📌 First-degree AV BlockPR interval prolonged (>0.16 sec in infants, >0.18 sec in children). All atrial impulses conducted. Usually benign. May be congenital (maternal lupus), post-operative, or due to increased vagal tone.
📌 Second-degree AV Block – Mobitz I (Wenckebach)Progressive PR prolongation until a dropped QRS. Typically due to AV node disease. Benign in athletes, can be vagal. Rarely progresses.
📌 Second-degree AV Block – Mobitz IIConstant PR interval with intermittent non-conducted P waves. Infranodal (His-Purkinje) disease. Can progress to complete heart block. Symptomatic → pacemaker indicated.
📌 Third-degree AV Block (Complete Heart Block)No atrial impulses conducted. Atrial and ventricular rates independent (AV dissociation). Ventricular escape rhythm (narrow QRS if junctional, wide if ventricular). Symptoms: fatigue, syncope, heart failure in infants.
📌 Congenital Complete AV BlockMaternal anti-Ro/SSA or anti-La/SSB antibodies (SLE, Sjogren's). Infiltrative injury to conduction system. Pacemaker if: neonatal HR <55 bpm, wide QRS, structural CHD, ventricular dysfunction, syncope.
📌 Postoperative Heart BlockComplication of VSD closure, AVSD repair, tetralogy of Fallot. Temporary pacing wires placed. If persistent >10-14 days → permanent pacemaker. NKX2-5 mutations associated with AV block + ASD.
📌 Lyme carditisLyme disease can cause first-degree to complete AV block. Treatment: IV ceftriaxone. Usually resolves. Temporary pacing if symptomatic.
📌 Indications for Permanent PacemakerComplete heart block with symptoms (syncope, exercise intolerance, heart failure). Neonatal CHB with HR <55, wide QRS, CHD. Mobitz II with symptoms. Postoperative CHB >10-14 days. Sinus node dysfunction with symptoms (tachy-brady).
📌 Pacemaker Modes & Pediatric ConsiderationsDDDR preferred for active children (dual chamber, rate responsive). Epicardial leads for small infants. Transvenous leads after ~15 kg. Regular interrogation every 6-12 months.
📌 Transition & AV Block in ACHDPost-operative CHB (VSD, AVSD, TOF). Lifelong pacemaker follow-up. End-of-life battery management, lead extraction. Pregnancy: pacemaker safe, but need electrophysiology evaluation for underlying cardiomyopathy.
🚨 Step 5: Assess need for pacing Symptomatic (syncope, heart failure, exercise intolerance). Neonatal CHB with HR <55, wide QRS, structural CHD. Mobitz II with symptoms. High-grade second-degree block. Postoperative CHB >10-14 days.
1️⃣ Acute management of symptomatic bradycardia ▪ Atropine 0.02 mg/kg IV (max 0.5 mg) for vagal-mediated block. ▪ Isoproterenol infusion (0.05-1 mcg/kg/min) for emergency pacing. ▪ Transcutaneous or transvenous temporary pacing. ▪ Treat underlying cause: IVIG for neonatal lupus (no proven benefit for block).
2️⃣ Congenital Complete AV Block (neonate) ▪ Pacemaker indicated if: HR <55 bpm, wide QRS escape, structural CHD, ventricular dysfunction, syncope. ▪ Epicardial lead placement – generally after first week. ▪ Asymptomatic, HR >55, narrow QRS → observation with serial ECGs/holters.
3️⃣ Acquired AV Block (Lyme, myocarditis) ▪ Lyme carditis: IV ceftriaxone 50-75 mg/kg/day for 14-21 days. Temporary pacing if Mobitz II/complete heart block with symptoms. ▪ Myocarditis: supportive care; temporary pacing if needed; often resolves. ▪ Drug-induced: discontinue offending agent (digoxin, beta-blockers).
4️⃣ Postoperative Heart Block ▪ Temporary epicardial pacing wires placed in OR. ▪ Observe for 10-14 days; if return of AV conduction → no permanent pacemaker. ▪ Persistent complete heart block >14 days → permanent pacemaker (epicardial if infant, transvenous if >15 kg).
