Woman with postpartum ventricular tachycardia and hypomagnesemia.

A 28-year-old Japanese woman who had received continuous intravenous infusion of magnesium sulfate from 24 weeks of pregnancy until delivery underwent cesarean section at 30 weeks and gave birth to twins. Serum magnesium sharply declined to a subnormal level of 1.5 mg/dL on postpartum day 4. The patient exhibited sinus bradycardia (48 b.p.m.) with intermittent supraventricular contraction on postpartum day 2, intermittent ventricular bigeminy on postpartum day 3, and frequent selfterminated polymorphic ventricular tachycardia on postpartum day 4. The electrocardiogram (ECG) disclosed that the patient had prolonged QTc of 0.45-0.67. Correction of serum magnesium improved ECG findings promptly, resulting in the disappearance of arrhythmias. Hypomagnesemia due to postpartum diuresis may have played a role causing ventricular tachyarrhythmia in this patient.