During the first eight weeks of a pregnancy, the fetal heart develops. An atrioventricular canal defect, also known as AV canal defect, occurs at birth when there is an error in the heart’s normal development, resulting in a large hole in the center of the heart. Your doctor may refer to the defect by other names, including endocardial cushion defect or atrioventricular septal defect (AVSD).
An AV canal defect is not a single defect, but rather a group of abnormalities affecting the major structures of the heart—the atria, the ventricles, the septa and the valves. The heart’s upper chambers are known as atria, and the lower chambers are called ventricles. The heart also has a wall (septum) that divides this muscular, fist-sized organ into right and left halves, creating the heart’s four chambers: the left atrium, the right atrium, the left ventricle and the right ventricle.
The heart also has four valves that open and close as blood pushes through the chambers and into the body. The two atrioventricular valves are the mitral valve and the tricuspid valve. These valves are located between the atria and the ventricles.
An AV canal defect can consist of the following structural problems within the heart:
There may be a genetic component to this condition, but science has yet to determine the exact cause. This type of defect is frequently seen in children with Down syndrome.
Untreated AV canal defects can cause serious damage to the heart and lungs. Because of the hole in the heart, blood flow is not properly regulated. Shunting of blood from left to right in the AV canal allows too much blood to flow into the lungs. This increased volume makes the heart work harder than normal and can eventually enlarge the heart muscle. Without treatment, the increased volume of blood flowing into the lungs may also cause congestive heart failure.
Increased blood flow to the lungs and large shunts at the ventricular level, can lead to elevated pressure in the lungs—a condition called pulmonary hypertension. Over time, this increased pressure begins to cause changes to the pulmonary blood vessels, making them thicker and more muscular. These changes can often correct themselves if the heart is repaired early. Left unattended, this can lead to irreversible damage to the lungs.
In children who develop increased pressure in the lungs, some blood starts to mix from the right side of the heart (the oxygen-poor side) into the left side (the oxygen-rich side). One consequence of this mix is that the body receives blood that is lower than normal in oxygen, which can result in a blue discoloration of the skin. The medical term for this is “cyanosis.”
Symptoms of Atrioventricular Canal Defect
The size of the hole in the septal wall and the degree and severity of the valve involvement can influence symptoms of AV canal defects, which may include:
Another clue that can suggest an AV canal defect (or other cardiac abnormality) is a heart murmur—a noise produced by the blood flow through the heart. Not all heart murmurs are problematic, and many can be normal in children. Doctors may perform other tests to determine the nature of a heart murmur.
Your physician may suggest non-invasive tests such as a chest x-ray or an electrocardiogram (EKG). An EKG is a quick, painless measure of the electrical activity of the heart. It offers useful information about the condition of the heart.
Another non-invasive diagnostic tool is an echocardiogram. This ultrasound test uses sound waves to create a picture showing the major structures of the heart, as well as the pumping action of the heart. An echocardiogram also provides valuable information about:
Cardiac catheterization can also diagnose an AV canal defect. During this test, a catheter (a thin tube) is inserted into a blood vessel in the groin. From there, doctors carefully maneuver it through the chambers of the heart, the arteries and veins. The test allows your physician to gain additional information about the pressure and oxygen levels in the various parts of the heart, as well as structural information about the chambers, valves and septa. It is rarely used as the primary diagnostic test in patients with AV canal because the echocardiogram is an easier, non-invasive method. Cardiac catheterization is useful when there are concerns about pulmonary hypertension.
AV canal defects can be surgically repaired at Riley at IU Health. This surgery targets the septal openings and valves and has a high success rate. Individual circumstances determine the right timing for surgery.
Prior to surgery, AV canal defects are managed through combinations of various medications including Digoxin, diuretics and ACE inhibitors. Each of these drugs target different areas.
When the heart does not function efficiently, infants may tire while eating. This limits their ability to gain weight properly. Your doctor may suggest adding fortified nutritional supplements to milk or formula to boost weight gain. A nasogastric feeding tube can also be helpful in addressing weight gain issues in certain children. This tube is inserted in the nose and guided down the esophagus and into the stomach to administer the baby’s feedings.
Your cardiologist can determine which treatment is best for your child, as well as the timing of treatment. The age and health of the child, the seriousness of the defect, the child’s medical history, and other factors are all taken into consideration when choosing the best treatment.
These resources can be helpful for parents and caregivers whose children are diagnosed with congenital heart defects.
Riley at IU Health offers a broad range of supportive services to make life better for families who choose us for their children's care.
This not-for-profit organization provides information and support to adults living with congenital heart disease.
This U.S. government website includes resources to educate parents and caregivers of children with congenital heart disease. It also shares information for the growing population of adults who are living with congenital heart disease.
As part of the National Institutes of Health, the National Heart, Lung and Blood Institute advances research and understanding of heart, lung and blood diseases and shares easy-to-digest information about congenital heart defects.
Researchers at Herman B Wells Center for Pediatric Research are studying early gene transcription factors that affect formation of the heart, including formation of the endocardial cushions. To date, they have identified a unique family of genes that control many aspects of the heart, including the possible development of congenital heart defects such as tetralogy of Fallot, double outlet right ventricle and atrioventricular canal defects.
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