Congenital Heart Symposium

Question 1

What fetal lung maturation takes place before birth?

Answer 1

• breathing movements begin before birth
• fetus removes 60% of fluid out from the lungs
• surfactant is produced by the type 2 pneumonocytes in the lungs from 24 weeks, to prevent the collapse of the lungs
  
  • more successful lung outcome if a premature birth happens after 24 weeks

Question 2

How are respiratory fluids expelled?

Answer 2

• prelabour hormonal changes removes 40ml/kg to 10ml/kg
• compression of vaginal birth removes 1/3
• adrenaline secreted in labour promotes reabsorption 2/3
• Transient tachypnoea of the newborn if not enough fluid is removed from the lungs

Question 3

What are motivators for a baby to take their first breath

Answer 3

• negative pressure in the chest cavity from recoil after birth
• temperature change
• light stimulation
• physical stimulation
• lack of oxygen supply

Question 4

What is the effect of a first breath in the lungs?

Answer 4

• there is a drop in the intrapulmonary pressure (the air sacs are no longer squashed, no longer high resistance environment)–>
• dilation of pulmonary vascular bed –>
• large amount of blood to move into the pulmonary circulation

Question 5

What are the main changes in the circulatory changes at birth

Answer 5

• Ductus venosus - does most of the filtering instead of the liver
  
  • the umbilical vessels do most of the filtering instead of the liver so not required
    
    • if this doesn’t fall off within 5 days or so of birth raises a few concerns about the immune function of the infant
• Foramen ovale - opening between the two atria, shunt blood away from entering the right ventricle
  
  • the lungs are not used as much
• Ductus arteriosus: connecting the trunk of the pulmonary artery to the proximal descending aorta.
  
  • It allows most of the blood from the right ventricle to bypass the fetus’s fluid-filled non-functioning lungs
    *

Question 6

The Foramen ovale changes at birth

Answer 6

• there is a functional closure due to increased left atrial pressure- decrease in right atrial pressure
• flexible septum primum pressed against rigid septum secundum
• the fossa ovalis takes up to 6-12 months to properly form from te foramen ovale

Question 7

Ductus Arteriosus changes at birth

• use first

Answer 7

• protects the lungs against circulatory overload by shunting 90% of blood away from lungs
  
  • only 10% needed for the development of pulmonary tissue
• the closure is mediated by bradykinin - from the lung during initial inflation - requires high O₂
  
  • _​causes constriction of muscular contraction
• the initial closure at 6-48 hours,
  
  • full anatomical closure may take 1-3 months
  • some congenital heart diseases can only be discovered once the ductus art. is closed (may need to keep it open if their or cardio. resp. issues)

Question 8

How would the Ductus arteriosus be kept open and why would this be done?

Answer 8

• Prostoglandin
  
  • can be given exogenously if it needs to be kept open
  • or can be open in premature babies due to abnormal prostaglandin levels
• In the adult, it forms the ligamentum arteriosum
• if the ductus arteriosum is patent a murmur will be heard

Question 9

Umbilical arteries changes at birth

Answer 9

• umbilical arteries and veins constrict but remain patent
  
  • if there is enough pressure in the portal system the umbilical veins can re-cannulise –> caput medusa
• can have a patent ductus venosus
  
  • not many clinical issues as a child
  • may have cardiac and

Question 10

Cardiac anomalies

Answer 10