VT Polymorphic features are

• A. QRS morphology remains constant.
• B. P waves before each QRS.
• C. Narrow QRS complexes.
• D. QRS morphology varies in shape and amplitude.

Answer: (D)

Polymorphic ventricular tachycardia shows QRS complexes that change shape and amplitude from beat to beat. This variation happens because the ventricular activation vector shifts with each beat, so the depolarization pattern isn’t fixed. A classic example is torsades de pointes, where the QRS morphology and axis rotate around the baseline as the rhythm continues. Because the origin of activation isn’t the same location with every beat, you don’t get a single, consistent QRS appearance. By contrast, a rhythm with a constant QRS shape is more characteristic of monomorphic VT, where the ventricular activation pattern stays the same each beat. If P waves reliably precede each QRS, that points toward atrial involvement with AV conduction rather than a pure ventricular tachycardia pattern. A narrow QRS complex would suggest a supraventricular mechanism with rapid conduction, not a ventricular tachycardia. Therefore, the defining feature of polymorphic VT is that the QRS morphology varies in shape and amplitude.