May also be called: Endocardial Cushion Defect; ECD; Atrioventricular Canal Defect An atrioventricular septal defect is an abnormal heart condition caused by a poorly formed central area of the heart. Atrioventricular septal defects are congenital, meaning they are present at birth. More to Know The heart consists of four chambers — the left atrium and left ventricle, and the right atrium and right ventricle. The chambers are separated by a wall of tissue called the septum. Two valves — the mitral and tricuspid valves — separate the atria (plural of atrium) from the ventricles. With atrioventricular septal defects, the tissues that form the septum don't grow completely while a baby is in the womb, leaving one or more holes between the atria or the ventricles. In some cases, instead of two separate valves, there is only one large common valve, which may be malformed (formed incorrectly). The causes of atrioventricular septal defects aren't fully understood, but they're commonly seen in children with Down syndrome. The defects can make the heart have to work harder to pump blood and cause symptoms like difficulty feeding, failure to gain weight, lung congestion, and a bluish tint to the skin (called cyanosis). Atrioventricular septal defects are usually corrected through surgery while a child is still an infant. Keep in Mind If left untreated, an atrioventricular septal defect can cause complications (including heart failure) and may be life threatening. Once surgery has been done to correct the defect, however, most kids lead a normal life. All A to Z dictionary entries are regularly reviewed by KidsHealth medical experts. Back to Articles Related Articles Congenital Heart Defects Heart defects happen when there's a problem with a baby's heart development during pregnancy. Most heart defects can be treated during infancy. Read More Patent Ductus Arteriosus (PDA) The ductus arteriosus is a blood vessel that connects two major arteries before birth and normally closes after a baby is born. If it stays open, the result is a condition called patent ductus arteriosus (PDA). Read More Atrial Septal Defect (ASD) Atrial septal defect (ASD) — also known as a "hole in the heart" — is a type of congenital heart defect. Most ASDs are diagnosed and treated successfully. Read More Atrial Septal Defect Atrial septal defect, or ASD, is a heart defect that some people are born with. Most ASDs are diagnosed and treated successfully with few or no complications. Read More Ventricular Septal Defect Ventricular septal defect, or VSD, is a heart condition that a few teens can have. Find out what it is, how it happens, and what doctors do to correct it. Read More Ventricular Septal Defect (VSD) Ventricular septal defect (VSD) — also known as a "hole in the heart" — is a congenital heart defect. Most VSDs are diagnosed and treated successfully. Read More Heart and Circulatory System The heart and circulatory system are our body's lifeline, delivering blood to the body's tissues. Brush up on your ticker with this body basics article. Read More Note: All information is for educational purposes only. For specific medical advice, diagnoses, and treatment, consult your doctor. © 1995-2021 KidsHealth®. All rights reserved. Images provided by The Nemours Foundation, iStock, Getty Images, Veer, Shutterstock, and Clipart.com.