Recurrent SVT in pregnancy — case discussion

Objectives

1. Choose acute treatment of SVT in pregnancy according to whether she is haemodynamically stable or unstable (2025 ESC).^[2]
2. Choose long-term prophylaxis in pregnancy and plan definitive therapy after delivery.^[1][2]

Candidate brief

Practice case discussion; this is not a real patient. You are the cardiologist called to the emergency department. In 15 minutes, give your immediate management, your plan for the rest of the pregnancy and your advice for after delivery.

Expected actions

• Assess stability first. In pregnancy, vagal manoeuvres and IV adenosine are recommended for conversion of haemodynamically stable SVT, and immediate electrical cardioversion for SVT with haemodynamic instability (both Class I, level C); she is alert and normotensive without chest pain or heart failure.^[2]
• Terminate it. While she is haemodynamically stable, use vagal manoeuvres and IV adenosine; the pregnancy guideline figure for narrow QRS tachycardia gives adenosine as a 6–18 mg bolus.^[2]
• If she becomes unstable. Immediate electrical cardioversion is recommended for SVT with haemodynamic instability (Class I, level C); it is safe and effective in all phases of pregnancy, and the fetal heart rate should be monitored afterwards.^[2]
• Use her history. Her AVNRT was confirmed at an electrophysiology study and her sinus rhythm ECG shows no pre-excitation; ESC 2019 notes that episodes are more frequent during pregnancy in women with pre-existing SVT.^[1]
• Prevent recurrences. In pregnancy (2025 ESC), beta-1-selective blockers (except atenolol) or verapamil are recommended for prevention of SVT in women without pre-excitation on the resting ECG (Class I, level C); metoprolol is the beta-blocker named for chronic prophylaxis.^[2]
• If drugs fail. The 2025 ESC pregnancy guideline text (no class given) says that for drug-refractory SVT or contraindications to these drugs, flecainide or sotalol are reasonable alternatives, as is propafenone if flecainide is not available. Catheter ablation may be considered in pregnant women with recurrent, long symptomatic SVT, or with contraindications to pharmacological therapies (Class IIb, level C), and when it is performed, the use of non-fluoroscopic mapping and navigation systems should be considered (Class IIa, level C).^[2]
• After delivery. Catheter ablation is recommended for symptomatic, recurrent AVNRT (ESC 2019, Class I, level B), with a 97% success rate and an AV block risk under 1% in previous reports for slow-pathway ablation.^[1]

Marking

Pass:

• Uses vagal manoeuvres and IV adenosine while she is haemodynamically stable, and immediate electrical cardioversion if she develops SVT with haemodynamic instability in pregnancy.^[2]
• Chooses a beta-1-selective blocker other than atenolol, or verapamil, for prophylaxis in pregnancy without pre-excitation on the resting ECG.^[2]
• Plans catheter ablation after delivery for symptomatic, recurrent AVNRT.^[1]

Fail:

• Prescribes atenolol in pregnancy.^[2]
• Withholds adenosine solely because she is pregnant, while she is haemodynamically stable.^[2]