Primidone in the treatment of the long QT syndrome: QT shortening and ventricular arrhythmia suppression.

We studied a family with the long QT syndrome. The initial case was in a patient who presented with seizures, ventricular fibrillation, and syncope. After a trial of conventional modalities of treatment including left stellate ganglionectomy, primidone (Mysoline) therapy was initiated. This drug has been successful in suppressing ventricular arrhythmias and shortening the QT interval over a 2-year follow-up period. Two additional family members with QT prolongation have been treated with primidone. During an 8-month follow-up, electrocardiographic and Holter recordings showed shortening of the QT interval.