This defect refers to any abnormal development of the endocardial cushions. These cushions control the separation of the parts
of the heart near the tricuspid and mitral valves. It's also referred to as an atrioventricular canal defect or an AV canal
defect. It's a fairly common defect, accounting for about 5% of all congenital heart defects. AVSD is the most common heart
defect to occur in children with Down syndrome. It can also occur with other types of congenital heart diseases like coarctation
of the aorta or tetralogy of Fallot.
The defect involves atria and ventricles that have not separated into their own chambers and mitral and tricuspid valves that
have also not separated. As a result, there is a large hole between the two atria, the two ventricles, and one single atrioventricular
valve instead of separate mitral and tricuspid valves.
AVSD is usually divided into three types: complete, partial, or transitional. A complete AVSD, which is the most severe type,
involves defects in all the parts of the heart controlled by the endocardial cushions. This means there are holes in the atrial
septum and the ventricular septum, which results in an undivided AV valve.
Depending on the type of AVSD, the already oxygenated blood may be recirculated to the lungs, which is inefficient. The left
ventricle also tends to have to work harder, which increases pressure to the lungs. This can cause the lungs to overfill with
blood, potentially causing it to leak into the air around the lungs. This pulmonaryedema can lead to congestive heart failure.
| Atrioventricular Septal Defect |
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| A large hole between the two atria and the two ventricles results in oxygenated blood mixing with deoxygenated blood. Less
oxygenated blood is able to reach the body. The heart has to pump harder to get oxygen to the body, and pressure in the lungs
also increases.
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How is AVSD diagnosed?
The condition is usually identified through a heart murmur. Diagnosis is confirmed by doing an echocardiogram, and possibly
a chest X-ray or electrocardiogram.
Children with this defect are often diagnosed within a week or 2 of birth and managed with drugs, and rarely with pulmonary
artery banding until they are old enough for corrective surgery. Surgery can use patches to close the holes in the atrial
septum or the ventricular septum, and reconstruct the atrioventricular valve.
What is the long-term outlook for children with AVSD?
The outlook is very good in these children following surgery. A leaky mitral valve is a rare complication that may require
re-operation.
