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Endocardial cushion defect (ECD) is an abnormal heart condition in which there is no separation between the chambers of the heart. Essentially, the middle part of the heart is missing. It is a congenital heart disease, which means it is present from birth.

Atrioventricular (AV) canal defect; Atrioventricular septal defect; AVSD

Endocardial cushion defect occurs while a baby is still growing in the womb. The endocardial cushions are two areas of thickening that eventually develop into the wall (septum) that separates the four chambers of the heart. They also form the mitral and tricuspid valves.

The lack of separation between the two sides of the heart causes several problems:

• Increased blood pressure in the lungs. In persons with this condition, blood flows through the abnormal openings from the left to the right side of the heart, then to the lungs. The increased blood flow into the lungs leads to a rise in blood pressure in the lungs.
• Lung irritation and inflammation. Increased blood flow into the lungs causes irritation and swelling.
• Heart failure. Because the heart has to pump more blood to the lungs, it has to work much harder than normal. The heart may enlarge and weaken.
• Lack of oxygen. As the blood pressure increases in the lungs, blood flow starts to move from the right side of the heart to the left. The heart starts pumping oxygen-poor blood throughout the body, and will have to work harder at it. The body will not get enough oxygen.

There are two types of ECD:

• Complete ECD: A complete ECD involves an atrial septal defect (ASD) and a ventricular septal defect (VSD). Persons with a complete ECD have only one large heart valve (common AV valve) instead of two distinct valves (mitral and tricuspid).
• Partial (or incomplete) ECD: Only an ASD is present. There are two distinct valves, but one of them (the mitral valve) is often abnormal with an opening ("cleft") in it, letting blood leak between the two left chambers of the heart.

ECD is strongly associated with Down syndrome. Several gene changes are also connected to ECD. However, the exact cause of ECD is unknown.

ECD may be associated with other congenital heart defects such as:

• Double outlet right ventricle
• Single ventricle
• Transposition of the great vessels
• Tetralogy of Fallot

Symptoms of ECD may include:

• Baby tires easily
• Bluish skin color (the lips may also be blue)
• Failure to gain weight and grow
• Frequent pneumonia
• Lack of appetite
• Pale skin (pallor)
• Rapid breathing
• Rapid heartbeat
• Sweating
• Swollen legs or abdomen (rare in children)
• Trouble breathing, especially during feeding

Signs of ECD may include:

• An abnormal electrocardiogram (ECG)
• An enlarged heart
• Heart murmur
• High blood pressure in the lungs

Children with partial ECD, who have only a small VSD and normal valves, may not have signs or symptoms of the disorder during childhood.

Tests to diagnose ECD include:

• Ultrasound of the heart (echocardiogram) to see blood flow
• An electrocardiogram (ECG), which measures the electrical activity in the heart
• Chest x-ray, which may show an enlarged heart
• Magnetic resonance imaging (MRI) of the heart, which provides a detailed image of the heart through the use of powerful magnets
• Cardiac catheterization (in some cases), a procedure in which a thin tube (catheter) is placed into the heart to see blood flow and take accurate measurements of blood pressure and oxygen levels

Complications from ECD may include:

• Congestive heart failure
• Death
• Eisenmenger syndrome
• High blood pressure in the lungs
• Irreversible damage to the lungs

Certain complications of ECD surgery may not appear until the child is an adult. These include heart rhythm problems and a leaky mitral valve.

All children with congenital heart disease should take antibiotics before dental treatment. This helps prevent complications related to heart infections.

ECD is associated with several genetic abnormalities. Couples with a family history of ECD may wish to seek genetic counseling before becoming pregnant.

Park MK. Pediatric Cardiology for Practitioners, 5th ed. Philadelphia, Pa: Mosby Elsevier; 2008:181-189:chap 12.

Townsend Jr. CM, Beauchamp RD, Evers BM, et al. Sabiston Textbook of Surgery, 18th ed. Philadelphia, Pa: Saunders Elsevier; 2008:1760-1762.