Congenital Complete Heart Block
⚠️ Because of the high complication rate of permanent pacemaker insertion during the neonatal period, it should be reserved for selected cases only.
ℹ️ About
- 🍼 Rare disorder in newborns – ~1 in 20,000 pregnancies
- 🕐 Onset usually detected between 18–34 weeks gestation
- Represents the most common cause of congenital bradycardia
🧬 Aetiology
- ⚡ Atrophy and fibrosis of the fetal/neonatal AV node
- 🧪 Caused by maternal autoantibodies (anti-Ro/SSA, anti-La/SSB) crossing the placenta → immune-mediated injury
- 🤰 Strong association with maternal autoimmune disease, especially SLE and Sjögren’s syndrome
🩺 Clinical Features
- 👩🦰 Mother may have active or latent connective tissue disease (e.g. SLE)
- 🚼 In utero: fetal hydrops, intrauterine death, or congestive heart failure
- 👶 Many infants are asymptomatic at birth
- ⚡ Symptomatic children: syncope, presyncope, poor feeding, or lethargy
- 📉 Long-term: risk of dilated cardiomyopathy, heart failure
- 💀 Risk of Stokes–Adams attacks (transient asystole) or sudden cardiac death if untreated
🔎 Investigations
- 📈 ECG + 24-hour Holter: shows persistent complete heart block (atria and ventricles beating independently)
- 🩻 Echocardiogram: exclude structural congenital heart disease
- 🧪 Maternal serology: check anti-Ro/SSA and anti-La/SSB antibodies
- 📡 Fetal echocardiography during pregnancy for early detection
💊 Management
- 👶 Careful monitoring in neonatal period; watchful waiting if asymptomatic with adequate heart rate
- 🔌 Permanent pacemaker for symptomatic children or those with severe bradycardia
- 💉 Antenatal maternal steroids (e.g. dexamethasone) may reduce progression in selected fetal cases
- 📅 Affects risk in future pregnancies → mothers require close monitoring in subsequent pregnancies
📚 References
💊 Case Reports
- 💓 Case 1 – Neonatal Lupus–Associated Heart Block (Age: 2 days): Term infant born to a mother with known systemic lupus erythematosus (anti-Ro/SSA positive). Detected to have persistent bradycardia (HR 50 bpm) shortly after birth, with no structural cardiac abnormality on echocardiography.
Investigations: ECG showed complete atrioventricular (AV) dissociation with narrow QRS complexes.
Diagnosis: Congenital complete heart block secondary to transplacental passage of maternal autoantibodies damaging the fetal conduction system.
Management: Close neonatal monitoring; later required pacemaker implantation at 4 months due to symptomatic bradycardia and poor feeding.
Teaching point: Maternal anti-Ro/SSA and anti-La/SSB antibodies can cause irreversible fetal AV nodal fibrosis - early detection by fetal echocardiography enables timely planning for neonatal pacing.
- 🩺 Case 2 – Isolated Congenital Heart Block (Age: 12 years): Previously well child presented with exertional fatigue and dizziness. No maternal autoimmune disease. Pulse rate persistently 45 bpm.
Investigations: ECG showed complete heart block with junctional escape rhythm (rate 45 bpm); echocardiogram normal.
Diagnosis: Idiopathic congenital complete AV block.
Management: Dual-chamber pacemaker insertion with good symptomatic improvement.
Teaching point: Isolated congenital complete heart block may present later in childhood due to stable compensatory escape rhythms - pacing is indicated if symptomatic or with ventricular dysfunction.
