Patent ductus arteriosus

Question 1

How many shunts are there in the foetal circulation?

What are the called?

Answer 1

here are 3 shunts present in the foetal circulation:

1. Ductus venosus, connecting the umbilical vein to the inferior vena cava
2. Foramen ovale, connecting the right atrium to the left atrium
3. Ductus arteriosus, connecting the pulmonary artery to the aorta

Question 2

What is the pathophysiology of these shunts in the foetal circulation?

Answer 2

Foetal circulation:
=> Pulmonary circulation has a very high resistance as the lungs are not yet inflated.

=> This high resistance diverts blood away from the lungs and into the aorta via the ductus arteriosus (right to left shunt).

=> After birth, as the lungs expand the resistance in the neonate’s lung capillary bed rapidly decreases. Blood then flows through the lung circulation.

=> As oxygenated blood goes through the ductus arteriosus, it’s triggered to close.

=> However, if ductus arteriosus does not close, there will be a left-to-right shunt due to the now higher pressures in the left atrium.

Question 3

How does persistent patent ductus arteriosus present?

Answer 3

=> asymptomatic

=> signs of heart failure

=> collapsing pulse from increased pressure gradients (bounding pulse)

=> continuous murmur from turbulent flow across the ductus arteriosus

Question 4

How is persistent patent ductus arteriosus managed?

Answer 4

Treatment only required if baby is symptomatic.

1/3 of patients with PDA require medical treatment with indomethacin.

~8% of patients require surgical ligation to close the PDA.

Question 5

What is Indomethacin and how does it work?

Answer 5

Indomethacin is an NSAID that inhibits prostaglandin synthesis.

Inhibition of prostaglandin causes vasoconstriction which closes the ductus arteriosus.