ligamentum arteriosum

During fetal development, the ductus arteriosus shunts blood from the pulmonary trunk to the descending aorta, bypassing the non-aerated lungs. After birth, increased oxygen tension and decreased prostaglandin E1/E2 levels (due to placental separation and increased pulmonary flow) cause functional closure of the ductus within 10-15 hours, followed by anatomic closure via fibrosis over 2-3 weeks, forming the ligamentum arteriosum.

Clinical significance: 1. Anatomic landmark: The ligamentum arteriosum lies between the pulmonary trunk (near the bifurcation) and the aortic arch (distal to the left subclavian artery). The left recurrent laryngeal nerve hooks under the aortic arch just lateral to the ligamentum arteriosum, then ascends in the tracheoesophageal groove. This relationship is important in thoracic surgery and in understanding hoarseness from mediastinal masses (e.g., aortic aneurysm, lung cancer, or mediastinal lymphadenopathy compressing the nerve - Ortner syndrome).

2. Patent ductus arteriosus (PDA): Failure of the ductus arteriosus to close results in a PDA, a left-to-right shunt causing a continuous "machine-like" murmur. PDA is associated with maternal rubella infection, prematurity, and high altitude. It is kept open pharmacologically with prostaglandin E1 (alprostadil) in conditions requiring ductal patency for survival (e.g., transposition of the great vessels, coarctation of the aorta) and closed with indomethacin or other NSAIDs (COX inhibitors) that decrease prostaglandin synthesis.

3. Coarctation of the aorta: In adult-type coarctation, the narrowing typically occurs near the ligamentum arteriosum, distal to the left subclavian artery, which is a key distinguishing feature from infantile-type coarctation (which occurs proximal to the ductus and is often associated with a patent ductus arteriosus).

4. Traumatic aortic injury: The ligamentum arteriosum, along with the ligamentum teres (fixation points), makes the aortic isthmus (just distal to the left subclavian artery) a common site of traumatic aortic transection in high-speed deceleration injuries (e.g., motor vehicle accidents), because this fixed point creates a shear force during sudden deceleration.