“An atrioventricular septal defect (AVSD) is a heart defect in which there are holes between the chambers of the right and left sides of the heart, and the valves that control the flow of blood between these chambers may not be formed correctly. This condition is also called atrioventricular canal (AV canal) defect or endocardial cushion defect. In AVSD, blood flows where it normally should not go. The blood may also have a lower than normal amount of oxygen, and extra blood can flow to the lungs. This extra blood being pumped into the lungs forces the heart and lungs to work hard and may lead to congestive heart failure.
There are two general types of AVSD that can occur, depending on which structures are not formed correctly:
A complete AVSD occurs when there is a large hole in the center of the heart which allows blood to flow between all four chambers of the heart. This hole occurs where the septa (walls) separating the two top chambers (atria) and two bottom chambers (ventricles) normally meet. There is also one common atrioventricular valve in the center of the heart instead of two separate valves – the tricuspid valve on the right side of the heart and the mitral valve on the left side of the heart. This common valve often has leaflets (flaps) that may not be formed correctly or do not close tightly. A complete AVSD arises during pregnancy when the common valve fails to separate into the two distinct valves (tricuspid and mitral valves) and when the septa (walls) that split the upper and lower chambers of the heart do not grow all the way to meet in the center of the heart.
Partial or Incomplete AVSD
A partial or incomplete AVSD occurs when the heart has some, but not all of the defects of a complete AVSD. There is usually a hole in the atrial wall or in the ventricular wall near the center of the heart. A partial AVSD usually has both mitral and tricuspid valves, but one of the valves (usually mitral) may not close completely, allowing blood to leak backward from the left ventricle into the left atrium.” Read More
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