New data on the antiarrhythmic value of parenteral magnesium treatment: magnesium and ventricular arrhythmias.

Antiarrhythmic magnesium (Mg) therapy was evaluated in 20 normomagnesaemic patients affected by ischaemic dilated cardiomyopathy (ID) and severe ventricular arrhythmias, and in 10 patients with torsade de pointes (TdP) occurring in the setting of acquired QT interval prolongation. In the group with IDC, magnesium sulphate was given as slow infusions (50 mg/min over 60 min) twice a day for 7 d. This was antiarrhythmic in all of the patients: ventricular premature contractions and couplets decreased from 13,979 +/- 8964 (mean +/- SD) to 382 +/- 265 (P < 0.001), and from 516 +/- 274 to 9 +/- 6 (P < 0.001), respectively; runs of ventricular tachycardia (41.9 +/- 14.2) disappeared by the fifth day of treatment. The efficacy of antiarrhythmic treatment was evaluated by 24 h Holter monitoring obtained in baseline conditions and after 3, 5 and 10 d from beginning of therapy. In patients with TdP, Mg infusions were instituted at a slow rate (50 mg/min) and continued for 2 h after disappearance of Tdp, which occurred within 20 to 30 min from the start of the Mg infusions. These were followed by prophylactic infusions at rate of 30 mg/min for 90 min twice a day over the next 3 to 4 d. No side effects were observed, and heart rate and QTc remained unchanged from baseline values. In conclusion, Mg infusions may be an effective antiarrhythmic treatment for short and medium-term control of severe ventricular arrhythmias associated with IDC, and may prove useful in the acute treatment of TdP, especially in situations where conventional therapy might prove deleterious or difficult.