Atrioventricular canal defect symptoms & causes in children

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Contact the Complex Biventricular Repair Program

It’s natural for you to be concerned right now about your child’s health—a diagnosis of complete atrioventricular canal defect can be overwhelming. But you can rest assured that at Boston Children's Hospital, your child is in expert hands.

Consistently ranked among the top pediatric hospitals in the United States, Boston Children’s is home to the world's most extensive pediatric hospital research enterprise; and we partner with elite health care and biotech organizations around the globe. But as specialists in innovative, family-centered care, our physicians never forget that your child is precious, and not just a patient.

What is atrioventricular canal defect?

Atrioventricular canal defect (AV canal or AVC) is a combination of several heart problems that result in a large defect in the center of the heart. The condition is congenital, which means it is present at birth.

The combination of defects includes:

  • atrial septal defect (ASD)
    • wall of tissue (atrial septum) that separates the upper heart chambers (atria) has a hole
    • allows oxygen-rich (red) blood to pass from the left atrium through the opening, and then mix with oxygen-poor (blue) blood in the right atrium
  • ventricular septal defect (VSD)
    • wall of muscle tissue (ventricular septum) that separates the lower chambers of the heart (ventricles) has a hole
    • allows oxygen-rich (red) blood to pass from the left ventricle through the opening, and then mix with oxygen-poor (blue) blood in the right ventricle
  • abnormalities of the atrioventricular (AV) mitral and tricuspid valves
    • These AV valve defects range from a simple gap or “cleft” in one of the mitral leaflets, to a single large “common” AV valve instead of two separate valves.
    • These “common” AV valves can sometimes be leaky (or regurgitant), allowing blood to flow backwards into the atrium when the heart beats instead of being pumped forward out of the heart. This makes the heart less efficient at pumping and can result in more symptoms. 

Why is atrioventricular canal defect a concern? What are its effects?

If it’s not treated, AV canal can cause many problems involving the heart and lungs. When there are holes in the heart, blood flow follows the path of least resistance, which usually means that excess blood flows to the right side of the heart and out the pulmonary artery to the lungs. In those with atrioventricular canal defect, the extra volume of blood handled by the right side of the heart and the lungs can be quite significant, sometimes as much as three times the normal amount. 

This extra blood flow through the lung blood vessels often results in higher blood pressure in the lungs and the right side of the heart. Over time, the increased flow of blood and the higher pressure can lead to pathologic changes in the lung blood vessels. Over the long term, these changes in the lung blood vessels can become difficult to treat and irreversible.

As the heart is pumping more blood than normal to the lungs, this adds to the amount of work the right ventricle and the heart as a whole have to do. The heart can become larger or dilated over time, and more muscular than normal. Sometimes as the heart becomes larger, the atrioventricular valve becomes more leaky, which makes the heart less efficient.

AVC Heart

Because blood is pumped at high pressure through the septal openings, the lining of the right and left ventricles can become irritated and inflamed. Bacteria in the bloodstream will sometimes infect this injured area, causing a serious illness known as bacterial endocarditis.

Is atrioventricular canal defect genetic?

Genetics may play an important role in the development of atrioventricular canal defect.

  • The majority of cases have associated genetic syndromes.
  • AV canal affects about 15 to 20 percent of children with Down syndrome.
  • The condition affects about 45 percent of children with Down syndrome who have a heart defect.
  • About one-third of children born with AV canal also have Down syndrome.
  • Fourteen percent of mothers with an AV canal defect give birth to a child with the disease.

Will my child be OK? Will there be complications?

Open heart surgery at Children’s has among the highest success rates in the United States among large pediatric cardiac centers. In particular, the methods used to repair AV canal have improved greatly in the past two decades, and the operation has a high likelihood of success.

Complications after surgery are not common, but may include the following:

  • Residual septal defects can occur, although often these are inconsequential.
  • The AV valves, both tricuspid and mitral, can remain leaky, or sometimes the valve openings are narrow (stenotic).
  • The exit or outflow from the left ventricle may become narrow.
  • Abnormally high pulmonary vascular resistance that was present before surgery may still be elevated, and some may have higher than normal blood pressure in the lungs.
  • The heart’s electrical system may have problems.

