Tricuspid Atresia – TA

Tricuspid atresia and the Fontan principle are rather complex congenital heart defects. So if you can’t figure out the condition even after reading this article, please understand that this anomaly is so complex that even cardiologists have trouble understanding its repair.

So if you don’t, console yourself that you are in distinguished company!

What is tricuspid atresia ?

Triscupid Atresia is a condition where the Tricuspid Valve, which guards the junction between the right atrium and the right ventricle, is either absent or is imperforate – that is, it does not have an opening to allow blood flow across it. There are many ways the valve can be imperforate – the leaflets of the valve may be formed but tightly stuck to each other, or may not be formed at all, with muscle tissue of the heart forming a wall where the valve should have been.

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Pulmonary Stenosis – PS

Pulmonary Stenosis (PS) is one of the simpler abnormalities of the heart. But even this requires some basic knowledge about the structure of the heart.

What is Pulmonary Stenosis ?

The word “pulmonary” denotes “to do with the lungs”.

The pulmonary valve is located between the right ventricle and the pulmonary artery. It regulates blood flow into the lungs, and prevents blood from leaking back into the right ventricle.

Sometimes, this pulmonary valve is extremely narrow, and blocks the smooth flow of blood into the lungs. This condition is called Pulmonary Stenosis – or PS, in short.

At other times, the pulmonary valve itself is normal, but there is an obstruction to blood flow from the right ventricle at other levels. For instance, there may be abnormal bundles of muscle below the pulmonary valve which obstruct flow. This is called “sub-valvular” pulmonary stenosis.

Or occasionally, there may be a narrowing of the pulmonary artery or its branches above the pulmonary valve. This is called “supra-valvular” pulmonary stenosis.

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Transposition of Great Arteries – TGA

I hope you still remember about the great arteries of the body, and the chambers of the heart from which they arise. In this article, we will discuss the condition called Transposition of the Great Arteries (TGA) in which these great vessels are inter-changed in position.

Here’s what you’ll learn about:

  • What is Transposition of the Great Arteries (TGA) ?
  • What happens in TGA ?
  • What if TGA is left untreated ?
  • When should TGA be treated ?
  • What are the treatment options ?
  • Initial stabilization
  • Palliative treatment
  • Definitive treatment
  • Arterial Switch Operation (ASO)
  • Atrial Switch Procedures
  • Some Special Circumstances

What is Transposition of the Great Arteries?

The two “great” arteries of the body are the aorta and the pulmonary artery. The aorta comes out of the left ventricle, and carries pure blood to the rest of the body. The pulmonary artery arises from the right ventricle and carries impure blood from the veins into the lungs for oxygenation.

Transposition of the Great Arteries – TGA, for short – as the name implies, means the two arteries are “transposed”. That is, the aorta arises from the right ventricle, and the pulmonary artery from the left ventricle.

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Tetralogy of Fallot – ToF

We’re now getting to a more complicated condition called the Tetralogy of Fallot – or ToF, for short. The diseases discussed until now had just one abnormality in the heart – Atrial Septal Defect (ASD) or Ventricular Septal Defect (VSD) or Patent Ductus Arteriosus (PDA).

As the name tetralogy implies, there are FOUR abnormalities combined together in this complex heart defect. ToF is also commonly called the “blue-baby” disease.

In this article, you’ll learn:

  • What are the components of ToF?
  • Why is it called “Blue Baby Disease”?
  • What exactly happens in ToF?
  • What is a “cyanotic spell”?
  • What happens if ToF is left uncorrected?
  • What are the surgical options?
  • How is a single stage intra-cardiac repair done?
  • Variations in ToF needing modified repair
  • What is an “outflow patch”?
  • When is an intracardiac repair NOT possible?
  • What are the palliative operations for ToF?
  • The Blalock-Taussig shunt
  • Other systemic-pulmonary shunt procedures
  • What is the outcome after a total correction operation?
  • What is the future course after a shunt procedure?

Basics of Tetralogy of Fallot

What are the four components of ToF ?

