Magnesium therapy for torsades de pointes

This is the first report of the successful use of magnesium sulfate (MgSO₄) in 3 consecutive patients with torsades de pointes (TdP). In 1 patient, TdP was induced by a combination of quinidine and amiodarone, in the second by procainamide, and in the third by an overdose of imipramine. The QT intervals before TdP were 0.70, 0.64 and 0.56 second, respectively. A bolus of 1.0 to 2.0 g MgSO₄ 25% abolished the TdP in all 3 patients; but in the third patient, because of recurrent TdP, a second bolus of 1.0 g and a continuous 24-hour infusion of 1.0 mg/min were administered, preventing TdP. There was no immediate shortening in the QT interval in any patient after MgSO₄. Magnesium can be given safely even in patients with acute myocardial infarction, angina pectoris or systemic hypertension, conditions in which isoproterenol is contraindicated; it can be applied faster than temporary cardiac pacing; and its use for TdP appears worthy of additional trials.