CVS 8 - Congenital Heart Defects

Question 1

What are the 3 potential causes of congenital heart defects?

Answer 1

1) Genetic - e.g.: Marfan’s
2) Environmental - teratogenicity from drugs, alcohol etc
3) Maternal infections - e.g.: rubella

Question 2

Describe the normal flow of blood through the heart, include oxygen saturation and pressure values for each region.

Answer 2

1) Blood comes from venous circulation into RA via IVC + SVC (67%).
2) Into RV, through the pulmonary trunk and to lungs via pulmonary artery (67%)
3) Back to the left atrium via pulmonary vein (99%), into LV.
4) From LV, out through aorta and into systemic circulation (99%).

RA = 4mmHg
LA = 5mmHg
RV = 25/3mmHg
LV = 80/4mmHg
Pulmonary trunk = 25/10mmHg
Aorta = 80/40mmHg

Question 3

What 2 classifications can congenital HD be split into?

Answer 3

1) Cyanotic = defect lowers amount of oxygen in the body. (Caused by a hole, and an obstruction beyond it)
2) Acyanotic = defect does not affect amount of oxygen in the body.

Question 4

What are the 4 main shunts in the heart?

What are the haemodynamics effects of L to R/R to L shunts?

Answer 4

• Atrial, Ventricular, Atrio-ventricular + Aorto-pulmonary
• L to R shunts = require a hole, means blood from left heart returned to lungs instead of going to body.
• R to L shunts = requires a hole + distal obstruction. Allows de-oxygenated blood to bypass the lungs.

Question 5

What are the haemodynamics effects of atrial septal defects?

Answer 5

Blood flows from LA to RA (due to pressure difference), therefore …

1) Increased pulmonary blood flow
2) RV volume overload
3) Pulmonary hypertension (rare)
4) Eventual right heart failure

Question 6

What are the haemodynamic effects of ventricular septal defects?

Answer 6

1) There is L to R shunting
2) LV volume overload
3) Pulmonary venous congestion
4) Eventual pulmonary hypertension

Question 7

Are atrial/ventricular septal defects and patent ductus arteriosus cyanotic or acyanotic?

Answer 7

ASD, VSD + PDA are all acyanotic heart defects.

Question 8

What is tetralogy of fallot?

Answer 8

A condition consisting of 4 heart defects:

1) Ventricular septal defect (hole between ventricles)
2) Overriding aorta (allowing blood from both ventricles to enter aorta)
3) Pulmonary stenosis (narrowing of the pulmonary valve)
4) RV hypertrophy

Question 9

Describe the pathophysiology of tricuspid atresia (TCA)

What are the consequences?

Answer 9

1) Complete absence of tricuspid valve (right)
2) R to L atrial shunt of entire venous return
3) Blood flows to lungs via VSD or PDA (as there is a lack of a right ventricle)

Absence of a right AV connection leads to a hypoplastic right ventricle. Causes systemic circulation to be filling with deoxygenated blood. Blood must flow to lungs via alternative pathway (either VSD or PDA)

Question 10

Describe the pathophysiology of transposition of the great arteries.

Answer 10

1) RV now connected to aorta
2) LV now connected to pulmonary artery
3) Not viable for life unless 2 circuits communicate, via atrial, ventricular or ductal shunts.

Question 11

What are the pathophysiological effects of a hypoplastic left heart?

Answer 11

1) Left ventricle underdeveloped
2) Ascending aorta very small
3) Right ventricle supports systemic circulation
4) Obligatory R to L shunt

Question 12

Are TOF, TCA, TGA and HLH cyanotic or acyanotic diseases?

Answer 12

• Cyanotic