What is the first-line pharmacological management for a pregnant woman with Wolff-Parkinson-White (WPW) syndrome experiencing tachycardia?

Pharmacological Management of WPW Syndrome Tachycardia in Pregnancy

First-Line Acute Treatment

For hemodynamically stable pregnant patients with WPW syndrome experiencing supraventricular tachycardia, adenosine is the drug of choice after attempting vagal maneuvers, while flecainide or propafenone should be used for ongoing prophylaxis in patients without structural heart disease. 1, 2

Immediate Management Algorithm

Step 1: Assess Hemodynamic Stability

• If hemodynamically unstable (hypotension, altered mental status, severe chest pain), proceed immediately to electrical cardioversion with 120-200 J biphasic shock, placing the lateral pad under breast tissue 1, 3
• Cardioversion is safe at all stages of pregnancy and should never be delayed due to pregnancy concerns 3

Step 2: For Stable Patients - Acute Termination

• First attempt: Vagal maneuvers (Valsalva, carotid massage, ice-cold wet towel to face) 3, 4
• Second line: IV adenosine 6 mg rapid push, followed by up to two 12 mg doses if ineffective 1, 3, 2
  • Adenosine has a very short half-life preventing significant fetal exposure 4
  • Approximately 30% of atrial tachycardias may terminate with adenosine 1, 4
• Third line: IV procainamide is preferred for WPW with wide-complex tachycardia or atrial fibrillation with pre-excitation 1, 5
  • Procainamide has been used safely for maternal and fetal arrhythmias 1
  • Administer 100 mg IV every 5 minutes until arrhythmia suppresses or 500 mg total given 6

Critical Medications to AVOID in WPW

Never use AV nodal blocking agents (digoxin, beta-blockers, verapamil, diltiazem, or amiodarone) in patients with manifest pre-excitation on resting ECG, as these can precipitate ventricular fibrillation by preferentially blocking the AV node and forcing conduction down the accessory pathway. 1, 3, 7

• Digoxin is specifically contraindicated in adults with WPW syndrome 7
• Verapamil increases the risk of ventricular fibrillation in WPW 7
• Amiodarone should not be used for pre-excited atrial fibrillation and is contraindicated during pregnancy except as last resort 1

Long-Term Prophylactic Management

For recurrent symptomatic episodes requiring prophylaxis:

First-Line Options for WPW in Pregnancy

• Flecainide or propafenone are recommended as first-line prophylactic agents for WPW syndrome in pregnant women without structural heart disease 1
  • These agents can be used with caution after the first trimester 1
  • Both have been used effectively to treat maternal and fetal tachycardias 1

Second-Line Option

• Sotalol may be considered as second-line therapy 1
  • Has longer safety record but less specific efficacy for WPW 1

Important Timing Consideration

• All antiarrhythmic drugs should be avoided in the first trimester if possible, when risk of congenital malformations is greatest 1, 5
• Use the lowest effective dose with careful monitoring 1

Special Considerations for Atrial Fibrillation with WPW

If atrial fibrillation develops with pre-excitation (wide, irregular QRS complexes):

• This is a medical emergency requiring immediate treatment 1
• IV procainamide is the drug of choice (not adenosine, not AV nodal blockers) 5, 8
• Electrical cardioversion should be performed if hemodynamically unstable 1
• Anticoagulation with therapeutic LMWH is mandatory for AF ≥48 hours duration, continuing for at least 4 weeks post-cardioversion 1

Monitoring and Follow-Up

• Obtain 12-lead ECG to document pre-excitation pattern and guide therapy 3
• Perform echocardiography to exclude structural heart disease, which would contraindicate flecainide/propafenone 1, 3
• Continuous fetal monitoring during acute episodes to assess fetal well-being 9
• Regular monitoring of maternal symptoms and drug levels throughout pregnancy, as pharmacokinetics are altered 4

Common Pitfalls to Avoid

• Never assume narrow-complex SVT is safe to treat with beta-blockers or calcium channel blockers without first reviewing the baseline ECG for pre-excitation 3
• Do not use atenolol for any arrhythmia in pregnancy due to association with fetal growth restriction 1, 3
• Avoid amiodarone except when all other therapies fail, due to 17% risk of fetal hypothyroidism 1
• Do not delay cardioversion in unstable patients due to pregnancy concerns—maternal stability is essential for fetal survival 3, 4

Definitive Management Consideration

• Catheter ablation should be considered for drug-resistant cases causing hemodynamic compromise, though typically deferred until after delivery if possible 1, 4