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Encainide for resistant supraventricular tachycardia in children: follow-up report
J F Strasburger1, R T Smith, J P Moak
1Department of Pediatrics, Baylor College of Medicine, Houston, Texas.
Insights
Encainide effectively treated drug-resistant supraventricular tachycardias, particularly permanent junctional reciprocating tachycardia and AVRT, in children. However, infants under 6 months and those with prior adverse events faced higher risks.
Area of Science:
- Pediatric Cardiology
- Electrophysiology
- Pharmacology
Background:
- Drug-resistant supraventricular tachycardia (SVT) poses a significant challenge in pediatric patients.
- Limited therapeutic options exist for managing complex pediatric SVT cases.
- Encainide's efficacy and safety profile in pediatric populations require further investigation.
Purpose of the Study:
- To evaluate the effectiveness of oral encainide in treating drug-resistant SVT in children.
- To assess the safety and tolerability of encainide in this pediatric cohort.
- To identify specific SVT subtypes and patient characteristics associated with encainide response and adverse events.
Main Methods:
- Forty-one children (26 weeks gestational age to 20 years) with drug-resistant SVT received oral encainide.
- Diagnoses included permanent junctional reciprocating tachycardia (PJRT), paroxysmal atrioventricular reciprocating tachycardias (AVRT), and various atrial tachycardias.
- Efficacy and adverse events were monitored over a mean follow-up of 15 months.
Main Results:
- Encainide demonstrated complete efficacy in 54% and partial efficacy (with adjuncts) in 24% of patients.
- The drug was most effective for PJRT (60%) and AVRT (69%), with lower efficacy for primary atrial tachycardias (40%).
- Adverse effects, including QRS widening and proarrhythmia, were more common in infants <6 months and those with prior adverse events or cardiac dysfunction.
Conclusions:
- Encainide is effective for treating resistant PJRT and AVRT in otherwise healthy children.
- Infants under 6 months and patients with a history of proarrhythmia or severe cardiac dysfunction are at higher risk for adverse effects.
- Careful patient selection and monitoring are crucial when initiating encainide therapy in pediatric SVT patients.
Abstract:
Forty-one children (26 weeks gestational age to 20 years) with drug-resistant supraventricular tachycardia were treated with oral encainide, and 29 were followed for 3 to 34 months (mean 15). Diagnoses obtained by electrocardiographic criteria (23 patients) or electrophysiologic testing (18 patients) included permanent junctional reciprocating tachycardia in 15 children, paroxysmal atrioventricular reciprocating tachycardias (AVRT) in 13, atrial ectopic tachycardia in 4, atrial flutter in 1, chaotic atrial tachycardia in 5 and junctional ectopic tachycardia in 3. Encainide was completely effective in 54% (22 of 41 study patients) and partially effective in an additional 24% (10 of 41 patients), when combined with propranolol or verapamil. Within 1 month, 13 (32%) discontinued encainide for inefficacy or intolerance. Encainide was most effective in the treatment of permanent junctional reciprocating tachycardia (60% effective) and AVRT (69% effective). It controlled only 40% of primary atrial tachycardias. Encainide was well tolerated on a long-term basis in patients not experiencing symptoms during initiation. In study infants younger than age 6 months, encainide was associated with excessive QRS aberrancy during initiation in 4 of 13 (31%), compared with 3 of 28 (11%) in older children. Ventricular proarrhythmia occurred in 2 children and 1 died suddenly. Mean effective encainide dose was 3.5 mg/kg/day or 86 mg/m2/day. In 4 children who had nonextensive metabolism of encainide, the drug was ineffective. Encainide is effective in the treatment of some resistant forms of permanent junctional reciprocating tachycardia and AVRT in otherwise healthy children. Children younger than age 6 months and those with either previous proarrhythmic events or severe cardiac dysfunction appear to have a high incidence of adverse effects.