Atrial Septal Defect (ASD)

This condition, commonly called “a hole in the heart,” is an abnormal opening in the wall that separates the left and right atria. These are the heart’s upper chambers. This congenital defect creates abnormal blood flow through the heart. ASD may result in a murmur that can be heard during an exam. It can be diagnosed by an echocardiogram.

Normal Heart

In a normal heart, oxygen-depleted blood enters the right atrium and empties into the right ventricle, which then pumps the blood to the lungs to be reoxygenated. Oxygen-rich blood from the lungs enters the heart’s left atrium and is pumped out to the body through the left ventricle.

Heart With Atrial Septal Defect

In a heart with an ASD, a defect in the wall between the two atria allows oxygen-rich blood to pass from the left atrium to the right atrium. The oxygen-rich blood mixes with oxygen-depleted blood being sent to the lungs. This increases the volume of blood that is being passed through the lungs and returned to the left side of the heart. This inefficiency causes the heart and lungs to work harder.


ASD may cause symptoms such as irregular heartbeat, shortness of breath and fatigue. A child with the condition may exhibit poor growth. However, many patients with ASD have few noticeable symptoms. The problem can go undetected until adulthood.