How should supraventricular tachycardia be managed in a pregnant woman?

Management of Supraventricular Tachycardia in Pregnancy

For acute SVT in pregnancy, start with vagal maneuvers, then adenosine 6 mg IV rapid bolus (up to 12 mg x2 if needed), and proceed to synchronized cardioversion if the patient is hemodynamically unstable or medications fail. 1

Acute Management Algorithm

Step 1: Initial Stabilization

• Attempt vagal maneuvers first (Valsalva, carotid sinus massage after confirming no bruit, or ice-cold wet towel to face) in all hemodynamically stable pregnant patients 1
• These are safe at all stages of pregnancy and should be the first intervention 1

Step 2: Pharmacological Treatment (if vagal maneuvers fail)

First-line: Adenosine

• Adenosine is the drug of choice when vagal maneuvers fail, with Class I recommendation 1
• Dosing: 6 mg rapid IV bolus; if ineffective, give 12 mg (may repeat 12 mg once more) 1
• Safe at all trimesters because its extremely short half-life prevents fetal circulation exposure 1
• Maternal side effects (chest discomfort, flushing) are transient 1
• Higher doses up to 24 mg have been safely administered in some cases 1

Second-line: Beta-blockers (if adenosine fails or is contraindicated)

• IV metoprolol or propranolol are reasonable alternatives with Class IIa recommendation 1
• Beta-blockers have extensive safety data from decades of use in pregnancy for various maternal conditions 1
• Administer as slow infusion to minimize hypotension risk 1
• Never use atenolol due to significant risk of intrauterine growth retardation 2

Third-line: Calcium channel blockers (if both adenosine and beta-blockers fail)

• IV verapamil may be reasonable but carries Class IIb recommendation due to higher maternal hypotension risk compared to adenosine 1
• Limited data on IV diltiazem, but similar effects expected 1
• One case series showed successful conversion with up to 10 mg IV verapamil without significant fetal heart rate changes 3

Fourth-line: Procainamide

• IV procainamide may be reasonable for acute conversion with Class IIb recommendation 1
• Has been used safely for maternal and fetal supraventricular and ventricular arrhythmias 1
• Avoid for long-term therapy due to lupus-like syndrome risk 1

Step 3: Electrical Cardioversion

Immediate cardioversion indications:

• Hemodynamic instability (hypotension, shock, pulmonary edema) 1
• Drug-refractory SVT 1

Cardioversion technique:

• Synchronized cardioversion is safe at all stages of pregnancy with Class I recommendation 1
• Apply electrode pads with energy trajectory directed away from the uterus 1
• Use same energy dosing as non-pregnant patients 1
• Perform fetal monitoring during and immediately post-cardioversion if time permits 1

Ongoing Management for Recurrent SVT

For highly symptomatic, recurrent SVT requiring chronic suppression:

First-line oral agents (Class IIa):

• Digoxin 1
• Metoprolol (preferred beta-blocker) 1
• Propranolol 1
• Flecainide 1
• Propafenone 1
• Sotalol (FDA Pregnancy Category B, crosses placenta but no teratogenic potential in animal studies) 1, 4
• Verapamil 1

Catheter ablation (Class IIb):

• May be reasonable for drug-refractory, highly symptomatic recurrent SVT 1
• Requires efforts to minimize radiation exposure (preferably zero-fluoroscopy technique) 5, 6
• Consider in second or third trimester if medications fail 5

Amiodarone (Class IIb - last resort only):

• May be considered only for potentially life-threatening SVT when all other therapies fail 1
• Avoid due to fetal thyroid toxicity and growth restriction 2

Critical Pitfalls to Avoid

• Never delay cardioversion in hemodynamically unstable patients to attempt pharmacologic conversion 2
• Avoid all medications in first trimester if possible when congenital malformation risk is highest 1, 7
• Never use atenolol at any stage due to intrauterine growth retardation risk 2
• Do not confuse physiologic sinus tachycardia with SVT - sinus tachycardia has gradual onset/offset, rate typically <150 bpm, and should not be treated with antiarrhythmics 8
• Avoid verapamil as first-line due to higher hypotension risk compared to adenosine 1
• Reserve amiodarone only for life-threatening situations refractory to all other options 1, 2

Monitoring Considerations

• Multidisciplinary team coordination involving cardiology, obstetrics, anesthesia, and neonatology 2
• Continuous maternal cardiac monitoring during acute episodes 2
• Fetal heart rate monitoring during cardioversion and medication administration 1, 3
• Regular prenatal follow-up for confirmed recurrent SVT 8