The diagnosis and management of fetal cardiac arrhythmias

M R C O G PA R T 2 · S O S P O C K E T C A R D · K N O W L E D G E A R E A 5 – A N T E N ATA L C A R E

The Diagnosis and Management of Fetal Cardiac Arrhythmias Stott D et al. The diagnosis and management of fetal cardiac arrhythmias. TOG 2022;24:119–130. doi:10.1111/tog.12803

20% 3% 90%→60% REFERRALS TO FETAL CARDIOLOGISTS ARRHYTHMIAS ON ROUTINE ANOMALY SCAN TX SUCCESS: NO HYDROPS VS HYDROPS

DO N' T-M IS S FA C TS

  1. Fetal tachycardia = HR >200 bpm; bradycardia = HR <100 bpm consistently

  2. SVT 1:1 conduction: rate 240–260 bpm (~66% of tachycardias); atrial flutter: atrial rate 450–500 bpm, usually 2:1 block

  3. Treatment success ~90% without hydrops vs ~60% with hydrops

  4. Drugs: digoxin, flecainide, sotalol – no RCT consensus on best agent; flecainide/sotalol need baseline maternal ECG

  5. Complete heart block >90% due to anti-Ro/La antibodies when no structural heart disease; surveillance window 18–28 weeks

  6. Ventricular rate >60 bpm + no hydrops in complete block = good prognosis for term live birth

  7. Previously affected pregnancy → hydroxychloroquine before 10 weeks; echo at 18 weeks; FHR Doppler every 2 weeks from 20 weeks

  8. Non-conducted ectopics can mimic 2:1 block – avoid premature delivery; observe/rescan at 1 week if no compromise

DRUG QUICK REFERENCE

Digoxin: load 1200–1500μg/24h IV; reduced transfer in hydrops Flecainide 100–300mg/day; QTc <0.48s target

Sotalol 160–480mg/day; slightly less effective than flecainide Amiodarone/direct fetal therapy: anecdotal, higher risk

ABBREVIATION KEY

bpm — beats per minute STAN — ST analysis

SVT — supraventricular tachycardia fMCG — fetal magnetocardiography

AVRT — atrioventricular re-entry tachycardia WPW — Wolff–Parkinson–White syndrome

A-V interval — atrial–ventricular interval (equivalent to PR interval) IVIG — intravenous immunoglobulin

V-A interval — ventricular–atrial interval MDT — multidisciplinary team

2D — two-dimensional (ultrasound) BBB — blood–brain barrier

fECG — fetal electrocardiography QTc — corrected QT interval

Source: The Obstetrician & Gynaecologist (TOG), RCOG journal — Stott D et al. The diagnosis and management of fetal cardiac arrhythmias. TOG 2022;24:119–130. doi:10.1111/tog.12803

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