Clinical experience with propafenone for cardiac arrhythmias in the young.

Seventy-two children were treated with propafenone between 1980 and 1990. The mean age was 34 months (range 0-192). Arrhythmias included atrioventricular re-entry tachycardia in 32 patients (44%), atrial flutter in 16 (22%), atrial or junctional ectopic tachycardia in 10 (14%), atrial re-entry tachycardias in three (4%) and ventricular arrhythmias in 11 patients (16%). The efficacy of oral treatment was good in patients with atrio-ventricular re-entry tachycardia (80%), atrial flutter (71%) and atrial ectopic tachycardia (83%); it was poor in ventricular arrhythmias (40%). The mean oral dose was 13.5 mg.kg-1. day-1. Dosage and serum levels of propafenone did not differ whether the patients were treated successfully or not. No correlation between dosage and serum level was observed. Intravenous propafenone administration was only partially successful in suppressing supraventricular tachycardias (6 of 11 patients). The presence of a congenital heart defect and the time of onset of the arrhythmias had a significant influence on the efficacy of propafenone. Better results were observed in patients with normal hearts and in whom onset of arrhythmia was pre-natal (success 80%) as well as in patients with arrhythmias seen early after surgery for congenital heart defects (success 87%). Success (65%) was also observed in patients without congenital heart defects and postnatal onset of supraventricular arrhythmias. Patients with ventricular or supraventricular arrhythmias late after corrective surgery showed the poorest response (31%).