Session 3 - Congenital heart defects Flashcards
What are the groups of causes of congenital heart defects?
- Genetic factors
- Environmental factors
- Maternal infections
Provide an example of genetic disease which has heart defects?
- Downs
- Marfans
Provide examples of enviornmental factors which can cause of heart defects
- Drugs
- Alcohol
Give examples of maternal infections which can cause congenital heart defects
- Rubella
- Toxoplasmosis
What are the most common heart defects?
- ASD
- VSD
What two groups can congenital heart defects be broken into?
- Acyanotic
- Cyanotic
What are the characteristical features of acyanotic heart defects
- Require a hole in the heart
- Shunting of blood from LH to RH
- Blood oxygen levels not effected
What commonly causes acyanotic defects?
-Structural defects such as ASD, VSD and PDA
Apart from structural defects, what other things can cause acyanotic defects?
- Aortic, mitral and pulmonary stenosis
- Coarctation of the aorta
What happens to the blood in the LH in a structural acyanotic defect?
-Returned to the lungs instead of the body
What is an ASD?
-Artial septal defect-> opening anywhere along the atrial septum which persists after birth
What is the most common place for ASD to occur?
-Foreman ovale
What happens to the flow of blood when an ASD is present?
-The blood is shunted from left atrium to right atrium and thus pulmonary bloodflow is greater
What are the haemodynamic effects of an ASD?
- Increased pulmonary blood flow
- RV volume overload
- Pulmonary hypertension (rare)
- Eventually RH failure
Why is there no mixed blood pumped around the body with an ASD?
- There is higher pressure within the LA and thus blood flows from left to right
- Therefore oxygenated blood mixes with deoxygenated blood in the RA which gets pumped to the RV then the lungs to become oxygenated
What is the name for when the foreman ovale doesnt close?
-Patent foreman ovale
Why is PFO not a true ASD?
-Remains clinically silent
What is a paradoxical embolism and how does it occur?
- An embolism of the venous system which enters the systemic circulation
- Occurs when there is an ASD (including PFO) and RA pressure increases, even transiently, allowing blood to flow from right to left, ie allowing passage of the embolus
What is a VSD?
- Ventricular Septal Defect
- An opening anywhere along the interventricular septum
How common are VSD?
150-350/100,000 live births
How common are ASD?
67/100,000 live births
Which way does blood flow with a VSD?
-From left to right
Why is there no cyanosis with VSD?
-Blood flows from L->R and thus oxygenated blood mixes with deoxygenated blood in the RV and thus is pumped to the lungs, not the systemic circulation
Where does the most common VSD occur?
-In the membranous portion of the septum
What are the haemodynamic effects of a VSD?
- RV volume overload
- Pulmonary venous congestion
- Eventual pulmonary hypertension
What is a PDA?
- Patent ductus arteriosus
- Failed closure of the ductus arteriosus
What happens to blood flow with a PDA?
-Blood flows from the aorta into the pulmonary artery (High to low pressure)
When can PDA become cyanotic?
- Constant L->R shunting can cause vascular remodelling of the pulmonary circulation with increased pulmonary resistance
- If the resistance becomes so great the shunt can reverse
What is eisenmenger syndrome?
- Pulmonary hypertension, when associated with a septal defect, causes blood to flow from the right side of the heart to the left or from the pulmonary artery to aorta
- Deoxygenated blood enters circulation and pt becomes cyanotic
What is coarctation of the aorta?
-Narrowing of the aortic lumen in the region of the ligamentum arteriosum
What consequences does coarctation of the aorta have on the left ventricle?
-Increases the afterload of the LV which can lead to LV hypertrophy
What parts of the body are not comprimised in coartcation of the aorta and why?
-The head and upperlimb as the arteries emerge proximal to the coarctation
Why can the severity of symptoms of coarctation of the aorta vary?
-It is dependant on how narrowed the aorta is
What are clinical signs of coarctation of the aorta?
- Weak and delayed femoral pulses
- Upper body hypertension
In very severe cases, how do infants present after birth with coarctation of the aorta?
-With symptoms of heart failure shortly after delivery
Which way is blood shunted in cyanotic congenital heart diseases?
-From RH to LH
What are the general features of a cyanotic heart disease?
- Structural hole
- Distal obstruction
- Cyanosis of skin and mucus membranes
What is tetrology of fallot?
- A group of 4 lesions as a result of a single developmental defect of rotation
- Over-riding aorta
- Pulmonary stenosis
- VSD
- RV hypertrophy
Which lesions in tetralogy of fallot are variable?
- Pulmonary stenosis
- RV hypertrophy
What is an over-riding aorta?
-The aorta is laced above both ventricles
How does over-riding aorta cause pulmonary stenosis?
-Displaces the pulmonary artery out of the way making it smaller
Why does RV hypertrophy occur in tetralogy of fallot?
-Pulmonary stenosis increases the afterload of the RV so the RV must operate at a higher pressure causing hypertrophy
Why does cyanosis occur with tetralogy of fallot?
- Increased pressure on the right side of the heart, along with the VSD causes right to left shunting
- Mixed blood is pumped into systemic circulation from LV
What determines the magnitude of severity of tetralogy of fallot?
-The severity of pulmonary stenosis as this determines the level of shunting of blood
What is tricuspid atresia?
-Lack of development of the tricuspid valve, leaving no inlet to the RV
What must be present in order for tricuspid atresia to be compatible with life?
- A complete right to left shunt of the entire venous return to right atrium (ASD of PFO)
- A VSD of PDA to allow blood to flow to the lungs
What is pulmonary atresia?
-Lack of development of the pulmonary outflow valve meaning there is no RV outlet
What must be present for pulmonary atresia to be present with life?
- A right to left shunt of venous return eg ASD/VSD
- PDA in order to allow bloodflow to the lungs
What is transposition of the great vessels?
- The great vessels are not connected to the right chambers, ie the RV is connected to the aorta and the LV connected to the pulmonary artery
- This produces two unconnected parallel circulations
How does transposition of the great vessels occur?
-The conotruncal septum within the truncus arteriosus does not a spiral course, instead it is straight
What is necessary for transposition of the great arteries to be compatible with life?
-A shunt between the two sides of the heart VSD/PDA to allow the two circulations to communicate
How is transposition of the great arteries treated?
-A shunt must be maintained or created immediately following birth until permanent surgical correction can be made
What is hypoplastic left heart?
-Underdevelopment of the LV and ascending aorta
What must occur for hypoplastic left heart to be viable?
- There must be a left to right shunt (PFO/ASD) so the RV can support the systemic circulation (blood returning from lungs shunts right)
- PDA must be present in order to supply the systemic circulation with adequate blood, as PDA connects at descending aorta which is Okay
Why does cyanosis occur in hypoplastic left heart?
-PDA from pulmonary artery provides mixed-oxygenated blood into descending aorta -> cyanosis due to insufficient oxygen
How common are congenital heart defects?
6-8/1000 live births
