Atrial Septal Defect Explained: Causes, Symptoms, and Treatment Insights

14 March,2024

Most of us have heard about a disorder in which there is a hole in the heart. Did you know it is medically termed as an atrial septal defect or ASD? ASD is one of the most common congenital (birth) heart defects, accounting for ~19% of all congenital cardiac anomalies. In India, approximately 25% of infants are born with atrial septal defects. Only some people require treatment, as most of the defects resolve on their own in the first year. However, if the hole does not close itself, surgical intervention is required. 

It is not necessary for a baby to develop symptoms of ASD as soon as he or she is born. Sometimes, the symptoms are so mild that they become difficult to identify until adulthood. Read the blog further to learn complete details about the disease, its symptoms, diagnosis, and treatment. 

What is an Atrial Septal Defect?

An atrial septal defect is marked by an opening in the wall (septum) separating the heart's upper right and left chambers (atria). During pregnancy, several openings in the heart occur, which close as the baby develops. Some of them even close after the child is born. However, if these openings do not close, a hole is created, which increases blood flow to the lungs.

If left untreated, an ASD can cause the heart and lungs to work more and even damage the lung arteries. Surgery is usually recommended to treat large ASDs.

There are four types of ASDs:

• Secundum: The most common type of ASD in which the hole is present in the middle of the wall.
• Primum: A hole is present at the lower part of the septum.
• Sinus Venosus: A rare type of ASD in which the hole is at the upper part of the septum.
• Coronary Sinus: Another rare type of ASD in which the wall between the coronary sinus and the upper left atrium is missing.

What are the Signs and Symptoms of Atrial Septal Defects?

Atrial septal defects are present from birth. However, if the defect is not large enough (<5mm), it may not affect the functioning of the heart and lungs. Small ASDs do not show any distinctive signs and symptoms.

ASD symptoms in children: A child with ASD shows heart murmurs as the most prominent symptom. Other signs include being underweight, growth delays, and recurrent respiratory infections. Some of the rare symptoms are arrhythmias, trouble breathing, and fatigue.

ASD symptoms in adults: Atrial septal defect symptoms in adults can be delayed until the age of 40. The extent of damage to the heart and lungs decides the symptoms ASD will show. Typical signs in adults include:

• Fatigue
• Shortness of breath
• Heart palpitations
• Tachycardia (fast heartbeat)
• Blue skin coloring (cyanosis)
• Swelling in limbs

How is ASD Diagnosed?

ASD can be diagnosed in infancy, childhood, or even adulthood, depending on its size and severity. Various diagnostic tools and tests are used to identify ASD:

• Physical Examination: During a routine physical exam, a doctor might detect a heart murmur, which can indicate the presence of an ASD.
• Echocardiogram (Echo): This is a primary imaging test that helps diagnose ASD. It uses sound waves to make a detailed picture of the heart's chambers and valves, allowing doctors to visualize the abnormal opening.
• Electrocardiogram (ECG or EKG): An ECG records the heart's electrical activity, helping to identify any abnormal rhythms or strain on the heart the defect causes.
• Chest X-ray: A chest X-ray can provide additional information about the size and shape of the heart, which ASD can affect.
• Cardiac CT Scan and MRI: Patients with rare or least common ASDs are usually diagnosed using a heart MRI or cardiac CT scan.
• Transesophageal Echocardiography (TEE): TEE is an ultrasound done through the esophagus. It helps identify the location, shape, and size of the ASD.
• Cardiac Catheterization: In some cases, a cardiac catheterization procedure may be necessary to confirm the diagnosis. During this procedure, the cardiologist will insert a catheter (thin tube) into a blood vessel, guiding it to the heart to take measurements and images.
• Transthoracic Echocardiography (TTE): TTE helps in evaluating pulmonary hypertension and left to right shunting of the blood, which is caused by ASDs.

What are the Causes and Risk Factors of Atrial Septal Defect?

