At what age is it appropriate to transition a pediatric patient with a history of neonatal Supraventricular Tachycardia (SVT) and Wolff-Parkinson-White (WPW) pattern on Electrocardiogram (ECG) from Propranolol (Propranolol) Three Times a Day (TID) to Metoprolol (Metoprolol) Twice a Day (BID) for simplified dosing?

Transitioning from Propranolol to Metoprolol in Pediatric WPW with SVT

Transition from propranolol TID to metoprolol BID can be considered at age 6 years and above when the child can reliably take twice-daily medication and has demonstrated stable control of SVT symptoms. 1

Age-Based Considerations for Beta-Blocker Transition

• Propranolol is commonly used in infants and young children with SVT and WPW pattern due to its established safety profile and TID dosing that provides consistent blood levels throughout the day 2
• Metoprolol is typically used in older children (≥6 years) who can reliably take twice-daily medication and have shown stable control of their arrhythmia 1
• The 2015 ACC/AHA/HRS guidelines for SVT management indicate that metoprolol is appropriate for twice-daily dosing in older children and adolescents, with recommended starting doses of 25 mg BID 1

Clinical Factors to Consider Before Transition

• Ensure the patient has demonstrated stable control of SVT symptoms on propranolol for at least 6-12 months 2
• Verify normal growth and development, as beta-blockers can occasionally affect growth parameters in very young children 1
• Confirm the absence of any breakthrough SVT episodes in the preceding 3-6 months 1
• Assess the child's ability to reliably take twice-daily medication (typically achieved by school age) 1

Transition Protocol

1. Initial Assessment:

   • Perform ECG to confirm stable WPW pattern and absence of other conduction abnormalities 1
   • Check vital signs including heart rate and blood pressure to ensure they are within normal range for age 1

2. Dosing Conversion:

   • Start metoprolol tartrate at 1 mg/kg/day divided BID (maximum starting dose 25 mg BID) 1
   • Alternatively, use metoprolol succinate (extended-release) at 2 mg/kg once daily 1
   • Titrate dose based on clinical response, with maximum daily dose of 200 mg for metoprolol tartrate 1

3. Monitoring During Transition:

   • Schedule follow-up within 2-4 weeks of transition to assess efficacy and tolerability 1
   • Monitor heart rate and blood pressure at each visit 1
   • Perform ECG to ensure continued suppression of SVT and stable WPW pattern 1

Special Considerations for WPW Patients

• Beta-blockers like propranolol and metoprolol primarily prevent SVT by slowing conduction through the AV node but have minimal effect on accessory pathway conduction 3, 4
• In patients with WPW, avoid abrupt discontinuation of beta-blockers as this may precipitate rebound tachycardia 1
• Consider gradual transition with overlapping therapy: maintain propranolol while initiating metoprolol, then gradually taper propranolol over 1-2 weeks 1

Potential Pitfalls and Cautions

• Metoprolol has less effect on bronchial smooth muscle than propranolol, making it potentially safer in patients with reactive airway disease 1
• Both medications can mask symptoms of hypoglycemia, which is particularly important in younger children 5
• If the patient experiences breakthrough SVT after transition, consider returning to propranolol TID dosing or referral for electrophysiology study and possible ablation 1
• Avoid transitioning during periods of illness, stress, or growth spurts which may affect medication metabolism 1

Follow-up Recommendations

• After successful transition, continue regular follow-up every 3-6 months to adjust dosing based on weight changes 1
• Perform annual ECG to monitor for changes in the WPW pattern 1
• Consider electrophysiology study and possible ablation as the child approaches adolescence, particularly if symptoms persist despite medical therapy 2