CVS - Patent Ductus Arteriosus

Question 1

Risk Factors of PDA (3).

Answer 1

1. Premature Babies.
2. Babies born at high altitude.
3. Maternal rubella infection in the 1st trimester.

Question 2

What is a PDA?

Answer 2

A connection between the pulmonary trunk and the descending aorta.

Question 3

Physiology of Ductus Arteriosus.

Answer 3

1. In the foetal circulation, the pulmonary circulation has a very high resistance as the lungs are not yet inflated. High resistance diverts blood into the aorta. After birth, as the lungs expand, the resistance in the neonatal pulmonary capillary bed rapidly decreases so blood flows to the lungs.
2. It usually closes with the first breaths due to increased pulmonary flow which enhances Prostaglandin clearance. Oxygenated blood triggers closure of the Ductus Arteriosus.

Question 4

Shunts in the Foetal Circulation (3).

Answer 4

1. Ductus Venosus (connects Umbilical Vein to IVC).
2. Foramen Ovale (connects RA to LA).
3. Ductus Arteriosus (connects Pulmonary Artery to Aorta).

Question 5

Nature of Murmur in PDA (2).

Answer 5

1. May not cause any abnormal heart sounds.
2. More significant PDAs - normal S1 with a Crescendo-Decrescendo ‘Machinery’ Murmur that may continue during S2 making S2 more difficult to hear.

Question 6

Clinical Features of PDA (4).

Answer 6

1. Subclavicular Thrill.
2. Large-Volume, Bounding, Collapsing Pulse.
3. Wide Pulse Pressure.
4. Heaving Apex Beat.

Question 7

Management of PDA.

Answer 7

Neonate : Indomethacin or Ibuprofen to inhibit Prostaglandin synthesis, which closes connection.
BUT give Prostaglandin E1 if associated with another congenital heart defect.