Truncus Arteriosus

What is Truncus Arteriosus ?

Truncus arteriosus is a rare complex birth defect of the heart in which only one artery leaves the heart, instead of the normal pattern where two great arteries – the aorta and the pulmonary artery – carry blood away from the heart.

In truncus arteriosus, a single large arterial trunk arises in common from both the right and left ventricles. It then divides into the aorta and pulmonary artery, after first giving off coronary artery branches.

The method of branching allows the classification of truncus arteriosus into three types.

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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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Hypoplastic Left Heart Syndrome – HLHS

The “Hypoplastic Left Heart Syndrome” – or more conveniently, “HLHS” – is a unique defect of the heart in many ways. Until a decade ago, the diagnosis was a virtual death sentence. Today, the revolution in cardiac surgical thinking and technique has changed the situation radically.

Whereas survival beyond the first few months of life was previously unheard of, many centers are today reporting encouraging results. And it is bound to improve further as more knowledge is gained from the early experience.

What is the HLHS ?

The heart has two upper and two lower chambers – one of each is right sided and the other left sided. The left sided chambers, with their blood vessels and valves are sometimes referred to as the LEFT HEART. ( This does not mean that the person has TWO hearts! )

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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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