What is polymorphic ventricular tachycardia (VT) and how is it characterized on electrocardiogram (ECG)?

Updated: Dec 05, 2017
  • Author: Steven J Compton, MD, FACC, FACP, FHRS; Chief Editor: Jeffrey N Rottman, MD  more...
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Answer

When the QRS complex varies from beat to beat, the rhythm is described as polymorphic ventricular tachycardia (VT) and suggests a variable electrical activation sequence. The most notorious, and probably the most common, form of polymorphic VT is torsade de pointes, a French term meaning “twisting of the points” and refers to the unusual shifting-axis QRS complexes that appear as if the heart is rotating upon an axis.

Torsade de pointes typically occurs during sinus rhythm and in the presence of drugs or conditions that prolong the QT interval (eg, class IA antiarrhythmics, hypomagnesemia, droperidol). The dysrhythmia may occur either in the presence or in the absence of myocardial ischemia or infarction. The term torsade de pointes is reserved for polymorphic VT observed in the setting of a prolonged QT interval (see the images below). Other polymorphic VTs are occasionally observed during ischemia or myocarditis.

The typical initiation of torsade de points occurs with a “long-short” sequence—that is, a longer RR interval resulting in further prolongation of the QT interval, followed by an early depolarization occurring at a time of heterogeneous repolarization.

Torsade de pointes.

Image A: This is polymorphi Torsade de pointes. Image A: This is polymorphic ventricular tachycardia associated with resting QT-interval prolongation. In this case, it was caused by the class III antiarrhythmic agent sotalol. This rhythm is also observed in families with mutations affecting certain cardiac ion channels. Image B: Torsade de pointes, a form of ventricular tachycardia. Courtesy of Science Source/BSIP.
This electrocardiogram reveals torsade de pointes. This electrocardiogram reveals torsade de pointes.

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