Endocardial Cushion Defect (also called atrioventricular (AV) canal or septal defects)


Condition Description

Endocardial cushion defects are congenital heart conditions that occur early in fetal life due to improperly developed heart tissue in the center of the heart (the endocardial cushion area of the heart). This results in a range of defects that are included in this category of endocardial cushion defects.

These include conditions such as atrioventricular canal (called AV canal), atrial septal defects (ASDs), ventricular septal defects (VSDs), and conditions involving the valves within the heart (the AV valves). There are 2 general categories of endocardial cushion defects: the complete form of endocardial defect (involving atria, ventricles and valves), and the partial form of endocardial defect (typically involving the atria only). These conditions have unique characteristics, and each child's heart structure is quite unique within this category of disorders. In addition to holes between the chambers of the heart, the valves may be improperly placed or the leaflets of the valves may not be completely formed for good closing function.

The symptoms will vary greatly, depending on the size and location of the defects. Partial defects may not be discovered until later in life because they cause few symptoms. The complete form of the endocardial defects can severely affect a baby's health. Because the left side of the heart is the stronger pump, blood that has received oxygen typically passes through the holes between the chambers (called left-to-right shunt), overloading the right side of the heart. The problems with valve closure can also overload the heart.

Some symptoms include back-pressure into the lungs (pulmonary hypertension), congestive heart failure, heart enlargement (cardiomegaly), difficulty feeding due to fatigue, frequent respiratory infections, and slow growth. Prolonged pulmonary hypertension can permanently damage the delicate blood vessels of the lungs, so it is very important to treat endocardial cushion defects promptly and effectively.


This rare condition makes up about 3% of children who have congenital heart disease. Sixty to seventy percent of children with these defects have the complete form of endocardial cushion defect.

Common Associated Conditions

More than half of children who have the complete form of the endocardial defect have Down syndrome. These conditions can also be associated with an absent spleen (called asplenia) or the presence of multiple spleens.

Short-term Treatment and Outcomes

The baby will first receive a chest x-ray, echocardiogram and cardiac catheterization (threading a thin plastic tube visible on x-ray into the vessels and heart to view the heart anatomy and pressures). Medications will be given to relieve the congestive heart failure. Typically digoxin is given to strengthen the heart function and diuretics will be used to remove excess fluid from the circulation and thus reduce the pumping load on the heart.

Babies with the partial endocardial cushion defects will not have surgery for several years if their symptoms are minimal to allow the heart to grow. They will be closely observed by cardiologists in order to choose the very best time for surgery when the baby's health is stable and before any lung damage occurs.

There are several ways endocardial cushion defects can be treated. Typically a Dacron patch is used to close the holes in the atrial and ventricular walls and the AV valve is repositioned and/or repaired. A few babies have such severe symptoms that a heart-lung transplant is the best option.

Long-term Treatment and Outcomes

Individuals with congenital heart defects will typically require antibiotics when they have dental work because the bacteria in the mouth can circulate through the blood and cause infection in the heart structures (endocarditis). They will need to be followed long-term by cardiologists to be sure that any complications or new conditions are quickly detected and treated.

Common Complications

Undetected partial endocardial defects cause no symptoms until adulthood, when they may cause congestive heart failure and problems with an irregular heart rate or rhythm (atrial arrhythmias). Sometimes a child will need a mitral valve replacement in the future if this important valve becomes less functional as years go by. As with all major congenital heart conditions, the complications include infection of the heart (called endocarditis). Endocarditis can occur after surgery or in the future when bacteria become lodged in the heart's scar tissue and set up infections.

There can also be problems long-term with the heart's rate and rhythm (called cardiac arrhythmia) since the nerve fibers that cause the heart muscle to contract run through the wall of the heart that divides the chambers. Over time scarring can cause arrhythmias and sometimes pacemakers are needed to provide a strong and steady heartbeat. Long-term damage to the lungs (pulmonary complications) may also affect individuals in childhood and later life.

Implications for Children's Development

The effect of endocardial cushion defects on a child's life can vary greatly depending on how severe the symptoms are. There may be minimal effect and very successful surgery with totally normal development. Other children have considerable difficulty with symptoms affects growth, energy, resistance to infection and overall physical development. Children with heart defects who do not have genetic conditions such as Down syndrome can have normal intellectual development. Social and emotional development can be affected by frequent illnesses and hospitalizations.

For more information about Atrioventricular septal defect (endocardial cushion defect), including resources for parents and general information about congenital cardiac conditions, visit the following websites:

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