Atrioventricular Canal Defect


An atrioventricular (AV) canal defect is a problem in the connection between the heart’s upper chambers (atria) and the lower chambers (ventricles) that results in extra blood being circulated to the lungs.

This defect consists of a hole in the center of the heart between the upper and lower chambers, as well as problems with the heart valves.

AV canal defects, also known as atrioventricular septal defects or endocardial cushion defects, account for about 5% of all congenital heart disease and are most common in infants with Down syndrome (15%–20% of all newborns with Down syndrome have atrioventricular canal defects).

Cardiothoracic Doctor and Nurse with a congenital patient
Cardiothoracic Doctor and Nurse with congenital patient
Types of AV canal defects

Types of AV canal defects

There are two main types of AV canal defects – partial and complete: 

  1. Partial – there is a hole between the two upper chambers of the heart, which also affects the mitral valve. 
  2. Complete – there is a large hole in the center of the heart that affects the wall (septum) that separates the left and right sides of the heart. A complete defect also causes one large abnormal valve to develop between the upper and lower chambers of the heart (rather than the two separate valves that normally develop) and the valve may not close properly. 
Causes and Symptoms

Causes and Symptoms

Congenital heart defects, such as AV canal defects, are the result of problems that occurred early in the heart’s development. Often, there is no direct cause but it is thought that genetics and environmental factors may play a role.

Other factors that can increase the risk of developing an AV canal defect include: 

  • Having rubella (German measles) or another viral illness during early pregnancy
  • Drinking alcohol during pregnancy
  • Taking certain types of medications during pregnancy

Babies with a complete AV canal defect usually show signs or symptoms within the first few weeks after birth. Symptoms include:

  • Breathing problems 
  • Pounding heart
  • Weak pulse
  • Ashen or bluish skin color
  • Lack of appetite 
  • Little weight gain
  • Easily tired 
  • Swollen legs or abdomen

A partial defect may not cause any symptoms early in life and, therefore, may not be diagnosed for years. Early symptoms of a partial defect can include: 

  • Congestive heart failure
  • High blood pressure in the lungs
Diagnosis and Treatment Options

Diagnosis and Treatment Options

After your baby is born, his or her primary pediatrician might notice a heart murmur and order additional tests; however, it is not uncommon for a heart murmur to be absent right at birth so your pediatrician may look for other symptoms. 

If your doctor finds any signs of an AV canal defect, your baby likely will undergo additional testing.

Tests that your doctor may order include chest x-ray, echocardiogram (echo), electrocardiogram (EKG), pulse oximetry, cardiac catheterization, or magnetic resonance imaging (MRI). For more information on these tests, visit our common diagnostic tests page. 

The only treatment for AV canal defects is surgery. Having surgery to treat the defect will help your child avoid potential complications, such as:

  • Enlargement of the heart
  • Heart failure
  • High blood pressure in the lungs (pulmonary hypertension)
  • Pneumonia
  • Heart infection

Be sure to speak with your child’s cardiothoracic surgeon about what you should expect during and after surgery. You can print these sample questions to use as a basis for discussion with the doctor.

Expected outcomes: The Society of Thoracic Surgeons (STS) Congenital Heart Surgery Database shows an expected outcome of 2.6% mortality for isolated atrioventricular septal defect. Outcomes will vary across different programs. It is appropriate to inquire about the outcomes of a surgical group or surgeon during your consultation.


The only treatment for AV canal defects is surgery.

During the procedure, the cardiothoracic surgeon will close the holes in the heart. Sometimes, patches are used to close the hole, and these patches will become part of the heart as your child grows. At the same time, defective heart valves also will be repaired. Under rare circumstances, the valve cannot be repaired and may need to be replaced with an artificial valve. 




While treating the AV canal defect early in life greatly improves your child’s long-term health, some children who have corrective surgery still may be at risk of developing certain complications later in life, including:

  • Leaky heart valves (regurgitation)
  • Narrowing of the heart valves (stenosis)
  • Heart rhythm abnormalities (arrhythmias)
  • Obstruction to blood flow out of the heart
  • Breathing difficulties associated with damage to the lungs (pulmonary vascular disease)

Your child will need regular follow-up visits with a heart specialist to monitor his or her progress, avoid complications, and check for other health conditions that might develop as they get older. 

Congenital patient visitng the doctor

Your child also may be required to take antibiotics during dental procedures to prevent infections that may cause inflammation of the heart (endocarditis).

Preventive antibiotics are almost always recommended for people who have artificial valves or who’ve had repair with prosthetic material. Be sure to ask your doctor about what is right for your child.


Reviewed by: Ram Kumar Subramanyan, MD, PhD
December 2017