Effective use of magnesium for acquired torsade de pointes in a 4-month-old infant.

We report a 4-month-old infant with torsade de pointes secondary to procainamide treatment. The infant presented with atrial flutter and converted to normal sinus rhythm with intravenous procainamide. Oral procainamide therapy was initiated as the infusion was tapered, and the patient subsequently developed incessant torsade de pointes. Once the proarrhythmia was recognized, procainamide was withheld, and intravenous magnesium was administered. The torsade de pointes resolved after one bolus of magnesium sulfate. An infusion regimen of magnesium was given until the procainamide and N-acetylprocainamide concentrations became undetectable. Intravenous magnesium should be administered to newborns with acquired torsade de pointes; dosing guidelines for its use are suggested.