How is supraventricular tachycardia (SVT) managed in pregnancy?

Management of Supraventricular Tachycardia (SVT) in Pregnancy

Vagal maneuvers followed by adenosine are the first-line treatments for SVT in pregnancy, with synchronized cardioversion reserved for hemodynamically unstable patients. 1, 2

Acute Treatment Algorithm

First-Line Approaches:

1. Vagal Maneuvers (Class I recommendation, Level C-LD) 1

   • Perform with patient in supine position
   • Valsalva maneuver: Patient bears down against closed glottis for 10-30 seconds (equivalent to 30-40 mmHg)
   • Carotid sinus massage: Apply steady pressure over right or left carotid sinus for 5-10 seconds (after confirming absence of bruit)
   • Cold stimulus: Apply ice-cold wet towel to face

2. Adenosine (Class I recommendation, Level C-LD) 1, 2

   • Use when vagal maneuvers fail
   • Initial dose: 6 mg IV rapid bolus
   • If ineffective: Up to 2 subsequent doses of 12 mg
   • Safe in all trimesters due to short half-life (unlikely to reach fetal circulation) 3

Second-Line Approaches:

1. IV Beta-Blockers (Class IIa recommendation, Level C-LD) 1

   • Use when adenosine is ineffective or contraindicated
   • Options: IV metoprolol or propranolol
   • Administer as slow infusion to minimize risk of hypotension

2. IV Verapamil (Class IIb recommendation, Level C-LD) 1

   • Consider when adenosine and beta-blockers are ineffective or contraindicated
   • Higher risk of maternal hypotension compared to adenosine

3. IV Procainamide (Class IIb recommendation, Level C-LD) 1

   • May be reasonable for acute treatment

4. IV Amiodarone (Class IIb recommendation, Level C-LD) 1

   • Consider only for potentially life-threatening SVT when other therapies are ineffective or contraindicated

For Hemodynamically Unstable Patients:

• Synchronized Cardioversion (Class I recommendation, Level C-LD) 1, 2
  • Safe at all stages of pregnancy
  • Apply electrode pads to direct energy trajectory away from uterus
  • Perform fetal monitoring during and after procedure if time allows
  • Use same energy dosing as for non-pregnant patients

Ongoing Management for Recurrent SVT

Pharmacological Options (Class IIa recommendation, Level C-LD) 1:

The following drugs, alone or in combination, can be effective for ongoing management in pregnant patients with highly symptomatic SVT:

• Digoxin
• Flecainide
• Metoprolol
• Propafenone
• Propranolol
• Sotalol
• Verapamil

Non-Pharmacological Options:

• Catheter Ablation (Class IIb recommendation, Level C-LD) 1
  • May be reasonable in pregnant patients with highly symptomatic, recurrent, drug-refractory SVT
  • Efforts should be made to minimize radiation exposure
  • Non-fluoroscopic ablation has shown definitive resolution without recurrence 3

Important Considerations and Pitfalls

• Medication Timing: If possible, avoid medications in the first trimester when risk of congenital malformations is greatest 1
• Dosing: Use the lowest recommended dose initially with regular monitoring of clinical response 1
• Medication Contraindications: Atenolol and verapamil are contraindicated in the first trimester but may be used in second and third trimesters 3
• Amiodarone Caution: Avoid amiodarone when possible due to potential fetal toxicity; use only when other therapies have failed 2
• Underlying Causes: Always evaluate for potential underlying causes such as hyperthyroidism or structural heart disease 2, 4
• Labor Considerations: Risk of arrhythmias is relatively higher during labor and delivery; adenosine remains safe during labor 3, 4
• Avoid: Abrupt discontinuation of beta-blockers, delaying cardioversion in unstable patients, and applying pressure to eyeballs (dangerous and abandoned practice) 1, 2

The goal of therapy is to protect both the mother and fetus through delivery, after which definitive therapy can be administered if needed 5, 6.