What is Atrial Septal Defect?
An Atrial Septal Defect (ASD) is a common type of congenital heart defect, affecting about 25% of children. This condition happens when the connection between the right and left sections of the heart, called atria, doesn’t close properly. This can involve actual defects in the dividing wall, or septum, as well as other irregularities that allow the two atria to communicate.
There are five types of ASD, listed from most to least common: patent foramen ovale, ostium secundum defect, ostium primum defect, sinus venosus defect, and coronary sinus defect. Small ASDs often close on their own during early childhood. Large defects that do not close naturally may require non-invasive or surgical procedures to avoid complications like stroke, irregular heart rhythms, and high blood pressure in the arteries of the lungs.
What Causes Atrial Septal Defect?
Atrial septal defects (ASDs) are holes in the wall separating the two upper chambers of the heart. They can occur on their own but are also associated with some specific genetic factors and environmental influences.
ASDs can be a part of genetic diseases passed down through families, like Down syndrome, Treacher-Collins syndrome, Thrombocytopenia-absent radii syndrome, Turner syndrome, and Noonan syndrome. Additionally, babies are more likely to be born with ASDs if a pregnant mother is exposed to rubella or substances like cocaine and alcohol.
ASDs can also be found in genetic disorders that run in families and can be associated with issues that affect the heart’s electrical system. Certain proteins, which help control the development of the heart, are important during this process. For example, the Holt-Oram syndrome is often linked to the TBX5 protein and is characterized by ASDs, heart rhythm problems, and upper limb malformations, especially in the hands. Similarly, changes in the NKX2-5 protein have been tied to ASDs, a condition called Tetralogy of Fallot, heart blockages, and sudden unexpected death during youth.
ASDs can coincide with other congenital heart defects, such as ventricular septal defects. In some individuals with such defects, the opening provided by the ASD plays a vital role in survival by allowing blood to mix between the left and right sides of the heart. This unusual blood flow pattern can be a temporary solution for newborns with more severe heart problems like tricuspid atresia, transposition of the great vessels, and hypoplastic left heart syndrome, until they can get the necessary medical intervention.
Risk Factors and Frequency for Atrial Septal Defect
Over the past 50 years, there’s been a rise in the number of people diagnosed with congenital heart disease and atrial septal defects (ASDs). Congenital heart disease is a condition that’s present from birth. Back in the 1930s, fewer than 1 in 1000 babies were born with this condition. Today, it’s diagnosed in about 9 in 1000 births. Similarly, ASDs were found in fewer than 0.5 in 1000 births between 1945 and 1949. Now, the rate is approximately 1.6 per 1000 births.
But these increases might not mean there’s more disease. Instead, they could reflect advancements in medical imaging and better training for doctors. They’re simply getting better at spotting these heart issues.
- Several factors have been linked to the increase in congenital heart disease diagnoses.
- One key factor is that mothers are now older when they give birth.
- Interesting trends have been observed with regards to wealth and location too. People living in developed countries with higher incomes are more likely to be diagnosed.
Signs and Symptoms of Atrial Septal Defect
An atrial septal defect is a hole in the wall between the heart’s upper chambers. This defect often doesn’t cause symptoms, making it likely to go undetected until adulthood. When symptoms do appear, they may include a specific type of heart murmur, palpitations, difficulty exercising, increased chances of pneumonia, and even an increased risk of death.
In some severe cases, a condition called Eisenmenger syndrome can develop. This is caused by an increase in blood flow through the opening (called a left-to-right shunt), resulting in things like bluish skin (cyanosis), shortness of breath during physical activity, fainting, and an increased likelihood of infections.
- No symptoms in many cases
- Specific type of heart murmur
- Palpitations
- Difficulty exercising
- Increased chances of pneumonia
- Increased risk of death
- Possible development of Eisenmenger syndrome with symptoms like:
- Bluish skin (cyanosis)
- Shortness of breath during physical activity
- Fainting
- Increased likelihood of infections
People with small defects may not have any symptoms, while those with holes between 5 to 10 mm across usually don’t start showing symptoms until their 40’s or 50’s. People with larger defects will often develop symptoms earlier, commonly in their 30’s. Around 20% of adult patients develop a rapid heart rate condition pre-surgery. If a person suffers a stroke or a transient ischemic attack (an episode where blood flow to part of the brain stops briefly) after diagnosis of a blood clot in the body, it may indicate the presence of an atrial septal defect.
