What is Truncus Arteriosus?

What is Truncus Arteriosus

Truncus arteriosus, a rare congenital heart defect, occurs during fetal development when the main pulmonary artery and the aorta artery remain connected as a single common blood vessel instead of separating into two separate arteries. This lack of separation between the pulmonary artery and the aorta artery can leave a hole between the two bottom chambers of the heart called a ventricular septal defect. This is a critical congenital heart defect, which means it is present at birth and requires surgery as soon as possible.

Hearts of babies born with truncus arteriosus have trouble pumping oxygen-rich blood throughout the body. Instead, the blood that is pumped from the right side of the heart, through the pulmonary artery, to the lungs, lacks oxygen. This is contrary to the left side of the heart which continues to pump oxygen-rich blood through the aorta and to the rest of the body.

This condition causes oxygen-poor blood to mix with oxygen-rich blood. The resulting mixture causes too much blood to be pumped into the lungs, and extra work for the heart to maintain the excess blood flow. With truncus arteriosus, the child lacks both an aortic valve and a pulmonary valve; this produces a single, common valve, called the truncal valve, that controls the flow of blood from the heart. This abnormal truncal valve may begin to thicken and narrow, reducing blood flow from the heart. In addition, the valve may leak, causing blood exiting the heart to backflow into the heart.

Types of Truncus Arteriosus


Truncus arteriosus is classified into four types. Each type involves a single trunk vessel exiting the heart. The types of truncus arteriosus are categorized according to how and where the pulmonary arteries (right and left) separate to carry blood to each lung. Surgery differs for each type depending on where the split of the pulmonary arteries occurs.
The four types are:

  • Truncus arteriosus type 1 – This is the most common form of truncus arteriosus encompassing 60% of the cases. Both the right and left pulmonary arteries share a common arterial trunk.
  • Truncus arteriosus type 2 – The right and left pulmonary arteries branch off separately from the common trunk.
  • Truncus arteriosus type 3 – One pulmonary artery branches off the common trunk while the other artery branches off the aorta.
  • Truncus arteriosus type 4 – The right and left pulmonary arteries do not branch off the main artery; instead, they branch off the aorta (the section that descends into the chest).

Sign & Symptoms of Truncus Arteriosus


Truncus arteriosus is a serious condition for an infant, and immediate attention must be given to the signs and symptoms which usually appear within the first few days of life. A pediatric cardiologist or heart specialist can examine and evaluate your child’s condition.
Symptoms may include:

  • Rapid, heavy, and congested breathing
  • Fatigue
  • Pale skin that is cool to the touch
  • Poor feeding with little weight gain
  • Excessive sweating
  • Cyanosis, which causes skin, lips, and nail beds to turn blue

If your baby is having difficulty breathing or their skin color begins to turn blue, seek immediate medical attention. If you are unable to reach the child’s pediatrician, seek immediate emergency medical attention.

What Causes Truncus Arteriosus?


There is no clear explanation for why the pulmonary artery does not form two separate blood vessels. This condition occurs during the early stages of fetal development. Some babies may have congenital heart defects caused by chromosomal changes.
There are some thoughts that environmental conditions a mother was exposed to during fetal development could possibly cause truncus arteriosus. Also, what a mother eats, drinks, or certain medications may be possible causes of a birth defect.

Risk Factors

Risk Factors

The exact cause of truncus arteriosus is unknown. However, there are certain factors that could increase the likihood of a baby being born with a heart defect:

  • Uncontrolled diabetes during pregnancy – Pregnant women with high blood sugar, also known as gestational diabetes, who are not properly monitored, may be at increased risk of having a baby born with birth defects, including heart defects.
  • Viral infections during pregnancy – Contracting rubella (German measles) or another type of viral infection during early pregnancy increases a baby’s risk for developing a congenital heart defect.
  • Medications – There are certain medications that pregnant women should avoid because of the risk of harm to their unborn child.
  • Chromosomal disorders – Children born with an extra chromosome or chromosomal damage are at greater risk of developing DiGeorge’s syndrome or Velocardiofacial syndrome, which increases the risk of developing truncus arteriosus.
  • Smoking during pregnancy – Smoking during pregnancy increases the risk for a baby to be born with a heart defect.
  • Drinking alcohol while pregnant – Drinking alcohol, especially during the first trimester of pregnancy, increases a baby’s risk of developing a congenital heart defect.
  • Obesity – Women who are obese have an increased risk of having a baby with a congenital heart defect.



