Increased beat-to-beat variability of repolarization (BVR) has been suggested to indicate increased susceptibility to drug-induced arrhythmia. This study aimed to characterize BVR in patients before and after administration of sotalol, a torsadogenic antiarrhythmic drug, in the search for new biomarkers of proarrhythmic risk. ECG Recordings pre and post sotalol injection in two groups of patients (with and without history of drug-induced torsades de pointes) were obtained from THEW. ECG wave detection and delineation were performed via dyadic wavelet transform. BVR was evaluated by short-term variability (STV) of QTc interval and JT area. In both groups, sotalol resulted in significant increase in STV of JT area, while no significant change occurred in STV of QTc interval. Thus, STV of JT area, as a measure of BVR, has the potential to be a biomarker for drug toxicity.