What is a truncus arteriosus defect?
Truncus arteriosus is a congenital heart defect (the baby is born with it) in which there is only one main artery or large blood vessel that carries blood to the body and lungs, instead of two separate arteries. The condition occurs in the womb, while the fetus’s heart is still developing.
During normal development of the heart and circulatory system, the single large vessel (also called the truncus arteriosus) divides into two vessels: the aorta and the pulmonary artery. The aorta carries blood from the heart to the rest of the body. The pulmonary artery has two sections or branches to carry blood to the lungs, so that the blood can receive oxygen.
Babies who are born with truncus arteriosus have a ventricular septal defect. This is a hole in the septum, the wall that divides the right and left ventricles (the two lower pumping chambers of the heart). This opening allows blood that has picked up oxygen from the lungs to mix with blood that has not, so that the blood leaving the heart does not carry enough oxygen. Poorly oxygenated blood that circulates throughout the body can cause severe circulatory problems and damage to all organs, in addition to the heart and lungs.
Sometimes the valve (truncus valve) located between the ventricles and the single large blood vessel can be either stenotic (too tight) or regurgitant (leaking), which can adversely affect the entire circulation.
Truncus arteriosus is a serious condition. Unless it is treated, it usually results in death within the first year of life. Truncus arteriosus is treated with surgery, which is often successful, especially if it is performed before the infant is two months old.
Symptoms and Causes
What causes truncus arteriosus?
It is not known exactly what causes truncus arteriosus. The condition occurs while the fetal heart is developing.
Several factors may increase the risk of truncus arteriosus, including the following:
- A family history of congenital heart problems.
- Children with chromosomal disorders, velocardiofacial syndrome, or DiGeorge’s syndrome may be at greater risk for developing truncus arteriosus.
- Pregnant women who take certain medications during pregnancy that could damage the fetus, or those who contract a viral illness such as German measles (rubella), may have a greater chance of giving birth to an infant with truncus arteriosus.
What are the symptoms of truncus arteriosus?
Symptoms of truncus arteriosus are usually seen within the first week of life. Signs may include:
- Rapid or heavy breathing.
- Shortness of breath or lung congestion.
- Poor feeding.
- Poor weight gain.
- Irregular heartbeat.
- Excessive sweating.
- Pale or cool skin.
- A bluish tinge to the skin (cyanosis).
Diagnosis and Tests
How is truncus arteriosus diagnosed?
The pediatrician will ask if you have noticed any changes in your child’s feeding and sleeping behaviors. The doctor will measure your child’s height, weight, and head circumference to see if there has been any delay in development.
The doctor will perform a physical examination and listen to the child’s lungs and heart. If the doctor detects a heart murmur (an unusual heart sound) or irregular heartbeat, or the presence of fluid in the lungs, he or she may order additional tests, including:
- Chest X-ray
- Electrocardiogram (EKG or ECG): This test measures the electrical activity of the heart to detect whether there is any stress on the heart muscle.
- Echocardiogram: A procedure that uses sound waves to produce a moving picture of the heart and heart valves to see the heart "in action."
- Cardiac catheterization: A procedure in which a small, flexible tube is inserted into the body through the groin and passed through to the inside of the heart. Contrast dye may be used to provide a more detailed picture of the heart.
- Magnetic resonance imaging (MRI): A test that produces very clear pictures, or images, of the human body without the use of x-rays. MRI uses a large magnet, radio waves, and a computer to produce these images.
- Computed tomography (CT) scan: Uses X-rays and computers to produce images of a cross-section of the body. The patient must lie as still as possible as the table moves through the large, donut-shaped scanning device.
Management and Treatment
What are the complications associated with truncus arteriosus?
Children who are born with truncus arteriosus may have an excessive amount of blood flowing to the lungs, which can cause congestive heart failure. Symptoms of congestive heart failure can include:
- Shortness of breath.
- Wheezing or noisy breathing.
Other complications associated with truncus arteriosus include respiratory and circulatory problems, including the following:
- High blood pressure in the lungs (pulmonary hypertension) and breathing problems: The excessive amount of blood flowing into the lungs and constriction (tightening) of blood vessels can cause respiratory problems.
- Enlargement of the heart (cardiomegaly): Excessive blood flow to the lungs and heart put additional stress on the heart, which may cause it to increase in size and weaken.
- Heart failure: Stress on the heart caused by a greater workload, along with reduced oxygen supply, can lead to heart failure.
How is truncus arteriosus treated?
Truncus arteriosus is treated with surgery to repair the heart defect. Surgery is usually performed in the neonatal period (1-2 weeks after birth).
During the surgery, the ventricular septal defect (hole in the wall between the right and left ventricles) is closed with a patch. The upper part of the pulmonary artery is separated from the single common artery (truncus arteriosus). Then a tube or conduit and a valve are inserted to connect the right ventricle of the heart with the pulmonary artery. The single large vessel is reconstructed to create a new aorta. The surgeon might also repair the truncal valve, if necessary.
Before the surgery is performed, your child may receive medications such as diuretics and digoxin to regulate the function of the heart and lungs. Digoxin improves the strength of heart muscle contractions, helping the heart to pump blood more efficiently. Diuretics help remove extra fluid from the body, which often occurs in cases of heart failure.
What happens after the surgery?
Your child will have to spend several days in the hospital after the surgery. He or she may need pain medications such as ibuprofen or acetaminophen. Your child may require more sleep or rest after the operation, or may tire more easily. Full recovery usually takes a few weeks.
Your child may need additional surgery later to replace the conduit or tube that has been implanted to connect the right ventricle and pulmonary artery. The conduit usually has to be replaced 2 or 3 times while the child is growing, to keep the blood flow from being blocked. These surgeries usually require a hospital stay of less than 1 week.
Some medical procedures are being developed that use a cardiac catheter instead of a replacement conduit in order to avoid the need for traditional surgery. There is also a chance that the truncal valve might leak. If this occurs, surgery to repair the leaky valve should be performed within five to seven years of the initial surgery to prevent serious heart damage.
Outlook / Prognosis
What is the prognosis (outlook) following surgery to repair truncus arteriosus?
The prognosis is good for most children after surgery to repair truncus arteriosus. More than 90% of children survive the surgery. Your child must continue to obtain follow-up care from a cardiologist for the rest of his or her life. Some children have to restrict their physical activities, and some might not be able to participate in competitive sports. Children who have had surgery for truncus arteriosus will need to take antibiotics before undergoing dental procedures or surgery in order to prevent endocarditis, an infection of the lining of the heart.
Complications may arise later in life, even when the heart defects have been surgically repaired. These complications may include abnormal heart rhythms (arrhythmias), pulmonary hypertension (high blood pressure in the lungs), and leaky heart valves. These complications may produce symptoms such as dizziness, shortness of breath, and heart palpitations (rapid fluttering heartbeats).