Congenital heart disease Flashcards
What is meant by congenital heart disease?
A gross structural abnormality of the heart or intra-thoracic great vessels that is actually or potentially of functional significance
When is antenatal screening performed?
Between weeks 18 and 22 of gestation
What is performed in antenatal screening?
An ultrasound allowing the 4 chambers of the heart and the outflow tracts to be examined
What measurements are taken in antenatal pulse oximetry?
Pre-ductal saturation
Post ductal saturation
What are some examples of cyanotic congenital heart defects?
Hypoplastic left heart syndrome
Tetralogy of Fallot
Transposition of the great vessels
What are some examples of acyanotic congenital heart defects?
Ventricular septal defect
Atrial septal defect
Patent ductus arteriousus
Coarction of the aortic arch
Interruption of the aortic arch
What are the main functions of the placenta in development?
It functions in circulation and gas exchange as well as providing nutritio, waste excretion and homeostasis
Why is there no pulmonary circulation in a foetus?
The lungs are filled with fluid and are unexpanded, meaning that blood doesn’t need to pass through the lungs to receive oxygen
What is the function of the liver and gut in a foetus?
The gut is not in use
The liver plays only a small role in nutrition and waste management
Which blood vessel supplies blood to the foetal heart from the placenta?
Umbilical vein (x1)
Which blood vessel carries blood from the foetal aorta back to placenta?
Umbilical artery (x2)
What are the 3 shunts of foetal circulation?
Ductus venosus
Ductus arteriosus
Foramen ovale
What is the function of the ductus venosus?
This connects the umbilical vein to the inferior vena cava, therefore bypassing the liver and allowing blood flow straight to the foetal heart
What is the function of the ductus arteriosus?
This connects a pulmonary vein branch to the descending aorta, allowing some blood flow from the right ventricle to move directly into the aorta
What is the function of the foramen ovale?
This is an opening between the left and right atria and allows blood to flow straight from the right side of the heart to the left, as the pulmonary circulation is not required
On which side of the heart is the flap of the foramen ovale?
Left
What maintains the patency of the ductus arteriosus?
Prostaglandin E2 which is produced by the placenta
How is blood directed through the foramen ovale?
By the rough wall of the right atrium
What is the average foetal blood saturation level?
70%
What causes the rapid rise in SVR after birth?
The cutting of the umbilical cord causes a rapid increase in vasoconstriction therefore greatly increasing SVR
What causes the rapid decrease in pulmonary vascular resistance after birth?
As the baby breaths and cries, the lungs expand and fill with air
The oxygen tension increases and as oxygen is a potent vasodilator, this causes vasodilation which decreases vascular resistance
What causes closure of the foramen ovale after birth?
The decrease in pulmonary vascular resistance decreases pressure on the right side of the heart
The increase in SVR increases pressure on the left side of the heart
The pressure gradient switches from left to right and so causes closure of the flap on the left side
What causes closure of the ductus arteriosus after birth?
Increased left sided pressure due to increased SVR changes direction of flow
Removal of placenta reduces circulating prostaglandin E2 levels
Oxygen causes contraction of oxygen sensitive muscular layers in the ductus arteriosus
What is formed by closure of the ductus arteriosus?
Ligamentum arteriosus
What is the name of the congenital heart condition in which the ductus arteriosus does not close?
Patent ductus arteriosus
What is the function of the lung fluid in foetal lungs?
This prevents the movement of amniotic fluid into the lungs, which cannot be absorbed