The precise cause of ASD is often unknown, but it is a congenital condition, meaning it occurs during fetal development. Several factors may contribute to the development of ASD:

• Genetic Factors: Evidence suggests a genetic component to congenital heart defects like ASD. If a parent has a congenital heart defect, the risk of their child having one increases. Some genetic mutations associated with atrial septal defect affect the TBX5 and NKX2.5/CSX genes.
• Chromosomal Abnormalities: Certain genetic conditions, such as Down syndrome, are associated with a higher occurrence of ASD.
• Environmental Factors: Factors such as infections like rubella during pregnancy, exposure to certain medications, or maternal alcohol or drug abuse can increase the probability of ASD.
• Multifactorial Causes: In many cases, ASD is likely due to a combination of certain environmental factors and genetic predisposition.

Although most of the atrial septal defects occur spontaneously and without a particular reason, several factors increase the chances of an infant being born with ASD, including:

• Family History: Individuals with a family history of congenital heart defects, including ASD, have a higher risk.
• Maternal Age: Older Mothers, particularly those over the age of 40, have a slightly higher risk of having a child with ASD.
• Maternal Health Conditions: Certain maternal health conditions, such as diabetes or obesity, may increase the risk of ASD in the offspring.
• Medications: Some medications taken during pregnancy, particularly certain anti-seizure medications and medications for acne, have been associated with an increased risk of ASD.
• Environmental Factors: Exposure to environmental factors during gestation, such as smoking, alcohol, or infections like rubella, can increase the risk.

How is ASD Treated?

There is a ~80% chance that a small ASD or hole in the heart will close within the first 18 months of life. If the hole does not close after three years, the cardiologist will recommend medical/surgical intervention. The type of treatment will depend upon the size of ASD and how it affects the heart and lungs. The standard treatment approach for ASD includes:

Medicines for ASD Management: 

Currently, no medicines can repair or close atrial septal defects. The cardiologist might prescribe a few drugs to manage symptoms. These include:

• Beta-blockers to normalize heartbeat
• Blood thinners and anticoagulants to prevent blood clots
• Diuretics to reduce fluid build-up in the lungs

Cardiac Catheterisation: 

• Small ASDs are treated with cardiac catheterization, in which a thin tube or a catheter enters the body through the blood vessels in the legs. No incision is needed in the chest. 
• The interventional cardiologist will then move the catheter up to the heart and place a unique device (septal occlude) to close the hole. 
• With time, heart tissue grows over the device and becomes a part of the body. 
• Before cardiac catheterization, the cardiologist checks the shape and size of the defect and measures the blood flow and pressure in the heart. This helps decide the most suitable size of the implant.
• It is a non-surgical treatment that is suitable for small ASDs and has a shorter recovery time.

Open Heart Surgery: 

• For larger ASDs and those present close to the heart's walls, device closure might not be possible. Cardiac surgeons manage such ASDs using open-heart surgery.
• The procedure involves a surgeon cutting open the chest and then stitching the hole in the upper chambers of the heart closed.
• They might use tissue from the pericardium (the membrane covering the heart) or sew a patch made of surgical material (Gore-Tex) over it. 
• With time, the tissue of the heart grows over the patch/stitches.
• The chest scar will heal within a few weeks, and antibiotics will be prescribed to prevent infections post-surgery.

Traditional open heart surgeries are now replaced with minimally invasive and robotic heart surgeries. They offer smaller incisions, better results, quicker recovery, and fewer complications.

What are the Complications of ASD?

Minor atrial septal defects are not likely to cause any complications. However, more significant and long-term ASDs can have the following consequences –

• Swelling in veins of limbs, neck, and liver
• Increased blood flow to the right atrium and lungs (pulmonary overcirculation) 
• Pulmonary congestion
• Increased chances of lung infections
• Pulmonary hypertension
• Right ventricular weakening 
• Irregularities in the heartbeat
• Heart infection (endocarditis)
• Heart failure
• Stroke

To Conclude

In conclusion, atrial septal defect (ASD) is a congenital heart defect with various causes, including genetic factors, environmental influences, and maternal health conditions. Getting to know that you have a hole in the heart can be an alarming experience. It's more daunting to know if your child has it. However, with the help of modern medicine, ASDs are now effectively managed with various techniques. And you or your child might not require surgery as most ASDs resolve on their own. Talk to expert cardiologists who will help you decide the best course of treatment for you. With appropriate treatment, individuals with ASD can lead healthy lives and reduce the risk of complications.