Patent ductus arteriosus (PDA) is a condition in which there is persistant patency of the ductus arteriosus. The ductus is a direct connection between the aorta and the pulmonary artery which is present and functional during fetal life but which is unnecessary once air-breathing begins. Its patency is normally obliterated by the constriction resulting from the inhibition of prostaglandins. This condition is common in rubella infection and high altitudes or prematurity.
The hemodynamic effects are similar to aortic incompetence. In cases complicated with Eisenmenger's syndrome there is reversal of the shunt with consequent differential cyanosis.
Treatment is always to close the patency. This may be attempted with indomethacin in premature infants. Surgery is delayed in infective endocarditis. It is contraindicated if the pulmonary vascular resistance exceeds 70% of the systemic resistance.