AUTHOR AND EDITOR INFORMATION

Section 1 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

INTRODUCTION

Section 2 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Background

Congenital atrioventricular block (CAVB) can occur in a structurally normal heart (isolated CAVB) or with congenital heart disease (CAVB with congenital heart defects). Isolated CAVB is seen in association with certain autoimmune antibodies in the mother that cross the placenta and damage the atrioventricular (AV) node of the fetus.

CAVB can also be seen with certain complex congenital heart defects such as heterotaxy with accompanying AV canal defects and L-transposition of the great arteries.

Pathophysiology

Isolated CAVB, although not definitively proven, is thought to be the result of transplacental passage of immunoglobulin G (IgG) autoantibodies from the mother who may have a clinical autoimmune disease such as lupus or Sjögren syndrome or who may be clinically asymptomatic. These autoantibodies damage the AV conduction tissue by inflammation in the early stage and later by fibrosis.

CAVB with structural heart disease is considered to be caused by failure of the AV conduction system to connect. This disconnection is a result of increased distance between the AV node and the ventricular conduction tissues.

Frequency

International

Autoimmune AV block occurs in approximately 1 per 14,000-20,000 live births. However, because significant fetal loss is thought to result from this disease, the true incidence of the disease (per conception) may be significantly higher. Structural congenital heart block is also rare but with a higher proportion of fetal loss.

Mortality/Morbidity

The fetal mortality rate of isolated CAVB may be up to 30-50%. Patients diagnosed and treated in the neonatal period have a survival rate of 94%, and patients who are diagnosed and treated in childhood have a survival rate of 100%.

Fetal and newborn mortality rates in congenital heart block with structural heart disease remain high, even if effective pacing is used.

Risk factors for death in isolated CAVB include fetal diagnosis, premature gestation, hydrops fetalis, endocardial fibroelastosis, and diminished ventricular function. Hydrops fetalis is the risk factor for patients with structural heart disease and CAVB. Patients with L-transposition of the great arteries or with well-repaired structural heart defects typically have a better overall outcome than infants with complex structural cardiac defects and/or ventricular dysfunction.

Sex

The prevalence of isolated CAVB may be slightly higher in females than in males.

Age

Patients who present with symptoms as fetuses or newborns may have a more severe course or require earlier pacing than those who present with symptoms later in childhood.

CLINICAL

Section 3 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

History

Congenital atrioventricular block (CAVB) may be identified during prenatal examinations, in the perinatal period, or during childhood or adulthood. Historical and other features vary greatly and depend particularly on the timing of presentation and accompanying structural heart disease.

• Isolated CAVB
• • A minorty of mothers confirmed to have a fetus with autoimmune AV block have symptoms related solely to autoantibodies. Occasionally, the 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. The fetus in whom isolated CAVB is identified during the prenatal period usually presents with an incidental finding of bradycardia or hydrops fetalis.
  • In addition to fetuses who are incidentally identified, siblings of children with known isolated heart block usually undergo fetal ultrasonographic screening because the recurrence rate for heart block in subsequent siblings is 17-22%.
  • In the perinatal period, fetal bradycardia may also be an incidental finding. 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.
  • Some centers recommend cesarean delivery and preterm delivery for fetuses with CAVB and hydrops fetalis.
  • Newborns with congenital heart block may present with a hydropic appearance secondary to fetal heart failure or may develop signs of low cardiac output or failure 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 in autoimmune or isolated CAVB may be the presence of discoid skin lesions.
  • 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, 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

The fetus is remote from physical examination but may be monitored with ultrasonography. 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 heart block 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 structural heart disease may manifest symptoms and signs related to the specific congenital heart defect. Patients with heterotaxia syndrome and unbalanced AV canal defects may be cyanotic. Patients with L-transposition of the great arteries may be completely asymptomatic or may demonstrate a murmur.

Causes

Isolated CAVB has been described since 1901. It has been related to the presence of maternal connective tissue disease since the early 1970s.

• Isolated CAVB is presumed to be caused by injury from the placental passage of maternal anti-Ro and anti-La (or related) antibodies, which are present in more than 90% of mothers during pregnancy or at the time of delivery. CAVB occurs in up to approximately 5% of children born to mothers with anti-Ro antibody.
• Children with isolated complete CAVB are most likely to have acquired the disease as a complication of subclinical or clinical maternal lupus erythematosus, maternal Sjögren syndrome, or another maternal autoimmune disease. As such, they may have other manifestations of neonatal lupus syndrome in the newborn period and other cardiac sequelae of neonatal lupus during follow-up treatment. This may also be true of infants who are born to these mothers but do not manifest AV block. Other complications of maternal autoimmune disease include second-degree AV block and cardiomyopathy.

