ABSTRACT
The ductus arteriosus, arising from the distal portion of the embryonic sixth aortic arch, is a vascular communication between the systemic and pulmonary vasculature, usually between the isthmus of the aortic arch and the origin of the left pulmonary artery, which forms a vital part of fetal anatomy. The ductus normally closes spontaneously within 72 hours after birth in full-term infants. The resulting nonpatent ductus is called the ligamentum arteriosum. The persistent ductus arteriosus (PDA) is defined as persistent patency of the fetal ductus beyond its normal time of spontaneous closure. The most common risk factor for persistence of ductal patency is prematurity. The probability of PDA is inversely proportional to birth weight and gestational age (EGA), reaching 77% at 28 weeks EGA. The risk is further increased by the presence of infant respiratory distress syndrome (RDS), reaching 90% for EGA of less than 32 weeks. In these subsets, spontaneous closure can occur beyond 1 week but the risk of late patency is substantial.
