Tetralogy of Fallot is the most common type of cyanotic congenital heart disease. There are a few others which I will write somewhere in the future:

• Transposition of great arteries
• Arterioventricular septal defect
• Tricuspid Atresia
• Hypoplastic left heart syndrome
• Total anomalous pulmonary venous drainage
• Truncus Arteriosus

Now, let’s focus on the management of the Tetraology of Fallot (TOF). Just some information on TOF:

• There are four congenital heart deformities that can be seen in people with Tetralogy of Fallot; ventricular septal defect (VSD), overriding aorta, right ventricular hypertrophy and finally, sub-pulmonic stenosis.
• The severity of symptoms would depend on several factors such as the size of the hole in the VSD, whether or not the ductus arteriosus (a connection between the proximal descending aorta and the pulmonary artery) is present and the degree of the ventricular outlet obstruction (pulmonary stenosis).
• The direction of blood flow will be determined by the pressure gradient inside the respective chamber or blood vessel. For example, when there is a small VSD, blood will flow from the left ventricle to the right and not the other way around; not until the pressure gradient level reverse as a result of certain pathology.

Clinical Presentation

When we are talking about clinical presentation, it’s important to know that, there are a few aspect or information that need to be gathered in order to achieve an accurate provisional diagnosis:

• Patient’s history
• Physical examination
• Provisional diagnosis
• Differential diagnoses

After obtaining all of the above information, finally, we’re ready to proceed to the managing part. Management of a disease can be divided into two which are:

• Investigation
• Treatment modalities

I will talk about management later in the article. For now, let’s focus on the clinical presentation of a patient, how they look like when they were first presented to the clinic/hospital. There are a few signs which indicate a baby is in heart failure. Among all of them, the most important signs to be elicited by a clinician is a heart murmur. Listening to murmur is kinda subjective, it will depend whether or not the clinician in charge has sufficient training or not. Hearing sounds, sometimes, can be deceiving and in paediatric populations, checking heart murmur can be a challenging task (patient often cries especially when they have the stranger or white coat anxiety).

There a few types of heart murmur and all of them correspond to a different kind of heart’s pathology. Refer to the video below to know more.

The age of presentation will depend on the severity of symptoms which would be determined by a few cardiac pathologies. Two of the commonest type of pathologies are:

• A large VSD
• A high degree of right ventricular outlet obstruction

A baby which have one of two of those signs will be presented with cyanosis; blue discolouration of the skin and mucous membrane as a result of a low blood oxygen concentration. If for the sake of argument, the baby presented with both, then they will show symptoms related to hypoxia, a couple months early than the other babies. Parents were usually concerned with the bluish appearances of the baby rather than other symptoms which they might have thought “normal” such as lethargy and irritability.

Clubbing of the finger is a common sign for heart-related diseases but in patients with TOF, they rarely presented with clubbing unless their pathology was detected later in life (if the defect was not severe).

The pathophysiological processes which could lead to the formation of a club finger would take normally around 6 months. Clubbing of the finger is not a specific sign which indicates any type of disease.

They can be found in patients with heart diseases, lung diseases, hyperthyroidism and liver diseases; it signifies that clubbing of the finger is actually a poor indicator of either disease.

Sometimes, people who have clubbing of the finger doesn’t really have anything.

Their exact pathophysiology was not known but it was speculated that clubbing of the finger was caused by interstitial oedema which progresses into an increase of the vascular connective tissue making the finger appears like a club.

Hypercyanotic spell also known as the Tet spell is another condition which could be caused by TOF. If you noticed, some children who have TOF can suddenly become:

• Hyperpnea (increase in deep breathing).
• Irritable
• Prolonged crying
• Cyanosis

If the one who was affected by the hypercyanotic spell is an older child, he/she will know to squat immediately after getting the attack. There are a few reasons why that will cause a temporary fix to the hypercyanotic spell so before going into that, I will explain a little bit more about the pathophysiology of the hypercyanotic spell. There are a few factors which would determine the onset of a hypercyanotic spell:

• Systemic venous return
• Systemic vascular resistance
• The degree of pulmonary stenosis

In several TOF patients especially those with severe pulmonary stenosis, there will be an increase in both of the cardiac output and systemic venous return.

This will cause the pressure of the right ventricle to be higher than the pressure in the left ventricle.

This would cause a reverse flow of blood from the right ventricle into the left ventricle through the VSD due to the pressure difference.

