Ductus arteriosus
Great vessels · SaO2 ~50-55% PGE2 keeps open
Wide muscular vessel from the pulmonary trunk near the origin of the left pulmonary artery to the descending aorta just distal to the left subclavian artery, carrying most right ventricular output around the unventilated lungs.
Traced from the start
Detail
- Saturation
- ~50-55% (right ventricular blood)
- Share
- ~90% of right ventricular output in lamb data (about half of combined output); somewhat less in the human fetus, whose lungs take more
- Patency in utero
- Low PO2 plus PGE2 from the placenta (and little pulmonary PGE2 breakdown) keep the muscular wall relaxed
- Closure
- Rising PaO2 constricts the wall (O2-sensitive K+ channels) and PGE2 falls once the placenta is gone and the lungs metabolise it; functional closure within 10-15 h, anatomical closure by 2-3 weeks
- Preterm
- Immature duct is less sensitive to oxygen and more sensitive to PGE2, so it stays open
- Adult remnant
- Ligamentum arteriosum at the aortic isthmus (hover to see)
When it goes wrong
Patent ductus arteriosus (prematurity, congenital rubella, high altitude, trisomy 21)
Continuous 'machinery' murmur below the left clavicle, bounding pulses with wide pulse pressure, heart failure in the preterm; closed pharmacologically with indomethacin, ibuprofen or paracetamol (COX inhibition), otherwise device or surgical ligation
Duct-dependent lesion (pulmonary atresia, critical pulmonary stenosis, hypoplastic left heart, interrupted arch, critical coarctation, transposition)
Collapse or profound cyanosis when the duct closes in the first days; alprostadil (PGE1) infusion reopens it while awaiting surgery, with apnoea, fever, flushing and hypotension as side effects
Long-standing unrepaired PDA with Eisenmenger reversal
Right-to-left ductal flow enters the aorta beyond the left subclavian: differential cyanosis with clubbing of the toes but not the fingers
Maternal NSAID use in the third trimester
Premature ductal constriction in utero: right ventricular strain and tricuspid regurgitation on fetal echo, persistent pulmonary hypertension after birth
Practise this structure
No question in the bank is tagged to Ductus arteriosus yet. Questions appear here automatically once one is — the question bank is free to browse in the meantime.