What about later in life?

Your cardiologist will help you create a long-term care program as your baby matures into childhood, the teen years and even adulthood. Most people who have had congenital heart disease repair will have an ongoing relationship with their cardiologist. We will treat complications, and will advise on daily-life issues such as exercise and activity levels, nutrition and precautions related to pregnancy.

Surgical techniques for AV canal and its associated defects are continually being refined, and long-term outcomes are continually improving. Nevertheless, patients will need lifelong monitoring and medication, since they’ll always be at some risk for arrhythmias, infections, leaky valves, heart failure or stroke.

A small minority of patients (~10%) will need repeat surgery at some point in later childhood or as an adult, most commonly to address residual mitral valve problems.

How common or rare is AV canal?

Atrioventricular canal defect occurs in two out of every 10,000 live births, equally in boys and girls.

Where can my child find care and support when he grows up?

  • The Boston Adult Congenital Heart and Pulmonary Hypertension Service (BACH) provides long-term inpatient and outpatient care and advanced therapeutic options for patients with congenital heart disease and pulmonary hypertension as they reach and progress through adulthood.

    BACH is an international center for excellence, with physicians and services from Children’s, Brigham and Women’s Hospital and Beth Israel Deaconess Medical Center. The center promotes and supports clinical and scientific research for the advancement of care of these patients, and is a leader in the education of providers caring for this unique population.
     
  • The Adult Congenital Heart Association (ACHA) is a national not-for-profit organization dedicated to improving the quality of life—and extending the life—of adults with congenital heart defects. The organization serves and supports many of the adults with congenital heart defects (thought at this time to be as many as one million), their families and the medical community, as well as conducting research and providing advocacy, outreach and education.

Causes of Atrioventricular Canal Defect

It’s important for parents to know that nothing you’ve ingested—and no virus you’ve had—is responsible for your child’s AV canal.

Genetics may play an important role in the development of atrioventricular canal defect. And some studies have investigated a possible link between the use of retinoic acid (for the treatment of acne and facial wrinkles) while pregnant and the development of atrioventricular canal in the fetus.

The structural cause of AV canal is as follows: When the heart is forming during the first eight weeks of fetal development, it begins as a hollow tube. Over time, partitions that form within the tube eventually become the walls dividing the right side of the heart from the left.

Atrial and ventricular septal defects occur when the partitioning process doesn’t occur completely, leaving openings in the atrial and ventricular walls (septa). The valves that separate the upper and lower heart chambers are formed toward the end of this eight-week period, and often they don’t develop properly. Frequently, instead of two separate AV valves (tricuspid and mitral valve), there is a single large common valve that sits between the upper and lower chambers of the heart.

Signs and symptoms of Atrioventricular Canal Defect

  • disinterest in feeding, or tiring while feeding
  • poor weight gain
  • fatigue
  • sweating
  • pale skin
  • cool skin
  • rapid breathing
  • heavy breathing
  • rapid heart rate
  • congested breathing
  • blue color
  • heart murmur (detected by doctor)

If your child has any of these symptoms, your pediatrician will probably refer you to a pediatric cardiologist for testing, diagnosis and a determination of treatment.

When to seek medical advice

Call your health care provider immediately if your baby or child is having difficulty breathing or is breathing rapidly, has a bluish color, tires easily or is uninterested in eating.

Who’s at risk

Genetics may play an important role in the development of atrioventricular canal defect.

  • The majority of cases have associated genetic syndromes.
  • AV canal affects about 15 to 20 percent of children with Down syndrome.
  • The condition affects about 45 percent of children with Down syndrome who have a heart defect.
  • About one-third of children born with AV canal also have Down syndrome.
  • Fourteen percent of mothers with an AV canal defect give birth to a child with the disease.

Some studies have investigated a possible link between the use of retinoic acid (a medication used for the treatment of dermatologic problems such as acne and facial wrinkles) while pregnant and the development of atrioventricular canal in the fetus.

