Patent Ductus Arteriosus

The ductus arteriosus is a fetal vessel that allows the oxygenated blood from the placenta to bypass the lungs in utero. At birth, the lungs fill with air with the first breaths, pulmonary vascular resistance drops, and blood flows from the right ventricle to the lungs for oxygenation. The increased arterial oxygen tension and the decreased flow through the ductus arteriosus allow the ductus to constrict. The ductus arteriosus is functionally closed by 12 to 24 hours of age in healthy, full-term newborns. Permanent (anatomic) closure is complete within 2 to 3 weeks.

In the premature infant, the ductus arteriosus does not close rapidly and may require pharmacologic or surgical closure to treat side effects.

Anatomy

During fetal life, the ductus is a normal structure that permits blood leaving the right ventricle to bypass the pulmonary circulation and enter the descending aorta. Less than 10% of this blood enters the pulmonary circulation. After birth, the ductus closes within 24-48 hours. The ductus is a remnant of the distal sixth aortic arch and connects the proximal descending aorta to the main pulmonary artery. The ductus can be found just posterior to the arch of the aorta where it enters the anterior pulmonary artery. The ductus has a conical shape which is large at the aortic end and narrow at the pulmonary end. However, the shape, size, and length of the ductus are very variable.

For surgeons, an anatomical marker of the patent ductus is the recurrent laryngeal nerve which loops posteriorly around the ductus and ascends behind the aorta en route to the larynx. The recurrent laryngeal nerve is often injured during surgical ligature of the ductus.

The Patent ductus is classified based on its angiographic features and includes the following:

1. Type A: Conical

2. Type B: Window

3. Type C: Tubular

4. Type D: Complex

5. Type E: Elongated