DIFFERENTIALS

Section 4 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Other Problems to be Considered

Heterotaxia
Atrioventricular septal defect
Myopathies
Metabolic disorders
Infections

WORKUP

Section 5 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Lab Studies

• Neonatal assessment should include a measurement of anti-Ro and anti-La antibody levels, preferably using an enzyme-linked immunosorbent assay (ELISA). 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.
• Mothers of infants with isolated congenital complete heart block should undergo measurement of anti-Ro and anti-La antibody levels, preferably by means of ELISA.

Imaging Studies

• Echocardiography should be performed initially and in periodic follow-up care in affected fetuses, infants, and children to assess ventricular function and size and to rule out congenital or acquired cardiac malformations or valve dysfunction. Fetal echocardiography can reveal the complete AV block. After birth, electrocardiography is recommended to assess for congenital atrioventricular block (CAVB) and to assess the QT interval.
• 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. All children, regardless of fetal findings, should undergo an ECG after birth to check the conduction intervals. Children with first- or second-degree AV block have been known to progress to CAVB.
• Mothers with one affected child should undergo regular fetal ultrasonographic assessments, including detailed fetal echocardiography to identify subsequent affected pregnancies.

Other Tests

• ECG and Holter ambulatory ECG monitoring are routinely performed initially and periodically in patients with complete CAVB. Holter monitoring (ambulatory electrocardiography) is recommended to determine if the AV block is intermittent or persistent.
• Exercise testing is performed on a regular basis in patients who are capable, usually in patients older than 7 years.

Procedures

• Electrophysiologic testing is not routinely performed in patients with CAVB, although it occasionally provides information regarding pathophysiology and prognosis in certain cases.

Histologic Findings

Myocardial biopsies are not routinely performed in patients with CAVB. However, histologic findings have been reported from experimental studies and autopsy specimens; these findings demonstrate 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.

TREATMENT

Section 6 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Medical Care

The medical care of congenital atrioventricular block (CAVB) is currently focused on identifying the optimal timing of pacemaker therapy to ensure a positive outcome. Additional care is aimed at identifying and treating the associated conditions that arise.

Little evidence suggests that the administration of steroids or the performance of plasmapheresis in the mother can reverse third-degree AV block. However, these therapies may be helpful in reducing associated myocardial dysfunction. Hopefully, with further understanding of the pathophysiology of CAVB, a preventive therapy will be identified.

Surgical Care

Symptoms referable to bradycardia are an indication for pacing in complete CAVB. Because severe symptoms (eg, syncope) occasionally arise suddenly, additional risk factors identified from monitoring have been recommended as indications for pacing.

Major criteria for pacing based on ECG or Holter monitoring include an average heart rate less than 50 bpm, a nighttime or sleeping average heart rate less than 45 bpm, or pauses secondary to atrioventricular block that are longer than 3 seconds. In the setting of borderline major criteria, other criteria that may influence the decision for timing of pacemaker implantation include cardiomegaly, a high atrial rate, junctional instability (eg, junctional exit block), a broad complex escape rhythm, diminished ventricular response to exercise, QT prolongation, and complex ventricular ectopy.

When criteria are met, surgical implantation of a pacemaker should be performed with a knowledge of the implications of pacing in children and a recognition of the lifelong need for pacing and pacemaker lead access. Multiple backup pacing systems at the time of surgery (eg, temporary transvenous pacing, transthoracic pacing units) are helpful to avoid the extremes of bradycardia that may be associated with anesthesia and pacemaker surgery.

• Venous obstruction, small patient size, and actual or potential right-left shunting are relative contraindications for transvenous pacing. Fortunately, epicardial pacing leads have greatly improved and allow for successful pacing system insertion under these conditions.
• In children older than the neonatal period, a transvenous approach is possible. The risk of venous occlusion appears to correlate with the ratio of available transvenous lead body sizes and the patient's body surface area (Figa, 1997). Exceeding this ratio may lead to a high incidence of venous obstruction. In addition, imaging of the subclavian-innominate venous channels before pacemaker lead placement is helpful for transvenous lead placement. The course of the lead should be evaluated in 2 planes to avoid inadvertent lead placement into the foramen ovale, an unroofed left superior vena cava to coronary sinus, or left-sided circulation via the subclavian artery. Either a subcutaneous or subpectoral pocket may be formed inferior to the clavicle (see Pacemaker Therapy).

