Posted in Web Tetralogy of Fallot (TOF): Causes, Symptoms & Diagnosis January 10, 2021 Tetralogy of Fallot (TOF) is a congenital heart defect that can be fatal if it’s left untreated. It’s also known as “tet.” The “tetra” in the name of the condition comes from the four problems… https://www.healthline.com/health/tetralogy-of-fallot