A patent ductus arteriosus (PDA) is a persistent fetal shunt which remains patent in some newborns. It represents a connection between the aorta and pulmonary artery. Physiologically, it represents a left to right shunt which may cause hemodynamic burden depending on the size of the PDA. During fetal life, the PDA serves to divert blood away from the developing fetal lungs. Following birth, the PDA typically closes within the first 24 hours of life. In some infants, in particular premature infants, the PDA may persist and if large enough may represent a significant left to right shunt.
Image above used with permission from Texas Children's Hospital and courtesy of the department of cardiothoracic surgery