Atrioventricular canal defect

Atrioventricular canal defect (endocardial cushion defect (ECD)) is an abnormal heart condition in which the walls separating all four chambers of the heart, formed incorrectly or entirely missing. This anomaly is a congenital heart defect.

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Causes and risk factors
Endocardial cushion defect occurs during fetal development. Endocardial cushions are two areas of thickening, which eventually are transformed into a partition separating the four chambers of the heart. They also form the mitral and tricuspid valves that separate the atria from the ventricles.

Atrioventricular canal causes several problems:
Increased blood pressure in the lungs. In children with heart disease abnormal blood flows through the holes from the left to the right side of the heart and then into the lungs. More intensive blood flow increases the blood pressure in the lungs.

Irritation and swelling. This is due to increased blood flow in the lungs.

Heart failure. Because the heart has to pump more blood to the lungs, it has to work much harder than usual. Under these conditions, the heart may increase and diminish.

Cyanosis. As the blood pressure in the lungs, blood flow begins to flow from right to left. Poor blood oxygen mixed with oxygenated blood resulting in poor body receives oxygenated blood. This causes cyanosis, or bluish skin.

Complete endocardial cushion defect includes:
atrial septal defect (ASD)
ventricular septal defect (VSD)

In children with complete endocardial cushion defect there is only one large heart valve (common atrioventricular valve) instead of two separate valves (mitral and tricuspid).

Upon partial or incomplete defect present both valves, but one of them (the mitral valve) often has an opening which blood passes in the reverse direction.

Atrioventricular canal is strongly associated with Down syndrome. However, the exact cause of the defect is not known.

Endocardial cushion defect may also be associated with other congenital heart defects, such as:

Transposition of the great vessels

Tetralogy of Fallot

Symptoms in children at an early age may include: fast fatigue, skin and lips bluish color, slow growth and weight gain, frequent pneumonia, lack of appetite, pale skin, rapid breathing and heartbeat, sweating, swollen legs or abdomen (rare), shortness of breath, especially during feeding.

Diagnostics
The child with endocardial cushion defect may show an enlarged heart and heart murmurs. Children with partial DEP, which have only a small atrial septal defect and normal valves, may not have signs or symptoms of the disorder in childhood.

Tests for the diagnosis of early childhood include:
1. Cardiac ultrasound (ECHO, echocardiography) to assess blood flow.
2. An electrocardiogram (ECG), which measures the electrical activity of the heart.
3. Chest X-ray, which shows an enlarged heart.
4. Magnetic resonance imaging (MRI) of the heart, which provides a clear picture of the heart.
5. Cardiac catheterization (coronary angiography) is used in some cases. During the procedure a thin tube (catheter) is placed in the heart, so that the doctor could see a clear picture of blood flow and accurate measurements of blood pressure and oxygen levels.

Treatment
Operation is necessary to close the holes between the chambers of the heart and the total separation of the valve into two separate – the tricuspid and mitral valves. Terms of operations depend on the child’s condition and the severity of congenital blemish. As a rule, the operation is performed in 3 – 6 months years old. When the defect correction may require more than one surgery.

Doctor may also prescribe medication before surgery if condition of a child is very weak. Medicines will help the child gain weight and strengthen the heart muscle before surgery. Recommended medications such as diuretics, inotropic agents (create a stronger contraction of the heart), such as digoxin.

In the case of a complete defect operation must be performed in the first year of the child’s life before there is permanent damage to the lungs. Children with Down syndrome tend to develop lung disease earlier and consequently the early operation is very important for these children.

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