Foetus vs. Neonate

Question 1

What is the role of the umbilical artery and umbilical vein? How does the blood compare in these vessels?

Answer 1

Umbilical arteries = Placental input (baby –> placenta)
- blood is deoxygenated and under high pressure
Umbilical veins = Placental output (placenta –> baby)
- blood is oxygenated and under high pressure

Question 2

Describe the role of the ductus arteriosus, ductus venosus and foramen ovale in foetal circulation.

Answer 2

Ductus arteriosus:

• protects lungs against circulatory overload
• allows RV to strengthen
• high pulmonary vascular resistance, low pulmonary blood blow

Ductus venosus (continuation of umbilical vein):
- connects the umbilical vein to the IVC

Foramen ovale:

• Shunts highly oxygenated blood from RA to LA
• RV pumps 2/3 of cardiac output

Question 3

What does the umbilical vein become at/after birth?

Answer 3

Ligamentum teres

Question 4

What forms the falciform ligament?

Answer 4

Embryonic ventral mesentery

Question 5

What happens/should happen to the foramen ovale at birth?

Answer 5

Septum primum and secundum fuse together –> foramen closes over
Becomes the fossa ovale
(due to higher pressure in the LA than RA)

Question 6

What happens/should happen to the ductus arteriosus at birth?

Answer 6

Closed by increased PaO2
Becomes the ligamentum arteriosum

There is decreased pulmonary vascular resistance, pulmonary artery pressure falls –> blood flow through DA is diminished

Question 7

What inflammatory mediator ensures the closure of the ductus arteriosus?

Answer 7

Bradykinin

Question 8

What can reopen the ductus arteriosus?

Answer 8

Prostaglandin E2

Question 9

What are the 4 main cardiac abnormalities that occur in Tetralogy of Fallot?

Answer 9

1. Ventricular septal defect
2. Overriding aorta
3. RV hypertrophy (due to high RV pressure)
4. Narrow RV outflow
   - -> infundibular stenosis = obstruction of flow from RV within the body of the RV, rather than valve)

Question 10

What is a “Tet spell” and why does it occur?

Answer 10

Hypercyanotic episode

due to blood shunting from right to left via ventricular septal defect

Question 11

What is presistent truncus arteriosus? Is it a cyanotic or acyanotic lesion?

Answer 11

• Truncus arteriosus fails to completely separate the aorta and the pulmonary trunk
• There is one arterial trunk whcih supplies both the aorta and the pulmonary trunk –> only one valve
• Ventricular septal defect below truncal valve - allows mixing of blood in right and left ventricles

CYANOSIS occurs

Question 12

What is transposition of the great vessels? Is it a cyanotic or acyanotic lesion?

Answer 12

Septum fails to follow its spiral course - runs straight down connecting RV to aorta and LV to pulmonary trunk
It is a cyanotic lesion

Question 13

What is transposition of the great vessels usually accompanied with?

Answer 13

Patent ductus arteriosus

Question 14

How is transposition of the great vessels treated?

Answer 14

Requires immediate intervention
Fossa ovalis is catheterised (increase the mixing of blood)
Prostaglandins to keep the ductus arteriosus open and allow mixing of blood

Question 15

How does artrial septal defect usually occur? What effects can this have on the heart?

Answer 15

Foramen ovale does not close
The left –> right shunt can cause pulmonary hypertension and increase pulmonary arterial pressure
This eventually can lead to a right –> left shunt = RV hypertrophy?

Question 16

What is Eisenmenger’s syndrome/shunt?

Answer 16

When a long standing left –> right shunt causes pulmonary hypertension and eventual reversal of the shunt (right –> left)

Question 17

What are the symptoms of an atrial septal defect?

Answer 17

Exercise intolerance
Dyspnoea
Fatigue (due to R sided heart failure and pulmonary hypertension)

Question 18

What % of all CHDs are ventral septal defects? Where do VSDs usually occur?

Answer 18

~25%
90% occur in the membranous septum
10% occur in muscular septum

Question 19

What does patent ductus arteriosus increase the risk of? What might prevent the duct form closing?

Answer 19

Low risk of heart failure (small PDA)
Increased risk of bacterial endocarditis
Large pressure differences between aortic and pulmonary pressure may cause increased blood flow –> prevents duct from closing

Question 20

How is patent ductus arteriosus treated?

Answer 20

Prostaglandin inhibitor such as ibuprofen

Or surgical clip is infants >3 months

Question 21

What % of CDHs are coarctations of the aorta? What is the difference between pre-ductal and post-ductal aortic coarctation? What the implications of the condition? How is it treated?

Answer 21

10-15% of all CHDs
Pre-ductal = ductus arteriosus is open = allows for blood flow
Post-ductal = collateral circulation established for perfusion of the body and legs
Mild to moderate = asymptomatic for many years except hypertension + reduced lower extremity pulses
Causes systemic coarctation and secondary LVH with congestive heart failure
Treatment: balloon angioplasty