Atrial Septal Defect (ASD) In Infants

Definition and overview

Atrial septal defect (ASD) is one of the most common types of congenital heart defects (CHDs), affecting roughly 13 out of every 10,000 babies born in the United States annually.^1,2 Characterised by an opening in the septum - the wall that separates the upper chambers (atria) - this condition originates during foetal development when the hole fails to close either before birth or shortly after.² Left untreated, this opening between the left and right atria can significantly compromise heart health.¹

Importance of early detection

An ASD can vary in size and may close by itself without requiring medical intervention in infancy.² ASD in infants is usually asymptomatic and may go unnoticed until much later in life, depending on the size of the opening.¹ The hole between the atria can increase blood flow to the lungs, causing damage to the blood vessels.² If untreated, ASD may lead to severe symptoms such as hypertension (high blood pressure), abnormal heartbeat, heart failure or increased risk of stroke.^2,3 Early screening in prenatal mothers can increase the likelihood of detection and prevent delayed treatment.⁴ 

This article will explore the following key points:

1. What is ASD?
2. The anatomy of the heart
3. Types of ASD
4. Causes and risk factors
5. Signs and symptoms
6. Diagnosis 
7. Treatment options
8. Prognosis
9. Prevention and Awareness
10. Support for families?

Heart defects represent a major global health problem. In Europe, one-third of infants are diagnosed with CHD due to an anomaly (prenatally or in infancy).⁴ Raising awareness of ASD in infants will benefit early detection and treatment success.

Anatomy of the heart

Fig.1. Diagram to show the anatomy of a normal, healthy heart. Image from Pixabay. 

Understanding the heart's chambers

The heart is a muscular organ, positioned in the centre of the chest near the lungs.⁵ The upper two chambers are called the left and right atria; the lower chambers are referred to as the left and right ventricles (see Fig. 1).⁵ The heart’s chambers pump blood into your systemic and pulmonary circulatory systems.⁵ Systemic circulation refers to oxygen-rich blood carried from the left ventricle to the arteries, capillaries and tissues throughout the body.⁶ Pulmonary circulation carries oxygen-poor blood from the right ventricle to the lungs, where it is then pumped into the left atrium.⁶ During systemic circulation, the blood picks up waste products such as carbon dioxide and returns to the heart's right atrium through a system of veins.⁶

Role of the atrial septum

During pregnancy, the baby receives oxygen and nutrients from the mother via the umbilical cord.⁶ The septum between the two atria is open, allowing the pulmonary circulatory system to be bypassed via the foramen ovale as the foetal lungs are not yet functioning.^1,5 The foramen ovale is an opening that allows blood to be pumped from the right atrium to the left atrium during foetal development.⁷ Post-birth the atrial septum connections rapidly close, establishing the systemic and pulmonary circulatory systems.⁵ The atrial septum is vital in separating the two circulatory pathways, ensuring oxygenated blood can be delivered to the body’s tissues and is re-oxygenated in the lungs. Failure of the foramen ovale to close causes multiple conditions, including ASD.⁷ 

What is atrial septal defect (ASD)?

Types of atrial septal defects

Ostium secundum ASD

Ostium secundum is the most common type of ASD.⁸ It accounts for 75-80% of ASDs.⁹ The opening that causes this subtype of ASD is in the middle of the atrial septum (wall between upper heart chambers).⁸ This results in oxygen-rich and oxygen-poor blood mixing, which can cause health complications. 

Ostium primum ASD

The second most common type of ASD is the primum defect, which occurs in ~15% of cases.⁹ Primum defects are characterised by the hole in the lower part of the atrial septum, close to the ventricles.⁸ This defect may occur alongside other heart problems at birth.¹⁰

Sinus venosus ASD

Sinus venosus is a rare defect that is classed as superior or inferior, depending on the location. It is found in an area close to the major blood vessels (vena cava) that transport deoxygenated blood back to the heart.⁸ Sinus venosus defects can be located near the entrance to the superior vena cava (the upper part of the wall between the heart chambers) or inferior vena cava (lower part of the wall) of the right atrium and comprise 5-10% of all ASDs diagnosed.^9,11

Coronary sinus ASD

An even rarer form of ASD is coronary sinus, a part of the vein system in the heart.¹⁰ Deoxygenated blood from the heart muscle drains into the right atria via the coronary sinus.⁵ In this ASD (also referred to as ‘unroofing’), part of the wall connecting the coronary sinus to the left upper heart chamber is missing.¹⁰ This creates a channel between the right and left atria, where blood can flow directly between these two chambers.¹

Causes and risk factors

Genetic factors

The causes of ASD in infants are relatively unknown.² Genetic factors combined with environmental influences can play a vital role in CHDs. Down syndrome is linked with CHD, with approximately 40% diagnosed with an atrioventricular septal defect (AVSD).¹² A family history of heart defects can lead to the inheritance of an ASD during the development of the fetus.¹⁰ In some countries, parents sharing a common ancestor may influence the rate of CHD births.¹³ If you are concerned about a pregnancy due to a family member having a heart defect present at birth, please seek advice from a healthcare professional. 