Truncus arteriosus combined with an abnormal heart structure results in serious blood circulation problems. The lack of separation of the blood ventricles causes all the blood to flow through one single artery. The oxygen-rich blood mixes with the oxygen-poor blood—this mixture flows throughout the whole body supplying the heart and other organs with oxygen-depleted blood. Babies with truncus arteriosus experience abnormal blood circulation.
This can result in:

  • Respiratory issues – The lungs receive too much blood at one time; this increase in fluid makes breathing difficult for a baby.
  • Pulmonary hypertension (high blood pressure in the lungs)There is an increase of blood flow to the lungs causing the blood vessels in the lungs to narrow. The narrowing of the blood vessels increases the blood pressure in the lungs. The increased blood pressure in the lungs makes it difficult for the baby’s heart to pump blood to the lungs.
  • Enlarged heart (cardiomegaly) – The increased blood flow through the heart combined with pulmonary hypertension may cause the baby’s heart to work too hard, which may cause the heart muscle to grow larger.
  • Heart failure The combination of overworking the heart muscle and a poor oxygen supply weakens the baby’s heart. This may contribute to heart failure because of the lack of oxygen-rich blood.

Adults who have successful surgery during infancy for truncus arteriosus may experience complications later in life. These may include:

Symptoms and signs of truncus arteriosus in adults can include:

Most people born with truncus arteriosus require surgery during infancy. Although there are rare cases where a person may survive into adulthood without surgical repair of the heart, they almost always develop future heart failure and pulmonary hypertension. An experienced cardiologist or heart specialist can diagnose and treat this condition.



Congenital heart disorders, like truncus arteriosus, are difficult to prevent since their exact cause is unknown. Doctors may suggest talking to a genetic counselor if a couple has previously given birth to a child with a congenital heart defect. For a person with a family history of congenital heart disease, a cardiologist can explain about congenital heart defects before getting pregnant.

Your healthcare provider may suggest additional ways for you to avoid complications, to prepare your body and ensure that your baby is born as healthy as possible. Some suggestions may include:

  • Get vaccinated before becoming pregnant – Viruses, such as German measles (rubella), may cause significant complications and birth defects to an unborn child. Stay updated with immunizations, including the COVID-19 vaccine.
  • Medications – Beware of medications that are known to cause birth defects. Discuss all medications you are taking with your doctor before getting pregnant.
  • Folic acid –Studies show that taking 400 micrograms of folic acid while pregnant may be heart healthy and can help prevent various birth defects.
  • Diabetes – Monitor your glucose and discuss with your doctor the best way to manage your diabetes before and during pregnancy.
Get Care

Trust NewYork-Presbyterian for Truncus Arteriosus Care

NewYork-Presbyterian provides compassionate and comprehensive care for infants with with truncus arteriosus. Our dedicated and experienced pediatric cardiologists at NewYork-Presbyterian offer complete evaluations, patient education, and various treatment options for truncus arteriosus.

NewYork-Presbyterian Morgan Stanley Children’s Hospital and NewYork-Presbyterian Komansky Children’s Hospital are national front-runners in pediatric care. Our Congenital Heart Center is one of the largest and most comprehensive pediatric cardiology and cardiac surgery centers in the nation. With state-of-the-art equipment, modern facilities, and innovative techniques, we provide treatments for pediatric and adult patients with congenital heart defects.

NewYork-Presbyterian uses advanced treatment options, from cardiac surgery using minimally invasive techniques to pediatric heart transplants by a team of specialists, to deliver the most effective clinical outcomes.