Experience with flecainide for the treatment of cardiac arrhythmias in children.

We treated 22 children, aged 3 days to 16 years 6 months (median 11 years 1 month), with flecainide for a variety of arrhythmias where a Class I agent was indicated. In 16, conventional antiarrhythmic treatment had failed. Structural heart disease was present in nine. The arrhythmia was paroxysmal re-entry atrioventricular tachycardia in nine; paroxysmal atrial tachycardia, flutter or fibrillation in five; paroxysmal ventricular tachycardia in five and frequent ventricular extrasystoles (with couplets) in three. Sinus rhythm was achieved in all four children who received flecainide during tachycardia (three received intravenous flecainide, one oral). During follow-up of 3-24 months (median 12 months), arrhythmia control was obtained in 13 children (59%). Combination therapy was used in seven of these; with digoxin in four and a beta blocker in three. Flecainide doses used in this study ranged from 1-11 mg kg-1 day-1 (median 4 mg kg-1 day-1), 25-297 mg m-2 day-1 (median 113 mg m-2 day-1). The median, pre-dose flecainide concentration in those responding to therapy was 225 micrograms l-1 and in those failing to respond was 417 micrograms l-1. An arrhythmogenic effect occurred in one child.