Author + information
- Received March 4, 2009
- Accepted March 12, 2009
- Published online September 22, 2009.
Bidirectional ventricular tachycardia is a hallmark of severe digitalis toxicity. The 12-lead electrocardiogram obtained from a 54-year-old man with acute heart failure and digitoxin intoxication shows typical features of this potentially life-threatening arrhythmia: a regular right bundle-branch block tachycardia with relatively narrow QRS complex (140 ms) and alternating left- and right-axis deviation. Atrioventricular dissociation is present, indicating that the tachycardia is ventricular in origin. Dissociated P waves can clearly be discerned in lead V1(*). The proposed arrhythmia mechanism is triggered activity arising alternately from the left anterior and posterior fascicle. This results in an alternating left and right frontal-plane axis, giving rise to a typical “bidirectional” appearance. An important differential diagnosis of this scarce ventricular arrhythmia is catecholaminergic polymorphic ventricular tachycardia, which can manifest as bidirectional. However, the clinical circumstance of exercise- or stress-induced tachycardia in a usually young individual without structural heart disease points to the correct diagnosis.
- Received March 4, 2009.
- Accepted March 12, 2009.
- American College of Cardiology Foundation