Electrocardiographic Parameters Indicating Worse Evolution in Patients with Acquired Long QT Syndrome and Torsades de Pointes

Background Acquired long QT syndrome (a-LQTS) is associated with life-threatening ventricular arrhythmias, mainly torsades de pointes (TdP). ECG parameters predicting evolving into ventricular fibrillation (VF) are ill defined. Aims To determine ECG parameters preceding and during TdP associated with higher risk of developing VF. Methods We analyzed 151 episodes of TdP, recorded in 28 patients with a-LQTS (mean QTc 638 ms ± 57). Results All 28 patients had prolonged QT interval, (mean QTc 638 ms ± 57) ranging from 502 ms to 858 ms correcting by Bazett's formula. The mean TdP heart rate was 218 bpm ± 38 (mean cycle length of TdP 274 ± 47 ms). We classified TdPs episodes into “slower”-TdP (s-TdP) 1. Macro T wave alternans was observed in 4 patients. The QT interval was not different in patients with VF(+) and VF(−) episodes, 633 ± 60 and 639 ± 57, respectively. Conclusions Some electrocardiographic parameters can be helpful in determining the risk of TdP evolving into VF. The slower ventricular rate ( 30 ms) and the short episodes < 20 beats could predict benign evolution.