Congenital heart block: clinical features and therapeutic approaches

Isolated congenital heart block is strongly associated with anti-Ro antibodies. It occurs in 2% of anti-Ro antibody positive pregnancies with a recurrence rate of 17-19%. Mortality is high in the first year of life (12-41%) and is predominantly due to dilated cardiomyopathy. A prolonged QTc occurs in 15-22% of cases and minor structural defects such as atrial septal defects and patent arterial ducts are well recognized. The 'mechanical' PR interval can now be measured in utero allowing for the detection of first-degree heart block. Both first and second-degree heart block detected in utero respond to therapy with fluorinated steroids. Complete congenital heart block is not reversible. Progression from a normal PR interval to complete heart block can occur within a week. IVIG is under investigation for the prevention of recurrence of congenital heart block, while dexamethasone should not be used for this purpose due to unacceptable toxicity. Data on the use of fluorinated steroids for established complete heart block is conflicting, although their use in cases where there is evidence of hydrops, poor ventricular function or both is not controversial.