Clinical meaning
The ductus arteriosus is a normal fetal blood vessel connecting the pulmonary artery to the aorta, allowing blood to bypass the non-functioning fetal lungs. After birth, rising oxygen levels and falling prostaglandin E2 levels normally trigger smooth muscle constriction and closure of the ductus within 24-48 hours. In patent ductus arteriosus (PDA), the ductus fails to close, creating a left-to-right shunt where oxygenated blood from the high-pressure aorta flows back into the lower-pressure pulmonary artery. This increases pulmonary blood flow and volume overloads the left heart, potentially causing heart failure if the shunt is large.