Truncus Arteriosus in Children
Basics of Truncus Arteriosus
Truncus arteriosus is a rare type of heart disease that occurs at birth (or is “congenital”) in which a single blood vessel (truncus arteriosus) emerges from the right and left ventricles, instead of the normal two vessels, the pulmonary artery and aorta.
The defect occurs due to abnormal development of the fetal heart during the first eight weeks of pregnancy. In a normal heart, the aorta and pulmonary artery start as a single blood vessel that eventually divides and becomes two separate arteries.
But in truncus arteriosus, the single great vessel fails to separate completely, leaving a connection between the aorta and pulmonary artery.
Another congenital heart defect that occurs with truncus arteriosus is a ventricular septal defect. (The ventricular septum is the dividing wall between the two lower chambers of the heart known as the right and left ventricles.)
In a normal heart, oxygen-poor (blue) blood returns to the right atrium from the body, travels to the right ventricle, and then is pumped through the pulmonary artery into the lungs, where it receives oxygen. Oxygen-rich (red) blood returns to the left atrium from the lungs, passes into the left ventricle, and then is pumped through the aorta out to the body.
In truncus arteriosus, oxygen-poor (blue) and oxygen-rich (red) blood mix back and forth through the ventricular septal defect. This mixed blood then flows through the common truncal vessel. Some of the mixed blood flows through the branch that becomes the pulmonary artery and on to the lungs, and some of the mixed blood goes into the aortic branch and continues to the body. The mixed blood that goes to the body does not have as much oxygen as normal, causing varying degrees of cyanosis (blue color of the skin, lips and nail beds).
Fast Fact of Truncus Arteriosus
Truncus arteriosus affects 1 percent to 4 percent of children with congenital heart disease.
Causes of Truncus Arteriosus
Some congenital heart defects may have a genetic link, either occurring due to a gene defect, chromosome abnormality or environmental exposure. Thus heart problems tend to occur more often in certain families. Some heart defects occur sporadically (by chance), with no clear cause.
Symptoms of Truncus Arteriosus
Each child may experience symptoms of truncus arteriosus differently, but common symptoms may include:
- Pale skin
- Cool skin
- Rapid breathing
- Heavy breathing
- Rapid heart rate
- Congested breathing
- Disinterest in feeding, or tiring while feeding
- Poor weight gain
Because symptoms of truncus arteriosus may resemble other medical conditions or heart problems, it’s important to always consult a child's physician for a diagnosis.
Health Problems Associated with Truncus Arteriosus
The blood that passes through the common truncal vessel has a lower oxygen content than normal. Oxygen-poor (blue) blood from the right ventricle and oxygen-rich (red) blood from the left ventricle mix together before entering the common vessel. Some of this mixed blood goes into the aorta and on to the body, producing cyanosis (blue color of the skin, lips and nail beds).
The pulmonary artery section of the common vessel gets more blood flow than the aorta does, because the pressure is lower in the lungs than the body and it is easier for blood to travel in that direction. If not repaired, the extra blood damages the lungs’ blood vessels. As the pressure in the lungs’ blood vessels rises, less blood goes to the lungs and more goes to the body. Cyanosis worsens as blood with lower amounts of oxygen travels to the body.
Tests, Procedures and Diagnosis of Truncus Arteriosus
A child's physician may hear a heart murmur during a physical examination and refer the child to a pediatric cardiologist, who specializes in the diagnosis and treatment of congenital heart defects and heart problems that may develop later in childhood. To make a diagnosis, the cardiologist performs a physical examination, listens to the child’s heart and lungs and makes other observations. Heart murmurs are evaluated on the basis of pitch, loudness and duration, which give a cardiologist an initial idea of which heart problem a child may have. Diagnostic testing for congenital heart disease varies by a child's age and clinical condition, and may include:
- Chest X-ray. This diagnostic test uses X-ray beams to produce images onto film of internal tissues, bones and organs.
- Electrocardiogram (ECG or EKG). This test records the electrical activity of the heart, showing abnormal rhythms (arrhythmias or dysrhythmias) and detecting heart muscle stress.
- Echocardiogram (or “echo”). This procedure evaluates the structure and function of the heart by using sound waves recorded on an electronic sensor that produce a moving picture of the heart and its valves.
- Cardiac catheterization. This invasive procedure gives very detailed information about the structures inside the heart. Under sedation, a small, thin, flexible tube (catheter) is inserted into a blood vessel in the groin, and then guided to the inside of the heart. Blood pressure and oxygen measurements are taken in the four chambers of the heart, pulmonary artery and aorta. In addition, contrast dye is injected to more clearly visualize the structures inside the heart.
Treatment for Truncus Arteriosus
A child’s physician determines the specific treatment for truncus arteriosus based on:
- A child's age, overall health and medical history
- Severity of the condition
- A child's tolerance for specific medications, procedures or therapies
- Expectations for the course of the condition
- Parents’ opinions or preferences
Truncus arteriosus must be treated by surgical repair of the defects. Surgery is usually performed after the infant is 2 weeks old, but before the blood vessels in the lungs are overwhelmed by extra blood flow and become diseased. The operation is performed under general anesthesia, and involves the following:
- The pulmonary arteries are detached from the common artery (truncus arteriosus) and connected to the right ventricle using a homograft (a section of pulmonary artery with its valves intact from a tissue donor). Occasionally, a conduit (a small tube containing a valve) is used instead of a homograft (human tissue valve).
- The ventricular septal defect is closed with a patch.
Until surgery, the condition may be managed by:
- Medications. Many children with the condition eventually need to take medications to help their heart and lungs work better. Medication that may be prescribed includes:
- Digoxin. A medication that helps strengthen the heart muscle, enabling it to pump more efficiently.
- Diuretics. The body's water balance can be affected when the heart is not working as well as it could. These medications help the kidneys remove excess fluid from the body.
- ACE (angiotensin-converting enzyme) inhibitors. Dilates the blood vessels, making it easier for the heart to pump blood forward into the body.
- Adequate nutrition. Infants may become tired when feeding, and may not be able to eat enough calories to gain weight. Options to ensure a baby has adequate nutrition include:
- High-calorie formula or breast milk. Special nutritional supplements can be added to formula or pumped breast milk to increase the number of calories per ounce, thereby allowing a baby to drink less and still consume enough calories to grow.
Supplemental tube feedings. Feedings given through a small, flexible tube that passes through the nose, down the esophagus, and into the stomach, can either supplement or replace bottle feedings. Infants who can drink part of their bottle, but not all, may be fed the remainder through the feeding tube. Infants who are too tired to bottle feed may receive their formula or breast milk through the feeding tube alone.