Congenital heart defects arise in the fetal stage in life when the development of the heart and/or great blood vessels is disrupted in some manner. This leads to a structural abnormality in the heart or vessels which depending on the type and extent may case mild to severe symptoms or can even be life threatening. The heart is a a muscular pump with four chambers – two atria that receive blood and two ventricles that push out blood. The atrium and ventricle on each side are separated by heart valves which open and close at different stages of the cardiac cycle. Similarly the ventricles and arteries communicating it are separated by valves.
However, the atria and ventricles are kept separate from each other by the atrioventricular (AV) septum. This means that the blood from the right atrium or ventricle cannot mix with the blood in the left atrium or ventricle. The septum is essential to keep oxygen deficient blood in the right chambers of the heart separate from the oxygen rich blood in the left chambers. In certain types of congenital heart defects, the septum is compromised thereby allowing for a mixing of the blood.
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