Tetralogy of Fallot

Question 1

What is Tetralogy of Fallot?

Answer 1

It is defined as a congenital condition in which there is anterior malalignment of the aorticopulmonary septum

This results in the development of four co-existing pathologies; ventricular septal defect, overriding aorta, pulmonary stenosis and right ventricular hypertrophy

Question 2

What class of congential heart disease is Tetralogy of Fallot?

Answer 2

Cyanotic

Question 3

Describe the pathophysiology of Tetralogy of Fallot

Answer 3

The ventricular septal defect allows blood to flow through the ventricles

The ‘overriding aorta’ refers to the aortic valve being placed further to the right than normal – above the ventricular septal defect

This means that when the right ventricle contracts, the aorta is in the direction of travel of that blood, therefore a greater proportion of deoxygenated blood enters the aorta from the right side of the heart

The pulmonary stenosis results in greater resistance against the flow of blood from the right ventricle

This encourages blood to flow through the ventricular septal defect and into the aorta, rather than the normal route into the pulmonary vessels

Therefore, blood is shunted from the right heart to the left, leading to cyanosis

Ultimately, there is increased strain of the muscular wall of the right ventricle, as it attempts to pump blood against the resistance of the ventricle and pulmonary stenosis, resulting in right ventricle hypertrophy

Question 4

What determines the degree of cyanosis and the clincial severity of Tetralogy of Fallot?

Answer 4

The degree of pulmonary stenosis, therefore the right ventricular outflow tract obstruction

Question 5

What four risk factors are associated with Tetralogy of Fallot?

Answer 5

Older Mother Age > 40 Years Old

Pregnancy Alcohol Consumption

Diabetic Mother

Rubella Infection

Question 6

What are the six clincial features of Tetralogy of Fallot?

Answer 6

Failure To Thrive

Feeding Difficulties

Cyanosis

Tet Spells

Syncope

Ejection Systolic Murmur

Question 7

Describe the murmur associated with Tetralogy of Fallot

Answer 7

There is a crescendo-decrescendo murmur with a harsh ejection systolic quality

It is loudest in the pulmonary area, which is the second intercostal space, left sternal border

Question 8

What is the pathophysiological cause of the murmur associated with Tetralogy of Fallot?

Answer 8

It due to right ventricular outflow obstruction caused by pulmonary stenosis - not the ventricular septal defect

Question 9

What are hypercyanotic ‘tet’ spells?

Answer 9

They are defined as intermittent symptomatic periods, in which the right-to-left shunt becomes temporarily worsened, precipitating a cyanotic episode

Question 10

What is the pathophysiology of hypercyanotic ‘tet’ spells?

Answer 10

These episodes occur when the pulmonary vascular resistance increases or the systemic resistance decreases

This increases the right-to-left shunt

Question 11

What are the three causes of hypercyanotic ‘tet’ spells?

Answer 11

Crying

Physical Exertion

Pain

Question 12

What are the five clincial features of hypercyanotic ‘tet’ spells?

Answer 12

Irritability

Cyanosis

Tachypnoea

Reduced Consciousness

Seizures

Question 12

What are the five clincial features of hypercyanotic ‘tet’ spells?

Answer 12

Irritability

Cyanosis

Tachypnoea

Reduced Consciousness

Seizures

Question 13

What three investigations are used to diagnose Tetralogy of Fallot?

Answer 13

ECG Scans

Chest X-Ray (CXR)

ECHO Scans

Question 14

What are the four features of Tetralogy of Fallot on ECG scans?

Answer 14

Right Bundle Branch Block

Right Axis Deviation

Anterior Prominent R Waves

Posterior S Waves

This indicates right atrial enlargement and right ventricular hyerptrophy

Question 15

What are the three features of Tetralogy of Fallot on CXR?

Answer 15

Boot Shaped Heart

Right Aortic Arch

Right Ventricular Hypertrophy

Question 16

What is the gold standard investigation used to diagnose Tetralogy of Fallot?

Answer 16

ECHO Scans

Question 17

What is the feature of Tetralogy of Fallot on ECHO scans?

Answer 17

Right-to-left shunt

Question 18

What is the conservative management option of hypercyanotic ‘tet’ spells?

Answer 18

We advise younger children to bring their knees to their chest and older children to squat

Question 19

What are the six pharmacological management options of hypercyanotic ‘tet’ spells?

Answer 19

Oxygen Therapy

IV Fluids

Morphine

Phenylephrine Infusion

Beta-Blockers

Sodium Bicarbonate

Question 20

What are the two pharmacological management options of Tetralogy of Fallot?

Answer 20

Prostaglandin Infusions

Loop Diuretics

Question 21

When are prostaglandin infusions used to diagnose Tetralogy of Fallot?

Answer 21

They are used to manage neonates with severe stenosis, who are awaiting surgical management

Question 22

How are prostaglandin infusions used to diagnose Tetralogy of Fallot?

Answer 22

They maintain the patency of the ductus arteriosus - enabling blood to flow through the aorta back to the pulmonary arteries

Question 23

When are loop diuretics used to manage Tetralogy of Fallot?

Answer 23

They are used when there is development of heart failure complications

Question 24

Name a loop diuretic used to manage Tetralogy of Fallot

Answer 24

Furosemide

Question 25

What is the surgical management option of Tetralogy of Fallot?

Answer 25

Open Heart Surgery

Question 26

What is the definitive management option of Tetralogy of Fallot?

Answer 26

Open Heart Surgery

Question 27

What is the open heart surgery used to manage Tetralogy of Fallot?

Answer 27

It involves closure of the ventricular septal defect, shunt placement between the aorta and the pulmonary aorta and widening of the pulmonary valve

In most cases, a second surgical procedure is required in older children, involving pulmonary valve replacement