Atrioventricular Canal Defect

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

Three forms of endocardial cushion defects include a partial, complete, and transitional AV canal defects. A partial AVC has a malformed mitral valve and low lying atrial septal defect. A complete AV canal defect 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 AV canal defect is similar to a complete canal, but the common AV valve 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 University of Louisville, have the skill 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.

The Society of Thoracic Surgeons has rated Norton Children’s Heart Institute’s pediatric heart care among the best in the region. Norton Children’s has a network of outreach diagnostic and treatment services throughout Kentucky and Southern Indiana.

AV Canal Defect Symptoms

Atrioventricular canals (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:

  • Irregular heart rhythm (arrhythmia)
  • Failure to thrive
  • Fast breathing
  • Fatigue
  • Heart palpitations
  • Shortness of breath or working hard to breathe when feeding
  • Sweating, particularly when an infant is feeding
  • Trouble exercising

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

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

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

Diagnosing an AV Canal Defect

To diagnose an atrioventricular canal, 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.

Atrioventricular Canal Defect 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’sss 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.

Atrioventricular canal 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.

In rare cases, heart block can occur in the atrioventricular post-operative patient. This condition occurs when the sinoatrial impulses that make your 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 Norton Children’s Heart Institute?

Norton Children’s Heart Institute, affiliated with the University of Louisville, is a comprehensive pediatric heart surgery, heart failure and heart transplant program serving Kentucky, Southern Indiana and beyond.

The goal of the full-service Norton Children’s Heart Institute is to provide care for the child and the whole family. Our specialists are prepared to repair even the most complex congenital and acquired heart conditions.

Our heart team includes:

  • Pediatric cardiothoracic surgeons
  • Pediatric transplant surgeons
  • Pediatric cardiologists
    • Fetal cardiologists
    • Adult congenital heart cardiologists
    • Heart failure/heart transplant cardiologists
    • Pediatric electrophysiologists
    • Pediatric cardiac catheterization cardiologists
  • Pediatric cardiovascular anesthesiologists
  • Pediatric intensive care physicians
  • Cardiac critical care nurses
  • Critical care pharmacists
  • Family support team
  • Child life specialists
  • Rehabilitation specialists
  • Social workers
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