Tetralogy of Fallot (TOF) it's a common congenital cardiac abnormality that represents the most common form of cyanotic congenital cardiac disease. The TOF classical presents as four morphologic abnormalities: right ventricular outflow tract obstruction, ventricular septal defect, deviation of the origin of the aorta to the right, and concentric right ventricular hypertrophy. 
There are three major subtypes of TOF:

• with pulmonary atresia
• with pulmonary stenosis
• with absent pulmonary valve

The main cause of TOF is unknown, but it´s an important association with chromosomal anomalies, reaching 17% in some studies. 
Clinical manifestation of TOF depends on the severity of the disease and the coexistence of chromosomal and other abnormalities. TOF with severe flow obstruction leads to cyanosis. 
It's important to make an antenatal diagnosis for planing early treatment after birth. 

Images: Dr José Roberto Festugato