Atrioventricular Septal Defects
(Atrioventricular Canal Defect; Endocardial Cushion Defect)
(See also Overview of Heart Defects.)
Atrioventricular (AV) septal defect is a combination of heart defects. These include a hole in the wall that separate the upper chambers of the heart (atrial septal defect), a single valve separating the upper and lower chambers of the heart (instead of two valves) and sometimes a hole in the wall separating the lower chambers of the heart (ventricular septal defect).
Children who have no defect in the ventricle or only a small defect may have no symptoms.
If the ventricular septal defect is large, infants may have difficulty breathing while they are eating, poor growth, a rapid heart rate, and sweating.
The diagnosis is suspected based on a typical heart murmur that a doctor can hear through a stethoscope and is confirmed by echocardiography.
Defects are repaired with surgery.
Atrioventricular septal defects account for about 5% of birth defects of the heart.
Most infants with the complete form have Down syndrome. Atrioventricular septal defect is also common among infants who are born without a spleen or with multiple small spleens.
An AV septal defect may be
Complete, with a large ventricular septal defect
Transitional, with a small or moderate-sized ventricular septal defect
Partial, with no ventricular septal defect
Complete atrioventricular septal defect often causes a large left-to-right shunt, which means some blood that has already picked up oxygen from the lungs goes through the hole and back to the lungs. These infants may develop heart failure (see Figure: Heart Failure: Pumping and Filling Problems), which causes symptoms such as rapid breathing, shortness of breath while eating, poor weight gain, and sweating) by age 4 to 6 wk. Eventually, the blood vessels between the lungs and the heart may develop high blood pressure (pulmonary hypertension) and lead to heart failure (Eisenmenger syndrome).
Children with transitional AV septal defects may have no symptoms if the ventricular defect is small. Children with larger defects may have signs of heart failure.
Partial AV septal defects do not usually cause symptoms during childhood unless valve leakage (regurgitation) is severe. However, symptoms (eg, exercise intolerance, fatigue, palpitations) may develop during adolescence or early adulthood. Infants with moderate or severe valve regurgitation often have signs of heart failure.
Diagnosis is suggested by a doctor's findings during an examination of the infant. ECG may give an important clue to help make this diagnosis. Chest x-ray may be done to look at the size of the heart and the blood flow to the lungs.
Echocardiography is done to confirm the diagnosis and provide details regarding the size of the defect and the amount of blood that is leaking through the valves. Sometimes cardiac catheterization is done if doctors need additional information about the severity of the defects before they plan treatment.
Because most infants with complete atrioventricular septal defect have heart failure and failure to thrive, these defects are usually repaired with surgery when the child is 2 to 4 months of age. Even if infants are growing well and do not have symptoms, surgical repair is usually done before the infant is 6 months old to prevent development of complications.
For children with a partial defect and no symptoms, surgery is done when the child is older, usually between age 1 year and age 3 years.
If the infant develops heart failure before surgery is done, doctors give drugs such as diuretics, digoxin, and angiotensin-converting enzyme inhibitors to help manage symptoms before surgery.
Some children need to take antibiotics before visits to the dentist and before certain surgeries (such as on the bowel or bladder). These antibiotics are used to prevent serious heart infections called endocarditis.