Long-term outlook

Surgical techniques for AV canal and its associated defects are continually being refined, and long-term outcomes are continually improving. Nevertheless, patients will need lifelong monitoring and medication, since they will always be at some risk for arrhythmias, blood clots, infections, leaky valves, heart failure or stroke.

For teens

If you’re a teen who’s had surgical repair of a congenital heart defect, you have a lot to cope with. Besides the typical issues any teenager faces—from social acceptance to body changes and more—you’ll also have to deal with medical appointments and procedures … some delay of your natural wish for independence … feeling different … and assuming a lot of personal responsibility for maintaining your own good health.

If you feel overwhelmed, depressed or anxious through this important time in your transition to adulthood, speak to your doctor or counselor to get help.

For adults

If you were treated for congenital heart disease as a child, you’re probably being followed by your cardiologist, since complications from early heart disease can arise in adulthood.

You may need lifelong monitoring and medication, since you’ll continue to be at some risk for arrhythmias, blood clots, infections, leaky valves, heart failure or stroke. Going forward, your cardiologist will also advise you on activity levels, pregnancy issues and certain lifestyle choices.

Fortunately, Boston Children’s can help adults with congenital heart defects. Many adults who were patients as babies or children continue to be monitored by the clinicians who have followed them since childhood.

In addition, our Boston Adult Congenital Heart and Pulmonary Hypertension Service (BACH) provides long-term inpatient and outpatient care and advanced therapeutic options for patients with congenital heart disease and pulmonary hypertension as they reach and progress through adulthood.

BACH is an international center for excellence, with physicians and services from Children’s, Brigham and Women’s Hospital and Beth Israel Deaconess Medical Center. The center promotes and supports clinical and scientific research for the advancement of care of these patients, and is a leader in the education of providers caring for this unique population.

What you can do at home after your child’s surgery

Your child’s cardiologist will offer recommendations for post-operative follow-up care, including:

  • wound care while your baby is healing
  • a nutritional program to encourage weight gain
  • an oral hygiene program to prevent infection
  • an appropriate exercise regimen to build body mass and achieve fitness

As your baby recovers and grows, be sure to follow a regular program of well-baby/well-child checkups.


Atrioventricular Canal Defect (AV) glossary

aorta  one of the heart’s two great arteries. In a normal heart, the aorta arises from the left ventricle and carries oxygen-rich blood out to the body. 

atrial septal defect (ASD)  a congenital (present at birth) heart defect that is usually present in children with AV canal, in which there is an opening in the tissue wall (septum) that divides the two upper chambers of the heart (right and left atria)

(complete) atrioventricular canal defect (AV canal or AVC)  a combination of several heart problems that result in a large defect in the center of the heart involving both atrial and ventricular septal defects and affecting the atrioventricular valves. AV canal must be repaired surgically. 

cardiac catheterization  an invasive diagnostic procedure performed under sedation to obtain detailed visual information and m
easurements about the structures inside the baby’s heart. Blood pressure and oxygen measurements are taken in the four chambers of the heart, as well as the pulmonary artery and aorta. 

cardiac/cardio
pertaining to the heart 

cardiac magnetic resonance imaging (MRI)
a non-invasive diagnostic tool using 3-D imaging technology produced by magnets to accurately determine the blood flow and functioning of your child's heart

cardiac surgery  surgical procedure performed on the heart or one of the blood vessels connected to the heart

cardiac surgeon
doctor who performs surgery on the heart. A pediatric cardiac surgeon performs surgery on the hearts of infants and children.

cardiologist  doctor who diagnoses and treats heart problems non-surgically. A pediatric cardiologist treats infants, children and some adults with heart problems.

chest x-ray  a diagnostic tool chest to evaluate the size and spatial relationships of the heart within the child’s chest, as well as the presence of AV canal and its associated defects 

cyanosis (cyanotic)  blue color of skin, lips and nailbeds caused by a reduction in the amount of oxygen-rich (red) blood circulating in baby’s bloodstream

congenital heart defect  heart defect present at birth. The heart usually starts to form in the first eight weeks of fetal development. It is thought that most congenital heart defects develop during this period.

diagnosis  medical determination of illness or disease based on history, physical examination 

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