Atrial septal defect (ASD) occurs when the atrial septum, the wall between the heart’s left and right atria (upper chambers), fails to close during heart development. This is a common type of congenital heart defect affecting 25% of children (1). ASD can be due to true defects in the septal membrane or other defects, allowing communication between both atria of the heart.
Smaller atrial defects may spontaneously close in childhood without interventions. But more significant defects may not close themselves and require surgical or percutaneous closure to prevent complications.
Read this post to know about types, causes, symptoms, complications, and treatment of atrial septal defects in babies.
Types Of Atrial Septal Defects
Separation of the atrium begins in the fourth week of gestation with the primary atrial septum (septumprimum) growth. Atrial septal defects may occur in various locations during development. The four types of atrial septal defects are the following (2).
- Ostiumprimum atrial septal defect is the defect in the atrioventricular canal, and it may cause cleft or split in the mitral valve leaflets.
- Ostiumsecundum atrial septal defect is the most common type of ASD, affecting more than two-thirds of ASD cases. This may cause an opening in the middle of the atrial septum. This may occur due to the failure of the atrial septum to close entirely during heart development.
- Sinus venosus atrial septal defect happens in the right atrium at the superior vena cava or inferior vena cava junction where the right pulmonary vein enters the heart. This is called inferior defect or superior defect, depending on the location. This may cause one or more pulmonary veins to drain into the right atrium instead of the left atrium.
- Coronary sinus atrial septal defect is located behind the left atrium on the wall of the coronary sinus. The coronary sinus drains blood from the heart’s veins to the right atrium. It is a rare type of ASD.
Patent foramen ovale (PFO) is a small opening between the heart’s atria, which may allow little blood flow through the flaps. This is normal in unborn babies and usually closes soon after birth. However, some babies may have open PFO due to various reasons and often require surgical closure.
What Happens In An Atrial Septal Defect?
In a normal heart, the pressure in the right atrium is usually lower than the left atrium. Therefore, when there is a defect in the septum, the blood flows from the left atrium to the right atrium. This is called a left-to-right shunt. A significant shunt may occur if the size of the atrial septal defect is larger (1).
When there is increased blood in the right atrium, it is pumped to the lungs and remodels the lung vasculature. Changed pulmonary vessels may cause increased pulmonary resistance and lead to high pulmonary blood pressure (pulmonary hypertension). Changes in flood flow can result in complications of ASD in babies.
Eventually, the shunt may reverse if the pulmonary pressure equals the systemic pressure (pressure in the left atrium). This may cause deoxygenated blood from the right atrium to enter the left atrium and to the body. This condition is called Eisenmenger syndrome. Reversal of shunt in ASD can compromise oxygenation in the body.
Symptoms Of Atrial Septal Defects
Many babies may not develop signs and symptoms of the atrial septal defect, even though they have it from birth. ASD symptoms may occur any time from birth through childhood or later, depending on its severity. Untreated or larger atrial septal defects may cause the following signs and symptoms in babies (3).
- Breathing difficulties
- Frequent lung or respiratory infections
- Shortness of breath (dyspnea)
- Heart murmur (heard on stethoscope) occurs due to abnormal blood flow
- Tiredness while feeding
- Swelling of feet, legs, and abdomen
Usually, small atrial septal defects of less than five millimeters can be asymptomatic until middle age or later if the baby does not have any other heart defects(4). You may seek medical care if your baby has any of these symptoms.
Risk Factors And Causes Of Atrial Septal Defects
The definite cause of the atrial septal defect is not known in many babies, even if ASD is diagnosed at birth. Congenital heart defects may present with genetic conditions, such as Down syndrome, or run in families.
The following maternal factors during pregnancy may also increase the risk of ASD or other heart defects in babies (5).