Testing for Atrial Septal Defect
Diagnosing the size of a heart defect is key to identifying the right treatment options. The most reliable method for this is an imaging technique called a transthoracic echocardiogram. This imaging technique can measure the size of the defect in the heart, understand how blood is flowing, identify any related abnormalities, assess the structure and health of the heart, estimate lung artery pressure, and determine the ratio of blood flow between the lungs and the body.
Another useful technique for identifying less common heart defects is a transesophageal echocardiogram. In addition to echocardiograms, other methods such as cardiac CT scans and MRI scans can be used. Both of these scans can also examine structures surrounding the heart and inside the chest cavity.
A chest X-ray may not provide a definitive diagnosis, but it can help doctors monitor a patient’s condition by identifying an enlarged heart and lung artery. Exercise testing may also be used to see how the flow of the shunt can be reversed and how patients with lung artery hypertension respond to activity. However, for young patients with small and simple heart defects, a procedure called cardiac catheterization is usually not recommended.
Treatment Options for Atrial Septal Defect
Atrial septal defects, or holes in the wall dividing the heart’s upper chambers, are common congenital heart defects. When these holes are smaller than 5 mm, they often close on their own within the first year of life. However, if the defect is greater than 1 cm, medical or surgical intervention might be required.
If someone with atrial septal defects starts experiencing irregular heartbeats, the first priority is to get those under control and begin anticoagulation treatment to prevent blood clots. Once the rhythm issues are managed, further treatments can be considered. For adults who have small defects and no signs of heart failure, monitoring the situation is usually sufficient. This can be done with an echocardiogram every 2 to 3 years, which allows doctors to evaluate the structure and function of the right side of the heart. If there is a history of transient ischemic attacks or strokes, more active monitoring and potentially surgical intervention is needed.
When it comes to closing an atrial septal defect, there are two options—percutaneous and surgical intervention. This might be needed in cases where there’s been a stroke, a shunt allowing abnormal blood flow, or signs of low blood oxygen levels. Percutaneous transcatheter closure is less risky and is only suitable for certain types of defects, known as ostium secundum defects. This method has a complication risk of 7.2%, compared to a 24% risk with surgical intervention. However, it can lead to complications like irregular heartbeats, blocks in the heart’s electrical signals, heart erosion, and formation of blood clots. Some defects are not suitable for this procedure, including small ones that don’t affect blood flow, other types of defects, and secundum defects with advanced pulmonary hypertension. After a percutaneous procedure, patients need to take antiplatelet medicines for six months to prevent blood clots from forming.
For women with large atrial septal defects and Eisenmenger Syndrome, a condition related to heart defects, pregnancy should be avoided due to increased health risks, including an aggravation of existing high blood pressure in the lungs and a higher chance of developing rhythm disorders.
Surgical closure, the other option, involves sewing a patch over the hole through an incision in the right atrium of the heart.
In conclusion, while many small atrial septal defects will close on their own, larger ones may require medical or surgical intervention, particularly if they lead to serious health problems like pulmonary hypertension, blue skin from poor blood oxygen levels, or vascular issues such as strokes.
What else can Atrial Septal Defect be?
When doctors look at heart diseases that are present from birth, also known as congenital heart diseases, they usually consider various conditions. Some examples of these conditions include:
- Atrioventricular septal defect (a condition where there’s a hole in the wall between the heart’s chambers)
- Ventricular septal defect (this is a defect where there’s a hole in the wall separating the two lower chambers of the heart)
- Cyanotic congenital heart disease (these are heart defects where there’s not enough oxygen in the blood, some types are:
- Sinus venosus defects and coronary sinus defects (these involve the veins that bring blood back to the heart)
- Total anomalous pulmonary venous return (when the veins bringing blood from the lungs back to the heart are not connected properly)
- Pulmonary stenosis (a condition that narrows the passage from the heart to the lungs)
- Truncus arteriosus (when there’s only one vessel instead of two separate ones to carry blood from the heart to the body and lungs)
- Tricuspid atresia (this is when the tricuspid heart valve hasn’t formed properly )
Keep in mind that it’s essential for doctors to run in-depth tests when considering these possibilities to make a correct diagnosis.
Possible Complications When Diagnosed with Atrial Septal Defect
Here are some of the conditions that might occur:
- Atrial dysrhythmias (irregular heart rhythms)
- Pulmonary arterial hypertension (high blood pressure in the lungs)
- Right-sided congestive heart failure (a condition where the right side of the heart doesn’t pump blood as well as it should)
- Transient ischemic attack/stroke (a mini stroke that usually lasts for a short time)
- Eisenmenger syndrome (a type of heart disease)
