Magnesium reversal of digoxin-facilitated ventricular rate during atrial fibrillation in the Wolff-Parkinson-White syndrome.

In patients with Wolff-Parkinson-White syndrome and atrial fibrillation, digoxin may increase the ventricular rate by facilitating conduction over the accessory pathway either directly by enhancing accessory pathway conduction and/or indirectly as a consequence of its effect on atrioventricular nodal conduction. Two cases are presented in which the intravenous administration of magnesium sulfate reversed digoxin facilitation of the ventricular rate to atrial fibrillation in the Wolff-Parkinson-White syndrome.