Combined antiarrhythmic drug therapy is an occasionally necessary but problematic approach to the child with recalcitrant supraventricular tachycardia. There is little experience with the combined use of amiodarone and class 1-C agents (flecainide, propafenone and encainide) in children. To judge the efficacy and safety of this combination, we reviewed the case notes and results of investigation in all nine children with supraventricular tachycardia who received such therapy between 1984 and 1993. These nine children received combined therapy on 12 occasions. Five were infants with either atrioventricular reentrant tachycardia (n=3) or atrial ectopic tachycardia (n=2), and four were older children with atrial flutter seen after a Fontan procedure. Amiodarone was combined with flecainide on eight occasions, with propafenone on three occasions, and with encainide on one occasion. Both infants with atrial ectopic tachycardia were successfully controlled, but only one of three infants with atrioventricular reentrant tachycardia had successful control on combination therapy. In three of the four patients with atrial flutter, the combination was useful in reducing the number of arrhythmic episodes. Three infants suffered side effects. At electrophysiologic study to judge efficacy, ventricular tachycardia was induced in two patients (one infant and one Fontan patient), necessitating a change in the 1-C agent. One patient had skin rash due to flecainide and was placed on propafenone with success. One Fontan patient died of complications after an elective surgical procedure. No deaths occurred attributable to proarrhythmia. Thus, combined therapy with amiodarone and 1-C agents was found to be safe and fairly effective in children with certain types of intractable supraventricular tachycardia.

Progressive granulocytopenia (neutrophil count <1000/ml) developed in a newborn during treatment with propafenone (200 mg/m2) for recurrent paroxysmal supraventricular tachycardia. The total white blood cell count, however, remained within normal limits. The neutrophil count increased gradually after propafenone had been stopped. The time course of treatment and the development of granulocytopenia make it very likely, but not certain, that propafenone was the responsible agent. Pediatricians, and especially pediatric cardiologists, should be aware of this rare adverse effect when they consider treatment with propafenone in children with cardiac arrhythmias. Analysis of the white cell blood count, including a differential count, is recommended in all children in order to assess the true incidence of this adverse effect.

Our objective was to assess the efficacy of pharmacological treatment in reducing the incidence of permanent junctional reciprocating tachycardia in young children, or to bring the mean heart rate over 24 h to a normal level.

We included 21 children with a median age of 0.05 year seen with permanent junctional reciprocating tachycardia over the period 1990 through 2001. Of these children, two had abnormal left ventricular function. Follow-up visits were made at least every 6 months. We registered the presence of the tachycardia over 24 h, the mean heart rate over 24 h, and cardiac function. Treatment was started with propafenone alone, or in combination with digoxin as the first choice. Treatment was effective in 14 cases (67%), with either complete disappearance of the tachycardia after discontinuation of medication, or continuation in sinus rhythm with medication; partially effective in 4 cases (20%) when the mean heart rate over 24 h on the last Holter recording was less than 1 standard deviation above the normal for age; but was not effective in the remaining 3 cases (14%). In 3 patients treated with propafenone, or 13 given propafenone and digoxin, treatment was effective in 12 (75%), partially effective in 2 (13%), and ineffective in the other 2 (13%).

All 21 children had a normal left ventricular function at the end of follow-up. The median duration of follow-up was 2.4 years. Permanent junctional reciprocating tachycardia had disappeared spontaneously in one-third of the children, 5 being less than 1 year old. Adverse effects, seen in 5 cases, were mild or asymptomatic. No signs of proarrhythmia were registered.

Pharmacological treatment, either with propafenone alone, or in combination with digoxin, is safe and effective in young children with permanent junctional reciprocating tachycardia. The mean heart rate is normalized, and cardiac function is restored and preserved. Radiofrequency ablation may be delayed to a safer age, with the arrhythmia disappearing spontaneously in one-third.

A previously healthy 73-year-old woman presented to hospital with acute atrial fibrillation. After intravenous procainamide failed to restore sinus rhythm, she was treated with 300 mg of oral propafenone and discharged with a prescription for propafenone and propranolol. Six hours later she took 150 mg of propafenone as prescribed. Within 1 hour she became dyspneic and collapsed. On arrival in hospital she was unconscious, with a wide complex tachycardia and no obtainable blood pressure. After defibrillation and lidocaine, she converted to a wide complex sinus rhythm, but remained profoundly hypotensive despite intravenous epinephrine and dopamine. Hypertonic sodium bicarbonate (HCO3) was administered and, shortly thereafter, her blood pressure increased, her QRS duration normalized and her clinical status improved dramatically. In this case of severe refractory propafenone-related cardiac toxicity, intravenous HCO3 led to a profound clinical improvement. Emergency physicians should be familiar with the syndrome of sodium-channel blocker poisoning and recognize the potentially important role of bicarbonate in its treatment.