What is the difference between monomorphic and polymorphic ventricular tachycardia?

What is the difference between monomorphic and polymorphic ventricular tachycardia?

• A. Polymorphic VT has uniform QRS morphology.
• B. Monomorphic VT shows beat-to-beat variations in morphology.
• C. Polymorphic VT has uniform QRS morphology and stable rhythm.
• D. Monomorphic VT has uniform beats, while polymorphic VT shows beat-to-beat variations in morphology.

Answer: (D)

The key idea is how the ventricles depolarize across successive beats as seen on the ECG. In monomorphic VT, every beat looks the same—the QRS morphology is uniform because the ventricle is activated by the same abnormal focus or reentry circuit each time. In polymorphic VT, the QRS shapes change from beat to beat, reflecting a changing activation pattern or multiple foci driving the ventricles. That beat-to-beat variation creates the irregular, twisting appearance you may see, such as torsades de pointes. So the correct statement is that monomorphic VT has uniform beats, while polymorphic VT shows beat-to-beat variations in morphology. The other descriptions either imply uniform morphology for polymorphic VT or variation for monomorphic VT, which isn’t accurate.

The key idea is how the ventricles depolarize across successive beats as seen on the ECG. In monomorphic VT, every beat looks the same—the QRS morphology is uniform because the ventricle is activated by the same abnormal focus or reentry circuit each time. In polymorphic VT, the QRS shapes change from beat to beat, reflecting a changing activation pattern or multiple foci driving the ventricles. That beat-to-beat variation creates the irregular, twisting appearance you may see, such as torsades de pointes.

So the correct statement is that monomorphic VT has uniform beats, while polymorphic VT shows beat-to-beat variations in morphology. The other descriptions either imply uniform morphology for polymorphic VT or variation for monomorphic VT, which isn’t accurate.