Congenital Heart Block: Pathophysiology, Diagnosis, and Management

Congenital heart block (CHB) is a rare but potentially life-threatening form of conduction disease that manifests in utero or shortly after birth, resulting from disruption of the normal electrical conduction pathway between the atria and ventricles. The severity of CHB varies depending on the degree of atrioventricular conduction impairment, ranging from first-degree atrioventricular block, characterized by prolonged conduction, to complete third-degree block, in which atrial and ventricular activity are entirely dissociated and function independently. The most common etiology is passive transplacental transfer of maternal anti-Ro/SSA and anti-La/SSB autoantibodies, most frequently in the setting of maternal systemic lupus erythematosus or Sjögren syndrome, even when the mother is clinically asymptomatic. Less commonly, CHB arises in association with structural congenital heart disease, most notably left atrial isomerism and corrected transposition of the great arteries. The clinical spectrum ranges from an incidental prenatal finding to fetal hydrops and in utero death, with third-degree CHB carrying a perinatal mortality rate of approximately 15-30%. This review integrates current evidence on the pathophysiology, maternal autoimmune contributions, diagnostic approach, and management strategies for CHB, with an emphasis on the emerging roles of fetal surveillance, pharmacologic interventions, and postnatal pacing.