CVS - Fallot's Tetralogy

Question 1

What is Fallot’s Tetralogy?

Answer 1

A cyanotic congenital heart condition where there are four co-existing pathologies :

1. VSD.
2. Over-riding Aorta.
3. Pulmonary Valve Stenosis.
4. Right Ventricular Hypertrophy.

Question 2

Give 4 Risk Factors of Fallot’s Tetralogy.

Answer 2

RAID :

1. Rubella Infection.
2. Alcohol Consumption in Pregnancy.
3. Increased Age of Mother (Above 40).
4. Diabetic Mother.

Question 3

Epidemiology of Fallot’s Tetralogy.

Answer 3

1. Commonest cause of Cyanotic CHD (but TGA is commonest at birth).
2. Typically presents at around 1-2 months of age.

Question 4

Diagnoses of Fallot’s Tetralogy.

Answer 4

1. Most cases are picked up using antenatal scans.

2. Newborn Baby Check - Pulmonary Stenosis (Ejection Systolic Murmur).

Question 5

Clinical Features of Fallot’s Tetralogy (6).

Answer 5

1. Cyanosis.
2. Clubbing.
3. Poor Feeding.
4. Poor Weight Gain.
5. Ejection Systolic Murmur (loudest in Pulmonary Area).
6. ‘Tet’ Spells.

Question 6

Clinical Presentation of Severe Fallot’s Tetralogy.

Answer 6

Presents with Heart Failure, even before one year of age.

Question 7

What is a ‘Tet’ Spell?

Answer 7

Intermittent symptomatic period where there is a temporary worsening of the right-to-left shunt, precipitating a cyanotic episode.

Question 8

Clinical Features of ‘Tet’ Spells (3).

Answer 8

1. Irritable.
2. Short of Breath.
3. Severe - Reduced Consciousness, Seizures and Potentially Death.

Question 9

Pathophysiology of Fallot’s Tetralogy (5).

Answer 9

1. VSD allows blood to flow between the ventricles.
2. Overriding Aorta (entrance to the aorta - aortic valve) is placed further to the right than normal, above the VSD).
3. When the RV contracts and sends blood upwards, the aorta is in the direction of travel of that blood so a greater proportion of deoxygenated blood enters.
4. Stenosis of Pulmonary Valve provides greater resistance against the flow of blood from the RV so encourages blood to flow through VSD.
5. Increased strain on muscular wall of RV and Pulmonary Valve Stenosis cause RV Hypertrophy.

Question 10

What does the degree of cyanosis depend on in Fallot’s Tetralogy?

Answer 10

Severity of Pulmonary Valve Stenosis.

Question 11

Pathophysiology of ‘Tet’ Spells (2).

Answer 11

1. Pulmonary Vascular Resistance increases.

2. Systemic Vascular Resistance decreases.

Question 12

Aetiology of ‘Tet’ Spells (3).

Answer 12

1. Physical Exertion (CO2 Generation - Vasodilator).
2. Crying.
3. Waking.

Question 13

Investigations of Fallot’s Tetralogy (3).

Answer 13

1. Investigation of Choice - Echocardiogram + Doppler Flow Studies (direction of flow of blood).
2. CXR - ‘Boot-Shaped’ Heart due to RV Hypertrophy.
3. CXR - Right-sided Aortic Arch is seen in 25% of patients.

Question 14

Management of Fallot’s Tetralogy in Neonates.

Answer 14

Prostaglandin Infusion to maintain Ductus Arteriosus. This will allow blood to flow from aorta into pulmonary arteries.

Question 15

Definitive Management of Fallot’s Tetralogy (3).

Answer 15

1. Total Surgical Repair by Open Heart Surgery in 2 parts.
2. Mortality is 5% from surgery.
3. Corrective surgery allows 90% of patients to live into adulthood.

Question 16

Management of ‘Tet’ Spell (7).

Answer 16

1. Encourage squatting or knees to chest (increased systemic vascular resistance = more blood enters pulmonary vessels).
2. Supplementary Oxygen (Hypoxia).
3. B-Blockers (relax RV and improve flow to pulmonary vessels and reduce infundibular spasm).
4. IV Fluids (increase preload and flow to pulmonary vessels).
5. Morphine (reduce respiratory drive to allow effective breathing).
6. Sodium Bicarbonate (metabolic acidosis buffer).
7. Phenylephrine Infusion (increase systemic vascular resistance).