What is an atrial septal defect (ASD)?

An atrial septal defect (ASD) is a congenital heart defect where there is a hole in the atrial septum, the wall which separates the right and left atria. A small opening between the two atria (foramen ovale) is always present at birth, but usually seals off shortly thereafter. If the natural opening persists, it is called patent foramen ovale, if the opening is bigger than that and involves a defect in the muscular septum, it is called ASD. Each year about 1,966 babies in the United States are born with an ASD. Girls are twice as often affected than boys. 

What symptoms can an ASD cause?

Symptoms can develop in childhood or later in life, depending on the size of the defect. Some may experience shortness of breath, fatigue, heart palpitations, or a decrease in exercise capacity. Patients usually have an audible heart murmur that is caused by the extra blood flow across the pulmonary valve to the lungs. 

Why is an ASD potentially dangerous?

Patients with a big ASD are more likely to develop congestive heart failure or stroke. Because of the excessive flow of blood into the right atrium, right ventricle and lungs, this enlarges the right atrium and right ventricle and increases pressures in the pulmonary artery. An enlarged right atrium can cause arrhythmias. The lung vessels can become stiff and increase the resistance of the pulmonary circulation and result in a so-called Eisenmenger syndrome. Such patients are very sick, acquire a blue tinge to the skin, and are in heart failure.   

When should an ASD be treated?

A significant ASD should always be treated, regardless of the age of the patient. Some of the structural changes in the heart caused by an ASD over time are not entirely reversible. ASD closure before irreversible changes occur is therefore recommended. Most patients, children as well as adults, usually experience marked improvement of their symptoms after ASD closure.