Truncus Arteriosus

Heart with Truncus Arteriosus

An animation of a heart with truncus arteriosus

Note: To view the truncus arteriosus heart animations, you need the latest version
of the Adobe Flash Player.


Normally, the aorta originates from the left ventricle and the pulmonary artery originates from the right ventricle. In the case of truncus arteriosus, the aorta and pulmonary artery are not fully separated, resulting in a single arterial trunk that arises above a VSD. The low-oxygen blood from the right ventricle and the oxygen-rich blood of the left ventricle mix and are pumped to both the lungs and the body. As a result, the lung circulation is exposed to high pressure and increased blood flow.

Corrective surgery must be performed in the first six months of life. Complete repair requires closure of the VSD and separation of the great arteries. The VSD is closed with a patch such that the truncus originates in the left atrium. Next, a connection is made between the branch pulmonary arteries and the right atrium using a valved conduit (tube containing a valve). Any connections between the branch pulmonary arteries and the truncal vessel are also patched closed.


What Is Normal Cardiac Anatomy?

When your child has a congenital heart defect, there's usually something wrong with the structure of his or her heart's structure.

 
Learn More About Normal Cardiac Anatomy

Heart With Normal Cardiac Anatomy

Note: To view heart animations, you need the latest version of the
Adobe Flash Player.


When your child has a congenital heart defect, there's usually something wrong with the structure of his or her heart's structure.

The heart is composed of four chambers. The two upper chambers, known as atria, collect blood as it flows back to the heart. The two lower chambers, known as ventricles, pump blood with each heartbeat to the two main arteries (the pulmonary artery and the aorta). The septum is the wall that divides the heart into right and left sides. The atrial septum separates the right and left atria; likewise, the ventricular septum separates the two ventricles.

There are four valves that control the flow of blood through the heart. These flap-like structures allow blood to flow in only one direction. The tricuspid and mitral valves, also known as the atrioventricular valves, separate the upper and lower chambers of the heart. The aortic and pulmonary valves, also known as the arterial valves, separate the ventricles from the main arteries. Oxygen-depleted blood returns from the body and drains into the right atrium via the superior and inferior vena cavas. The blood in the right atrium then passes through the tricuspid valve and enters the right ventricle.

Next, the blood passes through the pulmonary valve, enters the pulmonary artery, and travels to the lungs where it is replenished with oxygen. The oxygen-rich blood returns to the heart via the pulmonary veins, draining into the left atrium. The blood in the left atrium passes through the bicuspid, or mitral, valve and enters the left ventricle.

Finally, the oxygen-rich blood flows through the aortic valve into the aorta and out to the rest of the body.

Patent Ductus Arteriosus (PDA)

The lungs are not used while a fetus is in the amniotic fluid because the baby gets oxygen directly from the mother's placenta. When a newborn breathes and begins to use the lungs, the DA is no longer needed and usually closes during the first 2 days after birth.

But when the DA fails to close, a condition called patent (meaning "open") ductus arteriosus (PDA) results, in which oxygen-rich blood from the aorta is allowed to mix with oxygen-poor blood in the pulmonary artery. As a result, too much blood flows into the lungs, which puts a strain on the heart and increases blood pressure in the pulmonary arteries.

Causes

The cause of PDA is not known, but genetics might play a role. PDA is more common in premature babies and affects twice as many girls as boys. It's also common among babies with neonatal respiratory distress syndrome, babies with genetic disorders (such as Down syndrome), and babies whose mothers had German measles (rubella) during pregnancy.

In the vast majority of babies with a PDA but an otherwise normal heart, the PDA will shrink and go away on its own in the first few days of life. Some PDAs that don't close then will close on their own by the time the child is a year old.

In premature infants, the PDA is more likely to stay open, particularly if the baby has lung disease. When this happens, treatment to close the PDA might be considered.

In infants born with additional heart defects that decrease blood flow from the heart to the lungs or decrease the flow of oxygen-rich blood to the body, the PDA could actually be beneficial and the doctor might prescribe medicine to keep the ductus arteriosus open.

Symptoms and Tests

Babies with a large PDA might experience symptoms such as:

  • a bounding (strong and forceful) pulse
  • fast breathing
  • poor feeding habits
  • shortness of breath
  • sweating while feeding
  • tiring very easily
  • poor growth

If a PDA is suspected, the doctor will use a stethoscope to listen for a heart murmur, which is often heard in babies with PDAs. Follow-up tests might include:

  • a chest X-ray
  • an EKG, a test that measures the heart's electrical activity and can show if the heart is enlarged
  • an echocardiogram, a test that uses sound waves to diagnose heart problems. These waves bounce off parts of the heart, creating a picture of the heart that is shown on a monitor. In babies with PDA, an echo shows how big the opening is and how well the heart is handling it.

Treatment

The three treatment options for PDA are medication, catheter-based procedures, and surgery. A doctor will close a PDA if the size of the opening is large enough that the lungs could become overloaded with blood, a condition that can lead to an enlarged heart.

A PDA also might be closed to reduce the risk of developing a heart infection known as endocarditis, which affects the tissue lining the heart and blood vessels. Endocarditis is serious and requires treatment with intravenous (IV) antibiotics.

Reviewed by: Gina Baffa, MD
Date reviewed: February 2012