Treatment of atrial fibrillation with mexiletine in Wolff-Parkinson-White syndrome

It is reported on 6 patients with Wolff-Parkinson-White syndrome in whom spontaneously appeared auricular fibrillation with high ventricular frequency. By the intravenous administration of mexiletine in three patients the sinus rhythm could be restored. In two patients at first only a reduction of the tachycardia and a disappearing of the QRS-broadening took place; the additional administration of quinidine then led to the return of the sinus rhythm. In one patient, despite combined treatment, the return of sinus rhythm could not be achieved, mexiletine, however, led at once to the decrease of the ventricular rate, to the normalisation of the QRS-duration and to the disappearance of all signs of congestive heart failure. The therapeutic mechanism of mexiletine in the Wolff-Parkinson-White syndrome is discussed and it administration for the treatment of the cases complicated by auricular fibrillation is recommended.