Ductus arteriosus

The ductus arteriosus (Botallo's duct) is a vascular connection between the pulmonary artery and the aorta that is essential during fetal life. It connects the proximal left pulmonary artery (or pulmonary trunk) to the descending aorta, just distal to the left subclavian artery.

During fetal development, the ductus arteriosus serves a critical physiological function by allowing blood to bypass the fluid-filled, non-functioning fetal lungs. It shunts the majority of right ventricular output away from the pulmonary circulation directly into the systemic circulation, since oxygenation occurs at the placenta rather than the lungs. This right-to-left shunt reduces the workload on the fetal heart and ensures efficient circulation.

After birth, the ductus arteriosus normally closes within the first few days of life in response to multiple physiological signals, including increased oxygen tension, decreased prostaglandin levels, and other biochemical changes. When closure occurs, the vessel becomes a fibrous remnant called the ligamentum arteriosum.

When the ductus arteriosus fails to close after birth, the condition is called patent ductus arteriosus (PDA), which occurs in approximately 0.3% to 0.8% of term infants and is more common in premature infants. The hemodynamic consequences of PDA depend on the size of the vessel and the pressure gradient between the systemic and pulmonary circulations, ranging from clinically insignificant to causing heart failure and pulmonary hypertension.