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.

Activity

Patients with permanent pacing systems should be restricted from activities that result in repeated intentional direct trauma to the pacemaker area (eg, martial arts). Patients with permanent pacing systems should be restricted from exposure to high magnetic fields, such as direct MRI exposure.

MEDICATION

Section 7 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Intrauterine treatments used for congenital atrioventricular block (CAVB) include chronotropic agents, inotropic agents, steroids, and plasmapheresis.

In general, medications are not necessary in children with complete CAVB. Emergency use of chronotropic medications, with or without inotropic agents, may be helpful in fetuses and newborns with hydrops fetalis, congestive heart failure, or low cardiac output. Some investigators have suggested the use of immunosuppressive agents in fetuses and newborns to potentially slow or halt progressive CAVB in utero. This is currently being evaluated as a prospective study.

FOLLOW-UP

Section 8 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Further Inpatient Care

• Prophylactic antibiotic therapy during and following surgery appears to reduce the incidence of pacemaker system infections, although current studies do not reach statistical significance because of the relative rarity of this complication (approximately 1%).

Further Outpatient Care

• Routine pacemaker follow-up visits should be maintained according to national or international guidelines. Transtelephonic pacemaker monitoring may allow for improved follow-up care and longer intervals between outpatient visits.

Transfer

• According to a long-term follow-up study by Michaelsson and colleagues, adults with complete congenital atrioventricular block (CAVB) who did not receive pacing systems had a poorer prognosis than those with pacing because of multiple complications related to their disease. Therefore, in the adolescent who has not yet developed indications for pacing (an unusual case), recommendations for a pacing system should be considered, regardless of symptoms or underlying escape rate.

Complications

• Long-term potential complications in all patients include development of ventricular dilatation and dysfunction. Patients without pacemakers may develop AV valve regurgitation, atrial rhythm disorders, thromboembolism, congestive failure, or sudden death. Patients with a pacemaker may develop pacing system–related complications, including lead fracture, malsensing, and pacing system infections.

Prognosis

• The prognosis in complete CAVB is relatively good but may be influenced by the patient's age at presentation. Congenital complete heart block is an increasingly recognized cause of fetal loss. In addition, patients presenting as fetuses or at birth have significantly higher morbidity and mortality rates than patients presenting later in childhood.

Patient Education

• Parents who are at risk of having a child with CAVB must be informed that this disease is easily identifiable and relatively easily treated after birth. The stigma of pacing as a therapy associated with elderly persons should be avoided. Parents should recognize that their affected offspring are likely to receive and benefit from pacing therapy at some point during childhood but that pacemaker therapy is intentionally deferred until indications are present to preserve lifelong access for pacing systems.

MISCELLANEOUS

Section 9 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Medical/Legal Pitfalls

• Major lawsuits related to pacing in congenital atrioventricular block (CAVB) have arisen primarily because of inadvertent placements of pacing leads into the left-sided circulation. This complication can be recognized at or immediately following system placement using complementary radiographic views, usually lateral and posteroanterior (PA) or anteroposterior (AP).
• Other important pitfalls relate to patients with CAVB who have had a morbid or fatal event secondary to not receiving a permanent pacemaker.

Special Concerns

• Fetuses with hydrops fetalis secondary to maternal autoimmune disease have successfully received pacing in utero; however, this has not prevented fetal demise.

