L8: Congential Heart Defects

Question 1

What are the causes (aetiology) of congenital heart defects?

Answer 1

Genetic –> Down syndrome (↑40% heart defects)
Environmental –> Obesity, diabetes, teratogenicity from drugs
Maternal infections –> Rubella, Toxoplasmosis

Question 2

What are the basic concepts about the heart?

Answer 2

Right Ventricle–> DeO2 blood –> lungs, pulmonary circulation
Left Ventricle–> O2 blood –> rest of body, systemic

Question 3

What is the pressure in each of the chambers of the heart? Why is it important to have a pressure gradient?

Answer 3

RA--> 4mmHg
RV--> 25/3 mmHg
PT--> 25/10 mmHg
LA--> 5 mmHg
LV--> 80/4 mmHg
Aorta--> 80/40 mmHg
Ensures the blood circulates the body, even when we're not doing anything

Question 4

What is the oxygen saturation in each chamber?

Answer 4

RA --> 67%
RV --> 67%
PT --> 67%
LA --> 99%
LV --> 99%
Aorta --> 99%

Question 5

What causes a left to right shunt?

Answer 5

Hole
Pressure in left&raquo_space; right
O2 blood returns to lungs
↑ pulmonary pressure –> damaging

Question 6

What causes a right to left shunt?

Answer 6

Hole and obstruction distal to hole

Flow from low to high pressure initially–> pressure on right will become greater after a while

Question 7

How can congenital heart diseases be classified?

Answer 7

Acyanotic (non blue)

Cyanotic (blue)

Question 8

Which congenital heart defects fit into each category?

Answer 8

Acyanotic–> L to R shunt (ASD, VSD, PDA)
–> Obstructive - Pulomary stenosis, aortic stenosis, coarctation of aorta (narrowing of aorta), mitral stenosis

Cyanotic–> R to L shunt

• -> Tetraology of fallot
• -> Transposition of the great vessels
• -> Total anomalous pulmonary venous drainage
• -> Univentricular heart

Question 9

What shunts are there in the heart? Normal and congenital?

Answer 9

Normal –> Foramen ovalae, ductus arteriosus, Atrioventricular (usually valves there)
Congenital–> Ventricular

Question 10

What is an atrial septal defect?

Answer 10

Defect is speta–> R and L atria communicate
1. Sinus venous defect–> PV join onto LA sometimes miss forming a hole between RA and LA–> under the SVC
2. Secundum atrial defect–> Foramen ovale doesn’t develop properly so doesn’t close properly
3. Primum atrial defect–> Failure of separation of atria and ventricles
All –>increased pulmonary blood flow
–> RV Volume overload
–> Pulmonary hypertension
–> Right heart failure

Question 11

What are ventricular septal defects?

Answer 11

Holes on interventricular septum 
--> Membranous septum doesn't develop properly
All --> Left to right shunt
--> LV Volume overload
--> pulmonary venous congestion 
--> eventially pulmonary hypertension

Question 12

What are atrio-ventircular defects?

Answer 12

Failure of endocardial cushions to separate the atria and the ventricles
Common valve
Holes above and below valve connecting L and R side of heart

Question 13

What is aortic stenosis?

Answer 13

Narrowing of valve

Valve get thicker–> reduces blood flow through valve

Question 14

What is coarctation?

Answer 14

Narrowing of the aortic lumen
Region of ligamentum arteriosum
↑ afterload–> left ventricular hypertrophy
Collateral vessels form to bypass the obstruction

Question 15

What is a patent ductus arteriosus?

Answer 15

At birth DA should close
Failure to close leads to blood in aorta–> PT
Not cyanotic but can lead to complication later in life

Question 16

What is tetralogy of Fallot?

Answer 16

Group of 4 common congenital heart defects
1. Pulmonary stenosis–> Narrowing of valve –> obstruction
2. Ventricle septal defects –> Blood flow into left/ mixing of blood before leaving via aorta
3. Right ventricle hypertrophy –> has to work harder to pump blood out of RV
4. Over riding aorta–> linked to both ventricles
Blood from right into left–> not O2–> cyanosis

Question 17

What is tricuspid atresia?

Answer 17

No RV inlet–> valve fused
R–> L shunt of blood in fetus through ASD/foramen ovalae
Blood flows to lungs via VSD or PDA from left to right and back again

Question 18

What do we mean by transposition of the great arteries?

Answer 18

RV–> Aorta
LV–> Pulmonary Trunk
Systemic circulation would only receive deo2 blood however ductus arteriorsus and foramen ovale on foetus means mixing of blood can occur –> bidirectional shunting
not viable with adult life–> prostaglandins given to keep shunts open until operation

Question 19

What is hypoplastic left heart?

Answer 19

LV and aorta fail to develop properly 
LV underdeveloped 
Ascending aorta --> very small 
RV supports sytemic circulation 
R--> L shunt through DA

Question 20

What is univentricular heart?

Answer 20

Single ventricle to both the PT and aorta
Mixing of oxygenated and deoxygenated blood
Occurs with or without transposition of the great arteries