Expert ECG 4
- Bidirectional ventricular tachycardia
- Digoxin toxicity
Bidirectional ventricular tachycardia is a rare, but pathognomonic rhythm for digoxin toxicity. There are two distinct QRS morphologies alternating every other beat. The QRS is wide. Both morphologies meet Brugada criteria for a ventricular origin. They are both in a right bundle branch block pattern since they are upright in lead V1. One of the QRS complexes is upward concordant in the precordial leads (all upward) indicating a ventricular origin. The other morphology has an R larger than the R' in lead V1 indicating a ventricular origin. Note the pause, one sinus beat, then the resumption of the bidirectional ventricular tachycardia.