Environmental influences

Exposure to certain risk factors during pregnancy can also increase the likelihood of a heart defect being present at birth. Environmental influences may include:¹⁰

• Smoking
• Drug or alcohol abuse
• Diabetes 
• German measles (rubella)
• Lupus
• Some types of medication (e.g. to treat seizures)

Signs and symptoms

Common symptoms in infants

ASD can be diagnosed during pregnancy, just after birth or later in adulthood.⁸ Physical examination findings in infants depend on the degree of shunting (movement of blood) from the left atrium to the right atrium.⁴ A doctor can check for a heart murmur (an unusual heartbeat) using a stethoscope which could be the only sign that a defect is present.⁸ If the ASD is large causing significant shunting then the following symptoms soon after birth or during the first few months of life can aid diagnosis:^2,8,14

• Shortness of breath during feeding (poor weight gain)
• Fatigue
• Rapid breathing
• Frequent respiratory or lung infections
• Arrhythmias (irregular heartbeats)
• Cyanosis (pale grey or blue lips, tongue or fingernails)
• Swelling in the legs, belly or around the eyes

Potential complications without treatment

If a large ASD is untreated and persists into adult life, it can cause severe health issues including heart failure, leaky heart valves and stroke.⁸ Another complication is pulmonary hypertension, where permanent lung damage occurs due to a higher volume of blood in the right atrium forcing the lungs to work harder.¹⁰ If this persists over several years it can lead to Eisenmenger syndrome.⁸

Diagnosis

Imaging and tests

Following a physical examination, diagnostic imaging can confirm the presence of an ASD. Below is a table summarising some of the frequently used diagnostic tests.  

Treatment options

Monitoring and observation

Treatment of ASDs in infants depends on the size and specific type of heart problem.¹⁴ If a large ASD is diagnosed during pregnancy or soon after birth, monitoring the baby’s heart rate, oxygen levels and growth are essential to determine the best course of treatment. 

Medications

Certain medications may be prescribed for children or be combined with heart surgery to treat severe ASD.¹⁴ General medications for CHDs include:

• Blood pressure drugs
• Diuretics (water pills that increase water expulsion via urine which helps to reduce strain on the heart)
• Heart rhythm drugs (antiarrhythmics) 

Interventional procedures

Catheter procedures

Catheters are thin, flexible tubes that can repair some CHDs using keyhole surgery.¹⁴ This is called cardiac catheterisation, a procedure which involves the insertion of a tube (or tubes) into the groin to reach the heart and pass tools or place a patch on the heart to close the opening.^8,14 

Surgical repair

In some instances, open heart surgery, a heart transplant or foetal cardiac intervention (during pregnancy) may be required to close the hole. Foetal cardiac intervention is rare but can help reduce complications as the baby develops.¹⁴ Less invasive surgery is a much-preferred option to repair a CHD. 

Follow-up care

Following an interventional procedure, most patients will fully recover and will have an improved quality of life. Surgical repair may also require medication to lower the risk of blood clots.⁸ Children with severe ASD may have multiple procedures to cure their heart defect throughout their lives so regular check-ups by a doctor (pediatric cardiologist) are imperative to ensure the success of each surgery.¹⁴ 

Prognosis

Expected outcomes after treatment

Treating ASDs in children using surgical repair or medication is generally a successful course of treatment and is associated with outstanding long-term survival.¹⁵ Minimally invasive surgery reduces the time to full recovery as it removes the need for a large incision. ASD diagnosis of a baby can be extremely concerning for the parents, however, the advances in treatments available for fixing severe defects ensure an excellent prognosis for infants with ASD. 

