The most important malformation in Tetralogy of Fallot is pulmonary artery stenosis. Tetralogy of Fallot is the most common type of cyanotic congenital heart disease and includes four malformations: ventricular septal defect, pulmonary stenosis, aortic span, and right ventricular hypertrophy. Although it is called tetralogy of Fallot, these four malformations are actually sexually related to each other. The most important of these four malformations is pulmonary artery stenosis. Due to the stenosis, the right ventricular blood drainage is blocked and the blood flow is diverted through the riding aorta above the ventricular septal defect and a right-to-left shunt occurs. Long-term afterload overload in the right ventricle due to overcoming the main force of the pulmonary stenosis and the pressure of the aorta leads to the secondary formation of symptoms of right ventricular hypertrophy. Parents are advised to hospitalize their children for surgical treatment once they are diagnosed with tetralogy of Fallot to improve their quality of life.