Truncus arteriosus is a rare congenital heart defect in which a single large blood vessel exits the heart instead of the normal two (the aorta and the pulmonary artery). It occurs in roughly 9 to 11 out of every 100,000 live births, accounting for 1% to 4% of all congenital heart disease cases. Because this single vessel carries both oxygen-rich and oxygen-poor blood to the body and lungs simultaneously, babies born with the condition need surgical repair early in life.
How the Defect Develops
During normal fetal development, the single vessel that initially leads out of the embryonic heart divides into two separate arteries: the aorta, which sends blood to the body, and the pulmonary artery, which sends blood to the lungs. In truncus arteriosus, that division never fully happens. The baby is born with one shared “trunk” sitting over both ventricles of the heart, along with a hole between the lower chambers (a ventricular septal defect, or VSD). A single valve controls blood flow out of the heart rather than the usual two separate valves.
The result is that oxygen-rich blood returning from the lungs mixes with oxygen-poor blood returning from the body before being pumped out through the common trunk. Some of that mixed blood heads to the lungs, some to the rest of the body. The lungs end up receiving far more blood flow than they should, which forces the heart to work harder and can quickly lead to heart failure if untreated.
Types of Truncus Arteriosus
Doctors classify the defect based on exactly where the pulmonary arteries branch off from the common trunk. The most widely used system, developed by Collett and Edwards, describes four types:
- Type I: A main pulmonary trunk branches off from the shared vessel, then splits into right and left pulmonary arteries. This is the most common form.
- Type II: The right and left pulmonary arteries arise separately but close together from the back of the trunk.
- Type III: The right and left pulmonary arteries originate separately and farther apart from the trunk.
- Type IV: The pulmonary arteries come off the descending aorta rather than the trunk itself. Some experts consider this a distinct condition rather than true truncus arteriosus.
The type matters mainly for surgical planning, since it determines how the pulmonary arteries will be detached and reconnected during repair.
Genetic Links and Risk Factors
A significant number of babies with truncus arteriosus also carry a genetic deletion known as 22q11.2 deletion syndrome, previously called DiGeorge syndrome. This chromosomal abnormality affects the development of several body systems and is strongly associated with heart defects that involve the outflow tracts of the heart, including truncus arteriosus, tetralogy of Fallot, and interrupted aortic arch. About 4% of individuals with 22q11.2 deletion syndrome specifically have truncus arteriosus, but the overlap is notable enough that genetic testing is routinely offered to families after diagnosis.
Symptoms in Newborns
Babies with truncus arteriosus typically show signs within the first days or weeks of life. Because too much blood floods the lungs, symptoms often look like heart failure: rapid breathing, poor feeding, sweating during feeds, and slow weight gain. Skin color may appear bluish or dusky, especially around the lips and fingertips, because the blood reaching the body contains less oxygen than normal. As pulmonary blood flow increases in the first weeks after birth (when the natural resistance in the lung vessels drops), symptoms tend to worsen quickly rather than improve.
How It Is Diagnosed
Echocardiography, an ultrasound of the heart, is the primary tool for confirming truncus arteriosus. It can show the single outflow vessel, the VSD beneath it, and the number and position of the valve leaflets. In some cases, the defect is detected before birth during a routine fetal ultrasound or a specialized fetal echocardiogram. Prenatal detection allows the delivery to be planned at a center with pediatric cardiac surgery capability, which improves early outcomes.
Surgical Repair
Open-heart surgery is the only treatment, and it is typically performed within the first few weeks of life. The procedure, sometimes called a Rastelli repair, involves three key steps. First, the pulmonary arteries are disconnected from the common trunk. Second, a patch is placed to close the VSD, directing oxygen-rich blood from the left ventricle out through the remaining vessel (which now functions as the aorta). Third, a tube containing a valve, called a conduit, is placed between the right ventricle and the pulmonary arteries. This conduit takes over the role of the missing pulmonary artery, sending oxygen-poor blood to the lungs.
The goal is to create two completely separate circulatory pathways: one to the body and one to the lungs, just as a normally formed heart would have.
Long-Term Outlook and Reoperations
Survival after initial repair has improved dramatically over recent decades, and the majority of babies who undergo surgery in infancy survive into adulthood. However, truncus arteriosus is not a one-surgery condition. The conduit placed during the initial repair does not grow with the child, so it will need to be replaced at least once, and often multiple times, as the child’s body outgrows it. One study found a 92.9% freedom from reoperation at five years, meaning most children go several years before a second procedure is needed, though the timeline varies.
The truncal valve, which becomes the aortic valve after repair, is another source of long-term concern. About 25% of patients have significant valve leakage (regurgitation), which is a known risk factor for poorer outcomes and future surgery. Research tracking patients over time found that reoperation rates for any reason reach roughly 50% by seven years and as high as 77% by ten years in some series. Valves with four leaflets instead of the typical three carry more than double the risk of needing reoperation.
Interestingly, not all cases of moderate valve leakage get worse. In patients where moderate regurgitation was left untreated during the first surgery, nearly 30% saw their leakage naturally decrease from moderate to mild over time, while about 43% eventually needed a valve operation. This unpredictability means that lifelong follow-up with a cardiologist is essential. Adults who were repaired as infants will continue to need periodic imaging, and some will require catheter-based or surgical interventions to replace conduits or address valve problems well into adulthood.
Living With Truncus Arteriosus After Repair
Children who have a successful repair generally lead active lives, though the degree of physical activity they can tolerate varies depending on how well the repair holds up and whether the valve functions normally. Regular cardiology visits, typically once or twice a year, track heart function, conduit size, and valve performance over time. Many patients will eventually transition from a pediatric cardiologist to an adult congenital heart disease specialist, a relatively newer subspecialty designed for the growing population of adults living with repaired heart defects.
Exercise restrictions, if any, are individualized. Some patients participate in sports with few limitations, while others with significant valve leakage or reduced heart function may be advised to avoid high-intensity competitive activities. Each follow-up visit helps refine those recommendations as the heart’s condition evolves.