A newborn is noted to have a heart rate of 52 beats per minute with congestive failure. ECG shows regular atrial activity at 145 bpm with ventricular bradycardia at 52 bpm and no relationship between P waves and QRS complexes. The mother had a photosensitive facial rash during pregnancy. What is the most likely cause?
- A Maternal anti-Ro/SSA antibody mediated destruction of the fetal AV node ✓
- B Congenital Ebstein anomaly
- C Maternal lithium ingestion
- D Fetal myocarditis from coxsackievirus
Correct answer: A. Maternal anti-Ro/SSA antibody mediated destruction of the fetal AV node
Explanation
Isolated congenital complete atrioventricular block in a structurally normal heart is caused by transplacental passage of maternal anti-Ro and anti-La antibodies, seen in mothers with Sjogren syndrome or lupus. The mother's photosensitive rash points to lupus. Lithium causes Ebstein anomaly, producing a different picture of right atrial enlargement and supraventricular arrhythmia rather than isolated heart block. Maternal autoantibody screening and steroid therapy in utero are the relevant management issues.
Reference: Park's Pediatric Cardiology for Practitioners, 7th ed.
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Written and medically reviewed by the StethoPrep medical team.