[Torsades de Pointes: analysis of 105 episodes]

To analyze episodes of Torsades de Pointes (TP), in search of its electrocardiographic characteristics.

We analyzed 105 episodes of TP, in 4 patients using quinidine and diuretics, recorded by 24-hour Holter monitoring. The following parameters were studied; ventricular repolarization out of TP, rhythm disturbances before TP; EKG characteristics of the onset, the bouts and the end of the TP.

Ventricular repolarization, out of the TP, was abnormal, with the presence of U-waves at the end of the T-waves, resulting in prolongation of the QT (QU) interval. The U-wave voltage was noted to be cycle-length dependent. Ventricular bigeminy preceded TP in 100 episodes (95%) and the mean interval between both parameters was 18 +/- 16 min. The onset of the TP episodes showed the "short/long/short cycle rule", hereby called "pre-pause cycle", "preparing cycle" and "trigger cycle" respectively. The rotatory QRS-T morphology around the baseline, was seen in 75% of episodes, at the beginning or throughout the bout. Monomorphic ventricular tachycardia pattern was seen in the other 25% of episodes. Termination of bouts was sudden in all cases, and persistent ventricular bigeminy led to another bout in 90 episodes (85%).

In TP patients, there is enlargement of QT intervals mostly due to U-waves appearance. The U-waves seen in these cases, probably have an important role in the genesis of TP and are probably related to ventricular after-potentials (triggered activity). Ventricular bigeminy is a premonitory sign of TP in patients using class 1A antiarrhythmic drugs. Persistent ventricular bigeminy post-TP episodes is a strong indicator of another bout of TP. The onset of TP is more important than its morphology for the correct diagnosis of this arrhythmia.