1. The first is a Ventricular Septal Defect – or VSD.

2. Next is a narrowing of the Pulmonary Valve, which guards the junction of the right ventricle with the pulmonary artery. This narrowing is called Pulmonary Stenosis (PS).

3. The third feature is a thickening of the wall of the right ventricle (RV). This increases the strength of the right ventricle and helps it pump blood more forcibly. This thickening is called RV Hypertrophy.

4. And the last component is an over-riding aorta.

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Patent Ductus Arteriosus – PDA

As you already know about the large blood vessels – the aorta and pulmonary artery – it’s easy to learn about the birth defect called Patent Ductus Arteriosus (or PDA).

What is a Patent Ductus Arteriosus?

As a child develops inside its mother’s womb, it is not able to “breathe”. So, even though the child’s lungs are well developed, they do not carry out their normal work.

The blood which flows through the right ventricle and pulmonary artery to the lungs has no function. It is “wasted” blood flow.

In an attempt to make use of this flow, nature provides man with a “shunt” or “bypass”. A small tube, or blood vessel, connects the pulmonary artery to the large artery called the aorta. This tube is the ductus arteriosus.

Through this tube, blood which enters the pulmonary artery, instead of going to the lungs, flows into the aorta. From the aorta, the blood reaches other parts of the body. It is now useful to these other parts, which get energy to do their work.

At birth, when the child draws its first breath, the lungs begin to work. Now, when blood flows into the lungs, it is mixed with oxygen and “purified”. At this time, the ductus arteriosus normally closes. At first, it closes by spasm or contraction of the muscle in its wall. Later, the tube becomes permanently blocked by a scar.

Sometimes, it does not close normally. It then remains open, and the condition is called Patent Ductus Arteriosus – or PDA.

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Double Outlet Right Ventricle – DORV

What is Double Outlet Right Ventricle (DORV) ?

Some of the defects I have described are “simple”, some are a little “complex” – but DORV is something else.

It is a common term that actually describes a wide spectrum of heart disease, ranging from something similar to a Ventricular Septal Defect (VSD), through Tetralogy of Fallot (ToF) to Transposition of the Great Arteries (TGA).

It is sometimes like one, at other times like another, and occasionally a mixture of some of them. So if at first you are baffled, don’t worry. I too was, and figured it out only after a long hard struggle.

What is Double Outlet Right Ventricle ?

Normally, a ventricle has just ONE outlet. For the left ventricle, this is the aorta. For the right ventricle it is the pulmonary artery. In DORV, both of these “outlet” blood vessels – aorta and pulmonary artery – arise from the RIGHT VENTRICLE, either totally or to a great extent.

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Coarctation of the Aorta – CoA

You have read something of congenital heart defects inside the heart. Now let us consider a defect that is outside the heart itself, in one of the great arteries of the body – the aorta.

What is COARCTATION of the aorta ?

Coarctation of the aorta (CoA) is an area of localized narrowing of the large artery called the aorta. (“Coarctatio” – Latin : a drawing or pressing together). The narrowing may be caused by a “shelf” of tissue inside the blood vessel which reduces its area. Alternately, it may be caused by under-development of a portion of the aorta itself, which causes a longer area of reduced diameter.

Where does CoA occur ?

The narrowing that occurs in CoA is most commonly seen at a portion called the ISTHMUS.

But what is the isthmus ?

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Ventricular Septal Defect – VSD

What is a Ventricular Septal Defect?

Ventricular septal defects – also called VSD – are similar to ASD.

A VSD is a “hole” in the wall between the two lower chambers of the heart – the ventricles.

VSD may be small, medium-sized or large, and may be single or multiple. It may occur in different parts of the ventricular septum, and may sometimes be found along with other heart defects.

What happens when there is a VSD ?

The wall between ventricles is meant to separate blood passing through each. This is to prevent mixing of “impure” blood from the veins with “pure” blood going to the arteries. When the wall is “broken”, mixing occurs.

However, only “pure” blood flows from the left ventricle into the right; no flow is seen from the right ventricle into the left side across the VSD and so “impure” venous blood does not reach the arteries. This is because pressure in the left ventricle is much higher than the right, and fluids always flow from places of high to lower pressure.

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