What is Atrioventricular Septal Defect?
The atrioventricular septal defect is a type of heart defect that someone is born with. It involves varying levels of damage to the walls of the heart, specifically the walls between the heart’s chambers and the openings connecting these chambers. This heart defect can take two forms: a partial and a complete defect. A partial one includes a hole in the area between the upper heart chambers, separated heart valves with a shared junction, a hole in the area near the bottom heart chambers, and a slit-like opening in the mitral valve which controls the blood flow in the heart. On the other hand, a complete defect involves a shared heart valve and an unrestricted hole in the bottom heart chamber.
The frequency of people born with an atrioventricular septal defect ranges from 0.24 to 0.31 out of 1000 live births, with equal chances of boys and girls developing it. Moreover, this heart defect is highly linked to Down’s syndrome. Even though the success of surgical repair for this heart defect is affected by other existing malformations like underdeveloped heart muscles and Down’s syndrome, advances in surgical treatments for this heart defect over the past years have greatly improved the survival rate in the long term. This review will delve into the cause, commonness, how it affects the body and the importance of managing this heart defect, as well as possible complications and its overall significance to health.
What Causes Atrioventricular Septal Defect?
The atrioventricular septal defect, a heart condition, is usually caused by changes in a person’s genes. Often, it’s found alongside certain genetic disorders. For example, among every six people with Down syndrome, usually, someone will also have an atrioventricular septal defect. This is likely due to a specific gene related to both Down syndrome and heart defects.
Besides Down syndrome, other genetic disorders have been linked to the atrioventricular septal defect. These include CHARGE syndrome, Ellis-van-Creveld syndrome, Smith-Lemli-Opitz syndrome, and a condition linked to the short arm of chromosome 3. But you don’t need to have a syndrome to inherit this heart defect; some people get it because of a dominant gene passed down through their family.
Lastly, certain pregnancy conditions like diabetes and obesity can also increase the risk of having a baby with an atrioventricular septal defect without any other accompanying syndrome.
Risk Factors and Frequency for Atrioventricular Septal Defect
An atrioventricular septal defect (also known as a hole in the heart), occurs in around 0.24 to 0.31 out of every 1,000 babies born. It is responsible for about 3% of all heart deformities present at birth. Although both boys and girls can have this defect equally, some evidence suggests there might be a slightly higher amount in girls, with a ratio of 1.3 to 1. This ratio is particularly noticed in children with Down syndrome.
Signs and Symptoms of Atrioventricular Septal Defect
Atrioventricular septal defects are heart conditions that present differently depending on the type of defect, how serious the shunt (abnormal connection) inside the heart is, and any other heart deformities a person may have. In infants with a complete atrioventricular septal defect, which is a hole in the wall that separates the top two chambers of the heart, early signs often include breathing issues and right heart failure. This happens because a large amount of blood is sent to the lungs instead of the body, as the resistance to blood flow in the lungs drops after birth. If the infant also has issues with the heart valves, uneven chambers of the heart, or a narrow aorta, heart failure can develop even quicker.
Those with a partial atrioventricular septal defect, meaning the hole is less pronounced, typically do not show symptoms early on if they don’t have other severe heart deformities and minimal heart valve leakage. These cases are usually discovered by chance due to certain signs such as an abnormal heart murmur and a constant splitting of the second heart sound due to the hole in the heart.
The symptoms of heart failure in infants may be feeding struggles, excessive sleepiness, lethargy, and not gaining weight or growing at the expected rate, while older kids might complain of shortness of breath.
Doctors look out for signs of heart failure, such as:
- Rapid breathing and heartbeat
- A unique sound (“gallop”) in the heart rhythm
- Crackling sounds on listening to the chest
- Raised neck veins
- Enlarged liver that is tender to touch
- Constant splitting of the second heart sound because of the hole in the heart
- Heart murmur throughout the heartbeat due to leaky heart valves
- Heart murmur due to too much blood going through the pulmonary valve
- Heart murmur during the resting phase of the heartbeat due to increased flow through the tricuspid valve.
In a general check-up, doctors may spot a bluish skin color when there’s a reversed blood flow (known as Eisenmenger syndrome) and unusual physical features if the patient has associated syndromes.
Testing for Atrioventricular Septal Defect
During pregnancy, a screening called an antenatal ultrasound is typically used to check for a heart condition known as an atrioventricular septal defect. This test focuses on a part of the heart called the “four-chamber view.” It looks for a shared valve between heart chambers and any irregularities in the walls separating the heart’s upper or lower chambers. However, this method isn’t always very effective in detecting the condition.
After the baby is born, further evaluations can be done:
1. Chest X-ray: An X-ray can show if the baby’s heart is larger than usual and if there’s too much blood flow to the lungs. These symptoms are especially common if the valves between the heart chambers aren’t working properly.
2. Electrocardiogram (ECG or EKG): This test checks the heart’s electrical activity. It can pick up on abnormalities like an unusual upward route of electrical signals through the heart, an overly muscular right side of the heart, and delays in the electrical signals that regulate heartbeat. Some other related issues it might spot are an unusual upward direction of specific electrical waves and a partial blockage of electrical signals to the right side of the heart.
3. Echocardiogram: This is a more detailed ultrasound of the heart. It can flag several irregularities including issues with the heart’s valves, unusual heart muscle positions, a mismatch in size between the left-side sections of the heart, a hole in the upper heart wall, a hole in the lower heart wall inlet, and other associated heart issues.
4. Cardiac Magnetic Resonance Imaging (MRI): This test gives findings similar to an echocardiogram but is even more precise when it comes to measuring defect sizes and assessing the leakiness of the valve separating the heart chambers.
