Congenital Cardiac Anesthesia Society
A Section of the Society for Pediatric Anesthesia.

EXPLANATION

Congenital complete heart block (CCHB) is a rare but potentially life-threatening condition that often results in permanent pacemaker implantation.^1,2 In structurally normal hearts, immune-mediated CCHB accounts for the majority of cases and is strongly associated with trans-placental passage of maternal anti-Ro/SSA and anti-La/SSB IgG antibodies.¹ These antibodies bind fetal cardiac conduction tissue, triggering inflammation and progressive fibrosis at the AV node.¹ Approximately 2-5% of pregnancies with maternal anti-Ro/SSA antibodies result in CCHB; the risk is substantially higher in subsequent pregnancies after an affected child.¹

Current guidelines designate permanent pacemaker implantation as a Class I recommendation for infants with CCHB who have symptomatic bradycardia, a ventricular rate below 60–70 bpm in the setting of congenital heart disease, or a ventricular rate below 50 bpm with a structurally normal heart.³ Expert panels emphasize that implantation decisions should incorporate consistent heart rate parameters alongside other risk factors, including birth weight and ventricular dysfunction.³

Epicardial lead placement is standard in neonates and infants due to small vessel size and the impracticality of transvenous implantation in this age group.¹ A single ventricular lead can be placed via a minimally invasive subxiphoid incision, whereas dual-chamber pacing requires a sternotomy to access both the right atrium and right ventricle (RV).¹ VVI pacing is often the initial pacing strategy, with upgrade to a dual-chamber system deferred until the patient is older.^1,4,5 Beyond these technical constraints, clinical outcome data also favor VVI: a multicenter retrospective study of 109 infants with isolated CCHB found that DDD pacing was independently associated with a greater risk of left ventricular (LV) dysfunction compared to VVI pacing. The proposed mechanism for that phenomenon is that frequent RV pacing may lead to LV dysfunction, which may be amplified during DDD pacing while tracking high atrial rates in infants, similarly to tachycardia-induced cardiomyopathy. This reinforces that single-chamber ventricular pacing is an appropriate approach in early infancy.⁴

AAI pacing senses and paces only the atrium and relies on intact AV nodal conduction to deliver the impulse to the ventricles; it is therefore ineffective in the setting of complete AV block. DDD pacing maintains AV synchrony and is the preferred mode for complete AV block in older children and adults, but its use in infancy may be limited by surgical complexity, device size, and the associated risk of ventricular dysfunction. VVI pacing provides reliable ventricular rate support early in life.

REFERENCES

1. Bordachar P, Zachary W, Ploux S, Labrousse L, Haissaguerre M, Thambo JB. Pathophysiology, clinical course, and management of congenital complete atrioventricular block. Heart Rhythm. 2013;10(5):760-766. doi:10.1016/j.hrthm.2012.12.030

2. Mikulski MF, Well A, Shmorhun D, Fraser CD Jr, Mery CM, Fenrich AL Jr. Pacemaker Management and In-Hospital Outcomes in Neonatal Congenital Atrioventricular Block. JACC Clin Electrophysiol. 2023;9(9):1977-1986. doi:10.1016/j.jacep.2023.05.003

3. Shah MJ, Silka MJ, Silva JNA, et al. 2021 PACES expert consensus statement on the indications and management of cardiovascular implantable electronic devices in pediatric patients. Cardiol Young. 2021;31(11):1738-1769. doi:10.1017/S1047951121003413

4. Tan RB, Pierce KA, Nielsen J, et al. Dual- vs Single-Chamber Ventricular Pacing in Isolated Congenital Complete Atrioventricular Block in Infancy. JACC Clin Electrophysiol. 2025;11(5):987-998. doi:10.1016/j.jacep.2024.12.025.

5. Garg S, Balaji S. Pacing Induced Ventricular Dysfunction in a Child: Improvement with Reduction in Paced Rate. Pediatr Cardiol. 2017;38(6):1309-1310. doi:10.1007/s00246-017-1629-2