REFERENCES

Section 10 of 10

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

• Boutjdir M, Chen L, Zhang ZH, et al. Serum and immunoglobulin G from the mother of a child with congenital heart block induce conduction abnormalities and inhibit L-type calcium channels in a rat heart model. Pediatr Res. Jul 1998;44(1):11-9. [Medline].
• Boutjdir M, Chen L, Zhang ZH, et al. Arrhythmogenicity of IgG and anti-52-kD SSA/Ro affinity-purified antibodies from mothers of children with congenital heart block. Circ Res. Mar 1997;80(3):354-62. [Medline].
• Claus R, Hickstein H, Kulz T, et al. Identification and management of fetuses at risk for, or affected by, congenital heart block associated with autoantibodies to SSA (Ro), SSB (La), or an HsEg5-like autoantigen. Rheumatol Int. Aug 2006;26(10):886-95. [Medline].
• Copel JA, Buyon JP, Kleinman CS. Successful in utero therapy of fetal heart block. Am J Obstet Gynecol. Nov 1995;173(5):1384-90. [Medline].
• Costedoat-Chalumeau N, Georgin-Lavialle S, Amoura Z, et al. Anti-SSA/Ro and anti-SSB/La antibody-mediated congenital heart block. Lupus. 2005;14(9):660-4. [Medline].
• Costedoat-Chalumeau N, Amoura Z, Villain E, et al. Anti-SSA/Ro antibodies and the heart: more than complete congenital heart block? A review of electrocardiographic and myocardial abnormalities and of treatment options. Arthritis Res Ther. 2005;7(2):69-73. [Medline].
• Cutler NG, Karpawich PP, Cavitt D, et al. Steroid-eluting epicardial pacing electrodes: six year experience of pacing thresholds in a growing pediatric population. Pacing Clin Electrophysiol. Dec 1997;20(12 Pt 1):2943-8. [Medline].
• Figa FH, McCrindle BW, Bigras JL, et al. Risk factors for venous obstruction in children with transvenous pacing leads. Pacing Clin Electrophysiol. Aug 1997;20(8 Pt 1):1902-9. [Medline].
• Friedman DM, Zervoudakis I, Buyon JP. Perinatal monitoring of fetal well-being in the presence of congenital heart block. Am J Perinatol. 1998;15(12):669-73. [Medline].
• Hamilton R, Gow R, Bahoric B, et al. Steroid-eluting epicardial leads in pediatrics: improved epicardial thresholds in the first year. Pacing Clin Electrophysiol. Nov 1991;14(11 Pt 2):2066-72. [Medline].
• Hamilton RM, Chiu C, Gow RM, Williams WG. A comparison of two stab-on unipolar epicardial pacing leads in children. Pacing Clin Electrophysiol. Mar 1997;20(3 Pt 1):631-6. [Medline].
• Jaeggi ET, Hornberger LK, Smallhorn JF, Fouron JC. Prenatal diagnosis of complete atrioventricular block associated with structural heart disease: combined experience of two tertiary care centers and review of the literature. Ultrasound Obstet Gynecol. Jul 2005;26(1):16-21. [Medline].
• Karpawich PP, Walters H, Hakimi M. Chronic performance of a transvenous steroid pacing lead used as an epi- intramyocardial electrode. Pacing Clin Electrophysiol. Jul 1998;21(7):1486-8. [Medline].
• Karpawich PP, Stokes KB, Proctor K, et al. "In-line" bipolar, steroid-eluting, high impedance, epimyocardial pacing lead. Pacing Clin Electrophysiol. Mar 1998;21(3):503-8. [Medline].
• Michaelsson M, Jonzon A, Riesenfeld T. Isolated congenital complete atrioventricular block in adult life. A prospective study. Circulation. Aug 1 1995;92(3):442-9. [Medline]. [Full Text].
• Miranda-Carus ME, Boutjdir M, Tseng CE. Induction of antibodies reactive with SSA/Ro-SSB/La and development of congenital heart block in a murine model. J Immunol. Dec 1 1998;161(11):5886-92. [Medline].
• Moak JP, Barron KS, Hougen TJ, et al. Congenital heart block: development of late-onset cardiomyopathy, a previously underappreciated sequela. J Am Coll Cardiol. Jan 2001;37(1):238-42. [Medline].
• Neiman AR, Lee LA, Weston WL, Buyon JP. Cutaneous manifestations of neonatal lupus without heart block: characteristics of mothers and children enrolled in a national registry. J Pediatr. Nov 2000;137(5):674-80. [Medline].
• Rao V, Williams WG, Hamilton RH, et al. Trends in pediatric cardiac pacing. Can J Cardiol. Dec 1995;11(11):993-9. [Medline].
• Suarez-Penaranda JM, Munoz JI, Rodriguez-Calvo MS, et al. The Pathology of the heart conduction system in congenital heart block. J Clin Forensic Med. Aug-Nov 2006;13(6-8):341-3. [Medline].
• Weng KP, Chiou CW, Huang SH, et al. The long-term outcome of children with isolated congenital complete atrioventricular block. Acta Paediatr Taiwan. Sep-Oct 2005;46(5):260-7. [Medline].

Article Last Updated: Nov 6, 2006