Which ECG finding characterizes polymorphic ventricular tachycardia caused by a prolonged QT interval?

• A. Regular P waves
• B. Torsades de pointes
• C. Normal QRS duration
• D. Shortened PR interval

Answer: (B)

Polymorphic ventricular tachycardia, particularly in the context of a prolonged QT interval, is primarily characterized by Torsades de pointes (TdP). This arrhythmia manifests as a unique pattern on the ECG, where the QRS complexes vary in amplitude and appear to "twist" around the baseline, resulting in a characteristic sinusoidal waveform. This phenomenon is specifically linked to disturbances in the heart's electrical conduction system, often due to delays in repolarization, which is the hallmark of a prolonged QT interval.

Torsades de pointes is directly associated with a variety of underlying causes, such as congenital long QT syndrome or can result from medications that affect cardiac repolarization. Identifying Torsades de pointes in an ECG reading is crucial for assessment and management, as it can lead to more severe arrhythmias or hemodynamic instability if not promptly treated.

The other options do not describe the distinctive changes seen in this specific type of arrhythmia associated with a prolonged QT interval. Regular P waves would typically indicate concurrent atrial activity, which is not seen in Torsades de pointes. Normal QRS duration is also not consistent with this type of tachycardia, as the Q