What is the appropriate evaluation and management of tachycardia in a pregnant woman (any trimester)?

Management of Tachycardia in Pregnancy

Immediate Stabilization Based on Hemodynamic Status

For any pregnant woman with tachycardia causing hemodynamic instability (hypotension, altered mental status, chest pain, or signs of shock), perform immediate electrical cardioversion without delay using biphasic shock energy of 120-200 J with the lateral defibrillator pad placed under the breast tissue. 1, 2, 3

• Maternal stability is essential for fetal survival—never delay cardioversion due to pregnancy concerns, as cardioversion is safe in all trimesters including labor. 1, 2, 3
• Continuous fetal monitoring is essential during any arrhythmia episode, as maternal arrhythmias can cause fetal hypoperfusion. 2, 3
• Position the patient in left lateral decubitus to relieve inferior vena cava compression if symptomatic bradycardia or hypotension develops. 2, 4

Acute Management of Stable Supraventricular Tachycardia

For hemodynamically stable SVT, follow this stepwise algorithm: 2, 3

1. First-line: Vagal maneuvers (Valsalva, carotid massage, or ice-cold wet towel to face) 1, 2, 3

2. Second-line: IV adenosine if vagal maneuvers fail—give 6 mg rapid IV push, followed by up to two 12 mg doses if ineffective. 2, 3

   • Adenosine is safe in all trimesters with a short half-life preventing fetal exposure. 2, 3
   • Approximately 30% of atrial tachycardias will terminate with adenosine. 2
   • Critical pitfall: Do NOT use adenosine (or any AV nodal blocker) if pre-excitation is visible on ECG, as this can precipitate ventricular fibrillation. 2, 3

3. Third-line: IV metoprolol or propranolol as a slow infusion if adenosine fails, to minimize hypotension. 2, 3

   • IV verapamil may be used if beta-blockers are contraindicated, but carries higher risk of maternal hypotension. 2

Long-Term Prophylaxis for Recurrent Tachycardia

For recurrent or symptomatic SVT requiring prophylaxis, prescribe cardioselective beta-blockers as first-line therapy after the first trimester: 1, 2, 4, 3

• Metoprolol (50-100 mg twice daily) or propranolol (80-160 mg daily in long-acting form) are preferred agents with extensive safety data. 2, 4, 3
• Atenolol is absolutely contraindicated in pregnancy due to association with fetal growth restriction. 2, 4, 3
• Second-line agents if beta-blockers are ineffective: sotalol, flecainida, or propafenone. 1, 2
• Digoxin can be considered for rate control in atrial tachycardia to prevent tachycardia-induced cardiomyopathy. 2

Management of Atrial Fibrillation/Flutter

For AF/flutter of ≥48 hours duration or unknown duration: 1

• Therapeutic anticoagulation with LMWH or warfarin (substituting LMWH in first and last trimester) is mandatory for at least 3 weeks before elective cardioversion. 1
• Continue anticoagulation for at least 4 weeks post-cardioversion due to risk of atrial stunning. 1
• For AF <48 hours without thromboembolic risk factors, IV heparin or therapeutic LMWH may be given peri-cardioversion without need for prolonged oral anticoagulation. 1

For rate control: Use cardioselective beta-blockers or digoxin as first-line agents. 2

Management of Ventricular Tachycardia

For hemodynamically unstable VT: Immediate electrical cardioversion. 1, 3

For stable monomorphic VT: 1, 3

• IV sotalol can be considered for acute termination. 1
• IV procainamide may be used if available. 1
• IV amiodarone should only be used for sustained VT that is hemodynamically unstable, refractory to cardioversion, or recurrent despite other agents—it is NOT ideal for stable VT conversion. 1, 3

Critical differential: Always rule out peripartum cardiomyopathy in any woman presenting with new-onset VT during the last 6 weeks of pregnancy or postpartum period. 1, 2, 4

Essential Diagnostic Workup

Obtain immediately: 2, 3

• 12-lead ECG to confirm tachycardia type and evaluate for pre-excitation or conduction abnormalities
• Echocardiogram to rule out structural heart disease, particularly peripartum cardiomyopathy
• Thyroid function tests, as thyroid storm can precipitate AF/flutter 2
• Holter monitor if symptoms are intermittent 2, 4

Assess for: 2, 4

• Personal history of previous arrhythmias, structural heart disease, or congenital heart disease
• Family history of sudden cardiac death, cardiomyopathy, or inherited arrhythmia syndromes
• Pre-eclampsia (BP ≥140/90 after 20 weeks, proteinuria, visual changes, severe headache) 4

Critical Medications to Avoid

Absolutely contraindicated: 2, 4, 3

• Atenolol (fetal growth restriction)
• ACE inhibitors, ARBs, renin inhibitors (teratogenic)
• Amiodarone except as absolute last resort at lowest effective dose (fetotoxic effects including thyroid dysfunction, growth restriction, and neurodevelopmental issues) 1, 2, 3

Special Considerations for Catheter Ablation

Catheter ablation may be considered for: 1, 2

• Drug-refractory tachycardias causing hemodynamic compromise
• Should be postponed to second trimester if possible
• Must be performed at experienced center with lead shielding and maximal use of echocardiographic/electroanatomic guidance to minimize radiation 1

Monitoring and Follow-Up

• Drug levels need more careful monitoring during pregnancy due to altered pharmacokinetics from increased blood volume, cardiac output, and renal clearance. 2, 3
• Regular follow-up to monitor both maternal symptoms and fetal well-being is essential. 2, 4
• Women with long QT syndrome have greater risk of cardiac arrest postpartum compared to during pregnancy—beta-blockers are recommended throughout pregnancy and especially postpartum. 1