Reproductive · Year 2 · from Reproductive
Case 2: Patent Ductus Arteriosus in Premature Infant
Clinical Image
Source: Wikipedia - Patent ductus arteriosus - CC BY-SA 3.0
Case Presentation
A premature male infant is born at 28 weeks gestation to a mother who presented with preterm labor. The mother received antenatal betamethasone 24 hours before delivery. The infant weighs 1100 grams and requires surfactant administration and mechanical ventilation for respiratory distress syndrome. At 5 days of life, the infant has increasing ventilator requirements and develops metabolic acidosis. Physical examination reveals a continuous "machinery" murmur best heard at the left upper sternal border, bounding peripheral pulses, and a widened pulse pressure (systolic 65, diastolic 25 mmHg). An echocardiogram confirms a moderate-sized patent ductus arteriosus with left-to-right shunting and evidence of pulmonary overcirculation with left atrial dilation. Medical management is attempted with ibuprofen (a prostaglandin synthesis inhibitor) for 3 days. Repeat echocardiogram shows significant reduction in ductal flow. The PDA closes by day 10 of life, and the infant's respiratory status improves over the following weeks.
Key Learning Points
- In fetal circulation, the ductus arteriosus shunts blood from the pulmonary artery to the descending aorta, bypassing the non-functional lungs
- The ductus normally closes after birth due to rising oxygen tension and falling prostaglandins; prematurity is associated with delayed closure
- A patent ductus arteriosus causes left-to-right shunting after birth (now that pulmonary vascular resistance is low), leading to pulmonary overcirculation and heart failure
- Prostaglandin synthesis inhibitors (indomethacin, ibuprofen) promote ductal closure by blocking prostaglandin E2, which maintains patency