Mexiletine Prevents Recurrent Torsades€de€Pointes in Acquired Long€QT€Syndrome Refractory to Conventional Measures

RESULTS No recurrence of TdP occurred within 2 h after initiation of treatment with mexiletine in all 12 patients. Macro T-wave alternans accompanied by QT prolongation, an electrocardiographic precursor of TdP that was seen in 3 patients, was also abolished by mexiletine. Treatment with mexiletine shortened the QTc interval from 599 27 ms to 514 16 ms (p 1⁄4 0.001). The interval from the peak to the end of the T-wave (Tp-e interval) decreased from 145 18 ms to 106 9 ms (p 1⁄4 0.005). The Tp-e/QT ratio decreased from 0.27 0.02 to 0.23 0.018 (p 1⁄4 0.01). Mexiletine had no significant effect on QRS complex duration.