What distinguishes torsades de pointes from other tachycardias on ECG?

• A. Polymorphic VT with twisting of QRS around baseline and often prolonged QT.
• B. Monomorphic VT with fixed QRS.
• C. Atrial flutter with variable block.
• D. Sinus tachycardia.

Answer: (B)

Torsades de pointes is a polymorphic ventricular tachycardia, so its defining feature on the ECG is a QRS pattern that continuously changes shape, amplitude, and axis, giving a twisting or “swinging” appearance around the baseline. This twisting pattern is almost always seen with a prolonged QT interval, reflecting delayed repolarization that promotes early afterdepolarizations and the chaotic rhythm of torsades.

This differs from monomorphic VT, where the QRS complexes all look the same—one fixed morphology—indicating a single reentrant circuit or focus. Atrial flutter with variable block is an atrial tachycardia with sawtooth flutter waves and an irregular ventricular response depending on the degree of AV block, not a ventricular tachycardia. Sinus tachycardia is a normal rhythm originating in the SA node with upright P waves before each QRS and a regular rate, not a chaotic, twisting VT pattern.

So the key distinguishing ECG feature is the polymorphic, twisting QRS complexes often tied to a prolonged QT interval.