| From your Guide Dr.MANI |  | |
Tetralogy of Fallot | ||
| From your Guide Dr.MANI | | |
Tetralogy of Fallot | ||
| |
BASICS OF TETRALOGY OF FALLOT
What are the four components of ToF ?
The first is a Ventricular Septal Defect - or VSD. 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). 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. And the last component is an over-riding aorta.
As you know already, the aorta normally arises from the left ventricle. In ToF, the aorta is moved
away from its normal position so that it arises partly from the RIGHT ventricle too. Since there is a
wall - or ventricular septum - between the two ventricles, it is obvious that the aorta must be
positioned right above this wall - or in other words, the aorta OVER-RIDES the ventricular
septum.
Why is ToF called "Blue Baby Disease" ?
Because a baby with ToF is "blue". I'm not joking ! The child has a bluish color, most obvious on
the tongue, lips, finger tips and toes. Although ToF is not the only disease to cause this blue color -
called "cyanosis" - it is the most common one.
What causes this blue color ?
Blood contains a "pigment" - or coloring substance - called "hemoglobin". This hemoglobin has a
special property - it can carry oxygen. You can imagine hemoglobin to be a sort of pick-up truck.
It travels on the highway of the blood-vessels, and reaches the lungs, where oxygen is loaded onto
it. It then continues along arteries to different parts of the body, where it unloads its oxygen. The
oxygen is converted into energy, which is used by different organs to do their work. The "empty"
hemoglobin then returns to the lung to pick up its next load.
When hemoglobin is carrying oxygen, it is bright red in color. That's why we call the "pure" blood
of the arteries "red blood". When it has given up its oxygen load, hemoglobin changes color. It
beomes blue or purple. That is why we refer to "impure" blood that returns to the heart in the veins
as "blue blood".
Normally, the two kinds of blood are separated by the wall between the two ventricles. But in ToF,
the aorta arises above this wall, and is connected partly to the right ventricle too. So "impure" blue
blood from the veins mixes with "pure" red blood from the left ventricle, before entering the aorta.
The mixed blood is not bright red, but has a bluish hue. When this blood is pumped to all parts of
the body, a "blue" tinge is visible. This is obvious in places where the skin is thin, and the color of
blood flowing in the arteries is visible through it - like the tongue, nailbeds and lips. Because ToF
causes this blue color (called cyanosis), it is a CYANOTIC congenital heart disease.
What exactly happens in ToF ? Read on .....
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