Polymorphic ventricular tachycardia (VT) is a malignant ventricular tachyarrhythmia with changing QRS pattern that will either terminate spontaneously (causing syncope if it lasts more than a few seconds) or will deteriorate to ventricular fibrillation (VF), causing cardiac arrest.

How does polymorphic ventricular tachycardia happen?

Polymorphic VT associated with a normal QT interval is most often caused by acute ischemia or infarction and may rapidly degenerate into VF. When polymorphic VT is associated with a long QT interval, the syndrome is called torsades de pointes (Figure 23-7).

What is the treatment for polymorphic ventricular tachycardia?

Polymorphic ventricular tachycardia (a.k.a. Torsades de Pointes) is best treated with intravenous magnesium. Patients with a prolonged QT interval have a higher risk of developing polymorphic VT. Remove offending drugs that prolong the QT interval and correct potassium or calcium imbalances as well.