Atrioventricular Canal Defect

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An endocardial cushion defect, or atrioventricular canal defect (AVC), is a condition in which the center of the heart does not fully form before birth. AVCs are a combination of defects, including an atrial septal defect (ASD), a ventricular septal defect (VSD) and abnormalities of the atrioventricular valves (mitral and tricuspid).

Three forms of endocardial cushion defects include a partial, complete and transitional AVCs. A partial AVC has a malformed mitral valve and low lying ASD. A complete AVC refers to a lack of separation between the two sides of the heart — the atrial and ventricular sides. The two atrioventricular valves are not formed correctly. The child may have one large common valve in the middle of the heart, instead of one on each side of the heart. In addition, there are both atrial and ventricular septal defects connecting the right and left sides of the heart. A transitional AVC is similar to a complete canal, but the common AV leaflets are fused to the ventricular septum, almost creating two separate valves and a VSD closure.

Depending on the size of the septal defects and the resistance of the lung arteries, infants may have too much pulmonary blood flow and be at risk for congestive heart failure, or not enough pulmonary blood flow and deliver less oxygen to their body.

The board-certified and fellowship-trained specialists at Norton Children’s Heart Institute, affiliated with the UofL School of Medicine, have the skills and experience to provide a precise diagnosis of an atrioventricular canal defect and will develop a customized treatment plan for you and your child.

Norton Children’s Heart Institute is the leading provider of pediatric heart care in Louisville and Southern Indiana.

Norton Children’s has a network of outreach diagnostic and treatment services throughout Kentucky and Southern Indiana.

AVC Defect Symptoms

AVCs range from small to large, partial to complete, and balanced to unbalanced. Depending on the size of the AVC and how much blood is going to the lungs versus the body, symptoms may vary.

AVC symptoms can include:

Most children with AVCs show symptoms within the first weeks after birth. Following diagnosis, children will be treated with medications to treat congestive heart failure symptoms, if present. Examples include furosemide, a diuretic, and enalapril, a medication to lower the blood pressure to make it easier for the heart to pump.

If not repaired, an AVC can lead to serious health conditions, such as high blood pressure in the lungs and heart failure.

In many cases, it’s unclear why heart defects develop. In other cases, it may be related to Down syndrome. Up to 50% of children with Down syndrome may have congenital heart disease.

Diagnosing an AVC Defect

To diagnose an AVC, a pediatric cardiologist will examine your child, check the heartbeat and listen to the heart. Other tests performed may include:

  • Chest X-ray: This shows pictures of the heart and lungs, and can show heart and lung issues, including extra blood flow or fluid in the lungs.
  • Echocardiogram (echo): This test uses sound waves (ultrasound) to produce images of the heart and blood vessels’ structures on a screen. It can show the structure and function of the heart. Norton Children’s Heart Institute has 28 tele-echo locations in Kentucky and Southern Indiana so many patients don’t have to travel far for an echocardiogram.
  • Electrocardiogram (ECG or EKG): A test that checks the heart’s electrical activity to show damage or irregular rhythms.
  • Heart catheterization: This invasive procedure studies the structure, function, and provides direct pressure measurements of the heart.

AVC Treatment

Treatment requires surgery to restore the separation of the heart’s right and left chambers and reconstruction of the atrioventricular valve. Prior to surgery, our pediatric cardiologists will monitor symptoms related to heart failure, including weight gain, before choosing the best treatment option and best time for your child’s surgery.

Some children will need a pulmonary artery band early in life for a period of time to limit blood flow to their lungs so they can effectively grow. Infants with a complete endocardial cushion defect usually are big enough to undergo surgery at 3 to 6 months of age. Infants with a partial endocardial cushion defect usually can wait a little longer before undergoing surgery.

AVC surgery involves closing the holes in the atrial and/or ventricular septa with a patch or patches and reconstructing the atrioventricular valve. Most patients can receive a complete two ventricle repair. However, some children may have one ventricle that is not adequately developed and will need to undergo procedures involved with a single ventricle repair (Glenn and Fontan operations).

All AVC patients will need to be followed by a pediatric cardiologist to look for signs of valve dysfunction as they age. When the child becomes an adult, they will need to see an adult congenital heart disease (ACHD) specialist for care.

In rare cases, a heart block can occur after surgery. This condition occurs when the sinoatrial impulses that make the heart beat are not conducted, or delayed, from getting to the ventricles. If the condition does not resolve with time, a pacemaker may be needed.

Why Choose Norton Children’s Heart Institute

  • Norton Children’s Hospital has been a pioneer in pediatric cardiothoracic surgery, performing Kentucky’s first pediatric heart transplant in 1986 and becoming the second site in the United States to perform an infant heart transplant.
  • The American Board of Thoracic Surgery has certified our cardiothoracic surgeons in congenital heart surgery.
  • The Adult Congenital Heart Association has accredited Norton Children’s Heart Adult Congenital Heart Disease Program as the only comprehensive care center in Kentucky and Indiana treating adults born with a heart defect.
  • More than 17,000 children a year visit Norton Children’s Heart Institute for advanced heart care.
  • Norton Children’s Heart Institute has offices across Kentucky and Southern Indiana to bring quality pediatric heart care closer to home.
  • The Jennifer Lawrence Cardiac Intensive Care Unit (CICU) at Norton Children’s Hospital is the largest dedicated CICU in Kentucky, equipped with 17 private rooms and the newest technology available for heart care.

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