Congenital heart block
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# Overview
Congenital heart block is a rare congenital heart disease caused by defects in the heart conduction system diagnosed on or before 28 days of life. It can lead to slowed heart rate.

# Historical Perspective
- Congenital heart block was first discovered by , a , in  during/following .
- In ,  mutations were first identified in the pathogenesis of .
- In , the first  was developed by  to treat/diagnose .

# Classification
- Congenital Heart Block may be classified according to cause into 3 groups:
- First Degree Congenital Heart Block
- Second Degree Congenital Heart Block
- Third Degree Congenital (Complete) Heart Block

# Pathophysiology
The normal physiology of congenital heart block can be understood as follows:
- Mother's antibodies cross from the fetus placenta and damage of cardiac conduction system.  The majority of anti bodies are from mother to response an infectionin  or in response to an autoimmune disorder (SLE).
- Genetic disorde (autosomal recessive/dominant genetic trait).
- In some patients, congenital heart block is a secondary characteristic disorders or heart muscle tumors (myocardium).
- Fibrous tissue that either replaces the atrioventricular (AV) node and its surrounding tissue or by an interruption between the atrial myocardium and the AV nod.

# Causes
The most common cause of congenital  heart block is neonatal lupus.
cardiac conduction system is damaged by antibodies that cross from the mother to the fetus via the placenta
It accounts for almost all cases presenting in the intrauterine and neonatal period.  Other causes include:
- Myocarditis
- Mother's antibodies cross from the fetus placenta and damage of cardiac conduction system
- Genetic disorde (autosomal recessive/dominant genetic trait)
- Levo transposition of great arteries
- Atrioventricular discordance
- Hurler cardiomyopathy
- Polysplenia with atrioventricular canal defect
- In some patients, congenital heart block is a secondary characteristic disorders or heart muscle tumors (myocardium).

# Differentiating  from other Diseases
- Congenital heart block must be differentiated from other diseases:
Pediatric viral myocarditis
Transposition of the Great Arteries
- Pediatric viral myocarditis
- Transposition of the Great Arteries

# Epidemiology and Demographics
- The prevalence of congenital heart block is approximately 1 per 22,00 live births individuals worldwide. 
- In , the incidence of  was estimated to be  cases per 100,000 individuals in .

## Age
- Congential heart block is diagnosed among patients aged from brith to 28 days old.
- Congential heart block is observed among children.

## Gender
- Congenital heart block affects men and women equally.

## Race
- There is no racial predilection for congenital heart block.

# Risk Factors
- One form of congenital heart block occurs in babies whose mothers have autoimmune diseases, such as lupus.
- Patients with congenital heart block make proteins called antibodies that attack and damage the body's tissues or cells.

# Natural History, Complications, Prognosis

## Prognosis
The damaged heart may beat extremely slowly.  In some cases, the heart rate is so slow that it is fatal in nearly 20% of affected babies (with most deaths occurring as fetal demises).  Patients presenting as fetuses or at birth have significantly higher morbidity and mortality rates than do patients presenting later in childhood.

# Diagnosis
- The prenatal diagnosis of congenital heart block is more common. 
- Fetal echocardiography (with doppler techniques)
- Fetal electrocardiography.
- Cardiac imaging techniques
- Diagnosis of congenital heart block is confirmed by maternal fetal monitoring (MFM) in during infancy or early childhood.
- First degree:
Patient asymptomatc
- Patient asymptomatc
- Second degree:
Patients with second degree of heart block maybe have symptoms such as:
Fainting
Feeling dizzy
Feeling tired
- Patients with second degree of heart block maybe have symptoms such as:
Fainting
Feeling dizzy
Feeling tired
- Fainting
- Feeling dizzy
- Feeling tired
- Third degree
Patients with third degree of congenital heart block has symptoms same as second degree but more severe.
- Patients with third degree of congenital heart block has symptoms same as second degree but more severe.

## Symptoms
- Signs and symptoms depend on the type of heart block the child has. First-degree heart block rarely causes symptoms.
- Symptoms of second- and third-degree heart block include:
- First degree:
Patient with first degree of congenital heart block are asymptomatc.
- Patient with first degree of congenital heart block are asymptomatc.
- Second degree:
Patients with second degree of heart block maybe have symptoms such as:
Fainting
Feeling dizzy
Feeling tired
- Patients with second degree of heart block maybe have symptoms such as:
Fainting
Feeling dizzy
Feeling tired
- Fainting
- Feeling dizzy
- Feeling tired
- Third degree
Patients with third degree of congenital heart block has symptoms same as second degree but more severe.
- Patients with third degree of congenital heart block has symptoms same as second degree but more severe.

## Physical Examination
- Patients with congenital heart block usually appear :
- Annular lesions (Face, particularly around eyes)
- Photosensitive

## Laboratory Findings
- There are no specific laboratory findings associated with congenital heart block.
- May be autoantibodies to Ro/SSA and La/SSB ribonucleoproteins using ELISAW are helpful when when congenital heart block  detected.
- Other laboratory findings consistent with the diagnosis of congenital heart block include Sera, ELISA, counter-immunoelectrophoresis (CIE) method.

# Treatment

## Medical Therapy
- Supportive therapy for congenital heart block includes symptomatic patients.
- The mainstay of in utero therapy for congenital heart block is corticosteroids.
- Corticosteroids act by decreasing inflammation and damage caused by maternal antibodies.
- Response to Corticosteroids can be monitored with fetal echocardiogram every few weeks.

## Surgery
- Surgery is the mainstay of therapy for Congenital Heart Block.
- Cardiac pacemaker implantation in conjunction with Corticosteroids is the most common approach to the treatment of Congenital Heart Disease.
- Cardiac pacemaker implantation can only be performed for patients with Mobitz Type II and above Congenital Heart Block.

## Prevention
- There are no primary preventive measures available for Congenital Heart Disease.
- Fetus with second or third degree heart block are less in women who take HCQ.
- Women of childbearing age with systemic autoimmune disorders should be tested fo anti-Ro and anti-La antibodies.
- Effective measures to decrease the severity of Congenital Heart Block include in utero administration of Corticosteroids and plasmapheresis. 
- Once diagnosed and successfully treated, patients with Congenital Heart Block are followed-up regularly. Follow-up testing includes fetal echocardiogram, electcrocardiogram, and serologic antibodies.

## Electrocardiogram
Electrocardiographic findings in congenital heart block depend on the type of block.

# Treatment

## Surgery
Treatment depends on the type of heart block.
- First-degree heart block usually needs no treatment.
- For second-degree heart block, patient may need a pacemaker. A pacemaker is a small device that's placed under the skin of your chest or abdomen. This device uses electrical pulses to prompt the heart to beat at a normal rate.
- For third-degree heart block, patient will need a pacemaker.
Nearly all surviving children with congenital heart block require permanent implantation of an pacemaker device.

## Prevention
Because it is so difficult to treat or repair the damaged heart, a high-priority strategy is to try to prevent the inflammatory process before irreversible scarring can occur.  The mother of the child 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.

# Source
- ClinicalTials.gov

# Related Chapters
- Electrical conduction system of the heart
- Electrocardiogram (ECG or EKG)
- SA node
- AV node
- Second degree AV block
- Third degree AV block
- Bundle branch block
- Hemiblock
- Infra-Hisian Block
- Left anterior fascicular block
- Left posterior fascicular block
- Heart block
- Systemic lupus erythematosus
- IVIG