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What is truncus arteriosus?

Truncus arteriosus is a rare congenital (present at birth) heart disease where a baby is born with a large hole between the two ventricles (ventricular septal defect). The hole allows oxygenated blood to mix with blood that is low in oxygen. Some of this mixed blood goes to the lungs, and some goes to the rest of the body. Usually, more blood goes to the lungs. Over time, the blood vessels are permanently damaged and it becomes harder for the heart to pump blood to the lungs, resulting in pulmonary hypertension. Untreated cases of truncus arteriosus result in death, often during the first year of life.


Because of too much blood in the lungs, extra fluid may build up in and around them, making breathing difficult. Other symptoms include:

  • Bluish skin (cyanosis)
  • Delayed growth or growth failure
  • Fatigue, lethargy
  • Poor feeding
  • Rapid breathing (tachypnea)
  • Shortness of breath (dyspnea)
  • Widening of the finger tips (clubbing)


In the developing embryo, the great arteries begin as a single tube called the truncus arteriosus that eventually divides into the aorta and the pulmonary artery. Failure to divide properly, or not dividing at all, results in a single great vessel arising from the heart’s pumping chambers.


A physician will examine the heart with a stethoscope. Diagnostic tests include:

  • Electrocardiogram (ECG)
  • Echocardiogram
  • Heart catheterization (sometimes necessary to plan a treatment strategy)
  • Magnetic resonance imaging (MRI)
  • X-ray of the chest


Truncus arteriosus cannot be prevented, but early treatment often can prevent serious complications.