Truncus Arteriosus

The Centers for Disease Control and Prevention estimate that 300 babies are born each year in the United States with a rare, congenital heart defect known as truncus arteriosus. In healthy babies, there are two blood vessels leaving the heart, the pulmonary artery and the aorta. The pulmonary artery carries blood to the lungs and the aorta carries blood to the body. In children with truncus arteriosus, however, there is only one large artery that exits the heart.

Truncus arteriosus is typically accompanied by another heart abnormality known as a ventricular septal defect. This is a hole in the wall (septa) separating the heart’s two lower chambers, or ventricles. This opening allows a mix of oxygenated blood from the left ventricle and oxygen-depleted blood from the right ventricle. These abnormalities have three consequences.

The volume of blood flowing to the lungs is increased.
The amount of blood coursing to the body may be decreased.
The body’s blood supply carries less oxygen than normal.

In truncus arteriosus, there is only a single (sometimes malformed) truncal valve instead of the two normal valves: aortic and pulmonary. This abnormal valve inhibits blood from leaving the heart and allows blood that has already left the heart to leak back inside.

This combination of structural abnormalities can lead to a number of serious problems, including:

Respiratory problems
High blood pressure in the lungs (“pulmonary hypertension”)
Enlargement of the heart
Weakening of the heart
Heart failure
Decreased blood flow to body organs

Symptoms of Truncus Arteriosus

Within the first week of life, infants with truncus arteriosus often begin to show respiratory problems and occasionally cyanosis (blue lips, skin and extremities). Babies may also have irritability, excessive sleep, weak pulse, rapid breathing and poor ability to feed.

Patients with truncus arteriosus sometimes have additional health problems not directly related to the heart. A small deletion on the long arm of chromosome 22 can lead to abnormally low calcium levels in the blood. There may also be an increased risk of infection caused by a low number of certain white blood cells, called T-cells. This 22q11.2 deletion is sometimes referred to as DiGeorge syndrome.

Diagnosis of Truncus Arteriosus

Truncus arteriosus can be diagnosed during pregnancy by a routine prenatal ultrasound or fetal echocardiogram. A fetal echocardiogram not only provides an accurate and detailed picture of the structures of the heart, it also allows the doctor to see how the heart functions.

After birth, a heart murmur may alert doctors to a potential problem. However, because not all heart murmurs are serious, additional diagnostic testing through chest x-ray, EKG and echocardiogram are required. Many states (including Indiana) require testing (pulse oximeter screening) of all newborn babies for low oxygen levels before discharge from the newborn nursery. Failing this test sometimes leads to a diagnosis of truncus arteriosus.

Treatments

All babies with truncus arteriosus require surgery to survive. In all likelihood, the surgery needs to happen in early infancy. If a baby is too weak for surgery, your physician may prescribe medications that help stabilize and improve the baby’s health. Depending on the infant’s specific issues, diuretics may be given to eliminate extra fluid from the body as well as medications that prevent heart failure.

Once a baby is healthy enough for surgery, cardiac surgeons can repair the heart. This surgery involves patching the hole between the two ventricles so oxygen-rich and oxygen-poor blood can no longer mix. Surgeons also reconstruct a new aorta that allows oxygenated blood from the left ventricle to flow to all parts of the body. The right ventricle is surgically connected to the arteries going to the lungs with the placement of a connecting tube. Additional surgeries to replace the tube are needed as a child grows.

Key Points to Remember

Truncus arteriosus is a congenital heart defect in which the pulmonary artery and the aorta originate as a single, large artery that leaves the heart.
A ventricular septal defect and a malfunctioning truncal valve usually accompany truncus arteriosus.
Truncus arteriosus can be diagnosed prenatally by a routine prenatal ultrasound or fetal echocardiogram.
Newborns with truncus arteriosus can sometimes exhibit cyanosis, respiratory problems and have difficulties feeding.
Surgical repair of the defects is required to avoid heart failure and pulmonary hypertension, and to restore proper cardiac anatomy.

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Centers for Disease Control and Prevention (CDC)

The CDC is the nation’s health protection agency and provides information to help Americans understand and/or prevent diseases, including truncus arteriosus.

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