PMC5420028_01
A: Initial 12-lead electrocardiogram shows bidirectional premature ventricular beats. B: QT prolongation during sinus bradycardia at night. C: Torsades de pointes with increasing heart rate.
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An infusion of dopamine induced premature ventricular contractions, singly and in bidirectional couplets, which responded to xylocaine (Figure 1A). At midnight, he developed polymorphic ventricular tachycardia, which degenerated to VF with remarkable QT prolongation (Figure 1B). When the patient awoke the next day, torsades de pointes recurred with an increasing heart rate, despite the continuous infusion of xylocaine (1 mg/kg/h) (Figure 1C).