We report the case of a female neonate admitted to the neonatal ICU with a rapid, narrow-complex tachyarrhythmia determined to be supraventricular tachycardia. Multimodality imaging and genetic testing confirmed a diagnosis of tuberous sclerosis complex with multiple cardiac rhabdomyomas. At 13 days of age, the patient was readmitted, exhibiting recurrent supraventricular tachycardia non-responsive to first-line treatment. Management required triple-drug therapy, whereafter the patient remained stable without recurrences. This is a rare report of supraventricular tachycardia in a functionally normal heart with the occurrence of supraventricular tachycardia due to structural abnormalities, with the possibility of multiple concealed accessory pathways.

Therapeutic drug monitoring of flecainide in children using plasma concentration measurements is undertaken by some clinicians. There is very little published evidence surrounding factors which influence plasma flecainide concentration, particularly in paediatric populations. We undertook a retrospective study of 45 children receiving flecainide to identify factors that influence its plasma concentration. Patients receiving a dose of 6 mg/kg/day had a higher mean plasma flecainide concentration than those receiving lower doses. Younger age and lighter weight were also associated with higher plasma flecainide concentrations. Children aged younger than 1 year receiving flecainide three times a day had a higher mean plasma flecainide concentration than older children who received flecainide twice a day. All supratherapeutic levels occurred in children aged less than 1 year who were receiving flecainide three times a day. Supratherapeutic levels were more common in those receiving 6 mg/kg/day while subtherapeutic levels were more common in those receiving 2 mg/kg/day. A supratherapeutic level did not correlate with adverse effects or clinical toxicity. Our results would suggest the need for a change of practice from prescribing flecainide at a frequency of three times a day in children aged younger than 1 year to twice a day in line with other ages.

Some asymptomatic patients with Wolff–Parkinson–White syndrome have severe left ventricular dyssynchrony and dysfunction. We describe a patient who was given a diagnosis of Wolff–Parkinson–White syndrome in infancy and had a complete response to pharmacologic therapy with flecainide. Our findings suggest that flecainide is a suitable resynchronisation therapy for such infants.

Antiepileptic medications have been reported to cause disturbances in cardiac conduction. Lacosamide decreases seizure burden by modulating sodium channels. Although it has been demonstrated to have few side effects, there have been reports of clinically significant cardiac conduction disturbances. We report the case of a child with hypoplastic left-heart syndrome and well-controlled multifocal atrial tachycardia who developed haemodynamically significant atrial tachycardia after receiving two doses of lacosamide.

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.

After repair of an atrioventricular septal defect with common atrioventricular junction in a 2-month-old girl, rapid atrial tachycardia, in combination with junctional ectopic tachycardia, led to severe postoperative cardiovascular compromise. Intercurrent runs of ectopic atrial tachycardia made atrial pacing impossible, despite high doses of intravenous amiodarone. Following the addition of flecainide to the infusion, we were able to control the rhythm, and when combined with atrial pacing, this led to an immediate haemodynamic improvement. Treatment of refractory supraventricular tachycardias with amiodarone combined with flecainide can be very effective in the setting of postoperative cardiac intensive care.