[Our experience with flecainide acetate in resistant arrhythmias in children. Apropos of 35 cases].

Thirty-five patients aged 6 days to 18 years (average 7.5 +/- 5.2 years) were treated for an average period of 16 months (range 8 days to 50 months) with flecainide acetate at an average dose of 4.8 +/- 1.4 mg/kg (2.9 to 10 mg/kg) or 130 +/- 30.5 mg/m2 administered twice daily. The cardiac arrhythmia was a resistant paroxysmal junctional tachycardia due to a Wolff-Parkinson-White syndrome in 27 cases, intranodal reentry in 6 cases and a chronic reciprocating rhythm in 2 cases. Treatment was successful with complete suppression of the tachycardia in 24 cases. Partial success with a good clinical result was obtained in 4 cases and there were 7 failures, 6 due to inefficacy of the drug, and 1 because of an extracardiac secondary effect. One case of incessant junctional tachycardia was observed in a 9 month old child in whom the preexcitation disappeared. Atrioventricular preexcitation persisted in 20 out of 24 cases. The duration of the non-preexcited QRS complexes increased significantly from 73.6 +/- 13.8 to 82.2 +/- 15.2 ms; n = 14, p less than 0.01. The minimal effective plasma concentration was 347 +/- 147 ng/ml. The plasma concentration/dose ratio of children over 4 years of age was the same as in adults. It was significantly higher in babies and infants suggesting a progressive acquisition of the capacity to metabolise flecainide during the first year of life. In conclusion, flecainide acetate was easy to use with respect to administration and follow-up, and seems to be a drug of choice for the treatment of junctional tachycardia in children.