Antiarrhythmic Drugs in Pediatrics
Antiarrhythmic Drugs in Pediatrics
Key Points
- Antiarrhythmic medications are used to treat and prevent cardiac arrhythmias in children
- Choice of drug depends on the type of arrhythmia, age of patient, and underlying cardiac condition
- Careful monitoring is essential due to potential proarrhythmic effects
- Vaughan Williams classification system helps organize these drugs based on mechanism of action
Mechanism of Action
Antiarrhythmic drugs work by modifying the electrical conduction system of the heart through various mechanisms:
- Sodium channel blockade
- Beta-adrenergic blockade
- Potassium channel blockade
- Calcium channel blockade
Classification of Antiarrhythmic Drugs
Class I (Sodium Channel Blockers)
Class IA
- Quinidine
- Use: SVT, AF, VT
- Side effects: QT prolongation, GI disturbance
- Procainamide
- Use: SVT, VT
- Monitoring: QT interval, ANA levels
Class IB
- Lidocaine
- Use: Ventricular arrhythmias
- Advantage: Short half-life, minimal hemodynamic effects
Class IC
- Flecainide
- Use: SVT, especially in structurally normal hearts
- Contraindication: Structural heart disease
Class II (Beta Blockers)
- Propranolol
- Use: SVT, Long QT syndrome
- Dosing: Start low, titrate based on response
- Esmolol
- Use: Acute arrhythmias
- Advantage: Ultra-short acting, IV administration
Class III (Potassium Channel Blockers)
- Amiodarone
- Use: Life-threatening arrhythmias
- Major considerations: Long-term toxicity
- Sotalol
- Use: SVT, VT
- Monitoring: QT interval essential
Class IV (Calcium Channel Blockers)
- Verapamil
- Use: SVT in older children
- Caution: Avoid in infants
Clinical Applications
Supraventricular Tachycardia (SVT)
- First-line: Adenosine
- Maintenance: Beta blockers, flecainide
- Refractory cases: Amiodarone, sotalol
Ventricular Tachycardia (VT)
- Acute: Lidocaine, amiodarone
- Chronic: Beta blockers, sotalol
- Special considerations for channelopathies
Long QT Syndrome
- Beta blockers are mainstay
- Avoid QT-prolonging agents
- Consider mexiletine in specific genotypes
Dosing & Administration
Common Pediatric Doses
Amiodarone
- Loading: 5-10 mg/kg IV over 30-60 minutes
- Maintenance: 5-15 mg/kg/day divided q8-24h
- Maximum: 1200 mg/day
Propranolol
- Initial: 0.5-1 mg/kg/day divided q6-8h
- Titrate to: 2-4 mg/kg/day
- Maximum: 16 mg/kg/day
Flecainide
- Initial: 2-3 mg/kg/day divided q8-12h
- Maximum: 150-200 mg/day
- Target serum level: 200-1000 ng/mL
Monitoring & Precautions
General Monitoring Parameters
- ECG monitoring
- QT interval
- PR interval
- QRS duration
- Drug levels when applicable
- Organ function
- Liver function tests
- Thyroid function
- Renal function
Drug-Specific Monitoring
- Amiodarone
- Thyroid function every 3-6 months
- Liver enzymes every 6 months
- Annual ophthalmologic exam
- Chest X-ray baseline and annually
- Flecainide
- ECG monitoring for QRS widening
- Drug levels
Special Populations
- Neonates: Careful with dosing and monitoring
- Renal impairment: Dose adjustment needed
- Genetic variants: Consider pharmacogenetic testing
