Tetralogy of Fallot (T4F) is a heart disease (the pathology of the heart) that arises in the formation of the baby, in the womb of the mother (it is a pathology congenital). There are no specific causes. What is known is that there is an "error" during the formation of the heart that cause the four defects: VSD Communication (intra-ventricular), pulmonary stenosis, displacement of the aorta and hypertrophy of right ventricle.