How should recurrent supraventricular tachycardia be managed in a pregnant woman to ensure safety for both mother and fetus?

Management of Recurrent Supraventricular Tachycardia in Pregnancy

For recurrent SVT in pregnancy, start with vagal maneuvers followed by adenosine for acute episodes, then use oral beta-blockers (metoprolol or propranolol) or digoxin for ongoing prophylaxis, reserving catheter ablation for highly symptomatic, drug-refractory cases. 1

Acute Episode Management

First-Line Interventions

• Vagal maneuvers are the initial treatment for any acute SVT episode, performed with the patient supine 1, 2
• The Valsalva maneuver is more effective than carotid sinus massage for terminating SVT 2
• Avoid pressure to the eyeball as it is potentially dangerous 2

Second-Line Pharmacological Treatment

• Intravenous adenosine (6 mg rapid IV bolus) is the drug of choice when vagal maneuvers fail 1, 2
• Up to two additional 12 mg doses may be given if the initial dose is ineffective 2
• Adenosine is safe for the fetus due to its extremely short half-life, and maternal side effects are transient 2

Third-Line Options

• IV metoprolol or propranolol are reasonable alternatives when adenosine is ineffective or contraindicated 1
• IV verapamil may be considered if both adenosine and beta-blockers fail, though evidence is more limited 1
• IV procainamide may be reasonable as an additional option 1

Emergency Cardioversion

• Synchronized electrical cardioversion is indicated for hemodynamically unstable SVT regardless of gestational age 1, 2
• Apply electrode pads with energy trajectory directed away from the uterus 3
• Cardioversion is safe at all stages of pregnancy and should not be delayed when indicated 2, 4

Ongoing Management for Recurrent Episodes

First-Line Prophylactic Medications

The following oral medications can be effective for preventing recurrent SVT, used alone or in combination: 1

• Metoprolol (preferred beta-blocker)
• Propranolol
• Digoxin
• Verapamil
• Flecainide
• Propafenone
• Sotalol

Key Medication Considerations

• Avoid all medications during the first trimester if possible, as this is when the risk of congenital malformations is greatest 1
• Never use atenolol due to significant risk of intrauterine growth retardation 3, 5
• Start with the lowest recommended dose and monitor clinical response regularly 1
• Beta-blockers may cause intrauterine growth retardation if administered during the first trimester 4

Medication Selection Strategy

• Beta-blockers (metoprolol or propranolol) and digoxin are first-line agents for prophylaxis 1, 2
• If first-line agents fail, consider sotalol, flecainide, or propafenone 1
• Do not use AV nodal blocking agents in patients with manifest pre-excitation on resting ECG 1

Amiodarone: Last Resort Only

• Oral amiodarone may be considered only when highly symptomatic, recurrent SVT is refractory to all other therapies 1
• Amiodarone should be avoided due to significant fetotoxic effects including thyroid dysfunction, growth restriction, and congenital abnormalities 1, 3
• Use only at the lowest effective dose if absolutely necessary 1

Catheter Ablation Considerations

Catheter ablation may be reasonable for highly symptomatic, recurrent, drug-refractory SVT during pregnancy with efforts to minimize radiation exposure 1

When to Consider Ablation

• Drug therapy is ineffective, contraindicated, or poorly tolerated 1, 6
• SVT causes significant hemodynamic compromise 7
• Patient experiences debilitating symptoms despite medical management 6

Technical Approach

• Preferably use zero-fluoroscopy or minimal radiation techniques 7, 8
• Transseptal approach has been successfully performed during pregnancy for left-sided pathways 6
• Modern catheter ablation techniques have revolutionized SVT treatment with very low complication rates 8

Critical Management Principles

Medication Timing

• Avoid all antiarrhythmic drugs during the first trimester whenever possible 1, 8
• All antiarrhythmic medications cross the placenta 7, 4
• Physiological changes during pregnancy alter pharmacodynamics and kinetics, requiring close monitoring 4

Monitoring Requirements

• Establish a multidisciplinary care plan early in pregnancy involving maternal-fetal medicine, cardiology, and anesthesiology 5, 7
• Plan for maternal and fetal monitoring during pregnancy, delivery, and postpartum 7
• Regular monitoring of serum drug concentrations and clinical response is essential 4

Common Pitfalls to Avoid

• Do not delay electrical cardioversion when hemodynamically indicated - it is safe throughout pregnancy 1, 2, 4
• Never use atenolol for any indication in pregnancy 3, 5
• Do not assume conservative management is always safer - untreated recurrent SVT can cause fetal hypoperfusion and maternal complications 1, 9
• Recognize that pregnancy increases susceptibility to arrhythmias and may cause more frequent, refractory episodes even with pre-existing substrates 1