Tetralogy of Fallot (TOF)

Tetralogy of Fallot, commonly known as TOF, is a particular combination of abnormalities of the heart. It is the most common cause of the “blue baby” syndrome, where the oxygen content of the blood is low. In addition to a large VSD, there is a narrowing of the pulmonary valve which guards blood flow to the lungs. This narrowing does not allow the blue blood that needs oxygen from the lungs to go to the lungs.


TOF is a disease where the severity can be different for each child. In some children, the narrowing in the pulmonary valve can be so mild that there is no blue color at all. These children might get diagnosed because of a heart murmur. On the other extreme, the narrowing is so severe that there is hardly any blood flowing to the lungs. Such babies can turn blue even in the first few days of life, needing emergency procedures. The vast majority of patients with TOF fall somewhere between these two extremes. They are generally not blue at birth. As they grow up, changes occur in the heart and the body that brings out the bluish color. Some children with TOF can develop something called a “spell”. When this happens, the breathing becomes faster and the bluish color worsens. These episodes need urgent medical attention, without which they can be life-threatening.


The treatment of TOF is open-heart surgery, under cardiopulmonary bypass to close the VSD and to remove the narrowing in the blood pathway to the lungs. It is generally done around 6 months of age. Sometimes, the oxygen levels and hence the blue color worsen much before the time when the open heart correction can be safely performed. In that case, a temporary procedure will have to be performed in the catheterization laboratory or operation theatre to improve the oxygen levels. The open-heart surgery is then planned at a later date. 

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Tetralogy of Fallot before and After Repair