Atrial Septal Defect

Description of the Disease

The heart is a muscular organ consisting of four chambers: the right and left atria and the right and left ventricles. The atria are the upper chambers, while the ventricles are the lower chambers. The right and left sides of the heart are separated by muscular walls known as the atrial and ventricular septa.

Normally, oxygen-poor (venous) blood enters the right atrium, passes into the right ventricle, and is pumped through the pulmonary artery to the lungs, where it becomes oxygenated. Oxygen-rich blood then returns to the left atrium, flows into the left ventricle, and is pumped through the aorta to supply the body’s tissues.

An atrial septal defect (ASD) is a congenital heart defect characterized by an opening in the atrial septum, allowing blood to flow between the left and right atria (a left-to-right shunt). Because pressure in the left atrium is normally higher than in the right atrium, oxygen-rich blood flows from the left atrium into the right atrium. This results in increased blood flow through the right side of the heart and the lungs, causing enlargement of the right atrium and right ventricle over time. If left untreated, prolonged overload may lead to dilation of these chambers and impaired heart function.

Atrial septal defects account for approximately 8% of all congenital heart defects.

Risk Factors

An atrial septal defect is a congenital condition that develops before birth. Although its exact cause is often unknown, genetic factors are believed to play a role, as congenital heart defects may occur in multiple members of the same family. The risk is also increased if the mother contracts rubella during pregnancy or is exposed to harmful substances such as alcohol or recreational drugs.

Symptoms

Symptoms depend on the size of the defect and the amount of blood flowing through it. As pressure in the pulmonary circulation increases, symptoms generally become more pronounced. Most newborns with an atrial septal defect have no symptoms. Small defects may remain unnoticed until childhood or even adulthood.

Common symptoms include:

• Shortness of breath during physical activity.
• Pale skin.
• Fatigue and weakness.
• Frequent respiratory infections.

Diagnosis

Diagnosis begins with evaluation of the patient’s symptoms and a physical examination. A heart murmur may be detected during cardiac auscultation. Additional diagnostic tests include:

• Electrocardiography (ECG) to identify signs of right heart enlargement or overload.
• Chest X-ray to assess enlargement of the right-sided heart chambers.
• Echocardiography, the primary diagnostic test, to determine the location, size, and hemodynamic significance of the defect.
• In selected cases, cardiac catheterization or angiography may be performed for further evaluation.

Treatment

In infants and young children, small atrial septal defects may close spontaneously, so careful observation may be recommended. Medications may be used to relieve symptoms when necessary. Very small defects that do not cause symptoms or affect heart function may require no treatment.

However, many atrial septal defects require closure to prevent long-term complications. This is usually achieved through surgical repair using a patch made from the patient’s own pericardium or a synthetic material. In suitable cases, the defect can also be closed using a catheter-based transcatheter device.

Source | Author Doctor Nikas Samuolis, reviewed by Prof. Virginijus Šapoka | Vilnius University | Faculty of Medicine | Head of the Department of Internal Medicine, Family Medicine, and Oncology