Purpose or Case Report: The ductus arteriosus is normal structure of fetal circulation derived from the embryologic left 6th aortic arch that connects the aorta to the pulmonary arterial circulation. Patent ductus arteriosus (PDA) is a congenital cardiac anomaly in which the ductus arteriosus fails to undergo physiologic closure after birth. PDA is associated with prematurity, trisomy 21, and other diseases. When isolated, a PDA acts as a left to right cardiac shunt. In the setting of a right aortic arch, a PDA completes the vascular ring. A PDA may be treated with medical closure with indomethacin, endovascular closure, or surgical closure.

Several congenital heart defects are dependent on a PDA to maintain circulation either to the systemic or pulmonary circulations. In these cases of ductal-dependent postnatal circulation, the PDA can be kept open with prostaglandins.

Examples include:
- Pulmonary atresia without a ventricular septal defect
- Critical pulmonary stenosis
- Tricuspid atresia
- Severe Ebstein anomaly
- Severe tricuspid regurgitation
- Hypoplastic left heart syndrome
- Critical aortic valve stenosis
- Interruption of the aortic arch
- Severe coarctation of the aorta

Additional important anatomic and physiologic variations of PDA anatomy will be presented:
- Reverse oriented ductus
- To and fro blood flow
- Reversal of PDA blood flow
- Right ductus arteriosus
- Completion of a vascular ring

Other important structures to evaluate:
- Trachea and main bronchi which may be compressed by the PDA
- Main and branch pulmonary arteries which may be stenotic or have isolated origin from the PDA
- Aortic arch sidedness and caliber (arch hypoplasia, coarctation, interruption) which may only become physiologically apparent as the PDA closes
- Vascular ring which may include the PDA or its ligament as a component of the ring

The purpose of this education exhibit is to describe:
- Embryology of the ductus arteriosus
- Normal anatomy and blood flow physiology of the ductus arteriosus
- Anatomy and physiology of the ductus arteriosus in congenital heart disease
- Abnormalities of adjacent mediastinal structures (trachea, bronchi, aorta, pulmonary arteries) due to PDA
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