The Heart

Abnormalities of the cardiovascular system are common with Down syndrome. Approximately half of all infants born with Down syndrome have a heart defect. Many of these defects have serious implications.

What are the Most Common Heart Defects in Children With Down Syndrome?

The most common defects are Atrioventricular Septal Defect (formally called Endocardial Cushion Defect), Ventricular Septal Defect, Persistent Ductus Arteriosus and Tetralogy of Fallot.


What is an Atrioventricular Septal Defect?

An Atrioventricular Septal Defect is caused by a failure of tissue to come together in the heart during embryonic life. This results in a large opening in the center of the heart, usually with a hole between the two pumping chambers (a Ventricular Septal Defect) and between the two collecting chambers (an Atrial Septal Defect) as well as abnormalities of the two atrioventricular valves, the mitral and tricuspid valves. Of those children with Down syndrome who are born with congenital heart disease, an Atrioventricular Septal Defect is the most common. In less severe cases, Ventricular Septal Defects and Atrial Septal Defects can also occur separately.


What is Persistent Ductus Arteriosus?

The ductus arteriosus is a channel between the pulmonary artery and the aorta. During fetal life it diverts blood away from the lungs because prenatal blood is already oxygenated from the mother. After birth, this cannel usually closes on the first day of life. If it does not close, it is termed “persistent” and results in an increased flow of blood into the lungs.


What is Tetralogy of Fallot?

This is a term given to a heart condition composed of four abnormalities:
  • Ventricular Septal Defect
  • A narrowing of the passage from the right ventricle to the lungs
  • An enlarged right ventricle because of the backup of blood
  • An enlarged aorta that carries blood from the left ventricle to the body


What is the Relationship of Heart Defects to the Respiratory System?

The lungs of children with Down syndrome do not develop as fully as they do in the general population. Consequently, the growth of blood vessels throughout the lungs is limited. The narrowed arteries of the lungs hold potential for lasting consequences due to the increased pressure and flow of blood through the lungs.

How are the Defects Diagnosed?

Some children with Down syndrome that have major heart defects will present with heart failure, difficulty breathing and failure to thrive as newborns. In others, the defect may not be apparent at first. It is therefore important that all children born with Down syndrome - even those who have no symptoms of heart disease - have an echocardiogram in the first two or three months of life. Some heart conditions are also identified during prenatal ultrasounds.

What is the Recommended Treatment?

Heart surgery to correct the defects is recommended and it must be done before the age of five or six months in order to prevent lung damage. Although the complexity of the defects raises the risk of surgery slightly above that of surgery on children without Down syndrome, successful surgery will allow many children with heart conditions to thrive as well as any child with Down syndrome who is born with a normal heart. There may be residual defects (such as imperfect valves in cases of Atrioventricular Septal Defect), but their effect on health is often minimal.


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