Introduction
Cardiovascular abnormalities are very common in individuals with Down syndrome. Approximately half of all infants with Down syndrome are born with a heart defect, and many of these defects have serious health implications.
What Are the Most Common Heart Defects?
- Atrioventricular septal defect (AVSD), also known as endocardial cushion defect
- Ventricular septal defect (VSD)
- Patent ductus arteriosus (PDA)
- Tetralogy of Fallot
Atrioventricular Septal Defect (AVSD)
An atrioventricular septal defect occurs when tissues in the heart fail to fuse properly during foetal development, resulting in a large opening in the centre of the heart. This defect is typically associated with a hole between the two ventricles (VSD), a hole between the two atria (ASD), and abnormalities of both the mitral and tricuspid valves. AVSD is the most common heart defect among children with Down syndrome born with congenital heart disease. In less severe cases, ventricular or atrial septal defects may occur in isolation.
Patent Ductus Arteriosus (PDA)
The ductus arteriosus is a vessel connecting the pulmonary artery to the aorta. During foetal life it diverts blood away from the lungs, as blood is pre-oxygenated by the mother. After birth it normally closes within the first day of life. If it remains open it is termed "patent" and results in increased blood flow to the lungs.
Tetralogy of Fallot
Tetralogy of Fallot is a cardiac condition comprising four simultaneous abnormalities:
- Ventricular septal defect.
- Narrowing of the passage between the right ventricle and the lungs (pulmonary stenosis).
- Enlargement of the right ventricle due to excess blood volume (right ventricular hypertrophy).
- Enlargement of the aorta carrying blood from the left ventricle to the body (overriding aorta).
The Relationship Between Heart Defects and the Respiratory System
The lungs of a child with Down syndrome do not develop as fully as those of other children, which limits blood vessel growth throughout the lungs. Narrowing of the pulmonary arteries may lead to permanent consequences due to elevated pressure and increased blood flow through the lungs.
How Are Defects Diagnosed?
Some children with large heart defects present from birth with heart failure, respiratory difficulties, and failure to thrive. In other cases the defect may not be immediately apparent. It is therefore important that all children with Down syndrome — even those without cardiac symptoms — undergo an echocardiogram within the first two to three months of life. Some conditions may also be identified on prenatal ultrasound.
Recommended Treatment
Surgical correction is recommended and should ideally be performed before the age of five to six months to prevent permanent lung damage. Although the complexity of these defects makes the surgical risks slightly higher than for other children, successful surgery allows many children with heart disease to grow and develop like any child with Down syndrome born with a healthy heart. Some minor structural abnormalities may remain (such as incomplete valve repair in AVSD cases), but their impact on health is usually minimal.
Source: Reproduced under an exclusive agreement with the National Down Syndrome Society (NDSS) — www.ndss.org