Tetralogy of Fallot is a congenital heart disorder meaning that children are born with it. It is named after a French physician who described it in the late 1800’s. Tetralogy of Fallot is the most common cause of blue baby syndrome occurring in five out of every 10,000 babies born. There are four problems with the heart that comprise the tetrad. They are:

Large Ventricular Septal Defect. This is a hole that connects the bottom two chambers of the heart and allows blood with less oxygen to mix with blood that has oxygen. Blood with less oxygen has a bluish color. This is the reason that the babies appear to have a bluish color when they have this disorder.

Pulmonary Stenosis is a narrowing of the normal flow of the blood from the heart to the lungs. This narrowing can occur in the heart itself, at the level of the pulmonary valve, or after the valve in the pulmonary artery or in any combination of the three locations. This narrowing to flow helps to inhibit the natural flow of blood to the lungs and can encourage additional mixing of blood through the ventricular septal defect.

Right ventricular hypertrophy results from the fact that the right bottom chamber of the heart has to pump harder than it normally would against the obstruction of the pulmonary stenosis. The heart muscle then becomes thickened just like any other muscle that is exercised excessively.

The final problem of the four is an overriding aorta. This means that the aorta is actually shifted over the ventricular septal defect and essentially straddles the left and right side of the hearts allowing the mixture of the blood with oxygen and with less oxygen to travel to the body. This contributes to the bluish color as well.

It is helpful for parents of babies with Tetralogy of Fallot to understand what is wrong with their baby’s heart and to seek the advice of professionals trained in treating this disorder.