What Is Atrioventricular Canal Defect?

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Atrioventricular canal (AV canal) defect is a problem that exists from birth in which there appears some abnormalities in the heart. There develops a hole between the chambers of the heart and an impairment of the valves that regulate the blood flow in the heart, even during the first weeks of pregnancy. Triscupid and mitral valves, the two valves that separate the upper and lower chambers of the heart form as one big valve that crosses the hole (the defect).

The defect is also known as endocardial cushion defect and antrioventricular septal defect. In the normal scenario, the right chamber of the heart pumps blood to the lungs and the left chamber pumps blood to the rest of the body. A child who suffers from the AV canal defect will have a hole between the two chambers which may cause the blood from the left chamber to flow towards the right chamber. This extra blood, in turn, would flow to the lungs. This leads to higher pressure in the blood vessels in the lungs. This may ultimately damage these blood vessels and children may become cyanotic, causing their lips, skin and nail-beds to exhibit a blue colour.​

There are two types of atrioventricular canal defect. One is a partial form which affects two chambers in the heart and the other is the complete form which involves all four chambers. In both these types, excess blood flows into the lungs. The extra blood can cause the heart and lungs to overwork. This may finally cause the heart to enlarge and the lungs to get congested.


The cause is not known in most cases. But it is a common problem among children who have Down syndrome. Other chromosome problems can also lead to AV canal. The child could inherit the defect from its mother. It could also be an impact of the maternal age.


The symptoms may be different for different children. Some of the common symptoms include fatigue, rapid heart beat, poor weight gain, sweating, difficulty in feeding, rapid or heavy breathing, pale or cool skin. It is always good to consult the child’s physician.


A heart murmur that results from the free blood flow within the chambers due to the defect is one of the first tests in diagnosing the AV canal. Other tests include chest x-ray, ECG, echocardiogram, and cardiac catheterization.


Treatments are based on the child’s age, health, extent of disease, and tolerance. The atrioventricular canal defect can be treated and removed by means of an open heart surgery. Medicines can be used to temporarily help the affected children, but it will not be a permanent cure.

Adequate nutrition and infection control are also important measures in keeping the disease in check.

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