Teratology of fallot

Question 1

What type of congenital heart condition is teratology of Fallot?

Answer 1

Cyanotic

Question 2

What percentage of congenital heart diseases is teratology of Fallot?

Answer 2

10%

Question 3

List the tetrad which comprises teratology of fallot

Answer 3

Ventricular septal defect
Pulmonary stenosis
Right ventricular hypertrophy
Overriding aorta

Question 4

List some risk factors for teratology of fallot

Answer 4

1st degree FH
Males
Teratogens - alcohol, warfarin, trimethadione
Genetics - CHARGE (coloboma, heart defects, atresia choanae, retardation of growth/development, GU anomalies, ear anomalies), Di George syndrome, VACTREL association (vertebral anomalies, anorectal malformations, cardiac defects, tracheoesophageal fistula, renal anomalies, limb abnormalities)
Associated congenital defects - right aortic arch and congenital diaphragmatic hernia

Question 5

Describe the shunt direction in VSD

Answer 5

Left to right if small

If severe then shunt reversal right to left

Question 6

What happens when there is a shunt reversal?

Answer 6

Child becomes cyanotic

Question 7

What is the most common site of pulmonary stenosis?

Answer 7

Infundibular septum/Right ventricular outflow tract

Question 8

What does pulmonary stenosis lead to?

Answer 8

Intermittent right ventricular outflow tract obstruction - tet spells

Question 9

Describe right ventricular hypertrophy in teratology of fallot

Answer 9

Occurs in response to high pressures needed to overcome and pump deoxygenated blood through RVOTO

Question 10

When does RVH usually develop?

Answer 10

In utero

Question 11

Describe the overriding aorta in teratology of fallot

Answer 11

Compared to the normal heart, the aorta is dilated and displaced over the intraventricular septum
Aortic dilation is caused by an increase in blood flow through the aorta as it receives blood from both ventricles via the VSD
In severe TOF, multiple aorto-pulmonary collateral arteries may also form to help increase pulmonary flow

Question 12

List the 3 classes of TOF

Answer 12

Mild
Moderate/severe
Extreme

Question 13

Describe mild TOF

Answer 13

Mild PS/RVH
Asymptomatic
Disease progresses as the child grows - age of 1-3yrs they develop cyanosis

Question 14

Describe moderate/severe TOF

Answer 14

Present within the first weeks of life with cyanosis and respiratory distress
Prone to recurrent chest infections and failure to thrive

Question 15

Describe extreme TOF

Answer 15

Present within the first hours of life with respiratory distress and cyanosis

Question 16

How can extreme TOF be divided?

Answer 16

TOF with pulmonary atresia

TOF with absent pulmonary valves

Question 17

How can deoxygenated blood flow into the lungs in extreme TOF?

Answer 17

Through patent ductus arteriosus

Question 18

What is the peak age of incidence of tet spells?

Answer 18

2-4 months

Question 19

How do tet spells present?

Answer 19

Paroxysms of hyperpnoea
Irritability
Increasing cyanosis

Question 20

What might precipitate a tet spell?

Answer 20

Dehydration
Anaemia
Prolonged crying (induces tachycardia and systemic vascular resistance)

Question 21

What is seen on examination of TOF?

Answer 21

Central cyanosis
Clubbing
Thrill (depends on intensity of murmur) or heave (RVH)
Auscultation - Loud, single S2, pansystolic murmur, ejection click, continuous machinery murmur, signs of congestive heart failure

Question 22

What investigations do you do for TOF?

Answer 22

ECG - right axis deviation and right ventricular hypertrophy
Microarray - genetic disorders
CXR - boot shaped heart and reduced pulmonary markings
Echocardiogram - standard for diagnosis
Cardiac CT angiogram - Anatomy
Cardiac MRI - anatomy and cardiac function
Cardiac catheter - performed under GA, done as part of pre-op assessment to measure haemodynamic and cardiac function

Question 23

Describe the management of TOF

Answer 23

Medical
- Squatting - increases venous return and systemic resistance
- Prostaglandin infusion - Helps maintain the PDA and must be started urgently after delivery to avoid the neonate collapsing - PGE1 (alprostadil) or PGE2 (dinoprostone)
Beta blockers- propranolol - used in tet spells
Morphine - reduces resp drive
Saline 0.9% bolus - used in tet spells as a volume expander

Surgical

• Palliative - transcatheter RVOT stent insertion or Modified BlalockTaussig shunt (helps mimic a PDA)
• definitive repair - performed under cardiopulmonary bypass via median sternotomy involving RVOT stenosis resection, RVOT/pulmonary artery augmentation and VSD patch closure

Question 24

List the side effects of prostaglandin infusion

Answer 24

Apnoea
Bradycardia
Hypotension

Question 25

List the complications of untreated TOF

Answer 25

Polycythaemia
Cerebral abscess 
Stroke
Infective endocarditis
Congestive cardiac failure 
Death

Question 26

List the post corrective surgical complications those with TOF are at risk of?

Answer 26

Pulmonary regurgitation
Arrhythmias
Exercise intolerance
Sudden death

Question 27

When is definitive surgery carried out?

Answer 27

3months - 4 yr

Question 28

What percentage of those with TOF survive till adulthood after corrective surgery?

Answer 28

85%