Truncus arteriosus
DEFINITION
Truncus arteriosus (TRUNG-kus ahr-teer-e-O-sus) is a rare heart defect that’s present at birth (congenital). If your baby has truncus arteriosus, it means that one large blood vessel leads out of the heart. Normally, there are two separate vessels coming out of the heart.
In addition, the two lower chambers of the heart are missing a portion of the wall that divides them. As a result of truncus arteriosus, oxygen-poor blood that should go to the lungs and oxygen-rich blood that should go to the rest of the body are mixed together. This creates severe circulatory problems.
If left untreated, truncus arteriosus can be fatal. Surgery to repair truncus arteriosus is generally successful, especially if the repair occurs before your baby is 2 months old.
CAUSES
Truncus arteriosus occurs during fetal growth when your baby’s heart is developing and is, therefore, present at birth (congenital). In most cases the cause is unknown. An overview of typical heart structure and function is helpful in understanding the defects of truncus arteriosus.
The heart
Your heart has four pumping chambers that circulate your blood. The “doors” of the chambers (valves) control the flow of blood, opening and closing to ensure that blood flows in a single direction.
The heart’s four chambers are:
- The right atrium, the upper right chamber, receives oxygen-poor blood from your body and delivers it into the right ventricle.
- The right ventricle, the lower right chamber, pumps the blood through a large vessel called the pulmonary artery and into the lungs, where the blood is resupplied with oxygen.
- The left atrium, the upper left chamber, receives the oxygen-rich blood from the lungs and delivers it into the left ventricle.
- The left ventricle, the lower left chamber, pumps the oxygen-rich blood through a large vessel called the aorta and on to the rest of the body.
Normal heart development
The formation of the fetal heart is a complex process. At a certain point, all fetuses have a single large vessel (truncus arteriosus) exiting the heart. During normal development of the heart, however, this very large single vessel divides into two parts. One part becomes the lower portion of the aorta, which is attached to the left ventricle. The other part becomes the lower portion of the pulmonary artery, which is attached to the right ventricle. Also during this process, the ventricles develop into two chambers separated by a wall (septum).
Truncus arteriosus in newborns
In babies born with truncus arteriosus, the single large vessel never finished dividing into two separate vessels. And the wall separating the two ventricles never closed completely, resulting in a large hole between the two chambers (ventricular septal defect).
In addition to the primary defects of truncus arteriosus, the valve controlling blood flow from the ventricles to the singe large vessel (truncal valve) is often defective, allowing blood to flow backward into the heart.
SYMPTOMS
Signs and symptoms of truncus arteriosus often develop in the first few weeks of life. They include:
- Blue coloring of the skin (cyanosis)
- Poor feeding
- Excessive sleepiness
- Poor growth
- Shortness of breath (dyspnea)
- Rapid breathing (tachypnea)
- Irregular heartbeats (arrhythmia)
- Excessive sweating (diaphoresis)
When to see a doctor
Seek medical treatment if you notice that your baby has any of the following problems:
- Blue coloring of the skin (cyanosis)
- Poor feeding
- Poor weight gain
- Excessive sleepiness
- Excessive sweating
Some signs of truncus arteriosus may indicate a problem that needs urgent care. If your baby experiences any of the following signs and symptoms and you can’t see your baby’s doctor immediately, seek emergency medical care:
- Rapid, shallow or labored breathing
- Worsening of blue coloring of the skin
- Loss of consciousness
