tetralogy of fallot/ta
What is tetralogy of Fallot? Tetralogy of Fallot (TOF) is a serious, congenital heart defect, affecting about two in 10,000 babies. In TOF, the abnormal connections prevent enough oxygen-poor (blue) blood from flowing to the lungs as it should. As a result, a person with TOF has a lower-than-normal amount of oxygen in the blood and typically, surgical correction is necessary.