Management of Congenital Complete Heart Block – Recent Insights

The management of congenital complete heart block (CCHB) has evolved from a reactive approach to one that emphasizes prenatal risk stratification, pharmacological prevention, and long-term pacing strategies designed to mitigate pacing-induced cardiomyopathy.

Antenatal Screening and Pharmacological Prevention

For immune-mediated CCHB, which is typically associated with the transplacental passage of maternal anti-Ro/SSA and anti-La/SSB autoantibodies, management begins early in pregnancy.

• Surveillance: In pregnancies complicated by positive autoantibodies, serial fetal echocardiography is the standard of care. Monitoring typically occurs weekly or biweekly starting between 16 to 18 weeks and continuing until 28 weeks of gestation to catch early signs of atrioventricular (AV) conduction delay (Clowse et al., 2018).
• Prevention: Recent retrospective data strongly support the use of hydroxychloroquine (HCQ) to prevent the development of CCHB. Administering HCQ prior to conception or early in pregnancy significantly reduces the rate of CCHB in asymptomatic women with Ro/SSA antibodies or those with a prior infant affected by neonatal lupus (Clowse et al., 2018).

Fetal Intervention for Established AV Block

Once a fetus progresses to complete (third-degree) heart block, the condition is generally considered irreversible. Pharmacotherapy focuses on preventing progression in the early stages or managing secondary complications:

• Corticosteroids: Fluorinated glucocorticoids (such as dexamethasone or betamethasone) can cross the placenta and are often initiated when first- or second-degree blocks are detected to reduce immune-mediated myocardial inflammation. However, their routine use is debated due to mixed evidence regarding their ability to resolve established heart block and the associated maternal and fetal risks, including the potential for impaired fetal neurological development (Pruetz et al., 2019).
• Beta-Sympathomimetics: If the fetal ventricular rate drops precipitously (typically <55 bpm) or if hydrops fetalis develops, maternal administration of beta-agonists is sometimes used to augment fetal heart rate and cardiac output, though robust, standardized protocols are lacking (Pruetz et al., 2019).

Postnatal Management and Pacing Criteria

Permanent pacemaker implantation remains the definitive therapy, with the timing dictated by the patient’s age, symptoms, and specific risk factors.

• Neonates and Infants: Pacing is unequivocally indicated for symptomatic bradycardia, ventricular dysfunction, or a markedly low resting heart rate. For neonates, a rate <55 bpm or the presence of complex structural heart disease strongly supports early pacing intervention (Pruetz et al., 2019).
• Adults: While some adults with CCHB remain asymptomatic and physically active, prophylactic pacing is widely recommended. Unpaced CCHB carries a high overall mortality rate and a persistent risk of unpredictable, potentially fatal Stokes-Adams attacks (syncope). Prophylactic pacing may be considered in asymptomatic patients with any of the following risk factors: mean daytime heart rate <50/min, pauses greater than three times the cycle length of the ventricular escape rhythm, a broad QRS escape rhythm, prolonged QT interval, or complex ventricular ectopy.

Long-Term Pacing Strategies

Because infants requiring pacemakers face a lifetime of cardiac pacing, the physical constraints and long-term physiological consequences of the hardware dictate the surgical approach.

• Epicardial Pacing: Due to the small vascular caliber of neonates and infants (typically weighing <10 kg), transvenous leads are avoided. Epicardial leads are instead placed surgically via a limited sternotomy or thoracotomy.
• Preventing Pacing-Induced Cardiomyopathy: There is growing clinical focus on the deleterious effects of chronic right ventricular (RV) apical pacing, which induces ventricular dyssynchrony and can lead to dilated cardiomyopathy over time. To counter this, alternative strategies such as cardiac resynchronization therapy (biventricular pacing) and conduction system pacing are increasingly considered to preserve physiological ventricular activation in patients requiring lifelong support (Glikson et al., 2021).

References

Clowse, M. E. B., Eudy, A. M., Kiernan, E., et al. (2018). The prevention, screening and treatment of congenital heart block from neonatal lupus: a survey of provider practices. Rheumatology, 57, v9-v17.

Glikson, M., Nielsen, J. C., Kronborg, M. B., et al. (2021). 2021 ESC Guidelines on cardiac pacing and cardiac resynchronization therapy: Developed by the Task Force on cardiac pacing and cardiac resynchronization therapy of the European Society of Cardiology (ESC) With the special contribution of the European Heart Rhythm Association (EHRA). European Heart Journal.

Kukla, P., Podlejska, B., & Wiliński, J. (2024). Congenital Complete Heart Block—To Stimulate (When?) or Not to Stimulate?. Healthcare, 12, 1158.

Pruetz, J. D., Miller, J. C., Loeb, G. E., et al. (2019). Prenatal diagnosis and management of congenital complete heart block. Birth Defects Research, 111, 380-388.