Treatment Options for Atrioventricular Septal Defect
The treatment of atrioventricular septal defects, which are abnormalities related to the heart’s structure, is split into two categories – medical and surgical treatment.
Medical treatment might include the use of medication like diuretics and vasodilators to relief heart-related symptoms as a result of these defects. These drugs lower the strain on the heart and can relieve discomfort related to heart failure and lung congestion. Patients might also experience complications like problems swallowing and failure to grow and develop properly, which can be managed with a special feeding tube and a high-calorie diet. Typically, doctors aim to optimize the patient’s condition with these interventions before planning for surgery.
Surgical correction is generally considered the definitive treatment for atrioventricular septal defects. However, this procedure has its challenges, including a mortality rate of 3%, even with advanced surgical techniques. Additionally, patients may face significant risks after the surgery, such as residual shunts, valve regurgitation, obstruction, abnormal heart rhythm, among others.
Before surgery, doctors analyze pre-operative images and data on the patient’s blood flow to choose the best surgical procedures, aiming to minimize repeat surgeries and potential complications post-surgery. Some studies have indicated a high rate of recurrent procedures – up to 18.2% in 15 years after the initial correction. Several factors, like dysplastic left atrioventricular valves, failure to close clefts, and other heart deformities can increase the likelihood of requiring more surgeries.
In cases of complete atrioventricular septal defects, it’s usually best to perform surgery in early infancy to prevent lung complications. If the defects are incomplete, the timing of the repair can be slightly delayed if the patient isn’t showing symptoms.
The preferred method of repair for partial defects includes patch closure and valvuloplasty whilst for balanced complete defects, early primary repair using two patch closure techniques is preferred. This is because using only one patch has shown to increase chances of recurrent procedures due to complications. Pulmonary artery banding is rarely used in these cases, nowadays.
If the defects are unbalanced, the repair technique might involve single ventricle palliation with staged biventricular repair or primary biventricular repair.
What else can Atrioventricular Septal Defect be?
In trying to diagnose AVSD (atrioventricular septal defect), there are other heart conditions that can show similar symptoms. This includes conditions like an atrial septal defect (a hole in the wall between the heart’s upper chambers), an isolated ventricular septal defect (a hole in the wall between the heart’s lower chambers), and Tetralogy of Fallot (a combination of four heart defects present at birth).
In these heart conditions, signs of heart failure, such as shortness of breath, fatigue, and swelling in the legs, ankles and feet, together with an enlarged heart, are typically seen. One effective way to tell the difference between AVSD and these other conditions is by using an echocardiogram, which is a test that uses sound waves to create pictures of the heart’s chambers, valves, walls and the blood vessels attached to the heart.
What to expect with Atrioventricular Septal Defect
The outcomes for untreated atrioventricular septal defect, a heart condition, can be severe. Roughly half of the patients, typically infants, may not survive. This can often be due to heart failure or lung infections. If these children manage to live beyond their first year, they may still go on to develop permanent lung vascular disease, leading to further complications.
Nevertheless, those who have surgical repair stand a much better chance of survival. Approximately 90% of these patients survive for about 15 years post-surgery. However, a small percentage (9% to 10%) may need additional surgery within those 15 years.
Possible Complications When Diagnosed with Atrioventricular Septal Defect
AVSD, or atrioventricular septal defect, can lead to several complications. Many of these complications relate to issues like blood flowing incorrectly within the heart or blood backflow due to defective heart valves. The consequence of these problems is mainly a stress on the right side of the heart and the symptoms of heart failure, such as breathing problems and fatigue. These symptoms are often noticeable at a very early age and contribute to the high mortality rate in infancy.
If this defect is not corrected early on, the incorrect blood flow can cause a severe lung disease leading to high blood pressure in the lungs and Eisenmenger syndrome, a heart condition arising from untreated heart defects.
The backflow of blood can also lead to an enlargement of the upper heart chamber or the atrium, causing it to work harder than normal. This can then lead to heart rhythm disorders. Other complications can include poor feeding leading to malnutrition and making it hard for the child to grow and develop normally.
Common Complications of AVSD:
- Incorrect blood flow within the heart
- Symptoms of heart failure at a very early age
- High mortality rate in infancy
- Severe lung disease if the defect is not corrected
- Enlargement of the upper heart chamber
- Heart rhythm disorders
- Poor feeding causing malnutrition
- Difficulty in growing and developing normally.
Preventing Atrioventricular Septal Defect
If you need to diagnose a condition called an atrioventricular septal defect, a heart specialist (also known as a cardiologist) can help. They usually use specific symptoms of heart failure and checks, including listening for any unique heart sounds or ‘murmurs,’ as clues to this condition. On top of that, the cardiologist may recommend several tests to further confirm their diagnosis.
These tests can include:
A chest x-ray: Produces an image of your heart and lungs.
An Electrocardiogram (or ECG): This helps identify any strange electrical behaviour in your heart.
An Echocardiogram: Uses soundwaves to form an image of your heart, letting doctors check its internal structure and different components.
Cardiac catheterization: Measures blood pressure and oxygen concentration within your heart, helping the cardiologist identify if blood is being directed incorrectly within the heart.
If you have an atrioventricular septal defect, it will likely need to be treated through surgery, usually within the first year of life. In some cases, doctors may prescribe medicine to lessen heart failure symptoms. Medications can include diuretics that help remove extra water from your body through the urine and pills that allow blood vessels to expand, reducing resistance within these vessels.
