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Atrioventricular Canal Defect: Overview

What is an atrioventricular canal defect?

An atrioventricular canal defect is a form of congenital heart defect, meaning a child is born with the condition. This condition is sometimes called an AVCD or AVSD.

An AVCD happens when the valves and muscle walls that separate the heart’s chambers do not form completely while a baby is still in the womb. Atrioventricular canal defects can be complete or partial. The two types are equally common.

Children with complete atrioventricular canal defects have a combination of three separate defects:

  • A hole in the heart wall (septum) that separates the two atria, which are the upper chambers of the heart. This is also called an atrial septal defect.
  • A hole in the septum that separates the two ventricles, which are the lower chambers of the heart. This is called a ventricular septal defect.
  • One large valve between the atrium and ventricles instead of the normal two.

Children with partial atrioventricular canal defects have:

  • A hole in the heart wall separating the atria, known as atrial septal defect.
  • A partial abnormality known as a “cleft” in the left valve or mitral valve.

The holes in the heart and the incorrectly formed valves allow blood to mix inside the heart. This results in too much blood going to the lungs, making the heart have to work harder. The extra effort can weaken the heart muscles and cause the heart to enlarge.

Most atrioventricular canal defects are detected early in life, within the first few months. Depending on whether it is a complete AVCD or a Partial AVCD, treatment may be necessary within the first few months or few years of life. Atrioventricular canal defects are common in children with Down syndrome.