Tetralogy of Fallot is a common syndrome of congenital heart defects. This condition, present in utero, is caused by the narrowing of the pulmonary artery and a hole between the ventricles of the heart. When the baby is born and begins to breathe on its own, the baby turns cyanotic, or blue, due to the deoxygenated blood that bypasses the lungs as a result of this deformity.

Each defect acts in combination with the other to create a malfunction of the heart. The problem starts very early in the uterus with a narrowed pulmonary valve and a hole between the ventricles. This is not particularly a problem for a fetus because hardly any blood flows through the lungs until birth. It is only after birth that the defects pose a problem. The blood that is supposed to start flowing through the lungs cannot easily...