Atrio-Ventricular Block-Induced Torsades de Pointes: An Update

Torsades de pointes is a potentially life threatening form of rapid, polymorphic ventricular tachycardia. Literally meaning “twisting of the points”, torsades de pointes is electrocardiographically characterized by QRS axis undulations over runs of several beats, with a specific twist of the QRS complex around the isoelectric baseline. The definition also requires that an abnormal QT-prolongation be present (usually to 600 msec or greater) and / or abnormal TU complexes. The arrhythmia usually terminates spontaneously, with the exception of rare degeneration into ventricular fibrillation. The episodes are often repetitive and frequency dependent. In 1966, Dessertenne first described torsades de pointes in a patient with atrio-ventricular block (Dessertenne, 1966). Ever since, several reports have associated torsades de pointes with bradycardia, especially with atrio-ventricular block (Viskin, 1999). From 5% to 30% of patients with atrio-ventricular block have been reported to develop torsades de pointes (Motté, 1970, Jensen, 1975, Guize, 1993) an observation that suggests the participation of yet other intrinsic or extrinsic sensitising factors. Most episodes of torsades de pointes are paroxystic, not longer than 5-20 beats, with a very elevated heart rate (160-300 bpm). The typical morphology of torsades de pointes includes a complete twist at 180° of QRS complexes and a progressive change of the surface ECG. A QT interval prolongation to 600 ms or longer is always evident. These episodes are often preceded by ventricular bigeminism with fixed and long coupling interval.