Management of Congenital Heart Block
Permanent pacing is recommended for adults with congenital complete heart block who have symptomatic bradycardia, wide QRS escape rhythm, mean daytime heart rate below 50 bpm, complex ventricular ectopy, or ventricular dysfunction, and permanent pacing is reasonable even in asymptomatic adults with congenital complete atrioventricular block. 1
Indications for Permanent Pacing
Class I Recommendations (Definitive Indications)
Symptomatic patients with congenital complete heart block require permanent pacing when presenting with any of the following 1:
- Any symptomatic bradycardia
- Wide QRS escape rhythm
- Mean daytime heart rate below 50 bpm
- Complex ventricular ectopy
- Ventricular dysfunction
Postoperative complete heart block requires permanent pacing when second-degree Mobitz type II, high-grade, or third-degree atrioventricular block persists at least 7-10 days after cardiac surgery and is not expected to resolve 1
Class IIa Recommendation (Reasonable Approach)
Asymptomatic adults with congenital complete atrioventricular block should receive permanent pacing even without symptoms, as this is a reasonable preventive strategy 1. This recommendation reflects the favorable long-term outcomes with early pacing and the unpredictable nature of symptom development.
Pacing Strategy and Technical Considerations
Preferred Pacing Mode
Atrial-based permanent pacing is the recommended approach for adults with congenital heart disease and bradycardia 1. This maintains physiologic atrioventricular synchrony and optimizes cardiac output.
For patients requiring pacing who also have atrial arrhythmias, a bradycardia device with atrial antitachycardia pacing capabilities is reasonable 1. This addresses both the bradycardia and the common comorbidity of atrial tachyarrhythmias in this population.
Lead Placement Approach
Epicardial lead placement is often necessary in congenital heart disease patients due to anatomic constraints 1. Transvenous leads may be impossible or contraindicated in patients with:
- Postoperative Fontan circulation
- Intracardiac shunting (venous to systemic shunts make endocardial lead placement potentially harmful) 1
- Atrial switch procedures (Mustard/Senning) with baffle redirection
- Significant venous stenosis from prior surgeries 1
Intraoperative placement of epicardial permanent pacing leads is reasonable for adults with congenital heart disease who have preexisting sinus node or atrioventricular conduction disease and are undergoing cardiac surgery 1.
Special Populations and Prognostic Factors
Isolated Congenital Complete Heart Block
Isolated congenital complete heart block has a favorable outcome, particularly when the escape rhythm has a narrow QRS complex 1. Thirty percent of congenital atrioventricular blocks remain undiscovered until adulthood and may present during pregnancy 1.
High-Risk Neonates
Neonates with congenital complete heart block and structural heart disease have poor outcomes (mortality exceeding 80%), while those with structurally normal hearts who receive early pacing have favorable outcomes 2. Risk factors for poor outcomes include:
- Prematurity
- Low birth weight
- Hydrops fetalis
- Low ventricular rates
- Associated congenital heart disease 2
Temporary pacing in the first 24 hours after birth is indicated for high-risk neonates, with conversion to permanent pacing typically occurring after 30-40 days 2.
Pregnancy Considerations
Supportive pacing during pregnancy is usually not necessary for isolated congenital complete heart block 1. Vaginal delivery carries no extra risks unless contraindicated for obstetric reasons 1.
Temporary pacing during delivery is recommended in selected women with complete heart block and symptoms due to risk of bradycardia and syncope 1.
Monitoring and Follow-Up
Patients with specific anatomic defects merit periodic assessment of atrioventricular conduction with serial ECGs and Holter monitoring 1. This is particularly important for:
- Congenitally corrected transposition of the great arteries (CCTGA)
- Atrioventricular septal defects, especially with Down syndrome
- Patients who may develop spontaneous atrioventricular block at any point from fetal life to adulthood 1
Common Pitfalls to Avoid
Do not use atenolol for any arrhythmia management in this population 1.
Avoid endocardial pacing leads in patients with venous-to-systemic intracardiac shunts due to risk of paradoxical embolization 1.
Do not delay permanent pacing in symptomatic patients or those with high-risk features, as outcomes are favorable with early intervention and the natural history without pacing includes risk of sudden death 3.