Cyanotic Congenital Heart Disease Part 1 || Tetralogy of Fallot (TOF)

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Acyanotic defect on the other hand doesn't affect the flow of blood, since it is always left-to-right shunts.

In my previous post, Another Child Born With a Heart Defect || Acyanotic Congenital Heart Disease, I explained congenital heart defect and I explained Acyanotic heart defect. If you missed the post, you should take time to read it. In today's post, I will be looking into Cyanotic heart defect and this is the part one where I will be discussing Tetralogy of Fallot (TOF). See you at the end of the post.

Hey, We are about to get serious. I think I am going to be learning about blue babies today!! - my thought

Let's begin. Have you heard about the word "Blue Baby"? It is usually associated with an infant not getting enough oxygen delivered in blood to their body. It could be as a result of two reasons, one being Methemoglobinemia where the baby is fed, or exposed to certain toxins, or drugs, and/or inhales Nitric oxide, causing the red blood cell to contain methemoglobin at a high rate, thereby causing the iron in the heme of the red blood cell to be oxidized to a ferric state (Fe3+), from its normal Ferrous (Fe2+) state, thereby causing lack of oxygen flow in the body since Methemoglobin doesn't bind with oxygen in the blood. , the other being Cyanotic Congenital Heart Disease (especially Tetralogy of Fallot (TOF)). I am not going into Methemoglobinemia at all in this post, I will be discussing Cyanotic Congenital Heart Disease.

With Cyanotic Congenital Heart Disease, babies usually have a bluish coloration in the body. This is as a result of deoxygenated blood being pumped into the body, as a result of a shunt from the right part of the heart to the left part of the heart. Remember that with Acyanotic, the blood was shunting from the left part of the heart to the right part, and the blood was oxygenated, but with cyanotic, the blood is deoxygenated. There are a lot of heart disorders or conditions that could cause Cyanotic Congenital Heart Disease, and I will be going through them.

Etiology is a Good Place to Start

According to Center for Disease Control and Prevention (CDC), 1% of all children born in the United States are born with Congenital Heart Diseases, and according to a worldwide systematic review which includes 114 papers and a total of 24,091,867 deliveries, the research confirmed 164,396 infants with Congenital Heart Disease. In a research titled "Mortality for Critical Congenital Heart Diseases and Associated Risk Factors in Newborns. A Cohort Study", the result showed that 64.7% of newborns with critical congenital heart diseases are lethal, but only 12.0% mortality was recorded.

An article titled Cyanotic Heart Disease, published on the National Library of medicine, says 25% of the 1% are said to be diagnosed with Cyanotic Congenital Heart Disease. Also, 5% of all Cyanotic Congenital Heart Disease are related to the Tetralogy of Fallot (FOT) disorder.

Pathophysiology is all about Understanding the Disease

To explain the pathophysiology of Cyanotic Congenital Heart Disease, we need to understand the Diseases/Defects in question. They are; Tetralogy of Fallot, Transposition of the Great Arteries, Truncus Arteriosus, Ebstein Anomaly, Total Anomalous Pulmonary Hypoplastic Left Syndrome, Venous Return, and Tricuspid Atresia. Let's take it one step at a time.

Tetralogy of Fallot

Being the most common type of Congenital heart disease, as a result of pulmonary stenosis, from the heart to the lungs, thereby causing obstruction of blood to the lungs and leading to low oxygen level in the blood.. According to a Dane Niels Stensen, in his paper titled Dissection of a Monstrous Foetus in Paris, there are four components that makes up the Tetralogy of fallot, and these are Ventricular Septal Defect (VSD), Pulmonary Stenosis (PS), Overriding Aorta, and Right Ventricular Hypertrophy (RVH). Ventricular septal defect has to do with the anterior mal-alignment (opening/hole) in the septum of the Ventricles, Pulmonary Stenosis is an obstruction of blood flow from the right ventricle to the pulmonary valve also in the distal pulmonary artery. Overriding Aorta is a defect from the mal-alignment of the aorta outlet septum in the right, thereby allowing oxygen poor blood to move to the body, and Right Ventricular Hypertrophy, is when the right ventricle thicken more than the left ventricle thereby causing it to pump more blood.

If you check well, these four defects that makes up the Tetralogy of Fallot, often fall in line with one another. When there is a ventricular septal defect, where the Conal Septum is in the superior-anterior towards the right ventricle, then there is a hole/opening. When this happens, the pulmonary artery which is supposed to fix to the right ventricle narrows, causing Pulmonary Stenosis. The narrow pulmonary artery and the mal-alignment of Cornal Septum, allows the Aorta to override the septum since the septum has a hole toward the right. With all these, the right ventricular muscle will hypertrophy, as a result of pressure placed on the right ventricle of the heart to the left. This is why a Tetralogy of fallot has the four component/disorders.

It Should Be Treatable

When Diagnosing Tetralogy of Fallot, Chest X-ray, Electrocardiogram (EKG), and Echocardiogram (ECHO) are very important.

Chest X-ray shows the heart with an upturned apex with a concave pulmonary valve, regarded as a boot-shaped heart. With EKG, there will be a right axis deviation of the heart, showing prominent force from the right ventricle., Echocardiogram (ECHO) shows an exclusive detail with diagnosis. It shoes the right ventricular hypertrophy, the Ventricular Septal Defect VSD size and location, the Pulmonary stenosis including the size of the right and left pulmonary arteries, the severity of the obstruction, and all other information needed.. Tetralogy of Fallot can also be identified in fetus, as early as 12 weeks of gestation, via ultrasound and in severe cases, the foetal echocardiography .

In the case of management and the treatment of Tetralogy of Fallot, complete neonatal repair is required for severe cases, thereby relieving the pressure on the right ventricle, minimizing cyanosis, and removing the risk of stenosis. The Surgical timing may defer depending on the state and severity of the condition..


It should be noted that this congenital heart disease most times do not have anyone to blame, as it is still difficult to find a specific cause. TOF which allow a decrease of blood to the lungs and pumping of deoxygenated blood to the Aorta due to the overriding of the aorta, can be successfully repaired via undergoing surgery, although, the timing may differ depending on when it is noticed or exhibition of symptoms. Finally, it is important to state that surgeries performed on Tetralogy of Fallot are palliative and not curative.

Image 1 || Wikimedia Commons
Image 2 || Wikimedia Commons


I was reading through for the cause of a TOF but I thought I might as well just ask here. Maybe I missed it whole reading through.

Lovely post. I like what you are doing with heart conditions here.

Similar to all CHDs, TOF isn't excluded. In my previous post, I made mention of risk factors that could lead to these heart disorders and wouldn't want to repeat the same thing in this post. The cause of most Congenital heart diseases are still very unknown. According to research by Hasti Sanandajifar, MD, 25% of TOF patients suffer chromosomal abnormality from fetus, especially the 22q11 deletion syndrome.

Thanks a lot for reading through my post, I really appreciate the time.

Very nice. Thank you for responding.

I was thinking we could work together for a post. What do you think?

It will be great to work with you on a post... When you are ready, we could look into the post via Discord.... Thanks a lot.

Interesting conclusion sometimes we blame ourselves for our childs genetics defects! It is good to say that no one can be blamed

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In this case, most times, there really isn't anyone at fault. Thanks for always reading my post @gwajnberg, I am always happy anytime I see you around


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Thanks for the reminder. I enjoyed reading it.

Thanks a lot for reading. I am glad you did

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