5️⃣ Long-term follow-up & transition ▪ Pacemaker interrogation every 6-12 months. Monitor battery life, lead thresholds. ▪ Avoid contact sports that may damage pacemaker (boxing, football lineman). ▪ Transition to adult electrophysiologist with expertise in congenital heart disease. ▪ Pregnancy: pacemaker safe; genetic counselling for LQT syndromes (if SCN5A mutation).
❓ Reflex prompt 1: A newborn with HR 45 bpm, narrow QRS. Mother has SLE. What is the most likely diagnosis and next step? ✅ Answer: Congenital complete AV block due to maternal anti-Ro/SSA antibodies. Echocardiogram to exclude structural CHD. Pacemaker indicated if HR <55 bpm or wide QRS.
❓ Reflex prompt 2: A 14-year-old with repaired VSD 3 years ago presents with syncope. ECG shows complete heart block. What is the management? ✅ Answer: Permanent pacemaker implantation. Postoperative heart block can present late. Evaluate for pacing indications (symptomatic).
❓ Reflex prompt 3: A 12-year-old with Lyme disease rash, now has ECG showing first-degree AV block. Treatment? ✅ Answer: Oral doxycycline for localized Lyme. First-degree block usually benign, monitor. If progresses to higher degree, IV ceftriaxone and temporary pacing.
❓ Reflex prompt 4: A 16-year-old with asymptomatic first-degree AV block on routine ECG. Family history of sudden death. Next step? ✅ Answer: Evaluate for myotonic dystrophy type 1, NKX2-5 mutations, or other conduction disease. Cardiac MRI, genetic testing, exercise test. First-degree block with family history requires further evaluation.
❓ Reflex prompt 5: A 6-year-old after AVSD repair has complete heart block on post-op day 10. Pacemaker? ✅ Answer: If no return of AV conduction after 10-14 days → permanent pacemaker. Epicardial leads appropriate for age/weight.
❓ Reflex prompt 6: A 17-year-old with pacemaker for congenital CHB is transitioning to adult care. What must be included? ✅ Answer: Portable medical summary: indication, pacemaker model, lead type, battery longevity, last interrogation. Adult electrophysiology follow-up, activity restrictions, pregnancy counselling.
1. Definitions:
- First-degree: PR prolongation (all beats conducted). Benign.
- Second-degree Mobitz I (Wenckebach): progressive PR until dropped QRS. AV node level.
- Second-degree Mobitz II: fixed PR with intermittent dropped beats. Infranodal; may progress.
- Third-degree (complete): AV dissociation; no conducted beats. 2. Causes:
- Congenital: maternal anti-Ro/La antibodies (SLE, Sjogren's) – most common cause of CHB.
- Postoperative: VSD, AVSD, TOF repair.
- Acquired: Lyme disease, myocarditis, drugs (digoxin, beta-blockers, CCB), infiltrative diseases.
- Genetic: NKX2-5 (ASD + AV block), SCN5A (progressive conduction disease), TRPM4. 3. Diagnosis: ECG definitive. Narrow QRS escape suggests AV node level, better prognosis. Wide QRS escape indicates infranodal block. 4. Management:
- Asymptomatic first-degree/Wenckebach → observation.
- Symptomatic or Mobitz II/complete heart block → pacemaker.
- Neonatal CHB: pacemaker if HR <55, wide QRS, structural CHD, ventricular dysfunction.
- Postoperative CHB: permanent pacemaker if persistent >10-14 days.
- Lyme carditis: IV ceftriaxone, temporary pacing if needed. 5. Pacemaker indications: Symptomatic bradycardia (syncope, heart failure), neonatal CHB with risk factors, Mobitz II, postoperative CHB, high-grade block. 6. Pacemaker types: Epicardial for infants/young children; transvenous for older children (>15 kg). Dual-chamber rate-responsive (DDDR) preferred. 7. Transition: Lifelong follow-up; battery replacement every 5-10 years; lead extraction if infection/fracture. Pregnancy with pacemaker is safe but need baseline echocardiogram. 💡 Clinical pearls:
➤ Congenital complete AV block is NOT associated with structural heart disease in 60% – but always rule out with echo.
➤ First-degree AV block after cardiac surgery may be a marker for future complete heart block; follow closely.
➤ In Lyme carditis, AV block often resolves with antibiotics.
➤ Syncope + Mobitz II or complete heart block is a pacemaker indication regardless of symptoms.
➤ Transition planning must include pacemaker longevity, lead status, and adult EP contact.