Patent ductus arteriosus (PDA) is a congenital heart defect characterized by persistence of the ductus arteriosus, which typically constricts and obliterates after birth. Patency of the ductus is caused by low arterial oxygen and higher concentrations of prostaglandin E2 and nitrous oxide. PDA leads to left-to-right shunting of oxygenated blood from the aorta into the main pulmonary artery. PDA can occur alone or in conjunction with other congenital heart disease. The incidence of an isolated PDA is 2.9 per 10 000 live births with a 2:1 female predominance in full-term infants. The incidence is higher in premature infants, infants born at higher altitudes, and infants with congenital rubella. Isolated PDA is also associated with genetic disorders such as Down syndrome, cri-du-chat syndrome, Holt-Oram syndrome, and Noonan syndrome.

Signs and symptoms of PDA can present from infancy to adulthood and vary according to the size and length of the ductus. Preterm infants typically have severe presentations with pulmonary edema, bronchopulmonary dysplasia (BPD), pulmonary hemorrhage, heart failure, necrotizing enterocolitis, and intraventricular hemorrhage. They typically require ventilation and oxygenation while hospitalized prior to PDA closure. Full-term infants, children, and adults with a small PDA will be asymptomatic but may have a murmur. The murmur changes as the patient ages but is usually described as a continuous 3/6 murmur best heard at the left infraclavicular region. Patients with a moderately sized PDA can have exercise intolerance, difficulty feeding, and poor weight gain with failure to thrive. On examination, in addition to a murmur, they can have a wide systemic pulse pressure and evidence of left ventricular dysfunction. Large PDAs can present with cyanotic heart disease with clubbing and cyanosis worse in the lower extremities, wide pulse pressure, and precordial thrill.

The diagnosis is made based on clinical manifestations and confirmed with echocardiogram. Complications from PDAs include pulmonary hypertension, infective endocarditis, and heart failure.