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||What Is It?
A Ductus Arteriosus is a minor vessel, sometimes persisting from the fetal structure of the heart in a newborn baby, which connects the aorta to the pulmonary artery (PA in diagram).
It is termed a Patent Ductus Arteriosus (PDA) when it is open, allowing blood to flow from the aorta into the pulmonary artery. After the PDA closes, the resulting fiber-like structure is known as a ligamentum arteriosum.