymorphic ventricular tachycardia known as torsades de pointes. If torsades continues, it can degenerate into ventricular fibrillation and sudden death, so QT prolongation directly raises the risk for this arrhythmia.

This isn’t about AV conduction, so changes in AV nodal timing (PR interval) aren’t the main issue here. It’s not about reducing arrhythmia risk, and hyperkalemia has its own distinct ECG effects (often shortening QT and producing other conduction abnormalities), not causing QT prolongation.