Atrioventricular (AV) canal defect is when there is a hole in the central wall of the heart, allowing blood to mix in the upper (atria) and lower chambers (ventricles) of the heart.1,2 This defect can present in two different ways: partial and complete. In a partial defect, the hole exists only in the upper chamber of the heart and can present with abnormal tricuspid and mitral valves. A complete defect, on the other hand, extends to the lower chambers of the heart, which means that all of the blood being pumped through the heart can mix interchangeably between ventricles and atria. In complete AV Canal, the tricuspid and mitral valves are not formed individually and instead form one single, large valve that does not close properly when the heart beats. This further allows blood to flow from the ventricles (the lower chambers of the heart) into the atria (the upper chambers) and mix even more.2

Since blood can travel from the left atria and ventricle to the right side of the heart, more blood than normal is pumped to the lungs (as the right side of the heart pumps blood to the lungs to get oxygenated).1 This makes the heart work harder as it is pumping more blood, but it can also lead to lung damage due to high blood pressure from an increased volume. Additionally, deoxygenated and oxygenated blood mix as deoxygenated blood from the right atria and ventricle mixes with oxygenated blood from the left ventricle. This limits the efficiency of the heart to pump oxygenated blood to the rest of the body as well.

What is Atrioventricular Canal Defect?

Septal wall defect: allows for mixing of blood between the atria and ventricles and can be partial or complete. 

Symptoms:

Patients with partial AV Canal have less obvious symptoms and may not be diagnosed until their 20s or 30s.1

Symptoms of partial AV Canal may include:1–5

  • Fatigue

  • Weakness

  • Lack of appetite

  • Poor weight gain and growth

  • Persistent cough or wheezing

  • Shortness of breath

  • Swelling in the legs, ankles and feet (can be called edema)

  • Chest pressure or pain

  • Irregular or rapid heartbeat (arrhythmias)

Symptoms of complete AV Canal are more obvious from birth and can include:

  • Blue or gray skin color (cyanosis)

  • Difficult/rapid breathing

  • Excessive sweating

  • Fatigue

  • Irregular or rapid heartbeat (arrhythmias)

  • Lack of appetite

  • Poor weight gain and growth

  • Swelling in the legs, ankles, and feet (can be called edema)

  • Wheezing

  • Heart murmurs

Diagnosis:1-5

Echocardiogram (Echo)

Cardiac MRI

Chest X-ray (CXR)

Electrocardiogram (EKG)

Pulse Oximetry

Cardiac Catheterization

Treatments

At first, medical management may be used to temporarily treat infants before they require heart surgery.2,3 Within the first few months, the patient will need heart surgery.1-5 During the procedure, the surgeon will close the large hole in the heart using one or more patches.1,2 These patches are stitched into the heart muscle, and as the child grows, their heart tissue will naturally grow over the patches, creating a permanent repair. Additionally, the surgeon will divide the single large valve into two separate valves, creating two functional atrioventricular (AV) valves—one for each side of the heart.1-3 This aims to restore normal heart function. In a partial AV Canal defect, surgery is still required to repair the atrial septal defect (ASD). The surgeon will need to patch the hole between the atria, and then may need to repair the mitral valve or replace it with an artificial or donor valve.1,2 In cases of severe defects, additional procedures may be performed to manage symptoms and reduce high blood pressure. 2 For example, pulmonary artery banding may be used to temporarily narrow the pulmonary artery, limiting excessive blood flow to the lungs. Once the child is older and better able to tolerate surgery, the band will be removed, and the complete repair of the AV canal defect will be performed through open-heart surgery. If the heart’s electrical system has been damaged during surgery, a pacemaker may be necessary.2

Additional Resources

References

1. Children’s Hospital of Philadelphia. Atrioventricular Canal (AVC) Defects. Children’s Hospital of Philadelphia. Accessed January 25, 2025. https://www.chop.edu/conditions-diseases/atrioventricular-canal-defects

2. American Heart Association. Complete Atrioventricular Canal defect (CAVC). American Heart Association. Accessed January 25, 2025. https://www.google.com/url?q=https://www.heart.org/en/health-topics/congenital-heart-defects/about-congenital-heart-defects/complete-atrioventricular-canal-defect-cavc&sa=D&source=editors&ust=1737859140258153&usg=AOvVaw3RJ9iJ84xJI12ZbmMLiOpW

3. Boston Children’s Hospital. Atrioventricular Canal Defect. Boston Children’s Hospital. Accessed January 25, 2025. https://www.childrenshospital.org/conditions/atrioventricular-canal-defect

4. Mayo Clinic Staff. Atrioventricular canal defect. Mayo Clinic. Accessed January 25, 2025. https://www.mayoclinic.org/diseases-conditions/atrioventricular-canal-defect/symptoms-causes/syc-20361492

5. Cincinnati Children’s. Atrioventricular Septal Defect - AV Canal (AVSD). Cincinnati Children’s. April 2024. Accessed January 25, 2025. https://www.cincinnatichildrens.org/health/a/avsd