- Rubella infection (German measles) during initial months of pregnancy
- Narcotics, alcohol, or tobacco use
- Certain medications
- Obesity, diabetes, and lupus (SLE)
- Phenylketonuria (PKU) if not following PKU meal plan
ASD in infants may also be associated with other maternal factors, such as advanced age, poor health and lifestyle, and family history of heart diseases. However, fetal heart defects may also occur without the presence of any risk factors.
Complications Of The Atrial Septal Defects
Small atrial septal defects may not cause any complications in babies, and this may often close itself during infancy. The following complications may occur if larger defects are left untreated (6).
- Arrhythmias (heart rhythm abnormalities)
- Right-sided heart failure
- Higher risk of stroke
- Reduced life expectancy
Large atrial septal defects lead to increased blood flow to the lungs and increased blood pressure in the pulmonary arteries, resulting in pulmonary hypertension. This may further lead to lung damage and heart failure. This condition is called Eisenmenger syndrome.
Diagnosis Of Atrial Septal Defects In Babies
Prenatal ultrasound and other prenatal screening tests may detect ASD in some cases, depending on the size and location of the defect. Sometimes, the heart murmur is the first finding during routine examinations. A pediatric cardiologist evaluates babies with heart problems, and they may order the following tests for further diagnosis (7).
- Electrocardiogram (ECG) records the electrical activity of the heart. Arrhythmias (abnormal rhythms) are often seen in ASD if it is located in the conduction system.
- Echocardiogram uses sound waves to visualize blood flow and valve functions of the heart. This can also show blood flow through ASD and measure the size of defects.
- Chest X-ray helps visualize lung changes, and enlarged heart occurs due to blood flow changes in ASD.
- Cardiac catheterization uses flexible, thin wires inserted near the heart to get a detailed view. Contrast dye is used to enhance the view. This procedure may also be used to close the defect in some cases.
Treatment For Atrial Septal Defects In Babies
Pediatric cardiologists may choose the following treatment options depending on the size of the ASD (8).
Medical therapy with antiarrhythmic drugs, anticoagulants, and diuretics are prescribed to treat symptoms of ASD. These medications do not repair the defect. Medical therapy is also given after surgical closure to prevent complications.
2. ASD closure
ASD closure is the definitive way to treat ASD in babies. The following two approaches are available to close the defect.
- Open heart surgery involves an incision in the chest wall and heart to repair the ASD. This is recommended for the repair of ostiumprimum and sinus venous atrial septal defect in early childhood. Smaller ASD is closed with sutures, and larger defects are sealed with synthetic or pericardial patches.
- Catheter-based closure(percutaneous closure) is a method of placing a septal occluder to close the defect through a guided tube (wire) from the femoral artery to the heart. The occluder device contains flexible wire with nitinol (nickel and titanium). This may often be done during the diagnostic procedure itself, and babies may receive medications such as Plavix (clopidogrel) and aspirin to prevent platelet adhesion in the device.
Doctors may recommend frequent follow-up visits for larger ASDs after treatment. Simple defects may require occasional follow-ups.
Prevention Of Atrial Septal Defects
The atrial septal defect may not be preventable in most babies. However, proper preconception and prenatal care may reduce the risk of congenital heart defects in some cases. The following steps may prevent ASD in some babies (6).
- Test immunity to rubella before planning pregnancy and get vaccinated if you don’t have immunity to rubella.
- Monitor existing health problems, such as diabetes or hypertension, before pregnancy. Inform the doctor about pregnancy plans, and they may change certain medications if needed.
- Keep all medical conditions under control with appropriate treatment during pregnancy.
- Avoid the use of alcohol, narcotics, and tobacco during pregnancy.
Parents with a family history of genetic problems and heart defects or already with children with heart defects should seek genetic counseling before planning the subsequent pregnancy. Genetic counselors can help you understand the risk of having a baby with similar conditions.
Smaller size ASD may resolve without issues in most cases. Treatments help to prevent complications of larger ASD as well. You may consult a pediatrician if your baby has any symptoms of ASD to diagnose and provide early treatment. Never skip follow-up visits of a child with treated or untreated cardiac defects.