What is a truncus arteriosus defect?

Truncus arteriosus is a congenital heart defect (the baby is born with it) in which there is only one main artery or large blood vessel that carries blood to the body and lungs, instead of two separate arteries. The condition occurs in the womb, while the fetus’s heart is still developing.

During normal development of the heart and circulatory system, the single large vessel (also called the truncus arteriosus) divides into two vessels: the aorta and the pulmonary artery. The aorta carries blood from the heart to the rest of the body. The pulmonary artery has two sections or branches to carry blood to the lungs, so that the blood can receive oxygen.

Babies who are born with truncus arteriosus have a ventricular septal defect. This is a hole in the septum, the wall that divides the right and left ventricles (the two lower pumping chambers of the heart). This opening allows blood that has picked up oxygen from the lungs to mix with blood that has not, so that the blood leaving the heart does not carry enough oxygen. Poorly oxygenated blood that circulates throughout the body can cause severe circulatory problems and damage to all organs, in addition to the heart and lungs.

Sometimes the valve (truncus valve) located between the ventricles and the single large blood vessel can be either stenotic (too tight) or regurgitant (leaking), which can adversely affect the entire circulation.

Truncus arteriosus is a serious condition. Unless it is treated, it usually results in death within the first year of life. Truncus arteriosus is treated with surgery, which is often successful, especially if it is performed before the infant is two months old.

What causes truncus arteriosus?

It is not known exactly what causes truncus arteriosus. The condition occurs while the fetal heart is developing.

Several factors may increase the risk of truncus arteriosus, including the following:

  • A family history of congenital heart problems.
  • Children with chromosomal disorders, velocardiofacial syndrome, or DiGeorge’s syndrome may be at greater risk for developing truncus arteriosus.
  • Pregnant women who take certain medications during pregnancy that could damage the fetus, or those who contract a viral illness such as German measles (rubella), may have a greater chance of giving birth to an infant with truncus arteriosus.

What are the symptoms of truncus arteriosus?

Symptoms of truncus arteriosus are usually seen within the first week of life. Signs may include:

  • Rapid or heavy breathing.
  • Shortness of breath or lung congestion.
  • Poor feeding.
  • Poor weight gain.
  • Irregular heartbeat.
  • Excessive sweating.
  • Pale or cool skin.
  • A bluish tinge to the skin (cyanosis).

Last reviewed by a Cleveland Clinic medical professional on 01/29/2011.

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