Congenital Heart Disease

Question 1

Briefly describe the embryology of the heart.

Answer 1

There are clusters of angiogenic cells (mesodermal cardiogenic plate).
The right and left endocardial tubes fuse to single cardiac tube by day 21 and this is beating by day 23. This then folds into the bulboventricular loop, then separates into the atria, ventricles and outflow tract by day 28.
The closure of foetal connections happens postnatally.

Question 2

If there is failure of atrial, ventricular and outflow tract separation - what does this cause?

Answer 2

Primary (AVSD)

Secondary (ASD or VSD)

Question 3

What anatomical connections are there in the foetal circulation?

Answer 3

Foramen ovale
Ductus arteriosus
Ductus venosus

Question 4

Describe the resistance of the pulmonary and systemic circulation in the foetus.

Answer 4

High resistance pulmonary circulation

Low resistance systemic circulation

Question 5

What is persistent pulmonary hypertension of the newborn?

Answer 5

This is where there isn’t the normal drop in pulmonary resistance at birth, so there is still high pressure in pulmonary artery. Shunting doesn’t reverse so it is still right-to-left shunting through the foramen ovale and ductus arteriosus. This causes cyanosis.

Question 6

In capillary blood, how much of the neonate’s Hb needs to be deoxygenated to appear cyanotic?

Answer 6

> 5g/dl

Question 7

In arterial blood, how much of the neonate’s Hb needs to be deoxygenated to appear cyanotic?

Answer 7

> 3.4g/dl

Question 8

What is the difference in presentation of cyanosis due to congenital heart disease compared to cyanosis due to lung disease?

Answer 8

In heart disease there is normal alveolar gas exchange (this is impaired in lung disease).
In heart disease the cyanosis is due to shunting of deoxygenated blood from the right to left side of circulation, but in lung disease it is due to oxygen diffusion problems of ventilation-perfusion mismatch.
In lung disease there is tachypnoea and recession and reduced pulmonary venous saturations

Question 9

Give some examples of cyanotic congenital heart disease.

Answer 9

Transposition of the great vessels (ductus arteriosus and foramen ovale allow mixing)
Tetralogy of fallot
Tricuspid atresia
Pulmonary valve atresia
Critical pulmonary stenosis
Truncus arteriosus
Total anomalous pulmonary venous drainage

Question 10

What are the problems in tetralogy of fallot?

Answer 10

Ventricular septal defect
Overriding aorta
Pulmonary stenosis
RV hypertrophy

Question 11

What is the problem in truncus arteriosus?

Answer 11

There is a single outflow tract

Question 12

What is the problem in total anomalous pulmonary venous drainage?

Answer 12

Pulmonary veins come back to the right atrium, and so there is an abnormal mixing of blood.

Question 13

What are the two major groups of acyanotic CHD?

Answer 13

Left to right shunts which increase pulmonary blood flow, causing pulmonary oedema/hypertension.

Left heart outflow tract obstruction, causing pulmonary oedema, impaired tissue perfusion, and lactic acidosis.

Question 14

Give an example of a left-to-right shunting condition. How does this affect the ratio of pulmonary to systemic blood flow.
What is the secondary effect of this?

Answer 14

VSD
Increased ratio
Secondary pulmonary hypertension, which reserves the direction of the shunt (Eisenmenger syndrome)

Question 15

Give an example of a LV outflow tract obstruction condition.

Answer 15

Preductal coarctation of the aorta

Question 16

Name some other forms of acyanotic CHD. (5)

Answer 16

ASD
AVSD
Patent ductus arteriosus
A-V malformations
Critical aortic stenosis

Question 17

Name two complex mixed presentations.

Answer 17

Hypoplastic left heart

Double outlet right ventricle

Question 18

How can the ductus arteriosus be re-opened?

Answer 18

Prostaglandin E

Question 19

How can the foramen ovale be enlarged?

Answer 19

Balloon septostomy

Question 20

How is cyanotic CHD treated?

Answer 20

Prostaglandin E
Laser and balloon valvotomy
Modified Blalock-Taussig shunt
Arterial switch operation (for transposition)
Surgical valvotomy
Closure of ventricular/atrial septal defects

Question 21

How are left-to-right shunts treated?

Answer 21

Diuretics +/- ACE inhibitor for left to right shunts

Question 22

How are LV outflow tract obstructions treated?

Answer 22

Prostaglandin E

Question 23

What surgery can be done for acyanotic CHD?

Answer 23

Percutaneous catheter closure of PDA
Balloon dilatation of valvular stenosis
Repair of coarctation
Open heart surgery for VSD/ASD

Question 24

What are neural tube defects caused by?

Answer 24

Failure of normal “zipping up” of neural tube. Closure should be complete by day 28.

Question 25

Give some examples of neural tube defects.

Answer 25

Spina bifida occulta
Meningocoele 
Myelomeningocoele (spina bifida) 
Encephalocoele 
Anencephaly

Question 26

How are myelomeningocoele and hydrocephalus treated?

Answer 26

Closure (reduces risk of infection but doesn’t restore normal neural function)
Hydrocephalus needs V-P shunt

Question 27

What are the neurological complications of a lumbar myelomeningocoele? (4)

Answer 27

Mixed sensory, motor and autonomic problems
Loss of bladder control
Faecal incontinence
Paralysis and loss of sensation in legs

Question 28

What is gastroschisis?

Answer 28

Full thickness small defect in abdominal wall lateral to umbilicus
Bowel free within amniotic cavity

Question 29

What is exomphalos and what may it be associated with?

Answer 29

Membrane covers herniated viscera.

It may be associated with other abnormalities and genetic disorders.

Question 30

What is cleft lip and palate due to?

Answer 30

Failure of fusion of maxillary and frontonasal processes.