Patent Ductus Arteriosus

Pathophysiology of Patent Ductus Arteriosus

1) patent ductus arteriosus is failure of closure of ductus arteriosus (which during fetal development shunts blood around the lungs from the pulmonary artery to the aorta) in the first few days of life
2) causes an initial left-to-right shunt (flow from high-pressure aorta to low-pressure pulmonary artery
3) eventually progresses to Eisenmenger’s syndrome (pulmonary hypertension with reversal of flow and a right-to-left shunt with blood moving from pulmonary artery to aorta)
4) conditions that delay closing are hypoxemia, acidosis, prematurity
5) death in patent ductus arteriosus is from cardiac failure or infective endocarditis

patent ductus arteriosus

Patent ductus arteriosus seen in the center of the illustration

Signs and Symptoms

1) coninuous machinery murmur (both diastolic and systolic components) best heard to the left of the pulmonic area
2) soft S3
3) differential cyanosis (upper body is pink and lower body is cyanotic

Associated Conditions

1) ventricular septal defect
2) atrial septal defect


1) isolated defect in 75% of cases
2) 8% of congenital heart disease


1) indomethacin
2) surgical ligation

Tips for USMLE

1) if question mentions continuous machinery murmur, think PDA
2) diastolic component disappears if pulmonary hypertension is present
3) other causes of a continuous murmur – coarctation of aorta, anomalous left coronary artery from the pulmonary artery, and ruptured congenital sinus of Valsalva aneurysm

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