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.
Exam relevance
Risk factors: - Prematurity (most significant risk factor — PDA occurs in up to 60% of infants <28 weeks) - Low birth weight - Maternal rubella infection during first trimester - High altitude birth (lower oxygen tension) - Female sex (2:1 female predominance) - Family history of congenital heart disease - Fetal alcohol syndrome
Diagnostics: - Auscultation of continuous (machinery-like) murmur best heard at left upper sternal border - Echocardiography (confirms PDA, measures shunt size and direction) - Bounding peripheral pulses (widened pulse pressure) - Chest X-ray showing cardiomegaly and increased pulmonary vascular markings - Pulse oximetry (usually normal unless Eisenmenger physiology develops)