Prevention and awareness

Role of prenatal care

Preventing an ASD in infants is not always possible however prenatal care is vital to ensure both the mother and the baby are healthy. . Mothers with pre-existing heart conditions or a family history of ASDs will need additional support throughout their pregnancy to prevent complications.¹⁶ Midwives play a vital role as they are often the first healthcare professionals to see expectant mothers with cardiac conditions and can aid management of the health issue.¹⁶ Supplementing with multivitamins containing folic acid during the peri-conceptive period (5-6 month window spanning from just before preconception to post-conception), has been shown to have protective benefits for the foetus and reduce the risk of a CHD.¹⁷ 

Importance of early screening

Early prenatal screening tests (e.g. an ultrasound) are crucial to help identify birth defects or any other health conditions before birth that could complicate the baby’s development.¹⁰ These tests are offered to the majority of women in European countries.³ Healthcare providers need to be aware of the baby’s heart condition for preparation of treatment or cardiac monitoring that may be required immediately post-birth. In some instances, a severe ASD diagnosis in a prenatal test may lead to pregnancy termination.³

Support for families

Resources and support groups

Parents can join online and local support groups to share their experiences and gain insight into the lives of others who have been affected by CHDs. These organisations are dedicated to supporting families and patients with ASD. More information on these organisations is linked below.

• American Heart Association (effects, risks, symptoms, treatment for children with a CHD).
• Children’s Heart Federation (funding research to prevent CHDs).
• Mended Little Hearts (support for infants with CHD and their families).
• Children’s Heart Surgery Fund (a charity)
• Tiny Tickers

Summary

ASD is a common congenital heart defect. Large ASDs may fail to close on their own following a child’s first breath and lead to severe health problems in later life. ASDs are usually asymptomatic and their diagnosis relies on early detection using prenatal screening. This is crucial to ensure rapid treatment and management of the heart defect to preserve the health of both mother and baby. Following birth, observation of the infant for certain signs such as shortness of breath during feeding, a heart murmur and cyanosis can aid diagnosis using imaging tests to confirm the size and specific type of ASD. A range of genetic and environmental factors can influence the development of an ASD during pregnancy such as a family history of CHDs, certain medications, smoking and drug or alcohol abuse. 

Advances in paediatric cardiology have enabled the development of successful intervention procedures that are linked with excellent long-term survival. Raising awareness of ASDs in infants is vital to ensure continuous funding of a vast network of charities, organisations and support groups. The services that this large network offers both parents and children can help guide them through an emotionally and psychologically exhausting situation. Future research in paediatric cardiology may lower the likelihood of an ASD being undiagnosed and persisting into adulthood causing heart problems in later life. 

FAQs

What is an atrial septal defect (ASD)?

An ASD is a heart defect that is present at birth (congenital) due to a hole that fails to close between the wall (septum) that separates the upper chambers (atria) of the heart.

How common is ASD in infants?

ASD is the most common congenital heart defect (CHD). According to the Centres for Disease Control and Prevention (CDC), ASD occurs in 1 in every 769 babies in the United States per year.

What causes ASD in infants?

The exact cause of ASD is unknown, however, multiple genetic and environmental factors can influence ASD development during pregnancy. These include a family history of CHDs, smoking, diabetes, lupus, rubella, drug or alcohol abuse and certain medications. 

What are the signs and symptoms of ASD in infants?

Most ASDs remain undiagnosed as it is often asymptomatic in infants. However, large ASDs may cause swelling, shortness of breath during feeding, slow development, rapid breathing, heart murmur and cyanosis. 

How is ASD diagnosed in infants?

Observation of infants post-birth is vital to spot any of the common signs of an ASD such as hearing a heart murmur with a stethoscope. A paediatric cardiologist may carry out further tests using imaging tools such as an electrocardiogram, echocardiogram or cardiac MRI to confirm the size and specific type of ASD.

What treatment options are available for ASD?

Depending on the severity of the ASD, it can be treated using medication or surgical repair. 

What is the prognosis for an infant with ASD?

If an ASD requires treatment the prognosis in infants is very good, especially if it is detected early. Repair of ASDs has an outstanding long-term survival rate with many patients leading normal, healthy lives.

Can ASD close on its own without treatment?

Yes, if the ASD is small it may close by itself as the child grows without the need for medical intervention. This situation requires constant monitoring and health check-ups to assess the defect.

Are there any long-term effects of ASD in children?

Large, untreated ASDs can persist into adulthood and lead to heart failure, enlargement, pulmonary hypertension and stroke. Early detection and treatment is vital to prevent these complications.

How can parents support a child with ASD?

Parents can ensure their child receives regular medical care, follow treatment recommendations, give emotional support and encourage a healthy lifestyle. 

Is genetic counselling recommended for families with a history of ASD?

Yes, families with a genetic history of CHDs should seek advice from a healthcare professional to understand the potential risks involved with pregnancy.