What is AV Canal Defect?

Definition:

Atrioventricular Canal Defect is a combination of several abnormalities in the heart present at birth (congenital abnormalities). This defect includes a hole between the chambers of the heart and problems with the valves that regulate blood flow in the heart. Atrioventricular canal defect may also be called endocardial cushion defect or atrioventricular septal defect.

There are two common types of atrioventricular canal defect — partial and complete. The partial form involves only the two upper chambers of the heart. The complete form allows blood to travel freely among all four chambers of the heart. Both types allow extra blood to circulate to the lungs. Ensuing problems overwork the heart and cause it to enlarge.

Atrioventricular canal defect is often associated with Down syndrome. If left untreated, atrioventricular canal defect may cause congestive heart failure and high blood pressure in the lungs. To correct this defect, doctors often recommend surgery during the first year of life to close the hole and reconstruct the valves.

Signs & Symptoms:

Signs and symptoms of Complete Atrioventricular Canal Defect usually develop in the first several weeks of life. They include:

Difficulty breathing (dyspnea)
Lack of appetite
Poor weight gain
Bluish discoloration of the lips and skin (cyanosis)

If your baby has complete atrioventricular canal defect, he or she may also develop signs and symptoms of congestive heart failure, including:

Fatigue and weakness
Persistent cough or wheezing with white or pink blood-tinged phlegm
Swelling (edema) in the legs, ankles and feet
Swelling of the abdomen (ascites)
Sudden weight gain from fluid retention
Decreased alertness
Irregular or rapid heartbeat

Signs and symptoms of a Partial Atrioventricular Canal Defect may not appear until later in life, often in the 20s and 30s. When they do become noticeable, signs and symptoms are usually related to complications that develop as a result of the defect, such as abnormal heart rhythm (arrhythmia), congestive heart failure and high blood pressure in the lungs (pulmonary hypertension).

Details:

In Partial Atrioventricular Canal Defect, a hole exists in the wall (septum) that separates the upper chambers (atria) of the heart. Also, the mitral valve between the upper and lower left chambers does not close completely (mitral valve regurgitation).

In Complete Atrioventricular Canal Defect, there’s a large hole in the center of the heart where the walls between the upper chambers (atria) and lower chambers (ventricles) meet. Instead of two separate valves — one on the right (tricuspid) and one on the left (mitral) — one large common valve exists between the upper and lower chambers. Often, this valve doesn’t close tightly.

Oxygen-rich and oxygen-poor blood mix through the hole in the septum, and the abnormal valves leak blood into the heart’s lower chambers (ventricles). These problems make the heart work harder, causing it to enlarge.

Risk Factors:

Although the exact cause of atrioventricular canal defect is unknown, several factors may increase the risk of a congenital heart defect:

The baby also has Down syndrome, a genetic condition resulting from an extra 21st chromosome. Close to half of children with Down syndrome have congenital heart disease. Of these, 45 percent have atrioventricular canal defect.
A mother who had German measles (rubella) or another viral illness during early pregnancy.
A parent who had a congenital heart defect.
Excessive alcohol consumption during pregnancy.
A mother who has diabetes.
Taking some types of medications during pregnancy. Medications that increase risk include the acne drug isotretinoin (Accutane) and lithium (Eskalith), which is used to treat bipolar disorder, a condition that causes intense mood swings.

Complications:

Correcting an atrioventricular canal defect helps your child avoid potential complications, such as:

Pneumonia. If your baby has an untreated atrioventricular canal defect, he or she may have recurrent bouts of pneumonia — a serious lung infection.
Enlargement of the heart (cardiomegaly). Increased blood flow through the heart forces it to work harder than normal, causing it to enlarge.
Congestive heart failure. Untreated, atrioventricular canal defect will result in congestive heart failure — a condition in which the heart is unable to pump enough blood to meet the body’s needs.
High blood pressure in the lungs (pulmonary hypertension). When the heart’s left ventricle weakens and can’t pump out enough blood, the increase in pressure backs up through the pulmonary veins to the arteries in the lungs, causing high blood pressure in the lungs.

Although treatment greatly improves the outlook for children with atrioventricular canal defect, some who have corrective surgery may still be at risk of the following associated conditions later in life: leaky heart valves (regurgitation), narrowing of the heart valves (stenosis), heart rhythm abnormalities (arrhythmias), and/or breathing difficulties associated with damage to the lungs (pulmonary vascular disease).

Common signs and symptoms of these complications include shortness of breath, fatigue, fever and a rapid, fluttering heartbeat, among others. In some cases, such as a leaky heart valve, a second surgery may be needed.

With treatment, most kids improve steadily — their appetite increases, they can be more active without tiring as easily, and their growth returns to normal.

Surgery is necessary to correct atrioventricular canal defect. During the procedure, a surgeon closes the hole in the septum with one or two patches. The patches remain in the heart permanently, becoming part of the septum as the heart’s lining grows over it.

For a Partial Atrioventricular Canal Defect, the surgery also involves repair of the mitral valve so it will close tightly. If repair isn’t possible, the valve may need to be replaced instead.

If your baby has Complete Atrioventricular Canal Defect, the surgery also includes separation of the single valve into two valves, one on the left side and one on the right side of the repaired septum. If reconstruction of the single valve into two valves isn’t possible, heart valve replacement may be necessary.

Source: MayoClinic.com