History
Congenital atrioventricular block (CAVB) may be identified during prenatal examinations, in the perinatal period, or during childhood or adulthood. Historical and other features widely vary and particularly depend on the timing of presentation and accompanying structural heart disease.
Isolated CAVB
Many of the mothers confirmed to have a fetus with autoimmune AV block may have no symptoms. The fetus in whom isolated CAVB is identified during the perinatal period usually presents with an incidental finding of bradycardia or hydrops fetalis.
Occasionally, these mothers may have a history of recurrent fetal loss. Fetuses of such mothers should be routinely evaluated for CAVB.
The mother is often completely asymptomatic. In addition to fetuses who are incidentally identified, siblings of children with known isolated heart block are at a higher risk with a recurrence rate for heart block of 17%-22%.
In the perinatal period, fetal bradycardia may have myriad causes. However, when persistent bradycardia is identified in the third trimester, emergency delivery is sometimes inappropriately carried out without differentiating acute causes of bradycardia related to fetal distress from the more chronic condition of isolated CAVB.
Newborns with congenital heart block may present with a hydropic appearance secondary to fetal heart failure or may develop signs of low cardiac output within hours to days after birth. However, affected newborns often appear asymptomatic and may have accelerated ventricular rates approaching those of healthy newborns. Congenital heart block is not likely to be identified in many such infants until well after birth. An associated finding of neonatal lupus may be present.
In older infants or children, signs of low cardiac output due to bradycardia, such as pallor, mottling, lethargy, exercise intolerance, palpitations, dizziness, or syncope, may occur. Children may have sleep disturbances or be asymptomatic.
CAVB with structural heart disease
The diagnosis of a congenital heart defect in one child or first-degree relative is an indication for fetal echocardiography to check for cardiac malformations.
Children with structural heart defects may present with cyanosis, murmur, failure to thrive, or recurrent pneumonias or may be completely asymptomatic in childhood (such as children with L-transposition of the great arteries and intact ventricular septum).
Physical Examination
The fetus may be monitored with ultrasonography for varying degrees of heart block and hydrops fetalis. In the newborn, the findings may range from asymptomatic to signs of congestive heart failure and low cardiac output.
The most typical physical finding is a low heart rate for age. Because the block is usually complete and the escape rhythm is usually junctional in origin, a regular rhythm at 60-80 beats per minute (bpm) is often found. Auscultation demonstrates a variable first heart sound caused by the AV asynchrony.
Congenital atrioventricular block (CAVB) may be associated with findings of low cardiac output or congestive heart failure. Low cardiac output may manifest with physical findings of irritability or lethargy, cool skin, mottling, or cyanosis.
Congestive heart failure may manifest with tachypnea and hepatomegaly. If congestive heart failure has been present prenatally, marked edema may be part of the complex of hydrops fetalis.
Children with neonatal lupus can present with rash, as well as with neurologic and hepatic manifestations. The rash can occur some days after birth and is worsened with sun exposure. Annular or elliptical erythematous plaques can be present on the skin of face, scalp, and extremities. It usually resolves without scarring but can be associated with residual hypopigmentation or, rarely, telangiectasias.
Children with structural heart disease may manifest symptoms and signs related to the specific congenital heart defect. Patients with heterotaxia syndrome may be cyanotic. Patients with L-transposition of the great arteries may be completely asymptomatic or may demonstrate a murmur.
