Truncus arteriosus is a rare heart defect present at birth in which a single large blood vessel exits the heart instead of the normal two (the aorta and the pulmonary artery). It affects roughly 1 in 10,000 live births in the United States. Because oxygen-rich and oxygen-poor blood mix together in that single vessel, the heart has to work much harder to deliver enough oxygen to the body, and babies with this condition typically need surgery within the first few months of life.
How a Normal Heart Compares
In a healthy heart, two separate vessels leave the lower chambers. The pulmonary artery carries oxygen-poor blood from the right ventricle to the lungs, and the aorta carries oxygen-rich blood from the left ventricle out to the rest of the body. These two streams never mix.
In truncus arteriosus, the single vessel (called the “common trunk”) sits over both ventricles and receives blood from both sides of the heart. There is also almost always a hole between the two lower chambers, called a ventricular septal defect (VSD). This hole allows oxygen-poor and oxygen-rich blood to mix before being pumped into that one shared vessel. The lungs, brain, and other organs all receive this mixed blood, which carries less oxygen than it should.
Types of Truncus Arteriosus
Doctors classify the defect based on where the pulmonary arteries branch off from the common trunk. The system most often referenced was developed by Collett and Edwards in 1949:
- Type I: A single pulmonary trunk branches off the common vessel and then splits into the left and right pulmonary arteries heading to each lung. This is the most common form.
- Type II: The left and right pulmonary arteries arise separately but close together from the back of the common trunk.
- Type III: The pulmonary arteries originate independently from opposite sides of the common trunk or from the aortic arch.
- Type IV: Originally included in this classification, type IV is now recognized as a different condition entirely: a severe form of tetralogy of Fallot with pulmonary atresia. No pulmonary arteries arise from the trunk at all.
The type matters for surgical planning because it determines exactly how the blood supply to the lungs needs to be rerouted.
Symptoms in Newborns
Because oxygen-poor and oxygen-rich blood mix in the single vessel, babies with truncus arteriosus often show signs of trouble within the first days or weeks of life. Common symptoms include rapid breathing, poor feeding, excessive sweating during feedings, and a bluish or grayish tint to the skin (cyanosis) caused by low oxygen levels. The heart is essentially doing double duty, pumping extra blood to the lungs, which can lead to heart failure surprisingly fast in a newborn.
Some babies initially seem stable because the pressure in their lungs is still high right after birth, limiting how much extra blood floods into the lungs. As lung pressure naturally drops over the first week or two, more blood rushes to the lungs, and symptoms tend to worsen rapidly. This is why early detection is critical.
How It Is Diagnosed
Truncus arteriosus can sometimes be spotted before birth. A routine prenatal ultrasound may raise suspicion, and a fetal echocardiogram (a detailed ultrasound focused specifically on the baby’s heart) can confirm the diagnosis by showing the single large vessel leaving the heart.
After birth, the primary diagnostic tool is again an echocardiogram. It can reveal the common trunk, the hole between the ventricles, blood leaking backward through the trunk’s valve, and how well the heart is managing. Newborn pulse oximetry screening, which clips a small sensor to the baby’s hand or foot to measure blood oxygen levels, can also flag the condition before obvious symptoms appear. This is one reason hospitals now routinely screen newborns with pulse oximetry before discharge.
Connection to DiGeorge Syndrome
About 30% of babies with truncus arteriosus also have a chromosomal deletion known as 22q11.2, the genetic change behind DiGeorge syndrome. DiGeorge syndrome can affect the immune system, calcium levels, palate development, and learning. Genetic testing is standard for any baby diagnosed with truncus arteriosus so that these additional needs can be identified and managed early.
Surgical Repair
Surgery is the only treatment, and it is typically performed within the first few months of life. In one large study, the median age at repair was about 3 months, with many babies operated on earlier depending on how quickly symptoms develop. The goal of surgery is to separate the blood flow into two distinct paths: one to the lungs, one to the body.
During the operation, the pulmonary arteries are detached from the common trunk, and the remaining trunk becomes the aorta. A tube (called a conduit), often containing a valve, is then placed between the right ventricle and the pulmonary arteries to restore the normal route of blood to the lungs. The hole between the ventricles is closed with a patch. This effectively recreates the two-vessel system the baby should have been born with.
One challenge is sizing. Because the baby is so small, surgeons must balance placing a conduit large enough to last as the child grows against making the incision in the right ventricle too large, which can impair heart function. A conduit that is too big can also be compressed by the chest wall, potentially requiring early replacement.
Long-Term Outlook
Survival after surgical repair has improved dramatically. Over 90% of babies survive the initial surgery. At 10 years after repair, survival is approximately 97%, and even at 20 and 40 years, it remains around 93%, according to data from NewYork-Presbyterian.
That said, this is not a one-surgery condition. Children outgrow the conduit placed during the initial repair, so follow-up surgeries to replace it are expected as the child grows. The conduit’s valve can also stiffen or narrow over time, a complication called conduit stenosis. In some cases, a catheter-based procedure using an inflatable balloon can open a narrowed area without requiring open-heart surgery.
People who have had truncus arteriosus repaired need lifelong heart medication and regular follow-up with a cardiologist, including into adulthood. Cardiac imaging at regular intervals helps track how the conduit, valves, and heart muscle are performing over time. With modern surgical techniques and ongoing monitoring, most people who had this repair in infancy go on to lead active lives, though they remain under the care of a congenital heart disease specialist throughout adulthood.