Couple this with a reduced systemic vascular resistance, the cells in the body would be deprived of oxygen which would cause hypoxia.

Low concentration of arterial oxygen along with an increase in the level of carbon dioxide will be detected by the respiratory centre in the brain.

This will cause them to send a signal to a few respiratory muscles to increase the depth and frequency of breathing thus the hyperpnea.

Squatting or putting the affected patient in a knee-to-chest position would allow both the systemic vascular resistance and systemic venous return to decrease, relieving the increase in right ventricle pressure gradient.

It worth noting that, when a child presented with the hypercyanotic spell, they should have been brought for medical consultation for further assessment.

Investigation and Treatment Modalities

When it comes to investigations for TOF, the diagnostic one would be imaging tests.

Well, we can order the standard workup to establish the baseline value such as full blood count (FBC), full blood picture (FBP), renal profile, liver function test and maybe acute phase reactant if the patients came with fever or anything that indicates some kind of inflammation or infection.

An electrocardiogram (ECG) can be performed to check for any sign of right ventricular hypertrophy which can be presented as a right axis deviation. Well, I would not go deeper into the ECG pattern analysis, maybe I will cover it sometime in the future.

Radiological investigations such as a chest X-ray and an echocardiogram can delineate some anatomical abnormalities in the heart structure. The most common finding in the chest X-ray of people with TOF is the boot-shaped heart.

The appearance was caused by a right ventricular hypertrophy which would cause an upward displacement of the apex of the right ventricle coupled with a concave pulmonary artery making it look like a boot.

Before echocardiogram was widely used, cardiac catheterisation was used to check the degree of blockage at the outlet of the right ventricle.

Now, echocardiography has been a gold standard imaging modality to delineate the structural defect of the heart.

Treatment modalities can be divided into two which are conservative and surgical.

Whether or not to proceed with surgical interventions, it will be determined by the severity of the clinical presentation.

The earliest treatment which could be given is prostaglandin.

If you remember, in the introduction part, I did say the importance of keeping the ductus arteriosus open to help reoxygenated any deoxygenated blood which has been pumped through the aorta.

It’s a temporary fix but an effective one.

The bad news is, this kind of treatment is only available if the patient was admitted early (when the ductus arteriosus is not yet closed). Keeping the ductus arteriosus open will provide a constant deoxygenated blood flow to the lungs which would alleviate the hypoxia.

If patients with TOF were suspected to have a hypercyanotic spell, parents should be taught some manoeuvres to fix the problem.

The easiest one would be to put their child in a knee-to-chest position thus making the systemic vascular resistance increase and systemic venous return decrease.

There is some medical intervention that can be given such as:

• Oxygen
• Morphine to alleviate pain and provide a sedative effect
• Bicarbonate to correct acidosis
• Beta-blocker to reduce infundibular spasm

Usually, palliative treatment would be given up until the baby reaches 4-6 months old before corrective surgical options could be discussed. In Malaysia, the most common bypass tube which has been used to improve blood flow into the pulmonary circulation is the modified Blalock-Taussig shunt.

So this shunt would be installed to provide a communication between the subclavian artery and the pulmonary artery.

After the baby has reached the age of 6 months old, a corrective surgery would be done.

There are a few types of corrective surgeries, which I would not mention it here, and if they were performed before the age of 1 year old, the chances of reintervention would be low throughout life and the rate of survival would be up to 85% (to reach 30 years old).

Conclusion

Even though people with TOF are subjected to a life-long follow-up, even after the corrective surgery, their quality of life has been increasing greatly.

It’s important to diagnose this disease as early as we could to yield a good outcome out of all the treatment modalities that are available.

The long-term management will be handled by a paediatrician and a cardiologist.

That’s the much we can take on the topic “The Blue Baby Syndrome | Introduction & Management Of The Tetralogy of Fallot“.

Thanks For Reading

O3SCHOOLS TEAM

See Other Articles People Are Reading

• Cry Me A River – From Biology To Psychology Of Tears
• Redefining ‘Health’ For The 21st Century | Health Care Changes In The 21st Century
• Missile Technology – The Weapon Of Destruction
• Discussing Day-to-Day Fear | Types Of Fears & How To Overcome Them
• Electromagnetism – Antenna Radiation Patterns | How To Read Antenna Radiation Patterns
• Do Robots Really Have Emotions? | Can Artificial Intelligence Feel Emotions?