Brugada syndrome masked by ibutilide treatment in a patient with atrial flutter.

We present a case of Brugada syndrome in a young patient whose typical ECG pattern was 'masked' after ibutilide was administered for atrial flutter cardioversion. Ibutilide, a class III antiarrhythmic agent used for the treatment of atrial fibrillation and flutter, prolongs the action potential duration plateau phase by augmenting the slow component of the inward Na(+) current and by blocking the rapid component of the delayed rectifier potassium current. Insights into the pathophysiology of Brugada syndrome and this first-reported action of ibutilide are supplied, providing a plausible scientific basis for the masking effect of ibutilide. Furthermore, issues concerning the safety of ibutilide administration in patients with Brugada syndrome along with the importance of programmed ventricular stimulation and especially short-long-short sequence protocol in inducing ventricular fibrillation in these patients are also discussed.