Torsade de pointes is an uncommon and distinctive form of polymorphic ventricular tachycardia (VT) characterized by a gradual change in the amplitude and twisting of the QRS complexes around the isoelectric line (see the image below). Torsade de pointes, often referred to as torsade, is associated with a prolonged QT interval, which may be congenital or acquired. Torsade usually terminates spontaneously but frequently recurs and may degenerate into ventricular fibrillation.
Torsade de pointes. Asymptomatic patient on erythromycin had marked QT prolongation on ECG findings. Patient was profoundly hypomagnesemic and hypokalemic. This shows an example of recurrent nonsustained torsade de pointes that occurred several hours after the ECG was performed. With discontinuation of the erythromycin and aggressive repletion of the magnesium and potassium, no further torsade de pointes occurred and the patient’s QT interval returned to normal.
In torsade, the morphology of the QRS complexes varies from beat to beat. The ventricular rate can range from 150 beats per minute (bpm) to 250 bpm.
The original report described regular variation of the morphology of the QRS vector from positive to net negative and back again. This was symbolically termed torsade de pointes, or “twisting of the point” about the isoelectric axis, because it reminded the authors of the torsade de pointes movement in ballet. Most cases exhibit polymorphism, but the axis changes may not have regularity.
The definition also requires that the QT interval be increased markedly (often to ≥600 msec). Cases of polymorphous ventricular tachycardia in which the QT interval is not prolonged are treated as generic ventricular tachycardia. Torsade usually occurs in bursts that are not sustained; thus, the rhythm strip usually shows the patient’s baseline QT prolongation.
The etiology and management of torsade are, in general, quite different from those of garden-variety VT. In particular, the use of group IA antidysrhythmic drugs, which tend to prolong the QT interval, can have disastrous consequences in torsade. Differentiating between these entities, therefore, is critically important.
For more information, go to Ventricular Tachycardia.
See Can’t-Miss ECG Findings, Life-Threatening Conditions: Slideshow, a Critical Images slideshow, to help recognize the conditions shown in various tracings.