ASD (Atrial Septal Defect)

ASD (Atrial Septal Defect) refers to a defect (hole) in the interatrial septum-the structure that separates the two atrial chambers of the heart.

Normally in the intrauterine life there is an opening in the interatrial septum which allows blood from the right atrium to flow into the left atrium and then to the left ventricle.

This opening is called foremen ovale. This is absolutely essential as the fetus cannot inhale atmospheric oxygen and is dependent on oxygen delivered by maternal blood.

Soon after birth the pressure in the right side of heart decreases and the opening in the interatrial septum closes.

There are three types of atrial septal defect.

• Ostium secundum type is the most common. The term ASD unless otherwise qualified usually refers to this. The defect is situated in the middle of the interatrial septum in the region of foremen ovale. It is more common is females than is males.

• Sinus verosus type is situated high in the septum. This type is usually associated with abnormal drainage of the blood coming from the lungs. This is the least common type.

• Ostium primum. This defect is situated in the lower part of the septum. This is also associated with other abnormalities of the atrioventricular valves.

Symptoms and signs: Babies with atrial septal defect usually do not have any problem. The condition is detected on routine check up. Cyanosis does not occur in uncomplicated atrial septal defect.

Older children may develop fatigue easily. If left untreated some children develop pulmonary hypertension. Rarely right to left shunt can occur due to severe pulmonary hypertension resulting in cyanosis. A murmur may be heard over the left upper chest due to increased blood flow across the pulmonary value.

X ray may reveal enlargement of heart and increased pulmonary vascular markings.

Echo with color Doppler will confirm the diagnosis and detect any other associated abnormalities.

Spontaneous closure is less common unlike in VSD. Surgery is indicated to prevent complications like pulmonary hypertension and arrythmias (abnormal heart beat). Infective endocarditis is not common in atrial spetal defect.

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