Approach Considerations
After birth, electrocardiography (ECG) is recommended to assess for congenital atrioventricular block (CAVB) and to assess the QT interval that can be prolonged. ECG and Holter ambulatory ECG monitoring are routinely performed initially and periodically in patients with complete CAVB.
All children, regardless of fetal findings, should undergo an electrocardiogram after birth to check the conduction intervals. Children with first-degree or second-degree AV block have been known to progress to third-degree CAVB.
Holter monitoring (ambulatory ECG) is recommended to determine if the AV block is intermittent or persistent and to evaluate for associated arrhythmias.
Exercise testing is performed on a regular basis in patients who are capable, usually in patients older than age 7 years. Electrophysiologic testing is not routinely performed in patients with CAVB, although it provides information regarding pathophysiology and prognosis in certain cases.
Chest radiography may reveal cardiomegaly and pleural effusions. Heterotaxia may be suspected in presence of visceroatrial discordance. One should look for a midline liver, rightward stomach bubble, and dextrocardia. Looking at lead placement in temporary and permanent pacemakers is helpful.
Consultations
The mother should consult with a rheumatologist to begin monitoring for possible autoimmune disease. Consultation with a rheumatologist is also advised for the infant, particularly if other manifestations of neonatal lupus erythematosus are present.
Genetic consultation is recommended for children with first-degree relatives with structural heart disease or those with storage disorder or cardiomyopathy.
Pediatric cardiology consultation is necessary for every case.
Laboratory Studies
In patients with congenital atrioventricular block (CAVB), routine electrolyte assays should be performed to assess for metabolic derangements (especially hyperkalemia), and a complete blood count (CBC) should be obtained to assess for anemia, neutropenia, and thrombocytopenia.
Neonatal assessment should include a measurement of anti-Ro and anti-La antibody levels, preferably using a line immunoassay [3] in the mother. Assessment for other organ and/or tissue damage should include a platelet assessment to rule out thrombocytopenia and an assessment of liver enzymes to rule out alloimmune hepatitis.
If inflammatory disease is suspected, workup for various infectious etiologies (eg, human immunodeficiency virus [HIV]) should be performed. Cardiac troponins and pro-brain natriuretic peptide (BNP) levels can be helpful in assessing the severity of the disease.
If hypertrophic cardiomyopathy is suspected, evaluation for lysosomal storage diseases should be included.
Preductal and post-ductal saturations by pulse oximetry should be performed. Check for hypoxemia and acidosis using arterial blood gas (ABG) findings. Also, check lactic acid for perfusion. A hyperoxia test is very helpful in differentiating lung disease–related hypoxemia versus hypoxemia due to a cyanotic heart disease. One can evaluate for Howell-Jolly/Heinz bodies on peripheral smear for evaluation of asplenia that is seen with heterotaxia syndromes.
Ultrasonography
Echocardiography should be performed initially and during periodic follow-up care in affected fetuses, infants, and children in order to assess ventricular function and size and to rule out congenital or acquired cardiac malformations or valve dysfunction. [16]
Children of mothers with the anti-Ro and anti-La antibodies should undergo regular fetal ultrasonographic assessments, including detailed fetal echocardiography to identify conduction delay, bradycardia, and ventricular function.
Mothers with the autoimmune antibodies or those with one affected child should undergo regular fetal ultrasonographic assessments, [15] including detailed fetal echocardiography, to identify subsequent affected pregnancies starting early, at 16 weeks' gestation. Fetal echocardiography may reveal varying degrees of AV block. Fetal monitoring should be performed to look for bradycardia, fetal distress, and hydrops fetalis.
Fetal echocardiography is geared towards looking for early heart block, bradycardia, arrhythmias, pericardial effusion, cardiomegaly, valvular insufficiency (especially tricuspid regurgitation), decreasing contractile function, and abnormal venous and arterial pulsations.
Histologic Findings
Myocardial biopsies are not routinely performed in patients with congenital atrioventricular block (CAVB). However, histologic findings have been reported from experimental studies and autopsy specimens; these findings demonstrated various stages of fibrosis and calcification of the AV conduction area, depending on the timing of the specimen.
Immune deposition is also a frequent finding, although whether this is specific for the conduction system or occurs throughout the myocardium in general is unclear. The mechanisms of cell death and fibrosis are unclear. Hypotheses include alloimmune-mediated inflammatory responses and immune-triggered apoptosis.
In some cases, the sinoatrial node has also been found to be affected and may be hypoplastic, fibrotic, or completely absent.
