Successful uses of magnesium sulfate for torsades de pointes in children with long QT syndrome

Background: Administration of magnesium sulfate (MgSO4) is an effective and safe treatment for torsades de pointes (TdP) associated with acquired long QT syndrome (LQTS) in adults. As for children, there are few reports focusing on it. The authors discuss the efficacy of MgSO4, for TdP in children with congenital and acquired LQTS. The authors also discuss the optimal administration dosage and serum magnesium (SMg) concentration during MgSO4 therapy. Methods: The authors studied seven consecutive LQTS children undergoing M-SO therapy for TdP. Of the seven children, five were congenital LQTS and two were acquired LQTS. A bolus injection of MgSO was given intravenously over 1-2 min followed by continuous infusion for the next 2-7 days. Results: Of the seven patients, six responded completely to the initial bolus. The bolus dosage was 5.9 +/- 3.8 mg/kg (range, 2.3-12 mg/kg) in these six, and the other remaining one (neonate with congenital LQTS) required a total of 30 mg/kg until complete abolishment. The continuous infusion was given at rates of 0.3-1.0 mg/kg per h and patients did not show recurrence of TdP. The SMg concentration was 3.9 +/- 1.0 mg/dL (2.9-5.4 mg/dL) immediately after bolus injection. The mean corrected QT (QTc) interval before and after bolus injection did not show significant difference. Conclusion: Intravenous infusion of MgSO4 was effective for TdP in children with LQTS, and MgSO4 abolished TdP without shortening the QTc interval. The optimal bolus dosage, infusion rates and SMg concentration were 3-12 mg/kg, 0.5-1.0 mg/kg per h and 3-5 mg/dL, respectively.