The ligamentum arteriosum is a short band of fibrous tissue in the chest that connects the aortic arch to the pulmonary artery. It’s a remnant of a blood vessel called the ductus arteriosus, which plays a critical role during fetal development but closes shortly after birth and transforms into this small ligament. In most people, it sits quietly in the chest without causing any problems, but its fixed position makes it relevant in trauma, surgery, and certain congenital heart conditions.
What It Does Before Birth
Before a baby is born, the lungs are filled with fluid and aren’t yet breathing air. Blood doesn’t need to pass through the lungs to pick up oxygen because the placenta handles that job. So the fetal circulatory system includes a shortcut: the ductus arteriosus, a muscular vessel that routes blood directly from the pulmonary artery to the aorta, bypassing the lungs almost entirely.
This vessel develops from one of the early embryonic arch arteries (the sixth branchial arch). It remains wide open throughout pregnancy, kept that way by the low-oxygen environment inside the womb and by chemical signals that relax its muscular wall.
How It Closes After Birth
When a newborn takes its first breaths, rising oxygen levels trigger the muscles in the ductus wall to contract. Chemical signals like bradykinin and endothelin contribute to this process. In healthy, full-term newborns, the ductus arteriosus is functionally closed within 12 to 24 hours of birth, meaning blood is no longer flowing through it even though the structure is still physically present.
Over the next two to three weeks, the inner lining folds inward, the tissue breaks down, and the vessel undergoes fibrosis, essentially scarring shut. What’s left is a dense cord of connective tissue with no open channel: the ligamentum arteriosum. This permanent seal is typically complete by about three weeks of age.
When the Ductus Doesn’t Close
If the ductus arteriosus fails to close, the condition is called patent ductus arteriosus, or PDA. After the first few weeks of life, a persistent opening is considered abnormal, though some clinicians don’t formally diagnose PDA until after three months of age. A PDA can range from “silent” (detected only by chance on an echocardiogram) to large enough to cause significant strain on the heart by allowing too much blood to flow to the lungs.
Echocardiography is the standard tool for confirming PDA. It can visualize whether the ductus still has an open channel or has properly converted into a sealed ligament. A normal ligamentum arteriosum has no lumen at all.
Where It Sits in the Chest
The ligamentum arteriosum runs from the upper surface of the pulmonary trunk (near where the left pulmonary artery branches off) to the underside of the aortic arch, just beyond where the left subclavian artery originates. It’s a short structure, only a few centimeters long, but its position makes it an important landmark in chest surgery and imaging.
One of its most notable neighbors is the left recurrent laryngeal nerve, a branch of the vagus nerve that controls the muscles of the voice box. This nerve loops underneath the aortic arch and hooks directly beneath the ligamentum arteriosum before traveling back up to the larynx. Surgeons operating in this area must carefully identify the ligamentum to avoid damaging this nerve, which could cause hoarseness or vocal cord paralysis.
Its Role in Vascular Rings
In some congenital heart conditions, the ligamentum arteriosum helps form what’s called a vascular ring, a circle of blood vessels and fibrous tissue that wraps around the trachea and esophagus. The most common scenario involves a double aortic arch, where both the right and left aortic arches persist from embryonic development. The ligamentum connects the aorta to the pulmonary trunk, completing a “napkin ring” around the airway and food pipe.
This ring can compress or squeeze the trachea, the esophagus, or both. Children with vascular rings may have noisy breathing, difficulty swallowing, or recurrent respiratory infections. Surgical treatment typically involves cutting the ligamentum arteriosum to break the ring and relieve the compression.
Why It Matters in Trauma
The ligamentum arteriosum anchors a specific point on the aorta called the aortic isthmus, the zone where the relatively mobile aortic arch meets the fixed descending aorta along the spine. During sudden deceleration, like a high-speed car crash or a fall from height, the mobile portion of the aorta continues moving forward while the fixed portion stays in place. The ligamentum acts as a tether point that amplifies the shearing forces at this junction.
This is why traumatic aortic injuries, including partial or complete tears of the aortic wall, occur most frequently at the isthmus. These injuries are one of the leading causes of immediate death in high-speed collisions. For those who survive the initial event, rapid diagnosis (usually by CT scan) and surgical repair are critical.
Calcification on Imaging
The ligamentum arteriosum sometimes calcifies, and this shows up on routine chest CT scans more often than many clinicians realize. A study using multi-slice CT found calcification of the ligamentum in about 37.8% of children and 11.2% of adults. The highest rates appeared in young children, with nearly half (48.7%) of one pediatric age group showing visible calcium deposits.
This calcification is generally harmless and considered an incidental finding. Its main significance is diagnostic: radiologists need to recognize it so they don’t mistake it for something more concerning, like a calcified lymph node or a foreign body near the great vessels.